The present invention relates to a linkspan, otherwise known in the art as adjustable ship to shore boarding ramp, which provide vehicular or personnel access to a ship or vessel from a port quay side . In particular it relates to large scale linkspan arrangements for providing vehicular access to and from roll-on/roll-off (RORO) ships .

Linkspans , or adj ustable ship to shore boarding ramps, are used to connect and provide a flat access to and from ^" a ship and port quay . Such linkspans comprise part of the port facility and are mounted on the quay . They can be contrasted with, and are distinct with ship mounted ramps which may also be used with such linkspans . A particular problem which linkspans address is to accommodate the changing height of the ship access relative to the quay due to changes in sea level due to tides for example, as well for different ships .

In their simplest form linkspans comprise a deck element with one end resting and supported on the quay, and the other end resting and supported upon the ship (or ship ramp) . As the tide rises and falls , and/or to accommodate different ship configurations , the linkspan pivots about the quay and ship ends and adopts differing angles maintaining access and a connection with the ship .

Various simple gangway arrangements for providing pedestrian access to and from a quay and ship (or between ships ) are descried for example in US 4133067 , GB 1525501 and US 4403362. These arrangements all comprise simple lightweight gangway type arrangements subject to relatively light loading in which the load traversing the gangway is relatively small and so does not overly affect the structure .

Such gangway and simple linkspan arrangements are not however generally suitable for large loads , are cumbersome to position, and are not generally suitable for RORO

operations .

In more sophisticated conventional arrangements , suitable for RORO operations , a tower or pylon incorporating lifting gear supports the seaward/ship end of the linkspan deck allowing it to be raised and lowered in response to the sea level and/or for different ships . The support towers are generally located in the water adj acent to the quay to support the linkspan deck over the sea, and so are susceptible to sea loading and corrosion as well as possible collision damage . With the towers and lifting machinery located away from the shore, access for maintenance is also difficult . In addition if the lifting gear fails the linkspan, and any loads on it, will fall and drop downwards into the water . An example of such an arrangement is described in GB 1442983 which includes a tower mounted in the water containing lifting cables to suspend the linkspan .

In a yet further alternative linkspan arrangement a seaward end of the linkspan may incorporate a float or tank whose buoyancy supports the seaward end of the linkspan and any loads travelling over it . The float, and so end of the linkspan, rises and falls in response to the tide and sea level, whilst the height of the seaward end of the linkspan above the float/sea level may be adjusted by adjusting the buoyancy of the float and/or via other ramps from the linkspan or ship . In a further variation a separate floating pontoon may be provided adj acent the quay with a link bridge between and resting on the quay and pontoon . Ramps from the pontoon or from the ship to the pontoon provide the final connection to and from the vessel . Examples of such pontoon arrangements are described for example in EP 0245227 and GB 1499741. Such floats and flotation chambers of any pontoons require regular inspection and maintenance with the floats and chambers being susceptible to corrosion form the sea water and also wave and/or collision damage . In addition various stability problems arise from such floating

arrangements both generally and when loads traverse across the linkspan .

It is therefore desirable to provide an improved linkspan which addresses the above described problems and/or which offers improvements generally .

According to the present invention there is provided a linkspan as described in the accompanying claims .

In an embodiment of the invention there is provided a linkspan for connecting and providing access to and from a quay to a ship . The linkspan comprises a linkspan deck proj ecting from the quay and having a distal end, a pivot assembly pivotally mounting the linkspan deck from the quay, an actuator arrangement for raising and lowering the distal end of the linkspan, and a counterweight counterbalancing and supporting the linkspan deck proj ecting from the quay about the pivot . Such an arrangement provides a cantilevered linkspan supported from the quay and shore by the counterweight which address a number of the above described problems with conventional arrangements . In particular since none of the linkspan is located in the sea, the linkspan is less susceptible to corrosion, is not subj ect to wave loading and is easier to inspect .

Preferably the linkspan deck proj ects from one side of the pivot assembly and the counterweight is disposed on an opposite side of the pivot . The counterweight preferably normally biases and pivots the linkspan deck and the distal end of the linkspan deck towards a raised position . The actuator arrangement operates in use against the counterweight . Furthermore the actuator arrangement is preferably disposed on the opposite side of pivot to the distal end of the linkspan with the actuator

arrangement is adapted to push distal end downwards against the counterbalancing load of the counterweight .

This ensures that the linkspan advantageously fails safe towards a raised position and out of the sea . The counterweight may preferably entirely counterbalance and support all of the weight of the linkspan proj ecting from the quay and in use loads . Alternatively the counterweight counterbalances and supports only a proportion of the weight of the linkspan proj ecting from the quay and in use loads .

The counterweight may be mounted above a plane of the linkspan deck .

The pivot assembly is preferably slidably mountable to the quay . Dampers may also be provided to dampen sliding movement of the pivot assembly .

