GB833729A - Automatic adjuster for brakes - Google Patents

Abstract

833,729. Internal shoe-drum brakes. BENDIX AVIATION CORPORATION. June 4, 1957 [Aug. 8, 1956], No. 17755/57. Class 103 (1). A brake has an automatic adjuster, of the position of a pair of shoes relative to a drum, mounted between one pair of shoe ends and including a lever pivoted to one shoe adjacent one of the pair of ends and turnable responsive to movement of at least one shoe against spring means connecting the lever and the other end of the pair for biasing the lever to its normal position. The adjuster 34 engages the ends 32 of shoes 12, 14 and consists of an internallythreaded nut 36 and a socket 38 which receive a threaded stem 42 and a non-threaded stem 44, respectively, of a ratchet wheel 48. An adjusting lever 51 pivoted at 52 to the shoe 14 is connected to shoe 12 by spring 54, a tooth 53 on the lever 51 engaging the ratchet wheel 50; the spring 54 biases the lever 51 downwards to rotate the wheel 50, urges the shoe ends together and ensures engagement of the tooth 53 and wheel 50. The lever 51 is connected to a stationary part of the brake via rod 60, bell crank lever 64 pivoted to the web of shoe 14, and rod 62, a turnbuckle 70 being provided in rod 60 to vary its length to compensate manufacturing errors. The adjustment takes place when the vehicle is moving backwards, i.e. clockwise movement of the drum in Fig. 1; assuming lining 24 has worn sufficiently for adjustment to take place, then shoe 12 becomes anchored and shoe 14 moves away from anchor 30, pivot 74 is therefore displaced causing bell-crank 64 to rotate to move lever 51 clockwise, the tooth 53 moves upwardly to engage a next tooth of ratchetwheel 48, on release of the brake the spring 54 rotates lever 51 to its normal position so rotating wheel 48, forcing sleeves 36 and 38 apart to spread the shoe ends 36 to take up the wear of linings 24. In an embodiment, Figs. 3-6, not shown, the adjusting lever 51 is connected to the brake anchor by a flexible cable passing over a groove in a metal stamping carried by the shoe to which the adjusting lever is attached. In a further embodiment, Figs. 7-8, not shown, similar to Fig. 1, the bell-crank lever is eccentrically mounted on the shoe web and is connected by a rod to a brake shoe returnspring, the eccentric attachment being turnable to permit manufacturing errors to be taken up. Specification 779,889 is referred to.