AU2019285373A1

AU2019285373A1 - Drill bit replacement apparatus

Info

Publication number: AU2019285373A1
Application number: AU2019285373A
Authority: AU
Inventors: Jeffrey William Branson; David Bruce Carnegie-Smith; John Edward Kennedy; Steven John Payne
Original assignee: Intelligent Drilling Applications & Tech Pty Ltd
Current assignee: Intelligent Drilling Applications & Technology Pty Ltd
Priority date: 2018-06-11
Filing date: 2019-06-11
Publication date: 2020-12-24
Also published as: US20210198960A1; WO2019237150A1; BR112020024883A2

Abstract

The present invention relates to a drill bit replacement apparatus for replacing a drill bit on a drilling tool, the apparatus comprising: a drill bit holder comprising one or more drill bit receptacles, each drill bit receptacle adapted to receive at least one drill bit; and a positioning means adapted to move the drill bit holder between at least one storage position and one or more replacement positions, wherein each replacement position aligns at least one drill bit receptacle with the drilling tool.

Description

i

Drill Bit Replacement Apparatus TECHNICAL FIELD

[0001 ] The present invention relates to a drill bit replacement apparatus for replacing a drill bit on a drilling tool. More specifically, the apparatus of the present invention is adapted to store multiple drill bits and make them available for replacement on the drilling tool.

BACKGROUND ART

[0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] Mobile drilling units are typically employed to drill holes for blasting in mining operations. Such units commonly comprise a pivoting mast mounted on a drill platform. A drill string is mounted within or onto the mast to drill into the earth. The drill string comprises a drilling tool and series of drill rods. The drilling tool is mounted on the working end of the drill string and retains a drill bit that is driven into the earth to create a hole. The drill rod connects the drilling tool to a drill rotation source mounted on the mast. Rotational torque and drilling fluid for impact on the drill bit and/or flushing out broken rock are provided through the drill rod to the drilling tool to drive the drilling tool. As the drilling operation continues, additional lengths of drill rod are added to the drill string.

[0004] As the drill bit is driven into the earth, the mechanical force that is imparted on the drill bit eventually wears down and blunts the drill bit. In certain circumstances, the drill bit may fracture and break. Worn or fractured drill bits need to be replaced. In order to complete this, the drilling operation must be halted and the drilling tool is retrieved to the surface to enable the replacement of the drill bit. The drill bit is typically threadably connected to the lower end of the drilling tool. The threaded connection is orientated so that this rotational force does not unfasten the threaded connection, but rather acts to tighten the connection. In order to change the drill bit a breakout mechanism is used to‘break’ the drill bit from the drilling tool, loosening the tension in the screw joint. Once the tension has been released an operator typically removes the drill bit and positions it clear of the drilling tool. A replacement drill bit is then physically moved into position beneath the drilling tool to attach drill bit to the drilling tool. The positioning of the drill bit is either completed by hand or may be assisted with the use of a winch on the drill or a truck mounted crane. Whilst these devices do assist with the replacement process, they do not allow for precise positioning of the drill bit and an operator is still required to complete the coupling or decoupling of the drill bit to the drill string. This presents a significant danger to operators and injuries can occur as a result of uncontrolled movement of the drilling tools during the changeover process. The risks increase with large diameter drilling operations where the increased size and weight of the drill bits make them much more difficult to manoeuvre.

[0005] Whilst many parts of drilling operations may be completed autonomously or semi-autonomously, the changing of drill bits still requires at least some manual intervention from an operator, usually at the machine. If a drilling rig is being autonomously operated, then the drilling rig needs to be switched to manual operation every time the drill bits need replacement. Because of the need for manual intervention, the safety, capital, operational cost or production advantages offered by autonomous drilling rig are diminished during bit changes. This is particularly problematic in hard rock drilling operations where multiple bit changes can be required during every drill shift.

[0006] Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

SUMMARY OF INVENTION

[0007] In accordance with the present invention, there is provided a drill bit replacement apparatus for replacing a drill bit on a drilling tool, the apparatus comprising: a drill bit holder comprising one or more drill bit receptacles, each drill bit receptacle adapted to receive at least one drill bit; and a positioning means adapted to move the drill bit holder between at least one storage position and one or more replacement positions, wherein each replacement position aligns at least one drill bit receptacle with the drilling tool.

[0008] The drill bit replacement apparatus of the present invention is adapted to position a drill bit receptacle beneath a drilling tool. In this manner, a drill bit located in the drill bit receptacle may be positioned beneath the drilling tool to permit the coupling of the drill bit to the drilling tool. Alternatively, an empty drill bit receptacle may be positioned beneath the drilling tool to permit the uncoupling of the drill bit from the drilling tool.

