Clamp device

Abstract

Provided is a clamp device equipped with a detection valve which can be reliably opened and closed by minimizing the area of a sealing part. Also provided is a clamp device having a simple configuration and comprising a plurality of detection valves for detecting the operating state of the detection valves. An output member (23) is inserted into a cylinder hole (10) in a housing (1). A detection valve (80) is provided in an intermediate portion of a detection pressure fluid flow path (79) formed in the housing (1). An operation unit (69) of the output member (23) moves a valve member (85) of the detection valve (80) in the radial direction, and the valve member (85) closes the flow path (79). Thus, the detection valve (80) is closed.

Description

Clamping device

[0001] This invention relates to a clamping device that fixes a clamping object, such as a workpiece, mold, or tool, to a table, robot hand, etc., by pressing the inner circumferential surface of a hole formed in the clamping object. More specifically, it relates to a clamping device equipped with a detection valve for detecting the operating state of the clamping device.

[0002] Conventional clamping devices of this type include one described in Patent Document 1 (Japanese Patent Publication No. 2014-008598). This prior art is configured as follows: A piston is inserted into a cylinder bore formed in a housing so as to be movable in the vertical direction. A piston rod is integrally provided protruding from the piston, and the lower end of a clamping rod is inserted horizontally so as to be movable into a cylindrical bore of a cylindrical portion formed at the upper end of the piston rod. A wedge portion is formed at the upper end of the clamping rod, and a grip member is engaged with the wedge portion. The grip member is moved horizontally by the vertical movement of the clamping rod. The grip member is capable of engaging with the inner circumferential surface of the bore when fitted to the bore of a workpiece. Furthermore, a flow path for a detection pressure fluid is formed in the housing. A detection valve is provided in the middle of this flow path. When the piston is moved downward from the upper limit position, the flow path is switched from a closed state to an open state by the detection valve. The detection valve is configured as follows: A ring-shaped valve member is inserted between the outer circumferential surface of the clamping rod and the inner circumferential surface of the cylinder bore so as to be movable in the vertical direction. An operating portion is provided projecting radially outward from the outer circumferential wall of the clamp rod. This operating portion is positioned opposite the valve member at a predetermined distance so as to be able to engage with the valve member from above. The valve surface formed on the upper part of the valve member is able to engage with the valve seat formed in the cylinder bore. When the piston descends (overstrokes) from the upper limit release position beyond the lock position where the engaging member engages with the inner circumferential surface of the workpiece hole, the operating portion of the piston rod engages with the valve member, moving the valve member downward. As a result, the valve surface is separated from the valve seat, and the detection valve opens. Consequently, the detection valve detects that the piston has overstroked.

[0003] Japanese Patent Application Laid-Open No. 2014-008598

[0004] In the prior art, a detection valve for detecting an operating state is sealed by a valve seat formed in a cylinder hole and a valve surface formed by the upper surface of a ring-shaped valve member. The sealing portion extends over substantially the entire upper surface of the ring-shaped valve member, and the sealing range is wide. There is a risk that the output member may tilt due to the action of an external force on the output member via the engagement member or the like, or that the valve surface or the valve seat may be worn over time. In such a case, the detection fluid may leak from the sealing portion, making it impossible to reliably open and close, and it may become difficult to detect the state of the clamping device. Therefore, there has been room for improvement in ensuring that the detection valve can be reliably opened and closed. An object of the present invention is to provide a clamping device including a detection valve that can be reliably opened and closed by minimizing the area of the sealing portion.

[0005] To achieve the above objective, the present invention provides, for example, a cylinder device equipped with a detection valve for detecting the release state, as shown in Figures 1 to 5C, as follows: An output member 23, inserted into a cylinder bore 10 formed in a housing 1, is moved axially in the cylinder bore 10 by a drive mechanism. The axial movement of the output member 23 causes an engaging member 39 to move radially in the cylinder bore 10. The engaging member 39 is fitted onto the inner circumferential wall of a hole 46 in a clamped object 45. The engaging member 39 is also capable of engaging with the inner circumferential surface of the hole 46. A flow path 79 for detection pressure fluid is formed in the housing 1. A detection valve 80 is provided in the middle of the flow path 79. When the output member 23 is moved to a predetermined position in the axial direction, the detection valve 80 opens or closes the flow path 79. The detection valve 80 is configured as follows: An operating part 69 protrudes from the outer circumferential wall of the output member 23 in a direction intersecting the axial direction. A valve member 85 is inserted between the outer circumferential surface of the output member 23 and the inner circumferential surface of the cylinder bore 10 so as to be movable in the radial direction of the cylinder bore 10. The valve member 85 is positioned opposite the operating part 69 at a predetermined distance in the axial direction so as to be able to engage with the operating part 69. A valve seat 84 is formed on the periphery of an opening that is part of the flow path 79 and is opened on the inner circumferential surface of the cylinder bore 10 in a direction intersecting the axial direction. A valve surface 86 formed on the outer circumferential surface of the valve member 85 is positioned opposite the valve seat 84 with a gap in the radial direction so as to be able to engage with it. When the operating part 69 is engaged with the valve member 85, the valve member 85 is moved in the radial direction, and the valve surface 86 engages with the valve seat 84.

