Fluid pressure cylinder

A fluid pressure cylinder comprises a rod insertion hole formed in a piston member, an auxiliary rod provided to a head side wall member so as to be inserted into the rod insertion hole, an open/shut valve mechanism for detection, and a fluid passage that is opened and shut by the open/shut valve mechanism. The open/shut valve mechanism includes a valve body reception hole formed in the auxiliary rod, a valve body that is movably held in the valve body reception hole and that has a recessed engagement portion on its external peripheral portion, and a spherical body mounted on the auxiliary rod so as to engage with the recessed engagement portion; when the piston member has reached a set shifting position, the valve body is changed over to the closed position or to the opened position due to cooperation between the spherical body, the recessed engagement portion, and the inner peripheral wall portion of the rod insertion hole.

TECHNICAL FIELD

The present invention relates to a fluid pressure cylinder that, when in particular a piston member has reached a predetermined shifting position that is set in advance, is able to detect the position of the piston member via air pressure that is changed over by a valve mechanism that opens or closes the state of communication of an air passage within a clamp main body, and that operates together with the operation of the piston member.

BACKGROUND OF THE INVENTION

Up to now, a fluid pressure cylinder employed in a clamp device or the like that clamps an object to be clamped, such as a workpiece etc. that is to be subjected to machining, has a main cylinder body, a piston member that is provided so as to move forwards and backwards freely within the main cylinder body, a fluid pressure operation chamber for driving the piston member toward at least one of the advance side and the retraction side.

Now, various types of rod position detection technique have been implemented in practice for detecting the forward limiting position, the rearward limiting position, an intermediate position of the piston member of the fluid pressure cylinder.

For example, the clamp device of Patent Document #1 detects the position of a piston rod with a pressure sensor that detects a fluid pressure supplied to a fluid pressure cylinder, and two position sensors that, detect a raised position and a lowered position of a detected element on the lower end portion of an actuation rod that is projected downward from a piston member of the fluid pressure cylinder to the exterior.

And, in the clamp device of Patent Document #2, a mechanism that operates together with the raising and lowering operation of an output rod of a fluid pressure cylinder to open and close an air passage is provided at the exterior of one end of the main cylinder body, and thereby this structure is capable of detecting the raised position and the lowered position of the output rod.

Moreover, with the clamp device of Patent Document #3, a workpiece holding stand that supports and holds the object to be clamped is provided independently. The workpiece holding stand includes a pad member in which an air ejection outlet is formed and an external barrel member that supports the pad member while elastically biasing it toward the object to be clamped. When the pad member is in its projected position, pressurized air is ejected from the air ejection outlet, and when the clamp device is driven for clamping and the pad member is pressed and retracted by the object to be clamped, the air ejection outlet is blocked by the outer barrel member, so that the pressure of the pressurized air rises and the fact that the clamp device has gone into its clamped state can be detected.

Patent Document #1: JP Laid Open Patent Publication 2001-87991.

Patent Document #2: JP Laid Open Patent Publication 2003-305626.

Patent Document #3: JP Laid Open Patent Publication 2009-125821.

SUMMARY OF THE INVENTION

With the clamp device of Patent Document #1 since the actuation rod is projected from the piston member of the fluid pressure cylinder to the exterior, and the raised position and the lowered position of the detected element provided, at the lower end portion of this actuation rod are detected with the two position sensor, accordingly it is necessary to provide a space for detection at the lower side of the fluid pressure cylinder in order for the detected element to be able to shift and for installation of the position sensor, and therefore the problem arises that the clamp device (in other words, the fluid pressure cylinder) is increased in size.

With the clamp device of Patent Document #2, the mechanism that detects the raised position and the lowered position of the output rod is provided externally to the clamp main body. Due to this, in a similar manner to the case with the clamp device of Patent. Document #1, it is necessary to provide a space for detection externally to the main body of the clamp, so that it is not possible to make the clamp device compact.

And since, when the clamp device is in its unclamped state, the air ejection outlet of the workpiece holding stand of the clamp device of Patent Document #3 opens at a portion in the neighborhood of the clamp device and of the object that is to be clamped, accordingly there is a fear that swarf due to mechanical processing or coolant (i.e. cutting fluid) may undesirably get into the air ejection outlet and block it.

The object of the present invention is to provide a fluid pressure cylinder that, with a simple structure, can open or close an open/shut valve mechanism for detection in coordination with the operation of a piston member, and that is thus capable of detecting via a fluid pressure and with excellent operational reliability, the fact that the piston member has shifted to a set shifting position.

