The present invention relates to an auxiliary flotation, propulsion and steering unit for tracked and/or wheeled land vehicles, particularly multipurpose tracked cargo carrier vehicles of the type known as "Cargo Carrier M548", manufactured by the US company FMC Corporation, California.

Vehicles of the above type already have a hull-like structure with watertightness characteristics which allow them to cross waterways by resting on the bottom of the waterway and also give them limited amphibian characteristics which allow them to cross small bodies of water and to move in swampy land however in shallow water.

It is also known, from EP-A-0 872 366 by the same Applicant, to equip said multipurpose vehicles with an auxiliary apparatus which is capable of significantly improving their amphibian characteristics, allowing them in particular to navigate in deep and even relatively rough water.

This known auxiliary apparatus is substantially composed of two floating sections, respectively a bow section and a stern section, which are constituted by watertight metallic containers filled with foamed material, which can be detachably associated with the hull of the multipurpose vehicle.

The bow section has profiled submerged surfaces so as to generate lift for hydrodynamic support and the stern section includes two propulsion propellers of the ducted type, driven by respective auxiliary hydraulic motors, which can be simultaneously or selectively actuated for propulsion and steering, respectively.

In multipurpose cargo carriers of the specified type, the hydrodynamic lift generated by the prow section may be insufficient, on its own, to ensure correct navigation of the fully laden vehicle, especially during deceleration, when due to the decrease in hydrodynamic lift the bow section, burdened by the weight of the powerplant and stressed by pitching moments, tends to sink below the waterline.

The aim of the present invention is to provide an auxiliary flotation unit adapted for multipurpose cargo carriers of the specified type and more generally for cargo carriers having a considerable tonnage, particularly between 10 and 30 tons when fully laden.

This aim is achieved, according to the present invention, with an auxiliary flotation unit which comprises at least one bow flotation section and one stern flotation section, both whereof are constituted by watertight metallic containers filled with foamed material, wherein the bow section, in besides being profiled so as to generate lift for hydrodynamic support, includes two propulsion and steering propellers of the ducted type, which can be simultaneously or selectively actuated and in which the containment ducts are orientated so that the jets of water generated by said ducted propellers have vertical thrust components which are directed upwardly and are designed to provide auxiliary supporting actions for said bow section.

The invention will become apparent from the following detailed description and with reference to the non-limitative accompanying drawings, wherein:

• Figure 1 is an elevation view of the known tracked cargo carrier type M548, with the auxiliary unit according to the present invention;
• Figure 2 is a schematic plan view of the vehicle of Figure 1, illustrating in particular the hydraulic means for driving the propulsion propellers;
• Figures 3 and 4 are a front view and a rear view, respectively, of the vehicle of Figure 1.

In the drawings, 10 generally designates the M548 cargo carrier, which comprises a watertight hull-like structure 11, with a loading deck 12, a steering cabin 13 and a powerplant 14 which is located between the cabin and the deck and is suitable to drive, through a pair of gears 15, a corresponding pair of tracks 16 with which driving wheels 17 and supporting wheels 18 cooperate.

Reference numeral 20 generally designates the auxiliary unit according to the present invention, which is composed of at least one bow flotation section 21 and one stern flotation section 22. Both of said flotation sections are constituted by watertight metallic containers or tanks, advantageously made of aluminum alloy, in which the watertight cavity is filled with foamed and/or expanded polymeric material MP; said sections are detachably connected to the hull 11, preferably by means of bolts (not shown) which engage the holes of corresponding L-shaped brackets provided on said hull. The bow flotation section 21 has submerged surfaces 23 which are profiled in order to generate lift for hydrodynamic support when the vehicle is navigating and is further provided with a pair of propellers 24 which are suitable for vehicle propulsion and steering.

As clearly shown in figure 2, the propellers 24 are of the ducted type and the ducts 25 that contain them have, with respect to the direction of the water jet ϕ generated by said propellers, front hydrodynamic intakes 26 and axes "a" which are inclined downwardly so as to produce water flows or jets which have upward vertical thrust components which constitute auxiliary actions for supporting the vehicle 10.

According to the invention, the axes "a" of the ducts 25 also diverge, so as to produce jets with lateral thrust components which facilitate the steering of said vehicle when the propellers 22 are actuated selectively for maneuvering.

For this purpose, each propeller 24 is driven by a corresponding hydraulic motor 27 of the reversible variable-displacement type and maneuvering means MM are provided in order to operate said motors simultaneously or selectively. The motors 27 are driven by respective hydraulic pumps P1-P2 which are supplied by a tank 28 and are mechanically connected to each other in a tandem configuration and are driven, by means of a power take-off, by the powerplant 14 of the vehicle 10.

Each pump is connected to the respective motor 27 by means of a corresponding hydraulic circuit Ci1-Ci2, which comprises pressurized delivery and return pipes Tp1-Tp2 and a drainage duct D. The pipes of the hydraulic circuits Ci1-Ci2 extend in a protected position however outside the hull 11 and below the waterline, preferably under the loading deck 12, so as to be cooled by the surrounding water; optional heat exchangers are located on said pipes in order to improve the cooling of the hydraulic fluid.

The effects of the present invention of course cover models that achieve equal utility by using the same innovative concept.

In particular, the alternative arrangement in which the propulsion propellers are driven directly by the powerplant 14 by means of a mechanical transmission achieves equal utility.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.