EP3894314A2

EP3894314A2 - Faired towing cable

Info

Publication number: EP3894314A2
Application number: EP19817297.5A
Authority: EP
Inventors: François Warnan; Jean-Philippe LONGUET; Laurent HELIAS; Frédéric GREGOIRE; Paul TANNIOU
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2018-12-11
Filing date: 2019-12-11
Publication date: 2021-10-20
Anticipated expiration: 2039-12-11
Also published as: US20220024545A1; ES2932007T3; CA3121379A1; FR3089488B1; PL3894314T3; DK3894314T3; AU2019396568A1; WO2020120544A2; SG11202105205PA; WO2020120544A3; EP3894314B1; FR3089488A1

Abstract

The present invention relates to a faired towing cable used on a ship to tow a sea-launched submersible body. The cable (14) comprises a core (24) and a fairing (26, 28) mounted on the core (24). The fairing (26, 28) is profiled in such a way as to reduce the hydrodynamic drag of the cable (14). The fairing comprises several leading edges (26) and several trailing edges (28) mounted on the leading edges (26). A trailing edge (28) is held directly on two adjacent leading edges (26).

Description

Faired tractor cable

The present invention relates to faired tractor cables used on a ship to tow a submersible body dropped at sea. It more particularly relates to faired tractor cables by means of scales or sections hinged together. The invention can be implemented for any type of elongated streamlined element intended to be at least partially submerged.

The context of the invention is that of a ship intended to tow a submersible object such as a variable immersion sonar antenna integrated in a towed body. In such a context, in the non-operational phase, the submersible body is stored on board the ship and the cable is wound around the reel of a winch making it possible to wind and unwind the cable, in order to put into the sea and recover the submersible object. In the operational phase, the submersible body is immersed behind the ship and towed by the latter using the cable, the end of which is connected to the submersible body. The cable is wound / unwound by the winch through a cable guide device which guides the cable.

To obtain a high immersion at high towing speeds, the towing cable is faired which reduces its hydrodynamic drag as well as the vibrations generated by the hydrodynamic flow around the cable. The cable is coated with a segmented fairing composed of hulls having shapes intended to reduce the hydrodynamic drag of the cable. The role of the hulls is to reduce the wake turbulence produced by the movement of the cable in the water, when it is immersed in the water and towed by the ship. The rigidity of the hulls is necessary for large immersions going hand in hand with high towing speeds which can exceed 20 knots. It is recalled that the knot is a unit of speed commonly used in the maritime and aeronautical fields. One knot is equal to 1.852 km / h. Flexible fairings are only useful for economically profiling chains or cables of buoys subjected to sea currents or towed at low speeds, typically less than 6 to 8 knots. In the case of the use of rigid fairing elements, the segmentation of the fairing into hulls is necessary so that the cable can be wound on the reel of a winch and pass through guide elements of the pulley type, and so as to be able to withstand a lateral movement of the cable in the event of a change of course of the ship.

In normal operating condition, the hulls are rotatable around the longitudinal axis of the cable. It is indeed necessary that the hulls can rotate freely around the cable in order to be correctly oriented with respect to the flow of water. Excluding the end hull, each hull is however linked to its two neighbors axially and in rotation around the cable. The link is provided by intermediate mechanical parts called fishplates assembled between each of the hulls. The set of hulls and sides is called the hull column.

A functional play is present between each fishplate and the associated hulls in particular in order to allow the streamlined cable to pass fluidly through all the guide elements, such as pulleys or fairleads and to wind around a reel for the cable storage on the deck of the ship. The rotation of a hull causes a rotation of its neighbors and gradually that of all the hulls. Consequently, both when the cable is deployed in water and when it is wound around the reel, any change in orientation of one of the hulls, gradually affects all the hulls of the cable. When the cable is deployed at sea, the hulls naturally orient in the direction of the current generated by the movement of the vessel. Similarly, the guide device is conventionally configured to orient and guide the hulls which pass through it so that they have a predefined orientation relative to the winch reel. All of the hulls adopt the same orientation with respect to the cable reel as the cable goes up, an orientation which makes it possible to wind the cable while keeping the hulls parallel to each other.

The Applicant has realized several difficulties when using shrouded cables.

