EP0245227A2

EP0245227A2 - Device for a port ramp having a pontoon float

Info

Publication number: EP0245227A2
Application number: EP87850148A
Authority: EP
Inventors: Said Oleborg; Göran Johansson
Original assignee: MacGregor Navire International AB
Current assignee: MacGregor International AB
Priority date: 1986-05-05
Filing date: 1987-04-30
Publication date: 1987-11-11
Also published as: SE8602054D0; EP0245227A3; SE456338B; SE8602054L

Abstract

A port ramp (11) having a pontoon float (15), and forming a connecting path between a roll-on/roll-off ship (18) and a harbour installation (10) being subjected to variations in water level. A ramp bridge (11a) is vertically pivotably connected to the edge of the quay and to the pontoon float (15) respectively. Damping means (19) are mounted between the ramp bridge and the pontoon float, in order to slow down the speed of pivot angle variations between both said units, so that these together form an interconnected, rigid unit in relation to the load produced by vehicles intermittently moving over the pontoon float, as well as independently pivotable units in relation to the action of variations in water level, e.g. caused by the tides.

Description

The present invention relates to a port ramp having a pontoon float, and forming a connecting path between a roll-on/roll-off ship and a quay in a harbour installation being subjected to variations in water level, and wherein a ramp bridge is vertically pivotably connected to the edge of the quay and to the pontoon respectively.
Port ramps having a pontoon float are normally used as a connecting path between ship and quay when loading and unloading roll-on/roll-off ships in harbours being subjected to variations in water level, e.g. caused by the tides. A port ramp of this kind is known, e.g. from SE-A 415.583. This prior construction comprises a comparatively large pontoon float. The reason for this large float is primaly to minimize the trim movements occuring when a heavy vehicle is moving over the pontoon float. Modern handling of goods into and from a roll-on/roll-off ship implies horizontal transfer of heavy goods units, resulting in assymmetrical loading of the pontoon float, in relation to its centre of floatation. From this follows trimming which must be minimized in order to reduce the stresses on the ramp and enable vehicle movement. The large pontoon floats necessary for this effect is, however, expensive to build and is space consuming in a harbour installtion. SE-A 419.741 discloses a device for reduction of heeling forces on a pontoon float, who are caused by a load passing over it. This device uses a system with chains, counterweights and a balance mass to balance the heeling moment caused by a load moving over the pontoon float. The benefits of this device, i.e. the possibility to reduce the size of the pontoon float, is limited by that the weight of the balance mass and the chains have to be carried by the pontoon float. Further, this arrangement is expensive and rises the cost of maintenance.
The object of the present invention is to provide a device making it possible to reduce both size and cost of a pontoon float affording a vehicular track for handling of roll-on/roll-off cargo, and with excellent trim characteristics.
According to the invention the port ramp is characterized in that at least one hydraulic cylinder s pivotably mounted between the ramp bridge and the pontoon float, that both hydraulic cylinder fluid chambers are interconnected via at least one check valve and connected to a fluid reservoir, in order to slow down the speed of pivot angle variations between the ramp bridge and the pontoon float, so that these together form an interconnected, rigid unit in relation to the load produced by vehicles intermittently moving over the pontoon float, as well as independently pivotable units in relation to the action of variations in water level, e.g. caused by the tides.
Preferably, the damping means comprize at least one hydraulic cylinder, which is pivotably mounted between the ramp bridge and the pontoon float.
According to another preferable embodiment of the invention, the hydraulic cylinder fluid chambers are interconnected via at least one check valve and connected to a fluid reservoir.
One embodiment of the invention will now be described with reference to the accompanying drawings, wherein:

Fig. 1 is a side view of a port ramp according to the invention,
Fig. 2 diagrammatically illustrates a hydraulic circuit belonging to the invention, and
Figs. 3 and 4 show the ramp in reduced scale and at two different water levels.

