BALL JOINT

Abstract

A ball joint has a bushing with a defined housing space sized to receive ball joint components. The ball joint further has a cage member having an exterior surface that fits within the housing recess and an interior surface with a pattern of raised and recessed portions, and a cup member over-molded on the cage member component. The cup member complements the interior surface pattern of the cage member and includes an interior surface having a circular configuration. The ball joint also has a stem having a ball portion dimensioned to fit within and complement the interior surface of the cup member.

Description

FIELD OF INVENTION

This invention relates generally to ball joint that is part of a suspension system. Because ball joints are designed for applications that connect different parts requiring relative motion, they are subject to tensile and compressive loads. More particularly, the present invention relates to ball joints that do not require greasing.

BACKGROUND

Ball joints have long been common on motor vehicles. The earlier designs comprised a metal housing having a spherical, concave socket that received a complementary spherical metal ball that was at the end of a threaded stud. Because of the metal-on-metal construction, the mating parts experience rapid wear and required regular lubrication. Later ball joint constructions incorporated a self-lubricating plastic insert for encasing the ball for movement within the socket. This self-lubricating construction has experienced failure under high compressive loads.

It is an object of the present invention to provide an improved self-lubricating ball joint construction.

SUMMARY

The present construction provides a robust self-lubricating ball joint with a simplified assembly that resists the damage from high compressive loads associated with various vehicle-operating conditions.

In one aspect, the present disclosure is directed to ball joint. The ball joint includes a bushing with a defined housing space sized to receive ball joint components. The ball joint further includes a cage member having an exterior surface that fits within the housing recess and an interior surface with a pattern of raised and recessed portions, and a cup member over-molded on the cage member component. The cup member complements the interior surface pattern of the cage member and includes an interior surface having a circular configuration. The ball joint also includes a stem having a ball portion dimensioned to fit within and complement the interior surface of the cup member.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 illustrates a common exterior configuration of a ball joint;

FIG. 2 is a section along the line A-A of FIG. 1;

FIG. 3 is a section through the bushing that forms the bottom of the ball joint;

FIG. 4 is an perspective view of the cage portion of the assembly according to the present invention;

FIG. 5 is a sectional view of the cage portion of FIG. 4;

FIG. 6 is a top plan view of the cage portion of the assembly according to the present invention;

FIG. 7 is a perspective view of the over-molded cup portion of the assembly according to the present invention; and,

FIG. 8 is a sectional view of the over-molded cup portion of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, the ball joint 10 has a bushing 12 that is generally configured to fit in an aperture in a first suspension component and a stem 14, usually threaded, that is fastened to a second suspension component. The stem 14 is movable relative to the housing or bushing 12 to allow for corresponding relative movement between the suspension components.

With reference to FIG. 2, the stem 14 terminates in a ball portion 16 that provides the mobility for the joint. The ball portion 16 is generally spherical and is connected to the stem 14 near a top portion thereof. In a typical construction, the ball portion 16 and stem 14 are integrally formed as one piece. For example, the stem 14 and ball portion 16 may be a single metal casting configured and sized according to the original equipment manufacturer's specification for the part.

The ball joint 10 further includes an assembly 18 that retains the ball portion 16. In an exemplary embodiment, the assembly 18 includes the bushing 12, a cage member 20, and a cup member 30. The cage member 20 and cup member 30 are made as an over-molded assembly, as is explained herein. The combined cage member 20 and cup member 30 are sized and shaped to fit within the bushing 12. The cup member 30 forms a bearing for contacting the ball portion 16.

FIG. 3 further illustrates the bushing 12 of the assembly 18. As shown, the bushing 12 forms a housing space for receiving the combined cage member 20 and cup member 30. The bushing 12 includes an opening near a top portion thereof for allowing the stem 14 to extend therethrough. The opening may include a conical sidewall to accommodate movement of the stem 14.

FIGS. 4-6 further illustrate the cage member 20 which is to be over-molded by the cup member 30. The cage member 20 has a pattern of raised and recessed portions around a bowl shaped interior cavity 22. In an exemplary embodiment, the raised portions form vertically-extending ribs which are separated by individual grooves. The grooves may include curved surfaces. The exterior 24 of cage member 20 is generally cylindrical with a circumferential recess 26 in the lower portion of the cage member 20. A series of apertures 28 extend between the interior 22 and the recess 26. The configuration of cage 20 is beneficial for the subsequent step of over-molding the cage member 20 with the cup member 30 that will ultimately receive the ball portion 16.

With reference to FIG. 7, there is illustrated the final over-molded combined cage and cup assembly that will be placed within the housing space of the bushing 12. With reference to FIG. 8, there is a sectional view illustrating the configuration of the over-molded combined cage and cup assembly. The cage member 20 is over-molded with a polymeric or plastic material that forms an interior surface 32, which contacts ball portion 16, and the exterior surface 34, which is received within housing space of the bushing 12. Opposite from the interior surface 32, a first surface of the cup member 30 which faces the cage member 20 from an interior of the cage member 20 complements the pattern of raised and recessed portions in the interior cavity of the cage member 20. The interior surface 32 forms a second surface that defines the smooth circular configuration. The exterior surface 34 forms a third, cylindrical surface which fits within the housing space of the bushing 12.

