GB1485241A - Drum brake - Google Patents

Abstract

1485241 Internal shoe drum brakes; wear adjusting SOC ANON DBA 9 Feb 1976 [4 March 1975] 05001/76 Heading F2E In a drum brake comprising brake shoes 10, 12, a fixed fulcrum block 24 inserted between two adjacent shoe ends 28, 30, actuating means 18 inserted between the other shoe ends 20, 22, a hand-brake lever 32 pivoted on shoe 12 adjacent the actuating means and connected to shoe 10 by a strut 35, a wear-compensating de- vice 46, and control means to actuate device 46 in response to predetermined relative shoe movement, the wear-compensating device 46 is associated with the fulcrum block 24 and the control means comprises the hand-brake lever 32, the strut 35 and retractable connecting means 48; the retractable connecting means 48 connects the hand-brake lever 32 to the wear compensating device 46 upon actuation of actuating means 18 and disconnects them upon direct actuation of the hand-brake lever. As shown, when actuating means 18 is actuated, hand-brake lever 32 is pivoted clockwise, so that a member 76 pivoted to its lower end moves leftward, thus tending to close a gap between an abutment surface 90 on member 76 and an out-turned lip at the top of an arm 82 of a lever 72, Fig. 1. With excessive travel due to lining wear, surface 90 contacts lever 72 and pivots the latter counterclockwise about pivot 74 on the lower end of shoe 12; thereby a slot 84 in an arm 80 of lever 72 moves end 68 of a spring downwards (in the plane of Fig. 1), causing the spring to slip around a threaded member (not shown). In brake release the parts are restored, and the now-upward movement of spring end 68 causes the spring to rotate the threaded member to increase the distance between shoe ends 28, 30. On the other hand, when hand-brake lever 32 is actuated directly by a cable 42, a gap between a stop member 44 on the cable and the righthand lower end of lever 32 is taken up, so handbrake lever 32 is pivoted clockwise, and a gap is created between member 76 and a locking member 98 (moved by member 44 through a spacer, not shown); member 76 is now caused to pivot counter-clockwise when abutment surface 90 contacts the out-turned lip on arm 82 of lever 72, and eventually edge 92 of lug 88 slides over the top of it, Fig. 7. Lever 72 remains stationary, so it exerts no action on spring end 68, so no wear compensation occurs.