JP6364341B2 - Power lift equipment - Google Patents

Description

  The present invention relates to a power lift device used when changing the conveyance direction of an article on a conveyance line or the like.

  In the article transfer line, when changing the transfer direction of a transfer object to a right angle, the electric lift that receives the transfer object in the transfer direction, lowers the transfer object as it is, and places it on another transfer line arranged in a direction perpendicular to the transfer direction. A device is used.

  For example, in Patent Document 1, a lift arm is interposed between a base and a table supported by raising and lowering the base, and the lift arm is rotated by an electric motor to raise and lower the table. Discloses an electric lift device that is arranged on both sides of the electric motor and is rotated by power transmission means arranged symmetrically on both sides of the output shaft of the electric motor.

  In this electric lift device, when the weight of the transported object placed on the table increases, the overhang load applied to the shaft of the electric motor also increases, which reduces the durability of the electric motor. It has been conceived to solve the problem.

  In Patent Document 1, as a solution to this problem, a lift arm that lifts the table is arranged on both sides of the electric motor, and a chain of lift arms on both sides is engaged with the rotating shaft of the electric motor (power transmission means), thereby Cancel the overhang load on the rotating shaft of the motor.

Japanese Patent Laid-Open No. 10-182084

  In the power lift device, a dedicated conveyor is placed on a table, and a conveyed product is placed thereon. Therefore, a large load may be applied. Therefore, the power lift device is required to have the ability to raise and lower a large load.

  Moreover, when incorporating in a conveyance line, it is calculated | required that the lift height of a table becomes free. However, in the power lift device of Patent Document 1, the lift arm of the table must be replaced with a lift arm. Therefore, in order to adjust the lift height of the table, it is necessary to have a plurality of lift arms as replacement parts.

  Further, in configuring the transfer line, the power lift device itself is desired to be reduced in weight. Therefore, the ability to raise and lower a large load with a small driving device is required.

  In addition, even when there is an overload when the transported object is placed on the table, the transported object may be damaged if the table is rapidly lowered. Therefore, the power lift device needs a mechanism for preventing the table from dropping when an overload is applied.

  The present invention has been conceived in view of such problems, and provides a power lift device having a heavy lifting load even if it is lightweight.

Specifically, the power lift device according to the present invention is:
A base 10 and a lifting table 12 disposed above the base 10;
An upper fixed end 21u and a lower fixed end 21d are provided in the vertical direction of the base 10, and an upper link bar 22u pivotally supported by the upper fixed end 21u and a lower link pivotally supported by the lower fixed end 21d. A pair of four-bar links 20 composed of a bar 22d and a connecting link bar 23 that connects the upper link bar 22u and the lower link bar 22d;
A connecting bar 26 for connecting the connecting link bars 23 of the pair of four-bar links 20;
A push-up roller 25 provided on the upper link bar 22u side of the connection link bar 23 and in contact with the back surface 12b of the lifting table 12,
The lifting table 12 is provided with one fixed end (table fixing end 32), the base 10 is provided with the other fixed end (base fixing end 31), and the back surface of the lifting table 12 at two free ends. A table support roller 33 that contacts 12b and a base support roller 34 that contacts the surface of the base 10
A pair of X links 30 in which are arranged,
An oscillating end bracket 43 provided on the bottom lid portion 42 of the main body 41 is pivotally supported on the base 10, and the distal end of the shaft 61 is pivotally supported on the connecting bar 26 of the four-bar link 20. It is characterized by having.

  In the power lift device according to the present invention, the lifting / lowering table is moved up and down by pushing up the connecting link bar of the four-bar link fixed to the base by the expansion / contraction device (drive cylinder or the like). Even with a slight pressure, a large lifting force can be generated.

  Further, the lift height of the lifting table can be adjusted only by adjusting the extension controller attached to the drive cylinder. Therefore, no other parts are required to adjust the lift height of the lifting table.

  Moreover, since it is comprised with a drive cylinder, it can comprise in light weight compared with an electric motor. In addition, by using a drive cylinder with a stopper, there is no accident that the lifting table is rapidly lowered and the conveyed item falls from the conveying line even when the conveyed item is heavy.

It is a front view which shows the form (FIG.1 (a)) which the raising / lowering table of the power lift apparatus which concerns on this invention went up, and the form (FIG.1 (b)) which lowered. It is the front view and side view of a power lift device concerning the present invention. It is an enlarged view near the raising / lowering table of a power lift apparatus. It is an enlarged view of a drive cylinder. It is a figure which shows the structure of a single lever hinge mechanism. It is a figure explaining operation | movement of a four-section link. It is a figure which shows the other form of a power lift apparatus.

