JP7801764B2 - Telescopic device - Google Patents

Description

The present invention relates to an extension device, for example, an extension device that can be used for a height-adjustable side table.

As shown in Figures 1 to 3 of Patent Document 1, for example, a conventional telescoping device has a length adjustment mechanism that includes a locking plate with multiple engaging portions attached to an outer cylinder and a locking claw that is pivotally supported on an inner cylinder and engages with the engaging portions of the locking plate only in the direction in which the inner cylinder is retracted into the outer cylinder. The inner cylinder is slidably inserted into the outer cylinder via the length adjustment mechanism. A cap is fitted into one end opening of the outer cylinder to close the opening, and the locking plate is detachably secured to the cap. The outer cylinder also has a locking portion that fits between the cap and the locking plate to prevent the locking plate from detaching from the outer cylinder (see Patent Document 1).

Utility Model Publication No. 61-95330

However, the leg structure described above is not only complicated in terms of the number of components, but also in terms of the complex shape of the locking claw 6, which is a major component and is prone to stress concentration, making it difficult to design and manufacture. In particular, assembly is time-consuming, resulting in low productivity.
In view of the above problems, an object of the present invention is to provide an extension device that has a small number of parts, whose main components have simple shapes, is easy to design and manufacture, and has high productivity.

In order to solve the above problems, the expansion device according to the present invention comprises:
An outer cylinder body 20;
an inner cylindrical body 30 that is inserted into the outer cylindrical body 20 and is slidable along the longitudinal direction;
a lock bar (50) having a first protrusion (51) at one end and a second protrusion (52) at the other end, with engagement holes (54) provided at a predetermined pitch between the first protrusion (51) and the second protrusion (52), the lock bar (50) being housed within the outer cylindrical body (20) and fixed to the outer cylindrical body (20) so as not to be displaced in the longitudinal direction;
a lock block 60 having a cross-sectional area that allows it to slide within the outer cylinder 20, and that can be divided into a first block body 61 and a second block body 62, the first block body 61 having a guide groove 64 for guiding the lock bar 50 on its mating surface, and the second block body 62 having a position regulating recess 65 on its mating surface, and that is slidably attached to the lock bar 50;
a spring member 70 assembled in the position regulating recess 65 of the second block body 62;
a lock ball (90) having a diameter that allows it to be engaged with and disengaged from the engagement hole (54) of the lock bar (50), housed in the position regulating recess (65) of the second block body (62), and biased toward the lock bar (50) by the spring member (70);
When the lock block 60 is pulled down to the lowest position, the lock ball 90 is locked in the lock area 65 a of the position restriction recess 65 via the first protrusion 51 of the lock bar 50,
When the lock block 60 is pulled up to a predetermined position and then pushed down, the lock ball 90 is clamped between the engagement hole 54 of the lock bar 50 and the bottom surface of the lock area 65 a in the position restriction recess 65, and the lock block 60 is locked by a wedge effect.
When the lock block 60 is raised to the top, the lock ball 90 is elastically held in the holding area 65 c in the position restricting recess 65 via the second protrusion 52 of the lock bar 50 .

According to the present invention, the lock ball is clamped between the engagement hole of the lock bar and the bottom surface of the positioning recess of the lock block, creating a wedge effect that locks the lock block. This not only allows height adjustment with fewer parts than conventional models, but also eliminates the need for complex-shaped components, making design and manufacturing easier and resulting in a highly productive telescoping device.

