FIELD OF THE INVENTION

The present invention concerns a boat and a propulsion device for boats according to the preamble of the independent claims 1 and 10.

The propulsion device in question is applied in the field of propulsion systems intended to be used in the nautical sector to move boats forward.

Advantageously, the propulsion device in question is suitable to be applied to boats of any size (from pleasure boats to commercial container ships) and is intended to be used both for navigation in the open sea, or on lakes or rivers, and also for maneuvers for positioning the boat.

In particular, the propulsion device is suitable to operate by interacting in optimal conditions with the boundary layer of the water flow during the forward motion of the boat, that is, as a boundary layer ingestion propulsor.

BACKGROUND OF THE INVENTION

As is known, in the field of marine propulsion, propulsion devices with propellers have been used for some time, which comprise one or more propellers driven by one or more internal combustion engines or electric motors, connected to the propellers by means of a mechanical transmission system. These known devices, although they guarantee important advantages in terms of constructive and operational simplicity, have significant limits in terms of propulsive efficiency and therefore of the energy necessary to produce a determinate thrust, connected to the open configuration of the propeller.

Furthermore, these known devices have limits with regard to production and installation costs, since, in order to guarantee adequate propulsive thrust, the propeller has to have relatively big sizes. In fact, as is known, as the thrust necessary to set the boat in motion grows, it is necessary to increase the diameter of the propeller linearly, with production and installation costs that grow more than linearly with respect to the diameter of the propeller.

In order to at least partly solve these disadvantages, naval propulsion devices are known which employ the principles of distributed electric propulsion technology.

One example of these known devices is described in CN 111547217. In accordance with this example, the naval propulsion devices comprise a plurality of propulsion units of contained sizes, identical to each other from a structural and mechanical point of view, and fixed below the hull of the boat in different zones of the hull itself. More specifically, each propulsion unit comprises a ducted type propeller and an electric motor, which makes the propeller rotate and is connected, by means of an electric transmission system, to a battery pack.

The provision of a plurality of propulsion units allows, given the same propulsive thrust obtained, to use smaller propellers, with a consequent reduction in production and installation costs. Furthermore, in order to sustain a determinate forward speed of the boat, a thrust is required that is able to compensate for the hydrodynamic resistance of the hull.

With a traditional propeller, the thrust acts on a circular surface at a certain distance from the hull. In particular, the propulsion units described in CN 111547217 consist of azimuth pods, each of which, as is known, is connected to the hull of the boat by means of a support rotatable about a vertical axis and can be driven in rotation about this horizontal axis in order to vary the direction of the propulsive thrust, in such a way as to increase the maneuvering capacity of the boat. Although they have obvious advantages in terms of maneuverability of the boat, the naval propulsion devices of the type described in the document CN 111547217 entail disadvantages from the point of view of mechanical complexity, without significantly increasing the propulsive efficiency of the boat.

WO 2014/111844 describes an outboard propulsion system equipped with a plurality of propulsors adjacent to each other and associated with the rear part of the hull of a boat, in which each propulsor comprises an electric motor with toroidal geometry that has an annular rotor that rotates inside an annular stator. Rotor and stator define a central aperture inside which the blades of the propulsor extend. With said propellers the thrust always acts on a respective circular surface at a certain distance from the hull.

PRESENTATION OF THE INVENTION

In this situation, the problem at the basis of the present invention is therefore to obviate the disadvantages demonstrated by the above known solutions, by providing a propulsion device for boats, and the corresponding boat, able to guarantee a better propulsive performance.

Another purpose of the present invention is to provide a propulsion device for boats able to guarantee reduced mechanical complexity. Another purpose of the present invention is to provide a propulsion device for boats able to guarantee a reduction in the resistance to the forward motion of the boat.

Another purpose of the present invention is to provide a propulsion device for boats able to guarantee a reduction in production and installation costs. Another purpose of the present invention is to provide a propulsion device for boats that is operationally totally efficient and reliable, in particular able to guarantee the forward motion of the boat even in the event of a propulsor breaking, thanks to the remaining propulsors of the propulsion device.

