DOUBLE CORE DRILL Russian patent published in 1997 - IPC

FIELD: mining engineering. SUBSTANCE: drill operates together with pneumatic and hydropercussion machine and has internal pipe free of axial force wherein core-admitting tube with crown bit is disposed. Percussion energy is transmitted to crown bit through internal pipe. Core-admitting tube is installed freely abutting adapter connector with upper end and tail of crown bit with its lower end. Crown bit is movably joined with lower part of external pipe by means of spline connection, and axial displacement is limited by split spring-loaded ring embraced by nut joined to external pipe. Slurry-conveying slots of drill end of crown bit are made expanding inwards, back wall (with regard to direction of crown bit rotation) being directed tangentially and bottom of slots being inclined upwards, toward central passage of crown bit. EFFECT: enhanced reliability and efficiency in operation due to easy assemblage- disassembling of drill and collecting core-slurry material all along the diameter of borehole. 2 cl, 3 dwg