COUPLING FOR STEPWISE CEMENTATION OF CASING STRING Russian patent published in 1995 - IPC

FIELD: oil and gas industry. SUBSTANCE: coupling is a device having a composite body with circulation holes and an internal shoulder. Inside the body there is a movable bushing. The movable bushing has circulation holes and a seat. The movable bushing and the body combine to form an annular space. A differential bushing mounted in this annular space covers the aforesaid circulation holes of the body and the movable bushing. The device is provided with an additional retaining unit. The retaining unit is a split spring ring. The movable and differential bushings have annular grooves arranged in a spaced relation for placement of the split spring ring. The split spring ring is mounted for engagement with the shoulder of the body. The main retaining unit is mounted in a spaced relation between the engaged surfaces of the movable bushing and the body. This clearance is multiple of that between the engaged surfaces in the additional retaining unit. EFFECT: higher reliability. 5 dwg