WO2018194017A1

WO2018194017A1 - Gripping device

Info

Publication number: WO2018194017A1
Application number: PCT/JP2018/015680
Authority: WO
Inventors: 真樹瀧口
Original assignee: Ｋｙｂ株式会社
Priority date: 2017-04-19
Filing date: 2018-04-16
Publication date: 2018-10-25
Also published as: JP2018176382A; JP6868452B2

Abstract

The purpose of the present invention is to efficiently perform alignment while ensuring piston assembly quality. A gripping device (1) is provided with an upper pressing member (11) for pressing the upper part (23B) of a piston assembly (23) and a lower pressing member (13) for pressing the lower part (23C) of the piston assembly (23). The gripping device (1) is provided with a centering shaft (29) that can expand and contract in the vertical direction. The centering shaft (29) is inserted in a hole (25A) of the piston (25). The piston assembly (23) is clamped between the upper pressing member (11) and the lower pressing member (13).

Description

Gripping device

The present invention relates to a gripping device.

2. Description of the Related Art Conventionally, a workpiece gripping device for gripping a workpiece (workpiece) in order to transfer a columnar workpiece to a desired position is known (see, for example, Patent Document 1). In this apparatus, the outer peripheral surface of a columnar workpiece is sandwiched and gripped from both the left and right sides.

JP 2011-25377 A

However, the conventional gripping device cannot efficiently center each steel member of the piston assembly while ensuring the quality of the piston assembly.
The piston assembly is a part of a component constituting a shock absorber attached to a vehicle or the like. Generally, the shock absorber is a cylinder attached to the wheel side and filled with hydraulic oil, a rod attached to the vehicle body side and reciprocally inserted into the cylinder, and a piston assembly attached to the rod. In the piston assembly, the piston divides the inside of the cylinder into a compression side chamber and an extension side chamber and slides relative to the cylinder. The piston is provided with a damping force adjusting unit that adjusts the damping force, and the hydraulic oil in the cylinder flows from one of the compression side chamber and the extension side chamber to the other through the damping force adjusting unit of the piston, Attenuates the force generated when the shock absorber contracts or expands. When a scratch is generated on the sliding surface of the piston, the compression side chamber or the extension side chamber flows in through the scratch, so that the amount flowing in through the damping force adjusting unit decreases. Therefore, a desired damping force may not be generated.
In order to avoid scratches on the sliding surface of the piston, it is required not to grip the sliding surface, but this cannot be realized with a conventional gripping device.

The present invention has been made in view of the above-described conventional situation, and an object to be solved is to perform positioning efficiently while ensuring the quality of the piston assembly.

The gripping device of the present invention includes a piston having a hole in the central axis, an outer peripheral portion, an upper pressing member that holds an upper portion of the piston assembly having an upper portion and a lower portion with the outer peripheral portion as a side portion, and a lower portion of the piston assembly. A lower pressing member for pressing, and a centering shaft that protrudes downward from the lower end of the upper pressing member, is reciprocable in the vertical direction, and is inserted into the hole of the piston. In addition, at least one of the upper pressing member and the lower pressing member can be reciprocated in the vertical direction, and the centering shaft is connected to the piston while the upper pressing member and the lower pressing member are relatively close to each other to sandwich the piston assembly. It is inserted into the hole.

This gripping device grips the piston assembly while the piston assembly is sandwiched between the upper pressing member and the lower pressing member. Thus, since it does not contact the outer peripheral part of a piston assembly in the case of a holding | grip, the quality of a piston assembly can be ensured. Further, since the centering shaft is inserted into the hole of the central axis of the piston, the centering of the piston assembly can be performed.

The piston assembly is provided with a nut at the top, and the upper pressing member is formed with a socket-shaped portion on the surface facing the nut, and the upper pressing member can reciprocate in the vertical direction. It can be set as a certain aspect. The upper pressing member is biased toward the lower pressing member. When the upper pressing member and the lower pressing member are relatively close to each other and sandwich the piston assembly, the nut and the socket-shaped portion may be fitted. preferable.
In this gripping device, the piston can be assembled by tightening the nut with the socket-shaped portion of the upper pressing member. And when tightening a nut, the upper part of a nut is fitted by the socket shape part, and the inclination of a nut is suppressed. That is, initial tightening can be performed while keeping the nut level.

