Chuck apparatus

A piston is displaced by a pressure fluid supplied to a chuck body, whereupon a pair of first and second fingers that constitute a gripping member are operated to open and close along a base body. Further, a shaft-shaped bobbin is inserted through the interior of the first and second fingers, and a coil is wound around a small diameter portion of the bobbin. Accompanying opening/closing operations of the first and second fingers, an opening/closing amount thereof is detected based on a change in impedance of the coil.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chuck apparatus, which is capable of gripping a workpiece under an opening/closing action of a gripping member. More specifically, the invention concerns a chuck apparatus incorporating a detector therein that can detect an opening/closing amount of the gripping member.

2. Description of the Related Art

Heretofore, a chuck apparatus has been known, for example, which is mounted on the end of a shaft or the like of a machine tool. By performing opening/closing operations of a pair of gripping members, upon supplying a pressure fluid or an electric signal thereto, workpieces made up of various parts or the like are gripped by the chuck apparatus.

In this type of chuck apparatus, for example as disclosed in Japanese Laid-Open Patent Publication No. 11-114869, gripping of the workpiece is performed by controlling an opening/closing amount of the gripping members, corresponding to the size of the workpiece to be gripped. For this purpose, it is known to provide a detector, which is capable of detecting the opening/closing amount of the gripping members. In such a detector, the pair of gripping members is disposed on the upper surface of a displaceable guide rail, and the detector comprises a plurality of coils arranged along the guide rail. Further, in a similar manner, a plurality of other coils is disposed as well on the upper surface of an opposite side, sandwiching the guide rail therebetween. Additionally, by displacement of the gripping members between two coils, which are arranged in confronting positions sandwiching the guide rail, the amount of opening/closing of the gripping members is detected based on an induced output signal that is output.

However, in the aforementioned conventional technique, since the detector is constructed from plural coils, which are arranged along the displacement direction of the gripping members, an increase in the number of parts and a greater manufacturing cost for the chuck apparatus is incurred, and the apparatus becomes large in scale due to the coils, which are provided in plurality.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a chuck apparatus in which an increase in size and scale as a result of the detection device is suppressed, while the opening/closing amount of a gripping member can be detected with high accuracy by means of a simple and efficient structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

InFIG. 1, reference numeral10indicates a chuck apparatus according to a first embodiment of the present invention.

The chuck apparatus10, as shown inFIGS. 1 to 3, includes a cylindrically shaped chuck body12, a piston14displaceably disposed in the interior of the chuck body12, a gripping member22having a pair of first and second fingers (chucks)20a,20bthat are operated to open and close through levers18a,18bwhich are engaged with a rod16of the piston14, and a detection mechanism (detector)24disposed on an end of the chuck body12for detecting an opening/closing amount of the gripping member22.

The chuck body12is formed with a substantially rectangular shape in cross section, having a through hole26that penetrates in the axial direction formed in the interior thereof. First and second ports28a,28b, through which a pressure fluid is supplied to the interior of the through hole26, open onto a side surface of the chuck body12.

A cap30is fitted into the through hole26on one of the open end sides thereof, the through hole26being blocked by the cap30. Further, an annular seal member32is installed on an outer circumferential surface of the cap30, such that the inside of the through hole26is maintained in an airtight condition by abutment against the inner circumferential surface of the through hole26. The cap30is retained with respect to the through hole26by an engagement ring34, which is installed on an inner side surface of the through hole26.

The first and second ports28a,28bare separated from each other by a predetermined interval in the axial direction (the direction of arrows X1and X2) of the chuck body12. The first port28acommunicates with one end surface (in the direction of the arrow X1) of the piston14, whereas the second port28bcommunicates between the other end surface of the piston14and the cap30. Moreover, the first and second ports28a,28bare connected to an unillustrated pressure fluid supply source.

Further, a base body36in the form of a plate is connected to the other end of the chuck body12. A rail groove38, through which a pair of first and second fingers20a,20bconstituting the gripping member22are guided, is formed in the base body36. The rail groove38is formed along a straight line on a side surface of the base body36, on a side opposite to that of the chuck body12, and further, extends along the longitudinal direction thereof, substantially perpendicular to the axis of the chuck body12. In addition, a pair of end blocks40a,40bare fixed to both ends of the base body36through bolts42.

Furthermore, a cover44is installed on an upper portion of the base body36so as to cover portions of the base body36and the gripping member22. The cover44is formed from a bent plate material, for example, covering the base body36. An end of the cover44is fixed with respect to the base body36by bolts46(seeFIG. 3).

