WO1998009091A1

WO1998009091A1 - Friction pad assembly

Info

Publication number: WO1998009091A1
Application number: PCT/GB1997/002279
Authority: WO
Inventors: Kenneth James Bunker
Original assignee: T & N Technology Limited
Priority date: 1996-08-29
Filing date: 1997-08-26
Publication date: 1998-03-05
Also published as: GB9618011D0; GB2316725A; GB9717555D0

Abstract

A friction pad assembly (10) is suitable for use in a disc brake. The assembly (10) comprises a backing plate (12), a block of friction material (14) secured to a surface (16) of the backing plate (12), and a spring (22) secured to the backing plate (12) at an edge region thereof. Said region of the backing plate (12) has a pillar (20) extending therefrom normally of the plate (12), the backing plate (12) and the pillar (20) being cast as a unit. The spring (22) comprises a central coil (24) which passes around the pillar (20) and is an interference fit thereon so that the spring (22) is retained on the pillar (20).

Description

FRICTION PAD ASSEMBLY

This invention is concerned with a friction pad assembly suitable for use in a disc brake. Such assemblies comprise a backing plate and a block of friction material secured to a surface of the backing plate.

In most constructions of disc brake, friction pad assemblies are mounted on opposite sides of a disc to be urged into contact with the disc by a piston and cylinder assembly. The backing plates, which are normally formed from mild steel, are supported on guides which control their movement and absorb the braking forces. To enable the pad assemblies to make their movements, there has to be clearance between the backing plates and the guides. This means that there is the potential for the backing plates to rattle in their guides creating an undesirable noise.

One known method of preventing the backing plates from rattling in their guides is to provide each backing plate with a spring at an edge thereof. The spring projects beyond the backing plate and engages the guide so that, deformation of the spring by contact with the guide causes the spring to urge the backing plate against an opposite side of the guide, thereby preventing rattling. However, the mounting of such springs on backing plates has hitherto required several additional operations and/or the provision of a complex spring.

One example of a friction pad assembly comprising a spring is described in GB 1,533,976. In this example, the backing plate is provided with a projection in a central region thereof which is clear of the friction material and a rivet is secured to this projection. The spring is made of wire and comprises a central portion formed into a coil. The rivet passes through the coil to secure the spring to the backing plate. The spring also comprises two end portions which are spaced from the backing plate and engage one side of the guide to urge the backing plate against the other side of the guide. In this case, the assembly requires a rivet and, usually, a washer. Furthermore, manufacture of the assembly requires formation of a hole for the rivet, fitting of the spring (and usually a washer) on to the rivet, and setting of the rivet.

Another example can be found in GB 2,036,211 which describes a friction pad assembly comprising a backing plate having a projection extending upwardly from the top edge of the plate. The projection has laterally facing undercuts which retain an anti-rattle spring. This construction requires a complex operation to form the undercuts.

Another example can be found in GB 2,159,221 in which a pin projects from a projection of a backing plate and a central coil of a spring is fitted on to the pin. In this case, the pin has to be provided and fixed to the projection of the backing plate. Also, the spring has to be secured to the pin.

It is an object of the present invention to provide a friction pad assembly which requires less components and manufacturing operations thereby reducing costs.

According to the present invention there is provided a friction pad assembly suitable for use in a disc brake, the assembly co.r.pri ing a De-eking plate, a block of friction material secured to a surface of the backing plate, and a spring secured to the backing plate at an edge region thereof, characterised in that said region of the backing plate has a pillar extending therefrom normally of the plate, the backing plate and the pillar being cast as a unit, and the spring comprises a central coil which passes around the pillar and is an interference fit thereon so that the spring is retained on the pillar.

In an assembly according to the invention, the number of components and manufacturing operations is reduced as the spring can be secured on the backing plate siiύpiy by enlarging the coil and slipping it on to the pillar. The spring can also easily be removed, eg for replacement, by enlarging the coil and slipping it off the pillar. Removal of springs is very difficult with conventional rivetted springs.

Preferably, the coil consists of one complete loop of wire.

Preferably, the spring is arranged so that, deformation of the ends of the spring, which in service engage the guide in which the assembly slides, towards the backing plate causes the coil of the spring to tighten around the pillar, thereby reducing the possibility that the spring will ecome detached in service.

