Abstract:
An earth boring drill bit comprising cones, each cone having rows of inserts, where the inserts are in the form of a pyramid with four sides. The insert includes ridges at the juncture of each adjacent side. The ridges extend to the top of the insert and meet at a crest. Oppositely disposed ridges on the insert lie substantially in the same plane, thereby forming two planes intersecting on the crest. The two planes are substantially perpendicular. The inserts are arranged on the cone such that one plane is substantially parallel with the insert row, and the other is substantially parallel with the cone axis.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/016,243, filed Dec. 21, 2007, the full disclosure of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The disclosure herein relates in general to rolling cone earth boring bits, and in particular to the shape and orientation of compacts used on the cones. 
         [0004]    2. Description of Prior Art 
         [0005]    Drilling systems having earth boring drill bits are used in the oil and gas industry for creating wells drilled into hydrocarbon bearing substrata. Drilling systems typically comprise a drilling rig (not shown) used in conjunction with a rotating drill string wherein the drill bit is disposed on the terminal end of the drill string and used for boring through the subterranean formation. 
         [0006]    Drill bits typically are chosen from one of two types, either drag bits or roller cone bits. Rotating the bit body with the cutting elements on the outer surface of the roller cone body crushes the rock and the cuttings may be washed away with drilling fluid. A rolling cone earth boring bit has a bit body with typically three legs. A bearing pin depends from each leg and a cone mounts rotatably to each bearing pin. The cones have rows of cutting teeth on the outer surface of the cone. In one type, the cutting elements comprise teeth machined into the surface of the cone. In another type, the cutting elements comprise carbide compacts or inserts that are pressed-fitted into mating holes in the cone surface. 
         [0007]    Compacts generally have a cylindrical base that is inserted into a hole and a protruding cutting tip. The cutting tips may have chisel, hemispherical, ovoid or other shapes. Particularly on the heel row, which is located near the gage surface of each cone, the compacts may have asymmetrical shoulder surfaces for engaging the sidewall of the bore hole. Depending upon the formation being drilled, different shapes are utilized for aggressiveness of cutting and durability. 
         [0008]    One example of a roller cone bit is provided in side view in  FIG. 1 , which illustrates a bit  11  having a body  13  with a leg  15 . Roller cone bits typically comprise three legs  15 . A cone  17  rotatably mounts to a bearing pin (not shown) of each leg  15 . Each cone  17  has a plurality of inserts  19 , arranged in at least one inner row. A plurality of outer or heel row compacts  21  are adjacent to a gage surface  23  of each cone  17 . In the embodiment shown, heel row compacts  21  are generally ovoid, although different shapes could be used. 
       SUMMARY OF INVENTION 
       [0009]    Disclosed herein is an earth boring drill bit having a roller cone with cutting inserts on the outer surface of the roller cone. The inserts comprise a generally circular base and a peal. The sides of the inserts comprise four faces that extend from the base to the peak. Each face has a generally triangular configuration wherein a portion of its surface is generally planar. The region where adjacent sides join is rounded thereby defining ridges. The four substantially similar sides form four ridges that meet at the crest. A first set of two ridges form on opposite sides of the base with respect to one another and are substantially parallel. A second set of two ridges also form on opposite sides with respect to one another and are also parallel. The inserts are oriented on the cone in rows so that the first set of ridges is aligned with the cone axis and the second set of ridges is aligned with the row. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a side perspective view of a roller cone bit. 
           [0012]      FIG. 2  provides a bottom view of a roller cone bit having shaped inserts. 
           [0013]      FIG. 3  is an overhead view of an insert for a roller cone bit. 
           [0014]      FIG. 4  shows a side view of a roller cone bit having an embodiment of inserts of the present disclosure. 
           [0015]      FIG. 5  illustrates in a perspective view a roller cone bit having embodiment of an insert of the present disclosure. 
           [0016]      FIGS. 6-8  depict examples of insert embodiments. 
       
    
    
       [0017]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0018]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0019]    A bottom view of an embodiment of an earth boring bit  30  is provided in  FIG. 2 . The bit  30  comprises three cutter cones  32  wherein each cone includes rows of inserts formed thereon. The outermost or heel row is formed on the heel surface  34  and includes heel row teeth  36 . As shown, the heel row teeth  36  have a generally hemispherical configuration. Inner rows  40 ,  42  are formed on each cone between the heel row and the nose of each cone  32 . The inner row  40  includes inserts  46  disposed on its outer surface. The inner row  42  proximate to the nose of the cone  32  also includes inserts  44 . In the embodiment shown, the inserts  44 ,  46  resemble a four sided pyramid. 
         [0020]      FIG. 3  provides an overhead view of an example of a pyramid shaped insert  52 . As shown, the insert  52  has a generally circular base  53  with its sides  54  extending upward towards a crest  58 . Each side  54  may have substantially the same dimension. The surface  55  of each side  54  can be generally planar, include contours, or have both planar and contoured portions. The respective surfaces  55  of adjacent sides are depicted as being angled roughly 90° to one another. The sides  54  join each adjacent side along a rounded ridge  56 , the ridge  56  extends from the base  53  and terminates at the crest  58 . Here, the circular base  53  is shown with each side  54  (also referred to herein as a face) extending upward in a generally triangular fashion and terminating at the crest  58 . The insert surface  55  is curved where the adjacent sides  54  meet thereby giving the ridge  56  a curved cross section. Other embodiments exist wherein the ridge  56  cross section is defined by the sides  54  intersecting at an angle. 