Another purpose of the present invention is to provide a propulsion device for boats able to operate even in shallow waters.

Another purpose of the present invention is to provide a propulsion device for boats which guarantees greater safety in the event of a collision with bathers.

Another purpose of the present invention is to provide a propulsion device for boats with a reduced impact on the ecosystem (in particular by reducing the risk of killing or injuring fish).

The invention is characterized in that it provides a boat equipped with a propulsion system formed by several propulsion units, or propulsors, disposed adjacent to each other in a direction substantially orthogonal to the direction of development of the boat, and disposed inside a support body that has a shape elongated transversely with respect to the surface of the hull, fixed to the lower surface of the hull, said body defining a plurality of housing seatings for each of said propulsion units. In this way, the effect is obtained of distributing the thrust on a substantially rectangular surface, created by means of an offset that follows and substantially adapts to the shape of the hull. The localization of the thrust on an almost rectangular area, and very close to the hull, allows to interact advantageously with the boundary layer, which reduces the aerodynamic drag of the hull. In this way, given the same thrust, or power delivered by the engines, since the resistance that opposes the forward motion is lower than in known solutions, the boat can reach higher forward speeds.

BRIEF DESCRIPTION OF THE DRAWINGS The technical characteristics of the invention, according to the purposes above, can be clearly ascertained from the content of the claims included below, and its advantages will become more evident in the detailed description that follows, made with reference to the attached drawings which show some purely non-limiting examples of the invention, wherein:

- fig. 1 shows a front perspective view of the propulsion device object of the present invention; - fig. 2 shows a front view of the propulsion device shown in fig. 1 ;

- fig. 3 shows a rear view of the propulsion device shown in fig. 1;

- fig. 4 shows a section view of the propulsion device shown in fig. 2 along the line IV-IV of fig. 2;

- figs. 5 and 6 show, respectively, a front view and a bottom view of a hull of a boat with the devices object of the present invention mounted thereon, in accordance with a first example embodiment;

- fig. 7 is a perspective view of the propulsion device in question, according to a different embodiment;

- figs. 8 and 9 show, in front and rear perspective views respectively, a detail of the propulsion device of fig. 7.

DETAILED DESCRIPTION OF SOME EXAMPLES OF A PREFERRED

EMBODIMENT

With reference to the attached drawings, number 1 indicates as a whole a propulsion device for boats, object of the present invention. The propulsion device 1 in question is intended to be mounted on a boat 2 in an outboard configuration, in which the propulsion device 1 is intended to be completely immersed in water.

In particular, with reference to the examples of figs. 5-6, the boat 2 comprises a hull 21 , which develops along a prevalent development axis Z and is equipped with an external surface 22 intended to be at least partly immersed in the water. Furthermore, the boat 2 can comprise at least one propulsion device 1, which is able to be driven in order to make the boat 2 advance in a direction of advance substantially parallel to the prevalent development axis Z of the hull 21. The propulsion device 1 according to the invention comprises a support body 3, which develops according to a direction of development X and is intended to be connected to an attachment zone 25 of the hull 21 of a boat 2, assuming a position with a direction of development X that is substantially orthogonal to the prevalent development axis Z of the boat 2.

Furthermore, the support body 3 is suitable to be positioned with the direction of development X substantially parallel to the external surface 22 of the hull 2 in correspondence with the attachment zone 25 of the hull 2 itself.

With reference to the example of figs. 1-4, the propulsion device 1 comprises at least one propulsor 4, which is mounted on the support body 3 and comprises an impeller 41, which is rotatably constrained to the support body 3 and is provided with an axis of rotation Y that is orthogonal to the direction of development X of the support body 3.

Furthermore, the propulsion device 1 comprises drive means, which are operatively connected to the impeller 41 of the propulsor 4 and are able to be driven in order to make the impeller 41 rotate about its own axis of rotation Y.

In this way, operationally, the propulsion device 1 is able to generate a propulsive thrust, in particular in an orthogonal direction with respect to the direction of development X of the support body 3. Advantageously, the propulsion device 1 is positioned on the hull 21 with the direction of development X substantially orthogonal to the prevalent development axis Z of the hull 21 itself, so that the axis of rotation Y of the impeller 41 is substantially parallel to the prevalent development axis Z.

