Patent Publication Number: US-11028692-B2

Title: Rock bolt with meshing adapter

Description:
RELATED APPLICATION DATA 
     This application is a § 371 National Stage Application of PCT International Application No. PCT/EP2018/080884 filed Nov. 12, 2018 claiming priority to AU 2017904776 filed Nov. 27, 2017. 
     FIELD OF INVENTION 
     The present invention relates to a rock bolt and a wire meshing assembly for installation of meshing sheet against a surface and rock strata and in particular although not exclusively to a rock bolt and assembly for mounting meshing sheets in overlapping configuration at the rock surface. 
     BACKGROUND ART 
     Roof and wall support is vital in underground mining and tunnelling operations. Mine and tunnel walls and roofs often consist of rock strata which require reinforcement to prevent failure, such as fragmentation or collapse. Rock bolts and wire meshing are used widely for reinforcement purposes and containment purposes respectively. Rock bolts are driven into the rock strata and provide reinforcement against major rock fracture, while wire mesh sheets are fixed across the rock surface and are used principally to contain smaller fragments of rock from dislodging and/or falling away from the rock surface. 
     Rock bolts are installed in a bore which is drilled into the rock strata and the rock bolt is usually secured in the bore by a resin or a cement grout, or they can be frictionally fixed within the bore by mechanical expanders. The trailing end of a rock bolt normally projects a short distance outside of the bore for supporting ancillary fixtures such as rock plates and mining services; pipes and cables for example. The projecting end of the rock bolt can be threaded for connection of ancillary fixtures. 
     Safety wire meshing or meshing (hereinafter ‘meshing’) is employed to protect mining workers and equipment from rock fracture or fall whereby the wire meshing is fixed over a section of the rock wall or surface of the underground mine. It is typically convenient for the meshing to be secured against the rock surface by attachment to the projecting ends of several rock bolts. In some arrangements, the rock bolts are installed through the meshing and the rock plate of the rock bolt bears against the meshing to fix or press the meshing against the rock surface. The intention is for the meshing to be installed as close as possible to the rock surface. As mining continues and new sections of rock surface are exposed requiring reinforcement and containment, new meshing must be installed in overlapping arrangement with the edges of the existing or already installed meshing. Depending on the types of rock bolts used, the new meshing may be fixed to the last rock bolts that secure the existing meshing, or additional rock bolts need to be installed. 
     Australian Patent No 2004100042 relates to the installation of wire meshing, utilising rock bolts for anchoring the meshing and discloses an overlapping arrangement of wire meshing using a single rock bolt. The first or initial meshing is secured against the rock surface via the projecting end of the rock bolt and a rock plate, while the second meshing is secured overlapping the first meshing via a meshing plate and a second nut that threads onto the projecting end of the rock bolt. 
     The arrangement of Australian Patent No 2004100042 can operate effectively. However, there can be difficulty where the projecting end of the rock bolt does not project sufficiently for attachment of the meshing plate and nut. This can occur where the rock bolt is installed in a ‘valley’ in the rock surface for example, or where the rock bolt is driven into the rock strata too far or too deeply for the projecting end to sufficiently extend proud of the rock surface for the connection of the second nut and second meshing. 
     Also, some forms of rock bolts have blind nuts applied to the projecting end of the rock bolt and so a threaded section of the rock bolt does not project for attachment of a meshing plate and nut. In these kinds of rock bolts the first section of wire meshing can be installed as described above to the projecting end of the rock bolt, with the rock plate in bearing engagement with the first section of wire meshing, however the second section of wire meshing cannot be installed. While in some forms of these kinds of rock bolts the blind nuts have an external thread for attachment of an adapter, the thread is usually relatively short and so does not provide sufficient thread for attachment of wire meshing and a meshing plate, particularly if the rock bolt is installed in a ‘valley’ in the rock surface. 
     Australian Patent No 2011236039 discloses a rock bolt that includes an adapter for hanging mining services such as pipes and cables. The rock bolt of Australian Patent No 2011236039 has a blind nut of the kind described above that is externally threaded for attachment of a hanger. The hanger provides a point for hanging pipes and cables and the short threaded connection that the hanger makes with the blind nut is sufficient for the hanger to support these types of mining services, but would not be sufficient for supporting wire meshing. 
     US Patent Application 20170067340 discloses a similar arrangement to that disclosed in Australian Patent No 2011236039, in that an adapter for attaching a safety line for an assembly worker is provided. 
