EP3341530B1 - Dredger for the dispersion of aquatic sediments - Google Patents

Description

The invention relates to the field of dredging of aquatic bottoms and in particular dredging in ports.

Dredging is a port engineering operation that involves the extraction of materials, such as sediments, from an aquatic bottom. In particular, dredging is carried out in ports to limit siltation of the aquatic bottom or in the channels to ensure a minimum draft to allow navigation.

Several dredging techniques are known.

The so-called traditional techniques are divided into two main families: mechanical dredging and hydraulic dredging. Mechanical dredging involves excavating the aquatic bottom by means of a mechanical shovel; Hydraulic dredging consists of breaking up, vacuuming and then rejecting the sediments by means of a pump equipped with a rotary cutter. The sediments are then recycled or simply discharged by sea, for example during operations of clapage (that is to say of rejection at sea).

These traditional techniques are restrictive.

First, their costs and implementation time are dissuasive. Port managers therefore limit dredging operations, which impedes good port operations and reduces their attractiveness for users. In addition, a long interval between two dredging operations increases the amount of sediment to be removed during the next dredging operation. Therefore, the administrative authorizations, which are mandatory for all dredging operations, are more difficult to obtain because they are only issued after studying the technical feasibility of the dredging, the nature of the sediments, the consultation of the local residents if necessary. , and are valid only for a specific volume of sediment to be treated. Thus, the larger the volume of sediment to be evacuated, the more difficult it is to obtain an administrative authorization with regard to the duration of the dredging operation.

Then, these traditional techniques impose the delimitation of a dredging zone whose extent and randomness (due in particular to climatic hazards) limit and make uncertain the navigable zones. In fact, it is common for a port to be completely sentenced because of a dredging operation, to the detriment of a good exploitation of the port.

In addition, traditional techniques are not without consequences for the local flora and fauna, which adapt to the aquatic background in which they evolve and which are disturbed by an excavation or a sudden aspiration in their environment.

In addition, local residents may object to the issuance of administrative authorizations due to noise and aesthetic disturbances caused by traditional dredging operations (presence of cranes, excavators, suction pipes, treatment units, transport trucks). extracted sediments, palisades).

Another technique is to periodically resuspend sediment in the water that accumulates on the aquatic bottom. This technique replaces traditional techniques because it is less expensive, which makes it possible to reduce the intervals between two dredging operations.

In this sediment resuspension technique, an agitator mixes the aquatic bottom by taking advantage of the natural hydrodynamics of the harbor basins (eg the tide) to drain sediments: the ebb tide draws suspended sediments out of the sea. which limits their accumulation and allows for regular dredging without the need for excavation or removal of sediments.

The impact of resuspension on the ecosystem is low because this technique simply increases and accelerates the natural dynamics of current flows in the port basin.

Resuspension also uses essentially submarine means, whose visibility, clutter and noise are low, which residents do not have to complain about.

The document US 4,073,078 (LEITZ ) describes a machine for dispersing sediments accumulated on an aquatic background, this machine comprising a floating vessel having a bow and a stern, and an underwater structure having at least one leg and a rotary agitator mounted on the leg, the leg being hingedly mounted relative to the building between a working position in which the leg is deployed to anchor in the aquatic bottom, and a rest position in which the leg is retracted to the building.

This machine has a big problem of stability.

First, the use of a single leg creates a shelter for the building and makes it difficult for an operator to move on the slanted deck.

Then, the use of both legs, if it avoids the heel, puts the building in rocking around the anchors of the legs on the aquatic bottom. Starting the propellers creates a torque effect that increases this rocking movement. This is why it appears necessary to anchor the building on a fixed structure (including dock) by means of cables (ends), which limits the radius of action of the machine.

Finally, the current created by the agitator can carry objects likely to block or even damage its propeller, to the detriment of its efficiency, hence frequent (and expensive) maintenance operations.

The main object of the present invention is to meet the disadvantages of the known techniques.

A first objective is to propose an autonomous sediment dispersion machine, which is perfectly stable during dredging.

A second objective is to propose a sediment dispersion machine ensuring precise and constant quality dredging.

