ROCK BIT HAVING CUTTINGS CHANNELS FOR FLOW OPTIMIZATION

Abstract

A rock bit for blast hole drilling includes a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side and a ported boss, and a plurality of roller cones. Each roller cone is secured to the respective bearing shaft for rotation relative thereto. A row of crushers is mounted around each roller cone. Each leading side and each trailing side are recessed relative to the respective shirttail. Each side has a cuttings channel formed therein. The rock bit further having a nozzle disposed at each ported boss. wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle.

Claims

1. A rock bit for blast hole drilling, comprising: a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side, and a ported boss; a plurality of roller cones, each roller cone secured to the respective bearing shaft for rotation relative thereto; a row of crushers mounted around each roller cone, wherein each leading side and each trailing side are recessed relative to the respective shirttail, and each side has a cuttings channel formed therein; and a nozzle disposed in each ported boss, wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle.

2. The rock bit of claim 1, wherein each leading cuttings channel and the respective trailing cuttings channel are asymmetric.

3. The rock bit of claim 1, wherein each outward angle ranges between five and twenty-five degrees.

4. The rock bit as claimed in claim 3, wherein the outward angle is between eight to fifteen degrees.

5. The rock bit as claimed in claim 3, wherein the outward angle is between ten to thirteen degrees or between eleven to twelve degrees.

6. The rock bit of claim 1, wherein each leading side is concave and each trailing side is faceted.

7. The rock bit of claim 6, wherein each leading cuttings channel has a cross-sectional shape of a circular segment, each trailing cuttings channel has a fillet, and a radius of each leading cuttings channel is at least twice a radius of each trailing cuttings channel.

8. The rock bit of claim 7, wherein each leading side further has a first bevel extending from an edge thereof adjacent to the respective shirttail to the respective leading cuttings channel, and each leading side further has a second bevel extending from the respective leading cuttings channel to an edge thereof adjacent to an adjacent other leg.

9. The rock bit of claim 7, wherein each trailing cuttings channel further has a first face extending from an edge of the respective trailing side adjacent to the respective shirttail to the respective fillet, and a second face extending from the fillet to a bevel, each trailing side having a respective bevel extending to either an edge thereof or to the respective ported boss.

10. The rock bit of claim 1, wherein each leading cuttings channel has an inlet located at a lower edge of the respective leading side and an outlet located at an upper edge thereof adjacent to the respective base, and each trailing cuttings channel has an inlet offset from a lower edge of the respective trailing side and an outlet located at an upper edge thereof adjacent to the respective base.

11. The rock bit of claim 10, wherein a longitudinal centerline of each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit, and a longitudinal centerline of each trailing cuttings channel is slightly curved extending from the inlet thereof for a short portion of the length and is then straight along the rest thereof and inclined relative to the longitudinal axis of the rock bit.

12. The rock bit of claim 11, wherein each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between ten and thirty degrees, and the straight portion of each trailing cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between two and fifteen degrees.

13. The rock bit of claim 10, wherein longitudinal centerlines of each leading and the respective trailing cuttings channels converge toward each other from the respective inlets thereof to the respective outlets thereof.

14. The rock bit of claim 1, wherein each leg has a lubricant reservoir formed therein and a pressure compensator disposed therein.

15. The rock bit of claim 14, wherein each lubricant reservoir is located adjacent to the respective trailing cuttings channel.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0025] A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0026] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0027] FIGS. 1 and 2A illustrate a rock bit having cuttings channels for flow optimization, according to one embodiment of the present disclosure.

[0028] FIG. 2B illustrates an orientation of a nozzle of the rock bit.

[0029] FIG. 3A illustrates a cutting face of the rock bit.

[0030] FIGS. 3B, 4A, and 4B illustrate the cuttings channels.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

[0031] FIGS. 1 and 2A illustrate a rock bit 1 having cuttings channels 15, 16 for flow optimization, according to one embodiment of the present disclosure. FIG. 2B illustrates an orientation of a nozzle 8 of the rock bit. FIG. 3A illustrates a cutting face of the rock bit. The rock bit 1 may include a body 2, a plurality of roller cones 3a-c, a plurality of crushers 4a-c, and a backflow valve 14. The roller cones 3a-c and crushers 4a-c may form the lower cutting face of the rock bit 1.

