Abstract:
The invention relates to a method and a tool for producing cylindrical workpieces having longitudinal grooves, wherein the actual rolling operation is preceded by a drawing stage integrated in the tool and wherein the forming rollers are realized with an improved mounting.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of International Application No. PCT/DE2007/000264, filed Feb. 9, 2007, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2006 007 501.3 filed Feb. 16, 2006, the entireties of which are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The invention relates to a rolling method and a tool for producing cylindrical workpieces having longitudinal grooves, by means of forming rollers having an improved mounting. In addition, the actual rolling operation is to be optionally preceded by a drawing stage integrated in the tool. 
   BACKGROUND OF THE INVENTION 
   In the production of profiled pieces such as, for example, clutch disk-carriers, toothed-belt disks or similar workpieces having a basic cylindrical structure, high levels of accuracy and precision are frequently required. In particular, the accuracy and the surface quality are important. 
   The workpieces described are high-grade production parts which in some cases are produced in large quantities. Thus, in the case of a production installation for such workpieces, the costs and the output are also important criteria, in addition to the qualitative characteristics. 
   DE 20 17 709 A1 describes a method suitable for the production of the workpieces described above. A special rolling tool enables the workpiece to be produced from a raw piece having a smooth outer contour by means of a press, each press stroke forming a workpiece out of a raw piece. Upon each press stroke there is executed a rolling operation in which the profiling rollers impress the desired outer profile into the circumferential surface of the workpiece. The profiling rollers in this case are arranged in a lower die along the circumference of the workpiece to be worked. When the workpiece is pressed between the rollers by means of an upper die attached to the press ram, these rollers are supported on support rollers having corresponding mounting. 
   The lower die can be of a rotationally symmetrical structure, the individual profiling rollers that produce the profile of the workpiece being distributed regularly and at a uniform angle in relation to one another along the circumference of the workpiece. Consequently, and owing to the resultant rotationally symmetrical apportioning of forces during a forming operation, the individual grooves produced by the respective profiling rollers are practically like one another. In particular, an offset-free contour is achieved. 
   The disadvantage of the method is that a raw piece that has been preformed to be close to contour has to be readily available before the rolling procedure. This means that the raw piece must be produced in a separate forming procedure, for example a drawing procedure. A further disadvantage in the embodiment described above is in the structural design of the profiling roller support by means of the support rollers. Although this embodiment renders a profiling roller diameter of reduced size, it is structurally very complex and cost-intensive because of the arrangement of the support rollers. In addition, the tool has a large overall height as a result. 
   SUMMARY OF THE INVENTION 
   The invention is based on the object of developing a method and a tool in which both the forming of a blank to produce a raw piece and the forming on the raw piece by rolling are attained in a common apparatus during one press stroke. In addition, the overall height of the tool is to be reduced through a new type of profiling roller mounting. 
   The invention is based on the concept of using the downwardly directed stroke of a forming press for a combined forming operation, consisting of deep-drawing and forming by rolling, within one tool. An advantageous result in this case is that the overall height of the tool part provided for forming by rolling is significantly reduced by a new type of profiling roller mounting. The mounting of the profiling rollers consists of two bearing shell halves, which cover the profiling rollers on the majority of the circumferences of the profiling rollers. The profiling rollers project out of the bearing shell halves on the side facing towards the workpiece. Lubricant is entered between the profiling rollers and the bearing shells via a pressure-feed lubrication. The two bearing shell halves are preferably realized as solid bearing shell halves and with an overall height that is only slightly higher than the circumference of the profiling rollers. This enables a drawing ring to be mounted in the upper region of the tool. This drawing ring, together with the upper part of the die, which is fixedly connected to the ram, performs the function of deep-drawing from a flat blank the cylindrical raw piece that is required for the rolling operation. This is preferably performed without a plate holder. The structure of the tool, however, also allows the drawing operation to be performed by means of an additionally installed plate holder. 
