Casing tool

Abstract

A casing tool for installing a casing tube into a hole, said casing tool comprising an elongate body having a first end adapted to be attached to a distal end of a rotary head or drill rod, a plurality of elongate gripping members mounted on said elongate body to be moveable between retracted positions, to allow the elongate body to be inserted into a casing tube, and extended positions, wherein said gripping members engage an inner surface of the casing tube, the gripping members being biased to said extended positions by biasing means, said casing tool incorporating actuation means operable to urge said gripping members to their retracted positions, against the action of said biasing means.

Description

FIELD OF THE INVENTION This invention relates to a tool for introducing a casing tube into a hole and to a drilling rig incorporating same. BACKGROUND OF THE INVETION One of the first operations when starting a new sample hole is to drill and line an oversized hole with a series of casing tubes, thus giving support to the walls of the hole and thereby reducing the risk of collapse. Putting a casing tube into a hole is currently a largely manual operation. One way this is often achieved is by affixing a collar around a drill rod. This collar is adapted to rest on an upper end of a casing section located over the drill rod so that the casing can be forcibly pushed into an already drilled hole. The collar and the casing tube must both be manually applied to the drill rod and the collar subsequently manually removed after use. Furthermore, existing manual methods of installing casing tubes, for example using such drill rod collars, cannot be also used to subsequently remove a casing tube from the hole, if required. An object of the present invention is to provide a casing tool that can be used to install and remove casing tubes from a hole without requiring manual intervention. SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a casing tool for installing a casing tube into a hole, said casing tool comprising an elongate body having a first end adapted to be attached to a distal end of a rotary head or a drill rod, a plurality of elongate gripping members mounted on said elongate body to be moveable between retracted positions, to allow the elongate body to be inserted into a casing tube, and extended positions, wherein said gripping members engage an inner surface of the casing tube, the gripping members being biased to said extended positions by biasing means, said casing tool incorporating actuation means operable to urge said gripping members to their retracted positions, against the action of said biasing means. Preferably said elongate body of the casing tool comprises a cylindrical tube, said gripping members being adapted to be moveable radially with respect to said elongate body. Preferably the gripping members extend parallel to the axis of the cylindrical tube. In one embodiment, the actuation means may comprise a piston located within a cylinder defined within said elongate body and adapted to be axially moveable within the cylinder, the piston being operatively coupled to the gripping members, means being provided for supplying pressurised fluid into the cylinder on a first side of the piston to thereby urge the piston against said biasing means and move said gripping members from their extended to their retracted positions. The biasing means may comprise a compression spring acting against the piston to urge the gripping members to their extended positions. Preferably the piston is coupled to a rod extending through a tubular central portion of the elongate body, a distal end of said rod being coupled to a slider located at a second end of the elongate body, opposite said first end thereof, said slider being operatively coupled to the gripping members via respective first linkage members, the gripping members being coupled to the tubular central portion of the elongate housing via a plurality of second linkage members, whereby axial displacement of said slider due to movement of the piston within its cylinder causes radial movement of said gripping members between their retracted and extended positions. Each of said first linkage members may be pivotally coupled to the slider at a first end and to a respective gripping member at an second end, one or more second linkage members being pivotally coupled to each gripping member at one end and to respective stationary pivot points defined on said tubular central portion of the elongate body at a respective second end. 3 Said rod may extend through said compression spring, said spring being located around said rod to act between a second side of the piston, opposite said first side, and a spring seat provided on or within a portion of the elongate body through which the rod passes. The first end of the elongate body may be provided with a threaded coupler adapted to receive a threaded end of a rotary head or drill rod. The coupler may