GB453153A - Improvements relating to braking mechanism of the internally expanding brake shoe type - Google Patents

Abstract

453,153. Internally-expanding brakes. KERSHAW, A. G., and WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., 82, York Road, King's Cross, London. March 6, 1935, No. 7040. [Class 103 (i)] Actuating mechanism for internally-expanding brakes comprises a substantially cylindrical member rotatable about its axis which is substantially tangential to the brake drum, balls or rollers being disposed in inclined recesses between the end faces of this member and those of thrust members which engage the ends of the shoes. Automatic slack adjusting means for the shoes may be provided within the drum. The outer ends of a pair of thrust members 10, Fig. 2, non-rotatably slidable in a casing 11 fixed within the brake drum, engage each a shoe end. An operating member 15 rotatable about the axis of the members 10 by means of pivots 16 extending into the members 10, has attached to it by a pin 19 a pair of discs 17 each formed with arcuate recesses 18 each of increasing depth from end to end. Balls 20 are disposed between these recesses and corresponding recesses in the members 10. The member 15 has an arm 21 to which is attached a link 24 by which the member can be turned, thus forcing the thrust members 10 apart by the cam action of the balls and recesses. To compensate for wear of the shoes, the effective length of the right-hand member 10 is automatically adjustable and for this purpose comprises an intermediate part 27 screwing into an end part 25 and having a ring of ratchet teeth 30 engaged by a locking ratchet ring 31 connected to the part 10 to prevent rotation. The teeth 30 are also engaged by teeth on an annular member 32 splined to the pivot 16 of the operating member 15. When rotation of the member 15 in applying the brake is excessive, the ratchet member 32 slips a tooth and during the release movement turns the member 27, thus extending the thrust member 10, 25 as a whole. The thrust members are urged towards each other by a spring 36 bearing on a plug 35 in the member 25 and on a rod secured to the left hand member 10. In a modification, Fig. 6, the rotatable operating member comprises two parts slidable in but non-rotatable with respect to the member 45 and connected by a screwed member 50 carrying a ratchet disc 51 engaged by a locking pawl mounted on the fixed casing 44 and a driving pawl carried by the arm 47 of the member 45 to which the operating link 46 is connected. Excessive rotational movement of the members 45, 48 in applying the brake causes the driving pawl to slip a ratchet tooth so that the member 50 is turned during releaso to extend the members 48. Indicators, applications of.-To indicate the amount of wear that has been taken up, a crank member 38, 40, Fig. 2, carrying a pointer 37 is mounted in the casing 11 and engages a slot in the thrust member 25.