Patent ID: 8210829

Claim:
A pump comprising: a housing; a stator supported in the housing, the stator comprising a stator core and motor windings wrapped around the stator core, the core and windings having a cylindrical configuration defining a cylindrical space having a central axis, the stator core having an axial length measured along the axis; and a rotor assembly comprising: a cylindrical rotor supported in the cylindrical space housing for rotation relative to the stator about the axis; a first impeller operatively coupled to a first axial end of the rotor for rotation with the rotor about the axis; and a second impeller operatively coupled to a second axial end of the rotor, opposite the first axial end, for rotation with the rotor about the axis; wherein the rotor comprises a motor magnet that has an axial length that is shorter than the axial length of the stator core, the rotor assembly being free to move along the axis relative to the housing within the axial length of the stator core to adjust hydraulic performance characteristics of the pump.