Abstract:
Disclosed is a method for producing a thin-walled part ( 33 ), especially a pipe section. According to said method, the wall ( 11 ) of the part ( 33 ) is drawn out from a strip ( 1 ) of material, an inner contour ( 17 ) is cut out, the wall is stretched to size, and an outer contour is cut out of the strip ( 1 ) of material.

Description:
The invention relates to a method for the production of a thin-walled part, especially a pipe section, and a device for that purpose. 
     PRIOR ART 
     Parts are required and produced in many and diverse forms and executions at the present time. For example, parts are formed from a metal strip by punching or precision blanking. Previously disclosed by DE 199 53 059 A1, for example, is a receiving bearing for receiving and/or moving at least one reading head arrangement, in which two plate elements are set at a distance and positioned exactly. This is effected by means of spacer elements, which are formed from the plate element by precision blanking and/or cold-forming. 
     Previously disclosed by CH 636 542 is a method for the production of flared bushes and flared bushes, in which the deep-drawing process is used. For this purpose, the starting material is supplied to a series of deep-drawing stations, so that a kind of cup is produced. The base of the cup is then perforated, in conjunction with which the liberated material is forced to the side. Further deep-drawing processes are then performed until production of the flared bush is complete. 
     The present invention is concerned with the production of cylindrical structural members or, for example, pipe sections. It is concerned in particular with the production of cam rings for assembled camshafts intended for installation in internal combustion engines. The individual cams are manufactured today as a forging blank with subsequent machining and cutting from a precision pipe and with subsequent forming without cutting. 
     OBJECT OF THE INVENTION 
     The object of the present invention is to make available a method and a device of the above-mentioned kind, with which thin-walled parts can be produced with high precision. In addition, unlike conventional precision blanking, the weight of the material and the proportion of the material cost should be significantly reduced. 
     Achievement of the Object 
     The characterizing features of patent claim  1  lead to the achievement of this object. 
     This means that a pipe section, for example, can be manufactured by the precision blanking metal forming process. The special feature of the production process is that punching or precision blanking is conventionally performed on the thick-walled plate, and forming is performed on the thin-walled component by cold-forming. Material wastage can be reduced to a minimum in this way. In addition, thin-walled pipe sections are produced to the required precision, for example with a tolerance of 1/10 in the thickness deviation and a dimensional accuracy of ±0.06. No pipes of this kind, from which such pipe sections can be cut, are currently available on the market. 
     Production of the part preferably takes place in at least five stages. A clamping plate, a guide plate and a drawing die are used in a first stage. A cavity is formed in the face of the clamping plate, in conjunction with which importance must be attached here above all to the inclination of the cavity to a cavity floor. A suitable strip of sheet metal is clamped between the clamping plate and the guide plate. The drawing die is moved in an opening in the guide plate as far as the strip of sheet metal, in conjunction with which the drawing die presses an area of the strip of sheet metal down into the cavity. The preferred thinning of the areas that are drawn into the cavity already takes place in this “deep-drawing process”. 
     In a second tool, and in a second operating stage, the strip of material is now clamped with the deep-drawn area between a clamping plate and a further guide plate, in conjunction with which these two plates are formed in such a way that one supporting surface of the clamping plate engages beneath the inclined area of the deep-drawn area, whereas the guide plate engages with a pressure wall above the inclined area. Provided in addition on the guide-plate is a knife-edged ring, which prevents the further flow of material from the strip of material. A guide opening in the guide plate and an opening in the clamping plate each exhibit an inner contour, which lies in approximately the same plane. A cutting die is introduced into both openings so that an internal contour is cut from the deep-drawn area of the strip of material. 
     In a further process stage, a peripheral area of the part, which consists essentially of the obliquely inclined area, is bent in one or more stages. If a pipe section is to be produced, the bending or the ironing takes place at about 90° in relation to the strip of material, which for the time being continues to be held between the clamping plate and the guide plate. 
     To ensure that space remains available for the wall area of the part, an appropriate clamping plate exhibits a corner bead, which possesses a depth corresponding more or less to the wall thickness of the part. In addition, a further reduction in the wall thickness of the part is achieved in conjunction with the ironing of the part. 
     Cutting of the part from the strip of material takes place in the next operating stage, in conjunction with which a part of the outer contour of the part is ultimately produced. In one illustrative embodiment, a tool is provided for this purpose, in which a fixed die makes an indentation in accordance with a shoulder form. The edge of the shoulder forms a cutting edge. The depth of the indentation in turn corresponds to the wall thickness of the part. 
     Cutting is effected by a lifting movement of a guide plate and a clamping plate in relation to the cutting edge of the die. In conjunction with this, the guide plate envelops the die and holds the strip of sheet metal with the part, which engages above the clamping plate, still arranged thereon. 
     Following parting, for example calibration of the part in the indentation of the die can take place of its own accord, for example, by subjecting the part to a corresponding ejection die. The latter can then also be used for ejecting the part. 
     Through the method according to the invention, or in the device according to the invention, cam rings can be produced in this way, for example, which are pushed onto a bar-shaped or pipe-shaped shaft and are secured thereto. In order to prevent radial movement of the pipe section in relation to the shaft, the pipe section can exhibit an egg-shaped cross section. 
     Thus, according to the present invention, a highly precise ring-shaped body can be produced from a thin metal sheet by a process of radial stretching, with simultaneous forming by ironing. The inner and outer form of the ring can have optional geometries; for example, the ring can be oval, toothed, round, etc. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Further advantages, characteristics and details of the invention can be appreciated from the following description of preferred illustrative embodiments and with reference to the drawing; in the drawing, 
         FIG. 1  shows a schematically represented section through a tool for drawing the contour of a part from a strip of material; 
         FIG. 2  shows a partially represented section through a tool for cutting an inner contour of the part; 
         FIG. 3  shows a partially represented section through a tool for bending a wall area of the part; 
         FIGS. 4 and 5  show partial sections through a tool for ironing the part; 
         FIG. 6  shows a partially represented section through a tool for cutting an outer contour of the part; 
         FIG. 7  shows a partially represented section through a tool for calibrating and ejecting the part; 
         FIG. 8  shows a perspective view of a part in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A strip  1  of material, preferably a strip of sheet metal, is held between a clamping plate  2  and a guide plate  3 , as shown in  FIG. 1 . A cavity  4  is formed on a face of the clamping plate  2 , while the guide plate  3  exhibits an opening  5  for guiding a drawing die  6 . This drawing die  6  preferably exhibits a face  7 , which more or less corresponds to the contour of the cavity  4 . 
     If the drawing die  6  is caused to move against the clamping plate  2 , the drawing die  6  presses a contour  8  of a subsequent part from the strip  3  of material. 
     In a further process stage according to  FIG. 2 , the strip  1  of material together with the contour  8  are held by a further clamping plate  9  and a guide plate  10 . The clamping plate  9  in this case engages below a wall area  11  of the part with a supporting surface  12 , which corresponds to an incline of the contour  4  according to  FIG. 1 . 
     A pressure wall  13  on the guide plate  10  interacts with the supporting surface  12 , so that the wall area  11  is received between the pressure wall  13  and the supporting surface  12 . In addition, the guide plate  10  engages with a knife-edged ring  14  in the material strips  11 . A cutting die  16  is guided in an opening  15  in the guide plate  10 , by-means of which die an inner contour  17  of the wall area  11  can be cut. For this purpose, the cutting die  16  moves in the opening  15  in the guide plate  10 , and after cutting engages in an opening  18  in the clamping plate  9 . 
     Bending of the wall area  11  takes place in a further process stage according to  FIG. 3 , in conjunction with which the strip  1  of material together with the wall area  11  is held between a guide plate  19  with the knife-edged ring  14  and a clamping plate  20 . A supporting surface  21  of the clamping plate  20  in this case exhibits a greater inclination than the supporting surface  12  of the clamping plate  9  according to  FIG. 2 . 
     The pressure wall according to  FIG. 2  is missing from the guide plate  19 , although a bending die  23  is guided in an opening  22  in the guide plate  19 . 
     According to  FIG. 4 , the strip  1  of material is held between the guide plate  19  and a clamping plate  24 , which possesses a corner bead  25 , which exhibits a depth t that corresponds more or less to the thickness s of the wall area  11 . The guide plate  19  also projects above the clamping plate  24  to more or less the same extent. 
     Guided in the opening  22  in the guide plate  19  is a drawing die  26 , which causes the wall area  11  to be bent through about 90° in relation to the strip  1  of material and, as can be appreciated in  FIG. 5 , to be ironed into the corner bead  25 . This takes place preferably by cold-forming, i.e. material from the wall area  11  is used to fill the corner bead  25 , so that the thickness s of the wall area  11  is reduced. 
     According to  FIG. 6 , the wall area  11  is now separated from the strip  1  of material. A static cutting die  26  is used for this purpose, which exhibits a cutting edge  27 . An indentation  28  is formed on the cutting die  26  after the cutting edge  27 , in conjunction with which a depth t 1  of the indentation  28  corresponds more or less to a wall thickness s of the finished part. 
     The strip  1  of material is held by a guide plate  29  and a clamping plate  30 , which together are capable of movement relative to the cutting die  26 , as indicated by the arrows  31 . 1  and  31 . 2 . This movement causes the wall area  11  of the strip  1  of material to be parted in interaction with the cutting edge  27 . 
     As shown in  FIG. 7 , calibration of the part  33  now takes place in conjunction with the cutting die  26  and an ejector  32 , to which parts its ultimate form is now imparted. 
     After removal of the cutting die  26 , the part  33  can be ejected from the clamping plate  30 . 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of Reference Designations 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Strip of material 
               
