SE545970C2

SE545970C2 - A dredging system and a method for handling a dredging device of a dredging system

Info

Publication number: SE545970C2
Application number: SE2051367A
Authority: SE
Inventors: Ulf Rickardsson
Original assignee: Kalmar Kommun
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2024-04-02
Also published as: SE2051367A1

Abstract

The invention relates to a dredging system (1). The dredging system (1) comprises a dredging device (10), a first (11), second (12), third (13) and fourth (14) attachment element, a first (15) and second (16) movement control element, a first line (17) connecting the first attachment element (15), the first movement control element (15), the second attachment element (12) with each other and a first motor (18), a second line (19) connecting the third attachment element (13), the second movement control element (16), the fourth attachment element (14) with each other and a second motor (20), and a third line (21) connecting the first movement control element (15), the dredging device (10), the second movement control element (16) with each other and a third motor (22). The invention also relates to a method for handling a dredging device (10) of a dredging system (1).

Description

A DREDGING SYSTEM AND A METHOD FOR HANDLING A DREDGING DEVICE OF A DREDGING SYSTEM Technical field The invention relates to a dredging system and a method for handling a dredging device of a dredging system.

Background art Dredging is the removal of sediments and debris from the bottom of lakes, rivers, harbours, and other water bodies. lt is a routine necessity in watervvays around the world because sedimentation -the natural process of sand and silt washing downstream - gradually fills channels and harbours.

Dredging often is focused on maintaining or increasing the depth of navigation channels, anchorages, or berthing areas to ensure the safe passage of boats and ships. Vessels require a certain amount of water in order to float and not touch bottom. This water depth continues to increase over time as larger and larger ships are deployed. Since massive ships carry the bulk of the goods imported into the country, dredging plays a vital role in the nation's economy.

Dredging is also performed to reduce the exposure of fish, wildlife, and people to contaminants and to prevent the spread of contaminants to other areas of the water body. This environmental dredging is often necessary because sediments in and around cities and industrial areas are frequently contaminated with a variety of pollutants.

When dredging the bottom of a lake for example it is a common measure to use a dredging device especially design for the purpose. EP2434061 A1 discloses such a dredging device. The dredging device comprises a dredging vessel and a dredge suction head connected to the dredging vessel and having a dredge suction opening. The dredge suction opening of the dredge suction head is provided with smooth edges and the dredging device comprises a measuring device for measuring the distance between the dredge suction head and the bottom.

A problem with conventional dredging systems is that one or several educated operators are required to control and monitor the dredging process at all times. The dredging process currently available is therefore both time consuming and costly.

Summarv of the invention lt is an object of the present invention to provide an improvement of the dredging devices according to prior art. A particular object is to provide an automatized dredging system.

According to a first aspect, these and other objects, and/or advantages that will be apparent from the following description of embodiments, are achieved, in full or at least in part, by a dredging system :accordircj to the independent _ -The--eirestging»--aysterïfi--sempsﬁšses-»a--ëifeešgšng--tzietæëeeï-a w j u r är š' :nam rxmrå š-HÉPN ﬂvvå wcms :PHN ﬂH-ﬂiﬂífxrww- vv* niﬂm-wmvx* f: 'ïšaﬂﬂir fsrærå wnmmvxri ! \ NÖ \- \Å) \ Ü RÄÉ l i KÄ l K\ K-*ií \.Vi l\ KJ' íl\§ KJ Él \J' KÄ \Ã \n' \4'\l5 l\v! YYMN :ﬁiﬁﬁﬁš iiw..1f\«..: i rxnnê-"ni mlmvwnmš m är u* Eine* ﬂnwﬂsriﬂﬁsﬂsm *ha ﬁïšvcvl fatta ifs-nä men* \J 5' il\fl fi!! KM Å? I. K-IÉÉ \r'\nïn li »YQÉÜÉJ \ \( IÜÉ\'5.ÅÅ~iÅÅ i. II ø' Å attaeèëaﬁietﬂtt-ešeaﬂieitt,--the-seeentä--ifëevesﬂtteitt--eentifel--eš-ementï--tète--šati-sﬁtšt ﬂH-ﬂiﬂífxrww- vv* niwrwwnvx* n-wïš-ïw *s-'mﬂífx fxtlfw *av Iwan: fw anwa-Pan: Wﬂmšlmr fwwrå f: Hﬁiwfš ii-mzw l\ Kåií \.Vil\ KJ' íl\ !K!! SQ Såií \ Q! L! ! l v' S! l l K\ll§ RÃI \Ã Kﬂí MÉÉ !\Å i I! This is advantageous in that the dredging system is completely automatized and requires no operators, which in turn makes it extremely cost- efficient.

