EP2593356B1

EP2593356B1 - A propulsion unit for a marine vessel and a marine vessel having a propulsion unit

Info

Publication number: EP2593356B1
Application number: EP11807145.5A
Authority: EP
Inventors: Gunnar Styrud; Per Nahnfeldt
Original assignee: Kongsberg Maritime Sweden AB
Current assignee: Kongsberg Maritime Sweden AB
Priority date: 2010-07-12
Filing date: 2011-06-22
Publication date: 2021-03-24
Anticipated expiration: 2031-06-22
Also published as: WO2012008901A1; CN103097238B; EP2593356A4; RU2013103749A; EP2593356A1; CN103097238A; RU2584038C2

Description

FIELD OF THE INVENTION

The present invention relates to a propulsion unit for a marine vessel that is intended to operate in icy waters and which has a propeller arranged to act on ice in the water to cut the ice. The invention also relates to a marine vessel intended to operate in icy waters and which has a propulsion unit arranged to be able to act on ice to cut the ice.

BACKGROUND OF THE INVENTION

Some marine vessels use a kind of propulsion unit that is known as an azimuthing thruster (sometimes also referred to as azimuth thruster). An azimuthing thruster comprises a nacelle or capsule which is arranged as a separate unit attached to the outer part of the hull. At one end of the nacelle or capsule, a propeller is attached. The motor for driving the propeller may be placed inside the nacelle/capsule or inside the hull. When the motor is placed inside the nacelle/capsule, the motor is usually an electrical motor and such an azimuthing thruster with an electrical motor inside the nacelle is usually called a pod. The power for the electrical motor may in turn come from an inboard engine, usually a diesel or gas turbine. When the motor is placed inside the hull, the motor is often a diesel or diesel-electric motor and power may be transmitted to the propeller through a mechanical transmission. Depending on the shaft arrangement, the transmission may be an L-drive or a Z-drive. In an L-drive, there is a vertical input shaft and a horizontal output shaft. In a Z-drive, there is a horizontal input shaft, a vertical shaft and a horizontal output shaft with two right-angle gears. An azimuthing thruster is typically connected to the hull in such a way that it can be rotated in any horizontal direction. Thereby, thruster or thrusters can be used for maneuvering such that a rudder is no longer necessary. Azimuthing thrusters can actually give ships a better maneuverability than a system that uses a fixed propeller and a rudder.
Many marine vessels must be able to operate in icy waters. They must therefore be able to make a path through the ice. Marine vessels having azimuthing thrusters (for example pods) may be used in icy waters and it has been suggested in for example US 5996520 that an icebreaker may be provided with steerable propulsion mechanisms. In US patent 4198917 , it has also been suggested that a screw may be used to break ice that may block the path of the marine vessel.
Furthermore, it has also been suggested that azimuthing thrusters (for example pods) may be used as ice breaking devices. When azimuthing thrusters are used for icebreaking, the thruster(s) is/are turned such that the propeller faces the ice. The propeller is then used as a cutting tool to cut the ice. A problem in connection with this is that the azimuthing thruster may be subjected to very high counter-forces in the horizontal plane.
In CA 2025507 , a device has been suggested which comprises a nozzle inside which a propeller is arranged. In front of the propeller, a front piece acting as an ice crusher has been arranged. The front piece in that device serves only to protect the propeller and the propeller is not capable of acting on the ice to cut through an ice sheet or to cut an ice block since the propeller is arranged inside the nozzle and the front piece actively prevents ice blocks from reaching the propeller altogether.
US2010/0162934 discloses a method for improving the ice-breaking properties of a water craft by using an oblique aft end that is capable of breaking ice and allowing the movement of the water craft against the ice. The water craft then bores into the ice with its propeller ahead. A considerable drawback with this construction, however, is the high load on the propeller and its hub, and thereby also the risk of damages associated with that load, since considerable ice blocks that are not sufficiently crushed by the aft end of the vessel may be encountered by the propeller itself, resulting in considerable horizontal forces. Although the propeller is often designed to withstand such forces, the hub and surrounding components, e.g. shaft bearings, are at considerable risk for damages.
WO99/14113 discloses another propulsion system intended for operation in ice-covered waters and/or in ice conditions.
It is an object of the present invention to provide an improved propulsion unit which is suitable for icebreaking (ice-crushing, ice-milling) and in which horizontal forces on the propulsion device can be reduced.

