Earth-boring tools including cutting element profiles configured to reduce work rates

Abstract

Earth-boring tools may include a body including blades projecting therefrom, an axis of rotation, and cutting elements secured to the blades. A profile of the cutting elements intersecting outermost points of cutting faces of the cutting elements as viewed projected rotationally onto a plane may be parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 0°. In other embodiments, a first section of the profile may extend at a first slope, and a second section of the profile may extend at a second, different slope. In still other embodiments, a tangent line to the profile may be oriented at an angle of at least 15° at a location proximate to the axis of rotation.

What is claimed is: 
     
         1 . An earth-boring tool comprising:
 a body comprising blades projecting therefrom, the blades extending generally radially outwardly from an axis of rotation of the tool; and   cutting elements secured to the blades;   wherein a profile of the cutting elements secured to the blades intersecting outermost points of cutting faces of the cutting elements as viewed projected rotationally onto a plane, within which an axis of rotation of the body is located, is parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 0°.   
     
     
         2 . The earth-boring tool of  claim 1 , wherein a slope of the profile proximate to the axis of rotation of the body is such that an angle between the profile and a plane perpendicular to the axis of rotation is at least about 15°. 
     
     
         3 . The earth-boring tool of  claim 1 , wherein a slope of the profile proximate to the axis of rotation of the body is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 35° or less. 
     
     
         4 . The earth-boring tool of  claim 1 , wherein the nose point is located at least one-half of a radius of the body from the axis of rotation. 
     
     
         5 . The earth-boring tool of  claim 1 , wherein the nose point is located at less than three-fourths of a radius of the body from the axis of rotation. 
     
     
         6 . The earth-boring tool of  claim 1 , wherein surfaces of the blades as projected onto the plane perpendicular to the direction of rotation of the blades comprise a plurality of line segments, each line segment extending tangent to a parabolic curve extending from proximate to the axis of rotation to proximate to the nose point. 
     
     
         7 . The earth-boring tool of  claim 6 , wherein a number of the line segments is at least five. 
     
     
         8 . An earth-boring tool comprising:
 a body comprising blades extending outward from a remainder of the body; and   cutting elements secured to the blades;   wherein a first section of a profile of a face formed by a least squares fit to outermost points of cutting faces of the cutting elements secured to the blades as viewed projected rotationally onto a plane, within which plane an axis of rotation of the body is located, may be linear and may extend at a first slope relative to a plane perpendicular to the axis of rotation of the body from proximate to the axis of rotation of the body radially outward;   wherein a second section of the profile of the face surrounding and extending radially outward from the first section may be linear and may extend at a second, different slope relative to the plane perpendicular to the axis of rotation of the body; and   wherein a third section of the profile may be located radially outward from the second section, the third section arcing from the second slope away from a leading end of the body.   
     
     
         9 . The earth-boring tool of  claim 8 , wherein the first slope is two to four times as great as the second slope relative to the plane perpendicular to the axis of rotation of the body. 
     
     
         10 . The earth-boring tool of  claim 8 , wherein the first slope is such that an angle between the first section and a plane perpendicular to the axis of rotation is between about 10° and about 35° relative to the plane perpendicular to an axis of rotation of the body. 
     
     
         11 . The earth-boring tool of  claim 8 , wherein the second slope is such that an angle between the second section and a plane perpendicular to the axis of rotation is between about 10° and about 20° relative to the plane perpendicular to the axis of rotation of the body. 
     
     
         12 . The earth-boring tool of  claim 8 , wherein a transition between the first slope and the second slope occurs a radial distance at least about one-half of a radial distance occupied by the first and second slopes. 
     
     
         13 . The earth-boring tool of  claim 8 , wherein a transition between the first slope and the second slope occurs a radial distance less than about three-fourths of a radial distance occupied by the first and second slopes. 
     
     
         14 . An earth-boring tool comprising:
 a body comprising blades extending outward from a remainder of the body; and   cutting elements secured to the blades;   wherein a profile formed by a least squares fit to outermost points of cutting faces of the cutting elements secured is oriented at an angle of at least 15° relative to a plane perpendicular to an axis of rotation of the body at a location proximate to an axis of rotation of the body.   
     
     
         15 . The earth-boring tool of  claim 14 , the profile is oriented at an angle of about 30° or less relative to the plane perpendicular to the axis of rotation at the location proximate to the axis of rotation. 
     
     
         16 . The earth-boring tool of  claim 14 , wherein the profile is parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between a line tangent to the profile and a plane perpendicular to the axis of rotation is about 0°. 
     
     
         17 . The earth-boring tool of  claim 16 , wherein the nose point is located at least one-half of a radius of the body from the axis of rotation. 
     
     
         18 . The earth-boring tool of  claim 16 , wherein the nose point is located at less than three-fourths of a radius of the body from the axis of rotation. 
     
     
         19 . The earth-boring tool of  claim 14 , wherein surfaces of the blades as projected onto a plane perpendicular to a direction of rotation of the blades comprise a plurality of line segments, each line segment extending tangent to a parabolic curve extending from proximate to the axis of rotation to proximate to the nose point. 
     
     
         20 . The earth-boring tool of  claim 19 , wherein a number of the line segments is at least five.