A third objective is to propose a sediment dispersion machine that is easy to use and can be quickly moved during a dredging operation.

A fourth objective is to provide a sediment dispersing machine compact enough to be easily transported, for example from one port to another, by sea or even land.

• un bâtiment flottant ayant une proue et une poupe,
• une structure subaquatique ayant au moins une jambe et un agitateur rotatif monté sur la jambe, la jambe étant montée articulée par rapport au bâtiment entre une position de travail dans laquelle la jambe est déployée pour venir s'ancrer dans le fond aquatique, et une position de repos dans laquelle la jambe est rétractée vers le bâtiment ;

la structure subaquatique comprenant au moins une paire de jambes de - proue montées du côté de la proue du bâtiment et au moins une jambe de poupe montée du côté de la poupe du bâtiment, l'agitateur étant monté entre les jambes de proue, et chaque jambe étant articulée par un mécanisme à parallélogramme déformable.For this purpose, it is proposed, in the first place, a machine for dispersing sediments accumulated on an aquatic background, this machine comprising:

• a floating vessel having a bow and a stern,
• an underwater structure having at least one leg and a rotary agitator mounted on the leg, the leg being articulated relative to the building between a work position in which the leg is deployed to anchor in the aquatic bottom, and a position rest in which the leg is retracted towards the building;

the underwater structure comprising at least one pair of bow legs mounted on the bow side of the vessel and at least one stern leg mounted on the stern side of the vessel, the agitator being mounted between the bow legs, and each leg being articulated by a deformable parallelogram mechanism.

• la structure subaquatique comprend deux jambes de poupe indépendantes l'une de l'autre ;
• la ou chaque jambe de poupe est orientable par rapport au bâtiment flottant ;
• la ou chaque jambe de poupe est orientable d'un angle compris entre 0° et 45° par rapport au bâtiment flottant ;
• l'agitateur comprend un cadre, un concentrateur monté dans le cadre et dans lequel est montée une hélice ;
• le cadre l'agitateur est monté pivotant par rapport à un axe sensiblement perpendiculaire à l'extension des pieds des jambes de proue ;
• le concentrateur est monté en rotation sur le cadre, par rapport à un axe sensiblement perpendiculaire à l'axe autour duquel le cadre pivote par rapport aux pieds. ;
• l'agitateur comprend une grille avant et une grille arrière pour protéger l'hélice de tout corps solide ;
• la machine possède un calculateur et des capteurs d'assiette, de gîte et de niveau de mer, pour déterminer et commander le mouvement des jambes de manière automatique ;
• la liaison entre le calculateur, les capteurs et les jambes est une liaison sans-fil.

Various additional features may be provided, alone or in combination:

• the underwater structure comprises two stern legs independent of one another;
• the or each stern leg is orientable relative to the floating building;
• the or each stern leg is adjustable from an angle between 0 ° and 45 ° relative to the floating building;
• the agitator comprises a frame, a concentrator mounted in the frame and in which is mounted a propeller;
• the frame agitator is pivotally mounted relative to an axis substantially perpendicular to the extension of the legs of the bow legs;
• the concentrator is rotatably mounted on the frame, with respect to an axis substantially perpendicular to the axis about which the frame pivots with respect to the feet. ;
• the agitator comprises a front gate and a rear gate to protect the helix from any solid body;
• the machine has a calculator and sensors of attitude, heel and sea level, to determine and control the movement of the legs automatically;
• the connection between the computer, the sensors and the legs is a wireless link.

• la figure 1 est une vue en perspective d'une machine de dispersion de sédiments dans une configuration de transport ;
• la figure 2 est une vue de côté de la machine de la figure 1 dans une première position de dragage, cette vue comprenant deux médaillons de détail à échelle agrandie ;
• la figure 3 est une vue similaire à celle de la figure 2, la machine étant représentée dans une seconde position de dragage ;
• la figure 4 est une vue de détail, selon l'encadré IV de la figure 3, montrant la dispersion de sédiments lors d'une opération de dragage ;
• la figure 5 est une vue de face de l'agitateur de la machine de dispersion de sédiments des figures précédentes, cette figure comportant deux médaillons de détail à échelle agrandie ;
• la figure 6 est une vue de dessus de la machine de dispersion de sédiments des figures précédentes ;
• la figure 7 est une vue de détail d'une jambe de la machine des figures précédentes ;
• la figure 8 est une vue en perspective arrière de l'agitateur de la machine des figures précédentes, et
• la figure 9 est une vue de détail montrant la cinématique de pliage des jambes de la machine des figures précédentes.

