CLAW TOOTH ROTARY BIT

Abstract: A claw tooth rotary bit having teeth (10, 11) that are constructed from a hard material (13) that is combined with a softer material (12) so that the teeth (10, 11) wear unevenly as the bit is used to bore through an earth formation. Adjacent teeth (10, 11) may be provided with complementary patterns of hard and soft material shapes. Two adjacent teeth (10, 11) form a set that wear in a complementary pattern such that the high points of one tooth register with the low points of the adjacent tooth. As the bit rotates, the formation is randomly engaged by the high and low areas on the teeth to increase cutting effectiveness. The alternating layers of hard (13) and soft material (12) provide a self-sharpening configuration as the teeth wear unevenly. The presence of the hard material in the tooth structure improves tooth rigidity. In a preferred form, the hard material (13) is a polycrystalline diamond while the softer material is steel (12).

Description: CLAW TOOTH ROTARY BIT Background of the Invention Field of the Invention The present invention relates generally to the tooth structure of rotary bits used to bore through earthen formations More specifically, the present invention relates to a new and improved tooth design for rotary bits in which dissimilar materials are combined to enhance the durability and penetrating capability of a rotary drill bit Description of the Prior Art The design and composition ol rotary bit teeth have undergone changes that have significantly improved the life and penetration rates of rotary drill bits Tooth contour, hard facing, tooth positioning, and orientation on the bit. matenal composition, and other variables have been adjusted in small increments that have frequently resulted in significant improvements in bit performance Advances in metallurgy have also made it possible to create and physically combine materials in a way not previously possible, resulting in sometimes dramatic improvement in the durability and performance characteristics of the bit Significant bit improvement was recognized with the introduction of superhard facing materials, such as polvcrystalline diamond compact structures For some applications, the improved design or construction is accompanied by a significantly increased cost that cannot be justified based on the level or nature of the improvements obtained In such situations, it may be less expensive to replace a worn bit or extend the drilling time than it is to employ a better performing, but more costly, bit Accordingly, the importance of design and material changes that produce improved rate of penetration and bit life must be measured against the cost of building a bit incorporating the changes It is recognized in the prior art that spalling and chipping of superhard cutter facings can be reduced by rounding or chamfering the edges of the facings See. foi example. U S Patent No 5.437,343 to Cooley. et al . which describes specific chamfer configurations that are machined on a cutting element to provide increased fracture resistance. It is also recognized that reinforcing the layer of superhard matenal with a suitable underlying tooth material can also improve the fracture resistance of the superhard material. See. for example, U.S. Patent No. 4.109,737 to Bovenkerk that describes various support bodies for bit cutting elements having overlying hard matenal facings These configurations result from the use of special fabncation techmques to apply the superhard material in a controlled pattern to a specially shaped support body. The pnor art has also disclosed a vanety of methods for bonding superhard facing matenal to a bit insert to prevent delamination of the facing material. See. for example, U S. Patent Nos 4,784.023 to Dennis and 4,972.637 to Dyer Both of these latter patents also disclose the concept of bit wear producing multiple cutting edges in the cutting element that is attached to a supporting body or carrier The cutting edges of the cutting element are formed as the dissimilar materials in the cutting element unevenly wear away dunng usage All of the previously cited prior art patents relate to cutting teeth m which special cutting surfaces are mounted on a supporting stud or other earner element where the stud or carrier element is not intended as a normal part of the cutting surface of the bit In these prior art designs, the bit life is essentially exhausted when the cutting surfaces wear to the supporting earner. Summary of the Invention Some or all of the cutting elements of a conventional bit are provided with layers of hard matenal in a defined pattern that extends substantially through the entire body of the cuttmg element. In the layered elements, the layers of hard matenal extend away from the bit body and are spaced laterally from each other by layers of softer bit matenal. Normal bit rotation through the formation eventually wears away the hard matenal to gradually expose the layered soft and hard materials. The hard matenal thus protects the softer metal core of the tooth when wear begins at the crest of the tooth. Moreover, because the hard matenal wears at a rate that is slower than the main cutter body matenal, alternating grooves and ndges are formed in the cutting profile of the cutter. The wearing away process also has the effect of chamfering the edges of the hard matenal. The close lateral support of the softer bit material along the side of the hard matenal provides structural strength to the hard layer to further resist fracturing By extending the hard layers substantially through the full lengths of the cutter element, the rigidity of the cutter is improved, and the effective cutting length of the tooth is increased The bit design of the present invention provides longer tooth life and tooth integnty, which are particularly