Arrangement for Ice-Breaking

Abstract

A device for ice-breaking with a vessel has two functionally separate upper and lower elements of different widths. The upper, wider element is situated next to the water line for breaking unbroken ice, and the lower, narrower element is situated below the upper element and for transporting broken ice sideways and under the unbroken ice. The upper wider element has a flat lower portion abaft an inclining front part with a small frame angle and breaks ice downward when moving ahead, and a flat stern part with a small frame angle and breaks ice downward when moving astern. The lower element has vertical side portions which in the forebody and the afterbody have a marked wedge-shape and shove broken ice sideways. Transport of broken ice sideways and astern can be augmented by bow propellers and wing propellers.

Claims

1.-10. (canceled)

11. A device for icebreaking with a vessel, comprising: a vessel hull having two functionally separate elements of different widths, of which an upper and wider element is situated next to a water line for breaking unbroken ice and a lower and narrower element is configured to transport broken ice sideways and under the unbroken ice; wherein the upper and wider element has a substantially flat inclined front part with a front frame angle and breaks ice downward, and has a substantially flat stern part with a stern frame angle, and has between the front and stern parts a substantially flat lower portion that is situated underneath an underside of a thickest ice that the vessel is configured to break at a continuous speed and that is situated outside the width of the lower and narrower element; the front part, the stern part, and the lower portion of the upper and wider element are situated at a maximal width of the vessel; and the lower and narrower element has substantially vertical side portions and is wedge-shaped at the front and stern parts of the upper and wider element in a direction of travel of the vessel, the wedge shape having an opening angle and being configured to force broken ice sideways and at least partly under unbroken ice when the vessel moves forward and to force broken ice sideways along the stern part and lower portion when the vessel moves astern, thereby decreasing an amount of broken ice that contacts a main propeller of the vessel.

12. The device of claim 11, wherein at least one of the front frame angle is less than 15, the stern frame angle is less than 20, and the opening angle is less than 40.

13. The device of claim 11, wherein the vessel includes at least two wing propellers mounted at a bottom of the side portions and directed so that the wing propellers direct water upward at a first angle to hit the lower portion of the upper and wider element, whereby broken ice is forced aftward and prevented from contacting the main propeller when the vessel moves ahead.

14. The device of claim 13, wherein the first angle is less than 10.

15. The device of claim 13, wherein the vessel includes at least two bow propellers mounted at a bottom of forward side portions of the lower and narrower element and directed so that the bow propellers direct water upward at a second angle and sideways at a third angle to hit the lower portion of the upper and wider element, whereby broken ice is forced sideways under unbroken ice when the vessel moves ahead in flat ice at continuous speed; and the bow propellers and wing propellers direct water astern when the vessel moves ahead in ridged ice, a lower part of the ridged ice extending under the flat part of the upper and wider element, to force the ridged ice to an area abaft the vessel.

16. The device of claim 15, wherein the second angle is less than 10 and the third angle is half of the opening angle.

17. The device of claim 15, wherein the wing and bow propellers are mounted on extrusions to decrease contact between the vertical side portions and water directed by the wing and bow propellers.

18. The device of claim 17, further comprising wing-like projecting elements arranged in front of the wing and bow propellers, wherein the projecting elements and extrusions rotate broken ice to reduce blockage of the wing and bow propellers by the broken ice.

19. The device of claim 18, wherein a projecting element has a side length that extends at least to a center of a respective wing or bow propeller.

20. The device of claim 13, wherein the wing propellers are rotatable on support points at sides of the vessel to direct water forward or aftward, upward or downward.

21. The device of claim 11, wherein the main propeller is rotatable on a support point below the vessel's stern.

22. The device of claim 11, wherein the vessel has a driving propeller driven by propulsion machinery situated in front of propellers in the lower and narrower element.

23. The device of claim 11, further comprising a cantilever disposed on a deck of the vessel, the cantilever being configured to decrease risk of broken ice landing on the deck.

24. The device of claim 11, wherein sides of the upper and wider element include inward-inclining side portions having frame angles between 45 and 60 and arranged to, when turning, break ice upward when the vessel moves in unbroken ice.