[0009] In one form of the present invention, each drill bit receptacle receives a single drill bit. Alternatively, a single drill bit receptacle may receive two or more drill bits. In such an arrangement, it is envisaged that locating means or dividers may be used to separate the drill bits in the drill bit receptacle.

[0010] In one form of the present invention, each drill bit receptacle receives a drill bit in a vertical orientation. The term“vertical orientation” should be understood to refer to an orientation where the cutting face is received by the drill receptacle with the drill bit shaft pointing upwards. As would be appreciated by a person skilled in the art, this orientation is substantially similar to the orientation in which the drill bit is received by the drilling tool. In this manner, the drill bit may be positioned beneath a drilling tool and the drilling tool may be lowered to couple with the drill bit.

[001 1 ] Preferably, each replacement position aligns an approximate centre of a drill bit receptacle with the drilling tool. More preferably, each replacement position aligns an approximate centre of a drill bit receptacle with an approximate centreline of the drilling

[0012] When in the storage position, the drill bit holder is preferably clear of the drilling tool. When in the storage position, the drill bit holder does not impinge the operation of the drilling tool.

[0013] In one form of the present invention, the drill bit replacement apparatus is mounted on a mobile drill unit. More preferably, the drill bit replacement apparatus is mounted on the drill platform of a mobile drill unit. [0014] Preferably, the drill bit receptacles are provided in a linear arrangement.

[0015] Preferably, each drill bit receptacle is appropriately shaped and sized to receive a drill bit. More preferably, each drill bit receptacle is generally cylindrical.

[0016] In one form of the present invention, at least 20% of the length of the drill bit is received by the drill bit receptacle. More preferably, at least 30% of the length of the drill bit is received by the drill bit receptacle. Still preferably, at least 40% of the length of the drill bit is received by the drill bit receptacle. Still preferably, at least 50% of the length of the drill bit is received by the drill bit receptacle. Still preferably, at least 60% of the length of the drill bit is received by the drill bit receptacle. Still preferably, at least 70% of the length of the drill bit is received by the drill bit receptacle. Still preferably, at least 80% of the length of the drill bit is received by the drill bit receptacle.

[0017] In one form of the present invention, the positioning means comprises a support assembly. Preferably, the drill bit holder is mountable on or in the support assembly.

[0018] In one form of the present invention, the drill bit holder is integrally formed with the support assembly. In an alternative form of the present invention, the drill bit holder is releasably retained on or in the support assembly. The inventors have found that by releasably retaining the drill bit holder on or in the support assembly that the entire drill bit holder, including any drill bits in the drill receptacles, can be loaded onto or unloaded from the support assembly in a single action.

[0019] In one form of the present invention, the support assembly is adapted to move in a direction perpendicular to the longitudinal axis of the drilling tool. More preferably, the support assembly is adapted to move in a direction substantially parallel to the surface of the drill platform.

[0020] In one form the present invention, the positioning means further comprises a linear actuator to move the support assembly between the storage position and the one or more replacement positions. Preferably, the support assembly is coupled to the linear actuator. More preferably, the linear actuator is selected from mechanical actuators, hydraulic actuators or pneumatic actuators. [0021 ] In one form of the present invention, the support assembly is fully supported on the linear actuator. In this embodiment, the full weight of the support assembly is supported by the linear actuator which can then extend out to the replacement positions in a cantilever arrangement. Preferably, the linear actuator telescopes to extend and retract.

[0022] In an alternative form of the present invention, the support assembly is provided on a framework. Preferably, the framework is adapted to move between the storage position and the one or more replacement positions.

[0023] In an alternative form of the present invention, the support assembly engages with a track. Preferably, the track comprises two parallel rails. Alternatively, the track comprises a monorail. More preferably, the track is mounted on the drill platform. It is envisaged that the support assembly may move along the track to move the drill bit holder between the storage position and the one or more replacement positions. It is envisaged that a linear actuator may be used to move the support assembly along the track.

[0024] In one form of the present invention, the support assembly comprises rollers that engage with the tracks. In an alternative form of the present invention, the support assembly comprises pinion drive gears that engage with the tracks. Preferably, the tracks comprise rack teeth to engage with the pinion gear. Advantageously, the rack and pinion tracks also provide linear actuation to move the support assembly between the storage position and the one or more replacement positions.

