GB2110295A

GB2110295A - Improvements in or relating to joint means

Info

Publication number: GB2110295A
Application number: GB08233103A
Authority: GB
Inventors: Alan Moore
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1981-12-01
Filing date: 1982-11-19
Publication date: 1983-06-15
Also published as: GB2110295B

Abstract

Joint means for flexibly coupling a first member (12) having a body portion (14) and at least two arms (17) extending from the body portion (14) generally parallel to and radially spaced from the longitudinal axis of the joint means to a second member (11) positioned radially inwards of the arms (17) comprises elastomeric means (16) acting between an internal curved surface (15) on the body portion (14) of the first member (12) and an external curved surface (13) on the second member (11) opposite to and axially spaced from the internal curved surface (15).

Description

SPECIFICATION Improvements in or relating to joint means This invention concerns improvements in or relating to joint means for flexibly coupling a pair of members and in particular to joint means which accommodates relative pivotal movement between the members.

According to the present invention there is provided joint means for flexibly coupling a first member having a body portion and at least two arms extending from the body portion generally parallel to and radially spaced from the longitudinal axis of the joint means to a second member positioned radially inwards of said arms, the joint means comprising an internal curved surface on the body portion of the first member, an external curved surface on the second member opposite to and axially spaced from said internal curved surface and elastomeric means acting between said curved surfaces.

The curved surfaces may be part-cylindrical but more preferably are part-spherical to allow relative pivotal movement between the members in any direction through 3600 about the longitudinal axis of the joint means, i.e. omnidirectional movement in any plane containing the longitudinal axis of the joint means.

Preferably the curved surfaces have a common central axis (part-cylindrical) or centre of curvature (part-spherical).

Preferably the arms of the first member are uniformly spaced in a circumferential direction and the free ends of the arms may be adapted for connection to a common attachment member for securing the arms to one of two components to be connected by the joint means.

The elastomeric means preferably comprises a laminated bearing consisting of interleaving layers of elastomeric material e.g. rubber and substantially inextensible reinforcement material e.g. metal plate but may comprise elastomeric material only. The bearing has end faces complementary to the profile of the curved surfaces and where it is of laiminated construction the individual layers are of similar curved profile.

The end faces of the bearing may be bonded to the curved surfaces or attached to metal end rings which are secured to the curved surfaces by any known means.

The bearing, which may have a central opening serving as a vent to prevent air being trapped during moulding of the bearing, may be one-piece or consist of a plurality of individual segments.

Two of the joint means may be arranged backto-back with the arms of the first members being intercalated with one another and extending in opposite directions and the second members being positioned in the recess formed between the body portions of the first members and the axially extending arms.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings wherein: Figure 1 shows in longitudinal section a known joint means; Figure 2 shows in longitudinal section a first embodiment of joint means according to the present invention; Figure 3 shows in longitudinal section a second embodiment of joint means according to the present invention; Figure 4 shows an alternative laminated bearing for use in joint means of the type shown in Figures 2 and 3.

One form of known joint means shown in Figure 1 of the accompanying drawings for flexibly coupling a pair of rigid members 1 and 2 comprises an external part-spherical surface 3 on a body portion 4 of inner member 1 axially aligned with and opposite to an internal part-spherical surface 5 of outer member 2 and an annular spherical laminated bearing 6 acting between and bonded to the confronting surfaces 3, 5. The surfaces 3, 5 have a common centre of curvature.

Inner member 1 is adapted for connection to a component (not shown) via a stem 7 integral with the body portion 4 which projects through a central opening 8 in the end face of member 2 and is coaxial with the longitudinal axis of the joint means. Member 2 is adapted for connection to a second component (not shown) by any suitable means (not sh6wn) e.g. bolting, welding, etc.

The laminated bearing 5 comprising a plurality of annular part-spherical rings consisting of layers of elastomer 6a and rigid reinforcement plates 6b arranged alternately with the end rings being of complementary profile to the confronting surfaces 3, 5.

In use axial loads generated for example by a tension force applied to the stem 7 in the direction of arrow A are accommodated by the bearing 6 in compression and conical deflection of the stem 7 in any direction through 3600 about the longitudinal axis of the joint means is accommodated by the bearing 6 in shear.

Referring now to Figure 2 a first embodiment of joint means according to the present invention for flexibly coupling a pair of rigid members 11 and 12 is shown which comprises an external partspherical surface 13 on inner member 11 axially aligned with and opposite to an internal partspherical surface 1 5 on a body portion 1 4 of outer member 12 and an annular spherical laminated bearing 1 6 acting between and secured to the confronting surfaces 13, 1 5. The surfaces 13, 1 5 have a common centre of curvature.

Outer member 12 has, integral with the body portion 14, a pair of diametrically opposed arms 1 7 extending parallel with and radially spaced from the central longitudinal axis of the joint means for connecting the member 12 to a component (not shown). Inner member 11 is adapted for connection to a second component (not shown) by any suitable means e.g. by bolting, welding etc.

The laminated bearing 1 6 comprises a plurality of annular part-spherical rings consisting of layers of elastomer 1 spa and rigid reinforcement plates 1 6b arranged alternately with the end rings being of complementary profile to the confronting surfaces 13, 15.

In use axial loads generated for example by a tension force applied to the arms 1 7 in the direction of arrow B are accommodated by the bearing 1 6 in compression and conical deflection of the arms 17 in any direction through 3600 about the longitudinal axis of the joint means is accommodated by the bearing 16 in shear.