Description

DESCRIPTION OF THE DRAWINGS

[0030] The invention is described in the following in the form of a preferred embodiment example, reference being made to the accompanying drawings in which;

[0031] FIGS. 1 and 2 show two different three-dimensional views of a vessel having a device according to the present invention as seen obliquely from below from the stern and the stem, an upper hull part indicating element I and a lower hull part indicating element II, the upper element I at the deck showing a cantilever intended to decrease the risk of broken ice penetrating in onto the deck,

[0032] FIGS. 3 and 4 show in principle the same views as FIGS. 1 and 2 but only the part of the upper element I that is situated underneath the water line, more precisely the part of the hull that contacts broken and unbroken ice. FIGS. 1-4 show a version of the ship where the main propellers by lines of shafting are driven by machineries mounted inside the lower element II and a version wherein the vertical side portions of the lower element II are running continuously along the entire element,

[0033] FIG. 5 shows a line drawing of the vessel as seen from above,

[0034] FIG. 6 shows a line drawing of the vessel as seen from the side where it is seen how the inward inclining side portions amidships and at the afterbody are running parallel to the water line while they in the forebody are bent upwards since they are following the inclination of the flat bow portion,

[0035] FIG. 7 shows a line drawing of the vessel as seen from below indicating a version of the invention wherein the vertical side portions of the lower element II are not running continuously along the entire element but wherein they at the afterbody intersect a hull part that is more slender than the corresponding hull part of the mid ship,

[0036] FIG. 8 shows a body plan of the forebody of the vessel as seen from the front,

[0037] FIG. 9 shows a body plan of the forebody of the vessel as seen from the stern,

[0038] FIG. 10 shows a body plan of the afterbody of the vessel as seen from the stern where it is indicated how the full width of the bow provides a broken channel that is wider than the water line portions of the mid ship and the afterbody, which in turn decreases the friction between hull and ice and also contributes to the turning ability in ice by giving room for the afterbody to accelerate sideways until the upward breaking side portion contacts the unbroken ice to provide, by sideways icebreaking, a wider channel for the afterbody,

[0039] FIGS. 11 and 12 show the line drawings presented in FIGS. 6 and 7 extended with propellers and rudders,

[0040] FIG. 13 shows the wing or bow propeller as seen from the front,

[0041] FIG. 14 shows the wing or bow propeller as seen from the side,

[0042] FIG. 15 shows the wing or bow propeller as seen from above, and

[0043] FIGS. 16-18 show how the forebody of the ship when moving ahead in unbroken ice transports the broken ice under the unbroken ice by the side of the ship.

THE INVENTION

[0044] A new hull concept has been developed that consists of two elements I,II that functionally are totally different. In the upper part I a portion that comes into contact with unbroken ice 14 when moving ahead in a straight line is totally flatthe frame angle is zerowhich breaks the ice and forces the broken pieces far enough down so that they may be transported sideways under the unbroken ice sheet on both sides of icebreaker. The lower element is wedge shaped at the bow and the stern and has vertical sidesthe frame angle is 90 degrees against the horizontalto efficiently push broken ice under the solid ice cover on both sides and also to provide support for propellers and rudders. When moving astern the novel hull form combination, presented in FIGS. 6,7 and 10, functions virtually in the same manner.

[0045] The new hull form combination is also provided with a novel type of reamer as may be seen in FIGS. 5-10. Reamers used so far on icebreakers or icebreaking ships are located at or close to the intersection between bow and mid body in order to create a broken channel that is wider than the mid body, which thus is able to turn in this wider channel. The new type of reamer presented here covers the entire distance from the most forward portion of the bow all the way to the most aft portion of the stern. To make it possible to turn in a solid ice cover the upper portion of the reamer in inclined in such a manner that it is able to break the ice upwards when the ship is turning, as shown in FIG. 10, thus providing room for the sideways movement of the ship. To prevent broken ice from reaching deck level during a turning maneuver a cantilever may be introduced well above the water line as shown in FIG. 18.

[0046] A propulsion configuration that augments the functions of the hull combination presented above is shown in FIGS. 11-18. The most radical novelty is to introduce bow propellers on icebreakers intended for operation in multi-year ice and to bring them back to icebreakers intended for operation in first year ice. The proposed bow propellers are, however, very different from bow propellers used previously. On the five icebreakers of Atle type delivered in the 1970's, the latest icebreakers provided with propellers in the front, the bow propellers are mounted on shafts that are directly connected to the electric propeller motors and thus the propeller stream will hit the side of the wedge shaped bow before being turned into a direction following the water lines of the ship. This greatly reduces the net thrust of the propeller and more seriously limits the possibility to transport broken ice within ice ridges towards the stern of the ship when the thickest portion of the ice ridge is located at or close to the widest part of the ship. When ramming into heavy ridges both bow propellers on an Atle type icebreaker will stall when the ice is compacted around the bow which very effectively will stop the ship. Then it will take some time to get the propellers rotating again and then some further time to free the ship from the embrace of the ice.

