Title:
FIXED-ANGLE STABILIZING FIN SYSTEM
United States Patent 3757723
Abstract:
A ship stabilization system comprising at least one pair of fixed-angle fins retractable into the hull of the ship. The moment developed by each fin is proportional to the area of the fin exposed to the external waters. In one embodiment, the fin is composed of a plurality of spinning rods or tubes. Also disclosed is a system for linking the fins with the ship's rudder thereby compensating for expected course changes of the ship.
Application Number:
05/132160
Publication Date:
09/11/1973
Filing Date:
04/07/1971
View Patent Images:
Export Citation:
Assignee:
John J. McMullen Associates, Inc. (New York, NY)
Primary Class:
International Classes:
B63B39/06; B63B39/00; B63B43/04
Field of Search:
114/126 244/123
Primary Examiner:
Buchler, Milton
Assistant Examiner:
Goldstein, Stuart M.
Claims:
What is claimed is
1. A system for counteracting and opposing the roll of a ship, the system comprising: means for sensing the roll of a ship and for issuing control signals in response thereto; at least one pair of stabilizing fins, each pair of fins comprising one fin retractably mounted on the port side and one fin retractably mounted on the starboard side of said ship, the plane of each fin defining, with the horizontal, a preset and fixed angle; positioning means associated with each of said port and starboard fins for responding to said control signals and for extending one fin of each fin pair while simultaneously retracting the other fin of each pair with respect to the hull of the ship; said system further characterized in that each fin is defined by a set of parallel rods, sized, shaped and positioned so that each set serves, when extended, to develop a moment about the longitudinal centerline of the ship, and means for rotating each of said rods in the same sense.
2. The system recited in claim 1, wherein said sensing means includes means for sensing roll direction and roll acceleration; and wherein said positioning means is in operative relationship to be activated and reversed in operation shortly before and near each time the roll acceleration reaches zero.
3. The system recited in claim 1, wherein one fin of each fin pair is fully extended over substantially one-half of each roll cycle; and wherein the other fin of each fin pair is fully extended over substantially the other one-half of each roll cycle.
4. The system recited in claim 1, and comprising two fin pairs; wherein one fin pair is preset for lift; wherein the other fin pair is preset for descent; and wherein the positioning means operate so that substantially the same fin exposure exists on each side of the ship at all times during the roll cycle.
5. The system recited in claim 1, wherein each fin retracts into the hull of the ship through an opening provided in said hull; and further comprising closure means for closing the hull openings when the fins are fully retracted.
6. The system recited in claim 5, wherein one closure means is fixedly mounted on the outermost end of each fin and is of a size substantially equal to the size of the respective hull openings.
7. The system recited in claim 1, wherein said preset and fixed angle is equal to 28° to 30°.
8. The system recited in claim 1, and further comprising means for fully and simultaneously extending each of said fins for purposes of emergency drag development.
9. The system recited in claim 1, wherein said rods are adapted to rotate in the sense increasing the moment developed by the respective sets.
10. The system recited in claim 9, wherein said positioning means are adapted to extend and retract said rods without affecting the rotation thereof.
11. The system according to claim 1 wherein said set of parallel rods is defined by a single row of rods.
12. A ship system for counter-acting and opposing the roll of a ship, the system comprising: means for sensing the roll of the ship and issuing control signals in response thereto; at least one stabilizing fin retractably mounted with respect to the ship's hull and each such fin defining a fixed angle with the horizontal; positioning means for extending and retracting each fin from and into the hull of said ship, said positioning means operating in response to said control signals; said apparatus further characterized in that said at least one stabilizing fin is defined by a set of parallel rods, sized, shaped and positioned so that each set serves, when extended, to develop a moment about the longitudinal centerline of the ship, and means for rotating each of said rods in the same sense.
13. The ship system recited in claim 12, wherein the fixed angle defined between each fin and the horizontal lies between 28° and 30°.
14. The ship system recited in claim 12, wherein the stabilizing fins are four in number; wherein two fins are positioned on each side of said ship; wherein one fin on each side of said ship is set for lift; wherein the other fin on each side of said ship is set for descent; and wherein the fins on each side of said ship are adapted to be alternately extended and retracted during the roll cycle of said ship.
15. The ship system recited in claim 12, wherein each of said rods rotates in a sense adding to the moment developed by its set.
16. The system according to claim 12 wherein said set of parallel rods is defined by a single row of rods.
17. The method for stabilizing a ship against roll, comprising the steps of: sensing the roll of the ship; extending at least one fixed angle stabilizing fin defined by a set of parallel rods adapted to create a moment with respect to the longitudinal centerline of the ship on one side of the said ship when the roll is in a first sense and rotating each of said rods in the same sense; extending at least one fixed angle stabilizing fin defined by a set of parallel rods adapted to create a moment with respect to the longitudinal centerline of the ship on the other side of said ship when the roll is in a second and opposite sense and rotating each of said rods in the same sense; and wherein the fixed angle of each stabilizing fin is equal and is defined between the plane of the fin and the horizontal.
18. The method recited in claim 17, wherein each of said stabilizing fins is extended from and retracted into the hull of said ship in a direction parallel to the major axis thereof.
19. The method recited in claim 17 wherein each of said rods is rotating in a sense enhancing the moment developed by its respective set.
1. A system for counteracting and opposing the roll of a ship, the system comprising: means for sensing the roll of a ship and for issuing control signals in response thereto; at least one pair of stabilizing fins, each pair of fins comprising one fin retractably mounted on the port side and one fin retractably mounted on the starboard side of said ship, the plane of each fin defining, with the horizontal, a preset and fixed angle; positioning means associated with each of said port and starboard fins for responding to said control signals and for extending one fin of each fin pair while simultaneously retracting the other fin of each pair with respect to the hull of the ship; said system further characterized in that each fin is defined by a set of parallel rods, sized, shaped and positioned so that each set serves, when extended, to develop a moment about the longitudinal centerline of the ship, and means for rotating each of said rods in the same sense.
2. The system recited in claim 1, wherein said sensing means includes means for sensing roll direction and roll acceleration; and wherein said positioning means is in operative relationship to be activated and reversed in operation shortly before and near each time the roll acceleration reaches zero.
3. The system recited in claim 1, wherein one fin of each fin pair is fully extended over substantially one-half of each roll cycle; and wherein the other fin of each fin pair is fully extended over substantially the other one-half of each roll cycle.
4. The system recited in claim 1, and comprising two fin pairs; wherein one fin pair is preset for lift; wherein the other fin pair is preset for descent; and wherein the positioning means operate so that substantially the same fin exposure exists on each side of the ship at all times during the roll cycle.
5. The system recited in claim 1, wherein each fin retracts into the hull of the ship through an opening provided in said hull; and further comprising closure means for closing the hull openings when the fins are fully retracted.
6. The system recited in claim 5, wherein one closure means is fixedly mounted on the outermost end of each fin and is of a size substantially equal to the size of the respective hull openings.
7. The system recited in claim 1, wherein said preset and fixed angle is equal to 28° to 30°.
8. The system recited in claim 1, and further comprising means for fully and simultaneously extending each of said fins for purposes of emergency drag development.
