Patent ID: 6499974
Filing Date: 2002-12-31
Classification: F04B

Abstract:
A piston pump, comprising:a pump housing (11); a piston (12) which has an end surface that delimits an operating chamber (13) within said pump housing, said operating chamber (13) being connected to a hydraulic medium supply via a first check valve (14) and to an operating cylinder (16) via a second check valve (15), said piston (12) being axially moveable in reciprocating fashion within said operating chamber (13) from an end position providing a maximum displacement volume to an opposite end position providing a minimum displacement volume against a force of a spring (18); a section of said piston (12), which extends into said operating chamber, having a reduced diameter extension (19) that extends from a shoulder (21) of said end surface of said piston (12), said extension (19) having a thickened end (22) providing a sealing surface (23) which faces said shoulder (21); and at least one valve disk (26) being located between said shoulder (21) and said sealing surface (23) and being guided within said operating chamber (13) to seal closed a connection (35) from said operating chamber (13) to said second check valve (15); said valve disk (26) having an axial thickness that is less than a gap formed between said sealing surface (19) and shoulder (21) so that said valve disk (26) is movable back and forth on said extension (19) between said shoulder (21) and said sealing surface (23); and said valve disk (26) being provided with at least one opening (27) providing a passageway for hydraulic medium from said operating chamber (13) to said second check valve (15), said opening (27) being sealed shut when said valve disk engages said sealing surface (23).