Abstract:
A three-dimensional driving system for a transfer feeder of a transfer press for feeding a work into successive processing stations which is surrounded by a plurality of uprights comprises a feed mechanism linked to a pair of transfer bars arranged parallel to a work feed direction for gripping and transferring the work and a feed mechanism driver linked to the feed mechanism to drive it. The three-dimensional driving system further comprises, a lift mechanism which is provided on a bed surrounded by the uprights and causes the transfer bars to ascend and descend, a clamp mechanism which is linked to the lift mechanism and causes the transfer bars to grip and release the work, a clamp and lift box accommodating the lift mechanism and the clamp mechanism, a lift mechanism driver linked to the lift mechanism to drive it, and a clamp mechanism driver linked to the clamp mechanism to drive it. The lift mechanism driver and the clamp mechanism driver have their own drive shafts and servomotors connected to the lift mechanism and the clamp mechanism, respectively, and are disposed separately from each other in opposite terminal portions of the clamp and lift box.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a three-dimensional driving system for a transfer feeder of a transfer press for feeding works into successive processing stations that are individually surrounded by a plurality of uprights. 
     2. Description of the Related Art: 
     In an automatic press system, a transfer press has conventionally been equipped with a servo-assisted three-dimensional driving system for a transfer feeder that is driven by servomotors. To feed works into processing stations of the transfer press, the three-dimensional driving system comprises a pair of transfer bars arranged parallel to the feed direction of the works, a feed mechanism provided at one end of the transfer bars, and clamp and lift mechanisms provided closer the other end of the transfer bars. As the transfer bars are caused to move in the feed direction by the feed mechanism and to move in lifting and clamping directions by the clamp and lift mechanisms, the transfer bars grip and release each work between themselves to thereby carry the works into and out of dies of successive stages of a press process automatically. 
     If it is desired to successively feed a series of works from one die location to the next along a line of processing stations for sequential processing, for example, the clamp and lift mechanisms are provided between successive uprights or between the successive die locations of the transfer press, and individual sections of the feed, clamp and lift mechanisms are driven in three-dimensional directions in a controlled manner, so that each work is automatically processed by the transfer press through a sequence of steps. 
     A related art example of a servo-assisted three-dimensional driving system for a transfer feeder is disclosed in JP-B-2-1 1934U. Since servomotors are directly connected to individual mechanisms including a feed mechanism, clamp mechanisms and lift mechanisms in this servo-assisted three-dimensional driving system, it is possible to move transfer bars at high speeds in a three-dimensional space and thereby achieve an improvement in productivity. 
     Another example of the related art is a three-dimensional driving system for a mechanical transfer feeder that is driven by motive power supplied from a drive system of a press. This mechanical three-dimensional driving system takes the motive power from the drive system of the press through transmission mechanisms, which include a bevel gear mechanism, pinions and cam shafts. Therefore, when installing a servo-assisted three-dimensional driving system instead of the existing mechanical three-dimensional driving system, an extra installation space that has not been required will become necessary, and mounting sites for individual servomotors will pose a serious problem. Especially when a press process involves many stages and feed lengths of transfer bars are short, the distances between successive uprights become small and, therefore, great limitations will be imposed on the availability of mounting sites for the servomotors. 
     It is necessary to install individual servomotors so that they would not interfere with the main structure and dies of the transfer press. Furthermore, although large-sized servomotors having a large capacity are required, it is practically impossible to install the large-sized servomotors for reasons stated above. Therefore, it has conventionally been necessary to install a number of small-sized servomotors. 
     SUMMARY OF THE INVENTION 
     In the light of the aforementioned problems of the related art, it is an object of the invention to provide a three-dimensional driving system for a transfer feeder which makes it possible to achieve a reduction in installation space required for clamp and lift mechanisms. 
