A rock anchor with fastening and indicator mechanisms

Abstract

A rock anchor has an impact driven expansion assembly that includes a wedge with a collar. A tool is used to deliver impacts to the wedge for activation of the expansion assembly. A deformable spacer at an outer end of the rock anchor receives impacts for insertion of the rock anchor and is configured to yield when subjected to a predetermined force for activation of the expansion assembly. The spacer provides an indication that the anchor fastening mechanism is properly installed. Alternative indicator and fastening mechanisms are disclosed.

Description

[0001] A ROCK ANCHOR WITH FASTENING AND INDICATOR MECHANISMS

[0002] FILED OF THE INVENTION

[0003] The invention relates to a rock or friction anchor and more particularly such an anchor of the kind commonly referred to as a split set. The invention provides for a fastening mechanism and a driving tool for use in installation of the anchor. The invention also provides for an indicator mechanism that shows that the fastening mechanism has been activated inside the anchor.

[0004] BACKGROUND TO THE INVENTION

[0005] These split sets include a tubular body with a longitudinal slot and a taper at the inner (or front) end. The split set is driven / pressed into a hole that has been formed by a rock drill. A driving tool with suitable coupling / fitting that employs a percussive action allows the use of a rock drill (or jack hammer type equipment) to drive the split set into place. These rock anchors are well known and have not changed significantly over the many years that they have been in use.

[0006] The tubular body with forward taper is rolled to form and a ring or split ring (of the kind with a body that has two adjacent ends and does not overlap) is welded at or adjacent to the outer (or back) end and across the slot. There may be some variations on the taper and how it is formed. The ring provides a stop to retain a bearing plate (also referred to as a washer plate) against the rock face around the drill hole. The bearing plate is suitably formed with a hole that fits around the split set body and may be configured (with a domed or conical formation around the hole, for example) to deform / yield under a given load. These relatively simple configuration products are used in vast numbers. The relevant industries include mining and construction.

[0007] In underground mining, there is often a need to achieve a higher pull test (load) rating from these split sets. A disadvantage of the tapered inner end section is that it does not serve to provide frictional engagement with a wall of the drill hole. For more fiction surface contact, a longer split set needs to be used.

[0008] In some situations, the split sets or similar type friction anchors may be used with internal fastening or expansion heads / mechanisms to increase the load rating. There are generally two types: one that is screw-thread activated and the other that is impact driven. A problem with these internal mechanisms is that proper installation is not visible from outside the hole. Pull tests may be conducted on every tenth or hundredth anchor, for example, to provide data that gives an indication of how the anchors were installed. It is not viable to test every anchor.

[0009] OBJECT OF THE INVENTION

[0010] It is an object of the invention to provide a rock anchor and particularly a split set that includes a fastening mechanism for adequate and / or improved engagement inside a drill hole, particularly where it is used along an inner tapered section of the split set. It is a further object of the invention to provide an indicator mechanism that shows that a fastening mechanism has be actuated inside the rock anchor. A tool is provided for use in installation of the rock anchor including the fastening mechanism and / or indication mechanism.

[0011] SUMMARY OF THE INVENTION

[0012] In accordance with a first aspect of the invention there is provided a combination of a rock anchor and a tool: the rock anchor having an impact driven expansion assembly supported by a body of the rock anchor; a flange formation on the body of the rock anchor which stops travel of the rock anchor on insertion into a drill hole; the expansion assembly includes a wedge with a collar located over the wedge and is supported adjacent a front end of the rock anchor; the tool includes a backend with a coupling configured for engagement with a percussion mechanism and a central elongate impacting rod locatable inside the rock anchor extending from a stop on the tool provided to abut the outer end of the rock anchor; wherein, once the rock anchor has been inserted into an installed position in a drill hole in a first stage of installation, the tool is used in a second stage of installation, to deliver impacts to the wedge providing longitudinal impact driven travel of the wedge relative to a collar resulting in activation of the expansion assembly through radial expansion of the collar and outward deformation of a sidewall of the rock anchor; a length of the impacting rod provides a space between the stop on the tool and the outer end of the rock anchor that corresponds to a required travel of the wedge for activation of the expansion assembly; and the stop on the tool is arrested by the outer end of the rock anchor before a front end of the rod reaches the collar.

[0013] The invention further provides for the wedge to, in the second stage of installation, be extruded through the collar and / or for a region at an inside of the collar to be drawn with the wedge [to accommodate a smaller diameter drill hole size].

[0014] Further features of the invention provide for the wedge to have an elongate body with a conical region providing a forward taper located (at least partly) inside the collar; for the wedge and collar have a tapered interface providing co-operating bearing surfaces; for the collar to be provided as a split ring with an internal taper corresponding substantially to the taper of the wedge; and for an expansion gap provided by an opening in the split ring collar to be aligned with a slot of the rock anchor.

[0015] The wedge is preferably frusto-conical and the collar is a ring with substantially cylindrical external form and a tapered bore.

[0016] The collar preferably has a single ring component with a single transverse split (to receive the wedge with a friction fit) but may be provided as two or more ring components resulting from more than one split.

[0017] Further features of the invention provided for the expansion assembly to be supported adjacent the inner end of the rock anchor; for the expansion assembly to be supported (at least partly) inside a tapered section at a front end of the rock anchor; and for an outside of the collar to be supported against the sidewall of the rock anchor.