9. The system recited in claim 1, wherein said rods are adapted to rotate in the sense increasing the moment developed by the respective sets.
10. The system recited in claim 9, wherein said positioning means are adapted to extend and retract said rods without affecting the rotation thereof.
11. The system according to claim 1 wherein said set of parallel rods is defined by a single row of rods.
12. A ship system for counter-acting and opposing the roll of a ship, the system comprising: means for sensing the roll of the ship and issuing control signals in response thereto; at least one stabilizing fin retractably mounted with respect to the ship's hull and each such fin defining a fixed angle with the horizontal; positioning means for extending and retracting each fin from and into the hull of said ship, said positioning means operating in response to said control signals; said apparatus further characterized in that said at least one stabilizing fin is defined by a set of parallel rods, sized, shaped and positioned so that each set serves, when extended, to develop a moment about the longitudinal centerline of the ship, and means for rotating each of said rods in the same sense.
13. The ship system recited in claim 12, wherein the fixed angle defined between each fin and the horizontal lies between 28° and 30°.
14. The ship system recited in claim 12, wherein the stabilizing fins are four in number; wherein two fins are positioned on each side of said ship; wherein one fin on each side of said ship is set for lift; wherein the other fin on each side of said ship is set for descent; and wherein the fins on each side of said ship are adapted to be alternately extended and retracted during the roll cycle of said ship.
15. The ship system recited in claim 12, wherein each of said rods rotates in a sense adding to the moment developed by its set.
16. The system according to claim 12 wherein said set of parallel rods is defined by a single row of rods.
17. The method for stabilizing a ship against roll, comprising the steps of: sensing the roll of the ship; extending at least one fixed angle stabilizing fin defined by a set of parallel rods adapted to create a moment with respect to the longitudinal centerline of the ship on one side of the said ship when the roll is in a first sense and rotating each of said rods in the same sense; extending at least one fixed angle stabilizing fin defined by a set of parallel rods adapted to create a moment with respect to the longitudinal centerline of the ship on the other side of said ship when the roll is in a second and opposite sense and rotating each of said rods in the same sense; and wherein the fixed angle of each stabilizing fin is equal and is defined between the plane of the fin and the horizontal.
18. The method recited in claim 17, wherein each of said stabilizing fins is extended from and retracted into the hull of said ship in a direction parallel to the major axis thereof.
19. The method recited in claim 17 wherein each of said rods is rotating in a sense enhancing the moment developed by its respective set.
Description:
BACKGROUND OF THE INVENTION
There are many generic types of ship stabilizers known to the prior art. For purposes of this invention, however, only the fin-type stabilizers will be discussed.
The operation of the conventional fin-type ship's stabilizer is as follows. A pair of retractable fins are fitted below the water line on each side of the hull amidships; and control and drive systems are located somewhere within the hull of the ship. The standard control unit senses roll angle and rate of roll, and sometimes senses roll acceleration as well. The data received by the control unit is evaluated by electronic computers and is transmitted as electrical impulses to the prime movers which orient the fins so that the stabilizing moment produced by the water flow around the fins compensates for the disturbing moments of the wave. The ship's rolling motions are thereby damped. In the conventional fin-type stabilizer system, the fins remain fully extended when in use and are pivoted about substantially horizontal axes, oppositely but in unison, and thereby changing their angles of encounter with the external waters in accordance with the stabilizing moment needed. Often these fins are provided with tail flaps so as to increase the moment developed thereby.
In some installations, the fins are of the non-retractable type always remaining positioned for use, but usually the fins are either retractable or foldable into the hull of the ship. When the fins are of the retractable-type, they move linearly, along their major axes, until they are fully retracted into the hull of the ship when not in use. This type of retractable fin requires the minimum size opening in th shell plating, thereby affecting only a small number of frames. Moreover, with this type of fin, the lifting forces can easily be transmitted to the double bottom structure of the ship. The foldable-type fins are stored within the hull of the ship by pivoting about vertical axes just inside the hull. This type of fin offers the advantage that the space between the two fin housings can be used for the storage of cargo.
One feature common to each type of stabilizing fin system known to the prior art is that during operation of the system, the fins are continuously pivoted so as to change their respective angles of encounter with the external waters, thereby changing the direction in which the stabilizing moment is developed. All types of prior art fin systems, therefore, require motor and gearing arrangements for varying the angles of encounter of the fins in accordance with the needs of the ship. If the fin-type stabilizer is provided with the often used tail flap, then an additional motor and gearing arrangement is needed to adjust the angle of encounter of this tail flap. And, in addition to these two motor and gearing arrangements, if the prior art fins are either made retractable or foldable into the hull of the ship, then a third motor and gearing arrangement becomes necessary. It should be obvious, therefore, that the prior art stabilizing fin systems are bulky, complex, and accordingly, expensive.
The present invention is related to a fin-type stabilizing system which overcomes many of the disadvantages found in the fin-type stabilizing systems known to the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a fin-type ship stabilizing system wherein at least one fixed angle fin is located below the water line on each side of the hull amidships. The encounter angles of the respective fins are equal so as to develop equal but oppositely directed moments. That is, when all fins are fully extended, the rolling moments developed thereby add to zero. Each fin is adapted, when the system is operative, to retract into the hull of the ship, either by sliding linearly or by pivoting. The inventive system is also provided with a sensing and control unit for sensing the roll of the ship and controlling the surface area of the respective fins exposed to the external waters.
In operation, roll-opposing moments are developed when the fins are alternately retracted and extended in response to the roll of the ship. If the common angle of each fin is fixed so as to impart an upwardly directed moment, and if the ship is rolling toward starboard, then the starboard fin is extended to its fully outboard position while the port fin is retracted into the hull of the ship. Thus, a moment is developed which opposes the starboard roll of the ship. When the ship begins to roll toward port, then the sensing and control unit issues a signal which retracts the starboard fin and extends the port fin.
The advantages of the inventive system described in the preceding paragraphs should now be readily apparent. With the prior art fin systems, the fins and associated prime movers encounter tremendous resistance from the external waters when the respective angles of the fins are changed; very little resistance is encountered when the fixed-angle fins are extended or retracted. Therefore, the inventive fin system is stressed far less than are the prior art systems. The retractable fin systems of the prior art require one motor and gearing system for extending and retracting the fins and at least one additional motor and gearing system for operating the fins. Only one motor and gearing system is used in the operation of the present invention. The same motor and gearing system which extends and retracts the inventive fins during operation serves also to retract the fins into the ship's hull for storage. Prior art fins are frequently provided with auxiliary flaps to enhance the stabilizing moments developed by the fins since the fins are designed and mounted for maximum efficiency.
In another embodiment of the present invention, two fin pairs are provided, one fin from each pair being located below the waterline on each side of the hull amidships. The angles of the fins from one set are fixed for maximum upward lift while the angles of the fins from the other set are fixed for maximum descent. When the ship is rolling to starboard, the fin for lifting the starboard side of the ship is extended while the fin for causing the descent of the starboard side is retracted; at the same time, the fin for causing descent of the port side of the ship is extended while the fin for lifting the port side is retracted. With such a balance arrangement, the resistive forces tending to change the direction of travel of the ship are balanced, and hence unwanted changes in direction of travel of the ship are minimized.
