FRICTION MATERIAL SUPPORTING ASSEMBLY FOR A DISC BRAKE

Abstract: A friction material supporting assembly (10) comprises a support (16), and friction material (24) rigidly supported thereon. The support (16) defines two sockets (26) which have openings (28) facing in opposite directions. The sockets (26) communicate with one another by means of a passage (32) through the support (16). The friction material (24) comprises two blocks (25), one of which is mounted in each of said sockets (26) so that it projects through the opening (28) thereof. The sockets (26) have side surfaces (26a) which are in contact with the friction material (24) so that braking forces can be transmitted to said support (16). The blocks (25) of friction material contact one another through said passage (32) and are secured together. A method of manufacturing the assembly is also claimed.

Description: FRICTION MATERIAL SUPPORTING ASSEMBLY FOR A DISC BRAKE This invention is concerned with a friction material supporting assembly for a disc brake. In a conventional disc brake, a disc is mounted for rotation with a hub, eg of a vehicle's wheel, and, in order to brake the hub, friction material is brought into engagement with oppositely-facing radially-extending surfaces of the disc. In most cases, a disc brake comprises a hydraulic piston and cylinder assembly mounted on a caliper which bridges an edge of the disc, the caliper being slidable relative to the disc in a direction parallel to the axis of the hub. Such a brake also comprises a pad of friction material fixedly mounted on the caliper on the opposite side of the disc to the cylinder, and a pad of friction material which is slidable relative to the caliper. The brake is operated by pressurising the cylinder so that the piston presses the slidable pad against the disc. This action causes the caliper to slide bringing the pad on the opposite side of the disc into engagement with the disc. The disc is now subject to frictional braking forces on both sides of the disc. Disc brakes are known in which two discs are provided on the same hub and friction material is provided between the two discs to engage the facing surfaces of the discs (this friction material is referred to hereinafter as "central friction material") . Such disc brakes are disclosed in GB 2 184 801 A, GB 2 076 087 A, GB 2 049 845 A, GB 1 396 503, US 4 598 799 and WO 98/25804. It is possible to have more than two discs; in which case, central friction material is required in each gap between discs. In the case of multiple discs, all the discs, or all except one, have to be slidable relative to the hub and so does the support or supports for the central friction material. It is, however, difficult to provide supports for central friction material which are light, can withstand differential, thermal expansion and also have the ability to transmit braking forces without the friction material being torn off the support. This invention has the object of providing a friction material supporting assembly which provides improved support for central friction material. The invention provides a friction material supporting assembly for use in a disc brake, the assembly comprising a support for friction material and friction material rigidly supported on said support, said support comprising a mounting portion arranged to slide on a slideway of the disc brake, the friction material having two generally- planar disc-engaging surfaces which face away from one another in opposite directions, characterised in that the support of the assembly defines two sockets which have openings facing in said opposite directions, the sockets communicating with one another by means of at least one passage through the support, and the friction material comprises two blocks, one of which is mounted in each of said sockets so that it projects through the opening thereof, the sockets having side surfaces which are in contact with the friction material so that braking forces can be transmitted to said support from the friction material across said side surfaces, the blocks of friction material contacting one another through said passage and being secured together. In a friction material supporting assembly according to the invention, the use of sockets enables the risk of the friction material being torn off its support by braking forces to be minimised. Furthermore, as a single support supports oppositely-facing friction material, the weight of the assembly can be minimised. The use of pre-formed blocks of friction material simplifies manufacture. An assembly according to the invention is suitable for use in a disc brake system as disclosed in WO 98/25804. This brake system comprises two discs which are slidable on the same hub under the control of leaf springs which act between the hub and the discs. The system also comprises a cylinder which is integrally formed with a suspension link and a bridge also fixed to the suspension link, the bridge having supports for friction pads mounted thereon. These supports comprise a support for a pad which is moveable by operation of the cylinder, a support for a pad which is fixed on the bridge on the opposite side of the discs from the cylinder, and a support for two pads between the discs which is slidable on the bridge. An assembly according to the invention would replace the support and pads between the discs. Preferably, in order to increase the area of friction material which can contact the disc, the friction material extends over portions of the surface of the support around the openings of said sockets. In order to secure the friction material more firmly in the sockets, the side surfaces of said sockets and adjacent surfaces of said friction material may interlock with one another. For example, the side surfaces of the sockets may be convexly curved, in a plane normal to the openings of the sockets, and side surfaces off the friction material be concavely curved with the curves being nested into one another. Preferably, the assembly also comprises sealing material arranged to prevent the entry of water between the support and the friction material. This sealing material reduces the risk of water damaging the assembly. The sealing material may also act as an adhesive to retain the friction material in the sockets by securing the blocks together and/or to the support. Suitable sealing materials are based, for example, on silicon rubber. The two blocks of friction material may be interlocked with one another, eg they may have