Abstract:
A method for making a frustro-conical ring collar by providing a metal band, helically winding the band, cutting off a length of the band which corresponds to one lead of the helix, axially acting on the two ends of the band length to place them in facing positions, welding together the aligned ends to form a cylindrical ring, an conferring a frustro-conical shape to the ring.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention concerns the production of ring collars of the type used in some diaphragm clutch mechanisms to provide an axial support to the diaphragm on the side opposite the axial support which is found at the bottom of the cover of such a mechanism. 
     These ring collars are in the shape of a truncated cone overall. 
     2. Description of the Prior Art 
     To produce ring collars it is possible, for example, to cut and stamp a metal blank. 
     But the corresponding production method leads, expensively, to large amounts of waste, notably on the inside of the ring collar obtained. 
     It is also possible to cut and stamp a tube. 
     But this production involves, in an equally expensive manner, the prior production of such a tube, and if this is a blind tube, there is still a considerable amount of waste at the corresponding end of the latter. 
     SUMMARY OF THE INVENTION 
     The object of the invention is a more economical production method. 
     Relating, therefore, to the production of a ring collar, this method is characterised in that, stating with a metal strip, this strip is wound helically, a length corresponding to one pitch of the helix is cut from this strip, the two ends of this length are acted upon axially in such a way that they are brought opposite one another, the two ends thus aligned are welded to one another so as to obtain a cylindrical ring, and this ring is formed into a truncated cone. 
     All these operation, which advantageously involve no waste, can advantageously be executed one after the other on the same machine. 
    
    
     The characteristics and advantages of the invention will moreover emerge from the description which follows, by way of example, with reference to the accompanying schematic drawings, in which: 
     FIG. 1 is a partial view in axial section of a clutch mechanism using a ring collar; 
     FIG. 2 is a partial view in axial section of this ring collar; 
     FIG. 3 repeats to a larger scale, the detail of FIG. 2 marked by an inset III on this FIG. 2; 
     FIGS. 4A,  4 B,  4 C are views in perspective illustrating three first phases of the production method according to the invention of this ring collar; 
     FIGS. 4D and 4E are plan views illustrating a subsequent phase of this method; 
     FIG. 5 is a plan view of the cylindrical ring obtained at this stage of this method; 
     FIG. 6A is a partial view of the end of this ring, illustrating an optional complementary phase of the method according to the invention; 
     FIG. 6B is a partial view in axial section of this ring, illustrating another optical complementary phase of the method according to the invention; 
     FIG. 6C is a view in axial section of the ring collar obtained at the end of the production method according to the invention; 
     FIG. 7 is a view in perspective illustrating an optional phase prior to the production method according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a clutch mechanism  10  having, in the form of overall annular parts, a cover  11 , by means of a transverse rim  12  of which it is designed to be connected to a reaction plate  13 , represented by broken lines in FIG. 1, a diaphragm  14  and a pressure plate  15 . 
     The diaphragm  14  itself has a peripheral part  16 , forming a Belleville washer, and a central part  17 , divided into radial fingers  18  by slits. 
     By means of its peripheral part  16 , the diaphragm  14  rests on the bottom  20  of the cover  11 , and bears against the pressure plate  15 , for forcing the latter in the direction of the reaction plate  13  and thus axially clamping a friction disc  21  inserted between this pressure plate  15  and this reaction plate  13 , as shown schematically in broken lines in FIG.  1 . 
     To provide axial support to the peripheral part  16  of the diaphragm  14  on the side opposite the bottom  20  of the cover  11 , a ring collar  22  is provided which itself finds axial support on the elements  23  acting circularly from place to place and fixed to the cover  11 . 
     Here these elements  23  are formed by lugs which, made in one piece with the bottom  20  of the cover  11 , starting from the central aperture of the latter, are duly folded at right-angles and the ring collar  22  rests on theses elements  23  by means of a washer  24 , which serves as a counter-tool when these elements  23  are folded and which prevents the ring collar  22  from being jammed in the folding bend of these elements. 
     The ring collar  22  is overall in the shape of a truncated cone. 
     By means of its larger-diameter periphery, it bears against the peripheral part  16  of the diaphragm  14 . 
     Here the corresponding edge  25  is duly profiled accordingly, with a broad rounded part. 
     By means of its smaller-diameter periphery, the ring collar  22  rests on the washer  24 . 
     Here its corresponding edge  26  is also duly profiled accordingly, with a broad rounded part. 
     The transverse section of the ring collar  22  therefore has, here, a specific profile. 
     This profile being well known, and not relating to the present invention, it will not be described in detail here. 
     For the production of the ring collar  22 , which extends continuously in a circle, the following method according to the invention can be implemented. 
     Starting with a metal strip  28 , FIG. 4A, this strip  28  is wound helically, FIG. 4B, and, first of all, a length 29 is cut from this strip  28  corresponding to one pitch of this helix, FIG.  4 C. 
     Secondly, FIG. 4D, the two ends  30 A,  30 B of this length 29, offset axially in relation to one another, are acted upon axially so that they are brought exactly opposite one another, as depicted in FIG.  4 E. 
     For example, as depicted schematically in FIGS. 4D and 4E, the two ends  30 A,  30 B of the length 29 are acted upon axially by means of the two movable arms  31 A,  31 B, of a clamp  32 , in the direction of the arrows F 1  in FIG. 4D, whilst buttressing this length 29, on the side diametrically opposite to these ends  30 A,  30 B, by means of the fixed arms  33 A,  33 B of another clamp  34 . 
     The two thus aligned ends  30 A,  30 B of the length 29 are then welded to one another, so as to obtain a cylindrical ring  35  as depicted in FIG.  5 . 
     Then it suffices to form this ring  35  into the shape of a truncated cone, for example by pressing. The required ring collar  22  is thus obtained as depicted in FIG.  6 C. 
     According to a first possible embodiment of the invention, a strip  28  having in transverse section the profile desired for the transverse section of the ring collar  22  to be produced is chosen as the starting strip, as depicted in FIG.  4 A. 
     In a variant, and as depicted in FIG. 7, a strip  28 ′ of rectangular transverse section is chosen as the starting strip and, prior to its winding in a helix, this strip  28 ′ is profiled according to the transverse section desired for the ring collar  22  to be produced. 
     For example, and as depicted in FIG. 7, this starting strip  28 ′ is engaged, in the direction of the arrow F 2 , between two profiling rolls  36  acting simultaneously on both of its faces. 
     At the exit of these profiling rolls  36  there is thus obtained the strip  28  having in transverse section the profile desired for the transverse section of the ring collar  22  to be produced. 
     The ring  35  inevitably having, along its welding generatrix  38 , a weld seam which projects both on its external surface and internal surface, this ring  35  is preferentially subjected, prior to its formation into a truncated cone shape, to deburring along this welding generatrix  38 . 
     Here, FIG. 6A, this deburring is effected using two wheels  39 ,  391 , one acting on the side of the external surface of the ring  35 , the other on the side of its internal surface, and duly profiled accordingly. 
     Finally, prior to forming the ring  35  as a truncated cone, its edges  25 ,  26  are also preferentially deburred, FIG.  6 B. 
     Here this deburring is effected using abrasive wheels,  40 ,  41 , one acting on its edge  25 , the other on its edge  26  and duly profiled accordingly. 
     Naturally, the present invention is not limited to the embodiment described and depicted but encompasses all variant embodiments.