GB2235033A

GB2235033A - Leaf spring assemblies

Info

Publication number: GB2235033A
Application number: GB9017569A
Authority: GB
Inventors: Leighton Richard Harris; Colin Edward Spedding
Original assignee: GKN Technology Ltd
Current assignee: GKN Technology Ltd
Priority date: 1989-08-16
Filing date: 1990-08-10
Publication date: 1991-02-20
Also published as: GB9017569D0; GB8918693D0

Abstract

An assembly of a first spring leaf (10) and a second leaf (11) of composite material, secured together between their ends, has a covering (14) of plastics material on the second leaf (11) having associated therewith a surface for sliding engagement with the first leaf and defining a recess (15) engaging a transverse bracket structure (19) which embraces the first leaf. The spring leaves are thus held in alignment with one another. <IMAGE>

Description

LEAF SPRING ASSEMBLIES This invention relates to a leaf spring assembly of :ind which comprises first and second spring leaves idling generally parallel to one another, the leaves held together at a position between their ends and ng on one another at or adjacent their ends, so that ;tiffness of the spring assembly is equal to the sum iose of the individual spring leaves.

The invention has been devised in relation to such a ig assembly wherein the first leaf is of steel and ts ends provided with formations for attachment to quipment, e.g. a motor vehicle or trailer, where the ig assembly is to be used. The second leaf is of )site (fibre-reinforced plastics) material, and ;ts the first leaf. The use of the composite ial for the second leaf provides an appreciable it saving compared with a spring assembly wherein all eaves are of steel. However, the invention is cable in its broadest aspect to a spring assembly in both the first and second leaves are of steel.

In such a leaf spring assembly, one design problem at of resisting wear at the end of the spring leaves the second leaf bears on the first leaf and must therealong when the springs bend in service. This em is one which arises particularly when the second is of composite material, since such a material is resistant to abrasive wear than is spring steel.

,perating environment of a spring assembly for a vehicle is inherently one in which there is ive dirt present, which aggravates the problem.

rather design problem is to ensure that the leaves in in the correct alignment relative to one another.

edition known as "scissoring" in which the leaves relative to one another about the position between ends where they are secured together, such that wends are not in alignment, must be resisted.

It is broadly the object of the present invention to ide a spring assembly wherein the problems above jibed are overcome or reduced.

According to the present invention, we provide a spring assembly comprising a first spring leaf; a ld spring leaf extending generally parallel to the spring leaf; means securing the first and second zs together at a position spaced from the ends -of; a covering of a plastics material on an end ion of the second spring leaf, applied thereto by a ling process; the covering of plastics material lg associated therewith a surface engaging a facing sce of the first spring leaf for sliding movement z along, and also affording, at a position spaced the end of the second leaf, a recess formation ding transversely at least partially around the d spring leaf; and a bracket structure engaging recess formation and including parts extending on site sides of the first spring leaf and connected her beyond the first spring leaf, to hold the first second spring leaves together.

Preferably, and as in the embodiment described sifter, the first spring leaf is of steel and the d spring leaf is of composite material.

A spring assembly according to the invention has the tage that the necessary sliding movement lengthwise le spring leaves, when the spring bends in service, rs between the covering of plastics material on the d spring leaf and the facing surface of the first lg leaf. The second spring leaf itself is not ect to abrasive wear.

Further, the bracket structure prevents scissoring e spring leaves relative to one another.

If required, the covering of plastics material on second spring leaf may itself be provided with an znt affording a wear resistant surface.

The bracket structure may comprise two generally ped metal pressings, secured together.

The invention will now be described by way of Dle with reference to the accompanying drawings, of Figure 1 is an elevation of an end of a spring bly according to the invention; Figure 2 is a composite view showing two transverse s-sections of the spring assembly, the cross-sections indicated at 2A and 2B in Figure 1.

Referring firstly to Figure 1, there is shown part spring assembly comprising two spring leaves, namely st leaf 10 and a second leaf 11. The first leaf 10 steel, and has its end formed at 12 as an eye ling a transverse aperture 13 to receive a fastening nt and bush by which the spring is attached to the pment where it is to be used, e.g. to a shackle or ting bracket of a motor vehicle. The spring 11 is of site, fibre-reinforced plastics, material, and ads generally parallel to the spring leaf 10 spaced from in the direction in which the spring assembly s in use. The spring leaves are secured together in required relationship at a position generally midway ae lengths of the spring leaves between their ends, 3 in a typical installation they would be connected vehicle axle.

