GB1559326A

GB1559326A - Fenders

Info

Publication number: GB1559326A
Application number: GB15863/76A
Authority: GB
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1976-04-20
Filing date: 1976-04-20
Publication date: 1980-01-16
Also published as: AU2409877A

Description

(54) FENDERS (71) We, DUNLOP LIMITED, a British Company of Dunlop House, Ryder Street, St.

James's, London S.W.1, 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 fender.

The purpose of a fender is to control the final deceleration of an object to be fendered (e.g.

a berthing ship) by limiting both the force applied by the object to the fender and the opposing reaction experienced by the object.

A fender should be made of a material which is sufficiently flexible not to bring the object to be fendered to an abrupt halt, but sufficiently stiff to halt the object in the distance over which the system is capable of deflection.

The present invention provides a fender comprising a hollow, flexible, substantially cylindrical container, filled with a liquid, and closed save for a pipe projecting outwardly of the container, the end of the pipe remote from the container being located above the container, in which impact of an object to be fendered on a peripheral surface of the container arranged parallel to the container axis displaces the liquid from the container and through the pipe, whereby the kinetic energy of the object to be fendered is substantially all converted into potential energy of the displaced liquid.

A fender according to the present invention may comprise a container attached to or freely suspended adjacent to the bows of a berthing ship, whereby impact of the container displaces the liquid through the pipe and into the surroundings.

In a preferred embodiment of the present invention, the pipe discharges into a tank located at a level higher than that of the container. Impact of the object to be fendered on the container displaces the liquid from the container, through the pipe and into the tank, whereby the kinetic energy of the object to be fendered is substantially all converted into potential energy of the displaced liquid.

A fender according to this preferred embodiment may be attached to or freely suspended adjacent a dock, and the object to be fendered may be a berthing ship approaching the dock.

The pipe may be closeable by means of a valve located between the container and the tank.

Preferably, the valve may be a non-return valve, so that the fender will not "rebound" after impact and force the ship away from the dock. Suitable devices may be provided to open the valve and re-set the system after use.

The container and pipe may be made of flexible material (e.g. rubber, plastics, fibrereinforced rubber or plastics) and the tank may be made of any convenient material, rigid or flexible.

The liquid may be water.

Preferably, the tank has a cross-sectional area which is large relative to that of the container, whereby the displaced liquid is raised to a substantially constant height irrespective of the amount of deflection of the container on impact. Thus, the pressure in the system will remain substantially constant and the force-deflection characteristic of the system approach the "ideal" (i.e. deflection-dependent) state.

Such an "ideal" state may be achieved by minimising the resistance to liquid flowing up the connecting pipe, e.g. by ensuring that the pipe has a sufficiently large diameter and a sufficiently smooth inner surface.

If the pipe has a relatively small diameter and/or a rough (e.g. convoluted) inner surface, viscous drag in the system, caused by turbulent flow of liquid, can be appreciable. In such a case, there will be a larger initial reaction when the object to be fendered impacts the fender, and this reaction decays as the viscosity of the liquid expelled through the pipe decreases.

Thus, if required, the reaction force exerted by the fender on the object to be fendered can be adjusted to some extent by varying the internal dimensions of the pipe.

The present invention will be illustrated, merely by way of example, with reference to the accompanying drawing, the single Figure of which shows, in section, a dock fender according to the preferred embodiment of the present invention.

The fender comprises a hollow, generally cylindrical container 10 and a tank 12, the container and the tank being connected by a pipe 11. Container 10, which is made of a flexible material (e.g. rubber, plastics, fibre-reinforced rubber or plastics), is located adjacent to and in contact with a dock 20 and may be partly or wholly immersed in the sea, the level of which is shown by line AA. Tank 12, which may be made of any suitable material, is located at a level higher than that of container 10 and above sea-level AA. Pipe 11 is of substantially smaller transverse cross-section than that of container 10, and is closeable by means of a valve shown schematically at 13. Preferably, valve 13 may be a non-return valve. The fender contains sufficient water to completely fill (and therefore fully expand) container 10.

When a berthing ship impacts and distorts container 10, water is displaced from the container by being forced through pipe 11 into tank 12. The kinetic energy of the berthing ship is substantially all converted into potential energy of the displaced water. If valve 13 is a non-return valve, the fender will not "rebound" and force the ship away from the dock. If the cross-sectional area of the tank 12 is large relative to that of the container 10, the displaced water will be raised to a constant height above sea-level AA, irrespective of the amount of deflection in the container caused by impact of a berthing ship. Thus the pressure of water in the system will remain constant and the force-deflection characteristic of the fender will approximate to the ideal (deflection-independent) state.

A fender according to the present invention was used to control the deceleration of a ship of mass 107Kg, approaching the dock at a velocity of 0.2 m/sec.

Kinetic energy of ship = i.mass. (velocity)2 = +.107.(0.2)2 = 2 x 105Kg.m2/sec2 The volume of water displaced from the container to the upper tank was found to be 104 (i.e. the mass of water displaced was 104Kg).

Potential energy of displaced water = mass.g.(height of displacement) = 104 x 9.81 x h Kg.m2/sec2 where g is the acceleration due to gravity (9.81 m/sec2) and his the height of displacement of water from the container to the upper tank.

