Clamp unit

Abstract

To provide a clamp unit that can ease malfunction due to a pressure drop of a working fluid.SOLUTION: A hydraulic clamp unit (1) comprises a pressure accumulation device (70) connected to a fluid channel (21). The pressure accumulation device (70) includes a pressure accumulation chamber (72) for accumulating a portion of a pressure oil (23A) to be fed from a pressure oil feeding / discharging device (4) to swivel type clamps (3), and discharges the pressure oil (23A) accumulated in the pressure accumulation chamber (72) to the fluid channel (21), in accordance with a pressure drop of the pressure oil (23A) in the fluid channel (21).SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a clamp unit including a clamp device and a fluid supply / discharge device that supplies and discharges a working fluid to and from the clamp device. [Background technology]

[0002] Conventionally, a clamping device is known in which a locked state or a released state is switched by a hydraulic fluid supplied to and discharged from an operating chamber in order to fix a workpiece (Patent Document 1). This type of clamping device, together with a fluid supply / discharge device that supplies and discharges the hydraulic fluid to the clamping device, can be mounted on a conveying member configured to be movable along a track and used as a clamping unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 186136 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional clamp unit, if a pressure drop occurs in the working fluid due to, for example, leakage of the working fluid, there is a possibility that the clamp device will not operate normally.

[0005] An object of one aspect of the present invention is to provide a clamp unit that can mitigate operational malfunctions caused by a pressure drop of the working fluid. [Means for solving the problem]

[0006] In order to achieve the above object, in the present invention, as shown in, for example, FIGS. 3, 5, 7, 8, 9, 11 to 13, 16 and 17, a clamp unit is configured as follows. The clamp unit 1, 1A, 1B includes a clamp device 3, 3A that fixes a workpiece W, a fluid supply / discharge device 4, 4A that supplies / discharges a working fluid 23 for operating the clamp device 3, 3A to the clamp device 3, 3A, a fluid passage 21 that communicates with the clamp device 3, 3A and the fluid supply / discharge device 4, 4A and passes the working fluid 23, and a pressure accumulator 70, 70A connected to the fluid passage 21. The pressure accumulator 70, 70A includes a pressure accumulator chamber 72 that stores a portion of the pressurized fluid 23A that is the pressurized working fluid 23 supplied from the fluid supply / discharge device 4, 4A to the clamp device 3, 3A, and discharges the pressurized fluid 23A stored in the pressure accumulator chamber 72 to the fluid passage 21 in response to a pressure drop of the pressurized fluid 23A in the fluid passage 21.

[0007] Therefore, one aspect of the present invention provides the following advantageous effects. A part of the pressurized fluid supplied from the fluid supply / discharge device to the clamp device is stored in the pressure accumulator of the pressure accumulator. When a pressure drop occurs in the pressurized fluid in the fluid passage, the pressurized fluid stored in the pressure accumulator is discharged to the fluid passage in response to the pressure drop. This makes it possible to mitigate the pressure drop of the pressurized fluid and maintain the fluid pressure.

[0008] The present invention preferably includes the following configurations (1) to (8). (1) For example, as shown in Figures 3, 5, 7 to 9, 11 to 13, 16 and 17, the clamping units 1, 1A and 1B further include a conveying member 2 configured to be movable along a track. The clamping devices 3 and 3A, the fluid supply and discharge devices 4 and 4A and the pressure accumulating devices 70 and 70A are mounted on the conveying member 2. In this case, since the clamp unit is movable, the clamp unit can be moved to a desired position on the track to fix the workpiece.

[0009] (2) For example, as shown in Figures 4 and 8, the pressure accumulator 70, 70A includes a housing 71 having a pressure accumulator chamber 72 formed therein, a piston member 73 that is inserted into the housing 71 so as to be axially movable and has the pressure accumulator chamber 72 disposed on one axial side thereof, and a biasing member 74, 74A that biases the piston member 73 toward the pressure accumulator chamber 72. In this case, the piston member compresses the pressure accumulator chamber due to the biasing force of the biasing member in response to a pressure drop of the pressurized fluid in the fluid passage, whereby the pressurized fluid stored in the pressure accumulator chamber is discharged to the fluid passage, thereby mitigating the pressure drop of the pressurized fluid.

[0010] (3) For example, as shown in Figures 4, 7, 8, 12 and 17, the pressure accumulator 70, 70A further includes a rod member 77 provided to protrude in the axial direction on the other axial side of the piston member 73. A tip end 77B of the rod member 77 protrudes to the outside of the housing 71 through a through hole 71C formed on the other side of the housing 71 as the piston member 73 moves to the other side. In this case, when pressurized fluid is stored in the pressure accumulator, the tip of the rod member protrudes outside the housing. Therefore, based on the protruding state of the tip, it can be visually confirmed whether the piston member is moving normally. Therefore, it is easy to find a malfunction of the pressure accumulator.

[0011] (4) For example, as shown in Figures 9, 11 to 13, 16 and 17, the clamp units 1A, 1B further include a pressure reducing device 80 that is disposed in the fluid passage 21 and reduces the pressure of the pressurized fluid 23A supplied from the fluid supply / discharge devices 4, 4A and supplies the reduced pressure to the clamp devices 3, 3A. In this case, the pressure on the clamp device side (secondary side) relative to the pressure reducing device can be kept constant, reducing damage to the clamp device and leakage of pressurized fluid.

[0012] (5) For example, as shown in Figures 3, 5, 7 to 9, 11 to 13, 16 and 17, the transport member 2 includes a first surface 2A and a second surface 2B that face each other in the thickness direction, and the fluid supply / discharge devices 4, 4A are mounted on the first surface 2A, and the pressure accumulator devices 70, 70A are mounted on the second surface 2B. The fluid supply / discharge devices 4, 4A and the pressure accumulator devices 70, 70A are mounted facing each other with the transport member 2 in between. In this case, the fluid supply / discharge device and the pressure accumulator are mounted on the front and back surfaces of the conveying member so as to face each other, thereby making it possible to effectively utilize the mounting space on the front and back surfaces of the conveying member and to reduce the size of the clamp unit.

[0013] (6) For example, as shown in FIG. 2, the clamping device 3, 3A includes a plurality of pivoting clamps. In this case, the plurality of rotary clamps can be operated by the fluid pressure of the pressurized fluid supplied and discharged from the fluid supply and discharge device to lock or release the workpiece.

[0014] (7) For example, as shown in FIGS. 5, 7, 11 and 12, the fluid supply / discharge device 4 supplies the pressurized fluid 23A to the clamp device 3 when the clamp device 3 is released from the locked state to the released state. In this case, the clamp device can be released from the locked state to the released state by the pressure fluid supplied from the fluid supply / discharge device.