nesting surfaces, one possibility being for one or both blocks to have one or more projections fitted into corresponding recesses in the other block. The blocks may meet one another in said passage or one may extend into the socket provided for the other. For example, one of the blocks may extend from one of the disc-engaging surfaces to the other, the other block fitting around a projection of that block. In order to strengthen the friction material, the sockets may have one or more ribs extending across them transversely of said openings, the ribs being engaged by said friction material. The mounting and the support of an assembly according to the invention are, preferably, formed integrally with one another, eg from cast metal such as iron, aluminium etc. The invention also provides a method of manufacturing a friction material supporting assembly for use in a disc brake, characterised in that the method comprises forming a support for friction material which comprises a mounting portion arranged to slide on a slideway of the disc brake, and which defines two sockets which have openings facing in opposite directions, the sockets communicating with one another by means of at least one passage through the support, the method also comprises introducing a block of friction material into each of said sockets so that each block projects through the opening of the socket, and so that the friction material contacts side surfaces of the socket, and so that the blocks contact each other through said passage, the method also comprising securing said blocks together, and providing the friction material with two generally-planar disc-engaging surfaces which face away from one another in opposite directions. If the friction material is of the type which is held together by a binder, the blocks of friction material may be introduced into the sockets in an uncured or not fully cured condition. In this case, curing is completed with the friction material in said sockets. The curing action may cause the blocks to fuse together, thereby securing them together. Alternatively, adhesive can be used. Preferably, the disc-engaging surfaces are provided by grinding the blocks before or after their introduction into the sockets but such surfaces may be provide in other ways, eg they may be moulded when the block is formed. It is also possible to mould one or both of the blocks in situ in a socket of the support. There now follows a detailed description, to be read with reference to the accompanying drawings, of three friction material supporting assemblies which are illustrative of the invention, all the illustrative assemblies are for use in a disc brake for supporting central friction material between two discs, and of an illustrative method of manufacturing such an assembly. In the drawings: Figure 1 is a perspective view of a plate and a block of the first illustrative friction material supporting assembly; Figure 2 is a cross-sectional view taken through the first illustrative assembly; Figures 3 and 4 are similar views to Figures 1 and 2, respectively, but of the second illustrative assembly and omitting the block from Figure 3 ; and Figures 5 and 6 are similar views to Figures 3 and 4, respectively, but of the third illustrative assembly. Figures 1 and 2 show the first illustrative friction material supporting assembly 10 for use in a disc brake. The assembly 10 comprises a support 16 for friction material provided by a generally plate-like piece 12 of cast iron having two parallel oppositely-facing side surfaces 12a and 12b. The support 16 comprising a mounting portion 14 arranged to slide on a slideway (not shown) of the disc brake. The mounting 14 portion is formed by two upwardly projecting ears of the piece 12 each of which has a cylindrical hole 18 therethrough, the holes 18 extending normally of the surfaces 12a and 12b. The mounting portion 14 is arranged to cooperate with a slideway so that the assembly 10 is supported for sliding movement and so that braking forces can be transmitted from said mounting portion 14 to said slideway. Specifically, the slideway comprises two parallel cylindrical rods which pass through the holes 18 so that forces can be transmitted through the side surfaces of the holes 18 to the rods forming the slideway. Other forms of mounting may be used in an assembly according to the invention, eg the ears may be hook-like and slide along curved surfaces on either side of an elongated member which forms the slideway in the manner described in WO 98/25804. The support 16 of the assembly 10 is provided by the remainder of the piece 12 (other than the ears thereof) . The support 16, as it is integral with the mounting portion 14, is rigidly secured to said mounting 14 so that braking forces can be transmitted from the support 16 to said mounting portion 14. The assembly 10 also comprises friction material 24 rigidly supported on said support 16. The friction material 24 is in the form of two blocks 25. Each block 25 provides one of two generally-planar disc-engaging surfaces 24a and 24b which face away from one another in opposite directions so that they can engage two adjacent discs (not shown) , when the assembly 10 is positioned with the friction material 24 between two discs of a disc brake. Only one of the blocks 25 of friction material 24 is shown in Figure 1 but both are shown in Figure 2. Specifically, in order to mount the friction material 24 on the support 16, the support 16 defines two sockets 26 which have openings 28 facing in said opposite directions, one opening 28 being in the surface 12a and the other being in the surface 12b. One of the blocks 25 of the friction material 24 is mounted in each of said sockets 26. Each block 25 of friction material 24 has a step therein between a smaller portion thereof, which enters one of the sockets 26 and is a close fit therein, and a larger portion thereof, which provides the surface 24a or 24b and extends over portions of the surface 12a or 12b of the support around the opening 28 of said socket 26. Each block 25 of friction material 24 projects through the opening 28 of its socket 26 so that the surfaces 24a and 24b are spaced from the surfaces 12a and 12b. The sockets 26 are arranged back-to-back in the support 16 and communicate with one another by means of a passage 32 through the support 16. In the case of the assembly 10, the sockets 26 and the passage 32 are all of the same constant transverse cross-section and merge into one another but this need not be