WO2008122086A1

WO2008122086A1 - Extendable member

Info

Publication number: WO2008122086A1
Application number: PCT/AU2008/000494
Authority: WO
Inventors: Peter Andrew Gray
Original assignee: Peter Andrew Gray
Priority date: 2007-04-05
Filing date: 2008-04-04
Publication date: 2008-10-16
Also published as: AU2008235258A1

Abstract

The invention provides an extendable member for use in construction, the extendable member comprising: a first elongate member; a second elongate member, wherein the second elongate member is movably engaged with the first elongate member; wherein relative rotation between the first and second elongate members causes relative axial movement between the first and second elongate members, thereby changing the extendable member between a shortened condition and a lengthened condition. Embodiments of the extendable member adapted to be a self drilling rock bolt, a drill rod or a rock bolt are also provided, as is a method of drilling a hole.

Description

EXTENDABLE MEMBER

Technical Field

The invention broadly relates to extendable members, and more specifically, relates to extendable members adapted to be inserted, fastened, or screwed into a surface. More specifically still, the invention relates to extendable members adapted to perform the function of a self drilling rock bolt, a drill rod or a rock bolt.

Background to the Invention

Rock bolts are now a common method to support the roof and walls of tunnels and mines worldwide. There are a wide variety of rock bolts available including steel, fibreglass and plastic rock bolts. Rock bolts usually consist of a long elongate bar which is anchored into a borehole in rock to provide reinforcement support to the rock mass. Rock bolts are typically solid, but may also be hollow.

Rock bolts are also rigid such that they cannot be bent by hand. Some very soft plastic rock bolts can be bent with difficulty, but the majority of rock bolts cannot be bent and are straight and rigid. Therefore the longest rigid rock bolt that can be installed into a mine roadway or tunnel is restricted to the height of the opening. Typically a 3 m high roadway would use a maximum length rock bolt of 2.4 m long to allow some additional room for the drilling machine below the end of the rock bolt. If a longer length rock bolt needs to be installed for geotechnical reasons, then rock bolts can be increased in length by screwing a separate coupler onto the end of the rock bolt and joining multiple bars together. The coupler typically has an internal female thread that will screw onto the end of one rock bolt and onto the end of another rock bolt. Typically, a coupler to join together 22 mm diameter rock bolts, would be 140 mm long by 33 mm in diameter with a central hole with a female thread that would screw over the male-threaded 22 mm diameter rock bolts or bars. These coupled bolts are typically installed by firstly drilling a large diameter borehole that will accommodate the diameter of the coupler, and then pushing the first rigid bar up the borehole with a coupler screwed onto the bottom end of the bar. Once this first bar is almost fully inside the borehole, another rigid bar is screwed into the exposed female thread in the coupler and then this second rigid bar is also pushed up the borehole. In this way multiple rigid bars and couplers can be used to increase the length of a coupled bolt to any required length. However, if multiple bars and couplers are required, then the installation process becomes very labour intensive and cumbersome, and cable bolts are often used in preference. Cable bolts which are made up of multiple small diameter wires, can be bent and installed in long boreholes and cables 10m long or more are often used in the mining industry in roadways or tunnels which are typically 3m high. Nevertheless, there are also problems in installing cable bolts, particularly in weak or collapsing ground where it can often be difficult to push a cable up a long borehole. In addition, long cable bolts really need to be fully grouted to provide good rock support and this can be a time consuming and labour intensive process. Finally, it is difficult to put a thread onto the end of a cable without the use of additional expensive fittings, which adds to the, cost of the cable bolt, and so typically cable bolts are often not tensioned with a nut but use a barrel and wedge end fitting. If cables are required to be tensioned, a hydraulic jack is often used to apply tension to the cable bolt, and this is also a very cumbersome, labour intensive process. Similarly, drill rods are typically made from hollow steel bars that are rigid. If a vertical borehole has to be drilled that is longer than the maximum height of a mine roadway or tunnel, then multiple rigid drill rods have to be progressively coupled together as the borehole is drilled. In this manner a long borehole can be drilled in a mine roadway or tunnel even though the roadway may have a restricted height. However, it is often a cumbersome process to stop drilling to screw a coupler and an additional drill rod onto the existing coupled drill rods already in the borehole, called the "drill string", for the purpose of, for example, drilling a long borehole. In addition, once the long borehole is drilled, the drill rods and couplers have to be progressively unscrewed from the drill string, to remove all the drill rods and couplers from the borehole.

Some attempts have been made to overcome the above problems of drilling long holes with rigid drill rods, and drilling through a pre-installed borehole casing is well known prior art in the oil drilling industry, typically for drilling deep vertical boreholes from the surface. There is a need for improved apparatus and methods for overcoming or ameliorating some or all of the abovementioned problems. The present inventor has developed an extendable member that has a number of uses. Summary of the Invention

According to a first aspect, the present invention provides an extendable member for use in construction, the extendable member comprising: a first elongate member; a second elongate member, wherein the second elongate member is movably engaged with the first elongate member; wherein relative rotation between the first and second elongate members causes relative axial movement between the first and second elongate members, thereby changing the extendable member between a shortened condition and a lengthened condition.

The shortened condition is preferably achieved when the first and second elongate members are relatively axially retracted with respect to one another. Conversely, the lengthened condition is preferably achieved when the first and second elongate members are relatively axially extended with respect to one another. In one preferred embodiment, when the extendable member is in the shortened condition, the second elongate member is substantially axially retracted with respect to the first elongate member and when the extendable member is in the lengthened condition, the second elongate member is substantially axially extended with respect to the first elongate member. In another preferred embodiment, when the extendable member is in the shortened condition, the first elongate member is substantially axially retracted with respect to the second elongate member and when the extendable member is in the lengthened condition, the first elongate member is substantially axially extended with respect to the second elongate member. In a preferred embodiment the first elongate member and the second elongate member are threadably engaged. Preferably, the threadable engagement has a coarse pitch thread. In a preferred embodiment, the pitch is between 3 mm and 50 mm.

The threadable engagement is preferably provided by a threaded section which may be integral with or connected to the first elongate member or the second elongate member. In some preferred embodiments, the threaded section represents a small part of the entire length of the first elongate member or the second elongate member. In alternative embodiments, the threaded section extends substantially along the entire length of the first elongate member or the second elongate member.

In one preferred embodiment, the threaded section is threadably connected to an inner wall of the first elongate member. In this embodiment, the second elongate member has a corresponding or mating threaded external profile.

. In another preferred embodiment, the threaded section is threadably connected to an outer wall of the first elongate member. In this embodiment, the second elongate member has a corresponding or mating threaded internal profile.

In alternative embodiments, the threaded section is threadably connected to either an inner wall or an outer wall of the second elongate member in which case the first elongate member has a corresponding or mating threaded external or internal profile as the case may be.

In one preferred embodiment, the first elongate member is adapted to substantially house the second elongate member when the extendable member is in the shortened condition.

In another preferred embodiment, the second elongate member is adapted to substantially house the first elongate member when the extendable member is in the shortened condition.

Preferably, the extendable member further comprises disengagement prevention means adapted to inhibit disengagement of the first and second elongate members from one another. In one preferred embodiment, the disengagement prevention means includes a lip member connected adjacent a trailing end of the second elongate member. The lip member is adapted to prevent the second elongate member from threadably disengaging from the first elongate member when the lip member comes into contact with a trailing end of the threaded section.

In other embodiments, the lip member is connected adjacent a leading end of the second elongate member, a trailing end of the first elongate member or a leading end of the first elongate member. The disengagement prevention means can, however, take other forms or be of different configurations and be connected, placed or otherwise located adjacent other parts of the extendable member in accordance with the invention.

In some preferred embodiments, a change in the extendable member from the shortened condition to the lengthened condition is achieved by causing the extendable member to be drilled into a surface, typically a rock, soil or other ground surface, or a cement or brick surface.

In one such embodiment, as the first elongate member (or second elongate member of another such embodiment) is rotated, it may threadably unscrew from the second elongate member (or vice versa) or may cause the second elongate member (or the first elongate member of the other such embodiment) to also rotate thereby causing the second elongate member (or the first elongate member of the other such embodiment) to drill a borehole into a surface.

In a preferred embodiment the unscrewing or drilling or a combination of both unscrewing and drilling, may occur at high speed when a drilling device, such as a drilling machine, drilling means, or other device or means capable of drilling the extendable member into the surface, is rotating at high speed.