The cover44includes a finger hole48through which the first and second fingers20a,20bof the gripping member22are inserted. The finger hole48has an opening size that corresponds with the displacement range of the first and second fingers20a,20b. Therefore, when undergoing opening/closing movements, the first and second fingers20a,20bdo not come into contact with the cover44.

A damper50, made of an elastic material such as rubber or the like, is installed on one end surface of the piston14, so shocks are absorbed when the piston14is displaced toward the gripping member22(in the direction of the arrow X1) and abuts against the inner wall surface of the through hole26.

On the other hand, the outer circumferential surface of the piston14is disposed in sliding contact along the inner circumferential surface of the through hole26, and a piston packing52, which is installed in an annular groove on the outer circumferential surface, abuts against the inner circumferential surface of the through hole26. Owing thereto, airtightness at the interior of the through hole26, on respective sides of both end surfaces of the piston14, is suitably maintained.

Further, a magnet54adjacent to the piston packing52is arranged on the outer circumferential surface of the piston14. The displacement position of the piston14is confirmed by an unillustrated position-detecting sensor, which senses the magnetism from the magnet54.

A rod16, which is radially reduced in diameter and extends toward the side of the gripping member22(in the direction of the arrow X1), is formed on one end surface side of the piston14, whereas the other end surface of the piston14is arranged to confront the cap30. The rod16is inserted through a rod hole56, which is reduced in diameter with respect to the through hole26, and a rod packing58disposed on the inner circumferential surface of the rod hole56abuts against the outer circumferential surface of the rod16.

A pair of levers18a,18bare engaged rotatably with the rod16through a pin60. The levers18a,18bare each L-shaped in cross section, wherein substantially central bent portions thereof are rotatably axially supported, respectively, through a pair of link pins62disposed in the chuck body12.

Further, ends of each of the levers18a,18bare formed with cutouts64therein, cut respectively in a semicircular shape, which engage with the pin60installed in the end portion of the rod16. On the other hand, the levers18a,18bare formed in a gradually narrowed shape, which narrows toward the other end sides thereof from the regions supported by the link pins62, and are axially supported respectively within interior portions of the first and second fingers20a,20bthat constitute the gripping member22.

More specifically, the pair of levers18a,18bare displaceable rotatably through the link pins62upon displacement of the rod16along the axial direction (in the directions of arrows X1and X2), such that the other end side portions thereof approach and separate away from each other.

As shown inFIG. 2, the gripping member22includes the pair of first and second fingers20a,20b, which are disposed displaceably along the rail groove38of the base body36. The first and second fingers20a,20binclude block-shaped main bodies66, which are guided within the rail groove38, and claw portions68that project from the main bodies66and grip the workpiece.

Grooves70(seeFIG. 3) are formed respectively along the axial direction on both side portions on the main bodies66. A plurality of balls (not shown) is installed linearly within the grooves70. Additionally, the balls are retained in the grooves70by cover plates72that are installed on both end surfaces of the base body36. The balls are retained in abutment against inner wall surfaces of the rail groove38confronting the grooves70. Owing thereto, displacement resistance is reduced when the first and second fingers20a,20bthat constitute the gripping member22are displaced along the rail groove38, and the first and second fingers20a,20bcan be displaced smoothly along the rail groove38.

Further, first bobbin holes74a,74b, which extend substantially perpendicularly with respect to the claw portions68, and penetrate substantially parallel to the displacement direction of the first and second fingers20a,20b, are formed respectively inside the main bodies66. In addition, the respective first bobbin holes74a,74bare disposed along a straight line, under a condition in which the first and second fingers20a,20bare installed in the rail groove38(seeFIG. 1).

Furthermore, second bobbin holes76a,76bare formed in the end blocks40a,40bin positions facing the first bobbin holes74a,74b, such that large diameter portions80a,80bof a bobbin78are inserted into the second bobbin holes76a,76b. In addition, because the first bobbin holes74a,74band the second bobbin holes76a,76bare disposed on the same axis, both ends of the bobbin78are retained by the second bobbin holes76a,76b.

Screw holes82, which open upwardly and communicate with the second bobbin holes76a,76b, are formed in the end blocks40a,40b, with fixing bolts84being threaded into the screw holes82. Since the screw holes82penetrate perpendicularly with respect to the second bobbin holes76a,76b, the fixing bolts84, by screw-rotation thereof, are displaceable in directions (the directions of arrows X1and X2) to approach and separate away from the second bobbin holes76a,76b.