The streamlined towing cables are subject to a random phenomenon of torsion at their aerial part, that is to say between the surface of the water and the towing device disposed on the deck of the ship. This twist is not dangerous immediately but can easily become so if it is not detected in time and absorbed. The minimum damage that can result is the crushing of part of the hull column. This crushing can lead to limited consequences but it can also degenerate, tear the cable sheath, block the winch or damage it and thus lead to the unavailability of the entire submerged system.

The torsion phenomenon can also appear on the submerged part of the cable. This phenomenon coupled with the speed of the cable in water causes very high torques on the hulls and their links.

As the hulls are often made from plastics and the stresses applied by the water flow are very high, a twist can lead to permanent deformation of the hulls related to creep. Gradually the torsion tightens which increases the mechanical stresses between the hulls. Over time, this inevitably evolves towards the breaking of hulls or inter-hull links. Once this break has occurred, a discontinuity in the hull column can block the cable when it passes over a pulley and when it is wound on its reel.

Other deformations similar to creep can also occur when the faired cable is wound on its reel. More specifically, the links, their attachments to the hulls or the hulls themselves can relax due to the radius of curvature undergone by the cable. This permanent elongation impedes the free movement of the entire column of hulls during the unwinding of the cable.

Still during the winding of the cable, on the reel or in the passage of a pulley, the parts forming the leading edges of the hulls approach each other and are likely to touch and even exert forces on each other, forces which may cause deformations or ruptures.

The cable can be equipped with crimped rings for longitudinally blocking the hulls along the cable. The rings take up the forces undergone by the hulls along the axis of the cable. These rings are regularly distributed along the cable with a pitch for example of several tens of hulls. During the longitudinal bending of the cable, which passes over a pulley, the column of hulls which forms like a sheath not linked to the cable naturally adopts a running speed which is necessarily lower than that of the cable. The column of hulls is then gradually pushed against the rings crimped on the cable. This pressure caused by the passage on pulley can lead to very high pressures and damage the faces of the hulls in contact with the rings.

The Applicant has also found damage to the hulls at their trailing edge forming the thinnest part of the hull and therefore the most fragile part. Despite all the precautions taken in the guide surfaces of the pulleys and the winch, the trailing edges are often damaged due to violent contact or even jamming in slots or interstices.

The invention aims to overcome all or part of the problems mentioned above by proposing a faired tractor cable intended to tow a submersible body, the cable comprising a core and a fairing assembled on the soul, the fairing being profiled so to reduce the hydrodynamic drag of the cable, the fairing comprising several leading edges and several trailing edges assembled on the leading edges. A trailing edge is directly maintained on two neighboring leading edges.

Advantageously, the core mainly extends along an axis and the trailing edges are staggered relative to the leading edges along the axis.

Advantageously, the core mainly extends along an axis. The leading edges form a shell folded around the core. The trailing edges are formed of a profile ensuring the hydrodynamic function of the trailing edge and of two arms each arranged inside one of the two neighboring leading edges. Each arm extends at least in a direction perpendicular to the axis. Each arm is held at the corresponding leading edge.

Advantageously, each arm has two ends, a first of which is secured to the profile and a second of which is free. Each arm is held at the leading edge corresponding to the level of its second. Advantageously, each arm is held at the leading edge by a pivot link.

Advantageously, the pivot link is arranged at the second free end of the corresponding arm and each leading edge comprises two stops which can each come into contact with one of the arms) corresponding so as to limit the relative movement of the edge trailing edge and leading edge connected by the pivot link.

Advantageously, the trailing edge comprises an intermediate arm connecting the two arms.

Advantageously, the core extends mainly along an axis and for the different leading edges and trailing edges, perpendicular to the axis of the core, the fairing occupies a distance D relative to the axis and in that a distance d occupied by the leading edges is at least equal to half of the distance D.

Advantageously, in a plane containing the axis, a projection of the leading edge is substantially rectangular, one side of which is limited by the distance d. The trailing edge comprises a profile ensuring the hydrodynamic function of the trailing edge. A projection of the profile is substantially rectangular, one side of which is limited by the distance d and the other side of which is limited by the distance D.

Advantageously, the ends on the leading edge side have rounded corners and the profile is configured to follow the rounded corners.

