Technical field

The invention concerns a propulsion device, according to the preamble of patent claim 1.

Background

Vessels are used for different purposes such as transporting of personal and transporting of goods. For different reasons such as environmental aspects, operating economy and flexibility regarding alternative fuels there is a need for flexible propulsion of vessels.

A known solution is shown in EP 1 250 256 B 1 where so called diesel electric operation is used in order to operate a vessel. This means that a combustion engine is rotating a generator producing a current, which is used to operate an electric motor placed in conjunction to the propeller, either inside or outside the hull of the vessel.

However, known systems, such as for example the one shown in the patent document above, comprises several components that make them expensive and complicated. In the above described system the efficiency is also relatively low since losses take place both in the combustion engine, in the generator and in the electric motor.

Thus, there is a need for propulsion systems with higher flexibility and higher efficiency.

Summary of the invention

The purpose with the present invention is to provide a propulsion device that satisfies the requests above. This will be achieved by a propulsion device according to the independent claim. The claimed propulsion device is intended for propulsion of vessels in water and comprises: a connecting unit; an electric motor/ generator connected to the electric system of the vessel and comprising a stator and a rotor contained in the connecting unit; and a propeller with at least two blades mounted on a propeller hub placed in conjunction to the connecting unit and rotationally connected to said rotor; whereby said device is intended to be placed with the side of the connecting unit facing away from the propeller against the side of the stern part of the vessel facing the water, and is caracterised in that a shaft extends from the combustion engine through the stern part of the vessel and further trough the connecting unit to the hub for operation of the propeller, and in that the shaft from the combustion engine also is connected to the rotor in the electric motor/generator.

The device as specified above will enable propulsion either by the com- bustion engine or the electric motor, alternatively a combination of these two alternatives during certain periods when high power is required. This will result in higher flexibility since the operator might choose power source depending on the amount of fuel/ electricity available and that the size of the engine might be reduced since the electric motor could be used as complement to the combustion engine if higher power for some reason is desirable.

Furthermore, the electric motor/ generator is placed on the outside of the hull of the vessel in such a way that the stator, which is placed near the periphery of the connecting unit, will be surrounded by the surrounding water. Thereby the surrounding water acts as an efficient cooler of the electric motor/ generator, which is very favourable to en- sure reliable operation and high efficiency in the electric motor/generator.

A further advantage with the device according to the present invention is that when the propeller, and thereby also the rotor, is operated by the combustion engine, the generator will generate electric current, which either could be used directly in a thereto connected current consuming function, or be stored in appropriate storing means to be used at a later occasion.

In an embodiment of the invention the electric motor/ generator is configured to act as an electric motor in order to rotate the propeller together with the combustion engine to get maximum supply of power to the propeller. This embodiment of the invention results in maximum power of propulsion to be used during periods when the batteries of the vessel contain sufficient electricity. Direct powering of the propeller with the shaft from the combustion engine also results in a high efficiency since no conversion of the rotational movement from the combustion engine takes place in the generator.

In another embodiment of the propulsion device is configured to act as a generator in order to generate current to the electric system and the battery of the vessel when the combustion engine via the shaft rotates the propeller and the rotor. The electric motor/ generator is in this em- bodiment used as generator, which means that the generator, normally placed in conjunction to the combustion engine and operated by the combustion engine, could be eliminated, thus simplifying installation and maintenance since the number of parts is reduced.

In another embodiment of the propulsion device the shaft has a disengagement clutch so that the propulsion could be achieved by the electric motor/ generator configured to act as electric motor without influ- ence by the combustion engine. The disengagement clutch facilitates and makes the propulsion with only the electric motor more efficient since the majority of the shaft and the components connected thereto not have to be rotated by the electric motor.

In another embodiment of the propulsion device the stator is placed mainly parallel with the surface of the stern part of the vessel and the shaft is passing through the stern part and the centre of the stator.

In another embodiment of the propulsion device the propeller is a surface cutting propeller and/ or a propeller with adjustable blades. Surface cutting propellers and/ or propellers with adjustable blades are during certain circumstances very efficient and flexible since they could be adapted to present circumstances and use, which make them appropri- ate to be used in combination with the propulsion device according to the present application.

