Rotary clamp

A piston (4) is inserted in a housing (1) so that the piston (4) is vertically movable. A housing hole (5) is vertically provided in the piston (4), and an output rod (6) is inserted in the housing hole (5) so that the output rod (6) is vertically movable. A converting mechanism (22) converts vertical movement of the piston (4) into rotary movement of the output rod (6). A guide groove (28) is provided in a circumferential direction on an inner circumferential wall of the housing hole (5), and a stopping part (29) is provided at an end part, in the circumferential direction, of the guide groove (28). An engaging member (31) which is provided on an outer circumferential wall of the output rod (6) is caused to face the stopping part (29) of the guide groove (28) at a given distance in the circumferential direction from the stopping part (29) so that the engaging member (31) can be in contact with the stopping part (29).

TECHNICAL FIELD

The invention relates to a clamping device configured such that an output rod is rotated.

BACKGROUND ART

As this kind of rotary clamp, one that is disclosed in Patent Literature 1 (Japan, Japanese Patent Application Publication, Tokukaihei, No. 10-109239) has been conventionally known. Such a conventional clamping device is configured as follows.

A piston is inserted in a housing so that the piston is vertically movable. A housing hole is provided in an upper surface of the piston, and a lower part of an output rod is inserted in the housing hole so that the output rod is vertically movable. A lock spring is disposed on an upper side of the piston, and a lower end part of the lock spring is caused to be in contact with the upper surface of the piston. A stepwise part is provided on an outer circumferential wall of the output rod, and the lower end part of the lock spring is caused to face an upper surface of the stepwise part at a given distance from the upper surface of the stepwise part so that the lower end part of the lock spring can be in contact with the upper surface of the stepwise part. An operation chamber to/from which pressurized oil is supplied and discharged is provided on a lower side of the piston. A compression spring is disposed between a lower end part of the output rod and a bottom wall of the housing hole. An actuation groove is helically provided on an inner circumferential wall of the housing hole, and a rotary groove is provided on the outer circumferential wall of the lower part of the output rod so that the rotary groove faces the actuation groove. A driving hall is inserted between the actuation groove and the rotary groove.

In a case where the rotary clamp is caused to carry out lock driving, the pressurized oil in the operation chamber is discharged. This causes the lock spring to move the piston directly downward. Then, the compression spring causes the piston to be separated from the output rod, and thereby the piston causes the output rod to rotate, via the actuation groove, the driving ball, and the rotary groove. Next, the upper surface of the stepwise part of the output rod is caused to be in contact with the lower end part of the lock spring. This causes rotation of the output rod to be stopped. Then, the piston and the output rod are integrally moved directly downward.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The above conventional technique has the following problems.

In a case where the stepwise part of the output rod is gently caused to be in contact with the lower end part of the lock spring from below in the middle of a process of the lock driving of the foregoing conventional rotary clamp, the output rod is stopped at a given position in a circumferential direction with respect to the piston. In contrast, in a case where the stepwise part of the output rod is roughly caused to be in contact with the lower end part of the lock spring, the rotary groove of the output rod is forcefully screwed in the actuation groove of the housing hole via the driving ball due to an inertial force of the output rod in the circumferential direction, and the output rod is stopped at a position beyond the given position in the circumferential direction with respect to the piston.

Furthermore, abrasion of the rotary groove, the actuation groove, or the driving ball causes an increase in dimension of an engagement gap between the driving ball and the rotary groove and an increase in dimension of an engagement gap between the driving ball and the actuation groove. This causes the output rod to be stopped at a position beyond the given position in the circumferential direction with respect to the piston.

An object of the present invention is to provide a rotary clamp, which is configured such that it is possible to absolutely stop an output rod of the rotary clamp at a given position in a circumferential direction.

Solution to Problem

In order to attain the above object, a rotary clamp in accordance with an aspect of the present invention is configured as below, as illustrated in, for example,FIGS. 1 through 3C.

