GB2128663A

GB2128663A - Trailing suction dredger

Info

Publication number: GB2128663A
Application number: GB08327719A
Authority: GB
Inventors: Jan Brouwer; Jan Peter Koert
Original assignee: LIESBOSCH BV; Amsterdamse Ballast Bagger En Grond (Amsterdam Ballast Dredging) BV; Ballast Nedam Groep NV
Current assignee: LIESBOSCH BV; Ballast Nedam NV; Amsterdamse Ballast Bagger En Grond (Amsterdam Ballast Dredging) BV
Priority date: 1982-10-15
Filing date: 1983-10-17
Publication date: 1984-05-02
Also published as: NL8203985A; SE8305657D0; SE8305657L; AU2021983A; GB8327719D0; GB2128663B

Abstract

A trailing suction dredger for working a subaqueous bottom comprises a floating vessel, a suction pipe 5 suspended from the vessel, and a trailing head 11 attached to the pipe. The trailing has a row of teeth 15 attached to it by means of a frame 18 which is vibrated by a vibrator 69 to increase the penetrating force when dredging stony bottoms. <IMAGE>

Description

SPECIFICATION Trailing suction dredger The invention relates to a trailing suction dredger for working a subaqueous bottom, comprising a floating body, at least one suction pipe supported by the body, a trailing head attached to the suction pipe and teeth attached to the trailing head for the loosening of stony particles from the sub water bottom.

Such a trailing suction dredger is known from Dutch Patent 161222 and is especially designed to work a stony subaqueous bottom.

The object of the invention is to provide a trailing suction dredger which can work even better on a stony subaqueous bottom. To this aim the trailing suction dredger is characterised by vibrating means for the vibrating of the teeth. The adding of the vibrating means increases the horizontal penetration force (trailing force) as well as the vertical penetration force. This combination of the energy supply enables an increase of the dredge production while maintaining the same cutting depth.

The invention will be described more fully hereinafter with reference to a drawing in which: Fig. 1 is a perspective view of a trailing suction dredger in accordance with the invention, Fig. 2 is, on an enlarged scale, an elevation partly broken away of detail II of figure 1, Fig. 3 is, on an enlarged scale, a perspective view of the detail il of figure 1, Fig. 4 is an elevation in the direction of the arrow IV of figure 2, Fig. 5 is, on an enlarged scale, an elevation of the detail V of figure 3, Fig. 6 is a cross section on the line VI--VI of figure 5, Fig. 7 is a side-elevation of another embodiment of the detail shown in figure 6 of a trailing suction dredger according to the invention, Fig. 8 is, on an enlarged scale, a cross section through detail VIII of figure 2, and Figure 9 is, on an enlarged scale, a cross section through detail IX of figure 4.

A trailing suction dredger 2, according to the invention, sailing on water 1, comprises a floating body or vessel 3 with at least one driven propeller 47, at least one suction pump 4, which may be installed on board of the floating vessel 3 and at least one flexible suction tube 5 connected to the pump 4. The suction tube 5 is suspended from the floating vessel 3 by means of cables 7 and winches 6. A hold 8 in the vessel is connected to the outlet 10 of pump 4 via a conduit 9. A trailing suction head 11 is carried by the lower end of the suction tube 5. The trailing suction head 11 comprises a middle section 33 communicating with the suction tube 5 and mounted on it by means of a flange 13. The middle section 33 communicates with a suction box 12. A suction mouth 14 is situated in the suction box 12.

The trailing suction head 11 includes a cutting tool 19, consisting of a vibrating frame 1 8 with a row of teeth 1 5, extending transversely to the trailing direction 1 6. When the cutting tool 1 9 is in the cutting position these teeth extend into the bottom 17 of the water 1. The cutting tool 1 9 is pivotably arranged on the suction box 12 (and consequently on a visor 21) by pivotably connecting the cutting tool 1 9 to shafts 20 on the suction box 12.The suction mouth 14 at the bottom end of the suction box 12 is in fact divided by the cutting tool 19, into two parts, namely a suction mouth part 22 through which mainly loosened particles of bottom material enter into the suction box 1 2 and a suction mouth part 24 through which mainly water is sucked in. The amount of water to be sucked in depends on the height a the lower rim 25 is set above the cutting level 26 of the cutting tool 1 9. The suction box 12 and consequently the visor 21 are maintained in a determined position relative to the suction tube 5 by means of a hydraulic piston and cylinder. The cylinder 28 is secured pivotably around an axle 29 mounted on the suction tube 5. The piston rod 30 is pivotably arranged in ears 31 on the suction box 12.The cylinder 28 holds the cutting tool 1 9 in its cutting position but when a predetermined load on the cutting tool 19 is exceeded, for example, upon impact of the teeth 1 5 on a too hard rock 32 or the like, it will deflect.

The fluid pressure of said hydraulic cylinder 28 depends upon a gas cushion 38, which is enclosed in the fluid cylinder 28 by a piston 39 which is freely movable in the direction of the axis of the cylinder. A piston 46 displacing the fluid and connected with the piston rod 30 separates two fluid chambers 40, 41 from one another. The fluid chambers 40 and 41 communicate with one another through throttle means, formed by a throttle channel 49 and a very narrow throttle opening on constriction 42 of a valve body 43.

