Rock bolt

Abstract

A rock bolt (40) comprising: an elongated, substantially circular tube (41) having a leading end (13) and a trailing end (42); an expander mechanism (15) arranged within the tube and located in the region of the leading end (13); an elongated reinforcement (44), which is arranged in the tube (41) in the longitudinal direction and which is connected to the expander mechanism (15) at a first end of the reinforcement or towards the first end of the reinforcement, the expander mechanism (15) is arranged at or towards a first opposite end of the rib (44) and is connected at or towards a second opposite end of the rib with an anchor arrangement (46) positioned at the trailing end (42) of the tube (41), and the rib (44) has a radially extending projection (56) positioned between the expander mechanism (15) and the anchor arrangement (46), and the tube (41) has a latch (58) having an opening (62) through which the rib (44) extends, and the projection (56) has a radial dimension that is too large such that the rib (44) cannot pass through the opening (62), where the latch (58) is secured in place within the tube (41) and between the projection (56) of the rib (44) and the tail end (42) of the tube (41).

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority from European Patent Application 23174806.2 filed on 23 May 2023, the contents of which are incorporated herein by this reference. TECHNICAL FIELD

[0003] The present invention relates to a rock bolt for use in a rock formation or mass, with the purpose of stabilising the rock formation or mass, preventing it from breaking or collapsing. This is sometimes referred to as “ground support”. Such rock bolts are widely used in the mining, tunnelling and excavation industries for the purpose of supporting rock walls, preventing them from breaking or collapsing. BACKGROUND

[0004] The following discussion of the background of the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not

[0005] The applicant has in the past developed different forms of rock bolts, examples of which are seen in Australian patents No. 2016363530, No. 2018265326, No. 2010223134 and No. 2015273708. Rock bolts according to these patents have been used for ground support for many years and have proven to be able to provide effective and reliable anchoring within rock formations. These rock bolts typically employ a split tube with an expander mechanism inside at the leading end of the tube and an anchor arrangement at the opposite or trailing end. The rock bolt is typically inserted into a pre-drilled hole by impact hammering, the hole being slightly smaller than the outer diameter of the split tube, and once the rock bolt is inserted into the hole, the expander mechanism is activated to increase the frictional engagement between the tube and the facing hole wall, particularly at the leading end of the rock bolt.

[0006] The expander mechanism is typically connected to the anchor arrangement by a rod extending from the anchor arrangement and through the tube to the expander mechanism. The expander mechanism is typically attached to a threaded end of the rod. The opposite end of the rod at the anchor arrangement can have a fixed nut, and in these arrangements, the rod is rotated by rotating the nut, causing the expander mechanism to move in a manner that causes it to expand, thereby activating the expander mechanism. Alternatively, the opposite end of the rod can also be threaded, and a nut can be rotated on the threads, causing the rod to retract within the tube, and by this retraction, the expander mechanism is activated.

[0007] The anchor arrangement generally includes a rock plate that is pressed against the rock face of the rock surrounding the hole by the nut when the nut is tightened to activate the expander mechanism. The rock plate exerts a compressive force against the rock face of the rock that resists displacement of the rock formation. In the installation of the rock bolts of Australian Patent Nos. 2016363530 and 2018265326, when rock displacement occurs, the anchor arrangement can move away from the tail end of the tube, beneficially allowing further expansion of the expander mechanism if possible. Movement of the anchor arrangement also increases the tensile load on the rod, which can cause the rod to elongate. Beneficially, the rod elongation absorbs dynamic loads on the anchor bolt, but if the load is great enough to reach the limit of elongation, the rod will fail.

[0008] In the rock bolts according to Australian Patent Nos. 2010223134 and 2015273708, a ring is welded around the outside surface of the tail end of the tube and the rock plate engages with the ring. These rock bolts operate differently to the anchors according to Australian Patent Nos. 2016363530 and 2018265326 when rock displacement occurs, because the anchor arrangement cannot move away from the tail end of the tube due to the engagement between the ring fixed to the tube and the rock plate. Advantageously, in these rock bolts, the tensile load during rock displacement is shared by the rod and the tube, so a lighter weight rod can be used. However, in these rock bolts, there is no opportunity for the expander mechanism to further expand or the rod to elongate during rock displacement. In these anchors, the tube and rod can fail if the load is great enough.

[0009] In the various forms of rock bolts described above, failure of the rod can result in a portion of the rod being ejected from the installation hole. This presents a significant safety issue in a mining environment to personnel and equipment, and the ejected rod portion can strike personnel and equipment. Accordingly, rock bolts have employed a capture arrangement to capture the ejected rod portion so that it does not completely eject from the hole in which the rock bolt is installed.

[0010] One example of a capture arrangement is disclosed in WO201855536, in which the shank of the anchor rod has a reduced diameter end portion in the region of the tail end of the split tube, adjacent to a larger diameter shank portion. A sleeve is fitted over the reduced diameter end portion, and at the transition between the reduced diameter portion and the larger diameter portion of the shank, the sleeve can abut the end of the larger diameter shank portion. The sleeve is loose fitting around the reduced diameter portion, and is therefore free to move along the reduced diameter end portion. The reduced diameter end portion of the shank is in a portion of the shank that will separate from the main portion of the shank if the shank fails. This shank portion will therefore have the larger diameter portion adjacent to it, and the reduced diameter portion on which the sleeve is located. If the shank portion starts to pop out, it will travel through the sleeve until the sleeve abuts the larger diameter portion of the shank portion. The sleeve will then move with the shank portion, and will be pushed towards the tail end of the tube. The tail end of the tube includes an abutment against which the sleeve will eventually engage, and this engagement prevents movement of the sleeve and hence the shank portion. The shank portion is therefore prevented from popping out of the rock anchor completely.

