GB1022467A - Improvements in or relating to automatic adjusting devices for vehicle brakes - Google Patents

Abstract

1,022,467. Internal shoe drum brakes. AUTOMOTIVE PRODUCTS CO. Ltd. Feb. 3, 1965 [Feb. 6, 1964], No. 5095/64. Heading F2E. An internal shoe drum brake comprises a pair of brake shoes 11 and 12 bearing against a fixed abutment 13 between one pair of adjacent shoe ends and having applying means in association with automatic wear adjusting means between the other pair of adjacent shoe ends. A wheel cylinder 18 is slidably-mounted on a backplate 10 in a housing 17 which is itself slidablymounted on the backing-plate, the closed end of the cylinder having an abutment 26 for the shoe 12. As illustrated in Figs. 2 and 3 (not shown), a piston 19 in cylinder 18 has a coaxial bore which slidably-receives a first stem part 27 of a thrust and wear - adjustment member threadedly-interengaged with a peripherallytoothed, second disc part 28, said first part abutting the shoe 11 and said second part abutting the piston. On supplying pressurized liquid to the cylinder, piston 19, through the thrust member, urges shoe 11 into engagement with the brake drum 14 and cylinder 18 reactively slides to the right to apply shoe 12. The housing 17 has axial-extending parts 30 abutting the disc 28 and pivotally mounts a cranked adjusting lever 35. One arm 35 of this lever forms a pawl member engaging the teeth on the disc, and the second arm is connected by a rigid link 36 and a tension-spring 37 to shoes 12 and 11, respectively. A mechanically-operated applying lever 32, linked to a hand brake or similar device, is pivoted on the shoe 12 at 31 and abuts the housing 17 at 26. On operation of the applying lever, shoe 12 is directly applied to the drum and thrust is transmitted through the sliding housing, extending parts 30 thereon, and the two-part thrust and adjustment member 27, 28 to the shoe 11. Simultaneously, relative movement between the housing and shoe 12 rocks the adjusting lever about its pivot on the housing. If sufficient wear has taken place for the pawl arm to engage a fresh tooth on disc part 28, said disc will be rotated relative to the stem part 27 to increase the effective length of the thrust member on return of the adjustment lever by spring 37 when the brake is released. In modified embodiments, Figs. 4-6 (not shown), the adjusting lever is T-shaped, one arm of the T being connected to shoe 11 by spring 37 and the other arm being connected to shoe 12 by a rigid link and resilient means 44 or 45. Wear adjustment in these embodiments is made on brake application by the applying lever, said resilient means preventing damage to the parts in the event of friction in the screw-threads of the thrust member parts 27, 28 causing excessive loading of the rigid link.