The lower pressing member may have a plurality of claws that are close to and away from the centering shaft in the radial direction of the centering shaft. The plurality of claws are preferably close to the centering shaft when the upper pressing member and the lower pressing member are relatively close to each other and sandwich the piston assembly.
In this case, the piston assembly can be firmly held as compared with the case where the lower pressing member has one claw. That is, when the lower pressing member has one claw, the weight of the piston assembly is applied to one claw, and the claw may hang down and the piston assembly may tilt. When the piston assembly has a plurality of claws accessible from the periphery of the centering shaft, the weight of the piston assembly can be distributed by the plurality of claws, so that the piston assembly can be maintained in a more stable posture.

The centering shaft can be detachable from the gripping device. The centering shaft can be replaced according to the type of piston.

The upper pressing member having the socket-shaped portion may be detachable. By exchanging the upper pressing member according to the type of the nut, it can be applied to assembly of a wide range of pistons.

It is a side view which shows the holding apparatus of Embodiment 1. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is sectional drawing which shows the holding | gripping apparatus of Embodiment 1. FIG. It is a fragmentary perspective view which shows the holding | gripping apparatus of Embodiment 1. FIG.

Embodiment 1 that embodies the gripping device of the present invention will be described with reference to the drawings.

<Embodiment 1>
(Configuration of the apparatus of the embodiment)
As shown in FIGS. 1, 2, and 5, the gripping device 1 according to the first embodiment includes an upper pressing member 11 that presses the upper portion 23 B of the piston assembly 23, a lower pressing member 13 that presses the lower portion 23 C of the piston assembly 23, And a centering shaft 29. The piston assembly 23 includes a piston 25, and has an outer peripheral portion 23A, and an upper portion 23B and a lower portion 23C having the outer peripheral portion 23A as side portions. The gripping device 1 according to the first embodiment can be moved back and forth, left and right and up and down by a robot (not shown).

Specifically, the gripping device 1 includes a base body part 5 and a gripping part 7 positioned below the base body part 5. The gripping part 7 includes an upper pressing member 11 and a lower pressing member 13. The grip portion 7 is rotatable with respect to the base portion 5 by an electric actuator 36. By this rotation, the nut 17 which will be described later is tightened.
The electric actuator 36 includes a disk part 36A and a flange part 36B disposed below the disk part 36A. The flange portion 36B is fixed to the upper portion of the grip portion 7. A pinion (not shown) fixed to the shaft of a motor (not shown) of the electric actuator 36 meshes with a large gear (not shown) on the flange portion 36B side. When the motor of the electric actuator 36 rotates, the flange portion 36 B rotates integrally with the grip portion 7.
The gripping portion 7 includes a floating shaft 19, an upper pressing member 11 having a socket-shaped portion 21 formed thereon, a lower pressing member 13, and a cylinder 39 as constituent elements.
The upper pressing member 11 includes a socket-shaped portion 21 and a ball plunger 37 as components.

An upper presser member 11 is provided in the approximate center of the grip portion 7. The upper pressing member 11 has a substantially cylindrical shape as a whole. The upper part of the upper pressing member 11 is fitted to the floating shaft 19. The upper pressing member 11 is urged downward by a spring S 2 disposed above the floating shaft 19.
Here, the floating mechanism of the upper pressing member 11 will be described. The upper part of the floating shaft 19 is in sliding contact with the central cylindrical part 50 A of the disk body 50. The upper surface of the cylindrical portion 50 A of the disk body 50 is in contact with the lower surface of the annular portion 38. The upper surface of the annular portion 38 is urged downward by the spring S2. When the floating shaft 19 to which the upper pressing member 11 is fixed is urged downward by the spring S2 via the annular portion 38, the upper pressing member 11 itself is also urged downward. In the present embodiment, the floating mechanism of the upper pressing member 11 having the above configuration is employed.
A socket-shaped portion 21 is formed at the lower portion of the upper pressing member 11. When the piston assembly 23 is pressed and held, the nut 17 at the top of the piston assembly 23 is pressed from above by the socket-shaped portion 21. The piston assembly 23 includes a nut 17, a piston 25 positioned below the nut 17, and an annular body 18 positioned below the piston 25. The piston 25 has a substantially cylindrical shape, and a hole 25A is formed at the center. On the upper surface of the piston 25, a recess 25B that is recessed from the outer periphery is formed. The lower part of the nut 17 is accommodated in the recess 25B. Details of the socket-shaped portion 21 will be described later.

As shown in FIG. 2, the upper pressing member 11 has a circular center hole 27 penetrating vertically. A centering shaft 29 projects downward from the center hole 27. The centering shaft 29 reciprocates in the vertical direction independently of the upper pressing member 11. The centering shaft 29 is detachably attached to the floating shaft 31 provided in the base portion 5, and is biased downward by a spring S1. The centering shaft 29 has a substantially round bar shape, and the tip end portion 29A (lower end portion) has a tapered shape that becomes narrower toward the tip end. As shown in FIG. 7, the tip 29A is slightly smaller than the recess 33A at the tip of the rod 33 to which the piston assembly 23 is assembled. The piston assembly 23 and the rod 33 can be aligned by inserting the tip portion 29A of the centering shaft 29 into the recess 33A at the tip of the rod 33.

As shown in FIG. 2, a groove 29 B is formed around the outer periphery on the base end (upper end) side of the centering shaft 29. The ball plungers 35, 35 of the floating shaft 31 are fitted into the groove 29B, and the centering shaft 29 is positioned. More specifically, a pair of

ball plungers

35 and 35 are attached to a position near the lower end of the floating shaft 31 at positions facing each other. The tips of the pair of

ball plungers

35, 35 protrude inward from the inner wall of the floating shaft 31 and fit into the groove 29 B. When the centering shaft 29 is pulled in a direction (downward) away from the base portion 5, the ball plunger 35 is detached from the groove 29 B, and the centering shaft 29 can be detached from the base portion 5. A plurality of types of centering shafts 29 having different shapes of the tip portions 29A are prepared. The centering shaft 29 is exchanged by selecting an appropriate type according to the combination of the piston assembly 23 and the rod 33 to be assembled. Each centering shaft 29 is formed with a groove 29 B around the outer periphery on the base end side, and is attachable to and detachable from the floating shaft 31 by the action of the

ball plungers

35 and 35. Due to the floating function of the floating shaft 31, the centering shaft 29 is subjected to an elastic member such as a spring and is given an elastic force in the downward direction.
Here, the floating mechanism of the centering shaft 29 will be described. As described above, the centering shaft 29 is detachably fixed to the floating shaft 31 by the

ball plungers

35 and 35. At the lower end of the floating shaft 31, a protrusion 40 for accommodating the

ball plungers

35, 35 is formed. The lower surface of the protrusion 40 is in contact with the upper surface of the contact plate 42. The upper surface of the protrusion 40 is biased downward by the spring S1. When the floating shaft 31 to which the centering shaft 29 is fixed is biased downward by the spring S1, the centering shaft 29 itself is also biased downward. In the present embodiment, the floating mechanism of the centering shaft 29 having the above configuration is employed.

As shown in FIGS. 1 and 2, a socket-shaped portion 21 for tightening the nut 17 is formed at the lower portion of the upper pressing member 11. The socket-shaped portion 21 is formed with a fitting hole 21 A having a polygonal (for example, hexagonal) inner surface corresponding to the outer surface of the nut 17. The upper pressing member 11 is prepared in a plurality of types having different sizes and / or shapes of the fitting holes 21 A of the socket-shaped portion 21.

The upper pressing member 11 having the socket-shaped portion 21 can be attached to and detached from the floating shaft 19 having a floating function, and can be exchanged depending on the type of the nut 17. In the lower part of the floating shaft 19, a positioning through hole 19A penetrating in the lateral direction is formed. As shown in FIGS. 1 and 2, a ball plunger 37 is attached slightly above the vertical center of the upper pressing member 11. The tip of the ball plunger 37 protrudes from the inner wall of the upper pressing member 11. The ball plunger 37 of the upper pressing member 11 is fitted into the positioning through hole 19A of the floating shaft 19, and the upper pressing member 11 is attached to the floating shaft 19 while being positioned. When the upper pressing member 11 is pulled downward, the ball plunger 37 is detached from the positioning through hole 19 A, and the upper pressing member 11 can be detached from the floating shaft 19.

As shown in FIGS. 1, 2, and 11, in the grip portion 7, a pair of lower

pressing members

13 and 13 are attached at positions that are symmetric about the centering shaft 29. The pair of lower

pressing members

13, 13 has a substantially L-shaped claw shape that extends below the lower surface 11 B of the upper pressing member 11 and is bent in a direction approaching the centering shaft 29. The pair of lower

pressing members

13 and 13 can be moved in the horizontal direction by a cylinder 39 so as to be close to and remote from each other.

