EP0406394A1 - Container crane - Google Patents

Abstract

A quay container crane intended for loading and unloading containers on a ship moored to a quay, comprises a jib (8) capable of covering the width of the ship, a rolling carriage moving along this jib, as well as 'a lifting means for containers suspended from said rolling carriage. The boom is supported by a floating support structure (19) located on the side of the ship facing the sea. The land-based support structure has an extendable tower to keep the boom horizontal. The floating support structure comprises two independently manoeuvrable barges (17, 18) which can be moored end to end in order to move and side by side for the control of said crane. One barge carries a first tower (12) supporting the boom so as to allow it to move longitudinally relative to the first tower, and the other barge carries an auxiliary tower (13) supporting said boom fixedly. The first tower comprises an inner column (28) resting on a self-aligned thrust bearing, said column being kept straight but being free to rotate in order to pivot the boom using a surrounding structure (29) supporting the column by means of a plurality of elastomeric energy absorbing pads, damping the swinging movement of said column.

Description

CONTAINER CRANE

TECHNICAL FIELD

The use of ship-borne cargo containers, in the form of large steel boxes, in a small number of standardised sizes has become widespread since their introduction in the 1950s and port facilities for their handling have become largely- standardised.

The present invention relates to container cranes, that is to say cranes of the kind used to load and off-load such containers at ports.

BACKGROUND ART

Typically a present day container crane comprises a travelling gantry mounted for movement along rails extending along a quay, a boom supported by and extending horizontally from the gantry in a direction perpendicular to the direction of travel of the gantry, a crab moveable along the boom, a so-called "spreader", that is to say a container engaging device suspended from the crab, and a hoist for raising and lowering the spreader. The hoist is usually carried on the crab but may be in a separate machinery house at one end of the boom.

The boom usually extends further from the gantry on the sea side of the crane, as it is required to extend fully across a ship at the quayside, than it does on the land side. Indeed where the gantry is designed to straddle road or rail trucks on the quay, the boom may not extend from the gantry on the land side at all. To enable ships to be docked at the quay, that part of the boom extending beyond the quayside is usually able to be swung upwardly into a more or less vertical alignment.

The gantry usually comprises a sea side portal arch, a land side portal arch and heavy cross members tying the two arches together so that they become the main components of a four-legged gantry supporting the boom at two spaced apart positions. Usually the two sea side legs of the gantry and the two land side legs are respectively joined together by longitudinal beams close to ground level, which, in turn, are supported by multi-wheeled bogies near their ends.

Such cranes are large structures and, to ensure stability under wind loadings and when lifting a container at the maximum outreach of the crab, are necessarily massive. It is not unusual, for example, for a crane intended to lift a 4-0 tonne container to weigh in excess of 900 tonnes. Thus the loads imposed on the rails are high and particularly on the sea side rail due to the increased reaction needed to overcome the turning moment of the burden at maximum outreach.

It follows from the foregoing that the supporting foundation structure for the quay must be extensive and costly, a situation which is often exacerbated because at the shore there is usually a considerable depth of soft alluvial deposit overlying the bedrock. As a consequence it will be apparent that to convert more traditional berths into container berths is an expensive process.

It frequently happens that the initial conversion of an old berth or the establishment of a completely new container berth proves to be inadequate because of an unexpected increase in the number of ships and/or volume of freight to be serviced, but the deficiency has to be accepted because of the high cost of extending a berth or providing another berth at the containerised freight facility in question. Indeed at some ports there are no container handling facilities even though the operating efficiency of the port would be enhanced thereby, because the country in which the port is located simply cannot afford the capital outlay required for the civil works needed to provide a quay able to support a container crane at the relevant site. On the other hand the flow of freight may decline at a particular berth, in which event expensive capital works are under-utilised^* with consequent economic loss.

DISCLOSURE OF INVENTION An object of the invention is to ameliorate the above indicated disadvantages of container cranes.

That object is achieved primarily by providing a container crane supported in part by a pontoon or like floating vessel, thereby relieving the quay structure of a part, preferably a major part, of the weight of the crane. That is to say, according to the invention, at least part, preferably a major part, of the weight loadings of a container crane are carried by a floating support and only the remainder, preferably only relatively small stabilising loadings, are transferred to the quay.

Furthermore, in preferred embodiments the floating part of the crane is detachable from the land mounted part, so that the major part of the crane may be shifted as needed from berth to berth, and maybe even from port to port, to suit temporary variations in demand. This requires the provision of much less expensive civil works at each site by comparison with those required for a conventional fully land based crane.