A piston4is inserted in a housing1so that the piston4is movable in an axial direction. A housing hole5is provided in the axial direction in the piston4. An output rod6is inserted in the housing hole5so that the output rod6is movable in the axial direction. A biasing means9is disposed between the piston4and the output rod6, and biases the piston4and the output rod6so that the piston4and the output rod6are separated from each other. An operation chamber15is provided on a base end side of the piston4, and a pressurized fluid is supplied and discharged to/from the operation chamber15. A lock spring16is provided on a top end side of the piston4in the housing1so that the lock spring16biases the piston4toward the base end side in the axial direction. A converting mechanism22converts axial movement of the piston4into rotary movement of the output rod6. A guide groove28is provided in a circumferential direction on one of an inner circumferential wall of the housing hole5and an outer circumferential wall of the output rod6, and a stopping part29is provided at an end part, in the circumferential direction, of the guide groove28. An engaging member31which is provided on the other one of the inner circumferential wall of the housing hole5and the outer circumferential wall of the output rod6is inserted in the guide groove28. The engaging member31is caused to face the stopping part29at a given distance in the circumferential direction from the stopping part29so that the engaging member31can be in contact with the stopping part29.

The present invention brings about the following effects.

According to the rotary clamp, the engaging member is configured such that the engaging member can be received by the stopping part of the guide groove from the circumferential direction. This causes the output rod to be absolutely stopped at a given position in the circumferential direction with respect to the piston.

In aspects of the present invention, the following configurations (1) through (3) are preferably added.(1) The converting mechanism22has an actuation groove23, a rotary groove24, a circulation groove25, and a driving member26. The actuation groove23is helically provided on the inner circumferential wall of the housing hole5. The rotary groove24is provided on the outer circumferential wall of the output rod6. The circulation groove25is provided on the outer circumferential wall of the output rod6so that a base end part24aof the rotary groove24is communicated, in the axial direction, with a top end part24bof the rotary groove24. The driving member26is inserted between the actuation groove23and the rotary groove24and between the inner circumferential surface of the housing hole5and the circulation groove25.

This allows a force which presses the piston in the axial direction to be absolutely transferred to the output rod via the actuation groove, the driving member, and the rotary groove.(2) A flow passage is provided to the housing1so that a pressurized fluid for detection is supplied. A detection valve40,50which opens and closes the flow passage by the piston4is provided in the flow passage. The flow passage has a supply passage36,37, a valve hole42,52, and a discharge passage. The supply passage36,37is provided in the housing1. The valve hole42,52which is provided in the detection valve40,50is communicated with the supply passage36,37. The discharge passage which is provided between the housing1and the piston4is communicated with the valve hole42,52.

In this case, it is absolutely detected by the detection valve that the piston is moved to the given position.(3) The detection valve40,50has a valve seat44,54and a valve member45,55. The valve seat44,54is provided on an inner circumferential wall of the valve hole42,52. The valve member45,55is inserted in the valve hole42,52so that valve member45,55can advance and retract and be in contact with the valve seat44,54. The valve member45,55is biased toward the piston4by a biasing means46,56provided in the valve hole42,52.

In this case, in a case where the piston is moved to the given position, the piston causes the valve member to be separated from the valve seat. This allows absolute detection.

DESCRIPTION OF EMBODIMENTS

The following description will discuss Embodiment 1 of the present invention with reference toFIGS. 1 through 3C.

In Embodiment 1, a case where a cylinder device is applied to a rotary clamp for fixing a workpiece is taken as an example. First, a general structure of the rotary clamp will be described with reference toFIG. 1.

A housing1is mounted on a table T, serving as a fixing base, with use of a plurality of bolts (not illustrated). The housing1has, in order from bottom, a lower wall1a, a barrel part1b, and an upper wall1c. A cylinder hole2is provided in the barrel part1bof the housing1. The cylinder hole2has, in order from bottom, a large-diameter hole2aand a small-diameter hole2b.

A piston4is hermetically inserted in the large-diameter hole2aso that the piston4is vertically movable. A housing hole5is provided in the piston4so that an opening of the housing hole5is directed upward. A lower part of an output rod6is inserted in the housing hole5so that the output rod6is vertically movable, and an upper part of the output rod6is hermetically inserted in the upper wall1cof the housing1so that the output rod6is vertically movable and is rotatable on its axis. A clamp arm7is disposed on the upper part of the output rod6. A disposition hole8is provided in the lower part of the output rod6. A compression spring (biasing means)9is disposed in the disposition hole8. The compression spring9is disposed so that an upper end part of the compression spring9is in contact with a ceiling wall of the disposition hole8and a lower end part of the compression spring9is in contact with a bottom wall of the housing hole5via a spring receiving member10and an engaging ball11. Thus, a biasing force of the compression spring9acts in a direction in which the piston4and the output rod6are separated from each other.

