Patent Publication Number: US-2023150144-A1

Title: Machine tool hand

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 16/939,329, which is based on Japanese Patent Applications Nos. 2019-147321 and 2020-115692, the contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a machine tool hand. 
     BACKGROUND 
     There is a known gripping device that drives a plurality of hand members so as to be opened and closed by utilizing a coolant liquid supplied to a spindle of a machining center (for example, see Publication of Japanese Examined Utility Model Registration No. 3206020). 
     This gripping device includes: a cylinder into which a coolant liquid supplied to a spindle is injected; a piston that is movably disposed in the cylinder and that is moved by the pressure of the coolant liquid; and a plurality of hand members that are pivotably coupled to the piston. 
     SUMMARY 
     An aspect of the present disclosure is a machine tool hand including: a body portion that is mounted so as to be attachable to and detachable from a spindle of a machine tool, and that is provided with a flow path connected to a coolant-liquid supply path formed in the spindle; and two or more hand members that are attached to the body portion such that at least one of the hand members is pivotable about a prescribed axis, and that are capable of gripping an object therebetween by being closed. The flow path is provided with discharge ports via which a coolant liquid supplied from the coolant-liquid supply path is discharged toward surfaces of the hand members that are exposed to an outside, and a pressure of the coolant liquid causes an opening operation or a closing operation of the hand members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a front view showing a machine tool hand according to an embodiment of the present disclosure, in a state in which a pair of hand members are closed. 
         FIG.  2    is a front view showing the machine tool hand in  FIG.  1   , in a state in which the pair of hand members are opened. 
         FIG.  3    is a front view showing a state in which a workpiece is gripped by the machine tool hand in  FIG.  1   . 
         FIG.  4    is a longitudinal sectional view showing the machine tool hand in  FIG.  2   . 
         FIG.  5    is an enlarged longitudinal sectional view showing the flow of a coolant liquid in the machine tool hand in  FIG.  2   . 
         FIG.  6    is an enlarged longitudinal sectional view showing a first modification of the machine tool hand in  FIG.  1   , in a state in which a pair of hand members are closed. 
         FIG.  7    is an enlarged longitudinal sectional view showing the machine tool hand in  FIG.  6   , in a state in which the pair of hand members are opened. 
         FIG.  8    is a front view showing a second modification of the machine tool hand in  FIG.  1   , in a state in which a pair of hand members are opened. 
         FIG.  9    is a front view showing the machine tool hand in  FIG.  8   , in a state in which the pair of hand members are closed. 
         FIG.  10    is a longitudinal sectional view showing the machine tool hand in  FIG.  9   . 
         FIG.  11    is a front view showing a machine tool hand according to another embodiment of the present disclosure, in a state in which a pair of hand members are closed. 
         FIG.  12    is a front view showing the machine tool hand in  FIG.  11   , in a state in which the pair of hand members are opened. 
     
    
    
     DETAILED DESCRIPTION 
     A machine tool hand  1  according to an embodiment of the present disclosure will be described below with reference to the drawings. 
     As shown in  FIGS.  1  and  2   , the machine tool hand  1  according to this embodiment includes a body portion  2  and a pair of hand members  3 . 
     The body portion  2  includes: a distal end portion  4  that is formed in a cuboid block shape; and a cylindrical shaft portion  5  that is disposed closer to the base end than the distal end portion  4  is, and that is for mounting the body portion  2  so as to be attachable to and detachable from a spindle  100  of a machine tool. As shown in  FIG.  4   , the shaft portion  5  is provided with a flow path  7  that extends along a central axis from an opening  6  at one end. When the shaft portion  5  is attached to the spindle  100 , the opening  6  is connected to a coolant-liquid supply path  110  provided in the spindle  100 , and a coolant liquid supplied from the coolant-liquid supply path  110  is allowed to flow into the flow path  7 . 
     The pair of hand members  3  are disposed on both sides of the distal end portion  4  of the body portion  2 , and are individually attached to the body portion  2  so as to be pivotable about two parallel pivot axes (axes) A, B extending along a plane orthogonal to the central axis of the shaft portion  5 . 
