A Mine Bearing Element

Abstract

A mine bearing element for holding a mesh sheet in place against a rock formation is disclosed. The mine bearing element includes a body having (a) a rock bolt engagement portion, (b) a mesh engagement portion, and (c) a transition that connects together the mesh engagement portion and the rock bolt engagement portion in an as-manufactured form of the bearing element. The transition includes a stiffening rib.

Claims

1. A mine bearing element for holding a mesh sheet in place against a rock formation, the mine bearing element comprising: a body having (a) a rock bolt engagement portion, (b) a mesh engagement portion, and (c) a transition that connects together the mesh engagement portion and the rock bolt engagement portion in an as-manufactured form of the bearing element, with the transition including a stiffening rib.

2. The mine bearing element of claim 1, wherein the transition and the mesh engagement portion define a cavity configured to receive a nut on a preinstalled rock bolt.

3. The mine bearing element of claim 2, wherein the rock bolt engagement portion comprises a threaded nut that is configured to threadably engage with the preinstalled rock bolt.

4. The mine bearing element of claim 3, wherein the rock bolt engagement portion comprises an integral washer that engages with the transition, the washer having a curved engagement surface that enables the an angle of engagement with the transition to be adjustable.

5. The mine bearing element of claim 1, comprising a plurality of stiffening ribs.

6. The mine bearing element of claim 5, wherein the plurality of stiffening ribs is radially disposed about the body.

7. The mine bearing element of claim 6, wherein the stiffening ribs are equally spaced from each other.

8. The mine bearing element of claim 7, wherein the stiffening ribs are arranged in a star pattern.

9. The mine bearing element of claim 5, wherein the stiffening ribs are integrally formed with the body.

10. The mine bearing element of claim 1, wherein the transition is in the form of a flat plate or a shaped plate.

11. The mine bearing element of claim 1, wherein the mesh engagement portion includes a tubular element.

12. The mine bearing element of claim 11, wherein the tubular element is a cylindrical shape, i.e., with a circular cross-sectional area having an edge which defines the mesh engagement portion.

13. The mine bearing element of claim 1, wherein the body is made from steel.

14. (canceled)

15. A mine bearing element for holding a mesh sheet in place against a rock formation, the mine bearing element comprising: a body having (a) a rock bolt engagement portion, (b) a mesh engagement portion, and (c) a transition that connects together the mesh engagement portion and the rock bolt engagement portion in an as-manufactured form of the bearing element, the transition including a stiffening rib, the transition and the mesh engagement portion defining a cavity configured to receive a nut on a preinstalled rock bolt, and the mesh engagement portion comprising a tubular element with a cylindrical side wall having an edge which in use contacts a mesh, and the transition and the mesh engagement portion being formed as separate components and assembled together to form the mine bearing element.

16. The mine bearing element of claim 10, wherein the shaped plate includes a flat section, and the stiffening rib extends outwardly from the flat section.

17. The mine bearing element of claim 1, wherein the stiffening rib extends axially in use in relation to an installed rock bolt.

18. The mine bearing element of claim 1, wherein the stiffening rib extends axially in relation to an installed rock bolt and radially outwardly in relation to the rock bolt engagement portion.

19. A method of manufacturing the mine bearing element defined in claim 1, the method comprising: forming the rock bolt engagement portion; forming the mesh engagement portion; forming the transition having the stiffening rib; securing together the transition and the mesh engagement portion; and securing together the transition and the rock bolt engagement portion.

20. The method defined in claim 19, comprising forming the transition by deforming a flat steel plate and forming the stiffening rib.

21. The method defined in claim 20, comprising pressing a flat sheet of metal and deforming the sheet and forming the stiffening rib.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The invention is described further by way of example with reference to the accompanying drawings of which:

[0080] FIG. 1 is a top perspective view of a mine bearing element according to an embodiment of the present invention.

[0081] FIG. 2 is a bottom perspective view of the mine bearing element shown in FIG. 1.

[0082] FIG. 3 is a side view of the mine bearing element shown in FIG. 1.

[0083] FIGS. 4A-4D show schematic illustrations of a method of using a mine bearing element according to the embodiment of FIG. 1 to secure overlapping mesh sheets to a rock formation according to another embodiment of the present invention, including:

[0084] FIG. 4A showing a plan view of a 1st mesh sheet against a rock formation with a pair of rock bolts in the rock formation, and with a left-hand-side of FIG. 4A showing a mine bearing plate secured to the mesh using a nut threaded onto an end of one of the rock bolts;

[0085] FIG. 4B showing a cross-sectional view of the arrangement shown on the left-hand-side of FIG. 4A;

[0086] FIG. 4C showing a plan view of a 2nd mesh sheet positioned in an overlapping relationship with the 1st mesh sheet, with a right-hand-side of FIG. 4C showing a mine bearing element according to the embodiment of FIG. 1 used to secure the 1st and 2nd mesh sheets in an overlapping relationship; and

[0087] FIG. 4D shows a cross-sectional view of the arrangement shown on the right-hand-side of FIG. 4C.

