AU2010270277B2 - Cutter head for dredging ground, cutter suction dredger provided with such a cutter head and use of the cutter head for dredging ground - Google Patents

Abstract

The invention relates to a cutter head (10) for dredging ground under water, this cutter head being suitable for attachment rotatably around a central axis to the ladder (2) of a cutter suction dredger (1) and for being moved through the ground therewith in a lateral sweeping movement, the cutter head comprising a base ring(13), a hub(14) situated at a distance in the direction of the central axis from the base ring, and a plurality of support arms (15) extending from the base ring to the hub, wherein a passage opening(16) is located between support arms and wherein the cutting tools (20) are axisymmetrical, at least at their free outer end. The invented cutter head has an increased efficiency, in particular for ground with an Unconfined Compressive Strength (UCS) of at least 50 MPa.

Description

11 gw itertoen NRPontDC OGW J I WI do-%l10 2015 CUTTER HEAD FOR DREDGING GROUND, CUTTER SUCTION DREDGER PROVIDED WITH SUCH A CUTTER HEAD AND USE OF THE CUTTER HEAD FOR DREDGING GROUND The invention relates to a cutter head for dredging ground under the water surface, this cutter 5 head being suitable for attachment to the ladder of a cutter suction dredger and for being moved over the ground therewith in a lateral sweeping movement. The invention also relates to a cutter suction dredger provided with such a cutter head, and to the use of the cutter head for dredging ground, in particular relatively hard ground. A cutter head of the type described in the preamble is for instance known from NL- 1031253. 10 The known cutter head is a revolving body which is rotatable around a central axis and formed by a base ring and a hub placed at a distance therefrom and concentrically thereto, between which extend a number of support arms provided with cutting tools. The known cutting tools are bit-like, which means that they comprise a flattened part at their free outer end, with the end surface of which they make contact with the ground over a determined linear distance. 15 For a good cutting action the cutting tools must be first to come into contact with the ground during rotation of the known cutter head. The cutting tools are therefore situated on a leading part of the support arms as seen in the direction of rotation of the cutter head. The cutter head is applied in combination with a cutter suction dredger (also referred to as cutter dredger). A cutter suction dredger comprises a vessel anchored in the ground by means 20 of so-called spud posts. Owing to this anchoring the reaction forces occurring during dredging can be absorbed and transmitted to the ground. Attached to the ladder of the cutter suction dredger is a suction conduit which is connected to the cutter head and along which the dredged ground is removed. During dredging the cutter head is set into rotation and with ladder and suction conduit lowered into the water at a generally oblique angle until it touches the ground. 25 The cutter head is dragged through the ground by hauling the ladder alternately from port side to starboard side using winches. Because the cutter head rotates about the axis of the cutter head - the line connecting the centres of rotation of the base ring and the hub - the end surfaces of the cutting tools strike the ground with great force under the weight of the cutter head, ladder ard suction conduit Via pssage opein be the support arms the hereby formed fragmerrts are suctioned up and discard by the suction conduit, A whole ground surface can be drcdged by moving the cuner sucion dredger over a determined distance at a time and repeating dhe above stated swveeping movement, 5 US-A-4 319 415 discloses a cutter head for a cutter The cutter head comprises a revolving body that is rotatable around an axis of revolution awihh is ftorred by a base ring and a hub located at a distance" thereof, beteen which a niwnmr of support arms extend, The support arms are provided wth teeth holders fb.r cutting teeth. The teeth holders have a Tashaped profile with which they can be releasably attached to the support arms, 10 WO 2005/035884 A describes a robotic manipulator fAr removing a worn toothom a dredger cutter head, and for replacing the removed tooth with a new tooth. The manipulator is installed on a dredger veel. The disclosed cutter heads are of the usual type including about 5 support arms carrying about 8 teeth each, (B-AK2 032 492 discloses a cutter head conprisig a ceraral hub onto which at least one 15 spiral-helical veb is mounted. The web is provided with an arry of cutter bits spaced along the web and projecting therefrom such that in use successive bits on the same web cut deeper than a previous bit, NL-Al8 104 969 discloses a conventional cutter head for a cutter suction dredger, the cutter head comnprising the usual amount of 5 support arms with about 8 teeth attached to it, 20 US-A-4 470 210 discloses an adapter for a cutter head, The adapter is rotatable around a longitudinal and a transverse axis, such that the optimum cutting angle of the cutting teeth can be adjusted, U S-A-4 986 011 discloses a cutting tooth tor a cutter dredger that may be attached to a support armi of a cutter head by clamping part of it in an adapter, making use of an intermittent flexible 25 element, Hix i r ntme NRPoniDCCG~~th I 50)4 _I docx-bIO1S The known cutter head has the drawback that relatively hard ground, such as for instance rock, defined in the context of the present application as ground with an Unconfined Compressive Strength (UCS) of at least 50 MPa, either cannot be dredged or