GB2227807A

GB2227807A - Assembly including leaf spring of composite material

Info

Publication number: GB2227807A
Application number: GB8926608A
Authority: GB
Inventors: Bruce Nicholas Jones
Original assignee: GKN Technology Ltd
Current assignee: GKN Technology Ltd
Priority date: 1988-11-25
Filing date: 1989-11-24
Publication date: 1990-08-08
Also published as: GB8926608D0; GB8827609D0; WO1990006454A1

Abstract

A leaf spring (10) of composite material, with an end portion (11) defining a recess, has force transmitting connection with another component through an assembly comprising a member (14) which lies in the recess and a member (13) which presses against the surface of the spring adjacent the end portion and facing in the direction opposite to the recess.

Description

ASSEMBLY INCLUDING LEAF SPRING OF COMPOSITE MATERIAL This invention relates generally to leaf springs made of composite (fibre reinforced plastics) material, and more particularly it relates to the provision of means whereby a force transmitting connection is established with such a spring for use in, for example, a vehicle suspension.

In our European Patent No. 0070122, there is disclosed a leaf spring made from a composite material, having an end fitting which comprises an attachment member lying in a recess defined by the spring, the attachment member being held in the recess by a clamping member. This end fitting is designed for a leaf spring for use in vehicle suspension in which the spring fulfils the function of determining the path of wheel travel relative to a vehicle structure as well as providing springing, and therefore the end fitting is designed to withstand forces occurring in all directions between the spring and the component to which it is attached. An important feature of the end fitting is that the attachment member, in the form of a tubular bush to receive a bolt, lies in the recess at the spring end portion. For some applications, however, this end fitting is not convenient.Further, not all spring applications require an end fitting which is able to transmit forces in all directions as in the fitting disclosed in EP 0070122.

It is broadly the object of the present invention to provide a leaf spring of composite material with a force transmitting assembly which is more convenient for some applications, in respects which will be pointed out in detail hereafter together with other advantages of the invention.

According to the present invention, we provide the combination of a leaf spring of composite material having a spring end portion defining a recess extending across the width of the spring and facing in a direction transverse to the length of the spring, and a surface facing in the opposite direction to said recess; and a force transmitting assembly comprising a member lying in said recess, a member bearing on said oppositely facing surface of the spring adjacent said end portion thereof and means disposed beyond the end of the spring for connection to another component, said oppositely facing surface of said end portion of the spring not being engaged by said assembly.

In one direction of force transmission between the spring and the component to which the force transmitting assembly is connected the members of the assembly are urged into engagement with the recess and oppositely facing surface of the spring, so that the assembly will not become detached from the spring. To ensure that the force transmitting assembly does not become detached from the spring in the event of reversal of the direction of force transmission, a retaining member may be provided to engage the surface of the spring adjacent and facing in the same direction as the recess therein.

Preferably the force transmitting assembly comprises an element generally of U-section with a base wall and two side walls extending therefrom, said base wall of the element affording said member bearing on said oppositely facing surface of the spring adjacent said end portion thereof and being spaced from said oppositely facing surface of said end portion, said member lying in said recess extending between said side walls and said side walls extending beyond the end of the spring to provide for said connection to another component.

The force transmitting assembly of the invention effectively transmits force in the particular direction above referred to. This effectiveness is not decreased if, for example, production tolerances mean that mass produced springs have slightly different thicknesses from one another, individual manufacture of force transmitting assemblies is not necessary to suit such slightly different springs. When fitted to a particular spring, the assembly will assume an orientation such that it firmly engages the recess and the oppositely facing surface of the spring adjacent its end portion.

Preferably the side walls of the U-section element converge beyond the end of the spring, so that the assembly occupies the smallest possible volume and is therefore more readily accommodated in, for example, a vehicle suspension.

A leaf spring having a force transmitting assembly according to the invention may be used, for example, in a vehicle suspension where a path of wheel movement is determined by means, e.g. an appropriate linkage, other than the spring, and the spring is merely required to exert a springing force on a suspension component.

In known manner, load-spreading elements, e.g. of elastomeric material, may if required be interposed between one or more of the members of the force transmitting assembly and the spring.

The invention will now be described by way of example with reference to the accompanying drawings, of which Figure 1 is a diagrammatic elevation of a spring assembly according to the invention; Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 shows diagrammatically the use of a spring assembly according to the invention in a vehicle suspension.