A driving means13which causes the piston4to move vertically (in an axial direction) is provided in the housing1. The driving means13is configured as follows.

A spring chamber14is provided on an upper side of the piston4, and an operation chamber15is provided on a lower side of the piston4. A lock spring16is disposed in the spring chamber14, and the lock spring16biases the piston4downward with respect to the upper wall is of the housing1. The spring chamber14is communicated with a breathing hole14awhich is communicated with outside air. A supply-and-discharge passage17through which pressurized oil (pressurized fluid) is supplied to and discharged from the operation chamber15is provided to the barrel part1bof the housing1.

As illustrated inFIG. 1(andFIG. 3A), a guide groove18is vertically provided on an outer circumferential wall of the piston4. A pin19is inserted in the guide groove18so that the pin19protrudes radially inward from the barrel part1bof the housing1. By the pin19and the guide groove18, the piston4is vertically guided, and rotation of the piston4is prevented with respect to the housing1.

A converting mechanism22which converts vertical movement of the piston4into rotary movement of the output rod6is provided between an inner circumferential wall of the housing hole5of the piston4and an outer circumferential wall of the output rod6. The converting mechanism22is configured as follows, as illustrated inFIG. 3A through 3C.

As illustrated inFIG. 3B(andFIG. 1), an actuation groove23is helically provided on the inner circumferential wall of the housing hole5of the piston4. Further, as illustrated inFIG. 3C(andFIG. 1), a rotary groove24, corresponding to approximately 1 (one) pitch, is provided on the outer circumferential wall of the output rod6so that the rotary groove24faces the actuation groove23. A circulation groove25via which a lower end part (base end part)24aof the rotary groove24is communicated, substantially in a vertical direction, with an upper end part (top end part)24bof the rotary groove24is provided on the outer circumferential wall of the output rod6. Therefore, it is possible to shorten a circumferential dimension of the circulation groove25, as compared with a case where the circulation groove25is provided so as to be inclined with respect to the vertical direction. A plurality of driving balls (driving member)26are inserted between the actuation groove23and the rotary groove24and between an inner circumferential surface of the housing hole5and the circulation groove25so that the plurality of driving balls26are rollable. In a case where the piston4is vertically moved, the piston4causes the output rod6to vertically move while rotating, via the actuation groove23, the plurality of driving balls26, and the rotary groove24.

As illustrated inFIG. 3A(andFIG. 1), a guide groove28is provided in a circumferential direction on the inner circumferential wall of the housing hole5of the piston4. A stopping part29is provided at an end part, in the circumferential direction, of the guide groove28. A depressed part30is vertically provided on the outer circumferential wall of the output rod6. An engaging pin (engaging member)31is disposed in the depressed part30. The engaging pin31is inserted in the guide groove28, and is caused to face the stopping part29of the guide groove28at a given distance in the circumferential direction from the stopping part29so that the engaging pin31can be in contact with the stopping part29. A threaded hole31ais vertically provided in the engaging pin31. A screw for removing the engaging pin31from the depressed part30can be screwed into the threaded hole31a.

The cylinder device operates as follows, as illustrated inFIGS. 1 and 2.

In a release state illustrated inFIG. 1, the pressurized oil is supplied to the operation chamber15. The pressurized oil in the operation chamber15presses the piston4upward against a biasing force of the lock spring16. This causes the bottom wall of the housing hole5of the piston4to push the lower end part of the output rod6upward. As a result, a stepwise part6aprovided in the middle, in a height direction, of the output rod6is received, at an upper limit position by a thrust bearing34disposed on the upper wall1cof the housing1.

In a case where the rotary clamp is switched from the release state illustrated inFIG. 1to a lock state illustrated inFIG. 2, the pressurized oil is discharged from the operation chamber15. This causes the lock spring16to move the piston4downward. Then, in a state in which the output rod6remains at the upper limit position by the compression spring9disposed in the disposition hole8of the output rod6, the piston4is separated downward from the output rod6. Then, the actuation groove23of the piston4pushes the rotary groove24of the output rod6downward via the plurality of driving balls26. Next, the output rod6is rotated 90 degrees clockwise with respect to the piston4, as viewed from above. In so doing, the engaging pin31located at a release position, which is indicated by a solid line inFIG. 3B(andFIG. 3A), is moved to a lock position of the engaging pin31, which lock position is indicated by a chain double-dashed line in FIG.3B (andFIG. 3A), and is received by the stopping part29of the piston4from the circumferential direction. Then, the lock spring16moves the piston4and the output rod6directly downward. This causes a left end part of the clamp arm7to be in contact with a workpiece (not illustrated) from top. As a result, the rotary clamp is switched from an unclamping state illustrated inFIG. 1to a clamping state illustrated inFIG. 2.

