GB2170265A

GB2170265A - Ball-and-socket joint

Info

Publication number: GB2170265A
Application number: GB08600764A
Authority: GB
Inventors: Gunther Henkel; Peter Busch
Original assignee: TRW Fahrwerksysteme GmbH and Co KG
Current assignee: TRW Fahrwerksysteme GmbH and Co KG
Priority date: 1985-01-24
Filing date: 1986-01-14
Publication date: 1986-07-30
Also published as: DE3502233C1; GB2170265B; FR2576374B1; FR2576374A1; IT1204439B; GB8600764D0; IT8619166A0

Abstract

A ball-and-socket joint has a ball (1) held in the inner space off housing, with two bearing shells (3) placed between the joint housing (8) and the ball (1). Two pressure rings (6) apply by their inner circumferential surfaces (7) onto the outer circumferential surfaces of respective bearing shells (3), and are made of a resilient plastics material. The bearing shells (3) have conical surfaces engaging the pressure rings (6). The pressure rings (6) apply against the inner wall of the housing (8) through two narrow contact strips (18,19) at edges of the concavely-arched outer circumferential surface (9), and through a projecting annular web (16) with grooves (17) adjoining it on both sides. The entire arrangement of pressure rings (6) and bearing shells (3) is compressed axially by flange 12 and ring 13 abutting the pressure rings (6), giving resilient deformation thereof. <IMAGE>

Description

SPECIFICATION Ball-and-socket joint The invention relates to a ball-and-socket joint. It is known from West German Utility Model Specification 1937933 to provide a ball-and-socket joint with a ball held in the inner space of a housing, with two bearing shells made of a hard, resilient plastics material placed between the joint housing and the ball, with two pressure rings made of a soft synthetic plastics material, applying by their inner circumferential surfaces on respective outer circumferential surfaces of the bearing shells, the bearing shells being provided in the area of application of the pressure rings with conical surfaces tapering inwardly towards the outside of the joint, the pressure rings each applying over a narrow contact area and each having its outer circumferential surface extending onto the inner wall of the joint housing, and front areas of the pressure rings abutting respective stops, between which stops the entire arrangement of pressure rings and bearing shells is compressed in the axial direction of the inner space of the housing.

This ball-and-socket joint suffers from the drawback that the compact cross-sectional shape of the pressure rings permits of only slight material deformation under load. Thus, even when the tolerances of the outer circumferential surface of the pressure rings and of the inner diameter of the joint housing are very close, great forces are required for assembly, which lead to a high initial stress in the bearing shells and result in an excessively high torque in the ball-and-socket joint. With specific tolerance ranges in the constructional elements concerned there is a high tolerance in the torque. In operation, load fluctuations result in widely varying torques which are not cushioned.

The invention provides ball-and-socket joint comprising: a ball held in the inner space of a housing; two bearing shells made of a hard, resilient plastics material disposed between the joint housing and the ball; two pressure rings made of a soft, synthetic plastics material applying through their inner circumferential surfaces against respective outer circumferential surfaces of the bearing shells, the bearing shells being provided in the application area of the pressure rings with conical surfaces tapering inwardly towards the outside of the joint, the pressure rings each having a concavely-arched outer circumferential surface in which a projecting annular web is formed, on both sides of which web an annular groove is formed, and each pressure ring applying againsdt the inner wall of the joint housing through two narrow contact strips of the outer circumferential surface of the pressure ring and through the outer circumferential surface of the web; and stops provided in the joint housing against which front areas of the pressure rings applying thereby to tension the pressure rings and bearing shells in the axial direction of the inner space of the housing.

This ball-and-socket joint has the advantage that the improved deformability of the pressure rings brings about smaller deformation forces after assembly. The revolving web cushions the forces occurring in the radial direction, and by the selection of the web width and the groove depth it is possible to influence the spring characteristics of the pressure rings. The small area of application of the external circumferential surfaces of the pressure rings simplifies insertion of the pressure rings into the joint housing. The stated properties of the pressure rings permit the manufacture of ball-and-socket joints with smaller tolerances in the torque.

In a preferred embodiment the inner surfaces of the pressure rings are convexly arched pressure surfaces which, on assembly, apply onto the conical surfaces of the bearing shells and provide for the compensation of axial inaccuracies in manufacture.

The ball-and-socket joint is preferably constructed with identical bearing shells and identical pressure rings. This arrangement has the advantage that all the constructional elements have the same loading properties.