As shown in FIG. 11, notches 13 C and 13 C are formed in a substantially half-circular shape at the center of the tips 13 A and 13 A of the lower pressing member 13. Then, as shown in FIG. 5, in the state where the tips of the pair of lower

pressing members

13 and 13 are close to each other, the notches 13 C and 13 C are combined to form a substantially circular hole 43. The dimensions of the notches 13 C and 13 C are larger than the outer diameter of the rod 33 and smaller than the outer diameter of the parts provided at the lower end of the piston assembly 23. As shown in FIG. 5, when the piston assembly 23 is pressed and gripped, even if the

tips

13A and 13A of the pair of lower

pressing members

13 and 13 are close to each other, a hole 43 larger than the diameter of a rod-shaped member 41 described later is formed. Thus, the rod-shaped member 41 is allowed to escape into the hole 43 so that the lower pressing member 13 and the rod-shaped member 41 do not come into contact with each other. Further, the

tips

13A and 13A of the lower pressing

members

13 and 13 are flat surfaces that support the lower portion 23C of the piston assembly 23 except for the

notches

13C and 13C for forming the holes 43. The gripping device 1 also assembles the piston assembly 23 with respect to the rod 33.

(Operation of the apparatus of the embodiment)
Now, the operation of the gripping device 1 will be described. The piston assembly 23 is stored in a pallet (not shown). In the pallet, a plurality of rod-like members 41 (pins) face upward and are regularly arranged at equal intervals in the front, rear, left, and right. As shown in FIGS. 1 and 2, the piston assembly 23 is stored in a form in which the rod-like member 41 penetrates the hole 25 A of the piston 25 and the hole 17 A of the nut 17.

Prior to assembly, the rod 33 is carried in advance to the assembly location (see FIG. 7). The rod 33 is held with the tip side facing upward. The rod 33 has a threaded portion 33B in which a screw is formed on the outer periphery of the tip. A spigot joint portion 33C having an outer diameter substantially the same as the outer diameter of the screw portion 33B is provided below the screw portion 33B. The lower portion of the spigot portion 33C is an inlay portion 33C. The larger diameter portion 33D is larger than the diameter. Further, the top of the tip of the rod 33 is a recess 33 A for centering by the centering shaft 29.

Then, the piston assembly 23 is carried to the assembly place. A series of operations from transportation to assembly of the piston assembly 23 will be described (see FIGS. 1 to 10). First, the gripping device 1 moves to the pallet and presses and grips the piston assembly 23. Specifically, as shown in FIGS. 1 and 2, the gripping device 1 moves to above the piston assembly 23. At this time, the pair of lower

pressing members

13, 13 are opened apart.

Next, as shown in FIGS. 3 and 4, the gripping device 1 is lowered until the tips 13 A and 13 A of the lower pressing

members

13 and 13 are lower than the lower surface of the piston assembly 23. The amount of descent is determined based on position information obtained by a 6-axis articulated robot that is a moving device. The centering shaft 29 is pushed up against the force of the spring S 1 by coming into contact with the rod-shaped member 41, and the upper holding member 11 is pushed up against the force of the spring S 2 by fitting into the nut 17. . And a pair of lower

pressing members

13 and 13 makes

tip

13A and 13A adjoin (refer to Drawing 4).

Next, as shown in FIGS. 5 and 6, the gripping device 1 is raised. At this time, the socket-shaped portion 21 of the upper pressing member 11 is fitted to the outer periphery of the nut 17 of the piston assembly 23. Thus, the gripping device 1 is in a state where the piston assembly 23 is sandwiched between the upper pressing member 11 and the lower pressing member 13 in the vertical direction. Furthermore, since the upper pressing member 11 is biased downward by the spring S 2, the upper pressing member 11 and the lower pressing member 13 press and hold the piston assembly 23. Therefore, the gripping device 1 can prevent the side portion from being damaged without touching the side portion of the piston assembly 23.

The gripping device 1 moves to the assembly position while pressing and gripping the piston assembly 23. Then, as shown in FIG. 7, after the gripping device 1 moves to above the rod 33, the gripping device 1 is lowered while pressing and gripping the piston assembly 23. At this time, the tip portion 29A of the centering shaft 29 is protruded downward through the hole portion 17A of the nut 17 and the hole portion 25A of the piston 25. Then, the tip portion 29A of the centering shaft 29 is inserted into the recess 33A of the rod 33. Thereby, the piston assembly 23 and the rod 33 are centered, and both are positioned.
As shown in FIG. 8, the gripping device 1 is lowered while the centering shaft 29 is pushed up against the force of the spring S1.

