Technical Field

The present invention relates to a tri cone drill bit. Background With, reference to figure 1, a typical tri cone drill bit is shown which includes a main body portion with a generally cylindrical outer surface which include a threaded portion (not shown) by which the drill bit is connected to the end of a drill string (not shown).

Extendin from the main body 12 in an axial downward direction (although figure 1 shows the drill bit in the reversed orientation), are three legs equally spaced about a central longitudinal axis of the main body portion.

The three legs are connected to three conical cutter elements which are able to rotate relative to the legs which are fixed with respect to the main body portion. Th conical cutting elements are typically provided with several rows of teeth.

Inspection of drill bits during operational life has consistently shown that the flow of air and fragmented material must take a specific path in order to exit from under and then around the bit.

The present invention seeks to provide a drill bit which facilitates die removal of fragmented material from under the drill bit and hence provide a drill bit. which provides increased efficiency during the drilling operation. Summary

According to a first aspect, the present invention provides a drill bit including; a main body portion including three legs extending therefrom, the three legs arranged around a periphery of the main body portion;

conical cutter rotatably mounted on each leg, the conical cutters positioned to allow a clearance between the conical cutter and the main body portion;

a protrusion extending from the main body portion into the clearance,

wherein the protrusion encourages drill cuttings away from a base region of the main body portion where the legs meet the main body portion.

In one form, the protrusion forms an apex substantially equidistant to the three legs. I a further form the protrusion includes a sloping surface between the apex and a base region of the main body portion. I an additional form the sloping surface continues through the base region of the main body portion, emerging at an outer surface of the main body portion, in a still further form, the protrusion includes plurality of sloping faces converging at the apex. In another form the sloping faces are convex, defining a. ridge between the sloping faces.

In one form, the drill bit further includes one or more air outlets located on the base region of the main body portion and configured to direct air substantially toward the conical cutters. In anothe form the one or more air outlets are elongated with a lon axis in the direction radial to the longitudinal axis of th main body portion. In a further form, the air outlets are located at the periphery of the base region of the main body portion, between the region occupied by the legs. In a still further form, the legs and one or more air outlets are positioned within the ridges, the sloping face then forming channels for drill cuttings to flow therethrough, the channels originating from the apex, passing; between the legs and one or more air outlets, and continuing through to the outside surface of the main body portion. According to a final form the air outlets are in the form of nozzeis. Brief Description of the Accompanying Figures

The present invention will become better understood from the following detailed description of various non-limiting embodiments thereof, described in connection with the accompanying figures, wherein:

Figure 1 is a view of a prior art tri cone drill bit;

Figure 2 is a view of a tri cone drill bit in accordance with the present invention;

Figure 3 is an alternative view of a tri cone bit in accordance with the present invention, shown in a rendered presentation;

Figure 4 is. a plan view e^ *®^^^

accordance with the present invention;-?

Parts List

1 Prior art drill bit

2 Main body portion of the drill bit

3 Legs

4 Cutting cones

5 Base region of main body portion

6 Air outlet

7 Drill bit according to present invention

8 protrusion

9 apex of protrusion

10 ridge

1 1 sloping face of protrusion

12 channel

13 outer surface of the main body portion

14 scallops

5 modified air outlet

16 Shirt tail

! 7 Bearings Detailed Description of Embodiments and the Accompanying Figures

The foregoing describes only some embodiments of the present invention, and modifications and/or changes ca be made thereto without departing from the scope and spirit of the invention, the embodiments being illustrative and not restrictive.

In the context of this specification, the word "comprising" means "including principally but not necessarily solely" or "having" or "including", and not "consisting only of. Variations of the word "comprising", such as "comprise" and "comprises" have correspondingly varied meanings.

A typical tri-cone drill bit is shown in figure 1. This drill bit 1 may be coupled with a drill string (not shown). The drill bit has a main body portion .2, from which three legs 3 extend in a direction substantially co-linear with the main body portion 2 and the attached drill string. The legs 3 are positioned at even intervals around the periphery of the drill bit, and are each adapted to mount a conical cutter 4, The conical cutters 4 arc each configured to rotate around an axis of rotation. The conical cutters 4 will generally have teeth or an abrasive surface such that the three rotatin cones form a drill face, cutting or grinding through material placed in contact thereof.

