NO20240613A1 - Minesweeping system - Google Patents

Description

[0001] Minesweeping system

[0003] Field of the invention

[0005] 5 The present invention relates to a surface vessel having a cable towing system, in particular a cable towing system being part of a minesweeping system.

[0007] Background

[0009] 10 Minesweeping systems play a crucial role in ensuring the safety and security of maritime operations by activating and neutralizing underwater mines. Traditionally, these systems have been deployed on manned vessels, requiring human operators to navigate hazardous waters and manually operate the minesweeping equipment.

[0010] 15 Magnetic influence minesweeping by use of towed electrodes or closed loop electric cables are well-known from manned minesweeping vessels. See e.g. https://apps.dtic.mil/sti/tr/pdf/ADA129354.pdf for a review of common minesweeping methods performed by manned surface vessels.

[0012] 20 US5063850A and US2937611A disclose minesweeping systems wherein at least two cables featuring electrodes are towed by a surface vessel.

[0014] US3613629A discloses a manned minesweeping vessel for towing a loop of sweep cable. To avoid magnetic fields close to the vessel, two strands of the sweep cable 25 are combined along a section being closest to the vessel when the sweep cable is towed, such that the loop is arranged at a sufficiently safe distance from the vessel. Although not described in detail, the prior art winch system required for correctly spooling on/off the sweep cable via the combined section of cable is both complex and heavy, as well as being dependent on manual intervention during both launch 30 and recovery of the sweep cable. Further, the size/extent of the magnetic signature provided by the prior art loop of sweep cable is predetermined by the size of the loop.

[0016] US4697522A discloses a manned minesweeping system featuring either a loop of 35 sweep cable or two separate sweep cables having electrodes. The sweep cables may be spooled/unspooled for recovery/launch by a simple winch. Both launch and recovery require manned operations to e.g. connect/disconnect the cables from a voltage source and connect/disconnect the cables from the winch.

[0017] Advancements in technology have paved the way for unmanned surface vehicles (USVs) to take on the sometimes-dangerous tasks of minesweeping, reducing the risk to human lives.

[0019] 5 Various minesweeping systems for USVs have been developed, see e.g.

[0020] https://www.saab.com/products/minesweeping-usv-sam-3 and https://www.atlaselektronik.com/fileadmin/user_upload/01_Images/Solutions/ARCIMS/Sweep_Broch ure.pdf.

[0022] 10 Although the present USV-based minesweeping systems have demonstrated some level of effectiveness in activating and neutralizing underwater mines, there is a need for further improvements to enhance their capabilities, efficiency, and overall performance.

[0024] 15 The goal of the present invention is to provide an improved cable towing system for a minesweeping system suitable for autonomous surface vessels, in which at least some of the disadvantages of the prior art systems are avoided or alleviated.

[0026] Summary of the invention

[0027] 20

[0028] The present invention is defined by the appended claims and in the following:

[0030] In a first aspect, the present invention provides a surface vessel comprising a cable towing system, the cable towing system comprises a winch arrangement, a first 25 length of cable, a second length of cable and a cable collector, wherein

[0032] - the winch arrangement is for deploying and towing the first length of cable and the second length of cable behind the surface vessel;

[0033] - the cable collector is configured to hold a section of the first length of cable 30 and a section of the second length of cable together, and

[0035] the cable collector is moveable between a first position and a second position along the first length of cable and the second length of cable, the first position being closer to the surface vessel than the second position.

[0036] 35

[0037] When the cable collector holds a section of the first length of cable and a section of the second length of cable together, the sections of the first and second length may be separated by a maximum distance, i.e. the sections of the first and second length may be in close contact or separated by up to a maximum distance. In other words, 40 when the sections of the first and second length of cable are held together by the cable collector, the distance between the sections is within the range of 0.0 m and a maximum distance.

[0039] The maximum distance may be less than 1.0 m, less than 0.8 m or less than 0.5 m.

[0040] 5 The maximum distance may alternatively be less than ten times the diameter of the first or second length of cable, less than eight times the diameter or less than five times the diameter. The maximum distance between the sections of the first and second length of cable may be dependent on several parameters, such as the voltage/current strength of an electric current in the lengths of cable, the type of 10 cable(s) etc. The magnetic field generated between the sections of the first and second length of cable may be calculated before deciding the maximum distance, but the above mentioned distances have been shown to be sufficient in most instances.

