DEVICE FOR WINDING AND UNWINDING A CABLE AROUND A DRUM
The domain of the invention is naval mine warfare, and more
specifically the implementation of a device able to wind, unwind and lock in a
5 winding and unwinding state a cable about the drum of a winch. A winch may
be carried on board a mine warfare ship such as a minehunter or a dredger
to wind and unwind a cable connected to a mine warfare device such as a
sonar or a device for simulating a magnetic and/or acoustic signature. Such a
winch is used to place in the sea, tow and recover the mine warfare device.
10 In the context of mine warfare, it is desirable to minimize the
magnetic signature of ships. Magnetic signature means the strength of the
magnetic field generated by the ship at a point located at a predetermined
distance from the ship. Keeping the magnetic signature of a ship beneath a
certain threshold prevents mines from triggering when the ship passes, since
15 mines conventionally trigger on detection of a magnetic field above a
predetermined threshold.
For this purpose, weakly magnetic towing winches, such as
winches with hydraulic motors and mechanical or hydraulic brakes, are
conventionally used. However, such winches have the drawback of requiring
20 a hydraulic power unit on board the ship, as well as staff trained to carry out
hydraulic maintenance tasks (routine maintenance and part replacement).
Furthermore, these devices are large, costly and difficult to control.
One purpose of the invention is to overcome the aforementioned
drawbacks.
25 For this purpose, the applicant proposes an electric winch, i.e. a
winch in which the means for driving the drum rotating in relation to the
chassis of the winch include an electric motor. This type of winch overcomes
the aforementioned drawbacks since it is compact, easy to control using
control electronics, and easier to maintain than a hydraulic power unit. In
30 particular, the applicant proposes a device for winding and unwinding a cable
comprising electromagnetic locking/unlocking means for preventing and
permitting rotation of the drum in relation to the chassis of the winch, which is
static in relation to the ship.
However, using this type of device poses a new problem specific
35 to the context of mine warfare. Indeed, an electromagnetic brake is, by its
nature, the source of a strong magnetic field and has a significant magnetic
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PCT/EP2013/069675
signature that is incompatible with use of the winch in mine warfare. It
conventionally includes an induction coil that generates a strong magnetic
field when crossed by a current.
Another purpose of the invention is to propose a solution enabling
5 the magnetic signature of the device for winding and unwinding a cable to be
iimited.
For this purpose, the invention relates to a device enabling a cable
to be wound and unwound comprising a winch comprising a chassis, drive
10 means and a drum, the drive means comprising an electric motor for driving
a drum in rotation in relation to the chassis, locking/unlocking means of
rotation of the drum in relation to the chassis to prevent and permit rotation of
the drum in relation to the chassis, locking/unlocking means including a first
induction coil referred to as the locking/unlocking coil. The locking/unlocking
15 means are designed to immobilize the drum in relation to the chassis when
the locking/unlocking coil is not powered electrically, the device also including
a second induction coil, referred to as the feedback coil, said feedback coil
being powered electrically, and dimensioned and designed such that the
magnetic field generated by the assembly formed by the locking and
20 feedback coils, when the locking/unlocking coil is powered electrically, is less
than the magnetic field generated by the locking/unlocking coil at a point
located at a distance at least equal to a predetermined threshold (greater
than 0) of the winch, the electrical energizing and de-energizing of the
feedback coil being synchronized with the electrical energizing and
25 respectively de-energizing of the locking/unlocking coil.
This solution at least partially compensates for the magnetic field
generated by the locking/unlocking coil away from the winch. In other words,
the feedback coil enables the magnetic signature of the device to be limited
30 away from the winch. Consequently, the device according to the invention
generates a magnetic field weaker than the magnetic field of the winch. As
such, it can be used in mine warfare on board a mine warfare ship.