[0018] Further features of the invention provide for the collar to include two or more split rings provided in spaced apart arrangement along the wedge; for the collar to comprise a radial arrangement of at least two leaf components located (at least partly) over the wedge; and for each of the leaf components to provide an external ridge formation.

[0019] The invention still further provides for the rock anchor to include an indicator mechanism comprising a deformable spacer adjacent the outer end of the rock anchor that:

[0020] - receives impacts for insertion of the rock anchor into an installed position within a drill hole; and

[0021] - is configured to yield when subjected to a predetermined force; for the tool to have a driving head that engages the deformable spacer and the central impacting rod extending forwardly from the driving head [past the deformable spacer] inside the rock anchor, the tool configured for the rod to engage and activate the expansion assembly [once the flange formation has stopped travel of the rock anchor into the drill hole and] as the predetermined force is delivered by the driving head to the deformable spacer; and wherein the driving head provides the stop on the tool.

[0022] The deformable spacer provides an indicator that shows that the tool has been driven adequately to activate the expansion assembly inside the rock anchor.

[0023] The invention further provides for:

[0024] I. the first stage to be carried out, while the flange formation on the rock anchor approaches a rock face, with the driving head of the tool acting against the rock anchor through the deformable spacer; and

[0025] II. the second stage to be carried out, when the flange formation of the rock anchor is stopped by the rock face, with the impacting rod acting against the wedge of the expansion assembly, while the deformable spacer yields under action of the driving head.

[0026] The invention further provides for the deformable spacer to be located behind the flange formation.

[0027] Further features of the invention provide for the deformable spacer to be a cuff at the outer end of the rock anchor with a deformable wall; for the wall of the cuff to include a region of weakness; for a front of the cuff to incorporate the flange formation of the rock anchor; for the cuff to be welded to the body of the rock anchor; and for the cuff to have a cylindrical wall.

[0028] Further features of the invention provide for the region of weakness in the wall to be provided by: an arrangement of openings; spaced apart longitudinal slots; one or more lines of reduced material thickness; and / or one or more fold lines.

[0029] Further features of the invention provide for the deformable spacer to be a telescopic sleeve that protrudes rearwardly from an annular guide at the outer end of the rock anchor; for the guide to have a cylindrical wall; for the sleeve to be supported within the guide and for the guide and / or outer end of the rock anchor to resist forward travel of the sleeve; for the sleeve to be a friction fit into the guide; for the sleeve to be a press (or interference) fit into the outer end of the rock anchor; for a front of the guide to incorporate the flange formation of the rock anchor; and for the guide to be welded to the body of the rock anchor.

[0030] The invention still further provides for the flange formation to abut against a bearing (or washer) plate that engages against rock around a drill hole.

[0031] Further features of the invention provide for the tool to include a rigid insert that is removably locatable in a first position adjacent the rod between the stop on the tool and the outer end of the rock anchor during the first stage, wherein the insert engages against the rock anchor for insertion of the rock anchor into a drill hole, and wherein the insert is moved to a second position spaced away from the rod for the second stage.

[0032] Further features of the invention provide for the insert to be a longitudinally split sleeve yoke that fits over the shaft or for the insert to be two halves of a longitudinally split cylinder that are supported together around the shaft. The insert may alternatively be a telescopic sliding component on the backend, which slides forward and is locked in an extended condition. A shear pin provided to break at a predetermined force may hold the sliding component in the first position. The invention still further provides for the tool to include a stamping formation provided at a rear end of the rod adjacent the stop on the tool, with the stamping formation to provide a mark at an outer end of the rock anchor indicating travel of the tool required to activate the expansion assembly.

[0033] In accordance with a second aspect of the invention there is provided a combination of a rock anchor and a tool: the rock anchor having an impact driven expansion assembly supported by a body of the rock anchor; a flange formation on the body of the rock anchor which stops travel of the rock anchor on insertion into a drill hole; and an indicator mechanism comprising a deformable spacer adjacent an outer end of the rock anchor that:

[0034] - receives impacts for insertion of the rock anchor into an installed position within a drill hole; and

[0035] - is configured to yield when subjected to a predetermined force; the tool having a coupling for engagement with a percussion mechanism, a driving head that engages the deformable spacer and a central impacting rod that extends forwardly from the driving head [past the deformable spacer] inside the rock anchor, the tool configured for the rod to engage and activate the expansion assembly [once the flange formation has stopped travel of the rock anchor into the drill hole and] as the predetermined force is delivered by the driving head to the deformable spacer.

[0036] The deformable spacer provides an indicator that shows that the tool has been driven adequately to activate the expansion assembly inside the rock anchor.

[0037] The invention further provides for: I. a first stage of installation to be carried out, while the flange on the rock anchor approaches a rock face, with the driving head of the tool acting against the rock anchor through the deformable spacer; and

[0038] II. a second stage of installation to be carried out, when the flange of the rock anchor is stopped by the rock face, with the impacting rod acting against the wedge of the expansion assembly, while the deformable spacer yields under action of the driving head.

[0039] The invention further provides for the deformable spacer to be located behind the flange formation.

