DIAMOND SETTING IN A CUTTING TOOTH IN A DRILL BIT WITH AN INCREASED EFFECTIVE DIAMOND WIDTH

Abstract: A diamond cutting tooth (26, 28, 30) (= A) for use in a petroleum drag bit (10) is provided with an extended and expanded effective diamond cutting surface by providing a linear sequence of triangular prismatic, synthetic, polycrys­ talline, diamond cutting elements (32, 36, 38, 40) generally along the line of direction of cutting within each tooth (A). Each element (36, 38, 40) is offset from the preceding element in the sequence in a direction nonparallel to the line of cutting. More particularly, equilateral triangular prismatic diamond elements (36, 38, 40) are laid within a V-shaped groove (44a, 44b) within a mold (42) from which the cutting tooth (A) is molded through conventional infiltration matrix techniques. The apical opening of the groove (44a, 44b) is 70 degrees, wheras the apical extent of each of the triangular apexes is 60 degrees. Each triangular element (36, 38, 40) is laid on one side or other of the longitudinal groove (44a, 44b). Matrix metal or binder is filled in the groove (44a, 44b) between the diamond elements (36, 38, 40) thus forming a diamond cutting tooth (A) having an effective apical dihedral angle of 70 degrees while using only 60-degree triangular pismatic elements (36, 38, 40). Worn triangular prismatic elements (36, 38, 40) can be particularly adapted to this tooth structure by orienting at least one worn portion of each triangular element (36, 38, 40) oriented toward the interior of the tooth (A) with the remaining unworn point or points disposed nearest the exterior of the cutting tooth (A).

Description: The present invention relates to a cutting tooth for use in a drill bit of the kind referred to the pre-caracterizing portion of claim 1 and to a method for fabricating a cutting tooth for a drill bit as set forth in the pre-characterizing portion of claim 11. A known cutting tooth (BE-A-901 037) comprises three cutting elements disposed in the body in a double row configuration. A first row of elements including two radially spaced elements is succeeded by a second row or trailing element which is placed halfway of the spacing of the leading elements. By this disposition both leading elements partly overlap with the trailing element to provide a uniform annular swath cut into the rock formation as the bit rotates. What is needed is a compact tooth structure and a method for fabricating a cutting tooth with an effectively larger cutting element width overcoming the limitations of the size of thermally stable diamond elements. The invention is a cutting tooth as characterized in claim 1 and a method as characterized in claim 11. Further embodiments of the cutting tooth are characterized in claims 2 to 10 and of the method in claims 12 and 13. By reason of this structure an increased effective area is provided, even by using elements having a worn portion which may be oriented toward the interior of the tooth and disposed within the overlapping extent of at least two adjacent elements. Figure 1 is a schematic plan diagram of a petroleum drag bit incorporating the invention. Figure 2 is a simplified diagram in perspective view, shown in enlarged scale, of diamond elements laid within a mold indentation in which the teeth illustrated in plan view in Figure 1 are manufactured. Figure 3 is a front elevational view of Figure 2. Figure 4 is a perspective view of the completed tooth structure manufactured from the mold setting as depicted in Figures 2 and 3. Figures 5a - 5e are diagrammatic views of new and used portions of triangular prismatic diamond cutting elements defining the type of used diamond. Figure 6 is a front elevational view of a two-point mold setting. Figure 7 is front elevational view of a one-point mold setting. Figure 8 is a perspective view of a two-point used diamond elements in a mold setting used to manufacture teeth such as shown in Figure 1. Figure 9 is a cross-sectional view of a diagrammatic mold setting used for gage protection. Figure 10 is a diagrammatic cross-sectional view of diamonds set in a mold for manufacture of gage protection teeth. Figure 11 is a plan elevational view of a mold setting of the teeth of Figures 9 and 10 arranged to provide gage protection. The invention and its various elements may be better understood by now turning to the following detailed description. The invention is a method and structure for increasing the effective diamond exposure of a diamond cutting tooth on a drag bit which comprises the steps of setting a plurality of diamond elements one behind each other with respect to the direction of cutting so that each of the elements is angularly or spatially offset with respect to the preceding