Three directional opening/closing chuck

Cylinder mechanisms are provided for driving three jaw members each of which includes a cylinder hole having a long circular cross section, a piston which slides in the cylinder hole and has a long circular cross section, and a piston rod extending from the piston. The cylinder mechanisms are disposed at a position in the chuck body which is adjacent to corresponding jaw member in a state in which an axis of the cylinder hole in a direction parallel to a moving direction of the jaw member and a shorter diameter of the cylinder hole is directed in an axial direction of the chuck body.

TECHNICAL FIELD

The present invention relates to a chuck of a type in which three jaw members are opened and closed in a radial direction to grasp a workpiece, and more particularly, to a three directional opening/closing chuck which is thin as a whole and has a great grasping force of the jaw members.

PRIOR ART

A chuck of a type in which three jaw members grasp a workpiece is conventionally known in Japanese Patent Application Laid-open No. 11-262885, No. 11-254370, No. 2001-105372 and the like for example. This kind of chuck comprises three jaw members which move in radial directions, three cylinder mechanisms for individually actuating the jaw members, and a rotary disc type synchronizing mechanism for operating the jaw members in synchronism with each other. The cylinder mechanisms are disposed at positions corresponding to the jaw members of the chuck body, respectively.

In such a chuck, in order to increase the grasping force of the jaw members, a large cylinder mechanism having a great driving force should be used. In the case of the large cylinder mechanism, however, since diameters of a cylinder and piston are large, if they are incorporated, the size of the chuck body in its axial direction becomes large, and the chuck is increased in size.

Thereupon, in the chuck described in the above publications, pairs of small cylinder mechanisms which are actuated in synchronism with each other are used instead of the single large cylinder mechanism, and such pairs of small cylinder mechanisms are respectively disposed at positions corresponding to the jaw members in parallel.

According to the method for disposing the pairs of small cylinder mechanisms in parallel in this manner, however, although it is possible to reduce the vertical size of the chuck body and to make the chuck body thin, since both the cylinder mechanism must be disposed a distance from each other, the lateral size of the chuck body is increased at the installation position. Further, the individual cylinder mechanism is small in size and a driving force thereof is small. Therefore, if the entire cylinder mechanisms are taken into consideration, there is a drawback in that, although the lateral size is large, the grasping force of the jaw members is small.

In the chuck, when a workpiece is grasped, a piston rod of each cylinder mechanism and each jaw member moves forward and backward in the radial direction, but since a rotary disc constituting a synchronizing mechanism for synchronizing the operations of the jaw members is disposed at a central portion of the chuck, the stroke of the piston rod is limited by the rotary disc, and the rotary disc hinders the opening and closing stroke of the jaw member from increasing.

DISCLOSURE OF THE INVENTION

In a chuck of a type which opens and closes three jaw members in a radial direction to grasp a workpiece, it is a main technical object of the present invention to make a cylinder mechanism which drives each jaw member into a special structure so that the chuck is thin in size as a whole and a great grasping force can be obtained.

It is another technical object of the invention to provide a thin three directional opening/closing chuck having great opening and closing stroke of the jaw members.

To achieve the above objects, the present invention provides a three directional opening/closing chuck comprising a chuck body having a plurality of ports, three jaw members movably disposed in the radial direction around a center axis of the chuck body, three cylinder mechanisms for individually driving the jaw members, a synchronizing mechanism for synchronizing motions of the three jaw members, and a flow path assembly connecting the ports and the cylinder mechanisms, wherein each of the cylinder mechanisms includes a cylinder hole having a long circular cross section, a piston which slides in the cylinder hole and has a long circular cross section, and a piston rod extending from the piston, the cylinder mechanism is disposed at a position in the chuck body which is adjacent to corresponding jaw member in a state in which an axis of the cylinder hole in a direction parallel to a moving direction of the jaw member and a shorter diameter of the cylinder hole is directed in an axial direction of the chuck body.

