A device for winding up and unwinding a cable and method for winding up a cable

Abstract

 Device (2) for winding a cable (3), that comprises a top and a bottom cable carousel (4), whereby in a first operating mode the bottom cable carousel (4) can rotate independently of the top and in a second operating mode it can rotate with the top, whereby the top cable carousel (5) has a central cable passage (10) underneath, whereby the device (2) has a guide arm (13) between the top and the bottom cable carousel (4) for the cable (3), which in the first operating mode can be fastened so that the bottom cable carousel (4) is rotatable with respect to the guide arm (13), whereby in the second operating mode the guide arm (13) can be connected to the bottom cable carousel (4).

Description

[0001] The present invention relates to a device for winding up and unwinding a cable and method for winding up a cable.

[0002] More specifically, the invention is intended for very long cables that are laid on a seabed or the bed of another body of water.

[0003] It is known that it is preferable for such cables to have as few connections as possible. Connections are a possible source of interference in the signal transmission. Moreover, it costs a lot of time and money to make these connections, so that laying a cable that consists of various connected sections is expensive.

[0004] The quantity of cable that can be taken on board a ship as one continuous length is limited, however.

[0005] This is because the diameter of the cable carousels used is of course limited by the width of the ship. The height of these cable carousels is also limited because below deck there is a limited height and the deck may not be removed over a large area for structural reasons, while on deck the maximum height is limited because the stability of the ship does not allow the centre of gravity to be too high.

[0006] As a result a relatively large number of connections have to be made, which greatly increases the cost of laying cables and somewhat reduces the reliability of the signal transmission through the cable.

[0007] The purpose of the present invention is to provide a solution to the aforementioned and other disadvantages, by providing a device for winding up and unwinding a cable, whereby this device comprises a drum-shaped top cable carousel that is rotatable around a top rotation axis and comprises a drum-shaped bottom cable carousel that is rotatable around a bottom geometric rotation axis, whereby in a first operating mode the bottom cable carousel can rotate independently of the top cable carousel, and in a second operating mode is rotatable synchronously with the top cable carousel, whereby the bottom of the top cable carousel is provided with a central cable passage, whereby between the top cable carousel and the bottom cable carousel the device is provided with a first guide arm for the cable, whereby this first guide arm leads away from the bottom rotation axis and is rotatable around the bottom rotation axis, whereby the first guide arm is arranged to be connected to a fixed point in the first operating mode such that the bottom cable carousel is rotatable with respect to the first guide arm, and whereby in the second operating mode the first guide arm is arranged to be connected to the bottom cable carousel so that the first guide arm and the bottom cable carousel can only rotate together.

[0008] This has the advantage that a much longer length of cable than with traditional devices, i.e. a cable length that can be stored in the device, can be laid without making use of a connection and that this can therefore be done more quickly and with better quality.

[0009] In a preferred embodiment the top rotation axis coincides with the bottom rotation axis and the top rotation axis is vertical.

[0010] This is the most practical embodiment on a ship or other floating structure.

[0011] In a further preferred embodiment the top cable carousel is provided with an upright barrier around the cable passage and the device is provided with a second guide arm for the cable that is connected to the top cable carousel so that the second guide arm and the top cable carousel can rotate together, whereby this second guide arm has a first end that is on the top rotation axis and has a second end that lies at a point that is above the barrier or outside it in the radial direction and that lies above the top cable carousel.

[0012] As a result the cable making a curve with a smaller radius than is allowed for quality reasons can be prevented.

[0013] The invention further comprises a floating structure that is provided with a device as described above, which is preferably provided with a deck whereby the top cable carousel is above the deck and the bottom cable carousel is below the deck.

[0014] This has the advantage that the strength and/or stability of the floating structure is not negatively affected. On account of the presence of the deck this also enables the top cable carousel to be removed in situations in which a shorter cable length has to be laid and the section of the deck provided to this end can be used for other purposes, such as the storage of machines or filler material such as stones to cover the cable after laying.

[0015] The invention further concerns a method for winding up a cable, whereby in a first step a cable is guided through a central cable passage in the bottom of the top cable carousel to a rotatable but not rotating first guide arm, and from there is guided to a rotating bottom cable carousel and wound up therein, whereby then in a second step the first guide arm, the top cable carousel and the bottom cable carousel are turned together and the cable is wound up in the top cable carousel.

[0016] With the intention of better showing the characteristics of the invention, a preferred embodiment of a device according to the invention is described hereinafter by way of an example, without any limiting nature, with reference to the accompanying drawings, wherein:

Figure 1 shows a side view of a ship according to the invention, provided with a device according to the invention;

figure 2 shows a cross-section of the ship of figure 1 according to line II-II, whereby for some parts of the device the cross-section is shown according to lines II'-II';

figure 3 shows a combined side view/cross-section of the ship of figure 2 according to line III-III;

figure 4 shows a top view according to arrow F4 of the ship of figure 1;

figure 5 shows a cross-section according to line V-V of the ship of figure 1;

figures 6 and 7 show a similar view as figures 3 and 4 with the ship in a different operating situation; and

figure 8 shows a similar view as figure 7 in another operating situation.

[0017] The ship 1 shown in the drawings is a ship for laying cables at sea. To this end the ship is provided with a device 2 for winding up a cable 3, keeping it wound up, and unwinding it when this cable 3 has to be laid.

[0018] This device 2 comprises a bottom cable carousel 4 and a top cable carousel 5, that are both placed rotatably on rollers. Both cable carousels 4,5 are drum-shaped with an open top and a base. They are oriented horizontally so that their respective geometric rotation axes A coincide and are oriented vertically.

[0019] Both cable carousels 4,5 are provided with a barrier 6,7 around their central point, with a diameter D of approximately 8 metres. The bottom cable carousel 4 has a diameter O of approximately 22 metres. The top cable carousel 5 has a diameter B of approximately 28 metres. Around its central point the top cable carousel 5 is provided with a hollow bush 8 that is placed around a hollow shaft 9. The hollow bush 8 fits on a cable passage opening 10 in the bottom of the top cable carousel 5.

[0020] At the location of the device 2 the ship 1 is provided with a deck 11, whereby the bottom cable carousel 4 is mounted below the deck 11 and the top cable carousel 5 above the deck 11, and whereby the deck 11 is provided with a hole below the cable passage opening 10.

[0021] The cable carousels 4,5 each have an independent drive, not shown in the drawings, so that in principle they can rotate independently of one another. They can also be coupled together mechanically by means of connecting pieces, not shown, that run via the central cable passage opening 10 so that a synchronous rotation can be assured.

[0022] The device 2 further comprises a swivelling arm 12 placed above the top cable carousel 5 that is provided with a guide for the cable 3.

[0023] The device 2 also comprises two guide arms for a cable 3. The first guide arm 13 is essentially between the deck 11 and the bottom cable carousel 4. This first guide arm 13 is rotatably suspended around the same rotation axis A as the cable carousels 4,5 and rests on the outside edge 14 and the inside edge of the bottom cable carousel 4 by means of two supporting arms 15 with small wheels.

[0024] The first end 16 of the first guide arm 13 connects to the cable passage opening 10. Its second end 17 is above the bottom cable carousel 4, approximately halfway between the rotation axis A and the outside edge 14.

[0025] The first guide arm 13 is arranged to be connected to the deck 11 or another fixed point of the ship 1, or alternatively to the bottom cable carousel 4.

[0026] The second guide arm 18 extends upwards in a question-mark shape from a first end 19 above the cable passage opening 10. The second end 20 of this second guide arm 18 is approximately above the barrier 7 of the top cable carousel 5.

[0027] The second guide arm 18 is connected immovably to the top cable carousel 5 and can thus rotate with it.

[0028] The operation of the device 2 is very simple and as follows. Here the procedure for winding up a cable 3 is described, whereby the procedure for unwinding proceeds in reverse.

[0029] A cable 3 is wound up on the device 2 from a cable stock that is on the quay to which the ship 1 is moored. The cable 3 runs from this cable stock to the end of the swivelling arm 12.

[0030] First the cable 3 is wound on the bottom cable carousel 4. To this end the first guide arm 13 is fastened to the underside of the deck 11 and disconnected from the bottom cable carousel 4. The top cable carousel 5 is blocked. The swivelling arm 12 is placed above the vertical section 21 approximately halfway between the two ends 19, 20 of the second guide arm 18.

[0031] Via the second guide arm 18 the cable is now guided through the hollow shaft, and thereby through the cable passage opening 10 and from there, via the first guide arm 13, to the bottom cable carousel 4. This is then set in operation so that it will turn in the direction indicated by the arrow P, with a speed of approximately 1 rpm. The guide arms 13, 18 and the top cable carousel 5 are stationary here.

[0032] This is the situation as shown in figures 1 to 5.

[0033] The cable 3 is now wound on the bottom cable carousel 4 until it is full.

[0034] Then the first guide arm 13 is disconnected from the deck 11 and connected to the bottom cable carousel 4.

[0035] A mechanical connection is also made between the two cable carousels 4,5 to ensure that they will later turn completely synchronously.

[0036] The swivelling arm 12 is now moved such that the cable 3 is laid over the second guide arm 18 and the end of the swivelling arm is positioned approximately above the outside edge 22 of the top cable carousel 5. This is the situation as shown in figures 6 and 7.

[0037] Both cable carousels 4,5 are now made to turn at an equal speed. The first guide arm 13 hereby turns with the two cable carousels 4,5. The cable 3 is now wound from the swivelling arm 12 on the top cable carousel 5, whereby there is no tension on the cable 3 going through the cable passage opening 10 due to the synchronous rotation of the two cable carousels 4,5 and the two guide arms 13, 18.

[0038] The start of the winding of the cable 3 on the top cable carousel 5 is shown in figure 8.

[0039] The barriers 6,7 of the cable carousels 4,5 ensure that upon winding, the cable does not go through a smaller radius of curvature than allowed for quality reasons.

[0040] When the top cable carousel 5 is full, the cable 3 is cut. The ship 1 can now sail to the place where the cable 3 must be laid, whereby the method is applied in reverse in order to lay the cable 3.

[0041] It is also possible for the cable 3 not to be cut and laid by the ship 1 from the location where the cable 3 is wound up on the device 2.

[0042] Although the above device 2 is shown on board a ship 1, the device 2 can of course also be placed on other floating constructions such as pontoons. A device 2 according to the invention can also be placed on or in other vehicles and also placed autonomously, independently of any vehicle, at a fixed or temporary location.

[0043] The present invention is by no means limited to the embodiment described as an example and shown in the drawings, but a device and method according to the invention can be realised in all kinds of embodiments and variants, without departing from the scope of the invention.

Claims

1. A device (2) for winding up and unwinding a cable (3), whereby this device (2) comprises a drum-shaped top cable carousel (5) that is rotatable around a top rotation axis (A) and comprises a drum-shaped bottom cable carousel (4) that is rotatable around a bottom geometric rotation axis (A), whereby in a first operating mode the bottom cable carousel (4) can rotate independently of the top cable carousel (5), and in a second operating mode is rotatable synchronously with the top cable carousel (5), whereby the bottom of the top cable carousel (5) is provided with a central cable passage (10), whereby between the top cable carousel (5) and the bottom cable carousel (4) the device (2) is provided with a first guide arm (13) for the cable (3), whereby this first guide arm (13) leads away from the bottom rotation axis (A) and is rotatable around the bottom rotation axis (A), whereby the first guide arm (13) is arranged to be connected to a fixed point in the first operating mode such that the bottom cable carousel (4) is rotatable with respect to the first guide arm (13), and whereby in the second operating mode the first guide arm (13) is arranged to be connected to the bottom cable carousel (4) so that the first guide arm (13) and the bottom cable carousel (4) can only rotate together.

2. Device according to claim 1, characterised in that the top rotation axis (A) coincides with the bottom (A) rotation axis.

3. Device according to claim 2, characterised in that the top rotation axis (A) is vertical.

4. Device according to any one of the previous claims, characterised in that the top cable carousel (5) is provided with an upright barrier (7) around the cable passage.

5. Device according to claim 4, characterised in that it is provided with a second guide arm (18) for the cable (3), that is connected to the top cable carousel (5) so that the second guide arm (18) and the top cable carousel (5) can rotate together, whereby this second guide arm (18) has a first end (19) that is on the top rotation axis (A) and has a second end (2) that is at a point above the barrier (7) or outside it in a radial direction but lies above the top cable carousel (5).

6. Device according to claim 5, characterised in that the second guide arm (18) is curved in the shape of a question mark, whereby the first end (19) connects to the cable passage (10).

7. Device according to any one of the previous claims, characterised in that it is provided with a swivelling arm (12) for guiding the cable (3) from a cable stock to the device (2), whereby this swivelling arm (12) has an end with at least a first position directly above the cable passage (10) or directly above the second guide arm (18) and a second position directly above the section of the top cable carousel (5) that lies outside the barrier (7).

8. Floating structure (1) that is provided with a device (2) according to any one of the previous claims.

9. Floating structure according to claim 8, characterised in that it is provided with a deck (11), whereby the top cable carousel (5) is above the deck (11) and the bottom cable carousel (4) is below the deck (11).

10. Floating structure according to claim 8 or 9, characterised in that the floating structure is a ship (1).

11. Floating structure according to claim 10, characterised in that the floating structure is a ship (1) for laying cables on or in the bed of a body of water.

12. Method for winding up a cable (3), whereby in a first step a cable (3) is guided through a central cable passage (10) in the bottom of the top cable carousel (5) to a rotatable but not rotating first guide arm (13), and from there is guided to a rotating bottom cable carousel (4) and wound up therein, whereby then in a second step the first guide arm (13), the top cable carousel (5) and the bottom cable carousel (4) are turned together and the cable (3) is wound up in the top cable carousel (5).

13. Method for laying a cable (3) on or in the bed of a body of water, characterised in that it makes use of a floating structure (1) from where the cable is laid and that it comprises a method according to claim 12 to provide the floating structure (1) with a quantity of cable (3) before the cable (3) is laid.

14. Method according to claim 12 or 13, characterised in that it makes use of a device according to any one of the claims 1 to 7 or a floating structure according to any one of the claims 7 to 11.

Drawing