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 one 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 of the pad assemblies 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 which, when deformed by contact with the guide urges the backing plate against the opposite side of the guide. Such a spring is described in GB 1,533,976 in which 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 coil passes around the rivet 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. GB 2,111,619 describes a similar spring in which a central coil is received in a large recess in the side of the backing plate, the recess reducing the area available for the friction material. GB 2,027,141 describes a similar spring in which central coils of the spring are received in

a passage which passes through a projection of the backing plate. GB 2,111,618 describes a similar spring but without a central coil. This spring has its central portion passing through two spaced slots in a projection of the backing plate. GB 2,036,211 describes a similar spring in which the central coil is wrapped around a projection of the backing plate. GB 1,535,720 describes a leaf spring which is used in place of the springs mentioned above. The leaf spring has a clip in a central region thereof which enters a recess in a projection of the backing plate. EP 0,153,280 A describes springs which are wrapped around a projection of the backing plate and also describes the use of two springs, on opposite sides of a projection. In the latter case, the springs each have one end in a recess in the backing plate.

The known springs described above require there to be a projection of the backing plate or, in the case of GB 2,111,619, there to be a large recess in the edge of the backing plate. The provision of such projections or large recesses is undesirable since it adds complication to the manufacture of the backing plate. Furthermore, the assembly of the springs on to the backing plate is, in most cases, complex.

It is an object of the present invention to provide a friction 3 assembly having a spring of the type referred to, the spring being mounted on the backing plate of the assembly in a simple manner which does not require projections or large recesses.

The invention provides a friction pad assembly suitable for use in a disc brake, the assembly comprising a backing plate, and a block of friction material secured to one surface of the backing plate, the assembly also comprising a spring mounted on the backing plate to prevent the assembly from rattling in its guide in service,

characterised in that the spring comprises two end portions, which are received in recesses in an edge of the backing plate, and a central portion which is spaced from the edge of the backing plate.

In a friction pad assembly according to the invention, the mounting of the spring on the backing plate does not require a projection of the backing plate and only requires recesses which are sufficiently large to receive the end portions of the spring. The central portion of the spring has many possible shapes to provide one or two abutments to engage the edge of the guide.

Preferably, the spring is formed from a length of wire or strip, eg of steel, which is bent into the required shape. The wire may have a circular or a rectangular transverse cross-sectional shnpe.

In order to more securely retain the end portions of the spring in the recesses, it is advantageous if the end portions each have an undulation in them which grips the sides of the recess. Alternatively, or in addition, the spring may be arranged so that the end portions have to be pressed towards one another against the resilience of the spring to enable them to enter the recesses, ie the end portions press against these sides of the recesses due to the resilience of the spring.

The recesses in the backing plate may be provided by cylindrical bores in the edge of the backing plate. These bores may be parallel to one another or inclined towards or away from one another.

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 cross-sectional view taken through a backing plate of the illustrative friction pad assembly; and

Figure 2 is a view of the spring of the illustrative assembly taken in the direction of the arrow II in Figure

1, but on an enlarged scale.

The illustrative friction pad assembly 10 is suitable for use in a disc brake. The assembly 10 comprises a backing plate 12 which is shown in cross-section in Figure

2, the cross section being taken parallel to the surface of the pad assembly which engages a disc when the assembly is in service. The backing plate 12 is made of cast iron but, in variations of the illustrative assembly 10, may be made of other materials.

The assembly 10 also comprises a block of friction material (not shown) which is secured, in conventional manner, to one surface of the backing plate 12.

The pad assembly 10 also comprises a spring 20 mounted on the backing plate 12 to prevent the assembly 10 from rattling in its guide in service. The spring 20 is formed from a single length of steel wire of circular cross- section and is 1.5mm in diameter.

The spring 20 has first and second opposite end portions 22 and 24, respectively, which are generally straight and parallel to one another except for undulations 22a and 24a, respectively, therein.

To mount the spring 20 on the assembly 10, the end portions 22 and 24 of the spring 20 are received in recesses 16 in an edge of the backing plate 12 (in Figure 1, the spring 20 is shown with the end portions 22 and 24 about to be located in the recesses 16) . The recesses 16

are in the form of cylindrical bores having a diameter of 3mm which extend parallel to one another from an edge of the backing plate 12. When in the recesses 16, the undulations 22a and 24a of the end portions 22 and 24 grip the sides of the recesses 16 to resist withdrawal of the end portions from the recesses.

The end portion 22 of the spring 20 is co-terminous with a portion 26 of the spring 20 which bends inwardly towards the other end portion 24, making an angle of approximately 135 degrees with the portion 22. The portion 26 is also co-terminous with an arcuate portion 28 of the spring 20. This portion 28 bends outwardly away from the other end portion 24 making an angle of approximately 45 degrees with the portion 26. The arcuate portion 28 subtends an angle of approximately 25 degrees about a point 30 which is spaced from the assembly 10.

The end portion 24 is co-terminous with a portion 32 of the spring 20, the portion 32 being a mirror image of the portion 26. The portion 32 is also co-terminous with an arcuate portion 34 of the spring 20 which is a mirror image of the portion 28.

The arcuate portions 28 and 34 are both co-terminous with a central arcuate portion 36 of the spring 20 which subtends and angle of approximately 60 degrees about the point 30. The junctions between the portions 28 and 36 and between the portions 34 and 36 are formed by 180 degree turns in the wire from which the spring 20 is formed. These turns provide abutments 40 of the spring 20. The arcuate portions 28 and 34 are aligned with one another and lie alongside the arcuate portion 36 (see Figure 2) .

It will be apparent that the spring 20 is mounted on the backing plate 12 without the need for a projection of the backing plate 12 or a large recess therein.