  A power lift device according to the present invention will be described below with reference to the drawings. Note that the following description exemplifies an embodiment of the present invention, and the present invention can be modified without departing from the gist of the present invention.

  FIG. 1 shows the configuration of a power lift device according to the present invention. FIG. 1A is a front view of the power lift device when the lifting table is raised, and FIG. 1B is a front view when the lifting table is lowered. Moreover, Fig.2 (a) is a front view of the power lift apparatus at the time of the same raising / lowering table as FIG.1 (a) raising, FIG.2 (b) is the side view.

  Referring to FIG. 2, the power lift device 1 according to the present invention includes a base 10, a lifting table 12, a pair of four-bar links 20, a push-up roller 25, a pair of X links 30, and a drive cylinder 40. Have. Further, the piston 45 (see FIG. 4) is extended to the drive cylinder 40 by sending drive air, and the expansion and contraction operation of the piston 45 is fixed by the braking force of the cylinder built-in spring by sending brake air. That is, the drive cylinder 40 with a stopper is used. The driving air and the braking air are controlled by a control device that controls the operation of the transport line.

  The base 10 has a substantially rectangular plate shape in plan view and supports the entire power lift device 1. The base 10 may be square. Here, it is assumed to be a rectangle for explanation. The lower surface 10b of the base 10 is preferably formed in a plane. The entire surface of the base 10 is not plate-shaped and may be cut out. However, it is preferable that the peripheral side has a width that can ensure sufficient strength.

  Further, the base 10 may be provided with an edge 10a perpendicular to the lower surface 10b. This is for securing the strength of the base 10 itself and for fixing the X link 30 and the like to be described later.

  On the base 10, a four-bar link 20, an X link 30, and a drive cylinder 40 are pivotally supported. Therefore, you may provide the bracket 11 for pivots. The pivot support bracket 11 may also be used as the edge 10 a of the base 10. Here, for the sake of explanation, it is assumed that a pivot bracket 11 is provided. That is, the pivot bracket 11 may be formed integrally with the base 10.

  The pivot support bracket 11 is provided on the opposite long side (reference numeral 3 in this case) on one short side of the base 10. Further, the pivot support bracket 11 provided on one long side is referred to as a pivot support bracket 11a, and the pivot support bracket 11 provided on the other long side is referred to as a pivot support bracket 11b (see FIG. 2B). Here, an example is shown in which the four-bar link 20 is pivotally supported on the pivot bracket 11 and the X link 30 is pivotally supported on the edge 10 a of the base 10.

  A four-bar link 20 is provided along the long side of the base 10. One long-side four-bar link 20 is a four-bar link 20a, and the other long-side four-bar link 20 is a four-bar link 20b. Hereinafter, when calling collectively, it calls the four-bar link 20. A pair of four-bar links 20 is provided like one four-bar link 20a and the other four-bar link 20b (see FIG. 2B).

  The fixed end 21 of the four-bar link 20 is provided on the pivot bracket 11 of the base 10. The fixed end 21 is juxtaposed side by side with the pivot support bracket 11. The fixed end 21 closer to the base 10 is referred to as a lower fixed end 21d, and the fixed end 21 far from the base 10 is referred to as an upper fixed end 21u.

  The lower link bar 22d is rotatably connected to the lower fixed end 21d, and the upper link bar 22u is rotatably connected to the upper fixed end 21u. The upper link bar 22u is slightly shorter than the lower link bar 22d. As will be described later, the upper link bar 22u is shorter than the lower link bar 22d, which is a feature of the power lift device 1 of the present invention.

  A connecting link bar 23 is rotatably connected to the free end sides of the upper link bar 22u and the lower link bar 22d. A connection point where the connection link bar 23 and the lower link bar 22d are connected is a lower joint 24d, and a connection point where the connection link bar 23 and the upper link bar 22u are connected is an upper joint 24u.

  Accordingly, the four-bar link 20 includes the pivot support bracket 11, the lower link bar 22 d, the upper link bar 22 u, and the connection link bar 23.

  A push-up roller 25 is provided on the upper link bar 22 u side of the connection link bar 23. The push-up roller 25 is in contact with the back surface 12 b of the lifting table 12. Therefore, the push-up roller 25 may be provided anywhere as long as the four-bar link 20 moves and is always in contact with the back surface 12b of the lifting table 12.

