A rock anchor assembly

Abstract

A rock anchor assembly includes a split set and a bearing plate. The split set has an elongate tubular body with a longitudinal slot and a tapered section at an inner end. The bearing plate has a hole to receive the body of the split set. The split set is formed with an external lateral ridge that is folded into a wall of the body adjacent an outer end. The ridge extends around the body between a first edge of the slot and a second edge of the slot. The ridge provides a stop to retain the bearing plate on the body of the split set. The assembly includes a spacer to resist closure of the slot in a region of the ridge.

Description

[0001] A ROCK ANCHOR ASSEMBLY

[0002] FILED OF THE INVENTION

[0003] The invention relates to a friction type rock anchor of the kind commonly referred to as a split set or a friction bolt which is assembled with a bearing plate for use in providing rock support.

[0004] BACKGROUND TO THE INVENTION

[0005] A tubular body has a longitudinal slot and a taper at an inner (or front) end. The split set is driven / pressed into a hole that has been formed by a rock drill. 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 slot and forward taper is rolled to form and a ring or split-ring is welded at or adjacent an 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.

[0007] 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. The bearing plate may, for some applications, simply be flat with a hole in the middle. The shapes include round and four sided versions.

[0008] These relatively simple configuration products are used in vast numbers. The relevant industries include mining and construction. OBJECT OF THE INVENTION

[0009] It is an object of the invention to provide a split set that, depending on the embodiment, has a reduced material cost, manufacturing cost, carbon footprint, and / or environmental impact. The split set may also provide additional strength under load due to its construction and / or over time where galvanizing is required for the product to resist rust.

[0010] SUMMARY OF THE INVENTION

[0011] In accordance with the invention there is provided a rock anchor comprising an assembly of a split set and a bearing plate: the split set having an elongate tubular body with a longitudinal slot, the bearing plate having a hole to receive the body of the split set, characterized in that: the body has an external lateral ridge that is folded into a wall of the body adjacent an outer end (of the body) to extend around the body between a first edge of the slot and a second edge of the slot; the ridge provides a stop to retain the bearing plate on the body of the split set; and the assembly includes a spacer resist closure of the slot in a region of the ridge.

[0012] The invention further provides for a spacer to be located in a vicinity of the outer end; and for the spacer to be located at or adjacent the ridge.

[0013] A further feature of the invention provides for the spacer to be located between the first edge and the second edge of the slot.

[0014] Further features of the invention provide for the spacer to be an inwardly disposed lug on a collar; the lug to be provided on a washer that is pressed to form from sheet metal; the lug to be positioned through the slot with a pair of lips that extend at opposite sides of the lug to locate on an inside of the body adjacent the first edge and the second edge of the slot; the lug to have a material thickness that is greater than a thickness of the wall material of the body; and an inner edge extending between the lips to be located to an inside of the body across the slot.

[0015] Further features of the invention provide for the collar to be located between the ridge and bearing plate; and the bearing plate to includes an annular cylindrical cuff that is located around the body and abuts the collar.

[0016] A further feature of the invention provides for the spacer to be an inwardly disposed lug provided in the hole of the bearing plate.

[0017] A further feature of the invention provides for the spacer to be provided by an insert that is located within the body of the split set and configured to abut wall sections of the body to either side of the slot.

[0018] Further features of the invention provide for the spacer to be an outwardly disposed lug provided on an annular insert; and for the annular insert to be pressed into engagement with an inside of the lateral ridge.

[0019] A further feature of the invention provides for the insert to be a plug that is fitted into the tubular body; and for the plug to include a cylindrical wall with a circumferential rib that is pressed into engagement with an inside of the lateral ridge.

[0020] A further feature of the invention provides for the insert to be an annular component that is pressed into engagement with an inside of the lateral ridge.

[0021] A further feature of the invention provides for the spacer to be a separate component that is fitted into a gap between the first edge of the slot and the second edge of the slot and secured in place. A further feature of the invention provides for the outer end of the tubular body to be folded forward to provide an annular flange.

[0022] A further feature of the invention provides for the outer end to be folded forward to provide an annular flange with curved return that engages over a collar.

[0023] The collars / inserts can be provided as a circular pressed washer or a split-ring that is bent to form. The collar / insert may be pressed to include an inwardly / outwardly disposed lug or an inwardly / outwardly disposed lug may be welded onto the split-ring, respectively.

[0024] A further feature of the invention provides for the first edge of the slot and / or the second edge of the slot to be provided with a protrusion that is spaced apart from the ridge to secure a lug supported on a collar against or adjacent to the ridge.

