Canned pump having reduced hydraulic thrust

Claim 1

A CENTRIFUGAL PUMP COMPRISING, IN COMBINATION, A HOUSING HAVING FLUID INLET AND FLUID OUTLET PASSAGES, AN IMPELLER ROTATABLY DISPOSED ACROSS THE LINE OF FLUID FLOW THEREBETWEEN, AN AXIAL OPENING IN THE IMPELLER FOR ENTRY OF FLUID, AND A CIRCUMFERENTIAL OPENING FOR DELIVERY OF PUMPED FLUID UNDER CENTRIFUGAL PRESSURE THEREFROM, A MOTOR ROTOR AND A MOTOR STATOR IN THE HOUSING, AN IMPELLER SHAFT HAVING THE IMPELLER ATTACHED AT A FRONT END AND THE ROTOR AT A POSITION BEHIND THE IMPELLER, BEARING MEANS IN THE HOUSING ROTATABLY SUPPORTING THE SHAFT, THRUST-OPPOSING MEANS ATTACHED TO THE SHAFT HAVING A SURFACE FIXED INTO ROTATABLE ENGAGEMENT WITH A BEARING MEANS, THE JUXTAPOSED BEARING MEANS AND THRUST-OPPOSING MEANS SURFACES DEFINING PASSAGES THEREBETWEEN FOR ENTRY OF FLUID FOR LUBRICATING THE BEARING, AN AXIAL PASSAGE IN THE SHAFT OPEN AT EACH END, A FLUID CHAMBER BEHIND THE ROTOR, THE REAR END OF THE AXIAL PASSAGE OPENING INTO SAID CHAMBER, THE OTHER END OF THE PASSAGE OPENING INTO THE INLET SIDE OF THE IMPELLER, A PRESSURE SURFACE EXPOSED TO PRESSURE IN THE OUTLET SIDE OF THE IMPELLER AND ATTACHED TO THE SHAFT, TENDING TO URGE THE SHAFT REARWARDLY, AND A PRESSURE SURFACE ATTACHED TO THE SHAFT AND EXPOSED TO PRESSURE IN THE FLUID CHAMBER BEHIND THE ROTOR, TENDING TO URGE THE SHAFT FORWARDLY, THE PRESSURE SURFACES AND THE AXIAL PASSAGE BEING DIMENSIONED TO PRODUCE A NET FORWARD THRUST OF REDUCED MAGNITUDE AGAINST THE FRONT BEARING.