GB2222646A

GB2222646A - Brake pad

Info

Publication number: GB2222646A
Application number: GB8821166A
Authority: GB
Inventors: William Ernest Haines
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1988-09-09
Filing date: 1988-09-09
Publication date: 1990-03-14
Anticipated expiration: 2008-09-09
Also published as: GB8821166D0; GB2222646B

Abstract

A brake pad has a backing plate (10) with a pad (11) of friction material secured to one face. A clip formation (22, 23) is secured to the other face of the backing plate (10), said clip formation (22, 23) being formed from resilient strip material and being adapted to engage a formation (26) on the associated limb of a brake caliper. An integral extension (28) of the clip formation (22, 23) projects beyond the face of the backing plate (10) to which the friction material is secured. <IMAGE>

Description

BRAKE PADS The present invention relates to brake pads for disc brakes.

Typically a disc brake comprises disc secured for rotation with the road wheel of the vehicle, a caliper which straddles a portion of the peripheral edge of the disc and a support member mounted on a non-rotary part of the vehicle, upon which the caliper is slidingly located for movement relative to the disc, in a direction parallel to the axis of rotation of the disc.

The caliper comprises a pair of parallel limbs which overlap and are parallel to the disc, these limbs being interconnected by a pair of transverse limbs which are spaced radially from the periphery of the disc.

Brake pads are located, one on either side of the disc, between the parallel limbs of the caliper. The brake pads comprise a backing plate having a pad of friction material on the face thereof adjacent the disc. These pads are located radially by means of a pair of pins which extend between the parallel limbs of the caliper, outside the periphery of the disc, the pins passing through holes in the backing plates. The holes in the backing plates are elongated to permit the pads to move over a small distance circumferentially relative to the disc, so that when brought into engagement with the rotating disc, one of the radial edge faces of each backing plate will be brought into engagement with the corresponding radial face on the caliper, depending on the direction of rotation.

A hydraulic cylinder/piston assembly is associated with one of the parallel limbs of the caliper and arranged to act on the backing place of the adjacent pad. Application of the brakes will cause the hydraulic piston to force the adjacent brake pad into engagement with the disc and then further pressure will cause the caliper to slide on the support member, thereby bringing the opposite pad into engagement with the disc.

On release of the brake, the hydraulic piston moves back sufficiently to provide a clearance for the adjacent pad and permit the caliper to slide relative to the support member, so that a clearance is provided for the other pad.

Alternatively, the caliper may be fixed with respect to the support member, and hydraulic cylinder/piston assemblies provided on both limbs of the caliper.

With such disc brake assemblies, if no means is provided to maintain the pads in engagement with the limbs of the caliper, it is possible that the pads may remain in engagement with the disc, which will result in drag and also lead to unnecessary wear of the pads. Furthermore, the pads -will be free to rattle or oscillate between the disc and the parallel limbs of the caliper, especially when the disc is out of true or suffers from "run-out".

The present invention provides means for positively locating the pads with respect to the limbs of the caliper and for indicating wear of the pads.

Accordiny to one aspect of the present invention, a brake pad for a disc brake comprises a backing plate having a pad of friction material secured to one face, a clip formation being secured to the other face of the backing plate, said clip formation being formed from resilient strip material and being adapted to engage a formation on the associated limb of a brake caliper, an integral extension of the clip formation projecting beyond the face of the backing place to which the friction material is secured.

The extension of the clip formation defines a wear limit for the pad of friction material, the extension making engagement with the disc to provide an audible warning, when the pad of friction material has worn down to that limit.

Various embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a plan view of the rear face of the brake pad formed in accordance with the present invention; Figure 2 shows a section on the line II-II of Figure 1, including a piston of a disc brake assembly to illustrate the means of securing the brake pads to the piston; Figure 3 is a section on the line III-III including the piston of the disc brake assembly; Figure 4 shows a plan view of the rear face of an alternative brake pad formed in accordance with the present invention; and Figure 5 shows a section along the line V-V of Figure 4 including the piston of a disc brake assembly.

As illustrated in Figures 1 - 3, a brake pad includes a backing plate 10 with a pad 11 of friction material bonded to one face 12 thereof. In conventional manner, holes 13 are provided through the backing plate 10 and the pad 11 is moulded with plug formations 14 which extend into the holes 13 to provide a mechanical key for the pad 11, which will withstand sheer loads applied to the pad 11. A retaining clip/wear indicator 15 is secured to the other face 16 of the backing plate 10. The retaining clip/wear indicator 15 is made of resilient strip material of generally T-shape.

The retaining clip/wear indicator 15 is secured to the backing plate 10 at the junction of the limbs 17, 18 and 19, by means of rivet 20 which engages in hole 21 which is central of the backing plate 10. The transverse limbs 17 and 18 are bent away from the backing plate 10 and then back towards one another, adjacent their ends, to provide clip formations 22 and 23.

;;hen the brake pad is assembled in the caliper of a disc brake and the backing plate 10 is abutted by piston 25 of the brake assembly, the clip formations 22 and 23 will engage an internal flange formation 26 at diametrically opposed positions, thereby positively locating the brake pad with respect to the piston 25.

The limb 19 of the retaining clip/wear indicator 15 extends across the backing plate 10 to the edge thereof, a portion 24 thereof being depressed into one of the holes 13 to provide a clearance, so that the piston 25 can abut the face 16 of the backing plate 10.

Adjacent the edge of the backing plate 10, limb 19 is secured to the backing plate 10 by rivet 27. The limb 18 is then bent to provide a formation 28 which extends forwardly parallel to the edge of the backing plate and beyond the face 12, so that the end 19 of the limb 18 overlaps the pad 11 by a small amount. Formation 28 provides a wear detector, when the pad 11 is worn down to the limit the end 29 of formation 28 will engage the brake disc to provide an audible warning, before the pad 11 is completely worn away and the backing plate 1U is permitted to come into engagement with the brake disc.

In the modification illustrated in Figures 4 and 5, the rivet 27 is replaced by an additional limb 30 On the retaining clip/wear indicator 15. The end of limb 30 is bent down towards the backing plate 10 to form a lug 31 which engages in a hole 32 in the backing plate 10, to provide location of the retaining clip/wear indicator 15 which will prevent rotation about rivet 20.

Claims

1. A brake pad comprising a backing plate having a pad of friction material secured to one face, a clip formation being secured to the other face of the backing plate, said clip formation being formed from resilient strip material and being adapted to engage a formation on the associated limb of a brake caliper, an integral extension of the clip formation projecting beyond the face of the backing place to which the friction material is secured.

2. A brake pad according to Claim 1 in which the clip formation is secured centrally of the backing plate.

3. A brake pad according to Claim 2 in which the clip formation and integral extension are of generally T-shaped configuration.

4. A brake pad according to Claim 3 in which the extension is secured to the backing plate adjacent the edge thereof.

5. A brake pad according to Claim 3 in which a further extension of the clip formation is provided with a lug which engages a hole in the backing plate, said hole being spaced from the centre of the backing plate.

6. A brake pad according to any one of the preceding claims in which a portion of the extension is recessed into the backing plate to provide a clearance for the formation on the associated limb of the caliper, so that said formation can engage said other face of the backing plate.

7. A brake pad substantially as described herein with reference to, and as shown in, Figures 1 to 3 or Figures 4 and 5 of the accompanying drawings.