In an ideal situation, the kinetic energy of the ship will equal the potential energy of the water displaced from the fender on impact, so that 2x105 = 9.81xhx104 i.e. h = 2.04 m Thus, the height at which the upper tank must be positioned above the lower container or above sea-level if the lower container is completely submerged, may be deduced from the expression h = (mOv2)/(2mlg), where mO is the mass of the ship; ml the mass of displaced water; v the velocity of the ship; and g the acceleration due to gravity.

WHAT WE CLAIM IS: 1. A fender comprising a hollow, flexible, substantially cylindrical container filled with a liquid and closed save for a pipe projecting outwardly of the container, the end of the pipe remote from the container being located above the container in which impact of an object to be fendered on a peripheral surface of the container arranged parallel to the container axis displaces liquid from the container and through the pipe, whereby the kinetic energy of the object to be fendered is substantially all converted into potential energy of the displaced liquid.

2. A fender according to Claim 1, is which the pipe discharges into a tank located at a level higher than that of the container.

3. A fender according to Claim 2 in which the pipe is closeable by means of a valve located between the container and the tank.

4. A fender according to Claim 3, in which the valve is a non-return valve.

5. A fender according to any one of the preceding claims, in which the container and the pipe are each made from a resiliently-flexible material.

6. A fender according to Claim 5, in which the resiliently-flexible material is rubber or a plastics material.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. viscous drag in the system, caused by turbulent flow of liquid, can be appreciable. In such a case, there will be a larger initial reaction when the object to be fendered impacts the fender, and this reaction decays as the viscosity of the liquid expelled through the pipe decreases. Thus, if required, the reaction force exerted by the fender on the object to be fendered can be adjusted to some extent by varying the internal dimensions of the pipe. The present invention will be illustrated, merely by way of example, with reference to the accompanying drawing, the single Figure of which shows, in section, a dock fender according to the preferred embodiment of the present invention. The fender comprises a hollow, generally cylindrical container 10 and a tank 12, the container and the tank being connected by a pipe 11. Container 10, which is made of a flexible material (e.g. rubber, plastics, fibre-reinforced rubber or plastics), is located adjacent to and in contact with a dock 20 and may be partly or wholly immersed in the sea, the level of which is shown by line AA. Tank 12, which may be made of any suitable material, is located at a level higher than that of container 10 and above sea-level AA. Pipe 11 is of substantially smaller transverse cross-section than that of container 10, and is closeable by means of a valve shown schematically at 13. Preferably, valve 13 may be a non-return valve. The fender contains sufficient water to completely fill (and therefore fully expand) container 10. When a berthing ship impacts and distorts container 10, water is displaced from the container by being forced through pipe 11 into tank 12. The kinetic energy of the berthing ship is substantially all converted into potential energy of the displaced water. If valve 13 is a non-return valve, the fender will not "rebound" and force the ship away from the dock. If the cross-sectional area of the tank 12 is large relative to that of the container 10, the displaced water will be raised to a constant height above sea-level AA, irrespective of the amount of deflection in the container caused by impact of a berthing ship. Thus the pressure of water in the system will remain constant and the force-deflection characteristic of the fender will approximate to the ideal (deflection-independent) state. A fender according to the present invention was used to control the deceleration of a ship of mass 107Kg, approaching the dock at a velocity of 0.2 m/sec. Kinetic energy of ship = i.mass. (velocity)2 = +.107.(0.2)2 = 2 x 105Kg.m2/sec2 The volume of water displaced from the container to the upper tank was found to be 104 (i.e. the mass of water displaced was 104Kg). Potential energy of displaced water = mass.g.(height of displacement) = 104 x 9.81 x h Kg.m2/sec2 where g is the acceleration due to gravity (9.81 m/sec2) and his the height of displacement of water from the container to the upper tank. In an ideal situation, the kinetic energy of the ship will equal the potential energy of the water displaced from the fender on impact, so that 2x105 = 9.81xhx104 i.e. h = 2.04 m Thus, the height at which the upper tank must be positioned above the lower container or above sea-level if the lower container is completely submerged, may be deduced from the expression h = (mOv2)/(2mlg), where mO is the mass of the ship; ml the mass of displaced water; v the velocity of the ship; and g the acceleration due to gravity. WHAT WE CLAIM IS:

1. A fender comprising a hollow, flexible, substantially cylindrical container filled with a liquid and closed save for a pipe projecting outwardly of the container, the end of the pipe remote from the container being located above the container in which impact of an object to be fendered on a peripheral surface of the container arranged parallel to the container axis displaces liquid from the container and through the pipe, whereby the kinetic energy of the object to be fendered is substantially all converted into potential energy of the displaced liquid.

4. A fender according to Claim 3, in which the valve is a non-return valve.

7. A fender according to Claim 5, in which the resiliently-flexible material is a fibre

reinforced rubber or a fibre-reinforced plastics material.

8. A fender according to any one of the preceding claims, in which the liquid is water.

9. A fender according to any one of Claims 2 to 4 and according to any one of Claims 5 to 8 when dependent on Claim 2, in which the tank has a cross-sectional area which is large relative to that of the container, whereby the displaced liquid is raised to a substantially constant height irrespective of the amount of deflection of the container on impact.

10. A fendering system according to Claim 2, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawing.