WO1992007146A1

WO1992007146A1 - Cutter wheel assembly

Info

Publication number: WO1992007146A1
Application number: PCT/AU1991/000474
Authority: WO
Inventors: Murray Howard Pryor
Original assignee: Coal Recoveries Pty., Ltd.
Priority date: 1990-10-16
Filing date: 1991-10-15
Publication date: 1992-04-30

Abstract

A bucket wheel assembly particularly adapted for use on a suction dredge for dredging fine particulate materials. The cutter wheel assembly (10) comprises a support arm (11) on which is rotatably mounted a hub (12) carrying a pair of substantially parallel circular plates (14). Each of the plates (14) is formed with a number of apertures (18) each of which is bounded on its trailing edge by an outwardly projecting scoop (19). The space (16) between the plates is enclosed by a housing (15) extending between the circumferential edges of the plates (14). A suction inlet pipe (17) extends into the space (16). Water jets (24) and water inlets (22) direct water around the space (16) into the inlet pipe (17) sweeping with it the solid particulate material drawn into the space (16) by the scoops (19).

Description

CUTTER WHEEL ASSEMBLY FIELD OF THE INVENTION

The present invention relates to a cutter wheel assembly for use on a suction dredge and more particularly to such a cutter wheel assembly for use in dredging finely divided materials. BACKGROUND ART

Such dredges normally have a cutter wheel rotatably mounted at the end of a boom to excavate or loosen the submerged material to be dredged, and to convey or direct the material to a suction pipe. Examples of suction dredges can be found in United States patent numbers 1393680; 1701430; 3171220; 3476498; 3738029; 3823495; German patent specification numbers 1634808; 1902792; and Australian patent application numbers 79565/75 and 89028/82. Most cutter wheels comprise a rotatable hub having a series of buckets around its periphery for excavating. Some cutter wheels, however, have radial blades or teeth which are designed to loosen material at the leading end of the wheel, so that the material can be sucked into the suction pipe.

It has been found that conventional cutter wheels are not particularly suitable for dredging fine material, such as the coal particles found in submerged tailings dumps from coal mines, very fine sand and silt. Although some of these materials are easily loosened by conventional cutter wheels, they are not able to be efficiently directed to the inlet of the suction pipe. Since some of these materials normally comprise very small light particles which do not coalesce or coagulate, they tend to billow underwater and are not easily shovelled by the buckets or blades of conventional cutter wheels. Other materials form tightly bonded structures which while being easily cut do not break up in water and adhere strongly to cutting blades and buckets. When these materials do not adhere to the cutting blades they provide large cohesive lumps which are difficult to pump.

It its preferred embodiments the present invention is directed to providing an improved cutter wheel suitable for use on a suction dredge, which is particularly adapted for use in dredging relatively fine material. DISCLOSURE OF THE INVENTION

The present invention consists in a cutter wheel assembly for use on a suction dredge, the cutter wheel assembly comprising a support arm, a hub mounted on the support arm and adapted to be rotated about an axis extending transversely of the support arm, at least one, preferably substantially circular, plate mounted on the hub and adapted to be rotated therewith, the plate being provided with a plurality of apertures therethrough, each aperture being provided on its trailing edge on one side of the plate with an outwardly extending scoop member, a housing surrounding the plate on the side thereof distal to the scoops to form a receiving space adjacent to the plate and an intake pipe for a suction line extending into communication with the receiving space.

In a preferred embodiment of the invention there are two plates mounted on the hub in spaced apart array. Each of the plates being provided with a plurality of apertures and each aperture carries on its trailing edge on its face distal to the other plate a scoop member. In this embodiment of the invention a stationary housing extends between the plates adjacent the periphery of the plates to define the receiving space between them. The cutter wheel according to this invention is, in use, mounted on an elongate boom on the suction dredge which can be lowered into a dredging pond containing the fine materials to be dredged up. As the cutter wheel is rotated the boom is caused to sweep across the face of the material being dredged. The scoops on the plate bearing against the material being dredged engage with that material and scoop it into the receiving space from where it is drawn, by suction, into the intake pipe for the dredge suction line. The embodiment of the invention utilising two plates allows the boom to sweep in either direction across the face of the material being dredged. In a further preferred embodiment of the invention liquid discharge means are provided within the receiving space which are adapted to direct a stream of liquid, such as water, towards the intake pipe. This serves to ensure that dredged material within the receiving space is moved efficiently towards the inlet pipe. It is also preferred that the housing is provided with liquid inlet apertures only at a position at an upper and rearward position such that make-up water from the dredging pond will flow into and around the receiving space to the inlet pipe which further assists in carrying the dredged material to the inlet pipe. It is desirable to keep these apertures to a minimum in order to keep the pulp density of the material pumped by the dredge as high as possible.

