SAFETY LOCK Russian patent published in 2006 - IPC E21B17/06 

FIELD: emergency protection tools, particularly safety locks adapted to disconnect free section of pipe string from pipe string section stuck in well.

SUBSTANCE: lock comprises composite body and splined bush. Body comprises upper part provided with splines in outer surface thereof and lower part having grooves on upper end thereof. The upper and lower parts are connected one to another by threaded connection. Splined bush is spring-loaded from top and has extensions on lower end thereof. The extensions are congruent to grooves of lower body part. The lock is provided with free fall valve seat. Upper body part in place of spring arrangement is perforated. Perforated body part in initial position is closed with the seat connected with the body by shear member.

EFFECT: extended field of safe lock operation.

2 cl, 2 dwg