Advantageously, the leading edges and the leaking edges are in one piece and made of homogeneous materials and a Young's modulus of the material forming the leading edges is larger than a Young's modulus of the material forming the trailing edges.

Advantageously, rings fixed to the core are distributed regularly along the core, the leading edges being able to bear on the rings. The rings are arranged between two neighboring attack edges.

Advantageously, the core mainly extends along an axis. Each leading edge comprises a channel extending essentially along an axis and in which the core is disposed. The channel flares on either side of a section center of the leading edge, the middle section being perpendicular to the axis of the channel.

[0027]

The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, description illustrated by the attached drawing in which:

• Figure 1 shows a ship towing an object towed by means of a faired tractor cable according to the invention;

• Figure 2 shows a portion of the shrouded cable;

• Figures 3a and 3b show in perspective two variants of shrouded cable subjected to torsion;

• Figures 4a and 4b partially show the cable along two perpendicular cutting planes;

• Figure 5 shows the cable passing over a pulley;

• Figures 6a, 6b, 6c and 6d illustrate a variant of a leading edge of the cable.

For the sake of clarity, the same elements will have the same references in the different figures.

Figure 1 shows a ship 10 towing a submersible object 12 by means of a towing cable 14. The submersible object 12 is for example a sonar antenna, often called fish, the depth of which can be variable. The invention is not limited to a sonar antenna. It can be used for any type of submersible object, such as seismic detectors or fishing gear.

The submersible object 12 is secured to the cable 14. The launching and the exit of water from the submersible object 12 is carried out by means of a winch 16 disposed on a deck 18 of the ship 10 The winch 16 comprises a reel 20 dimensioned to allow the winding of the cable 14. The cable 14 can be wound on the reel 20 by passing through a guide device 22, such as for example a pulley or a fairlead. The reel 20 and the guide device 22 are dimensioned so as to limit the curvature of the cable 14. The guide device 22 also makes it possible to limit the lateral movement of the cable 14 downstream, that is to say on the sea side, in order to allow the use of the submersible object 12 in heavy sea conditions. The guide device can also be equipped with upstream cutting, that is to say on the drum side 20, making it possible to store the cable 14 on the drum 20.

The cable 14 can only be a mechanical link between the ship 10 and the submersible object 12. Alternatively, the cable 14 can transmit power and signals between the ship 10 and the submersible object 12. The cable can include a sheath formed of a strand of metal son ensuring a certain flexibility in particular to allow the cable 14 to bend. Inside the sheath of the conductors can ensure the transmission of signals and power. These conductors can be of any kind: electrical, optical, fluid ... The sheath provides mechanical protection for the internal conductors.

The outer sheath of the cable is generally of circular section. The sheath and any internal conductors are hereinafter called core 24. As stated in the introduction, the core 24 is advantageously streamlined, in particular to limit its hydrodynamic drag. In order to reach high traction speeds, the fairing is at least partly rigid. To allow the curvature of the cable, the fairing is segmented.

Figure 2 shows a part of the cable 14. There are the core 24 and its fairing. According to the invention, the fairing comprises several leading edges 26 and several trailing edges 28 assembled on the leading edges 26.

By leading edge 26 is meant a mechanical part surrounding the core 24 and intended to orient itself facing the current prevailing in the water in which the cable 14 is immersed. Similarly, the trailing edge is a mechanical part located downstream of the leading edge relative to the current. The leading edges 26 and the trailing edges 28 include external surfaces making it possible to reduce the drag of the cable 14 when the latter is subjected to current. The different leading edges 26 and trailing edges 28 are advantageously identical to facilitate their realization. The leading edges 26 can slide along the core 24 and as mentioned above, the core 24 can be fitted with crimped rings not shown in FIG. 2 and making it possible to longitudinally block the leading edges 26 along of the core 24. The rings take up the forces undergone by the leading edges 26 along the longitudinal axis 30 of the core 24. The leading edges 26 intended to come into contact with the rings can be configured differently from the others edges of attacks. In the configuration shown in FIG. 2, a trailing edge 28 is directly held on two neighboring leading edges 26 without an intermediate mechanical part.

