Rotary percussion earth boring bit

Abstract

Disclosed herein is a rotary-percussion earth boring bit that has an improved geometric configuration to extend cutting insert life and reduce cutting insert breakage. The bottom surface contains a flat transverse face with a bevelled edge. Two rows of circumferentially spaced cutting inserts protrude from the bevel. One of the rows is spaced inwardly from an outer row to define an inner row, which has inserts positioned between the circumferentially spaced inserts of the outer row. The longitudinal axes of these inserts are substantially perpendicular to the bevel and inclined outward at an acute angle to the axis of rotation of the bit. A generally longitudinally extending groove is formed between each two adjacent inserts of the outer row. This arrangement produces a symmetry that tends to minimize the number of reflective surfaces. This equalizes the stresses generated by the impact induced shock waves transmitted through the bit.

I claim: 
     
       1. An improved geometric configuration for a rotary-percussion earth-boring bit that includes a body having torque transmission means on an upper region, an anvil upper surface and an enlarged lower region with a transverse face containing button type inserts, the improvement comprising: a bevel formed at the corner between the transverse face and the enlarged lower region;   an outer row of circumferentially spaced inserts protruding from said bevel;   an inner row of circumferentially spaced inserts located inwardly wholly on said bevel and between the circumferentially spaced inserts of the outer row;   the inserts of the inner and outer rows having longitudinal axes that are substantially normal to the bevel.   
     
     
       2. An improved geometric configuration for a rotary-percussion earth-boring bit that includes a body having torque transmission means on an upper region, an anvil upper surface and an enlarged lower region with a transverse face containing button type inserts, the improvement comprising: a bevel formed at the corner between the transverse face and the enlarged lower region;   an outer row of circumferentially spaced inserts protruding from said bevel;   an inner row of circumferentially spaced inserts located inwardly on said bevel and between the circumferentially spaced inserts of the outer row;   the inserts of the inner and outer rows having longitudinal axes that are substantially normal to the bevel;   a longitudinally extending groove formed in the enlarged lower region between each two adjacent circumferentially spaced inserts of the outer row.   
     
     
       3. An improved geometric configuration for a rotary-percussion earth-boring bit that includes a body having torque transmission means on an upper region, an anvil upper surface and an enlarged lower region with a transverse face containing button type inserts, the improvement comprising: a frusto-conical bevel formed at the corner between the transverse face and the enlarged lower region;   an outer row of circumferentially and substantially .Iadd.equally .Iaddend.spaced inserts protruding from said bevel;   an inner row of circumferentially .[.and substantially equally.]. spaced inserts located inwardly wholly on said bevel and between the circumferentially spaced inserts of the outer row;   the inserts of the inner and outer rows having longitudinal axes that are substantially perpendicular to the bevel.   
     
     
       4. An improved geometric configuration for a rotary-percussion earth-boring bit that includes a body having torque transmission means on an upper region, an anvil upper surface and an enlarged lower region with a transverse face containing button type inserts, the improvement comprising: a frusto-conical bevel formed at the corner between the transverse face and the enlarged lower region;   an outer row of circumferentially and substantially .Iadd.equally .Iaddend.spaced inserts protruding from said bevel;   an inner row of circumferentially .[.and substantially equally.]. spaced inserts located inwardly on said bevel and between the circumferentially spaced inserts of the outer row;   the inserts of the inner and outer rows having longitudinal axes that are substantially perpendicular to the bevel;   a longitudinally extending groove formed in the enlarged lower region between each of the inserts of the outer row.