TECHNICAL FIELD

The present invention relates to a marine drive system in which the height position of the propeller can be adjusted. The drive system is positioned in a housing mounted inside the hull of a marine vessel, and the propeller can be lowered from a parking position to a drive position. The drive system comprises a drive motor and a marine propulsion system provided with at least one propeller.

BACKGROUND ART

Electric propulsion of vehicles is getting more and more common in order to replace combustible fuels. Slowly, electrical propulsion of marine vehicles are also gaining more interest. Electrical drive systems for slower boats, such as gigs or sailboats, are relatively energy efficient when the boat travels at low speeds. A further advantage for sailboats is that they normally do not need the motor, and that the motor is mostly used in emergencies and when docking. In such cases, an electric drive may be plausible.

Smaller sailboats are often provided with an outboard combustion motor that is used to drive the sailboat when there is no wind or when docking. Larger sailboats have an inboard combustion engine that is either provided with a straight axle that drives a propeller arranged at the rear of the sailboat, or is provided with a so called saildrive mounted to the hull of the sailboat. The saildrive may be provided with a fixed propeller or a foldable propeller. A foldable propeller will induce less drag when sailing, but is not suitable for charging a battery when sailing. A fixed propeller induce more drag when sailing but is more suited for charging a battery when sailing. When charging a battery, the propeller is connected to a generator that is powered by the propeller which will induce some drag. When not charging, the propeller is disconnected from the generator and rotates more or less freely, but will still induce a small amount of drag. WO 2019160509 and US 2014022097 show examples of a fixed propeller that can be retracted into the hull of a boat. In a retracted position, drag is minimized and the propeller is less vulnerable.

Even if these systems functions well for their intended use, there is room for an improved drive system for a marine vessel.

DISCLOSURE OF INVENTION

An object of the invention is therefore to provide an improved drive system for a marine vessel. A further object of the invention is to provide a marine vessel comprising such a drive system.

The solution to the problem according to the invention is defined by the features of the main claims. The other claims contain advantageous further developments of the drive system.

In a drive system for a marine vessel comprising a first housing fixed to an opening inside a hull of the marine vessel, and a drive unit arranged inside the first housing, where the drive unit comprises a second housing comprising a drive motor and a marine propulsion system attached to the second housing, where the marine propulsion system comprises a leg and a hub provided with at least one propeller, where the drive system comprises an adjustment mechanism arranged to adjust the position of the drive unit in the first housing, where the drive system is provided with a parking position in which the marine propulsion system is positioned inside the first housing and a drive position in which the marine propulsion system is positioned outside of the first housing, the object of the invention is achieved in that the first housing and the second housing are non- cylindrical.

By this first embodiment of the drive system for a marine vessel, the height position of the propeller can be adjusted. In a parking position, the complete drive unit is positioned within the first housing and thus within the hull of the marine vessel, such that the propeller is completely concealed. In this position, the marine propulsion system and the propeller will not induce any drag which is of advantage when sailing. A further advantage is that the marine propulsion system is less prone to be subjected to biofouling. By filling the space with a gas, such as air or exhaust gas, the biofouling problem is further minimized. In a drive position, the lower side of the second housing of the drive unit is aligned with the hull, and the marine propulsion system extends completely into the water. This position is used when the boat is driven by the motor, and can also be used when the battery needs to be charged when sailing. The drive motor is in one example an electric drive motor, and in another example a combustion engine.

The drive unit is rotationally fixed in the first housing, such that it cannot rotate and such that the propeller is directed in a fixed orientation. This is achieved with the non-cylindrical shape of the first housing and the second housing. The shape of the first housing and the second housing does not allow a rotation of the second housing inside the first housing. In this way, there is no need for any anti-rotational means arranged between the first housing and the second housing. The shape of the first housing and the second housing may e.g. be oval, elliptic or the shape may be a parallelogram of some sort. The drive unit may be provided with a single propeller or with two propellers that rotate in different directions.