Other extension devices according to the present invention include:
An outer cylinder body 20;
an inner cylindrical body 30 that is inserted into the outer cylindrical body 20 and is slidable along the longitudinal direction;
a lock bar (50) having a first protrusion (51) at one end and a second protrusion (52) at the other end, with engagement holes (54) provided at a predetermined pitch between the first protrusion (51) and the second protrusion (52), the lock bar (50) being housed within the outer cylindrical body (20) and fixed to the outer cylindrical body (20) so as not to be displaced in the longitudinal direction;
a lock block 60 having a cross-sectional area that allows it to slide within the outer cylinder 20, and that can be divided into a first block body 61 and a second block body 62, the first block body 61 having a guide groove 64 for guiding the lock bar 50 on its mating surface, and the second block body 62 having a position regulating recess 65 on its mating surface, and that is slidably attached to the lock bar 50;
a spring member 70 assembled in the position regulating recess 65 of the second block body 62;
a lock ball (90) having a diameter that allows it to be engaged with and disengaged from the engagement hole (54) of the lock bar (50), housed in the position regulating recess (65) of the second block body (62), and biased toward the lock bar (50) by the spring member (70);
When the lock block 60 is lowered to the lowest position, the lock ball 90 is locked in the lock area 65 a of the position restriction recess 65 via the control plate 80 whose one end 81 abuts against the first protrusion 51 of the lock bar 50,
When the lock block 60 is pulled up to a predetermined position and then pushed down, the lock ball 90 is clamped between the engagement hole 54 of the lock bar 50 and the bottom surface of the lock area 65 a in the position restriction recess 65, and the lock block 60 is locked by a wedge effect.
When the lock block 60 is raised to the highest position, the lock ball 90 may be elastically held in the holding area 65c within the position control recess 65 via the control plate 80, whose other end 82 abuts against the second protrusion 52 of the lock bar 50.

According to the present invention, the height can be adjusted by regulating the position of the lock ball via the control plate, and the same effects as those described above can be obtained.
In particular, since the position of the lock ball can be regulated via the control plate, the positioning accuracy of the lock ball is increased, the variations in operating characteristics are reduced, and reliability is improved.

In another embodiment of the present invention, the lock ball 90 may be elastically held by a pair of spring portions 66, 66 provided so as to face each other in the holding region 65c.
According to this embodiment, the lock ball is held by being sandwiched from both sides by a pair of spring portions, thereby improving the holding strength.

In another embodiment of the present invention, a configuration may be adopted in which positioning portions 66a, 66a with which the lock ball 90 can be engaged and disengaged are provided at opposing positions of the pair of spring portions 66, 66, respectively.
According to this embodiment, the lock balls are engaged with and disengageable from the pair of positioning holes, which has the effect of providing an extension device with little variation in operating characteristics.

1 is a perspective view of a side table to which a first embodiment according to the present invention is applied. FIG. 2 is a front view of the side table shown in FIG. 1 . FIG. 2 is a left side view of the side table shown in FIG. 1 . FIG. 2 is a left side view showing the side table shown in FIG. 1 in a state where the support column (extension device) is extended. FIG. 2 is a perspective view of the side table shown in FIG. 1 as seen from below. FIG. 2 is a perspective view of a modified example of the side table shown in FIG. 1, as viewed from below. 7 is a right side view of the side table shown in FIG. 6. FIG. 7 is a perspective view showing the main components of the side table shown in FIG. 6. FIG. 2 is an exploded perspective view of the extension and retraction device (support) of the side table shown in FIG. 1 . FIG. 2 is an exploded perspective view of the telescopic device shown in FIG. 1, seen from a different angle. FIG. 2 is a cross-sectional view of the extension device shown in FIG. 1 . FIG. 2 is a perspective view showing the arrangement of the main components of the expansion device shown in FIG. 1 . FIG. 2 is a perspective view showing the arrangement of the main components of the expansion device shown in FIG. 1 from a different viewpoint. FIG. 11 is a perspective view of the second block body shown in FIG. 10 . 11A and 11B are cross-sectional views for explaining the operation of the lock ball shown in FIG. 10. FIG. 2 is a partially sectional perspective view for explaining the operation of the extension device shown in FIG. 1 . FIG. 17 is a partial cross-sectional perspective view illustrating the operation of the extension device subsequent to FIG. 16 . FIG. 18 is a partial cross-sectional perspective view illustrating the operation of the extension device subsequent to FIG. 17 . FIG. 19 is a partial cross-sectional perspective view illustrating the operation of the extension device subsequent to FIG. 18 . FIG. 20 is a partial cross-sectional perspective view illustrating the operation of the extension device following FIG. 19 . FIG. 10 is an exploded perspective view of an extension device according to a second embodiment of the present invention. FIG. 22 is an exploded perspective view of the extension device shown in FIG. 21 viewed from a different viewpoint. FIG. 22 is a partial cross-sectional perspective view showing the arrangement of the main components of the telescopic device shown in FIG. 21 . FIG. 22 is a partially sectional perspective view showing the arrangement of the main components of the telescopic device shown in FIG. 21 from a different viewpoint. FIG. 22 is a partial cross-sectional perspective view for explaining the operation of the extension device shown in FIG. 21 . FIG. 26 is a partial cross-sectional perspective view illustrating the operation of the extension device following FIG. 25 . FIG. 27 is a partial cross-sectional perspective view illustrating the operation of the extension device subsequent to FIG. 26 . FIG. 28 is a partial cross-sectional perspective view illustrating the operation of the extension device following FIG. 27 . FIG. 29 is a partial cross-sectional perspective view illustrating the operation of the extension device subsequent to FIG. 28 .

