Patent GB-1382046-A (GB)
Title: Caliper disc brakes
IPC: F16D55/227
Filed: 1971-03-09
Abstract: 1382046 Spot-type disc brakes GIRLING Ltd 3 March 1972 [9 March 1971] 6409/71 Heading F2E A sliding caliper disc brake comprises a caliper member 18 carrying friction pads for engagement with opposite faces of a brake disc (not shown) and supported on a torque plate member 10 for sliding movement relative to the torque plate member, motor means 32 in the caliper member directly to urge one pad or set of pads on to one side of the disc whereby to cause the caliper member to slide relatively to the torque plate member to apply the opposed indirectly actuated pad or set of pads to the other side of the disc and means for slidable mounting of the caliper member on the torque plate member, said means including sliding surfaces, and part of which means remain in situ even when the caliper member is detached from the torque plate member. In the construction shown in Fig. 1 the mounting m ans consists of two pins 42 and two bushes 50; the bushes are disposed in apertures in lugs 36 of the caliper member, the lugs being slidable on the bushes to permit the movement of the caliper member; the pins pass through apertures 40 in the torque plate member and a threaded portion 48 of each pin engages an internally threaded region of each bush 50 to secure the bush to the torque plate member; protective rubber or plastics boots 51 are engaged over the bushes 50 and the lugs 36 to exclude dirt and moisture and to retain the bushes in the lugs 36 when the caliper member is detached from the torque plate member. To prevent rotation of the bushes during engagement and release of the pins each is provided with a hole 50a for engagement by a screwdriver or tommy bar. Alternatively each bush can be provided with a shoulder engageable by a spanner; as a further alternative a key and keyway between each lug and the corresponding bush can be provided. In a further construction, Fig. 6, the bushes are omitted and instead pins 70 having plain outer surfaces on which the caliper member slides are provided, the pins being clamped to the torque plate member by screws 80 which engage a threaded bore in the pin; each pin has a reduced diameter portion 84 on which is mounted a friction ring 86 secured in position by a washer 88 and lock-nut 90, dished spring washers 92 mounted into back-to-back relation being interposed between the friction ring 86 and washer 88; in operation, as the brake friction pads wear, the caliper member and pins 70 move to the left as viewed in the Figure, but when the brake is released the caliper member is reset by the spring washers 92; when the pad wear exceeds a predetermined amount the friction rings 86 are moved so that the caliper member adopts a new position. In a modification, the spring washers 92 are omitted. In a further modification, an elastomeric sealing ring is provided in a groove near the inner end of each of the pins 70 in place of the friction ring 86 and washers &c. The two latter modifications also use a blind bore so that one of the sealing boots for each aperture can be omitted. A further modification using blind bores for the pins is described in which to allow air to escape from the blind bores each pin has an axial bore opening into a radial port to allow air to escape as each pin is introduced into its aperture. In yet another modification the caliper member is constructed so that it has portions straddling the torque plate to present lugs at each side thereof so that each of the pins on which the caliper is slidable can be engaged at opposite end portions by screws so that each end portion of each pin is supported. In yet another modification the apertures in the caliper instead of sliding directly on the pins are oversize and between the pins and the aperture surfaces resilient bushes of plastics material are provided. This construction also has provision for mechanical actuation of the caliper by means of a peg 110, Fig. 11, which incorporates an automatic adjuster mechanism; the peg abuts against the piston 112 of the hydraulic motor and is displaceable by the rotation of a shaft 114 coupled to the peg 110 by a dolly 116; the shaft 114 in use is connected to a handbrake linkage of the vehicle. In all of the constructions so far shown the pins are widely spaced apart to clear the disc when the brake is assembled in a vehicle; in a modification however the pins can be disposed rearwardly of the directly actuated brake pad which allows them to be brought closer together to lie within the periphery of the disc.