Abstract: A pump assembly with a combination reciprocating high-pressure seal and fluid inlet check valve for use within brake systems. The pump assembly comprises a housing having a bore formed therethrough and a piston disposed within the bore for reciprocal movement therein. An annular seal is disposed around the piston for reciprocal movement thereon. The annular seal cooperates with the piston and/or the housing to form at least one longitudinally extending passageway. The passageway, the piston, the annular seal, and the housing cooperating to form a check valve assembly. The annular seal is moveable to a first position relative to the piston in which the check valve assembly is in a flow-through position to fill a pump chamber with fluid from an inlet chamber during a fluid inlet stroke. The annular seal is moveable to a second position relative to the piston in which the check valve assembly is closed.

Abstract: A piston for a low pressure fluid accumulator of a hydraulic control unit of a vehicle brake system includes a cylindrical body having an outer surface defining a first end surface of the piston. The first end surface includes a plurality of interconnected ridges. The ridges have outer surfaces and form cavities therebetween. Each ridge is adapted to provide a sealing surface between the first end surface of the piston and an inner surface of a fluid accumulator in which the piston may be inserted. In one embodiment of the invention, the closed end of the piston includes a thick self-supporting wall. A thin skirt extends from the thick self-supporting wall toward the open end of the piston. A plurality of axially extending skirt support ribs is formed on the inner surface of the piston skirt.