An embodiment of the present invention will be described with reference to the accompanying drawings of FIGS.
The first embodiment is applied to the side table shown in FIGS.
The side table is configured by attaching a table plate 13 to an extension device 11, which is a support pillar erected on a base 10, via a mounting bracket 12 that is approximately rectangular in plan view.

Note that the side table to which the present invention is applicable is not limited to the side table described above. For example, as shown in Figures 6 to 8, a mounting bracket 12 that is circular in plan view may be used; the shape of the mounting bracket is not particularly limited.

As shown in Figures 9 to 11, the extension device 11 is composed of an outer cylinder 20, an inner cylinder 30, a fixing block 40, a lock bar 50, a lock block 60, a spring member 70, a lock ball 90, and a control plate 80.

As shown in Figures 9 to 11, the outer cylinder 20 has a polygonal cross-section that allows the inner cylinder 30, described below, to be slidably accommodated. The outer cylinder 20 has a fixed block 40, described below, fixed to its lower end. The outer cylinder 20 also has a two-part, annular guide cap 24 attached to its upper opening to guide the inner cylinder 30, described below.

As shown in Figures 9 to 11, the inner cylinder 30 has a cross-sectional shape that allows it to slide along the inner surface of the outer cylinder 20, and has anti-slip holes 31 at opposing positions on its lower end.

As shown in Figures 9 to 11, the fixed block 40 has a cross-sectional shape that allows it to be stored within the outer cylindrical body 20. The fixed block 40 also has an insertion groove 41 (see Figure 17) with a roughly Pi-shaped cross section that is provided along its axis and into which the lower end of the lock bar 50 (described below) can be inserted. The insertion groove 41 communicates with a through-hole 42 through which a screw 22 that prevents the lock bar 50 from coming loose can be inserted. The fixed block 40 may also be shaped so that it can be separated into two parts.

As shown in Figures 9 to 11, the lock bar 50 is a rod with a roughly Pi-shaped cross section (see Figure 11), with a first protrusion 51 cut and raised near one end (lower end) for positioning, and a second protrusion 52 cut and raised at the other end (upper end) for positioning. A through hole 53 is provided near one end of the first protrusion 51. Furthermore, engagement holes 54 are provided at a predetermined pitch between the first protrusion 51 and the second protrusion 52. The lock bar 50 may also be, for example, a flat rod with a rectangular cross section.

As shown in Figures 9 to 11, the lock block 60 has an outer circumferential shape that can be stored in the outer cylindrical body 20, and can be separated into a first block body 61 and a second block body 62. The lock block 60 also has a fitting receiving portion 63 on its upper end surface into which the lower end of the inner cylindrical body 30 can be fitted. The fitting receiving portion 63 has anti-detachment protrusions 63a protruding from opposing positions on its inner circumferential surface (Figure 13).