The first movement control element may be movable between the first and second attachment element along the first line by means of the first motor, and the second movement control element is movable between the third and fourth attachment element along the second line by means of the second motor.

The dredging device may be movable between the first and second movement control element along the third line by means of the third motor.

The first motor may be arranged on the first or second attachment element and the second motor may be arranged on the third or fourth attachment element.

The third motor may be arranged on the dredging device.

The dredging system may further comprise a first sensor detecting when the first movement control element is located adjacent to the first or the second attachment element, and a second sensor detecting when the second movement control element is located adjacent to the third or fourth attachment element.

The dredging system may further comprise a third sensor detecting when the dredging device is located adjacent to the first movement control element and fourth sensor detecting when the dredging device is located adjacent to the second movement control element.

The dredging system may further comprise a line tensioning device connected to the third line and adapted to tighten the lines of the dredging system.

The attachment elements may form a four-sided polygon when placed in an area to be dredged by being arranged at a respective corner thereof.

The dredging system may further comprise a control system, such as a PLC-system, adapted to control the first, second and third motor based on input from the first, second, third and fourth sensor.

The first line may extend from a first attachment point on the first movement control element, to a connection point on the first attachment element, from there to a connection point on the second attachment element, and from there to a second attachment point on the first movement control element.

The second line may extend from a first attachment point on the second movement control element, to a connection point on the third attachment element, from there to a connection point on the fourth attachment element, and from there to a second attachment point on the second movement control element.

The third line may extend from a first attachment point on the dredging device, to a connection point on the first movement control element, from there to a connection point on the second movement control element, and from there to a second attachment point on the dredging device.

Each attachment element may comprise a floating device adapted to be placed in a water area to be dredged.

Each floating device may comprise an anchor connected thereto and adapted to maintain the position of the floating device in the water area to be dredged.

According to a second aspect, the objects are achieved in full, or at least in part, by a method for handling a dredging device of a dredging system accordifto to the šrtaiepeizdent bistått: 'i ä. . g f ,. "t . , *i 4?irst-eisfes-tierä--ašeng--a-titšrë-išite--šsy--rtt-sesrts-eš-e--tšsirsl-me-ïserï-rßiasaftigthe-first- vassarementsplittral--eierneriﬂë-be:avsett-a-first-»anci--seeenel-attaeh-sﬁiteiat--eletæfeiat--ètﬁi f: *aßmmﬂ rišrﬁßtšmnﬂ fslmrwre f: 'ïšaﬂﬂlr Hann if' f rm *a-"waﬂ nu* f: 'Fšwﬂr nämt-fw Hmm ﬁwwrwxﬁ ﬂü ÄÄ \ø!5 *ni Ä KJ \ll hu? KJ ÄI\J Ä Ä y Q' !Ä\J' Ä Kﬂí i \ ÄÄÄ \ Ä, l \J'\,I' il .Nïwnßšårxvw šﬂﬁåmw :se ziwcﬂšm-wtiﬁïi .- rxnrr nrvwišﬂs slav tm Hmm íïirrﬂ- *iïs-“ﬂwå-šnw www' wnmxfinrw KÄ ÄKÖ J in \ø 'd är Kqíäv lÜ-É lÉ-š *JKO FKO \JÄ \c'\JÄ ÅÅÉ i\n" Å I .' n ~\.\ Gli v' \\n"n v I G I n J nimr mi' Er Frun o* - :- å Åimß i: n - Énnm - ~ nnnfå :in Ém s ha »w ~ -Ff ~ A4 J) JÉÉÄ\>VÉI\ I!! \1!\.F K >'\J ::\»'l \Ä!) \.F\>'XÜ\JÜÉ .4) J! )§ .4 \>\\>VJJF) .Å :li :\>V Ä ï ÉÉÜ\J\AI Ä\J \J: 'LJ \J \>'\v\li Å *äte-iirst--rwfieverttsnt-eerttrei--såassets-t--š-s-dšspšaeee-a-preëstarnfišnetš-sšš-staassa--šiä- the--sfeeentà-diireetšesﬂiï When the first and second movement control element simultaneously is located adjacent to one respective attachment element, a moving direction of the first and second movement control element may be changed from moving towards said one respective attachment element to moving away from said respective attachment element. lt should be noted that the different embodiments of the dredging system that is described above are exemplifying only. The embodiments may be combined with each other in any suitable way depending on the requirements established for the dredging system. lt should be further noted that the different steps of the method described above may be conducted in any suitable order.