be provided with passages for selectively supplying pressurised air into said cylinder to act against the piston. In one embodiment four gripping members may be provided on the elongate body of the tool, equally spaced around the outer surface of the casing tool and extending coaxially along a portion of the elongate body of the casing tool. Each gripping member may be provided with a gripping pad on an outer surface thereof, preferably formed from an elastomeric material, such as rubber. According to a further aspect of the present invention there is provided a drilling rig comprising a mast for supporting axially coupled drill rods of a drill string and further comprising a casing tool in accordance with the first aspect of the invention for installing casing tubes into a hole. Preferably the drilling rig is provided with a breakout assembly adapted to facilitate coupling and decoupling of the casing tool from the rotary head or the lower end of a drill rod of the drill string. A rotary head is preferably provided on the mast above the breakout assembly, said rotary head being adapted to impart rotation to the drill string supported on the mast. The mast may be mounted on a self-propelled chassis. The mast may be pivotally mounted at one end of the chassis for movement between a substantially horizontal transport position and an angled or upright drilling position. A rod magazine may be provided on the drilling rig, adapted to support a plurality of drill rods and a rod handling system adapted to selectively add and remove drill 4 rods to and from the drill string on the mast and a tool cassette adapted to automatically add and exchange tools to and from the lowermost drill rod on the mast, including said casing tool. BRIEF DESCRIPTION OF THE DRAWINGS A casing tool 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 casing tool in accordance with an embodiment of the present invention; Figures 2 and 3 are longitudinal sectional views of the casing tool of figure 1; and Figure 4 is a longitudinal sectional view illustrating the casing tool of Figure 1 in use on a drilling rig. DETAILED DESCRIPTION OF THE DRAWINGS As illustrated in the drawings, a casing tool 2 in accordance with an embodiment of the present invention comprises an elongate cylindrical body having a threaded coupling 4 at a first (upper) end adapted to be coupled to a lower end of a drill rod / rotary head of a drilling rig and having a plurality of elongate casing gripping members 6 arranged parallel to a longitudinal axis of the tool and extendable from the sides of the casing tool 2 to engage and grip an inner surface of a casing tube into which the casing tool is inserted. The gripping members 6 may be provided with rubber pads on their outer sides to enhance grip and minimise damage to the casing tubes. The gripping members 6 are mounted in respective openings in the outer periphery of the elongate body of the casing tool 2 to be radially moveable (with respect to the longitudinal axis of the elongate body) between extended positions (as shown in 5 Figure 2), wherein said gripping members engage an inner surface of a casing tube within which the casing tool 2 is located, and retracted positions (as shown in Figure 3) to allow the casing tool to be inserted into or removed from a casing tube. The gripping members 6 are preferably biased to their extended positions by suitable biasing means, a pneumatically operated piston 10 being provided within the elongate body of the casing tool 2, the piston 10 being operatively coupled to the gripping members 6 to urge said gripping members 6 to their retracted positions, against the action of said biasing means, when air pressure is supplied into a cylinder 12 in which the piston 10 is slideably mounted, as will be described in more detail below. As illustrated in Figures 2 and 3, the elongate body of the casing tool 2 comprises an outer tube 14 having openings therein within which the gripping members 6 are located, a coupling interface 16 defining said threaded coupling 4 of the casing tool 2 being provided in a first end of the outer tube 14. The piston 10 is slidingly located within the outer tube 14, with a cylinder 12 defined by an inner surface of a portion of the outer tube 14 adjacent the coupling interface 16. The coupling interface 16 preferably incorporates passages 15 adapted to communicate with a supply of pressurised air via the adjacent drill rod / rotary head to selectively supply pressurised air into the cylinder 12 to act one the head of the piston 10. A pressure relief valve 18 may be provided within the coupling interface 16. A piston rod 20 is coupled to and extends from the piston 10, extending though a central guide tube 22 within the elongate body of the casing tool 2 and terminating in an axially slideable guide member 24 located within a second end of the outer tube 14, opposite said first end. A stationary guide member 26 is mounted within the outer tube 14 adjacent the piston 