AU2012267199A1 - Improvements in self-drilling rock bolts - Google Patents

Abstract

An improved method for installing a self-drilling rock bolt (10) as well as components and tools for use in the installation of such bolts is disclosed. The rock bolt (10) has a central bore (14), a drill bit (18) mounted at one distal end, and a nut (16) mounted on the other end. An assembly comprising a plate (102) having an aperture defining an engagement surface, and a part convex dome ball (120) defining a central bore having a central axis for receiving the rock bolt (10) and a convex external surface slideably engaged with the engagement surface of the plate is against a rock face; The rock bolt is then rotated to drill a hole in the rock face using the drill bit until the rock bolt is almost fully located inside the hole. The nut (16) defines springy arms (44) which engage with the dome ball (120) preventing axial movement of the nut and therefore the entire bolt, relative to the plate, while permitting relative rotation of the nut and plate. Next, an elongate generally cylindrical capsule (50) containing a two part resin separated by a film and having a first end and a second end is inserted into the bore of the rock bolt the first end of the capsule being covered by a cap. A plunger device (200) is used to apply a force to the cap, forcing the cap and capsule into the bore thereby forcing resin through the mixing means and out past the drill bit into the hole. The resin is allowed to set and the nut is turned using the plunger device (200) to tension the rock bolt.

Description

WO 2012/167308 PCT/AU2012/000645 1 "Improvements in self-drilling rock bolts" Cross-Reference to Related Applications The present application claims priority from Australian provisional patent application No 2011902235 filed on 7 June 2012 entitled "Improvements in self 5 drilling rock bolts" the entire content of which is incorporated herein by reference. Field of the Invention This invention relates to improvements in self-drilling rock bolts, and to an improved method for installing a rock bolt as well as components and tools for use in 10 the installation of such bolts. Background of the Invention Rock bolts are extensively used for strata reinforcement applications such as soil nailing and most often in underground mining applications. For tunnels which are not 15 intended for subsequent mining, steel rock bolts are most typically used. The current, and most economic system for installing rock bolts involves an operator of a drilling rig first drilling a hole using a hollow steel rod having a screw-in replaceable steel bit. The average cost of a drill steel is $100 and that of a drill about $8. Each drill steel will drill 300 to 400 holes before requiring replacement, whereas 20 the drill bit will only drill about 10 to 30 holes. The first stage in the process is the drilling of a hole in the strata. It typically takes about 45 seconds to drill a hole for a rock bolt and subsequently remove the drill steel from the drilling rig. Conditions underground are cramped and difficult, and operators often get shoulder strains from removing the drill steels from the rigs. 25 Replacing a worn drill bit on a drill steel is also awkward and dangerous, with operators often striking the drill bits with a hammer to remove them which can lead to stray tungsten chips hitting nearby personnel. Because conditions underground are cramped and often poorly lit, the operator does not always drill a hole of the correct depth for the rock bolt, particularly when the hole is drilled at an angle to the head plate 30 of the drilling rig. The second stage in the process is the insertion of a capsule containing a two part resin mix in the drilled hole. This may take about 20 seconds, often longer in coal mines where the strata is more frangible and the drill holes are often blocked by small coal fragments and require re-drilling.

WO 2012/167308 PCT/AU2012/000645 2 In third stage a spanner for rotating a rock bolt is inserted into the drilling rig. This takes about 10 seconds and involves the operator bending over to insert a 300mm long spanner in the drilling rig: The fourth stage is arguably the most critical for successful and safe engagement 5 of the rock bolt in the strata. The bolt is attached to the spanner, inserted into the hole and spun to mix the resin. In this step the spinning breaks the capsule and mixes the hardener into the resin. Typically it takes about 3 minutes to install a single rock bolt. Because of the problems with traditional methods of installing rock bolts, self drilling rock bolts have 10 been developed. One such self-drilling rock bolt is described in Australian patent application No 2007203409 filed by the applicant of the present application, the entire contents of which are incorporated herein by reference. In the self drilling rock bolt the drill bit is provided at a distal end of a hollow rock bolt and the rock bolt is rotated in a first direction to drill a hole in the strata. 15 Once the hole is drilled, the direction of rotation is reversed and an expansion sleeve at the distal end of the rock bolt expands to secure the rock bolt in the hole. A cement, grout mixture or the like is then injected through the hollow tube to the distal end of the rock bolt and the drilled hole is filled to secure the rock bolt in position. However, this system has its drawbacks which include the fact that the design of the rock bolt is more 20 complex requiring a expanding shell to lock the bolt in place and thus more expensive and difficult to manufacture. Reliability of anchorage to the rock may also be a problem with such expanding shell self-drilling rock bolts. Another drawback is the requirement to pump polyester, polyurethane or cementitious grout through high pressure lines from a bulk storage tank and past the drilling rig operator's position if 25 immediate full support is required. In almost all cases, the anchoring of a rock bolt by an expansion shell only (without grout, resin or the like) would not be considered to be adequate rock support in underground mines in Australia. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that 30 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 as it existed before the priority date of each claim of this application.

