Abstract:
A ball joint assembly ( 10 ) comprises a socket ( 12 ) with a chamber ( 18 ), an opening extending through a first axial end ( 20 ) of the socket ( 12 ), and electrically conductive structure ( 60 ) closing the second axial end ( 22 ) of the socket ( 12 ). An electrically conductive ball stud ( 30 ) has a head portion ( 32 ) that is received in the chamber ( 18 ) and a shank portion ( 34 ) that extends through the opening. An electrically conductive bearing member ( 40 ) is received in the chamber ( 18 ) and provides an electrical connection between the structure ( 60 ) and the ball stud ( 30 ). An electrically non-conductive biasing member ( 50 ) is interposed between the structure ( 60 ) and the bearing member ( 40 ) and urges the bearing member away from the structure such that, in response to a predetermined amount of wear, the electrical connection between the structure ( 60 ) and the ball stud ( 30 ) is discontinued.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a ball joint assembly. More particularly, the present invention relates to a ball joint assembly with structure for indicating wear within the ball joint assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    A conventional ball joint assembly includes a joint socket, a ball stud, and a bearing. The bearing is supported in a chamber of the joint socket. The bearing supports a head portion of the ball stud within the joint socket. A shank portion of the ball stud extends outwardly of the socket and is rotatable and tiltable relative to the socket.  
           [0003]    During use, movement of the head portion of the ball stud on the bearing and relative to the socket results in wear of the bearing within the ball joint assembly. When wear within the ball joint assembly reaches a predetermined amount, the ball joint assembly should be either replaced or repaired.  
           [0004]    It is desirable to determine when wear of the predetermined amount occurs within the ball joint assembly. One conventional ball joint assembly that indicates wear includes an electrical contact that is embedded in the bearing. Electrical power is applied to the electrical contact and to the ball stud. When the bearing wears by the predetermined amount, the ball stud engages the electrical contact. When the ball stud engages the electrical contact, an indicator device is energized to indicate wear of the predetermined amount.  
           [0005]    In the conventional ball joint assembly, damage to the electrical system may result in failure to indicate wear of the predetermined amount within the ball joint assembly. For example, if a lead wire of the conventional ball joint assembly is severed, the indicator device may not be energized when the ball stud engages the electrical contact. As a result, the conventional ball joint assembly may fail to properly indicate wear of the predetermined amount.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention relates to a ball joint assembly. The ball joint assembly comprises a socket and an electrically conductive ball stud. The socket includes an internal socket chamber, an opening that extends through a first axial end of the socket and connects to the socket chamber, and electrically conductive structure closing the second axial end of the socket. The ball stud has a head portion that is received in the socket chamber and a shank portion that extends through the opening and outward of the first axial end of the socket. A bearing member is received in the socket chamber and enables the ball stud to tilt relative to the socket. The bearing member is electrically conductive and provides an electrical connection between the structure and the ball stud. An electrically non-conductive biasing member is interposed between the structure and the bearing member. The biasing member urges the bearing member away from the structure such that, in response to a predetermined amount of wear within the ball joint assembly, the electrical connection between the structure and the ball stud is discontinued.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which:  
         [0008]    [0008]FIG. 1 is an elevation view, partially in section, of a ball joint assembly constructed in accordance with the present invention prior to a predetermined amount of wear within the ball joint assembly;  
         [0009]    [0009]FIG. 2 illustrates the ball joint assembly of FIG. 1 after a predetermined amount of wear within the ball joint assembly;  
         [0010]    [0010]FIG. 3 is an elevation view, partially in section, of a ball joint assembly constructed in accordance with a second embodiment of the present invention prior to a predetermined amount of wear within the ball joint assembly; and  
         [0011]    [0011]FIG. 4 illustrates the ball joint assembly of FIG. 3 after a predetermined amount of wear within the ball joint assembly.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    [0012]FIG. 1 is an elevation view, partially in section, of a ball joint assembly  10  constructed in accordance with the present invention. The ball joint assembly  10  includes a housing or socket  12 . The socket  12  is formed from an electrically conductive material, such as steel. The socket  12  has a generally cylindrical side wall  14  that is centered on axis A. A mounting flange  16  extends radially outward of the side wall  14  of the socket  12  for mounting of the socket on a piece of equipment. A socket chamber  18  is defined within the side wall  14  of the socket  12 .  
