Patent Publication Number: US-2022219223-A1

Title: Punching and clinching of metal sheets

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2020/100252 filed Mar. 27, 2020, which claims priority to DE 102019114050.1 filed May 27, 2019, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a method for the punching and clinching of metal sheets. 
     BACKGROUND 
     The joining of metal sheets by punching and clinching is known as a variant of the clinching method. With this method, a hole is created in one metal sheet and a region of a metal sheet placed over it is pressed into this hole, resulting in a joint between the two metal sheets. Further metal sheets can be added. 
     This well-known method is unsuitable for particularly thin metal sheets, such as metal sheets with a thickness of 0.35 mm and below. At such low thicknesses, there is insufficient overlap between the individual metal sheets to ensure an adequate joint strength. 
     SUMMARY 
     The object of the disclosure is therefore to provide a method through which metal sheets can be reliably jointed to one another, in particular even when the metal sheets are thin. 
     This object is achieved by the method described herein. The claims contain advantageous configurations. 
     In the method for the punching and clinching of metal sheets according to the disclosure, the metal sheets to be joined are divided into two stacks of metal sheets. A hole is created in the metal sheets of the first of the two stacks, for example by punching. In particular, this can be done individually for each of the metal sheets of the first stack. In any case, the holes of the metal sheets are congruent within the stack. 
     A contour is cut into each metal sheet of the second stack of the two stacks of metal sheets. This can be done individually for each metal sheet of the second stack. The metal sheets of the second stack lie on the metal sheets of the first stack. A region of each metal sheet of the second stack of metal sheets is then deformed in a stack direction, i.e., in the direction of the underlying metal sheets of the first stack and, if necessary, also of metal sheets of the second stack already lying on the first stack. Due to the deformation, the deformed region of a metal sheet, viewed in perpendicular to the stack direction, comes to lie next to the regions of underlying sheets. In particular, the deformed region of a metal sheet of the second stack can penetrate into the hole formed in the metal sheets of the first stack. 
     The deformed region of a metal sheet of the second stack is also determined by the contour cut into the sheet. The deformation can be done individually for each metal sheet of the second stack. The cutting of the contour into a metal sheet of the second stack and the deformation of the region of this second sheet can be done in one operation by a correspondingly shaped punch. At least the region to be deformed of the metal sheet of the second stack closest to the first stack must be deformed to such an extent that part of the deformed region comes to lie next to each metal sheet of the first stack, i.e., the deformed region must completely pass through the first stack through the holes of the metal sheets of the first stack. 
     Because the first stack comprises a plurality of metal sheets in which a hole is formed, a deformed region of one or a plurality of metal sheets of the second stack can penetrate sufficiently far into the hole present in the first stack to provide sufficient overall overlap with the metal sheets of the first stack, thereby providing sufficient strength for a reliable joint between the sheets. In this way, even thin metal sheets can be joined together, since the small thickness of the individual metal sheets is compensated for by the stacking of the metal sheets in the first stack and the fact that a region of at least one metal sheet of the second stack completely penetrates the first stack as explained above. In particular, metal sheets with a thickness of 0.35 mm and below can also be joined in this way, at least down to 0.1 mm or even 0.05 mm in thickness. 
     In a preferred embodiment, the metal sheets of the second stack are plastically deformed during deformation in such a way that an interlocking results between the respective deformed region of a metal sheet of the second stack and at least one underlying metal sheet. The metal sheet below can be a metal sheet of the first stack or a metal sheet of the second stack. 
     In one embodiment, the hole introduced into the metal sheets of the first stack has an elongated shape with a reduced width at the center. 
     In one embodiment, the contour cut into the metal sheets of the second stack corresponds to part of a contour of the hole. This is advantageous for deforming the region of the metal sheet of the second stack to be deformed into the first stack. 
     The disclosure also includes arrangements made of sheet metal which have been joined by the method described herein. Such arrangements are used, for example, and without limiting the disclosure thereto, in rotors of electrical machines or in cores of transformers. Depending on the design of the particular arrangement, the person skilled in the art must select the points at which the sheets are joined by the method according to the disclosure. Given the method according to the disclosure, the person skilled in the art has the freedom to use thinner metal sheets in the design of the respective arrangement than can be joined by punching and clinching according to the state of the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure and the advantages thereof are explained in more detail below with reference to the accompanying schematic drawings. 
         FIG. 1  shows a sectional view through an arrangement of metal sheets joined according to the disclosure. 
         FIG. 2  shows a plan view of an arrangement of metal sheets joined according to the disclosure. 
     