Other objects and advantages of the invention will become apparent in the light of the description of embodiments, given below with reference to the accompanying drawings in which:

• the figure 1 is a perspective view of a sediment dispersion machine in a transport configuration;
• the figure 2 is a side view of the machine from the figure 1 in a first dredging position, this view comprising two medallions of detail on an enlarged scale;
• the figure 3 is a view similar to that of the figure 2 the machine being shown in a second dredging position;
• the figure 4 is a detail view, according to Box IV of the figure 3 , showing sediment dispersion during a dredging operation;
• the figure 5 is a front view of the agitator of the sediment dispersion machine of the preceding figures, this figure comprising two detail medallions on an enlarged scale;
• the figure 6 is a top view of the sediment dispersion machine of the preceding figures;
• the figure 7 is a detail view of a leg of the machine of the preceding figures;
• the figure 8 is a rear perspective view of the agitator of the machine of the preceding figures, and
• the figure 9 is a detail view showing the folding kinematics of the legs of the machine of the preceding figures.

On the figure 1 shows a machine 1 dispersion of sediment 2, hereinafter simply referred to dredge 1, used for dredging funds aquatic 3.

Dredge 1 includes a floating building 4 (the water is represented by a dashed line on the figures 2 and 3 ) having a bow 5 and a stern 6, and an underwater structure 7 comprising a set of legs 8 bow, a set of stern legs 9 and a stirrer 10 for ensuring the dispersion of sediment 2 aquatic background 3 .

Footwork 8 bow comprises two legs 8 of bow each positioned on an edge of the building 4 floating at the bow 5 thereof, and the set of legs 9 of Stern comprises two 9 stern legs each positioned on a floating building edge 4 , at the stern 6 of it.

The floating vessel 4 comprises a hull 11 defining a bridge 12 on which mooring bollards 13 are mounted, at least one engine 14 (two in the example shown in the figures), and a wheelhouse 15 in which are located controls steering of the dredge 1 both for the displacement of it as for the dredging operations themselves.

The motors 14 are for example outboard motors that can be raised to allow the transport of the dredge 1 or its loading on a trailer. However, the engines 14 could be of the inboard type to facilitate the movements on the deck 12 of the dredge 1 and accessibility thereto.

According to embodiments not shown, the floating building 4 may comprise a crane for loading and unloading objects on the dredge 1, and additional floats that are positioned on the port and starboard edges of the hull 11, these floats used to increase the floatation surface (and hence the stability) of the dredge 1.

Advantageously, the floating building 4 has a width strictly less than 3m and a height less than about 3m. These dimensional characteristics allow the transport of the dredge 1 by land without having recourse to an exceptional transport of accompanied convoy type.

According to an advantageous embodiment, the floating building 4 as well as the bow legs 8 , the stern legs 9 and the stirrer 10 are made of a metallic material and preferably an aluminum alloy which, while being rigid , limits the weight of the dredge 1 and thus facilitates its transport and its movements.

The bow legs 8 and the stern legs 9 comprise a number of common elements, which, in the remainder of this description, are given the same names and the same numerical references.

Each leg 8, 9 comprises a base 16 and is articulated relative to the building 4 floating between a working position in which the leg 8, 9 is deployed to anchor its base 16 in the aquatic floor 3 , and a rest position wherein the leg 8, 9 is retracted to the floating building 4 . The articulation of the legs 8, 9 with respect to the floating building 4 is carried out using actuators, in this case a cylinder 17 for folding and an extension cylinder 18 . Alternatively, the actuators could be of any other type such as, for example, a pinion and rack assembly.

