Abstract:
In a method for producing a pivotable bearing between a gripper and a gripper tube bearing the latter or between a gripper shaft and a gripper tube enclosing the latter coaxially, provision is made for all the components to be mounted on the gripper tube to be fixed before a sliding bearing formed as a resin-hardener system is introduced between the respectively pivotably connected parts. In this manner, deformations brought about by the fixing of the components can be compensated for.

Description:
BACKGROUND OF THE INVENTION  
     Field of the Invention  
       [0001]     The invention relates to a mounting for a gripper system for the transport of sheets in a sheet processing machine, and contains a gripper shaft which is mounted in a gripper tube. The invention further pertains to a method for producing the mounting.  
         [0002]     It is known, for example from German patent DE 43 17 429 C2 (corresponding to U.S. Pat. No. 5,588,773), to mount a gripper shaft such that it can be pivoted in a gripper tube enclosing the latter coaxially. For this purpose, use is made of bronze bushes that are bonded into the gripper tube.  
         [0003]     In particular in the case of tongs grippers, there is the problem that both the gripper shaft and the gripper tube bear gripper elements that in each case have to be fixed to the gripper shaft and tube. Fixing the gripper elements to the gripper tube necessarily causes deformations of the gripper tube, which can impair the function of the mountings and thus lead to greater wear and bearing play caused thereby, as well as a shorter lifetime of the mountings.  
       SUMMARY OF THE INVENTION  
       [0004]     It is accordingly an object of the invention to provide a sliding-surface mounting and a method of producing the mounting which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type.  
         [0005]     With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing a pivotable mounting of a gripper shaft in a gripper tube in a sheet-processing machine. The method includes coating the gripper shaft with a release agent in a region of the pivotable mounting, fixing necessary components on the gripper tube, mounting the gripper shaft in the gripper tube, and introducing a liquid resin-hardener system between the gripper shaft and the gripper tube in a region of an envisaged bearing point.  
         [0006]     A particular advantage of the invention is that a virtually play-free, low-wear mounting for a shaft/tube system as a functional element for a sheet holding system is provided, it being possible for components to be fixed to the tube with sufficiently high forces at the same time without exerting any disadvantageous effect on the shaft/tube mounting.  
         [0007]     Advantageously, as a result of applying a coating of a release agent to the shaft, following the solidification of a liquid resin introduced between shaft and tube, the shaft remains rotatable, while the resin enters into a firm adhesive and/or form-fitting connection with the tube, which is roughened on its inside.  
         [0008]     It has proven to be particularly advantageous if the components to be fixed are disposed on the tube before being filled with the liquid resin. Any pipe deformations that may arise in this case can then be compensated for by the resin.  
         [0009]     As a result of supplying heat during the solidification of the sliding layer material (resin-hardener systems) or heating the shaft before the filling, a defined minimum play can be produced between the shaft and the tube by utilizing material shrinkage properties.  
         [0010]     Other features which are considered as characteristic for the invention are set forth in the appended claims.  
         [0011]     Although the invention is illustrated and described herein as embodied in a sliding-surface mounting and a method of producing the mounting, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.  
         [0012]     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a diagrammatic, sectional view of a sheet-processing press;  
         [0014]      FIG. 2  is a diagrammatic, perspective view of a tongs gripper system for transporting sheets according to the invention; and  
         [0015]      FIG. 3  is a diagrammatic, sectional view of a conventional sheet gripper. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a machine for processing sheets  7 , for example a press  1 . The press has a feeder  2 , at least one printing unit  3 ,  4  and a deliverer  6 . The sheets  7  are removed from a sheet stack  8  and are supplied, separated or overlapping, over a feed table  9  to the printing units  3  and  4 . The printing units  3 ,  4  each contain, in a known way, a plate cylinder  11 ,  12 . The plate cylinders  11  and  12  each have an apparatus  13 ,  14  for fixing flexible printing plates. Furthermore, each plate cylinder  11 ,  12  is assigned an apparatus  16 ,  17  for semiautomatic or fully automatic printing plate change.  
         [0017]     The sheet stack  8  rests on a stack board  10  which can be raised under control. The removal of the sheets  7  is carried out from the upper side of the sheet stack  8  by what is known as a suction head  18  which, inter alia, has a number of lifting and dragging suckers  19 ,  21  for separating the sheets  7 . Furthermore, blowing devices  22  for loosening the upper sheet layers and sensing elements  23  for tracking the stack are provided. In order to align the sheet stack  8 , in particular the upper sheets  7  of the sheet stack  8 , a number of lateral and rear stops  24  are provided.  
         [0018]     A number of sheet transporting cylinders is equipped with gripper systems and transport the sheets through the printing units  3 ,  4  as far as the deliverer  6 . A turner device  26 , for example, can be provided between two printing units  3 ,  4 . In the exemplary embodiment, this contains a storage drum  27  with a turner drum  28  disposed downstream. The latter has what is known as a tongs gripper system  29 .  
         [0019]     The tongs gripper system  29  substantially contains a gripper shaft  31  and a gripper tube  32  enclosing the latter coaxially ( FIG. 2 ). The gripper tube  32  is mounted such that it can pivot in bearing points on the turner drum  28 . The gripper shaft  31  is in turn mounted such that it can pivot in the gripper tube  32 . The bearing points contain a sliding layer  33  derived from a resin-hardener system, which is disposed between the gripper shaft  31  and the gripper tube  32 . The gripper shaft  31  has a number of first grippers  34  which are disposed at a distance from one another and are in gripping contact with a corresponding number of second grippers  36 , which are disposed on the gripper tube  32 . For the purpose of fixing and sprung support of the second gripper  36 , for example a clamp  37  having a steel band  38  enclosing the gripper tube  32  and a pressure piece  39  are provided. This configuration is substantially also known from German patent DE 43 17 429 A1 (corresponding to U.S. Pat. No. 5,588,773).  
         [0020]     The sliding layer  33  for forming a pivotable bearing point between the gripper tube  32  and the gripper shaft  31  is formed as a resin-hardener system  33 , which is introduced between the tube  32  and the shaft  31  in a liquid state and then cures. In order to be able to compensate for distortions of the tube  32 , first, components such as the second grippers  36 , stops, etc., are fixed to the gripper tube  32 . The shaft  31  coated with a release agent is then disposed in the gripper tube  32  and the liquid resin-hardener system  33  is then introduced between tube  32  and shaft  31 . For this purpose, the tube  32  has a roughened surface, which ensures good retention of the resin-hardener system  33 , while the release agent on the shaft  31  ensures its ability to pivot with respect to the tube  32  and the cured resin-hardener system (sliding layer  33 ).  
         [0021]     During the curing phrase of the resin-hardener system  33 , by a specific supply of heat during the solidification of the sliding layer material  33  or heating the shaft  31  before the introduction of the sliding layer material  33 , a defined minimum play can be produced by utilizing material shrinkage properties.  
         [0022]     Of course, the invention can be used not only in tongs gripper systems but also in conventional gripper systems which need a sliding bearing to produce pivoting movements or between the gripper shaft and the stationary shaft or between a housing and the gripper shaft, in particular in sheet-processing machines, preferably presses.  
         [0023]      FIG. 3  shows such a conventional gripper  40 , which is pivotably mounted on a gripper tube  42  and interacts with a stop  43  that is fixed firmly to the gripper tube  42 . In order to produce the pivotable mounting, first the gripper  40  or the gripper housing  41  is coated with a release agent in the region of the envisaged bearing point and other components that are needed, such as the stop  43  seated firmly on the gripper tube  42 , are fixed on the gripper tube  42 . The resin-hardener system  33  is then introduced in the region of the envisaged bearing point between the gripper  40  or gripper housing  41  and the gripper tube  42 .  
         [0024]     This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 050 011.8, filed Oct. 14, 2004; the entire disclosure of the prior application is herewith incorporated by reference.