  For example, FIG. 2A shows a case where the upper joint 24u is provided coaxially. However, the push-up roller 25 may be provided at a location where the upper link bar 22u extends outward from the upper joint 24u. Further, the push-up roller 25 may be provided at a location where the connecting link bar 23 extends outward from the upper joint 24u.

  Referring to FIG. 2B, the four-bar link 20a and the four-bar link 20b are connected by a connecting bar 26 that connects each other. The connection bar 26 connects the connection link bars 23a and 23b and the upper link bars 22ua and 22ub to each other. You may provide coaxially with the axial center of mutual push-up roller 25a, 25b. By driving the connecting bar 26, the four-bar link 20a and the four-bar link 20b perform the same movement. The connection bar 26 is preferably provided coaxially with or near the upper joint 24u of the connection link bar 23 (a portion closer to the upper joint 24u than half of the connection link bar 23).

  Referring to FIG. 2A again, an X link 30 is provided in parallel with the four-bar link 20. As for X link 30, one fixed end (base fixed end 31) is provided in the edge 10a of the base 10, and the other fixed end (table fixed end 32) is provided in the raising / lowering table 12. FIG. Link bars 37 and 38 having the same length are pivotally supported at the respective fixed ends. The link bars 37 and 38 are connected by a pivot 36 in the middle.

  A table support roller 33 is provided at the free end of the link bar 37 that is pivotally supported by the base fixed end 31. A base support roller 34 is provided at the free end of the link bar 38 pivotally supported by the table fixed end 32.

  The table support roller 33 is always in contact with the back surface 12 b of the lifting table 12, and the base support roller 34 is always in contact with the top surface of the base 10. The X link 30 also has a pair of base fixing ends 31 on the edge 10a of the base 10 provided on the long sides facing each other. FIG. 2B shows an X link 30a and an X link 30b.

  In FIG. 3, the figure which expanded the upper part of FIG.2 (b) is shown. FIG. 3 shows the elevating table 12, table support rollers 33a and 33b, and push-up rollers 25a and 25b. The table support rollers 33a and 33b and the push-up rollers 25a and 25b are provided with guides so as not to be separated from the back surface 12b of the elevating table 12.

  The guide is provided with support roller guides 15a and 15b for guiding the table support rollers 33a and 33b and push-up roller guides 16a and 16b for guiding the push-up rollers 25a and 25b. These guides may be formed integrally. FIG. 3 illustrates a guide in which the support roller guide 15a and the push-up roller guide 16a and the support roller guide 15b and the push-up roller guide 16b are integrally formed, respectively. Of course, they may be provided separately.

  The support roller guide 15 sandwiches the table support roller 33 between the back surface 12 b of the elevating table 12 and the surface of the support roller guide 15. Further, the push-up roller guide 16 sandwiches the push-up roller 25 between the back surface 12 b of the lifting table 12 and the surface of the push-up roller guide 16. Therefore, when the lifting table 12 is moved up and down by the push-up roller 25, the table support roller 33 is also moved by the movement of the lifting table 12.

  Due to the presence of this guide, the table support roller 33 and the push-up roller 25 operate together with the lifting table 12.

  FIG. 4 shows an enlarged view of the drive cylinder 40. FIG. 4A shows a case where the piston 45 is extended, and FIG. 4B shows a case where the piston 45 is contracted. The piston 45 extends in the drive cylinder 40 when fluid is supplied. At one end of the main body 41, a bottom cover portion 42 is provided to separate the outside and the inside in an airtight manner. The bottom cover part 42 is provided with a swing end bracket 43. The swing end bracket 43 is provided with a pivotal through hole 43h. A so-called cylinder clevis type may be used.

  Further, the drive cylinder 40 is preferably provided with a stopper inside. The internal stopper fixes the movement of the piston 45 by an external control device or the like, and also fixes the movement of the piston 45 when the supplied air pressure drops or the supplied power supply voltage drops. What to do is desirable.

  The upper lid portion 44 is provided with a through hole 44h into which the piston 45 is inserted and a flange 44f in which an extension controller 47 is provided. A tip block 46 is fixed to the tip of the piston 45. A restriction rod 47 a of an extension controller 47 is also fixed to the distal end block 46.