WO 2012/167308 PCT/AU2012/000645 3 Summary of the Invention In a first aspect of the present invention there is provided an assembly for use in installing a rock bolt in a hole in a rock face, earth strata or the like defining a surface 5 plane, the assembly comprising: a plate for engagement with the rock face, earth strata or the like, the plate having an aperture defining an engagement surface, which is typically generally concave or conical; and a part convex dome ball defining a central bore having a central axis for 10 receiving the rock bolt and maintaining the rock bolt generally aligned with the central axis of the bore, and a convex external surface for engaging with the engagement surface of the plate, the arrangement being such that when the plate located at or near the surface plane and the dome ball engaged with the plate, a rock bolt may be inserted through the 15 dome ball into the hole in the rock face, which may be non-perpendicular to the surface plane, with movement of the convex external surface of the dome ball relative to the engagement surface of the plate adjusting the relative orientation of the dome ball and washer to maintain the alignment of the rock bolt substantially co-axial with the axis of the bore. 20 In use, therefore, this enables insertion of the rock bolt at an angle of +/- 15 to 200 to the rock face. Typically, the central bore of the dome ball has a conical taper diminishing in diameter towards the convex external surface. In a preferred embodiment the assembly further includes a nut mounted on one 25 end of the rock bolt wherein the nut defines a series of flexible arms defining barbs at their free ends which are deflected inwardly when a rock bolt with the nut attached at one end is inserted through the central bore of the dome ball and spring outwardly after passing through the bore thereby locking the nut to the dome ball, while permitting rotational movement of the nut relative to the dome ball about the axis of the dome ball. 30 In use this feature enables the rock bolt to stay within the drill hole during insertion of a resin capsule and mixing of the resin as is described in more detail below. The plate is typically generally annular in plan view defining a central aperture and the annular portion of the plate is typically generally convex in cross-section. The assembly may further include a cover which is fixed to the plate and which 35 defines a central aperture which is sized to allow the passage of the rock bolt but not the dome ball.

