Field of the invention

The present invention relates to a coupling element for connection of a number of clamps which are attached to a cable bundle. The invention also relates to a cable arrangement with clamps and coupling elements, and a method for pulling a cable arrangement through a borehole.

Background of the invention.

High voltage cables are normally held in stretches in the air over a land formation or in ditches in the ground. However, there has been a growing need to lay such cables in boreholes in rock formations or in the ground and soil. How to drill holes for laying cables is known, but the equipment presently available does not allow for pulling cables through long boreholes. For example, it is desirable to be able to pull such cables through boreholes which are several hundred metres long and also several kilometres long.

In order to pull such cables through long boreholes, it is important that the friction between the cable bundle and the interior of the borehole is low. Furthermore, in many cases it will also be important that the cables are in an ordered cable bundle. Purpose of the present invention.

It is an aim of the present invention to develop a solution that ensures that one can pull long cables through boreholes. The cables are bundled together with clamps, and it is an aim to be able to couple together the various clamps to achieve a uniform distribution of pulling forces applied to the cables when pulling through a borehole. It is a further aim to reduce friction between the cable bundle and the borehole, and coupling elements or clamps, or both parts, are therefore equipped with friction reducing means. When pulling cables through long boreholes, such as horizontal, inclined, arched or vertical boreholes, friction forces between the cable bundle and the inside surface of the borehole arise. These frictional forces have until now not allowed for the pulling of cables through long boreholes without causing damage to the cables.

Furthermore, it may also be necessary to lay the cables in ordered bundles such as when one-wire high voltage cables are laid in a three-foil arrangement. It is therefore an aim of the invention to provide coupling elements which connect clamps that bundle together a number of cables. It is a further aim of the invention that the coupling elements are either directly or indirectly equipped with friction reducing means.

When pulling cables through long boreholes or through boreholes with a steep incline, forces can be so great in the cables that they can be overloaded if the pull is directly on the cable. Therefore clamps are described which can directly or indirectly be attached to the cable so that parts of the pulling forces will go through the clamps, i.e. so that in practice one exerts forces at several points along the elongated length of the cable. Preferably, the clamps are evenly distributed along the longitudinal direction of the cable bundle, and connected together by a number of coupling elements. It is an aim of the invention to provide a pulling arrangement which enables pulling cables through long boreholes. The system must therefore;

1 . Include friction reducing means (such as wheels) between clamps and/or coupling elements and the inner surface of the borehole, for transferring the cables into (and out of) the borehole

2. Avoid damage to the outer sheath of the cable when pulling. 3. Bundling of cable, such as for example in a three-foil arrangement. For example, for a single-wire high voltage cables it is important that they lie in a three- foil arrangement to reduce power loss.

4. Securing the cable set in case of short circuiting. That the system keeps the cables in position when a short circuit occurs in the cable set.

5. To be able to withdraw the cable set when a faulty system occurs or during renewal/upgrades on the installation.

6. A coupling element, preferably in the form of rails (mechanical reinforcement) which is used when the forces during pulling or during the operational phase become too large for the cables to be exclusively present in the clamps. Wheels can then be mounted on the rails to reduce friction during pulling. With the use of rails (coupling elements) the clamps will then be anchored to the rail.

Summary of the Invention

Thus, the present invention relates to, in a first aspect, a coupling element for connecting together a number of clamps which are attached to a cable bundle, characterised in that the coupling element is in the form of an elongated rail which extends externally in relation to the cable bundle and comprises the attachment means for attachment to a number of clamps.

In one embodiment said attachment means are flexible in the longitudinal direction so that clamps can be attached to the coupling element in nearly any position in the longitudinal direction of the coupling element.

In one embodiment, the coupling element has a longitudinal pin in all or part of the longitudinal direction of the coupling element, adapted to be received within and engage with a recess in said clamps. In one embodiment, the coupling element comprises a number of friction-reducing means radially externally in a cable arrangement to reduce friction as the cable arrangement is pulled over a surface or through a borehole. In some embodiments, one, two, three or more coupling elements are fastened to the same clamp in the radial outer periphery of the clamp. In one embodiment, the coupling element in a cable arrangement, characterised in that the cable arrangement is comprised of a number of cables held together in a cable bundle, uses a number of clamps attached to the cable bundle and preferably arranged uniformly distributed in the longitudinal direction of the cable bundle, and that the coupling element connects in the longitudinal direction of the cable bundle of clamps to a stable cable arrangement.

In one embodiment, the width of the coupling element extends mainly radially outwards from the longitudinal axis of the cable bundle as the coupling element is fastened to the clamps and the cable bundle.

In one embodiment, said friction reducing means is comprised of a number of wheels, and said centre axis of the wheels is embedded in the coupling element.

In a second aspect the present invention provides a cable arrangement comprising;

- a number of cables held together in a cable bundle,

- a number of clamps fastened to the cable bundle and arranged preferably with a uniform distribution in the longitudinal direction of the cable bundle,

- one or more coupling elements which connect said clamps in the

longitudinal direction of the cable bundle.

In one embodiment, the arrangement is comprised of two or three coupling elements, connected to one clamp preferably evenly over the radial outer periphery of the clamp. In one embodiment, said coupling element is comprised of a number of friction- reducing means for the reduction of friction as the cable arrangement is pulled through a borehole. In one embodiment, said clamps are comprised of a number of friction-reducing means for the reduction of friction as the cable arrangement is pulled through a borehole.

In one embodiment, said coupling element and/or said clamps are comprised of means for receiving additional cables such as fibre and/or signal cables.

In a third aspect the present invention provides a method for pulling one cable, or a number of cables bundled together to form a cable bundle through a borehole, characterised in that a number of clamps are fastened to the cable or cable bundle evenly distributed over the longitudinal direction of the cable bundle, that fastened to said clamps, radially in the outer periphery of the clamp, is a number of coupling elements, where the coupling elements have an elongated shape corresponding to the elongated shape of the cable bundle so that a cable arrangement is established, and that the friction between the cable arrangement and the inner surfaces of the borehole in the pulling of the cable arrangement through the borehole is reduced.

In one embodiment, total friction is reduced between the cable arrangement and the borehole as the cable arrangement is provided with a uniformly distributed number of contact points against the inner surfaces of the borehole.

In one embodiment, said multitude of contact points are friction reducing means, such as wheels or balls.

Description of Figures

Preferred embodiments of the invention shall in the following be described in more detail with reference to the accompanying figures, where: Figure 1 shows schematically in perspective an arrangement where clamps and coupling elements hold together a number of cables. Figure 2 shows schematically in cross section a cable arrangement with clamps, friction reducing means against the borehole and coupling means.

Description of preferred embodiments of the invention. Figure 1 shows schematically in perspective how a number of elongated coupling elements 30 connect together a number of clamps 20 which hold together a number of elongated cables 12,14,16. The clamps 20 bundle together the cables 12, 14,16, and the coupling elements 30 connect the clamps, which are preferably uniformly distributed along the entire length of the cables 12,14, 16. A number of cables which are arranged together for pulling through a borehole 1 1 , for example, three cables 12, 14, 16, are now described here as a cable bundle 15. The coupling elements 30 can be fastened to the clamps 20 in any way, and figure 1 shows an embodiment where each clamp 20 has a number of attachment lugs 20c arranged so that one with the fastening means 20d such as screws, bolts, snap locks etc. can be attached to the coupling elements 30.

In the radial periphery of the clamp 20 there are customised fasteners 20c for attachment to a number of coupling elements 30. In a preferred embodiment, to each clamp 20 there are fastened three coupling elements 30 (as shown in figure 2). In other embodiments there is only one coupling element 30 fastened to the clamps 20 and in further embodiments the clamps 20 have two or four coupling elements 30 attached, and in further embodiments there are five or more coupling elements 30 attached to each clamp 20.

Preferably, each of the coupling elements 30 extends as long as the length of the cable bundle15, but in some embodiments the cable bundle 15 is longitudinally equipped with multiple coupling elements 30. If the clamp 20 is adapted for attaching several coupling elements 30, then at least one of these can extend along the whole length of the cable bundle 15, while one or more of the remaining coupling elements 30 can be arranged in only parts of the length, and also so that several coupling elements in total cover the whole or large parts of the cable bundle 15, in the longitudinal direction.

The clamps 20 can be of any type that is securely fastened to the cable bundle 15, so that one in the pulling of the cable bundle 15 through a borehole 1 1 can apply pull forces to the coupling elements 30 and that these, via a number of clamps 20, transfer the pulling forces to the cable bundle 15 in anchor points of all the clamps 20 to the cable bundle 15. As mentioned, in the clamps 20 there are attachment lugs 20c equipped for connecting a coupling element 30 to clamps 20. In a preferred embodiment, clamps 20 are equipped with recesses 20e for receiving the

corresponding longitudinal coupling elements 30. By such a joining of the coupling elements 30 in recesses 22e in the clamps 20, the stability of the cable arrangement

10 will be improved. The clamps 20 and coupling elements 30, and with the attachment of the clamps 20 to the cable bundle 15, provide a very stable cable arrangement 10, i.e. an arrangement 10 which is sufficiently stable such that very long cable bundles 15 can be pulled through an elongated borehole 1 1 . The considerable forces that are used to pull the cable bundle 15 through the borehole

1 1 can be applied directly to the cable bundle 15, or indirectly to the cable bundle 15 and the cables 12,14,16 via coupling elements 30 and clamps 20.

With a sufficient number of clamps 20 in the length of the cable bundle 15, one will prevent the cable bundle 15 from rubbing against the inner surfaces 1 1 a of the borehole 1 1 when pulling through the borehole 1 1 .

Although the purpose of the invention is to enable the pulling of heavy cable bundles 15 in a borehole 1 1 , the arrangement 10 can, with an attachment of clamps 20 and coupling elements 30, also be used on lighter cable bundles 15 and also for solutions which shall not be pulled through boreholes 1 1 . The coupling elements 30 can, for example, be provided with means for attachment to other constructions, for instance, for suspension in pipelines, tunnels, etc.

In a preferred embodiment, the cable arrangement 10 is intended for pulling over a surface or through a borehole 1 1 and is therefore equipped with a number of friction reducing means 28. In an embodiment of the arrangement 10, there is a coupling element 30 which is comprised of a number of friction reducing means 28, and the friction reducing means 28 on the coupling element 30 is then connected to a cable arrangement 10 in a radial extension projecting beyond the clamps 20.

A particularly preferred embodiment extends the width of the coupling element 30 radially, with respect to the centre axis of the cable arrangement 10. Hence, the coupling element 30 is in the form of a rail with a length, width and height. The width is substantially larger, perhaps 1 -10 multiples of the height. The rail-shaped coupling element 30 is arranged as edged (width extending radially outwards), and not flat on the circumference of the cable arrangement 10. This causes a significant stiffening of the cable arrangement 10.

It is preferable that the friction reducing means is in the form of wheels. When the width of the coupling element has a given extension, the centre of the wheels 28 are embedded in the coupling element 30. Thus, one can use the wheels 28 of a relatively large diameter as the centre of the wheel 28 is embedded in the rail, i.e. at a considerable distance from the radial outer periphery of the coupling element 30. In another embodiment of the cable arrangement 10 the friction reducing means 28 are arranged on the clamps 20. The friction reducing means 28 projects radially outermost, and is in contact with the inner surface 1 1 a of the borehole 1 1 , and then extends out between two coupling elements 30. Often, it is preferred that a cable arrangement 10, in addition to high voltage cables 12, 14, 16, also contains other cables, such as a fibre cable 29. It is then preferred that this is held radially in place by the clamp 20, that it is arranged externally with respect to the cable bundle 15, and that it is arranged within the coupling elements 30.