Patent ID: 7438542

Claim:
A fluid pump assembly comprising: a pump housing and a fluid pump disposed within said pump housing; said fluid pump including an impeller member and a rotor member cooperating with said impeller member and disposed substantially therewithin for rotation about a central axis, said fluid pump having axially opposite first and second side faces; inlet and outlet ports disposed adjacent to said first side face of said fluid pump; a pressure chamber formed within said pump housing adjacent to said second side face of said pump; and an end plate disposed within said pressure chamber and movable relative to said pump between a first position and a second position; said end plate having axially opposite inner and outer end surfaces oriented so that said inner end surface facing said fluid pump and said outer end surface facing away from said fluid pump; an area of said outer end surface of said end plate being greater than the area of said inner end surface thereof; said end plate being in the form of a stepped piston having a smaller diameter section delimited by said inner end surface, and a larger diameter section delimited by said outer end surface; said pressure chamber within said pump housing being defined by a stepped bore including a smaller diameter bore slidably receiving the smaller diameter section of said piston, and a larger bore slidably receiving the larger diameter section thereof.