Conduit for conveying air to small bearings in journal region of rotary drill bit

Abstract

A conduit for delivering air to a small bearing of a journal region of a rotary drill bit (200) includes: a plurality of rotary cones (206), each rotary cone including a plurality of cutting tips (210); and a plurality of support legs (208), wherein the plurality of cones (206) are respectively supported on the plurality of support legs. Each leg (208) includes: a journal region (220) configured to rotatably support the respective cone (206); a main conduit (250) extending internally within the leg (208) and configured to receive air from an air compressor (36); a first journal duct (252) downstream of the main duct (250) and extending to a first air hole (242) of the journal region (220); and at least one second journal duct (254) downstream of the main duct (250) and extending to at least one corresponding second air hole (244) of the journal region (220). A ratio of a cross-sectional diameter (253) of the first journal conduit (252) to a cross-sectional diameter (253) of at least one of the second journal conduits (254) is in a range of about 1 to about 1.4.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to drilling rigs, and more particularly, to rotary drill bits having air conduits for supplying cooling air to the journal region of the drill bit. BACKGROUND

[0002] Surface drilling is a necessary operation in many industries, including mining, oil and gas extraction, construction, geothermal drilling, and many others. Surface drilling is performed with a drilling rig that uses various types of drill bits to create a cutting force to break up rock, soil, clay, and the like. One type of drill bit, known as a rotary drill bit, performs the cutting operation with one or more rotating cutting heads. The rotary drill bit is mounted at the end of a drill string of the drilling rig.

[0003] Drilling generates a significant amount of heat, which can damage various components of the drill bit and shorten its useful life. For example, heat can reduce the useful life of the bearings of a rotary drill bit. To inhibit heat, rotary drill bits utilize a cooling fluid (liquid or gas) to cool the bearings and other components of the drill bit. In some configurations, an air compressor of the drilling rig provides air to cool the components (e.g., bearings and thrust surfaces) of the drill bit. Typically, the drill bit includes multiple conduits for splitting the air from the drill string and directing the air to relevant regions of the drill bit for cooling. In other configurations, the bearings are sealed and cooled with lubrication.

[0004] Rotary drill bits typically include multiple rows of bearings (e.g., cylindrical roller bearings and / or ball bearings) that should be kept cool to prevent premature wear or failure associated with overheating.

[0005] U.S. Patent No. 8,337,085 to Nagaraj et al. (“the ‘085 Patent”) describes a thrust bearing system for a roller cone drill bit that includes a cone disposed on a leg having an air passage therethrough. A primary thrust bearing surface on the leg contacts a corresponding primary bearing surface on the cone. The primary thrust bearing surface on the leg includes at least one air circulation port in fluid communication with the air passage. A secondary thrust bearing surface on the leg contacts a corresponding secondary bearing surface on the cone. The secondary thrust bearing surface on the leg includes at least two air circulation ports in communication with the air passage. The drill bit further includes a radial load bearing surface that supports a roller bearing and a ball bearing.

[0006] The '085 patent describes utilizing air from an air passage to cool components of a roller cone drill bit. However, the '085 patent does not describe the relative proportions of the size of the air passage or the flow of air to components such as roller bearings and ball bearings. In the arrangement exemplified by the '085 patent, the roller bearing closest to the cone tip can receive insufficient air and / or uneven distribution of air, resulting in heat-related wear and ultimately failure.

[0007] The systems and methods of the present disclosure can address or solve one or more of the problems set forth above and / or other issues in the art. However, the scope of the present disclosure is not limited by the ability to solve any particular problem. SUMMARY

[0008] One aspect of the present disclosure is a rotary drill bit for a drilling system that includes a drill rig having an air compressor to supply air to the rotary drill bit. The rotary drill bit includes a plurality of rotating cones each including a plurality of cutting tips, and a plurality of legs on which the plurality of cones are respectively supported. Each leg includes a journal region configured to rotatably support the respective cone, a main conduit extending internally within the leg and configured to receive air from the air compressor, a first journal conduit downstream of the main conduit and extending to a first air bore of the journal region, and at least one second journal conduit downstream of the main conduit and extending to at least one corresponding second air bore of the journal region. A ratio of a cross-sectional diameter of the first journal conduit to a cross-sectional diameter of at least one of the second journal conduits is in a range of about 1 to about 1.4.

