The present invention is related to a flap damper device for a flap of an air supported vessel, and an air supported vessel comprising such a flap damper device. Further the flap damper device may be a control device for the flap.

Air cushioned vessels are known, such as surface-effect ships (SES), which combine features from hovercraft and catamaran hull design. There is also known a catamaran vessel from US 6672234 which includes an air cushion arranged in each of the hulls of the vessel. The air cushions, however, cover a relatively small area of the horizontal projection of each hull of the catamaran vessel. Furthermore, the angle of attach of the flap of each air cushion can be adjusted to a desired angle, but the flap is arranged in a static position and is not movable as such when the vessel is travelling. Consequently, there is no damping of the flaps.

For air cushioned vessels it is generally desirable to maintain a stable air cushion as the air supported vessel is travelling in water. Such vessels may, as shown in US 6672234, be provided with a recess in the hull for the air cushion and may further be provided with a flap. However, the flap of known solutions are controlled with hydraulics, which has a number of drawbacks. The hydraulic system is stiff and a hydraulically controlled flap and basically provides no damping effect on the flap. Further, a stiff hydraulic system causes reaction forces on the hull of the vessel when the vessel and the flap travel across waves in the water. In addition, a hydraulic system is heavy, large and takes up a large amount of space on the vessel.

An objective of the present invention has been to improve the efficiency and to minimize energy losses of air supported vessels.

A further objective has been to effectively regulate the air cushion of air supported vessels.

A further objective has been to provide a good damping effect on the flap of an air supported vessel.

A further objective has been to reduce reaction forces on the hull of an air supported vessel when the vessel is travelling.

A further objective has been to obtain an air supported vessel with less need for maintenance and repair.

These objectives are met with a flap for an air supported vessel as defined in independent claim 1 , an air supported vessel as defined in claim 15 and a use of the flap defined in claim 22 for regulation of an air cushion on an air supported vessel. The present invention provides a pneumatic flap damper device which is preferably cushioned by air. The flap damper device provides a number of advantages over the known hydraulic control systems for flap control. Air is much more compressible than hydraulic fluids and therefore provides a much better damping of the flap when the air supported vessel travels in water and waves hit the flap. The excellent dynamic damping provided by the pneumatic flap damper device prevents no or very small reaction forces on the hull of the air supported vessel when it is travelling through water and waves hit the flap. Since the flap is subjected to dynamic damping forces, the forces on the attachment devices that attached the flap to the hull, will be small causing less wear than a hydraulic damping device would do. In addition, a pneumatic system is substantially lighter than a hydraulic system and takes up less space on the vessel.

It should be noted that the longitudinal length and axis of the flap damper device and the longitudinal direction and axis of the bellow element are all the same and run through the centre of the flap damper device and the bellow element and generally extends in the direction of the movements that the flap damper device is designed to damp.

Hence, there is provided a flap damper device for damping of motions of an airsupported vessel flap relative to the hull of an air supported vessel, where the vessel flap is rotatably mounted to the hull along an inner edge of the vessel flap. The flap damper device comprises a first attachment unit and a second attachment unit where the first attachment unit is adapted to be securely attached to the hull of the air supported vessel and the second attachment unit is adapted to be securely attached to the vessel flap of the air-supported vessel so that the flap damper device is capable of damping flap motions when the vessel is travelling in water. The flap damper device further comprises a damper element which is attached to the first attachment unit and to the second attachment unit such that an air cavity is formed within the flap damper device for damping of vessel flap motions.

The damper element damps motions arising when the vessel is travelling in water.

The first attachment unit preferably comprises a first attachment ring for attachment of the damper element to a first attachment plate of the first attachment unit and the second attachment unit preferably comprises a second attachment ring for attachment of the damper element to a second attachment plate of the second attachment unit. The air cavity within the flap damper device is preferably filled with pressurized air with a pressure which is controlled so that the flap damper device provides a desired damping effect. The desired pressure will be set so that the flap damper device is capable of providing sufficient damping and will depend on factors like the speed of the vessel, the size of the water waves where the vessel is travelling, the size of the vessel and the vessel flap, the weight of the vessel varying with passenger number, etc. The pressure control adjusts the pressure so that the flap damper device 24 dynamically extends to give a desired angle of said vessel flap 19 and provides a desired damping effect during travelling. The air pressure in the air cavity is taken to be at a desired level or within a desired range when the air pressure of the air cavity is at the desired level when no external forces acts on the flap damper device. The pressurized air will usually have a pressure that is substantially larger than atmospheric pressure.