[0011] In WO201855536, the abutment at the tail end of the tube is a ring welded to the outside of the tube. It is advantageous that the ring is welded on the outside of the tube, meaning that the insertion of the shank into the tail end of the tube is not hindered when the rock anchor is assembled. However, the sleeve must be inserted from the leading end, as it cannot be inserted into the tube past the already welded ring.

[0012] Other rock anchors employing capture arrangements are disclosed in Australian patent 2015273708 and Australian patent 2019202781.

[0013] Australian patent 2015273708 includes a restraining member that fits closely around the shank and extends through a split in the tube to engage the facing hole wall of the hole into which the rock anchor is inserted. The tube of the rock anchor has a weakened region at the tail end, such that when the anchor is subjected to a sufficiently large load, the tube will fail at the weakened region. While in normal circumstances this can cause the tail end of the rock anchor to pop out, the restraining member simultaneously grips both the facing hole wall of the hole and the shank, preventing this from happening, such that the restraining member is fixed by engagement with the facing hole wall of the hole, and the shank is fixed by engagement with the restraining member, to prevent popping out of the hole. The function of the restraining member in Australian patent 2015273708 is satisfactory, although its assembly structure is somewhat complex. The assembly also grips the shank relatively tightly, resulting in a reduction in the mechanical torque available to inflate the inflator mechanism.

[0014] Australian patent 2019202781 employs a stop member welded to the trailing edge of a tube of a rock bolt. The stop member is a disc having a central opening through which a shank of a rock bolt extends. The rock bolt has upset portions which do not fit through the central opening and so, if the shank fails, the portion that would otherwise pop out is caught when the upset portions engage the stop member around the central opening. SUMMARY

[0015] According to the invention there is provided a rock bolt comprising: an elongate, generally circular tube having a leading end and a trailing end; an expander mechanism disposed within the tube and located in the region of the leading end; an elongate bar disposed longitudinally within the tube and connected at or towards a first end of the bar to the expander mechanism and connected at or towards a second, opposite end of the bar to an anchor arrangement located at the trailing end of the tube; the bar having a radially extending protrusion located between the expander mechanism and the anchor arrangement and the tube having a catch having an opening through which the bar extends and through which the protrusion is too large to pass, characterised in that the catch is fixed in place within the tube and located between the protrusion of the bar and the trailing end of the tube.

[0016] In most forms of the rock bolt according to the invention, the bar will be a shank or rod, typically a steel rod, and the length of the rod can be in the range 1 m to 4 m. The rod can have ribs applied to the outside surface and can have a nut fixed to one end and have threads at the other end. While the bar can alternatively be a flexible cable, it is expected that the invention will be used primarily in the case of rock bolts employing steel rods.

[0017] The rock bolt according to the invention has a catch fixed in place within the tube so that it is located on the inside of the trailing edge of the rock bolt tube. As will be apparent from the discussion that follows, the rock bolt according to the invention allows the rod and associated components to be inserted through the trailing end of the tube rather than the leading end. This is preferred because it makes assembly of the rock bolt much easier.

[0018] The catch can be a ring. The ring can be a complete ring or an open ring. An open ring has the advantage that it can be reduced in diameter for insertion inside the tube and then expanded in a spring-like manner within the tube. This makes insertion easier and allows the ring to expand before it is fixed to the tube to make a firm engagement with the inner surface of the tube.

[0019] The wall of the ring can be of any suitable shape, for example circular, square or rectangular.

[0020] The opening of the catch can be of any suitable shape. For example, the opening can be circular and thus have a constant diameter, or the opening can be non-circular, for example oval, or square or rectangular.

[0021] The opening of the catch can have an axis which is substantially coaxial with the axis of the tube. It is contemplated that in certain forms of the invention the catch will be a circular ring and the axis of the ring will be coaxial with the axis of the tube.

[0022] Alternatively, when the catch is a ring, the axis of the ring can be arranged at an angle to the axis of the tube. In certain forms of the invention the ring will be installed within the tube at an angle to the axis of the tube. By installing the ring at an angle to the axis of the tube the opening provided for the bar to pass through is reduced so that the available space through which the protrusion of the bar passes is smaller. This can make the protrusion smaller than it would be if the ring were installed coaxially with the axis of the tube. A further advantage is that the bar can be inserted with the ring coaxial with the axis of the tube rather than at an angle to the axis of the tube. At this time the opening provided for the bar to pass through the ring will be at its maximum extent to make it easy for the bar to be installed through the ring. After the bar has been inserted through the ring the ring will be tilted to an angle to the axis of the tube.

[0023] Furthermore, by installing the ring at an angle to the axis of the tube the ring can protrude further into the interior of the tube towards the axis of the tube than it would if the ring were installed substantially coaxially with the axis of the tube. For example, if the wall of the ring is rectangular in cross-section and if the ring is installed substantially coaxially with the axis of the tube the wall of the ring will extend substantially parallel to the tube wall of the tube. However, if a ring of this type is installed at an angle to the axis of the tube the wall of the ring will extend inwards of the tube wall. By choosing the dimensions of the ring the wall of the ring can extend into the tube so that it engages the side wall of the bar before the protrusion engages the ring. This engagement can help to prevent the bar from partially ejecting from the hole in which the rock bolt is installed.

