GB1569564A

GB1569564A - Floating platform for loading and unloading cargoships

Info

Publication number: GB1569564A
Application number: GB46815/75A
Authority: GB
Original assignee: SEAFARM DESIGN Ltd
Current assignee: SEAFARM DESIGN Ltd
Priority date: 1976-11-11
Filing date: 1976-11-11
Publication date: 1980-06-18

Description

(54) FLOATING PLATFORM FOR LOADING AND UNLOADING CARGOSHIPS (71) We, SEAFORM DESIGN LIMITED, a British Company, and JOHN GEORGE BROWN, a British subject, both of Garvel Shipyard, Greenock, Renfrewshire, Scotland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a load-carrying platform.

In several parts of the world, it is impracticable, either because of a lack of adequate port facilities, port congestion or because of the nature of the shore, to bring ocean-going ships alongside a fixed quay in order to unload them. It is then necessary to provide some form of floating, load-carrying platform onto which cargo can be discharged from an ocean-going ship thereafter the load-carrying platform can be brought adjacent the shore and unloaded with the aid of ramps or simple handling apparatus.

Various forms of load-carrying platform have been used for this purpose in the past, but all of them suffer from the disadvantage that their platforms will not remain horizontal as cargo is loaded onto them. It is impossible to maintain a perfect balance of cargo on the load-carrying platform whilst its loading is in progress and due to the limited horizontal reach of ships cranes or derricks unless very small platforms are used (which is often impossible on account of dangers from weather and other causes), it is usually only possible to load part of each platform at any one time. The problem is becoming more acute as the weight of the individual units of cargo handled by the cranes or derricks increases; a single modern container may weigh 30 to 40 tonnes.

The present invention seeks to provide a load-carrying platform which minimizes the problem associated with tilting of the platform as it is being loaded and facilitates the transfer of cargo between the platform and the cargo vessel.

Accordingly, the invention provides a load-carrying platform comprising a buoyant vessel having a substantially horizontal loadcarrying surface for supporting at least one vehicle having a load-carrying surface at a predetermined height above said load-carrying surface of said vessel, at least one ballast tank spaced from the centre of gravity of the vessel, a tilt sensor for emitting a signal when the tilt of the loadcarrying surface from the horizontal about a given axis falls outside a predetermined range, and adjusting means for adjusting the amount of ballast in the ballast tank, wherein there is provided adjacent one side of the vessel a substantially horizontal landing platform at a predetermined height above the vessel load-carrying surface corresponding to said predetermined height of the vehicle load carrying surface.

Although the platform of the invention need only be provided with one ballast tank, it is preferred that it be provided with two ballast tanks spaced from one another along the said axis. Furthermore, since it is normally desirable to be able to control the tilt of the platform about two perpendicular horizontal axes it is desirable that the platform be equipped with two tilt sensors each capable of emitting a signal when the tilt of the load-carrying surface from the horizontal about a given axis falls outside a predetermined range, the axes associated with the two tilt sensors not being parallel to one another, two ballast tanks spaced from the centre of gravity of the vessel, the centres of the ballast tanks and the centre of gravity of the vessel not being co-linear, and two adjusting members each capable of adjusting the amount of ballast in one of the ballast tanks Desirably in such a platform, there are two pairs of ballast-tanks one pair being spaced from one another along one of the two axes and the other pair spaced from one another along the other axis.

The platform of the invention is also desirably equipped with means for varying its draught so that, as it is loaded or un loaded, its draught can be kept substantially constant.

The ballast used in the ballast tanks of the platform is conveniently water. The water may be introduced with the tanks either by pumps or simply by opening sea-cocks below the water level of the platform. The water may be removed from the tanks by pumps or by blowing compressed air into the tanks, thus expelling water through open sea-cocks.

The invention also provides a method of loading a vessel with cargo, the method comprising: bringing a load-carrying platform of the invention adjacent the vessel to be loaded, said load-carrying platform having thereon adjacent the landing platform thereof at least one said vehicle with a load-carrying surface at a predetermined height above the loadcarrying surface of said load-carrying platform, said vehicle being loaded with cargo; and transferring the cargo from the vehicle across the landing platform to the vessel whilst adjusting the quantity of ballast in the ballast tank(s) of the load-carrying platform so as to maintain the tilt of the load-carrying surface about the given axis within the predetermined range.