     In one aspect of the invention, a three-dimensional driving system for a transfer feeder of a transfer press for feeding a work into a processing station which is surrounded by a plurality of uprights comprises a feed mechanism linked to a pair of transfer bars arranged parallel to a work feed direction for gripping the work and transferring it to the aforementioned processing station, a lift mechanism which is provided on a bed surrounded by the uprights and causes the transfer bars to ascend and descend, a clamp mechanism which is linked to the lift mechanism and causes the transfer bars to grip and release the work, a clamp and lift box accommodating the lift mechanism and the clamp mechanism, a feed mechanism driver linked to the feed mechanism to drive it, a lift mechanism driver linked to the lift mechanism to drive it, and a clamp mechanism driver linked to the clamp mechanism to drive it, wherein the lift mechanism driver and the clamp mechanism driver have their own drive shafts and servomotors connected to the lift mechanism and the clamp mechanism, respectively, and are disposed separately from each other in opposite terminal portions of the clamp and lift box. 
     This construction of the three-dimensional driving system for the transfer feeder makes it possible to provide the individual drivers, including the servomotors and the drive shafts, separately from one another and, more particularly, they can be installed in the clamp mechanism and the lift mechanism disposed in the opposite terminal portions of the clamp and lift box. Since the servomotors and the drive shafts of both the clamp and lift mechanisms are so configured as to operate in synchronism with each other, loads applied to the individual servomotors are reduced and necessary motive power can be obtained by using servomotors having a lower capacity. Further, as a result of a reduction in physical size, it becomes possible to accommodate the servomotors and other elements of the driving system in limited spaces. 
     In another aspect of the invention, the bed surrounded by the uprights has an opening and the clamp mechanism driver and the lift mechanism driver are accommodated in the opening. 
     This construction allows space for installing the servomotors and the drive shafts inside the opening formed in the bed, in addition to achieving the effects of the aforementioned construction according to the first aspect of the invention. As a consequence, it is possible to create large spaces inside the main structure of the transfer press and in the vicinity of dies and achieve an improvement in maintainability and a reduction in acoustic noise. 
     In a still another aspect of the invention, the drive shafts of the lift mechanism driver and the clamp mechanism driver are fitted in through holes formed in the bed, the servomotors of the lift mechanism driver and the clamp mechanism driver are installed in accommodating spaces formed in a lower portion of the bed, and the drive shafts are linked to their corresponding servomotors. 
     Since the drive shafts fitted in the through holes in the bed can be linked to the respective servomotors installed in the accommodating spaces formed in the lower portion of the bed in this construction, it is possible to efficiently use installation spaces for the lift and clamp mechanisms and thereby achieve further space savings. Furthermore, the lift and clamp mechanisms can be combined into a single unit. This makes it possible to reduce overall costs and factory areas required for installing an automatic press system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevation showing a three-dimensional driving system for a transfer feeder of a transfer press according to the invention; 
     FIG. 2 is a partially cutaway plan view of the three-dimensional driving system; 
     FIG. 3 is a side view showing clamp and lift mechanisms of the three-dimensional driving system; 
     FIG. 4 is a partially cutaway plan view especially showing one form of openings made in a bed of the transfer feeder for accommodating clamp and lift boxes; and 
     FIG. 5 is a partially cutaway front elevation especially showing another form of openings made in the bed of the transfer feeder for accommodating the clamp and lift boxes. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the invention is now described, by way of example, with reference to the accompanying drawings, in which FIG. 1 is a front elevation showing a three-dimensional driving system for a transfer feeder of a transfer press according to the invention, FIG. 2 is a partially cutaway plan view of the three-dimensional driving system of the invention, and FIG. 3 is an explanatory diagram showing clamp and lift mechanisms of the three-dimensional driving system of the invention. 
     In FIGS. 1 to  3 , the numeral  1  designates the transfer press and the numeral  2  designates a bed installed below the level of a floor FL. Each of the three uprights  3  is provided above the bed  2  on both sides (front and rear) along a work feed direction A as illustrated. Two moving bolsters  4  are movably provided on the bed  2  and a plurality of lower dies (not shown) are mounted on top of the moving bolsters  4  at equal intervals. Mounted above the moving bolsters  4  are two slides  5  which are made ascendable and descendable between the successive uprights  3  by driving mechanisms provided in crowns (not shown). A plurality of upper dies (not shown) are attached to the slides  5  in one-to-one correspondence with the lower dies mounted on the moving bolsters  4 . When replacing the dies, the individual moving bolsters  4  can be drawn out, with the upper and lower dies mounted on them, from between the uprights  3 . Although not illustrated, the moving bolsters  4  are mounted on wheels and can travel on rails. 