[0006] The present invention provides the following advantages. In the clamping device described above, a valve seat for a detection valve is formed on the periphery of an opening that is opened on the inner circumferential surface of the cylinder bore in a direction intersecting the axial direction. When the valve member moves radially toward the valve seat, the valve seat, which is the periphery of the opening, and the valve surface of the valve member engage. Since the engagement portion between the valve seat and the valve surface is only a small portion of the periphery of the opening, the area of ​​the sealed portion can be minimized. This makes it possible to provide a clamping device that can reliably open and close a detection valve that detects the operating state.

[0007] The present invention preferably includes the following configurations (1) to (6).

[0008] (1) As shown in Figures 1 to 4C, the valve member 85 is made of an elastic material and is expandable in the radial direction. In this case, when the operating part of the output member engages with the valve member, which is an elastic material, the valve member moves while elastically deforming in the radial direction of the cylinder bore. When the valve surface of the valve member engages with the valve seat, the detection valve can reliably close by blocking the flow path.

[0009] (2) As shown in Figures 1 to 4C, the valve member 85 is formed in an annular shape and has a slit 85a formed in its peripheral wall. In this case, compared to the case without a slit, the valve member can be elastically deformed much more in the radial direction by a small external force, and the amount of diameter expansion can also be increased. As a result, the valve surface of the valve member is securely engaged with the valve seat. Also, since it can be greatly reduced in diameter to release the engagement, a sufficient gap (flow path) can be secured between the valve surface and the valve seat.

[0010] (3) As shown in Figures 1 to 4C, a tapered inner surface 88 inclined with respect to the axial direction is formed on the inner circumferential wall of the valve member 85. The tapered inner surface 88 is engageable with the operating part 69. In this case, the operating part of the output member slides along the tapered inner surface of the valve member and pushes the valve member, causing the valve surface of the valve member to move smoothly toward the valve seat in the radial direction of the cylinder bore. In addition, the force with which the operating part of the output member pushes the valve member in the axial direction is amplified by the wedge effect of the tapered inner surface and converted into a force pushing the valve member in the radial direction. As a result, the valve member is strongly pushed radially toward the valve seat, so that the detection valve is reliably closed.

[0011] (4) As shown in Figures 1 to 4C, a tapered outer surface 89 inclined with respect to the axial direction is formed on the outer wall of the operating part 69, and the tapered outer surface 89 is capable of engaging with the valve member 85. In this case, the valve member slides along the tapered outer surface of the operating part of the output member, causing the valve surface of the valve member to move smoothly toward the valve seat in the radial direction of the cylinder bore. Furthermore, the force with which the operating part of the output member pushes the valve member in the axial direction is amplified by the wedge effect of the tapered outer surface and converted into a force pushing the valve member in the radial direction. As a result, the valve member is strongly pushed radially toward the valve seat, so that the detection valve is reliably closed.

[0012] (5) As shown in Figures 5A to 5C, the operating portion 69 is formed on the outer circumferential wall of the output member 23 at a position facing the valve seat 84. The operating portion 69 has a tapered outer circumferential surface 89 inclined with respect to the axial direction, or the inner circumferential wall of the valve member 85 has a tapered inner circumferential surface 88 inclined with respect to the axial direction. When the operating portion 69 engages with the valve member 85, the valve member 85 is moved radially toward the valve seat 84. As shown in (1) above, when the valve member is made of an elastic material, it is subjected to repeated elastic deformation by a large force that resists the elastic force of the valve member over a long period of time. This can lead to wear or fatigue failure of the valve member. In contrast, since the valve member is not made of an elastic material, the possibility of wear or failure due to elastic deformation can be kept low. Also, in this case, a large force is not required for elastic deformation, and the valve member can be pushed radially and moved with a small force from the output member.

[0013] (6) As shown in Figures 1 to 4C, or Figures 5A to 5C, a large-diameter hole 13 and a small-diameter hole 14 are formed by a part of the cylinder bore 10. A stopper 82 is formed by a stepped portion formed between the large-diameter hole 13 and the small-diameter hole 14. The valve member 85 is received by the stopper 82 from the axial end side. In this case, by providing a stopper in the cylinder bore, the valve member is reliably received by the stopper. For this reason, axial movement is restricted at the engagement position between the valve member and the stopper, and movement is limited to the radial direction only at that engagement position. Thus, the valve surface of the valve member is reliably engaged with the valve seat at a predetermined axial position (engagement position) without displacement. As a result, the detection valve is reliably closed.

[0014] Figure 1 shows one embodiment of the present invention and is a cross-sectional view showing the released state of the clamping device. Figure 2 is a cross-sectional view showing the locked state of the clamping device. Figure 3 is a cross-sectional view showing the overstroke state of the clamping device. Figure 4A is a perspective view showing the valve member of the clamping device. Figure 4B is an enlarged cross-sectional view of portion 4B in Figure 1. Figure 4C is an enlarged cross-sectional view of portion 4C in Figure 1. Figure 5A is a perspective view showing a modified example of the valve member shown in Figure 4A. Figure 5B is a partial cross-sectional view showing a clamping device equipped with the valve member of Figure 5A, and is similar to Figure 4B. Figure 5C is a cross-sectional view similar to Figure 4C.