Finally, the invention provides a method of unloading cargo from a vessel, the method comprising: transferring cargo from the vessel onto an adjacent load-carrying platform of the invention whilst adjusting the quantity of ballast in the ballast tank(s) of the platform so as to maintain the tilt of the load-carrying surface about the given axis within the predetermined range, said load-carrying platform having thereon adjacent the landing platform thereof at least one said vehicle with a load-carrying surface at a predetermined height above the load-carrying surface of said load-carrying platform, said cargo being transferred onto the vehicle load-carrying surface via said landing platform: and removing the load-carrying platform from adjacent the vessel.

Preferred embodiments of the invention will now be described, though by way of illustration only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a first loadcarrying platform incorporating ballasting arrangements and other constructional features suitable for use in a load-carrying platform according to the invention; Figure 2 is a section on a reduced scale, along the line II--II in Figure 1 and shows the layout of the ballast tanks of the platform; Figure 3 is a section along the line B--B in Figure 2; Figure 4 is a side elevation of a loadcarrying platform according to the invention; Figure 5 is a top plan view of the platform shown in Figure 4;; Figure 6 is a part section along the line VI-VI in Figure 5 and shows the apparatus used to prevent the platform damaging a ship adjacent which it lies; and Figure 7 is a top plan view of a third loadcarrying platform used as a cargo terminal for load-carrying platforms according to the invention.

The first load-carrying platform shown in Figures 1, 2 and 3 comprises a buoyant vessel 1 having a substantially flat, horizontal load-carrying surface 2 which is provided with eight substantially U-shaped channel sections 3. (The channel sections 3 may be replaced by eight tubes fixed to the surface 2, the tubes being spaced apart by a distance slightly greater than the distance between the outer faces of the tyres on the bogies of the trailers.) These channel sections 3 serve as guides for the wheels of conventional trailers 4 of articulated lorries which constitute vehicles having load-carrying surfaces, twenty of these trailers being capable of being parked on the platform load-carrying surface 2 in, for example, five rows of four).

At the bow end of the vessel (to the right in Figure 1), there is provided a roll-on/ roll- off ramp 5, which can be raised or lowered by hydraulic piston-and-cylinder assemblies (not shown). When the ramp 5 is lowered, the trailers 4 can be driven on or off the load-carrying surface 2 by a conventional tractor unit 6. To ensure that the bow of the vessel is not damaged when it berths bow-on to a quay, the quay is provided with a floating fender 7.

The stern end of the vessel (to the left in Figure 1) is provided with a bridge section (generally designated 8) which contains a control cabin, a compressor and crew accommodation. The bridge section 8 is provided with floodlights 9 for illuminating the load-carrying surface 2 and a water-cannon 10 for security or firefighting purposes. Also, at the extreme stern end of the vessel is a recessed docking area 11 into which can be fitted one or more propulsion modules (not shown) to move the vessel 1 between a ship and the shore (in order that the propulsion modules and crew can be used in as efficient a manner as possible, the vessel 1 contains no propulsion unit but relies on separate propulsion modules to move it).

In order to maintain the position of the vessel adjacent the side of a ship doubledrum winches (not shown) may be provided adjacent the docking area their cables extending from one drum of a winch adjacent the ship to a pulley assembly adjacent the bow of the vessel and thence to the ship. Other cables would extend directly from the other drum of this winch to the opposed end of the ship. The double-drum winch on the side of the vessel adjacent the ship would then keep both sets of cables under tension, so keeping the vessel fixed relative to the ship. When it is desired to adjust the position of the vessel relative to the ship; this could be effected by paying out cable from one drum of the winch whilst hauling in the other set of cables.

The ballast tanks themselves comprise a pair of trim control tanks 14 adjacent the bow and stern of the vessel, three pairs of heel control tanks 15, three on either beam of the vessel and five pairs of draught control tanks 16 running along the centre line of the vessel within the double bottom of the vessel. Each of the tanks 14, 15 and 16 is equipped with a sea-cock (not shown) in its base and adjacent its upper end, with an air inlet (also not shown) through which compressed air from the compressor in the bridge section 8 can be introduced into the tank, thereby forcing water from the tank.

