FI67813B - ISBRYTARFARTYG - Google Patents

Description

Ι · Α ^ · 1 ADVERTISEMENT £ .Πθ.Λ ~ 2 1J ^; UTLÄGGN, NGSSKRIFT O / o I ό C (45) n ..: i (51) Kv.lk//lnt.CI.* B 63 B 35/08, 35/12 SUOMI FINLAND (21) Patent application - Patentansökning 783 ^ 62 (22) Application date - Ansökningsdag 13-11-78 (Fl) (23) Starting date - Giltighetsdag 13-11-78 (41) Has become public - Blivit offentlig 20.06-79

National Board of Patents and Registration Date of publication and publication. -

Patent- and Register-Register '' Ansökan utiagd och utl.skriften publicerad 28.Ο2.85 (32) (33) (31) Privilege claimed — Begärd priority 19-12.77 USA (US) 861737 (71) Exxon Production Research Company, P.O. Box 2189, Houston, Texas 77001, USA (72) Hans Otto Friedrich Jahns, Houston, Texas, Joe Darr Wheeler, Bellaire, Texas, USA (7 ^) Berggren Oy Ab (51+) Icebreaker - I sbrytarfartyg

The present invention relates to an ice-breaking vessel which breaks ice at its front.

Proposed methods for breaking and removing ice for fixed structures have included installing cones on the support members of the structure to force the ice cover to bend and break as it moves against the inclined surface of the cone, melting the ice layer around the structure and grinding the ice layer into relatively small pieces. Many of these proposed methods could also be applied to floating vessels, with the most advanced and promising ice grinding method. However, the energy requirements for grinding ice are very high and the technical and economic viability of this method is by no means certain.

Systems for ice breaking are described in U.S. Patent Nos. 3,768,428 and 3,888,544. A system for actual ice cutting is described in U.S. Patent No. 3,921,560.

The apparatus for cutting ice according to U.S. Patent No. 3,921,560, 2 6781 3, is located at the bow of the ship and the cutting member is a rotating, horizontally mounted, helical member.

In addition, it is known that screw devices of a certain shape can be used to provide thrust to a ship, with the screw being located below the surface of the water. This is described in U.S. Patent No. 2,806,441.

In addition, U.S. Patent No. 1,482,511 discloses a series of endless chains having ice-scratching and fracturing teeth mounted on the bow of a ship.

This known device differs from the present invention in that it is installed inside a ship, which of course makes installation, especially afterwards, cumbersome. In addition, it is based on intermittent impact movement and not smooth screw movement.

U.S. Patent 3,985,091 discloses wheels mounted on the sides of a ship to facilitate forward travel and which, due to the long bow, adhere to a substantially intact surface of ice.

The object of the present invention is to provide the vessel with screw means which help to raise the bow of the vessel onto the ice and thus to break the ice by means of the weight of the vessel. To this end, the invention is characterized in that two ice-engaging rotating screws are mounted on the front of the vessel so that their shafts are fixed to the vessel and spaced from the hull, each axis of the screws extending obliquely upwards and forwards and the lower surface of the screws engaging the ice. to pull the bow up onto the ice, whereby the traction of the bolts and the downward force of the bow together cause the ice to break.

When the screw means are rotated at a suitable speed, these act on the adjacent ice layer and develop transfer forces, 3 6781 3 which tend to move the vessel onto the ice layer and thus allow the vessel weight to provide a bending moment in the ice until it breaks. The ice-breaking devices according to the invention, in operation, break the ice into much larger blocks than the previously known grinding processes and therefore consume much less energy than the previously known devices and achieve results which have not been possible so far.

If desired, the movement of the vessel over the ice layer can be assisted by additional pushing means in addition to the said towing or towing means. These propulsion means may be means located on the ship either internally or externally, or both.

In the accompanying drawings, Figure 1 is a schematic top view of the bow of an ice-breaking vessel according to the invention, Figure 2 is a schematic side view of the bow of the vessel of Figure 1, Figure 3 is a cross-sectional view of bearing and gear housings used to support and drive the screws of Figures 1 and 2; 4 shows graphically the resistance and power of the vessel in relation to the speed of rotation of the screws and Fig. 5 shows graphically the power of the screw and propeller in relation to the speed of rotation of the screws.