The position of the drive unit may be controlled manually by a user. A user may e.g. retract the drive unit in shallow waters, or may control the charging of the battery by adjusting the height position of the propeller. A user may further retract the drive unit when the boat is parked. The height position of the drive unit may also be controlled automatically by an ECU. In one example, the drive unit is lowered when the drive motor is engaged, e.g. when a user selects the drive mode of the boat, and the drive unit is retracted when the drive mode is deselected. The ECU may further control the height position of the propeller in dependency of charge requirements for the battery, depending on the speed of the boat or depending on the water depth.

The height position of the drive unit in the first housing is controlled by an adjustment mechanism that extends and retracts the drive unit out of and into the first housing. The position may e.g. be set with a linear actuator of some kind, such as a hydraulic cylinder or an electric linear actuator. The adjustment mechanism may also comprise a locking means that fixates the drive unit in the selected position. The locking means may e.g. be a selflocking gear of an electric motor that is used to position the drive unit in the first housing.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described in greater detail in the following, with reference to the attached drawings, in which

Fig. 1 shows a schematic marine vessel provided with a drive system according to the invention,

Fig. 2 shows the drive unit in the parking position,

Fig. 3 shows the drive unit in the drive position, and

Fig. 4a-e shows different examples of the shape of the first housing and the second housing.

MODES FOR CARRYING OUT THE INVENTION

The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims.

Fig. 1 shows a schematic marine vessel 30 provided with a drive system 1 for propelling the marine vessel or for generating electric energy. The drive system 1 comprises a first housing 2 that is mounted to an opening 32 in the hull 31 of the marine vessel 30. The opening 16 of the first housing 2 is mounted flush with the hull such that the first housing 2 does not extend out of the hull. The first housing is fixedly mounted to the hull. The opening 16 is provided with a flange 17 extending inwards from the inner side of the first housing. The flange 17 may be straight or angled. The vessel is also provided with a gas pressure source 14 that can supply pressurized gas, such as air or another suitable gas.

A drive unit 3 is arranged inside the first housing 2. The drive unit 3 comprises a second housing 4 that comprises a drive motor 5 that drives a drive shaft to the propeller 9. The drive shaft may be driven directly by the motor and may be directly attached to the motor, or may be driven through a transmission of some type. The drive unit may also comprise an electronic control unit (ECU) 12 used to control the motor. The second housing 4 is arranged to slide inside the first housing 2 such that the height position of the drive unit in the first housing 2 can be adjusted. The second housing is in on example watertight.

The drive motor 5 is in one example an electric motor powered by a battery 13. One advantage of using an electric drive motor is that the motor can also be used to charge the battery when the drive system is installed in a sailboat. The drive motor may also be an internal combustion engine, either fuelled by petrol or diesel. In the shown example, an electric motor is used as the drive motor.

A marine vessel 30 may be provided with one or more drive systems 1 . A smaller regular sailboat may e.g. be provided with a single drive system that replaces a regular saildrive installation, where the sailboat is steered with a rudder. Larger sailboats may also be provided with two or more drive systems. The drive system is also suitable for motorboats. A smaller motorboat may e.g. be provided with a single drive system where the boat is steered with a rubber. A larger motorboat may be provided with two or more drive systems, where the steering may be performed by driving the propellers with different rotational speeds.

The edge 18 of the lower side 15 of the second housing 4 is provided with a taper of some kind, arranged to cooperate with the flange 17 of the first housing 2. The flange 17 can function as an end stop for the second housing 4 of the drive unit 3, and can also centre the second housing when it is the drive position. The shape of the edge 18 and the flange 17 is preferably the same, such that they can cooperate with each other with a form fit. The shape of the flange may be straight or may be tapered with an angle relative to the vertical axis 19 of the drive unit. In one example, the flange is tapered with a 45 degrees angle, and the edge 18 is consequently provided with a 45 degrees angle. Other angles or shapes are also possible. The flange and/or the edge may also be provided with a seal of some type.

