WELL ROUNDER Russian patent published in 2012 - IPC E21B7/28 

FIELD: mining.

SUBSTANCE: device comprises a casing with inclined surfaces and a steam installed in it to form a chamber, a circular piston with a pusher arranged in the chamber, legs made with the possibility of interaction with appropriate inclined surfaces of the casing and the piston pusher and limited radial displacement to outside. The piston pusher is made in the form of a polyhedral prism arranged above the piston, and the leg at the bottom is equipped with a face for the appropriate face of the piston prism, besides, the casing is equipped with upper and lower limiters, arranged as capable of interaction with accordingly upper and lower ends of the legs; for limitation during their radial displacement to outside.

EFFECT: improved reliability and durability, quality of operation.

2 dwg