[0025] In one form of the present invention, the drilling platform comprises an aperture or deck bush through which the drilling tool passes. Preferably, the positioning means is adapted to position the drill bit holder over the aperture. Where the positioning means comprises tracks, it is envisaged that the tracks are arranged to allow the support assembly to be positioned over the aperture. In one form of the present invention, there is provided a track on each side of the aperture. In an alternative form of the present invention, the arrangement of the tracks allows for the support assembly to cantilever over the aperture. In this arrangement, it is envisaged that a portion of the support assembly may extend beyond the tracks and that appropriate stoppers are incorporated into the support assembly and/or tracks to prevent the support assembly from disengaging with the tracks.

[0026] In one form of the present invention, the movement of the positioning means is remotely operated. In an alternative form of the present invention, the movement of the positioning means is actuated by a control system. The inventors have found that each replacement position and the storage position can be programmed into the control system, allowing for automated positioning of the support assembly or the drill bit holder.

[0027] As would be appreciated by a person skilled in the art, the drill bit must remain stationary to permit the drilling tool to screw onto or off the drill bit. In one form of the present invention, a drill bit is retained in each drill bit receptacle by a clamping means. Preferably the clamping means engages with the drill bit during coupling/decoupling of the drill bit and the drilling tool.

[0028] In an alternative form of the present invention, each drill bit receptacle is provided with a one or more resistance members. Preferably, the resistance members are adapted to prevent the rotation of the drill bit in the drill bit receptacle.

[0029] In one form of the present invention, a replaceable insert is mountable in the drill bit receptacle. As would be understood by a person skilled in the art, drill bits come in a range of diameters and shapes. Preferably, different replaceable inserts may be associated with each drill bit. It is envisaged that the replaceable inserts allow for a range of drill bits to be received in the drill bit receptacle

[0030] In an alternative form of the present invention, the drill bit receptacle imparts a frictional force on the drill bit to prevent rotation during coupling/decoupling of the drill bit and the drilling tool. As would be appreciated by a person skilled in the art, each drill bit can be of substantial weight. The inventors have found that by constructing or lining the bottom of the drill bit receptacle with a non-slip material, the combination of the weight of the drill bit and the resistance of the non-slip material will prevent the rotation of the drill bit during coupling/decoupling of the drill bit and the drilling tool.

[0031 ] As would be appreciated by a person skilled in the art, the coupling of a drill bit to a drilling tool often requires the use of an adapter means. Such adapter means include, for example, a drive sub, bit rings and bushings. In one form of the present invention, each drill bit in the drill bit holder has any required adapter means loaded thereon.

[0032] In one form of the present invention, a protective cover is provided over the drill bits in the drill bit holder. Preferably, each drill bit receptacle has a separate protective cover. Alternatively, a single protective cover is provided across all drill bit receptacles. The inventors have found that the protective cover prevents dust and other foreign materials from fouling the thread of the drill bit. This is especially useful when the drill bit holder is in the storage position and the drilling tool is being operated. In one form of the present invention, the protective cover may be removed during the loading and unloading of the drill bit. In an alternative form of the present invention, the protective cover is fixed in a position above the drill rod holder when in the storage position

[0033] In one form of the present invention, the apparatus further comprises a breakout means. As would be appreciated by a person skilled in the art, operation of the drilling tool will impart a rotational force onto the threaded connection between the drilling tool and the drill bit. The threaded connection is orientated so that this rotational force does not unfasten the threaded connection, but rather acts to tighten the connection. A breakout means is used to breakout threaded connections on drilling tools. Preferably, once the threaded connection has been broken, the drill bit is lowered into the drill bit receptacle and the drilling tool is operated in reverse to screw off the drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

Figure 1 a is a plan view of the drill bit replacement apparatus of the present invention;

Figure 1 b is an enlarged portion of Figure 1 a; Figure 2 is an upper perspective view of the drill bit replacement apparatus of the present invention;

Figure 3 is a side elevation of the drill bit holder and support assembly of the present invention; and

Figure 4 is a side elevation of a drill bit.

DESCRIPTION OF EMBODIMENTS

[0035] In Figures 1 - 4, there is shown a drill bit replacement apparatus 10 in accordance with the present invention. The drill bit replacement apparatus 10 is primarily adapted for use on a drilling unit 12.

[0036] In Figures 1 a and 1 b there is shown the drill bit replacement apparatus 10 as mounted on a drilling unit 12. In the embodiment shown in Figure 1 a and 1 b the drill bit replacement apparatus 10 is mounted on a drill platform 14. The drill platform 14 is typically supported on a crawler undercarriage 16 (not shown) that allows the drill platform 14 to be positioned relative to the area to be drilled. The drill platform 14 further comprises levelling jacks (not shown) that may be positioned to provide stability when drilling.

