Abstract:
A transfer drive is proposed for a press and in particular for a forging machine, in which the intention is to dispense with guides which are sensitive to dirt. For this purpose, the gripper rails are suspended on a hinged-rod arrangement with a three-axis guide system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a transfer drive for a press that preferably has a three-axis transport of workpieces through machining stations. 
     2. Discussion of the Related Art 
     A conventional transport device for transporting parts in a transfer press comprises two gripper rails which extend in the transport direction of the parts and, in addition to the longitudinal and lifting movements, carry out an additional transverse movement, gripper elements being provided on the gripper rails themselves. In order that the transport elements do not interfere within the tool space during the machining operation of the press, the gripper rails in the three-dimensional transfer system have to be moved laterally out of the tool space again. 
     DE 38 42 182 C1 has disclosed a gripper-rail drive for transfer presses, in which the gripper rails execute a three-dimensional traveling movement. In particular, in addition to the conventional longitudinal movement and lifting movement of the two gripper rails extending in parallel, provision is made for an additional transverse movement as a clamping or closing movement for gripping or clamping the workpieces. For this purpose, each gripper rail is hinge-mounted via a push rod on a carriage which can be displaced transversely, in order to adapt to the respective workpiece size. The respective closing movement of the gripper rail is then carried out as a lateral pivoting movement on a carriage which is stationary in the transverse direction, by means of appropriate ball joints. In order to carry out the advancing, clamping and lifting movement of the carrying rails, provision is made for conventional cam disks over which cam-follower levers travel, the drive to the gearbox being provided by the press head. A basic illustration of such a drive or a pair of gripper rails is also reproduced in EP 0 210 745 A2 (FIG.  4 ). 
     In addition, DE 39 13 663 A1 has disclosed a transposing device for a transfer press, in which the drive for trolleys in the parts transport direction is provided by a cam-follower lever arrangement. The lifting movement of the running rail is provided via the drive of a cam-follower lever, whose movement is transmitted to the running rail via a longitudinal rod and a deflection device. 
     The drawback with this conventional art is the fact that the three-dimensional movements have to be assisted by guides which are complicated and sensitive to dirt for the individual movement elements, and make complicated protective coverings necessary. In the case of rough operating conditions with a high accumulation of dirt, such as is the case, for example, in forging presses, the guides for the individual movements are very highly stressed, and functional faults are unavoidable as a result, for example, of grooves or the so-called “fretting” of the guide surfaces. It is particularly disadvantageous if the guides are arranged in the area of the transport plane or even underneath the transport plane. 
     Object and Advantages of the Invention 
     The claimed invention is based on the object of providing a transfer drive which, to the greatest possible extent, dispenses with guides which are sensitive to dirt for the individual movement elements. 
     This object is achieved by the features of the claimed invention. 
     Advantageous and expedient developments of the transfer drive claimed in Patent Claim  1  are specified in the subclaims. 
     The claimed invention is based on the knowledge that a transfer drive that is used under rough production conditions must manage as far as possible without guides which are sensitive to dirt for the individual movement elements. Using this knowledge, the claimed invention proposes a transfer drive which comprises movable hinged rods in a suspended arrangement, as a result of which a type of “floating mounting” without additional guides is achieved. In particular, as a result of the use of a three-dimensional drive, a type of “multi-point suspension” is provided, which means that the gripper rails are suspended in a defined way on hinges in all three axes of movement, so that it is possible to dispense with conventional guides because of their sensitivity to dirt. At the same time, it is advantageous that all the hinged rods and push rods are arranged above the transport plane of the parts, so that the transport space located underneath can be equipped without any guides which can become dirty for the transfer drive. Accordingly, the transfer drive is equipped with hinged rods or push rods and levers for all movements of the gripper rails in all three directions of movement, since these items of equipment are connected to one another via rotary joints, which can be sealed off much better against dirt than conventional linear guides. In particular for use in a forging company, the arrangement of the transfer above the transport plane is advantageous, that is to say the dirt which accumulates at the bottom cannot hamper the transfer drive. 
     A further significant advantage of this arrangement consists in the good accessibility of the working space, for example for the spraying system of the mold engraving or in the event of a die change. 
     Further details and advantages of the claimed invention emerge from the following description of exemplary embodiments in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to  3  show a first embodiment of a transfer for a forging machine with a transfer drive for a gripper-rail arrangement, 
     FIG. 1 shows an end view of the forging machine with the transfer drive in the press inlet area, 
     FIG. 2 shows a front view of the transfer drive in the end area of the press, and 
     FIG. 3 shows a side view of the press with a side view of FIGS. 1 and 2, 
     FIGS. 4 to  6  show a second embodiment of a transfer of a forging machine in a variant having a common lever and closing drive, with the same arrangement as specified in relation to FIGS. 1 to  3 . 
