EP0054498B1 - Installation for dredging a sea bottom, particularly for great depths - Google Patents

Description

The present invention relates to an installation for dredging an underwater bottom, for example for carrying out underwater earthworks or for extracting ores at great depths.

Various dredging installations are already known, in particular for dredging at great depths, in particular by suction.

One of these known installations, mentioned in American patent n ° 4212 121 comprises a working head, in contact with the seabed mounted on one end of a rigid arm whose other end is articulated to the hull a floating body, pivotally about a horizontal axis. The working head is able to carry out dredging passes on the seabed having a trajectory in the form of an arc of a circle, under the control of two butterfly cables which are anchored to the seabed in places located on either side of the working head and pass through means fixed to the working head to come and wind on two winches mounted on the floating body and actuable in the opposite direction of rotation. The positioning and advancement of the installation are generally carried out using two vertical anchoring piles mounted vertically mobile at the ends of the floating body. The advancement of the installation is done by pivoting the floating body around one of the two piles which is driven into the seabed, while the other pile is raised.

However, such an installation has considerable drawbacks. Since the carrying arm of the working head is articulated directly to the hull of the floating body, this installation does not allow dredging at great depth and its use is practically limited to depths of the order of twenty meters. Due to the articulation of the arm at a fixed location on the floating body, the working head can only perform one dredging pass for a fixed position of the installation. It is obvious that the obligation to advance the installation using two piles, after each dredging pass, constitutes an extremely troublesome constraint.

Another known dredging installation is mentioned in French patent application No. 2 383 273 which discloses a dredging installation comprising an arm carrying a working head which is mounted on a support movable vertically on the anchoring device . The lateral movement of the working head is controlled by means forming part of the carriage to which the support is connected. On the other hand, the arm has several working positions.

However, the vertical movement of the carriage to which the work head support is connected is used exclusively to bring the support into the work area close to the ground. This results in the major drawback that such an installation cannot work a large area of the ground without it being necessary to change the position of the floating body.

The present invention aims to eliminate the aforementioned drawbacks by providing a solution which allows both dredging at great depth over a large area of the ground without the need to change the position of the floating body.

According to the present invention, this solution consists of a dredging installation, in particular for dredging at great depth, by which an arm carrying a working head is articulated to a support so as to pivot about a horizontal axis and two butterfly cables are provided for the control of each dredging pass movement in the form of a circular arc, which are respectively anchored to the seabed at places located on either side of the working head, outside of the sweep pass trajectory and pass by means fixed to the working head to come and wind on two winches mounted on the floating body, the latter comprising at least one device for anchoring the floating body to the seabed in a fixed working position, which is mounted on the vertically movable floating body between an anchoring position pressed into the seabed and a raised position out of this bottom, characterized in that said arm carrying the head work is mounted on a support which is vertically movable on the anchoring device, at least in the lower part thereof, between a working position in which the arm forms a relatively small angle with the anchoring device and another working position in which it is substantially parallel to the bottom, the vertical movement of the support between the two working positions causing a movement of the working head on the seabed, forwards or backwards, depending on the direction of movement of the support.

According to an advantageous characteristic of the installation according to the invention, it comprises an auxiliary anchoring device vertically movable between a position pressed into the seabed and a position released from this bottom, the auxiliary device being located offset in the direction of widening of the aforementioned annular sector, of the aforementioned anchoring device, along a variable distance.

• La figure 1 est une vue en élévation de l'installation de dragage selon l'invention, dans sa position de travail.
• La figure 2 est une vue de dessus avec arrachement partiel, de l'installation de dragage suivant la figure 1.
• La figure 3 montre l'installation suivant l'invention pendant son avancement vers une nouvelle position de travail, en une vue en élévation; et La figure 4 est une vue en coupe schématique et à plus grande échelle, suivant la direction IV-IV de la figure 3.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating a mode of the invention and in which:

• Figure 1 is an elevational view of the dredging installation according to the invention, in its working position.
• FIG. 2 is a top view, partially broken away, of the dredging installation according to FIG. 1.
• Figure 3 shows the installation according to the invention during its progress towards a new working position, in elevation view; and FIG. 4 is a schematic sectional view on a larger scale, in the direction IV-IV of FIG. 3.