An application of the present invention to an icebreaker is illustrated in Figures 1 and 2. Figure 1 is a top view and Figure 2 is a side view of a conventional bow 21 of a conventional icebreaker 20 equipped with the apparatus of the present invention.

As shown in Fig. 1, the screw 1 is placed on both sides of the bow. Each screw 1 comprises a helical vane 2 attached to a spindle 3. For use in an ice-breaking vessel, it is required that screws of the required size can be either cast or forged. The whole screw can be formed at once or parts of the screw, perhaps the length of the thread pitch, can be formed 4 6781 3 separately and then welded together. The optimal combination of screw pitch, taper, length and blade depth in different applications depends on many factors, e.g. the size of the structure, the rotational speed of the screw, the thickness of the ice, the relative speed at which the ice layer and the structure move against each other, and the strength of the ice.

In its simplest aspect, the screw means used in the present invention can be considered as a simple machine, analogous to a barb or feed screw in a screw rack. In fact, the screw is an inclined plane wrapped around the cylinder. The inclined plane usually takes a helical shape, which is called a screw surface.

A simple screw can be described as having a rotatable core provided with spaced apart helical blades mounted in a fixed position on said core. The wings form channels, smooth gaps between the threads.

The total length of the wings or between the wings depends on the inclination of the wings and the diameter of the heart. The wing angle is called a helical pitch. Typically, the axial length of the wings is in the range of 1 / 10-5 of the core diameter. The ratio of screw length to diameter (L / D) is 2: 1-25: 1, preferably 2: 1-15: 1 and even more preferably 2: 1-10: 1.

5 6781 3

The pitch of a thread is defined as the length along the longitudinal axis of the core along one complete revolution of the wing or as a projection of this complete revolution along the axis of the helix.

The screw can be said to be right-handed or left-handed depending on the direction of the helical wings compared to their initial position.

The wings can also be called screw blades. In this explanation, the term blade seems quite appropriate.

Since the rotational movement of the screw causes the blades to groove in the ice, which causes adhesion and displacement, which in turn makes it possible to convert the rotational movement of the screw into a horizontal traction that raises the bow above the ice layer, it is important to provide ice cutting edges. The grooves cut by the blades are called traction grooves.

The drive units 30 mounted on the vessel 20 generate the necessary power to rotate the screws. The drive units may be powered by the ship's main transport system or may be independent motors used only to propel the screws. The drive units are schematically illustrated in Figure 1, as they can be of any type of machine or power source, including internal combustion engines, hydraulic motors, electric motors, or steam engines.

In the particularly preferred embodiment described, the power for rotating the screw is transferred from the drive unit 30 to the screw 1 via a drive articulation comprising a drive shaft 31 and a series of bevel gears. Details of the drive articulation and bearing housings 23 and 23a are illustrated in Figure 3. The drive shaft 31 extends from the drive unit 30 on board through the protective housing tube 32 to the gear housing 34. The drive shaft 31 is rotatably mounted on a bearing 33 in the gear housing wall. Inside the gear housing 34, a bevel gear 35 is attached to the drive shaft 31. The bevel gear 35 is toothed on a second bevel gear 36 fixed to the end of the screw spindle 3.

The mandrel 3 is rotatably mounted in two bearing housings 23 and 23a which are rigidly attached to the vessel 20 by support arms 22 and 22a. Inside each bearing housing 23 and 23a, the screw mandrel 3 tapers to 6 6781 3 smaller diameter bearings 25 and 25a. A plurality of bearing rings 26 and 26a are formed in each bearing 25 and 25a. The bearing housings 26 and 26a are positioned and machined to fit the bearing frames 27 and 27a of the wedges 24 and 24a. The bearings (no reference number) are, of course, located in said bearing rings to allow free rotation of the screw spindle 3.

It is preferred that the screws be oriented so that the respective lines of contact are inclined upwards towards the front ends of the screws at an angle greater than 0 ° but less than 45 ° from the horizontal when the ship is at rest in the water. The screws should be located on the bow 21 so that when the vessel 20 and the ice layer 10 move against each other, the ice layer contacts the undersides of the screws. More specifically, the ice layer should contact at least one or more points along the edge of the screw blades on the line of contact.