WO 2012/167308 PCT/AU2012/000645 4 In a pieferred embodiment the dome ball defines an external flange which engages with the plate when the orientation of the dome ball relative to the plate is more than about +/- 200 to the perpendicular. The flange may also prevent the dome ball passing through the central aperture of the cover. 5 Typically, the nut defines two separate, typically hexagonal, drive portions for engagement with a drive socket, linked by a frangible portion. Preferably, the nut further includes a flange or head between the drive portions and the end of the nut distal from the flexible arms defines-an internal flange having a central aperture. 10 In a second aspect there is provided a plunger device for use in injecting a capsule into a rock bolt defining a central bore, the device comprising a central shaft defining a central axis drive means at a first end for engagement with a chuck or the like, and-at a second distal end, a plunger rod, and further including a socket mounted so as to rotate with the shaft when the shaft turns about its central axis but which is 15 mounted for axial movement relative to the shaft and plunger rod in the direction of the central axis and further including biasing means, biasing the socket away from the first end. In a preferred embodiment the socket is defined on one end of a annular shaft. Typically, the annular shaft is mounted via a spline connection to the central 20 shaft. Typically, an annular external housing surrounds the central shaft and annular socket shaft. In a related aspect there is provided a method of installing a rock bolt in a rock/strata face or the like defining a surface plane, comprising the steps of: 25 providing a rock bolt comprising a bar, rod, pipe or the like having a hollow central bore and a drill bit mounted at one distal end, and a nut mounted on the other end, the bore allowing the passage of a pressure seal along its length; providing a plate having an aperture defining an engagement surface, and a part convex dome ball defining a central bore having a central axis for receiving the rock 30 bolt and a convex external surface slideably engaged with the engagement surface of the plate, and positioning the plate against the rock face; drilling a hole in a rock/strata face using the drill bit until the rock bolt is almost fully located inside the hole, and wherein the nut defines arms which engage with the dome ball preventing axial movement of the nut and therefore the entire bolt, relative to 35 the plate while permitting relative rotation of the nut and plate WO 2012/167308 PCT/AU2012/000645 5 inserting a elongate generally cylindrical capsule containing a two part resin separated by a film and having a first end and a second end into the bore of the rock bolt wherein the first end of the capsule is engaged in a cap or plunger; and applying a force to the cap, forcing the cap and capsule into the bore thereby 5 forcing resin through the mixing means and out past the drill bit into the hole; and allowing at least part of the resin to set; and tensioning the rock bolt. The method may utilise the various embodiments of the assembly and plunger device described above. 10 In a related aspect there is provided a method of installing a rock bolt comprising the steps of: providing a rock bolt comprising a bar, rod, pipe or the like having a hollow central bore and a drill bit mounted at the one distal end, the bore allowing the passage of a pressure seal along its length; 15 drilling a hole in a rock/strata face using the drill bit until the rock bolt is almost fully located inside the hole; . inserting a elongate generally cylindrical capsule containing a two part resin separated by a film and having a first end and a second end into the bore of the rock bolt wherein at least the first end of the capsule is engaged in a cap or plunger and the 20 second end is optionally attached to a static mixing means; and applying a force to the cap and forcing the cap and capsule into the bore thereby forcing resin through the mixing means and out past the drill bit into the hole, and allowing the resin to set. The method will typically include using a nut pn the proximal threaded end of 25 the rock bolt and disposing a plate between the rock/strata face and the nut. When the resin is set, the nut is tightened to apply pressure to the bearing plate. The nut preferably includes means for engaging with the bearing plate and preventing axial movement of the nut relative to the plate while permitting relative rotation. Typically the bar will be externally deformed for aiding bonding between the 30 rock, resin and bolt and/or threaded for engagement with a nut. The hollow bar will define a smooth internal bore of constant circular cross-section. In a related aspect the present invention provides a resin capsule comprising an elongate generally cylindrical capsule containing a two part resin separated by a film and having a first end and a second end, wherein the first end of the capsule is engaged 35 in a cap or plunger and the second end is attached to a static mixer.

WO 2012/167308 PCT/AU2012/000645 6 The static mixer is preferably suited for mixing thixotropic resin containing limestone fillers. The invention also encompasses an elongate generally cylindrical capsule containing a two part resin separated by a film and having a first end and a second end, 5 wherein with one end of the capsule contains a two part resin which when mixed sets relatively faster than the resin mix at the other end of the capsule. Preferably the resin at the one end of the capsule sets in less than 30 seconds typically about 10 to 20 seconds, whereas the resin at the other end of the capsule sets in 60 to 90 seconds. 10 Brief Description of the Drawings A specific embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a schematic partly-sectioned view of a self-drilling rock bolt; 15 Figure 2 illustrates a plunger cap and a resin capsule; Figure 3 shows the a plunger cap, resin capsule and mixer assembly; Figure 4 shows an isometric view of a puncture device for the rock bolt Figure 5 shows a side view of a dome, nut and plate assembly; Figure 6 shows -a section through the assembly of Figure 5; 20 Figure 7 shows a close up view of part of Figure 6, showing in particular a barb on a spring clip fixing the nut to the assembly; Figure 8 shows how the assembly adjusts where the installation angle is not perpendicular to a rock/strata face; Figure 9 shows a section through a plunger for use in a rock bolt installation 25 process; Figures 10 and 11 illustrate the working of the plunger during the installation process; Figure 12 shows a first stage in the installation of the bolt in a mine roof; Figure 13 shows a second stage in the installation process; 30 Figure 14 shows a third stage in the installation process; Figure 15 shows a fourth stage in the installation process; Figure 16 shows a fifth stage in the installation process; Figure 17 shows a sixth stage in the installation process; and Figure 18 shows the seventh and final stage in the installation process; 35 Detailed Description of Preferred Embodiments WO 2012/167308 PCT/AU2012/000645 7 Referring to the drawings, Figures 1 to 3 show a self drilling rock bolt 10 comprising an externally threaded hollow bar/pipe 12 with a central hole/bore 14 which is of substantially constant size and shape to allow a pressure seal to move and seal along its entire length. 5 A nut 16, described in more detail below with reference to Figures 4 to 7, is threaded onto a proximal end 12a of the bar. A drill bit 18 is mounted on the opposite distal end of the bar 12b. The precise means of fixing the drill bit is not critical. As shown, the drill bit is in threaded engagement with the interior of the bar, however it could be threaded over the exterior of the bar, press fitted, swaged or welded to the bar. 10 The mounting should however resist pressure up to an in excess of 300 Bar or a one tonne pushing force exerted from the proximal end 12a through the central hole 14, and resist in excess of 300 Nm of torque required for rotary drilling of rock. Also located within the bar is a static mixer 20 and a puncture device 22. The puncture device (also shown in Figure 4) is generally annular in cross-section defining 15 an annular ring 24 and a series of elongate members 26 defining sharp points 28 at one end, distal from the ring 24, designed to pierce a capsule/bag. The static mixer 20 means 22 is also generally annular in cross-section and defines a central bore 30. A series of baffles 32 project into the bore for mixing fluids forced through the mixer. Note that the exact design and shape of the puncture device and mixer are not critical 20 and these will be varied depending on the properties of the resin capsule and components used in the installation. The nut 16, best seen in Figures 5 to 8, is internally threaded and engages over the correspondingly threaded outer surface of the bar 12. The nut includes two hexagonal portions 40 (a drive portion) and 41 (a tensioning portion - to be described in 25 more detail below) an enlarged head/flange 42 and a series of spring clips 44, defining barbs 46 (best seen in Figure 7) for attaching the nut to a dome and plate assembly, described in more detail below. Figures 2 and 3 show a resin capsule 50 which is an elongate tube of film (about 50 microns thick) containing a two part resin typically polyester based, tied and sealed 30 at both ends. The capsule 50 contains a resin mastic matrix 52 and a catalyst/hardener 54 separated into two compartments by another sheet 56 of plastic film, also typically about 50 micron thick. At one end 50b of the capsule, the resin is faster setting, typically setting in 10-20 seconds, than- the other end 50a where setting takes about 60 to 90 seconds. This can be achieved in different ways with accelerators or retardants 35 placed into either the resin mastic or catalyst compartments.

