Patent GB-1005382-A (GB)
Title: Improvements in and relating to disc brakes
Inventor: PARNELL FRANK GORDON
IPC: F16D65/14
Filed: 1961-07-04
Abstract: 1,005,382. Disc brakes. AUTOMOTIVE PRODUCTS CO. Ltd. July 4, 1962, [July 4, 1961], No. 24134/61. Heading F2E. A disc brake for a vehicle comprises a caliper straddling a peripheral portion of a disc assembly which is composed of two rings adapted to rotate with a wheel axle but also capable of axial and rotational displacement relative to one another to bring a brake pad carried by each ring into contact with a stationary braking surface of the caliper adjacent the outer face of the respective ring, and means to cause such displacement as a result of applying a braking force to one of the rings. In one embodiment, Fig. 1, the caliper consists of two parts, one comprising a limb 2 to provide one braking surface and joined by a wall 3 to a ring portion surrounding an axle casing 4, and the other comprising a limb 1 secured to the casing 4, limb 1 providing a second braking surface and incorporating a fluid pressure cylinder 14. A ring portion is joined to the cylinder to receive the ring portion of the first part, the two ring portions having a threaded engagement 24 to allow adjustment of the spacing between the braking surfaces, which is set by a locking ring 25. Between the two braking surfaces is a disc assembly comprising a ring 6 splined on to a rotatable part 5 of the axle assembly so that it is free to move axially but rotates with the axle, and a second ring 7 coupled to ring 6 by balls 10 each engaged in a cam-shaped recess formed by slots 9 in the rings. Ring 7 has a portion 11 of reduced thickness adapted to be engaged by a pad 12 on a primary brake shoe 13 which is actuated by a piston 15 of the cylinder 14 via a ball and tapered slot connection 19, 20 to provide a self-servo effect. Upon supply of fluid to the cylinder 14, pad 12 engages the portion 11 and in turn presses a pad 21 carried by the ring 7 into contact with the braking surface of limb 2. The resultant braking action, increased by the servo effect of ball 19, causes ring 7 to lag behind ring 6, resulting in a further servo operation by the balls 10 which move in the slots 9 to force a pad 22 carried by ring 6 into contact with the braking surface of limb 1. The brake may alternatively be applied by hand-operated linkage acting on a piston rod 33 extending through a sealed opening in the end 18 of the cylinder. Cooling ducts 23 are provided in the limbs 1 and 2, and in the shoe 13 through which cooling liquid is circulated. In a second embodiment, Fig. 2, the arrangement is similar to that of the first embodiment except that the caliper is formed by a single casting without provision for adjustment of the spacing between the limbs 1, 2, the piston of the fluid pressure cylinder (not shown) acting directly on the shoe 13, and servo effect on the shoe 13 being instead obtained by a ball 26 operating in cam grooves in the shoe 13 and in a plug 28 which is tapped into the limb 1 to allow adjustment for pad wear to be effected by rotating the plug. In a third embodiment (Fig. 3, not shown) the feature of the independent ball and cam groove mounting for the shoe 13 is retained, but, as in Fig. 1, a two-part caliper is again used so that adjustment of the spacing of limbs 1, 2 can be effected. In a fourth embodiment, Fig. 4, self-servo effect on the primary shoe 44 is not present, a link 47 replacing the ball 19 of the Figure 1 embodiment. Also, the caliper is formed of a single casting and an adjustable ring 54 used to provide the braking surface engaged by the pad 53 of the first ring 39, adjustment for wear being effected by screws bearing against the outer face of ring 54. The cooling ducts are omitted and, instead, the second ring 40 is provided with grooves 56 in its periphery to provide air cooling. The second ring may alternatively be made thinner, and the grooves omitted (Fig. 5, not shown), where less cooling is required.