The present invention also relates to a system for automatically controlling the ship's rudder in response to the positioning of the stabilizing fins. While the two-pair embodiment of the present invention outlined above minimizes the turning effects of the fins on the ship, the fins still tend, to some degree, to change the ship's direction of travel. This turning effect is particularly noticeable when only one pair of fins is provided. The present invention contemplates that the control unit which serves to adjust the positioning of the fins be also associated with the rudder. In this manner, the control unit corrects for anticipated turning of the ship.
As an example of the invention described in the preceding paragraph, when the starboard fin is fully extended and the port fin retracted, the ship tends to turn toward starboard. The invention contemplates "correcting" for the expected starboard turn, before it happens, by adjusting the rudder at the same time as the fins. The rudder is adjusted, in this example, for a slight direction change toward port.
In another embodiment of the present invention, each of the fixed-angle fins is defined by a plurality of rotating rods or tubes. As is well known, a rotating object moving linearly through a fluid experiences a force directed transverse to its linear motion. This embodiment of the present invention makes use of the principle defined immediately above to enhance the righting effect of the fins on the ship. The spinning rods being associated in the outline of a pair of fins, the lift developed is dependent upon two independent lift forces.
Each embodiment of the inventive fin described above may be constructed so that the fins retract into the hull of the ship in directions along the major axes thereof or into the hull of the ship by pivoting about vertical axes. For purposes of description, however, the linearly retractable-type fixed-angle stabilizing fin will be described, as this fin is the preferred embodiment of the present invention. With the linearly retractable fin, the area of fin exposure may be changed and fin storage may be accomplished with a single set of motors. Any one of a large number of conventional guiding and retracting mechanisms can be used to retract the inventive fins.
It is the main object of the present invention to provide a fixed-angle stabilizing fin system for stabilizing the roll of a ship in a manner far simpler than those fin systems known to the prior art.
A more specific object of the present invention is to provide a fixed-angle stabilizing fin system wherein a single motor arrangement serves both to adjust the moment developed by the respective fins and to retract the fins into the hull of the ship when not in use.
A further object of the present invention is to provide a fixed-angle stabilizing fin system such as that described above, wherein the forces exerted on each side of the ship are substantially balanced.
Still another object of the present invention is to provide a fixed-angle stabilizing fin system wherein the fins are designed and angled in such a manner as to maximize the moment developed thereby.
Still a further object of the present invention is to provide a fixed-angle stabilizing fin system wherein adjustment to the righting moment developed by the fins is carried out with minimum resistance by the external waters.
Yet a further object of the present invention is to provide a fixed-angle fin stabilizing system wherein the turning effect of the fins is corrected by an automatic steering system.
Still a further object of the present invention is to provide a stabilizing fin system wherein the respective fins rotate and are constructed so as to develop two independent righting moments.
These and other objects of the present invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified front view of a ship equipped with a fixed-angle fin stabilizer system constructed in accordance with the teachings of the present invention;
FIG. 2 is a perspective view of an inventive fin stabilizer fit in the starboard side of a ship;
FIG. 3, (a) through (i), is a sequential showing of a rolling ship equipped with a fin stabilizer system constructed in accordance with the teachings of the present invention;
FIG. 4, (a) and (b), is an illustration of an inventive fixed-angle fin provided with a cover plate for streamlining the ship when the fin is in storage;
FIG. 5 is a front view, partially in section, of another embodiment of the inventive fixed angle fin stabilizer system;
FIG. 6 is a side view of one of the elements of the fin illustrated in FIG. 5; and
FIG. 7 is a block diagram illustrating the manner in which a roll sensor controls the operation both of the fixed-angle stabilizing fin system and the steering rudder.
DETAILED DESCRIPTION OF THE DRAWINGS
With reference to FIGS. 1 through 3, the first embodiment of the present invention will be described. A ship equipped with the inventive stabilizing fin system is indicated generally at 10. Both the port and starboard hulls 12 of the ship 10 are opened at 14 so as to accept port and starboard fixed-angle stabilizing fins 16 and 18, respectively. The angle that each of the stabilizing fins makes with the horizontal is fixed, with both fins set at the same angle. Preferably, and for maximizing the stabilizing effect of the fins, the set angle should be between 28° and 30°. As shown, each fin is set for lift, but it should be appreciated that both may be set for descent.
In FIG. 1, the starboard fin 18 is fully extended while the port fin 16 is in its retracted position. As each fin is designed to develop a lift moment, the fin orientation indicated in FIG. 1 would counteract the roll of the ship when the ship is rolling in the direction of arrow 20. When the ship's direction of roll reverses, the starboard fin 18 is retracted and the port fin 16 is extended. A more detailed description of the operation will be given below when specific reference is made to FIG. 3.
The inventive stabilizing fin system derives its novelty over those fin systems known to the prior art in that the angle that the inventive fin makes with the horizontal is fixed. In this manner, the moment developed by a plurality of fixed angle fins is dependent upon the exposure between the fins and the external waters. Therefore, while prior art systems rely upon angle changes of the fins to alter the direction of righting moments, the inventive system relies upon the relative distance that respective fins extend into the water.
With the present invention, the angle that the fin makes with the horizontal is set for maximum moment, and so too is the shape of the fin. Accordingly, the necessity for auxiliary flaps and other such moment-enhancing apparatus, with the usual operating equipment, is avoided. It should be appreciated, however, that if for some technical reason, flaps and other such apparatus are desired, they may be used in conjunction with the inventive fixed-angle stabilizing fin system.
Since the advantages of the various fin shapes are well known in the art, they will not herein be discussed. Suffice it to say that while the stabilizing effect of the inventive fin system can be maximized by proper fin design, the inventive system is operable with any known prior art fin. Similarly, because there are numerous known systems for sensing roll and moving the fins into and out of the hull of the ship, such systems will not herein be described in detail. Suffice it to say that with the present invention, any one of many known devices may be used to position the fins in accordance with the roll sensed.
Before beginning a discussion of the operation of the inventive stabilizing system, the operational sequence being illustrated in FIG. 3, two types of sensing and control mechanisms will be described. The first type, the simplest of the two, is the type wherein the sensing system senses only the direction of roll of the ship. Accordingly, with this system, changes in the fin positions take place only after the ship changes its direction of roll. With such a system, the starboard fin would be extended and the port fin retracted when the ship is rolling to starboard. It is only when or slightly after the ship reaches its full starboard heel that the starboard fin is retracted and the port fin extended. The fins would so remain during the entire roll toward port and would be repositioned only at the time of or shortly after the full port heel. With such a system, there would be a slight time delay at the beginning of each roll cycle, due to the time necessary to change the orientation of the fins, when the fins operate to roll rather than to stabilize the ship.