WO 2012/167308 PCT/AU2012/000645 8 Figures 2 and 3 also shows a cap 60 for'the plunger. The cap has an outside diameter which is approximately the same as the internal diameter of the bar 12. The cap includes a cylindrical recess 62 at one end for receiving one end 50b of the capsule 30. 5 Typically, as will be described in more detail below, the cap and capsule will be inserted in the hollow rock bolt during installation with the end 50a inserted first. It is envisaged that, instead of being fixed inside the rock bolt, the static mixer could be attached to the end 50a of the resin capsule as shown in Figure 3. In Figure 3, the end 50a of the capsule receives a large diameter static mixer 64. The mixer also 10 includes a cylindrical recess 66 for receiving the distal end of the capsule. The mixer includes a frusto-conical portion of decreasing diameter and a tubular portion defining a series of apertures and internal projections/baffles In use, the two part resin is forced into the tubular portion and the forcing of the resin through the apertures or against the projections causes turbulence and mixing of the resin and catalyst. Figure 3 shows the 15 components assembled for insertion into the centre of a bar without an internal static mixer. Figures 5 to 8 show a novel bearing plate assembly for use with the self-drilling rock bolt, generally shown at 100. The assembly includes a relatively thick bearing plate 102 which is annular in plan view and defines a central aperture 104. The annular 20 portion of the plate is convex in cross-section. 'At its outer edges, the plate is generally planar but curves towards its centre, so that when the plate is located against a planar surface such as a rock face, earth strata or the like, the perimeter of the plate contacts the rock face, with the centre of the plate spaced from the surface plane defined by the rock face, due to the curvature of the plate. As is best seen in Figure 6, the end faces of 25 the central aperture 104 define a generally frusto-conical engagement surface 106. The plate is typically made of mild steel, but could be made of a higher quality tensile steel to minimise weight. The nut 16 is best seen in Figures 6 and 7. The nut 16 has a first hexagonal (drive) portion 40 linked by a portion of reduced thickness 108 to a second hexagonal 30 (tensioning) portion 41 which joins the head/flange 42 which has a cylindrical perimeter. The proximal end or head of the nut is partly closed by an inwardly directed annular flange 110. The flange defines an aperture 112 through which materials may pass into the bore 14 of the rock bolt, but which prevents the nut from moving along the external thread of the tube once the annular flange 110 contacts the end of the tube. 35 A series of thin elongate arms 44 extend in an annulus from the flange 42 and each of the defines a retaining barb or half arrow head 46 at its end distal from the flange 42.