element in order to present a portion of the diamond element in a nonoverlapping relationship with the adjacent diamond elements. What results is a tooth structure with an effectively wider or larger diamond width available for cutting than would otherwise be possible. Moreover, the method of the invention is particularly adapted to fabricating effective cutting teeth through the use of used diamond elements without any substantial penalty resulting from the employment of used diamond elements. A diamond cutting tooth for use in a petroleum drag bit is provided with an extended and expanded effective diamond cutting surface by providing a linear sequence of triangular prismatic, synthetic, polycrystalline, diamond cutting elements generally along the line of direction of cutting within each tooth. Each element is offset from the preceding element in the sequence in a direction nonparallel to the line of cutting. More particularly, equilateral triangular prismatic diamond elements are laid within a V-shaped groove within a mold from which the cutting tooth is molded through conventional infiltration matrix techniques. The apical opening of the groove is 70 degrees, whereas the apical extent of each of the triangular apexes is 60 degrees. Each triangular element is laid on one side or other of the longitudinal groove. Matrix metal or binder is filled in the groove between the diamond elements thus forming a diamond cutting tooth having an effective apical dihedral angle of 70 degrees while using only 60-degree triangular prismatic elements. Worn triangular prismatic elements can be particularly adapted to this tooth structure by orienting at least one worn portion of each triangular element oriented toward the interior of the tooth with the remaining unworn point or points disposed nearest the exterior of the cutting tooth. Turn specifically to Figure 1. Figure 1 is a plan view of a coring bit 10 characterized by an outer gage 12 and inner gage 14. Between gages 12 and 14 is a crown or face 16 of bit 10 through which a plurality of waterways 18 are defined. Between waterways 18 is a core segment, generally denoted by reference numeral 20. In the illustrated embodiment each segment 20 includes a collector 22 which generally divides segment 20 into equal halves. Each half forms a portion of the bit surface which appears in the plan view of Figure 1 as a V-shaped segment with the apex at inner gage 14. Bit surface 16, defined by each segment 20, carries a plurality of cutting teeth of which only four are depicted in Figure 1, namely teeth 24 - 30. Each tooth includes a plurality of diamond cutting elements 32, which in the present embodiment are triangular prismatic elements manufactured by General Electric Company under the trademark, GEOSET. The structure of the teeth and their method of manufacture will be described in greater detail below. Certain ones of the segments 20 fully extend to outer gage 12 while other ones of the segments terminate within a conventional junk slot 34. Each tooth 24-30 forms an elongated tooth with a longitudinal axis lying approximately on a constant radius of bit 10 and spanning a predetermined azimuthal angle. Turn now to the perspective illustration of Figure 2 which illustrates one of the teeth of Figure 1, for example tooth 30, in enlarged scale as would be seen in a mold from which tooth 30 would be manufactured. The tooth as seen in Figure 2 is inverted when viewed in its mold setting as compared to the plan view of Figure 1 of the completed bit. Tooth 30 includes three triangular prismatic diamond elements 36-40. Each element 36-40 is disposed within a mold cavity 42. In the illustrated embodiment, diamond elements 36-40 are equilateral triangular prismatic elements and thus have opposing triangular end-faces characterized by three 60-degree corners. The side edges of each element 36-40 thus form 60-degree dihedral angles. Mold cavity 42 is formed with the use of an end mill having a 70-degree conical point. In other words, the dihedral angle defined by the opposing lateral surfaces 44a and 44b of cavity 42 from a dihedral angle in the illustrated embodiment of 70 degrees. Therefore, according to the invention, diamond element 36 is placed within cavity 42 so that it lies in contact with one lateral side 44a. The next adjacent diamond element 38 is placed within cavity 42 so that it lies in contact with the opposing lateral surface 44b of cavity 42. Similarly, the next following diamond element, element 40, is disposed within cavity 42 so that it lies against the opposing lateral surface 44a of cavity 42. If the length of the tooth were extended, or similarly if the length of cavity 42 were extended, each of the next adjacent diamond teeth would