     Where there is an absence of a sufficient extent of a projecting end of the rock bolt to attach wire meshing, usually additional rock bolts need to be installed just for the meshing to be installed. This is much more costly than using the existing rock bolts, because of the additional cost of the rock bolt and the additional time taken for installation. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a rock bolt and a wire meshing assembly for insulation of meshing sheet against a surface of rock strata in which common rock bolts are utilised to secure first and second sections of meshing sheet in overlapping arrangement. It is a specific objective to provide a rock bolt and assembly that avoids the need for additional rock bolts at the interface or junction between sections of meshing. 
     It is a further specific objective to provide a rock bolt and insulation assembly configured for the secure mounting of containment meshing at highly contoured or uneven surfaces of rock strata that include troughs, cavities, valleys and the like. 
     The objectives are achieved via a rock bolt and meshing installation assembly having an adapter connectable to an exposed trailing end of a rock bolt with the adapter configured to mount a meshing plate to bear against and urge a further second section of meshing sheet in overlapping contact against a first meshing sheet section already mounted at the rock surface via the rock bolt. The adapter is advantageous to provide an axial extension of the trailing end of the rock bolt where the rock bolt does not protrude a sufficient axial length to receive and mount a meshing plate (to bear against the second or further section of meshing sheet). Accordingly, via the present adapter, the need for additional rock bolts to secure the further second meshing sheet at the same overlapping location of the first sheet is avoided so as to enable the same and common rock bolts to be utilised to secure both overlapping meshing sheet sections. A rock bolt according to the present invention advantageously facilitates attachment of the second section of wire meshing overlapping the first section via a single (common) rock bolt which saves time, cost and effort. 
     The present invention can be employed with any type rock bolt that has an end that protrudes from a bore. Thus, the present invention can be used with resin or cement grouted bolts and mechanical friction bolts. Resin or cement grouted rock bolts normally comprise a bar that is installed in a bore and a resin or grout is injected or otherwise introduced into the bore about the bar for the purpose of anchoring the bar in the bore. Mechanical friction bolts usually comprise an outer tube that is split longitudinally to allow radial expansion and contraction of the diameter of the tube and an expander mechanism within the tube that can be activated once the rock bolt is inserted into a bore to apply a load tending to cause the tube to radially expand in order to increase the frictional engagement between the tube and the bore wall or surface. 
     In all forms of rock bolt, an end of the bolt will protrude from the bore for the purpose of for example, supporting a rock plate and other mining services as might be required, such as pipes and cables. The protruding end will sometimes be threaded for connection of a nut or the like as required to secure a rock plate or other mining services. Each of Australian Patent No 2004100042 and International PCT Patent Application No 2012053965 and US Patent Application 20170067340 disclose such arrangements. Australian Patent No 2004100042 shows a resin or grouted bolt in which the protruding end supports a nut for securing a rock plate and a further nut for securing a meshing plate. The present invention could be applied to Australian Patent No 2004100042 by applying an adapter of the invention to the protruding end of the rock bolt in circumstances where the protruding end does not protrude sufficiently for the nut that secures the meshing plate to be attached. 
     International PCT Patent Application No 2012053965 discloses a rock bolt that has a blind nut secured to one end. Because the nut is blind, there is not sufficient room for a meshing plate and nut to be applied to the rock bolt. Accordingly, the present invention could be applied to a rock bolt of the type described in International PCT Patent Application No 2012053965 in which the nut is configured with an external thread and applying an adapter of the invention to the nut. The adapter then provides the necessary extension for attachment of a meshing plate and nut. 
     The present invention thus can be applied to various forms of rock bolt and includes cable bolts as well. This form of rock bolt can be seen in International PCT Patent Application No 2013203198 and as with the other rock bolts discussed above, also includes a protruding end for the attachment of a meshing plate and nut, or where the protruding end is not sufficient, for the attachment of an adapter of the invention. It follows that the present invention is applicable to many forms of rock bolt subject to the bolt having a protruding end to which the adapter of the invention can be applied. 
     Advantageously, the manner in which the nut is fixed to the extension of the adapter means that a single installation device or equipment can be used to attach the adapter to the shaft of the rock bolt and to thereafter drive the mesh clamp to the mesh clamping position. This differs from prior art arrangements, in which a connector or adapter suitable to attach a meshing plate is first attached to the rock bolt and thereafter the meshing plate is attached to the connector or adapter. This two-stage installation process of the prior art is required as a result of the particular form of the prior art adapters and meshing plates and means that installation of the meshing plates is more time consuming and thus less convenient than in the present invention. 
