GB2475939A

GB2475939A - A dredger or excavator with a cylindrical excavating tool having an axial fluid flow

Info

Publication number: GB2475939A
Application number: GB201015286A
Authority: GB
Inventors: Nicholas Harris
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-09-28
Filing date: 2010-09-14
Publication date: 2011-06-08
Also published as: GB0916961D0; GB201015286D0

Abstract

The present invention relates to dredging and scouring of submerged material. The device includes a body, a pair of arms 20, 21 carrying a grating cylinder 30 between them. The grating cylinder or drum has an axial inlet 31 at one end and an axial outlet 32 at the other end with a discharge pipe attached to the outlet. The apparatus includes a fluid flow means for providing an axial flow between the inlet 31 and the outlet 32 of the grating cylinder, The pair of arms 20, 21 may branch from and articulated arm (figs 4 and 5) or be pivotally mounted to the body (figs 1 to 3). The grating may include teeth projecting radially outwards (figs 4 and 5) which are formed from perforations in the cylinder or drum and the drum may include internal paddles (33, fig 3).

Description

IMPROVEMENTS IN OR RELATING TO DREDGING AND SCOURING

The present invention relates to dredging and scouring particularly in rivers and other relatively shallow waterways such as the seabed.

Numerous types of apparatus are used and have been proposed for use in dredging sea or riverbeds. One such device is described in US 4 819 346, in which a rotatable open cage of cutterbars is mounted within a frame acting as a suction outlet for the device.

Excavated material is removed through a longitudinally central outlet. GB 1 518 439 describes a broadly similar device but the cutterbar cage is more enclosed to reduce loss of excavated material through spreading of material across the sea-bed.

The present invention seeks to provide an alternative dredging or excavating apparatus.

A dredging or excavating apparatus comprising an apparatus body and a pair of arms mounted to the apparatus body and carrying between respective ends a longitudinally mounted grating cylinder assembly; wherein the grating cylinder includes an axial inlet at a first end thereof and an axial outlet at a second end thereof; and wherein the apparatus further comprises fluid flow means for providing an axial fluid flow, in use, between the inlet and outlets of the grating cylinder.

Preferably, the apparatus further comprises a discharge pipe couplable to the axial outlet of the grating cylinder.

Preferably, the apparatus further comprises drive means adapted to cause rotation of the grating cylinder.

Preferably, the drive means is a chain drive assembly.

Suitably, the pair of arms form a yoke supporting the grating cylinder assembly.

Preferably, the yoke is pivotally mounted to the apparatus body by means of a yoke arm.

Alternatively, the pair of arms are formed as a pair of swing arms adjustably pivotally mounted at respective second ends to the apparatus body.

Preferably, the apparatus further comprises a propulsion apparatus.

Preferably, the grating cylinder comprises a perforated drum comprising grating teeth projecting therefrom.

Preferably, the grating teeth are formed by perforating the drum.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of an apparatus in accordance with the present invention in an intermediate operative configuration; Figure 2 is a front view of the embodiment of Figure 1; Figure 3 is a side view of the embodiment of Figure 1 in a non-operative configuration; Figure 4 is a perspective view of a second embodiment of an apparatus in accordance with the present invention; and Figure 5 is a perspective view of a third embodiment of an apparatus in accordance with the present invention.

Referring to Figures 1 to 3, there is shown a dredging vessel 10 comprising a propulsion vessel 11 to which is mounted a dredging apparatus. The propulsion vessel 11 can substantially be of any design. The vessel shown provides an example of a suitable construction in which propulsion vessel 11 comprises a pair of spaced pontoons 12 providing buoyancy. Pontoons 12 are joined by means of a platform 13 on which is mounted a control claim 14 and main propulsion engine 15. Suitably, the vessel is propellable across a body of water by means of a water-jet drive motor associated with each pontoon 12. Other forms of propulsion are equally suitable.

The dredging apparatus shown comprises swing arms 20,2 1 on respective port (left) and starboard (right) sides of the propulsion vessel. Swing arms 20,2 1 are pivotally mounted at a first end thereof to a swing arm motor and gearing assembly 22 mounted on the propulsion vessel. As shown, for means of weight-saving, to improve flow of water around the arms during movement through the water and reduced frictional contact with propulsion vessel 11, arms 20, 21 include cut-out slots 23. Pontoons 12 are fitted with replaceable swing arm wear plates 24 to protect the body of the pontoon from wearing contact with respective swing arm. Mating arm locking eyes are provided on respective portions of adjacent pontoons 12 and swing arms 20, 21 for securing the swing arms to the propulsion vessel during transit or storage.

A grating cylinder 30 is provided transversely between swing arms 20, 21 for rotation about its cylindrical axis. Grating cylinder 30 is suitably caused to rotate about this axis by means of a chain-drive assembly powered from the propulsion vessel. Other arrangements will be apparent to the skilled person, including belt or direct-drive assemblies.

The grating cylinder is rotated by a stand-alone diesel motor situated to the rear of the cylinder. The chain of the chain-drive passes around teeth formed about the circumference of the cylinder allowing that end of the cylinder to remain "open" to the water when submerged. The direction of rotation is advantageously counter to that of normal motion to enhance the scouring effect.

As the cylinder rotates when in contact with the seabed, its grating teeth bite away sediment which is drawn into the body of the cylinder by the negative hydrostatic pressure. The dredged sediment is pushed along the cylinder by the continual ingress of water into the cylinder, and out through the exit vent, along the pipe sections, and discharged wherever required.

Grating cylinder 30 comprises a perforated cylindrical drum in which the perforations are punched or pressed outwardly to form grating teeth (not shown for clarity).