     The transfer press  1  is equipped with the three-dimensional driving system  6  for the transfer feeder. The three-dimensional driving system  6  has a pair of transfer bar assemblies  7  which are arranged parallel to each other between front and rear rows of the uprights  3 . The individual transfer bar assemblies  7  are fitted with a plurality of fingers (not shown) and can move works (not shown) gripped by the fingers to positions in a three-dimensional space. Each of the transfer bar assemblies  7  is constructed of two each central bars  9  and end bars  10  that are detachably joined together by connectors  8  as shown in FIG.  2 . When replacing the dies or fingers, the central bars  9  can be drawn out together with the upper and lower dies from between the uprights  3 , positioned on bar supports  11  that are provided on the moving bolsters  4 . 
     Referring to FIG. 1, a feed mechanism  12  and a feed box  13  are provided at one end of the transfer bar assemblies  7  while clamp and lift boxes  16 , each incorporating a clamp mechanism  14  and a lift mechanism  15 , are provided closer at the other end of the transfer bar assemblies  7 . The feed box  13  is mounted on vertical supports  18  which are erected on a mounting base  17  below the floor FL, and a feed carrier  19  is suspended inside the feed box  13 . The feed box  13  also incorporates a feed servomotor  20  which is connected to a pair of feed pinions  21  located on both sides (front and rear) with respect to the work feed direction A via a power transmission mechanism formed of a reducer, a spline shaft, etc., which are not illustrated. The feed pinions  21  mesh with a pair of feed racks  22  fixed to an upper part of the feed carrier  19 , so that the feed carrier  19  can be moved parallel to the work feed direction A. There are provided a pair of parallel guide rails  23 , running at right angles to the work feed direction A in which the feed racks  22  are aligned, at a lower part of the feed carrier  19 ; and a pair of feed sub-carriers  24  are provided in such a way that they can travel along the guide rails  23 . Guide posts  25  are attached to lower parts of the feed sub-carriers  24  and the transfer bar assemblies  7  are guided up and down by these guide posts  25 . In a varied form of the above-described construction, the feed box  13  may be directly mounted to end surfaces of the rightmost uprights  3  of FIG.  1 . 
     The clamp and lift boxes  16 , each incorporating the clamp mechanism  14  and the lift mechanism  15 , are provided on the bed  2  between the paired (front and rear) uprights  3 . The clamp mechanism  14  and the lift mechanism  15  are two separate power transmission mechanisms. There are provided two clamp and lift sub-units  26  in opposite terminal portions of each clamp and lift box  16  as shown in FIG.  3 . One of these clamp and lift sub-units  26  accommodates a drive shaft  47  associated with a clamping servomotor  27  and a bevel gear  28  as one driver while the other accommodates a drive shaft  32  associated with a lifting servomotor  29  and a bevel gear  30  as another driver. These clamp and lift sub-units  26  provided in the opposite terminal portions (front and rear) of each clamp and lift box  16  are accommodated in openings  31  in the bed  2 . 
     The openings  31  shown above as a first practical example of implementation of the invention are pits, through holes or cutouts that are formed in the bed  2  immediately beneath the clamp and lift boxes  16  and serve as spaces for housing the sub-units  26 . Referring to FIGS. 1 to  3 , the drive shafts  32  of the individual lift mechanisms  15  and the drive shafts  47  of the individual clamp mechanisms  14  are inserted into shaft holes  31 ′ in the openings  31 , and the servomotors  29 ,  27  of the lift mechanisms  15  and the clamp mechanisms  14  are accommodated at the bottoms of the respective shaft holes  31 ′. As can be seen from FIGS. 1 and 3, each of the openings  31  is formed of a vertical hole (shaft-accommodating space)  31 A extending downward in a straight line from a portion of the bed  2  between each pair of front and rear uprights  3  which are aligned in a direction B perpendicular to the work feed direction A and an elongate horizontal cavity (servomotor-accommodating space)  31 B extending horizontally in the same plane from the bottom of the vertical hole  31 A. The horizontal cavities  31 B thus formed close to the lower parts of the uprights  3  individually accommodate the servomotor  27 ,  29  while the vertical holes  31 A individually accommodate the drive shafts  32 ,  47  associated with the bevel gears  28 ,  30 . 