[0032] The body 2 may be made by attaching a plurality (one for each roller cone 3a-c) of parts 2a-c, such as forgings, together, such as by welding. Each part 2a-c may have a portion of an upper coupling 5 and a lower leg 6. The body 2 may also have a dome 7 formed between the legs 6. The body 2 and the roller cones 3a-c may each be made from a metal or alloy, such as steel. The roller cones 3a-c may be equally spaced around the body, such as three at one hundred twenty degrees. The upper coupling 5 may be a threaded pin for connection to a drill rod (not shown). A bore may be formed through the upper coupling 5 and extend to a plenum 13 formed adjacent to the dome 7.

[0033] Each leg 6 may have a top base 6e, an upper shoulder 6s, a mid shirttail 6h, a lower bearing shaft 6b, a leading side 6d, a trailing side 6t, and a ported boss 6p. Each bearing shaft 6b may extend from the respective shirttail 6h in a radially inclined direction toward a center of the rock bit 1. Each bearing shaft 6b and the respective roller cone 3a-c may have one or more pairs of aligned grooves (not shown) and each pair may form a race for receiving a set of roller bearings (not shown) or a journal bearing sleeve (not shown). One or more thrust washers (not shown) may be disposed between each bearing shaft 6b and the respective roller cone 3a-c. The roller or journal bearings and thrust washers may support rotation of each roller cone 3a-c relative to the respective leg 6.

[0034] Each roller cone 3a-c may be mounted to the respective leg 6 by a plurality of balls 9 received in a race formed by aligned grooves in each roller cone and the respective bearing shaft 6b. The balls may be fed to each race by a ball passage formed in each leg 6a-c and retained therein by a respective keeper (not shown) disposed in the ball passage and a respective ball plug closing the ball passage. Each ball plug may be attached or fastened to the respective leg 6.

[0035] Each leg 6 may have a lubricant reservoir formed therein and a lubricant passage (not shown) extending from the reservoir to the respective roller or journal bearings and thrust washers. The lubricant may be retained within each leg 6 by one or more seals (not shown) disposed in respective one or more glands (not shown) formed in an inner surface of the respective roller cone 3a-c, thereby preventing leakage of lubricant into the blast hole (not shown). A pressure compensator 10 may be disposed in each reservoir for regulating lubricant pressure therein to be slightly greater than bottomhole pressure.

[0036] Each roller cone 3a-c may have a plurality of lands formed therein, such as a heel land, a gage land, one or more inner lands, and a nose land. A row of gage crushers 4a may be mounted around each cone 3a-c at the respective gage land. A row of first inner crushers 4b may be mounted around each cone 3 at a respective first one of the inner lands. A row of second inner crushers 4b may be mounted around each cone 3a-c at a respective second one of the inner lands. One or more nose crushers 4c may be mounted on each cone 3a-c at the respective nose land. Each crusher 4a-c may be an insert mounted in a respective socket formed in the respective roller cone 3a-c by an interference fit. Each crusher 4a-c may be made from a cermet, such as a cemented carbide, and may have a cylindrical or conical portion mounted in the respective roller cone 3a-c and a conical, chisel, or a proprietary shaped portion protruding from a respective land of the respective roller cone. The rows of inner crushers 4b and nose crushers 4c may be offset relative to one another to obtain a complete cutting profile.

[0037] A first row of heel protectors 11a may be mounted around each roller cone 3a-c at the respective heel land. A second row of heel protectors 11a may be mounted around each roller cone 3a-c between the respective heel land and the respective gage land. Each heel protector 11a may be an insert mounted in a respective socket formed in the respective roller cone 3a-c by an interference fit. The shirttail 6h and the shoulder 6s of each leg 6 may also be protected from erosion and/or abrasion by respective protectors 11b mounted therealong. Each leg protector 11b may be an insert mounted in a respective socket formed in the respective leg portion by an interference fit. Each protector 11a,b may be made from a cermet, such as a cemented carbide, and may have a cylindrical or conical portion mounted in the respective socket and a dome shaped portion protruding from the respective socket.

[0038] Alternatively, the crushers 4a-c and/or protectors 11a,b may be capped with polycrystalline diamond (PCD). Alternatively, each crusher 4a-c may be a hardfaced milled tooth.