The screws 1 should preferably be located far enough away from the vessel 20 so that the ice pieces do not tend to wedge between the screws and the vessel in order to stop or prevent the rotation of the screws. Depending on the shape of the bow of the vessel, it is possible that the longitudinal axes of the screws form an angle towards the bow of the vessel (see Figure 1). If they are at such an angle, the vertical planes in which the axes of the screws are located shall intersect the vertical plane containing the longitudinal axis of the vessel at angles not exceeding 45 °. Of course, it is perfectly acceptable that these levels are substantially parallel.

As the vessel and the ice layer move against each other, the screws are rotated to act on the ice layer to create a traction that tends to pull the ice-breaking bow of the vessel 1 forward and up to the ice layer 10. This, of course, exerts high forces on the screws with both vertical and horizontal components. The bolt support arms 22 and 22a should be strong enough to withstand these forces and transmit them to the vessel 20. The bearings in the bearing housings should also be designed to operate with the expected radial and axial forces.

When the bow of the vessel is raised, at least a portion of the weight of the vessel bends the ice layer downward to break it by bending. The rotating screws 6781 3 try to clear the broken ice out of the ship's passageway. If the width of the vessel increases from bow to stern, the amount of crushed ice also increases from bow to stern, because a continuously wider road is broken through the ice layer from bow to stern. To more effectively remove broken ice from the vessel's passageway, the screws may be tapered so that the wing depth increases from front to back, as shown in Figures 1 and 2. The screws may also be tapered so that the diameters of the screw spindles or cores increase from front to back.

As the vessel advances through the ice layer, the ice layer comes into contact with at least some of the points along the outer edges of the screw vanes located on the line of contact. Naturally, as the screw rotates, different points on the edge of the thread are located on the line of contact and make an adhesive contact with the ice layer at different times. Although different points along the edge of the screw thread make contact with the ice layer at different times, the contact points between the screw thread and the ice layer remain continuous. When the screws are rotated to pull the vessel forward onto and through the ice layer, the points of contact indicated by the troughs in the ice layer move backwards along the line of contact, i. towards the bow when viewed from the stern of the vessel.

As for the ice layer, the displacement of the points of contact in a direction parallel to the direction of movement of the ship may be backwards, i. towards the stern of the vessel or they may move forward or not move completely in the direction of the vessel. It should be noted that the points of contact may move in a direction not exactly parallel to the direction of travel of the vessel due to the orientation of the screws on the vessel, but nevertheless have a velocity component parallel to the direction of movement of the vessel. Assuming that the screws are rotated to move the vessel forward through the ice layer, the movement of the contact points relative to the ice layer in the same direction as the ship's course of travel has some meaning.

If the touch points move forward, i.e. in the same direction as the vessel moves through the ice layer, the screws actually cause resistance to the vessel’s movement. The ship's second conveying system forces the ship to move through the ice so fast that the screws scrape the ice in the opposite direction to the ship's movement. This is known as negative slippage and should be avoided because the screws are actually an obstacle to the movement of the vessel through the ice layer.

6781 3

If the points of contact do not move in the direction of the vessel's direction of movement, known as zero slip, the screws may or may not promote the vessel's forward movement. It is possible that the screws can be rotated under zero skating conditions with just enough torque to stay level with the movement of the vessel but not to cause this movement. But if a torque of more than this amount is produced on the screws, these then promote the forward movement of the vessel.

It is preferred that the screw means and means for rotating the screws in a particular vessel be arranged so that the screws can be rotated to move the points of contact with the ice relative to the ice layer in a direction parallel to the intended direction of the vessel but in the opposite direction (i.e. positive slip). always twice the design maximum speed of the vessel. The design maximum speed is defined as the maximum speed of the vessel in relation to the ice layer as the vessel moves in the water covered by the ice layer, when the screws are intended to assist the movement of the vessel. It is desirable that the slip speed be less than or equal to (but in the opposite direction) than the speed of the vessel relative to the ice.