   Owing to the small overall height of the tool according to the invention, it is also conceivable for a plurality of roller sets to be installed in the stroke direction, and consequently the operation of forming by rolling can be effected in multiple stages. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details and advantages of the invention are evident from the exemplary embodiment represented in the drawings. 
       FIG. 1  shows a tool with die and blank at the start of the deep-drawing operation; 
       FIG. 2  shows a tool with die and raw piece during the operation of forming by rolling; and 
       FIG. 3  shows a rolling unit, in a top view. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a sectional representation of the tool  1  according to the invention. The tool  1  consists of a drawing unit  6  and a rolling unit  7 . The drawing unit  6 , in turn, consists of a die upper part  2 , which is fixedly connected to the ram  4 , and of a die lower part  3 , which can be moved vertically via the lifting unit  5 . 
     FIG. 1  shows the position at the start of the drawing operation. The ram  4 , with the die upper part  2 , has already moved downwards to such an extent that the forming of the blank  8  can commence. In this case, the blank  8  is drawn downwards via the drawing ring  9 . The die lower part  3  is displaced downwards. Owing to the contour of the die upper part  2  and the design of the drawing ring  9 , after the drawing operation there is produced a raw piece  10  which serves as a basic form for the subsequent operation of forming by rolling. 
     FIG. 2  shows a position during the operation of forming by rolling. It shows the rolling unit  7 , with the upper bearing shell  11  and the lower bearing shell  12 . The two bearing shell halves  11 ,  12  serve to accommodate or mount the profiling rollers  13 . These profiling rollers  13  are arranged in a distributed manner on the circumference of the rolling unit  7 . The raw piece  10  is now taken past the profiling rollers by the vertical downward movement of the ram  4  with the die upper part  2 , and thereby acquires, on the outer diameter, the longitudinal groove profile resulting from the arrangement of the profiling rollers. A lubricating connection  14  can be seen at the outer edge of the tool  1  according to the invention. Via this lubricating connection  14  and via the lubricating line  15 , lubricant is forced between the bearing shell halves  11 ,  12  and the profiling rollers by means of a pressure-feed lubrication. This lubricant covers the profiling rollers  13  and enters the region in which the profiling rollers  13  are in engagement with the raw piece  10 , passes back out of the bearing shells and is supplied to a lubricant circuit. The lubricant outlet in the forming region assists the operation of forming by rolling and results in improved quality of the rolling result. 
   After the forming operation, the ram  4 , with the die upper part  2 , moves back upwards, while the finish-formed workpiece is likewise moved upwards by means of the lifting unit  5 . The finish-formed workpiece can then be grasped by an automation apparatus and transported further. After a new blank  8  has been inserted in the tool  1  according to the invention, the combined operation of drawing and forming by rolling can recommence. 
   The arrangement of the profiling rollers  13  is shown clearly in  FIG. 3 . These profiling rollers are arranged in the circumference, corresponding to the final contour of the finish-formed workpiece. Also shown is the lower bearing shell  12 , in which the profiling rollers  13  are mounted or guided. 
   The invention is not limited to the exemplary embodiment that is represented and described. It also includes all developments, by persons skilled in the art, within the scope of the concept according to the invention. 
   For example, as already mentioned, the rolling unit  7  can be arranged in multiples over one another, so as to thereby render possible multistage forming by rolling. It is likewise conceivable for the drawing unit to be additionally equipped with a controlled plate holder. 
   LIST OF REFERENCES 
   
       
         1  Tool 
         2  Die upper part 
         3  Die lower part 
         4  Ram 
         5  Lifting unit 
         6  Drawing unit 
         7  Rolling unit 
         8  Blank 
         9  Drawing ring 
         10  Raw piece 
         11  Upper bearing shell 
         12  Lower bearing shell 
         13  Profiling rollers 
         14  Lubricating connection 
         15  Lubricating line