As shown in Figure 11, the first block body 61 has a pair of parallel guide grooves 64, 64 formed on the joint surface with the second block body 62 to guide the lock bar 50 so that it can slide.

14, the second block body 62 has a position restriction recess 65 formed in the axial direction at the center of its joining surface. The position restriction recess 65 is provided on the same straight line so as to communicate the locking region 65a, the loose-fitting region 65b, and the holding region 65c.
15, the locking area 65a has a shallow bottom, and uses a wedge effect to hold the locking ball 90 (shown by dotted lines in FIG. 15) engaged with the engaging hole 54 of the locking bar 50. This restricts the downward sliding movement of the locking block 60, making it possible to adjust the height of the table top 13.
The loose fit area 65b is a spatial area that rotatably holds the lock ball 90. However, since the lock ball 90 is biased toward the lock bar 50 by the elastic arm portion 72 of the spring member 70, no rattle occurs.
As shown in Figure 14, the holding area 65c has spring portions 66 with positioning portions 66a formed on both sides. Therefore, the lock ball 90 engaged with the positioning portions 66a is elastically held by the spring portions 66. This embodiment has the advantage that the lock ball 90 can be accurately positioned at a desired position with high positioning accuracy by engaging with the positioning portion 66a provided on the spring portion 66. Note that the positioning portions 66a are not limited to through holes and may be simple recesses.

As shown in Figure 14, the second block body 62 has a slit 67 formed in it that allows the spring member 70 to be inserted along the bottom surface of the position restriction recess 65 from the lower end surface of the second block body 62 toward the loose fit area 65b. The elastic arms 72, 72 of the spring member 70 press against the lock ball 90, biasing it toward the lock bar 50.

Furthermore, a guide slit 68 is formed in the second block body 62 from the bottom surface of the fitting receiving portion 63a of the second block body 62 toward the holding region 65c and along the bottom surface of the position restriction recess 65. A control plate 80, which will be described later, is fitted into the guide slit 68 so as to be slidable.
Therefore, the lock ball 90 moves and is held in position within the position restricting recess 65 via the spring member 70 and the control plate 80 attached to the second block body 62 .

The spring member 70 is formed by bending a rod-shaped spring material into a substantially U-shape in a plan view and then into a substantially L-shape in a side view, thereby forming an engaging portion 71 and a pair of elastic arm portions 72, 72.
The spring member 70 is press-fitted into the slit 67 provided in the second block body 62, thereby constantly biasing the lock ball 90 toward the lock bar 50. Therefore, the spring member 70 prevents the lock ball 90 from falling out due to its own weight when it engages with the engagement hole 54, so that the lock block 60 can move smoothly.

The control plate 80 is a plate-like body with a substantially Pi-shaped control unit 83 integrally formed between one end 81 and the other end 82, which are positioned on the same straight line. The control unit 83 has a size and shape that allows the lock ball 90 to be housed therein in a rotatable manner.
The control plate 80 has a control section 83 slidably inserted into a guide slit 68 provided in the second block body 62, and slides along the surface of the lock bar 50. One end 81 and the other end 82 of the control plate 80 can alternately protrude from the bottom surface of the fitting receiving section 63 of the lock block 60 and the lower end surface of the lock block 60, respectively.

The lock ball 90 is a sphere and is housed in a position-regulating recess 65 formed in the second block body 62 of the lock block 60, which can be separated into two parts. The lock ball 90 rolls along the surface of the lock bar 50 via the spring member 70 and control plate 80, repeatedly engaging and disengaging with the engagement hole 54.