Next, the assembly operation of the piston assembly 23 is performed on the rod 33 so that the state of FIG. 8 is changed to the state of FIG. Specifically, the nut 17 is fastened to the rod 33.
More specifically, the following series of operations is performed.
[S1] The entire gripping part 7 having the socket-shaped part 21 rotates backward (rotates counterclockwise) at a low speed in the state shown in FIG. By this operation, the inner surface of the socket-shaped portion 21 is fitted into the nut 17 at a normal position.
[S2] Subsequently, the entire gripping part 7 having the socket-shaped part 21 rotates forward (rotates clockwise) at a low speed in the state shown in FIG. At this time, the tightening torque is monitored.
[S3] When the tightening torque is less than or equal to the predetermined value, the pair of lower

pressing members

13 and 13 are remote from each other as shown in FIG. The whole rotates normally at high speed, and the nut 17 is finally tightened to the rod 33.
When the entire gripping part 7 having the socket-shaped part 21 is rotated forward at a low speed of [S2], if the tightening torque is larger than a predetermined value, the socket-shaped part 21 is in the normal position on the nut 17. Since there is a possibility that it is not fitted, the operation of [S3] is not performed immediately. In this case, the operation of [S1] and the operation of [S2] are repeated until the tightening torque in the operation of [S2] becomes a predetermined value or less. Then, the following operation [S3] is performed on condition that the tightening torque is equal to or less than a predetermined value.
As a result of the above series of operations, as shown in FIG. 10, the nut 17 is properly tightened to the rod 33, and the desired piston is assembled.
In [S2], in the initial stage where the nut 17 is tightened, that is, in the stage shown in FIG. 8 where the gripping part 7 is rotated forward at low speed, the lower pressing

members

13 and 13 and the socket-shaped part 21 are biased in the approaching direction. Has been. As a result, the upper surface of the nut 17 comes into contact with the socket-shaped portion 21, and the inclination of the nut 17 is suppressed. That is, initial tightening can be performed while keeping the nut 17 horizontal.

(Effect of the device of the embodiment)
The gripping device 1 of the present embodiment includes an upper pressing member 11 that presses the upper portion 23B of the piston assembly 23, and lower

pressing members

13 and 13 that press the lower portion 23C of the piston assembly 23. The gripping device 1 includes a centering shaft 29 that can reciprocate in the vertical direction. The centering shaft 29 is inserted into the hole 25A of the piston 25. Then, the upper pressing member 11 and the lower pressing member 13 sandwich the piston assembly 23.

The gripping device 1 presses and grips the piston assembly 23 in a state where the piston assembly 23 is sandwiched between the upper pressing member 11 and the lower pressing member 13. In this way, since the outer periphery 23A of the piston assembly 23 is not contacted during pressing and gripping, the piston assembly 23 can be prevented from being damaged and quality can be ensured. Further, since the centering shaft 29 is inserted into the hole 25A of the piston 25, the piston assembly 23 can be centered.

The nut 17 is arranged on the upper part of the piston assembly 23, and the upper pressing member 11 has a socket-shaped portion 21 for tightening the nut 17. The piston 17 is assembled to the rod 33 by fitting the nut 17 into the socket-shaped portion 21 of the upper pressing member 11 and rotating the nut 17.

The lower

pressing members

13, 13 are a pair of claw-shaped portions. Therefore, as compared with the case where the number of the lower pressing members 13 is one, the pressing and holding of the piston assembly 23 can be firmly performed. That is, when the number of the lower pressing members 13 is one, the weight of the piston assembly 23 is applied to one lower pressing member 13, and the lower pressing member 13 may hang down and the piston assembly 23 may tilt. In this embodiment, since the piston assembly 23 is supported by the pair of lower

pressing members

13 and 13 so as to be surrounded from the surroundings, the piston assembly 23 can be maintained in a more stable posture.

Further, the centering shaft 29 is detachable. Therefore, it is possible to easily replace the centering shaft 29 according to the types of the piston assembly 23 and the rod 33.

Moreover, the upper pressing member 11 having the socket-shaped portion 21 is detachable. Therefore, the upper pressing member 11 can be easily exchanged according to the type of the nut 17 and the piston assembly 23.
Further, since the centering shaft 29 is inserted into the hole 25A of the piston 25 with the piston assembly 23 sandwiched therebetween, even if a lateral force is applied to the piston assembly 23 during the transfer of the piston assembly 23, the radial direction of the piston assembly 23 is increased. Since the movement is suppressed by the centering shaft 29, the rod 33 can be easily assembled.
The piston assembly 23 is disposed on the rod-shaped member 41. The rod-shaped member 41 has a small diameter portion whose upper end is tapered, a large diameter portion, and an inclined portion that connects the small diameter portion and the large diameter portion. The posture of the nut 17 is maintained by the small diameter portion and the inclined portion, and the piston 25 and the torus 18 are arranged concentrically with the nut 17 by the large diameter portion. By being arranged in this manner, the piston 25, the nut 17 and the torus 18 are gripped in a concentric state when being sandwiched between the upper pressing member 11 and the lower pressing member 13.

