Self-centering polycrystalline diamond cutting rock bit

A self-centering drill bit for drilling subterranean formations, the drill bit comprising:

• a head portion;
• a number of blades arranged transversely across a surface of the head portion, each blade extending outwardly away from the surface of the head portion;
• a plurality of cutting elements arranged on the blades, at least one of the blades and the cutting elements being arranged on the head portion to permit a portion of the drill bit to transmit a centering force onto a core formed from the formation during drilling operation of the bit;
• a cavity located centrally on the surface of the head portion, the cavity having wall surfaces formed from centrally located adjacent end portions of at least two blades, wherein the cavity extends from substantially flat cavity floor formed from the surface of the head portion to an upper-most surface of the blades forming the cavity wall surface, the cavity having an approximately constant diameter, wherein at least one cutting element disposed on a blade is positioned adjacent an opening to the cavity to form the core from the formation during drilling operation of the bit, wherein the cavity includes at least one wall surface formed from a low friction abrasion resistant material different than remaining wall surface materials, wherein the cavity includes at least one open wall section for removing core particles therefrom, and wherein the centering force is transmitted from the cavity wall surface to an adjacent wall surface of the core to center the drill bit about its rotational axis;
• and
• means included within the cavity for limiting the core formed in the cavity to a predetermined length, the means being static within the cavity.

A self-centering polycrystalline diamond compact drill bit for drilling subterranean formations comprising:

• a bit head having a face portion, a shoulder portion, and a gauge portion;
• a number of cutting blades disposed transversely along the bit head and extending outwardly away from a surface of the bit head;
• a plurality of polycrystalline diamond compact cutting elements disposed on the blades, wherein at least one of the blades and the cutting elements are arranged on the bit head to produce a centering force for transmitting from a portion of the bit head to the formation;
• a cavity centrally located on a surface of the face portion of the bit head, the cavity being adapted to accommodate a core formed from the formation therein, the cavity including wall surfaces formed from adjacent terminal end surfaces of at least two blades, wherein at least one of such wall surface is formed from a low friction abrasion resistant material, and wherein the centering force is transmitted from the wall surface comprising such low friction abrasion resistant material to an adjacent surface of a core disposed in the cavity formed from the formation during drilling operation of the bit;
• and
• a rigid element disposed statically within the cavity for reducing the core portion to a predetermined length, wherein the cavity includes at least one open wall section for removing core particles therefrom.

A self-centering drill bit comprising:

• a bit head having a number of cutting blades disposed on a surface thereof and extending outwardly therefrom, wherein each cutting blade includes a number of cutting elements arranged thereon for engaging a subterranean formation;
• and
• a cavity centrally located on the bit head surface for housing a core portion formed from the formation by action of the cutting elements, the cavity having wall surfaces formed from adjacent terminal ends of at least two blades, a generally flat cavity floor defined by the head surface, at least one open wall section between two blades, and an approximately constant cavity diameter;
• and
• means for limiting the core portion disposed within the cavity to a predetermined length, wherein core particles are removed from the cavity by the open wall sections, wherein at least one of the blades and the cutting elements are arranged on the bit head to form and transmit a centering force to a wall surface of the core portion by the cavity wall surface, and wherein at least one cavity wall surface is formed from a low friction abrasion resistant material.