SE1450545A1 - Ice breaking device - Google Patents

Abstract

S283 P5SE LG / KOE SUMMARY The invention relates to a device for icebreaking with icebreaking screws on vehicles. According to the invention, two functionally separate elements (I, II) with different widths (B; D) are used, of which an upper and wider element (I) is beldget adjacent to the waterline (13) for breaking unbroken ice (14), while a below this coated narrower element (II) Or intended for the transport of the broken ice laterally and under the unbroken ice (14). The upper wider element (I), which Or provided with a substantially flat lower part portion (11) aft a sloping front part (10), Or arranged to break the ice (14) downwards at a small angle of attack (a), preferably less On ° walk forward. With a substantially flat stern part (12), which has a small angle of attack (c), preferably less On °, Or arranged to break the ice (14) downwards when walking aft, the lower and narrower element (II) has substantially vertical side sections (7,8,9) which in the father ship (7) and the stern ship (9) are provided with a marked wedge-shaped corn side, shovel the broken ice (15) whose transport sideways and aft is accelerated by bow propellers (17) and side propellers (18) .

Description

S283 PBSE LG/KOE STENA Rederi AB, Göteborg Anordning för isbrytning Anordning för isbrytning Den föreliggande uppfinningen avser anordning för isbrytning med isbrytande skrov på fartyg.

Background A scientific treatment of icebreaking resistancewas published in 1888-1889 in Great Britain by RobertRuneberg, a Finnish engineer, in Reference [Runeberg,Robert; “On Steamers for Winter Navigation and Ice-breaking” Paper No. 2371 of the Proceedings of theInstitution of Civil Engineers 1888-1889]. In thisreference only the resistance caused by the breaking ofthe ice is considered and a formula for the calculation ofthe relationship between the resisting force, R, and thevertical force, V, when breaking a solid ice sheet ofuniform thickness is presented. Among many the formula includes the following input parameters: coefficient of friction ® angle between the mean inclination of the buttocklines and the water line ß angle between water line and mean inclination of cross sections taken perpendicular to buttock lines Commenting on how these angles influence theefficiency of icebreaking Runeberg states the following ontop of page 293 in said Reference [Runeberg, Robert: “OnSteamers for Winter Navigation and Ice-breaking” Paper No.2371 of the Proceedings of the Institution of Civil Engineers 1888-1889]: “Turning attention to the design of the vessel, it will be inferred from the formula for V, that in order to increase the ice-breaking capacity; the angles ® and ß should bemade as small as possible." In other words the inclinationof the buttocks and the frames against the water lineshould be as small as possible in order to maximize icebreaking efficiency.

This scientific illumination has been widely used on icebreakers built to break level ice on inland waterways. The most extreme examples have a frame angle ß of zero degrees, which results in a totally flat landing craft bow, in combination with a buttock angle ® of less than 10 degrees. lcebreakers intended mainly for service in open sea, where heavy ridges are present, have experienced a different evolutionary process. The first Europeanicebreaker intended for operation in open sea was designedand built in Sweden for the Finnish government in 1890 andwas given the name Murtaja, which in Finnish meansBreaker. This design by C.A. Lindvall had a length of 47.5m, a beam of 10.9 m, a draft of 6.7 m and a displacementof 930 tonnes. It had one propeller and a power of 1 MW.The lines and body plan of this ship are shown in“Steamers for Winter 3191 of the Reference [Runeberg, Robert: Navigation and Ice~breaking”, Paper No.Proceedings of the Institution of Civil Engineers 1900],and indicate a spoon shaped bow with an average buttock angle of about 40 degrees and an average frame angle of about 60 degrees. The water line was rather blunt with an opening angle of about 48 degrees at the stem.

In heavy pack ice the performance of Murtaja washighly unsatisfactory because the blunt bow pushed brokenice in front of itself and the ship got so badly stuckaxes and ice anchors had to be used that dynamite, saws, to free the ship from the grip of the ice. This extremelynegative experience resulted in the conclusion that anicebreaker intended for operation in open sea must beequipped with a relatively sharp wedge shaped bow in orderto avoid pushing ice in front of itself.