This solution also makes it possible to ensure that, when the
locking/unlocking coil is powered electrically, the magnetic field that it
35 generates is at least partially compensated for, regardless of the value of the
current crossing the locking/unlocking coil. It should be noted that the
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electrical field generated by the locking/unlocking coil is variable due to the
fact that there are at least two usage phases of the winch in which the drum
is immobilized or respectively in motion (to wind or unwind the cable).
5 Advantageously, the feedback coil and the locking/unlocking coil
are powered by the same generator.
This advantageous solution makes it possible to at least partially
compensate for the magnetic field generated by the electromagnetic brake
when the locking/unlocking coil is powered electrically, and it does not
10 require means for synchronizing generation of a magnetic field by the two
coils. Synchronization occurs automatically on account of the two coils being
powered by the same generator. Furthermore, this solution does not require
a specific generator dedicated to reducing the magnetic signature, which
makes the device less cumbersome.
15
Advantageously, the feedback coil is mounted in series with the
locking/unlocking coil.
Advantageously, the product N1*S1 is substantially equal to the
product N2*S2, in which N1 is the number of turns in the locking/unlocking
20 coil, N2 is the number of turns in the feedback coil, S1 is the surface area of
the turns of the locking/unlocking coil and S2 is the surface area of the turns
of the feedback coil.
Advantageously, the feedback coil is powered electrically by a
second generator and the device includes means for synchronizing the
25 electrical energizing and de-energizing of the feedback coil with the electrical
energizing and respectively de-energizing of the locking/unlocking coil.
Advantageously, the feedback coil is arranged such that the first
current passing through the locking/unlocking coil and the second current
passing through the feedback coil flow counterclockwise.
30 Advantageously, the locking/unlocking and feedback coils are
coaxial.
Advantageously, the feedback coil is dimensioned and arranged
such as not to disturb operation of the locking/unlocking means.
Advantageously, the feedback and braking coils are spaced along
35 the axis of the locking/unlocking coil.
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Advantageously, the section of the conducting wire forming the
winding of the feedback coil, the length of same and the material from which
same is made are chosen such that the resistance of the feedback coil is at
least 10 times less than the resistance of the locking/unlocking coil.
5 Advantageously, the device includes means for at least partially
compensating, at a point located away from the vicinity of the winch, for the
magnetic field generated by the permanent residual magnetization of the
winch resulting from the electrical powering of the locking/unlocking and
feedback coils used to release the drum without exerting any braking torque
10 on same.
Advantageously, the means for at least partially compensating for
the magnetic field generated by the permanent residual magnetization of the
winch include a permanent magnetization assembly including at least one
permanent magnet.
15 Advantageously, the device includes at least one permanent
magnet having a north-south axis parallel to the axis of the locking/unlocking
coil.
Advantageously, the device includes a third coil mounted to be
powered permanently by a supplementary generator able to generate a direct
20 current, the third coil being dimensioned and arranged such as to
compensate at least partially, at a point located away from the vicinity of the
winch, for the magnetic field generated by the permanent residual
magnetization of the winch caused by the electrical powering of the locking
and feedback coils used to release the drum without exerting any braking
25 torque on same.
The invention also relates to mine warfare equipment including a
mine warfare ship carrying a device according to the invention, said device
also including said towing cable and a mine warfare device such as a sonar
or a device for simulating the magnetic and/or acoustic signature.
30
Other features and advantages of the invention are set out in the
detailed description below, given as a non-limiting example and with
reference to the attached drawings, in which:
- Figure 1 is a schematic representation of a ship fitted with a
35 device according to the invention,
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- Figure 2 is a schematic representation of the elements of the
device according to the invention,
- Figure 3 is a schematic representation of the elements of an
example of locking/unlocking means,
5 - Figure 4 is a schematic representation of the magnetic fields
generated by the locking/unlocking and feedback coils on the
axis of the coils when they are coaxial, as shown in figure 2,
- Figure 5 is a schematic representation of an assembly in series
of the locking/unlocking and feedback coils,
10 - Figure 6 is a schematic representation of an assembly in
parallel of the locking/unlocking and feedback coils.
