Downhole shape memory alloy actuator and method

Abstract

A downhole actuator includes, a sleeve, a mandrel, and at least one of the sleeve and the mandrel is in operable communication with a downhole tool to be actuated. The actuator further includes, a follower disposed at one of the sleeve and the mandrel, a pathway disposed at the other of the sleeve and the mandrel, the pathway being receptive to the follower and configured to cause rotational motion and limit a stroke length between the sleeve and the mandrel in response to longitudinal motion between the follower and the pathway. The actuator also has a shape memory alloy in operable communication with the sleeve and the mandrel configured to longitudinally move the sleeve in relation to the mandrel in response to temperature changes thereof.

1 . A downhole actuator comprising:
 a sleeve;   a mandrel, at least one of the sleeve and the mandrel being in operable communication with a downhole tool to be actuated;   a follower disposed at one of the sleeve and the mandrel;   a pathway disposed at the other of the sleeve and the mandrel, the pathway being receptive to the follower and configured to cause rotational motion and limit a stroke length between the sleeve and the mandrel in response to longitudinal motion between the follower and the pathway; and   a shape memory alloy in operable communication with the sleeve and the mandrel configured to longitudinally move the sleeve in relation to the mandrel in response to temperature changes thereof.   
   
   
       2 . The downhole actuator of  claim 1 , wherein the pathway has a plurality of tracks receptive of the follower and each of the plurality of tracks defines a unique stroke limit. 
   
   
       3 . The downhole actuator of  claim 2 , wherein each of the plurality of tracks causes rotational indexing of the sleeve in relation to the mandrel with each longitudinal stroke. 
   
   
       4 . The downhole actuator of  claim 1 , further comprising a biasing member in operable communication with the sleeve and the mandrel to cause relative movement between the sleeve and the mandrel in a direction counter to that of the shape memory alloy. 
   
   
       5 . The downhole actuator of  claim 1 , wherein the follower is a pin and the pathway is a slot. 
   
   
       6 . The downhole actuator of  claim 1 , wherein increases in temperature of the shape memory alloy cause a decrease or increase in a longitudinal dimension thereof. 
   
   
       7 . The downhole actuator of  claim 1 , wherein the shape memory alloy is configured to reverse the longitudinal motion between the sleeve and the mandrel in response to additional temperature changes of the shape memory alloy. 
   
   
       8 . The downhole actuator of  claim 1 , wherein the sleeve and the mandrel are connectable to the downhole tool such that rotational motion between the sleeve and the mandrel cause actuation of the downhole tool. 
   
   
       9 . The downhole actuator of  claim 1 , wherein the pathway is a J-slot. 
   
   
       10 . The downhole actuator of  claim 1 , wherein the shape memory alloy is at least one of the sleeve and the mandrel. 
   
   
       11 . The downhole actuator of  claim 1 , wherein the longitudinal motion between the sleeve and the mandrel is greater at a first portion of the sleeve and a first portion of the mandrel than at a second portion of the sleeve and a second portion of the mandrel. 
   
   
       12 . The downhole actuator of  claim 1 , further comprising a heater in operable communication with the shape memory alloy. 
   
   
       13 . A method of actuating a downhole tool, comprising:
 altering a dimension of a shape memory alloy with altering temperature thereof;   displacing a sleeve in relation to a mandrel, the sleeve and the mandrel being in operable communication with the downhole tool;   repositioning a follower disposed at one of the sleeve and the mandrel within a pathway disposed at the other of the sleeve and the mandrel; and   limiting a stroke of the sleeve in relation to the mandrel with the follower in the pathway.   
   
   
       14 . The method of actuating a downhole tool of  claim 13 , wherein the repositioning the follower within the pathway includes rotationally indexing the sleeve in relation to the mandrel. 
   
   
       15 . The method of actuating a downhole tool of  claim 14 , wherein the rotationally indexing repositions the follower into a different track of the pathway. 
   
   
       16 . The method of actuating a downhole tool of  claim 15 , wherein each different track has a different stroke limit. 
   
   
       17 . The method of actuating a downhole tool of  claim 13 , wherein the altering temperature is an increasing of temperature. 
   
   
       18 . The method of actuating a downhole tool of  claim 13 , wherein the altering of the dimension is a shortening or lengthening of a longitudinal dimension. 
   
   
       19 . The method of actuating a downhole tool of  claim 13 , further comprising:
 further altering temperature of the shape memory alloy; and   reshaping the shape memory alloy; and   repositioning the follower within the pathway.   
   
   
       20 . The method of actuating a downhole tool of  claim 13 , wherein a reshaping of the shape memory alloy is in response to biasing the shape memory alloy.