The present invention will now be described by way of example only with reference to the following figures in which : Figure 1 is a schematic illustration of a linkspan in accordance with an embodiment of the invention connecting and providing vehicular access to a ship from a port quay;

Figure 2 is a more detailed side view of the linkspan shown in figure 1 ; Figure 3 is a plan view of the linkspan shown in figure 2.

Referring to figure 1 , a linkspan 10 provides a flat roadway for vehicles 1 to drive over the linkspan 10 onto a ship 8 moored in the dock 3 allowing roll-on/roll-off (RORO) operation . The linkspan 10 in accordance with an embodiment of the present invention is mounted on a dock quay 4 and proj ects from the quay 4 over the sea 2 towards a ship 6 moored in the dock 3 with the distal end of the linkspan 10 disposed adj acent the ship access (not shown) . As will be

explained further below, the linkspan 10 is pivotally mounted on the quay 4 such that the height of a distal , seaward/ship, end 25 of the linkspan 10 above the quay 4 and level of the sea 2 can be adjusted and aligned with the ship access to accommodate differing heights of ship access and changes in sea level . A small ship ramp 8 , or transition ramp mounted on the distal end of the linkspan 10 , may bridge the small final gap between the distal end 25 of the linkspan 10 and ship 6. The linkspan 10, without the ship 6, is shown in more detail in figures 2 and 3. The linkspan 10 comprises a pivotally mounted cantilevered arrangement with the proj ecting linkspan portion and distal seaward/ship end 25 of the linkspan 10 supported by a counterweight 16 located at a quay 4 ( shore) end of the linkspan 10 rather than being supported by floats or lifting machinery as is conventional . Specifically the portion of the linkspan 10 proj ecting from the quay 4 , and seaward distal end 25 of the linkspan 10 is cantilevered about the pivotal mounting of the link span 10 to the quay 4. Accordingly with none of the linkspan in the sea it is less susceptible to corrosion, is not subj ect to sea and wave loading, and can more easily be inspected and maintained . In addition there is no need to anchor any guide posts or other assembled below the sea and into the seabed . The linkspan 10 comprises a structural frame 14 pivotally mounted to the quay 4 about a laterally extending pivot axis A by a pair of laterally spaced pivot assemblies 18 such that the linkspan 10 can pivot about the laterally extending pivot axis A as shown by arrow X in figure 2. The pivot assemblies 18 comprise pivot shafts mounted in corresponding pivot bearing housings . A flat planar .linkspan deck 12 is mounted upon the frame 14 proj ecting from the quay 4 on one side of the pivot assemblies 18 and pivots about axis A with the frame 14. The linkspan deck 12 in use defines the roadway for vehicles 1 to drive over the

linkspan 10. A planar flat transition flap or ramp 28 with one end resting or mounted upon the shore end of the linkspan deck 12 bridges the gap between the pivoting linkspan deck 12 and quay surface 30 , continuing the linkspan deck roadway, and allowing vehicles 1 to drive from the quay 4 onto the linkspan deck 12.

The counterweight 16 is mounted on the frame 14 on the opposite side of the pivot assemblies 18 to, in use, counterbalance the weight of the linkspan 10 and linkspan deck 12 proj ecting from the quay 4 on the other side of the pivot assemblies 18. The counterweight 16 is preferably significantly oversized, including a significant safety factor, to counterbalance and support both the weight of the linkspan 10 and linkspan deck 12 proj ecting from the quay 4 and in use loads ( for example vehicle weight of traffic over the linkspan 10 and loads from ship ramps 8 etc . ) applied to the proj ecting linkspan 10. As a result the distal seaward end 25 of the linkspan 10 is normally biassed and pivoted upwards towards a raised position . The oversizing, and relative massive size of the counterweight 16 also reduces movement of the linkspan 10 in use as the vehicles 1 and loads (both static and dynamic loads generated) cross and travel along the length of the linkspan 10.

An actuating arrangement comprising a pair of hydraulic extending rams 24 are connected to the structural frame 14 and are arranged to in use act against the weight of the counterweight 16 to raise and lift the counterweight 16 against gravity (as shown by arrow B) , pivoting the linkspan 10 about the pivot axis A and allowing the distal seaward end 25 of the linkspan 10 to be lowered (as shown by arrow X) as required to align with the ship access . As shown in this embodiment the hydraulic rams 24 are arranged vertically directly below the counterweight 16 and are connected to a distal shore end 23 of the frame 14. It will be appreciated however that other hydraulic ram arrangements

could be used . For example the hydraulic rams could be provided on the other side of the pivot assemblies 18 , and operate in the opposite sense/direction . This is however less preferable since access to the rams 24 is less easy. Other actuating arrangements could also be used . For example suitably configured winch arrangements connected to ^' the frame 14 could be used . Such winch arrangements if acting on the seaward side of the pivots 18 would pull the seaward side and distal seaward end 25 of the linkspan 10 downward . Alternatively the winch arrangements could be connected to a support tower to lift the counterweight 16 if acting on the shore side of the linkspan 10. In a yet further variation the actuating arrangement could comprise rotary motors driving rotary movement of the pivots 18 and linkspan 10.

