DRILL STRING OVERFLOW VALVE WITH SCREW WELL BOTTOM ENGINE Russian patent published in 2018 - IPC E21B21/10 

FIELD: oil and gas industry.

SUBSTANCE: device comprises a body with threaded projection in its lower part and an inner thread in the upper part, and radial holes in the middle part. In the body, there is a hollow step piston, a spring is placed on its lower step, in the wall of the piston lower step there is a first radial hole, a second radial hole made in the wall of the piston upper step. The piston has a middle step. A bushing is installed between the piston and the body. In the middle part of the bushing there is an inner circular belt which encloses the middle step of the piston. The first radial holes are made above the circular belt in the bushing wall communicating with radial holes the in body and with second radial holes made in the middle step of the piston. A conical bore is made in the upper step of the piston which inner diameter widens to the end face of the piston upper step, the bushing and the piston are fixed in a body in the working position by a nut, which inner surface is made conical and flush with conical recess of the upper step of the piston. The spring has a multilayer anticorrosive coating, its lower end is located in the lower circular groove which is made in the valve body.

EFFECT: reduced valve wear.

9 cl, 1 dwg