More specifically, by displacing the fixing bolts84toward the bobbin78(in the direction of the arrow X2inFIG. 1), because the outer circumferential surface of the bobbin78, which is inserted through the second bobbin holes76a,76b, is pressed by the ends of the fixing bolts84, the bobbin78is fixed firmly inside the second bobbin holes76a,76b.

Accordingly, the bobbin78is prevented from being displaced in the axial direction (the direction of arrows A1, A2), and is retained in a state whereby the bobbin78is inserted through the first bobbin holes74a,74bof the gripping member22.

Stated otherwise, the fixing bolts84disposed in the end blocks40a,40bfunction as stoppers, which regulate axial displacement of the bobbin78.

The detection mechanism24, as shown inFIGS. 2 and 4, is made up from the bobbin78, which is inserted through the interior of the first and second fingers20a,20b, a coil86that is wound around the outer circumferential surface of the bobbin78, and a substrate88(seeFIG. 1), which is connected to the coil86.

The bobbin78is formed from an elongate shaft, having large diameter portions80a,80bthat are inserted through the first and second bobbin holes76a,76bof the first and second fingers20a,20b, and a small diameter portion90disposed substantially centrally along the axial direction thereof, which is reduced in diameter with respect to the large diameter portions80a,80b, with the coil86being wound around the small diameter portion90. Specifically, on the bobbin78, the small diameter portion90is disposed such that it is sandwiched between the large diameter portions80a,80b, which are disposed on both respective ends of the bobbin78.

The diameter of the large diameter portions80a,80bis set roughly equivalent to the inner circumferential diameters of the first and second bobbin holes74a,74b,76a,76b, so that the bobbin78can be supported by insertion thereof through the second bobbin holes76a,76aand by the fixing bolts84.

Further, in the open state (seeFIG. 2) in which the first finger20aand the second finger20bare maximally separated, the small diameter portion90is arranged between the first finger20aand the second finger20b, such that the small diameter portion90is exposed to the outside with respect to the first bobbin holes74a,74b. Both ends of the small diameter portion90are arranged such that the ends are inserted slightly into the respective first bobbin holes74a,74bwhen the gripping member22is opened. More specifically, a state is provided in which both ends of the coil86, which is wound around the small diameter portion90, also are inserted slightly inside the first bobbin holes74a,74b.

The coil86is wound in a spiral shape with respect to the small diameter portion90, such that the outer circumferential diameter thereof is set to be roughly the same or just slightly smaller than that of the large diameter portions80a,80b.

Furthermore, a coil groove (groove)92is formed linearly along the axial direction on the outer circumferential surface of the large diameter portion80band small diameter portion90, which are inserted through the second finger20b, wherein the coil86is installed along the coil groove92. Further, on the end of the small diameter portion90on the side of the large diameter portion80a, a coil hole (hole)94is formed (seeFIG. 4), such that the coil hole94connects with the coil groove92.

In greater detail, after the coil86has been inserted through and along the coil groove92of the large diameter portion80band the small diameter portion90, on the side of the second finger20b, the coil86is wound with respect to the outer circumferential surface of the small diameter portion90, so that the coil86, which was inserted through the coil hole94, returns toward the side of the second finger20bfrom the side of the large diameter portion80a, which is inserted through the first finger20a.

Accordingly, the coil groove92is disposed so that the coil86can be fed therein until reaching the side of the large diameter portion80a, where winding of the end portion of the coil86commences, and the coil86which has been inserted through the coil groove92is covered by the wound coil86, which is wound over the small diameter portion90. As a result, the coil86does not drop out externally from the coil groove92and is retained within the coil groove92, and also, the position where winding commences is regulated by insertion through the coil hole94.

Both ends of the coil86are connected respectively to the substrate88. In the substrate88, a change in impedance produced by the coil86is detected, and the opening/closing amount of the gripping member22is calculated based on the change in impedance.

The chuck apparatus10in accordance with the first embodiment of the present invention is constructed basically as described above. Next, operations and effects of the invention shall be explained. As shown inFIG. 1, a non-gripped state of the workpiece, in which the piston14is elevated toward the side of the gripping member22(in the direction of the arrow X1) and the pair of first and second fingers20a,20bis opened, is assumed as the initial condition.

First, a pressure fluid is supplied with respect to the first port28afrom an unillustrated pressure fluid supply source, whereby the piston14is displaced in a direction to separate from the gripping member22(in the direction of the arrow X2), and the ends of the pair of levers18a,18bengaged with the rod16of the piston14are pulled downward respectively. In this case, the second port28bis placed in a state of being open to atmosphere.