can only be dredged with limited efficiency. The UCS is a concept known to the skilled person and represents the 5 compressive strength of a ground mass, the side walls of which are not supported during compression. Efficiency is understood in the context of this application to mean the volume of ground dredged per unit of time and unit of power. Embodiments of the present invention seek to provide a cutter head for a cutter suction dredger which, in addition to other advantages, can dredge ground surfaces more efficiently 10 and which makes it particularly possible to dredge relatively hard types of ground with an increased efficiency relative to the known cutter head. According to a first aspect of the invention, there is provided cutter head for dredging ground under the water surface, comprising a revolving body which is rotatable around a central axis and which is formed by a base ring and a hub placed at a distance therefrom, between which 15 extend a number of support arms provided with cutting tools, between which support arms passage openings are present for discharge of the dredged ground, wherein the cutter head comprises at least 50 cutting tools, which cutting tools are axisymmetrical at least at their free outer end. Preferably the cutting tools are axisymmetrical along their entire length, thereby allowing free 20 rotation around their longitudinal axis. It has been found that, by providing inter alia the support arms of the cutter head with cutting tools that are axisymmetrical at the soil contact side thereof, relatively hard ground in particular, such as for instance rock, can be dredged with an increased efficiency relative to the known cutter head. The axisymmetry of the cutting tools has been found to have a favourable effect on the breaking of the ground, and 25 particularly relatively hard ground. The known cutting tools are relatively wide at their free outer end to be able to withstand the great forces to which they are subjected during the dredging. The weight of the underwater -4 conimonents of the cutter suction dredger is after all distributed over the contact surface area between the cutting tools and the ground, By giving the known cutting tool a relatively wide free outer end this contact surace area is relatively large. whereby the thrce transmitted to the ground is distributed over a r vetily large surface area. Th average pressure on the contact 5 surface is thus kept limited whereby breaking of the cutting toos is prevented. Because the cutting tools are axisynimetrical at least at their free outer end, and come into contact with the ground with this part Lth cttng tools already peretrate the ground at relatively tow forces, The pressure exercte oal on the garoundr is moreover relatively high, whereby the gromd. and particularly relatively hard ground, is crushed effectively, 10 h should be mentioned that US-A-4 488 608 describes a rotary stone-cutting head Or cutting dry rock and te ike. the cutting head carrying conical cutting tools, a part of which comprise a hardened (Iungstoen carbide) insert. The tools having the inserts are placed in a somewhat retracted position vis-aais the other cutter tools to avoid early breakage when coming in contact with an irregular rock surtace 15 D 10 2005 051450 A l discloses an axisymmetrical cutting tool that can be rotated freely around its axis of rotation srmetry in a ease, whereas 1.S-A-4 575 156 relates to a similar, axisymnmetrical cutting tool for use in coal mining. Both documents do not suggest using sueh tools in underwater dredging; A preferred embodiment of the cutter head has the feature that the cutting tools are 20 rottionSymetrical and are .ore preterably of cotical form. Such a gometry afllos highIer average pressures to be transmitted to the ground than is possible with the known cuttin tool, A further advantage of the cutting tioo- and particularly the conical preferred variant is tihat owing to its shape, it takes up less space than the known cutting tool. It hereby comes possible to provide the cutter head with a large number of cutting tools, and this has been 25 found advantageous tor the dre-dging eftciencv of the cutter head. For the same reason the passage openings which are present between the support arnis ot tie cutter head and along which the dredged ground is discharged can likewise be smaller than is the case in the known -5 cutter head. This is because the cutting tools obstruct the passage less. The number of support arms can hereby also increase. According to another preferred embodiment of the invention, the cutting tools comprise a substantially cylindrical shank part with a reduced diameter with respect to a conical top part. 5 The cutting tool according to this embodiment is arranged with its cylindrical shank part in coupling means, provided on the arms of the cutter head. The coupling means preferably comprise a block socket with a central bore in which the cylindrical shank part is inserted for ready rotation. In this embodiment, the conical part will protrude outside the block socket over an active length, which is relatively short in comparison with the total length of the 10 cutting tool. This has the advantage that much larger forces can be withstood than with the state of the art cutting teeth. The block socket moreover effectively supports the cutting tool against bending deformations. In a preferred embodiment the cutting tools have a length protruding outside its holder lying between 10 and 500 mm, more preferably between 20 and 250 mm, and most preferably between 50 and 150 mm. 15 In a particularly preferred embodiment, the cutting tool is arranged, preferably in its socket, such that it can be rotated