Discharging bulk materials

Abstract: A ship-mounted bucket wheel unloader for bulk cargoes comprising coaxial bucket wheels (44) supported on a carriage (2) which straddles the cargo hold (6) and which is displaceable fore and aft along the hold. The axis of rotation of the bucket wheels extends in the direction of displacement of the carriage and the diameter of each wheel occupies a major part of the width of the hold. A transfer conveyor (46) extends transversely from between the bucket wheels to a discharge conveyor (64) alongside the hold and receives material from one or other of the bucket wheels depending on the direction of displacement of the unloader. The bucket wheels and transfer conveyor are upwardly and downwardly adjustable as a unit on the carriage to lift the bucket wheels out of or to lower them into material in hold. A compact arrangement is achieved which can be installed on existing bulk-carrying vessels such as dredgers.

Description: This invention relates to unloaders for discharging bulk materials, in particular from a ship's hold, eg. for off-loading a dredger, and to ships provided with such unloaders. It is known to employ fixed discharge equipment such as grabbing cranes or bucket wheel unloaders at the dockside to discharge bulk cargoes in port. Examples of such bucket wheel unloaders are described in GB 1498458 and DE 2711573. It is not always convenient, or even possible, to provide adequate fixed discharge equipment at a desired quayside location, however. It has been proposed in EP 020167 to mount a bucket wheel unloader on board ship. The bucket wheel is mounted on one end of a generally horizontal boom which extends fore and aft, longitudinally of the ship's hold. The boom is in its turn mounted at its other end on a cross-carriage which runs on rails on the deck at opposite sides of the hold to advance the bucket wheel along the hold. The boom is cantilevered from the cross-carriage through a pivot connection which allows the bucket wheel to be raised and lowered. Transfer conveyors on the boom and the cross-carriage take material gathered by the bucket wheel to an off-loading conveyor running along one side of the hold. This known arrangement works satisfactorily but in general it must be installed in a purpose-built ship because of the space it occupies. In particular, space must be found to accommodate the unloader clear of the ship's hold when material is being loaded, but the boom must have a substantial length if the bucket wheel is to operate effectively through the full depth of the hold. It is rarely the case that an existing dredger will have sufficient deck space available to accommodate such bulky equipment. According to one aspect of the invention, there is provided a watercraft having a bulk cargo hold accessible from above, and a bucket wheel unloader for said hold comprising a carriage extending athwartships to straddle the hold and being displaceable fore and aft along the hold, at least one bucket wheel supported on said carriage with an axis of rotation extending generally in the direction of displacement of the carriage, and conveying means for the transfer of material gathered by said bucket wheel to a discharge means, said conveying means being maintained extending transversely to said direction of displacement of the carriage, said bucket wheel and conveying means being jointly linearly displaceable on the carriage, upwardly and downwardly along a vertical axis. Such a construction can be made very compact in the longitudinal or travel direction of the carriage, and so can be more easily fitted in an existing vessel. Moreover, it can remain within the length of the hold without impeding the loading of cargo into the hold. Preferably, the carrier, bucket wheel or wheels, and transfer conveyor are all disposed within the extent of the carriage in said longitudinal direction. The provision of a compact arrangement has its own advantages, independently of the facility with which it can be mounted on a vessel, and it can also be installed at a discharge dock or berth. According to another aspect of the present invention, therefore, there is provided a bucket wheel unloader comprising a carriage arranged to be displaceable along a storage space such as a ship's hold, at least one bucket wheel supported by said carriage with its rotary axis extending generally in the direction of displacement of the carriage, for transferring to a discharge means material gathered by the bucket wheel, a transfer conveying means being maintained extending transversely to the direction of displacement of the carriage, and said bucket wheel together with the transfer conveying means being linearly displaceable upwardly and downwardly along a vertical axis. In a preferred arrangement according to the invention, the unloader has two coaxial bucket wheels between which the transfer conveyor is located to receive material from both wheels. This ensures that the unloader can clear material effectively from both ends of a space such as a ship's hold, without requiring special adaptation of the contours of the ends of the hold. The invention will be described by way of example with reference to the accompanying schematic drawings, in which: Fig. 1 is a transverse cross-section of a ship's hold provided with a bucket wheel unloader according to the invention, Fig. 2 is a longitudinal sectional view illustrating the relative dispositions of the carriage, carrier and bucket wheels, and Fig. 3 is a plan section view illustrating the relative dispositions of the bucket wheels, bucket elevator and off-loading conveyor. Fig. 1 shows a cross-carriage 2 of the unloader mounted on coamings 4 on opposite sides of the hold 6 of a ship 8, wheels 10 of the carriage sitting on rails 12 on the coamings. The carriage 2 comprises a frame-like structure with a pair of beams 14 straddling the top of the hold and connected together at one side of the hold through a main body part 16 of the carriage and at the opposite side by a stretcher 18. On opposite sides of the body part 16, which carries the driving cabin for the unloader, pairs of guide pads 22 are secured. A carrier 24 is provided with vertical guide tracks 26 on its opposite sides which are slidably engaged by the guide pads 22. The carrier 24 is suspended from the cross-carriage by a sheaved cable 28 depending from the top frame of a bridge structure 32 which rises from the beams 14. A winch 34 on the carriage can reel the cable 28 in and out to raise and lower the carrier 24. The carrier 24 includes an arm 42 at its lower end on which are mounted a pair of coaxial bucket wheels 44 and, between the bucket wheels, the lower end of a bucket chain conveying means forming a bucket elevator 46. The bucket elevator 46 has only a pivot support connection 48 with the arm 42; cables 52 extend transversely between the elevator and an upper region of the carrier 24 and in conjunction with the pivot support to locate the bucket elevator 46 in a fixed position relative to the carrier 24 and bucket wheels 44. The bucket wheels 44 are both cell-type wheels, the wheel buckets 50 discharging radially inwardly into side chutes 54 which direct the material into the space between the wheels. Fixed sector-shaped guard plates 56 on the carrier 24 lie close to the opposed side faces of the respective bucket wheels to screen the outlets of the side chutes 54 over the greater part of the rise of the buckets from the bottom of the hold as the wheels rotate in the arrowed direction. As each chute outlet opening passes the top of its guard plate the contents of the chute can fall into a feeder hopper 58 channelling the material to the base of the bucket elevator 46 from where the elevator buckets carry it away. Mounted at the upper end of the bucket elevator is a telescopic discharge sleeve 60 leading to a hopper 62. The hopper 62 is secured to the stretcher 18 of the carriage to be located at a fixed height over an off-take conveyor 64 which extends along the side of the hold to discharge the material from the ship. As the carriage moves the bucket wheels along the hold, therefore, material is delivered from the hold through the bucket elevator 46, telescopic sleeve 60 and hopper 62 to fall onto the conveyor 64. The carrier, bucket wheels and bucket elevator are shown in full lines in Fig. 1 in their lowest position. By driving the winch 34 to raise the carrier they can reach an upper position, indicated in broken lines in Fig. 1, in which loading the hold will not be impeded. If desired, it may be arranged that they can be raised further so that the carriage can be driven clear of the hold. The carrier drive also allows the height of the bucket wheels to be adjusted during unloading to the depth of the material remaining in the hold. Vertical displacements of the bucket elevator 46 are accompanied by adjustment of the length of the discharge sleeve 60 to maintain a closed path to the hopper 62 and Fig. 1 indicates in broken lines two upper telescopic sections 60a,60b of the sleeve 60. The cross-carriage 2 has a drive means 72 which engages with a fixed chain (not shown) extending the length of the hold, which may be five times or more the length of the carriage. The drive means 72 can be powered by a positive displacement hydraulic motor, like the similar motors 74,76 driving the bucket wheels 44 and bucket elevator 46. Pressurized hydraulic fluid for all the drives on the carriage is transmitted through a reel 82. An individual motor 76 is provided for each bucket wheel; these motors cannot be placed directly on the carrier 24 at the bucket wheel mountings so they are provided with torque reaction links 78 extending to the vertical column of the carrier to hold them against rotation. The use of the opposed pair of bucket wheels with the bucket elevator between them ensures that the unloader can be lowered into the material in the hold and can remove material working in either direction along the hold without obstruction from the bucket elevator. The pair of bucket wheels also protect the bucket elevator from the material in the hold caving in upon it, which could otherwise easily result in jamming and even damage to the elevator.