[0037] The mobile drilling unit 12 includes drill mast 20 which is hinged to the drill platform 14 such that the drill mast 20 is able to tilt relative to the drill platform 14. The drill mast 20 is able to move between a horizontal position to an upright positon for drilling at varying angles. The horizontal positon allows for the transport of the drill platform 14. Hydraulic actuators (not shown) control the movement of the drill mast 20.

[0038] The drilling unit 12 further comprises an operator cab 22 which houses the operating controls for the drilling operation, along with monitoring instruments. Whilst the embodiment shown in Figure 1 comprises an operator cab, it is envisaged that operation of the drilling unit 12 may be controlled autonomously. Where drilling is completed by autonomous drilling methods, it is envisaged that the operator cab 22 may be replaced / used as a control room for remote signalled drilling operations, along with monitoring instruments. [0039] As best seen in Figure 2, the drilling unit 12 comprises a drill rotation source 24 supported on the drill mast 20 (not shown in Figure 2). The drill rotation source 24 is guided for longitudinal movement along the drill mast 20. Movement of the drill rotation source 24 is controlled by a hoist (not shown). Hydraulic head actuators (not shown) control the movement of the drill rotation source 24 and the hoist. Whilst the drill rotation source 24 shown in the Figures is adapted to move along the drill mast 20, it is envisaged that other rotation drive mechanisms may be employed, such as for example a Table Drive. As would be understood by a person skilled in the art, where a Table Drive is utilised, it does not move along the drill mast 20.

[0040] The drilling unit 12 further comprises a hydraulic pump mechanism (not shown) adapted to supply hydraulic fluid for hydraulic operations. The hydraulic pump mechanism is operated by a diesel engine (not shown) mounted on the drill platform 14.

[0041 ] The drill bit replacement apparatus 10 of the present invention is adapted to facilitate the addition and removal of drill bits 26 from a drilling tool 28. As would be appreciated by a person skilled in the art a drilling tool 28 is a piece of drilling equipment that retains a drill bit 26 and permits operation of the drill bit 26. The drilling tool 28 is coupled to a drill rod which is in turn coupled to the drill rotation source 24. The coupling of the drill rod to the drill rotation source 24 permits rotational forces and drilling fluid to travel to the drilling tool 28 by way of the drill rod. The drill rotation source 24 is moved down the drill mast 20 to force the drill bit 26 of the drilling tool 28 into the earth. As drilling progresses, additional drill rods 30 are added to the drill string.

[0042] As would be appreciated by a person skilled in the art, the drilling operation imparts a mechanical force on the drill bit 26. Over time, this force eventually wears down and blunts the drill bit 26 or may fracture the drill bit 26. Once the drill bit 26 has worn or fractured, the drilling operation must be halted and the drilling tool 28 must be retrieved to the surface to enable the replacement of the drill bit 26. The drill bit replacement apparatus 10 of the present invention is envisaged to permit the replacement of a drill bit 26 from a drilling too! 28 on a drill string with another drill bit 26 without the need for manual handling of the drill bits 26 by an operator. Similarly, the drill bit replacement apparatus 10 of the present invention may be used to load the first drill bit 26 onto a drilling tool 28 at the commencement of drilling operations and remove the drill bit 26 when dri!iing operations are ceased. Addition and removal of drill bits can be performed manually by an operator, semi-autonomously or autonomously.

[0043] The drill bit replacement apparatus 10 comprises a drill bit holder 32 which is adapted to receive one or more drill bits 26. As best seen in Figure 2, the drill bit holder 32 comprises one or more drill bit receptacles 34. In the embodiment shown in the Figures, the drill bit receptacles 34 are arranged in a linear array along the length of the drill bit holder 32. It is envisaged that a rotary drill bit holder may also be used, in which case the drill bit receptacles 34 would be arranged in a circular array. Each drill bit receptacle 34 is appropriately shaped and sized to receive a drill bit 26. As drill bits 26 have a generally cylindrical shape, it is envisaged that the most appropriate shape for each drill bit receptacle 34 will also be cylindrical. With reference to Figure 3, when a drill bit 26 is placed in a drill bit receptacle 34, the tip 36 of the drill bit 26 will rest on a bottom surface of the drill bit receptacle 34. As would be appreciated by a person skilled in the art, drill bits 26 may come in a range of diameters. Accordingly, the drill bit receptacle 34 will need to be wide enough to allow a particular drill bit 26 to be received therein.

