An expandable rock bolt

Abstract

The present invention relates to an expandable rock bolt (1) and a method for manufacturing the same. A cap (2) is welded to the end of a pipe (3). A fold (9) is formed from a first side of the rock bolt (1) and extends along a section of the pipe (3). The bottom (10) of the fold (9) is formed to extend from the pipe (3) into the side wall (5) of the cap (2) and outwardly towards the first side to a position separated from a first part (13) of the end wall held outside the fold (9) by a ridge (12), wherein a second part (14) of the end wall is drawn into the fold (9).

Description

Technical Field

[0001] The present invention relates to an expandable rock bolt, comprising a sealed tubular (metal pipe) body formed by at least one longitudinal fold to provide a reduced and substantially circular cross-sectional profile for insertion into a borehole and, in use, expanded by introducing a pressurized fluid into the interior of the body to frictionally engage with the borehole wall. Background Art

[0002] These rock bolts typically have a sealed tube with a longitudinal channel formed by folds, thereby reducing the cross-sectional size of the tube (sufficient for the desired purpose). A check valve at one end remains outside the borehole into which the rock bolt is inserted, allowing the pipe to expand or dilate. The pressurized fluid is usually water. When the body expands by deforming outward through the folds, the surface of the tube engages with the hole.

[0003] An improved version of such a rock bolt is disclosed in PCT / 2016 / 053817 and PCT / 2016 / 054864. The first of these two international applications teaches a beneficial structure for a preferred inner end of the rock bolt. Summary of the Invention

[0004] An object of the present invention is to provide a rock bolt having a sealed inner end with a configuration that provides improved durability against the pressure exerted on the folded region of the material during the expansion operation in use.

[0005] According to a first aspect of the present invention, there is provided an expandable rock bolt, comprising:

[0006] a pipe having a cap with a sealed joint welded to the end of the pipe in a preformed state;

[0007] the cap having a side wall extending from the edge of the cap to a closed end provided by an end wall of the cap;

[0008] the rock bolt being provided with folds formed from a first side of the rock bolt and extending along a section of the pipe;

[0009] the bottom of the fold being located near an opposite second side of the rock bolt and extending along the section of the pipe; and

[0010] the bottom of the fold extending from the pipe to the side wall of the cap and outwardly towards the first side of the rock bolt to a position separated by a ridge from a first part of the end wall held outside the fold, wherein a second part of the end wall is drawn into the fold.

[0011] The present invention provides that the second part of the end wall is arranged in the front region of the fold, and the first part of the end wall is located at a relatively set position in front of the plug.

[0012] The present invention further provides a plug as defined, wherein:

[0013] A larger part of the end wall of the cap remains substantially in a preformed state as the first part, and an adjacent smaller part is bent backward and pressed in the direction of the fold as the second part.

[0014] The present invention also further provides a plug as defined, wherein:

[0015] The ridge extends from the front of the plug as a substantially U-shaped ridge formed around the fold at the cap of the plug;

[0016] The closed end of the cap is extruded outward to align with the fold, thereby forming the foremost part of the U-shaped ridge;

[0017] The edge of the ridge is located on one side of the pipe axis as it exists in the preformed state of the pipe;

[0018] The end wall of the cap transitions uniformly from the side wall, via a curve, to the closed end of the cap that is substantially flat [relative to the transition curve]; and

[0019] The side wall of the cap includes a substantially cylindrical region at the edge, which is positioned in the preformed pipe by means of a press fit.

[0020] According to a second aspect of the present invention, there is provided a method of manufacturing an expandable plug, comprising the steps of:

[0021] Providing a preformed pipe having at least one open end,

[0022] Welding a cap to the open end, and

[0023] Then deforming the pipe and the cap into a folded shape to provide a fold extending along the pipe,

[0024] Characterized in that the fold is formed by a tool covered with a working edge that just interrupts at the end wall of the closed end of the cap to:

[0025] - Keep the first part of the end wall aligned with the fold on the outside of the fold; and

[0026] - Draw the second part of the end wall in a curve, backward and into the fold.

[0027] The invention further provides a defined method, wherein the fold is formed as:

[0028] - Provide a substantially U-shaped ridge that extends around the fold from the front of the plug at the cap, the edge of the ridge being on one side of the pipe axis as it exists in the preformed state of the pipe.

