Abstract:
A transporting apparatus, in particular a 3-way transfer means, for transfer presses, in the case of which, for horizontal movement, linear drives are attached and actuated such that, along with a compact construction, the linear drives allow the gripper rails to be changed straightforwardly during tool-changing operations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of International Application No. PCT/EP2005/000800, having an international filing date of Jan. 27, 2005, which designated the United States, and claims the benefit of German Application No. 10 2004 005 046.5, filed Jan. 30, 2004, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to an apparatus for transporting workpieces through processing stations of a press, in particular a transfer press or the like.  
       BACKGROUND OF THE INVENTION  
       [0003]     If the production of a workpiece necessitates a number of processing sequences, such as cutting and forming, then, for cost-effective production, the necessary individual operations are carried out in a so-called transfer press. The number of tools then corresponds to the number of operating stages which are necessary for producing the workpieces.  
         [0004]     The presses contain transporting apparatuses which transport the workpieces from one work station to the next. The transporting apparatus may be configured as a 2-way transfer means or 3-way transfer means, the movement axes of the transporting means thereby being defined. Provided for a 2-way transfer means are supporting rails which run through the press on both sides and on which crossmembers equipped with suction devices or the like are fastened for workpiece-transporting purposes, these crossmembers executing simultaneous horizontal and vertical movements.  
         [0005]     In the case of a 3-way transfer means, the supporting rails are designed as so-called gripper rails which, in addition to horizontal and vertical movements, also execute a transverse movement and grip the workpiece by means of gripper elements in order to transport the workpiece from one processing stage to the next. The 3-way or gripper-type transfer means is preferably used in practice for transporting flexurally rigid sheet-metal parts which can be gripped from the outside.  
         [0006]     Driving action along the 3 axes can take place directly, via cam plates and levers, by means of the press drive, or each movement axis is provided with a dedicated drive. A 3-way transfer means with dedicated drives in each case is disclosed in U.S. Pat. No. 4,887,446. The vertical movement and the closing movement, in the direction transverse to that in which workpieces run through the press, take place by means of electric motors or hydraulic cylinders. An electric linear drive is proposed for executing the horizontal movement of the supporting rails.  
         [0007]     No further details are given in U.S. &#39;446 regarding the linear drive and, in particular, the lengths of the primary and secondary parts. Similarly, U.S. &#39;446 does not disclose the gripper-rail change which is necessary for retooling purposes.  
         [0008]     An arrangement for coupling and uncoupling gripper-rail parts is described in detail in DE 36 36 010. An arrangement based on the principle of a swivel-type tensioning clamp is proposed as the connecting element or gripper-rail lock. In addition to the complex configuration which is necessary, the task, in particular, of achieving a clearance between the gripper-rail parts, for the changeover operation, requires considerable outlay.  
         [0009]     Instead of the horizontal movement of the supporting rails, this movement can also be produced by virtue of transporting carriages on the supporting rails.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the invention is to design, for a press and in particular for a transfer press with 2-way or 3-way transfer means, a linear drive for the horizontal movement such that the linear drive is of cost-effective design and, even while meeting stringent power-related requirements, provides for a compact construction. In addition, during tool-changing operations, the linear drive is intended to allow the gripper rails to be exchanged straightforwardly.  
         [0011]     The present invention is based on the idea of providing two linear drives per supporting rail for the horizontal movement. These linear drives are arranged such that the supporting rail can be changed straightforwardly. For this purpose, the linear motors are located essentially at the outer ends of the supporting rail. These outer ends are separate from the supporting rail which is to be changed over and are connected to the latter in a releasable manner via supporting-rail locks. The supporting-rail locks are likewise located in separate endpieces, and merely a clamping head engages in the supporting rail which is to be changed over. For the changeover operation, the connection is released and, by means of the linear motors, the endpieces are moved horizontally apart from one another by a defined distance, this resulting in a straightforward tool-changing operation. This movement sequence advantageously allows the supporting-rail lock to be designed in a very straightforward form. In the case of a preferably used 3-way transfer means, the supporting rail is designed as a gripper rail.  
         [0012]     For the actual retooling operation, the press bed is designed as a sliding table, on which the tool is located. It is also the case that all the component-dependent accessories which are necessary for workpiece-transporting purposes are likewise set down on the sliding table and moved out of the press.  
         [0013]     A new tool is clamped in place, and the component-dependent accessories are arranged, on a sliding table located outside the press. Following changeover of the sliding tables, the press is converted, fully automatically, to the new production and the supporting-rail parts which have been exchanged are also clamped in position by the supporting-rail locks. For this purpose, the linear drives move the supporting-rail endpieces, with the supporting-rail locks located therein, in the direction of the supporting rail to the extent where the clamping heads can engage in the mount provided in the supporting rail. The supporting-rail locks clamp together the supporting rail and the endpieces, and the supporting rail is also thereby fixed to the linear drive.  
         [0014]     The use of linear drives advantageously fulfills the object of the invention. Relatively recent developments make available highly dynamic drives with quick displacement sequences. Since these drives operate without any wear, a constant high level of positioning accuracy throughout the service life is ensured.  