[0015] (8) For example, as shown in FIGS. 16 and 17, the fluid supply / discharge device 4A supplies the pressurized fluid 23A to the clamp device 3A when the clamp device 3A is locked from the released state to the locked state. In this case, the clamp device can be locked from the released state to the locked state by the pressure fluid supplied from the fluid supply / discharge device. Effect of the Invention

[0016] According to one aspect of the present invention, it is possible to provide a clamp unit that can mitigate operational malfunctions caused by a pressure drop of the working fluid. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a plan view of the hydraulic clamp unit according to the first embodiment. [Diagram 2] FIG. 4 is a side view of a pair of swivel clamps provided in the hydraulic clamp unit. [Diagram 3]FIG. 2 is a cross-sectional view showing a main part of the hydraulic clamp unit. [Figure 4] 4 is an enlarged cross-sectional view showing a pressure accumulator provided in the clamp unit. FIG. [Diagram 5] 5A to 5C are cross-sectional views showing the operation of the hydraulic clamp unit. [Figure 6] 5 is a cross-sectional view showing the operation of the pressure oil supply and discharge device. FIG. [Figure 7] FIG. 4 is a cross-sectional view showing a state in which pressure oil is supplied to the pressure accumulator. [Figure 8] 5 is a cross-sectional view showing a modified example of the pressure accumulator shown in FIG. [Figure 9] FIG. 11 is a cross-sectional view showing a main part of a clamp unit according to a second embodiment. [Figure 10] 4 is an enlarged cross-sectional view showing a pressure reducing device provided in the clamp unit. FIG. [Figure 11] 5A to 5C are cross-sectional views showing the operation of the hydraulic clamp unit. [Figure 12] FIG. 4 is a cross-sectional view showing a state in which pressure oil is supplied to the pressure accumulator. [Figure 13] FIG. 11 is a cross-sectional view showing a main part of a hydraulic clamp unit according to a third embodiment. [Figure 14] FIG. 4 is an enlarged cross-sectional view showing a swivel clamp provided in the hydraulic clamp unit. [Figure 15] FIG. 4 is an enlarged cross-sectional view showing a pressure oil supply / discharge device provided in the hydraulic clamp unit. [Figure 16] 5 is a cross-sectional view showing the operation of the pressure oil supply and discharge device. FIG. [Figure 17] FIG. 4 is a cross-sectional view showing a state in which pressure oil is supplied to the pressure accumulator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [First embodiment] An embodiment of the present invention will be described below. Note that the following description is an example of a clamp unit according to the present invention, and the technical scope of the present invention is not limited to the illustrated example.

[0019] (Configuration of hydraulic clamp unit 1) Fig. 1 is a plan view of a hydraulic clamp unit 1 (clamp unit) according to the first embodiment. Fig. 2 is a side view of a pair of swivel clamps 3 provided in the hydraulic clamp unit 1.

[0020] The hydraulic clamp unit 1 includes a conveying member 2 configured to be movable along a track, a pressure oil supply and discharge device 4 (fluid supply and discharge device) provided on the conveying member 2, and a pair of swivel clamps (clamp devices) 3 provided on the conveying member 2 so as to receive hydraulic oil (working fluid) from the pressure oil supply and discharge device 4 and discharge the hydraulic oil to the pressure oil supply and discharge device 4. The hydraulic clamp unit 1 also includes a pressure accumulator 70 for maintaining the hydraulic pressure of the hydraulic oil when a pressure drop (drop in hydraulic pressure) occurs due to, for example, a hydraulic oil leak or the like (see FIG. 1).

[0021] The transport member 2 is plate-shaped and includes a first surface (front surface) 2A and a second surface (back surface) 2B that face each other in the thickness direction. A pair of swivel clamps 3 are provided to hold down the workpiece W from above and fix it on the front surface 2A of the transport member 2. A support device 22 is provided between the pair of swivel clamps 3 to support the workpiece W from below.

[0022] The hydraulic clamp unit 1 is used, for example, in a processing machine, so that an operator operates the swivel clamp 3 to fix the workpiece W on the transport member 2, closes the door of the processing machine and processes the workpiece W with the processing machine while the operator is away. After that, the door is opened again and the operator operates the swivel clamp 3 to release the workpiece W from the transport member 2.

[0023] In addition, the hydraulic clamp unit 1 may be used such that, for example, an operator operates the swivel clamp 3 outside a processing machine to fix the workpiece W on the transport member 2, and then the hydraulic clamp unit 1 is transported into the processing machine installed in a different location. Then, the workpiece W is processed by the processing machine, and when the hydraulic clamp unit 1 returns from the processing machine, the operator releases the workpiece W from the transport member 2.

[0024] The number of swivel clamps 3 provided in the hydraulic clamp unit 1 is not particularly limited and can be changed as appropriate depending on the shape, dimensions, weight, etc. of the workpiece W to be fixed. As shown in the illustrated example, the hydraulic clamp unit 1 includes multiple swivel clamps 3, so that the multiple swivel clamps 3 can be operated by the hydraulic pressure of the hydraulic oil supplied and discharged from one pressure oil supply and discharge device 4 to lock or release the workpiece W.

[0025] For example, when the hydraulic clamp unit 1 includes three or more swivel clamps 3, the swivel clamps 3 may be mounted on the transport member 2 so as to be arranged at equal intervals along the circumferential direction of a circle centered on the support device 22 in a plan view seen from the thickness direction of the transport member 2. This makes it possible to more reliably fix the workpiece W on the transport member 2 and improve the machining accuracy of the workpiece W by the machining machine.

[0026] Fig. 3 is a cross-sectional view showing a main part of the hydraulic clamp unit 1. Fig. 3 shows a locked state in which the swivel clamp 3 fixes the workpiece W.

[0027] The pressure oil supply / discharge device 4 includes a piston 5 inserted axially movably into a cylindrical housing 10, a female screw member 6 provided in an accommodating hole 11 formed in the piston 5 in the axial direction, a male screw member 7 screwed into the female screw member 6, a cap member 8 axially slidably fitted to the end opposite the male screw end of the male screw member 7 and fitted so as to be able to transmit a rotational force around the axis to the male screw member 7, a working chamber 9 formed on the cap member 8 side of the piston 5 and into which hydraulic oil 23 is supplied and discharged as the piston 5 moves, and a pressing mechanism that presses the cap member 8 in the axial direction. This pressing mechanism contains the hydraulic oil 23 supplied to and discharged from the working chamber 9 as the piston 5 moves.

[0028] The cap member 8 has a fitting hole 13 into which the male screw member 7 fits, and a guide groove 14 extending in the axial direction on the inner wall of the fitting hole 13. The male screw member 7 has a pin member 12 that engages with the guide groove 14.