Each leg 8 bow comprises a pair of legs 19 in the form of long bars and a deformable parallelogram mechanism comprising a pair of upper connecting rods 20, a pair lower rods 21 substantially parallel to the upper rods 20 and a pair of latches 22, each member of one pair being spaced from the other by spacers 23.

The upper rods 20 of the same pair are separated from each other by spacers 23 fixed at a first end 24 and at a second end 25 of the upper rods 20 , these spacers 23 forming axes of rotation allowing the passage legs 8, 9 from their working position to their rest position v (and reciprocally), as we shall see below.

Similarly, the lower rods 21 of the same pair are spaced apart from each other by other spacers 23 fixed at a first end 24 and at a second end 25 of the lower links 21 , these spacers 23 also forming rotation axes allowing the legs 8, 9 to move from their working position to their rest position.

At their first end 24, the pairs of rods 20, 21 are rotatably mounted relative to the pair of legs 19, the axis of rotation of each pair of rods 20, 21 relative to the pair of legs 19 being formed by the spacers 23.

At their second end 25, the pairs of rods 20, 21 are rotatably mounted on a pair of latches 22, the axis of rotation of each pair of rods 20, 21 relative to the pair of latches 22 being also formed by the spacers 23.

Flip-flops 22 are flat pieces of substantially triangular shape which comprise, at each of their vertices, a hole to allow the rotation of flip-flops 22 relative to another element. Two of the holes rotate the flip-flops 22 relative to the connecting rods 20, 21, the third hole serving to rotate the flip-flops 22 on a pair of plates 26. For the bow legs 8 , the plates 26 are integral with the hull 11 of the floating building 4 , being fixed there for example by welding.

A cylinder 17 for folding is rotatably mounted on the plates 26 and the pair of connecting rods 21 below. More precisely, the body of the folding ram 17 is articulated on the plates 26 and the rod of the folding cylinder 17 is articulated on the spacer 23 connecting the two lower links 21 at their second end 25.

An extension cylinder 18 is rotatably mounted on the pair of upper connecting rods 20 and on the pair of legs 19. Specifically, the body of the extension cylinder 18 is rotatably mounted via a new spacer 23 on the connecting rods. 20 , and the rod of the extension cylinder 18 is rotatably mounted, also via a new spacer 23, on the feet 19.

Advantageously, the bow legs 8 are synchronized in their displacement and connected to one another by the stirrer 10.

In a situation, the cylinder 17 for folding makes it possible to move the bow legs 8 from their rest position to their working position and vice versa, the extension cylinder 18 allowing, in addition to the cylinder 17 for folding, to maintain the feet 19 of the bow legs 8 substantially vertical in their working position, that is to say substantially perpendicular to the deck 12 of the floating building 4 , this orientation of the bow legs 8 improving the efficiency of the agitator 10 as we see below.

As the legs 8 of bow, each leg 9 of Stern comprises a pair of legs 19 in the form of long bars and a deformable parallelogram mechanism comprising a pair of connecting rods 20 above, a pair of connecting rods 21 lower substantially parallel to the connecting rods 20 upper and a pair of rods 27, each element of the same pair being separated from the other by spacers 23.

The upper rods 20 of the same pair are separated from each other by spacers 23 fixed at a first end 24 and at a second end 25 of the upper rods 20 , these spacers 23 forming axes of rotation allowing the passage 9 stern legs from their working position to their rest position (and vice versa), as we will see below.

Similarly, the lower rods 21 of the same pair are spaced apart from each other by other spacers 23 fixed at a first end 24 and at a second end 25 of the lower links 21 , these spacers 23 also forming rotation axes allowing the passage of the stern legs 9 from their working position to their rest position (and vice versa).

At their first end 24, the pairs of rods 20, 21 are mounted in rotation to the pair of feet 19, the axis of rotation of each pair of connecting rods 20, 21 with respect to the pair of feet 19 being formed by the spacers 23.

At their second end 25, the pairs of rods 20, 21 are rotatably mounted on a pair of rods 27, the axis of rotation of each pair of rods 20, 21 with respect to the pair of links 27 being also formed by the rods 27. spacers 23.

At their second end 25, the upper links 20 are, in line with their assembly with the rods 27, rotatably mounted on a pair of plates 26.

