Patent Publication Number: US-2007122232-A1

Title: Ball joint assembly

Description:
BACKGROUND OF INVENTION  
      The present invention relates generally to ball joint assemblies.  
       FIG. 1  illustrates a prior art ball joint assembly  10 , also called a ball and socket joint. This ball joint assembly  10  includes a stud  12  having a ball portion  14  between a pair of shank portions  16 . The ball portion  14  engages a bearing  18  of a socket  20 . A socket shell  22  surrounds and supports the bearing  18 . Grease seals  24  engage each end of the socket shell  22  and shank portions  16  to define a grease cavity  26 . Annular retaining rings  36  and annular washers  38  provide biasing forces to the grease seals  24  to assure that an adequate seal is maintained.  
      In this ball joint assembly  10 , a central bore  28  extends through the ball portion  14  and the shank portions  16 . The central bore  28  includes washer mounting counter-bores  30  at either end. A pair of washers  32  each include a mounting lip  34  that mounts into its corresponding mounting counter-bore  30  and is secured therein by an interference fit. In order to assure an adequate interference fit, the stud  12  and washers  32  must be machined to tight tolerances at the locations where the interference fit occurs. This tight tolerance machining is more expensive than is desirable for fabricating and assembling the ball joint assembly  10 . Moreover, the stud  12  and washers  32  require a certain minimum hardness in order to account for the high contact stresses at the locations of the interference fit. Again, the cost is more than is desirable.  
     SUMMARY OF INVENTION  
      According to an aspect of the invention, there is provided a ball joint assembly including a stud having a ball portion adjacent to a shank portion and a central bore extending through the stud, with the shank portion having an end. The ball and joint assembly also includes a bearing mounted about the ball portion, a shell mounted about and securing the bearing to the ball portion, and a washer having a central hole concentric with the central bore and a mounting recess mounted about the end of the shank portion.  
      According to another aspect of the invention, there is provided a ball joint assembly for use with a vehicle suspension. The ball and joint assembly may include a stud having a ball portion between a first and a second shank portion, with the first shank portion having a first end and the second shank portion having a second end; and a central bore, extending through the stud and adapted to receive a rod therethrough for operative engagement with vehicle frame flanges. The ball and joint assembly may also include a bearing mounted about the ball portion; a shell mounted about and securing the bearing to the ball portion, with the shell being adapted to operatively engage a suspension link; a first washer having a first central hole concentric with the central bore and a first mounting recess mounted about the first end of the first shank portion; and a second washer having a second central hole concentric with the central bore and a second mounting recess mounted about the second end of the second shank portion.  
      According to another aspect of the invention, there is provided a ball joint assembly including a stud having a ball portion adjacent to a shank portion and a central bore extending through the stud, with the shank portion having an end and the ball portion adapted to operatively engage a bearing. The ball and joint assembly may also include a washer having a central hole concentric with the central bore and a mounting recess mounted about the end of the shank portion, and an adhesive between the end of the shank portion and the mounting recess of the washer.  
      The present invention advantageously provides a ball joint assembly having washers adequately mounted and retained on a stud, while—contrary to the prior art—not requiring an interference fit or generating high contact stresses. This allows for the use of a lower hardness material and avoids the need to machine tight tolerance features where the washers mount to the stud.  
      Another advantage of an embodiment of the present invention is that the washers, since they do not require machining to tight tolerances, can be cold formed, without requiring post forming machining operations.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross section of a prior art ball joint assembly.  
       FIG. 2  is a cross section of a ball joint assembly according to the present invention. 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIG. 2 , a ball joint assembly, indicated generally at  110 , is shown. The ball joint  110  may be used in various applications, such as, for example, to secure a suspension link  150  to flanges  152  of a vehicle frame while allowing relative rotation and pivotal movement between the link  150  and flanges  152 .  
      The ball joint assembly  110  includes a stud  112  having a ball portion  114  between a pair of shank portions  116 . The stud  112  may be made of steel, although other suitable materials may be employed if so desired. A central bore  128  extends through the stud  112 . A rod  154  with threaded end portions (not shown), for example, may extend through the central bore  128  and engage holes  156  in the vehicle frame flanges  152 . A pair of nuts (not shown) may thread onto the threaded end portions to secure the rod  154  to the flanges  152 .  
      The ball portion  114  of the stud  112  engages a bearing  118 . The bearing  118  may be made of a plastic, such as nylon, or some other suitable material. The bearing  118  mounts in and is supported by a socket  120  of a socket shell  122 . The socket shell  122  may be made of steel, although other suitable materials may be employed, if so desired. The suspension link  150  may include a passage  158  within which the socket shell  122  is secured.  
      A pair of grease seals  124  each engage a respective end of the socket shell  122  and corresponding shank portions  116  to define a pair of grease cavities  126 . Annular retaining rings  136  and annular washers  138 —or, alternatively ring springs—bias the grease seals  124  into contact with the socket shell  122  and shank portions  116 . The grease seals  124  may be made of rubber or some other suitable elastomeric material. The purpose of the seals  124  is to prevent lubricant (such as grease) from leaking from the ball joint assembly  110  and also to prevent contaminants from entering.  
      A pair of washers  132  each mount between a respective one of the ends  117  of the shank portions  116  and a corresponding one of the vehicle frame flanges  152 . The washers  132  may be made of steel, although other suitable materials may be employed if so desired. Each washer  132  includes central holes  142  that are axially aligned with the central bore  128  in the stud  112  in order to receive the rod  154  therethrough.  
      Each washer  132  also includes a mounting recess  140  that mounts about the end of its respective shank portion  116 . The fit between the mounting recesses  140  and their respective shank portions  116  may be transition-to-slight interference. Adhesive  148  is applied between the contact areas of the washers  132  and shank portions  116  to enhance retention of the washers  132  on the shank portions  116 . The shank portions  116  may include chamfers  144  about their outer corners that mate with corresponding features  146  in the mounting recesses  140  of the washers  132 .  
      Since an interference fit is not required, the shaft portions  116  and washers  132  do not need to be machined to tight tolerances, thus reducing the overall cost of the ball joint assembly  110 . Moreover, the area of contact between the stud  112  and washers  132  is relatively large, and, in addition, without the need for an interference fit at these locations, the minimum hardness required for the material of the ball stud  112  and washers  132  can be relatively less than otherwise might be required. Again, this allows for a reduced overall cost of the ball joint assembly  110 .  
      While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.