Abstract:
A work conveyance device for a pressing machine, consuming less energy and enabling reduction in production costs. The workpiece conveyance device has a pair of transfer bars provided in parallel to a feed direction, support members for moving each of the transfer bars freely in the feed direction while restricting the transfer bars in a lift direction, linear motors interposed between the support members and the transfer bars for moving the transfer bars in the feed direction relative to the support members, lift devices for moving the support members in the lift direction, and workpiece holding jigs detachably mounted to the transfer bars for holding a workpiece.

Description:
TECHNICAL FIELD 
   The present invention relates to a workpiece conveyance device for conveying a workpiece within a press machine. 
   BACKGROUND ART 
   In conventional transfer presses, in which a plurality of processing steps are provided in a press main body, a transfer feeder for conveying a workpiece in sequence to a subsequent step is provided between each processing step. A commonly known transfer feeder is a 3-dimensional transfer feeder in which a workpiece is held by workpiece holding jigs, the workpiece being conveyed in sequence to a subsequent step by 3-dimensional direction movement of the workpiece holding jigs in the feed direction (workpiece conveyance direction), clamp direction (horizontal orthogonal direction to the feed direction), and the lift direction. 
     FIG. 7  shows the overall configuration of a transfer press in which a conventional 3-dimensional transfer feeder is employed. 
   A transfer feeder  110  has a left/right pair of transfer bars  113  parallel to the feed direction, a plurality of workpiece holding jigs not shown in the diagram for holding a workpiece being detachably mounted in these transfer bars  113 . A workpiece  106  is moved in sequence to a downstream-side mold  130  by the 3-dimensional movement operation for the reciprocating feed/return movement in the feed direction (forward-backward movement), the reciprocating lift/down movement (rise-fall movement) in the lift direction (up-down direction) and the reciprocating clamp/unclamp movement (left-right movement) in the clamp direction (direction orthogonal in the horizontal plane to the feed direction) of these transfer bars  113 . The fundamental operating pattern of the transfer bars  113  is as follows: clamp, lift, feed, down, unclamp and return. In addition, as devices for facilitating the operation of the transfer bars  113  as described above, a feed device (not shown in the diagram) that provides for movement in the feed direction and a lift/clamp device  140  that provides for movement in the lift direction and clamp direction are provided in the transfer feeder  110 . 
   A feed box  111  in which the feed device is installed is protrudingly provided in either the upstream or downstream side face of a press main body  101  and, in addition, a lift clamp box in which the lift/clamp device  140  is installed is provided between left and right uprights  103  at both the front and rear on a bed  102 . 
   In addition, the patent literature 1 discloses a technology configured from a feed carrier to which a feed bar is connected to allow free movement in the up-down and left-right directions but restrict movement in the forward-backward direction (feed direction), a feed unit for moving the feed carrier forward and backward, and a linear motor serving as a drive source for the feed unit. 
   Patent literature 1: Japanese Patent Application Laid-Open No. H10-314871 
   DISCLOSURE OF THE INVENTION 
   Problems to be Solved by the Invention 
   In workpiece conveyance devices as shown in  FIG. 7  and disclosed by the patent literature 1, the movement of the transfer bars in the lift direction and clamp direction is avoided by a lift/clamp device and, in addition, the feed carrier for supporting the transfer bars is large and heavy. Accordingly, a high output servomotor or linear motor must be provided as a drive source for driving the feed carrier in the feed direction, and this is undesirable from the aspects of both energy reduction and manufacturing costs. 
   In addition, because servomotors with a rotating output shaft necessitate the use of a power converting mechanism such as a rack and pinion mechanism to convert rotational motion to linear motion there is an inherent problem of noise, particularly at times of high-speed rotation. 
   Furthermore, the inertial force produced when a drive source of a capacity that is not correspondent to the load of the moving body is employed is a cause of, for example, increased prevalence of the occurrence of chatter at times of starting, stopping, and inching, as well as premature wear of the component parts of the drive device and fallout of the workpiece. In addition, due to insufficient force at times of acceleration, there are times when the workpiece conveyance device is unable to comply with the speed required by the press machine whereupon, accordingly, a reduced production speed must be set. 
