JPS6147756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables a ship on an ice-covered body of water to resist lateral forces created by the ice layer and to move through the ice layer. This relates to a ship equipped with the following equipment.

DESCRIPTION OF THE PRIOR ART When drilling and producing oil offshore, it is important that the structures performing such operations are parked at a location above the wellbore. In the southern and northern climates of the world, large ice layers form on bodies of water during cold winter weather. Wind, tides, and currents tend to move these ice layers. The forces exerted by these moving ice layers can often destroy fixed structures and are sometimes great enough to displace floating ships. To avoid such accidents and disturbances, it is necessary to reduce the magnitude of the lateral forces of the ice layer acting on offshore structures. The obvious solution, other than designing a fixed structure to withstand the forces of the expected ice layer, is to fracture and remove the ice around the structure.

The ice crushing device is US Patent No. 3768428.
No. 3888544. The actual ice-cutting device is a U.S. patented device.
It is described in the specification of No. 3921560.

The ice cutting device of US Pat. No. 3,921,560 is placed on the bow of a ship, and the cutting member is a horizontally supported rotating helical member.

Furthermore, it is known that certain designs of screw devices are used to provide propulsion for ships, which screws are placed below the surface of a body of water. This is described in US Pat. No. 2,806,441.

Furthermore, U.S. Patent No. 1,482,511 specifies that
It shows multiple endless chains with ice-breaking teeth supported on the bow of the ship.

U.S. Patent No. 3,667,416 describes “a ship having a bow that slopes from the front to the rear, in which the bow of the ship is placed on the ice by the action of the propulsive force, and the bow of the ship is placed on the ice by the action of the weight of the ship. The technology for ``a ship that crushes a ship'' is described. However, in order to make more effective use of the ship's weight in combination with the ship's propulsion power, it has been proposed to assist the ship in breaking the ice by using a towing or pulling device. is not mentioned. Also,
Nor is there any mention of the use of drag or pulling devices, without other propulsion, to push the ship's plow onto the ice layer.

Canadian Patent No. 1011605 describes a steel boat-shaped foredeck that rests on unbroken ice.
An icebreaker is described with a supporting device supported by a shaped forecastle.

SUMMARY OF THE INVENTION In its most general aspect, the invention can be viewed as a ship having an improved ice contact system for large ice covering navigable waters.
These devices that act on ice break it up without bending it.

A preferred ice contacting device is a screw device having a relatively large length to diameter ratio.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides, in its preferred embodiment, a ship:
Eliminates the above-mentioned problems and resists the lateral forces created by moving the floating vessel into or through the ice layer by operating it in a unique ice-breaking manner. To provide a ship with a device, preferably a screw device, with which it can be held in position.

The present invention, in its broadest sense, uses a floating ice contacting device, particularly a screw device, on the surface of a body of water to contact adjacent ice layers at various predetermined angles for moving a ship.

In an embodiment, the screw device, when rotated at a suitable speed, interacts with the adjacent ice layer and creates a tensile force to move the ship onto the ice layer, so that the weight of the ship causes the ice layer to A bending moment is applied to bend and fracture the ice layer. When operated, the ice crushing device according to the invention breaks the ice layer into larger pieces of ice than prior art drilling methods, and therefore consumes less energy and provides better results than prior art devices. It will be done.

In the present invention, a pair of screws are installed, one on each side of the hem. These screws are constructed and arranged in such a way that, when rotated, they pull the bow of the ship onto the adjacent ice layer. The hesaki is designed to ride on the ice. The additional load from the hesaki bends the ice downward and breaks it.

By successive rotations of the screw, ice debris above and below adjacent ice layers can be easily cleared from the ship's passage.

According to the invention, it is possible not only to help the ship move in ice-covered waters, but also to keep the ship in place without being displaced by the movement of ice blocks, i.e. ice floes. It can be used as it is possible.

Certain embodiments of the invention allow a ship to resist the lateral forces of a moving ice layer and remain in place, and by fracturing the ice layer into small pieces, the ship can allow you to move.

In other embodiments of the invention, the icebreaker can be equipped with a single or two screws on its prong. Propulsion is provided by an external power source (e.g. push boat)
or by power integrated in the stern.

The ice crushing device according to the invention thus offers even greater benefits than the prior art.