     As shown in  FIG.  4   , the flow path  7  provided in the body portion  2  is branched into branched flow paths  8  in two directions in the distal end portion  4 . The branched flow paths  8  are individually branched in the directions toward the individual hand members  3 . The branched flow paths  8  have discharge ports  9  opening at two locations on each side surface of the distal end portion  4 . The total of the opening areas of the four branched flow paths  8  and the discharge ports  9  thereof is set to be substantially equal to the cross-sectional area of the flow path  7  in the shaft portion  5 . 
     Gears  10  that rotate about the pivot axes A, B are fixed to the respective hand members  3 . The gears  10  fixed to the two hand members  3  mesh with each other. 
     In addition, a coil spring (urging member)  11 , which urges the hand members  3  in the closing direction by means of an elastic restoring force, is bridged between the two hand members  3 . 
     In this embodiment, opposing side surfaces of the pair of hand members  3  are disposed so as to face the positions where these opposing side surfaces close off the discharge ports  9  provided in the distal end portion  4  of the body portion  2 . 
     In a state shown in  FIG.  1    in which the pair of hand members  3  are closed, the side surfaces of the individual hand members  3  are disposed closest to the discharge ports  9 , at positions where the side surfaces substantially close off the individual discharge ports  9 . In a state shown in  FIG.  2    in which the pair of hand members  3  are opened, the side surfaces of the individual hand members  3  are slightly inclined so as to be separated from the discharge ports  9  as a result of the individual hand members  3  pivoting about the pivot axes A, B, and gaps are formed between the body portion  2  and the hand members  3 . 
     The individual hand members  3  are constantly urged in the closing direction by means of the elastic restoring force of the coil spring  11 . In other words, in a state in which a workpiece (object) W is not held between the hand members  3  and the coolant liquid is not supplied into the flow path  7 , the side surfaces of the individual hand members  3  close the discharge ports  9  in the body portion  2  by means of the elastic restoring force of the coil spring  11 . 
     Then, when the coolant liquid is supplied into the flow path  7 , the individual hand members  3  are pushed by the coolant liquid discharged from the discharge ports  9  and are caused to pivot in directions in which the hand members  3  are separated from each other against the elastic restoring force of the coil spring  11 . The pressure of the coolant liquid discharged from the discharge ports  9  is, for example, 0.4 MPa to 2 MPa. 
     In the figures, reference sign  12  indicates an end stopper that abuts against the hand members  3  at the open positions and that restricts further movement of the hand members  3  by means of elastic deformation. In addition, reference sign  13  indicates an elastic member, such as a sponge, that comes into contact with the workpiece W and is elastically deformed when the workpiece W is gripped. 
     The operation of the thus-configured machine tool hand  1  according to this embodiment will be described below. In the description hereinafter, since the machine tool hand  1  according to this embodiment is formed symmetric laterally, there will be described only for one side, and the description for the other side will be omitted. 
     The machine tool hand  1  according to this embodiment is, for example, stored as one of the tools in a tool magazine of a machine tool and is attached to the spindle  100  in place of another tool, as needed or periodically, by an automatic tool changing device (not shown) provided in the machine tool. 
     For example, when it is necessary to supply a workpiece W to a chuck provided on a rotary table, to change the orientation of a workpiece W, or the like, the machine tool hand  1  is attached to the spindle  100 . 
     Then, in a state in which the machine tool hand  1  is attached to the spindle  100 , with the hand members  3  thereof directed downward, the machine tool hand  1  is raised or lowered in accordance with an elevating operation of the spindle  100 . 
     As shown in  FIG.  1   , in the case of gripping a workpiece W disposed vertically below the machine tool hand  1 , the machine tool hand  1  is lowered by lowering the spindle  100 , and as shown in  FIG.  2   , the pair of hand members  3  are brought into an open state by supplying the coolant liquid from the spindle  100 . Then, in a state in which the workpiece W is disposed between the pair of hand members  3 , as shown in  FIG.  3   , the pair of hand members  3  are brought into a closed state by stopping the supply of the coolant liquid, thus allowing the workpiece W to be gripped. 
