Motor housing and method of making the same
United States Patent Schmitt et al.  
 1 Apr. 22, 1975 MOTOR HOUSING AND METHOD OF MAKING THE SAME lnventors: Jakob Schmitt, Oberwurzbach; Willy Voit, St. lngbert, both of Germany Assignee: Robert Bosch G.m.b.l1., Stuttgart.  
 Germany Filed: June 15, 1973 Appl. No.: 370,412  
 Foreign Application Priority Data July 25, 1972 Germany 2236408 US. Cl 113/120 UE; 29/521 Int. Cl. H02k 15/14 Field of Search 113/120 R, 116 R, 116 D, 113/116 P, 120 UE,120 Y, 7 R, 120 F, 120 HA, 120 K, 120 NA, 120 V, 120 Y, 116 F. 116 G, 116 QA, 116 CC; 29/415, 521, 416, 438, 439; 220/75, 76; 310/42, 89, 85-88 [56] References Cited UNITED STATES PATENTS 2,544,266 3/1951 Kennedy 113/120 UE 3,214,803 11/1965 Amt 113/116 R 3.273.601 9/1966 DeGain 29/521 3,653,116 4/1972 Lov et all 29/243.52 3,732,616 5/1973 Massrodonato et al. 29/521 Primary E.\&#39;uminerRichard .l. Herbst Attorney, Agent, or Firm-Flynn &amp; Frishauf ABSTRACT A housing wall of sheet metal is bent around an end piece which engages the wall thus bent around it near one edge of the tube thus formed in such a way as to be held fast at least against axial displacement. The firmness of engagement is provided by perforations in the wall into which tongues of the end piece may penetrate. As the bending of the wall around the end piece is completed, a dove tail joint of the meeting edges of the wall completes the continuity of the wall.  
 2 Claims, 3 Drawing Figures MOTOR HOUSING AND METHOD OF MAKING THE SAME This invention relates to two-pieced pot-shaped housings of the type used for small electric motors and the method of their manufacture.  
  One well-known method to manufacture pot-shaped housings is to use a blank made of expensive deepdrawing sheet metal and to shape it in the desired way with one or more sets of drawing tools and dies designed for use with each other. This relatively expensive and wasteful procedure must take into account a comparatively high percentage of rejects. because the housing. which is commonly used as the magnetic return yoke. must be made of relative thick material.  
  On the other hand. the manufacture of similar housings out of separate end and wall pieces is also known in which the end piece is either welded to the wall piece or peened over it. Such housings are indeed cheaper. but they often fail to meet the technical requirements with regard to stability and splash proofing. In addition. they do not meet the requirements for centering the end piece of the housing. on which most commonly the bearing for the armature shaft of the motor is seated. It is an object of the invention to overcome these disadvantages of composite housings without recourse to expensive one-piece manufacture.  
 SUBJECT MATTER OF THE PRESENT INVENTION Briefly. the wall piece for the housing is made ofa flat strip which is bent around the end piece while at the same time the end piece engages holding means provided on the strip which. when this assembly is complete. prevent at least axial displacement of the end piece relative to the housing wall. The holding means are perforations near one edge of the wall piece into which projections on the circumference of the end piece engage. The housing wall is closed on itself to form a tube. usually cylindrical. the closing seam of which can conveniently and effectively be provided by an interlocking array of tabs or tongues on the edges thereby joined together. this joint being readily effected as the bending of the wall piece around the end piece is completed.  
  The invention will be described by way of example with reference to the accompanying drawings. wherein:  
 FIG. I is a perspective view of the housing end piece;  
  FIG. 2 is a plan view of the stamped strip which can be bent to form the housing wall. and  
  FIG. 3 is an elevation view of a completed motor housing according to the invention.  
  The housing end piece shown in FIG. 1 is an essentially circular disc in the center of which a seat .11  
 for the bearing of the armature shaft of the motor has been embossed. At equal intervals around the edge 12 of the disc 10 are three radially directed tongues 13 projecting beyond the edge 12.  
  In FIG. 2 is shown a substantially flat strip I4. along the edge region 15 of which perforations 16 are provided. On one side edge 17 of the strip 14 are three dovetail type tabs 19, whereas the other side edge 18 of the strip 14 has indentations 20 shaped to match the dovetail form of the tabs I9. The length L of the projections 13 is smaller than the thickness D of the strip 14.  
  In order to make a motor housing from the disc type end piece I0 and the flat sheet metal strip 14. the strip I4 is bent progressively around the disc 10 in such a way that the tongues 13 penetrate into the perforations I6 of the strip. The perforations 16. in cooperation with the projections 13. provide holding means by which the end piece is axially and radially secured in the now tube shaped housing wall. The distances between the perforations l6 must accordingly correspond to the arc length between two neighboring projections I3 along the disc edge 12. Theperforations 16 must furthermore be of such dimensions that the tongues l3 of the disc 10 can easily penetrate into the perforations 16 during the bending process.  
  The side edges 17 and 18 which are alongside each other after the bending process are interlocked with each other during the latter part of the bending process as the result of pressing the dovetail tabs I9 of the edge I7 into the matching indentations 20 of the edge 18. where they are ultimately tamped fast.  
  The end piece I0 is rolled into the housing wall I4 at the same time as the end piece I0 engages the holding means 16. 21 or 22. Such housings are therefore very simple to manufacture. They are cheaper than housings drawn from a single sheet of metal. but they correspond closely to such housings in their technical properties. Stability of structure. splash proof effectiveness and shaft centering of the housings of this invention are better than in the case of the known housings in which the end piece is welded or pecned onto the housing wall.  
  A further advantage of the invention arises from the fact that the choice of the material thickness for the end piece and the housing wall can be respectively suited to the particular requirements. Thus. for example. the housing wall thickness can be determined by the magnetic flux requirements. whereas for the choice of thickness for the end piece the mechanical stress arising in operation of the motor can be taken into consideration.  
  The method of manufacture of this invention can also be applied when instead of a disc shaped end piece. a U-shaped bearing bracket is to be held fast in an iron member serving as the magnetic return path yoke which is rolled into shape.  
  The method of this invention is useful both for cylindrical housings and for other pot-shaped housings such. for example. as housings of rounded square or triangular contour. What is essential is that the housing should be put together in a simple way out of two pieces which. for example may be stamped out of a strip of sheet metal. in such a way that the housing wall can be rolled around the end piece in a single operation.  
  The two edges that are next to each other after the bending operation are connected to each other in a locking manner. For this purpose. at least on one edge of the strip at least one dovetail tab is provided which during the bending operation will be pressed into an edge indentation in the other edge of the strip which is of matching dovetail form.  
  Because the wall piece is provided with perforations into which projections of the end piece penetrate. a form of mechanical locking results which opposes both axial displacement and also rotation of the end piece with respect to the wall.  
 We claim:  
  I. A method of producing pot-shaped housings. of the type used to house small electric motors. from a housing end piece and a housing wall piece. comprising the steps of: I  
 making the end piece so as to provide a plurality of radially projecting tabs on its periphery:  
 making the housing wall piece in the form of a flat strip with holding slots in which said tabs of said end piece may engage when said wall piece is bent around said end piece:  
 bending said wall piece around said end piece while sequentially engaging said end piece tabs in said holding slots so that by the time said wall piece is fully bent around said end piece. said end piece is already fully held against axial and rotational displacement with respect to said wall piece. and  
 completing the bending of said wall piece around said