GB580334A - Improvements in or relating to internal shoe drum brakes - Google Patents

Abstract

580,334. Brakes. AUTOMOTIVE PRODUCTS CO., Ltd., and PARNELL, F. G. June 30, 1944, No. 12527. [Class 103 (i)] In an internal shoe drum brake of the kind wherein the shoes are free to move circumferentially between abutments, the shoe-spreading means comprise a pair of toggle linkages 57, 65; 58, 66 and a member 52 for moving the ends of the links 57, 58 inwardly so that the elbows of the links are moved outwardly and move the shoes correspondingly. Alternatively, one shoe may be operated by the toggle arrangement and the other shoe otherwise. The abutments 23, 24, 33, 36 have middle portions which fit loosely between spaced webs 19 on the shoes 14, 15, the rounded ends of the web being accommodated on stepped parts' of the abutments which are themselves carried on the supporting member 10. The abutments 33, 36 are adjustable by a wormoperated right and left-handed screw 27 and vertical projections on the support 10 may be provided to back up the abutments against the outward thrust of the links. The elbow assemblies each comprise a member 62 having limbs 69, 70 with semi-cvlindrical projections 71, 72 which engage and pivot in similarly curved recesses in the edges of the webs 19. A spring 76 anchored between a pin 75 and the support 10 keeps the member 62 in engagement with the toggle-link ends, and the pivoted mounting 71, 72 permits the toggle-elbow to have limited circumferential movement relatively to the shoe. The shoes are held against axial movement by fingers 78, 79 on the member 10, a spring- pressed plunger 80 keeping the shoe towards the finger 78. The member 52, which is shaped to accommodate the ends of the links 57, 58 is circular in section and is held in a bore 51 in the end of an operating lever 45, rotation of the member 52 in the bore being prevented by a grub screw. According to the Provisional Specification, each toggle linkage comprises a bent link and a straight link, the former being the longer so that it extends beyond the centre of the shoe. The end of the bent link is socketed to receive a ball on the end of the short link.