In the figures, the same elements are indicated using the same
reference signs.
15 Figure 1 shows a ship 2 fitted with a device for winding and unwinding
a cable according to the invention.
This device includes a winch 1 installed on a mine warfare ship 2
towing a mine warfare device 3 using a tow cable 4 arranged such that it can
be wound about the winch 1. The water level is shown using a dot-dash line.
20 In the embodiment in the figure, the mine warfare device 3 is an active
sonar in the form of a volumetric transceiver antenna. This device could be
any other type of sonar or a device for simulating the magnetic and/or
acoustic signature of a ship. These devices make it possible to simulate the
magnetic field or the acoustic waves generated by a ship away from the ship
25 such as to cause any mines to explode away from the ship.
The winch 1 is dimensioned such that it can wind the tow cable 4
about a drum 6, shown in figure 2, unwind same and lock same in winding
and unwinding states to enable the mine warfare device 3 to be recovered,
placed in the sea and respectively held in operational position, as shown in
30 figure 1, or in stowed position.
As shown in figure 2, the winch 1 includes a chassis 5 and the drum 6
which is movable in rotation in relation to the chassis 5 about a first axis x1. It
also includes means for driving the drum 6 including an electric motor 7
enabling the drum 6 to be driven in rotation in relation to the chassis about
35 the first axis x1.
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The drive means also include a device 8 for coupling the motor 7 to
the drum 6 to transform a rotational movement of the rotor 10, shown in
figure 3, of the motor 7 in relation to the chassis 5 about a second axis x2,
that is for example but not necessarily perpendicular to the axis x1, into a
5 rotational movement of the drum about the axis x1.
In other words, the rotation of the rotor 10 in relation to the chassis 5
about the axis x2 drives the drum 6 in rotation about the axis x1.
The coupling means 8 are, for example, a chain or a belt or a gear
mechanism. The person skilled in the art is able to effect such coupling using
10 a multitude of technical means.
The winch 1 also includes locking/unlocking means 9. These
locking/unlocking means 9 include an electromagnet with a first induction coil
90 referred to as the locking/unlocking coil and shown in figure 3, arranged to
be powered by power supply means including a generator 11.
15 The generator 11 may be built into the winch, as is the case in
figure 2. In figure 2, it is rigidly connected to the chassis 5. It is more
specifically built into a housing or cabinet 12 rigidly connected to the chassis
5. In a variant, the generator is located remotely on the ship, for example in a
cabinet.
20 The generator 11 generates a direct current. The direct current may
be constant or unidirectional variable current that can have several different
values, or rectified alternating current.
The locking/unlocking means 9 are zero-current locking/unlocking
means. This is then referred to as a parking brake. They are arranged to
25 immobilize the drum in relation to the chassis when the coil 90 is not being
electrically powered. In other words, they exert a braking torque on the drum
6 when the locking/unlocking coil is not electrically powered. The braking
torque is used to immobilize the drum 6 in relation to the chassis 5 of the
winch.
30 They are also designed to permit the drum 6 to rotate about the axis
x1 when the first coil 90 is electrically powered by the generator without
exerting any braking torque on the drum 6.
This is an ideal arrangement in the context of mine warfare since the
locking/unlocking coil is powered and generates a magnetic field that
35 increases the magnetic signature of the winch only when deploying and
recovering the towed member, and not when the drum is immobilized to hold
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the towed member in operational position (tow line deployed with, for
example, an immersed towed member 3a, 3b, as shown in figure 1) or in
stowed position (tow cable wound about the drum). The drum 6 is more often
immobilized than pivoting.
5 The locking/unlocking means 9 are advantageously arranged such
that the braking torque exerted on the drum 6 is generated by a first braking
torque exerted on the rotor 10.