[0040] Further features of the invention provide for the deformable spacer to be a cuff at the outer end of the rock anchor with a deformable wall; for the wall of the cuff to include a region of weakness; for a front of the cuff to incorporate the flange formation of the rock anchor; for the cuff to be welded to the body of the rock anchor; and for the cuff to have a cylindrical wall.

[0041] Further features of the invention provide for the region of weakness in the wall to be provided by: an arrangement of openings; spaced apart longitudinal slots; one or more lines of reduced material thickness; and / or one or more fold lines.

[0042] Further features of the invention provide for the deformable spacer to be a telescopic sleeve that protrudes rearwardly from an annular guide at the outer end of the rock anchor; for the guide to have a cylindrical wall; for the sleeve to be supported within the guide and for the guide and / or outer end of the rock anchor to resist forward travel of the sleeve; for the sleeve to be a friction fit into the guide; for the sleeve to be a press (or interference) fit into the outer end of the rock anchor; for a front of the guide to incorporate the flange formation of the rock anchor; and for the guide to be welded to the body of the rock anchor.

[0043] The invention still further provides for the flange formation to abut against a bearing (or washer) plate that engages against rock around a drill hole.

[0044] The invention still further provides for the deformable spacer to be provided by a region of weakness in the wall of the rock anchor body, between the flange formation and the outer end of the rock anchor. The flange formation may be a ring that is welded onto the rock anchor or it may be an external lateral ridge that is folded into the wall of the rock anchor body adjacent the outer end of the body to extend around the body from a first edge of a slot along the body and a second edge of the slot.

[0045] The invention still further provides for the expansion assembly to include a wedge with a collar located over the wedge and to be supported adjacent a front end of the rock anchor, with the impacting rod to deliver impacts to the wedge providing longitudinal impact driven travel of the wedge relative to a collar resulting in activation of the expansion assembly through radial expansion of the collar and outward deformation of a sidewall of the rock anchor.

[0046] The invention further provides for the wedge to, in the second stage of installation, be extruded through the collar and / or for a region at an inside of the collar to be drawn with the wedge to accommodate a smaller diameter drill hole size.

[0047] Further features of the invention provide for the wedge to have an elongate body with a conical region providing a forward taper located (at least partly) inside the collar; for the wedge and collar have a tapered interface providing co-operating bearing surfaces; for the collar to be provided as a split ring with an internal taper corresponding substantially to the taper of the wedge; and for an expansion gap provided by an opening in the split ring collar to be aligned with a slot of the rock anchor.

[0048] The wedge is preferably frusto-conical and the collar is a ring with substantially cylindrical external form and a tapered bore.

[0049] The collar preferably has a single ring component with a single transverse split (to receive the wedge with a friction fit) but may be provided as two or more ring components resulting from more than one split.

[0050] Further features of the invention provided for the expansion assembly to be supported adjacent the inner end of the rock anchor; for the expansion assembly to be supported (at least partly) inside a tapered section at a front end of the rock anchor; and for an outside of the collar to be supported against the sidewall of the rock anchor.

[0051] Further features of the invention provide for the collar to include two or more split rings provided in spaced apart arrangement along the wedge; for the collar to comprise a radial arrangement of at least two leaf components located (at least partly) over the wedge; and for each of the leaf components to provide an external ridge formation.

[0052] In accordance with a third aspect of the invention there is provided a rock anchor having an expansion assembly supported by a body of the rock anchor; an indicator mechanism comprising a deformable spacer adjacent an outer end of the rock anchor the expansion assembly activated by applying a force with a tool; the deformable spacer

[0053] - arranged to be subjected to the force that is applied to the expansion assembly; and

[0054] - configured to yield when subjected to a predetermined force; wherein the predetermined force corresponds to an installation requirement for activation of the expansion assembly.

[0055] The deformable spacer provides an indicator that shows that adequate force has been applied through a tool to activate the expansion assembly inside the rock anchor.

[0056] Further features of the invention provide for the deformable spacer to be a cuff at the outer end of the rock anchor with a deformable wall; for the wall of the cuff to include a region of weakness; for the cuff to be welded to the body of the rock anchor; and for the cuff to have a cylindrical wall.

[0057] Further features of the invention provide for the region of weakness in the wall to be provided by: an arrangement of openings; spaced apart longitudinal slots; one or more lines of reduced material thickness; and / or one or more fold lines.

[0058] Further features of the invention provide for the deformable spacer to be a telescopic sleeve that protrudes rearwardly from an annular guide at the outer end of the rock anchor; for the guide to have a cylindrical wall; for the sleeve to be supported within the guide and for the guide and / or outer end of the rock anchor to resist forward travel of the sleeve; for the sleeve to be a friction fit into the guide; for the sleeve to be a press (or interference) fit into the outer end of the rock anchor; and for the guide to be welded to the body of the rock anchor.

[0059] The invention provides for the expansion assembly to be activated by torque applied to an external nut or bolt on a screw-threaded shaft with a tightening hub provided between the nut or bolt and the deformable spacer and an inner end of the shaft engaged with the expansion assembly; and for the tool to have a coupling for engagement with a rotation mechanism and a socket to engage the nut or bolt.

