System For Mooring Ships To Structures

Abstract

This invention concerns a system for mooring ships to structures consisting of two rigid arms ( 3 and 4 ), jointed at one end to two diametrically opposite points ( 7 and 8 ) on a crown-wheel, which can revolve on the mooring structure ( 2 ), and at the other end, by means of universal joints ( 31 and 32 ), to two floating caissons ( 5 and 6 ); these are connected by flexible couplings ( 51, 52 and 53 ), and the stem-post of the ship ( 1 ) passes between them. The invention concerns the mooring of oil-tankers or other vessels, floating appliances, etc.

Description

This invention concerns devices for mooring ships, particularly oil-tankers, or floating appliances, to structures which are also floating or consist of fixed columns.

The purpose of these devices is to keep a ship moored in position in such a way that it lies constantly in the direction of the resultant of wind and current forces. They allow ships to be loaded, particularly oil-tankers, equipment to be transferred from appliances, and assistance to be given during special operations to prospect for or work mineral, biological or other resources. They also have to take account of the fact that loaded ships lie lower in the water than one that has been unloaded.

The invention more specifically concerns devices of this type containing two rigid arms, one end of which is attached to the mooring structure and the other to floating ship-berthing units.

In existing systems, the ship is steered against the floating arms and attached to them by mooring lines. There are difficulties, however, since long lines are required and the ends of them are often hard to recover. Such systems also lack precision, especially when the sea is rough or there is wind or current; furthermore, they may endanger installations, since the mooring structure can be subjected to considerable strain.

The present invention aims at providing a mooring system which avoids these drawbacks.

According to this invention, the connection between the two arms and the supporting structure consists of two jointed couplings located at two diametrically opposite points on a horizontal crown-wheel which fits loosely on to the structure and can revolve on it, the floating ship-berthing units consist of two elongated caissons, connected to the two arms by two joints, and a flexible coupling is provided between the two arms or floating units.

In one embodiment of the invention, the floating caissons are connected by slack, flexible couplings, against which the stem-post of the ship pushes as it moves forward between the arms, causing the caissons to pivot on the joints connecting them to the arms and bringing them against the sides of the ship's bows.

This special structure makes berthing operations very simple : the stem-post of the ship is first guided in between the two caissons (which is easy because the caissons can move freely, pivoting on the arms, which themselves pivot on the mooring structure); as the ship moves forward, the stem-post pushes against the flexible couplings between the caissons, causing them to move automatically towards the sides of the ship's bows. The ship is thus properly berthed against the floating caissons, in a very adaptable operation, merely being brought close to the caissons, which then automatically and flexibly press against the sides of the ship's bows. It can then be moored to the caissons by means of easily handled short lines.

In one embodiment of the invention, the articulations providing a link between the arms and supporting structure are all single or double articulations, such as single or double cardan joints, or a universal joint.

The joints between the caissons and arms and between the arms and mooring structure provide a connection between ship and mooring structure that has almost no play in it, and yet which allows all the relative movements required by wind, currents, waves or differences in the depth at which the ship lies in the water, depending on whether it is being loaded or unloaded.

In one recommended embodiment, the flexible couplings between the two caissons are of different lengths and/or attached to the caissons at different points, so that they are stretched in turn by the stem-post of the ship, absorbing its force as it moves between the caissons. This makes the installation extremely adaptable, and ensures much safer, faster and easier berthing. Excess energy is absorbed by the successive couplings as they stretch, and possibly break, offering effective protection against damage to the mooring structure or ship. Any broken couplings can easily be replaced for the next mooring operation.

In another embodiment of the invention, and to make the installation even safer, the universal joint situated at one end at least of the arms has some elasticity, compression-wise at any rate.

Other features and advantages of the invention will appear from the following detailed description of one embodiment of a ship-mooring system, and the accompanying figures, which illustrate the present invention without its being in any way confined to this particular version.

In the drawings :

FIG. 1 is an elevation of the whole device;

FIG. 2 is the corresponding plan-view;

FIG. 3 is a view in perspective of one of the arms and the joint between it and the mooring structure, on a larger scale;

FIG. 4 shows an elevation, also on a larger scale, of one embodiment of the joint between a caisson and the end of the corresponding arm;

FIG. 5 is a detailed cross-sectional view along the line V -- V in FIG. 3;

FIG. 6 is a cross-sectional view along the line VI -- VI in FIG. 5.

The system shown in FIGS. 1 and 2 is designed to allow a ship 1, such as an oil-tanker, to be moored to a fixed structure 2. In this particular example, the fixed structure consists of a column, but the system could equally well be used for mooring ships to a floating structure.

The mooring system consists basically of two rigid arms 3 and 4, one end of which is connected to the mooring structure 2 and the other to floating ship-berthing units 5 and 6. In this example, the two arms each consist of a lattice girder (see also FIG. 3), and the floating berthing units of an elongated watertight caisson.

The connection between the two arms 3 and 4 and the mooring structure 2 is provided by two universal joints 7 and 8, located at two diametrically opposite points on a horizontal crown-wheel 11, which fits loosely on the structure and can revolve on it (see also FIG. 3).

These two universal joints between the two arms and the mooring structure may be replaced by any kind of single or double jointed coupling, such as a single or double Cardan joint.

FIGS. 3, 5 and 6 show one of these two universal joints 7 consisting basically of a casing 13, which can pivot on a vertical axle-pin 14. In this example, the axle is fixed to the upper surface of the rotating crown wheel 11. To prevent the casing from coming off the axle, there is a suitable standard clamping system, shown diagrammatically here in the form of a pin 15, which fits into a slot 16 at the top of the axle.

