TECHNICAL FIELD

This invention relates to a rock bolt. More specifically, the invention relates to a rock bolt commonly known as a split set, and a method of manufacturing a rock bolt.

SUMMARY OF THE INVENTION

According to the invention, there is provided a rock bolt including: - an elongate tube-like member having an elongate aperture defined along its length; and a retaining formation defined by the elongate tube-like member at a first end region thereof for retaining a support member thereon in an operative condition, the retaining formation being formed integrally with and having a larger diameter than that of the elongate tube-like member.

The elongate tube-like member may have a length in the range of Im to 5m, preferably having a length in the region of 3m. The elongate tube-like member may have a thickness in the range of 1mm to 10mm, preferably being in the region of 3mm. The elongate tube-like member may have a tapered end opposite the first region for facilitating receipt thereof by a hole drilled into a rock face. The elongate tube-like member may be manufactured from any suitable resiliently deformable material. The elongate tube-like member may be manufactured from any suitable synthetic, plastic or metallic material, preferably being manufactured from a metallic material. Further preferably, the elongate tube-like member may be manufactured from steel. Yet further preferably, the elongate tube-like member may be manufactured from mild steel. Yet even further preferably, the elongate tube-like member may be manufactured from 3CR12 stainless steel.

The elongate aperture may have width, when viewed in plan, in the range of 15mm to 40mm, preferably having a width, when viewed in plan, in the region of 20mm. It is to be appreciated that the aperture serves to provide the elongate tube-like member with an ability to flex about a central longitudinal axis of thereof, which permits a friction fit of the elongate tube-like member within a hole drilled into a rock face, wherein the friction fit is sufficient to retain the elongate tube-like member and with it, the support member in the operative condition.

The retaining formation may be formed in the elongate tube-like member during manufacturing thereof. More particularly, the retaining formation and the elongate tube-like member may be formed from a single sheet of material with the use of a press. The retaining formation may be in the form of a shoulder or ridge formation which may define a retaining surface. The retaining surface may be inclined relative an outer surface of the elongate tubelike member, wherein the retaining formation may taper in diameter. Preferably, the retaining surface may be arranged to extend from the elongate tube-like member at an angle in the region of 90 degrees. The retaining surface may have a length in the range of 2mm to 20mm, preferably having a length in the region of 8mm. The retaining formation may have a smoothed, arcuate, rounded or continuous profile for reducing stress concentrations therein.

The retaining formation may be spaced from the end region of the elongate tube-like member a distance in the range of 10mm to 40mm, preferably being spaced a distance in the region of 22mm. The retaining formation may have a thickness in the range of 1mm to 10mm, preferably having a thickness in the region of 3mm.

A retaining member may be provided for increasing a retaining force applied to the support member. The retaining member may be in the form of a ring which may be connected to the elongate tube-like member on one side region of the retaining formation. More particularly, the one side region of the retaining formation may be opposite the end region of the elongate tube-like member. The ring may be welded to the elongate tube-like member. The retaining member may be manufactured from any suitable metallic material, preferably being manufactured from steel. Further preferably, the retaining member may be manufactured from stainless-steel, yet further preferably being manufactured from 3CR12 stainless-steel.

The support member may be in the form of a generally planar member which may have an aperture defined therein for receiving the elongate tube-like member therethrough. The aperture may be sized so as to receive the elongate tube-like member therethrough and permit abutment between a surface peripheral to the aperture and the retaining formation and/or retaining member. The support member may be in the form of a plate having a surface area sufficient to support a rock surface and/or a netting arrangement in the operative condition.

A mounting formation may extend from the support member for allowing articles to be mounted thereon and supported in a secured condition wherein the support member and elongate tube-like member are retained in position within a hole in a rock face. The mounting formation may be in the form of an extension which may be integrally formed with the support member. The extension may have a generally planar form. The extension may be arranged at an angle relative to the support member. More particularly, the extension may be angled away from the rock face in the secured condition. The articles may be in the form of air flow ducts, piping and the like.

Strengthening formations may be provided for reducing the likelihood of bending of the mounting formation relative to the support member. The strengthening formations may be in the form of rib- or web-like formations which may be positioned astride a juncture between the mounting formation and the support member.

