WO2018112540A1

WO2018112540A1 - Drill bit and drill head assembly

Info

Publication number: WO2018112540A1
Application number: PCT/AU2017/051434
Authority: WO
Inventors: Henry Albert Wilson; Nathan Brooks
Original assignee: TallyWalker Pty Ltd
Priority date: 2016-12-23
Filing date: 2017-12-21
Publication date: 2018-06-28

Abstract

A drill bit for use with a drill head coupled to a drill pipe, the drill head having a return passageway extending inside the drill pipe, the drill bit including: an annular body defining a body hole extending through the body, the body including: a first body end for attachment to the drill head such that the body hole is in fluid communication with the return passageway in use; and a second body end having a funnel surface that slopes inwardly around the body hole to thereby funnel loose material into the body hole to allow the loose material to be transported through the return passageway; and one or more drill cutter blades protruding from the second body end, at least one of the drill cutter blades at least partially extending across the body hole.

Description

DRILL BIT AND DRILL HEAD ASSEMBLY Background of the Invention

[0001] The present invention relates to a drill bit for use with a drill head coupled to a drill pipe, and a drill head assembly including such a drill bit and a drill head, being particularly suitable for exploration drilling operations in which rock chip samples are collected.

Description of the Prior Art

[0002] A range of drilling techniques is known for forming holes in the ground, passing through rock or the like. Exploration drilling operations are carried out in the mining and resources industries to obtain information about the composition of the ground beneath the surface, such as to identify deposits of minerals or other desirable substances within the rock.

[0003] In general, exploration drilling will utilise drilling rigs having particular adaptations for allowing rock chip samples to be collected and returned to the surface from the cutting face at the bottom of the hole. Techniques for returning the samples to the surface by supplying compressed air down the hole are collectively referred to as air drilling. In most air drilling techniques, the drilling rig will include a drill head which provides an interface between one or more drill cutters which cut the rock and at least a drill rod which extends down the hole from the surface. The drill head will typically be configured to direct the flow of compressed air and transfer loads as the drill cutters are driven through the rock.

[0004] Rotary air blast drilling is a simple form of air drilling which involves supplying compressed air down the hole through a hollow drill rod. The compressed air blows the rock chips up to the surface in the space between the drill rod and the sidewall of the hole. However, rotary air blast drilling is not desirable for deep drilling operations because there will be significant contamination of the rock chips from the cutting surface as these come into contact with the sidewall rock in higher parts of the hole.

[0005] Air core drilling is more often employed in deep drilling operations to allow for reduced contamination of the rock samples. This technique will usually operate using a rotary drilling mechanism, with rotary drill cutters mounted on a lower end of the drill head and an upper end of the drill head being connected to a drill rod which is rotated to drive the drill cutters through the rock. The drill rod is hollow and an inner tube extends inside the drill rod. Compressed air is injected into the hole via an annular area between the drill rod and the inner tube. The drill head will typically have ports for directing the compressed air to the bottom of the hole around the cutting surface, and further provide an opening for allowing rock cuttings to be blown up the inner tube due to the compressed air.

[0006] Reverse circulation drilling is similar to air core drilling but utilises a pneumatic reciprocating piston arrangement known as a hammer to drive the drill cutters, rather than rotating of the drill rod and the drill head. This drilling mechanism can provide for better penetration of hard rock, and also removes the need for rotation of the drill tube to drive the drill cutters. Despite the use of a different drilling mechanism, a flow of compressed air is nevertheless supplied to the bottom of the hole in a similar manner as discussed above, to force rock chip samples up an inner tube, by providing a suitably configured drill head. Water may also be used to assist in pushing the cutting back up the inner tube.

[0007] Air core and reverse circulation drilling techniques may require a seal in the form of a collar or the like to be provided in the hole around the drill head to prevent samples from being blown between upwardly between the sidewall of the hole and the drill rod. Even with such a seal, there will still usually be some contamination between the rock cuttings from the cutting surface and cuttings from higher layers in the hole, due to the forceful supply of compressed air into the bottom of the hole.

[0008] Furthermore, existing air drilling techniques often result in relatively small rock chip samples being collected. This may be due to the flow of compressed air being inadequate to blow larger rock chips from the cutting face and/or due to these being broken into smaller rock chips as these are blown past the drill cutters.

[0009] AU2015215842A1 discloses a drill head including: an elongate housing, a first end of the housing being coupled to an end of a drill pipe in use; a base at a second end of the housing, one or more drill cutters being attached to the base; a supply passageway at least partially within the housing, the supply passageway being supplied with a flow of gas in use; a return passageway at least partially within the housing, a first end of the return passageway being connected to an end of an inner tube extending inside the drill pipe in use, and a second end of the return passageway forming an opening in the base proximate to the one or more drill cutters; and one or more ports for directing at least some of the flow of gas from the supply passageway into the return passageway in a flow direction extending away from the base and towards the inner tube, to thereby cause loose material to be drawn into the return passageway through the opening and transported away from the drill head via the inner tube in use.

[0010] Whilst the drill head arrangement of AU2015215842A1 provides a number of improvements in contrast to conventional air drilling techniques, it is desirable to provide an improved drill bit for use with this form of drill head or conventional air drilling drill heads.

[0011] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Summary of the Present Invention

[0012] In one broad form the present invention seeks to provide a drill bit for use with a drill head coupled to a drill pipe, the drill head having a return passageway extending inside the drill pipe, the drill bit including: an annular body defining a body hole extending through the body, the body including: a first body end for attachment to the drill head such that the body hole is in fluid communication with the return passageway in use; and a second body end having a funnel surface that slopes inwardly around the body hole to thereby funnel loose material into the body hole to allow the loose material to be transported through the return passageway; and one or more drill cutter blades protruding from the second body end, at least one of the drill cutter blades at least partially extending across the body hole.

[0013] In one embodiment the second body end has a ridge offset outwardly from the body hole, the funnel surface sloping inwardly around the body hole inside of the ridge.

[0014] In one embodiment the ridge is a protruding annular ridge.

[0015] In one embodiment the funnel surface is curved between the ridge and the body hole. [0016] In one embodiment the second body end has an outer surface that slopes inwardly outside of the ridge.

[0017] In one embodiment the body includes a shoulder about a periphery of the second body end.

[0018] In one embodiment the outer surface is curved between the ridge and the shoulder.

[0019] In one embodiment the drill bit includes a plurality of drill cutter blades that are spaced apart circumferentially relative to the body.

[0020] In one embodiment each of the plurality of drill cutter blades partially extends across the body hole.

[0021] In one embodiment the drill bit includes an even number of drill cutter blades, the drill cutter blades alternatingly extending and not extending across the body hole.

[0022] In one embodiment each of the drill cutter blades has a swept configuration.

[0023] In one embodiment each of the drill cutter blades has an arched shape.

[0024] In one embodiment each of the drill cutter blades includes a curved cutting edge.

[0025] In one embodiment each of the drill cutter blades includes fixed cutters arranged along the cutting edge.

[0026] In one embodiment the drill bit includes fixed cutters arranged on a cylindrical surface of the body between the first body end and the second body end.

[0027] In one embodiment the one or more drill cutter blades do not substantially protrude outside the annular body in a radial direction.

[0028] In one embodiment the drill head has a supply passageway that is supplied with a flow of gas in use, the drill bit including one or more supply ports extending through the body between the first body end and the second body end such that each supply port is in fluid communication with the supply passageway in use, to thereby allow at least some of the flow of gas to pass from the supply passageway to a region proximate to the one or more drill cutter blades.

[0029] In one embodiment each supply port defines a supply opening in the second body end that is located proximate to a cutting edge of a respective drill cutter blade.

