Patent Publication Number: US-10780540-B2

Title: Workpiece clamp apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority to Japanese Patent Application No. 2016-103934 filed on May 25, 2016, the content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to workpiece clamp apparatus and more specifically to a workpiece clamp apparatus for clamping a workpiece to be machined with a machine tool. 
     BACKGROUND ART 
     As an example of this type of known workpiece clamp apparatus for a machine tool, there is a known workpiece clamp apparatus including: a plurality of clamp palettes each having a plurality of clamping members that grip a workpiece; a cylinder provided on each of the clamped palettes and drives, in the workpiece-gripping direction, at least one of the plurality of clamping members; a set-up device provided outside the machining chamber of the machine tool; and a hydraulic-fluid supply section provided on the set-up device, wherein when a clamped palette is connected to the set-up device, the cylinder of the clamped palette is connected to the hydraulic-fluid supply section of the set-up device, thereby allowing the clamping members to grip or release the workpiece (refer to, for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     {PTL 1} 
     Japanese Unexamined Patent Application, Publication No. H10-328965 
     SUMMARY OF INVENTION 
     A workpiece clamp apparatus according to one aspect of the present invention includes: a robot arm having a workpiece holding section for holding a workpiece at a distal-end portion thereof; a hydraulic-fluid supply coupler provided at the distal-end portion of the robot arm; a hydraulic-fluid supply device which supplies a hydraulic fluid to the hydraulic-fluid supply coupler; a clamping device having a plurality of clamping members that grip the workpiece for machining with a machine tool; and a cylinder that is provided on the clamping device, that has a hydraulic-fluid supply port to which the hydraulic-fluid supply coupler can be connected, and that drives at least one of the plurality of clamping members in a workpiece-gripping direction as a result of the hydraulic fluid being supplied via the hydraulic-fluid supply port, wherein the robot arm is configured to connect the hydraulic-fluid supply coupler to the hydraulic-fluid supply port, and the hydraulic-fluid supply port is configured such that the hydraulic fluid does not flow out of the cylinder in a state where the hydraulic-fluid supply coupler is not connected. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic configuration diagram of a workpiece clamp apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a schematic block diagram of the workpiece clamp apparatus of the first embodiment. 
         FIG. 3  is a flowchart illustrating an example of operation of a robot control unit of the first embodiment. 
         FIG. 4  is a flowchart illustrating an example of operation of the robot control unit of the first embodiment. 
         FIG. 5  is a diagram depicting an operation of a clamping device of the first embodiment. 
         FIG. 6  is a diagram depicting an operation of the clamping device of the first embodiment. 
         FIG. 7  is a front view of the clamping device, showing a modification of the first embodiment. 
         FIG. 8  is a schematic configuration diagram of a workpiece clamp apparatus according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A workpiece clamp apparatus according to a first embodiment of the present invention will now be described with reference to the drawings. 
     As shown in  FIG. 1 , this workpiece clamp apparatus is used in a machining system having a machine tool that rotates a main shaft  20  supported on a frame  10  to carry out the machining of a workpiece W with a tool mounted on the main shaft  20 . The main shaft  20  of this machine tool is supported on the frame  10  via a main-shaft support section  21 , and this main shaft  20  not only moves in the vertical direction but also rotates by means of a known machine tool structure. 
     In addition, a clamping device  40  on which the workpiece W is placed and held and the main shaft  20  may move relatively to each other in the horizontal direction by means of a known machine tool structure. For example, the clamping device  40  may be configured so as to move along the X-axis in the horizontal direction with a servomotor and a linear motion screw and may also move along the Y-axis in the horizontal direction with another servomotor and another linear motion screw. 
     In this machine tool, a tool  30 , such as an end mill, a milling cutter including a face milling cutter, or a drill, is mounted on the main shaft  20  via a tool holder  22 . 
     This machining system further includes a robot  50  having a robot arm  60  for moving an unmachined workpiece W from an unmachined-workpiece storage space to the clamping device  40  and for moving a machined workpiece W from the clamping device  40  to a machined-workpiece storage space. 