The present invention presents a fluid pressure cylinder comprising a main cylinder body having a cylinder bore is formed, a piston member having a piston portion that is movably received in the cylinder bore and an output rod extending from the piston portion to an exterior of the main cylinder body, and a fluid pressure operation chamber that is defined in the cylinder bore, and characterized by comprising: a rod insertion hole that is formed at a central portion of a base end portion of the piston member and that opens to the base end, and into which a fluid pressure in the fluid pressure operation chamber is introduced; an auxiliary rod that is provided on a head side end wall member of the main cylinder body so as to project within the cylinder bore, and that can be inserted into the rod insertion hole; an open/shut valve mechanism for detection that is installed to the auxiliary rod; and a fluid passage that is formed in the main cylinder body and the auxiliary rod, and that is opened and shut by the open/shut valve mechanism; wherein the open/shut valve mechanism comprises: a valve body reception hole that is formed in an top end side portion of the auxiliary rod to be parallel to an axis of the cylinder bore, and that; communicates with the rod insertion hole; a valve body that is movably received in the valve body reception hole and that has a recessed engagement portion on an external peripheral portion; and a spherical body that is movably fitted to the auxiliary rod so as to engage with the recessed engagement portion; and, when the piston member reaches a set shifting position that is set in advance, the valve body is changed over to a shut position or to an open position due to cooperation between the spherical body, the recessed engagement portion, and a rod insertion hole inner circumferential wall portion.

The present invention may have the following configurations.

As 1st example, preferably, an engagement portion for retraction is formed on an inner circumferential wall portion of the rod insertion hole and, when the piston member is in the set shifting position, puts the valve body into the shut position by permitting the spherical body to retract in a direction to recede away from the axis.

As 2nd example, preferably, when the piston member is shifted from the set shifting position, the valve body is changed over to the open position due to cooperation between the spherical body, the recessed engagement portion, and the rod insertion hole inner circumferential wall portion.

As 3rd example, preferably, an engagement portion for pressing is formed on an inner circumferential wall portion of the rod insertion hole, and, when the piston member is in the set shifting position, puts the valve body into the open position by causing the spherical body to shift in a direction to approach toward the axis.

As 4th example, preferably, the valve body is biased toward the shut position by fluid pressure in the rod insertion hole which is communicated with the fluid pressure operation chamber.

As 5th example, preferably, a compression spring is provided that elastically biases the valve body toward the head side end wall member.

As 6th example, preferably, a shut state of the open/shut valve mechanism can be detected via a fluid pressure that is supplied to the fluid passage.

According to the present invention, the fluid pressure cylinder comprises the rod insertion hole, the auxiliary rod, the open/shut valve mechanism for detection, and the fluid passage that is opened and closed by the open/shut valve mechanism; the open/shut valve mechanism comprises the valve body reception hole that is formed in an end side portion of the auxiliary rod; the valve body that is movably received in the valve body reception hole and that has a recessed engagement portion in an external peripheral portion; and the spherical body that is movably installed to the auxiliary rod and that can engage with the recessed engagement portion; and, when the piston member reaches the set; shifting position that is set in advance, it is arranged for the valve body to be changed over to the shut position or to the opened position due to cooperation between the spherical body, the recessed engagement portion, and the rod insertion hole inner circumferential wall portion.

Accordingly it is possible to detect the fact that the piston member has shifted to its set shifting position via the fluid pressure supplied to the fluid passage and to the open/shut valve mechanism, since, when the piston member has shifted to its set shifting position, the open/shut valve mechanism changes over to its shut position or to its opened position and intercepts, or cancels interception of, the fluid passage.

Since the open/shut valve mechanism is provided to the auxiliary rod that is installed to the head side end wall member so as to project into the cylinder bore, accordingly the open/shut valve mechanism is disposed internally to the main cylinder body, so that it is possible to make the fluid pressure cylinder more compact. And since, when the piston member reaches its set shifting position, it is arranged for the open/shut valve mechanism to change over the valve body to the shut position or to the opened position due to cooperation between the spherical body, the recessed engagement portion, and the rod insertion hole inner circumferential wall portion, accordingly it is possible to change over the open/shut valve mechanism together with the movement of the piston member with a simple structure.

According to theist example, it is possible to put the valve body into the shut position with a simple structure, since the valve body is into the shut position by the spherical body being permitted to retract in the direction to recede away from the axis by the engagement portion for retraction which is formed on the inner circumferential wall portion of the rod insertion hole.

According to the 2nd example, it is possible to detect the fact that the piston member has shifted from its limit shifting position reliably and in a simple manner, since, when the piston member is shifted from the set shifting position, the valve body is changed over to the opened position due to cooperation between the spherical body, the recessed engagement portion, and the rod insertion hole inner circumferential wall portion.

