DREDGER

Abstract

 A dredger is provided in which a wire is hung down from an extremity part of a boom that tiltably has an axial support on a hull, a winch device provided on the hull is capable of taking up and letting out the wire, a bucket device is suspended from the wire, and the bucket device scoops up and excavates sediment on a water bottom and can feed the sediment under pressure to a sediment collection location above water through a sediment transport pipe, wherein the boom (B) tiltably has the axial support on the hull (1) and is tiltably formed in a vertical direction underwater, and the wire (W) can hang down from the extremity part (Ba) of the boom (B) underwater, the winch device (2) provided on the hull (1) being capable of taking up and letting out the wire (W). This enables the problems of a conventional device accompanying the use of the wire hanging down length wise from above water to near the water to be solved while exploiting an advantage, such that excavation can be conducted efficiently by utilizing the self-weight of the bucket device, of the bucket device suspended from the wire.

Description

TECHNICAL FIELD

[0001] The present invention relates to a dredger, and in particular to a dredger in which a bucket device is suspended from a boom that is tiltably and axially supported on a hull via a wire that can be taken up and let out by a winch device provided on the hull, and the bucket device scoops up and excavates sediment on a water bottom and can feed it under pressure to a sediment collection location above water through a sediment transport pipe.

BACKGROUND ART

[0002] The dredger is conventionally known, as disclosed in Patent Document 1 below, and this arrangement has the advantage that, since a heavy bucket device is suspended by a wire and raised and lowered, sediment on the water bottom can be scooped up and excavated efficiently by utilizing the self-weight of the bucket device itself.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003] Patent Document 1: Japanese Patent Application Laid-open No. 7-26580

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In the dredger of Patent Document 1 above, when carrying out dredging, it is necessary to extend the wire, via which the bucket device is suspended underwater, lengthwise downward from an extremity part of the boom raised above the water to the bucket device near the water bottom. The wire thus extended lengthwise is easily affected by wind and waves above the water surface or by tides underwater, and this could considerably degrade the precision of positional control of the bucket device at the lower end of the wire, which is a problem.

[0005] In the conventional dredger, since dredging operations are carried out while the hull is fixed in a state in which it is immobile with respect to the water bottom by fixing means such as a spud, each time the dredging range (position) is changed, it is necessary to repeat operations such as releasing operation of the fixing means, moving the hull, and fixing it again to the water bottom by the fixing means at the position thus moved to, these change operations being troublesome.

[0006] The present invention has been proposed in light of the above circumstances; it is a first object thereof to solve the above problems accompanying the use of a wire hanging down lengthwise from above water to near the water bottom while exploiting the above advantages of a bucket device suspended from the wire, and it is a second object thereof to enable dredging to be carried out with good precision over a wide range without fixing a hull to the water bottom.

MEANS FOR SOLVING THE PROBLEMS

[0007] In order to attain the above object, according to a first aspect of the present invention, there is provided a dredger in which a wire is hung down from an extremity part of a boom that has an axial support on a hull so as to be tiltable, a winch device provided on the hull is capable of taking up and letting out the wire, a bucket device is suspended from the wire, and the bucket device scoops up and excavates sediment on a water bottom and can feed the sediment under pressure to a sediment collection location above water through a sediment transport pipe, characterized in that the boom is formed so as to be tiltable in a vertical direction underwater, and the wire can hang down from the extremity part of the boom underwater.

[0008] Further, according to a second aspect of the present invention, in addition to the first aspect, the dredger comprises a hull propulsion device that can propel the hull along water surface in order to adjust a horizontal position of the bucket device underwater, and a control device that can control, based on GPS positional information of at least one of the hull, the boom and the bucket device, the position of the hull by controlling operation of the hull propulsion device so that the bucket device can move on an excavation target section of the water bottom along a predetermined excavation route.

[0009] Furthermore, according to a third aspect of the present invention, in addition to the first or second aspect, the bucket device is provided with a sediment flow assistance device that injects pressurized air and/or pressurized water toward excavated sediment scooped up into the bucket device so as to assist flow of the sediment from the bucket device toward the sediment collection location via the sediment transport pipe.

[0010] Moreover, according to a fourth aspect of the present invention, in addition to any one of the first to third aspects, the hull is provided with a sediment collection tank that becomes the sediment collection location.

EFFECTS OF THE INVENTION

[0011] In accordance with the first aspect, since the boom axially supported on the hull is formed so as to be tiltable in the vertical direction underwater, and the wire let out from the winch device on the hull hangs down from the boom extremity part underwater and suspends the bucket device, it is possible to sufficiently reduce the length of the wire hanging down from the boom extremity part to the bucket device while exploiting the original advantage of the bucket device due to suspension by the wire, and it is possible to make it impossible or difficult for the wire to be influenced by wind or waves above the water surface or by tides in the water. Deviation of the horizontal position of the bucket device with respect to the position of the hull (and consequently the horizontal position of the boom extremity part) can thereby be made small, thus contributing to an improvement in the precision of positional control of the bucket device based on positional control of the hull (and consequently the boom).

[0012] In accordance with the second aspect, there are provided the hull propulsion device, which can drive the hull along the water surface in order to adjust the horizontal position of the bucket device in the water, and the control device, which controls operation of the hull propulsion device. The control device controls the position of the hull by operating the hull propulsion device based on GPS positional information of at least one of the hull, the boom and the bucket device, thus enabling the bucket device to be moved along a predetermined excavation route in an excavation target section of the water bottom. This enables the bucket device to move along a predetermined excavation route in an excavation target section of the water bottom by utilizing the GPS positional information, without fixing the hull to the water bottom, and it is thereby possible to carry out dredging of a wide range of the water bottom thoroughly using the bucket device. Moreover, in combination with the effect of eliminating or curbing the influence of waves, tide, etc. by hanging down the wire via the boom extremity part in the water as described above, positional control of the bucket device during dredging can be carried out with good precision.

[0013] In accordance with the third aspect, since the bucket device is provided with the sediment flow assistance device, which injects pressurized air and/or pressurized water toward the excavated sediment scooped up into the bucket device so as to assist flow of the sediment from the bucket device toward the sediment collection location via the sediment transport pipe, even when the bucket device is left underwater, it is possible to disperse the excavated sediment scooped up into the bucket device so as to enhance the flowability and to forcibly feed it smoothly to the sediment collection location above water through the sediment transport pipe.

