Patent Description:
Rock bolts (or large wall bolts) are commonly used in mining and sometimes in rock-based construction. Such rock bolts include a head or thread and a shank with or without an engagement formation, to engage sides of a hole within which the rock bolt is inserted. For reference, an end of the rock bolt with the head/thread or nut, which remains outside the hole when installed, is referred to as the live end and the opposite end, which is inserted into the hole, is referred to as the dead end.

Exemplary bolt assemblies are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

In some installations, the bolt actually comprises two bolt sections or shanks joined end-to-end by means of a coupling; this may be considered a compound bolt. Opposed ends of the bolt sections are typically threaded, and the coupling is hollow with an internal thread. This may be useful where headroom is limited, and a single bolt will be too long to have sufficient space to be inserted into the hole. Instead, the hole may be deeper than usual and require two bolt sections to be joined together to be long enough.

The bolt sections are often only coupled together when they, or at least the first shank, are in the hole. The coupling is not visible or observable once inside the hole. This leads to a difficulty to ensure that the coupling is complete or sufficient, and that both sections of the compound bolt have been installed. The outer section (at the live end) may be rotated, in the belief that it has engaged the coupling properly, until it cannot be rotated further, in the belief that it has fully engaged the coupling.

The Applicant desires a rock bolt assembly with an indication function to indicate when the sections have been coupled together.

Accordingly, the invention provides a rock bolt assembly which includes:.

One or both of the shaft sections may be of ferrous metal, e.g., steel.

One or both shafts may include a coating, covering, or sleeve. The outer shaft section specifically may include the coating, covering, or sleeve. The outer shaft section may include a PET (or other polymer) coating. The coating, covering, or sleeve may be around the outer shaft section and the electrical conductor. The coating, covering, or sleeve may serve to locate or hold the electrical conductor in place alongside the outer shaft section during installation.

The electrical contact arrangement may include two exposed electrical contacts, one connected to the outer shaft section and the other connected to the conductor. Interconnecting, or shorting out, the exposed electrical contacts may therefore interconnect the outer shaft section and the conductor. The exposed electrical contacts may be interconnected by the inner shaft section and/or by the coupler itself.

In a more basic embodiment of the rock bolt assembly, named a passive rock bolt assembly, the electrical terminals may merely be provided on the head without any device connected thereto. They may be provided such that they are exposed or accessible for a device to be connected, at least temporarily, thereto. The device may be a continuity measuring device, configured to measure or display whether or not the electrical contact arrangement has interconnected the outer shaft section, the inner shaft section and the conductor, thus indicating whether or not the rock bolt assembly is properly coupled together.

In a more developed embodiment, named an active rock bolt assembly, the rock bolt assembly may include a device, e.g., a continuity measuring device, coupled or attached thereto in the region of the head. The device may be electronically connected to the electrical terminals. The device may be, or may include, a continuity indicator. The device may provide an indication (e.g., an illuminated light) to indicate that the two shaft sections are properly coupled.

By way of further development, the indication by the continuity measuring device that two shaft sections are properly coupled is a first indication, the rock bolt assembly may further include:.

The continuity measuring device (functioning as a second continuity indicator) may further be configured to provide a second indication to indicate whether the secondary contacts have made contact, thereby indicating that the frangible or deformable element has broken or deformed, and that the predefined load has been reached or exceeded.

The second continuity indicator may also provide a visual indication of continuity. The device may include two different coloured lights (e.g., LEDs) for indicating (<NUM>) that the two shaft sections are coupled and (<NUM>) that the predefined load has been reached. The lights may be green and blue (or other desired colour combination).

The frangible or deformable element may be in the form of an annulus or ring provided around the outer shaft section adjacent the head. The frangible element may be of hard plastic or a section of a PCB (Printed Circuit Board), or ferrous steel or aluminium, optionally that has an insulating coating.

The device may define a channel or aperture for accommodating the outer shaft section so that the device can be mounted onto the outer shaft section adjacent the head. The device may include a protective housing, e.g., made from a plastic material.

The device may include a power source like a battery for powering one or both continuity indicators.