be laid within cavity 42 on alternating opposing sides 44a or 44b. After diamond cutting elements 36 - 40 are placed within cavity 42 of the mold, the mold is filled with metallic matrix powder and furnaced according to conventional techniques to form a matrix infiltrated drag bit. The metallic matrix fills within and between elements 36-40 to form an integral and rigid tooth structure extending from bit surface 16 of segment 20. Figure 3 graphically illustrates the effective extension or expansion of available diamond area by virtue of the setting described in connection with Figure 2 above. Figure 3 is a front elevational view of tooth 30 as seen through line 3-3 of Figure 2. The leading diamond element 36 as seen in Figure 3 forms the leftmost portion of tooth 30 while the next adjacent subsequent element 38 forms the rightmost portion of tooth 30. Element 40 is behind diamond element 36 and thus cannot be seen in the depiction of Figure 3 but serves as a redundant extension of the diamond element on the left side of tooth 30. Clearly in other teeth, such as teeth 24 and 26, where more than three diamond elements are employed, the redundancy is increased a number of times both on the left and right sides of each tooth. Turn now for example to Figure 4 wherein tooth 26 is shown in perspective view in enlarged scale as completed following manufacture. Tooth 26 forms a raised longitudinal ridged structure above matrix surface 16 of bit 10. The structure is characterized by a radial of longitudinal apical ridge 48 with a leading matrix face 50 and a trailing matrix support 52. Embedded within tooth 26 along the length of apical ridge 48 is a plurality of diamond elements 54. Each of the plurality of diamond elements 54 is disposed within tooth 26 so that the apical edge of each triangular prismatic diamond 54 coincides and lies along apical ridge 48 of tooth 26. In the illustrated embodiment a space of approximately .0005 to .0006 mm. of matrix material is provided between each consecutive diamond element 54 within tooth 26. The amount of matrix material forming a supporting cushion and space 56 between each diamond element may be varied according to the diamond density desired in view of the rock cutting application for which bit 10 is intended. The illustrated embodiment described above has been described in connection with new or substantially unworn prismatic diamond elements. However, the methodology and structure of teeth formed according to the invention is particularly adaptable to the advantageous use of used diamond elements without any substantial penalty with even severly worn diamonds. For example, turn to Figures 5a - 5e. Figure 5a is a diagrammatic cross-sectional illustration of an unused or substantially unworn triangular prismatic diamond element as described in connection with the embodiment of Figures 2 - 4. Figure 5b is a cross-sectional illustration of a triangular prismatic element in which one point has been worn or broken away. A used diamond element of this characteristic is described as a two-point element. Similarly, Figure 5c is a cross-sectional view of a used triangular prismatic element in which two adjacent triangular points have been worn or broken away. An element characterized by the shape of Figure 5c is defined as a one-point element. Figure 5d is a cross-sectional illustration of a triangular prismatic element in which substantially more than 50% of one point has been worn or broken away leaving what is in effect a thin trapezoidal shape with a jagged and irregular upper surface. A used diamond element of the shape shown in Figure 5d is defined as a kicker. Finally, Figure 5e is a cross-sectional illustration of a diamond element which has been substantially worn away but in which one or more portions or segments of irregular shape are left embedded within the used bit. Elements having such small irregular shapes such as shown in Figure 5e are defined as scrap. According to the invention, each of the used elements as depicted in Figures 5b - 5e can be profitably used in manufacturing of new cutting teeth. When a diamond drag bit has been used to the limit of its practical extent in the field, it is returned by the customer for salvage credit. The metal matrix bit is melted or dissolved and the diamond elements removed. Turn now to the depiction of Figure 6 which is a front elevational view of a cutting tooth similar to that previously shown in connection with Figure 3 but wherein the adjacent diamond elements 58 and 60 are two-point elements such as shown in Figure 5b rather than new elements depicted in Figure 5a. It may readily be appreciated that two-point elements 58 and 60 are placed within cavity 42 in a manner such that the broken point is