[0030] In another broad form the present invention seeks to provide a drill head assembly including: a drill head including: an elongate housing, a first end of the housing being coupled to an end of a drill pipe in use; a base at a second end of the housing; a supply passageway at least partially within the housing, the supply passageway being supplied with a flow of gas in use; and a return passageway at least partially within the housing, a first end of the return passageway being connected to an end of an inner tube extending inside the drill pipe in use, and a second end of the return passageway forming an opening in the base; and a drill bit as described above, the drill bit being attached to the base of the drill head such that the body hole of the drill bit is in fluid communication with the opening in the base in use, to thereby allow the flow of gas supplied via the supply passageway to cause loose material to be funnelled into the body hole and transported through the return passageway and away from the drill head via the inner tube in use.

[0031] In one embodiment the drill head includes one or more ports for directing at least some of the flow of gas from the supply passageway into the return passageway in a flow direction extending away from the base and towards the inner tube, to thereby cause loose material to be drawn into the return passageway via the body hole of the drill bit.

[0032] It will be appreciated that the broad forms of the invention and their respective features can be used in conjunction, interchangeably and/or independently, and reference to separate broad forms is not intended to be limiting.

Brief Description of the Drawings

[0033] An example of the present invention will now be described with reference to the accompanying drawings, in which: -

[0034] Figure 1A is a perspective view of an example of a drill head; [0035] Figure IB is an end view of the drill head of Figure 1A;

[0036] Figure 1C is a side view of the drill head of Figure 1 A;

[0037] Figure ID is a side cross-section view of the drill head at section A-A of Figure IB;

[0038] Figure IE is a perspective cross-section view of the drill head at section A-A of Figure IB, without drill cutters;

[0039] Figure IF is an exploded perspective view of components for forming the drill head of Figure 1A, without drill cutters;

[0040] Figure 2 is a cross section view showing the drill head of Figure 1A in use;

[0041] Figure 3A is an end view of an outer housing component of the drill head of Figure IF;

[0042] Figure 3B is a side view of the outer housing component of Figure 3A;

[0043] Figure 3C is a side cross-section view of the outer housing component at section B-B of Figure 3B;

[0044] Figure 4 A is an end view of a base component of the drill head of Figure IF;

[0045] Figure 4B is a side view of the base component of Figure 4A;

[0046] Figure 4C is a side cross-section view of the base component at section C-C of Figure 4B;

[0047] Figure 5A is an end view of an inner housing component of the drill head of Figure IF;

[0048] Figure 5B is a side view of the inner housing component of Figure 5A;

[0049] Figure 5C is a side cross-section view of the inner housing component at section C-C of Figure 5B;

[0050] Figure 6 A is an end view of a port component of the drill head of Figure IF; [0051] Figure 6B is a side view of the port component of Figure 6A;

[0052] Figure 6C is a side cross-section view of the port component at section D-D of Figure 6B;

[0053] Figure 7A is a perspective view of a first example of a drill bit; [0054] Figure 7B is a side view of the drill bit of Figure 7A; [0055] Figure 7C is an end view of the drill bit of Figure 7A;

[0056] Figure 7D is a side cross-section view of the drill bit at section X-X of Figure 7C;

[0057] Figure 7E is a side cross-section detail view of the drill bit at detail Y of Figure 7D;

[0058] Figure 8 is a cross-section view showing the drill bit of Figure 7A in use with the drill head of Figure 1A;

[0059] Figure 9A is a perspective view of a second example of a drill bit; [0060] Figure 9B is an end view of the drill bit of Figure 9A; [0061] Figure 10A is a perspective view of a third example of a drill bit; and [0062] Figure 10B is an end view of the drill bit of Figure 10A.

Detailed Description of the Preferred Embodiments

[0063] An example embodiment of a drill bit 700 will now be described with reference to Figures 7A to 7E.

[0064] The drill bit 700 will generally be provided for use with a drill head that is coupled to a drill pipe and that has a return passageway extending inside the drill pipe. The drill head will typically be configured for allowing loose material such as rock chip samples to be collected from the cutting face and transported to the surface via the return passageway.

[0065] For example, the drill bit 700 may be provided for use with a drill head 100 as described below with regard to Figures 1A to IF and Figure 2, as originally disclosed in AU2015215842A1. In this case a return passageway 102 of the drill head 100 can be seen in Figure ID, and an example showing the drill head 100 coupled to a drill pipe 260 can be seen in Figure 2, which also shows an inner tube 270 coupled to the return passageway 102 for effectively extending the return passageway 102 inside the drill pipe 260.

[0066] Alternatively, the drill bit 700 may be provided for use with other forms of drill heads for use in conventional air drilling techniques, such as air core drilling or reverse circulation drilling. It will be appreciated that drill heads provided for these techniques will typically be configured to have a return passageway in the form of an inner tube or the like for transporting loose material such as rock chip samples to the surface. In conventional air drilling techniques a flow of compressed air is typically used to blow the loose material into the return passageway via an opening in the drill head.

[0067] In any event, returning to the example of Figures 7A to 7E, the drill bit 700 includes an annular body 710 defining a body hole 711 extending through the body 710. The body 710 includes a first body end 720 for attachment to the drill head, such that the body hole 701 is in fluid communication with the return passageway of the drill head in use. The body 710 further includes a second body end 730 having a funnel surface 731 that slopes inwardly around the body hole 701, to thereby funnel loose material into the body hole 701 to allow the loose material to be transported through the return passageway. The drill bit 700 also includes one or more drill cutter blades 740 protruding from the second body end 730. At least one of the drill cutter blades 740 at least partially extends across the body hole 701.

[0068] As the drill bit 700 is used in a drilling operation, such as by rotationally driving a drill pipe coupled to the drill head which will in turn rotationally drive the drill bit 700, the drill cutter blades 740 will progressively cut into material such as rock at the cutting face to thereby drill a hole in the material. This will generate loose material such as rock chips at the cutting face, which may be entrained in a flow of gas that will be funnelled into the body hole 701.

[0069] It will be appreciated that the configuration of the drill bit 700, and especially the funnel surface that slopes inwardly around the body hole 701, will facilitate an improved flow of loose material generated by the drill cutter blades 740 towards the centre of the body and into the body hole 701. This can help to more effectively remove loose material from the cutting face and may allow for improved efficiency, such as with regard to the power requirements for supplying a suitable flow of gas to cause the loose material to be drawn into or blown into the return passageway (depending on the particular air drilling technique being used).

[0070] The arrangement of the funnel surface 731 will also allow for larger cuttings and a greater volume of loose material to travel more freely into the body hole 701 and be transported by the return passageway. This can allow for higher quality samples of rock chips or the like to be transported from the cutting face to the surface for collection.

[0071] It is worth noting again that the drill bit 700 can be used with drill heads adapted for different air drilling techniques.

[0072] For instance, as mentioned above, the drill bit 700 is suitable for use with a drill head 100 as described in further detail below regard to Figures 1A to IF and Figure 2. To facilitate further understanding of the operation of the drill bit 700, an example of a drill head assembly including the drill head 100 and the drill bit 700 is shown in use in Figure 8.

[0073] As will be explained below, the drill head 100 is coupled to a drill pipe 260 and includes a supply passageway 101 that is supplied with a flow of gas in use (as indicated by arrows 211, 212), a return passageway 102 having a first end 103 that is connected to an inner tube 270 extending through the drill pipe 260, and a second end 104 that forms an opening 121 in a base 120 of the drill head 100, and one or more ports 105 for directing at least some of the flow of gas from the supply passageway 101 into the return passageway 102, towards the inner tube 270 (as indicated by arrows 213, 214). This causes gas and entrained loose material 203 to be drawn into the return passageway 102 from the cutting face 202 due to a venturi effect induced by the flow of gas through the ports 105.