     In this case, with the machine tool hand  1  according to this embodiment, when the pair of hand members  3  are brought into the open state, the coolant-liquid supply path  110  utilized during processing of the workpiece W is utilized, and the coolant liquid is supplied into the flow path  7  in the body portion  2  from the coolant-liquid supply path  110  through the opening  6 . By doing so, the coolant liquid supplied into the flow path  7  in the body portion  2  is discharged from the discharge ports  9  opening in two directions and presses the side surfaces of the individual hand members  3 , thereby allowing the individual hand members  3  to pivot about the pivot axes A, B. 
     Because the flow path  7  in the body portion  2  is open to the outside at the discharge ports  9 , the coolant liquid discharged from the discharge ports  9  flows along the side surfaces of the hand members  3  while pressing the side surfaces of the hand members  3 , and flows downward from the distal ends of the hand members  3 . The coolant liquid that has flowed down is recovered in a coolant tank (not shown) and is allowed to circulate in the same manner as in the processing. 
     Although fine chips or the like become mixed into the coolant liquid at this time, in this embodiment, the coolant liquid for opening and closing the hand members  3  is released to the outside from the discharge ports  9  of the flow path  7  in the body portion  2 , and the hand members  3  are caused to pivot by the flow energy during the release. Therefore, because the coolant liquid is not supplied into a closed space, there is an advantage in that it is possible to perform handling, etc. of a workpiece W without causing a malfunction due to chip clogging even when fine chips or the like become mixed into the coolant liquid. 
     In addition, with the machine tool hand  1  according to this embodiment, the pair of hand members  3  are constantly urged in the closing direction by means of the elastic restoring force of the coil spring  11 ; thus, the hand members  3  can be easily brought into the closed state by stopping the supply of the coolant liquid. In addition, because the gears  10  meshing with each other are fixed to the pair of hand members  3 , there is an advantage in that it is possible to place the gripping position of the workpiece W at the center as a result of the pair of hand members  3  pivoting by the same angles distributed from the center. 
     In addition, when the pair of hand members  3  are brought into the open state, as shown in  FIGS.  4  and  5   , the hand members  3  pivot about the pivot axes A, B, and the side surfaces pushed by the coolant liquid are each disposed so as to form an angle larger than 90° relative to the discharge direction. With this configuration, a guide means for the coolant liquid is formed, and the coolant liquid is allowed to flow along the side surfaces while being guided toward the distal ends of the hand members  3 . As a result, there is an advantage in that portions for gripping the workpiece W can be washed with the coolant liquid every time the pair of hand members  3  are opened. 
     In addition, in this embodiment, the flow path  7  in the body portion  2  is branched into the four branched flow paths  8 , and the cross-sectional area of each of the branched flow paths  8  and the discharge ports  9  is set to be ¼ of the cross-sectional area of the flow path  7 . Thus, the cross-sectional area of flow does not change between the flow path  7  and the branched flow paths  8 , and loss can be reduced. 
     Note that, in this embodiment, the side surfaces of the hand members  3  are pushed by the coolant liquid itself discharged from the discharge ports  9 . Alternatively, as shown in  FIGS.  6  and  7   , spherical metal (e.g., steel) bodies (movable bodies)  15  movable in the branched flow paths  8  in the vicinity of the discharge ports  9  may be disposed. 
     As shown in  FIG.  6   , the spherical body  15  has a diameter size smaller than an internal diameter of the branched flow path  8 ; and a gap of which the coolant liquid flows out is formed between the spherical body  15  and an inner surface of the branched flow path  8 . In the figures, reference sign  16  indicates a cylindrical body that forms an inner wall of the branched flow path  8  in a movable range of the spherical body  15 . Reference sign  17  indicates an abutting member embedded in the side surface of each of the hand members  3  opposing to the discharge ports  9 . 