[0060] The invention alternatively provides for expansion assembly to be impact activated and for the tool to have a coupling for engagement with a percussion mechanism, a driving head that engages the deformable spacer and a central impacting rod that extends forwardly from the driving head [past the deformable spacer] inside the rock anchor, the tool configured for the rod to engage and activate the expansion assembly as the predetermined force is delivered by the driving head to the deformable spacer.

[0061] A further feature of the invention provides a flange formation to be provided on the body of the rock anchor which stops travel of the rock anchor on insertion into a drill hole. The invention still further provides for the flange formation to abut against a bearing (or washer) plate that engages against rock around a drill hole.

[0062] The invention still further provides for the expansion assembly to include a wedge with a collar and for these parts to be as defined in the statements above.

[0063] The rock anchor referred to in the statements of the three aspects set out above is preferably a friction anchor and more specifically a split set. The percussion mechanism referred to will include a rock drill and the tool backend engagement may be into a chuck of the rock drill.

[0064] BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Preferred embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a front perspective view of a split set having a longitudinal slot with an expansion assembly located inside, adjacent an inner end and with broken lines showing hidden detail of the expansion assembly;

[0066] Figure 2 shows a side view of a split set (facing a longitudinal slot) with a deformable spacer on an outer end and an expansion assembly for a fastening mechanism located inside, adjacent an inner end;

[0067] Figure 3 shows a cross-section of the split set in Figure 1, as from the opposite side;

[0068] Figure 4 shows an inner perspective view of an outer end of a split set, fitted with an alternative deformable spacer prior to activation of an expansion assembly;

[0069] Figure 5 shows a side cross-section of the split set and deformable spacer of Figure 3 located through a bearing plate;

[0070] Figure 6 shows an outer perspective view of the parts shown in Figure 4;

[0071] Figure 7 shows an outer perspective view of the parts from Figure 5 with the deformable spacer after activation of an expansion assembly;

[0072] Figure 8 shows an outer perspective view of an outer end of a split set, fitted with an alternative deformable spacer prior to activation of an expansion assembly;

[0073] Figure 9 shows a side cross-section of the split set and deformable spacer of Figure 8;

[0074] Figure 10 shows an outer perspective view the parts in Figure 8 after activation of an expansion assembly;

[0075] Figure 11 shows a side cross-section of the parts in Figure 10;

[0076] Figure 12 shows an exploded perspective view of a tool that serves to insert a split set with a deformable spacer (as shown in Figures 1, 3 or 7) and activate an expansion assembly; Figure 13 shows a side cross-sectional view of the tool in Figure 11, with its parts assembled;

[0077] Figures 14-17 show a series of side cross-sectional views of a tool as shown in Figure 11 being used to insert a split set with a deformable spacer on an outer end and an expansion assembly for a fastening mechanism located inside, adjacent an inner end;

[0078] Figure 18 shows a side cross-section of a deformable spacer prior to activation of an expansion assembly (not shown), which requires tightening of a nut;

[0079] Figure 19 shows a side cross-section of a further embodiment of deformable spacer prior to activation of an expansion assembly (not shown), which requires tightening of a nut; and

[0080] Figure 20 shows a side cross-section of the parts in Figure 19 after activation of the expansion assembly.

[0081] The drawings are representative and provided to facilitate an understanding of the features of the invention rather than being exact and to scale. Dimensions, proportions and variations will be within the design competence and understanding of a person skilled in the art.

[0082] DETAILED DESCRIPTION OF THE INVENTION

[0083] Referring to Figures 1 to 3 of the drawings, a rock anchor 100 is shown as a split set 100 to which the features of the invention are applied. A fastening mechanism 102 and indicator mechanism 104 of the invention will also find application in other suitably configured rock anchors. The split set 100 has an impact driven expansion assembly 102 supported by a body 106 of the split set and more specifically inside a sidewall 107 of the split set. The expansion assembly 102 includes a wedge 108 with a collar 110. The collar is located over the wedge and the expansion assembly 102 is supported adjacent a front or inner end 112 of the split set.

[0084] The wedge 108 has an elongate body with a conical region providing a forward taper located (at least partly) inside the collar 110. The wedge is preferably frusto-conical and the collar is a ring 110 with substantially cylindrical external form and a tapered bore. More specifically, the collar is provided as a split ring 110 with an internal taper corresponding substantially to the taper of the wedge.

[0085] The wedge 108 and collar 110 have a tapered interface providing co-operating bearing surfaces. The collar preferably has a single ring component with a single transverse split (to receive the wedge with a friction fit) but may be provided as two or more ring components resulting from more than one split.

[0086] The expansion assembly 102 is supported adjacent the inner end 112 of the split set and, at least partly, inside a tapered section. An expansion gap provided by an opening 114 in the split ring collar 110 is aligned with a slot 116 of the split set 100 when the expansion assembly 102 is fitted, prior to supply of the rock anchor for installation.

[0087] The expansion assembly 102 is inserted into a reduced diameter portion at the front of the split set 100 - see Figures 2 and 3. The outside of the collar 110 abuts the sidewall 107 of the split set with a front side locating against an arrangement of inwardly pressed stop formations in the sidewall 107 - see Figure 1. The wedge 108 is retained in the collar 110 with a friction fit and the collar is retained by the sidewall 107 with a friction fit (these fits are facilitated by the split in the collar and the slot in the split set). Once the expansion assembly 102 is in place, inwardly pressed stop formations may also be provided behind the wedge. The split set 100 includes a flange formation 118 on the body 106, which stops travel of the split set on insertion into a drill hole. The indicator mechanism 104 is provided as a deformable spacer 104 located between the flange formation 118 and an outer end 120 of the split set.