Referring firstly to Figures 1 and 2 of the drawings, part of a leaf spring made of composite, fibre-reinforced plastics, material is indicated at 10, and the spring has an end portion 11 which defines a part circular recess 12 extending across the width of the spring. This shape of spring end portion is substantially the same as is shown in our European Patent 0070122 aforesaid. The recess faces in the direction, transverse to the length of the spring, in which the spring is to exert its force in use.

The spring end portion 11, and part of the spring immediately adjacent thereto, lie within a sheet metal pressing 13 which is generally of U-section as shown in Figure 2 having a base wall 13A and side walls 13B extending therefrom. A tubular member 14 extends transversely of the pressing between opposed side walls thereof, and engages the recess 12. In the region of the spring end portion 11, the base wall 13A of the pressing is spaced from the surface of the spring facing in the opposite direction to the recess 12. Adjacent the spring end portion 11, the base wall 13A of the pressing bears on the surface of the spring facing in the opposite direction to the recess 12, with the interposition of a load spreading element 15, e.g. of an elastomeric material. The load spreading element is not essential to the present invention.Beyond the end of the spring, the side walls of the pressing 13 afford aligned apertures 16 to receive a bolt or pin for force transmitting connection to another component, e.g. a vehicle suspension component.

Preferably, beyond the end p rtion 11 of the spring, the side walls 13B of the pressing converge towards one another so that the connection to another component such as a vehicle suspension component occupies minimum space.

In the above described assembly, when the spring is caused resiliently to bend, by a load applied to the pressing 13 in the direction indicated by arrow 17, the tubular member 14 is pressed firmly into the recess 12 whilst the pressing 13 bears, through the loadspreading element 15, on the oppositely facing upper surface of the spring adjacent the spring end portion 11.

The assembly 13, 14 thus remains firmly attached to the spring. To retain the assembly in the event of reversal of this direction of load application, a retaining member 18 is provided, extending transversely of the spring and bearing on the spring surface adjacent the recess 12 with the interposition of a load spreading element 19. The retaining member 18 is to be held to the pressing 13 by bolts passing at 20 through the staining member and flanges on the pressing 13.

Figure 3 of the drawings shows diagrammatically how a spring assembly according to the invention would be used in a vehicle suspension. In this figure, reference 30 designates a suspension member which at its one end 32 is pivotally secured to an appropriate part of the chassis structure of a vehicle and at its other end carries a wheel 31. A spring as above described in detail is indicated in outline at 10, mounted to the vehicle chassis structure by a mounting 34. The force transmitting assembly at the end of the spring is pivotally connected to a link 33 which in turn is pivotally connected to the member 30. Thus the normal direction in which the spring force is applied to support the weight of the vehicle on its wheels is that above described in which the member 14 is urged into engagement with the recess in the spring, and the base wall 13A of the pressing into engagement with the oppositely facing surface of the spring adjacent its end portion.

It will be noted that in this diagrammatic example the spring takes no part in determining the path of the wheel movement relative to the chassis structure of the vehicle, this being determined by the member 30 alone or in combination with other links or suspension members not shown. Link 33 transmits only a force to the spring in the direction generally transverse to the length of the spring.

Claims

1. The combination of a leaf spring of composite material, having a spring end portion defining a recess extending across the width of the spring and facing in a direction transverse to the length of the spring, and a surface facing in the opposite direction to said recess; and a force transmitting assembly comprising a member lying in said recess, a member bearing on said oppositely facing surface of the spring adjacent said end portion thereof and means disposed beyond the end of the spring for connection to another component, said oppositely facing surface of said end portion of the spring not being engaged by said assembly.

2. The combination according to Claim 1 wherein said force transmitting assembly comprises an element generally of U-section with a base wall and two side walls extending therefrom, said base wall of the element affording said member bearing on said oppositely facing surface of the spring adjacent said end portion thereof and being spaced from said oppositely facing surface of said end portion, said member lying in said recess extending between said side walls and said side walls extending beyond the end of the spring to provide for said connection to another component.

3. The combination according to Claim 2 wherein said side walls converge beyond the end of the spring.

4. The combination according to any one of the preceding claims further comprising a retaining member engaging the surface of the spring adjacent to and facing in the same direction as the recess therein.

5. The combination according to any one of the preceding claims further comprising at least one load-spreading element interposed between one or more of said members and the spring.

6. The combination of a leaf spring and a force transmitting assembly, substantially as hereinbefore described with reference to the accompanying drawings.

7. A force transmitting assembly for engagement with a leaf spring, substantially as hereinbefore described with reference to the accompanying drawings.

8. A vehicle suspension including the combination according to any one of the preceding claims, and means connecting the force transmitting assembly to a suspension member, the arrangement being such that the springing force urges said member of the assembly into said recess.