Tricone drill assembly

Abstract

The present invention relates to a tricone drill assembly having a drilling direction and a direction of rotation thereof, the tricone drill assembly comprising at least a set of three drill cones that are able to rotate, each drill cone comprising a conical tooth mount, and a set of teeth that are arranged into a plurality of concentric cutter rings along the conical tooth mount, each cutter ring substantially encircling the conical tooth mount at a particular cone height, wherein each tooth outwardly projects from the conical tooth mount, the drill cone substantially lacks cutter grooves or intermesh areas between adjacent cutter rings and each tooth is sized and shaped to inhibit interference with teeth on an adjacent drill cone of the set of three drill cones.

Description

TRI CON E DRI LL ASSEMBLYPRI ORI TY CLAI M

[0001] The present application claims priority from Australian provisional application No. 2023903179, filed on 04 October 2023. The contents of the priority application are hereby incorporated herein by reference.TECHNI CAL Fl ELD

[0002] The present invention relates generally to the field of drilling, and more particularly to the field of tri-cone drilling.BACKGROUN D

[0003] Tricone drills are widely used for drilling into geological formations, and are used in a variety of industries ranging from m ining exploration through to construction of water well and oil and / or gas rigs. Tricone drill bits comprise a central shank that mounts to a drill string, with three ‘legs’ extending longitudinally from the shank. A cone is mounted to the end of each leg, with a plurality of ‘teeth’ arranged across each cone’s surface. The teeth are typically rounded, wedge-shaped or bullet-shaped and any edges are generally rounded. As the tricone drill head rotates, the cones also rotate or roll across the surface of the formation being drilled, and the teeth impact thereagainst to induce cracking and ham mering.

[0004] The skilled person will appreciate that tricone drill bits are not designed through a “one size fits all” approach - each tricone drill bit is designed for drilling into a formation of a particular hardness, and one particular variable is the level of cone drag. Cone drag occurs when a particular cone momentarily ceases its rolling action, so the rotation of the tricone drill head results in the cone and its teeth slipping, skidding or otherwise being dragged across the formation surface. The rate of cone drag is affected by the ‘offset’ between the cones, or a lateral shifting of each cone away from a geometric centre of the tricone drill bit. Tricone drills for soft formations typically have increased offset between the cones, which results in increased cone drag - this leads to the soft formation also being shearedor gouged by the teeth of dragging cones as well as impacted by the teeth of rolling cones. However, tricone drill bits sized for harder formations utilise progressively smaller offset values. Greater cone drag results in more rapid wear and degradation of the cone teeth, which is exacerbated as formation hardness increases, while the effectiveness of gouging becomes more lim ited.

[0005] With reference to Figure 1 which depicts a prior art tricone drill assembly P10, prior art tricone drill assemblies comprise three unique drill cones P12A - C. Each cone is designed with ‘cutter grooves’ or intermesh areas P14, being an open space, groove or otherwise ‘blank’ and open area that matches with a ring of teeth P16 on one of the other two cones - in prior art Figure 1 , the particular labelled cutter grooves P14 which are present on both the first and third unique prior art cones P12A,P12C match with the third row of teeth P16 on the second of the unique cones P12B. These cutter grooves provide space for the teeth of the other two cones to move through and prevent the cones from impacting, meshing with or otherwise interfering with one another, as the existence of drag means that the rotation of adjacent drill cones cannot be relied upon to remain asynchronous with one another.

[0006] With reference to Figures 2A & B, depicted is a drill face, being the circular area that will be cut, reamed, scraped, bored or otherwise drilled by a tricone drill assembly, which is further subdivided into a set of ‘drill face rings’, each corresponding to a ring of teeth of one of the drill cones. Figure 2A depicts an example cutting pattern of an example prior art tricone drill assembly P10 rotating through 120° , wherein the different hatching styles horizontal, rising diagonal and falling diagonal) depict the areas cut by each separate prior art drill cone P12A - C, while Figure 2B depicts the same example cutting pattern through a full 360° rotation of the prior art tricone drill assembly. As depicted, an effect of the need for cutter grooves in prior art tricone drill assemblies is that each drill face ring is cut by (on average) only one ring of teeth on one drill cone, since cutter grooves / intermesh areas are arranged at the matching positions on the other two prior art drill cones. The exception is typically at the outermost position, where the teeth of neighbouring drill cones may be too far apart to interfere with one another, or at the innermost position, where the teeth of each cone may be arranged to protrude at different angles and so will not impede one another. Assuch, a ‘complete cut’ of the entire area of the drill face is only achieved once the entire tricone drill assembly has rotated through 360°.