In 1893 an icebreaking ferry, the Saint Marie, wasbuilt in Detroit, Michigan to the design of Frank E.Kirby. It was fitted with two propellers, one at the sternwith a power of 1.4 MW and one at the bow with a power of1.14 MW for a total power of 2.54 MW. The lines and bodyplan of this ship are shown in Reference [Runeberg,Robert: “Steamers for Winter Navigation and Ice~breaking”,Paper No. 3191 of the Proceedings of the Institution ofCivil Engineers 1900], and indicate almost identicalrather sharp wedge forms at the bow and stern, which is tobe expected in order to accommodate the propellers.According to reports reaching Finland this ferry operatedwith great success in heavy pack ice by alternativelyrunning the bow propeller full astern and full ahead whenmaking slow progress. In 1895 a Finnish engineer,Konstantin Jansson, was sent to document the operation ofthese ferries and the following year a Finnish seacaptain, L. Melan, was also sent to the Great Lakes inorder to assert the operational efficiency of the Kirby design. Jansson and Melán both recommended that the next Finnish icebreaker should be fitted with two propellers,one at each end, even if the cost of the ship should increase, Reference [Ramsay, Henrik: “I kamp medÖstersjöns isar” Struggling with the Ice in the BalticSea", (in Swedish), Helsinki 1947].The second Finnish icebreaker was built inNewcastle upon Tyne ln 1898 and given the name Sampo, witha draft of 5.56 m a length of 61.6 m, a beam of 13.1 m, and a displacement of 2,050 tonnes. It was fitted with twopropellers, one at the stern with a power of 1 MW and oneat the bow with a power of 0.88 MW for a total power of1.88 MW. The lines and body plan of this ship are shownin said Reference [“Steamers for Winter Navigation and Ice-breaking", Paper No. 3191 of the Proceedings of the Institution of Civil Engineers 1900] and are very much inaccordance with Kirby's design for the Great Lakes.Obviously the operators were satisfied with a wedge shapedhull form provided with propellers at the bow as well asthe stern as this design did not change materially until the 1980's for icebreakers intended for operation in the northern portion of the Baltic Sea.

The evolution of icebreakers intended for polarregions has been somewhat different from that oficebreakers intended for more temperate climates. Thefirst icebreaker to be tested in the Arctic was theRussian icebreaker Ermak sponsored by Admiral Makaroff andbuilt 1898 in Newcastle upon Tyne. In said Reference[“Steamers for Winter Navigation and Ice-breaking", PaperNo. 3191 of the Proceedings of the Institution of Civil Engineers 1900] this is described as follows: “In February, 1983, the author read a paper beforethe Russian Imperial Technical Society on “The Possibilityof Winter Navigation to St.Petersburg.” In this Paper theconclusion was arrived at that winter navigation toSt.Petersburg should not be impossible. It is to AdmiralMakaroff that the honor is due of having put thissuggestion to a practical test. The Minister of Financehaving found the money, Admiral Makaroff ordered theicebreaker from Messrs. Armstrong, Whitworth & Company,and on the 16w March, 1899, she arrived at Kronstadt, metby an enthusiastic crowd on the ice. The lines of thisvessel are very similar those of the Sampo, though the Ermak is much larger." Ermak's length was 97.5 m, beam 21.6 m, draft 8.54 m and displacement 7,875 tonnes.

Initinally she was fitted with four propellers, each of1.56 MW for a total power of 6.24 MW. One propeller wasfitted at the bow while the three others with a singlecenterline rudder were located at the stern. In saidReference [“Steamers for Winter Navigation and Ice- breaking”, Paper No. 3191 of the Proceedings of the Institution of Civil Engineers 1900] the first voyage ofErmak is described as follows: On the 5” March, the Ermak sailed from the Tyne.Fast ice was met in the Gulf of Finland, between Reval andHogland, the vessel passing through this difficulty; but,and had the thickness of encountering severe pack ice, she stuck at times, to use ice-anchors in order to get free,the pack~ice being estimated between 25 and 30 feet. Itthus took the ship nearly three and a half days to passfrom the beginning of the continuous ice to Kronstadt, butduring that time the boat was stopped to allow some restto the crew, which was not up to full strength. Though the end was successfully gained, it is evident that Admiral Makaroff was right in insisting in the power being notless than 10,000 IHP.” In a footnote in Reference[“Steamers for Winter Navigation and Ice-breaking", PaperNo. 3191 of the Proceedings of the Institution of CivilEngineers 1900] Ermak's initial experience in arcticwaters is described in the following manner: “Since the foregoing was written the Ermak hasreturned from her summer cruise in the Arctic Ocean, whereshe has not been entirely successful. After an attempt atthe ice near Spitsbergen, she was taken back to Newcastleto have more web-frames and longitudinal stringers put in,some new plates replaced and a number of plates re-riveted. One blade of the fore propeller having broken,and the shaft having got out of line, it was decided toremove the fore propeller altogether, and the Ermak wenton her second trip to force the Arctic ice; but this washardly more encouraging, and her general seagoingqualities proved to be unsatisfactory, as might have been predicted from her highly inclined sides.