    
    
     The drawings merely represent exemplary embodiments of the disclosure. The drawings are in no way to be interpreted as a restriction of the disclosure to the exemplary embodiments shown. 
     DETAILED DESCRIPTION 
       FIG. 1  shows an arrangement of metal sheets  11 ,  12 ,  13 ,  21 ,  22 ,  23 . The metal sheets  11 ,  12 ,  13  form the first stack  1  of metal sheets for the purposes of this application, the metal sheets  21 ,  22 ,  23  form the second stack  2  of metal sheets for the purposes of this application. In a connecting region  3 , a hole  4  is cut into the metal sheets  11 ,  12 ,  13  of the first stack  1 , and the regions  31 ,  32 ,  33  of the metal sheets  21 ,  22 ,  23  of the second stack  2  are deformed in such a way that they can penetrate this hole  4 . In particular, the region  31  of the metal sheet  21  completely penetrates the hole  4  and is therefore adjacent to all the metal sheets  11 ,  12 ,  13  of the first stack  1  in the connecting region  3 . The deformation of the regions  31 ,  32 ,  33  occurs in the direction of a stack direction  110 , which forms a normal direction to the undeformed metal sheets stacked on top of one another. A thickness  8  of a metal sheet  11  is also indicated. 
       FIG. 2  shows a plan view of the arrangement  100  from  FIG. 1 , the stack direction  110  being directed into the plane of the drawing here. Correspondingly, a part of the uppermost metal sheet  23  and its deformed region  33  are shown. The cross-sectional shape of the hole  4 , perpendicular to the stack direction  110 , corresponds to the plan view of the region  33 . The deformation of the regions  31 ,  32 ,  33  corresponding to this shape is achieved by cutting contours  5  into the metal sheets  21 ,  22 ,  23  which correspond to the shape of the hole  4 . The contours  5  do not form a closed curve, and no cut is made in the region of the deformation edges  6 . The hole  4  (and accordingly the deformed region  33 ) extends along a direction  120 . In the embodiment shown, the hole  4  is elongated, its dimension in the direction  120  being greater than any of its dimensions perpendicular to the direction  120  in the plane of the metal sheet. Along the extension of the hole  4  in the direction  120 , a width  41 , i.e., an extension perpendicular to the direction  120 , of the hole  4  is reduced at the center, i.e., is smaller than a width  42  of the hole  4  at another position along the direction  120 . In the embodiment shown, the hole  4  has a symmetrical, fitted shape. The reduced width of the hole  4  and the deformed regions  31 ,  32 ,  33  favors a plastic deformation of the deformed regions  31 ,  32 ,  33  and thus a more reliable joining to the metal sheets  11 ,  12 ,  13  of the first stack  1 . 
     LIST OF REFERENCE NUMBERS 
     
         
         
           
               1  First stack 
               2  Second stack 
               3  Joining region 
               4  Hole 
               5  Contour 
               6  Deformation edge 
               8  Thickness 
               11 ,  12 ,  13  Metal sheet 
               21 ,  22 ,  23  Metal sheet 
               31 ,  32 ,  33  Deformed region 
               41  Width 
               42  Width 
               100  Arrangement 
               110  Stack direction 
               120  Direction