In another embodiment of the propulsion device the diameter of the hub close to the connecting unit mainly corresponds to the diameter of the connecting unit. This configuration results in a more advantageously water flow to the propeller, which improves the efficiency of the propulsion device.

In another embodiment of the propulsion device the diameter of the connecting unit mainly corresponds to the width of the stern part of the vessel where the connecting unit is intended to be placed. This configuration results in a more advantageously water flow to the propeller, which improves the efficiency of the propulsion device further.

The propulsion device according to the definition in the patent claims might be used for different types of vessels. Vessels that are very suitable to be equipped with the propulsion device according to the descrip- tion above are catamaran or trimaran. A propulsion device is placed at the stern part of each of the hulls.

Short description of drawing The invention is explained in more detail below with references to figure 1 that shows a cross section along the longitudinal axis of the shaft of an embodiment of the claimed propulsion device.

Detailed description of the invention The present invention is intended to be used for propulsion of different types of vessels in water. The propulsion device is placed on a stern part of the hull of the vessel or on the stern part of a step on the bottom of the hull if the hull has one or a plurality of steps, in order to improve the propulsion conditions during certain conditions. The hull might be a single hull, a hull of a catamaran or a hull of a trimaran and provided with at least one propulsion device according to the invention. If the hull is of catamaran or trimaran type the propulsion device is preferably placed on the stern part of each hull or step.

In figure 1 an embodiment of a propulsion device 10 according to the present invention is illustrated. The propulsion device 10 comprises a connecting unit 11 with cylindrical shape. In the connecting unit 11 the stator 12 of the electric motor/ generator is arranged around the inside of the periphery of the connecting unit 11. The diameter of the stator 12 corresponds to the diameter of the connecting unit 11 so that the stator 12 will be located as close as possible to the surrounding water in order to get maximum cooling from the surrounding water. The length of the stator 12 depends on the desired power of the electric motor/ generator and the connecting unit is adapted to the chosen length so that it corre- sponds to the dimensions of the stator 12. In connection to the connecting unit a propeller hub 13 is arranged. Around the periphery of the propeller hub at least two propeller blades are arranged for propulsion of the vessel when the propeller is rotated in the water. The rear part 21 of the propeller hub is in this embodiment configured as a part of a sphere but other shapes might also exist as long as sufficient water is ensured to flow around the propeller.

The outer diameter of the propeller hub 13 at the connection to the connecting unit is substantially the same, or slightly smaller, than the outer diameter of the connecting unit in order to ensure favourable flow conditions for the water floating to and around the propeller, which is important in order to get sufficient efficiency. A slightly narrower part 14 of the propeller hub 13 extends forward and into the connecting unit 11. On this narrower part 14 the rotor 15 of the electric motor/generator is placed in order to be aligned with the stator 12 inside of the periphery of the connecting unit 11. From the inner end of the narrower part 14 an inclined section extends 16 inclined inwardly and outwardly against the outer side of the connecting unit where it is connected to a drive shaft 17 from a not shown combustion engine or a connecting part 17 that is connected to the drive shaft at an appropriate place somewhere along the drive shaft to the combustion engine. Around the drive shaft or the connecting part 17 bearings 19 are arranged to steer the drive shaft 17, or the connecting part 17, and in its extension the propeller hub in relation to the connecting unit 11. The drive shaft or the connecting part 17 extends through the stern part of the vessel, not shown, and abutted against the front edge 18 of the connecting unit is the stern part of the vessel, against which it is attached with appropriate bracing, for example screw joint, so that the connecting unit 11 with associated stator 12 is held in place. The propulsion device is also equipped with, not shown, gaskets placed on appropriate places in order to prevent penetration of water into the con- necting unit, the propeller hub and the vessel at the bushing for the drive shaft or the connecting part 17, and, not shown, connecting de- vice in order to connect the electric motor/ generator to the electric system of the vessel and to control the electric motor/ generator.

The propeller blades might be articulated mounted in the propeller hub and a device to articulate the blades in relation to the propeller hub mounted in the propeller hub. Articulated blades makes it possible to optimise the angle of the blade in relation to specific operating conditions at a certain moment, which might be used to reduce fuel consumption or to accelerate the velocity or the possibility to decelerate or reverse the vessel.

The invention is described by some exemplified embodiments, but the invention is not limited to these embodiments since it is defined by the appended claims.