Patent Application
20240400175
The present disclosure describes technology related to the field of devices for providing flotation in water, using inflated balloon-like structures, especially for use in situations where a high level of flexibility is required of the device.
Drowning is a major cause of death worldwide, claiming the lives of more than 300,000 people every year. Many of the drowning events occur in natural waters such as the sea and lakes in the absence of a supervising life guard, and many would have been preventable with use of a personal flotation device. In addition, there exist many types of devices whose function is to provide flotation to save people who find themselves in distress in bodies of water, not because of negligence or unpredicted circumstances during swimming or bathing, but rather as a result of a failure of another system. Some such examples are emergency landings in water of aircraft, or the sinking of watercraft in which the persons were travelling, or the need to pass through a water environment during professional, military or recreational activities. In such circumstances, devices such as safety vests, inflatable lifeboats, lifebelts or life buoys are used to provide emergency support in the water.
Many previous references describe bracelets, armbands, jackets, belts and other inflatable devices designed for emergency use. Most of these inflation devices use inflation of the flotation balloon by means of the user of the device, who blows into a mouthpiece, which is connected through a one-way valve to the flotation balloon. However such types of devices are dependent on the consciousness and the physical ability of the user to inflate the device, and in emergency situations, this may not always be the situation. Therefore, flotation devices which do not require the breath of the user or wearer, may be preferable in many instances.
Some such inflation gas devices use chemical reactions that, when actuated, produce gas to inflate the device. In International Published Patent Application WO/2019/106677, for “Emergency Flotation Device with Chemical Reaction Chamber”, having common inventors with the present application, there are described a number of novel devices using this principle, in addition to some earlier prior art devices.
Inflation devices of a third type, based on a charge of pressurized gas which is released on activation, into an inflatable flotation chamber, are the most commonly used devices today. Such devices have been known for very many years, and are preferred for emergency use since they can reduce the need of the user for activating the device, or can even be automatically self-activated. One common example of such devices are the life-vests or lifejackets used in aircraft, which are intended to be inflated in times of emergency by a gas cylinder, generally containing compressed carbon dioxide, or by the breath of the wearer, if the compressed gas inflation fails. A number of such compressed gas inflation devices include U.S. Pat. No. 547,808 to A. von der Ropp, for “Life Preserver”, U.S. Pat. No. 572,109 to T. Gordon, for “Life Preserver”, U.S. Pat. No. 1,117,639 to H. W. Cooey for “Portable Life Buoy”, U.S. Pat. No. 1,367,225 to W. H. Barker, for “Life Belt”, U.S. Pat. No. 2,028,651 to R. F. Dagnall et al, for “Release Mechanism for Pressure Fluid Containers, U.S. Pat. No. 2,518,750 to E. H. Burkhardt for “Lifesaving Device”, U.S. Pat. No. 2,627,998 to C. W. Musser et al, for “Inflator for Pneumatic Lifesaving Devices”, U.S. Pat. No. 2,684,784 to R. G. Fox, for “Inflator for Pneumatic Life Preserving Apparatus”, U.S. Pat. No. 2,904,217 to J. T. Gurney for “Automatic Life Preserver”, U.S. Pat. No. 3,693,202 to T Y. Ohtani, for Sea Rescue Ball Unit “, CH 569611 for “Automatic Rescue Apparatus”, WO83/04234 to J. Bissig for “Rescue Apparatus”, WO 2014/077728 to P. P. Mukhortov for “Life-saving wristband”, DE 202012007732 to G. Schmelzer for “Rescue bracelet or water airbag for bathers or swimmers, such as children, young people of all ages, adults, seniors”, WO 2004/048193 for “Novel Inflation System for Inflatable Life Jackets” to P & P Utveckling AB, and WO 2020/208636 for “Emergency Flotation Device using Compressed Gas”, commonly owned and having a common inventor with the present application.
Earlier models of such flotation devices used metallic cylinders to contain the high pressure flotation gas, especially those which used gases requiring compressing to a high pressure of tens of bar to attain the liquid phase at normal environmental temperatures. Two of such gases are air or carbon dioxide, especially the latter, which was a widely used gas in these earlier models, and is still in common use today. More recent models of such flotation devices use gases which maintain their liquid phase at normal environmental temperatures, at much lower pressurizations, typically of the order of 10 bar or so. Some such gases are used in the devices described in the above cited WO 2020/208636 for “Emergency Flotation Device using Compressed Gas”, where the gas examples quoted are some gases developed for refrigeration and air conditioning applications, such as R1234ze(E) or R1234yf or R1224yd(Z). Because of the lower pressures of these pressurized gases, the gas container may be manufactured of a much lighter material, such as plastic materials, and can also be thinner. Whatever material is used, and whatever gas fill is accordingly used, all such stored gas inflation devices must ensure that the gas fill is maintained over the useful lifetime of the device.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.
One of the main problems that beset such pressurized gas flotation devices is the need to ensure that the amount of gas in the pressurized gas container remains sufficient over the expected period of storage of the device, to ensure that leakage with time does not render the gas supply insufficient to inflate the flotation balloon sufficiently to support at least a person having a weight which the device was intended to support. A second problem is the need to ensure that the flotation balloon which supports the person in the water, also maintains a sufficient amount of gas to provide flotation support for the maximum estimated amount of time, that it is expected that a person will need support in the water.
The present disclosure attempts to provide novel systems and methods that overcome at least some of the disadvantages of prior art appliances and methods for providing emergency flotation support for a person or persons in water. Since many such flotation devices are intended for use in emergency only, they are often kept in storage for long periods of time until needed. Gas leaks out of such containers by diffusion processes which are dependent, inter alia, on the type and thickness of the material used, whether for the pressurized gas container or for the inflation balloon, and on the internal pressure of the pressurized gas charge. Additionally, leakage of the pressurized gas through the actuation valve, which is intended to release the pressurized gas into the inflatable balloon, may also need to be taken into account, depending on the type of valve used.
Lightweight pressurized gas containers of the type used in the flotation devices of the present disclosure, are usually made of a polymer material. Therefore, such polymer layers are used in this disclosure as an example of diffusion phenomena of a gas through a solid layer. However, it is to be understood that the pressurized gas containers of the present disclosure should not be limited to polymer layers, but may also be of other materials such as thin metallic layers.
The transport of gases through a polymer membrane, such as the thin plastic wall layer of a pressurized gas container of a flotation device, assuming a constant temperature gradient across the layer, is caused primarily by the pressure gradient across the wall layer, i.e. between the pressurized gas within the container and the outside atmosphere. The permeation of a gas through polymer layers is usually described in terms of a “solution-diffusion” mechanism, consisting of the following steps: (1) absorption of the gas molecules into the polymer layer at the side of higher potential, i.e. pressure in the cases of the flotation devices described herewithin; (2) molecular diffusion of the gas molecules in and through the polymer layer; and (3) release or desorption of the diffused molecules from the polymer layer at the opposite side into the gas phase at lower potential, i.e. the surrounding atmosphere. The term permeation describes the overall mass transport of the penetrant gas across the entire polymer layer, whereas the term diffusion describes the movement of the penetrant gas molecules inside the bulk of the polymer material itself. Usually, the molecular diffusion through the polymer layer is the slowest mechanism, and thus, the rate-determining step in the permeation process.
Diffusion can be described using Fick's Law (1855). As applied to the presently described flotation devices, Fick's Law states that at a steady state, the flux going through a unit area of polymer membrane (A) is proportional to the pressure gradient (dp/dx) which is the “driving force” of the diffusion process:
where dm/dt is the mass of gas transferred per unit time, i.e. the flux, and the proportionality constant D is the so called diffusion coefficient which depends on the temperature and on the penetrant/polymer system and is also a function of penetrant concentration.
The overall process, i.e. the flux of permeant (Q) is proportional to the membrane area A, the pressure difference (Δp) between the two sides of the layer, and inversely proportional to the thickness of the polymer (L):
where P is the permittivity of the polymer layer, to describe the overall transfer of gas through the entire layer.