     FIGS. 7 to  8  show a third embodiment of a transfer with separate drives for the movement axes, so-called electronic transfer, and 
     FIGS. 9 and 10 show a fourth embodiment of a transfer with separate drives with the additional function “width adjustment”. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first gripper as rail  5  and a second gripper rail  6 , run in a transport direction  4  through a forging machine or forging press  1 , and are suspended cardanically on four hinged rods  7  to  14  each. In this embodiment the gripper rail  5  in a front machine area  15  is carried by the two hinged rods  7 ,  8 , and in a rear machine area  16  by the hinged rods  9 ,  10 . This can be seen in the side view of FIG.  3 . The further gripper rail  6 , located outside the plane of the drawing in FIG. 3, is carried in the front area  15  by the hinged rods  11 ,  12  and in the rear area  16  by the hinged rods  13 ,  14 . 
     Located in a cam box  17  in the front machine area  15  is a lever shaft  18 , and in the rear machine area  16  is a lever shaft  19 , which are operatively connected to each other via levers  20 ,  21  and a push rod  22  in each case. 
     Fixed to the lever shafts  18 ,  19  are levers  23  to  26 , on which the individual hinged rods  7  to  14  are suspended cardanically. 
     The lever shaft  18  is rotatably mounted in the cam box  17  and is driven by a pair of cams  27  via a roller lever  28  (cam-follower lever) . The lever shaft  19  arranged in the rear machine area  16  is rotatably mounted in bearing blocks  29 ,  30 . Drive to the lever shaft  19  is provided by the lever shaft  18  via the lever arrangement  20 ,  21  with push rod  22 . The lifting movement of the gripper rails  5 ,  6  is carried out by means of this kinematic system. 
     Closing movement of the gripper rails  5 ,  6  is carried out via additional hinged rods  31  to  34 , the hinged rods  31 ,  32  being articulated cardanically at a side of the gripper rail  5  in the front machine area  15  and rear machine area  16 . Equally, the hinged rods  33 ,  34  are articulated cardanically at the side to the gripper rail  6  in the front and rear machine areas  15 ,  16 . In this regard, reference is made to FIGS. 1,  2 . 
     The hinged rods  31  to  34  are each articulated to a first leg  40  of an angled lever  35  to  38 , which is in each case held in a bearing  39 . A respective further leg  40 ′ of the respective angled lever  35  to  38  is in each case connected to a hinged rod  41  to  44  which for their part are connected via levers  45  to  48  to a lever shaft  49 ,  50  in each case. The drive to the lever shaft  49  in the front machine area  15  is in turn provided via a roller lever  51  by means of a pair of cams  52  in the cam box  17  in the front machine area  15 . This rotary movement of the lever shaft  49  in the front machine area  15  is in turn transmitted, via a lever  53 , a push rod  54  and via a lever  55  to the lever shaft  50  in the rear machine area  16 . 
     Advancing movement for the gripper rails  5 ,  6  is provided by hinged rods  56 ,  57 , which are in each case connected cardanically to the gripper rails  5 ,  6 . Via a cardanic connection to a lever  58 ,  59  in each case, a common lever shaft  60  is reached, which is driven via a roller lever  61  by a pair of cams  62 . 
     A camshaft  63  is driven by the press drive itself and serves to drive the advancing mechanism, the clamping and closing mechanism and the lifting/lowering mechanism. 
     The possible distortions which arise as a result of the lever and push-rod mechanisms are taken into account when calculating the cam paths, so that the movements of the gripper rails take place precisely with the appropriate intercepting movement curves. 
     Second Embodiment 
     A second embodiment of the claimed invention according to FIGS. 4 to  6  shows a transfer having a common lifting and closing drive. In this embodiment, FIG. 4 shows a basic position with a lowered transfer in an opened clamping and closing device. FIG. 5 shows the position for parts removal, with the transfer lowered in a closed position. Finally, FIG. 6 shows a transfer in the lifted transport position with a closed closing and clamping mechanism. 
     In a three-axle transfer, it is usual for three movements, namely advancing, lifting and closing, each to be produced by a cam mechanism. This is also indicated in the first embodiment, previously described. 
     A saving in costs can be achieved by the lifting and closing movements being carried out by a common cam mechanism, that is to say a vertical and a transverse movement are produced from one movement. According to the illustration in FIGS. 4 to  6 , this is achieved by means of the following measures in the transfer drive  100  illustrated there. 
     In a rocker  101 , which is mounted such that it can be pivoted about a pivot  102 , two angled levers  105 ,  106  and one articulated lever  107 ,  108  in each case are rotatably mounted in two vertically displaceable carriages  103 ,  104 . Gripper rails  109 ,  110  are suspended cardanically on the angled and articulation levers  105  to  108  by means of cardan joints  111 . 