Maintaining the leading edges 26 and the trailing edges 28 therebetween ensures continuity of the hydrodynamic profile of the fairing parallel to the axis 30 making it possible to limit the effects of torsion of the cable around the axis 30. Directly maintaining a trailing edge 28 on two neighboring leading edges 26 avoids the installation of intermediate junction pieces often called fishplates.

In the segmentation of the fairing, it is possible to have a trailing edge 28 facing each leading edge 26. More precisely, along the axis 30, the outer surfaces of a leading edge 26 and a trailing edge 28, ensuring their hydrodynamic function, occupy the same portion along the axis 30. Maintaining a trailing edge 28 on two adjacent leading edges 26 is then ensured by protuberances of the trailing edge linked to two neighboring leading edges inside them. However, this arrangement opposite the leading edges 26 and the trailing edges 28 results, in the event of twisting of the cable 24, in a "staircase" arrangement of the various trailing edges. More precisely, the downstream end of the leakage edges 28 forms a discontinuous line, which harms the hydrodynamics of the cable. This staircase arrangement is shown in Figure 3a.

Preferably, as shown in Figure 2 and in Figure 3b, the trailing edges 28 are staggered relative to the leading edges 26 along the axis 30. Thus during a twist of the cable 14, the downstream end of the leakage edges 28 form a substantially continuous line as shown in FIG. 3b. During a twist the downstream end of the trailing edges 28 takes a continuous form of propeller. The continuous line has an advantage during the passage of the cable in the guide device 22. In fact, in the event of strong twisting of the cable 14, the discontinuities appearing in FIG. 3a risk escaping from the guide device 22 or striking and hang some imperfections when the winch 16 is in action. More specifically, a trailing edge 28 can come into proper abutment in the guide device 22 and the next can come out of the guide device 22 due to the presence of a discontinuity. Leaving the device, the risk of rupture of the fairing is very high. On the other hand, the absence of discontinuity, as shown in FIG. 3b allows the different trailing edges 28 to come to bear continuously against the guide device 22, in particular when passing from a trailing edge 28 to the next. The risk of a trailing edge 28 leaving the guide device 22 is then much lower.

Figure 4a shows the cable 14 in section in a plane perpendicular to the axis 30 and Figure 4b shows a portion of the cable 14 in section in a plane containing the axis 30. The leading edge 26 is in one piece . It is made of a homogeneous material. The leading edge 26 surrounds the core 24. The leading edge 26 includes a channel 32 in which the core 24 is arranged. A functional clearance is present between the core 24 and the channel 32 in order to allow the leading edge 26 to rotate freely around the core 24. The leading edge 26 is placed around the core 24 in folding it back in order to close the channel 32. In other words, the leading edge 26 forms a shell folded around the core 24.

More specifically, the leading edge 26 includes two faces 26a and 26b and a connecting portion 26c joining the two faces 26a and 26b. The faces 26a and 26b as well as the connection part 26c are substantially in the extension of one another during the manufacture of the leading edge 26. The leading edge 26 is for example made of molded plastic. Any other manufacturing process is of course possible, such as machining or 3D printing.

After folding the leading edge 26 around the core 24, the connecting portion 26c forms the surface of the channel 32 and the two faces 26a and 26b come into contact with one another. The two faces 26a and 26b are fixed to each other, for example by means of screws 34 or rivets. The external surfaces of the faces 26a and 26b and of the connection part 26c ensure the hydrodynamic function of the leading edge 26. During the orientation of the hull in the current, the connection part 26c is positioned most upstream.

The trailing edge 28 comprises a profile 28a ensuring the hydrodynamic function of the trailing edge 28 and two arms 28b and 28c each arranged inside two neighboring leading edges 26.

Perpendicular to the axis 30 of the core 24, the fairing formed by the leading edges 26 and the trailing edges 28 occupy a distance D relative to the axis 30. The distance d occupied by the edge of attack is at least equal to half the distance D.

In a plane containing the axis 30 and forming a plane of symmetry of the fairing, the projection of the leading edge 26 is substantially rectangular with one side 36 is limited by the distance d. The projection of the profile 28a is also substantially rectangular. For profile 28a, one of the sides 38 of the rectangle is limited by the distance d and another side 40 is limited by the distance D.