[0024] The catch can be secured in place within the tube in any suitable manner. For example, the catch can be secured by fusion welding or brazing. The catch can be secured to the inside surface of the tube. In certain forms of the application, the tube will have a longitudinal slot or slit and the catch is secured to one or both of the opposing edges of the slot, such as by welding. This makes it easy to weld the catch within the tube as the slot provides access to the catch within the tube whilst the catch is connected to the tube at only one location or, more preferably, at two locations, sufficient to secure the catch firmly within the tube. Furthermore, securing the catch at one or both edges of the slot does not require any part of the catch or securing medium to extend outside of the tube, so in this form of the application the catch is secured in a manner which does not present any obstruction to the insertion of the rock bolt into the hole.

[0025] If the catch is secured on each side of the slot, the slot will not be able to contract or expand in the region of the catch, although if desired the catch can include a break or opening, such as a slit, to avoid bridging the slot across the tube, and this break or opening can be opened or closed to allow the tube to expand or contract.

[0026] The catch can be secured in place by welding as described above, or in alternative arrangements of the application a connector can be employed to connect the catch to the inside of the tube. The connector can take any suitable form. In certain forms of the application the connector is an elongate finger or post (hereinafter referred to as a "post") which is connected to the tube and extends in the longitudinal direction of the tube. The catch can be attached to the post to connect the catch to the tube. The post can be connected to the tube at one end and can be free at the opposite end so that this free end can pass through an opening in the catch to mount the catch to the post.

[0027] In certain forms of the application the post has a trailing end and a leading end, the trailing end being welded to the tube and the leading end not being connected to the tube. In forms of the application in which the tube has a longitudinal slot or slit, the trailing end of the post can be welded to the tube to one or both of the opposing edges of the slot.

[0028] In other forms of the application the post can be cut from the solid wall of the tube so that the trailing end of the post is integral with the wall of the tube and the post is urged inwards of the tube, out of the plane of the tube wall, so that the free end of the post can present to extend through an opening in the catch to secure the catch in place within the tube. The post can be cut from the tube wall by known metal cutting techniques or by a stamping process.

[0029] Other arrangements for attaching columns to pipes can also be used, such as using rivet connections to attach columns.

[0030] When using a post to attach the locking element to the inside of a pipe, the post can be constructed such that once the locking element is connected to the post, it is not easily released from the post. Therefore, the post can be bent or shaped to have: a region spaced apart from the inner pipe wall for receiving the wall of the locking element, this region being, for example, in the central portion of the post; and regions on both sides extending toward or bending back towards the pipe wall, or extending or bending to the pipe wall, to prevent the locking element from disengaging from the post. This region can form recesses to receive the wall of the locking element. In these arrangements, the free end of the post can be temporarily displaced away from the pipe wall to allow the locking element to be fed onto the post, after which the post can spring back or deform (bend) to a position where the free end is adjacent to or connected to the pipe wall.

[0031] In other forms of the invention, the locking element may include axially spaced first and second locking element members, each of which is fixedly positioned within the tube and located between the protrusion of the reinforcing bar and the tail end of the tube. Each of the first and second locking element members may include openings coaxial with each other and with the axis of the tube, and these openings have misaligned keys to receive the protrusion of the reinforcing bar, such that the protrusion of the reinforcing bar adapts to pass through the first locking element member in one axial rotational orientation and adapts to pass through the second locking element member in a second and different axial rotational orientation. In these forms of the invention, the reinforcing bar of the rock anchor may be inserted into the tube from the tail end by orienting the reinforcing bar in a first position such that the protrusion is aligned with the key of the opening of the first locking element member, and once the protrusion has passed through the opening of the first locking element member, the reinforcing bar may be axially rotated such that the protrusion is aligned with the key of the opening of the second locking element member. Once the protrusion has passed through the opening of the second locking member, the reinforcing bar can be fully pushed into the tube.

[0032] The advantage of this arrangement is that the ejection of the tail end portion of the reinforcing bar from the rock anchor is prevented by the engagement of the reinforcing bar protrusion against the second locking member. This engagement will occur as long as the protrusion of the reinforcing bar is not aligned with the key of the second locking member. During the ejection of the tail end portion of the reinforcing bar, except in very rare cases, it is expected that the protrusion of the reinforcing bar will not be precisely aligned with the key of the second locking member. In those rare cases, the protrusion of the reinforcing bar will pass through the second locking member, but due to the rotational displacement of the keys of the first and second locking members, the protrusion will lock onto the first locking member and capture the ejected portion of the reinforcing bar.

[0033] The first and second catch member can be secured in place within the tube by any suitable arrangement, but it is expected that it will most conveniently be secured by welding. The first catch member can be secured at the tail end of the tube and either slightly inboard of the tail end edge, or flush with the tail end edge. In either case, good access to the first catch member is provided for welding.