freely or at least readily around its axis of rotation-symmetry. This is possible due to the fact that the cutting tools are rotation-symmetric. Allowing free or ready rotation of the tools during operation reduces the risk for breakage and also self-sharpens the soil-contacting tip of the cutting tools by friction with the soil. The useful life of the cutting 20 tools is hereby extended and precious time is saved in not having to replace broken or blunt cutting tools frequently. The conical part of the cutting tool is preferably provided with a hardened tip at the outer end which comes into contact with the soil. The tip may for instance be made of carbide. In another preferred embodiment the cutter head is characterized in that the top part of the 25 conical cutting tools has a radius of curvature of a maximum of 500 mm, more preferably of a maximum of 350 mm, still more preferably of a maximum of 100 min, and most preferably of a maximum of 50 mm. Yet another preferred variant comprises conical cutting tools, the top 1 ignlInicmor cnNRBPonN\DCCiG~tXS I 5:,1 doca- 1000 IS -6 part of which has a radius of curvature lying between 1 and 100 mm, and more preferably between 5 and 80 mm. In yet another preferred variant the cutting tools comprise a holder in which a conical hard metal insert is received. A preferred embodiment of the cutter head has the feature that the cutter head comprises at 5 least 5 support arms, more preferably at least 10 support arms, and most preferably at least 15 support arms, It is even possible for the cutter head to comprise a revolving surface provided with passage openings between the base ring and the hub. The part of the revolving surface lying between the openings then forms the 'support arms' of the cutter head. Another option is to provide the cutter head with axially running support arms on which are mounted 10 transverse arms running in the peripheral direction. The number of cutting tools can be varied within broad limits, wherein it is advantageous if the number of cutting tools is as high as possible. In a preferred embodiment the cutter head comprises at least 100 cutting tools, still more preferably at least 140 cutting tools, and most preferably at least 180 cutting tools. The cutting tools can here be distributed regularly, but 15 also irregularly, over the revolving surface of the cutter head. The number of cutting tools per support arm preferably comprises at least 10 cutting tools, more preferably at least 15 cutting tools, still more preferably at least 20 cutting tools, and most preferably at least 25 cutting tools. The cutter head cuts the ground in a fundamentally different manner than the known cutter 20 head. Where the known cutter head strikes large fragments out of the ground with great force, the cutter head will break off much smaller pieces of ground. Owing to the greater number of cutting tools in the direction of rotation of the cutter head the ground is moreover cut in more rapid succession. This operation is found to result in a higher efficiency, particularly in harder grounds, 25 It has further been found advantageous for the support aims to comprise a first series of cutting tools on a leading part as seen in the direction of rotation of the cutter head, and at least one support arm comprises a second series of cutting tools on a part facing away from the central H ;g IrlernocWNR~ortnihDCCC '"I 5911_ I does-I/10Q205 -7 axis. Although it is unusual to provide a part of a support arm facing away from the central axis with cutting tools, an improved efficiency is obtained. It has been found, surprisingly, that the connection of the cutting tools to the part of the support arm facing away from the central axis is sufficiently strong to transmit to the support arm the forces resulting from the 5 cutting tools striking against particularly hard ground such as rock. More cutting tools can in this way be placed on a single support arm than according to the prior art. This provides advantages, particularly in the dredging of relatively hard ground. In an advantageous embodiment the cutting tools of the first series on a support arm are offset relative to the cutting tools of the second series. This further increases the efficiency of the 10 dredging process. Because the cutting tools are offset, an increased working area of the cutting tools is obtained. This is because cutting tools of the second series are not obstructed by cutting tools of the first series. In yet another embodiment the support arms have a length and the cutting tools are located on either side of the middle of the support arms along a maximum of 80% of the length of the 15 support arm. The absence of cutting tools close to the outer ends of the support arms is not found to adversely affect the efficiency of the cutter head, while owing to this measure the construction of the cutter becomes simpler and therefore cheaper. On the other hand, the presence of cutting tools close to the hub of the cutter head is advantageous for the progression of the cutter head. 20 The cutting tools can be formed integrally with the support arms of the cutter head. Another method is to connect them directly to the support arms, for instance by welding cutting tools embodied substantially in steel to support arms manufactured substantially from steel, this resulting in a strong connection. The cutting tools can particularly be connected to the support arms via coupling means. Cutting tools can hereby be replaced easily, which may be 25 necessary as a result of wear or damage. It is advantageous here to connect the coupling means themselves integrally with the support arms, such as by making use of a welded connection.