[0007] Tricone drill assemblies typically have air and / or water or m ud nozzles arranged to blast rock cuttings away from the drill face, so as to avoid the drill cones repeating drilling into already-separated material unnecessarily. With further reference to prior art Figure 1 and Figure 2A in particular, prior art tricone drill assemblies P10 utilising cutter grooves P14 will drill into the drill face 24 by form ing ‘channels’ surrounded by un-drilled material - the hatched portions of the drill face rings in Figure 2A represent channels cut by the teeth of the respective prior art drill cone P12, while the empty drill face ring portions correspond to undrilled material. These channels provide space for rock cuttings to get stuck and embedded in, with the air, water or m ud being blown out of the nozzles simply passing over the channels and only removing a portion of the cuttings. As the channels only get fully ‘flattened out’ once the prior art tricone drill assembly has completed a full 360° rotation, each prior art drill cone P12 is consistently encountering and re-drilling already-separated cuttings. The cuttings can additionally get caught in the cutter grooves P14 directly, eventually building up enough to get ground out by the teeth of a neighbouring drill cone. These cuttings getting ‘re-drilled’ induce additional and unnecessary wear in the teeth of the prior art drill cones P12, leading to reduced lifespan.

[0008] Polycrystalline Diamond Composite (PDC) drill bits work in a very different manner to tricone drill bits. PDC bits comprise a single head with a number of planar teeth extending outwardly therefrom at an angle. Rather than drilling via m ultiple impacts and cracking of the rock formation, the entire PDC bit head rotates as a single entity, and the teeth are ‘scraped’ across the surface of the rock formation, thereby cutting, shaving or ream ing into the rock formation. As PDC bits primarily rely upon shearing or cutting forces, they are very well suited to softer formations or formations prone to shear failure.

[0009] It would be advantageous to provide a hybrid drilling means capable of drilling into harder rock formations both with impact-style drilling and with scrapestyle drilling in order to increase drilling rate. It would be further advantageous to provide a means of enabling each drill face ring of the drill face to be cut, reamed,bored or otherwise drilled by all three cones, thereby potentially speeding up drilling rate. Finally, it would be advantageous to provide a means of potentially extending drill cone lifespan by inhibiting unnecessary re-drilling of cuttings. These and other advantages may be provided by one or more embodiments disclosed herein.DI SCLOSURE OF THE I NVENTI ON

[0010] I n a first aspect, the present invention comprises a tricone drill assembly having a drilling direction and a direction of rotation thereof, the tricone drill assembly comprising at least a set of three drill cones that are able to rotate, each drill cone comprising, a conical tooth mount, and a set of teeth that are arranged into a plurality of concentric cutter rings along the conical tooth mount, each cutter ring substantially encircling the conical tooth mount at a particular cone height, wherein each tooth outwardly projects from the conical tooth mount, the drill cone substantially lacks cutter grooves or intermesh areas between adjacent cutter rings, and each tooth is sized and shaped to inhibit interference with teeth on an adjacent drill cone of the set of three drill cones.

[0011] I n an embodiment, rotation of the tricone drill assembly in the direction of rotation defines a drill face, being a circular area that will be cut, reamed, scraped, bored or otherwise drilled by the set of teeth of each drill cone, the drill face is divided into concentrically arranged drill face rings, each drill face ring corresponding to a particular cone height, for each drill cone of the tricone drill assembly, the plurality of concentric cutter rings are arranged such that at least one cutter ring is provided at each corresponding particular cone height, such that each drill face ring is cut, reamed, scraped, bored or otherwise drilled by each drill cone of the tricone drill assembly. I n an embodiment, a projection height of each tooth in at least one of the rings is less than or equal to one half of a m inim um distance between a base of the particular tooth and a surface of the conical tooth mount of the adjacent drill cone. I n an embodiment, each of the drill cones of the set of three drill cones are substantially identical to one another.

[0012] I n an embodiment, the tricone drill assembly may be formed of three roller bits being joined together, wherein each roller bit comprises, a shank subassembly shaped to form one third of a shank of the tri-cone drill and having afirst and second inner face, each first inner face meeting the second inner face of the shank sub-assembly of a separate one of the three roller bits, a leg base on an outer surface of the shank sub-assembly, a leg extending from the leg base, and one of the three drill cones rotatably mounted to a cone mount arranged at a distal end of the leg, wherein a centreline of the leg, extending from the leg base to the cone mount, is substantially straight, and the leg is tilted in the direction of rotation of the tricone drill assembly relative to the drilling direction thereof.

[0013] I n an embodiment, for each roller bit, the first and second inner faces are defined by first and second facial planes projected thereacross, respectively, the first and second facial planes intersecting at a longitudinal axis, an angle between the first and second facial planes about the longitudinal axis is essentially 120o, and the first and second inner faces are angled, relative to the leg base, such that the centreline of the leg is laterally tilted, in a direction of rotation of the tricone drill, with respect to the longitudinal axis.

[0014] I n an embodiment, each roller bit further comprises a channel formed into the shank on a leeward side of the leg relative to the direction of rotation of the tricone drill. I n an embodiment, each roller bit further comprises a jet nozzle arranged on a or the leeward side of the leg relative to the direction of rotation of the tricone drill, the jet nozzle being adapted to direct air or other fluid towards a surface being drilled by the tricone drill.