[0029] The cap member 8 has an operating portion 15 at the tip opposite to the male screw member 7 for receiving a rotational force in the direction around the axis.

[0030] The operation portion 15 has a polygonal protrusion protruding in the axial direction. The operation portion 15 may have a polygonal recess. In this embodiment, an example in which the operation portion 15 has a hexagonal protrusion is illustrated in FIG. 1.

[0031] The housing 10 has a receiving portion 20 for preventing the cap member 8 from falling off due to pressure from the hydraulic pressure (fluid pressure) of the hydraulic oil (working fluid) 23. The cap member 8 has a stopper portion 16 that can be engaged with the receiving portion 20.

[0032] The cap member 8 is configured to slide toward the piston 5 in response to a decrease in the hydraulic pressure of the hydraulic oil 23.

[0033] The cap member 8 has a retaining ring 30 arranged on the inner wall of the fitting hole 13. The housing 10 has a retaining ring 31 arranged on the inner wall of the working chamber 9 on the cap member 8 side. The piston 5 has a guide groove 32 formed in the axial direction on the inner wall of the accommodation hole 11. The female screw member 6 has a guide groove 33 formed in the axial direction opposite the guide groove 32, and a pin 34 provided in the guide groove 33 opposite the guide groove 32. The piston 5 has a guide groove 36 formed in the axial direction on its outer circumferential wall, and a guide hole 38 formed so that the male screw member 7 can be inserted. The housing 10 has a pin 37 arranged opposite the guide groove 36. A ring member 39 made of a ring-shaped rubber or resin is provided on the lower side of the piston 5.

[0034] A receiving member 56 is attached to the male screw member 7 on the cap member 8 side of the working chamber 9 so as to be rotatable around the axis. The receiving member 56 is prevented from coming off by a retaining ring 31 arranged on the inner peripheral wall of the working chamber 9. A sliding groove 58 is formed in the circumferential direction on the outer peripheral wall of the receiving member 56, and a sliding groove 57 is formed in the circumferential direction on the inner peripheral wall of the receiving member 56. A plurality of ball members 59 are attached to the sliding groove 58, and a plurality of ball members 60 are attached to the sliding groove 57. The ball member 59 on the outer peripheral wall side is capable of rolling between the sliding groove 58 on the outer peripheral wall of the receiving member 56 and the inner peripheral wall of the working chamber 9. The ball member 60 on the inner peripheral wall side is capable of rolling between the sliding groove 57 formed on the inner peripheral wall of the receiving member 56 and an engagement portion formed on the outer peripheral wall of the male screw member 7 in a tapered shape so as to widen toward the cap member 8 side.

[0035] The swivel clamp 3 and the pressure oil supply and discharge device 4 are in communication with each other via a fluid passage 21 through which hydraulic oil 23 passes. The hydraulic oil 23 discharged from the pressure oil supply and discharge device 4 is supplied to the swivel clamp 3 through the fluid passage 21. In addition, the hydraulic oil 23 discharged from the swivel clamp 3 is supplied to the pressure oil supply and discharge device 4 through the fluid passage 21. At least a portion of the fluid passage 21 may be provided inside the conveying member 2.

[0036] Fig. 4 is an enlarged cross-sectional view showing the pressure accumulator 70 shown in Fig. 3. The pressure accumulator 70 is an accumulator connected to the fluid passage 21. The pressure accumulator 70 includes a housing 71 in which a pressure accumulator chamber 72 for storing hydraulic oil 23 is formed, a pressure accumulator piston (piston member) 73 inserted into the housing 71 so as to be movable in the axial direction (left-right direction in the figure), and a compression spring (biasing member) 74 which is an elastic member that biases the pressure accumulator piston 73 towards the pressure accumulator chamber 72.

[0037] The housing 71 includes a first accommodating hole 71A and a second accommodating hole 71B having a larger diameter than the first accommodating hole 71A. An accumulator piston 73 is hermetically fitted into the first accommodating hole 71A so as to be movable in the axial direction. An accumulator chamber 72 is disposed on the left side (one side) of the accumulator piston 73 in the axial direction.

[0038] The accumulator chamber 72 communicates with the fluid passage 21 via a supply and discharge passage 75 provided in the housing 71. Through this supply and discharge passage 75, the hydraulic oil 23 in the fluid passage 21 is supplied to the accumulator chamber 72, and the hydraulic oil 23 stored in the accumulator chamber 72 is discharged to the fluid passage 21. A sealing member 76 is provided in the circumferential direction on the inner peripheral wall of the first accommodating hole 71A facing the outer peripheral wall of the accumulator piston 73. The sealing member 76 is capable of hermetically engaging with the outer peripheral wall of the accumulator piston 73.

[0039] The pressure accumulator 70 further includes an indicator rod (rod member) 77 provided on the axial right side (the other side) of the pressure accumulator piston 73 so as to protrude in the axial direction. The indicator rod 77 is accommodated in the second accommodating hole 71B. A spring chamber 78 that accommodates a compression spring 74 is formed between the outer circumferential wall of the indicator rod 77 and the inner circumferential wall of the second accommodating hole 71B. In this spring chamber 78, the compression spring 74 that biases the indicator rod 77 toward the pressure accumulator chamber 72 is arranged around the outer circumferential wall of the indicator rod 77. The indicator rod 77 has a flange on the end side connected to the pressure accumulator piston 73, and the flange functions as a spring receiver 77A that receives the compression spring 74.

[0040] As described later, a tip 77B of the indicator rod 77 on the opposite side to the spring receiver 77A is adapted to pass through a through hole 71C formed in the housing 71 and protrude to the outside of the housing 71 as the accumulator piston 73 moves to the right (see FIG. 7). Therefore, when the hydraulic oil 23 is stored in the accumulator chamber 72, the tip 77B of the indicator rod 77 is in a state of protruding to the outside of the housing 71. This makes it possible to visually check whether the accumulator piston 73 is moving normally based on the protruding state of the tip 77B, making it easy to find a malfunction of the accumulator device 70.

[0041] The pressure oil supply / discharge device 4 is mounted on a first surface 2A of the conveying member 2. In addition, the pressure accumulator 70 is mounted on a second surface 2B of the conveying member 2 such that the axial direction of the pressure accumulator piston 73 is parallel to the conveying member 2.

[0042] The pressure oil supply / discharge device 4 and the pressure accumulator 70 may be mounted opposite each other with the conveying member 2 in between. In other words, the pressure oil supply / discharge device 4 and the pressure accumulator 70 may be separately mounted on the front and back surfaces of the conveying member 2 so that they at least partially overlap each other in a plan view seen from the thickness direction of the conveying member 2. As a result, the pressure oil supply / discharge device 4 and the pressure accumulator 70 are mounted opposite each other on the front and back surfaces of the conveying member 2, so that the mounting space of the conveying member 2 can be effectively utilized to reduce the size of the hydraulic clamp unit 1.

