BACKGROUND

Cutter- suction dredgers ("CSD") are vessels which can be used to cut and loosen material which is at least partly underwater. They can be used to remove material from harbors, shipping channels, mining operations and other marine environments.

CSD's typically use a cutter head mounted on the end of a ladder. The cutter head moves across the waterway bottom, and teeth on the cutter head are used to loosen material from the seabed. A suction mouth is located in the lower part of the cutter head, and the loosened material mixed with water is directed toward the suction mouth. The suction mouth is connected to a suction tube that can transport the loosened material away from the cutter head, for example, by a floating pipe line to a dumping location.

During this process, a substantial portion of the loosened material does not reach the suction mouth, and falls outside the cutter head, causing spillage. This spillage remains partly on the waterway bottom or will be thrown around in the water causing turbidity. Subsequently, turbidity causes plumes and resuspension of sediments.

Environmental dredging projects involve removal of contaminated sediments from a water body for the purposes of sediment remediation. Environmental dredging is required for the maintenance of water reservoirs and other sensitive locations where resuspension is not allowed. When conducting these kinds of projects, it is of great importance to avoid turbidity and resuspended sediment particles because they may be transported downstream, causing further expansion of the contaminated water body.

For environmental dredging projects, various devices have been developed to avoid this, such as a cutter head with a cover over it. Examples of this are shown in EP0557619 Al, CN101538873 and U.S. Pat. No. 5,060,404. Each of these covers is designed and built specifically for the cutter head, following its shape very closely and connecting to the cutter head uniquely.

Another example of a system for use in environmental dredging projects is shown in KR-A-10-2011-0053099, which shows a cutter head with a cover. The cover is arranged to sit on the outside of the cutter on the side opposite to the horizontal movement direction of the cutter, and can change sides when the cutter changes direction. The movement is performed by a switching system, which uses a motor supported by a retaining ring for switching the cover from side to side. The cutter is positioned to help direct stirred water flow into the suction head during a horizontal dredging movement. The cover is stated to be not all encompassing of the outer periphery of the cutter, and only covers a portion of the outer cutter, specifically the side opposite to the horizontal movement direction of the cutter.

SUMMARY

According to a first aspect of the invention, a cover for a cutter head connected to a ladder includes a first portion shaped to fit around at least a portion of a cutter head; a second portion connected to the first portion and shaped to fit at least partially around the cutter head and at least partially within the first portion; and at least one movement system for moving at least one portion of the cover. Such a cover can be used with a variety of cutter heads to perform environmental dredging operations and/or to reduce or eliminate resuspension and/or turbidity during a dredging operation.

According to an embodiment, the at least one movement system comprises a linear movement system to move the cover in a linear direction. Optionally, the linear movement system comprises one or more linear movement devices connected to at least one of the first and second portions to enable movement in a linear direction in relation to the cutter head. Further optionally, the one or more movement devices comprise one or more cylinders.

According to an embodiment, the linear movement system comprises one or more guides for guiding linear movement.

According to an embodiment, the linear direction is perpendicular to an axis of rotation of the cutter head.

According to an embodiment, the at least one movement system comprises a pivoting movement system to rotate at least the first portion of the cover with a pivoting movement.

According to an embodiment, the pivoting movement system comprises one or more rotating movement devices connected to the first portion and the second portion to enable rotation of the first portion. Optionally, the one or more rotating movement devices comprise one or more cylinders. According to an embodiment, the pivoting movement system rotates around a pivot point. Optionally, the pivot point is at a lower end of the first portion.

According to an embodiment, the one or more guides comprise one or more guiding skids.

According to an embodiment, the cover further comprises one or more connecting devices to connect the cover to the ladder. Optionally, the one or more connecting devices comprise one or more connecting brackets.

According to an embodiment, the cover further comprises one or more plates connected to the second portion to cover any space between the ladder and the second portion when the cover is connected to the ladder. Optionally, the one or more plates comprises two plates able to slide to cover the space between the ladder and the second portion.

