GB2233385A

GB2233385A - Ball and socket joint

Info

Publication number: GB2233385A
Application number: GB8914045A
Authority: GB
Inventors: Akira Nemoto; Yasunori Hamaguchi; Hironori Koga; Tatsuyoshi Tsuji
Original assignee: Musashi Seimitsu Industry Co Ltd
Current assignee: Musashi Seimitsu Industry Co Ltd
Priority date: 1989-06-19
Filing date: 1989-06-19
Publication date: 1991-01-09
Anticipated expiration: 2009-06-19
Also published as: GB2233385B; DE3920683A1; GB8914045D0; DE3920683C2

Abstract

A ball and socket joint assembly for use in motor vehicle suspensions comprises a socket (6) and a spherical head (4) of a ball stud (2) with an interposed open-side bearing (11) and a closed-side bearing (20). The closed-side bearing (20) has a substantially semispherical concave seat surface (25) made up of a radially outer annular curved surface (26) and a radially inner annular curved surface (27). Under normal load, the outer surface (5) of the spherical head (4) is in sliding contact with only the inner surface (27), while under increased load, through resilient deformation of the bearing, both the inner and outer surfaces (26, 27) are brought into contact with the head, whereby small torque is required under normal load and the load withstanding capability is increased under heavy load. The bearings (11) and (20) abut each other whereby the load withstanding capability is further increased. A seal (60) has an interference fit on the socket. Lubricating grooves (32) are formed in the bearing (20). <IMAGE>

Description

X 1 4 1 BALL AND SOCKET JOINT ASSEMBLY :2,- The present invention relates

to a tension type ball and socket joint assembly used, for example, for a suspension system of a motor vehicle or the like.

A teAsion type ball and socket joint assembly in which the bearing for the ball is divided in the axial direction into two halves leaving a gap therebetween in order to attain low torque is well known in the art as is disclosed in Japanese Utility Model Laid-Open No. 57-203,136.

The demand for low torque and a high degree of capability of withstanding high load is becoming increasingly strict, and especially the recent trend attaches great importance to the capability of withstanding high load. Therefore, there is a demand for development of tension type ball and socket joints which can operate at low torque as in the cases of the conventional tension type ball and socket joint assemblies and which additionally has a high degree of capability of withstanding high load.

In view of the above, the primary object of the present invention is to provide a ball and socket joint assembly which operates at low torque, but can withstand high load.

To the above and other ends, according to the present invention, in a tension type ball and socket joint assembly of the type in which a spherical head formed at one end of a ball stud is pivotably supported in a socket, which has a smaller opening at one axial end thereof and a larger opening at the other axial end that is closed by a closing plate, and in which there are interposed between the spherical head and the socket an open-side bearing disposed adjacent to the smaller opening and comprising a cylindrical portion and a shoulder portion integrally connected to said cylindrical portion, and a closed-side bearing disposed adjacent to 1 2 the larger opening and comprising a semispherical cupshaped bearing portion and an outer peripheral wall portion integrally connected to said bearing portion so as to encircle the same: a semispherical seat surface forming the inner concave surface of said cup-shaped bearing portion is provided which is made up of coaxial different annular curved surfaces joined with each other, and the end part of said cylindrical portion of said open-side bearing, remote from said smaller opening, is in abutment against the end part of said outer peripheral wall portion of the closed-side opening, remote from said larger opening.

With the above-described construction, when normal load is imposed on the ball stud, the surface of the spherical head of the ball stud is in sliding contact only with the radially inner annular curved surface so that the area of the surface of the sliding contact between the bearing and the spherical head is relatively small, while when high load is imposed on the ball stud, the closed-side bearing is elastically deformed so that the surface of the spherical head of the ball stud is brought into contact also with the radially outer annular curved surface, and consequently the surface of sliding contact between the bearing and the spherical head is increased in area.

Furthermore, within the socket, the open-side bearing is supported by the closed-side bearing in the axial direction without leaving any gap therebetween so that even when high load is imposed on the ball stud, no plastic deformation of the open-side bearing occurs and therefore an undesirable increase in gap (causing chattering) -between the open-side and closed-side bearings is prevented.

