Abstract:
The invention relates to a novel design of hydraulic processing pincers for processing workpieces, with a tool which, in a first tool part, has an axially displaceable tool plunger which, with a first end or with a tool provided there and an opposite work rest, forms a working region or a working gap and can be moved with the first end towards and away from the work rest, and made up of a hydraulic actuating device for applying a force to the tool plunger via a movable pressure-transmitting element, said force moving said tool plunger in the direction of the work rest. The piston and/or the piston rod are/is designed with a cavity in which the tool plunger is accommodated in its initial position at least over part of its length.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to hydraulic processing grippers or hydraulic processing pincers. 
     “Processing gripper”, according to the invention, generally refers to a device with which workpieces can be gripped, machined or processed hydraulically and, therefore, with a high application of force. The processing gripper comprises at least two elements that can move in relation to each other and form a working gap between them, one of the elements is a hydraulically actuated press ram and the other element forms a workpiece assembly or a further workpiece element. 
     A generic hydraulic processing gripper is known in the art from DE 103 59 879 and is used to provide functional elements or connecting elements, such as nuts, bolts etc. in workpieces made of sheet metal by means of joining and subsequent pressing. 
     Especially for pressing there is a press ram or plunger, which for closing of the processing gripper during feeding can be moved from a press ram or plunger starting position into a working position, in which the plunger is supported on the functional element to be inserted into the workpiece and the functional element is supported on the workpiece. A hydraulic pressure cylinder then fixes the functional element in the workpiece by means of pressing, i.e. by means of permanent material deformation for example of the functional element and/or of the workpiece. 
     The basic advantage of the known setting gripper is that the feed movement of the press ram or plunger can be executed with a large stroke, and with reduced force, while the increased force required for processing or pressing when the processing gripper is closed is generated by the pressure cylinder, with an extremely short stroke. In order to achieve this, the processing gripper is designed so that the pressure piston of the pressure cylinder is arranged on the same axis with the press ram or plunger. As a result, the plunger, when advanced, is at an axial distance from the pressure piston of the pressure cylinder. Via a pressure element, which can be moved radially to the axis of the press ram, the distance between the pressure piston of the pressure cylinder and the advanced press ram is bridged. The pressure piston then acts on the press ram via this pressure element during pressing. When the press ram is retracted into starting position with the processing gripper open, the pressure element is located to the side of the press ram and therefore provides the free space necessary for the press ram to return to its starting position. 
     The disadvantage of the known processing gripper is its relatively large overall height, which is due in particular to the fact that the size of the pressure transfer element or pressure element in the axis direction of the workpiece is at least equal to the stroke of this press ram from its starting position to the working position. 
     It is an object of the invention to present a processing gripper that enables a more compact design while retaining the basic advantages of the existing gripper. This object is achieved by a processing gripper made up of a tool having an axially displaceable tool plunger, which, with a first end and an opposite work rest, forms a working region or a working gap and can be moved with the first end towards and away from the work rest. The processing gripper has a hydraulic actuating device for applying a force to the tool plunger via a movable pressure-transmitting element, the force moving the tool plunger in the direction of the work rest. 
     SUMMARY OF THE INVENTION 
     The advantage of the invention is, in particular, that the press ram or plunger in its retracted position or starting position is accommodated at least partially in the pressure cylinder or in the piston there or in the piston rod, so that the dimensions of the pressure transfer element in the direction of the axis of the press ram can be much smaller than the stroke of the press ram. 
     To eliminate this disadvantage, it has already been suggested to provide the pressure cylinder so that it is radially movable to the axis of the press ram, which however entails a more complex design due to the high pressure forces that have to be transferred from the pressure cylinder to the press ram. 
     The invention is characterized by a reduced overall height with a simplified design. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described below based on the drawings with sample embodiments, as follows: 
         FIG. 1  the elements of a work station for inserting components, for example connecting elements, in a workpiece; 
         FIGS. 2 and 3  a processing or setting gripper of the workstation in  FIG. 1  in various operating states; and 
         FIG. 4  a schematic representation of the pressure cylinder of the processing gripper in a further possible embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The work station depicted in  FIG. 1  is used for the insertion of components, e.g. for the insertion of nuts  1  in workpieces  2  made of sheet metal. 
