Patent Description:
Roof and wall support is vital in underground mining and tunnelling operations. Tunnel walls and roofs are typically formed from rock strata that requires reinforcement to prevent failure, fragmentation or collapse. Typically, a bore hole is formed in the rock strata by a drilling operation and then the rock bolt is installed into the as-formed bore where it is secured to provide reinforcement against major rock fracture and strata fragmentation.

Different forms of rock bolts have been developed including resin or cement grout bolts that are frictionally secured in the bore using a resin or grout introduced into the bore prior to the bolt which sets to lock the bolt into position. Mechanical friction rock bolts have expander mechanisms positioned towards a leading end that function to expand radially within the bore to prevent axial withdrawal. The trailing end of resin, grout and mechanical friction rock bolts typically project a short distance outside of the bore and remain visible. In some instances, the trailing end of the bolt is used for supporting ancillary fixtures such as containment meshing (via meshing plates), mining services utilities, pipes, cables etc. In some installations, the projecting end of the rock bolt can be threaded for connection of mechanical fixtures.

A locking nut at the trailing end of the rock bolt may be a blind nut which in the case of a mechanical friction bolt is configured to engage the rearward end of the bar such that further rotation of the nut provides a corresponding rotation of the bolt shaft to provide installation via a translated expansion of the expander mechanism. Typically, product information is stamped on an external exposed face of the locking nut that may include an alphanumeric code for material traceability, bolt ID etc. However, this exposed face is often damaged by the bolt installation driver tool as the bolt is hammered into the bore. Accordingly, such stamped information often becomes unreadable.

<CIT> discloses an inflatable friction boll wherein a central portion is radially expandable upon application of fluid pressure to an interior of the body and the trailing portion has an enlarged head. <CIT> relates to a rock bolt anchor mechanisms.

It is an objective of the present invention to provide a rock bolt configured to display information that is prevented from damage during bolt installation into a receiving bore hole in the rock strata so as to preserve the information to be capable of being displayed after bolt installation.

It is a specific objective to provide a locking nut for a rock bolt adapted to carry relevant information such as bolt identification (ID), material traceability information, manufacturer information, rock bolt type information, codes, logos, trademarks and other indicia to be visible to personnel within a mine tunnel where a rock bolt is installed for example in a wall or roof.

The objectives are achieved by providing a rock bolt having an axially rearward nut attached to an elongate shaft of the bolt with the nut having a recessed portion that in turn provides a display face that is axially recessed relative to an axially rearwardmost exposed face of the nut. As the display face is recessed axially (relative to the rearward exposed face), the display face is protected from the bolt driver tool and in particular the driver socket that is typically positioned over and about the nut to deliver the percussive hammering action.

Conventionally, bolt driver tools and in particular driver sockets are at least part tubular having a cylindrical inner cavity. Optionally, the nut of the rock bolt of the present invention is provided with a recessed portion having a diameter that is approximately equal to or less than a diameter of the internal cylindrical cavity of the driver socket such that no part of the driver socket is positioned in contact with or extends over the recessed portion and in particular the axially recessed display face. According to a preferred implementation, the recessed portion and the recessed display face are positioned centrally at a rearward facing exposed face of the nut with the exposed face being annular to extend around the recessed portion and the display face. In such an implementation, the driver socket and in particular an abutment contact area of the driver socket is adapted to sit into contact with the annular exposed face and not to overlay onto the recessed portion.

According to a first aspect of the present invention there is provided a rock bolt for installation within a bore formed in rock according to claim <NUM>.

Optionally, the nut is a blind or semi-blind nut optionally when used within a mechanical friction bolt system. Optionally, the nut may be non-blind to comprise a through-bore internally threaded between a first and second axial end, for example within a resin or cement grouted bolt system. The thread may extend completely or partially the axial length of the nut.

Optionally, the exposed face is annular and the display face is positioned centrally and surrounded by the exposed face. Optionally, the nut is semi-blind, the display face is annular and extends around a central opening into an internal threaded cavity of the nut. Optionally, the nut may be semi-blind and comprise a non-circular recess wall. Where the nut is fully blind, the display face may be circular, polygonal and in particular hexagonal or heptagonal.

Optionally, the bolt further comprises a tab mounted within the recessed portion and having an axially rearward facing tab display face. The tab may be disc-shaped, or at least part disc-shaped. Optionally, the tab may be generally planar or may be mushroom-shaped having a forward and a rearward facing face. The tab may comprise indicia provided at each of the forward and rearward faces. Accordingly, the tab may be positioned in two different orientations within the recessed portion. Optionally, the tab may be non-circular (e.g., hexagonal). Optionally, the tab may be non-planar and may comprise a head part and a shaft extending from the head. Preferably, the shaft is capable of locating within an opening of a semi-blind nut.