Some preferred embodiments of the present invention will now be described in detail hereinafter with reference to the accompanying drawings in which:

3 FIG. 1 is a sectional elevation illustrating a first preferred embodiment of the tension type ball and socket joint assembly in accordance with the present invention; FIG. 2 is a partial sectional view, on an enlarged scale, thereof illustrating major component parts thereof; FIG. 3 is a sectional ' elevation illustrating a bearing on the closed side of the assembly according to the first embodiment shown in FIG. 1; FIG. 4 is a plan view thereof; FIG. 5 is a sectional elevation of a second preferred embodiment of the tension type ball and socket joint assembly in accordance with the present invention; FIG. 6 is a sectional elevation of a bearing on the closed side of the assembly according to the second embodiment shown in FIG. 5; FIG. 7 is a plan view thereof; FIG. 8 is a view similar to FIG. 2, but illustrating a third preferred embodiment of the tension type ball and socket joint assembly in accordance with the present invention; FIG. 9 is a view illustrating one example of a socket of the ball and socket joint assembly in accordance with the present invention when the joint assembly is covered with a dust cover; FIG. 10 is a view, on an enlarged scale, of a portion of FIG. 9 indicated by a circle X; FIG. 11 is a graph illustrating the length of time in which a dust cover is installed in place in case of the construction shown in FIG. 9; and FIG. 12 is a view for explaining the advantages of the construction shown in FIG. 10.

First Embodiment (FIGS. 1-4) FIG. 1 illustrates a first preferred embodiment of the ball and socket joint assembly in accordance with the present invention, the assembly being generally indicated by 1. A ball stud generally designated by 2 comprises a i 1 1 4 shank 3 and a spherical head 4. The spherical head 4 is received in a socket 6 substantially in the form of a cylinder of which the bottom is closed by a closing plate 10. An open-side bearing 11 is disposed on the side of a smaller opening 7 within the socket 6, and a closed-side bearing 20 is disposed on the side of a larger opening 9 of the socket 6 closed by the closing plate 10.

The spherical head 4 at one end of the ball stud 2 are supported by both the open-side bearing 11 and the closed-side bearing 20 in such a way that the head 4 can pivot within the socket 6, and the shank 3 of the ball stud 2 extends outwardly through the smaller opening 7 of the socket 6.

As best shown in FIG. 2 on an enlarged scale, the open-side bearing 11 is made of a synthetic resin and has a cylindrical portion 13 of which the outer surface snugly mates with the inner wall of a cylindrical portion 34 of the socket 6. The open-side bearing 11 further has a shoulder portion 12 of which the outer surface snugly mates with the inner surface of a shoulder portion 8 on the open side of the socket 6. The shoulder portion 12 is in the form of a wedge of which the thickness increases from the diametrically inner side to the diametrically outer side. The shoulder portion 12 is integrally connected at its thickest portion to the cylindrical portion 13. The cylindrical portion 13 comprises a small-diameter section 16, a conical section 17 which is integrally connected to the small-diameter portion 16 and is enlarged in diameter like a frustum of H a cone in a direction away from the portion 16, and a large-diameter section 18 connected integrally with the conical section 17.

An inner spherical surface 15 of the open-side bearing 11 is in sliding contact with the outer surface 5 of the spherical head 4 of the ball stud 2. The inner spherical surface 15 is defined as a toroidal surface of which the radium R2 is greater than the radius R, of the 1 spherical head 4 so that the inner spherical surface 15 is caused to make the strongest contact with the outer surface of the head 4 at an intermediate region of the surface 15 between the shoulder portion 12 and the cylindrical portion 13. That is, the imaginary center 02 of the toroidal surface is located at a position closer to the lower end (as viewed) of the spherical head 4 than the center 0. of the spherical head 4 and is offset from the axis of the socket 6 in the radial direction. As a lo result, the outer surface 5 of the spherical head 4 defines gaps 19a and 19b between the open-side bearing 11 and the surface 5 of the spherical head 4 at the opened rim of the open-side bearing 11 and at the equator of the head 4, respectively, or the surface 5 makes weaker contact with the surface 15 at the shoulder portion 12 and the cylindrical portion 13 than at the intermediate portion.

