Permanent magnet pump with bearings separating modular sections

Abstract

A well fluid pump has a housing with a stator having a stack of discs through which windings extend. First and second stage modules in a bore of the stator have rotating impellers and non-rotating diffusers. Magnets mounted in each of the stage modules rotate the impellers in response to electromagnetic fields generated by the windings. Anti-rotation members join adjacent ones of the impellers together in each of the stage modules for rotation in unison. A bearing assembly between the first and second stage modules has a rotatable inner portion in engagement with the impellers in the first and second stage modules for causing them to rotate in unison. The bearing assembly has a non-rotating outer portion in engagement with the stator to prevent rotation.

1 . An apparatus for pumping fluid, comprising:
 a housing having a longitudinal axis;   a stator mounted for non-rotation in the housing, the stator having a stack of discs through which windings extend, the stator having a central bore extending along the axis;   first and second stage modules in the central bore, each of the stage modules having a plurality of impellers and diffusers, the diffusers being mounted within each stage module for non-rotation;   a set of magnets mounted in each of the stage modules for rotating the impellers in response to electromagnetic fields generated by the windings;   anti-rotation members in each of the first and second modules joining adjacent ones of the impellers in each of the stage modules together for rotation in unison;   a bearing assembly between the first and second stage modules;   the bearing assembly having a rotatable inner portion in engagement with the impellers in the first stage module and in engagement with the impellers in the second stage module for causing the impellers in the first stage module to rotate in unison with the impellers in the second stage module; and   the bearing assembly having a non-rotating outer portion in engagement with a sidewall of the bore of the stator to prevent rotation of the outer portion, the inner portion of the bearing assembly being in rotating sliding engagement with the outer portion of the bearing assembly.   
     
     
         2 . The apparatus according to  claim 1 , further comprising:
 a down thrust pad between the inner and outer portions of the bearing assembly for transferring down thrust from the inner portion to the outer portion.   
     
     
         3 . The apparatus according to  claim 2 , further comprising:
 an up thrust pad between the inner and outer portions of the bearing assembly for transferring up thrust from the inner portion to the outer portion.   
     
     
         4 . The apparatus according to  claim 1 , further comprising:
 a plurality of impeller sleeves, each of the impeller sleeves extending from one end to another end of one of the stage modules, each of the sleeves surrounding and rotating in unison with the impellers within one of the stage modules; and   fasteners that secure the impeller sleeves of the first and second stage modules to the inner portion of the bearing assembly.   
     
     
         5 . The apparatus according to  claim 1 , wherein:
 the anti-rotation members within the first and second stage modules comprise a tab and recess arrangement between adjacent ones of the impellers.   
     
     
         6 . The apparatus according to  claim 1 , wherein:
 the stator has a first section surrounding the first stage module and a second section surrounding the second stage module; the stator further comprising:   a bearing locator sandwiched between the first and second sections of the stator, the bearing locator having an inward facing sidewall surrounding the axis and the bearing assembly;   a slot formed in the inward facing sidewall; and   a key on the outer portion of the bearing assembly that engages the slot to prevent rotation of the outer portion of the bearing assembly.   
     
     
         7 . The apparatus according to  claim 6 , wherein the bearing assembly is free to move axially a limited extent relative to the bearing locator. 
     
     
         8 . The apparatus according to  claim 6 , further comprising:
 windings passages in the bearing locator; and wherein   the windings passing through the first and second sections of the stator pass through the windings passages.   
     
     
         9 . The apparatus according to  claim 1 , wherein:
 the inner portion of the bearing assembly has a central passage for flowing well fluid from the second stage module to the first stage module.   
     
     
         10 . The apparatus according to  claim 9 , further comprising:
 a torque sleeve extending between a lowest impeller in the first stage module and the inner portion of the bearing assembly to cause the inner portion of the bearing assembly to rotate with the impellers of the first stage module.   
     
     
         11 . The apparatus according to  claim 1 , further comprising:
 a shaft mounted on the axis for non-rotation relative to the housing; wherein   each of the impellers has a hub through which the shaft extends, allowing rotating of the impellers and allowing limited axial movement of the impellers relative to the shaft; and   a key and slot arrangement between the diffusers and the shaft that prevents rotation of the diffusers relative to the shaft, but allows limited axial movement of the diffusers relative to the shaft.   
     
     
         12 . The apparatus according to  claim 1 , further comprising:
 a shaft mounted on the axis for non-rotation relative to the housing; wherein   at least some of the diffusers in each of the modules comprise inter-stage diffusers that are axially movable a limited extent on the shaft;   each of the inter-stage diffusers is configured for receiving down thrust from an adjacent upper one of the impellers; and   each of the inter-stage diffusers is configured to transfer the down thrust received to an adjacent lower one of the impellers.   
     
