AU2018203430B2 - Dolly - Google Patents

Abstract

DOLLY ABSTRACT 5 A rock bolt dolly arranged to connect a rock bolt assembly to a rock bolt apparatus and operative to accommodate percussive loading applied by the apparatus during installation of the rock bolt assembly in a bore in rock strata, the dolly comprising a housing having a first end arranged to engage an end of the rock bolt, a 10 fluid arrangement configured to convey fluid through the dolly to the rock bolt, a seal arrangement having one or more seals for sealing between the rock bolt and the dolly, the seal arrangement operable in a first mode when the dolly is subjected to the percussive loading to allow movement between the housing and the rock bolt, and the seal arrangement operable in a second mode when the one or more seals is arranged to 15 seal between the housing and the rock bolt to allow conveyance of the fluid through the dolly to the rock bolt, wherein the one or more seals has a profiled surface to facilitate the relative movement in the first mode. 10228239_1 (GHMatters) P105812.AU.1 15/05/18 1/3 t0)

Description

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DOLLY

Technical Field The disclosure relates to a rock bolt dolly arranged to connect a rock bolt assembly to a rock bolt apparatus and operative to accommodate percussive loading applied by the apparatus during installation of the rock bolt assembly in a bore in rock strata, and particularly to a dolly including a seal arrangement having a profiled surface.

Background Rock bolts are used in underground mines, such as coal mines, to provide support for the mine walls. Use of percussive forces can be beneficial for facilitating insertion of rock bolts into bore holes that are susceptible to collapse from loose material. Some rock bolts comprise a longitudinally expandable tube that includes a longitudinally extending depression between two curved outer portions where the tube is partially collapsed on itself. The ends of the tube are folded over to create two enclosed cavities in the curved outer portions of the tube while a temporary passageway defined by the depression remains open on the ends. After placing the rock bolt in the pre-drilled borehole, pressurized fluid is delivered into the two cavities to force the depression outward, expand the tube, and compress it against the surrounding rock. Dollies are used to install a rock bolt in the bore hole in combination with a rock bolt apparatus, and need to be capable of withstanding the percussive forces and deliver the pressurized fluid to the rock bolt. It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

Summary The present application discloses a rock bolt dolly arranged to connect a rock bolt assembly to a rock bolt apparatus and operative to accommodate percussive loading applied by the apparatus during installation of the rock bolt assembly in a bore in rock strata, the dolly comprising a housing having a first end arranged to engage an

20880684_1 (GHMatters) P105812.AU.1 12/06/24 end of the rock bolt; a fluid arrangement configured to convey fluid through the dolly to the rock bolt; a seal arrangement having one or more seals for sealing between the rock bolt and the dolly, the seal arrangement operable in a first mode when the dolly is subjected to the percussive loading to allow movement between the housing and the rock bolt, and the seal arrangement operable in a second mode when the one or more seals is arranged to seal between the housing and the rock bolt to allow conveyance of the fluid through the dolly to the rock bolt, wherein the one or more seals has a profiled surface to facilitate the relative movement in the first mode, and wherein at least one ridge is formed on the profiled surface to allow movement between the housing and the rock bolt in the first mode. The seal arrangement is advantageous because, in the first mode, it facilitates the relative movement by the profiled surface which in one form, provides a reduced surface contact of the seal with the housing and the rock bolt, and in the second mode, it forms an effective seal to convey fluid to the rock bolt. In some forms, the seal arrangement further comprises a plate located within the housing such that the one or more seals is/are disposed between the plate and the rock bolt. In some forms, the seal arrangement further comprises a piston, and the piston is moveable to drive the sealing arrangement between the first and second modes. In some forms, the dolly extends longitudinally and the one or more seals are in the form of two seals spaced apart longitudinally by a spacer. In some forms, when in the second mode, the piston applies a compressive force on the one or more seals to cause the seals to engage the housing and the rock bolt and prevent the egress of fluid from the dolly. In the second mode, a sealed chamber is formed about the spacer by the one or more seals. In some forms, each of the one or more seals is/are annular and include(s) opposite annular end faces, and an internal circumferential surface and an external circumferential surface extending between the faces wherein at least one of the surfaces includes the profiled surface. In some forms, at least one ridge is formed on the profiled surface to allow movement between the housing and the rock bolt in the first mode. It is understood that the profiled surface is not limited to including a ridge, and may include points, a