[0014] In accordance with the fourth aspect, since the hull of the dredger is provided with the sediment collection tank, the dredged sediment can be stored in the dredger itself without having a barge alongside the dredger and on standby; it is therefore possible to continue dredging when there is no barge, and also when the bucket device, etc. malfunctions and dredging is discontinued, sediment that has been stored in the dredger up to that time can be transshipped to a barge, thus increasing the overall operating efficiency.

BRIEF DESCRIPTION OF DRAWINGS

[0015] 

[FIG. 1] FIG. 1 is an overall side view of a dredger related to a first embodiment of the present invention.

[FIG. 2] FIG. 2 is a plan view of an essential part of the dredger (a sectional view along line 2-2 in FIG. 1), a partial enlarged plan view and a partial enlarged perspective view.

[FIG. 3] FIG. 3 is a front view of a grab bucket (an enlarged view of part shown by arrow 3 in FIG. 1).

[FIG. 4] FIG. 4 is a side view of the grab bucket (a view in the direction of arrow 4 in Fig. 3).

[FIG. 5] FIG. 5 is a sectional view of the grab bucket when viewed from the same direction as in FIG. 3 (a sectional view along line 5-5 in FIG. 4).

[FIG. 6] FIG. 6 is a plan view of the grab bucket (a view in the direction of arrow 6 in Fig. 5).

[FIG. 7] FIG. 7 is a sectional view, corresponding to FIG. 5, showing the relationship between the water bottom and the grab bucket at a position shown by the double-dotted broken line in FIG. 1.

[FIG. 8] FIG. 8 is a process diagram showing one example of a closing process of the grab bucket.

[FIG. 9] FIG. 9 is a sectional view, corresponding to FIG. 5, showing a modified example of an extended plate portion.

[FIG. 10] FIG. 10 is a side view of a grab bucket related to a second embodiment (view corresponding to FIG. 4).

[FIG. 11] FIG. 11 is a sectional view along line 11-11 in FIG. 10 (view corresponding to FIG. 5).

[FIG. 12] FIG. 12 is a plan view of the grab bucket related to the second embodiment (view corresponding to FIG. 6).

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

[0016] 

A

Sediment flow assistance device

B

Boom

Ba

Extremity part

C

Control device

D

Hull propulsion device

E

Water bottom

G, G'

Grab bucket as bucket device

S

Dredger

M2

Second winch device as winch device

W2

Second wire as wire

p1

Axial support

1

Hull

3

Sediment collection tank as sediment collection location

4

Sediment

8

Sediment transport pipe

MODES FOR CARRYING OUT THE INVENTION

[0017] Embodiments of the present invention are explained below by reference to the attached drawings.

[0018] In FIG. 1 and FIG. 2, a dredger S includes a hull 1 that floats on the water surface, for example, on the sea surface, a hull propulsion device D that can propel the hull 1 along the water surface, a boom B that is axially supported p1 on the hull 1 so that it can swing (tilt) in the vertical direction, a first wire W1 that has one end linked to an extremity part Ba of the boom B, a first winch device M1 for boom tilting that is provided on the hull 1 and can take up and let out the other end side of the first wire W1, a grab bucket G as a bucket device that is suspended from the extremity part Ba of the boom B via a second wire W2, a second winch device M2 for bucket raising/lowering that is provided on the hull 1 and can take up and let out the second wire W2, and a pair of left and right sediment collection tanks 3 that are disposed on the hull 1 so as to form a sediment collection location above the water.

[0019] The first winch device M1 includes a drum that can take up the first wire W1 and a motor that rotates the drum. Taking up or letting out the first wire W1 by means of the first winch device M1 enables the boom B linked to the wire W1 to be tilted upward or downward.

[0020] The second winch device M2 includes a drum that can take up the second wire W2 and a motor that rotates the drum. Taking up or letting out the second wire W2 by means of the second winch device M2 enables the grab bucket G hanging down from the wire W2 to be raised or lowered. The first and second wires W1, W2 are each provided as left and right pairs, but there may be one of each or three or more of each.

[0021] The grab bucket G is, as described later, formed so as to scoop up and excavate a sediment 4 on a water bottom E, and the excavated sediment scooped up into the grab bucket G is fed under pressure to the sediment collection tank 3 above water through a sediment transport pipe 8 having flexibility. Therefore, it is not necessary to pull up the grab bucket G above water each time when carrying out dredging, and the work efficiency is thus improved. The grab bucket G is one example of the bucket device of the present invention. The structure of the grab bucket G is more specifically described later.

[0022] The boom B has a base end part Bb thereof axially supported p1 on a carriage portion 5b of a movable support body 5 mounted on a front part of the hull 1 so that it can move only in the fore-and-aft direction, and the boom B can swing around the axially supported p1 part in the vertical direction not only above water but also underwater. The carriage portion 5b has a cutout-shaped boom clearance portion 5bk as is clear from a partial enlarged perspective view of FIG. 2 in order to avoid interference between the boom B and the movable support body 5 regardless of the attitude of tilting of the boom B.

[0023] The movable support body 5 is linked and coupled to a drive device that is provided between the carriage portion 5b thereof and the hull 1 and can be driven on the hull 1 in the fore-and-aft direction together with the base end part Bb of the boom B. As the drive device, for example, a structure in which as shown in FIG. 2 a brake mechanism-equipped driven wheel 5w axially supported on the carriage portion 5b and being capable of running along a guide rail 9 fixed to the hull 1 is driven at reduced speed by a motor, which is not illustrated, or a structure, although not illustrated, in which a brake mechanism-equipped pinion meshing with a rack fixed to the hull 1 and axially supported on the carriage portion 5b is driven at reduced speed by a motor, etc. can be employed.

[0024] In a state in which the movable support body 5 is advanced all the way forward, the boom B attains a state in which as shown in FIG. 1 it protrudes toward the foremost side and can swing vertically between an upward swing limit at which it rises above the water surface and a downward swing limit at which it is submerged under the water surface. Provided in a front end part of the hull 1 is a clearance portion 1a for allowing the boom B to swing to the downward swing limit underwater, the clearance portion 1a being formed as a cutout opening upward, downward and forward.

[0025] In a state in which the movable support body 5 is withdrawn all the way back with the boom B in a horizontal attitude, the boom B attains a withdrawn state in which it is most withdrawn as shown in a chain line in FIG. 1. This withdrawn state is selected when the dredger S is moved over a long distance, when the grab bucket G is subjected to inspection and maintenance, etc.