In this way, the direction in which the propulsion device 1 generates the propulsive thrust is parallel to the prevalent development axis Z of the hull 2, thus increasing the overall efficiency of the boat 2.

In accordance with the idea at the basis of the present invention, the propulsion device 1 comprises several propulsors 4, which are disposed aligned side by side to each other in the direction of development X of the support body 3. This configuration of the propulsion device 1 allows to position it at a distance from the external surface 22 of the hull 21 such as to allow the propulsion device 1 itself to operate, for a substantial part thereof, also in relation to the type of boat and to the design speed, within the boundary layer of the water in cruising conditions. In more detail, in this way, the propulsion device 1 is suitable to operate in conditions of the boundary layer of the water flow during the forward movement of the boat 2, that is, as a boundary layer ingestion propulsor, achieving an increase in propulsive efficiency. The boundary layer, as is known, is a characteristic of the fluid, in this case water, and is due to the effect of the interaction of the fluid itself with a wall, in this case the hull 21 of the boat 2. In particular, the size of the boundary layer, understood as the distance between the hull 21 and the edge of the boundary layer itself along an axis that is normal to the external surface 22 of the hull 21 , strongly depends on the speed of the boat. For this reason, in order to be able to operate mainly within the boundary layer, the propulsion device 1 has to have a size that is suitably defined in the design phase in relation to the various applications, which will be relatively small compared to the size of the hull 21 of the boat 2 itself. For example, for a boat 2 about 5 meters long that moves at a cruising speed that is typical of a pleasure boat, the size of the boundary layer is in the order of 20 centimeters.

In this regard, the configuration of the present invention, which provides to dispose the propulsors 4 in the direction of development X of the support body 3, which is parallel to the external surface 22 of the hull 2, allows to dispose several propulsors 4 as close as possible to the external surface 22, allowing to easily keep, with a suitable sizing, the propulsion device 1 within the boundary layer.

Advantageously, the support body 3 of the propulsion device 1 develops mainly in the direction of development X, in particular with an elongated shape, in order to assume a substantially rectangular conformation with rounded and joined edges. Furthermore, the support body 3 comprises several seatings 31, each of which houses a corresponding propulsor 4 inside it.

It falls within the scope of the invention that not all the seatings 31 are occupied by a corresponding propulsor 4. For example, in one embodiment one or more seatings 31 can be without a corresponding propulsor 4 and be advantageously outlined in such a way as to perform the function of induced propulsion passive element.

The induced propulsion is achieved with the same principle according to which propulsion is achieved if the propulsor 4 is present inside the corresponding seating 31.

The propulsor develops about 70% of the thrust while the seating 31 which ducts the impeller 41 is responsible for about the remaining 30%.

The seatings 31 provided with an impeller 41 operate in a manner completely similar to that described above.

The seatings 31 which do not have an impeller 41, if suitably outlined, are able to exploit the same principle. This works because near a seating 31 without an impeller 41 there is another one with an impeller 41 which “triggers” the flow of water flow for both seatings 31. In more detail, each of the seatings 31 is equipped with a tubular wall 32, which develops around the axis of rotation Y of the impeller 41 of the corresponding propulsor 4. Furthermore, the tubular wall 32 develops along the axis of rotation Y in a through manner between an inlet aperture 33 and an outlet aperture 34 of the corresponding seating 31. Operatively, the impeller 41 of the propulsor 4 is capable of sucking the water inside the seating 31 through the inlet aperture 33, and is capable of expelling the same water through the outlet aperture 34.

In one embodiment, the seatings 31 are separated from each other by suitable rigid partitions 35, which guarantee that the seatings 31 are not in fluid communication with each other, thus allowing total operational independence between the different propulsors 4 of the propulsion device 1.

Without thereby departing from the scope of protection of this patent, the support body 3 can also be without dividing partitions between the seatings 31 , with possible advantages in terms of reduction of the hydrodynamic resistance. Advantageously, the impeller 41 of the propulsor 4 is equipped with a central hub 43 (aligned with the axis of rotation Y) rotatably mounted on the support structure 3, and several blades 42 fixed to the central hub 43, which is suitable to rotate about the axis of rotation Y of the propulsor 4, making the blades 42 rotate.

