Patent ID: 6834889
Filing Date: 2004-12-28
Classification: E21B

Abstract:
Torque release coupling for use in drill strings comprising:a radially outer string part rotatably mounted outside a radially inner string part; and a rotation lock positioned between the outer string part and inner string part, wherein the rotation lock is fastened to a first of said string parts with a coupling device adapted to allow axial movement of the rotation lock relative to the first string part, wherein the rotation lock comprises axially oriented gripping organs adapted to releasable engage into corresponding gripping organs in a second of the string parts, the rotation lock also comprising a spring to provide an axial force on the rotation lock and to bias the gripping organs on the rotation lock into engagement with the gripping organs on the second of the string parts, wherein the gripping organs of the rotation lock and the corresponding gripping organs of the second string part have angled engaging surfaces that are configured such that when a relative moment between the first of the string parts and the second of the string parts, reaches a predetermined value, an axial force sufficient to overcome the bias of the spring is produced, and the rotation lock is moved to a position wherein interlocking between the first of the string parts and the second of the string parts, by the rotation lock, is released, and wherein the torque release coupling has an annular main shape to allow through flow of fluids and being provided in its upper and lower parts with coupling means for connecting to parts of a drill string.