beneficial in directional drilling and drilling in amsotropic formations In one embodiment of the invention, adjacent teeth are provided with differing patterns of softer bit material and superhard cutter material so that the resulting wear pattern in adjacent teeth is different In a preferred form, the adjacent patterns form complements to each other so that the wear groove of one tooth is in the same relative position as the wear crest in an adjacent tooth In such a configuration, as the bit is rotated, the crest of a cutter is randomly forced into engagement with the crest of a formation cut by one or more preceding teeth so that maximum cutting interference occurs between the rotating bit and the formation, resulting in an mcreased rate of penetration In another embodiment of the invention, adjacent teeth are provided with the same pattern of hard and soft materials extending substantially through the full length of the cutter element Even though adjacent teeth develop similar wear patterns, interference between cutter profiles and formation cuts is also enhanced since adiacent teeth in the bit cone traverse different paths as they toll or drag against the formation Another embodiment of the invention alternates layered teeth with standard, hardsurfaced teeth to form yet another pattern of cutter profiles that also seeks to optimize interference with the profile of the cutaway formation Selection of the tooth arrangement to provide the best bit performance may be dictated by the type of formation to be bored Thus, for certain formations, a tooth configuration in which layered materials in the teeth produce complementary wear patterns in adjacent teeth may optimize bit life or rate of penetration, or both In other formations, a bit having normal bit teeth alternating with wear patterned teeth or a bit employmg only a single pattern of alternating hard and soft matenal may produce superior results From the foregoing, it will be appreciated that an object of the present invention is to economically build a bit having improved penetration and life usmg an improved tooth construction in an established, conventional bit design Another object of the invention is to employ conventional bit tooth matenals in a novel arrangement to improve bit performance Still another object of this invention is to combine dissimilar bit tooth matenals using conventional matenal combining techniques to provide an improved tooth design that can increase the rate of penetration and life of a conventional bit Yet another object of this invention is to provide a self-chamfering bit design that can reduce spatting and chipping in superhard materials incorporated into a bit tooth An important object of the present invention is to provide a bit tooth that is constructed of dLssimilar materials layered together through substantially the entire tooth profile to increase the bit life A related object bf the invention is provide a bit tooth design m which softer bit tooth material adjacent superhard material provides lateral support to the superhard matenal throughout the wear life of the tooth to minimize fracturing of the superhard material Another object of the invention is to make a bit in which adjacent teeth are constructed with different patterns of adjoined dissimilar materials to produce different tooth profiles as the teeth wear whereby the crests of the earthen formation left m the cut of one tooth are randomly engaged by the crest of another tooth on succeeding teeth to optimize bit penetration Yet another object of the present invention is to provide a bit in which adjacent teeth follow different paths through the formation and have similar patterns of adjoined dissimilar materials extendmg substantially through the tooth bodies whereby similar wear patterns of multiple crests and valleys are formed in adjacent teeth It is also an object of the present invention to alternate normal, hardsurfaced, homogeneous bit teeth with teeth formed of dissimilar materials layered together through substantially the entire tooth profile to produce a formation contact surface as the bit teeth wear that optimizes mterference between the bit and the formation as the bit is rotated These and further objects, features, and advantages of the present invention will become apparent from the following descnption. wherein reference is made to the figures in the accompanying drawings Brief Description of the Drawings Fig 1 is a vertical section, broken away, illustrating complementary geometnc patterns of hard and soft material m an adjacent bit tooth set, Fig. 2 is a view similar to Fig 1 illustrating the wear pattern of the tooth set of Fig 3 is a perspective view of a portion of a rotary bit equipped with the claw tooth design of the present mvention. Fig 4 is a vertical section, partially broken away, illustrating adjacent cylindrical insert teeth having complementary geometric hard and softer metal patterns. Fig 5 is a horizontal section taken along 5-5 of Fig 1 illustrating the softer material pattern contained within the harder material pattern of the cylindrical insert, Fig 6 is a schematic representation of alternating layered composite material teeth and conventional homogeneous material teeth, Fig 7 is a view similar to Fig 6 illustrating the wear pattern of the tooth set of Fig 8 is a schematic representation of adjacent bit teeth having similar layered composite material configurations, and Fig 9 is a view similar to Fig 8 illustrating the wear pattern of the tooth set of Fig 8 Detailed Description of the Preferred Embodiments Fig 1 illustrates a pair of adjacent teeth indicated generally at 10 and 11 that may be employed, for example, on a conventional rolling cone rock bit Such a cone is schematically illustrated in Fig 3 The tooth 10 is constructed of a mam body section 12 and a harder matenal section 13 The tooth 11 is similarly constructed with a mam body section 14 and a harder material section 15 The mam body 12 mcludes radially extendmg tooth body sections 16, 17, and 18 Complementary, radially extendmg sections of harder matenal 19. 