It should be remembered that the power of the forepropeller is only 25 percent of the total power, whileaccording to American experience - successfully followedon the Sampo ~ it is desirable to have the power nearlyequally divided, or, say 45 percent on the fore propeller.The comparative inefficiency of the Ermak may to some extent be explained by this disproportion.” It should be noted that after removing the bowpropeller it was possible to increase the steam pressurein the three remaining steam engines in order to increasethe power of each from 1.56 MW to 1.88 MW for a total of 5.94 MW, or only a 5 percent reduction in total power. lO Runeberg also makes a comment about the well known factthat the conventional wedge shaped icebreaker hull form with inclined sides is highly inefficient in large waves.

Runebergs comment that the Ermak would havebenefitted from more power in the bow is certainly correctin Baltic ice conditions as the displacement of the Ermakwas almost four times larger than that of the Sampo whilethe power of the bow propeller was only 77% larger. It isdescribed that better progress with Sampo in Baltic iceconditions is made by charging than by proceeding slowlyand having the bow propeller alternating between fullahead and astern, as preferred on the Great Lakes. If youcharge with high speed with the almost fourfolddisplacement and more than threefold power of the Ermakyou will penetrate much further into the pack ice whichconsiderably increases the possibility of becoming beset in the ice when compared to Sampo.

Runebergs comment that larger power on the bowpropeller may have been of benefit in arctic iceconditions shows ignorance about the strength andthickness of old multi-year ice that unbroken will come incontact with a bow propeller fitted on a conventionalwedge Shaped bow when making the necessary charge with isthe only possible method to force the ship through icethat cannot be penetrated with a continuous speed ofadvance. After the negative experience with the bowpropeller of the Ermak no polar icebreaker has been seriously proposed to be fitted with bow propellers.

Following Ermak and Sampo the design of icebreakers intended for operation in open sea did not experience any major changes for almost 70 years, themajor improvement being the installation of diesel-electric propulsion on the Swedish icebreaker Ymer builtat Kockums in Malmö in 1933. This was a bold andsuccessful experiment in order to improve fuel efficiency.The wedge shaped hull remained virtually unchanged withthree propellers at the stern with a centerline rudder forpolar icebreakers. For icebreakers intended for non polaroperation the number of propellers gradually increased tofour, two at the bow and two at the stern with a singlecenterline rudder. With increasing power levels thedistance between the two stern propellers had to beincreased with the result that the propeller streams could no longer reach the centerline rudder making this inefficient at low speeds.

After this period of stagnation several novelconcepts have been tested in full scale the most importantof which are listed below.

In l969 Esso modified the oil tanker Manhattan toan icebreaking ship in order to test the feasibility ofyear round oil transport through the North West Passage.The tanker was fitted with two propellers and two ruddersat the stern which after proper reinforcing operatedsatisfactorily even in multi-year ice, albeit the ship wasunable to Operating efficiently in the astern mode as the steam turbine machinery could only deliver 35% of the total power when backing.

In 1974 the Swedish government took delivery ofAtle, the first icebreaker fitted with twin rudders built at the Wärtsilä shipyard in Helsinki, Finland. Initially both steering gears were connected by rods to each other. lO When running astern in heavy ice ridges the shear ringsinstalled on these rods failed and some hours had to bespent replacing the shear rings. Once the two steeringgears were separated the twin rudders operated fully satisfactorily.

In l976 the US Coast Guard icebreaker Polar Starwas delivered with a gas turbine machinery andcontrollable pitch propellers, a brave but unsuccessfulexperiment. As soon as the propellers operated in thickpolar ice the pitch changing mechanism failed and the shiphad to return to port for major repairs.

Canada took In l979 Dome Petroleum of Calgary, Alberta, delivery of the combined icebreaker, anchor handling tugand supply ship Kigoriak built at Saint John Shipbuilding& Dry Dock Co Ltd in New Brunswick, Canada. This ship wasfitted with a blunt spoon shaped bow and a singlecontrollable pitch propeller protected by an extremelystrong nozzle around the propeller. Operating aggressivelyin heavy multi-year ice while traversing the North WestPassage on the delivery voyage from the builder's yard tothe Beaufort Sea the protection provided by the nozzle wasentirely demonstrated. Only relatively small pieces of iceare able reach the propeller blades inside the nozzle andthus the loads on the pitch changing mechanism aredramatically reduced. ln addition as there is no wedgingof ice between the propeller blade and the hull of theship it is easy to reduce the pitch when ice enters thepropeller and thus retain full rotational speed which isneeded to enable the diesel engine to deliver full power.Kigoriak was also fitted with a bow lubrication system with pumps lifting large amounts of sea water on top of the ice in front of the bow in order to reduce thefriction between the ice and the hull. This together withthe considerable increase in power compared to the oldMurtaja, removed the tendency to push ice ahead of the bowwhich had resulted in abandoning blunt bows on open seaicebreakers in 1890. Kigoriak was fitted with a relativelylong parallel mid body with vertical sides. In order tomake it possible to turn the ship in a solid ice cover shewas fitted with reamers that made the bow portion 2 mwider than the mid ship portion and thus providing room for the stern to move sideways in the broken channel.