   With the foregoing problems in mind, it is an object of the present invention to provide a workpiece conveyance device for a press machine which consumes less energy, enables reduction in production costs and noise level by simplifying the work conveyance device, and reduces the output of the drive source in the feed direction. 
   Means for Solving the Problems 
   A workpiece conveyance device for a press machine of a first invention for achieving these objects comprises a pair of transfer bars provided in parallel to the feed direction, support members for moving the transfer bars freely in the feed direction while restricting the transfer bars in the lift direction, linear motors interposed between the support members and the transfer bars, for moving the transfer bars in the feed direction relative to the support members, lift devices for moving the support members in the lift direction, and workpiece holding jigs detachably mounted on the transfer bars, for holding the workpiece. 
   In addition, the workpiece conveyance device for a press machine of the first invention further comprises cross bars provided between the pair of transfer bars and spanning in the clamp direction orthogonal to the feed direction, the workpiece holding jigs being preferably arranged in the cross bars. 
   Furthermore, a workpiece conveyance device for a press machine of a second invention is configured to comprise a pair of transfer bars provided in parallel to the feed direction, support members for moving the transfer bars freely in the feed direction while restricting the transfer bars in the lift direction and the clamp direction, linear motors interposed between the support members and the transfer bars, for driving the transfer bars in the feed direction relative to the support members, lift devices for moving the support members in the lift direction, clamp devices for moving the support members in the clamp direction, and workpiece holding jigs detachably mounted on the transfer bars, for holding the workpiece. 
   Effects of the Invention 
   According to the first invention, the transfer bars are moved in the feed direction relative to the support members and the support members are rise/fall driven by a lift device by feed devices configured from linear motors in which the magnet side or coil side of a direct linear motor is laterally installed in the transfer bars and which are interposed between the support members and transfer bars. By isolating the feed devices and lift devices in this way, the load of a moving body with respect to the feed device can be reduced and the workpiece conveyance device is able to more easily comply with the high-speed rotation of the press machine. Accordingly, the output of the linear motor can be suppressed, energy reduction can be achieved, and the manufacturing costs can be suppressed. 
   In addition, because a linear motor drive is used a power converting mechanism for converting rotational motion to linear motion is unnecessary and, accordingly, a lowering of noise can be achieved particularly at times of high-speed rotation. 
   Furthermore, in the first invention, the provision in the transfer bars of cross bars that span in the direction orthogonal to the longitudinal direction thereof and the arrangement of workpiece holding jigs in the cross bars facilitating the holding of thin or thick workpieces in the appropriate position in the middle part thereof. Accordingly, deformation of the workpiece during conveyance is reduced and reliable conveyance of the workpiece is ensured and, in addition, the generation of defective products due to deformation of the workpiece occurring during conveyance can be suppressed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an overall block diagram of a press in which a first embodiment of the workpiece conveyance device is employed; 
       FIG. 2  is a block diagram of the first embodiment of the workpiece conveyance device; 
       FIG. 3  is a diagram showing the motion of the first embodiment; 
       FIG. 4  is a block diagram of a second embodiment of the workpiece conveyance device; 
       FIG. 5  is a diagram showing the motion of the second embodiment; 
       FIG. 6  is a block diagram pertaining to another mode of the second embodiment of the workpiece conveyance device; and 
       FIG. 7  is an overall block diagram of a press in which a conventional 3-dimensional transfer feeder is employed. 
   

   According to the second invention which constitutes a 3-dimensional transfer feeder based on, in addition to the lift device of the first invention, the provision of a clamp device for moving the support members in the clamp direction, identical effects to those of the first invention are achieved. 
   DETAILED DESCRIPTION OF THE INVENTION 
   A first embodiment of the workpiece conveyance device pertaining to the present invention will be described hereinafter with reference to  FIGS. 1 to 3 . 