oriented within the tooth near its base or what will become the area of its base, leaving the sharp and unused portions along apical ridge 48 and embedded in matrix surface 16 of the bit at the exterior periphery of the tooth. Figure 7 similarly illustrates a front elevational view similar to that of Figure 6 in which each of the diamond elements used within the bit are one-point elements as depicted in Figure 5c. In each case, the single undamaged point 62 is disposed within mold cavity 42 so that point 62 remains embedded in or below the matrix surface 16 of bit 10 of the completed tooth. The undamaged dihedral sides of each point 62 thus form the base and outer sides of the diamond elements in the tooth. In other words, one of the undamaged sides of the one-point element would be laid against lateral surfaces 44a or 44b of cavity 42 while the remaining undamaged side is placed uppermost extending from the mold cavity (embedded lowermost in the completed tooth manufactured therefrom). Fabrication of tooth structure employing used diamond elements is better understood by now turning to the perspective view of Figure 8 which is similar to the view of Figure 2 described above. In Figure 8 three two-point elements 64-68 have been placed within mold cavity 42 in the manner depicted in connection with Figure 6. One undamaged dihedral edge of two-point elements 64-68 is placed along apical edge 48 within cavity 42 and the remaining dihedral edge is placed uppermost as depicted in Figure 8. The undamaged surface between two undamaged points is thus appropriately laid against the lateral surface 44a or 44b as appropriate. The damaged point is therefore oriented to be placed within the interior and near the base of the tooth. The three two-point elements are alternately laid in cavity 42 in the same manner described above in connection with Figure 2 which results in essentially the same type of tooth as depicted in Figure 4. The kicker and scrap elements may be usefully employed according to the invention within the gage protection teeth defined within inner gage 14 or outer gage 12. Turn to Figure 9 wherein a cross-sectional view of a plurality of longitudinal broaches 70 is defined within a mold for bit 10 and into which kicker or scrap elements 72 have been placed. In the case where kicker elements such as depicted in Figure 5d are employed, elements 72 are placed in an edgewise fashion within broaches 70 to orient a side surface of the trapezoidal shape as the uppermost diamond portion. This will allow the maximum exposure and amount of diamond material of each kicker element 72 to be made available to each gage protection tooth. Scrap such as shown in Figure 5e can be similarly be oriented within broaches 70 according to the same principle in order to maximize the amount of diamond material made available for wear within the broach tooth. Figure 10 similarly illustrates a cross-sectional view of broaches 70 defined within gage portion of the mold bit 10 into which two- or one-point elements as depicted in Figures 5b and 5c, respectively, have been disposed. The two- or one-point element is placed within broach 70 so as to orient the worn point or points within broach 70, thus providing the broken surface of the element as the uppermost available diamond portion in the gage protection tooth. It is also possible that the two- or one-point element could be similarly oriented to placed one of the undamaged points within broach 70 of the mold. Figure 11 is a simplified plan elevational view of broaches 70 as seen in the mold illustrating how both kicker and scrap material, and one- or two-point material may be combined within gage protection teeth. Although a coring drag bit has been illustrated in connection with Figure 1 it is to be expressly understood that any other type of drill bit incorporating diamond teeth could have similarly been shown and may be appropriately combined with teeth for the present invention. In addition, although the illustrated embodiment has been described in connection with triangular prismatic elements, the principles illustrated with respect to the the use of this geometric shape could also be extended to other geometric shapes. Further, the illustrated embodiment has been similarly described in connection with synthetic diamond elements, but the principles of the invention apply with equal applicability to any type of cutting element including natural diamond elements, tungsten carbide elements, boron nitride elements and the like. In addition the invention has been illustrated in connection with a specific type of tooth design, namely a full ridge tooth. It is to be expressly understood that many other tooth structures could also incorporate the invention.

