Cutter head for dredging device, in particular for cutter suction dredgers

Abstract: Cutter head for a suction dredger, comprising: a first and a second disc-shaped plate (2,24), being spaced from each other along a cutter head axis and defining an interspace between them; cutting means with a plurality of blades (25) disposed in a pheripheral zone located on the radial outer zone of said interspace and spaced from each other in the pheripheral direction, said blades defining between them apertures for allowing material cut by the blades to pass to said interspace, wherein said cutting means are arranged for rotation about said cutter head axis with respect to stationary parts of said cutter head; and discharge means (23) for discharging the material present in said interspace through a suction line. The cutter head comprises shielding means acting in at least the radial direction and pertaining to the stationary parts, such as e.g. an outer sleeve provided with a controllable aperture.

Description: The invention relates to a cutter head according to the preamble of claim 1. Furthermore, the invention relates to a method of dredging which is provided with such a cutter head. A cutter head as described in the preamble of claim 1 is known from JP-A-58168731. These and other cutter heads are also referred to by the term disc bottom cutter and they are particularly useful in cases where it is desirable to be able to leave a bottom surface that is quite or even extremely flat after dredging. If the material to be dredged is easily brought into suspension, as is the case with silt, using a cutter head presents the drawback that the rotating parts, and particularly the blades, create flows that result in the water in the environment of the cutter head becoming turbid with silt. In this way material that was initially in suspension might settle again in areas that have already been treated. Under special flow conditions such sedimentations may even be deposited at considerable distances from the area of operation. Although the disc bottom cutter considerably reduces turbidity in comparison with conventional crown cutters, further improvement is nevertheless required. When a dredging operation is put to tender, nowadays increasing demands are made of the contractor when it comes to the extent in which pollution of the environment should be prevented. The known cutter head is provided with a semicircular head for shielding a part of the circumference of the cutter head, which can be changed in position in response to the change of direction of swing. The cutter head comprises an upper plane blade and a lower plane blade provided with lower excavating blades, wherein peripheral excavating blades connect to curved, inwardly extending guide blades, which are attached to a rotationally driven hub member. Above the downwardly and inwardly concavely sloping upper edges of the guide blades a chamber is formed in the cutter head, which is upwardly bounded by a cover positioned just above the upper plane blade. The cover is provided with a downwardly opening mud sucking port which is in communication with a mud sucking pipe extending along the ladder of the dredge towards a dredge pump. The cover is furthermore provided with water intake means for balancing the water pressure inside the cutter head and the outside of the cutter head when the pressure in the cutter head lowers due to the mud sucking effect. An object of the invention is to provide a cutter head with an improved dredging capacity or performance, with which a reduced turbidity during use can be achieved. For this purpose, the cutter head according to the invention is characterized in that said inner space is annular and delimited in the downward direction of the cutter head axis by said lower plate, in that said suction piece fits in said inner space and extends to the lower plate, and in that said blades are arranged for rotation towards said suction piece to urge excavated material against and into the discharge means. In the cutter head of the invention, the sleeve, the rotating blades and the suction piece cooperate in densifying the mixture present in the inner space, while at the same time increasing the pressure near the suction mouth of the discharge line promoting a smooth discharge of the densified mixture. It is remarked that UK-A-202717 discloses a disc bottom cutter head which has a rotating closed bottom plate provided with cutting blades on its curcumference, wherein in the inner space a suction nozzle is arranged to which loosened soil is urged by the co-action of under-pressure in the suction nozzle and the thrust of the bottom plate. The sleeve is preferably arranged for possible adjustment of its position with respect to the non-rotating parts, so that the position of the portion of the radial outer side of the peripheral zone through which material is allowed to enter can be adjusted. Preferably, the sleeve comprises an aperture and is arranged for possible adjustment in the direction of rotation, for example over the angle enclosed by the aperture, being e.g. 120°. Thus the cutter head according to the invention can be selectively adjusted at either an undercutting or an overcutting (with respect to the swing direction of the cutter suction dredger) dredging process. The size of the aperture in the sleeve is preferably adjustable, so that e.g. dependent on the chosen dimensions of the breach, an optimum aperture size is feasible so as to prevent subsidiary flows that cause turbidity. For this purpose the sleeve is preferably provided with a visor plate wherein means are provided for adjustment of the position of this visor plate with respect to the aperture. In this respect it is advantageous that the means for adjusting the position of the visor plate with respect to the aperture are adapted for displacement of the visor plate in the direction of the cutter head axis. Thus it is possible to adjust the size of the aperture in axial direction, while the height of the breach can be taken into account in order to reduce undesired flows to the highest possible extent. In a further preferred embodiment of the cutter head according to the invention the shielding means act both in the radial and in the tangential direction. Furthermore, apart from the above-described sleeve, radial transverse partitions may have been disposed in the interspace. The shielding means preferably comprise a filling means for filling up a part of the interspace. In a preferred embodiment the discharge means are displacable in rotational direction and the filling means and the discharge means are interconnected for simultaneous adjustment in the peripheral direction. This filling means, which is stationary with respect to the rotating blades, constitutes a means to control inflow which does not itself generate flow, however, it is now situated on the radial inner side of the peripheral zone and moreover helps to increase the suction efficiency by filling up a part of the interspace, and thus reducing the possibility of undesired flows. In this respect it is preferred that the filling means occupies more than 50% of the interspace so as to form a boundary for a substantially tangential passage of cut material through the interspace to the discharge means. The filling means may then resemble a disc-shaped box having a cut-out portion so as to form the passage to the discharge means. As stated above, the present invention also relates to a method of using a cutter suction dredger, which is provided with a cutter head according to the invention. If use is being made of such a suction dredger with a cutter head having a sleeve of which the aperture is of adjustable size as disclosed in the foregoing, it is advantageous, with a view to controlling the inflow so as to prevent too much turbidity, to use sounding means on the dredge to determine the height of the breach as well as first control means for controlling the size of the portion on the radial outer side of the peripheral zone closed off by the sleeve as a function of the data from said sounding means. In order to further enhance this control capacity, the width of the breach and the swing velocity of the cutter suction dredger is measured and the suction rate is controlled as a function of the data from said sounding means and the data of said measuring means. The invention will be further described hereinafter on the basis of a preferred embodiment as represented in the enclosed drawings, in which: figure 1 is a section of the cutter head of the examplary embodiment of the invention; figures 2A and 2B are schematic top views of the cutter head of figure 1 in an undercutting and an overcutting dredging process, respectively, and figures 3A and 3B are schematic top views similar to those of figures 2A and 2B, however, a filling piece has now been disposed in the cutter head. The cutter head of the preferred embodiment of the invention as represented in figures 1, 2A and 2B is attached to a cutter suction dredger (not shown) by means of a ladder construction 6a, 6b. A suction line 13 extends between the pump 12 on the cutter head 1 and the cutter suction dredger. The pump 12 is driven by driving means 3. At the top of the cutter head a unit 7 is furthermore disposed at the center for rotating the rotary parts of the cutter head. The cutter head 1 comprises a top plate 2, forming an assembly together with the suction passage 23, the pump 12 and the ladder 6a, 6b. A bottom plate 24 is provided at the bottom of the cutter head 1, which bottom plate is rotatable by means of rotary means 7, in particular rotary shaft 14. Blades 25 are circumferentially disposed on the radial outer periphery, and are connected to one another at their tops by means of a ring 26. More radially inwards a cylindrical wall 27 is secured to the bottom plate 24, thus defining an annular space 28 within the cutter head between the wall 27 and the blades 25. In the left- hand portions of the cutter head as represented in figure 1 suction piece 4 with suction mouth 5 can be observed, fitting into the annular space 28 and, as shown in figures 2A and 2B, being curved along the curvature of the annular space 28. If the rotary means 7 and the pump 12 are in operation, soil cut with the aid of the blades 25 will enter the annular space 28 and will be passed through there to the suction mouth 4 and be discharged via passage 23 and pump 12 and via the conduit 13. According to the invention the cutter head 1 comprises a sleeve 11 surrounding on the radial outer side the zone in which the blades 25 are disposed, and being fixedly connected to a setting plate 15 disposed below the top plate 2. On the right-hand side of the cutter head 1 represented in figure 1 it can be seen that the sleeve comprises an aperture 11a, a visor plate 31 being arranged on the sleeve for