[0015] I n an embodiment, the tooth comprises a tooth body having at least a root portion and a distal portion that includes an impacting head, the impacting head being a substantially solid and hardened protrusion, and a substantially flat scraping surface being at least partially bounded by a substantially unrounded scraping edge.

[0016] I n an embodiment, the distal portion of the tooth body is shaped to substantially form the impacting head, and the scraping surface extends for at least a portion of a length of the tooth body, a distal end of the scraping surface being proximal to a distal end of the tool body and impacting head.

[0017] I n an embodiment, the impacting head comprises or is at least partially formed by a lobe laterally protruding from the distal portion of the tooth body, thelobe having a lateral protrusion height defined by a lobe spine, the lobe extends for at least a part of a length of the distal portion and a distal end of the lobe is at a distal end of the distal portion, the scraping surface comprises a distal end surface of the tooth, said distal end surface extending at least partially onto the distal end of the lobe.

[0018] I n an embodiment, a portion of the lobe spine has, in a direction towards the distal end thereof, a positive slope with an increasing curvature. I n an embodiment, a portion of the lobe spine has, in a direction towards the distal end thereof, a positive slope with a decreasing curvature. I n an embodiment, a distal end of the tooth has a substantially teardrop-shaped cross-section.

[0019] I n an embodiment, rotation of a particular drill cone brings, in sequence, each tooth in a particular ring of teeth to bear in the drilling direction of the tricone drill assembly, and each tooth is arranged within the particular ring of teeth so that, when brought to bear in the drilling direction of the tricone drill assembly, the scraping surface of the tooth substantially points in the direction of rotation of the tricone drill assembly.

[0020] Further or alternative embodiments of the invention may be disclosed herein or may otherwise become apparent to the person skilled in the art through the disclosure herein. These and other embodiments are considered to fall within the scope and object of the invention.DESCRI PTI ON OF Fl GURES

[0021] Embodiments of the present invention will now be described in relation to figures, wherein:Figure 1 depicts a prior art tricone drill assembly;Figures 2A & 2B depict cutting patterns of a prior art tricone drill assembly;Figure 3 depicts an embodiment of a tricone drill assembly of the present invention;Figure 4 is a side-on depiction of a single roller cone of the above embodiment;Figures 5A & 5B depict cutting patterns of an embodiment of the present invention;Figures 6 & 7 depict embodiments of a roller bit of the present invention;Figures 8A & 8B depict alternate embodiments of the tricone drill assembly of the present invention;Figures 9 & 10 depict embodiments of a roller bit of the present invention;Figure 1 1 depicts various embodiments of a tooth of the present invention; and Figure 12 is a side-on depiction of an arrangement of teeth in a an embodiment of a drill cone of the present invention.DETAI LED DESCRI PTI ON OF PREFERRED EMBODI MENTS

[0022] I n an embodiment and with reference to Figures 3 & 4, the present invention may lie in a tricone drill assembly 10 that, in operation, will have a defined drilling direction 12 being directly out of Figure 3 and towards the viewer in the arrangement as depicted) as well as a defined direction of rotation 14. I n an embodiment, the tricone drill assembly 10 comprises at least a set of three drill cones 16 that are able to rotate. Each drill cone 16 may comprise a conical tooth mount 18, being the cone-shaped body thereof, and a set of teeth 20 that are concentrically arranged into a plurality of cutter rings 22, 22-1 - 22-n along the conical tooth mount 18. The embodiment depicted in Figures 3 & 4 has seven cutter rings 22-1 - 22-7, but more or fewer cutter rings 22 may be present depending upon drilling needs without departing from the scope of the present invention. Figure 4 does not show the teeth 20 other than those visible along the edge of the profile in order to maintain clarity - instead, the cutter rings 22 are defined by dot-and-dash lines. As depicted and as the skilled person will understand, each cutter ring 22 substantially encircles the conical tooth mount 18 at a particular cone height h relative to the base of the cone shown in Figure 4 as measuring the height h of the third cutter ring 22), and each tooth 20 outwardly projects from the conical tooth mount 18. I n an embodiment, the drill cone 16 of the present embodiment may substantially lack cutter grooves or intermesh areas between adjacent cutter rings 22, and each tooth 20 is sized and shaped to inhibit interference with teeth 20 on an adjacent drill cone 16 in the tricone drill assembly 10. This may be contrasted to Figure 1 depicting a prior art drill cone P10 with cutter grooves P14 between adjacent cutter rings P16 of teeth.

