Abstract:
A ball joint assembly ( 28 ) for a vehicular steering or suspension application includes a cap-like housing ( 42 ) in which is captured the articulating ball portion ( 32 ) of a stud ( 30 ). A shank ( 34 ) extends from the ball portion ( 32 ), outwardly from the housing cap ( 42 ), to provide a connection and anchoring interface for the suspension member ( 16 ) or other anchoring component. The connection interface with the anchoring suspension member ( 16 ) is characterized by a specially designed surface which is convenient to machine, provides increased surface-to-surface contact area, and provides additional advantages such as improved stress distribution and NVH benefits. A washer-like cone adaptor ( 54 ) mates with a specially formed adaptor interface region ( 48 ) on the stud ( 30 ). On its outer surface, the adaptor ( 54 ) has a broad tapering feature ( 56 ) designed to seat in a complementary-shaped receiving flare ( 58 ) in the anchoring suspension member ( 16 ). The mating contact region between the adaptor ( 54 ) and the stud ( 30 ) is formed with spherical or spheroidal curvatures, or by single or multiple step configurations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority to U.S. provisional application entitled Cone Adaptor For Ball Joint Studs, Tie Rods, Sway Bar Links And The Like having Ser. No. 60/718,708 and filed on Sep. 20, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to a ball and socket type joint of the type used in vehicular steering and/or suspension applications, and more particularly toward such a ball joint assembly for use in applications where one of the anchoring members, such as a steering knuckle or tie rod for example, is made from a relatively soft material like aluminum.  
         [0004]     2. Related Art  
         [0005]     Ball joints are typically used in vehicular applications where three-dimensional movement of a wheel, and in particular a steerable wheel, is required when a vehicle is turning and the suspension is accommodating movement over rough terrain. In the normal course of operation, ball joints are subjected to very high stresses. These stresses are transmitted through the stud of a ball joint assembly into the suspension member, which may be a steering knuckle, control arm, steering link, frame member or other feature.  
         [0006]     The recent emphasis on reducing vehicular weight is driving material selections toward lighter options. Sometimes, there is a motivation to substitute aluminum for traditional cast iron materials, even in the area of chassis and suspension components. Unfortunately, lighter materials are often softer than the heavier materials they replace, and therefore less suited to endure the localized and concentrated stresses which may arise during normal vehicular operations.  
         [0007]      FIGS. 9 and 10  illustrate two different prior art attempts to accomplish similar functionality for ball joint assemblies, and in particular studs which are intended to be anchored in relatively soft material like aluminum.  FIG. 9 , in particular, is intended to correspond to the design depicted in U.S. Pat. No. 6,527,468, the entire disclosure of which is hereby incorporated by reference. These designs are either difficult to produce on a high volume basis, or result in unacceptable attributes such as NVH issues and provide less surface-to-surface contact in the interface regions. By contrast, the subject invention as depicted in various embodiments in  FIGS. 1-8 , overcomes some or all of these issues and represents a significant improvement over prior art constructions.  
         [0008]     Accordingly, there is a need for an improved method of interconnecting a ball joint assembly to vehicular steering and suspension features to accommodate the anchor points being made from a softer material.  
       SUMMARY OF THE INVENTION  
       [0009]     The subject invention comprises a ball and socket joint assembly of the type used in vehicular steering and suspension applications in which an anchoring and control member is made from relatively soft material. The assembly comprises a stud having a ball portion on one end thereof and a shank extending therefrom. The shank includes a thread form for attaching the stud to an anchoring control member made from a relatively soft material. The shank includes an adaptor interface region between the ball portion and the thread form. An annular, loose piece adaptor is slidably disposed on the shank and matingly engages the adaptor interface region in abutting surface-to-surface contact therewith. The adaptor has a frustoconical exterior surface tapering inwardly toward the thread form, and an interior surface. The interior surface of the adaptor includes a generally spheroidal female surface configuration and the adaptor interface region of the shank has a complementary-shaped generally spheroidal male surface configuration. The generally spheroidal female and male mating surfaces provide enhanced stress distributions and load carrying capabilities with less adaptor-to-shank slippage in operation.  