Alternatively, the eight tanks 14 and 15 may be replaced by four tanks, one at each corner of the vessel and all connected to a common control system.

Although not shown in the drawings, within the bridge section 8 of the vessel 1 are housed two tilt sensors of the type commonly known as "electronic spirit levels".

One of these sensors is a trim sensor and emits an electronic signal whenever the tilt of the load-carrying surface from the horizontal about a horizontal axis perpendicular to the mid-line of the vessel exceeds 0.2 in either direction. The electronic signal from the trim sensor is fed, via an amplifier, to a trim control circuit which opens the seacocks in both trim control tanks 14 whilst blowing compressed air into the trim control tank at the end of the ship which is lying lower in the water. Thus, water is expelled from the trim control tank 14 at the lower end of the ship, which therefore rises, whilst water enters the trim control tank at the higher end of the vessel, therefore causing that end to settle lower in the water.This process continues until the tilt becomes less than 0.2", whereupon the signal from the trim sensor ceases, the seacocks in the trim control tanks are closed and the air supply from the compressor to one trim control tank is cut off.

The other level sensor is a heel sensor and emits an electronic signal whenever the tilt of the load-carrying surface from the horizontal about a horizontal axis along the longitudinal mid-line of the vessel exceeds 0.2 in either direction. The electronic signal from the heel sensor is then used to adjust the level of ballast in the heel control tanks 15 is exactly the same way as the signal from the trim sensor if used to control the level of ballast in the trim control tanks 14.

The amount of ballast in the draught control tanks 16 is adjusted by a draught sensor (not shown) located centralling in the vessel 1. This sensor comprises a vertical tube, open at both ends and having two spaced pair of electrodes projecting thereinto. When either pair of contacts is submerged, a current flows between them, whilst when the electrodes are in air no current can pass. The two pairs of electrodes are positioned at heights corresponding to the highest and lowest points to which water should rise in the tube if the draught of the vessel 1 is to be kept within the desired limits.If the vessel 1 rises in the water so that both pairs of electrodes are in air, a draught control circuit is actuated and the sea-cocks are opened in both draught control tanks 16, so allowing water to enter therein and the vessel 1 to sink in the water until the lower pair of electrodes are submerged, whereupon the sea-cocks are closed. If the vessel -1 becomes lower in the water so that both pairs of electrodes are submerged, the draught control circuit opens the sea-cocks in the draught control tanks 16 and simultaneously blows compressed air into the upper ends of both tanks, so expelling water from the tanks and reducing the draught of the vessel.

The most rapid adjustment of the draught of the vessel is required when loaded trailers are being hauled off the load-carrying surface 2 by tractor units 6. Under these circumstances, it may be necessary to allow 500 or more tonnes of water to flood into the tanks 16 within about 30 minutes and the placing of the tanks 16 as low as possible allows this amount of water to enter purely by passive flooding. Since the trailers 4 are first removed from the bow end of the vessel during this unloading operation, it may be desirable to control the flooding of the draught ballast tanks manually, ensuring that the tanks nearest the bows are flooded first, then the second pair from the bow and so on. During such an operation, the tanks 16 will also, of course, partially control the trim of the vessel.

To ensure that the various control systems are not triggered by momentary changes in the vessel's attitude, caused for example by waves, the trim, heel and draught control circuits are each fitted with an electronic delay so that alteration of the amount of ballast in the tanks under the circuit's control is only initiated after the corresponding sensor has been emitting a signal continuously for a predetermined time (usually 5 to 10 seconds). The control circuits may also, if desired, be fitted with further delay circuits so that they continue to adjust the amount of ballast in the tanks for a short period (say 3 seconds) after the signal from the sensor is cut off.This helps to keep the attitude of the vessel as near perfect as possible; for example although the signal from the heel sensor will cease as soon as the list of the vessel becomes less than 0.2", the continued alteration of the amount of ballast in the heel tanks after the signal has ceased will suffice to reduce the list to zero.

To prevent the vessel 1 damaging a ship alongside which it is berthed, it is provided with a side fender 18 running along each side. For security purposes, the vessel may, if desired, be provided with a booth adjacent the ramp 5 for a security guard.

