GB1590631A

GB1590631A - Disc brakes

Info

Publication number: GB1590631A
Application number: GB48276/76A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1976-11-19
Filing date: 1976-11-19
Publication date: 1981-06-03
Also published as: ZA776686B

Description

(54) IMPROVEMENTS IN DISC BRAKES (71) We, GIRLING LIMITED, a British Company, of Kings Road, Tyseley, Birmingham B26 lAW, West Midlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a friction pad assembly for use in a disc brake and a disc brake incorporating such a friction pad assembly.

In most constructions of disc brakes, the friction pads are supported on or between guides to which forces due to braking are transmitted from the pad and hence to the vehicle frame. It is necessary to provide some degree of clearance at these guides to permit the pads to slide towards and away from the disc during braking and to ensure freedom from pad seizure. This can result in the pads rattling in these guides. To reduce this problem it is known to incorporate a resilient means, usually a spring, to bias the pad against one side of the guide and to ensure that the pad starts each brake application from a constant position in the guide, since otherwise it could wander in the clearances. The "fit" of the pad to the disc would change, which can lead to squeal and other noises. Problems with such resilient means, specifically springs, are that the springs heretofore known are subject to many of the following: 1. They do not exert substantially the same force between pad and guide throughout the life of the pad.

2. They are not easy to assemble in and dismantle from a brake.

3. They give rise to spurious loads and couples that tend to displace the pad from its desired position and attitude in a brake caliper.

4. Careless assembly can cause them to cut, or otherwise damage the flexible rubber boots which are provided to protect the piston or pistons in a brake caliper.

5. They are not particularly cheap to manu facture or install.

6. They take up space which could be usefully filled by other brake components to enhance brake performance, parti cularly the rigidity of the brake.

To try and solve at least some of these problems we have proposed in our copending British Patent Application No. 55727/74 (Serial No. 1,533,976), that a spring be securely fixed to the backing plate of the friction pad assembly prior to installation of the pad assembly in a disc brake and preferably during the manufacture of the friction pad assembly. The prime purpose of the spring is to act as an anti-rattle spring by biasing the pad assembly against its guide in a disc brake. The benefits of the prior attachment of the anti-rattle spring are several. For example, it assures the correct fitting of the spring in the brake. Further, the spring cannot slip and is thus less likely to damage the flexible boot normally provided in a disc brake to protect the hydraulic piston and cylinder against the ingress of dirt and moisture.

In our British Patent Application No.

55727/74 (Serial No. 1,533,976), the embodiment described comprises a wire pad antirattle spring which has a coiled region which is attached to the backing plate of the pad assembly by a rivet. This construction requires a certain amount of free space to be available within a disc brake to allow for the desired movement of the pad assemblies.

The aim of the present invention is to provide a friction pad assembly incorporating a securely attached pad anti-rattle spring, wherein the location and attachment of the spring is improved so that a designer has freedom to design the pad assembly to suit the shape of the area into which the assembly is to be fitted.

According to the present invention there is provided a friction pad assembly for use in a disc brake, comprising a backing plate and a pad of friction material secured thereto, part of a wire spring being embedded within the friction material or held between the pad and the backing plate, the end regions of said part of the wire spring projecting from the pad and backing plate, and being coiled, the coils terminating in free ends extending in generally opposite directions.

In addition to the increased design freedom which this structure provides, the cost of providing a separate attachment means, such as a rivet, is saved.

In one embodiment of the present invention said part of the spring is located in a groove provided in the surface of the backing plate, and covered by the pad of friction material. The ends of said part of the wire spring project from between the backing plate and the pad of friction material and are adapted with regard to the design of the particular type of brake in which the assembly is to be used, to spring bias the assembly against its guides and thus reduce the possibility of pad rattle.

In one embodiment of friction pad assembly the backing plate has laterally projecting shoulders which, in use, engage and slide along supporting guides. The respective coils of the spring lie substantially on a common axis and the free ends of the said coils extend in generally opposite directions though subtending an angle of less than 1800 therebetween. In use the said end regions of the spring engage part of a brake and are flexed to increase the angle therebetween, thus biasing the lateral shoulders of the backing plate against their respective support guides.

In an alternative embodiment the respective coiled parts of the wire spring are spaced from each other and, in use, the end regions of the spring engage part of the brake. In the case of a friction pad assembly wherein the backing p]ate has a region free of friction material which is provided with two spaced apart holes through which support pins engage, the end regions of the spring are adapted to engage the pins and thus take up any clearance between the support pins and the holes in the backing plate to reduce the possibility of rattling both of the pads and the pins. The end regions may both be adapted to engage around the pins to accurately hold the assembly with respect to the support pins or alternatively only one end region may be adapted to engage around a support pin to just prevent so-called 'klonking' at the instant the brake is applied.

