Expandable rock bolt and rock bolting system

The present invention is related to a rock bolt (7), expandable by means of a pressure media, for insertion into a borehole. The expandable bolt (7) comprises a connection unit (8) with means (11) for detachable interaction with an expansion means (10) for expansion of the rock bolt (7), as well as with a suspension element (16). The connection unit is designed with such external dimensions so that it may be inserted into the bore-hole. The invention also relates to such a rock bolting system.

TECHNICAL FIELD

The present invention is related to expandable rock bolts for use as suspension attachments.

BACKGROUND OF THE INVENTION

In tunneling and in mines there is often a need for suspending different devices used in the work, for example ventilators, drilling equipment and the like. Additionally, in mines and in tunneling one often uses platforms in order to transport excavated material and other material. These platforms are hung up in the roof of the tunnel or mine, which for example may be done by attaching a beam in the roof and then fastening the platform to the beam.

In order to fasten such devices, for example a service platform, to the roof, bolts of different types may be used. Often one uses expandable bolts, so called swelling bolts where the bolt comprises a tube, the interior of which is pressurized by means of a pressure means, such as a high pressure fluid, and thereby expands. An example of such an expandable bolt is showed in the Swedish patent nr. 7902129-1. The expansion bolts may be used with a special coupling, that is fastened to the expansion bolt. The platform, or the devices that one wishes to suspend in the roof, is then fastened in these couplings.

A disadvantage with using these bolts as suspension devices is that they, together with the special suspension coupling, protrude substantially from the roof of the tunnel, and must therefore be cut and/or covered by a thick layer of rendering concrete. This is a costly and time-consuming operation and it would be desirable to be able to minimize it. This bolt with suspension device may not be ranked as supporting of rock in the safety estimates.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a rock bolt that solves the above-mentioned problems. More specifically, it is an object of the present invention to provide an improved rock bolt for suspension, which entails minimized stress concentrations in the bolt. Another object of the present invention is to provide a suspension device that simplifies the work when moving into a rock.

These and other objects are achieved in accordance with the present invention by an expandable rock bolt as defined in claim1.

In accordance with the present invention the above mentioned objects are achieved by providing a expandable rock bolt, that can be expanded by means of a pressure media, with a connection unit including means for interaction with means for expanding the rock bolt as well as suspension elements. The connection unit is further designed with such exterior dimensions that it may be inserted into a borehole. Thereby a suspension device is provided that gives a smaller protrusion from the rock, and that provides a better strength.

In accordance with a preferred embodiment, the connection unit comprises a connection sleeve fastened to the rock bolt. Thereby a practical and easy to use connection of the suspension elements and expansion means, respectively, is provided. This connection sleeve may be inserted into the borehole and thereby gives a minimal protrusion from the rock into the tunnel being covered, which results in a faster and more efficient tunneling work.

In accordance with another preferred embodiment the connection sleeve may be welded to the rock bolt, which gives a more safe and at the same time economical and practical attachment of the connection sleeve to the rock bolt.

In accordance with another preferred embodiment the connection unit's connection sleeve comprises an organ, for example a flange, against which a rock plate may abut. This gives the rock bolt according to the present invention rock supporting qualities, whereby the rock bolt combines two important and useful functions, namely supporting of rock and suspension, in one and the same rock bolt. The rock plate may further be chosen as appropriate and depending on the requirements, and may for example comprise a regular flat rock plate or e.g. a domed rock bolt. In accordance with this aspect of the invention the expandable rock bolt may thus be used both as rock support and as a suspension device. Thereby the total cost for providing suspension devices and rock support may be decreased, giving an economical solution.

In accordance with another preferred embodiment the connection unit comprises a supporting sleeve, surrounding at least parts of the seat of the connection unit. Thereby the rock bolt is prevented from being exposed to bending moment due to the fact that the bolt rests against the wall of the hole.

In accordance with another preferred embodiment two rock bolts may be joined and thereby provide a longer rock bolt. The rock bolt in accordance with the present invention may alternatively be used only as the outermost part, protruding from the rock, whereby regular on the market existing likewise or otherwise expandable rock bolts, without a connection unit for suspension and plate, may be used farthest in, in the borehole.

In accordance with another preferred embodiment the suspension element may comprise one of the following: mounting lug, a single hook, a double hook, a catch or a combination thereof. Great flexibility is thereby provided, and the suspension element may be adapted as required.

The present invention also relates to a rock bolting system comprising an expandable rock bolt as above, and expansion nipple and suspension element, whereby advantages, corresponding to the above described, are achieved.

Further advantages are achieved by different aspects of the invention and will become clear by the following detailed description.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As was described above there is often a need for suspending various devices in a mine or in a tunneling work. In rock drilling supporting of rock of some kind is needed, for example rock bolts, cables or other elements, in order to strengthen and stabilize the rock and thereby making the rock self-supporting. As was described in the introductory part there are expandable, tubular rock bolts that may be used for this purpose, see for example the Swedish patents no. 427 764 and 443 398.

The present invention provides an improved rock bolt, which may also be provided with a suspension device giving a minimal protrusion, and that at the same time provides a way to combine these two needs existing in a rock drilling environment, for example in a mine, in one and the same rock bolt.

With reference now toFIG. 1, a rock bolt7in accordance with the present invention is shown. The by a pressure media expandable rock bolt7comprises a connection unit for connection both of an expansion means10(seeFIG. 2) and for connection of a suspension element16(seeFIG. 3). The connection unit preferable comprises a connection sleeve8with a seat comprising internal means11for reception both of the expansion organ10for expanding the rock bolt7and of a suspension element16. The internal means11of the seat may for example comprise threads, whereby the expansion means10and the suspension element16, respectively, may be screwed on to the rock bolt7. Alternatively, as is shown in theFIGS. 4aand4b, the connection sleeve8may instead comprise external threads for interaction with the expansion means10and suspension element16, respectively. This must however be done without substantially lengthen the protrusion of the rock bolt from the rock, for example so that a sleeve like part of the expansion means10and the suspension means16have such dimensions that they may be inserted into the borehole. Other suitable detachable connections are also conceivable.

The connection unit preferably also comprises a supporting sleeve9, which is fastened to the rock bolt7. The parts of the connection unit, that is, the connection sleeve8and the supporting sleeve9in case such is present, may in an alternative embodiment be integrated. Furthermore, the supporting sleeve9prevents any undesired angular displacements between the connection sleeve8and the rest of the rock bolt7thanks to the fact that the sleeve supports against the wall of the hole.

InFIG. 2the expansion means10is shown in the form of an expansion nipple, but in other embodiments the expansion means10may for example be a simple, straight tube or a hollow cable. The function of the expansion means10is to allow expansion of the rock bolt7, and thereby anchorage of the rock bolt7in the rock12. Expansion requires only that the expansion means10comprises some kind of hollow body, through which for example water may be fed in under high pressure, whereby the rock bolt7expands to abutment against the borehole. An expansion nipple is advantageous in that the pressurization may then be performed by means of a radial injection tube, whereby a manual pressurization is facilitated.

The expansion means10preferably fits into an ordinary standard chuck for rock bolt used in rock bolting, and a specially designed chuck is thus not needed for the rock bolt7in accordance with the present invention.

In the shown embodiment, the connection sleeve8comprises a flange13against which a rock plate14abuts. Means other than a flange are also conceivable as support for a rock plate14. By the fact that a rock plate14thus may be used in conjunction with the rock bolt7, the rock bolt7may be used also as supporting of rock, which is not possible with prior art suspension devices. The rock plate14may be an ordinary, flat plate or may be domed, as is shown in the figure.

When the rock bolt7has been expanded by means of the expansion means10, which expansion means10has been connected to a source of the pressure media, not shown, the expansion means10may be unscrewed. This provides a rock bolt giving a small protrusion. It is also possible, if desired, to connect a suspension element16, seeFIG. 3. The rock bolt7may thereby be used as a suspension device for e.g. service platforms and the like. The suspension element16is provided with means for interaction with the connection sleeve's8internal (or external) means11, for example screw threads. InFIG. 3the suspension element16is shown in the form of a mounting lug, but in alternative embodiments the suspension element16may comprise any suitable suspension means, for example a single hook, a double hook, a crook or any combination of these. A flexible suspension device, which may be adjusted according to need, is thus provided.

Moreover, the suspension element16may be unscrewed and be reused as the tunneling is advancing. This gives at least two advantages. Firstly, the cost for the suspension element16is reduced, since it may be used several times. Secondly, the protrusion from the rock is small, whereby the need for cutting bolts after use is eliminated, which otherwise is a time-consuming process. Thereby the procedure is speeded up, and moreover, the required thickness of the covering with rendering concrete or the like is reduced, which per se again reduces the costs. The installation is further very fast, with only a few, simply assembled parts.

As is shown inFIG. 5the connection unit may be adjusted so that two and more rock bolts7′,7″ may be joined together in order to form a long bolt. This may be done in different ways. If one wishes to join together two rock bolts7′,7″ in accordance with the present invention, an outer rock bolt7′ has to have a through cable with a connection nipple17, that are joined together with a connection sleeve8on an internal rock bolt7″. Application of a pressure media external to the borehole then entails expansion of both bolts7′ and7″.

The inner part of the rock bolt7may alternatively be exchanged to a male mounting that is pieced together with an ordinary expandable rock bolt. The rock bolt7in accordance with the present invention is then used only as the outermost part, protruding from the rock, while regular jointed expandable rock drills are used farthest in, in the rock12.