Drill rig

Abstract

A drill rig comprising a mast and a tool changer assembly mounted on the mast to carry a selection of well tools, and moveable perpendicular to the mast between a retracted position and an extended position, at least one rotatable tool carousel mounted within a housing 8 including plurality of circumferentially spaced tool holders on the carousel. The tool carousels can be rotated to bring a selected tool holder into alignment with the drill string when the tool changer assembly is in its extended position. The housing may include an opening through which the drillsting may pass and a door 28 with another opening 30 that conforms with the surface of the drillstring to align the drillstring with a tool. Each tool holder may include gripping formations to grip a tool placed within the holder.

Description

FIELD OF THE INVENTION This invention relates to a drill rig and in particular to an improved drill rig incorporating a tool changer assembly. BACKGROUND OF THE INVENTION Exploration drilling is an important step in establishing new mining operations for the recovery of valuable minerals. Exploration drilling is essential for obtaining temperature measurements, rock samples, and retrieving fluid samples for chemical analysis. Exploration drilling is also used in the mining industry to probe the contents of known ore deposits and potential sites. By withdrawing samples of rock and soil at from specific depths, geologists can analyse the samples by chemical assay and conduct petrologic, structural, and mineralogical studies of the underground structures. Mineral exploration is carried out extensively in the harsh conditions of the Australian outback to identify underground mineral resources to establish new mining operations. Drilling provides most of the information for the final evaluation of a prospect and will determine if the prospect is mineable. Drilling is used to search for mineral occurrences or clues in the rocks that may lead to mineral deposits. The information gathered during this stage may or may not lead to a discovery of valuable minerals. Drilling penetrates deep into the ground and brings up samples of whatever it finds on its way. If there is any mineralisation at given points far beneath the surface, drilling can quantify its presence at that particular point. However, existing exploration drill rigs require skilled operators, often working in difficult and hazardous conditions. Exploration drill rigs are frequently used in remote areas of difficult terrain and harsh weather conditions. Drilling in any environment is potentially hazardous but mineral exploration in remote locations, such as those encountered in Western Australia, presents additional risk factors. Therefore, there is a desire to move towards autonomous exploration drill rigs, requiring less direct manual intervention during operation. Drill rigs generally comprise a converted truck chassis carrying a drill mast to transport the drill mast to a desired location to conduct a drilling operation, the drill mast being pivotally mounted at one end of the chassis for movement between a substantially horizontal transport position and an upright drilling position. The drill rig is often equipped with a rod magazine or holder of some sort, which is adapted to support a plurality of drill rods with a system to selectively add drill rods to the drill string on the drill mast for drilling a hole having a desired depth. A commonly used drilling tool is a down-the-hole hammer, comprising a hammer body incorporating a pneumatically operated reciprocating piston adapted to impart a reciprocating hammer action on a drill bit located at a lower end of the hammer body as the hammer is rotated. After a certain amount of usage in the drilling operation, it is often desirable or necessary to remove and replace the current tool due to accumulated wear of an in-service drill bit, or there may be a need to change the tool, for example to change between a smaller down-the-hole hammer and a larger casing hammer (or vice versa), etc. In order to minimize downtime in the drilling operation due to change-out of tools, mechanisms may be provided to facilitate removing one drilling tool from the end of the drill string and replacing it with another tool from a storage or supply location. What is needed is a system to facilitate automated changing of drilling tools, and in particular to facilitate easy changing of drill bits and down-the-hole hammers, without requiring manual intervention. Choosing the right hammer or drill bit is largely determined by type of application, hole size and type of rock formation. SUMMARY OF THE INVENTION According to the present invention there is provided a drill rig comprising a mast for supporting axially coupled drill rods of a drill string and a tool changer assembly mounted on the mast and adapted to carry a selection of tools to be selectively attached to the drill string; said tool changer assembly being moveable in a direction perpendicular to the mast between a retracted position, wherein the tool changer assembly is laterally spaced from the drill string on the mast, and an extended position, wherein the tool changer assembly is aligned with the drill string such that a selected tool carried by the tool changer assembly can be attached to the drill string; at least one tool carousel mounted within the housing to be rotatable about an axis parallel to the mast, plurality of tool holders being provided