WO 2012/167308 PCT/AU2012/000645 9 The nut and arms are made in one piece from high tensile steel with the result that the arms 44 are spring-like and resilient and flexible. The inner surface of the arms is not threaded and in use when the nut 16 is threaded on the bar 12, the arms are spaced from the bar 12/threads 14. 5 A mild steel dome ball 120 is provided for engagement between the nut and the plate 102. The dome ball has a generally hemispherical outer surface 122 with an aperture 124 defined in the centre of that surface for receiving the rock bolt 10. The interior shape 126 of the dome ball is generally conical, tapering towards the aperture 124. The diameter of the aperture 124 is slightly smaller than the outside diameter of 10 the spring clips 44 of the nut, so that the spring clips flex and are pushed inwards by the taper when they are inserted in the aperture and spring back when the barb 46 passes through the aperture 124 inhibiting disengagement of the nut from the dome ball 120, but allowing the nut to turn. A flange 128 is defined on the exterior of the dome ball where its diameter is greatest. 15 The dome ball is held in place by a frusto conical cover 130 which is fixed to the plate 102, by any suitable means such as welding or adhesive, which has a front face 132 and aperture 134 too small to allow the flange 128 of the dome ball 120 to pass. In one embodiment, (not shown) the cover 130 may define additional holes to allow drill cuttings to clear the gap between the cover and the dome ball during drilling of a 20 hole. Figure 8 illustrates how the dome ball may be used to install a rock bolt at angles of +1- i5 to 20 degrees to the perpendicular which the plate is still fully engaged with the rock face. In an alternative embodiment, the dome ball may be omitted and the nut 25 engaged directly with an aperture the plate in a similar fashion to its engagement with the dome ball, that allows the nut to rotate but not disengage from the plate. This embodiment clearly is less suitable for installations where the rock bolt is installed in a hole which is not substantially perpendicular to the rock surface. Figures 9 and 10 and 11 illustrate a plunger dolly 200 for use in the installation 30 of the rock bolts, which enables the injection of the capsule and tensioning with changing dollies. In Figures 9 to 11, the plunger dolly 200 is shown engaged with the rock bolt and dome and plate assembly. The plunger can be seen separated from those components in Figure 15. The plunger includes a generally annular external housing 202 having a closed end which defines a hexagonal drive nut 204 and an open end 206. 35 A central shaft 208 extends from the closed end towards the open end and defines a WO 2012/167308 PCT/AU2012/000645 10 blind bore 210 which receives one end of an elongate plunger rod 212, shown in full in Figure 15. An annular socket shaft 214 is located between the external housing 202 and the central shaft 208. Spline engagement with the central shaft and or exterior housing 5 allows the socket shaft to slide inside the housing relative to the shaft but constrains the shaft to rotate with the plunger dolly when the nut 204 is turned. A hexagonal socket 216 is defined at one end of the shaft. The axial length of the socket 216 is approximately the same as or slightly shorter than the axial length of the portion 41 of the nut 16. A biasing means in the form of a spring 215 is located between the other 10 end of the shaft and the interior of the housing which biases the shaft 214 and socket 216 away from the socket end of the plunger dolly. A stop prevents the socket shaft 214 from separating from the housing 202. In use, the biasing means ensures that the socket is engaged over that part 41 of the nut that is adjacent to the flange/head 42 of the nut, and maintains connection with the nut as the nut moves along the bolt 10, when 15 applying tension to the rock bolt, as illustrated in Figures 10 and 11. Installation of the rock bolt using a standard bolting rig, will now be described with'reference to Figures 12 to 18. Figure 12 shows a first stage in the process in which the bearing plate 102 and dome ball 120 engaged in the aperture 104 of the bearing plate 102 are placed onto the 20 bolting rig head plate 300 and positioned near the rock face held by the bolting rig, typically about 300mm away from the rock surface. The rock bolt 10 including the nut 16, as shown in Figure 1, is inserted into the bolting rig and the drill bit 18 is guided through the aperture in the centre of the dome ball and plate assembly into contact with the rock face. The nut 16 locates in a hexagonal socket 302 of the bolting rig's chuck 25 304. Water is injected up the central bore 14 of the rock bolt through the static mixer 20 and drill bit 18 and drilling is commenced by rotating the chuck 304. The water both cools the drill tip and flows back around the outside of the rock bolt, removing cuttings. Figure 13 shows the next stage after drilling has been completed. At this stage 30 the bolt 10 has passed almost fully through the plate and extends in a hole 310 formed in the rock face dome assembly and the arms 44 of the nut pass through the dome ball 120 and the barbs 46 engage with the dome ball and prevent separation of the nut and dome, whilst allowing the nut to turn relative to the dome ball. The dome and plate assembly are held in place by the frame 308 of the bolting rig.