As shown in FIGS. 1, 3 and 4, the closed-side bearing 20 is made of polyurethane and comprises a bearing portion 21 in the form of a semispherical cup and an outer peripheral wall 22 which is formed integrally so as to surround the bearing portion 21 and which is substantially in the form of a cylinder. As shown in FIG. 1, the outer peripheral surface of the outer peripheral wall portion 22 is snugly mated with the inner surface of the socket 6. An end surface 29 (FIGS. 3 and 4) of an end part 23 of the wall portion 22, opposite to the larger opening 9 is pressed by the closing plate 10 against an end surface 19 (FIG. 2) of an end part 14 of the open-side bearing 11, opposite to the smaller opening 7. As a consequence, the open-side bearing 11 is supported by the closed-side bearing 20 without leaving any gap therebetween in the axial direction so that even when heavy load is imposed on the ball stud 2, no plastic deformation of the open-side bearing 11 occurs, and therefore an abnormal increase in play between the open- 4F 1 6 side and closed-side bearings is prevented, and chattering is eliminated.

The spherical seat 25 which is the inner concave surface of the closedside bearing 20 comprises a radially inner curved surface 27 of a radius R3 with the center 01 and a radially outer curved surface 26 of the same radius R3 with the center 03 offset from the center 01 toward the bearing 20. The surface 26 is recessed relative to the surface 27. The outer curved surface 26 is joined with the inner curved surface 27, an annular stepped portion 28 being formed at the joint between the inner curved surface 27 and the outer curved surface 26. It therefore follows that when normal load is imposed on the ball stud 2, the surface 5 of the spherical head 4 is in sliding contact only with the inner curved surface 27 of the closed- side bearing 20 so that the area of sliding contact between the bearing 20 and the head 4 is small, and therefore operation torque of the ball and socket joint assembly 1 is maintained at a low level. On the other hand, when a heavy load is imposed on the ball stud 2, elastic deformation of the closed-side bearing 20 occurs so that the surface 5 of the spherical head 4 is caused to make sliding contact also with the outer curved surface 26. As a result, the area of the sliding contact between the bearing 20 and the head 4 is increased so that the ball and socket joint assembly 1 can withstand the heavy load.

An annular projected portion 31 extending from the edge of an upper opening of the bearing portion 21 of the closedside bearing 20 is located radially inwardly of the large diameter section 18 of the cylindrical portion 13 of the open-side bearing 11 so as to prevent displacement of the closed-side bearing 20 in the horizontal direction.

A through hole 24 extending through the center of the bearing 20 serves as an air vent. Radial grooves 32 are formed in the inner curved surface 27 and serve as a 9 7 grease reservoir. An annular groove 33 is formed at the bottom surface of the bearing 20.

When the ball and socket joint assembly 1 is to be assembled, the openside bearing 11 is first press-fitted into the socket 6, and then the inner surface of the bearing 11 is applied with a lubricating oil. Thereaftert the ball stud 2 is inserted from the opened bottom of the socket until the head 4 is brought into contact with the bearing 11. Then, the closed-side bearing 20 is fitted in position into the socket 6 through the open bottom thereoft and finally the closing plate 10 is attached to the socket 6 to close the open bottom by clinching the bottom edge of the socket 6.

Second Embodiment (FIGS. 5r 6 and 7) Referring next to FIGS. 5, 6 and 7, a second preferred embodiment of the present invention will be described. This is also a tension type ball and socket joint assembly and is generally designated by la. The second embodiment is different from the first embodiment in that the end surface of the projected portion 31 (FIG. 3) of the closed-side bearing 20 and the end surface 29 (FIG. 3) of the end part 23 of the outer peripheral wall portion 22 are joined with each other to form a coplanar surface 29a (FIG. 6) and that the end surface of the bearing portion 21 of the closed-side bearing 20 is pressed against the end surface 19 of the cylindrical portion 13 of the open-side bearing 11.

