GB2034369A

GB2034369A - Cutter head for suction dredger

Info

Publication number: GB2034369A
Application number: GB7833976A
Authority: GB
Original assignee: WESTMINSTER DREDGING
Current assignee: WESTMINSTER DREDGING
Priority date: 1978-08-21
Filing date: 1978-08-21
Publication date: 1980-06-04
Also published as: EP0008534A1

Description

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GB2 034 369A 1

SPECIFICATION

Cutter head for suction dredger

5 This invention relates to cutter heads for floating suction dredgers. A conventional cutter head consists of a set of curved spiral-helical blades mounted on an axial boss for rotation under power for the purpose of breaking up 10 the sea or river bed, the broken fragments being removed from the head by suction and delivered to the dredger for disposal.

When the sea bed consists of a soft clay, or sand a typical dredger can operate, at what is 15 considered a satisfactory output rate, but when harder conglomerates, or rock are encountered, then the rate of removal decreases very significantly. For example, with a hard rock, having a compressive strength of 20 2000-3000 Ib/sq. in. the rate may reduce by as much as 90%, though it would still be generally regarded as an acceptable rate of working. For harder rocks the rate is even lower until one reaches rock compressive 25 strengths approaching 7,000 Ibs/sq. in.,

when other methods must be adopted, such as blasting, which significantly increases the time and cost of the whole operation.

Attempts have been made to adopt dry rock 30 cutting techniques, for example by fitting teeth or picks to the cutter blades, but these have not been particularly successful due in part to a lack of understanding of the physical properties of underwater rock formations. 35 It is an object of the present invention to provide an improved cutter head for a suction dredger which is capable of operating on harder rocks than at present possible, or which can achieve a higher rate of removal 40 than can be obtained at present for a given rock strength.

The present invention consists in a cutter head for a suction dredger which includes a central boss mountable upon a power drive 45 shaft and suction head of the dredger,

wherein the boss carries an array of cutter bits spaced longitudinally and circumferentially so that their tips define a generally part-ellipsoi-dal envelope.

50 In the accompanying drawings:—

Figure 1 is a side view of one form of cutter head according to the present invention,

Figure 2 is a longitudinal section through the cutter head of Fig. 1, and 55 Figure 3 is a cross section taken in spiral plane starting at line 3-3 of Fig. 1.

In carrying the invention into effect according to one convenient mode by way of example, a cutter head for a suction dredger in-60 eludes a central boss 11 adapted to be fitted on the drive shaft 12 of a suction head of known form of a suction dredger.

Welded to the central boss are four interposed closely-spaced pairs of spiral-helical 65 webs 13 thus forming a four-start spiral channel system, between adjacent pairs of web pairs, each channel being of about \ \ turns. At the large diameter end the webs 13 are joined to a pair of annular rings 14 positioned 70 coaxially with the axis of the boss 11 and at right angles thereto.

At the small diameter end the webs 1 3 are joined to a pair of conical rings 23 positioned coaxially with the axis of the boss, and whose 75 included angle is about 60°.

The webs 1 3 are so dimensioned that in longitudinal profile they define a curve 15 which is part of a near ellipse and is chosen so as to present the optimum angle of attack 80 to the sea bed whatever the angle of the axis of the cutter to the horizontal in use.

The peripheries of the webs and the annular rings are provided with cut outs 16 in which are welded mounting plates 17 each of which 85 bridges the pair of webs or rings and upon which is mounted a block 18 holding a cutter bit 19 so that an array of cutter bits 1 9 is formed.

The cut outs are so dimensioned that the 90 tips of the cutter bits 1 9 project beyond the peripheries of the webs, the extent to which they project defining the maximum cutting depth of the bits. The tips of the cutter bits thus define a generally part-ellipsoidal envel-95 ope of the same form as curve 15. The cutter bits 1 9 are spaced at such intervals around the pairs of webs 13 that in use the cuts made by successive bits are staggered relatively to one another.

100 The pairs of webs 1 3 are provided with apertures 20 to prevent "bridging" of material between adjacent pairs, and to permit material to be fed rearwardly to the mouth 21 of the suction head under the action of the 105 helical form of the webs 13. To assist this feed action scoops 22 are provided between adjacent pairs of webs. As shown, two cutter bits 1 9 are provided between adjacent pairs of scoops 22, but other arrangements may be 110 advantageous.

Various modifications may be made within the scope of the present invention. For example, the spiral-helical webs may be replaced by annular rings having apertures, the feeding 11 5 action then being obtained solely by scoops between adjacent rings. Alternatively, the cutter bits may be mounted at the end of supporting arms extending radially and/or obliquely, the rearward feeding action again be-120 ing obtained by scoops. The cutter bits may be replaced by other forms of mining tools such as picks or chisels.

Claims

125 1. A cutter head for a suction dredger which includes a central boss mountable upon a power drive shaft and suction head of the dredger, wherein the boss carries an array of cutter bits spaced longitudinally and circum-130 ferentially so that their tips define a generally

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GB2 034 369A

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part-ellipsoidal envelope.

2. A cutter head as claimed in claim 1, wherein the boss carries at least one spiral-helical web upon which the cutter bits are

5 mounted.

3. A cutter head as claimed in claim 2, wherein the boss carries at least one pair of closely spaced webs and the cutter bits are mounted upon plates bridhing the webs.

10

4. A cutter head as claimed in claim 2 or 3, wherein the cutter bits are mounted in cutouts in the or each web.

5. A cutter head as claimed in claim 2, 3 or 4, wherein the or each web is provided

15 with axial apertures.

6. A cutter head as claimed in any one of claims 1 to 5, wherein scoops are provided which, in use, serve to feed dredged material towards the suction head mouth.

20

7. A cutter head substantially as described with reference to the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd.—1980.

Published at The Patent Office. 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.