         [0013]    The socket  12  includes first and second axial ends  20  and  22 , respectively. The side wall  14  of the socket  12  at the first axial end  20  is thickened, relative to the remainder of the side wall  14 , and forms a first bearing member  24  of the ball joint assembly  10 . The first bearing member  24  includes an annular, curvilinear bearing surface  26  that narrows toward the first axial end  20  of the socket  12 . The bearing surface  26  is a smooth, low friction surface.  
         [0014]    The second axial end  22  of the socket  12  includes a cylindrical opening (not shown) that is defined within the side wall  14 . After assembly of the ball joint assembly  10 , as will be described below, the side wall  14  adjacent the second axial end  22  of the socket  12  is bent radially inwardly to form a radially inwardly bent portion  28  of the socket  12 .  
         [0015]    The ball joint assembly  10  also includes a ball stud  30 . The ball stud  30  is formed from an electrically conductive material, such as steel. The ball stud  30  includes a head portion  32  and a shank portion  34 . The head portion  32  of the ball stud  30  illustrated in FIG. 1 is spherical and is defined by a smooth outer surface  36 . The shank portion  34  of the ball stud  30  extends axially along axis B from the ball stud. FIG. 1 illustrates axis A and axis B being coaxial. In the assembled ball joint assembly  10 , axis is B is rotatable and tiltable relative to axis A. An end  38  of the shank portion  34  of the ball stud  30  opposite the head portion  32  may be threaded.  
         [0016]    A second bearing member  40  of the ball joint assembly  10  is formed from an electrically conductive material, such as steel. The second bearing member  40  includes a cylindrical outer surface  42 , an upper surface  44  that includes a semi-spherical bearing surface  46 , and a lower surface  48  that is domed. The semi-spherical bearing surface  46  of the second bearing member  40  is a low friction surface.  
         [0017]    The ball joint assembly  10  also includes an electrically non-conductive spring/seal element  50 . The spring/seal element  50  is formed from a resilient material, such as rubber. The spring/seal element  50  has a generally U-shaped cross-sectional shape that includes upper and lower wall portions  52  and  54 , respectively, and an outer wall portion  56  that interconnects the upper and lower wall portions. An annular groove  58  is formed in the spring/seal element  50  between the upper and lower wall portions  52  and  54 . The outer wall portion  56  of the spring/seal member  50  defines a radially outer end of the annular groove  58 . As an alternative to the spring/seal element  50 , an electrically non-conductive spring and a separate electrically non-conductive seal may be used.  
         [0018]    The ball joint assembly  10  also includes a cover member  60  for closing the second axial end  22  of the socket  12 . The cover member  60  is formed from an electrically conductive material, such as steel. The cover member  60  is disk-shaped and includes upper and lower surfaces  62  and  64 , respectively. The upper surface  62  includes an annular protruding portion  66  that extends axially outwardly of the remainder of the upper surface  62 . The lower surface  64  includes an annular recessed portion  68  at a location corresponding to the annular protruding portion  66  on the upper surface  62 .  
         [0019]    According to an exemplary method of assembling the ball joint assembly  10  of the present invention, the shank portion  34  of the ball stud  30  is inserted through the opening at the second axial end  22  of the socket  12 , through the socket chamber  18 , and outward through the opening on the first axial end  20  of the socket  12  so that the ball head  32  of the ball stud  30  rests on the curvilinear bearing surface  26  of the first bearing member  24 . The second bearing member  40  is then inserted through the opening on the second axial end  22  of the socket  12  and is positioned so that the semi-spherical bearing surface  46  of the second bearing member  40  contacts the smooth outer surface  36  of the ball head  32 .  
         [0020]    The cover member  60  is positioned in the annular groove  58  of the spring/seal element  50  so that the upper wall portion  52  of the spring/seal element overlies the periphery of the upper surface  62  of the cover member, the lower wall portion  54  of the spring/seal element overlies the periphery of the lower surface  64  of the cover member, and the outer wall portion  56  of the spring/seal element radially surrounds the cover member. The spring/seal element  50  electrically insulates the periphery of the cover member  60 .  