The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

The following description of an example embodiment of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that changes can be made to the example embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the example embodiment without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the example embodiment are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description of the example embodiment is provided as illustrative of the principles of the present invention and not a limitation thereof.

<FIG> illustrates a passive embodiment of a rock bolt assembly <NUM> in accordance with the invention. As reference points, the rock bolt assembly <NUM> has a live end <NUM> which, in use, will project out of a hole drilled in a rock wall and has structures which will abut against the rock wall, and a dead end <NUM> which, in use, is inserted as far as it will go into the hole in the rock wall. It will be appreciated that, when inserted, much of the rock bolt assembly <NUM> towards the dead end <NUM> will not normally be visible or observable.

The rock bolt assembly <NUM> may be thought of as a compound bolt and includes components which may be largely conventional, namely an outer shaft section <NUM> (towards the live end <NUM>), an inner shaft section <NUM> (towards the dead end <NUM>), and a coupler <NUM>. The shaft sections <NUM>, <NUM> may include textured or gripping surfaces as desired. Opposed ends of the shaft sections <NUM>, <NUM> in the middle (at the coupler <NUM>) include a male thread while the coupler <NUM> is largely hollow and defines an internal female thread. The rock bolt assembly <NUM> includes a head <NUM> which may include various nuts or washers (see below) depending on its intended application.

The coupler <NUM> is configured to receive the threaded ends of the shaft sections <NUM>, <NUM> and join them together in situ, that is, inside the hole in the rock wall. This is useful, for the reason mentioned above in the BACKGROUND but also gives rise to those problems mentioned.

Accordingly, the rock bolt assembly <NUM> includes an electrical conductor <NUM> extending from a dead end of the outer shaft <NUM>, along the outer shaft section <NUM>, and towards the head <NUM>. The conductor <NUM> is insulated from the outer shaft section <NUM>. The shaft sections <NUM>, <NUM> are made of steel, to be strong and support a load, as is their purpose. The coupler <NUM> is also made of steel.

An electrical contact arrangement <NUM>, <NUM>, <NUM> is provided at the dead end of the outer shaft section <NUM>. A plastic (insulating) collar or disc <NUM> mounted to an end of the outer shaft section <NUM> supports two exposed electrical contacts <NUM>, <NUM>, with a first contact <NUM> being electrically connected to the outer shaft section <NUM> and a second contact <NUM> being electrically connected to the conductor <NUM>.

Interconnecting, or shorting out, the exposed electrical contacts <NUM>, <NUM> therefore interconnects the outer shaft section <NUM> and the conductor <NUM>. More specifically, this interconnection is configured to occur when the inner and outer shaft sections <NUM>, <NUM> are coupled. A flat metal (conductive) structure pressed across the contacts <NUM>, <NUM> would do this. Therefore, this may be realised by a metallic wall of the coupler <NUM> shorting out the contacts <NUM>, <NUM> or by an end of the inner shaft section <NUM> doing so. Either way, this should only occur when the shaft sections <NUM>, <NUM> are sufficiently interconnected and coupled by the coupler <NUM>.

At the live end <NUM>, electrical terminals are provided. The head <NUM> may include a large domed washer <NUM> and a nut <NUM> but the configuration of these may vary depending on an application of the rock bolt assembly <NUM>. The nut <NUM> (being of steel) is threadingly mounted to, and therefore electrically connected to, the outer shaft section <NUM>. The nut thus serves as a first electrical terminal. A plastic support disc <NUM> is provided, sandwiched between the nut <NUM> and the washer <NUM>. An exposed end of the conductor <NUM> is fixed to the plastic disc <NUM> and this exposed end serves as the second electrical terminal.

Although not separately illustrated, the conductor <NUM> is insulated with, e.g., a plastic sleeve, and a PET coating is applied to the combination of the outer shaft section <NUM> and the insulated conductor <NUM> to bind them securely together.

It may be noted that there is only one external conductor <NUM> provided and the outer shaft section itself <NUM> acts as a second conductor. In a different embodiment (not illustrated), the outer shaft section <NUM> may be configured not to be a conductor and two external wires may be provided to serve as respective conductors.