[0034] The second catch member can also be welded, and where the tube has a longitudinal slot or slit, the second catch member can be welded to one or both of the opposing edges of the slot. This makes it easy to weld the second catch member within the tube, as the slot provides access for welding the second catch member, while the second catch member is connected to the tube at only one location, or more preferably at two locations, sufficient to secure the second catch member firmly within the tube, and the strength of this connection is sufficient to prevent ejection of the bar portion by the second catch member.

[0035] Where the present invention employs first and second catch members, the projection of the bar must necessarily be shaped to pass through the opening and key of each of the catch members, and so the projection of the bar will not be axially symmetrical. To this end, the bar can be upset to form a hump in the bar extending to either side of the bar, and the first and second catch members can each comprise a generally circular opening, with the perimeter of the opening broken to form a pair of opposing key sections for receiving the hump sections of the bar.

[0036] Alternatively, the projection of the bar can be an additional component adapted to the bar, such as by welding or crimping. The additional component can be a ring adapted to the bar by welding or crimping. For the case where the bar is formed as a bar with longitudinal ribs, crimping is a particularly suitable simple attachment mechanism for the adaptation.

[0037] Alternatively, the projection of the bar can be an attachment adapted to the bar. This form of the present invention is particularly suitable for a bar formed as a ribbed bar, whereby the attachment securely clamps the outer surface of the bar by interaction with the ribs. The attachment can be formed of a resilient material and comprise an opening for receiving the bar and a slot in the opening which allows the attachment to open for adaptation to the bar and enables it to close around the bar in a resilient manner. The attachment can be formed in a U-shape.

[0038] Where the tube has a longitudinal slot or slit, advantageously the attachment can be formed to be inserted through the slot, so that the bar can be fully installed within the tube before the attachment is attached to the bar.

[0039] The attachment portion can have a tapered end to ensure that the attachment portion enters into the opening of the catch and movement of the rod is prevented by the tapered end catching on the opening. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order for the application to be more fully understood, some embodiments will now be described with reference to the accompanying drawings, in which:

[0041] Figure 1 and Figure 2 are prior art drawings taken from Australian Patent No. 2015273708.

[0042] Figure 3 is a cross-sectional view of the tail end of a rock bolt according to one embodiment of the application.

[0043] Figure 4 is a cross-sectional view of the tail end of a rock bolt according to another embodiment of the application.

[0044] Figure 5 illustrates a section of a rock bolt rod and an attachment portion attached to the rod.

[0045] Figure 6 is a cross-sectional view taken through the attachment portion and rod of Figure 5 .

[0046] Figure 7 is a cross-sectional view of the tail end of a rock bolt according to another embodiment of the application.

[0047] Figure 8 is a perspective view of a section of a rock bolt of Figure 7 .

[0048] Figure 9 is a cutaway perspective view of a modified section of a rock bolt of Figure 7 .

[0049] Figure 10 is a perspective view of the tail end of a rock bolt according to another embodiment of the application.

[0050] Figure 11 is a cross-sectional view taken through the rod of a rock bolt suitable for use in Figure 10 . DETAILED DESCRIPTION

[0051] Figure 1 and Figure 2 shows a rock bolt according to Australian Patent No. 2015273708, which is known in the industry as the MD rock bolt. Figure 1is a perspective view of a rock bolt 10 and shows an elongate, generally circular tube 11 which includes a longitudinal split 12 which enables the tube 11 to be radially expanded. The tube 11 has a leading end 13 and a trailing end 14. An expander mechanism 15 is disposed within the tube 11 and in the region of the leading end 13 and is operable to apply a load tending to at least radially expand the leading end 13 of the tube 11. The expander mechanism 15 is shown as comprising a wedge arrangement comprising at least a pair of wedge elements which expand as they move relative to one another.

[0052] The rock bolt 10 also includes reinforcement in the form of a ribbed bar 16 which is disposed longitudinally within the tube 11 and is connected at one end to the expander mechanism 15 and at the other end to an anchor arrangement (indicated generally by reference 17). In some forms of rock bolt, the end of the bar 16 which is connected to the anchor arrangement 17 is connected by a wedge arrangement.

[0053] The anchor arrangement comprises a collar 18 which is welded to the trailing end 14 of the tube 11, a washer 19, a nut 20 which is screwed onto the trailing end of the bar 16 and a centralising plug 21. The nut 20 is a blind nut which is screwed onto the end of the bar 16 but once the nut 20 is fully rotated onto the end of the bar 16, the nut 20 cannot be rotated further relative to the bar 16. Thus, further rotation of the nut 20 causes the bar 16 to rotate. By this arrangement, rotation of the nut 20 in one direction causes the bar 16 to rotate in a direction which causes the expander mechanism 15 to expand.

[0054] Figure 2 A schematic cross-section of the rock bolt 10 is illustrated in Figure 2 In the Figure 2 In the orientation of the rock bolt 10 shown, downward movement of the wedge element 25 relative to the wedge element 26 will cause the expander mechanism 15 to expand, causing the tube 11 to radially expand at least in the region of the expander mechanism 15. Downward movement of the wedge element 25 relative to the wedge element 26 is achieved by rotating the nut 20 to cause the bar 16 to rotate.

[0055] Figure 2 A rock plate 27 is also illustrated which rests against the inner surface of the collar 18. Figure 2 The weld shown in is between the collar 18 and the tube 11.

