ROCK PLATE AND ANCHOR ASSEMBLY

Abstract

 A rock plate and anchor assembly 22 comprising a rock plate 24 and a barrel and wedges anchor 26. The barrel and wedges anchor 26 comprising an external barrel 34 and internal cable gripping wedges 38. The barrel 34 having a leading end and a trailing end. The leading end being fixed to the rock plate by a join 62 that fixes the rock plate 24 and the barrel and wedges anchor 22 together in an assembly position. The join 62 providing a resistance load that resists movement of the rock plate 24 relative to the barrel and wedges anchor 26 from the assembly position. The rock plate 24 being movable relative to the barrel and wedges anchor 26 from the assembly position upon an external load being applied to the rock plate 24 that is greater than the resistance load of the join 62 and that is applied in a direction to move the rock plate 24 relative to the barrel and wedges anchor 26.

Description

Technical Field

[0001] The present invention relates to a rock plate and anchor assembly for use with cable rock bolts and to cable rock bolts and cable rock bolt installations.

Background of Invention

[0002] The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

[0003] Rock bolts for use in underground mining include solid bar rock bolts and cable rock bolts. Solid bar rock bolts employ a rigid bar or rod and because the bar is rigid, the maximum length of the rock bolt is determined by the position and orientation in which it is to be installed and the dimensions of the space in the area installation. For example, if the rock bolt is to be installed in the roof of a mine tunnel perpendicular to the floor of the tunnel, then the length of the bolt can be no longer than the height of the tunnel.

[0004] In contrast, because cable rock bolts employ a flexible cable rather than a solid bar, cable rock bolts have the benefit that the length of the bolt can be greater than the dimensions of the space in the area of installation because the cable can be fed into a hole from a direction not aligned with the hole. Advantageously, the length of a cable rock bolt can be significantly greater than the height of the mine tunnel and in many circumstances, many times greater than the height of the tunnel.

[0005] A typical cable bolt installation involves drilling a hole into the wall of the mine, such as a 10m hole. A resin or a cement grout is then pumped into the hole and then the cable is inserted through the reason or grout.

[0006] An expansion anchor can be attached to the leading end of the cable prior to insertion of the cable into the hole and once the expansion anchor is in place at the inner end of the hole, the expansion anchor can be activated by applying tension to the cable to secure the leading end of the cable within the hole. A rock plate can be attached to the trailing end of the cable to bear against the facing surface of the rock body in which the cable bolt is installed and a rock plate anchor can be used to grip the trailing end of the cable just beyond the rock plate to retain tension that is applied to the cable. Tension that is applied to the cable can vary depending on the type of rock in which the rock bolt is installed, but can be in the order of up to 100 Nm. The rock plate anchor that is applied at the trailing end of the cable is usually a barrel and wedges anchor.

[0007] The use of an expansion anchor to secure the leading end of the cable within the hole is beneficial in that it secures the cable from falling out of the hole as soon as it is activated and prior to the resin or cement grout curing and once a rock plate and rock plate anchor have been installed at the trailing end of the cable and the cable is tensioned, the rock bolt provides instant support to the rock body in which the cable bolt is installed. This allows installation personnel to immediately access the bolted area safely, in contrast to having to wait for the resin or cement grout to cure, which can take in the order of 24 hours.

[0008] A disadvantage with current cable bolt installation, is that installation personnel need to attach both the expansion anchor and the rock plate and rock plate anchor manually to the leading and trailing ends of the cable as the cable bolts are installed. This is disadvantageous, because the area is not deemed to be safe until the area is suitably bolted.

[0009] Moreover, the application of the three components, the expansion anchor, the rock plate and the rock plate anchor, to leading and trailing ends of a cable, takes time and so different arrangements which are quicker, or which do not require the presence of installation personnel in the bolting area, are desirable.

[0010] The rock plate and the rock plate anchor are in firm engagement with each other once the cable has been tensioned and the cable bolt is operational. The engaging surfaces of the rock plate and the rock plate anchor allow movement, predominantly rotational movement, between the rock plate and the rock plate anchor where necessary to accommodate installations in which the rock face against which the rock plate bears is not perpendicular to the axis of the hole in which the cable and expansion anchor have been inserted. In these installations, the rock plate anchor will remain generally aligned with the axis of the hole, while the rock plate will reorient to sit flat against the rock face about the hole. The rock plate needs to be able to rotate or pivot relative to the rock plate anchor through 360° as the alignment of the rock face relative to the hole is random. This requirement has necessitated the separation of the rock plate and the rock plate anchor to allow freedom of movement between these two components.

[0011] The present invention has been developed in relation to cable bolts that employ rock plate and the rock plate anchors of the above general kind, but the invention has been developed with the aim to overcome or at least alleviate one of more of the drawbacks associated with the prior art arrangements.