         [0021]    The spring/seal element  50  and cover member  60  are then inserted through the opening on the second axial end  22  of the socket  12  such that the upper wall portion  52  of the spring/seal element  50  contacts the lower surface  48  of the second bearing member  40 . The side wall  14  of the second axial end  22  of the socket  12  is then bent radially inwardly to form the radially inwardly bent portion  28 . The radially inwardly bent portion  28  applies a predetermined load on the spring/seal element  50  and axially deforms the spring/seal element so that the annular protruding portion  66  of the upper surface  62  of the cover member  60  contacts the lower surface  48  of the second bearing member  40 , as shown in FIG. 1. The axially deformed spring/seal element  50  urges the second bearing member  40  toward the first axial end  20  of the socket  12 . Additionally, the axially deformed spring/seal element  50  seals between the cover member and the socket  12  for preventing contaminants from entering the socket chamber  18  through the second axial end  22  of the socket.  
         [0022]    The ball joint assembly  10  of the present invention advantageously compensates for wear within the ball joint assembly  10 . Specifically, the ball joint assembly  10  of the present invention compensates for wear of the first and second bearing members  24  and  40 . To compensate for wear of the second bearing member  40 , the axially compressed spring/seal element  50  urges the second bearing member  40  against the head portion  32  of the ball stud  30 . To compensate for wear of the first bearing member  24 , the axially compressed spring/seal element  50  urges both the second bearing member  40  and the head portion  32  of the ball stud  30  toward the first bearing member  24 .  
         [0023]    Additionally, the ball joint assembly  10  of the present invention may be used in a system, indicated by  90  in FIGS. 1 and 2, for determining when a predetermined amount of wear within the ball joint assembly  10  has occurred. The wear determining system  90  includes an electric power source  92  and a power indicator  94 . The electric power source  92  includes first and second leads  96  and  98 , respectively. The power indicator  94  indicates when power is transferred between the first and second leads  96  and  98 . The electric power source  92  and the power indicator  94  may be included in the form of a probe that may be used for determining wear of the ball joint assembly  10 .  
         [0024]    When the cover member  60  contacts the second bearing member  40 , as shown in FIG. 1, and the first lead  96  of the electric power source  92  is applied to the shank portion  34  of the ball stud  30  and the second lead  98  is applied to the electrically conductive cover member  60 , the power indicator  94  indicates electrical power passing through the ball joint assembly  10 . When electrical power passes through the ball joint assembly  10 , the wear within the ball joint assembly is considered to be less than the predetermined amount. By connecting the second lead  98  to the cover member  60  of the ball joint assembly  10 , there is no need to provide a seal around the second lead  98  as the second lead does not extend into the socket chamber  18  of the ball joint assembly  10 .  
         [0025]    As the ball joint assembly  10  wears, the spring/seal element  50  urges the second bearing member  40  away from the cover member  60 . When wear within the ball joint assembly increases beyond the predetermined amount, the spring/seal element  50  urges the second bearing member  40  away from the cover member  60  and contact between the second bearing member  40  and the cover member  60  discontinues, as is shown in FIG. 2.  
         [0026]    When the cover member  60  is spaced away or electrically separated from the second bearing member  40 , as shown in FIG. 2, and the first lead  96  of the electric power source  92  is applied to the shank portion  34  of the ball stud  30  and the second lead  98  is applied to the cover member  60 , the power indicator  94  indicates no electrical power passing through the ball joint assembly  10 . When no electrical power passes through the ball joint assembly  10 , the wear within the ball joint assembly  10  is considered to be greater than the predetermined amount. Moreover, wear to the system  90  that results in the power indicator  94  not receiving electrical power will indicate the need for replacement or repair.  
         [0027]    Thus, when included in the wear determining system  90 , the ball joint assembly  10  acts as a normally closed switch. The ball stud  30  acts as a first electrical contact, the cover member  60  acts as a second electrical contact, and the second bearing member  40  acts as a switch member in the normally closed switch. When the wear within the ball joint assembly  10  is less than the predetermined amount, the switch remains closed. The switch opens in response to the wear within the ball joint assembly  10  exceeding the predetermined amount.  
         [0028]    [0028]FIG. 3 is an elevation view, partially in section, of a ball joint assembly  110  constructed in accordance with a second embodiment of the present invention prior to a predetermined amount of wear within the ball joint assembly. The ball joint assembly  110  includes a socket  112  that is formed from an electrically conductive material, such as steel. The socket  112  has a generally cylindrical side wall  114  that is centered on axis A. A mounting flange  116  extends radially outward of the side wall  114  of the socket  112  for mounting of the socket on a piece of equipment. A socket chamber  118  is defined within the side wall  114  of the socket  112 .  