The air cavity formed within the flap damper device is preferably limited by the first attachment unit and the second attachment unit in a longitudinal direction of the flap damper device and the damper element in a radial direction of the flap damper device.

The damper element preferably comprises a bellow element that is securely attached to the first attachment unit and to the second attachment unit, where the bellow element in its entirety, or at least partially, is made of an elastic material.

The bellow element comprises a plurality of bulges in the longitudinal direction of the bellow element, each bulge extending around the entire circumference of the bellow element.

The bellow element is preferably made of an elastomer, such as a rubber material.

The first attachment ring is preferably a first bead ring and the first attachment plate is preferably a first bead plate, and the bellow element preferably comprises a first bead at a first end portion of the bellow wherein the bellow can be attached to the first bead plate with the first bead ring.

Similarly, the second attachment ring is preferably a second bead ring and the second attachment plate is preferably a second bead plate, and the bellow element preferably comprises a second bead at a second end portion of the bellow wherein the bellow can be attached to the second bead plate with the second bead ring.

The bellow element is preferably at least partially made of an elastic material such that the length of the bellow element in its longitudinal direction is variable. The elastic bellow element and the pressurized air cavity within the bellow element will ensure that the flap damper device is capable of damping vessel flap motions when the air cavity is filled with air at a desired pressure as mentioned above.

The pressure of the air in the bellow element is preferably controlled and the desired pressure of the air can thus be continuously changed and adapted to the prevailing condition in sea, the travelling speed of the vessel etc.

The flap damper device preferably comprises a coupling socket for pressure air supply, the coupling socket which is arranged in the first attachment unit and is fluidly connected to the air cavity, and the coupling socet is adapted for fluid connection to an air supply on the air supported vessel for supply of pressurized air to the air cavity, for example with a suitable tubing, pipe or any other suitable means for conducting air from the air supply to the coupling socket.

In an embodiment, the flap damper element comprises a piston/cylinder arrangement (68) where the piston is attached to the first attachment unit (26) and the cylinder is attached to the second attachment unit (38) or vice versa.

The piston/cylinder arrangement is preferably rotatably attached to the first attachment unit and the second attachment unit. In an embodiment such a piston/cylinder arrangement (68) is arranged in combination with one or two strap elements (58) arranged between the first and second attachment pins (49, 54). An embodiment of this strap and shock damper combination is illustrated in Fig. 6.

The piston/cylinder arrangement is preferably a hydraulic piston/cylinder arrangement provided with a hydraulic fluid where the pressure of the hydraulic fluid is controlled to a desired level.

The pressure of the pressurized hydraulic fluid in the hydraulic system is preferably chosen so that the piston/cylinder arrangement provides a desired damping effect.

The pressure in the hydraulic system is preferably controlled so that the desired pressure of the hydraulic fluid can be continuously changed and adapted to the condition in sea, the travelling speed of the vessel etc.

The flap damper device is preferably provided with a motion limiter device which limits the maximum distance between the first attachment unit and the second attachment unit to a desired maximum distance. The motion limiter device will ensure that the that the flap damper device is not damaged when the vessel, on which the flap damper device is mounted, is travelling in rough waters. The motion limiter device preferably comprises a first strap attachment device which is securely attached to the first attachment unit, a second strap attachment device which is securely attached to the second attachment unit, and a strap element which is connected to or attached to the first motion limiter part and the second motion limiter part.

The first strap attachment device preferably comprises a first attachment pin, the second strap attachment device preferably comprises a second attachment pin, and the strap element is preferably loop-shaped and arranged over the first attachment pin and the second attachment pin. When the flap damper device is extended in its longitudinal direction, it can only be extended to the point where the strap element is stretched to its maximum length and the first attachment pin and the second attachment pin, over which the strap element is arranged, will prevent the bellow element from being further extended.

The first strap attachment device is preferably provided with at least one first adjustment shim for adjustment of the position of the first adjustment pin and/or the second strap attachment device is preferably provided with at least one second adjustment shim for adjustment of the position of the second adjustment pin.

The strap element is preferably inelastic or at least essentially inelastic.

The strap element can, for example, be made of nylon. Hence, the strap element is a nylon strap, which is readily available commercially.

The motion limiter is preferably arranged within the air cavity of the flap damper device.

In a further embodiment of the motion limiter device, the motion limiter device comprises a double-acting piston/cylinder arrangement where the piston is attached to the first attachment unit and the cylinder is attached to the second attachment unit or vice versa.

The piston/cylinder arrangement is preferably a hydraulic piston/cylinder arrangement provided with a hydraulic fluid where the pressure of the hydraulic fluid is controlled to a desired level.

