JPS633105B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an air enclosure placed in ambient air at an atmospheric pressure, such as 14.7 psia (1 Kg/cm ² absolute), which enclosure initially contains a gas other than air or a mixture of gases other than air or It is partially or completely inflated to the desired pressure by such a mixture of gas and air. Energy is then extracted from the ambient air by selective diffusion, increasing the pressure within the enclosure, thereby increasing the level of potential energy within the enclosure and/or causing the enclosure to perform useful work. Extracting energy from the surrounding air to increase the pressure energy within the enclosure or to do useful work is called "diffusion pumping" and is a self-pressurization phenomenon. The diffusion pump action can be briefly explained as follows. In the present invention, the gas used to inflate the elastomeric air device is different, or at least partially different, from the ambient air surrounding the device. This inflation gas (referred to herein as a "supergas") is selected from the group of gases with large molecules and low solubility; such gases exhibit very low permeability and are made at least partially from elastomeric materials. cannot easily diffuse through closed enclosures. It is observed that when the enclosure is surrounded by ambient air, the pressure within the enclosure increases relatively quickly after the initial expansion. This pressure increase continues until the partial pressure of the air inside the enclosure equals the atmospheric pressure outside the enclosure.
This is believed to be due to nitrogen, oxygen, and argon in the surrounding air diffusing into the enclosure. While the ambient air is diffusing inward, the initial inflation gas diffuses outward from the enclosure only very slowly and therefore essentially loses no pressure, so that all of the gas inside the enclosure is Pressure increases considerably. This total pressure is therefore the sum of the partial pressure of the air within the enclosure and the pressure of the initial inflation gas within the enclosure. In some devices, the pressure is higher than the initial inflation pressure for the first 2-4 months of diffusion pumping and then slowly begins to fall. When the total pressure increase reaches its peak level, the diffusion pumping action has progressed to the point where the partial pressure of air within the device has reached its highest possible value of 14.7 psia. Two important things are happening at this point. Firstly, the enclosure is filled with a maximum amount of pressurized medium (air) and this air cannot diffuse outwards from the device, i.e. the pressure of the internal air is in equilibrium with the external ambient air, i.e. both is at 14.7 psia. Second, the supergas pressure is lower than the initial inflation pressure because the volume of the device is increasing due to the stretching of the elastomeric film. At this low pressure, the normally very low diffusion rate of the supergas is reduced to even lower values. These two factors, maximum air at equilibrium pressure and minimum supergas, contribute to long-term pressurization at essentially constant pressure. This pressurization approach is referred to here as “Permanent Inflation Technology”.
Techniquer). After the pressure reaches its peak, the rate of decompression is very slow and, depending on the particular inflation gas used, the closure material and the inflation pressure, the total pressure within the closure will remain below the initial pressure for a period of approximately 2 years or longer. Maintain high values. As mentioned above, the pressure drop may continue, but
Because of the slow rate of diffusion of gas from the closure, the pressure within the closure remains sufficiently high to allow the elastomer closure to continue to be used effectively for several additional years. This closure is therefore permanently expanded. Conventional elastomeric air devices are typically inflated with air to a desired initial pressure above ambient pressure. In these devices, air diffuses outward rather quickly whether used or not, rendering the device flattened and useless. Additionally, elastomeric materials often stretch under pressure, increasing their internal volume and increasing the rate at which the device becomes unusable. Also, a load applied to the device further increases the air pressure inside it, thereby accelerating the outward diffusion of a portion of the air through the elastomeric device, resulting in an even more rapid pressure drop below its initial pressure when the load is removed. wake up As loads are repeatedly applied and removed, the internal air pressure gradually decreases and the expansion device loses its usefulness very quickly. Many gases (other than supergases) behave similarly, with the pressure in the air system gradually decreasing to very low values in a relatively short period of time. In the present invention, as described above, not only is the device permanently inflated, but the pressure within the device remains substantially constant due to the diffusion pumping action even as the internal volume increases due to the stretching of the elastomeric material. be done. When such a volume increase occurs, additional ambient air diffuses into the device to maintain air pressure regardless of the volume increase. Additionally, as discussed below, the diffusion pumping action can maintain the internal pressure at a relatively constant level as the device is subjected to repeated application and removal of external loads. One object of the invention is to reduce the volume of an enclosure partially or completely filled to a volume less than the fully expanded volume with one or more special supergases or to mechanically inject additional gaseous medium into the enclosure. It is an object of the present invention to provide an elastomeric enclosure placed in an ambient air atmosphere in which the pressure within the enclosure increases above its initial inflation pressure without relying on the air. Another object of the invention is that the gas is initially fully inflated to a preset pressure by one or more gases and does not require a reduction in the volume of the enclosure or mechanical introduction of an additional gaseous medium into the enclosure. where the pressure inside the enclosure increases above the initial inflation pressure due to the extraction of energy from the surrounding air without
An object of the present invention is to provide an elastomeric enclosure that is placed in an ambient air atmosphere. Yet another object of the invention is to extract energy from ambient air and thereby perform useful work.
