US3109403A

US3109403A - Ship stabilizer

Info

Publication number: US3109403A
Application number: US64935A
Authority: US
Inventors: Ripley Kenneth Clay
Original assignee: John J Mcmullen Associates Inc
Current assignee: John J Mcmullen Associates Inc
Priority date: 1960-10-25
Filing date: 1960-10-25
Publication date: 1963-11-05
Anticipated expiration: 1980-11-05

Description

Nov. 5, 1963 K. c. RIPLEY 'SHIP STABILIZER Filed Oct. 25, 1960 2 Sheets-Sheet 1 FIG. I.

INV EN TOR Kenneth Clay Ripley BY mfim M TTORNEY8 Nov. 5, 1963 K. c. RIPLEY 3,109,403

SHIP STABILIZER Filed Oct. 25, 1960 2 Sheets-Sheet 2 FIG. 5.

O w I I INVENTOR Kenneth Clay Ripley ATTORNEYS United States Patent No. 64,935 or. 114-125 The present invention relates to a stabilizer and more particularly to a stabilizer for ships and boats which embodies new and revolutionary principles.

In the art of ship stabilization, there are two principal approaches. In one approach, stabilization is achieved by means of an activated system; for example, activated fins or a pumping system after Minorsky. In the other approach, a passive stabilization system is achieved after Frahm by utilizing a pair of tanks arranged athwart the vessel and interconnecting them by a U tube. All of the systems that have been advanced to date have been subject to one or more disadvantages including mechanical complexity, noise, difficulty of control, excessive expense of operation, high cost of installation, diiliculty of installation, etc.

More recently, there has been advanced a new concept in the theory of passive stabilization wherein liquid storage means are arranged athwart a vessel and interconnected by means of a duct or other structure to transfer liquid into and from the storage means responsive to rolling of the vessel due to wave action. The system is uniquely characterized by velocity square damping means associated with the storage means and the duct to act upon the liquid during transfer and to produce required energy dissipation. The timing of the system is designed so that the liquid will be transferred into and from the tanks approximately 90 out of phase leading the rolling angle of the vessel, depending somewhat upon the ratio of exciting frequency to ship natural frequency of roll. The damping of the liquid by means of the velocity squared damping arrangement is, of course, non-linear and serves to produce a coupling moment which acts in opposition to the rolling of the vessel.

Further study and experimentation in the direction of passive stabilization systems, as those described immediately above, has led to the discovery of an entirely new theory and concept of stabilization. More especially, it has been discovered that the stabilization system can be greatly simplified from a structural standpoint and the improved simplified structures give rise to new and unexpected advantages over far more complicated counterparts. For instance, using an assigned weight of liquid for the stabilizer, the simplified structures of the present invention provide more efiective and better stabilization by producing greater energy dissipations and more coupling moment. The simplified structures of the present invention result in a much tighter stabilization system and are able to produce stabilized rolls of smaller residual values than characterize systems heretofore known.

Accordingly, it is a principal object of the present invention to provide a simplified passive stabilization system which functions more effectively and efiiciently than systems heretofore advanced for this purpose.

It is a further object of the present invention to provide a simplified novel basic stabilization unit which can be used as a building block in the design of complex stabilization systems.

Other and further objects of the present invention will become more readily apparent from a detailed consideration of the following description of preferred embodiments of the present invention when taken in conjunction with the appended drawings in which:

FIGURE 1 illustrates in vertical section a novel simplified stabilization unit according to the concepts and teachings of the present invention;

FIGURE 2 shows in horizontal section taken along line 2-2 of FIGURE 1 the stabilization unit portrayed in FIGURE 1;

FIGURE 3 shows in a horizontal section like that of FIGURE 2 an alternative stabilization unit according to the teachings of the present invention;

FIGURE 4 illustrates in a horizontal section like that of FIGURE 2 a further alternative arrangement for a stabilization unit embodying the principles of the present invention and characterized by a coupling moment that shifts in the direction of liquid transfer;

FIGURE 5 is a view in vertical section taken along line 55 of FIGURE 6 and portrays a stabilization system built from a plurality of stabilization units of the type illustrated in FIGURE 1 and 2; and

FIGURE 6 is a view in horizontal section taken along line 6-6 of FIGURE 5.

Referring now to the drawings in detail, the present invention will now be described with reference to preferred embodiments.

FIGURES l and 2 illustrate a specific preferred embodiment of the present invention. The structure portrayed in FIGURES 1 and 2 is extremely simple and comprises a pair of tanks, generally designed by the reference numerals 1t) and 12, which are connected together. Both of the tanks are rectangular in horizontal and vertical cross section. One end of each of the side walls of tank 12 is connected to vertically arranged pipes 14 which are spaced apart. Pipes 14 are also attached to the sides of an opening 18 defined by one of the side walls 16 of the tank it). The two tanks 19 and 32 are of the same height, as will be evident from FIGURE 1, and tank 12 is substantially narrower than tank lit. In the design of the unit, as shown in these figures, the horizontal cross-sectional area of tanks Ill and I2 is equal. The two tanks are filled with water or other liquid to the level indicated by the reference numeral 2-0. This level is predetermined as a result of computation and will determine both the energy dissipation of the unit after construction, and the natural frequency of the unit as a simple oscillatory system. The tanks 1% and 12 are composed of metal plates welded or otherwise fastened together at their edges and consist of side walls, a floor and a top.

The unit depicted in FIGURES 1 and 2 can be mounted between a pair of decks of a vessel or in any desired location in or on a ship or vessel so that. the tanks It and 12 extend athwart the vessel. When the vessel rolls due to Wave action, the liquid in tanks w and 12 will be set in motion and will transfer back and forth between the tanks in and 12. The pipes 14 are circular and constitute a nozzle design. The liquid transferring from one tank to the other will pass through space 18 and will be subjected to a throttling or damping action as a result of the nozzle design. The throttling or damping will be non-linear in character and will actually be a function of the square of the velocity of the liquid transferring from tank to tank. The net result of this action will be to produce a coupling moment that leads the rolling angle of the vessel by and, therefore, stabilizes the vessel against roll by dissipating the energy imparted to the vessel by the wave action. By virtue of the operation of the stabilizing unit portrayed in FIGURES 1 and 2, it is possible to hold the roll of the vessel to a small residual value; for example, a mean roll of less than 2 amplitude for most conditions of seaway.

Whereas the stabilizing unit illustrated in FIGURES 1 and 2 comprises a pair of tanks interconnected in the manner described, each tank of which is characterized by a rectangular horizontal cross section, it will be appreelated that these tanks may be of other configuration; for example, either or both of the tanks may be trapezoidm in horizontal or vertical cross section and conceivably could be of any other regular, or even irregular, geometrical design in cross section, both horizontal and vertical.

A previous point that has been emphasized is that tank T2 is narrower than tank lltl but that both tanks are characterized by horizontal cross-sectional areas that are equal. This condition makes analysis of the system comparatively simple, but is not necessarily the best solution for every set of design specification circumstances. Thus, the horizontal cross-sectional areas of the two tank subassemblies need not be equal, or, alternatively, the width of the tanks may be equal.

The principal advantage that is achieved by the specific design shown in FlGURES v1 and 2 is that all of the available liquid surface constitutes What could be construed as working free surface. This means that all of the (free surface contributes to the stabilization since all of the free surface undergoes displacement in the direction of gravity, This aspect of the present invention is a result of the simplification of the stabilizing design and the geometry of the physical structure. Comparing the design of the present invention with the best effort of the prior art designs, the nozzle concept for energy dissipation is known; however, it has always been considered necessary to have a basic stabilization system wherein side or wing tanks are employed interconnected by a crossover duct. The duct itself constitutes a dead, or inactive, region and liquid therein does not contribute substantially to the stabilizing moment. his the discovery of the present invention that the crossover duct can be eliminated and also that in this Way the nozzle design can be reduced to that between the two storage points. The net result will be to achieve even greater energy dissipation and more effective operation of the stabilizing unit with the same assigned weight of liquid.

A special advantage is obtained from the design shown in FIGURES l and 2 when one of the tanks is substantially elongated, with or without the horizontal crosssectional areas of the tanks being equal. This achieves an important requirement of the design, namely, that when the unit is inclined, a substantial head of liquid is created at the nozzle as a driving force. This has the effect of making the system comparatively tight as regards control.

It should :be noted, in passing, that the system of the invention-two tanks without a crossover du'cthas a further important advantage. For a given differential head of water at the nozzle, the required static depth of water to tune the system is less in the stabilizer of the present invention than would be required in a conven tional stabilizer; that is, one employ-ing a crossover duct. This feature of the present invention--allowing the Water to :be relatively shallowenables one to do more with an assigned weight of water than hitherto.

Referring now to FIGURE 3, a further stabilizing unit is illustrated. The unit in this instance is comprised of a pair of tanks and 32 interconnected in the manner of the tanks of FIGURES l and 2, through the intermediary of a pair of vertical circular pipes 34 which are attached to the sides of an opening 36 defined in side wall 38 of tank 3d. One of the end walls of tank 32 is eliminated and the side walls 4!) and 42 of tank 32 are connected tangentially to the pipes 34. The design of El- URE 3 is such that a nozzle or jet effect will be produced only when liquid is transferred from tank 32 to tank 3%. Transfer of the liquid in the opposite direction does not produce a nozzle or jet effect due to the streamlined character of the flow path. For this reason, the energy dissipation or d-ampingoccurs only when the fluid flows from tank 32 to tank Sil The coupling moment for roll stabilization, when utilizing a stabilizing unit designed according [0 FIGURE 3, will be produced only during alternate half-cycles of ship roll. If it is desired to pr duce stabilization during both halves of the ship roll cycle when using structures as shown in FIGURE 3, it will be necessary to mount such structures athwart the vessel and oppositely in a back-to1back relationship. In this manner, tte structures will be in a paired relationship with each member of the pair being effective in successive halfcycles of ship roll.

FIGURE 4 illustrates a further refinement of the present invention, and the structure portrayed therein comprises a pair of tanks $0 and 52 defining

openings

54 and 56, respectively, in

side walls

58 and 60, respectively, which are arranged in an adjacent or opposed fashion.

Vertical pipes

62 and 64 are attached to opposite sides of the opening 54- and

vertical pipes

66 and 70 are attached to opposite sides of the opening 56. An interconnecting duct means generally designated by the reference numeral 72 is tangentially attached to all of the vertical pipes. The structure bears some similarities to the one portrayed in FIGURE 3, and in this particular instance, a single nozzle, operative in both directions, is defined by all of the vertical pipes and the interconnecting duct 72.

The stabilizing unit illustrated in FIGURE 4 is filled with a liquid to a predetermined level; for example, about half full, and placed in a vessel athwartship. When the vessel rolls due to wave action, the liquid will be transferred from tank 56 to tank 5'2 and vice versa through the nozzle defined between them. As the liquid transfers from tank 5% to tank 52, it will enter the nozzle system at the opening 54 in a streamlined non-energy dissipating fashion and will emerge at the opening 56, whereat the jet efi'ect, damping, or throttling will occur. Consequently, the free surface coupling moment arm will extend from a point within tank 52 to a point determined by the free surface of tank 5t} and the duct means 72. When the liquid transfers from tank 52 to tank 50, the damping or jet effect will occur at the opening 54, and at this time, the coupling moment will shift to the left as it will be determined in this case by the free surface area of tank 5% and the free surface area of tank 52 and duct means 72.

