GB2155539A - Improvements in or relating to flexible joints or bearings - Google Patents

Abstract

In a flexible ball-type joint having a layer of elastomeric material positioned between outer and inner surfaces respectively of inner (13) and outer (15) rigid members, the outer rigid member is of a segmental and composite construction. The outer rigid member comprises a plurality of segments circumferentially spaced relative to the longitudinal axis of the joint, and each segment has an outer metal element 17 of part-cylindrical shape at longitudinally spaced ends of which are provided inwardly directed end flanges 18. Between said end flanges and secured to the outer element is an inner element of non-resilient plastics material the inner surface of which is of a part-spherical shape to conform with the outer surface of the elastomeric material 12. The elastomeric material has groove-like formations 19 aligned with the respective spaces between successive segments of the outer rigid member. <IMAGE>

Description

SPECIFICATION Improvements in or relating to flexible joints or bearings This invention relates to flexible joints or bearings of the kind commonly known as ball joints and comprising a rigid inner member of ball-like shape, and an outer rigid member which extends around the inner rigid member and is maintained spaced therefrom by one or more components of resilient elastomeric material.

Commonly, but not necessarily, the elastomeric material is bonded to metallic material of the inner and outer rigid members and on assembly in an outer housing is subject to compression between said rigid members so that the required relative orientation of the rigid members and the resilient material is maintained during use of the joint or bearing.

Although the conventional design of a ball joint or bearing gives satisfactory operation in service, it is expensive to manufacture and assemble. Thus, for example, the production of a solid ball-like inner rigid metal member is expensive and time consuming even if numerically controlled machine tools are employed. In respect of the outer metal member there is a similar manufacturing difficulty in prodicing an annular component having a surface shaped to conform to the part-spherical surface of the elastomeric material.

The present invention seeks to provide a construction of a ball joint or bearing which is easier and less expensive to manufacture.

In accordance with the present invention there is provided a flexible joint or bearing comprising a layer of elastomeric material which surrounds an inner rigid member of part-spherical shape, and a segmental outer rigid member which surrounds said layer of elastomeric material, said outer rigid member being comprised of at least two composite segments each comprising a substantially part-cylindrical outer element of substantially rigid material and an inner element of a layer of substantially non-resilient moulded material located between end abutment means associated with said outer element, one surface of said inner element of moulded material being secured to the outer element and the other surface being of a part-spherical shape which conforms to the outer surface of the layer of resilient elastomeric material, the segments of the outer rigid member being circumferentially spaced when the elastomeric material is in an unstressed condition and the layer of elastomeric material having groove-like formations each aligned with a respective space between successive segments of the outer rigid member.

Preferably the outer element of each composite segment comprises formations which extend over those end faces of the moulded material lying between said longitudinally extending edges so as to serve as end abutments to provide axial location of the moulded material relative to the outer element.

The groove-like formations may be comprised by grooves formed in an outer surface of a layer, for example a part-spherical shaped layer, of elastomeric material, or may be defined by spaces between successive segments of resilient elastomeric material each of which is of a part-spherical shape.

Preferably the part-cylindrical composite segments each comprise edges which extend between end abutment means in a direction substantially parallel with the longitudinal axis of that cylindrical surface defined by the outer surfaces of the assembled composite segments and preferably it is said neighbouring edges of successive composite segments which are slightly spaced in a circumferential direction at least when the resilient elastomeric material is in an unstressed condition.

The spacing between the segments of the outer rigid member enables the elastomeric material to be subject to compression by urging said neighbouring edges towards one another to reduce the outer diameter of the assembly which may then be located in a rigid outer housing having a bore of similar diameter to that of the compressed assembly such that said compression of the resilient elastomeric material is maintained. Furthermore the groove-like formations aligned with the spaced edges of the successive composite segments facilitate compression of the resilient elastomeric material without said material tending to spread into the spaces between the outer segments and risk becoming damaged thereby.