In the chuck of the present invention having the above structure, the cylinder mechanism which drives the jaw member includes the cylinder hole and the piston both having the long circular cross sections, and the cylinder mechanism is disposed in a state in which the axis of the cylinder hole is directed parallel to the moving direction of the jaw member and a short diameter of the cylinder hole is directed to the axial direction of the chuck body. Therefore, as compared with a case in which the shape of the cross section of the cylinder hole is circle and its cross sectional area is the same as that of the present invention, it is possible to reduce the length of the chuck body in its axial direction and to reduce the chuck body in thickness. Further, as compared with a case in which a pair of small cylinder mechanisms are arranged side-by-side at a distance therebetween, the present invention does not require such distance, it is possible to reduce the chuck body in its lateral size, and to increase the areas of cross sections of the cylinder hole and the piston. Therefore, there is a merit in that the driving force is increased and the grasping force of the jaw members is increased.

In the present invention, it is preferable that the shapes of the cross sections of the cylinder hole and the piston are long circular shapes comprising semi-circular portions located at opposite ends of the long axial direction and straight line portions connecting the semi-circular portions, and the length of the straight line portion is 1.5 times or more than a radius of the semi-circular portion.

In the present invention, it is preferable that the synchronizing mechanism includes a central member rotatably disposed on the center axis of the chuck body, and a link for connecting to the piston rod and jaw member of the cylinder mechanism having three connection arms extending in the radial direction of said central member, the central member including a recessed escaping portion into which a tip end of the piston rod is fitted at the forward stroke end between the adjacent connection arms.

In this manner, if the central member is provided with the escaping portion, the tip end of the piston rod is fitted into the escaping portion at the position of the forward stroke end, since the stroke of the piston rod is not limited by the central member, the stroke of the piston rod, i.e., the opening and closing stroke of the jaw member can be increased.

According to a concrete embodiment of the present invention, one end of the link and the piston rod and the jaw member are rotatably connected with each other by a first connection pin which connects the piston rod and the jaw member with each other, and the other end of the link and the connection arm of the central member are rotatably connected to each other by a second connection pin.

In the present invention, the flow path assembly includes two central flow paths arranged on an outer periphery of a rotary support shaft located at a center of the central member, and a plurality of distribution flow paths which extend from the central flow paths toward the cylinder mechanism through the chuck body and which are respectively in communication with pressure chambers on opposite sides of the piston, and a portion of the distribution flow paths is in communication with the ports.

In this case, it is preferable that a hole lid which closes an outer end of the cylinder hole is provided with an elastic body which functions as a seal of the pressure chamber and a damper for the piston, the elastic body includes a groove which brings an end of the distribution flow path and the pressure chamber.

In the present invention, a through hole into which a pipe or other member is inserted can be provided at a central portion between the central member and the rotary support shaft.

DETAILED DESCRIPTION

FIGS. 1 to 8show a first embodiment of the three directional opening/closing chuck of the present invention. This chuck1A includes a chuck body2provided at its side surface with two, i.e., first and second ports P1and P2, three jaw members3disposed around a center axis L1of the chuck body2such that the jaw members3can move in the radial direction, three cylinder mechanisms4for respectively driving the three jaw members3, and a synchronizing mechanism5for synchronizing the operations of the three jaw members3.

The chuck body2has a substantially trifurcated flat shape. Therefore, the chuck body2includes three extending portions2aextending in the radial direction at equal angles from one an other around the center axis L1. Each of the extending portions2ais provided with the jaw member3and the cylinder mechanism4one each. Each jaw member3has substantially T-shaped cross section, and the jaw member3is movably mounted in a guide groove10having substantially T-shaped cross section formed along the radial axis L2in the extending portion2asuch that a portion of the jaw member3projects outward. An attachment is mounted to each jaw member3which is suited to a workpiece to be grasped, and the workpiece is grasped between the three jaw members3through the attachments.

As shown inFIGS. 4 and 5, the cylinder mechanism4includes a cylinder hole12having long circular cross section, a piston13having a long circular cross section which slides in the cylinder hole12in a sealed state, and a piston rod14having a circular cross section extending from the piston13toward a center of the chuck body2. The cylinder mechanisms4are disposed at positions in the extending portions2aadjacent to the jaw members3, i.e., at a position where the cylinder mechanisms4are parallel to the jaw members3in the vertical direction in a state in which the axis of the cylinder hole12is directed in a direction parallel to the moving direction of the jaw member3, i.e., in a direction of the radial axis L2, and in a state in which a short diameter of the cylinder hole12is directed toward the axis L1of the chuck body2.

