Minesweeping system

Abstract

The present invention provides a surface vessel comprising a minesweeping system (1), the minesweeping system comprises a sweep cable (3), a sweep cable winch (4) and an electric power source (5), the sweep cable (3) is 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); the sweep cable (3) has a first end (6) connected to the sweep cable winch (4), such that the sweep cable can be spooled on / off the sweep cable winch as a single strand, and a second end connected to the electric power source; the first end and the second end of the sweep cable (3) are electrically connectable via a connector assembly (8,22,23).

Description

[0001] Minesweeping system

[0002] Field of the invention

[0003] The present invention relates to a minesweeping system, in particular a minesweeping system suitable for unmanned surface vehicles, and an unmanned surface vehicle comprising the minesweeping system.

[0004] Background

[0005] 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.

[0006] Magnetic influence minesweeping by use of towed bare 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.

[0007] US5063850A and US2937611 A disclose minesweeping systems wherein at least two cables featuring electrodes are towed by a surface vessel.

[0008] 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 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 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.

[0009] US4697522A discloses a manned minesweeping system featuring either a loop of sweep cable or two separate cables having bare electrodes. The 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.

[0010] Advancements in technology have paved the way for unmanned surface vehicles (US Vs) to take on the sometimes-dangerous tasks of minesweeping, reducing the risk to human lives. Various minesweeping systems for USVs have been developed, see e.g. https: / / www.saab.com / products / minesweeping-usv-sam-3 and htt s : / / www . atl as- lektronik.com / fileadmin / user upload / Ol Images / Solutions / ARCIMS / Sweep Broch ure.pdf.

[0011] 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.

[0012] The goal of the present invention is to provide an improved minesweeping system suitable for autonomous boats, in which at least some of the disadvantages of the prior art systems are avoided or alleviated.

[0013] Summary of the invention

[0014] The present invention is defined by the appended claims and in the following:

[0015] In a first aspect, the present invention provides a surface vessel comprising a minesweeping system, the minesweeping system comprises a sweep cable, a sweep cable winch and an electric power source, the sweep cable is configured to provide a closed electric loop with the electric power source when the sweep cable is spooled off the sweep cable winch, i.e. fully spooled off, and towed by the surface vessel; the sweep cable has a first end connected to the sweep cable winch, such that the sweep cable can be spooled on / off the sweep cable winch as a single strand, and a second end connected to the electric power source; the first end and the second end of the sweep cable are electrically connectable via a connector assembly, i.e. the first and second end of the sweep cable may be electrically connected to provide a closed electric loop together with the electric power source.

[0016] The sweep cable may be spooled on the sweep cable winch via the first end as a single strand, i.e. such that at least a major section of the sweep cable including the first end can be spooled on / off the sweep cable winch as a single strand.

[0017] The sweep cable is neutrally buoyant (or equipped with buoyancy elements) and configured to carry an electric current. When the sweep cable is configured to provide a closed electric loop with the electric power source, the sweep cable is insulated from the seawater in which it is towed. The electric power source may also be termed a power generator module (PGM).

[0018] The second end may be directly and / or mechanically connected to the electric power source, the connection being configured to withstand drag forces during towing of the sweep cable, the second end is further electrically connected to the electric power source, alternatively via the connector assembly.

[0019] In an embodiment of the surface vessel, the sweep cable winch and the electric power source may be arranged such that a first section of the sweep cable extends from the sweep cable winch to the stern of the surface vessel, and a second section of the sweep cable extends from the electric power source to the stern of the surface vessel, when the sweep cable is spooled off the sweep cable winch and towed by the surface vessel, the first and second sections of the sweep cable are adjacent such that any magnetic field developed or generated between the first and second section is minimized.

[0020] In an embodiment of the surface vessel, the first and second section of the sweep cable may be parallel.

