Spring devices – Fibrous
Patent
1988-09-12
1989-12-19
Halvosa, George E. A.
Spring devices
Fibrous
267262, F16F 136
Patent
active
048878022
DESCRIPTION:
BRIEF SUMMARY
This invention relates to leaf springs made of composite (fibre-reinforced plastics) material. More particularly the invention relates in its broadest aspect to the attachment to such a leaf spring, adjacent an end thereof, of a member affording a wear resistant surface.
Leaf springs are commonly used in the suspension of motor vehicles. In a typical installation, the leaf spring may be required to have a so-called "slipper end", which is a means by which the change in the straight-line distance between the ends of the spring can be accommodated as the configuration of the spring changes with changes in the load it is bearing. One end of the spring may be pivotally mounted at a fixed position to the chassis or body structure of the vehicle, and the other end of the spring bears against a supporting surface relative to which it has sliding movement, lengthwise of the spring, as the spring load changes. If the spring comprises two or more individual leaves, relative sliding movement is also required between such individual leaves as their configuration changes under changing load conditions.
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 adhesives 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.
It is the broadest object of the present invention to provide for effective attachment to the end of a leaf spring of composite material of a member affording a wear resistant surface.
Therefore, according to the invention, we provide a spring comprising an elongate leaf of composite material provided, adjacent a free end thereof, with a first member and a second member extending along respective oppositely facing surfaces of the leaf, the members extending lengthwise of the leaf and being secured together beyond the free end thereof, and being secured to the leaf at a position spaced from said free end by a fastening element extending transversely around the leaf, the members and leaf having formations which interfit to prevent relative movement lengthwise of the spring therebetween, and at least one of the members affording a wear resistant surface.
In a spring according to the invention, the securement of the members to one another beyond the free end of the spring, and to the spring by a transverse fastening element spaced from the free end of the spring, has the advantageous result that the assembly does not occupy a large volume such as may make installation in a motor vehicle (or any other required apparatus or equipment) difficult, and yet the members are firmly attached in such a manner that they cannot readily be detached in use. It is not necessary to provide a hole or holes in the spring, and hence the problems which would be caused thereby are overcome.
Preferably the interfitting formations of the spring and members comprise a curved portion of the spring adjacent the free end thereof, and complementary curved portions of the members. It is relatively easy to provide a leaf spring of composite material, which typically is made by a process involving a moulding step to form the spring to its final shape, with a suitably curved portion adjacent it
REFERENCES:
patent: 2776135 (1957-01-01), Assmus
patent: 4505460 (1985-03-01), LeGallais
patent: 4556204 (1985-12-01), Pflederer
patent: 4611793 (1986-09-01), Nishiyama et al.
GKN Technology Limited
Halvosa George E. A.
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