         [0010]     According to another aspect of the invention, a ball and socket joint assembly is provided of the type used in vehicular steering applications in which an anchoring control member is made from relatively soft material. A stud has a ball portion on one end thereof and a shank extending therefrom. The shank includes a thread form for attaching the stud to an anchoring control member made from a relatively soft material. The shank includes an adaptor interface region between the ball portion and the thread form. An annular, loose piece adaptor is slidably disposed on the shank and matingly engages the adaptor interface region in abutting surface-to-surface contact therewith. The adaptor has a frustoconical exterior surface tapering inwardly toward the thread form, and an interior surface. The interior surface of the adaptor includes a generally cylindrical major side wall establishing a major inside diameter thereof and a generally cylindrical minor side wall, concentric with the major side wall, establishing a minor inside diameter thereof. The interior surface of the adaptor also includes at least one annular shoulder between the major and minor side walls. The adaptor interface region of the shank includes a generally cylindrical major shaft matingly received with the major side wall of the adaptor, a minor shaft matingly received within the minor side wall of the adaptor, and at least one annular shoulder between the major and minor shafts. The shoulder of the adaptor is pressed in face-to-face contact with the shoulder of the shank.  
         [0011]     Both aspects of the invention as set forth herein overcome the shortcomings and disadvantages present in prior art designs, by providing an improved construction for interconnecting a ball joint assembly to a vehicular steering and/or suspension feature to accommodate anchor points made from a softer material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein:  
         [0013]      FIG. 1  is a perspective view of an exemplary application for the subject ball and socket joint assembly wherein the steering knuckle is supported between upper and lower control arms made from a relatively soft material such as aluminum;  
         [0014]      FIG. 2  is a cross-sectional view taken generally along lines  2 - 2  in  FIG. 1 ;  
         [0015]      FIG. 3  is a front elevation view of a stud according to the subject invention showing an annular, loose piece adaptor operatively disposed thereon and depicted in cross-section;  
         [0016]      FIG. 4  is a perspective view of the annular, loose piece adaptor shown in quarter section;  
         [0017]      FIG. 5  is a view as in  FIG. 3  but depicting a first alternative embodiment of the geometric surface formations between the female and male mating surfaces of the stud and the adaptor;  
         [0018]      FIG. 6  is a view as in  FIG. 3  but showing a second alternative embodiment for the mating interface between the stud and adaptor;  
         [0019]      FIG. 7  is a view as in  FIG. 3  but depicting a third alternative embodiment of the adaptor interface region;  
         [0020]      FIG. 8  is a view as in  FIG. 3  but illustrating a fourth alternative embodiment of the abutting surface-to-surface contact region between the adaptor and the stud;  
         [0021]      FIG. 9  is a depiction of a prior art style stud and adaptor configuration; and  
         [0022]      FIG. 10  is another depiction of a prior art stud and adaptor configuration. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a vehicular steering and suspension assembly such as used in the front, dirigible wheels of a motor vehicle is generally shown at  12  in  FIG. 1 . Although the front suspension system  12  is shown here comprising upper  14  and lower  16  control arms interconnecting a steering knuckle  18 , it will be appreciated by those of skill in the art that the contemplated invention may find application in other steering and/or suspension components. For example, the invention, as will be described in multiple embodiments, may be deployed in not only steering knuckles and control arm interfaces, but also in steering linkages, frame member connections, and other articulating features.  
         [0024]     Returning to the illustrative application depicted in  FIG. 1 , a suspension system  12  is shown including a combined spring and dampening device  20  interconnecting the lower control arm  16  to interposing portions of the vehicle chassis or frame (not shown). The steering knuckle  18  includes a spindle  22  upon which a vehicular wheel assembly  24  is mounted, together with appropriate braking and bearing components as is well known to those of skill in this art. A steering arm  26  extends transversely from the steering knuckle  18 , ready to connect with an appropriate steering link (not shown). Although purely depicted for its illustrative value in  FIG. 1 , the steering suspension system  12  in this example includes components made from relatively soft material such as aluminum or other light-weight materials or alloys, as compared with the traditional steel and cast iron constructions. For example, the lower control arm  16  in this example is made from aluminum or an aluminum alloy having material properties and characteristics which are softer and more ductile than traditional iron and steel constructions. The suspension system  12  includes, in this example, a pair of ball joint assemblies, generally indicated at  28 , interconnecting the upper  14  and lower  16  control arms to the steering knuckle  18 , respectively.  