According to an embodiment, the cover further comprises a seal between the first portion and the second portion.

According to an embodiment, the cover further comprises a cover extension piece connected to the first portion. Optionally, the cover extension piece extends below the first portion when the cover is in use.

According to an aspect of the invention, a method of environmental dredging with a cutter head connected to a ladder includes connecting a cover around at least a portion of the cutter head; lowering the ladder with cutter head to a dredging depth; adjusting the cover in a linear direction with a linear movement system; and rotating a first portion of the cover with a pivoting movement system so that a lower side of the first portion lays generally parallel to the seabed to be dredged.

According to an embodiment, the step of connecting a cover around at least a portion of the cutter head further comprises connecting the cover so that one or more plates connect between a second portion of the cover and the ladder.

According to an embodiment, the step of adjusting the cover in a linear direction with a linear movement system comprises adjusting one or more linear movement devices connected to a second portion of the cover to move the first and second portions in a linear direction with respect to an axis of rotation of the cutter head. Optionally, the one or more linear movement devices comprise one or more cylinders. According to an embodiment, the linear direction is perpendicular to the axis of rotation of the cutter head.

According to an embodiment, the step of rotating the first portion of the cover with a pivoting movement system so that a lower side of the first portion lays generally parallel to the seabed to be dredged comprises adjusting one or more rotating movement devices to rotate the first portion about a pivot point. Optionally, the one or more rotating movement devices comprise one or more cylinders.

According to an embodiment, the step of connecting a cover around at least a portion of the cutter head comprises connecting one or more connecting devices to the cover and to the ladder so that the first portion and a second portion of the cover at least partially cover the cutter head. Optionally, the one or more connecting devices comprise one or more connecting brackets.

According to an embodiment, the steps of adjusting a first and a second portion of the cover in a linear direction with a linear movement system; and rotating the first portion of the cover with a pivoting movement system so that a lower side of the first portion lays generally parallel to the seabed to be dredged positions form an enclosure over cutter head so that turbidity and sediment resuspension is limited when dredging.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. la schematically illustrates an example vessel with a cutter head connected to a ladder in a raised position.

Fig. lb shows the vessel of Fig. la with the cutter head and ladder in a lowered position for use.

Fig. lc shows a close-up see-through view of the cutter head and cover of Fig. lb during a dredging operation.

Fig. 2a shows a perspective view of a cutter head and cover from a back side. Fig. 2b shows a perspective view of the cutter head and cover of Fig. 2a from a front side.

Fig. 3 shows a perspective view of a cutter head and cover with an extension.

DETAILED DESCRIPTION

Fig. la schematically illustrates an example vessel 10 with ladder 12 holding cutter head 14 in a raised position, Fig. lb schematically shows vessel 10 with ladder 12 holding cutter head 14 in a lowered position for use, and Fig. lc shows a close-up and see-through view of the cutter head 14 and cover 16 of Fig. lb. Figs, la-lc include vessel 10 with ladder 12 and suction tube 20, cutter head 14 with axis of rotation RA, and cover 16 with first portion 22, second portion 24, linear movement system 26 (with cylinder 27), rotational movement system 28 (with cylinder 29), and brackets 30. Vessel 10 can be, for example, a cutter suction dredger.

Cover 16 is connected to ladder 12 through brackets 30. Brackets 30 connect to linear movement system 26, and linear movement system 26 connects to second portion 24 of cover 16. First portion 22 is connected to second portion 24 of cover 16. First portion 22 and second portion 24 of cover 16 are shaped to fit around at least a portion of cutter head 14, with second portion 24 able to fit at least partially within first portion 22. In other embodiments, first portion 22 may be shaped and positioned to at least partially fit within second portion 24.

Linear movement system 26 includes cylinder 27 which is used to move cover 16 in a linear direction, perpendicular to axis of rotation RA. Rotational movement system 28 includes cylinder 29, and is used to rotate first portion 22 of cover 16 around pivot point P, located in the lower corner of first portion 22 in this embodiment.