on the or each carousel at circumferentially spaced locations thereon, the or each carousel being rotatable under the control of a controller to bring a selected tool holder into alignment with the drill string when the tool changer assembly is in its extended position. The housing may have an opening in a side thereof to provide clearance of the drill string when the tool changing assembly is in its extended position. The or each carousel may have a gap or opening therein, whereby said gap or opening can be brought into alignment with said opening in the housing to allow the housing to be moved to its extended position without interfering with the drill string. The opening in the housing may be provided with a door moveable to selectively close said opening. The door may be moveable between a closed position wherein it closes said opening in the housing, and an open position, an opening being provided in an upper end of the door adapted to be aligned with the drill string so that the drill string can extend into the housing with the door in said closed position. The shape of the opening in the upper end of the door may be adapted to engage with the drill string to correctly align the drill string in the housing of the tool changer assembly during changing of a tool. The opening in the upper end of the door may be closable by a closure. Said closure may be biased towards a closed position and it held in an open position by the presence of the drill string in said upper end of the door. The housing may comprise a side wall, an upper end and a lower end, said opening extending along a portion of the length of the side wall and along a portion of the upper end. The side wall of the housing may be cylindrical and the door may be concentric with the side wall of the housing to be rotatable about an axis coaxial with a longitudinal axis of the housing between its open and closed positions. Preferably the or each carousel is rotatable about an axis coaxial with a longitudinal axis of the housing. Two or more vertically spaced tool and independently rotatable carousels may be coaxially mounted within the housing, each having plurality of tool holders, depending upon the number of tools required and the size of the tools. Preferably each tool holder incorporates mounting formations adapted to engage cooperating gripping formations on a tool held therein. In one embodiment the mounting formations may comprise upwardly extending pins adapted to engage cooperating gripping formations on the sides of a tool held therein such that the mounting formations prevent rotation of the tool in the tool holder to allow the tool to be screwed onto or off the end of the drill string. BREIF DESCRIPTION OF THE DRAWINGS A drill rig in accordance with an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which :- Figure 1 is a perspective view of a mast assembly of a drill rig in accordance with an embodiment of the present invention incorporating a tool changer assembly with the tool changer assembly in its retracted position; Figure 2 is a perspective view of the mast assembly of Figure 1 with the tool changer assembly in its extended position; Figure 3 is a detailed perspective view of the tool changer assembly of the mast assembly of Figure 1; Figures 4, 5 and 6 show an upper region of a door of the tool changer assembly of Figure 3 illustrating the operation of the door; Figure 7 is a detailed view of a tool holder of the tool changer assembly of Figure 3 with a drill bit mounted therein; Figures 8 to 12 illustrate the operation of the tool changer assembly; and Figure 13 is a side view of the mast assembly of Figure 1 showing the tool changer assembly in a maintenance or loading configuration. DETAILED DESCRIPTION OF DRAWINGS A drill rig incorporating a tool changer assembly in accordance with an embodiment of the present invention may comprise a self-propelled tracked chassis (not shown) having a longitudinal axis aligned with a normal direction of travel and upon which is mounted a drill mast 2, pivotally mounted at one end of the chassis for movement between a substantially horizontal transport position, and a raised drilling position, at an inclined or vertical angle with respect to the ground, about a pivot axis extending perpendicular to said longitudinal axis of the chassis. In the embodiment shown, the mast 2 may include a rotary head 4 adapted to impart rotation to a drill string 6 supported on the mast 2 and extending through the rotary head. A slips table (omitted for clarity in the drawing) may be located at a lower end of the mast 2 and adapted to centralise drill rods or casings. The slips table may be adapted to grip a selected drill rod or a tool at an end of the drill string to facilitate breakout of the tool or rod, being threadedly attached to the remainder of the drill string. A breakout system (not shown in the drawings) may be provided above the slips table being adapted to break loose a threaded coupling between a lowermost drill rod or a tool attached to the remainder of the drill string. Once the threaded coupling has been loosened by the breakout system the lowermost rod or tool can be completely unscrewed from the drill string by rotating the drill string using the rotary head 4. The tool changer assembly comprises an elongate, substantially tubular housing 8 having an upper wall, lower wall and a tubular side wall and having an opening 9 extending along the length of the side wall and through a portion of the