GB424676A - Improvements in and relating to hydraulic brakes - Google Patents

Abstract

424,676. Fluidpressure brakes. KEBRT, J., 4, PalackÚho nßm., Olomouc, Czecho-Slovakia. July 17, 1934, No. 20949. Convention date, July 17, 1933. [Class 103 (i)] In a hydraulic brake system of the kind comprising coaxially arranged high and low pressure master cylinders and a relief valve by which liquid is transferred to the reservoir from the low pressure cylinder, at the completion of the low pressure stage a restricted passage or other hydraulic resistance is arranged in front of the valve to prevent or retard premature opening of the valve. When the low and high pressure pistons 1, 4 are pressed downwardly by the lever 8, liquid is at first delivered from the cylinder 2 through openings 11 and also past a non-return valve 12, to the pipe line 14 as well as from the smaller cylinder 3. When the openings 11 are closed by the piston 4, the brake shoes are in contact with the drum and with continued movement of the pistons liquid is delivered from the cylinder 2 past the valve 17 until the pressure reaches a value sufficient to lift a spring-loaded valve 20, Fig. 3, by which liquid is then delivered to the reservoir 19, the piston 4 alone being then operative. The valve 20 is contained in a non-return valve 26 supported by a spring 27 and which permits a return flow from the reservoir to the cylinder 2 during the release movement of the pistons. The passage in the valve 26 leading to the valve 20 comprises a calibrated bore 22 which offers resistance to the flow of liquid such as to prevent or minimize opening of the valve 20 arising from a premature rise of pressure in the cylinders due to rapid movement of the pistons.