JP7638157B2 - chair - Google Patents

Description

The present invention relates to a chair.

Chairs have been known that have a backrest that is supported on a support base via a back support so that it can tilt backward (see, for example, Patent Document 1).

For this type of chair, consideration is being given to providing a mechanism for setting the degree of backward tilt of the backrest, which allows the user to select from two or more options.

However, in conventional chairs, the engagement points on the backrest and the engagement points on the support base that determine the maximum backward tilt position of the backrest are each scattered in two or more locations, so the feeling of bottoming out that can be felt by the user varies depending on the degree of backward tilt.

A typical example of a conventional chair (a chair with a backrest that has first and second degrees of backward tilt) is as follows:

In other words, when the first degree of backward tilt was set, the limit position of backward tilt was determined by the locking body provided on the backrest engaging with the locking body engaging portion provided on the support base. However, when the second degree of backward tilt was set, the limit position of backward tilt was determined by engaging other portions on the backrest and support base without engaging the locking body and locking body engaging portion.

JP 2004-180783 A

The present invention was made with the above in mind, and aims to provide a chair with a backrest that can provide a common feeling of the seated person hitting the bottom at least at any selected degree of backward tilt, and contributes to a comfortable use by the seated person.

That is, the present invention has the following configuration.

The invention described in claim 1 is a chair having a backrest supported on a support base via a back support so as to be able to tilt backward, and provided with a backward tilt degree setting mechanism that can select the backward tilt degree of the backrest from two or more pluralities, the backward tilt degree setting mechanism comprising: an operating lever rotatably supported on either the back support or the support base; a rotating member that is rotatably attached to the operating lever and has a plurality of contact surfaces corresponding to the plurality of backward tilt degrees, the contact surfaces being arranged at intervals in the rotational direction; and a damper member that is arranged on the other of the back support or the support base and against which a specific contact surface of the plurality of contact surfaces can selectively come into contact. and each of the plurality of degrees of backward inclination is determined by the contact surface contacting the damper member , the operating lever includes a lever shaft portion extending in the left-right direction and pivotally supported in a shaft hole, and a handle portion attached to one end of the lever shaft portion, the rotating member includes a base end portion having an insertion hole through which the lever shaft portion is inserted, and a rotating member main body integrally formed with the base end portion and having the plurality of contact surfaces, the plurality of degrees of backward inclination being first, second, third, and fourth degrees of backward inclination, and the plurality of contact surfaces being determined by the first, second, third, and fourth degrees of backward inclination. a first contact surface provided on the rotating member body in correspondence with four degrees of backward inclination, the first contact surface being provided at a position farther away from the base end than the second contact surface, the second contact surface being provided at a position farther away from the base end than the third contact surface, and the third contact surface being provided at a position farther away from the base end than the fourth contact surface, and when the first contact surface comes into contact with the damper member, the first degree of backward inclination is set at which the backrest hardly tilts backward, and the rotating member body is substantially rectangular in side view. The chair comprises a rectangular prism-shaped portion having the first contact surface which is approximately triangular in side view and has a substantially rectangular shape that faces downward when it contacts the damper member, a first mountain-shaped portion having the second contact surface which is approximately triangular in side view and has a substantially rectangular shape that faces downward when it contacts the damper member, a second mountain-shaped portion having the third contact surface which is approximately triangular in side view and has a substantially rectangular shape that faces downward when it contacts the damper member, and a third mountain-shaped portion having the fourth contact surface which is approximately triangular in side view and has a substantially rectangular shape that faces downward when it contacts the damper member .

The invention described in claim 2 is the chair described in claim 1, in which the operating lever is supported on the back support, and the damper member is disposed on the support base.

The invention described in claim 3 is the chair described in claim 1 or 2, wherein the shapes of the rectangular columnar portion, the first mountain-shaped portion, the second mountain-shaped portion, and the third mountain-shaped portion are set so that the first contact surface, the second contact surface, the third contact surface, and the fourth contact surface can contact the damper member at approximately the same contact angle.

The invention described in claim 4 is a chair described in claims 1, 2 or 3, wherein the rotating member main body is arranged in a pair on the left and right, and the damper members are arranged in a pair on the left and right at corresponding positions on the rotating member main body.

The invention recited in claim 5 is the chair recited in claim 4 , wherein the left and right rotating member bodies are connected to each other by a connecting wall extending from the base end portion.

The invention described in claim 6 is a chair described in claims 1, 2, 3, 4 or 5, wherein the operating lever is supported on the back support body, the damper member is arranged on the support base, and the support base comprises a support base main body formed integrally from synthetic resin, and the damper member is separate from the support base main body and attached to the rear end of the support base main body.

The invention described in claim 7 is a chair described in claims 1, 2, 3, 4, 5 or 6, which is provided with a moderation mechanism for moderating and locking the rotating member at one of a plurality of rotational positions corresponding to the plurality of degrees of backward tilt.

As explained above, the present invention provides a chair with a backrest that provides a common feeling of bottoming out to the seated occupant at least for any selected degree of backward tilt, making it possible to provide a chair with a backrest that contributes to comfortable use by the seated occupant.

FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. 4 is a plan view of the adjustment lever (reaction force adjustment lever) in the embodiment. 9(a) is a cross-sectional view taken along line AA in FIG. FIG. FIG. FIG. FIG. FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. 3 is a cross-sectional view taken along line CC in FIG. 2 . Cross-sectional view taken along line D-D in FIG. FIG. FIG. FIG. FIG. FIG. 16 is an enlarged view of part E in FIG. Cross-sectional view taken along line FF in Figure 19. FIG. FIG. FIG. 31 is a view taken in the direction of the arrow G in FIG. 30 . FIG. FIG. FIG. FIG. 3 is a cross-sectional view taken along line JJ in FIG. 2. FIG. FIG. FIG. FIG. FIG. Cross-sectional view of line HH in Figure 41. Cross-sectional view of line II in Figure 41. Cross-sectional view taken along line L-L in FIG. FIG. 45 is a cross-sectional view for explaining the operation corresponding to FIG. 44 . FIG. 45 is a cross-sectional view for explaining the operation corresponding to FIG. 44 . FIG. FIG. FIG. 4 is a cross-sectional view taken along line K-K in FIG. 3. FIG. 4 is a perspective view of a support base main body in the embodiment. FIG. FIG. FIG. 4 is a right side view of the support base main body in the embodiment. FIG. 4 is a left side view of the support base main body in the embodiment. FIG. FIG. 4 is a bottom view of the support base main body in the embodiment. FIG. Cross-sectional view of line M-M in Figure 58. Cross-sectional view of line N-N in Figure 52. FIG. 2 is a perspective view showing a support base, a back support, and the like in the embodiment. FIG. FIG. FIG. FIG. FIG. Cross-sectional view of line O-O in Figure 66. Cross-sectional view of line P-P in Figure 66. FIG. FIG. FIG. Cross-sectional view of line QQ in Figure 71. Cross-sectional view of line R-R in Figure 71. FIG. FIG. 4 is a central cross-sectional view of a main part of the rearward tilt degree setting mechanism in the embodiment. FIG. 4 is a central cross-sectional view of a main part of the rearward tilt degree setting mechanism in the embodiment. FIG. 4 is a central cross-sectional view of a main part of the rearward tilt degree setting mechanism in the embodiment. FIG. 4 is a central cross-sectional view of a main part of the rearward tilt degree setting mechanism in the embodiment. FIG.

One embodiment of the present invention will be described below with reference to Figures 1 to 79.

In this embodiment, the present invention is applied to a swivel chair (hereafter simply referred to as "chair") suitable for use in an office or similar setting.

The chair comprises legs A, a support base B which is a support member supported rotatably on the legs A, a seat C placed on the support base B, a backrest E supported on the support base B via a back support D so that it can tilt backward, a lumbar support R attached to the backrest E, and a backrest surface extension member F and a hanger G which are options that can be selectively attached to the backrest E.

The chair is provided with a backward tilt setting mechanism X between the support base B and the back support D, which can set the backward tilt degree of the backrest E.

The chair in this embodiment is equipped with a so-called weight-sensing rocking mechanism V that moves the seat C upward and backward in response to the backward tilting of the backrest E.

<<Leg A>>
The leg A includes a plurality of leg blades a1 arranged radially, each having a caster a11 at its tip, and a leg support a2 erected at the base end of the leg blade a1.

The leg support a2 is configured to be extendable and retractable in the vertical direction. The leg support a2 is capable of supporting the support base B so that its vertical position can be changed by a gas spring (not shown).

<<Support Base B>>
The support base B is mainly composed of a support base main body 1 which is integrally formed from synthetic resin. The support base B is attached onto the legs A.

<Support base body 1>
The support base body 1 is integrally molded from synthetic resin. The support base body 1 has an internal storage space sp and is box-shaped with an open top. The support base body 1 is designed not to be covered by a cover body that is a separate member.

The support base body 1 not only performs the function of supporting the seat C and backrest E, but also exhibits design features that act as a cover without spoiling the aesthetic appearance.

At least a portion of the outer surface of the support base body 1, i.e., a portion of the downward surface 11s of the foundation bottom structure 11, the downward surface 12s of the inclined bottom wall 12, the downward surface 13s of the front bottom wall 13, and a portion of the outward surface 14s of the left and right side walls 14, are exposed to the outside and can be directly seen by the user.

The support base body 1 is provided with a foundation bottom structure 11 having a downward surface 11s and attached to the leg support a2, an inclined bottom wall 12 having a downward surface 12s facing diagonally downward and rearward and extending diagonally downward and forward from the front end of the foundation bottom structure 11, a front bottom wall 13 having a downward surface 13s and extending forward from the front end of the inclined bottom wall 12 and inclined to be positioned gradually upward as it moves forward, the foundation bottom structure 11, the inclined bottom wall 12, and left and right side walls 14 having outward surfaces 14s and extending upward from both left and right ends of the front bottom wall 13 in an upright position, and a front wall 15 having a forward surface 15s and in an upright position connecting the front ends of the left and right side walls 14.

The support base body 1 is surrounded by a foundation bottom structure 11, an inclined bottom wall 12, a front bottom wall 13, left and right side walls 14, and a front wall 15, and is provided with a reaction force generating part HG, a bearing shaft d4 that engages with the reaction force generating part HG, a bearing shaft support member d3 that supports the bearing shaft d4, and an accommodation space sp that accommodates the lever base shaft part k3 of the reaction force adjustment lever K.

[Foundation bottom structure 11]
The foundation bottom structure 11 comprises a bottom wall portion 111 having a downward surface 11s, a boss portion 112 erected on the bottom wall portion 111, a rear curved wall 113 erected on the bottom wall portion 111, located behind the boss portion 112 and curved along the boss portion 112, a side upright wall 114 erected on the bottom wall portion 111, extending in the front-rear direction, and positioned between the boss portion 112 and the left and right side walls 14, a rear connecting wall 115 erected on the bottom wall portion 111 and extending in the front-rear direction connecting between the left-right central portion of the rear of the boss portion 112 and the left-right central portion of the rear curved wall 113, and the side connecting wall 116 which is inclined in plan view and connects between the side portion of the boss portion 112 and the side upright wall 114; a front connecting wall 117 which is erected on the bottom wall portion 111 and connects between the front portion of the boss portion 112 and the side upright wall 114 and which is inclined in plan view; an outer connecting wall 118 which is erected on the bottom wall portion 111 and connects between the side upright wall 114 and the left and right side walls 14 and which is inclined in plan view; and an undershaft connecting portion 119 which is erected on the bottom wall portion 111 and connects between the side upright wall 114 and the left and right side walls 14 and is disposed below the main shaft jk1 inserted in the shaft hole 1b.

The shaft lower connecting portion 119 has a shaft holding recess 1e at its upper portion that constitutes a shaft holding portion JH capable of holding the main shaft jk1. The shaft holding portion JH will be described in detail later.

The foundation bottom structure 11 has a fitting hole 11a that is a connection part that penetrates the bottom wall part 111 and the boss part 112 and is externally fitted onto the leg support a2.

A mounting seat 111a is provided at the rear end of the bottom wall 111 for mounting a damper member XM, which is a buffer attachment that can engage with the rotating member Re attached to the rearward tilt degree setting lever H. The mounting seats 111a are provided in pairs on the left and right sides of the partition wall 111d. The mounting seat 111a is provided with a hole 111b for mounting the damper member XM, which is an attachment that penetrates in the vertical direction. A recess 111c is formed on the underside of the bottom wall 111 corresponding to the mounting seat 111a.

A nut portion n7 is provided on the boss portion 112 for mounting a gas spring operating mechanism (not shown) that can be operated by transmitting the operating force to the operating piece L arranged on the seat receptacle c1.

[Inclined bottom wall 12]
The inclined bottom wall 12 has a downward surface 12s facing diagonally downward and rearward, and is in a rearward inclined position extending diagonally downward and forward from the front end of the bottom wall portion 111 of the foundation bottom structure 11. A pair of left and right intermediate connecting walls 121 extending in the front-rear direction and connected to the front part of the foundation bottom structure 11 and the rear part of the front bottom wall 13 are provided on the inner surface of the inclined bottom wall 12.

The inclined bottom wall 12 has a side upright wall 122 extending in the front-rear direction and connected to the side upright wall 114 of the foundation bottom structure 11. In other words, the side upright wall 122 is provided on the inside of the left and right side walls 14.

[Front bottom wall 13]
The front bottom wall 13 has a downward surface 13s, extends forward from the front end of the inclined bottom wall 12, and is inclined so as to be positioned gradually higher as it moves forward.

The front bottom wall 13 is provided with side upright walls 131 that are continuous with the side upright walls 122 of the inclined bottom wall 12 and extend in the front-rear direction. In other words, the side upright walls 131 are provided on the inside of the left and right side walls 14. In addition, the front bottom wall 13 is provided with a number of connecting walls 132 that connect the side upright walls 131 to the left and right side walls 14.

At the front of the front bottom wall 13, there are provided a number of bearings 133a, 133b, 133c that receive the multiple retained shaft portions k31a, k31b, k31c provided on the lever base shaft portion k3 of the reaction force adjustment lever K, namely, the right bearing portion 133a on one side, the central bearing portion 133b, and the left bearing portion 133c on the other side.

The radius of curvature of the central bearing part 133b is set to be larger than the radius of curvature of the right bearing part 133a, and the radius of curvature of the left bearing part 133c is set to be larger than the radius of curvature of the central bearing part 133b.

The right bearing portion 133a and the left bearing portion 133c are each in an upwardly open position. The right bearing portion 133a and the left bearing portion 133c are provided on the upper portion of the side upright wall 131. The right bearing portion 133a and the left bearing portion 133c have a grease retaining groove 1j on the recessed surface.

The central bearing portion 133b is open toward the rear. The central bearing portion 133b is provided on the back support portion 13a that supports from the back side the reaction force adjustment lever K that is erected in the center of the front bottom wall 13 in the left-right direction and is constantly pressed by the reaction force generating portion HG. The central bearing portion 133b also has a grease retaining groove 1j on its recessed surface.