Advantageously, the blades 42 have a profile with an increasing chord, which preferably grows as a function of the radius of the impeller, in such a way as to promote the creation of a finite pressure jump between the fluid upstream and downstream of the propulsor 4 itself.

Preferably, each propulsor 4 constitutes a pump of the axial type (for example, single- way, multi-way, two-way counter-rotating, etc.), which allows to process relatively high volumetric flow rates in relation to the head, guaranteeing a high value of the propulsive efficiency and, consequently, a containment of consumptions. Optionally, in accordance with a particular embodiment, the propulsion device 1 can be equipped with discharge pipes located at exit of the pump in order to discharge into the air and reach a configuration of the water-jet propulsion type.

Advantageously, the propulsor 4 comprises a straightening stator blading of the fixed type, which is preferably positioned downstream of the blades 42 of the impeller 41, in particular between the blades 42 and the outlet aperture 34 of the seating 31.

In particular, the stator blading comprises several stator blades 44 disposed radially with respect to the axis of rotation Y of the impeller 41 and fixed to the tubular wall 32 of the respective seating 31. Conveniently, the stator blades 44 have a profile such as to straighten the flow at exit from the propulsor 4, so as to increase the propulsive efficiency of the propulsion device 1.

Advantageously, the stator blades 44 develop toward the axis of rotation Y from corresponding external ends, which are fixed to the tubular wall 32 of the seating 31, and corresponding internal ends, which carry fixed a hub holder 45 in which the hub 43 of the impeller 41 is rotatably mounted.

According to a different embodiment, not shown in the attached drawings, the impeller 41 can be of the hubless type. In particular, the hubless impeller has no hub and comprises a peripheral ring, which extends around the axis of rotation Y, carries the blades 42 fixed and is rotatably constrained in the seating 31 of the support body 3 in order to rotate about the axis of rotation Y.

In accordance with the particular embodiment shown in figs. 1-4, the support body 3 comprises a peripheral wall 39, in the shape of a ring that is elongated according to the direction of development X, which is provided with an external surface 36 and an internal surface 40, which partly defines the tubular walls 32 of the seatings 31 of the support body 3.

In particular embodiments, the support body 3 can be suitably outlined and sized to perform a load-bearing function. This aspect determines the advantage that a single element performs both the propulsive thrust function and also the hydrodynamic lift function.

In particular, the internal surface 40 of the peripheral wall 39 defines an internal compartment, which is divided by the partitions 35 into the seatings 31 in which the corresponding propulsors 4 are housed.

In other embodiments, the peripheral wall 39, or part of it, is made of, or coated with a layer of, deformable material, for example a rubber, an elastomer in general or in any case a soft material. This solution allows to make the support body 3 adhere more precisely to the external surface of the hull, preventing the flow of water between the hull 21 and the support body 3 and facilitating the housing of several propulsors 4 in the respective seatings 31 of the support body 3. Furthermore, since the support body 3 assumes a conformation which at least partly adapts to the lower part of the hull, the propulsive efficiency is also improved. Preferably, the propulsion device 1 comprises a first connection element 6 and a second connection element 7, both fixed to the support body 3.

In more detail, the second connection element 7 of the propulsion device 1 is suitable to couple in a relation of retention to the first connection element 6 of another propulsion device 1, in order to be able to connect to each other two or more propulsion devices 1 in an adjacent position (as shown in the examples of figs. 5-6).

In this way, it is possible to create a modular structure of several propulsion devices connected to each other by means of the respective first and second connection elements 6, 7, in order to be able to adapt, in a flexible manner, the conformation of the modular structure to the required thrust and to the characteristics of the boat 2.

Advantageously, the support body 3 of the propulsion device 1 develops in the direction of development X between a first end 37, in correspondence with which the first connection element 6 is positioned, and an opposite second end 38, in correspondence with which the second connection element 7 is positioned.