[0026] Standingly provided on a front part of the hull 1 is a support frame 6 that is formed into a gate shape so as to straddle the locus of fore-and-aft movement of the movable support body 5. Rotatably supported on an upper part of the support frame 6 is a first guide roller r1 through which an intermediate part of the first wire W1 let out from the first winch device M1 is guided.

[0027] On the other hand, an intermediate part of the second wire W2 let out from the second winch device M2 is guided through a second guide roller r2 rotatably supported on the movable support body 5 and a pair of front and rear third guide rollers r3 rotatably supported on the extremity part Ba of the boom B, and hangs down via the extremity part Ba of the boom B. The second guide roller r2 is axially supported on an upper end part of a support platform 5a standingly provided on the carriage portion 5b of the movable support body 5. The arrangement is such that the second wire W2 passes through between the pair of front and rear third guide rollers r3.

[0028] An example of the structure of the grab bucket G is now explained by reference mainly to FIG. 3 to FIG. 8. The grab bucket G includes a bottomed cylindrical main frame 11, a raise/lower tube 12 as a raise/lower body that is formed into a cylindrical shape having upper and lower ends open and is vertically slidably fitted onto the outer periphery of the main frame 11 via a plurality of annular seal members 18, a pair of scoop plates 13 that have their base part linked by pivot support link (axial support) p2 to a lower end part of the raise/lower tube 12 via hinge brackets b2, b3 so that they can open/close an open lower end of the raise/lower tube 12 and scoop the sediment 4 on the water bottom E into the interior, a first hydraulic cylinder Cy1 as an open/close drive device that opens and closes the two scoop plates 13, a second hydraulic cylinder Cy2 as a raise/lower drive device that raises and lowers the raise/lower tube 12 with respect to the main frame 11, a sand discharge pipe P that is fixed within the main frame 11 so as to have one end Pi opening on a bottom wall 11b of the main frame 11 and has the other end Po connected to the upstream end of the sediment transport pipe 8, and a check valve 15 that prevents reverse flow of the sediment 4 pushed out from the sand discharge pipe P toward the sediment transport pipe 8 side.

[0029] The annular seal member 18 is fitted into an annular groove provided in either one of mutually opposing peripheral faces of the main frame 11 and the raise/lower tube 12, and is in sliding contact with the other of the opposing peripheral faces.

[0030] An upper end wall 11a of the main frame 11 is linked to and supported by a free end of the second wire W2, that is, the lower end thereof. The second wire W2 can drive the main frame 11 (and therefore the grab bucket G) in the horizontal and vertical directions in the water in association with movement of the hull 1, the second winch device M2 and the boom B.

[0031] A lower end wall, that is, the bottom wall 11b, of the main frame 11 is formed into a hemispherical plate shape curving protrudingly downward, and a large diameter lower end (that is, one end of the sand discharge pipe P) Pi of a lower half pipe part, forming a truncated cone shape, of the sand discharge pipe P opens and is fixed to a center part of the bottom wall 11b, that is, a central apex part of the hemispherical surface bulging downward. An upper half pipe part of the sand discharge pipe P is formed into a cylindrical shape, the lower end of the upper half pipe part is connected integrally to a small diameter upper end of the lower half pipe part, and the upper end of the upper half pipe part (that is, the other end of the sand discharge pipe P) is connected to the upstream end of the sediment transport pipe 8 via a joint.

[0032] The sand discharge pipe P has its intermediate part fixed to and supported on an inner peripheral wall of the main frame 11 via a plurality of support plates 16, and has its upper part extending through and fixed to the upper end wall 11a of the main frame 11.

[0033] The check valve 15 prevents downward reverse flow of sediment; in the illustrated example only one thereof is placed on the upper half pipe part of the sand discharge pipe P, but the number and the position of check valves 15 placed and the valve body structure are not limited to those of the embodiment and can be set as appropriate. For example, in addition to or instead of the mode of placement in the embodiment, the check valve 15 may be placed also in the vicinity of the lower end Pi of the lower half pipe part of the sand discharge pipe P or an intermediate part thereof.

[0034] The check valve 15 of the present embodiment has a valve structure with a single-sided opening type single leaf valve body, but when the check valve 15 is placed in a large diameter portion in particular (for example, in the vicinity of the lower end Pi of the lower half pipe part or an intermediate part thereof) of the sand discharge pipe P, a valve structure having a double-sided opening (that is, double opening from the center) type pair of leaf valve bodies may be employed. Wherever the check valve 15 is placed, it is desirable that a valve body clearance part (not illustrated) is recessed in an inner face of the sand discharge pipe P in order to avoid interference with the valve body of the check valve 15 and ensure smooth opening and closing of the valve body. Furthermore, a stopper projection (not illustrated) is provided on an inner peripheral face of the sand discharge pipe P, the stopper projection being capable of engaging with the valve body in order to prevent the valve body of the check valve 15 from unnecessarily opening downward and pivoting from the fully closed position.

[0035] The pair of scoop plates 13 have a symmetrical shape to each other and are formed into a hemispherical plate shape such that in a state in which the two are closed (see FIG. 3 and FIG. 5) they closely oppose a lower face of the bottom wall 11b having the hemispherical plate-shape of the main frame 11 (that is, a hemispherical plate form further divided equally into two). The excavated sediment 4 that has been scooped up by means of the two scoop plates 13 is forcibly pushed into the sand discharge pipe P by raising the raise/lower tube 12 with respect to the main frame 11 in a state in which the scoop plate 13 is closed.

[0036] Edges of the pair of scoop plates 13 as mutually mating faces are formed so as to have a slightly tapered cross section in order to make it harder for sediment to be sandwiched when the two scoop plates 13 are closed. The edges of the two scoop plates 13 (in particular, the lower edge) may be fixedly provided as necessary with a plurality of claws in an alternating manner that can efficiently break the sediment on the water bottom.

[0037] Connectedly provided on the lower end part of the raise/lower tube 12 is a base part of a short cylindrical extended plate portion 12a that extends downward from the lower end of the raise/lower tube 12. The extremity, that is, the lower end, of the extended plate portion 12a abuts against upper edges of the two scoop plates 13 when the two scoop plates 13 are closed. Since this enables the gap between the lower edge of the raise/lower tube 12 and the upper edges of the two scoop plates 13 in a fully closed state to be made substantially zero or very small, in combination with the sealing effect of the annular seal member 18, a space 40 between the two scoop plates 13 in a fully closed state and the bottom wall 11b of the main frame 11 can be put into a substantially sealed state, and it becomes possible to suppress effectively leakage to the outside, through the gap, of excavated sediment, or pressurized air and pressurized water from a sediment flow assistance device A, which is described later.

