GB622616A - Improvements in or relating to automatic adjusting devices for internal shoe drum brakes - Google Patents

Abstract

622,616. Drum brakes. AUTOMOTIVE PRODUCTS CO., Ltd., and CHOUINGS, L. C. April 1, 1947, No. 8852. [Class 103 (i)] Adjusting means for the shoe or shoes of a drum brake comprises a screw-and-nut adjusting member, the rotatable part of which carries a flange or disc formed on its face with teeth or holes engaged by the end of a pivoted arm which extends obliquely from the face of the flange, the arrangement being such that when the brake is applied, the adjusting-member moves-relatively away from the pivot of the arm so that if the movement is excessive, the arm engages the next tooth or hole in the flange, which with the rotatable element of the adjusting-member is turned during the release movement to adjust the shoe or shoes. According to Figs. 1, 2; brake shoes 10, 11 abut at the lower ends on a stop and are applied by a hydraulic cylinder 13, slidable on the back-plate 12 and engaging the upper end of shoe 11, the piston 17 acting through a plunger 16 and a rod 27 screwed into a socket 24 on the upper end of the shoe 10. The shoes may also be applied by a mechanical linkage through a lever 22, pivoted at 23<SP>1</SP> in a slot in the cylinder, and engaging the plunger 16. The socket 24 carries a flange 25 formed with holes 26 engaged by the end 38 of an arm 34 pivoted at 35 on the cylinder 13. When the brake is applied the end of the arm 34, urged by a spring 37, moves upwards along the face of the flange 25 and if, due to wear of the shoe lining, this movement is sufficient, engages the next hole so that during the return movement of the shoe the flange with the socket 24 is turned to effect outward displacement of the shoe. The adjustment is shared between the two shoes as described in Specification 535,527. The device is shown also as applied to a hydraulic cylinder for a brake of the kind comprising a pair of cylinders, each having a pair of oppositely-moving pistons acting on a pair of adjacent shoe ends so that both shoes act as leading shoes with either direction of rotation of the drum. The arm is shown in this case as mounted to yield lengthwise relatively to its pivot against the action of a spring when subject to undue stress. As applied to a brake of the kind described in Specification 584,544, in which one shoe 60, Fig. 7, is circumferentially slidable on a lever or carrier 61, which engages an anchor at one end and a spreading means at the other end, the anchor comprises a rod 64 screwed into a fixed casing 62 and receiving a tappet 65 which is slotted to take one end of the carrier. The rod 64 carries a flange 68 formed with peripheral holes 74 engaged by the arm 67 pivoted upon the shoe 60. The adjusting device operates when the brake is applied with the drum rotating in counter-clockwise direction so that the upper end of the shoe is urged against a fixed abutment and the lower end with the lever moving away from the anchor. The rod 64 also screws into a socket 71 which serves as the anchor for the shoe 72, the screw-thread being of opposite hand and greater pitch than the thread between the rod 64 and the casing 62, whereby simultaneous adjustment of the shoe 72 is effected.