The first attachment unit preferably comprises an inspection hatch which can provide access into the air cavity for inspection and maintenance of the motion limiter. The inspection hatch is preferably securely and disconnectably connected to the first attachment unit, for example with attachment elements such as bolts, screws or any other suitable attachment elements.

The first strap attachment device is preferably attached to the inspection hatch.

There is further provided an air supported vessel comprising a hull which is provided with an exterior hull recess at the bottom of the hull for an air cushion, and at least one vessel flap which is rotatably mounted to the hull in a rear part of the hull recess, where the air supported vessel further comprises at least one flap damper device as described above for damping of motions of the vessel flap, where the first attachment unit of the flap damper device is securely attached to the hull of the air supported vessel and the second attachment unit of the flap damper device is securely attached to the vessel flap of the air supported vessel.

The hull recess preferably extends in a longitudinal direction of the hull, where the hull recess is open in a rearward direction of the hull, and the air supported vessel, and preferably comprises a first sidewall, a second sidewall and a hull recess bottom which extends between the first sidewall and the second sidewall.

The hull of the air supported vessel preferably comprises at least one hull aperture, and the first attachment unit of the flap damper device is preferably attached to the hull of the air supported vessel in a watertight manner such that water is prevented from entering the hull through the hull aperture, and such that the inspection hatch of the flap damper device can be accessed through the hull aperture from inside the hull, i.e. enabling the inspection hatch to be disconnected from and connected to the first attachment unit (i.e. unbolted/unscrewed from and bolted/screwed to the first attachment unit).

The vessel is preferably provided with a source of pressurized air which is fluidly connected to the coupling socket of the at least one flap damper device, for example with a tube element, a pipe or any other suitable means for conducting air, for supply of pressurized air to the air cavity of the flap damper device.

The source of pressurized air is preferably an air compressor or an air pump.

The air supported vessel preferably comprises a plurality of flap damper devices for damping of motions of the vessel flap.

The flap damper devices are preferably spaced out so that a balanced damping force is applied to the vessel flap when the vessel is travelling in water. The vessel flap preferably has the shape of a plate which is flat, or at least substantially flat.

A non-limiting embodiment of the present invention will now be described with reference to the figures, where

Figure 1 shows the hull of a vessel according to the present invention.

Figure 2a and 2b is view from behind a vessel according to the present invention looking forward where a vessel flap arranged in a hull recess is shown with two flap damper devices mounted to the hull and the vessel flap.

Figure 3 shows a flap damper device according to the present invention.

Figure 4 shows an exploded perspective view of a flap damper device according to the present invention and shown in figures 2a-b and 3.

Figure 5 shows a sideview of a flap damper device shown in figure 4.

Figure 6 illustrates a sideview of a flap damper device similar to Fig. 5, with an embodiment combining with one or two strap elements arranged between the first and second attachment pins.

The flap damper device 24 according to the present invention is shown in figures 2-5, and an air-supported vessel 10 according to the [present invention, on which one or more flap damper devices 24 is mounted, is shown in figure 1.

As shown in figure 1 , the air-supported vessel 10 comprises a hull 12 with a hull recess 14 extending along at least a portion of the outer bottom of the hull 12, and preferably along nearly the entire outer bottom of the hull 12 as indicated in figure 1 . The hull recess 14 is formed by a first side wall 16 and a second side wall 17 which extends from the aft of the hull 12, where they are substantially parallel to each other, and to a front portion of the hull 12 where the first side wall 16 and the second side wall 17 are bent towards each other until they meet in a bow portion as shown in figure 1. An air inlet opening 11 are provided within the hull recess 14, preferably at the fore of the hull recess 14, where air is pumped in to produce an air cushion which improves the seafaring characteristics and properties of the vessel 10.

At the aft of the hull recess 14, a vessel flap 19 is arranged in the hull recess 14. The vessel flap 19 is rotatably mounted to the ceiling of the hull recess about an axis of rotation that is substantially transverse to the fore-aft direction of the hull 12. Preferably, the vessel flap 19 is hingedly attached to the hull recess 14, for example with one or more bolt devices or any other suitable devices that will allow the vessel flap 19 to be rotatably attached to the ceiling 18 of hull recess 14.

The hull recess is further provided with at least one, but preferably two or more hull apertures 13 arranged aft of the attachment of the vessel flap 19 to the hull recess ceiling 18. In figure 1 there is shown two hull apertures 13. The hull recesses 13 are used to access to the interior of flap damper devices 24, as shown in figures 2a-2b and 3, which are attached in one end to the vessel flap 19 and the other end to the hull so that they cover respective hull apertures 13 in a water tight manner so that water is prevented from entering the hull 12 through the hull apertures 13.