[0056] Figure 2 The cross-sectional view of the rock bolt 10 of is relative toFigure 1 The view shown is modified to show the failure of the rock bolt 10 at three locations. First, the tube 11 has failed near the loop 18. Second, the shank 16 has failed and now includes a leading portion 29 and a trailing portion 30. Third, the tube 11 has failed near the free end of the shank portion 29. This type of failure often occurs when the shank 16 fails. Due to the first and second failures, the portion of the rock bolt 10 including the trailing portion 30 of the shank 16, the anchor mechanism 17, a small portion 31 of the tube 11, and a portion of the rock plate 27 can be ejected from the borehole 32 in which the rock bolt 10 is inserted under load. The present invention is intended to prevent the ejection of the trailing portion 30 of the shank 16 and related components.

[0057] Figure 3 is a cross-sectional view of the trailing end of a rock bolt 40 having a similar structure to the rock bolt of Figure 1 and Figure 2 Figure 3 The rock bolt 40 of FIG. 1 has an elongate, generally circular tube 41, only the trailing end 42 of which is shown. An elongate tendon in the form of a ribbed shank 44 is disposed longitudinally within the tube 41 and extends between an expander mechanism (not shown) at the leading end of the tube 41 and an anchor arrangement 46 at the trailing end 42 of the tube 41.

[0058] The anchor arrangement 46 includes a loop 48 welded to the outside surface of the tube 41, a washer 50 bearing against the loop 48 and the trailing edge 52 of the tube 41, and a nut 54 fixed to the shank 44 such that rotation of the nut 54 imparts rotation to the shank 44. Typically, a rock plate (not shown) would be applied to the trailing end 42 of the tube 41, and the rock plate would bear against the loop 48 in the manner shown. Figure 2

[0059] The shank 44 has a protrusion 56 that is a portion of the shank 44 that is upset to form a ridge in the tendon that extends to either side of the tendon in the orientation of the shank 44 shown. Figure 3 The upsetting increases the diameter of the shank 44 in one plane (as shown) and decreases the diameter of the shank 44 in a perpendicular plane. Figure 3

[0060] The rock bolt 40 also includes a catch in the form of a loop 58. Although only shown in cross-section, the loop 58 is a complete circle having a generally constant diameter (both inside and outside) and a generally constant wall thickness.

[0061] ​​​The plane of the ring 58 is shown at an angle to the lengthwise axis of the rod 44. Further, the ring 58 is shown as being attached to the inside surface 60 of the tube 41 at the weld W by spot welding. The ring 58 can be welded to the inside surface 60 at only one point. However, when the tube has a longitudinal slot or slit, as shown at item 12 in the middle, Figure 1 the ring 58 can be welded to one or both of the opposing edges of the slot. Figure 6 is a cross-sectional view of another embodiment of the invention which will be described later in this document, but Figure 6 shows a cross-section of the tube 41 and shows the opposing edges 59 of the longitudinal slot formed in the tube 41. This makes it easy to weld the ring 58 within the tube 41 because the slot provides access to the ring 58 for welding.

[0062] The ring 58 has an opening 62 through which the rod 44 extends and the radial dimension of the protrusion 56 is upset too large to pass through the opening 62. Thus, once the protrusion 56 engages the ring 58, the ring 58 is operable to prevent movement of the rod 44. Referring to Figure 2 by employing Figure 3 the arrangement shown in the middle, after the rod 16 has failed, the tail end portion 30 of the rod 16 and associated components will be prevented from moving.

[0063] Advantageously, the ring 58 is fixed in place within the tube 41 and between the protrusion 56 and the tail end end 42 of the tube 41 so that the ring 58 is on the inside of the tail end edge 52. This arrangement causes the rod 44 to be jammed by the ring 58 earlier than in prior art arrangements in which a stop member is welded to the tail end edge of the rock anchor tube, rather than on the inside of the tail end edge, such as in Australian patent 2019202781.

[0064] Further, by installing the ring 58 at an angle to the axis of the tube 41 and the rod 44, the wall of the ring 58 protrudes further into the interior of the tube 41 towards the axis of the tube 41 than if the ring 58 were installed substantially coaxially with the tube 41. This reduces the amount of the opening 62 available for the protrusion 56 to pass through and, therefore, the protrusion 56 can have a reduced diameter. In addition, by installing the ring 58 at an angle to the axis of the tube 41, the ring 58 can be brought into engagement with the side wall 64 of the rod 44 when the rod 44 is ejected from the tube 41, providing further assistance in preventing ejection of the rod 44.

[0065] While the ring 58 is shown attached to the tube 41 at an angle to the lengthwise axis of the tube 41 and the bar 44, the ring 58 can alternatively be attached so that the axis of the opening 62 is substantially coaxial with the axis of the tube 41 and the bar 44. In these forms of the invention, the plane of the ring 58 will extend substantially perpendicular to the axis of the tube 41 and the bar 44. If this arrangement is employed, the diameter of the protrusion 56 needs to be greater than the protrusion diameter in the arrangement of Figure 3 to ensure that the protrusion 56 cannot fit through the opening 62, with the caveat that the available area in the opening 62 decreases as the ring 58 is tilted.

[0066] Figure 4 A rock bolt 70 is shown in cross-section, constructed in the same way as the rock bolt 40 in Figure 3 , but with the difference that instead of the bar 44 having a swaged protrusion 56, an attachment 72 is attached to the bar 44 to increase the diameter of the bar 44 above the ring 58. As many of the components of the rock bolt 70 are the same as the rock bolt 40, the same reference numerals are used for the same components.