Summary of Invention

[0012] According to the present invention there is provided a rock plate and anchor assembly comprising:

i. a rock plate and

ii. a barrel and wedges anchor,

i. the barrel and wedges anchor comprising an external barrel and internal cable gripping wedges, the barrel having a leading end and a trailing end, the leading end being fixed to the rock plate by a join that fixes the rock plate and the barrel and wedges anchor together in an assembly position,

ii. the join providing a resistance load that resists movement of the rock plate relative to the barrel and wedges anchor from the assembly position,

iii. rock plate being movable relative to the barrel and wedges anchor from the assembly position upon an external load being applied to the rock plate that is greater than the resistance load of the join and that is applied in a direction to move the rock plate relative to the barrel and wedges anchor.

[0013] A rock plate and anchor assembly according to the present invention advantageously forms a single or unitary component or device for attachment to the cable of a cable rock bolt. This means that if manual application of the assembly to the cable of a cable rock bolt, the application will be quicker and easier. However, the assembly according to the present invention is also suitable for automatic application to the cable of a cable rock bolt and development of suitable automation should allow for the application of both an expansion anchor and a rock plate and anchor assembly to a cable without the presence of installation personnel.

[0014] A rock plate and anchor assembly also beneficially takes a single or unitary component form for application to a cable, but the join or connection between the rock plate and the anchor assembly can allow movement of the rock plate relative to the barrel and wedges anchor if the rock face against which the rock plate bears is not perpendicular to the axis of the hole in which the cable and expansion anchor have been inserted. The join or connection therefore does not restrict use of the rock plate and anchor assembly to only installations in which the rock face is perpendicular to the axis of the hole in which the cable and expansion anchor have been inserted (which is very often not the case), but rather can be used for those installations as well as for installations in which the rock face is not perpendicular to the axis of the hole.

[0015] The movement that the rock plate will undergo relative to the anchor can include, but is not restricted to rotational, angular or pivoting movement. Some lateral or linear movement may also occur. The exact motion that can occur between the rock plate and the anchor can be complex and not necessarily just one of these types of movement.

[0016] The anchor will generally retain its position on installation and the rock plate will move, with the movement mainly comprising rotation or pivoting about the leading end of the barrel. The movement can be relatively minor or small, as the rock surface will generally be close to perpendicular to the axis of the hole and so rotation through angles of up to 20° is what is considered to be expected, but with most angles of rotation being with 0° to 10°. It is to be noted that the barrel can also move, so that there can be installations in which both of the rock plate and anchor move from their starting positions in the assembly position, or even installations in which just the anchor moves from its starting position in the assembly position.

[0017] The external load which is applied to the anchor is one which is applied most likely if the rock face and the rock plate are not parallel as the rock plate is pressed against the rock face during installation of the rock plate and anchor assembly. This will normally be the case if the rock face is not perpendicular to the axis of the hole. Where the rock face is at an angle to the axis of the hole, even at a slight angle, one part of the rock plate, such as an edge of the rock plate, will engage the rock face ahead of other parts of the rock plate and that part of the rock plate will be subject to the external load that causes the rock plate to tip or rotate, ie move, relative to the anchor. As the rock plate is pressed into engagement with the rock face, the rock plate continues to tip or rotate in order for the rock plate to engage flat against the angled rock face. The connection between the rock plate and the anchor is provided to allow that relative movement and thus to allow proper engagement between the rock plate and the rock face. That is, the rock plate is intended to have broad or flush engagement with the rock face about the hole and where the rock face is at an angle to the axis of the hole, the rock plate needs to be able to tip, rotate or pivot or otherwise move relative to the anchor to engage flat against the rock face. The anchor can remain axially aligned with the hole despite any movement or reorientation of the rock plate relative to the anchor, although in some installations, there can also be movement of the anchor from the assembly position relative to the rock plate.

[0018] It is to be noted that the rock face will not generally be a smooth, planar or completely flat face against which the rock plate can engage, but typically the rock face area for engagement by the rock plate will generally be at one general angle of inclination.

[0019] It is also to be noted that the assembly position is not necessarily a rigid position between the rock plate and the barrel and wedges anchor, although it can be a rigid position depending on the type of join that is employed to join the leading end of the barrel to the rock plate. It will be evident from the discussion that follows, that some joins will rigidly secure the barrel relative to the rock plate, whereas other joins could allow some slight or minor relative movement between the rock plate and the anchor which is sufficiently slight or minor to be acceptable and to not disturb the single or unitary construction of the assembly.

[0020] The join between the rock plate and the barrel and wedges anchor can be any suitable join that maintains the rock plate and anchor in the assembly position until such time as the external load is applied to the rock plate during installation of the rock plate and anchor assembly. Such suitable joins include frangible joins, whereby the join breaks or fractures upon the external load being applied to the rock plate to free the rock plate from restraint against movement relative to the anchor and to allow the rock plate to move into a position for engagement flush against the rock face. These types of joins will largely be rigid joins.

[0021] Suitable frangible joins comprise tack weld joins. A single tack weld join can be made between the leading end of the barrel and the rock plate, or multiple tack weld joins can be made. Multiple tack weld joins can comprise a pair of tack weld joins that are spaced apart diametrically, or three or four tack weld joins that are spaced apart equidistantly, although it is to be appreciated that equidistant spacing is not required.

[0022] Suitable tack weld joins can be made at the join between the rock plate and the leading end of the barrel either from outside the rock plate and anchor assembly, or inside the assembly.