Claims: A bucket wheel unloader comprising a carriage (2) arranged to be displaceable along a bulk material storage space (6) such as a ship's hold, at least one bucket wheel (44) supported by said carriage to maintain its rotary axis extending generally in the direction of displacement of the carriage, and transfer conveying means (46) for transferring material gathered by said bucket wheel to discharge means (64), wherein the transfer conveying means (46) extend from said bucket wheel (44) transversely to said direction of displacement of the carriage, and that said bucket wheel together with the transfer conveying means are upwardly and downwardly displaceable along a vertical axis. A bucket wheel unloader according to claim 1 wherein the transfer conveying means (46) are mounted in a fixed position relative to said bucket wheel (44) and adjustable guide means (60) are provided for directing the material from said conveying means to the discharge means (64). A bucket wheel unloader according to claim 2 wherein the adjustable guide means comprise a telescopic chute (60). A bucket wheel unloader according to any one of the preceding claims wherein said bucket wheel and transfer conveying means are supported on a carrier (24) which is mounted in a substantially vertically displaceable manner on the carriage (2). A bucket wheel unloader according to any one of the preceding claims having two bucket wheels (44) between which the transfer conveying means (46) is located to receive material from each wheel. A bucket wheel unloader according to any one of the preceding claims wherein the transfer conveying means (46) extends obliquely upwards from the bucket wheel for transferring material to a discharge means (64) at one side of the storage space. A bucket wheel unloader according to any one of the preceding claims wherein the or each bucket wheel (44) is driven by a motor (76) at its hub and said motor is rotationally restrained by a torque link (78) to a position that is fixed with respect to the bucket wheel axis. A watercraft having a bulk cargo hold (6) accessible from above and a bucket wheel unloader for said hold comprising a carriage (2) extending athwartships to straddle the hold and being displaceable fore and aft along the hold, at least one bucket wheel (44) supported on said carriage with an axis of rotation extending generally in the direction of displacement of the carriage and being upwardly and downwardly displaceable along a vertical axis on the carriage, and conveying means (46) for the transfer of material gathered by said bucket wheel to a discharge means, wherein said transfer conveying means (46) extend from said bucket wheel transversely of the hold, and that said bucket wheel and transversely extending conveying means jointly displaceable are upwardly and downwardly on the carriage. A watercraft according to claim 8 wherein said bucket wheel (44) extends a major part of the width of the hold and is maintained in a position fixed centrally of the hold. A watercraft according to claim 8 or claim 9 wherein the bucket wheel unloader is constructed and arranged in accordance with any one of claims 2 to 7.

Inventors: DOWDEN PAUL JOHN, DOWDEN, PAUL JOHN
Applicants: STRACHAN & HENSHAW LTD, STRACHAN & HENSHAW LIMITED
Application year: 1993
Main classification: B65G65
IPC codes: B65G67, B63B27