PROPULSION UNIT FOR MULTIHULL SUCH AS A CATAMARAN

Abstract

The invention concerns a propulsion unit for a multihull such as a catamaran, comprising at least one turbine, seawater suction means and seawater backflow means. The invention is characterized in that said device comprises a seawater turbine directly driven by a motor inside each of the hulls (1), the seawater suction means being positioned at the front, outside each hull (1) in an overpressure zone generated by the bow wave and the seawater backflow means being positioned inside each hull (11), on the rear of the boat pitch pivot pin, said backflow means having an outlet (5) capable of being pivoted and emerging inside the channel defined between two hulls (1).

Description

The present invention concerns a propulsion unit for multihull boats such as catamarans.

The boat propulsion units are used, on the one hand, for port and positioning maneuvers and, on the other, for transit. These two types of use require, however, different properties. In fact, port and positioning maneuvers require great flexibility and little power, while transit demands high power making it possible to attain maximum speed, while necessitating little or no maneuvers.

It is therefore necessary to propose boat propulsion units making it possible to access those two types of use satisfactorily.

Standard propulsion units generally consist of three main parts, which are the power generating means (engine or turbine), the means using the power (propeller or jet) and the means ensuring transmission among them.

Thus, propulsion units can comprise a engine, a speed reducer, a clutch, a reverser, a thrust bearing, a shaft line and a propeller. Other propulsion units consist of an engine, a multiplier, the shortest possible shaft line and a jet turbine equipped with an inversion chamber and a thrust bearing. These propulsion units can also contain a gas or steam turbine, a speed reducer, a thrust bearing and a propeller or jet turbine.

Now, it has been observed that to obtain good efficiency and not foul up, the engines must run at approximately 2,000 rpm, while the turbines must run at 8,000 rpm at least, in order to have power.

Likewise, in order to have power, the jets must run at approximately 3,000 rpm, while the propellers must average 100 rpm to obtain good efficiency.

In the case of engine and turbine units, the result is generally too much power during maneuvers, which disrupts their good performance. Furthermore, in the case of an engine and propeller unit, the clutch and the propeller must be stopped between each maneuver, which results in both a waste of time and squandering power in order to restart.

In the case of a jet propulsion unit, the minimum power required for good operation can damage the docks on port maneuvers. Furthermore, the suction of the jets generally placed under the hull can result at shallow depth in the suction of sand and mud capable of damaging the turbine blades.

Hydraulic propulsion units of vessels, situated in the hull of a monohull, have been described. Thus, in U.S. Pat. No. 512,591, a monohull is proposed with suction means proposed in front on each side of the hull toward the turbines and backflow means on both sides of the single hull and in the rear. In US document 2002/037,675 a propulsion system is described mounted in the hull of a boat, such as a yacht or a pleasure trawler, comprising symmetrical exhaust pipes, water inlets on both sides of the hull, near the bow and connected to the pipes, a mixing chamber, nozzles at the pipe opening and at least one pump gear in each pipe, driven by a motor.

GB 1,194,510 proposes seawater suction for a monohull at the front of the boat toward a pump driven by a motor and connected to that pipe and two steering units situated on the center line of the boat, one toward the front and the other toward the rear, each steering unit consisting of a water backflow nozzle that can change direction.

In document DE 3,125,887, a catamaran is provided with a channel crossing each floating body from an inlet in front, at the front end of the float (dead center), to the rear end, the channel being connected to a pressure generator placed on the deck between each float, so that water is sucked in front with a view to creating “impulse water” and is expelled in the rear by an outlet nozzle or else is expelled as “brake water” in front through the front channel opening. Such a unit is conceivable only in a float catamaran rather than hull catamaran system, the problems not being the same.

Furthermore, in the case of catamaran-type boats, the propulsion units have to be adapted to the specific problems associated with the shape of the boat. In particular, on picking up speed, a standard catamaran tends to sink back, thus increasing the wet surface of the hulls and the drag.

The object of the present invention is, therefore, to propose a propulsion unit for multihulls, such as a catamaran, overcoming those problems by making it possible to obtain good performance during port maneuver phases as well as during transit phases.

The object of the present invention is thus a propulsion unit for multihull boats, such as a catamaran, comprising, notably, at least one turbine, seawater suction means and seawater backflow means, characterized in that it contains a seawater turbine driven directly by an engine in each of the hulls, the seawater suction means being positioned in front preferably outside each hull in an overpressure zone generated by the bow wave and the seawater backflow means being positioned in each hull on the rear of the boat pitch pivot pin, said backflow means having an outlet capable of pivoting and emerging preferably inside the channel defined between two hulls.