20, and 21 are provided on the tooth 11 The tooth 11 is also equipped with radially extending main body sections 22 and 23 that are geometric complements to hard matenal radial extensions 24 and 25 of the tooth 10 As thus illustrated, it will be appreciated that the mam body pattern of the tooth 10 comprised of the sections 16, 17, and 18 functions as a geometnc complement to the hard matenal sections 19, 20, and 21 of the tooth 11 Each tooth mcludes a crest and side faces with the hard material extendmg from the crest into the mam tooth body between the side faces As the crest wears away, the mam tooth body is exposed so that the resulting wear area produces a cuttmg profile, as illustrated in Fig 2 This complementary relationship is further defined by the travel of the teeth 10 and 1 1 during the rotary boring operation In this regard, if the tooth 10 leads the tooth 11 dunng rotary bonng, the tooth 11 will not follow the same contact path as the tooth 10. but other teeth in the same cone will engage the same contact point The provision of different cut patterns on the teeth mcreases the probability of a tooth ridge strikmg a formation ridge to mcrease the interference between the bit and formation on any given full revolution of the bit When the hard material covering of the tooth has worn away, the worn tooth begins to wear unevenly, as mdicated in Fig 2 At this point, it may be appreciated that the hard material 13 wears less quickly than the softer material of the mam body 12. producing a senes of crests and grooves such as the crest 26 and grove 27 of the tooth 10 and the crest 28 and groove 29 of the tooth 1 1 Fig 3 illustrates the rotary cone bit after it has been worn through use As may be seen, the tooth 11 is left with a profile havmg three crests while the adjacent tooth 10 is left with a profile havmg four crests This pattern is repeated around the cone In this way, the teeth 10 and 11 work as a complementary set to produce differing cut patterns at each contact pomt where they engage the formation Fig 4 illustrates an insert-type tooth equipped with the alternating hard and softer matenal construction of the present mvention The tooth set of Fig 4 mcludes a tooth 30 and adjacent tooth 31 The teeth 30 and 31 are adapted to be received m a bore formed in a bit body in a conventional manner As with the embodiment of Figs 1 -3, the tooth form of Fig. 4 may be employed in any suitable conventional bit configuration. Complementary geometric patterns are formed in the adjacent teeth 30 and 31 by the combined construction of hard material and softer material in the main tooth body. Thus, in the construction of the tooth 30, hard material 32 overlies and is interspersed within the softer material 33. Similarly, in the tooth 31, hard material 34 is interspersed in the softer body material 35. The pattern of the soft material and hard material configuration is illustrated in more detail in Fig. 5. As with the previously described embodiment of Figs. 1-3, the tooth set 30 and 31 wears to form different tooth profiles that maximize the interference of the teeth with the formation and provide sett-shaφening as the dissimilar wear occurs. Presence of the hard material within the softer body material also increases tooth rigidity to further increase bit penetration into the formation. While the previous invention has been specifically described for use in rotary cone bit applications, it will be appreciated that the invention has broader application and may be employed in any bit that produces increased performance through increased interference between bit tooth and formation profile and through increased tooth rigidity and sett-sharpening. It will further be appreciated that while the invention has been described with teeth having alternating, complementary geometric hard material patterns, benefits of the described invention can be obtained in a bit wherein the patterns are essentially the same in adjoining teeth. In such applications, if the bit action produces interference with the formation as a result of prior tooth cutting, the benefits of the dissimilar wear and sett-shaφening and rigidity features of the invention are also attained. Figs. 6-8 illustrate variations in the configuration and wear patterns of bit teeth of the present invention. Fig. 6 illustrates an unworn rolling bit having a first tooth 35 with a hard material 36 covering the softer bit material 37. The softer material projects through the tooth away from the bit body (not illustrated) in layers that are laterally positioned between the hard material layers. The hard and soft materials are bonded to each other along their interfacing contact areas. The bonded union may be produced by any conventional technique employed for securing dissimilar bit tooth materials to each other. An adjacent tooth 38 is provided with an outer layer 39 of hard matenal that covers an inner, softer matenal section 40 of the bit body A tooth 41 is configured like the tooth 35 The sequence of tooth matenal patterns is repeated around the roller Fig 7 illustrates the wear pattern of the roller illustrated in Fig 6 Fig 8 illustrates a modified material layering pattern for bit teeth in which a hard outer matenal layer 50 is disposed over softer bit body matenal 51 The pattern is similar for all teeth on the roller Fig 9 illustrates the wear pattern of the roller of Fig 8 While the hard matenal of the mvention has been descnbed as a polycrystalttne diamond, it will be appreciated that other matenals that are hard compared to the mam tooth body may also advantageously be employed in the present mvention It will also be appreciated that the polycrystalttne diamond of the tooth structure may take the form of synthetic diamond wedges Similarly, the underlying body need not be steel but can be another material softer than the hard material, and still provide the benefits of the piesent mvention While the mvention has been illustrated and described with reference to certain preferred embodiments thereof, it will be apparent to those skilled m the art that modifications, substitutions, additions, and deletions may be made without departing from the spirit and the scope of the mvention as defined m the appended claims