The flap damper devices 24 will damp the motion of the vessel flap 19 when the air-supported vessel 10 is travelling through water and help to maintain the air- cushion that is formed within the hull recess 14.

An embodiment of the flap damper device 24 according to the present invention will now be described with reference to figures 2-5.

As can be seen in figures 4 and 5, the embodiment of the flap damper device 24 comprises a first attachment unit 26 which is adapted to be attached to the hull of an air-supported vessel, such as the air-supported vessel 10 shown in figure 1. The flap damper device 24 further comprises a second attachment unit 38 which is adapted to be attached to the vessel flap 19 of an air-supported vessel, such as the air-supported vessel 10 shown in figure 1.

The embodiment of the flap damper device 24 shown in the figures 2-5 is further provided with a bellow element 44. The bellow element 44 is at least partially, but preferably completely, made of an elastic material such that the length of the bellow element 44 in its longitudinal direction V (see figure 5) is variable, i.e. the bellow element 44 can be extended and compressed. The bellow element 44 can, for example, be made of a rubber material, such as a rubber materials used in conventional tyres.

The bellow element 44 is preferably designed, or made, with at least one bellow bulge 45. The at least one bellow bulge 45 improves the damping effect of the flap damper device 24 and makes the bellow element 44 more durable. The embodiment of the bellow element 44 shown on figures 2a-2b and 3, is provided with two bellow bulges 45, but the bellow element 44 can be made with any number of bulges 34.

The bellow element 44 is, at one end in the longitudinal direction of the bellow element 44, adapted to be securely attached to the first attachment unit 26. The bellow element 44 is further, at the opposite end of the bellow element 44 in its longitudinal direction, adapted to be securely attached to the second attachment unit 38.

With this arrangement an air cavity (42) is obtained limited by the first attachment unit 26 and the second attachment unit 38 in the longitudinal direction, and the bellow element 38 in a radial direction. The pressure of the air in the air cavity is adjusted to a desired pressure which is at least equal to the atmospheric pressure, but in most instances larger than atmospheric pressure. The desired pressure of the air in the air cavity will depend on the external loads on the vessel flap, to which the flap damper device 24 is attached. Parameters like the travelling speed of the vessel and the sea conditions will affect the external loads and forces on the vessel flap 19. The pressure of the air in the air cavity (42) may therefore be adjustable, either manually by an operator or automatically by a control system including sensors that feed travelling speed, and/or external forces on the vessel flap and/or parameters related to wave conditions and/or other relevant parameters to the control system’s control unit which continuously controls and adjusts the air pressure in the air cavity based on data received from the sensors and a desired damping effect of the flap damper device 24.

To attach the bellow element 44 to the first attachment unit 26 and the second attachment unit 38 the bellow element 44 can be provided with respective bead elements (not shown in the figures), or similar attachment elements, at its ends in the longitudinal direction The bead elements comprise bead flanges (46). It should be mentioned that the bellow element 44 can be attached to the first attachment unit 26 and the second attachment unit 38 in many different ways as long as the attachment to the first and second attachment unit 26, 38 is secure and watertight.

The first attachment unit 26 comprises a first attachment plate or bead plate 27 and a first attachment ring or bead ring 28 which can be securely attached to the first bead plate 27 for example with bolts or screws 29, or any other suitable fastening means.

Similarly, the second attachment unit 38 comprises a second attachment plate or bead plate 39 and a first attachment ring or bead ring 40 which can be securely attached to the second bead plate 39, for example with bolts or screws 41 , or any other suitable fastening means.

The bead flange 46 provided at either end of the bellow element 44 are attached to the respectively the first attachment unit 26 and the second attachment unit 38 by letting the bead flange 46 be squeezed between the first bead ring 28 and first bead plate 27 and between the second bead ring 40 and the second bead plate 39. Since the bellow element 44, and hence the bead flange 46 elements, are made of a rubber material, a watertight attachment of the bellow element 44 to the first attachment unit 26 and to the second attachment unit 38 is obtained.

To avoid that the length of the bellow element 44 is extended too far, the flap damper device 24 is preferably provided with a motion limiter device 47 which limits the extent to which the bellow element 44 can be extended to a maximum length to prevent that the flap damper device 24 and/or the vessel flap 19, to which the flap damper device is attached, is damaged.