According to the 3rd example, it is possible to make the open/shut valve mechanism go to the opened state when the piston member has reached its set shifting position, since the engagement portion for pressing and shifting is formed on the inner circumferential wall portion of the rod insertion hole, and, when the piston member is in its limit shifting position, puts the valve body into the opened position by causing the spherical body to shift in the direction to approach toward the axis.

According to the 4th example, it is possible to enhance the valve closing performance and to maintain the closed state in a stable manner, since it is arranged for the valve body to be biased toward the closed position by fluid pressure in the rod insertion hole which is communicated with the fluid pressure operation chamber.

According to the 5th example, it is possible to enhance the valve closing performance and to maintain the closed state in a stable manner, since the compression spring is provided that biases the valve body toward the head side end wall member.

According to the 6th example, it is possible to detect the closed state with a simple structure, since the closed state of the open/shut valve mechanism is detected via a fluid pressure that is supplied to the fluid passage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, best mode for implementation of the present invention will be explained on the basis of embodiments thereof.

In the following embodiments, “hydraulic pressure” means compressed oil.

The twist-type clamp device1of this embodiment will now be explained on the basis ofFIGS. 1 through 6.

This twist-type clamp device1comprises a hydraulic pressure cylinder2(fluid pressure cylinder), a clamp arm3that is fixed to the upper end portion of an output rod6of the hydraulic pressure cylinder2, and a twisting mechanism8that causes the output rod6to twist through a set angle around its axis (for example, 90°). The base end portion of the clamp arm3is fitted over a tapered axis portion6aof the output rod6, and is fixed there by a nut3athat is screwingly engaged to the upper end portion of the output rod6.

In the state in which the output rod6is retracted to its lower limit position or to a position in the neighborhood thereof, this twist-type clamp device1goes into its clamped state in which the object to be clamped is pulled downward by the clamp arm3; and, when the output rod6is extruded from the clamped state, the clamp device1goes into its unclamped state. When the device1transitions from its unclamped state shown inFIG. 2to its clamped state shown inFIG. 5, the output rod6twists, for example, around its axis by 90° in the anticlockwise rotational direction as seen in plan view. And, conversely to the above, when the device1transitions from its clamped state to its unclamped state, the output rod6twists by 90° in the clockwise rotational direction.

First, the hydraulic pressure cylinder2will be explained.

As shown inFIGS. 1, 2, and 5, the hydraulic pressure cylinder comprises a main cylinder body10, a piston member4, a hydraulic pressure operation chamber for unclamping12a, a hydraulic pressure operation chamber for clamping12b, an auxiliary rod7, an open/shut valve mechanism11, an air passage32, and so on. The main cylinder body10comprises an upper main cylinder body portion10A and a head side end wall member10B.

The upper main cylinder body portion10A comprises a rectangular main cylinder body portion10athat is rectangular in plan view, and a main cylinder body portion10bthat extends downward from the lower end of the rectangular main cylinder body portion10aand is shaped like a barrel. An installation surface14is formed at the lower end of the rectangular main cylinder body portion10afor installation on the upper surface of a base member13. The upper main cylinder body portion10A is fixed to the base member13by four bolts that are inserted in four bolt holes17.

A rod hole18athrough which the output rod6passes is formed in the rectangular main cylinder body portion10a, and a large diameter rod hole18b, concentric with and of larger diameter than the rod hole18a, is formed in the rectangular main cylinder body portion and the barrel shaped main cylinder body portion101), and a cylinder bore15is formed in the interior of the barrel shaped main cylinder body portion10bso as to communicate with the lower end of the large diameter rod hole18b, and with the lower end side of the cylinder bore15being blocked by the head side end wall member10B.

The upper end portion of the head side end W member10B is fitted into a fitting hole15athat connects to the cylinder bore15and is sealed by a seal member16. A male screw portion10mthat is formed on the lower end portion of the head side end wall member10B is screwingly engaged into a screw hole10nin the barrel shaped main cylinder body portion10b, and thereby that the head side end wall member10B is fixed to the barrel shaped main cylinder body portion10b. An auxiliary rod7is formed integrally with the center portion of the head side wall number10B so as to project into the cylinder bore15, and has a diameter of around ¼ to ⅓ of the diameter of the cylinder bore15. It would also be acceptable for the auxiliary rod7to be formed as a separate member from the head side end wall member10B, and to be fixedly attached thereto.