20880684_1 (GHMatters) P105812.AU.1 12/06/24 combination of ridges and points, or any suitable profile that allows the sealing arrangement to be in both the first mode and the second mode. In some forms, the piston includes a shaft extending from a head, and the sealing arrangement further comprises a seal about the shaft and a seal about the head to prevent the egress of fluid from the dolly. The piston seals may include the same profiles surface as the one or more seals. In some forms, the piston seals are formed from polyurethane. In some forms, the one or more seal is/are formed from polyurethane. In some forms, the hardness of the one or more seal is/are harder than the hardness of the piston seals. In some forms, the profiled surface of the one or more seals is/are deeper than the profiled surface of the piston seal. In some forms, the dolly extends between the first end and a second end, and the sealing arrangement is biased towards a second end of the dolly in the first mode. In the second mode, transmission of the fluid overcomes the bias on the piston and moves the piston towards the one or more seals to place the seals under compression. In operation, the dolly allows for transmission of percussive loading to the rock bolt assembly to assist in inserting the rock bolt assembly into the bore. In combination with a thrust element positioned at a leading end of the rock bolt to facilitate movement of material past the rock bolt when installed in a borehole in a surface, the dolly may inhibit compaction of that material in the blind end of the bore. In a particular application, the rock bolt comprises an expandable tube having a longitudinally extending depression disposed between a pair of outer portions of the tube, wherein the exterior of the tube defines a temporary, enclosed longitudinal passageway; and the tube is expandable by providing pressurized fluid to the interior of the tube via the dolly, which provides frictional engagement between an exterior of the tube and an interior of the borehole. The fluid is subsequently drained from the interior of the tube.

Brief Description of the Drawings Embodiments will now be described by way of example only, with reference to the accompanying drawings in which Fig 1 shows a perspective view a dolly of an embodiment of the disclosure;

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Fig 2 shows an exploded perspective view of the dolly of Fig 1; and Fig 3 shows a close-up cross-sectional side view of an embodiment of a seal assembly the dolly of Fig. 1.

Detailed Description of the Drawings In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure. Referring now to the Fig. 1, disclosed is a dolly 10 arranged to connect a rock bolt assembly 1 (shown in Fig. 3) to a rock bolt apparatus (not shown). The dolly 10 is operative to accommodate percussive loading applied by the rock bolt apparatus during installation of the rock bolt assembly in a bore in rock strata. The dolly 10 also includes a fluid arrangement (shown but not referenced) that is configured to convey fluid through the dolly 10 to the rock bolt 1. The dolly 10 has a housing 12 that extends longitudinally between a first end 14 and a second end 16. The first end 14 engages an end of the rock bolt 1, and may also be known as the leading end 14 of the dolly 10. As best shown in Figs. 2 and 3, a seal arrangement 18 is located within the housing 12 having one or more seals 20 for sealing between the rock bolt 1 and the dolly 10. The seal arrangement 18 has a first mode and a second mode. In a first mode when the dolly 10 is subjected to the percussive loading, the seal arrangement 18 is operable to allow movement between the housing 12 and the rock bolt 1. In the second mode when the fluid arrangement is conveying fluid through the dolly 10 to the rock bolt 1, the one or more seals 20 of the seal arrangement 18 is/are arranged to seal between the housing 12 and the rock bolt 1 to prevent fluid leaking from the dolly 10.