DISCLOSURE OF THE INVENTION

The invention relates to a propulsion unit for a marine vessel intended to operate in icy waters according to claim 1. The propulsion unit comprises a propeller which is rotatable about a propeller axis in a plane of rotation for the propeller. The propeller is mounted on a hub that is rotatable together with the propeller and the propeller is arranged such that the propeller can act on a piece of ice (e.g. a block or sheet of ice) in the water to cut the ice, even when the piece of ice has an extension that exceeds the diameter of the propeller. For convenience, the term "block of ice" will be used in the following to designate any piece of ice in the water, whether it is an irregular block, an ice-berg or a flat sheet of ice. According to the invention, the hub is designed as a cutting element that is capable of cutting ice that encounters the hub.
In embodiments of the invention, the hub is shaped as a cone that extends in the direction of the propeller axis.
In most realistic embodiments, the hub extends beyond the plane of rotation of the propeller such that the hub can meet a wall of ice before the propeller meets the same wall of ice.
In embodiments of the invention, the hub may be provided with elevations that are arranged to cut ice that encounters the hub. The elevated parts may be shaped as fins (i.e. flanges, ribs) or the elevations may be formed by nipples that give the hub a grainy surface.
Instead of providing elevations on the hub, the hub may have a polygonal cross section. For example, the hub may have a square cross section or a triangular cross section. The propulsion unit is preferably an azimuthing thruster.
The invention also relates to a marine vessel intended to operate in icy waters. The marine vessel has at least one propulsion unit which is preferably an azimuthing thruster with an elongate capsule/nacelle extending from a first end and a second end. A propeller is mounted on the capsule/nacelle together with a hub for the propeller and arranged to be rotatable about a propeller axis in a plane of rotation for the propeller. Both the propeller and the hub are mounted at the first end of the capsule. The propulsion unit is arranged to be capable of driving the marine vessel both in a forward direction and in a backward direction. The propeller is further arranged such that it can act on a block of ice (e.g. a sheet of ice) to cut the ice, even when the block of ice has an extension that exceeds the diameter of the propeller. According to the invention, the hub is designed as a cutting element that is capable of cutting ice that encounters the hub.
It should be understood that the inventive propulsion unit and all embodiments thereof may be used in the marine vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematical representation of a marine vessel with a propulsion unit.
Figure 2 shows, schematically, the same marine vessel but with the propulsion unit in a different orientation.
Figure 3 shows, schematically, how the propulsion unit encounters a block of ice.
Figure 4 is a propeller end view of a propulsion unit according to the invention.
Figure 5 is a side view of the same propulsion unit as in Figure 4.
Figure 6 is a perspective view of the same propulsion unit as in Figure 4 and Figure 5.
Figure 7 is a view corresponding to Figure 1 but in a different scale.
Figure 8 is a side view of an alternative embodiment of the invention.
Figure 9 is a rear view of yet another embodiment.
Figure 10 is a side view of yet another embodiment.
Figure 11 is a side view of a further embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to Figure 1, a marine vessel 2 is passing through water in which there are ice blocks (for example in the shape of an ice sheet or in the shape of ice bergs). In Figure 1, a block of ice is schematically indicated by the letter J. The marine vessel 2 has a propulsion unit 1 which can be seen in greater detail in Figure 7. The propulsion unit 1 is preferably an azimuthing thruster.
The propulsion unit 1 shown in Figure 1 has a nacelle or capsule 6. The nacelle serves as housing for either a motor inside the nacelle (not shown) or for a transmission from an engine (not shown) inside the hull 10 of the marine vessel 2. The capsule 6 has a first end 7 and a second end 9. The capsule 6 is shown suspended on a strut 11 which may suitably have a streamlined shape. The strut 11 may suitably have a top piece 12 which is rotatably attached to the hull 10 of the marine vessel 2. In the hull 10 of the marine vessel 2, there is equipment (not shown) for rotating the propulsion unit 1 about a substantially vertical axis. In this context, "vertical" refers to what is vertical when the marine vessel rests in the water without being inclined to either the starboard side or the port side. This vertical axis about which the propulsion unit 1 may be rotated is thus substantially perpendicular to the propeller axis. In realistic embodiments, the substantially vertical axis about which the propulsion unit 1 may be rotated may deviate by up to 10° or about 10° from a perfectly vertical axis. The propulsion unit 1 may thus be rotated in a plane that is essentially horizontal. The propulsion unit 1 has a propeller 3 which is arranged to be rotatable about a propeller axis A (see Figure 7) in a plane of rotation for the propeller 3. The plane of rotation for the propeller 3 is perpendicular to the