An installation hole21into which the barrel shaped main cylinder body portion10band the head side end wall member10B are inserted from above and installed is formed in the base member13to which the twist-type clamp device1is attached, and the installation hole21is made as a lower installation hole portion22and an upper installation hole portion23that is slightly larger in diameter than the lower installation hole portion22, and the lower end side portion of the barrel shaped main cylinder body portion10band a seal member24afitted on its external periphery is installed in the lower installation hole portion22. An annular cylindrical gap25is defined in the upper installation hole portion23around the external circumference of the barrel shaped main cylinder body portion10b. A seal member24bis installed at the upper end portion of the barrel shaped main cylinder body portion10b.

As shown inFIG. 2, 5, the piston member4comprises a piston portion5that is installed in the cylinder bore15so as to slide freely in the vertical direction, the output rod6extending from the piston portion5upwards to the exterior of the main cylinder body10, and a rod insertion hole20that is formed in the center portion of the base end portion of the piston member4(i.e. lower end portion) so as to open to its base end lower end). A seal member26is fitted on the external circumference of the piston portion5. And a hexagonal opening6bfor insertion of a wrench is formed at the upper end of the output rod6. The output rod6comprises a small diameter rod portion6cthat passes through the rod hole18aand extends upward horn the clamp main body10, and a large diameter rod portion tad that extends integrally downward from the lower end of the small diameter rod portion6cand is inserted into the large diameter rod hole18b. The rod insertion hole20is a cylindrical aperture that has the same diameter over its entire length and is formed as a cylindrical hole having a slightly larger diameter (for example, 1 to 2 mm greater) than the external diameter of the auxiliary rod7; and this rod insertion hole20is communicated with the hydraulic pressure operation chamber12a, and is formed so that the auxiliary rod7can be inserted into the rod insertion hole20.

Now an explanation will be given of the twisting mechanism8, which causes the output rod6(i.e., the piston member4) to twist by a set angle (for example, 90°) around its axis together with the forwards and backwards movement of the output rod6, and which is installed to the large diameter rod6dand the main cylinder body10of the hydraulic pressure cylinder2. The twisting mechanism8has three reception apertures8a, three steel balls8bthat are held in these reception apertures8a, and three helical grooves8c. The three reception apertures8aare hemispherical, and are formed near the lower end of the circumferential wall portion of the large diameter rod hole18bin three positions deriding equally the circumference, and the three helical grooves8care formed in the external circumferential wall portion of the large diameter rod portion6d, and are engaged with the three steel balls8bwhich are held in the three reception apertures8a.

Due to this twisting mechanism8, the piston member4twists by 90° in the anticlockwise rotational direction as seen in plan view when it is lowered from its unclamp position shown inFIG. 2(i.e. its upper limit position) to an almost intermediate position that is in the middle between its upper limit position and its lower limit position, and thereafter is further lowered straightly downward to its clamp position (i.e. lower limit position; along approximately half its stroke (refer toFIG. 5).

Conversely to the above, when changing over from its clamp position to its unclamp position, the piston member4first rises straightly upward along approximately half its stroke, and then, when further rising from its almost intermediate position to its upper limit position shown inFIG. 2, it twists by 90° in the clockwise rotational direction as seen in plan view to reach its unclamp position.

The cylinder bore15is divided by the piston portion5into upper and lower volumes, and thereby the hydraulic pressure operation chamber for clamping12bdefined above the piston portion5and the hydraulic pressure operation chamber for unclamping12ais defined below the piston portion5. The hydraulic pressure operation chambers12a,12bcorrespond to the “fluid pressure operation chambers”.

Hydraulic pressure ports30,31are formed in the rectangular main cylinder body portion10aof the upper main cylinder body portion10A, with the hydraulic pressure port30being communicated with the hydraulic pressure operation chamber12aby a hydraulic passage30aformed in the main cylinder body10while the hydraulic pressure port31is communicated with the hydraulic pressure operation chamber12bby a hydraulic passage31aalso formed in the main cylinder body10, and with the hydraulic pressure ports30,31being connected to a hydraulic pressure supply source (not shown in the figures) by hydraulic hoses or the like.

Next, the open/shut valve mechanism11and the air passage32(fluid passage) will be explained. This open/shut valve mechanism11is installed in the upper end portion of the auxiliary rod7, and an intermediate portion of the an passage32, which is formed in the main cylinder body10and the auxiliary rod7, is opened and shut by the open/shut valve mechanism11. The air passage32includes an upstream side air passage33and a downstream side air passage34. The upper end of the upstream side air passage33is communicated with the central portion of the lower end of a valve body reception hole35, and the upper end of the downstream side air passage34is communicated with an outer peripheral portion of the lower end of the valve body reception hole35. Pressurized air is supplied from a pressurized air supply source40to the upstream side air passage33via an air passage42in the base member13and the lower to installation hole portion22, and, when the open/shut valve mechanism11is in its open state, the pressurized air flows to the downstream side air passage34, and passes out through the annular gap25and an air passage43in the base member13and is vented to the atmosphere.