In a further preferment the inlet pipe extends into a lower portion of the receiving space. The inlet pipe also preferably has an inlet end which extends across substantially the full cross-sectional area of the receiving space between the hub and the housing. This arrangement ensures that water flowing into the receiving space through the apertures is directed around the receiving space into the inlet pipe. This flow of water, as has been indicated above, assists in directing dredged material into the inlet pipe.

The apertures in the plate or plates are preferably very small relative to the size of the plate, typically the maximum dimensions of the apertures is less than 12 inches (300mm), preferably less than 8 inches (200mm), and more preferably less than 6 inches (150mm). The apertures are preferably arranged, both radially and circumferentially, around the plate in spaced apart array such that with each revolution of the plate the complete face of the material to be dredged is swept at least once by an aperture and its associated scoop.

Each aperture has an associated scoop which is preferably angled at an acute angle (preferably 20 to 75°, more preferably 25 to 40°) to the plane of the plate and is inclined towards the direction of rotation of the plate. Each scoop is preferably connected to the trailing edge and the two side edges of each of the rectangular apertures. The scoops are preferably formed of a hardened steel, such as bisalloy, to avoid excessive wear on the scoops. The relatively small size of the scoops allows them to be thin and sharp but still robust which is advantageous particularly when dredging cohesive materials.

In a preferred embodiment of the invention, the or each, plate has on its periphery a cylindrical flange directed towards the housing. The flange is preferably formed with apertures therethrough. Each aperture is preferably provided, at least on its trailing edge with an outwardly extending scoop member. This arrangement allows the cutter wheel assembly to cut material ahead of it as well as material beside it during the dredging operation. In use it has been found that the cutter assembly according to preferred embodiments of the invention efficiently dredges very cohesive and sticky materials having the consistency of plasticine. These materials are very difficult to dredge with conventional bucket wheels as the material sticks to the bucket and clogs the bucket wheel. The assembly according to this invention appears to work by each scoop cutting spaghetti-like strands of the cohesive material which are extruded into the receiving space. These strands are swept into the intake pipe by the flow of liquid passing around the receiving space into the intake pipe. BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter given by way of example only is a preferred embodiment of the present invention described with reference to the accompanying drawings in which: -

Figure 1 is a side elevational view of a cutter wheel according to the present invention;

Figure 2 is a horizontal sectional view through a partly diagrammatic representation of the cutter wheel of Figure 1;

Figure 3 is a longitudinal sectional view through an aperture and scoop on the plates of the cutter wheel of Figure 1; Figure 4 is a sectional view along IV-IV of Figure 3;

Figure 5 is a partly cut away side elevational view of a bucket wheel assembly according to a second embodiment of the present invention; and

Figure 6 is a partly cut away plan view of the bucket wheel assembly of Figure 5.

BEST MODE FOR CARRYING OUT THE INVENTION

The cutter wheel 10 is adapted for use on a suction dredge for dredging sand and silt including coal fines from a dredging pond. The cutter wheel 10 is adapted to be connected at the free end of an elongate boom (not shown) extending from a dredge (not shown) in conventional manner.

The cutter wheel 10 includes a support arm 11, a hub 12 extending transversely from the support arm 11, a motor 13 adapted to rotate the hub 12, a pair of apertured, circular plates 14, a stationary housing 15 extending between the plates 14 around their circumference to define a receiving space 16 and an inlet pipe 17 extending into the receiving space 16. The support arm 11 includes at one end an end plate 18 adapted to be bolted to the boom of the dredge. At its other end the support arm 11 carries the hydraulic motor 13 which is adapted to rotate its spindle (not shown) about an axis substantially normal to the axis of the support arm 11. The hub 12 is mounted on the spindle of the motor 13 and rotates with it.

The circular plates 14 are mounted on the hub 12 in spaced apart parallel planes. Each plate 14 is provided with an array of small rectangular apertures 18. The apertures 18 are spaced apart both radially and circumferentially on each plate 14 but are so arranged that substantially the whole of any one radial line extending from the hub would be swept by an aperture during each rotation of the plate. Each aperture 14 is associated with a scoop 19. The scoops 19 are each U-shaped in cross section and project from the plate at an angle of 30° opening in the direction of rotation of the plate. Each scoop 19 is welded to the trailing and side edges of its associated aperture 18.

Each plate 14 is provided around its circumference with a plurality of radially directed teeth 21 to help break up and/or remove foreign bodies and tramp materials contained in the material being dredged. The stationary housing 15 is substantially cylindrical in shape and is mounted on the support arm. It extends between the two plates 14 and its outer surface is aligned with the circumferential periphery of the two plates 14. The housing 15 is provided with apertures 22 to allow the flow of make up water into the receiving space 16. A high pressure water duct 23 extends into receiving space 16 and lies adjacent the inside surface of the housing 15. The duct 23 is provided with a plurality of spray nozzles 24 directed in the direction of rotation of the cutter wheel 10. The inlet pipe 17 is connected to a suction pump on the dredge (not shown) and extends into the receiving space 16. The inlet pipe extends across the full width of the receiving space 16 and into that space sufficiently that its upper edge lies closely adjacent the hub 12.