     The work station includes a workplace comprising a C-shaped or setting gripper  3  and of a hydraulic working cylinder  4  that drives the setting gripper  3  and is spatially separate from this gripper. The working cylinder  4 , or its working piston  4 . 1 , is actuated in the depicted embodiment by a motor (not depicted), via a threaded spindle  7 . The setting gripper  3  or a pressure cylinder  5  located there and the working cylinder  4  are connected with each other by means of a hydraulic pressure line  6 . 
     The setting gripper  3 , which is fastened to a machine frame or a mount (not depicted), consists of a C-shaped gripper frame  8  comprising the gripper arms  8 . 1  and  8 . 2  and the yoke section  8 . 3  connecting the arms. By means of the yoke section the gripper  8  is also fastened to a machine frame (not depicted). A tool head  9  with a matrix-type tool element  10  is provided on the arm  8 . 1  depicted as the lower arm in the drawings. 
     A punching head-shaped pressing tool  11  is fastened to the other gripper arm  8 . 2 , which is opposite the gripper arm  8 . 1  and depicted in the drawings as the upper arm. The pressing tool  11  is depicted only schematically in the drawings and consists essentially of a ram or plunger  12 , which is movably guided in a housing  13  fastened to the gripper arm  8 . 2  for an axial stroke in the plunger axis AP, extends with a partial length over the side of the housing  13  facing the gripper arm  8 . 1 , and supports a tool element  14  on the end of the partial length. The tool element  14  together with the tool element  10  joins and fixes (by pressing) the respective components  1  in the workpiece  2 . 
     A special characteristic of the setting gripper  3  or of the pressing tool  11  is that the closing of the setting gripper  3 , i.e. the moving of the plunger  12  with the tool element  14  and the components  1  to be inserted from the plunger starting position toward the workpiece  2  or into the plunger working position and the re-opening of the setting gripper  3 , i.e. the moving of the tool element  14  away from the workpiece  2  and the moving back of the plunger  12  into its plunger starting position, takes place by axial movement of the plunger  12  with a large stroke A, namely by a drive  15  indicated schematically in  FIG. 2 , for example a pneumatic, electric or hydraulic drive, which effects this axial movement of the plunger  12  with relatively little force. The pressing of the components  1  takes place with great force and a short stroke B by the pressure cylinder  5 , which is provided on the top of the housing  13 . 
     The pressure cylinder  5 , as schematically depicted in  FIGS. 2 and 3 , consists of a cylinder housing  16  and a piston rod  17  that is axially movable in the cylinder housing  16  with a piston  18 . The piston  18  delimits two cylinder chambers  16 . 1  and  16 . 2 , of which the cylinder chamber  16 . 1  can be pressurized with the hydraulic pressure of the working cylinder  4  during pressing. 
     The axis of the piston rod  17  is the same as the axis AP of the plunger  12 . The piston rod  17  is designed as a hollow rod, namely with an inner diameter that is somewhat larger than the outer diameter of the plunger  12  so that the plunger  12  in its raised, i.e. retracted plunger starting position, in which the tool element  14  is at the greater distance from the tool element  10  and therefore the setting gripper  3  is opened, is accommodated with a partial length in the piston rod  17 . This results in a low overall height for the setting gripper  3 . 
     To create the necessary driven connection between the piston rod  17  and the plunger  12  for pressing, a slide  19  is movably guided (double arrow C) on the top of the gripper arm  8 . 2  radially to the setting gripper axis AP, namely by a drive  20 . The drive  20  is an electric motor, hydraulic or pneumatic drive. A pressure plate  21  is provided or guided in the slide  19  so that it can be moved in the slide with a short stroke in an axis direction parallel to the axis SA. 
     By means of the drive  20 , the slide  19  can be moved from a starting position, in which the slide  19  including the pressure plate  21  is completely outside the sphere of movement of the plunger  12  ( FIG. 3 ), into a working position in which the slide  19  and its pressure plate  21  are located on the same axis as the axis SA. 