A greater amount of slip (slip, slip) must be accepted for limited periods of time under certain conditions, such as when leaving essentially thick ice. The present invention can be used to help an icebreaker-shaped vessel either move through ice-covered water or maintain a fixed position in water. In addition, the present invention can be used in both self-propelled vessels and non-self-propelled vessels such as barges. Under certain circumstances, some means may be required to push the vessel against the ice layer to prevent it from sliding backwards. This force can be provided by a number of means, including the screws themselves, a conventional anchoring system, a ship's main conveying system, or one or more pushing means, such as tugs.

It is particularly preferred that the screws are opposite-handed, i. one right-handed and the other left-handed 6781 3 (see Figure 1). This makes it necessary to rotate the screws in opposite directions so that both screws act simultaneously on the ice layer by pulling the bow of the vessel over the ice layer. If the screws with opposite hands were rotated in the same direction, the ship would tend to turn and take a new direction.

In some cases, it may also be desirable for the screw means and their support means, i. the support arms are designed in such a way that the screws can be tilted up from the water or even removed from the vessel when the vessel is moving in ice-free water. Otherwise, the screws may block the flow of water caused by the vessel and thus provide additional resistance to the vessel. The situation can be the same when there is only a thin or broken ice cover on the water. Alternatively, the screw means may be designed to assist in the transport of the vessel.

From time to time, it may be desirable to improve the bite of the screw coils, i.e. the adhesion and thus their traction. Screwdriving can be especially important when a ship has to cope with thick ice formations such as stagnant ice. Screw drive can be increased by equipping the thread brush with additional means to cut the grooves in the ice. Cutting means, such as cutting teeth, cut the ice with a greater capacity than a normal threaded edge to create a traction groove in which a screw thread can pass, thus increasing the traction of said screw means.

Example

A test program model was performed in order to determine the advantage of the structure using a pair of screws mounted on the bow of an icebreaker-shaped vessel. A 1/36 scale Wind Class icebreaker model was used in these tests. The surface of the model was made especially with the aim of obtaining the same coefficient of friction as the hull of a full-size ship has with ice. The surface was sandblasted to produce a coefficient of friction of 0.25 between maHin and ice. The model was loaded with weights divided over its length in order to obtain a gyration radius typical of an icebreaker. Two tapered screws with helix angles of 30 ° were mounted one on each side of the bow substantially as shown in Figures 1 and 2.

A 550 W DC motor was chosen to use the screws. The speed of the motor was changed with the speed controller of the DC motor. A gear housing with two output shafts was installed, each connected to one screw by a flexible shaft. The rotational speed of the screws was measured by counting the pulses generated by a magnetic probe attached to a plate driven by a wedge belt from the motor shaft. A torque meter was used during some experiments to measure the torque of a single screw. The power unit mounted on the model measured the resistance of the model to the ice layer when the model was towed against it. During each experiment, the model was towed in an ice layer and its velocity relative to the ice layer was measured.

The results of the model tests obtained were corrected by a scale factor in order to predict the ice-breaking capacity of a full-size Wind Class icebreaker when this is equipped with a pair of bolts mounted on the bow. Figures 4 and 5 illustrate some of the predicted capabilities in a full-size icebreaker.

Figure 4 shows graphically the resistance of an icebreaker with a pair of screws through the ice and the power required to rotate the screws as a function of the rotational speed of the screws. For this graph, the reduced model was drawn through a layer of ice with a full-size equivalent thickness of 168 cm at a full-speed equivalent speed of 2.3 knots. The resistance to the movement of the ship through the ice decreased as the screw speed increased, as can be seen from the curve "resistance with screws". The power required to rotate the screws increased as the rotational speed increased. This relationship is illustrated by the "power" curve. For comparison, the motion resistance of a full-size Wind Class icebreaker without screws through a 168 cm thick layer of ice at a speed of 2.3 knots is shown by a horizontal dashed line "resistance without screws".

67813 The "Resistance with Screws" and "Power" curves are based on test results of the actual model resistance and screw torque converted to full size by a scale factor. The "Resistance without screws" curve is an estimate calculated from Vance's prediction formula. Vance's prediction formula showed close agreement with the results of model tests (GP Vance, 1975, A scaling system for ships modeled in ice: article presented in Ice Tech 75, Soc. Naval Architects and Marine Engineers, pp. H ^ -1— H ^ -34).

