Brake valve with prefill chamber unloading valve

摘要

Left and right two stage brake valves communicate fluid pressure to left and right brake mechanisms, each brake valve having an inlet for receiving pressurized brake fluid, a reservoir, a stepped bore and a stepped piston. The stepped bore and the stepped piston forming a high volume prefill chamber and a high pressure chamber. A prefill drain valve communicates the prefill chambers to the reservoir only when pump pressure is available at the inlet and blocks communication between the left and right prefill chambers and between the prefill chambers and a reservoir when pump pressure is not available at the inlet.