Patent ID: 6861777

Claim:
A motor pump comprising: a pump head having one or more pressure generating elements for pressurizing a fluid; an electric motor for driving said one or more pressure generating elements to pressurize the fluid, the electric motor comprising: a stator with one or more magnetic field producing elements for producing a magnetic field in response to a flow of electrical current through the one or more magnetic field producing elements; a rotor having a rotor shaft for driving said one or more pressure generating elements in response to the magnetic field produced by the stator, said rotor shaft being axially movable with respect to said one or more pressure generating elements such that the rotor shaft is free to move in an axial direction independently of said one or more pressure generating elements, said rotor shaft having opposed ends exposed to a flow of fluid establishing balanced pressure on each end of said rotor shaft so that the fluid produces substantially no axial load on the rotor shaft; and an air gap between the stator and the rotor; and pressurized fluid disposed in and flowing through the air gap and the pump head to cool the motor.