EXTERNAL RELEASING OVERSHOT Russian patent published in 2006 - IPC E21B31/18 

FIELD: well drilling and overhaul in oil and gas industries, particularly overshot tools.

SUBSTANCE: overshot comprises sub, load-bearing body with inner spiral conical surface and screw ledge, spiral band gripping member having driving flag, longitudinal slot on spiral conical body surface, annular seat under spiral conical surface, guiding ring and guiding funnel. Spiral conical surface is formed on outer surface of gripping member. Inner surface of gripping member is provided with screw fishing threading. Hollow control-rod and leading body are arranged between load-bearing body and sub. Cylindrical abutment is made in upper part of hollow control-rod. Movable valve is installed in initial position in through sub channel so that the valve may cooperate with upper abutment end. Sealing members are arranged between contact surfaces. Inner diameters of through channels provide free broken tube passage.

EFFECT: increased reliability of tube gripping and pipe cleaning efficiency, possibility to trap sludge.

2 cl, 10 dwg