Patent Publication Number: US-2002010027-A1

Title: Wide-angle constant velocity joint with oil-bath lubrication, for universal transmissions

Description:
DESCRIPTION  
       [0001] In transmissions used in agricultural machinery and for other applications, widespread use is made of wide-angle constant velocity joints, operating at angles up to approximately 80°. Up to the present time, these constant velocity joints have been designed for grease lubrication, requiring a continuous replacement of the lubricant, which is rapidly dispersed in the environment. This leads to environmental problems, high costs due to the consumption of lubricant, manual operations and down time, and risks of serious damages to the joints, regular lubrication of which is essential for the life of the joint.  
       [0002] The invention achieves the object of overcoming all the drawbacks mentioned above, which are well known to those skilled in the art. These and other objects and advantages will be made clear by the following text.  
       [0003] The constant velocity joint in question essentially comprises flexible protective means which are sealingly engaged with the input and output members of the joint, and which delimit a space which surrounds the joint and which can contain liquid lubricant, or lubricant which becomes fluid in normal conditions, in order to provide oil-bath lubrication of the joint.  
       [0004] An advantageous embodiment is designed for a constant velocity joint of the aforesaid type, which comprises two yokes forming the input and output members of the joint, two cross journals and a central core forming a sliding housing in a transverse geometrical plane for a securing member for the ball ends of the two yokes; constant velocity joints of this kind are currently equipped for grease lubrication. According to the invention, however, the joint can comprise, on the central core and on the base of each of the two yokes, annular tracks for a sealed fit to the edges of protective bellows means, which delimit a space which surrounds the joint and can contain liquid lubricant for oil-bath lubrication. This solution is directly derived from the conventional configuration of a wide-angle joint with grease lubrication.  
       [0005] Other characteristics of the invention are specified by the attached subsidiary claims. 
     
    
    
     [0006] The invention will be more clearly understood from the description and the attached drawing, which shows a practical and non-restrictive example of the invention. In the drawing,  
     [0007]FIG. 1 shows a general view of a telescopic transmission shaft with a constant velocity joint;  
     [0008]FIGS. 2 and 3 show an enlarged detail of FIG. 1, with the constant velocity joint in the in-line and angled configuration respectively;  
     [0009]FIGS. 4 and 5 show a yoke component in isolation, in an enlargement of the cross section in FIG. 2 and in the cross section through V-V in FIG. 4;  
     [0010]FIG. 6 shows in isolation a central core of the constant velocity joint, in partial section;  
     [0011]FIGS. 7 and 8 show local views through VII-VII and VIII-VIII of FIG. 6;  
     [0012]FIGS. 9 and 10 show in isolation a discoid securing member of the joint, in a front view and in a cross section through X-X in FIG. 9;  
     [0013]FIG. 11 shows in isolation a protective bellows, in section;  
     [0014]FIGS. 12, 12A and  13 ,  13 A show, in isolation, two flat rings to be combined with the protective bellows, each in a view and in an enlarged detail;  
     [0015]FIGS. 14 and 15 show a tightening band, in a front view and in a view through XV-XV in FIG. 14;  
     [0016]FIGS. 16 and 17 show in isolation a cross journal, in partial section and in an enlarged detail; and  
     [0017]FIGS. 18 and 19 show a screw plug for the supply of lubricating oil, in section through XVIII-XVIII and in an axial view. 
    
    
     [0018] According to the illustrations in the attached drawing, and with initial reference to FIGS. 1 and 2, the number  1  indicates a telescopic shaft, formed by two tubular components  1 A and  1 B extending in the form of a telescope, with an end joint  3  at one end and a wide-angle constant velocity joint  5  at the other end; the telescopic shaft  1  is provided with a protective sleeve  7 . The whole is essentially a known embodiment.  
     [0019] The constant velocity joint  5  is of the wide-angle type; it comprises a yoke member  9 , for input to the joint or output from it, this yoke having a grooved seat  9 A for coupling to a transmission member with which the constant velocity joint is combined. The member  9  is integral (see FIG. 3 and subsequent figures) with the base  10 A of a yoke  10  forming part of the said joint  5 . The telescopic shaft  1  is engaged with a member  12  which is integral with the base  14 A of a yoke  14  forming part of the said constant velocity joint. The two yokes  10  and  14  (see, in particular, FIGS. 4 and 5) are extended by terminal cross-pieces  10 C,  14 C, from which ball ends  10 B,  14 B extend, the two ball ends being opposite each other. The constant velocity joint also comprises a central core  16  (see also FIG. 6), which consists of two parts which are essentially symmetrical with respect to a plane which is transverse with respect to the overall axis of the joint in question when the components for input to and output from the members  9  and  12  are aligned with each other; the said two parts of the member  16  are welded together at  16 S. The central core  16  has two opposing extensions  16 A, the extensions of each pair forming rotary seats for a cross journal  18  (see also FIGS. 16 and 17); each cross journal  18  is additionally pivoted on the corresponding yoke  10  or  14  described above. The arrangement described above forms a typical constant velocity joint, which is completed with a securing member  20  (see also FIGS. 9 and 10) extending in the form of a disc  20 B having at its center a circular cylindrical through hole  20 A, which houses the opposing ball ends  10 B and  14 B of the two yokes  10  and  14 ; the discoid securing member  20  is housed in such a way to be able to slide in a housing  24  which is formed by two parallel and opposing walls  24 A,  24 B of the two components of the central core  16 ; these two components are suitably machined and then welded at  16 S to slidably engage the discoid securing member  20 ,  20 B. The whole of what has been described up to this point is an example of a shaft with a constant velocity joint of a known type, of the class which can provide transmission even in conditions of considerable angulation, as shown in FIG. 3.  
     [0020] According to the invention and the illustrated example, the disc part  20 B of the said discoid member  20  has (see also FIGS. 9 and 10) a number of through holes  26  together with radial ducts  28  which extend between the periphery of the discoid member  20 B and the central through seat  20 A of the said securing member  20 . The walls  24 A and  24 B—which delimit the sliding housing  24  in a plane transverse with respect to the axis of the central core  16  for the disc part  20 B of the securing member  20 —have (see also FIGS.  6  to  10 ) suitably distributed recesses  30  and  32  respectively. These recesses  30  and  32 , together with the through holes  26  and the radial ducts  28 , allow the circulation of a liquid lubricant intended for the lubrication of the surfaces, which slide with respect to each other, of the housing  24  and of the disc  20 B, and of the through seat  20 A and of the ball ends  10 A,  10 B and  14 B, which are housed in the said through seat.  
     [0021] Each of the bases  10 A and  14 A of the yokes  10  and  14  (see also, in particular, FIGS. 4 and 5) has a track  110 A,  114 A which is essentially cylindrical, with an intermediate annular channel such as that indicated by  110 B, for the purposes stated below; a further channel  110 C is also provided adjacently to the annular track  110 A of the base  10 A of the yoke  10 , and a similar channel is provided adjacently to the track  114 A of the base  14 A of the yoke  14 . Correspondingly, in the central core  16  there are provided (see, in particular, FIG. 6) two cylindrical annular tracks  116 A and  216 A, on the sides facing the yokes  10  and  14  respectively, each track having a central annular channel  116 B,  216 B; the diameters of the tracks  116 A and  216 A are greater than the diameters of the tracks  110 A and  114 A.  
     [0022]FIG. 11 shows in isolation a protective bellows  36  made from elastomeric material, and particularly from a rubber resistant to lubricating oils; one of these bellows  36  is designed to be fitted on the tracks  110 A,  116 A; a similar protective bellows  38  is designed to be fitted on the annular tracks  114 A of the base  14 A of the yoke  14  and on the track  216 A,  216 B of the central core  16 .  
     [0023] With regard to the details of the bellows  36  (see FIG. 11), this is made in the form of a bellows, and therefore has a certain number of external annular grooves  36 A. The said bellows  36  has an annular terminal edge  36 B having an internal diameter matching that of the annular track  110 A, and a second terminal edge  36 C having an internal diameter matching that of the annular track  116 A. The terminal edge  36 B is provided with an internal metal ring  40 , while the terminal edge  36 C has an internal annular projection  42 . The protective bellows  36  is fitted so that it extends between the base  10 A of the yoke  10  and the central core  16 ; in particular, the edge  36 B with the metal ring  40  is fitted onto the track  110 A, a sealing ring being housed in the channel  110 B and interacting with the inner surface of the metal ring  40 . The terminal edge  36 C of the protective bellows  36  is engaged with the annular track  116 A, the internal projection  42  being housed in the annular channel  116 B. To ensure the engagement of the edge  36 C with the annular track  116 A, a tightening band  44  is applied (see also FIGS. 14 and 15) and is provided with a screw clamp  46  of a known type, by means of which the tightening is carried out. A fitting of an entirely similar type is provided for the protective bellows  38 .  
     [0024] Flat rings  48 ,  50  (see also FIGS.  12  to  13 A), extending approximately in planes transverse with respect to the axis of the joint in its aligned configuration, are fitted in the annular external grooves such as those indicated by  36 A,  36 A 1 ,  38 A,  38 A 1  of the protective bellows  36  and  38 , before the said bellows are fitted; these flat rings  48  and  50  are made from synthetic resin (such as nylon or the like), have a radial widths approximately equal to the depths of the external grooves of the bellows, and are designed to provide a considerable degree of stability of the bellows configuration of the individual protective bellows  36  and  38 , and to prevent the direct contact of the rubber surfaces of the opposing sides of the grooves. The flat rings  50  (see also FIGS. 13 and 13A), which are present at least on the annular grooves  36 A 1  and  38 A 1  closest to the edges  36 B and  38 B which are fitted on the bases  10 A and  14 A respectively of the yokes  10  and  14 , are extended with two annular spacers  50 A,  50 B (FIGS. 13 and 13A) which are thinner than the thicknesses of the other flat rings  48 , and are therefore more flexible, to permit the greater cyclical curvature which they undergo in the conditions of greater angulation of the constant velocity joint  5 .  
     [0025]FIGS. 16 and 17 show one of the cross journals  18 , whose ends are typically provided with needle bearings  18 A or the like, with an external rolling track formed by cups  18 B. According to the invention, the conventional annular seals which are usually housed in the seats  18 C to retain the dense lubricant (grease) are dispensed with for the oil-bath lubrication of these bearings.  
     [0026] It is clear from the above description that the constant velocity joint, indicated in a general way by  5  and extending essentially between the bases  10 A and  14 A of the yokes  10  and  14  which are integral with the input and output members such as those indicated by  9  and  12 , is protected by the two bellows  36  and  38 ; this is because these two bellows  36  and  38  form a completely enclosed space around the constant velocity joint  5 , and this space can have a part of its volume (particularly a part which is of the order of 60%) occupied by a liquid lubricant, or by a lubricant which when heated takes on a fluidity comparable to that of the liquid lubricant; thus the constant velocity joint can be lubricated essentially by the “oil-bath” system, rather than by a conventional grease lubrication system.  
     [0027] This overcomes the drawbacks of grease lubrication, which requires continual intervention for replacement of the lubricant grease, to compensate for the losses of grease which occur regularly during use and which constitute an environmental problem, as well as representing a considerable cost and entailing the risk of damage due to a possible failure to perform maintenance operations. By contrast, the liquid lubricant which is contained and retained in the space delimited by the protective bellows  36  and  38  does not require continual interventions for replenishment and does not cause any dispersion to the exterior, with evident advantages in terms of economy and environmental protection.  
