A DISC BRAKE

Abstract: A disc brake comprises an annular disc 17 which is slid­ able on six pins 16 which are equally spaced around a wheel hub 11 which carries a rim 15. Two friction pads 25 and 26 are supported in a caliper 21 which in turn is mounted on a non-rotatable part 13. A hydraulic actuator 24 in the caliper urges pad 26 against the disc and also urges the disc against pad 25, thus providing a braking force be­ tween the pads and the disc. An annular anti-rattle spring member 31 slides on pins 16 with the disc and has projec­ tions 33 which engage lugs 18 on the disc and urge the disc resiliently into engagement with the pins to prevent rattling of the disc on its pins.

Description: A Disc Brake This invention relates to disc brakes and particularly but not exclusively to disc brakes suitable for use on two wheeled vehicles such as motor scooters. A problem that arises when fitting disc brakes to the front wheels of scooters is that because the diameter of a typical scooter wheel is small (approximately 25 cm without a tyre) it is difficult to fit a disc brake caliper within the envelope of the wheel. An object of the present invention is to provide a compact arrangement of a disc brake. Accordingly there is provided a disc brake comprising an annular disc which is axially slidable on but constrained to rotate with a rotary member to be braked, two opposed friction pads one on each side of the disc, a caliper which straddles a periphery of the disc and has an actuator to directly thrust one pad against the disc such that the disc is moved into engagement with the other pad as well as said one pad when the actuator thrusts said one pad against the disc and means acting between the disc and the rotary member to bias guide surfaces on the disc and rotary member into mutual contact. Preferably the rotatable member incorporates a circular array of pins and the disc is slidable on the pins. The means acting between the rotary member and the disc may be an annular plate having holes through which the pins pass and spring projections that react against the disc to bias the disc against the pins. The invention will be described by way of example and with reference to the accompanying drawings in which: Figure 1 is an elevation of a disc brake according to this invention as fitted to a motor scooter, Figure 2 is a section on the line Il-Il of Figure 1; Figure 3 is an elevation of an anti-rattle spring as is utilised in the disc brake showing one of the radial projections as a development of the projection and tags prior to bending; and Figure 4 is a section on the line IV-IV of Figure 3. With reference to figures 1 to 3 of the drawings a wheel hub 11 rotates on an axle 12 carried in a front fork shock absorber stanchion 13 and a swinging arm 14 also carried by the front fork. The wheel hub 11 carries a wheel rim 15 at its outer periphery, and has a circular array of six axially extending pins 16 around its inner margin adjacent the axle. An annular brake disc 17 has six radially inwardly projecting lugs 18 on its inner periphery. Each lug 18 has a circular hole 19 through which the pin 16 slides so that the disc 17 is axially slidable but is rotationally fast relative to the wheel hub. A caliper 21 comprises two arms 22 and 23 located on opposite sides of the disc interconnected by a bridge portion 20 which passes over the outer periphery of the disc. The arm 22, located on the side of the disc away from the hub 11, carries a hydraulic actuator 24 and is also utilised for the attachment by bolts of the caliper 21 to the fork stanchion 13. Two opposed friction pads 25 and 26 are located one on each side of the disc, one of the pads 26 being carried by the arm 22 and the other 25 by the arm 23. To apply the brake the hydraulic actuator 24 thrusts the pad 26 directly against the disc 17, which then slides axially on the pins 16 to engage the opposed pad 25. A braking force is thus generated between each pad and the disc. An annular anti-rattle spring 31 (see figure 3) has six equi-angularly spaced holes 32 therein through which the pins 16 pass. On the inner periphery of the spring adjacent each hole 32 are located six radially inward projections 33. One of the projections 331 is shown as a development prior to bending into its finished shape. All the projections are bent to the said side of the spring to form a 'U' section, as shown in Ligure 4, with an outwardly directed location tag 30. The base of each 'U' shaped projection 33 has a spring tag 34 that projects substantially radially outward and parallel to the annular part of the anti-rattle spring. The anti-rattle spring 31 is located on the side of the disc 17 adjacent the hub 11, as can best be seen in figure 1. The 'U' shaped radial projections 33 on the spring each pass around the radially inner edge of a respective lug 18 on the disc with a clearance so that the spring is positioned axially with respect to the disc. The tags 34 each react against the radial side of a respective lug Co bias the disc against the pins 16 causing a frictional engagement between the guide surfaces of the disc and the hub, namely the pins and the wails #I; the bores in the disc in which the pins slide. This has two advantages: (a) it prevents the disc from chattering during brake applications and while the wheel is running free. (b) it helps to prevent the disc from moving axially during rotation of the wheel and thereby causing "knock-back" of the actuator piston to an undesired extent.

Claims: CLAIMS 1. A disc brake comprising an annular disc (17) which is axially slidable on but constrained to rotate with a rotary member (11) to be braked, two opposed friction pads (25 and 26) one on each side of the disc, a caliper (21) which straddles a periphery of the disc and has an actuator (24) to directly thrust one pad (26) against the disc, such that the disc is moved into engagement with the other pad (25) as well as said one pad when the actuator thrusts said one pad against the disc characterised by the provision of means (31) acting between the disc and the rotary member to bias guide surfaces on the disc and rotary member into mutual contact. 2. A disc brake according to claim 1,characterised in that the rotatable member (11) incorporates a circular array of pins (16) and the disc is slidable on the pins. 3. A disc brake according to claim 2,characterised in that spring means (31) reacts between the pins (16) and the disc (17) to bias the pins against the sides of bores in the disc in which the pins slide. 4. A disc brake according to claim 3,characterised in that the spring means comprises a single annular plate having circumferentially spaced holes (32) therein through each of which one of the pins (16) passes and radial projections (33) that react against the disc to bias the disc against the pins. 5. A disc brake according Co claim 4,characterised in that the projections each have a spring tag (34) that reacts against a portion of the disc, to bias the disc against the pins. 6. A disc brake according to claim 5, characterised in that the annular portion of the plate spring is located on one side of the disc and each projection passes axially across the disc and has a location tag (30) to hold the disc and plate spring axially together.

Inventors: BASS, RICHARD ARNOLD
Applicants: AUTOMOTIVE PRODUCTS PUBLIC LIMITED COMPANY
Application year: 1983
Main classification: F16D55
IPC codes: F16D55, F16D65