Abstract:
The joint comprises two spiders ( 10, 14 ) and a central core forming a cavity for sliding movement in a transverse plane for two constraint members ( 120 ) with seats ( 120 A) for the spherical heads ( 10 B;  14 B) on the ends of the two forks ( 10, 14 ); a divider ( 150 ) divides said cavity into two housings ( 124 ) for the two constraint members ( 120 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a wide-angle constant-velocity joint for drive shafts and the like, improved to give a reduction in the stresses to which the internal members of conventional joints are usually subjected. These and other objects and advantages will become clear in the course of the following text. 
     DESCRIPTION OF RELATED ART 
     The present wide-angle constant-velocity joint is of the type comprising two forks forming the input and output members of the joint, two spiders, and a central core forming a cavity for sliding movement in a transverse plane for means forming constraint seats for the spherical heads on the ends of the two forks. 
     SUMMARY OF THE INVENTION 
     According to the invention, the joint comprises a divider which divides said cavity into two housings for two substantially symmetrical constraint members forming the respective seats for the spherical heads of said forks; each of the two constraint members slides simultaneously with the other member between said divider and the wall of the corresponding one of the two parts of said central core or a laminar ring that bears against said wall. 
     The two constraint members are joined together by two central protrusions that slide one inside the other and the divider has a large central window inside which said protrusions are able to move about. 
     Communication holes for lubrication of said seat are formed between each housing and the seat of the constraint member housed in said housing. 
     The two housings communicate through holes, to allow the supply of lubricating grease from a single grease nipple. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A clearer understanding of the invention will be provided by the description and the attached drawing, the latter showing a practical, non-restrictive example of the invention. In the drawing: 
         FIGS. 1 and 2  show a constant-velocity joint of an essentially conventional kind, in longitudinal, section and in two positions which it is capable of assuming; 
         FIGS. 3 and 4  show an improved constant-velocity joint according to the invention in longitudinal section and in two positions; 
         FIG. 5  shows a partial enlargement of  FIG. 3 ; 
         FIGS. 6 and 7  show in isolation one of two components constructed in accordance with the invention, in end view and in section on VII—VII as marked in  FIG. 6 ; and 
         FIG. 8  is an exploded view in axial section of three internal components of a central core. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The accompanying drawing ( FIGS. 1 and 2 ) illustrates a wide-angle constant-velocity joint of an essentially conventional kind. Reference  1  denotes a tubular component of a telescopic shaft ending in a wide-angle constant-velocity joint  5 . The telescopic shaft  1  may be fitted with a protective sheath. The constant-velocity joint  5 , of the wide-angle kind, comprises a power coupling member  9 , for input to or output from the joint, forming a grooved seat  9 A for connection to a drive member with which the constant-velocity joint is combined. Integral with the member  9  is the base  10 A of a fork  10  forming part of said joint  5 . The telescopic shaft  1  is linked to a member  12  integral with the base  14 A of a fork  14  forming part of said constant-velocity joint. Each of the two forks  10  and  14  comprises a terminal crosspiece  10 C,  14 C, from which a spherical head  10 B,  14 B extends, the said two spherical heads being opposite each other. The constant-velocity joint also includes a central core  16  that is made in two parts which are basically symmetrical about a plane at right angles to the overall axis of the joint considered with the input and output components of the members  9  and  12  in line with each other. The said two parts of the member  16  are connected together by welding at  16 S, or by other means, such as bolts. The central core  16  has two opposing pairs of projections  16 A, the projections of each pair forming seats of rotation for a corresponding spider, and each spider  18  is further hinged to the corresponding fork  10 ,  14 , respectively, described above. 