upper wall to allow the housing 8 to be moved over the drill string 6, as described below. A plurality of interchangeable tools 25A,25B are retained within the housing 8. The housing 8 is mounted on a frame 10 attached to the mast 2. The housing 8 of the tool changer assembly is mounted on the frame 10 to be laterally moveable in a direction perpendicular to the mast 2 between a retracted position, shown in Figure 1, wherein the housing 8 of the tool changer assembly is laterally spaced from the drill string 6 on the mast 2, and an extended position, shown in Figure 2, wherein the opening 9 in the housing 8 of the tool changer assembly is aligned over the drill string 6 such that a selected tool 25A,25B carried by the tool changer assembly can be attached to the drill string 6. As best illustrated in Figure 3, the housing 8 of the tool changer assembly is slideably mounted on the frame 10 upon upper and lower carriage assemblies 12,14 to be laterally slideable between said retracted and extended positions under the action of respective double acting rams 16,18. In the embodiment shown in the drawings, a pair of vertically spaced tool holding carousels 20,22 are mounted within the housing 8 to be rotatable about an axis coaxial with a central axis of the tubular housing 8 and extending parallel to the mast 2, a plurality of tool holders 24 being provided on an upper side of each carousel 20,22 at circumferentially spaced locations thereon, each carousel 20,22 being independently rotatable under the control of a controller to bring a selected tool holder 24 into alignment with the opening 9 in the housing 8 and thereby into alignment with the drill string 6 when the housing 8 is in its extended position so that a tool in the respective tool holder 24 can be attached to the drill string 6 or so that a tool on the drill string 6 can be returned to the respective tool holder 24 to facilitate attachment of a different or replacement tool. Each carousel 20,22 has a gap or opening in one side thereof which can be brought into alignment with the opening 9 in the housing 8 so that the carousels 20,22 do not interfere with movement of the drill string 6 into and out of the open side 9 of the housing 8 as the housing 8 is moved from its retracted position to its extended position. In the embodiment shown a lower carousel 20 is provided for carrying a plurality of drill bits 25A and an upper carousel 22 is provided for carrying a plurality of downhole hammers 25B. One or more retainment rings 26, having guide openings therein, may be located coaxially above one or both of the carousels 20,22, in particular the upper carousel 22 for supporting an upper portion the tools mounted on the tool holders of the respective carousel, in particular when the relatively tall hammers 25B are mounted on the upper carousel 22, to prevent the tools from tipping over. It is envisaged that a single carousel may be provided within the housing of the tool changer assembly or three or more carousels may be provided depending upon the type and number of tools to be carried. A door 28 in preferably provided from selectively closing said opening 9 in the housing 8 of the tool changer assembly. The door 28 is preferably mounted for rotation about / coaxially with the vertical axis of the housing 8 for movement of the door 28 between a fully closed position, as shown in Figure 4, a fully open position, as shown in Figure 3. As shown in Figure 5, an opening 30 may be provided in an upper end of the door 28, arranged so that the drill string 6 can extend into the housing 8 through said opening 30 in the door 28 with the door 28 in said intermediate position. The shape of the opening 30 in the upper end of the door 28 may be adapted to engage with the drill string 6 to correctly align the drill string 6 within the housing of the tool changer assembly during changing of a tool. A spring loaded closure 31 may be provided for closing the opening 30 in the door, said closure 31 being spring biased to a closed position and being held open by the presence of the drill string 6 extending through the opening 30 in the door, as shown in Figure 9. Alternatively the closure 31 may be actively moved between its closed and open positions by a suitable actuator. As shown in Figure 6, stops 32 may be provided on an underside of the upper end of the housing 8 for delimiting the fully open and fully closed positions of the door 28. The door 28 enables the housing 8 to be fully enclosed to minimise 8 contamination, allowing the tool changer assembly to function reliably in the harsh environment in which the drill rig operates. A shown in Figure 8, each tool holder 24 incorporates upwardly extending locating and holding pins 34 adapted to engage cooperating gripping formations on a tool held therein to locate and hold a tool therein. The pins 34 may also prevent rotation of the tool as it is attached to and detached from a drill rod 6. Figure 8 to 12 illustrate operation of the tool changer assembly to load a hammer drill onto a drill rod 6. In Figure 10 and 11 the outer side of the door 28 is rendered transparent for clarity. In a first step, shown in Figure 8, the housing 8 of the drill changer assembly is moved from its retracted to its extended position with its door 28 in its fully open position and the carousels 20,22 are rotated to move all tools clear of the opening 9 in the side of the housing 8, with the gap in each carousel 20,22 aligned with the opening 9 in the side of the housing 8. Next the drill rod 6 lowers into an upper end of the housing and the door 28 of the housing is moved to its closed position to close the open outer side of the housing 8, the opening 30 in the upper end of the door 28 being aligned with the opening in the upper end of the housing 8 and the closure 31 being pushed to its open position by the presence of the drill string in the opening 30 so that the drill string 6 can extend through said opening 30 in the upper end of the door 28. The upper carousel 22 is then rotated to bring a selected hammer 25B into alignment with the drill string 6, as illustrated in Figure 10 and the drill string 6 is lowered and rotated by the rotary head 4 to attach the selected hammer 25B to the drill string 6, as shown in Figure 11. As illustrated in Figure 12, the door 28 of the housing 8 is then moved to its fully open position and the drill string 6 is raised to lift the hammer 25B out of the housing 8. The housing 8 may then be moved to its retracted position and its door 28 fully closed before a drilling operation is begun. As shown in Figure 13, the frame 10 of the tool changer assembly is mounted on the mast 2 so that, with the housing 8 in its retracted position, it can be swung through 90° to a loading and maintenance position, extending rearwardly from the mast 2, to allow manual loading and unloading of tools into and out of the housing 8, for example to allow the replacement of worn-out bit / hammers with new ones. Guides 36 may be provided on the inner walls of the housing 8 to support tools contained therein, in particular where said tools comprise hammers. Such guides 34 may be made from a metal, nylon or both. The tool retaining pins 34 of the tool holders 24, particularly those intended for holding hammers 25B, may be modified to have a slight taper. This will ensure contact with the respective tool and potentially help reduce tipping of the tools, particularly during 60° and 45° drilling operations. The tapered pins may promote self-centring and positive engagement with the bits. Each tool holder 24 may be interchangeable to facilitate mounting of different tools, and may be adapted to hold selected tools and resist the torque from the rotary head, thus allowing the respective tool to be fully unthreaded from the drill string via the rotary head with no extra tooling required. Maintaining the concentricity between the start of the thread at the end of the drill string 6 and the hammer thread is the biggest challenge especially when the mast 2 is operated in the 60° and 45° operation positions. To achieve this, without using mechanical clamps, guide 34 may be provided on the inner walls of the housing 8 and / or on an inner side of the door 28. This may reduce the amount of misalignment between the drill string 6 and tool threads, particularly where the tool comprises a hammer. The retainment rings 26 may prevent tools, in particular hammers and bits, from falling out of the housing during maintenance operations. Without the retainment rings 26, once the housing started to swing away from the mast towards its maintenance position, momentum of the tools may cause the tools to fall over and cause damage. Each carousel 20,22 may be provided with a rotary encoder adapted to transmit the position of the respective carousel to the on-board controller to allow the controller to determine the location and position of each tool. The tool changer assembly in accordance with the present invention may provide an autonomous tool changing system with the ability to house multiple tools, such as drill bits and / or hammers, depending on the configuration required by the customer. It has the ability to allow automatic changing of tools during drilling operation at any achievable drilling angle of the mast (e.g. 45° to 90°). The tool changer assembly is preferably integrated into the mast of the drill rig and may have the ability to automatically swing out of the mast to allow manual replacement of worn-out bit / hammers with fresh ones. This design requires the hammers and bits to be lifted vertically completely out of the carousel before the carousel can be retracted. The complete surround at the mid location is to stop the hammers from falling out during the maintenance removal of the hammers. The invention is not limited to the embodiment described herein but can be amended or modified without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A drill rig comprising a mast for supporting axially coupled drill rods of a drill string and a tool changer assembly mounted on the mast and adapted to carry a selection of tools to be selectively attached to the drill string;said tool changer assembly being moveable in a direction perpendicular to the mast between a retracted position, wherein the tool changer assembly is laterally spaced from the drill string on the mast, and an extended position, wherein the tool changer assembly is aligned with the drill string such that a selected tool carried by the tool changer assembly can be attached to the drill string;at least one tool carousel mounted within the housing to be rotatable about an axis parallel to the mast, plurality of tool holders being provided on the or each carousel at circumferentially spaced locations thereon, the or each carousel being rotatable under the control of a controller to bring a selected tool holder into alignment with the drill string when the tool changer assembly is in its extended position.