[0025] A further feature of the invention provides for the spacer to be a collar that is includes a flat section located across the slot for engagement of outer comers along the first edge and the second edge to resist closure of the slot. The collar may be provided by a bearing plate.

[0026] In accordance with a second aspect of the invention there is provided a split set having an elongate tubular body with a longitudinal slot, characterized in that: the body has an external lateral ridge that is folded into a wall of the body adjacent an outer end of the body to extend around the body between a first edge of the slot and a second edge of the slot; and the ridge provides a stop to resist passage of the split set through the bearing plate. The invention further provides for the split set to be for use in an assembly with a bearing plate, wherein the assembly includes a spacer to resist closure of the slot in a region of the ridge.

[0027] The split set of the invention will include the features as defined above in relation to the assembly.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Preferred embodiments of the invention will be described, by way of example only, with reference to the accompanying illustrations in which:

[0030] Figure 1 shows a perspective view of an outer end of a split set from the side of a slot;

[0031] Figure 2 shows another perspective view of the split set in Figure 1 ;

[0032] Figure 3 shows a washer with an inwardly disposed lug proving a spacer for location into the slot of the split set of Figure 1 ;

[0033] Figure 4 shows a perspective view of the washer in Figure 3;

[0034] Figure 5 shows an end view of the washer in Figure 3 fitted to the split set of

[0035] Figure 1 ;

[0036] Figure 6 shows a perspective view of a rock anchor assembly including the split set of Figure 1 fitted with the washer of Figure 3 and a bearing plate with annular cylindrical cuff (the cuff is spaced from the washer in this drawing);

[0037] Figure 7 shows the same view as Figure 5 but with the cuff abutting the washer;

[0038] Figure 8 shows a further embodiment of a spacer with inwardly disposed lug on a collar;

[0039] Figure 9 shows a bearing plate with spacer as inwardly disposed lug;

[0040] Figure 10 shows a further embodiment of a spacer with an outwardly disposed lug provided on an annular insert;

[0041] Figure 11 shows a side cross-sectional view of a further embodiment of split set with an annular flange at the outer end; Figure 12 shows a side cross-sectional view of a further embodiment of split set with an annular flange having a curved return that engages over a ring;

[0042] Figure 13 shows a perspective view of a further embodiment of a spacer that is provided as a plug insert;

[0043] Figure 14 shows a top view of a further embodiment of a spacer that is provided as an annular insert;

[0044] Figure 15 shows a perspective view of a further embodiment of a spacer that is provided as a bearing plate with a flat section in the hole locatable across the slot;

[0045] Figure 16 shows a cross-section of a split set with a folded ridge similar to that shown in Figures 1 and 2; and

[0046] Figure 17 shows a cross-section of a split set with an alternative form of folded ridge.

[0047] DETAILED DESCRIPTION OF THE INVENTION

[0048] Referring to Figures 1 and 2, an outer end (100) of a split set (102) is shown with a longitudinal slot (104) that extends to an inner end (not shown). The split set will include an elongate tubular body (106) with a tapered section provided at the inner end. The tapered section facilitates the initial insertion of the anchor into a drill hole. The features of the spit set along its length and at the inner end may be varied.

[0049] In accordance with the invention, the body (106) has a stop (108) that is provided as an external lateral ridge (110). The ridge is folded into a wall (112) of the body adjacent the outer end (100) of the body and extends around the body from a first edge (114) of the slot (104) to a second edge (116) of the slot (104).

[0050] The ridge (110) accordingly protrudes to an outer surface or a length of the body (106) and will generally be provided at a position similar to that of the welded ring on a conventional split set. This position is stated to be adjacent the outer end (100) and it should be understood that this is meant to cover a range of workable embodiments. A process is used to form the lateral ridge (110) which involves applying an axial pressing force from the outer end (100) of the body (106), which will already be formed into the slotted tube configuration, using a first tool with the portion of the body held in a second tool (or die). A cavity or space is provided between the two tools. The operation causes the wall material to bulge into the cavity. The tool components are suitably configured and arranged to produce the result shown in Figures 1 and 2.

[0051] Figure 16 shows a cross section of a split set (202) with a bulge (210) similar to that shown in Figures 1 and 2. This bulge may be referred to as a 180 degree bulge with opposite shoulders (211 ) substantially or almost perpendicular to the outer surface of the body (206) of the split set. In Figure 17, a split set (302) is provided with a tapered or arrow-shaped bulge (310). This is achieved with a tapered cavity on the first tool that presses towards a perpendicular face of the second tool. The latter provides a shoulder (311 ) which is almost at a right angle to the body (306) and forms an abutting face of the stop (308) on the split set.