[0015] One embodiment of the present invention will be described with reference to Figures 1 to 4C. First, the structure of the clamping device will be described based on Figure 1, which shows the released state.

[0016] The housing 1 of the clamping device is inserted into a mounting hole formed in the table T of a machine tool and bolted to the table T. The housing 1 comprises a lower housing 3 and an upper housing 4. The lower half of the lower housing 3 is inserted into the mounting hole of the table T in a tight seal. The upper half of the lower housing 3 protrudes upward from the table T and is fixed to the table T by a plurality of bolts (not shown). The upper housing 4 is inserted into a mounting hole 6 formed vertically in the upper part of the lower housing 3 and bolted to the bottom of the mounting hole 6.

[0017] A cylinder bore 10 is formed in the lower housing 3 described above, extending vertically (axially). The cylinder bore 10 has a first hole 11, a second hole 12, a third hole 13, and a fourth hole 14, which are formed so that their diameters decrease sequentially from the bottom. A piston 16 is inserted into the first hole 11 in a sealed manner so as to be movable vertically (axially). A piston rod 17 is inserted into a hole formed in the piston 16, and is movable relative to it in the axial direction. A retaining ring is attached to the outer peripheral wall of the lower end of the piston rod 17 to prevent the piston rod 17 from coming out of the piston 16. The piston rod 17 protrudes upward from the piston 16. The piston rod 17 is inserted into the fourth hole 14 in a sealed manner so as to be movable vertically, passing through the second hole 12 and the third hole 13. A cylindrical portion 18 is formed on the upper part of the piston rod 17, and a clamp rod 20 is inserted into the cylindrical hole 19 of the cylindrical portion 18 so as to be movable horizontally. A projection 21 is provided on the inner circumferential wall of the cylindrical portion 18, extending radially inward. This projection 21 faces a flange portion 22 that protrudes radially outward from the lower part of the clamp rod 20, allowing it to abut against it from above. This prevents the clamp rod 20 from slipping out upward from the cylindrical hole 19 of the piston rod 17. In this embodiment, the output member 23 is formed by the piston rod 17 and the clamp rod 20.

[0018] A locking chamber 26 is formed above the piston 16, and a release chamber 27 is formed between the piston 16 and the bottom wall of the mounting hole in the table T. A locking supply / discharge passage 28 is formed in the housing 1 and communicates with the locking chamber 26. As a result, pressurized oil from a pressurized oil source is supplied to the locking chamber 26 through the locking supply / discharge passage 28, and the pressurized oil in the locking chamber 26 is discharged to the outside through the supply / discharge passage 28. In addition, a release supply / discharge passage 29 is formed in the bottom wall of the mounting hole in the table T. As a result, pressurized oil from a pressurized oil source is supplied to the release chamber 27 through the supply / discharge passage 29, and the pressurized oil in the release chamber 27 is discharged to the outside through the supply / discharge passage 29. In this embodiment, the locking chamber 26 through which pressurized oil is supplied and discharged, the release chamber 27 through which pressurized oil is supplied and discharged, and the piston constitute the drive mechanism.

[0019] A housing hole 32 communicating with the cylinder hole 10 is formed inside the upper housing 4. A cylindrical cap member 33 is inserted into the housing 1 so as to be movable horizontally and vertically. The upper half of the cap member 33 protrudes upward from the upper surface of the upper housing 4. A flange portion 34 is formed circumferentially on the lower part of the cap member 33 so as to protrude radially outward. The upper surface of the flange portion 34 faces the ceiling wall of the housing hole 32 from below so as to be able to abut against it, preventing the cap member 33 from coming out of the housing hole 32 upward.

[0020] A clamp rod 20 is inserted into the cylindrical hole 35 of the cap member 33 so as to be movable in the vertical direction. Two support holes 36 are radially penetrated through the peripheral wall of the cap member 33, and an engaging member 39 is inserted into each support hole 36 so as to be movable along the support hole 36. A receiving surface 40 is formed on the inner wall of the engaging member 39 so as to taper towards the tip (upwards). In addition, a wedge surface (wedge portion) 41 is formed on the side wall of the upper end of the clamp rod 20 so as to become thicker (away from the axis) towards the tip (upwards), and this wedge surface 41 engages with the receiving surface 40 of the engaging member 39 from above.

[0021] An engaging portion 42 is formed on the upper half of the outer wall of the engaging member 39 described above. Multiple protrusions are formed on the engaging portion 42 in the vertical direction, with the protrusions extending horizontally. These protrusions can engage with the inner circumferential wall of the hole 46 of the workpiece (object to be clamped) 45 shown in Figure 2.

[0022] Furthermore, a mounting groove 43 is formed horizontally in the lower half of the outer wall of the engaging member 39, and a mounting groove 49 is also formed on the outer circumferential wall of the cap member 33 so as to correspond to the height of the mounting groove 43 of the engaging member 39. An elastic ring 50 is fitted so as to straddle the mounting groove 43 of the engaging member 39 and the mounting groove 49 of the cap member 33. The elastic force of the elastic ring 50 biases the engaging member 39 radially inward of the cap member 33. In this embodiment, the elastic ring 50 is made of rubber, but is not limited to this, and may be made of resin, a metal spring, or the like.