In a case where the rotary clamp is switched from the lock state illustrated inFIG. 2to the release state illustrated inFIG. 1, the pressurized oil is supplied to the operation chamber15. This causes a pressing force corresponding to the pressurized oil in the operation chamber15to act so that the piston4moves upward against the biasing force of the lock spring16. Then, the piston4moves the output rod6directly upward via the compression spring9. Next, in a case where the stepwise part6aof the output rod6is received by the thrust bearing34from top, the piston4compresses the compression spring9. Then, the actuation groove23of the piston4presses the rotary groove24of the output rod6upward via the plurality of driving balls26. Then, the output rod6is rotated 90 degrees counterclockwise with respect to the piston4, as viewed from above. Then, the bottom wall of the housing hole5of the piston4is received from top by the lower end part of the output rod6. As a result, the rotary clamp is switched from the clamping state illustrated inFIG. 2to the unclamping state illustrated inFIG. 1.

Embodiment 1 brings the following advantages.

According to the above-described rotary clamp, the engaging pin31of the output rod6is configured such that the engaging pin31can be received by the stopping part of the guide groove28of the piston4from the circumferential direction. This allows the piston4to absolutely stop the output rod6at a given position in the circumferential direction via the converting mechanism22. This consequently allows the clamp arm to press a workpiece at a given position on the workpiece.

FIGS. 4A through 4Cillustrate Embodiment 2 of the present invention. In description of Embodiment 2, members identical (or similar) to those in Embodiment 1 are given respective identical reference numerals as a general rule.

As illustrated inFIGS. 4A through 4C, a first supply passage36, through which lock detection air is supplied, and a second supply passage37, through which release detection air is supplied, are provided to a barrel part1bof a housing1. A first disposition hole38, which is communicated with the first supply passage36, is provided in the barrel part1bof the housing1. A second disposition hole39, which is communicated with the second supply passage37, is provided in the barrel part1bof the housing1. The first disposition hole38and the second disposition hole39are each communicated with a large-diameter hole2aof a cylinder hole2.

A first detection valve (detection valve)40, which is for detecting a piston4having been moved to a lock position, is disposed in the first disposition hole38. A second detection valve (detection valve)50, which is for detecting the piston4having been moved to a release position, is disposed in the second disposition hole39.

As illustrated inFIGS. 4A and 4B, the first detection valve40is configured as follows.

A valve case41of the first detection valve40is hermetically screwed into the first disposition hole38. A first valve hole (valve hole)42is provided in a left part of the valve case41. A first communication hole43is provided in a cylindrical wall of the valve case41. The first supply passage36and the first valve hole42are communicated with each other via the first communication hole43. A first valve seat (valve seat)44having a tapered shape is provided on an inner circumferential wall of the first valve hole42. A first engaging ball (valve member)45and a first advancing spring (biasing means)46are disposed in the first valve hole42. The first engaging ball45is biased toward the first valve seat44by the first advancing spring46.

As illustrated inFIGS. 4A and 4C, the second detection valve50is configured as follows.

A valve case51of the second detection valve50is hermetically screwed into the second disposition hole39. A second valve hole (valve hole)52is provided in a left part of the valve case51. A second communication hole53is provided, in a cylindrical wall of the valve case51. The second supply passage37and the second valve hole52are communicated with each other via the second communication hole53. A second valve seat (valve seat)54having a tapered shape is provided on an inner circumferential wall of the second valve hole52. A second engaging ball (valve member)55and a second advancing spring (biasing means)56are disposed in the second valve hole52. The second engaging ball55is biased toward the second valve seat54by the second advancing spring56.

