GB950530A - Improvements in or relating to internal shoe drum brakes - Google Patents

Abstract

950,530. Internal shoe drum brakes. AUTOMOTIVE PRODUCTS CO. Ltd. Sept. 17, 1962 [Oct. 5, 1961], No. 35902/61. Heading F2E. In an internal shoe drum brake of the type having a single spreading means and in which at least one shoe is mounted for circumferential movement on a carrier extending between the spreading means and an abutment, and in which circumferential movement of the shoes is limited by further abutments so that the shoes operate as leading shoes in both directions of rotation of the brake drum, such abutments are provided for both shoes adjacent the spreading means by a U-shaped member secured to or formed integrally with the back plate and having its limbs directed radially inwardly to provide abutments on opposite sides of the spreading means, the limbs being apertured for the reception of push rods transmitting the applying force from the spreading means to the shoes. As shown, the U-shaped member 13 is a separate pressing including a base secured by rivets 15 to the back plate 10. A similar U-shaped member 14 is secured to the back plate diametrically opposite to member 13 and supports a strut assembly 22 whereby in one direction of rotation of the drum (clockwise in Fig. 1) the drag force on circumferentially movable shoe 34 is transmitted to shoe 33, which is anchored on the member 13, to give a servo effect, the assembly 22 acting as a fixed anchorage in the opposite direction of rotation so that the shoes are then separately anchored at their leading ends against the member 13 and assembly 22 respectively. The assembly 22 consists of interengaged sleeves 23, 24, Fig. 3, internally screw-threaded and both rotatable and slidable in apertures in the limbs of member 14. A spring 28 normally maintains a shoulder 26 of sleeve 24 in contact with one limb of the member 14, and the sleeves are rotatable in opposite directions by a manually rotated shaft 32 and crown and pinion gears 31, 29, 30 to move in opposite directions studs 27 threadedly engaging the sleeves. The shoe 33 directly engages on e stud 27, being located by a slot in the stud, the opposite end of shoe 33 similarly engaging a push rod 18 extending through an aperture in one limb of member 13 from a piston 17 in an hydraulic cylinder 16 which is secured to the back plate separately from the member 13. The cylinder 16 contains another piston 17 which acts through another push rod 18 passed through an aperture in the other limb of member 13 and having a convex end to engage a shoe carrier 38 of channel section within which the web 37 of shoe 34 is located. Shoe 34 is mounted on the carrier by a pivoted link 39 and the arrangement is such that the carrier is urged by the shoe return springs 44, 45 against the ends of the other push rod 18 and the sleeve 24 which have deep slots to receive the ends of the shoe web 37 for allowing limited circumferential movement of shoe 34. The abutting surfaces 42 of the sleeve 24 and carrier 38 are of complementary curved form to locate the carrier. An alternative manual applying means comprises a lever 46 rotatable about a pivot on shoe 33 and engaging one end of a push rod 47 slidable in apertures in the limbs of member 13 and engaging at its other end the shoe carrier 38.