[0043] (Operation of hydraulic clamp unit 1) Next, an example of the operation of the hydraulic clamp unit 1 will be described. Fig. 5 is a cross-sectional view showing the operation of the hydraulic clamp unit 1. Fig. 6 is a cross-sectional view showing the operation of the pressure oil supply and discharge device 4. Fig. 5 shows a release state in which the swivel clamp 3 has released the workpiece W. Components similar to those described above are given the same reference symbols, and detailed descriptions of these components will not be repeated.

[0044] The pressure oil supply / discharge device 4 supplies hydraulic oil 23 to the rotary clamp 3 when the rotary clamp 3 is released from the locked state shown in FIG. 3 to the released state shown in FIG.

[0045] 3, when the swivel clamp 3 is in the locked state, the piston 5 of the pressure oil supply / discharge device 4 is in a lower position away from the cap member 8. The cap member 8 is pressed by the hydraulic oil 23 in the working chamber 9 and rises to a position where the stopper portion 16 engages with the receiving portion 20 of the housing 10.

[0046] Then, as shown in FIG. 6, when a recess formed at the tip of the rotational force transmission tool 25 for transmitting rotational force to the cap member 8 is engaged with the operating part 15 of the cap member 8, if the rotational force transmission tool 25 shifts horizontally and the tip of the rotational force transmission tool 25 comes into contact with and presses the operating part 15, the cap member 8 pressed against the operating part 15 will slide downward against the hydraulic pressure of the working oil 23 in the working chamber 9.

[0047] Therefore, even if the rotational force transmission tool 25 shifts horizontally and the tip of the rotational force transmission tool 25 comes into contact with the operating portion 15, defects such as damage to the cap member 8 and related members can be avoided.

[0048] In addition, the cap member 8, which is pressed by the hydraulic oil 23 in the working chamber 9 and rises to a position where the stop portion 16 engages with the receiving portion 20 of the housing 10, is axially slidably engaged with the male thread member 7, so that it descends when the oil pressure of the hydraulic oil 23 decreases.

[0049] Therefore, when a malfunction occurs in which the hydraulic pressure of the hydraulic oil 23 decreases, the cap member 8, which is normally raised, is lowered, making it easy to discover the malfunction of the pressure oil supply / discharge device 4.

[0050] Next, as shown in FIG. 5, when the recess formed at the tip of the torque transmission tool 25 fits into the operating portion 15 of the cap member 8, the cap member 8 slides axially due to the hydraulic pressure of the hydraulic oil 23 until the stop portion 16 of the cap member 8 engages with the receiving portion 20 of the housing 10.

[0051] Thereafter, when the rotational force transmitting tool 25 is rotated in a first direction about its axis by the operation of an operator or a robot, the cap member 8, whose operation part 15 is fitted into a recess of the rotational force transmitting tool 25, transmits the rotational force to the male screw member 7. When the male screw member 7 rotates due to the rotational force, the piston 5, which is provided with the female screw member 6 that screws into the male screw member 7, moves axially upward so as to approach the cap member 8 as shown in FIG.

[0052] As a result, the hydraulic oil 23 is pressurized in the working chamber 9, and the pressurized hydraulic oil 23, that is, pressurized oil (pressurized fluid) 23A, is supplied to the rotating clamp 3 through the fluid passage 21. The rotating clamp 3 to which the hydraulic oil 23A is supplied is released from the locked state (clamped state) shown in Fig. 3 to the released state (unclamped state) shown in Fig. 5.

[0053] When the pressure oil 23A is supplied to the working chamber 40 of the swivel clamp 3 from the working chamber 9 of the pressure oil supply and discharge device 4 through the fluid passage 21, the pressing force based on the pressure oil 23A supplied to the working chamber 40 acts to move the piston 42 toward the output rod 44 against the biasing force (pressing force) of the lock spring 41. Then, the piston 42 moves the output rod 44 straight upward on the opposite side to the piston 42 via the compression spring 43. Next, when the step portion 44a of the output rod 44 is received from above by the thrust bearing 45, the piston 42 compresses the compression spring 43. Then, the operation groove 46 of the piston 42 presses the rotation groove 48 of the output rod 44 upward via the transmission ball 47, and the output rod 44 is rotated by 90 degrees counterclockwise in a plan view relative to the piston 42.

[0054] Subsequently, the bottom wall of the receiving hole 49 of the piston 42 is received from above by the lower end of the output rod 44. This causes the swivel clamp 3 to switch from the locked state of FIG. 3 to the released state of FIG.

[0055] Next, in the released state shown in Fig. 5, the torque transmitting tool 25 further rotates the cap member 8 of the pressure oil supply / discharge device 4 in the first direction about the axis. This causes the piston 5 to move and the pressure of the pressure oil 23A to be further increased. As a result, the pressure oil 23A in the working chamber 9 of the pressure oil supply / discharge device 4 is supplied to the pressure accumulator chamber 72 of the pressure accumulator 70 through the fluid passage 21.

[0056] Fig. 7 is a cross-sectional view showing a state in which pressure oil 23A is supplied to the pressure accumulator 70. Fig. 7 also shows a release state in which the swivel clamp 3 releases the workpiece W. As shown in Fig. 7, a pressing force corresponding to the oil pressure of the pressure oil 23A supplied to the pressure accumulator chamber 72 moves the pressure accumulator piston 73 to the right in the axial direction against the biasing force of the compression spring 74. As the pressure accumulator piston 73 moves to the right, the tip 77B of the indicator rod 77 projects outside the housing 71. This makes it possible to visually confirm that pressure oil 23A is being supplied to the pressure accumulator chamber 72 based on the projecting state of the tip 77B.

[0057] The biasing force of the compression spring 74 of the pressure accumulator 70 is set to be larger than the biasing force of the lock spring 41 of the swivel clamp 3. In other words, the magnitude relationship of the biasing forces (pressing forces) of the springs is compression spring 74>lock spring 41. For this reason, when the hydraulic pressure of the pressure oil 23A passing through the fluid passage 21 of the hydraulic clamp unit 1 increases, first the lock spring 41 of the swivel clamp 3 is compressed, and the swivel clamp 3 is switched to the release state. Thereafter, the compression spring 74 of the pressure accumulator 70 is compressed, and the pressure oil 23A is stored in the pressure accumulator chamber 72.