[0029] The invention also further provides a defined method, wherein:

[0030] When the fold is formed, the first part is the larger part of the end wall and the second part is the smaller part of the end wall; and

[0031] In a second forming operation, the plug is tightly squeezed around the fold. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] These and other features of the invention will become more apparent from the following description of preferred embodiments, given by way of example only, with reference to the accompanying drawings, in which:

[0033] Figure 1 Three inner ends of the preformed, intermediate and final formed plugs are shown, with their positions towards the fold;

[0034] Figure 2 Perspective views of the intermediate and final formed plugs are shown;

[0035] Figure 3 Shows Figure 2 A side view of the middle plug end from the lateral position of the fold; and

[0036] Figure 4 The preformed and final formed plug ends are shown, marked with an axis of the preformed plug. DETAILED DESCRIPTION

[0037] Referring to the drawings, a plug (1) with a cap (2) at its inner end, manufactured according to the invention, is shown. The plug (1) in the drawings is illustrated in the following progressively formed states:

[0038] "A" preformed state;

[0039] "B" intermediate state; and

[0040] "C" formed state.

[0041] The rock bolt (1) is made from a section of pipe (3) which initially has a circular cross-section in a preformed state. The pipe (3) is made from a suitable metal. A cap (2) is used to seal the open end of the pipe (3) which will be located within a rock bolt bore (not shown). Only this inner end of the rock bolt (1) is shown in the figure.

[0042] The structures and components used at the opposite, outer end of the rock bolt (1) can be diverse and will be within the understanding of those skilled in the art. The second of the two PCT applications mentioned in the above "Background Art" lists some examples.

[0043] The cap (2) is made from a suitable ductile metal and has a side wall or skirt (5) extending from the edge (not shown) of the cap (2) to the closed end (6). The side wall (5) extends forward from the pipe (3) and is slightly inclined inwards. The closed end of the cap (2) in this embodiment is substantially flat and provides an end wall (7) to the front of the side wall (5). The end wall (7) transitions substantially uniformly from the side wall (5) through a curve in the annular outer region to the central region of the closed end (6), which in this embodiment is substantially flat (relative to the transition curve).

[0044] The side wall (5) of the cap (2) has an outer diameter on a substantially cylindrical region at the edge (not shown). This short region (not shown) of the side wall (5) near the edge has substantially parallel walls for press fitting into the preformed pipe (3) by friction or interference fit. The pipe (3) with the cap (2) so fitted is as Figure 1 shown as "A" in. Then it is welded (8) at the joint along the outer edge of the end of the pipe (3). By fixing the cap (2) to the pipe (3) in this way, the open and operative inner end of the rock bolt (1) is sealed.

[0045] Once the cap (2) is welded in place, the preformed rock bolt will undergo subsequent metalworking processes where the pipe (3) and the cap (2) are formed into an intermediate state of the rock bolt (1) having a crimped or corrugated shape, as Figure 1 、 2 and "B" in 3 show. The configuration described involves an initial first step of pressing to form longitudinal folds or channels (9) to reduce the cross-sectional dimensions of the post-formed rock bolt (1) as shown as "C" in Figure 1 、 2 and 3.

[0046] According to the present invention, the fold (9) is formed on the first side "x" of the rock bolt (1) and extends along a section of the pipe (3). The bottom (10) of the fold (9), which is near the opposite second side "y" of the rock bolt (1), extends along this section of the pipe (3).

[0047] A fold (9) is formed such that the bottom (10) extends from the pipe (3) into the side wall (5) and has a concave curve into the front region (11), outwards towards the first side "x" of the plug (1) to a position separated from the first part (13) of the end wall side (7) held outside the fold (9) by the front region of the U-shaped ridge (12), wherein the second part (14) of the end wall (7) is pulled towards and / or into the front region (11) of the fold (9).

[0048] In the current embodiment, a larger part of the end wall (7) remains substantially in the preformed state [except being slightly squeezed forward when forming the front part of the U-shaped ridge (12)] as the first part (13), and a smaller adjacent part of the end wall (7) bends backward and is squeezed towards and / or into the fold (9) as the second part (14).

[0049] After welding is completed, the pipe (3) and the cap (2) still have a circular profile or shape in cross-section. In the first forming step, the pipe (3) and cap (2) assembly is placed in the grooved cavity of the first die. Then, using the extrusion tool in the hydraulic press, the pipe (3) and cap (2) assembly is deformed into an intermediate state, accompanied by some lateral bulges or deformations towards the outer shape on both sides of the fold, and the forward displacement of the end wall (7) forming the U-shaped ridge (12).

[0050] The tool is in the shape of a long and narrow blade, having a straight working edge (parallel to the pipe) bent between two planar sides. When in use, the working edge directly contacts the outer surface of the pipe (3) and cap (2) assembly. The first die is supported by a hydraulic press, which is used to bias the tool to engage with the outer surface of the pipe. The tool deforms the pipe (3) and cap (2) assembly radially inwards to form a relatively deep fold or channel (9), as shown in the figure.