Broadly stated the invention consists in a container crane of the kind comprising a substantially horizontal boom supported at two spaced apart positions by two support structures, a crab able to travel along said boom and hoisting means for containers suspended from said crab, characterised in that one of said support structures is a floating structure comprising a floating base and a first tower rising from said base, in that the other of said support structures is a land based structure comprising a mobile trolley and a second tower rising from said trolley, and in that at least one of said support structures is adjustable as to its effective height to enable the boom to be kept substantially horizontal notwithstanding changes in

« water level at the site.

For preference it is the land based support structure which is adjustable by virtue of its tower being telescopic, but in one class of embodiments it is the floating structure which is adjustable by virtue of the controlled intake or discharge of water ballast to cause its base to ride higher or lower in the water to compensate for changes in the water level.

Preferred embodiments of the invention comprise a floating barge, a tower on said barge comprising a load- bearing column extending from a self-aligning thrust bearing on said barge and stay means to maintain the column upright, which stay means may resiliently yield to a limited extent and include energy absorbing devices to damp out swinging movement of the column about the bearing, a substantially horizontally extending boom supported by the column in a manner permitting positional adjustment of the boom longitudinally of itself, a crab adapted to travel along the boom, a spreader depending from the crab, a hoist whereby the spreader may be raised and lowered, crab driving means to effect travel of the crab along the boom, a mobile trolley moveable along a quay and a second tower on said trolley adapted to engage the boom for the partial support thereof.

For preference the engagement between the boom and the land based second tower is releasable to enable at least the barge mounted part of the crane to be shifted from berth to berth as and when required. In this instance the barge may comprise two separable parts, each with a supporting tower extending upwardly to the boom to enable the boom to be supported at two spaced apart positions as and when the barge is moving from place to place or while the boom is being extended across a ship to be loaded or unloaded before it is engaged by the land based tower.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagrammatic perspective view of a container crane according to the invention shown in position for the unloading of a ship.

Figure 2 is a diagrammatic sectional elevation taken on line 2-2 of figure 1 drawn to a slightly larger scale.

Figure 3 is a diagrammatic sectional detail taken on line 3-3 of figure 2 drawn to a slightly larger scale.

Figure 4- is a cross-section of a shock-absorbing buffer, being a component appearing in figure 3 drawn to a still larger scale.

Figures 5_> 6 and 7 are views similar to figure 1 showing the crane of that figure at successive stages of its approach to a ship to be unloaded.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The illustrated container crane comprises a substantially horizontal boom 8 which, when the crane is in use, is supported at two spaced apart positions by two support structures 9 and 10 respectively, a main crab 11 able to travel along the boom 8 intermediate the structures 9 and 10, an auxiliary crab 22 able to travel along an end part of the boom 8 projecting beyond the land based structure 10, and hoisting means for conventional container spreaders 23 and 24- from the crabs 11 and 22.

The support structure 9 is a floating structure comprising a floating base, a first tower 12, an auxiliary tower 13 and a boom rest 14 , whereas the support structure 10 is a land based structure comprising a mobile trolley 15 and a second tower 16.

In the diagrammatic drawings the boom 8 and tower components have been drawn as if they were fabricated from plate, but in practice it is probable that they would be triangulated skeletal components as customarily used in strong but light fabricated steelwork. In either event the boom 8 is usually of inverted U shaped section so that the crab ^"may run within the boom with the hoist cables extending from the crab through the open bottom face of the boom.

The base of the floating support structure 9 comprises a large, essentially rectangular, flat bottomed main barge 17, together with a similar but smaller auxiliary barge 18. Both barges are furnished with propulsion devices of known kind comprising tubular under water ducts 19 accommodating electrically or hydraulically powered, reversible propellers 20. Two of the ducts 19 extend from end to end of each barge disposed respectively adjacent the barge sides and two more of the ducts 19 extend from side to side of each barge disposed respectively adjacent the barge ends. Thus, by selective operation of the propellers 20, both barges may manoeuver with great versatility. In particular the auxiliary barge 18 may move from a travelling position where it is secured to one end of the main barge 17 (as in figure 6, for example) to an operating position where it is secured to one side of the main barge 17 (as in figure 1, for example) .