As shown inFIGS. 2 and 5, the open/shut valve mechanism11comprises the valve body reception hole35, a valve body36that is movably received in the valve body reception hole35, an annular recessed engagement portion37that is formed on the external peripheral portion of the valve body36, two spherical bodies38that consist of steel balls and that are capable of engaging with the recessed engagement portion37, and an annular engagement portion39for retraction that is formed on the internal circumferential wall portion of the rod insertion hole20and that is capable of partial engagement with the spherical bodies88.

The valve body reception hole35is formed in the end portion of the auxiliary rod7(i.e. upper end portion), approximately in the form of a cylinder that is concentric with the axis of the cylinder bore15, and the valve body reception hole35is communicated with the hydraulic pressure operation chamber12avia a minute annular gap between the auxiliary rod7and the rod insertion hole20. The internal diameter of the approximately ¼ to ⅓ portion of the valve body reception hole35at its upper end is formed to be slightly larger than the internal diameter of the other portions thereof, and the internal diameter reduces smoothly from the large diameter portion.

As shown inFIG. 2andFIG. 4, the valve body36is received in the valve body reception hole35so as to be movable therein in the vertical direction, and is adapted to be capable of receiving the hydraulic pressure in the rod insertion hole20, with the length of the valve body36in the vertical direction and the length of the valve body reception hole35in the vertical direction being almost equal. The annular recessed engagement portion37is formed around the external peripheral portion of an intermediate portion of the valve body36. This recessed engagement portion37has a small diameter cylindrical surface37aat this intermediate portion, an upper side conical surface portion37bthat continues upward from the upper end of this cylindrical surface37aand increases in diameter upwards, and a lower side conical surface portion37cthat continues downward from the lower end of the cylindrical surface37aand increases in diameter downwards. A flat surface is formed at the central portion of the lower end portion of the valve body36, and, so as to continue to the external periphery of this flat surface, a valve surface36vis formed consisting of a conical surface portion that increases in diameter upwards. A seal member36ais installed on the external periphery of the lower portion of the valve body36.

For example, two reception apertures45are formed in the wall portion44of the auxiliary rod7, around the external circumference of its valve body reception hole35. These reception apertures45are small diameter cylindrical apertures oriented in the horizontal direction. The spherical bodies38are installed in these reception apertures45so as to be movable in the horizontal direction, and are held so as to be capable of engagement with the recessed engagement portion37. The diameter of the spherical bodies38is set to be greater than the thickness of the wall portion44.

As shown inFIG. 4, a shallow annular groove shaped engagement portion for retraction39to which the spherical bodies38engage when the piston member4is in its unclamp position (i.e. upper limit position) is formed around the inner circumferential wall portion of the rod insertion hole20in the neighborhood of its lower end portion. The upper half portion to of the engagement portion for retraction39is formed as a tapered hole39athat increases in diameter downward, and the lower half portion of the engagement portion for retraction39is formed as a cylindrical hole39bthat connects to the lower end of the tapered hole39a. The maximum internal diameter of the engagement portion for retraction39is slightly larger (for example, 3 to 4 mm larger) than the external diameter of the auxiliary rod7. And a conical surface portion46that increases in diameter downward is formed at the lower end portion of the internal circumferential wall portion, so as to connect to the lower end of the engagement portion for retraction39.

As shown inFIGS. 2 and 4, in the unclamped state, since hydraulic pressure in the rod insertion hole20acts on the upper end of the valve body36and the spherical bodies33engage into the engagement portion for retraction39and the spherical bodies38shift slightly outward, accordingly shifting downward of the upper side conical surface portion37bof the recessed engagement portion37is permitted and the valve body36lowers, so that the valve surface36von the lower end of the valve body36contacts against a valve seat33aon the upper end of the upstream side air passage33, and the open/shut valve mechanism11goes into its shut state. This shut state is detected by using the detection signal from a pressure switch41or a pressure sensor that is connected in the pressurized air supply system.