This conventional type of locking/unlocking means is known to the
person skilled in the art, who may implement different means to carry out
10 same.
Figure 3 shows an example of zero-current locking/unlocking means 9
arranged such that the braking torque exerted on the drum 6 is generated by
a first braking torque exerted on the rotor 10, the value of which depends on
the magnetic field created by the locking/unlocking coil 90.
15 In this example, the locking/unlocking means 9 include a
locking/unlocking coil 90 rigidly connected to the chassis 5 of the winch. They
also include a disk 91 made of a magnetic material, such as steel or another
metal, constrained to rotate, in relation to the chassis 5, about the second
axis x2, and movable along the second axis x2 under the effect of the
20 magnetic field created by the coil 90. It is arranged such that it bears against
the rotor 10 if there is no voltage at the terminals of the coil 90, thereby
creating a first braking torque on the rotor 10 that prevents the rotor from
rotating about the first axis x1. This torque is passed onto the drum 6 via
coupling means 8, and the drum 6 is immobilized.
25 The disk 91 is arranged such that when there is voltage at the
terminals of the locking/unlocking coil 90, under the effect of the first
magnetic field generated by the locking/unlocking coil 90, it is attracted by the
coi! 90 such as to bear against same and to cease to exert any braking force
on the rotor 10. The rotor can then turn unhindered, the drum 6 is freed to
30 rotate and the coil exerts no braking force on the drum 6.
The person skilled in the art is able to carry out this type of
locking/unlocking means in different ways.
The electromagnet may be formed by the first coil 90 or also include a
core of soft ferromagnetic material. In the absence of current, the disk 91 can
35 be held against the rotor 10 by a spring. In the presence of current, the first
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magnetic field opposes the force exerted by the spring such as to move the
disk 91 against the coil 90 thereby permitting the rotor and the drum to rotate.
Significant force is required to move the disk 91, which means that the
first coil has to be supplied with a strong current, which results in generation
5 of a significant magnetic field by the coil of the brake 90.
The device also includes means for reducing the signature of the
winch. These means also include a second coil 100, referred to as the
feedback coil. In other words, the winch is fitted with a feedback coil. The
feedback coil 100 is powered electrically, dimensioned and arranged such
10 that the module, i.e. the intensity of the magnetic field generated by the
assembly formed by the locking/unlocking and feedback coils 90, 100, when
the locking/unlocking coil is powered electrically is less than the module of
the magnetic field generated by the locking/unlocking coil 90 at a point
located at a distance at least equal to a predetermined distance threshold.
15 Furthermore, the electrical energizing and de-energizing of the feedback coil
100 are synchronized with the electrical energizing and respectively deenergizing
of the locking/unlocking coil 90.
In other words, the feedback coil 100 is arranged to at least partially
compensate for the magnetic field generated by the locking/unlocking coil
20 away from the coils or from the winch when the locking/unlocking coil is
energized electrically.
The distance threshold is a distance threshold guaranteeing that the
point is away from the winch and advantageously from the ship to which it is
attached. The distance threshold is for example 10 m.
25 Advantageously, the feedback coil 100 is assembled to be powered
electrically by said generator 11. The two coils are therefore powered by the
same generator.
In addition to the advantages set out above, if the generator is built
into the winch 1, the device according to the invention does not require an
30 external energy source to power the winch. It is independent of the ship. This
makes assembly and disassembly of such a device on the mine warfare ship
simple.
In another embodiment, not shown, the feedback coil is powered
35 by a second generator separate from the first generator. The device includes
means for synchronizing the electrical energizing and de-energizing of the
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feedback coil with the electrical energizing and respectively de-energizing of
the locking/unlocking coil.
It should be noted that an induction coil has an axis that passes
5 through the center of the coil and that extends substantially perpendicular to
the plane in which a turn of the coil extends. A turn may have different
shapes, for example an overall square or circular shape.
