REAMER Russian patent published in 2007 - IPC E21B7/28 

FIELD: drilling equipment, particularly devices to underream well bore within predetermined interval.

SUBSTANCE: reamer comprises body with flushing channels and side grooves. Arranged in the side grooves are rock-cutting tools. The reamer also has spring-loaded hollow piston with hollow shaft and pusher. The reamer is provided with additional spring-loaded piston with hollow shaft, which has radial channels for fixing means receiving. Corresponding thrust channels are created in outer surface of hollow shaft and inner surface of the body. The flushing channels may be communicated with each other by means of bypass chamber after reamer fixation in working position. Additional hollow shaft has flushing channels and connected with pusher in lower part thereof.

EFFECT: increased reliability and efficiency due to possibility of reamer fixation in working position.

2 cl, 1 dwg