The ends of the side 36 may have rounded corners 42, having the shape of chamfers or connecting leaves. The profile 28a can follow the rounded corners 42. These shape arrangements allowing the trailing edges 28 to better follow the relative movements of the leading edges 26 not induced by curvatures or twists in the cable 14.

The leading edge 26 occupies the largest external surface of the fairing.

In other words, leading edge 26 fulfills most of the hydrodynamic function of the fairing.

The leading edge 26 and the trailing edge 28 may be made of the same material which allows to standardize the manufacture of the different mechanical parts forming the fairing. Alternatively, it is possible to adjust the relative flexibility of the leading edge 26 and the trailing edge 28, in particular, by retaining significant rigidity at the leading edge 26 and by giving greater flexibility to the trailing edge 28. The different leading edges 26 and the different trailing edges 28 can be in one piece and made of materials homogeneous. The Young's modulus of the material (also called longitudinal elasticity modulus) forming the leading edges 26 is then greater than the Young's modulus of the material forming the trailing edges 28. This allows the fairing to better follow the movements of the cable 14 in water, during bending or twisting. In addition, the trailing edges 28 have a smaller cross section than that of the leading edges 26. The trailing edges 28 are therefore more fragile than the leading edges 26. By choosing a more flexible material for the trailing edges 28, the risk of breakage of these is reduced. For example, tests have been carried out internally by the applicant with leading edges 26 produced by molding a plastic material formed from a mixture of polycarbonate (PC) and polybutylene terephthalate (PBT) having a Young's modulus of the order of 2150 MPa. The trailing edges 28 were, in turn, produced by molding a polyurethane-based material having a Young's modulus of the order of 548 MPa. More generally, as soon as the Young's modulus of the material forming the leading edges 26 is greater than that of the material forming the trailing edges 28, the result is already interesting. Indeed, the leading edges 26 having thicknesses, defined perpendicular to the plane of FIG. 4b, greater than those of the trailing edges 28, a slight difference between the Young's modules already allows greater deformation of a trailing edge 28 relative to a leading edge 26 under the same force. With a Young modulus of the material forming the leading edges 26 at least twice as large as the Young modulus of the material forming the trailing edges 28, the results are better and with a Young modulus of the material forming the leading edges 26 at least four times larger than the Young's modulus of the material forming the trailing edges 28, the results are excellent.

For plastic materials, the determination of the Young's modulus can be made with reference to ISO 178. In practice, the characterization of the Young's moduli of the materials is relative. It therefore suffices to implement the same measurement conditions to compare the Young's moduli of the materials forming the leading edges 26 and the trailing edges 28.

The arms 28b and 28c extend at least in a direction perpendicular to the axis 30. Thus, the trailing edge 28 has a general U-shape. More specifically, the profile 28a forms the lower part of the U-shape and the arms 28b and 28c form the branches of the U-shape.

The arms 28b and 28c allow the trailing edge 28 to be held at two neighboring leading edges 26. The arms 28b and 28c are anchored in the profile 28a. The arms 28b and 28c have no hydrodynamic function. The arms 28b and 28c are each entirely disposed inside one of the leading edges 26. Thus, the definition of the arms 28b and 28c can be much freer, in particular to adapt their deformation if necessary and in particular to allow the fairing to support the flexions and twists of the core 24. The definition of the shapes and dimensions of the arms 28b and 28c is not subject to the constraints of the hydrodynamic functions of the fairing.

More specifically, each of the arms 28b and 28c comprises two ends, 28b1, 28b2 for the arm 28b and 28c1, 28c2 for the arm 28c. The ends 28b1 and 28c1 are integral with the profile 28a. The ends 28b2 and 28c2 are free and each maintained at a leading edge 26. The maintenance of an arm 28b or 28c at a leading edge 26 can be achieved by means of a complete connection. The relative movements of the trailing edge 28 with respect to the two leading edges 26 on which the trailing edge 28 is fixed is ensured by the elasticity of the arms 28b and 28c.

Alternatively and as shown in Figures 4a and 4b, the free ends 28b2 and 28c2 are each linked to a leading edge 26 by means of a pivot connection 44. This pivot connection 44 allows less stress on the elasticity arms 28b or 28c during relative movements of the trailing edge 28 with respect to the leading edges 26 to which the trailing edge 28 is linked during twists or bends in the cable 14.

