WELL REAMER Russian patent published in 1994 - IPC

FIELD: mining. SUBSTANCE: well reamer includes hollow body with internal projection on top end and radial holes accommodating extensible roller cutters with shanks; ring piston with means for connecting to drill string and through radial channel located in body hollow with locking from turning; stop device of roller cutters in idle position, and retainer installed in ring piston for interaction with roller cutter shanks. Roller cutter stop device is made in form of bell-cranks hinged to body top end and located in reamer diametrical plane to enhance reliability of roller cutter locking during roundtrip operation in well. Upper arms of bell-cranks are spring-loaded in direction of longitudinal axis of reamer rigidly attached to stop of ring piston and additional ring piston located between body and piston for interaction with body inner projection. Additional piston forms chamber together with piston and body. Chamber is communicated with body hollow by means of piston radial channel. Top arms of bell-cranks are installed for interaction with stop and bottom arms for interaction with additional piston. EFFECT: higher efficiency. 4 dwg