CROWN DRILLING BIT Russian patent published in 2008 - IPC E21B10/48 

FIELD: machine building.

SUBSTANCE: invention relates to rock destructing tools, namely, to crown drilling bits reinforced by synthetic diamonds designed for drilling with extracting cores. The crown bit includes a casing and a matrix divided by the flushing slots into separate sectors furnished with well-forming, central and core-forming superhard inserts and protective elements. Note here that well-forming and core-forming inserts are set up with a negative angle of inclination and with an advance in height relative to the central inserts. Mind that wear resistance of the central inserts W_c, well-forming inserts W_w and core-forming inserts W_cr are interrelated by the following ratio, i.e. W_c:W_cr:W_w = 1:(1.10-1.20):(1.25-1.35). The central inserts, depending upon physical and mechanical properties of bored rocks, can be arranged on both the sector front edge and shifted from the said edge but with an advance relative the well-forming and core-forming inserts in direction of rotation.

EFFECT: higher efficiency of crown bit operation.

3 cl, 4 dwg