[0009] Another aspect of the present disclosure relates to a method for operating a rotary drill bit including a cone rotatably supported on a leg. The method includes rotating the cone relative to a journal region of the leg, supplying air from an air compressor to a main conduit within the leg, supplying air from the main conduit to a first journal conduit and a second journal conduit within the leg, cooling at least a portion of the journal region with air from the first journal conduit, and cooling at least a portion of the journal region with air from the second journal conduit. A ratio of a cross-sectional diameter of the first journal conduit to a cross-sectional diameter of the second journal conduit is in a range of about 1 to about 1.4.

[0010] Another aspect of this disclosure relates to a drilling system comprising: a drilling rig including an air compressor; a drill string extending from the drilling rig; and a rotary drill bit connected to an end of the drill string and receiving air from the air compressor via the drill string. The rotary drill bit includes a plurality of legs, each leg including: a journal region configured to rotatably support a roller cone; a main guide tube extending internally within the leg and configured to receive air from the air compressor; a first journal guide tube located downstream of the main guide tube and extending into a first air cavity in the journal region; and a second journal guide tube located downstream of the main guide tube and extending into a second air cavity in the journal region. The ratio of the cross-sectional diameter of the first journal guide tube to the cross-sectional diameter of the second journal guide tube is in the range of about 1 to about 1.4. Attached Figure Description

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and, together with the specification, serve to explain the principles of this disclosure.

[0012] Figure 1 A schematic side view of a drilling rig according to various aspects of this disclosure is shown, the drilling rig including a drill string and a rotary drill bit.

[0013] Figure 2A Examples Figure 1 A perspective view of the rotating drill bit of the drilling rig.

[0014] Figure 2B Examples Figure 2A Bottom view of the rotary drill bit.

[0015] Figure 3 Examples Figure 2A The rotating drill bit along Figure 2A The cross-sectional view is a portion of the section marked AA.

[0016] Figure 4 Examples Figure 2A A perspective view of the legs of a rotating drill bit, with the toothed cones removed.

[0017] Figure 5 Examples Figure 2A A perspective view of the legs of a rotary drill bit, with the gears and bearings removed.

[0018] Figure 6 Examples Figure 5 A detailed perspective view of the journal area of ​​the outrigger.

[0019] Figure 7 Examples Figure 5 A detailed perspective view of the journal area of ​​the outrigger.

[0020] Figure 8 This is an example of the flow direction. Figure 2A A chart showing the relative percentage of airflow to the bearings of a rotating drill bit.

[0021] Figure 9 It is used for operation Figure 2A The flowchart shows the method for rotating the drill bit. Detailed Implementation

[0022] The foregoing general description and the following detailed description are merely exemplary and illustrative and do not limit the claimed features. As used herein, the terms “comprising,” “having,” “including,” or other variations thereof are intended to cover non-exclusive inclusions, such that a process, method, object, or apparatus that comprises a list of elements includes not only those elements but may also include other elements not expressly listed or inherent to such process, method, object, or apparatus. Furthermore, relative terms (such as, for example, “about,” “substantially,” “approximately,” and “about”) are used to indicate possible variations of ±10% of the stated values.

[0023] Figure 1 A schematic side view of an exemplary drilling rig 10 is shown. The disclosure herein is applicable to any type of drilling rig; however, specific reference will be made below to mobile blasting hole drilling rigs. Figure 1 As shown, the mobile drilling rig 10 may include a frame 12, machinery 14, and a drill mast 16. The frame 12 may be supported on the ground surface by a transport mechanism (such as tracks 18). The tracks 18 allow the mobile drilling rig 10 to be moved across the ground surface to a desired location for drilling operations. The frame 12 may include one or more jacks 20 for supporting and leveling the mobile drilling rig 10 on the ground surface during drilling operations. The frame 12 may support the machinery 14, which may include an engine, motor, battery, pump, hydraulic fluid tank, and air compressor 36. Figure 1 (Illustrated) and / or any other equipment required to power and operate the mobile drilling rig 10. The frame 12 may further support the operator's cab 22, through which the user or operator can manipulate and control the mobile drilling rig 10 via a user interface and display 40.

[0024] like Figure 1 As further shown, the drill mast 16 may include a mast 24 that can support a drill motor assembly or a rotary head 26 movably mounted on the mast 24. The rotary head 26 may be coupled to a drill string 28 of a drill rod section and can be controlled to rotate the drill string, on which a drill bit 200 may be mounted for down-the-hole drilling into the ground surface, as further described below.

[0025] The rotating head 26 can be any type of rotating head, such as a hydraulic rotating head. The rotating head 26 may further include hydraulic fluid lines (not shown) for receiving hydraulic fluid. The hydraulic fluid can be used to rotate the shaft of the rotating head 26 connected to the drill string 28, thereby rotating the drill string 28 (and thus the drill bit 200). The hydraulic fluid lines of the rotating head 26 may be coupled to a hydraulic valve 32 (…). Figure 1 (Shown schematically) for controlling the amount and flow rate of hydraulic fluid flowing into the rotary head 26. In an exemplary embodiment, the hydraulic valve 32 may be located on the hydraulic fluid reservoir 38. However, the hydraulic valve 32 may be located anywhere along the hydraulic fluid line of the rotary head 26 as needed.

[0026] The drill mast 16 may further include a hydraulic feed cylinder 34 (located within the mast 24) connected to the rotary head 26 via a cable and pulley system (not shown) for moving the rotary head 26 up and down along the mast 24. Thus, when the hydraulic feed cylinder 34 is extended, it can apply force to the rotary head 26 to pull it down along the mast 24. Similarly, when the hydraulic feed cylinder 34 is retracted, it can apply force to the rotary head 26 to lift it up along the mast 24. Therefore, the hydraulic feed cylinder 34 can be controlled to move the rotary head 26 up and down on the mast 24, allowing the drill bit 200 on the drill string 28 to be lowered toward and drill into the ground surface or lifted upward from the ground surface. As used herein, the term “feed” in the context of the feed cylinder 34 includes movement of the drill string 28 in either direction (up or down). The hydraulic feed cylinder 34 may include a hydraulic fluid line (not shown) for receiving hydraulic fluid from and supplying hydraulic fluid to the feed cylinder 34. The hydraulic fluid can be used to actuate the hydraulic cylinder 34, allowing the rod of the hydraulic cylinder 34 to extend or retract. The hydraulic fluid line of the hydraulic cylinder 34 may be coupled to a hydraulic valve for controlling the amount, flow rate, and pressure of the hydraulic fluid flowing into the hydraulic cylinder 34. In an exemplary embodiment, the hydraulic valve may be located on the hydraulic fluid reservoir 38. However, the hydraulic valve may be located anywhere along the hydraulic fluid line of the hydraulic cylinder 34 as needed. It should be understood that the hydraulic fluid can be any type of hydraulic fluid, such as hydraulic oil.

[0027] Figure 1 A drill string 28 is shown located in a hole 50 having a desired depth to the bottom 54 of the hole 50. (See diagram) Figure 1As shown by the arrows in FIG. 1, the drill string 28 can be rotated and moved up and down (e.g., fed and retracted / lifted), causing the drill bit 200 to rotate and move up and down, respectively. The drill bit 200 can also be moved reciprocally in the rotational or up-and-down direction. In addition, the drill string 28 can include an air line for supplying compressed air from the air compressor 36 to the drill bit 200. Further, the drill string 28 can include a water line (not shown) for supplying water through the drill bit 200 to the bore 50.

[0028] Referring now to Figure 2A and Figure 2B , the rotary drill bit 200 includes a body 204 and one or more rotary cones 206. The adapter 202 extends from a proximal end of the body 204 and can include, for example, a threaded interface for connection to the drill string 28 (e.g., the drill string 28 of FIG. 1). The body 204 extends from the adapter 202 and supports the cones 206. In particular, the body 204 can include a plurality of legs 208, each leg rotatably supporting one of the cones 206. Thus, the number of legs 208 is equal to the number of cones 206, which in the illustrated aspect is three (although other numbers of legs and cones, such as two, four, or more, are also possible and within the scope of the present disclosure). Figure 1