[0023] Within the aforementioned housing hole 32, the spring receiving member 51 and the extension spring 52 are inserted below the cap member 33. The lower end of the extension spring 52 is received by the upper surface of the lower housing 3, and the upper end of the extension spring 52 is received by the ceiling surface of the housing hole 32 via the spring receiving member 51. As a result, the extension spring 52 biases the cap member 33 upward relative to the lower housing 3. In this embodiment, the extension spring 52 and the spring receiving member 51 constitute a support mechanism 53 that pushes up the engaging member 39 with a predetermined force.

[0024] The base end of the dust seal 54 is attached to the upper part of the inner circumferential wall of the housing hole 32. The tip of the dust seal 54 is in close contact with the outer circumferential surface of the cap member 33 and the outer wall surface of the engaging member 39. This dust seal 54 prevents foreign matter such as metal shavings from entering the housing 1 through the gap between the cap member 33 and the housing 1, and the gap between the engaging member 39 and the housing 1. In addition, the radially inward elastic force of the dust seal 54 biases the clamp rod 20, the engaging member 39, and the cap member 33 radially inward toward the axis of the cylinder hole 10.

[0025] A seating surface (seating portion) 57 is formed by a part (or all) of the upper end surface of the upper housing 4 described above, and a workpiece 45 can be placed on this seating surface 57. An outlet 58 is opened in the seating surface 57, and a supply passage 59 communicating with the outlet 58 is formed inside the housing 1. For this reason, compressed air for seating detection from a compressed air source (pressure fluid source) is ejected from the outlet 58 via the supply passage 59.

[0026] In the clamping device of this embodiment, a first passage 61 for supplying compressed air (pressure fluid) for detecting the operating state is provided inside the housing 1. A first detection valve 62 is provided in the middle of the first passage 61. The first detection valve 62 detects when the piston 16 or output member 23 has been lowered beyond the lock position by a predetermined distance (an overstroke state among the operating states), and is configured as shown in Figure 1.

[0027] A cylindrical first valve member 63 is inserted between the outer circumferential surface of the piston rod 17 and the inner circumferential surface of the second hole 12 of the cylinder bore 10, and is sealed by an outer sealing member 64 and an inner sealing member 65 so as to be movable in the vertical direction (axial direction). A retaining ring 67 is fitted into a mounting groove 66 formed at the lower part of the inner circumferential wall of the second hole 12, and the retaining ring 67 prevents the first valve member 63 from falling out of the second hole 12. The aforementioned locking chamber 26 is partitioned between the first valve member 63 and the piston 16. A first valve chamber 68 is also formed above the first valve member 63.

[0028] The lower surface of the first valve member 63 described above is capable of engaging with the upper surface of the piston 16. Furthermore, the inner circumferential portion of the first valve member 63 is formed to be shorter in height than the outer circumferential portion of the first valve member 63. The lower surface of the annular operating portion 69, which protrudes radially outward from the outer circumferential surface of the piston rod 17, is capable of engaging with the upper surface of the inner circumferential portion of the first valve member 63. The upper surface of the first valve member 63 is capable of contacting the stepped portion (ceiling surface of the second hole) 70 formed between the second hole 12 and the third hole 13. As a result, when the piston 16 descends from the upper limit position to the lower limit position, the operating portion 69 engages with the first valve member 63 at an intermediate position, and the operating portion 69 lowers the first valve member 63 to the engagement position between the first valve member 63 and the retaining ring 67. Furthermore, as the piston 16 moves from the lower limit position to the upper limit position, the piston 16 engages with the first valve member 63 at an intermediate position, and then the piston 16 raises the first valve member 63 to the engagement position (upper limit position) between the first valve member 63 and the stepped portion 70.

[0029] An annular first valve seat 71 is formed on an annular stepped portion 70 formed between the second hole 12 and the third hole 13 of the cylinder bore 10. A first valve surface 72 that abuts against the first valve seat 71 is formed on the upper surface of the outer peripheral portion of the first valve member 63. When the first valve surface 72 engages with the first valve seat 71, the first valve chamber 68 is divided into a first inlet chamber 73 on the outer peripheral side and an outlet chamber 74 on the inner peripheral side.

[0030] A first supply passage 75 communicating with the first inlet chamber 73 is formed within the housing 1, and this first supply passage 75 opens to the inner circumferential surface of the second hole 12. As a result, compressed air (pressure fluid) from a compressed air source (pressure fluid source) is supplied to the first inlet chamber 73 of the first valve chamber 68 through the first supply passage 75. The first supply passage 75 is part of the first flow path 61 described above, and is a flow path that branches off from the first flow path 61 into a supply passage 59 and the first supply passage 75. In addition, a discharge passage 76 communicating with the outlet chamber 74 is formed within the housing 1, and this discharge passage 76 opens to the inner circumferential surface of the third hole 13. As a result, compressed air in the first valve chamber 68 is discharged to the outside of the housing 1 through the discharge passage 76. In this clamp device of this embodiment, the first flow path 61 is composed of the first supply passage 75, the first valve chamber 68 consisting of the first inlet chamber 73 and the outlet chamber 74, and the discharge passage 76, etc.