         [0029]    The socket  112  includes first and second axial ends  120  and  122 , respectively. The side wall  114  of the socket  112  includes a first radially inwardly bent portion  124  adjacent the first axial end  120  of the socket  112 . The first radially inwardly bent portion  124  defines an opening  126  at the first axial end  120  of the socket  112 . The second axial end  122  of the socket  112  includes a cylindrical opening (not shown) that is defined within the side wall  114 . After assembly of the ball joint assembly  110 , as will be described below, the side wall  114  adjacent the second axial end  122  of the socket  112  is bent radially inwardly to form a second radially inwardly bent portion  128  of the socket  112 .  
         [0030]    The socket  112  illustrated in FIG. 3 also includes first and second bearing members  130  and  132 , respectively. The first bearing member  130  is annular and is sized to fit within the socket chamber  118 . Preferably, the first bearing member  130  is formed from a low friction material, such as plastic. The first bearing member  130  includes an outer wall  134  that fits snugly against the side wall  114  of the socket  112  and an end wall  136  for resting against the first radially inwardly bent portion  124  of the socket  112 . A curvilinear bearing surface  138  of the first bearing member  130  defines an internal channel through the first bearing member  130  that narrows toward end wall  136 .  
         [0031]    The second bearing member  132  is formed from an electrically conductive material, such as steel. The second bearing member  132  includes a cylindrical outer surface  140 , a semi-spherical bearing surface  142  that is a low friction surface, and an outer surface  144  that includes a central domed portion  146  and an annular rim portion  148 .  
         [0032]    The ball joint assembly  110  also includes a ball stud  150 . The ball stud  150  is formed from an electrically conductive material, such as steel. The ball stud  150  includes a head portion  152  and a shank portion  154 . The head portion  152  of the ball stud  150  illustrated in FIG. 3 is spherical and is defined by a smooth outer surface  156 . The shank portion  154  of the ball stud  150  extends axially along axis B of the ball stud. FIG. 3 illustrates axis A and axis B as being coaxial. In the assembled ball joint assembly  110 , axis B is rotatable and tiltable relative to axis A. An end  158  of the shank portion  154  of the ball stud  150  opposite the head portion  152  is threaded.  
         [0033]    The ball joint assembly  110  also includes a cover member  160  for closing the second axial end  122  of the socket  112 . The cover member  160  is formed from an electrically conductive material, such as steel. The cover member  160  is disk-shaped and includes upper and lower surfaces  162  and  164 , respectively. The upper surface  162  includes an annular protruding portion  166  that extends axially outwardly of the remainder of the upper surface  162 . The lower surface  164  includes an annular recessed portion  168  at a location corresponding to the annular protruding portion  166  on the upper surface  162 .  
         [0034]    An electrically non-conductive spring/seal element  172  for the ball joint assembly  110  is formed from a resilient material, such as rubber. The spring/seal element  172  has a generally U-shaped cross-sectional shape that includes upper and lower wall portions  174  and  176 , respectively, and an outer wall portion  178  that interconnects the upper and lower wall portions. An annular groove  180  is formed in the spring/seal element  172  between the upper and lower wall portions  174  and  176 . The outer wall portion  178  of the spring/seal member  178  defines a radially outer end of the annular groove  180 . As an alternative to the spring/seal element  160 , an electrically non-conductive spring and a separate electrically non-conductive seal may be used.  
         [0035]    According to an exemplary method of assembling the ball joint assembly  110  of the present invention, the first bearing member  130  is inserted into the socket chamber  118  through the opening on the second axial end  122  of the socket  112 . The first bearing member  130  is pressed toward the first axial end  120  of the socket  112  until the end wall  136  of the first bearing member  130  rests against the first radially inwardly bent portion  124  of the socket  112 . The shank portion  154  of the ball stud  150  is then inserted through the opening at the second axial end  122  of the socket  112 , through the socket chamber  118 , and outward through the opening  126  on the first axial end  120  of the socket  112  so that the head portion  152  of the ball stud  150  rests on the curvilinear bearing surface  138  of the first bearing member  130 . The second bearing member  132  is then inserted through the opening on the second axial end  122  of the socket  112  and positioned so that the semi-spherical bearing surface  142  of the second bearing member  132  contacts the smooth outer surface  156  of the head portion  152  of the ball stud  150 .  