[0023] Without lim iting the invention through theory, it is envisaged that by providing drill cones 16 with “full” sets of teeth {i.e. no cutter grooves, intermeshareas or other gaps between rings of teeth) , the drilling rate of the tricone drill assembly 10 may be increased. With reference to Figures 5A & B, and at least for the sake of explanation, depicted is a drill face 24, which is a circular area that will be cut, reamed, scraped, bored or otherwise drilled by the set of teeth of each drill cone 16 by rotation of the tricone drill assembly 10. Again for at least the sake of explanation, the drill face 24 can be sub-divided into concentrically arranged drill face rings 26, each of which corresponds to a particular cone height and subsequently defines the portion of the drill face that will be cut, reamed, scraped, bored or otherwise drilled by the teeth of the cutter ring at that particular cone height. Figure 5A depicts an example cutting pattern of an embodiment of the tricone drill assembly 10 of the present invention rotating through 120° , wherein the different hatching styles horizontal, rising diagonal and falling diagonal) depict the areas cut by each separate drill cone 16A-C, while Figure 5B depicts the same example cutting pattern through a full 360° rotation. As depicted, the entire drill face 24 may be cut, reamed, bored or otherwise drilled by 120° of rotation, with three ‘complete cuts’ being achieved by a full 360° rotation of the tricone drill assembly 10 of the present invention. As there are no cutter grooves or intermesh areas, the plurality of concentric cutter rings 22 of each drill cone 16 are arranged such that at least one cutter ring 22 is provided at each corresponding particular cone height and thus for corresponding drill face ring 26) , such that each drill face ring 26 is cut, reamed, scraped, bored or otherwise drilled by a cutter ring 22 of all of the drill cones 16 of the tricone drill assembly 10.

[0024] With return, contrasting reference to Figures 2A & B, as previously discussed, an effect of the need for cutter grooves in prior art tricone drill assemblies is that each drill face ring corresponds only to one cutter ring of one drill cone, as cutter grooves / intermesh areas are arranged at the matching particular height on the other two prior art drill cones {Except possibly at the outermost position, where the teeth of neighbouring drill cones may be too far apart to interfere with one another) . I n contrasting Figures 5A & B to Figures 2A & B, it can be seen that the prior art tricone drill assembly requires a full 360° rotation thereof in order to achieve a ’complete cut’, i.e. the entire drill face 24 is cut, reamed, scraped, bored or otherwise drilled, while the present invention achieves the same coverage through only 120° of rotation, and a full 360° rotationenables the tricone drill assembly 10 of the present invention to cut, ream , scrape, bore or otherwise drill the entire drill face 24 three times. This may enable improved drilling rate, and / or may also enable the use of shorter teeth in order to prevent or inhibit interference between drilling cones 16 without negatively affecting the drilling rate.

[0025] Again without lim iting the scope of the invention through theory, it is envisaged that providing drill cones 16 with “full” sets of teeth may enable improved removal of cuttings and may inhibit unnecessary ‘re-drilling’ thereof. With reference to Figure 5A and in contrast to prior art Figure 2A, the skilled person will appreciate that no significant channels will form during the drilling process, and therefore the ability for cuttings to become entrained against removal by the flow high pressure air, water or m ud is negated, inhibited, ameliorated or otherwise reduced. It is envisaged that this may mean that cuttings are more completely removed from the drill face 24, thereby resulting in the drill cones 16 more consistently drilling against undrilled rock material and for a greater fraction of operational time. The reduced quantity of cuttings being ‘re-drilled’ may subsequently extend a drill cone’s operational life. Furthermore, the more complete removal of cuttings away from the drill face 24 may enable further improvements in rate of penetration, and therefore even if a particular drill cone’s operational life is not extended, the amount of useful drilling provided across said lifespan may be substantially improved - i.e. an embodiment of a drill cone 16 with a “full set” of teeth may be capable of digging further and / or faster than a prior art drill cone P12 with cutter grooves P14.

[0026] I n an embodiment, a projection height of each tooth 20 in at least one of the cutter rings 22 may be less than or equal to one half of a m inim um distance between a base of the particular tooth (i.e. where the tooth 20 meets the conical tooth mount 18) and a surface of the conical tooth mount 18 of the adjacent drill cone. By keeping the projection height of teeth to one half of the distance between drill cones or less, it may be ensured that the teeth of adjacent drill cones will never be able to contact against one another.

[0027] I n an embodiment, each of the three drill cones 16, 16A-C may be substantially identical to one another. This may enable reduced manufacturing costs due to fewer different moulds, production lines and so on being required.

[0028] I n an embodiment and with reference to Figures 6 & 7, the tricone drill assembly 10 may be formed of three roller bits 28 being joined together. I n a further embodiment, each roller bit 28 may comprise a shank sub-assembly 30 that is shaped to form one third of a shank of the tri-cone drill assembly 10, a leg base 32 on an outer surface of the shank sub-assembly 30, a leg 34 extending from the leg base 32, and one of the three drill cones 16 rotatably mounted to a cone mount that is arranged at a distal end of the leg 34. I n an embodiment, the shank sub-assembly 30 may have a first and second inner face 36,38, each first inner face 36 meeting the second inner face 38 of the shank sub-assembly 30 of a separate, neighbouring roller bit 28 in order to form the shank of the tricone drill assembly 10. I n an embodiment, a centreline 40 of the leg 34 extends from the leg base 32 to the cone mount 18 and is substantially straight. Ideally, there is no twist or bend along the length of the leg 34.