And since, as shown inFIGS. 5 and 6, when the piston member4shifts more downward than its unclamp position, the engagement portion for retraction39shifts further downward than the spherical bodies38and thereby the spherical bodies38are pushed toward the valve body36by the cylindrical inner circumferential wall surface of the rod insertion hole20, accordingly the spherical bodies38press the upper side conical surface portion37bof the recessed engagement portion37upward. Due to this, the valve body36shifts slightly upward, and a gap is formed between the valve surface36vof the valve body36and the valve seat33a, so that the open/shut valve mechanism11goes into its opened state.

Next, the operation and the advantageous effects of this twist-type clamp device1will be explained.

As shown inFIGS. 1 and 2, in the unclamped state, the piston member4is positioned at its upper limit position (which corresponds to the “set shifting position that is set in advance”) and hydraulic pressure is charged into the hydraulic pressure operation chamber12a, and since, at this time, in the open/shut valve mechanism11, the hydraulic pressure in the hydraulic pressure operation chamber12aand the same hydraulic pressure in the rod insertion hole20act on the upper end of the valve body36, and moreover the spherical bodies38engage into the engagement portion for retraction39and the spherical bodies33do not press on the upper side conical surface portion37aof the recessed engagement portion37of the valve body36, accordingly, as shown inFIGS. 2 and 4, the valve body36is lowered to its lower limit position, and the valve goes into its closed state. Since, due to this, the air pressure in the air passage42rises and the pressure switch41goes ON, accordingly the fact that the twist-type clamp device1is in its unclamped state can be detected by a control unit that is connected to the pressure switch41.

When, in order to clamp an object, to be clamped, the hydraulic pressure in the hydraulic pressure operation chamber12ais changed over to drain pressure, and hydraulic pressure is supplied to the hydraulic pressure operation chamber for clamping12b, then the piston member4lowers to its clamp position, and, as shown inFIG. 5, the object is clamped in the state in which the output rod6has been twisted by 90° in the anticlockwise direction.

And, in the state in which the piston member4has been lowered below its upper limit position (i.e. unclamp position), since the engagement portion for retraction39goes into the state of being lowered below the spherical bodies38and the spherical bodies38are pressed toward the valve body36by the inner circumferential wall surface of the rod insertion hole20, so that these spherical bodies38press the upper side conical surface port ion37bof the recessed engagement portion37of the valve body36upward, accordingly the valve body36shifts slightly upward, and the open/shut valve mechanism goes into its open state, as shown inFIGS. 5 and 6. Since, due to this, the pressure switch41returns to OFF, accordingly it is possible to detect the fact that the unclamped state has ceased.

Since, in this manner, when the piston member4has shifted to its unclamp position (its limit shifting position, in other words its set shifting position), the open/shut valve mechanism11changes over to its shut position and the air passage32is intercepted, accordingly it is possible to detect the fact that the piston member4is shifted to its unclamp position via the open/shut valve mechanism11and via the air pressure supplied to the air passage32. And, since the valve body36is biased to the shut position by the hydraulic pressure in the hydraulic pressure operation chamber for unclamping12a, accordingly the closing performance and the operational reliability of the open/shut valve mechanism11are excellent.

Since the open/shut valve mechanism11is installed in the auxiliary rod7that does not project to the exterior of the main cylinder body10, and is thus installed in the interior of the main cylinder body10, accordingly it is possible to anticipate that the hydraulic pressure cylinder2can be made more compact. And, since the valve body36of the open/shut valve mechanism11has the annular recessed engagement portion37on its external peripheral portion, and the spherical bodies38are capable of engaging into the recessed engagement portion37, and since the open/shut valve mechanism11is built so as to be closed by the engagement portion for retraction39that is formed in the internal circumferential wall portion of the rod insertion hole20of the auxiliary rod7and the spherical bodies38, accordingly it is possible to make the open/shut valve mechanism11open and close together with the movement of the piston member4with a simple structure.

While, in this embodiment, a structure is provided in which the engagement portion for retraction39is formed at a portion in the neighborhood of the lower end of the internal circumferential wall portion of the rod insertion hole20, so as to detect the fact that the piston member4has reached the unclamp position, it would also be possible to provide a structure in which the engagement portion for retraction39is formed at a position at a desired height on the internal circumferential wall portion, so as to detect the fact that the piston member4has reached a desired set shifting position. Moreover, the set shifting position is not to be considered as being limited to being located at a specified position having no length in the vertical direction; it could also be set to a position having a certain length in the vertical direction; and, in this case, the engagement portion far retraction39would be formed on the engagement portion so as to have a certain length in the vertical direction.

Since the closing of the open/shut valve mechanism11is detected via the air pressure of the pressurized air that is supplied to the air passage32, accordingly it is possible to detect the closed state with a simple structure.