Preferably, the bolt further comprises indicia provided at the display face. The indicia at the display face of the nut may be additional to any indicia provided at the tab display face(s). Accordingly, the information at the display face of the nut may be the same or different to the information provided on the display face(s) of the tab.

Optionally, an outside surface of the nut comprises a polygonal, square or hexagonal cross sectional profile. Such a configuration provides a nut that is conveniently engageable and drivable by conventional bolt drive apparatus having an engaging driver socket.

Preferably, the nut comprises threads at the outside surface. This is beneficial for attachment of auxiliary fixtures to the nut with such auxiliary fixtures having an internally threaded socket for the threading onto the outside surface of the nut.

Optionally, the recessed portion comprises an undercut such that a diameter of the recessed portion increases in an axial direction from the exposed face. Optionally, the recessed portion may be provided with an adhesive, crimping, weld or at least one radial projection extending radially to overlay at least a portion of the tab. Optionally, where the recessed portion comprises an undercut, the tab may be secured within the recessed portion by abutment underneath the undercut. Optionally, the recessed portion may be threaded such that the tab may be screwed into the recessed portion via a suitable forked tool or other engagement tool.

Preferably, an axial thickness of the tab is less than an axial depth of the recessed portion. In particular, a thickness of the tab is less than a minimum axial depth of the recess portion, where the recessed portion depth is non-uniform at the nut. Optionally, a distance by which the display face is recessed axially relative to the exposed face is less than a radial wall thickness of the nut. Optionally, said distance is less than a thickness of an end wall of a semi-blind or fully blind nut.

Optionally, the rock bolt may be a resin, cement grouted or mechanical friction bolt or any other bolt with a nut.

The present locking nut is suitable for use with a variety of different types of rock bolt including resin, cement grout and mechanical friction rock bolts where the nut is attachable via cooperating screw threads to a trailing end of an elongate shaft of the rock bolt. The present locking nut according to its use with different types of rock bolt, may be used to actuate an expander mechanism within a mechanical friction rock bolt and/or to secure a rock or meshing plate against the rock strata at the region around the bore hole within which the rock bolt is mounted. According to all the implementations, the present locking nut is internally threaded and adapted for releasable securing onto the threaded trailing end of an elongate shaft extending through the rock bolt.

For the purposes of describing the aspects of the present invention, a locking nut configured for the display of information is described with reference to a mechanical friction bolt. In particular, and referring to <FIG>, a friction rock bolt assembly <NUM> is configured for mounting and securement within a bore <NUM> extending within a rock strata <NUM>. The friction bolt <NUM> is generally elongate being centred on longitudinal axis <NUM> and comprises primarily an elongate tube <NUM> that is split axially; an expander mechanism indicated generally by reference <NUM>; and an anchor mechanism indicated generally by reference <NUM>. Expander mechanism <NUM> is mounted towards a leading end <NUM> of tube <NUM> whilst anchor mechanism <NUM> is positioned towards a trailing end <NUM> of tube <NUM>. In particular, anchor mechanism <NUM> projects rearwardly from tube <NUM> and is positioned at and extends from an open end of bore <NUM> adjacent a surface <NUM> of the rock strata <NUM> that surrounds the bore open end.

Expander mechanism <NUM> may be formed from a pair of cooperating wedges <NUM>, <NUM>. A first wedge <NUM> is formed generally as a collar having an internal bore with radially inwardly facing threads to engage and cooperate with corresponding threads <NUM> provided at a first leading end <NUM> of an elongate bar <NUM> that extends axially through tube <NUM> from tube trailing end <NUM> to tube leading end <NUM>. First wedge <NUM> is accordingly axially adjustable at bar <NUM> via the respective threads. Second wedge <NUM> is mounted rigidly to an internal facing surface <NUM> of tube <NUM> at a position towards tube leading end <NUM>. The first and second wedges <NUM>, <NUM> each comprise a respective engaging surface <NUM>, <NUM> aligned transverse to axis <NUM>. Accordingly, by linear axial adjustment of first wedge <NUM> along bar <NUM>, engaging surface <NUM> of first wedge <NUM> abuts engaging surface <NUM> of second wedge <NUM> so as to force the first wedge <NUM> radially outward from axis <NUM> and against tube internal surface <NUM>. The radial expansion of expander mechanism <NUM> acts to force and deform tube <NUM> radially outward against the internal facing surface of bore <NUM> to lock the friction bolt assembly <NUM> within the bore <NUM>.