  The restriction rod 47a is inserted through a through hole 44fh provided in the flange 44f, and a restriction nut 47b is fixed on the side opposite to the tip block 46. Therefore, the piston 45 extends only until the restriction nut 47b fixed to the restriction rod 47a comes into contact with the flange 44f. The extension controller 47 may not have the above-described configuration as long as the extension length of the piston 45 can be regulated to a certain length.

  A coupling hole 46 h is formed in the tip block 46. The coupling hole 46h is pivotally supported by the connecting bar 26 (see FIG. 2B). Further, the swing end bracket 43 of the bottom cover part 42 is rotatable to the telescopic device bracket 17 fixed to the bracket connection bar 13 (see FIG. 2B) for connecting the pivot support brackets 11a and 11b. Connected (pivot).

  The drive cylinder 40 and the tip block 46 push up the upper joint 24 u of the four-bar link 20, but may not be the drive cylinder 40 as long as the entire length expands and contracts. In that sense, more generally, the drive cylinder 40 may be provided with a telescopic device 60 that can push up the upper joint 24u (the connection bar 26 connecting the connection link bars 23).

  The telescopic device 60 is provided with a swing end bracket 43 on the bottom lid portion 42 and a tip block 46 at the tip of a shaft 61 that extends. The drive cylinder 40 corresponds to the telescopic device 60, and the shaft 61 corresponds to the piston 45 (see FIG. 1). When the telescopic device 60 is the drive cylinder 40 described above, the tip of the piston 45 (shaft 61) is pivotally supported by the connecting bar 26 of the four-bar link 20 although the tip block 46 is interposed. May be.

  The operation of the power lift device 1 configured as described above will be described. The structure of the single lever hinge mechanism will be described with reference to FIG. A roller 81 that rolls on the surface G <b> 1 is pivotally supported at one end 80 a of the lever 80. The other end 80b is pivotally supported by one end 82a of the lever 82 so as to be rotatable. The lever 82 is fixed at a fulcrum 83 so as to be swingable. The other end 82b of the lever 82 presses the workpiece 84, for example. It is assumed that a force Q is applied to the support shaft of the roller 81 in parallel with the surface and the whole is balanced.

  The lever N pushes up one end of the lever 82, and the reaction force N received from the surface G1 as a reaction force acts as a force R in the direction of the lever 80 together with the force Q. When this force R is divided in the vertical direction at the other end 80b of the lever 80, it can be decomposed into an upward force W (same as the drag N) and a force Q parallel to the surface. This can be regarded as a force for lifting the other end 80b of the lever 80.

  Further, when the angle between the perpendicular and the force R is α, the upward force W is expressed as Q / tnaα. That is, when α is small, the upward force W is larger than the force Q. For example, if α is 26.5 degrees or less, the upward force W becomes twice or more the force Q. As α becomes smaller, the upward force W ideally increases to infinity.

  Thus, the single lever hinge mechanism can obtain a large upward force W with a small force Q.

  FIG. 6 shows a schematic diagram of the four-bar link 20. 6A shows an initial state, and FIG. 6B shows a state in which the lower link bar 22d is inclined with respect to the horizontal line L by an angle φ and the upper joint 24u is raised. As described above, the four-bar link 20 includes the pivot support bracket 11, the lower link bar 22 d, the upper link bar 22 u, and the connection link bar 23. Of these, the pivot bracket 11 is fixed. The pivot bracket 11 is considered as a link bar between the upper fixed end 21u and the lower fixed end 21d.

  The upper link bar 22u is shorter than the lower link bar 22d. As a result, the connecting link bar 23 is longer than the length of the pivot support bracket 11 (the distance between the upper fixed end 21u and the lower fixed end 21d). Preferably, the upper link bar 22u and the lower link bar 22d are set to be substantially parallel, and the pivot bracket 11 is set to be perpendicular to the upper link bar 22u and the lower link bar 22d. The Therefore, the four-bar link 20 has a trapezoidal shape.

  Here, the connecting link bar 23 is seen as the lever 80 in FIG. 5, and the lower link bar 22d is seen as the lever 82 in FIG. Then, it is assumed that a force Q is applied to the upper joint 21u from the lower fixed end 21d toward the upper joint 21u. The direction of the force Q is represented by a one-dot chain line LineQ. Although FIG. 6 is not a single lever hinge mechanism, the connecting link lever 23 cannot move in the same manner as the lever 80 in FIG. 5, and therefore, the connecting link lever 23 has a drag force in its length direction (the drag axis direction DN). N4 is generated.

