This invention relates generally to marine landing craft.

Conventionally, marine landing craft are flat-bottomed vessels with a substantially box shaped cross-section. The forward end of a conventional landing craft comprises a hinged ramp rather than a v-shaped bow typical of other boats and marine vessels. The ramp is provided to facilitate the loading and unloading of cargo onto a beach, for example. Furthermore, the ramp is generally attached to the landing craft via an external hinge and is raised or lowered by a pair of winch operated chains.

In operation, conventional landing craft tend to be slow and difficult to manoeuvre due to the square shape of the bow of the hull.

One way to increase the speed of a typical landing craft is to streamline the hull of the craft, that is to say introduce a v-shaped profile to at least the bow section of the vessel. However, and as shown in Figure 1 of the accompanying drawings, profiling the bow section in this manner necessarily leads to a narrowing of the hull opening which in turn restricts the type and size of cargo that can be usefully transported on the vessel. In other situations, a profiled bow section may result in the ramp having to be located higher up from the waterline. In situations where the ramp is in a position substantially above the waterline, the ability of the craft to be utilised in beach landing operations is negated, since this type of ramp will require a dock or quay to effect the disembarkation of personnel or the unloading of cargo.

A further problem arises when beaching a craft having a keel with a v-shaped profile: the keel edge will act as the only grounding point, leading to both transverse and longitudinal stability problems. These problems are exacerbated if the vessel is subjected to incoming waves that are breaking obliquely on the beach. For this reason, conventional landing craft incorporate a flat-bottomed bow section to circumnavigate the aforementioned problem. GB 1 402 735 A discloses a marine landing craft having a hinged ramp with fender means. US 6 176 192 B1 discloses a pivoting ramp for a ferry or floating bridge and having a differential cylinder with a pressure limiting valve to limit the bending moment in the area of the pivot.

According to the present invention there are provided a landing craft and a method of operating a landing craft as defined in independent product claim 1 and independent method claim 11, respectively. Additional technical features or method steps of the invention are disclosed in the dependent claims. The landing craft has a ramp pivotally mounted at an open end thereof, and includes biasing means for exerting a downward force on the ramp when in a lowered position exposing said open end, so as to move the ramp to a grounded position in which the landing craft is partially supported by the ramp. The ramp forms part of a forward portion of the landing craft, the forward portion having a substantially V-shaped keel region.

Preferably, the biasing means also operates as an actuating device for lowering and raising the ramp.

Preferably, the biasing means comprises at least one hydraulic ram or actuator. Preferably, the landing craft includes locking means for locking the ramp in a lowered position.

Preferably, the ramp includes lateral guide portions adapted to co-operate with landing craft frontal portions that delimit an opening of said open end.

Preferably, a surface of the ramp that faces outward when said ramp is in a raised position is faceted and includes a triangular portion disposed so as to provide a ramp ground contact portion when said ramp is in a lowered position.

Preferably, the landing craft has a substantially v-shaped keel and a forward section that tapers inwardly towards the bow.

Preferably, the lateral guide portions of the ramp form a contiguous bow section of a landing craft forward section when said ramp is in a raised position.

Preferably, the ramp is pivotally mounted to said landing craft via a hinge system that is internal to the hull of the craft.

Preferably, the ramp includes a sensing system adapted to detect loads that exceed a predetermined safety level and to deactivate said locking means in response to predetermined safety parameters.

A method of operating the landing craft includes the steps of: lowering the ramp until a forward grounding edge of the ramp is grounded; applying a required amount of downforce at the grounding edge until a predetermined proportion of the landing craft displacement is supported by the grounding edge; and locking the ramp in place so as to maintain support for the predetermined proportion of the landing craft displacement. Preferably, the required amount of downforce is applied to the grounding edge via at least one hydraulic ram or actuator.

Preferably, the method includes the step of detecting when a ramp load exceeds a predetermined safety limit.

Preferably, the method also includes the step of unlocking the ramp when one or more predetermined safety parameters have been breached.

Also described, yet not forming part of the present invention, is a landing craft having a ramp pivotally mounted at an open end thereof, wherein a forward facing surface of said ramp is non-planar and includes a grounding section, and wherein said grounding section is adapted to anchor the ramp in response to an applied downward force when the ramp is in a lowered position. Preferably, the grounding section is a triangular planar surface.

