Technical Field:

The invention relates to a marine operation device used for regulating the course of a marine vessel. The device comprises a thruster unit and has a set of rotatable symmetrically wing-shaped blades with synchronised adjustable pitch which can be regulated to produce a transverse lift to port or starboard side at the same rotational direction.

Background art: A thruster mounted in a frame for attaching to a ship's hull is described in the patents EP 1876094 A2 and WO 2012074465 A1 which both describe a set of rotating blades mounted in a rotatable ring inserted in a frame which is attached to a ship in order to produce a transverse lift.

Bow and stern thrusters are primarily used for manoeuvring a ship at low speed and especially for docking manoeuvres. However for primary regulation of the ship's course the traditional rudder is used. When the rudder blade is turned it produces a lift which pulls the stern in the desired direction. The size of a rudder is relatively small compared to the size of a ship, and when the rudder is turned the course of the ship changes quite slowly. Furthermore when the ship is going slowly through the water, the effect of the rudder is very small. In order to make the rudder more effective it is therefore placed behind the propellers which increase the flow of water across the rudder blade, thus increasing the lift and the effect of the rudder.

However, the disadvantage of placing the rudder in the propeller stream is that part of the propulsion energy is lost due to the resistance of the rudder.

B TIT TE HEET RULE 26 Summary of the invention:

It is the object of the invention to provide a steering system for primary regulation of the course of a marine vessel.

This is achieved by an operational device comprising a set of rotatable blades with adjustable pitch mounted on a wheel consisting of an outer ring and a hub which is connected by shafts onto which the blades are mounted. The wheel, with the blades of which are mounted rotatable around a central shaft, is transversally supported by forks that are mounted onto the frame. The frame is mounted on the hull with a top which is specially formed to fit the hull of the ship.

The steering system is characterised by the adjustable pitch of the rotatable blades around their longitudinal axes combined with the constant rotational direction of the steering system. With a constant rotational direction and blades that can be turned from side to side, the steering lift produced by the system can quickly be changed from side to side, enabling the system to be used for regulating the course of a marine vessel without being dependent on the increased water flow behind the propellers.

The steering system can be used on any marine vessel with a fixed double propeller arrangement where the steering system can be mounted in the centre line between the two propellers.

The advantages of the steering system compared with a traditional rudder arrangement are:

- the steering system can produce a lift when the vessel's speed through the water is very low. - the rotational direction of the blades is unchanged when the lift is changed from side to side since this is determined by the angle of the blades.

- the steering system can be mounted independently of the vessel's propellers.

SUBSTITUTE SHEET RULE 26 - the resistance from the rudders placed in the propeller flow can be eliminated when the rudders are replaced by a rotational steering system.

Brief description of the drawings:

The above objects, features and advantages of the invention will be fully appreciated by reference to the following illustrative and non-limiting detailed description where:

Fig.1 shows the steering system with the rotatable blades turned 10 degrees and where the sailing direction is towards the right and the rotational direction of the blades is clockwise. Fig.2 shows the steering system with the blades in their neutral position.

Fig.3 shows the main parts of the system and the order of assembly.

Detailed description of the embodiments of the description:

As shown in Fig.1 and 2, the blades (1) are mounted on a wheel comprising an outer ring (2) and a hub (3) connected by shafts (4). The shafts are only visible on Fig.3 and are only indicated in Fig.1 and 2 with a dotted line as they are hidden by the blades. The wheel (2, 3, 4) with the blades (1) is mounted in the frame (7) and rotates around the centre shaft (5) which is supported by a fork (6) mounted on the frame (7). The frame is mounted on the hull of the ship with a top (8) specially built to fit the shape of the hull. The angle of the blades can be regulated through the hub using hydraulic pressure, and the rotation of the wheel can be driven by a gearwheel or a similar mechanical connection acting on the outer ring through the top (8).

The blades are shaped as symmetrical wing shaped profiles and are balanced with their centroid behind the mounting shaft in order for the blades to return to their neutral position when the regulation of the pitch is neutralised.

SUBSTITUTE SHEET RULE 26 As shown in Fig.3 the system can be built so it can be assembled in order from one side.

In order to achieve the necessary rotational rigidity of the wheel (2, 3, 4) the shafts are firmly fixed in to both the hub and the outer ring. Another option would be to cast the wheel (2, 3, 4) in one piece.

The blades are made in two parts and are mounted rotatable around the shafts (4).

The wheel and the blades are mounted in the frame (7) rotatable around the horizontal centre shaft (5) which is supported on each side by the forks (6) which are mounted on the frame (7).

The frame (7) is mounted to the top part (8) which is specially made to fit the shape of the hull.

The wheel (2, 3, 4) is secured in the frame (7) by a closing ring (9).

The assembled steering system is mounted on the ship's hull with bolts to allow easy dismantling.

SUBSTITUTE SHEET RULE 26