GB1072435A - Disc brakes - Google Patents

Abstract

1,072,435. Disc brakes. DUNLOP RUBBER CO. Ltd. Aug. 24, 1964 [Aug. 31, 1963], No. 34491/63. Heading F2E. In a disc brake a caliper-type housing 2 having a pair of limbs 3, 4 straddling a portion of a periphery of a rotatable brake disc 1 and mounted so that the housing 2 can move in a direction parallel to the braking surfaces of the disc and can also move axially relative to the disc, one of the limbs of the housing 4 has a friction element 10 fixed thereto and the other limb 3 supports a friction element 12 which is movable axially into engagement with the disc by means of a piston and cylinder device 17, 16, a connecting rod 18 and a wedge device 20 being positioned between the movable friction element 12 and the adjacent limb 3 of the housing and connected to a non-rotatable support. The arrangement of the wedge device and the housing is such that movement of the housing in a forward direction parallel to the normal direction of forward rotation of the disc causes the wedge device to generate an axial thrust turning to increase the pressure acting to force the friction elements against the disc. The wedge device consists of two axially outer cylindrical members 22 and 23 and an intermediate cylindrical member 24 each provided with radially extending corrugations 25, 26, the intermediate cylindrical member 24 being provided with a lug 29 which engages a socket 30 formed in the outer end of a non-rotatable supporting plate 7. When the brake is applied, the resulting drag on the friction pads tends to rotate the housing 2 about the axis of its mounting pin 9 which is rotatably mounted in a non-rotatable bush member 8 secured to the supporting plate 7. The wedge device 20 moves with the caliper housing 2 in a forward direction parallel to the normal direction of forward rotation of the disc but the intermediate member 24 being anchored against rotation with the housing by the engagement of its lug 29 with the socket 30 in the supporting plate 7 causes a turning moment to be applied to the intermediate member 24 rotating the latter relatively to the outer members 22 and 23 to allow the corrugations on the wedge members to act to convert the turning moment exerted on the intermediate member into an axial thrust generated between the housing and the backing plate 13 of the movable friction pad 12. In an alternative embodiment (Figs. 5 and 6, not shown) the intermediate member 53 is prevented from moving with a caliper housing 41 which is mounted on and fixed to a pin 42 which is rotatably and axially slidably supported in bearings 43 and 44 carried on a non-rotatable member 45. The outer members 51 and 52 of the wedge device rotate about the axis of the pin 42 relative to the stationary intermediate member 53 and the corrugations of the outer members inter-engage with the corrugations of the intermediate member to generate an axial thrust between the housing 41 and the movable friction element 47, the reaction on the caliper housing 41 causing the friction element secured to the opposite limb of the caliper housing to frictionally engage the opposite side of the rotatable brake disc 40 when the brake is actuated by means of an hydraulic piston and cylinder device 49, 48. The member 52 is provided with a flat surface, for engagement with the housing 41, by moulding a block of heatresisting material 70 on its axially inner surface. The invention may be applied to an opposedcylinder type of disc brake wherein both the housing and the disc are axially fixed and both friction elements are movable relative to the housing, it being necessary in this case to provide two wedge devices one for the friction element on each side of the disc in order to balance the reaction forces set up on the housing by each wedge device.