The manner in which the extendable member extends in several such embodiments may depend on factors such as the hardness of the surface to be drilled, the axial thrust applied by the drilling device, the thread pitch of the threadable engagement between the first and second elongate members, the torque applied by the drilling machine, drilling device or drilling means, or a combination of one or more of these and other factors.

Preferably, the unscrewing and drilling is facilitated when a distance between a point at which the extendable member engages the drilling device (for example, where the extendable member engages with a chuck) and a point on a surface into which the extendable member is to be drilled is substantially fixed throughout the drilling process. As the drilling device rotates the extendable member against the surface and one elongate member attempts to threadably disengage from the other elongate member, axial thrust within the extendable member increases and so to does the resistive torque on the threads engaging the elongate members increase.

This resistive torque preferably eventually exceeds any torque required to rotate the extendable member against the surface and both elongate members rotate together as unscrewing is substantially not possible (or inhibited or "locked") at that point in the drilling process. A first portion of a borehole into the surface is thus drilled. As the first portion of the borehole is drilled, the axial thrust in the extendable member decreases^' which causes the resistive torque on the threads engaging the elongate members to also decrease, thereby enabling unscrewing (or "unlocking") of the first and second elongate members. A first segment of unscrewing of the elongate members thus occurs. These steps are repeated as second, third, fourth and so forth portions of the borehole are drilled when unscrewing is 'locked', with corresponding second, third, fourth and so forth segments of unscrewing occurring between the elongate members resulting in a corresponding increase in length of the extendable member. ' The length of a portion of drilled borehole may or may not be substantially the same as the length by which the extendable member lengthens with each corresponding segment of unscrewing of the elongate members. The extendable member may increase in length progressively or may increase in length intermittently as the borehole is drilled. Preferably, the extendable member will ultimately achieve the lengthened condition, and can then be completely drilled into the surface by causing the distance between the point at which the extendable member engages the drilling device and the point on the surface into which the extendable member is being drilled to decrease to a essentially negligible distance, for example, while continuing to drill. At this point, the depth of the borehole is substantially equivalent to the length of the extendable member in the lengthened condition.

Further preferred embodiments of the extendable member include a third elongate member moveably engaged with the first elongate member or the second elongate member or both. In some preferred embodiments, a plurality of elongate members are moveably engaged to one or more other elongate member, substantially moving in the same or a similar way as described above for the relative movement between the first and second elongate members. In other preferred embodiments which include more elongate members than two, any such additional elongate members may also be fixedly or otherwise not moveably engaged with the first elongate member or the second elongate member or each of the first and second elongate members.

In one preferred embodiment, a difference in length of the extendable member when in the shortened condition versus when in the lengthened condition is at least about 10 mm.

In a particularly preferred embodiment, the extendable member is adapted to be a self drilling rock bolt. Typically, the self drilling rock bolt comprises a first (outer) elongate member with an external profile which is typically a coarse thread profile. This first elongate member may, in some embodiments, have one or more surface penetration means, such as a reamer drill bit, on its leading end. In some such embodiments, there is at least one female threaded section on an inner wall of the first elongate member. In one preferred embodiment, there is at least one threaded section adjacent a leading end of the first elongate member. In another preferred embodiment, there is a second threaded section adjacent a trailing end of the first elongate member.

At least one second (inner) elongate member is threadably engaged with the leading end of the first elongate member through the threaded section adjacent the leading end of the first elongate member. In some embodiments, a surface penetration means, such as a drill bit is connected to a leading end of the second elongate member.

It will be appreciated by persons skilled in the art that further preferred embodiments of the extendable member adapted to be a self drilling rock bolt could be physically configured such that the second elongate member corresponds to an 'outer' member and the first elongate member corresponds to an 'inner¹ member. These embodiments essentially have a reverse physical configuration to those described above for the first and second elongate members.

In some preferred embodiments, a third (inner) elongate member is threadably engaged with the first elongate member (or second elongate member) via the threaded section adjacent the trailing end of the first elongate member (or second elongate member). In some such embodiments, the third elongate member preferably has a nut for rotation and tensioning on a trailing end of the third elongate member. The nut is typically assembled onto a thread on the outside of the third elongate member, but could be permanently fixed to the trailing end of the third elongate member or be permanently fixed to the trailing end of the first elongate member (or second elongate member). If the nut is assembled onto a thread on the outside of the third elongate member, then a nut stop is typically fixed to the trailing end of the third elongate member to prevent the nut from threadably disengaging from the third elongate member. Preferably, one or more of the elongate members respectively have disengagement prevention means adapted to inhibit each from threadably disengaging from the respective threaded sections with which they are engaged. Each of the threaded sections or threads are all typically right-handed threads, but could all be left- handed threads also. In another particularly preferred embodiment, the extendable member is adapted to be a drill rod. Preferably, the drill rod comprises a first (outer) elongate member and a second (inner) elongate member threadably engaged with the first elongate member. The drill rod typically includes surface penetration means, such as a drill bit, connected to a leading end of the second elongate member and may also include surface penetration means, such as a reamer drill bit, on a leading end of the first elongate member.

The threadable engagement of the first elongate member with the second elongate member preferably has a thread pitch adapted to suit the particular application. Typically the thread pitch is more than about 3 mm but less than about 50 mm. In some embodiments, the range for the thread pitch is greater than or different to the abovementioned range. The invention is not limited by the thread pitch of the threadable engagement between the first and second elongate members, or, in some embodiments, by the thread pitch of the threadable engagement between these and other elongate members.

In one preferred embodiment of the extendable member adapted to be a drill rod, the second elongate member has a continuous thread along its length, but in other embodiments, the second elongate member may have a discontinuous thread along its length. In this embodiment, the first elongate member may have a threaded external profile or may have a smooth or rough external profile or any other external profile.

As with preferred embodiments of the extendable member adapted to be a self drilling rock bolt, persons skilled in the art will appreciate that further embodiments of the extendable member adapted to be a drill rod could be physically configured such that the second elongate member corresponds to an 'outer¹ member and the first elongate member corresponds to an 'inner¹ member. These embodiments essentially have a reverse physical configuration to those described above for the first and second elongate members.

In some preferred embodiments, the extendable member adapted to be a drill rod further includes a third elongate member substantially as described above in respect ^' of the extendable member adapted to be a self drilling rock bolt.

In embodiments of the extendable member adapted to be a self drilling rock bolt or a drill rod, the drill bit attached or connected to the leading end of the second elongate member may be of any suitable shape or type. An example of a drill bit for use in this application is disclosed and claimed in Australian Patent Application No. 2006204633.

Preferably, for embodiments of the extendable member adapted to be a self drilling rock bolt or a drill rod, the extendable member is capable of drilling its own borehole and 'automatically' or 'semi-automatically' increasing in length as it is being installed. In such embodiments, typically a trailing end of the first elongate member is adapted to engage a chuck of a drilling machine.

In some such embodiments, the extendable member is preferably caused to change from the shortened condition to the lengthened condition by: engaging the extendable member in the shortened condition with the chuck and positioning the drill bit in forcible contact with a surface to be drilled; inhibiting a distance between the chuck and the surface from increasing; and causing the drilling machine to rotate the first or second elongate member against friction created by the forcible contact between the drill bit and the surface; thereby increasing shear strength across the threadable engagement between the first elongate member and the second elongate member until the extendable member is forced to rotate and drill the elongate member into the surface.

In another particularly preferred embodiment, the extendable member is adapted to be a rock bolt. Preferably, when the extendable member is adapted to be a rock bolt, the leading end of the second (inner) elongate member includes a rotation inhibition means.

Preferably, the rotation inhibition means may be a plastic cap, or an expansion shell friction anchor device, or a piece of wire or plurality of wires welded to the leading end of the second (inner) elongate member, or any other suitable device capable of inhibiting the second (inner) elongate member from rotating inside a borehole.

Preferably, the rotation inhibition means is adapted to engage a wall of the borehole, and provide a resistance or inhibition to the second (inner) elongate member rotating in the borehole.