[0042] 15 In other words, the cable collector is configured such that the first length of cable and the second length of cable are kept sufficiently close together along a section extending between the stern of the surface vessel and the second position when the lengths of cable are towed, such that no detrimental magnetic field is generated along the section.

[0043] 20

[0044] The winch arrangement is configured to deploy the first length of cable and the second length of cable by unspooling the lengths of cable from at least one winch drum, and to recover/retrieve the first length of cable and the second length of cable by spooling the lengths of cable onto the at least one winch drum.

[0045] 25

[0046] In an embodiment of the surface vessel, the cable towing system may comprise a collector line and a collector line winch, the collector line winch is connected to the cable collector such that the cable collector may be moved from the second position to the first position by spooling the collector line onto the collector line winch. 30 The cable collector may be launched/released from the first position when the collector line is unspooled from the collector line winch.

[0048] In an embodiment of the surface vessel, a distance between the cable collector and the stern of the surface vessel may be controlled by operating the collector line 35 winch. The distance between the stern of the surface vessel and the second position of the cable collector may be regulated. In this manner, the length of the section wherein the first length of cable and the second length of cable is held together may be regulated.

[0050] 40 In an embodiment of the surface vessel, the first length of cable and the second length of cable may be separate lengths of a single cable forming a loop.

[0051] In an embodiment of the surface vessel, the first length of cable and the second length of cable may be lengths of a first cable and a second cable, respectively, i.e. the first length of cable and the second length of cable are two separate cables. 5

[0052] In an embodiment of the surface vessel, the cable collector may be configured to extend around the section of the first length of cable and the section of the second length of cable.

[0054] 10 In an embodiment of the surface vessel, the cable collector may comprise a cable passage through which the first length of cable and the second length of cable are arranged.

[0056] In an embodiment of the surface vessel, the cable collector may be configured to 15 slide, i.e. is slidable, between the first position and the second position along the first length of cable and the second length of cable.

[0058] In an embodiment of the surface vessel, the cable collector may be configured to provide a drag force on the collector line when deployed (and towed) behind the 20 surface vessel, the drag force being sufficient to move the cable collector from the first position to the second position. In other words, the cable collector provides a drag force when deployed and towed behind the surface vessel, the drag force being sufficient to drag the cable collector from the first position to the second position.

[0060] 25 In an embodiment of the surface vessel, the cable collector may be operably connected to a sea anchor. The sea anchor is configured to pull the cable collector from the first position to the second position when the cable collector is deployed/launched, i.e. when the collector line is unspooled from the collector line winch.

[0061] 30

[0062] In an embodiment of the surface vessel, the cable towing system may comprise a paravane to be towed from the surface vessel by a paravane line, and a paravane winch to which winch a first end of the paravane line is connected, the paravane or paravane line is connected to the first length of cable or the second length of cable 35 via a pilot line. In other words, the paravane or paravane line is connected to the first length of cable or the second length of cable via the pilot line, such that the lateral displacement of the first or second length of cable is controlled. The lateral displacement is relative to the direction in which the surface vessel moves during towing of the lengths of cable.

[0063] In an embodiment of the surface vessel, the minesweeping system may comprise a first paravane and a second paravane, each paravane connected by a corresponding paravane line and a paravane winch as defined above, each of the paravanes being configured to laterally displace one of the first or second length of cable relative to 5 the direction in which the surface vessel travels.

[0065] The term “paravane” is intended to cover any type of paravane, otter, trawl door, sea kite or active propulsion module suitable for controlling the lateral extent of a sweep cable loop.

[0066] 10

[0067] In an embodiment of the surface vessel, the travel depth of the paravane, i.e. the sea depth at which the paravane is arranged, may be remotely or autonomously controlled by actuatable rudders on the paravane or passively by use of a float.

[0068] 15 In an embodiment of the surface vessel, the cable connector may be operably connected to the pilot line such that the cable collector is dragged from the first position to the second position when the paravane is deployed. The cable collector may be operably connected to the pilot line via the collector line, i.e. the collector line is connected to both the cable collector and the pilot line.