[0088] A first embodiment of the deformable spacer 104 is provided as a cuff 122 with a deformable wall 124. This is shown in Figures 2 and 3 and, also in a varied form in Figures 4 to 7. The wall 124 of the cuff 122 is cylindrical and provided to include a region of weakness 126. A front of the cuff to is folded to provide the flange formation 118 at a position where the cuff is welded to the body 106 of the split set 100.

[0089] The region of weakness 126 in the wall 124 may be provided by: an arrangement of openings 127; spaced apart longitudinal slots; one or more lines of reduced material thickness; and / or one or more fold lines.

[0090] Figures 2 and 3 show the cuff 122 with four equally spaced apart elongate openings 127, with rounded ends.

[0091] In Figures 4 to 6, the cuff 122 has four circular openings 127, with Figure 7 showing the deformable spacer 104 after it has yielded to a predetermined force, as referred to. Additionally, the flange formation 118 in Figures 5 to 7 is shown against a bearing (or washer) plate 128. The split set 100 is preferably or commonly used in assembly with the bearing plate, which may be provided in various embodiments. The flange formation 118 abuts the bearing plate 128 which engages against the rock face around a drill hole.

[0092] In some embodiments, the cuff 122 will be provided with a small internal protuberance in the wall 124 between the openings 127. This serves to react to contact with a part of a tool when the cuff 122 is being deformed, sufficiently for the wall 124 to be directed to fold outwardly (rather that inwardly to clamp against the tool). The protuberance may, for example, be a bump formed by pressing the wall to create a dimple. A ridge or flange could also be provided. The protuberance may involve press-forming, punching or welding, for example.

[0093] In a development of cuffs as illustrated, a rim may be folded into the cuff material around the opening. The rim serves to re-enforce the opening and deter against closure of the opening when the cuff is deformed. The maintained size of the opening will avoid closure onto the tool.

[0094] A second embodiment of deformable spacer 104 is shown in Figures 8 to 11, where the first two drawings show a deformable spacer in a pre-installation condition and the second two drawings show a post-installation condition after it has yielded to a predetermined force.

[0095] This deformable spacer 104 is provided as a telescopic sleeve 130 that protrudes rearwardly from an annular guide 132 at the outer end 120 of the split set 100. The guide 132 has a cylindrical wall 134 and the sleeve 130 is supported within the guide. The wall 134 of the guide has an internal diameter portion that fits over the body 106 of the split set 100 and is welded in place. A slightly smaller diameter portion of the wall 134 receives the sleeve which partially abuts the split set body 106 as shown.

[0096] In this embodiment, the guide 132 and / or outer end 120 of the split set body 106 are arranged to resist forward travel of the sleeve 130: the sleeve 130 is a friction fit into the guide 132; and the sleeve 130 to be a press (or interference) fit into the outer end 120 of the body 106. It will be appreciated that it is the press fit into the split set that generates a greater resistance in this embodiment and that there will be various design options to achieve a predetermined force to which the spacer will yield.

[0097] Figures 12 and 13 show a tool 136 for installation of a split set 100, which includes a deformable spacer 104. The installation operation is shown in Figures 14 to 16 and Figure 17 shows the installed split set 100 with activated expansion assembly (fastening mechanism) and post- installation deformed spacer (indicator mechanism).

[0098] The invention is implemented in combination with the installation tool 136. The tool has a rear coupling 138 for engagement with a percussion mechanism (shown in broken lines in Figures 14 to 16). A driving head 140 is provided to engage the deformable spacer 104. A central impacting rod 142 extends forwardly from the driving head.

[0099] In this embodiment, the impacting rod 142, which has a hex-profile, is slidably retained in a hex-shaped socket 144 of the driving head 140 by a removable retaining pin 146. The pin 146 locates across the socket 144 in a recess 148 machined into the rod 142. The coupling of these separate parts in this manner has been found to avoid breakages where the rod is fixed (welded or otherwise) to the head. The limited sliding arrangement allows for a dissipation of energy that is transmitted from the percussion mechanism.

[0100] In a development of the tool as shown, a second retaining pin and machined recess will be provided on the opposite side of the socket and rod, respectively. Also, the front of the driving head may be provided with a guide rube that fits into a deformable spacer (to assist with an aligned application of force and symmetrical deformation). Furthermore, the driving head may be provided with an annular groove that receives the outer edge of the deformable spacer and serves to retain a circular form and resist inward or asymmetrical buckling. The function of the driving head 140 is to engage at a first position against the deformable spacer 104 for insertion of the split set 100 and then move past the first position by an adequate degree for activation of an anchor mechanism 102, which happens on yielding of the deformable spacer. In use, the rod 142 extends through the deformable spacer and is located inside the split set 100.