The second spring leaf 11 has its end portion ided with a covering 14 of plastics material, applied ato by an injection moulding process, preferably a tion injection moulding process. A suitable material a appropriate grade of a nylon-type copolymer rial, with a suitable filler. The shape of the ring 14, as determined by the mould wherein it is ied, provides a recess 15 extending transversely all ad the end portion of the spring leaf 11 but spaced the free end of the leaf, and, adjacent the free end ae second spring leaf 11, a portion 16 facing the rsurface of the first spring leaf 10.The portion 16 ae plastics covering 14 is either provided itself a surface which is suitable for sliding movement on Jndersurface of the first spring leaf 10 or, as in 3embodiment illustrated, has secured thereto a wear stant sliding element 17. One possible way of ring such a wear resistant element 17 is by the use zuntersunk screws engaging with internally threaded 3S 18 set in the material of the plastics covering The wear resistant element 17 may be of a suitable tics material or a metal, or may be a metal-rubber1 sandwich.One or more of the surfaces of the end ion of the spring leaf 11 may be provided with a ition or formations, e.g. a pattern of raised or ssed features, to assist keying of the plastics -ial covering 14 thereto so that the covering remains -e in service.

The spring assembly further comprises a bracket ture indicated generally at 19. This comprises two -ally U-shaped metal pressings of which the first ises a base 20 and spaced parallel limbs 21, and the Id comprises a base 22 and spaced parallel limbs 23.

are dimensioned so that the limbs 23 of the second ;ing fit closely within the limbs 21 of the first ;ing, and the base parts 20, 22 of the pressings her with the lower parts of the limbs 21 of the pressing fit closely within the transverse recess fined in the moulded plastics covering 14 around the g leaf 11. The limbs 21, 23 extend on opposite ; of the first spring leaf 10, and are connected her beyond such leaf by a transverse bolt 24 within ,wear spacer 25. If required, the limbs of the loped pressings may be additionally secured together lading therebetween, and/or by fasteners such as 5 applied, for example, where indicated at 26.

Further to assist security of the covering 14 of ics material on the spring leaf 11, the latter may a depression where indicated at 28, beneath the base 22 of the second pressing. The plastics material, of course enters the depression 28 during the ling process in which it is applied to the spring, is firmly in engagement with the depression by the ing force of the pressing.

In use of the spring assembly, the bracket structure -events the above-described phenomenon of scissoring occuring, and also prevents the spring leaves from -ating from one another. The engagement of the surface of the first spring leaf 10 by the wear stank sliding element 17 overcomes the problem of ,ive wear of the second spring leaf 11 of composite ial. For the purpose of preventing scissoring, a tet structure as 19 need only be provided at one end e spring assembly, in which case the other end of second spring leaf 11 would require merely to be ded with the moulded covering of plastics material, welcome the wear problem.

It is desirable that there is a large area of sst between the element 17 and the surface of the g leaf 10. The portion 16 of the plastics covering le leaf 11 is preferably so shaped so that the znt 17 lies flat against the surface of the leaf 10.

Llow for variations in the angle at which the end ion of the leaf 11 approaches the adjacent portion of Leaf 10 in different spring installations, which all ser use a covering 14 of basically the same duration, a mould may be used which has a ceable insert determining the shape of the covering on 16. Then, use of different inserts gives the red variations in the shape of the covering portion thout requiring an entirely different mould. In -e 1, dotted lines 29 show, to an exaggerated extent, he shape of the covering portion 16 may be thus zd to achieve the required engagement between element d spring leaf 10.

The leaf spring assembly above described has only wo spring leaves 10, 11. It would be within the of the invention, however, if the assembly were to one or more additional leaves, which could be trained relative to the two leaves by suitable ion to or modification of the described bracket turn.

Claims

1. A leaf spring assembly comprising a first spring leaf; a second spring leaf extending generally parallel to the first spring leaf; means securing the first and second leaves together at a position spaced from the ends thereof; a covering of a plastics material on an end portion of the second spring leaf, applied thereto by a moulding process; the covering of plastics material having associated therewith a surface engaging a facing surface of the first spring leaf for sliding movement there along, and also affording, at a position spaced from the end of the second leaf, a recess formation extending transversely at least partially around the second spring leaf; and a bracket structure engaging said recess formation and including parts extending on opposite sides of the first spring leaf and connected together beyond the first spring leaf, to hold the first and second spring leaves together.

2. A leaf spring assembly according to Claim 1 wherein the first spring leaf is of steel and the second spring leaf is of composite material.

3. A leaf spring assembly according to Claim 1 or 2 wherein the bracket structure comprises two generally U-shaped metal pressings, secured together.

4. A leaf spring assembly according to any one of the preceding claims further comprising an element secured to said covering of plastics material and affording a wear resistant surface.

5. A leaf spring assembly substantially as hereinbefore described with reference to the accompanying drawings.