DEVICE FOR HOLE CASING IN INSECURE ROCKS Russian patent published in 1997 - IPC

FIELD: mining industry. SUBSTANCE: device includes casing string and drill string. The latter is accommodated inside the casing string for combined rotation and disconnection. Casing string is made in form of concentric arrangement of internal and external strings. Internal string is made for extension towards hole bottom and fixing in lower position with respect to external string and with seat in hollow lower part. The device has check valves located in upper part of internal string and drills unit located on seat of internal string. Drilled unit is made in form of shoe with axial channel in which check valve and spring ring are installed. Spring ring fixes valve relative to shoe, and member for fixing the shoe in seat of internal string. Drilled unit is secured to drill string by means of shear member. EFFECT: higher efficiency. 1 dwg