Patent GB-416406-A (GB)
Title: Improvements in and relating to ratchet or like devices
IPC: F16D65/48
Filed: 1932-12-09
Abstract: 416,406. Compensating for wear in brakes. FURNESS, J. A., 6, Freelands Road, Bromley, Kent. Dec. 9, 1932, Nos. 34947/32 and 23039/33. [Class 103 (i).] An automatic means for compensating for wear in brake shoes comprises a locking device which allows the brake shoes to move towards the drum to take up the wear, but only permits a limited movement away from the drum whereby a constant " set off " clearance is obtained. In Figs. 1, 2 the brake shoe 144 is provided with a pin 143 projecting through a slot in the housing 140. A threaded spindle 139 is secured to the housing 140 and is engaged by a nut 138 which also engages a locking member 141 formed integral with a projection 145 which co-operates with a pin 146 attached to the housing 140. The nut 138 has a projection formed with a slot 142 through which passes the pin 143. Movement of the brake shoe towards the drum due to wear rotates the nut in an anti-clockwise direction and is permitted through the projection 145 engaging the pin 146 and bringing the locking member 141 in pitch with the spindle 139. Movement of the brake shoe away from the drum is permitted due to the clearance in the slot 142, but further movement is restricted due to the locking of the threads. Two other modifications of the arrangements of the threads in the locking device is described in the Specification. In a fixed fulcrum brake fitted as above, the wear will cause clearance between the ends of the shoes and the actuating cam in the " off " position, and to counteract this, means are provided for increasing the width of the fulcrum. Figs. 6, 7 show the fulcrum composed of two cam members 150, 151 each connected to a shoe 163 by a spring 164. The cam 151 is fitted with a threaded spindle 152 engaging the threaded recess in a member 153 formed in the cam 150. External threads in the member 153 engage internal threads on the sleeve 154 rotatably mounted in the brake housing 155. A bolt 161 engages the end of the member 152. A pin 166 on the sleeve 154 co-operates with a lug 165 on the cam 151 so that when they engage the cams 150, 151 may move apart but cannot return due to the locking of the threads. A modified form of the arrangement of the threads is described. The above described devices are illustrated as applied to a floating fulcrum brake wherein the shoe anchors at one end when the drum is rotated in one direction and at the other end when the drum is rotated in the other direction. Figs. 12, 14 show a modification wherein a camshaft 183 is actuated by a lever 187 in an anti-clockwise direction, Fig. 14, to apply the brakes. The cam is progressively moved in a direction to take up the wear in the shoes, but is only allowed to rotate a certain angle in the reverse direction to obtain a constant clearance between the brake shoes and drum. A member 188 is pinned to the spindle 183 and is connected by pins 191 to a member 190. The members 188, 190 are provided with right and left hand threads which engage similar threads in a sleeve 192. A nut 184 engages the spindle 183 and a fixed pin 186 engages a slot 185 in a flange on the nut. A pin 193 on the nut co-operates with a pin 194 on the sleeve 192. In applying the brakes the nut 184 and the sleeve 192 move with the spindle an amount equal to the clearance in the slot 185 and any further movement of the spindle 183 causes the nut to move from right to left followed by the member 190. The amount that the spindle can return in the reverse direction is controlled by the slot 185 at the end of which locking between the members 184 and 190 takes place. Associated with the lever 187 is a similar arrangement whereby members 196, 197 on a squared portion 198 of the spindle 183 cooperate with a sleeve 200. In applying the brakes, the lever 187 and the member 197 engage and rotate the shaft and in the reverse direction the amount of wear taken up will cause the lever to rotate on the spindle followed by the member 197 until the lever again engages the pins 191 so that in operating the brake, the lever 187 always assumes the same positions when the brake shoes are " on " and " off."