[Left and right side walls 14]
The left and right side walls 14 have outward surfaces 14a facing outward and are in an upright position extending upward from both left and right end portions of the bottom wall portion 111 of the foundation bottom structure 11, the inclined bottom wall 12, and the front bottom wall 13.

The left and right side walls 14 are provided with an axle hole 1b penetrating in the left-right direction at a position corresponding to the front of the bottom wall portion 111 of the foundation bottom structure 11 and capable of rotatably holding the main shaft jk1, a recess 1a provided on the periphery of the axle hole 1b and recessed in the thickness direction of the side wall 14, a long hole 1c penetrating in the left-right direction and capable of holding the front axle jk2 provided at the front end and for supporting the front part of the seat C so that it can move forward and backward, an annular protrusion 141 protruding outward so as to surround the opening edge of the axle hole 1b in a side view, and a lever insertion hole 142 provided on the rear side of the long hole 1c in the left side wall 14 and through which the reaction force adjustment lever K is inserted.

The shaft hole 1b is capable of rotatably supporting the main shaft jk1 that is installed between the left and right arms d1 of the back support D. In this embodiment, the shaft holes 1b provided in the left and right side walls 14 are parts that constitute the shaft holding portion JH for suitably holding the main shaft jk1 in the support base main body 1 made of synthetic resin.

That is, the shaft holding portion JH is composed of a shaft hole 1b, which is a through hole formed in the left and right side walls 14 corresponding to the size of the main shaft jk1, and a shaft holding recess 1e, which is connected to the inner side of the left and right side walls 14 and is provided on the upper part of the side upright wall 114 and the undershaft connecting portion 119 of the foundation bottom structure 11.

The shaft holding recess 1e is formed at a position corresponding to the shaft hole 1b. The shaft holding recess 1e is open upward. The shaft holding recess 1e has a continuous recessed surface 1f formed on the inner peripheral surface of the lower part of the shaft hole 1b.

The shaft holding recess 1e has a recessed shape so that it can rotatably hold the lower part of the main shaft jk1. The shaft holding recess 1e has multiple grease holding grooves 1g that extend in the front-rear direction along the recessed surface 1f and are spaced apart in the left-right direction.

The recess 1a is formed on the periphery of the shaft hole 1b, more specifically, below the shaft hole 1b. The recess 1a is provided approximately directly below the shaft hole 1b. The recess 1a is provided on the outer surface side of the left and right side walls 14. The recess 1a forms a space se that is approximately rectangular prism-shaped and open to the outside.

A resin portion JN is interposed between the recess 1a and the shaft hole 1b. The vertical dimension w4 of the resin portion JN is set to be shorter than the diameter w2 of the shaft hole 1b. The resin portion JN is composed of the lower part of the shaft hole 1b in the left and right side walls 14 and the undershaft connecting part 119 of the foundation bottom structure 11.

The inner dimension w1 in the front-to-rear direction of the recess 1a is set to be approximately equal to or shorter than the diameter w2 of the shaft hole 1b. The inner dimension w3 in the up-down direction of the recess 1a is set to be shorter than the diameter w2 of the shaft hole 1b. In a side view, the recess 1a is covered by the seat support c1 of the seat C.

The long hole 1c extends diagonally so that the lower end is located forward of the upper end in side view. A sleeve member SL made of a material that slides easily on the front axle jk2 is fitted into the long hole 1c. The front axle jk2 is supported by the long hole 1c via the sleeve member SL.

The annular protrusion 141 is configured so that the protruding end surface facing outward can contact the inner surfaces of the left and right arms d1 of the back support D.

[Front wall 15]
The front wall 15 has a forward surface s15 and is in an upright position connecting the front ends of the left and right side walls 14. The upper part of the front wall 15 is provided with a horizontally extending protruding wall 151 that is a rib extending in the left-right direction, and a plurality of vertically extending protruding walls 152 that are disposed on the horizontally extending protruding wall 151 and spaced apart in the left-right direction and extend in the up-down direction.

Inside the support base main body 1, i.e., in the storage space sp, there is disposed a reaction force generating part HG for generating a reaction force of the backrest E that can tilt backward. The reaction force generating part HG is interposed between a reaction force adjustment lever K pivotally supported on the support base B and a back support body D pivotally supported on the support base B and connected to the backrest E. The reaction force generating part HG is mainly composed of a coil spring HG1, which is a spring material.

A reaction force adjustment lever K, which is an adjustment lever for adjusting the reaction force of the backrest E, is rotatably supported on the support base B. The reaction force adjustment lever K is rotatably held between the support base main body 1 and a cover body Ba that covers the upper side of the lever base shaft part k3 of the reaction force adjustment lever K and is attached to the support base main body 1 by a screw v8. The screw v8, which is inserted through a screw insertion hole (not shown) provided in the cover body Ba, is screwed into a nut part n8 provided in the front bottom wall 13.

<<Reaction force adjustment lever K>>
The reaction force adjustment lever K is rotatably supported on the support base 1. The reaction force adjustment lever K is pivotally supported on the support base 1 so that its longitudinal axis is in the left-right direction. The reaction force adjustment lever K is rotated by the user's hand, and as the lever is rotated, the degree of compression of the coil spring HG1, which is the spring material constituting the reaction force generating part HG, can be adjusted.

The reaction force adjustment lever K is provided with an operating part k1 at the tip, which is one end portion, and is gripped by the user to apply a rotational operating force; an intermediate connecting part k2, which is connected to the operating part k1 with its axis js aligned and has a shape in which the outer diameter dimension decreases with distance from the operating part k1; and a lever base shaft part k3, which is connected to the intermediate connecting part k2 with its axis js aligned and has multiple, i.e., left, right and center, retained shaft parts k31a, k31b, k31c, which are pivotally supported on the support base main body 1.

The operating part k1, intermediate connecting part k2, and lever base part k3 that make up the reaction force adjustment lever K are integrally formed from synthetic resin.

<Operation unit k1>
The operation unit k1 includes an operation unit body k11 having a generally cylindrical shape that is open to the outside, and a protrusion k12 that is a marker provided at an end of the operation unit body k11 and extends toward the center of the operation unit body k11. The protrusion k12 is a single protrusion provided from the inner peripheral surface of the operation unit body k11 toward the center of the operation unit body k11.

[Operation unit body k11]
The operation unit body k11 can form a substantially cylindrical space s1 inside. The operation unit body k11 is configured such that the outer peripheral surface of the tip portion k111 is gradually closer to the tip. In addition, the outer peripheral surface of the tip portion k111 of the operation unit body k11 is provided with a plurality of grooves k112 along the axis js to prevent finger slippage.

A marking recess k114 having a width dimension substantially equal to the thickness dimension of the protrusion k12 is formed on the outer peripheral surface of the tip portion k111 of the operating unit main body k11 corresponding to the protrusion k12. In other words, the recess k114 is provided on the outer peripheral surface of the tip portion k111 located directly behind the inner peripheral surface of the operating unit main body k11 from which the protrusion k12 protrudes.

[Protrusion k12]
The protrusion k12 protrudes from the inner peripheral surface of the operation unit main body k11 toward the axis js. The protrusion k12 is in the form of an upright wall extending along the longitudinal direction of the reaction force adjustment lever K. When viewed from the axis js direction, the protrusion k12 has a tip k121 which is a shaped portion that gradually narrows toward the axis js. In this embodiment, the shaped portion that gradually narrows is only present at the tip k121 of the protrusion k12. More specifically, the tip k121 of the protrusion k12 is in the form of a semicircular arc in a side view.

The protrusion k12 has an outward-facing end surface k122 that serves as a marker, located on the outward-facing edge of the operating unit body k11, i.e., outside the opening edge k113 of the operating unit body k11.

<Intermediate connecting portion k2>
The intermediate connecting portion k2 has an outer diameter that gradually decreases from the side having the operating portion k1 toward the side having the lever base portion k3. That is, the intermediate connecting portion k2 has a partial cone shape interposed between the operating portion k1 and the lever base portion k3.

Inside the intermediate connecting part k2, a roughly conical inner space s2 is formed, which is continuous with the cylindrical space s1 of the operating part main body k11. A protrusion k12 provided on the operating part main body k11 is connected to the inner peripheral surface of the tip side portion of the intermediate connecting part k2, i.e., the inner peripheral surface on the operating part k1 side.

<Lever base shaft portion k3>
The lever base shaft portion k3 is provided with a plurality of retained shaft portions k31a, k31b, k31c which are connected to the intermediate connecting portion k2 with their axis js aligned and journaled relative to the support base B, an engaging protrusion k32 which can engage with a protrusion for regulating the rotation range (not shown) provided on the cover body Ba of the support base B, and a cam portion k33 which can engage with a reaction force generating portion HG arranged inside the support base B.

The retained shaft portions k31a, k31b, and k31c are arranged in multiple numbers on the lever base shaft portion k3. Of the left, right, and center retained shaft portions k31a, k31b, and k31c arranged on the lever base shaft portion k3, the diameter of the retained shaft portion k31a at the base end (right) is the smallest, and the diameter of the left retained shaft portion k31c, i.e., the retained shaft portion k31c at the tip side (operating portion k1 side), is set to be the largest.

In other words, the lever base shaft portion k3 is provided with multiple held shaft portions k31a, k31b, k31c of different diameters from the base end to the tip end, with the tip end having a larger diameter than the base end. More specifically, the diameter of the central held shaft portion k31b is set to be larger than the diameter of the right held shaft portion k31a, and the diameter of the left held shaft portion k31c is set to be larger than the diameter of the central held shaft portion k31b.

The engaging protrusions k32 are arranged at two positions on the left and right of the lever base shaft k3, spaced apart from each other. The engaging protrusions k32 can restrict the range of rotation around the axis js of the reaction force adjustment lever K, which receives the operating force from the user, by engaging with a protrusion for restricting the range of rotation (not shown) provided on the cover body Ba of the support base B.

The cam portion k31 is disposed at two locations on the left and right of the lever base shaft portion k3, spaced apart.

<<Seat C>>
The seat C is disposed on the support base B. The seat C includes a seat support c1, which is also called an outer shell, and a seat body c2 having a seat surface and provided on the seat support c1 so that its front-rear position can be changed.

In other words, the seat C is configured such that the seat body c2 is supported on the seat support c1 so as to be slidable in the front-rear direction between a front position (i1) and a rear position (i2). The seat body c2 has a support member c21 made of synthetic resin, also known as an inner shell.

The seat C is equipped with a shell-shaped seat support c1 made of synthetic resin, a seat body c2 that is placed on the seat support c1 and supported so that it can slide back and forth relative to the seat support c1, and an operating member ct that is supported so that it can move up and down relative to the seat body c2 between an upper position and a lower position, and that can cause the seat body c2 to slide back and forth when in the upper position.

<Receiving seat c1>
The seat support c1 has a shell-like shape large enough to support the seat body c2 at its upper part. The seat support c1 has a curved shape that is convex backward when viewed from the bottom, and the four corners are rounded, forming a substantially rectangular shape overall.

The seat support c1 can support the seat body c2 so that it can slide in the front-rear direction between a front position (i1) where the front part of the seat body c2 protrudes significantly forward from the front edge of the seat support c1 when viewed from the bottom, and a rear position (i2) located behind the front position (i1).

The front part of the seat support c1 engages with the front axle jk2. In other words, the front part of the seat support c1 is supported by the support base B via the front axle jk2. In addition, the center part of the seat support c1 in the front-to-rear direction engages with the rear axle jk3. In other words, the center part of the seat support c1 in the front-to-rear direction is supported by the support base B via the back support D having the rear axle jk3.

The seat support c1 has a seat support body ca that constitutes a shell-shaped main part capable of supporting the seat body c2 at the top, and four approximately T-shaped retaining projections cb that protrude upward from the seat support body ca. The seat support body ca and the retaining projections cb are integrally formed from synthetic resin.

[Seat support body ca]
The seat support main body ca comprises a seat support base c10 having a lower support area c13 formed on its upper surface which can be attached to the underside of the support member main body c211, a front lower extension wall c11 provided in the left-right center of the front part of the underside of the seat support base c10, left and right lower extension walls c12 extending downward in a pair on the left and right from the left and right center of the underside of the seat support base c10 and extending rearward from both ends of the front lower extension wall c11, and a rear lower extension wall c14 provided in the left-right center of the rear part of the underside of the seat support base c10 and connected between the rear parts of the left and right lower extension walls c12.

The seat support base c10 has multiple exposed ribs (not shown) that extend in the front-rear and left-right directions on the upper surface to ensure rigidity. The upper ends of the ribs erected on the upper surface of the seat support base c10 form a lower support area c13 that can be pressed against and rub against the lower surface of the support member main body c211 of the support member c21.

The lower support area c13 of the seat support base c10 is designed to be in contact with the lower surface of the support member main body c211. In addition, the lower support area c13 is designed to be in sliding contact with the lower surface of the support member main body c211 when the seat body c2 slides forward and backward. The lower support area c13 is curved so that the center is located lower than the outer parts when viewed from the front and rear.

Both side edges of the seat support body ca, i.e., both side edges of the seat support base c10, extend in a substantially straight line in the front-to-rear direction. The upper end portion c101 of both side edges of the seat support base c10 constitutes the uppermost portion of the seat support body ca.

When the seat body c2 is in the rear position (i2), substantially the entire upper end portion c101 of both side edges of the seat support base c10 is disposed in a position facing the left and right peripheral wall portions c213 of the support member c21 and the space sr.

On the other hand, when the seat body c2 is in the front position (i1), the rear of the upper end portion c101 of each side edge of the seat support base c10 is disposed at a position intersecting with the support wall c214 located on the left and right side portions c21p at the rear of the support member c21, as viewed from the bottom.

The vertical portion c221 of the seat cushion c22 corresponding to the intersecting position is provided with a notch c221k to avoid the upper end c101 of the seat support base c10. That is, the vertical portions c221 located on both the left and right sides c22p at the rear of the seat cushion c22 and disposed adjacent to the support walls c214 of the support member c21 have a shape with a notch at the bottom so as not to interfere with the seat support c1 when the seat body c2 is in the front position (i1).

The left side of the front part of the seat base c10 is provided with a seat base slit ca1 that penetrates vertically and extends in the front-rear direction in which the operating member ct is disposed. In addition, the left and right sides of the underside of the seat base c10 are provided with armrest attachment parts ca2 in which screw insertion holes h7 are formed for screwing in an armrest (not shown).

A recess ca6 is provided in the left-right center of the rear underside of the seat base c10 to avoid interference with the lower frame material 4 of the backrest E. An operating piece L that acts on a gas spring (not shown) and can expand and contract the leg support a2 in the vertical direction is pivotally supported in a flapable manner at the bottom of the seat base c10.

A rear axle holder ca3 capable of holding the rear axle jk3 is provided in the center of the underside of the seat base c10 in the front-to-rear direction. When viewed from the bottom, the rear axle holder ca3 is provided in a portion of the seat base c10 located between the left and right lower extension walls c12.