[0058] For example, when a pressure drop occurs in the pressure oil 23A in the fluid passage 21 due to leakage of the pressure oil 23A or the like, in the pressure accumulator 70, the pressure accumulator piston 73 compresses the pressure accumulator chamber 72 by the biasing force of the compression spring 74. Therefore, the pressure oil 23A stored in the pressure accumulator chamber 72 is discharged to the fluid passage 21 in response to the pressure drop of the pressure oil 23A. Therefore, the pressure drop of the pressure oil 23A can be mitigated.

[0059] On the other hand, in the released state shown in Fig. 7, when the torque transmitting tool 25 rotates in a second direction opposite to the first direction about its axis, the piston 5 moves axially downward so as to move away from the cap member 8. Then, the pressure oil 23A is reduced, and first the pressure oil 23A stored in the accumulator chamber 72 of the accumulator 70 is discharged into the fluid passage 21 by the biasing force of the compression spring 74, and then the pressure oil 23A in the swivel clamp 3 is discharged into the operating chamber 9 of the pressure oil supply / discharge device 4 through the fluid passage 21. As a result, the hydraulic clamp unit 1 is locked and driven from the released state shown in Fig. 7 to the locked state shown in Fig. 3.

[0060] (Summary of hydraulic clamp unit 1) Thus, the clamp unit 1 according to this embodiment includes the swivel clamp 3 that fixes the workpiece W, the pressure oil supply and discharge device 4 that supplies and discharges the hydraulic oil 23 that operates the swivel clamp 3 to the swivel clamp 3, a fluid passage 21 that communicates with the swivel clamp 3 and the pressure oil supply and discharge device 4 and passes the hydraulic oil 23A, and a pressure accumulator 70 connected to the fluid passage 21. The pressure accumulator 70 includes a pressure accumulator chamber 72 that stores a portion of the pressure oil 23A, which is the pressurized hydraulic oil 23 supplied from the pressure oil supply and discharge device 4 to the swivel clamp 3, and discharges the pressure oil 23A stored in the pressure accumulator chamber 72 into the hydraulic oil 21 in response to a pressure drop of the pressure oil 23A in the fluid passage 21.

[0061] In the hydraulic clamp unit 1, a portion of the pressure oil 23A supplied from the pressure oil supply / discharge device 4 to the revolving clamp 3 is stored in the pressure accumulator 72 of the pressure accumulator 70. When a pressure drop occurs in the pressure oil 23A in the fluid passage 21, the pressure oil 23A stored in the pressure accumulator 72 is discharged to the fluid passage 21 in response to the pressure drop. Therefore, the hydraulic clamp unit 1 can mitigate the pressure drop in the pressure oil 23A.

[0062] (Modification) FIG. 8 is a cross-sectional view showing a pressure accumulator 70A which is a modified example of the pressure accumulator 70 shown in FIG. 4. As shown in FIG. 8, the pressure accumulator 70A includes a fluid spring 74A instead of the compression spring 74 as a biasing member for biasing the pressure accumulator piston 73. The fluid spring 74A has a gas (fluid) G, such as air or nitrogen, sealed in a fluid chamber 78A. In the pressure accumulator 70A, the pressure of the gas G sealed in the fluid chamber 78A biases the pressure accumulator piston 73 toward the pressure accumulator chamber 72. In this way, the fluid spring 74A may be used instead of the compression spring 74. Also, the fluid spring 74A may be used together with the compression spring 74.

[0063] Second Embodiment Other embodiments of the present invention are described below, in which like reference numerals refer to like components previously described, and detailed descriptions of these components will not be repeated.

[0064] (Configuration of hydraulic clamp unit 1A) Fig. 9 is a cross-sectional view showing a main part of the hydraulic clamp unit 1A according to the second embodiment. Fig. 10 is an enlarged cross-sectional view showing a pressure reducing device 80 provided in the hydraulic clamp unit 1A. Fig. 9 shows a locked state in which the swivel clamp 3 fixes the workpiece W.

[0065] 9, the hydraulic clamp unit 1A, unlike the hydraulic clamp unit 1 described above, includes a pressure reducing device 80 disposed in the fluid passage 21. Therefore, the hydraulic clamp unit 1A can keep the pressure on the revolving clamp 3 side (secondary side) constant with respect to the pressure reducing device 80, thereby reducing damage to the revolving clamp 3 and leakage of pressure oil 23A.

[0066] As shown in FIG. 10, the pressure reducing device 80 is mounted on the second surface 2B of the conveying member 2. The pressure reducing device 80 has an inlet hole 82 and an outlet hole 83 for the hydraulic oil 23 provided in the upper part of a valve case 81. The inlet hole 82 is connected to a fluid passage 21 communicating with the pressure oil supply and discharge device 4. The outlet hole 83 is connected to a fluid passage 21 communicating with the swivel clamp 3. Inside the valve case 81, an inlet chamber 84, a pressure reducing valve seat 85, and an outlet chamber 86 are formed in series from the right end wall 81A side to the left end wall 81B side of the valve case 81. The inlet hole 82 is connected to the outlet hole 83 via a flow path 87 formed to pass through the inlet chamber 84, the pressure reducing valve seat 85, and the outlet chamber 86.

[0067] An accommodation hole 88 is formed on the right end wall 81A side of the valve case 81, and a pressure reducing member 89 is inserted into this accommodation hole 88 so as to be movable back and forth in the left-right direction. A valve closing spring 90 attached between the right end wall 81A and the pressure reducing member 89 urges the pressure reducing member 89 leftward. A hole chamber 91 formed on the right side of the pressure reducing member 89 in the accommodation hole 88 is connected to the outlet chamber 86 by a passage 89A extending in the left-right direction (axial direction) that penetrates the inside of the pressure reducing member 89. An opening 85A is formed in the center of the pressure reducing valve seat 85, and the inlet chamber 84 and the outlet chamber 86 are connected via this opening 85A.

[0068] A piston hole 92 formed in the outlet chamber 86 has a large diameter hole 94 and a small diameter hole 93. A pressure-receiving piston 95 is inserted into the piston hole 92 so as to be able to advance and retreat in the left-right direction. The pressure-receiving piston 95 has a small diameter portion 96 that is hermetically inserted into the small diameter hole 93 via a sealing member 98, and a large diameter portion 97 that fits into the large diameter hole 94. A fluid chamber 99 is formed between the large diameter hole 94 and the small diameter portion 96. The fluid chamber 99 and the outlet chamber 86 are communicated with each other by a first passage 100 and a second passage 101 that are arranged in parallel.

[0069] In this embodiment, the first passage 100 is provided inside the pressure-receiving piston 95. A poppet-type check valve 102 is provided in the first passage 100, and a valve chamber 103 of the check valve 102 is formed so as to extend left and right. A valve seat 104 is provided on the left end wall of the valve chamber 103, and a ball 105 is biased against the valve seat 104 by a spring 106. An inlet passage 107 is connected to the center of the valve seat 104, and the inlet passage 107 is connected to the fluid chamber 99. The valve chamber 103 is also connected to the outlet chamber 86 via an outlet passage 108. The first passage 100 is made up of the inlet passage 107, the valve chamber 103, and the outlet passage 108.