     The robot  50  is provided with a base  51  that tilts in the horizontal direction (left/right direction and depth direction in  FIG. 1 ). 
     The robot arm  60  includes: a base section  61  supported on the base  51  so as to be capable of rotating about an axis extending in the vertical direction; a basal-end-side arm  62  supported on the base section  61  so as to be capable of rotating about an axis in a substantially horizontal direction; an intermediate section  63  supported on the distal end of the basal-end-side arm  62  so as to be capable of rotating about an axis in a substantially horizontal direction; a distal-end-side arm  64  supported on the intermediate section  63 ; and a distal-end portion  65  supported on the distal-end portion of the distal-end-side arm  64  so as to be capable of rotating about an axis in a substantially horizontal direction. The distal-end side of the distal-end-side arm  64  is configured to rotate about the central axis thereof. The distal-end portion  65  may be configured to rotate relatively to the distal-end-side arm  64  about an axis extending in the vertical direction. 
     The distal-end portion  65  includes a distal-end-portion base  65   a  extending in the horizontal direction, and a holding section  65   b  for holding the workpiece W is provided on the undersurface at one end in the longitudinal direction of the distal-end-portion base  65   a . Furthermore, in the vicinity of one edge in the width direction at another end in the longitudinal direction of the distal-end-portion base  65   a , a hydraulic-fluid supply coupler  65   c  is mounted via a known linear guide  65   d  serving as coupler-position changing means. The linear guide  65   d  is fixed to the distal-end-portion base  65   a  and has, for example: a rail that extends in the above-described longitudinal direction and on which the hydraulic-fluid supply coupler  65   c  is movably mounted; and a motor and a ball screw for driving the hydraulic-fluid supply coupler  65   c  along the rail. 
     The holding section  65   b  and the hydraulic-fluid supply coupler  65   c  are each connected to a hydraulic-fluid supply device  70 , such as a compressor. More specifically, the holding section  65   b  is connected to the hydraulic-fluid supply device  70  via a first valve  71 , and the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply device  70  via a second valve  72 . 
     The holding section  65   b  has a plurality of holding claws  65   g , and when the first valve  71  is opened and a hydraulic fluid is supplied from the hydraulic-fluid supply device  70  to the holding section  65   b , the plurality of holding claws  65   g  are driven in the workpiece-gripping direction. Furthermore, the holding section  65   b  includes a biasing member such as a spring, for urging the plurality of holding claws  65   g  in the direction opposite to the workpiece-gripping direction, and when the first valve  71  is closed, the plurality of holding claws  65   g  move in the direction opposite to the workpiece-gripping direction. 
     The robot  50  and the robot arm  60  include a servomotor  51   a  for tilting the base  51 , a servomotor  61   a  for rotating the base section  61 , a servomotor  62   a  for rotating the basal-end-side arm  62 , a servomotor  63   a  for rotating the intermediate section  63 , a servomotor  64   a  for rotating the distal-end side of the distal-end-side arm  64 , and a servomotor  65   e  for rotating the distal-end portion  65 . 
     The clamping device  40  includes: a clamping-device main body  40   a ; a first clamping member  41  fixed to the clamping-device main body  40   a ; a second clamping member  42  that is disposed so as to face the first clamping member  41  and that is guided along a rail  42   a ; and a cylinder  43 , fixed to the clamping-device main body  40   a , the operating rod  43   a  of which is fixed to the second clamping member  42 , that makes the second clamping member  42  move in the direction (workpiece-gripping direction) towards the first clamping member. The cylinder  43  is provided with a hydraulic-fluid supply port  43   b , which is a coupler as the companion part of the hydraulic-fluid supply coupler  65   c . The clamping device  40  is configured such that the second clamping member  42  is moved by the cylinder  43  in the workpiece-gripping direction when a hydraulic fluid is supplied via the hydraulic-fluid supply port  43   b  into the cylinder  43 , and such that the second clamping member  42  is moved in the direction opposite to the workpiece-gripping direction by a biasing member (not shown in the figure), such as a spring, provided on the clamping device  40  when the hydraulic fluid in the cylinder  43  is discharged via the hydraulic-fluid supply port  43   b.    