     FIG. 1  is an overall block diagram of a transfer press in which the workpiece conveyance device of the present invention is employed,  FIG. 2  shows the configuration pertaining to the workpiece conveyance device of the present invention, and  FIG. 3  is a diagram showing the motion of the first embodiment. 
   First, the overall configuration of the transfer press serving as an embodiment of the present invention will be described with reference to  FIG. 1 . 
   The transfer press is configured from a press main body  1  comprising a bed  2 , uprights  3 , crown  4  and slide  5 , and a mold  30 , moving bolster  33  and workpiece conveyance device  10 . In the following description the direction in which the workpiece is conveyed (left-right direction of  FIG. 1 ) is referred to as the feed direction or the forward-backward direction, the up-down direction of  FIG. 1  is referred to as to the lift direction or up-down direction, and the direction perpendicular to the feed direction in the horizontal plane (direction perpendicular to the plane of the paper surface of  FIG. 1 ) is referred to as the clamp direction or left-right direction. 
   The bed  2  serving as a pedestal for the press machine is provided below a floor (FL), the columnar uprights  3  being provided upright in four corners in the upper surface thereof. In addition, the crown  4  in which a slide drive device not shown in the diagram is installed is supported by the uprights  3 , and the slide  5  is suspended below the crown  4  to rise and fall freely. The crown  4 , uprights  3  and head  2  are fastened by a tie rod not shown in the diagram. 
   Upper molds  31  correspondent to each of the processing steps for press molding are fitted to the lower surface of the slide  5 . In addition, the moving bolster  33  is mounted on the bed  2 , lower molds  32  forming pairs with the plurality of upper molds  31  being detachably fitted on the upper surface thereof. The workpiece is press molded between the upper molds  31  and lower molds  32 . 
   The moving bolster  33  will be hereinafter described. 
   The moving bolster  33  is normally provided in two sets. That is to say, in addition to a first moving bolster  33  in a press machine on which the in-use or used lower molds  32  are fitted, a second moving bolster (not shown in the diagram) to which lower molds to be used in a subsequent step are fitted in advance is provided externally of the press machine. In addition, a part of the workpiece conveyance device  10  to which workpiece holding jigs not shown in the diagram correspondent to each of the lower molds  32  are fitted is mounted on these moving bolsters  33 . 
   The moving bolsters  33  comprise a self-propelling drive device, respectively. In addition, a rail not shown in the diagram is laid in the clamp direction on the floor FL and bed  2 . The moving bolsters  33  are able to be carried freely out of the press machine (or into the press machine from the exterior) by means of the drive device and rail passing in the clamp direction between the uprights  3 ,  3  provided upright in the feed direction in the upper surface of the bed  2 . As a result, used lower molds  32  can be promptly switched to the next lower mold to be used. 
   The first embodiment of the workpiece conveying device  10  of the present invention will be hereinafter described in detail with reference to  FIG. 2 . 
   The workpiece conveying device  10  is configured from a pair (hereinafter this is to be referred to as the left/right pair) of transfer bars  13 ,  13  being opposed to each other in the clamp direction, a feed device  11  for moving the workpiece along the transfer bars  13  in the feed direction, and a lift/clamp device  40  for moving the transfer bars  13  in the lift direction and clamp direction. 
   The transfer bars  13  are configured from fixed bars  13 B fixed to the workpiece conveyance device  10  and moving bars  13 A that separate from the fixing bars  13 B during mold switching and a carried out of the press machine with the moving bolsters  33 . 
   A plurality of pairs of bases  14 ,  14  are assembled in the left/right moving bars  13 A,  13 A. While not shown in the drawing, workpiece holding jigs correspondent to the mold  30  are detachably fitted to the bases  14 . 
   Feed devices  11  for moving the transfer bars  13  in the feed direction are provided in each of the left/right pairs of transfer bars  13 ,  13 . 
   The feed devices  11  comprise support members  19  for supporting the fixed bars  13 B of the transfer bars  13 , linear guides  18  for movably guiding the transfer bars  13  in the feed direction relative to the support members  19 , and linear motors  16  for driving the transfer bars  13  in the feed direction. 
   The transfer bars  13  are movably held in the feed direction by the linear guides  18  which are configured from a linear guide rail  18 A laid in the feed direction along the outer surface of the transfer bar  13  and a linear guide holder  18 B fixedly attached to the inner surface of the support members  19 . 
   Linear motors  16  for driving the feed devices  11  comprise a linear motor magnet  16 A laid in the feed direction along the outer surface of the transfer bar  13  and a linear motor coil  16 B fixedly attached to the inner surface of the support members  19 . 
   The linear coil  16 B and the linear motor magnet  16 A are provided in the transfer bar  13  side and the support member side respectively. 
   Because the present invention uses a linear motor  16  that has no rotational drive components and an overall fewer number of component parts as the drive source of the feed devices  11 , the feed devices  11  are weight-lightened and compacted. A reduction is noise is also achieved. Furthermore, because the linear motor  16  is provided between the transfer bars  13  and support members  19  and only the transfer bars  13  are moved, the load of the moving body can be reduced and the linear motor  16  can be operated at small output. In addition, because of the reduced load of the moving body, the occurrence of chatter of the transfer bars  13  at times of starting, stopping and inching can be suppressed, an increase in speed and the positioning precision of the feed devices  11  as a whole can be achieved, and high-speed rotation of the press machine is possible. In addition, the maintenance of the device is made easier because of the fewer component parts. 
   Next, the lift/clamp devices  40  for moving the transfer bars  13  in the lift direction and clamp direction will be described. 
   The lift/clamp devices  40  are configured from lift devices  41  for moving the transfer bars  13  in the lift direction, and a clamp device  61  for moving the transfer bars  13  in the clamp direction. The lift/clamp devices  40 ,  40  are housed in lift/clamp boxes  70 ,  70 . The lift/clamp boxes  70 ,  70  are arranged in the feed direction on the bed  2  below the support members  19  of the two end parts of the transfer bars  13 ,  13  and between the opposing uprights  3 ,  3  in the clamp direction. 
   The lift devices  41  from which the lower part of the lift/clamp devices  40  are configured comprises a lift drive motor  44  and a lift screw  46  rotated by the lift drive motor  44 . A lift carrier  42  is screwed into the upper end part of the lift screw  46 . The lower end part of lift bars  43 ,  43  opposing in the feed direction are movably affixed in the clamp direction to the lift carrier  42  by way of cam followers  43 A,  43 A. The upper end part of the lift bars  43 ,  43  are fixed by the support members  19 . 
   The normal/reverse rotation of lift screw  46  by the lift drive motor  44  results in the rise-fall movement of the lift carrier  42  screwed with the lift screw  46 . As a result, the transfer bars  13  are rise-fall moved in the lift direction by way of the lift bars  43 ,  43  and support members  18 . Lift balancers  47 ,  47  for ensuring the smooth rise-fall movement thereof and for balancing the load between, for example, the transfer bars  13  and lift carrier  42  are mounted in the two end parts in the clamp direction of the lift carrier  42 . 
   The clamp device  61  from which the upper part of the lift clamp device  40  is configured will be hereinafter described. The lift bars  43 ,  43  are inserted into a guide region of clamp carriers  62 ,  62 . A clamp screw  66  rotated by a clamp drive motor  64  provided in the interior of the lift/clamp box  70  is screwed in the clamp carriers  62 ,  62 . In addition, a left-right linear guide rail  63  is laid in the clamp direction on the upper surface of the clamp box  70 . The clamp carrier  62  is movably mounted in the clamp direction on the left-right linear guide rail  63  by way of a left-right linear guide holder not shown in the diagram. 
   The normal/reverse rotation of clamp drive motor  64  results in the reciprocating movement of the clamp carriers  62  screwed with the clamp screws  66  in the clamp direction along the left-right linear guide rail. 
   Because the support members  19  are provided above the lift/clamp devices  40  in this way, the feed box  111  of a conventional press main body protrudingly provided from the front side (upstream side) or rear side (downstream side) face is unnecessary, and a simple cover only is sufficient. For this reason, the overall length of the press line can be shortened, and the area occupied by the press line as a whole can be reduced. 