With the second type of sensing system, the more complex of the two, the sensing device operates to sense both the direction and the acceleration of the roll. With such a system, it is possible to begin the change in orientation of the respective fixed-angle stabilizing fins shortly before the ship reaches maximum heel in both directions. In this manner, when the ship reaches maximum heel, there is no destabilization effect. Further, the time required to fully extend one fin and to fully retract the other, when necessary, is greatly reduced.
As an example of the above, the starboard fin is fully extended and the port fin fully retracted during most of the roll cycle from port to starboard. Shortly before the ship reaches maximum heel toward starboard, when the roll acceleration becomes very small, the sensing and control system begins to reorient the respective fins by retracting the starboard fin and extending the port fin. Ideally, when the ship reaches full heel in the starboard direction, the port and starboard fins are each half extended and half retracted. In this manner, at the instant when no stabilization effect is needed, none is provided. The reorientation of the respective fins then continues so that shortly after the ship begins its roll toward port, the port fin is fully retracted. With this system, there is never an instant of time when the fixed-angle stabilizing fins destabilize rather than stabilize the ship.
With reference now to FIG. 3, the operational sequence of the inventive fixed-angle stabilizing fin system will be described. The positioning of the fins in FIG. 3 willl be explained based upon the provision of the second and more complex of the two types of sensing and control systems described above. That is, the sequential operation illustrated in FIG. 3 makes use of the sensing and control system which senses the roll direction as well as the acceleration of roll of the associated ship.
In FIG. 3(a), the ship 10 is shown when heeling maximum toward starboard. The port fin 16 is partially extended and the starboard fin 18 is partially retracted. The respective fins are, in FIG. 3(a), moving in the directions indicated by arrows 15 and 17.
When the ship 10 passes through its maximum starboard heeling position and reaches the position illustrated in FIG. 3(b), the starboard fin has been fully retracted into the hull of the ship while the port fin has been fully extended. In this position, and with roll in the direction of arrow 22, the port fin 16 develops a righting moment counteracting the roll of the ship. The starboard fin 18 has no effect. The port fin 16 remains fully extended, with the starbaord fin 18 remaining fully retracted, during the roll of the ship through the positions illustrated in FIGS. 3(c) and 3(d). But between the positions represented by FIGS. 3(d) and 3(e), the port fin 16 begins to retract while the starboard fin 18 is extended.
In FIG. 3(e), the heel of the ship is maximum toward port. Like in FIG. 3(a), each of the fins 16 and 18 is half extended and half retracted into the hull of the ship.
During the roll of the ship from position 3(e) to position 3(f), in the direction of arrow 24, the port fin 16 retracts while the starboard fin 18 extends. When the ship reaches the position shown in FIG. 3(f), the port fin 16 is fully retracted while the starboard fin 18 is fully extended. Under these circumstances, the starboard fin 18 develops a moment opposing the roll of the ship. The port fin 16 has no effect. And so the cycle continues.
Now, with reference to FIG. 4, a streamlining feature of the inventive fin system will be described. FIG. 4 represents, schematically, one side of a ship equipped with a fixed-angle stabilization fin system constructed in accordance with the present invention. The hull 26 of the ship is opened and accommodates a fixed-angle fin 28, the fin 28 being mounted for reciprocation in a fin guide track arrangement 30. During retraction and extension, the fin 28 is adapted to freely move over rollers 32 and is controlled by the operation of a drive rod 34 associated with the sensing and control unit (not shown).
On the outboard end of each fin is mounted a plate 36 of a size of configuration substantially conforming to the opening in the hull 26 and adapted to accommodate such inventive fin. Preferably, the extremity of each plate 36 is provided with an inwardly angled flange 38 conforming substantially to a similarly angled flange 40 integral with the hull 26 of the ship. In this manner, the flanges 38 and 40 define a smooth junction and coact to streamline the travel of the ship through external waters.
The manner in which the fin 28, with its fin plate 36, mates with the hull 26 of the associated ship is shown best in FIG. 4(b). In this figure, the fin 28 is shown fully retracted into the hull of the ship, and, in this position, the flange 38 integral with the fin-plate 36 runs parallel to and is in close proximity to the flange 40 integral with the hull 26. When in this position, the hull 26 of the ship is substantially streamlined, and in this manner minimizes the effects of the fin 28 when in its inoperative and stored position.
With reference now to FIGS. 5 and 6, a second embodiment of the present invention will be described. In FIG. 5, the hull of the ship is shown generally at 42 and has an opening 44 defined therein. A plurality of rods 46 extend through the opening 44 in the hull 42 and are adapted for reciprocating movement into and out of the hull. As is evident from FIG. 5, the rods 46 are varied in size and are arranged in such a manner that the outline of the rods, taken as a whole, approximates the shape of the fin 18 illustrated in FIG. 2.
For reasons which are fully explained below, each rod 46 associates with a bearing housing 48 supporting a plurality of ball bearings 50. The innermost portion of each rod 46 takes the form of an elongated gear 52 adapted to slidably mesh with a longitudinally fixed but rotating gear 54. The gear 54 is driven, via drive shaft 56, by a motor 58. A shaft 60 associates with each rod 46 and with the sensing and control unit (not shown), and serves to move the rod 46 into or out of the hull of the ship.
As is indicated in FIG. 5 by arrows 62, each rod 46 is made to rotate in the same sense. The reason for this rotation is as follows. When the ship is moving in the direction of arrow 64, the relative movement between the external waters and the rods 46 creates frictional forces focused at the surfaces of the rods. By rotating the rods, a force in the direction of arrow 66 is transmitted to the ship. At the same time, owing to the overall outline of the rods 46, an additional force is transmitted to the ship in the direction of arrow 66. Therefore, as the ship moves in the direction of arrow 64, the overall outline of the rods 46 develops a moment substantially equivalent to that developed by the stabilizing fin illustrated in FIG. 2, and at the same time develops an additional moment, in the same direction, resulting from the spinning action of the rods 46.
The embodiment of the invention illustrated in FIGS. 5 and 6 operates just as does the embodiment described with reference to FIGS. 1 through 3. When the ship is rolling toward port, the port rods 46 are extended, preferably in unison, by acting simultaneously on the shafts 60, while, at the same time, the starboard rods 46 are retracted. In view of the interaction between the gears 52 and 54, such extension and retraction does not affect the rotation of the rods 56. However, if desired, the rotation of the inactive fins could be periodically interrupted.
In FIG. 7, there is shown a block diagram of a novel sensing and control system for use with the inventive fins described above, and including an automatic rudder control for preventing off-course movement of the ship resulting from the operation of the fixed-angle stabilizing fins. The basic element in the inventive sensing and control system is a roll sensor 70, the roll sensor 70 serving to detect the roll of the ship and to issue output signals indicative thereof. These output signals are fed to an amplifier 72 which amplifier has a pair of output terminals 74 and 76. Output terminal 74 associates with a starboard fin control 78 and a port rudder control 80 while output terminal 76 associates with a port fin control 82 and a starboard rudder control 84.