         [0025]      FIG. 2  represents a cross-sectional view of the ball joint assembly  28  as taken through the lower control arm  16 . Here, the ball joint assembly  28  is shown including a stud, generally indicated at  30 , having a ball portion  32  at one end thereof. A shank  34  extends from the ball portion  32 , and includes a thread form  36  for attaching the stud  30  to an anchoring control member made from a relatively soft material, which in this case is the lower control arm  16 . A washer  38  and nut  40  are advanced onto the thread form  36  for establishing the requisite tensile stress through the stud  30  to maintain a secure connection to the lower control arm  16  in use.  
         [0026]     A housing cap  42  surrounds the ball portion  32  of the stud  30  for providing an articulating interface therewith. The housing cap  42 , while shown in but one purely exemplary configuration in  FIG. 2 , is seated via a press fit operation into a corresponding receiving pocket in the steering knuckle  18 . A polymer liner  44  may, in some circumstances, be interposed between the housing cap  42  and the ball portion  32  as a bearing surface. A resilient dust boot  46  is shown extending between the housing cap  42  and the shank  34  for preventing contaminant infiltration into the articulating interface. Of course, many other constructions and designs of the housing cap  42  and other components such as the dust boot  46  may be implemented in conjunction with the novel features of this invention. It is necessary only that the housing cap  42  complement the ball portion  32  and thereby provide a full articulating joint which facilitates the three-dimensional movement necessary to accommodate wheel turning, suspension travel, and other mechanical linkage movements.  
         [0027]     Referring now to  FIGS. 3 and 4 , the stud  30  portion of the ball joint assembly  28  is shown including an adaptor interface region  48  between the ball portion  32  and the thread form  36 . An imaginary central axis A is shown as a center-line for the various surface features formed as a body of revolution. The adaptor interface region  48  includes numerous surface features and contours including a generally cylindrical collar  50  which, among other functions, may serve to receive the clamped lower end of the dust boot  46 , as depicted in  FIG. 2 . In addition, the adaptor interface region  48  includes a generally spheroidal male surface configuration  52  formed in the concave direction. Thus, the spheroidal male surface configuration  52  takes the appearance of an enlarged fillet transitioning the collar  50  down toward the thread form  36 .  
         [0028]     The adaptor interface region  48  of the shank  34  is designed to receive an annular, loose piece adaptor, generally indicated at  54 . The adaptor  54  is slidably disposed over the shank  34  and matingly engages the adaptor interface region  48  in abutting surface-to-surface contact therewith. The adaptor  54  has a frustoconical exterior surface  56  tapering inwardly toward the thread form  36 . Thus, as shown in  FIG. 2 , the frustoconical exterior surface  56  of the adaptor  54  seats within a complementary shaped flare  58  in the lower control arm  16 . The relatively shallow taper presented by the frustoconical exterior surface  56  of the adaptor  54  accommodates a distribution of loading stresses over a wider area of the lower control arm  16 . This thereby reduces the pressure applied to the anchoring lower control arm  16  via the tightened nut  40 . By reducing the contact pressure in this manner, the use of softer material such as aluminum and alloys thereof for the lower control arm  16 , or other suspension member or linkage, can be enabled.  
         [0029]     The adaptor  54  also includes an interior surface, opposite the frustoconical exterior surface  56 , which is characterized in this embodiment by a generally spheroidal female surface configuration  60 . The spheroidal female configuration  60  complements the spheroidal male configuration  52  of the shank  34  and establishes an abutting surface-to-surface contact therewith. The spheroidal female configuration  60  is shown in the convex direction, and cooperates together with the mating male surface to provide enhanced stress distributions and load carrying capabilities for the ball joint assembly  28 . The spherical or spheroidal surface curvatures also facilitate less adaptor-to-shank slippage in operation. The surface configurations are conducive to manufacturability, and also provide other benefits such as enhanced NVH characteristics and the like. The interior surface of the adaptor  54  further includes a generally cylindrical side wall  62  adjacent its generally spheroidal female surface configuration  60 . The side wall  62  matingly receives a lower portion of the collar  50  of the shank  34 , and provides enhanced seating and radial stress distributions between the two components.  