   The operation of the first embodiment of the workpiece conveyance device will be hereinafter described with reference to  FIG. 2  and  FIG. 3  that shows the motion of the first embodiment. 
   (1) First, a workpiece  6  is carried in and mounted by a carry-in device not shown in the diagram to a workpiece pedestal not shown in the diagram of a workpiece carry-in position of the transfer bars  13  (front-end position of transfer bars  13 ,  13 ). 
   At this time, the transfer bars  13  in the down position (transfer bars  13 ,  13  lowered) are moved from the unclamp (transfer bars  13 ,  13  separate) position to the clamp (transfer bars  13 ,  13  together) position and the workpiece  6  on the workpiece pedestal is fixed by the workpiece holding jig  15  affixed to the base  14 . 
   (2) Next, the transfer bars  13 , in a state in which the workpiece  6  is fixed by the workpiece holding jig  15 , are lifted (transfer bars  13 ,  13  raised) by the lift devices  41  by way of the support members  19  and, furthermore, are fed (advance conveyed) by the feed devices  11  control-driven by the linear motors  16 . As a result, the workpiece  6  fixed by the workpiece holding jig  15  is fed (advance conveyed) to the position of the first processing step (in  FIG. 1 , the processing step at the left end of the slide  5 ) for press mold processing. 
   (3) Thereafter, by the down movement of the transfer bars  13  by the lift devices  41  subsequent to the workpiece  6  reaching the position of the first processing step for press mold processing, the workpiece  6  is set on the lower mold  32  for the first processing step for press mold processing arranged on the upper surface of the moving bolster  33 . 
   (4) Following the completion of the setting of the workpiece  6  on the lower mold  32 , the transfer bars  13  are unclamped by the clamp device  61  resulting in the withdrawal of the workpiece holding jig  15  from the workpiece  6 . After the transfer bars  13  have been unclamped and have reached the clamp retreat end, the transfer bars  13  are returned (retreat conveyed) to the initial carry-in position by the feed devices  11 . 
   (5) On the other hand, after the workpiece holding means  15  as described above have been unclamped (transfer bars  13 ,  13  retreated) and has retreated to a non-interfering region with the mold  30 , a predetermined first processing step is performed for press mold processing in which the slide  5  is lowered and the upper molds  31  affixed to the lower surface thereof are lowered so that the workpiece  6  is enclosed and pressurized between this and the lower molds  32 . 
   (6) Thereafter, the conveyance of the workpiece  6  to the next processing step and the mold processing thereof are similarly implemented by conveyance of the workpiece by the above-described workpiece conveyance device  10  from the carry in position to the position for first processing step for press mold processing (described by (1) to (4)) and the mold processing of the workpiece  6  of the first processing step (described by (5)) are carried out in the same way. That is to say, the conveyance of the workpiece by the workpiece conveyance device  10  from the position for the first processing step for press mold processing to the position for the second processing step and the mold processing of the workpiece  6  in the second processing step are carried out in the same way. In addition, the conveyance of the workpiece by the workpiece conveyance device  10  from the position for the second processing step for press mold processing to the position for the third processing step and the mold processing of the workpiece  6  of the third processing step are carried out in the same way. 
   (7) Once the mold processing of the third processing step of the workpiece  6  is completed at the position for the third processing step, the workpiece  6  is subsequently conveyed by the workpiece conveyance device  10  from the position of the third processing step for press mold processing to the workpiece pedestal of the workpiece carry-out position of the transfer bars  13  (rear end position of transfer bars  13 ,  13 ). 
   (8) The molded workpiece  6  carried to the workpiece pedestal of the workpiece carry out position is carried outside the press mold by a product carry out device not shown in the diagram. 
   In the workpiece conveyance device of the first embodiment outlined above a 3-dimensional operation for the reciprocating feed/return movement in the feed direction, the reciprocating rise/fall movement in the top-bottom direction and reciprocating clamp/unclamp movement in the clamp direction orthogonal in the horizontal orthogonal direction to the feed direction of the transfer bars  13  is performed. 