WO 2012/167308 PCT/AU2012/000645 11 With reference to Figure 14, the drill chuck 304 is then retracted away from the nut 16, with the spring clips holding the nut to the dome ball 120. A resin capsule 50 and end cap 60 are manually inserted into the bore 14 of the rock bolt. Figure 15 shows the plunger 200 attached to the drill chuck 304. This may be 5 done prior to, or after, insertion of the capsule 50. The plunging rod of the plunger engages with the cap 60 of the capsule 50 and together are pushed in the direction of the bolt forcing the capsule onto the puncture means 22 and static mixer 20. The distal end 50a of the 'capsule ruptures on contact with the puncture means 22 and the two fluid components 52 and 54 contained in the capsule are injected through the static 10 mixer. The drill chuck 304 is pushed forwards hydraulically with a force of around I tonne which forces the plunger rod into the central bore 14 of the bolt through the static mixer 20 out through the drill bit 18 and around the outside of the bolt. The slower setting resin at the distal end 50a moves through the mixer 20 and 15 along the side of the bolt back to the plate 102 while the faster setting resin from the proximal end 50b of the capsule moves down the bore 14 of the bolt to fill the far end part of the drill hole near the drill bit 18. Note that the flow of the resin will also be affected to an extent by gravity, depending on whether the bolt is inserted in a roof or wall. 20 With reference to Figure 16, the plunger length is set so that when the plunger cap 60 reaches to near the static mixer 20, and all resin is ejected, the drive socket 216 of the plunger 200 engages only the tensioning section 41 of the nut 16. The drive socket 216 of the plunger may be used to rotate the bolt immediately upon engagement with the nut 16 to provide additional mixing of the two resin 25 components already located between the hollow bar 12 and the wall of the borehole. The frangible connection 108 between the two portions 40 and 41 of the nut enables the rotation of the bolt whilst the resin is still uncured and the connection 108 can be set to break at various torque values to suit the various drill motor torque outputs. After a delay of 10-30 seconds to allow the faster setting resin to cure, the drill 30 chuck is rotated to turn the plunger which in turn turns the nut 16 and this breaks the connection 108 between the tensioning portion 41 of the nut and the end drive portion 40, and allows the nut to be tightened against the plate 102 against the rock face 103. the annular socket shaft is held in position over the nut 41 by the spring 215. The drill chuck is then retracted and the plunger 200 removed for use with the 35 next installation. Figure 18 shows the completed installation, and the drill chuck is lowered for installation of the next bolt.

WO 2012/167308 PCT/AU2012/000645 12 The present invention has a number of advantages over the prior systems. First drilling into frangible and broken strata often produces jagged drill holes and makes insertion of the resin capsule into the drill hole difficult to do without rupturing the capsule. Using the system described above the bolt itself provides a smooth bore for 5 insertion of the capsule therein. Secondly the process eliminates some of the steps required, in prior installation systems, namely the removal of the drill steel and manual insertion -of the bolt compared with non-self drilling systems and avoids the requirement of putting a tightening spanner into and out of the drill chuck. 10 The use of a static mixer reduces the possibility of operator error during the resin mixing step. Existing methods rely on the operator spinning the bolt for 8 to 12 seconds to mix the resin and hardener to obtain the correct mix, with inadequate mixing greatly reducing the final cure strength of the resin. Finally compared to existing self drilling rock bolt systems the system of the 15 present invention is relatively uncomplicated and thus can be expected to be more cost effective and reliable. In a alternative embodiment (not shown) a second seamless pipe having a smooth bore may be inserted into a hollow externally threaded bar. Instead of being externally threaded, the pipe may be generally smooth and 20 externally threaded at one end only to receive the nut and have a wire or the like would around it for engagement with the resin. In a yet further variant a series of wire "birdcage" may also be defined around the exterior of the bolt. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without 25 departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (20)