     As shown in  FIG. 2 , each of the servomotors  51   a ,  61   a ,  62   a ,  63   a ,  64   a , and  65   e  of the robot  50 , each of the valves  71  and  72  of the hydraulic-fluid supply device  70 , and the linear guide  65   d  are connected to a robot control unit  80  and are controlled by the robot control unit  80 . 
     The robot control unit  80  is operated with a workpiece-exchange program stored in a memory device  81  and controls each of the servomotors  51   a ,  61   a ,  62   a ,  63   a ,  64   a , and  65   e  and each of the valves  71  and  72  to move the unmachined workpiece W from the unmachined-workpiece storage space to the clamping device  40  with the robot arm  60  and also move the machined workpiece W from the clamping device  40  to the machined-workpiece storage space. One example of the operation of the robot control unit  80  when the unmachined workpiece W is moved from the unmachined-workpiece storage space to the clamping device  40  by using the robot arm  60  will be described below with reference to the flowchart in  FIG. 3 . 
     When the robot control unit  80  receives a command signal for workpiece supply and type information of the clamping device  40  from, for example, the machine tool or the like (step S 1 - 1 ), it controls the linear guide  65   d  so as to arrange the hydraulic-fluid supply coupler  65   c  at a position corresponding to the type information (step S 1 - 2 ). The type information of the clamping device  40  may be received when an operator inputs the type information via a predetermined input device, rather than together with a command signal of workpiece supply. 
     When the processing in step S 1 - 2  is performed, the robot control unit  80  refers to the coupler-position information stored in the memory device  81 . The coupler-position information includes information indicating association between the type of the clamping device  40  and the arrangement position of the hydraulic-fluid supply coupler  65   c , and hence, the robot control unit  80  can acquire information on the position at which the hydraulic-fluid supply coupler  65   c  should be arranged by referring to this coupler-position information. 
     Subsequently, the robot control unit  80  controls each of the servomotors  51   a ,  61   a ,  62   a ,  63   a ,  64   a , and  65   e  and the first valve  71  so as to move the unmachined workpiece W from the unmachined-workpiece storage space to the position at which the workpiece can be gripped with the first clamping member  41  and the second clamping member  42  of the clamping device  40  (step S 1 - 3 ). As shown in  FIG. 5 , in step S 1 - 2 , when the workpiece W held by the plurality of holding claws  65   g  of the holding section  65   b  is disposed at the position at which the workpiece W can be gripped with the first clamping member  41  and the second clamping member  42 , the hydraulic-fluid supply coupler  65   c  is arranged so that the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply port  43   b  of the clamping device  40 . 
     The hydraulic-fluid supply port  43   b  has a valve structure that becomes an open state when the hydraulic-fluid supply coupler  65   c  is connected and that becomes a closed state when the hydraulic-fluid supply coupler  65   c  is not connected. This valve structure includes, for example: a valve element, such as a metal sphere, provided in a fluid flow channel of the hydraulic-fluid supply port  43   b ; a bearing surface that is provided in the fluid flow channel and that closes the fluid flow channel when the valve element abuts therewith; and a biasing member, such as a spring, for urging the valve element towards the bearing surface. Then, as a result of being pushed by a part of the hydraulic-fluid supply coupler  65   c  when the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply port  43   b , the valve element moves in a direction away from the bearing surface against the biasing member, thereby causing the valve structure to become an open state. 
     Subsequently, as shown in  FIG. 6 , the robot control unit  80  controls the second valve  72  to become an open state so that the second clamping member  42  moves towards the first clamping member  41  side to allow the workpiece W to be gripped with the clamping members  41  and  42  (step S 1 - 4 ). Then, when the workpiece W is gripped with the clamping members  41  and  42 , the first valve  71  is controlled to become a closed state (step S 1 - 5 ). By doing so, the holding of the workpiece W by the plurality of holding claws  65   g  of the holding section  65   b  is released. 