[0038] In the illustrated example, the extremity of the extended plate portion 12a is abutted directly against the upper edges of the two scoop plates 13 in the fully closed state, but a seal member, which is not illustrated, formed from an elastic material (for example, a rubber material), may be attached to at least one of the extremity of the extended plate portion 12a and the upper edge of the two scoop plates 13 in the fully closed state, and in this case the effect in sealing the space 40 can be further enhanced. The illustrated example shows a case in which the extended plate portion 12a is formed integrally with the main body part of the raise/lower tube 12, but the extended plate portion 12a may be formed as a body separate from the main body part of the raise/lower tube 12 and subsequently fixed (for example, welded) to the raise/lower tube 12.

[0039] FIG. 9 shows a modified example of the extended plate portion. In this modified example, a base part of an arc plate-shaped extended plate portion 13a extending upward from the upper end of each scoop plate 13 is connectedly provided on an upper end part of the scoop plate 13, and the extremity, that is, the upper end, of the extended plate portion 13a is abutted against the lower edge of the raise/lower tube 12 when the two scoop plates 13 are closed. In accordance with the extended plate portion 13a of this modified example, in the same manner as for the extended plate portion 12a of the embodiment, the gap between the lower edge of the raise/lower tube 12 and the upper edge of the two scoop plates 13 in the fully closed state can be made substantially zero or very small.

[0040] A seal member may be attached to the extremity of the extended plate portion 13a and/or the lower end of the raise/lower tube 12, and in this case the effect in sealing the space 40 can be further enhanced. In addition, the extended plate portion 13a may be formed as a body separate from the scoop plate 13 and subsequently fixed (for example, welded) to the scoop plate 13.

[0041] A pair of the first hydraulic cylinders Cy1 are disposed per scoop plate 13. For example, a base end of the first hydraulic cylinder Cy1 is linked by a pivot support link p3 to an upper part of an outer peripheral wall of the raise/lower tube 12 via a hinge bracket b1, and an extremity end thereof is linked by a pivot support link p6 to a base part of each scoop plate 13 via a bending link mechanism 17 that is formed from a pair of links that can be bent with respect to each other. That is, opposite ends of the bending link mechanism 17 are linked by pivot support links p4, p5 to the raise/lower tube 12 and each scoop plate 13 via the hinge brackets b2, b3 respectively, and the extremity end of the first hydraulic cylinder Cy1 is linked by a pivot support link p6 to an intermediate part (that is, a pivot support linking part as a bending point) of the bending link mechanism 17.

[0042] The second hydraulic cylinders Cy2 are placed as a pair on each of the left and the right at positions out of phase with the first hydraulic cylinders Cy1. For example, a base end of the second hydraulic cylinder Cy2 is linked by a pivot support link p7 to an upper part of an outer peripheral wall of the main frame 11 via a hinge bracket b4, and an extremity end thereof is linked by a pivot support link p8 to a lower part of an outer peripheral wall of the raise/lower tube 12 via a hinge bracket b5.

[0043] Hydraulic oil pressure is supplied while being controlled to the first and second hydraulic cylinders Cy1, Cy2 from a hydraulic control circuit, which is placed on the hull 1 and includes a hydraulic source and a control valve, via a flexible hydraulic pipe extending underwater. Illustration of the hydraulic control circuit and the hydraulic pipe are omitted.

[0044] The grab bucket G is provided with the sediment flow assistance device A, which assists flow of the sediment 4 heading from the sand discharge pipe P to the sediment collection location 3 via the sediment transport pipe 8 by injecting pressurized air and pressurized water into the sediment 4 pushed into the sand discharge pipe P so as to disperse the sediment 4 within the sand discharge pipe P.

[0045] The sediment flow assistance device A of the present embodiment includes a large number of air jet nozzles Na placed and fixed facing inward on a peripheral wall of the sand discharge pipe P at intervals in the peripheral and vertical directions, a large number of water jet nozzles Nw similarly placed and fixed facing inward on the peripheral wall of the sand discharge pipe P at intervals in the peripheral and vertical directions, and an air supply pipe Lai and a water supply pipe Lwi supplying pressurized air and pressurized water to the air jet nozzles Na and the water jet nozzles Nw respectively.

[0046] Each of the air jet nozzles Na and each of the water jet nozzles Nw are disposed so that their jet openings are inclined slightly toward the downstream side (upward in the drawing) in going toward the axis of the pipe within the sand discharge pipe P, and by means of the flow pressure of pressurized air and pressurized water injected therefrom the excavated sediment 4 pushed into the sand discharge pipe P can be efficiently dispersed and efficiently fed under pressure toward the downstream side (that is, toward the sediment transport pipe 8 side).

[0047] Pluralities of air jet nozzles Na' and water jet nozzles Nw' are placed on and fixed to an outer peripheral part of the hemispherical plate-shaped bottom wall 11b of the main frame 11 at intervals in the peripheral and vertical directions so as to face outward (more specifically, inclined slightly downward in going outward in the radial direction of the sand discharge pipe P). These air jet nozzles Na' and water jet nozzles Nw' are also connected to the air supply pipe Lai and the water supply pipe Lwi respectively.

[0048] The pressurized air and the pressurized water discharged from the air jet nozzle Na' and the water jet nozzle Nw' are injected into the confined space 40 between the bottom wall 11b of the main frame 11 and the scoop plate 13 in a fully closed state to thus efficiently disperse the excavated sediment 4, scooped into the scoop plate 13, within the scoop plate 13 before being pushed into the sand discharge pipe P and to put it to a state with high flowability, thus enabling it to be efficiently pushed into the sand discharge pipe P.

[0049] The air jet nozzles Na and the water jet nozzles Nw form first jet means in the sediment flow assistance device A, and the air jet nozzles Na' and the water jet nozzles Nw' form second jet means in the sediment flow assistance device A.

[0050] Pressurized air and pressurized water are supplied while being controlled to the air supply pipe Lai and the water supply pipe Lwi from an air supply control device, which includes a pressurized air source and an air control valve placed on the hull 1, and a water supply control device, which includes a pressurized water source and a water control valve, via an air pipe Lao and a water pipe Lwo both having flexibility.

[0051] The present embodiment illustrates a case in which the first jet means (Na, Nb) of the sediment flow assistance device A injects both pressurized air and pressurized water toward the sediment 4 pushed into the sand discharge pipe P, but the first jet means (Na, Nb) of the sediment flow assistance device A may have a structure in which either one of pressurized air and pressurized water (for example, only pressurized water) is injected toward the sediment 4 pushed into the sand discharge pipe P. The same applies to the second jet means (Na', Nb') of the sediment flow assistance device A as for the first jet means, that is, either one of pressurized air and pressurized water (for example, only pressurized water) may be injected toward the space 40.

[0052] A downstream portion of the sediment transport pipe 8 is taken up so as to be taken up and let out by means of a drum device 20 provided on the hull 1 near the sediment collection tank 3. The drum device 20 has a pair of left and right sediment outlet pipes 20a communicating with the downstream end of the sediment transport pipe 8, and sediment transported through the sediment transport pipe 8 is charged into the pair of left and right sediment collection tanks 3 via the two sediment outlet pipes 20a and stored.

[0053] An intermediate part of the sediment transport pipe 8 let out from the drum device 20 passes through a fore-and-aft direction through hole portion 5ah provided in the support platform 5a of the movable support body 5 and substantially linearly extends forward above a plurality of fourth guide rollers r4 on an upper part of the boom B. In this case, the plurality of fourth guide rollers r4 are arranged so that the sediment transport pipe 8 naturally bends downward at the extremity part Ba in particular of the boom B.

[0054] A convex round face is formed on a bottom face of the through hole portion 5ah of the support platform 5a, the round face naturally guiding the sediment transport pipe 8. In addition, the bottom face of the through hole portion 5ah may be covered with a sheet material having a low coefficient of friction for smoothly guiding the sediment transport pipe 8 or provided with a guide roller (not illustrated).

[0055] Furthermore, the hydraulic pipe communicating with the first and second hydraulic cylinders Cy1, Cy2 may be bundled with the air pipe Lao and the water pipe Lwo and extended toward the hull 1 side, or at least part thereof may be individually extended toward the hull 1 side.

[0056] A main propulsion device 21 propelling the hull 1 in the fore-and-aft direction is provided in a rear part of the hull 1. The main propulsion device 21 includes for example a main screw 21a and a power unit 21u for rotating the main screw 21a.

[0057] A side thruster 22 for propelling a front part of the hull 1 in the left-and-right direction is provided on a bottom face of a front part of the hull 1. The side thruster 22 includes for example a thrust water jet portion 22a provided in left and right middle parts of the bottom face of the front part of the hull 1, and a high pressure water supply device 22s for supplying high pressure thrust water to the thrust water jet portion 22a. The front part of the hull 1 can be propelled in the left-and-right direction by means of the reaction force of high pressure thrust water injected from the left and right thrust water jet portions 22a of the side thruster 22 toward either one of the left and right sides.

[0058] The side thruster 22 is not limited to the structure shown in the embodiment in which thrust water is injected laterally, and for example the front part of the hull 1 may be propelled in the left-and-right direction by means of left and right lateral auxiliary screws provided on the left and right sides of the front part of the hull 1.

[0059] Provided in the rear part of the hull 1 are a support post frame 24 that is fixed to the hull 1, one long spud 25 that is vertically slidably supported on the support post frame 24 in a standing attitude and can have its tapered lower end driven into the sediment 4 at the water bottom E and fixed thereto, a spud raise/lower drive device 26 that can raise and lower the spud 25 while maintaining its standing attitude, and a spud fore-and-aft drive device 27 that precisely moves the hull 1 in the fore-and-aft direction within a predetermined stroke range with respect to the spud 25 by pushing in the fore-and-aft direction the spud 25 driven into and fixed to the sediment 4 of the water bottom E.

[0060] The spud raise/lower drive device 26 is placed on for example the support post frame 24, and has a conventionally known structure that can raise and lower the spud 25 with respect to the hull 1. As the structure, for example, a structure in which a wire having one end linked to the spud 25 is lifted or suspended by means of a winch device fixed to the hull 1 or the support post frame 24 may be employed.

[0061] An intermediate part of the spud 25 is inserted into a guide hole 1g that is long in the fore-and-aft direction and provided in the hull 1 so that the spud 25 can slide in the fore-and-aft direction, and an actuator 28 that pushes the spud 25 in the fore-and-aft direction is provided on the hull 1. The actuator 28 has an output arm portion 28a that engages with the spud 25 so that it cannot move in the fore-and-aft direction with respect thereto, and the hull 1 can be moved in the fore-and-aft direction with respect to the spud 25 by means of a reaction to the output arm portion 28a pushing the spud 25 in the fore-and-aft direction. The actuator 28 and the guide hole 1g form the spud fore-and-aft drive device 27 in cooperation with each other.

[0062] In this way, the spud 25, the spud raise/lower drive device 26, and the spud fore-and-aft drive device 27 form in cooperation with each other a spud-type hull propulsion mechanism SP that moves the hull 1 forward and backward precisely by a predetermined amount.

[0063] The main propulsion device 21, the side thruster 22 and the spud-type hull propulsion mechanism SP form the hull propulsion device D in cooperation with each other, and this hull propulsion device D can propel the hull 1 in the fore-and-aft and left-and-right directions along the water surface in order to adjust the horizontal position of the grab bucket G in the water.

[0064] The first winch device M1 can raise and lower the grab bucket G by vertically tilting the boom B via the first wire W1, and the second winch device M2 can raise and lower the grab bucket G via the second wire W2. Therefore, since both the winch devices M1, M2 can function as raise/lower drive means for the grab bucket G in the water, these winch devices M1, M2, the boom B and the second wire W2, from which hang the grab bucket G, and the hull propulsion device D form, in cooperation with each other, drive means K that moves the grab bucket G in the water.

[0065] Provided in an operation command room 30 provided close to a rear part of the hull 1 are a steering system for carrying out steering of the dredger S, various types of operating systems (not illustrated), other than the steering system, for operating each section of the dredger S (for example, the main propulsion device 21, the side thruster 22, the spud-type hull propulsion mechanism SP, the first and second winch devices M1, M2, the first and second hydraulic cylinders Cy1, Cy2, etc.) and a control device C that has a microcomputer as a main part and is connected to each of the operating systems.

[0066] The control device C can control, based on GPS positional information of at least one of the hull 1, the boom B and the grab bucket G, the position of the hull 1 by controlling operation of the hull propulsion device D so that the grab bucket G can move on an excavation target section of the water bottom E along a predetermined excavation route over each predetermined small section (hereinafter, simply called a predetermined section), and a control program that enables the control to be implemented based on an operation input to the operating system is incorporated in advance.

[0067] For example, a GPS antenna is mounted on the extremity part Ba of the boom B, positional information of the extremity part Ba of the boom B (and consequently positional information of the grab bucket G immediately below the extremity part Ba) is detected based on a GPS signal received by this antenna, operation of the hull propulsion device D is thus controlled, and in this way dredging by the grab bucket G can be carried out with good precision in sequence for each of the predetermined sections, which are formed by dividing the excavation target section into a plurality of sections.

[0068] Furthermore, for example, when a GPS antenna is mounted at an appropriate position of the hull 1 and positional information of the hull 1 is detected based on a GPS signal received by this antenna, the position of the boom extremity part Ba (and consequently positional information of the grab bucket G immediately below the extremity part Ba) is estimated from the positional information of the hull 1 and information about positional deviation between the GPS antenna mounting part of the hull 1 and the boom extremity part Ba, operation of the hull propulsion device D is controlled based on the estimated value, and in this way dredging by the grab bucket G can be carried out with good precision in sequence for each of the predetermined sections, which are formed by dividing the excavation target section into a plurality of sections.

[0069] In this case, the information about positional deviation can be estimated with better precision by taking into consideration the length or the angle of tilting of the boom B (the angle of tilting can be measured directly by an angle sensor or it can be estimated from the amount of the wire W1 taken up by the first winch device M1).

[0070] Moreover, the hull 1 is provided with a depth sensor (for example, an ultrasound sensor) 31, which is not illustrated, that can measure the depth of the water bottom E or the depth of the grab bucket G in a non-contact manner, and information detected by the depth sensor 31 is also outputted to the control device C and used for control of the grab bucket G.

[0071] The operation of the first embodiment is now explained.

[0072] When carrying out dredging, first, the dredger S is steered and made to travel by itself to a dredging water area, and in this process the boom B is retained at a standby position (for example, position X or position Y in FIG. 1) above water.

[0073] When the dredger S arrives at the dredging water area, the spud 25 is lowered and driven into and fixed to the water bottom E. In this process, the hull 1 is retained in advance at a predetermined backward limit within the guide hole 1g with respect to the spud 25 by means of the spud fore-and-aft drive device 27. Turning of the hull 1 around the spud 25 is suppressed by adjustment of the flow of water in the left and right directions that is injected from the thrust water jet portion 22a of the side thruster 22.

[0074] Subsequently, letting out the first wire W1 from the first winch device M1 swings the boom B downward and puts it in a tilted attitude under the water surface (for example, position Z in FIG. 1). Letting out the second wire W2 from the second winch device M2 makes the second wire W2 hang down from the extremity part Ba of the boom B present in the water and makes the grab bucket G sink down to the water bottom E, and an excavation operation, that is, dredging, of water bottom sediment by means of the grab bucket G, which is explained below, is started.

[0075] First, before the grab bucket G reaches the water bottom E, the pair of scoop plates 13 are fully opened by compressing the first hydraulic cylinder Cy1 and the raise/lower tube 12 is lowered to a lower limit with respect to the main frame 11 by extending the second hydraulic cylinder Cy2. When the two scoop plates 13 bite into sediment at the water bottom E as shown in FIG. 7, the two scoop plates 13 are forcibly pivoted in the closing direction as shown in FIG. 8 (a) to (b) by means of the first hydraulic cylinder Cy1, thus allowing the water bottom sediment to be scooped up and excavated into the two scoop plates 13.

[0076] Accompanying this dredging being started, pressurized air and pressurized water are injected via the air jet nozzles Na, Na' and the water jet nozzles Nw, Nw' respectively of the sediment flow assistance device A. The pressurized air and the pressurized water flow from the sand discharge pipe P only to the sediment transport pipe 8 side in particular when the two scoop plates 13 are closed, and are utilized for transport of excavated sediment that heads upward (that is, to the sediment collection tank 3 side) within the sediment transport pipe 8.

[0077] When the two scoop plates 13 are closed to a fully closed position as shown in FIG. 8 (b), the raise/lower tube 12 is raised up to the upper limit by means of the second hydraulic cylinder Cy2 as shown in FIG. 8 (c), accompanying the ascent the two scoop plates 13 move closer to the bottom wall 11b of the main frame 11 and mechanically and forcibly push the excavated sediment 4 within the two scoop plates 13 (that is, within the space 40) into the sand discharge pipe P via the opening lower end Pi. In a state in which the two scoop plates 13 are closed, sediment that has been scooped into the two scoop plates 13 is sufficiently stirred by means of the jet pressure of pressurized air and pressurized water in particular from the air jet nozzle Na' and the water jet nozzle Nw' and has increased flowability, and it is therefore efficiently and smoothly pushed into the sand discharge pipe P by the pushing action of the two scoop plates 13 accompanying raising of the raise/lower tube 12.

[0078] Sediment immediately after being pushed into the sand discharge pipe P is smoothly fed under pressure and made to flow toward the upstream side, that is, the sediment transport pipe 8 side, via the check valve 15 while being assisted by the jet pressure of pressurized air and pressurized water from the air jet nozzle Na and the water jet nozzle Nw.

[0079] In this way, one excavation cycle by the grab bucket G is completed, and the spud 25 is then pushed rearward by means of the spud fore-and-aft drive device 27 to thus move the hull 1 forward by a predetermined amount. The two scoop plates 13 are again put into a state in which they are made to open and swing up to the fully open position and then again made to descend and bite into sediment at the water bottom E as shown in FIG. 7. After that, the two scoop plates 13 are made to swing again in the closing direction, and the above excavation cycle is carried out. During this process, the excavated sediment 4 pushed into the sand discharge pipe P is fed under pressure into the sediment collection tank 3 of the hull 1 via the sediment transport pipe 8 by utilizing the jet pressure of pressurized air and pressurized water and stored. Repeating such an excavation cycle several times completes dredging for one predetermined section of the water bottom E.

[0080] Subsequently, the hull 1 is turned around the spud 25 only by a predetermined small angle by adjustment of the flow of water in the left-and-right direction injected from the thrust water jet portion 22a of the side thruster 22, and the hull 1 is stopped at the turned position. The spud 25 is then pushed in the fore-and-aft direction by means of the spud fore-and-aft drive device 27 so as to move the hull 1 forward or backward by a predetermined amount at a time, and during this process the same excavation cycle as described above is repeated, thus carrying out dredging for a next predetermined section that is adjacent to the previous predetermined section.