Linear axial movement of first wedge <NUM> is provided by anchor mechanism <NUM> that comprises an internally threaded nut <NUM> mounted to a second trailing end <NUM> of bar <NUM>. Accordingly, rotation of nut <NUM> about axis <NUM> provides a corresponding rotation of bar <NUM> that, in turn, pulls the first wedge <NUM> towards tube trailing end <NUM> (via threads <NUM>) to provide the radial expansion force. Anchor mechanism <NUM> further comprises a washer <NUM> (alternatively termed a gasket) having a central aperture <NUM> to sit about and around bar <NUM> at trailing end <NUM>. Gasket <NUM> is formed non-integrally with nut <NUM>, tube <NUM> and other components of the bolt assembly <NUM> so as to be an independent component. Gasket <NUM> projects radially outward from bar <NUM> and tube <NUM> such that an abutment surface <NUM> that is orientated generally axially towards tube leading end <NUM> extends radially outward beyond a radially external facing surface <NUM> of tube <NUM>. Gasket <NUM> and surface <NUM> extend radially outward beyond tube external surface <NUM> by a distance that is approximately equal to or greater than a corresponding radial distance by which gasket <NUM> projects radially inward from tube internal surface <NUM> towards bar <NUM> that is centred on axis <NUM>. As will be appreciated, the distance by the gasket <NUM> extends radially beyond the tube wall may be varied and selected to suit specific applications. Accordingly, gasket <NUM> provides a radially outward extending flange at the tube trailing end <NUM> and bar trailing end <NUM>. Gasket <NUM> accordingly projects radially outward beyond the diameter of bore <NUM> (formed within the rock strata <NUM>) such that at least a radial outer region of abutment surface <NUM> is capable of being braced, either directly or indirectly, against the rock strata surface <NUM> that surrounds radially the bore open end.

According to the specific implementation, the friction rock bolt assembly <NUM> comprises a rock plate indicated generally by reference <NUM> that is formed as a profiled generally annular gasket having a radially outer portion and a corresponding radially inner portion. The radially outer portion comprises a generally annular (or in other instances rectangular) abutment surface <NUM> configured to sit against the rock strata surface <NUM> whilst the inner portion terminates as an annular edge <NUM> that defines a central hole having a diameter slightly greater than a diameter of tube <NUM> but less than a corresponding diameter of gasket <NUM>. In particular, the radially inner edge <NUM> of rock plate <NUM> is configured to abut gasket surface <NUM> such that gasket <NUM> is braced against the rock strata surface <NUM> via rock plate <NUM>. Accordingly, gasket <NUM> projects radially outward from tube <NUM> to provide an appropriate radial overlap between the radially inner portion of rock plate <NUM> and a radially outer portion of gasket <NUM> in turn allowing gasket <NUM> to be braced against rock plate <NUM> which is, in turn, braced against rock strata surface <NUM> either directly or via an intermediate meshing sheet (not shown) to provide containment of the rock strata at a tunnel wall or roof. Tube trailing end <NUM> according to the specific implementation, is devoid of a ring or collar (not shown) positioned externally at tube external surface <NUM>. Such a ring or collar may be welded to trailing end <NUM> to provide a region of abutted mating with the radially inner edge <NUM> of rock plate <NUM>. According to further embodiments, gasket <NUM> may be configured to sit directly against the rock strata <NUM> via respective abutment between abutment surface <NUM> and rock surface <NUM>.

Referring to <FIG>, nut <NUM> comprises an outside surface <NUM> having a polygonal and in particular hexagonal cross sectional profile. Threads <NUM> are provided at outer surface <NUM> so as to provide mounting of auxiliary fixings to nut <NUM> either before or once bolt <NUM> is mounted and secured in position within bore <NUM>. Nut <NUM> comprises a generally cylindrical internal cavity <NUM> defined by a radially inward facing inner surface <NUM> onto which threads <NUM> are formed. Threads <NUM> extend substantially the full axial length of nut <NUM> between an axially forward facing annular contact face <NUM> and a semi-blind innermost end of cavity <NUM> defined by an end wall <NUM>. An opening <NUM> is formed within end wall <NUM>. However, according to further implementations, end wall <NUM> may be solid across the full diameter so as to define a fully blind nut <NUM>. An axially rearward end of nut <NUM> is defined by an axially rearward facing annular exposed face <NUM> that represents an axial end of nut wall <NUM> that define internal cavity <NUM>. The rearward end of nut <NUM> is further defined by end wall <NUM> and opening <NUM>.