     It is to be appreciated that the time taken to install meshing over a section of exposed rock face is important to maximise the safety of personnel working within a mining area. Therefore, the quicker the exposed rock face can be covered by wire meshing, the quicker the mining area can be rendered safe for mining personnel. 
     Moreover, the present invention can provide a significant advantage in that the adapter can be attached to the installation equipment and can remain attached to that equipment while that equipment lifts the meshing in to the position at which it is to be installed. Thus, the installation equipment can lift the meshing and position it at the installation position and when properly positioned, the equipment can then align the adapter with the trailing end of the rock bolt shaft, and engage the adapter to connect the adapter to the shaft. This connection of the adapter can be made while the installation equipment holds the meshing in the position for installation. Once the adapter has been connected to the rock bolt shaft, the installation equipment can cause a part of the adapter in order to drive the mesh clamp to clamp the section of meshing in place. This again differs from the prior art, in which an adapter is first connected to the trailing end of the rock bolt shaft, the meshing is placed over the adapter and then the meshing plate is rotated or placed into a clamping position. In the present invention, the installation equipment can connect the adapter to the rock bolt and clamp the meshing in place as a single installation operation. 
     The present invention has been developed with the connection portion of the adapter being threaded so that the nut connects to the connection portion. In this form of the invention, in internal region of the connection portion of the adapter and an external region of the trailing end of the elongate shaft are also both threaded for mutual threaded connection. In practice, the threaded connection between the adapter and the rock bolt shaft is achieved by rotating the adapter into connection with the bolt shaft. For this, installation equipment engages the nut with the nut in a first position at the connection portion of the adapter and rotates the nut. Because the nut is fixed to the connection portion against rotation relative to the connection portion, the nut will not rotate relative to the connection portion but rather, the nut and connection portion will rotate together and that will rotate the complete adapter for connection to the trailing end of the rock bolt shaft. 
     Once the adapter is connected to the trailing end of the elongate shaft, further rotation of the nut will cause the nut to adopt the second movable connection to the connection portion, so that the nut will rotate relative to the connection portion and will drive or push the mesh clamp to a mesh clamping position. 
     While aspects of the present invention has been developed with the threaded arrangement discussed above, other aspects of invention covers arrangements in which the adapter is not threaded onto the trailing end of the rock bolt shaft and/or in which the nut is not threaded onto the extension. For example, the adapter can be connected to the trailing end of the rock bolt shaft by an interference fit or by other connection in which rotation of the adapter is not required. In that form of the invention, the installation equipment can engage the adapter to force the adapter into connection with the trailing end of the rock bolt shaft. That engagement can be engagement of the nut of the adapter whereby nut is thus fitted to the extension in a first fixed connection for engagement by the installation equipment, but the engagement is not rotational engagement. However, the installation equipment could equally engage a different component or part of the adapter to force the adapter into connection with the trailing end of the rock bolt shaft. The installation equipment could for example apply a percussive load to the end of the extension, or the extension could have a step or shoulder that is provided for engagement with a percussive load. 
     Likewise, the nut can be a friction fit on the connection portion (such as by crimping) and in that fixed state on the connection portion, the nut can be rotated if the adapter rotatably connects to the trailing end of the rock bolt shaft or it can be percussively driven if the adapter frictionally connects to the trailing end of the rock bolt shaft. 
     In some forms the above form of the invention, the second movable connection of the nut on the connection portion can be a frictional movement in which the load applied to the nut overcomes the frictional load between the nut and the connection portion and shifts the nut relative to the connection portion to drive the mesh clamp to a mesh clamping position. Despite this movement of the nut along the connection portion, the nut will maintain a high frictional connection with the connection portion to support the mesh clamp in the mesh clamping position. The cooperating surfaces of the nut and the connection portion can be roughened or ribbed or otherwise treated or formed in order achieve this high frictional connection. 
     It will be appreciated that the use of the term ‘nut’ or ‘body’ is intended to cover a component that threadably connects to a threaded connection portion and/or elongate extension as well as a component that connects to the connection portion other than by thread and in particular by friction or interference fit. 
     Within this specification, reference to the rock bolt comprising an ‘elongate shaft’ encompass the rock bolt having an elongate bar, rod or cable to which tension is capable of being applied during anchorage of the rock bolt into the as-formed bore. Accordingly, reference within this specification to the elongate shaft having ‘a trailing end’ encompasses an end of a bar, rod or cable, a nut, socket or other connection component attached to the elongate shaft. Accordingly, the present invention encompasses the present adapter being connectable directly or indirectly to the trailing end of the elongate shaft. 