Effects and features of the second aspect of the present invention are Iargely analogous to those described above in connection with the first aspect the inventive concept. Embodiments mentioned in relation to the first aspect of the present invention are Iargely compatible with the further aspects of the invenüon.

Other objectives, features and advantages of the present invention will appear from the following detailed disclosure, from the attached claims, as well as from the drawings. lt is noted that the invention relates to all possible combinations of features.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined othervvise herein. All references to “a/an/the [element, device, component, means, step, etc.]” are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise.

As used herein, the term “comprising” and variations of that term are not intended to exclude other additives, components, integers or steps.

Brief description of the drawinqs The above objects, as well as additional objects, features and advantages of the present invention, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, when taken in conjunction with the accompanying drawings, wherein: Fig. 1 illustrates a perspective view of an exemplary embodiment of a dredging system according to a first aspect of the invention.

Fig. 2 illustrates a perspective view of the dredging system in Fig. 1 when a dredging device thereof is in an end position in a first direction.

Fig. 3 illustrates a perspective view of the dredging system in Fig. 1 when a dredging device thereof is in an end position in a second direction.

Fig. 4 illustrates a perspective view of an attachment element of the dredging system in Fig.

Fig. 5 illustrates a perspective view of a dredging device of the dredging system in Fig.

Fig. 6 illustrates a perspective view of a movement control element of the dredging system in Fig.

Detailed description of preferred embodiments of the invention Fig. 1 illustrates an exemplary embodiment of a dredging system The dredging system 1 is arranged to remove sediments and debris from the bottom of Iakes, rivers, harbours, and other water bodies by using the dredging device 10. The dredging system 1 comprises a dredging device 10, four attachment elements 11, 12, 13, 14, two movement control elements 15,16 and three lines 17, 19, As can be seen in Fig. 1 the attachment elements 11, 12, 13, 14 are positioned such that they together form a four-sided polygon by being arranged at a respective corner of the four-sided polygon. The four-sided polygon defines an area which is to be dredged by the dredging device 10 of the dredging system 1. The first 11 and third 13 attachment element is are arranged at an opposite half side of the area to be dredged compared to the second 12 and fourth 14 attachment element. The dredging device 10 is arranged inside of the four-sided polygon. The first movement control element 15 is arranged between the first 11 and second 12 attachment element and the second movement control element 16 is arranged between the third 13 and fourth 14 attachment element.

Each attachment element 11, 12, 13, 14 ﬂoats in the water and maintains its position in the area to be dredged. This is possible as each attachment element 11, 12, 13, 14 comprises a floating device 11, 12, 13, 14 and an anchor 29 connected to the floating device 11, 12, 13, 14. Also each the movement control element 15, 16 and the dredging device comprises a floating device 37, 40 adapted to keep them floating in the water.