According to the specific implementation, a recessed portion indicated generally by reference <NUM> is provided at the axially rearward end of nut <NUM> at the region of end wall <NUM>. In particular, the central region of exposed face <NUM> is recessed axially inward such that a display face <NUM> (that represents an axially rearward facing surface of end wall <NUM>) is recessed axially relative to exposed face <NUM>. Display face <NUM> is annular to surround circular opening <NUM> and is in turn surrounded by the annular exposed face <NUM>. According to the specific implementation, an axial distance by which display face <NUM> is recessed axially relative to exposed face <NUM> is less than a thickness of nut wall <NUM> and in particular is less than <NUM>%, <NUM>%, <NUM>% of the wall thickness and may be in the range <NUM> to <NUM>% or <NUM> to <NUM>% of a thickness of nut wall <NUM>.

Referring to <FIG>, recessed portion <NUM> may be formed with an undercut <NUM> such that a diameter of the recess from exposed face <NUM> increases in the axial direction from exposed face <NUM> towards end wall <NUM>. According to the embodiments of <FIG> and <FIG>, a display tab <NUM> having a disc-like configuration is capable of being mounted within recessed portion <NUM>. According to the embodiment of <FIG>, tab <NUM> may be secured by abutment contact underneath the undercut <NUM> that forms a securing lip around the perimeter of tab <NUM>.

Accordingly, tab <NUM> may be formed from a resiliently deformable and/or flexible material such as a metal or a polymer. Accordingly, tab <NUM> is secured in position by frictional contact between undercut <NUM> and wall <NUM> and is positioned in contact with and overlaying display face <NUM> (<FIG>). A thickness of tab <NUM> is less than the axial depth of recessed portion <NUM> such that tab display face <NUM> is aligned coplanar or preferably is recessed relative to exposed face <NUM>.

The recessed display face <NUM> at end wall <NUM> is capable of displaying information relative to the rock bolt <NUM>, the region of installation, the manufacturer of the components described herein, the installer or other relevant information including materials, dates, product codes, logos, trademarks etc. In particular, display face <NUM> is capable of displaying indicia that may be marked, printed, etched, stamped or in other ways adhered to face <NUM>. As will be appreciated, the same or similar information may be provided at tab display face <NUM> with such information being additional or alternative to the information displayed at end wall display face <NUM>.

The present arrangement of nut <NUM> is advantageous as detailed with referent to <FIG> by avoiding damage to the display faces <NUM>, <NUM> by a bolt driver tool and in particular driver socket <NUM> that is brought into contact with nut <NUM> for percussive hammering of the rock bolt <NUM> into the bore <NUM>. In particular, driver socket <NUM> comprises an annular leading end face <NUM> for abutment contact against gasket <NUM>. An internal cavity <NUM> extends axially from end face <NUM>. A shoulder <NUM> projects radially inward at an axially inner end of cavity <NUM> to define an annular cavity end face <NUM>. A generally cylindrical bore <NUM> extends axially rearward from cavity end face <NUM> and is defined by a radially inward facing surface <NUM>. Preferably, a diameter of recessed portion <NUM> and in particular display face <NUM> is approximately equal to or less than a diameter of driver socket bore <NUM> such that no part of driver socket <NUM> is capable of abutment contact with display face <NUM> of wall <NUM> and/or tab display face <NUM>. As will be appreciated, driver socket <NUM> may vary in design and may not include central bore <NUM> such that cavity end face <NUM> is circular and is capable of being brought into full abutment contact against the rearward facing end face of nut <NUM>. Via the recessed portion <NUM>, driver socket end face <NUM> abuts only the exposed face <NUM> so as to protect and preserve the information (indicia) <NUM> provided at the respective display faces <NUM>, <NUM>.

Claim 1:
A rock bolt (<NUM>) for installation within a bore (<NUM>) formed in rock strata (<NUM>) comprising:
an elongate shaft (<NUM>) having a leading end for installation into the bore (<NUM>) and a threaded trailing end (<NUM>) to project from an open end of the bore (<NUM>);
an internally threaded nut (<NUM>) attached at the trailing end (<NUM>) to mount a rock plate (<NUM>) against a surface (<NUM>) of the rock strata (<NUM>), the nut (<NUM>) having an axially forward facing contact face (<NUM>) for positioning opposed to the rock plate (<NUM>) and an axially rearward facing exposed face (<NUM>);
a recessed portion (<NUM>) extending axially inward from the exposed face (<NUM>) and defining an axially rearward facing display face (<NUM>), for displaying information relative to the rock bolt (<NUM>), being axially recessed relative to the exposed face (<NUM>);
characterised by:
a tab (<NUM>) mounted within the recessed portion (<NUM>) and having an axially rearward facing tab display face (<NUM>).