The assembly procedure for the above-mentioned components will now be described.
First, the spring member 70 is inserted into the slit 67 provided in the second block body 62 of the lock block 60, and then the control plate 80 is inserted into the guide slit 68. The lock ball 90 is then engaged with the positioning portions 66a, 66a of the spring portions 66, 66 located in the holding area 65c of the position restricting recess 65, thereby elastically holding it. The inner cylinder body 30 is then assembled into the fitting receiving portion 63 of the second block body 62, and the retaining projection 63a is engaged with the retaining hole 31. The lock bar 50 is then positioned in the second block body 62, and then the first block body 61 is assembled.

The lower end of the lock bar 50 is then inserted into the insertion groove 41, which has a generally Pi-shaped cross section, of the fixed block 40 for temporary assembly. The inner cylinder 30 and other components are then inserted into the outer cylinder 20 to assemble them, and the fixed block 40 is positioned at the lower end of the outer cylinder 20. Next, a screw 22 is inserted into the through-hole 21 of the outer cylinder 20 and the through-hole 42 of the fixed block 40, and the nut 23 is threaded onto the screw 22 to secure the fixed block 40 to the outer cylinder 20. The assembly process is then completed by attaching a guide cap 24 to the opening at the top end of the outer cylinder 20.

Next, a method for adjusting the height of the table board 13 will be described.
16, when the inner cylinder 30 is pulled down to the lowest end, one end 81 of the control plate 80 abuts against the first protrusion 51 of the lock bar 50 and slides within the guide slit 68, and the lower end surface of the lock block 60 comes closest to the upper end surface of the fixed block 40. As a result, the control plate 80 is pushed up relatively, and the control unit 83 pushes up the lock ball 90 that is elastically held between the spring portions 66, 66. As a result, the lock ball 90 disengages from the holding region 65c and moves from the loose-fit region 65b to the lock region 65a.

As shown in Figure 17, when the inner cylinder body 30 and lock block 60 are pulled up, the lock balls 90 repeatedly engage and disengage with the engagement holes 54, making a clicking sound as they rise.

Next, as shown in Figure 18, for example, the lock block 60 is raised to a height where the lock ball 90 engages with the second-lowest engagement hole 54, and then the lock block 60 is pushed down to apply a downward force. As a result, the lock ball 90 located in the loose fit area 65b engages with the engagement hole 54 and presses against the bottom surface of the lock area 65a of the second block body 62 (see Figure 15). This creates a wedge effect, locking the lock block 60 and restricting its downward movement. As a result, the table top 13 can be held at a predetermined height, allowing height adjustment.

To make a new height adjustment, the inner cylinder 30 is raised to its highest position, as shown in Figure 19. This operation also raises the lock block 60 to its highest position, causing the other end 82 of the control plate 80 to abut against the second protrusion 52 of the lock bar 50. As a result, the control plate 80 slides relatively within the guide slit 68 of the lock block 60, causing one end 81 to protrude from the lower end surface of the lock block 60. At this time, the control unit 83 of the control plate 80 presses the lock ball 90 downward against the spring force of the spring member 70. This causes the lock ball 90 to be pressed downward from the loose-fitting region 65b into the retaining region 65c. As a result, the lock ball 90 engages with the positioning portion 66a of the spring portion 66 and is elastically held between the spring portions 66, 66. Therefore, the lock block 60 enters a released state, allowing the inner cylinder 30 and lock block 60 to move back and forth along the lock bar 50.

Next, by pushing down the inner cylinder 30, one end 81 of the control plate 80 comes into contact with the first protrusion of the lock bar 50 (see Figure 20). Furthermore, by pushing down the lock block 60, the lower end surface of the lock block 60 comes closest to the upper end surface of the fixed block 40, resulting in the same state as shown in Figure 16 above. Thereafter, the height of the table plate 13 can be adjusted by performing the same operations as above.

As shown in Figures 21 to 29, the second embodiment of the present invention is substantially similar to the extension device according to the first embodiment described above, with the major difference being that the control plate has been eliminated. Therefore, the second block body 62 does not have a guide slit for guiding the control plate.