   A second embodiment of the present invention will be described with reference to  FIG. 4 . 
   The description of the structural sections thereof identical to those of the first embodiment has been omitted. 
   In the second embodiment the transfer bars  13 ,  13  are fixed in the clamp direction as a result of a stopping of the drive of the clamping devices  61  of the first embodiment. By virtue of this, cross bars  20  span between the transfer bars  13 ,  13  maintaining a constant clearance therebetween. Workpiece holding jigs  15  arranged in the cross bars  20  in the lower part thereof hold the workpiece  6  by means of vacuum caps utilizing a negative pressure. 
   Next, the operation of the workpiece conveyance device of the second embodiment will be described with reference to  FIG. 4  and  FIG. 5  that shows the motion of the second embodiment. 
   (1) First, a workpiece  6  is carried in and mounted by a carry-in device (not shown in the diagram) to a workpiece pedestal not shown in the diagram of a workpiece carry-in position of the transfer bars  13  (front-end position of the bars). 
   Following this, the cross bars  20  in the wait position are returned with the transfer bars  13 . After the cross bars  20  are returned to the workpiece pedestal they are moved downward whereupon the workpiece  6  is adsorbed onto the workpiece pedestal by means of the vacuum caps. 
   (2) Next, in a state in which the workpiece  6  has been adsorbed by the vacuum caps, the transfer bars  13  are lifted by the lift devices  41  by way of the support members  19  and then further fed (advance conveyed) by the feed devices  11  control-driven by the linear motors  16 . As a result, the workpiece  6  adsorbed by the workpiece holding jig  15  is fed (advance conveyed) to the position for the first processing step (processing step at the left end of the slide  5  of  FIG. 1 ) of the press mold processing. 
   (3) Thereafter, by the down movement of the transfer bars  13  by the lift devices  41  subsequent to the workpiece  6  reaching the position of the first processing step for press mold processing, the workpiece  6  is positioned on the lower mold  32  for the first processing step for the press mold processing arranged on the upper surface of the moving bolster  33  and the suction force of the vacuum caps is released. As a result, the workpiece  6  is set on the lower mold  32 . 
   (4) After completion of the setting of the workpiece  6  on the lower mold  32  the transfer bars  13  are lifted. They are subsequently returned to the initial wait position. 
   (5) On the other hand, after the workpiece holding jigs  15  as described above have been set on the lower mold  32  and the cross bars retreated to a non-interfering region with the mold  30 , a predetermined first processing step for press mold processing in which the slide  5  is lowered and the upper molds  31  affixed to the lower surface thereof are lowered so that the workpiece  6  is enclosed and pressurized between this and the lower molds  32  is performed. 
   (6) Thereafter, the conveyance of the workpiece  6  to the next processing step and the mold processing thereof are similarly implemented by conveyance of the workpiece by the above-described workpiece conveyance device  10  from the carry in position to the position for first processing step for press mold processing (described by (1) to (4)) and the mold processing of the workpiece  6  of the first processing step (described by (5)) are carried out in the same way. That is to say, the conveyance of the workpiece by the workpiece conveyance device  10  from the position for the first processing step for press mold processing to the position for the second processing step and the mold processing of the workpiece  6  in the second processing step are carried out in the same way. In addition, the conveyance of the workpiece by the workpiece conveyance device  10  from the position for the second processing step for press mold processing to the position for the third processing step and the mold processing of the workpiece  6  of the third processing step are carried out in the same way. 
   (7) Once the mold processing of the third processing step of the workpiece  6  is completed at the position for the third processing step, the workpiece  6  is subsequently conveyed by the workpiece conveyance device  10  from the position of the third processing step for press mold processing to the workpiece pedestal of the workpiece carry-out position of the transfer bars  13  (rear end position of bars). 
   (8) The molded workpiece  6  carried to the workpiece pedestal of the workpiece carry out position is carried outside the press mold by a product carry out device not shown in the diagram. 