[0051] According to the previous version of the plug, a fold is formed to extend through the cap and through its closed end, so as to reduce the profile of the cap along with the forming process of the applied section of the pipe.

[0052] The improvement that gives rise to the present invention relates to the use, in the first forming operation, of a tool covered with a fold or a working edge and just interrupted at the closed end (6) of the cap (2). At the relevant end located above the cap (2), the tool rounds the end of the tool from the working edge (parallel to the pipe) towards a position perpendicular to or inclined away from the working edge. This rounded part of the tool is pressed into the required position to form a fold in the cap (2).

[0053] Accordingly, the preformed rock bolt needs to be placed in a predetermined position in the hydraulic press so that folds are formed by the pressing tool, and the upwardly bent or rounded end of the working edge is just located near the closed end (6) of the cover (2). This arrangement avoids providing a transverse compressive force that aligns with the material passing through the end wall (7) of the cover, especially in its central flat area. Instead, the tool engages with the cover of the preformed rock bolt, so that a transverse bending force can be applied to the side wall (5).

[0054] The forming process of the present invention provides the following features:

[0055] - A substantially U-shaped ridge (12) formed around the fold (9) on the cover (2) of the rock bolt (1) - see Figure 1 "B" and "C" in

[0056] - A larger first part (13) of the end wall (7) aligned with the fold (9) remains substantially in the preformed state, and outside the fold (9), a closer smaller second part (14) is formed backward and pressed and / or pressed into the fold (9) - see Figure 3 "B" and "C" in

[0057] - The edge "e" of the ridge (12) is located on the first side "x" of the axis "a" of the pipe (3), as it exists in the preformed state of the pipe (3). This is shown as "A" and "C" in Figure 4 by comparison.

[0058] As a result, the second part (14) of the end wall is arranged in the front area (11) of the fold (9), and the first part (13) of the end wall is located at a position opposite to the front of the rock bolt (1) outside the fold (9). The bottom part of the "U" of the U-shaped ridge (12) separates the first part (13) of the end wall from the second part (14).

[0059] In the first forming step, the force applied by the tool is such that when the fold (9) is formed, the outer surface of the tube (3) and cover (2) assembly is no longer substantially circular. Then the intermediate-shaped rock bolt (1) undergoes the second step of the forming process. This operation involves placing the rock bolt (1) into a second die set that includes upper and lower dies, which together define a narrow die cavity with a circular cross-section and are located above the pipe (3) and cover (2). The second die set is closed hydraulically, and the intermediate-state rock bolt is located in the die cavity. As a result, except for the fold (9), the rock bolt is formed into a body with a substantially circular axial profile. This configuration of the finished product (post-formed rock bolt) is suitable for insertion into a circular borehole and has the ability to further expand on the intermediate shape.

[0060] The cover (2) remains connected to the pipe (3) by a leak-proof seal provided by welding. The pipe (3) then has a longitudinally extending narrow channel (9) that extends into the area occupied by the side wall (5) of the cover (2).

[0061] In a second forming operation, the rock bolt (1) is pressed closed around the fold (9). Thus, Figure 1 、 2 The post-formed rock bolt "C" with the fold (9) as shown in Figures 3 and 4 is formed, with the fold (9) having a substantially closed or adjacent configuration that extends along a major part of the pipe section. This is not the case in the area of the cover (2) as shown in the drawings of the present embodiment. The outer diameter of the cover (2) is smaller than the outer diameter of the pipe (3) that it fits into and is welded in place. In the first forming step, the material in the area of the cover (2) inside the fold (9) is pressed against the outside of the part of the cover (2) around the fold (9) near the second side "y" of the rock bolt (1). In the second forming step, when the two molds of the assembly are closed around the rock bolt (1), the degree of closure of the cover at the fold is different from that of the larger diameter pipe wall.

[0062] In use, the rock bolt is inserted into the borehole and expanded from its formed, folded state to a preformed state, where the fully preformed state represents (substantially) the maximum expansion, exceeding the expansion required for the rock bolt to engage with the borehole. In practice, the borehole wall typically engages with the rock bolt in a manner similar to Figure 1 、 2 and the intermediate state "B" as shown in Figure 3. The field conditions and the specific implementation of the rock bolt used will determine the shape of the expanded rock bolt.

[0063] The configuration of the cover formed in the manner illustrated and described is used to provide a configuration that relates to the folded area of the material, which can improve the durability of the stress applied to the material in these areas during the expansion of the rock bolt.