Referring now to FIGURES 5 and 6, there is illus trated a stabilization system that could effectively be employed in the stabilizing of small craft. The stabilizing assembly or system is fabricated as a plate-like member which can be incorporated into a housing or roof structure of the small craft and thereby incorporated without requiring extra structural detail. It is, of course, desirable to locate a stabilizing system as high as possible in the craft and, for this reason, it is suggested that a roof section be utilized for containing the stabilizer. As illustrated, the stabilizer is comprised of a host of stabilizing units employing the design of FIGURES 1 and 2. These units are arranged in an alternate interleaved relationship in two rows with reference to the center line of the roof section. More explicity, the roof section is comprised of a roof floor panel 100 and a roof ceiling panel fill; terminating at its edges in curved sections 104 to space it from the roof floor panel ltltl. The spacing between the panels 1% and 102 can be of the order of 3 to 4 inches. The panels may, for example, be about 40 inches by about inches. The space defined between the panels is subdivided by a central bulkhead 106 to divide the roof section into two principal compartments. Side bulkheads 1% serve to isolate the curved portions of the roof ceiling panel 102. The two compartments defined between the bulkheads 106 and 108 are further subdivided by a series of bulkheads and vertical pipes to define stabilizing units as portrayed in FIGURES 1 and 2. The larger compartments of these stabilizing units are approximately 6 inches wide and the narrower compartments are about 3 inches Wide. The vertical heights which are employed to establish nozzle structures define openings approximately 2 inches wide. The pipes have a diameter of about 1 /2 inches. It will be noted that the geometry of the stabilizing units enables them to be arranged in an interleaved side-by-side fashion. It will be appreciated, however, that whereas the horizontal cross-sectional configuration for the compartments of each stabilizing unit have been portrayed as being rectangular, that other configurations will lend themselves quite readily to a composite stabilizing system. For instance, the units could be easily dove-tailed were the horizontal cross sections to be trapezoidal in shape. Such a geometry might be useful to increase the difierence between the nozzle opening and the width of the duct (the vertical crosssectional area of the duct) to increase the energy dissipation due to the operation of the nozzle defined by the pair of vertical pipes.

Although the present invention has been shown and described in terms of specific preferred embodiments, it will be appreciated that changes and modifications will occur to those skilled in the art from a knowledge of the teachings of the present invention. Such changes and modifications as appear are deemed to be within the spirit, scope and contemplation of the invention.

What is claimed is:

1. A stabilizer for a vessel comprising first wall means defining an enclosure characterized by a restricted verti-, cally elongated opening, a pair of elongated members having curved exteriors attached radially to said wall means along each vertical edge of the opening, and a second wall means defining a second enclosure characterized by a second vertically elongated opening with each vertical edge thereof attached radially to one of said elongated members and a body of liquid in said enclosure.

2. A stabilizer as defined in claim 1 wherein the edges of said second opening are attached tangentially to said elongated members.

3. A stabilizer for a vessel comprising first wall means defining an enclosure characterized by a restricted vertically elongated opening, a first pair of elongated members having curved exteriors attached radially to said wall means along the vertical edges of the opening, a second wall means defining a second enclosure characterized by a second vertically elongated opening, a second pair of elongated members having curved exteriors attached radially to said second wall means along the vertical edges of said second opening, and further wall means defining an elongated enclosure open at its opposite ends with its vertical edges attached tangentially to said first and second pairs of elongated members and a body of liquid in said enclosure.

References Cited in the file of this patent UNITED STATES PATENTS 1,023,477 Oldham Apr. 16, 1912 2,464,957 Wood Mar. 22, 1949 FOREIGN PATENTS 13,784 Great Britain of 1908 435,100 Great Britain Sept. 13, 1935 675,003 Germany Apr. 27, 1939 688,796 Germany Mar. 2, 1940 911,182 France Mar. 4, 1946 OTHER REFERENCES A.P.C. application of Hort, Ser. No. 132,695 (Published May 11, 1943, now abandoned).

Claims

3. A STABILIZER FOR A VESSEL COMPRISING FIRST WALL MEANS DEFINING AN ENCLOSURE CHARACTERIZED BY A RESTRICTED VERTICALLY ELONGATED OPENING, A FIRST PAIR OF ELONGATED MEMBERS HAVING CURVED EXTERIORS ATTACHED RADIALLY TO SAID WALL MEANS ALONG THE VERTICAL EDGES OF THE OPENING, A SECOND WALL MEANS DEFINING A SECOND ENCLOSURE CHARACTERIZED BY A SECOND VERTICALLY ELONGATED OPENING, A SECOND PAIR OF ELONGATED MEMBERS HAVING CURVED EXTERIORS ATTACHED RADIALLY TO SAID SECOND WALL MEANS ALONG THE VERTICAL EDGES OF SAID SECOND OPENING, AND FURTHER WALL MEANS DEFINING AN ELONGATED ENCLOSURE OPEN AT ITS OPPOSITE ENDS WITH ITS VERTCAL EDGES ATTACHED TANGENTIALLY TO SAID FIRST AND SECOND PAIRS OF ELONGATED MEMBERS AND A BODY OF LIQUID IN SAID ENCLOSURE.