As shown in Figures 21 and 22, the outer cylinder 20 and inner cylinder 30 are both cylindrical bodies with a circular cross section. The fixed block 40 also has a circular cross section, and the rest of the structure is essentially the same as in the first embodiment described above. Therefore, like parts are designated by like numbers and their explanations are omitted.

Next, a method for adjusting the height of the table board 13 according to the second embodiment will be described.
25, when the inner cylinder body 30 is pulled down to the lowest end, the lower end surface of the lock block 60 comes closest to the upper end surface of the fixed block 40. At this time, the lock ball 90, which is elastically held between the spring portions 66, 66, comes into contact with the first protrusion 51 of the lock bar 50 and is pushed up relatively. As a result, the lock ball 90 disengages from the holding region 65c and moves from the loose-fit region 65b to the lock region 65a.

As shown in Figure 26, when the inner cylinder 30 and lock block 60 are pulled up, the lock balls 90 repeatedly engage and disengage with the engagement holes 54, making a clicking sound as they rise.

Next, as shown in Figure 27, for example, the lock block 60 is raised to a height where the lock ball 90 engages with the second-lowest engagement hole 54, and then a downward force is applied to the lock block 60. This operation causes the lock ball 90, located in the loose fit area 65b, to engage with the engagement hole 54 and press against the bottom surface of the lock area 65a of the second block body 62. As a result, the wedge effect locks the lock block 60, restricting its downward movement. As a result, the table top 13 can be held at a predetermined height, allowing height adjustment.

To make a new height adjustment, the inner cylinder 30 is raised to its highest position, as shown in Figure 28. This also raises the lock bar 50 to its highest position. As a result, the lock ball 90 comes into contact with the second protrusion 52 of the lock bar 50 and is pushed down against the spring force of the spring member 70. This causes the lock ball 90 to move from the loose fit region 65b into the retaining region 65c. As a result, the lock ball 90 engages with the positioning portion 66a of the spring portion 66 and is elastically retained between the spring portions 66, 66. This releases the lock block 60, allowing the inner cylinder 30 and lock block 60 to move back and forth along the lock bar 50.

Furthermore, by pushing down the inner cylinder 30 and pushing down the lock block 60, the lock block 60 approaches the fixed block 40, causing the lock ball 90 to abut against the first protrusion 51 (see Figure 29). Next, by bringing the lower end surface of the lock block 60 closest to the upper end surface of the fixed block 40, the same state as shown in Figure 25 above is achieved. Thereafter, the height of the table top 13 can be adjusted by performing the same operations as above.

For the sake of convenience, the above-described embodiment has been described as moving in the vertical direction, but this is not necessarily limited to this. For example, the device can also be used as a position adjustment device that slides the lock block horizontally or diagonally.

In the above embodiment, we have described the application to a side table, but this is not necessarily limited to this. Of course, it can also be applied to, for example, the legs of a chair that requires height adjustment.

10 Base 11 Expansion device (support)
12 Mounting metal fitting 13 Table plate 20 Outer cylinder body 21 Through hole 22 Screw 23 Nut 24 Guide cap 30 Inner cylinder body 31 Anti-slip hole 40 Fixing block 41 Insertion groove 42 Through hole 50 Lock bar 51 First protrusion 52 Second protrusion 53 Through hole 54 Engagement hole 60 Lock block 61 First block body 62 Second block body 63 Fitting receiving portion 63a Anti-slip protrusion 64 Guide groove 65 Position regulating recess 65a Lock area 65b Loose fit area 65c Holding area 66 Spring portion 66a Positioning portion 67 Slit 68 Guide slit 70 Spring member 71 Engagement portion 72 Elastic arm portion 80 Control plate 81 One end portion 82 Other end portion 83 Control unit 90 Lock ball

Claims (4)