To use the vessel 1 for unloading cargo from a ship, the following procedure is normally carried out. The vessel 1 is berthed near a suitable quay or beach and empty trailers 4 are driven via the ramps 5 on the load-carrying surface 2 by the tractor unit 6 so that their wheels are engaged by the channel sections 3, thus reducing the risk that the trailers might slide across the surface 2. The ramp 5 is then raised and the vessel moved by a propulsion module alongside a ship. If desired, the vessel may be secured to the ship by cables attached to the winch 12 adjacent the ship, as described above. The propulsion module is detached and cargo is unloaded by the ship's cranes or derricks on to trailers arranged in two lanes on the vessel 1.During this process, the trim, heel and draught control circuits automatically adjust the amounts of ballast in the tanks 14, 15 and 16 so as to keep the trim, heel and draught of the vessel 1 within predetermined ranges, even though the distribution of the cargo may be highly asymmetric.

When the loading of the two lanes of trailers is complete, a propulsion module is re-attached to the vessel and the vessel may be moved round to the opposed side of the ship to unload onto further trailers provided on the vessel 1, the control systems again being used to maintain the trim, heel and draught of the vessel within the predetermined ranges. (Alternatively, two vessels may be used in the unloading operation and a single propulsion module used with the two buoyant vessels 1 so that unloading may take place simultaneously on both sides of the ship. This system allows the ships' cranes or derricks on both sides to be used continuously.) When the platform has then been completely loaded, it is moved by the propulsion module back to the quay or shore, its ramp is lowered and the loaded trailers can then be removed by the tractor units.

Obviously, to use the vessel for loading a ship, loaded trailers are driven onto the vessel and the above sequence of operations repeated -mutafis mutandis Equally, the loading and unloading operations may be combined, one batch of cargo being carried from the quay, loaded onto the ship and replaced by a different batch which is then brought back to the quay.

The platform 20 of the invention, shown in Figures 4 to 6, is generally similar to the first platform described above and has a load-bearing surface 2 provided with channel sections 3 exactly as in the first platform.

The platform 20 of the invention has along one side of the load-carrying surface 2 and running the full length thereof, a horizontal landing platform 21 which is level with the load-carrying surfaces of the trailers both being at the same predetermined height above the load-carrying surface 2 of the buoyant vessel 1. Along this landing platform 21 run load-carrying transporters in the form of fork lift trucks 22 which can drive from the landing platform 21 onto the trailers 4 over cover plates 23 which cover the gaps between the landing platform 21 and the adjacent lanes of trailers 4 and between the lanes of trailers themselves. The cover plates 23 are substantially L-shaped in cross section, one (short) arm of the "L" shape fitting into grooves 24 which are provided adjacent the side edges of the load-carrying surfaces of the trailers.

The platform 20 has a bridge section 25, which as best seen in Figure 4, has three levels, with crew accommodation 26 on the lowest level, a garage 27 for the fork-lift trucks 22 on the middle level (which is at the same height as the landing platform 21).

and a control cabin 28 on the top level.

Otherwise, the stern area of the platform is substantially similar to that of the first platform described above.

The bow area of the vessel is also similar to that of the first platform and is provided with a ramp 4, but the side of the platform adjacent the landing platform 21 differs, being provided with a plurality of rubber rollers 29 which, when the platform 20 is lying alongside a ship, contact the hull of the ship and thus prevent damage to either the ship or the platform 20 as they can move relative to one another. The platform 20 is also provided with a flexible bulwark 30.

This bulwark 30 comprises a plurality of sections each approximately 10 feet long and each comprising two parallel, planar frame sections 30a and 30b, both mounted at their lower ends on a pivot 30c and supporting at their upper ends a vulcanised rubber cylinder 30d. The pivot 30c can be locked in a position such that the frame members 30a and 30b lie perpendicular to the loading platform 21, in which position the bulwark serves as a deck-rail. During loading or unloading operations, however, the bulwark is allowed to pivot outwards so that it lies adjacent the side of the ship alongside which the platform 20 is lying.

The bulwark 30 tends to align a load being deposited on the landing platform 21 to assist subsequent uplift by a fork-lift truck 22.

