GB727627A - Improvements in or relating to actuating means for internal shoe-drum brakes - Google Patents

Abstract

727,627. Internal shoe-drum brakes. GIRLING, Ltd. March 18, 1954 [March 19, 1953], No. 7579/53. Class 103 (1). In an actuating mechanism for an internal shoe drum brake in which the actuated ends of the shoes are separated by a single-ended hydraulic cylinder incorporated in a housing having a limited floating movement on the back plate in the direction of movement of the shoe ends, one shoe engages the closed end of the cylinder while the second shoe is engaged by the piston of the hydraulic cylinder through an interposed portion of a lever pivotally mounted in the housing and adapted to be actuated by a manually operated lever pivoting about the same axis. In the embodiment of the invention shown applied to the rear wheel brakes of a motor vehicle, two arcuate brake shoes 10, 11 are mounted on a stationary back plate 13; the upper ends of the shoes being adapted for separation hydraulically by means of a single-ended cylinder 14, the piston 22 of which acts against an arm 30 of a bell crank lever pivotally mounted on a pin 31 in the housing 15 to engage the web 33 of the shoe 10 and move the shoe outwardly into engagement with the drum. The reaction on the housing 15 moves the housing in the opposite direction to move the shoe 11 outwardly. The lower ends of the shoes have a rocking and sliding engagement with an adjuster (not shown). Alternatively, the brake may be actuated mechanically by means of the hand lever which is connected by a rod or cable to an operating lever 37 which extends through the back plate 13 and is pivoted also about the pivot pin 31 so that a lug 36 rocks the bell crank lever about the pivot pin 31 and the arm 30 of the bell crank lever urges the shoe 10 outwardly into engagement with the drum. The reaction on the housing 15 moves the housing bodily in the opposite direction so that the shoe 11 is also moved outwardly with equal force. Whether the brake is mechanically or hydraulically actuated, one form of operation does not affect the efficiency of the other. Rubber boots 39 and 40 are provided to prevent entry of dust and water and a hardened bearing block 21 is provided in the inner end of the slotted closed end of the cylinder 14 for engagement with the web 20 of the shoe 11. An alternative arrangement of levers is described and illustrated in the Specification.