An outer cylinder body 20;
an inner cylindrical body 30 that is inserted into the outer cylindrical body 20 and is slidable along the longitudinal direction;
a lock bar (50) having a first protrusion (51) at one end and a second protrusion (52) at the other end, with engagement holes (54) provided at a predetermined pitch between the first protrusion (51) and the second protrusion (52), the lock bar (50) being housed within the outer cylindrical body (20) and fixed to the outer cylindrical body (20) so as not to be displaced in the longitudinal direction;
a lock block 60 having a cross-sectional area that allows it to slide within the outer cylinder 20, and that can be divided into a first block body 61 and a second block body 62, the first block body 61 having a guide groove 64 for guiding the lock bar 50 on its mating surface, and the second block body 62 having a position regulating recess 65 on its mating surface, and that is slidably attached to the lock bar 50;
a spring member 70 assembled in the position regulating recess 65 of the second block body 62;
a lock ball (90) having a diameter that allows it to be engaged with and disengaged from the engagement hole (54) of the lock bar (50), housed in the position regulating recess (65) of the second block body (62), and biased toward the lock bar (50) by the spring member (70);
When the lock block 60 is pulled down to the lowest position, the lock ball 90 is locked in the lock area 65 a of the position restriction recess 65 via the first protrusion 51 of the lock bar 50,
When the lock block 60 is pulled up to a predetermined position and then pushed down, the lock ball 90 is clamped between the engagement hole 54 of the lock bar 50 and the bottom surface of the lock area 65 a in the position restriction recess 65, and the lock block 60 is locked by a wedge effect.
An extension device characterized in that when the lock block 60 is raised to the highest position, the lock ball 90 is elastically held in the holding area 65c within the position control recess 65 via the second protrusion 52 of the lock bar 50. An outer cylinder body 20;
an inner cylindrical body 30 that is inserted into the outer cylindrical body 20 and is slidable along the longitudinal direction;
a lock bar (50) having a first protrusion (51) at one end and a second protrusion (52) at the other end, with engagement holes (54) provided at a predetermined pitch between the first protrusion (51) and the second protrusion (52), the lock bar (50) being housed within the outer cylindrical body (20) and fixed to the outer cylindrical body (20) so as not to be displaced in the longitudinal direction;
a lock block 60 having a cross-sectional area that allows it to slide within the outer cylinder 20, and that can be divided into a first block body 61 and a second block body 62, the first block body 61 having a guide groove 64 for guiding the lock bar 50 on its mating surface, and the second block body 62 having a position regulating recess 65 on its mating surface, and that is slidably attached to the lock bar 50;
a spring member 70 assembled in the position regulating recess 65 of the second block body 62;
a lock ball (90) having a diameter that allows it to be engaged with and disengaged from the engagement hole (54) of the lock bar (50), housed in the position regulating recess (65) of the second block body (62), and biased toward the lock bar (50) by the spring member (70);
When the lock block 60 is lowered to the lowest position, the lock ball 90 is locked in the lock area 65 a of the position restriction recess 65 via the control plate 80 whose one end 81 abuts against the first protrusion 51 of the lock bar 50,
When the lock block 60 is pulled up to a predetermined position and then pushed down, the lock ball 90 is clamped between the engagement hole 54 of the lock bar 50 and the bottom surface of the lock area 65 a in the position restriction recess 65, and the lock block 60 is locked by a wedge effect.
An extension device characterized in that, when the lock block 60 is raised to the highest position, the lock ball 90 is elastically held in the holding area 65c within the position control recess 65 via the control plate 80, whose other end 82 abuts against the second protrusion 52 of the lock bar 50. The telescopic device described in claim 1 or 2, characterized in that the lock ball 90 is elastically held by a pair of spring portions 66, 66 arranged opposite each other in the holding area 65c. The telescopic device described in claim 3, characterized in that positioning portions 66a, 66a with which the lock ball 90 can engage and disengage are provided at opposing positions on the pair of spring portions 66, 66.