DRILLING CROWN BIT Russian patent published in 2008 - IPC E21B10/36 

FIELD: mining, particularly rock-cutting tools for rotary-percussion drilling, particularly to drill boreholes and wells in drilling-and-blasting works.

SUBSTANCE: crown bit comprises body with peripheral tooth-like rock-cutting members. Gage cylindrical surface of each tooth is defined by two cylindrical surfaces crossing each other at acute angle and has radius equal to well radius. Working part of teeth has spherical surface with axis shifted towards well center with respect to tooth axis. Distance between spherical surface axis and tooth axis is equal to S=d₃/D_h, where S is the distance in axial direction, d₃ is tooth diameter, D_h is hole diameter.

EFFECT: increased wear-resistance of rock-cutting members adapted to reinforce peripheral crown bit part, increased efficiency of hard abrasive rock drilling.

2 dwg