Patent ID: 7648349

Claim:
A pump comprising: a single rotating and reciprocating piston disposed in a pump housing, the housing including a single inlet, a single outlet, an interior and a middle seal, the piston being unitary in structure and comprising a proximal section connected to a pump section at an annular transition section that extends between the proximal and pump sections, the proximal section being linked to a motor, the proximal section having a first maximum outer diameter, the pump section having a second maximum outer diameter that is greater than the first maximum outer diameter, the annular transition section having an inner diameter equal to about the first maximum outer diameter of the proximal section and an outer diameter equal to about the second maximum outer diameter of the pump section, the pump section comprising a distal recessed section disposed opposite the pump section from the annular transition section, the pump section extending between the annular transition section and a distal end of the piston, the pump section of the piston being at least partially and frictionally received in the middle seal of the housing, the housing and piston defining two pump chambers including a first pump chamber defined by the distal recessed section and distal end of the pump section of the piston and the housing, the first pump chamber connected to the inlet, and a second pump chamber defined by the annular transition section and proximal section of the piston and the housing, the second pump chamber connected to the outlet, the first and second pump chambers being axially isolated from each other by the middle seal, the housing further comprising a passageway connected to the first pump chamber that extends around the middle seal and provides communication between the first and second pump chambers.