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In addition to the one or more seals 20, the seal arrangement 18 generally includes a piston 22, a plate 24, a biasing arrangement (not shown), and a spacer 28. The housing 12 defines an interior cavity and extends along a longitudinal axis and these components of the seal arrangement 20 are located within the interior cavity. The piston 22 is positioned towards the second end (also known as the trailing end) of the dolly 10 and is moveable to drive the sealing arrangement between the first and second modes. The plate 24 is positioned adjacent the piston 24 towards the first end of the dolly and the one or more seals 20 is/are disposed between the plate 24 and the rock bolt 1. The biasing arrangement (not shown) in the form of a compression spring extends from the piston 22 to bias the piston toward the second end 16 of the dolly 10. Movement of the piston 22 within the cavity is transmitted to the plate 24 which compresses the one or more seals 20. An end cap 29 is adapted to be engaged with the housing 12 by means of a helical thread, and retains the seal arrangement 18 within the housing. In the illustrated embodiment, the one or more seals 20 are in the form of two seals 20 spaced apart longitudinally by the spacer 28. Each seal 20 has a profiled surface to facilitate the relative movement between the housing and the seal arrangement in the first mode. Each seal is annular and includes opposite annular end faces, and an internal circumferential surface and an external circumferential surface extending between the faces. At least one surface of each seal 20 includes the profiled surface. And in the illustrated embodiment, both the internal circumferential surface and the external circumferential surface include the profiled surface. At least one ridge 32 is formed on the profiled surface, and in the illustrated form, two ridges 32 are formed on each of the internal surface and the external surface to allow movement between the housing and the rock bolt in the first mode. The piston 22 includes one or more seals 30 located about the periphery of the piston 22. The piston seal(s) 30 may also include the profiled surface. The piston 22 includes a shaft 34 that extends from a head 36. In the illustrated embodiment, one seal is located about the shaft 34 and one seal is located about the head 36. In the first mode, the dolly 10 is under percussive loading, and the profiled surface reduces the surface area of the seals in contact with the housing 12 and the rock bolt 1 to reduce break off friction while under loading conditions. The profiled surface

20880684_1 (GHMatters) P105812.AU.1 12/06/24 also allows the end of the rock bolt 1 to push past the seals 20 during installation to be received in the interior cavity of the housing 12 and abut against the plate 24 for installation by the dolly 10 and the rock bolt arrangement (not shown). In the second mode, the dolly 10 includes the fluid arrangement to inject water into the rock bolt. The piston 22 is biased towards the second end of the dolly. Fluid is pumped into a chamber proximate and about at least a portion of the piston 22 which moves the piston 22 forward against its bias. Movement of the piston 22 moves the plate 24. When the piston 24 and the plate 22 move forward, they compress the seals 20 forming a sealed chamber about the spacer 28. Fluid in the form of water passes through from the dolly 10 about through the sealed chamber about the spacer 28 and into the rock bolt 1 through a hole to inflate or expand the rock bolt. As the seals 20 compress, they expand radially towards the housing and the rock bolt to engage the interior surface of the housing 12 and the exterior surface of the rock bolt 1. When the seals 30 are under compression they prevent fluid from leaking from the dolly. In some forms, when the seals 20 are under compression they also inhibit relative movement between the housing 12 and the rock bolt 1. The fluid is injected at a high pressure, for example 300 Bar, and the seals and the piston seals are able to form a sealed chamber respectively in relation to the piston and the spacer and withstand this high pressure. In alternative embodiments, the profiled surface may include any number of ridges, one or more points or be any suitable shape that reduces the surface area of the seals in contact with the housing and the rock bolt in the first mode while also being able to compress for sealing in the second mode. The seals 20 and the piston seals 30 are formed from polyurethane. Polyurethane is able to adapt to the different dynamics of the dolly 10 and the different modes of the sealing arrangement 18. For example, polyurethane is able to both resist the percussion loading in the first mode and form a seal that prevents leakage in the second mode. In the second mode, water may be used as the fluid for injecting into the rock bolt 1. In the illustrated embodiment, the seals 20, 30 are formed from self lubricating hydrolysis resistant polyurethane, which is able to overcome stick slip and friction normally associated with using water. The seals 20 and the piston seals 30 have a similar profiled surface, but may be formed from a material of different hardness, and the exact profile of the ridge(s) may