[0029] The cones 206 are generally conical in shape and include a plurality of cutting tips 210 extending radially and / or axially outward from an outer surface of the cones 206. In various aspects, the cutting tips 210 can be integrally formed with the cones 206 or can be separate elements secured to the cones 206. The cutting tips 210 can be arranged such that the cutting tips 210 of adjacent cones 206 intermesh during rotation of the cones 206 to improve cutting and abrasion performance. In some aspects, each cone 206 can have a different arrangement of cutting tips 210. The cones 206 can be oriented such that a distal tip 212 of the cones 206 generally points toward the longitudinal axis 201 of the drill bit 200. The body 204 of the drill bit 200 can further include one or more air nozzles 214 for directing air supplied by the air compressor 36 of the rig 10 (see FIG. 1) to the debris cut by the cones 206. Figure 1

[0030] As Figures 3 to 5 ​​As shown, each leg 208 of body 204 defines a journal region 220 over which a corresponding cone 206 rotates. Journal region 220 supports one or more bearing assemblies that allow cone 206 to rotate. In the illustrated aspect, journal region 220 includes a first bearing assembly including a plurality of cylindrical roller bearings 230 proximate a distal tip 212 of cone 206, a second bearing assembly including a plurality of ball bearings 232 proximate the first bearing assembly, and a third bearing assembly including a plurality of cylindrical roller bearings 234 proximate the second bearing assembly and proximate a base of cone 206. The first, second, and third bearing assemblies generally support radial loads from cone 206.

[0031] Journal region 220 further includes a thrust pad 236 at a distal-most location of journal region 220 proximate distal tip 212 of cone 206. Thrust pad 236 supports axial thrust loads from a corresponding pad 207 of cone 206. Thus, thrust pad 236 acts as a first bearing surface 222. Journal region 220 further includes a second bearing surface 224 proximate cylindrical roller bearings 230. Thus, cylindrical roller bearings 230 are located between first bearing surface 222 and second bearing surface 224, while ball bearings 232 and cylindrical roller bearings 234 are proximate the second bearing surface. First bearing surface 222 and second bearing surface 224 support axial thrust loads from corresponding surfaces of cone 206.

[0032] First bearing surface 222 and second bearing surface 224 can each include or be associated with one or more apertures through which air from air compressor 36 (see Figure 1 may flow to journal region 220. In particular, a first air aperture 242 can extend at least partially through thrust pad 236. In Figure 3 and Figure 4 aspects, first air aperture 242 is substantially centered in thrust pad 236. In Figures 5 to 7 the illustrated aspect, first air aperture 242 extends through an outer edge of thrust pad 236 (not shown in Figures 5 to 7 ) and an inner edge of surrounding journal region 220. As Figure 4 shown, first air aperture 242 opens to a transverse air passage 246 that traverses an end face of thrust pad 236 and first bearing surface 222, allowing air from first air aperture 242 to flow outwardly to journal region 220. In Figures 5 to 7 aspects, the off-axis location of first air aperture 242 allows air from first air aperture 242 to flow outwardly to journal region 220, obviating the need for transverse air passage 246.

[0033] The outrigger 208 may include an insertion channel 260 through which the ball bearing 232 can be inserted into the journal region 220 after the gear 206 is mounted to the outrigger 208. A plug 262 may be inserted into the insertion channel 260 to hold the ball bearing 232 in place during drill operation.

[0034] like Figure 4 As shown, for example, one or more second air holes 244 lead to a second bearing surface 224. In some aspects, the second air holes 244 comprise two holes evenly spaced (e.g., spaced approximately 180° apart) around the centerline of the journal region 220, but more or fewer holes (e.g., one or more) and other arrangements of holes (including irregularly spaced holes) are all within the scope of this disclosure. The second air holes 244 may be surrounded by an outlet channel 248 that allows air to exit from the second air holes 244 and flow into the journal region 220. The outlet channel 248 is a recessed surface formed in the second bearing surface 224 and may extend partially around the circumference of the second bearing surface 224. Figure 4 As shown, the journal region 220 may further include a proximal exit channel 249 that provides fluid communication between the journal region 220 and the atmosphere outside the gear 206.