Preferably, in practice, the extendable member adapted to be a rock bolt is inserted into a pre-drilled borehole. A drilling machine which engages a trailing end of the first (outer) elongate member is positioned so as to inhibit a distance between the chuck and an opening of the borehole from increasing. The first (outer) elongate member is then rotated. As the drilling machine rotates the first (outer) elongate member, the second (inner) elongate member is inhibited from rotating by the rotation inhibition means. Relative rotational movement occurs between the first and second elongate members, which causes the second (inner) elongate member to extend from the first (outer) elongate member without itself rotating. This process is preferably continued until the second (inner) elongate member is fully extended from the first (outer) elongate member at which point a disengagement prevention means inhibits the second (inner) elongate member from disengaging from the first (outer) elongate member. Yet further rotation by the drilling machine of the first (outer) elongate member, then forces the second (inner) elongate to overcome the rotational resistance provided by the rotation inhibition means, and the first and second elongate members can rotate together. In a preferred embodiment, this rotation of the second (inner) elongate member can be used to mix a resin cartridge previously inserted inside the borehole, or activate an expansion shell anchoring device, or to carry out some other desirable task.

Once the rock bolt has been extended to its full length, it can be anchored or secured in the borehole by using a range of techniques including: an expansion shell anchoring device on the leading end of the second (inner) elongate member, the anchoring device is expanded and fixed inside the borehole by further rotation of the rock bolt; by pumping cement grout into the borehole and allowing it to cure and harden; by causing the second (inner) elongate member to rupture and rotate a frangible resin cartridge which had previously been inserted into the borehole allowing the resin in the resin cartridge to mix, cure and harden; and by pumping resin into the borehole and allowing it to cure and harden.

In some preferred embodiments of the extendable member adapted to be a rock bolt, surface penetration means, such as a drill bit may be connected to the leading end of the second (inner) elongate member and/or a reamer drill bit may be connected to the leading end of the first (outer) elongate member as may be the case, for example, in respect of the extendable member adapted to be a self drilling rock bolt or a drill rod. Also, the extendable member adapted to be a rock bolt may also be adapted to be engaged with a chuck on a drilling machine which can then advance the rock bolt into the pre-drilled borehole.

As with preferred embodiments of the extendable member adapted to be a self drilling rock bolt or a drill rod, persons skilled in the art will appreciate that further embodiments of the extendable member adapted to be a rock bolt could be physically configured such that the second elongate member corresponds to an 'outer¹ member and the first elongate member corresponds to an 'inner' member. These embodiments essentially have a reverse physical configuration to those described above for the first and second elongate members.

In embodiments where the extendable member is adapted to be a self drilling rock bolt, a drill rod, or a rock bolt, the extendable member can be formed from steel, stainless steel, fibreglass, carbon fibre, plastic or any other suitable material.

In some preferred embodiments of the extendable member adapted to be a self drilling rock bolt, a drill rod, a rock bolt, or any other member adapted for use in construction, the extendable member further includes a conduit adapted to be substantially housed by at least one of the elongate members. Preferably, the conduit is adapted to receive, carry or transfer fluids, such as air, water, air and water mist, liquid, resins, cement grout, expandable foams, or anything else which it may be desirable to transfer through the extendable member, such as rock cuttings, soil, sediment or dirt.

In one such preferred embodiment, the conduit is substantially housed by the first elongate member, and in another preferred embodiment, the conduit is substantially housed by the second elongate member.

Preferably, the conduit has a length which enables the conduit to be substantially housed by one of the elongate members. In a particularly preferred embodiment, the length of the conduit is such that, when the extendable member is in the lengthened condition, the conduit extends through at least a part of both the first and second elongate members.

Preferably, the extendable member has a central hole passing along its internal length and the conduit is housed by the first and/or second elongate members within that central hole.

In some preferred embodiments the conduit is fixed or connected to at least one of the elongate members, and in a particularly preferred embodiment, the conduit is fixed or connected to an internal part of one of the elongate members. In one embodiment, the conduit is fixed or connected to an internal part of the elongate member to which a drill tip or reamer is attached, and the fixation or connection of the conduit to that elongate member is adjacent the drill tip or reamer. One preferred mechanism for the connection or fixation of the conduit to the elongate member is via a washer that fixedly fits in a central hole in that elongate member. The washer can be fixed to the conduit by, for example, welding. Other mechanisms for connecting or fixing the conduit to the elongate member are also contemplated.

The conduit may, in preferred embodiments, slide or move along the interior of one or both elongate members as the extendable member is changed from the shortened condition to the lengthened condition.

Preferably a seal, such as an O-ring, is interposed between the conduit and at least one of the elongate members, such that a hydraulic seal can be maintained therebetween. Preferably, the hydraulic seal is maintained even as the extendable member changes from the shortened condition to the lengthened condition. Persons skilled in the art would appreciate that with embodiments of the invention wherein the extendable member is adapted to be a self drilling rock bolt, a drill rod or a rock bolt, the extendable member can be installed or used in a mine, roadway or tunnel which has restricted height. Preferably, the extendability of the extendable member enables the self drilling rock bolt, or the rock bolt according to the present invention to provide additional support to rock surrounding the roadway or tunnel. In some embodiments, this additional support is greater than that which is provided by prior art fixed length rigid rock bolts, and allows the drill rod according to the present invention to drill a longer hole than is currently possible with such fixed length rigid drill rods. In some preferred embodiments wherein the extendable member is adapted to be a self drilling rock bolt, drill rod or rock bolt or some other member for use in construction, a continuous passageway extends through the elongate members and is adapted to receive water, resin, cement grout or any other substance or means that may be desirable to pump through the extendable member during the course of installation. In a second aspect, the present invention provides a method of drilling a hole comprising: providing an extendable member of the first aspect of the present invention; placing a leading end of the second elongate member against a surface; applying rotation to the first elongate member, thereby causing the second elongate member to extend from the first elongate member, or to be substantially inhibited from rotating with respect to the first elongate member, and drill into the surface. In a preferred embodiment, a trailing end of the first elongate member is loaded into a drilling machine, drilling device or drilling means before rotation is applied. Preferably, the leading end of the second elongate member includes surface penetration means and is brought into forcible contact with the surface by a drilling machine, drilling device, or drilling means. Preferably, a distance between the trailing end of the first elongate member when loaded into the drilling device or drilling means and the surface is substantially fixed.

In one preferred embodiment, the second elongate member is inhibited from rotating because the drill bit on the leading end of the second elongate member is pushed against the surface to be drilled by the drilling machine. Therefore as the first elongate member is rotated, relative rotation between the first and second elongate members may occur. If relative rotation occurs between the first and second elongate members, the first member unscrews relative to the second member and the extendable member increases in length. As the extendable member increases in length, the axial force between the drilling machine and the surface to be drilled also increases, and this force is transferred to the threadable section between the first and second elongate members such that the shear strength along the threadable section also increases. This shear strength increases until the second elongate member begins to rotate as the first elongate member is rotated, and the drilling tip on the leading end of the second elongate member can then drill a borehole in the surface.

In preferable effect, the relative rotation between the first and second elongate members causes the second elongate member to extend from the first elongate member. This extension of the second elongate member will cause the axial force between the first and second elongate members to increase rapidly, particularly if the drilling device, drilling machine or drilling means is inhibited from moving away from the surface to be drilled. As the axial force increases, it causes the shear strength on the connecting threads between the first and second elongate members to also rapidly increase.

In a preferred embodiment, the extendable member will be caused to extend a predetermined length and then to drill into the surface a predetermined distance, over and over again until extended into the lengthened condition.

It will be appreciated that the method of the second aspect can be altered if the physical relationship between the first and second elongate members is reversed. In such embodiments, the method is correspondingly altered to accommodate this altered physical relationship so that, for example, a leading end of the first elongate member is placed against the surface and rotation is applied the second elongate member.

In a third aspect, the present invention provides an extendable member comprising: a first elongate member; a second elongate member having a leading end with surface penetration means, the second elongate member threadably engaged with the first elongate member, wherein the extendable member is adapted to be changeable between a shortened condition and a lengthened condition by relative axial movement between the first elongate member and the second elongate member.

In a preferred embodiment, the surface penetration means includes a sharp point, a drill bit, a reamer, or any other means that can penetrate a surface which it may be desirable to penetrate. In a fourth aspect, the present invention provides a method of drilling an extendable member into a surface, the method comprising: providing an extendable member according to the third aspect of the present invention; causing the extendable member to be in the shortened condition; engaging a trailing end of the first elongate member with a drilling device and positioning the surface penetration means in forcible contact with the surface; inhibiting a distance between a leading end of the drilling device and the surface from increasing; and causing the drilling device to rotate the first elongate member against friction created by the forcible contact between the drill bit and the surface.