An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying schematic drawings, in which:

• Figure 1 shows a conventional landing craft including a tapered bow;
• Figure 2 shows the forward section of a landing craft in accordance with an embodiment of the present invention;
• Figure 3 shows a ramp of a landing craft in accordance with an embodiment of the present invention;
• Figure 4 shows a partial view of a grounded landing craft in accordance with an embodiment of the present invention; and
• Figure 5 is a partial close-up view of the landing craft of Figure 4.

As shown in Figure 1, a conventional landing craft 1 comprises a generally box-shaped hull 2, a wheelhouse 6 situated in the stern section 3, and a ramp 4 allowing access to a cargo hold area 5. The ramp 4 is pivotally attached to the hull 2 via an external hinge (not shown) located proximal to the waterline.

As Figure 1 shows, the bow section 7 tapers inwardly towards the ramp 4. In order to maintain mechanical strength and structural stability with such a bow profile, it is necessary to incorporate bow reinforcement structures 10. These reinforcement structures introduce a bottleneck section 8 that results in an overall reduction of the cargo hold area 5. Not only does this reduce the total cargo capacity of the vessel, it also restricts the width 9 of the ramp 4, which in turn restricts the size and type of cargo that may access the landing craft 1.

In contrast, the landing craft 20 shown partially and beached in Figure 4 has no equivalent bottleneck section since the tapered forward section (or portion) 30 (see Figure 2) does not compromise the width 22 of the cargo hold area 21. Here, the forward section 30 includes a contiguous bow section 25 formed by the ramp 24. Structural integrity is maintained by constructing the ramp 24 to include lateral guide portions 28.

The lateral guide portions 28 advantageously serve as guide rails that aid the loading and unloading of vehicular cargo. Furthermore, they provide additional protection to the bow structure from impact or collision damage. Although not shown in the Figures, the hinging system interconnecting the ramp 24 with the forward section 30 is internal to the hull. The hinging system is disposed with respect to the ramp 24 such that the ramp 24 is clear of the hull opening when in a fully lowered position.

In operation, the landing craft 20 is beached by grounding the v-shaped keel 26 on a shore line, for example. Prior to beaching, ramp lowering will be initiated so that ramp 24 will come into contact with the beach shortly after the keel 26 has ground on the beach.

The ramp 24 is lowered under operation of a ramp actuator 11 (see Figure 5). In an embodiment of the present invention it is envisaged that there are a pair of ramp actuators 11, one situated either side of the hull, and that each actuator 11 comprises a hydraulic ram and any other such ancillary equipment as is known to be required for their controlled operation.

In another embodiment of the present invention, the ramp 24 is raised and lowered by means of a winch and chain system and the ramp actuators 11 provide ramp biasing means.

The external surface of the ramp, as shown in Figure 2, is faceted and includes a triangular section (or portion) 29. The forward edge 27 of the triangular section 29 constitutes a second grounding means and comes into contact with the ground shortly after the keel 26 has grounded. Once the ramp has made initial contact with the beach 12 (partially shown in Figures 4 and 5), downward pressure is applied through the forward edge 27 by continued operation of the ramp actuators 11. Downward pressure through the forward edge 27 is applied until a small, predetermined portion of the total displacement of the ship is borne by the forward edge 27, at which point the ramp is locked in place by suitable locking means (not shown).

If necessary, after the ramp has been locked in place, further pressure can be applied to the forward edge 27 to force the ramp to dig into the beach by engaging the landing craft engines, thus urging the craft forwards.

Once the ramp 24 has been locked in place, the landing craft 20 is stable with respect to both transverse and longitudinal disturbances, thus facilitating quicker and safer loading/unloading operations or the disembarkation of personnel from the cargo hold area 21.

In a preferred embodiment, the landing craft 20 includes a ramp safety system implemented to ensure that the ramp 24 when locked in a lowered position is automatically unlocked in the event that one or more predetermined safety parameters have been breached or compromised. The safety system would also incorporate an alarm for indicating when a ramp load has exceeded a predetermined maximum load capacity.