The width and the depth of the grooves are preferably selected that on resilient deformation of the pressure rings the side walls of the webs bulge without restriction. This arrangement has the advantage that the pressure rings deform over a large area in proportion to the initial stress.

In order that the invention may be better understood, a preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, wherein: Figure 1 is an exploded view of the ball and-socket joint in partial longitudinal section; Figure 2 is a view of the ball-and-socket joint of Figure 1, as assembled, in partial longitudinal section; Figure 3 is a longitudinal section of a pressure ring of the joint of Figure 1, to an enlarged scale; and Figure 4 is an enlarged section of the pressure ring.

A ball-and-socket joint has a ball 1 with integral diametrically-opposed journals 2. The ball 1 is of polyoxymethylene plastics material, so that the whole area of each respective sliding surface 4 of the bearing shells 3 applies onto the surface of the ball 1. The outer surfaces of the bearing shells 3 are formed partly as conical surfaces 5 tapering inwardly towards the outside of the joint, onto which surfaces two identical pressure rings 6 with convexly-arched inner pressure surfaces 7 apply. The pressure rings 6 support the bearing shells 3 in the joint housing 8. Outer surfaces 9 of the pressure rings 6 apply against an inner wall 10 of the joint housing 8, while flat front surfaces 11 of the pressure rings 6 apply respectively against an annular flange 12 of the joint housing 8 and against an abutment ring 13.The abutment ring 13 is retained by a securing ring 14 held in an annular groove 15 of the joint housing 8.

The pressure rings are made of a soft, resilient polyurethane plastics material, whose outer surfaces 9 are concavely-arched, each being formed with a projecting annular web 16 on both sides of which an annular groove 17 is formed, as shown in Figure 4. The dimensioning of the pressure rings is such that they apply against the inner wall 10 through the outer periphery of the web 16 and along two contact strips 18, 19 at the edges of the outer surface 9, while the front surfaces 11 of the pressure rings apply against the annular flange 12 and the abutment ring 13, in such a manner that the pressure rings 6 deform resiliently.

Figure 4 shows the way in which the pressure rings 6 are deformed resiliently under an axial stressing force P1, a reaction P2 in the application areas of the outer circumferential surface of the pressure rings 6, and a force P3 in the pressure area 7. The web 16 is bulged like a pressure spring on the sides, partly filling the surrounding grooves 17. Preferred deformation areas are also the external circumferential surfaces 9 of the pressure rings 6, which are deformed similarly to a bending beam mounted at three points, and the pressure area 7 which applies against the conical surface 5 of the bearing shell 3.

In Figure 4, surfaces 7 and 9 of the pressure ring, and the side walls of the web 16 thereof, are shown as unbroken lines 7a,9a,16 for the non-deformed state, and broken lines 7b,9b,16 for the deformed state.

The ball-and-socket joint consists of few constructional elements and meets adequately high demands on resilience and consistent values of torque.

Claims

1. Ball-and-socket joint comprising: a ball held in the inner space of a housing; two bearing shells made of a hard, resilient plastics material disposed between the joint housing and the ball; two pressure rings made of a soft, synthetic plastics material applying through their inner circumferential surfaces against respective outer circumferential surfaces of the bearing shells, the bearing shells being provided in the application area of the pressure rings with conical surfaces tapering inwardly towards the outside of the joint, the pressure rings each having a concavely-arched outer circumferential surface in which a projecting annular web is formed, on both sides of which web an annular groove is formed, and each pressure ring applying against the inner wall of the joint housing through two narrow contact strips of the outer circumferential surface of the pressure ring and through the outer circumferential surface of the web; and stops provided in the joint housing against which front areas of the pressure rings apply thereby to tension the pressure rings and bearing shells in the axial direction of the inner space of the housing.

2. Ball-and-socket joint according to claim 1, wherein the inner circumferential surfaces of the pressure rings are formed as convexlyarched pressure surfaces.

3. Ball-and-socket joint according to claim 1 or 2, wherein the bearing shells and the pressure rings are in each instance of identical construction.

4. Ball-and-socket joint according to any of claims 1 to 3, wherein the width and depth of the grooves of the pressure rings are such that on resilient deformation of the pressure rings the side walls of the webs are arched without restriction.

5. Ball-and-socket joint substantially as described herein with reference to the accompanying drawings.