[0052] The ridge (110) configuration shown in Figures 1 and 2 represents a preferred embodiment. The forming process provides the resulting stop (108) with a shoulder (at least part of) which is about 90 degrees to an outer surface of the body (106). The ridge bears against loads that result in use and it is this shoulder, on the inward side of the ridge that is opposite to the outer end, which provides the load engaging surface of the ridge.

[0053] Referring to Figures 3 to 5, the invention further provides for a spacer (118) to be located in the vicinity of the outer end to resist closure of the slot (104). A preferred position for the spacer is adjacent the ridge (110). A more specific embodiment of this spacer position is shown in Figures 5 to 7, where the spacer (118) is supported on a collar (122) that abuts the ridge. The spacer itself is located between the first edge (114) and the second edge (116) of the slot (104). The arrangement is achieved with the spacer provided as an inwardly disposed lug (120) on the collar (122). In this embodiment, the lug is provided on a washer (124) that is pressed to form from sheet metal. (The collar may be of various descriptions as referred to below.) This is cost effective, allows for the design / material features / specifications as required and avoids the need for welding.

[0054] The lug (120) extends inwardly through the slot (104) with a pair of lips (126) that each extend at opposite sides of the lug to locate on an inside of the body (106) adjacent the first edge (114) and the second edge (116). In this embodiment, the lips (126) are formed by a curved configuration provided along side edges of the lug (120), which fit between the first edge and the second edge of the slot. The lug is wider than a thickness of the wall material (112) of the body. An inner edge (128) of the lug extends between the lips (126) at a line or at a position which is to located an inside of an inner diameter line of the body (106) across the slot (104). This detail of the lug is most clearly shown in Figures 3 and 5. The inner edge (128) is only slightly to the inside of the body (not to obstruct the passage of a tool that is fitted into the split set) but this configuration / arrangement and radial width of the lug (120) is sufficient to provide an adequate degree of additional strength to resist compression at the edges (114; 116) of the slot and to also resist slipping of the edges to the inside of the lug.

[0055] The lug may also have a material thickness that is greater than the thickness of the wall material of the body, where this is required to provide further strength to resist compression across the slot.

[0056] Referring to Figures 6 and 7, the invention provides for the split set (102) to be used in an assembly with a bearing plate (130). It is the main function of the stop (108) to engage against and retain the bearing plate (130) which has a central hole (132) that receives the body (106). In this embodiment, the washer (124) is located between the stop (108) and the bearing plate (130). A further feature of the invention provides for the bearing plate to include an annular, cylindrical cuff (134) at an edge of the hole. The cuff is located with a close fit around the body (106) and abuts the washer (124). The width of the lug (120) with the lip (126) configuration engages on an inside of the body (106) at the first edge and the second edge. This structure serves not only to resist closure of the slot in a region of the ridge (at the interface with the bearing plate) but also reinforces against inward deformation of the body wall at the edges of the slot. The arrangement serves to preserve the annular symmetry of the body at the location of the spacer. This has been found to improve the load bearing capacity of the split set. If the body deforms at the bearing plate, there can be an asymmetrical application of the forces and the body material may be more likely to tear under severe loading.

[0057] In addition to the lips on the lug, the cylindrical cuff (134) also serves to maintain symmetry at the interface of the bearing plate (130), washer (124) and ridge (110). The cuff is guided in a substantially co-axial relationship to the split set body even though the bearing plate may bend around the cuff. This arrangement serves to facilitate face contact between the cuff and the washer, with the washer engaging the stop in the same manner. The contact between surfaces rather than point contacts developing through asymmetry also serves to provide an improved load bearing capacity. This serves to also protect the portion of the bearing plate around the hole which can be susceptible to tearing against the stop on the split set.

[0058] The description of a preferred embodiment is set out above. This version of the invention has demonstrated favorably in workshop simulated load / pull tests. It will however be appreciated that the formation of the ridge yields advantages even if it is not used with other features of the preferred embodiment. Some of the variations are described below. It will be appreciated that a conventional bearing plate of any configuration (having a suitably sized hole) may be used with the split set of Figure 1 . Where the washer of Figure 3 is also used, this will simply abut the portion of the bearing plate around the hole.

[0059] The bearing plate may be in any form of flange device with a hole which provided a rock engaging and / or supporting structure to achieve the result that is required of a rock anchor. It is also anticipated that such a flange device may be pinched between two closely formed ridges (the outer ridge providing a stop and the inner ridge holding the flange device in place).

[0060] An alternative collar (422) and spacer (418) are shown in Figure 8. The collar comprises a bent ring (which may have touching ends that are welded together) with a circular cross-section (similar to those that are welded onto the prior art split sets). The collar (422) carries an internal lug (420) that fits into the slot of the split set. This example of collar and spacer may use welding to secure the lug to the ring although the invention seeks to minimize this process from manufacture. An alternative to the pressed washer (124) referred to above (Figure 3) may involve the casting of a suitable collar and spacer. In a development of this external collar component, a lug may be provided that is located on a top side of the collar (rather than on the inside). Such a variation would place the spacer lug between inner shoulders provided by the ridge and not between edges of the slot (104). A further alternative may involve a larger (suitably configured) lug or two (substantially) right angle lugs that fill the gap both between edges of the slot (104) and between shoulders provided by the ridge.

[0061] Referring to Figure 10, another example of a spacer (518) is provided with an outwardly disposed lug (520). An annular body similar to that of the collar in Figure 8 is provided with a reduced diameter so as to form an insert (522). The annular insert is pressed into engagement with an inside of the lateral ridge (110). The spacer is sized and configured to provide an obstruction against closure of the slot in use. In a variation of this embodiment, the outward lug may be provided on a sleeve insert that is pressed into the split set. This may be similar to the plug (918) in Figure 13 but with a lug that extends into the slot (104).

[0062] Figure 9 shows a spacer (618) similar to that of Figure 3 but a bearing plate (630) provides the collar (622) component. An inwardly disposed lug (620) is provided in a hole (632) of the bearing plate. This embodiment preferably requires assembly of the plate (630) before it is taken to an installation site because the lug (620) must be slid along the slot (104), from the inner end to the ridge (110). A separate cuff (of similar size to that shown in Figures 6 and 7) may be located between the bearing plate and the ridge.

[0063] In Figure 11 , an outer end (700) of the tubular body (706) is folded forward to provide an annular flange (736). The flange provides additional rigidity at the outer end. In Figure 12, an outer end (800) of the tubular body (806) is folded forward to provide an annular flange, with a rigid ring providing a collar (838) placed between the flange and the ridge. The material of the flange is then bent to provide a curved return (840) that engages over the collar. This provides addition rigidity and the collar (838) that is clamped under the curved return (840) bridges the slot providing a spacer (which could be an additional spacer) that serves to resist against closure.

[0064] In a variation of the invention, the spacer may be provided by an insert that is located within the body of the split set and configured to abut wall sections of the body to either side of the slot. The internal obstruction provided by such an insert will resist closure of the slot as required to maintain the structural integrity at the bearing plate interface. Figure 13 shows one embodiment of such a spacer that is provided as a plug (918). The plug is deep drawn from a suitably sized steel plate and provided with a cylindrical wall (942) and an annular, circumferential rib (944) at one end. The plug will be pressed into the tubular body. (The actual product may have more rounded edges, particularly on the rib, resulting from the manufacturing process. The illustration however will provide an understanding of the structure and configuration.) The rib (944) on the plug will engage inside the groove formed internally by the ridge of the split set. Figure 14 shows another such spacer that is simply provided as a rigid ring forming an annular insert (1018) that is pressed into engagement with the groove formed internally by the ridge of the split set. This embodiment will locate inside the ridge (110) with a section of the insert (1018) bridging the gap of the slot (104). A press-fit into the groove will be sufficient to fasten the insert (1018) in place.

[0065] Figure 15 shows a spacer (1118) with bearing plate (1130) providing a collar (1122) and a flat section (1119) with the geometry of a chord is provided inside the hole (1132) for location across the slot (104). The flat section engages outer comers along the first edge (114) and the second edge (116) to resist closure of the slot. The embodiment may provide sufficient resistance to closure of the slot in certain applications.

[0066] In a development of the rock anchor assembly and split set described, the invention further provides for the first edge of the slot and / or second edge of the slot to be provided with a protrusion (not shown) that is spaced apart from the ridge and used to secure a lug supported on a collar against or adjacent to the ridge. The protrusions may be pressed from the material along the two edges. The sequence of assembly (spacer into place) and formation of the protrusions may be varied depending on whether the spacer can be maneuvered past the protrusions of whether the protrusions are an interference to passage of the spacer along the slot.