[0023] While the terminology "tack weld" is employed above, such welds can alternatively be spot welds, or any other light weld that is considered frangible, such that it can be broken or fractured when the external load is applied to the rock plate.

[0024] An alternative form of frangible join is a glue join. Like the tack weld joins discussed above, a single spot of glue could be applied between the rock plate and the leading end of the barrel, or multiple spots of glue could be applied. Still further, a single and continuous line of glue could be applied fully about the connection or engagement between the leading end of the barrel and the rock plate. The characteristics of the selected glue may influence the amount of glue that is applied. A stronger glue may require one or several spot applications, while a weaker glue my require additional spot applications, or a continuous line.

[0025] Another alternative form of frangible join can be a plastic clip that connects between the anchor and the rock plate and that fails when the external load is applied to the rock plate. The clip could extend externally for example, from the trailing end of the barrel to opposite edges of the rock plate. Alternatively, the clip could extend from the trailing end of the barrel through the internal cable gripping wedges and clip to the rock plate. Clearly the clip could take any suitable form as long as it can engage each of the anchor and the rock plate and retains them in the assembly position until an external load is applied to the rock plate during installation of the rock plate and anchor assembly. The clip could be sacrificial such that it disintegrates upon the external load being applied, or it could be flexible so that it stretches or deforms upon the external load being applied but remains in place.

[0026] Other forms of joins can be flexible or malleable or deformable, whereby the join flexes or deforms to upon the external load being applied to the rock plate to allow the rock plate to move relative to the barrel and wedges anchor. For example, the join could be formed by a flexible strap or sleeve such as a rubber or polymer strap or sleeve. Such a strap or sleeve may fail upon the external load being applied, although alternatively, the strap or sleeve may simply stretch or elongate under the external load, either resiliently or permanently. A strap could extend fully or continuously about the rock plate and anchor assembly, extending over the top of the barrel and about the rock plate. The strap might overlie the opening into the wedges of the barrel, but the strap may be formed of a material that a cable can push through to enter the barrel and wedges anchor.

[0027] Other forms of flexible joins include wrapping joins whereby the rock plate and anchor assembly is wrapped in shrink wrap, or a plastic film, or a fibre netting for example, and during installation, the cable of the cable rock bolt pushes through the wrapping to enter the barrel and wedges anchor. Indeed any suitable fabric could be employed to wrap about the rock plate and anchor assembly and to maintain the rock plate and the anchor in the assembly position. The wrapping might completely encompass the rock plate and anchor assembly, or extend about a portion of the assembly.

[0028] It is to be understood that the type of join that is applied only needs to be effective in maintaining the assembly position between the rock plate and the anchor. Once the rock plate and the anchor are displaced from the assembly position under the influence of the external load, the join is no longer required because the rock plate and anchor will then be held together by the tension in the cable. Accordingly, displacement, failure or disintegration of the join is acceptable. Likewise, continued connection of the join is acceptable where the joins are flexible or deformable, as long as the continued connection does not prevent the resistance load applied by the join being overcome by the external load.

[0029] The rock plate and anchor assembly can additionally comprise a cap that is connected to the trailing end of the barrel to overlie the internal wedges and to thus prevent release of the wedges from the barrel when the wedges are not otherwise constrained within the barrel. The cap can allow the internal wedges to move axially and radially within the barrel so that the wedges can assume a radially expanded position to allow or accept passage of a cable into and through the anchor. The cap can comprise an end wall and a side wall. The end wall can overlie the internal wedges when the cap is fitted to the anchor and the end wall can have an opening that is axially aligned with a cable passage through the internal wedges so that a cable can be inserted through the cap opening and then through the wedges. The side wall can extend from the end wall, such as from the periphery of the end wall and it can extend generally perpendicular to the end wall. The side wall can connect to the trailing end of the barrel. The side wall can be a circular wall or skirt.

[0030] The cap can connect to the trailing end of the barrel by an internal thread that is formed on the inside surface of the side wall that threads on to a complementary thread formed on an outer surface of the trailing end of the barrel. The cap can thread onto the barrel to the point at which a bottom edge of the side wall that is remote from the end wall, engages against an abutment of the barrel. The abutment can be a shoulder for example, that extends from adjacent the barrel thread. The bottom edge of the side wall can engage against an abutment of the barrel prior to the end wall of the cap engaging against the wedges. This ensures that a gap or space is provided between the end wall and the wedges so that the wedges can move axially and radially within the barrel as discussed above, and ensures that the cap cannot be threaded onto the trailing end of the barrel to the point at which it engages the wedges and prevents wedge movement.

[0031] An alternative form of cap includes an end wall and a side wall, and a flange that extends from the side wall, such as a bottom edge of the side wall of that is remote from the end wall. The flange can be a part circular flange that extends partially about the bottom edge of the side wall. The flange can be a tab for example. Two or more tabs can be spaced apart about the bottom edge. Alternatively, the flange can be a circular flange that extends fully about the bottom edge. The flange provides the opportunity to attach the cap to the barrel by one or more screws that can be screwed through the flange and into a facing surface of the barrel such as a shoulder of the barrel. The flange can be pre-drilled with screw holes and the barrel can include threaded openings to accept the screws.