The present invention will now be further described, by way of example, with reference to the drawings accompanying Provisional Specification No. 48277/76, in which: Fig. 1 is a frontal view of one embodiment of a friction pad assembly constructed according to the present invention; Fig. 2 is an enlareed cross-sectional view along line A-A in Fig. 1; Fig. 3 is a partial enlarged plan view of the friction pad assembly of Fig. 1; Fig. 4 is a detailed view of part of a modified form of the friction pad assembly of Fig. 1; Fig. 5 is a frontal view of another embodiment of a friction pad assembly constructed according to the present invention; Fig. 6 is a partial frontal view of a further embodiment of a friction pad assembly constructed according to the present invention.

In Figs. 1 to 3 one embodiment of a friction pad assembly according to the present invention is illustrated. This assembly comprises a backing plate 1 to which a pad 2 of friction material is secured. The backing plate 1 has laterally projecting shoulders 3 which are used to support the assembly on guides (not illustrated) in a disc brake, and a groove 4 (see Figs. 2 and 3) in which part of a wire spring generally designated 5, is located. The pad 2 covers part of the groove 4 and thus the wire spring 5 is secured in the assembly. In an alternative embodiment (not shown) no groove 4 is provided in the backing plate. The wire spring simply rests against the backing plate, and is secured thereto by the pad material during moulding.

The wire spring 5 has a generally triangular configuration when viewed in Fig. 1, and comprises a base section 6 from each end of which a side section 7 extends. The side sections 7 are inclined towards each other to form the generally triangular configuration, and form coiled regions 8 and 9 (see Figs. 2 and 3) which are arranged coaxially with respect to each other. The free end regions 10 of the coiled regions 8 and 9 extend away from the coiled regions in generally opposite directions and as shown in dashed lines on one side of Fig. 1, the end regions 10 normally have an angle of less than 1800 therebetween. However, in use within a disc brake caliper, the end regions ennage against part of the brake and flex (see full lines in Fig. 1) thus increasing the angle between the end regions 10 and biasing the assembly against guides within the brake.

In this embodiment the base section 6 and part of each side section 7 of the wire spring 5, engage in the complementary shaped groove 4 in the backing plate 1. However, in a modified form of this assembly (see Fig.

4), whereas the configuration of the wire spring 11 is identical with the spring 5 of Fig. 1, the groove in the backing plate 1 is not complementary in shape to the said base and side sections of the spring, but is so shaped that the side sections 12 of the spring clip onto portion 13 of the backing plate.

This is effected by, in the unassembled state.

the distance between the wall portions 14 of the groove being greater than the distance between the portions of the side sections 12 which will engage wall portions 14. Thus, when assembled, wall portions 14 force side sections 12 further apart flexing corner regions 15 of the spring, the spring force produced by corner regions 15 clipping the spring to wall portions 14. To allow for this flexing the regions 16 of the groove are larger than in the embodiment of Fig. 1.

This clipping of the spring to the backing plate holds the spring in place and thus facilitates the subsequent moulding of the friction material to the backing plate. Also the clipping of the spring to the backing plate takes up any manufacturing tolerances which may have allowed the spring 5 to move in groove 4 in the embodiment of Fig. 1. Such movement could possibly cause premature wear or damage to the assembly.

Two further embodiments of the present invention are illustrated in Figs. 5 and 6.

In each of these embodiments the friction pad assembly comprises a backing plate 17 to which a pad 18 of friction material is secured, the backing plate having a region free of friction material, in which two spaced apart holes 19 are provided. As viewed in Figs. 5 and 6, this region which is free of friction material is along the upper edge of the assembly and the holes 19 are located adjacent the side edges of the assembly. A spring 20 is secured in the central region of this upper edge of the assembly, a central part 21 of the spring being located in a groove (not illustrated) in the backing plate 17 and retained therein by the pad 18.

The central part of the spring 21, as viewed in Figs. 5 and 6, comprises a horizontal elongate section, each end of which is turned upwards and projected beyond the backing plate and the pad of friction material, to form coiled regions 22 and 23 which, unlike the embodiment of Fig. 1, are spaced apart from each other. The end regions 24 of the spring extend in generally opposite directions and are sufficiently long to engage under support pins 25 which, in use, extend through holes 19 to support the assembly in a brake. The normal unstressed position of one end region 24 is shown in dashed lines in Fig. 5. Thus it will be understood that when the end regions 24 of the spring engage under the support pins taking up any clearance therebetween and reducing the possibility of pad rattle. In the embodiment of Fig. 5 the ends 26 of the spring are both curved to engage part way around the support pins 25 and thus further secure the assembly in position relative to the pins.

However, in the embodiment of Fig. 6, the end 27 of only one of the end regions 24 is bent upwards to engage around a support pin. Taken in the direction of rotation of the disc of a brake it is the end region 24 nearest the leading edge, of the pad assembly, which is bent upwards. Part of the reaction to the spring force is now taken by the engagement of the pin in the brake, so that the spring acts to bias the pad backing plate against the guide, so preventing the so-called 'klonking' which can be produced by the assembly moving relative to and hitting, the guide as the brake is applied.

In the above described embodiments the concept of effectively sandwiching part of a wire pad anti-rattle spring between the backing plate and the pad of friction material provides the designer with more space within a brake to freely design his other brake components with a minimum of interference from the pads and springs, and also provides the benefits of the prior attachment of the spring.