     Next, the second open/close valve  72  is controlled to become a closed state (step S 1 - 6 ), and each of the servomotors  51   a ,  61   a ,  62   a ,  63   a ,  64   a , and  65   e  is controlled so that the holding section  65   b  and the hydraulic-fluid supply coupler  65   c  are arranged at predetermined standby positions outside the machine tool (step S 1 - 7 ). By doing so, the workpiece W gripped with the clamping device  40  can be machined with the machine tool. 
     On the other hand, one example of the operation of the robot control unit  80  when the machined workpiece W is moved from the clamping device  40  to the machined-workpiece storage space with the robot arm  60  will be described below with reference to the flowchart in  FIG. 4 . 
     When the robot control unit  80  receives a command signal for the collection of a workpiece from, for example, the machine tool or the like (step S 2 - 1 ), the workpiece W is held with the plurality of holding claws  65   g  of the holding section  65   b , as shown in  FIG. 6 , and the servomotors  51   a ,  61   a ,  62   a ,  63   a ,  64   a , and  65   e  and the first valve  71  are each controlled so that the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply port  43   b  of the clamping device  40  (step S 2 - 2 ). 
     When the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply port  43   b , the valve structure of the hydraulic-fluid supply port  43   b  becomes an open state in step S 2 - 2 . At this time, a hydraulic fluid is supplied into the cylinder  43  when the hydraulic fluid is supplied via the hydraulic-fluid supply coupler  65   c . However, when no hydraulic fluid is supplied via the hydraulic-fluid supply coupler  65   c , the hydraulic fluid in the cylinder  43  is configured to be discharged. Because of this, the second clamping member  42  moves in the direction opposite to the workpiece-gripping direction by the biasing member provided in the clamping device  40 . 
     Subsequently, the robot control unit  80  controls each of the servomotors  51   a ,  61   a ,  62   a ,  63   a ,  64   a , and  65   e  so that the machined workpiece W is moved from the clamping device  40  to the position above the machined-workpiece storage space (step S 2 - 3 ) and thereafter, controls the first valve  71  so that the holding of the workpiece W by the holding section  65   b  is released (step S 2 - 4 ). As a result, the machined workpiece W is extracted from the machine tool. 
     According to the this embodiment, in order to grip the workpiece W by driving the second clamping member  42 , it is configured to connect the hydraulic-fluid supply coupler  65   c  provided at the distal-end portion  65  of the robot arm  60  to the hydraulic-fluid supply port  43   b  of the cylinder  43  that drives the second clamping member  42 , and hence the workpiece W can be gripped with the second clamping member  42  in the operation range of the distal-end portion of the robot arm  60 . For this reason, this embodiment is not subject to a constraint in that the clamping device  40  needs to be moved to a predetermined position in order to grip the workpiece W, and also no need to provide a dedicated device for gripping the workpiece W with the clamping device  40 . 
     Furthermore, in this embodiment, when the workpiece W held with the holding section  65   b  is disposed by the robot arm  60  at a position where the workpiece W can be gripped with the clamping members  41  and  42 , the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply port  43   b . Therefore, a step of disposing the workpiece W held with the holding section  65   b  at a position where the workpiece W can be gripped with the clamping members  41  and  42  and a step of gripping the workpiece W with the clamping members  41  and  42  can be executed at the same time or substantially at the same time, thus advantageous in shortening the cycle time for machining. 
     Furthermore, this embodiment includes the linear guide  65   d  for changing the position of the hydraulic-fluid supply coupler  65   c  relative to the distal-end portion  65  of the robot arm  60 . Therefore, a step of disposing the workpiece W held with the holding section  65   b  at a position where the workpiece W can be gripped with the clamping members  41  and  42  and a step of gripping the workpiece W with the clamping members  41  and  42  can be executed at the same time or substantially at the same time for a plurality of types of clamping devices  40  having different distances between the position at which the workpiece W is gripped with the clamping members  41  and  42  and the hydraulic-fluid supply port  43   b.    