Moreover, since the engagement portion for retraction39is formed as an annulus around the inner circumferential wall portion of the rod101insertion hole20, accordingly it is possible to ensure the proper functioning of the engagement portion for retraction39, even if the piston member4rotates around its axis.

Furthermore since, in this twist-type clamp device1, the twisting mechanism8is installed to the piston member4and the main cylinder body10of the hydraulic pressure cylinder2and twists the output rod6around its own axis by a set angle together with the to and fro movement of the output rod6, accordingly this structure enables detection of the filet that the piston member4of the twisting type clamp device1is positioned in its set shifting position via the air pressure of the pressurized air.

Yet further, since the installation hole21in the base member13to which the twist-type clamp device1is attached, into which the lower portion of the clamp main body10is inserted from above and in which it is installed, consists of the lower installation hole portion22and the upper installation hole portion23that has a diameter slightly larger than that of the lower installation hole portion22, and since the lower end portion of the clamp main body10and the seal member24athat is installed on its external peripheral portion are installed in the lower installation hole portion22accordingly, even if some burring; remains at the upper end of the air passage43that opens into the upper installation hole portion23, still no damage is caused to the seal member24adue to this burring when the lower end portion of the clamp main body10is inserted into and installed in the lower installation hole portion22.

A twist-type clamp device1A according to a second embodiment of the present invention will now be explained on the basis ofFIGS. 7 through 10. However, the same reference symbols will be appended to structural elements having similar structures to elements in the first embodiment, and explanation thereof will be omitted, with only structural elements that are different being explained.

The hydraulic pressure cylinder2A of this twist-type clamp device1A is built so that, when the piston member4A is positioned in the upper half portion of its raising and lowering stroke (including its unclamp position), the open/shut valve mechanism11maintains its opened state; and, when the piston member4A is positioned in the lower half portion of its raising and lowering stroke (including its clamp position), the open/shut valve mechanism11maintains its shut state.

As shown inFIGS. 7 and 8, the lower half portion of the rod insertion hole20A is formed as a small diameter rod insertion hole20ahaving a similar internal diameter to that of the rod insertion hole20of the first embodiment, while the upper half portion of the rod insertion hole20A is formed as a large diameter rod insertion hole20bhaving an internal diameter that is slightly larger (for example, 3 to 4 mm larger) than the internal diameter of the small diameter rod insertion hole20a.

When the piston member4A is positioned in the upper half portion of its raising: and lowering stroke (which corresponds to the “set shifting position”), the valve body36receives the hydraulic pressure in the rod insertion hole20A; but, since the spherical bodies38are restricted by the internal circumferential wall surface of the small diameter rod insertion hole20aand therefore are pushed toward the valve body36(its axial side), accordingly the spherical bodies38push the upper side conical surface portion37bof the valve body36and shift it slightly upward, so that the open/shut valve mechanism11maintains its opened state. In other words, the internal circumferential wall surface of the small diameter rod insertion hole20a(i.e. its inner circumferential wall portion) is equivalent to an engagement portion39A for pressing and shifting.

And, when the piston member4A is positioned in the lower half portion of its raising and lowering stroke as shown inFIGS. 9 and 10, since the spherical bodies38shift outwards until they contact against the inner circumferential wall surface of the large diameter rod insertion hole20b,accordingly the valve body36shifts slightly downward due to the remaining pressure within the rod insertion hole20A that operates on the valve body36, and the open/shut valve mechanism11maintains its closed state.

A twist-type clamp device1B according to a third embodiment of the present invention will now be explained on the basis ofFIGS. 11 through 14. However, the same reference symbols will be appended to structural elements having similar structures to elements in the first embodiment, and explanation thereof will be omitted, with only structural elements that are different being explained.

Similarly to the hydraulic pressure cylinder2A of the second embodiment, the hydraulic pressure cylinder2B of this twist-type clamp device1B is built so that, when the piston member4B is positioned in the upper half portion of its raising and lowering, stroke (including its unclamp position), the open/shut valve mechanism11maintains its opened state; and, when the piston member4B is positioned in the lower half portion of its raising and lowering stroke (including its clamp position), the open/shut valve mechanism11maintains its closed state. However, the structure of this hydraulic pressure cylinder2B is different from that of the hydraulic pressure cylinder2A of the second embodiment, in that a compression spring50is installed to the open/shut valve mechanism11that elastically biases the valve body36in the valve shutting direction.

As shown inFIGS. 11 and 12, the auxiliary rod7B is extended upward, a cylindrical containment aperture51is formed in the upper end portion of the auxiliary rod7B and contains the spring50, the compression spring50that elastically biases the valve body36towards the valve shutting side is installed in the containment aperture51, and the upper end of the compression spring50bears against a stop ring52. In correspondence to the upward elongation of the auxiliary rod7B, the rod insertion hole20B is also extended upward.

