OVERFLOW VALVE OF DRILL STRING WITH GYROROTOR MOTOR Russian patent published in 2003 - IPC

FIELD: devices for drilling of oil and gas wells, particularly, overflow valves of drill string with gyrorotor motor for communication of drill string cavity with annulus in round-trip operations and filling of drill string with drilling mud and its emptying. SUBSTANCE: overflow valve has body with threads on its ends, radial holes, piston for sliding, and seat and spring between them. Piston is located inside seat and forms step pair together with piston. Upward motion of seat upper end and piston upper part is restricted by guide ring secured in valve body. Seat has diminished sliding belt with piston lower part as compared with increased sliding belt with piston upper part. Perimeter of sliding belt with piston lower part amounts up to 0.33-0.77 perimeter of sliding belt of seat with piston upper part. Spring is located in cavity between piston upper part and seat lower part. Piston has a row of radial channels located below radial holes in valve body. Valve body together with seat forms blind annular slot communicated with cavity between seat and piston by radial windows. EFFECT: higher reliability and prolonged service life of overflow valve used as a component of drill string provided with gyrorotor motor. 2 cl, 1 dwg