GB542713A - Improvements in or relating to brakes for vehicles - Google Patents

Abstract

542,713. Internally expanding brakes. AUTOMOTIVE PRODUCTS CO., Ltd., and PARNELL, F. G. Oct. 28, 1940, No. 15789. [Class 103 (i)] In a brake in which a pair of shoes are applied by a fluid pressure cylinder disposed between one pair of shoe ends and the shoes turn about fulcrum at the other ends, the fulera are adjustable relatively to each other and a parking brake applying means acts on the shoes at or near the ends upon which the cylinder acts, whereby the relative position of the points of connection of the parking means to the shoes is substantially unaltered by the shoe adjustment. In Fig. 1, the fulcrum of the shoes comprises a socket 23 fixed to the anchor plate and a tappet 25 screwed into a sleeve 24 having a flanged end 26 which abuts on the socket and by which the sleeve can be turned to effect adjustment. The base 29, 30 of slots formed in the ends of the tappet and socket to receive the shoe ends are convex for engagement with corresponding surfaces of the shoe ends. The hydraulic cylinder 12 is slidably mounted on the back plate by a spigot and slot and its end and that of the piston 16 have slots similarly to those in the parts 23, 24. The end of the shoe 14 that bears on the cylinder is plane and that of the shoe 13 that bears on the piston is concave and thus locates the cylinder against turning about its centre. The hand or parking brake linkage comprises a strut 31 the slotted ends of which engage the shoes and a lever 33 pivoted to the shoe 14 and engaging a projection 34 on the strut. The lever is operated by a cable 35. Adjustment is effected by turning the member 24 until both shoes are applied, the shoe 14 through the piston and cylinder, and then slacking back the member 24. When the brakes are released after an application following an adjustment, the cylinder 12 does not move but the drum centre which has been displaced slightly to the left due to the greater pressure of the shoe 13 which with the normal direction of drum rotation is the leading shoe, returns so that the drum moves away from the shoe 14 and thus centralizes the shoes. In a modification, Fig. 3, the shoes are fulcrummed as in Fig. 1 and the cylinder 36 is slidably mounted in the back plate 10 and acts on the shoe 13 but the piston acts on the shoe 14 through a plunger 46 which together with the piston is slotted at 47, 48 to receive the end of a handbrake lever 52 pivoted at 53 to the cylinder. Operation of the lever thus moves the plunger and cylinder in opposite directions without moving the piston in the cylinder. The cylinder slides in a slot 37 and has shoulders 38 and end projections 41 which engage the inner and outer faces of the back-plate and is attached by passing one end projection through the slot sliding the cylinder to the end of the slot, passing the other projection through the slot and then centralizing the cylinder.