in a preferred eibodiment of the cutter head tie support arms of the cutter head are provided with guides on ih the coupling means amd or the cutting tools are displaceably mounted, A suhable guide comprises for instance a g uide rail overwh the coupling means and/or the Cutting tools can slide. Thc present preferred iriant has the advantage that the coupling 5 means and/or the cutting tools can be displaced easiy The intermediate distance hetwee the cutting tools can thus be adjusted in simple manner depending on the properties, and in particular the hardness. of the ground. According to a second aspect of the invention, there is provided the use of a cutter head according to the first aspect for dredgng a ground with an inconfined Conpressive Strength 10 (UCS) of at least 50 MPa. Enbodimnents of the invention also relate to the use of a cutter head for cutting into grouidI parts a ground with an Uncornfined Compressive Strength UCS) of between 5000 MPa, preferably between 60-150 MPa and most pretbrably 80-100 PNa. For the advanmge of the use of the cuctr head reference is made to the advantages already stated above of the cutter 15 head. Accordig to a third aspect of the present invention, there is provided a cutter suction dredger provided with a cutter head according to the first aspect, The invention also relates to a cutter suction dredger provided with a cutter head, With a cutter suction dredger provided with a cutter headground and in particular relatively hard 20 ground, iye, a ground with a UCS of more than 50 MPa, can be dredged with an improved eficiencv, The present invention wk ill now be described by way of non-dimiting exarnple only, with reference to the acconpanying drawings. inwhich: Figure 1 is a schematic side view of a part of a cuter suction dredger with a ladder attached 25 thereto and provided with a cutter he:ad Figure 2 is a perspective view of a cutter head; Figure 3 is a side view of a detail of a cutting tool; H :.pgu~htntemo cinNRPonNilCVGW05$I1504_I do~M'I~lW2I 5 -9 Figure 4 is a side view of a detail of a cutting tool according to an embodiment of the invention; and Figure 5 is a side view of a detail of a cutting tool according to still another embodiment of the invention. 5 Figure 1 shows a cutter suction dredger 1 on which a ladder 2 is mounted pivotally around a horizontal shaft 3. Ladder 2 is provided with a suction pipe 4 which can suction up the loosened ground parts to a level above water surface 100, after which they are discharged. Ladder 2 is hauled over the ground surface 9 for dredging or breaking by means of a. winch 5 which is arranged on the deck of cutter suction dredger 1 and is provided with a number of 10 swing winches (not shown) and ladder winch 8. Ladder 2 is provided on the outer end thereof with a. cutter head 10. Cutter head 10 can be lowered under water by means of the ladder winch cables 8 and moved during use over ground surface 9 in a reciprocating, sweeping movement from the port side to the starboard side of cutter suction dredger I and back. In order to be able to absorb the forces generated here on the ground surface, cutter suction 15 dredger 1 is anchored in the ground by means of a spud post 101. Figure I shows the left hand (starboard) spud post in unanchored position and the right-hand (port side) spud post in anchored position. Referring to figure 2, cutter head 10 comprises a revolving body 11 which can be set into rotation around its rotation axis 12 by means of drive means (not shown). Rotation axis 12 20 herein coincides with the central axis of cutter head 10. In the shown embodiment revolving body 11 is set into rotation in clockwise direction R as seen from the bridge. Support arms 15 extend spirally between a. base ring 13 and a hub 14 located at a distance from base ring 13, these support arms 15 being connected to base ring 13 and hub 14. Support arms 15 are here arcuate, wherein the convex sides are directed in the rotation direction R. Base ring 13, hub 25 14 and support arms 15 are manufactured substantially from steel. This not only makes cutter head 10 strong but also gives cutter head 10 a great weight, whereby during dredging the cutter head 10 is urged in the direction of the ground for dredging under the influence of the gravitational force. Support arms 15 are herein placed regularly round the periphery of cutter head 10. Passage openings 16 are located between support arms 15. Coupling means 17 HI gIig cneowmNRotb%DCCGWV 459114 I.doc-tOi /201 - 10 manufactured substantially from steel are welded to a leading edge 15a of support arms 15 relative to the rotation direction of cutter head 10 for