[0032] The present invention also provides a method of installing a cable rock bolt into a pre-drilled hole, the method comprising:

a. aligning a leading end of a cable with a rock plate and anchor assembly of the kind described above,

b. feeding cable through the rock plate and anchor assembly,

c. attaching an expansion anchor to the leading end of a cable,

d. feeding the cable through the rock plate and anchor assembly and pushing the expansion anchor into the pre-drilled hole,

e. once the expansion anchor has been pushed into the hole to an expansion location, gripping a trailing end of the cable and applying tension to the trailing end to activate the expansion anchor and to activate the barrel and wedges anchor to retain the tension in the cable.

[0033] The method of the invention can further comprise cutting the cable behind the rock plate and anchor assembly to leave the trailing end of the cable extending through the rock plate and anchor assembly after the expansion anchor has been pushed into the hole to an expansion location and before tension is applied to the trailing end of the cable.

[0034] The rock plate and anchor assembly of the present invention can be provided as a supply of rock plate and anchor assemblies in bolting equipment. This allows a rock plate and anchor assembly to be selected from the supply and to be placed in alignment with a leading end of the cable, for the cable to be pushed through the assembly. The leading end of the cable can then be pushed through an expansion anchor and then pushed into a hole. Advantageously, the rock plate and anchor assembly can be picked up and placed by a robotic arm that is controlled by the operator of the bolting equipment, without the need for installation personnel to be present as in prior art arrangements.

[0035] The rock plate and anchor assembly of the present invention can alternatively be provided as a supply of rock plate and anchor assemblies and whereby a conveyor or shuttle arrangement is provided that is capable of taking a rock plate and anchor assembly from the supply of rock plate and anchor assemblies and conveying or shuttling the selected rock plate and anchor assembly into alignment with the leading end of the cable of a cable rock bolt for passage of the cable through the rock plate and anchor assembly.

[0036] The present invention also provides a cable rock bolt, comprising a cable that has a leading and trailing end, an expansion anchor being attached to the leading end of the cable and a rock plate and anchor assembly of the kind described above being attached to the trailing end of the cable.

[0037] The present invention also provides an installation of one or more cable rock bolts installed according to the method described above, or an installation utilising cable rock bolts of the kind described above.

Brief Description of Drawings

[0038] In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:

Figure one shows a prior art bolt installation.

Figure 2 is a perspective view of a rock plate and anchor assembly according to one embodiment of the present invention.

Figure 3 is an exploded view of the rock plate and anchor assembly of Figure 2.

Figure 4 is a cross-sectional view of the rock plate and anchor assembly of Figure 2.

Figure 5 is a side view of the rock plate and anchor assembly of Figure 2.

Figure 6 is a sequence of installation steps for a cable rock bolt in accordance with the present invention.

Figure 7 is an underneath view of a rock plate and anchor assembly according to another embodiment of the present invention.

Figure 8 is a top view of a rock plate and anchor assembly according to another embodiment of the present invention.

Figure 9 is a cross-sectional view of the rock plate and anchor assembly of Figure 8.

Figure 10 shows an installation of a rock bolt according to the present invention.

Figure 11 is a cross-sectional view of rock plate and anchor assembly according to another embodiment of the present invention.

Detailed Description

[0039] As background to the present invention, Figure 1 illustrates cable rock bolt 10 that has been installed within a drilled hole 12. The rock bolt 10 has an expansion anchor 14 at the leading end of the cable 16 of the rock bolt 10 and the cable 16 extends out of the open end of the hole and through a rock plate 18 and a second anchor 20. The second anchor 20 as shown is a barrel and wedges form of anchor.

[0040] The cable bolt 10 is installed by attaching the expansion anchor 14 to the leading of the cable 16 and pushing the cable 16 into the hole 12. The rock plate 18 and the second anchor 20 can be either attached to the trailing of the cable 16 once the cable 16 has been pushed fully into the hole 12, or the cable 16 can be fed through the rock plate 18 and the second anchor 20 as the expansion anchor 14 and the cable 16 are fed into the hole 12. The hole 12 is usually filled with grout or resin and the expansion anchor 14 pushes through the grout or resin to the inner end of the hole 12.

[0041] Regardless of when the rock plate 18 and the second anchor 20 are attached to the trailing end of the cable 16, once the cable 16 has been pushed fully into the hole 12, tension can be applied to the trailing end of the cable 16 to activate the expansion anchor 14 in order to anchor the leading end of the cable 16 within the hole 12. Further tension can then be applied to the cable 16 to pull the trailing end of the cable 16 through the anchor 20. The anchor 20 allows the cable to the pull through it in one direction but secures the cable against return movement, or movement in the opposite direction. Accordingly, tension that is applied to the cable 16 is retained in the cable 16 by the anchor 20.

[0042] The anchor 20 bears against the rock plate 18 and presses the rock plate 18 against the rock surface that surrounds the opening to the hole 12. Interaction between the cable and the hole via the grout or resin, as well as load imposed by the rock plate against the rock surface, supports the rock strata in which the cable bolt 10 is installed. Multiple cable bolts 10 are installed across a rock face to support the rock strata against fracture and collapse.