The inner rigid member preferably comprises a cylindrical shaped member such as a tube or rod to an outer surface of which is secured one or more elements which define said part-spherical surface of the inner rigid member. The part-spherical surface may be defined by a solid ring of material having a cylindrical bore of a diameter corresponding to the outer diameter of the tube or rod to which it is secured, and an outer surface which is of the required part-spherical shape.

The ring may be secured to the rod or tube by welding, brazing, adhesives or other means selected having regard to the materials involved and which may include metallic materials, plastics, and composites such as fibrereinforced plastics.

The part-spherical surface of the inner rigidmember alternatively may be defined by a shell-like structure, such as of pressed metal, provided around the rod or tube. The shell-like structure may be of an annular or segmental form, or may be formed from a strip of transversely curved material which is wrapped around the rod or tube, ends of the strip being secured together to maintain the strip in the required ring-like shape.

Two embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings wherein: Figure 1 is a side view, the lower half in longitudinal section, of a flexible bearing in accordance with a first embodiment of the present invention; Figure 2 is an end view of the bearing of Fig. 1 half in section on the line 2-2 of Fig.

1; Figure 3 is an end view of the bearing of Figs. 1 and 2 when compressed radially; Figure 4 is a side view, the left-hand half in longitudinal section, of another flexible bearing in accordance with the present invention; Figure 5 is an end view of the bearing of Fig. 4, half in section on the line 5-5 of Fig.

4, and Figure 6 is an end view of the bearing of Figs. 4 and 5 when compressed radially.

In a first embodiment of the invention a flexible bearing comprises an inner rigid assembly 10, an outer rigid assembly 11 and located between said inner and outer rigid assemblies a layer 1 2 of a resilient elastomeric material such as natural rubber.

The inner rigid assembly 10 comprises a metal tube 1 3 through which, for example, bolt means may extend to facilitate clamping of the assembly 10 to one of two components (not shown) to be interconnected by the bearing. Around the tube 1 3 there is provided a solid cross-section ring 1 4 of a fibre reinforced plastics material, said ring having a cylindrically shaped bore corresponding in size to the outer diameter of the tube 13, and an outer surface of part-spherical shape. The ring 14 is secured to the tube 1 3 by means of an adhesive.

The layer 1 2 of natural rubber is secured by adhesive to the outer part-spherical surface of the ring 14. Said layer 1 2 is of substantially uniform thickness and therefore presents an outer surface also of part-spherical shape and to which the outer rigid assembly 11 is secured by adhesive.

The outer rigid assembly 11 comprises three similar outer member segments 1 5 each of a composite, two-part construction. Each segment is of generally part-cylindrical shape and has a pair of edges which extend in the longitudinal direction of the bearing, that is a direction parallel with the plane of the section of Fig. 1. The segments 1 5 each comprise an inner element 1 6 of plastics material moulded so as to have an inner surface of part-spherical shape for adhesion to the rubber layer 12, and an outer surface of part-cylindrical shape.

An outer element 1 7 of pressed metal has a part-cylindrical shaped central portion which extends over the part-cylindrical shaped surface of the plastics inner element 1 6 and a pair of end flanges 1 8 which extend over end surfaces of the element 16. The inner and outer elements 16, 1 7 may be secured together by an adhesive, mechanical locking or friction fit of the inner member between the end flanges of the outer element.The dimensions of the segments 1 5 are selected such that when assembled around the rubber layer 12, with the rubber layer in an unstressed condition, there exists between neighbouring longitudinal edges of successive segments a small gap which typically subtends an angle in the order of 2 to 5 relative to the longitudinal axis of the bearing.

The rubber layer 1 2 is provided with three longitudinally extending grooves 1 9 which are aligned with the respective gaps between the segments 15, the grooves extending at least half and preferably approximately three quarters through the thickness of the rubber layer.

Said grooves 1 9 may be formed by cutting the rubber layer subsequent to location of the outer rigid assembly 11 around the rubber layer 12, or may be preformed in the rubber layer in which case case is taken to locate the segments 1 5 of the outer assembly such that the gaps therebetween are aligned with the grooves. In an alternative construction the rubber layer 1 2 is formed from three segments which when secured to the inner rigid assembly are circumferentially spaced one from another so as to define three grooves in the rubber layer.