     Referring to FIG. 4, there are shown openings  31  as a second practical example of implementation of the invention. These openings  31  are elongate channels formed between the front and rear uprights  3  along a longitudinal direction of the individual clamp and lift boxes  16 . Each of the openings  31  has shaft-accommodating spaces into which the drive shafts  32 ,  47  are inserted and servomotor-accommodating spaces formed at the bottoms of the shaft-accommodating spaces to accommodate the individual servomotor  29 ,  27 . 
     With the provision of the aforementioned openings  31  in the bed  2  as shown in FIGS. 1-4, it is possible to create large spaces inside the main structure of the transfer press  1  and in the vicinity of the dies and achieve an improvement in maintainability and a reduction in acoustic noise. It is also possible to efficiently use available installation space for the clamp and lift mechanisms  14 ,  15  and thereby achieve space savings. 
     Referring now to FIG. 5, there are shown openings  31  as a third practical example of implementation of the invention, in which through holes  31 ″ are formed in the bed  2  immediately beneath the drive shafts  32 ,  47  between each pair of front and rear uprights  3 . The drive shafts  32 ,  47  are inserted in these through holes  31 ″ while the servomotors  29 ,  27  are installed in accommodating spaces formed in lower portions of the bed  2 , the drive shafts  32 ,  47  being connected to their corresponding servomotors  29 ,  27 . According to this third practical example, it is possible to achieve further space savings by using available installation space for the clamp and lift mechanisms  14 ,  15  even more efficiently and the clamp and lift mechanisms  14 ,  15  of each stage can be combined into a single unit. Consequently, it is possible to reduce overall costs and factory areas required for installing an automatic press system. 
     The lifting servomotors  29  are connected to the bevel gears  30 . Each drive shaft  32  that has the bevel gear  30  projects upward from a bottom surface of the pertinent clamp and lift box  16 . A lift pinion  33  fixed to each drive shaft  32  meshes a gear  34 A of a gear-operated interlock mechanism  34  which is installed along the longitudinal direction of the clamp and lift box  16 . The gear-operated interlock mechanism  34  includes five gears designated  34 A,  34 B,  34 C,  34 D and  34 E. The gear  34 C located at a central position is rotatably connected to an output shaft  35  of the pertinent clamp mechanism  14  without interlocking with each other, and the gears  34 B and  34 D are rotatably supported by respective bearings  36 . The gears  34 A and  34 E located at both ends of the gear-operated interlock mechanism  34  are individually connected to ball screws  37 . These ball screws  37  are rotatably supported by respective bearings  38 , and ball nuts  39  screwed on the respective ball screws  37  are fixed to a lift beam  40 . The lift beam  40  is made ascendable and descendable, with guide rails  41  formed at both upper terminal portions of the lift beam  40 . Lower clamp carriers  42  of the clamp mechanism  14  are movably supported by these guide rails  41  and connected to upper clamp carriers  44  via respective guide posts  43 . The upper clamp carriers  44  are movably supported by guide rails  45  provided on the clamp and lift box  16  and top parts of the guide posts  43 , which are made vertically movable and connected to the respective upper clamp carriers  44 , support the transfer bar assemblies  7  via rollers  46 . 
     Rotary motion of each clamping servomotor  27  is transmitted to its corresponding bevel gear  28 . As previously described, each clamping servomotor  27  is accommodated in its corresponding horizontal cavity  31 B and the bevel gear  28  is housed in the relevant vertical hole  3 lA. The drive shaft  47  fitted with the bevel gear  28  projects upward from the bottom surface of the pertinent clamp and lift box  16  and a pinion  48  is fixed to an upper end of the drive shaft  47 . A gear-operated interlock mechanism  49  is installed along the longitudinal direction of each clamp and lift box  16  parallel to the gears  34 C,  34 D and  34 E of the gear-operated interlock mechanism  34  in such a way that the gear-operated interlock mechanism  34  and the gear-operated interlock mechanism  49  operate in synchronism with each other. 