Advantageously, as shown in figure 4, the feedback coil 100 is
assembled such that the first current i1 flowing through the locking/unlocking
10 coil 90 and the second current i2 flowing through the feedback coil 100 flow
counterclockwise. This is carried out by an electrical assembly and a suitable
arrangement of the winding of the feedback coil 100. The feedback coil can
be arranged such as to have a second winding of a second electrical
conductor provided in the opposite direction to the first winding of a first
15 electrical conductor forming the locking/unlocking coil 90.
Advantageously, the feedback coil 100 is arranged such that the axis
of same is parallel to the axis of the locking/unlocking coil 90.
Advantageously, as shown in figure 4, the feedback coil 100 is
arranged such that it is coaxial with the locking/unlocking coil 90.
20 Consequently, when the coils 90, 100 are powered electrically, the magnetic
field vectors B1 and B2 generated by the two respective coils 90 and 100, at
a point P of the axis of the coils, are opposed (for greater clarity, each coil is
shown as one turn in figure 4). This positioning optimizes compensation
since the fields generated by the coils are greatest on the axis of the coils.
25 In the embodiment shown in the figures, the axis x of the coils is the
first axis x1.
In a variant, the axis of the feedback coil 100 is the same as the axis
on which the intensity of the first magnetic field generated by the
locking/unlocking means is greatest. Indeed, this axis can be offset in relation
30 to the axis of the locking/unlocking coil 90.
Advantageously, the feedback coil 100 is dimensioned and arranged
such that the module, i.e. the intensity, of the magnetic field B generated by
the assembly formed by the first and second coils 90, when same are
powered electrically by the generator 11, is less than the module, i.e. the
35 intensity, of the magnetic field generated by the first coil 90 at a point located
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at a distance at least equal to the distance threshold and on the axis of the
coils.
In the embodiment shown in the figures, the feedback coil 100 is
positioned to surround the drive means. More specifically, it is positioned to
5 surround the motor 7.
In the embodiment in figure 2, the drive means and the
locking/unlocking means are arranged in a housing B or assembly rigidly
connected to the chassis 5, shown in bold. The motor 7 and the
locking/unlocking means 9 are shown using dotted lines since they are not
10 normally visible as they are surrounded by the housing B.
The feedback coil 100 is rigidly connected to said housing. In other
words, the coil 100 is rigidly connected to the chassis 5. The device
according to the invention is therefore mechanically and electrically
independent of the ship if the generator 11 is also rigidly connected to the
15 chassis 5.
The dimensioning of the coil 100 depends on the material of the
conducting wire forming the winding of the coil, the radius of the turns
forming the winding or the section of same, and on the number of turns in the
20 winding.
At a significant distance from the coils (i.e. at a distance greater than
the distance threshold), the respective coils 90, 100 are considered to be
assemblies comprising respective numbers N1 and N2 of turns with the same
respective centers C1 and C2 corresponding to the respective centers of the
25 coils 90, 100.
The first magnetic field B1 generated by the locking/unlocking coil 90
at a point P located on the axis of same is proportional to i1*N1*S1/D13 in
which i1 is the current flowing through the locking/unlocking coil 90, N1 is the
number of turns in the locking/unlocking coil 90, S1 is the surface area
30 delimited by the coils of the winding forming the locking/unlocking coil and D1
is the distance separating the point from the locking/unlocking coil 90.
The second magnetic field B2 generated by the feedback coil at a
point on the axis of same is proportional to i2*N2*S2/D23 in which i2 is the
current flowing through the feedback coil, N2 is the number of turns in the
35 feedback coil, S2 is the surface delimited by the turns of the winding forming
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the feedback coil and D2 is the distance separating point P from the
feedback coil 100.
Away from the vicinity of the winch 1, the distances D1 and D2 are
considered to be substantially equal.