[0101] The installation is carried out in:

[0102] I. a first stage, while the flange formation 118 on the split set approaches a rock face, with the driving head 140 of the tool 136 acting against the split set 100 through the deformable spacer 104; and

[0103] II. a second stage, when the flange formation 118 has reached or is stopped by the rock face, with the impacting rod 142 acting against the wedge 108 of the expansion assembly 102, while the deformable spacer 104 yields under action of the driving head 140.

[0104] The tool 136 is configured for the rod 142 to engage and activate the expansion assembly 102 once the flange formation 118 has stopped travel of the split set 100 into the drill hole and as the predetermined force is delivered by the driving head 140 to the deformable spacer 104.

[0105] As the spacer 104 deforms, the impacting rod 142 reaches deeper into the split set striking the wedge 108 of the expansion assembly 102.

[0106] In Figures 7 and 17, the deformed condition of the spacer 104 provided at the outer end 120 of the split set 100 provides a visual indication that the fastening mechanism 102 has been activated inside the installed split set. The deformed spacer 104 thus shows that the tool 136 has been driven adequately to activate the expansion assembly 102 inside the split set. The invention as described enables, in a single operation:

[0107] (a) installation of the split set 100;

[0108] (b) activation of the fastening mechanism 102; and

[0109] (c) marking of the outside, visible portion of the split set to show (b) above.

[0110] This is carried out in a first step that achieves (a) and a second step where (b) and (c) are achieved, without the need for any tool changes.

[0111] The distance that the driving head 140 travels on deformation of the spacer 104 is suitable for the rod 142 to activate the expansion assembly 102.

[0112] The configuration and operation of these components and the respective features as required for regular and reliable installation in relation to differing drill holes and conditions will be within the design competence of a person suitably skilled in the art.

[0113] In the illustrated embodiment, the driving head 140 provides a stop 150 on the tool from which the impacting rod 142 extends. The tool 136 is configured for the length of the impacting rod 142 to provide a space between the stop 150 on the tool and the outer end 120 of the split set 100 that corresponds to a required travel of the wedge 108 for activation of the expansion assembly 102 and for the stop 150 on the tool to be arrested by the outer end 120 of the split set 100 before a front end 143 of the rod 142 reaches the collar 110.

[0114] This working configuration of the tool 136 applies whether or not a deformable spacer 104 is present on the back of the split set 100. The feature of the invention is significant in that the energy / impact delivery of the rod 142 is limited to a position that prevents the wedge from being driven through the collar 110, which would result in failure of the anchoring effect of the fastening mechanism 102. With reference to Figures 16 and 17, in the second stage of installation, the wedge 108 will be extruded through the collar 110 and / or a region at an inside of the collar 110 to be drawn with the wedge 108. The degree to which this deformation takes place will depend on the drill hole size / diameter. In the preferred embodiment, both wedge 108 and collar 110 are machined from round bar (of a suitable mild steel). The manufacture may also be by way of or include an initial step of forging of the parts.

[0115] In the result, a fixed activation impact / travel stroke is provided for the rod 142 to wedge 108 activation (based on space between the stop 150 on the tool and the outer end 120 of the split set), with a tolerance for the drill hole size built into the in situ deformation of the wedge 108 and collar 110. The feature is a significant advantage in that one model of split set 100 can be used for installation in drill holes that start at one size (about 38mm diameter, for example) when the rock drill steel bits are new and progressively get smaller (to about 35mm diameter, for example) as the rock drill steel bits wear down. The split set and fastening mechanism of the invention therefore has a wide tolerance for working drill hole sizes and will thus accommodate a smaller diameter drill hole size.

[0116] The illustrated version of the expansion assembly has been found to pass a 10 ton pull test in drill holes between 35 to 38 mm, which covers the working conditions in many underground mines. Modification for different hole diameter ranges will be within the design competence of a person skilled in the art.

[0117] In an alternative embodiment of tool, which will operate on a split set that does not include the deformable spacer, there may be included a rigid insert that is removably locatable in a first position adjacent the rod between the stop on the tool and the outer end of the split set during the first stage, wherein the insert engages against the split set for insertion of the split set into a drill hole, and wherein the insert is moved to a second position spaced away from the rod for the second stage. The insert may be a longitudinally split sleeve yoke that fits over the shaft. Alternatively, the insert may be two halves of a longitudinally split cylinder that are supported together around the shaft. The insert may further alternatively be a telescopic sliding component on the backend, which slides forward and is locked in an extended condition. In the case of the latter, a shear pin that holds the sliding component in place may be provided to break at the predetermined force (similar to the deformable spacer).

[0118] The tool that is used may also include a stamping formation provided at a rear end of the rod adjacent the stop on the tool to provide a mark at an outer end of the split set indicating travel of the tool as required to activate the expansion assembly. The stamping formation may leave an "X" mark or an "0" mark, for example, on a surface at the outer end of the split set. It may also be as simple as a notch or other mark that is stamped onto the back end of the tubular split set body. Alternatively, the mark may be made on a bearing / washer plate. A marking mechanism may also incorporate an external coloured marker on the split set that is damaged by the stamping formation, which may be more visible or detectable through visual inspection.

[0119] Referring to Figure 18, a deformable spacer 104 similar to that in Figures 4 to 7 is shown fitted to a friction rock anchor 100. The rock anchor has an expansion assembly 102 that is activated by an external nut 152 on a screw-threaded shaft 154.