The auxiliary barge 18 may be detachably secured to the main barge 17 in the travelling and operating positions by more robust versions of the conventional "twist-locks" used to secure a spreader to a container. Briefly stated, a twist-lock comprises a tapered T-headed pin adapted to enter the rounded rectangular mouth of a socket and then be locked in place by rotation about its own axis by 90°. The rotation of the twist-lock pin is usually effected by an hydraulic motor, electric motor or magnet. At least four such twist-locks would be provided at each location.

The main barge 17 is very stable and may carry heavy off-centre loads safely without listing to any great extent. It and the auxiliary barge 18 are preferably made from durable, corrosion resistant material, for example, reinforced concrete. The barges, when secured end to end in the travelling position, are adapted to be shifted from place to place and manoeuvered into position by a tug boat, or one or both may be furnished with a prime mover providing power for the propellers 20 enabling them to be self propelling, albeit at a slow rate. Indeed the crane is preferably self-sufficient insofar as power supplies are concerned and the main barge 17 therefore preferably carries a machinery room housing a prime mover, for example a petrol or diesel engine.

When travelling from berth to berth as aforesaid the boom 8 is adequately supported at two positions by the main and auxiliary towers 12 and 13- Also the boom 8 may rest upon the top of the boom rest 14- with the suspended spreaders 23 and 24. then resting on shelves 21 projecting from the boom rest.

The barge prime mover, if present, may power an alternator or an hydraulic pump or both for energising electric or hydraulic motors, as the case may be, for driving the individual mechanisms of the crane as described below. In general, hydraulic drives are preferred over electric ones for use in at least the barge mounted components of the crane, because of the inherent safety problems associated with electricity in a salt water environment. The barges 17 and 18 generally present flat decks, apart from the machinery room, amenity buildings and the like on the main barge 17. They each may have a below deck plate web girder 25 or 26, as the case may be, extending from side to side for the support of the respective towers. The main barge 17 may have a second such girder for the support of the boom rest.

Girder 25 carries a large but conventional, spherical seated, barrel roller thrust bearing 27, for the support of a fabricated or tubular steel column 28, being an inner component of the first tower 12. The bearing 27 locates the bottom of the column 28 and carries its weight and downwardly imposed loads thereon but leaves the column free to tilt or sway in any direction about its bottom end. Of course the bearing 27 also allows the column 28 to be rotated about its own upright axis to allow a slewing motion for the boom 8 supported by the column.

The column 28 is kept substantially perpendicular to the barge by stay means including yieldable loading devices which apply a restoring force to the column 28 whenever it departs from the perpendicular.

For example, (see figures 3 and 4-)*. the column 28 may be surrounded by a rigid cylindrical or square sectioned framework 29 spaced radially from the column 28 and connected to the column near its top end by an array of equiangularly spaced, radially extending, resilient buffers 30. The radially outer end of each buffer 30 may be fixed to the surrounding framework 29 and the radially inner end of each buffer 30 may slidingly engage a circular track member 31 encircling the column 28 to permit it to rotate. This arrangement not only ensures that the buffers share the duty of restraining the column from swaying in any direction but also permits the column to be rotated for slewing the boom. It is necessary to prevent the column developing an oscillatory motion and so the resilient buffers 30 are energy absorbing devices able to heavily damp the column movement. More particularly described each buffer 30 may comprise a mass of a highly viscous elastomer 31 housed within a cylinder 32 and pressurised by a plunger 33 entering that cylinder. The plunger 33 is adapted to ride upon the track member 31 • It may extend through a cylinder head 3 - and retainer seal 34-a. One such buffer device well suited to this application is currently marketed under the trade mark JARRET. Although usually referred to as a shock absorber the JARRET device also functions as a compression spring.

In other embodiments the JARRET devices may be replaced by spring/shock absorber combinations or by other energy absorbing elastomeric supports.

In other embodiments of the invention the stay means may comprise three or more tensile guys extending from a guide ring encircling the column to anchorages on the deck. Each such guy may incorporate a tension spring and shock absorber combination or, preferably, two inter-linked loops of chain encapsulated in an elastomeric body to provide both the return force and damping effect. Such encapsulated chain devices are well known per se.