[0074] When the drill bit 700 is used with the drill head 100, the flow of gas and entrained loose material 203 will effectively funnelled into the body hole 701 by the funnel surface 731 (as indicated by arrow 801) and thus more efficiently drawn into the return passageway 102 via the body hole 701 (as indicated by arrow 802). [0075] In some examples, additional gas may flow from the surface through the annular gap 220 between sidewalls 204 of the drilled hole and a housing 110 of the drill head 100 and the drill pipe 260, as indicated by arrows 221, and subsequently drawn into the opening 121 through the body hole 701. This flow of additional gas can also beneficially sweep the cutting face 202 to help to collect loose materials 203 to be drawn into the opening 121.

[0076] The drill bit 700 may also be used with a drill head that is adapted for air core drilling or reverse circulation drilling. These drilling techniques will also typically involve the use of a drill head with a supply passageway and a return passageway or equivalent features. But instead of the ports 105 that direct gas from the supply passageway into the return passageway as discussed above, the flow of gas from the supply passageway may be directed to the bottom of the hole around the cutting surface, so that rock cuttings will be blown up the return passageway.

[0077] It will be noted that the drill head 100 may also be optionally adapted to further include one or more holes 107 through the base 120 for allowing some of the flow of gas to pass from the supply passageway 101 to the cutting face (as indicated by arrows 218, 219). This allows for part of the flow of gas that is directed from the supply passageway 101 into the return passageway 102 through the ports 105 to contribute to the above mentioned venturi effect for drawing loose material into the return passageway 102 and allows another part of the flow of gas through the holes 107 to contribute to blowing loose material 203 into the return passageway 102, in an effective hybrid of the above discussed functionalities.

[0078] However, in some embodiments of the drill head 100, no holes 107 may be provided such that all of the flow of gas may be directed through the ports 105 and into the return passageway 102. In such embodiments, the operation of the drill head 100 may rely on the additional flow of gas that may be drawn through the annular gap 220 between the sidewalls 204 of the drilled hole and the housing 110 andthe drill pipe 260 and as mentioned above, which will entrain loose material 203 from the cutting face 202 and flow into the return passageway 102 via the body hole 701, after being funnelled into the body hole 701 by the funnel surface 731. [0079] In any case, the funnel surface 731 will facilitate more efficient transfer of the loose material 203 into the body hole 701 and thus into the return passageway 102.

[0080] In forms of the drill head having a supply passageway 101 that is supplied with a flow of gas in use as mentioned above, and particularly where at least some of this flow of gas is directed to the cutting surface 202 to blow loose material 203 into the return passageway 102, the drill bit 700 may additionally include one or more supply ports 702. Examples of the supply ports 702 are best seen in Figures 7C and 7D, but one of the supply ports 702 can also be seen in the in use example of Figure 8. These supply ports 702 extend through the body 710 between the first body end 720 and the second body end 730, such that each supply port 702 is in fluid communication with the supply passageway 101 in use. This allows at least some of the flow of gas to pass from the supply passageway 101 to a region proximate to the one or more drill cutter blades 740.

[0081] In the example of Figure 8, the fluid communication between each supply port 702 and the supply passageway 101 is achieved via the holes 107 extending through the base 120 of the housing 110 of the drill head 100. It will therefore be appreciated that, in embodiments of the drill head 100 having holes 107 through the base 120 for allowing some of the flow of gas to pass from the supply passageway 101 to the cutting face 202 as mentioned above, the supply ports 702 may be aligned with the holes 107 to enable the above discussed fluid communication with the supply passageway 101.

[0082] Further optional features of embodiments of the drill bit 700 will now be described with regard to Figures 7A to 7E.

[0083] In some embodiments, the second body end 730 may have a ridge 732 that is offset outwardly from the body hole 701, as best seen in Figures 7D and 7E. The funnel surface 731 may thus slope inwardly around the body hole 701 inside of the ridge 732. The ridge 732 represents the outer edge of the funnel surface 731 and loose material will flow over the ridge as it is funnelled into the body hole by the funnel surface 731.

[0084] The ridge 732 may be provided as a protruding annular ridge, which may extend circumferentially around the body 710 on the second body end 730. It will be appreciated however, that ridge 732 may not extend continuously around the body 710 due to the drill cutter blades 740 protruding from the second body end 730.

[0085] In some embodiments, the funnel surface 731 may be curved between the ridge 732 and the body hole 701. The funnel surface 731 will preferably have a smoothly curved profile, such that this curvature may provide an improved aerodynamic flow path for funnelling loose material into the body hole 701.

[0086] In the depicted example of the drill bit 700, the second body end 730 may also have an outer surface 733 that slopes inwardly outside of the ridge 732. In some embodiments, the shape of the outer surface 733 may be selected to correspond to the shape of the drill cutter blades 740, being offset inwardly from cutting edges of the drill cutter blades 740. The sloped shape of the outer surface 733 will help to guide loose material drawn from the cutting face in the vicinity of the drill cutter blades 740 along a flow path that is swept between the second body end 730 and the cutting face, over the ridge 732, and is then funnelled into the body hole 701.

[0087] In some embodiments, the body 710 may also include a shoulder 734 about a periphery of the second body end 730. The shoulder 734 will effectively provide a gap between the cutting face and the outer surface 733 to allow space for the loose material to flow over the second body end 730 in it flow path towards the body hole 701. The outer surface 733 may then be curved between the ridge 732 and the shoulder 734. This will provide another smoothly curved profile for providing an improved aerodynamic flow path for loose material that is being drawn towards the body hole 701 across the second body end 730.

[0088] The drill bit 700 may include a plurality of drill cutter blades 740, and these may be spaced apart circumferentially relative to the body 710, as best seen in the end view of Figure 7C. This provides a regular pattern of cutters for evenly cutting material such as rock during drilling operations.

[0089] As mentioned above, at least one of the drill cutter blades 740 extends across the body hole 701. This helps to ensure that material in the cutting face ahead of the body hole 701 will be cut and removed by the drill cutter blades 740 in use. [0090] In some examples, each of the plurality of drill cutter blades 740 partially extends across the body hole 701, as can be seen in Figure 7C where the drill bit 700 includes three cutter blades 740 that each partially extend across the body hole 701 and come close to meeting near a central axis of the body 710. Another example showing a similar configuration of the drill cutter blades 740 can be seen in Figures 9 A and 9B, and this will be discussed in further detail below.

[0091] However, in some other examples, some of the drill cutter blades 740 may not necessarily extend across the body hole 701. For instance, in some embodiments, the drill bit may include an even number of drill cutter blades 740, which may alternatingly extend and not extend across the body hole. It is noted that an example of such an arrangement is shown in Figures 10A and 10B, which will be described in due course.

[0092] In some examples, the drill cutter blades 740 may have a swept configuration. For instance, cutting edges of the drill cutter blades 740 may be swept forward or backward relative to the rotational direction in which the drill bit 700 will be driven in use. The examples of Figures 9 A and 9B and Figures 10A and 10B both show swept drill cutter blades 740 of this type. The swept configuration may help to provide more desirable cutting performance and may also help to more effectively guide loose material into the body hole 701 as it is funnelled by the funnel surface 731.

[0093] Each of the drill cutter blades 740 may have an arched shape as shown in the depicted examples of the drill bits. Each of the drill cutter blades 740 may in turn include a curved cutting edge, which will typically extend across an outer leading edge of the arched shaped drill cutter blades 740. Curved cutting edges of this type will help to create a curved cutting surface which may correspond to the curved shape of the outer surface to provide a contoured passageway for loose material to flow between the second body end 730 and the cutting face before being funnelled into the body opening 701 by the funnel surface 731.

[0094] Each drill cutter blade 740 may include fixed cutters 751 arranged along the respective cutting edge. The fixed cutters 751 may be formed from a hard and abrasion resistant material such as polycrystalline diamond compact (PDC), grit hot pressed inserts (GHI), natural diamond, or the like. The drill bit 700 may include additional fixed cutters 752 arranged on a cylindrical surface of the body 710 between the first body end 720 and the second body end 730. These additional fixed cutters 752 can help to create a smooth cylindrical drill hole.

[0095] It will be appreciated that, in the depicted examples, the drill cutter blades 740 do not substantially protrude outside the annular body 710 in a radial direction. In other words, the drill cutter blades 740 do not substantially extend outside the cylindrical surface of the body 710 between the first body end 720 and the second body end 730. Accordingly, this will mean that the outside diameter of the drill bit may at least partially choke off the drill hole, which can help to reduce any flow of gases that can pass between the drill hole and the drill pipe. This also helps to encourage flow up the return passageway and connected inner tube extending along the drill pipe.

[0096] As mentioned above, embodiments of the drill bit 700 may be adapted for use with drill heads that supply a flow of gas from a supply passageway to the cutting face, by including one or more supply ports 702. The supply ports 760 may extend through the body 710 between the first body end 720 and the second body end 730 such that each supply port 760 is in fluid communication with the supply passageway in use. This allows at least some of the flow of gas to pass from the supply passageway to a region proximate to the drill cutter blades 740.

[0097] In other words, the supply ports 760 may be positioned so the gas flows across the cutters and towards the return passageway, with the loose material being entrained with the gas to allow it to be funnelled into the body hole 701.

[0098] It will be appreciated that the example of the drill bit 700 includes a supply port 702 associated with each drill cutter blade 740. This can be best seen with regard to the end view of Figure 7C. In particular, each supply port 702 may define a supply opening 704 in the second body end 730 that is located proximate to a cutting edge of a respective drill cutter blade 740. Thus, a flow of gas through may be supplied through each supply port 702 to a region ahead of the drill cutter blade 740 in the rotational direction to allow the flows of gas to sweep the cutting face in front of the drill cutter blades 740 and carry entrained loose material into the body opening 701. In the depicted example, the supply openings 704 are defined in the outer surface 733 so that the flow of gas supplied through each supply port 702 will need to flow between the cutting face and the outer surface 733 across the ridge 732 before it is funnelled into the body hole 701 by the funnel surface 731.

[0099] With regard to Figure 7D, it will be noted that the first body end 720 may include further features for allowing the drill bit 710 to be effectively attached to the drill head. For example, the first body end 720 may include an internal step 721 around the perimeter of the body hole 701, which may allow the body hole 701 and the return passageway of the drill head to be connected with a gas tight seal. The first body end 720 may additionally or alternatively include an external step 721 around the perimeter of the body 710 itself, which may be used for attaching the drill bit 710 to the drill head, for instance. Cylindrical surfaces of either step 721, 722 may be threaded to allow a threaded attachment to correspondingly threaded cylindrical surfaces of the drill head.

[0100] It will also be noted that the supply ports 702 may define supply openings 703 in the first body end 730. These supply openings 703 may be aligned with holes 107 extending through the drill head 100 or may otherwise provide for fluid communication with an annular shaped supply passageway in some examples.

[0101] In any event, it will be appreciated that the drill bit 700 as described above will provide an improved configuration that is especially well suited for use with drill heads for air drilling which function by blowing or drawing loose material into a return passageway. The shape of the second body end 130 of the drill bit 700 is particularly adapted to encourage loose material entrained in a gas flow to freely flow between the surfaces 731, 733 of the second body end 130 and the cutting face created by the drill cutter blades 740. The loose material is then funnelled into the body hole 701 by the funnel surface 731.

[0102] In another aspect, a drill head assembly may be provided which uses the drill bit 700 as described above. With regard to Figure 8, the drill head assembly may include a drill head 100 including: an elongate housing 110, a first end 111 of the housing 110 being coupled to an end of a drill pipe 260 in use; a base 120 at a second end 112 of the housing 110; a supply passageway 101 at least partially within the housing 110, the supply passageway 101 being supplied with a flow of gas in use; and a return passageway 102 at least partially within the housing 110, a first end 103 of the return passageway 102 being connected to an end of an inner tube 270 extending inside the drill pipe 260 in use, and a second end 104 of the return passageway 102 forming an opening 121 in the base 120. The drill head assembly 100 may further include the drill bit 700 as described above, the drill bit 700 being attached to the base 120 of the drill head 100 such that the body hole 702 of the drill bit 700 is in fluid communication with the opening 121 in the base 120 in use, to thereby allow the flow of gas supplied via the supply passageway 101 to cause loose material 203 to be funnelled into the body hole 701 and transported through the return passageway 102 and away from the drill head 100 via the inner tube 270 in use.

[0103] In view of the above, it will be appreciated that, in some embodiments of the drill head assembly, the drill head 100 may include one or more ports 105, as mentioned above, for directing at least some of the flow of gas from the supply passageway 101 into the return passageway 102 in a flow direction extending away from the base 120 and towards the inner tube 270, to thereby cause loose material 203 to be drawn into the return passageway 102 via the body hole 701 of the drill bit 700.

[0104] In some embodiments of the drill head assembly, the drill bit 700 may include supply ports 702 that are in fluid communication with the supply passageway 101, such as via holes 107 through the base, to additionally or alternatively direct at least some of the flow of gas from the supply passageway 101 towards the cutting face 202 for blowing loose material 203 into the body hole 701 of the drill bit 700.

[0105] An example of another embodiment of a drill bit 900 is shown in Figures 9A and 9B. This example includes generally similar features as described above with regard to Figures 7A to 7E, but specifically includes three swept drill cutting blades 740. In this example, the drill bit 900 does not include any supply ports 702, but these may be added separately, such as by drilling through holes in the outer surface 733 ahead of the drill cutting blades 740 to define the supply ports 702 as shown in the previous example of the drill bit 700.

[0106] Another example of a possible embodiment of a drill bit 1000 is shown in Figures 10A and 10B. In this case, the drill bit 1000 includes four drill cutting blades, alternating between a first type of drill cutting blade 1041 which extends across the body hole 701 and a second type of drill cutting blade 1042 which does not extend across the body hole 701. The two drill cutting blades 1041 of the first time meet in the centre of the body hole 701 to effectively form a continuous arch over the body hole 701. It is noted that the body 710 in this example is relatively flatter and that the shoulder 734 is noticeably wider compared to the same features in the previous examples of the drill bits 700, 900. Furthermore, as in the previous example, the drill bit 1000 does not show any supply ports 702, but these may be added as needed.

[0107] To provide further context for the above described drill bits, examples of drill heads suitable for use with the drill bits will now be described. It is noted that these examples refer to drill cutters that may be attached to the drill head, although it should be appreciated that these may be replaced with a drill bit as described above, provided suitable fluid communication connections are made when the drill bit is attached to the drill head, in order to enable the described functionalities of the drill head.

[0108] An example embodiment of a drill head 100 will now be described with reference to Figures 1A to IF and Figure 2 which illustrates an example of the drill head 100 in use.

[0109] The drill head 100 includes an elongate housing 110. As shown in Figure 2, a first end 111 of the housing 110 is coupled to an end of a drill pipe 260 in use. The drill head 100 also includes a base 120 at a second end 112 of the housing 111, and one or more drill cutters 130 are attached to the base 120.

[0110] It should be noted that a range of different styles of drill cutters 130 may be used with the drill head 100 without significantly impacting the above described functionality, and as such it should be appreciated that the particular drill cutters 130 depicted in Figures 1A to ID and Figure 2 are for the purpose of enabling understanding of the invention but are not intended to limit the type of drill cutters 130 that can be used.