1. An assembly for use in installing a rock bolt in a hole in a rock face, earth strata or the like defining a surface plane, the assembly comprising: a plate for engagement with the rock face, earth strata or the like, the plate 5 having an aperture defining an engagement surface, which is typically generally concave or conical; and a part convex dome ball defining a central bore having a central axis for receiving the rock bolt and maintaining the rock bolt generally aligned with the central axis of the bore, and a convex external surface for engaging with the engagement 10 surface of the plate, the arrangement being such that when the plate is located at or near the surface. plane and the dome ball engaged with the plate, a rock bolt may be inserted through the dome ball into the hole in the rock face, which may be non-perpendicular to the surface plane, with movement of the convex external surface of the dome ball relative to the 15 engagement surface of the plate adjusting the relative orientation of the dome ball and washer to maintain the alignment of the rock bolt substantially co-axial with the axis of the bore.

2. An assembly as claimed in claim I wherein the central bore of the dome ball has 20 a conical taper diminishing in diameter towards the convex external surface.

3. An assembly as claimed in claim 2 further including a nut mounted on one end of the rock bolt wherein the nut defines a series of flexible arms defining barbs at their free ends which are deflected inwardly when a rock bolt with the nut attached at one 25 end is inserted through the central bore of the dome ball and spring outwardly after passing through the bore thereby locking the nut to the dome ball, while permitting rotational movement of the nut relative to the dome ball about the axis of the dome ball.

4. An assembly as claimed in claim I or claim 2 or claim 3 wherein the plate in 30 generally annular in plan view defining a central aperture and wherein the annular portion of the plate is generally convex in cross-section.

5. An assembly as claimed in any one of claims 1 to 4 further including a cover which is fixed to the plate and which defines a central aperture which is sized to allow 35 the passage of the rock bolt but not the dome ball. WO 2012/167308 PCT/AU2012/000645 14

6. An assembly as claimed in any one of claims 1 to 5 wherein the dome ball defines an external flange which engages with the plate when the orientation of the dome ball relative to the plate is more than about +/- 15-20* to the perpendicular. 5 7. An assembly as claimed in any one of claims 3 to 6 wherein the nut define two separate, typically hexagonal, drive portions for engagement with a drive socket, linked by a frangible portion.

8. An assembly as claimed in claim 7 wherein the nut further includes a flange or 10 head between the drive portions and wherein the end of the nut distal from the flexible arms defines an internal flange having a central aperture.

9. A plunger device for use in injecting a capsule into a rock bolt defining a central bore, the device comprising a central shaft defining a central axis drive means at a first 15 end for engagement with a chuck or the like, and at a second distal end, a plunger rod, and further including a socket mounted so as to rotate with the shaft when the shaft turns about its central axis but which is mounted for axial movement relative to the shaft and plunger rod in the direction of the central axis and further including biasing means, biasing the socket away from the first end. 20

10. A plunger device as claimed in claim 9 wherein the socket is defined on one end of a annular shaft.

11. A plunger device as claimed in claim 10 wherein the annular shaft is mounted 25 via a spline connection to the central shaft.

12. A plunger device as claimed in any one of claims 10 or 11 wherein an annular external housing surrounds the central shaft and annular socket shaft. 30 13. 'A method of installing a rock bolt in a rock/strata face or the like defining a surface plane, comprising the steps of: providing a rock bolt comprising a bar, rod, pipe or the like having a hollow central bore and a drill bit mounted at one distal end, and a nut mounted on the other end, the bore allowing the passage of a pressure seal along its length; 35 providing a plate having an aperture defining an engagement surface, and a part convex dome ball defining a central bore having a central axis for receiving the rock WO 2012/167308 PCT/AU2012/000645 15 bolt and a convex external surface slideably engaged with the engagement surface of the plate, and positioning the plate against the rock face; drilling a hole in a rock/strata face using the drill bit until the rock bolt is almost fully located inside the hole, and wherein the nut defines arms which engage with the 5 dome ball preventing axial movement of the nut and therefore the entire bolt, relative to the plate while permitting relative rotation of the nut and plate inserting a elongate generally cylindrical capsule containing a two part resin separated by a film and having a first end and a second end into the bore of the rock bolt wherein the first end of the capsule is engaged in a cap or plunger; and 10 applying a force to the cap, forcing the cap and capsule into the bore thereby forcing resin through the mixing means and out past the drill bit into the hole; and allowing at least part of the resin to set.