Preferably, causing the first elongate member to rotate as such increases shear strength across the threadable engagement between the first elongate member and the second elongate member until the extendable member is forced to rotate and drill the second elongate member into the surface. Preferably, the drilling device is a screwdriver, an electric drill, a drilling machine, or any other device or means adapted to screw, or rotate, a member into a surface. Persons skilled in the art would appreciate that further embodiments of the invention described in the second to fourth aspects envisage that the first and second elongate members could be swapped in physical configuration. These embodiments have a reverse physical configuration to those described above for the first and second elongate members in the second to fourth aspects of the invention.

Throughout this specification, certain features and/or functions have been described by reference to embodiments of the extendable member respectively adapted to be a self drilling rock bolt, a drill rod, a rock bolt, or another member adapted for use in construction. In appropriate circumstances, one or more of such features and/or functions described for one such embodiment may be applicable to another such embodiment, and vice versa.

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 element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention.

In order that the present invention may be more clearly understood, preferred embodiments will be described with reference to the following drawings and examples.

Brief Description of the Drawings

Figure 1 is a schematic sectional view of an extendable member according to one preferred embodiment of the invention with an inner elongate bar substantially housed by an outer elongate bar. r Figure 2 is a schematic sectional view of an extendable member according to the embodiment depicted in Figure 1 with the inner elongate bar substantially extending from the outer elongate bar.

Figure 3 is a schematic sectional view of an extendable member according to the embodiment depicted in Figure 1 with the inner elongate bar extending from the outer elongate bar wherein a leading end of the outer elongate bar is pressed up against a surface into which the extendable member is to be drilled.

Figure 4 is a schematic sectional view of a section of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its extended form with the inner elongate bar substantially extending from the outer elongate bar.

Figure 5 is a schematic sectional view of a section of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt with the bolt in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 6 is a three dimensional view of a threaded section adapted for an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt. The threaded section has a through central hole with an internal female thread and may also have an external thread. Figure 7 is an overall sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 8 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its shortened form with the- inner elongate bar substantially contained within the outer elongate bar.

Figure 9 is a sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its extended form with the inner elongate bar substantially extended from the outer elongate bar.

Figure 10 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its extended form with the inner elongate bar substantially extending from the outer elongate bar.

Figure 11 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its shortened form with the outer elongate bar substantially containing the inner elongate bar.

Figure 12 is an overall side elevation view of an extendable member according to the preferred embodiment depicted in Figure 11 adapted to be a self drilling rock bolt showing the bolt in its extended form with the outer elongate bar substantially extending from the inner elongate bar.

Figure 13 is a schematic sectional view of a section of an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt showing the bolt in its extended form with the inner elongate solid bar substantially extending from the outer hollow elongate bar.

Figure 14 is a schematic sectional view of a section of an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt with the bolt in its shortened form with the inner elongate bar substantially contained within the outer elongate bar. Figure 15 is a three dimensional view of a threaded section adapted for an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt. The threaded section has a through central hole with an internal female thread and may also have an external thread.

Figure 16 is an overall sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt showing the bolt in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 17 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt showing the bolt in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 18 is a sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt showing the bolt in its extended form with the inner elongate bar substantially extended from the outer elongate bar.

Figure 19 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a rock bolt showing the bolt in its extended form with the inner elongate bar substantially extending from the outer elongate bar.

Figure 20 is a schematic sectional view of a section of an extendable member according to one preferred embodiment of the invention adapted to be a drill rod showing the drill rod in its extended form with the inner elongate bar substantially extending from the outer elongate bar.

Figure 21 is a schematic sectional view of a section of an extendable member according to one preferred embodiment of the invention adapted to be a drill rod with the drill rod in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 22 is a three dimensional view of the threaded section adapted for an extendable member according to one preferred embodiment of the invention adapted to be a drill rod. The threaded section has a through central hole with an internal female thread and may also have an external thread. Figure 23 is an overall sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a drill rod showing the drill rod in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 24 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a drill rod showing the drill rod in its shortened form with the inner elongate bar substantially contained within the outer elongate bar.

Figure 25 is a sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a drill rod showing the drill rod in its extended form with the inner elongate bar substantially extended from the outer elongate bar.

Figure 26 is an overall side elevation view of an extendable member according to one preferred embodiment of the invention adapted to be a drill rod showing the drill rod in its extended form with the inner elongate bar substantially extending from the outer elongate bar.

Figure 27 is a graph showing the relationship between axial thrust within an extendable member according to a preferred embodiment of the invention and resistive torque on the threadable engagement of the first (eg outer) and second (eg inner) elongate bars, as the extendable member is drilled into a surface.

Figure 28 is a side elevation and sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine or tunnel roof, wherein the leading end of the inner elongate bar with the drill bit has been raised to the exposed rock face by the drilling machine and the drill bit is pressing against the rock face.

Figure 29 is a side elevation and sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine or tunnel roof, wherein the bolt has partially drilled a borehole in the exposed rock face.

Figure 30 is a side elevation and sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine or tunnel roof wherein the bolt has substantially drilled a borehole in the exposed rock face.

Figure 31 is a side elevation and sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine roof or tunnel roof wherein the leading end of the outer elongate bar with the drill bit has been raised to the exposed rock face by the drilling machine and the drill bit is pressing against the rock face. Figure 32 is a side elevation and sectional view of an extendable member according to the embodiment depicted in Figure 31. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine roof or tunnel roof wherein the leading end of the outer elongate bar with the drill bit has partially drilled a borehole in the exposed rock face. Figure 33 is a side elevation and sectional view of an extendable member according to the embodiment depicted in Figure 31. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine roof or tunnel roof wherein the leading end of the outer elongate bar with the drill bit has substantially drilled a borehole in the exposed rock face. Figure 34 is a series of side elevation and sectional views (respectively marked A, B, C and D) of an extendable member according to the embodiment depicted in Figure 31. The self drilling rock bolt is shown engaged with a drill chuck of a drilling machine under a mine roof or tunnel roof. Views A, B, C and D illustrate successive events as the self drilling rock bolt drills a borehole. Each view provides curved arrows illustrating if the inner elongate bar or outer elongate bar is rotating at the particular time during drilling illustrated by that view.

Figure 35 is a series of side elevation and sectional views (respectively marked E, F and G) of an extendable member according to the embodiment depicted in Figure 31. Views E, F and G illustrate successive events following on from views A, B, C and D of Figure 34 as the self drilling rock bolt continues to drill the borehole. Each view provides curved arrows illustrating if the inner elongate bar or outer elongate bar is rotating at the particular time during drilling illustrated by that view.

Figure 36 is an overall sectional view of an extendable member according to one preferred embodiment of the invention adapted to be a self drilling rock bolt showing the bolt in its shortened form with the outer elongate bar substantially containing the inner elongate bar. A conduit according to one preferred embodiment is shown internally within the self drilling rock bolt.

Figure 37 is an overall side elevation view of an extendable member according to the preferred embodiment depicted in Figure 36.

Figure 38 is an sectional view of an extendable member according to the preferred embodiment depicted in Figure 36 showing the self drilling rock bolt in its extended form with the outer elongate bar substantially extending from the inner elongate bar. A conduit according to one preferred embodiment is shown internally within the self drilling rock bolt.

Figure 39 is an overall side elevation view of the extendable member depicted in Figure 38.

Detailed Description of the Preferred Embodiments Where the specification refers to "telescopic" it is to be understood that the invention includes 'extendable' in a telescopic manner, 'lengthened' in a telescopic manner, and all such variations and modifications of telescopic type extension or lengthening. Where the specification refers to a "self drilling rock bolt" it is to be understood that the invention includes all such variations and modifications of the above.

Where the specification refers to a "drill rod" it is to be understood that the invention includes all such variations and modifications of the above. Where the specification refers to a "bolt" or to a "rock bolt" or to a "bar" or to an

"elongate bar" or to a "member" or to an "elongate member" or to a "threaded bar" or to an "elongate threaded bar" or to a "hot rolled threaded bar" or to a "threaded member" or to a "threaded section" it is to be understood that the invention includes all such variations and modifications of the above and any other solid or hollow elongate bar or bolt that has an axial length.

Where the specification refers to a "rod" or to a "tube" or to a "hollow bar" or to a "hollow elongate bar" or to a "hollow elongate member" or to an "elongate hollow threaded bar" or to a "hollow threaded bar" or to a "hollow threaded member" or to a "hollow threaded section" it is to be understood that the invention includes all such variations and modifications of the above and any other hollow elongate bar or bolt or rod or tube that has a substantially centralised continuous hole within it along its axial length.