The above-described process is relevant for any specific gas, and relates the diffusion behavior of that gas through the polymer layer either of the container or of the flotation balloon. However, the diffusivity or permittivity of a barrier layer, such as the gas container wall, is dependent on the type of gas used. To be more specific, it is dependent primarily on the molecular size of the gas molecules involved in the diffusive process. Such diffusion can be most simply described by Graham's Law of 1848, which states that the rate of diffusion or of effusion of a gas is inversely proportional to the square root of its molecular weight. Thus, if the molecular weight of one gas is four times that of another, it would diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other. In other words, heavier gases diffuse more slowly. A complete theoretical explanation of Graham's law was provided years later by the kinetic theory of gases. Under the same conditions of temperature and pressure, the molar mass is proportional to the mass density. Therefore, the rates of diffusion of different gases are inversely proportional to the square roots of their mass densities. (The molar mass is numerically the same as the molecular weight, but it has units of grams per mole.)
However, this simple use of Graham's law is a simplification with regard to real life situations, of gas fills with complex molecules, and layer compositions with complex molecular structures, such as polymers. In the first place, a more rigorous description of the diffusion process through a barrier layer should relate to the molecular size, and not to the molecular weight of the gas molecule. In general, the molecular size follows the molecular weight, but there is generally no direct correlation between both of them. The relation between the molecular weight and the molecular size is highly complex, since molecules are rarely spherical bodies, an exception being methane, but that has no relevance in the context of this disclosure. Molecular size may instead be defined by the smallest ellipsoid that can envelope the molecule, and then, the three axis dimensions of the ellipsoid become the three dimensions which should be used to characterize molecular size. For macromolecules, a category to which some of the refrigeration gases can be characterized as belonging, the molecular size can be considered to be limited by the chain end-to-end distance.
Thus, the rate of diffusion of a gas through a barrier layer represented by the wall thickness of the pressurized gas container or of the flotation balloon, is a complex phenomenon, but a generalized criterion used in the devices of the present disclosure is that the greater the molecular size of the gas molecule being used, the lower the rate of diffusion of the gas through the barrier layer. Therefore, notwithstanding the thermodynamic properties required of the inflation gas, a gas with as great a molecular size as possible should be used to provide for minimal gas loss by diffusion, whether from the pressurized gas container or from the flotation balloon. Use of such a gas will provide superior shelf lifetime properties for the flotation device, and a superior duration of a required level of flotation once the device has been deployed. Typically, Gases having a molecular weight of at least 100 gm/mole should be suitable, but, depending on the molecular structure, gases with a molecular weight of 60 gm/mole may also have a molecular size making them suitable for this application. be useable.
Referring back now to the complexity of the material of the wall of the gas vessel, both the permeation of the gas and its diffusion through the polymer wall is often a complex process, especially when plasticizers and other additives are present in the polymer material, that might migrate to the surface of the wall, i.e. the interface with the gas. In this case, the diffusion coefficient is a function of polarity and is also a function of time and exposure history (non-Fickian diffusion).
To illustrate this complex relationship, reference is now made to Table 1, which is Technical Bulletin No. 110 as provided by the EVAL Division of Kuraray America Inc., of Houston, Texas. The table compares the transmission rate of water vapor and of oxygen, measured in units of the volume of gas measured in cc, diffusing every 24 hours through a 25μ polymer layer, per square meter of the polymer layer.