An outer end of the cylinder hole12is closed with a plate-like hole lid16. The hole lid16is provided at an inner surface thereof with an elastic body17made of rubber or synthetic resin which functions as seal means and a damper which absorbs impact when the piston13reaches its retreating stroke end. The piston13is formed at its opposite sides with first and second pressure chambers18aand18b. The pressure chambers18aand18bare connected to the ports P1and P2by means of a later-described flow path assembly6.

A tip end of the piston rod14and an inner end of the jaw member3, i.e., an end of the jaw member3closer to the center of the chuck are formed with connection holes20, respectively. If the first connection pin21is inserted into the connection hole20, the jaw member3and the piston rod14are connected to each other. If the piston13and the piston rod14move forward and backward by action of fluid pressure, each jaw member3reciprocates in the radial direction.

In this manner, the cross sections of the cylinder hole12and the piston13are formed into the long circular shapes and they are disposed as described above. Therefore, as compared with the conventional technique in which the cross section of the cylinder hole12is circular and an area of cross section is equal to that of the above-described cylinder hole12, it is possible to reduce the chuck body2in its axial direction and to make thinner the chuck body2.

In the illustrated embodiment, as shown inFIG. 5, the cylinder hole12includes the long circular cross section comprising semi-circular portions12aand12alocated at opposite ends in the long axial direction and having a certain radius of curvature, and straight line portion12bconnecting the semi-circular portions12aand12a, respectively, and a length m of the straight line portion12band a radium n of the semi-circular portion12aare set such that a relation m>2n is established. As is disclosed inFIG. 6, a lateral region Z occupied by the long circular cylinder hole12in the extending portions2ais substantially equal to that of a case in which two circular cylinder holes H1and H2having diameter of 2n are disposed at a distance G from each other. However, if attention is paid to the area of the cross section of the entire cylinder hole, one long circular cylinder hole12has a larger cross section. Therefore, long circular cylinder hole12has larger driving force of the cylinder mechanism4, i.e., grasping force of workpiece by the jaw members3.

However, the cylinder hole12may not always have the above-described dimensional relation. In order to obtain a grasping force which is equal to or greater than that when two cylinder holes H1and H2having the diameter 2n are arranged side-by-side, the length m of the straight line portion12band the radius n of the semi-circular portion12amay be set such that a relation of m≧1.5n is established. With this arrangement, it is possible to obtain a chuck having a great grasping force without reducing or at least increasing a lateral width W of the extending portion2aas compared with a case in which the two circular cylinder holes H1and H2are arranged side-by-side.

As is found fromFIGS. 2 to 4, the synchronizing mechanism5for synchronizing the operations of the three jaw members3comprises a substantially trifurcated central member25which is rotatably disposed on the center axis L1of the chuck body2, and a plurality of links26for connecting the central member25, the piston rods14of the cylinder mechanisms4and the jaw members3to each other. The central member25includes three-connection arms25aextending in the radial direction, and a rotary support shaft27located at a center of the connection arms25a. The central member25is disposed in a circular recess2bformed in the chuck body2, by rotatably inserting the rotary support shaft27into a support hole28formed at a central portion of a bottom surface of the recess2b. The connection arm25a, the piston rod14of the cylinder mechanism4and the jaw member3are connected to each other by the link26.

One end of the link26is inserted between the piston rod14and the jaw member3, and is rotatably connected to the first connection pin21. The other end of the link26is inserted into a recess25bformed in the connection arm25aof the central member25, and is rotatably connected to the connection arm25athrough a second connection pin22. Therefore, the first connection pin21functions as means for connecting the piston rod14and the jaw member3with each other, and as means for connecting the link26with the piston rod14and the jaw member3. If the piston rod14, the jaw member3and the link26are connected by the same first connection pin21, the structure becomes simple as compared with a case in which they are connected through individual connection pins.

The central member25is formed with a recessed escaping portion29between the adjacent connection arms25aby forming a flat surface shape of the central member25into a substantially trifurcated shape. As shown inFIG. 2, the escaping portion29functions such that when the piston rod14reaches the forward stroke end, the escaping portion29prevents the tip end of the piston rod14from being fitted and from contacting with the central member25. With this arrangement, the stroke of the piston rod14is not limited by the central member25, and it is possible to increase the stroke of the piston rod14, i.e., the opening and closing stroke of the jaw member3.

