Patent ID: 7758320

Claim:
A multistage sealed direct drive pump for pumping a fluid, said pump comprising: an electric motor having a motor shaft; a plurality of impellers mounted on said motor shaft; a housing enclosing said electric motor and said plurality of impellers; a fluid path providing fluid communication from a first area associated with a first of said plurality of impellers to a second area associated with a second of said plurality of impellers, said second area being adapted to define a second stage of said multistage sealed direct drive pump; and at least one hydrodynamic bearing for supporting said motor shaft, wherein said at least one hydrodynamic bearing comprising at least one surface and a generally opposing surface, said at least one surface comprising at least one fluid conduit for permitting said fluid to flow from said second area to said first area to lubricate said at least one hydrodynamic bearing and said electric motor, thereby removing heat generated by said electric motor and lubricating said at least one hydrodynamic bearing, wherein said fluid is a liquid refrigerant; said at least one fluid conduit extending across said at least one surface so that when said at least one fluid conduit receives said fluid, said fluid flows through said at least one fluid conduit and between said at least one surface and said generally opposing surface to lubricate said at least one hydrodynamic bearing when said at least one surface rotates relative to said generally opposing surface, and as fluid flows from said second area to said first area, said at least one hydrodynamic bearing being primarily supported with a force resulting from dynamic pressure of said fluid produced by rotation of said motor shaft.