Abstract:
The present invention provides a ball joint for use in interconnecting a pair of components to accommodate relative angular movement therebetween. The ball joint includes a socket assembly and a hybrid ball stud. The socket assembly includes a cup-shaped housing defining a cavity therein and an insert disposed within the housing cavity and which defines a spherical ball socket. The hybrid ball stud includes a standard bolt and a polymeric insert attached to, or encapsulating, the head of the bolt to define a spherical ball or a partial spherical ball. The polymeric insert is adapted to be retained in the ball socket. The bolt is a high-volume commercially-available component having a threaded shank segment and a head segment which is over-molded or fitted with the polymeric insert. As such, an inexpensive hybrid ball stud is provided for use in ball joints.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to ball joints and, more particularly, to a hybrid ball stud for a ball joint comprised of a bolt and a spherical polymeric component secured to the head of the bolt to define a ball segment of the ball stud. 
     2. Discussion 
     As is known, motor vehicles are equipped with suspension systems for absorbing road shock and other vibrations while providing a smooth and comfortable ride for the vehicle occupants. In virtually all vehicular suspension systems, ball joints are used to interconnect suspension components for accommodating changes in angularity therebetween. In general, most conventional ball joints include a ball stud, a ball socket, and a housing. Typically, the ball stud is a forged metallic component having an elongated shank segment and a ball segment. The shank segment of the ball stud is connected to one suspension component and the housing is fixed to the other suspension component. The ball segment of the ball stud is retained in a spherical cavity formed in the ball socket which, in turn, is mounted in the housing. To facilitate angular movement of the ball stud relative to the housing, the sphericity and surface profiles of the ball segment must be highly precise. These component characteristics have conventionally required the utilization of expensive and time-consuming secondary machining and finishing operations. 
     As an alternative to forged ball studs, it is known to provide a ball joint equipped with a ball stud having a polymeric layer molded over the ball segment. See, for instance, U.S. Pat. Nos. 2,862,740, 2,905,492 and 3,091,486. As a further alternative, some ball studs have a polymeric ball mounted to one end of a threaded stud. See, for example, U.S. Pat. Nos. 2,999,709, 3,023,038, 3,941,495 and 5,697,142. Finally, it is also known to surround a portion of a threaded stud with a partially spherical polymeric insert and which engages a radial flange extending from the stud. See, for example, U.S. Pat. Nos. 2,823,055, 2,846,252, 2,937,895, 2,953,401, 3,091,486, 4,334,795 and 4,629,352. In each case, a molded component is used as the ball segment to limit or eliminate the secondary surface finishing operations associated with conventional forged ball studs. 
     Although various composite assemblies have been proposed for constructing a ball stud to avoid the machining and heat treating requirements associated with forged ball studs, none have been successful in significantly reducing production costs. Therefore, it would be desirable to provide a ball joint having a composite ball stud requiring minimal labor and processing costs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a ball joint for use in interconnecting a pair of components to accommodate relative angular movement therebetween. The ball joint includes a socket assembly and a hybrid ball stud. The socket assembly includes a cup-shaped housing defining a cavity therein and an insert disposed within the housing cavity and which defines a spherical ball socket. The hybrid ball stud includes a standard bolt and a polymeric insert attached to, or encapsulating, the head of the bolt to define a spherical ball or a partial spherical ball. The polymeric insert is adapted to be retained in the ball socket. The bolt is a high-volume commercially-available component having a threaded shank segment and a head segment which is over-molded or fitted with the polymeric insert. As such, an inexpensive hybrid ball stud is provided for use in ball joints. 
     As a further feature of the present invention, a partially spherical polymeric member may be molded on, or attached to, the shank segment of the bolt such that the polymeric member and the spherical head segment of the bolt combine to serve as the ball segment of the ball stud. 