A first engaged groove47and a second engaged groove57are each vertically provided on an outer circumferential wall of the piston4. A first retreat groove48is provided on the outer circumferential wall of the piston4so that the first retreat groove.48leads to an upper side of the first engaged groove47. The first engaging ball45of the first detection valve40is inserted in the first engaged groove47and the first retreat groove48. A second retreat groove58is provided on the outer circumferential wall of the piston4so that the second retreat groove58leads to a lower side of the second engaged groove57. The second engaging ball55of the second detection valve50is inserted in the second engaged groove57and the second retreat groove58.

The first detection valve40and the second detection valve50of the above-described rotary clamp operate as follows.

In a release state illustrated inFIGS. 4A through 4C, the piston4is moved to an upper limit position by pressurized oil supplied to an operation chamber15.

In so doing, the first engaged groove47of the piston4causes the first engaging ball45to move rightward, as illustrated inFIGS. 4A and 4B. The first engaging ball45is accordingly separated from the first valve seat44. Therefore, the first detection valve40is opened. This causes compressed air in the first supply passage36to be discharged outside through the first communication hole43, the first valve hole42, an opened valve gap, the first engaged groove47, the first retreat groove48, and a breathing hole14a.

As illustrated inFIGS. 4A and 4C, the second engaging ball55is inserted in the second retreat groove58of the piston4. The second engaging ball55is accordingly caused to be in contact with the second valve seat54by the second advancing spring56. Therefore, the second detection valve50is closed. This causes an increase in pressure of compressed air in the second supply passage37, and the increase in the pressure is detected by a pressure sensor (not illustrated). As a result, it is detected that the piston4is moved to the release position (upper limit position).

In a case where the rotary clamp is switched from the release state illustrated inFIGS. 4A through 4Cto a lock state, the pressurized oil is discharged from the operation chamber15. This causes a lock spring16to move the piston4downward. Then, the piston4is moved downward by a compression spring9disposed in an disposition hole8of an output rod6. In so doing, an upper circumferential wall of the second retreat groove58of the piston4causes the second engaging ball55of the second detection valve50to move rightward. The second engaging ball55is accordingly separated from the second valve seat54, so that the second detection valve50is opened. This causes the compressed air in the second supply passage37to be discharged outside through the second communication hole53, the second valve hole52, an opened valve gap, the second engaged groove57, the second retreat groove58, and the breathing hole14a.

Then, a left end part of a clamp arm7is caused to be in contact with a workpiece (not illustrated) from top. As a result, the rotary clamp is switched from an unclamping state illustrated inFIG. 1to a clamping state illustrated inFIG. 2. In so doing, the first engaging ball45of the first detection valve40is inserted in the first retreat groove48. This causes the first advancing spring46to move the first engaging ball45leftward, and ultimately causes the first engaging ball45to be in contact with the first valve seat44. This causes an increase in pressure of the compressed air in the first supply passage36, and the increase in the pressure is detected by a pressure sensor (not illustrated). As a result, it is detected that the piston4is moved to the lock position (lower position).

Note that, in Embodiment 2, a first flow passage (flow passage) through which the lock detection air is supplied is constituted by the first supply passage36, the first communication hole43, the first valve hole42, the opened valve gap, a cylinder hole2(the first engaged groove47and the first retreat groove48), and the breathing hole14a. A second flow passage (flow passage) through which the release detection air is supplied is constituted by the second supply passage37, the second communication hole53, the second valve hole52, the opened valve gap, the cylinder hole2(the second engaged groove57and the second retreat groove58), and the breathing hole14a.

In Embodiment 2, a first discharge passage (discharge passage) through which the lock detection air is discharged is constituted by the cylinder hole2, space between the first engaged groove47and the first retreat groove48, and the breathing hole14a. A second discharge passage (discharge passage) through which the release detection air is discharged is constituted by the cylinder hole2, space between the second engaged groove57and the second retreat groove58, and the breathing hole14a.

The above embodiments can be altered as follows.

The pressurized fluid can be alternatively a liquid, other than the pressurized oil described as an example, or a gas such as compressed air.

The depressed part30in which the engaging pin31is disposed can be alternatively provided on the inner circumferential wall of the housing hole5of the piston4, instead of being provided on the outer circumferential wall of the output rod6. The guide groove28can be alternatively provided on the outer circumferential wall of the output rod6, instead of being provided on the inner circumferential wall of the housing hole5of the piston4.

Various other alterations can of course be made within the scope which a person skilled in the art would expect.

REFERENCE SIGNS LIST