GB2052620A - Ball and socket joints - Google Patents

Abstract

A ball and socket joint incorporates a conventional housing 15 and ball pin 11. The ball pin has a ball 12 located within the housing by two bearing parts 19 and 21 of plastics material. An end closure 17 holds the ball and bearing parts within the housing. In order to prevent rotation of the upper bearing part 21, it is provided with recesses 35 in which are engaged projections 33 of the lower bearing part. <IMAGE>

Description

SPECIFICATION Ball and socket joints The invention relates to ball and socket joints and particularly but not exclusively to such joints for use in steering or suspension linkages of motor vehicles.

A typical ball and socket joint incorporates a housing with an opening at each end, a ball pin with a ball disposed within the housing and a shank extending out through one end of the housing and a plastics or similar material bearing located within the housing and providing a spherical bearing surface to allow universal angular movement of the ball pin. It is convenient for the bearing to be made in separate upper and lower parts. It is then necessary to ensure that neither part of the bearing rotates in the housing because this could interfere with correct operation of the joint. The part of the bearing at the ball pin end of the housing tends to be a wedge fit in a part of the housing which has a small angle of taper. Normally the taper is not straight but is a part of the surface of a sphere.On the other hand, the upper part of the bearing is in a typical case installed within a parallel sided section of the housing between the first mentioned part of the bearing and an end closure for the opposite end of the housing.

With this type of ball and socket joint, prevention of rotation of the second part of the bearing has previously been achieved by providing a non-circular shape to the associated part of the housing but this requires a special operation which increases the cost of the joint.

Another known type of ball joint differs from the above in that one end of the housing is closed and the bearing assembly and ball pin are inserted into the housing from an opening out of which the ball pin projects. This opening is then partially closed after insertion of the ball pin and bearing assembly to hold these parts in the housing. With this latter type of ball joint there can be a tendency for one bearing part to rotate during use of the joint.

According to one aspect of the present invention there is provided a ball and socket joint of the kind comprising: a housing; a ball pin having a ball member disposed within the housing and a shank extending out through an opening in a first end of the housing; a bearing assembly located within the housing and having a part spherical bearing surface engaged with the surface of the ball to hold the hall within the housing but to allow universal angular rotation of the ball pin about the ball centre; the bearing assembly comprising a first annular part adjacent the first end of the housing having a part spherical inner face to engage the ball, an outer face tapered towards the first end and conforming generally with the interior wall of the housing, and an inner end face: the bearing assembly also comprising a second part adjacent a second end of the housing incorporating a part spherical face engaged with the ball, an inner end face and an outer face engaged against the housing; characterised in that one bearing part is held against rotation by a wedge action between that bearing part and the housing and that the other bearing part is held against rotation by co-operating projections and recesses in the two bearing parts at their inner ends.

According to a second aspect of the invention there is provided a ball and socket joint of the kind comprising: a housing open at both ends; a ball pin having a ball member disposed within the housing and a shank extending out through a first end of the housing; a bearing assembly located within the housing and having a part spherical bearing surface engaged with the surface of the ball to hold the ball within the housing but to allow universal angular rotation of the ball pin about the ball centre; and an end cover closing the second end of the housing and holding the bearing assembly and the ball within the housing; the bearing assembly comprising a first annular part adjacent the first end of the housing having a part spherical inner face to engage the ball, an outer face tapered towards the first end and conforming generally with the interior wall of the housing and an inner end face; the bearing assembly also comprising a second part adjacent the second end of the housing incorporating a part spherical face engaged with the ball, an inner end face and an outer end face engaged against the end cover; characterised in that one bearing part is held against rotation by a wedge action between that bearing part and the housing and that the other bearing part is held against rotation by cooperating projections and recesses in the two bearing parts at their inner ends.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a cross section through a complete ball and socket joint according to the invention; Figure 2 is a more detailed cross sectional view on a larger scale of the lower part of the bearing assembly incorporated in the joint of Figure 1; Figure 3 is a view corresponding to Figure 2 of the upper part of the bearing assembly; Figure 4 is a view corresponding to Figure 1 showing a modified bearing assembly; and Figure 5 is a cross section through an alternative ball and socket joint according to the invention.

In most respects the joint shown in Figure 1 is conventional. It incorporates a conventional ball pin 11 incorporating a part spherical ball member 12 at one end. A tapered portion 13 and threaded portion 14 of the ball pin are provided to mount it to a further member not shown.

The ball pin is enclosed within a housing 1 5 which is in the form of a casting having a first opening 1 6 at its lower end through which the ball pin projects and a second opening at its upper end which is closed by an end cover 1 7. The end cover is held in position in a recess in the upper end of the housing by means of a flange 1 8 which has been spun over to hold the end cover in position.