The auxiliary tower 13 is similar in construction to the first tower 12 in that it comprises an inner column 35 within an outer frame 36, but it is unnecessary to duplicate the shock absorbing devices of the first tower 12 or to provide for slewing of the boom relative to the axis of the tower, thus the column 35 is held upright by simpler guide rolls 37 or the like. On the other hand the effective height of the auxiliary tower 13 is preferably adjustable and to that end an hydraulic thrustor or jack cylinder 8 may be interposed between the base of column 35 and a support pedestal 39- The boom 8 is preferably an elongated lattice box frame comprising four longitudinal members and triangulated bracing, and is mounted on the top of the column 28 by means maintaining it substantially perpendicular to the column but permitting it to move longitudinally of itself to a limited extent relative to column 28. Thus column 28 may terminate in an open ended box-like frame 4-0 through which the boom 8 may move by virtue of support rollers 4-1 and hold down rollers 4-2 mounted on the box-like frame and engaging rails extending longitudinally of the longitudinal members of the boom. Preferably the support rollers 4-1 are otorised and toothed to engage rails on the boom in the form of racks. This enables positive drive between the boom and column and positive locking between them to be effected if need be.

The connection between the boom 8 and column 35 of the auxiliary tower may be similar to that described above in respect of column 28 of the first tower, but in its case there would be only minor positional adjustment between the boom and column which are basically required, in this embodiment, to move as one. This is because longitudinal movement of the boom relative to the first tower is effected by manoeuvering the auxiliary barge 18 while the boom is fixed to the column 35•

The crab 11 is able to travel along the boom 8 on rails extending along the boom for that purpose. Unlike more conventional container cranes in which the traversing motor for the crab and the hoist are mounted on the crab itself, those mechanisms are preferably mounted on the boom close to one or other of its points of support.

Thus the crab 11 may be hauled to and fro along the boom 8 by means of a capstan winch 4-3 on the boom 8 adjacent the top of tower 16 and a loop of wire rope 4-4- wrapped upon the winch drum and passing about a training sheave 4-5 at the far end of the boom 8. The crab 11 is joined to one flight of the loop and thus is caused to move to or fro by operation of the capstan winch 4-3-

The crab 11 itself is a simple, track wheeled trolley carrying two sheaves 4-6 able to rotate about respective horizontal, spaced apart axes extending transversely of the boom 8.

A hoist 47 is mounted on the boom 8 adjacent the top of the tower 10 with a hoist rope 48 extending from the hoist 47 along the boom to the crab. The hoist rope 48 turns about one of the crab sheaves 46, then descends as a loop to a pulley block 49, then up to and about the other crab sheave 46 and then on to an anchorage 50 at the far end of the boom. Thus, when the hoist rope 8 is wound in by the hoist 47 the loop of rope descending from the crab is shortened and the pulley block 49 is raised. Likewise when the rope is unwound the pulley block descends.

If the crab 11 is traversed along the boom 8 with the hoist 47 stationary the hoist rope 48 moves through the pulley block 49 but the length of the loop is unaltered and the pulley block 49 travels with the crab 11 without rising or falling.

The conventional spreader 23 suspended from the pulley block 49 is able to engage a container 51.

The trolley 15 of the land based support structure 10 may have rubber-tyred wheels 52 able to run on a concrete deck extending along the quay and outrigger stabilizer jacks 53 . The sets of wheels 52 are mounted on bogies able to turn through 90o to enable the structure 10 to travel along the quay and also towards and away from the quayside. The jacks 53 have sufficient capacity to lift the structure so that the wheels 52 come clear of the deck when being turned from one position to the other. As mentioned earlier the tower 16 is length adjustable, it may be a fabricated steel structure in two parts, with one part 54 able to be raised or lowered telescopically within the other part 55 , by means of an hydraulic jack cylinder 56.

The upper end of the tower part 54 and the boom 8 are provided with twist-locks or other separable fasteners to enable the mast 16 to be secured to and partly support the boom. The degree of support may be determined or varied by controlling the fluid pressure in the jack cylinder 56. Furthermore, if an accumulator is provided in the fluid system the mast 1 may automatically extend and contract to maintain unvarying support for the boom notwithstanding any tidal movement or heeling or listing of the floating support structure 9 that may occur. Of course the fluid pressure in the jack cylinder 56 likewise limits the load applied to the quay and permits a crane according to the invention to be adapted to suit the load carrying capacity of various berths at which it may be employed.