For the stern legs 9 , the plates 26 are connected to each other by a shaft, which is rotatably mounted about a vertical axis, on an arm integral with the hull 11 of the floating vessel 4 . This rotational assembly of the stern legs 9 on the floating building 4 allows the stern legs 9 to be oriented by an angle A (measured in a horizontal plane) of approximately 45 ° with respect to the building edge 4 floating, in a direction opposite the floating building 4 , as is visible on the figure 6 . This orientation of the stern legs 9 improves the stability of the dredge 1, as explained below.

A cylinder 17 for folding is rotatably mounted on the plates 26 and the pair of connecting rods 21 below. More precisely, the body of the folding ram 17 is articulated on the plates 26 and the rod of the folding cylinder 17 is articulated on the spacer 23 connecting the two lower links 21 at their second end 25.

As for the bow legs 8 , an extension jack 18 is rotatably mounted on the pair of upper rods 20 and on the pair of legs 19. Specifically, the body of the extension cylinder 18 is rotatably mounted via a spacer 23, on the upper rods 20 , and the rod of the extension cylinder 18 is mounted in rotation, also via a spacer 23, on the feet 19.

In situation, the cylinder 17 for folding allows the passage of the legs 9 stern from their rest position to their working position and vice versa, the cylinder 18 extension allowing, in addition to the cylinder 17 folding, the deployment more 9 stern legs 19 feet far to improve the stability of dredge 1 during dredging operations.

The stirrer 10, clearly visible on the figures 5 and 8 , comprises a frame 28, a concentrator 29, a propeller 30 and a motor 31.

The frame 28 is made by an assembly of tubes, preferably of square profile, welded to each other so as to form a substantially parallelepipedal structure.

Advantageously, the ends of the tubes are not plugged so as to facilitate the entry and exit of water into the tubes, this movement of water in the tubes having the effect of facilitating the descent of the stirrer 10 at the bottom of the tube. the water without the air trapped in the tubes opposes the downward movement.

The frame 28 is rotatably mounted between the pairs of legs 19 of the two bow legs 8 , by means of blocks 32. The rotation, which can then be performed by the frame 28, is a rotation about an axis substantially perpendicular to the extension of the feet 19 of the legs 8 of bow.

The concentrator 29 is in the form of a ring, it is rotatably mounted on the frame 28 of the stirrer by means of opposed fingers forming an axis of rotation of the concentrator 29 substantially perpendicular to the axis of rotation of the frame 28 compared to the feet 19 of the legs 8 of bow. Agitator 10 admits a rotation around a horizontal axis H (lower detail medallion on the figure 5 ) and a rotation around a vertical V axis (upper detail medallion on the figure 5 ). These rotations can be combined, that is to say performed simultaneously.

The propeller 30 is for example of Kaplan type, the angle of inclination of the blades of the propeller 30 can be modified during use.

The hub 29 has an inner diameter slightly greater than the overall diameter of the propeller 30 so that the hub 29 acts as a fluid accelerator to generate a strong current to resuspend sediment 2 present in the water bottom 3 .

In order to protect the helix 30 from any solid bodies present on the aquatic floor 3 and which could be sucked by the current generated by the helix 30, the stirrer 10 is advantageously provided with a rear grill 33 , fixed for example on the concentrator 29, or directly on the frame 28.

The motor 31, which drives the propeller 30 in rotation, is mounted for example on the gate 33 rear.

According to an advantageous embodiment, the dredge 1 further comprises a calculator 34 and sensors 35 attitude, heel and water level, to determine and control the movement of the legs 8, 9 automatically. When the sensors 35 detect heel, a plate or a lack of water, they return the information to the computer 34 which controls the cylinders 17, 18 to change the position of the legs 8, 9 to maintain the building 4 floating in. waterline.

Advantageously, the connection between the computer 34, the sensors 35 and the legs 8, 9 is performed by a wireless link.

In the rest configuration, the dredge 1 can either move on the water thanks to its motors 14, or be transported, by land, on a truck, thanks to its reduced dimensions.

