Patent Application
20240125233
This invention relates broadly to wall bolts for mines or construction and specifically to a rock bolt assembly having an indicator.
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.
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 (1) that the two shaft sections are coupled and (2) 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.
In the 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.
The rock bolt assembly 100 may be thought of as a compound bolt and includes components which may be largely conventional, namely an outer shaft section 120 (towards the live end 102), an inner shaft section 122 (towards the dead end 104), and a coupler 124. The shaft sections 120, 122 may include textured or gripping surfaces as desired. Opposed ends of the shaft sections 120, 122 in the middle (at the coupler 124) include a male thread while the coupler 124 is largely hollow and defines an internal female thread. The rock bolt assembly 100 includes a head 126 which may include various nuts or washers (see below) depending on its intended application.
The coupler 124 is configured to receive the threaded ends of the shaft sections 120, 122 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 100 includes an electrical conductor 136 extending from a dead end of the outer shaft 120, along the outer shaft section 120, and towards the head 126. The conductor 136 is insulated from the outer shaft section 120. The shaft sections 120, 122 are made of steel, to be strong and support a load, as is their purpose. The coupler 124 is also made of steel.
An electrical contact arrangement 130, 132, 134 is provided at the dead end of the outer shaft section 120. A plastic (insulating) collar or disc 130 mounted to an end of the outer shaft section 120 supports two exposed electrical contacts 132, 134, with a first contact 132 being electrically connected to the outer shaft section 120 and a second contact 134 being electrically connected to the conductor 136.
Interconnecting, or shorting out, the exposed electrical contacts 132, 134 therefore interconnects the outer shaft section 130 and the conductor 136. More specifically, this interconnection is configured to occur when the inner and outer shaft sections 120, 122 are coupled. A flat metal (conductive) structure pressed across the contacts 132, 134 would do this. Therefore, this may be realised by a metallic wall of the coupler 124 shorting out the contacts 132, 134 or by an end of the inner shaft section 122 doing so. Either way, this should only occur when the shaft sections 120, 122 are sufficiently interconnected and coupled by the coupler 124.
At the live end 102, electrical terminals are provided. The head 126 may include a large domed washer 144 and a nut 142 but the configuration of these may vary depending on an application of the rock bolt assembly 100. The nut 142 (being of steel) is threadingly mounted to, and therefore electrically connected to, the outer shaft section 120. The nut thus serves as a first electrical terminal. A plastic support disc 140 is provided, sandwiched between the nut 142 and the washer 144. An exposed end of the conductor 136 is fixed to the plastic disc 140 and this exposed end serves as the second electrical terminal.
Although not separately illustrated, the conductor 136 is insulated with, e.g., a plastic sleeve, and a PET coating is applied to the combination of the outer shaft section 120 and the insulated conductor 136 to bind them securely together.
It may be noted that there is only one external conductor 136 provided and the outer shaft section itself 120 acts as a second conductor. In a different embodiment (not illustrated), the outer shaft section 120 may be configured not to be a conductor and two external wires may be provided to serve as respective conductors.
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 204 of the device 200 to the electrical terminals, i.e., the nut 142 and the exposed end of the conductor 136 on the disc 140. If the light 208 illuminates, this means that the exposed contacts 132, 134 have been shorted or interconnected, which indicates that the two shaft sections 120, 122 have been coupled satisfactorily by means of the coupler 124.
The rock bolt assembly 300 may include a second indicating function. The rock bolt assembly 300 may include a frangible element (e.g., disc or sleeve 402) which is configured to fracture at a predetermined load. Once the frangible element 402 fractures, it may allow two secondary contacts (e.g., one provided inside the device 310 and the other provided by the nut 142) to make contact. This may cause a secondary light (not illustrated) to illuminate.
In such case, when installing the rock bolt assembly 300, a miner may couple the outer shaft section 120 by rotating the nut 142 until the indicator light 208 (provided on the continuity measuring device 310) illuminates, indicating that the shafts sections 120, 122 are coupled. He then continues rotating and tightening the nut 142 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).
The Applicant believes that the invention as exemplified is advantageous in that it provides a simple yet effective way to indicate whether or not a compound rock bolt has been sufficiently coupled. While some modifications to parts of the rock bolt are required, this can be done fairly cost effectively without hampering the support/bolting functionality of the rock bolt itself. This should increase the effectiveness and safety of installed compound rock bolts, by ensuring correct coupling the first time. Further, using some of the components already provided in the indicator device 310, a load indication can also be provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202101128 | Feb 2021 | ZA | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/051454 | 2/18/2022 | WO |