2. A drill rig as claimed in claim 1, wherein the housing has an opening in a side thereof to provide clearance of the drill string when the tool changing assembly is in its extended position.

3. A drill rig as claimed in claim 2, wherein the or each carousel has a gap or opening therein, whereby said gap or opening can be brought into alignment with said opening in the housing to allow the housing to be moved to its extended position without interfering with the drill string.

4. A drill rig as claimed in claim 2 or 3, wherein said opening in the housing is provided with a door moveable to selectively close said opening.

5. A drill rig as claimed in claim 4, wherein said door is moveable between a closed position wherein it closes said opening in the housing, and an open position, an opening being provided in an upper end of the door adapted to be the drill string so that the drill string can extend into the housing with the door in said closed position.

6. A drill rig as claimed in claim 5, wherein the shape of the opening in the upper end of the door is adapted to engage with the drill string to correctly align the drill string in the housing of the tool changer assembly during changing of a tool.

7. A drill rig as claimed in claim 5 or claim 6, wherein the opening in the upper end of the door is closable by a closure.

8. A drill rig as claimed in claim 7, wherein said closure is biased towards a closed position and it held in an open position by the presence of the drill string in said upper end of the door.

9. A drill rig as claimed in any of claims 5 to 8, wherein said housing comprising a side wall, an upper end and a lower end, said opening extending along a portion of the length of the side wall and along a portion of the upper wall of the housing.

10. A drill rig as claimed in claim 9, wherein the side wall of the housing is cylindrical, the door being concentric with the side wall of the housing and being rotatable about an axis coaxial with a longitudinal axis of the housing between its open and closed positions.11 A drilling rig as claimed in claim 9 or claim 10, wherein the or each carousel is rotatable about an axis coaxial with a longitudinal axis of the housing.

12. A drill rig as claimed in any preceding claim, wherein two or more vertically spaced tool and independently rotatable carousels are coaxially mounted within the housing, each having plurality of tool holders.

13. A drill rig as claimed in any preceding claim, wherein each tool holder incorporates mounting formations adapted to engage cooperating gripping formations on a tool held therein.

14. A drill rig as claimed in claim 13, wherein said mounting formations comprise upwardly extending pins adapted to engage cooperating gripping formations on the sides of a tool held therein such that the mounting formations prevent rotation of thetool in the tool holder to allow the tool to be screwed onto or off the end of the drill string.14

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