     According to a first aspect of the present invention there is provided a rock bolt for installation within a bore formed in rock strata comprising: an elongate shaft having a leading end for installation into the bore and a trailing end to project from an open end of the bore; an adaptor having: a connection portion connectable to the trailing end of the elongate shaft; and a body having an internal facing surface mateable with an external facing surface of the connection portion; and a mesh clamp mountable at the body or axially between an axially forwardmost part of the connection portion and the body such that the body is drivable axially on the connection portion via the engagement between the internal facing surface the external facing surface to force the meshing clamp towards the trailing end of the elongate shaft and to bare against and urge a meshing sheet into contact with a surface of the rock strata. 
     Optionally, the connection portion comprises an internal thread mateable with an external thread of a nut secured to the trailing end of the elongate shaft. 
     Optionally, at least a region of the connection portion comprises an external thread at the external facing surface and at least a region of the body comprises an internal thread mateable with the external thread of the connection portion such that the body is axially driveable along the connection portion via the threads. The threading is advantageous for convenient and reliable axial advancement of the body on the extension using common external tooling. 
     Optionally, the connection portion comprises an extension extending axially from said forwardmost part, wherein the meshing clamp is mountable on the extension between said forwardmost part and the body. Optionally, the external thread is provided at the extension. Optionally, the body is a nut rotatable on the extension towards said forwardmost part to drive axially the mesh clamp towards the socket. Optionally, the internal thread of the connection portion is formed within a socket at said forwardmost part from which the extension projects. 
     Optionally, the body comprises a nut head and a nut collar, the internal thread of the body provided at the collar such that the collar is axially drivable over and along the connection portion to force the meshing clamp towards the trailing end of the elongate shaft. 
     Optionally, the body comprises a first fixed connection to the connection portion, whereby installation equipment can rotate the body to rotate both the body and the adapter together for threadably connecting the adapter to the trailing end of the elongate shaft of the rock bolt. 
     Optionally, the first fixed connection of the body to the connection portion comprises a shear pin extending between the body and the connection portion. Optionally, the first fixed connection of the body to the connection portion comprises a spot weld or braze, gluing or crimping between the body and the connection portion. Preferably, the body has both a first fixed connection to the connection portion and a second movable connection to the connection portion. In the preferred arrangement, the first fixed connection enables the adapter to be rotated with the body in order for the adapter to be threadably connected to the trailing end of the rock bolt shaft. In the preferred arrangement, the second rotatable connection enables the body to be rotated relative to the threaded connection portion of the adapter in order to drive the mesh clamp forward and into a clamping position relative to the meshing. The first fixed connection can be made in any suitable form in the preferred arrangement such as by the use of a shear pin that extends between the nut and the extension. Thus, the body can be formed with an opening that can align with a complementary opening in the connection portion and a shear pin can be extended through the respective openings to fix the body to the connection portion. The shear torque strength of the shear pin must be high enough to overcome any resistance to the action of threadably coupling the adapter to the rock bolt shaft, but must be lower than the maximum torque output of the installation equipment, i.e. a mining Jumbo for example. Typically, in a mining Jumbo, the maximum torque output is 400 Nm and thus the shear torque strength of the shear pin can be in the region of 150 Nm to 300 Nm. Alternative arrangements to fix the body to the connection portion include spot welding or brazing, crimping or gluing. 
     Optionally, the mesh clamp comprises an opening through which the extension extends. Optionally, the opening has an internal diameter that is greater than the external diameter of the extension so that the mesh clamp is a loose fit about the extension. 
     Optionally, the mesh clamp comprises an opening through which a portion of the body extends axially between the nut head and the nut collar. 
     Optionally, the mesh clamp has a base in which the opening is formed and arms that extend from the base to a ring configured for engagement of the meshing sheet. 
     Optionally, the mesh clamp has a base in which the opening is formed and a skirt extends from the base, wherein the skirt has a distal end remote from the base for engagement of the meshing sheet. Optionally, the distal portion or end remote from the base may be annular, part annular or otherwise be configured for abutment against the meshing sheet. 
     Optionally, the base is planar and extends generally perpendicular to an axis of the rock bolt. Where the mesh clamp includes a base, it can also include fingers or a skirt or dish that extends from the base for engagement with the meshing to be clamped. The skirt can be a continuous skirt and can include an edge or portion which is remote from the base for engagement with the mesh. The skirt and/or the edge or portion may be circular/annular or any other suitable shape. Alternatively, where fingers are provided, these can extend to a ring for engagement with the meshing. A pair of fingers can extend to a ring from the base in a symmetrical manner or three or four fingers can extend to the ring symmetrically. This arrangement has advantages in that the adapter is open between the fingers which allows the installation personnel better ability to see the end of the rock bolt to which the adapter is to be connected. 