slidable movement within guide means 36 in the direction of the rotational axis. At the top of the sleeve 11 at the visor plate 31, lifting means 9 are provided, consisting of a cylinder 30 and a piston rod 33, of which one end is connected at 34 to the visor plate 31 for vertical adjustment of the visor plate and therefore for adjustment of the size of the aperture 11a in the sleeve 11. At its underside the visor plate 31 comprises an obliquely inclined plate 32 for promoting the supply of soil to the open part of the aperture 11a. As can also be seen on the right-hand side of figure 1, the sleeve 11 is fixedly connected to the setting plate 15, on which a gear ring is secured at the radial inner side thereof, which ring comprises an external toothing. The gear ring 17 is rotatably connected to ring 19 by means of a bearing 18, said ring 19 being fixedly connected to the upper plate 2. The external toothing 20 of the ring 17 meshes with the external toothing 21 on pinion 16. Pinion 16 is part of a rotary drive 8, which in turn is fixedly connected to the upper plate 2. So when the rotary drive 8 is activated and pinion 16 is therefore rotated, the gear ring 17 will be rotated via the gear transmission 20, 21 with respect to the ring 19 and thus the upper plate 2 as well. Upon rotation of the gear ring 17 the setting plate 15 as well as the sleeve 11 and preferably also the visor plate 31 are rotated. In this way the position of the aperture 11a of the sleeve 11 with respect to the ladder 6a, 6b can be adjusted, so that the positions represented in figures 2A and 2B can be obtained. In figure 2A the cutter head is swung by manipulating the anchoring of the cutter head suction dredger in direction A in order to cut the soil at breach D in the so-called undercutting process. In figure 2B the sleeve 11 and therefore also the aperture 11a are rotated clockwise over approx. 120° with respect to the position in figure 2A and the cutter head is swung in direction B in order to cut the soil in breach E in the so-called overcutting process. In both cases the blades 25 rotate clockwise. It can clearly be observed that the sleeve 11 prevents the blades 25 from causing any undesired water movements when they do not perform their cutting function, while at the same time it is prevented that the soil located between the blades radially passes out under exchange with the surrounding water. Figures 3A and 3B show the cutter head 1' which substantially corresponds to the cutter head 1 of figures 1, 2A and 2B. Corresponding parts have therefore been indicated by the same reference numerals. The cutter 1' comprises a box-shaped filling element 35, forming a peripherally adjustable unit with the suction piece 4'. In this embodiment the box-shaped filling element 35 is a closed body that locally completely fills up the interspace. The major parts of this filling element 35 are the radial wall 35' and the wall 35". For simplicity's sake the pump and the discharge line have been omitted. The pump can be arranged for simultaneous displacement with the suction piece 4' and be connected by a flexible tube to the pressing conduit. In figures 3A and 3B it can clearly be observed that the filling element fills up that portion of the interspace that is situated adjacent to the shortest soil passage path of aperture 11a to suction piece 4' and thus enhances the soil flow concentration by preventing soil to spread out in the interspace. Figures 2A and 2B also show lateral arms 10a and 10b extending to either side of the ladder 6a, 6b. The arms 10a and 10b comprise echo-sounders (not shown) with which the heights of the breaches D and E can be determined. The data derived from these echo-sounders can be used to control the piston cylinder assembly 9 in order to set the size of the opening 11a. Thus the height of the opening 11a can be made to correspond to the measured height of the breach, whereby the inflow of water is restricted and turbidity can be minimalized. The favourable ecological aspects of the cutter head and cutter suction dredger (suction dredger) according to the invention are even further increased if means (not shown) are provided for measuring the factual swing velocity (e.g. in the case of anchoring by means of spuds: by determining the angular velocity of the rotation of the cutter suction dredger about the anchoring spuds), as well as means (not shown) for determining the width of the breach, being the size of the breach in the stepping direction (e.g. in the case of spud anchoring, for measuring the step between two successive spud anchorings). The data from these measuring means, including that from the echo-sounders, can be processed in a processing unit onboard the cutter suction dredger, which is be able to present a number of relevant proces parameters real time to the operator. The incoming data can also be used for manipulating the suction rate so as to prevent water from being sucked up unnecessarily if the silt supply decreases and so as to prevent spilling if the silt supply increases. So height of the aperture 11a and the suction rate can be controlled as a function of the step, the swing velocity and the height of the breach in order to cause as little disturbance in the environment outside the breach as possible and at the same time allow a maximum suction efficiency. In the preferred embodiment these control operations can all be performed automatically.