[0081] Repeating such dredging for adjacent predetermined sections in succession enables a fan-shaped or annular excavation target section spreading over a desired turning angle range (maximum 360 degrees) with the spud 25 as a center to be dredged.

[0082] When dredging of one excavation target section is completed, the hull 1 is moved to a next excavation target section. During this movement, the spud 25 is first pulled up from the water bottom E, after that the hull 1 is moved forward or backward by a predetermined distance by means of the main propulsion device 21, and the spud 25 is then again driven into and fixed to the water bottom E.

[0083] In the same procedure as for dredging of the excavation target section immediately prior thereto, dredging is carried out in sequence for each of predetermined sections of the next excavation target section. In this case, the history of positional information about the extremity part Ba of the boom B (and consequently the grab bucket G immediately below the extremity part Ba) is all stored in a storage part of the control device C, and it is therefore possible to omit dredging of a predetermined section that is estimated from the positional information history to overlap a prior (that is, already dredged) predetermined section and to shift to a next predetermined section.

[0084] The grab bucket G can dredge a wide range of the water bottom E as an excavation target via the above process.

[0085] In the dredger S of the present embodiment described above, the boom B axially supported on the hull 1 is formed so as to be tiltable in the vertical direction not only above the water but also underwater. The second wire W2 let out from the second winch device M2 on the hull 1 hangs down from the extremity part Ba of the boom B in the water during the dredging process, thus enabling the grab bucket G to be suspended.

[0086] It is thereby possible to minimize the length of the second wire W2 hanging down from the boom extremity part Ba while exploiting the intrinsic advantage of the grab bucket G being suspended by the wire, that is, the grab bucket G being capable of efficiently excavating water bottom sediment by utilizing its large self weight, and it is therefore possible to make it impossible or difficult for the second wire W2 to be influenced by wind or waves above the water surface or by tides in the water (in particular in the water close to the surface). As a result, deviation of the horizontal position of the grab bucket G with respect to the position of the hull 1 (and consequently the horizontal position of the boom extremity part Ba) can be made small effectively, thus improving the precision of positional control of the grab bucket G in relation to positional control of the hull 1.

[0087] Furthermore, the dredger S of the present embodiment in particular includes the hull propulsion device D, which can propel the hull 1 along the water surface in order to adjust the horizontal position of the grab bucket G in the water, and the control device C which controls operation of the hull propulsion device D. The control device C controls the position of the hull 1 by operating the hull propulsion device D based on GPS positional information of at least one of the hull 1, the boom B and the grab bucket G, thus enabling the grab bucket G to be moved by a predetermined section at a time along a predetermined excavation route in an excavation target section of the water bottom E.

[0088] This enables the grab bucket G to move by a predetermined section at a time along a predetermined excavation route in an excavation target section of the water bottom E by utilizing the positional information of the hull 1, that is, the GPS positional information, without fixing the hull 1 to the water bottom E, and it is thereby possible to carry out dredging of a wide range of the water bottom E thoroughly using the grab bucket G. Moreover, in combination with the effect of eliminating or curbing the influence of waves, tide, etc. in particular by hanging down the second wire W2 via the boom extremity part Ba in the water as described above, positional control of the grab bucket G during dredging can be carried out with good precision.

[0089] Furthermore, since the hull 1 of the dredger S of the present embodiment is provided with the sediment collection tank 3, the dredged sediment 4 can be stored in the dredger S itself without having a barge alongside the dredger S and on standby. This enables dredging to be continued for example when there is no barge on standby, and also when the grab bucket G, etc. malfunctions and dredging is discontinued, sediment that has been stored within the sediment collection tank 3 during dredging up to that time can be transshipped to a barge, thus increasing the overall operating efficiency.

[0090] Moreover, in the grab bucket G of the present embodiment, the pair of scoop plates 13 are axially supported p2 at the lower end of the raise/lower tube 12, which can be raised and lowered with respect to the main frame 11, the scoop plates 13 being able to swing in order to open and close, and the excavated sediment 4 scooped up into the two scoop plates 13 is forcibly pushed into the sand discharge pipe P by raising the raise/lower tube 12 with respect to the main frame 11 in a state in which the two scoop plates 13 are closed. In this way, the function of scooping up (that is, excavating) water bottom sediment is carried out by the scoop plate 13, the function of pushing the scooped sediment into the sand discharge pipe P is mainly carried out by the raise/lower tube 12, and it is therefore possible to design the scoop plate 13 and the raise/lower tube 12 optimally so as to fit their respective functions, thereby enhancing the degree of freedom in design overall. Since the amount of scooped sediment pushed into the sand discharge pipe P is determined by the raise/lower stroke of the raise/lower tube 12, it is possible to ensure that a sufficient amount is pushed in without especially increasing the size of the scoop plate 13 or increasing the stroke in the open/close direction.

[0091] The bottom wall 11b of the main frame 11 is formed into a hemispherical surface protruding downward, and one end Pi of the sand discharge pipe P opens on the central apex part of the bottom wall 11b. The pair of scoop plates 13 in a closed state have a hemispherical plate form corresponding to the hemispherical shape of the bottom wall 11b, and in a state in which the raise/lower tube 12 attains the upper limit the space 40 between the inner faces of the two scoop plates 13 and the lower face of the bottom wall 11b is sufficiently confined, that is, the two scoop plates 13 are closely opposing the lower face of the bottom wall 11b. This enables the excavated sediment scooped up into the pair of scoop plates 13 to be efficiently and evenly pushed into the sand discharge pipe P, thus enhancing the efficiency with which it is pushed in.

[0092] Furthermore, in accordance with the grab bucket G of the present embodiment, since pressurized air and pressurized water are injected from the air jet nozzles Na, Na' and the water jet nozzles Nw, Nw' respectively of the sediment flow assistance device A toward the excavated sediment immediately before and immediately after being pushed into the sand discharge pipe P, the sediment can be sufficiently dispersed to thus enhance the flowability, and the flow of sediment from the sand discharge pipe P toward the sediment collection tank 3 via the sediment transport pipe 8 can be sufficiently assisted. Moreover, the jet pressure of pressurized air and pressurized water for dispersing sediment (improving flowability) can be used effectively as pressure for transporting sediment within the sediment transport pipe 8. This enables the efficiency with which sediment is fed under pressure through the sand discharge pipe P and the sediment transport pipe 8 to be enhanced effectively.