[0021] The first and second section of the sweep cable may preferably be separated by a distance less than 1.0 m, less than 0.8 m or less than 0.5 m. The distance may alternatively be less than ten times the diameter of the sweep cable, less than eight times the diameter or less than five times the diameter. The maximum distance between the first and second section of the sweep cable will be dependent on several parameters, such as the voltage / current strength of the electric current in the sweep cable, the type of sweep cable, the level of the deck of the surface vessel at which the first and second section of the sweep cable are arranged etc. The magnetic field generated between the first and second section may be calculated before deciding the maximum distance, but the above-mentioned distances have been shown to be sufficient in most instances.

[0022] In an embodiment of the surface vessel, the first and second sections of the sweep cable may be arranged closer to each other when the sweep cable is fully spooled off the sweep cable winch and towed by the surface vessel, than when the sweep cable is fully spooled onto the sweep cable winch.

[0023] In an embodiment of the surface vessel, the first section of sweep cable may extend towards the stern from a portion of the sweep cable winch being closest to or adjacent the electric power source, and the second section of sweep cable may extend from a portion of the electric power source towards the stern from a portion of the electric power source being closest to or adjacent the sweep cable winch. In an embodiment of the surface vessel, the sweep cable winch may comprise a main drum section and a cable connection section, the main drum section may be adjacent to the cable connection section, the first end of the sweep cable is connected to the cable connection section and the major part of the sweep cable may be spooled onto the main drum section, the cable connection section is arranged at a side of the sweep cable winch being closest to or adjacent the electric power source and / or a cable from the electric power source.

[0024] The cable connection section may be arranged at a side of the sweep cable winch being closest to or adjacent the electric power source, such that the first section of sweep cable may extend from the sweep cable winch at a minimal distance to the electric power source when the sweep cable is fully unspooled.

[0025] The side of the sweep cable winch, at which side the cable connection section is arranged, may be facing the electric power source.

[0026] In an embodiment of the surface vessel, the sweep cable winch may be configured such that the sweep cable extends in a straight line from the cable connection section towards the stern of the surface vessel when the sweep cable is fully spooled off the main drum section.

[0027] In an embodiment of the surface vessel, the cable connection section may comprise a ramp and an electrical connector to which electrical connector the first end of the sweep cable is connected, the ramp being configured to guide the sweep cable from the electrical connector to the main drum section during spooling of the sweep cable onto the sweep cable winch.

[0028] In an embodiment of the surface vessel, the sweep cable may be secured to a cable termination arranged such that the sweep cable extends through a centre of the sweep cable winch when the sweep cable is fully paid out (i.e. fully unspooled). In other words, the sweep cable may extend through a rotary axis of the main drum section when the sweep cable is fully paid out. The configuration is advantageous in that the pull force on the sweep cable extends through the centre and only minimal brake force is required to keep the sweep cable winch fixed during sweep.

[0029] In an embodiment of the surface vessel, the electrical connector is connectable to the electric power source by an actuatable plug or socket, such that an electrical connection between the first end of the sweep cable and the electric power source may be obtained when the sweep cable is spooled off the sweep cable winch, i.e. when the sweep cable is fully spooled off the main drum section and extends directly from the cable connection section towards the stern of the vessel in a straight line. In other words, the connector assembly may comprise the electrical connector and the actuatable plug or socket.

[0030] In an embodiment of the surface vessel, the electrical connector may comprise, or may be connected to, a socket or plug arranged on the cable connection section, the socket or plug being connectable to the electric power source via the actuatable plug or socket, respectively, when the sweep cable is spooled off the sweep cable winch.

[0031] The cable connection section and / or the electrical connector may be configured to only allow connection to the actuatable plug or socket when the sweep cable is fully spooled off (or paid out from) the winch.

[0032] In an embodiment of the surface vessel, the minesweeping system may comprise a paravane, 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 sweep cable to control the lateral extent of the closed electric loop, i.e. the closed electric loop provided by the sweep cable. In other words, the paravane is configured to pull one side of the closed loop formed by the sweep cable in a lateral direction relative to the direction in which the surface vessel travels, or lateral to the direction in which the sweep cable extends from the sweep cable winch towards the stern of the vessel.

[0033] In an embodiment of the surface vessel, the minesweeping system may comprise a first paravane and a second paravane, each paravane connected by a paravane line and a paravane winch as defined above, the paravanes being configured to pull opposite sides of the closed loop formed by the sweep cable in opposite lateral directions relative to the direction in which the surface vessel travels.

