Abstract: A hydraulic brake system that has a hydraulic unit for evacuation prior to initial filling, with the primary and secondary circuits dry, the brake system is equipped with special check valves, which are disposed between the primary circuit and the secondary circuit. When the brake system is evacuated, these check valves are in the open position, so that air escapes from the secondary circuits. This makes it unnecessary to open electromagnet valves, which are closed when without current and are present in the brake circuits I and II, electrically. The hydraulic brake system is intended for use in motor vehicles, and its hydraulic unit is designed to carry out anti-lock operation and/or traction controls.

Abstract: An accumulator comprises a cylinder formed with a substantially closed chamber and a piston formed with a small-diameter central region and a pair of large-diameter end regions flanking the central region and each formed with an outwardly open annular groove. This piston subdivides the chamber into a gas compartment at one of the end regions, a liquid compartment at the other end region, and an annular charging compartment surrounding the central region. The piston is displaceable in the cylinder to oppositely vary the volumes of the gas and liquid compartments. Respective gas and liquid seals are engaged in the grooves between the gas- and liquid-compartment end regions of the piston and the cylinder and are both constructed to inhibit fluid flow from the respective gas and liquid compartments into the charging compartment.