[0067] Figure 5 The attachment 72 and the bar 44 are shown separately. Figure 5 The bar is shown as having a plurality of raised ribs 74 protruding radially outwardly from an outer surface 76 of the bar 44. The attachment 72 is made of a resilient material that allows the attachment 72 to open to fit over the bar 44 and enables the attachment 72 to close around the bar 44 in a resilient manner. Figure 6 is a cross-sectional view through the tube 41, the attachment 72 and the bar 44. The figure shows that the attachment 72 is formed with a U-shape having a curved base 78 and a pair of sides 80. The attachment 72 is open on opposite sides of the base 78 and, in view of the resilience of the attachment 72, the sides 80 can be spread apart to fit around the bar 44 and then return to Figure 5 and Figure 6 the position shown, in which each of the sides 80 and the base 78 grip the outer surface 76 of the bar 44, in particular the raised ribs 74. By this gripping action, the attachment 72 is held in place on the bar 44 without being displaced in the axial direction along the bar 44.

[0068] The attachment 72 has a tapered end 82 to ensure that, in the event of failure of the rod 44, the attachment 72 enters the opening 62 of the ring 58. Therefore, the diameter of the leading end 84 of the tapered end 82 is smaller than the diameter of the opening 62 of the ring 58. However, the diameter of the tapered end 82 increases with distance from the leading end 84, such that once the tapered end 82 enters the opening 62, it will be locked within the opening 62 above the leading end 84. The side of the attachment 72 must be locked within the opening 62 before the straight side 80 reaches it.

[0069] Attachment 72 Figure 4 and Figure 5 The rock anchor 70 is securely fixed to the rod 44 at the position shown. In operation, the rock anchor 70 operates in the same manner as the rock anchor 40, such that if the rod 44 fails and begins to eject from the tube 41, the attachment 72 will shift with the rod 44, causing the tapered end 82 of the attachment 72 to enter the opening 62 of the ring 58, thereby preventing further ejection of the rod 44.

[0070] Figure 7 and Figure 8 Another embodiment of the invention is shown, and is related to Figure 3 and Figure 4 Similarly, in Figure 3 and Figure 4 Rock anchors 40 and 70 in Figure 7 and Figure 8 The rock anchor bolts 90 in the diagram share common components. Therefore, the same reference numerals are used for the same components.

[0071] Figure 7 An example of a rock anchor bolt 90 includes a ribbed member 92 having a protrusion 94 that is crimped onto the member 92. Thus, the protrusion 94 is formed as a ring and fitted onto the member 92, and crimped onto the member 92 in place. The crimping of the protrusion 94 causes the protrusion 94 to clamp the ribbed outer surface 96 of the member 92.

[0072] The rock anchor bolt 90 includes a locking element, which includes a ring 98 and a ring connector 100. Figure 8 It is shown that the two opposite side edges of the connector 100 are welded to the two opposite side edges 102 of the longitudinal slot formed in the tube 41.

[0073] Figure 7 and Figure 8The connector 100 is shown in an operational state. In these figures, the trailing end 104 is welded to the tube 41, while the leading end 106 extends into the slot between the opposing two edges 102. Between the trailing end 104 and the leading end 106, the connector 100 is bent inwardly and extends through the opening of the ring 98. The ring 98 can fit loosely over the connector 100.

[0074] Before placing the connector 100 in the operational state shown in Figure 7 and Figure 8 , the leading end 106 can be positioned within the tube 41 in an assembled state such that the leading end 106 does not extend into the slot between the opposing two edges 102. Figure 7 One example position of the leading end 106 is shown in dashed lines in Figure 7 and Figure 8 . This arrangement means that the ring 98 can fit over the rod 92 and, with the connector 100 in the assembled state shown in dashed lines, the ring 98 can be displaced past the leading end 106 of the connector 100, for example to the position shown by the ring 96a, and the ring 96a can be lowered over the connector 100. The leading end 106 of the connector 100 can then be bent to the operational state and then the ring 98 is securely positioned within the tube 41 relative to the rod 44, preventing release from the connector 100.

[0075] Advantageously, Figure 7 and Figure 8 , the arrangement allows the ring 98 to be fitted over the rod 92 before the protrusion 94 is fitted and crimped over the rod 92. Thus, the components can be fitted in the order, for example, of the nut 54, the centering plug 110, the ring 98 and the protrusion 94, thereby assembling the rod 92. The protrusion 94 can be crimped over the rod 92. The inflator mechanism can then be fitted to the opposite end of the rod 92 and the entire rod 92 inserted into the tube 41 from the trailing end of the tube 41. This is different from the arrangement of Figure 3 , in which Figure 3In the arrangement of Figure 1, if the ring 58 is welded into place before the rod 44 is installed in the tube 41, the rod 44 must be inserted into the tube 41 from the leading end (as the protrusion 56 cannot fit through the opening 62 in the ring 58 to install the rod 44 from the trailing end of the tube 41 ) and fed through the ring 58 before being connected to the nut 54. It is difficult to fit the ring 58 to the rod 44 before welding the ring 58 to the tube 41 and is accompanied by the risk that there will be heat damage to the rod 44 which can affect the performance of the rod 44, in particular the load carrying performance of the rod 44. This is a more difficult installation as it is difficult to connect the nut 54 to the rod 44 when the rod is located within the tube 41 as access to the rod 44 to do this is limited when the rod 44 is located within the tube 41 as it needs to be held to prevent it from rotating whilst the nut is attached.

