GB1198443A - Improvements in Brake Adjusters - Google Patents

Abstract

1,198,443. Disc brakes; ratchet gearing. GIRLING Ltd. 28 July, 1967 [30 July, 1966], No. 34331/66. Headings F2E and F2Q. In a disc brake having a brake pad assembly 12, 14 (Figs. 1 and 3) capable of limited circumferential movement in the caliper and a cooperating brake pad assembly 16, 18 selectively displaceable in a brake applying direction from a normal rest position by actuating means, a unidirectional drive means 32, 40 for effecting adjustment of the rest position during brake release in a brake applying direction is provided responsive to circumferential movements of the pad assembly 12, 14. Automatic brake adjustment is obtained when the thrust member 36 is actuated by hydraulic cylinder 24 or hand brake lever 56 via push rod 62, rubber block 64 and thrust pad 66. The thrust member 36 presses pad 18 and by reaction pad 14 against the rotating disc (not shown). This causes back plate 12, which has circumferential slots 22, to move circumferentially so that the arm 40 moves to the right (Fig. 3). As the braking is released spring 44 moves the arm 40 to the left and if any wear has occurred a projection 42 rotates the ratchet wheel 32 and piston 28. The internal bore of the piston 28 is screw threaded to the thrust member 36 which is held against rotation by a flange 54 so that the member 36 is axially displaced towards the disc to re-set the normal position of the pads 14, 18. The arm 40 may have a flexible portion intermediate its ends or may be longitudinally slotted including a rubber or resilient button at the pivot point 41 or may be made of two sliding parts spring biased together so that the arm is yieldable in its longitudinal direction. Alternatively the pawl 42 may he provided by a lever pivoted to the arm 40 in the form of a bell crank lever which is spring biased towards a stop on the arm 40 and into engagement with the ratchet teeth. In a modified hand brake actuating arrangement (Fig. 4, not shown), halls (74) are arranged to ride up ramps between the cams (70, 72) when a brake lever (68) is turned. In an alternative embodiment (Fig. 5) hydraulically actuated by cylinder 100 or mechanically actuated by lever 120 acting by cam 118 on the end of a push rod 104, the normal rest position of the brake pad 18 is adjusted by rotation of the rod 104 which has an end 108 screw threaded within a nut 110. When braking an arm 122 moves a member 124 of a one-way clutch clockwise and the edge 116 of the nut abuts a friction ring 138. If any wear has occurred on release of the brake the member 124 which moves anticlockwise due to the action of spring 136 (Fig. 6), moves by means of balls 134 the rod 104 and since the nut 110 is held against the friction ring 138 the axial position of the nat and piston is adjusted to compensate for the wear. The automatic adjustment of the brake is restricted, by suitable choice of the spring 136, so that an hydraulic pressure in the cylinder 100 of 100 p.s.i. or greater is necessary to extend the spring 136 and move the clutch member 124.