US 3276049 A
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Oct. 4, 1966 T. E. STIXRUD DEEP WATER BUOYANCY APPARATUS Filed Deo. 2, 1964 ufl/AD F5770) 4 L/TL//UM INVENTOR.
THU/VIAS E S7' /X E00 ATTORNEY@ United States Patent O 3,276,049 DEEP WATER BUOYANCY APPARATUS Thomas E. Stixrud, Lakeside, Calif., assignor to the United States of America as represented by the Secretary of the Navy Filed Dec. 2, 1964, Ser. No. 415,546 9 Claims. (Cl. 9 8) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any roya-lties thereon or therefor.
The present invention relates to apparatus for providing buoyancy in a deep body of water such as the ocean.
In recent years, man has begun to penetrate the great depths of water that cover the major portion of the earths surface. Such explorations are merely in an embryonic stage, however, since equipment which can practically be used with the tremendous underwater pressures has not been readily available. Conventional underwater equipment, when adapted to sustain the increased pressures of deep Water, becomes ineiiicient or extremely costly. With increasing ipressure and resultant increasing force exerted by the water on submerged structures, the problem of maintaining buoyancy becomes more diiiicult. Buoyancy providing means are necessary to suspend scientific equipment at various levels in the ocean, to retrieve Samples from the sea iloor, etc.
Piccard oiiered a solution to the problem with -gasoline in his bathyscaphe, however, handling and storage of such equipment becomes diiiicult because of the everpresent re hazard. Lithium floats are more eicient than gasoline, but are expensive and massive. Compressed gas in bottles or used in pumping systems loses eiiiciency bel-ow a few hundred feet. Hollow glass microspheres embedded in epoxy (Stycast 1090) work well to great depths but are bulky and expensive 'for large floats. Consequently, a need for buoyancy means which will be eiiicient, easy to handle, safe and inexpensive is present.
An object of the present invention is to provide a buoy for use in deep water.
A furthe-r object of this invention is to provide a deep water buoy which is elicient and yet inexpensive.
Another object of this invention is to provide a deep water buoy which is easy to handle both in and out of water and is readily reproducible with inexpensive materials.
A more particular object of this inventionI is to provide a deep water buoy which utilizes the vaporization of a liquid gas as a source of buoyancy.
The present invention achieves the above objects by utilizing the vaporization of a liquid gas as a source of buoyancy. The buoy Iof the present invention comprises two chambers one of which is open to the surrounding water. The other chamber contains a reservoir of liquid nitrogen which, when allowed to boil or vaporize, results in the production of nitrogen gas. The gas pressure produced is transmitted to the rst chamber where it opposes the entrance of Water and creates a volume of low density gas and, hence, buoyancy.
The above and other objects and features of the invention will be more fully understood from the following detailed description and accompanying drawing wherein:
FIG. 1 is a pictorial view of an embodiment of the buoy of the present invention;
FIG. 2 is a graph depicting the variation of buoyancy per unit volume, with respect to pressure, of various substances.
In FIG. l a buoy 1 of elementary conliguration is shown. The buoy 1 comprises an upper chamber 2 and a lower chamber 3. The two chambers are sealed with 3,276,049 Patented Oct. 4, 1966 respect to each other excepting interconnection by various vent means to be hereinafter described. Lower chamber `3 is vented to the exterior of the buoy by an opening 10 in its bottom side. In the upper chamber 2 there is disposed a reservoir 4 for containing a liquid gas, preferably nitrogen. Reservoir 4 is filled with the liquid gas through lill pipe 5. Upon completion of the filling process pipe 5 is sealed with cap 6 to prevent any leakage. Stand pipe 7 which extends into the body of liquid gas and substantially to the bottom thereof provides a passage from the interior of the reservoir to expansion spiace 12. The upper portion of reservoir 4 is connected by vent pipe 8 to the lower chamber 3. By providing coupling rings 9 on the bottom of the buoy a harness 11 may be attached thereto for supporting a desired load or anchor.
In operation, reservoir 4 first is iilled with liquid nitrogen through pipe 5. Cap 6 is then attached. The buoy is then launched and Water immediately enters the lower opening 10 compressing any air in chamber 3. The pressure of the water is transmitted by the air to the surfface of the nitrogen in reservoir 4 by vent pipe 8. This pressure forces the nitrogen out standpipe 7 into the space 12 where it boils furiously, drawing heat from the thin metal outer shell of chamber 2. It should be noted that the metal shell becomes extremely cold in the process causing ice to formy on the outside thereof. Moving water, however, removes any ice that tends to form. As the nitrogen in space 12 vaporizes the p-ressure increases and is transmitted back down standpipe 7, bubbled through the liquid in reservoir 4 and passed through vent 8 to the lower chamber 3. Increasing pressure in chamber 3 forces the water level down until the water pressure increases enough to repeat the cycle. It should be further noted that .gas arriving through Vent 8 is extremely cold. As it picks up heat in chamber 3 it expands, thus, increasing the pressure and further aiding the expulsion of water.
The basic embodiment may be modified by providingvalves 13 and 14. The addition of the valves make it possible to -control the buoyancy of the buoy. The controlled-buoyancy buoy may be operated in such a manner that it has a negative buoyancy until the desired operating depth is reached, at which time the valves are actuated so as to produce positive buoyancy. The advantage of such an embodiment is that large weights or anchors are unnecessary to lower the buoy to its desired level of submergence. Furthermore, it can be sunk in a more rapid fashion since the necessity of overcoming positive buoyancy is not present.
