Soft formation insert bits

Claim 2

A rotary drill bit for forming a well bore or the like, said bit comprising: a bit body having an axis of rotation, an upper end connectable with a drill string for rotating said bit, and three downwardly projecting arms, each said arm including an inwardly and downwardly inclined shaft defining an axis of cutter rotation, none of said axes intersecting any other of said axes; first, second and third cutter members of generally conical configuration, each of said cutter members being journaled on a respective one of said shafts and having a nose and a base, said base being oriented generally toward the wall of the well bore; and, a plurality of outwardly projecting, circumferentially-spaced inserts located in annular rows in each said cutter member for engaging the bottom of the well bore with the inserts of at least one annular row of each cutter member projecting from the surface of the respective cutter member a minimum of one-fourth of an inch.

Claim 3

The drill bit of claim 1 wherein said inserts projecting at least one-fourth of an inch have a wedge-shaped exposed end portion.

Claim 4

The drill bit of claim 1 wherein the inserts of at least one annular row of each cutter member project from the surface of the respective cutter member between one-fourth and nine-sixteenth of an inch.

Claim 5

A rotary drill bit for forming a well bore or the like, said bit comprising: a bit body having an axis of rotation, an upper end connectable with a drill string for rotating said bit, and three downwardly projecting arms, each said arm including an inwardly and downwardly inclined shaft defining an axis of cutter rotation, none of said axes intersecting any other of said axes; first, second and third cutter members of generally conical configuration, each of said cutter members being journaled on a respective one of said shafts and having a nose and a base, said base being oriented generally toward the wall of the well bore; and, a plurality of outwardly projecting, circumferentially-spaced inserts located in annular rows in each said cutter member for engaging the bottom of the well bore, wherein at least one of said annular rows of inserts is mounted in each said cutter member between said nose and base defining an intermediate row in each said cutter member, said intermediate rows being located on said cutter members at a different radial distance from said bit axis of rotation by more than the thickness of one of said intermediate row inserts, said radial distance being measured perpendicularly to and from a common point on said bit axis of rotation to each of said intermediate rows with the net surface area between said intermediate rows on said cutter members being between six and thirteen per cent of the total surface area between the nose and base of all of said cutter members.

Claim 6

A rotary drill bit for forming a well bore or the like, said bit comprising: a bit body having an axis of rotation, an upper end connectable with a drill string for rotating said bit, and three downwardly projecting arms, each said arm including an inwardly and downwardly inclined shaft defining an axis of cutter rotation, none of said axes intersecting any other of said axes; first, second and third cutter members of generally conical configuration, each of said cutter members being journaled on a respective one of said shafts and having a nose and a base, said base being oriented generally toward the wall of the well bore; and, a plurality of outwardly projecting, circumferentially-spaced inserts located in annular rows in each said cutter member for engaging the bottom of the well bore, wherein at least one of said annular rows of inserts is mounted in each said cutter member between said nose and base defining an intermediate row in each said cutter member, said intermediate rows being located on said cutter members at a different radial distance from said bit axis of rotation by more than the thickness of one of said intermediate row inserts, said radial distance being measured perpendicularly to and from a common point on said bit axis of rotation to each of said intermediate rows with the net surface area between said intermediate rows on said cutter members being between six and thirteen per cent of the total surface area between the nose and base of all of said cutter members.

Claim 7

The drill bit of claim 4 wherein the inserts in said intermediate rows project from the surface of said cutter members by at least one-fourth of an inch.

Claim 8

The drill bit of claim 5 wherein the projecting end portion of each of said intermediate row inserts is wedge-shaped.

Claim 9

A rotary drill bit for forming a well bore or the like, said bit comprising: a bit body having an axis of rotation, an upper end connectable with a drill string for rotating said bit, and three downwardly projecting arms, each said arm including an inwardly and downwardly inclined shaft defining an axis of cutter rotation, none of said axes intersecting any other of said axes; first, second and third cutter members of generally conical configuration, each of said cutter members being journaled on a respective one of said shafts and having a nose and a base, said base being oriented generally toward the wall of the well bore; a plurality of outwardly projecting, circumfentially-spaced inserts located in annular rows in each said cutter member for engaging the bottom of the well bore; The annular rows of inserts in said first cutter member include an intermediate row disposed between a nose insert and a row of gage inserts that are located adjacent said base with said intermediate row inserts projecting from the surface of said cutter member between one-fourth and nine-sixteenths of an inch and at least a portion of said intermediate row inserts having a wedge-shaped, exposed end portion; the annular rows of inserts in said second cutter member include an intermediate row disposed between a row of nose inserts and a row of gage inserts, the intermediate row in said second cutter member being spaced from a said bit axis of rotation by a greater distance than said intermediate row in said first cutter member by at least the thickness of one of said intermediate row inserts with said intermediate row inserts projecting from the surface of said cutter member between one-fourth and nine-sixteenths of an inch and at least a portion of said intermediate row inserts having a wedge-shaped, exposed end portion; and, the annular rows of inserts in said third cutter member include first and second intermediate rows disposed between the nose of said cutter member and a row of gage inserts, one of said intermediate rows in said third cutter member being spaced from said bit axis of rotation by a distance less than the intermediate row in said first cutter member by at least the thickness of one of said intermediate row inserts with said intermediate row inserts projecting from the surface of said cutter member between one-fourth and nine-sixteenths of an inch and at least a portion of said intermediate row inserts having a wedge-shaped, exposed end portion, whereby one or more annular portions of the well bore bottom are not subjected to the downward impression of inserts thereon.

Claim 10

A rotary drill bit for forming a well bore or the like, said bit comprising: a bit body having an axis of rotation, an upper end connectable with a drill string for rotating said bit, and three downwardly projecting arms, each said arm including an inwardly and downwardly inclined shaft defining an axis of cutter rotation, none of said axes intersecting any other of said axes; first, second and third cutter members of generally conical configuration, each of said cutter members being journaled on a respective one of said shafts and having a nose and a base, said base being oriented generally toward the wall of the well bore; a plurality of outwardly projecting, circumfentially-spaced inserts located in annular rows in each said cutter member for engaging the bottom of the well bore; The annular rows of inserts in said first cutter member include an intermediate row disposed between a nose insert and a row of gage inserts that are located adjacent said base with said intermediate row inserts projecting from the surface of said cutter member between one-fourth and nine-sixteenths of an inch and at least a portion of said intermediate row inserts having a wedge-shaped, exposed end portion; the annular rows of inserts in said second cutter member include an intermediate row disposed between a row of nose inserts and a row of gage inserts, the intermediate row in said second cutter member being spaced from a said bit axis of rotation by a greater distance than said intermediate row in said first cutter member by at least the thickness of one of said intermediate row inserts with said intermediate row inserts projecting from the surface of said cutter member between one-fourth and nine-sixteenths of an inch and at least a portion of said intermediate row inserts having a wedge-shaped, exposed end portion; and, the annular rows of inserts in said third cutter member include first and second intermediate rows disposed between the nose of said cutter member and a row of gage inserts, one of said intermediate rows in said third cutter member being spaced from said bit axis of rotation by a distance less than the intermediate row in said first cutter member by at least the thickness of one of said intermediate row inserts with said intermediate row inserts projecting from the surface of said cutter member between one-fourth and nine-sixteenths of an inch and at least a portion of said intermediate row inserts having a wedge-shaped, exposed end portion, whereby one or more annular portions of the well bore bottom are not subjected to the downward impression of inserts thereon.

Claim 11

The drill bit of claim 7 wherein the net surface area between said intermediate rows on said cutter member is between six and thirteen per cent of the total surface area between the nose and base of all of said cutter members.