[0043] The present invention relates to the rock plate and anchor assembly attached to the trailing end of the cable of cable rock bolts. Figure 2 is a perspective view of a rock plate and anchor assembly 22 according to the present invention. The rock plate and anchor assembly 22 comprises a rock plate 24 and a barrel and wedges anchor 26. The rock plate 24 Is a generally flat and square plate but it has a raised central section 28 that includes a circular bearing surface 30 (see Figure 3) for bearing engagement with the anchor 26. A cap 32 is fitted to the top of the anchor 26.

[0044] The barrel and wedges anchor 26 comprises a barrel 34 and a wedge arrangement 36. The wedge arrangement 36 comprises three separate wedges 38 (only two of which are visible in Figure 3). The wedges 38 fit together as shown in Figure 3 and form a central opening or passage through which the cable of a cable bolt can extend. The central opening is generally cylindrical and of generally constant radius between the opposite ends of the wedge is 38 and the wedges 38 can move radially inwardly and outwardly so as either to grip the outside surface of the cable, or to allow the cable to move through the wedges 38 and thus the wedge arrangement 36, such as during installation of a rock bolt that includes the rock plate and anchor assembly 22.

[0045] The relative radial position of the wedges 38 is dependent on the axial position of the wedges 38 within the barrel 34. As can be seen in Figure 3, The outer surface of the wedges 38 is tapered or inclined, so that the assembly of the wedges 38 has an outer conical shape. The internal surface of the barrel 34 is likewise tapered, so that as the assembly of the wedges 38 pushes into the barrel 34, the wedges 38 radially contract, while movement of the assembly of the wedges 38 in a direction out of the barrel 34 allows the wedges 38 to expand radially. It will be clear, that radial contraction of the wedges 38 facilitates gripping of a cable, whereas radial expansion of the wedges 38 reduces or removes gripping load to allow the cable to pass through the anchor 26.

[0046] Radial contraction and expansion of the wedges 38 takes place based on the direction of movement of a cable within the anchor 26. Accordingly, movement of a cable within the anchor 26 in the direction of arrow A tends to push the wedges 38 in a direction out of the barrel 34 and allows the wedges 38 to expand radially and to slip against the outside surface of cable. In contrast, movement of a cable within the anchor 26 in the opposite direction to arrow A tends to push or draw the wedges 38 into the barrel 34, causing the wedges 38 to radially contract or close about the outside surface of cable and to grip the outside surface. Thus, as described in relation to Figure 1, the anchor 26 allows a cable to the pull through it in one direction to install the rock bolt, but it grips the cable and thus secures the cable against return movement, thus maintaining tension that is applied to the cable.

[0047] Returning to Figures 2 and 3, the cap 32 has a central opening 40 through a top wall 42 and a circular side wall or skirt 44. The cap 32 aligns with the passage through the wedges 38 so that a cable that extends through the wedges 38 can extend through the central opening 40. The cap 32 has an internal thread 46 formed on the inside surface of the skirt 44 that threads on to the thread 48 of the barrel 34. The cap 32 threads onto the barrel 34 to the point at which the bottom edge 50 of the skirt 44 engages against the axial face 52 of the barrel 34. This is shown in Figure 4, which is a cross- sectional view taken through IV-IV of Figure 5.

[0048] The central opening 40 of the cap 32 allows the rock plate and anchor assembly 22 to be fitted to a cable of a cable bolt without removing the cap 32. Thus, the cable of a cable bolt can be fed through the central opening 40 and into the other components of the rock plate and anchor assembly 22.

[0049] When the cap 32 is threaded onto the barrel 34, there is a space S (see Figure 4) between the top wall 42 of the cap 32 and the facing top surface 54 of the wedge arrangement 36. This allows the wedge arrangement 36 to move actually relative to the barrel 34 if a cable is inserted through the rock plate and anchor assembly 22 with the cap 32 attached. In particular, this allows the wedge arrangement 36 to expand radially by movement in the direction of arrow A (see Figure 3) to allow a cable to push through the wedge arrangement 36 without being gripped by the wedge arrangement 36.

[0050] It can be seen in Figure 4, that a wire retainer 56 is disposed within a recess 58 formed in each of the wedges 38 of the wedge arrangement 36, to bias the wedges 38 towards each other in synchronous movement regardless of their axial position relative to the barrel 34. The wire retainer 56 limits radial expansion of the wedges 38 so that the wedges 38 only expand sufficiently to allow passage of a cable through the rock plate and anchor assembly 22. The wire retainer 56 is intended to ensure that the internal surfaces 60 of the wedges 38 maintain sliding contact with the outer surface of a cable that is being pushed through the rock plate and anchor assembly 22, so that when the cable is tensioned, the internal surfaces are immediately able to grip and hold the cable against pulling through the barrel and wedges anchor 26.

[0051] Each of Figures 2, 4 and 5 show a tack weld 62 between a bottom end 63 (see Figure 3) of the barrel 34 and an upper edge of the raised central section 28 or of the circular bearing surface 30. Figure 3 also shows the tack weld 62, but in the exploded view of Figure 3, the tack weld 62 is shown as part of the rock plate 24 and not in connection with the barrel 34.

[0052] The tack weld 62 secures the barrel and wedges anchor 26 to the rock plate 24. This is advantageous for transport and storage, whereby the rock plate and anchor assembly 22 is a single connected component. It is also advantageous for installation whereby the rock plate and anchor assembly 22 can be fitted as one component to a cable. In this respect, during installation, cable can be fed off a reel whereby the leading end of the cable can be fed through the rock plate and anchor assembly 22 and then into an expansion anchor. The expansion anchor will attach to the leading end of the cable and the cable can continue to be fed from the reel with the cable and expansion anchor being fed into a drilled hole, which will likely be filled already with resin or grout. The rock plate and anchor assembly 22 will remain outside the hole and the cable will pass through the rock plate and anchor assembly 22 with the wedges 38 of the barrel and wedges anchor 26 sliding against the surface of the cable, but not gripping the cable. Once the leading end of the cable and the attached expansion anchor have reached either the inner end of the hole, or an appropriate position within the hole, the trailing end of the cable can be cut, leaving about 300mm extending out of the open end of the hole, including a trailing cable section that extend from the rock plate and anchor assembly 22. The trailing cable section can then be tensioned by pulling on the cable in the opposite direction to the installation direction to activate the expansion anchor. The tension will be retained within the cable by the barrel and wedges anchor 26 gripping the trailing cable section.

[0053] The steps of installation discussed above are unique at least by the use of the rock plate and anchor assembly 22. In prior art arrangements, installation personnel would be required to fit the wedge arrangement 36 over the leading end of the cable and then separately the rock plate 24. This requires the installation personnel to be present at the site of installation prior to the cable bolt being installed and tensioned. For safety reasons, it is always preferred to maintain installation personnel away from sites that are not already protected or secured by existing bolting. The applicant considers that the application of the rock plate and anchor assembly 22 to the leading end of the cable can be automated as part of a robotic application, whereby each of the expansion anchor and the rock plate and anchor assembly 22 can be fitted to the cable by the installation equipment, thus dispensing with the need for installation personnel to be present for manual fitting of these components. The automation is made possible by the rock plate and anchor assembly 22 being formed as one component, rather than being formed as separate components. The robotic application could include a robotic arm that picks an assembly 22 from a supply of assemblies 22 and places the assembly 22 in alignment with the leading end of a cable for subsequent feed of the cable through the assembly 22. The robotic application could alternatively include conveyor or shuttle arrangements to shift an assembly 22 from a supply position, within a cartridge or cassette for example, into alignment with the leading end of a cable.

[0054] The automation is also assisted by the use of the cap 32 that maintains the wedges 38 of the wedge arrangement 36 in connection with the barrel 34. This means that the barrel and wedges anchor 26 can be lifted and manoeuvred without the prospect of the wedges 38 disconnecting from the barrel 34. Moreover, the cap 32 can be made from suitable material that prevents it from interfering with the cable tensioning process. For example, the cap 32 can be made from a suitable plastic material which can be allowed to fail once the cable bolt is installed and tension is applied to the trailing end of the cable. At that point, the wedges 38 will be in a gripping position against the outside surface of the cable and the cap 32 will no longer be operational to maintain the wedges 38 within the barrel 34.

[0055] The steps of installation discussed above are illustrated in Figure 6 and show the use of cassettes, cartridges or supplies of rock plate and anchor assemblies and expansion anchors. Accordingly, step one in Figure 6 shows the leading end of a cable 62 being fed between two rollers 64 and being aligned for insertion through a rock plate and anchor assembly 22 and an expansion anchor 66. Each of the rock plate and anchor assembly 22 and the expansion anchor 66 have been positioned by robotic arms 68 and 70 along the axis Ax of insertion of the cable 62 which axis Ax is aligned with the axis of the drilled hole 72. Each of the rock plate and anchor assembly 22 and the expansion anchor 66 have been taken from supplies 74 and 76 that are accessible to the robotic arms 68 and 70.

[0056] Step 2 in Figure 6 shows that the leading end of the cable 62 has passed through the rock plate and anchor assembly 22 and has entered the expansion anchor 66. The robotic arms 68 and 70 have now been withdrawn and the supplies 74 and 76 of the rock plate and anchor assemblies 22 and the expansion anchors 66 have been shifted forward as shown so to make the next rock plate and anchor assembly 22 and expansion anchor 66 available for selection by the robotic arms 68 and 70 for the next cable bolt installation.

[0057] In step 3, the rollers 64 (or the cable feed mechanism) have been shifted towards the hole 72 to shift each of the rock plate and anchor assembly 22 and the expansion anchor 66 to the opening of the hole 72.

[0058] Step 4 of Figure 6 shows the cable 62 being fed further into the hole 72 so that the cable 62 and the expansion anchor 66 push into the hole 72 and through any resin or grout within the hole 72. The rock plate and anchor assembly 22 remains at the rock face 78 with the rock plate 24 pressing against the rock face 78 about the opening to the hole 72.

[0059] Step 5 of Figure 6 shows the cable 62 and the expansion anchor 66 having reached the inner end of the hole 72. At this point, the rollers 64 (or the cable feed mechanism) can be shifted rearwardly away from the rock face 78 and a cable cutter 80 can be introduced to cut the cable just beyond the barrel and wedges anchor 26 of the rock plate and anchor assembly 22.

[0060] Step 6 of Figure 6 shows the cable 62 having been cut and shows a tensioner 82 gripping the trailing end of the cable 62 and applying tension to the cable 62. This activates the expansion anchor 66 so that the leading end of the cable 62 is secured at the inner end of the hole 72 even though the resin or grout is yet to cure. Also, tension applied to the cable 62 is retained by the wedges 38 of the barrel and wedges anchor 26 gripping the trailing end of the cable 62.

[0061] It will be appreciated, that steps 1 to 6 of Figure 6 can be completely automated. This is advantageous for the reasons explained hereinbefore, whereby the installation personnel previously required to separately apply a rock plate and a barrel and wedges anchor to the leading end of a cable are no longer required.

[0062] The barrel 34 is shown in Figures 2, 4 and 5 as being tack welded to the rock plate 24. In those figures, a pair of diametrically opposed tack welds are illustrated. These tack welds are intended to only lightly connect the barrel 34 to the rock plate 24. The intention is that tack welds can fail if the orientation of the barrel 34 relative to the rock plate 24 changes when the cable is tensioned. This is common in rock bolt installation and occurs where the surface surrounding the drilled hole is not perpendicular to the axis of the drilled hole. In these installations, the barrel and wedges anchor 26 will remain oriented along the axis of the drilled hole, but the rock plate 24 will shift to assume a position flush against the rock face. In these installations, the rock plate 24 thus needs to move relative to the barrel 34 and that movement necessitates breakage of the tack welds. Thus the provision of tack welds that can survive installation of the rock bolt prior to tensioning of the cable is all that is required.

[0063] While a pair of diametrically opposed tack welds are illustrated in Figures 2, 4 and 5, Figure 5a illustrates a second alternative in which the rock plate and anchor assembly 22 includes four tack welds 62, space apart equidistantly, at 90° to each other, although only three of the tack welds are visible in Figure 5a. In all other respects, the arrangement illustrated in Figure 5a is the same as that of Figures 2 to 5.

[0064] Figure 7 shows another rock plate and anchor assembly 84 which is similar to the rock plate and anchor assembly 22 of Figures 2 to 5 but shows internal tack welds 84. The selection of external tack welds according to Figures 2 to 5 or internal tack welds according to Figure 7, is a manufacturing selection.

[0065] Figure 8 is a top perspective view of the rock plate and anchor assembly 84, while Figure 9 is a cross- sectional view taken through VIII-VIII of Figure 8. In Figures 8 and 9, the cap 86 has a top hat shape, so that it has a top wall 88 with a central opening 90, a circular side wall or skirt 92 and a circular flange 94. The circular flange 94 extends perpendicular to the skirt 92 and overlies the axial face 52 of the barrel 34, so that the flange 94 can be secured to the barrel 34 by one or more screws 96. The flange 94 can be pre-drilled with screw holes and the barrel 34 can include threaded openings that open through the axial face 52 to accept the screws 96.

[0066] The rock plate and anchor assembly 84 shows that alternative arrangements exist that remain within the scope of the present invention. This is particularly the case with the joins that can be made between the bottom end of a barrel of an anchor and a rock plate. Tack welds are shown in the figures, but it will be appreciated that the joins could take other forms. For example, and with reference to Figure 3, a glue join could be made between bottom end 63 of the barrel 34 and the circular bearing surface 30 of the rock plate 24. This could be a single spot or short line of glue, or multiple spaced apart, spots or lines of glue, or a continuous line of glue extending fully about the bearing surface 30.

[0067] Alternatively, a plastic or plate metal clip can connect between the anchor and the rock plate. The clip may fail once the rock plate engages the rock wall and shifts relative to the anchor, or it could be flexible and stretch or deform.

[0068] Figure 10 illustrates how the rock plate and anchor assembly 22 operates to allow relative movement between the rock plate 24 the anchor 26. In Figure 10, the hole 100 has an axis 102 which is not perpendicular to the plane P of the rock face 104. Accordingly, where the assembly 22 is installed according to steps 1 to 6 of Figure 6, the edge 106 engages the rock face 104 before the opposite edge 108. The edge 106 will therefore be subject to an external load tending to rotate the rock plate 24 about the connection between the rock plate 24 and the leading end of the barrel 34 of the anchor 26. The join between the rock plate 24 and the barrel 34 as discussed above will resist that rotation, but if the external load is sufficient, it will overcome the resistance load the tack welds between the rock plate 24 and the barrel 34 will fracture or break permitting rotation. This rotation will allow the opposite edge 108 to rotate into engagement with the rock face 104, so that the rock plate 24 engages the rock face 104 from edge to edge.

[0069] Figure 10 illustrates how the benefits of the present invention can be utilised for installation of a rock plate and anchor assembly, but still permit proper and full rock plate engagement with a facing rock surface.