As shown inFIGS. 11 and 12, the lower portion of the rod insertion hole20B (approximately ⅖ thereof) is formed as a small diameter rod insertion hole20chaving an internal diameter similar to that of the rod insertion hole20of the first embodiment, with the internal circumferential wall surface of the small diameter rod insertion hole20c(i.e. its internal circumferential wall portion) being equivalent to an engagement portion39B for pressing and shifting, in the same manner as the engagement portion39A for pressing and shifting of the second embodiment. And the upper half portion of the rod insertion hole20B (approximately ⅗ thereof) is formed as a large diameter rod insertion hole20dhaving an internal diameter that is slightly larger (for example, 3 to 4 mm larger) than the internal diameter of the small diameter rod insertion hole20c.

When the piston member4B is positioned in the upper half portion of its raising and lowering stroke (which corresponds to the set shifting position), the valve body36receives the hydraulic pressure in the rod insertion hole20A; but, since the spherical bodies38are restricted by the internal circumferential wall surface of the small diameter rod insertion hole20cand therefore are pushed toward the valve body36(its axial side), accordingly the spherical bodies38push the upper side conical surface portion37bof the valve body36and shift it slightly upward against the resistance of the compression spring50, so that the open/shut valve mechanism11maintains its opened state. In other words, the internal circumferential wall surface of the small diameter rod insertion hole20c(i.e. its inner circumferential wall portion) is equivalent to an engagement portion39B for pressing and shifting.

And, when the piston member4B is positioned in the lower half portion of its raising and lowering stroke as shown inFIGS. 13 and 14, since the spherical bodies38shift outwards until they contact against the inner circumferential wall surface of the large diameter rod insertion hole20d, accordingly the valve body36shifts slightly downward due to the biasing force of the compression spring50, and the open/shut valve mechanism11maintains its closed state, in this hydraulic pressure cylinder2B, since the compression spring50is installed that biases the valve body36in the shutting direction, accordingly the valve closing performance and the operational reliability are enhanced.

Variant examples in which the twist-type clamp devices of the above embodiments are partially altered will now be explained.

(1) If a similar engagement portion to the engagement portion for retraction39is formed on the inner circumferential wall portion of the rod insertion hole20at a portion corresponding to the position of the spherical bodies38inFIG. 5, then it also becomes possible to detect the fact that the piston member4has shifted to the clamp position in addition to the fact that the piston member4is in the unclamp position.

(2) Instead of the annular recessed engagement portion37, it would also be acceptable to arrange to form a recessed engagement portion, into which the spherical bodies38are capable of engaging, on a portion of the valve body36in its circumferential direction that is not annular.

(3) The direction of flow of the pressurized air that flows in the air passage32is not limited to being the direction shown in the above embodiments; it would also be acceptable to provide a structure in which the pressurized air supply source40is connected to the air passage34, and the air flows from the air passage34toward the air passage33.

(4) Since the engagement portion for retraction39that is formed on the piston member4is a configuration for allowing the spherical bodies38to retract outward, accordingly it is not necessary for the portion for retraction to be in linear contact or in planar contact with the spherical bodies38; any construction will be acceptable that can allow the spherical bodies to retract outward, and that can make them return to the state shown inFIGS. 5 and 6.

(5) It would be acceptable to form the engagement portion39A for pressing and shifting shown inFIG. 7only at a site that corresponds to the unclamp position; or, alternatively, it would also be possible to form such portions at two sites, one of which corresponds to the unclamp position and one of which corresponds to the clamp position.

(6) The hydraulic pressure cylinders2,2A, and2B of the present invention could also be applied to clamp devices of various types, other than the twist-type clamp devices1,1A, and1B.

DESCRIPTION OF NUMERALS

1,1A,1B: twist-type clamp device2,2A,2B: hydraulic pressure cylinders (fluid pressure cylinders)3: clamp arm4,4A,4B: piston members5: piston portion6: output rod7: auxiliary rod8: twisting mechanism10: main cylinder body10B: head side end wall member11: open/shut valve mechanism for detection12a: hydraulic pressure operation chamber for unclamping12b: hydraulic pressure operation chamber for clamping13: base member15: cylinder bore20: rod insertion hole32: air passage (fluid passage)35: valve body reception hole36: valve body37: recessed engagement portion38: spherical body39: engagement portion for retraction39A,39B: engagement portions for pressing and shifting50: compression spring