GB469841A - Improvements in or relating to brakes - Google Patents

Abstract

469,841. Internal - expanding brakes. AUTOMOTIVE PRODUCTS CO., Ltd., and BROCK, D. T. March 17, 1936, No. 8014. [Class 103 (i)] In a brake-applying device comprising actuating means adapted to force a pair of rollers in side-by-side relationship between a pair of converging cam surfaces formed on the oppositely-disposed ends of the shoes of an internal-expanding brake, the actuating means impart to the rollers a positive rotational movement about their respective axes independently of the action of the cam surfaces on the rollers. As shown in sectional plan view in Fig. 1, the cam surfaces 21, 22 are formed on the ends of plungers 15, 16 slidably and non- rotatably mounted in a housing 13 and each carrying a rotatable adjusting member 17 or 18 fitted with a screw-threaded stem 19 or 20 having a grooved head for engaging the corresponding web 11 or 12 of the adjacent brake shoe, rotation of the member 17 or 18 causing the stem 19 or 20 to adjust the " off " clearance of the corresponding shoe. The end portions of the rollers 23, 24 are of larger diameter than the middle portions which are grooved to accommodate two roller link chains 25, 26, the outer ends of which are anchored to lugs 27, 28 on the back-plate 10 and the inner ends connected with an actuating member 29. In a modification, Fig. 3, the chains are replaced by flexible strips 34, 35, e.g. of spring steel, which space the rollers from the cam surfaces 21, 22, and the rollers are maintained in alignment by means of a cage 41, 42, 43. In a further modification, the strips are squeezed between the rollers. Fig. 6 shows another construction in which the centre parts of the rollers are formed as pinions adapted to mesh with an operating rack-bar 44 and with toothed cam surfaces 47, 48. According to the description, (a) the rollers or the cam surfaces may be flanged to locate the rollers axially ; (b) the metal tapes may be secured to the back-plate so as to permit simultaneous adjustment thereof or of each individually, e.g. by attaching the ends of the tapes to eccentrically-mounted pins ; (c) instead of metal tapes, wire cables &c. may be used ; (d) the rollers may be formed with flats at those parts which are contiguous when the brake shoes are in the '' off " position, in order to produce an increased movement of the brake shoes during the initial rotation of the rollers ; (e) the cam surfaces may be so disposed that the rollers move between them radially relatively to the drum axis instead of towards and away from the back-plate; (f) the rear wheel brakes at each side of a vehicle may be operated simultaneously, e.g. by connecting the free ends of the operating tapes to a transverse yoke adapted to be acted on by separate mechanical connections from hand and foot controls or by the piston of a single-ended hydraulic cylinder &c., or by both a hydraulic or pneumatic operating device and a mechanical connection ; and (g) the invention is also applicable to a servo brake in which the main shoes are applied by partial rotation of a servo shoe due to frictional engagement with the revolving drum, the movement of the servo shoe producing a pull on tapes or cables to apply the main shoes by means of the rollers.