Preferably, the first connection element 6 comprises a coupling body 61, and the second connection element 7 comprises a coupling seating 71, which has a shape corresponding to the coupling body 61, so that the latter is suitable to be inserted in a same-shape relation inside the coupling seating 71.

Advantageously, the first and second connection elements 6, 7 are disposed on the external surface 36 of the peripheral wall 39 of the support body 3.

More in detail, the coupling body 61 develops projecting from the external surface 36 of the peripheral wall 39. Furthermore, the second connection element 7 preferably comprises two retention pins 72, which in turn develop projecting from the perimeter surface 36 of the support body 3 and define the coupling seating 71 between them.

Advantageously, the propulsion devices 1 in question are intended to be installed on the boat in a distributed configuration in order to form a distributed propulsion system.

This distributed configuration allows, with the same propulsive thrust generated, to keep the sizes of the propulsors 4 (and in particular the diameter of their impellers 41) small, promoting the allocation of the propulsion device 1 within the boundary layer.

Obviously, the propulsion devices 1 can be disposed in different specific positions, as a function of the particular type of application.

For example, the propulsion devices 1 can be connected to the hull 21 in adjacent attachment zones 25, with the propulsion devices 1 connected by means of the first connection elements 6 and the second connection elements 7 (as shown in figs. 4 and 5). According to another configuration example, as shown in figs. 7 and 8, the propulsion devices 1 can be connected to the hull 21 in distanced attachment zones 25, without the propulsion devices 1 being connected to each other by means of the connection elements 6, 7. Advantageously, the propulsion devices 1 can be disposed in different positions on the external surface 22 of the hull 21 , for example in a central zone of the latter’s bottom, in particular with the direction of development X of the support body 3 substantially horizontal (as in the examples of figs. 5 and 6), or also in a lateral zone of the hull immersed in water. Conveniently, in accordance with some embodiments not shown, the propulsion device 1 can be mounted on a support bar (connected to the hull of the boat), on a load bearing wing of the boat or on any fixed or mobile component connected to the hull. Preferably, the drive means of the propulsion device 1 comprise at least one electric motor (not shown in the attached drawings) operatively connected to the impellers 41 of the propulsors 4 to drive them in rotation.

In particular, the propulsion means comprise several electric motors, each of which is mounted on the support body 3 and is connected to a corresponding impeller 41, in order to be able to command each propulsor 4 independently.

Preferably, the propulsion device 1 can comprise an electronic control unit (not shown in the attached drawings), which is electrically connected to each of the electric motors and is suitable to control each one of them independently of the others.

More in detail, when the boat 2 is equipped with a plurality of propulsion devices 1 connected to each other by means of the connection elements 6, 7 described above, the latter can comprise electrical connections. These electrical connections allow the passage, in addition to electrical energy, also of information, data and commands between the various propulsion devices 1 and the electronic control unit. In this way, it is possible to create a single control network between all the propulsion devices 1 that the boat 2 is equipped with.

Advantageously, the electric motors are mounted on the support body 3, in particular inside the seating 31 of the corresponding propulsor.

Each electric motor is powered, through suitable electrical connections, by a source of electrical energy that is located inside the hull 21 of the boat 2.

In this way, in particular, it is possible to set the propulsors 4 in motion by means of simple electrical connections between the latter and the electrical energy generator, without the need for mechanical transmissions connected to the propulsors, with a consequent significant structural simplification of the boat 2.

Advantageously, the source of energy can be an electric generator of a known type, for example an internal combustion generator, or fuel cells, which are suitably recharged before the boat leaves the port.

In accordance with a possible embodiment, the electric motor is positioned inside the central hub 43 of the impeller 41. In accordance with a different embodiment, the electric motor can be disposed in a rim-driven configuration (in particular with impellers 41 of the hubless type).

Advantageously, a speed reduction unit can be positioned between the blading and the motor, which has the purpose of transmitting the torque of the motor allowing the two components to work at different rotation speeds. Normally, the optimum rotation speed of the motor differs from that of the propeller for technological reasons. By making each component work in the maximum efficiency zone, the efficiency of the system is maximized.