In summary, the invention comprises a screw device rotatably supported on a ship designed to be placed in ice-covered bodies of water, and a device for rotating the same. When the screw device rotates, it acts on the ice layer,
Bend it and eventually crush it.

An embodiment of the invention, which is an icebreaker, is shown in FIGS. 1 and 2. FIG. 1 is a plan view of a conventional vessel 20 for crushing ice by riding on it, with the device of the present invention installed on a conventional head 21, and FIG. 2 is a side view thereof.

As shown in FIG. 1, screws 1 are placed on each side of the hem. Each screw 1 consists of a helical wing 2 fixed to a shaft 3. For use on icebreakers,
It is already known that screws of the required size can be cast or forged. The entire thread can be formed from multiple parts, each part being one part of the thread.
These can then be welded together. The optimal combination of thread pitch, taper, length, and wing depth for any particular application depends on a number of factors, including vessel size, thread rotational speed, This includes the thickness of the ice, the relative speed of the ice layer and the ship, and the strength of the ice.

In the simplest case, the screw device used in the invention can be considered as a simple machine similar to the worm of a jack or screw rack. fact,
A thread is an inclined surface wrapped around a cylinder. This inclined surface is generally helical in shape and can sometimes be thought of as a helix.

A simple screw can be described as having a continuous helical blade supported in a fixed position on a rotatable core. The vanes form grooves and can sometimes be referred to as peaks between the grooves.

The total length of the vane or mountain depends on the slope or angle of the mountain and on the diameter of the core. The angle of a mountain can be thought of as a pitch. Typically, the axial length of the vane may range from 1/10 to 5 times the diameter of the core. The length to diameter ratio (L/D) of the thread may be from 2:1 to 25:1, preferably from 2:1 to 15:1, most preferably from 2:1 to 15:1. :1 to 10:1.

Pitch is defined as the length across one rotation of the blade along the longitudinal axis of the core, or as the projection of the blade along the helical axis.

A thread can be described as right-handed or left-handed depending on the direction of the helix relative to its initial position.

The vanes or ridges can also be referred to as the wings of the screw. For purposes of this description, the term wing is most appropriate.

Due to the rotational movement of the screw, the wings cut grooves in the ice,
If necessary, a blade for cutting the ice, e.g. an ice-cutting device, is used, since the rotational movement of the screw creates a gripping force and a traction force that converts into a horizontal pulling force to raise the bow of the ship above the ice layer. It is important to install it on the wing. The groove cut by the wing can be called a traction groove.

The drive unit 30 supported on the side of the ship 20 is
Generates the power necessary to rotate the screw. The drive unit can be powered by the ship's main propulsion system, or it can be an independent prime mover used only to turn the screw. The drive unit may be any type of engine or power source, including internal combustion, hydraulic, electric or steam, so the first
It is shown schematically in the figure.

In the particularly preferred embodiment shown, the power for rotating the screw is transmitted to the screw 1 from a drive unit 30 via a drive mechanism, which drive mechanism consists of a drive shaft 31 and a set of bevel gears. . Details of drive mechanism and bearing boxes 23, 23a
is shown in FIG. The drive shaft 31 extends from the drive unit 30 through a protective casing tube 32 into a gear box 34 on the ship's side. The drive shaft 31 is rotatably supported by a bearing 33 on the wall of the gear box. Inside the gear box 34, a bevel gear 35 is fixed to the drive shaft 31. The bevel gear 35 meshes with a second bevel gear 36, which is fixed to the end of the screw shaft 3.

The screw shaft 3 is rotatably supported within two bearing boxes 23, 23a fixed to the ship 20 by support arms 22, 22a. Each bearing box 23, 2
In 3a, the screw shaft 3 tapers towards a smaller diameter journal 25, 25a. Several bearing races 26, 26a are formed in each journal 25, 25a. The bearing races 26, 26a are machined and arranged to match the bearing races 27, 27a of the keys 24, 24a. Bearing (not shown)
is, of course, arranged within the bearing race so that the screw shaft 3 can rotate freely.

Although the drive unit in this particular embodiment is located on a ship, in some cases it may be more advantageous to mount the drive unit directly on the screw shaft. For example, if electric power is used to drive a screw, part of the shaft in the bearing housing can be engineered as the rotor of the electric motor, and the bearing housing can be made as the stator of the electric motor. .

As previously discussed, screws for use on board icebreakers can be made by casting or forging. It was anticipated that the large screws used in the legs of semi-submersible platforms and the supports of gravity-based structures would be too large to be forged or cast. FIG. 4 is a sectional view of the assembled screw helical wing 2 and screw sleeve 4. The sleeve 4 is made from a piece of steel plate. The wing 2 is formed by a plate welded at right angles to the steel plate of the sleeve 4. The blade 2 is inclined at a predetermined helical angle with respect to the cylinder axis. Reinforcement plates 5 and 6 are welded to the top and bottom of the wing 2 to reinforce it. If desired, the cutting teeth 7 can be welded to the outer edge of the wings 2 of the screw. The utility of cutting teeth will be obvious.

In order to use the invention for breaking up ice layers in a body of water surrounding a vessel placed in a body of water, the screw is suitably supported, for example by bearing on the vessel at a number of positions along its length. It is necessary.

The screws should be placed in alignment so that the ice layer contacts the wings of the screw. As the screw rotates, its wings act on the ice layer, raising or pushing it down depending on the direction of rotation, imparting a bending moment to the ice layer. A sufficiently large bending moment will bend and fracture the ice layer.

For embodiments of the invention for ships with ice-breaking shaped heads, the line of contact between the screw and the top surface of the ice (defined below) is in the same vertical plane as the axis of rotation of the screw, but It's below. The contact line is the line in the vertical plane that contacts the lowest point above the crest or edge of the wing of the screw. If the thread is not tapered, the line of contact will be parallel to the axis of rotation of the thread.

A single screw centered longitudinally on the longitudinal axis of the ship can be used. As shown in Figure 1, using two screws supported at the bow of the ship,
One on each side of the longitudinal axis of the ship is preferred. Each contact line of screw 1 is
When the ship is at rest in a body of water, the screw 1 is inclined upwardly toward the tip of the screw at an angle greater than 0° to the horizontal, but less than or equal to 45°. It is preferable to align them. The screw 1 should be placed in the head 21 such that the ship 20 and the ice layer 10 move towards each other so that the ice layer contacts the underside of the screw. More particularly, the ice layer should contact at least one or more locations along the crest or edge of the screw wing that is on the line of contact.

Screw 1 is attached to ship 2 to prevent ice chips from getting stuck between the screw and the ship and stopping the rotation of the screw.
Preferably, it is placed sufficiently far away from 0. Depending on the shape of the bow of the ship, the longitudinal axis of the screw can also be tilted towards the bow of the ship (see Figure 1). If the longitudinal axis of the screw is so inclined, then the vertical plane in which the axis of the screw lies is at an angle equal to or less than 45° to the vertical plane containing the longitudinal axis of the ship. intersect with Typically, these planes should be substantially parallel in a substantially vertical position.

When the ship and the ice layer move toward each other, the screw rotates and acts on the ice layer, exerting a tensile force,
The ship's icebreaker will now point its plow toward the ice layer 10 and pull it over it. This, of course, exerts a large force on the screw with a vertical and a horizontal component. The screw support arms 22, 22a must be sufficiently robust to withstand and transmit such forces to the vessel 20. Also, the bearings in the bearing housing must be designed to operate within the range of expected radial and axial forces.

When the ship's bow is raised, at least a portion of the ship's weight bends the ice layer downward and fractures it. The rotating screws will clean the crushed ice from the ship's passageways. If the width of the ship increases from the bow to the stern, the amount of broken ice also increases from the bow to the stern. This is because the tail, which is gradually wider than the bow, goes into the ice layer. In order to more effectively clean broken ice from the ship's passageways, the screws may be tapered to increase the depth of the wing from the front to the rear, as shown in Figures 1 and 2. can. The screw can also taper by increasing the diameter of the axis or core of the screw from the front to the rear.

As the ship advances through the ice layer, the ice layer contacts at least a location along the outer side of each screw wing along the line of contact. Typically, as the screw rotates, different locations along the edge of the wing will exist along the line of contact and make gripping contact with the ice layer at different moments. Even if different locations along the edge of the wing actually make gripping contact with the ice layer at different moments, the contact location is
It is maintained continuously between the edge of the screw wing and the ice layer. When the screw rotates and pulls the ship forward into the ice layer, the contact point marked by the kerf on the ice layer will move backwards relative to the ship, i.e. from forward to aft, along the line of contact. Move along.