As shown in Figure 6, a chamber 31 is provided below the landing platform 21; this chamber may conveniently be used to store pallets to be used by the fork-lift trucks 22.

To prevent the cargo from being damaged by heat when the trailers 4 are used in hot climates or by other weather conditions, each trailer is provided with a retractable awning (generally designated 32) one of which is shown extended in Figure 4. Each awning 32 comprises a plurality of inverted "U"shaped hoops 33 the lower ends of whose legs slide on rollers in the grooves 24 in the load-carrying surfaces of the trailers 4 and a pair of lazy-tong mechanisms 34, one on each side of the trailer, interconnecting the legs of the hoops 33. A canvas cover member 35 is attached to the hoops to provide shade for the trailer loads when the awning is in its extended position. The awnings 32 can be completely removed from the trailers when desired simply by lifting the hoops 33 clear of the grooves 24.

The trim, heel and draught sensors and control circuits and the ballast tanks of the platform 20 of the invention are identical to those of the first platform described above.

The platform 20 of the invention shown in Figures 4 to 6 is used as follows. To unload cargo from a ship, empty trailers are loaded onto the platform which is then brought, by means of a propulsion module, alongside the ship with its rollers 29 and its bulwark 30 in contact with the ship's hull. The cover plates 23 are placed in position to cover the gaps between the trailers and the landing platform 21. Cargo is then lowered from the ship into the landing platform 21; if the cargo is not already palletized it may either be placed on pallets on the deck and transferred together with the pallets to the landing platform or lowered onto the pallets which have previously been placed on the landing platform 21. Any cargo which is lowered very close to the ship's side and which strikes the flexible bulwark 30 will be deflected thereby onto the landing platform 21.

The palletized cargo on the landing platform 21 is carried by the fork-lift trucks 22 onto the top surfaces of the trailer platforms and deposited on the desired trailers 4.

Thereafter if necessary the awnings 32 are spread to protect the cargo. It will be appreciated that, with this embodiment of the invention, it is possible to load all the trailers from one side of the ship, even though the ship's cranes or derricks have only a very limited reach. Throughout the loading operation, the trim, heel and draught control systems function automatically to keep the trim, heel and draught of the vessel within predetermined ranges. Furthermore, if it is desired to unload heavy pieces of cargo such as containers, the reach of ship-borne cranes or derricks will normally be sufficient to load the heavy pieces of cargo directly on to at least the lane of trailers adjacent the landing platform 21, in the same way as the first platform is loaded.

After loading, the platform 20 of the invention is moved adjacent a quay by a propulsion module and unloaded. To load a ship, the sequence of operations is reversed, and it is also possible to combine loading with unloading in a manner similar to that described above with reference to the first platform.

The third platform 40 shown in Figure 7 is a port control terminal intended for use on shores where the slope of the beach is so small or the tidal range so large that the Iprovision of fixed quays is impracticable.

The platform 40 is rectangular, having overall dimensions of 400 ft. by 60 ft. and is provided with trim, heel and draught sensors, control circuits and ballast tanks similar to those in the first two embodiments of the invention described above. The platform 40 is anchored to the sea-bed by the anchors (not shown) at its four corners, sufficient slack being left in the anchor chains to allow for the rise and fall of the platform with waves, tides or other causes. s(Alternatively, this type of platform may be fixed horizontally relative to the sea bed by at least three vertical legs, the platform being free to slide vertically along the legs in response to tides, waves or the like.) Two access ramps 41, each of which is pivoted at one end on the platform and whose other end rests freely on the shore, provide access for vehicles from the shore to the platform 40.

The seaward side of the platform 40 is provided with a plurality of floating fenders 42 spaced so that load carrying platforms 43 of the invention (such as those shown in Figures 4 to 6) can berth bow-on to the main platform 40 and lower their ramps onto the main platform. (The ramps may alternatively be pivoted on the main platform 40 and lowered onto the decks of the load-carrying platforms 43. In this way, four of the comparatively expensive ramps can service perhaps a dozen load-carrying platforms, whilst the sea-worthiness of the loadcarrying platforms will be increased by the removal of the ramps therefrom.) To enable the load carrying platform 43 to be secured to the main platform 40 by hawsers, capstans 44 are provided on the main platform adjacent the ends of the floating fenders 42.