[0047] The bow propellers in this invention operate very differently as the propeller stream is directed along the wedge and away from the mid ship portion of the lower hull as shown in FIGS. 11 and 12. The propeller stream is also directed upwards in order to meet the bottom of the upper hull at an angle and thus forcing the broken ice under the solid ice cover when operating in level ice. In ice conditions where there is more ice around the ship the propeller stream will be forced towards the stern where there is room for the broken ice. The transport of ice towards the stern will be augmented by the propeller streams of one or several pairs of wing propellers, as also shown in FIGS. 11 and 12. The propeller stream caused by the main propellers located at the aft end of the lower hull will provide room for the broken ice behind the ship. Without the ice transport caused by the bow and wing propellers the thick ice in ridges will remain where it has been broken by the icebreaker and will thus remain as a main obstacle for ships following the icebreaker. The bow and wing propellers shown here will distribute the ice ridge over a much larger distance and thus make it easier for the assisted ships to follow in the track opened up by the icebreaker.

[0048] The configuration of the bow and wing propellers is shown in FIGS. 13-15. In order to achieve the necessary strength to withstand collisions with large and thick multi-year ice pieces the propeller is set at a fixed angle against the bottom of the upper hull which the propeller is flushing when the ship is processing in the forward direction. The nozzle is attached to a long extrusion fitted with a wing like portion at its leading edge in order to rotate large ice pieces away from the front of the nozzle. Protected by the nozzle is a controllable pitch propeller which is able to adjust the propeller pitch in such a manner that a constant propeller speed as well as the appropriate power level is maintained even when ice pieces are forced through the propeller disc. By keeping the propeller speed high it is easy for the propeller blades to efficiently cut the ice into pieces small enough to pass between the blades in order to join the propeller stream behind the propeller.

[0049] A body plan of the bow looking towards the stern is shown in FIG. 8. A body plan of the bow looking towards the front is shown in FIG. 9 and a body plan of the stern looking towards the front is shown in FIG. 10. The width of the upper hull must always be wide enough to provide protection for the bow and wing propellers. The hull form combination presented in FIGS. 6-10 shows an upper hull which is about two times wider than the lower hull but the upper hull may be considerably wider than this in order to efficiently assist large ships. It should be noted that the maximum width of existing icebreakers is about 30 m which is considerably smaller than the beam of large cargo ships needing icebreaker assistance. The reason for this is that a conventional wedge shaped icebreaker with 60 m width and 12 m draft will push most of the broken ice below the bottom of the ship and into the propulsion machinery. The form combination presented here does not have this problem and thus the maximum beam may be chosen to fit the ships being assisted.

[0050] The propulsion arrangement shown in FIGS. 11 and 12 includes two main propellers at the stern together with two large rudders, two wing propellers and two bow propellers. Normally the power of the main propeller would be chosen to be about equal to the combined power of the bow and wing propellers on one side of the ship in order to facilitate sideways movement of the ship at low speed in the same manner as used on conventional four propeller icebreakers. Controllable pitch propellers have the disadvantage that if the pitch is reversed without also reversing the rotation direction then the reverse thrust will suffer as a portion of the blades will operate in the wrong direction at full reverse power. But when the propeller is driven by an electric motor then the rotation direction may easily be reversed causing the controllable pitch propeller to be as efficient as a fixed pitch propeller in the reverse direction.