[0076] The rock bolt 70 is also configured to allow the rod 44 to be inserted from the trailing end of the tube 41 as the attachment 72 can be fitted to the rod 44 through the longitudinal slot of the tube 41 after the rod 44 has been fitted into the tube 41.

[0077] Another embodiment of the invention is shown in Figure 10 and Figure 11 . Figure 10 A section of a rock bolt tube 120 is illustrated having a longitudinal split defined by opposing two edges 122. Figure 10 This section of the tube 120 shown in

[0078] In Figure 10 a form of catch is illustrated having first and second axially spaced apart catch members in the form of a pair of discs 124, 125. The discs 124, 125 are welded to spaced apart locations within the tube 120 so that there is a gap between them. The disc 124 is welded near the trailing edge 126 of the tube 120 and so the weld can extend around the periphery of the disc 124 but except in the region of the longitudinal split. As the disc 125 is located on the inside of the trailing edge 126, it is not so easy to weld around most of its periphery and so the disc 125 can be welded to one or both of the opposing two edges 122 of the longitudinal split.

[0079] Discs 124 and 125 each include non-circular openings 128 and 129 through which a rock anchor rod can extend. Openings 128 and 129 are coaxial with each other and with the axis of the tube, but are shaped to have misaligned keys or keyways. Openings 128 and 129 are shaped to correspond to protrusions of the rod to be inserted into the tube 120. In this embodiment, the protrusions are non-circular or asymmetrical, such that the protrusions can only pass through openings 128 and 129 when they are in a specific angular orientation. Furthermore, since openings 128 and 129 are misaligned, once a protrusion has passed through opening 128 of disc 124, the rod must be rotated to allow the protrusion to pass through opening 129 of disc 125.

[0080] Once the rock anchor bolt is assembled with the welded discs 124 and 125, the bolt can be inserted through the tail end of the tube 120 by aligning the protrusion of the bolt with the opening 128 of the disc 124. Once the protrusion has passed through the opening 128, the bolt is rotated to align with the opening 129 of the disc 125. Once the protrusion has passed through the opening 129 of the disc 125, the bolt can be fully pushed into the tube 120.

[0081] Figure 10 The advantage of this arrangement is that the protrusion of the rod engages with the disc 125, preventing the tail end portion of the rod from ejecting from the rock anchor. This engagement occurs as long as the protrusion of the rod is not aligned with the opening 129 of the disc 125. However, in the unlikely event that the protrusion of the rod is aligned with the opening 129 of the disc 125 and thus able to pass through the opening 129, the protrusion of the rod will still be misaligned with the opening 128 of the disc 124. The protrusion will engage with the disc 124, and further ejection of the rod will be prevented.

[0082] Figure 9 Examples of the Figure 7 and Figure 8 A modification to the arrangement, in which Figure 7 and Figure 8 The connector 100 is integrated with the tube 41, rather than being a separate component soldered to the tube 41. Figure 9 In this process, connector 112 is cut from the wall of tube 41, for example by laser cutting, and the cut section is bent in the manner shown to form a recess 114 in the wall that can accommodate ring 98.

[0083] Figure 9 Modifications to be consistent with Figure 7 and Figure 8 The rock anchor 90 operates in the same manner, and therefore, the free end 116 of the connector 112 can be bent to extend into the interior of the tube 41, as... Figure 7and once the loop 98 is fed over the connector 112, it can flex outwardly and into a slot 118 formed when the tube 41 is cut to form the connector 112.

[0084] Figure 9 Modifications of the above-described embodiments can be used with tubes for non-longitudinally split rock bolts, or, because of the lack of welding in the tail end region of the tube 41, with tubes for split rock bolts. Figure 9 Modifications of the above-described embodiments can be used with tubes for non-longitudinally split rock bolts, or, because of the lack of welding in the tail end region of the tube 41, with tubes for split rock bolts.

[0085] The protrusion of the rod can have any suitable non-circular or asymmetric shape. As one example, Figure 11 is a cross-sectional view of the rod 130 as viewed from the leading end to the trailing end of the rod, and shows that the protrusion 132 has a pair of side "wings" 134 that protrude radially outward from opposite sides of the entire rod 130. The openings 128, 129 can be shaped to accommodate the circular portion of the rod 130 and the wings 134, but require that the rod 130 be rotated 90°, for example after the protrusion 132 passes through the opening 128 and before it can pass through the opening 129. It will be appreciated that if the rod 130 fails, the rod will move very rapidly to engage the disc 125, and in the unlikely event that the protrusion 132 is aligned with the opening 129 so that the protrusion 132 passes through the opening 129, the rod 130 will then almost immediately engage the disc 124 without sufficient time for the rod 130 to rotate 90°. Thus, the likelihood of the protrusion 132 passing through each of the openings 128, 129 is almost negligible.

[0086] In this specification (including claims) the singular encompasses the plural unless the context otherwise requires. In this specification (including claims) the term "comprise", "comprises" or "comprising" will be understood to enable the inclusion of zero or more steps or components, and will not be construed as implying that any steps or components are essential.