[0070] Figure 11 illustrates generally the same rock plate and anchor assembly 22 of Figure 4, with the exception that tack welds 62 are not used to secure the barrel and wedges anchor 26 to the rock plate 24. Rather, a plastic component 110 is employed to secure the barrel 34 to the rock plate 24. The plastic component 110 is screw connected to the barrel 34 and has an expansion, flaring or lip 112 that extends underneath the raised central section 28 of the rock plate 24. The plastic component 110 is designed to break or fracture under load in the same manner as the tack welds 62 described earlier to allow the the barrel and wedges anchor 26 to shift relative to the rock plate 24.

[0071] Where any or all of the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

[0072] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.

[0073] Future patent applications may be filed on the basis of or claiming priority from the present application. It is to be understood that the following claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future application. Features may be added to or omitted from the claims at a later date so as to further define or re-define the invention or inventions.

Claims

1. A rock plate and anchor assembly (22) comprising:

i. a rock plate (24) and

ii. a barrel and wedges anchor (26),

i. the barrel and wedges anchor (26) comprising an external barrel (34) and internal cable gripping wedges (38), the barrel (34) having a leading end and a trailing end, the leading end being fixed to the rock plate by a join (62) that fixes the rock plate (24) and the barrel and wedges anchor (22) together in an assembly position,

ii. the join (62) providing a resistance load that resists movement of the rock plate (24) relative to the barrel and wedges anchor (26) from the assembly position,

iii. rock plate (24) being movable relative to the barrel and wedges anchor (26) from the assembly position upon an external load being applied to the rock plate (24) that is greater than the resistance load of the join (62) and that is applied in a direction to move the rock plate (24) relative to the barrel and wedges anchor (26).

2. An assembly (22) according to claim 1, the join (62) being a frangible join, whereby the join (62) breaks upon the external load being applied to the rock plate (24) to allow the rock plate (24) to move relative to the barrel and wedges anchor (26).

3. An assembly (22) according to claim 2, the frangible join being a tack weld join.

4. An assembly (22) according to claim 2, the frangible join being a glue join.

5. An assembly (22) according to claim 2, the frangible join being a clip join.

6. An assembly (22) according to claim 1, the join (62) being a flexible join, whereby the join (62) flexes to upon the external load being applied to the rock plate (24) to allow the rock plate (24) to move relative to the barrel and wedges anchor (26).

7. An assembly (22) according to claim 1, the join (62) being a deformable join, whereby the join (62) deforms upon the external load being applied to the rock plate (24) to allow the rock plate (24) to move relative to the barrel and wedges anchor (26).

8. An assembly (22) according to claim 7, the deformable join being a stretchable join.

9. An assembly (22) according to any one of claims 1 to 8, comprising a cap (32) connected to the trailing end of the barrel (34), the cap (32) overlying the internal wedges (38) to prevent release of the wedges (38) from the barrel (34).

10. An assembly (22) according to claim 9, the cap (32) comprising an end wall (42) and a side wall (44), the end wall (42) overlying the internal wedges (38) and having an opening (40) aligned with a cable passage through the internal wedges (38) and the side wall (44) connecting to the trailing end of the barrel (34).

11. A method of installing a cable rock bolt into a pre-drilled hole (72), the method comprising:

i. aligning a leading end of a cable (63) with a rock plate and anchor assembly (22) according to any one of claims 1 to 10,

ii. feeding the cable through the rock plate and anchor assembly (22),

iii. attaching an expansion anchor (66) to the leading end of the cable (63),

iv. feeding the cable (63) through the rock plate and anchor assembly (22) and pushing the expansion anchor (66) into the pre-drilled hole (72),

v. once the expansion anchor (66) has been pushed into the hole (72) to an expansion location, gripping a trailing end of the cable (63) and applying tension to the trailing end to activate the expansion anchor (66) and to activate the barrel and wedges anchor (26) to retain the tension in the cable (63).

12. A method according to claim 11, comprising after the expansion anchor(66) has been pushed into the hole (72) to an expansion location and before tension is applied to the trailing end of the cable (63), cutting the cable (63) behind the rock plate and anchor assembly (22) to leave the trailing end of the cable (63) extending through the rock plate and anchor assembly (22).

13. A method according to claim 11 or 12, the method comprising providing a supply of rock plate and anchor assemblies (22) and whereby aligning a leading end of the cable (63) with the rock plate and anchor assembly (22) is by a robotic arm (68) that picks a rock plate and anchor assembly (22) from the supply (74) of rock plate and anchor assemblies (22) and places the rock plate and anchor assembly (22) into alignment with the leading end of the cable (63).

14. A method according to claim 11 or 12, the method comprising providing a supply of rock plate and anchor assemblies (74) and whereby aligning a leading end of the cable (63) with the rock plate and anchor assembly (22) is by a conveyor or shuttle arrangement that takes a rock plate and anchor assembly (22) from the supply of rock plate and anchor assemblies (74) and conveys or shuttles the rock plate and anchor assembly (22) into alignment with the leading end of the cable (63).

15. An installation of one or more cable rock bolts installed according to the method of any one of claims 11 to 14.

Drawing