Raise bit with cutters stepped in a spiral and flywheel

A rotary drill bit for producing a raise hole by disintegrating the earth formation surrounding a preformed pilot hole, such bit being connectible to a rotatably powered drill stem extending through the pilot hole, and comprising:

• a cutter carrier frame structure detachably connectible to the drill stem to rotate therewith;
• central cutter means mounted on said frame structure at a location disposed adjacent the drill stem;
• a plurality of intermediate roller cutters mounted on said frame structure at locations outwardly of said central cutter means, said intermediate roller cutters having peripheral cutting portions projecting upwardly of said frame structure to sweep concentric circles about the longitudinal axis of the drill stem upon rotation of said frame structure, with said intermediate roller cutters arranged on said frame structure so that the profile of the circles swept by said intermediate roller cutters collectively defining a cutting profile on each side of the longitudinal axis of the drill stem in the form of a portion of a spiral, which profile curves radially outwrdly and downwardly from said central cutter means, with the angle separating the two adjacent chords corresponding to a set of any three adjacent cutting profile circles progressively decreasing as the radial distance between said intermediate cutters and the longitudinal axis of the drill stem increases;
• a flywheel assembly;
• step-up means interconnecting the cutter carrier frame structure to said flywheel assembly for driving said flywheel assembly at a speed at least one order of magnitude faster than the rotational speed of said cutter carrier frame structure;
• and
• stabilizer means journaled with said cutter carrier frame structure to transmit reaction torque generated by said step-up means to the wall of the larger diameter raise hole.

A rotary bit for forming a hole in the earth, said bit being connectible to a rotary power source to rotate the bit about a center and simultaneously advance the bit upwardly through the earth to form the hole, said bit comprising:

• a cutter carrier frame structure;
• means for connecting said cutter carrier frame structure to the power source to rotate said frame structure about the bit rotational center;
• and
• a plurality of roller cutters mounted on said frame structure and having peripheral cutting edge portions extending upwardly of said cutter carrier structure to define, upon rotation of said frame structure, an arcuate cutting profile extending radially outwardly and downwardly from the bit rotational center at a decreasing curvature, said arcuate cutting profile being established by tilting radially adjacent roller cutters relative to each other to increase the angle of tilt of the roller cutter axles as the location of the roller cutters from the bit rotational center increases while simultaneously decreasing the relative angle of tilt between the rotational axles of radially adjacent roller cutters as the location of said roller cutters from the rotational center of the bit increases.

In a rock cutting bit for upreaming a pre-existing pilot hole to form a larger diameter hole, including a rotary cutter carrier connectible to the lower end portion of a rotary drill stem suspended from a rotary drilling machine located above the pilot hole, and rock cutting means carried by the cutter carrier and adapted to cut the rock formation surrounding the pilot hole during rotation of the cutter carrier by the drill stem, the improvement comprising:

• a flywheel assembly;
• step-up means drivingly interconnecting the cutter carrier to said flywheel assembly to that rotational drive applied to the cutter carrier by the drill stem drives said flywheel assembly at a rotational speed at least an order of magnitude faster than the rotational speed of the cutter carrier;
• and
• stabilizer means for transmitting reaction torque generated by said step-up means to the wall of the larger diameter hole.

A rotary drill bit connectible to a rotary drill stem for upreaming a pre-existing pilot hole to form a larger diameter hole by cutting the rock formations surrounding the pilot hole during rotation of the drill stem, said drill bit comprising:

• a cutter carrier frame structure connectible to the drill stem to rotate therewith;
• a plurality of roller cutters mounted on said frame structure, said roller cutters having peripheral cutting edges extending upwardly of said frame structure for cutting concentric kerfs about the rotational center of said frame structure upon rotation of the drill stem, with the cutting edges of at least a portion of said roller cutters defining a segment of a downwardly convex, generally spiral shaped profile which decreases in curvature as the radial distance separating said roller cutters from the drill stem increases;
• a flywheel assembly journaled with said cutter carrier frame structure;
• step-up means interconnecting said cutter carrier frame structure and said flywheel assembly for driving said flywheel assembly at a speed at least one order of magnitude faster than the rotational speed of said cutter carrier frame structure;
• and
• stabilizer means journaled with said cutter carrier frame structure to transmit reaction torque generated by said step-up means to the wall of the larger diameter holes.