As is observed, the permeability and solubility of gases in a polymer can be very different for different polymers and permeants. The most noteworthy feature of the table is that there are some polymers which are orders of magnitude more diffusive than others, and that the diffusivity of those especially, do not seem to show any clear relationship to the molecular weight or size of the penetrant gas. Obviously, because of the high porosity of those polymers, they would be assiduously avoided in selecting the optimal materials for the walls of the pressurized gas container and the inflation chamber. In general, permeability and solubility at a given temperature depend on the degree of crystallinity (morphology), the molecular size, the type of permeant and its concentration or pressure, and, in the case of copolymers, also on the composition. For example, butadiene-acrylonitrile copolymers with high acrylonitrile content have low permeability to gases of low polarity and high permeability to gases of high polarity. The explanation for this behavior is rather simple; the polarity of the polymer (acrylonitrile content) determines the gas solubility and, thus, the permeability. As the acrylonitrile content of the copolymer increases, the solubility of polar gases such as CO2 and water vapor increases as well, whereas that of gases of low polarity (H2, N2, 02) decreases. Besides the polarity of the polymer being used, the polarity of the gas being used also has an effect on the diffusion rate, though much less noticeably than the effect of the material.
Once polymers having unacceptably high diffusivity have been eliminated for use in constructing the flotation device, the particular polymer of the acceptably low diffusivity group that is to be used to construct the parts of the device having contact with the inflation gas, would be chosen in order to provide the desired combination of, not only diffusivity, but also (i) the cost of the polymer material, (ii) the case of manufacture using that material, (iii) the physical properties of the material, in particular its flexibility, (iv) the ability of the material to maintain its properties over a long period of time, which will depend largely on its ability to withstand chemical reaction with the inflation gas and the environment, (v) its environmental durability, which will depend on additional properties such as resistance to exposure to sunlight or environmental temperature, and (vi) any other properties that would be regarded as important for use in the device.
Once the optimum materials for construction have been chosen, the choice of which gas to use for the predefined polymer construction material when considering the shelf life and flotation duration of the device, will depend strongly on the molecular dimensions of the gas. Therefore, for a predefined device structure, for optimum longevity considerations, a gas with the greatest molecular size should be selected, commensurate with the desired thermodynamic properties of the gas. One practical outcome of this is that the modern refrigeration gases such as those described in the above referenced published patent application WO 2020/208636 for “Emergency Flotation Device using Compressed Gas”, provide an increased shelf life for use of the device, and an increased flotation duration time once the device has been deployed, as compared to the common gases historically used in such flotation devices, such as air, carbon dioxide, and others.
There is thus provided in accordance with an exemplary implementation of the devices described in this disclosure, a method for increasing the shelf life of a life-saving flotation device, the method comprising the steps of (i) providing a life-saving flotation device comprising a pressurized gas container, at least one flotation chamber, and an actuating valve connecting the pressurized gas container to the at least one flotation chamber, and (ii) selecting a gas fill for the pressurized gas container, the gas having a molecular size such that the diffusion rate of the gas fill out of the pressurized gas container is sufficiently low that the pressurized gas container maintains a predetermined charge of gas for a predetermined minimal time requirement.
In the above method, the gas fill selected may have a molecular weight of more than 100 gm/mole, or at least more than 60 gm/mole.
Furthermore, the pressurized gas container may comprise a single polymer layer.
In any of the above described methods, the gas selected further results in the at least one flotation chamber maintaining a volume of the gas sufficient to support the user of the device for a predetermined minimum time requirement.
Finally, the gas selected may comprise at least one of R1234ze(E), R1234yf, R1224yd(Z) or R515B mixture, as used in refrigeration and air conditioning applications.
It is to be emphasized that in this disclosure, and as claimed, the use of the term balloon for the flotation or inflation element is not intended to be limited specifically to a balloon-like element, but is intended to be a generic name for any flexible gas container or chamber which is intended to be inflated with the flotation gas and to support the person or article using the flotation device.
The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which
Reference is made to
The compressed gas container 2 can be formed of a vessel having thin metallic walls, or, more advantageously to provide a lighter and more readily storable, a vessel formed with polymer walls, manufactured at low cost by a plastic forming operation, on condition that the polymer vessel can withstand the pressure of the gas charge even at very high environmental temperatures. The inflatable flotation chamber or chambers 3 can be in the form of one or more pouches as shown in
Although the flotation device of
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. Furthermore, it is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.
| Number | Date | Country | |
|---|---|---|---|
| 63506101 | Jun 2023 | US |
