SECURING COMPONENTS TO SPRINGS OF COMPOSITE MATERIAL

Abstract: An element comprising a sheet 20 of resilient material having on one side a protruding formation 21 engagabie with a shallow, sloping walled, recess 17 in a composite spring, and, on the other side, a further formation 22 engagable with a recess in a component 18 to be secured to the spring. When the component 18, eg an axle part, is secured to the spring by being clamped thereto, the resilient material acts as a load spreading element and provides relative location between the spring and component during assembly.

Description: SECURING COMPONENTS TO SPRINGS OF COMPOSITE MATERIAL This invention relates to leaf springs of composite, fibre reinforced resin, material, and more particularly to the securing of other components to such springs by being clamped thereto. One example of a component which may be so secured to a spring, is an axle beam for use in an automotive vehicle, which typically is held to a leaf spring in the centre region thereof by clamping means such as Ubolts. Whilst the clamping means, when tightened, holds the component in a fixed position relative to the spring, it is. desirable to provide some form of locating means to provide a desired relative position between the spring and component during assembly. A further desirable provision is that of some form of load distributing element between the clamped surfaces between the spring and component, to spread the load into the composite material of the spring and prevent the initiation of fatigue cracks into the spring material. The resilient element also, if bonded to the spring, resists penetration of dirt to the clamped surfaces of the spring and component, which would otherwise potentially cause abrasive damage to the surface of the spring. It is the object of the present invention to meet these requirements as far as possible in a manner which is economical, convenient and effective in use, requiring a minimum of separate parts. According to one aspect of the present invention, we provide an element adapted to be interposed between the surface of a spring of composite material and a component secured to the spring by clamping means, the element comprising a sheet of resilient material having, on one side, a protruding formation engagable with a shallow, sloping walled, recess in the spring and, on the other side, a further protruding formation engagable with a recess in the component. By the use of such an element, the necessity of providing any other locating means operative between the spring and component to maintain them in the correct relative position during assembly is avoided. The resilient material preferably is a polyurethane rubber material, and, although such a material is not sufficiently strong to resist shear stresses imposed thereon if the clamping means permitted the component to move relative to the spring under loads when in service, in practice the clamping means does not permit any tendency towards such relative movement and hence the material is not excessively stressed. The provision of the protruding formations on opposite sides of the element of resilient material is adequate to ensure correct relative positioning between the spring and component during assembly. Said one protruding formation may be of frusto-conical form, or comprise a shallow dome, to engage with a recess of like form in the spring. The further protruding formation may be of cylindrical form, to engage in a cylindrical socket or aperture in the component. The advantage of the formation, which engages with a recess in the spring, being of shallow frusto-conical or domed configuration is that such a form of recess can be incorporated in a composite spring during manufacture thereof in a moulding process without having a disadvantagous effect on the disposition of fibres in the spring. The characteristics of a composite spring are dependant inter alia on the fibre disposition in the spring, and to provide a deep recess therein or one with sharp corners would provide serious discontinuities in the fibres of a spring, adversely affecting the properties thereof. On the other hand, to provide a cylindrical socket or aperture in the component to be secured to the spring, which usually will be of iron, steel or aluminium, is not in general so disadvantagous. A reinforcing member, eg a metal peg, may be incorporated in one or both of said formations of the element of resilient material The invention also provides an assembly comprising a spring, a component held against a surface thereof by clamping means, and an element, according to the first aspect of the invention, interposed between the spring and the component. The invention will now be described by way of example with reference to the accompanying drawings, of which Figure 1 is a side elevation of an assembly according to the invention. Figure 2 shows a resilient element according to the invention. Referring firstly to figure 1 of the drawings, this shows a central portion of a leaf spring 10, made of composite, fiber reinforced resin, material. By way of example, the spring may comprise glass fibres set in an epoxy resin, the spring being formed to its final shape in a moulding process during which the resin is cured. In a typical motor vehicle installation as illustrated a component 11, which here is a seat for an axle beam 12, is held to the spring in its central region by clamping means in the form of U bolts 14 and nuts 15. On the side of the spring opposite the component 11, the U bolts embrace an abutment plate 13. An element 16 in the form of a sheet of a resilient material is interposed between the component 11, and the undersurface of the spring 10. Referring now to Figure 2 of the drawings, this shows in side elevation the element 16 comprising a flat sheet 20 of a resilient material such as an appropriate grade of polyurethane rubber. An example of a suitable material is Dunlop 'Prescollan 80-C-13', which has been found suitable for use generally in automotive spring installations. Clearly however the material would be selected so that its properties, eg hardness, are suitable for the particular installation under consideration. On one side, the element has a protruding formation 21 in the form of two superimposed frusto-conical portions of different apex angle. On the opposite side, the element has a cylindrical protruding formation 22. These formations are integral with the flat sheet part 20 of the element and the whole element is manufactured by a moulding process. When in use, the element is interposed between the surface of the composite spring 10 and the component 11 which is secured to the spring by being clamped thereto. The formations 21, 22 engage in a correspondingly shaped recess in the spring and socket or aperture 18 in the component, respectively. These provide for correct relative positioning between the spring and component during assembly. To prevent penetration of abrasive dirt to the spring surface, the element preferably is secured to the spring by use of a suitable adhesive. The element may be reinforced by a metal peg or the like 23 occupying a bore formed in the element during moulding thereof. As illustrated, the reinforcing member extends through the formation 22 into the base of the formation 21. An element in the form of a plain sheet of resilient material is interposed between the abutment plate 13 and spring 10. Such element has no projecting formations, since the requirement for alignment with the spring is with component 11 rather than plate 13.

Claims: CLAIMS 1. An element (16) adapted to be interposed between the surface of a spring (10) of composite material and a component (11) secured to the spring by clamping means (14, 15), the element (16) comprising a sheet of resilient material characterised by having, on one side, a protruding formation (21) engagable with a shallow, sloping walled, recess in the spring (10) and, on the other side, a further protruding formation (22) engagable with a recess in the component (16). 2. An element according to claim 1 further characterised in that said resilient material is a polyurethane rubber material. 3. An element according to claim 1 or claim 2 further characterised in that said one protruding formation (21) is of shallow domed or frusto-conical form, to engage with a recess (17) of like form in the spring (10). 4. An element according to any one of claims 1 to 3 further characterised in that said further protruding formation (22) is of cylindrical form, to engage in a cylindrical socket or aperture (18) in the component (11). 5. An element according to any one of the preceding claims further characterised in that a reinforcing member (23) is incorporated in at least one of said formations (21, 22) of the element (16) of resilient material. 6. An assembly comprising a spring (10) of composite material, a component (11) lying against a surface of the spring, and clamping means (14, 15) holding said component to the spring, characterised by an element (16) in the form of a sheet of resilient material interposed between the spring and component and having formations (21, 22) on opposite sides engaging in recesses (17, 18) in the spring and component respectively. 7. An assembly according to claim 6 wherein said element (16) of resilient material is secured by adhesive to the spring.

Inventors: TUCKER-PEAKE, ADRIAN
Applicants: GKN TECHNOLOGY LIMITED
Application year: 1984
Main classification: F16F1
IPC codes: F16F1, B60G11