A first line 17 extends from a point on a first movement control element 15 to a point on a first attachment element 11, further to a point on a second attachment element 12 and further to a point on the first movement control element 15 again. The first line 17 is also connected to a first motor 18. The first motor 18 is positioned on the second attachment element 12 but may be positioned on the first attachment element 11 instead. The first line 17 thus connects the first attachment element 11, the first movement control element 15, the second attachment element 12 with each other and with the first motor 18. The first line 17 is fixedly attached to the points on the first movement control element 15. The first line 17 is connected to the points on the first 11 and second 12 attachment element in such a way that the first line 17 may run freely through the points, for example by running through a ring on the attachment element 11, ln a similar manner to the first line 17, a second line 19 extends from a point on a second movement control element 16 to a point on a third attachment element 13, further to a point on a fourth attachment element 14 and further to a point on the second movement control element 16 again. The second line 17 is also connected to a second motor 20. The second motor 20 is positioned on the fourth attachment element 14 but may be positioned on the third attachment element 13 instead. The second line 19 thus connects the third attachment element 13, the second movement control element 16, the fourth attachment element 14 with each other and with the second motor 20. The second line 19 is fixedly attached to the points on the second movement control element 16. The second line 19 is connected to the points on the third 13 and fourth 14 attachment element in such a way that the second line 19 may run freely through the points, for example by running through a ring on the attachment element 13, A third line 21 extends from a point on the dredging device 10 to a point on the first movement control element 15, further to a point on the second movement control element 16 and further to a point on the dredging device 10 again. The third line 21 is also connected to a third motor 22. The third motor 22 is positioned on the dredging device 10. The third line 21 thus connects the dredging device 10, the first movement control element 15, the second movement control element 16 with each other and with the third motor 22. The third line 21 is fixedly connected to the points on the dredging device . The third line 21 is connected to the points on the first 15 and second 16 movement control element in such a way that the third line 21 may run freely through the points, for example by running through a ring on the movement control element 15, As is seen in the figure, the third line 21 also connects to a point on the dredging device 10 on its extension between the first 15 and second 16 movement control element. The third line 21 is connected to this point in such a way that the third line 21 may run freely through the point, for example by running through a ring on the dredging device 10. This point is positioned at an opposite half side of the dredging device 10 compared to the points which the third 21 line is fixedly attached to.

The first motor 18 is adapted to feed the first line 17 through itself. By doing this the first line 17 will move and the first movement control element 15 will move along with it. The first movement control element 17 is in this way moveable between the first attachment element 11 and the second attachment element 12 in a second direction by means of the first motor 18. The second direction is defined as a direction which at least partially extends along a direction between the first 11 and second 12 attachment element and at least partially between the third 13 and fourth 14 attachment element. ln a similar manner, the second movement control element 16 is moveable between the third 13 and fourth 14 attachment element by means of the second motor 20. This as the second motor 20 is adapted to feed the second line 19 through itself such that the second line 19 moves and the second movement control element 16 moves along with it in the second direction.

The third motor 22 is adapted to feed the third line 21 though itself. Thus, the third line 21 will move and the dredging device 10 will move along with it. The dredging device 10 is in this way moveable between the first movement control element 15 and the second movement control element 16 in a first direction by means of the third motor 22. The first direction is defined as a direction which at least partially extends along a direction between the first 15 and second 16 movement control element.

Each line 17, 19, 21 of the system 1 is made of carbon fibre. The motors 18, 20, 22 feed the respective lines 17, 19, 21 through the respective motors 18, 20, 22 by means of a silicone coated surface in contact with respective line 17, 19, 21. This material combination is such that a motor 18, 20,22 grips a line 17, 19, 21 even if the line is wet and such that a motor 18, 20,22 no longer grips a line 17, 19,21 when the line 17, 19,21 is stuck and can no longer move.

The dredging device 10 comprises a line tensioning device 27. The line tensioning device 27 is connected to the third line 21 and is adapted to tighten the third line 21. By tightening the third line 21 the lines of the dredging system 1 are all tightened. This as by tightening the third line 21, the first 15 and second 16 movement control element are moved towards the dredging device 10. This until the first line 17 is tightened enough to stop movement of the first movement control element 15 and the second line 19 is tightened enough to stop movement of the second movement control element The line tensioning device 27 is in the form of a reel with the third line 17 attached to it. The reel may tighten the third line 17 by turning by means of a spring or other resilient means, or by a motor. The line tensioning device 27 is arranged to tighten the first line 17 to a predetermined tension which is does when the dredging device 10 is at and end position in the first direction. The predetermined tension is chosen low enough that the motors 18, 20, 22 of the system 1 grip the lines 17, 19, 21 of the system 1and chosen high enough that the lines 17, 19, 21 of the system 1 are kept above the water.