Where the specification refers to a "rotation inhibition means" or to an "expansion shell friction anchor device" or to a "friction anchor device" or to a "plastic cap" or to a "piece of wire" or to a "plurality of wires" in the context of inhibiting rotation, it is to be understood that the invention includes all such variations and modifications of the above and any other such device or means capable of inhibiting rotation of a member.

Where the specification refers to a "nut" or to a "drive nut" it is to be understood that the invention includes hexagonal, square and any other non-circular shaped nuts and all such variations and modifications of the above and any other member that could fit into a drive socket and be used to rotate or tension a rock bolt or a self drilling rock bolt or a drill rod or other member for use in construction.

Where the specification refers to a "domed ball" it is to be understood that the invention includes all such variations and modifications of the above and any other member that could be used to provide angular adjustment against a bearing plate or rock face and is typically a separate thick washer with one hemispherical face, but the domed ball could be incorporated as an integral part of a nut. Where the specification refers to a "drill tip" or to a "drilling tip" or to a "drilling bit" or to a "drill bit" or to "surface penetration means" or to a "sharp point" in the context of penetrating a surface, it is to be understood that the invention includes all such variations and modifications of the above and any other member, device or means that could drill or form a hole in a surface, including rock or clay or soil or concrete or brick among other kinds of surfaces.

Where the specification refers to a "static mixer" or to "static mixer elements" or to a "mixer" it is to be understood that the invention includes all such variations and modifications of the above, including mixer spirals, offset mixer spirals, offset mixer segments, offset mixer elements, either with or without a surrounding plastic tube, and any other device or means that could be used to mix two or more fluids together.

Where the specification refers to a "hollow injection sleeve" or to an "injection sleeve" or "sleeve" or "female injection sleeve" it is to be understood that the invention includes all such variations and modifications of the above, including a sleeve with a substantially centralised hole and any other member that could be used to accommodate a male injection nozzle.

Where the specification refers to "passageways" or to "waterways" or to a "hole" or to "holes" it is to be understood that the invention includes all such variations and modifications of the above, including tubes, pipes, holes, and any other member that could be used to transport fluids.

Where the specification refers to a "stop" or to an "nut stop" or to an "end stop" or to a "thread stop" or to a "disengagement prevention means" or to a "lip member" it is to be understood that the invention includes all such variations and modifications of the above, including any device that can prevent or substantially inhibit further movement once the device is contacted or touched.

Where the specification refers to a "thread" or to a "female thread" or to a "male thread" or to a "threaded section" or to a "threadable section" or to a "section of thread" or to a "screw" or to a "screw thread" it is to be understood that the invention includes all such variations and modifications of the above. Where the specification refers to "construction" it is to be understood that the invention includes all such variations and modifications of the above, including civil engineering, tunneling, mining, building, fabrication, developing, manufacturing, assembly, and any other activity relating to construction of any kind. Where the specification refers to "threadable engagement" it is to be understood to include engaging along a thread or threads or screwing or screwing on, so that, for example, threadable engagement of elongate members includes screwing the elongate members together along a thread or threads. Similarly, where the specification refers to "threadable disengagement" it is to be understood to include disengaging along a thread or threads or unscrewing, so that, for example, threadable disengagement of elongate members includes unscrewing the elongate members along a thread or threads and does not necessarily include completely unscrewing one elongate member from the other so that they are entirely disenagaged. Figures 1 , 2 and 3 provide basic illustrations of one embodiment of the extendable member 1 in a broad form. The inner elongate bar 6 has an external threaded profile 26 and can be substantially contained within outer bar 4. As the elongate bars 4 and 6 are unscrewed from one another, the overall length of the extendable member 1 increases. Figure 3 shows a leading end of outer bar 4 pressed up against a surface 41 into which the extendable member is to be drilled. As this is for illustrative purposes only, no surface penetration means (which may be required to penetrate the surface 41) are illustrated on the leading end of the outer elongate bar 4. The curved arrow illustrates the direction in which the inner bar 6 can be unscrewed from the outer bar 4. This description now turns to focus on various preferred embodiments of the extendable member 1 respectively adapted to be a self drilling rock bolt, a rock bolt and a drill rod.

Self Drilling Rock Bolt The telescopic self drilling rock bolt 1 shown in Figure 4 comprises a hollow outer elongate bar 4 with a central hole 21 with a threaded section 5 at one end of the outer elongate bar 4. An inner elongate bar 6 is connected to the outer elongate bar 4 by a screw thread in the threaded section 5, and the threaded section 5 is fixed to the outer bar 4 typically by an internal thread 29 in the outer bar 4 and by welding 10. The inner elongate bar 6 has an external screw thread 26 and has a central hole 22 and an end stop 30 at the trailing end of the elongate bar 6 which prevents the bar 6 from being unscrewed from the threaded section 5. The inner elongate bar 6 also has a drill bit 7 fixed or welded 9 to the leading end of the bar 6. The drill bit 7 may be accommodated in a larger diameter hole 24 in the inner bar 6. The outer bar 4 has optional reamer drill bits 8 fixed to the leading end of the outer bar 4.

Turning to Figure 5, rotation of the inner bar 6 with respect to the outer bar 4 will cause the inner bar 6 to move axially through the threaded section 5. Figure 6 illustrates a threaded section 5 adapted for the self drilling rock bolt 1.

The threaded section 5 has an internal female thread 27 which screws over and along the external thread 26 on the inner elongate bar 6, and the external thread 28 may be used to screw into a female thread 29 in the end of the outer elongate member 4.

Figure 7 illustrates one preferred embodiment of the telescopic self drilling rock bolt 1 with a second inner elongate bar 11 (persons skilled in the art will appreciate that this 'second' inner elongate bar 11 is a third elongate member in accordance with a preferred embodiment of the invention) at the trailing end of the outer elongate bar 4. This elongate bar 11 typically has an external threaded profile which has a drive and tensioning nut 16 and a hemispherical domed ball 15 on it, as well as a nut stop and injection sleeve 17 to prevent the nut 16 from being unscrewed from the inner elongate bar 11. The nut stop and injection sleeve 17 has an internal central hole to allow water or grout or resin to be pumped through the bolt 1. The elongate bar 11 may contain a static mixer 18 in a central hole 20. The elongate bar 11 is typically screwed into a threaded sleeve 12 which is in turn screwed into the outer elongate bar 4. The threaded sleeve 12 is fixed to the outer bar 4 by welds at 13, and the threaded sleeve 12 is fixed to the inner bar 11 by welds at 14.

Figure 8 shows that, in one embodiment, the outer elongate bar 4 also has an external threaded profile 34.

The inner elongate bar 6 can be screwed through the threaded sleeve 5 until the end stop 30 contacts the threaded sleeve 5, as illustrated in Figure 9.

As shown in Figure 10, in one embodiment, the inner elongate bar 6 has an external threaded profile 26 which can screw through the threaded section 5. The outer elongate bar 4 can have any suitable external surface and it could have a threaded external surface 34 as shown in Figure 10, or have any other suitable surface profile. Figures 11 and 12 illustrate a further embodiment of the extendable member adapted to be a self drilling rock bolt 1 with the physical configuration or relationship of the inner and outer elongate bars 6 and 4 effectively reversed. In this embodiment, operators can visualise the outer bar 4 extending from the inner bar 6 as the bolt 1 extends, thus confirming extension of the bolt 1 during installation.

Figure 11 shows the telescopic self drilling rock bolt 1 in its shortened condition with a single inner bar 6 substantially contained within a larger diameter hollow outer bar 4. The inner bar 6 has an optional fine threaded section 46 to allow nut 16 to be tensioned up along this threaded section 46. The inner bar 6 is screwed into a threaded ' sleeve 5 which is fixed to the outer bar 4 by welds 10. The outer bar 4 has an external threaded profile 34 but may have any suitable external surface profile. A drill bit 7 is fixed to the leading end of the outer bar 4 by welding, brazing or any other suitable means 9. The drill bit 7 has cutting or drilling faces or surfaces 25 on its leading end.

Figure 12 shows the telescopic self drilling rock bolt 1 in its lengthened condition with the inner elongate bar 6 having an external screw thread 26 over most of its length and an optional fine threaded section 46 for the nut 16. This inner bar 6 also has a hemispherical washer 15 and a nut stop and injection sleeve 17 either side of the nut 16 as shown in Figure 12.