[0044] The drill bit replacement apparatus 10 further comprises a positioning means 38 that is adapted to move the drill bit holder 32 between a storage position and one or more replacement positions. Each replacement position will align one of the drill bit receptacles 34 with the drilling tool 28 to either present a drill bit 26 for coupling with the drilling tool 28 or to present an empty drill bit receptacle 34 to the drilling tool 28 to facilitate the uncoupling of a drill bit 26 from the drilling tool 28. In the embodiment shown in the Figures, the positioning means 38 is configured to move the drill bit holder 32 in a direction that is parallel to the plane of the drilling platform and perpendicular to the longitudinal axis of the drilling tool 28. In this manner, the inventors envisage that during coupling/decoupling of the drill bit 26 and the drilling tool 28, the drilling tool 28 can be raised vertically to a position above the drilling platform and the drill bit holder 32 can be moved to a replacement positon with a drill bit receptacle 34 positioned beneath the drilling tool 28. Once the coupling/decoupling of the drill bit 26 and the drilling tool 28 has been completed, the drill bit holder 32 can be moved to a storage position and drilling can commence. [0045] In the embodiment shown in the Figures, the positioning means 38 comprises a support assembly 40 that is adapted to receive and retain the drii! bit holder 32 thereon. In one embodiment of the present invention, the drill bit holder 32 is integrally formed with the support assembly 40. In an alternative embodiment of the present invention, the drill bit holder 32 is replaceably received by the support assembly 40. The inventors have found that by configuring the support assembly 40 to releasably receive the drill bit holder 32, the entire drill bit holder 32, together with any drill bits 26 can be fully placed in or removed from the support assembly 40. The inventors envisage that this arrangement will permit a drill bit holder 32 loaded with blunt / failed drill bits 26 to be replaced with a second drill bit holder 32 loaded with sharp drill bits 26 in a single action. It is envisaged that the drill bit holder 32 may advantageously be changed out when the mobile drilling rig is being refuelled or otherwise serviced.

[0046] In the embodiment shown in the Figures, the support assembly 40 is mounted on tracks 42. The engagement of the support assembly 40 and the tracks 42 permits the movement of the support assembly 40 along the tracks 42. The engagement of the support assembly 40 and the tracks 42 can be any arrangement that permits the movement of the support assembly 40 along the tracks 42. In the embodiment shown in the Figures, the engagement of the support assembly 40 and the tracks 42 is a rack and pinion type engagement. As best seen in Figure 3, the support assembly 40 is provided with a pinon gears 44 that are adapted to engage with complementary teeth on the tracks 42. This arrangement has been found to be particularly advantageous as the movement of the support assembly 40 along the tracks 42 can be accurately controlled by a drive means, such as a motor 45, coupled to the pinion gears 44. The accurate control of the movement is important in ensuring that the drill bit holder 32 is accurately moved into the one or more replacement positions so that the drilling tool 28 can be accurately and repeatable aligned with the drill bit receptacles 34. It is envisaged that the rack and pinion arrangement will also easily permit the movement of the support assembly 40 to be remotely or autonomously controlled. In an alternative embodiment the engagement of the support assemble 40 is a trolley wheel and rail arrangement. In this form of the present invention, the support assembly 40 is provided in the form of a support trolley that engages with the track. Other arrangements are available to those skilled in the art and can be as simple as wheels provided on the support assembly 40. In embodiments where a rack and pinion drive is not used, the movement of the support assembly 40 is controlled by a linear actuator (not shown). Suitable linear actuators include, for example, hydraulic cylinders or pneumatic cylinders that extend and retract to move the support assembly 40 between the storage positon and the one or more replacement positions.

[0047] The tracks 42 are orientated to permit the drill bit holder 32 to be positioned beneath the drilling tool 28. This arrangement is dependent on the exact configuration of the drill mast. In the embodiment shown in the Figures, the drilling tool 28 is adapted to pass through a drilling aperture 46 in the drilling rig. As best seen in Figure 2, the tracks 42 are mounted on the drilling platform on either side of the drilling aperture 46. This arrangement permits the support assembly 40 to be positioned directly under the drilling tool 28 and over the drilling aperture 46. Alternatively, it is envisaged that the tracks 42 could be positioned up to, but not extend past, the drilling aperture 46. In this arrangement, part of the support assembly 40 may extend past the tracks 42 to cantilever across the drilling aperture 46.