The graphical representation of Figure 4 shows, under certain conditions, that the screws of the present invention provide a significant reduction in the ship's resistance to movement through ice-covered water. In fact, screws can reduce the resistance to movement between a ship and ice to zero if they are rotated at a speed slightly greater than 110 rpm.

This means that the screws alone, operating at this speed, carry the vessel through a 168 cm thick layer of ice at a speed of 2.3 knots. It should also be noted that approximately 24,000 kW of power would be required to rotate the screws at a speed of just over 110 rpm.

Since the power required to rotate the screws increases faster than the resistance of the vessel's movement through the ice decreases with increasing speed of the screw, it is obvious that the screws are more efficient at lower rotational speeds in the described area.

Therefore, in a preferred embodiment, it may be advantageous to use screws at low rotational speed and to supplement the rest of the thrust required to move the vessel through the ice from a conventional source of propulsion, such as a propeller system. The estimated total female power required for the total number of bolts and propellers is plotted as a function of screw speed in Figure 5.

Like Figure 4, the graphical representation of Figure 5 illustrates a Wind Class icebreaker moving through 168 cm thick ice at a speed of 2.3 knots. The curve labeled "screw power" indicates the power required to rotate the screws at the corresponding screw speed. The additional thrust required to move the vessel through a 168 cm thick layer of ice at a speed of 2.3 knots is obtained from the marine propeller system. The power required to develop the required thrust from the ship-propeller system is shown by the "ship-propeller power" curve. The sum of the rust power and the propeller power is the total power required to move the vessel through 163 cm of ice at a speed of 2.3 knots and this power is described by the "total power" curve.

The minimum power of the combined propeller and propeller system required to move the vessel through 168 cm of ice at a speed of 2.3 knots is approximately 18 to 60 rpm in the 18,000 kW screw speed range. This compares with the 24,000 kW needed to move the vessel through 168 cm of ice at a speed of 2.3 knots solely with screws and the 37,000 kW needed to move the vessel through 168 cm of ice with a speed of 2.3 knots. exclusively with a marine propeller system.

The experimental results provided herein are merely illustrative of the performance and advantages of the present invention. There are a large number of variables that will be apparent to those skilled in the art that, under certain circumstances, may alter the precise performance of the invention under the circumstances in question. These variables include screw pitch, screw thread depth, screw taper, screw contact line slope, ship weight distribution, coefficient of friction between ship and ice, ice strength, and so on.

It will be appreciated that the present invention significantly reduces the overall power required to move an icebreaker vessel with an icebreaking bow adapted to cause a downward force on the ice through the ice-covered water and to help a structure located in the ice-covered water resist , the horizontal forces caused by the moving ice layer and also helps the vertical support members to resist the moving ice layers.

An important additional advantage of the invention is that it provides means for movement and stability in ice-covered water, which means have not previously been available for previously known devices, regardless of power requirements.

Claims (10)

1. An icebreaker, which breaks the ice with the foreshore, characterized in that two pre-mounted rotatable screws (1) are mounted in its foreshore, that their axles are attached to the ship and are located at some distance from the ship's hull, each shaft of the screw (1) extending obliquely upright and front easterly, in that the lower surface of the front directed portion of the screws engages the ice and pulls up the front (21) of the vessel (20) onto the ice (10), (21) downward directed force together causes the ice breaking. Vessel according to claim 1, characterized in that the screws (1) are provided with means for cutting a latch in the ice which is in front of the vessel (20). Vessel according to claim 1, characterized in that the screws (1) are rotatable so that their contact surfaces with the ice layer move rearward parallel to the longitudinal axis of the vessel. Vessel according to claim 1, characterized in that the screws (1) are stored in bearings which are firmly fixed in the vessel (20) and allow the screws (1) to rotate freely from the ship's hull. 5. A vessel according to claim 1, characterized in that a screw (1) is mounted on one side of the vessel and is right-handed and the other screw is mounted on the opposite side of the vessel and is left-handed. A vessel according to claim 1, characterized in that it is provided with drive means for advancing the vessel in a known manner.