Owing thereto, the pair of levers18a,18bare rotated respectively in directions so that the other ends approach mutually toward each other about fulcrums defined by the link pins62, and the pair of first and second fingers20a,20b, which are engaged with the other ends, are displaced substantially horizontally in directions (the directions of arrows A1) to approach one another, mutually along the rail groove38of the base body36. As a result, the workpiece is interposed between and gripped at a predetermined pressure by the first and second fingers20a,20bthat constitute the gripping member22.

In this case, by displacement of the first and second fingers20a,20bmutually in directions to approach each other (in the directions of the arrows A1), the coil86is inserted mutually from both ends sides thereof into the first bobbin holes74a,74band the outer circumferential side of the coil86is covered. In addition, along with a change of the relative positions of the gripping member22and the coil86, the impedance of the coil86changes, and by detecting a voltage change of the coil86based on the change in impedance, the displacement amount of the first and second fingers20a,20bis calculated in the substrate88.

Further, at this time, the displacement amounts of the first and second fingers20a,20bare substantially the same, respectively, with respect to the coil86.

On the other hand, when the gripped state of the workpiece by the chuck is released, the pressure fluid that was supplied to the first port28ais supplied with respect to the second port28b, by means of a switching operation of an unillustrated switchover valve. In this case, the first port28ais placed in a state of being open to atmosphere.

Accordingly, the piston14is displaced toward the side of the gripping member22(in the direction of the arrow X1) under a pressing action of the pressure fluid directed to the through hole26from the second port28b, and along therewith, the pair of levers18a,18b, which are engaged with the rod16, are rotated respectively in directions so that the other ends separate mutually from each other about the fulcrums defined by the link pin62. Owing thereto, the pair of first and second fingers20a,20b, which are engaged with the levers18a,18b, are displaced substantially horizontally in directions (the directions of arrows A2) to separate from one another, mutually along the rail groove38of the base body36, and the first and second fingers20a,20bthat grip the workpiece are displaced in directions to separate mutually from each other. As a result, the gripped state of the workpiece is released by the first and second fingers20a,20b.

In this case as well, by displacement of the first and second fingers20a,20bmutually in directions to separate from each other (in the directions of the arrows A2), portions of the coil86accommodated in the first bobbin holes74a,74bare displaced respectively toward the outside, and the outer circumferential side of the coil86is gradually exposed outside of the first and second fingers20a,20b. In addition, along with a change of the relative positions of the gripping member22and the coil86, the impedance of the coil86changes, and by detecting a voltage change of the coil86based on the change in impedance, the displacement amount of the first and second fingers20a,20bis calculated.

In the foregoing manner, in the first embodiment, a detection mechanism24capable of detecting an opening/closing amount of the gripping member22is made up of the bobbin78that is inserted through the interior of the first and second fingers20a,20b, and a single coil86wound about a central portion of the bobbin78, such that the coil86is wound in a spiral with respect to the small diameter portion90of the bobbin78. In addition, by displacement of the first and second fingers20a,20balong the outer circumferential side of the coil86through the first bobbin holes74a, based on the change in impedance of the coil86, the displacement amount of the first and second fingers20a,20bcan be continuously detected. As a result, because the opening/closing amount of the gripping member22can be detected directly by the detection mechanism24, detection with minimal detection errors and high accuracy can be carried out. Workpieces can be gripped reliably by the gripping member22, and the detection mechanism24can be formed of a simple structure from the coil86and the bobbin78.

Further, because the coil86and bobbin78making up the detection mechanism24are structured such that they are capable of being accommodated respectively inside the gripping member22, an increase in scale of the chuck apparatus10including the detection mechanism24disposed therein can be suppressed. That is, the detection mechanism24can be provided without causing the chuck apparatus10to become large in size.

Furthermore, because the detection mechanism24is capable of highly accurately detecting the opening/closing amount of the gripping member22that grips the workpiece, the opening/closing amount of the gripping member22can be controlled with high accuracy corresponding to the size of the workpiece. For example, compared to a case in which a displacement amount of the piston14is detected, which causes opening and closing movements of the gripping member22, and the opening/closing amount of the gripping member22is detected based on the piston displacement amount, in the present invention, since the opening/closing amount of the gripping member22is detected directly, errors in the opening/closing amount are small, and detection can be performed with greater accuracy.