The actuating arrangement acts against the counterweight and in effect ' pushes ' the distal seaward end 25 of the linkspan 10 down to the required height and angle . This can be contrasted with conventional linkspan arrangements in which lifting gear raises and directly supports the seaward end of the linkspan such that if the lifting machinery fails the seaward end of such a conventional linkspan will drop and fall towards the sea . In contrast with the linkspan of this embodiment of the invention if the actuating arrangement fails then the seaward distal end 25 of the linkspan is raised and lifts upwards towards a safe position out of the water 2. Furthermore the linkspan 10 can be ' parked ' in a suitable position and with the distal seaward end 25 of the linkspan at a desired height by simply chocking the shore end and counterweight of the linkspan 10.

The structural frame 14 may be of any suitable configuration to support the linkspan deck 12 , counterweight 16 and pivots 18 , and resist the forces applied to the linkspan 10 in use . In the embodiment shown the structural

frame 14 comprises a pair of deck support arms 11 rigidly connected at their ends and at an angle to a pair of counterweight support arms 15 , and a pair of support stay arms 13 rigidly connected at their ends and at an angle to the deck support arms 11 and counterweight support arms 15. The deck support arms 11 proj ect and extend from the pivots 18 and quay 4 towards the ship 6 along either lateral side of and supporting the linkspan deck 12. The pair of counterweight support arms 15 proj ect from the deck support arms 11 and at a vertical angle to the deck support arms on other side of the pivots 18 and support the counterweight 16 in a vertically elevated position . The counterweight 16 is mounted upon a distal shore end of the counterweight support arms 15 extending between an interconnecting the support arms 15. Of course in other embodiments the counterweight 16 may comprise two separate counterweight elements each attached to a respective support arm 15. In alternative embodiments however the counterweight support arms may simply continue the deck support arms 11 , or be angled vertically below the deck support arms 11 such that the counterweight 16 is not elevated or is below the deck support arms 11. In such an arrangement suitable pits may be provided in the quay 4 to receive the distal shore ends 23 of the counterweight arms and the counterweights 16. The pair of support stay arms 13 proj ect vertically from the deck support arms 11 generally above the pivots 18 and pivot axis A . The distal ends of the support stay arms 13 are interconnected by a end frame beam 17. Cable stays 24 , 26 are attached between the distal ends of the support stay arms 13 and deck support arms 11 and counterweight support arms 15 respectively . The support stay arms 13 and cable stays 24 , 26 stabilises and strengthen the frame 14 and linkspan 10, and supports the distal end of the deck support arm 11.

To accommodate ship impact with the linkspan 10 the pivot assemblies 18 are preferably slidingly mounted to the

quay 4 on sliders 22. This allows the pivot assemblies 18 , and so linkspan 10 to slide to some degree longitudinally (as indicated by arrow Y) on its foundations as well as allowing a limited degree of slewing of the linkspan 10 (as indicated by arrow Z ) in a generally horizontal plane and about a vertical axis orthogonal to the pivot axis A. Energy absorbing devices 18 , such as rubber fenders , are disposed between the pivots 18 and sliders 22 to resist damp and absorb such sliding movement of the pivot assemblies 18 on the sliders 22 and so of the linkspan 10.

Whilst as described above the counterweight 16 is sized and arranged to support and counterbalance both the weight of the linkspan 10 and linkspan deck 12 proj ecting from the quay 4 and in use loads applied, in alternative embodiments the counterweight 16 may be much lighter and arranged to only substantially counterbalance the weight of the linkspan 10 and linkspan deck 12 projecting from the quay 4. In such cases when the linkspan is in use the distal seaward end 25 of the linkspan either rests on the ship 6, or is otherwise supported to a limited degree from the ship 6 in order to take the in use loads of the vehicles 1 passing over the linkspan 10. Alternatively such loads may be resisted and supported by the actuating arrangement holding the linkspan 10 in the required position . It should be noted however that even in such arrangements the linkspan 10 and distal seaward end 25 of the linkspan 10 are still principally supported by the counterweight 16 with the maj ority of the loads being off set by the counterweight 16. Whilst less preferred, an advantage of such arrangements is that the counterweight 16 does not need to be so heavy so reducing costs and the strength and size of the structural frame 14 to support the counterweight 16. Also smaller actuating arrangements can be used to operate the linkspan 10.

In a yet further variation the counterweight 16 can have a variable weight ( for example comprising a tank that

is filled or emptied of water) , and/or comprise moveably mounted weights , to alter the counteracting moment provided by the counterweight 16 on the linkspan 10. In such arrangements the counterweight could be adjusted for the particular in use loads and/or to move and pivot the linkspan to the required position either replacing, or reducing the loads on the actuating arrangement .

Other further modifications , variations and alternate embodiments of the cantilevered linkspan arrangement described above and shown in the accompanying figures will be apparent to those skilled in the art .