Advantageously, the propulsion unit according to the invention is thus particularly well-integrated to the specific shape of a multihull and, in particular, a catamaran and thus exploits all the advantages.

The suction means are preferably positioned on the front outside each hull in an overpressure zone linked to the bow wave, affording the turbines natural supercharging.

When the outlets of the backflow means are turned vertically downward or upward, no propulsive force is produced on starting the engines, which makes it possible not to provide a clutch between the engine and the turbine.

Thus, the propulsion unit according to the invention is considerably simplified, inasmuch as the outlet of the pivoting backflow means allow the absence of a clutch between engine and turbine. Furthermore, the absence of moving parts in the water eliminates the problems of locking which can occur with propellers, as well as the risks of deterioration or jamming of the latter. Furthermore, there is no longer any danger for divers, as might be the case of a boat equipped with a propeller.

According to a preferred embodiment of the invention, the seawater backflow means consist of at least one pivoting elbowed nozzle.

That nozzle consists of a first tube, in which a second tube is pivoted, of diameter slightly less than that of the first tube. The difference in diameter between the tubes can be compensated by sleeving of the inner tube pivoting by means of a “slippery” material compatible with the seawater, such as a PVC-type plastic, a polyamide like that known by the trade name “Ertalon.” Housings are cut into the sleeving in order to receive the O-ring seals ensuring tightness between the tubes.

The tubes used can advantageously be stainless steel tubes of standard diameters or else tubes of a similar appropriate material.

At one end of the inner tube, there is a reduction cone (ratio close to 2/1, for example), making possible water jet pressure, the elbow or outlet nozzle being welded to the cone on the small diameter side.

Thus, each outlet nozzle or elbow can be rotated between two outlet positions of the water jet downward or upward, in which no propulsive force is produced, the outlet positions of the water jet of the front and rear motions being at 90° from either vertical position.

The means making it possible to rotate the outlet nozzles consist of cables, chains, pinion rods or the like, automatically or manually controlled without stopping the engine. These drive means are welded to the base of the outlet elbow near the reduction cone, the cables, chains or rods passing inside vertical tubes welded to the outer tube of the nozzle and rising well above the water level, which makes it possible to avoid the placement of expensive and unreliable stuffing boxes. These means of rotating the nozzles can be actuated without having to stop the engine.

Consequently, to control the propulsion of the boat, it is sufficient to turn the outlet nozzles forward to secure backward propulsion and backward to secure forward propulsion.

When the outlet nozzles are turned vertically downward, they can advantageously help refloat the boat, especially considering that the quantity of water ejected produces an underwashing effect under the hulls.

An intermediate position of the outlet nozzles and, consequently, of the tubes pivoting at 45° from either of the vertical positions makes it possible to block, at least in large part, the delivery of the outlet nozzle and/or to place the openings existing in each of the tubes, pivoting or stationary, opposite each other. When those openings are opposite, the backflow jets are directed to pipes ending in a nozzle connected to the rudder post for one of them, and in a pivoting nozzle situated under a third bow for the other (that nozzle can deliver only under the effect of pressure).

The horizontal forces thus obtained advantageously make it possible to move the boat in all directions, assuring a manual dynamic positioning.

These secondary nozzles also make swinging in place possible.

The propulsion unit according to the invention likewise makes it possible to control and diminish deck movements such as roll and pitch.

Thus, the outlet nozzles being at the rear of the pitch pivot pin of the boat, the oscillation of those nozzles around the “forward motion” position can create a torque countering that generated by the pitch.

Likewise, by using the propulsion unit according to the invention in dynamic positions, as previously described, and providing spherical valves, manually controlled, for example, mounted on the pipes in front and in back, trimming tanks, one situated in front and the other in the rear in the space between hulls, can be filled rapidly. Thus, if the boat dips its head, the rear trimming tank is filled, while rapidly emptying the front trimming tank by gravity, and the opposite maneuver is performed if the front is lightened.

The tanks can also be filled to make the boat heavier when grounded, so that it will not be subjected to swells.

To control the roll, the tanks formed by walls of the hull, lined inside the boat by a bulkhead going from the upper deck to the water level, are filled, as described above. These tanks further constitute a double hull advantageous in case of collision, which reduces the infrared radiation and can serve as protection in case of small arms firing.

The propulsion unit according to the invention can further contain additional means of propulsion or “boosters” set up at the back of the engines of said unit.