According to the embodiment of the invention, shown in the figures, the dredging installation comprises a floating body 1, such as a ship in the shape of a catamaran, an anchoring device for the ship, produced in the form a vertical stake 2 and a rigid arm 3 which carries at one end a working head 4 and is articulated by its other end to a support in the form of a carriage 5 mounted vertically movable along the anchoring stake 2.

As illustrated in FIG. 4 schematically, the arm 3 is connected to the support carriage 5 by an articulation having a horizontal axis 7.

To ensure its movement along the anchoring stake 2, the carriage is provided with a set of pinions 8 driven by a motor 9 and each meshing with a rack 10 extending along the stake 2. To ensure the retention of the carriage on the pile, the latter may be provided with laterally projecting flanges 11 behind which engage appropriate retaining members 12 associated with the carriage and which for example comprise rollers intended to come into rolling contact with the rear face of the flanges 11.

The dredging installation according to the invention comprises an auxiliary vertical pile 13 which is connected by a connecting device in the form of a parallelogram 14 to a carriage 15 mounted vertically movable along the pile 2 in the same manner as the carriage 5 In the figures, only the carriage drive motor 15 and the rack are shown at 9 'and 10'. This auxiliary pile 13 is further equipped with means allowing a pivoting movement in a vertical plane around the articulation connection of the parallelogram 14 to the carriage 15. Of course the connection between the parallelogram 14 and the auxiliary pile 13 also allows a movement of relative pivoting of these two parts. The means for controlling the pivoting movement of the pile 13 are formed by a cable 17 fixed at one end to the pile and winding at its other end on a winch 18 mounted on the ship 1. It should also be noted that the auxiliary pile 13 is situated substantially in the vertical plane in which the anchor pile 2 and the arm 3 are located with the work head 4, but, with respect to the pile 2, on the side opposite to that of the work head 4.

For the control of the working head 4, the installation comprises a cable 19 which is wound on a winch 20 on board the ship 1 and is fixed at 21 to the end of the arm 3, on which the working head is mounted 4. Thanks to this cable 19, the arm 3 can pivot vertically about its horizontal pivot axis 7 of its articulation to the support carriage 5. The device ensuring the pivoting of the arm 3 around the vertical axis comprises two butterfly cables 22 anchored at 23 to the seabed 16 on either side of the arm 3. Each cable22 passes over a pulley 24 fixed to the lower or free end of the arm 3 and is wound on a winch 25 mounted on the vessel 1, passing over another deflection pulley 26 provided in the upper part of arm 3.

As is apparent in particular from FIGS. 1 and 3, the anchor pile 2 is mounted at 34 on the ship 1, vertically sliding between an anchor position in which its lower end is pressed into the seabed (FIG. 1) and a raised underwater bottom release position (Figure 3). The auxiliary pile 13 is also likely to be driven into the seabed or to assume a raised position.

It should also be noted that the working head 4 can be produced in the form of a suction head whether or not equipped with a cutting tool such as a shovel wheel 27 which can be held in position by a jack 28. Associated with the suction head is a suction pump 29 mounted inside the arm 3 and which delivers the materials sucked through a transfer pipe 30 of these materials to a storage location, not shown.

It should also be emphasized that the motors 9 and 9 'intended for the movement of the carriages 5 and 15 and the suction and discharge pump 29 as well as the actuator 28 can be remote-controlled, for example from the vessel 1, in any case appropriate and known.