The region of the backing plate to which the spring is secured is conveniently provided by a projection which is free of the friction material, the integrally formed pillar being on the projection. Alternatively, however, said region may be provided by a portion of the backing plate which is in a gap or recess in the friction material, the pillar extending from that portion. This is advantageous when it is not desirable to have a projection of the backing plate, for example, where the space for the friction pad assembly in a calliper is limited. The pillar advantageously extends perpendicularly to the plane of the backing plate. This improves the ease with which the spring can be fitted on to (or removed from) the pillar.

It is preferred that the backing plate is formed of cast iron or cast aluminium.

Preferably, the pillar is of substantially constant cross-section.

Conveniently, the pillar is generally cylindrical, so enabling interference fit with a spring with a generally circular coil.

There now follows a detailed description to be read with reference to the accompanying drawings, of a friction pad assembly which is illustrative of the invention.

In the drawings:

Figure 1 is a front view of a preferred embodiment of a backing plate and a block of friction material of the illustrative friction pad assembly;

Figure 2 is a partial front view of the illustrative assembly including a spring thereof; and

Figure 3 is a perspective view of the portion shown in Figure 2 showing the spring disassembled from the backing plate.

The illustrative friction pad assembly 10 is suitable for use in a disc brake. The assembly 10 comprises a backing plate 12. The backing plate 12 is made of cast iron but, in variations of the illustrative assembly 10, may be made of other materials, for example, cast aluminium. The assembly 10 also comprises a block of friction material 14 secured to a generally planar surface 16 of the backing plate 12. The backing plate 12 has an integral projection 18 at an edge region thereof. The projection 18 is free of the friction material 14.

The projection 18 has a pillar 20 extending therefrom normally of the backing plate 12. The pillar 20 is cast as a unit with the backing plate 12 so that it is integral therewith. The pillar 20 is cylindrical, of constant circular cross-section, and extends perpendicularly to the plane of the backing plate 12, ie to the surface 16.

The assembly 10 also comprises a spring 22 secured to the backing plate 12 at an edge region thereof. The spring 22 is made of wire and comprises a central coil 24. The coil 24 consists of one loop of wire. The spring 22 also comprises ends 26 and 28 which in service engage a guide in which the assembly 10 slides. The ends 26 and 28 extend from opposite ends of the coil 24 in substantially opposite directions and are bent by approximately 180° at their ends.

The central coil 24 of the spring 22 passes around the pillar 20 and is an interference fit thereon so that the spring 22 is retained on the pillar 20.

In order to secure the spring 22 on the pillar 20, the ends 26 and 28 of the spring 22 are pressed towards one another, thereby enlarging the coil 24 and enabling the spring to be slipped on to the pillar 20. When the coil 24 has been placed over the pillar 20, the ends 26 and 28 are released. The coil 24 then resumes its normal size and forms an interference fit with the pillar 20. The spring 22 can also be removed from the pillar 20 by pressing the ends 26 and 28 together.

When the spring 22 is secured to the pillar 20, the ends 26 and 28 extend laterally of the projection 18 in opposite directions. The spring 22 is secured with the coil 24 arranged so that the ends 26 and 28 project from the side of the coil 24 which is furthest from the friction material 14, ie nearest to the free end of the projection 18. This means that deformation of the ends 26 and 28 of the spring, which in service engage the guide in which the assembly 10 slides, towards the backing plate 12 causes the coil 24 of the spring to tighten around the pillar 20.

Claims

A friction pad assembly (10) suitable for use in a disc brake, the assembly comprising a backing plate (12), a block of friction material (14) secured to a surface (16) of the backing plate, and a spring (22) secured to the backing plate at an edge region thereof, characterised in that said region of the backing plate has a pillar (20) extending therefrom normally of the plate, the backing plate and the pillar being cast an a unit;, and ths spring compri es a central coil (24) which passes around the pillar and is an interference fit thereon so that the spring is retained on the pillar.

An assembly according to claim 1, characterised in that the coil (24) consists of one complete loop of wire.

An assembly according to either one of claims 1 and 2, characterised in that the spring (22) is arranged so that, deformation of the ends (26, 28) of the spring, which in service engage the guide in which the assembly (10) slides, towards the backing plate (12) causes the coil (24) of the spring to tighten around the pillar (20) .

An assembly according to any one of claims 1 to 3 , characterised in that the region of the backing plate (12) to which the spring (22) is secured is provided by a projection (18) which is free of the friction material (14) , the integrally formed pillar (20) being on the projection. An assembly according to any one of claims 1 to 4 , characterised in that the pillar (20) extends perpendicularly co the plane of the oacking plate (12) .

An assembly according to any one of claims 1 to 5, characterised in that the backing plate (12) is formed of cast iron or cast aluminium.