     The angled levers  105 ,  106  are suspended via a cardanically mounted push rod  112 ,  113  each in a lever  114 ,  115  each, the latter being driven by the cam mechanism  118  via a lever shaft  116  and roller lever  117 . 
     Closing movement for the gripper rails  109 ,  110  is limited at the bottom by a stop  119 , and the lifting movement is limited at the bottom by a stop  120 . 
     As a result of the levers  114 ,  115  being lifted, the gripper rails  109 ,  110  carry out a closing movement as far as the stop  119 . As a result of further lifting of the levers  114 ,  115 , a lifting movement is carried out, the carriage  103 ,  104 , which is mounted in the guides  121 , being lifted. 
     As a result of the levers  114 ,  115  being lowered, the carriage  103 ,  104  carries out a lowering movement down to the stop  120 . During the further lowering of the levers  114 ,  115 , the gripper rail  109 ,  110  carries out an opening movement, brought about by the angled levers  105 ,  106  being pivoted. 
     Between lifting and closing, the cam mechanism assumes a latching position, in order to avoid the stops being struck hard. The rest of the drive mechanism is carried out in a manner similar to the embodiment according to FIGS. 1-3. 
     From the illustration in FIGS. 7 and 8, the suspension, mounting and guidance of the gripper rails  5 ,  6  is virtually identical to the embodiments already described. For the purpose of better understanding, the same reference numbers have been used. 
     The new feature is that the movements are no longer carried out via the central press drive, but separate, controllable drives are used. As a result of forcible synchronization with the press movements the movement sequences described in FIGS. 1 through 6 are broken up in favor of a flexible transfer system which can be adjusted optimally to the respective reforming process. Synchronization is carried out in the form of the known electronic shaft. The drive motors (not shown) used are preferably controlled-speed, electrically or hydraulically driven motors. Control can be carried out as a closed control loop. Magnitude of the respective movement is no longer predefined by a cam but can be carried out individually by controlling the drives. 
     A lifting drive  122  moves a lifting shaft  123 , on which levers  23 ,  24  are fixed. Execution of the lifting movement corresponds to the sequence already described, but time, magnitude of lift and lifting speed can be selected freely by controlling the lifting drive  122 . 
     Closing movement is initiated by closing drive  124 , via closing shaft  125 . Closing shaft  125  drives, via levers  45 ,  47 , a kinematic chain for the closing stroke of the gripper rails  5 ,  6  in the form already described. 
     In order to transmit lifting and closing movement or pivoting movement of the shafts  123 ,  125  from the start of the transfer to the end of the transfer, use is again made of push rods  22 ,  54 . 
     An advance drive  126  produces a horizontal part of a transport step of the gripper rails  5 ,  6  via advance shaft  127 , levers  58 ,  59  and hinged rods  56 ,  57 . 
     If adaptation to different width dimensions of workpieces is also required in a transfer system, such as is the rule in an automatic stamping machine, for example, a design according to FIGS. 9 and 10 is proposed. 
     Drive  128  drives the spindle  129 , which is connected to nuts  130  fixed to fitting plates  131 ,  132 . The fitting plates  131 ,  132  are mounted in guides  133  such that they can be displaced horizontally. Since the drive and guide elements of the lifting and closing movement of the gripper rails  5 ,  6  are located on the fitting plates  131 ,  132 , a width adjustment can be carried out in a simple way by means of a horizontal movement. 
     In another embodiment, the lifting and closing shafts  123 ,  125  are omitted, and for each gripper rail  5 ,  6  a separate lifting drive  122  and closing drive  124  are proposed. By this means, flexibility of the transfer system is further increased and permits, for example, transversely with respect to the transport direction, oblique positioning of the gripper rails  5 ,  6  in relation to each other or an asymmetrical closing movement referred to the closing drive. If push rods  22 ,  54  are also omitted, and if dedicated lifting drives  122  and closing drives  124  are likewise provided at the transfer end, then oblique positioning of the gripper rails in the transport direction is also possible. In a simple constructional design, the closing movement is carried out by levers  134  to  137  being fixed to the respective closing drive  124  and initiating the closing movement of the gripper rails  5 ,  6  via hinged rods  31  to  34 . In the function described in FIGS. 7,  8 , the advance drive  126  is common. 
     If width adjustment is not required, this device illustrated in FIGS. 9 and 10 can be omitted. The embodiment then comprises an arrangement of the drives for closing, lifting and advancing, according to the illustration and description of FIGS. 9 and 10. 
     While the claimed invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the claimed invention, as defined in the appended claims. Accordingly, it is intended that the claimed invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.