Ball joint assembly with wear indication

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.

TECHNICAL FIELD

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

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.

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.

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.

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

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.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an elevation view, partially in section, of a ball joint assembly10constructed in accordance with the present invention. The ball joint assembly10includes a housing or socket12. The socket12is formed from an electrically conductive material, such as steel. The socket12has a generally cylindrical side wall14that is centered on axis A. A mounting flange16extends radially outward of the side wall14of the socket12for mounting of the socket on a piece of equipment. A socket chamber18is defined within the side wall14of the socket12.

The socket12includes first and second axial ends20and22, respectively. The side wall14of the socket12at the first axial end20is thickened, relative to the remainder of the side wall14, and forms a first bearing member24of the ball joint assembly10. The first bearing member24includes an annular, curvilinear bearing surface26that narrows toward the first axial end20of the socket12. The bearing surface26is a smooth, low friction surface.

The second axial end22of the socket12includes a cylindrical opening (not shown) that is defined within the side wall14. After assembly of the ball joint assembly10, as will be described below, the side wall14adjacent the second axial end22of the socket12is bent radially inwardly to form a radially inwardly bent portion28of the socket12.

The ball joint assembly10also includes a ball stud30. The ball stud30is formed from an electrically conductive material, such as steel. The ball stud30includes a head portion32and a shank portion34. The head portion32of the ball stud30illustrated inFIG. 1is spherical and is defined by a smooth outer surface36. The shank portion34of the ball stud30extends axially along axis B from the ball stud.FIG. 1illustrates axis A and axis B being coaxial. In the assembled ball joint assembly10, axis B is rotatable and tiltable relative to axis A. An end38of the shank portion34of the ball stud30opposite the head portion32may be threaded.

A second bearing member40of the ball joint assembly10is formed from an electrically conductive material, such as steel. The second bearing member40includes a cylindrical outer surface42, an upper surface44that includes a semi-spherical bearing surface46, and a lower surface48that is domed. The semi-spherical bearing surface46of the second bearing member40is a low friction surface.

The ball joint assembly10also includes an electrically non-conductive spring/seal element50. The spring/seal element50is formed from a resilient material, such as rubber. The spring/seal element50has a generally U-shaped cross-sectional shape that includes upper and lower wall portions52and54, respectively, and an outer wall portion56that interconnects the upper and lower wall portions. An annular groove58is formed in the spring/seal element50between the upper and lower wall portions52and54. The outer wall portion56of the spring/seal member50defines a radially outer end of the annular groove58. As an alternative to the spring/seal element50, an electrically non-conductive spring and a separate electrically non-conductive seal may be used.

The ball joint assembly10also includes a cover member60for closing the second axial end22of the socket12. The cover member60is formed from an electrically conductive material, such as steel. The cover member60is disk-shaped and includes upper and lower surfaces62and64, respectively. The upper surface62includes an annular protruding portion66that extends axially outwardly of the remainder of the upper surface62. The lower surface64includes an annular recessed portion68at a location corresponding to the annular protruding portion66on the upper surface62.

According to an exemplary method of assembling the ball joint assembly10of the present invention, the shank portion34of the ball stud30is inserted through the opening at the second axial end22of the socket12, through the socket chamber18, and outward through the opening on the first axial end20of the socket12so that the ball head32of the ball stud30rests on the curvilinear bearing surface26of the first bearing member24. The second bearing member40is then inserted through the opening on the second axial end22of the socket12and is positioned so that the semi-spherical bearing surface46of the second bearing member40contacts the smooth outer surface36of the ball head32.

The cover member60is positioned in the annular groove58of the spring/seal element50so that the upper wall portion52of the spring/seal element overlies the periphery of the upper surface62of the cover member, the lower wall portion54of the spring/seal element overlies the periphery of the lower surface64of the cover member, and the outer wall portion56of the spring/seal element radially surrounds the cover member. The spring/seal element50electrically insulates the periphery of the cover member60.

The spring/seal element50and cover member60are then inserted through the opening on the second axial end22of the socket12such that the upper wall portion52of the spring/seal element50contacts the lower surface48of the second bearing member40. The side wall14of the second axial end22of the socket12is then bent radially inwardly to form the radially inwardly bent portion28. The radially inwardly bent portion28applies a predetermined load on the spring/seal element50and axially deforms the spring/seal element so that the annular protruding portion66of the upper surface62of the cover member60contacts the lower surface48of the second bearing member40, as shown in FIG.1. The axially deformed spring/seal element50urges the second bearing member40toward the first axial end20of the socket12. Additionally, the axially deformed spring/seal element50seals between the cover member and the socket12for preventing contaminants from entering the socket chamber18through the second axial end22of the socket.

The ball joint assembly10of the present invention advantageously compensates for wear within the ball joint assembly10. Specifically, the ball joint assembly10of the present invention compensates for wear of the first and second bearing members24and40. To compensate for wear of the second bearing member40, the axially compressed spring/seal element50urges the second bearing member40against the head portion32of the ball stud30. To compensate for wear of the first bearing member24, the axially compressed spring/seal element50urges both the second bearing member40and the head portion32of the ball stud30toward the first bearing member24.