[0034] 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.

[0035] The paravane or paravane line may be connected to the sweep cable by a pilot line, the pilot line having an end slidably connected to the sweep cable.

[0036] 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.

[0037] In an embodiment of the surface vessel, the minesweeping system comprises a float configured to hold the paravane at a predetermined sea depth. In an embodiment of the surface vessel, the paravane line may extend through a tackle element and is connected to the float via a second end of the paravane line, the tackle element is connected to the paravane via a set of guide lines. The tackle element may be termed a pulley or sheave when comprising rollers / wheels for guiding the paravane line.

[0038] In an embodiment of the surface vessel, the paravane line has a stopper configured to limit a length of the paravane line passing through the tackle element, such that the distance between the float and the tackle element is limited to a predetermined distance. In other words, the stopper limits the length of a section of paravane line extending between the tackle element and the float. The stopper may be any element arranged on the paravane line having a size sufficient to prevent the element from passing through the tackle element. The tackle element may also comprise a locking arrangement configured to lock / fix the tackle element to the paravane line when the stopper has engaged with the tackle element. The locking element may prevent the paravane and float from being dragged closer to each other during higher towing speeds.

[0039] In an embodiment of the surface vessel, the minesweeping system may comprise a paravane boom having an upper line guide section, the paravane line runs between the paravane winch and the paravane via the upper line guide section, the paravane boom is configured to pivot between a retracted position and a launch position, when in the retracted position the paravane line is fully spooled onto the paravane winch, and the launch position is entered when the paravane line is paid out.

[0040] In the retracted position the upper cable guide section may be within the horizontal circumference of the vessel. In the launch position, the upper cable guide section may be arranged beyond the horizontal circumference of the vessel such that the paravane may be freely deployed.

[0041] In the retracted position the upper line guide section may be closer to the paravane winch than in the launch position.

[0042] The paravane boom may be configured to move from the retracted position to the launch position by use of gravity when the paravane winch starts to pay out the paravane line, i.e. when the paravane line is unspooled from the paravane winch.

[0043] In an embodiment, the surface vessel may comprise a first cable pusher for the length of sweep cable extending from the sweep cable winch, the first cable pusher being moveable in a lateral direction relative to the direction in which the sweep cable extends from the sweep cable winch. The first cable pusher may be arranged between the sweep cable winch and the stern of the surface vessel or arranged at the stern of the vessel.

[0044] The first cable pusher may be configured to guide spooling of the sweep cable both onto and off the sweep cable winch. The first cable pusher ensures that the sweep cable is both paid out from the winch and spooled onto the winch in a correct manner without human intervention.

[0045] In an embodiment of the surface vessel, the first cable pusher may be laterally moveable between a first position in line with the main drum section and a second position in line with the cable connection section, the first cable pusher being configured to be in the first position when the sweep cable is fully paid out from the sweep cable winch.

[0046] In other words, when the first cable pusher is in the first position it may be within a projection of the lateral extent, or width, of the main drum section, and when the first cable pusher is in the second position it may be within a projection of the lateral extent, or width, of the cable connection section

[0047] In other words, in the first position, the first cable pusher and the main drum section may be within a same distance range to a centreline of the surface vessel, similarly, in the second position, the first cable pusher and the cable connection section may be within a same distance range to the centreline of the surface vessel.

[0048] The first cable pusher may ensure that a section or length of sweep cable extending between the sweep cable winch and the first cable section is parallel to a centreline of the vessel.

[0049] In an embodiment, the surface vessel may comprise a second cable pusher for the length or section of sweep cable extending from the electrical power supply to the stern of the vessel.

[0050] When in the second position, the first cable pusher may be closer to the second cable pusher than in the first position. When in the second position, the first cable pusher may be adjacent to the second cable pusher.