[0069] 20

[0070] In an embodiment of the surface vessel, the collector line may be connected to the cable collector via a pulley arranged on any of the first length of cable and the second length of cable. In this manner, the cable collector may be dragged out to a desired second position by spooling the collector line onto the collector line winch.

[0071] 25

[0072] In an embodiment, the surface vessel may be an unmanned surface vessel, the unmanned surface vessel may be autonomous or remote controlled.

[0074] In an embodiment of the surface vessel, the cable towing system may constitute a 30 part of a minesweeping system or a seismic surveying system. In other words, the surface vessel may comprise a minesweeping system comprising the cable towing system, or it may comprise a seismic surveying system comprising the cable towing system.

[0076] 35 In an embodiment of the surface vessel, the cable towing system may be termed a minesweeping system.

[0078] When the cable towing system is a minesweeping system, the first length of cable and the second length of cable may be part of a single sweep cable for forming a loop behind the surface vessel, or the first length of cable and the second length of cable may be two separate sweep cables each having an electrode.

[0080] In an embodiment of the surface vessel, the cable towing system may comprise a 5 cable pusher or cable guide for each of the first length of cable and the second length of cable. At least one of the cable pushers or cable guides may be moveable in a lateral direction relative to the direction in which the first length of cable and the second length of cable extend from the winch arrangement.

[0082] 10 In a second aspect, the present invention provides a method of minimizing a magnetic field, or minimizing the generation of a magnetic field, close to the stern of a surface vessel towing a first length of cable and a second length of cable, each length of cable having an electric current, the surface vessel comprising a cable towing system comprising a winch arrangement for deploying and towing the first 15 length of cable and the second length of cable, and a cable collector configured to hold a portion or section of the first length of cable and the second length of cable together, wherein the method comprises the steps of:

[0084] - moving the cable collector along the first and the second length of cable 20 from a first position at the stern of the surface vessel to a second position removed from the stern of the surface vessel, i.e. behind the stern of the surface vessel; and

[0085] - obtaining a section of the first and the second length of cable wherein the first and the second length of cable are sufficiently close to minimize a 25 magnetic field caused by the electric current.

[0087] Description of the drawings

[0089] 30 Embodiments of the invention is described in detail by reference to the following drawings:

[0091] Fig. 1 is a perspective view of a first exemplary surface vessel comprising a 35 cable towing system according to the invention, the cable towing system being part of a minesweeping system.

[0093] Fig. 2 is a perspective view of the surface vessel and minesweeping system in fig. 1, wherein a sweep cable is fully paid out and towed behind the 40 vessel.

[0094] Fig. 3 are perspective views of the surface vessel and minesweeping system in fig. 1, illustrating the steps performed to launch the sweep cable.

[0095] Figs. 4a-4d are topside views of the minesweeping system in fig. 1.

[0096] 5

[0097] Fig. 5 is an expanded view showing details of the surface vessel and minesweeping system in fig. 1.

[0099] Fig. 6 is a perspective view of a sweep cable winch.

[0100] 10

[0101] Fig. 7 is a sideview of the sweep cable winch in fig. 6.

[0103] Fig. 8 is a perspective view of a paravane and a float used in the minesweeping system in fig. 1.

[0104] 15

[0105] Fig. 9 is a perspective view of a tackle element connecting the paravane and the float in fig. 8.

[0107] Fig. 10 are side views of the paravane and the float shown in fig. 8,

[0108] 20 illustrating the steps performed during retrieval of the paravane and the float.

[0110] Fig. 11 are perspective views of a second exemplary surface vessel and minesweeping system according to the invention illustrating the steps 25 performed to launch the sweep cable.

[0112] Fig. 12 are perspective views of a third exemplary surface vessel and minesweeping system according to the invention illustrating the steps performed to launch the sweep cable.

[0113] 30

[0114] Fig. 13 are perspective views of a fourth exemplary surface vessel and minesweeping system according to the invention illustrating the steps performed to launch the sweep cable.

[0116] 35 Fig. 14 is a perspective view of a surface vessel and minesweeping system comprising two separate sweep cables having bare electrodes.

