GB561301A - Improvements in or relating to internal shoe drum brakes - Google Patents

Abstract

561,301. Brakes. AUTOMOTIVE PRODUCTS CO., Ltd., and CHOUINGS, L. C. Oct. 9, 1942, No. 14223. [Class 103 (i)] In a 'brake comprising a pair of shoes that are anchored at their diametrically opposite ends, the shoes are applied by a single fluidpressure cylinder or other operating means which acts upon the free end of one shoe directly and on the free end of the other shoe through a linkage comprising a pair of interconnected bell-cranks of which one is pivoted on a fixed support and is engaged by the operating means and the other is pivoted on the free end of the second shoe and engages a fixed abutment. Shoes 11, 12 anchor respectively on fixed pins 19, 21. The pistons of a hydraulic cylinder 24 engage respectively the other end of shoe 11 and a bell-crank 34 mounted on a fixed pivot 35 and connected by a strut 39 to a bell-crank 42 pivoted at 44 on the other end of shoe 12. The bell-crank 42 also engages a normally fixed but adjustable abutment comprising a pin 49 screwed into a member 55 freely mounted upon a member 53 that bears on the anchor pin 19. The member 55 can be turned by a toothed head 56 to adjust the pin 49 which extends through a fixed slotted lug 59. Adjustment of shoe 11 is effected by turning a knurled head 29 which bears on the cylinder 24 and has screwed engagement with a pin 31 having a forked end embracing the end of the shoe. Operation of the cylinder 24 thus applies the'shoe 11 directly and by actuation of the linkage 34, 39, 42 forces the pivot 44 of the bell-crank 42 outwardly thus applying shoe 12, both shoes acting as leading shoes. To prevent lateral movement of the shoes, the web of each is lightly gripped between a pair of fingers, the outer of which is shown at 60 and the inner of which is springy and which are secured to the fixed support 16 at 61. To permit ready tensioning and attachment of the' pull-off springs 68, one end is attached to a plate 71 pivoted at 72.on the shoe and normally held by the spring tension in engagement with the shoe flange 14. By turning the plate 71 downwardly, the tension is released. A device by which both shoes may be adjusted simultaneously, Fig. 3, comprises plungers 79, 80 engaging respectively the shoe 11 and the bellcrank 42 and movable outwardly in a casing 75 . by engagement of their inclined ends with a wedge 89 which can be advanced by turning a screw 97 extending through the wedge. The shoes may be, expanded by mechanical means such as described in Specification 495,834.