14. A method as claimed in claim 13 wherein the step of applying a force to the cap 15 includes the use of a plunger device comprising a central shaft defining a central axis and drive means at a first end for engagement with a chuck or the like for rotation of the plunger device, and at a second distal end, a plunger rod, and further including a plunger socket mounted so as to rotate with the shaft when the shaft turns about its central axis but which capable of movement relative to the shaft and plunger rod in the 20 direction of the central axis and further including biasing means, biasing the plunger socket away from the first end.

15. A method as claimed in claim 13 or claim 14 wherein the nut defines a series of flexible arms defining barbs at their free ends which are deflected inwardly when the 25 rock bolt with the nut attached at one end is inserted through the central bore of the dome ball and spring outwardly after passing through the bore thereby locking the nut to the dome ball, while permitting rotational movement of the nut relative to the dome ball about the axis of the dome ball. 30 16. A method as claimed in claim 15 wherein the nut further defines two separate, typically hexagonal, first and second drive portions for engagement with a chuck, linked by a frangible portion and wherein in use after the step of forcing the cap and capsule into the bore, the plunger socket engages only the second drive portion closest to the dome ball and wherein after setting of the resin, further rotation of the nut breaks 35 the frangible portion allowing the second drive portion to travel down the bolt and tension the same, the connection being preset or designed to fracture at a pre-set torque. WO 2012/167308 PCT/AU2012/000645 16

17. A method as claimed in claim 16 wherein the nut further includes a flange or head between the drive portions and the arms and wherein the end of the nut distal from the flexible arms defines an internal flange having a central aperture, the flange 5 preventing the first drive portion from travelling further along the bolt.

18. A method of installing a rock bolt in a rock/strata face or the like comprising the steps of: providing a rock bolt comprising a bar, rod, pipe or the like having a hollow 10 central bore and a drill bit mounted at one distal end, the bore allowing the passage of a pressure seal along its length; drilling a hole in a rock/strata face using the drill bit until the rock bolt is almost fully located inside the hole; inserting a elongate generally cylindrical capsule containing a two part resin 15 separated by a film and having a first end and a second end into the bore of the rock bolt wherein the first end of the capsule is engaged in a cap or plunger and the second end is optionally attached to a static mixing means; applying a force to the cap, forcing the cap and capsule into the bore thereby forcing resin through the mixing means and out past the drill bit into the hole; and 20 optionally, using a plunger socket associated with the plunger to rotate the bolt via the nut the provide additional mixing to the resin located between the rock bolt and the hole; and allowing at least part of the resin to set. 25 19. A method as claimed in claim 18 wherein at least the proximal end of the rock bolt is threaded and further including the step of threading a nut via a torque break-out mechanism on the proximal threaded end of the rock bolt; disposing a plate between the rock/strata face and the nut and securing/retaining the same against the rock/strata face prior to the drilling step. 30

20. A method as claimed in claim 19 wherein the nut includes means for engaging with the bearing plate and preventing axial movement of the nut and therefore the entire bolt, relative to the plate while permitting relative rotation of the nut and plate. 35 21. A method as claimed in claim 20 wherein the means for engaging with the bearing plate include a spring means attached to or integrally formed with the nut WO 2012/167308 PCT/AU2012/000645 17 which deflect inwards to pass through a central hole in the washer and subsequently expand thereby retaining the nut against the washer.

22. A method as claimed in any one of claims 18 to 21 wherein the rock bolt 5 comprises a bar which is externally deformed and/or threaded and define a smooth internal bore of constant circular cross-section.

23. A method as claimed in any one of claims 18 to 21 wherein the rock bolt comprises a first hollow bar, optionally having a reinforcing wire wound around its 10 exterior and wherein a further seamless tube is located inside the first hollow tube defining the smooth internal bore.

24. A resin capsule assembly, particularly for use in the method of any of claims 13 to 23 comprising an elongate generally cylindrical capsule containing a two part resin 15 separated by a film and having a first end and a second end, wherein the first end of the capsule is engaged in a cap or plunger defining a seal and the second end is attached to a static mixer.

25. A resin capsule assembly as claimed in claim 24 wherein the static mixer ' 20 defines a cylindrical recess for receiving the distal end of the capsule, a frusto-conical portion of decreasing diameter and a tubular portion defining a series of apertures and internal projections causing mixing and turbulence in resin forced through the tubular portion. 25