In use the cutter wheel 10 is connected to the boom of the dredge and lowered into a dredging pond. The motor 13 is actuated to cause the hub 12 and the plates 14 to rotate. This rotation is preferably such as to cause the leading edge of the plates to cut downwardly into the material to be dredged. The cutter wheel 10 could, however, be rotated such that the leading edge of the plates is cutting upwardly. High pressure water is pumped into the receiving space 16 through the spray nozzles 24 and make-up water flows into that space through apertures 22. When one of the plates 14 is brought to bear against material to be dredged the scoops 19 direct the material to be dredged through apertures 18 into the receiving space 16. The flow of water around the receiving space and into the inlet pipe 17 carries the material being dredge from the apertures into the inlet pipe 17 from which it is drawn into the dredge by the dredge pump.

The use of a plurality of small apertures on the plate prevents the ingress into the receiving space of large stones and the like which might block the dredge pump. The relatively short distance from the mouth of the scoop 19 into the receiving space 16 reduces the energy required to convey the material being dredged into the cutter wheel against surface adhesion forces. The limitation on water inflow into the receiving space 16 combined with the efficient cutting actions of the scoops 19 ensures the slurry entering the dredge pump has the desired high pulp density. A second embodiment of a bucket wheel assembly according to the present invention is shown in Figures 5 and 6. The same numerals are used to indicate parts of this embodiment of the invention which are similar to those of the embodiment of the invention described with reference to Figures 1 to 4.

The bucket wheel assembly 10 of Figures 5 and 6 differs from that described with reference to Figures 1 to 4 in that each plate 14 is provided around its circumference with an inwardly extending cylindrical flange 25 the free edge of which lies closely adjacent the housing 15. Each of the flanges 25 is provided around its circumference with a plurality of spaced apart apertures 26. Each aperture is bounded on its trailing edge by an outwardly extending scoop 27. The inlet pipe 17 extends through the stationary housing 15 and expands in width once inside the receiving space 16 such that the side edges of the mouth of the inlet pipe 17 lie closely adjacent the inside faces of the plates 14. In another embodiment of the invention the housing may be connected to the free end of the support arm and a double ended motor mounted centrally within the housing. A plate having apertures and scoops can then be directly mounted to each end of the motor. This arrangement has the advantage that the support arm will not exert a blanking effect on one side of the cutter wheel assembly. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS: -

1. A cutter wheel assembly for use on a suction dredge, the cutter wheel assembly comprising a support arm, a hub mounted on the support arm and adapted to be rotated about an axis extending transversely of the support arm, at least one, preferably substantially circular, plate mounted on the hub and adapted to be rotated therewith, the plate being provided with a plurality of apertures therethrough, each aperture being provided on its trailing edge on one side of the plate with an outwardly extending scoop member, a housing surrounding the plate on the side thereof distal to the scoops to form a receiving space adjacent to the plate and an intake pipe for a suction line extending into communication with the receiving space.

2. A cutter wheel assembly as claimed in claim 1 in which the assembly includes two spaced apart plates mounted on the hub, each of the plates being formed with the through apertures and outwardly extending scoop members, the housing extending between the two plates to form the receiving space therebetween.

3. A cutter wheel assembly as claimed in claim 1 in which liquid discharge means are provided within the receiving space which are adapted to direct a stream of a liquid towards the intake pipe.

4. A cutter wheel assembly as claimed in claim 1 in which the housing is provided with a liquid inlet aperture so positioned that in use, make-up water from the dredging pond will flow into the receiving space and around at least part of the hub to the inlet pipe.

5. A cutter wheel assembly as claimed in claim 1 in which the inlet pipe extends into a lower portion of the receiving space, the inlet pipe terminating in an inlet end which extends across substantially the full cross-sectional area of the receiving space between the hub and the housing.

6. A cutter wheel assembly as claimed in claim 1 in which the apertures are very small relative to the size of the plate.

7. A cutter wheel assembly as claimed in claim 6 in which the apertures have a maximum dimension of 6 inches (300mm) .

8. A cutter wheel assembly as claimed in claim 1 in which the apertures are arranged radially and circumferentially about the plate in spaced apart array such that in use with each revolution of the plate the complete face of the material to be dredged is swept at least one by an aperture and its associated scoop member.

9. A cutter wheel assembly as claimed in claim 1 in which each scoop member includes a face adjacent the trailing edge of its associated aperture, which face is inclined at an acute angle to the plane of the plate and is inclined towards the direction of rotation of the plate.

10. A cutter wheel assembly as claimed in claim 1 or claim 2 in which the, or each, plate has on its periphery a cylindrical flange directed towards the housing, a plurality of apertures extend through the flange and being each formed on its trailing edge with an outwardly extending scoop member.