As described in the background, cutter head 14 is connected to ladder 12, which can lower cutter head 14 to the seabed 18 to be used for a dredging operation, as shown in Figs, lb and lc. Cutter head 14 can be driven by a drive shaft (not shown) to rotate cutter head 14 around axis of rotation RA, thereby loosening material from seabed 18. Material can then be drawn into suction tube 20.

Cover 16 can act to at least partially enclose cutter head 14 during a dredging operation. Linear movement system 26 can connect to at least one of first portion 22 and second portion 24, and can work to move both first portion 22 and second portion 24 of cover 16 in a direction perpendicular to the axis of rotation RA to ensure proper positioning for enclosing cutter head 14 and to set a layer thickness LT when dredging. Rotational movement system 28 can rotate first portion 22 around pivot point P so that first portion sits generally parallel and close to or touching seabed 18, setting the dredge depth DD.

As previously mentioned, during a cutting or dredging process, some of the loosened material does not reach the suction mouth, and thus is not drawn into suction tube 20. This can be thrown around in the water, causing turbidity, plumes and resuspension of sediments. Cover 16 can lessen and/or prevent resuspension of these particles by limiting the area of turbidity through at least partially enclosing the area around cutter head 14 during a dredging operation. Linear movement system 26 and rotational movement system 28 work to ensure cover 16 is able to be properly positioned to at least partially enclose cutter head 14 down to seabed 18 to ensure maximum effectiveness of cover 16 and limit the space within cover 16 subjected to turbidity and resuspension. Thus, further contamination of the liquid body is reduced or eliminated.

Additionally, linear movement system 26 and rotational movement system 28 allow for easy access to cutter head 14 when needed, for example, to remove debris from cutter head 14. By positioning ladder 12 in a horizontal position, as show in Fig. la, and moving cover 16 upward with linear movement system 26 and/or rotating first portion 24 of cover 26 upward with rotational movement system 28, cutter head 14 is easily accessible (for example, by using a workboat). Thus, this can allow the vessel 10 and cutter head 14 to remain on location, reducing downtime required for certain maintenance tasks and operations.

Fig. 2a shows a perspective view of cutter head 14 and cover 16 from a back side, and Fig. 2b shows a perspective view of cutter head 14 and cover 16 from a front side. Cover 16 includes first portion 22, second portion 24, linear movement system 26 with cylinders 27, rotational movement system 28 with cylinders 29 and pivot point P, connection brackets 30, guidance skids 32, cover plates 34, 36 and seal 38. Also shown in Figs. 2a-2b is ladder 12, cutter head 14 and suction tube 20.

Brackets 30 are connection points to connect cover 16 to ladder 12 and/or suction tube 20. The embodiment shown in Figs. 2a-2b include two brackets 30 on each side of ladder 12 to secure cover 16 to ladder 12. Other embodiments can include a different number of brackets 30 and/or a different type of bracket(s) or connecting devices.

Guidance skids 32 connect to brackets 30 on either side of ladder 12, and act as guides to assist the movements of linear movement system 26.

Linear movement system 26 includes, on each side of ladder 12, a cylinder 27 connected to second portion 24 of cover 16, and to brackets 30. Cylinder 27 works to move first portion 22 and second portion 24 of cover 16 in a direction perpendicular to the axis of rotation RA. In the embodiment shown, linear movement system 26 moves both first portion 22 and second portion 24 simultaneously, though in other embodiments, only one portion could be moved by linear movement system at a time. Furthermore, in other embodiments, linear movement system 26 could connect to cover 16 differently, for example, connect to first portion 22 or to first and second portions 22, 24. Linear movement system 26 can be controlled manually or automatically.

Rotational movement system 28 includes, on each side of ladder 12, a cylinder 29 which connects to first portion 22 and to second portion 24 of cover 16. Rotational movement system 28 works to rotate first portion 22 upwards around pivot point P. In other embodiments, rotational movement system 28 could also work to rotate second portion 24 in addition or in alternative to first portion 22.