The system comprises a control system 28 in the form of a PLC- system 28. The PLC-system 28 is positioned on the dredging device 10 and is connected to the internet such that it can be controlled remotely via the internet. The PLC-system 28 is further connected to the motors 18, 20, 22 and to sensors 23, 24, 25, 26 of the system wirelessly. The PLC-system 28 may be connected by wire to any sensors 25, 26 positioned on the dredging device The dredging system comprises a first 23, a second 24, a third 25 and a fourth 26 sensor. The first sensor 23 is positioned on the first movement control element 15 and is arranged to detect when the first movement control element 15 is located adjacent to the first 11 or the second attachment element 12. The second sensor 24 is positioned on the second movement control element 16 and is arranged to detect when the second movement control element 16 is located adjacent to the third 13 or the fourth attachment element 14. The third sensor 25 is positioned on the dredging device 10 and is arranged to detect when the dredging device 10 is located adjacent to the first movement control element 15. The third sensor 25 may also be arranged to detect when the first movement control element 15 is located adjacent to the first 11 or the second attachment element 12. The fourth third sensor 26 is positioned on the dredging device 10 and is arranged to detect when the dredging device 10 is located adjacent to the second movement control element 16. The fourth sensor 26 may also be arranged to detect when the second movement control element 16 is located adjacent to the third 13 or the fourth attachment element 14. The sensors 23, 24, 25, 26 are arranged to send information to the PLC-system 28 regarding whether the attachment elements 11, 12 ,13 14, movement control elements 15, 16 and dredging device 10 are located adjacent to each other. The PLC-system 28 is arranged to control the motors 18, 20, 22 based on this received input from the sensors 23,24, 25, Regarding the position of the motors 18, 20, 22 and sensors 23, 24, 25, 26 of the system 1 they can be positioned in the system in alternative ways.

The first motor 18 may alternatively be arranged on the second attachment element 12 or on the first movement control element The second motor 20 may alternatively be arranged on the fourth attachment element 14 or on the second movement control element The third motor 22 may alternatively be arranged on the first movement control element 15 or on the second movement control element lnstead of having a first sensor 23 positioned on the first movement control element 15 there may be one sensor arranged to detect when the first movement control element 15 is located adjacent to the first attachment element 11 and another sensor arranged to detect when the first movement control element 15 is located adjacent to the second attachment elementThe one sensor may be positioned on the first attachment element 11 and the other sensor on the second attachment element 12, respectively, or both positioned on the first movement control element lnstead of having a second sensor 24 positioned on the second movement control element 16 there may be one sensor arranged to detect when the second movement control element 16 is located adjacent to the third attachment element 13 and another sensor arranged to detect when the second movement control element 16 is located adjacent to the fourth attachment element 14. The one sensor may be positioned on the third attachment element 13 and the other sensor on the fourth attachment element 14 respectively or both positioned on the second movement control element The third sensor 25 may alternatively be positioned on the first movement control element The fourth sensor 26 may alternatively be positioned on the second movement control element Fig. 2 illustrates the dredging system 1 in Fig. 1 when the dredging device 10 thereof is in an end position in the first direction. ln this position the dredging device 10 is located adjacent to the first movement control element 15. Another end position in the first direction which is not shown here is when the dredging device 10 is located adjacent to the second movement control element Fig. 3 illustrates the dredging system 1 in Fig. 1 when the dredging device 10 thereof is in an end position in the second direction. ln this position the first movement control element 15 is located adjacent to the second attachment element 12 and the second movement control element 16 is located adjacent to the fourth attachment element 14. Another end position in the second direction which is not shown here is when the first movement control element 15 is located adjacent to the first attachment element 11 and the second movement control element 16 is located adjacent to the third attachment element Fig. 4 illustrates an attachment element 11, 12, 13, 14 of the dredging system 1 in Fig.As can be seen in the attachment element attachment element 11, 12, 13, 14 comprises a floating element 11, 12, 13, 14 adapted to keep the attachment element 11, 12, 13, 14 floating in water. The attachment element 11, 12, 13, 14 further comprises a hole 31 in the floating device 11, 12, 13, 14, a bar 32 positioned over the hole 31 and an anchor 29 connected to the bar 32 and to a winch 33 with a line and which anchor 29 may be raised from and lowered into the water through the hole by means of the winch 33 and line. The anchor 29 is adapted to maintain the position of the floating device 11, 12, 13, 14 in waterwhen the anchor 29 is lowered into the water.

Optionally the attachment element may be device standing on land or on the bottom of the water body. For example the attachment element may be a pole or a rock which has a fixed position.