• La figure 1 montre l'installation dans une position fixe de travail. La pointe du pieu d'ancrage 2 est enfoncée dans le fond sous-marin 16. Le chariot 5 auquel est articulé le bras 3 porteur de la tête en travail 4 se trouve dans sa position haute. Le chariot est maintenu dans cette position pendant toute la durée d'une passe de dragage effectuée par la tête de travail 4. La trajectoire de cette passe de dragage est en forme d'un arc de cercle représenté en 31 sur la figure 2. Ce mouvement de balayage de la tête 4 suivant l'arc de cercle 31 est commandé à l'aide des deux treuils 25 et des deux câbles de papillonnage 22. Suivant la direction désirée du mouvement de balayage au cours de la passe de dragage, on enroule l'un des deux câbles 22 sur un treuil 25 et relâche l'autre câble en faisant tourner son treuil dans le sens de rotation inverse, de façon synchrone avec la rotation du treuil 25 fonctionnant dans le sens d'un enroulement de son câble.

The dredging installation according to the invention operates as follows:

• Figure 1 shows the installation in a fixed working position. The tip of the anchoring stake 2 is driven into the seabed 16. The carriage 5 to which the arm 3 carrying the working head 4 is articulated is in its high position. The carriage is kept in this position for the entire duration of a dredging pass carried out by the working head 4. The trajectory of this dredging pass is in the form of an arc of a circle represented at 31 in FIG. 2. This sweeping movement of the head 4 along the circular arc 31 is controlled using the two winches 25 and the two butterfly cables 22. According to the desired direction of the sweeping movement during the dredging pass, the winding is carried out one of the two cables 22 on a winch 25 and releases the other cable by rotating its winch in the opposite direction of rotation, synchronously with the rotation of the winch 25 operating in the direction of winding its cable.

After completion of the dredging pass 31, the shovel wheel 27 of the working head 4 can be advanced to line 32 representing the trajectory of the next dredging pass, without it being necessary to move the vessel 1 For this, it suffices to move the carriage 5 to which the arm 3 carrying the working head 4 is articulated, at an appropriate distance. Indeed, any vertical movement of the carriage 5 causes movement of the shovel wheel 27 on the seabed, forward or backward in the direction of movement of the carriage 5, since the anchor pile 2 is kept fixed and the shovel wheel 27 is in contact with the seabed 16. The advancement operation of the wheel 27 completed, or immobilizes the carriage 5 and causes the working head 4 to carry out the dredging pass along the arc of circle 32 using winches 25 and cables 22. It is easily understood that the working head 4 can thus sweep by successive parallel passes an annular sector 33 (FIG. 2). The limit of scanning by successive parallel passes without changing the position of the vessel 1 is reached when the carriage 5 is in the position shown in phantom lines in FIG. 1, in which the arm 3 extends horizontally. The exact position of the shovel wheel 27 can be adjusted by means of its jack 28.

It is only after the scanning of the annular sector 33 (FIG. 2) that the ship must be advanced to its next fixed working position. The working head 4, with its shovel wheel 27, remains placed on the bottom 16 and constitutes a fixed point, because of its weight. The auxiliary pile 13 is lowered by displacement of its support carriage 15 downwards, along the anchor pile 2, and inserted into the seabed 16. Then, the anchor pile 2 is lifted out of the bottom 16. Then the carriage 5 is raised to which the arm 3 carrying the working head 4 is articulated, by means of the motor 9 of the carriage for example until the angle a is formed between the axes of the pile 2 and of the arm 3 reaches a value of approximately 45 °. Due to the immobility of the heavy working head 4 on the seabed 16, the upward movement of the carriage 5 causes the desired advancement of the ship 1. Simultaneously the throttle cables 22 are kept taut to prevent the working head 4 from skids on the bottom and moves backwards. Since the auxiliary pile 13 remains in its depressed position in the bottom 16 during the whole operation of advancing the ship 1, the latter is always anchored to the seabed and the advancement operation is perfectly controllable.

When the ship has arrived in its new fixed working position, the anchor stake 2 is again stuck in the bottom and the auxiliary stake 13 raised using its cable 17 and the winch 18. Then the carriage is reassembled 15 along the pile 2 until the auxiliary pile 13 returns to the position shown in Figure 1. The advancement operation is thus completed, and a new dredging operation can begin.

