Abstract:
A combination of a thrust washer and lubrication baffle adapted for a press fitting installation into lubrication chamber of a universal joint cross-member journal. The thrust washer and lubrication baffle incorporate one or more lubrication grooves, facilitating the flow of lubricant between the surfaces of the cross-member and bearing cap. Elastomeric properties of the thrust washer eliminate the need for grinding of the journal surfaces to desired tolerances, while incorporation of lubrication grooves into the thrust washer surface eliminates the need for pressing of lubrication grooves directly into the journal ends prior to hardening or heat treating.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0002]     Not Applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates generally to universal joints having cross-member journals provided with internal lubrication channels which open at the ends of the journals to provide for replenishment of lubricant in bearing cups within which the journals are pivotally supported in respective yoke members, and in particular, to a washer and lubrication baffle configured for press-fitting retention within an enlarged end portion of the lubrication channel.  
         [0004]     Typically, within the cross-members or trunnions of a universal joint, the lubrication channels intersect at a central location, adjacent an external lubrication fitting, whereby lubricant can be introduced to the universal joint when required, as shown in U.S. Pat. No. 4,103,512 to McElwain, et al. The lubricant introduced to the central location of the universal joint typically flows radially outward towards the ends of the cross-member journals through the individual lubrication channels. During operation, the rotational movement of the universal joint about an axis perpendicular to the cross-members generates centrifugal forces which assists the outward flow of lubricant to the bearing cups.  
         [0005]     When rotation of the universal joint is stopped, one or more of the journals may be disposed in a vertically upward orientation, such that the force of gravity acts to draw lubricant back downward from the bearing cups and into the lubrication channels. Upon resumption of rotational motion, the associated bearing caps may be left with little or no lubricant, resulting in higher frictional forces and undesired wear.  
         [0006]     In addition to the use of lubricant to reduce frictional wear between the cross-member ends and bearing caps, manufacturers often dispose a thrust washer as a buffer between the inner surface of the bearing cap and the cross-member or trunnion end, such as is shown in U.S. Pat. No. 6,264,566 B1 to Nieman et al., or in U.S. Pat. No. 5,813,916 to Lentini, et al. During manufacture, these thrust washers are installed in the bearing caps prior to placement over the cross-member ends, using spacers to ensure proper location. The corresponding faces of the cross-member ends are ground in a machining operation to ensure a desired tolerance for the thrust washers, and are pressed to provide for one or more lubrication grooves facilitating a flow of lubricant between the thrust washer and the cross-member end.  
         [0007]     Accordingly, it is an object of the present invention to overcome the potential problems associated with lubricant drainage from the proximity of the bearing cups in a universal joint while simultaneously eliminating one or more grinding and machining steps from the universal joint manufacturing process.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     Briefly stated, the present invention provides a combination of a thrust washer and lubrication baffle adapted for a press fitting installation into an enlarged lubrication passage of a universal joint cross-member or trunnion. The thrust washer and unitary lubrication baffle incorporates one or more lubrication grooves, facilitating the flow of lubricant between the surfaces of the cross-member and bearing cap. Elastomeric properties of the thrust washer eliminate the need for grinding of the cross-member ends to desired tolerances, and the incorporation of lubrication grooves into the thrust washer surface eliminates the need for pressing of lubrication grooves directly into the cross-member ends prior to hardening or heat treating.  
         [0009]     The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0010]     In the accompanying drawings which form part of the specification:  
         [0011]      FIG. 1  is a plan view of a prior art universal joint cross member;  
         [0012]      FIG. 2  is a side sectional view of a washer baffle of the present invention;  
         [0013]      FIG. 3  is a top plan view of the washer baffle of  FIG. 2 ;  
         [0014]      FIG. 4  is a bottom plan view of the washer baffle of  FIG. 2 ;  
         [0015]      FIG. 5  is an enlargement of a portion of  FIG. 4 , illustrating a vertically aligned rib for press-fit attachment to a cross-member;  
         [0016]      FIG. 6  illustrates the placement of a washer baffle of  FIG. 2  in a cross member; and  
         [0017]      FIG. 7  is a sectional view of a washer baffle of  FIG. 2  press fitted to a cross-member of a universal joint. 
     
    
       [0018]     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.  
         [0020]     Turning to  FIG. 1 , a conventional Hookes-type universal joint cross-member or trunnion is shown generally at  10 . The cross-member  10  consists of four equidistantly spaced journals  12  disposed about a central body  14 . A lubricant channel  16  extends axially through each journal  12 , from a common central point C, to an open-ended lubrication chamber  18  adjacent a radially outward end  20  of each journal  12 . At the central point C in the central body  14 , one or more lubricant access passages  22  are provided for the introduction of a lubricant into the lubricant channels  16 .  
         [0021]     Each lubrication chamber  18  is defined by an enlarged diameter portion of the associated lubrication channel  16  having a generally frustoconical radially inner surface  24  receiving the lubrication channel  16 , and cylindrical sidewalls  26 . The radially outer end of the lubrication chamber  18  is open, and includes a chamfered peripheral edge  28  transitioning between the cylindrical sidewalls  26  and the outward end  20  of the journal  12 .  