In the centre of the seaward face of the main platform 40 is located a propulsion module berth 45 equipped with capstans 46 to which a plurality of propulsion modules 47 may be berthed beam-on, whilst along the shorter sides of the platform 40 may be berthed auxiliary boats 48, which may be used for police launches, customs boats, crew transport boats for carrying dockers to and from ships, cargo surveyors' boats or boats for other purposes.

A port control building 49 is located centrally on the platform 40 and includes accommodation for ship crews and/or dock workers. On the building 49 are mounted a radar array 50 and a short wave radio-telephone mast 51 which are connected to a control room within the building, from which movements of all vessels and shore vehicles within the port and its environs can be controlled.

Adjacent the main platform 40 there may be berthed a further platform of the invention for the maintenance of all vehicles, platforms and boats used in the operation of the port terminal. Such a platform may include, for example, at one end a garage for the maintenance of the motor vehicles and at the other end a dry dock and/or lifting platform for use in underwater work on the platforms or boats.

WHAT WE CLAIM IS:- 1. A load-carrying platform comprising a buoyant vessel having a substantially horizontal load-carrying surface for supporting at least one vehicle having a load-carrying surface at a predetermined height above said load-carrying surface of said vessel, at least one ballast tank spaced from the centre of gravity of the vessel, a tilt sensor for emitting a signal when the tilt of the loadcarrying surface from the horizontal about a given axis falls outside a predetermined range, and adjusting means for adjusting the amount of ballast in the ballast tank, wherein there is provided adjacent one side of the vessel a substantially horizontal landing platform at a predetermined height above the vessel load-carrying surface corresponding to said predetermined height of the vehicle load carrying surface.

2. A platform as claimed in Claim 1, which is provided with two tanks spaced from one another along said axis.

3. A platform as claimed in Claim 1 or Claim 2, which is provided with two tilt sensors, each capable of emitting a signal when the tilt of the load-carrying surface from the horizontal about a given axis falls outside a predetermined range, the axes associated with the two sensors not being parallel to one another, two ballast tanks spaced from the centre of gravity of the vessel not being co-linear, and two adjusting means each capable of adjusting the amount of ballast in one of the ballast tanks.

4. A platform as claimed in Claim 3, in which there are two pairs of ballast tanks, one pair being spaced from one another along one of the two axes and the other pair spaced from one another along the other axis.

5. A platform as claimed in Claim 3 or 4, in which the two axes are perpendicular to one another.

6. A platform as claimed in Claim 5, in which the two axes lie along the longitudinal mid-line of the vessel and perpendicular thereto.

7. A platform as claimed in any of the preceding claims which is iprovided with means for varying its draught.

8. A platform as claimed in Claim 7, which is provided with a draught sensor capable of emitting a signal when the draught of the vessel falls outside a predetermined range.

9. A platform as claimed in Claim 7 or 8, in which the means for varying its draught comprises a draught-control ballast tank separate from the aforementioned ballast tank(s) and provided with adjusting means capable of adjusting the amount of ballast therein.

10. A platform as claimed in any of the preceding claims, in which the or each ballast tank is provided with a sea-cock through which water can enter the ballast tank when the sea-cock is opened and an air-valve through which compressed air can be blown into the tank.

11. A platform as claimed in any of the preceding claims, in which the or each tilt and draught sensor is connected to a control circuit capable of automatically adjusting the amount of ballast in the appropriate tank(s) on receipt of a signal from the sensor.

12. A platform as claimed in Claim 11, in which the or each control circuit incorporates a delay mechanism such that the control circuit will not begin to adjust the amount of ballast in the appropriate tank(s) until the sensor has emitted a continuous signal for a predetermined period of time.

13. A platform as claimed in Claim 11 or 12, in which the or each control circuit is provided with a delay mechanism such that the control circuit will continue to adjust the amount of ballast in the appropriate tanks for a predetermined period after the signal from its sensor ceases.

14. A platform as claimed in any of the preceding claims and provided with a loading ramp along which, when it is in an operative position, a said at least one vehicle can be driven onto the load-carrying surface.