One embodiment of the invention adapted to be a telescopic self drilling rock bolt 1 is shown in Figures 4, 5, 7 to 10 and 28 to 30. (Another embodiment of the invention adapted to be a self drilling rock bolt 1 is shown in Figures 11 , 12 and 31 to 39, however, unless otherwise indicated, the following text largely focuses on the embodiment depicted in Figures 4, 5, 7 to 10 and 28 to 30). In operation, the drilling machine (not shown) pushes the telescopic self drilling rock bolt 1 , against the exposed rock face 41 to be drilled as shown in Figure 28 (and Figures 31 and 34A with respect to another embodiment of the extendable member adapted to be a self drilling rock bolt). The drilling machine (not shown) pushes the drill bit 7 on the leading end of the inner elongate bar 6 of the telescopic self drilling rock bolt 1 up against the exposed rock face 41.

The drilling machine then locks the drill chuck 43 in position such that it will not move away from the exposed rock face 41. The drilling machine then rotates the drive nut 16 which in turn rotates the trailing inner bar 11 and the outer bar 4. The outer bar 4 is connected to the leading inner bar 6 by a section of screw thread 5. The direction of rotation of the outer bar 4 by the drilling machine, causes the inner bar 6 to tend to unscrew along the section of screw thread 5 connecting the two bars (4 and 6) together, and causes the drill bit 7 to be forced up hard against the exposed rock face 41. However, since the drilling machine will not permit the telescopic self drilling rock bolt 1 to move away from the rock face 41 , and the rock face 41 will not permit further advancement of the inner bar 6 without drilling a borehole 44, then the telescopic self drilling rock bolt 1 cannot get any longer and the inner bar 6 cannot unscrew from the outer bar 4 along the section of screw thread 5. Therefore further rotation of the outer bar 4 by the drilling machine also causes the inner bar 6 to rotate, and the drill bit 7 pressing against the rock face 41 then also rotates and drills a borehole 44.

As the borehole 44 is drilled, the telescopic self drilling rock bolt 1 can then get longer, and the inner bar 6 can progressively unscrew along the section of screw thread 5 out of the hollow outer bar 4. In effect, as the bolt 1 increases in length, the axial force on the screw threaded section 5 increases to the point where the threads between the screw threaded section 5 and the outer bar 4 "lock", and enable the outer bar 4 to rotate the inner bar 6 and hence drill a further section of the borehole 45. As a further section of the borehole is drilled, the axial force on the screw threaded section 5 decreases because the drill chuck 43 remains a substantially fixed distance from the rock face 41 , and the threads between the screw threaded section 5 and the outer bar 4 "unlock", and enable the outer bar 4 to rotate relative to the inner bar 6 and hence the telescopic self drilling rock bolt 1 increases in length.

This process of progressively "locking" and "unlocking" the outer bar 4 with respect to the inner bar 6, and hence progressively drilling and then lengthening the bolt 1 , is repeated many times and may occur very rapidly depending upon the rotational speed of the drilling machine (not shown) and the thread pitch of the screw threaded section 5. This rapid sequential drilling and then lengthening of the bolt 1 , can create a hammering or percussive drilling action, which has advantages in drilling some rock types. The process continues until the inner bar 6 has fully extended and unscrewed out of the outer hollow bar 4 when it typically contacts an end stop 30 which prevents the inner bar 6 from completely unscrewing from the outer bar 4.

The drilling machine (not shown) can then advance the outer bar 4 into the borehole 44 drilled by the inner bar 6, and optional reamer drill bits 8 may be on the leading end of the outer bar 4 to ream out a larger diameter borehole 45 to accommodate the larger diameter outer bar 4. Alternatively the drill bit 7 may drill a borehole large enough to accommodate the outer bar 4, and reamer drill bits 8 may not be required. As previously indicated, another embodiment of the extendable member adapted to be a self drilling rock bolt 1 is shown in Figures 11 , 12 and 31 to 39. This embodiment, with the physical configuration or relationship of the inner and outer elongate bars 6 and 4 reversed, operates in a largely similar manner to the embodiment described above. A comparison of Figures 28 to 30 with corresponding Figures 31 to 33 clearly illustrates the differences in these embodiments, and persons skilled in the art would readily appreciate the construction and manner of operation of this other (reversed physical configuration) embodiment. Nevertheless, reference is now made to Figures 34 and 35 which also provide a 'step-by-step¹ type illustration of one preferred sequence of events in the operation of the embodiment of the self drilling rock bolt 1 depicted in Figures 11, 12 and 31 to 35, shown by consecutive views A to G. The curved arrows indicate if the inner bar 6 or outer bar 4 is rotating at the particular point in the sequence illustrated by that view.

In Figure 34A, as the drilling machine (not shown) is activated, it attempts to rotate inner bar 6 in the direction of the curved arrow and thereby unscrew the inner bar 6 from outer bar 4. As the drill tip 7 is pressed hard up against the surface 41 to be drilled and distance 42 is substantially fixed, unscrewing does not occur and axial thrust within the bolt 1 increases as does the resistive torque on the thread 5 engaging the inner and outer bars 4 and 6. Threadable disengagement of the inner and outer bars 4 and 6 is substantially inhibited or "locked" and, as shown in Figure 34B both bars 4 and 6 rotate together, and a borehole begins to be drilled.

As the first portion of borehole is drilled, the axial thrust in the bolt 1 decreases as does the resistive torque on the threaded section 5 decrease, enabling or "unlocking" threadable disengagement of the bars 4 and 6, and a first segment of threadable disengagement occurs as inner bar 6 unscrews from outer bar 4. The curved arrow in Figure 34C shows only the inner bar 6 turning at this point.

This occurs repetitively until the inner bar 6 is prevented from fully unscrewing from the outer bar 4 by an internal thread stop (not shown). Further rotation of the inner bar 6 now causes the outer bar 4 to rotate (as illustrated in Figure 34D with curved arrows on both inner bar 6 and outer bar 4), and no further extension of the bolt 1 is possible. Note that the borehole 45 has been drilled with the drill chuck remaining a substantially fixed distance from the rock face 41 as shown at 43.

With continued drilling activity and both inner bar 6 and outer bar 4 continuing to rotate together, as shown in Figure 35E, the drill chuck (not shown) is now being pushed toward the exposed rock face 41 by the drilling machine (not shown). The inner bar 6 and the outer bar 4 continue to rotate together until the borehole 45 is completely drilled as shown in Figure 35F.

Once the borehole 45 is drilled, the rotation and water flushing by the drilling machine are turned off, and resin or cement grout are pumped through the bolt 1 until all or part of the borehole 45 is filled with resin or cement grout 47 as shown in Figure 35G. Once the resin or cement grout 47 have cured and hardened and have anchored the bolt 1 in the borehole 45, the drill chuck (not shown) rotates the drive nut in the opposite - direction to tighten up the nut against the rock face 41 (as illustrate by the curved arrow in Figure 35G).

Figure 27 is a graph showing the relationship between the axial thrust within the bolt 1 and the resistive torque between the threads between the inner bar 6 and the outer bar 4. Figure 27 shows that above the graph line, the threads "lock" and drilling occurs because the inner bar 6 and the outer bar 4 rotate together, and that below the graph line the threads "unlock" and the bolt extends because the inner bar 6 can unscrew from the outer bar 4 (or vice versa).

In practice the threads between the inner bar 6 and the outer bar 4 will not "lock" and "unlock" at a exactly the same resistive torque value because of slight differences in parameters such as static and rotational torque, variations in friction and rotational momentum, among other factors. Therefore, "locking" and "unlocking" of the threads will vary about the graph line shown in Figure 27 as indicated by the small arrows and lines. In other words, "locking" and "unlocking" of the threads occur alternately and repeatedly during drilling of the borehole. Additionally, since the rotational speed of the drilling machine (not shown) may typically be 500 rpm, this "locking" and "unlocking" can occur very rapidly, and cause a slight hammering action during the drilling process which can assist with drilling the surface, particularly for example, a rock surface.

Liquid , resin or cement grout 42 and anything else which it may be desirable to transfer through the bolt 1 , such as rock cuttings, may pumped through a central hole 19, 20, 21 , 22 and 24. Figures 36 to 39 depict one embodiment of the extendable member adapted to be a self drilling rock bolt illustrating the preferred location of a conduit 48 which may be included to receive, transfer or carry, or assist in receiving, transferring or carrying, fluids, resin, cement grout, rock cuttings or anything else which may be desirable to transfer, through bolt 1. In some preferred embodiments conduit 48 is internally fixed or connected to the outer bar 4 adjacent the drill tip 7. This conduit 48 is typically longer than the outer bar 4, and may also fit inside the inner bar 6. The conduit 48 may slide or move along the interior of the inner bar 6 as the bolt 1 is extended and increased in length, and because the conduit is longer than the outer bar 4 it will extend into the interior of the inner bar 6 even when the bolt 1 is fully extended. In some embodiments, the conduit 48 is substantially housed by the central hole 19, 20, 21 , 22 and 24.