In the rest configuration, the feet 19 of the bow legs 8 and the stern legs 9 are substantially parallel to the deck 12, and the folding jack 17 and the extension jack 18 are respectively substantially in the maximum stroke position, c that is, the cylinder rod is out of the body, and in the minimum stroke position, i.e., the cylinder rod is retracted into the cylinder body.

When drag 1 arrives at its dredging site, an operator deploys the bow step 8 and the stern leg set 9 in their working position.

The kinematics of deployment of the leg games 8, 9 is partially represented on the figure 9 , which more precisely represents the bow step 8 , equipped with the stirrer 10.

During the deployment of the bow legs 8 , from the rest position to the working position, the rod of the cylinder 17 folding gradually enters his body, causing the rotation of the latches 22 relative to the floating building 4 . When the feet 19 are substantially vertical, that is to say substantially perpendicular to the deck 12 of the floating building 4 , the rod of the extension jack 18 protrudes from its body in order to keep the legs 19 substantially vertical until the agitator 10 is in the dredged position.

The dredging position, represented in figure 4 , is obtained when the stirrer 10 is close to the aquatic bottom 3 and the base 16 of the bow legs 8 is anchored in the aquatic bottom 3 .

The angle of inclination of the stirrer 10 can then be adjusted by rotating the frame 28 relative to the feet 19 on the one hand, then by rotation of the concentrator 29 relative to the frame 28 on the other hand. Thus, the stirrer 10 is positioned so as to achieve effective remission of sediment 2 in suspension.

The deployment of the legs 9 of Stern, their rest position to their working position, is similar to that of the legs 8 of bow.

Initially, the rod of the cylinder 17 folding enters slightly in his body, causing the tilting of the rods 27 relative to the building 4 floating and directing the feet 19 of the legs 9 stern to the water. When the pairs of rods 20, 21 are spaced apart from the bridge 12 and do not present any danger for an operator working on the deck 12, the stern legs 9 can be pivoted up to 45 ° with respect to the floating building 4 , in the aim to increase the stability of the dredge 1.

Once the stern legs 9 oriented, the rod of the cylinder 17 folding can continue its entry into the body to direct the pairs of rods 20, 21 to the water. Simultaneously, the stem of the extension cylinder 18 can out of the body to separate the feet 19 of the pairs of rods 20, 21 until the feet 19 are anchored in the aquatic floor 3 .

The figure 3 represents the dredge 1 in a high position of dredging. In this position, the bow legs 8 and the stern legs 9 are both substantially submerged.

During the dredging operation, the sea level falls after the ebb tide. In order to avoid excessive forces being applied to the bow legs 8 and the stern legs 9 , they can be folded back to their rest position, on the control of the computer 34, so as to keep the building 4.

The figure 2 shows the drag 1 in an intermediate dredging position in which the bow legs 8 and the stern legs 9 are partially immersed, the base 16 of the legs 8, 9 still being anchored in the aquatic bottom 3 .

The figure 4 represents a dredging operation, and more precisely illustrates the effect of the agitator 10 on the aquatic background 3 . When the base 16 of the bow legs 8 is anchored in the aquatic bottom 3 and the agitator 10 is actuated, the stirrer 10 generates a current which mixes the aquatic bottom 3 and causes the resuspension of the sediments packed in the bottom. 3 aquatic. The current generated by the agitator 10 produces a sediment cloud 2, which is driven offshore by the sea currents accompanying the ebb tide.

At the end of the dredging operation, the legs 8, 9 are folded back to their rest position, the retraction of the rod of the extension cylinder 18 in its body combined with the outlet of the rod of the cylinder 17 of folding its body causing the withdrawal of the base 16 of the legs 8, 9 out of the aquatic bottom 3 . When the legs 8, 9 are no longer anchored in the aquatic floor 3 , they are folded back to their rest position, in which the dredge 1 can be moved to another dredging site by land or sea, or be moored to a dock pending next use or displacement.

In a variant not shown in the figures, the dredge 1 includes only one leg 9 stern. Advantageously, the single leg 9 is positioned in a central portion of the stern 6 of the dredge 1.

