DISC BRAKE PAD ASSEMBLY

Abstract: A disc brake pad assembly for use in a disc brake having a plurality of discs. The assembly comprises a support (12), and friction material (14) mounted on said support. The support (12) comprises a mounting portion (16; 96) by which the assembly can be supported for non-rotational sliding movement, and a friction material-carrying portion (20; 72; 82; 92; 94) on which the friction material (14) is mounted. The friction material (14) has two generally-planar disc-engaging surfaces (14a, 14b) which face away from one another in opposite directions. The friction material (14) is in the form of a single block extending from one of said disc-engaging surfaces (14a, 14b) to the other.

Description: DISC BRAKE PAD ASSEMBLY This invention is concerned with a disc brake pad assembly for use in a disc brake having a plurality of discs. 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 pads, which do not rotate, are 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 pads are provided between the two discs to engage the facing surfaces of the discs (these pads are referred to hereinafter as "central pads") . 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 pads are required in each gap between discs. In the case of a plurality of 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 pads. In the prior art documents referred to above, the central pads each comprise two blocks of friction material either mounted on separate supporting plates or mounted on opposite sides of a single supporting plate. Thus, the central pads are relatively heavy and occupy a significant space in a direction parallel to the axis of the hub. It is an object of the present invention to provide a disc brake pad assembly for use in supporting a central pad, the assembly being light and compact. The invention provides a disc brake pad assembly for use in a disc brake having a plurality of discs, the assembly comprising a support, and friction material mounted on said support, the support comprising a mounting portion by which the assembly can be supported for non- rotational sliding movement, and a friction material- carrying portion on which the friction material is mounted, the friction material having two generally-planar disc- engaging surfaces which face away from one another in opposite directions, characterised in that the friction material is in the form of a single block extending from one of said disc-engaging surfaces to the other. In an assembly according to the invention, the use of a block of friction material extending from one disc- engaging surface to the other enables the assembly to be lighter and more compact. An assembly according to the invention is suitable for use in a disc brake system as disclosed in WO 98/25804. That 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 calliper also fixed to the suspension link, the calliper 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 caliper on the opposite side of the discs from the cylinder, and a support for two pads between the discs which is slidable on the caliper. An assembly according to the invention would replace the support and pads between the discs . In an assembly according to the invention, said friction material-carrying portion of the support may comprise a band passing around an edge portion of said block of friction material. The band may be formed from rigid material, or partly from rigid material and partly from flexible material. In order to secure the friction material on the support, said block may extend over portions of opposite surfaces of said band so that an inner surface of the band is interlocked with an adjacent surface of said block. In one embodiment of an assembly according to the invention, said band comprises a rigid portion of said support, and a flexible portion either secured at both ends thereof to said rigid portion, or passing around the friction material and the rigid portion of the support. In the first case, the flexible portion is first wrapped around the block of friction material and then secured to the rigid portion. In the second case, the ends of the flexible portion are secured together after wrapping around both the block of friction material and the rigid portion of the support. The flexible portion may fit into a groove in the peripheral surface of the block of friction material. In one possibility, the band is supplied with one end of the flexible portion fixed to said rigid portion and with means for securing the free end of the flexible portion to the rigid portion after the flexible portion has been wrapped around the block. In another embodiment of an assembly according to the invention, said support comprises projections which are embedded in the block, eg the block is moulded in situ around the projections. In order to prevent corrosion, an assembly according to the invention may also comprise sealing material arranged to prevent the entry of water between said support and said block. Said block of friction material may be moulded separately and then mounted on the support, or may be moulded in situ on the support, or may comprise two block portions which are bonded together. Said block of friction material is preferably formed from particulate material bonded together by a binder, eg phenolic resin. In some assemblies according to the invention, the block is moulded to shape in situ on the support and then the binder is cured. Alternatively, the block is moulded away from the support, the block is fitted to the support in an uncured ("green") state, and