Abstract:
A method for producing a cover, wherein a special steel blank is deep-drawn and can be placed on an end of a motor vehicle exhaust pipe. Immediately successive method steps makes it possible to economically produce a one-piece cover without subjecting the surface to deterioration and subsequently working the same.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a method for producing a cover made of a special steel blank which can be deep-drawn and placed on the end of a motor vehicle exhaust pipe, and a cover produced in accordance with this invention. 
   2. Discussion of Related Art 
   Known covers are used as an ornamentation on an end of an exhaust pipe protruding from the rear of a motor vehicle. For this reason the non-rusting basic material, the special steel, and the appearance of the surface of the cover are of decisive importance. 
   Similar known covers are bent from a special steel blank into a sleeve-shaped body and are welded together at the joint on the shell circumference. This requires a considerable outlay for labor, particularly during the manufacture and finishing work for the weld seam. Thus, covers produced in this way are very expensive. 
   SUMMARY OF THE INVENTION 
   It is one object of this invention to provide a method of the type mentioned above but in which covers can be produced in one piece without welding work and without the finished cover experiencing impairments which make the cover less valuable or even turn it into waste. 
   In accordance with this invention, this object is accomplished by the combination of the following method steps which follow each other directly: a) making a circular blank from a special steel plate; b) drawing cup-shaped beakers with a bottom, which is inclined with respect to the longitudinal axis, wherein diameters are uniform over an entire shell length, but are more and more decreased, and the shell lengths are more and more increased, are drawn in several deep-drawing operations; c) punching a centered hole ( 13 ) with a rim ( 14 ) which is ring-shaped toward the shell ( 12 . 4 ) into the bottom ( 11 . 4 ); d) cutting the shell ( 12 . 4 ) vertically with respect to the longitudinal axis ( 25 ) of the beaker ( 10 . 4 ) to the required length (Lo) and a condensate drain opening ( 16 ) and a fastening hole are cut into the shell ( 12 . 5 ); e) subsequently crimping the rim ( 14 ) of the bottom ( 11 . 4 ) is bent-in parallel with respect to the longitudinal axis ( 25 ) and is subsequently crimped into the beaker ( 10 . 6 ) to form an end ( 17 ) in the shape of an arc of a circle; and f) at the finish the end section ( 18 ) tapering the cut open front ( 15 ) of the beaker ( 10 . 7 ) for decreasing the diameter. 
   It is important that these method steps are performed directly, such as in short periods of time, one after the other. Because the axial dimension of the cover is considerable for a deep-drawing method, the deep-drawing process occurs in several deep-drawing steps with diameters decreased in steps and a shell length increased in steps. These are followed by the method steps for forming the two open front faces of the cover, wherein the crimped rim and the tapered end section of the cut-off shell result in the final shape of the cover by appropriate method steps. 
   In one embodiment, care is taken in the method steps, so the transition from the inclined bottom to the shell of the various deep-drawing steps is always rounded, so that no damage occurs, particularly in the transition area from the bottom to the shell of the drawn beaker. 
   Regarding the inclination of the bottom with respect to the longitudinal axis of the beaker the bottom is inclined with respect to the shell of the various deep-drawing steps at a diameter by approximately 70°, or 110°, with respect to the longitudinal axis. 
   So that the front face of the cover facing the motor vehicle, and possible openings and/or holes in the shell of the beaker can be cut in a simple manner, in one embodiment the cutting-off of the shell to the required length and the cutting of the condensate drain opening and/or fastening hole are performed together. These method steps can be performed together because they are performed in the same processing direction. 
   If prior to crimping of the end in the form of an arc of a circle the bore in the bottom is shaved, the crimped end of the beveled front of the beaker becomes uniform. 
   A cover produced in accordance with this invention is distinguished because it is embodied in one piece in a sleeve-like manner, wherein a front end, which is inclined with respect to the longitudinal axis, has an end crimped in the shape of an arc of a circle, and the other front end extending perpendicularly with respect to the longitudinal axis in the adjoining end section has a diameter which is less than the diameter of the remaining shell. The crimped end provides stiffening and avoids sharp edges, while the tapered end section stabilizes the drawn cover and prevents undesired contractions of the material because of tensions occurring in the material. 
   The shell of the sleeve-shaped cover has a condensate drain and a fastening hole. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This invention is explained in greater detail in view of an exemplary embodiment represented in the drawings, wherein: 
       FIG. 1  is a front view of a circular blank as the initial basis for producing a cover made of special steel; 
       FIGS. 2 to 5  show diagrammatic views of four deep-drawing processes for beakers as the pre-products with increasingly reduced diameters and increasingly increased shell lengths; 
       FIGS. 6 and 7  each shows a diagrammatic view of cutting and punching a hole in a bottom of a beaker; 
       FIG. 8  shows a diagrammatic sectional view of cutting the shell of the beaker to size and cutting an opening and/or a bore into the shell of the beaker; 
       FIG. 9  shows shaving a hole in a bottom; 
       FIG. 10  shows a tool for the vertical alignment of the rim in the bottom; 
       FIG. 11  shows a tool for crimping the rim; 
       FIG. 12  shows tapering the end section of the shell; 
       FIG. 13  shows a vertical section taken through the finished cover; 
       FIG. 14  shows a plan view from a front end with the tapered end section on the sleeve-shaped cover; and 
       FIG. 15  shows a crimped end of the beveled front end of the finished cover in an enlarged partial view. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   The circular blank  10  represented in a lateral view in  FIG. 1  is produced, preferably cut, from a special steel plate which can be deep-drawn, of a diameter D 1  of 190 mm, for example, and a thickness of 1 to 1.2 mm, for example. 