It is easy to understand that the dredging installation according to the invention makes it possible to work on the seabed at depths up to 100 meters and even more and scanning by successive parallel passes without changing the working position of the installation, and this in particular thanks to the articulation of the carrier arm of the working head to a motor carriage movable along the anchoring stake 2 to the seabed 16.

The embodiment which has just been described and which is shown in the figures has been given only by way of example. Of course, many variants can be made to this embodiment. The configuration and mounting of the two carriages on the main anchor pile 2 can be different and of any suitable nature known to those skilled in the art. The working head is also not limited to the structure described and shown. The ship can be equipped with an autonomous or additional propellant device to facilitate the advancement maneuver. It should also be noted that the anchoring stake can be produced in any suitable form and have a cross section of any suitable form.

The extreme part of the pile, which is intended to be inserted into the seabed, is advantageously made in the form of a separate body mounted to rotate and, if necessary, vertically movable in the pile.

The pile can be made up of a multitude of assemblable sections so that it is adaptable to the depth of the seabed.

Claims (9)

1. Dredging plant, particularly for dredging at great depths, whereby an arm (3) carrying a working head (4) is articulated to a support pivotally about a horizontal axis (7) and two circular dredging cables (22) are provided for the control of each movement of dredging pass in the form of an arc of circle, which are anchored to the bottom of the water at places located on both sides, respectively, of the working head, outside the sweeping pass trajectory, and pass through means (21) attached to the working head before winding round two winches (25) mounted on the floating body (1), the latter being provided with at least one device (2) for anchoring the floating body to the bottom of the water in a stationary working position, which is mounted on the floating body vertically movable between an anchoring position driven into the bottom of the water and a position raised out of said bottom, characterized in that the said arm (3) carrying the working head (4) is mounted on a support (5) which is vertically displaceable on the anchoring device (2), at least in the lower portion of the latter, between a working position in which the arm forms a relatively small angle a with the anchoring device and another working position in which it is substantially parallel with the bottom, the vertical displacement of the support (5) between the two working positions bringing about a forward or backward movement of the working head on the said bottom depending on the direction of displacement of the support.

2. A plant according to claim 1, characterized in that the support (5) of the arm (3) carrying the working head (4) is designed in the form of a carriage displaceable by means of a driving device with pinions (8) and a toothed rack (10), the- toothed rack being preferably associated with the anchoring device which may be constituted by a vertical post.

3. A plant according to claim 1, characterized in that it includes an auxiliary anchoring device (3) such as a post, vertically movable between a position of anchoring to the bottom (16) of the water and a raised position, the auxiliary anchoring device (13) being shifted with respect to the anchoring device (2) in the direction of advance of the floating body (1), at a variable distance.

4. A plant according to claim 3, characterized in that the auxiliary anchoring device (13) is connected to a carriage (15) mounted and vertically movable on the anchoring device (2).

5. A plant according to claim 4, characterized in that the carriage (15) includes a driving device with pinions and with a toothed rack (10').

6. A plant according to one of claims 4 or 5, characterized in that the auxiliary anchoring device (13) is connected to the carriage (15) by a parallelogram linkage device (14) of variable shape, pivotally in a vertical plane under the action of actuating means such as a cable (17) and a winch (18) mounted on the floating body.

7. A plant according to one of claims 2 to 6, characterized in that the toothed racks (10,10') for the displacement of the carriages (5, 15) are provided on the anchoring device (2) and in that the carriages (5, 15) carry pinions and motors for driving them.

8. A plant according to one of claims 1 to 7, the working head being a suction head, characterized in that a suction pump (29) is mounted in the arm (3) carrying the working head (4) and intended to force the sucked material into a transfer conduit (30) also extending partially in the arm (3).

9. A plant according to one of claims 1 to 8, characterized in that the position of the working head (4), equipped, if appropriate, with a cutting tool such as a shovel-wheel (27), is adjustable through the medium of an actuator (28) which may be remote-controlled and is mounted between the end of the arm (3) and the working head (4).

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