Vibration mitigation tool

Abstract

A vibration mitigation tool may include a mandrel portion, a sleeve portion arranged about the mandrel portion and configured to move longitudinally and rotationally relative to the mandrel portion. The tool may also include a spring stack configured to control compression on the vibration mitigation tool through compression of the spring stack and to control tension on the vibration mitigation tool through compression of the spring stack. A helical engagement between the mandrel portion and the sleeve portion may also be provided.

What is claimed is: 
     
         1 . A vibration mitigation tool, comprising:
 a mandrel portion;   a sleeve portion arranged about the mandrel portion and configured to move longitudinally and rotationally relative to the mandrel portion;   a spring stack comprising a first spring and a second spring, the second spring distal of the first spring, the spring stack configured to control compression on the vibration mitigation tool through compression of both the first spring and the second spring toward one another, wherein a proximal end of the first spring moves closer to a distal end of the second spring, and to control tension on the vibration mitigation tool through compression of both the first spring and the second spring toward one another, wherein the proximal end of the first spring moves closer to the distal end of the second spring; and   a helical engagement between the mandrel portion and the sleeve portion.   
     
     
         2 . The vibration mitigation tool of  claim 1 , wherein relative rotation of the sleeve portion and the mandrel portion compresses the spring stack. 
     
     
         3 . The vibration mitigation tool of  claim 1 , wherein the helical engagement comprises a helical groove that is engaged by isolated spline segments. 
     
     
         4 . The vibration mitigation tool of  claim 3 , wherein the helical groove has a rectangular cross-sectional profile. 
     
     
         5 . The vibration mitigation tool of  claim 3 , wherein the helical groove is arranged on the mandrel portion and the isolated spline segments are arranged on the sleeve portion. 
     
     
         6 . The vibration mitigation tool of  claim 3 , wherein the isolated spline segments are arranged on spline blocks fitted in receiving pockets of the sleeve portion or the mandrel portion. 
     
     
         7 . The vibration mitigation tool of  claim 1 , wherein the mandrel portion comprises a lead screw and the helical engagement comprises a helical groove on an outside surface of the lead screw. 
     
     
         8 . The vibration mitigation tool of  claim 7 , wherein the sleeve portion comprises a spline body configured for engaging the lead screw in the helical engagement. 
     
     
         9 . The vibration mitigation tool of  claim 8 , wherein the spline body comprises pockets for receiving spline blocks, the spline blocks having spline segments for engaging the helical groove. 
     
     
         10 . The vibration mitigation tool of  claim 9 , wherein the spline segments have a substantially rectangular cross-sectional profile. 
     
     
         11 . The vibration mitigation tool of  claim 1 , further comprising a bearing sleeve for regulating a degree of axial compression of a portion of the spring stack. 
     
     
         12 . The vibration mitigation tool of  claim 11 , wherein a length of the bearing sleeve or a rib location on the bearing sleeve is selected based on a suitable degree of axial compression for the portion of the spring stack. 
     
     
         13 . The vibration mitigation tool of  claim 1 , further comprising a stop ring configured to prevent motion of an end of the spring stack when the vibration mitigation tool is placed in tension and to slide along a spring tube when the vibration mitigation tool is in compression. 
     
     
         14 . The vibration mitigation tool of  claim 1 , wherein the second spring comprises between 75 and 90 percent of an entire length of the spring stack. 
     
     
         15 . The vibration mitigation tool of  claim 14 , wherein the second spring has a higher spring constant than the first spring. 
     
     
         16 . The vibration mitigation tool of  claim 15 , wherein:
 both the first spring and the second spring are active when a tension or compression force on the vibration mitigation tool is below a specified threshold; and   only the second spring is active and the first spring is at a maximum compression when the tension or compression force on the vibration mitigation tool is above the specified threshold.   
     
     
         17 . The vibration mitigation tool of  claim 16 , wherein the specified threshold is selected to prevent damage to the first spring due to over-compression. 
     
     
         18 . The vibration mitigation tool of  claim 16 , wherein the spring stack provides a progressive spring rate. 
     
     
         19 . A vibration mitigation tool, comprising:
 a mandrel portion;   a sleeve portion arranged about the mandrel portion and configured to move longitudinally and rotationally relative to the mandrel portion;   a spring stack comprising a first spring and a second spring, the spring stack configured to control compression on the vibration mitigation tool through compression of both the first spring and the second spring, wherein an opposite end of the first spring moves closer to the opposite end of the second spring, and to control tension on the vibration mitigation tool through compression of both the first spring and the second spring, wherein the opposite end of the first spring moves closer to the opposite end of the second spring; and   a helical engagement between the mandrel portion and the sleeve portion.   
     
     
         20 . A vibration mitigation tool, comprising:
 a mandrel portion;   a sleeve portion arranged about the mandrel portion and configured to move longitudinally and rotationally relative to the mandrel portion;   a spring stack comprising a first spring and a second spring, the second spring distal of the first spring, the spring stack configured to control compression on the vibration mitigation tool through compression of both the first spring and the second spring toward one another, wherein a proximal end of the first spring moves closer to a distal end of the second spring, and to control tension on the vibration mitigation tool through compression of both the first spring and the second spring toward one another, wherein the proximal end of the first spring moves closer to the distal end of the second spring; and   a helical engagement between the mandrel portion and the sleeve portion, wherein the mandrel portion and the sleeve portion together form a lubrication chamber including a first portion configured for lubricating a helical engagement, a second portion in fluid communication with the first portion and for lubricating a biasing mechanism, and a third portion in fluid communication within the vibration mitigation tool with the first portion and the second portion and for interfacing with a pressure equalizing chamber.