[0029] I n an embodiment and with reference to Figure 7 in particular, the leg 34 may be tilted in the direction of rotation 14 of the tricone drill assembly 10, relative to the drilling direction 12 thereof. As depicted, the leg 34 is tilted and said tilt extends along substantially the entire length thereof. I n order to illustrate this embodiment further, reference is made to Figures 8A & 8B, wherein depicted is a tricone drill assembly 10 having the typical ‘straight leg’ arrangement (Figure 8A) and a tricone drill assembly 10 having a tilted leg 34, wherein said tilt is in the direction of rotation 14 relative to the drilling direction 12.

[0030] Without lim iting the scope of the invention through theory, it is envisaged that tilting the legs in the direction of drill rotation will increase their ability to withstand forces, as the centrelines of each leg will be more aligned with said forces. This may be particularly beneficial in embodiments of the present invention that may be subject to increased occurrences of drag, as the accompanying drag forces - especially when occurring while drilling hard rock surfaces - can otherwise be substantial and may damage the tricone drill legs. I n particular, it is considered that the use of an embodiment of the invention comprising drill cones 16 having ‘complete’ sets of teeth ( / .e. no cutter grooves or intermesh areas) will result inthe forces being applied to the tricone drill assembly 10 to intensify due to the increase in drill face penetrative ability as discussed above and depicted in contrasting Figures 2A & B to Figures 5A & B. These forces may comprise drag forces, impact forces and other forces that the tricone drill assembly 10 would be typically subjected to in operation. It is envisaged that a leg 34 that is tilted in the direction of rotation 14 may provide improved resistance to these intensified forces, as the leg is “leaning into” the opposing forces and can more directly oppose them .

[0031] I n an embodiment, the first and second inner faces 36,38 may be angled, relative to the leg base 32, such that the centreline 40 of the leg 34 is tangentially tilted with respect to a longitudinal axis 42 which coincides with drilling direction 12) , and as a result, the leg 34 itself is ‘tilted’. I n one ideal embodiment, the leg 34 is not twisted, bent, curved or otherwise shaped along its length to induce the tilt, nor is the leg base 32 otherwise shaped to induce tangential displacement of the drill cone 16. Rather, in at least one embodiment, the tangential displacement may be induced by shaping the first and second inner faces 36,38. This may be through cutting, ream ing, planing or other methods.

[0032] It is further envisaged that shaping the first and second inner faces 36,38 to laterally tilt the leg 34 may, in some embodiments, enable more efficient manufacturing or production of the roller bits 28 of the present embodiment, as existing moulds or casts may be modified rather than entirely new moulds being designed, which may otherwise be necessary if the legs were to be twisted as may be known in the prior art.

[0033] With reference Figures 9 & 10, depicted is an unshaped ‘leg lug’ of an embodiment of the invention, being a cast of a roller bit 28 that awaits the final machining stages. Figures 9 & 10 depict an uncut first inner face 36 and second inner face 38, a leg base on an outer surface of the shank sub-assembly 30, a leg 34 extending substantially longitudinally from the leg base, and a drill cone rotatably mounted to a distal end of the leg not shown in Fig. 10) . As depicted, an initial longitudinal axis 42-1 and a leg centreline 40 are substantially aligned. As previously discussed, the longitudinal axis 42 - which is where the first and second facial planes intersect - is analogous to the centreline of a shank formedby three shank sub-assemblies being joined together, and therefore is also aligned with the drilling direction 12 of the tricone drill assembly 10. As such, the leg 34, extending substantially parallel to the initial longitudinal axis 42- 1 , is currently substantially parallel to the drilling direction 12 of the tricone drill assembly 10.

[0034] By cutting, ream ing or otherwise reshaping the first inner face 36 along cutting plane 44, the angle of the longitudinal axis 42 may be altered from initial position 42- 1 to align with adjusted longitudinal axis 42-2, which therefore causes a tangential tilt in the leg centreline 40 relative thereto. The second facial plane may then be cut, reamed or otherwise shaped along a further cutting plane (not depicted) in order to ensure that the angle between the first and second facial planes about the adjusted longitudinal axis 42-2 is substantially or essentially 120°, as well as to further adjust the angle between the longitudinal axis and the leg centreline 40, and / or to control alignment therebetween with respect to other frames of reference. For example, cutting the first and second inner faces 36,38 at a particular angle may result in the legs 34 of a constructed tricone drill head to be splayed outwards as well as laterally tilted, which may or may not be desirable depending upon the characteristics of the formation being drilled.