The extension may include an aperture defined therein for allowing attachment of an elongate load bearing member thereto. The load bearing member may be in the form of a rope, cable or chain, preferably being in the form of a chain. The aperture may include a first portion for receiving the load bearing member therethrough and a second portion, sized, shaped and configured to receive a portion of the load bearing member complementally and retainably therein. In particular, the second portion of the aperture may be sized, shaped and/or configured to receive a rope or cable in a friction fit manner. Alternatively, the second portion of the aperture may be sized and/or shaped to receive a link of a chain and provide an abutment surface for a subsequent link such that the abutment surface inhibits passage of the subsequent link through the second portion of the aperture. The first portion of the aperture may have any suitable geometric shape. The second portion of the aperture may be in the form of an elongate slot for receiving a portion of a chain link therein or in the form of a slit for receiving a portion of a rope or cable therein. The elongate slot may extend towards a ground surface in the secured condition for allowing gravity to facilitate receipt and retention of the chain link therein.

According to a second aspect of the invention, there is provided a method of manufacturing a rock bolt as hereinbefore described, which method includes the steps of: - cutting an elongate blank from a metallic sheet; inserting the blank into a press which defines a generally W- or wave-like shape in crosssection along its width and a generally W- or wave-like shaped, complementary male-female shoulder formation towards one end region thereof; initiating the press to form an elongate metallic body having a generally W- or wavelike shaped cross-section along its width and a generally W- or waves like shaped shoulder formation towards one end region thereof; and bending opposing side regions of the elongate metallic body about a longitudinal axis thereof to form an elongate tube-like member having a generally C-shaped cross-section and a generally C-shaped shoulder formation at one end thereof.

The elongate blank may be generally rectangular in shape, preferably having a length, width and thickness in the ranges of Im to 5m, 75mm to 200mm, and 1mm tO 5mm, respectively. Preferably, the elongate blank may have a length, width and thickness in the region of 3m, 110mm and 3mm, respectively. The sheet may be in the form of a stainless-steel sheet, preferably being in the form of a 3CR12 stainless-steel sheet. The method may include the step of heating the metallic sheet before initiating the press. The method may include the step of heating the elongate metallic body before bending thereof.

The method may include the step of tapering an end region of the elongate tube-like member opposite to the shoulder formation, preferably with the use of a swage.

The method may further include the step of forming a retaining member for fastening to the shoulder formation. Forming the retaining member may include the steps of: - cutting a metallic rod to a length which corresponds to a diameter of the C-shaped elongate tube-like member; bending the rod into a W- or wave-like shape; and bending opposing end regions of the W- or wave-like shape rod towards each other to form a generally ring-like member.

The metallic rod may be manufactured from any suitable metallic material, preferably being manufactured from steel. Further preferably, the metallic rod may be manufactured from stainless-steel, yet further preferably being manufactured from 3CR12 stainless-steel.

The method may further include welding the ring-like member to a side region of the shoulder formation of the elongate tube-like member, preferably a side region towards a central portion of the elongate tube-like member.

BRIEF DESCRIPTION OF THE DRAWINGS

A rock bolt in accordance with the invention will now be described by way of the following, non-limiting examples with reference to the accompanying drawings. In the drawings: -

Figure 1 is an enlarged side view showing a part of a rock bolt in accordance with the present invention;

Figure 2 is an enlarged sectioned side view of the part of the rock bolt shown in Figure 1 along the line D-D;

Figure 3 is an enlarged sectioned end view of the part of the rock bolt shown in Figure 1 along the line C-C;

Figure 4 is an enlarged side view of the rock bolt with a retaining member mounted thereon;

Figure 5 is a plan view of a support member through which an elongate tube-like member of the rock bolt is to be inserted in use;

Figure 6 is a three-dimensional view of an elongate metallic body having a generally W- or wave-like shaped cross section;

Figure 7 is a three-dimensional view of the elongate metallic body shown in Figure 6 after being bent to form a generally C-shaped elongate tube-like member;

Figure 8 is a three-dimensional view showing an opposite end of the elongate tube-like member having a tapered form;

Figure 9 is a three-dimensional view showing a rod bent into a W- or wave-like shape;

Figure 10 is a three-dimensional view showing the rod shown in Figure 9 after being bent into a generally ring-like shape; and

Figures 11 to 13 are three-dimensional views showing various support members for use with the rock bolt.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to Figures 1 to 5, reference numeral 10 refers generally to a rock bolt in accordance with the present invention. The rock bolt 10 includes an elongate tube-like member 12 having an elongate aperture 14 defined along its length so as to define a generally C-shaped cross-section, and a retaining formation 16 defined by the elongate tube-like member 12 at a first end region 18 thereof for retaining a support member 20 thereon in an operative condition, the retaining formation 16 being formed integrally with and having an increased diameter relative to the elongate tubelike member 12.

