Torsional isolator

Abstract

A torsional isolator ( 200, 300, 400 ) designed to reduce vibrations and shock experienced by electronics used during directional drilling is disclosed. The torsional isolator allows the drillstring electronics to oscillate at a slower rotational velocity than the data acquisition rate of associated sensors, such that the sensors record an average value of the azimuth heading thereby allowing for a higher accuracy measurement of the azimuth heading. The sample rate of the sensors is such that the sensors maximum error is reduced by the torsional isolator, as the output angular displacements are lower than the input angular displacements.

What is claimed is: 
     
         1 . A torsional isolator for a drillstring, wherein the torsional isolator is positioned in the drillstring between electronics of the drillstring and a drillbit of the drillstring, the torsional isolator comprising:
 a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics;   a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and has the second end positioned proximate to the drillbit, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities;   at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and an outer wall of the second assembly and provides for rotation therebetween;   a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount;   a stop-key having a first key element and a second key element, wherein the first key element is positioned on the first assembly and the second key element positioned on the second assembly, and wherein the first key element and the second key element are capable of preventing a rotation of the second assembly beyond a pre-defined limit from a static position;   a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly; and   a viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.   
     
     
         2 . The torsional isolator of  claim 1 , wherein the predefined limit is ±120 degrees. 
     
     
         3 . The torsional isolator of  claim 1 , further comprising at least three bearings. 
     
     
         4 . The torsional isolator of  claim 3 , wherein at least one of the bearings is a radial bearing. 
     
     
         5 . The torsional isolator of  claim 3 , wherein at least one of the bearings is a thrust bearing. 
     
     
         6 . The torsional isolator of  claim 3 , wherein at least one of the bearings is a needle bearing. 
     
     
         7 . A torsional isolator for a directional drilling tool having at least a electronics housing, at least one interconnect and a drillbit, the electronics housing contains at least a drillstring electronics and is joined with the interconnect, wherein the drillbit is oppositely positioned from the drillstring electronics on the directional drilling tool, the torsional isolator comprising:
 a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is positioned proximate to the drillbit;   a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and the second end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities;   at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and an outer wall of the second assembly and provides for rotation therebetween;   a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount;   a stop-key having a first key element and a second key element, wherein the first key element is positioned on the first assembly and the second key element positioned on the second assembly, and wherein the first key element and the second key element are capable of preventing a rotation of the second assembly beyond a pre-defined limit from a static position;   a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly; and   a viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.   
     
     
         8 . The torsional isolator of  claim 7 , wherein the predefined limit is ±120 degrees. 
     
     
         9 . The torsional isolator of  claim 7 , further comprising at least three bearings. 
     
     
         10 . The torsional isolator of  claim 9 , wherein at least one of the bearings is a radial bearing. 
     
     
         11 . The torsional isolator of  claim 9 , wherein at least one of the bearings is a thrust bearing. 
     
     
         12 . The torsional isolator of  claim 9 , wherein at least one of the bearings is a needle bearing. 
     
     
         13 . A torsional isolator for a drillstring, wherein the torsional isolator is positioned in the drillstring between electronics of the drillstring and a drillbit of the drillstring, the torsional isolator comprising:
 a first assembly, the first assembly having a first end, a second end, at least one annular cavity, and a first spring mount, wherein the first end is joined to the interconnect opposite of the electronics housing and is proximate the drillstring electronics;   a second assembly, the second assembly having a first end, a second end, and a second spring mount, wherein the second assembly is movably disposed within the first assembly and has the second end positioned proximate to the drillbit, wherein the second spring mount is interiorly positioned within one of the at least one annular cavities;   at least one bearing, wherein the bearing is movably secured between an inner wall of the first assembly and an outer wall of the second assembly and provides for rotation therebetween;   a torsional spring having a first end and a second end, wherein the first end is affixed to the first spring mount and the second end is affixed to the second spring mount;   a damper element affixed to the second assembly and positioned proximate the inner wall of the first assembly; and   a viscous fluid filling the annular cavity, wherein the viscous fluid provides viscous damping by having a thin film of viscous fluid adhering to the damper element as the first assembly and second assembly rotate relative to each other.