[0070] The second passage 101 is formed by a fitting gap between the large diameter hole 94 and the large diameter portion 97, and the entire fitting gap constitutes a throttle portion 109. An operating rod 110 protrudes rightward from the large diameter portion 97. This operating rod 110 passes through the opening 85A and comes into contact with the pressure reducing member 89.

[0071] The throttle portion 109 may be formed in a part of the fitting gap instead of being configured by the entire fitting gap.

[0072] A pressure setting spring 111 that urges the pressure receiving piston 95 rightward is attached between the left end wall 81B of the valve case 81 and the pressure receiving piston 95 via spring receivers 112A, 112B. This pressure setting spring 111 has a large diameter spring 111A and a small diameter spring 111B.

[0073] 9, the pressing force of the hydraulic pressure in the outlet chamber 86 of the pressure reducing device 80 is smaller than the biasing force of the pressure setting spring 111. As a result, the pressure setting spring 111 advances the pressure receiving piston 95 to the right, and the pressure receiving piston 95 separates the pressure reducing member 89 from the pressure reducing valve seat 85 via the operating rod 110. As a result, the pressure reducing device 80 is in an open state.

[0074] (Operation of hydraulic clamp unit 1A) Next, an operation example of the hydraulic clamp unit 1A equipped with the pressure reducing device 80 configured as described above will be described. Fig. 11 is a cross-sectional view showing the operation of the hydraulic clamp unit 1A. Fig. 12 is a cross-sectional view showing a state in which pressure oil 23A is supplied to the pressure accumulator 70. Fig. 11 shows a release state in which the swivel clamp 3 has released the workpiece W.

[0075] In the locked state shown in Figure 9, when the rotational force transmission tool 25 rotates the cap member 8 of the pressure oil supply and discharge device 4 in a first direction around the axis, the piston 5 moves axially upward so as to approach the cap member 8, as shown in Figure 11.

[0076] As a result, the pressure of the hydraulic oil 23 is increased in the working chamber 9, and pressure oil 23A is supplied to the revolving clamp 3 through the pressure reducing device 80 arranged in the fluid passage 21. The revolving clamp 3 to which the hydraulic oil 23A is supplied is released and driven from the locked state shown in Fig. 9 to the released state shown in Fig. 11. Then, the hydraulic pressure in the working chamber 40 of the revolving clamp 3 and the outlet chamber 86 of the pressure reducing device 80 increases, and the hydraulic pressure of the pressure oil 23A in the outlet chamber 86 becomes greater than the biasing force of the pressure setting spring 111, and the pressure receiving piston 95 moves to the left. As a result, the pressure reducing member 89 is pushed by the valve closing spring 90 and comes into contact with the pressure reducing valve seat 85, and the pressure reducing device 80 is closed.

[0077] Next, in the released state shown in Fig. 11, the cap member 8 of the pressure oil supply / discharge device 4 is further rotated in the first direction around the axis by the rotational force transmitting tool 25. Then, as shown in Fig. 12, the piston 5 moves and the pressure of the pressure oil 23A is further increased. As a result, the pressure oil 23A in the working chamber 9 of the pressure oil supply / discharge device 4 is supplied to the pressure accumulator chamber 72 of the pressure accumulator 70 through the fluid passage 21.

[0078] In the hydraulic clamp unit 1A, the biasing force of the compression spring 74 of the pressure accumulator 70 is set to be larger than the biasing force of the lock spring 41 of the swivel clamp 3 and the pressure setting spring 111 of the pressure reducing device 80. The biasing force of the pressure setting spring 111 of the pressure reducing device 80 is set to be larger than the biasing force of the lock spring 41 of the swivel clamp 3. In other words, the magnitude relationship of the biasing force (pressing force) of each spring is compression spring 74>pressure setting spring 111>lock spring 41. For this reason, when the hydraulic pressure of the pressure oil 23A passing through the fluid passage 21 of the hydraulic clamp unit 1A increases, first the lock spring 41 of the swivel clamp 3 is compressed, and the swivel clamp 3 is switched to the release state, and then the pressure setting spring 111 of the pressure reducing device 80 is compressed, and the pressure reducing device 80 is closed. Thereafter, the compression spring 74 of the pressure accumulator 70 is compressed, and the pressure oil 23A is stored in the pressure accumulator chamber 72.

[0079] For example, when a pressure drop occurs in the pressure oil 23A on the swivel clamp 3 side (secondary side) relative to the pressure reducing device 80 due to leakage of the pressure oil 23A or the like, the pressure in the outlet chamber 86 of the pressure reducing device 80 drops. As a result, the pressure-receiving piston 95 pushes the pressure reducing member 89 to the right due to the biasing force of the pressure setting spring 111, and the pressure reducing device 80 opens, causing a pressure drop in the fluid passage 21 on the pressure oil supply / discharge device 4 side (primary side) relative to the pressure reducing device 80. In response to this pressure drop, the pressure oil 23A is discharged from the pressure accumulator 70 to the fluid passage 21, so that the pressure drop of the pressure oil 23A can be mitigated.

[0080] On the other hand, in the released state shown in Fig. 12, when the torque transmitting tool 25 rotates in a second direction opposite to the first direction about the axis, the piston 5 moves axially downward so as to move away from the cap member 8. Then, the pressure of the pressure oil 23A is reduced, and the pressure oil 23A stored in the accumulator chamber 72 of the accumulator 70 is first discharged to the fluid passage 21 by the biasing force of the compression spring 74, and then the pressure reducing device 80 opens as the pressure in the inlet chamber 84 decreases. Thereafter, the pressure oil 23A in the swivel clamp 3 is discharged into the operating chamber 9 of the pressure oil supply / discharge device 4 through the fluid passage 21. As a result, the hydraulic clamp unit 1A is locked and driven from the released state shown in Fig. 12 to the locked state shown in Fig. 9.

[0081] Third Embodiment Other embodiments of the present invention are described below, in which like reference numerals refer to like components previously described, and detailed descriptions of these components will not be repeated.

[0082] (Configuration of hydraulic clamp unit 1B) Fig. 13 is a cross-sectional view showing a main part of a hydraulic clamp unit 1B according to the third embodiment. Fig. 13 shows a released state in which the swivel clamp 3A has released the workpiece W.