[0118] 40

[0119] Detailed description of embodiments of the invention

[0121] The present invention provides a novel cable towing system. The cable towing system is illustrated by its use as part of a minesweeping system. The minesweeping 5 system is highly advantageous for the detection and neutralization of underwater mines and is further adapted for use with unmanned surface vessels (USVs).

[0123] A surface vessel 2 featuring an embodiment of the inventive cable towing system forming part of a minesweeping system 1 is shown in fig. 1. The illustrated surface 10 vessel 2 may be manned or unmanned, however, the minesweeping system 1 itself is fully automated and may be remote or autonomously controlled.

[0125] The minesweeping system comprises a sweep cable 3, a sweep cable winch 4 (i.e. a winch arrangement), an electric power source 5 and a control system 29. The sweep 15 cable 3 is insulated and configured to provide a closed electric loop with the electric power source 5 when the sweep cable 3 is spooled off the sweep cable winch 4 and towed by the surface vessel 2, see fig. 2. The sweep cable 3 comprises a first length of cable and a second length of cable extending behind the surface vessel.

[0127] 20 The sweep cable 3 has a first end 6 connected to the sweep cable winch 4, such that the sweep cable 3 can be spooled on/off the sweep cable winch 4 as a single strand, and a second end 30 connected to the electric power source, see figs. 4a and 6. The illustrated configuration of the sweep cable as a single strand cable with to separate ends (i.e. not having an end section of two combined strands of cable connected to a 25 single winch), allows for a less complex and service/operator demanding sweep cable winch.

[0129] The first end 6 and the second end 30 of the sweep cable 3 are electrically connectable via a socket 23 and an actuatable plug 22 (i.e. an actuatable connector 30 assembly), see fig. 6, to provide the closed electric loop together with the electric power source.

[0131] When the sweep cable 3 is spooled off the sweep cable winch 4 and towed by the surface vessel 1, a first section 3a of the sweep cable 3 extends from the sweep 35 cable winch 4 to the stern of the surface vessel 1, and a second section 3b of the sweep cable extends from the electric power source 5 to the stern of the surface vessel 3, while the remaining part of the sweep cable forms a loop towed behind the vessel. When an electric current is provided to the sweep cable 3 from the electric power source 5, a magnetic field is induced by the loop of sweep cable 3. The presence of any magnetic field at the vessel 1 is minimized by arranging the first and second sections 3a,3b adjacent to each other.

[0133] When the minesweeping system is mounted on an unmanned vessel, the presence of 5 magnetic fields at the vessel is not detrimental since human operators are not in any danger in case a mine is triggered too close to the vessel. However, the survivability of the vessel itself is improved.

[0135] In the illustrated embodiment, the sweep cable winch 4 comprises a main drum 10 section 20 and an adjacent cable connection section 21. The first end 6 of the sweep cable 3 is connected to the cable connection section 21 and the major part of the sweep cable 3 may be spooled onto the main drum section 20. The cable connection section is arranged at a side of the sweep cable winch 4 being closest to the electric power source 5, i.e. at a side adjacent to the electric power source 5. This

[0136] 15 configuration is advantageous since it allows the first section 3a of sweep cable 3 to extend from the sweep cable winch 4 at a minimal distance to the electric power source 5 and the second section 3b of sweep cable 3, when the sweep cable 3 is fully unspooled.

[0138] 20 The cable connection section 21 features a ramp 7, an electrical connector 8 and a socket 23. The first end 6 of the sweep cable 3 is connected to the socket 23 via the electrical connector 8. The ramp 7 is configured to guide the sweep cable 3 from the electrical connector 8 to the main drum section 20 during spooling of the sweep cable 3 onto the sweep cable winch 4. The actuatable plug 22 is connected to the 25 electric power source 5 and may be connected to the socket 23 when the sweep cable is fully paid out to provide an electric current in the sweep cable 3. An actuating mechanism for moving the plug 22 is not shown but may e.g. comprise a linear actuator configured to move the plug between a first position in which the plug is connected to the socket 23 and a second position in which the plug is 30 removed from the socket 23.

[0140] The sweep cable 3 is secured to a cable termination 31. The cable termination 31 is arranged such that the sweep cable 3 extends through a centre of the sweep cable winch 4 when the sweep cable 3 is fully paid out, i.e. the sweep cable 3 extends 35 through the rotary axis R of the main drum section 20. The configuration is advantageous in that a pull force on the sweep cable 3 during towing is directed through the centre of the rotary axis and only minimal brake force is required to keep the sweep cable winch 4 fixed during sweeping.

[0141] To ensure correct spooling/unspooling of the sweep cable 3 onto/off the sweep cable winch 4, as well as dampening any forces acting on the sweep cable winch 4 during towing, the minesweeping system features a first cable pusher 18 for the length of sweep cable 3 extending from the sweep cable winch 4. The illustrated 5 cable pusher has two rollers 32a,b on opposite sides of the sweep cable. At least one of the rollers 32a,b is driven by a motor 33. Examples of alternative cable pusher are described in e.g. AU2005200477A1 and https://products.katimex.com/winches-cable-pusher/cable-pusher-vsg-h/

[0143] 10 The first cable pusher 18 is moveable in a lateral direction relative to the direction in which the sweep cable extends from the sweep cable winch, between a first position in line with the main drum section, see figs. 4a-4c and a second position in line with the cable connection section, see fig. 4d. When paying out or spooling the sweep cable 3, the first cable pusher 18 moves laterally back and forth in line with 15 the main drum section 20 to guide the sweep cable 3 off or onto the main drum section 20 in a correct manner. When the sweep cable 3 is fully paid out from the sweep cable winch 4, the first cable pusher 18 is in the second position. Details of the mechanism for lateral movement of the first cable pusher 18 is not shown in the drawings, but may e.g. comprise a lateral rail on which the first cable pusher 18 20 may be moved back and forth by a suitable actuator or motor.

[0145] In the second position, the first cable pusher 18 ensures that the section of sweep cable 3a extending between the cable connection section 21 and the first cable pusher 18 is parallel and close to a section of sweep cable 3b extending between the 25 electrical power source 5 and the stern of the surface vessel 1, see fig. 4d. The first cable pusher 18 contributes to hold the sections of sweep cable 3a,3b close to minimize any magnetic field that may be generated. In addition to minimizing the magnetic field close to the vessel, the cable collector 24 may also be used to adapt/control the size of the magnetic field generated by the loop of the sweep cable 30 3.

[0147] When the sweep cable 3 is fully paid out, the sections of sweep cable 3a,3b extending to the stern are parallel to a centerline C of the vessel, see fig. 4b.

[0149] 35 The illustrated embodiment features a second cable pusher 19 for the section of sweep cable 3b extending from the electrical power supply 5 to the stern of the vessel 1. The second cable pusher is similar to the first cable pusher 18 and keeps the section of sweep cable 3b in correct position and alignment towards the stern.

[0150] To control the lateral extent of the loop of sweep cable 3 (or of the closed electric loop), the minesweeping system 1 comprises a paravane 9, a paravane line 10 and a paravane winch 11. The paravane line 10 is connected to the sweep cable 3 by a pilot line 28, see figs. 8 and 9.

[0151] 5

[0152] The paravane 9 is configured to pull one side of the closed loop formed by the sweep cable 3 in a lateral direction relative to the direction in which the vessel 1 travels, or lateral to the direction in which the sweep cable 3 extends from the sweep cable winch 4 towards the stern of the vessel 1.

[0153] 10

[0154] A float 12 is connected to the paravane line 10 to hold the paravane 9 at a predetermined sea depth. The paravane line 10 extends through a tackle element 13, and the tackle element 13 is connected to the paravane 9 via a set of guide lines 14. The paravane line 10 has a stopper 15 configured to limit the length of paravane 15 line 10 passing through the tackle element 13. In this manner, a distance D1 between the float 12 and the tackle element 13 may limited to a predetermined distance which in turn decides the sea depth at which the paravane 9 is held.

[0156] To facilitate autonomous launch and recovery of the paravane 9 and the float 12, the 20 minesweeping system features a paravane boom 16 having an upper line guide section 17, see fig. 10D. The paravane boom 16 is configured to pivot between a retracted position, see fig. 10E, and a launch position, see fig. 10D. When the paravane boom 16 is in the retracted position the paravane line 10 is fully spooled onto the paravane winch, and the launch position is entered when the paravane line 25 is paid out. The launch/recovery process is simply controlled by operating the paravane winch 11.

[0158] The steps performed in recovery of the paravane 9 and the float 12 are illustrated in figs. 10A-10E. The tackle element 13 and the stopper 15 ensures that the float 12 30 and paravane 9 are moved into close proximity during the initial steps to provide a compact bundle that may easily be recovered and stored on the surface vessel 1. The paravane boom 16 is moved from the launch position to the retracted position after the tackle element 13 reaches the upper line guide section 17 and movement of the paravane 9 relative to the paravane boom is prevented. Further spooling of the 35 paravane line 10 onto the paravane winch 11 will then drag the paravane boom 16 to the retracted position.

[0160] When launching the paravane 9 and the float 12, the steps are performed in the opposite order and the paravane boom 16 is initially moved to the launch position 40 by gravity when the paravane line 10 is spooled off the paravane winch 11.

[0161] The configuration of the assembly comprising the paravane 9 and float 12 is highly advantageous as it is easily remote controlled.

[0163] 5 In the illustrated embodiment, the travel depth of the paravane is controlled by the float 12. However, in alternative embodiments the travel depth of the paravane 9, and optionally the lateral movement of the paravane 9, may be remotely or autonomously controlled by actuatable rudders on the paravane 9.

[0165] 10 To further improve the survivability of the surface vessel, and optionally the safety of any human operator in case the surface vessel is manned, the minesweeping system may feature a cable collector 24. The cable collector 24 is configured to hold a third section 3c and a fourth section 3d of the sweep cable 3 together, see figs. 2 and 4d. The third section 3c and the fourth section 3d extend between the 15 stern of the surface vessel 1 and the cable collector 24 when the sweep cable 3 has been spooled off the sweep cable winch 4 and towed by the surface vessel 1. The distance between the cable collector 24 and the stern may be controlled by use of a collector line 25 and a collector line winch 26, i.e. the cable collector may be moved between a first position, see fig. 1, and a second position, see fig. 2. In this 20 manner any magnetic field developed close to the surface vessel, i.e. between the third and fourth section 3c,3d is minimized. The cable collector 24 is configured to extend around a portion of the third and fourth section 3c,3d of the sweep cable 3 (i.e. around a section 3c of the first length of cable and a section 3d of the second length of cable).

[0166] 25

[0167] Drag from the cable collector 24 is normally sufficient to move the cable collector 24 from a position at the stern of the surface vessel to a desired position further away from the surface vessel 1 when the collector line 25 is paid out.

[0169] 30 Alternative methods of moving the cable collector 24 in case the provided drag is insufficient are shown in figs 11-13.

[0171] In fig. 11, the cable collector 24 is connected to a sea anchor 27 to increase the drag.

[0172] 35

[0173] In fig. 12, the pilot line 28 connected to the paravane 9 is also connected to the collector line 25, such that the cable connector 24 is dragged out to a desired position by help of the paravane 9.

[0174] In fig. 13, the collector line 25 is connected to the cable collector 24 via a pulley 34 arranged on the sweep cable 3. In this manner, the cable collector 24 may be dragged out to a desired position by spooling the collector line onto the collector line winch 26.

[0175] 5

[0176] An embodiment of a surface vessel featuring a minesweeping system based on the deployment of two separate sweep cables 3,3’’ (i.e. a first length of cable and a second length of cable), each sweep cable having an electrode 35’,35’’, is shown in fig. 14. As discussed in the referenced prior art, in this solution an electric current 10 will travel between the electrodes 35’,35’’ via the seawater, and generate a magnetic field (as opposed to the loop of sweep cable above, in which the electric current is insulated from the seawater). Both sweep cables 3’,3’’ are connected to a single sweep cable winch 4’ (i.e. a winch arrangement) and connectable to an electric power source 5’. In alternative embodiments, each sweep cable 3’,3’’ may 15 be connected to a corresponding sweep cable winch, e.g. the minesweeping system may have two sweep cable winches 4 as shown in fig. 6 wherein the respective cable connection sections 21 are adjacent each other. The minesweeping system illustrated in fig. 14 comprises the same technical features described in connection with figs. 1-13 except the looped sweep cable 3.

[0177] 20

[0178] The minesweeping system described above may comprise further advantageous features not shown in the drawings, such as a towable acoustic source. The acoustic source may e.g. be connected by an acoustic cable to an acoustic cable winch mounted on the surface vessel.

[0179] 25

[0180] The function and features of the cable towing system is illustrated by reference to a surface vessel comprising a minesweeping system. However, the above described cable towing system may advantageously be used in other applications wherein two or more lengths of cable are towed, such as seismic surveying systems in which 30 multiple cables and sensors may be streamed/towed behind a surface vessel.

[0182] 35

[0184] 40

Claims (15)

1. Claims

1. A surface vessel comprising a cable towing system, the cable towing system comprises a winch arrangement (4), a first length of cable (3,3’), a second length 5 of cable (3,3’’) and a cable collector (24), wherein

- the winch arrangement is for deploying and towing the first length of cable (3,3’) and the second length of cable (3,3’’) behind the surface vessel;

- the cable collector (24) is configured to hold a section (3c) of the first length 10 of cable and a section (3d) of the second length of cable together, and

the cable collector is moveable between a first position and a second position along the first length of cable and the second length of cable, the first position being closer to the surface vessel than the second position.

15

2. A surface vessel according to claim 1, wherein the cable towing system comprises a collector line (25) and a collector line winch (26), the collector line winch connected to the cable collector (24) such that the cable collector (24) may be moved from the second position to the first position by spooling the 20 collector line onto the collector line winch (26).

3. A surface vessel according to claim 1 or 2, wherein the first length of cable (3c) and the second length of cable (3d) are separate lengths of a single cable forming a loop.

25

4. A surface vessel according to claim 1 or 2, wherein the first length of cable (3c) and the second length of cable (3d) are lengths of a first cable and a second cable, respectively.

30 5. A surface vessel according to any of the preceding claims, wherein the cable collector (24) is configured to extend around the section of the first length of cable and the section of the second length of cable.

6. A surface vessel according to any of the preceding claims, wherein the cable 35 collector (24) comprises a cable passage (36) through which the first length of cable and the second length of cable are arranged.

7. A surface vessel according to any of the preceding claims, wherein the cable collector (24) is configured to slide between the first position and the second 40 position along the first length of cable and the second length of cable.

8. A surface vessel according to any of the preceding claims, wherein the cable collector (24) is configured to provide a drag force on the collector line (25) when deployed behind the surface vessel, the drag force being sufficient to move 5 the cable collector (24) from the first position to the second position.

9. A surface vessel according to claim 8, wherein the cable collector (24) is operably connected to a sea anchor (27).

10 10. A surface vessel according to any of the preceding claims wherein the cable towing system comprises a paravane (9) to be towed from the surface vessel by a paravane line (10), and a paravane winch (11) to which winch a first end of the paravane line is connected, the paravane (9) or paravane line (10) is connected to the first length of cable (3c) or the second length of cable (3d) via a pilot line 15 (28).

11. A surface vessel according to claim 10, wherein the cable connector is operably connected to the pilot line (28) such that the cable collector is dragged from the first position to the second position when the paravane is deployed.

20

12. A surface vessel according to any of claims 1-10, wherein the collector line is connected to the cable collector (24) via a pulley (34) arranged on any of the first length of cable and the second length of cable.

25 13. A surface vessel according to any of the preceding claims, being an unmanned surface vessel, the unmanned surface vessel may be autonomous or remote controlled.

14. A surface vessel according to any of the preceding claims, wherein the cable 30 towing system is a minesweeping system.

15. A method of minimizing a magnetic field close to the stern of a surface vessel towing a first and a second length of cable having an electric current, the surface vessel comprising a cable towing system comprising a winch arrangement (4) 35 for deploying and towing the first length of cable (3c) and the second length of cable (3d), and a cable collector (24) configured to hold a portion of the first length of cable and the second length of cable together, wherein the method comprises the steps of:

- moving the cable collector (24) along the first and the second length of cable from a first position at the stern of the surface vessel to a second position removed from the stern of the surface vessel; and

- obtaining a section of the first and the second length of cable wherein the 5 first and the second length of cable are sufficiently close to minimize a magnetic field caused by the electric current.

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