  The drag N4 generates a force for lifting the upper joint 24u. Here, the force lifted in the vertical direction is defined as a vertical force F. The vertical force F is defined as QM / tan θ from the component force QM of the force Q in the horizontal direction when the angle between the connecting link bar 23 and the vertical axis H is θ and the horizontal direction (Line L in the figure). Is required. In other words, it can be said that the vertical force F is obtained as a combined component of the horizontal component QM of the force Q and the drag N.

  This means that a large upward force F can be obtained in the vertical direction even with a relatively small force QM, as described with reference to FIG. Further, since the upper fixed end 21u and the lower fixed end 21d of the four-bar link 20 are fixed, the upper joint 24u is raised by the upward force F.

  In the initial state (FIG. 6A), the upper link bar 22u and the lower link bar 22d are parallel to each other, and the pivot bracket 11 is set at a right angle to the upper link bar 22u and the lower link bar 22d. Then, by keeping the upper link bar 22u shorter than the lower link bar 22d, the angle θ formed by the connecting link bar 23 and the perpendicular does not change much even when the upper joint 24u rises. Therefore, even if the elevating table 12 is raised, the upward force F can continue to rise without largely changing.

  FIG. 6B shows a state where the upper joint 24u is raised. The magnitude of the force Q is the same as in the case of FIG. The angle θ1 formed by the drag axis direction DN and the perpendicular H does not change abruptly from θ in FIG. Therefore, the upward force F is not rapidly attenuated as the lifting table 12 is raised.

  As described above, when a force is applied to the upper joint 24u from the direction of the lower fixed end 21d, a vertical upward force and a horizontal force are applied to the upper joint 24u, and a large upward force F is generated. Therefore, the tip of the shaft 61 of the telescopic device 60 may not be connected to the upper joint 24u as long as horizontal and vertical forces can be applied to the upper joint 24u. That is, as long as it is around the upper joint 24u, the connecting link bar 23 may be connected to the upper link bar 22u.

  Reference is again made to FIG. When drive air is not supplied to the drive cylinder 40, the lifting table 12 is in the lowest lowered position.

  Next, when driving air is injected into the driving cylinder 40, the piston 45 of the driving cylinder 40 extends. At this time, the drive cylinder 40 extends between the lower fixed end 21d of the four-bar link 20 and the upper joint 24u. Then, the push-up roller 25 pivotally supported by the upper joint 24u of the four-bar link 20 rises. At this time, the push-up roller 25 rotates while lifting the back surface 12b of the lift table 12, and moves in the direction in which the pivot support bracket 11 is disposed. Further, since the table support roller 33 is regulated by the support roller guide 15a (see FIG. 3), the X link 30 also extends upward following the ascent of the elevating table 12.

  Since the driving cylinder 40 has a force acting in the direction of extending the diagonal line of the four-bar link 20, it continuously generates a toggle press. This doubles the pressing pressure of the drive cylinder 40. Thus, the power lift device 1 according to the present invention produces a large rising pressure even with a small force. In other words, even heavy transported items can be lifted.

  The rising height of the elevating table 12 is regulated by the extension controller 47. That is, the lifting table 12 does not become higher than the expansion of the piston 45 of the extension controller 47 is restricted (see FIG. 4).

  Next, a case where the lifting table 12 is raised will be described. When a heavy load is loaded on the lifting table 12, the control device that controls the transfer line first supplies braking air to the control air inlet (not shown) of the main body 41 of the drive cylinder 40 in order to operate the stopper. ). Then, a stopper (not shown) in the drive cylinder 40 works and the piston 45 is locked. Therefore, even if the conveyed product is heavy, the lifting table 12 is rapidly lowered, and the conveyed product does not fall from the lifting table 12.

  On the other hand, when the braking air As is gradually removed, the elevating table 12 is gradually lowered. Thus, the power lift device 1 according to the present invention generates a large rising pressure by doubling the piston 45 extension pressure of the drive cylinder 40 by the toggle action.

  Moreover, since it is comprised by the drive cylinder 40 and a link structure, it can comprise lightweight as a total weight. Further, by using the stopper-equipped drive cylinder 40, the lifting table 12 does not rapidly descend even when a heavy load is applied.