the purpose of coupling a first series of cutting tools to support arms 15. Coupling means 17 likewise manufactured substantially from steel are welded to the edge I5b of support arms 15 facing away from the central axis of 5 cutter head 10 for the purpose of coupling a second series of cutting tools 20 to support arms 15. Coupling means 17 are oriented such that the front side or striking side of cutting tools 20 of the first and second series are directed in rotation direction R. Referring to figure 3, an embodiment of a cutting tool 20 is shown. The shown cutting tool 20 with overall length 27 comprises a substantially cylindrical part 22 with diameter 25, and a 10 conical second part 23. Cutting tool 20 can be arranged with cylindrical part 22 in an above described coupling means 17 of cutter head 1, for instance by means of a snap connection 220. A permanent connection is also possible, or other form of releasable connection. In the situation where cutting tool 20 is arranged in coupling means 17, conical part 23 will protrude outside the coupling means or holder 17 over an active length 26. Conical part 23 of cutting 15 tool 20 is provided with a hardened tip 28 at the outer end which comes into contact with the soil. The appropriate radius of curvature of the tops of cutting tools 20 depends on, among other factors, the properties of the ground and on the specific design of the cutter head, but preferably lies between 1 and 100 mm. A suitable overall length 27 of a cutting tool 20 preferably amounts to between 20 and 400 mm. Suitable transverse dimensions 25 preferably 20 amount to between 10 and 100 mm. In a preferred embodiment the cutting tools 20 have a length 26 protruding outside holder 17 lying between 10 and 500 mm, more preferably between 20 and 250 mm, and most preferably between 50 and 150 mm. As shown in figures 4 and 5, the cutting tool 20 is preferably coupled to the support arms 15 through coupling means 17 in the form of a block socket with a central bore 70 in which the 25 cylindrical shank part 22 of a cutting tool 20 is inserted for ready rotation. In the embodiment of figure 4, the conical part 23 with the carbide tip 28 protrudes outside the block socket over an active length that is relatively short in comparison with the total length of the cutting tool 20. The block socket 17 supports the cutting tool 20 against bending deformations and allows to transfer large compressive forces in the axial direction 171 of the cutting tool 20. The -11 cutting tool 20 is inserted into the central bore 170 from the left until the snap connecuon 220 engages correspondi annular groove 221 in the socket. in the engaged state, the cutting tool 20 is free to roate around the axis 171 in the central bore 170, due to the faet that the cutting tool 20 is rThitatioation may be hindered sonew-hat' by frictional 5 forces between th oiter surface of the shank part 22 and the inner surface of the central bore 170, or between the contact surfaices of socket and conical part 23, but is essential a free rotation. Another embodiment shown in fuure 5, uses a separate holding ring 172 with a slot 173 such thtit may :e made smaller by comnpressing it once engag'ed wh a corresnonding amnnar 10 groove 22i (as in the enbodniment shown in gure 4) it expands and leaves the outer surface of the shank part 22 lrce to rotate. Locking of the cutting tool 20 in the axial direction 171 is accomplished by engagement of the rear part 222 of cutting toot 20 against the annular ring ] 72, A cuter head is particularly suitable fbr breaking relatively hard ground, is self sharpening 15 and has an extended service life. While various enbodinents of the present invention have been described above, it should. be understood that they have been presented by way of exatriple only, and not by \way of limitation, It will be apparent to a person skihLed in the relevant art that various changes in form and detail can be made therein without departnin frm the spirit and scope of ithe 20 invention. Thus, the present invention should not be limited by any of the above described exemplary embodirrients. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "Comprise", and variations such as "comprises" and "cowprising"will be understood to imply the inclusion of a stated integer or step or group of integers or steps bit 25 not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or ifori'ation derived. from it), or to any matter which is known, is not, and should not be taken as an acknowledgtment or II psgnunIeme etNRB>onb1DCCiGXiaS 9 1 5 0 4 _1.doc I-2/102I5 - 12 admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 5