20880684_1 (GHMatters) P105812.AU.1 12/06/24 be different. Preferably, the seals 20 are designed to be able to withstand the constant percussion being transmitted to the rock bolt 1. When the seals 20 are formed from polyurethane, a hardness may be selected to better resist the percussion loading, for example 60 shore D hardness. The piston seals 30 do not sustain the same intensity of percussion loading as the seals 20 and are designed to facilitate dynamic sealing. When the piston seals 30 are formed from polyurethane, a hardness for the polyurethane may be selected to provide good dynamic sealing such as 93 shore A hardness. In the illustrated embodiment, to accommodate the different dynamics placed on the dolly 10 and the rock bolt 1 in the different modes, a harder material was used for the seals 20 than for the piston seals 30. Further, each ridge 32 may have different depths, and need not be identical. In the illustrated embodiment, the ridges 32 of the profiled surface of the seals 20 are deeper than the ridges 32 of the profiled surface of the piston seals 30. By deepening the ridges compression on the seal is reduced. This increases flexibility of the material to ensure the correct compression for static sealing in the second mode, and ensure the correct hardness to resist the percussive loading in the first mode. Further, having a deeper ridge 32 on the seals 20 facilitates pushing the rock bolt 1 through the two seals 20 to abut against the plate 24. In operation, a borehole is drilled into a surface such as a rock surface to the desired depth. The bolt 1 is engaged with the dolly 10 at the first end 14. The bolt 1 is inserted into the borehole with percussive loading on the dolly 10 by the rock bolt apparatus facilitating the insertion. Percussive loading on the dolly 10 is transmitted through the plate 24 to the end of the rock bolt 1. The plate 24 acts to place percussive force upon the shaft of the rock bolt 10, which enables additional force to insert the rock bolt 1. Ordinarily the bolt 1 is inserted through a bearing plate (not illustrated) into the borehole. The dolly 10 is particularly useful for inserting the rock bolt 1 into risible surfaces or ground into which it is difficult to insert an expandable bolt 1. In these cases, a thrust element (not shown) may be provided at the leading end of the rock bolt. In some forms the thrust element may comprise a cover for the leading end, or may be

20880684_1 (GHMatters) P105812.AU.1 12/06/24 otherwise associated with the leading end, such as being directly connected to the leading end or form an extension of the cover. The thrust element may be arranged in use to deflect loose material disposed in the bore as the rock bolt is inserted. This may assist insertion of the rock bolt in the bore and/or may inhibit compaction of that material in the blind end of the bore. Compaction of loose material in the bore end is problematic as it reduces the effective length of the bore and may prevent the rock bolt from being fully inserted into a bore unless that bore hole is of extended length. It is undesirable to extend the length of the bore hole as this adds both time and expense to the strata support operation. In general use, the expandable rock bolt with thrust element is inserted into a pre-drilled borehole, without rotation thereof necessary, although in certain instances the expandable rock bolt with thrust element may be at least slightly rotated about its longitudinal axis. Such pre-drilled boreholes may at least partially refill with loose rock or the like. The thrust element deflects such loose material to ease the insertion of the bolt into the borehole, with the remainder of installation of the expandable rock bolt with thrust element being the same or similar to the expandable bolt with shielded tip as described above. The inclusion of a plate 24 within the dolly 10 allows for insertion to involve percussive loading on the dolly 10 to facilitate movement of the bolt 1 into the bore hole. The thrust element positioned on the distal end of the expandable rock bolt 1 reduces the difficulty of inserting the expandable rock bolt 1 into a bore made in risible or gravelly earth. In these circumstances the material tends to move past or be deflected by the element into the wall of the bore. The thrust element allows the bolt 1 to be more easily inserted by compacting the loose material against the wall of the bore or moving loose earth material away from the advancing front of the rock bolt 1 as it is being inserted in the bore. This allows the expandable bolt 1 to be inserted into the bore without the risk that there will be a build-up of material in the end of the bore that would prevent the rock bolt from being fully inserted. The use of the thrust element on the rock bolt 1 is particularly useful when a percussive force is applied to drive the rock bolt in place and typically does not require any rotation to be applied to the bolt.