The resulting bearing assembly of the inner and outer rigid assemblies 10, 11 and the rubber layer 1 2 is intended to be used with the rubber subject to residual compression.

This is achieved by fitting the bearing assembly in a housing (not shown) having a cylindrical bore of a diameter corresponding to the outer diameter of the bearing assembly when subject to radial compression to bring the neighbouring edges of the successive segments into contact one with another. By virtue of the grooves 1 9 provided in the rubber layer, the rubber material does not tend to spread radially outwards between the outer members 1 7 and it is therefore possible to compress the mounting such that the outer members 1 7 come into contact one with another.

In a second embodiment of the invention, illustrated with reference to Figs. 4 to 6, a flexible bearing comprises a rubber layer 1 2 and an outer assembly substantially similar to the corresponding items described in respect of the first embodiment, but the inner rigid assembly is of a different construction.

In the second embodiment of the invention the flexible bearing comprises an inner rigid assembly 20 of a two-part construction of a solid rod 21 and an outer metal shell 22 secured to an outer surface of the rod.

Therod 21 of circular cross-sectional shape is formed at each end with a tongue-like portion 23 through which extends a hole 24, said holes of the two end portions facilitating attachment of the bearing assembly to one of two components to be interconnected by the bearing.

The outer shell 22 is formed from a small length of initially circular section tube which is deformed by axial compression so as to result in an outer surface of part-spherical shape.

The outer shell 22 is secured to the solid rod 21 by welding.

A rubber layer 1 2 and outer rigid assembly are than constructed around said shell 22 in a manner similar to that described in respect of the first embodiment of the invention

Claims (9)

1. A flexible joint or bearing comprising a layer of elastomeric material which surrounds an inner rigid member of part-spherical shape, and a segmental outer rigid member which surrounds said layer of elastomeric material, said outer rigid member being comprised of at least two composite segments each comprising a substantially part-cylindrical outer element of substantially rigid material and an inner element of a layer of substantially nonresilient moulded material located between end abutment means associated with said outer element, one surface of said inner element of moulded material being secured to the outer element and the other surface being of a part-spherical shape which conforms to the outer surface of the layer of resilient elastomeric material, the segments of the outer rigid member being circumferentially spaced when the elastomeric material is in an unstressed condition and the layer of elastomeric material having groove-like formations each aligned with a respective space between successive segments of the outer rigid member.

2. A flexible joint or bearing according to Claim 1 wherein said end abutment means of a segment each comprise a formation which extends over an end face of the moulded material of the associated inner element of the segment.

3. A flexible joint or bearing according to Claim 2 wherein the end abutment means of a segment comprises a pair of end flanges formed integral with the outer element of the segment and arranged to extend over the ends of the inner element of the segment.

4. A flexible joint or bearing according to any one of the preceding claims wherein the groove-like formations of the layer of elastomeric material are comprised by grooves formed in an outer surface of the layer of elastomeric material.

5. A flexible joint or bearing according to any one of Claims 1 to 3 wherein the groovelike formations are comprised by spaces between successive segments of resilient elastomeric material each of which is of a partspherical shape.

6. A flexible joint or bearing according to any one of the preceding claims wherein each outer element of part-cylindrical shape comprises a pair of parallel longitudinal edges which extend parallel with the longitudinal axis of that cylindrical surface defined by the outer surface of the outer elements of the assembled composite segments.

7. A flexible joint or bearing according to any one of the preceding claims wherein the inner rigid member comprises a cylindrical shaped member to an outer surface of which is secured one or more elements which define said part-spherical surface of the inner rigid member.

8. A flexible joint or bearing according to any one of the preceding claims wherein the inner and outer elements of a segment of the outer rigid member are bonded or otherwise secured together.

9. A flexible joint or bearing construction arranged substantially as hereinbefore described with reference to the accompanying drawings.