5 Advantageously, as shown in figure 5, the feedback coil 100 is
mounted in series with the locking/unlocking coil 90. As such, the current
flowing through the two coils 90, 100 is identical. This facilitates dimensioning
of the device. The locking/unlocking and feedback coils are shown as
inductors with a first value L1 and respectively a second value L2 associated
10 with a first resistor R1 and respectively a second resistor R2.
Advantageously, the feedback coil 100 is dimensioned and arranged
such that the intensity of the magnetic field generated by the device at a point
located on the axis of the coils is less than a first predetermined intensity
when the coils are powered by a predetermined current greater than zero
15 ensuring the drum is free to rotate.
To compensate at least partially for the first magnetic field B1 at point
P, it is sufficient to experiment with the second number of turns and on the
second turn surface.
The locking/unlocking coil is advantageously dimensioned such that
20 the product N1*S1 is substantially equal to the product N2*S2. Such
dimensioning results in a good compromise between the actual
compensation rate of the magnetic field and ease of dimensioning.
In practice, to dimension the coil, a feedback coil 100 with a
predetermined surface area (or radius) is selected and installed on the winch
25 1. A position is selected at a predetermined point P located at a significant
distance from the coils on the axis of the coils, then the number of turns in
the winding forming the feedback coil is adjusted until the module of the
magnetic field measured at the point in question is below a first
predetermined threshold for a predetermined current flowing through the
30 locking/unlocking coil. The products N1*S1 and N2*S2 are now not equal but
substantially.equal on account of the significant external disturbances caused
by any other components making up the electromagnet (presence of
magnetic material inside the coii (core effect)) and due to the fact that the
center of the coils is distant on the axis x2 and the fact that the first threshold
35 can be not zero. "Substantially" means that N1*S1 and N2*S2 are between
5% and 10%, to the nearest percentage point.
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In a variant, as shown in figure 6, the feedback coil 100 is mounted in
parallel with the locking/unlocking coil 90.
Advantageously, the feedback coil 100 is arranged and dimensioned
5 such as not to disturb operation of the locking/unlocking means. In other
words, the position of the feedback coil is selected such that when it is
powered electrically with the predetermined current, the drum is not subject
to any braking force.
To do so, the feedback coil 100 is advantageously positioned away
10 from the locking/unlocking means 9, i.e. the extremities of the feedback and
braking coils facing one another are spaced out on the axis of the
locking/unlocking coil 90. Advantageously, the distance separating the coils
is greater than a second predetermined threshold between 5 and 50 times
the distance separating the locking/unlocking coil 90 and the magnetic
15 element 91. The distance separating the two coils is the distance separating
the adjacent (i.e. facing) extremities of the respective windings of same,
parallel to the axes of the coils. This embodiment is shown in figure 2, the
locking/unlocking coil 100 surrounds the motor 7 and not the
locking/unlocking means 9.
20 Advantageously, the section of the conducting wire forming the
winding of the feedback coil 100, the length of same and the material of
same are chosen such that the resistance of the feedback coil is at least 10
times less than the resistance of the locking/unlocking coil. This obviates the
need to significantly reduce the current that the generator causes to flow
25 through the first coil.
The resistance of the locking/unlocking coil is given by the following
formula R1 = pl*H/ s1 in which s1 is the section of the cable from which it is
made, pi is the conductivity of the conducting wire from which it is made and
11 is the length of the conducting wire from which it is made. The resistance
30 of the feedback coil is given by the following formula R2 = p2*!2/ s2 in which
s2 is the section of the cable from which it is made, p2 is the conductivity of
the conducting wire from which it is made and 12 is the length of the
conducting wire from which it is made.
Advantageously, the section of the conducting wire forming the
35 winding of the feedback coil is greater than the section of the conducting wire
forming the winding of the locking/unlocking coil.
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In order to limit the magnetic signature of the towing device according
to the invention, the number of magnetic elements it comprises, in particular
to form the winch 1, is advantageously limited.