Unlike the pair of stern legs 9 , previously described, the single stern leg 9 is for example steerable +/- 20 ° with respect to the main direction of extension of the dredge 1, in order to maintain the stability of the latter, especially when the movement of the tide is perpendicular to the main direction of extension of the dredge 1.

The dredge 1 which has just been described has several advantages.

Firstly, the dredge 1 is autonomous and can be used in any aquatic environment (sea, port, lake, river, ...).

With its legs 8, 9, the dredge 1 can stabilize, safely, in a dredging zone, even if it is away from a fixed anchor point. In addition, the presence of the motors 14 makes it possible to move the dredge 1 without using an external element such as a tugboat or a boat for example.

Second, the transport of the drag 1 is easy thanks to its small size. Thus, the dredge 1 can be moved by sea with its engines 14 or by land using a simple truck, without having recourse to an exceptional transport convoy accompanied.

Thirdly, the drag 1 is reliable since it comprises protection elements of the propeller 30 of the stirrer 10 and that it limits the forces applied to the legs 8, 9 by following the level of the water when of a falling tide. Thus, the building 4 is still floating, which limits the effort to be provided by the legs 8, 9 to support it.

Fourthly, the swiveling nature of the stern legs 9 makes it possible to move the support points away from each other, which increases the stability of the dredge 1 during the dredging operations, in particular in the face of the thrust generated by the agitator 10 .

Fifth, the dredge 1 is relatively discreet and compact in situation. It does not present a nuisance or discomfort or inconvenience to the operation of a port, for the benefit of users who can navigate without difficulty in the port even during a dredging operation. Thanks to the exploitation of the tidal phenomenon, the systems of decontamination or the trucks for the transport of the evacuated sediments 2 are not necessary, for the benefit of the tranquility and the quality of life of possible residents.

Claims (10)

1. Machine (1) for dispersing sediments (2) that have collected on a bed (3) of a body of water, this machine (1) comprising:

   - a floating vessel (4) having a bow (5) and a stern (6),

   - an underwater structure (7) having at least one leg (8) and a rotary agitator (10) mounted on the leg (8), the leg (8) being mounted in an articulated manner with respect to the vessel (4) between a working position in which the leg (8) is deployed so as to be anchored in the bed (3) of the body of water, and an idle position in which the leg (8) is retracted towards the vessel (4);

   this machine (1) being characterised:

   - in that the underwater structure (7) comprises at least one pair of bow legs (8) mounted next to the bow (5) of the vessel (4) and at least one stern leg (9) mounted next to the stern (6) of the vessel (4);

   - in that the agitator (10) is mounted between the bow legs (8);

   - in that each leg (8, 9) is articulated by a deformable parallelogram mechanism.
2. Machine (1) according to the preceding claim, characterised in that the underwater structure (7) comprises two stern legs (9) independent of one another.
3. Machine (1) according to any preceding claim, characterised in that the or each stern leg (9) can be oriented with respect to the floating vessel (4).
4. Machine (1) according to the preceding claim, characterised in that the or each stern leg (9) can be oriented by an angle between 0° and 45° with respect to the floating vessel (4).
5. Machine (1) according to any preceding claim, characterised in that the agitator (10) comprises a frame (28), a concentrator (29) mounted in the frame (28) and in which a propeller (30) is mounted.
6. Machine (1) according to the preceding claim, characterised in that the frame (28) of the agitator (10) is pivotably mounted with respect to an axis that is substantially perpendicular to the extension of the feet (19) of the bow legs (8).
7. Machine (1) according to the preceding claim, characterised in that the concentrator (29) is mounted in rotation on the frame (28), with respect to an axis that is substantially perpendicular to the axis about which the frame (28) pivots with respect to the feet (19) .
8. Machine (1) according to any of claims 5 to 7, characterised in that the agitator (10) comprises a rear grating (33) to protect the propeller (30) from any solid body.
9. Machine (1) according to any preceding claim characterised in that it has a calculator (34) and sensors (35) of the trim, of the list and of the level of the sea, in order to determine and control the movement of the legs (8, 9) automatically.
10. Machine (1) according to the preceding claim, characterised in that the connection between the calculator (34), the sensors (35) and the legs (8, 9) is a wireless connection.

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