Rotary drive apparatus

Abstract

A rotary drive apparatus ( 24 ) for a downhole tool ( 22 ), the rotary drive apparatus ( 24 ) comprising a drive stage ( 36 a ) comprising a rotor ( 40 a ) and a stator ( 42 a ) and a connecting stage ( 38 a ) for connecting to the drive stage ( 36 a ). The connecting stage ( 38 a ) comprises a rotor connector ( 44 a ) suitable for connecting to the rotor ( 40 a ) and a stator connector ( 46 a ) suitable for connecting to the stator ( 42 a ).

What is claimed is: 
     
         1 . A rotary drive apparatus for a downhole tool, the rotary drive apparatus, comprising:
 a drive stage comprising a rotor and a stator; and   a connecting stage for connecting to the drive stage, wherein at least one of the rotor, the stator and the connecting stage is configured to flex in response to a force applied to the rotary drive apparatus to move the rotary drive apparatus from a first configuration to a second configuration.   
     
     
         2 . The apparatus of  claim 1 , wherein the connecting stage comprises a rotor connector configured to connect to the rotor of the drive stage. 
     
     
         3 . The apparatus of  claim 2 , wherein the rotor connector is configured to flex in response to the force applied to the rotary drive apparatus. 
     
     
         4 . The apparatus of  claim 1 , wherein the rotor connector is at least partially constructed from at least one of: a polymeric material; a plastic material; and a composite material. 
     
     
         5 . The apparatus of  claim 1 , wherein the connecting stage comprises a stator connector configured to connect to the stator of the drive stage. 
     
     
         6 . The apparatus of  claim 5 , wherein the stator connector is configured to flex in response to the force applied to the rotary drive apparatus. 
     
     
         7 . The apparatus of  claim 5 , wherein the stator connector is at least partially constructed from at least one of: a polymeric material; a plastic material; and a composite material. 
     
     
         8 . The apparatus of  claim 1 , comprising a plurality of the connecting stages. 
     
     
         9 . The apparatus of  claim 8 , wherein two or more of the connecting stages are configured to be connected in series. 
     
     
         10 . The apparatus of  claim 8 , wherein two or more of the connecting stages are configured to connect to respective ends of the drive stage. 
     
     
         11 . The apparatus of  claim 8 , wherein at least two of the connecting stages are of different flexibility, compressibility and/or elasticity. 
     
     
         12 . The apparatus of any preceding claim, wherein at least one of the stator and the rotor are at least partially constructed from: a polymeric material; a plastic material; and/or a composite material. 
     
     
         13 . The apparatus of  claim 1 , wherein the drive stage is fluid powered. 
     
     
         14 . The apparatus of  claim 1 , wherein the drive stage comprises or defines a motor. 
     
     
         15 . The apparatus of  claim 14 , wherein the drive stage comprises a positive displacement motor. 
     
     
         16 . The apparatus of  claim 1 , wherein the drive stage is arranged such that the rotor surrounds the stator. 
     
     
         17 . The apparatus of  claim 1 , comprising a plurality of the drive stages. 
     
     
         18 . The apparatus of  claim 1 , wherein at least part of the rotary drive apparatus is configured to facilitate drilling through the rotary drive apparatus. 
     
     
         19 . The apparatus of  claim 1 , comprising an access bore therethrough. 
     
     
         20 . The apparatus of  claim 1 , comprising or operatively associated with a pressure relief device. 
     
     
         21 . The apparatus of  claim 20 , wherein the pressure relief device comprises a valve, comprising: a valve body; an actuator; and an arrangement for fluid pressure surge mitigation. 
     
     
         22 . The apparatus of  claim 20 , wherein the pressure relief device comprises an anti-surge valve comprising: a valve body; a valve member disposed in the valve body, the valve member axially moveable relative to the valve body between a first configuration in which fluid passage through the anti-surge valve is prevented and a second configuration in which fluid passage through the anti-surge valve is permitted. 
     
     
         23 . A pressure relief device comprising an anti-surge valve for a downhole tool, the anti-surge valve comprising:
 a valve body; and   a valve member disposed in the valve body, the valve member axially moveable relative to the valve body between a first configuration in which fluid passage through the anti-surge valve is prevented and a second configuration in which fluid passage through the anti-surge valve is permitted.