The arms 28b and 28c extend at least in a direction perpendicular to the axis 30. More precisely, between their ends, the arms 28b and 28c can extend perpendicular to the axis 30 or be inclined relative to to a direction perpendicular to the axis 30 as shown in Figure 4b. It is however important to keep in the projection of a direction connecting the ends of an arm, a component perpendicular to the axis 30. This component, and more generally the U shape of the trailing edge 28, allows a better flexibility of the link between the trailing edge 28 and the two corresponding leading edges 26 during bending or during twisting of the cable 14. More specifically, in the prior art, the ribs holding the fairings between them extend parallel to the axis 30 and are therefore subjected to traction or compression during bending and even during cable twists. On the other hand, in the proposed variant of the invention, the arms 28b and 28c, due to their orientation, undergo bending which allows greater deformation than traction, hence the better flexibility of the links proposed. Furthermore, during twisting of the cable 14, the base of the U, that is to say the profile 28a, undergoes both traction and bending. Thus, the proposed variant improves the flexibility of the fairing during bending of the cable 14, which makes it possible to facilitate the passage of the cable 14 by the guide means 22, such as a pulley, a passage which tends to bend the cable 14. In however, the proposed variant retains a great stiffness vis-à-vis twists of the cable 14, which allows to limit these twists.

The arms 28b or 28c can be independent of each other. Alternatively, as shown in FIG. 4b, the trailing edge 28 may include an intermediate arm 28d connecting the two arms 28b or 28c. The intermediate arm 28d is essentially arranged inside two neighboring leading edges 26. The intermediate arm 28d can be integral with each of the arms 28b or 28c midway between each of the ends of the arms 28b or 28c. The intermediate arm 28d forms with the free parts of the arms, extending to the free ends 28b2 and 28c2 in a U shape which has the same advantages as those described above. The presence of the intermediate arm 28d makes it possible to adjust the flexibility of the fairing, with respect to the effects of curvature of the cable 14 and its stiffness with respect to twists of the cable 14.

5 shows a section of cable 14 whose direction of the axis 30 is deflected by a pulley 50 forming an example of guide device 22. In Figure 5, the cable 14 is shown schematically and only the core 24 and the leading edges 26 are shown. The trailing edges 28 are not shown. The cable 14 moves in the direction 52 carried by the axis 30. Upstream of the pulley 50, the speed of the cable 14 is denoted Vc. More specifically, when the cable 14 is straight, the speed of the core 24 and the speed of the leading edges 26 is the same, that is to say Vc. On the other hand when the cable 14 bends, in particular when passing around the pulley 50, the axis 30 of the core 24 continues to follow this same speed Vc but the different zones of the leading edge 26 do not all have the same linear speed which is a function of their distance from the axis of the pulley 50.

More specifically, we have seen previously that the leading edge 26 surrounds the core 24. When the cable 14 is in contact with the pulley 50, in the area where the axis 30 follows a portion of a circle, the part 26c of the leading edge 26, closest to the center of the pulley, 50 and materialized by the arrow 54 has a speed less than Vc. This lower speed tends to cause the leading edges 26 to slide upstream of the cable 14. The leading edges 26 are thus pressurized against each other generating stresses in the leading edge 26 oriented along the axis 30. This pressure is taken up by a ring 56 crimped on the core 24.

Several rings are distributed along the core 24 in order to periodically resume the axial forces of the different fairings. It is possible to make a groove on some leading edges 26 at their respective channels, bleeding perpendicular to the axis 30. Thus a leading edge includes a ring. This particular leading edge can then be supported either on one side of the ring or on the other. In other words, a leading edge takes up the forces in both directions carried by the axis 30. However, such a configuration requires a leading edge to take up axial forces both in traction and in compression.

It is also possible to suppress the recovery of tensile force in order to limit the risk of creep of the leading edges 26. To do this, as shown in FIG. 5, the rings 56 are arranged between two edges d 'neighboring attacks.

Furthermore, the part 26c is pressurized by the core 24 against the pulley 50. This pressure against the pulley generates stresses in the leading edge 26 oriented radially towards the center of the pulley 50.