[0067] Such an arrangement of protrusions provides one example for securing in place a spacer that is provided as a separate component (not on a collar or insert), which is fitted into a gap between the first edge of the slot and the second edge of the slot. Such a spacer would serve the purpose of and correspond to the lug in Figures 3 and 4 but not have the collar / insert to hold it in place. The separate component spacer may have four lips that engage on both the inside and outside of the body wall at the first edge and the second edge of the slot. The component may be a curved insert with the lips at each corner (such as those on the inside of the lug in Figures 3 and 4. The opposite side ends may be angled for a close fit to the first edge and the second edge of the slot.

[0068] In the relevant views of the drawings, only an outer end of a split set is shown. It will be appreciated that the slotted body extends a variable length from the outer end portion and will have a suitable tapered portion at the opposite, inner end. The length is made to match a depth of drill hole as required for different applications of the product. The invention may be applied to any such variations or and a different diameter of split set.

[0069] It will be understood that the collars or annular inserts can be provided as a circular pressed washer or a split-ring that is bent to form. A further alternative involves the use of a bearing plate to provide a collar. The collar or annular insert may be pressed to include an inwardly / outwardly disposed lug or an inwardly / outwardly disposed lug may be welded onto the split-ring, respectively. A further alternative may involve casting of these components.

[0070] The welded ring of a conventional split set is eliminated and, in this manner, the carbon footprint of a product that is used extensively and in vast numbers is transformed to the benefit of the environment. The remaining parts of the rock anchor assembly can also be provided without the necessity of welding. This is specifically a feature of the novel spilt set component. The separate parts can be galvanized where this is required and then fitted together in a separate step. This allows exposure of the full external surfaces to the galvanizing process (the inside of the ridge in Figures 1 and 2 is not pressed closed for this reason). In the prior art split set, galvanizing of the product does not penetrate under the welder ring and this has been known to cause a rust site which weakens the load bearing structure that is provided.

[0071] The description above has been directed to a particular preferred embodiment 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. It is the intention that the patent claims will cover all equivalent modifications and variations which fall within the scope of the present invention.

Claims

CLAIMS1 . A rock anchor comprising an assembly of a split set and a bearing plate: the split set having an elongate tubular body with a longitudinal slot, the bearing plate having a hole to receive the body of the split set, characterized in that: the body has an external lateral ridge that is folded into a wall of the body adjacent an outer end to extend around the body between a first edge of the slot and a second edge of the slot; the ridge provides a stop to retain the bearing plate on the body of the; and the assembly includes a spacer resist closure of the slot in a region of the ridge.

2. The assembly as claimed in claim 1 in which the spacer is located at or adjacent the ridge.

3. The assembly as claimed in claim 1 or claim 2 in which the spacer is located between the first edge and the second edge of the slot.

4. The assembly as claimed in claim 3 in which the spacer is an inwardly disposed lug provided on a collar that fits around the body.

5. The assembly as claimed in claim 4 in which the lug is provided on a washer that is pressed to form from sheet metal.

6. The assembly as claimed in claim 4 or claim 5 in which the lug is positioned through the slot with a pair of lips that extend at opposite sides of the lug to locate on an inside of the body adjacent the first edge and the second edge of the slot.

7. The assembly as claimed in claim 6 in which the lug has an inner edge extending between the lips that is located to an inside of the body across the slot.

8. The assembly as claimed in any one of claims 4 to 7 in which the collar locates between the ridge and bearing plate.

9. The assembly as claimed in claim 8 in which the bearing plate includes an annular cylindrical cuff that is located around the body and abuts the collar.

10. The assembly as claimed in claim 3 in which the spacer is an inwardly disposed lug provided in the hole of the bearing plate.

11. The assembly as claimed in claim 3 in which the spacer is an outwardly disposed lug provided on an annular insert.

12. The assembly as claimed in claim 3 in which the spacer is a separate component that is fitted into a gap between the first edge of the slot and the second edge of the slot and secured in place.

13. The assembly as claimed in claim 1 or claim 2 in which the spacer is provided by an insert that is located within the body of the split set and configured to abut wall sections of the body to either side of the slot.

14. A split set having an elongate tubular body with a longitudinal slot, characterized in that: the body has an external lateral ridge that is folded into a wall of the body adjacent an outer end to extend around the body between a first edge of the slot and a second edge of the slot; and the ridge provides a stop to retain a bearing plate on the body of the split set.

5. The split set as claimed in claim 14 for use in an assembly with a bearing plate, wherein the assembly includes a spacer to resist closure of the slot in a region of the ridge.

Images