15. A platform as claimed in any of the preceding claims, in which the loadcarrying surface has fixed thereon guide means capable of engaging the wheels of a said at least one vehicle.

16. A platform as claimed in any of the preceding claims, which is provided with

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. sides of the platform 40 may be berthed auxiliary boats 48, which may be used for police launches, customs boats, crew transport boats for carrying dockers to and from ships, cargo surveyors' boats or boats for other purposes. A port control building 49 is located centrally on the platform 40 and includes accommodation for ship crews and/or dock workers. On the building 49 are mounted a radar array 50 and a short wave radio-telephone mast 51 which are connected to a control room within the building, from which movements of all vessels and shore vehicles within the port and its environs can be controlled. Adjacent the main platform 40 there may be berthed a further platform of the invention for the maintenance of all vehicles, platforms and boats used in the operation of the port terminal. Such a platform may include, for example, at one end a garage for the maintenance of the motor vehicles and at the other end a dry dock and/or lifting platform for use in underwater work on the platforms or boats. WHAT WE CLAIM IS:-

1. A load-carrying platform comprising a buoyant vessel having a substantially horizontal load-carrying surface for supporting at least one vehicle having a load-carrying surface at a predetermined height above said load-carrying surface of said vessel, at least one ballast tank spaced from the centre of gravity of the vessel, a tilt sensor for emitting a signal when the tilt of the loadcarrying surface from the horizontal about a given axis falls outside a predetermined range, and adjusting means for adjusting the amount of ballast in the ballast tank, wherein there is provided adjacent one side of the vessel a substantially horizontal landing platform at a predetermined height above the vessel load-carrying surface corresponding to said predetermined height of the vehicle load carrying surface.

a propulsion-module-receiving recess within which a propulsion module can dock.

17. A platform as claimed in any one of the preceding claims, which has a flexible bulwark on the edge of the landing platform adjacent the said side of the vessel, the flexible bulwark having an upper surface which slopes downwardly toward the landing platform.

18. A load-carrying platform as claimed in Claim 1 and substantially as herein described, with reference to and as illustrated in Figures 4 to 6 of the accompanying drawings.

19. A method of loading a vessel with cargo, the method comprising: bringing a load-carrying Iplatform as claimed in Claim 1 adjacent the vessel to be loaded, said load-carrying platform having therein adjacent the landing platform thereof at least one said vehicle with a load-carrying surface at a predetermined height above the load-carrying surface of said load-carrying platform, said vehicle being loaded with cargo; and transferring the cargo from the vehicle across the landing platform to the vessel whilst adjusting the quantity of ballast in the ballast tank(s) of the load-carrying platform so as to maintain the tilt of the loadcarrying surface about the given axis within the predetermined range.

20. A method of unloading cargo from a vessel, the method comprising: transferring cargo from the vessel onto an adjacent load-carrying platform as claimed in Claim 1 whilst adjusting the quantity of ballast in the ballast tank(s) of the platform so as to maintain the tilt of the load-carrying surface about the given axis within the predetermined range, said load-carrying platform having thereon adjacent the landing platform thereof at least one said vehicle with a load-carrying surface at a predetermined height above the load-carrying platform said cargo being transferred onto the vehicle load-carrying surface via said landing platform; and removing the load-carrying platform from adjacent the vessel.

21. A method as claimed in Claim 19 or Claim 20, in which the vehicle is an articulated lorry trailer adapted to be moved by a tractor unit.

22. A method as claimed in any one of Claims 19 to 21, in which the landing platform is provided with at least one loadcarrying transporter for transferring cargo between the load-carrying surface of said at least one vehicle and the landing platform.

23. A method as claimed in Claim 22 in which a gap between the landing platform and the load-carrying surface of said at least one vehicle is covered by a cover plate so that the load-carrying transporter can run directly from the landing platform on to the load-carrying surface of the vehicle.

24. A method of loading a vessel as claimed in Claim 19 and substantially as herein described with particular reference to Figures 4 to 6, or Figures 4 to 7 of the accompanying drawings.

25. A method of unloading a vehicle as claimed in Claim 20 and substantially as herein described with particular reference to Figures 4 to 6, or Figures 4 to 7 of the accompanying drawings.