The elongate tube-like member 12 has a length in the range of Im to 5m, typically having a length in the region of 3m. The elongate tube-like member 12 has a thickness in the range of 1mm to 10mm, typically being in the region of 3mm. The elongate tube-like member 12 has a tapered end 13 opposite the first region for facilitating receipt thereof by a hole drilled into a rock face. The elongate tube-like member 12 is manufactured from any suitable resiliently deformable material. The elongate tube-like member 12 is manufactured from mild steel or 3CR12 stainless steel.

The elongate aperture 14 has width, when viewed in plan as shown in Figures 1 and 4, in the range of 15mm to 40mm, typically having a width in the region of 20mm. It is to be appreciated that the aperture 14 serves to provide the elongate tube-like member 12 with an ability to flex about a central longitudinal axis 22 of thereof, which permits a friction fit of the elongate tube-like member 12 within a hole (not shown) drilled into a rock face (not shown), wherein the friction fit is sufficient to retain the elongate tube-like member 12 and with it, the support member 20 in the operative condition.

The retaining formation 16 is formed in the elongate tube-like member 12 during manufacturing thereof. More particularly, the retaining formation 16 and the elongate tubelike member 12 are formed from a single sheet of material with the use of a press. The retaining formation 16 is in the form of a shoulder formation 24 which defines a retaining surface 26. Edge regions 28 of the shoulder 24 are generally rounded so as to reduce stress concentrations therein. As shown in the Figures, the retaining surface 26 is arranged to extend from the elongate tube-like member 12 at an angle in the region of 90 degrees. The retaining surface 26 h as a length in the range of 2mm to 20mm, typically having a length in the region of 8mm. The retaining formation 16 has a smoothed, arcuate, rounded, or continuous profile for reducing stress concentrations therein.

The retaining formation 16 is spaced from the end region 18 of the elongate tube-like member 12 a distance in the range of 10mm to 40mm, typically being spaced a distance in the region of 22mm. The retaining formation 16 has a thickness in the range of 1mm to 10mm, typically having a thickness in the region of 3mm.

A retaining member in the form of a ring 30 is provided for increasing a retaining force applied to the support member 20. The ring 30 is connected to the elongate tube-like member 12 on one side region 32 of the retaining formation 16. More particularly, the one side region 32 of the retaining formation 16 is opposite the end region 18 of the elongate tube-like member 12. The ring 30 is typically welded to the elongate tube-like member 12.

The support member 20 is in the form of a generally planar member or plate 34 which has an aperture 36 defined therein for receiving the elongate tube-like member 12, typically a second end region (not shown) thereof which is opposite the first end region 18, therethrough. The aperture 36 is sized so as to receive the elongate tube-like member 12 therethrough and permit abutment between a surface 38 peripheral to the aperture 36 and the retaining formation 16 or ring 30 should the ring 30 be utilised. The plate 34 typically has a surface area sufficient to support a rock surface (not shown) or a netting arrangement in the operative condition.

Referring now to Figures 11 to 13, a mounting formation in the form of an extension 56 extends from the support member 20 for allowing articles (not shown) to be mounted thereon and supported in a secured condition wherein the support member 20 and elongate tube-like member 12 are retained in position within a hole (not shown) in a rock face (not shown). The extension 56 is integrally formed with the support member 20. The extension 56 has a generally planar form. The extension 56 is arranged at an angle relative to the support member 20. More particularly, the extension 56 is angled away from the rock face (not shown) in the secured condition. The articles (not shown) are typically in the form of air flow ducts, piping and the like.

Strengthening formations in the form of rib-like formations 58 are provided for reducing the likelihood of bending of the extension 56 relative to the support member 20. The rib-like formations 58 are positioned astride a juncture 60 between the extension 56 and the support member 20.