so. In other words, the sockets 26 are provided by opposite end portions of a hole of constant transverse cross-section which passes through the support 16. The blocks 25 of friction material contact one another through said passage 32 on an area 42 and are secured together. The sockets 26 have side surfaces 26a which extend normally of the surfaces 12a and 12b. The friction material 24 fits tightly in the sockets 26 so that the side surfaces 26a are in contact with the friction material 24 so that braking forces can be transmitted to said support 16 from the friction material 24 across said side surfaces 26a. The blocks of friction material 24 are held in the sockets by silicon rubber adhesive (not shown) extending across the area 42 of contact between the blocks 25 securing the blocks together and also extends across the side surfaces 26a. The adhesive also serves to seal between the support 16 and the friction material 24 to prevent egress of water. The assembly 10 is manufactured by the illustrative method. The illustrative method comprises forming the support 16 for friction material, and introducing one of the blocks 25 into each of said sockets 26 so that each block projects through the opening 28 of the socket, and so that the friction material 24 contacts side surfaces 26a of the socket, and so that the blocks 25 contact each other through said passage 32. The illustrative method also comprises securing said blocks 25 together by adhesive over the area 42, and providing the friction material with the two generally-planar disc-engaging surfaces 24a and 24b by grinding the blocks 12. If said blocks 25 of friction material are introduced into said sockets 26 in an uncured or not fully cured condition, curing is completed with the friction material in said sockets 26 by heating. The second and the third illustrative friction material supporting assemblies are similar to the assembly 10 except as hereinafter described and like reference numerals are used for like parts which are not further described. Figures 3 and 4 show the second illustrative friction material supporting assembly 50 which is similar to the assembly 10 except as hereinafter described. The assembly 50 differs from the assembly 10 in that the side surfaces 26a of the sockets 26 are convexly curved in a plane normal to the openings of the sockets 26. The surfaces 24c of the blocks 25 correspond to the convex surfaces so that there is interlocking between the surfaces. Figures 5 and 6 show the third illustrative friction material supporting assembly 60. The assembly 60 is similar to the assembly 50 except that it has a rib 62 extending across its sockets 26 transversely of said openings 28. The rib 62 is contacted by said friction material 24. The rib 62 has convexly-curved side surfaces 62a which interlock with concavely curved surfaces of the friction material 24.

Claims: CLAIMS A friction material supporting assembly (10) for use in a disc brake, the assembly comprising a support (16) for friction material, and friction material (24) rigidly supported on said support, said support (16) comprising a mounting portion (14) arranged to slide on a slideway of the disc brake, the friction material (24) having two generally-planar disc-engaging surfaces (24a, 24b) which face away from one another in opposite directions, characterised in that the support (16) of the assembly (10) defines two sockets (26) which have openings (28) facing in said opposite directions, the sockets (26) communicating with one another by means of at least one passage (32) through the support (16) , and the friction material (24) comprises two blocks (25) , one of which is mounted in each of said sockets (26) so that it projects through the opening (28) thereof, the sockets having side surfaces (26a) which are in contact with the friction material (24) so that braking forces can be transmitted to said support (16) from the friction material (24) across said side surfaces, the blocks (25) of friction material contacting one another through said passage (32) and being secured together. An assembly according to claim l, characterised in that the friction material (24) extends over portions of the surface (12a, 12b) of the support (16) around the openings (28) of said sockets (26) . An assembly according to either one of claims 1 and 2, characterised in that the side surfaces (26a) of said sockets (26) and side surfaces (24c) of said friction material (24) interlock with one another. I An assembly according to any one of claims 1 to 3 , characterised in that the assembly (10) also comprises sealing material arranged to prevent the entry of water between the support (16) and the friction material (24) . 5 An assembly according to any one of claims 1 to 4 , characterised in that the sockets (26) have one or more ribs (62) extending across the sockets transversely of said openings (28) , the ribs (62) being engaged by both blocks (25) of friction material. > A method of manufacturing a friction material supporting assembly (10) for use in a disc brake, characterised in that the method comprises forming a support (16) for friction material which comprises a mounting portion (14) arranged to slide on a slideway of the disc brake, and which defines two sockets (26) which have openings (28) facing in opposite directions, the sockets communicating with one another by means of at least one passage (32) through the support, the method also comprises introducing a block (25) of friction material (24) into each of said sockets (26) so that each block projects through the opening (28) of the socket, and so that the friction material contacts side surfaces (26a) of the socket, and so that the blocks (25) contact each other through said passage (32) , the method also comprising securing said blocks (25) together, and providing the friction material with two generally-planar disc-engaging surfaces (24a, 24b) which face away from one another in opposite directions. t A method according to claim 6, characterised in that said blocks (25) of friction material are introduced into said sockets (26) in an uncured or not fully cured condition, and curing is completed with the friction material in said sockets.

Inventors: BUNKER GAVIN, BUNKER KENNETH JAMES, BUNKER, GAVIN, BUNKER, KENNETH, JAMES
Applicants: BUNKER GAVIN, BUNKER KENNETH JAMES, FEDERAL MOGUL TECHNOLOGY LTD, BUNKER, GAVIN, BUNKER, KENNETH, JAMES, FEDERAL-MOGUL TECHNOLOGY LIMITED
Application year: 1999
Main classification: F16D55
IPC codes: F16D65, F16D69