The movement of the contact position in the direction parallel to the direction of movement of the ship relative to the ice layer is backwards, i.e. towards the rear of the ship, or forward, or the contact position does not move at all in the direction parallel to the direction of movement of the ship. . The contact position moves in a direction that is not parallel to the direction of movement of the ship due to the orientation of the screws on the ship, but has a velocity component force that is parallel to the direction of movement of the ship.
As the screw rotates, the point of contact with the ice layer moves parallel to the direction of movement of the ship, so that the ship moves forward through the ice layer.

If the contact point moves forward, ie in the same direction as the ship moves through the ice layer, the screw actually presents a resistance to the movement of the ship. Because the ship's other propulsion systems push the ship to move faster into the ice, the screws will drag on the ice against the ship's movement. This is known as negative slip and should be avoided as the screw becomes a practical hindrance to the ship's movement through the ice layer.

If the contact point does not move in a direction parallel to the direction of movement of the ship (known as zero slip), the screw may or may not contribute to the forward movement of the ship. It has just enough torque to keep the ship moving, but does not contribute to the ship's movement.
We can imagine that a screw can rotate in a state of zero slip. However, if a torque in excess of this amount is applied to the screw, the screw will contribute to the forward movement of the ship.

In a direction parallel to the ship's intended direction of movement,
However, in the opposite direction of such movement (i.e. with positive slip) the screw rotates so as to shift the point of contact with the ice relative to the ice layer at a speed up to twice the ship's maximum design speed. It is preferable to apply a screw and a device for rotating the screw in a special vessel so that it is possible to do so. The maximum design speed is defined as the maximum speed of the ship relative to the ice layer in ice-covered waters when the screws are adapted to assist the ship's movement. Preferably, the slip speed should be less than or equal to (but in the opposite direction) the speed of the ship relative to the ice.

Large amounts of slips may also be tolerated for limited periods of time, such as when starting from essentially stationary conditions on thick ice.

The invention moves in ice-covered bodies of water;
It can be used to assist icebreakers, either to maintain a fixed position in a body of water or to maintain a fixed position in a body of water. Furthermore, the invention can be used in both self-propelled and non-self-propelled ships, such as barges. In some cases, devices for pushing the ship against the ice layer may be necessary to prevent backward slipping. This pushing force can be provided by devices including pushing devices such as the screw itself, conventional mooring equipment, the ship's main propulsion system or one or more tugboats.

It should be noted that in the preferred embodiment of the invention for use on icebreakers, two screws are preferably utilized. As two screws,
It is particularly preferred that one of them has a right-handed thread and the other has a left-handed thread (see FIG. 1). In order to draw the bow of the ship onto the ice layer, it is necessary to rotate the two screws in opposite directions so that they act on the ice layer at the same time. If you turn opposite screws in the same direction, the ship will rotate and change direction. In some cases, when the ship moves through ice-free waters, the screw device and its support devices, e.g. It may be desirable to design Also,
The screws can interfere with the flow of water through the boat and add a pulling force to the boat. The same is true when a body of water is covered only by thin or broken ice. Alternatively, the screw device can be designed to aid in propulsion of the vessel.

In some cases, it is also desirable to increase the grip of the screw wings on the ice and therefore the traction of the screw. Screw traction is particularly important when the ship has to deal with thick ice, such as ice bumps. The traction force of the screw can be increased by providing an auxiliary device on the wing crest for cutting grooves in the ice. Cutting devices, such as cutting teeth, can cut through the ice more easily than normal wing edges, creating traction grooves in the ice over which the screw wings ride, increasing the pulling force of the screw device.

As for the preferred screws for use on ships, as already mentioned, the optimum combination of thread pitch, taper, length and wing depth for a particular application will depend on the size of the ship and the speed of rotation of the screw. , depends on a number of factors including the thickness of the ice, the speed of the ice layer moving relative to the ship, the strength of the ice and the thickness of the ice layer. Industrial design in the art can determine appropriate values for the above parameters.