[0031] In the clamping device of this embodiment, a second flow path (flow path) 79 for supplying compressed air (pressure fluid) for detecting the operating state is provided inside the housing 1 in order to detect an operating state other than the overstroke described above. A second detection valve (detection valve) 80 is provided in the middle of the second flow path 79. The second detection valve 80 detects when the piston 16 or output member 23 has been raised to near the release position (the release state among the operating states), and is configured as shown in Figure 1.

[0032] A portion of the second flow path 79 opens to the inner circumferential surface of the third hole 13 of the cylinder bore 10. The flow path on the compressed air source side of the opening is configured as the second valve chamber 83. The compressed air from the second valve chamber 83 is discharged to the outside of the housing 1 through the outlet chamber 74 and the discharge passage 76. A second valve seat 84 is formed on the inner circumferential surface of the third hole 13, at the periphery of the opening. An annular second valve member 85 is fitted onto the piston rod 17 so as to face the second valve seat 84 with a gap between them. A second valve surface 86 formed on the outer circumferential surface of the second valve member 85 can contact the second valve seat 84 with a gap between them. A retaining ring 87 is fitted into a groove formed in the circumferential direction on the inner wall surface of the third hole 13. The retaining ring 87 restricts the axial movement of the second valve member 85. A slit 85a is formed in the circumferential wall of the second valve member 85. The inner circumferential wall of the second valve member 85 is formed such that a tapered inner circumferential surface 88 approaches the axis as it extends upward. The outer circumferential wall of the operating portion 69 of the piston rod 17 is formed such that a tapered outer circumferential surface 89 tapers towards the top as it extends upward. The tapered inner circumferential surface 88 faces the tapered outer circumferential surface 89 with an axial gap between them and is capable of contacting it. When the piston rod 17 is moved upward in the axial direction, the tapered outer circumferential surface 89 engages with the tapered inner circumferential surface 88 of the second valve member 85. Next, the piston rod 17 pushes the second valve member 85 upward in the axial direction. As a result, the upper surface of the second valve member 85 is received from above by a stepped portion (stopper) 82 formed between the third hole 13 and the fourth hole 14 of the cylinder bore 10. When the piston rod 17 is moved further upward in the axial direction, the tapered outer surface 89 pushes open the second valve member 85 (elastically deforms it to increase its diameter), and the valve surface 86 of the second valve member 85 engages with the valve seat 84. Therefore, in the release state of the clamp device when the piston 16 has moved to the upper limit position, the second detection valve 80 is reliably closed. In this embodiment, the second valve member 85 is made of a metal such as iron, steel, stainless steel, or aluminum, but it is not limited to these materials and may be a resin or rubber ring.

[0033] A mounting groove is formed in the circumferential direction on the inner circumferential wall of the fourth hole 14 of the cylinder hole 10 described above. An O-ring is fitted into this mounting groove as a sealing member. This O-ring prevents compressed air from the second flow path 79 from flowing into the front end of the housing 1.

[0034] The clamping device described above operates as follows, as shown in Figures 1 to 3. First, in the released state of the clamping device shown in Figure 1, pressurized oil is discharged from the locking chamber 26, and pressurized oil from the pressurized oil source is supplied to the release chamber 27. The pressurized oil in the release chamber 27 moves the clamping rod 20 to the upper limit position via the piston 16 and piston rod 17.

[0035] In the released state of the clamping device described above, the piston 16 is supported by the stepped portion 70 of the housing 1 via the first valve member 63. As a result, the first valve surface 72 of the first valve member 63 engages with the first valve seat 71, and the first detection valve 62 for detecting overstroke is closed.

[0036] Furthermore, in the released state of the clamping device described above, the piston rod 20 is moved to the upper limit position. As a result, the tapered outer surface 89 of the piston rod 20 presses the second valve member 85 against the stepped portion 82, expanding the diameter of the second valve member 85. The second valve surface 86 of the second valve member 85 engages with the second valve seat 84, closing the second detection valve 80 for release detection.

[0037] In the released state described above, the workpiece (object to be clamped) 45 is lowered from above the clamping device by some means of transport, such as a robot, or by the weight of the workpiece itself. Then, the hole 46 in the workpiece 45 is fitted onto the cap member 33 and the engaging member 39. Next, the lower surface of the workpiece 45 is received by the seating surface 57 of the housing 1. At this time, the lower surface of the workpiece 45 shields the nozzle 58 for seat detection. Also, as mentioned above, the first detection valve 62 for overstroke detection is closed. As a result, the pressure of the compressed air in the supply passage 59 that supplies compressed air to the nozzle 58 and the pressure of the compressed air in the first supply passage 75 that communicates with the supply passage 59 exceeds a preset value. This rising pressure is detected by a pressure switch (or pressure sensor), which is not shown. As a result, the pressure of the compressed air in the supply passage 59 is detected by the pressure sensor, etc., to indicate that the workpiece 45 is placed on the seating surface 57 and that the piston 16, etc., is not in an overstroke state where it has descended beyond the locked position.