   In the workpiece conveyance device  10  of the second embodiment outlined above a 2-dimensional operation is performed for the reciprocating feed/return movement in the feed direction and the reciprocating rise/fall movement in the top-bottom direction of these transfer bars  13 . 
   While in the second embodiment the vacuum caps that serve as the workpiece holding jigs  15  are arranged on the cross bars  20 , as shown in  FIG. 6 , the vacuum caps may be arranged on the transfer bars  13 . 
   In addition, in the second embodiment the drive of the clamp device  16  as of the first embodiment is stopped and the transfer bar is 2-dimensionally moved. If the use of the workpiece conveyance device  10  is restricted to vacuum conveyance alone in which 2-dimensional movement is employed, the clamp device is unnecessary at this time. For this reason, a configuration based on the use of a lift device alone from the beginning and that does not comprise a clamp device may be adopted. 
   In addition, while for switching of the molds in the second embodiment the transfer bars  13  are separated into a moving bar  13 A and a fixed bar  13 B, the moving bar  13 A being set on the moving bolster  33  and conveyed to the exterior of the press, the cross bars  20  may be separated from the transfer bars  13  and the separated transfer cross bars  20  set on the moving bolster  33  and conveyed to the exterior of the press. 
   In this case there is no need for the transfer bars  13  to be separated. 
   An example in which the workpiece conveyance device  10  of the present invention of the embodiments described above has application in a twin-column press comprising two uprights  3 ,  3  in the feed direction will be described. However, there is no restriction to this configuration and, for example, application thereof in a three-column press comprising three uprights  3  in the feed direction or in a press machine comprising a greater number of uprights is also possible. 
   In addition, the lift drive motor  44  and clamp drive motor  64  of the embodiments described above may be configured as linear motors such as the linear motors  16  serving as the drive source of the feed devices  11 . 
   In addition, while in the embodiments described above the lift/clamp box  70  is arranged on the bed  2  below the transfer bars  13 , it may be arranged between the uprights  3 ,  3  above the transfer bars  13 . In this case the transfer bars  13  are of a shape that suspends downward by way of the support members  19 . 
   Furthermore, in the embodiments described above, as a result of the provision of the lift/clamp box  70  in the front and rear end parts of the transfer bars  13 , two support members  19  positioned above the lift/clamp box  70  may be provided for each individual transfer bar  13 . However, the number of support members  16  with respect to each single transfer bar  13  may be 3 or more. 
   In addition, provided the output of the servomotor is further increased, there is no need for the provision of a linear motor for any support members. For example, a linear motor and linear guide may be provided in the front side (upstream side) of the support member  16  only, and only the linear guide may be provided in the rear side (downstream side) support member  16 . 
   The effects of the invention of the subject application can also be achieved in retrofitting. 
   The retrofitting of a press based on the replacement of a cam-driven workpiece conveyance device of an existing press machine with servocontrol-driven device to improve functions including increased speed and capacity to deal with various types of workpiece has become a frequently implemented trend in transfer presses in recent years. When retrofitting is carried out the conventional case in which a servomotor is used as the feed direction drive source the feed box which is the main part of the feed device and which is protrudingly arranged in the carry-out side (or workpiece carry-in side) face of the press main body remains and, as a consequence, the feed box is replaced. Because of the large size and weight of the feed box and, moreover, because it is protrudingly provided in the side face of the press main body, it takes a significant number of construction days to carry out the construction necessary for replacement of the feed box which includes welding of feed box brackets to the press main body. 
   Because of the long period of stoppage to the operation of the production manufacturing line necessitated by this retrofitting it interferes with the production principles of the user. 
   The feed carrier for supporting the transfer bars of the patent literature 1 is also large and heavy and is accompanied by the installation of a large feed box. 
   The support members of the present invention are provided above (or below) the lift/clamp device only and, accordingly, either the feed box is unnecessary or a simple cover advantageous in terms of safety or as a scrap countermeasure is sufficient. For this reason, the construction period required for retrofitting construction can be shortened and the interference to the production principles of the user can be minimized.