CASING CENTRALIZER Russian patent published in 2002 - IPC

FIELD: casing cementing in wells. SUBSTANCE: centralizer includes stem with casing string coupling screwed on it, cylinder rigidly connected to casing string coupling and whose cavity accommodates working and locking pistons, centering members in the form of levers. Installed in cylinder cavity are bushings engageable with one another by their wedge-shaped surfaces locked to one another by pins. Casing string coupling cavity accommodates slide valve in the form of sleeve for closing holes communicating cylinder cavity with internal cavity of casing string. Working and locking pistons are installed for motion in one direction and locked relative to cylinder by shear pin. Working piston has recesses on generating line of external side. Locking piston whose length exceeds working piston is connected with levers by means of locking devices and has wedge-shaped surface for engagement with one end of levers whose other ends are hinged by means of pins with locknut rigidly connected through sub with centralizer stem. EFFECT: higher operating reliability. 2 cl, 3 dwg