     Optionally, the body is mounted to the connection portion via a friction fit and the body is movable axially along the connection portion by application of a load applied to the body which is sufficient to overcome a friction connection between the body and the connection portion. Accordingly, the body may be capable of sliding axially along the connection portion by a compressive external force applied to the body in the direction of the longitudinal axis of the rock bolt. 
     According to a second aspect of the present invention there is provided a meshing assembly for installation of meshing sheet against a surface of rock strata comprising: a rock bolt as claimed herein; a first section of meshing positionable against the surface of the rock strata; a rock plate connectable to the trailing end of the rock bolt to bear against and urge the first section into contact with the surface of the rock strata; a second section of meshing positionable against the surface of the rock strata and overlapping the first section; and a meshing clamp connectable to the connection portion and configured to bear against and urge the second section into contact with the surface of the rock strata. 
     According to a further aspect of the present invention there is provided an adapter for connection to a rock bolt of the kind that has an elongate shaft which has leading and trailing ends for installation in a bore which is drilled into a rock strata, the adapter having a connection portion which is connectable to the trailing end of the elongate rock bolt shaft and including an elongate extension on which is mounted a mesh clamp and a nut, the mesh clamp being mounted between the connection portion of the adapter and the nut, the adapter being connectable to the trailing end of the elongate rock bolt shaft with the nut movable along the elongate extension to drive the mesh clamp to a mesh clamping position. 
     The present invention also provides a rock bolt with an adapter according to the invention attachable to one end of the rock bolt. The invention may be provided in kit form or fully assembled 
     According to a further aspect of the present invention there is provided a method of installing wire meshing against a wall surface, the method including: 
     i. installing a rock bolt in a bore drilled into a rock strata, the rock bolt having an elongate shaft which has leading and trailing ends, 
     ii. installing a first section of wire meshing between a wall surface of the rock strata adjacent the bore and connecting a rock plate to the trailing end of the shaft and fixing the rock plate in place to sandwich the wire meshing between the wall surface and the rockplate, 
     iii. installing a second section of wire meshing into an overlapping position with the first section of wire meshing by inserting an adapter into an opening of the wire meshing and lifting the adapter with installation equipment to lift the wire meshing into the overlapping position, the adapter having a section for connecting to the trailing end of the rock bolt shaft and having a connection portion on which is mounted a mesh clamp and a body, 
     iv. causing the installation equipment to engage the adapter to connect the adapter to the trailing end of the elongate shaft, 
     v. subsequently causing the installation equipment to engage and move the body relative to the connection portion to drive the mesh clamp to a mesh clamping position to clamp the second section of wire meshing in the overlapping position with the first section of wire meshing. 
     In the first fixed connection of the body the installation equipment can rotate the body to rotate the body and the adapter together for threadably connect the adapter to the trailing end of the elongate shaft, and in the second rotatable connection to the threaded extension the installation equipment can rotate the body relative to the threaded extension to drive the mesh clamp to a mesh clamping position. 
     According to a further aspect of the present invention there is provided a method of installing a second section of wire meshing overlapping a first section of wire meshing where the first section of wire meshing is already installed against a wall surface by connection to an installed rock bolt, the method including: 
     i. installing a second section of wire meshing into an overlapping position with the first section of wire meshing by inserting an adapter into an opening of the wire meshing and lifting the adapter with installation equipment to lift the wire meshing into the overlapping position, the adapter having a section for connecting to the trailing end of the rock bolt shaft and having a connection portion on which is mounted a mesh clamp and a body, 
     ii. causing the installation equipment to engage adapter with the body in the first fixed connection to connect the adapter to the trailing end of the elongate shaft, 
     iii. subsequently causing the installation equipment to engage and move the body relative to the connection portion to drive the mesh clamp to a mesh clamping position to clamp the second section of wire meshing in the overlapping position with the first section of wire meshing. 