[0051] In an embodiment of the surface vessel, the second cable pusher may be replaced by a cable guide ensuring correct positioning of the length or section of sweep cable extending from the electrical power supply to the stern of the surface vessel. In an embodiment, the surface vessel may comprise a cable collector, a collector line and a collector line winch, the cable collector is configured to hold a third section and a fourth section of the sweep cable together, the third section and the fourth section of the sweep cable extending between the stern of the surface vessel and the cable collector when the sweep cable has been spooled off the sweep cable winch and is towed by the surface vessel. In other words, the third section and the fourth section of the sweep cable extend from the stern of the surface vessel and to a position behind the surface vessel, at which position the cable collector is arranged.

[0052] In an embodiment of the surface vessel, the distance between the cable collector and the stern of the surface vessel may be controlled by operating the collector line winch.

[0053] In an embodiment of the surface vessel, the cable collector may be configured to extend around a portion of the third and fourth section of the sweep cable. The cable collector may comprise a passage through which portions of the third and fourth section of the sweep cable are arranged. The passage may have an oval crosssection. The dimension of the oval cross-section is preferably configured such that the third and fourth section of the sweep cable may not cross over each other within the passage.

[0054] In an embodiment, the surface vessel may be an unmanned surface vessel, the unmanned surface vessel being autonomous or remote controlled.

[0055] In an embodiment of the surface vessel, the minesweeping system may comprise a towable acoustic source connected by an acoustic cable to an acoustic cable winch mounted on the surface vessel.

[0056] In an embodiment of the surface vessel, the minesweeping system may comprise a first and a second towable electrode for providing an underwater electric potential. The first or second towable electrode may be arranged on, or form a part of, the cable collector.

[0057] In an embodiment of the surface vessel, the minesweeping system may comprise a control system, the control system configured to control any of the sweep cable winch, the paravane winch, the collector line winch, the acoustic cable winch, the first cable pusher, the second cable pusher, the connector assembly (e.g. the actuatable plug or socket) and the electric power source. In other words, all controllable features of the minesweeping system defined in the various embodiments of the surface vessel may be autonomous or remote controlled. The control system of the minesweeping system, and optionally the surface vessel, may be operated remotely, e.g. by a suitable radio frequency (RF) remote control protocol.

[0058] In a second aspect, the present invention provides a minesweeping system for mounting on an unmanned surface vehicle, the system comprises a sweep cable, a sweep cable winch and an electric power source, the sweep cable is configured to provide a closed electric loop with the electric power source when the sweep cable is spooled off the sweep cable winch and towed by the unmanned surface vehicle; the sweep cable has a first end connected to the sweep cable winch, such that the sweep cable can be spooled on / off the sweep cable winch as a single strand, and a second end connected to the power source; the first end and the second end of the sweep cable are electrically connectable by a connector assembly.

[0059] The minesweeping system according to the second aspect may comprise any feature of the minesweeping system defined in the embodiments of the first aspect.

[0060] In a third aspect, the present invention provides a method of launching the minesweeping system of a vessel according to any embodiment of the first aspect, the method comprising the steps of spooling the sweep cable off the sweep cable winch to obtain a loop of sweep cable towed by the surface vessel; electrically connecting the first end and the second end of the sweep cable by actuating the connector assembly; and obtaining a magnetic field provided by a closed electric loop formed by the sweep cable and the electric power source.

[0061] In an embodiment of the method, the minesweeping system comprises a paravane connected to a paravane winch by a paravane line, and a paravane boom, the paravane boom features an upper line guide section via which the paravane line runs between the paravane winch and the paravane, the paravane boom is configured to pivot (i.e. pivot around a horizontal axis) between a retracted position and a launch position, wherein the method comprises the step of paying out the paravane line during or after the step of spooling the sweep cable off the sweep cable winch, such that the paravane boom is moved from the retracted position to the launch position due to gravity; and launching the paravane at the stern of the surface vessel to control the lateral extent of the closed electric loop. In an embodiment of the method, the minesweeping system comprises a first cable pusher for the length of sweep cable extending from the sweep cable winch, and the method comprises the step of: pulling at least an initial section of sweep cable off the sweep cable winch, during the step of spooling the sweep cable off the sweep cable winch, by use of the first cable pusher until drag on the sweep cable is at a level sufficient to allow paying out the spool cable without excessive kinking / bending / curl.