propeller axis A. The propeller 3 is mounted on a hub 4 that is rotatable together with the propeller 3. Both the propeller 3 and the hub 4 are mounted at the first end 7 of the capsule 6. There is no nozzle that surrounds or encloses the propeller 3. The propeller 3 is therefore capable of acting directly on ice without being blocked by any nacelle or other elements. In Figure 1 however, the propulsion unit 1 is in a position where the propeller 3 faces the hull 10 of the marine vessel 3. In Figure 2 on the other hand, the propulsion unit 1 has been rotated 180° about a vertical axis compared to the position of Figure 1. In this position of the propulsion unit 1, the propeller 3 can be driven such that the marine vessel 2 moves towards the ice J. When the propeller 3 reaches the ice J, the propeller 3 will start to act on the ice to cut the ice. The propulsion unit may thus cut a path through a block of ice that would otherwise have presented an obstacle for the marine vessel 2. Since there is no nozzle that surrounds the propeller 3, the propeller 3 is free to act on a block of ice J (for example an ice sheet or an ice berg) in the water to cut the ice, even when the block of ice J has an extension that exceeds the diameter of the propeller 3. It should be understood that the "extension" of the ice block refers to the extension of the ice block on the side facing the propeller, i.e. the extension in a plane parallel to the plane of rotation of the propeller.
However, if the propeller 3 should be used to cut the ice when the propeller 3 is in the position of Figure 2, such an ice-cutting operation entails a problem which is illustrated in Figure 3. The propeller 3 is mounted on a hub 4 that may in many embodiments be shaped as a cone that extends in the direction of the propeller axis. The hub 4 extends beyond the plane of rotation of the propeller 3, at least to some extent. When this is the case, the hub 4 can meet a wall of ice before the propeller 3 meets the same wall of ice. As used herein, the term "wall of ice" refers to a surface of an ice block. When the propeller 3 hits ice, it may happen that ice is pressed against the hub 4. This may in particular be the case if the hub 4 or a part of it extends beyond the plane of rotation of the propeller 3 but may happen also when this is not the case. If the hub 4 is pressed against the ice, this will generate a considerable horizontal force F on the hub 4 and the propulsion unit 1. According to the invention this problem is solved in that the hub 4 is designed as a cutting element that is capable of cutting ice that encounters the hub 4. When the hub 4 is designed as a cutting element, the hub 4 will be capable of cutting the ice such that the horizontal force on the propulsion unit becomes significantly smaller. A number of suitable embodiments of cutting elements are described below. These cutting elements comprise elevations, fins, nipples, polygonal cross sections and cut-out portions, among others, and it is to be noted that any of these embodiments or a combination thereof can serve the same purpose, namely that of cutting ice that encounters the hub 4. In this way, the load in the form of horizontal forces on the hub 4 is significantly reduced, resulting in a reduced risk of damages to the hub 4 as well as an increased ice-cutting ability and a smoother and more efficient passage through ice and icy waters.
In embodiments of the invention, the hub 4 is provided with elevations 5 that are arranged to cut ice that encounters the hub 4. In one embodiment that can be seen in Figure 4 - Figure 7, the elevations 5 are shaped as fins (flanges/ribs). The fin-shaped elevations 5 that are shown in Figures 4 - 7 may have a slightly twisted shape such that they are comparable to the threads of a screw. Such a form may improve the ability of the elevations 5 to break up the ice. The fins may be ribs having a height over the surface of the hub 4 which is in the range of, for example, 3 mm - 35 mm. They may also have a height which is more than 35 mm, for example up to 50 mm or up to 200 mm. The maximum height of the fins or ribs may be dependent on the diameter of the propeller and the maximum height of the fins or ribs may be up to 25 % of the propeller diameter.
In Figure 4 - 6, an embodiment with four elevations 5 is shown. It should be understood that embodiments with a different number of elevations 5 are possible. For example, embodiments with two, three, five or six elevations are possible. Embodiments with only one single elevation 5 are also possible.
In another embodiment that is illustrated in Figure 8, the elevations 5 are formed by nipples that give the hub 4 a grainy surface.
As an alternative to elevations 5, the hub 4 may have a polygonal cross section. Such an embodiment is shown in Figure 9. As can be seen in Figure 9, the hub 4 has straight edges 13 that divide the surface of the hub 4 into four surfaces 14 that taper toward the end of the hub 4. The hub 4 will then have a sharp point that can penetrate the ice.
Since the hub 4 rotates with the propeller, the elevations 5 in the embodiments of Figure 6 and Figure 8 can act on a block of ice to break up the ice such. Thereby, the horizontal force on the hub 4 and the propulsion unit 1 will decrease significantly. In the embodiment of Figure 9, the edges 13 will serve the same function as the elevations 5 in the embodiments of Figure 6 and Figure 8.