Cover plates 34, 36 cover the area between second portion 24 and ladder 12, helping to enclose the entire area around cutter head 14. In some embodiments, cover plate 34 can be connected to ladder 12 and cover plate 36 can be connected to second portion 24 of cover 16. Cover plates 34, 36 can then overlap to a varying degree depending on the displacement amount of linear movement system 26, ensuring that the area is covered throughout all possible movements of linear movement system 26. Seal 38 can be a rubber lip or other type of seal to seal any gap between first portion 22 and second portion 24 of cover 16.

Cover 16 is a universal cover which can connect to a large variety of cutter heads 14 for use in a variety of situations. Cover 16 is shaped to fit around cutter head 14 at a given distance so as to not be limited to use with a particular cutter head 14. Linear movement system 26, rotational movement system 28, cover plates 34, 36 and seal 38 additionally allow for cover to be able to form at least a partial enclosure around and therefore be used with a wide variety of cutter heads 14, making the cover 16 easily adaptable and effective for use with different systems and/or in varying dredging situations.

FIG. 3 shows a perspective view of a cutter head 14 and cover 16 with an extension 40 for dredging a very thin layer thickness. Cover 16 includes first portion 22, second portion 24, linear movement system 26 (with cylinder 27), rotational movement system 28 (with cylinder 29), brackets 30 and extension 40.

In this embodiment, second portion 24 is much smaller than first portion 22, and is shown completely within first portion 22. Extension 40 can connect to first portion 22, and can be secured through bolts or other securing means. Extension 40 can be secured to cover 16 when ladder 12 and cover 16 are in a raised position (see Fig. la), for example, with the use of a workboat. Extension 40 can be made of various materials, such as steel, composite, rubber and/or plastic.

Cover 16 connects to ladder 12 and works in the same manner as described in relation to Figs. la-2b. Extension 40 can extend beneath first portion to help enclose the area around cutter head 14 during a dredging operation. Extension 40 can be especially useful when dredging a very thin layer thickness LT, making the dredge angle very steep.

As described above in relation to Figs, la-lc, cover 16 forms at least a partial enclosure around cutter head 14 to minimize turbidity and resuspension during operations. As part of this, first portion 22 moves linearly with linear movement system 26 and is rotated using rotational movement system 28 so that the lower portion is generally parallel to and close-to or touching seabed 18. With a very steep dredge angle and/or small layer thickness, it can be difficult for first portion 22 of cover 16 to come close to or touch seabed 18, thereby leaving a lower portion of cutter head 14 not enclosed. Extension 40 works to fully enclose cutter head 14 all the way to seabed 18, allowing cover 16 to decrease turbidity and resuspension when dredging even at a very steep dredge angle.

In summary, cover 16 through the use of a first portion, a second portion and one or more movement systems 26, 28, can minimize or prevent turbidity and sediment resuspension sometimes experienced during dredging operations. Linear movement system 26 and rotational movement system 28 work to allow cutter head 14 to be effective at different depths and angles for cutting by being able to move one or both portions 22, 24 of cover 16 to enclose the area around cutter head 14 during a dredging operation. The geometric shape of cover, one or more movement systems 26, 28, connecting brackets 30 and seals 34, 36, 38 give cover 16 the ability to be used with a variety of different types of cutter heads 14 normally used for maintenance and/or land reclamation dredging, eliminating the need for a special cutter when environmental dredging is desired or required. Additionally, the possibility of using extension 40 enables cover 16 to work effectively despite a small layer thickness and/or steep dredge depth. Movement systems 26, 28 can also enable easy access to cutter head 14, for example, for maintenance operations. While linear movement system 26 and rotational movement system 28 are shown using cylinders 27, 29, in other embodiments, movement systems can be adjusted by other drivers or bolts, and can even be adjusted above water level. Additionally, the number of cylinders 27, 29 and/or other movement devices used can vary depending on system requirements.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.