Claims: Cutting tooth (30) for use in a drill bit (10), said tooth (30) having a cutting direction and comprising a body having at least two cutting elements (36, 38, 40) disposed therein and forming a sequence of elements extending along said cutting direction of said cutting tooth, each cutting element (36, 38, 40) of said sequence comprising a geometric shape including a plurality of apical edges and a portion of each said element (36, 38, 40) extending in a nonparallel direction to said cutting direction and having a nonoverlapping projection in said cutting direction with respect to at least one other cutting element (36, 38, 40) within said sequence to define a nonoverlapping extent of said element (36, 38, 40), characterized in that: at least one apical edge of each of said geometric elements (36, 38, 40) lies generally on a common line, and each remaining apical edge of said geometric elements is nonaligned with at least one apical edge of at least one other of said geometric elements. The cutting tooth of Claim 1, characterized in that said body is composed of metal matrix and wherein each of said plurality of cutting elements (36, 38, 40) is separated one from each other by a thickness of said metal matrix. The cutting tooth of Claim 1, characterized in that each of said plurality of cutting elements (36, 38, 40) is separated by a portion of said body along said cutting direction. The cutting tooth of Claim 2, characterized in that each cutting element (36, 38, 40) is polycrystalline synthetic diamond. The cutting tooth of Claim 1 wherein said body has an exterior surface and an interior volume, and wherein at least two of said cutting elements (36, 38, 40) are elements having at least one worn portion, each element (36, 38, 40) disposed within said body to orient said worn portion within said body away from the exterior surface of said body so that only unworn portions comprise said nonoverlapping extent of each of the said elements (36, 38, 40). The cutting tooth of Claim 5 characterized in that at least two of said cutting elements are triangular prismatic elements (64, 66, 68) characterized by three apical dihedral edges with at least one of said dihedral edges worn away, said worn elements (64, 66, 68) disposed within said body to orient said at least one worn away apical edge into said interior volume of said body. The cutting tooth of claim 1, wherein each cutting element (36, 38, 40) is a triangular prismatic element (36, 38, 40) having two opposing triangular faces and three dihedral edges connecting said opposing triangular faces, and at least one dihedral edge of each cutting element (36, 38, 40) lies along said common line. The cutting tooth of Claim 7 characterized in that said common line is defined by and parallel to said line of cutting. The cutting tooth of Claim 8 characterized in that each of said triangular prismatic cutting elements (36, 38, 40) is perpendicularly offset from said common line with the exception of said dihedral edge of said cutting element lying on said common line. The cutting tooth of Claim 9 characterized in that each of said cutting elements (36, 38, 40) is a polycrystalline synthetic diamond element and wherein said body is composed of infiltrated metal matrix. Method for fabricating a cutting tooth (30) for a drill bit (10) to provide an enhanced cutting area, wherein said tooth includes a sequence at geometric cutting elements (36, 38, 40) forming a fixed array extending in the direction of cutting of said tooth (30) and each cutting element (36, 38, 40) in the array in offset from at least one other cutting element (36, 38, 40) in said direction of cutting, characterized in: generally aligning at least one apical edge of each cutting element (36, 38, 40) along a common line. The method of Claim 11 further characterized by disposing said cutting elements (36, 38, 40) within a mold cavity (42), said mold cavity (42) defining an opening of greater angular extent than the corresponding portion of said cutting elements (36, 38, 40) disposed into contact with said mold cavity (42), and alternating disposition of said cutting elements (36,38,40) within said mold cavity (42) in at least two opposing directions. The method of Claim 11, wherein each element (36, 38, 40) includes a worn-away portion and wherein each element (36, 38, 40) is disposed in said sequence with said worn-away portion opposing said direction of offset.

Inventors: PETERSON, LYNN
Applicants: EASTMAN TELECO COMPANY
Application year: 1987
Main classification: E21B10
IPC codes: E21B10