In the second embodiment, the spherical seat surface 25 of the closedside bearing 20 is made up of a radially inner curved surface 27 of a radius R4 with the center coincident with the center 01 of the spherical head 4 and of a radially outer curved surface 26 of a radius R. with the center 0. which is displaced from the center 01 toward the shank of the ball stud and is offset radially outwardly from the axis of the s.ocket 6, the outer curved surface 26 being merged with the inner curved surface 27.

p 8 According to the above-described first and second embodiments, when a normal load is imposed on the ball stud 2, the surface of the spherical head 4 of the ball stud 2 is in sliding contact only with the radially inner curved surface 27 so that the area of the sliding contact between the bearing 20 and the spherical head 4 is small, while when a heavy load is imposed on the ball stud 2, elastic deformation of the closed-side bearing 20 occurs so that the surface of the spherical head 4 is further brought into sliding contact with the other curved surface 26 of the spherical seat surface, and consequently the area of the sliding contact between the bearing 20 and the spherical head 4 is increased.

Furthermore, within the socket 6, the open-side bearing 11 is supported in the axial direction by the closed-side bearing 20 without any gap therebetween. Therefore, even when a high load is imposed on the ball stud 2, plastic deformation of the open-side bearing 11 is prevented so that an abnormal increase in play between the open-side and closed-side bearings is eliminated. (That is, chattering is eliminated.) As a result, low operation torque of the ball and socket joint assembly is ensured while a high resistance to high load is obtained.

In the first and second embodiments, in order to ensure a low degree of operation torque and a high degree of capability to withstand high load. mainly the closedside bearing 20 is improved, but in the case of a third embodiment to be described hereinafter, the open- side bearing is so improved that a low degree of operation torque and a high degree of capability to withstand high load may be ensured.

Third Embodiment (FIG. 8) Referring now to FIG. 8, within the small opening 7, the socket 6 has a conical seat 40 extending substantially tangentially to the surface 5 of the spherical head 4 of the ball stud 2. The socket 6 has also a cylindrical seat 41 which is connected to the 9 largest diameter portion of the conical seat 40 and extends in the axial direction of the socket 6 slightly beyond the equater of the spherical head 4 toward the lower end (as viewed) thereof. A stepped surface 42 in the form of a frustum of a cone is connected to the lower end (as viewed) of the cylindrical seat 41, and a largediameter cylindrical seat 43 is formed at the largest diameter side of the surface 42.

in the third embodiment, the angle 0 of intersection between the conical seat 40 and the axis of the socket 6 is determined approximately 520. The gap or spacing between the conical and cylindrical seats 40 and 41 and that surface portion of the spherical head 4 which is closest to the conical and cylindrical seats 40 and 14 must be reduced to a minimum as practically as possible. For instance, in the third embodiment, the gap is selected to be of the order of about 0.8 mm.

An open-side bearing 11 which is molded from a synthetic resin has an inner surface which mates with a part of the surface of the spherical head 4 on the side of the shank 3. The outer surface of the open-side bearing 11 mates with the conical and cylindrical seats and 41 and the large-diameter cylindrical seat 43 of the socket 6.

The open-side bearing 11 has a shoulder portion 44 which has the greatest thickness in the vicinity of a portion at which the conical seat 40 is joined with the cylindrical seat 41. The bearing 11 further has an extremely thin opening edge portion 45 in the region in which the conical seat 40 and the spherical head 45 are closest to each other, an equater portion 46 of which the thickness is substantially the same as that of the opening edge portion 45, a cylindrical portion 47 extending downwardly (as viewed) from the lower portion of the equater portion 46, a flange shoulder portion 48 which extends downwardly (as viewed) from the lower portion of the equater portion 46 which diverges in the 0.

form of a frustum of a cone, and a thick flange portion 49. Thus, the portions extending from the upper and lower portions, respectively, of the thick shoulder portion 44 are in the form of a wedge which is extremely thin in the region in which the head 4 and the bearing 11 are closest to each other.

As in the case of FIG. 2, a seat surface 51 which is the inner surface of the shoulder portion 44 of the bearing 11 is defined as a'toroidal surface of which the lo radius of curvature R2 is greater than the radius of curvature R1 of the spherical head 4 so that the seat surface 51 is caused to make the strongest contact with the spherical head 4 in the region between the conical and cylindrical seats 40 and 41. ' That is, the imaginary center 02 of the toroidal surface is displaced off the center 01 of the spherical head 4 toward the extreme end thereof and is offset radially from the axis of the socket 6. As a result, gaps lga and 19b are formed adjacent to the opening edge portion 45 and the equater portion 46 of the bearing 11, or the surface 5 of the head 4 makes weaker contact with the portions 45 and 46 than with the thick shoulder portion 44.