     The gear-operated interlock mechanism  49  is constructed of three gears  49 A,  49 B,  49 C which are engaged with one another. The gear  49 A is rotatably fitted into the bearing  38  of one ball screw  37  and the pinion  48  is engaged with the gear  49 A. The gear  49 C is engaged with the gear  49 A by way of the gear  49 B that is rotatably supported by one of the bearings  36 . The gear  49 C located at a central position is fixed to the output shaft  35  of the pertinent clamp mechanism  14 . The output shaft  35  of the clamp mechanism  14  is rotatably supported on the clamp and lift box  16 , and two clamp racks  51  fitted to project from offset positions on facing surfaces of the upper clamp carriers  44  supported by the front and rear guide rails  45  are engaged with a pinion  50  mounted at an output end of the output shaft  35 . With this arrangement, the output shaft  35  of the clamp mechanism  14  causes the individual upper clamp carriers  44  to reciprocate such that they are brought closer to and separated from each other. In FIG. 3, designated by the numeral  53  are balancing cylinders and designated by the numeral  54  are air tanks. 
     Due to the above-described construction, it is possible to properly distribute driving means for the individual servomotors  27 ,  29  and drive shafts  47 ,  32  and, more particularly, the driving means can be distributed at opposites ends of the clamp and lift mechanisms  14 ,  15 . Since individual portions of the driving means operate in synchronism with each other in this construction, loads applied to the individual servomotors  27 ,  29  are reduced so that necessary motive power can be obtained by using servomotors having a lower capacity. It is also possible to combine each pair of clamp and lift mechanisms  14 ,  15  into a single unit. Furthermore, the individual servomotors  27 ,  29  and associated drive mechanisms can be installed in limited spaces. 
     Operation of the three-dimensional driving system  6  for the transfer feeder of the invention is now described referring to FIGS. 1 to  3 . 
     When a work (not shown) to be processed is brought into processing stations of the transfer press  1  of FIG. 1 from left to right as illustrated, the clamping servomotors  27  are caused to turn in their forward running direction by a command from non-illustrated control means. Then, the drive shaft  47  fitted with the bevel gear  28  is rotated and the pinion  48  fixed to the drive shaft  47  cause the individual gears  49 A- 49 C of the gear-operated interlock mechanism  49  to rotate as shown in FIG.  3 . As a result, the output shaft  35  rotatably meshed with the gear  49 A rotates and moves the clamp racks  51  that are fitted to project from offset positions on the facing surfaces of the upper clamp carriers  44 , so that the upper clamp carriers  44  come closer to each other along the guide rails  45 . At the same time, the lower clamp carriers  42  linked to the upper clamp carriers  44  via the guide posts  43  move along the guide rails  41  of the clamp and lift box  16  and the feed sub-carriers  24  travel along the guide rails  23 . Then, the transfer bar assemblies  7  held by the rollers  46  of the guide posts  43  at the respective upper clamp carriers  44  move in clamping directions and the work is gripped between the fingers attached to the transfer bar assemblies  7 . 
     When the above-described work clamping operation has been completed, the lifting servomotors  29  are caused to turn in their forward running direction by a command from the non-illustrated control means. Then, the drive shaft  32  fitted with the bevel gear  30  is rotated and the lift pinion  33  fixed to the drive shaft  32  cause the individual gears  34 A to  34 E of the gear-operated interlock mechanism  34  to rotate as shown in FIG.  3 . The ball screws  37  rotatably meshed with the gears  34 A and  34 E are rotated simultaneously and the lift beam  40  connected to the ball screws  37  via the ball nuts  39  is lifted in the direction of arrow C. At this time, the lower clamp carriers  42  provided on the lift beam  40  ascend along the guide posts  43  and, as a consequence, the transfer bar assemblies  7  held by the rollers  46  of the guide posts  43  at the respective upper clamp carriers  44  are smoothly lifted up to a specified height. 