The polymeric material fills the grooves and covers the ribs of the interior surface pattern of the cage member 20 to form a smooth interior surface 32 for contacting the ball portion 16. The polymeric material also fills the circumferential recess 26 to form a flat exterior surface which is sized to fit in the housing space of the bushing 12. The polymeric material flows through and fills the series of apertures 28 during the over-molding process.

One known material suitable for use in moving part applications where low friction and long wear life are desired is a combination of PTFE fibers uniformly dispersed in Delrin acetal resin that is available as Delrin AF Blend from Interstates Plastics. The polymeric material over-molds the cage member 20 to produce a unified structure that fits within and is fully support by the bushing 12. This construction has the benefit of the polymeric wear surface and metallic components that provide the desired load bearing strength.

The combined cage and cup assembly is formed such that the interior surface 32, which is formed by the over-molded polymeric plastic material, contacts the ball portion 16. This excludes the possibility of undesirable metal-on-metal contact while allowing the structural support of the cage member 20 embedded in the cup member 30. The pattern of raised and recessed portions around the interior of the cage member 20 increase a surface area with which the over-molded cup material contacts and produce a series of undulations and/or grooves which help to frictionally retain the over-molded material. The circumferential recess 26 and the series of apertures 28 further help to retain the over-molded material. The resulting combined cage and cup assembly is a robust component for use in the ball joint 10.

In an exemplary method of forming the ball joint 10, the cage member 20 is provided and a polymeric material is over-molded on the cage member 20. The polymeric material fills the grooves and covers the ribs of the interior surface pattern of the cage member 20 to form a smooth interior surface for contacting the ball portion 20. The polymeric material also flows through the apertures 28 and fills the recess 26 forming an integral structure which includes the cage member 20 embedded in the cup member 30. In the method, the bushing 12 is also provided, and the combined cage and cup assembly is inserted in the housing space. In addition, the stem 14 is provided and the ball portion 16 thereof is inserted in the interior space defined by the combined cage and cup assembly such that the stem 14 extends through the opening in the bushing 12.

Having thus described the presently preferred embodiments in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiments and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein

Claims

1. A ball joint comprising: a bushing that defines a space sized to receive ball joint components;a cage member that fits within the defined space of the bushing and has an interior cavity with a pattern of raised and recessed portions;a bearing having a first surface that complements the pattern of raised and recessed portions in the interior cavity of the cage member and a second surface that defines a smooth circular configuration; and,a stem having an end with a ball portion dimensioned to fit within the second surface of the bearing.

2. The ball joint of claim 1, wherein the bushing is metallic.

3. The ball joint of claim 1, wherein the cage member is metallic

4. The ball joint of claim 3, wherein the bearing is non-metallic

5. The ball joint of claim 4, wherein the bearing is a polymeric material.

6. The ball joint of claim 1, wherein the pattern of raised and recessed portions include alternating ribs and grooves.

7. The ball joint of claim 6, wherein the alternating ribs and groove extend vertically.

8. The ball joint of claim 6, wherein the material of the bearing fills the grooves and covers the ribs to form a smooth interior surface of the bearing.

9. The ball joint of claim 1, wherein the cage member further includes a circumferential recess in a lower portion of the cage member.

10. The ball joint of claim 1, wherein the cage member has a series of apertures, the bearing is a polymeric material, and the polymeric materials of the bearing is in the series of apertures.

11. The ball joint of claim 1, wherein the bearing includes a third surface which is cylindrical and sized to fit within the housing space of the bushing.

12. A method of making a ball joint comprising the steps of : providing a bushing with a defined housing space sized to receive ball joint components;providing a cage member having an interior cavity with a pattern of raised and recessed portions;over-molding a polymeric material on the cage member to define a bearing having a first surface that complements the pattern of raised and recessed portions of the cage member, a second surface that forms a smooth circular configuration, and a third surface which fits within the defined space of the bushing; andproviding a stem having a ball portion dimensioned to fit within the second surface of the cup member.

13. The method of claim 13, wherein the pattern of raised and recessed portions include alternating ribs and grooves, and wherein the polymeric material fills the grooves and covers the ribs during the over-molding step to form the smooth circular configuration of the bearing.

14. The method of claim 12, wherein the cage member further includes a circumferential recess in a lower portion of the cage member, and wherein the polymeric material fills the circumferential recess.

15. The method of claim 14, wherein the cage member further includes a series of apertures extending between the interior cavity of the cage member and the circumferential recess, and wherein the polymeric material fills the series of apertures.

16. A ball joint comprising: a bushing with a defined housing space sized to receive ball joint components;a cage member having an exterior surface that fits within the housing recess and an interior surface with a pattern of raised and recessed portions;a cup member over-molded on the cage member component, the cup member complements the interior surface pattern of the cage member and an includes an interior surface having a circular configuration; and,a stem having a ball portion dimensioned to fit within and complement the interior surface of the cup member.

17. The ball joint of claim 16, wherein the bushing is metallic.

18. The ball joint of claim 16, wherein the cage member is metallic

19. The ball joint of claim 18, wherein the cup member is non-metallic

20. The ball joint of claim 19, wherein the cup member is a polymeric material.