A gap L is formed between the flange shoulder portion 48 and the stepped surface 42 of the socket so that the surface of the bearing 11 in oppposing relationship with the conical seat 40 can be brought into close contact therewith and that the bearing 11 is positively and securely fixed in the socket 6. Furthermore, as indicated by the two-dot chain lines, the flange portion 49 is interference-fitted into the largediameter seat 43 with an interference P from its free state. Because of the interference P of the flange portion 49 and the gap L, when the bearing 11 is pressfitted into the socket 6, the cylindrical portion 47 is deformed so as to form a curved embracing portion 52 which embraces the portion of the spherical head 4 lower (as viewed) than the equater portion 46 thereof. As 11 described above, when the flange portion 49 is pressfitted into the largediameter cylindrical portion 43 of the socket 6, the gap L is defined between the opposing surfaces of the stepped surface 42 of the socket 6 and the flange shoulder 48. The gap L enables the embracing portion 52 to be elastically enlarged when the spherical head 4 of the ball stud 2 is press-fitted into the bearing 11.

Furthermore, since the embracing portion 52 is forced radially outwardly when the head 4 is fitted, the equater portion 46 of the bearing 11 receives a force tending to cause it to move away from the surface 5 of the head 4. As a result, the pressure of contact between the surface 5 of the head 4 and the equater portion 46 is reduced and kinetic torque of the ball stud 2 is effectively decreased.

In the third embodiment, the closed-side bearing 20 is substantially the same as those shown in FIG. 1 or FIG. 5 and is assembled in the state compressed in the axial direction.

Next, how the ball and socket joint assembly la is assembled will be described below.

First, the bearing 11 is press-fitted into the socket 6, and the flange portion 49 is securely fitted to the large-diameter seat 43 while the bearing 11 is brought into intimate contact with the conical seat 40. Then, after the inner surface of the bearing 11 is applied with a lubricating oil, the ball stud 2 is inserted from the opened bottom of the socket 6 until the H head 4 is brought into contact with the bearing 11. Thereafter, the closed-side bearing 20 is inserted from the lower side through the open bottom of the socket 6 and brought into contact with the head 4. Finally, the closing plate 10 is attached to the socket 6 to cover its open bottom and is securely held in position by deforming the bottom edge of the socket 6.

1 12 I.

In the third embodiment, a load transmitted from the spherical head 4 of the ball stud 2 is concentrated at the thick shoulder portion 44 of the bearing 11 in the vicinity of the line of intersection between the seats 40 and 41. Since the two portions 45 and 47 extending from the thick shoulder portion 44 of the bearing 11 are in the form of extremely thin wedges disposed in the regions in which the surface 5 of the head 4 is closest to the seats 40 and 41, the synthetic resin material of the two portions 45 and 47 will tend to move like a wedge into the extremely thin spaces between the head surface 5 and the bearing 11 when the thick shoulder portion 44 is subjected to compression. On the other hand, the load imposed on the head 4 causes an action which forces the resin material of the portions 45 and 47 to be pushed back from within the extremely thin spaces toward the thick shoulder portion 44 so that the resin material is confined between the two extremely thin spaces on both sides of the thick shoulder portion 44 and is prevented to flow. Thereforer the capability of withstanding high load of the ball and socket joint assembly is increased while a low degree of operation torque is maintained.

Furthermore, in the third embodiment, there exists a sufficient difference in length between the cylindrical portion 47 and the cylindrical seat 41, so that the gap L is produced between the stepped surface 42 and the flange shoulder portion 48. This gap L allows the insertion of the head 4 after the bearing 11 is press- fitted into the socket 6, without causing deformation of the essential portions of the bearing 11. Moreover, when the ball and socket joint assembly is assembled, the gap L and the interference P coact to curve the cylindrical portion 47 of the bearing 11 so as to embrace and hold the portion below the equater 46 of the head 4 so that the pressure of contact between the equater portion 46 of the bearing 11 and the portion of the surface 5 of the head 4 in opposing relationship with the equater portion 46 is 13 decreased. Therefore, the capability of withstanding high load of the ball and socket joint assembly is increased while a low degree of operation torque is maintained.