Operation of the modilied embodiment is identical to the elementary one when Valves 13 and 14 are in their closed positions. When valve 14 is opened, however, a major portion of lower chamber 3 is iilled with water, thus, preventing the accumulation of a large volume of low density gas with its resultant buoyancy effect. The position of valve 14, relative to its height above opening 10, can be chosen so that enough positive buoyancy will be attained with valve 14 open and the liquid nitrogen dissipated, to surface -the buoy with no load attached, hence, preventing loss of same. After the buoy reaches its desired level of submergence, valve 14 is closed and gas pressure from the boiling nitrogen forces the water level down and positive buoyancy is achieved. In order to hasten the vaporization of the liquid gas, some manner of adding heat more rapidly to the liquid gas may be provided. Valve 13 functions in such a manner. By opening valve 13, a quantity of liquid nitrogen is permitted to pass into the space 12 where heat from the ocean vaporizes it. The more liquid nitrogen available in space 12 for vaporization the more gas there is developed in a given period of time and, consequently, the more rapidly the buoy achieves its positive buoyancy. More ice Will form on 'the outside walls of chamber 2 when valve 13 is opened, however, formation of ice actually enhances the buoyancy because of -the lesser density of ice with respect to water.
Valves 13 and 14 in a practical arrangement could be operated remotely or by some sort of Itimer or pressure activated mechanism, or by an underwater manned vehicle.
In FIG. 2 the densities of various materials are plotted with respect to pressure. Ideally, for use in a buoy, material is desired which maintains its density at a near constant level with varying pressure. In the graph, line 15 represents a hollow aluminum sphere, line 16 a hollow steel sphere, line 17 a hollow aluminum sphere iilled with hydrogen at one half the external pressure, line 18 a hollow steel sphere tilled with hydrogen at one half the external pressure, line 20 a hollow glass sphere, line 19 nitrogen gas and line 21 hydrogen gas.
As can be seen from the graphs, compressibility of nitrogen closely follows that of an ideal gas through the rst 3,000 pounds of the pressure range. This means that at 6,000 feet the nitrogen needed is double that needed at 3,000 feet. Going on to 12,000 feet, somewhere near the average depth of the ocean, a benefit is realized from the diminishing compressib-ility of the denser nitrogen although the buoyancy is now down to about 70% of its value at 3,000 feet. Because of decreasing efficiency as above noted, the deeper the oat is submerged, the more expensive it becomes to maintain a certain buoyant force since more nitrogen is required to produce the same buoyancy. Hydrogen gas as plotted in line 2.1 of the graph has very little variation of buoyancy with increasing pressure. Consequently, it is an ideal substance to be used in a buoy such as that of the present design. Its higher cost and ammability, however, detract from its excellent el'iciency with the result that nitrogen is more practical for average use. Hydrogen, of course, could be used in situations where eliiciency was of paramount importance. The critical characteristic of the liquid gas chosen Ais that it be vaporizable under the pressure at the buoy operating depth.
Because of the equilibrium of pressures in an operating buoy of the instant type, the structural members may be of light and inexpensive construction. As an example of the construction in one model, the chambers 2 and 3 were made from ordinary 5S gallon oil drums. Another model tested was made from two common ve gallon cans.
Reservoir 4 should be a well insulated container. The Iinsulation should be a permeable material in order to minimize premature vaporization of the liquid nitrogen and the development of any substantial pressure dilerentials.
As an example of typical physical characteristics, it may be noted that a nitrogen-buoy constructed from two 55 gallon drums displaces 850 pounds of water (hence, 850 pounds of gross buoyancy), Uses about 100 pounds of nitrogen at 3,000 feet, and weighs 175 pounds in air.
In case of long periods of time at the bottom, diiusion of the gas into the ocean might be a problem and a simple intake and exhaust system would be needed to provide a barrier. Where times are on the order of days, d-ilusion should not be a problem.
Liquied gas has provided a satisfactory solution to the problem of maintaining buoyancy in deep water. The economy and ease of handling makes its use potentially valuable in many other applications although it may introduce engineering problems.
While the invention has been described by means of a specific example and in a specific embodiment, it is not limited thereto for obvious modications will occur to those skilled in the art Without departing from the spirit and scope of the invention.
What is claimed is:
. =1. `A deep-water buoy comprising:
a hollow closed-end cylinder having upper and lower sealed chambers;
a liquid gas reservoir insulated with permeable material disposed in said upper chamber;
said reservoir being sealed with respect to said upper chamber;
vent means connecting the interior of said reservoir with said lower chamber;
stan dpipe vmeans connecting the interior of said reservoir with said upper chamber;
other vent means for venting said lower chamber to the exterior of said cylinder so that Water may pass from said exterior to said lower chamber; and
means for attaching a load to said buoy.
2. The buoy of claim 1 wherein said reservoir contains liquid gas vaporizab'le at the water pressure at which buoyancy is desired.
3. The apparatus of claim Z .wherein said liquid gas is nitrogen.
4. The apparatus of claim 2 wherein said liquid gas is hydrogen.
5. The buoy of claim 1 further including:
a normally-closed first valve means communicating sai-d reservoir with said upper chamber; and
.a normally-closed second valve means communicating said lower chamber with external water when said buoy is submerged.
said second valve means being disposed in the upper part of said lower chamber whereby a major portion of said lower chamber is iilled with external water when said buoy is submerged.
6. The buoy of claim 5 wherein the positioning of said second valve means -is selected for providing positive buoyancy when said second valve is open.
7. The buoy of claim 6 wherein said reservoir contains liquid gas vaporizable at the water pressure at which buoyancy is desired.
8. The buoy of claim 7 wherein said liquid gas is nitroseni 9. The buoy of claim 7 wherein said liquid gas is hydrogen.
References Cited by the Examiner UNITED STATES PATENTS 3,046,925 7/1962 De Lisio 114--54 3,070,059 12/1962 Testa 114-54 lMILTON BUCHLER, Primary Examiner.
T. MAJOR, Assistant Examiner.