GB2174174A - Securing components to leaf springs - Google Patents

Abstract

A leaf spring 10 of composite, fibre reinforced plastics, material, bears a component such as a slipper member 12 secured to the spring by fastening elements 13 in the form of endless metal loops, deformed to tighten around the spring and slipper member. The position of the slipper member relative to the spring is determined by projections 17 on the slipper member, engaging recesses in the spring. <IMAGE>

Description

SPECIFICATION Securing components to leaf springs of composite material This invention relates to leaf springs made of composite, fibre-reinforced plastics, material, and more particularly to the securing of components to such springs.

One example to which the invention is applicable is a leaf spring having a so-called "slipper end". This is one means by which the change in the distance between the ends of the spring can be accommodated, as the load on the spring changes. One end of the spring is pivotally mounted at a fixed position on the structure or apparatus, e.g. the chassis of a motor vehicle, where it is to be used, and the other end of the spring bears against a supporting surface on the structure or apparatus and has sliding movement relative thereto as the spring load changes. Sliding movement is also required between individual leaves of a spring comprising two or more leaves, as the spring deflects.

In leaf springs made of steel, it is usual to arrange for such sliding movement to occur directly on the surface of the spring leaf or leaves. The resistance of the spring leaves to abrasion is adequate for this purpose. In the case of leaf springs made of composite material, however, the resistance of the spring material to abrasion is not satisfactory, particularly if the spring is operating in a dirty environment as would be the case in a motor vehicle. Accordingly it is desirable to provide a composite leaf spring with an element of an appropriate wear resistant material at any point where relative sliding movement is likely to occur. It is difficult satisfactorily to attach such a wear resistant element to a composite spring in a manner which does not take up excessive space and yet is reliable.It has been found that the use of adhesive alone for such purpose is not satisfactory in service, and any method involving the provision of a hole or holes in the spring is not acceptable because of the detrimental effect on the properties of the spring caused thereby.

Further examples to which the invention is applicable are the securement of components to springs to protect the springs against impacts. For example, the component may be a plastics or rubber pad arranged to engage a stop to limit deflection of the spring. The component may carry an elastomeric element which acts as or forms part of an auxiliary spring. The component may even be simply a weight, secured to the springs so as to alter a resonant vibration frequency of the spring, which is a requirement which sometimes arises particularly in motor vehicle applications.

Also in motor vehicles, the component may be required to protect the springs from engagement by a jack, if the spring is used as a jacking point.

Accordingly it is the object of the present invention to provide for an effective attachment of a component to a leaf spring of composite material.

According to the present invention, we provide a leaf spring of composite material having a component secured thereto abutting a surface of the spring, said component and spring having interfitting projection and recess means to determine the position of the component relative to the spring, and said component being secured to the spring by at least one fastening element extending transversely of the spring, around said component and spring.

For security of the component if it is of elongate form, there are preferably provided two of said fastening elements, spaced lengthwise of the spring. Each fastening element preferably comprises an endless metal loop, deformable to tighten around the component and spring.

Advantages of the invention are that the position of the component relative to the spring is effectively fixed by the interfitting projections and recesses of the component and spring. The use of fastening elements extending transversely around the component and spring occupies relatively little space, and yet ensures that the projection and recess formations remain in engagement. The connection is not dependent upon use of adhesive or the like, although if desired an adhesive may be used between the abutting surfaces of the component and spring as a means, inter alia, of preventing penetration of dirt to such surfaces. The assembly is capable of accommodating any deformation of the spring which might occur in the region of the component, without detriment to the integrity of the connection between the spring and component.

Each fastening element may embrace a protective member at the surface of the spring opposite the surface on which the component is provided. This ensures that no damage to the spring can arise from any tendency for the fastening element to indent the spring surface.

The component may be a slipper member of wear resistant material, as in the embodiment described hereafter.

The invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a perspective view of part of a spring according to the invention; Figure 2 is a plan view of the spring part of Fig. 1; Figure 3 is a section on the line 3-3 of Fig.