Dust Cover PIGS. 9-11 illustrate a dust cover for enclosing any one of the ball and socket joint assemblies described above.

FIG. 9 illustrates a state immediately before a dust cover 60 is attached to the socket 6. The dust cover 60 is made of an elastic material such as a rubber and has a smallerdiameter opening 61 and a larger-diameter opening 62 at the upper and lower (as viewed) portions, respectively. The shank 3 of the ball stud 2 is fitted into the smaller opening 61 while a dust-cover attachment portion 8 of the socket 6 is fitted into the larger opening 62. A reinforcing ring 71 is embedded in the rim portion of the smaller opening 61 and the rim portion of the larger opening 62 is securely held in an annular groove 70 of the socket 6 by means of an annular clip or circlip 72.

The dust-cover attachment portion 8 of the socket 6 and the larger opening 62 of the dust cover 60 are shown on an enlarged scale in FIG. 10 which shows the portion surrounded by the circle X in FIG. 9. An annular flange 65 of the dust-cover attachment portion 8 has a tapered flange surface 66 formed by chamfering the outer edge portion of the upper surface of the flange portion 65 at an angle a of from 150 to 600, and an outer peripheral surface 68 in parallel with the axis. The abovementioned annular groove 70 is defined adjacent to the flange portion 65.

When the outer diameter of the upper end surface 67a of the flange portion 65 is represented by A; the outer diameter of the lower end surface 67b, B; and the inner diameter of the larger opening 62 of the dust cover 60, 14 C# they are so determined to satisfy the following relation:

A < C < B Next, the method for attaching the dust cover 60 to the socket 6 will be described.

In order to attach the dust cover 60 to the socket 6 f or the assembly of the ball and socket joint assembly, the pressing operation is carried out in such a way that the dust cover 60 is compressed in the axial direction by using a jig 73 in order for the larger opening 62 of the dust cover 60 to be attached to the dust-cover attachment portion 8 of the socket 6. When the dust cover 60 is compressed by the jig 73, the pressure inside the dust cover 60 rises so that the inner diameter of the larger opening 62 is enlarged. Therefore, the larger opening 62 of the dust cover 60 passes over the flange 65 of the dust-cover attachment portion 8, and the rim of the larger opening 62 is fitted into the annular groove 70 of the socket 6 as indicated by the two-dot chain lines in FIG. 9.

FIG. 11 illustrates the relation of the chamfered angle of the tapered flange surface 66 and the time required for attaching the dust cover to the socket. As shown in this figure, since the angle of chamfer selected is at a value from 1510 to 600, the pressure of the surface contact between the tapered flange surface 66 of the socket 6 and the rim of the larger opening 62 of the dust cover 60 can be increased so that the leakage of air from within the dust cover is prevented and therefore the attachment of the dust cover 60 to the socket 6 can be carried out within a short period of time.

Since the outer edge of the upper end surface 67a of the flange 65 is chamfered, there is no fear that the dust cover 60 is damaged by the edge of the flange during the attachment of the dust cover 60 to the socket 6.

On the other hand, in the case of the prior art as shown in FIG. 12, the outer diameters A and B of the upper and lower end surfaces, respectively, of the flange 65 of the dust- cover attachment portion 8 are equal. Therefore, when the dust cover 60 is to be attached to the socket 6, air leakage occurs through the surface of the contact between the inner peripheral surface of the larger opening 62 of the dust cover 60 and the outer peripheral surface of the flange 65 of the dust-cover attachment portion 8 of the socket 6 so that the pressure inside the dust cover 60 drops. Therefore, the enlargement of the diameter of the larger opening 60 is retarded and consequently it becomes difficult to attach the dust cover 60 to the socket 6.

is J 16

Claims

CLAIMS:

1. A tension type ball and socket joint assembly of the type in which a spherical head formed at one end of a ball stud is pivotably supported in a socket which has a smaller opening at one axial end thereof and a larger opening at the other axial end that is closed by a closing plate, and in which there are interposed between the spherical head and the socket an open-sided bearing disposed adjacent to the smaller opening and comprising a cylindrical portion and a shoulder portion integrally connected to said cylindrical portion, and a closed-side bearing disposed adjacent to the larger opening and comprising a semispherical cup-shaped bearing portion and an outer peripheral wall portion integrally connected to said bearing portion so as to encircle the same, wherein a semispherical seat surface forming the inner concave surface of said cup- shaped bearing portion is made up of coaxial, different annular curved surfaces which are joined with each other, and that the end part of said cylindrical portion of said open-side bearing, remote from said smaller opening, is in abutment against the end part of said outer peripheral wall portion of the closed-side opening remote from said larger opening.