         [0036]    The cover member  160  is positioned in the annular groove  180  of the spring/seal element  172  so that the upper wall portion  174  of the spring/seal element overlies the periphery of the upper surface  162  of the cover member, the lower wall portion  176  of the spring/seal element overlies the periphery of the lower surface  164  of the cover member, and the outer wall portion  178  of the spring/seal element radially surrounds the cover member. The spring/seal element  172  electrically insulates the periphery of the cover member  160 .  
         [0037]    The spring/seal element  172  and cover member  160  are then inserted through the opening on the second axial end  122  of the socket  112  such that the upper wall portion  174  of the spring/seal element  172  contacts the outer surface  144  of the second bearing member  132 . The second axial end  122  of the socket  112  is then bent radially inwardly to form the second radially inwardly bent portion  128 . The second radially inwardly bent portion  128  applies a predetermined load on the spring/seal element  172  to axially deform the spring/seal element. The annular protrusion  170  of the cover member  160  contacts the second bearing member  132  when the spring/seal element  172  is deformed axially, as shown in FIG. 3. The spring/seal element  172 , when deformed axially, urges the second bearing member  132  toward the first axial end  120  of the socket  112  and also creates a seal between the second radially inwardly bent portion  128  of the socket  112  and the cover member  160  for preventing contaminants from entering the socket  112 .  
         [0038]    The ball joint assembly  110  of FIG. 3 also compensates for wear within the ball joint assembly. To compensate for wear of the second bearing member  132 , the axially compressed spring/seal element  172  urges the second bearing member  132  against the head portion  152  of the ball stud  150 . To compensate for wear of the first bearing member  130 , the axially compressed spring/seal element  172  urges both the second bearing member  132  and the head portion  152  of the ball stud  150  toward the first bearing member  130 .  
         [0039]    Similarly to the ball joint assembly  10  of FIG. 1, the ball joint assembly  110  of FIG. 3 may be used in a system  190  for determining when a predetermined amount of wear within the ball joint assembly  110  has occurred. The wear determining system  190  includes an electric power source  192  and a power indicator  194 . The electric power source  192  includes first and second lead wires  196  and  198 , respectively. The power indicator  194  indicates when power is transferred between the first and second lead wires  196  and  198 . The wear determining system  190 , including the electric power source  192  and the power indicator  194 , may be included in the form of a probe that may be used for determining wear of the ball joint assembly.  
         [0040]    When the cover member  160  contacts the second bearing member  132 , as shown in FIG. 3, and the first lead wire  196  of the electric power source  192  is applied to the shank portion  154  of the ball stud  150  and the second lead  198  is applied to the cover member  160 , the power indicator  194  indicates electrical power passing through the ball joint assembly  110 . When electrical power passes through the ball joint assembly  110 , the wear within the ball joint assembly  110  is considered to be less than the predetermined amount.  
         [0041]    As the ball joint assembly  110  wears, the spring/seal element  172  biases the second bearing member  132  away from the cover member  160 . When wear increases beyond the predetermined amount, contact between the second bearing member  132  and the cover member  160  discontinues. FIG. 4 illustrates the ball joint assembly  110  after wear beyond the predetermined amount.  
         [0042]    When the cover member  160  is spaced away from the second bearing member  132 , as shown in FIG. 4, and the first lead wire  196  of the electric power source  192  is applied to the shank portion  154  of the ball stud  150  and the second lead wire  198  is applied to the cover member  160 , the power indicator  194  indicates no electrical power passing through the ball joint assembly  110 . When no electrical power passes through the ball joint assembly  110 , the wear within the ball joint assembly  110  is considered to be greater than the predetermined amount.  
         [0043]    Thus, when included in the wear determining system  190 , the ball joint assembly  110  acts as a normally closed switch. The cover member  160  acts as one electrical contact, and the ball stud  150  acts as another electrical contact, and the second bearing member  132  acts as a switch member in the normally closed switch.  
         [0044]    From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. For example, the socket  112  of FIG. 3 may be closed at the second axial end  122  and the ball joint assembly  110  may be assembly through the opening  126  at the first axial end  120  of the socket  112  prior to forming of the first radially inwardly bent portion  124 . In such an embodiment, the second bearing member is preferably electrically insulated from the socket. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.