the binder is cured in situ on the support. Said support is, preferably, formed of cast metal, eg iron or aluminium, but may be formed from other materials or by other methods . There now follows a detailed description to be read with reference to the accompanying drawings, of seven disc brake pad assemblies which are illustrative of the invention. In the drawings: Figure 1 is an exploded view of components of the first illustrative 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; Figures 5 and 6 are similar views to Figures 1 and 2, respectively, but of the third illustrative assembly; Figures 7 and 8 are similar views to Figures 1 and 2, respectively, but of the fourth illustrative assembly; Figures 9 and 10 are similar views to Figure 1 and 2, respectively, but of the fifth illustrative assembly; Figure 11 is a similar view to Figure 1 but of the sixth illustrative assembly; and Figure 12 is a perspective view of the seventh illustrative assembly. The first illustrative disc brake pad assembly 10 is shown in Figures 1 and 2. The assembly 10 is for use in a disc brake having a plurality of discs. The assembly 10 comprises a support 12, and friction material 14 mounted on said support. The support 12 is formed from a plate-like iron casting. The support 12 has parallel side surfaces 12a and 12b which face in opposite directions. The support 12 comprises a mounting portion 16 comprising two ears each of which has a hole 18 therethrough, the holes 18 extending normally of the surfaces 12a and 12b. The holes 18 are arranged to receive parallel cylindrical rods (not shown) which form a slideway of a disc brake. Thus, the assembly 10 can be supported for non-rotational sliding movement in the disc brake in a direction normal to the surfaces 12a and 12b with the mounting portion 16 positioned above a gap between two discs of the brake. 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, as described in WO 98/25804. The support 12 also comprises a friction material- carrying portion 20 on which the friction material 14 is mounted. The portion 20 is cast integrally with the mounting portion 16 of the support 12. When the mounting portion 16 is positioned on the slideway of a disc brake as aforesaid, the friction material-carrying portion 20 extends between the two discs of the brake. The friction material-carrying portion 20 comprises a band of cast iron which passes around a hole 22 in the support 12. The hole 22 passes through the support 12 and has openings 22a and 22b, respectively, in the surfaces 12a and 12b of the support 12. The friction material 14 of the assembly 10 is mounted in the hole 22 and projects through both opening 22a and 22b thereof. Thus, said friction material-carrying portion 20 of the support 12 comprises a band passing around a central portion of the friction material 14. In order to interlock the friction material 14 with the portion 20 to retain it on the support 12 , the friction material 14 extends over portions of the surfaces 12a and 12b around the openings 22a and 22b. The friction material 14 has two generally-planar disc-engaging surfaces 14a and 14b which face away from one another in opposite directions. The surface 14a is parallel to the surface 12a of the support 12 and is spaced therefrom, and the surface 14b is parallel to the surface 12b of the support 12 and is spaced therefrom. The friction material 14 is in the form of a single block extending from one of said disc-engaging surfaces 14a and 14b to the other. In the case of the assembly 10, the block of friction material 14 may be moulded in situ as one piece or may be formed from two preforms (one of which is shown in Figure 1) which are introduced into the openings 22a and 22b from opposite directions so that the preforms engage one another within the hole 22. The preforms are then secured together, eg by adhesive or fusing of the material, within the hole 22, eg on the line 24 in Figure 2. A sealant (not shown) , eg a silicon rubber, is provided on the side walls of the hole 22 and on the portions of the surfaces 12a and 12b which are covered by the friction material 14. The sealant serves to seal between the support 12 and the friction material 14 to prevent egress of water. The sealant may also act as an adhesive securing the friction material 14 to the support 12 and, in some cases, securing two friction material preforms together. The second to the fifth illustrative assemblies shown, respectively, in Figures 3 and 4, Figures 5 and 6, Figures 7 and 8, and Figures 9 and 10, are similar to the first illustrative assembly 10 except as hereinafter described and like reference numerals are used for like parts which are not further described. The second illustrative friction material supporting assembly 40 is shown in Figures 3 and 4. The assembly 40 differs from the assembly 10 in that side walls 22c of the hole 22 are convexly curved in a plane normal to the openings 22a and 22b. Also, the friction material 14, which is moulded in situ, has its surfaces which are adjacent to the side walls 22c concavely curved and, thus, the side walls 22c and adjacent surfaces of said friction material 14 interlock with one another. The third illustrative assembly 50 shown in Figures 5 and 6, is similar to the second illustrative assembly 40 except that it also has a rib 52 extending across the hole 22 and embedded in the friction material 14. The rib 52 is cast integrally with the remainder of the support 12. The rib 52 has convexly curved side surfaces 52a which interlock with concavely curved surfaces