     The functional principle of the setting gripper  3  is shown in  FIGS. 2 and 3 . It is assumed that the setting gripper  3  is opened. In this case the plunger, in the case of the slide  19  being retracted into the starting position, is moved upward by the drive  15  until the tool element  14  is at the greater distance from the tool element  10  and the upper partial length of the plunger  12  is accommodated in the piston rod  17  designed as a hollow rod. After insertion of the workpiece  2 , the setting gripper  3  is closed, i.e. the plunger  12  is moved downward by the drive  15  into the plunger working position so that the tool element  14  bears with the functional element  1  already present on said tool element against the workpiece  2 . The upper end  12 . 1  of the plunger  12  is then in the plane of the bottom of the slide  19  and of the pressure plate  21  or somewhat lower. However in any case the upper end  12 . 1  of the plunger  12  is at a distance below the lower end  17 . 1  of the piston rod  17 , which is at the level or somewhat above the level of the top of the slide  19  and the top of the pressure plate  21 . 
     Afterwards, the drive  20  moves the slide  19  from its starting position into the working position (arrow C). In the working position the pressure plate  21  is between the end  17 . 1  of the piston rod  17  and the top  12 . 1  of the plunger  12 , so that the pressure plate  21  creates a driven connection between the piston rod  17  and the plunger  12 . By pressurizing the cylinder chamber  16 . 1  with the hydraulic pressure supplied by the working cylinder  4 , the functional element  1  (e.g. nut) can be pressed in the workpiece  2  (e.g. sheet metal part) with a short stroke B via the piston rod  18 , the pressure plate  21 , the plunger  12  and the tool element  14 . 
     After pressing, the slide  19  moves back to its starting position so that the plunger  12  can be moved back up via the drive  15  to open the setting gripper  3  and the upper length of the plunger  12  is again accommodated in the piston rod  17 . The retraction of the piston  18 , is achieved for example, by pressurizing the cylinder chamber  16 . 2  with the hydraulic pressure. 
     It was assumed above that the piston rod  17  is designed as a hollow tube. Fundamentally, other designs are also possible. For example, and as shown in  FIG. 4 , it is also possible to use instead of the piston  18  a piston  18   a , which is axially guided in the cylinder chamber of the cylinder housing  16  and has a suitable ratio of piston length to piston diameter for this purpose. The piston  18   a  is provided with an opening  22 , which is open on the side facing the plunger  12  and in which the plunger  12  is accommodated with a partial length in the plunger starting position. For pressing, the opening  22  is then again closed by the pressure plate  21 , i.e. the latter is located between the piston  18   a  and the upper plunger end  12 . 1 . 
     Further, it is possible to design in particular the tool element  14  so that it has a corresponding hold-down device, which for example presses the workpiece  2  against the tool element  10  prior to pressing and holds it in position there. 
     The invention was described above based on sample embodiments. It goes without saying that numerous modifications and variations are possible without abandoning the underlying inventive idea of the invention; all embodiments have in common that the piston or the piston rod of the pressure cylinder  5  is designed so that a partial length of the plunger  12  is accommodated in this pressure cylinder when the setting gripper is open. 
     REFERENCE LIST 
     
         
           1  functional element, for example nut 
           2  workpiece 
           3  setting gripper 
           4  working cylinder 
           5  pressure cylinder 
           6  hydraulic pressure hose 
           7  threaded spindle 
           8  C-shaped gripper frame 
           8 . 1 ,  8 . 2  gripper arm 
           8 . 3  section 
           9  tool head on gripper arm  8 . 1   
           10  tool element 
           11  pressing tool 
           12  plunger 
           12 . 1  top end of plunger  12   
           13  housing 
           14  tool element 
           15  drive 
           16  cylinder housing of pressure cylinder  5   
           16 . 1 ,  16 . 2  cylinder chamber 
           17  piston rod 
           17 . 1  end of piston rod  17   
           18 ,  18   a  piston 
           19  slider 
           20  drive for slider  19   
           21  pressure plate 
           22  opening 
         A feed movement of plunger  12  or of tool element  14   
         B movement stroke of pressure cylinder  5   
         C movement of slide  19