[0083] As shown in Fig. 13, the hydraulic clamp unit 1B includes a swivel clamp 3A and a pressure oil supply / discharge device 4A. Unlike the previously described swivel clamp 3, the swivel clamp 3A is in a released state when pressure oil 23A is not supplied, and is in a locked state when pressure oil 23A is supplied (see Fig. 16). Also, unlike the previously described pressure oil supply / discharge device 4, the pressure oil supply / discharge device 4A has an operating chamber 9 formed on the opposite side of the piston 5 to the cap member 8.

[0084] Fig. 14 is an enlarged cross-sectional view showing a swivel clamp 3A provided in the hydraulic clamp unit 1B. As shown in Fig. 14, in the swivel clamp 3A, an operating chamber 40 is formed above a piston 42. Therefore, when pressure oil 23A is supplied to the operating chamber 40, the piston 42 moves downward. A spring chamber 50 is provided below the piston 42. A release spring 51 that biases the piston 42 is housed in this spring chamber 50. When pressure oil 23A is discharged from the operating chamber 40, the release spring 51 moves the piston 42 upward. Therefore, the volume of the spring chamber 50 changes as the piston 42 moves up and down.

[0085] Therefore, a ventilation hole 53 is provided at the bottom of the swivel clamp 3A to supply and exhaust air from the spring chamber 50 to the outside. The ventilation hole 53 is connected to an air passage 2C provided in the conveying member 2. A check valve 54 is provided in this ventilation hole 53. The check valve 54 prevents relatively large foreign objects from being sucked in when air is sucked into the spring chamber 50.

[0086] The output rod 44 includes a lower rod 44A that protrudes downward. A guide groove 44B is provided on the outer circumferential surface of the lower rod 44A. When the output rod 44 moves in the up-down direction (axial direction), it rotates in the circumferential direction by the guide groove 44B and the transmission balls 47 inserted into the guide groove 44B.

[0087] Here, if the release spring 51 rotates together with the output rod 44, there is a possibility that the release spring 51 will be twisted and damaged. For this reason, a ball (bearing) 61 is provided between the inner peripheral surface of the spring receiver 55 that receives the release spring 51 and the outer peripheral surface of the output rod 44 so that the release spring 51 can rotate relative to the spring receiver 55.

[0088] Fig. 15 is an enlarged cross-sectional view showing a pressure oil supply / discharge device 4A provided in the hydraulic clamp unit 1B. As shown in Fig. 15, in the pressure oil supply / discharge device 4A, an operating chamber 9 is disposed below a piston 5. In addition, a male thread member 7 and a cap member 8 are integrally formed.

[0089] The piston 5 is a cylindrical member with a bottom, and has a female screw member 6A on its inner peripheral surface. This makes it possible to prevent foreign matter, including wear powder generated by the engagement between the male screw member 7 and the female screw member 6A, from being mixed into the hydraulic oil 23, and therefore makes it possible to maintain the hydraulic oil 23 in a clean state.

[0090] Furthermore, the pressure oil supply / discharge device 4A has a hydraulic oil supply unit 62 which is a supply port used when supplying hydraulic oil 23 to the working chamber 9. For example, when the amount of hydraulic oil 23 decreases, the hydraulic oil 23 can be supplied from the hydraulic oil supply unit 62 to the working chamber 9. A check valve is disposed inside the hydraulic oil supply unit 62 so as to prevent the hydraulic oil 23 from flowing back. Furthermore, an air vent hole 63 is provided in the working chamber 9. A sealing member (air vent valve) 64 is disposed in this air vent hole 63.

[0091] When the swivel clamp 3A is in the released state, the piston 5 of the pressure oil supply / discharge device 4B is located at an upper side close to the cap member 8. The cap member 8 is pressed in the axial direction by the elastic member 26 and rises to a position where the stop portion 16 engages with the receiving portion 20 of the housing 10.

[0092] (Operation of hydraulic clamp unit 1B) Next, an example of the operation of the hydraulic clamp unit 1B equipped with the swivel clamp 3A and pressure oil supply / discharge device 4A configured as described above will be described. Fig. 16 is a cross-sectional view showing the operation of the hydraulic clamp unit 1B. Fig. 17 is a cross-sectional view showing a state in which pressure oil 23A is supplied to the pressure accumulator 70. Figs. 16 and 17 show a locked state in which the swivel clamp 3A fixes the workpiece W.

[0093] 13, the piston 5 of the pressure oil supply / discharge device 4B is disposed at an upper position close to the cap member 8. In this state, when the torque transmission tool 25 rotates the cap member 8 of the pressure oil supply / discharge device 4A in a first direction about its axis, the piston 5 moves axially downward so as to move away from the cap member 8 as shown in FIG.

[0094] As a result, the pressure of the hydraulic oil 23 is increased in the working chamber 9, and pressurized oil 23A is supplied to the revolving clamp 3A through a pressure reducing device 80 disposed in the fluid passage 21. As the pressurized oil 23A is supplied to the working chamber 40 of the revolving clamp 3A, the pressing force based on the pressurized oil 23A moves the piston 42 downward against the biasing force of the release spring 51, and the clamp arm of the revolving clamp 3A comes into contact with the workpiece W from above.

[0095] After this, pressure oil 23A is further supplied to the operating chamber 40. Then, the pressure in the operating chamber 40 of the rotating clamp 3A increases, and the clamp arm strongly presses the workpiece W toward the conveying member 2. When the pressure in the operating chamber 40 exceeds the pressure set by the pressure setting spring 111 of the pressure reducing device 80, the pressure reducing device 80 is closed. As a result, the rotating clamp 3A is locked and driven from the released state shown in FIG. 13 to the locked state shown in FIG. 16. In this way, the pressure oil supply and discharge device 4A supplies pressure oil 23A to the rotating clamp 3A when the rotating clamp 3A is locked and driven from the released state to the locked state.

[0096] Next, in the locked state shown in Fig. 16, the torque transmitting tool 25 further rotates the cap member 8 of the pressure oil supply / discharge device 4A in the first direction about the axis. Then, as shown in Fig. 17, the piston 5 moves and the pressure of the pressure oil 23A is further increased. As a result, the pressure oil 23A in the working chamber 9 of the pressure oil supply / discharge device 4A is supplied to the pressure accumulator chamber 72 of the pressure accumulator 70 through the fluid passage 21.