Still further, because the coil86is inserted through the coil groove92of the bobbin78and both ends of the coil86can be consolidated, the substrate88to which both ends are connected can be disposed on one side only of the coil86, and the substrate88can be consolidated therewith, thus furthering a reduction in scale of the chuck apparatus10.

Next, a chuck apparatus100according to a second embodiment is shown inFIG. 5. In the respective chuck apparatuses100,120,140,150according to the second through fifth embodiments indicated below, structural elements thereof which are the same as those of the chuck apparatus10according to the first embodiment, shall be designated with the same reference numerals, and detailed explanations of such features shall be omitted.

The chuck apparatus100according to the second embodiment differs from the chuck apparatus10according to the first embodiment in that, a pair of coils106a,106bare arranged on both end sides of the bobbin104that constitutes the detection mechanism (detector)102, and that in a state in which the gripping member22is opened, the coils106a,106bare arranged so as to be capable of accommodation, respectively, within the interiors of the first bobbin holes74a,74b.

With the chuck apparatus100, a large diameter portion108is formed at a substantially central portion of the bobbin104that makes up the detection mechanism102, and a pair of small diameter portions110a,110b, around which coils106a,106bare wound, are formed on both ends about the central large diameter portion108. The length of the small diameter portions110a,110bis formed to be slightly greater than the length of the first bobbin holes74a,74b. In addition, in a open state in which the first and second fingers20a,20bconstituting the gripping member22are separated mutually from each other, parts of the small diameter portions110a,110bare exposed to the outside. That is, parts of the coils106a,106bthat are wound around the small diameter portions110a,110bbecome exposed to the exterior.

Further, a first coil groove (groove)112is formed along the axial direction on an outer circumferential surface of the small diameter portion110athat is inserted through the first finger20a, with the coil106a, which is wound around the small diameter portion110abeing inserted through the first coil groove112. The first coil groove112extends from the one small diameter portion110aand via the large diameter portion108until reaching the outer circumferential surface of the small diameter portion110b, which is inserted through the second finger20b.

Further, in addition to the coil groove112through which the coil106ais inserted, a second coil groove (groove)114through which the coil106bis inserted is provided on the small diameter portion110b, which is inserted through the second finger20b. In addition, the coils106a,106binserted through the first and second coil grooves112,114are led to the exterior respectively through the end block40b.

In this manner, with the second embodiment, a pair of coils106a,106bis disposed respectively corresponding to the first and second fingers20a,20b, and by displacement of the first and second fingers20a,20b, the displacement amounts of the first and second fingers20a,20bcan be detected continuously based on a change in impedance of the coils106a,106bthat are accommodated within the first bobbin holes74a,74b.

Next, a chuck apparatus120according to a third embodiment is shown inFIG. 6.

The chuck apparatus120according to the third embodiment differs from the chuck apparatuses10,100according to the first and second embodiments in that, in an open state in which the first and second fingers20a,20bare separated mutually from each other, the first coil124making up the detection mechanism (detector)122is arranged in the first bobbin hole74aof the first finger20a, while a separate second coil126is arranged at a substantially central portion of the bobbin128between the first and second fingers20a,20b.

With the chuck apparatus120, small diameter portions130a,130bare formed respectively on one end, and substantially in the center, of the bobbin128that constitutes the detection mechanism122, and a large diameter portion132is formed on the other end of the bobbin128, which is accommodated inside the second finger20b. In addition, first and second coils124,126are wound respectively around the small diameter portions130a,130b, such that the first coil124is accommodated within the first bobbin hole74aof the first finger20a.

Further, the other second coil126is arranged between the first finger20aand the second finger20band exposed externally. Also, while the gripping member22is in a closed state, the second coil126is accommodated in the first bobbin hole74bof the second finger20b.

In this manner, in the third embodiment, when the first and second fingers20a,20bundergo opening and closing movements, the first coil124is gradually exposed outwardly, while conversely, the other second coil126is gradually covered, and vice versa.

More specifically, because the changes in impedance by the two first and second coils124,126have opposite characteristics respectively, a large deviation therebetween can be obtained, and the detection accuracy of the displacement amounts of the first and second fingers20a,20bcan be further improved, when the displacement amounts are detected by the changes in impedance.

Next, a chuck apparatus140according to a fourth embodiment is shown inFIGS. 7 and 8.

The chuck apparatus140according to the fourth embodiment differs from the chuck apparatuses10,100,120according to the first through third embodiments in that tubular bodies142a,142bare inserted respectively into the first bobbin holes74a,74bof the first and second fingers20a,20b, while a bobbin146making up the detection mechanism (detector)144is inserted through the tubular bodies142a,142b, and together therewith, paired coils148a,148bare disposed respectively on both ends of the bobbin146.