[0111] In this example, the drill head 100 is used in a rotary drilling arrangement, such that when the drill pipe 260 is rotationally driven this will cause the drill cutters 130 to rotate and cut into material 201 such as rock at a cutting face 202 to thereby drill a hole in the material 201, in a generally conventional manner. Accordingly, the drill cutters 130 shown in the Figures are rotary drill cutters particularly adapted for rotary drilling. [0112] However, alternative embodiments of the drill head 100 may be used in other drilling arrangements and may thus use different forms of drill cutters 130, such as for hammer drilling where the drill cutters 130 are periodically driven by a pneumatic motor to cut into the material 201, rather than through rotation of the drill pipe 260.

[0113] With regard to the cross section views of Figures ID and IE, the drill head 100 includes a supply passageway 101 at least partially within the housing 110. The supply passageway 101 is supplied with a flow of gas in use. For example, with reference to Figure 2, arrows 211 indicate a flow of gas being supplied to the supply passageway 101 from a corresponding passageway inside the drill pipe 260 and arrows 212 indicate the flow of gas through the supply passageway 101 itself.

[0114] The flow of gas may be provided, for example, by a compressed gas source (not shown) at the surface. Typically, the compressed gas source will be an air compressor or the like for compressing atmospheric air from the surface. Although air is readily available and easily compressible, it should be understood that any suitable gas may be used. In any event, the compressed gas source would typically be connected to the drill pipe 260 at the surface to supply compressed gas into the drill pipe 260 to in turn supply the flow of gas to the supply passageway 101.

[0115] The drill head 100 further includes a return passageway 102 at least partially within the housing 110. A first end 103 of the return passageway 102 is connected to an end of an inner tube 270 extending inside the drill pipe 260, whilst a second end 104 of the return passageway 102 forms an opening 121 in the base 120 proximate to the drill cutters 130. The inner tube 270 will typically extend inside the drill pipe 260 to the surface to provide a continuous path from the return passageway 102 to the surface via the inner tube 270.

[0116] One or more ports 105 are provided for directing at least some of the flow of gas from the supply passageway 101 into the return passageway 102, in a flow direction extending away from the base 120 and towards the inner tube 270. For example, with reference again to Figure 2, arrows 213 indicate flows of gas entering the ports 105 from the supply passageway 101, whilst arrows 214 indicate flows of gas exiting the ports 105 into the return passageway 102. It is noted that this results in a flow of gas through the return passageway 102 and into the inner tube 270 as indicated by arrow 215.

[0117] The flow of gas through the ports 105 causes loose material 203, such as drill chips in the form of chips of rock or the like cut by the drill cutters 130 at the cutting face 202, to be drawn into the return passageway 102 through the opening 121 and transported away from the drill head 100 via the inner tube 270. For example, with reference to Figure 2, arrow 216 indicates a flow of gas which draws loose material 203 from the cutting face 202 into the opening 121 in the base 120, and arrow 217 indicates a flow of gas with entrained loose material 203 passing into the return passageway 102 due to the flow of gas from the ports 160 as indicated by arrows 213 and 214.

[0118] It will be appreciated that loose material 203 entrained in the flow of gas through the return passageway 102 will subsequently pass through the inner tube 270 and thus may be transported to the surface via the inner tube 270. Thus, samples of rock chips or the like may be transported from the cutting face 202 to the surface for collection.

[0119] It will be understood that the loose material 203 may be drawn upwardly from the cutting face 202 towards the opening 121, and subsequently into the return passageway 102 and the inner tube 270, under the influence of different physical effects, such as by generating a partial vacuum to move loose material by suction or by causing an additional flow of gas to flow supplied to the cutting face 202 to flow into the opening 121 with entrained loose material 203.

[0120] For example, the loose material 203 may be drawn into the opening 121 due to suction caused by the flow of gas through the ports 105 into the return passageway 102. In preferred implementations, the flow of gas directed into the return passageway 102 by the ports 105 will generate a gas pressure difference between the opening 121 and the return passageway 102, to thereby cause the loose material to be drawn into the return passageway 102 through the opening 121 due to suction. However, it should be understood that this gas pressure difference can be due to different mechanisms depending on the particular design configuration, as will be discussed in further detail below. [0121] In any event, the above described arrangement can be contrasted from conventional air drilling techniques in that at least some of the flow of air is directed into the return passageway 102 via the ports 105, so that at least some of the supplied flow is diverted back towards the surface via the inner tube 270 without passing through the region proximate to the drill cutters 130 or cutting face 202. In general, this diverted flow causes loose material 203 to be drawn into the opening 121 by suction rather than by directly blowing loose material 203 from the cutting face 202 as is generally the case in conventional air drilling techniques. In this regard is noted that conventional air drilling techniques usually direct all of the supplied flow of gas through holes arranged around the drill cutters so that the gas flows across the cutting surface and subsequently blows the loose material back to the surface, either through an inner tube extending inside the drill rod or in the space surrounding the drill rod.

[0122] In contrast to conventional air drilling techniques, the above described arrangement allows for improved quality of rock chip samples, because the suction mechanism of collecting rock chip samples from the cutting face 202 is less prone to contamination compared to forcefully blowing the cutting face 202 with gas.

[0123] Furthermore, loose material 203 can be removed from the cutting face 202 more efficiently due to the loose material being drawn into the opening 121, in comparison to conventional air drilling techniques in which forcefully supplying gas to the cutting face 202 does not reliably blow loose material directly into the inner tube and can undesirably blow some loose material into the space outside the drill rod or otherwise induce circulation of loose material about the drill cutters.

[0124] In addition, the drill head 100 as described above may allow for the collection of larger rock chip samples than in similar conventional air drilling techniques, because the rock chips are less likely to be broken into smaller chips by the drill cutters when they are more efficiently drawn away from the cutting face 202.

[0125] In view of the above advantages, it has been found that the above described arrangement can allow for significant productivity improvements for exploratory drilling operation, when compared to the use of conventional air drilling techniques employed to delivery rock chip samples with similar quality and size parameters.

[0126] As will be understood by persons skilled in the art, the improved functionality of the above described arrangement is at least in part due to the arrangement of the passageways 101, 102, ports 105 and the opening 121 defined within the housing 110 and the base 120, to provide the flow of gas that draws loose material 203 from the cutting face 202 into the drill head 100 and transports it to the surface via the inner tube 170.

[0127] It should therefore be appreciated that embodiments of the drill head 100 may be provided with different structural configurations whilst still providing the above discussed functionality, as long as these provide suitable passageways 101, 102, ports 105 and an opening 121 and thus establish suitable flows of gas through the drill head 100.

[0128] For instance, the example embodiment depicted in Figures 1A to IF and Figure 2 shows an assembly of multiple components for constructing the drill head 100, and such a configuration may be convenient from a manufacturing perspective. However, it will be understood that the use of an assembly of components as shown is not essential, and it is possible to construct a suitable drill head 100 from an assembly of fewer components or even as a single part integrating the required features, such as by utilising 3D printing or additive manufacturing techniques, or the like.

[0129] Furthermore, the specific arrangement of the passageways 101, 102, ports 105 and the opening 121 as depicted in the Figures is not essential. For instance, it will be appreciated that the relative positioning of the passageways 101, 102 and the ports 105 providing for gas flow therebetween does not need to be as shown, although as discussed below there may be certain structural and functional advantages for using the depicted arrangement. Whilst some examples of alternative arrangements will be mentioned in the discussion of the construction of depicted embodiment, it should be understood that other variations which nevertheless provide the above described basic functionality are possible, even if these are not explicitly discussed.

[0130] Further preferred and/or optional features of the drill head 100 will now be described with reference to the Figures. As discussed above, it should be noted that whilst the particular embodiment shown in the Figures illustrates a preferred drill head 100 configuration, different configurations may also be suitably employed to provide the above described functionality and at least some of the features to be outlined below.

