GB830284A - Improvements in or relating to hydraulic brake-operating mechanisms - Google Patents

Abstract

830,284. Fluid pressure braking systems. CLAYTON DEWANDRE CO. Ltd. June 30, 1958 [July 10, 1957], No. 21908/57. Class 103 (1)] An hydraulic brake-operating mechanism comprises a pumped constant flow circuit throttled by manually operable control means to create pressure for transmission to the brake actuating cylinders, and an hydraulic accumulator for supplying pressure liquid to the brake actuating cylinders should the required rate of pressure build up be greater than can be provided by the constant flow circuit, or should the circulating pump fail, the control means incor. porating two valve units each controlling independent brake systems or service lines fed by independent accumulators, the units being interconnected so that pressure generated in the first system operates the valve unit in the second system, and being arranged such that should pressure failure occur in the first unit then the second unit can be operated mechani. cally through the first unit by the brake pedal. A valve seat 22 is moved against the coned.end of a stem 11 by a foot pedal operated plunger 3 to interrupt the constant fluid flow through passage 7, bore 2, bore and ports 4 in plunger 3, and passage 9 to build up pressure in a brake service line, this pressure reacting on plunger 3 to provide " feel " at the brake pedal. Increased displacement of plunger 3 moves stem 11 in a fixed sleeve 10 to raise valve head 12 from its seat 15 to connect an accumulator via port 21, 20, space 18, enlarged bore 2a and passage 24 to the brake line. Pressure in bore 2a acts on a piston 30 of valve V 2 to move, through body 29 and abutment 34, valve elements 11a, 12a against spring 16a to connect an accumulator via port 37, 38, valve elements 11a, 12a, ports 35, 36 to a related brake line. On brake release the valve elements are closed on to their seats by springs 16, 16a and plunger 3 and piston 30 return to the shown position 5, fluid from the second brake line exhausting past a one-way ball valve 33 and piston 30 which is raised from body 29, to valve unit V 1 , the return of the piston assembly 29, 30 being limited by a ring 40 abutting an insert 14 in bore 2a. On failure of pressure in unit V 1 continued movement of the foot pedal is transmitted via plunger 3, valve elements 11, 12 and extension 12x to the piston assembly of unit V 2 . The units V 1 , V 2 are formed separately and are connected together, but in one embodiment in the Provisional Specification they are formed in a common housing.