Material removed by the conical cutters 4, referred to as drill cuttings or cuttings, is substantially drawn towards base region ,5 of the main body portion 2, through the rotating action of the cutlers 4 and the advance of the drill bit into the hole being dri lled. The base region 5 of the main body portion 2 is located in the general region where the leg 3 meet the main body portion 2.

Dril cuttings that are not drawn away from the base region 5 may accumulate in the hole being drilled an in the general vicinity of the drill bit. This accumulation of material can lead to the regrindin o the material, which lowers the productivit of drilling, and leads to additional abrasive wear of (he drill bit. Removal of drill cutting away from the conical cutters 4 and more generally, away from the base region 5, is critical to. the drilling efficiency and operational life of the drill bit 1.

Referring ^' still to figure L the drill bit 1 includes one or more air outlets 6. The air outlets are configured to blast high pressure air into the hole being drilled. This air dislodges and removes drill cuttings from in front of the drill face for reasons already described. The air outlets 6 are generally located at the periphery of the main body portion 2. between the legs 3. In certain embodiments, the air outlets 6 are located adjacent or substantially adjacent to the legs 3» wherea in the embodiment of figure 1 , they are equidistant to the legs.

Inspection of tri cone drill bits during operational life has consistently shown that the flow of air and fragmented material must take a specific path in order to exit from under the cones 4 and away from the base region 5. Cuttings generated by the cones 4 fail are projeeted onto the base region 5 of the main body portion 2 as a hole is being chilled. Due to the flat characteristic of base region 5, drill cuttings will accumulate here and interfere with the flow of cuttings awa from the hole. This result in significant turbulence of drill cuttings i the region of the drill bit 1, which causes disruption to the flow of particles trying to exit from under the drill bit; and out of the hole.

In addition, the positioning of the air outlet 6 results in a portion of drill cuttings moving away from the base region 5 will become entrained in the air flow directed toward the hole. This entrainment will continuall return a portion of the drill cuttings into the hole being drilled by the drill bit 1 , instead of exiting awa from the drill bit as intended. This phenomenon also adds to the turbulence in the flow of drill cuttings discussed in the paragraph above.

The present invention seeks to improve the removal rate of drill cuttings, both from the hole being drilled and from the drill bit in order t increase productivity of drillin and reduce abrasive wear on the drill bit. Figure 2 shows a certain embodiment of a tri cone drill bit 7 according to the present invention. In this embodiment the base region 5 is adapted to include a protrusion 8. This protrusion 8, is configured to extend from the base region 5 into the clearance, or space, between the base region 5 and the cutting cones 4.

According to certain embodiments, the protrusion 8 will converge substantially to an apex 9. In the embodiment of figure 2, this apex 9 is sharply defined, but in other embodiments, apex 9 may be blunt, or less defined. In the embodiment of figure 2, the protrusion 8 and the apex 9 are symmetricall arranged on the base region 5 of the main body portion 2. Such a configuration includes the apex 9 being positioned substantially equidistant from each of the legs 3 and the cones 4. Also, in such a configuration, the ape 9 is centred underneath the meeting poi nt of the three cones 4.