of the friction material 14. The rib 52 serves to improve the strength of the interlocking between the support 12 and the friction material 14. The fourth illustrative assembly 60, shown in Figures 7 and 8, is similar to the third illustrative assembly 50 except that it has a plurality of ribs 62 which are similar to the rib 52. The ribs 62 cross one another to form a mesh mounted in the hole 22. The side walls 62a of the ribs 62 are convexly curved. In the fifth illustrative assembly 70, shown in Figures 9 and 10, the friction material-carrying portion of the support 12 does not form a band around the friction material 14 as in the previously-described assemblies. Instead, the friction material-carrying portion comprises a bar of cast metal connecting the ears of the mounting portion 16. This bar abuts an edge of the friction material 14. The friction material-carrying portion also comprises a metal mesh 72 welded to said bar and embedded in the friction material 14. The sixth illustrative assembly 80 shown in Figure 11 differs from the assembly 10 in that the friction material- carrying portion of the support 12 is not provided by a band around the block of friction material 14 but instead comprises two projections 82 which are embedded in the friction material 14. The seventh illustrative assembly 90 shown in Figure 12 differs from the assembly 10 in that the support 12 thereof comprises a band which provides the friction material carrying portion of the support. This band comprises a rigid portion 92 of said support, and a flexible portion 94 which passes around the rigid portion 92 and a block of friction material 14. The rigid portion 92 of the support 12 is generally U-shaped in transverse cross-section and extends parallel to the disc engaging surfaces 14a and 14b of the block 14. The mounting portion of the support 12 is provided by ears 96 two of which extend upwardly at each end of the rigid portion 92. Each ear 16 has a hole 98 there through which are arranged to receive rods or bolts providing a slideway of a disc brake. The two holes 98 at each end of the rigid portion both receive the same rod or bolt. The rigid portion 92 has a generally rectangular (in plan view) bottom having an upper surface 100 and a lower surface 102. The surface 102 lies against an upper surface of the block 14 and has a ridge 104 projecting into a groove in the upper surface of the block so that the block 14 is interlocked with the rigid portion 92. The flexible portion 94 is in the form of a steel band having a ratchet mechanism 106 secured to one end thereof. The ratchet mechanism 106 is positioned on the upper surface 100 of the bottom of the rigid portion 92. The band 94 extends away from the ratchet mechanism 106 across the surface 100 and then wraps around the friction material block 14, being located in a peripheral groove in the edge of the block 14 , before returning to the ratchet mechanism 106 where the ends of the band 94 are secured together. This type of ratchet mechanism 106 is well-known for use in joining the ends of steel bands wrapped around packing cases etc. The steel band 94 is designed to break at a predetermined tension leaving a short end 108.

Claims: CLAIMS A disc brake pad assembly (10; 40; 50; 60; 70; 80; 90) for use in a disc brake having a plurality of discs, the assembly comprising a support (12) , and friction material (14) mounted on said support, the support comprising a mounting portion (16; 96) by which the assembly can be supported for non-rotational sliding movement, and a friction material-carrying portion (20; 72; 82; 92, 94) on which the friction material (14) is mounted, the friction material having two generally-planar disc-engaging surfaces (14a, 14b) which face away from one another in opposite directions, characterised in that the friction material (14) is in the form of a single block extending from one of said disc-engaging surfaces (14a, 14b) to the other. An assembly according to claim 1, characterised in that said friction material-carrying portion (20; 92, 94) of the support (12) comprises a band passing around a central portion of said block of friction material (14) , the band being interlocked with said block. An assembly according to claim 2, characterised in that said block of friction material (14) extends over portions of opposite surfaces of said band (20) . An assembly according to claim 2, characterised in that an inner surface (22c) of said band (20) is interlocked with an adjacent surface of said block of friction material (14) . An assembly according to any one of claims 2 to 4 , characterised in that said band comprises a rigid portion (92) of said support, and a flexible portion (94) passing around said rigid portion of the support and said block of friction material (14) . An assembly according to claim 1, characterised in that said support (12) comprises projections (82) which are embedded in the block of friction material (14). An assembly according to any one of claims 1 to 6, characterised in that the assembly (10) also comprises sealing material arranged to prevent the entry of water between said support (12) and said block of friction material (14) . An assembly according to any one of claims 1 to 7 , characterised in that said block of friction material (14) comprises two block portions which are bonded together. An assembly according to any one of claims 1 to 8 , characterised in that said support (12) comprises a metal mesh (72) embedded in said friction material (14).

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