[0035] I n some embodiments, the roller bit shown in Fig. 8 may be produced by providing an extra manufacturing step following production of a roller bit 28 through known methods. I n an embodiment, the roller bit ‘lug’, i.e. the unfinished roller bit 28, may be produced through known processes and then the final machining steps may include a step of machining the first or second inner face 36,38 to tangentially tilt the leg 34. I n an alternate embodiment, the present invention may comprise a method of modifying an existing mould, cast or sim ilar template to shape the first and second inner faces 36,38, either to include additional material to enable angular reshaping, or to directly form the first and second inner faces 36,38 at the correct angles to induce a desired tangential tilt in the leg 34 . Either embodiment is considered to enable efficient and econom ically feasible implementation, due to being able to be implemented through modification of existing manufacturing lines and processes for tricone drill assemblies.

[0036] I n a further embodiment and with return reference to Figure 7, the roller bit 28 may comprise a channel 46 formed into the shank sub-assembly 30 on aleeward side of the leg 34. The channel 46 may provide a path for drill cuttings to be ejected from the path of the tricone drill bit assembly 10. The channel 46 may be arranged to be partially sheltered by the leg 34.

[0037] I n an embodiment, the roller bit 28 may comprise a jet nozzle 48 that is arranged on a leeward side of the leg 34. The jet nozzle 48 may be adapted to direct air or other fluid towards the drill face 24 drilled in order to clear out and eject drill cuttings from the path of the tricone drill bit assembly 10.

[0038] I n an embodiment and with reference to Figure 1 1 , the tooth 20 of the tricone drill assembly may comprise a tooth body 50 having at least a root portion 52 and a distal portion 54 that includes an impacting head 56, which is a substantially solid and hardened protrusion, and a substantially flat scraping surface 58 that is at least partially bounded by a substantially unrounded scraping edge 60. As the skilled person will appreciate, the impacting head 56 does not need to be a defined structure on the tool body 50. Rather, the term ‘impacting head’ refers to a portion of the drill cone tooth 20 that is substantially solid and hardened, and is shaped, arranged or otherwise adapted to impact, ham mer, crack or otherwise break hard rock of the formation being drilled. I n some embodiments, such as depicted in tooth 20A, the impacting head 56 may at least partially comprise or include a specialised protrusion extending from the tool body. I n other embodiments such as depicted in tooth 20B, the impacting head 56 may be a distal region of the tool body 50. I n some embodiments, at least a portion of the tool body 50 may form a remaining portion of the impacting head 56, i.e. if a protrusion is present it may only form a part of the impacting head 56. I n an embodiment, the scraping surface 58 and scraping edge 60 are shaped, arranged or otherwise adapted to scrape, shave and / or shear hard rock of the formation being drilled.

[0039] I n an embodiment of the drill cone tooth 20A and with further reference to Figure 1 1 , the impacting head 56 of the drill cone tooth 20A may comprise or be at least partially formed by a lobe 62 laterally protruding from a distal portion of the tooth body 50. I n an ideal embodiment, the lobe 62 extends for at least a part of a length of the distal portion 54, and a distal end of the lobe 62 is at, adjacent to or otherwise concurrent with a distal end of the distal portion 54. Thelobe 62 may have a lateral protrusion height that is defined by a lobe spine, which is not necessarily a defined structure but rather is the ‘local maxim um ’ of the lobe or a theoretical line defining the two-dimensional shape of the lobe along the length of the tooth 20A. I n such an embodiment, the scraping surface 58 may comprise a distal end surface of the drill cone tooth 20, and the distal end surface and therefore scraping surface) may extend onto the distal end of the lobe 62.

[0040] I n an embodiment and with particular reference to the side view of tooth 20A shown in Figure 1 1 , a portion of the lobe spine may have, in a direction towards the distal end thereof, a positive slope with an increasing curvature. I n an embodiment, a portion of the lobe spine may have, in a direction towards the distal end thereof, a positive slope with a decreasing curvature. The person skilled in the art will appreciate that these embodiments are not m utually exclusive, and may both be present in different portions of the lobe 62. I n a further embodiment, the lobe 62 may have a gradual slope leading from proximal the root portion 52 of the tooth 20 to a lobe peak 64 that is proximal to the distal end of the tooth 20.

[0041] I n an embodiment, a distal end of the tooth may have a substantially teardrop-shaped cross-section, formed by the combination of lobe 62 and tooth body 50. The sides of the lobe 62 may be flat, or may be curved or rounded. I n some embodiments, one side of the lobe may be rounded while the other side is at least partially flattened.

[0042] With further reference to Figure 1 1 , an alternate embodiment of the drill cone tooth 20B may comprise the tooth body 50 that is substantially capped at a distal portion thereof by the impacting head 56. I n such an embodiment, the scraping surface 58 may be laterally facing and may extend for at least a portion of a length of the tooth body 50. I n a further embodiment, a distal end of the scraping surface 58 may be proximal to or substantially aligned with a distal end of the tool body 50 and impacting head 56.