In 1986 the modified Russian icebreaker Mydyug wastested in relatively thick ice in the fjords of Spitsbergen, Reference [Günter R. Varges, Thyssen Nordseewerke GMBH: “Advances in Icebraker Design - The conversion of the Soviet Polar Icebraker Mydyug into a // 6131 Thyssen/Waas Ship WEMT Symposium Travemünde, June 2 to 5, 1987]. The ship had originally been built inFinland with a wedge shaped bow with an average buttockangle of 24.4 degrees and an average frame angle of 49 a water line beam of degrees, a water line length of 79 m, 20 m, a draft of 6.5 m and a displacement of 6,211 tonnes.After the conversion, performed at the German shipbuildingcompany Thyssen Nordseewerke, the average buttock angle is12 degrees, the average frame angle is O degrees - atotally flat bow - the water line length 93.2 m, the waterline beam 20 m at the mid body and 22.2 m over the bow,the draft unchanged at 6.5 m and the displacementincreased to 7,744 tonnes - about 25% larger than beforeThe propulsion power is the same, the conversion. 7 MW, before and after the conversion. The new bow resulted in a dramatic increase in the thickness of ice the ship is 11 able to break at a speed of 3 knots, it increased fromabout 0.8 m to about 1.5 m. The open water speed remainedunchanged at 16.1 knots even if the displacement had increased by about 25%. The ship motions in a sea stateimproved radically with the new bow although slamming increased. Ändamålet Huvudändamålet med den föreliggande uppfinningenär att i första hand lösa problemet att med rimlig effektpå isbrytaren ifråga kunna bryta en så bred ränna i isensom krävs och även effektivt kunna få den brutna rännan fri från större delen av den brutna isen.

Lösningen Sagda ändamål uppnås medelst en anordning enligtden föreliggande uppfinningen, som i huvudsak kännetecknasdärav, att man nyttjar två funktionellt separata elementmed olika bredd, varav ett övre och bredare element ärbeläget intill vattenlinjen för brytning av obruten is,medan ett under detta beläget smalare element är avsettför transport av den brutna isen sidlänges och under denobrutna isen, att det övre bredare elementet, som ärförsett med ett i huvudsak platt underdelsparti av enlutande framdel, är anordnat att med liten änfallsvinkel,företrädesvis mindre än 15°, bryta isen nedåt vid gångframåt och med en i huvudsak platt akterdel, som uppvisaren liten anfallsvinkel, företrädesvis mindre än 20° brytaisen nedåt vid gång akterut, att med ett mellan för ochakter beläget helt platt underparti, som är beläget nedan-för undersidan på den tjockast jämna is som farkosten äravsedd att bryta med kontinuerlig fart och samtidigt med större bredd än den bredd som det sagda smalare elementet 12 uppvisar, att det nedre smalare elementet, som är försettmed i huvudsak vertikala sidopartier och som i för och iakter i körriktningen uppvisar en kilform med litenöppningsvinkel, företrädesvis mindre än 40°, vid gångframåt tack vare kilformen tvingar den därvid brutna isensidlänges samt till en del under den obrutna jämna isenoch vid gång akterut tack vare kilformen tvingar denbrutna isen sidlänges utmed akterdel och underparti föratt minska mängden av is att komma i kontakt med farkos-tens huvudpropellrar, för manövrering i is är framdel,underparti och akterdel vid skrovets maximala breddförsedda med inåt lutande sidopartier med en relativt storanfallsvinkel mot vattenlinjen, företrädesvis mellan 45och 60°, anordnat att bryta isen sidlänges och uppåt vid girning i obruten is.