Typically a seal (not shown), such as an O-ring is interposed between the conduit 48 and the interior of inner bar 6, such that a hydraulic seal can be maintained therebetween as the bolt 1 is extended in length. Liquids or other transferable substances can be pumped or transferred along the interior of the inner bar 6 and the conduit 48. This may preferably have an advantage that the volume of resin or cement grout 47 required to anchor the bolt 1 in the borehole 45 may be reduced and the time required to pump the requisite quantity of resin or cement grout 47 may also be reduced. A further step of the installation of the telescopic self drilling rock bolt 1 is that the hydraulic valves or similar on the drilling machine are opened to allow the drill chuck 43 to be lowered away from the rock face 41 back to its starting position.

Rock Bolt The telescopic rock bolt 2 shown in Figure 13 comprises a hollow outer elongate bar 4 with a central hole 21 with a threaded section 5 at one end of the outer elongate bar 4. An inner elongate bar 31 is connected to the outer elongate bar 4 by a screw thread in the threaded section 5, and the threaded section 5 is fixed to the outer bar 4 typically by an internal thread 29 in the outer bar 4 and by welding 10. The inner elongate bar 31 has an external screw thread 26 and an end stop 30 at the trailing end of the elongate bar 31 which prevents the bar 31 from being unscrewed from the threaded section 5. The inner elongate bar 31 also has rotation inhibition means 32 located, fixed or welded to the leading end of the bar 31. The rotation inhibition means 32 on the bar 31 can be pushed into a pre-drilled borehole (not shown) and is adapted to inhibit the bar 31 from being rotated in that borehole.

As can be seen from Figure 14, rotation of the inner bar 31 with respect to the outer bar 4 will cause the inner bar 31 to move axially through the threaded section 5. Figure 15 illustrates a threaded section 5 adapted for the rock bolt 2. The internal female thread 27 of the threaded section 5 screws over and along the external thread 26 on the inner elongate bar 31 , and the external thread 28 may be used to screw into a female thread 29 in the end of the outer elongate member 4. Figure 16 shows one embodiment of the telescopic rock bolt 2 which has a rotational and drive nut 16 fixed to the outer bar 4 at 33 typically by welding. The bar 4 also has a hemispherical washer or dome ball 15 fitted to it against the nut 16. The inner bar 31 has an end stop 30 at one end of the bar 31 and rotation inhibition means 32 at the opposite end. As shown in Figure 17, the outer elongate bar 4 can have any suitable external surface and it could have a plain surface as shown in Figure 17, or it could have a threaded external surface, or have a ribbed external surface, or have a deformed ^• external surface, or have any other rough or other external surface.

The inner elongate bar 31 can be screwed through the threaded sleeve 5 until the end stop 30 contacts the threaded sleeve 5, as shown in Figure 18.

Figure 19 illustrates the outer elongate bar 4 also has a drive nut 16 and a hemispherical washer 15. The inner elongate bar 31 has an external threaded profile 26 which can screw through the threaded section 5. The outer elongate bar 4 can have any suitable external surface and it could have a plain surface as shown in Figure 19, or have any other suitable surface profile.

Accordingly, one embodiment of the invention adapted to be a telescopic rock bolt 2 is shown in Figures 13, 14, 16, 17, 18, and 19. In operation, in the case of the telescopic rock bolt 2, the drilling machine (not shown) pushes the leading end of the telescopic bolt 2 into a pre-driven borehole 45 and 44, and rotation inhibition means 32 on the end of the bolt 2 is caused to engage a wall of the borehole 45 and 44, such that the leading inner elongate bar 31 of the bolt 2 will be inhibited from rotating inside the borehole 45 and 44. The drilling machine (not shown) then locks the drill chuck 43 in position such that it will not move away from the rock face 41. The drilling machine then rotates the outer elongate bar 4 but the inner bar 31 does not rotate because the rotation inhibition means 32 inhibits it from rotating and the relative rotational movement between the outer bar 4 and the inner bar 6 causes the inner bar 6 to advance out from the outer bar 4 and into the borehole 45 and 44. This process is continued until the telescopic rock bolt 2 has reached its full extended length. The drilling machine can then advance the outer bar 4 into the borehole 45 and 44. If a resin cartridge is also used to anchor this bolt 2 inside the borehole 45 and 44, then the bolt 2 is continued to be rotated and pushed into the borehole 45 and 44 by the drilling machine (not shown) to rupture and rotate a frangible resin cartridge (also not shown) inside the borehole 45 and 44 until the resin is fully mixed, and is then allowed to cure. Once the resin is cured and hardened, the nut 16 on the end of the telescopic rock bolt 2 may be tensioned up if it is on a screw thread, or if it is fixed to the end of the bolt 2, then the nut 16 is held against the rock face by the drilling machine until the resin has cured and hardened. Alternatively if a friction anchor device (not shown) acts as the rotation inhibition means 32, then the friction anchor device will initially prevent rotational movement of the inner bar 31 until it is fully extended, then further rotational movement of the inner bar 31 will cause the friction anchor device to expand and anchor the inner bar 31 inside the borehole 44, 45.

Fluid, resin or cement grout 42 and anything else which it may be desirable to transfer through the bolt 2, such as rock cuttings, may be pumped through a central hole (not shown). A conduit 48 substantially as described in relation to embodiments of the extendable member adapted to be a self drilling rock bolt (and depicted in relation to a self drilling rock bolt in Figures 36 to 39), may be used to facilitate this transfer of liquids, rock cuttings and the like.

Persons skilled in the art would appreciate that as with the various embodiments of the extendable member adapted to be a self drilling rock bolt, other embodiments of the extendable member adapted to be a rock bolt may be also be constructed such that the inner elongate member and outer elongate member are effectively swapped in physical configuration or relationship. It would also be appreciated that, in broad terms, the general principles outlined for the mechanism of extension of the extendable member adapted to be a self drilling rock bolt are also generally applicable to the mechanism of extension of various embodiments of the extendable member adapted to be a rock bolt.

Drill Rod The telescopic drill rod 3 shown in Figure 20 comprises a hollow outer elongate bar 4 with a central hole 21 with a threaded section 5 at one end of the outer elongate bar 4. An inner elongate bar 6 is connected to the outer elongate bar 4 by a screw thread in the threaded section 5, and the threaded section 5 is fixed to the outer bar 4 typically .by an internal thread 29 in the outer bar 4 and by welding 10. The inner elongate bar 6 has an external screw thread 26 and has a central hole 22 and an end stop 30 at the trailing end of the elongate bar 6 which prevents the bar 6 from being unscrewed from the threaded section 5. The inner elongate bar 6 also has a drilling bit 35 fixed or welded 9 to the leading end of the bar 6. The drill bit 35 may be accommodated in a larger diameter hole 24 in the inner bar 6. The drill bit 35 may be any suitable diameter. The outer bar 4 has optional reamer drill bits 8 fixed to the leading end of the outer bar 4.

As shown in Figure 21 , rotation of the inner bar 6 with respect to the outer bar 4 will cause the inner bar 6 to move axially through the threaded section 5. Figure 22 shows a threaded section 5 adapted for the drill rod 3. The internal female thread 27 of the threaded section 5 screws over and along the external thread 26 on the inner elongate bar 6, and the external thread 28 may be used to screw into a female thread 29 in the end of the outer elongate member 4.

Figure 23 shows one embodiment of the telescopic drill rod 3 which has a hollow, rotational drive nut 36 which may be any suitable shape which is fixed to the outer bar 4 at 39 typically by welding. In this embodiment, there is also typically a hollow round sealing spindle 37 designed to fit inside an O-ring (not shown) in the drilling machine (not shown). Drilling fluid, typically water, can then be pumped through the hollow spindle 37 at 38 and through the hollow drive nut 36 and through the passageways 21 , 22 and 24 to the drill bit end of the drill rod 3. Typically the spindle 37 and drive nut 36 are made from one piece of steel which also has a locating spigot 40 to position the spindle 37 and nut 36 inside the end of the hollow outer bar 4.