[0062] In an embodiment of the method, the minesweeping system comprises a first cable pusher for the length of sweep cable extending from the sweep cable winch, the method comprises the step of moving the first cable pusher in a lateral direction, relative to the direction in which the sweep cable extends from the sweep cable winch, such that a first section of the sweep cable extending from the sweep cable winch to the stern of the surface vessel, and a second section of the sweep cable extending from the electric power source to the stern of the surface vessel are moved closer together before the step of electrically connecting the first end and the second end of the sweep cable by actuating the connector assembly.

[0063] In an embodiment of the method, the minesweeping system comprises a first cable pusher for the length of sweep cable extending from the sweep cable winch, the method comprising the steps of ensuring correct spooling of the sweep cable onto the sweep cable winch by sequentially moving the cable pusher in opposite lateral directions, relative to the direction in which the sweep cable extends from the sweep cable winch, during spooling.

[0064] The present specification also discloses a surface vessel comprising an alternative minesweeping system, the alternative minesweeping system comprises a winch arrangement, a first sweep cable, a second sweep cable and an electric power source, wherein each of the first sweep cable and the second sweep cable comprises an electrode;

[0065] - the winch arrangement is for deploying and towing the first sweep cable and the second sweep cable behind the surface vessel; and each of the first sweep cable and the second sweep cable is connectable to the electric power source such that an electric current may pass between the electrodes to generate a magnetic field. In an embodiment, the alternative minesweeping system of the surface vessel may comprise a cable pusher for each of the first sweep cable and the second sweep cable, the cable pushers being moveable in a lateral direction relative to the direction in which the first sweep cable and the second sweep cable extend from the winch arrangement.

[0066] The cable pushers of the alternative minesweeping system may be arranged between the winch arrangement and the stern of the surface vessel or arranged at the stern of the surface vessel.

[0067] The cable pushers of the alternative minesweeping system may be configured to guide spooling of the first sweep cable and the second sweep cable onto and off the winch arrangement. The cable pushers ensure that the first sweep cable and the second sweep cable are both paid out from the winch and spooled onto the winch in a correct manner without human intervention.

[0068] The cable pushers of the alternative minesweeping system may be configured to be adjacent, i.e. closest to each other, when the first sweep cable and the second sweep cable are deployed and towed behind the surface vessel to generate a magnetic field.

[0069] In an embodiment, the surface vessel comprising the alternative minesweeping system may comprise a paravane (i.e. a first paravane), 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 or the second sweep cable to control the lateral displacement of the respective sweep cable. In other words, the paravane is configured to pull one of the sweep cables in a lateral direction relative to the direction in which the surface vessel travels, or lateral to the direction in which the sweep cables extend from the winch arrangement towards the stern of the surface vessel.

[0070] The surface vessel comprising the alternative minesweeping system may comprise any compatible feature of the minesweeping system according to the embodiments of the first aspect.

[0071] Description of the drawings

[0072] Embodiments of the invention is described in detail by reference to the following drawings: Fig. 1 is a perspective view of a first exemplary surface vessel and minesweeping system according to the invention.

[0073] 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 vessel.

[0074] Fig. 3 are perspective views of the surface vessel and minesweeping system in fig. 1, illustrating the steps performed to launch the sweep cable.

[0075] Figs. 4a-4d are topside views of the minesweeping system in fig. 1.

[0076] Fig. 5 is an expanded view showing details of the surface vessel and minesweeping system in fig. 1.

[0077] Fig. 6 is a perspective view of a sweep cable winch.

[0078] Fig. 7 is a sideview of the sweep cable winch in fig. 6.

[0079] Fig. 8 is a perspective view of a paravane and a float used in the minesweeping system in fig. 1.

[0080] Fig. 9 is a perspective view of a tackle element connecting the paravane and the float in fig. 8.

[0081] Fig. 10 are side views of the paravane and the float shown in fig. 8, illustrating the steps performed during retrieval of the paravane and the float.

[0082] Fig. 11 are perspective views of a second exemplary surface vessel and minesweeping system according to the invention illustrating the steps performed to launch the sweep cable.