[0039] Each ported boss 6p may be in fluid communication with the plenum 13 via a respective port formed in the upper coupling 5 and may have one of the nozzles 8 fastened therein for discharging for discharging drilling fluid, such as air, into interfaces between the roller cones 3a-c. Each ported boss 6p may be located adjacent to the trailing side 6t of the respective leg 6. The port of each boss 6 and the respective nozzle 8 therein may be inclined relative to a longitudinal axis of the rock bit 1 by an outward angle 12 such that the stream of drilling fluid discharged by the respective nozzle is aimed toward the interface between adjacent rows of gage crushers 4a. The outward angle 12 may range between five and twenty-five degrees. Each nozzle 8 may be made from an erosion resistant material, such as a ceramic or cermet, such as a cemented carbide.

[0040] The backflow valve 14 may be fastened to the body 2 in the bore of the coupling 5. The backflow valve 14 may include a seat, a valve member, and a biasing member. The biasing member may operate to bias the valve member toward a closed position. The valve member may be moved from the closed position to an open position by injection of the drilling fluid down the bore of the bit body 2 and may close if flow is ceased or may close to block upward flow.

[0041] FIGS. 3B, 4A, and 4B illustrate the cuttings channels 15, 16. While only the part 2a is shown, the part 2a may be typical of the other two parts 2b,c. Each top base 6e may be a cylindrical segment having an outer base diameter (when considered cumulatively with the other top bases). The outer base diameter may be a minimum outer diameter of the legs 6. An outer profile of the legs 6 may increase significantly along the shoulders 6s from the bases 6e to the shirttails 6h and then gradually along the shirttails from the shoulders to the bearing shafts 6b. An outer profile of the legs 6 may also increase significantly from the bases 6e to nozzle ends of the ported bosses 6p. The leading side 6d and the trailing side 6t may be recessed relative to the shirttail 6h, thereby serving as passages for cuttings transport during blast hole drilling. The trailing side 6t may also be recessed relative to the ported boss 6p.

[0042] The leading side 6d may be concave and include the leading cuttings channel 15. The leading side 6d may further include a first bevel 17a extending from an edge of the leading side adjacent to the shirttail 6h to the leading cuttings channel 15. The leading cuttings channel 15 may have a cross-sectional shape of a circular segment with a radius 15r. The circular segment may be less than one-quarter of a circle. The leading side 6d may further include a second bevel 17b extending from the leading cuttings channel 15 to an edge of the leading side adjacent to the leg 2c.

[0043] The leading cuttings channel 15 may have an inlet 15n located at a lower edge of the leading side 6d and an outlet 15o located at an upper edge of the leading side adjacent to the base 6e. A longitudinal centerline (not shown) of the leading cuttings channel 15 may be inclined relative to the longitudinal axis of the rock bit 1, such as by an angle ranging between ten and thirty degrees.

[0044] The trailing side 6t may be faceted and include the trailing cuttings channel 16. The trailing cuttings channel 16 may include a first face 16a, a fillet 16f, and a second face 16b. The first face 16a may extend from an edge of the trailing side 6t adjacent to the shirttail 6h to the fillet 16f. The fillet 16f may have a radius 16r. The leading radius 15r may be greater than the trailing radius 16r, such as at least twice that of the trailing radius. The second face 16b may extend from the fillet 16f to a bevel 18. The first 16a and second 16b faces may be perpendicular or essentially perpendicular, such as having an angle therebetween ranging between eighty and one-hundred degrees. Depending on location along the leg 6, the bevel 18 may extend to either an edge of the trailing side 6t or to the ported boss 6p.

[0045] The trailing cuttings channel 16 may have an inlet 16n offset from a lower edge of the trailing side 6t and an outlet 16o located at an upper edge of the trailing side adjacent to the base 6e. A longitudinal centerline of the trailing cuttings channel 16 may be slightly curved extending from the inlet 16n thereof for a short portion of the length and may then be straight along the rest thereof and inclined relative to the longitudinal axis of the rock bit 1, such as at an angle ranging between two and fifteen degrees. The pressure compensator 10 and lubricant reservoir may be located in a portion of the trailing side 6t delineated by the bevel 18. The pressure compensator 10 and lubricant reservoir may also be located adjacent to the trailing cuttings channel 16.

[0046] The longitudinal centerlines of the cuttings channels 15, 16 may converge toward each other from the inlets 15n,16n thereof to the outlets 15o,16o thereof. The cuttings channels 15, 16 may be asymmetric.

[0047] Advantageously, the recessed sides 6d,t (having the respective cuttings channels 15, 16) and the oriented nozzles 8 may prevent or minimize the regrinding of cuttings, thereby extending the service life of the rock bit 1.

[0048] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow.