EP0230416A1

EP0230416A1 - Mountings for springs

Info

Publication number: EP0230416A1
Application number: EP85905417A
Authority: EP
Inventors: Adrian Tucker-Peake; David 18 Dunlin Close COWBURN
Original assignee: GKN Technology Ltd
Current assignee: GKN Technology Ltd
Priority date: 1984-11-07
Filing date: 1985-10-28
Publication date: 1987-08-05
Also published as: GB2191262A; WO1986002886A1; ES290185U; GB8710515D0; ES290185Y

Abstract

Montage pour ressort à lames en matériau composite plastique armé de fibres, comportant par exemple un élément en plastique moulé par injection (13) renfermant le ressort, enveloppé par une structure de montage (14, 15) se conformant aux surfaces portantes de l'élément (13), un matériau élastomère (16, 17) étant interposé. Les surfaces portantes peuvent être partiellement cylindriques de sorte que le ressort est maintenu pour un mouvement de pivotement limité autour d'un axe transversal. Dans une variante, l'élément peut être solidaire du ressort (21), et peut offrir des surfaces portantes tronconiques (22, 23).Assembly for leaf spring made of plastic composite material reinforced with fibers, comprising for example an injection molded plastic element (13) enclosing the spring, enveloped by a mounting structure (14, 15) conforming to the bearing surfaces of the element (13), an elastomeric material (16, 17) being interposed. The bearing surfaces can be partially cylindrical so that the spring is held for a limited pivoting movement around a transverse axis. Alternatively, the element may be integral with the spring (21), and may offer frustoconical bearing surfaces (22, 23).

Description

MOUNTINGS FOR SPRINGS

This invention relates to a mounting assembly, by which a spring is mounted in apparatus or equipment with which it is to be used. More particularly, the invention relates to a mounting assembly for a spring made of composite, fibre-rein orced plastics, material, in the form of a leaf thereof, and the invention has been developed in relation to motor vehicle suspensions.

When springs made of composite material are used in motor vehicles, in addition to requirements for the performance of mountings for such springs, there are constraints on design features which can be adopted. For example, it is undesirable to drill holes in composite springs because of the interruption caused thereby to the fibre structure, upon which the performance of the spring depends. Mountings which do not involve fasteners or the like extending through the spring preferably should therefore be used.

It is the broad object of the present invention to provide an effective mounting suitable for a Spring of composite material. More particularly, an object is to provide a mounting by which a composite spring is able to undergo limited pivotal movement relative to the article or structure to which it is mounted, about an axis extending transversly to the normal or principal direction of bending of the spring in use. Such a mounting is commonly required when the spring is used in a motor vehicle suspension, either in the cantilever mode or in an arrangement wherein the spring extends transversely of the vehicle, e.g. as disclosed in International Patent Application Publication WO-83/01758. The mountings disclosed for the spring in such application are relatively complex, and do not fully meet the requirement for a compact, economical and effective spring mounting.

According to the invention, we provide an assembly comprising a spring leaf of composite, fibre-reinforced plastics, material; affording or at least partially transversely embraced by an element providing a bearing surface extending transversely of the spring, and a mounting element or structure engaging said bearing surface thereby to constrain the spring.

The mounting element or structure constrains the spring to a desired relationship (or movement) relative thereto, and the mounting element or structure may then be secured to, for example, a motor vehicle with which the spring is to be used. It would be possible for the mounting element or structure to form part of a motor vehicle or other equipment with which the spring is used.

Said element, which at least partially transversely embraces the spring, is preferably of a plastics material, and conveniently may be applied to the spring by an injection moulding process. An injection moulding process, e.g. a reaction injection moulding (RIM) process, used with a plastics material such as a suitable grade of nylon, enables an element to be moulded onto the spring with closely controlled dimensions, accurate positioning on the spring, and adequate structural strength. It would be within the scope of the invention for the spring itself to incorporate in its structure an element or portion of increased thickness affording the bearing surface. However, such elements are difficult to incorporate in a composite spring, and hence it will generally be more convenient to provide an element of plastics material.

Preferably such a moulded element completely embraces the spring. The spring itself need not then be directly contacted by any part of the mounting element or structure.

Said element may afford part cylindrical bearing surface portions, extending transversely of the spring so that, when engaged by an appropriate mounting structure, the spring is mounted for the limited pivotal movement as above described. Alternatively, but also to provide for such pivotal movement, with improved constraint laterally of the spring, said element may afford opposed part-frusto-conical surface portions.

Preferably an element or elements of elastomeric material is or are interposed between said mounting element or structure and said bearing surface. The use of an elastomeric material provides a certain amount of flexibility in the mounting, and prevents, or attenuates, transmission of noise and vibration from the spring to the structure in which it is used. In the embodiment described hereafter, the elastomeric element may include apertures or other formations to increase its flexibility in a desired manner.

The invention will now be described by way of example with reference to the accompanying drawings, of which:- Figure 1 is a longitudinal section through an embodiment of assembly according to the invention;

Figure 2 is a plan view of part of the assembly of Figure 1.

Figure 3 is a transverse section through the assembly of Figures 1 and 2.

Figure 4 is a transverse section through a further embodiment of assembly according to the invention.

Figure 5 is a longitudinal section through the embodiment of Figure -\ .

The assembly shown in Figures 1 to 3 includes a leaf spring 10 made of composite, fibre-reinforced plastics, material and is the mounting adjacent one end of such a spring in a suspension of the kind described in International Published Patent Application ¥0-83/01758. The spring comprises a central portion 11 which is of constant cross-sectional shape and two end portions 12 each of decreasing width and increasing thickness towards the free ends of the spring, the spring being supported relative to a motor vehicle by mountings as shown at each end of its central portion 11.

The spring mounting assembly comprises an element 13 of a plastics material such as a suitable grade of nylon, embracing the spring transversely and applied thereto by a moulding process such as injection moulding. Thereby the element is effectively secured to the spring. The element 13 has portions with part-cylindrical bearing surfaces extending transversely above and beneath the spring, joined by portions at the side of the spring. A mounting structure having upper and lower parts 14, 15 of a shape which substantially conforms to the part-cylindrical surfaces of the element 13 supports the latter, with the interposition of elements 16, 17 of elastomeric material. The parts 14, 15 ma be secured together by means not shown, and the assembly then secured as a unit to the motor vehicle. They may have parts which engage the parts of the element 13 which extend between the part-cylindrical portions thereof, so

10 that the spring is also constrained in directions along the axis of the element 13- Elastomeric material may also be interposed here, between the element 13 and the mounting structure. The elastomeric material may be bonded to the element 13 and/or the parts 14, 15-

15. The parts 14, 15 of the mounting structure may, instead of being separate components, themselves form parts of the structure of the vehicle with which the spring is to be used.

It will be appreciated that the mounting assembly 20 described provides for limited pivotal movement of the spring about an axis extending transversely of the spring, i.e. longitudinally of the element 13« Such pivoting is achieved by virtue of the shape of- element 13_» and the interposition of the elastomeric elements 16, 25 17 between it and the parts of the mounting structure. It will be appreciated that the element 13 may be of a shape other than the cylindrical one illustrated, and may, for example, include frusto-conical portions, e.g. so that the element is of greatest thickness at the 30 centre of the spring, tapering transversely to opposite sides of the spring. If the pivoting motion of the spring is not required, the element 13 could, for example, be rectangular in cross-section. In a suspension of the kind disclosed in ¥0-83/01758, it will be appreciated that as the central portion 11 of the spring bends, the distance between the elements 13 at the mountings thereof will change. This is accommodated by resilient deflection of the elastomeric elements 16, 17. This may be facilitated by providing apertures 18 extending therethrough, transversely of the spring, or other appropriate formations to increase the flexibility of the elements in the desired sense. Alternatively, it could be achieved by use of material of appropriate flexibility.