  FIG. 7 illustrates another configuration of the power lift device according to the present invention. In the power lift device 2, a motor 48, a box-type screw nut 49, and a screw shaft 50 are used instead of the drive cylinder 40. The box type screw nut 49 is connected to the rotating shaft of the motor 48. Further, one end of the screw shaft 50 is screwed into the box-type screw nut 49, and the other end is rotatably connected to the tip block 46. The tip block 46 is rotatably connected to the connecting bar 26.

  Like the drive cylinder 40, the motor 48 is provided with a swing end bracket 43 on the bottom cover portion 42 of the main body. Therefore, the swing end bracket 43 is pivotally supported on the base 10.

  When the motor 48 rotates, the screw shaft 50 rotates the box-type screw nut 49 and the screw shaft 50 is fed out. Then, the drawn-out screw shaft 50 pushes up the connecting bar 26 via the tip block 46. As a result, for the same reason as the power lift device 1, the lifting table 12 is lifted upward.

  In the case of using the stretching device as described above, devices such as an internal stopper and the stretching controller 47 are not necessary. The combination of the motor 48, the box-type screw nut 49, and the screw shaft 50 does not move even if a force is applied in the direction in which the screw shaft 50 is contracted. Further, the expansion / contraction amount (feeding amount) of the screw shaft 50 can be easily controlled by the number of rotations of the motor 48.

  The motor 48, the box-type screw nut 49, and the screw shaft 50 correspond to the expansion / contraction device 60. Further, the screw shaft 50 corresponds to the shaft 61. Although the tip block 46 is interposed, it can be said that the tip of the screw shaft 50 is rotatably connected (pivotally supported) to the connecting bar 26.

  The power lift device according to the present invention can be suitably used in a transfer line where the transfer direction of a transfer object is changed by 90 degrees.

DESCRIPTION OF SYMBOLS 1 Power lift apparatus 10 Base 10a Edge 10b Bottom surface 11 of base 10, 11, 11a, 11b Pivoting bracket 12 Lifting table 12b Back surface 13 Bracket connection bar 15 Support roller guide 16 Push-up roller guide 17 Telescopic device bracket 20 Four joint link 21 fixed end 21d lower fixed end 21u upper fixed end 22d lower link bar 22u upper link bar 23 connection link bar 24d lower joint 24u upper joint 25 push-up roller 26 connection bar 30 X link 31 base fixed end 32 table fixed end 33 Table support roller 34 Base support roller 36 Axis 37, 38 Link bar 40 Drive cylinder 41 Main body 42 Bottom cover 43 Swing end bracket 43h Through hole 44 Upper cover 44h Through hole 45 Piston 44f Flange 44f h Through-hole 47 Extension controller 47a Restriction rod 47b Restriction nut 46 End block 46h Connection hole 48 Motor 49 Box-type screw nut 50 Screw shaft 60 Telescopic device 61 Shaft

Claims (7)

The base ,
A lifting table disposed above the base;
An upper fixed end and a lower fixed end are provided in the vertical direction of the base, an upper link bar pivotally supported by the upper fixed end, a lower link bar pivotally supported by the lower fixed end, and the upper link A pair of four-bar links composed of a link bar connecting the bar and the lower link bar;
A connecting bar that connects the connecting link bars of the pair of four-bar links;
A push-up roller that is provided on the upper link bar side of the connection link bar and that contacts the back surface of the lifting table;
One fixed end (table fixed end) is provided on the lift table, the other fixed end (base fixed end) is provided on the base, and two free ends are in contact with the back surface of the lift table. A pair of X links in which a roller and a base support roller in contact with the surface of the base are disposed;
A swinging end bracket provided on the bottom cover of the main body is pivotally supported on the base, and a shaft has a telescopic device pivotally supported on the connecting bar of the four-bar link. Lift device.   The power lift device according to claim 1, wherein the upper link bar is shorter than the lower link bar. On the back of the lifting table,
A support roller guide for guiding the table support roller;
The power lift device according to claim 1, further comprising a push-up roller guide for guiding the push-up roller.   The power lift device according to any one of claims 1 to 3, wherein the expansion and contraction device includes a motor, a box-type screw nut, and a screw shaft. The power lift device according to any one of claims 1 to 3, wherein the telescopic device is a drive cylinder having a piston . When the drive cylinder which force is applied in the direction in which the piston retracts, the power lift device according to claim 5, characterized in that it comprises a stopper for stopping the movement of the piston.   The power lift device according to any one of claims 5 and 6, wherein the drive cylinder is provided with an extension controller of the piston.