The above-described joint means of Figures 1 and 2 are each suitable for applications in which tension loadings are applied to the stem 7 of inner member 1 in the case of the joint means of Figure 1 and to the arms 17 of outer member 12 in the case of the joint means of Figure 2 and the other member is attached to a fixed structure. One such application is the fastening of the ends of an anchor line to a floating oil rig platform and to the sea bed respectively where the anchor line is subjected to varying tension forces and deflection.

However, from a comparison of the joint means it is apparent that the stem 7 of inner member 1 of the joint means of Figure 1 restricts the space available for location of the bearing 6 wherein no such space restriction is present in the joint means of Figure 2 where the arms 17 are radially spaced from the longitudinal axis of the joint means. Thus assuming the joint means of Figure 1 is to accommodate the same axial loading as the joint means of Figure 2 the radius R of the curved surface 3 must exceed the radius r of the curved surface 13 by an amount sufficient to ensure the surface areas over which the bearings 6, 16 act are the same. Consequently it is clear that the joint means of Figure 1 will require a larger space envelope than the joint means of Figure 2 for a given load.

A further advantage of the radius of the curved surface of the inner member in the joint means according to the present invention being less than that of the known joint means is that for a given conical deflection the relative movement between successive layers of elastomer and reinforcement plates in the laminated bearing is less in the joint means according to the present invention than in the known joint means of Figure 1. Consequently the elastomer layers in the joint means according to the present invention may be made thinner which together with the overall reduction in size contributes to a cost saving as compared with the known joint means. Furthermore the conical fatigue life of the bearing 1 6 is improved due to the reduction in relative movement between successive layers of elastomer and reinforcement plates for a given conical deflection.

A second embodiment of joint means according to the present invention is shown in Figure 3 and essentially comprises two of the joint means shown in Figure 2 arranged back-to-back and like reference numerals are used to indicate corresponding parts.

As shown the joint means is able to accommodate axial loads generated by tension forces applied to the arms 1 7 in the direction C and to the arms 17' in the direction D opposite to the direction C. The joint means may therefore be used as an intermediate connection for example in an anchor line or as an end connection in which one pair of arms 17 or 17' is connected to a fixed structure.

In addition the back-to-back arrangement of the joint means increases the conical deflection that can be accommodated compared with either one of the joint means individually by allowing a conical deflection to be shared between the bearings 16, 16' so that the full conical deflection is not applied to a single bearing.

Figure 4 shows an alternative laminated bearing for use in joint means of the type shown in Figures 2, 3 in which the layers of elastomer and reinforcement plates are of part-cylindrical profile.

In an assembled joint means incorporating the bearing of Figure 4 the confronting surfaces 13, 1 5, 13', 1 5' on the inner and outer members are of complementary part-cylindrical profile allowing relative rotational movement between the members about the central axis of the bearing i.e.

relative movement in one plane containing the longitudinal axis of the joint means. The partcylindrical bearing may be one-piece as shown in full lines in Figure 4 or divided into two or more segments as shown in broken lines in Figure 4.

It will be understood the invention is not restricted to the above-described embodiments.

For example the or each outer member of Figures 2 and 3 may have three or more axially extending arms uniformly spaced in a circumferential direction around the longitudinal axis of the joint means.

The number of interleaving layers of elastomer and reinforcement plates and the thickness thereof may be varied to give a bearing having the desired load capability and for certain applications the reinforcement plates may be omitted. The or each bearing may be attached to one or both of the confronting surfaces by conventional means for example bonding, welding or mechanical means.

The spherical bearings 16, 16' may have a central opening as shown of relatively small dimensions or the opening may be omitted.

The arms of the or each outer member may be integral with the associated body portion as above-described or formed separately and attached to the body portion by any suitable means, e.g. bolting, welding etc. The arms of the or each outer member may be parallel to or inclined relative to the longitudinal axis of the joint means.

Claims

1. Joint means for flexibly coupling a first member having a body portion and at least two arms extending from the body portion generally parallel to and radially spaced from the longitudinal axis of the joint means to a second member positioned radially inwards of said arms, the joint means comprising an internal curved surface on the body portion of the first member, an external curved surface on the second member opposite to and axially spaced from said internal curved surface and elastomeric means acting between said curved surfaces.

2. Joint means according to claim 1 wherein said curved surfaces are part cylindrical and have a common central axis.

3. Joint means according to claim 1 wherein said curved surfaces are part spherical and have a common centre of curvature.

4. Joint means according to any one of the preceding claims wherein the arms of the first member are uniformly spaced in a circumferential direction.

5. Joint means according to any one of the preceding claims wherein the free ends of the arms of the first member are adapted for connection to a common attachment member.

6. Joint means according to any one of the preceding claims wherein the elastomeric means comprises laminated bearing consisting of interleaving layers of elastomeric material and inextensible reinforcement material.

7. Joint means according to claim 6 wherein the bearing has end faces complementary to the profile of the curved surfaces and the individual layers are of similar curved profile.

8. Joint means according to claim 6 or claim 7 wherein the bearing has a central opening.

9. Joint means comprising two of the joint means according to any one of the preceding claims arranged back to back with the arms of the first members being interrelated with one another and extending in opposite directions and the second members being positioned in a recess formed between the body portions of the first members and the axially extending arms.

10. Joint means substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

11. Joint means substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

12. Joint means substantially as hereinbefore described with reference to either Figure 2 or Figure 3 as modified by Figure 4 of the accompanying drawings.