Patent ID: 7987913

Claim:
An apparatus for pumping well fluid, comprising: a submersible rotary pump assembly having a rotatable driven drive shall driven by a motor; a housing forming part of the pump assembly, the drive shall extending into the housing; first and second annular chambers that are fixed in the housing at strategic locations along an axis of the drive shaft; first and second annular pistons extending sealingly into the first and second chambers, respectively, and a fluid disposed in each of the chambers; a communication passage communicating the fluid in the first chamber with the fluid in the second chamber; annular first and second thrust runners mounted to the shaft axially and rotationally; and annular first and second thrust bearing bases within the housing and being rotatably engaged by the first and second thrust runners, respectively, the first and second thrust bearing bases being axially movable with the first and second pistons, respectively, wherein down thrust imposed by the pump on the shaft through the first and second thrust runners transfers to the first and second thrust bearing bases and through the fluid in the first and second chambers to the housing.