Rotary cone drill bit with truncated rolling cone cutters and dome area cutter inserts

A rotary cone drill bit having a rotatable bit body and at least two support arms extending therefrom, said support arms defining a dome area below said bit body, comprising:

• at least two truncated conical cutter assemblies rotatably coupled to said support arms and each rotatable about a respective axis directed downwardly and inwardly, said truncated conical cutter assemblies being conical frustums in shape having a back face connected to a flat truncated face by conical sides, said back face and said truncated face having a predetermined angled relationship;
• a plurality of primary cutting elements arranged in a predetermined pattern and coupled to said flat truncated face of said truncated conical cutter assemblies, said plurality of cutting elements of each cutter assembly being in spaced relationship with respect to cutting elements of other cutter assemblies;
• and
• a plurality of secondary cutting elements mounted in downward facing surfaces of said dome area of said bit body and rotating therewith, and wherein said plurality of secondary cutting elements are doughnut-shaped ultra-hard inserts mounted on nubs formed in dome area surfaces of said bit body.

An earth-boring drill bit cutter assembly, comprising:

• a frusto-conical body having a back face connected to a substantially flat truncated face by conical sides;
• a plurality of cutter elements arranged in rows and disposed on said conical sides;
• a plurality of nubs protruding from said substantially flat truncated face;
• and
• a plurality of doughnut-shaped inserts bonded to said nubs.

A method for manufacturing a rotary cone drill bit having a bit body and a predetermined number of support arms depending therefrom forming a dome area under said bit body, comprising the steps of:

• forming the same predetermined number of truncated conical cutter assemblies, each cutter assemblies being frusto-conical in shape having a back face connected to a substantially flat truncated face by conical sides, said cutter assemblies being adapted to rotate about respective rotational axes thereof in spaced relation with one another;
• bonding a plurality of cutter inserts to said flat truncated face of said cutter assemblies;
• and
• bonding a plurality of cutter inserts to downward facing surfaces of said dome area;
• and
• wherein said cutter insert bonding to said flat truncated face step further comprises the steps of:
• forming a plurality of protruding nubs on said flat truncated face of said cutter assemblies;
• and
• bonding a plurality of doughnut-shaped cutter inserts to said nubs and surrounding surface areas.

A method for manufacturing a rotary cone drill bit having a bit body and a predetermined number of support arms depending therefrom forming a dome area under said bit body, comprising the steps of:

• forming the same predetermined number of truncated conical cutter assemblies, each cutter assemblies being frusto-conical in shape having a back face connected to a substantially flat truncated face by conical sides, said cutter assemblies being adapted to rotate about respective rotational axes thereof in spaced relation with one another;
• bonding a plurality of cutter inserts to said flat truncated face of said cutter assemblies;
• and
• bonding a plurality of cutter inserts to downward facing surfaces of said dome area;
• and
• wherein said cutter insert bonding to said dome area step further comprises the steps of:
• forming a plurality of protruding nubs on said downward facing surfaces, of said dome area;
• and
• bonding a plurality of doughnut-shaped cutter inserts to said nubs and surrounding surface areas.

A rotary cone drill bit having a rotatable bit body and at least two support arms extending therefrom comprising:

• at least two truncated conical cutter assemblies rotatably coupled to said support arms and each rotatable about a respective axis directed downwardly and inwardly, said truncated conical cutter assemblies being conical frustums in shape having a back face connected to a flat truncated face by conical sides, said back face and said truncated face having a predetermined angled relationship;
• said truncated conical cutter assemblies being spatially located to form a core in the center section of the borehole;
• a plurality of cutting elements arranged in a predetermined pattern and coupled to said flat truncated face of said truncated conical cutter assemblies, said plurality of cutting elements of each cutter assembly being in spaced relationship with respect to cutting elements of other cutter assemblies;
• and
• said plurality of cutting elements are doughnut-shaped ultra-hard inserts mounted on nubs formed in said flat truncated face of said cutter assembly.