2.

Referring to the drawings, there is shown a part of a leaf spring 10 made of composite, fibre reinforced plastics, materials. By way of example, the material may comprise glass fibres embedded in a matrix of a epoxy resin.

The illustrated part of the spring would nor mally be provided, in a typical application of such a spring to a motor vehicle, adjacent one end thereof.

The spring is of rectangular cross-sectional shape, and on its upper surface 11 there is provided a component in the form of a slipper member 12. This is intended to bear for sliding movement against an appropriate surface, and accordingly is made of a material having wear resistant properties. By way of example, the slipper member may be an injection moulding of a nylon material having a filling of molybdenum disulphide.

The slipper member 12 is held to the spring by two fastening elements 13 spaced longitudinally thereof. Each fastening element is in the form of an endless loop or band of sheet metal, and extends transversely around the spring, slipper member, and a respective protective member 14 provided at the surface of the spring opposite the surface 11. Each fastening element 13 lies in a respective groove 15 extending transversely of the slipper member 12, and a groove 16 in its protective member 14. Each fastening element 13 is tightened by being permanently deformed into its groove 15 in the slipper member, which groove may have a portion between its ends of increased depth, firmly to hold the slipper member to the spring.Protective member 14 prevents the fastening element from indenting the undersurface of the spring where it embraces it, and the fastening element may also be deformed into the groove in the protective member.

The position of the slipper member relative to the spring is determined by inter-engaging projection and recess formations thereof. The slipper member has part-spherical projections 17 beneath the grooves 15 therein, and these engage in correspondingly shaped recesses formed in the surface 11 of the spring. The projections 17 and corresponding recesses in the spring are relatively shallow, so that the strength of the spring is not adversely affected as might be the case if deep recesses or discontinuities were provided therein. The projections and recesses are, however, effective at preventing relative movement between the spring and slipper member, particularly since they are provided in regions which are firmly held together by the fastening elements 13. In practice, one interengaging projection and recess may be adequate to prevent such relative movement.

To fit the slipper member to the spring in manufacture of the illustrated assembly, the fastening elements in their undeformed state would be slidden lengthwise of the spring from the adjacent free end thereof, and the slipper member and protective elements positioned thereunder with the slipper member in the desired position such that its projections can enter the recesses in the spring. The fastening elements can then be deformed to tighten them around the spring, e.g. by use of a suitable press.

The invention thus provides for effective-securement and positioning of the slipper member relative to the spring. The arrangement is not excessively bulky, since the fastening elements lie within grooves 15 and either do not protrude or protrude to no significant extent above the surface of the slipper member 12.

The principle of the invention may also be used for the provision of slipper members on individual leaves of a spring having two or more such leaves, where the relative movement between such leaves has to be accommodated by a slipper arrangement. Further, a slipper member is described as an example only of the type of component which may be secured to the spring, and other examples are mentioned above.

Claims (9)

1. A leaf spring of composite material having a component secured thereto abutting a surface of the spring, said component and spring having interfitting projection and recess means to determine the position of the component relative tp the spring, and said component being secured to the spring by at least one fastening element extending transversely of the spring, around said component and spring.

2. A spring according to Claim 1 wherein there are provided two of said fastening elements, spaced lengthwise of the spring.

3. A spring according to Claim 1 or Claim 2 wherein the or each said fastening element comprises an endless metal loop, -deformable to tighten around the component and spring.

4. A spring according to Claim 3 wherein the or each said loop is deformed into a respective recess in said component.

5. A spring according to any one of the preceding claims wherein the or each fastening element embraces a or a respective protective member at a surface of the spring opposite said surface thereof.

6. A spring according to any one of the preceding claims wherein said component has one or more projections engaging in one or more recesses in the spring.

7. A spring according to Claim 6 wherein the or each said projection is provided adjacent the or each said fastening element.

8. A spring according to any one of the preceding claims wherein said component comprises a slipper member of a wear resistant material.

9. A spring substantially as hereinbefore described with reference to the accompanying drawings.