     The installation equipment can be of any suitable form but a common form used in underground mining for the installation of rock bolts, is known generically as a mobile bolter or as a ‘Jumbo’ which is a mining vehicle that includes an arm or boom which has the capability of percussion driving and rotation for installing rock bolts and components within underground mines. With the adapter of the invention, a mining Jumbo can have the adapter attached to the arm or boom and the adapter can remain attached to the arm or boom while the meshing is lifted by the arm or boom and the arm or boom can then bring the adapter into position for connection to the rock bolt as explained above. The adapter can even be used to lift the meshing, given that in some forms of an adapter according to the invention, the end of the adapter which connects to the shaft of the rock bolt includes an enlarged diameter socket, which can be inserted through an opening in the meshing in order to hook the meshing when the arm or boom is lifted. Thus, the adapter advantageously can facilitate lifting of the meshing so that the arm or boom is not required to include an alternative component to do this. Of course, the Jumbo can raise the meshing quite separately without the adapter being used to hook the meshing. Suitable installation equipment can engage either the body or other parts of the adapter to connect the adapter to the trailing end of the elongate shaft of the rock bolt. The installation equipment could for example, engage the end of the connection portion, or the connection portion could have a step or shoulder that is provided for engagement. 
     An adapter according to the present invention can be sized so that the leading end of the adapter can fit through an opening in the meshing to be installed, while the manner of connecting the body to the connection portion by appropriate ‘connections’ mean that the adapter does not need to be connected to the rock bolt prior to the meshing being fitted over the adapter. Advantageously, the adapter and the meshing can be lifted as one for subsequent connection to the installed rock bolt. 
     According to a further aspect of the present invention there is provided a wire meshing installation, the installation including: 
     i. a rock bolt having an elongate shaft which has leading and trailing ends installed in a bore drilled into a rock strata, the trailing end being threaded, 
     ii. a first section of wire meshing installed between a wall surface of the rock strata adjacent the bore and a rock plate connected to the trailing end of the shaft, 
     iii. an adapter according to any of the forms described herein, connected to the trailing end of the shaft, 
     iv. a second section of wire meshing installed overlapping the first section of wire meshing and being clamped in the overlapping position by the mesh clamp. 
     According to a further aspect of the present invention there is provided an adapter for connection to a rock bolt of the kind that has an elongate shaft which has leading and trailing ends for installation in a bore which is drilled into a rock strata, the adapter having a connection portion which is connectable to the trailing end of the elongate rock bolt shaft and including a connection portion on which is mounted a mesh clamp and a body, the mesh clamp being axially moveably mounted at the adapter, the adapter being connectable to the trailing end of the elongate rock bolt shaft with the body mounted in a first position thereon and the body being axially movable relative to the connection portion (ie. from a first position distal to the rock bolt to a second position proximal to the rock bolt) to drive the mesh clamp to a mesh clamping position. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: 
         FIG. 1  is an exploded sectional view of a wire meshing installation according to the invention; 
         FIG. 2  is an assembled sectional view of the wire meshing installation of  FIG. 1 ; 
         FIG. 3  is an end view of an adapter according to the invention; 
         FIG. 4  is a side view of an adapter according to the invention in engagement with installation equipment and wire meshing; 
         FIG. 5  is a cross section view of a further implementation of the present adaptor and rock bolt. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , a rock bolt  10  according to the invention is illustrated and comprises a split tube  11  that extends into a bore  12  that is drilled into rock strata  13 . The length of the split tube  11  can be in the order of 1 m to 3 m. 
     The rock bolt  10  is of the kind that includes an expander mechanism within the split tube  11  towards the leading end of the tube  11 . The expander mechanism is shown in simplified form at reference numeral  28  in  FIG. 1 . The expander mechanism comprises a wedge arrangement and one component of the wedge arrangement connects to a bar  14  that is positioned within the tube  11 . In the embodiment illustrated in  FIG. 1 , rotation of the bar  14  within the tube  11  is operable to activate the expander mechanism to shift the wedge arrangement to expand inside the tube  11 , thus tending to expand the tube  11  radially against the facing surfaces of the bore  12 . This serves to cause the tube  11  to more firmly engage the surface of the bore  12 , so as to firmly anchor the tube  11  within the bore  12 . By this action, the rock bolt  10  provides rock strata reinforcement. An expander mechanism that operates in this manner is disclosed in Australian Patent Application No 2017901751. 
     The trailing end of the bar  14  projects out of the bore  12  and thus forms a projecting end  15 . As shown in  FIG. 1 , a blind nut  16  is attached to the projecting end  15  and has a closed end  17 . By this arrangement, threading the blind nut  16  onto the projecting end  15  eventually brings the closed end  17  into contact with the end face of the projecting end  15 , so that further rotational movement of the blind nut  16  relative to the bar  14  is prevented. That is, any further rotation of the blind nut  16  results in combined rotation of the bar  14  and the nut  16 . By this mechanism, rotation of the nut  16  facilitates activation of the expander mechanism  28 . 
