Release equipment for a drill string

A release piece to be joined coaxially into a drill string having a bore, and adapted to be activated in connection when the drill string has a stuck bit, comprising:

• two substantially coaxial sleeve parts adapted to be screwed together at adjacent end portions and which are internally equipped with longitudinal tooth-inter-tooth space-like locking members, the sleeve parts having a through-going bore in which is disposed an axially displaceable, sleeve-like locking device having cooperating, complementary locking members which, in a first, locking position the locking device is pressed by a coaxial, helical spring to place the locking members of the locking device into engagement with the locking members of both sleeve parts in order to secure the mutual interconnection of the sleeve parts to maintaining them screwed firmly together, and which, in a second, release position of the locking device, the locking members of the locking device only engage the locking members of one sleeve part thus neutralizing the locking of the other sleeve part so that the other screw part can be unscrewed and removed from said one sleeve part leaving the locking device in engagement with the one sleeve part only, and wherein all locking members consist of straight, axially extending grooves and intermediate, straight, axially extending, list-shaped projections exerting no wedging function when in engagement with each other, and wherein the locking members of one sleeve part in the end portion thereof, extend from a radial contact face common for the two sleeve parts, axially away therefrom, from where the other sleeve part's locking members extend in the opposite direction, axially away therefrom, and wherein one sleeve part's straight, axially extending grooves are axially aligned with the other sleeve part's straight, axially extending grooves and also aligned with the locking device's straight, list-like projections, while said one sleeve part's straight, list-like locking members are axially aligned with the other sleeve part's straight axially extending projections, and the locking device's straight, axially extending grooves, and wherein a loose ball-shaped sealing body is used in order to close the through-going bore of the pipe string in the area of the locking device to enable a subsequent displacement of the locking device toward the second, release position by exerting a hydraulically force on said ball-shaped sealing body, and wherein the sleeve-like locking device further comprises a toothed rim-like portion on a coaxial, elongate, axially displaceable, tubular spindle that is spaced from both ends portions of the spindle, said end portions being dimensioned for rectilinear guidance in the bore of the drill string during the longitudinal displacement of the locking device when the locking device is being moved from one of its end positions to the other and vice versa, one axial end of said tubular spindle having a free seat for sealingly receiving said ball-shaped sealing body, and wherein the locking device in the form of a toothed rim-like portion on the substantially more elongated, tubular spindle is formed as a concentrically, thickened portion thereon, exhibiting opposite, annular, radially extending faces, of which one forms a stop face for one end of the helical spring, with an opposing end of the spring resting supportingly against an internal, radial stop face of the sleeve part, restricting a spring room in one axial direction thereof, the helical spring being housed and guided within said spring room, the spring surrounding a portion of said elongated, tubular spindle.