GB588035A - Improvements in brakes - Google Patents

Abstract

588,035. Brakes. NEALE, F. July 6, 1944, No. 12884. [Class 103 (i)] A unit for interposition between a brake shoe and a fixed member and/or in the brake shoe applying means to effect automatic adjustment to compensate for wear, comprises a plunger carried by a first member and urged in one direction by a spring to abut on a second member, movement of the plunger relatively to the first member in the opposite direction being prevented by the resilient engagement of ratchet segments with annular ratchet teeth formed on the plunger. As shown, shoes 3 pivoted at their lower ends are operated by a pair of pistons 12 through levers 13 pivoted on the shoe carrier 5. The pistons may be operated either by pressure fluid or by a cam 7 connected by an Oldham coupling 10 to an operating shaft 9. A bush 8 on which the cam is rotatable has a rectangular slot engaged by a fixed pin 11 so that the cam can move laterally to equalize the pressure applied to the shoes. An automatically adjustable stop device for determining the clearance between the shoe and drum in release comprises a plunger 55 slidable in a housing 54 secured to the shoe and prevented from movement towards the drum by ratchet segments 57 held in engagement with annular ratchet teeth formed on the plunger by a coil spring 58. An auxiliary plunger 21 slidable in the plunger 55 abuts on a fixed stop 30 and normally is held in the depressed position shown against the action of a spring 22 by the brake shoe release spring 6. A similar unit comprising the plunger 15 and housing 14 but without an auxiliary plunger is provided between the shoe 3 and lever 13. When the shoe is applied by the piston 12 acting through the lever 13 and plunger 15, the plunger 21 moves outwards relatively to the plunger 55 until it engages the cap 21. This movement corresponds to the normal clearance between the shoe and the drum and if due to wear of the shoe lining, this movement is exceeded, the plunger 55 is moved outwards relatively to the shoe by the spring 56 so as'to take up one or more ratchet teeth. In releasing the shoe returns until the plug 21 is again fully depressed so that the clearance of the shoe from the drum is maintained substantially constant. Also as the piston 12 returns to its original position, the plunger 15 is moved outwards relatively to the shoe by the spring 16 to an extent corresponding to the advanced position of the shoe as determined by the adjustment of the stop device. Specification 588,036 is referred to in the Provisional Specification.