[0043] Figure 12 is a side-on depiction of an embodiment of a tricone drill assembly 10 of the present invention, although only a single drill cone 16 is visible for clarity. With reference to Figure 12, in an embodiment wherein the plurality of cutter rings 22 on the drill cones 16 of the tricone drill assembly 10 are at leastpartially formed of an embodiment of the teeth 20A,B described above, the teeth may be arranged such that the scraping surface 58 bears against the drill face in a particular direction. As previously described, the tricone drill assembly 10 rotates in a particular rotation direction 14, and each drill cone 16 is also capable of rotation about their axis. As can be appreciated, rotation of a particular drill cone 16 brings, in sequence, each tooth 20 in a particular cutter ring of teeth to bear (or point) in the drilling direction 12 of the tricone drill assembly 10, at which point it will also bear against the drill face 24. I n an embodiment, each tooth 20 is arranged within the particular cutter ring 22 so that, when brought to bear as described above, the scraping surface 58 of the tooth 20 substantially points in the direction of rotation 14 of the tricone drill assembly 10. As an alternative explanation, each drill cone tooth 20 may be arranged within the particular cutter ring 22 such that, when positioned at a distal-most position from the drill bit shank by rotation of the drill cone 16, the scraping surface 58 of the particular drill cone tooth 20 substantially points in a direction of rotation 14 of the tricone drill assembly 10. I n some embodiments, particularly in embodiments employing drill cone teeth 20A having a laterally protruding lobe 62, the drill cone teeth 20A may be arranged such that the scraping surface 58 is at an angle 0 relative to a direction of rotation 14 of the drill bit shank. The arrangement of the teeth 20A within the drill cone 16 and their direction of projection relative thereto may vary so as to alter angle 0, for example to increase or decrease a severity or strength of a cutting, ream ing, scraping or gouging action induced when the associated drill cone 16 does not rotate ( / .e. when the teeth 20 A are dragged across the formation being drilled) . As used herein, the term ‘substantially points’ should therefore be understood to not require that the scraping surface 58 is facing exactly in the direction of rotation 14 of the tricone drill assembly 10, but rather that the scraping surface faces predominantly in said direction of rotation 14. I n an embodiment, the magnitude of sin(0) is greater than or equal to 0.5.

[0044] Without lim iting the scope of the invention through theory, when the drill cone 16 of a tri-cone drill is rotating, it is anticipated that the drill cone teeth 20 mounted thereto will impact against the formation being drilled ( / .e. drill face 24). I n particular, rotation of the drill cone 16 in the direction of rotation 14 will present the impacting head 56 of the tooth 20 to the drill face 24. Conversely, when the particular drill cone 16 is not rotating, then that drill cone 16 will be dragged acrossthe drill face 24 by the overall rotation of the drill shank. I n such an event, the teeth 20 on the portion of the drill cone 16 that are against the drill face 24 will be able to cut, gouge or otherwise scrape thereagainst, as the scraping surface 58 will move in the direction of rotation 14 of the tricone drill assembly 10. I n a further embodiment wherein the tooth 20A comprises a lobe 62 with a lobe peak 64, it is envisaged that the peak may promote significant focused cutting or gouging against the drill face 24.

[0045] With further reference to the embodiments of the invention depicted in Figure 12, it is therefore considered that a drill cone tooth 20 having an impacting head 56 and a scraping surface 58 that substantially faces in a direction of rotation 14 may enable increased penetration of hard rock surfaces by the associated tricone drill. I n particular, it is considered that embodiments of the present aspect may combine the beneficial properties of Polycrystalline Diamond Composite (PDC) drill bits, which are typically designed to drill by applying a scraping or gouging action, and traditional tri-cone drill bits, which are shaped to drill by applying a cracking, ham mering or impacting action.

[0046] While the invention has been described with reference to preferred embodiments above, it will be appreciated by those skilled in the art that it is not lim ited to those embodiments, but may be embodied in many other forms, variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps, features, components and / or devices referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

[0047] I n this specification, unless the context clearly indicates otherwise, the word “comprising” is not intended to have the exclusive meaning of the word such as “consisting only of”, but rather has the non-exclusive meaning, in the sense of “including at least”. The same applies, with corresponding gram matical changes, to other forms of the word such as “comprise”, etc.

[0048] Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwisedefined, all other scientific and technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

[0049] Any prom ises made in the present document should be understood to relate to some embodiments of the invention, and are not intended to be prom ises made about the invention in all embodiments. Where there are prom ises that are deemed to apply to all embodiments of the invention, the applicant / patentee reserves the right to later delete them from the description and they do not rely on these prom ises for the acceptance or subsequent grant of a patent in any country.