[0048] In alternative embodiments, the support assembly 40 may be supported by the linear actuator. In this embodiment the linear actuator would extend to position the support assembly 40 beneath the drilling tool 28. To permit this, it is envisaged that one end of the linear actuator would be fixed to the drilling unit 12 and would facilitate the extension of the support assembly 40 out to a position underneath the drilling tool

[0049] As would be appreciated by a person skilled in the art, the drill bit 26 is coupled to the drilling tool 28 by way of threaded connection. As discussed above, the drill rotation source 24 provides rotational torque to the drilling tool 28. This rotational torque is utilised to couple / decouple the drill bit 26 and the drilling tool 28. In order to permit this action, the drill bit 26 must be held stationary in the drill bit receptacle 34 whilst the drilling tool 28 is screwed on / off. In one embodiment, the drill bit receptacle 34 is provided with a clamping means (not shown) that engages the drill bit 26 during coupling / decoupling. Alternatively, the drill bit receptacle 34 is provided with a resistance member (not shown) that imparts a frictional force on the drill bit 26 that resists the rotation of the drill bit 26. It is envisaged that such a resistance member would abut the tip 36 of the drill bit 26 and resist the rotation. As would be appreciated by a person skilled in the art, the drill bit 26 used on most rotary drills are of a tricone construction, three separate resistance members are preferably provided in the drill bit receptacle 34 to fit between the cones of the drill bit 26. For down hole hammer drills, it is envisaged that the resistance members are configured to fit the drill bit face flushing configurations. The resistance members are preferably tapered to allow different sized drill bits 26 to engage with the various resistance members.

[0050] As would be understood by a person skilled in the art, drill bits 26 come in a range of diameters and shapes. In order to correctly position and retain different sized drill bits 26 in the drill bit receptacle 34, the drill bit replacement apparatus 10 is further provided with a number of replaceable inserts (not shown). Each replaceable insert is designed to have an outer diameter that fits within the drill bit receptacle 34, with an inner section that is shaped and sized to fit a particular drill bit 26. It is envisaged that the replaceable inserts allow for a range of drill bits 26 to be received in the drill bit receptacle 34. In order to adapt the drill bit receptacle 34 to fit another drill bit, the replaceable insert is preferably removed and a different replaceable insert is placed in the drill bit receptacle 34. Alternatively, due to the weight of the drill bit 26, the inventors have found that the resistance member can be as simple as a non-slip lining on the bottom of the drill bit receptacle 34 that the drill bit 26 rests on to resist movement of the drill bit 26 during coupling/decoupling.

[0051 ] As would be appreciated by a person skilled in the art, the coupling of a drill bit to a down the hole hammer drilling tool 28 often requires the use of an adapter means 48. Such adapter means 48 include, for example, a drive sub, bit rings and bushings. Each drill bit 26 in the drill bit holder 32 has any required adapter means 48 loaded thereon. It is understood by the inventors that by providing the drill bits 26 with any adapter means 48 already coupled thereto there is no need to swap out such adapter means 48 when the drill bit 26 is replaced. As such, the coupling / uncoupling of the drill bit 26 and the drilling tool 28 may be fully automated. It is envisaged that the adapter means 48 coupled to a worn drill bit 26 may be replaced onto a sharp drill bit 26 during the servicing of the drill rig.

[0052] A protective cover 50 may be provided on each drill bit 26 in the drill bit holder 32. The protective cover 50 acts to cover the drill bit 26 and any adapter means 48 to prevent dust and other foreign materials from fouling the drill bit 26 threads and interfering with the coupling to the drilling tool 28. In the embodiment shown in Figures 1 a and 1 b, the protective cover 50 is provided in a fixed position over the storage position !n the embodiment shown in Figure 4, the protective cover 50 is comprised a hollow container 52 that surrounds the drill bit receptacle. A lid 54 is hingedly coupled to the hollow container 52. The lid 54 is fixed to an actuator, for example a cylinder 58, which may be retracted and extended to open and close the lid 54.

[0053] The drill bit replacement apparatus 10 further comprises a breakout means (not shown). Typical breakout means comprise a pair of hydraulically operated clamps that grip the drilling tool 28 and drill bit 28 respectively. Once engaged, the clamps rotate in opposite directions to unscrew the drili bit 26 from the drilling tool 28. As would be appreciated by a person skilled in the art, operation of the drilling tool 28 will impart a rotational force onto the threaded connection between the drilling tool 28 and the drill bit 26. The threaded connection is orientated so that this rotational force does not unfasten the threaded connection, but rather acts to tighten the connection. A breakout means is used tor breakout of threaded connections on drilling tools 28.

