CROWN BIT FOR ROTARY-PERCUSSION DRILLING Russian patent published in 1994 - IPC

FIELD: mining industry. SUBSTANCE: crown bit has peripheral inserts parallel to crown axis. Insert edges are straight. Straight line transforms towards crown axis into quadratic curve formed by curved surfaces which are located symmetrically and are convex relative to insert symmetry plane. Part of insert surface facing crown axis is made in form of body part. Insert edge may be made with blunting of same width over edge entire length. Insert body may have protrusion over its entire length and confined in plan by tangents to circle circumscribing insert cross-section, and by part of circle circumscribing the crown head. Tangent lines when assumably extended intersect each other in one point on edge symmetry plane. EFFECT: higher efficiency. 3 cl, 11 dwg