By connecting the three jaw members3and the cylinder mechanisms4with each other through the synchronizing mechanism5, the jaw members3are opened and closed in synchronism with each other. That is, in a state in which the piston13and the piston rod14of each cylinder mechanism4are at the forward stroke end and each jaw member3is moved to a position closer to an inner side of the extending portion2a, i.e., at a position closer to the center of the chuck as shown inFIG. 2, if the piston13of each cylinder mechanism4is retreated by fluid pressure as shown inFIGS. 3 and 4, the piston rod14is also retreated and the jaw member3moves to a position closer to an outer end of the extending portion2aalong the radial axis L2. At that time, the central member25is pulled by the link26and rotated in the clockwise direction, and the motions of the three jaw members3are synchronized through the links26. When the second connection pin22which connects the links26and the connection arms25awith each other reaches positions slightly forward of the axes of the jaw members3, i.e., at positions slightly forward of the radial axes L2, the central member25stops. At that time, the links26are slightly inclined with respect to the radial axes L2. If the central member25stops at such a position, the jaw members3can easily move in the opposite direction.

Next, from a state shown inFIGS. 3 and 4, if the piston13and the piston rod14of each cylinder mechanism4move forward, the jaw member3moves forward to a position closer to a center of the chuck as shown inFIG. 2. At that time, the central member25is pushed by the links26and rotated in the counterclockwise direction, and synchronizes the motions of the three jaw members3through the links26, and stops when the connection arms25areach just intermediate positions of the adjacent jaw members3. In other words, the central member25stops such that the piston rod14of each cylinder mechanism4is located just at the intermediate position of the adjacent connection arms25aof the central member25, and the central member25stops at a position where the tip end of the rod is fitted into the escaping portion29.

An upper surface of the recess2bis closed with a circular cover (not shown). At that time, this cover is provided with notches in the radial direction at positions corresponding to the jaw members3so that the circular cover does not hinder the motions of the jaw members3.

The flow path assembly6connecting the pressure chambers18aand18band the ports P1and P2on the opposite sides of the piston13of the cylinder mechanism4is constituted as follows. That is, as shown inFIG. 4, a plurality of annular seal members30are arranged and mounted to an outer periphery of the rotary support shaft27located at a center of the central member25such that necessary distance between the adjacent seal members30is maintained in the axial direction of the rotary support shaft27. Two flow paths, i.e., first and second annular central flow paths31aand31bdefined by the seal members30are formed between an outer peripheral surface of the rotary support shaft27and an inner peripheral surface of the support hole28.

As shown inFIGS. 4,7and8, first and second distribution flow paths32aand32bwhich respectively brings the two central flow paths31aand31binto communication with the pressure chambers18aand18bon the opposite sides of the piston13are formed in the chuck body2at positions corresponding to the three cylinder mechanisms4. The distribution flow paths32aand32brespectively extends from the central flow paths31aand31btoward the cylinder mechanisms4on upper and lower two flat surfaces which are perpendicular to the center axis L1of the chuck body2and respectively corresponds to the two central flow paths31aand31b. As shown inFIG. 7, the first distribution flow path32awhich is in communication with the first central flow path31ais in communication with the first pressure chamber18aon the side of the rod. As shown inFIG. 8, the second distribution flow path32bwhich is in communication with the second central flow path31bis in communication with the second pressure chamber18bon the side of the rod through the groove (seeFIG. 6)17aprovided in the elastic body17inside the hole lid16.

Here, each of the first and second distribution flow paths32aand32bincludes a main flow path34awhich extends parallel to the radial axis L2and which is in communication with the pressure chambers18aand18b, and auxiliary flow paths34bwhich extends from a side surface of the chuck body2in the center axis L1direction and in communication with the main flow path34aand the central flow paths31aand31b. Since one flow path whose intermediate portion is bent can not formed by boring work, the straight main flow path34aand the auxiliary flow path34bas shown are combined, thereby forming the distribution flow paths32aand32bwhich connect the pressure chambers18aand18band the central flow paths31aand31b. In this case, an unnecessary opened end of the auxiliary flow path34bis closed with a plug.