[0088] FIG. 5 shows a method of manufacturing a mine bearing element according to another embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0089] FIGS. 1-3 show a mine bearing element 10 according to an embodiment of the present invention.

[0090] The mine bearing element 10 is used for holding a mesh sheet in place against a rock formation that defines a wall or a roof in an underground mine.

[0091] It is noted that the use of the mine bearing element 10 is not confined to rock formations in underground mines and can be used elsewhere, such as in relation to rock formations in above-ground mines, rail tunnels, road tunnels, and civil engineering works adjacent railways or roads or elsewhere.

[0092] The mine bearing element 10 comprises a body 12 defined by: [0093] (a) rock bolt engagement portion in the form of a nut 14 with an integrally formed washer 15, [0094] (b) a mesh engagement portion in the form of a tubular element, more particularly in the form of a ring 16, and [0095] (c) a transition in the form of a shaped plate 18 (as described herein including by way of example in the next paragraph) that connects together the ring 16 and the nut 14/washer 15.

[0096] In the embodiment shown in FIGS. 1-3, the transition is a plate 18 that includes a flat section and a plurality of stiffening ribs 20 that extend outwardly from the flat section and are radially disposed around the nut 14 in a star pattern (or any other suitable pattern). The stiffening ribs 20 are included in the transition to increase the rigidity of the plate 18 over that of a flat plate with an equivalent thickness. The stiffening ribs 20 are located in a region of the transition (and the body 12 generally) that experiences high stresses when tensioned against the mesh sheet.

[0097] A distal end of the ring 16 forms a contact surface that, in use, abuts the mesh sheet.

[0098] The plate 18 and the ring 16 define a cavity 22.

[0099] In the embodiment shown in the Figures (particularly FIG. 2), the cavity 22 is configured to receive a nut of a preinstalled rock bolt in the rock formation. As a consequence, the mine bearing element 10 can be applied onto a preinstalled rock bolt/bearing plate/nut assembly that already secures a mesh sheet to the rock formation. This makes it possible to secure two mesh sheets in an overlapping relationship.

[0100] The plate 18 extends from the ring 16 so as to provide an outer lip. The ring 16 is secured to the plate 18 via a weld 24 on the outer lip.

[0101] The nut 14 has a hexagonal profile body having an end with a washer 15 integrally formed thereon. The washer 15 has a curved engagement surface that abuts the plate 18 when the nut 14 is tensioned on an end of a rock bolt. The curved engagement surface enables the angle of engagement with the plate 18 to be adjustable, for example to adjust for an uneven surface of the rock formation.

[0102] The nut 14/washer 15 is secured to the plate 18 via a temporary connection in the form of a tack weld 26.

[0103] When the nut 14 is tensioned above a toque limit, i.e., a breakaway torque, the tack weld 26 is sheared. This allows the nut 14/washer 15 to rotate about the rock bolt without imparting movement to the rest of the body 12, i.e., the plate 18 and the ring 16. It is advantageous to avoid rotating the body 12 as doing so may damage the mesh sheet.

[0104] The mine bearing element 10 is formed from steel, although it is noted that it may be formed from any other suitable material. The steel may be any suitable steel grade, such as steel grades currently used for known mine bearing plates.

[0105] However, it is also envisaged that the body may be made from any other suitable material. Suitable materials may include metals or metal alloys comprising one or more of iron, aluminium, stainless steel, and titanium. Suitable materials may be plastics materials and composites such as carbon fiber reinforced polymers or glass fiber reinforced polymers.

[0106] The three components of the mine bearing element 10, namely the nut 14/washer 15, ring 16, and the plate 18, are manufactured as separate components and are assembled together. As noted above, forming these components as separate components makes it possible to optimize the mechanical properties for each component for an end-use application. This may mean different materials selection and/or thicknesses of the components.

[0107] It is noted that the invention is not confined to this arrangement. The invention extends to embodiments where any two or more of the components are integrally formed.

[0108] The mine bearing element 10 is capable of carrying high loads.

[0109] The capacity of the mine bearing element 10 to carry high loads is dependent on a number of factors. Factors relating to the mine bearing element 10 itself include the structure of each of the components, the combination of the three components, the materials selection(s) for the components, and the dimensions of the components. Another factor is the selection of the rock bolt, including the diameter. Another factor is the standard practice for rock bolts to be designed to fail under load before mine bearing plates fail (to obtain the full capacity of the rock bolt). Another factor is the standard practice for the lengths of nuts to be sufficiently long so that the nuts do not strip the threads on rock bolts. A skilled person would realize that the list of factors is not exhaustive and other factors may be relevant.