[0131] Typically, the supply passageway 101 will define a supply cross section area and the return passageway 102 will define a return cross section area, as can be best seen in the end view of Figure IB. Each of the passageways 101, 102 may be defined such that their respective cross section areas are substantially constant along at least a portion of their length, to thereby allow for stable flow of gas through each of the passageways 101, 102.

[0132] In some examples, the supply passageway 101 and the return passageway 102 may be configured so that the supply cross section area is greater than the return cross section area. It will be understood that these different cross section areas will result in the flow of gas in the respective passageways 101, 102 having different pressures and velocities. In particular, when the supply cross section area is greater than the return cross section area, the flow of gas in the return passageway 102 will have a greater velocity and a reduced pressure compared to the flow of gas in the supply passageway 101. Accordingly, the supply cross section area and the return cross section area can be selected to provide a pressure reduction between the supply passageway 101 and the return passageway 102, due to the venturi effect. The design of the drill head 100 may thus take advantage of this pressure differential due to the venturi effect draw loose material 203 into the opening 121 and in turn through the return passageway 102.

[0133] In preferred embodiments, the one of more ports 105 will be configured to direct the flow of gas into the return passageway 102 in a manner which further assists in drawing loose material 203 into the return passageway 102. Typically this is achieved by having the ports direct the flow of gas in a particular direction relative to the return passageway 102, for establishing preferable flow conditions within the return passageway 102.

[0134] In most examples, the one or more ports 105 will usually be configured so that the at least some of the flow of gas directed into the return passageway 102 includes an axial flow component relative to an axis of the return passageway 102. It will be understood that this will aid in establishing the flow of gas through the return passageway 102 in the flow direction extending away from the base 120 and towards the inner tube 170, for transporting loose material 203 entrained within the flow of gas to the surface.

[0135] However, it may also be desirable to configure the ports 105 so that the flow of gas directed into the return passageway 102 further includes a rotational flow component relative to the axis of the return passageway 102. This may be achieved, for example, by having the ports 105 oriented at an angle relative to the axis of the return passageway 102. The particular orientation angle may be selected to control the amount of rotational flow in the flow of gas directed into the return passageway 102. In rotational drilling arrangements, the orientation angle of the ports 105 may be selected in view of the rotation direction of the drill head 100 in use, so that the rotational flow of the gas in the return passageway 102 can be assisted by the rotation of the drill head 100.

[0136] Whilst it is generally convenient to form the ports 105 as straight holes having a particular orientation angle, at least for ease of manufacture, it should be noted that the ports 105 may be formed in other ways, whilst still being capable of directing the flow of gas into the return passageway 102 in a suitable manner. Typically, a portion of each port 105 near its exit into the return passageway 102 will have the greatest influence over the direction of flow entering the return passageway 102 from the ports. Thus, in some examples, the amount of axial and rotational flow may be determined by selection of the exit conditions of the ports 105 without changing the overall orientation of the ports 105.

[0137] In some examples, the ports 105 may be configured so that the flow of gas directed into the return passageway 102 forms a vortical flow in at least a portion of the return passageway 102. In other words, the flow of gas may be directed so as to establish a vortex within the return passageway. Those skilled in the art will understand that the vortical flow will usually have a reduced pressure in a core region about an axis of the vortex, which can further assist in drawing loose material 203 into the return passageway 102 by suction. Such a vortical flow may be established through appropriate design of the ports 105, and particularly their orientation angle relative to the axis of the return passageway 102 to encourage sufficient rotation in the flow directed into the return passageway 102. [0138] As is the case in this example, the drill head 100 includes a plurality of the ports 105 arranged around the return passageway 102. In this case, eight ports 105 are provided, although different numbers of ports 105 may be used. It will be appreciated that such an arrangement of multiple ports 105 can assist in effectively establishing desirable flow conditions within the return passageway 102 with a reduced transitional flow region as the flow of gas enters the return passageway 102 from the ports 105. Furthermore, a suitable number of ports 105 evenly arranged around the return passageway 102 can help to induce a rotational or vortical flow within the return passageway 102, if required.

[0139] It will be appreciated that as the flow of gas is directed from the supply passageway 101 into the return passageway 102 via the ports 105, some gas may be drawn from the region proximate to the cutting face 202 into the opening 121 and through the return passageway 102, along with the loose material 203, as indicated in Figure 2 by arrow 216. In some examples, additional gas may flow from the surface through the annular gap 220 between the sidewalls 204 of the drilled hole and the housing 110 and the drill pipe 260, as indicated by arrows 221, and subsequently drawn into the opening 121. This flow of additional gas can also beneficially sweep the cutting face 202 to help to collect loose materials 203 to be drawn into the opening 121.

[0140] However, in some circumstances such a flow of additional gas can be undesirable as it may result in contamination of the loose material 203 from the cutting face 202 with other materials from higher in the drilled hole. Accordingly, in some embodiments, the drill head 100 may further include one or more holes 107 through the base 120 for allowing some of the flow of gas to pass from the supply passageway 101 to a region proximate to the one or more drill cutters 130. Examples of these holes 107 can be seen in Figures ID and IF and Figure 2.

[0141] With regard to Figure 2, it will be seen that the holes 107 are formed to receive gas from the supply passageway 101 such that some of the flow of gas supplied to the supply passageway 101 can flow through the holes 107 rather than through the ports 105 into the return passageway 102. The gas flowing through the holes 107 will exit through the base 120 near the drill cutters 130 as indicated by arrows 218, to blow onto the cutting face 202. This gas flow can beneficially sweep the cutting face 202 as indicated by arrows 219 so that loose materials 203 can be more effectively drawn into the opening 121. [0142] In other words, the holes 107 effectively allow some of the flow of gas supplied to the supply passageway 101 to bypass the ports 105 and instead pass directly to the region proximate to the drill cutters 130. As a result, the gas flowing through the holes 107 is able to sweep the cutting face 202 formed by the drill cutters 130 in use prior to being drawn back into the opening 121 with loose material 203.

[0143] Although a similar effect may be achieved by allowing an additional flow of gas from the surface to enter the opening 121 as mentioned above, the use of the holes 107 to supply the gas for sweeping the cutting face 202 may remove or at least significantly reduce the need for gas to flow from the surface, thus reducing or eliminating contamination of the rock chip samples by material from higher parts of the drill hole.

[0144] In this example, the drill head 100 includes a plurality of the holes 107 arranged around the opening 121 in the base 120. It will generally be preferable to provide a number of evenly spaced holes 107 around the opening 120 to allow for desirable flow conditions across the cutting face 202. It will be appreciated that the number and spacing of the holes 107 may be dictated to at least some extent by the arrangement of drill cutters 130 attached to the base 120. In this example, four drill cutters 130 are attached to the base 120, and correspondingly, four holes 107 are provided, each for allowing gas to flow between adjacent drill cutters 130.

[0145] The relative amount of gas flowing through the ports 105 and through the holes 107 may be controlled by selecting the total number of and sizes of the ports 105 and the holes 107. For example, a greater proportion of flow can be directed through the ports 105 by ensuring the holes 107 are smaller than the ports 105 and/or by providing fewer holes 107 than ports 105.

[0146] In any event, it will be appreciated that allowing for some of the flow of gas from the supply passageway to bypass the ports 105 and sweep the cutting face 202 before being drawn into the opening 121 and rejoining the rest of the flow of gas directed into the return passageway 102 via the ports 105 can assist in removing loose material 203 from the cutting face 202 and improve the quality of rock chip samples returned to the surface.