The front lower extension wall c11 is an upright wall. The front lower extension wall c11 extends downward from the seat base c10. The front lower extension wall c11 can cover the upper part of the front part of the support base main body 1. The front surface of the front lower extension wall c11 is exposed to the outside and is visible to the user.

The left and right lower extension walls c12 are upright walls. They extend downward from the seat base c10 in pairs. The left and right lower extension walls c12 can cover the upper parts of both the left and right sides of the support base main body 1. The outer surfaces of the left and right lower extension walls c12 are exposed to the outside and can be seen by the user.

The left and right lower extension walls c12 are designed to cover and conceal the recess 1a provided on the outer surface of the support base main body 1 when viewed from the side.

A front axle holding portion ca4 capable of holding the front axle jk2 is provided at the front of the left and right lower extension walls c12. The left and right lower extension walls c12 are configured to cover from the outside the outwardly opening recess 1a provided in the support base main body 1. In addition, of the left and right lower extension walls c12, a notch c121 is formed in the left lower extension wall c12 so as to avoid the reaction force adjustment lever K protruding from the support base main body 1.

The rear lower extension wall c14 is an upright wall. The rear lower extension wall c14 is disposed between the rear portions of the left and right lower extension walls c12. On both the left and right sides of the rear lower extension wall c14, a pair of slits ca5 are provided, one on each side, which extend vertically and open downward to avoid interference with the left and right arm bodies d11 of the back support D.

[Prevention protrusion cb]
The retaining projection cb is provided on the seat support body ca and has a generally T-shaped appearance in a front view. The retaining projection cb is engaged with a guide slit c211b provided in the support member c21 of the seat support body c2, thereby supporting the seat support body c2 against the seat support c1 so that the seat support body c2 cannot be separated from the seat support c1 and positioning the seat support body c2 so that the seat support body c2 can slide forward and backward relative to the seat support c1.

<Seat body c2>
The seat body c2 is configured to be slidable in the front-rear direction relative to the seat support c1. The seat body c2 includes a shell-shaped support member c21 having dimensions larger in the front-rear direction and the left-right direction than the seat support c1, a seat cushion c22 supported by the support member c21 and having dimensions larger in the front-rear direction and the left-right direction than the support member c21, and a seat upholstery c23 that covers the peripheral portions of the seat cushion c22 and the support member c21 from the outside.

When the seat body c2 is in the rear position (i2), the entire peripheral edge of the seat support c1 is located inside the entire peripheral edge of the support member c21 in a bottom view.

When the seat body c2 is in the front position (i1), the rear of the seat support c1 is located behind the rear of the support member c21 in a bottom view. In other words, the rear end c21t of the support member c21 on the seat body c2 can be located in front of the rear end c1t of the seat support c1 in the front position (i1).

[Support member c21]
The support member c21 is made of synthetic resin and is attached to the lower surface of the seat cushion c22 to evenly support the weight of a seated person.

The support member c21 has a curved shape with the center portion positioned lower than the outer portions when viewed from the front and rear. When viewed from the bottom, the support member c21 has a curved shape with the rear portion convex rearward, and is generally rectangular overall. When viewed from the bottom, the outer edge shape of the support member c21 is similar to the outer edge shape of the seat support c1.

The support member c21 comprises a support member main body c211 disposed in the center in the front-rear and left-right directions, a peripheral wall portion c213 that extends outward from the peripheral portion of the support member main body c211 via a step portion c212 and whose lower surface is located above the lower surface of the support member main body c211, and a support wall c214 that is provided so as to protrude downward around the entire outer peripheral edge of the peripheral wall portion c213.

The support member body c211 is provided with a plurality of seat center slits c211a extending in the front-rear direction at the center of the front-rear direction and provided in the left-right direction corresponding to the recesses c222 of the seat cushion c22, a guide slit c211b extending in the front-rear direction with which the anti-removal protrusions cb provided on the seat support c1 can engage, and an operating member holding hole c211c that is provided in the vertical direction and can support the operating member ct so that it can move up and down but cannot slip out downward.

The peripheral wall portion c213 is located outside the support member main body c211 and is disposed above the support member main body c211. The step portion c212 interposed between the support member main body c211 and the peripheral wall portion c213 is intended to position the peripheral wall portion c213 above the support member main body c211. In this embodiment, the step portion c212 is mainly composed of a wall portion erected on the outer peripheral edge of the support member main body c211.

The peripheral wall portion c213 is disposed so as to surround the outside of the support member main body c211 when viewed from the bottom. The edge c23e of the seat upholstery c23 is disposed below the peripheral wall portion c213, i.e., on the underside of the peripheral wall portion c213.

In other words, the support member c21 is surrounded by the peripheral wall portion c213, the step portion c212, and the support wall c214 in a generally downward U-shape, forming a downwardly open space sr capable of accommodating the edge c23e of the seating material c23.

In addition, the four corners of the peripheral wall portion c213 and the left-right center of the front and rear parts of the peripheral wall portion c213 are provided with hook pieces c21h for hooking the edge c23e of the seat upholstery c23.

The support wall c214 is a downwardly protruding wall provided around the entire outer peripheral edge of the support member c21. The support wall c214 is a wall extending downward from the outer peripheral edge of the peripheral wall portion c213. The support wall c214 plays a role in stably holding the peripheral portion c22e of the seat cushion c22 in cooperation with the seat upholstery c23, and the outer surface c21s can be attached to the inner surface c22s of the hanging portion c221, which is the inner surface of the seat cushion c22.

In this embodiment, the support wall c214 located at the rear of the support member c21 is set to a vertical dimension that does not interfere with the seat support c1. More specifically, the vertical dimension of the support wall c214 formed on both left and right side portions c21p at the rear of the support member c21 is set to be shorter than the vertical dimension of the support wall c214 in other portions. More specifically, the support wall c214 in other portions can be the support wall c214 located in the left-right central portion at the front and rear of the support member c21, or the support wall c214 located in the front-rear central portion at both left and right side portions of the support member c21.

The left and right side portions c21p at the rear of the support member c21 (i.e., the left and right corner portions at the rear of the support member c21) are set at left and right positions that match the both side ends of the seat support body ca when viewed from behind. The upper end portions c101 at both side ends of the seat support body ca form the uppermost portion of the seat support body ca.

In other words, the support wall c214 of the support member c21 extends vertically as a whole to stably hold the peripheral edge c22e of the seat cushion c22 in cooperation with the seat upholstery c23, but the vertical dimension is set extremely short only in the portion located on both left and right sides c21p at the rear in order not to interfere with the upper end c101 at both ends of the seat support body ca when the seat body c2 slides in the front-rear direction.

The height of the support walls c214, which are located on both the left and right sides c21p and have a relatively short vertical dimension compared to other parts, gradually returns to a higher level toward the center in the front-to-rear direction on both the left and right sides of the support member c21, and also gradually returns to a higher level toward the center in the left-to-right direction at the rear of the support member c21.

Therefore, even when the seat body c2 slides forward and backward while the seat occupant is seated on the seat C, the support wall c214 is unlikely to interfere with the sliding movement of the seat body c2. In addition, the support walls c214 located on both the left and right side portions c21p and corresponding to the area that is gently cut out as a whole can smoothly abut against the seat support c1, so that the seat body c2 that is receiving the weight of the seat occupant can be suitably supported by the seat support c1.

[Seat cushion c22]
The seat cushion c22 is made mainly of a urethane foam material. A shell-shaped support member c21 is attached to the underside of the seat cushion c22. When viewed from the bottom, the outer edge shape of the seat cushion c22 is similar to the outer edge shape of the support member c21.

The seat cushion c22 is shaped so that it can be fitted onto the support member c21 from above.

The seat cushion c22 is larger than the support member c21 when viewed from the bottom. In other words, the dimensions of the seat cushion c22 in the front-rear and left-right directions are set to be longer than the dimensions of the support member c21 in the front-rear and left-right directions.

The peripheral portion of the seat cushion c22 is provided with a hanging portion c221 having an inner surface c22s that is an inner surface that can be attached to the outer surface of the support wall c214. The hanging portion c221 is a portion that hangs downward on the peripheral portion of the seat cushion c22. The hanging portion c221 is disposed outside the support wall c214.

The peripheral portion c22e of the seat cushion c22, including the vertical portion c221, is shaped to protrude outward from the support member c21. In other words, the peripheral portion c22e of the seat cushion c22 overhangs the support member c21.

In addition, a number of recesses c222 that open downward are provided in the center of the underside of the seat cushion c22 in the front-rear direction, corresponding to the seat center slits c211a provided in the support member c21.

The rear part of the peripheral portion c22e of the seat cushion c22, i.e., the rear part including the left and right side portions c22p of the seat cushion c22, is shaped to be lowered upward compared to the front part of the peripheral portion c22e of the seat cushion c22 in order to avoid interference with the rear part and upper end portion c101 of the seat support base c10. In other words, the rear part of the seat cushion c22 including the left and right side portions c22p is also set to a suitable shape to avoid interference with the seat support c1, similar to the support member c21.

[Seat upholstery c23]
The seat upholstery c23 is mainly made of a stretchable fabric and is capable of covering the upper surface, outer surface, and lower surface of the peripheral portion c22e (lower surface of the hanging portion c221) of the seat cushion c22 from the outside, and also covering the support wall c214 provided to hang down from the peripheral edge of the support member c21 from the space sr side.

The seat upholstery c23 is attached to the seat cushion c22 and the support member c21 in a taut state by wrapping the underside of the peripheral portion of the seat cushion c22 and the support member c21, and the end edge c23e is tightened by a string member (not shown).

In other words, the edge c23e of the seat upholstery c23 is narrowed in the direction in which the opening formed by the edge c23e becomes smaller (the direction in which the diameter becomes smaller). After the worker has finished narrowing the edge c23e of the seat upholstery c23, it is disposed under the peripheral wall portion c213 of the support member c21 and is hooked onto the hook piece c21h.

The peripheral portion c22e of the seat cushion c22, particularly the vertical portion c221 of the seat cushion c22 located on the outside of the support wall c214, is tensile in the direction of the edge c23e by the tensioned seat upholstery c23, and is stably supported by the support wall c214.

<Operation member ct>
The operating member ct is supported on the seat body c2 so as to be movable up and down between an upper position and a lower position. The lower end portion, which is the operating end of the operating member ct, is exposed below the seat receiver c1 through the seat receiver slit ca1.

When no load is applied, the operating member ct is positioned at the lower position by the biasing force of the seat cushion c22. The operating member ct is capable of being moved to the upper position by the user's operating force against the biasing force of the seat cushion c22.

When the operating member ct is in the lower position, it can position the seat body c2 at a predetermined position on the seat support c1. On the other hand, when the operating member ct is in the upper position, it can release the restriction on the movement of the seat body c2 in the front-rear direction relative to the seat support c1, allowing the seat body c2 to slide in the front-rear direction relative to the seat support c1.

<<Back support body D>>
The back support D is interposed between the support base B and the backrest E, and between the support base B and the seat C. The back support D has a rear shaft jk3 extending in the left-right direction that engages with a bearing portion (not shown) provided in the seat support c1 of the seat C. In other words, the back support D also functions as a seat support interposed to support the seat C on the support base B.

A rearward tilt setting lever H that can selectively set the degree of rearward tilt of the backrest E is rotatably supported on the back support D.

The back support D is covered and concealed by a cover body I that is integrally formed from synthetic resin.

The back support D is equipped with a pair of left and right arms d1 that are pivotally supported on the support base body 1 of the support base B via the main shaft jk1, which is an upright plate-like shaft extending in the front-rear direction, a connecting member d2 that is an upright plate-like member connecting the rear portions of the pair of left and right arms d1, a rear shaft jk3 that extends in the left-right direction and is supported in a position forward of the main shaft insertion hole d13 in the pair of left and right arms d1, a pair of left and right bearing shaft support members d3 that are disposed inside the pair of left and right arms d1, i.e., toward the center in the left-right direction, and have their upper portions connected to the rear shaft jk3, and a bearing shaft d4 that is connected between the lower portions of the pair of left and right bearing shaft support members d3.

<Left and right arms d1>
The left and right arms d1 are made of metal. The left and right arms d1 are in the form of upright walls having left and right arm bodies d11 which are portions extending in the front-rear direction. The left and right arms d1 are disposed outside the left and right side walls 14 of the support base body d1.

The left and right arms d1 are provided with left and right arm bodies d11 that extend in the front-rear direction and can support the main shaft jk1 at their front ends, left and right front arm sections d12 that extend diagonally upward and forward from the front ends of the left and right arm bodies d11 and support the rear shaft jk3 that engages with the seat C at its upper end, and a main shaft insertion hole d13 that is provided between the left and right arm bodies d11 and the left and right front arm sections d12 and penetrates in the left-right direction and can hold the main shaft jk1.

[Left and right arm body d11]
The left and right arm bodies d11 extend in a substantially straight line in the front-rear direction. The rear portions of the left and right arm bodies d11 are connected by a connecting member d2. The rear ends of the left and right arms d11 protrude rearward beyond the connecting member d2, and the protruding portion d111 can be fitted into the back support body connecting portion 41 of the lower frame material 4 of the backrest E.

A shaft hole d112 is provided penetrating in the left-right direction in a portion of the left and right arm bodies d11 located forward of the portion where the connecting member d2 is attached. A rearward tilt setting lever H is rotatably supported in the shaft hole d112, which can selectively set one of the multiple types of rearward tilt degrees of the backrest 5.

[Left and right front arm parts d12]
The left and right front arm portions d12 are integrally extended obliquely upward and forward from the front ends of the left and right arm bodies d11. A rear shaft jk3 extending in the left-right direction and capable of engaging with the seat C is rigidly connected to the tip ends of the left and right front arm portions d12.

[Main shaft insertion hole d13]
The main shaft insertion hole d13, through which the main shaft jk1 is inserted, is provided at the front ends of the left and right arm bodies d11 and the base ends of the left and right front arm portions d12, i.e., in the dogleg-shaped bent portions of the left and right arms d1.

<Connecting member d2>
The connecting member d2 is made of metal and has an upright plate shape extending in the left-right direction. The left and right ends of the connecting member d2 are rigidly connected to the inner parts of the left and right arms d1 by welding.

The connecting member d2 is provided with a nut portion n6 into which a screw v6 for attaching the backrest E is screwed. In other words, the rear portion of the back support D is provided with a backrest attachment portion da to which the backrest E is attached.

The backrest attachment portion da is composed of the rear portions of the left and right arms d1 and the connecting member d2 that connects the rear portions of the left and right arms d1, forming an H-shape in plan or bottom view.

<Rear axle jk3>
The rear axle jk3 extends in the left-right direction and is connected to the front ends of the left and right arms d1, i.e., the upper ends of the left and right front arm portions d12. The rear axle jk3 is located above the support base main body 1 and extends outward beyond both sides of the support base main body 1.

<Left and right bearing shaft support members d3>
The left and right bearing shaft support members d3 support the bearing shaft d4 pressed by the reaction force generating portion HG. The left and right bearing shaft support members d3 rigidly connect both ends of the bearing shaft d4 at their lower ends.

The left and right bearing shaft support members d3 are plate-shaped and arranged parallel to each other. The left and right bearing shaft support members d3 are arranged inside the left and right arms d1 and inside the side walls 14 of the support base main body 1. In other words, the left and right bearing shaft support members d3 are arranged closer to the center in the left-right direction than the left and right side walls 14 of the support base main body 1.

The upper parts of the left and right bearing shaft support members d3 are connected to the left-right center of the rear axle jk3. In addition, the rear parts of the left and right bearing shaft support members d3, which are located lower than the upper parts of the left and right bearing shaft support members d3, are provided with a main shaft insertion hole d31 through which the main shaft jk1 can be inserted. In other words, the rear parts of the left and right bearing shaft support members d3 are engaged with the main shaft jk1.

<Bearing shaft d4>
The receiving shaft d4 extends in the left-right direction and is disposed inside the support base main body 1. The receiving shaft d4 is connected to the reaction force generating part HG disposed in the support base B, and receives the biasing force generated by the reaction force generating part HG for biasing the backrest E in the direction of the normal posture. In this embodiment, the receiving shaft d4 is supported by the receiving shaft support member d3 so as to be located approximately directly below the rear axle jk3.

The back support D described above has a bearing shaft d4 supported at the lower end of the left and right bearing shaft support members d3, and is connected at the upper end to the rear shaft jk3 and engaged at the rear end with the main shaft jk1. Therefore, the back support D is configured so that the biasing force transmitted from the reaction force generating part HG to the bearing shaft d4 can be transmitted smoothly to the left and right arms d1 rotating around the main shaft jk1 via the left and right bearing shaft support members d3 and the rear shaft jk3 while avoiding interference with the support base main body 1 that opens upward.

<<Main shaft jk1>>
The spindle jk1 is held by the shaft holding portion JH of the support base main body 1. The spindle jk1 is equipped with a spindle body jk11 extending in the left-right direction, a flange portion jk12 that is integrally provided at one end of the spindle body jk11 and can engage with the outer surface of either the left or right arm d1 of the back support body D, and a retaining ring jk13 that is attached to the other end of the spindle body jk11 and can engage with the outer surface of the other of the left and right arms d1.

<<Rearward tilt degree setting mechanism X>>
The rearward tilt degree setting mechanism X allows the user to select from two or more rearward tilt degrees the backrest E, which is supported so as to be capable of rearward tilting relative to the support base B via the back support body D, by operating it.

In this embodiment, the tilt setting mechanism X can set the degree of tilt of the backrest E to four different degrees of tilt, i.e., first, second, third and fourth degrees of tilt (x1), (x2), (x3) and (x4).

The first backward tilt degree (x1) is such that the backrest E is maintained in the basic position and hardly tilts backward at all. The second backward tilt degree (x2) is such that the backrest E can tilt backward within a certain range by rotating from the basic position around the main axis jk1. The third backward tilt degree (x3) is such that the backrest E can tilt backward within a wider range than the second backward tilt degree (x2) by rotating from the basic position around the main axis jk1. The fourth backward tilt degree (x4) is such that the backrest E can tilt backward within a wider range than the third backward tilt degree (x3) by rotating from the basic position around the main axis jk1.

In other words, the backward tilt setting mechanism X is configured to be able to set the backward tilt degree of the backrest E to gradually increase from the first backward tilt degree (x1), which is the smallest degree of backward tilt of the backrest E, to the second, third, fourth backward tilt degrees (x2), (x3), and (x4). In other words, the fourth backward tilt degree (x4) is the one that allows the backrest E to be tilted backward in the widest range.

The backward tilt setting mechanism X includes a backward tilt setting lever H, which is an operating lever rotatably supported on the back support D; a rotating member Re, which is attached to the backward tilt setting lever H so as to be rotatable as one unit and has a plurality of contact surfaces corresponding to the first, second, third and fourth backward tilt degrees (x1), (x2), (x3) and (x4), i.e., the first, second, third and fourth contact surfaces at1, at2, at3 and at4, which are arranged at intervals in the rotational direction; a damper member XM, which is arranged on the support base B and can selectively contact a specific contact surface among the first, second, third and fourth contact surfaces at1, at2, at3 and at4; and a detent mechanism XD for detent-locking the rotating member Re at one of a plurality of rotation positions corresponding to the first, second, third and fourth backward tilt degrees (x1), (x2), (x3) and (x4).

In this embodiment, the rearward tilt degree setting mechanism X determines the first, second, third, and fourth rearward tilt degrees (x1), (x2), (x3), and (x4) by abutting the first, second, third, and fourth contact surfaces at1, at2, at3, and at4 against the damper member XM, which is a common contact member.

The rearward tilt setting mechanism X is covered by a cover body I except for the operating end of the rearward tilt setting lever H. In other words, most of the rearward tilt setting mechanism X is covered by the cover body I and cannot be seen from the outside.

<Rearward tilt degree setting lever H>
The rearward tilt degree setting lever H comprises a lever shaft portion ha which is pivotally supported in an axial hole d112 provided in the left and right arms d1 which extend in the left-right direction and constitute the back support body D, and a handle portion hb which is attached to the right end portion which is one end of the lever shaft portion ha.

[Lever shaft ha]
The lever shaft ha is made of metal. A pair of protrusions hat protruding in a direction perpendicular to the axis are formed in the left-right central portion of the portion of the lever shaft ha located between the left and right arms d1. The protrusions hat on the lever shaft ha can be engaged with a groove e12 provided in the base end portion e1 of the rotating member Re. The engagement of the protrusions hat of the lever shaft ha with the groove e12 of the rotating member Re allows the entire rotating member Re to rotate integrally with the rearward tilt degree setting lever H.

A retaining member han is attached to the tip of the lever shaft ha and is disposed on the outside of the left arm d1. This prevents the lever shaft ha from slipping out of the left and right arms d1.

[Handle part hb]
The handle portion hb is made of synthetic resin and includes a cylindrical shaft connection portion hb1 that is fitted onto the lever shaft portion ha, and a lever piece hb2 that protrudes in a cantilever manner from the shaft connection portion hb1.

<Rotating member Re>
The rotating member Re is made of synthetic resin and configured to be able to rotate integrally with the rearward tilt degree setting lever H. The rotating member Re includes a base end e1 in which an insertion hole e11 through which the lever shaft ha is inserted is formed, left and right rotating member bodies e2 which are integral with the base end e1 and have a plurality of contact surfaces, i.e., first, second, third and fourth contact surfaces at1, at2, at3 and at4, which are provided in pairs on the left and right sides, a connecting wall e3 which extends from the base end e1 in a wall shape and connects the left and right rotating member bodies e2 to each other, and a moderation engaging portion e4 which extends in a direction perpendicular to the longitudinal direction of the base end e1 and has an engaging protrusion e41 formed on an outer end thereof.

[Base end e1]
The base end e1 forms a portion that is connected to the lever shaft ha of the rearward tilt degree setting lever H. The base end e1 is shaped to rotate the rotating member Re integrally with the lever shaft ha and to support the rotating member Re so as to be movable relative to the lever shaft ha in the longitudinal direction, i.e., the axial direction, of the lever shaft ha. A groove e12 that extends in the left-right direction is provided at the left-right center of the insertion hole e11 in the base end e1 and can be engaged with the protruding piece hat of the lever shaft ha.

The left end, which is one end of the base end e1, is provided with a spring housing e13 that is cylindrical with a larger diameter than the other parts and can house a coil spring xd2 inside, which is a biasing spring. The spring housing e13 can house a part of the coil spring xd2 that is wound around the lever shaft ha and can bias the rotating member Re in the direction of the right arm d1.

The outer end of the coil spring xd2 is in elastic contact with the inner surface of the left arm d1, and the inner end of the coil spring xd2 is in elastic contact with a spring receiving portion (not shown) formed inside the spring housing portion e13.

[Rotating member body e2]
The rotary member body e2 is a block-shaped body that is cantilevered from the base end e1. The rotary member bodies e2 are arranged in pairs on the left and right sides with a fixed interval between them.

The rotating member main body e2 is provided with a quadrangular prism portion e20 that is substantially rectangular in side view and abuts against the damper member XM of the support base B, a first mountain-shaped portion e21 that is located closer to the base end e1 than the quadrangular prism portion e20 and is substantially triangular in side view and abuts against the damper member XM of the support base B, a second mountain-shaped portion e22 that is located closer to the base end e1 than the first mountain-shaped portion e21 and is substantially triangular in side view and abuts against the damper member XM of the support base B, and a third mountain-shaped portion e23 that is located closer to the base end e1 than the second mountain-shaped portion e21 and is substantially triangular in side view and abuts against the damper member XM of the support base B.

The rectangular columnar portion e20 has a first contact surface at1 that is substantially rectangular and faces downward when it contacts the damper member XM attached to the support base main body 1.

The first mountain-shaped portion e21 has a second contact surface at2 that is substantially rectangular and faces downward when it contacts the damper member XM attached to the support base main body 1.

The second mountain-shaped portion e22 is provided with a third contact surface at3 that is substantially rectangular and faces downward when it contacts the damper member XM attached to the support base main body 1.

The third mountain-shaped portion e23 has a fourth contact surface at4 that is substantially rectangular and faces downward when it contacts the damper member XM attached to the support base main body 1.

The first, second, third and fourth contact surfaces at1, at2, at3 and at4 are provided on the rotating member main body e2 in correspondence with the first, second, third and fourth backward inclination degrees (x1), (x2), (x3) and (x4).

The first contact surface at1 is located farther from the base end e1 than the second contact surface at2. The second contact surface at2 is located farther from the base end e1 than the third contact surface at3. The third contact surface at3 is located farther from the base end e1 than the fourth contact surface at4.

When the first contact surface at1 contacts the damper member XM, the backrest E is set to a first backward tilt degree (x1) at which the backrest E hardly tilts backward.

[Connecting wall e3]
The connecting wall e3 connects the left and right rotating member bodies e2. The connecting wall e3 serves to increase the rigidity of the entire rotating member e1. The connecting wall e3 extends from the base end e1 and connects the left and right rotating member bodies e2 at their portions close to the base end e1.

[Moderation engagement portion e4]
The moderation engagement portion e4 has an engagement protrusion e41 that can engage with an engagement recess xd11 of an adapter xd1 attached to the right arm d1, which is one of the left and right arms d1.

The moderation engagement portion e4 and the right-side rotating member body e1 are connected by a reinforcing wall e5 that extends from the base end portion e1 in the same direction as the connecting wall e3.

<Damper member XM>
The damper members XM are made of a synthetic resin that is softer than the support base main body 1. The damper members XM are arranged in pairs on the left and right at the rear of the support base B, which is the fixed side. In other words, the support base B includes the support base main body 1 that is integrally formed from synthetic resin, and the left and right damper members XM that are separate from the support base main body 1 and attached to the rear end of the support base main body 1.

The damper member XM is a block-shaped damper member body xm1 whose bottom surface is attached to the mounting seat 111a of the support base body 1, and a mounting protrusion xm2 that protrudes downward from the damper member body xm1 and is inserted into a hole 111b provided in the mounting seat 111a.

The damper member XM is a part that does not move in conjunction with the backward tilting movement of the backrest E.

[Damper material body x m1]
The damper member main body xm1 is in the shape of a substantially rectangular block. The upper surface of the damper member main body xm1 is curved. That is, the upper surface of the damper member main body xm1 is curved so that the left-right center is located higher than both left-right ends.

[Mounting protrusion x m2]
The mounting projection xm2 is provided integrally with the damper member main body xm1. A flange portion xm3 is formed in the vicinity of the lower end portion, which is the protruding end of the mounting projection xm2. The mounting projection xm2 is configured so that the flange portion xm3 is caught on the support base main body 1, making it difficult for the mounting projection xm2 to slip out of the hole 111b.

<Moderation mechanism XD>
The moderation mechanism XD is intended to allow the user to conveniently operate the rearward tilt degree setting lever H to set the first, second, third and fourth rearward tilt degrees (x1), (x2), (x3) and (x4) relative to the backrest E.

The moderation mechanism XD is mainly composed of a moderation engagement part e4 provided at the right end, which is one end of a rotating member Re supported rotatably integrally with the rearward tilt degree setting lever H, a synthetic resin adapter xd1 attached to the right arm d1 of the left and right arms d1 and provided with multiple (i.e., four) recesses xd11 with which the moderation engagement part e4 can be modestly engaged, and a coil spring xd2 that biases the moderation engagement part e4 toward the adapter ed1.

The left and right arms d1 are formed with fitting holes d113 into which the mounting protrusions x12 on the adapter xd1 can fit. In this embodiment, the protrusions xd2 on the adapter xd1 fit into the fitting holes d113 on the right arm d1.

<<Backrest E>>
The backrest E comprises a back frame M which is a backrest base having a screw insertion hole h6 and attached to the backrest mounting portion da of the back support body D with a screw v2, a back frame cap T which is a concealing member which is removably attached to the back frame M and can cover the storage space sd of the recess U formed in the lower frame material 4 of the back frame M, and a mesh-like tensioning member P which is stretched over the back frame M.

The backrest E has a backrest surface pm that supports the back of the seated person from behind, and is made of an upholstery member P that is mainly made of mesh fabric.

The chair of this embodiment is configured so that optional backrest surface extension members F and hangers G can be selectively attached to the upper frame material 3 of the backrest E.

In this embodiment of the chair, a lumbar support R is attached to the left and right side frame members 2 of the backrest E, which can support the lower back of the seated person from behind.

<Back frame M>
The back frame M comprises left and right side frame members 2 each having a tension member mounting groove mz opening outward, an upper frame member 3 having a tension member mounting groove mz opening upward and connecting the upper parts of the left and right side frame members 2, a lower frame member 4 connecting the lower parts of the left and right side frame members 2, and an intermediate connecting frame member 5 having a tension member mounting groove mz opening downward and connecting the left and right side frame members 2 together while forming an upper cavity sa between the upper frame member 3 and a lower cavity sb between the lower frame member 4.

The left and right side frame members 2, the upper frame member 3, and the lower frame member 4 are integrally molded from synthetic resin. The intermediate connecting frame member 5 is attached to the left and right side frame members 2 with screws v5.

The back frame M has an upper frame portion w1 that is made up of left and right side frame members 2, an upper frame member 3, and an intermediate connecting frame member 5, forming an upper cavity sa therein, and a lower frame portion w2 that is made up of left and right side frame members 2, a lower frame member 4, and an intermediate connecting frame member 5, forming a lower cavity sb therein.

In this embodiment, the backrest E is configured by tensioning a tension member P that can form the backrest surface pm to an upper frame portion w1 that is a frame portion provided on the back frame M.

The lower frame portion w2 is not provided with tension member P. In other words, a cavity sb is formed between the lower frame member 4 and the intermediate connecting frame member 5, which is a cross member, and in which no tension member P is provided.