[0083] 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.

[0084] 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. Fig. 14 is a perspective view of a surface vessel and minesweeping system comprising two separate sweep cables having bare electrodes.

[0085] Fig. 15 is a perspective view of an exemplary cable collector.

[0086] Fig. 16 is a perspective view of an exemplary cable collector comprising an electrode for providing underwater electric potential (UEP).

[0087] Detailed description of embodiments of the invention

[0088] The present invention provides a novel minesweeping system which is highly advantageous for the detection and neutralization of underwater mines. The minesweeping system is further adapted for use with unmanned surface vessels (USVs).

[0089] A surface vessel 2 featuring an embodiment of the inventive minesweeping system 1 is shown in fig. 1. The illustrated surface vessel 2 may be manned or unmanned, however, the minesweeping system 1 itself is fully automated and may be remote or autonomously controlled.

[0090] The minesweeping system comprises a sweep cable 3, a sweep cable winch 4, an electric power source 5 and a control system 29. The sweep 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.

[0091] 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 single winch), allows for a less complex and service / operator demanding sweep cable winch.

[0092] 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 assembly), see fig. 6, to provide the closed electric loop together with the electric power source.

[0093] When the sweep cable 3 is spooled off the sweep cable winch 4 and towed by the surface vessel 1, a first section 3 a of the sweep cable 3 extends from the sweep 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.

[0094] When the minesweeping system is mounted on an unmanned vessel, the presence of 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.

[0095] In the illustrated embodiment, the sweep cable winch 4 comprises a main drum 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 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.

[0096] 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 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 removed from the socket 23.

[0097] 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 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. 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 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 /

[0098] 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 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 may be moved back and forth by a suitable actuator or motor.

[0099] 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 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 3 a, 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 3.

[0100] Exemplary cable collectors 24’,24”are also shown in figs. 15 and 16. The passage Both cable collectors

[0101] 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.

[0102] 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. 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.

[0103] 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.

[0104] 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 line 10 passing through the tackle element 13. In this manner, a distance DI 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.

[0105] To facilitate autonomous launch and recovery of the paravane 9 and the float 12, the 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 is paid out. The launch / recovery process is simply controlled by operating the paravane winch 11.

[0106] 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 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 paravane line 10 onto the paravane winch 11 will then drag the paravane boom 16 to the retracted position.

[0107] 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 by gravity when the paravane line 10 is spooled off the paravane winch 11. The configuration of the assembly comprising the paravane 9 and float 12 is highly advantageous as it is easily remote controlled.

[0108] 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.

[0109] 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 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. In this 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.

[0110] 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.

[0111] Alternative methods of moving the cable collector 24 in case the provided drag is insufficient are shown in figs 11-13.

[0112] In fig. 11, the cable collector 24 is connected to a sea anchor 27 to increase the drag.

[0113] 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.

[0114] 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.

[0115] An embodiment of a surface vessel featuring a minesweeping system based on the deployment of two separate sweep cables 3,3”, each sweep cable having a bare electrode 35’, 35”, is shown in fig. 14. As discussed in the referenced prior art, in this solution an electric current 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 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.

[0116] Two exemplary embodiments of cable collectors 24’, 24” are shown in figs. 15 and 16. Both cable collectors features a passage 36 through which portions of the third and fourth section of the sweep cable are arranged. The passage 36 has an oval cross-section. The dimension of the oval cross-section is preferably configured such that the third and fourth section of the sweep cable may not cross over each other within the passage 36. The cable collector 24” illustrated in fig. 15 features an electrode 37 in the shape of an external jacket. The electrode is one of a set of electrodes for providing an underwater electric potential (UEP). The set of electrodes may further comprise a separately towed electrode (not shown), i.e. the UEP is formed between the electrode 37 on / of the cable collector 24” and the separately towed electrode.

[0117] The minesweeping system described above may comprise further advantageous features not shown in the drawings, such as a towable audio source. The audio source may e.g. be connected by an audio cable to an audio cable winch mounted on the surface vessel.