The roll sensor 70 may be of the type capable of sensing only the direction of roll or of the type capable of sensing both the direction of roll and the acceleration thereof. In either case, the roll sensor 70 serves to sense the roll of the ship and to issue output signals whose polarity is indicative of the sensed roll. If the roll sensor 70 can sense only the direction of roll of the ship, then a positive signal could represent the roll of the ship toward starboard while a negative signal could represent the roll of the ship toward port. If, on the other hand, the roll sensor 70 can measure roll acceleration as well as direction, then the signals issued by the roll sensor could be made to change polarity shortly before the actual change of roll direction of the ship, when the roll acceleration nears zero.
For purposes of this invention the amplifier 72 could be of the type which receives an input signal of a given polarity and which issues a pair of signals in response thereto, the output signals appearing at its respective output terminals. For example, the amplifier 72 could be programmed so that when the roll sensor 70 issues a positive signal, the amplifier 72 issues a positive signal at output terminal 74 and issues a negative signal at output terminal 76. And when the roll sensor 70 issues a negative signal, then the amplifier 72 could be made to issue a negative signal at output terminal 74 and a positive signal at terminal 76.
The fin controls 78 and 82 and the rudder controls 80 and 84, for purposes of description, will be assumed to operate as follows. The fin controls 78 and 82 extend their respective fins when they are in receipt of positive input signals and retract their fins when in receipt of negative input signals. The rudder controls 80 and 84 move the rudder only when in receipt of positive input signals; negative input signals have no effect. For example, when a positive signal appears at output terminal 74 of the amplifier 72, and is received by the port rudder control 80, the port rudder control will move the rudder toward port. The negative signal appearing at terminal 76 and reaching the starboard rudder control 84 has no effect on the rudder.
With the functional assumptions set forth in the preceding paragraphs, the system illustrates in block diagram in FIG. 7 operates as follows. With the roll of the ship hard toward starboard, the roll sensor 70 detects such roll and, in response thereto, issues a signal of positive polarity. The positive signal issued from the roll sensor 70 is transmitted to the amplifier 72, the amplifier, in turn, issuing a positive signal at output terminal 74 and issuing a negative signal at output terminal 76. The positive signal appearing at output terminal 74 is transmitted to the starboard fin control 78 and the port rudder control 80. Similarly, the negative signal appearing at output terminal 76 is transmitted to the port fin control 82 and the starboard rudder control 84.
The conditions set forth in the preceding paragraph are illustrated in FIG. 7 and have the following effects. The positive signal impressed upon the input to the starboard fin control 78 activates this control and extends the starboard fin. The negative signal input to the port fin control 82 in the same manner activates the port fin control, but retracts the port fin. The port rudder control 80, being in receipt of a positive signal, turns the rudder toward port, with the negative signal reaching the starboard rudder control 84 having no effect on the rudder.
With the roll of the ship toward starboard, as described above, the extension of the starboard fin and the retraction of the port fin results in the development of a stabilizing moment opposing the starboard roll of the ship. (Both port and starboard fins are designed to develop lift forces.) Concurrent with the development of stabilizing forces, however, the extension of the starboard fin and the retraction of the port fin have another effect. The extended starboard fin and the retracted port fin develop a moment tending to turn the ship toward starboard. Ordinarily, such turning moment would result in an off-course movement of the ship; but such movement is prevented by means of the FIG. 7 sensing and control system. The rudder position is changed, with the inventive system, before the ship turns off-course, hence presenting such off-course movement. With the inventive system, therefore, the direction of travel of the ship is steady despite the development of forces tending to change such direction. The inventive system reacts to anticipated direction changes and avoids same, rather than reacting to actual direction changes and correcting same.
With the ship rolling hard toward port, precisely the opposite conditions would be set up in the sensing and control system. The roll sensor 70 would issue a signal of negative polarity. In response to the negative input signal, the amplifier 72 would develop a positive signal at output terminal 76, and would develop a negative signal at output terminal 74. Hence, the port fin would be extended by the port fin control 82 while the starboard fin would be retracted by the starboard fin control 78. Simultaneously, the starboard rudder control 84 would turn the rudder toward starboard. These conditions would bring about the development of a stabilizing moment opposing the roll of the ship and would also develop counteracting turning movements in the ship, with the result being the stabilization of the ship without direction change.
Several specific embodiments of the present invention have heretofore been described. It should be understood, however, that numerous modifications and alterations may be practiced by those skilled in the art without departing from the spirit and scope thereof. For example, while the foregoing specific description has concentrated on a single pair of stabilizing fins, more than one fin pair could be provided such as is shown, in phantom, in FIG. 1. The fins of the respective fin pairs would then be fixed and equal in angle, with one fin pair being set for lift and the other set for descent. Further, while the above description has been limited to the use of the stabilizing fins for stabilization purposes, it should be understood that under emergency conditions, each of the fins could be fully extended so as to provide a drag and hence a stopping action on the ship. These are only two of many alterations which may be practiced within the scope of the invention, and hence it is the intent that the present invention not be limited by the above but be limited only as defined in the appended claims.
There are many generic types of ship stabilizers known to the prior art. For purposes of this invention, however, only the fin-type stabilizers will be discussed.
The operation of the conventional fin-type ship's stabilizer is as follows. A pair of retractable fins are fitted below the water line on each side of the hull amidships; and control and drive systems are located somewhere within the hull of the ship. The standard control unit senses roll angle and rate of roll, and sometimes senses roll acceleration as well. The data received by the control unit is evaluated by electronic computers and is transmitted as electrical impulses to the prime movers which orient the fins so that the stabilizing moment produced by the water flow around the fins compensates for the disturbing moments of the wave. The ship's rolling motions are thereby damped. In the conventional fin-type stabilizer system, the fins remain fully extended when in use and are pivoted about substantially horizontal axes, oppositely but in unison, and thereby changing their angles of encounter with the external waters in accordance with the stabilizing moment needed. Often these fins are provided with tail flaps so as to increase the moment developed thereby.
In some installations, the fins are of the non-retractable type always remaining positioned for use, but usually the fins are either retractable or foldable into the hull of the ship. When the fins are of the retractable-type, they move linearly, along their major axes, until they are fully retracted into the hull of the ship when not in use. This type of retractable fin requires the minimum size opening in th shell plating, thereby affecting only a small number of frames. Moreover, with this type of fin, the lifting forces can easily be transmitted to the double bottom structure of the ship. The foldable-type fins are stored within the hull of the ship by pivoting about vertical axes just inside the hull. This type of fin offers the advantage that the space between the two fin housings can be used for the storage of cargo.
One feature common to each type of stabilizing fin system known to the prior art is that during operation of the system, the fins are continuously pivoted so as to change their respective angles of encounter with the external waters, thereby changing the direction in which the stabilizing moment is developed. All types of prior art fin systems, therefore, require motor and gearing arrangements for varying the angles of encounter of the fins in accordance with the needs of the ship. If the fin-type stabilizer is provided with the often used tail flap, then an additional motor and gearing arrangement is needed to adjust the angle of encounter of this tail flap. And, in addition to these two motor and gearing arrangements, if the prior art fins are either made retractable or foldable into the hull of the ship, then a third motor and gearing arrangement becomes necessary. It should be obvious, therefore, that the prior art stabilizing fin systems are bulky, complex, and accordingly, expensive.