[0035] Now for reference Figures 5 to 7 Each leg 208 of the main body 204 may include a main guide tube 250 within the leg 208, the main guide tube receiving air from the air compressor 36 (see...). Figure 1 The air is received and distributed to air holes 242, 244 via one or more journal conduits. The main guide tube 250 extends internally within the leg 208 and has a diameter or maximum cross-sectional width 251 (see...). Figure 5 For example, the main guide tube 250 may be integrally formed with the structure of the outrigger 208. The proximal end of the main guide tube 250 (i.e., the end closest to the adapter 202) may include an air plug 216, which is connected to the nozzle 214 (see, for example, see...). Figure 3 Fluid communication is maintained. Air supplied from air compressor 36 is diverted between nozzle 214 and main pipe 250. Like main pipe 250, nozzle 214 can extend from within support leg 208. In some aspects, approximately 65% ​​to 85% of the inlet air from air compressor 36 flows to nozzle 214, and approximately 15% to 35% of the inlet air flows to main pipe 250. In other aspects, approximately 70% of the inlet air from air compressor 36 flows to nozzle 214, and approximately 30% of the inlet air flows to main pipe 250.

[0036] like Figure 3 ,Figure 6 and Figure 7 As shown, a first axial conduit 252 extends downstream of the main guide tube 250 and connects to a first air hole 242. The first axial conduit 252 has a width or maximum cross-sectional diameter 253 (see [reference]). Figure 6 ).like Figure 7 As shown, a second axial conduit 254 extends downstream of the main tube 250 and connects to a second air vent 244. The second axial conduit 254 has a diameter or maximum cross-sectional width 255. The first axial conduit 252 and the second axial conduit 254 typically extend from the distal end of the main tube 250 (i.e., the end furthest from the adapter 202). The first axial conduit 252 and the second axial conduit 254 may extend internally within the leg 208. For example, conduits 252 and 254 may be integrally formed with the structure of the leg 208. The main tube 250, the first axial conduit 252, and the second axial conduit 254 may extend generally linearly as illustrated, or non-linearly in other respects. The main tube 250, the first axial conduit 252, and the second axial conduit 254 may have a generally circular cross-section as illustrated, but other contours such as oval, elliptical, or polygonal shapes may also be used.

[0037] The dimensions of the main guide tube 250, the first journal guide tube 252, and the second journal guide tube 254 can be designed to be in a specific proportion to each other to balance the airflow to the various parts of the journal region 220. Specifically, the cross-sectional diameters of the first journal guide tube 252 and the second journal guide tube 254 can be designed relative to each other to ensure sufficient volume and flow of cooling air to reach the cylindrical roller bearing 230.

[0038] Now for reference Figure 8 Figure 800 illustrates the relationship between airflow to the cylindrical roller bearing 230 of drill bit 200 (e.g., shown as a percentage on the 'y' axis) and the ratio of the cross-sectional diameter 253 of the first journal duct 252 to the cross-sectional diameter 255 of each of the second journal ducts 254 (shown on the 'x' axis). The data in Figure 800 correspond to airflow simulations applied to multiple ratios of the diameter 253 of the first journal duct 252 to the diameter 255 of the second journal duct 254. The airflow to the cylindrical roller bearing 230 is optimal when the ratio of the cross-sectional diameter 253 of the first journal duct 252 to the cross-sectional diameter 255 of the second journal duct 254 is in the range of 1 to 1.4 or about 1 to about 1.4. That is, the cross-sectional diameter 253 of the first journal duct 252 is 1 to 1.4 times the cross-sectional diameter 255 of each of the second journal ducts 254 (or one second journal duct). In at least some embodiments, this ratio maximizes the total airflow volume to the cylindrical roller bearing 230.