10, coupled to the central guide tube 22, and through which the rod 20 passes. A compression spring 28 is located between the piston 10 and a spring seat 29 defined by the stationary guide member 26, the piston rod 20 extending through the spring 28 and through an opening in the spring seat 29 of the stationary guide member 26. The piston 10 is slideable within the cylinder 12 defined by the outer tube 14, between a first position, shown in Figure 2, wherein the piston 10 abuts the coupling interface 16, and a second position, shown in Figure 3, wherein the piston 10 abuts the stationary guide member 26, the spring 28 biasing the piston 10 towards its first position. A peripheral edge of the piston may be provided with one or more sealing members, such as an O-ring 30, and / or a wear ring 32. The slideable guide member 24 may also be provided with a peripheral wear ring 34. A further wear ring or wear members may be provided between the slideable guide member 24 and the central guide tube 22 to guide sliding movement of the slideable guide member 24. In order to translate movement of the piston 10 into movement of the gripping members 6, the gripping member 6 are coupled to the central guide tube 22 and to the slideable guide member 24 via a plurality of pivotal linkages defined by respective first linkage members 36, each first linkage member 36 pivotally coupled to the slideable guide member 24 at a first end and to a respective gripping member 6 at a second, opposite end, and second linkage members 38,40, each second linkage member 38,40 being pivotally coupled to the fixed central guide tube 22 at a first end and to a respective gripping member 6 at a second end, opposite said first end. In order to maintain each gripping member 6 parallel to the piston rod 20, each gripping member 6 may be provided with two axially spaced second linkage member 38,40 arranged in parallelogram relationship. The first linkage members 36 extend from one first end 14 of the outer tube 14 towards the opposite end of outer tube while the second linkage members 38,40 extend towards said one end of the outer tube 14 in a direction substantially opposite to said first linkage member 36. The arrangement of the first and second linkage member 36,38,40 causes the gripping members 6 to be moved inwardly from their extended positions to their retracted positions when pressurised air is supplied into the cylinder 12, pushing the piston 10 to its second position against the biasing action of the spring 28 and moving the slideable guide member 24 to the right as shown in Figures 2 and 3. 7 Release of such pressurised air causes the spring 28 to push the piston 10 back to its first position, moving the piston rod 20 and slideable guide member 24 to the left, thereby moving the gripping member 6 outwardly to their extended positions. The openings in the outer tube 14 within which the gripping members 6 are located may be slightly longer than the gripping members 6 to allow the necessary limited axial movement of the gripping members 6 as they move between their retracted and extended positions under the action of the piston 10 and first and second linkage members 36,38,40. As shown in Figure 4, in use, the casing tool 2 is attached to the rotary head 50 of a drilling rig, preferably by means of an automated tool changing arrangement avoiding the need for any manual intervention, and pressurised air is supplied to the casing tool 2 to act against the piston 10 and withdraw the gripping members 6 to their retracted positions, allowing the casing tool 2 to be inserted into a casing tube 60. The supply of air to the casing tool 2 is then cut off, causing the gripping members 6 to return to their extended positions in engagement with an inner surface of the casing tube 60 due to return movement of the piston 10 under the action of the spring 28. The casing tube 60 may then be forced into a hole. Pressurised air may once again be supplied to the casing tool 2 to move the piston 10 to its second position and retract the gripping members 6, thereby allowing the casing tool 2 to be removed from the casing tube 60. The same process may be used to remove a casing tube 6 from the hole. The casing tool 2 can be detached from the rotary head 50 at a breakout assembly or modified slips table of the drilling rig so that the rotary head can be loaded with one or more drill rods between the rotary head 50 and the casing tool 2 to further push the casing tube into the ground if required. The casing tool can be used with both steel and PVC casing tubes and is able to both install casing tubes into a hole and retrieve casing tubes from the ground when required. A safety aspect of this design is that if the rig was to suddenly lose power when holding a casing tube the casing tool will naturally continue to hold the casing tube as there will be no air available to retract the gripping members 6. 5 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 in the following claims.