Claims (18)

1. Cutter head for dredging ground under the water surface, comprising a revolving body which is rotatable around a central axis and which is formed by a base ring and a hub placed at a distance therefrom, between which extend a number of support arms provided with cutting 5 tools, between which support arms passage openings are present for discharge of the dredged ground, wherein the cutter head comprises at least 50 cutting tools, which cutting tools are axisymmetrical at least at their free outer end.

2. Cutter head as claimed in claim 1, wherein the cutting tools are arranged on the support arms such that they can be rotated freely around their axis of rotation symmetry. 10

3. Cutter head as claimed in claim 1 or 2, wherein the cutting tools are conical.

4. Cutter head as claimed in any one of the foregoing claims, wherein the top part of the conical cutting tools has at the free outer end a radius of curvature of a maximum of 50 mm.

5. Cutter head as claimed in any of the foregoing claims, wherein the cutter head comprises at least 10 support arms. 15

6. Cutter head as claimed in any of the foregoing claims, wherein a support arm comprises at least 20 cutting tools.

7. Cutter head as claimed in any one of the foregoing claims, wherein the cutting tools are oriented relative to the support arms such that during rotation of the cutter head through the ground they strike substantially perpendicularly of the ground surface. 20

8. Cutter head as claimed in any one of the foregoing claims, wherein a support arm comprises a first series of cutting tools on a leading part thereof as seen in the direction of rotation of the cutter head, and the support arm comprises a second series of cutting tools on a part facing away from the central axis.

9. Cutter head as claimed in claim 8, wherein on the same support arm the cutting tools of 25 the first series are disposed offset relative to the cutting tools of the second series. lH prae re~ ~ obhCC uw 1j4 I dac-It "U - 14

10. Cutter head as claimed in any one of the foregoing claims, wherein the cutting tools are connected to the support arms via coupling means.

11. Cutter head as claimed in claim 10, wherein the support arms of the cutter head are provided with guides on which the coupling means and/or the cutting tools arc displaceably 5 mounted.

12. Use of a cutter head as claimed in any one of the foregoing claims for dredging a ground with an Unconfined Compressive Strength (UCS) of at least 50 MPa.

13. Use of a cutter head as claimed in claim 12 for dredging a ground with an Unconfined Compressive Strength (UCS) of at least 60 MPa. 10

14. Use of a cutter head as claimed in claim 12 for dredging a ground with an Unconfined Compressive Strength (UCS) of at least 80 MPa.

15. Cutter suction dredger provided with a cutter head as claimed in any one of claims I to 11.

16. A cutter head substantially as hereinbefore described with reference to the 15 accompanying drawings.

17. Use of a cutter head substantially as hereinbefore described with reference to the accompanying drawings.

18. A cutter suction dredger substantially as hereinbefore described with reference to the accompanying drawings. 20