A sensor 34 is positioned on the attachment element 11, 12, 13, 14 which sensor 34 is arranged to detect when a movement control element 15, 16 is located adjacent to the attachment element 11, 12, 13, 14 and to send this information to the PLC-system 28. The placement of this sensor 34 on the attachment element 11, 12, 13, 14 is optional as a similar sensor may be placed on a movement control element 15, 16 instead.

A motor 35 is positioned on the attachment element 11, 12, 13, 14, this motor 35 is adapted to feed a line 17, 19 through the motor 35 such that a movement control element 15, 16 is moved and is arranged to be able to work in reverse. Thus, the motor 35 is adapted to move the movement control element 15, 16 in two opposite directions.

Fig. 5 illustrates a dredging device 10 of the dredging system 1 in Fig.

The dredging device 10 comprises a floating device 40 which is in the form of four tanks and which is adapted to keep the dredging device 10 floating in water. The floating device 10 also comprises an underwater dredging unit 36 which is arranged such that it can be lowered to the bottom of the area to be dredged and to remove sediments and debris from the bottom. The underwater dredging unit is connected to the dredging unit 10 through lines and is dragged by the dredging device 10 along the area to be dredged.The PLC-system 28 is positioned on the dredging device as well as the line tensioning device 27 and the motor 22 which is connected to the third line The motor 22 adapted to feed the third line 21 through the motor 35 such that the dredging device 10 is moved and is arranged to be able to work in reverse. Thus, the motor 22 is adapted to move the dredging device in two opposite directions.

The line tensioning device 27 is in the form ofa reel and is turned by means of a motor. This motor is connected to the PLC-system 28 wirelessly and is arranged to be controlled by the PLC-system 28 based on input from the sensors 23, 24 ,25, 26 of the dredging system A first sensor 25 of the dredging device 10 is positioned on the dredging device 10. Which sensor 25 is arranged to detect when the dredging device 10 is located adjacent to the first movement control element 15 and to send this information to the PLC-system 28. A second sensor 26 of the dredging device 10 is positioned on an opposite half side of the dredging device 10 compared to the first sensor 25 of the dredging device 10. The second sensor 26 is arranged to detect when the dredging device 10 is located adjacent to the second movement control element 16 and to send this information to the PLC-system Fig. 6 illustrates a movement control element 15, 16 of the dredging system 1 in Fig.

The movement control element 15, 16 comprises a floating device 37 which adapted to keep movement control element 15, 16 floating in water. The movement control element 15, 16 also comprises an anchoring device 41 which is adapted to keep the movement control element 15, 16 stable in water. The anchoring device 41 is arranged at a bottom side of the movement control element 15, 16 below the ﬂoating device A sensor 23, 24 is positioned on the movement control element 15, 16 which sensor 22, 23 is arranged to detect when the movement control element 15, 16 is located adjacent to an attachment element 11,12, 13, 14. ln relation to Fig. 1 this sensor is referred to as the first sensor 23 on the firstmovement control element 15 and as the second sensor 24 on the second movement control element Alternatively, as shown in Fig. 6 the movement control element 15, 16 may comprise two sensors 38, 39 arranged at a respective opposite half side of the movement control element 15, 16. Each sensor 38, 39 being arranged to detect when the detect when the movement control element 15, 16 is located adjacent to the an attachment element at each sensor's 38, 39 respective side of the movement control element 15, With reference to the figures a method for handling a dredging device 10 of a dredging system 1 will be described.

The method involves moving the dredging device 10 over the area to be dredged. The movement of the dredging device 10 is controlled through the PLC-system 28 which controls the motors 18, 20, 22 of the dredging system 1 based on input form the sensors 23, 24 ,25 ,26 of the dredging system The dredging device 10 is moved between the first 15 and second movement control element 16. This is done by means of the third motor 22 moving the dredging device 10 along the third line When the dredging device 10 reaches the first movement control element 15, that is when the dredging device 10 is located adjacent to the first movement control element 15, the third sensor 25 will detect this. The third sensor 25 will then send information to the PLC-system 28 that the dredging device 10 is located adjacent to the first movement control element 15. Based on this received input from the third sensor 25 the PLC-system 28 will instruct the second motor 20 to run for a predetermined time such that the second movement control unit 16 is displaced a predetermined distance in the second direction, towards the first 11 or second 12 attachment element. The PLC-system will further instruct the third motor 22 to reverse such that the dredging device 10 starts to move towards the second movement control unit 16. Optionally the PLC-system 28 may instruct the third motor 22 to stop and only to start to reverse once the predetermined time has passed and the second movement control unit 16 has been displaced the predetermined distance.