As a portion of the drill cuttings are conveyed towards the base region 5 of the main body poition 2 by the rotation of the cones 4 and the advance of the drill bit into the hole being drilled, the cuttings will fall incident on the protrusion 8 rather than the flat base region 5 of the prior art drill bit 1 of figure 1. Cuttings incident on the protrusion 8 are guided by the- sloping face of the protrusion 11 towards, the periphery of the base region 5 of the main body portion Z. The effect of the protrusion 8 is to prevent accumulation and turbulence of cutting in the region of the drill bit. This results in an increase in the speed by which cuttings are moved away from the drill bit 7 and the hole being drilled, reducing the regrinding of the cuttings, which in turn leads to greater drillmg productivity and reduced abrasive wear on the drill bit, The protrusion 8 of the drill bit 7 is also advantageous when drilling in soft boggy ground. As is the case with particulate cuttings, the protrusion 8 guides the soft ground and cuttings away from the base region 5 more efficiently than the flat base region of the prior art drill bit L This will decrease in tances of the drill bit becoming plugged by soft material, which can lead to the drill bit becoming bogged in the hole. The boggin of a drill bit is a majo problem which can take extensive down time to rectify and can ultimately lead to early bit failure. The protrusion 8 of th embodiment showing in figure 2 is formed from a plurality of sloping faces converging at the apex 9. In the non-limiting embodiment shown, each sloping face is concave, resulting in ridges 10 being formed between adjacent sloping faces 1 1. In other embodiments, the protrusion and/or faces thereof can take any shape desirable. Examples of protrusions listed herein are not exhaustive, but are simply intended to illustrate potential forms. The protrusion can take any shape desired, with different shapes potentially offering different advantages in drilling speed, machining cost, and wear profiles for different drill mediums, for example. One such example form, is a protrusion. without a plurality of faces, such as a smooth mound or dome. Such a protrusion could be have either a concave or convex profile, dependin on the application of the drill. Alternatively, the protrusion could have a combination of a concave and convex portion, such as protrusion with the shape of a three dimensional Gaussian curve. The protrusion could also have flat; faces, similar to a pyramid with as many faces as desired for the application. Conical protrusions, with or without a sharp apex, may also he desirable in some drilling applications.

Different angles for the sloping face of the protrusion 1 1 may also find benefit for different applications. For example, when drilling hard ground, it may be advantageou to use a shallow angle, allowing the legs 3 to he larger and henc stronger. In applications suc as this, the amount of steel used internally in the bit could also be increased to impart additional strength.

Returning; to the embodiment of figure 2, the ridges 1.0 have been arranged in such a manner as to define clear channels 12. These channels offer a path for cuttings to pass unobstructed past obstacles such as the leg 3 and air outlet 15. This effect is further enhanced by smoothly moulding the legs 3 and air outlets 15 into the ridges 10.

According to the embodiment of figure 2, it is possible to continue the sloping face 1 1 of the protrusion 8 through the base region of the main body portion 2, emerging at an outer surface 13 of the main body portion. This effectively produces scallops 14 in the outside surface of the main body portion allowing the channels 12 to continue with a steeper gradient than would otherwise be possible.

The reduction in regrinding due to the present invention may also reduce abrasive wear to the shirt tails 16 of the bit 7. These shirt tails 16 protect the bearings 17 of the rotating cones. When sealed bearings are used, excessive shirt tail 16 wear causes the bearings 17 to become exposed and leak lubricating fluid, leading to drill failure. As sealed bearings are generally preferred to normal air bearings in mining and oil field applications, the present invention may lead to productivit gains in these industries.

The quick removal of drill cuttings and other debris from the hole being drilled is a. ke factor in drill, productivity. Referring once more to figure 1 , in typical tri cone bits, the exit point of the ai outlet 6 are positioned between legs 3 at a distance substantially equidistant to each leg. This arrangement results in the air outlet occupyin approximately 1/3 of the space available between the legs. Consequently, approximately 1/3 of the drill cuttings attempting t exit from the base region 5 of the main body portion 2, may become entrained in the high pressure air emanating from the air outlet 6. A portion of this entrained material will be re-blasted into the hole bein drilled instead of being removed, leading to the regrinding of cuttings,

According to an embodimen of the present invention, the air outlets 1.5 can be shaped to occupy a smalle portion of the path available to drill cuttings to flow away from the drill bit. In a particular non- limiting embodiment, the air outlet can elongated 15 with a long axis orientated in a direction substantially radial to the longitudinal axis of the main body portion. In another non-limiting form, the air outlet .15 can be positioned closer to the legs 3 of the drill bit 7. Such an arrangement reduces the resistance to drill, cuttings exiting the base region of the drill bit, and reduces the regrinding of material returned to the drill hole by entrainment in blast air. lit the embodiment of figure 2, the elongated air outlet 15 is positioned within a ridge 10 of the protrusion 8. Otherwise stated, the air outlet 15 is positioned outside of a channel 12, formed for the conveyance of drill, cuttings and debris away from the drill bit 7, This arrangement completely removes the air outlet 15 from the path of cuttings flowing away from the drill bit 7 by way of the channel 12. The air outlet in the present invention may be a simple aperture, as represented in figure 2, or a nozzle, is desired for the drilling application.