         [0021]      FIG. 4 , which illustrates a portion of a cone  60  in side view, provides some examples of the orientation of the inserts on the face of the cone. The cone  60  also comprises a lower row  67  with inserts  68 . The lower row  67  of inserts  68  circumscribes the axis A of the cone  60  and is disposed proximate to the heel row  62 . With reference now to the inserts  68  in the lower row  67 , each insert  68  has a first set of ridges running parallel to the row  67 . The ridges in this first set are referred to as the linear ridge  70 . A reference line L has been provided illustrating the row path. Similarly, a second set of ridges on the insert  68  extend substantially parallel with the axis A of the cone  60  and roughly perpendicular to the reference line L. This second set of ridges is referred to here as the axial ridge  72 . The axis A is provided in dashed outline for reference. Also in the embodiment of  FIG. 4 , the inserts  76  disposed on an upper row  74  also include a first and second set of ridges, wherein one set of ridges runs generally parallel with the line defining the path of the upper row  74 , and the other set of ridges on the insert  76  runs generally parallel with the axis of the cone  60 . In an embodiment of a roller cone bit described herein, the inserts on a cone of a roller cone bit comprise four sided pyramid shaped inserts with one set of ridges running generally parallel to its respective row and the other set of ridges running generally parallel with the axis of the cone. For the purposes of discussion herein, generally parallel includes an alignment of up to about 15° from parallel. Additionally, the line defining the path of the upper row  74  coincides with the rotational path of the associated roller cone. 
         [0022]    Aligning the ridges as described herein opens the insert face towards grooves or open space on the cone surface. As the insert penetrates the displaced material, the material is mechanically pushed into the open space and not trapped between adjacent inserts. The material trapped between conventional inserts, such as axially aligned chisels, may cause balling in shale thereby impeding its penetration rate. The axially and circumferentially aligned pyramid inserts also have a more streamlined shape allowing them to better withstand the sliding induced by cone offset and non-true-rolling cone geometry. Additionally, durability is enhanced with the disclosed cutting structure. Optionally, this advantageous result of the pyramid shape may be enhanced by strategically placed grooving between inserts to further enhance material flow. Moreover, inserts disposed proximate to the heel area may comprise a three sided pyramid due to the difficulty of displacement of material toward the gage of the bit. 
         [0023]    A schematic drawing of a side view of an embodiment of a cone cutter  32   a  is provided in  FIG. 5 . The cutter cone  32   a  includes an outer heel surface  34   a  on which are formed heel row teeth  36   a . As shown, the heel row teeth  36   a  are generally hemispherical in shape, but can have other shapes as well. Also included is an adjacent heel row  48  having a pyramid shaped insert  50 . The insert  50  also includes an upward and downward ridge substantially aligned with the adjacent heel row  48  and a corresponding perpendicular ridge substantially parallel to the axis of the cutter cone  32   a . Inner rows  40   a ,  42   a  are shown coaxially disposed between the adjacent heel row  48  and the nose of the cone  32   a . Corresponding inserts  44   a ,  46   a  are provided on these inner rows. As shown, the inserts  44   a ,  46   a  also have ridges that are aligned with their corresponding row as well as aligned with the axis of the cone  32   a.    
         [0024]    Alternative insert embodiments are provided in  FIGS. 6 through 8 . In  FIG. 6 , an insert  80  is shown in perspective view having a first ridge  81  formed on the insert  80  upper surface. A second ridge  82 , also on the insert  80  upper surface, intersects the first ridge  81  proximate the crest or uppermost portion of the insert  80 . In this embodiment the insert  80  is asymmetric, thus the first and second ridges have different lengths. 
         [0025]    In  FIG. 7 , an insert  83  shown in perspective view includes first and second ridges  84 ,  85  on its upper surface. Faces  86  are on the upper surface disposed between adjacent ridges  84 ,  85  extending between the insert  83  base and its upper crest. The adjacent faces  86  join at an angle to define a ridges  84 ,  85  having a cross section with an angled edge. Although shown as a rectangular base, circular and rounded base configurations exist. 
         [0026]    The insert  87  in  FIG. 8  includes a leading side  88  and a trailing side  93 . In this embodiment the leading side  88  is oriented to first contact the excavated material. The insert  87  includes a first ridge  89  aligned generally perpendicular to the cone direction of rotation. The first ridge  89  extends over a substantial portion of the insert  87  outer surface. Also included is a second ridge  90  that is generally aligned with or parallel to the cone rotational direction. The second ridge  90  is shown extending from the insert  87  base, along the leading side  88 , and terminating at the first ridge  89 . Faces  91 ,  92  are on the leading side  88  between the first ridge  89  and second ridge  90 . The faces  91 ,  92  may be planar or have a curved surface. However, the second ridge  90  should protrude outward from the leading side  88  so as to first penetrate formation. The sloping surfaces of the faces  91 ,  92  direct the displaced material outward and away from the next following insert. In the embodiment of  FIG. 8 , the trailing side  93  is shown having a consistent surface absent ridges or other contours. Accordingly, the present disclosure includes inserts whose a shaped surface is only on the leading side that performs a majority of the cutting or excavating action. 
         [0027]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the scope of this disclosure includes roller cone bits having different numbers of roller cones as well as inserts comprising pyramids having other than four sides. Additionally, the ridges&#39; intersection is not limited to the embodiments disclosed, but can include intersections on the insert having a large range of radii, including an intersection forming a point on the insert crest. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.