The dredging device then move towards the second movement control unit 16 by means of the third motor 22 moving the dredging device 10 along the third line When the dredging device 10 reaches the second movement control element 16, that is when the dredging device 10 is located adjacent to the second movement control element 16, the fourth sensor 26 will detect this. The fourth sensor 26 will then send information to the PLC-system 28 that the dredging device 10 is located adjacent to the second movement control element 16. Based on this received input from the fourth sensor 26 the PLC- system 28 will instruct the first motor 18 to run for a predetermined time such that the first movement control unit 15 is displaced a predetermined distance in the second direction, towards the third 13 or fourth 14 attachment element. The PLC-system will further instruct the third motor 22 to reverse such that the dredging device 10 starts to move towards the first movement control unit 15. Optionally the PLC-system 28 may instruct the third motor 22 to stop and only to start to reverse once the predetermined time has passed and the first movement control unit 15 has been displaced the predetermined distance.

The displacement of the first 15 and second movement control element 16 is in the same direction in the second direction.

After a while the first movement element 15 will have been displaced enough in the second direction that it will reach either the first 11 or the second 12 attachment element, that is it will be located adjacent to either the first 11 or the second 12 attachment element. When this happens the first sensor 23 will detect this and send information to the PLC-system 28 that the first movement control element 15 is located adjacent to an attachment element 11, 12. Based on this received input from the first sensor 23 the PLC- system 28 will instruct the first motor 18 to stop running. ln a similar manner, the second movement element 15 will after a while have been displaced enough in the second direction that it will reach either the third 13 or the fourth 14 attachment element, that is it will be located adjacent to either the third 13 or the fourth 14 attachment element. When this happens the second sensor 24 will detect this and send information to the PLC-system 28 that the second movement control element 16 is locatedadjacent to an attachment element 13, 14. Based on this received input from the second sensor 24 the PLC-system 28 will instruct the second motor 18 to stop running.

When both the first 11 and second 12 movement element simultaneously are located adjacent to a respective attachment element 11, 12, 13, 14 the PLC-system 28 will know this based on input from the first 23 and second 24 sensor and a moving direction of the first 15 and second movement control element 16 will be changed from moving towards said one respective attachment element 11, 12, 13, 14 to moving away from said respective attachment element 11, 12, 13, Since the displacement of the first 15 and second movement control element 16 is in the same direction in the second direction the movement control elements 15, 16 will either be located adjacent to the first 11 and third 13 attachment element respectively or to the second 12 and fourth 14 attachment element respectively. lf the movement control elements 15, 16 are located adjacent to the first 11 and third 13 attachment element respectively the PLC-system 28 will instruct both the first 18 and second 20 motor to reverse such that the next time the respective movement control element 15, 16 is to be displaced a predetermined distance, they will move from the first 11 and third 13 attachment element respectively towards the second 12 and fourth 14 attachment element respectively. As previously described a movement control element 15, 16 will move when the dredging device is located adjacent to the other movement control element 15, ln this manner the dredging device 10 will move over the area to be dredged, dragging the undervvater dredging unit 40 with it thus removing sediments and debris from the bottom.

Claims

1. A dredging system (1), comprising: a dredging device (10), a first (11), second (12), third (13) and fourth (14) attachment element, a first (15) and second (16) movement control element, a first line (17) connecting the first attachment element (1 1), the first movement control element (15), the second attachment element (12) with each other and a first motor (18) configured to move the first movement control element (15) in a second direction, a second line (19) connecting the third attachment element (13), the second movement control element (16), the fourth attachment element (14) with each other and a second motor (20) configured to move the second movement control element (16) in the second direction, and a third line (21) connecting the first movement control element (15), the dredging device (10), the second movement control element (16) with each other and a third motor (22) configured to move the dredging device (10) in a first direction, characterized in that, when the dredging device (10) is located adjacent to the first movement control element (15), the second movement control element (16) is configured to be displaced a predetermined distance in a second direction, and wherein, when the dredging device (10) is located adjacent to the second movement control element (16), the first movement control element (15) is configured to be displaced a predetermined distance in the second direction.