Claims: What is claimed is: 1. A bit for boring earthen formations comprising: a bit body; teeth extending from said bit body; said teeth including a main body section and a hard material section; said hard material section being comprised of a material having a wear characteristic different than the wear characteristic of the material comprising said main body section; and said hard material section combining in a first pattern with a first one of said teeth and combining in a second, different pattern with a second one of said teeth immediately adjacent to said first tooth whereby said first and second teeth comprise a tooth set of two teeth that wear dissimilarly while boring. 2. The bit as defined in Claim 1, wherein said first and second patterns are substantially geometric complements to each other whereby said first and second teeth of said set wear in complementary patterns. 3. The bit as defined in Claim 1, wherein said main body section is comprised of steel and said hard material section is comprised of a polycrystalttne diamond material. 4. The bit as defined in Claim 1, wherein each of said teeth includes a crest and side faces, and said hard material is positioned over said crest and said side faces and extends from said crest into said main body between said side faces whereby when said crest wears away, said main body and said hard material are adjacent each other in a wear area of said tooth to form a cutting interface. 5. The bit as defined in Claim 1, further including a plurality of tooth sets extending from said bit body. 6 The bit as defined in Claim 1, wherein said mam body sections of said teeth are integrally formed with said bit body 7 The bit as defined in Claim 1, wherein said mam body sections of said teeth are separably formed from said bit body and are secured to said bit body 8 The bit as defined in Claim 1 , where said first pattern comprises at least two laterally spaced, non-central areas of penetration of hard material mto said mam body of said first tooth and said second pattern comprises a central area of hard matenal penetration mto said mam body of said second tooth 9 The bit as defined in Claim 1 , wherem said bit is a roller cone bit 10 The bit as defined m Claim 7, wherem said bit is a roller cone bit 11 A method of making bit teeth for a rotary bit body, comprising the steps of alternating hard and soft material m a first bit tooth to form a first wear pattern, alternatmg hard and soft material in a second bit tooth to form a second wear pattern, different from said first pattern, and positioning said first and second bit teeth on said bit body relative to each other and to the direction of the bit rotation such that said first and second wear patterns are substantial complements to each other m the direction of bit rotation 12 The method as defined m Claim 11 , wherem said hard material comprises a polycrystalttne diamond matenal and said soft material comprises steel 13 The method as defined m Claim 11, wherem said teeth extend radially away from said bit body and said first bit pattern comprises at least one radially extendmg soft matenal section and said second pattern comprises at least two radially extendmg soft matenal sections spaced laterally from said soft matenal section of said first pattern 14. The method as defined in Claim 11, wherein said first and second bit teeth are inserted into said bit body. 15. The method as defined in Claim 11, wherein said first and second teeth are integrally formed with said bit body. 16. The method as defined in Claim 13, wherein said first and second teeth are integrally formed with said bit body. 17. A claw tooth bit for boring through an earthen formation, comprising: a bit body; a plurality of cutting elements, each such cutting element having an elongate body carried by said bit body and extending away from said bit body; and alternating, laterally spaced, layers of materials having different wear characteristics layered in said elongate bodies of said cutting elements and extending substantially the full body length of said cutting elements whereby wear of said cutting elements during boring produces alternating peaks and valleys in the formation contacting surface of said cutting elements. 18. The claw tooth bit as defined in Claim 17, wherein said alternating layers are comprised of steel and polycrystalttne diamond. 19. The claw tooth bit as defined in Claim 17, further including plural claw tooth patterns, such patterns having alternating layers of materials disposed in variable arrangements with differing patterns on said cutting elements whereby said cutting elements wear to produce alternating peaks and valleys in differing relative positions in their respective formation contacting surfaces. 20. The claw tooth configuration as defined in Claim 19, wherein said alternating layers of materials comprise steel and polycrystalttne diamond. 21. The claw tooth configuration as defined in Claim 17, wherein said layers include synthetic diamond wedges.

Inventors: SPATZ EDWARD C, SPATZ, EDWARD, C.
Applicants: DRESSER IND, DRESSER INDUSTRIES, INC.
Application year: 1998
Main classification: E21B
IPC codes: E21B10