Figures 6a and 6d show a particular shape of the leading edges 26 to limit the effects of the reduction in speed of the portion 26c of the leading edge 26. Figure 6a shows a leading edge 26 alone and FIG. 6d represents a section of cable wound on a pulley 50. The channel 32 mainly extends along an axis 60 of the leading edge 26 and coincides with the axis 30 of the core 24 when the cable 14 is straight. The channel 32 flares on either side of a middle section 62 of the leading edge 26, the section 62 being perpendicular to the axis 60. This allows better distribution of the pressure exerted by the core 24 on the walls of channel 32 during bending of the cable 14. By flaring the channel 32, the pressure is reduced in the sections farthest from the section 62. The sections can be defined so that for a given curvature of the cable 14, in particular as a function of the diameter of the pulley 50, the core 24 is not in contact with the sections farthest from section 62 but only with sections closest to section 62. This makes it possible to limit the risks creep of the material forming the leading edge 26 when it is put under pressure by the core 24.

The channel 32 can be formed of circular sections around the axis 30.

Alternatively, in order to improve the rigidity of the leading edge 26, the sections of the channel 32 are defined asymmetrically around the axis 60 as shown in FIGS. 6a and 6d. More precisely, in section 62, shown in section in FIG. 6b, the channel 32 has a circular outline and in the sections 64 furthest from section 62 and shown in section in FIG. 6c, the channel 32 has an outline oblong extending towards the inside of the pulley 50. Between the sections 62 and 64, the walls of the channel 32 follow for example a circular curve of radius r centered on a point belonging to the middle section 62. The radius r is defined so that re is less than the radius R of the pulley 50, e being the thickness of the part 26a at the level of the middle section 62. Thus, even if the core 24 partially crushes the internal surface of the channel 32 , the length of the support of the core 24, denoted I in FIG. 6d remains less than the length L of the leading edge 26, the lengths I and L being defined along the axis 60 of the channel 32.

When bending the tractor cable 14 around a pulley 50, the parts of the leading edges 26 furthest from the center of the pulley 50 tend to move away from each other. The corresponding trailing edges 28 must follow this spacing. The presence of the pivot link 44 at the free end 28b2 and 28c2 of each of the arms 28b and 28c allows the rotation of the trailing edge 28 relative to each of the leading edges 26 to which the trailing edge 28 is articulated. The pivot connections 44 are arranged as close as possible to the axis 30 in order to limit the spacing of the pivot connections 44 between them. For the trailing edge 28 this spacing is absorbed by elastic deformation of the arms 28b and 28c. The lower Young's modulus of the trailing edge 28 associated with the shape of the arms 28b and 28c allows this deformation. At the ends 28b1 and 28c1 of the arms 28b and 28c, the relative movement of two leading edges is greater than at the level of the pivot connections 44. In FIG. 4b, the possible movement of the edge has been shown in dotted lines. Attack 26 located on the right in the figure. In the lower part of FIG. 4b, the two leading edges 26 come into abutment and move apart in the upper part. At the ends 28b1 and 28c1, the arms 28b and 28c can slide in the plane of FIG. 4b relative to the corresponding leading edges 26.

Other relative movements of the leading edges 26 and the trailing edges 28 are possible, in particular a twist as shown in FIG. 3b. A twist can cause a greater relative movement than a bending as shown in dotted lines in FIG. 4b, the abutment of the leading edges 26 then being inoperative. It is however advantageous to provide a limitation of the relative movement between a leading edge 26 and a trailing edge 28 linked by their pivot link 44. This movement is essentially a rotation around the axis of the pivot link 44 to the functional clearances and to near deformations. To this end, the leading edge may include two boss-shaped stops 70 intended to come to bear each against an arm 28b or 28c. The bosses 70 can be used for the passage of the screws 34 as visible in FIG. 4a. The bosses 70 form protuberances connecting the faces 26a and 26b of the leading edge 26. In FIG. 4b, one of the bosses 70 is also shown in dotted lines during a bending of the core 24. In this position, the boss 70 is still at a distance from the arm 28c. During a larger relative movement, the boss 70 abuts on the arm 28c. This is illustrated by a point 72 of the boss 70 and a point 74 of the arm 28c coming into contact with one another. These two points 72 and 74 are shown by arrows in strong lines in FIG. 4b. It is of course possible to do without a stop between two leading edges 26 and to keep only the stop 70. The position of this stop is notably defined as a function of the diameter of the pulley 50 or that of a drum 20 and more generally of the maximum authorized deformation for cable 14.