     The arrangement described above gives a typical constant-velocity joint, which is further completed by a constraint member  20  which is of a discoidal shape with a central circular cylindrical through seat  20 A in which the opposing spherical heads  10 B,  14 B of the two forks  10  and  14  are housed. The discoidal constraint member  20  is housed movably inside a discoidal housing  24 , which is formed by two opposing parallel walls  24 A,  24 B formed by the two components of the central core  16 . These two components are machined appropriately and then welded at 16S or otherwise connected together to retain the discoidal constraint member  20 ,  20 B while allowing it to move. The central core  16  is provided with a grease nipple  28 , which reaches the discoidal housing  24  via the discoidal constraint member  20 . This member  20  has at least one radial hole  30  to allow communication between the housing  24  and the through seat  20 A. This allows lubrication of the sliding surfaces  24 A,  24 B and the discoidal constraint member  20 , and between the through seat  20 A and the spherical heads  10 B,  14 B. Laminar rings  40  are usually interposed between the surfaces  24 A and  24 B and the two faces of the discoidal constraint member  20  to limit the losses of lubricating grease, which must first lubricate between the heads  10 B or  14 B and their seats. 
     So far an example of a shaft with a constant-velocity joint of known type has been described, of the type designed to transmit drive even at large angles, such as the angle X° shown in  FIG. 2 , the purpose of which is well known. 
     In conventional solutions, such as that defined above and illustrated in  FIGS. 1 and 2 , fierce stresses are set out due to the simultaneous action of both spherical heads  10 C,  14 C rubbing against the discoidal constraint member  20  and against the seat  20 A. This creates wrenching and wear, necessitating continual and efficient lubrication between parts in relative motion, and limits the total life of the joint. 
     This invention solves these problems. As illustrated in  FIG. 3  and ff, where the same references in  FIGS. 1 and 2  are used for the corresponding parts, the single constraint member  20  is replaced with two substantially symmetrical separate constraint members  120 , each having a seat  120 A in which the corresponding spherical head  10 B or  14 B of the two forks  10  and  12 , respectively, is slidingly accommodated. The central core  16  still consists of two substantially symmetrical parts, shaped to form a discoidal housing similar to the housing  24  of the embodiment shown in  FIGS. 1 and 2 . When the two parts of the central core  16  are connected together (for example by the weld 16S), a discoidal divider  150  (see also  FIGS. 6 ,  7  and  8 ) with a large central circular window  151  is held peripherally between them. This divider  150  separates the abovementioned discoidal housing (similar to the housing  24 ) into two separate housings  124  communicating with each other through said window  151  and through a number of through holes  152 . The grease nipple  28  therefore supplies both housings  124 . Each of said two housings accommodates one of the two constraint members  120 , which can slide in a guided manner between the corresponding surface of the divider  150  and the corresponding wall  124 A or  124 B or the corresponding laminar ring  40 , if present. Each of said constraint members  120  has a number of radial holes  130  (for example three) which allow communication between the housing  124  and the corresponding seat  120 A, to allow lubrication between the seat  120 A and the corresponding head  10 B or  14 B. One of the two constraint members  120  (that on the right-hand side viewing the drawing) has a cylindrical protrusion  120 C with a large through hole  120 E into which the holes  130  lead. The other constraint member  120  has in turn a smaller cylindrical protrusion  120 F designed to fit into the through hole  120 E. When the components  120 ,  120  and  150  are brought together and the two parts of the core  16  welded at  16 S, the protrusions  120 C and  120 F engage one inside the other in a sliding manner and can move about inside the window  152  of the divider  150  during the identical and simultaneous movements of the two constraint members  120  inside the housings  124 . A through hole  120 G in the protrusion  120 F allows communication between the two seats  120 A of the two constraint members  120 . 
     As a result of the above arrangement, with the separation provided by the divider  150  and with the doubling up of the conventional constraint member  20  into two constraint members  120  constrained by each other in only a limited degree by the protrusions  120 C and  120 F, there is a reduction in the stresses which are otherwise very high between the members of the joints, especially those in relative sliding movement and in particular between the heads  10 B,  14 B and the corresponding seats  120 A, which now belong to two separate components. The resulting joint has a much longer life than conventional constant-velocity joints. 
     It will be understood that the drawing shows only an example given purely as a practical demonstration of the invention, which latter may be varied in its shapes and arrangements without thereby departing from the scope of the concept on which the invention is based. The presence of any reference numbers in the appended claims is purely for the purpose of facilitating the reading of the claims with reference to the description and drawing, and does not limit the scope of protection represented by the claims.