GB679742A - Improvements in or relating to automatic brake-adjusting devices - Google Patents

Abstract

679,742. Hydraulic brake adjustment. DUNLOP RUBBER CO., Ltd., and CHATFIELD, J. E. Jan. 10, 1951 [Jan. 21, 1950], No. 1652/50. Class 103 (i). The invention is concerned with hydraulic means for providing an automatic adjustment of the clearance between the braking surfaces of piston and cylinder operated brakes, particularly disc brakes. As shown in Fig. 1, the hydraulic supply to the main cylinder 2 is from a pipe 7 through an auxiliary or compensating cylinder 1, which may be an integral casting with the main cylinder, and a connecting port 4. A piston 9, having an aperture therein that may be closed by a valve member 10, is slidable in the cylinder 1 against the action of a spring 13 and is limited in its downward movement by a ledge 8. When the brake is released the piston 9 is normally at the top of its movement with its central passage 9A closed by the valve 10 and entry of liquid from pipe 7 causes downward movement of the piston so that the liquid on its other side is driven into the main cylinder 2 so as to cause the main piston 3 to apply the brakes. The cylinder 1 is of such a size that the movement of piston 9 between its limits causes a movement of main piston 3 sufficient to take up the normal clearance. Before the piston 9 reaches its lowest position, the flange 11 on the end of the spindle of valve 10 strikes a spigot 15 and causes the valve 10 to open so as to permit liquid to flow directly from pipe 7 through port 4 into the main cylinder to the extent that may be necessary to make up for any extra movement due to wear of the friction pads. When the brake is released only that volume of liquid displaced by the movement of the auxiliary piston is allowed to flow out of the main cylinder and thus the brake clearance is automatically reset. A modified piston 9 is described in which the valve 10 is normally held closed by a spring star washer element. In the arrangement shown in Fig. 3, a similar value is used, the compensating piston 9 being, in this case, annular and slidable on the rod 17 of the main piston 3. The valve 10 is caused to open, after a predetermined movement, by the action of a flange 27 on its end 21 abutting against a projecting flange on the spigot 26 of the cylinder casting.