[0038] When the clamping device is switched from the released state shown in Figure 1 to the locked state shown in Figure 2, the pressurized oil in the release chamber 27 is discharged, and pressurized oil is supplied to the lock chamber 26. Then, the pressurized oil in the lock chamber 26 lowers the piston 16, piston rod 17, and clamp rod 20 toward the locked position relative to the cap member 33 and engaging member 39, which are held in the upper limit position by the biasing force of the advance spring 52. At this time, the tapered outer surface 89 of the piston rod 17 moves downward, but the second valve member 85 is left behind as its downward movement is restricted by the retaining ring 87. The second valve member 85 shrinks in diameter due to its elastic restoring force, and the second valve surface 86 of the second valve member 85 is separated from the second valve seat 84. As a result, the compressed air in the second valve chamber 83 is discharged to the outside through the outlet chamber 74 and the discharge passage 76, and the pressure of the compressed air in the second valve chamber 83 decreases. This pressure decrease is detected by a pressure sensor (or pressure switch) (not shown). As a result, the second detection valve 80 detects that the piston 16, etc., has moved downward from the release position (upper limit position). Next, the wedge surface 41 of the clamp rod 20 pushes the receiving surface 40 of the engaging member 39, causing the clamp rod 20 to push the engaging member 39 radially outward. Then, the engaging portion 42 of the engaging member 39 engages with the inner circumferential surface of the hole 46 in the workpiece 45. At this time, the clamp rod 20 descends in such a way that it slightly compresses the advance spring 52 via the engaging member 39, the cap member 33, and the spring receiving member 51. As a result, the workpiece 45 is strongly pressed against the seating surface 57 of the upper housing 4.

[0039] In the locked state of the clamping device shown in Figure 2, the operating portion 69 of the piston rod 17 is separated from the first valve member 63 by a predetermined distance above it, and the operating portion 69 does not operate the first valve member 63. Therefore, the state in which the first valve member 63 is raised to the upper limit position is maintained by the pressure of the pressurized oil supplied to the locking chamber 26. Thus, the first valve surface 72 is engaged with the first valve seat 71, and the first detection valve 62 is closed. In addition, the state in which the lower surface of the workpiece 45 shields the outlet 58 of the housing 1 is maintained. Consequently, the state in which the pressure of the compressed air in the first supply passage 75 exceeds a predetermined pressure is maintained.

[0040] When switching the clamping device from the locked state shown in Figure 2 to the released state shown in Figure 1, the pressurized oil in the locking chamber 26 is discharged, and pressurized oil is supplied to the release chamber 27. As a result, the clamping device is switched to the released state in almost the reverse procedure of the locking operation described above.

[0041] In the clamping device described above, as shown in Figure 3, the piston 16 may descend beyond the locked position (overstroke) if a workpiece 45A with a hole diameter larger than expected is loaded, for example. In such cases, the clamping device operates as follows.

[0042] With the workpiece 45A having the excessively large hole 46A as described above placed on the seating surface 57 of the clamping device, the clamping device is driven to lock. Then, with the engaging member 39 held in the upper limit position by the biasing force of the extension spring 52, the wedge surface 41 of the clamping rod 20 pushes the receiving surface 40 of the engaging member 39. As a result, the clamping rod 20 pushes the engaging member 39 radially outward (expanding its diameter excessively). At this time, the engaging member does not come into contact with the inner circumferential wall of the hole 46A, which is larger than expected, and the clamping rod 20 descends beyond the expected locking position. Then, with the inner circumferential surface of the hole 46A of the workpiece 45A and the engaging portion 42 of the engaging member 39 not engaged, the operating portion 69 of the piston rod 17 engages with the first valve member 63. After that, the operating portion 69 lowers the first valve member 63. At this time, the first valve surface 72 of the first valve member 63 is separated from the first valve seat 71, and the compressed air in the first inlet chamber 73 of the first valve chamber 68 is discharged to the outside of the housing 1 through the outlet chamber 74. As a result, the pressure of the compressed air in the first inlet chamber 73 decreases, and this pressure drop is detected by a pressure sensor (or pressure switch) (not shown). Therefore, based on the detection result of the pressure drop, it is detected that the piston 16 has descended beyond the lock position and is in an overstroke state. Next, the first valve member 63 is received from below by the retaining ring 67 fitted in the first hole 11 of the cylinder bore 10, and the descent of the first valve member 63 and the piston rod 17, etc. is stopped.

[0043] In addition to the case where the work 45A having a larger hole diameter than the above assumption is clamped by the clamping device, there may be an overstroke state. For example, in the locked state (see FIG. 2) where the work 45 is fixed by the clamping device, for example, when the clamping rod 20 breaks at the middle height portion due to metal fatigue or the like. Also, when sufficient frictional force cannot be generated between the protrusion of the engaging portion 42 of the engaging member 39 and the inner peripheral surface of the work 45, the case where the protrusion slides down along the inner peripheral surface of the work 45. Also, when the peripheral equipment collides with the engaging member 39 and a part of the engaging member 39 is missing, and the clamping device is operated in a clamping manner. Even in these cases, similar to the case of the work 45A having the above-described excessive hole diameter 46A, the overstroke state of the clamping device is detected by the first detection valve 62 for overstroke detection.

[0044] The above-described embodiment has the following advantages. The middle part of the second flow path 79 is opened on the inner peripheral surface of the third hole 13 of the cylinder hole 10. The second valve seat 84 of the second detection valve 80 formed by the peripheral edge of the opening is formed in a direction intersecting the axial direction of the cylinder hole 10 (in the above embodiment, the radial direction of the cylinder hole 10). The engaging portion between the second valve seat 84 and the second valve surface 86 of the second valve member 85 is a narrow portion of the peripheral edge of the opening, and sealing can be performed at the narrow portion. The sealing portion of the present embodiment can be made narrower than the sealing portion by a valve surface or the like formed on the upper surface of the annular valve member in the clamping device of the conventional example. Thereby, it is possible to highly suppress the detection compressed air from leaking out from the sealing portion in the closed valve state of the second detection valve 80. As a result, false detection of the second detection valve 80 due to leakage of compressed air can be prevented.

[0045] The above-described embodiment and modification examples can be changed as follows.

[0046] In the second detection valve 80 of the above embodiment, an annular second valve member 85 is fitted onto the piston rod 17 and is configured to be elastically deformed by the tapered outer surface 89 of the piston rod 17 so as to increase its diameter. Alternatively, in a modified version of the above embodiment, as shown in Figures 5A to 5C, the second detection valve 80 is configured as follows: The second valve member 85 of the second detection valve 80 is formed in a ring shape and does not have a slit 85a. The second valve member 85 does not elastically deform. In addition, a gap is formed between the inner surface of the second valve member 85 and the outer surface of the piston rod 17, and a gap is formed between the outer surface of the second valve member 85 and the inner surface of the third hole 13 of the cylinder hole 10. A tapered inner surface is formed on the inner wall of the second valve member 85 so as to approach the axis as it goes upward. A second valve surface (valve surface) 86 is formed on the outer wall of the second valve member 85. The second valve surface 86 can contact the second valve seat 84 with a gap between them. A retaining ring 87 is fitted into a groove formed circumferentially on the inner wall surface of the third hole 13. The retaining ring 87 restricts the axial movement of the second valve member 85. The outer circumferential surface 89 of the operating portion 69 of the piston rod 17 is tapered as it extends upward, and is formed only on the portion of the circumference facing the second valve seat 84. When the piston rod 17 is moved upward in the axial direction, the tapered outer circumferential surface 89 engages with the tapered inner circumferential surface 88 of the second valve member 85. The piston rod 17 then pushes the second valve member 85 slightly upward in the axial direction. The upper surface of the second valve member 85 is then received from above by a stepped portion (stopper) 82 formed between the third hole 13 and the fourth hole 14 of the cylinder bore 10. When the piston rod 17 is moved further upward in the axial direction, the tapered outer surface 89 moves the second valve member 85 toward the second valve seat 84, and the valve surface 86 of the second valve member 85 engages with the valve seat 84. Therefore, in the release state of the clamp device when the piston 16 has moved to the upper limit position, the second detection valve 80 is reliably closed. Also, when the piston rod 17 is moved downward in the axial direction, the tapered outer surface 89 is separated from the second valve member 85, and the second valve member 85 becomes movable in the radial direction.And, a return portion 90 protrudes radially outward on the outer peripheral wall of the piston rod 17 and above the operation portion 69 in the axial direction, and is formed to extend in the circumferential direction. When the piston rod 17 descends, the return portion 90 engages with the inner peripheral surface of the second valve member 85, and the second valve member 85 is moved in a direction in which the axis of the second valve member 85 approaches the axis of the piston rod 17. For this reason, the second valve surface 86 of the second valve member 85 is separated from the second valve seat 84. Thereby, the compressed air in the second flow path 79 is surely discharged to the outside of the housing 1 through the gap.

[0047] Further, the following configuration may be added to the clamping device according to the modification of the above embodiment. An elastic member such as an O-ring, a coil spring, or a leaf spring may be provided between the outer peripheral surface of the second valve member 85 and the inner peripheral surface of the third hole 13, or between the outer peripheral surface of the piston rod 17 and the inner peripheral surface of the second valve member 85, so as to bias the second valve surface 86 to be separated from the second valve seat 84.

[0048] The above embodiment and its modification can be changed as follows.

[0049] Instead of the clamping device of the above embodiment being fixed to the movable part of a table or a robot hand, it may be provided at other places, for example, the movable part of a turntable or a pallet. Also, instead of a workpiece or a tool as the object to be clamped, a workpiece pallet or a mold may be used.

[0050] Instead of arranging two engaging members 39 in the circumferential direction, one or three or more engaging members 39 may be arranged. Also, instead of the engaging member 39 being formed in a substantially rectangular shape, it may be constituted by a ball or an annular collet provided with a slit.

[0051] In the clamping device drive mechanism of the above embodiment, it is composed of a hydraulic cylinder driven by pressurized oil supplied to the locking chamber 26 and the release chamber 27. Alternatively, it may be a hydraulic cylinder driven by another liquid such as a water pressure cylinder, or a pneumatic cylinder driven by a gas such as compressed air or compressed nitrogen. The hydraulic (fluid pressure) cylinder can be configured in a way that it is driven by pressurized fluid for locking and spring force for release, or by spring force for locking and pressurized fluid for release, instead of the double-acting type exemplified above. In addition, the drive mechanism may be configured by a motor and a ball screw, by a spring mechanism, by a manually driven screw mechanism, or by a lever mechanism.

[0052] The clamping device described above may be positioned upside down, sideways, or diagonally, instead of being positioned vertically.

[0053] Instead of the upper surface of the piston 16 being able to contact the lower surface of the first valve member 63, a projection or the like that protrudes radially outward from the outer peripheral wall of the piston rod 17 (and constitutes a part of the piston rod 17) may be made able to contact the lower surface of the first valve member 63.