A portion of the three sets of the distribution flow paths32aand32bcorresponding to the three cylinder mechanisms4is connected to the ports P1and P2. In the illustrated example, the auxiliary flow path34bin the first distribution flow path32aof the three sets of the distribution flow paths32a,32a,32a, is connected to the first port P1through a communication hole35a, and the auxiliary flow path34bin the distribution flow path32of the three sets of the second distribution flow paths32b,32b,32bis connected to the second port P2through a communication hole35b.

By forming the flow path assembly6by combining the central flow paths31aand31band the distribution flow paths32aand32b, it is possible to efficiently connect the pressure chambers18aand18band the ports P1and P2of each of the cylinder mechanisms4with each other while keeping the thin thickness of the chuck body2.

In the chuck1A having the above structure, if pressure fluid such as compressed air is supplied from the two ports P1and P2, the pressure fluid passes through the distribution flow paths32aand32bfrom the central flow paths31aand31band are supplied to the pressure chambers18aand18bof the cylinder mechanism4. The piston13and the piston rod14move forward and backward to move the jaw members3forward and backward in the radial direction. A work piece is grasped by the jaw members3through attachments (not shown) mounted to the jaw members3. At that time, motions of the jaw members3are synchronized by the synchronizing mechanism5comprising the central member25and the links26.

It is possible to provide the chuck with a detection device for detecting the operating positions of the jaw members3. The detection device may be of electric type, magnetic type or optical type, and its type is not limited if the device can detect the motions of the jaw member3, the piston13or the piston rod14. In the illustrated example, a magnetic detection device comprising a permanent magnet and a magnetic sensor is used. That is, as shown inFIGS. 1,4and5, the permanent magnet38is mounted to the piston13of any one of the cylinder mechanisms4, two magnetic sensors39and39are respectively mounted into two mounting grooves40and40formed on the side surfaces of the chuck body2, and the magnetic sensors39and39detect both the forward and backward stroke positions of the piston13. The mounting groove40may be formed in one or both side surfaces of one of the extending portion2a.

FIGS. 9 to 12show a second embodiment. A chuck1B of the second embodiment is different from the chuck1A of the first embodiment mainly in that the rotary support shaft27of the central member25constituting the synchronizing mechanism5has larger diameter than that of the first embodiment, and the rotary support shaft27is hollow and its through hole27acan be used for allowing a pipe, or other mechanical or electrical member to pass therethrough.

Since the diameter of the rotary support shaft27is increased, the diameter of the support hole28into which the rotary support shaft27is fitted and diameters of the central flow paths31aand31bof the outer peripheries of the rotary support shaft27are also increased. Therefore, when the central flow paths31aand31band the pressure chambers18aand18bof the cylinder mechanism4are connected to each other through the distribution flow paths32aand32b, they can be brought into communication with each other only through the main flow path34a, and it is unnecessary to establish the communication by combining the main flow path34aand the auxiliary flow path34bwith each other unlike the first embodiment. When the distribution flow paths32aand32band the ports P1and P2are brought into communication with each other, a portion of the distribution flow paths32aand32bis provided with the auxiliary flow path34bby branching to bring the auxiliary flow path34binto communication with the ports P1and P2through the communication holes35aand35blike the first embodiment.

Other structures and the effect of the second embodiment except those explained above are substantially the same as those of the first embodiment and thus, the same essential portions of the second embodiment are designated with the same symbols as those in the first embodiment, and an explanation thereof is omitted.

In each of the embodiments, as examples of the long circular cross sections of the cylinder hole12and the piston13, the semi-circular portions12alocated at the opposite ends of the long axial direction and having the certain radius of curvature, and the straight line portions12bconnecting the semi-circular portions12aare indicated. In the conception of this long circular shape of course includes an ellipse or a rectangular shape whose four corners are rounded into arcs.

As described in detail, according to the present invention, in the three directional opening/closing chuck for opening and closing the three jaw members to grasp a workpiece, the cylinder mechanism which drives each jaw member is formed into a special structure, thereby making it possible to obtain thin chuck as a whole and to obtain a great grasping force.