The present invention is related to a fin-type stabilizing system which overcomes many of the disadvantages found in the fin-type stabilizing systems known to the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a fin-type ship stabilizing system wherein at least one fixed angle fin is located below the water line on each side of the hull amidships. The encounter angles of the respective fins are equal so as to develop equal but oppositely directed moments. That is, when all fins are fully extended, the rolling moments developed thereby add to zero. Each fin is adapted, when the system is operative, to retract into the hull of the ship, either by sliding linearly or by pivoting. The inventive system is also provided with a sensing and control unit for sensing the roll of the ship and controlling the surface area of the respective fins exposed to the external waters.
In operation, roll-opposing moments are developed when the fins are alternately retracted and extended in response to the roll of the ship. If the common angle of each fin is fixed so as to impart an upwardly directed moment, and if the ship is rolling toward starboard, then the starboard fin is extended to its fully outboard position while the port fin is retracted into the hull of the ship. Thus, a moment is developed which opposes the starboard roll of the ship. When the ship begins to roll toward port, then the sensing and control unit issues a signal which retracts the starboard fin and extends the port fin.
The advantages of the inventive system described in the preceding paragraphs should now be readily apparent. With the prior art fin systems, the fins and associated prime movers encounter tremendous resistance from the external waters when the respective angles of the fins are changed; very little resistance is encountered when the fixed-angle fins are extended or retracted. Therefore, the inventive fin system is stressed far less than are the prior art systems. The retractable fin systems of the prior art require one motor and gearing system for extending and retracting the fins and at least one additional motor and gearing system for operating the fins. Only one motor and gearing system is used in the operation of the present invention. The same motor and gearing system which extends and retracts the inventive fins during operation serves also to retract the fins into the ship's hull for storage. Prior art fins are frequently provided with auxiliary flaps to enhance the stabilizing moments developed by the fins since the fins are designed and mounted for maximum efficiency.
In another embodiment of the present invention, two fin pairs are provided, one fin from each pair being located below the waterline on each side of the hull amidships. The angles of the fins from one set are fixed for maximum upward lift while the angles of the fins from the other set are fixed for maximum descent. When the ship is rolling to starboard, the fin for lifting the starboard side of the ship is extended while the fin for causing the descent of the starboard side is retracted; at the same time, the fin for causing descent of the port side of the ship is extended while the fin for lifting the port side is retracted. With such a balance arrangement, the resistive forces tending to change the direction of travel of the ship are balanced, and hence unwanted changes in direction of travel of the ship are minimized.
The present invention also relates to a system for automatically controlling the ship's rudder in response to the positioning of the stabilizing fins. While the two-pair embodiment of the present invention outlined above minimizes the turning effects of the fins on the ship, the fins still tend, to some degree, to change the ship's direction of travel. This turning effect is particularly noticeable when only one pair of fins is provided. The present invention contemplates that the control unit which serves to adjust the positioning of the fins be also associated with the rudder. In this manner, the control unit corrects for anticipated turning of the ship.
As an example of the invention described in the preceding paragraph, when the starboard fin is fully extended and the port fin retracted, the ship tends to turn toward starboard. The invention contemplates "correcting" for the expected starboard turn, before it happens, by adjusting the rudder at the same time as the fins. The rudder is adjusted, in this example, for a slight direction change toward port.
In another embodiment of the present invention, each of the fixed-angle fins is defined by a plurality of rotating rods or tubes. As is well known, a rotating object moving linearly through a fluid experiences a force directed transverse to its linear motion. This embodiment of the present invention makes use of the principle defined immediately above to enhance the righting effect of the fins on the ship. The spinning rods being associated in the outline of a pair of fins, the lift developed is dependent upon two independent lift forces.
Each embodiment of the inventive fin described above may be constructed so that the fins retract into the hull of the ship in directions along the major axes thereof or into the hull of the ship by pivoting about vertical axes. For purposes of description, however, the linearly retractable-type fixed-angle stabilizing fin will be described, as this fin is the preferred embodiment of the present invention. With the linearly retractable fin, the area of fin exposure may be changed and fin storage may be accomplished with a single set of motors. Any one of a large number of conventional guiding and retracting mechanisms can be used to retract the inventive fins.
It is the main object of the present invention to provide a fixed-angle stabilizing fin system for stabilizing the roll of a ship in a manner far simpler than those fin systems known to the prior art.
A more specific object of the present invention is to provide a fixed-angle stabilizing fin system wherein a single motor arrangement serves both to adjust the moment developed by the respective fins and to retract the fins into the hull of the ship when not in use.
A further object of the present invention is to provide a fixed-angle stabilizing fin system such as that described above, wherein the forces exerted on each side of the ship are substantially balanced.
Still another object of the present invention is to provide a fixed-angle stabilizing fin system wherein the fins are designed and angled in such a manner as to maximize the moment developed thereby.
Still a further object of the present invention is to provide a fixed-angle stabilizing fin system wherein adjustment to the righting moment developed by the fins is carried out with minimum resistance by the external waters.
Yet a further object of the present invention is to provide a fixed-angle fin stabilizing system wherein the turning effect of the fins is corrected by an automatic steering system.
Still a further object of the present invention is to provide a stabilizing fin system wherein the respective fins rotate and are constructed so as to develop two independent righting moments.
These and other objects of the present invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified front view of a ship equipped with a fixed-angle fin stabilizer system constructed in accordance with the teachings of the present invention;
FIG. 2 is a perspective view of an inventive fin stabilizer fit in the starboard side of a ship;
FIG. 3, (a) through (i), is a sequential showing of a rolling ship equipped with a fin stabilizer system constructed in accordance with the teachings of the present invention;
FIG. 4, (a) and (b), is an illustration of an inventive fixed-angle fin provided with a cover plate for streamlining the ship when the fin is in storage;
FIG. 5 is a front view, partially in section, of another embodiment of the inventive fixed angle fin stabilizer system;
FIG. 6 is a side view of one of the elements of the fin illustrated in FIG. 5; and
FIG. 7 is a block diagram illustrating the manner in which a roll sensor controls the operation both of the fixed-angle stabilizing fin system and the steering rudder.
DETAILED DESCRIPTION OF THE DRAWINGS
With reference to FIGS. 1 through 3, the first embodiment of the present invention will be described. A ship equipped with the inventive stabilizing fin system is indicated generally at 10. Both the port and starboard hulls 12 of the ship 10 are opened at 14 so as to accept port and starboard fixed-angle stabilizing fins 16 and 18, respectively. The angle that each of the stabilizing fins makes with the horizontal is fixed, with both fins set at the same angle. Preferably, and for maximizing the stabilizing effect of the fins, the set angle should be between 28° and 30°. As shown, each fin is set for lift, but it should be appreciated that both may be set for descent.
In FIG. 1, the starboard fin 18 is fully extended while the port fin 16 is in its retracted position. As each fin is designed to develop a lift moment, the fin orientation indicated in FIG. 1 would counteract the roll of the ship when the ship is rolling in the direction of arrow 20. When the ship's direction of roll reverses, the starboard fin 18 is retracted and the port fin 16 is extended. A more detailed description of the operation will be given below when specific reference is made to FIG. 3.
