SAFETY SUB Russian patent published in 2003 - IPC

FIELD: emergency tools, particularly, separating devices for disconnection of free part of pipe string from stuck part in well. SUBSTANCE: safety sub includes body, upper and lower adapters. Upper adapter is connected by means of right-hand thread, and lower adapter, by means of left-hand thread to unit of its locking, and made with seat for special valve. Located in body cavity is movable rod locked in initial position from axial motion and made with step external and internal surfaces. Diameter of large step of internal cavity is larger than diameter of rod upper step. Body and lower adapter are made with combined through radial channels accommodating locking units. Each locking unit is made in the form of spring-loaded hollow pin with circular bead and retainer forming working chambers accommodating spring and communicated with internal cavity of lower adapter by channel closed in initial position by rid lower step whose external surface is made with circular bore for engagement with end surfaces of pins. EFFECT: higher operating reliability and extended field of application. 6 cl, 2 dwg