BODY STRUCTURE AND NOZZLE FOR ENHANCING THE FLOW OF DRILLING FLUID IN A ROTARY DRILL BIT

摘要

A rotary drill bit for drilling a bore hole in the surface of the earth is provided in which the drill bit comprises a body having a duct therethrough for carrying drilling fluid. A conical cutting head having an axis at an acute angle with respect to the axis of the drill bit is mounted in the cutting head. An elongated nozzle is positioned at the end of the duct for injecting the drilling fluid into the bore hole. The nozzle has an opening which opens into the bore hole wherein the longitudinal center line of the opening follows the locus of the mid-point between the side wall of the bore hole and the outermost circumference of the cutting head. Drilling fluid injected through the nozzle removes detritus from between the teeth and the cutting head at the bottom of the bore hole. The body of the drill bit has a first portion having a truncated conical surface with the axis of the truncated cone coinciding with the axis of the cutting head. The surface of the truncated cone is tangent to the side surface of the bore hole at a line on the opposite side of the body from the nozzle. This forms a passage between the surface of the truncated cone and the side surface of the bore hole for the upward flow of drilling fluid and detritus.