FigurbeskrivningUppfinningen beskrives i det följande såsom ettföredraget utföringsexempel, varvid hänvisas till de bifogade ritningarna på vilka; Figur 1 och 2 visar två olika tredimensionellavyer av en farkost med en anordning enligtföreliggande uppfinning sedda snett underifrånfrån aktern och fören varvid en övre skrovdelanger element I och en nedre skrovdel angerelement II varvid övre elementet I vid däcketvisar en utsvällning avsedd att minska risken för att bruten is tränger in pä däcket, Figur 3 och 4 visar i princip samma vyer som figur1 och 2 men endast den del av övre elementet I som befinner sig nedanför vattenlinjen, närmare 13 bestämt den del av skrovet som kommer i kontaktmed bruten och obruten is. Figurerna 1-4 visar enversion av fartyget där huvudpropellrarna genomaxelledningar drivs av maskinerier monterade inutinedre elementet II samt en version där de vertika-la sidopartierna av nedre elementet II löper kontinuerligt längs hela elementet, Figur 5 visar en linjeritning av farkosten sedd ovanifrån, Figur 6 visar en linjeritning av farkosten seddfrån sidan där det framgår hur de inåt lutandesidopartierna midskepps och i akterskeppet löperparallellt med vattenlinjen medan de i förskeppetböjs uppåt eftersom de följer det platta bogpar- tiets lutning, Figur 7 visar en linjeritning av farkosten seddunderifrån som anger en version av uppfinningendär de vertikala sidopartierna av nedre elementetII inte löper kontinuerligt längs hela elementetutan där de i akterskeppet avskär en skrovdel som är smalare än motsvarande skrovdel i midskeppet, Figur 8 visar en spantruta av farkostens förskepp sett framifrån, Figur 9 visar en spantruta av farkostens förskepp sett akterifrån, Figur 10 visar en spantruta av farkostens akter- skepp sett akterifrån där det anges hur bogens lO l4 fulla bredd åstadkommer en bruten ränna som ärbredare än vattenlinjeportionerna i midskeppet ochakterskeppet vilket i sin tur minskar friktionenmellan skrov och is samt även bidrar till gir-ningsförmågan i is genom att ge plats för akter-skeppet att accelerera sidlänges tills den uppåt-brytande sidoportionen kommer i kontakt med denobrutna isen för att genom sidlänges isbrytning åstadkomma en bredare ränna för akterskeppet, Figur ll och l2 visar linjeritningarna presente-rade i figur 6 och 7 utökade med propellrar och roder, Figur l3 visar sido- eller bogpropellern sedd framifrån, Figur 14 visar sido- eller bogpropellern sedd från sidan, Figur l5 visar sido- eller bogpropellern sedd uppifrån, och Figur l6-l8 Visar hur fartygets förskepp vid gångframåt i obruten is transporterar den brutna isen under den obrutna isen via sidan om fartyget.

The Invention A new hull concept has been developed that consists of two elements I,II that functionally are totally different. ln the upper part I a portion lO that comes into contact with unbroken ice 14 when moving aheadin a straight line is totally flat - the frame angle iszero ~ which breaks the ice and forces the broken piecesfar enough down so that they may be transported sidewaysunder the unbroken ice sheet on both sides of icebreaker.The lower element is wedge shaped at the bow and the sternand has vertical sides - the frame angle is 90 degreesagainst the horizontal ~ to efficiently push broken iceunder the solid ice cover on both sides and also toprovide support for propellers and rudders. When movingastern the novel hull form combination, presented infunctions virtually in the same Figures 6,7 and 10, mannêr .

The new hull form combination is also providedwith a novel type of reamer as may be seen in Figures5-10. Reamers used so far on icebreakers or icebreakingships are located at or close to the intersection betweenbow and mid body in order to create a broken channel thatis wider than the mid body, which thus is able to turn inthis wider channel. The new type of reamer presented herecovers the entire distance from the most forward portionof the bow all the way to the most aft portion of thestern. To make it possible to turn in a solid ice coverthe upper portion of the reamer in inclined in such amanner that it is able to break the ice upwards when theas shown in Figure 10, ship is turning, thus providing room for the sideways movement of the ship. To preventbroken ice from reaching deck level during a turningmaneuver a cantilever may be introduced well above thewater line as shown in Figure 18.

A propulsion configuration that augments the functions of the hull combination presented above is shown 16 in Figures 11-18. The most radical novelty is to introducebow propellers on icebreakers intended for operation inmulti-year ice and to bring them back to icebreakersintended for operation in first year ice. The proposed bow propellers are, however, very different from bowpropellers used previously. On the five icebreakers ofAtle type delivered in the 1970's, the latest icebreakersprovided with propellers in the front, the bow propellersare mounted on shafts that are directly connected to theelectric propeller motors and thus the propeller streamwill hit the side of the wedge shaped bow before beingturned into a direction following the water lines of theship. This greatly reduces the net thrust of the propellerand more seriously limits the possibility to transportbroken ice within ice ridges towards the stern of the shipwhen the thickest portion of the ice ridge is located ator close to the widest part of the ship. When ramming intoheavy ridges both bow propellers on an Atle typeicebreaker will stall when the ice is compacted around thebow which very effectively will stop the ship. Then itwill take some time to get the propellers rotating againand then some further time to free the ship from the embrace of the ice.

The bow propellers in this invention operate verydifferently as the propeller stream is directed along thewedge and away from the mid ship portion of the lower hullas shown in Figures ll and 12. The propeller stream isalso directed upwards in order to meet the bottom of theupper hull at an angle and thus forcing the broken iceunder 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 lO l7 there is room for the broken ice. The transport of icetowards the stern will be augmented by the propellerstreams of one or several pairs of wing propellers, asalso shown in Figures ll and 12. The propeller streamcaused by the main propellers located at the aft end ofthe lower hull will provide room for the broken ice behindthe ship. Without the ice transport caused by the bow andwing propellers the thick ice in ridges will remain whereit has been broken by the icebreaker and will thus remainas a main obstacle for ships following the icebreaker. Thebow and wing propellers shown here will distribute the iceridge over a much larger distance and thus make it easierfor the assisted ships to follow in the track opened up by the icebreaker.

The configuration of the bow and wing propellersis shown in Figures l3-l5. In order to achieve thenecessary strength to withstand collisions with large andthick multi-year ice pieces the propeller is set at afixed angle against the bottom of the upper hull which thepropeller is flushing when the ship is processing in theforward direction. The nozzle is attached to a longextrusion fitted with a wing like portion at its leadingedge in order to rotate large ice pieces away from thefront of the nozzle. Protected by the nozzle is acontrollable pitch propeller which is able to adjust thepropeller pitch in such a manner that a constant propellerspeed as well as the appropriate power level is maintainedeven when ice pieces are forced through the propellerdisc. By keeping the propeller speed high it is easy forthe 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. 18 A body plan of the bow looking towards the sternis shown in Figure 8. A body plan of the bow lookingtowards the front is shown in Figure 9 and a body plan ofthe stern looking towards the front is shown in Figure 10.The width of the upper hull must always be wide enough toprovide protection for the bow and wing propellers. Thehull form combination presented in Figures 6-10 shows anupper hull which is about two times wider than the lowerhull but the upper hull may be considerably wider thanthis in order to efficiently assist large ships. Itshould be noted that the maximum width of existingicebreakers is about 30 m which is considerably smallerthan the beam of large cargo ships needing icebreakerassistance. The reason for this is that a conventionalwedge shaped icebreaker with 60 m width and 12 m draftwill push most of the broken ice below the bottom of theship and into the propulsion machinery. The formcombination presented here does not have this problem and thus the maximum beam may be chosen to fit the ships being assisted.

The propulsion arrangement shown in Figures ll and12 includes two main propellers at the stern together withtwo large rudders, two wing propellers and two bowpropellers. Normally the power of the main propeller wouldbe chosen to be about equal to the combined power of thebow and wing propellers on one side of the ship in orderto facilitate sideways movement of the ship at low speedin the same manner as used on conventional four propellericebreakers. Controllable pitch propellers have thedisadvantage that if the pitch is reversed without also reversing the rotation direction then the reverse thrust 19 will suffer as a portion of the blades will operate in thewrong direction at full reverse power. But when thepropeller is driven by an electric motor then the rotationdirection may easily be reversed causing the controllablepitch propeller to be as efficient as a fixed pitch propeller in the reverse direction.

UPPFINNINGEN DETALJERADEnligt uppfinningen bildas en anordningsom är anordnad för isbrytning med ett isbrytande skrov 2på ett fartyg 3 speciellt utformning av skrovet 2. Närmarebestämt bildas ett skrov 2 av två funktionellt separataelement I, II, vilka uppvisar olika bredd. Ett övre ochbredare element I är beläget intill vattenlinjen 13 och äranordnat för brytning av obruten is 14. Ett under dettaelement I beläget smalare element II är anordnat förtransport av den brutna isen 15 sidlänges och under denobrutna isen 14. Det övre bredare elementet I är försettmed ett i huvudsak platt underdelsparti av en lutandeframdel 10 och uppvisar liten anfallsvinkel a, företrädes-vis mindre än 15°, och som är anordnad för att byta isen14 nedåt vid gång framåt 9. Vidare är elementet I försettmed en i huvudsak platt akterdel 12, som är försedd med en liten anfallsvinkel C, företrädesvis mindre än 20° och somär anordnad att bryta isen 14 nedåt vid gång akterut,Vidare är anordnat ett mellan framdel 10 och akterdel 12beläget helt platt underparti 11, som är beläget nedanförundersidan på den tjockast jämna is som fartyget 3 äravsett att bryta med kontinuerlig fart, och samtidigtbeläget utanför den bredd D som det nedre smalare elemen-tet II uppvisar. Utanför den bredd D som det sagda nedresmalare elementet II uppvisar, med framdel 10 underparti 11 och akterdel 12 är vid farkostens maximala bredd B anordnade inåt lutande sidopartier 4, 5 med en relativt stor anfallsvinkel e företrädesvis mellan 45 och 60” somvid girning är anordnade att bryta isen uppåt vid gång iobruten is 14. Det nedre smalare elementet II är försettmed i huvudsak vertikala sidopartier 7, 8, 9 och som i för10 och i akter 12 i körriktningen uppvisar en kilform medliten öppningsvinkel n.r företrädesvis mindre än 40°,varvid vid gång framåt 7 tack vare kilformen är anordnadatt tvinga den därvid brutna isen sidlänges samt helteller till en del under den obrutna jämna isen 14 och vidgång akterut 9, tack vare kilformen tvinga den brutna isensidlänges utmed akterdel 12 och underparti 11 för attminska mängden av is att komma i kontakt med farkostenshuvudpropellrar och roder 19, 20.

För manövrering i is är framdel, under-parti och akterdel vid skrovets maximala bredd såledesförsedda med inåt lutande sidopartier med en relativt storanfallsvinkel mot vattenlinjen, företrädesvis mellan 45och 60°, anordnat att bryta isen sidlänges och uppåt vidgirning i obruten is.

Farkosten är försedd med åtminstone tvåsidopropellrar 18 som är monterade nertill på sidopartier-na 8 av skrovets smalare element 11, och som är riktade såatt propellerströmmen uppåt med liten vinkel u, före-trädesvis mindre än 10°, träffar underpartier 11 av detövre elementet I för att därvid vid gång framåt accelereraden brutna isen akteröver och förhindra att denna iskommer i kontakt med fartygets huvudpropellrar 19.

Förkosten är försedd med åtminstone tvåbogpropellrar 17, vilka är monterade nertill på de förligasidopartierna 7 av det nedre smalare elementet 11 såriktade att propellerströmmen uppåt med liten vinkel s, företrädesvis mindre än 10°, och sidlänges med liten 21 vinkel X, företrädesvis hälften av öppningsvinkeln n, träffar underpartiet 11 av sagda bredare element 1, föratt vid gång framåt i jämn is accelerera den därvid brutnaisen sidlänges under obruten is 14 och därigenom väsent-ligen eller helt göra den brutna rännan bakom fartygetisfri vid gång i jämn is och med kontinuerlig hastighet.Vid gång till exempel i isvallar vars undre del sträckersig under den platta delen 11 av övre elementet I riktaspropellerströmmen skapad av bogpropellrarna 17 akterut,varvid denna tillsammans med den akterut riktadepropellerströmmen skapad av sidopropellrarna 18 flyttarmestadelen av isvallen till området akterom farkosten ochsom sålunda sprids över ett större område och minskarismotståndet för efterföljande farkost. Sido- ochbogpropellrarna 17, 18 är monterade på en ansats 21 föratt minska propellerströmmens kontakt med de vertikalasidopartierna 7, 8 och ett vingliknande utskjutandeelement 22, företrädesvis med sidolängd som åtminstonesträcker sig till propellerns center, är anordnat framförsido- och bogpropellrarna 17, 18, för att tillsammans medansatasen 21 åstadkomma rotation av brutna isflak samtförhindra dessa att blockera propellrarna 17, 18.Propellrar 17, 18 är anordnade att roterakring en stödjepunkt vid sidorna av farkosten på sätt sommöjliggör riktning av propellerströmmen framåt ellerakteröver, uppåt eller nedåt.Farkostens huvudpropellrar 19 är anordnadeatt roteras kring stödjepunkter under aktern av farkostenpå sätt som möjliggör riktning av propellerströmmen framåteller akteröver, samt godtyckligt åt bägge sidor vilketgör att rodren 20 kan elimineras. Farkostens drivpropellrar 23, 24 är anordnade att drivas medelst axel lO 22 från en drivanläggning som är belägen framför sagdapropellrar i sagda nedre smalare element II.

På däcksnivàn är skapad en utsvällning 23som minskar risken för att bruten is hamnar på fartygetsdäck 14.