     [0028] In order to introduce the liquid lubricant into the space delimited as indicated above by the two bellows  36 ,  38 , a through hole is provided in the base of one of the yokes and in particular, according to the drawing, in the base  10 A of the yoke  10 , and is sealed by a screw plug  52  which is easily accessible through the axial grooved cavity  9 A of the terminal member  9 , which is provided with a conventional quick-release coupling  9 X for a grooved terminal of a shaft of the transmission of which the constant velocity joint  5  forms part.  
     [0029] It should be noted that the presence of the through holes  26  and of the radial channels  28  in the discoid member  20 B, and the presence of the recesses  32  and  30  in the walls  24 A and  24 B of the housing  24 , provide considerable possibilities for the circulation of the liquid lubricant, for lubricating the disc  20 B of the securing member  20  which is movable in the sliding housing  24 , and for lubricating the ball ends  10 B and  14 B of the yokes  10  and  14  in their common through seat  20 A of the securing member  20 , and in the roller bearings  18 A; the whole being achieved without any need for forced circulation but simply with the aid of the movements which are imparted to the constant velocity joint both by its rotation and by the angulation of the components of the joint with respect to each other. In particular, no maintenance or frequent inspection of the oil level are required. It is sufficient to make occasional brief inspections of the bellows  36 ,  38  for easy identification of possible oil leaks.  
     [0030] Because of its configuration, the constant velocity joint can also be produced to operate with grease lubrication; it is simply necessary to provide the described constant velocity joint—after removal of the bellows  36  and  38 —with the conventional greasers on the core  16  and with annular seals in the seats  18 C and other conventional arrangements for this type of joint. It is possible to dispense with some machining operations, such as those for forming the seats for the engagement of the terminal edges of the bellows  36  and  38  on the yokes and on the central core.  
     [0031] In order to provide an accident prevention device, according to current safety regulations, around the rotating parts consisting of the components  10 ,  14  and  16  and the bellows  36  and  38 , an annular channel  54  is provided (see FIGS. 1, 2,  3  and  6 ) in the central core  16  for an annular support  56  provided with a greaser  58  (FIG. 2), which is fairly easily accessible for periodic injections of lubricating grease, with a known type of arrangement, the greaser  58  being designed to lubricate only the annular groove  54 , in order to permit relative angular movement between the rotating core  16  and the annular support  56 , which for reasons of accident prevention must not rotate.  
     [0032] As shown in FIGS.  1  to  3 , the assembly consisting of the constant velocity joint and its two protective bellows  36  and  38  is protected by a further protective bellows  60 , which is fitted, in a known arrangement  62 , on the protective sleeve  7  of the telescopic tube  1 . This protective bellows  60  is engaged with the annular support  56 , with which a further guard  64  of the rigid type is also engaged. Two flat truncated conical guards  66  and  68  can be engaged with the bases  10 A and  14 A of the yokes  10  and  14 , as shown in the drawing, to complete the accident prevention device and to prevent contact between the internal components; in respect of this characteristic, reference should also be made to the angulated configuration shown in FIG. 3.  
     [0033] It is to be understood that the drawing shows only an example provided solely as a practical demonstration of the invention, and that this invention can be varied in its forms and arrangements without departure from the scope of the guiding principle of the invention. The presence of any reference numbers in the attached claims has the purpose of facilitating the reading of the claims with reference to the description and to the drawing, and does not limit the scope of the protection represented by the claims.  
     [0034] For example, it is also possible to apply the invention by providing in place of the two bellows  36 ,  38 —a single bellows extending between the two bases  10 A and  14 A of the yokes  10  and  14 , one at least of which is suitably oversized to meet the requirements of fitting. This single bellows, in an intermediate position, can be supported on the periphery of a core suitably modified from that indicated by  16 , and should be provided externally with a rigid component equivalent to that indicated by  56 ; the whole assembly will have equivalent functions to those of the components  56 ,  60  and  64 .