Claims

1. faired tractor cable intended to tow a submersible body (12), the cable (14) comprising a core (24) and a fairing (26, 28) assembled on the core (24), the fairing (26, 28) being profiled so as to reduce the hydrodynamic drag of the cable (14), the fairing comprising several leading edges (26) and several trailing edges (28) assembled on the leading edges (26), characterized in that a trailing edge (28) is directly held on two adjacent leading edges (26), in that the leading edges (26) and the trailing edges (28) are in one piece and made of homogeneous materials and in that that a Young's modulus of the material forming the leading edges (26) is larger than a Young's modulus of the material forming the trailing edges (28).

2. Cable according to claim 1, characterized in that the core mainly extends along an axis (30) and in that the trailing edges (28) are staggered relative to the leading edges (26) along the axis (30).

3. Cable according to one of the preceding claims, characterized in that the core (24) extends mainly along an axis (30), in that the leading edges (26) form a shell folded around the 'core (24), in that the trailing edges (28) are formed of a profile (28a) ensuring the hydrodynamic function of the trailing edge (28) and of two arms (28b, 28c) each arranged at the inside of one of the two adjacent leading edges (26), in that each arm (28b, 28c) extends at least in a direction perpendicular to the axis (30) and in that each arm (28b, 28c) is held at the corresponding leading edge (26).

4. Cable according to claim 3, characterized in that each arm (28b, 28c) comprises two ends (28b1, 28b2, 28c1, 28c2) of which a first (28b1, 28c1) is integral with the profile (28a) and of which a second (28b2, 28c2) is free, in that each arm (28b, 28c) is held at the leading edge (26) corresponding to the level of its second (28b2, 28c2).

5. Cable according to claim 4, characterized in that each arm (28b, 28c) is held at the leading edge (26) by a pivot connection (44).

6. Cable according to claim 5, characterized in that the pivot link (44) is arranged at the second end (28b2, 28c2) free of the arm (28b, 28c) corresponding and in that each leading edge ( 26) includes two stops (70) can each come into contact with one of the arms (28b, 28c) corresponding so as to limit the relative movement of the trailing edge (28) and the leading edge (26) connected by the pivot link (44) .

7. Cable according to one of claims 3 to 5, characterized in that the trailing edge (28) comprises an intermediate arm (28d) connecting the two arms (28b or 28c).

8. Cable according to one of the preceding claims, characterized in that the core (24) extends mainly along an axis (30) and in that for the different leading edges (26) and trailing edges ( 28), perpendicular to the axis (30) of the core (24), the fairing (26, 28) occupies a distance D relative to the axis (30) and in that a distance d occupied by the leading edges (26) is at least half the distance D.

9. Cable according to claim 7, characterized in that in a plane containing the axis (30), a projection of the leading edge (26) is substantially rectangular, one side (36) of which is limited by the distance d, in that the trailing edge (28) comprises a profile (28a) ensuring the hydrodynamic function of the trailing edge (28) and in that a projection of the profile (28a) is substantially rectangular, one of the sides (38) of which is limited by distance d and of which another side (40) is limited by distance D.

10. Cable according to claim 8, characterized in that the ends of the side (36) of the leading edge (26) have rounded corners (42) and in that the profile (28a) is configured to follow the rounded corners (42).

1 1. Cable according to one of the preceding claims, characterized in that rings (56) fixed to the core (24) are distributed regularly along the core (24), the leading edges (26) being able to bear on the rings, and in that the rings (56) are arranged between two adjacent leading edges (24).

12. Cable according to one of the preceding claims, characterized in that the core (24) extends mainly along an axis (30), in that each leading edge (26) comprises a channel (32) s extending essentially along an axis (60) and in which the core (24) is disposed and in that the channel (32) widens on either side of a median section (62) of the edge of attack (26), the middle section (62) being perpendicular to the axis (60) of the channel (32).