[0120] A tightening hub 156 is provided between the nut 152 and the deformable spacer 104. An inner end of the shaft 154 is engaged with a rearwardly tapered head 158, that is drawn into the end of a tube 160 to provide the expansion assembly 102. The deformable spacer 104 is provided as a cuff 122 at the outer end 120 of the rock anchor 100 with a deformable wall 124 having an arrangement of spaced apart openings 127.

[0121] In Figures 19 and 20, a deformable spacer 104 is similar to that shown in Figures 8 to 11 with a telescopic sleeve 130 that protrudes rearwardly from an annular guide 132 at the outer end 120 of a rock anchor 100. The rock anchor 100 similarly has an external nut 152 on a screw-threaded shaft 154 which will be connected for activation of an expansion assembly (not shown). A tightening hub 156 is provided between a nut 152 and the deformable spacer 104.

[0122] In these two embodiments, which involve a tightening nut 152, the rock anchors 100 will be used with a tool (not shown) having a coupling for engagement with a rotation mechanism and a socket to engage the nut 152. The expansion assembly is activated by torque applied to the external nut 152 on the screw-threaded shaft 154.

[0123] More specifically, the expansion assembly is activated by applying a force with the tool and the deformable spacer 104 is arranged to be subjected to the force that is applied to the expansion assembly and configured to yield when subjected to a predetermined force. The predetermined force corresponds to an installation requirement for activation of the expansion assembly.

[0124] (In a different arrangement, a bolt may be provided on the outside of the split set for activation of the expansion assembly, which may include a biasing nut.)

[0125] The torque is applied to the nut (or bolt) head using the tool drives the screw-threads to advance the shaft axially relative to mating screw-threads between the parts. This converts a portion of the torque into an axial force that acts on the deformable spacer.

[0126] It will be appreciated that the deformable spacer will be configured and constructed differently for use with different activation forces in different embodiments and applications of the invention.

[0127] The invention accordingly provides a convenient and effective rock anchor apparatus capable of installation with a single tool used in a single operation which installs the split set, activates the expansion assembly and leaves a mark to indicate from a visual inspection outside the hole that the installation has been properly carried out. This also prevents overtravel of the kind that can push a wedge all the way through an anchor mechanism.

[0128] A split set of given length can thus be installed with an increased engagement of rock inside a hole and will demonstrate a markedly improved pull test rating with a tolerance for use in holes of varying diameter according to the degree of rock drill but wear.

[0129] The force applied to the expansion assembly may be selected to be high for installation load rating or on the lower side where the split set is installed in softer or brittle rock, for example.

[0130] The expansion assembly may be supported or secured inside the split set through any suitable means.

[0131] The collar may include two or more split rings provided in spaced apart arrangement along the wedge. The collar may alternatively comprise a radial arrangement of at least two leaf components located (at least partly) over the wedge. Each of the leaf components may provide an external ridge formation.

[0132] In a development of the invention, a deformable spacer may be provided by a region of weakness in the wall of the split set body, between the flange formation and the outer end of the split set.

[0133] The flange formation may be a ring that is welded onto the split set or it may be an external lateral ridge that is folded into the wall of the split set body adjacent the outer end of the body to extend around the body from a first edge of a slot along the body and a second edge of the slot.

[0134] The deformable spacer of the invention may be deformable (elastic or plastic), foldable, bendable, compressible, weak or brittle and may include fold lines or lines of reduced material thickness or openings or cutaways, for example (to fold, bend, shear, break, bend, or crumple etc. under the predetermined load) with the resulting deformation providing the visual indicator. The variations covered will be appreciated by a person skilled in the art. The use of "yield" in this specification will have a meaning inclusive of the aforesaid when the predetermined force is reached.

[0135] The apparatus of the invention is considered to be cost effective and preferred embodiments can be made with minimal to no welding. The description above has been directed to particular preferred embodiments and variations thereof for purposes of explanation and illustration. It will be apparent, however, to those skilled in the art that the features shown and described may be changed without departing from the essence / scope of the invention.

Claims

CLAIMS1. A combination of a rock anchor and a tool: the rock anchor having an impact driven expansion assembly supported by a body of the rock anchor; a flange formation on the body of the rock anchor which stops travel of the rock anchor on insertion into a drill hole; the expansion assembly includes a wedge with a collar located over the wedge and is supported adjacent a front end of the rock anchor; the tool includes a backend with a coupling configured for engagement with a percussion mechanism and a central elongate impacting rod locatable inside the rock anchor extending from a stop on the tool provided to abut the outer end of the rock anchor; wherein, once the rock anchor has been inserted into an installed position in a drill hole in a first stage of installation, the tool is used in a second stage of installation, to deliver impacts to the wedge providing longitudinal impact driven travel of the wedge relative to a collar resulting in activation of the expansion assembly through radial expansion of the collar and outward deformation of a sidewall of the rock anchor; a length of the impacting rod provides a space between the stop on the tool and the outer end of the rock anchor that corresponds to a required travel of the wedge for activation of the expansion assembly; and the stop on the tool is arrested by the outer end of the rock anchor before a front end of the rod reaches the collar.

2. The rock anchor and tool of claim 1 in which the wedge, in the second stage of installation, is extruded through the collar and / or a region at an inside of the collar is drawn with the wedge.