[0039] Rotary drill bit 200 can be supplied in a variety of sizes (i.e., industry standard sizes such as 6-3 / 4”, 7-7 / 8”, 9”, 9-7 / 8”, 10-5 / 8”, 11 5 / 8”, 12 1 / 4”, 13 / 3 / 4”, 16”, etc.). The size of drill bit 200 can correspond to the widest cross-section (or diameter) 203 (see Figure 2A and Figure 2B ) of drill bit 200 (i.e., the width perpendicular to the longitudinal axis 201 of drill bit 200). The cross-sectional diameters of main conduit 250, first journal conduit 252, and second journal conduits 254 can be optimized for a particular diameter 203 of drill bit 200 to maximize the airflow to cylindrical roller bearing 230 while balancing other factors such as airflow to other components of journal region 220 and structural integrity of legs 208. In one aspect, for a drill bit 200 having a size of 12 1 / 4”, main conduit 250 has a diameter of about 20 millimeters (mm), first journal conduit 252 has a diameter of about 10 mm to about 13 mm, and second journal conduits 254 each have a diameter of about 8 mm to about 11 mm. In one example, for a drill bit 200 having a size of 12 1 / 4”, main conduit 250 has a diameter of about 20 mm, first journal conduit 252 has a diameter of about 12 mm, and second journal conduits 254 each have a diameter of about 10.5 mm. In this example, the ratio of the diameter 253 of first journal conduit 252 to the diameter 255 of one of second journal conduits 254 is 12:10.5 or 1.14, which is within the optimal range of 1 to 1.4 described above. The size of the cross-sectional diameter of main conduit 250 can be designed to optimize the airflow to the entire journal region 220. The ratio of the diameter 203 of drill bit 200 to the cross-sectional diameter 251 of main conduit 250 can be in the range of 13 to 16.5, or in the range of about 13 to about 16.5, or in some aspects, in the range of about 14 to 16.5. That is, the cross-sectional diameter 251 of main conduit 250 can be 13 to 16.5 times the diameter 203 (see Figure 2A and Figure 2B ) of drill bit 200. In at least some embodiments, this ratio is advantageous and maximizes the total airflow volume to journal region 220 including the bearing. For example, for a drill bit 200 having a diameter of 12 1 / 4” (311.15 millimeters), the optimal diameter of main conduit 250 is in the range of 18.8 mm to 24 mm.

[0040] It should be noted that the above ratio of the diameter of the first journal conduit 252 to the diameter of the second journal conduit 254 applies to a variety of sizes of drill bits 200. That is, for a variety of drill bit sizes, other than the 12 ¼" diameter used in the foregoing example, the ratio of the diameter 253 of the first journal conduit 252 to the diameter 255 of the second journal conduit 254 can be in the range of 1 to 1.4. For example, for drill bits having a diameter of 9 7 / 8" and 11 5 / 8", the ratio of the diameter 253 of the first journal conduit 252 to the diameter 255 of the second journal conduit 254 can be in the range of 1 to 1.4. Similarly, for drill bits other than the size of 12 ¼", the ratio of the diameter 203 of the drill bit 200 to the diameter 251 of the main conduit 250 can be in the range of 13 to 16.5.

[0041] As previously mentioned, the above ratio of the diameter 253 of the first journal conduit 252 to the diameter 255 of the second journal conduit 254 allows for maximum increase in airflow to the cylindrical roller bearing 230 while balancing other factors related to the performance of the drill bit 200, such as airflow to other components of the journal region and / or the structural integrity of the leg 108.

[0042] Further, the ratio of the diameter 203 of the drill bit 200 to the diameter 251 of the main conduit 250 in the range of about 13 to about 16.15 is advantageous because it allows for maximum increase in airflow to the journal region 220 while balancing other factors related to the performance of the drill bit 200, such as the structural integrity of the leg 208. Ratios less than 13 can compromise the performance and / or strength of the drill bit 200. Conversely, ratios greater than 16.5 can reduce airflow to the journal region 220, which can result in damage to the drill bit 200 and / or shorten its useful life.

[0043] Industrial applicability

[0044] The disclosed aspects of the rotary drill bit 200 can be used in conjunction with a drill rig 10 to drill into a substrate, such as soil, clay, rock, or other substrates.

[0045] Referring now to Figure 9 , a flowchart illustrating an example method 900 for operating the rotary drill bit 200 is illustrated. At step 902, the method 900 includes rotating the cone 206 relative to the journal region 220 (see Figure 3 ). Rotation of the cone 206 and downward pressure cuts into the substrate, allowing the drill bit 200 to advance downward. As mentioned above, the cutting tips 210 of adjacent cones 206 can intermesh during rotation of the cones 206.

[0046] At step 904, the method 900 includes supplying air (or other gas) from the air compressor 36 of the drilling rig 10 to the main conduit 250. As described above, the proximal end of the main conduit 250 is in fluid communication with the air compressor 36 via the drill string 28, so air initially enters the main conduit 250 through the proximal end and flows toward the distal end thereof. The air compressor 36 can supply air at, for example, about 30 psi to about 90 psi.