A bearing assembly constituted by two plastics mouldings 19 and 21 is arranged within the housing and provides spherical bearing surfaces for the ball 12. The lower part 1 9 of the bearing (shown in greater detail in Figure 2) has an outer part spherical face 22 which conforms to the interior of the lower part of the housing 1 5.

Bearing part 1 9 also has a part spherical interior surface 23 which conforms to and provides a bearing surface for the ball 1 2. A series of grooves 24, only one of which is shown, facilitate distribution of lubricant. Both bearing parts may be made from a material such as polyurethane, which has satisfactory bearing properties and a degree of softness to restrict transmission of shock loads through the joint. Alternatively, the lower bearing part, which wiil take the main loads on the joint, may be of a harder bearing material such as acetal, while the upper bearing part is of a softer material such as polyurethane.

Details of the upper bearing part 21 are shown in Figure 3. This bearing part has an outer cylindrical surface 25 for fitting within a corresponding cylindrical internal surface of the housing 1 5. A part spherical inner bearing 26 with lubricant grooves 27 is provided for engagement with the ball 12. At its upper end, the bearing part 21 has a cylindrical extension 28 terminating in an outer end face 29 which as shown in Figure 1 is engaged by the end cover 1 7.

The upper end of the bearing part 21 also has an annular part spherical extension 31 which provides part of the spherical bearing surface 26 and allows resilient deformation of the upper part of the bearing member in response to pressure applied between the ball 12 and the end face 29.

The junction between the two bearing parts is offset from the diammetral plane 30.

The inner end face 32 of the lower bearing part 19 incorporates a series of for example three axial projections 33 which taper slightly in an upward direction. The inner end face 34 of the upper bearing part 21 kas corresponding recesses 35 for receiving the proiestions 33. The dimensions of the upper and lower bearing parts 19 and 21, including the projections 33 and recesses 35, are such that when the bearing parts are assembled round a ball, there is an axial clearance between the bearing parts. There is also a small circumferential clearance between the tapered projections and recesses to allow the axial clearance to be effective. On assembly of the ball joint, the bearing halves and the ball pin are inserted into the housing from above and the end cover 1 7 is placed in position.An axial load is then applied to the end cover 17 to produce pre-load in the joint by deforming the bearing assembly and particularly the upper part thereof. The upper bearing part bears against the ball which in turn bears against the lower bearing part and forces it into firm engagement with the housing. The lower bearing part becomes wedged firmly against the housing due to the part spherical surfaces which are in effect a small angle of taper and this holds the lower bearing part against rotation. The inner surface of the housing 1 5 is rough machined, which helps the wedging action to hold the bearing part. Due to the engagement of the projections 33 in the recesses 35, the upper bearing part is also held against rotation apart from a possible small movement due to clearance between the bearing parts.The tapers on the projections and recesses facilitate assembly of the two bearing parts and also facilitate the moulding operation.

The main purpose of the clearance between the bearing parts is to allow them to move together to take up wear during use of the assembly. The upper bearing part which was compressed during assembly of the joint also expands during this take up of wear so that free play does not develop. The clearance between the bearing parts also acts as a reservoir for lubricant in the same way as the grooves 26 and 27.

If the lower bearing part is made of a hard material such as acetal and the upper bearing part is made of a softer material such as polyurethane, the upper bearing part may wedge in the housing as a result of a tendency to lateral expansion caused by axial loading but the lower bearing part may not grip the housing effectively. In this case the upper bearing part would tend to prevent rotation of the lower bearing part rather than vice versa.

As an alternative, the mating surfaces of the upper part of the housing and the bearing part 21 may be tapered so as to be slightly conical rather than cylindrical to provide a wedging action of the upper bearing part in the housing as the bearing is held down by end cover 17.

The gap between the ball pin 11 and the housing 15 which would otherwise give access to the interior of the housing for moisture and dirt is closed by a conventional flexible eiastomeric seal 36.

In the modification shown in Figure 4, the annular bearing member 21 has been replaced by a bearing member which is substantially hemispherical in that it extends completely across the opening in the upper end of the housing 15. In order to accommodate this hemispherical bearing member, a slightly modified configuration of end cover 1 71 is employed. In other respects, the ball and socket joint of Figure 4 corresponds to that of Figure 1.

Figure 5 shows a different form of ball joint assembly according to the invention. The ball pin 211, with its spherical ball member 212, tapered pdrtion 213 and threaded portion 214 corresponds broadly to that of the embodiment shown in Figure 1.