The motion limiter device 47 can be designed in several ways. An embodiment of a preferred motion limiter device 47 is shown on figures 4 and 5. As can be seen on the figures, the motion limiter device 47 is preferably arranged within the air cavity 42 of the flap damper device 24.

The motion limiter device 47 comprises a first strap attachment device 48 and a second strap attachment device 53.

The first strap attachment device 48 is securely attached to the first attachment unit 26, for example with bolts or screws 51 or any other suitable fastening means.

The second attachment device 53 is attached to the second attachment unit 38, for example with bolts or screws 56 or any other suitable fastening means.

The first strap attachment device 48 comprises a first attachment pin 49 and the second strap attachment device 53 comprises a second attachment pin 54. The motion limiter device 47 further comprises at least one strap element 58, which has the shape of a loop and is arranged over and around the first attachment pin 49 and below and about the second attachment pin 54. The strap element 58 is preferably made of a material which is inelastic, or at least substantially inelastic.

With the motion limiter device 47, the length of the strap element 58 limits the extent to which the bellow element 44 can be extended, and the extent to which the bellow element can be extended can be limited to a desired length by choosing a strap element with a length that will prevent the bellow to be extended beyond the desired length. The strap element 58 may be replaced while the vessel is in the sea, via the inspection hatch which provides access into the air cavity for inspection and maintenance.

The strap element can, for example, be made of a nylon material. Strap elements made of nylon are widely available commercially and can be provided in any desired width, height and thickness. These nylon straps have a high tensile strength and a strap element with a desired tensile strength can easily be obtained. Such nylon straps are commonly used for example in various types of outdoor equipment such as backpacks and in many other applications.

The first strap attachment device 48 and the second strap attachment device 53 are preferably provided with a rounded shape to prevent damage on the strap element.

The flap damper device 24 can further be provided with various shims 50, 55 which can be replaced with shims having different lengths in the longitudinal direction which will allow the distance between the first strap attachment pin 49 and the second strap attachment pin 54 to be adjusted to a desired length when the bellow element is in its neutral position, i.e. the bellow element 44 is neither extended nor compressed.

Although not shown in the figures, it should be mentioned that the motion limiter device could also be a conventional, double-acting piston/cylinder arrangement which is arranged in the air cavity (42). The piston could be attached to the first attachment unit 26 and the cylinder to the second attachment unit 38, or vice versa.

The first bead plate 27 is provided with a first bead plate aperture 60 which provides access to the interior of the flap damper device 24, i.e. the air cavity 42 of the flap damper device 24. The first attachment unit 26 is further provided with an inspection hatch 34 which is attached to the first bead plate 27 with screws or bolts 35, or any other suitable fastening means, such that the inspection hatch covers the first bead plate opening 60. The inspection hatch 34 can be detached from and reattached to the first bead plate 27, thereby providing access to the air cavity (42) when the flap damper device 24 is installed on the air-supported vessel 10.

The first attachment unit 26 further comprises a hull plate 30 with a hull plate aperture 31 for attachment of the flap damper device 24 to the hull of the airsupported vessel 10. The air-supported vessel 10 is provided with at least one hull aperture 13, as indicated on figure 1 , and the flap damper device is attached to the hull 12 by placing the first bead plate 27 against the outside surface of the hull 12 such that the first bead plate aperture 60 substantially aligns with the hull aperture 13. The hull plate 30 is placed against the inside surface of the hull 12 such that the hull plate aperture 31 substantially aligns with the hull aperture 13. The flap damper device 24 and the hull plate 30 are securely fastened to the hull 12 and the first bead plate 27 with bolts or screws 33, or any other suitable fastening means. The first bead plate bead plate 27 is preferably provided with a hull plate groove 32 in which a sealing element, such as an o-ring, is arranged to prevent water to leak into the inside of the hull 12 through the hull aperture 13. Because of the hull aperture 13, there is access to the inspection hatch 34 from the inside of the hull 12. When access to the interior of the flap damper device 24 is needed, for example to change a worn-out strap element or change the strap element to another strap element with a different length, the inspection hatch 34 can be detached to provide access to the air cavity and thereafter reattached from inside the hull 12.

The inspection hatch is preferably also provided with a pressure air coupling socket 36. The air-supported vessel 10 is preferably provided with a supply of compressed air, for example from a compressor or a pump, which is fluidly connected to the pressure air coupling socket 36 with the necessary pipe(s), tube(s) or any other suitable devices that is capable of conducting compressed air. The coupling socket 36 can, if desired, be actively controlled as mentioned above, such that the air pressure in the air cavity of the flap damper device 24 is continuously controlled and adjusted to the desired level. Components list