   In a first deep-drawing process, a beaker  10 . 1  with an inclined bottom  11 . 1  is drawn by a deep-drawing process, with a diameter D 1 =117.7 mm, and the shell  12 . 1  is brought to a shell length L 1 . In this case the inclination of the bottom  11 . 1  with respect to the longitudinal axis  25  of the beaker  10 . 1  on a diameter is 70° or 110°, as shown in  FIG. 2 . 
   In the following second deep-drawing process, the beaker  10 . 2  is drawn with a smaller diameter D 2 =96.95 mm, but a greater length L 2  of the shell  12 . 1 , so that the beaker  10 . 1  in accordance with  FIG. 1  becomes the beaker  10 . 2 , as shown in  FIG. 3 . 
   A further, third deep-drawing process follows, in which the beaker  10 . 2  in accordance with  FIG. 3  is changed into a beaker  10 . 3  in accordance with  FIG. 4 , with a diameter D 3 =79.5 mm and a length L 3  of the shell. 
   The deep-drawing process is ended in a fourth method step, in which finally the beaker  10 . 4  is created with the final diameter D 4 =68.7 mm and a length L 4  of the shell  10 . 4  in accordance with  FIG. 5 . The lengths L 1  to L 4  result automatically because the initial circular blank  10  is defined. 
   As  FIGS. 6 and 7  show, the slide is trimmed with a clipping punch  20  and a centered hole  13  is punched into the bottom  11 . 5  with the punch  30 , so that an annular rim  14  remains around the hole  13 . 
     FIG. 8  shows a cutting tool  40  and a punching tool  50 , by which the length Lo of the shell  12 . 5  of the beaker  10 . 5  in accordance with  FIG. 7  is shortened to the required length, wherein the resultant front face  15  is oriented perpendicularly with respect to the longitudinal axis  25  of the beaker  10 . 6 . A condensate drain  16  and a fastening hole are punched into the shell  12 . 5 , wherein cutting of the shell  12 . 6  and punching of the condensate drain  16  and the fastening hole occur simultaneously, because both work directions of the processes are the same. 
   As  FIG. 9  shows, the bore  13 . 1  can be shaved in order to position the rim  14 . 1  uniformly around the shell  12 . 5  of the beaker  10 . 6 . 
   Initially, an area of the rim  14 . 1  adjoining the hole  13 . 1  is crimped parallel with the longitudinal axis  25  of the beaker  10 . 6  by the two tools  50  and  55  and is thereafter shaped in the form of an arc of a circle by tool  60  and  65 . In this case the tools  60  and  65  are matched in the form of a semicircle in the facing corner areas, as shown in  FIGS. 10 and 11 . 
   As  FIG. 12  shows, the finished front end  11 . 5  of the beaker is held by the tool  65 , and a tool  70  tapers the end section  18  in the area of the cut-off front face  15  so that the diameter of the cover  10 . 7  in this area is reduced. In the process, the cover  10 . 7  is supported in the receiver  19  of the tool  70 . The crimped end  17  in the area of the front face  11 . 6  not only prevents sharp edges but, together with the tapered end section  18  of the shell  12 . 5 , is used for stabilizing the shaped cover  10 . 7 , so that tensions caused by tensions in the material cannot result in an uncontrolled contraction of the material and impairment of the surface of the cover  10 . 7 . 
   It is thus possible to produce in a cost-effective way and without worsening the shining surface a one-piece cover  10 . 7  from a special steel circular blank  10  in  FIG. 1 , which is made of a material which can be deep-drawn, as shown in  FIGS. 13 to 15 . 
   Here,  FIG. 13  shows a vertical section through the finished cover  10 . 7  with the crimped drain  17  on the inclined front face  11 . 6 , with the hole  13 . 2  and the tapered end section  18  at the cut-off front end  15 . The sectional view also shows the wall thickness of the cover  10 . 7 , which is obtained by a material which is approximately 1 to 1.2 mm thick, but can compulsorily also have different thicknesses, caused by the various processing steps. 
     FIG. 14  shows the view into the hollow space formed by the cover  10 . 7 , which is used as a receiver for the end of a motor vehicle exhaust pipe, from the direction of the front face  15 . 
   Finally, a portion of the crimped circular end  17  is shown in an enlarged view in  FIG. 15 .