<FIG> illustrate a continuity testing device <NUM> for indicating whether or not the exposed electrical contacts <NUM>, <NUM> of the rock bolt assembly <NUM> have been shorted. The device <NUM> comprises a plastic housing <NUM> with two electrical prongs <NUM> projecting outwardly therefrom. Internally, the device <NUM> has a battery <NUM> to power a light <NUM> when a circuit is completed. As spacing between the prongs <NUM> is designed to be matched, or at least similar, to a spacing between the nut <NUM> and the exposed end of the conductor <NUM> on the disc <NUM>. Instead of the specific continuity testing device <NUM>, a generic multimeter with a continuity test mode could be used.

In use, a user (who could be an installer doing a rock bolt installation or a foreman checking on a prior installation) merely touches the prongs <NUM> of the device <NUM> to the electrical terminals, i.e., the nut <NUM> and the exposed end of the conductor <NUM> on the disc <NUM>. If the light <NUM> illuminates, this means that the exposed contacts <NUM>, <NUM> have been shorted or interconnected, which indicates that the two shaft sections <NUM>, <NUM> have been coupled satisfactorily by means of the coupler <NUM>.

<FIG> illustrates an active embodiment of a rock bolt assembly <NUM> in accordance with the invention. The same reference numerals as those in <FIG> refer to the same or similar parts. The main difference between the rock bolt assemblies <NUM>, <NUM> is that the active rock bolt assembly <NUM> has a continuity measuring device <NUM> integrated therewith. The continuity measuring device <NUM> has a modified housing <NUM> which includes an aperture to accommodate part of the outer shaft section <NUM> so that the continuity measuring device <NUM> can be mounted to the head <NUM> of the rock bolt assembly <NUM>.

The rock bolt assembly <NUM> may include a second indicating function. The rock bolt assembly <NUM> may include a frangible element (e.g., disc or sleeve <NUM>) which is configured to fracture at a predetermined load. Once the frangible element <NUM> fractures, it may allow two secondary contacts (e.g., one provided inside the device <NUM> and the other provided by the nut <NUM>) to make contact. This may cause a secondary light (not illustrated) to illuminate.

In such case, when installing the rock bolt assembly <NUM>, a miner may couple the outer shaft section <NUM> by rotating the nut <NUM> until the indicator light <NUM> (provided on the continuity measuring device <NUM>) illuminates, indicating that the shafts sections <NUM>,<NUM><NUM> are coupled. He then continues rotating and tightening the nut <NUM> until the secondary light illuminates, indicating that the predefined load tension has been reached. Failure of either of the two lights to illuminate may indicate a problem (e.g., lack of coupling or lack of pre-tension).

Claim 1:
A rock bolt assembly (<NUM>) which includes:
two shaft sections (<NUM>, <NUM>), namely an inner shaft section (<NUM>) which is intended to be at a dead end (<NUM>) of the rock bolt assembly (<NUM>) and an outer shaft section (<NUM>) having a head at a live end which is intended to be at the live end (<NUM>) of the rock bolt assembly (<NUM>), the outer shaft section (<NUM>) being of an electrically conductive material;
a coupler (<NUM>) configured to couple the two shaft sections (<NUM>, <NUM>) together at proximate ends, namely a dead end of the outer shaft section (<NUM>) and a live end of the inner shaft section (<NUM>);
characterized in that an electrical conductor (<NUM>) insulated from the outer shaft section (<NUM>) and extending from the dead end of the outer shaft section (<NUM>) to the head at the live end of the outer shaft section (<NUM>);
an electrical contact arrangement (<NUM>, <NUM>, <NUM>) at the dead end of the outer shaft section (<NUM>), the electrical contact arrangement (<NUM>, <NUM>, <NUM>) configured to electrically interconnect the outer shaft section (<NUM>) and the conductor (<NUM>) when the inner and outer shaft sections (<NUM>, <NUM>) are coupled; and
electrical terminals provided at the head and connected respectively to the outer shaft section (<NUM>) and to the conductor (<NUM>), the electrical terminals being interconnected when the outer shaft section (<NUM>) and the conductor (<NUM>) are electrically interconnected.