A further feature which may be provided is that the element 13, above and/or beneath the spring, may be recessed as indicated at 19 so that the spring is not tightly constrained across its full width. This prevents or reduces stresses which would arise in the spring if its anticlastic bending were prevented.

The element 13 will, because of the shape of the spring, not be able to move longitudinally of the spring. If however such an element is to be provided at a part of the spring where the cross-sectional shape of the spring is not changing, it may be necessary to form the spring with recess formations in one or more of its surfaces, with which the element 13 will "key" to hold it stationary on the spring.

Referring now to Figures 4 and 5 of the drawings, there is shown part of a leaf spring 20 which is made of composite, fibre reinforced plastics, material. The spring may, for example, form part of the suspension system of a motor vehicle, mounted in the vehicle in the cantilever mode. At one end, the spring would be connected to a wheel, axle or other suspension component. At a position between its ends, the spring would be connected to the vehicle by the assembly to be described hereafter, and at its other end the spring would be supported relative to the vehicle in such a way as to provide a reaction force.

The spring mounting assembly comprises portion 21 which is of increased thickness, comprising two part- frusto-conical portions 22, 23 tapering in opposite directions towards respective sides of the spring. The portion 21 of the spring is substantially completely enclosed within a mounting structure which is two parts 26, 27 assembled from opposite sides of the spring. Flanges 28, 29 on the parts 26, 27 respectively abut one another. Appropriate fastenings through or between these flanges hold the parts 26, 27 of the structure together, and enable the structure to be mounted in a vehicle.

Elastomeric elements 24, 25 are interposed between the upper and lower surfaces, respectively, of the part 21 of the spring and the structure 26, 27« These are of a suitable grade of rubber. Further elastomeric elements 30 are interposed between the sides of the spring and the parts of the structure. The dimensions of the assembly are such that these elastomeric elements are ώider compression when the structure is assembled.

By virtue of the support of the spring within the structure 26, 27 by the elastomeric elements, and the double frusto-conical shape of the portion 21 of the spring, the spring is able to undergo limited angular movement about a transverse axis within the structure 26, 27. The spring is also effectively constrained against lateral movement, such that the pads 30 of elastomeric material providing additional lateral constraint on the spring may not be necessary.

The compressed state of the elastomeric elements in the assembly means that there is no necessity for them to be bonded to the spring, thereby eliminating a difficulty in manufacture of composite springs.

Claims

1. An assembly comprising a spring leaf (10, 20) of composite, fibre-reinforced plastics, material, affording or at least partially transversely embraced by an element (13, 21) providing a bearing surface (22, 23) extending transversely of the spring, and a mounting element or structure (1 , 15, 26, 27) engaging said bearing surface (22, 23) thereby to constrain the spring.

2. An assembly according to Claim 1 wherein said element (13), which at least partially transversely embraces the spring (10), is of a plastics material, applied to the spring by a injection moulding process.

3. An assembly according to Claim 2 wherein said moulded element (13) completely embraces the spring (10).

4. An assembly according to Claim 1 wherein said element (21) is integral with the spring (20).

5 - An assembly according to any one of the preceding claims wherein said element (13) affords part cylindrical bearing surface portions, extending transversely of the spring so that, when engaged by said mounting ^strueture (14, 15), the spring is mounted for limited pivotal movement about an axis extending transversely thereof.

6. An assembly according to any one of claims 1-4 wherein said element (21 ) affords part-frusto-conical bearing surface portions (22, 23) so that, when engaged by said mounting structure (26, 27), the spring is •constrained laterally as well as being mounted for limited pivotal movement about a transverse axis. 7- An assembly according to any one of the preceding claims wherein at least one elastomeric element (16, 17, 24, 25, 30) is interposed between said mounting element or structure and said bearing surface.