[0093] FIG. 10 to FIG. 12 show a second embodiment of the present invention, which is different from the first embodiment only in terms of the structure of the grab bucket. That is, in the first embodiment the main frame 11 of the grab bucket G has a cylindrical shape, the bottom wall 11b has a hemispherical plate shape, the raise/lower tube 12 also has a cylindrical shape, and the pair of scoop plates 13, 13 have a form that becomes a hemispherical plate shape in a closed state (that is, a form in which a hemispherical plate is equally divided into two), whereas in the second embodiment a main frame 1 1' of a grab bucket G' has an angular tubular shape having a rectangular cross section (more specifically a square), a bottom wall 11b' thereof has a semi-cylindrical shape, a raise/lower tube 12' also has an angular tubular shape having a rectangular cross section (more specifically a square), and a pair of scoop plates 13', 13' have a form that becomes a hemicylindrical plate shape in a closed state (that is, a form in which a hemicylindrical plate is equally divided into two via a cross section in a generatrix direction).

[0094] The structure of the second embodiment is otherwise the same as that of the first embodiment, and constituent elements of the second embodiment are denoted by the same reference numerals and symbols as those of the corresponding constituent elements of the first embodiment, further explanation being omitted.

[0095] In the second embodiment also, the same operational effects as those of the first embodiment can be achieved.

[0096] The first and second embodiments of the present invention are explained above, but the present invention is not limited to these embodiments and may be modified in a variety of ways as long as the modifications do not depart from the subject matter thereof.

[0097] For example, the embodiments illustrate a case in which the hull propulsion device D includes the spud-type hull propulsion mechanism SP in addition to the main propulsion device 21 and the side thruster 22, the hull 1 is moved forward and backward by a predetermined amount at a time by means of the spud-type hull propulsion mechanism SP, the hull 1 is turned and pivoted by means of the side thruster 22 over a predetermined angle at a time with the spud 25 as a center, and the bucket device V can move and dredge a predetermined section at a time of a fan-shaped or annular excavation target section of the water bottom E. However, in the present invention, without using such a spud-type hull propulsion mechanism SP, operation of the main propulsion device 21 and the side thruster 22 may be controlled based on GPS positional information of at least one of the hull 1, the boom B and the grab bucket G so as to move the hull 1 by a predetermined amount at a time forward, backward or laterally in either one of left and right directions, thus making it move and dredge a predetermined section at a time along a predetermined excavation route in an excavation target section of the water bottom E. In this case, the side thruster 22 is not only disposed in a front part of a bottom part of the hull 1 as in the embodiments but also disposed in a rear part of the bottom part of the hull 1.

[0098] Furthermore, the embodiments illustrate a case in which, when carrying out dredging, operation of the hull propulsion device D is controlled based on GPS positional information of at least one of the hull 1, the boom B and the grab bucket G so as to control the position of the hull 1, but instead of or in addition to the GPS positional information, operation of the hull propulsion device D may be controlled based on positional information from another position sensor that can detect the hull position, thus carrying out control of the position of the hull 1.

[0099] Moreover, the embodiments illustrate a case in which excavated sediment is fed under pressure into the sediment collection tank 3 of the hull 1 via the sediment transport pipe 8 by utilizing the jet pressure of pressurized air and pressurized water from the sediment flow assistance device A provided on the grab bucket G (for example, the sand discharge pipe P), but in addition to the sediment flow assistance device A, for example, jet pump means (JP) shown in FIG. 2 of Japanese Patent Application Laid-open No. 2008-115610 may be disposed partway along the sediment transport pipe 8, thus assisting the flow of sediment within the sediment transport pipe 8. In this case, in addition to the jet pressure of pressurized air and pressurized water injected from the sediment flow assistance device A into the sand discharge pipe P, the jet pressure of pressurized air and pressurized water from the jet pump means (JP) is also utilized for feeding sediment under pressure within the sediment transport pipe 8, and it therefore becomes possible to more efficiently feed excavated sediment under pressure into the sediment collection tank 3 of the hull 1.

[0100] Furthermore, the embodiments illustrate a case in which when the dredging water area is distant the dredger S is steered so as to travel by itself to the dredging water area, but in such a case the dredger S may be towed by another ship and moved to the dredging water area.

[0101] Moreover, the embodiments illustrate a case in which the sediment collection location above the water is the sediment collection tank 3 provided in the hull 1 of the dredger S, but the sediment collection location may be a sediment collection tank placed on another ship (for example, a barge) different from the dredger S, or a floating facility.

[0102] Furthermore, the first embodiment illustrates a case in which the bottom wall 11b of the main frame 11 is formed into a hemispherical plate shape, and the second embodiment illustrates a case in which the bottom wall 11b' of the main frame 11' is formed into a hemispherical plate shape, but in the present invention the bottom wall shape of the main frame is not limited to those of the embodiments, and it may be formed into an appropriate shape according to the shape of the pair of scoop plates in a closed state, for example, a horizontal flat plate shape.

Claims

1. A dredger in which a wire (W2) is hung down from an extremity part (Ba) of a boom (B) that has an axial support (p1) on a hull (1) so as to be tiltable, a winch device (M2) provided on the hull (1) is capable of taking up and letting out the wire (W2), a bucket device (G, G') is suspended from the wire (W2), and the bucket device (G, G') scoops up and excavates sediment on a water bottom (E) and can feed the sediment under pressure to a sediment collection location (3) above water through a sediment transport pipe (8),
characterized in that the boom (B) is formed so as to be tiltable in a vertical direction underwater, and the wire (W2) can hang down from the extremity part (Ba) of the boom (B) underwater.

2. The dredger according to Claim 1, comprising a hull propulsion device (D) that can propel the hull (1) along water surface in order to adjust a horizontal position of the bucket device (G, G') underwater, and a control device (C) that can control, based on GPS positional information of at least one of the hull (1), the boom (B) and the bucket device (G, G'), the position of the hull (1) by controlling operation of the hull propulsion device (D) so that the bucket device (G, G') can move on an excavation target section of the water bottom (E) along a predetermined excavation route.

3. The dredger according to Claim 1 or 2, wherein the bucket device (G, G') is provided with a sediment flow assistance device (A) that injects pressurized air and/or pressurized water toward excavated sediment (4) scooped up into the bucket device (G, G') so as to assist flow of the sediment (4) from the bucket device (G, G') toward the sediment collection location (3) via the sediment transport pipe (8).

4. The dredger according to any one of Claims 1 to 3, wherein the hull (1) is provided with a sediment collection tank (3) that becomes the sediment collection location.

Drawing