A marine propulsion system 6 is attached to the lower side 15 of the second housing 4. The marine propulsion system 6 comprises a leg 7 and a hub 8 and may be provided with a single propeller 9 or with two counter-rotating propellers 9, depending on the drive installation. The drive shaft of the drive unit extends through the leg and the hub is provided with a bevel gear which transfers the rotation of the motor to the propeller. In a double propeller installation, concentric drive shafts are used.

The position of the drive unit 3 is adjusted with an adjustment mechanism 10 which is arranged at the upper part of the drive unit. The adjustment mechanism may e.g. comprises one or more linear actuators, such as hydraulic cylinders or electric linear actuators. The adjustment mechanism may also comprise a threaded pin running in a threaded nut attached to the second housing.

The drive unit 1 can be set in different positions. One position is a parking position 20, shown in Fig. 2, in which the drive unit 1 and the marine propulsion system 6 is positioned completely inside the first housing 2. In this position, the complete drive unit is positioned within the first housing 2 and thus within the hull of the marine vessel, such that the propeller is completely concealed. In this position, the marine propulsion system and the propeller will not induce any drag which is of advantage when sailing. This may also be an advantage when the vessel is transported. A further advantage is that the marine propulsion system is less prone to be subjected to biofouling. By filling the space with a gas, such as air or exhaust gas, the biofouling problem is further minimized.

The drive unit 1 is also provided with a drive position 21 , shown in Fig. 3, in which the lower side 15 of the cylinder-shaped part 4 of the drive unit 1 is aligned with the hull 31 of the vessel 30. In the drive position, the leg 7 extends completely into the water. This position resembles a fixed, regular installation of a saildrive in a sailboat. This position is used when the boat is driven by the drive motor, and can also be used when the battery 13 needs to be charged when sailing.

The position of the drive unit 1 in the first housing 2 may be controlled manually by a user, or may be automatically controlled. A user may e.g. retract the drive unit to the parking position when the boat is parked, and may select the drive position when driving the vessel with the drive motor.

The position of the drive unit may also be controlled automatically by an ECU 12. In one example, the drive unit is lowered when the electric drive motor is engaged, e.g. when a user selects the drive mode of the boat, and the drive unit is retracted when the drive mode is deselected. The ECU may further control the position of the propeller in dependency of charge requirements for the battery 13, depending on the speed of the boat or depending on the water depth.

The drive unit 3 is rotationally fixed in the first housing 2, such that it cannot rotate and such that the propeller is directed in a fixed orientation. By providing the first housing and the second housing with a non-cylindrical shape, the second housing cannot rotate in the first housing. In this way, there is no need for any anti-rotation devices between the first housing and the second housing, which simplifies the design of the drive system. There is also no risk that the second housing will start to rotate if an anti-rotation device would break. Figs. 4a-e shows different examples of suitable shapes of the first housing 2 and the second housing 4. In Fig. 4a, the first housing and the second housing are oval. In Fig. 4b, the first housing 2 and the second housing 4 are provided with an elliptical shape. The first housing and the second housing may also be provided with a parallelogram shape. Fig. 4c shows a rectangular shape and Fig. 4d shows a rhombical shape. The first housing and the second housing may also have a prismatic shape as shown in Fig. 4e. Other shapes are also possible, such as a semi-circular shape, a teardrop shape, a keyhole shape, etc. If a parallelogram shape or a prismatic shape with straight sides is used, it is of advantage to provide the comers between the straight sides with a radius. When the drive unit is positioned in the drive position, this will resemble a regular saildrive installation of a sailboat that is used when the vessel is steered with a rudder.

The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims.

REFERENCE SIGNS

1 : Drive system

2: First housing

3: Drive unit

4: Second housing

5: Drive motor

6: Marine propulsion system

7: Leg

8: Hub

9: Propeller

10: Adjustment mechanism

11 : Centre axis

12: Electronic control unit

13: Battery

14: Gas pressure source

15: Lower side

16: Opening

17: Flange

18: Edge

19: Vertical axis

20: Parking position

21 : Drive position

30: Marine vessel

31 : Hull

32: Opening