         [0030]     Referring now to  FIG. 5 , a first alternative embodiment of the subject invention is depicted, wherein like or corresponding parts are depicted using the same reference characters with the prefix “1.” In this embodiment, the adaptor  154  is identical in every respect to that described previously in connection with the preferred embodiment, but the side wall  62  is omitted. In this case, the spheroidal female configuration  60  receives 100% of the axial and radial loading vectors between the adaptor  154  and the stud  30 . In some applications, this design may be preferred.  
         [0031]     Turning now to  FIG. 6 , a second alternative embodiment of the subject invention is depicted, wherein like or corresponding parts to those described above are indicated using the same reference numerals together with the prefix “2.” In the embodiment of  FIG. 6 , the interior surface of the adaptor  254  is characterized by the generally spheroidal female surface configuration  260  having a generally concave formation, whereas the mating, generally spheroidal, male surface configuration  252  on the adaptor interface region  248  has a generally convex formation. Thus, it can be seen that  FIG. 6  represents a mere reversal of concave and convex features in the surface contact regions between the adaptor  254  and the adaptor interface region  248 . Accordingly, similar performance characteristics can be expected.  
         [0032]     In  FIG. 7 , a third alternative embodiment of the subject invention is depicted. In this example, like or corresponding parts to those previously presented are shown with like reference numerals preceded by the prefix “3.” In this example, generally spheroidal interface surfaces between the adaptor  354  and the adaptor interface region  348  are substituted with one or more step configurations. A single step configuration is illustrated in  FIG. 7 , wherein the interior surface of the adaptor  354  includes a generally cylindrical major side wall  362  establishing a major inside diameter. A generally cylindrical minor side wall  364 , concentric with the major side wall  362 , establishes a minor inside diameter of the adaptor  354 . At least one annular shoulder  366  extends between the major  362  and minor  364  side walls, thereby providing a ledge generally perpendicular to the central axis A. The shoulder  366  therefore establishes a contact surface through which all axially vectored stresses are transferred between the adaptor  354  and the stud  30 . The adaptor interface region  348  of the shank  334  includes a generally cylindrical major shaft corresponding to the collar  350 . This major shaft is matingly received within the major side wall  362  of the adaptor  354 . The adaptor interface region  348  also includes a minor shaft  368  that is matingly received within the minor side wall  364  of the adaptor  354 . An annular shoulder  370  extends between the major  350  and minor  368  shafts to establish a generally transverse ledge, relative to the central axis A. The shoulder  370  is adapted to seat in face-to-face contact with the shoulder  366  of the adaptor  354 .  
         [0033]      FIG. 8  depicts a fourth alternative embodiment of the subject invention wherein like or corresponding parts to those described above are reiterated but with the prefix “4” for convenience. In this example, a pair of progressively sized steps are machined or otherwise formed on the adaptor interface region  448 , with complementary receiving shapes formed on the inner surface of the adaptor  454 . More specifically, the interior surface of the adaptor  454  is shown herein including a generally cylindrical intermediate side wall  472  that is concentrically disposed relative to the major side wall  462  and thereby establishing an intermediate sized diameter. The intermediate side wall  472  bisects the shoulder  466  into plural segments. The adaptor interface region  448  of the shank  434  likewise includes a generally cylindrical intermediate shaft bisecting the shoulder  470  into plural segments. The intermediate shaft  474  matingly engages the intermediate side wall  472  of the adaptor  454 . Thus, as can be seen upon consideration of  FIG. 8 , the multi-stepped configuration of the mating surfaces increases the integrity of fit between the adaptor  454  and the stud  430 . Of course, additional steps can be incorporated into the design, as can combinations of steps together with the spheroidal curvatures depicted in  FIGS. 2-6 .  
         [0034]     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, more steps can be formed in the interface portion, and the step configuration can be combined with spheroidal curvatures. It is, therefore, to be understood that the invention may be practiced otherwise than as specifically described.