Claims

Claims1. A surface vessel comprising a minesweeping system (1), the minesweeping system comprises a sweep cable (3), a sweep cable winch (4) and an electric power source (5), the sweep cable (3) is 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); the sweep cable (3) has a first end (6) connected to the sweep cable winch (4), such that the sweep cable can be spooled on / off the sweep cable winch as a single strand, and a second end connected to the electric power source; the first end and the second end of the sweep cable (3) are electrically connectable via a connector assembly (8,22,23).

2. A surface vessel according to claim 1, wherein the sweep cable winch (4) and the electric power source (5) are arranged such that a first section (3a) of the sweep cable (3) extends from the sweep cable winch (4) to the stern of the surface vessel, and a second section (3b) of the sweep cable extends from the electric power source to the stern of the surface vessel, when the sweep cable is spooled off the sweep cable winch and towed by the surface vessel, the first and second sections of the sweep cable are adjacent such that any magnetic field developed between the first and second section is minimized.

3. A surface vessel according to claim 1 or 2, wherein the sweep cable winch comprises a main drum section (20) and an adjacent cable connection section (21), the first end of the sweep cable 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, the cable connection section is arranged at a side of the sweep cable winch being closest to the electric power source.

4. A surface vessel according to claim 3, wherein the cable connection section comprises a ramp (7) and an electrical connector (8) to which electrical connector the first end of the sweep cable is connected, the ramp being configured to guide the sweep cable from the electrical connector to the main drum section during spooling of the sweep cable onto the sweep cable winch.

5. A surface vessel according to claim 4, wherein the electrical connector (8) is connectable to the electric power source (5) by an actuatable plug (22) or socket, such that an electrical connection between the first end of the sweep cable and the electric power source may be obtained when the sweep cable is spooled off the sweep cable winch.

6. A surface vessel according to claim 5, wherein the electrical connector (8) comprises, or is connected to, a socket (23) or plug arranged on the cable connection section (21), the socket (23) or plug being connectable to the electric power source via the actuatable plug (22) or socket, respectively, when the sweep cable is spooled off the sweep cable winch.

7. A surface vessel according to any of the preceding claims, wherein the minesweeping system comprises a paravane (9), 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 sweep cable to control the lateral extent of the closed electric loop.

8. A surface vessel according to claim 7, wherein the minesweeping system comprises a float (12) configured to hold the paravane (9) at a predetermined sea depth.

9. A surface vessel according to claim 8, wherein the paravane line (10) extends through a tackle element (13) and is connected to the float via a second end of the paravane line (10), the tackle element (13) is connected to the paravane (9) via a set of guide lines (14).

10. A surface vessel according to claim 9, wherein the paravane line (10) has a stopper (15) configured to limit a length of the paravane line (10) passing through the tackle element, such that the distance (DI) between the float (12) and the tackle element is limited to a predetermined distance.

11. A surface vessel according to any of claims 7 to 10, wherein the minesweeping system comprises a paravane boom (16) having an upper line guide section (17), the paravane line (10) runs between the paravane winch (11) and the paravane (9) via the upper line guide section, the paravane boom (16) is configured to pivot between a retracted position and a launch position, when in the retracted position the paravane line is fully spooled onto the paravane winch, and the launch position is entered when the paravane line is paid out.

12. A surface vessel according to any of the preceding claims, comprising a first cable pusher (18) for the length of sweep cable extending from the sweep cable winch, the first cable pusher being moveable in a lateral direction relative to the direction in which the sweep cable extends from the sweep cable winch.

13. A surface vessel according to claim 3 and 12, wherein the first cable pusher is laterally moveable between a first position in line with the main drum sectionand a second position in line with the cable connection section, the first cable pusher being configured to be in the first position when the sweep cable is fully paid out from the sweep cable winch.

14. A surface vessel according to any of the preceding claims, comprising a second cable pusher (19) for the length of sweep cable extending from the electrical power supply to the stern of the vessel.

15. A surface vessel according to any of the preceding claims, wherein the minesweeping system comprises a control system (29) by which it may be remote controlled.

16. A surface vessel according to any of the preceding claims, being an unmanned surface vessel, the unmanned surface vessel being autonomous or remote controlled.

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