For preference a turntable 57 is mounted on the tower 16 some distance below the boom 8. That turntable 57 may be a cantilevered platform projecting from the tower mounted for rotation through at least 180° about the vertical axis of the tower. To that end it may rest upon or engage with a bearing collar 58 having low friction liners on the surfaces contacting the turntable 57. Its rotation is motorised, for example by means of a gear motor 59 on the turntable engaging a ring gear encircling the tower. The purpose of the turntable 57 is to enable a container suspended from the pulley block 23 and travelling with the crab 11 along the boom 8 on the sea side of the tower 16 to be transferred to the land side of the tower. Thus the container may be set down on the turntable 57 on the sea side of the tower, carried by the turntable as it is rotated to the land side of the tower and picked up once more by the auxiliary crab 22 for deposit on a road or rail truck as the case may be.

As may be seen from figure 2 the travelling and hoisting arrangements for the auxiliary crab 22 are virtually the same as those for the main crab 11, and are therefore not further described herein.

For preference all of the electric drive motors for hoists, capstans and traversing rollers are geared brake motors of the kind which are normally held stationary by brakes which are disengaged automatically when, and only when, the motor is energised.

The operation of the illustrated embodiment may now be readily understood. Initially the two parts of the crane are brought into position on each side of a ship to be loaded or unloaded as shown in figure 5.

The floating support is then manoeuvered into position against the side of the ship and likewise the land based support is brought into close proximity with the opposite side of the ship, as seen in figure 6.

The barges 17 and 18 are then unlatched and barge 18 manoeuvered into the position shown in figure 7.

Barge 18 is then moved towards, and ultimately latched to, barge 17, during which manoeuvre the boom 8 extends across the ship until it may be engaged with the land based support structure. This movement may be assisted by operation of the supporting rolls 4 if they are motorised.

The crane is then ready for use, as seen in figure 1, and may be used in much the same manner as a conventional crane. It will be appreciated that structural and other details of the various crane mechanisms may take many design choices. All such come within the ambit of the invention which in its essence resides in the combination of a floating support and a land based support for the crane, with means for sharing the weight of the crane and its burden therebetween. In particular, it is mentioned that in another class of embodiments the floating support structure lies directly against the quayside and the ship comes up against and is moored to the seaward side of the floating structure itself. In this instance the crane may be similar in construction and operation to a conventional crane, especially if it is a more or less permanent installation not intended for frequent passage from one berth to another.

It is envisaged that as the use of the invention becomes widespread, ships may be provided with latching devices in alignment with the transverse rows of stacked containers for engaging the crane' s floating supporting structure to maintain the boom in corresponding alignment with the rows of containers as loading or unloading proceeds.

The term "tower" as used herein is intended as a reference to any upwardly extending, self supporting, load bearing structure.

Claims

1. A container crane of the kind comprising a substantially horizontal boom supported at two spaced apart positions by two support structures, a crab able to travel along said boom and hoisting means for containers suspended from said crab, characterised in that one of said support structures is a floating structure comprising a floating base and a first tower rising from said base, in that the other of said support structures is a land based structure comprising a mobile trolley and a second tower rising from said trolley, and in that at least one of said support structures is adjustable as to its effective height to enable the boom to be kept substantially horizontal notwithstanding changes in water level at the site.

2. A container crane according to claim 1 further characterised in that the tower of said at least one adjustable support structure comprises two parts and jacking means to raise and lower one of those parts relative to the other.

3. A container crane according to claim 2 further characterised in that said jacking means are hydraulic, and in that the hydraulic pressure in the jacking means is limited to a constant value.

4- A container crane according to claim 1 wherein the said adjustable support structure is the floating support structure, further characterised in that the floating support structure includes means to admit and discharge water ballast to effect the adjustment.

5. A container crane according claim 1 further characterised in that said first tower comprises a load bearing column extending from a self aligning thrust bearing on said base and stay means to maintain the column upright, and in that said stay means may resiliently yield to a limited extent and include energy absorbing devices to damp out swinging movement of the column about the bearing.

6. A container crane according to any one of the preceding claims further characterised in that said boom is supported by the first tower by means permitting or effecting positional adjustment of the boom longitudinally of itself relative to the first tower.

7. A container crane according to claim 6 further characterised in that said floating base comprises two separable parts, namely a main part and an auxiliary part.

8. A container crane according to claim 7, further characterised in that said main part carries said first tower and in that said auxiliary part carries an auxiliary tower connected to an end of the boom.

9. A container crane according to claim 8 wherein each said part is an independently self manoeuverable barge.

10. A container crane according to claim 7 further characterised in that said mobile trolley has wheels which are rotatable about an upright axis and outrigger jacks able to lift the wheels clear of the ground to enable such rotation to be effected.

11. A container crane substantially as described herein with reference to the accompanying drawings.