Such additional propulsion means are chosen in accordance with the size of the boat and its use. Thus, a self-contained motor pump unit of the type used by firemen can be employed. Their compactness, that is, they are simply placed in the hull and connected to the suction means and the backflow means, makes it possible to easily remove them for maintenance. Provision can also be made for the use of turbines of the same type as on helicopters.

The power supply of that motor pump unit is situated in front as low as possible in the channel between the hulls and as close as possible to the corresponding backflow under each hull in the back of the grounding plane. These means of propulsion are started without clutch and without rear motion, since they are employed only when high speed is sought or else when a propulsion unit according to the invention is used to control the roll.

The propulsion unit according to the invention is particularly well-suited for a catamaran, whose channel between hulls provides a Venturi effect, as described in patent EP 0,108,004, which proposes a catamaran-type boat with two hulls symmetrically arranged in relation to a mean vertical plane and joined by a connecting bridge above the water line, each hull being dissymmetrical to a vertical plane passed through the bow and parallel to the mean vertical plane, with a half main frame larger and more advanced on the inner side than on the outer side, while toward the rear, from the main frame, the inner wall of each hull is in the form of an appreciably helicoidal surface with horizontal generatrices, the upper generatrix being roughly parallel to the midplane of the boat and a lower generatrix coming under the hull. This particular geometry of each hull leads to defining a Venturi shape of the channel between the two hulls adding and controlling the interior bow waves, which tends to produce a lifting of the front of the boat, while the exterior bow waves are reduced. Such a boat, therefore, makes it possible to recover in positive action a part of the energy contained in the wave train formed in order to improve its navigation performance, particularly by lightening the boat in the rear and also in front and by limiting dipping of the rear.

Thus, the pivoting elbowed nozzles positioned in the rear of the pitch pivot pin of the boat preferably spit out seawater also in the rear of the Venturi neck in a zone where the wave train causes a slight depression to appear, which produces less back pressure on outlet. Furthermore, the jets are supported on the specific stationary wave of the boat and increases its volume. This advantageously results in the following wave forming part of the wake to be captive in the channel between hulls and contributes to propulsion.

Somehow integrated with the specific shapes of this hull, the propulsion unit thus has excellent efficiency and affords remarkable maneuverability.

The propulsion unit according to the invention can advantageously equip multihulls, such as catamarans of all sizes, that is, from a small pleasure craft to a large carrier.

The invention will now be described more in detail, with reference to the attached drawing in which:

FIG. 1 represents a view in front perspective of a catamaran equipped with a unit according to the invention;

FIG. 2 represents a cross section of the pivoting elbowed nozzles of a propulsion unit according to the invention;

FIG. 3 represents a lateral perspective of a rudder of a boat equipped with a unit according to the invention; and

FIG. 4 represents a sectional view of the lower part of a boat hull equipped with a nozzle according to FIG. 2.

The propulsion unit according to the invention is intended to be installed on multihulls, such as the catamaran C illustrated in FIG. 1 with two hulls 1 and a third bow 2.

This unit contains a seawater turbine directly driven by an engine in each of the hulls 1, seawater suction means positioned in front outside each hull 1 in an overpressure zone generated by the bow wave and seawater backflow means positioned in the rear inside each hull 1, on the back of the pitch pivot pin of the boat, said backflow means having an outlet capable of pivoting. In the unit according to the invention, it is possible to use turbines, such as those employed in boatyards and which can accept pebbles, sand, gravel, etc. without damage.

The seawater backflow means comprise a pivoting elbowed nozzle 3 consisting of a first tube 3a, in which a second tube 3b is pivoted, of diameter slightly less than that of the first tube 3a. The difference in diameter between the two tubes 3a, 3b is compensated by sleeving M of the inner tube pivoting by means of a slippery material compatible with the seawater, such as a polyamide, or the like. Tightness between the tubes 3a and 3b is obtained by O-ring seals (not represented) placed in housings cut into the sleeving.

At one end of the inner tube 3b, there is a reduction cone 4 making water jet pressure possible, the elbow or outlet nozzle 5 being welded to the cone 3b on the small diameter side.

The outer tube 3a is fastened inside the hull and perpendicular to the axis of the craft, while the inner tube 3b is engaged outside the hull (not represented in FIG. 2) in the tube 3a across the opening machined in the hull. There is then no risk of leakage.