[0054] In use, the drill bit replacement apparatus 10 of the present invention is intended to couple and decouple drill bits 26 trom a drilling tool 28 The drill bit replacement apparatus 10 is mounted on a mobile drilling rig. Prior to operation, the drill bit holder 32 is loaded with drill bits 26 in the drill bit receptacles 34. Each drill bit 26 has any required adapter means 48 fastened thereto and a protective cover 50 is placed over the drill bit 26 and adapter means 48. The drill bit holder 32 is loaded onto the support assembly 40. The support assembly 40 is moved to a storage position and retained in place. The mobile drill unit is then positioned at the intended drilling site and the drill mast is raised. The starter rod and the drilling tool 28 can then be loaded onto the drill rotation source 24. The drill rotation source 24 is raised so that the drilling tool 28 is positioned above the drilling platform of the drill rod. The liner actuator or pinion drive actuator of the positioning means 38 is then used to move the support assembly 40 along the tracks 42 to one of the replacement positions. In each replacement position, a drill bit receptacle 34 and the drill bit 26 contained therein is aligned with the drilling tool 28. The drilling tool 28 is lowered towards the drill bit 26 and the drill rotation source is operated to screw the drilling tool 28 onto the drill bit 26. During the coupling of the drill bit 26 to the drilling tool 28, the drill bit receptacle 34 retains the drill bit 26 in a stationary position relative to the drilling tool 28 to permit the coupling of the threaded connector. Once the drill bit 26 is coupled to the drilling tool 28, the drilling tool 28 may be lifted and the drill bit 26 will be lifted from the drill bit receptacle 34. Once the drill bit 26 is clear of the drill bit receptacle 34, the support assembly 40 can be moved back to the storage position and clear of the drilling tool 28. The drilling operation can then commence.

[0055] The drilling operation will impart a mechanical force on the drill bit 26 which will eventually wear and blunt the drill bit 26. Once the drill bit 26 is worn it must be replaced on the drilling tool 28. in order to complete this, the drilling tool 28 is retrieved and again positioned above the drilling platform. The support assembly 40 is then moved from the storage position to a replacement position which aligns an empty drill bit receptacle 34 with the drilling tool 28. The breakout means are then engaged with the drilling tool 28 and drill bit 26 to break the threaded connection of the drill bit 26 and the drilling tool 28. The breakout means is then disengaged and the drill bit 26 is lowered into the empty drill bit receptacle 34. The drill bit receptacle 34 again imparts a frictional resistance on the drill bit 26 and the drill rotation source 24 may be operated in reverse to unscrew the drill bit 26 from the drilling tool 28, thereby decoupling it. The drilling too! 28 is again lifted and the support assembly 40 is positioned in another replacement position to present a new drill bit 26 to the drilling tool 28 for coupling. Once coupled as described above, the drilling operation can then recommence with the new drill bit 26.

[0056] The worn drill bits 26 can be continued to be replaced as long as there are new / sharp drill bits 26 available in the drill bit holder 32. Advantageously, the inventors have found that the linear arrangement of the drill bit holder 32 allows for increased capacity of drill bits 26 to be stored on the drilling unit. As would be understood by a person skilled in the art, the operation of the drilling unit will typically be ceased at regular intervals to allow for servicing and refuelling of the drilling unit. These intervals are typically 12 hours apart. It is envisaged that the drill bit holder 32 will hold enough drill bit 26 to last the operation between intervals. During the service interval the drill bit holder 32 can be fully removed from the support assembly 40 and be replaced with another drill bit holder 32 that is loaded with new / sharp drill bits 26. Furthermore, an advantage of the track arrangement shown in the Figures, the weight of all the drill bits 26 is held by the drilling rig 12. [0057] Given the entire replacement process does not require any human handling of the drill bits 26, the entire process can either be remotely operated or fully automated. In this embodiment it is envisaged that the movement of the storage assembly to the one or more replacement positions can be fully programmed into a programmable logic controller (PLC). The drill bit replacement apparatus 10 can further be integrated with automated drill rod loading apparatus and/or drilling tool 28 loading apparatus to fully automate the drilling operations. This is believed to be particularly advantageous in blast hole drilling operations, where it is believed that the efficiency and safety of the operation can be increased.