2. A ball and socket joint assembly according to Claim 1 wherein a radially outer one of said annular curved surfaces is recessed relative to a radially inner one so 17 that an annular stepped portion is formed between the surfaces.

3. A ball and socket joint assembly according to Claim 2 wherein the radii of the annular curved surfaces are the same as that of the spherical head and wherein the centre of curvature of the radially inner surface coincides with the centre of the curvature of the outer surface of the spherical head, and the centre of the curvature of the radially outer surface is offset from the centre of the spherical head toward the closed-side bearing.

4. A ball and socket joint assembly according to Claim 2 or 3 wherein said radially inner curved surface is formed therein with radially extending grooves serving as a grease reservoir.

5. A ball and socket joint assembly according to Claim 1 wherein said end part of the outer peripheral wall portion of the closed-side bearing has an annular end surface abutting against the end part of the cylindrical portion of the open-side bearing, and an annular projected portion is formed on said cup-shaped bearing portion of the closed-side bearing so as to adjoin said annular end surface on a radially inner side thereof, said annular projected portion being fitted inside said open-side bearing.

6. A ball and socket joint assembly according to Claim 1 wherein the radius of said radially inner curved surface is the same as the radius of the spherical head, and the 18 centres of said radially inner curved surface and the spherical head coincide with each other, and wherein the radius of said radially outer curved surface is substantially the same as that of the spherical head and the centre of the curvature of the radially outer curved surface is offset from the centre of the radially inner curved surface toward the smaller opening, the radially inner and outer surfaces being merged along their joining line.

7. A ball and socket joint assembly according to Claim 6 wherein the centre of radius of the radially outer curved surface is offset from the longitudinal axis of the socket.

8. A ball and socket joint assembly according to Claim 1 or 6 wherein said closed-side bearing has an annular, entirely planar surface located on the said remote from the closing plate, said planar surface abutting against the end part of the cylindrical portion of the open-side bearing.

9. A ball and socket joint assembly according to Claim 1 wherein said shoulder portion of the socket and said spherical head define therebetween an annular space of a wedge shaped cross section of which the thickness decreases toward said smaller opening, and said shoulder portion of the open-side bearing is disposed in said annular space and has a corresponding wedge shape in cross section, and wherein the shoulder portion and the 19 cylindrical portion define internally an inner spherical surface forming such a toroidal surface as to contact the outer surface of the spherical head most strongly along a thickest annular portion between the shoulder portion and the cylindrical portion.

10. A ball and socket joint assembly according to Claim 9 wherein gaps are formed between the open-side bearing and the spherical head on the two sides of said thickest annular portion.

11. A ball and socket joint assembly according to Claim 9 wherein said open-side bearing has an annular flange shoulder portion integrally connected to the cylindrical portion of the bearing at the side remote from the shoulder portion, said flange shoulder portion having a conical shape of which the diameter increases in the direction away from the cylindrical portion, wherein the enlarged cylindrical flange portion is integrally connected to the flange shoulder portion along the portion thereof having the greatest diameter, and wherein an annular axial gap is formed between the flange shoulder portion and a conical stepped surface formed in the inner surface of the socket, and the cylindrical flange portion is elastically deformed radially inwardly by a cylindrical seat formed in the socket so as to cause the cylindrical portion to curve radially inwardly to partly embrace the spherical head.

12. Tension type ball and socket joint assemblies substantially as shown in and as hereinbefore described with reference to the accompanying drawings.

Published 1991 at Ite Patent Office, State House. 66171 High Holborn. LondonWC1R47P. Further copies may be obtained from The Patent Office Sales Branch. St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques lid. St Mary Cray. Kent. Con 1187