Claims

1. A casing tool for installing a casing tube into a hole, said casing tool comprising an elongate body having a first end adapted to be attached to a distal end of a rotary head or drill rod, a plurality of elongate gripping members mounted on said elongate body to be moveable between retracted positions, allowing the elongate body to be inserted into a casing tube, and extended positions, wherein said gripping members engage an inner surface of the casing tube, the gripping members being biased to said extended positions by biasing means, said casing tool incorporating actuation means operable to urge said gripping members to their retracted positions, against the action of said biasing means.

2. A casing tool as claimed in claim 1, wherein said elongate body of the casing tool comprises a cylindrical tube, said gripping members being adapted to be moveable radially with respect to said elongate body.

3. A casing tool as claimed in claim 1 or claim 2, wherein said actuation means comprises a piston located within a cylinder defined within said elongate body and adapted to be axially moveable within the cylinder, the piston being operatively coupled to the gripping members, means being provided for supplying pressurised fluid into the cylinder on a first side of the piston to thereby urge the piston against said biasing means and move said gripping members from their extended to their retracted positions.

4. A casing tool as claimed in claim 3, wherein said biasing means comprises a compression spring acting against the piston to urge the gripping members to their extended positions.

5. A casing tool as claimed in claim 3 or claim 4, wherein the piston is coupled to a rod extending through a tubular central portion of the elongate body, a distal end of said rod being coupled to a slider located at a second end of the elongate body, opposite said first end thereof, said slider being operatively coupled to the gripping members via respective first linkage members, the gripping members being coupled to the tubular central portion of the elongate housing via a plurality of second10linkage members, whereby axial displacement of said slider due to movement of the piston within its cylinder causes radial movement of said gripping members between their retracted and extended positions.

6. A casing tool as claimed in claim 5, wherein each of said first linkage members are pivotally coupled to the slider at a first end and to a respective gripping member at an second end, one or more second linkage members being pivotally coupled to each gripping member at one end and to respective stationary pivot points defined on said tubular central portion of the elongate body at a respective second end.

7. A casing tool as claimed in claim 5 or claim 6, when dependent on claim 4, wherein said compression spring acting between a second side of the piston, opposite said first side, and a spring seat provided on or within a portion of the elongate body through, said rod passing through both the compression spring and an opening in said spring seat.

8. A casing tool as claimed in any preceding claim, wherein said first end of the elongate body is provided with a threaded coupler adapted to receive a threaded end of a rotary head or drill rod.

9. A casing tool as claimed in any preceding claim, wherein four gripping members are provided on the elongate body of the tool, equally spaced around the casing tool and extending coaxially along a portion of the elongate body of the casing tool.

10. A casing tool as claimed in any preceding claim, wherein each gripping member is provided with a gripping pad on an outer surface thereof.

11. A drilling rig comprising a mast for supporting axially coupled drill rods of a drill string and further comprising a casing tool as claimed in any preceding claim for installing casing tubes into a hole.

12. A drilling rig as claimed in claim 11, further comprising a breakout assembly adapted to facilitate coupling and decoupling of the casing tool from the lower end of a drill rod of the drill string.

13. A drilling rig as claimed in claim 12, wherein a rotary head is provided on the mast above the breakout assembly, said rotary head being adapted to impart rotation to the drill string supported on the mast.

514. A drilling rig as claimed in any of claims 11 to 13, wherein the mast is mounted on a self-propelled chassis.

15. A drilling rig as claimed in any of claims 11 to 14, wherein the mast is pivotally 10 mounted at one end of the chassis for movement between a substantially horizontal transport position and an angled or upright drilling position.

16. A drilling rig as claimed in any of claims 11 to 15, comprising a rod magazine adapted to support a plurality of drill rods and a rod handling system adapted to 15 selectively add and remove drill rods to and from the drill string on the mast and a tool cassette adapted to automatically add and exchange tools to and from the lowermost drill rod on the mast, including said casing tool.

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