EXPERIMENTAL EXAMPLE A model test program was conducted to evaluate the feasibility of using a pair of screws supported in the bow of an icebreaker. For this test, a 1/36 scale model of a Wind Class ice crusher was used. The model's surfaces were specifically constructed to have the same coefficient of friction against ice as that of a full-scale ship. This surface was sanded to create a coefficient of friction of 0.25 between the model and the ice. The model is used to obtain the radius of gyration for the ice crusher.
It was ballasted with weights distributed over its length. Two tapered screws with a 30° helix angle were installed, one on each side of the hem, as shown in FIGS. 1 and 2.

A 3/4 horsepower DC motor was chosen to drive the screw. The motor rotation speed RPM was varied by a DC motor speed controller. The gearbox was equipped with two output shafts, each connected to each of the screws by a flexible shaft. The axis of rotation of the screw was measured by a coefficient pulse generated by an electromagnetic probe mounted on a disc driven by a V-belt from the motor shaft. A torque meter was used during one test period to measure the torque on one screw. When the model was pulled against the ice layer, the resistance of the model to the ice layer was measured with a force block placed on the model. During each test,
The model was dragged across a slab of ice and its speed was measured.

The resulting model test data was graphed to demonstrate the ice breaking capabilities of a full scale Wind class ice crusher with a pair of screws supported on the bow. Figures 5 and 6 show the capabilities of a full scale ice crusher.

FIG. 5 shows the resistance to movement through the ice of an icebreaker equipped with a pair of screws and the relationship between the horsepower required to rotate the screws and the speed of rotation of the screws. In this graph, the model has a current scale equivalent speed of 2.3 knots,
It was drawn in an ice layer with an equivalent current thickness of 167 cm (5.5 ft). The resistance to movement of the ship in the ice layer is
As shown by the graph of "resistance with screw", it decreased as the rotational speed of the screw increased. The horsepower required to rotate the screw increased as the rotational speed of the screw increased. This relationship is illustrated by the "horsepower" graph. For comparison purposes, the resistance of a full-scale unscrewed wind class ice crusher moving through a 167 cm (5.5 ft) thick layer of ice at a speed of 2.3 knots is 'resistance' is shown as a horizontal dotted line graph.

The "Threaded Resistance" and "Horsepower" graphs are based on actual model resistance and thread torque test data measured at full scale, respectively.
The graph of "resistance without screws" is a value calculated using Mr. Vance's formula. Vance's equation was shown to be consistent with model test results. (Gee, beep, bangs,
1975, graphing device for model ships in ice:
Society Naval Architects and
Paper submitted at Marine Engineers Ice Tech 75 P, H ¹ -1--H ¹ -34.) (6.P.
Vance.1975, A scaling system for vessels
modeled in ice：Paper presented at Ice Tech
75, Soc. Naval Architects and Marine
Engineers, PH ^1-1 --H ^1-34 .) The graph in Figure 5 shows that, under the conditions given, the screw of the present invention provides a sufficient reduction in resistance to vessel movement in ice-covered waters. It shows that it provides. In fact, the screw can reduce the resistance between the ship and the ice to zero when rotated at a speed slightly greater than 110 RPM.

This means that only the screws operating at the above speeds are 2.3
This means propelling the ship through a layer of ice 167 cm (5.5 ft) thick at the speed of a knot. Also,
It should be noted that at a speed slightly greater than 110 RPM, it takes approximately 33,000 horsepower to rotate the screw.

Since the horsepower required to turn the screw increases more than the resistance to movement of the ship in the ice layer, which decreases as the speed of the screw increases, the screw
It is clear that the efficiency is better at lower rotational speeds.

Therefore, it is advantageous and a preferred embodiment to operate the screw at a low rotational speed and to supply the thrust necessary for movement of the ship through the ice layer from a conventional propulsion source, such as a ship's propeller system. The total horsepower required for the screw and ship propeller combination is shown in FIG. 6 as a function of the rotational speed of the screw.

