Friction reducing drillstring component

Abstract

A friction and/or torque reducing drillstring component has a one-piece mandrel body 5 with a mandrel body recess 13 c considerably smaller than mandrel upper neck 13 a and mandrel body lower neck 13 b, dressed with an outer sleeve 18 which is interlocked with a two-piece inner bearing 20 through several integral dove-tailed splines 22 b and grooves 22 a. The combination of the outer sleeve 18 and inner bearing 20 is restricted in vertical movement over the said mandrel body 5 by an integral, optionally spirally, bladed first stop 15 and a removable second stop 16. The removable second stop 16 is locked onto the mandrel body upper neck 13 a by means of threaded retaining bolts 24. Once the second stop 16 is removed, the one-piece outer sleeve 18 is retractable over the mandrel body upper neck 13 a to allow the removal of the two-piece inner bearing 20. A second inner bearing 155 may also be provided.

I claim:  
     
         1 . A component for forming part of a drill string, the component comprising a mandrel having couplings for connection with the drill string, a bearing member mounted on the mandrel and a sleeve member mounted on the bearing member.  
     
     
         2 . A component as claimed in  claim 1 , wherein the bearing member is an inner bearing member, and the sleeve member is an outer sleeve member, and the component further comprises first and second retaining members for retaining the inner bearing member, and the outer sleeve member, on the mandrel.  
     
     
         3 . A component as claimed in  claim 2 , wherein at least one of the first and second retaining members is removable or retractable from the mandrel, to permit the inner bearing member, and the outer sleeve member, to be removed from the mandrel.  
     
     
         4 . A component as claimed in  claim 2 , wherein the inner bearing member comprises at least two portions, which when brought together, form a substantially tubular member.  
     
     
         5 . A component as claimed in  claim 4 , wherein the at least two portions are mounted in a recess of the mandrel, the recess comprising a reduced diameter portion with reference to the diameter of the drill string.  
     
     
         6 . A component as claimed in  claim 2 , wherein the outer sleeve member is arranged coaxially with the inner bearing member in use of the component.  
     
     
         7 . A component as claimed in  claim 6 , wherein a selective locking mechanism is provided to prevent relative rotational movement between the inner bearing member and the outer sleeve member in use of the component.  
     
     
         8 . A component as claimed in  claim 7 , wherein the selective locking mechanism comprises a first locking device provided on the inner bearing member and a second locking device provided on the outer sleeve member.  
     
     
         9 . A component as claimed in  claim 8 , wherein the first locking device is provided on the outer surface of the inner bearing member and the second locking device is provided on the inner surface of the outer sleeve member.  
     
     
         10 . A component as claimed in  claim 8 , wherein the first and second locking devices interact with one another to provide the locking action.  
     
     
         11 . A component as claimed in  claim 8 , wherein the first and second locking devices are formations provided on the respective surfaces of the inner bearing member and outer sleeve member.  
     
     
         12 . A component as claimed in  claim 11 , wherein the formations are arranged longitudinally at least partly along the length of the respective inner bearing member and outer sleeve member.  
     
     
         13 . A component as claimed in  claim 10 , wherein a third locking device is provided to interact with the first and second locking devices to provide the locking action.  
     
     
         14 . A component as claimed in  claim 2 , further comprising a second inner bearing member comprising at least two portions.  
     
     
         15 . A component as claimed in  claim 14 , wherein the portions when brought together form a substantially tubular member.  
     
     
         16 . A component as claimed in  claim 15 , wherein there are two portions, each portion comprising a half cylindrical member.  
     
     
         17 . A component as claimed in  claim 14 , wherein the at least two portions are mounted in the same recess of the mandrel that the two portions of the first inner bearing member are mounted.  
     
     
         18 . A component as claimed in  claim 14 , wherein the first and second bearing members each comprise a device which separates the outer sleeve member from the mandrel.  
     
     
         19 . A component as claimed in  claim 14 , wherein the first inner bearing member is capable of rotation with respect to the second inner bearing member.  
     
     
         20 . A component as claimed in  claim 14 , wherein a selective locking mechanism is provided to prevent relative rotational movement between the second inner bearing member and one of the first and second retaining members in use of the component.  
     
     
         21 . A component as claimed in  claim 2 , wherein the outer sleeve member is a one-piece outer sleeve member.  
     
     
         22 . A component as claimed in  claim 2 , wherein the component is dismantled by removing one of the retaining devices and removing, if present, the second inner bearing member and then removing the outer sleeve member over one end of the mandrel, and then removing the first inner bearing member.  
     
     
         23 . A component as claimed in  claim 1 , wherein a section of the mandrel directly above and/or below the first and/or second retaining member comprises spiral blades.  
     
     
         24 . A component as claimed in  claim 1 , wherein the mandrel is a one-piece mandrel body