2. The dredging system (1) according to claim 1, wherein the first movement control element (15) is movable between the first (11) and second (12) attachment element along with the first line (17) by means of the first motor (18), and the second movement control element (16) is movable between the third (13) and fourth (14) attachment element along with the second line (19) by means of the second motor (20).

3. The dredging system (1) according to claim 1 or 2, wherein the dredging device (10) is movable between the first (15) and second (16) movement control element along the third (21) line by means of the third motor (22).

4. The dredging system (1) according to any one of the preceding claims, wherein the first motor (18) is arranged on the first (1 1) or second attachment (12) element and the second motor (20) is arranged on the third (13) or fourth (14) attachment element.

5. The dredging system (1) according to any one of the preceding claims, wherein the third motor (22) is arranged on the dredging device (10).

6. The dredging system (1) according to any one of the preceding claims, further comprising a first sensor (23) detecting when the first movement control (15) element is located adjacent to the first (1 1) or the second (12) attachment element, and a second sensor (24) detecting when the second movement control element (16) is located adjacent to the third (13) or fourth (14) attachment element.

7. The dredging system (1) according to any one of the preceding claims, further comprising a third sensor (25) detecting when the dredging device (10) is located adjacent to the first movement control element (15) and a fourth sensor (26) detecting when the dredging device (10) is located adjacent to the second movement control element (16).

8. The dredging system (1) according to any one of the preceding claims, further comprising a line tensioning device (27) connected to the third line (21) and adapted to tighten the lines (17, 19, 21) of the dredging system (1)-

9. The dredging system (1) according to any one of the preceding claims, wherein the attachment elements (11, 12, 13, 14) form a four-sidedpolygon when placed in an area to be dredged by being arranged at a respective corner thereof.

10.The dredging system (1) according to claim dependent on claim further comprising a control system (28), such as a PLC-system, adapted to control the first (18), second (20) and third (22) motor based on input from the first (23), second (24), third (25) and fourth (26) sensor.

11.The dredging system (1) according to any one of the preceding claims, wherein the first line (17) extends from a first attachment point on the first movement control element (15), to a connection point on the first attachment element (11), from there to a connection point on the second attachment element (12), and from there to a second attachment point on the first movement control element (15).

12.The dredging system (1) according to any one of the preceding claims, wherein the second line (19) extends from a first attachment point on the second movement control element (16), to a connection point on the third attachment element (13), from there to a connection point on the fourth attachment element (14), and from there to a second attachment point on the second movement control element (16).

13.The dredging system (1) according to any one of the preceding claims, wherein the third line (21) extends from a first attachment point on the dredging device (10), to a connection point on the first movement control element (15), from there to a connection point on the second movement control element (16), and from there to a second attachment point on the dredging device (10).

14.The dredging system (1) according to any one of the preceding claims, wherein each attachment element (11, 12, 13, 14) comprises a floating device (30) adapted to be placed in a water area to be dredged.

15.The dredging system according to claim 14, wherein each floating device (30) comprises an anchor (29) connected thereto and adapted to maintain the position of the floating device (30) in the water area to be dredged.

16.A method for handling a dredging device (10) of a dredging system (1), comprising: moving the dredging device (10) between a first (15) and second (16) movement control element in a first direction along with a third line (21) by means of a third motor (22), moving the first movement control element (15) between a first (11) and second (12) attachment element in a second direction along with a first line (17) by means of a first motor (18), the second direction being substantially perpendicular to the first direction, and moving the second movement control element (16) between a third (13) and fourth (14) attachment element in the second direction along with a second line (19) by means of a second motor (20) characterized in that, when the dredging device (10) is located adjacent to the first movement control element (15), the second movement control element (16) is displaced a predetermined distance in the second direction, and wherein, when the dredging device (10) is located adjacent to the second movement control element (16), the first movement control element (15) is displaced a predetermined distance in the second direction.

17.The method according to claim 16, wherein, when the first (15) and second movement control element (16) simultaneously is located adjacent to one respective attachment element (11, 12, 13, 14), a moving direction of the first (15) and second (16) movement control element is changed from moving towards said one respective attachment element (11, 12, 13, 14) to moving away from said respective attachment element (11, 12, 13, 14).