During the inward stroke b of piston 46 in the direction of the arrow 53, the valve body 43 is lifted from its seat 44, the throttle means then being by-passed. Owing to the penetration of the piston rod 30 into the fluid cylinder 28 during stroke b, the fluid is displaced so that the gas cushion is compressed through the floating piston 39. The difference in diameter of the piston rod 30 and the floating piston 39 ensures a rapid penetration at the beginning of the inward stroke so that the cutting teeth 1 5 are rapidly moved out of the way of an obstacle. For this purpose the piston 46 is not damped during stroke b. During the return stroke b in the direction of the arrow 54, the movements of the piston 46 and of the cutting tool 1 9 are damped.

In the holding position of the hydraulic cylinder 28 shown in figure 8, the piston 46 is in an extreme position, in which the fluid chamber 41 is separated from a fluid chamber 50 by a fitting rim 51, cooperating with the lid 52 of the cylinder.

Thus at the end of the return stroke the fluid chamber communicates solely through the throttle opening 42 with the fluid chamber 40 so that the end of the return stroke b is additionally damped.

When the cutting teeth 1 5 of the cutting tool 19 impacts on a rock 32 that is too hard, it swings back into the position indicated by broken lines in figure 6. The hydraulic cylinder 28 yields. During the inward stroke b of, say, 45 cm of the piston 46, the gas cushion 38, for example of nitrogen, is compressed from 45 to 1 50 ato. The force exerted by the hydraulic cylinder 28 on the ears 31 may then increase from 22 to 73 tons.

The gas cushion 38 forms the return forcing means, pushing the cutting tool 1 9 back into the cutting position.

The trailing suction dredger 2 is, according to the invention, characterised by vibrating means for the vibrating of the teeth 1 5. The teeth 1 5 are firmly fixed to the vibrating frame 18, which is mounted to a frame 57 of the visor 21 for swinging movement around a horizontal axis 56, by means of swing arms 55 and shafts 22. The vibrating frame 18 is also supported on the frame 57 of the visor 21 by means of a series of sets of cushions 58 of elastic material, for instance rubber, which are connected to one another with interposing plates 60 which extend in the vibrating direction 59. The amplitude of vibration of the vibrating frame 18 in the vibrating direction 59 is limited by means of elastic butts 61 and 62, mounted on the frame 57 which bounce against the vibrating frame 18 at an excessive amplitude.

The configuration of the frame 57 and the vibrating frame 18 swingably mounted therein, with the interposed cushions, is shown in figures 2 to 6.

On top of vibrating frame 18 is mounted a vibrator 69 consisting, for example, of a motor driving excentrics 64 in opposite directions 63.

Although much energy is needed to vibrate the teeth 15, the specific energy (the amount of energy needed to loosen a unity of volume of bottom material) compared with the known arrangements, because the amount of energy needed to drive the propulsion propeller of the trailing suction dredger 2 is noticably decreased.

The rubber cushions 58 are preferably pretensioned in a direction transverse to the plates 60. It is important that the vibrating teeth 1 5 are better kept positioned on the adjusted cutting depth in the bottom 1 7.

In the embodiment of figure 7 the vibrating frame 18, carrying the teeth 1 5, is swingably mounted by means of swing arms 55 around an axis 56, and carries a plate 70 inserted between rubber cushions 71 which bear against the frame 57 of the visor 21. A vibrator 69 is mounted on top of the vibrating frame. The cushion 71 and 58 consist of medium hard rubber, for instance of 50--550 shore.

Should the total force on the teeth 1 5 rise to too high a value, the break bolts 75 will break, whereby the visor 21 and middle section 33 swing high in relation to the suction tube 5 around a hinge 76. The vibrating frame 18 vibrates preferably at a frequency of 10 to 20 Hz, preferably 17 Hz.

In order to damp the transmission of the cutting forces of the cutting tool 19 to the visor 21, preferably elastic torsion elements 65 are inserted in the bearing of the swing arms 55 with the shaft 20 (figure 9).

Claims

1. A trailing suction dredger for working a subaqueous bottom, comprising a floating body, at least one suction pipe supported by the body, a trailing head attached to the suction pipe and teeth attached to the trailing head for loosening stony particles from the subaqueous bottom, and including vibrating means for vibrating the teeth.

2. A trailing suction dredger according to claim 1, in which the teeth are mounted on the frame of the trailing suction head by means of a series of sets of cushions of elastic material which are connected to one another with interposed plates extending in the direction of vibration.

3. A trailing suction dredger according to claim 2, in which the cushions are of rubber.

4. A trailing suction dredger according to claim 1 or 2, or 3, in which the amplitude of vibration of he teeth is limited by elastic butts.

5. A trailing suction dredger according to any one of the preceding claims in which the teeth are mounted on a vibrating frame which is swingably mounted to the frame of the trailing head.

6. A trailing suction dredger according to claim 5, in which the vibrating energy is supplied mainly in the direction of the teeth by the positioning of the vibrating means relative to the swing axis of the frame.

7. A trailing suction dredger according to any one of the preceding claims in which swing arms of the frame are connected to the shafts around which the frame swings by elastic torsion elements.

8. A trailing suction dredger substantially as hereinbefore described with reference to the accompanying drawings.