The inventive stabilizing fin system derives its novelty over those fin systems known to the prior art in that the angle that the inventive fin makes with the horizontal is fixed. In this manner, the moment developed by a plurality of fixed angle fins is dependent upon the exposure between the fins and the external waters. Therefore, while prior art systems rely upon angle changes of the fins to alter the direction of righting moments, the inventive system relies upon the relative distance that respective fins extend into the water.
With the present invention, the angle that the fin makes with the horizontal is set for maximum moment, and so too is the shape of the fin. Accordingly, the necessity for auxiliary flaps and other such moment-enhancing apparatus, with the usual operating equipment, is avoided. It should be appreciated, however, that if for some technical reason, flaps and other such apparatus are desired, they may be used in conjunction with the inventive fixed-angle stabilizing fin system.
Since the advantages of the various fin shapes are well known in the art, they will not herein be discussed. Suffice it to say that while the stabilizing effect of the inventive fin system can be maximized by proper fin design, the inventive system is operable with any known prior art fin. Similarly, because there are numerous known systems for sensing roll and moving the fins into and out of the hull of the ship, such systems will not herein be described in detail. Suffice it to say that with the present invention, any one of many known devices may be used to position the fins in accordance with the roll sensed.
Before beginning a discussion of the operation of the inventive stabilizing system, the operational sequence being illustrated in FIG. 3, two types of sensing and control mechanisms will be described. The first type, the simplest of the two, is the type wherein the sensing system senses only the direction of roll of the ship. Accordingly, with this system, changes in the fin positions take place only after the ship changes its direction of roll. With such a system, the starboard fin would be extended and the port fin retracted when the ship is rolling to starboard. It is only when or slightly after the ship reaches its full starboard heel that the starboard fin is retracted and the port fin extended. The fins would so remain during the entire roll toward port and would be repositioned only at the time of or shortly after the full port heel. With such a system, there would be a slight time delay at the beginning of each roll cycle, due to the time necessary to change the orientation of the fins, when the fins operate to roll rather than to stabilize the ship.
With the second type of sensing system, the more complex of the two, the sensing device operates to sense both the direction and the acceleration of the roll. With such a system, it is possible to begin the change in orientation of the respective fixed-angle stabilizing fins shortly before the ship reaches maximum heel in both directions. In this manner, when the ship reaches maximum heel, there is no destabilization effect. Further, the time required to fully extend one fin and to fully retract the other, when necessary, is greatly reduced.
As an example of the above, the starboard fin is fully extended and the port fin fully retracted during most of the roll cycle from port to starboard. Shortly before the ship reaches maximum heel toward starboard, when the roll acceleration becomes very small, the sensing and control system begins to reorient the respective fins by retracting the starboard fin and extending the port fin. Ideally, when the ship reaches full heel in the starboard direction, the port and starboard fins are each half extended and half retracted. In this manner, at the instant when no stabilization effect is needed, none is provided. The reorientation of the respective fins then continues so that shortly after the ship begins its roll toward port, the port fin is fully retracted. With this system, there is never an instant of time when the fixed-angle stabilizing fins destabilize rather than stabilize the ship.
With reference now to FIG. 3, the operational sequence of the inventive fixed-angle stabilizing fin system will be described. The positioning of the fins in FIG. 3 willl be explained based upon the provision of the second and more complex of the two types of sensing and control systems described above. That is, the sequential operation illustrated in FIG. 3 makes use of the sensing and control system which senses the roll direction as well as the acceleration of roll of the associated ship.
In FIG. 3(a), the ship 10 is shown when heeling maximum toward starboard. The port fin 16 is partially extended and the starboard fin 18 is partially retracted. The respective fins are, in FIG. 3(a), moving in the directions indicated by arrows 15 and 17.
When the ship 10 passes through its maximum starboard heeling position and reaches the position illustrated in FIG. 3(b), the starboard fin has been fully retracted into the hull of the ship while the port fin has been fully extended. In this position, and with roll in the direction of arrow 22, the port fin 16 develops a righting moment counteracting the roll of the ship. The starboard fin 18 has no effect. The port fin 16 remains fully extended, with the starbaord fin 18 remaining fully retracted, during the roll of the ship through the positions illustrated in FIGS. 3(c) and 3(d). But between the positions represented by FIGS. 3(d) and 3(e), the port fin 16 begins to retract while the starboard fin 18 is extended.
In FIG. 3(e), the heel of the ship is maximum toward port. Like in FIG. 3(a), each of the fins 16 and 18 is half extended and half retracted into the hull of the ship.
During the roll of the ship from position 3(e) to position 3(f), in the direction of arrow 24, the port fin 16 retracts while the starboard fin 18 extends. When the ship reaches the position shown in FIG. 3(f), the port fin 16 is fully retracted while the starboard fin 18 is fully extended. Under these circumstances, the starboard fin 18 develops a moment opposing the roll of the ship. The port fin 16 has no effect. And so the cycle continues.
Now, with reference to FIG. 4, a streamlining feature of the inventive fin system will be described. FIG. 4 represents, schematically, one side of a ship equipped with a fixed-angle stabilization fin system constructed in accordance with the present invention. The hull 26 of the ship is opened and accommodates a fixed-angle fin 28, the fin 28 being mounted for reciprocation in a fin guide track arrangement 30. During retraction and extension, the fin 28 is adapted to freely move over rollers 32 and is controlled by the operation of a drive rod 34 associated with the sensing and control unit (not shown).
On the outboard end of each fin is mounted a plate 36 of a size of configuration substantially conforming to the opening in the hull 26 and adapted to accommodate such inventive fin. Preferably, the extremity of each plate 36 is provided with an inwardly angled flange 38 conforming substantially to a similarly angled flange 40 integral with the hull 26 of the ship. In this manner, the flanges 38 and 40 define a smooth junction and coact to streamline the travel of the ship through external waters.
The manner in which the fin 28, with its fin plate 36, mates with the hull 26 of the associated ship is shown best in FIG. 4(b). In this figure, the fin 28 is shown fully retracted into the hull of the ship, and, in this position, the flange 38 integral with the fin-plate 36 runs parallel to and is in close proximity to the flange 40 integral with the hull 26. When in this position, the hull 26 of the ship is substantially streamlined, and in this manner minimizes the effects of the fin 28 when in its inoperative and stored position.
With reference now to FIGS. 5 and 6, a second embodiment of the present invention will be described. In FIG. 5, the hull of the ship is shown generally at 42 and has an opening 44 defined therein. A plurality of rods 46 extend through the opening 44 in the hull 42 and are adapted for reciprocating movement into and out of the hull. As is evident from FIG. 5, the rods 46 are varied in size and are arranged in such a manner that the outline of the rods, taken as a whole, approximates the shape of the fin 18 illustrated in FIG. 2.