[0147] Further details of the structural configuration of the example drill head 100 shown in the Figures will now be described. [0148] In this example, the housing 110 has a generally cylindrical shape and the return passageway 102 is located coaxially inside the housing 110. It will be appreciated that a cylindrical housing 110 will allow for convenient attachment of the first end 111 of the housing 110 to a cylindrical drill pipe 260, such as by using a threaded portion 113 provided on the outside of the first end of 111 of the housing 110. Furthermore, a cylindrical housing 110 can be conveniently manufactured using a lathe or the like.

[0149] The supply passageway 101 may be located between the return passageway 102 and an outside surface of the housing 110. In other words, the return passageway 102 may extend through the centre of the housing and the supply passageway 101 may be offset from the centre. In the depicted embodiment, the supply passageway 101 is provided as an annular passageway, and the return passageway 102 is located concentrically inside the annular supply passageway 101. It will be appreciated that this allows for an axi- symmetrical arrangement of the passageways 101, 102, which can be particularly advantageous for rotational drilling where imbalanced masses due to asymmetry could result in undesirable vibrations. Moreover, as will be discussed below, this arrangement can facilitate the use of a straightforward multi-component construction for forming the drill head 110.

[0150] For example, the drill head 100 may include a hollow outer housing 140 and an inner housing 150 positioned inside the outer housing 110, with the return passageway 102 being defined within the inner housing 150 and the supply passageway 101 being defined between the inner housing 150 and the outer housing 140. In the depicted example, the outer housing 140 is provided by an outer housing component 140 and the inner housing 150 is provided by an inner housing component 150. As can be best seen in Figures IE and IF, the outer housing component 140 and the inner housing component 150 may each be formed as generally cylindrical bodies with open ends.

[0151] Further details of the outer housing component 140 are shown in Figures 3A to 3C, where it can be seen that the outer housing component 150 includes an outer wall 301 and a central bore defining an inner wall 302. The inner housing component 150 is located inside of the central bore of the outer housing component 140. Further details of the inner housing component 150 are shown in Figures 5 A to 5C, where it can be seen that the inner housing component 150 has its own outer wall 501 and its own central bore defining an inner wall 501. The central bore of the inner housing component 150 forms a main portion of the return passageway 102. The supply passageway 101 is formed between the outer wall 501 of the inner housing component 150 and the inner wall 301 of the outer housing component 140.

[0152] In this example, the inner housing component 150 includes one or more spacers 153 for locating the inner housing component 140 relative to the outer housing component 150. The spacers 153 will typically protrude outwardly from the outer wall 501 of the inner housing component 150, and be configured to engage with the inner wall 302 of the outer housing component 140, to thereby radially locate the inner housing component 150 within the bore of the outer housing component 140, whilst allowing gas to flow around the spacers

153 without substantially restricting the overall flow of gas through the supply passageway 101. In this case, four spacers 153 are arranged evenly around the inner housing component 150.

[0153] Turning back to the views of the outer housing component 140 in Figures 3A to 3C, it will be seen that the outer housing component 140 includes a threaded portion 143 which is configured for allowing the outer housing component 140, and thus the assembly of components forming the drill head 100, to be threadingly connected to the drill pipe 260 as shown in Figure 2. Such a threaded connection will be suitable for transferring rotary drilling loads from the drill pipe 260 to the drill head 100, whilst also providing a sealed connection suitable for allowing the gas flow to be supplied into the supply passageway 101 formed inside the outer housing component 140.

[0154] With regard to the views of the inner housing component 150 in Figures 5 A to 5C, it can be seen that in this case, a series of grooves 154 are formed at a first end 151 of the inner housing component 150. As shown in Figure 2, o-rings 271 may be placed into the grooves

154 to assist in sealing a connection between the inner tube 270 and the inner housing component 150, where the inner tube 270 is push fit onto the first end 151 of the inner housing component 150.

[0155] However, it will be appreciated that different techniques may be used for connecting the outer housing component 140 to the drill pipe 260 and for connecting the inner housing component 150 to the inner tube 270 extending inside the drill pipe 260, provided these are capable of transferring any required loads, such as drilling loads, and also allow for the required gas glows into the respective passageways 101, 102.

[0156] In the depicted example, the ports 105 are provided in a port component 160 connected to a second end 152 of the inner housing component 150. Providing the ports 105 in a separate port component 160 in this manner can have several advantages. For instance, different port component 160 configurations may be provided by simply exchanging the port component 160 with another port component 160 with a different arrangement of ports 105. Furthermore, the use of a separate port component 160 can allow for more straightforward manufacture rather than having the ports 105 formed, for instance, in the second end 152 of the inner housing component 150. Nevertheless, it will be understood that it will be possible to integrate the port component 160 and the inner housing component 150 to reduce the number of components and amount of assembly, typically at the expense of more complex manufacturing requirements.

[0157] As can be best seen in Figures IE and IF, the port component 160 may be configured to be connected between the inner housing component 150 and the base 120. The port component 160 will typically include a central aperture for extending the return passageway 102 in the inner housing component 150 to the opening 121 in the base 120. In this example, the base 120 is provided by a further base component 170 connected to the second end 142 of the outer housing component 140. The base component 170 will typically include the opening 121 and be configured to allow the attachment of the drill cutters 130. In this case, the base component 170 defines drill cutter receptacles 174 for receiving attachment portions of the drill cutters 130, which can be welded or otherwise fastened to the base component 170.

[0158] Further details of the base component 170 can be seen in Figures 4 A to 4C. The base component 170 may be formed as a cylindrical body having an outer wall 401 with an outside diameter generally corresponding to an outside diameter of the outer wall 301 of the outer housing component 140. In this example, the base component 170 includes a lip 172 configured to engage with a corresponding lip 144 at the second end 142 of the outer housing component. These lips 172, 144 may be connected by welding or any other suitable connection technique to thereby join the base component 170 to the outer housing component 140.

[0159] The internal details of the base component 170 can be seen in isolation in Figure 4C and in the context of the assembly in Figures ID and IE and Figure 2. The base component 170 has a central shaft having varying dimensions, which each have different functions. A first shaft portion having an enlarged diameter extends from the lip 172 into the base component 170 and defines a first inner wall 402 and ends at a step 173.

[0160] As can be seen in Figure ID, the port component 160 is positioned partially inside the first shaft portion, and as shown in Figure 2, the ports 105 receive a flow of gas from an annular region 106 between the port component 160 and the first inner wall 402 of the base component 170.

[0161] The holes 107 extend from the step 173 through to the base 120, and also receive a flow of gas from the same annular region 106 as the ports 105. The holes 107 and the ports 105 may be staggered relative to one another to ensure even distribution of gas supplied along the supply passageway 101 through the ports 105 and the holes 107. It is noted that the outer housing component 140 includes a flared inner wall portion 303 as indicated in Figure 3C, which helps to accommodate the port component 160 and direct the supplied flow of gas into the annular region 106 for distribution in to the ports 105 and the holes 107.

[0162] As shown in the hidden details in Figures 4 A and 4C, the holes 107 in the base component 170 may be angled relative to a central axis of the base component 170, which can provide for a rotational component in the flow of gas that bypasses the ports 105 and is directed via the holes 107 into the region proximate to the drill cutters 130.

[0163] The base component 170 includes a second shaft portion extending from the first shaft portion and defining a second inner wall 403 having a reduced internal diameter relative to the first inner wall 402. The second shaft portion receives a second end 162 of the port component 160 when the drill head 100 is assembled. Finally, a third shaft portion extends through the remainder of the base component 160 and defines a third inner wall 404, which in this case is flared outwardly to the opening 121. [0164] Turning to Figures 6 A to 6C, it can be seen that the port component 160 has different outer surfaces. The port component 160 includes a first outer surface 601 which generally matches the angle of the flared inner wall portion 303 of the outer housing component 140 so as to allow the flow of gas from the supply passageway 101 to pass around the port component 160 without substantial flow restrictions. The ports 105 are formed in a second outer surface 603 which provides entry points 611 for the port 105 to allow gas flow from the supply passageway 101 into the ports 105 from the annular region 106 discussed above.

