US3870006A

US3870006A - Stabilizing device for buoyant body

Info

Publication number: US3870006A
Application number: US362111A
Authority: US
Inventors: Masami Hashimoto
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-05-31
Filing date: 1973-05-21
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11
Also published as: FR2186379B1; JPS5620237B2; GB1432585A; FR2186379A1; JPS4913894A

Abstract

A stabilizing device for a buoyant body made from a section of material secured to the buoyant body and contacting the liquid, for example, water, upon which the buoyant body floats. This section of material increases the attractive force between the buoyanat body, such as a life raft, and the water. Further, when any upsetting force, such as the force of the wind, induces a slanting of the buoyant body, the stabilizing device hinders or precludes external air from entering the space between the buoyant body and the liquid surface. When the section of material takes the shape of a flat sheet, as is shown in one preferred embodiment, providing the material with one or more gascontaining ducts serves to spread the sheet upon the liquid.

Description

United States Patent 1191 Hashimoto 1451 Mar. 11, 1975 STABILIZING DEVICE FOR BUOYANT 211 App]. N6; 362,111

[30] Foreign Application Priority Data May 31, 1972 Japan 47-54051 [52] US. Cl. 114/121, 9/11 A [51] Int. Cl 1363b 43/04 [58] Field of Search 114/121, 68, 43.5, 123;

9/2A, 11 R, 11 A,8R,8P,8.3 R,8.3 E, 310 R,310 C,310 8,310 F,31O 6,310 .1, 340; 46/91, 92, 93

3,029,606 4/1962 Olsen 114/435 FORElGN PATENTS OR APPLICATIONS 1,201,914 8/1970 Great Britain 9/11 A Primary ExuminerTrygve M. Blix Assistant ExuminerCharles E. Frankfort Attorney, Agent, or FirmNeuman, Williams, Anderson & Olson [57] ABSTRACT A stabilizing device for a buoyant body made from a section of material secured to the buoyant body and contacting the liquid, for example, water, upon which the buoyant body floats. This section of material increases the attractive force between the buoyanat body, such as a life raft, and the water. Further, when any upsetting force, such as the force of the wind, inducesa slanting of the buoyant body, the stabilizing device hinders or precludes external air from entering the space between the buoyant body and the liquid surface. When the section of material takes the shape of a flat sheet, as is shown in one preferred embodiment, providing the material with one or more gascontaining ducts serves to spread the sheet upon the liquid.

11 Claims, 3 Drawing Figures STABILIZING DEVICE FOR BUOYANT BODY BACKGROUND OF THE INVENTION Buoyant bodies floating on the surface of a body of a water encounter the effects of the wind, the loads they carry, and waves or other turbulence, which often frustrate efforts made to stabilize them. A loss of stability can then cause such accidents as the overturning of the buoyant body with deleterious results.

This problem particularly arises with regard to the lightweight inflatable life raft. Although possessing buoyancy superior to either the solid raft or the conventional boat, the life rafts shallow draft and its concomitant high center of gravity give it a comparatively inferior stability. In fact, conventional life rafts carried by vessels generally display a lack of stability. At wind velocities exceeding meters/sec, the probability of their overturning becomes large, and at velocities in excess of meters/sec, most do overturn, carrying with them the probable loss of life.

Moreover, the International Convention for the Safety of Life at Sea of 1960 imposes strict requirements on inflatable life rafts for use in emergencies. Included amongst these are the following designed to facilitate the rafts handling and housing:

a. When the life raft inflates in an inverted position,

it must lie within the capabilities of a single person to readily right the raft;

b. When dropped into the water from a heightof 60 feet, neither the life raft nor its equipment may suffer any damage; and

c. The total weight of the life raft, its container, and all other included equipment must not exceed 400 lbs.

The requirements of'maximum buoyancy and convenient handling and storage thus compel the raft to possess a minimum of weight. As a result, any stabilizing devices added to the raft-should minimize any increase in weight while not appreciably reducing the buoyancy.

Prior efforts to stabilize buoyant bodies included devices to lower the center of gravity of the bodies and the shaping of the bodies to lessen their rolling within the water. One devicefor the life raft in particular included a water bag, which permitted water to flow easily into and out of it, installed on the bottom of the life raft. However, since the bag obviously cannot retain its water, it has little effectiveness as a stabilizing device.

Efforts to ameliorate the minimal effectiveness of the stabilizing water bag include making the bag itself larger or increasing the number of bags attached to the raft. However, either approach leads to the loss of some of the buoyancy which represents the most appealing facet of the raft. Moreover, both techniques also increased the amount of waves surging into the raft since the raft and the water bags moved together as a unit.

Another technique has seen the mounting of weights on the underside of the raft so as to lower its center of gravity. However, these weights, in addition to increas- SUMMARY OF THE INVENTION Attaching to the buoyant body a section of material which extends beyond at least a portion of the periphery of the body and which contacts the liquid upon which the buoyant body floats will increase the stability of the buoyant body. This stabilizing device achieves its stabilization primarily by increasing the suction or attractive forces between the buoyant body and the water surface. This increased suction tends to resist the slanting or overturning of the buoyant body when subjected to external forces. Extending the section of material around all or substantially all of the periphery of the body provides the maximum of suction and the utmost of stability.

Providing gas-tight ducts on the surface of the material or embedded within the material assists in the materials original extension upon first contacting the liquid and also helps to retain the effective surface area of the section of material over a period of time. The latter serves to enhance the efficiency of the suction and thus its stabilizing action.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 gives a perspective view of a life raft having a stabilizing sheet of material extending beyond the entire periphery of the raft.

FIG. 2 shows a plan view of the raft of FIG. 1.

FIG. 3 shows a cross-sectional view taken along the line 33 in FIG. 2.

DETAILED DESCRIPTION Buoyant bodies of various types designed to float on the surface of a liquid have seen service for different uses. All suffer to some extent from the instability problem. Accordingly, a device which reduces and minimizes this instability will provide at least some benefit to all of them.

The common inflatable rubberized life raft represents a particular example of a buoyant body to which a stabilizing device provides particular advantages. These life rafts, while carrying persons at sea, have on occasion overturned with unfortunate consequences.

Rafts are also sometimes made with a foam material for flotation and thus represent another buoyant body which can be combined with the stabilizing device described herein to realize the benefits of this invention. The drawings, however, all illustrate the more common inflatable raft.

The illustrated life raft includes a conventional raft body 10 formed from a main pair of

inflatable buoyancy tubes

12 and 14 stacked upon each other and bonded together at their contact line by an adhesive, for example. Rubberized cloth represents a common airtight material used in the construction of the

tubes

12 and 14. The seam lines 16 result from the joinder of the various pieces of rubberized cloth during the manufacture of the

tubes

12 and 14.

The raft body 10 also includes a pressurized gas container 18 provided with a rupture valve 20. When the raft drops into the water, the valve 20 either automatically or manually ruptures and permits the automatic introduction of the gas through passages into the main tubes. As a result, the raft body 10 inflates after it is removed from its storage location and prior to or after it drops onto the water surface.

The bottom sheet 22, secured, for example, by an adhesive or a seam to the bottom of the lower tube 14, forms an open-ended chamber with the

cylinders

12 and 14. Alternatively, a flat inflatable gas container may replace the sheet 22 and form the bottom of the open-ended chamber.

in use, serves to prevent the sea water or the wind from entering the open-ended chamber. The life raft also generally includes a'life rope 26 secured at various locations to the

cylinders

12 and 14.

The lifev raft in the figures also includes the strip of material28 attached to the raft body 10. This strip of material, in the form of a sheet, extends beyond the periphery of the raft body Y and represents a stabilizing device for the raft. The strip of material 28, formed from a single sheet of material, extends beyond the entire periphery of the raft body 10. This produces the maximum stabilization of the raft, and consequently the most desired stabilizer. Providing a, strip around only a portion of the periphery or several disconnected strips extending beyond only a portion of the periphery will still yield some, although less, stabilization.

To achieve the stabilization of the raft upon the surface of a liquid, the stabilizing sheet of material must contact the liquiditself. Attaching the strip to the bottommost location of the buoyant body will assure the contact between the stabilizing device and the liquid. Bonding the strip 28 to the bottom of the inflatable tube l4accomplishes this result. FIG. 3 gives an alternative and more facile method for bonding the strip 28 to the raft body 10. That figure portrays the stabilizing device 28 as an integral extension of the sheet of material 22 forming the bottom of the raft 10.

In use, the raft inflates and floats upon the water surface. There it becomes subject to forces generated by the wind, the weight carried by the raft and the waves.

These forces may cause the raft body to slant to one side which results in a portion of the bottom of the raft parting from the water surface and creating a space between this portion ofthe bottom and the water-surface. However, the stabilizing sheet of material 28 retains its outer portion within the water and encloses this space between the water and the raft. Forming this stabilizing strip 28 from a flexible material, such as the rubberized cloth of the raft itself, helps maintain the outer edge of the] strip within the water. Moreover, providing the edge of the strip with a downward curve, as shown in FIG. 3, counteracts the wind which tends to raise the edge from the water. i Because the stabilizing device strip 28 hinders or even precludes the external air from entering the space between the bottom of the raft and the water, especially if airtight, the air pressure in this space becomes less than in the external air. This reduced pressure generates a partial vacuum which results in a positive at mospheric pressure applied to the upper surfaces of the raft. urging the raft bottom into contact with the water surface.

Increasing the tilt of the raft body 10 enlarges the space enclosed by the raft body, the stabilizing strip 28,

and the surface of the water. This in turn results in a larger partial vacuum within this space and increases the stabilization of the life raft because of the larger effective force thus created urging the raft to conform to the water surface. An essential design criteria for the stabilized raft is that the center of the pneumatic forces generated by the strip 28 is related to the center of gravity and the hydraulic forces on the raft to urge the raft into conformance-with the water surface.

Moreover, when the raft body 10 slants or tilts, the portion of the stabilizing strip 28 on the lower side of the raft acts somewhat as a bilge keel. This behavior of the strip helps to retard and prevent further slanting of the raft.

} 1n the case of a stabilizing strip formed from a flexible material, the strip 28 may include one or more flotation means 30, preferably gas ducts, attached to the surface of the strip 28 or embedded within it. These gas ducts may communicate with the lower main tubes 14 of the raft or directly with the gas container 18 through appropriate conduits which, for convenience, are not shown. When inflated, these ducts 30 serve to automatically spread the stabilizing strip 28 when the raft becomes pressed into actual service. It is also possible to provide flotation means in the strip which does not require inflation- Moreover, for a flexible stabilizing strip 28, the gas ducts 30 also serve to maintain the stabilizing strip 28 in a stretched condition which thus presents a maximum area for contact with the water and enhances its effectiveness. The gas ducts also increase the buoyancy of the stabilizing strip 28 50 that the strip will not lower the overall buoyancy of the raft itself.

Further, the gas ducts provide a stabilizing strip 28 that has some stiffness during actual use while not detracting from the ease of handling a flexible material. However, a permanently stiff strip would also maintain the effective area of the stabilizing device. For a buoyant body itself formed from a stiff material, such a stabilizing device would not represent an appreciable loss in its ease of handling.

EXAMPLES EXAMPLE 1 Around the periphery of the bottom of a rubberized raft having an outer diameter of 54 cm., a height of 20 cm., and a weight of 1,280 gm. was attached a strip of rubberized cloth having a width of 25 cm., a thickness of 0.5 mm., and a weight of 720 gm. To a second and unstabilized raft was added a weight of 720 gm. in order to bring the weight on both rafts up to a total of 2,000 gm. After the placement of both of these rafts upon the surface of water, a torsion spring scale pulled upwardly upon each in turn. The stabilized raft separated from the water surface only under the application ofa force of 12,000 gm., while the unstabilized raft separated with a force of only 2,100 gm. Discounting the actual weight of the rafts themselves, the stabilized raft exhibited an attractive force to the water of 10,000 gm., which represents 100 times the 100 gm. of attractive force between the unstabilized body and the water.

EXAMPLE 2 A cylindrical raft of 290 cm. in diameter and cm. in height had attached to its bottom a stabilizing strip of 107 crri. in width and a thickness of 0.5 mm. This type of raft, which holds approximately 13 persons, represents a legally required fitting on vessels. The stabilized raft and a similar but unstabilized raft, while water beneath the bottom of the raft and moved in the downstream direction along with the raft itself.

What is claimed is:

1. In a buoyant body having a central load receiving cavity and designed to float on the surface of a liquid, the improvement of a stabilizing device comprising a substantially fluid-impermeable flaccid section of material attached adjacent to the bottom-most portion of said body having a substantially airtight surface area which cooperates with said flexible section so that when said body floats upon the surface of a liquid, said section of material substantially surrounds the periphery of said body and contacts said liquid, said flexible section producing a partial vacuum effect between the bottom of said buoyant body and such liquid as said buoyant body floats upon the surface of such liquid whereby said buoyant body resists overturning in said liquid.

2. The improvement of claim 1 wherein said section of material has the form of a sheet.

3. The improvement of claim 1 including flotation means attached to the surface of said section of material or embedded within said section of material.

4. The improvement of claim 3 wherein said flotation means is a gas-tight duct.

5. The improvement of claim 1 wherein said stabilizing device is an integral extension of the material form ing the bottom of said body.

6. The improvement of claim 5 wherein said device and said bottom are a flexible sheet of airtight rubberized cloth.

7. The improvement of claim 6 including gas-tight ducts attached to the surface of or embedded within said stabilizing device.

8. A raft comprising a gas-tight inflatable container made of rubberized cloth; a section of airtight flaccid material attached to the bottom portion of said container and constructed so that when said raft is inflated and floats upon the surface ofa body of water, said section of material extends beyond substantially all of the periphery of said container and contacts the water. said section effecting a partial vacuum between the bottom of said container and said body of water as said container floats upon the surface of said body of water whereby said container resists overturning in said body of water.

9. The life raft of claim 8 including a gas-tight duct attached to the surface of or embedded within said section of material.

10. The life raft of claim 8 wherein said section of flexible material is rubberized cloth and is formed integrally with the bottom of said raft.

11. The life raft of claim 10 including a gas-tight duct attached to the surface ofor embedded within said flexible material.

Claims

4. The improvement of claim 3 wherein said flotation means is a gas-tight duct.

5. The improvement of claim 1 wherein said stabilizing device is an integral extension of the material forming the bottom of said body.

8. A raft comprising a gas-tight inflatable container made of rubberized cloth; a section of airtight flaccid material attached to the bottom portion of said container and constructed so that when said raft is inflated and floats upon the surface of a body of water, said section of material extends beyond substantially all of the periphery of said container and contacts the water, said section effecting a partial vacuum between the bottom of said container and said body of water as said container floats upon the surface of said body of water whereby said container resists overturning in said body of water.