The housing 21 5 is generally cup shaped instead of being open.at both ends so that it incorporates a permanent integral closure for one end. The lower end of the housing is open to allow the ball pin 211 to project from the housing and to allow insertion of the ball 212 and two parts 219 and 221 of the bearing assembly. The bearing member 21 9 is generally hemispherical, both internally and externally and its outer hemispherical portion seats in a hemispherical interior wall of the housing 21 5. Slight variations from the hemispherical shape occur near the axis to facilitate production of the components. The lower bearing member 221 is annular, with a part spherical inner face and cylindrical external face.A retaining washer 21 7 which is held in position by a spun over flange 21 8 of the housing bears against the lower end face of bearing member 221 to hold the two bearing members and the ball 212 within the housing under compression in the same way as end cover 1 7 of Figure 1 holds corresponding components within the interior of the housing. As with the embodiment of Figure 1, there is a small gap between the two bearing parts 219 and 221 and these parts are held against relative rotation by means of projections 233 on the lower bearing member which project into recesses 235 in the upper bearing member. As in the other embodiments, a flexible elastomeric seal 236 is provided between the housing and the ball pin.

The ball and socket joint shown in Figure 5 is intended for taking end loads which are primarily in such a direction as to force the ball pin upward into the housing. For this reason it is desirable to make the upper bearing part 21 9 of a material such as acetal, which is a hard material with good bearing properties. In such a case, the lower bearing part 221 could be made from a more flexible material such as polyurethane. In such a case, the tendency to lateral expansion of the polyurethane bearing part, which presses it into firm engagement with the rough machined surface of the housing, tends to hold this bearing part against rotation. Contrary to this, there may be some tendency for the harder acetal bearing part to rotate in its housing because the hard material could tend to slide over rather than become embedded in the rough surface of the housing.

The projections and depressions 233 and 235 thus help to hold the upper bearing member 21 9 against rotation. With some other arrangement of bearing parts, it could be that the lower bearing part 221 would tend to rotate while the upper bearing part 21 9 is wedged against rotation. In that case, the projections and recesses 233 and 235 would tend to hold the lower bearing part 221 against rotation.

Claims (8)

1. A ball and socket joint of the kind comprising: a housing; a ball pin having a ball member disposed within the housing and a shank extending out through an opening in a first end of the housing; a bearing assembly located within the housing and having a part spherical bearing surface engaged wi?h the surface of the ball to hold the ball within the housing but to allow universal angular rotation of the ball pin about the ball centre; the bearing assembly comprising a first annular part adjacent the first end of the housing having a part spherical inner face to engage the ball, an outer face, conforming generally with the interior wall of the housing and an inner end face; the bearing assembly also comprising a second part adjacent a second end of the housing incorporating a part spherical face engaged with the ball, an inner end face and an outer face engaged against the housing; characterised in that one bearing part is held against rotation by a wedge action between that bearing part and the housing and that the other bearing part is held against rotation by co-operating projections and recesses in the two bearing parts at their inner ends.

2. A ball and socket joint of the kind comprising: a housing open at both ends; a ball pin having a ball member disposed within the housing and a shank extending out through a first end of the housing; a bearing assembly located within the housing and having a part spherical bearing surface engaged with the surface of the ball to hold the ball within the housing but to allow universal angular rotation of the ball pin about the ball centre; and an end cover closing the second end of the housing and holding the bearing assembly and the ball within the housing; the bearing assembly comprising a first annular part adjacent the first end of the housing having a part spherical inner face to engage the ball, an outer face tapered towards the first end and conforming generally with the interior wall of the housing, and an inner end face; the bearing assembly also comprising a second part adjacent the second end of the housing incorporating a part spherical face engaged with the ball, an inner end face and an outer end face engaged against the end cover; characterised in that one bearing part is held against rotation by a wedge action between that bearing part and the housing and that the other bearing part is held against rotation by cooperating projections and recesses in the two bearing parts at their inner ends.

3. A ball and socket joint as claimed in Claim 1 or Claim 2 wherein the second bearing part is of softer material than the first bearing part so that it tends to wedge in the housing and wherein the projections and recesses cause the second bearing part to prevent rotation of the first bearing part.

4. A ball and socket joint as claimed in Claim 2 wherein the mating surfaces of the housing and the second bearing part are tapered to provide a wedging action between the upper bearing part and the housing.

5. A ball and socket joint as claimed in Claim 1 or Claim 2 wherein the bearing assembly is constituted by plastics mouldings.

6. A ball and socket joint as claimed in any one of the preceding claims wherein the projections and recesses are tapered.

7. A ball and socket joint as claimed in any one of the preceding claims wherein a clearance is provided between the inner end faces of the two bearing parts and between the extremities of the projections and the roots of the recesses.

8. A ball and socket joint substantially as described with reference to and as illustrated by the accompanying drawings.