5 It is not possible to make a winch 1 with no magnetic elements.
Consequently, when the two coils 90, 100 generate magnetic fields, they
contribute to magnetizing the magnetic elements of the winch. This
magnetization tends to remain once the coils are no longer being powered
electrtcaliy (hysteresis). In other words, the winch 1 will generate a third
10 permanent magnetic field caused by the magnetization of the magnetic
elements of the winch under the effect of the magnetic fields created by the
coils. This third magnetic field is considered permanent since it exists
permanently, once the coils have been powered for the first time by the
generator.
15 The device according to the invention advantageously includes means
110 for compensating, at least partially and at a point located away from the
vicinity of the winch, preferably on the axis of the locking/unlocking coil, for
the magnetic field generated by the permanent residual magnetization of the
winch 1 caused by the electrical powering of the locking/unlocking and
20 feedback coils with a current flowing through the locking/unlocking coil
intended to release the drum without exerting any braking torque on same.
In other words, these means are dimensioned and arranged such that
the intensity of the magnetic field generated by the winch 1 away from the
vicinity of the winch, preferably on the axis of the locking/unlocking coil, when
25 the coils 90, 100 are not being powered electrically by the generator 11, is
less than a second predetermined magnetic field threshold (for example
around 5-10% of the intensity of the magnetic field created by the
locking/unlocking coil on its own) after the generator 11 has powered the
locking/unlocking coil with a current intended to permit the drum 6 to rotate
30 without exerting any braking torque on same.
In the embodiment in figure 2, these compensation means include a
permanent magnet 110 positioned such as to have a north-south axis parallel
to the coil axis and having a plane of symmetry passing through the axis of
the coils x1. This permanent magnet is for example rotationally symmetrical
35 about the axis of the coils. This permanent magnet is rigidly connected to the
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chassis 5. In the embodiment in figure 5, it is adjacent, along the axis x, to
the locking/unlocking means 9.
In a variant, these means include a permanent magnetization
assembly comprising at least one permanent magnet, and potentially more,
5 the number and respective positions of which are determined to at least
partially compensate, at a point located away from the vicinity of the winch,
for the magnetic field generated by the permanent residual magnetization of
the winch 1 resulting from the electrical powering of the locking/unlocking and
feedback coils, used to release the drum without exerting any braking torque
10 on same. They preferably have north-south axes parallel to the axis of the
locking/unlocking coil, and for example a plane of symmetry passing through
the axis of the locking/unlocking coil.
In a variant, these means include a third coil mounted to be powered
15 permanently by a supplementary generator able to generate a direct current,
the third coil being dimensioned and arranged such as to compensate at
least partially, at a point located away from the vicinity of the winch, for the
magnetic field generated by the permanent residual magnetization of the
winch 1 caused by the electrical powering of the locking/unlocking and
20 feedback coils used to release the drum without exerting any braking torque
on same.
Advantageously, the third coil is coaxial to the first and second coils.
Given that the residual permanent magnetization of the elements of
the winch is not known in advance, this dimensioning and this positioning are
25 carried out empirically, for example by measuring the residual magnetic field
generated by the winch when the coils are not being powered electrically,
after the generator 11 has powered the locking/unlocking coil with a current
to enable the drum 6 to rotate without exerting any braking torque on same.
The device comprises only the winch and the compensation means as
30 described above. It may also include the towing cable and the mine warfare
device.
The invention also relates to mine warfare equipment including a mine
warfare ship carrying a device according to the invention.