     
         13 . The apparatus according to  claim 1 , further comprising:
 a shaft mounted on the axis for non-rotation relative to the housing; wherein   the diffusers within each of the modules comprise inter-stage diffusers located above an axially fixed diffuser at a lower end of each of the modules;   each of the inter-stage diffusers within each of the modules is free to slide axially on the shaft a limited extent;   the axially fixed diffuser in each of the modules is axially and rotationally fixed to the shaft; and wherein the apparatus further comprises   an inter-stage thrust pad on an upper side of each of the inter-stage diffusers for receiving down thrust from an adjacent upper one of the impellers and transferring the down thrust to an adjacent lower one of the impellers; and   an axially fixed diffuser thrust pad on an upper side of the axially fixed diffuser in each of the modules for receiving down thrust from an adjacent upper one of the impellers.   
     
     
         14 . The apparatus according to  claim 1 , wherein each of the impellers comprises:
 impeller vanes with a vane intake on an lower side of the impeller vanes and a vane outlet on an upper side of the impeller vanes;   a coaxial, cylindrical wall defining a periphery of each of the impellers, the cylindrical wall having an upper portion extending upward from the upper side of the impeller vanes, the cylindrical wall having an upper rim; wherein   each of the diffusers is carried within and surrounded by the upper portion of one of the cylindrical walls; and   the anti-rotation members that rotationally locks each of the impellers to adjacent ones of the impellers is a tab and slot arrangement on the rim and on a lower end of the cylindrical wall of each of the impellers.   
     
     
         15 . The apparatus according to  claim 1 , further comprising:
 a capsule having a bulkhead at one end, the housing being carried within the capsule;   the housing having an intake member on one end and a discharge member on an opposite end;   one of the discharge and intake members being secured to an inner side of the bulkhead; and   a port extending through the bulkhead in registry with either the discharge member or the intake member for the flow of well fluid.   
     
     
         16 . The apparatus according to  claim 15 , wherein:
 the port extends along the axis of the housing.   
     
     
         17 . An apparatus for pumping fluid, comprising:
 a housing having a longitudinal axis;   a stator mounted for non-rotation in the housing, the stator having a stack of discs through which windings extend, the stator having a central bore extending along the axis;   a shaft mounted on the axis for non-rotation relative to the housing;   a plurality of impellers, each having a hub through which the shaft extends;   an impeller bearing in the hub of each of the impellers, facilitating rotation of each of the impellers relative to the shaft;   each of the impellers being free to move axially on the shaft a limited extent;   a set of magnets on each of the impellers for rotating the impellers in response to electromagnetic fields generated by the windings;   a plurality of inter-stage diffusers, each mounted between adjacent one of the impellers;   a key and slot arrangement between each of the inter-stage diffusers and the shaft for preventing rotation of each of the diffusers but allowing limited axial movement on the shaft; and   an axially fixed diffuser at the lower end of the inter-stage diffusers, the axially fixed diffuser being non-rotatable and axially fixed to the shaft.   
     
     
         18 . The apparatus according to  claim 17 , wherein:
 the impellers are configured to transfer down thrust to an adjacent lower one of the inter-stage diffusers; and   the inter-stage diffusers are configured to transfer the down thrust received to a next lower one of the impellers; and   the axially fixed diffuser is configured to receive and transfer the down thrust received to the shaft.   
     
     
         19 . An apparatus for pumping fluid, comprising:
 a housing having a longitudinal axis;   a stator mounted for non-rotation in the housing, the stator having a stack of discs through which windings extend, the stator having a central bore extending along the axis;   a shaft mounted on the axis for non-rotation relative to the housing;   a plurality of impellers, each having a hub through which the shaft extends;   each of the impellers being free to rotate on the shaft and move axially on the shaft a limited extent;   a set of magnets on each of the impellers for rotating the impellers in response to electromagnetic fields generated by the windings; wherein each of the impellers comprises:   impeller vanes with a vane intake on an lower side of the impeller vanes and a vane outlet on an upper side of the impeller vanes;   a coaxial, cylindrical wall defining a periphery of each of the impellers, the cylindrical wall having an upper portion extending upward from the upper side of the impeller vanes, the cylindrical wall having an upper rim;   a diffuser carried within and surrounded by the upper portion of each of the cylindrical walls; and   a tab and slot arrangement on the rim and a lower end of the cylindrical wall of each of the impellers that rotationally locks each of the impellers to adjacent ones of the impellers.   
     
     
         20 . The apparatus according to  claim 19 , wherein:
 the diffusers are secured to the shaft for non-rotation and have smaller outer diameters than the impellers.