[Left and right side frame material 2]
The left and right side frame members 2 extend in the vertical direction. A tension member attachment groove mz is formed on the outer surface of each of the left and right side frame members 2, and continues from the upper end of the side frame member 2 to a height position that corresponds approximately to the lower edge of the intermediate connecting frame member 5. A tension member P is tensioned between the left and right side frame members 2 that extend in the vertical direction.

Each of the left and right side frame members 2 has an extension portion 23 that extends toward each other and connects the intermediate connecting frame member 5. The extension portion 23 has a base end portion 231 that extends inward like a column, and a tip end portion 232 that extends inward from the extended end of the base end portion 231, has an upright plate shape, and is set to have a shorter thickness dimension in the front-to-rear direction than the base end portion 231.

The front surface of the tip portion 232 is substantially flush with the front surface of the base portion 231. Meanwhile, the back surface of the tip portion 232 is located forward of the back surface of the base portion 321. In other words, a recessed portion 233 that is recessed forward is formed on the back surface side of the tip portion of the extension portion 23. The side end portion of the intermediate connecting frame material 5 is arranged in the recessed portion 233 when the intermediate connecting frame material 5 is attached.

The tip 232 has a screw insertion hole h5a that penetrates in the front-rear direction, and a rectangular recess 232a is formed on the front side for arranging a nut n5.

The left and right side frame members 2 each have an outer frame portion 21 with a tension member mounting groove mz that opens outward, and an inner frame portion 22 that is located inside the outer frame portion 21 and has a front portion located rearward of the front portion of the outer frame portion 21.

A tension member mounting groove mz is formed on the outer surface of the left and right side frame members 2, which continues from the upper end of the side frame member 2 to a height position that approximately corresponds to the upper edge of the base end portion 231 of the extension portion 23.

In addition, a step 2a is formed on the front surface of the left and right side frame members 2, extending inwardly and approximately horizontally from near the lower end of the upholstery member mounting groove mz. The step 2a is formed on the front surface at a height position that approximately corresponds to the upper edge of the extension portion 23 of the side frame member 2. The step 2a has a shape in which the lower side protrudes forward more than the upper side, and the step dimension approximately corresponds to the thickness dimension of the upholstery member P.

A lumbar support holder N is provided in the vertical middle of the left and right side frame members 2, more specifically, in the vertical middle of the inner frame portion 22 of the left and right side frame members 2, which is at a height position corresponding to the waist of a seated person, and is capable of holding the lumbar support R so that its vertical position can be changed.

The lumbar support holder N is provided at a portion of the left and right side frame members 2 that is bent forwardly in a convex manner in side view (a portion that is bent in a dogleg shape in side view).

The lumbar support holding portion N is capable of holding the held portions r22 provided on both the left and right ends of the lumbar support R. The lumbar support holding portion N is equipped with an accommodation groove 221 that extends in the vertical direction and is open to the front and that accommodates the upper protruding portion r221 and the lower protruding portion r222, which are multiple, i.e., two, protruding portions provided on the held portion r22 of the lumbar support R, and a holding member Q that is disposed in front of the accommodation groove 22 and has a front restricting portion q1 that can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222.

The accommodation groove 221 is mainly formed by a rear groove forming wall 221a and a side groove forming wall 221b that engage with the retained portion r22. The accommodation groove 221 is provided with a rear groove forming wall 221a located on the rear side of the upper protruding portion r221 and the lower protruding portion r222, and a side groove forming wall 221b that extends forward from the inner side of the rear groove forming wall 221a and is located on the inner side of the upper protruding portion r221 and the lower protruding portion r222.

The front surface of the rear groove forming wall 221a forms an abutment portion that contacts the protruding ends of the upper protruding portion r221 and the lower protruding portion r222. The front surface, which is the abutment portion of the rear groove forming wall 221a, is inclined so that the inside is located behind the outside.

The inner surface of the side groove forming wall 221b, i.e., the surface facing the front side of the rear groove forming wall 221a, forms an abutment portion that contacts the inner portions of the upper protruding portion r221 and the lower protruding portion r222. The side groove forming wall 221b that can form the storage groove 221 is provided with an upper notch 221c and a lower notch 221d that are notches that allow the upper protruding portion r221 and the lower protruding portion r222 to pass through when attaching or detaching the lumbar support R to the backrest E.

That is, the side groove forming wall 221b has an upper notch 221c through which the upper protruding portion r221 can pass when the lumbar support R is attached to and detached from the backrest E, and a lower notch 221d through which the lower protruding portion r222 can pass. The upper notch 221c and the lower notch 221d are formed spaced apart above and below the side groove forming wall 221b. The upper notch 221c and the lower notch 221d are provided in the front half of the side groove forming wall 221b.

The shape of the upper cutout 221c is set to correspond to the upper protruding portion r221 of the lumbar support R so that the upper protruding portion r221 can pass through the upper cutout 221c. In addition, a protrusion 221e is provided in the center of the upper cutout 221c in the vertical direction so as to correspond to the shape of the upper protruding portion r221.

The shape of the lower cutout 221d is set to correspond to the lower protruding portion r222 of the lumbar support R so that the lower protruding portion r222 can pass through. Note that the shape of the upper protruding portion r221 and the shape of the lower protruding portion r222 of the lumbar support R are different.

By making the shape of the upper notch 221c corresponding to the upper protruding portion r221 and the shape of the lower notch 221d corresponding to the lower protruding portion r222 different, the user can easily grasp the up and down positions of the lumbar support R. In other words, the chair of this embodiment is designed to prevent the user from attaching the lumbar support R to the backrest E with the wrong up and down.

The retaining member Q is made of synthetic resin and is constructed from a separate member from the left and right side frame members 2. In other words, the retaining member Q is separate from the left and right side frame members 2. The retaining member Q is attached to each of the left and right side frame members 2. The retaining member Q is attached to the inner frame portion 22 of the left and right side frame members 2 via screws v3.

The retaining member Q extends in the vertical direction and includes a front restricting portion q1 that is disposed in front of the accommodation groove 221 and can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222 of the lumbar support R by abutting against the upper protruding portion r221 and the lower protruding portion r222, an attachment portion q2 that is connected to the upper and lower ends of the front restricting portion q1 and has a screw insertion hole h3 that penetrates in the front-rear direction, and a positioning wall q3 that extends from the outer side of the front restricting portion q1 toward the rear, i.e., the inner frame portion 22, and is disposed between the accommodation groove 221 and the outer frame portion 21.

The front restricting portion q1 is shaped like a rail extending in the vertical direction. The front restricting portion q1 is capable of clamping the upper protruding portion r221 and the lower protruding portion r222 in the front-rear direction by cooperating with the inner groove forming wall 221a that can form the accommodation groove 221.

Between the front restricting portion q1 of the retaining member Q and the side groove forming wall 221 of the accommodation groove 221, a communication space sc extending in the vertical direction is formed through which the retained portions r22 of the left and right arm members r2 of the lumbar support R, which has an upper protruding portion r221, a lower protruding portion r222, and a protruding portion 220 at its tip, can communicate.

In other words, the retaining member Q cooperates with the left and right side frame members 2 to clamp and hold the upper protruding portion r221 and the lower protruding portion r222. As a result, the lumbar support R is clamped in the front-to-rear direction between the forward surfaces of the left and right side frame members 2 and the rearward surface of the retaining member Q, and can be appropriately held in a predetermined vertical position within the accommodation groove 221 without sliding downward due to gravity.

The mounting portion q2 has a screw insertion hole h3 for mounting the retaining member Q to the inner frame portion 22 of the left and right side frame members 2. The mounting portion q2 also has an external fitting wall q21 protruding therefrom that can be fitted onto the peripheral edge of the nut portion n3 protruding from the inner frame portion 22 of the left and right side frame members 2.

The retaining member Q is attached to the inner frame portion 22 of the left and right side frame members 2 by screwing the screw v3 inserted through the screw insertion hole h3 into the nut portion n3 provided on the left and right side frame members 2.

[Upper frame material 3]
The upper frame material 3 extends in the left-right direction. The upper frame material 3 has an outer frame portion 31 in which a tension member mounting groove mz that opens upward for mounting a tension member P is formed, and an inner frame portion 32 disposed below the outer frame portion 31. The upper frame material 3 is provided with a nut holding recess nt in which a nut member J for mounting an option can be held, as will be described in detail later.

The outer frame portion 31 constitutes the upper portion of the upper frame material 3. The front surface of the outer frame portion 31 forms the portion that is attached to the back surface of the tension member P, i.e., the portion that backs the tension member P.

The inner frame portion 32 constitutes the lower portion of the upper frame material 3. The inner frame portion 32 is located inside the outer frame portion 31. In other words, the inner frame portion 32 is located in a position that is covered by the tension member P when viewed from the front.

The inner frame portion 32 includes a hanging wall 321 that hangs down from the rear of the outer frame portion 31, a lower end wall 322 that extends forward from the lower end of the hanging wall 321, and a number of connecting walls 323 that form upright walls connecting the lower end wall 322 to the outer frame portion 31 and the lower end wall 322 to the hanging wall 321.

The back surface of the hanging wall 321 is generally flush with the back surface of the outer frame portion 31. The bottom end wall 322 is provided at a distance in the vertical direction from the outer frame portion 31. The connecting walls 323 are provided to increase the connection strength between the bottom end wall 322 and the outer frame portion 31, and are provided in multiples at regular intervals in the horizontal direction.

The inner frame portion 32 is provided with a nut holding recess nt that is formed with an upper opening portion kh1 that opens upward, a lower opening portion kh2 that opens downward, and a front opening portion kh3 that opens forward and can hold a nut member J. The nut holding recess nt is provided in multiple locations on the inner frame portion 32.

The nut holding recess nt is provided in the lower end wall 322 of the inner frame portion 32. The nut holding recess nt has left and right standing wall portions nt1 and a rear standing wall portion nt2 that connects the rear portions of the left and right standing wall portions nt1. The nut holding recess nt is generally U-shaped and open to the front when viewed from the bottom.

The nut holding recess nt is formed by the left and right upright wall portions nt1 and the rear upright wall portion nt2, which defines an upper opening portion kh1 that opens upward, a lower opening portion kh2 that opens downward, and a front opening portion kh3 that opens forward.

The nut holding recess nt also forms a portion that can form the upper open portion kh1 with the upper edges of the left and right upright wall portions nt1 and the upper edge of the rear upright wall portion nt2, and also forms a flange engaging portion nt3 that can engage with the underside of the flange portion j2 of the nut member J.

A gap sk is formed between the nut holding recess nt and the outer frame portion 31, allowing the flange portion j2 of the nut member J to be accommodated.

In this embodiment, the inner frame portion 32 is provided with four nut holding recesses nt spaced apart in the left-right direction. A pair of nut holding recesses nt located on both the left and right outer sides are used when attaching a backrest surface extension member F for extending the backrest surface pm, and a pair of nut holding recesses nt located on both the left and right inner sides are used when attaching a hanger G for hanging clothes.

The nut member J held in the nut holding recess nt is made of metal. The nut member J has a boss portion j1 that is housed in the enclosed space of the nut holding recess nt and has a thread groove j11 on its inner circumferential surface, and a flange portion j2 that is connected to the boss portion j1 and can engage with a flange portion engagement portion nt3, the lower surface of which forms the upper open portion kh1.

The nut member J is generally T-shaped. That is, the flange portion j2 extends longitudinally outward in the left-right direction from the upper end of the generally cylindrical boss portion j1.

The method of holding the nut member J in the nut holding recess nt provided in the backrest E and attaching the optional backrest surface extension member F and optional hanger G will be described in detail later.

[Bottom frame material 4]
The lower frame member 4 has a portion that connects the lower portions of the left and right side frame members 2 and is connected to the back support member D. The lower frame member 4 is provided with a back support member connecting portion 41 that is recessed and open forward, for fitting externally to the backrest mounting portion da provided on the back support member D and connecting the backrest mounting portion da.

The back side of the lower frame material 4 is provided with a recess U in which an accommodation space sd is formed that can accommodate the head v61 of the screw v6 for connecting the back frame M to the back support D. The recess U is recessed so that the accommodation space sd can be formed inside while opening to the rear. In other words, the recess U has an opening uk that is open to the rear and has the accommodation space sd formed therein.

The lower frame material 4 is provided with screw insertion holes h6 through which the screws v6 are inserted, penetrating in the front-to-rear direction. The screw insertion holes h6 are provided in pairs on the left and right. The screw insertion holes h6 are provided so as to be able to communicate between the recess U that opens to the rear and the back support connecting portion 41 that opens to the front.

The recess U is provided with a screw engagement wall u1, which is a rear wall in which the screw insertion hole h6 is drilled and into which the head 61 of the screw v6 can engage; an upright wall u2, which is a front wall located behind the screw engagement wall u1 and in front of the opening uk; a peripheral wall u3 that extends in the front-to-rear direction and whose inner side faces the storage space sd; and an intermediate wall u4 that extends in the front-to-rear direction and has a surface facing the storage space sd and connects the outer end of the upright wall u2 and the inner end of the screw engagement wall u1.

The screw engagement walls u1 are provided in pairs on the left and right. When viewed from the rear, the screw engagement walls u1 are circular, with a screw insertion hole h6 formed in the center. The opposite surface of the screw engagement wall u1, that is, the forward surface, abuts against the rear surface of the connecting member d2 of the back support body D. In other words, the screw engagement wall u1 also serves as an engagement wall with the connecting member d2 of the back support body D.

The standing wall u2 is provided inside the screw engagement walls u1 provided on the left and right sides when viewed from the rear. The standing wall u2 is elongated in the left-right direction and is disposed in a position that is approximately parallel to the screw engagement walls u1. The standing wall u2 has a window hole u21 that serves as an engagement portion with which the locking protrusion t31 formed on the anti-detachment protrusion t3 of the back frame cap T can engage. The window holes u21 are approximately rectangular and are provided in pairs on the left and right sides.

The peripheral wall u3 has an inner peripheral surface u31 that faces in a direction substantially perpendicular to the front-to-rear direction, and an opening uk is formed by the inner peripheral surface u31 at the rear end of the peripheral wall u3. In other words, the opening uk does not have a portion that can restrict the cap body t1 of the rear frame cap T from advancing too far inward.

In other words, the opening uk has a shape that allows the cap body t1 to move toward the back, and does not have any parts that could prevent movement in the depth direction, such as steps, protrusions, ribs, etc.

<Back frame cap T>
The back frame cap T is removably attached to the lower frame material 4 and can cover the storage space sd of the recess U. In this embodiment, the screw v6 can be confirmed based on the relative position of the back frame cap T with respect to the lower frame material 4.

The back frame cap T is provided with a cap body t1, which is a concealing member body disposed in the opening uk of the recess U and capable of hiding the storage space sd from the outside, a screw head abutment protrusion t2 protruding from the cap body t1 and having a tip t21 capable of abutting against the head v61 of the screw v6, and a detachment prevention protrusion t3 protruding from the cap body t1 and engaging with the recess U to prevent the back frame cap T from coming off the back frame M.