In the embodiment of Figure 9, there are four edges 13 such that the hub 4 will have a square cross section. It should be understood that other polygonal shapes are also possible, for example triangular (with three edges 13), pentagonal or hexagonal. Embodiments with more than six edges 13 are also conceivable.
In the embodiment of Figure 10, the elevations 5 are shaped as fins/ribs that have, from the end of the hub 4, an increasing height over the surface of the hub 4 until they reach a maximum point from which the height decreases.
In the embodiment of Figure 11, the hub 4 has cut-out portions 16 such that the surface of the hub 4 becomes uneven. Embodiments with, for example, 2 - 12 cut-out portions 16 are conceivable. It should be understood that embodiments with more than 12 cut-out portions are also possible. Embodiments with only one such cut-out 16 are also conceivable. The hub 4 may thus have at least one cut-out portion 16 such that the surface of the hub 4 becomes uneven.
In the above described embodiments, various ways of achieving an uneven surface on the hub 4 have been described. It should be understood that such different embodiments could possibly be combined with each other. For example, the hub 4 could have a combination of both cut-outs 16 and nipples or nipples could be used on a hub with a polygonal cross section.
The invention also relates to a marine vessel 2 intended to operate in icy waters and which is equipped with the inventive propulsion unit. When a marine vessel 2 is equipped with such a propulsion unit 1, the propulsion unit 1 may either be in a fixed position such that the propeller 3 faces away from the hull 10 and is capable of acting on ice, or the propulsion unit can be rotated such that the propeller 3 points away from the hull 10 and is capable of acting on ice that would otherwise block the path of the marine vessel 2.
By rotating the propulsion unit 1 (or propulsion units 1 if there is more than one propulsion unit), it is possible to control the direction in which the marine vessel will travel. The propeller of each propulsion unit 1 can be driven both backward and forward. When the propulsion unit is in the position shown in Figure 1, the direction of movement of the marine vessel 2 can thus be changed either by rotation of the entire propulsion unit 1 or by reversing the direction of rotation of the propeller 3.
In use, a marine vessel 2 equipped with the inventive propulsion unit 1 may pass through icy waters. When the path of the marine vessel 2 is blocked by ice, the propulsion unit 1 may be rotated such that the first end 7 of the propulsion unit faces the ice. The propulsion unit 1 is activated such that the propeller 3 propels the marine vessel 2 toward the ice. The propeller 3 will hit the ice and start to cut the ice such that a path through the ice for the marine vessel 2 is created.
It should be understood that the marine vessel may have more than one such propulsion unit 1. For example, the marine vessel 2 may be equipped with two propulsion units according to the invention. It could also have more than two propulsion units 2. For example, it could have three, four, five or even more such propulsion units 1. When the marine vessel 2 has more than one propulsion unit 1, several propulsion units 1 may suitably be arranged at the stern end 15 of the marine vessel 2. For example, a pair of such propulsion units 1 may be placed side-by-side at the stem end 15 of the marine vessel 2. However, propulsion units 1 may also be placed at the stem end 8.
The propeller may have a diameter which is in the range of, for example, 0.4 m - 4 m. For example, the diameter may be in the range of 0.5 m - 3 m. The diameter could also be larger than 4 m. For example, the propeller diameter could be up to 6 m. In some cases, propellers used for icebreaking (ice-crushing, ice-milling) could conceivably even have a diameter up to 10 m or more and propulsion units according to the invention could conceivably have such large propellers.
The propulsion unit 1 may be an azimuthing thruster with an internal electrical engine or it may be an azimuthing thruster driven through a transmission by a diesel engine inside the hull or by a diesel-electric motor. The transmission may be an L-drive or a Z-drive.
The elevations 5 may optionally be retractable. When the marine vessel 2 is used in situations where the propulsion unit does not need to cut ice, the elevations 5 may thus be retracted. When there is a need to cut through ice, the elevations 5 may be caused to appear again.
In all embodiments of the invention, the hub 4 that is designed as a cutting element may be designed such that a part of the hub 4 is detachable. The detachable part of the hub 4 may be that part of the hub 4 that is designed as a cutting element that is capable of cutting ice. If the hub 4 has a detachable part, this entails the advantage that a damaged hub 4 which can no longer cut the ice can be easily repaired by change of the detachable part. The detachable part of the hub 4 may be a hub cap that is mounted on the rest of the hub. The hub cap can be regarded as a part of the hub 4. In many practical embodiments, the hub 4 will have a hub cap and the hub cap will be that part of the hub that first hits the ice.
The blades of the propeller 3 may have a variable pitch. The propulsion unit 1 may also be designed for variable speed of the propeller 3.

