Progressing cavity pump/motor

Abstract

A progressing cavity pump/motor includes a stator ( 12 ) having a metal interior surface ( 14 ) and one or more spiraling internal lobes ( 16 ). The rotor ( 18 ) has a metal exterior surface ( 20 ) and one or more spiraling external lobes ( 22 ) for cooperating with the stator to form progressing cavities between the stator and the rotor during rotation of the rotor. One or both the stator interior surface and the rotor exterior surface include a rough surface ( 30 ) having an Ra greater than 100 micro inches, such that fluid flowing to a gap between the stator and the rotor is disrupted by the rough surfaces to reduce fluid leakage between the stator and the rotor.

I claim: 
     
         1 . A progressing cavity pump/motor, comprising:
 a stator having an interior surface with two or more spiraling internal lobes;   a rotor rotatably received within an interior of the stator and having an exterior surface and one or more spiraling external lobes to cooperate with the stator to form progressing cavities between the interior surface of the stator and the exterior surface of the rotor during rotation of the rotor within the interior of the stator; and   at least one of the stator interior surface and the rotor exterior surface supporting a roughened surface having a surface roughness of at least 100 micro inches Ra to impair the flow of fluid across the roughened surface and to thereby disrupt the flow of fluid from a progressive cavity through a gap between the internal surface of the stator and the exterior surface of the rotor.   
     
     
         2 . The progressing cavity pump/motor of  claim 1 , wherein the roughened surface is formed on the interior surface of the stator. 
     
     
         3 . The progressing cavity pump/motor of  claim 1 , wherein the roughened surface is formed on the exterior surface of the rotor. 
     
     
         4 . The progressing cavity pump/motor of  claim 1 , wherein roughened surfaces are formed on both the interior surface of the stator and the exterior surface of the rotor. 
     
     
         5 . The progressing cavity pump/motor of  claim 1 , wherein the roughened surface preferably has a surface roughness of between 200 micro inches and 400 micro inches Ra. 
     
     
         6 . A progressing cavity pump, comprising:
 a metal stator having an interior surrounded by an interior surface with two or more spiraling lobes;   a metal rotor having an exterior surface and at least one spiraling lobes, the rotor rotatably received within the interior of the stator to form and progressively move fluid cavities along a length of the pump by rotation of the rotor within the stator; and   a roughened surface disposed on at least one of the interior surface of the stator and the exterior surface of the rotor to impair the flow of fluid across the roughened surface and to reduce leakage of fluid from a progressive cavity through gaps between the interior surface of the stator and the exterior surface of the rotor;   wherein the roughened surface is 100 micro inches Ra or greater.   
     
     
         7 . The progressive cavity pump of  claim 6 , wherein the roughened surface is disposed on the interior surface of the stator. 
     
     
         8 . The progressive cavity pump of  claim 6 , wherein the roughened surface is disposed on the exterior surface of the rotor. 
     
     
         9 . The progressive cavity pump of  claim 8 , wherein the roughened surface is also disposed on the interior surface of the stator. 
     
     
         10 . The progressive cavity pump of  claim 6 , wherein the roughened surface is 200 micro inches or greater. 
     
     
         11 . The progressive cavity pump of  claim 6 , wherein the roughened surface is 200 to 400 micro inches. 
     
     
         12 . The progressive cavity pump of  claim 6 , wherein the rotor is connectable to a workstring to transmit torque from the workstring to the rotor of the pump. 
     
     
         13 . A progressing cavity motor, comprising:
 a metal stator having an interior surrounded by an interior surface with two or more spiraling lobes;   a metal rotor having an exterior surface and at least one spiraling lobes, the rotor rotatably received within the interior of the stator to form and progressively move fluid cavities along a length of the pump by rotation of the rotor within the stator; and   a roughened surface disposed on at least one of the interior surface of the stator and the exterior surface of the rotor to impair the flow of fluid across the roughened surface and to reduce leakage of fluid from a progressive cavity through gaps between the interior surface of the stator and the exterior surface of the rotor;   wherein the roughened surface is 100 micro inches Ra or greater.   
     
     
         14 . The progressive cavity motor of  claim 13 , wherein the roughened surface is disposed on the interior surface of the stator. 
     
     
         15 . The progressive cavity motor of  claim 13 , wherein the roughened surface is disposed on the exterior surface of the rotor. 
     
     
         16 . The progressive cavity motor of  claim 15 , wherein the roughened surface is also disposed on the interior surface of the stator. 
     
     
         17 . The progressive cavity motor of  claim 13 , wherein the roughened surface is 200 micro inches or greater. 
     
     
         18 . The progressive cavity motor of  claim 13 , wherein the roughened surface is 200 to 400 micro inches. 
     
     
         19 . The progressive cavity motor of  claim 13 , wherein the rotor is connectable to a shaft to transmit torque from the motor to a power-consuming device through the shaft. 
     
     
         20 . The progressive cavity motor of  claim 13 , wherein the a roughened surface disposed on at least one of the interior surface of the stator and the exterior surface of the rotor to impair the flow of fluid across the roughened surface and to reduce leakage of fluid from a progressive cavity through gaps between the interior surface of the stator and the exterior surface of the rotor comprises a uniformly roughened surface with a recurring geometric pattern of hemispherical indentations.