         [0015]     A compact and low-cost configuration is achieved on account of the high power density of the linear drives and the fact that there are two drives per supporting rail and the drives are integrated directly at the supporting-rail ends.  
         [0016]     A further advantage of using two drives is that the operational reliability increases since, in the event of one drive failing, the second drive moves the supporting rail, and in particular the grippers on a gripper rail, out of the collision zone.  
         [0017]     The invention is used particularly advantageously in the case of a 3-way transfer means. Further advantages and details of the invention can be gathered from the description and from the figures showing an exemplary embodiment.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  shows a view of part of a transfer press with a supporting rail, which is designed as a gripper rail, clamped in place,  
         [0019]      FIG. 2  shows the view in  FIG. 1 , but with the gripper rail released, and  
         [0020]      FIG. 3  shows a detail of the gripper rail. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The following embodiment of the present invention describes a 3-way transfer means with gripper-rail drive.  FIG. 1  illustrates, of a transfer press  1 , the ram  2  and sliding table  3 , on which the upper tools  4  and lower tools  5  are fastened. The so-called closing boxes  8 ,  9  are arranged in the region of the uprights  6 ,  7 . These closing boxes  8 ,  9  are provided with drive means which execute a vertical and a closing displacement of the gripper rail  10 . Such closing boxes  8 ,  9  are known and are described in detail, for example, in the applicant&#39;s DE 43 36 854 A1, the entirety of which is incorporated herein by reference. The gripper rail  10  also has the gripper-rail endpieces  11 ,  12 . Gripper-rail locks  13  connect the gripper rail  10  to the endpieces  11 ,  12 . The gripper-rail locks  13  are configured as swivel-type tensioning clamps or rotary tensioning clamps, of which the basic bodies  14  are integrated, with the clamping drive, directly in the hollow profile of the gripper-rail endpieces  11 ,  12 , while the clamping heads  15  engage, and provide for clamping action, in the corresponding mounts of the gripper rail  10 .  
         [0022]     The linear drives are designated  16  and  17  and comprise a primary part  18 ,  19  and a secondary part  20 ,  21 . The primary part  18 ,  19  is arranged on the closing boxes  8 ,  9 . The secondary part  20  is connected to the gripper-rail endpiece  11 , while the secondary part  21  is divided, and is fastened both on the gripper rail  10  and on the gripper-rail endpiece  12 . In the case of the 3-way transfer means, the linear drives  16 ,  17  produce the horizontal movement of the workpieces in the transporting direction  22  and the return displacement counter to the transporting direction  22 .  
         [0023]     It is easy to recognize the short and compact construction of the drives as a result of the latter being in divided form, in accordance with the present invention.  
         [0024]      FIG. 2  shows a tool-changing situation. The gripper-rail locks  13  are open and, by virtue of the linear drives  16 ,  17 , the gripper-rail endpieces  11 ,  12  have been moved horizontally apart from one another, in opposite directions, in order to produce a clearance in relation to the gripper rail  10 . The uncoupled gripper rail  10  is set down, and retained, on mounts  23  located on the sliding table  3 .  
         [0025]     While providing for an extremely short construction and a short horizontal displacement path, dividing up the secondary part  21  into a part which is fastened on the gripper rail  10  and a part which is located on the gripper-rail endpiece  12  makes it possible to provide for the clearance which is necessary for gripper-rail-changing purposes.  
         [0026]      FIG. 3  shows a detail of the invention. The sectional illustration, in the region where the gripper rail is divided, shows the arrangement of the linear drive  16 . The primary part  18  is connected to a mount  23  of the closing box  8 . The secondary part  20  is fastened on the gripper-rail endpiece  11 . Of the gripper-rail lock, the clamping head  15  is located in a pivoted-in clamping position.  
         [0027]     The gripper-rail endpiece  11  is guided and retained in the mount  23  by the linear guides  24 .  
         [0028]     The invention is not restricted to the exemplary embodiment illustrated and described. It also covers all specialist developments within the context of the idea according to the invention.  
         [0029]     It is thus also possible to use just one linear drive in order to change the gripper rail. The following schematic sequence is then necessary: 
        opening the gripper-rail lock which is located on the side opposite to the active linear drive;     displacing the gripper rail into the changeover position;     opening the gripper-rail lock on the linear-drive side; and     displacing the endpiece, by way of the linear drive, by the distance which is necessary for changing the gripper rail.        
 
         [0034]     Of course, the apparatus according to the invention of the exemplary embodiment can also be transferred, in principle, to a 2-way transfer means with suction-bar workpiece transportation.  
       LIST OF DESIGNATIONS  
       [0000]    
       
           1  Transfer press  
           2  Ram  
           3  Sliding table  
           4  Upper tool  
           5  Lower tool  
           6  Upright  
           7  Upright  
           8  Closing box  
           9  Closing box  
           10  Gripper rail  
           11  Gripper-rail endpiece  
           12  Gripper-rail endpiece  
           13  Gripper-rail lock  
           14  Basic body  
           15  Clamping head  
           16  Linear drive  
           17  Linear drive  
           18  Primary part  
           19  Primary part  
           20  Secondary part  
           21  Secondary part  
           22  Transporting direction  
           23  Mount  
           24  Linear guide