[0087] Those skilled in the art will appreciate that the application described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the application includes all such variations and modifications which fall within the spirit and scope of the present application.

Claims

1. A rock bolt (40) comprising: an elongated, generally circular tube (41) having a leading end (13) and a trailing end (42), an expander mechanism (15) arranged within the tube and located in the area of the leading end (13), an elongated bar (44) arranged longitudinally within the tube (41) and connected with the expander mechanism (15) at or towards a first end of the bar (44) and with an anchor arrangement (46) located at the trailing end (42) of the tube (41) at or towards a second, opposite end of the bar (44), the bar (44) having a protrusion (56) extending radially located between the expander mechanism (15) and the anchor arrangement (46) and the tube (41) having a catch (58) having an opening (62) through which the bar (44) extends and through which the radial dimension of the protrusion (56) is too large to pass, characterized in that the catch (58) is fixed in place within the tube (41) and located between the protrusion (56) of the bar and the trailing end (42) of the tube (41).

2. The rock bolt (40) according to claim 1, the catch (58) being formed as a ring, such as a complete ring or an open ring.

3. The rock bolt (40) according to claim 2, the axis of the ring (58) being arranged at an angle to the axis of the tube (41).

4. The rock bolt (40) according to claim 2 or 3, the tube (41) having a longitudinal slot or slit and the catch (58) being fixed to one or both edges (102) of the slot, such as by welding.

5. The rock bolt (90) according to claim 1, the catch (98) being fixed in place within the tube (41) by a connector (100) formed as a post connected to the tube (41) and extending in the longitudinal direction of the tube (41) and having an end (106) free of connection to the tube (41) and the catch (98) having an opening (108) into which the post (100) extends to connect the catch (98) to the tube (41).

6. The rock bolt (90) according to claim 5, the post (100) extending in the longitudinal direction of the tube (41) and having a leading end and a trailing end and the post (100) being connected to the tube (41) at the trailing end and free of connection to the tube at the leading end (106).

7. Rock anchor (90) according to claim 5 or 6, the tube (41) having a longitudinal slot or slit and the column (100) being connected to the tube (41) at the tail end, such as to one or both edges of the slot (102) by welding.

8. Rock anchor (90) according to claim 5 or 6, the column (100) being integral with the tube (41) at the tail end.

9. Rock anchor (90) according to any one of claims 5 to 8, the column (100) having a section (114) of wall spaced from the inner tube wall and housing the shackle, for example a section located in a central portion of the column (100), and the column (100) having areas located on either side extending back towards or back to the tube wall of the tube.

10. Rock anchor (40) according to any one of claims 1 to 9, the protrusion (56) being a swaged section of the bar (44) or a separate part (94) crimped to the bar (44).

11. Rock anchor (40) according to any one of claims 1 to 9, the bar (44) being a ribbed rod and the protrusion (56) being formed as an attachment (72) of resilient material, wherein the attachment (72) has an opening for receiving the rod (44) and a slot in the opening allowing the attachment to open to fit to the rod (44) and enable the attachment to close around the rod (44) in a resilient manner.

12. Rock anchor (40) according to claim 1, the shackle comprising first and second shackle members (124, 125) axially spaced apart, each of the first and second shackle members (124, 125) being fixed in place within the tube (41) between a protrusion (132) of the bar and the tail end of the tube, each of the first and second shackle members (124, 125) comprising openings (128, 129) coaxial with each other and with the axis of the tube (41) and having misaligned keys or keyways to receive the protrusion (132) of the bar (44) such that the protrusion (132) of the bar (44) fits through the first shackle member (124) in one axial rotational orientation and through the second shackle member (125) in a second, different axial rotational orientation.

13. A rock bolt (40) according to claim 10, the first catch member (124) being fixed at the trailing end of the tube (120) and fixed slightly inboard of or flush with the trailing edge (126) of the tube (120), the tube (120) having a longitudinal slot or slit and the second catch member (125) being welded to one or both edges of the slot.

14. A method of assembling a rock bolt (40) a. the rock anchor (90) comprises: elongate tendon (92) provided with an expander mechanism (15) at one end and an anchor arrangement (46) at the opposite end; a protrusion (94) formed on the shank (44), the protrusion (94) extending radially and being positioned between the expander mechanism (15) and the anchor arrangement (46); and a catch (98) positioned between the protrusion (94) and the anchor arrangement (46), the catch (98) having an opening (108) through which the tendon (44) extends and through which the radial dimension of the protrusion (94) is too large to pass; a connector (100) fixed to the tube (41) for holding the catch (98) in place within the tube (41), the method comprising: b. installing the tendon (92) into the tube (41) of the rock bolt, the tube (41) having a leading end and a trailing end and the tendon (44) being installed through the trailing end (42), c. moving the catch (98) in a first direction past the connector (100) and then moving the catch (98) in the opposite direction so that the catch (98) is caught by the connector (100).

15. A method according to claim 14, the connector (100) being formed as a post connected to the tube (41) and extending in the longitudinal direction of the tube (41) and having an end (106) free from connection to the tube (41), the free end (106) in the assembled state being used for moving the catch (98) in a first direction past the connector (100) and for moving the catch (98) in the opposite direction so that the catch (98) is caught by the connector (100), and the method comprising moving the free end (106) into an operating position, such as by bending, in which the catch (98) is securely positioned within the tube (41) so as not to be released from the connector (100).

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