[Cap body t1]
The cap body t1 is in the form of an upright plate extending in the left-right direction. That is, the cap body t1 has a flat outer surface 4a and is in the form of a horizontally elongated plate that is in an upright position as a whole. The left and right side portions of the cap body t1 are formed in a semicircular shape when viewed from behind.

[Screw head contact protrusion t2]
The screw head abutment protrusions t2 are provided so as to protrude forward from the cap body t1. The screw head abutment protrusions t2 are provided in pairs on the left and right in correspondence with the left and right screw insertion holes h6. The screw head abutment protrusions t2 are provided so as to protrude forward from both the left and right ends of the cap body t1.

The protruding dimension of the screw head abutment protrusion t2 is set to a length such that when the screw v6 has been properly screwed into the nut portion n6 of the back support D (i.e., when the head v61 of the screw v6 abuts against the screw engagement wall u1 and cannot proceed any further forward), the outer surface t11 of the cap body t1 is approximately flush with the outer surface 4a of the peripheral portion of the recess U when the tip t21 engages with the head v61.

[Anti-fall protrusion t3]
The retaining projections t3 are provided so as to project forward from the cap body t1. The retaining projections t3 are provided in pairs on the left and right. The pair of retaining projections t3 are disposed between the pair of screw head abutment projections t2 provided on the left and right.

The anti-removal protrusion t3 is generally arrow-shaped in side view. The anti-removal protrusion t3 has a locking protrusion t31 that protrudes upward and downward near its tip. The anti-removal protrusion t3 is set to a size that allows the part other than the locking protrusion t31 to pass through the window hole u21 in the front-rear direction.

The locking projection t31 of the anti-detachment projection t3 engages with a window hole u21 provided in the upright wall u2 of the recess U, restricting only the rearward movement of the back frame cap T. When the locking projection t31 engages with the window hole u21 and restricts rearward movement, the outer surface t11 of the cap body t1 is substantially flush with the outer surface 4a of the peripheral portion of the recess U.

[Verification function for screw v6 based on the position of the back frame cap T]
In the chair of this embodiment, confirmation regarding the screw v6 can be performed based on the relative position of the back frame cap T with respect to the lower frame material 4.

More specifically, it is configured to be able to check whether the screw v6 is properly screwed in as intended and whether any screw v6 has been left in place based on the relative position between the outer surface t11 of the back frame cap T and the outer surface 4a of the lower frame material 4.

The back frame cap T is configured so that the outer surface t11 of the cap body t1 is approximately flush with the outer surface 4a of the peripheral portion of the recess U only when the screw v6 is inserted into the screw insertion hole h6 and has completed screwing into the nut portion n6 provided on the back support D, i.e., when the screw v6 is properly attached.

[If screw v6 is installed correctly]
As shown in FIG. 44, the tip t21 of the screw head abutment protrusion t2 abuts against the head v61 of the screw v6, so that the rear frame cap T is restricted from moving further forward.

In addition, the rear frame cap T is restricted from moving backward because the locking projection t31 of the anti-detachment projection t3 engages with the window hole u21 of the upright wall u2 in the recess U.

In this state, the outer surface t11 of the cap body t1 in the back frame cap T is substantially flush with the outer surface 4a of the peripheral portion of the recess U, so the assembly worker can see that the outer surfaces t11, 4a are substantially flush and can confirm that the backrest E is properly attached to the back support body D using the screw v6.

[If the screw v6 is not properly threaded (the screwing is not yet complete)]
As shown in FIG. 45, the tip t21 of the screw head abutment protrusion t2 abuts against the head v61 of the screw v6, so that the rear frame cap T is restricted from moving further forward.

However, in the example shown in Figure 45, the screw v6 has not yet fully engaged (the screw v6 is not fully tightened/screwed loosely), so in this state the outer surface t11 of the cap body t1 in the back frame cap T is positioned outside the outer surface 4a of the peripheral portion of the recess U.

As a result, the assembly worker can see that the positions of the outer surfaces t11, 4a are not approximately flush and can confirm that the backrest E is not properly screwed to the back support D.

[If screw v6 is not installed]
As shown in Figure 46, after the back support body connecting portion 41 of the backrest E is temporarily supported by being externally fitted onto the protruding portion d111 constituting the backrest mounting portion da of the back support body D, it is possible that the worker will forget to screw in the screw v6.

In this case, since the head v61 of the screw v6 is not disposed in the recess U, the tip t21 of the screw head abutment protrusion t2 of the back frame cap T cannot abut against the head v61 of the screw v6. Furthermore, the back frame cap T continues to move forward as the locking projection t31 of the anti-removal protrusion t3 passes through the window hole u21 of the upright wall u2 in the recess U.

At this time, the locking projection t31 of the anti-detachment projection t3 can only engage with the window hole u21 at a specified position to restrict only rearward movement, but cannot restrict forward movement.

As shown in FIG. 46, if the screw v6 for attaching the backrest E to the back support D is not inserted into the screw insertion hole h6, the back frame cap T will go deep into the recess U so that the outer surface t11 of the cap body t1 is not substantially flush with the outer surface 4a of the peripheral portion of the recess U.

As the retaining projection t3 continues to advance forward through the window hole u21, the tip t21 of the screw head abutment projection t2 of the back frame cap T hits the screw engagement wall u1, which is the rear wall that can form the recess U, and finally, movement toward the rear of the back frame cap T is restricted.

At least in this state, the back frame cap T is configured so that the outer surface t11 of the cap body t1 is located behind the outer surface 4a of the peripheral portion of the recess U, so that the assembly worker can see that the positions of the outer surfaces t11 and 4a are not approximately flush and can confirm that the backrest E is not properly screwed to the back support body D (the screw v6 is missing).

[Intermediate connecting frame material 5]
The intermediate connecting frame member 5, which is a cross member, extends in the left-right direction. The intermediate connecting frame member 5 is installed between the portions of the left and right side frame members 2 that are tilted forward when viewed from the side. The intermediate connecting frame member 5 is separate from the other frame members that make up the back frame M, i.e., the left and right side frame members 2, the upper frame member 3, and the lower frame member 4.

In this embodiment, the intermediate connecting frame member 5 is configured to be detachably attached to the left and right side frame members 2 via screws v5. Both left and right ends of the intermediate connecting frame member 5 are screwed to the left and right side frame members 2, respectively. The intermediate connecting frame member 5 has a curved shape that is convex toward the rear in a plan view. The intermediate connecting frame member 5 is formed with a tension member mounting groove mz that opens downward.

The intermediate connecting frame member 5 is capable of supporting the lower part of the tension member P. The intermediate connecting frame member 5 is equipped with an intermediate connecting frame member main body 51 in the form of an upright plate having a tension member mounting groove 5 that is open downward, and mounting parts 52 that are arranged at both ends of the intermediate connecting frame member main body 51 and have screw insertion holes h5b that penetrate in the front-to-rear direction.

The intermediate connecting frame member body 51 that constitutes the intermediate connecting frame member 5 has a tension member attachment groove mz that is open downward. The lower end portion pe of the tension member P is attached to the tension member attachment groove mz.

The left and right mounting parts 52 have screw insertion holes h5b formed therein, and are attached to the extension parts 23 provided on the left and right side frame members 2 with screws v5. In other words, the intermediate connecting frame member 5 is attached to the left and right side frame members 2 by screwing the screws v5 inserted through the screw insertion holes h5b and h5a into the nuts n5 of the extension parts 23.

The left and right mounting parts 52 are set to have a shorter thickness dimension in the front-to-rear direction than the intermediate connecting frame body 51. The rear surface of the mounting parts 52 is substantially flush with the rear surface of the intermediate connecting frame body 51. Meanwhile, the front surface of the mounting parts 52 is located behind the front surface of the intermediate connecting frame body 51. In other words, a recessed portion 53 recessed toward the rear is formed on the front side of both ends of the intermediate connecting frame 5. The tip portion 232 of the extension portion 23 is arranged in the recessed portion 53.

In this embodiment, as shown in FIG. 50, the tension member P is wrapped around the intermediate connecting frame member 5 so as to cover the back surface of the intermediate connecting frame member 5. More specifically, the tension member P is wrapped around the intermediate connecting frame member 5 from the lower end portion pe in the order of back surface, top surface, front surface, bottom surface, and back surface. Therefore, the tension member P is arranged in two layers, front and back, on the back surface side of the intermediate connecting frame member 5.

<Stretching member P>
The upholstery member P is mainly made of a mesh-like fabric capable of forming the backrest surface pm.

The tension member P is attached to the tension member attachment groove mz provided on the upper frame portion w1 of the back frame M at its peripheral portion. The tension member P is stretched over the front side of the upper frame portion w1 of the back frame M.

The end portion pe of the tension member P attached to the upper frame portion w1 has an inserted member ps sewn to it, which is inserted together with the tension member P into the tension member attachment groove mz. The inserted member ps of the end portion pe is of a size that allows it to be pressed into the tension member attachment groove mz of the upper frame portion w1 during assembly, and is, for example, a strip-shaped member made of synthetic resin.

The end portion pe of the lower edge of the tension member P is intended to be attached to the tension member attachment groove mz of the intermediate connecting frame material 5. As shown in FIG. 50, the tension member P is wrapped around the intermediate connecting frame material 5 from the lower end portion pe side in the order of back surface, top surface, front surface, bottom surface, and back surface.

An example of how to attach the intermediate connecting frame material 5 with the tension member P wrapped around it to the extension parts 23 of the left and right side frame materials 2 is as follows.

First, the part of the tension member P that is wrapped around the mounting part 52 is temporarily pressed toward the intermediate connecting frame body 51 and moved, and the mounting part 52 exposed to the outside is fastened to the extension part 23 with the screw v5.

Next, the portion that was temporarily pressed and moved toward the intermediate connecting frame body 51 is shifted and moved to a position where the mounting portion 52 and the extension portion 23 can be wound. As a result, the screw v5 for attaching the intermediate connecting frame 5 to the left and right side frame members 2 is doubly covered by the tension member P when viewed from behind, providing a favorable appearance.

Then, the upper and left and right end portions pe of the tension member P are attached to the tension member attachment grooves mz of the upper frame material 3 and the left and right side frame materials 2, completing the installation of the tension member P to the back frame M.

The above-mentioned installation procedure is merely one example. For example, the tension member P may be wrapped around the intermediate connecting frame material 5 while the intermediate connecting frame material 5 is screwed to the left and right side frame materials 2.

<<Lumbar Support R>>
The lumbar support R is installed between the left and right side frame members 2. The lumbar support R is located behind the tension member P and is capable of supporting the lower back of a seated person. The lumbar support R is vertically changeable relative to the left and right side frame members 2 of the backrest E, and is provided detachably without the need to attach or detach fasteners such as screws.

In other words, in this embodiment, whether the lumbar support R is attached to the backrest E after the fact or detached from the backrest E, this can be done by temporarily bending the lumbar support R and inserting or detaching the held portion r22 into or from the lumbar support holding portion N without using fasteners such as screws.

The lumbar support R comprises a lumbar support body r1 extending in the left-right direction, and left and right arm members r2 supported by the lumbar support body r1. The left and right arm members r2 are supported so as to be movable in the left-right direction relative to the lumbar support body r1.

<Lumbar support body r1>
The lumbar support main body r1 comprises a front main body member r11 and a rear main body member r12 which is approximately the same size as the front main body member r11 and is attached to the rear side of the front main body member r11.

[Front body member r11]
The front main body member r11 includes a front main body base r111 made of synthetic resin in the shape of a plate extending in the left-right direction, and a front cover material r112 that covers the front surface and peripheral edge portion of the front main body base r111.

The front body base r111 can be temporarily deflected in the thickness direction. The front body base r111 has an overall horizontally elongated plate shape in an upright position. Both left and right side portions of the front body base r111 are formed in a semicircular shape when viewed from the front.

The front body base r111 is provided with claw receiving portions r113 at multiple locations that receive the engagement claws r123 provided on the rear body base r121 of the rear body member r12.

A triangular prism-shaped positioning protrusion r114 protrudes rearward from the center of the front body base r111 in the left-right and up-down directions and can fit into a fitting recess r124 provided in the rear body base r121 of the rear body member r12.

On the left and right sides of the front body base r111, there are provided outwardly U-shaped guide walls r115 that engage with the outer edges of the arm bases r21 that constitute the left and right arm materials r2, respectively, and can guide the left and right movement of the left and right arm materials r2 relative to the lumbar support body r1.

[Rear body member r12]
The rear main body member r12 includes a rear main body base r121 made of synthetic resin in the shape of a plate extending in the left-right direction, and a rear skin material r122 that covers the rear surface and peripheral edge portion of the rear main body base r121.

The rear body base r121 is provided with engagement claws r123 at multiple locations that can engage with the claw receiving portions r113 provided on the front body base r111 of the front body member r11.

A fitting recess r124 is formed in the center of the rear body base r121 in the left-right and up-down directions, into which the triangular prism-shaped positioning protrusion r114 provided on the front body base r111 of the front body member r11 can fit.

On the left and right sides of the rear body base r121, there are provided outwardly U-shaped guide walls r125 that engage with the outer edges of the arm bases r21 constituting the left and right arm materials r2, respectively, and can guide the left and right movement of the left and right arm materials r2 relative to the lumbar support body r1.

In the inner area surrounded by the guide wall r125 of the rear body base r121, an upper convex portion r126 and a lower convex portion r127, which are the first engagement portions, are disposed toward the front, i.e., toward the front body base r111.

The upper convex portion r126 and the lower convex portion r127 are capable of engaging with the upper engaging hole r213 and the lower engaging hole r214, which are horizontally elongated holes and are second engaging portions provided on the inner plate-like portion r211 of the left and right arm members r2.

<Left and right arm material r2>
The left and right arm materials r2 are sandwiched between the front body member r11 and the rear body member r12. The outer ends of the left and right arm materials r2 are provided with held portions r22 that are held by the lumbar support holding portion N provided on the backrest E. The left and right arm materials r2 are each integrally formed from synthetic resin.

The left and right arm members r2 each have an arm base r21 having a rectangular plate-shaped portion extending in the left-right direction, and a held portion r22 that is connected to the outer end of the arm base r21 and is held by the lumbar support holding portion N of the backrest E.

The arm base r21 and the held portion r22 that make up the left arm material r2 are integrally formed from synthetic resin, and the arm base r21 and the held portion r22 that make up the right arm material r2 are integrally formed from synthetic resin.

[Arm base r21]
The arm base r21 has an inner plate-like portion r211 which is rectangular extending in the left-right direction and is located within the lumbar support main body r1, and an outer plate-like portion r212 which is plate-like and has a portion extending diagonally forward and outward from the outer edge of the inner plate-like portion r211.

The inner plate-like portion r211 has a generally rectangular shape with the upper and lower edges generally parallel to each other. The upper and lower parts of the inner end of the inner plate-like portion r211 are provided with an upper engagement hole r213 and a lower engagement hole r214, which are long hole-shaped second engagement parts extending in the left-right direction. In addition, the left-right center of the inner plate-like portion r211 is provided with an elongated interference avoidance hole r215 for avoiding the boss portion r128 having a screw insertion hole h4, and a rectangular interference avoidance hole r216 for avoiding the engagement claw r123 and claw receiver r113, which are the connecting mechanism for connecting the front main body member r11 and the rear main body member r12.