     When the above-described work lifting operation has been completed, the feed servomotor  20  is caused to turn in its forward running direction by a command from the non-illustrated control means. Then, the feed pinions  21  are rotated via the power transmission mechanism and, as the feed carrier  19  is moved rightward (as illustrated in FIG. 1) along non-illustrated guide rails by the feed racks  22 , the transfer bar assemblies  7  cause the rollers  46  of the guide posts  43  at the respective upper clamp carriers  44  to rotate so that the transfer bar assemblies  7  move rightward, as shown in FIG.  1 . When the individual transfer bar assemblies  7  reach specified positions, the feed servomotor  20  stops and the lifting servomotor  29  begins to turn in its reversing direction, causing the transfer bar assemblies  7  to descend. Then, the clamping servomotor  27  is caused to turn in its reversing direction so that the individual transfer bar assemblies  7  are moved away from each other, and the work (not shown) gripped between the fingers attached to the transfer bar assemblies  7  is released into a desired die. Subsequently, the feed servomotor  20  turns in its reversing direction, causing the individual transfer bar assemblies  7  to move leftward (as illustrated in FIG. 1) and return to their home positions where they grasped the work. The individual mechanisms of the transfer press  1  repetitively make the above-described three-dimensional movements to transfer each successive work from one processing station to the next. The work that has gone through all stages of a press process at the successive processing stations is ejected from the transfer press  1  by an output conveyor  52 . 
     When it is necessary to replace any of the dies or fingers, the central bars  9  of the individual transfer bar assemblies  7  are first disconnected and, with the central bars  9  placed on the bar supports  11  provided on the pertinent moving bolsters  4 , the dies or fingers to be replaced are taken out together with the moving bolsters  4  from between the uprights  3 . 
     As can be recognized from the foregoing discussion, the individual driving means of the clamp mechanism  14  and the lift mechanism  15  are separated into two groups and provided in the opposite terminal portions (front and rear) of the clamp and lift box  16  of each processing station and they operate in synchronism with each other in the three-dimensional driving system  6  for the transfer feeder of the transfer press  1  of the invention. Thus, loads applied to the individual servomotors  27 ,  29  are reduced and necessary motive power can be obtained by using servomotors having a lower capacity. 
     In addition, the aforementioned construction allows space for  2  of the transfer press  1  and, therefore, it is possible to create large spaces in the vicinity of the dies and achieve an improvement in maintainability and a reduction in acoustic noise. Furthermore, it is possible to minimize the spaces for installing the servomotors  27 ,  29  and drive shafts  47 ,  32  and achieve further space savings through efficient use of installation spaces for the clamp mechanism  14  and the lift mechanism  15 . Moreover, the clamp mechanism  14  and the lift mechanism  15  of each stage can be combined into a single unit and installed between the dies of the successive processing stations, and a series of such units can be controlled individually. This makes it possible to reduce overall costs and factory areas required for installing an automatic press system. 
     Furthermore, in the present invention, it is not necessary to provide a clamp mechanism  14  and a lift mechanism  15  for each upright  3 . For example, if there are five pairs of uprights (first, second, third, fourth and fifth pairs of uprights  13 ), three sets of a clamp mechanism  14  and a lift mechanism  15  are sufficient to move the work piece between the processing stations. In this situation a clamp mechanism  14  and a lift mechanism  15  can be provided at the first, third and fifth pair of uprights  3 , and no clamp mechanism  14  and a lift mechanism  15  need be provided at the second and fourth pair of uprights. In this arrangement the transfer bar assemblies  7  and associated structure are constructed of sufficient length or with sufficient capabilities, so that the work could be move through all stages of a press process including those in front of and behind the second and fourth uprights. 
     While the invention has been described with reference to its preferred embodiment, the foregoing discussion has revealed some typical examples of implementation of the invention. It should be understood that various changes and variations of these examples are possible within the scope of the following claims.