Claims

A propulsion unit (1) for a marine vessel (2) intended to operate in icy waters, the propulsion unit (1) comprising a pulling propeller (3) which is rotatable about a propeller axis in a plane of rotation for the propeller (3) and which is mounted on a hub (4) that is rotatable together with the propeller (3), the propeller (3) being arranged such that the pulling propeller (3) can act on a block of ice in the water to cut the ice, even when the block of ice has an extension that exceeds the diameter of the propeller (3), wherein the hub (4) is designed as a cutting element that is capable of cutting ice that encounters the hub (4), by means of having said hub (4) extending in the direction of the propeller axis, beyond the plane of rotation of the propeller (3) arranged to meet a wall of ice before the propeller (3) meets the same wall of ice and wherein said hub (4) is provided with elevated cutting members (5) or has a polygonal cross section or at least one cut-out portion (16) such that the surface of the hub (4) becomes uneven.
A propulsion unit according to claim 1, wherein said elevated cutting members (5) are shaped as fins or ribs, and have a height in relation to the surface of the hub (4) up to 200 mm.
A propulsion unit according to claim 2, wherein said elevated cutting members (5) shaped as fins or ribs have a height in relation to the surface of the hub (4) of 3 mm or more and up to 50 mm.
A propulsion unit according to claim 1, wherein said elevated cutting members_(5) are formed by nipples that give the hub (4) a grainy surface.
A propulsion unit according to any preceding claim, wherein said hub (4) comprises a detachable part with said elevated cutting members (5) or polygonal cross section or cut-out portion (16).
A propulsion unit according to claim 1, wherein the propulsion unit (1) is an azimuthing thruster.
A marine vessel (2) intended to operate in icy waters, the marine vessel (2) having at least one propulsion unit (1) which is an azimuthing thruster according to any of claims 1-6.
A marine vessel according to claim 7, wherein an elongated capsule (6) of the azimuthing thruster can be rotated in relation to the hull of the marine vessel (2) about a vertical axis.