     Adjacent the blind nut  16  is a washer  18  and inward of the washer  18  is a ring  19 . The ring  19  is welded by weld  20  to the outer surface of the tube  11  and provides a bearing surface for a rock plate  21 . The rock plate  21  bears against wire meshing  25  and urges the meshing  25  into surface contact with the rock surface  26  of the rock strata  13 . The rock bolt  10  is supplied with the ring  19  welded in place against the tube  11  and is installed by applying the washer  18  and the blind nut  16  to one side of the ring  19  and the rock plate  21  to the other side. The wire meshing  25  can be positioned against the rock surface  26  and the tube  11  can then be passed through the meshing  25  and driven into the bore  12  by suitable driving equipment, such as under percussion hammering by a mining Jumbo. When the tube  11  has been driven to the required depth within the bore  12 , the blind nut  16  can be rotated to rotate the bar  14  and to activate the expander mechanism which is located towards the leading end of the tube  11 . With these steps completed, the rock bolt  10  is installed and the meshing  25  is firmly positioned against the rock surface  26 . The rock strata is thus reinforced against rock fracture and the rock surface  26  above the meshing  25  is contained against dislodgment of smaller fragments. 
     A second section of wire meshing will be required to be installed as further sections of rock surface are exposed. It is necessary that the new section of wire meshing overlap an existing section, so that no sections of the rock face are left un-contained or un-protected. Accordingly, the same rock bolt  10  that is used to secure the wire meshing  25  in place against the rock surface  26  can be used in accordance with the present invention to secure a second section of wire meshing  27 . In accordance with the invention, an adapter  30  is employed and this threads on to the blind nut  16 . In that respect,  FIG. 1  shows the thread  31  of the blind nut  16  that is applied to the outer hexagonal surface of the nut  16 . The thread is thus made through the corners and flats of the nut  16 , so that the nut  16  can be threaded onto the projecting end  15  of the bar  14  and used to drive rotation of the bar  14  to activate the expander mechanism within the split tube  11 . 
     The adapter  30  includes a thread  32  within a socket or connection portion  33  so that the adapter  30  can be threadably connected to the blind nut  16 . An extension or bar  35  having an external surface  56  is coaxial with the socket portion  33  and extends from the socket portion  33 . Preferably bar  35  comprises a thread  55  at external surface  56  for the connection of a nut  36  having a corresponding internal facing surface with complementary thread (not shown) mateable with the thread  55  of the bar  35 . Between the socket  33  and the nut  36  is a mesh clamp  37 .  FIGS. 3 and 4  show the adapter  30  in end and side views respectively and it can be seen that the adapter  30  includes a base  38  and a pair of arms  39  that extend to a ring  40  and the ring  40  in use, bears against a facing surface of the meshing  27  to push the meshing  27  into the position shown in  FIG. 2  in an overlapping arrangement with the existing edge of the meshing  25 . 
     The base  38  of the mesh clamp  37  includes a central opening  41  through which the bar  35  extends. It can be seen in  FIG. 1 , that the internal diameter of the opening  41  is greater than the external diameter of the bar  35  (including the thread that is applied to the bar  35 ), so that the mesh clamp  37  is a close but loose fit about the bar  35 . In particular, the opening  41  is not intended to threadably connect with the bar  35 . The nut  36  includes an opening  44  which accommodates a shear pin. The shear pin extends through the opening  44  and into a complementary opening  45  (see  FIG. 2 ) in the bar  35  and with the shear pin accommodated within the respective openings  44  and  45 , the nut is in fixed connection with the bar  35 . In that connected state, installation equipment can engage the nut  36  and rotate it. By that rotation, each of the bar  35  and the socket  33  will also be rotated. Accordingly, by rotating the nut  36  in fixed connection to the bar  35 , the socket  33  can be rotated to threadably connect with the nut  16  of the rock bolt  10 . This connected arrangement is illustrated in  FIG. 2 . 
     Each of  FIGS. 1 and 4  show the nut  36  in engagement with installation equipment, although only the nut engagement end of the equipment is illustrated in  FIG. 1 . That engagement is via a suitable socket or spanner  48 .  FIG. 4  shows schematically, the end of a boom or arm  49  of a mining Jumbo or other suitable equipment, which carries the spanner  48  and which drives the spanner to rotate. Once the bar  35  and socket  33  have been driven to the position in which the socket  33  is in full engagement with the nut  16  of the rock bolt  10 , further rotation of the nut  36  will shear the shear pin and will then allow the nut  36  to be rotated relative to the bar  35  in the normal manner of a nut, so that the nut  36  traverses along the bar  35 . The nut  36  can thus move from the position shown in  FIG. 1  to the advanced position shown in  FIG. 2  and with that movement, the nut  36  will engage against a facing surface of the base  38  of the mesh clamp  37  and drive it forward to the position shown in  FIG. 2  in which it clamps the meshing  27  in overlapping relationship with the meshing  25 . 