Additionally, the ball joint assembly10of the present invention may be used in a system, indicated by90inFIGS. 1 and 2, for determining when a predetermined amount of wear within the ball joint assembly10has occurred. The wear determining system90includes an electric power source92and a power indicator94. The electric power source92includes first and second leads96and98, respectively. The power indicator94indicates when power is transferred between the first and second leads96and98. The electric power source92and the power indicator94may be included in the form of a probe that may be used for determining wear of the ball joint assembly10.

When the cover member60contacts the second bearing member40, as shown inFIG. 1, and the first lead96of the electric power source92is applied to the shank portion34of the ball stud30and the second lead98is applied to the electrically conductive cover member60, the power indicator94indicates electrical power passing through the ball joint assembly10. When electrical power passes through the ball joint assembly10, the wear within the ball joint assembly is considered to be less than the predetermined amount. By connecting the second lead98to the cover member60of the ball joint assembly10, there is no need to provide a seal around the second lead98as the second lead does not extend into the socket chamber18of the ball joint assembly10.

As the ball joint assembly10wears, the spring/seal element50urges the second bearing member40away from the cover member60. When wear within the ball joint assembly increases beyond the predetermined amount, the spring/seal element50urges the second bearing member40away from the cover member60and contact between the second bearing member40and the cover member60discontinues, as is shown in FIG.2.

When the cover member60is spaced away or electrically separated from the second bearing member40, as shown inFIG. 2, and the first lead96of the electric power source92is applied to the shank portion34of the ball stud30and the second lead98is applied to the cover member60, the power indicator94indicates no electrical power passing through the ball joint assembly10. When no electrical power passes through the ball joint assembly10, the wear within the ball joint assembly10is considered to be greater than the predetermined amount. Moreover, wear to the system90that results in the power indicator94not receiving electrical power will indicate the need for replacement or repair.

Thus, when included in the wear determining system90, the ball joint assembly10acts as a normally closed switch. The ball stud30acts as a first electrical contact, the cover member60acts as a second electrical contact, and the second bearing member40acts as a switch member in the normally closed switch. When the wear within the ball joint assembly10is less than the predetermined amount, the switch remains closed. The switch opens in response to the wear within the ball joint assembly10exceeding the predetermined amount.

FIG. 3is an elevation view, partially in section, of a ball joint assembly110constructed 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 assembly110includes a socket112that is formed from an electrically conductive material, such as steel. The socket112has a generally cylindrical side wall114that is centered on axis A. A mounting flange116extends radially outward of the side wall114of the socket112for mounting of the socket on a piece of equipment. A socket chamber118is defined within the side wall114of the socket112.

The socket112includes first and second axial ends120and122, respectively. The side wall114of the socket112includes a first radially inwardly bent portion124adjacent the first axial end120of the socket112. The first radially inwardly bent portion124defines an opening126at the first axial end120of the socket112. The second axial end122of the socket112includes a cylindrical opening (not shown) that is defined within the side wall114. After assembly of the ball joint assembly110, as will be described below, the side wall114adjacent the second axial end122of the socket112is bent radially inwardly to form a second radially inwardly bent portion128of the socket112.

The socket112illustrated inFIG. 3also includes first and second bearing members130and132, respectively. The first bearing member130is annular and is sized to fit within the socket chamber118. Preferably, the first bearing member130is formed from a low friction material, such as plastic. The first bearing member130includes an outer wall134that fits snugly against the side wall114of the socket112and an end wall136for resting against the first radially inwardly bent portion124of the socket112. A curvilinear bearing surface138of the first bearing member130defines an internal channel through the first bearing member130that narrows toward end wall136.

The second bearing member132is formed from an electrically conductive material, such as steel. The second bearing member132includes a cylindrical outer surface140, a semi-spherical bearing surface142that is a low friction surface, and an outer surface144that includes a central domed portion146and an annular rim portion148.

The ball joint assembly110also includes a ball stud150. The ball stud150is formed from an electrically conductive material, such as steel. The ball stud150includes a head portion152and a shank portion154. The head portion152of the ball stud150illustrated inFIG. 3is spherical and is defined by a smooth outer surface156. The shank portion154of the ball stud150extends axially along axis B of the ball stud.FIG. 3illustrates axis A and axis B as being coaxial. In the assembled ball joint assembly110, axis B is rotatable and tiltable relative to axis A. An end158of the shank portion154of the ball stud150opposite the head portion152is threaded.

The ball joint assembly110also includes a cover member160for closing the second axial end122of the socket112. The cover member160is formed from an electrically conductive material, such as steel. The cover member160is disk-shaped and includes upper and lower surfaces162and164, respectively. The upper surface162includes an annular protruding portion166that extends axially outwardly of the remainder of the upper surface162. The lower surface164includes an annular recessed portion168at a location corresponding to the annular protruding portion166on the upper surface162.