The upper convex portion r126 and the lower convex portion r127, which are the first engagement portions provided on the lumbar support main body r1, engage with the upper engagement hole r213 and the lower engagement hole r214, which are the second engagement portions provided on the inner plate-like portion r211 of the left and right arm materials r2, so that the left and right arm materials r2 are configured to be movable in the left and right direction relative to the lumbar support main body r1. The upper engagement hole r213 and the lower engagement hole r214 are set to a dimension longer in the width direction than the upper convex portion r126 and the lower convex portion r127.

The outer plate-like portion r212 is disposed outside the lumbar support body r1. The outer plate-like portion r212 includes an inclined extending plate portion r217 that extends diagonally forward and outward from the outer edge of the inner plate-like portion r211, and a horizontal extending plate portion r218 that extends outward from the extending end of the inclined extending plate portion r217.

[Holded portion r22]
The held portion r22 has an upper protruding portion r221 and a lower protruding portion r222 that protrude rearward and are arranged with a gap between them in the vertical direction.

The upper protruding portion r221 and the lower protruding portion r222 protrude rearward from the outer edge of the outer plate-like portion r212 that constitutes the arm base r21, i.e., the outer end of the horizontally extending plate portion r218 of the outer plate-like portion r212. The upper protruding portion r221 and the lower protruding portion r222 bulge outwardly and obliquely rearward from the outer end portion of the arm base r21.

The front ends of the upper protruding portion r221 and the lower protruding portion r222 are provided with forward-facing engagement surfaces r223, r227 that face forward and serve as front engagement portions that can engage with the front restriction portion q1 of the holding member Q that constitutes the lumbar support holding portion N.

The rear ends of the upper protruding portion r221 and the lower protruding portion r222 are provided with rearward engaging surfaces r224, r228 that face rearward and can engage with the groove forming wall 221a at the back of the accommodation groove 221 that constitutes the lumbar support holding portion N.

The inner ends of the upper protruding portion r221 and the lower protruding portion r222 are provided with lateral engagement surfaces r225, r226 that face inward and serve as side engagement portions that can engage with the groove forming wall 221b on the side of the accommodation groove 221 that constitutes the lumbar support holding portion N.

In this embodiment, the shape of the upper protruding portion r221 is set to be different from the shape of the lower protruding portion r222. More specifically, the upper protruding portion r221 has a notch r226 in the vertical middle of the rear end portion, which is the protruding end portion, but the lower protruding portion r222 does not have a similar notch. In addition, the vertical dimension of the upper protruding portion r221 is set to be shorter than the vertical dimension of the lower protruding portion r222.

The chair of this embodiment is designed to prevent a user from attaching the lumbar support R to the backrest E with the wrong top and bottom. The upper cutout 221c formed in the accommodation groove 221 of the lumbar support holding portion N corresponds to the shape of the upper protruding portion r221 of the lumbar support R. In other words, the upper cutout 221c is provided with a protrusion 221e that can pass through the cutout r226 of the upper protruding portion r221.

The supported portion r22 of the lumbar support R is provided with a eaves-like protruding portion r220 that connects the upper protruding portion r221 and the lower protruding portion r222 and protrudes outward from the outer end of the arm base r21 (i.e., the outer end of the horizontal extension portion r218 in the outer plate portion r212).

The upper and lower cutouts that allow the upper protruding portion r221 and the lower protruding portion r222 to pass through are not limited to those provided in the left and right side frame members 2, but may be provided, for example, in the front restricting portion q1 of the retaining member Q.

<<Backrest surface expansion member F>>
The backrest surface extension member F is for providing an extended backrest surface fm as a contact surface that can contact the user on the backrest surface pm formed by the backrest E. The backrest surface extension member F in this embodiment is called a "shoulder support" because the user's shoulders can mainly contact the extended backrest surface fm.

The backrest surface extension member F comprises a pad body f1, the front of which is an extended backrest surface fm that can come into contact with the user, and a base body f2 that can support the pad body f1.

The backrest surface extension member F has an upper frame material placement recess fu between the lower part of the base body f2 and the lower end of the pad body f1, which is open to the front and both sides.

The backrest surface extension member F is provided with a movement restriction portion ks located on the rear side of the upper frame material 3 in the backrest E at a position facing the upper frame material arrangement recess fu, and capable of restricting forward movement by engaging with the rear portion of the upper frame material 3.

<Pad body f1>
The pad body f1 comprises a pad body main body f3 attached to a pad body attachment portion f6 provided on the base body f2, and a front cover material f4 covering the front surface and peripheral edge portion of the pad body main body f3.

The pad body f1 has a generally rectangular shape with its elongated sides in the left-right direction when viewed from the front. The pad body f1 has a generally symmetrical shape when viewed from the front. The edges of both the left and right sides of the pad body f1 are gently curved so as to convex outward when viewed from the front. The extended backrest surface fm, which is the front surface of the pad body f1, is set to be generally flush with the backrest surface pm formed by the upholstery member P.

The vertical dimension of the pad body f1 is shorter than the vertical dimension of the base body f2. The position of the upper edge of the pad body f1 is approximately aligned with the position of the upper edge of the base body f2. The shape of the side edge of the pad body f1 in a front view is approximately aligned with the shape of the side edge at the same height position of the base body f2. The lower edge of the pad body f1 is set at a position that approximately abuts against the upper frame material 3.

[Pad body f3]
The pad body f3 includes a pad base f31 formed of synthetic resin in the shape of a generally upright plate, and a cushion f32 made of urethane foam attached to the front surface of the pad base f31.

A pair of hook engaging parts f311 are provided at the center of the back side of the pad base f31 in the vertical direction, spaced apart in the left-right direction. The hook engaging parts f311 have engaging holes f314 that are open in the vertical direction.

The hook engaging portion f311 has left and right protruding walls f312 protruding rearward and a connecting wall f313 connecting the rear portions of the left and right protruding walls f312, forming an engaging hole f314 that penetrates in the vertical direction. The hook engaging portion f311 can engage with the base body f2 by inserting a hook f61, which is an engaging portion protruding from the pad body mounting portion f6 of the base body f2, into the engaging hole f314.

The lower part of the rear side of the pad base f31 has left and right fitting protrusions f315 and a central fitting protrusion f316, which serve as engagement parts, at three locations on the left, right and center. Each fitting protrusion f315, f316 is roughly arrow-shaped and protrudes rearward. Each fitting protrusion f315, f316 can engage with a protrusion fitting part f62, which serves as an engagement part, provided on the pad body mounting part f6 of the base body f2. The left and right fitting protrusions f315 are set in a different position from the central fitting protrusion f316. More specifically, the left and right fitting protrusions f315 are set in a position rotated 90 degrees from the central fitting protrusion f316 when viewed from the rear.

[Front skin f4]
The front skin f4 is made of a fabric having an area larger than the front part of the pad body f3. The edge portion f4e of the front skin f4 can be stored between the pad body f3 and the base body f2 so as not to be visible from the outside. The front skin f4 can form an extended backrest surface fm provided on the backrest surface pm of the upholstery member P.

<Base body f2>
The base body f2 comprises a base plate-shaped portion f5 which is approximately in the shape of an upright plate, a pad body mounting portion f6 which is provided on the front side of the base plate-shaped portion f5 and to which the pad body f1 is attached, an upper frame material mounting portion f7 which is provided below the pad body mounting portion f6 and which is attached to the upper frame material 3 using a screw v1 which is a fastening device, and a rear skin material f9 which covers the peripheral portion and rear surface portion of the base plate-shaped portion f5.

The base plate portion f5, pad body mounting portion f6, and upper frame material mounting portion f7 that constitute the base body f2 are integrally formed from synthetic resin.

In this embodiment, the backrest surface extension member F is configured so that only the rear skin material f9 covering the base plate portion f5 of the base body f2 is visible when viewed from the rear. In other words, the backrest surface extension member F is configured so that no members other than the rear skin material f9 are visible when viewed from the rear.

[Base plate portion f5]
The base plate portion f5 has a generally rectangular shape with its elongated sides in the left-right direction in rear view. The edges of the left and right sides of the base plate portion f5 are gently curved so as to convex outward in rear view. The rear surface of the base plate portion f5 is covered with a rear skin material f9.

The front side of the base plate portion f5 is provided with an upper horizontal rib f52 extending in the left-right direction whose tip can abut against the back surface of the pad base f31, and multiple vertical ribs f53 extending in the up-down direction whose tip can abut against the back surface of the pad base f31. The multiple vertical ribs f53 are arranged at intervals in the left-right direction. A lower horizontal rib f54 extending in the left-right direction whose tip can abut against the upper frame material 3 of the backrest E is provided at the lower part of the front side of the base plate portion f5.

In this embodiment, the movement restriction section ks is mainly composed of the components located behind the upper frame member 3, namely the tip of the lower horizontal rib f54 and the tip of the vertical rib f53 located below the lower horizontal rib f54, and can restrict the forward movement of the backrest surface extension member F by engaging with the back surface of the upper frame member 3.

[Pad body mounting part f6]
The pad body mounting portion f6 has a hook f61 protruding at a position corresponding to the hook engagement portion f311 of the pad base f31, and a protruding engagement portion f62 protruding at positions corresponding to the left, right and central engagement protrusions f316 of the pad base f31.

The pad body f1 is attached to the base body f2 by engaging the hook engagement portion f311 with the hook f61 provided on the pad body attachment portion f6, and then engaging the left, right, and center fitting protrusions f315 and f316 with the protrusion fitting portions f62 provided on the pad body attachment portion f6.

[Upper frame mounting part f7]
The upper frame member mounting portion f7 is mainly composed of a portion that protrudes forward from the lower end of the base plate portion f5. The upper frame member mounting portion f7 has an upward surface f71 that extends in the left-right direction and serves as the mounting base surface for the upper frame member 3.

The upper frame member mounting portion f7 has two screw insertion holes h1 that penetrate vertically on the left and right. The backrest surface extension member F is configured to be attached to the upper frame member 3 by screwing a screw v1 inserted through the screw insertion hole h1 into a nut member J arranged in a nut holding recess nt in the upper frame member 3.

The upper frame member mounting portion f7 has a protruding wall portion f72 at the upper end of the front portion corresponding to the portion where the screw insertion hole h1 is formed, which can be positioned at the front opening kh3 of the nut holding recess nt provided in the upper frame member 3.

A storage groove f8 that is open downward and outward and can store the edge portion f9e of the rear skin f9 is formed in the lower part of the base body f2, i.e., between the upper frame mounting portion f7 and the base plate portion f5. A groove forming wall f73 is erected at the rear end of both sides of the upper frame mounting portion f7 to form the storage groove f8 between the peripheral portion of the base plate portion f5.

The front surface of the groove forming wall f73 can abut against the rear surface of the upper frame material 3, and also serves as a movement restriction portion ks that can restrict the forward movement of the backrest surface extension member F.

[Rear skin f9]
The rear skin f9 is made of a material having a larger area than the rear surface of the base plate portion f5. The edge portion f9e of the rear skin f9 can be accommodated between the base plate portion f5 and the pad body f1, and can also be accommodated in an accommodating groove f8 provided between the lower peripheral portion of the base plate portion f5 and the upper frame member mounting portion f7.

<< Hanger G >>
The hanger G is for hanging and fastening a user's clothes, etc. The hanger G is attached to the upper frame member 3 of the back frame M.

The hanger G is equipped with a hanger body g1 that extends in the left-right direction for hanging clothes, etc., a pair of left and right hanger legs g2 that extend downward from the underside of the hanger body g1 and extend forward at the lower part, and a base portion g3 that connects the lower ends of the left and right hanger legs g2 and has an upper frame member attachment portion g7 that is attached to the upper frame member 3.

The base portion g has a base portion main body g4 on which an upper frame material mounting portion g7 is provided, and a standing wall g5 serving as a movement restriction portion ks that is erected at the rear of the base portion main body g4 and can engage with the rear surface of the upper frame material 3.

The upper frame member mounting portion g7 extends in the left-right direction and has an upward surface g71 that serves as the mounting base surface for the upper frame member 3.

The upper frame member mounting portion g7 has two screw insertion holes h2 that penetrate vertically on the left and right. The hanger G is configured to be attached to the upper frame member 3 by screwing the screw v2 inserted into the screw insertion hole h2 into the nut member J arranged in the nut holding recess nt in the upper frame member 3.

The upper frame mounting portion g7 has a protruding wall portion g72 at the upper end of the front portion corresponding to the portion where the screw insertion hole h2 is formed, which can be positioned at the front opening kh3 of the nut holding recess nt provided in the upper frame 3.

<<How to install the option (backrest extension part F)>>
The chair of this embodiment is applied with a mounting structure that makes it easy to mount options to the backrest E. Hereinafter, a method of mounting the options to the upper frame material 3 of the backrest E will be described using the backrest surface extension member F as a specific example.

First, the nut member J is held in the nut holding recess nt that is open to the front and provided in the upper frame member 3. A tension member P is pre-tensioned on the front side of the upper frame portion w1 of the back frame M.

The worker passes the roughly T-shaped nut member J through the upper cavity sa surrounded by the upper frame portion w1 from the rear to the front, and then holds the nut member J in the nut holding recess nt that is open to the front.

The boss portion j1 of the nut member J is accommodated in the nut holding recess nt through the front open portion kh3. The flange portion j2 of the nut member J is accommodated in the gap sk between the nut holding recess nt and the outer frame portion 31. The flange portion j2 of the nut member J engages with the flange portion engagement portion nt3, which is the portion that forms the upper open portion kh1 in the nut holding recess nt, and cannot move downward. In other words, the nut member J is provisionally positioned relative to the upper frame material 3 by having the boss portion j1 accommodated in the nut holding recess nt and the flange portion j2 disposed in the gap sk.

Next, the backrest surface extension member F is moved from rear to front so that the upper frame material placement recess fu is positioned so that it surrounds the upper frame material 3.

Then, a screw v1 is inserted from the bottom to the top through the screw insertion hole h1 provided in the upper frame material mounting portion f7 of the backrest surface extension member F, and the screw v1 is screwed into the boss portion j1 of the nut member J. By screwing the screw v1 into the nut member J, the upper frame material mounting portion f7 of the backrest surface extension member F and the inner frame portion 32 of the upper frame material 3 are tightened.

The above attachment method allows the backrest surface extension member F to be attached to the upper frame material 3 of the backrest E.

The nut holding recess nt provided in the upper frame material 3 is open in the forward and vertical directions, making it easy for the worker to attach (temporarily place) the nut member J. The worker can properly hold the nut member J in the nut holding recess nt by simply feeling the inner frame portion 32 of the upper frame material 3 from the back side of the backrest E, without having to closely check the nut holding recess nt, which is covered by the upholstery member P and difficult to see.