     Advantageously, it will be appreciated that the two separate rotation stages of the nut  36  can be performed with the spanner  48  in constant engagement with the nut  36 . Thus, the spanner  48  does not need to be disengaged from the nut  36  once engagement has been made, so that both the attachment of the adapter  30  to the rock bolt  10  and the clamping of the meshing  27  by the mesh clamp  37  is all undertaken with the spanner  48  in driving connection with the nut  36 . The installation of the meshing  27  via the adapter  30  is thus effectively a single stage operation. 
     Moreover, a significate advantage provided by the present invention is that the adapter  30  can be utilised in the raising and positioning of the meshing  27  for installation of the meshing  27  in overlapping relationship with the meshing  25 .  FIG. 4  shows in schematic form, the adapter  30  with the socket  33  extended through an opening in the meshing  27 . In that position, the socket  33  can hook the meshing  27  and when the boom  49  is lifted, the meshing  27  will also be lifted in connection with the adapter  30 . Thus, with the meshing  27  being lifted by the boom  49  as shown in  FIG. 4 , the boom  49  can position the socket  33  for connection to the nut  16  of the rock bolt  10  still with the meshing  27  attached to the adapter  30  as shown in  FIG. 4 . By this arrangement, there is no need for a separate lifting and positioning of the meshing  27  in overlapping position with the meshing  25 . In this arrangement, it is necessary for the outside diameter of the socket  33  to be sized sufficiently that it can fit through an opening in the meshing  27  but with those dimensions, the adapter  30  can be used to hook the meshing  27  and lift it for installation into the position shown in  FIG. 2 . This further enhances the single stage operation for installation of the meshing  27 , as compared to the prior art, in which meshing is firstly positioned where required and thereafter, an adapter and then a meshing plate are subsequently installed. 
     A further embodiment of the adaptor is described referring to  FIG. 5 . According to the further embodiment, connection portion  30  is formed as a cylindrical socket  33  having an external surface  56  comprising a thread  55  and an internal surface  57  comprising a thread  32 . Thread  32  is configured for mateable engagement with thread  31  of blind nut  16  secured to the trailing end  15  of elongate shaft  14 . Socket  33  further comprises an external surface  56  comprising a thread  55 . Threads  55  and  32  extend substantially the full axial length of socket  33  between respective forward and rearward axial ends. 
     According to the further embodiment, adaptor  30  further comprises body  36  comprising a nut head  50  and a nut collar  53  connected axially via a neck section  51 . As described referring to the embodiment of  FIGS. 1 to 4 , nut head  50  is engageable by engagement apparatus  48  to drive rotation of the body  36 . Mesh clamp  37  is secured over and about body  36 . In particular, opening  41  is positioned around neck  51  with the arms  39  extending over and about nut collar  53  and a portion of socket  33 . 
     Nut collar  53  comprises an internal cavity defined by an internal facing surface  54 . A thread  52  is provided at surface  54  for mateable engagement with thread  55  of connection portion  30 . Accordingly, connection portion  30  is configured for mating onto blind nut  16  and nut collar  53  is capable of mating onto connection portion  30  via the respective threads  52 ,  55 ,  32  and  31 . As described referring to  FIGS. 1 to 4 , a shear pin is securable through respective openings  44 ,  45  at nut collar  53  and connection portion  30  so as to temporarily and rotationally lock body  36  to connection portion  30  during an initial installation of the adaptor  30  onto the rock bolt  10 . As described previously, further rotation of body  36  provides a shearing of the pin inserted through holes  44 ,  45  to provide continued rotation of body  36  axially along connection portion  30  to force meshing  27  onto the rock surface  26  to be overlapping onto the pre-installed meshing  25 . 
     The present invention is expected to provide significant time savings in the installation of meshing and that advantage has significant benefits in terms of the securing unsecured rock faces quickly and efficiently, thus reducing the likelihood of rock fracture or fall within underground mines. That is, the sooner a rock face is protected by wire meshing, the sooner the section of underground mine is rendered safe to personal and equipment operating within the mine environment.