In the chuck apparatus140, the tubular bodies142a,142b, which are made of a metal material such as aluminum, brass or the like, are arranged in the interior of the first and second fingers20a,20b. Further, the bobbin146is inserted through the inside of the tubular bodies142a,142b, and the pair of coils148a,148bare wound respectively with respect to small diameter portions110a,110bof the bobbin146. More specifically, in an open state of the gripping member22, the paired coils148a,148bare accommodated respectively in the first bobbin holes74a,74bof the first and second fingers20a,20b.

In this manner, with the fourth embodiment, by providing tubular bodies142a,142brespectively on the outer circumferential sides of the coils148a,148b, the output characteristics produced by the coils148a,148bcan be caused to change in accordance with the material properties of the tubular bodies142a,142b. Specifically, desired output characteristics are capable of being obtained, by arbitrarily selecting the material properties of the tubular bodies142a,142b.

Next, a chuck apparatus150according to a fifth embodiment is shown inFIGS. 9 through 11.

The chuck apparatus150according to the fifth embodiment differs from the chuck apparatuses10,100,120,140according to the first through fourth embodiments in that the detection mechanism (detector)152is disposed substantially parallel to and externally of the gripping member22.

In the chuck apparatus150, a pair of guide bodies154a,154bis disposed on an upper portion of the base body36, substantially parallel with the gripping member22, and large diameter portions158a,158bof the bobbin156are inserted through interiors of the guide bodies154a,154b. The guide bodies154a,154bare formed in cylindrical shapes, and are retained through cover plates160, which are mounted on ends of the first and second fingers20a,20b.

In greater detail, bulging portions162, which bulge outwardly toward sides of the guide bodies154a,154b, are disposed on the cover plates160, whereby the guide bodies154a,154bare retained between the bulging portions162of the cover plates160, which are mounted on both ends of the first and second fingers20a,20b. In this case, the bobbin156is inserted through the interior of the bulging portions162.

Further, the large diameter portions158a,158b, which are formed on both ends of the bobbin156, are accommodated in the guide bodies154a,154bthat are arranged on sides of the end blocks163a,163b, and are retained in the second bobbin holes76a,76bof the end blocks163a,163b. Further, a coil166is wound around the small diameter portion164, which is formed at a substantially central portion of the bobbin156. The coil166is disposed between the pair of guide bodies154a,154bwhile being exposed to the exterior.

Furthermore, a cover168is mounted on an upper portion of the base body36so as to cover portions of the guide bodies154a,154band the gripping member22.

In addition, by causing a closing operation of the first and second fingers20a,20b, the guide bodies154a,154bare displaced mutually in directions to approach one another (the directions of the arrows A1) along with the first and second fingers20a,20b, such that the guide bodies154a,154bcover the coil166. The displacement amount of the first and second fingers20a,20bis detected continuously based on the change in impedance of the coil166, as the coil166is covered by the guide bodies154a,154b.

In the foregoing manner, with the fifth embodiment, because the detection mechanism152is disposed on the outside substantially parallel to the first and second fingers20a,20b, it is unnecessary for first and second bobbin holes74a,74bto be provided in the fingers20a,20b, and hence the first and second fingers20a,20bof a conventional chuck apparatus can be appropriated for use therewith. Owing thereto, the detection mechanism152can be easily and inexpensively disposed with respect to the chuck apparatus150, and manufacturing costs can be reduced.

The chuck apparatus according to the first through fifth embodiments of the present invention is not limited by the aforementioned embodiments, and various other structures may be adopted as a matter of course, without deviating from the essential features and gist of the present invention.

Further, concerning the chuck apparatuses10,100,120,140,150according to the aforementioned first through fifth embodiments, an explanation has been given of an air-driven type, in which the gripping member22is opened and closed under the action of a supplied pressure fluid. However, the invention is not limited to such a feature and, for example, the above-described detection mechanism may also be provided in a electrically driven type of chuck apparatus, in which the opening/closing operation is accomplished by a rotary driving force of a rotary driving source, such as a motor or the like.

In this case as well, adverse effects of play or rattling of the transmitting mechanism, which transmits the rotary driving force to the gripping member22, are not received, thereby enabling the opening/closing amount of the gripping member22to be detected highly accurately.

While the invention has been particularly shown and described with reference to preferred embodiments, it will be understood that variations and modifications can be effected thereto by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.