[0058] A further advantage envisaged by the inventors is that the drill bit holder 32 may be loaded with drill bits 26 suitable for different drilling tools 28 As would be appreciated by a person skilled in the art, there are different types of drilling tools 28 that may be used. Common types of drilling tools 28 include rotary drilling (RD) tools, percussion assisted rotary drilling (PARD) tools or a down the hole hammer (DTHH) tools. As would be appreciated by a person skilled in the art, different drill bits 26 may be selected depending on the hardness of the rock that is being drilled. Rotary tools generally have a high penetration rate and are more economic for drilling in soft rocks. However, the use of rotary tools in hard rock requires a drilling rig with high puli down and rotation capacity to drive the bit through the rock. This presents a significant capital expenditure for the high capacity drill rig itself, along with higher operating costs to power the drills air compressor or fluid supply. Furthermore, the rotary drill bits 26 may wear at a quicker rate, requiring ongoing replacement costs. These factors together contribute to a much higher cost impediment to such operations. Unlike RD tools, DTHH tools are generally more suited and more economic for drilling of hard rock material. Accordingly, it is generally more economic to use DTHH tools in hard rock. The difference in economy increases when drilling larger diameter holes (+127 mm). As would be appreciated by a person skilled in the art, each of these drilling tools 28 operates in a different manner and requires different drill bits 26. By loading the drill bit holder 32 with each of these different drill bits 26, they are available for use by different drilling tools 28 during operation of the mobile drilling rig 12.

[0059] It is envisaged that the apparatus 10 of the present invention may be provided on a drilling rig 12 that comprises other means for automating the drilling process. Such means include, but are not limited to automated drill rod loading apparatus 60 (such as described in the Applicant’s co-pending PCT/AU2019/050135) and automated drilling tool replacement apparatus 62 (such as described in the Applicant’s co-pending

PCT/AU2019/050178).

[0060] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps, features, formulations and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

Claims

1 . A drill bit replacement apparatus for replacing a drill bit on a drilling tool, the apparatus comprising: a drill bit holder comprising one or more drill bit receptacles, each drill bit receptacle adapted to receive at least one drill bit; and a positioning means adapted to move the drill bit holder between at least one storage position and one or more replacement positions, wherein each replacement position aligns at least one drill bit receptacle with the drilling tool.

2. A drill bit replacement apparatus according to claim 1 , wherein each replacement position aligns an approximate centre of a drill bit receptacle with the drilling tool.

3. A drill bit replacement apparatus according to claim 1 or 2, wherein when in the storage position the drill bit holder is preferably clear of the drilling tool.

4. A drill bit replacement apparatus according to any one of the preceding claims, wherein the drill bit replacement apparatus is mounted on a mobile drill unit.

5. A drill bit replacement apparatus according to any one o! the preceding claims, wherein the drill bit receptacles are provided in a linear arrangement.

6. A drill bit replacement apparatus according to any one of the preceding claims, wherein each drill bit receptacle is appropriately shaped and sized to receive a drill bit.

7. A drill bit replacement apparatus according to any one of the preceding claims, wherein at least 20% of the length of the drill bit is received by the drill bit receptacle.

8. A drill bit replacement apparatus according to any one of the preceding claims, wherein the positioning means comprises a support assembly.

9. A drill bit replacement apparatus according to claim 8, wherein the drill bit holder is mountable on or in the support assembly.

10. A drill bit replacement apparatus according to claim 8 or 9, wherein the support assembly is adapted to move in a direction substantially parallel to the surface of the drill platform

1 1 . A drill bit replacement apparatus according to any one of claims 8 to 10, wherein the positioning means further comprises a linear actuator to move the support assembly between the storage position and the one or more replacement positions.

12. A drill bit replacement apparatus according to any one of claims 8 to 1 1 , wherein the support assembly is fully supported on the linear actuator.

13. A drill bit replacement apparatus according to any one of claims 8 to 1 1 , wherein the support assembly is provided on a framework.

14. A drill bit replacement apparatus according to any one of claims 8 to 1 1 , wherein the support assembly engages with a track

15. A drill bit replacement apparatus according to claim 14, wherein the track is mounted on the drill platform.

18. A drill bit replacement apparatus according to claim 14 or 15, wherein the support assembly comprises rollers that engage with the track.

17. A drill bit replacement apparatus according to any one of the preceding claims, wherein the positioning means is remotely operated.

18. A drill bit replacement apparatus according to any one of the preceding claims, wherein a drill bit is retained in each drill bit receptacle by a clamping means

19. A drill bit replacement apparatus according to any one of the preceding claims, wherein each drill bit receptacle is provided with a one or more resistance members.

20. A drill bit replacement apparatus according to any one of the preceding claims, wherein a protective cover is provided over the drill bits in the drill bit holder.