An electrically non-conductive spring/seal element172for the ball joint assembly110is formed from a resilient material, such as rubber. The spring/seal element172has a generally U-shaped cross-sectional shape that includes upper and lower wall portions174and176, respectively, and an outer wall portion178that interconnects the upper and lower wall portions. An annular groove180is formed in the spring/seal element172between the upper and lower wall portions174and176. The outer wall portion178of the spring/seal member178defines a radially outer end of the annular groove180. As an alternative to the spring/seal element160, an electrically non-conductive spring and a separate electrically non-conductive seal may be used.

According to an exemplary method of assembling the ball joint assembly110of the present invention, the first bearing member130is inserted into the socket chamber118through the opening on the second axial end122of the socket112. The first bearing member130is pressed toward the first axial end120of the socket112until the end wall136of the first bearing member130rests against the first radially inwardly bent portion124of the socket112. The shank portion154of the ball stud150is then inserted through the opening at the second axial end122of the socket112, through the socket chamber118, and outward through the opening126on the first axial end120of the socket112so that the head portion152of the ball stud150rests on the curvilinear bearing surface138of the first bearing member130. The second bearing member132is then inserted through the opening on the second axial end122of the socket112and positioned so that the semi-spherical bearing surface142of the second bearing member132contacts the smooth outer surface156of the head portion152of the ball stud150.

The cover member160is positioned in the annular groove180of the spring/seal element172so that the upper wall portion174of the spring/seal element overlies the periphery of the upper surface162of the cover member, the lower wall portion176of the spring/seal element overlies the periphery of the lower surface164of the cover member, and the outer wall portion178of the spring/seal element radially surrounds the cover member. The spring/seal element172electrically insulates the periphery of the cover member160.

The spring/seal element172and cover member160are then inserted through the opening on the second axial end122of the socket112such that the upper wall portion174of the spring/seal element172contacts the outer surface144of the second bearing member132. The second axial end122of the socket112is then bent radially inwardly to form the second radially inwardly bent portion128. The second radially inwardly bent portion128applies a predetermined load on the spring/seal element172to axially deform the spring/seal element. The annular protrusion170of the cover member160contacts the second bearing member132when the spring/seal element172is deformed axially, as shown in FIG.3. The spring/seal element172, when deformed axially, urges the second bearing member132toward the first axial end120of the socket112and also creates a seal between the second radially inwardly bent portion128of the socket112and the cover member160for preventing contaminants from entering the socket112.

The ball joint assembly110ofFIG. 3also compensates for wear within the ball joint assembly. To compensate for wear of the second bearing member132, the axially compressed spring/seal element172urges the second bearing member132against the head portion152of the ball stud150. To compensate for wear of the first bearing member130, the axially compressed spring/seal element172urges both the second bearing member132and the head portion152of the ball stud150toward the first bearing member130.

Similarly to the ball joint assembly10ofFIG. 1, the ball joint assembly110ofFIG. 3may be used in a system190for determining when a predetermined amount of wear within the ball joint assembly110has occurred. The wear determining system190includes an electric power source192and a power indicator194. The electric power source192includes first and second lead wires196and198, respectively. The power indicator194indicates when power is transferred between the first and second lead wires196and198. The wear determining system190, including the electric power source192and the power indicator194, may be included in the form of a probe that may be used for determining wear of the ball joint assembly.

When the cover member160contacts the second bearing member132, as shown inFIG. 3, and the first lead wire196of the electric power source192is applied to the shank portion154of the ball stud150and the second lead198is applied to the cover member160, the power indicator194indicates electrical power passing through the ball joint assembly110. When electrical power passes through the ball joint assembly110, the wear within the ball joint assembly110is considered to be less than the predetermined amount.

As the ball joint assembly110wears, the spring/seal element172biases the second bearing member132away from the cover member160. When wear increases beyond the predetermined amount, contact between the second bearing member132and the cover member160discontinues.FIG. 4illustrates the ball joint assembly110after wear beyond the predetermined amount.

When the cover member160is spaced away from the second bearing member132, as shown inFIG. 4, and the first lead wire196of the electric power source192is applied to the shank portion154of the ball stud150and the second lead wire198is applied to the cover member160, the power indicator194indicates no electrical power passing through the ball joint assembly110. When no electrical power passes through the ball joint assembly110, the wear within the ball joint assembly110is considered to be greater than the predetermined amount.

Thus, when included in the wear determining system190, the ball joint assembly110acts as a normally closed switch. The cover member160acts as one electrical contact, and the ball stud150acts as another electrical contact, and the second bearing member132acts as a switch member in the normally closed switch.

From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. For example, the socket112ofFIG. 3may be closed at the second axial end122and the ball joint assembly110may be assembly through the opening126at the first axial end120of the socket112prior to forming of the first radially inwardly bent portion124. 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.