THE INVENTION IN MORE DETAIL

[0051] According to the invention, there is formed a device that is arranged for icebreaking with an icebreaking hull 2 of a ship 3 having a particular design of the hull 2. More precisely, a hull 2 is formed of two functionally separate elements I, II, which have different width B, D. An upper and wider element I is situated next to the water line 13 and is arranged for breaking of unbroken ice 14. A more slender element II situated under said element I is arranged for the transport of the broken ice 15 sideways and under the unbroken ice 14. The upper wider element I is provided with an essentially flat lower part portion of an inclining front part 10 and has a small frame angle a, preferably less than 15, and which is arranged to break the ice 14 downwards when moving ahead F. Furthermore, the element I is provided with an essentially flat stern part 12, which is provided with a small frame angle c, preferably less than 20 and which is arranged to break the ice 14 downwards when moving astern R. Furthermore, between the front part 10 and stern part 12, there is arranged an entirely flat lower portion 11, which is situated underneath the underside of the thickest level ice that the ship 3 is intended to break at continuous speed, and simultaneously situated outside the width D that the lower more slender element II has. Outside the width D that said lower more slender element II has, with front part 10, lower portion 11, and stern part 12, there are arranged inward inclining side portions 4, 5 at the maximal width B of the vessel and with a relatively great frame angle e preferably between 45 and 60, which when turning are arranged to break the ice upwards when operating in unbroken ice 14. The lower more slender element II is provided with essentially vertical side portions 7, 8, 9 and which at the stem 10 and at the stern 12 in the direction of travel has a wedge-shape of a small opening angle n,r, preferably less than 40, when moving ahead F, thanks to the wedge-shape, being arranged to force the ice 15 broken thereby sideways and entirely or partly under the unbroken level ice 14, and when moving astern R, thanks to the wedge-shape, force the broken ice sideways along stern part 12 and lower portion 11 for decreasing the amount of ice to contact the main propellers 19 and rudder 20 of the vessel.

[0052] For the operation in ice, front part, lower portion, and stern part are, at the maximal width of the hull, accordingly provided with inward inclining side portions 4, 5 having a relatively great frame angle e to the water line, preferably between 45 and 60, arranged to break the ice sideways and upwards when turning in unbroken ice.

[0053] The vessel is provided with at least two wing propellers 18, which are mounted at the bottom of the side portions 8 of the more slender element II of the hull, and which are directed so that the propeller stream upwards at a small angle u, preferably less than 10, hits lower portions 11 of the upper element I in order to, in that connection, when moving ahead F accelerate the broken ice 15 aftwards and prevent the same ice from contacting the main propellers 19 of the ship.

[0054] The vessel is provided with at least two bow propellers 17, which are mounted at the bottom of the forward side portions 7 of the lower more slender element II directed in such a way that the propeller stream upwards at a small angle s, preferably less than 10, and sideways at a small angle x, preferably half of the opening angle n, hits the lower portion 11 of said wider element I, so as to, when moving ahead F, in level ice accelerate the ice 15 broken thereby sideways under unbroken ice 14 and thereby essentially or entirely make the broken channel behind the ship 3 ice-free when operating in level ice and at continuous speed. When operating, for example in ice ridges, the lower part of which extends below the flat part 11 of the upper element I, the propeller stream created by the bow propellers 17 is directed astern, wherein the same, together with the propeller stream directed astern and created by the wing propellers 18, moves the major part of the ice ridge to the area abaft the vessel and which accordingly is spread over a larger area and decreases the ice resistance for trailing vessel. The wing and bow propellers 17, 18 are mounted on an extrusion 21 to decrease the contact of the propeller stream with the vertical side portions 7, 8 and a wing-like projecting element 22, preferably having a side length that at least extends to the centre of the propeller, is arranged in front of the wing and bow propellers 17, 18, to provide, together with the extrusion 21, rotation of broken ice-floes 15 and prevent the same from blocking the propellers 17, 18.

[0055] Propellers 17, 18 are arranged to rotate on a point of support at the sides of the vessel in ways which allow directing the propeller stream forwards or aftwards, upwards or downwards.

[0056] The main propellers 19 of the vessel are arranged to be rotated on points of support below the stern of the vessel in ways which allow directing the propeller stream forwards F or aftwards R, and arbitrarily towards both sides, which makes that the rudders 20 can be eliminated. The driving propellers 19 of the vessel are arranged to be driven by means of shaft from a propulsion machinery, which is situated in front of said propellers 19 in said lower more slender element II.

[0057] On the deck level, a cantilever 23 is provided, which decreases the risk of broken ice ending up on the deck 30 of the ship.

[0058] Function and nature of the invention should have been clearly understood from the above-mentioned and also with knowledge of what is shown in the drawings but the invention is naturally not limited to the embodiments described above and shown in the accompanying drawings. Modifications are feasible, particularly as for the nature of the different parts, or by using an equivalent technique, without departing from the protection area of the invention, such as it is defined in the claims.