Alternatively grating arrangements and constructions are equally suitable and different grating cylinder designs and constructions will be required having regard to differing underwater conditions, such as whether excavating mud, silt, sand or gravel surfaces.

Grating cylinder 30 is open at a first end thereof to form an inlet 31. The second end of grating cylinder 30 is adapted for coupling to a discharge pipe (not shown), for example by means of a slip-ring coupling 32. The discharge pipe, or the first of a series of fluidly, linked discharge pipes, is coupled to a source of suction such that sediment removed from the seabed by action of rotating creating cylinder is flushed from the inner surfaces of the cylinder by flow of water from inlet 31 through the cylinder 30 to outlet 32 and then through the discharge pipe to appropriate disposal.

Disposal may be made directly to an adjacent portion of the seabed or adjacent land or into a storage vessel for remote disposal as required.

A number of internal paddles or blades 33 (Fig 3) are fitted to the inner circumference of the cylinder and are set axially. They extend a finite distance towards the axis rather than converging at the axis and have a fixed pitch so that when the grating cylinder is rotated water is drawn into the cylinder. A vortex is created and the resulting negative hydraulic pressure in the cylinder pulls the grated sediment inwards and creates a sediment suspension. The greater the speed of rotation, the stronger the negative pressure used to suck the excavated sediment suspension into the cylinder.

The vortex created by blades 33 may be supplemented by a pump operatively coupled to the discharge pipe. However, the present invention seeks, in preferred embodiments, to avoid the use of pumps or other secondary tools to dispose of excavated sediment by providing a single tool which both agitates and provides disposal or sediment.

It will be appreciated that the angle of swing arms 20,2 1 is adjustable to make an angle between swing arms and the water surface of between 00 and 90°, allowing corresponding variation in excavation depth between a maximum depth and a minimum depth corresponding to the length of swing arms 20,21.

The material weight of the grating cylinder and hydraulic "squat" will keep the grater cylinder at its lowest possible hang angle. The squat is caused by the grating teeth acting as hydrofoils trying to pull "outwards". A hydrodynamic force is created in all directions outwardly from the surface of the cylinder. Water pressure increases with depth and teeth momentarily passing the lowermost point of the cylinder create a net outwards force greater than the teeth momentarily passing the uppermost point of the cylinder, The cylinder therefore experiences a net downwards force and is kept pressed against the seabed (as far the pre-determined Maximum hang angle allows; which is advantageously constrained mechanically).

The arms are not constrained mechanically from swinging "upwards"; this is a safety measure in the event the cylinder encounters an underwater obstruction buried in the seabed.

The apparatus is equally suitable for excavations in shallow water whether in coastal locations, estuaries, tidal inlets, ports, anchorages, marinas, rivers, reservoirs, streams or canals and can be used for maintenance of existing facilities or establishment of new facilities.

By providing a water flow from one end of grating cylinder 30, large quantities of water can be provided to flush excavated material, whereas many prior art constructions can generate fluid flows only through the surface of the cylinder only, which can lead to clogging of the scouring surfaces.

Whilst described above in the form of a catamaran type construction vessel 11 can have any suitable arrangement. However, the catamaran form is considered advantageous in providing a shallow-draught vessel resilient to grounding. The embodiment shown includes self-propulsion apparatus. However, the apparatus can equally be provided without such apparatus, for propulsion by separate means, such as a tug or similar vessel.

Figure 4 shows a modification in which a grating cylinder 30 is mounted between forks 40 of a yoke 41. Yoke 41 is mounted on a swing arm 42 of a construction machine in the form of a wheeled excavator 43 and is operatable in a conventional manner by a suitable hydraulic mechanism including hydraulic rams 44.

Figure 5 shows a modification of this apparatus in which yoke 41 is mounted on the swing arm 42 of a caterpillar -tracked excavator. The embodiments of Figures 4 and 5 are particularly suitable for handling bulk materials in situations such as earthworking or shallow-water excavation or dredging.

Claims

Claims 1. A dredging or excavating apparatus comprising an apparatus body and a pair of arms mounted to the apparatus body and carrying between respective ends a longitudinally mounted grating cylinder assembly; wherein the grating cylinder includes an axial inlet at a first end thereof and an axial outlet at a second end thereof; and wherein the apparatus further comprises fluid flow means for providing an axial fluid flow, in use, between the inlet and outlets of the grating cylinder.
2. An apparatus as claimed in claim 1 further comprises a discharge pipe couplable to the axial outlet of the grating cylinder.
3. An apparatus as claimed in claim 1 or claim 2 further comprising drive means adapted to cause rotation of the grating cylinder.
4. An apparatus as claimed in claim 3 wherein the drive means is a chain drive assembly;
5. An apparatus as claimed in any one of claims 1 to 4, wherein the pair of arms form a yoke supporting the grating cylinder assembly.
6. An apparatus as claimed in claim 5, wherein the yoke is pivotally mounted to the apparatus body by means of a yoke arm;
7. An apparatus as claimed in any one of claims 1 to 4, wherein the pair of arms are formed as a pair of swing arms adjustably pivotally mounted at respective second ends to the apparatus body.
8. An apparatus as claimed in any preceding claim further comprising a propulsion apparatus.
9. An apparatus as claimed in any preceding claim wherein the grating cylinder comprises a perforated drum comprising grating teeth projecting therefrom.
10. An apparatus as claimed in claim 9 wherein the grating teeth are formed by perforating the drum.
11. A dredging or excavating apparatus substantially as herein described with reference to the accompanying drawings.