CROWN BIT Russian patent published in 2007 - IPC E21B10/48 

FIELD: rock-cutting tools, particularly drilling bits with diamond cutting structure for well drilling along with core taking.

SUBSTANCE: drilling bit comprises body and matrix separated into sectors with flushing grooves. The sectors are provided with hole-forming, central and core-forming inserts made of superhard alloy and with protective members for hole-forming and core-forming insert protection. The protective members for hole-forming and core-forming inserts are made as bushes with conical apexes and eccentric channels, which are open in outer surface of protective bush. The inserts are arranged in bush interior and are made of wear-resistant material having hardness decreasing from center to periphery thereof.

EFFECT: increased advancing and mechanical drilling speed due to improved protection of inserts against vertical loads acted on drilling bit during bit lowering and due to prevention of tear-outs and ships during rock drilling.

4 cl, 5 dwg