Abstract:
The invention relates to a device and a method for producing longitudinal grooves in cylindrical workpieces, especially for producing longitudinal grooves having an irregular profile. the forming process is carried out by means of segmental wheels in a similar manner to that of a rolling method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/DE2007/000556, filed Mar. 27, 2007, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2006 025 034.6, filed May 26, 2006, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a device and a method for producing longitudinal grooves in cylindrical workpieces, in particular for producing longitudinal grooves having an irregular profile, the forming process being effected by means of segmental discs in a manner similar to that of a rolling method. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the production of profiled bodies such as, for example, disc carriers of clutches, toothed-belt discs or similar workpieces having a cylindrical basic structure, high levels of accuracy and precision are frequently required. In particular, accuracy and the surface quality are important. 
         [0004]    Described in DE 20 17 709 is a method used for producing the above-mentioned components. A special rolling die enables the workpiece to be produced from a blank having a smooth outer contour by means of a press, each press stroke shaping a workpiece from a blank. Upon each press stroke, a rolling operation is executed, in which the profiled rollers impress the wanted external profile into the circumferential surface of the workpiece. The profiled rollers in this case are arranged in a bottom die along the circumference of the workpiece to be worked. If the workpiece is pressed between the rollers by means of a top die attached to the ram of the press, these rollers are supported on support rollers having a corresponding bearing system. The bottom die can be constructed to be rotationally symmetrical, the individual profiled rollers that produce the profile of the workpiece being distributed regularly and at a uniform angle in relation to each other along the circumference of the workpiece. As a consequence thereof, and owing to the resultant rotationally symmetrical apportioning of forces during a forming process, the individual grooves produced by the respective profiled rollers are practically the same as each other. In particular, an outer contour having no offset is achieved. 
         [0005]    The disadvantage of this method is that the rotation, and therefore the rolling of the profiled rollers, is produced only by the forces acting between the workpiece and the profiled roller during the forming process. There occurs as a result non-definable slip of the profiled roller in relation to the workpiece. In the case of continuous profiles that are uniform in the longitudinal direction, this slip does not normally result in problems. If the profile is irregular in the longitudinal direction, however, for example having a web, in the middle of the profile length, extending transversely relative to the longitudinal groove, the slip results in dimensional inaccuracies, and thus in quality defects. 
         [0006]    Disclosed in DE 195 06 391 A1 is a method in which the profiled rollers are driven in such a way that the circumferential speed in the forming region matches the speed of the workpiece. The drive is effected by transmission of the ram motion to the profiled rollers via transmission means, such as toothed racks and toothed wheels. This method, or the arrangement of the above-mentioned transmission means, reliably prevents the slip between the profiled rollers and the workpiece. 
         [0007]    The disadvantage of this method is the very resource-intensive structure and the resultant high costs of the device. It is further disadvantageous that the multiplicity of transmission means necessitates a large structural height of the device. 
         [0008]    A device for producing longitudinal grooves in a cylindrical workpiece is likewise described in EP 0 006 137 A1. In the case of this solution, the forming process is effected, not by profiled rollers, but by segmental discs. The segmental discs are not driven. The outer contours of the segmental discs roll on the surface of the downwardly-moving workpiece. As a result, the segmental discs move on a circular path curve. The positions of the segmental discs at the start of the engagement are defined by spring-actuated retaining pins. The segmental discs are connected to a housing by means of a spherical sliding bearing system. Since the segmental discs are moved exclusively by the forces acting during the forming process and do not have a drive synchronized with the ram motion, a slight slip between the segmental disc surface and the workpiece is unavoidable. In addition, a precisely defined starting position of the segmental discs for the forming process cannot be realized. This is a crucial disadvantage, especially for workpieces having grooved profiles that are irregular in the longitudinal direction. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention is based on the object of developing a method and a device for producing profiles in cylindrical workpieces, by means of a structurally simple and therefore inexpensive and functionally reliable die, slip between the workpiece surface and the forming die elements being reliably prevented, and a high precision of the profile to be produced being achieved through a precisely defined starting point of the forming engagement. 
         [0010]    The invention is based on the concept of executing the forming process in a manner similar to that of a method of forming by rolling, but with driven segmental discs, rather than with profiled rollers, as the forming die element. The segmental discs are guided on slide surfaces, and are synchronized with the motion of the workpiece through a forced coupling to the punch, or bottom die part. This means that the segmental discs are not moved by the forces acting during the forming process, but by the motion of the punch. Slip between the segmental discs and the workpiece during the forming process is thereby precluded. As already mentioned, the segmental discs are guided on slide surfaces. These slide surfaces are curved so as to enable the profiled segmental disc surfaces to roll on the workpiece. To enable the segmental discs to move along the curved slide surfaces, they are held and guided from beneath by the bottom die part, and from above by the top die part, or punch. Preferably the holding force is applied to the segmental discs by gas springs, which, in turn, are connected to the top die part. Other force transmitting means, such as, for example, springs, are also conceivable. 
         [0011]    The segmental discs are held between the top die part, or components attached thereto, and the bottom die part at each instant of the forming process, and they therefore execute exactly the same vertical motion as the workpiece, which likewise is connected to the top die part, or to components attached thereto. The contact surfaces of the components that are connected to the segmental discs are so realized that the horizontal component of the segmental disc motion is taken up. Preferably, the surfaces are so designed that a substantially horizontal sliding motion between the segmental discs and the contacting components is rendered possible. This described device constitutes a structurally simple, and therefore also robust and inexpensive solution, but also one that is very precise and of high quality. 
         [0012]    A further advantage of the method according to the invention and of the device consists in the possibility of lifting the workpiece out of the device after the forming process and releasing it for a workpiece transport system. This lifting-out is preferably effected by means of a gas spring. Other actuation mechanisms are also conceivable, for example the lifting-out of the formed workpiece can also be effected by means of hydraulic or pneumatic cylinders. 
         [0013]    A further feature of the method according to the invention and of the device is that, during the forming process, the bottom die part is displaced downward by the top die part, via the punch, the rolling rod and the workpiece, against a force. This force in opposition to the forming motion can result, for example, from the lifting-out mechanism. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Further details and advantages of the invention are disclosed by the exemplary embodiment represented in the figures. 
           [0015]      FIG. 1  shows a device after the insertion of a blank; 
           [0016]      FIG. 2  shows a device at the start of forming; 
           [0017]      FIG. 3  shows a device at the end of forming; 
           [0018]      FIG. 4  shows a device after the workpiece has been lifted out; and 
           [0019]      FIG. 5  shows an enlarged representation of the forming engagement during the forming process. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]      FIG. 1  shows a sectional representation of the device  1  according to the invention. The device  1  consists of a top die part  2  and a bottom die part  3 . The punch  4 , with the rolling rod  5 , is fixedly connected to the top die part  2 . The bottom die part  3  is mounted in a vertically movable manner in a cast housing  6 . The bottom die part  3  is connected to a workpiece holder  8  via a gas spring  7 . In the position represented, the workpiece  9 , as a blank, has already been placed on the workpiece holder  8  by the grippers  10  of a workpiece transport system, which is not represented in greater detail here. The punch  4 , with the rolling rod  5 , is at the upper reversal point. If the forming process then commences, the punch  4 , with the rolling rod  5 , moves downward, while the workpiece  9  likewise executes a downwardly directed vertical motion. The motion of the workpiece  9  is produced in that the workpiece holder  8 , with the workpiece  9 , is displaced downward against the force of the gas spring  7 . 
         [0021]    In  FIG. 2 , the device  1  has reached a position in which a driver  11 , which is connected to the top die part  2  via gas springs  12 , has reached the upper contact surfaces of the segmental discs  13 . The lower contact surfaces of the segmental discs  13  bear on the bottom die part  3 . Because the driver  11  is bearing on the segmental discs  13 , upon continuation of the downward motion of the punch  4 , with the rolling rod  5 , or of the top die part  2 , the gas springs  12  retract to an extent at which the position represented in  FIG. 3  is attained. The gas springs  12  are now retracted, the rolling rod  5  is located in the workpiece  9  and the segmental discs  13  are held in a precisely defined position, from above by the driver  11  and from beneath by the bottom die part  3 . Starting from this position, the forming of the workpiece  9  by the segmental discs  13  commences upon a further downward motion of the punch  4 . 
         [0022]    The positive connections of all moving components cause the segmental discs  13  to be moved downward in synchronism with the workpiece  9 , relative to their vertical motion component. The rolling of the segmental discs  13  on the workpiece  9 , which rolling is necessary for the forming process, is achieved in that the segmental discs  13  move along a curved slide surface  14 . This sliding guidance and the vertical drive by the driver  11 , or by the bottom die part  3 , cause the segmental discs  13  to move on a circular path, and thus enable them to roll exactly on the workpiece  9 . The sides of the segmental discs  13  facing toward the workpiece  9  are provided with the negative form of the profile to be produced on the workpiece  9 . In this exemplary embodiment, it is a profile having longitudinal grooves, which have a web  15  in the middle of the profile. This profile can be seen clearly in  FIG. 5 . In the position represented, the forming process has already been completed. The web  15  can be seen clearly in the middle of the profile. The form and, in particular, the position of this web  15  are subject to stringent quality requirements. Precise forming is possible only if, as in the device  1  according to the invention, there is a precisely defined starting position for the forming process that is independent of frictional ratios between segmental discs  13  and the workpiece  9  or of thickness tolerances of the workpiece  9 . 
         [0023]      FIG. 4  shows the position of the device  1  after the forming process. The segmental discs  13  have been pressed downward by the contact with the driver  11 , and have thus rolled the profile onto the workpiece  9 . The sliding motion of the segmental discs  13  on the slide surfaces  14  is rendered possible, or supported, by a pressure-feed lubrication, which is effected via the lubrication channel  16 . The circular motion of the segmental discs  13  along the slide surfaces  14  results in the occurrence of relative motions at the contact points between the driver  11  and the segmental discs  13 , or between the bottom die part  3  and the segmental discs  13 . The contact surfaces of the driver  11  and of the bottom die part  3  are therefore of such design that, at each instant during the forming process, the segmental discs  13  are held and guided both from above and from beneath. After completion of the forming process, the top die part  2  moves upward, with the punch  4  and the rolling rod  5 . At the same time, the gas spring  7  extends and moves the workpiece holder  8 , with the formed workpiece  9 , upward in the same manner as the punch  5 , until the position represented in  FIG. 1  is attained. The workpiece  9  is now free, and can be gripped by the grippers  10  of the workpiece transport system and transported further. 
         [0024]    The invention is not limited to the exemplary embodiment that is represented and explained. It also comprises all developments of persons skilled in the art, within the scope of the concept according to the invention. 
       LIST OF REFERENCES 
       [0000]    
       
           1  Device 
           2  Top die part 
           3  Bottom die part 
           4  Punch 
           5  Rolling rod 
           6  Cast housing 
           7  Gas springs 
           8  Workpiece holder 
           9  Workpiece 
           10  Gripper 
           11  Driver 
           12  Gas spring 
           13  Segmental discs 
           14  Slide surface 
           15  Web 
           16  Lubrication channel