The present invention is not limited to the first embodiment described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In Embodiment 1, although the example using a pair of lower pressing

member

13 and 13 was shown, the number of lower pressing members is not specifically limited.
(2) In the first embodiment, the gripping device 1 is configured to fasten the nut 17 to the rod 33 by low-speed reverse rotation, low-speed normal rotation, and high-speed normal rotation, but it is not always necessary to perform these series of operations. Part of the operation may be omitted or changed.
(3) In the first embodiment, the piston 25 and the torus 18 are used as the configuration of the piston assembly 23. However, the configuration of the piston assembly 23 is not limited to this, and various configurations can be selected.
(4) In the first embodiment, the inner diameters of the piston 25 and the torus 18 are larger than the inner diameter of the nut 17. Therefore, when the upper pressing member 11 and the lower pressing member 13 are clamped, the centering shaft 29 can suppress the movement of the nut 17, the piston 25, and the annular body 18 in the radial direction so that the nut 17, the piston 25, and the annular body 18 can be suppressed. In some cases, the piston 25 and the torus 18 may be displaced with respect to the nut 17.
Even in this case, the amount of deviation is limited. Therefore, the chamfered portion of the upper surface of the rod 33 or the tapered portion whose diameter is expanded downward is formed, so that the lower inner periphery of the piston assembly 23 is chamfered. It arrange | positions, abutting on a part or a taper part, sliding to an assembly position.
A chamfered portion and a tapered portion that open downward may be provided on the inner periphery of the lower portion of the piston assembly 23.

DESCRIPTION OF SYMBOLS 1 ... Gripping device, 11 ... Upper pressing member, 13 ... Lower pressing member, 17 ... Nut, 21 ... Socket shape part, 23 ... Piston assembly, 23A ... Side part, 23B ... Upper part, 23C ... Lower part, 25 ... Piston, 25A ... Hole part, 29 ... Centering shaft

Claims

An upper holding member for holding the upper part of the piston assembly including a piston having a hole in a central axis, an outer peripheral part, and an upper part and a lower part having the outer peripheral part as side parts;
A lower pressing member for pressing the lower portion of the piston assembly;
A centering shaft that protrudes downward from the lower end of the upper pressing member, is reciprocable in the vertical direction, and is inserted into the hole of the piston.
At least one of the upper pressing member and the lower pressing member can be reciprocated in the vertical direction, and the centering is performed while the upper pressing member and the lower pressing member are relatively close to each other and sandwich the piston assembly. A gripping device, wherein a shaft is inserted into the hole of the piston.
The piston assembly is provided with a nut at the top,
The upper pressing member has a socket-shaped portion formed on the surface facing the nut,
The upper pressing member is capable of reciprocating in the vertical direction, and is biased toward the lower pressing member,
The gripping device according to claim 1, wherein the nut and the socket-shaped portion are fitted when the upper pressing member and the lower pressing member are relatively close to each other to clamp the piston assembly.
The lower pressing member has a plurality of claws that are closely spaced in the radial direction of the centering shaft with respect to the centering shaft,
The gripping device according to claim 1, wherein the plurality of claws are close to the centering shaft when the upper pressing member and the lower pressing member are relatively close to each other and sandwich the piston assembly. .
The gripping device according to claim 2, wherein the centering shaft is detachable.
The gripping device according to claim 2, wherein the upper pressing member having the socket-shaped portion is detachable.
The lower pressing member has a plurality of claws that are closely spaced in the radial direction of the centering shaft with respect to the centering shaft,
The gripping device according to claim 2, wherein the plurality of claws are close to the centering shaft when the upper pressing member and the lower pressing member are relatively close to each other and sandwich the piston assembly. .
The gripping device according to claim 3, wherein the centering shaft is detachable.
The gripping device according to claim 3, wherein the upper pressing member having the socket-shaped portion is detachable.
The gripping device according to claim 6, wherein the centering shaft is detachable.
The gripping device according to claim 9, wherein the upper pressing member having the socket-shaped portion is detachable.