The outer elongate bar 4 can have any suitable external surface and it could have a plain round surface as shown in Figure 24, or it could have a threaded external surface, or have a ribbed external surface, or have a hexagonal external surface or have a deformed external surface, or have any other rough or other external surface.

As illustrated in Figure 25, the inner elongate bar 6 can be screwed through the threaded sleeve 5 until the end stop 30 contacts the threaded sleeve 5.

In the embodiment of the drill rod 3 illustrated in Figure 26, the inner elongate bar 6 has an external threaded profile 26 which can screw through the threaded section 5. The outer elongate bar 4 can have any suitable external surface and it could have a plain surface as shown in Figure 26, or have any other suitable surface profile. Accordingly, one embodiment of the invention adapted as a telescopic drill rod 3 is shown in Figures 20, 21 , 23, 24, 25, and 26. In operation, in the case of the telescopic drill rod 3, the drilling machine (not shown) pushes the drill bit 35 on the leading end of the inner bar 6 of the telescopic drill rod 3 up against the exposed rock face 41. The drilling machine then locks the drill chuck 43 in position such that it will not move away from the exposed rock face 41. The drilling machine then rotates the outer bar 4 which is connected to the inner bar 6 by a section of screw thread 5. The direction of rotation of the outer bar 4 by the drilling machine (not shown), causes the inner bar 6 to tend to unscrew along the section of screw thread 5 connecting the two bars 4 & 6 together. As inner bar 6 tends to unscrew out of the outer hollow bar 4, the drill bit 35 on the end of the bar 6 is forced up hard against the exposed rock face 41. .

However, since the drill chuck 43 on the drilling machine (not shown) is now locked in position, it will not permit the telescopic drill rod 3 to move away from the rock face 41 , and the rock face 41 will not permit further advancement of the inner bar 6 without drilling a borehole- Since the telescopic drill rod 3 cannot increase in length and the inner bar 6 cannot unscrew from the outer bar 4 along the section of screw thread 5, then further rotation of the outer bar 4 by the drilling machine also causes the inner bar 6 to rotate, and this in turn rotates the drill bit 35 pressing against the rock face 41.

As the drill bit 35 is rotated and pressed up against the rock face 41 then the drill bit 35 drills a borehole in the rock. As the borehole 44 is drilled, the telescopic drill rod 3 can now increase in length and the inner bar 6 can be progressively unscrewed along the section of screw thread 5 out of the hollow outer bar 4. As the inner bar 6 unscrews from the outer bar 4 the drill bit 35 is again forced hard up against the rock face 41 until the inner bar 6 cannot unscrew any further and the inner bar 6 is again forced to rotate and it begins to drill the borehole 44. This process is continued until the inner bar 6 has fully extended out of the outer hollow bar 4 when it typically contacts an end stop 30 which prevents the inner bar 6 from fully unscrewing from the outer bar 4.

The drilling machine can then advance the outer bar 4 into the borehole 44 drilled by the inner bar 6, and optional reamer drill bits 8 on the leading end of the outer bar 4 can then ream out a larger diameter borehole 45 to accommodate the diameter of the outer bar 4.

Throughout the drilling process, water is typically pumped through a central hole 38, 21 , 22, and 24 in the assembled telescopic drill rod 3 and out of the leading end of the drill rod 3 such that rock cuttings produced by the drill bit 35 and the reamer bits 8 can be flushed down the outside annulus (not shown) between the drill rod 3 and the borehole wall (not shown). A conduit 48 substantially as described in relation to embodiments of the extendable member adapted to be a self drilling rock bolt (and depicted in relation to a self drilling rock bolt in Figures 36 to 39), may be used to facilitate this transfer of liquids, rock cuttings and the like.

Persons skilled in the art would appreciate that as with the various embodiments of the extendable member adapted to be a self drilling rock bolt, other embodiments of the extendable member adapted to be a drill rod may be also be constructed such that the inner elongate member and outer elongate member are effectively swapped in physical configuration or relationship. It would also be appreciated that, in broad terms, the general principles outlined for the mechanism of extension of the extendable member adapted to be a self drilling rock bolt are also generally applicable to the mechanism of extension of various embodiments of the extendable member adapted to be a drill rod. In this detailed description, the invention is described with specific reference to self drilling rock bolts, rock bolts, and drill rods, but the invention is not limited to these applications only and could be applied to any extending elongate member. The invention is particularly applicable to hollow self drilling rock bolts but is not so limited.

Preferably, a telescopic rock bolt or a telescopic self drilling rock bolt or a telescopic drill rod according to the invention can be extended to be longer than the maximum opening height or width of a mine roadway or a tunnel.

Preferably, a telescopic rock bolt or a telescopic self drilling rock bolt or a telescopic drill rod according to the invention can be 'automatically¹ or "serni- automatically' extended during the installation process by the drilling machine. In preferred embodiments, the present invention does not require the use of separate bars or separate bolts or separate drill rods or separate couplers or separate drive dollies and hence removes considerable manual labour as well as reducing injuries to operators. However, the present invention does not exclude the use of multiple bars, bolts, rods, couplers or drive dollies, and envisages that such components may also be used in conjunction with the invention.

Preferred embodiments of the present invention make it possible to install long rigid rock bolts and long rigid drill rods using automatic or semi-automatic drilling machines. In some further preferred embodiments, the present invention also comprises an assemblage of components as previously described adapted to provide a telescopic rock bolt or a telescopic self drilling rock bolt or a telescopic drill rod or another extendable member for use in construction. It should be noted that the invention can be applied to both right hand threaded or left hand threaded mechanisms on bars, rock bolts and drill rods, among other elongate members and therefore a drilling machine, device or means could operate and extend the telescopic mechanism by operating in either left hand or right hand rotation depending on the thread form operating the telescopic mechanism. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

Claims:

1. An extendable member for use in construction, the extendable member comprising: a first elongate member; a second elongate member, wherein the second elongate member is movably engaged with the first elongate member; wherein relative rotation between the first and second elongate members causes relative axial movement between the first and second elongate members, thereby changing the extendable member between a shortened condition and a lengthened condition.

2. The extendable member of claim 1 , wherein, when in the shortened condition, the second elongate member is substantially axially retracted with respect to the first elongate member.

3. The extendable member of claim 1 or 2, wherein, when in the lengthened condition, the second elongate member is substantially axially extended with respect to the first elongate member.

4. The extendable member of any one of claims 1 to 3, wherein the first elongate member and the second elongate member are threadably engaged.

5. The extendable member of claim 4, wherein the threadable engagement has a course pitch thread.

6. The extendable member of claim 5 wherein the pitch thread is between about 3 mm and about 50 mm.

7. The extendable member of any one of claims 4 to 6, wherein the threadable engagement is provided by a threaded section.

8. The extendable member of claim 7, wherein the threaded section is integral with or connected to an inner wall of the first elongate member.

9. The extendable member of claim 8, wherein the threaded section is threadably connected to the inner wall of the first elongate member.

10. The extendable member of any one of claims 1 to 9, wherein the first elongate member is adapted to substantially house the second elongate member when the extendable member is in the shortened condition.

11. The extendable member of any one of claims 1 to 10, further comprising disengagement prevention means adapted to inhibit the second elongate member from disengaging from the first elongate member.

12. The extendable member of any one of claims 1 to 11 , further comprising a third elongate member engaged with the first elongate member or the second elongate member.

13. The extendable member of any one of claims 1 to 12 wherein a central hole passes through at least a portion of the length of the extendable member.

14. The extendable member of claim 13 further including a conduit housed within the central hole by at least one of the elongate members.

15. The extendable member of claim 14 wherein the conduit is connected or fixed to at least one of the elongate members.

16. The extendable member of claim 14 to 15 wherein the conduit is adapted to receive, carry or transfer fluid, liquid, resin, cement grout, rock cuttings or a combination of two or more thereof.

17. The extendable member of any one of claims 1 to 16 adapted to be a self drilling rock bolt, a drill rod, or a rock bolt.

18. A method of drilling a hole comprising: providing an extendable member of any one of claims 1 to 16; placing a leading end of the second elongate member against a surface; and applying rotation to the first elongate member, thereby causing the second elongate member to extend from the first elongate member, or to be substantially inhibited from rotating with respect to the first elongate member and to drill into the surface.

19. The method of claim 18, wherein a trailing end of the first elongate member is loaded into a drilling machine, drilling device or drilling means before rotation is applied.

20. The method of claim 19, wherein a distance between the trailing end of the first elongate member when loaded into the drilling device or drilling means and the surface is substantially fixed.