In addition, the reduction unit can have a variable reduction ratio, whether this is achieved with mechanical solutions or solutions that exploit electric and/or magnetic fields (magnetic reducers), active or passive (by means of permanent magnets). Magnetic reducers have the advantage of not having mechanical contact between the rotating part that is integral with the motor and the one that is integral with the blading; torque is transmitted by means of magnetic or electromagnetic forces. Wear of the reduction unit is minimized; moreover, the component is perfectly sealed and watertight and does not require dynamic packings which are subject to heavy wear. The “magnetic” solution reduces the mechanical complexity of the component.

Advantageously, the control unit is in data communication with the propulsors 4 (in particular with their electric motors), advantageously through the same cabling of the electrical connections, in order to send commands to or receive signals (relating for example to diagnostic information on efficiency, safety, etc.) from the same propulsors 4.

Preferably, the control unit is equipped with a communication module suitable to communicate with a remote unit (for example, a computer, a smartphone, etc.) accessible to a user. In this way, the control unit can send communication signals to the remote unit containing the information received relating to the propulsors (concerning efficiency, operation, safety systems, etc.).

Advantageously, the distributed configuration of the propulsors 4, controlled independently by the control unit, allows the latter to improve the maneuverability of the boat (for example during docking maneuvers or in confined spaces), and also to guarantee an operational redundancy of the distributed propulsion system that increases its safety.

Advantageously, the operational independence of the propulsors 4 allows to always operate them in optimal conditions. In fact, since the propulsor 4 has maximum efficiency in a very specific operating point, at reduced speeds, instead of making all the propulsors 4 operate at the same rotation speed, it is possible to turn some propulsors 4 off and keep others tuned on operating at maximum efficiency.

Conveniently, the independent management of the rotation speed for each propulsor 4 allows to significantly minimize consumption, in particular compared to traditional propeller systems.

Furthermore, the independent management of the drive of each propulsor 4 also allows to drive one or more propulsors 4 in the opposite direction with respect to one or more of the others, so as to generate a rotational motion of the boat according to determinate angles and axes of rotation, which are advantageously orthogonal to the axis Z and to the axis X.

Advantageously, in accordance with the particular embodiment shown in fig. 7, the support body 3 comprises several distinct modular bodies 50, disposed side by side to each other in the direction of development X of the support body 3 and each one connected to the next by means of attachment means 51. Each modular body 50 carries, mounted thereon, a corresponding propulsor 4, so that the number of propulsors 4 of the propulsion device 1 can be determined simply by bringing a determinate number of modular bodies 50 close to each other.

Preferably, each modular body 50 comprises the corresponding seating 31 in which the corresponding propulsor 4 is housed.

In particular, with reference to figs. 8 and 9, each modular body 50 is equipped with a first lateral wall 52 and a second lateral wall 53 disposed opposite each other according to the direction of development X and between which, advantageously, the corresponding seating 31 extends.

In particular, the first lateral wall 52 of each modular body 50 is disposed side by side with the second lateral wall 53 of the adjacent modular body 50, so that the first and second lateral walls 52, 53, which are side by side, define the corresponding partition 35 that separates the seatings 31 of the two adjacent modular bodies 50.

Advantageously, the attachment means 51 rigidly fix the modular bodies 50 of the support body 3 to each other, in particular without needing to make any modification to the modular bodies 50.

For example, the attachment means 51 comprise a fixing bar 54 inserted in through apertures 55, which are created on the modular bodies 50 parallel to the direction of development X of the support body 3 and are disposed aligned to each other in the direction of development X.

Conveniently, the first and second lateral walls 52, 53 of each modular body 50 are equipped with homologous coupling elements 56’, 56” (in the form, for example, of recesses on one of the lateral walls and corresponding recesses on the other lateral wall), in such a way that the first lateral wall 52 of each modular body 50 is engaged, for example by means of male-female coupling, to the second lateral wall 53 of the adjacent modular body 50 by means of the coupling elements 56’, 56”.

Conveniently, the modular bodies 50 are provided with corresponding passage channels 57 connected to each other (for example aligned with each other according to the direction of development X) and able to house electrical components of the propulsion device 1 (such as data and power transmission lines).