[0097] In the hydraulic clamp unit 1B, the biasing force of the compression spring 74 of the pressure accumulator 70 is set to be larger than the biasing force of the release spring 51 of the revolving clamp 3A and the pressure setting spring 111 of the pressure reducing device 80. The biasing force of the pressure setting spring 111 of the pressure reducing device 80 is set to be larger than the biasing force of the release spring 51 of the revolving clamp 3A. In other words, the magnitude relationship of the biasing force (pressing force) of each spring is compression spring 74>pressure setting spring 111>release spring 51. For this reason, when the hydraulic pressure of the pressure oil 23A passing through the fluid passage 21 of the hydraulic clamp unit 1B increases, first the release spring 51 of the revolving clamp 3A is compressed, and the revolving clamp 3A is switched to the locked state, and then the pressure setting spring 111 of the pressure reducing device 80 is compressed, and the pressure reducing device 80 is closed. Thereafter, the compression spring 74 of the pressure accumulator 70 is compressed, and the pressure oil 23A is stored in the pressure accumulator chamber 72.

[0098] For example, when a pressure drop occurs in the pressure oil 23A on the swivel clamp 3A side (secondary side) relative to the pressure reducing device 80 due to leakage of the pressure oil 23A, the pressure reducing device 80 opens, causing a pressure drop in the fluid passage 21 on the pressure oil supply / discharge device 4B side (primary side) relative to the pressure reducing device 80. In response to this pressure drop, the pressure oil 23A is discharged from the pressure accumulator 70 to the fluid passage 21, so that the pressure drop in the pressure oil 23A can be mitigated.

[0099] On the other hand, in the locked state shown in Fig. 17, when the torque transmitting tool 25 rotates in a second direction opposite to the first direction about the axis, the piston 5 moves axially upward so as to approach the cap member 8. Then, the pressure of the pressure oil 23A is reduced, and the pressure oil 23A stored in the accumulator chamber 72 of the accumulator 70 is first discharged to the fluid passage 21 by the biasing force of the compression spring 74, and then the pressure reducing device 80 opens as the pressure in the inlet chamber 84 drops. Thereafter, the pressure oil 23A in the swivel clamp 3 is discharged through the fluid passage 21 into the operating chamber 9 of the pressure oil supply / discharge device 4A. As a result, the hydraulic clamp unit 1B is released from the locked state shown in Fig. 17 to the released state shown in Fig. 13.

[0100] In the above-mentioned embodiments, the configuration in which the swivel clamp 3 and the pressure oil supply and discharge device 4 are combined (first and second embodiments), and the configuration in which the swivel clamp 3A and the pressure oil supply and discharge device 4A are combined (third embodiment) have been described, but the present invention is not limited to this. For example, the swivel clamp 3 and the pressure oil supply and discharge device 4A may be combined, or the swivel clamp 3A and the pressure oil supply and discharge device 4 may be combined.

[0101] In addition, in each of the above-described embodiments, an example of a pressure oil supply / discharge device that supplies hydraulic pressure to the clamp device has been described, but the present invention is not limited to this. For example, the present invention can also be applied to an air supply / discharge device that supplies compressed air to the clamp device instead of hydraulic pressure.

[0102] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0103] 1,1A,1B Hydraulic clamp unit (clamp unit) 2. Transporting parts 2A 1st page 2B 2nd side 3,3A Swivel clamp (clamp device) 4,4A Pressure oil supply / discharge device (fluid supply / discharge device) 21 Fluid passage (Fluid passage) 23 Hydraulic oil (working fluid) 23A Pressure oil (pressure fluid) 70,70A Pressure Accumulator 71 Housing 71C Through hole 72 Pressure accumulator 73 Accumulator piston (piston component) 74 Compression spring (biasing member) 74A Fluid spring (biasing member) 77 Indicator rod (rod component) 77B Tip 80 Pressure reducing device

Claims

1. A clamping device (3, 3A) for fixing a workpiece (W); a fluid supply / discharge device (4, 4A) that supplies / discharges a working fluid (23) for operating the clamp device (3, 3A) to / from the clamp device (3, 3A); a fluid passage (21) communicating with the clamp device (3, 3A) and the fluid supply / discharge device (4, 4A) and passing the working fluid (23); a pressure accumulator (70, 70A) connected to the fluid passage (21), the pressure accumulator (72) storing a portion of a pressurized fluid (23A) which is the pressurized working fluid (23) supplied from the fluid supply / discharge device (4, 4A) to the clamp device (3, 3A), and discharging the pressurized fluid (23A) stored in the pressure accumulator (72) to the fluid passage (21) in response to a pressure drop of the pressurized fluid (23A) in the fluid passage (21); A clamp unit (1, 1A, 1B) comprising:

2. The device further includes a conveying member (2) configured to be movable along a track, The clamp unit (1, 1A, 1B) of claim 1, wherein the clamp device (3, 3A), the fluid supply / drain device (4, 4A), and the pressure accumulator device (70, 70A) are mounted on the conveying member (2).

3. The pressure accumulator (70, 70A) a housing (71) in which the pressure accumulation chamber (72) is formed; a piston member (73) that is inserted into the housing (71) so as to be axially movably, and the pressure accumulator chamber (72) is disposed on one side of the piston member (73) in the axial direction; a biasing member (74, 74A) that biases the piston member (73) toward the pressure accumulator chamber (72); 3. A clamping unit (1, 1A, 1B) according to claim 1 or 2, comprising:

4. The pressure accumulator (70, 70A) further includes a rod member (77) provided on the other axial side of the piston member (73) so as to protrude in the axial direction, A clamp unit (1, 1A, 1B) according to claim 3, wherein a tip portion (77B) of the rod member (77) protrudes to the outside of the housing (71) through a through hole (71C) formed on the other side of the housing (71) as the piston member (73) moves to the other side.

5. The clamp unit (1A, 1B) of claim 1 or 2, further comprising a pressure reducing device (80) arranged in the fluid passage (21) for reducing the pressure of the pressurized fluid (23A) supplied from the fluid supply / discharge device (4, 4A) and supplying the reduced pressure to the clamp device (3, 3A).

6. The conveying member (2) includes a first surface (2A) and a second surface (2B) opposed to each other in a thickness direction, The fluid supply / drainage device (4, 4A) is mounted on the first surface (2A), The pressure accumulator (70, 70A) is mounted on the second surface (2B), 3. The clamp unit (1, 1A, 1B) according to claim 2, wherein the fluid supply / discharge device (4, 4A) and the pressure accumulator (70, 70A) are mounted opposite each other with the conveying member (2) interposed therebetween.

7. 3. The clamping unit (1, 1A, 1B) of claim 1 or 2, wherein the clamping device (3, 3A) comprises a plurality of pivoting clamps.

8. 3. The clamp unit (1, 1A) according to claim 1 or 2, wherein the fluid supply / discharge device (4) supplies the pressure fluid (23A) to the clamp device (3) when the clamp device (3) is released from a locked state to a released state.

9. 3. The clamp unit (1B) according to claim 1 or 2, wherein the fluid supply / discharge device (4A) supplies the pressure fluid (23A) to the clamp device (3A) when the clamp device (3A) is locked from a released state to a locked state.

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