     For example, as shown in  FIG. 7 , when the distance between the first clamping member  41  and the hydraulic-fluid supply port  43   b  is shorter than in the case of the clamping device  40  shown in, for example,  FIG. 5 , the hydraulic-fluid supply coupler  65   c  is moved towards the holding section  65   b  side by using the linear guide  65   d.    
     In addition, this embodiment allows a hydraulic fluid to be supplied to the hydraulic-fluid supply coupler  65   c  and to the holding section  65   b  by using a single hydraulic-fluid supply device  70 , thereby advantageous in suppressing an increase in the number of constituent components. 
     It should be noted that, in this embodiment, the holding section  65   b  may be configured to hold an iron workpiece W with a magnetic force. 
     Furthermore, in this embodiment, the hydraulic-fluid supply coupler  65   c  is connected to the hydraulic-fluid supply port  43   b  at the same time the workpiece W is disposed by the holding section  65   b  between the first and second clamping members  41  and  42 . Alternatively, the robot arm  60  may be moved to connect the hydraulic-fluid supply coupler  65   c  to the hydraulic-fluid supply port  43   b  after the workpiece W has been disposed by the holding section  65   b  between the first and second clamping members  41  and  42 . Also in this case, there is no constraint in that the clamping device  40  needs to be moved to a predetermined position in order to grip the workpiece W, nor does a dedicated device for gripping the workpiece W with the clamping device  40  need to be provided. 
     A workpiece-clamping apparatus according to a second embodiment of the present invention will now be described with reference to  FIG. 8 . 
     In this embodiment, unlike in the first embodiment, the clamping device  40  is not fixed to the machine tool. Furthermore, the second embodiment differs from the first embodiment in that: a plurality of clamping devices  40  are provided; a plurality of rollers  44  for assisting in the movement of the workpiece W are provided on each of the clamping devices  40 ; a holding section  65   f  for holding the iron workpiece W with a magnetic force, instead of the holding section  65   b , and a magnetic-force adjusting section for adjusting the magnetic force of the holding section  65   f  are provided so that the holding of the workpiece W by the holding section  65   f  is released as a result of the robot control unit  80  controlling the magnetic-force adjusting section; and the plurality of clamping devices  40  are disposed sequentially at the position where the workpiece W is machined with the machine tool by using a known palette changing mechanism. The robot control unit  80  controls a magnetic-force control unit, instead of the first valve  71 , in the same manner as in the first embodiment. The same structures as those in the first embodiment are denoted with the same reference signs, and descriptions thereof will be omitted. 
     In this embodiment, a plurality of rollers  23  for moving each of the clamping devices  40  to the machine tool and a motor, not shown in the figure, for driving each of the rollers  23  are provided as the palette changing mechanism. By doing so, the plurality of clamping devices  40  are arranged sequentially at the position where the workpiece W is machined with the machine tool. Furthermore, the machine tool of this embodiment is also provided with a shutter  24  that separates the inside of the frame  10  from the outside and that is movable in the vertical direction. 
     Each of the rollers  44  of each of the clamping devices  40  is a metal sphere and is rotatably supported on the clamping device  40 . 
     In this embodiment, unlike in the first embodiment, the workpiece W is gripped with a clamping device  40  that is disposed on the outside the machine tool with respect to the shutter  24 , for example, the clamping device  40  that is to be moved for the next machining, to the position where the workpiece W is machined with the machine tool. Although the location of each of the clamping devices  40  when the workpiece W is gripped differs from that in the first embodiment, the operation of the robot arm  60 , the holding section  65   b , the second valve  72 , and so forth for allowing the clamping device  40  to grip the workpiece W is the same as in the first embodiment. 
     With this configuration, the cycle time for machining can be shortened, compared with a case where the clamping device  40  is made to grip the workpiece W at the position where the workpiece W is machined with the machine tool. 
     From the above-described embodiments, the following aspects of the present invention are derived. 