CLAIMS
1. A device for winding and unwinding a cable comprising a winch
(1) comprising a chassis (5), drive means and a drum (6),
characterized in that the drive means include an electric motor (7)
used to drive a drum (6) in rotation in relation to the chassis (5),
means (9) for locking/unlocking rotation of the drum (6) in relation to
10 the chassis (5) to prevent and permit rotation of the drum in relation to
the chassis (5), the locking/unlocking means (9) including a first
induction coil (90) referred to as the locking/unlocking coil, the
locking/unlocking means being designed to immobilize the drum (6) in
relation to the chassis (5) when the locking/unlocking coil (90) is not
15 powered electrically, the device also including a second induction coil
(100), referred to as the feedback coil, said feedback coil (100) being
powered electrically, and dimensioned and designed such that the
magnetic field produced by the assembly formed by the locking and
feedback coils (90), (100), when the locking/unlocking coii is powered
20 electrically, is less than the magnetic field generated by the
locking/unlocking coil (90) at a point located at a predetermined
distance from the winch (1), the electrical energizing and deenergizing
of the feedback coil being synchronized with the electrical
energizing and respectively de-energizing of the locking/unlocking coil
25 (90).
2. The device as claimed in the preceding claim, in which the
feedback coil (100) and the locking/unlocking coil (90) are powered by
the same generator (11).
30
3. The device as claimed in claim 2, in which the feedback coil
(100) is mounted in series with the locking/unlocking coil (90).
4. The device as claimed in claim 2, in which the product N1*S1 is
35 substantially equal to the product N2*S2, in which N1 is the number of
turns in the locking/unlocking coil (90), N2 is the number of turns in the
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feedback coil (100), S1 is the surface area of the turns of the
locking/unlocking coil (90) and S2 is the surface area of the turns of
the feedback coil (100).
5 5. The device as claimed in claim 1, in which the feedback coil is
powered electrically by a second generator, the device including
means for synchronizing the electrical energizing and de-energizing of
the feedback coil with the electrical energizing and respectively deenergizing
of the locking/unlocking coii (90).
10
6. The device as claimed in any one of the preceding claims, in
which the feedback coil (100) is arranged such that the first current
flowing through the locking/unlocking coil (90) and the second current
flowing through the feedback coil (100) flow counterclockwise.
15
7. The device as claimed in the preceding claim, in which the
locking/unlocking and feedback coils (90), (100) are coaxial.
8. The device as claimed in any one of the preceding claims, in
20 which the feedback coil (100) is dimensioned and arranged such as
not to disturb operation of the locking/unlocking means.
9. The device as claimed in the preceding claim, in which the
feedback and braking coils (100), (90) are spaced along the axis of the
25 locking/unlocking coil (90).
10. The device as claimed in any one of the preceding claims, in
which the section of the conducting wire forming the winding of the
feedback coil (100), the length of same and the material from which
30 same is made are chosen such that the resistance of the feedback coil
(100) is at least 10 times less than the resistance of the
locking/unlocking coil (90).
11. The device as claimed in any one of the preceding claims,
35 including means for at least partially compensating, at a point located
away from the vicinity of the winch, for the magnetic field generated by
the permanent residual magnetization of the winch (1) resulting from
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PCT/EP2013/069675
the electrical powering of the locking/unlocking and feedback coils
(90), (100) used to release the drum without exerting any braking
torque on same.
12. The device as claimed in the preceding claim, in which the
means for at least partially compensating for the magnetic field
generated by the permanent residual magnetization of the winch (1)
include a permanent magnetization assembly including at least one
permanent magnet.
13. The device as.claimed in the preceding claim, including at least
one permanent magnet (110) having a north-south axis parallel to the
axis of the locking/unlocking coil.
14. The device as claimed in any one of claims 11 to 13, including
a third coil assembled to be powered permanently by a supplementary '
generator able to generate a direct current, the third coil being
dimensioned and arranged such as to compensate at least partially, at
a point located away from the vicinity of the winch (1), for the magnetic
field generated by the permanent residual magnetization of the winch
(1) caused by the electrical powering of the locking and feedback coils
(90), (100) used to release the drum without exerting any braking
torque on same.
15. Mine warfare equipment including a mine warfare ship carrying
a device as claimed in any one of the preceding claims, said device
also including said towing cable and a mine warfare device such as a
sonar or a device for simulating the magnetic and/or acoustic
signature.