Claims: Cutter head (1) for a suction dredger, comprising: an upper (2) and a lower (24) disc-shaped plate, being spaced from each other along a cutter head axis; cutting means with a plurality of blades (25) disposed in a peripheral zone located on the radial outer zone of said cutter head (1) and spaced from each other in the peripheral direction, said peripheral zone being delimited in the direction of the cutter head axis by said upper plate (2) and lower plate (24), wherein said cutter head (1) includes an inner space which is delimited radially by said peripheral zone and delimited in the direction of the cutter head axis by said upper plate (2), said blades (25) defining between them apertures for allowing material cut by the blades (25) to pass to said interspace, wherein said cutting means (1) are arranged for rotation about said cutter head axis with respect to stationary parts of said cutter head (1); and shielding means (11, 35) acting in at least the radial direction and pertaining to the stationary parts, wherein said shielding means (11, 35) comprise a sleeve (11) for closing at least one portion of the radial outer side of the peripheral zone while enabling the soil to pass through another portion thereof, and comprising a stationary discharge means (12, 13, 23) comprising a suction piece (23) for discharging the material present in said interspace through a discharge line (13), characterized in that said inner space is annular (28) and delimited in the downward direction of the cutter head axis by said lower plate (24), in that said suction piece (23) fits in said inner space and extends to the lower plate (24), and in that said blades (25) are arranged for rotation towards said suction piece (23) to urge excavated material against and into the discharge means (12, 13, 23). Cutter head according to claim 1, characterized in that the sleeve (11) is arranged for possible adjustment of its position with respect to the remaining stationary parts (2). Cutter head according to claim 2, characterized in that the sleeve (11) comprises an aperture (11a) and is arranged for possible adjustment in the direction of rotation. Cutter head according to claim 3, characterized in that the sleeve (11) is arranged for possible adjustment along the angle included by the aperture, preferably being 120°, in peripheral direction. Cutter head according to claim 3 or 4, characterised in that the aperture (11a) of the sleeve (11) is of adjustable size. Cutter head according to claim 5, characterized in that the sleeve (11) comprises a visor plate (31), and in that means (30, 33) are provided for adjustment of the position of the visor plate (31) with respect to the aperture (11a). Cutter head according to claim 6, characterized in that the means (30, 33) for adjustment of the position of the visor plate (31) with respect to the aperture (11a) are adapted for displacement of the visor plate in the direction of the cutter head axis. Cutter head according to one of the preceding claims, characterized in that the shielding means (35) act both in the radial and tangential direction. Cutter head according to one of the preceding claims, characterized in that the shielding means comprises a filling means (35) for filling up a part of the interspace (28). Cutter head according to claim 9 characterized in that the discharge means (12, 13, 23) are adjustable in the peripheral direction and in that the filling means (35) is connected to the discharge means for simultaneous displacement therewith. Cutter head according to claim 10, characteri-zed in that the filling means (35) occupies more than 50% of the interspace (28) so as to form a boundary for a substantially tangential passage of cut material through the interspace to the discharge means. Method of dredging using a suction dredger which is provided with a cutter head according to one of the preceding claims. Method of dredging according to claim 12, when using a cutter head assembly according to claim 5, characterized by determining the height of the breach by means of sounding means (10a, 10b) arranged on the suction dredger, and by controlling the size of the portion closed off by the sleeve (11) on the radial outer side of the peripheral zone as a function of the data from said sounding means. Method of dredging according to claim 13, characterized by measuring the width of the breach and the swing velocity of the cutter head dredger by measuring means and by controlling the suction rate as a function of the sounding means (10a, 10b) data and the measuring means data.

Inventors: ROSENBRAND WILLEM FLORIS M, ROSENBRAND, WILLEM FLORIS, ROSENBRAND, WILLEM FLORIS, M.SC.
Applicants: BOS KALIS BV, BAGGERMAATSCHAPPIJ BOSKALIS BV
Application year: 1990
Main classification: E02F3
IPC codes: E02F3