SELF-RELEASING MECHANICAL SPEAR Russian patent published in 2005 - IPC

FIELD: well drilling and repair, particularly grappling tools for engaging and removing broken pipe string sections from well.

SUBSTANCE: mechanical spear has sliding body with inner and outer parts connected one to another to perform limited axial movement provided with groove and thrust end, as well as collet resting upon inner part of sliding body. Two expanding rings put into stressed conditions are installed correspondingly on collet and on outer surface of inner body part so that the first ring installed in released condition may rest upon thrust end, the second one brought into released position may rest upon groove. Outer and inner parts are secured one relative another with self-releasing means snapped into action under critical load application. Inner surface of lower outer part section has recess defined by conical surface from top thereof. Expanding ring of the collet is located in the recess before self-releasing means actuation.

EFFECT: increased reliability, reduced manufacturing cost and material consumption.

2 dwg