               
                 2 
                 Clamping plate 
               
               
                 3 
                 Guide plate 
               
               
                 4 
                 Cavity 
               
               
                 5 
                 Opening 
               
               
                 6 
                 Drawing die 
               
               
                 7 
                 Face 
               
               
                 8 
                 Contour 
               
               
                 9 
                 Clamping plate 
               
               
                 10 
                 Guide plate 
               
               
                 11 
                 Wall area 
               
               
                 12 
                 Supporting surface 
               
               
                 13 
                 Pressure wall 
               
               
                 14 
                 Knife-edged ring 
               
               
                 15 
                 Opening 
               
               
                 16 
                 Cutting die 
               
               
                 17 
                 Inner contour 
               
               
                 18 
                 Opening 
               
               
                 19 
                 Guide plate 
               
               
                 20 
                 Clamping plate 
               
               
                 21 
                 Supporting surface 
               
               
                 22 
                 Opening 
               
               
                 23 
                 Bending die 
               
               
                 24 
                 Clamping plate 
               
               
                 25 
                 Corner bead 
               
               
                 26 
                 Cutting die 
               
               
                 27 
                 Cutting edge 
               
               
                 28 
                 Indentation 
               
               
                 29 
                 Guide plate 
               
               
                 30 
                 Clamping plate 
               
               
                 31 
                 Arrow 
               
               
                 32 
                 Ejector 
               
               
                 33 
                 Part 
               
               
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                     s 1   
                 Wall thickness 
               
               
                 s 
                 Thickness of 11 
               
               
                 t 
                 Depth of 25 
               
               
                     t 1   
                 Depth of 28