[0165] A third outer surface 605 extends from the second outer surface 603 to the second end 162 of the port component 160. This third outer surface 605 is configured to be received inside the second shaft portion of the base component 170 and mate with its second inner wall 403. The second end 162 of the port component 160 will rest on a shoulder region between the second inner wall 403 and the third inner wall 404 of the base component 170.

[0166] With regard to the internal features of the port component 160 as shown in Figure 6C, it will be seen that the central aperture extending through the port component 160 forms a generally straight internal wall 602. An enlarged internal shelf 604 is defined in the first end 161 of the port component 160, and this provides exit points 612 for the ports 105.

[0167] As can be seen in the internal views of the drill head 100 assembly in Figures ID and IE, the second end 152 of the inner housing component 150 will engage with the internal shelf 604 of the port component. It is noted that the inner housing component 150 has a flared inner wall portion 503 as indicated in Figure 5C, and this helps to prevent obstruction of the exit points 612 of the ports 105 and thus permit the flow of gas from the ports 105 into the return passageway 102.

[0168] It will be appreciated that each of the above described components in the assembly of the drill head 100 can be easily formed from suitable materials such as steel, other metals, ceramics or the like using conventional manufacturing techniques including casting, lathing, machining and drilling. However, the features described above do not need to be provided in separate components as per the depicted example, and may be provided in different components or integrated into fewer components without compromising the functionality of the drill head 100. [0169] For example, the inner housing component 150 and the port component 160 may be easily integrated into a single component including suitable ports 105 whilst still being capable of manufacture using conventional techniques. In an example of complete integration, 3D printing or additive manufacture techniques may be used to form the drill head 100 as a unitary body with all required passageways 101, 102, ports 105 and the opening 121.

[0170] Accordingly, there is substantial design flexibility in the specific construction of the drill head 100, such that a range of different configurations may be implemented whilst still providing a functional drill head providing improvements over conventional air drilling techniques as outlined above.

[0171] As mentioned above, the drill head 100 may alternatively be used in a hammer drilling configuration where suitably adapted drill cutters 130 are driven periodically by a pneumatic motor rather than by rotation of the drill pipe 260.

[0172] In one example, a hammer drilling module may be connected between the drill pipe 260 and the drill head 100, for driving the drill head 100 and attached drill cutters 130. In this case, the pneumatic motor may be supplied with some of the compressed gas flowing through the drill pipe 260 before it reaches the supply passageway 101 within the drill head 100.

[0173] In summary, the internally defined passageways 101, 102 and particularly the use of the ports 105 to direct at least some of the flow of gas from the supply passageway 101 into the return passageway 102 will tend to create positive suction for drawing samples into the return passageway 102 for transport to the surface via the inner tube 270.

[0174] The suction created also causes any other flow of gas (such as gas bypassing the ports 105 and flowing through the optional holes 107) being used to flush loose material 203 such as rock chips from the cutting face 202 to flow into the return passageway 102 and in turn into the inner tube 270. Greater sample weights can be collected in reduced timeframes using this approach.

[0175] It will be appreciated that as the volume and pressure of the flow of gas supplied into the supply passageway 101 is increased, the above discussed suction effect will correspondingly increase, aiding in sample recovery and the ability to use increased air pressure compared to traditional air drilling arrangements, where excessive air pressure may undesirable force loose material onto the cutting face 202.

[0176] Accordingly, suitable embodiments of the drill head 100 may effectively provide for an improved scavenging effect which allows for a cleaner drill hole compared to conventional air drilling arrangements. The resulting cleaner drill hole and more rapid sample removal due to this scavenging effect can also allow for a greater rate of penetration. The cleaner drill hole also reduces the chance of the drill pipe 260 becoming stuck in the hole.

[0177] Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

[0178] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1) A drill bit for use with a drill head coupled to a drill pipe, the drill head having a return passageway extending inside the drill pipe, the drill bit including:

a) an annular body defining a body hole extending through the body, the body including: i) a first body end for attachment to the drill head such that the body hole is in fluid communication with the return passageway in use; and

ii) a second body end having a funnel surface that slopes inwardly around the body hole to thereby funnel loose material into the body hole to allow the loose material to be transported through the return passageway; and

b) one or more drill cutter blades protruding from the second body end, at least one of the drill cutter blades at least partially extending across the body hole.

2) A drill bit according to claim 1, wherein the second body end has a ridge offset outwardly from the body hole, the funnel surface sloping inwardly around the body hole inside of the ridge.

3) A drill bit according to claim 2, wherein the ridge is a protruding annular ridge.

4) A drill bit according to claim 2 or claim 3, wherein the funnel surface is curved between the ridge and the body hole.

5) A drill bit according to any one of claims 2 to 4, wherein the second body end has an outer surface that slopes inwardly outside of the ridge.

6) A drill bit according to claim 5, wherein the body includes a shoulder about a periphery of the second body end.

7) A drill bit according to claim 6, wherein the outer surface is curved between the ridge and the shoulder.

8) A drill bit according to any one of claims 1 to 7, wherein the drill bit includes a plurality of drill cutter blades that are spaced apart circumferentially relative to the body.

9) A drill bit according to claim 8, wherein each of the plurality of drill cutter blades partially extends across the body hole.

10) A drill bit according to claim 8, wherein the drill bit includes an even number of drill cutter blades, the drill cutter blades alternatingly extending and not extending across the body hole.

11) A drill bit according to any one of claims 1 to 10, wherein each of the drill cutter blades has a swept configuration. 12) A drill bit according to any one of claims 1 to 11, wherein each of the drill cutter blades has an arched shape.

13) A drill bit according to any one of claims 1 to 12, wherein each of the drill cutter blades includes a curved cutting edge.

14) A drill bit according to claim 13, wherein each of the drill cutter blades includes fixed cutters arranged along the cutting edge.

15) A drill bit according to claim 14, wherein the drill bit includes fixed cutters arranged on a cylindrical surface of the body between the first body end and the second body end.

16) A drill bit according to any one of claims 1 to 15, wherein the one or more drill cutter blades do not substantially protrude outside the annular body in a radial direction.

17) A drill bit according to any one of claims 1 to 16, wherein the drill head has a supply passageway that is supplied with a flow of gas in use, the drill bit including one or more supply ports extending through the body between the first body end and the second body end such that each supply port is in fluid communication with the supply passageway in use, to thereby allow at least some of the flow of gas to pass from the supply passageway to a region proximate to the one or more drill cutter blades.

18) A drill bit according to claim 17, wherein each supply port defines a supply opening in the second body end that is located proximate to a cutting edge of a respective drill cutter blade.

19) A drill head assembly including:

a) a drill head including:

i) an elongate housing, a first end of the housing being coupled to an end of a drill pipe in use;

ii) a base at a second end of the housing;

iii) a supply passageway at least partially within the housing, the supply passageway being supplied with a flow of gas in use; and

iv) a return passageway at least partially within the housing, a first end of the return passageway being connected to an end of an inner tube extending inside the drill pipe in use, and a second end of the return passageway forming an opening in the base; and

b) a drill bit according to any one of claims 1 to 18, the drill bit being attached to the base of the drill head such that the body hole of the drill bit is in fluid communication with the opening in the base in use, to thereby allow the flow of gas supplied via the supply passageway to cause loose material to be funnelled into the body hole and transported through the return passageway and away from the drill head via the inner tube in use.

20) A drill head assembly according to claim 19, wherein the drill head includes one or more ports for directing at least some of the flow of gas from the supply passageway into the return passageway in a flow direction extending away from the base and towards the inner tube, to thereby cause loose material to be drawn into the return passageway via the body hole of the drill bit.