[0054] Instead of the valve member 85 having one slit 85a that divides the peripheral wall of the valve member 85, the valve member 85 may have one or more slits 85a that are formed partway up the height of the peripheral wall. The direction of the slit is not limited to being formed in the axial direction of the cylinder bore, but may be inclined with respect to that axial direction. Furthermore, the ends of the slit may be opened alternately on the upper and lower surfaces of the valve member, or they may be opened only on the upper surface or only on the lower surface.

[0055] Instead of forming the valve member 85 in a ring shape, it may be formed in a block shape or sphere shape, such as a rectangular or ring-shaped component with the peripheral wall cut off. In this case, a guide portion may be provided in the housing or the like so that the valve member is guided toward the valve seat.

[0056] In the above embodiment, the inner circumferential surface 88 of the second valve member 85 is formed so that it approaches the axis as it extends upward. Also, the outer circumferential surface 89 of the operating portion 69 of the piston rod 17 is formed so that it tapers towards the top as it extends upward. Alternatively, only one of the tapered inner circumferential surface 88 or the tapered outer circumferential surface 89 may be provided. In this case, the other may be a block-shaped member or a curved member, etc., and that member may slide along the tapered inner circumferential surface 88 or the tapered outer circumferential surface 89.

[0057] Instead of the tapered inner surface 88 of the second valve member 85 being formed so that it approaches the axis as it moves upward, it may be formed so that it approaches the axis as it moves downward. In this case, when the output member 23 is moved downward, the output member 23 is moved radially by the second valve member 85, and the second detection valve 80 is closed. Of course, various other modifications can be made within the scope that a person skilled in the art can imagine.

[0058] 1: Housing, 10: Cylinder bore, 13: Large diameter bore, 14: Small diameter bore, 23: Output member, 39: Engaging member, 45: Clamp object, 46: Hole, 69: Operating part, 79: Flow path, 80: Detection valve, 82: Stopper, 84: Valve seat, 85: Valve member, 85a: Slit, 86: Valve surface, 88: Tapered inner surface, 89: Tapered outer surface.

Claims

1. An output member (23) inserted into a cylinder bore (10) formed in a housing (1), the output member (23) being moved in the axial direction of the cylinder bore (10) by a drive mechanism; an engaging member (39) being moved radially in the cylinder bore (10) by the axial movement of the output member (23), the engaging member (39) being fitted onto the inner circumferential wall of a hole (46) in a clamp object (45) and being able to engage with the inner circumferential surface of the hole (46); a flow path (79) for detection pressure fluid formed in the housing (1); and a detection valve (80) provided in the middle of the flow path (79), the detection valve (80) being used to shut off or open the flow path (79) when the output member (23) is moved to a predetermined position in the axial direction, wherein the detection valve (80) includes an operating part (69) projecting from the outer circumferential wall of the output member (23) in a direction intersecting the axial direction, A clamping device characterized by comprising: a valve member (85) inserted between the outer circumferential surface of the output member (23) and the inner circumferential surface of the cylinder bore (10) so as to be movable in the radial direction of the cylinder bore (10), the valve member (85) facing the operating part (69) at a predetermined distance in the axial direction so as to be engageable with the operating part (69); a valve seat (84) formed on the periphery of an opening in which a part of the flow path (79) opens in a direction intersecting the axial direction to the inner circumferential surface of the cylinder bore (10); and a valve surface (86) formed on the outer circumferential surface of the valve member (85) and facing the valve seat (84) with a gap in the radial direction so as to be engageable with the valve seat (84), the valve surface (86) engaging with the valve seat (84) when the operating part (69) engages with the valve member (85) as the valve member (85) is moved in the radial direction.

2. A clamping device according to claim 1, characterized in that the valve member (85) is made of an elastic member and is expandable in the radial direction.

3. A clamping device according to claim 2, characterized in that the valve member (85) is formed in an annular shape and has a slit (85a) formed in its peripheral wall.

4. A clamping device according to claim 1, characterized in that a tapered inner surface (88) inclined with respect to the axial direction is formed on the inner circumferential wall of the valve member (85), and the tapered inner surface (88) is engageable with the operating part (69).

5. A clamping device according to claim 1, characterized in that a tapered outer surface (89) inclined with respect to the axial direction is formed on the outer wall of the operating portion (69), and the tapered outer surface (89) is capable of engaging with the valve member (85).

6. A clamping device according to claim 1, characterized in that the operating portion (69) is formed on the outer peripheral wall of the output member (23) at a position facing the valve seat (84), the operating portion (69) has a tapered outer peripheral surface (89) inclined with respect to the axial direction, or the inner peripheral wall of the valve member (85) has a tapered inner peripheral surface (88) inclined with respect to the axial direction, and the valve member (85) is moved radially toward the valve seat (84) when the operating portion (69) engages with the valve member (85).

7. A clamping device according to claim 1, characterized in that a large diameter hole (13) and a small diameter hole (14) are formed by a part of the cylinder hole (10), a stopper (82) is formed by a stepped portion formed between the large diameter hole (13) and the small diameter hole (14), and the valve member (85) is received by the stopper (82) from the axial end side.

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