     According to another feature of the present invention, a toroidal polymeric member is molded on, or attached to, the head of the bolt to serve as the ball segment of the ball stud. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order to appreciate the manner in which the advantages and objects of the invention are obtained, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings only depict preferred embodiments of the present invention and are not therefore to be considered limiting in scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
     FIG. 1 is a sectional view of a ball and socket assembly equipped with a hybrid ball stud made in accordance with one preferred embodiment of the present invention; 
     FIG. 2 is a side elevational view of the hybrid ball stud shown in FIG. 1; 
     FIG. 3 is a side elevational view of a hybrid ball stud made in accordance with another embodiment of the present invention; 
     FIG. 4 is a sectional view of the hybrid ball stud of FIG. 3; 
     FIG. 5 is a side elevational view of a hybrid ball stud made in accordance with yet another embodiment of the present invention; 
     FIG. 6 is a sectional view of the ball stud of FIG. 5; 
     FIGS. 7 and 8 are side elevational views of additional alternative embodiments for the hybrid ball stud of the present invention; 
     FIG. 9 is a side elevational view of another embodiment of the present invention; 
     FIG. 10 is a sectional view of the hybrid ball stud shown in FIG. 9; and 
     FIGS. 11 through 14 illustrates further alternative embodiments of the hybrid ball stud of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In general, the present invention is directed toward a ball joint for accommodating relative angular movement between a pair of suspension components such as, for example, a stabilizer bar and a control arm in a vehicle suspension. The ball and socket assembly of the present invention includes a hybrid ball stud adapted to replace most conventional ball studs and to work in conjunction with ball joints to provide reduced cost without impairing performance of the vehicle suspension. Thus, the ball joint of the present invention may be utilized with a wide variety of systems and is not intended to be limited to the particular application described herein. 
     Referring initially to FIG. 1, a ball and socket assembly, hereinafter referred to as ball joint  10 , is shown to be of the type adapted to interconnect a pair of suspension members and accommodate relative angular motion therebetween. In general, ball joint  10  includes a hybrid ball stud  12  and a socket assembly  14 . Socket assembly  14  is shown to include a housing  16 , an end cap  18  enclosing one end of housing  16 , and a polymeric liner  20  retained in an open-ended cavity  22  of housing  16 . Liner  20  is formed to include a spherical socket  24 . 
     Hybrid ball stud  12  includes a bolt  26  having a shank segment  28  on which external threads  30  are formed and a head segment  32 . As will be detailed, bolt  26  is a standard “off-the-shelf” component commonly referred to as a round head bolt. As such, head segment  32  of bolt  26  is hemispherical and defines an outer surface  34  that is adapted to engage the inner wall surface of socket  24  in liner  20 . Hybrid ball stud  12  is further shown to include a hemispherical component  36  that is made of a suitable polymeric material. Hemispherical component, hereinafter referred to as polymeric insert  36 , has an aperture defining an inner surface  37  which surrounds a proximal end portion of shank segment  28  adjacent to head segment  32  such that its planar top surface  38  is juxtapositioned adjacent to a planar underside surface  40  of head segment  32 . Polymeric insert  36  has an outer surface  42  adapted to engage the inner surface of socket  24  in liner  20 . Preferably, the radius of polymeric insert  36  is identical to that of head segment  32  so as to cooperatively define a spherical ball  44  which is retained in socket  24  for angular movement relative to housing  16  and liner  20 . 
     Referring again to FIG. 1, ball joint  10  is shown interconnecting two relatively movable components. In particular, an arm segment  46  of a stabilizer bar  48  is shown to have shank segment  28  of bolt  26  extending through a bore  50  formed therein. A nut  52  is threaded onto shank segment  28  and acts as a stop flange which is positioned against a planar face surface  54  of arm segment  46 . With threaded shank segment  28  extending through bore  50 , a lock nut  56  is tightened onto threads  30  and into engagement with an opposite planar face surface  58  of arm segment  46 . Accordingly, bolt  26  of ball joint  10  is secured to stabilizer bar  48 . In addition, housing  16  is fixed to a rod or link  60  which is suitably fixed to another suspension component or a frame component of the motor vehicle. If ball joint  10  is part of an end link, then a second ball joint is attached to the opposite end of link  60  and, in turn, its bolt is secured to a control arm. Those skilled in this art will appreciate that this particular arrangement is merely exemplary of but one of the many applications to which ball joint  10  can be employed. 
     Polymeric insert  36  can be molded insitu to surround the proximal end of shank segment  28  of bolt  26 . In the alternative, insert  36  may be preformed and include a through bore that is slid over the distal end of shank segment  28  with surface  37  then being adhesively bonded to the proximal end of shank segment  28  and/or surface  38  being adhesively bonded to underside surface  40  of head segment  32 . In either case, hybrid ball stud  12  is fabricated or assembled using a standard round-head bolt  26 . 
     As a further alternative, FIGS. 3 and 4 illustrate a ball stud  12   a  adapted for use in ball joint  10  and having a segmented polymeric insert  36   a  mounted to round-head bolt  26 . In particular, segmented polymeric insert  36   a  is identical to insert  36  except that is has been cut into sections  62 . In this application, sections  62  are preformed and then adhesively bonded to one another along section lines  64 , and/or bonded to bolt  26  along mating radial surfaces  38   a  and  40  as well as along the proximal portion of shank segment  28 . Outer surface  42   a  of insert sections  62  are spherical such that insert  36   a  and head segment  32  define spherical ball  44   a . Preferably, insert  36   a  consists of two quadrant sections  62 , however any number of sections is contemplated. 