The near end of the arm 3 has a ball-joint 21, in contact with a suitable synthetic material covering the sides of a spherical socket 23 in the casing 13. The assembly is held in place by a cover 25 attached to the casing by means of screws 26.

The other ends of the arms 3 and 4 are attached to the two caissons 5 and 6, also by means of universal joints 31.

In the particular embodiment shown in FIGS. 3 and 4, this joint 31 consists of a chain 32 formed from several metal links imbedded in a block of elastomer 33, and covered with a sheath 34. The two end links 36 and 37 are specially shaped to allow them to pivot on two axle-pins 38 and 39 in two jaws 41 and 42. One of these jaws 41 forms part of the corresponding end of the arm 3, and the other 42 is at the end of a cavity 45 in the caisson 5.

This means that each arm can pivot to a limited extent on the mooring structure 2 and on the caisson to which it is connected. This pivoting movement can be in any direction, in other words not just on the horizontal and vertical planes, but also on any oblique plane. In addition, the special design of the universal joints described here ensures a certain amount of flexibility in the connections, compression-wise at least.

The two floating caissons 5 and 6 are linked together by flexible, loose couplings 51, 52 and 53 in FIG. 2, preferably buoyant. Only three such couplings are shown here, but there could in practice be far more of them. They preferably consist of nets, made of a suitable synthetic material, for instance, which will stretch fairly considerably before breaking.

The ends of these couplings are preferably connected to the floating caissons by means of energy-absorbing jacks of some suitable standard type (not shown here).

The system operates as follows.

To moor the ship 1 to the structure 2, the stem-post is guided between the floating caissons 5 and 6, which have previously been separated as widely as possible to facilitate the operation. As soon as the stem-post reaches the first flexible coupling 51, it stretches it, causing the two caissons to move towards one another and thus against the sides of the ship's bows. As soon as they touch the ship's sides, the caissons set up considerable resistance to the flexible couplings, the elongation of which absorbs part of the ship's driving force. The couplings are preferably of different lengths and/or attached to different points on the two caissons. This means that they come in action one after another, providing increasing resistance to the forward movement of the ship towards the mooring structure. Some of these couplings may snap under the strain of the remaining kinetic energy of the ship, but they can easily be replaced with new ones for the next mooring operation.

The ship can be attached firmly to the caissons by convenient short mooring lines 55.

The whole unit formed by the mooring system and the ship can pivot around the vertical axis of the rotating crown-wheel 11, so that it is always facing the resultant of winds and currents. In addition, the flexible universal joints provide a firm connection between the ship and mooring structure, without hindering any of the movements that may be needed to adapt to outside agents, or to the variation in the depth at which the ship lies in the water, depending on the weight of its cargo.

Naturally, the invention is in no way confined to the embodiment described here and illustrated in the figures : many other variant forms are possible, for a person skilled in the art, and depending on the applications involved, without any departure from the spirit of the invention.

For instance :

The ball-and-socket joints connecting the arms with the revolving crown-wheel may be replaced by a horizontal pivotal axle-pin which would combine with the existing vertical pivotal axle-pin to provide the necessary universal joint;

The joints which in the description consist of some links imbedded in elastomer could be replaced by a ball-and-socket joint;

In general, the universal joints can consist of any other suitable type of joint which allows the components linked by it to move in relation to one another, in all directions and to the extent required.

The floating caissons can naturally consist of compartments which can be flooded, and the two arms and caissons can be lowered or raised, as required. When no ship is moored, they can be raised by some suitable device such as a winch. The caissons can be flooded and the system attached to the structure to form a rigid unit.

In this way the arms and caissons are protected from the effects of rough seas, which are felt mainly at the surface.

Claims

What is claimed is:

1. Apparatus for mooring floating objects to a mooring structure, said apparatus comprising:

two elongated floating caissons,

a horizontal ring rotatably mounted on said mooring structure,

two rigid arms, each having one end pivotally connected to said horizontal ring and the other end pivotally connected to one of said caissons, the pivotal connections to said ring being located diametrically opposite each other, and

elongated flexible means connecting the ends of the caisson attached to said rigid arms, so that an object moving between said caissons toward said mooring structure will strike said flexible means and thereby draw said caissons toward each other.

2. Apparatus as claimed in claim 1 in which said elongated flexible means comprises at least one net.

3. Apparatus as claimed in claim 1 in which the pivotal connection at at least one end of each arm has some elasticity.

4. Apparatus as claimed in claim 1 in which the pivotal connection at at least one end of each arm is a ball and socket joint in which the socket is lined with an elastomer.

5. Apparatus as claimed in claim 1 in which the pivotal connection between each arm and the corresponding caisson consists of a chain comprising a plurality of connected metal links embedded in a block of elastomer and covered with a protective sheath.

6. Apparatus as claimed in claim 1 in which said elongated flexible means are connected to the caissons by energy-absoring means

7. Apparatus as claimed in claim 1 in which said elongated flexible means comprises a line connected to said caissons between the pivotal connections of said caissons to said rigid arms, so that pressure against said line toward said mooring structure causes said caissons to swing toward each other about their pivotal connections to said rigid arms.

8. Apparatus as claimed in claim 7 comprising a plurality of lines attached to said caisson at different points.

9. Apparatus as claimed in claim 7 comprising a plurality of lines connecting said caissons, said lines being of different lengths.

10. Apparatus as claimed in claim 9 in which said lines are buoyant.