     In order to suppress abbration of the body portion  2  and the hand members  3  caused by contacts with the spherical bodies  15  when the body portion  2  and the hand members  3  are made lighter in weight by using an aluminum alloy or the like, the cylindrical body  16  and the abutting member  17  are constituted by a hard material, for example, steel. The abutting members  17  are secured to the hand material  3  in a replaceable matter by engagement and disengagement of screws. 
     Reference sign  12  indicates an end stopper that restricts a pivot angle about pivot axis A or B of the hand members  3 . The end stopper  12  according to this embodiment stops pivoting of the hand members  3  by abutting the hand members  3  at a pivot angle where a discharge amount of the spherical body  15  from the discharge port  9  is equal to or less than a hemisphere. In  FIGS.  6  and  7   , illustrations of the coil spring  11  are omitted. 
     When the coolant liquid is supplied into the flow path  7  from the coolant-liquid supply path  110 , a portion of the coolant liquid branched to the two branched flow paths  8  pushes the spherical body  15  to move the spherical body  15  to a side of the discharge port  9 , and the remainder is discharged to the outside from the discharge port  9  via the gap between the spherical body  15  and the inner surface of the branched flow path. Each of the spherical bodies  15  pushed by means of a pressure of the coolant liquid pushes the corresponding abutting member  17  of the corresponding hand member  3  by protruding from the corresponding discharge port  9  to the outside, thus causing the hand members  3  to pivot about the respective pivot axes A, B. By doing so, distal ends of the two hand members  3  are opened. 
     Since the center of the spherical body  15  is held at the inner side than the discharge port  9 , a minimum value of the coolant-liquid communication cross-sectional area formed by the gap between the inner surface of the branched flow path  8  and the spherical body  15  remains constant without depending on the pivot angle of the corresponding hand member  3 . That is, since the pressure applied to the spherical body  15  from the coolant liquid does not vary by the pivot angle of the corresponding hand member  3 , the hand members  3  can be opened with a large stable force only by increasing the pressure of the coolant liquid. As a result, there are advantages in that a spring rigidity can be improved, a gripping force for the workpiece W can be improved, and therefore a stable handling can be realized. 
     In addition, by providing the gap around the spherical body  15 , the coolant liquid can be discharged to the outside from the corresponding discharge port  9  without confining the coolant liquid in the flow path  7 . By doing so, it is possible to prevent malfunction caused by clogging with chips or the like contained in the coolant liquid. 
     In addition, an amount of the cooling liquid discharged from the discharge port  9 , of the coolant liquid supplied into the flow path  7 , can be restricted by means of the corresponding spherical body  15 . By doing so, there are advantages in that it can be prevented to discharge a large amount of the coolant liquid when the hand members  3  are opened, and an operator can easily confirm the state of the hand members  3  and the workpiece W visually. 
     In the above aspect, a spherical shape was illustrated as a shape of the movable object, however, it is not limited thereto. An arbitrary shape, such as a columner shape, a shell-type shape, or the like, may be employed. Even when the columner shape or the shell-type shape is employed, a posture change of the movable body can be suppressed, and the minimum value of the communication cross-sectional area formed by the gap between the inner surface of the branched flow path  8  and the movable body  15  can remain substantially constant. 
     Note that the gears  10  for synchronizing pivoting of the two hand members  3  need not be provided in this embodiment. In addition, although a case in which the two hand members  3  are both caused to pivot about the pivot axes A, B has been illustrated as an example, one of the hand members  3  may be fixed and only the other one may be caused to pivot. This configuration also allows gripping of the workpiece W. 
     In addition, although the machine tool hand  1  including the pair of hand members  3  has been illustrated as an example in this embodiment, alternatively, the present invention may be applied to a machine tool hand  1  including three or more hand members  3 . 
     In addition, although four branched flow paths  8  are provided in this embodiment, alternatively, it suffices that two or more branched flow paths  8  be provided for causing two or more hand members  3  to pivot. 
     In addition, the hand members  3  may have any shape, and a plurality of machine tool hands  1  having different shapes may be prepared according to the shapes of workpieces W to be gripped. 