For reasons which are fully explained below, each rod 46 associates with a bearing housing 48 supporting a plurality of ball bearings 50. The innermost portion of each rod 46 takes the form of an elongated gear 52 adapted to slidably mesh with a longitudinally fixed but rotating gear 54. The gear 54 is driven, via drive shaft 56, by a motor 58. A shaft 60 associates with each rod 46 and with the sensing and control unit (not shown), and serves to move the rod 46 into or out of the hull of the ship.
As is indicated in FIG. 5 by arrows 62, each rod 46 is made to rotate in the same sense. The reason for this rotation is as follows. When the ship is moving in the direction of arrow 64, the relative movement between the external waters and the rods 46 creates frictional forces focused at the surfaces of the rods. By rotating the rods, a force in the direction of arrow 66 is transmitted to the ship. At the same time, owing to the overall outline of the rods 46, an additional force is transmitted to the ship in the direction of arrow 66. Therefore, as the ship moves in the direction of arrow 64, the overall outline of the rods 46 develops a moment substantially equivalent to that developed by the stabilizing fin illustrated in FIG. 2, and at the same time develops an additional moment, in the same direction, resulting from the spinning action of the rods 46.
The embodiment of the invention illustrated in FIGS. 5 and 6 operates just as does the embodiment described with reference to FIGS. 1 through 3. When the ship is rolling toward port, the port rods 46 are extended, preferably in unison, by acting simultaneously on the shafts 60, while, at the same time, the starboard rods 46 are retracted. In view of the interaction between the gears 52 and 54, such extension and retraction does not affect the rotation of the rods 56. However, if desired, the rotation of the inactive fins could be periodically interrupted.
In FIG. 7, there is shown a block diagram of a novel sensing and control system for use with the inventive fins described above, and including an automatic rudder control for preventing off-course movement of the ship resulting from the operation of the fixed-angle stabilizing fins. The basic element in the inventive sensing and control system is a roll sensor 70, the roll sensor 70 serving to detect the roll of the ship and to issue output signals indicative thereof. These output signals are fed to an amplifier 72 which amplifier has a pair of output terminals 74 and 76. Output terminal 74 associates with a starboard fin control 78 and a port rudder control 80 while output terminal 76 associates with a port fin control 82 and a starboard rudder control 84.
The roll sensor 70 may be of the type capable of sensing only the direction of roll or of the type capable of sensing both the direction of roll and the acceleration thereof. In either case, the roll sensor 70 serves to sense the roll of the ship and to issue output signals whose polarity is indicative of the sensed roll. If the roll sensor 70 can sense only the direction of roll of the ship, then a positive signal could represent the roll of the ship toward starboard while a negative signal could represent the roll of the ship toward port. If, on the other hand, the roll sensor 70 can measure roll acceleration as well as direction, then the signals issued by the roll sensor could be made to change polarity shortly before the actual change of roll direction of the ship, when the roll acceleration nears zero.
For purposes of this invention the amplifier 72 could be of the type which receives an input signal of a given polarity and which issues a pair of signals in response thereto, the output signals appearing at its respective output terminals. For example, the amplifier 72 could be programmed so that when the roll sensor 70 issues a positive signal, the amplifier 72 issues a positive signal at output terminal 74 and issues a negative signal at output terminal 76. And when the roll sensor 70 issues a negative signal, then the amplifier 72 could be made to issue a negative signal at output terminal 74 and a positive signal at terminal 76.
The fin controls 78 and 82 and the rudder controls 80 and 84, for purposes of description, will be assumed to operate as follows. The fin controls 78 and 82 extend their respective fins when they are in receipt of positive input signals and retract their fins when in receipt of negative input signals. The rudder controls 80 and 84 move the rudder only when in receipt of positive input signals; negative input signals have no effect. For example, when a positive signal appears at output terminal 74 of the amplifier 72, and is received by the port rudder control 80, the port rudder control will move the rudder toward port. The negative signal appearing at terminal 76 and reaching the starboard rudder control 84 has no effect on the rudder.
With the functional assumptions set forth in the preceding paragraphs, the system illustrates in block diagram in FIG. 7 operates as follows. With the roll of the ship hard toward starboard, the roll sensor 70 detects such roll and, in response thereto, issues a signal of positive polarity. The positive signal issued from the roll sensor 70 is transmitted to the amplifier 72, the amplifier, in turn, issuing a positive signal at output terminal 74 and issuing a negative signal at output terminal 76. The positive signal appearing at output terminal 74 is transmitted to the starboard fin control 78 and the port rudder control 80. Similarly, the negative signal appearing at output terminal 76 is transmitted to the port fin control 82 and the starboard rudder control 84.
The conditions set forth in the preceding paragraph are illustrated in FIG. 7 and have the following effects. The positive signal impressed upon the input to the starboard fin control 78 activates this control and extends the starboard fin. The negative signal input to the port fin control 82 in the same manner activates the port fin control, but retracts the port fin. The port rudder control 80, being in receipt of a positive signal, turns the rudder toward port, with the negative signal reaching the starboard rudder control 84 having no effect on the rudder.
With the roll of the ship toward starboard, as described above, the extension of the starboard fin and the retraction of the port fin results in the development of a stabilizing moment opposing the starboard roll of the ship. (Both port and starboard fins are designed to develop lift forces.) Concurrent with the development of stabilizing forces, however, the extension of the starboard fin and the retraction of the port fin have another effect. The extended starboard fin and the retracted port fin develop a moment tending to turn the ship toward starboard. Ordinarily, such turning moment would result in an off-course movement of the ship; but such movement is prevented by means of the FIG. 7 sensing and control system. The rudder position is changed, with the inventive system, before the ship turns off-course, hence presenting such off-course movement. With the inventive system, therefore, the direction of travel of the ship is steady despite the development of forces tending to change such direction. The inventive system reacts to anticipated direction changes and avoids same, rather than reacting to actual direction changes and correcting same.
With the ship rolling hard toward port, precisely the opposite conditions would be set up in the sensing and control system. The roll sensor 70 would issue a signal of negative polarity. In response to the negative input signal, the amplifier 72 would develop a positive signal at output terminal 76, and would develop a negative signal at output terminal 74. Hence, the port fin would be extended by the port fin control 82 while the starboard fin would be retracted by the starboard fin control 78. Simultaneously, the starboard rudder control 84 would turn the rudder toward starboard. These conditions would bring about the development of a stabilizing moment opposing the roll of the ship and would also develop counteracting turning movements in the ship, with the result being the stabilization of the ship without direction change.
Several specific embodiments of the present invention have heretofore been described. It should be understood, however, that numerous modifications and alterations may be practiced by those skilled in the art without departing from the spirit and scope thereof. For example, while the foregoing specific description has concentrated on a single pair of stabilizing fins, more than one fin pair could be provided such as is shown, in phantom, in FIG. 1. The fins of the respective fin pairs would then be fixed and equal in angle, with one fin pair being set for lift and the other set for descent. Further, while the above description has been limited to the use of the stabilizing fins for stabilization purposes, it should be understood that under emergency conditions, each of the fins could be fully extended so as to provide a drag and hence a stopping action on the ship. These are only two of many alterations which may be practiced within the scope of the invention, and hence it is the intent that the present invention not be limited by the above but be limited only as defined in the appended claims.