[0064] The forming process involves a smaller laterally compressed part in the end wall area of the cover. The main deformation involves the bending of the side wall of the cover (similar to the side wall of the pipe). The side wall of the cover is more suitable for accommodating bending, while the end wall has most of the material set substantially at a right angle to the pressing tool. The bending at the end wall of the cover involves pressing or pulling and / or pressing or pulling the material backward towards the fold through the pressing tool, thereby forming a substantially U-shaped ridge around the front of the rock bolt.

[0065] It has been found that this folded configuration reduces the weakening of the material in the cover around the fold or folded area and prevents any leakage that may occur during the expansion of the rock bolt.

[0066] The terms used to describe the forming of the component and the lid sidewall and end wall represent and / or illustrate the process and the component. A person skilled in the relevant art will understand these terms and descriptions and will allow the present invention to be implemented as a modification or improvement of the teachings of PCT / IB2016 / 053817.

[0067] While the present invention describes and illustrates a configuration that has a single corrugation providing a longitudinal channel for a reduced rock bolt size, the present invention can also be used where multiple such channels are formed along the conduit.

[0068] The rock bolt end cap and corrugation configuration according to the present invention is particularly suitable for use at the inner or front end of a rock bolt located at the bottom of a borehole and facing the bottom of the borehole. However, this is not a limitation and the present invention can be well applied to both ends of the rock bolt. A pressurized fluid inlet can be provided through the conduit wall adjacent to the outer end protruding from the borehole.

[0069] Those skilled in the art will understand that various changes can be made to the features of the described embodiments without departing from the scope of the present invention.

Claims

1. An expandable rock bolt, comprising: A pipe having a cap with a sealed joint welded to the end of the pipe in a preformed state; The cap having a side wall extending from the edge of the cap to a closed end provided by an end wall of the cap; The rock bolt provided with a fold formed from a first side of the rock bolt and extending along a section of the pipe; and The bottom of the fold located near an opposite second side of the rock bolt and extending along the section of the pipe; Characterized in that The bottom of the fold extends from the pipe to the side wall of the cap and outwardly towards the first side of the rock bolt to a position separated by a ridge from a first part of the end wall held outside the fold, wherein a second part of the end wall is drawn into the fold; And The ridge extends from the front of the rock bolt as a substantially U-shaped ridge formed around the fold at the cap of the rock bolt, wherein the edge of the ridge is located on the first side relative to the axis of the pipe as it exists in the preformed state of the pipe.

2. The rock bolt according to claim 1, wherein the second part of the end wall is disposed in the front region of the fold, and the first part of the end wall is located at a relatively set position in the front of the rock bolt.

3. The rock bolt according to claim 1, wherein the closed end of the cap is extruded outward to align with the fold, thereby forming the foremost part of the U-shaped ridge.

4. The rock bolt according to claim 1, wherein the end wall of the cap uniformly transitions from the side wall and reaches the closed end of the substantially flat cap through a curve.

5. The rock bolt according to claim 1, wherein the side wall of the cap includes a substantially cylindrical region at the edge and is positioned in the preformed duct by means of a press fit.

6. The rock bolt according to claim 1, wherein a larger part of the end wall of the cap substantially remains in a preformed state as the first part, and an adjacent smaller part bends backward and is extruded toward the fold direction as the second part.

7. A method of manufacturing an expandable rock bolt, comprising the following steps: Provide a preformed pipe section having at least one open end, Weld a cap to the open end, and Then deform the pipe and the cap into a folded shape to provide a fold extending along the pipe, Characterized in that the fold is formed from the first side of the rock bolt by a tool covered with a working edge that just interrupts at the end wall of the closed end of the cap to: - Keep a first part of the end wall aligned with the fold on the outside of the fold; and - Draw a second part of the end wall in a curve, backward towards and into the fold; So that the bottom of the fold extends from the pipe to the side wall of the cap and outwardly towards the first side of the rock bolt to a position separated by a ridge from the first part of the end wall held outside the fold, wherein the second part of the end wall is drawn into the fold; Wherein the fold is formed to: - Provide a substantially U-shaped ridge that extends around the fold at the cap from the front of the rock bolt, and the edge of the ridge is located on one side of the pipe axis as it exists in the preformed state of the pipe.

8. The method according to claim 7, wherein when the fold is formed, the first part is the larger part of the end wall and the second part is the smaller part of the end wall.

9. The method according to claim 7, wherein in the second forming operation, the rock bolt is tightly extruded around the fold.

Images