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Subsequently, fluid is pumped through the dolly 10 and the rock bolt 1 at a high pressure, for example 300 Bar, to expand the longitudinally extending tube of the rock bolt 1. Once expanded, the tube achieves intimate contact with the irregular shaped borehole (e.g., collapsed boreholes) to provide support to the rock strata. The expanded tube retains its shape by undergoing plastic deformation. Once the installation and inflation or expansion process is complete, the dolly 10 and rock bolt arrangement are removed from the end of the rock bolt 1, and the water flows out of the rock bolt 1. The foregoing description sets forth the preferred embodiments of the disclosure at the present time. Various modifications, additions, and alternative designs will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the scope of the claims. The scope is indicated within the following claims rather than by the foregoing description. All changes and variations that fall within the meaning and range of equivalency of the claims are to be embraced within their scope. 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.

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Claims (11)

CLAIMS:

1. A rock bolt dolly arranged to connect a rock bolt assembly to a rock bolt apparatus and operative to accommodate percussive loading applied by the apparatus during installation of the rock bolt assembly in a bore in rock strata, the dolly comprising: a housing having a first end arranged to engage an end of the rock bolt; a fluid arrangement configured to convey fluid through the dolly to the rock bolt; a seal arrangement having one or more seals for sealing between the rock bolt and the dolly, the seal arrangement operable in a first mode when the dolly is subjected to the percussive loading to allow movement between the housing and the rock bolt; and the seal arrangement operable in a second mode when the one or more seals is/are arranged to seal between the housing and the rock bolt to allow conveyance of the fluid through the dolly to the rock bolt, wherein the one or more seals has/have a profiled surface to facilitate the relative movement in the first mode, and wherein at least one ridge is formed on the profiled surface to allow movement between the housing and the rock bolt in the first mode.

2. A dolly as claimed in claim 1, wherein the seal arrangement further comprises a plate located within the housing such that the one or more seals is/are disposed between the plate and the rock bolt.

3. A dolly as defined in either claim 2, wherein the seal arrangement further comprises a piston, and the piston is moveable to drive the sealing arrangement between the first and second modes.

4. A dolly according to claim 3, wherein when in the second mode, the piston applies a compressive force on the one or more seals to cause the seals to engage the housing and the rock bolt and prevent the egress of fluid from the dolly.

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5. A dolly according to any one of the preceding claims, wherein each of the one or more seals is/are annular and includes opposite annular end faces, and an internal circumferential surface and an external circumferential surface extending between the faces wherein at least one of the surfaces includes the profiled surface.

6. A dolly according to claim 3, wherein the piston includes a shaft extending from a head, and the sealing arrangement further comprises a seal about the shaft and a seal about the head of the piston to prevent the egress of fluid from the dolly.

7. A dolly according to claim 6, wherein the piston seals are formed from polyurethane.

8. A dolly according to any one of the preceding claims, wherein the one or more seal is/are formed from polyurethane.

9. A dolly according to claim 8 when dependent on claim 7, wherein the hardness of the one or more seal is harder than the hardness of the piston seals.

10. A dolly according to claim 8 when dependent on claim 6, wherein the piston seals comprise a profiled surface with at least one ridge formed on the profiled surface, and wherein the profiled surface of the one or more seals is deeper than the profiled surface of the piston seals.

11. A dolly according to any one of the preceding claims, wherein the housing of the dolly extends between the first end and a second end, and the sealing arrangement is biased towards the second end of the housing of the dolly in the first mode.

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