In the above embodiments, some difficulty is found in ensuring complete closure of the pad moulding dies in the region of the wire, whether it fits into a socket in the backing plate, or rests against the backing plate. If this difficulty is found to be significant in some cases, then square, or rectangular, wire may be used in place of the round wire shown. This has little effect on the wire's performance as a spring, but is slightly more expensive.

WHAT WE CLAIM IS:- 1. A friction pad assembly for use in a disc brake, comprising a backing plate and a pad of friction material secured thereto, part of a wire spring being embedded within the friction material or held between the pad and the backing plate, the end regions of said part of the wire spring projecting from the pad and backing plate, and being coiled, the coils terminating in free ends extending in generally opposite directions.

2. A friction pad assembly as claimed in claim 1, in which the respective coils of the wire spring lie substantially on a common axis.

3. A friction pad assembly as claimed in claim 1 or 2, in which the backing plate has laterally projecting shoulders which, in use, engage and slide along supporting guides.

4. A friction pad assembly as claimed in claim 1, in which the respective coils are spaced apart from each other.

5. A friction pad assembly as claimed in claim 4, in which the backing plate has a region free of friction material which is provided with two spaced apart holes through which, in use, support pins engage, the end regions of the spring then engaging the pins.

6. A friction pad assembly as claimed in any one of claims 1 to 5, in which said wire spring is located in a groove provided in the surface of the backing plate and covered by the pad of friction material, and the ends of said part of the spring project from between the backing plate and the pad of friction material.

7. A friction pad assembly for use in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. which will engage wall portions 14. Thus, when assembled, wall portions 14 force side sections 12 further apart flexing corner regions 15 of the spring, the spring force produced by corner regions 15 clipping the spring to wall portions 14. To allow for this flexing the regions 16 of the groove are larger than in the embodiment of Fig. 1. This clipping of the spring to the backing plate holds the spring in place and thus facilitates the subsequent moulding of the friction material to the backing plate. Also the clipping of the spring to the backing plate takes up any manufacturing tolerances which may have allowed the spring 5 to move in groove 4 in the embodiment of Fig. 1. Such movement could possibly cause premature wear or damage to the assembly. Two further embodiments of the present invention are illustrated in Figs. 5 and 6. In each of these embodiments the friction pad assembly comprises a backing plate 17 to which a pad 18 of friction material is secured, the backing plate having a region free of friction material, in which two spaced apart holes 19 are provided. As viewed in Figs. 5 and 6, this region which is free of friction material is along the upper edge of the assembly and the holes 19 are located adjacent the side edges of the assembly. A spring 20 is secured in the central region of this upper edge of the assembly, a central part 21 of the spring being located in a groove (not illustrated) in the backing plate 17 and retained therein by the pad 18. The central part of the spring 21, as viewed in Figs. 5 and 6, comprises a horizontal elongate section, each end of which is turned upwards and projected beyond the backing plate and the pad of friction material, to form coiled regions 22 and 23 which, unlike the embodiment of Fig. 1, are spaced apart from each other. The end regions 24 of the spring extend in generally opposite directions and are sufficiently long to engage under support pins 25 which, in use, extend through holes 19 to support the assembly in a brake. The normal unstressed position of one end region 24 is shown in dashed lines in Fig. 5. Thus it will be understood that when the end regions 24 of the spring engage under the support pins taking up any clearance therebetween and reducing the possibility of pad rattle. In the embodiment of Fig. 5 the ends 26 of the spring are both curved to engage part way around the support pins 25 and thus further secure the assembly in position relative to the pins. However, in the embodiment of Fig. 6, the end 27 of only one of the end regions 24 is bent upwards to engage around a support pin. Taken in the direction of rotation of the disc of a brake it is the end region 24 nearest the leading edge, of the pad assembly, which is bent upwards. Part of the reaction to the spring force is now taken by the engagement of the pin in the brake, so that the spring acts to bias the pad backing plate against the guide, so preventing the so-called 'klonking' which can be produced by the assembly moving relative to and hitting, the guide as the brake is applied. In the above described embodiments the concept of effectively sandwiching part of a wire pad anti-rattle spring between the backing plate and the pad of friction material provides the designer with more space within a brake to freely design his other brake components with a minimum of interference from the pads and springs, and also provides the benefits of the prior attachment of the spring. In the above embodiments, some difficulty is found in ensuring complete closure of the pad moulding dies in the region of the wire, whether it fits into a socket in the backing plate, or rests against the backing plate. If this difficulty is found to be significant in some cases, then square, or rectangular, wire may be used in place of the round wire shown. This has little effect on the wire's performance as a spring, but is slightly more expensive. WHAT WE CLAIM IS:-

1. A friction pad assembly for use in a disc brake, comprising a backing plate and a pad of friction material secured thereto, part of a wire spring being embedded within the friction material or held between the pad and the backing plate, the end regions of said part of the wire spring projecting from the pad and backing plate, and being coiled, the coils terminating in free ends extending in generally opposite directions.

7. A friction pad assembly for use in

a disc brake, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the drawings accompanying Provisional Specification No. 48277/76.