The extension 56 includes an aperture 62 defined therein for allowing attachment of an elongate load bearing member in the form of a chain thereto, a portion of which is labelled 64. As shown in Figure 11, the aperture 62 is generally circular. As shown in Figures 12 and 13, the aperture 62 includes a first portion 66, having a generally circular shape, for receiving the chain 64 therethrough and a second portion 68, sized, shaped and configured to receive a portion of the chain 64 complementally and retainably therein. In particular, the second portion 68 of the aperture 62 is sized and shaped to receive a link 70 of the chain 64 and provide an abutment surface 72 for a subsequent link 74 such that the abutment surface 72 inhibits passage of the subsequent link 74 through the aperture 62. The second portion 68 of the aperture 62 is in the form of an elongate slot 76 for receiving a portion of the chain link 74 therein. The elongate slot 76 extends in the direction generally towards a ground surface (not shown) or downward in the secured condition for allowing gravity to facilitate receipt and retention of the chain link 74 therein.

In order to assemble the rock bolt 10 before insertion into a rock face (not shown), an end (not shown) of the elongate tube-like member 12 which is opposite to the first end region 18, is inserted through the aperture 36 defined in the plate 34 until the surface 28 comes into contact with the retaining surface 26 of the shoulder formation 24. Thereafter, a hole (not shown) is drilled into the rock face (not shown) in an underground passageway (not shown). Once drilled, the elongate tube-like member 12 of the rock bolt 10 is forced into the hole (not shown) until one side of the plate comes into contact with the rock face (not shown). The C-shaped cross-section of the elongate tube-like member 12 provides a degree of flexibility about its longitudinal axis 22 which, when forced by friction fit into the hole (not shown), the elongate tube-like member 12 applies a frictional force against an inside surface (not shown) of the hole (not shown) which is sufficient to retain the elongate tube-like member 12 and plate 34 in the operative condition.

Referring now to Figures 6 to 10, there is provided a method of manufacturing a rock bolt 10 as hereinbefore described, which method includes the steps of cutting an elongate blank (not shown) from a metallic sheet (not shown), inserting the blank into a press (not shown) which defines a generally W- or wave-like shape (not shown) in cross-section along its width and a generally W-shaped, complementary male-female shoulder formation (not shown) towards one end region (not shown) thereof, initiating the press to form an elongate metallic body 40 having a generally W- or wave-like shaped cross-section along its width and a generally W-shaped shoulder formation 42 towards one end region thereof 44 and bending opposing side regions 46 of the elongate metallic body 40 about a longitudinal axis 48 thereof to form an elongate tube-like member 12 having a generally C-shaped cross-section and a generally C- shaped shoulder formation 24 at one end 18 thereof.

The elongate blank is generally rectangular in shape, typically having a length, width and thickness in the ranges of Im to 5m, 75mm to 200mm, and 1mm to 5mm, respectively. Typically, the elongate blank has a length, width and thickness in the region of 3m, 110mm and 3mm, respectively. The sheet is in the form a 3CR12 stainless-steel sheet.

The method includes the step of heating the metallic sheet (not shown) before initiating the press. The method includes the step of heating the elongate metallic body 40 before bending thereof. The method includes the step of tapering an end region 50 of the elongate tube-like member 12 opposite to the shoulder formation 24, typically with the use of a swage (not shown).

The method further includes the step of forming a retaining member 30 for fastening to the shoulder formation 24. Forming the retaining member 30 includes the steps of cutting a metallic rod (not shown) to a length which corresponds to a diameter of the C-shaped elongate tube-like member 12, bending the rod (not shown) into a W- or wave-like shape 52, and bending opposing end regions 54 of the W- or wave-like shape rod 52 towards each other to form a generally ring-like member 30.

The metallic rod (not shown) is manufactured from any suitable metallic material, typically being manufactured from 3CR12 stainless-steel.

The method further includes welding the ring-like member 30 to side region 32 of the shoulder formation 24.

It is, of course, to be appreciated that the rock bolt in accordance with the invention is not limited to the precise constructional and functional details as hereinbefore described with reference to the accompanying drawings and which is varied as desired.

Although only certain embodiments of the invention have been described herein, it will be understood by any person skilled in the art that other modifications, variations, and possibilities of the invention are possible. Such modifications, variations and possibilities are therefore to be considered as falling within the spirit and scope of the invention and hence form part of the invention as herein described and/or exemplified. It is further to be understood that the examples are provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and is not meant to be construed as unduly limiting the reasonable scope of the invention. The inventor believes that the rock bolt in accordance with the present invention is advantageous in that having a retaining shoulder formation which is formed integrally with the elongate tube-like member increases the force required to dislodge the rock bolt from the rock face, thus improving the safety in underground passageways which are susceptible to rockfalls.