[0047] At step 906, the method 900 includes supplying air from the main conduit 250 to the first journal conduit 252 and the second journal conduit 254. As described above, the first journal conduit 252 and the second journal conduit 254 are in fluid communication with the main conduit 250, so air entering the main conduit 250 automatically flows therethrough into the first journal conduit 252 and the second journal conduit 254.

[0048] At step 908, the method 900 includes cooling at least a portion of the journal region 220 with air from the first journal conduit 252. In particular, air from the first journal conduit 252 can flow out of the first air bore 242 to cool the thrust pad 236 and the first bearing surface 222. The air from the first journal conduit 252 can then flow outwardly and through the cylindrical roller bearing 230, the second bearing surface 224, the ball bearing 232, and the cylindrical roller bearing 234. The air can then continue to escape to the atmosphere by flowing out of the proximal exit passage 249 between the journal region 220 and the cone 206.

[0049] At step 910, the method 900 includes cooling at least a portion of the journal region 220 with air from the second journal conduit 254. In particular, air from the second journal conduit 254 can flow out of the second air bore 244 to cool the second bearing surface 224. The air from the second journal conduit 254 can then flow radially outwardly through the exit passage 248 toward the ball bearing 232 and the cylindrical roller bearing 234. The air can then continue to escape to the atmosphere by flowing out of the proximal exit passage 249 between the journal region 220 and the cone 206.

[0050] Steps 908 and 910 can particularly provide effective cooling when the ratio of the diameter 253 of the first journal conduit 252 relative to the diameter 255 of the second journal conduit 254 is within the disclosed range of about 1 to about 1.4. In at least some embodiments, this ratio maximizes the total air flow volume to the cylindrical roller bearings 230. Further, steps 908 and 910 can particularly provide effective cooling when the ratio of the diameter 203 of the drill bit 200 relative to the diameter 251 of the main conduit 250 is within the disclosed range of about 13 to about 16.5. In at least some embodiments, this ratio is advantageous and maximizes the total air flow volume to the journal region 220 including the bearings.

[0051] It should be appreciated that while steps 902 through 910 are described and illustrated in an exemplary order, any or all of steps 902 through 910 can be performed substantially simultaneously, in an overlapping manner, and / or in a different order. Further, steps 904 through 910 can be performed automatically, i.e., without additional intervention, as air is supplied from the air compressor 36 of the rig 10 to the drill bit 200.

[0052] Due to the particular ratio of the diameter 253 of the first journal conduit 252 relative to the diameter 255 of the second journal conduit 254 described herein, the rotary drill bit 200 of the present disclosure can exhibit improved cooling and, thus, a longer useful life. Specifically, the disclosed ratio of about 1 to about 1.4 can maximize the volume of cooling air supplied to the cylindrical roller bearings 230.

[0053] Because the cylindrical roller bearings 230 are physically smaller than the cylindrical roller bearings 234, the cylindrical roller bearings 230 are particularly susceptible to accelerated wear and failure. Additionally, the cylindrical roller bearings 230 are fewer in number than the cylindrical roller bearings 234, meaning that each cylindrical roller bearing 230 supports a relatively greater load. Further, the cylindrical roller bearings 230 are the farthest from the main conduit 250 of all the bearings 230, 232, 234, meaning that air must travel farther to reach the cylindrical roller bearings 230. Still further, due to the design of the drill bit 200, particularly due to the frictional heat generated by the first bearing surface 222 and the second bearing surface 224 with the cylindrical roller bearings 230, the temperature of the drill bit 200 reaches a maximum in the region surrounding the cylindrical roller bearings 230. Accordingly, the cylindrical roller bearings 230 significantly benefit from the additional cooling.

[0054] This additional cooling can be achieved using the disclosed ratio of the diameter 253 of the first journal conduit 252 to the diameter 255 of the second journal conduit 254, particularly a ratio of about 1 to about 1.4, to mitigate these issues associated with the cylindrical roller bearing 230 while still providing sufficient airflow to the other components of the journal region 220 to prevent premature wear and failure of these components. Specifically, a ratio of at least 1 can provide the desired airflow to the cylindrical roller bearing 230, while a ratio of no more than 1.4 ensures that the other components of the journal region 220 receive sufficient cooling air to avoid premature failure.