     A workpiece clamp apparatus according to an aspect of the present invention includes: a robot arm having a workpiece holding section for holding a workpiece at a distal-end portion thereof; a hydraulic-fluid supply coupler provided at the distal-end portion of the robot arm; a hydraulic-fluid supply means which supplies a hydraulic fluid to the hydraulic-fluid supply coupler; a clamping device having a plurality of clamping members that grip the workpiece for machining with a machine tool; and a cylinder that is provided on the clamping device, that has a hydraulic-fluid supply port to which the hydraulic-fluid supply coupler can be connected, and that drives at least one of the plurality of clamping members in a workpiece-gripping direction as a result of the hydraulic fluid being supplied via the hydraulic-fluid supply port, wherein the robot arm is configured to connect the hydraulic-fluid supply coupler to the hydraulic-fluid supply port, and the hydraulic-fluid supply port is configured such that the hydraulic fluid does not flow out of the cylinder in a state where the hydraulic-fluid supply coupler is not connected. 
     In order to grip the workpiece by driving a clamping member, this first aspect is configured to connect the hydraulic-fluid supply coupler provided at the distal-end portion of the robot arm to the hydraulic-fluid supply port of the cylinder that drives the clamping member, and hence the workpiece can be gripped with the clamping member in the moving range of the distal-end portion of the robot arm. For this reason, this aspect is not subject to a constraint in that the clamping device needs to be moved to a predetermined position in order to grip the workpiece, and also no need to provide a dedicated device for gripping the workpiece with the clamping device. 
     In the above-described aspect, the machine tool may include a palette changing mechanism for arranging a plurality of the clamping devices one by one at a machining position of the machine tool, and it is preferable that the robot arm is configured to connect the hydraulic-fluid supply coupler to the hydraulic-fluid supply port of the cylinder of the clamping devices that are not arranged at the machining position. 
     With this configuration, the cycle time for machining can be reduced, compared with a case where the clamping device grips the workpiece at the machining position. 
     In the above-described aspect, when the workpiece held with the workpiece holding section is disposed by the robot arm at a position where the workpiece can be clamped with the plurality of clamping members, it is preferable that the hydraulic-fluid supply coupler is configured to be connected to the hydraulic-fluid supply port. 
     With this configuration, it is possible to perform a step of disposing the workpiece held with the workpiece holding section at a position where the workpiece can be gripped with the clamping members and a step of gripping the workpiece with the clamping members at the same time or substantially at the same time, and is advantageous in shortening the cycle time of machining. 
     In the above-described aspect, it is preferable to further include a coupler-position changing means for changing a position of the hydraulic-fluid supply coupler relative to the distal-end portion of the robot arm. 
     With this configuration, for a plurality of types of clamping devices having different distances between the position at which the workpiece is gripped with the clamping members and the hydraulic-fluid supply port, it is possible to perform a step of disposing the workpiece held with the workpiece holding section at a position where the workpiece can be gripped with the each clamping members and a step of gripping the workpiece with the each clamping members at the same time or substantially at the same time 
     In the above-described aspect, it is preferable that the workpiece holding section is configured to hold the workpiece as a result of being driven by the hydraulic fluid supplied from the hydraulic-fluid supply means. 
     With this configuration, it is possible to supply the hydraulic-fluid supply coupler and the workpiece holding section with a hydraulic fluid by using a single hydraulic-fluid supply means, and is advantageous in suppressing an increase in the number of constituent components. 
     According to the above-described aspects, it is possible not only to prevent an increase in the number of constituent components in the machine tool and its peripheral equipment but also to reduce the cycle time for machining. 
     REFERENCE SIGNS LIST 
     
         
           10  Frame 
           20  Main shaft 
           30  Tool 
           40  Clamping device 
           41  First clamping member 
           42  Second clamping member 
           43  Cylinder 
           43   b  Hydraulic-fluid supply port 
           50  Robot 
           60  Robot arm 
           65  Distal-end portion 
           65   b  Holding section 
           65   c  Hydraulic-fluid supply coupler 
           70  Hydraulic-fluid supply device 
           71  First valve 
           72  Second valve 
           80  Robot control unit 
           81  Memory device