     In addition, although the coolant liquid is supplied in the case of opening the hand members  3  in this embodiment, alternatively, as shown in  FIGS.  8  to  10   , the coolant liquid may be supplied when the hand members  3  are to be closed. 
     In this case, a coil spring (urging member)  14  that constantly urges the hand members  3  in the opening directions may be employed. 
     Next, a machine tool hand  20  according to another embodiment of this disclosure will be described below. In the description of this embodiment, identical reference signs are assigned to portions having configurations common to those in the machine tool hand  1  according to the above embodiment, and a description thereof will be omitted. 
     As shown in  FIG.  11   , the machine tool hand  20  according to this embodiment includes a body portion  21 , a movable member  22 , and a pair of hand members  23 . 
     A distal end portion  24  of the body portion  21  is provided with a groove  25  that is arranged at the center of the width direction and that extends along the central axis of the shaft portion  5  from an end portion opposite to the shaft portion  5 . The flow path  7 , which extends along the central axis of the shaft portion  5  from the opening  6  at one end of the shaft portion  5 , is provided with the discharge port  9  at a groove bottom of the groove  25 . 
     The movable member  22  is disposed inside the groove  25  and is supported so as to be movable only in a direction along the central axis of the shaft portion  5  with respect to the distal end portion  24 . A coil spring (urging member) which is not shown is bridged between the movable member  22  and the distal end portion  24 . The movable member  22  is constantly urged in a direction closer to the discharge port  9  by means of the elastic restoring force of the coil spring. 
     The movable member  22  is moved closer to the groove bottom, thus being located at a position where the discharge port  9  is closed. 
     The pair of hand members  23  are supported to the movable member  22  in such a way that each proximal end thereof can pivot about a pivot axis (axis) C perpendicular to the central axis of the shaft portion  5 . At an intermediate position of each of the hand members  23 , an elongated guide hole  26  is provided so as to obliquely extend toward a direction of the distal end of the corresponding hand member  23  and a direction away from the central axis of the shaft portion  5 . 
     A pin  27  that is provided on a side surface of the distal end portion  24  and that extends parallel to the pivot axis C, is inserted into each of the guide holes  26 . 
     The operation of the thus-configured machine tool hand  20  according to this embodiment will be described below. 
     When the coolant liquid is supplied into the flow path  7 , the coolant liquid flows and is discharged toward the movable member  22  from the discharge port  9 . The discharged coolant liquid is sprayed into the movable member  22  that is being disposed at the position where the discharge port  9  is closed. By doing so, the movable member  22  is moved toward a direction away from the discharge port  9  along the central axis of the shaft portion  5 . 
     In response to the movement of the movable member  22 , each of the hand members  23  connected to the movable member  22  is moved along a longitudinal direction of the corresponding guide hole  26  with respect to the corresponding pin  27  secured at the distal end portion  24 . By doing so, as shown in  FIG.  12   , the hand members  23  pivot about the pivot axis C, and thus the distal ends of the hand members  23  are opened. 
     When the supply of the coolant liquid is stopped, the movable member  22  is pulled back toward the direction closer to the discharge port  9  by means of the elastic restoring force of the coil spring. By doing so, in response to the movement of the movable member  22 , each of the hand members  23  pivots in a direction in which the distal end is closed. Thereby, it is possible to grip the workpiece W between the hand members  23 . 
     Thus, similarly to the machine tool hand  1  according to the first embodiment, the machine tool hand  20  according to this embodiment can also open and close the pair of hand members  23  by means of the coolant liquid discharged from the discharge port  9 . There is an advantage in that, even when fine chips or the like become mixed into the coolant liquid, by releasing the coolant liquid to the outside from the discharge port  9 , it is possible to perform handling, etc. of the workpiece W without causing a malfunction due to chip clogging. 
     In addition, it is possible to cleanse the hand members  23  with the coolant liquid discharged from the discharge port  9  flowing along the surface of the hand members  23  every time the pair of hand members  23  are opened. 
     Note that, in this embodiment, the case where the hand members  23  are opened by discharging the coolant liquid was illustrated. Reversely, the hand members  23  may be closed by discharging the coolant liquid.