[0110] In one embodiment, where the mine bearing element 10 is designed to be used with 20 mm diameter rock bolts capable of carrying loads up to 20 tonnes: [0111] the plate 10 is formed from 5 mm thick steel of the same grade as steel used for standard mine bearing plates, [0112] the length of the nut 14 is at least 45 mm (to avoid thread stripping), [0113] the ring 16 is made from the same grade steel and can be a smaller thickness.

[0114] One embodiment of a method of using the mine bearing element 10 in accordance with the invention is now described with reference to FIGS. 4A-4D.

[0115] FIGS. 4A and 4B show a rock formation 30, a pair of rock bolts 32 installed in holes in the rock formation 30 and grouted therein, and a 1st mesh sheet 34a held against said rock formation 30.

[0116] On the left-hand-side of FIG. 4A a mine bearing element, in the form of a bearing plate 36, is tensioned against the 1.sup.st mesh sheet 34a by threading a nut 38 onto an end of the rock bolt 32 and driving it against the bearing plate 36. At this stage of the method, the 1.sup.st mesh sheet 34a is secured against the rock formation 30 on the left-hand-side of the rock formation 30.

[0117] The bearing plate 36 and the nut 38 are standard, known products.

[0118] FIGS. 4C and 4D show a 2nd mesh sheet 34b positioned over the bearing plate 36 such that it overlaps the 1st mesh sheet 34a in a region designated A.

[0119] On the right-hand-side of FIG. 4C, the mine bearing element 10 shown in FIGS. 1-3 is secured to the rock bolt 32 by threading the nut 14 of the mine bearing element 10 onto the end of the rock bolt 32 and driving it against the overlapped portion A of the 1.sup.st and 2.sup.nd mesh sheet 34a, 34b.

[0120] As can be seen from FIG. 4D, the mine bearing element 10 sits over the nut 38 of the pre-installed rock bolt 30. As previously described, the plate 18 and the ring 16 of the bearing element 10 define a cavity 22 that is configured to receive the nut 38 of the preinstalled rock bolt 30. This feature allows the mine bearing element 10 to be applied on the preinstalled rock bolt 30 and the bearing plate 36 and the nut 38 to secure two mesh sheets 34a, 34b in an overlapping relationship.

[0121] In the above-described method, the mine bearing element 10 is used to secure two mesh sheets 34a, 34b in an overlapping relationship and is configured to envelop an existing, preinstalled bearing plate 36 and nut 38. However, it can be appreciated that the same mine bearing element 10 shown in FIGS. 1-3 can also be used to secure a single mesh sheet against a rock formation. As such, the mine bearing element 10 may be used in place of the standard bearing plate 36.

[0122] A method 100 of manufacturing the mine bearing element 10 will now be described with reference to FIG. 5.

[0123] The method 100 comprises the following steps: [0124] 120: forming the rock bolt engagement portion, i.e., the nut 14/washer 15; [0125] 140: forming the tubular element, i.e., ring 16; [0126] 160: forming the transition, i.e., the plate 18, having a stiffening rib 20; [0127] 180: securing the transition, i.e., the plate 18, to the tubular element, i.e., the ring 16; and [0128] 200: securing the transition, i.e., the plate 18, to the rock bolt engagement portion, i.e., the nut 14/washer 15.

[0129] An advantage to forming the ring 16 and the plate 18 separately is that the wall thicknesses of each component can be carefully controlled and/or adjusted for specific applications. By contrast, if the components were integrally formed, for example in a machine press, the maximum wall thickness may be a limiting factor. This is because the amount of force that the machine press needs to apply to form the body 12 increases with wall thickness.

[0130] The step of forming the ring 16 involves rolling a sheet of steel such that the ends meet and then securing, i.e., welding, the ends together.

[0131] The step of forming the plate 18 involves pressing a flat sheet of metal to deform the sheet so as to provide a stiffening rib 20.

[0132] The nut 14 is secured to the plate 18 by tack welding to form a temporary connection 26.

[0133] When the nut 14 is tensioned above a toque limit, i.e., a breakaway torque, the temporary connection 26 between the nut 14 and the plate is sheared. This allows the nut 14 to rotate about the rock bolt without imparting movement to the rest of the body 12, i.e., the plate 18 and the ring 16. It is advantageous to avoid rotating the body 12 as doing so may damage the mesh sheet.

[0134] Whilst the preferred embodiment of the mine bearing element 10 has been described as having a tubular element, the present invention extends to embodiments in which the mine bearing element 10 does not include a tubular element.

[0135] In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose.

[0136] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word comprise or variations such as comprises or comprising is used in an inclusive sense, i.e., to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

[0137] Also, the various embodiments described above may be implemented in conjunction with other embodiments, for example, aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.

[0138] Further patent applications may be filed in Australia or overseas based on, or claiming priority from, the present application. It is to be understood that the following provisional claims are provided by use of example only and are not intended to limit the scope of what may be claimed in any such future applications. Features may be added to or omitted from the provisional claims at a later date so is to further define or re-define the invention or inventions.