Funktion och beskaffenhet av uppfinningentorde ha förstàtts klart av det ovan angivna och medkännedom även om det på ritningarna visade men uppfin-ningen är naturligtvis inte begränsad till de ovanbeskrivna och på de bifogade ritningarna visade utföran~dena. Modifieringar är möjliga, särskilt när det gäller deolika delarnas beskaffenhet, eller genom användande avlikvärdig teknik, utan att man fràngàr skyddsomràdet för uppfinningen, såsom den definieras i patentkraven.

Claims (9)

S283 P5SE LG / COW PATENT REQUIREMENTS Device for icebreaking with an icebreaking hull in a vessel can be a drawstring, in which the hull is formed by two functionally separate elements (I, I1) of different widths, of which a bar and wider element (I) are coated adjacent to the intended waterline (13) for breaking unbroken ice (14), while a lower narrower element (II) Or intended for transporting broken ice laterally and under the unbroken ice (14), that the wider element (I) Or provided with a substantially flat inclined front part (10) and has a small angle of attack (a), preferably less than °, and which is arranged above to break the ice (14) downwards when walking aft with a substantially flat stern part (12), which Or is provided with a small angle of attack (c), preferably less than ° and which between the front part (10) and the stern part (12) has a substantially completely flat lower part (11), which is coated below the underside on the thickest smooth ice which the vessel is intended to break at continuous speed and at the same time coated outside the width (D) as it said ne the narrower element (II) has, with front part (10), lower part (11) and stern part (12) located at the maximum width of the vessel (B) and provided with inwardly inclined side portions (4,5) with a relatively rigid angle of attack ( e), preferably between 45 and 60 °, arranged to break the ice upside down when turning in unbroken ice (14), and that the lower narrower element (II) is provided with substantially vertical side portions (7,8,9) and in Dir (10) and in stern (12) in the direction of direction a wedge shape with a small opening angle (n, r), preferably less than °, whereby when walking forward (7), thanks to the wedge shape Or arranged to force the ice broken thereby sideways and completely or 24 to some extent under the unbroken smooth ice (14) and when going aft (9), thanks to the wedge shape forcing the broken ice sideways along the stern (12) and lower part (11) to reduce the amount of ice to enter contact with the vehicle's 5 main propellers and rudders (19,20). Device according to claim 1, characterized in that the vessel Or is provided with at least two side propellers (18) which Or mounted at the bottom in the side portions (8) of the narrower element (II) of the hull, and which Or directed so that the propeller drum upwards at a small angle ( u), preferably smaller On °, strikes lower portions (11) of the upper element (I) in order to accelerate the broken ice aft to the front and prevent this ice from coming into contact with the ship's main propellers (19). Device according to any one of claims 1-2, characterized in that the vessel Or is provided with at least two bow propellers (17), which are mounted at the bottom of the front side portions (7) of the lower narrower element (II) so directed that the propeller drum upwards with a small angle (s), preferably less than °, and laterally with a small angle (x), preferably half of the opening angle (n), is arranged to strike the lower part (11) of said wider element (I), in order to in even ice, the ice broken thereby accelerates laterally under unbroken ice (14) and thereby substantially or completely make the broken gutter behind the vessel ice-free when walking in even ice and at a continuous speed, and as when walking, for example in ice banks, the lower part of which stretches below the flat part (11) of the upper element (I) and salunda Or arranged to direct the propeller drum created by the bow propellers (17) aft, so that this together with the aft-directed propeller drum created by side propeller The runners (18) move most of the ice sheet to the area aft of the vessel, which is thus spread over a larger area and reduces the ice resistance of subsequent vessels. Device according to claims 2 and 3, characterized in that the side and bow propellers (17, 18) are mounted on a shoulder (21) for reducing the contact of the propeller stream with the vertical side portions (7, 8). Device according to claim 4, characterized in that a wing-like projecting element (22), preferably with a side length which at least extends to the center of the propeller, is arranged in front of the side and bow propellers (17, 18), so that together with the shoulder (21) Perform rotation of broken ice floes and prevent them from blocking the propellers (17,18). Device according to claims 2-3, characterized in that propellers (17, 18) are arranged rotatable about standing point at the sides of the vessel p1 set as possible direction of the propeller drum forwards or aftwards, upwards or downwards. 7. Device according to claim 1, characterized in that the main propellers (19) of the vessel are arranged rotatable about support points below the stern of the vessel in a manner which allows the direction of the propeller current forward or aft, and arbitrarily dredge sides, which allows the rudder (20) to eliminated. 26 Device according to claim 1, characterized in that the vehicle has propulsion propellers which are arranged to be driven by means of a shaft from a propulsion system which is coated in front of said propellers in said lower narrower elements (II). Device according to claim 1, characterized in that a dowel (23) is created at the frequency level which is arranged to reduce the risk of broken ice ending up on the deck.