[0055] Still further, the cooling can be enhanced using a disclosed ratio of the diameter 203 of the drill bit 200 to the diameter 251 of the main conduit 250 in a range of about 13 to about 16.5. This conduit ratio can maximize the volume of cooling air supplied to the journal region 220, which includes the thrust pad 236, the first bearing surface 222, the cylindrical roller bearing 230, the second bearing surface 222, the ball bearing 232, and the cylindrical roller bearing 234. Moreover, the disclosed conduit ratio maintains sufficient velocity of the air expelled from the first and second air holes 242, 244 to ensure that the cooling air flow flows through the entire journal region 220. Thus, the cooling air does not stagnate in the journal region 220, but rather continues to flow through the entire journal region 220 and out of the proximal exit passage 249 while the air compressor 36 supplies fresh cooling air.

[0056] It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system and method without departing from the scope of the disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification and examples are intended to be exemplary only and the true scope and spirit of the invention is indicated by the claims which follow.

Claims

1. A rotary drill bit (200) for a drilling system, the drilling system including a drilling rig (10) having an air compressor (36) for supplying air to the rotary drill bit (200), the rotary drill bit (200) comprising: Multiple rotating gears (206), each rotating gear including multiple cutting tips (210); and Multiple support legs (208), with multiple toothed gears (206) respectively supported on the multiple support legs, each support leg (208) comprising: Journal region (220), the journal region being configured to rotatably support the corresponding toothed wheel (206); A main pipe (250) extends internally within the support leg (208) and is configured to receive air from the air compressor (36); A first journal guide (252) is located downstream of the main guide (250) and extends to a first air hole (242) in the journal region (220); and At least one second journal conduit (254) is located downstream of the main conduit (250) and extends to at least one corresponding second air hole (244) in the journal region (220). The ratio of the cross-sectional diameter (253) of the first cervical conduit (252) to the cross-sectional diameter (253) of at least one of the second cervical conduits (254) is in the range of about 1 to about 1.

4.

2. The rotary drill bit (200) according to claim 1, wherein the ratio of the diameter (255) of the rotary drill bit (200) to the cross-sectional diameter (253) of the main tube (250) is in the range of about 13 to about 16.

5.

3. The rotary drill bit (200) according to any of the preceding claims, wherein each leg (208) further includes a plurality of cylindrical roller bearings (234) on which the gear rotates, wherein the cylindrical roller bearings (234) are located between a first bearing surface (222) and a second bearing surface (224), the first bearing surface including a first air hole (242) and the second bearing surface including the at least one second air hole (244).

4. The rotary drill bit (200) according to any of the preceding claims, wherein the at least one second neck guide (254) comprises two second neck guides (254).

5. The rotary drill bit (200) according to any of the preceding claims, wherein the journal region (220) includes a thrust washer (236), and The first air hole (242) extends at least partially through the thrust pad (236).

6. The rotary drill bit (200) according to any of the preceding claims, wherein the journal region (220) includes a plurality of bearings (232, 234, 236) that radially support the roller cone (206), and The at least one second hole (244) is provided on the bearing surface (224) adjacent to the plurality of bearings (234).

7. The rotary drill bit (200) according to any one of claims 1 to 5, wherein the at least one second hole (244) is surrounded by an outlet channel (248) recessed in the bearing surface (224) of the journal region (220).

8. The rotary drill bit (200) according to any of the preceding claims, the rotary drill bit further comprising a nozzle (214) extending from each of the legs (208) such that air received from the air compressor (36) is diverted between the nozzle (214) and the main guide tube (250).

9. The rotary drill bit (200) according to claim 8, the rotary drill bit further comprising an air plug (216) in fluid communication with the nozzle (214).

10. The rotary drill bit (200) according to any of the preceding claims, wherein the main tube (250) has a diameter (255) of about 18.8 mm to about 24 mm, the first journal guide (252) has a diameter (255) of about 10 mm to about 13 mm, and each of the second journal guides (254) has a diameter (255) of about 8 mm to about 11 mm.

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