     Referring now to FIGS. 5 and 6, a ball stud  12   b  for use in ball joint  10  is shown to have a polymeric ball insert  36   b  secured to a round-head square-neck bolt  26   b . Bolt  26   b  is similar to bolt  26  except that shank segment  28  includes a four-sided neck flange  70  adjacent to underside surface  40  of round-head segment  32 . Those components or features of ball stud  12   b  that are similar to those previously disclosed are identified by common reference numbers. Neck flange  70  serves as an anti-rotation feature which assists in preventing rotation of ball insert  36   b  relative to shank segment  28 . As previously disclosed, insert  36   b  can be molded insitu or, in the alternative, be a preformed as a unitary component or as a series of sections which are adhesively secured to bolt  26   b  to cooperate with head segment  32  to define a spherical ball  44   b . Again, a standard round-head square neck bolt  26   b  is used to fabricate or assemble ball stud  12   b . As a further option, any other standard bolt configurations having a non-square neck flange (i.e., hexagonal) can be substituted for bolt  26   b.    
     Referring now to FIG. 7, a ball stud  12   c  for use in ball joint  10  is partially shown to include a polymeric insert  36   c  secured to a round-head bolt  26   c  having ribs or serrations  72  formed on the proximal end of shank segment  28  in adjacent to head segment  32 . Serrations  72  assist in preventing rotation of insert  36   c  relative to head segment  32  of bolt  26   c . Insert  36   c  can be molded insitu or can be preformed as a unitary component, or a series of preformed sections, adhesively bonded to mating surfaces on bolt  26   c.    
     FIG. 8 partially illustrates a ball stud  12   d  for use in ball joint  10  including a polymeric insert  36   d  secured to a head segment  74  and a shank segment  76  of a T-head bolt  78 . Head segment  74  has an arcuate portion  80  integrated with a rectangular hub  82 . Insert  36   d  is formed such that the radius of its outer surface  42  matches and is contiguous with outer surface  84  of head segment  74 . 
     Referring now to FIGS. 9 and 10, a ball stud  12   e  for use in ball joint  10  is disclosed as having a polymeric insert  86  molded over an end portion of a standard hexagon head bolt  88 . In particular, bolt  88  has a shank segment  90  and a hex-shaped head segment  92 . Head segment  92  and a portion of shank segment  90  are encapsulated by insert  86 . As is typical, shank segment  90  has external threads  94 . As an alternative, insert  86  can be segmented into distinct section, such as optionally indicated by joint line  96  (in phantom), and adhesively bonded to bolt  88 . Hex-shaped head segment  92  functions to prevent rotation of insert  86  relative to bolt  88 . While polymeric insert  86  is shown to be spherical, it is to be understood that insert  86  can have any geometric shape provided with an outer surface adapted to matingly engage at least a portion of the ball joint socket for facilitating angular motion therebetween. 
     FIG. 11 illustrates a ball stud  12   f  which is similar to ball joint  12   e  except that spherical polymeric insert  86   f  is segmented into sections  98   a  and  98   b  with a snap-lock type connection provided along joint line  100 . In particular, sets of lugs  102  are formed on section  98   a  and are adapted for receipt in sockets  104  formed in section  98   b  to define spherical ball  86   f . In addition, circular grooves  106  are formed in outer surface  108  of ball  86   f , either transversely or parallel to shank segment  90  of bolt  88  to permit lubricating grease to be packed therein. 
     FIG. 12 illustrates a hybrid ball stud  12   g  which is generally similar to ball stud  12   e  of FIGS. 9 and 10 except that spherical polymeric insert  110  includes a recessed portion  112  defining an opening  114  and a circumferential cantilevered spring flange  116 . This resilient spring flange arrangement functions to spring load ball stud  12   g  in socket  24  of ball joint  10 . 
     FIG. 13 illustrates another hybrid ball stud  12   h  having an insert  120  molded on, or affixed to, head segment  92  of hexagon bolt  88 . Insert  120  includes a body portion  122  and a hemispherical nobbin portion  124 . Nobbin is adapted for retention in a partially spherical spring seat formed in the ball socket while an outer surface  126  of body portion  122  is adapted to be retained in a modified socket  24  of liner  20 . 
     FIG. 14 illustrates another hybrid ball stud  12   i  having a toroidal polymeric insert  130  molded on, or affixed to, head segment  92  of hexagon bolt  88 . Insert  130  is doughnut-shaped and has an outer surface  132  adapted to engage the inner surface of socket  24  in liner  20  of ball joint  10 . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims.