Apparatus and Method

Abstract

The present invention provides an apparatus ( 10 ) and method for transmitting torque to a downhole device. The apparatus ( 10 ) comprises a first part and a second part adapted for connection to the downhole device. The apparatus ( 10 ) also comprises an engagement means ( 100, 120 ). The first and second parts are connected together such that relative axial movement between the first and second parts is constrained on a helical path. The engagement means ( 100, 120 ) are arranged to rotationally connect the first and second parts to thereby transmit torque from the first part to the second part when a coupling point is reached on the helical path.

1 . Apparatus for transmitting torque to a downhole device, the apparatus comprising a first part, a second part adapted for connection to the downhole device and an engagement mechanism, wherein the first and second parts are connected together such that relative axial movement between the first and second parts is constrained on a helical path, and wherein the engagement mechanism is arranged to rotationally connect the first and second parts to thereby transmit torque from the first part to the second part when a coupling point is reached on the helical path. 
   
   
       2 . Apparatus as claimed in  claim 1 , wherein the first and second parts are axially aligned. 
   
   
       3 . Apparatus as claimed in  claim 1 , wherein the engagement mechanism comprises a clutch having first and second mating portions, and wherein a first portion of the clutch is connected to the first part and a second portion of the clutch is connected to the second part. 
   
   
       4 . Apparatus as claimed in  claim 1 , wherein the first part is provided with a throughbore and a portion of the second part is arranged to be selectively movable in the throughbore of the first part. 
   
   
       5 . Apparatus as claimed in  claim 4 , having mating threads on the first and second parts to restrain relative movement therebetween to the helical path. 
   
   
       6 . Apparatus as claimed in  claim 1 , wherein the second part includes a connector for removable attachment to the downhole device, such that rotational movement of the second part causes rotational movement of the connector. 
   
   
       7 . Apparatus as claimed in  claim 1 , having a bearing between the first and second parts. 
   
   
       8 . Apparatus as claimed in  claim 1 , wherein the first part is provided with a linear displacement device. 
   
   
       9 . Apparatus as claimed in  claim 8 , wherein the first part has a housing and the linear displacement device comprises a shaft and a spring, such that the spring is biased to restrict relative movement of the shaft and the housing. 
   
   
       10 . Apparatus as claimed in  claim 9 , wherein the second part is provided with a lead screw and the shaft is axially aligned with the lead screw, such that on actuation of the linear displacement device the shaft moves in an axial direction against the lead screw. 
   
   
       11 . A method of imparting torque to a downhole device including the steps:
 providing a first part, a second part and engagement mechanism;   restraining relative movement of the first part and the second part on a helical path;   transmitting torque from the first part to the second part on engagement of the engagement mechanism.   
   
   
       12 . A method according to  claim 11 , comprising the step of engaging the first part and second part by providing a first portion of a clutch on the first part and a second portion of the clutch on the second part. 
   
   
       13 . A method according to  claim 11 , including providing a throughbore in a portion of the first part and selectively moving a portion of the second part within the throughbore of the first part. 
   
   
       14 . A method according to  claim 11 , including suspending the first part from a wireline and allowing the second part to move under gravity relative to the first part. 
   
   
       15 . A method according to  claim 14 , including preventing axial movement beyond a first position of the second part relative to the first part. 
   
   
       16 . A method according to  claim 15 , including releasing the wireline suspension thereby allowing the first part to move axially relative to the second part. 
   
   
       17 . A method according to  claim 11 , including providing linear displacement device in the first part and axially aligning the linear displacement device with the second part. 
   
   
       18 . A method according to  claim 17 , including moving the linear displacement device in an axial direction to jar the second part.