The backrest surface extension member F is also provided with a movement restriction portion ks that can restrict forward movement. Therefore, even if the backrest surface extension member F is pressed forward, the nut member J cannot move forward from the nut holding recess nt that is open to the front side.

<<Locking mechanism V>>
The locking mechanism V is for moving the seat C at a constant ratio in response to the tilting of the backrest E.

The rocking mechanism V in this embodiment has a so-called weight-sensing structure that can appropriately tilt the backrest E in accordance with the weight of the seated person. In other words, the rocking mechanism V is configured to move the seat C backward in conjunction with the backward tilting of the backrest E, while lifting the seat C against the weight of the seated person.

In other words, the rocking mechanism V includes a mechanism for lifting the seat C upward against the weight of the seated person, and is configured to require a backward tilt load proportional to the weight of the seated person in order to tilt the backrest E backward.

The locking mechanism V supports the front part of the seat support c1 so that it can move back and forth via the front shaft jk2 on the front end of the support base B, and pivots the middle part of the seat C in the fore-aft direction on the rear shaft jk3 connected to the front arm part d12.

The rear axle jk3 is disposed in front of and above the main axle jk1 on the left and right arms d1. In this embodiment, the rear axle jk3 is also connected to a bearing axle d4 disposed in the storage space sp of the support base main body 1 via a bearing axle support member d3.

The above-described embodiment can provide a chair having an operating unit main body k11 with a generally cylindrical outer shape that is less complicated, and a reaction force adjustment lever K that can optimally perform the indicator function of indicating the rotational position by the protruding portion k12.

In addition, with the above-described embodiment, the nut member J can be held in the nut holding recess nt that is open upward, downward, and forward, so that a chair having a suitable configuration can be provided in which options such as a backrest surface extension member F can be attached to the backrest E.

In the above-described embodiment, a backrest surface extension member F is attached to the upper frame member 3 of the backrest E. The backrest surface extension member F is configured so that only the rear skin material f9 covering the base plate portion f5 can be seen when viewed from behind, so that a favorable appearance based on the rear skin material f9 can be achieved when viewed from behind.

The above-described embodiment also provides a chair with a suitable configuration in which the lumbar support R, which can support the lower back of a seated person, can be adjusted in position in the vertical direction relative to the backrest E and can be attached and detached without having to attach or detach a fastening device.

In addition, in the above-described embodiment, the tension member P is wound and supported on the intermediate connecting frame member 5, which is a cross member, and therefore not only can the back surface of the intermediate connecting frame member 5 be effectively prevented from being exposed to the outside, but also a chair with excellent flexibility can be provided, which allows the tension member P to be tensioned to the back frame M with an appropriate tension.

In addition, in the above-described embodiment, the tip t21 of the screw head abutment protrusion t2 can engage with the head v61 of the screw v6, so that not only can the screw v6 for attaching the backrest E be concealed to obtain a suitable appearance, but it is also possible to provide a chair having a configuration in which it is possible to check whether the screw v6 is properly attached to the backrest E based on the position of the back frame cap T, which serves as a concealing member.

In addition, the above-mentioned embodiment includes a support base body 1 in which at least the foundation bottom structure 11 and the left and right side walls 14 are integrally molded from synthetic resin, and the left and right side walls 14 of the support base body 1 are formed with recesses 1a recessed in the thickness direction of the side walls 14. This makes it possible to suitably suppress abnormal deformation during molding of the left and right side walls 14, and provides a chair with a suitable configuration that allows the main axis jk1, which is an axis, to be supported by the left and right side walls 14 of the support base body 1 made of synthetic resin.

In addition, recesses 1a are formed in the left and right side walls 14, and these recesses 1a can be used to suitably position the support base body 1 during assembly and disassembly. Therefore, in this embodiment, in order to improve the design and strength of the support base body 1, a suitable external shape having curved surfaces or the like can be designed without difficulty, without having to worry about the difficulty of positioning during the assembly and disassembly processes.

The above-described embodiment allows the seat body c2 to slide in the front-rear direction with respect to the seat support c1, and provides a chair with excellent design freedom for obtaining a seat body c2 that is stably provided with a seat cushion c22 that is larger than the support member c21.

In the above-described embodiment, the degree of backward tilt of the backrest E can be selectively set from two or more multiples, and each of the multiple backward tilt degrees, the first, second, third and fourth backward tilt degrees (x1), (x2), (x3) and (x4), is determined by the first, second, third and fourth contact surfaces at1, at2, at3 and at4 contacting the damper member XM. Therefore, regardless of the selected backward tilt degree, the seated person can be given a common bottoming out feeling, and it is possible to provide a chair with a backrest E that contributes to comfortable use by the seated person.

As described above, the chair according to this embodiment has a backrest E supported on a support base B via a back support D so that it can be tilted backward, and is provided with a backward tilt setting mechanism X that can select the backward tilt degree of the backrest E from two or more multiple degrees, i.e., first, second, third, and fourth backward tilt degrees (x1), (x2), (x3), and (x4).

The rearward tilt degree setting mechanism includes a rearward tilt degree setting lever H, which is an operating lever rotatably supported on the back support D, a rotating member Re attached to the rearward tilt degree setting lever H so as to be rotatable as one unit and in which the first, second, third and fourth contact surfaces at1, at2, at3 and at4, which are a plurality of contact surfaces corresponding to the first, second, third and fourth rearward tilt degrees (x1), (x2), (x3) and (x4), are arranged at intervals in the rotational direction, and a damper member XM arranged on the support base B with which a specific contact surface of the first, second, third and fourth contact surfaces at1, at2, at3 and at4 can selectively come into contact.

The first, second, third and fourth backward tilt degrees (x1), (x2), (x3) and (x4) of the chair are determined by the first, second, third and fourth contact surfaces at1, at2, at3 and at4 abutting against the damper member XM.

Therefore, in this embodiment, at least in any of the selected first, second, third and fourth backward tilt degrees (x1), (x2), (x3) and (x4), the seated person can be given a common bottoming sensation by contacting the damper member XM, and it is possible to provide a chair with a backrest E that contributes to comfortable use by the seated person.

In other words, in this embodiment, the member on the backrest E side, which is the movable side for determining the limit position for the backrest E to lean backward, is the rotating member Re, and the member on the support base B side, which is the immovable side, is the damper member XM. Therefore, unlike the conventional system, the members for determining the limit position for the backrest E to lean backward are not scattered in two or more places, and it is easier to provide a common bottoming out feeling to the user.

The rearward tilt degree setting lever H is equipped with a lever shaft ha that extends in the left-right direction and is pivoted in an axial hole d112 provided in the back support D, and a handle hb that is attached to one end of the lever shaft ha.

The rotating member Re has a base end e1 in which an insertion hole e11 is formed, through which the lever shaft ha is inserted, and a rotating member main body e2 which is integral with the base end e1 and has a plurality of contact surfaces, namely, first, second, third and fourth contact surfaces at1, at2, at3 and at4.

For this reason, the rearward tilt degree setting mechanism X is suitably configured to selectively bring the first, second, third and fourth contact surfaces at1, at2, at3 and at4 into contact with the damper member XM.

The first, second, third, and fourth contact surfaces at1, at2, at3, and at4 are provided on the rotating member main body e2 in correspondence with the first, second, third, and fourth backward inclination degrees (x1), (x2), (x3), and (x4).

As a result, the user can rotate the rotation member Re by rotating the rearward tilt degree setting lever H, and flexibly set one of the first, second, third, and fourth rearward tilt degrees (x1), (x2), (x3), and (x4).

The first contact surface at1 is provided at a position farther away from the base end e1 than the second contact surface at2, the second contact surface at2 is provided at a position farther away from the base end e1 than the third contact surface at3, and the third contact surface at3 is provided at a position farther away from the base end e1 than the fourth contact surface at4. When the first contact surface at1 contacts the damper member XM, the backrest E is set to a first backward tilt degree (x1) at which it hardly tilts backward.

As a result, the rotating member Re can be adjusted to a desired degree of rearward tilt by using the first, second, third and fourth contact surfaces at1, at2, at3 and at4, which are positioned at different distances from the base end e1.

The rotating member main body e2 is provided with a quadrangular columnar portion e20 having a first contact surface at1 that is substantially rectangular in side view and faces downward when it contacts the damper member XM, a first mountain-shaped portion e21 having a second contact surface at2 that is substantially triangular in side view and faces downward when it contacts the damper member XM, a second mountain-shaped portion e22 having a third contact surface at3 that is substantially triangular in side view and faces downward when it contacts the damper member XM, and a third mountain-shaped portion e23 having a fourth contact surface at4 that is substantially triangular in side view and faces downward when it contacts the damper member XM.

For this reason, the rotating member body e2 has a suitable shape that allows the first, second, third and fourth contact surfaces at1, at2, at3 and at4 to come into contact with the damper member XM.

The shapes of the rectangular columnar portion e20, the first mountain-shaped portion e21, the second mountain-shaped portion e22, and the third mountain-shaped portion e23 are set so that the first contact surface at1, the second contact surface at2, the third contact surface at3, and the fourth contact surface at4 can contact the damper member XM at approximately the same contact angle.

In other words, the shape of the rotating member main body e2 is set so that each contact surface at1, at2, at3, and at4 can come into surface contact with the upper surface of the common damper member XM from the same direction.

As a result, the backward tilt load of the seated occupant acting on the backrest E is effectively transmitted to the damper member XM through the contact surfaces at1, at2, at3, and at4 of the rotating member Re, making it easy for the user to experience a common bottoming out sensation regardless of the state of the first to fourth backward tilt degrees (x1) to (x4).

The rotating member bodies e2 are arranged in a pair on the left and right, and the damper members XM are arranged in a pair on the left and right at the rear of the support base B.

As a result, the backward tilt of the backrest E can be supported in a well-balanced manner by the pair of rotating member bodies e2 on the left and right and the pair of damper members XM on the left and right.

The pair of left and right rotating member bodies e2 are connected to each other by a connecting wall e3 extending from the base end e1.

As a result, the rotating member Re can support the pair of rotating member bodies e2 on the left and right with excellent strength relative to the base end portion e1.

The support base B comprises a support base body 1 integrally formed from synthetic resin, and a damper member XM that is separate from the support base body 1 and attached to the rear end of the support base body 1.

This not only provides excellent design freedom for imparting suitable cushioning to the damper member XM, but also allows for flexibility in designing the structure for attaching the damper member XM to the support base body 1, as it is configured to be attached to the support base body 1 made of synthetic resin.

It is equipped with a detent mechanism XD for detentatively locking the rotating member Re at one of four rotation positions corresponding to a plurality of degrees of backward tilt, namely, first, second, third, and fourth degrees of backward tilt (x1), (x2), (x3), and (x4).

This allows the user to easily set the rotating member Re to a predetermined rotational position by using the detent mechanism XD.

The present invention is not limited to the embodiments described above.

It goes without saying that the specific configuration of the operating lever can be set in various ways without departing from the spirit of the present invention.

In the above-described embodiment, the operating lever constituting the rearward tilt degree setting mechanism is supported on the back support body, and the damper member is disposed on the support base, but this is not limited to this. In other words, the operating lever may be supported on the support base, and the damper member may be disposed on the back support body.

The rotating member may have various shapes, and the specific shapes are not limited to those shown in the above-mentioned embodiment. For example, the rotating member body does not have to be paired on the left and right, and may be a single member or a plurality of three or more members.

Of course, reinforcing ribs or reinforcing walls may be provided at appropriate locations on the rotating member.

The material and shape of the damper member can vary and are not limited to those shown in the above embodiment.

The specific configuration of each part is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

E: Backrest B: Support base D: Back support X: Rearward tilt degree setting mechanism H: Rearward tilt degree setting lever (operation lever)
Re... rotating member at1, at2, at3, at4... first, second, third, and fourth contact surfaces (contact surfaces)
XM: Damper member x1, x2, x3, x4: First, second, third, and fourth backward inclination degrees (backward inclination degrees)

Claims (7)

A chair having a backrest supported on a support base via a back support so as to be able to tilt backward, and provided with a backward tilt degree setting mechanism that can select a backward tilt degree of the backrest from two or more.
the rearward tilt degree setting mechanism comprises an operating lever rotatably supported on either the back support or the support base, a rotating member rotatably attached to the operating lever and having a plurality of contact surfaces corresponding to the plurality of rearward tilt degrees arranged at intervals in the rotational direction, and a damper member arranged on the other of the back support or the support base against which a specific contact surface of the plurality of contact surfaces can selectively come into contact,
any of the plurality of rearward tilt degrees is determined by the contact surface contacting the damper member ,
The operating lever includes a lever shaft portion extending in the left-right direction and pivotally supported in a shaft hole, and a handle portion attached to one end of the lever shaft portion,
the rotating member includes a base end portion having an insertion hole through which the lever shaft portion is inserted, and a rotating member main body that is integral with the base end portion and has the plurality of contact surfaces,
the plurality of backward leaning degrees are first, second, third, and fourth backward leaning degrees;
the plurality of contact surfaces are first, second, third, and fourth contact surfaces provided on the rotating member main body corresponding to the first, second, third, and fourth backward inclination degrees,
The first contact surface is provided at a position farther from the base end portion than the second contact surface,
The second contact surface is provided at a position farther from the base end portion than the third contact surface,
The third contact surface is provided at a position farther from the base end portion than the fourth contact surface,
When the first contact surface contacts the damper member, the backrest is set to the first backward tilt degree at which the backrest is hardly tilted backward,
A chair in which the rotating member main body comprises a quadrangular prism portion having the first contact surface which is approximately rectangular in side view and faces downward when it abuts against the damper member, a first mountain-shaped portion having the second contact surface which is approximately triangular in side view and faces downward when it abuts against the damper member, a second mountain-shaped portion having the third contact surface which is approximately triangular in side view and faces downward when it abuts against the damper member, and a third mountain-shaped portion having the fourth contact surface which is approximately triangular in side view and faces downward when it abuts against the damper member . The chair according to claim 1, wherein the operating lever is supported on the back support, and the damper member is disposed on the support base. 3. The chair according to claim 1 or 2, wherein the shapes of the rectangular columnar portion, the first mountain-shaped portion, the second mountain-shaped portion, and the third mountain-shaped portion are set so that the first contact surface, the second contact surface, the third contact surface, and the fourth contact surface can contact the damper member at approximately the same contact angle. The rotating member bodies are arranged in pairs on the left and right,
4. The chair according to claim 1, 2 or 3, wherein the damper members are disposed in pairs on the left and right sides at corresponding positions on the rotating member body. 5. The chair according to claim 4 , wherein the left and right rotating member bodies are connected to each other by a connecting wall extending from the base end portion. The operating lever is supported by the back support, and the damper member is disposed on the support base,
A chair as described in claims 1, 2, 3, 4 or 5, wherein the support base comprises a support base main body formed integrally from synthetic resin, and the damper member which is separate from the support base main body and attached to the rear end of the support base main body. 7. The chair according to claim 1 , further comprising a detent mechanism for detentatively locking said rotating member at any one of a plurality of rotation positions corresponding to a plurality of degrees of backward tilt.

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