In the figures, 10 refers to a quay and 11 in its entirety to a loading and off-loading ramp for vehicular goods and which is anchored to the quay and has a pontoon float. The ramp 11 is connected to the quay edge via a horizontal pivot 12, which is elastically mounted in the quay structure via fender means 13. The pivot 12 and fender 13 are bridged by a flap 14. The port ramp 11 comprises a pontoon float 15 and a vertically pivotably mounted ramp bridge 11a, which is principally equally supported by the quay and the pontoon float 15, and bridges the distance between these. This distance which is equal to the length of the ramp bridge 11a, is so chosen that the gradient of the ramp bridge is not too steep, even during extreme tidal conditions.
The quay 10 preferably forms, which is not shown in the figures, a L-shaped angle and is equipped with mooring means for the pontoon float 15.
At a conventional port ramp of this kind the pontoon float 15 tend to trim (pivot about its centre of floatation) when a terminal truck 17 moves onto it from a ship 18. This trimming moment complicates the transfer of cargo into or from the ship 18.
In order to avoid this trimming, the port ramp 11 according to the invention is equipped with damping means in the form of hydraulic piston cylinders 19 who are pivotably mounted with one end in the ramp bridge 11a and the other in the pontoon float 15, respectively. The piston cylinders 19 are connected to a hydraulic system shown in fig. 2, which is so arranged that it facilitates a certain bleed of hydraulic fluid between both fluid chambers 19a, 19b of each piston cylinder, i.e. from one side of the piston 19c to the other side. This bleed of fluid is so adjusted that the port ramp 11 can adapt its float level to the normal variations in water level, e.g. caused by the tides. However, during the much more rapid development occuring when a terminal truck 17 passes over the pontoon float 15, only a small amount of hydraulic fluid will have time to pass from one fluid chamber to the other, so that the bridge ramp 11a and the pontoon float 15 will cooperate as a rigid unit having its pivoting axis in the pivot 12 at the quay edge. This means that the total waterline area of the pontoon float will be influenced under load and therefore utilized, resulting in that the pontoon float 15 may be constructed smaller and less costly than in prior art constructions of this kind.
The hydraulic system shown in fig. 2 comprises check valves 20. Further, there are cut-off valves 21 allowing locking or insulation of some part of the system, i.e. for exchange of some component. Connection pieces 22 are mounted in the system allowing connection, e.g. of a hand pump into any part of the system. Nonreturn valves 23 are mounted in parallel with the check valves 20 to avoid resistance on the suction side of the piston 19c. Both piston cylinders 19 are connected to a mutual reservoir 24 containing hydraulic fluid and a rubber bladder 25 which communicates with the external atmosphere. The complete hydraulic system is normally pressure free and thus only acts to dampen the movements of the hydraulic pistons.
Figs. 3 and 4 show the port ramp 11 in two different extreme water level conditions wherein the pontoon float 15 maintains its parallel trim in relation to the water surface. Since the drive surface of the pontoon float 15 thus in unloaded condition always is parallel to the water surface, the transit of a terminal truck between the ship and the pontoon float is facilitated regardless of the float level of the ship in relation to the pontoon float.
The above described and disclosed embodiment is only one example of the invention and the details of it may be altered in several ways within the scope of the appendant claims. For example, the damping means 19 may be differently designed and in different ways connected to the ramp bridge and the pontoon float. The check valves 20 may be adjustable for different load conditions.

Claims

A port ramp having a pontoon float, and forming a connecting path between a roll-on/roll-off ship and a quay (10) in a harbour installation being subjected to variations in water level, and wherein a ramp bridge (11a) is vertically pivotably connected to the edge of the quay and to the pontoon (15) respectively, characterized in, that at least one hydraulic cylinder (19) is pivotably mounted between the ramp bridge (11a) and the pontoon float (15), that both hydraulic cylinder (19) fluid chambers (19a, 19b) are interconnected via at least one check valve (20) and connected to a fluid reservoir (24), in order to slow down the speed of pivot angle variations between the ramp bridge (11a) and the pontoon float (15), so that those together form an interconnected, rigid unit in relation to the load produced by vehicles intermittently moving over the pontoon float (15), as well as independently pivotable units in relation to the action of variations in water level, e.g. caused by the tides.