         [0022]     Turning to  FIGS. 2-4 , an washer baffle combination of the present invention is shown generally at  100 . The washer baffle consists of a thrust washer portion  102 , and an associated baffle portion  104  adapted for press-fitting into the lubrication chamber  18  of a universal joint journal  12 . Preferably, the thrust washer portion  102  and the associated baffle portion  104  are of a unitary elastomeric construction. One suitable material from which the washer baffle combination may be formed using conventional plastic forming techniques is a nylon elastomer identified as DuPont 70G33L, and sold under the “Zytel” brand name by E. I. duPont de Nemours &amp; Co. of Wilmington, Del. Those of ordinary skill in the art will recognize that other materials, not limited to elastomers, may be utilized in the construction of the washer baffle combination  100  of the present invention, provided that necessary tolerances for wear, temperature, and elasticity are met.  
         [0023]     As best seen in  FIG. 3 , the thrust washer portion  102  of the washer baffle  100  defines an annular surface substantially corresponding to the dimensions of the radially outward end  20  of a journal  12 . Disposed in at least the upper surface of the thrust washer portion  102  are a plurality of equidistantly spaced lubricant grooves  106  radiating outward from a central axis X of the thrust washer portion  102 . Optionally, lubricant grooves  106  may be provided in the lower surface of the thrust washer portion  102  as well.  
         [0024]     Associated with the thrust washer portion  102 , the baffle portion  104  is disposed concentrically about the central axis X, perpendicular to the lower surface of the thrust washer portion  102 . The baffle portion  104  is defined by a pair of concentric cylindrical elements  108 A and  108 B joined together by an annular base  110 . Cylindrical element  108 A defines the outer cylindrical surface of the baffle portion  104 , and is preferably contiguous with the thrust washer portion  102 . As best seen in  FIG. 5 , the outer surface of the cylindrical element  108 A preferably includes a plurality of ribs  111  aligned parallel to the central axis X. Each rib  111  is configured to provide a press fit engagement with an inner surface of the journal lubrication chamber  18 . Cylindrical element  108 B defines an inner cylindrical surface of the baffle portion  104 , as well as an open ended axial lubrication delivery passage  112 . The annular base  110  joins the concentric cylindrical elements  108 A and  108 B opposite the thrust washer portion  102 , defining an annular lubrication retaining volume  114  concentric with the axial lubrication delivery passage  112 . Preferably, the annular base  110  and the cylindrical element  108 B are contiguous with the cylindrical element  108 A, however, those of ordinary skill in the art will recognize that the components of the washer baffle combination  100  may be formed discretely and joined in conventional manners to provide the equivalent functionality of contiguously formed components.  
         [0025]     Turning to  FIGS. 6 and 7 , a press-fit insertion of the thrust washer baffle combination  100  axially into the lubrication chamber  18  of a journal  12  is shown. As the thrust washer baffle combination  100  is press-fitted to the lubrication chamber  18 , ribs  111  ensure sufficient engagement between the outer surface of the cylindrical element  108 A and the surfaces of the lubrication chamber  118 , retaining the thrust washer baffle combination therein in a centered position. Upon complete insertion into the lubrication chamber  118 , the underside of the thrust washer portion  102  is seated against the journal outward end  20 , and the axial lubrication delivery passage  112  is disposed coaxially with the lubrication channel  16  to receive a flow of lubricant there from. Elastomeric properties of the thrust washer portion  102  function to provide a limited range of tolerance for dimensional variations in the journal  12  and journal outward end  20 , eliminating the need to grind surfaces of the journal  20  to precise tolerances during a manufacturing process.  
         [0026]     Once the thrust washer baffle combination  100  is seated in the lubrication chamber  18  of a journal  12 , as shown in  FIG. 7 , a bearing cup  200  is fitted over the thrust washer portion  102  and journal outward end  20 . The bearing cup  200  is retained in a limb  202  of a joint yoke by a snap ring  204 . Needle roller bearings  206  are disposed between the outer circumferential surface of the journal  12  and the inner circumferential side wall of the bearing cup  200 . An annular seal  208  in a carrier  210  retains lubricant and excludes contaminants from the inside of the bearing cap  200 .  
         [0027]     During operation of a universal joint including one or more thrust washer baffle combinations  100  of the present invention, lubricant flows radially outward from the center of the universal joint cross-member  10  along the respective lubrication channels  16 , towards the journal outer ends  20 . When the lubricant flow enters the lubrication chamber  18 , outward flow is restricted by the annular base  110  to flow through the open ended axial lubrication delivery passage  112 , where it is delivered to the journal outer end  20 . From the journal outer end  20 , the lubricant flow continues between the various surfaces of the thrust washer portion  102 , along the equidistantly spaced lubricant grooves  106  to provide lubrication to the needle bearings  206  and other wear surfaces. When rotational motion of the universal joint stops and the flow of lubricant reverses, such as due to the influence of gravity, a volume of lubricant is retained in the annular volume  114 , and prevented from returning to the lubricant channel  16 , thereby ensuring an adequate lubricant supply at the journal outer end  20  upon a resumption of rotational motion.  
         [0028]     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.