As in Figure 5, the graph in Figure 6 is
It is for a wind class ice crusher that moves through a layer of ice 167 cm (5.5 ft) thick at a speed of 2.3 knots. The solid line indicating "screw horsepower" indicates the horsepower required to rotate the screw at the corresponding speed.
The additional thrust required to move the ship through a 167 cm (5.5 ft) thick layer of ice at a speed of 2.3 knots is provided by the ship's propeller system. The horsepower required to produce the required thrust from a ship's propeller system is shown in the "Ship Propeller Horsepower" graph. The sum of “screw horsepower” and “ship propeller horsepower” is the total horsepower required to move the ship through a layer of ice 167 cm (5.5 feet) thick at a speed of 2.3 knots, and is the sum of “total horsepower”. Shown as a solid line graph.

The minimum horsepower of a screw and ship propeller system combination to move a ship through a layer of ice 167 cm (5.5 feet) thick at a speed of 2.3 knots is approximately It has 25,000 horsepower. This should be compared to the 33,000 horsepower required to move a ship through a layer of ice 167 cm (5.5 feet) thick at a speed of 2.3 knots with screws alone, and with the ship's propeller system alone. This should be compared to the 50,000 horsepower required to propel a ship through 167 cm (5.5 feet) of ice at a speed of 2.3 knots.

The test results described herein merely demonstrate the operational capabilities and benefits of the present invention. There are numerous variables apparent to those skilled in the art for any given situation, under which the detailed operation of the invention will vary. These variables include thread pitch, thread wing depth, thread taper, slope angle of the thread contact line, weight distribution on the ship, coefficient of friction between the ship and the ice, ice strength, and others.

It is clear that the present invention significantly reduces the total power required to move an icebreaker having an ice breaking device adapted to exert a downward force on the ice through an ice-covered body of water.

A further important advantage of the present invention is that it provides a device for movement and stability in icy waters, which is not employed in prior art devices that do not take horsepower into consideration.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of the bow of an icebreaker adapted to the apparatus of the present invention, FIG. 2 is a schematic side view of the bow of the ship shown in FIG. 1, and FIG. Cross-sectional view of the bearing box and gear box used to support and drive the screw shown in Figures 4 and 2.
The figure is a sectional view of the screw sleeve and wing, and Figure 5 is
FIG. 6 is a graph showing screw rotational speed versus ship resistance and horsepower; FIG. 6 is a graph showing screw rotational speed versus propeller horsepower and propeller horsepower. 1... Screw, 2... Spiral wing, 3... Shaft, 20
……ship.

Claims (1)

[Scope of Claims] 1. In a ship having a device for crushing an ice layer in front of the ship, the ice crushing device includes: a. an ice-breaking device; b. placed on said ship in such a direction that the weight of the ship will break said ice layer by pulling the front of the ship in a combined forward and upward direction against the ice layer obstructing the ship's path; c) a device for rotating said ice gripping rotating screw device; (ii) an outer helical edge of the ice gripping rotating screw device is configured to cut through and engage the ice layer when it contacts the ice layer; (ii) the ice gripping rotating screw; The device is oriented symmetrically with respect to the longitudinal axis of the ship, and the ice gripping rotating screw device is configured to absorb rotational energy of the ice gripping rotating screw device when the ice gripping rotating screw device rotates into contact with the ice layer. of,
Convert the force to pull the bow of the ship onto the ice layer and the force to pull the bow of the ship forward into component forces, and the component force moves the ice breaking device onto the ice layer. A ship having an ice layer crushing device that is adapted to crush the ice layer by pushing. 2. A ship having an ice layer crushing device according to claim 1, wherein the ice gripping screw device comprises two independent screws supported separately. 3. A ship having an ice layer crushing device according to claim 2, wherein each screw is composed of a screw shaft and a helical blade fixed to the screw shaft. 4. In the ship according to claim 3, one screw is located on one side of the longitudinal axis of the ship and has a right-hand thread, and the other screw is located on the other side of the longitudinal axis of the ship. 1. A ship having an ice breaking device, characterized in that it is supported and has a left-hand thread. 5. The ship according to claim 3, which includes an auxiliary device provided on the crest of the screw wing in order to facilitate cutting of grooves in the ice layer, and the screw wing rides on the ice layer. 1. A ship having an ice layer crushing device, characterized in that the ship is configured to exert a traction force to move the ship upward toward the ice layer. 6. In the ship according to claim 2, each of the screws has a line of contact inclined upwardly and forwardly from the waterline at an angle greater than 0° and equal to or less than 45°. A ship equipped with an ice crushing device.