3. The rock anchor and tool of claim 1 or claim 2 in which the wedge has an elongate body with a conical region providing a forward taper located at least partly inside the collar and the collar is provided as a split ring with an internal taper corresponding substantially to the taper of the wedge.

4. The rock anchor and tool of any one of claims 1 to 3 in which the rock anchor includes an indicator mechanism comprising a deformable spacer adjacent the outer end of the rock anchor that:- receives impacts for insertion of the rock anchor into an installed position within a drill hole; and- is configured to yield when subjected to a predetermined force; for the tool to have a driving head that engages the deformable spacer and the central impacting rod extending forwardly from the driving head inside the rock anchor, the tool configured for the rod to engage and activate the expansion assembly as the predetermined force is delivered by the driving head to the deformable spacer; and wherein the driving head provides the stop on the tool.

5. The rock anchor and tool of claim 4 in which: the first stage is carried out, while the flange formation on the rock anchor approaches a rock face, with the driving head of the tool acting against the rock anchor through the deformable spacer; and the second stage to be carried out, when the flange formation of the rock anchor is stopped by the rock face, with the impacting rod acting against the wedge of the expansion assembly, while the deformable spacer yields under action of the driving head.

6. The rock anchor and tool of claim 4 or claim 5 in which the deformable spacer is a cuff at the outer end of the rock anchor with a deformable wall.

7. The rock anchor and tool of claim 4 or claim 5 in which the deformable spacer is a telescopic sleeve that protrudes rearwardly from an annular guide at the outer end of the rock anchor.

8. A combination of a rock anchor and a tool: the rock anchor having an impact driven expansion assembly supported by a body of the rock anchor; a flange formation on the body of the rock anchor which stops travel of the rock anchor on insertion into a drill hole; and an indicator mechanism comprising a deformable spacer adjacent an outer end of the rock anchor that:- receives impacts for insertion of the rock anchor into an installed position within a drill hole; and- is configured to yield when subjected to a predetermined force; the tool having a coupling for engagement with a percussion mechanism, a driving head that engages the deformable spacer and a central impacting rod that extends forwardly from the driving head inside the rock anchor, the tool configured for the rod to engage and activate the expansion assembly as the predetermined force is delivered by the driving head to the deformable spacer.

9. The rock anchor and tool of claim 8 in which the deformable spacer is a cuff at the outer end of the rock anchor with a deformable wall.

10. The rock anchor and tool of claim 9 in which the wall of the cuff to includes a region of weakness.

11. The rock anchor and tool of claim 8 in which the deformable spacer is a telescopic sleeve that protrudes rearwardly from an annular guide at the outer end of the rock anchor.

12. The rock anchor and tool of claim 11 in which the sleeve is supported within the guide and the guide and / or outer end of the rock anchor resist forward travel of the sleeve.

13. The rock anchor and tool of claim 12 in which the sleeve is a press fit into the outer end of the rock anchor.

14. The rock anchor and tool of any one of claims 8 to 14 in which the expansion assembly includes a wedge with a collar located over the wedge and is supported adjacent a front end of the rock anchor, with the impacting rod to deliver impacts to the wedge providing longitudinal impact driven travel of the wedge relative to a collar resulting in activation of the expansion assembly through radial expansion of the collar and outward deformation of a sidewall of the rock anchor.

15. The rock anchor and tool of claim 14 in which the wedge is extruded through the collar and / or a region at an inside of the collar to be drawn with the wedge on activation of the expansion assembly.

16. The rock anchor and tool of claim 15 in which the wedge to has an elongate body with a conical region providing a forward taper located at least partly inside the collar and for the collar to be provided as a split ring with an internal taper corresponding substantially to the taper of the wedge.

17. A rock anchor having an expansion assembly supported by a body of the rock anchor; an indicator mechanism comprising a deformable spacer adjacent an outer end of the rock anchor the expansion assembly activated by applying a force with a tool;the deformable spacer:- arranged to be subjected to the force that is applied to the expansion assembly; and- configured to yield when subjected to a predetermined force; wherein the predetermined force corresponds to an installation requirement for activation of the expansion assembly.

18. The rock anchor of claim 17 in which the deformable spacer is a cuff at the outer end of the rock anchor with a deformable wall.

19. The rock anchor of claim 17 in which the deformable spacer is a telescopic sleeve that protrudes rearwardly from an annular guide at the outer end of the rock anchor.

20. The rock anchor of any one of claims 17 to 19 in which the expansion assembly is activated by torque applied to an external nut or bolt on a screw-threaded shaft with a tightening hub provided between the nut or bolt and the deformable spacer and an inner end of the shaft engaged with the expansion assembly.

21. The rock anchor of claim 20 in which the tool has a coupling for engagement with a rotation mechanism and a socket to engage the nut or bolt.

22. The rock anchor of any one of claims 17 to 19 in which the expansion assembly is impact activated and for the tool to have a coupling for engagement with a percussion mechanism, a driving head that engages the deformable spacer and a central impacting rod that extends forwardly from the driving head inside the rock anchor, the tool configured for the rod to engage and activate the expansion assembly as the predetermined force is delivered by the driving head to the deformable spacer.

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