Claims

CLAI MS1 . A tricone drill assembly having a drilling direction and a direction of rotation thereof, the tricone drill assembly comprising at least a set of three drill cones that are able to rotate, each drill cone comprising: a conical tooth mount; and a set of teeth that are arranged into a plurality of concentric cutter rings along the conical tooth mount, each cutter ring substantially encircling the conical tooth mount at a particular cone height; wherein each tooth outwardly projects from the conical tooth mount; the drill cone substantially lacks cutter grooves or intermesh areas between adjacent cutter rings; and each tooth is sized and shaped to inhibit interference with teeth on an adjacent drill cone of the set of three drill cones.

2. The tricone drill assembly of claim 1 , wherein: rotation of the tricone drill assembly in the direction of rotation defines a drill face, being a circular area that will be cut, reamed, scraped, bored or otherwise drilled by the set of teeth of each drill cone; the drill face is divided into concentrically arranged drill face rings, each drill face ring corresponding to a particular cone height; for each drill cone of the tricone drill assembly, the plurality of concentric cutter rings are arranged such that at least one cutter ring is provided at each corresponding particular cone height; such that each drill face ring is cut, reamed, scraped, bored or otherwise drilled by each drill cone of the tricone drill assembly.

3. The tricone drill assembly of claim 1 , wherein a projection height of each tooth in at least one of the rings is less than or equal to one half of a minimum distance between a base of the particular tooth and a surface of the conical tooth mount of the adjacent drill cone.

4. The tricone drill assembly of any one of claims 1 to 3, wherein each of the drill cones of the set of three drill cones are substantially identical to one another.

5. The tricone drill assembly of any one of claims 1 to 4, being formed of three roller bits being joined together, wherein each roller bit comprises: a shank sub-assembly shaped to form one third of a shank of the tri-cone drill and having a first and second inner face, each first inner face meeting the second inner face of the shank sub-assembly of a separate one of the three roller bits; a leg base on an outer surface of the shank sub-assembly; a leg extending from the leg base; and one of the three drill cones rotatably mounted to a cone mount arranged at a distal end of the leg; wherein a centreline of the leg, extending from the leg base to the cone mount, is substantially straight; and the leg is tilted in the direction of rotation of the tricone drill assembly relative to the drilling direction thereof.

6. The tricone drill assembly of claim 5, wherein, for each roller bit: the first and second inner faces are defined by first and second facial planes projected thereacross, respectively, the first and second facial planes intersecting at a longitudinal axis; an angle between the first and second facial planes about the longitudinal axis is essentially 120°; and the first and second inner faces are angled, relative to the leg base, such that the centreline of the leg is laterally tilted, in a direction of rotation of the tricone drill, with respect to the longitudinal axis.

7. The tricone drill assembly of claim 6, each roller bit further comprising a channel formed into the shank on a leeward side of the leg relative to the direction of rotation of the tricone drill.

8. The tricone drill assembly of claim 6 or 7, each roller bit further comprising a jet nozzle arranged on a or the leeward side of the legrelative to the direction of rotation of the tricone drill, the jet nozzle being adapted to direct air or other fluid towards a surface being drilled by the tricone drill.

9. A tooth of the tricone drill assembly of any one of claims 1 to 8, the tooth comprising: a tooth body having at least a root portion and a distal portion that includes an impacting head, the impacting head being a substantially solid and hardened protrusion; and a substantially flat scraping surface being at least partially bounded by a substantially unrounded scraping edge.

10. The drill cone tooth of claim 9, wherein the distal portion of the tooth body is shaped to substantially form the impacting head; and the scraping surface extends for at least a portion of a length of the tooth body, a distal end of the scraping surface being proximal to a distal end of the tool body and impacting head.1 1 . The tooth of claim 9, wherein the impacting head comprises or is at least partially formed by a lobe laterally protruding from the distal portion of the tooth body, the lobe having a lateral protrusion height defined by a lobe spine; the lobe extends for at least a part of a length of the distal portion and a distal end of the lobe is at a distal end of the distal portion; the scraping surface comprises a distal end surface of the tooth, said distal end surface extending at least partially onto the distal end of the lobe.

12. The tooth of claim 1 1 , wherein a portion of the lobe spine has, in a direction towards the distal end thereof, a positive slope with an increasing curvature.

13. The tooth of claim 1 1 or 12, wherein a portion of the lobe spine has, in a direction towards the distal end thereof, a positive slope with a decreasing curvature.

14. The tooth of any one of claims 1 1 to 13, wherein a distal end of the tooth has a substantially teardrop-shaped cross-section.

15. The tricone drill assembly of any one of claims 1 to 8, wherein the plurality of cutter rings are at least partially formed of the teeth of any one of claims 9 to 14; further wherein rotation of a particular drill cone brings, in sequence, each tooth in a particular cutter ring to bear in the drilling direction of the tricone drill assembly; and each tooth is arranged within the particular cutter ring so that, when brought to bear in the drilling direction of the tricone drill assembly, the scraping surface of the tooth substantially points in the direction of rotation of the tricone drill assembly.

Images