Furthermore, a locking plate 8 is engaged on the outlet nozzle 5 and fastened outside the hull. That locking plate 8 has, in addition, a circular sector which makes it possible to block the opening of the outlet nozzle 5 at least partially when it is brought into a 45° position forward and upward. That circular sector also makes it possible to at least partially protect the outlet nozzle 5.

The locking plate 8 preferably also contains a rolling system which collects the thrust of the reduction cone on backflow or else a flat sliding joint.

As can be seen in FIG. 4, the pivoting elbowed nozzle is installed in the hull 1 at the bilge level (that is, the rounded lower part joining the grounding plane and the wall of the hull 1).

Thus, the outlet nozzle or elbow 5 can be rotated between two outlet positions of the water jet downward or upward, in which no propulsive force is produced, the outlet positions of the water jet of the front and rear motions being at 90° from either vertical position.

An intermediate position of the outlet nozzles 5 and, consequently, of the tubes 3a, 3b pivoting at 45° from either of the vertical positions makes it possible to block, at least in large part, the opening of the outlet nozzle 5, thanks to the circular sector of the locking plate 6, and/or to place the openings existing in each of the tubes 3a, 3b opposite each other.

When those openings are opposite, the backflow jets are directed to pipes ending in a nozzle 6 connected to the rudder post 7 for one of them, as shown in FIG. 3, and in a pivoting nozzle situated under a third bow 2 of the catamaran C for the other.

The rudder post 7 has a rear part 7a and a compensating front part 7b enabling the rudder 7 to collect the thrust forces associated with propulsion by the nozzle 6. The rudders rotates over the whole horizon.

The upper corner of the front part 7b contains a support device such as a roller bearing on the hull, preventing bending of the hollow post under the effect of thrust.

Claims

1. Propulsion unit for multihulls such as a catamaran, having at least one turbine, seawater suction means and seawater backflow means, characterized in that the propulsion unit comprises a seawater turbine directly driven by an engine in each of the hulls, seawater suction means positioned in front preferably outside each hull in an overpressure zone generated by the bow wave and seawater backflow means positioned in the rear inside each hull, on the back of a pitch pivot pin of the multihull, said backflow means having an outlet capable of pivoting and emerging inside a channel defined between two hulls.

2. Unit according to claim 1, characterized in that the suction means are positioned in front outside each hull in an overpressure zone linked to the bow wave affording the turbines natural supercharging.

3. Unit according to claim 1, characterized in that the seawater backflow means comprise at least one pivoting elbowed nozzle consisting of a first tube, in which a second tube is pivoted, of diameter slightly less than that of the first tube, a reduction cone enabling the pressure of the water jet at one end of the inner tube and an elbow or outlet nozzle welded to the cone on the small diameter side.

4. Unit according to claim 3, characterized in that the difference in diameter between the tubes is compensated by sleeving of the inner tube pivoting by means of a material compatible with the seawater, housings being cut into the sleeving to receive the O-ring seals ensuring tightness between the tubes.

5. Unit according to claim 3, characterized in that the outer tube can be fastened inside the hull opposite an opening machined in said hull, while the inner tube can be engaged outside the hull in the tube across the opening machined in the hull, and a locking plate can be engaged on the outlet nozzle and fastened on the outside of the hull.

6. Unit according to claim 3, characterized in that an outlet nozzle or elbow can be rotated between two outlet positions of the water jet downward or upward, in which no propulsive force is produced, the outlet positions of the water jet of the front and rear motions being at 90° from either vertical position.

7. Unit according to claim 5, characterized in that the locking plate has a circular sector intended to block the opening of the outlet nozzle at least partially, when the outlet nozzle is rotated to an intermediate position at 45° from either of the vertical positions of said outlet nozzle.

8. Unit according to claim 6, characterized in that an intermediate position of an outlet nozzle at 45° from either of the vertical positions of said outlet nozzle places the openings existing in each of the tubes opposite one another, the backflow jets being directed to pipes in front and in back, one ending in a nozzle situated at the rudder post and the other in a pivoting nozzle situated under the third bow.

9. Unit according to claim 8, characterized in that spherical valves are mounted on the pipes in front and in back in order to quickly fill trimming tanks, one situated in front and the other in back in the space between hulls.

10. Unit according to claim 9, characterized in that spherical valves are mounted on the pipes in front and in back in order to quickly fill tanks formed by the walls of the hulls lined inside the boat by a tight bulkhead going from the upper deck to the water line.

11. Unit according to claim 1, characterized in that it further contains additional means of propulsion, consisting of a motor pump provided in each hull in back of the motors of said unit, also usable as a fire pump, while the boat remaining maneuverable.