It is an object of the present invention to provide an elastomeric sealing device that is partially or completely filled with one or more special gases and placed in an ambient air atmosphere. Yet another object of the present invention is to provide a permanent system which utilizes as an expansion medium a maximum amount of air having a pressure of 14.7 psia and in equilibrium with the pressure of the external ambient air, and a minimum amount of supergas. It is to give expansion. This permanent expansion technique provides long-term expansion at relatively constant pressure. Also,
It is a cost effective approach since the major component, air, enters the device automatically and costlessly. The invention has many other advantages and objects that become apparent from its several embodiments. Such embodiments are illustrated in the accompanying drawings. Although these embodiments will now be described in detail for the purpose of illustrating the general principles of the invention, such detailed description is not to be construed in a limiting sense. Embodiments of the present invention will be described below with reference to the drawings. The present invention comprises a preformed, self-expanding, sealed chamber, at least a portion of which is a permeable elastomeric sheet material surrounded by ambient air at atmospheric pressure, and wherein the chamber initially has a low temperature after molding. The elastomeric material is inflated by a gas medium consisting of an inert, non-polar, large molecular gas having a solubility coefficient, and the elastomeric material has a characteristically relatively low permeability to the gas, thereby reducing the flow of the gas from the chamber. and has a relatively high permeability to the ambient air surrounding the chamber, thereby inhibiting the diffusion of the ambient air through the elastomeric material and into the expanded chamber. providing a total pressure within the chamber that is the sum of the partial pressure of the gas within the chamber and the partial pressure of the air within the chamber, the diffusivity of the gas passing through the elastomeric material being This is substantially lower than the diffusion rate of nitrogen through the . The gas used to initially inflate the elastomer chamber is one that can only diffuse outward from the chamber at a very slow rate. These gases may hereinafter be referred to as "supergases". These gases include: Namely, hexafluoroethane, sulfahexafluoride, perfluoropropane, perfluorobutane, perfluoropentane, perfluorohexane, perfluoroheptane, octafluorocyclobutane, perfluorocyclobutane, hexafluoropropylene, tetrafluoromethane,
Monochloropentafluoroethane, 1,2-dichloro-tetrafluoroethane, 1,1,2-trichloro-1,2,2 trifluoroethane, chlorotrifluoroethylene, promotrifluoromethane, monochlorotrifluoromethane. Supergases have the following common properties: i.e. unusually large molecules, very low dissolution rates, inert, non-polar, homogeneous/symmetrical, spherical, prolate (oblate or prolate) or symmetrically branched molecular shapes, non-toxic, non-flammable, metallic. Non-corrosive, excellent dielectric properties of gases and liquids, high levels of electron attachment and trapping ability, synthetic, significantly reduced diffusion rates in all polymers, elastomers and plastics (solid films). Typically, the larger the molecules of a gas, liquid or vapor, the more polar they also become. Supergases are the opposite; they are the least polar and most inert of all gases. Typical sheets or films used in the manufacture of chambered devices and which function properly with respect to supergas may be selected from the group of elastomeric materials described below. Namely, polyurethane, polyester elastomer, fluoroelastomer, chlorinated polyethylene, polyvinyl chloride, chlorosulfonated polyethylene, polyethylene/ethylene vinyl acetate copolymer, neoprene, butadiene acrylonitrile rubber, butadiene styrene rubber, ethylene propylene polymer, natural rubber, high strength silicone rubber. , low density polyethylene, adduct rubber, sulfide rubber, methyl rubber, thermoplastic rubber. The graphs in Figures 5 and 6 show the expansion tests carried out over a five-year period on sealed chambers made of permeable elastomer sheet materials pressurized with various large molecules and gases with low dissolution rates. There is. The curves shown were obtained by plotting superatmospheric air pressure against time and the sheet or film material used was polyurethane. For curve A, the inflation gas medium was hexafluoroethane (C ₂ H ₆ ) and the initial inflation pressure was 20 psig (1.4 Kg/cm ² gauge pressure). As shown, the pressure within the chamber decreased slightly over a period of approximately one week, then began to increase, reaching a maximum pressure of approximately 23.6 psig (1.7 Kg/cm ² gauge pressure) in approximately three months. The initial pressure drop is in chamber 1 due to tensile relaxation of the elastomer material.
This is thought to be due to the initial increase in the volume of No. 3. After reaching the peak, the pressure drops very gradually until 2
After a year, it has a value of about 21 psig (1.5 Kg/cm ² gauge pressure). Maintaining this pressure over a long period of time is possible by injecting nitrogen into the chamber made of polyurethane.
This is thought to be due to inward diffusion of oxygen and argon. Results of inflation tests using other large molecule inflation gases are shown in curves B, C, D, E, F, G, and H, with the specific gas used indicated on each curve. In each case the pressure first rose and then fell at a very slow rate. In curve B, which shows expansion with sulfur hexafluoride (SF ₆ ), the pressure in the chamber dropped to about 20 psig after two years. For octafluorocyclobutane (C ₃ F ₈ ), curve C, the total pressure drops to 20 psig after one year and about 16.5 psig (1.2 psig) after two years.
kg/ ^cm2 gauge pressure). The gas on curve D is 2
After a year, it dropped to 14 psig (1.0 Kg/cm ² gauge pressure). In contrast to the gases shown in curves A-H, the gas shown in the left-hand portion of FIG. 5 lost pressure relatively quickly. The lower left end portion of FIG. 5 is shown enlarged in the graph of FIG. In each case, the polyurethane closure was expanded to 20 psig. Chambers inflated with hydrogen, dinitrogen oxide, carbon dioxide, or oxygen lose all of their pressure and become flat within 10 to 40 hours. That is, it has completely shrunk. freon
The chamber inflated with 22 (CHCIF ₂ ) is approximately 3
Lost all of the pressure within days. Similarly, it was within 6 days for xenon, argon and krypton, within 18 days for Freon 12 (CHCI ₂ F ₂ ), and within 22 days for methane (CH ₄ ). The chamber, which was initially inflated to 20 psig with nitrogen, dropped to a pressure slightly above about 2 psig after 40 days. In all of these cases, the initial expansion chamber became incapacitated in a relatively short period of time when compared to the pressure retention in the gas-inflated chamber shown by curves A-H in FIG. In the curves shown in FIGS. 5 and 6, the diffusion rate of supergas is shown for a polyurethane barrier. FIG. 7 shows a graph showing the diffusion rate of hexafluoroethane in a variety of representative polymer barrier films. To obtain data for each curve, each chamber was pressurized to 20 psig.
As shown in curve A, when the barrier film is urethane-coated nylon cloth, a pressure increase of 8 psig is obtained in about 5 months, and the pressure increases to about 27.4 psig in about 2 years.
(1.9Kg/cm ² gauge pressure).
The pressure increase to a maximum pressure of 20 psig or more and the subsequent pressure drop are also shown in curves B, C, D, E, and F, with the barrier material noted on each curve. Within two years, the total pressure on the barrier film will still decrease.
The initial pressure is greater than 20 psig. Curves G, H, I, J,
The pressure inside the polymer barrier films shown in K and L all rose to some extent above the initial pressure of 20 psig, but
After that, the temperature dropped to less than 20 psig as shown. FIG. 8 is an enlarged graph showing the diffusion rate of nitrogen at an initial pressure of 20 psig through the exemplary polymeric barrier film shown. As a result of the relatively high diffusion rate of nitrogen in these barrier films, with the exception of PVDC and butyl, shown by curve M in FIG. The pressure will reach zero gauge pressure. Diffusion pumping phenomena are evident in elastomer enclosures that are initially expanded to low pressure levels.
For example, the pressure rise of a chamber initially inflated to 1.0 psig with a supergas such as hexafluoroethane is shown by curve 1 in FIG. This chamber is made from a relatively elastic material,
Due to the increase in internal pressure, its volume increased by 40-50%, and the pressure increased by about 550% in 6-8 weeks. If the diffusion pumping action were to take place in a constant volume enclosure made of one of the special elastomeric materials shown in the upper curve of Figure 7, the pressure rise would be even greater, e.g. 1420%.
(Curve 2 in Figure 9). The Birchaert of FIG. 11 illustrates the percent pressure rise possible in a constant volume enclosure made from a special elastomeric material and initially filled with 100% supergas at the gauge pressure shown. As Birchaert shows, the large percentage increase in gauge pressure occurs due to diffusion pumping. The maximum increment of pressure rise is
14.7 psig, which occurs at the end of the diffusion pump action, when the maximum amount of air has diffused into the enclosure. Since this increment is constant regardless of the initial gauge pressure, the percent increase in pressure is high when the initial gauge pressure is low. For example, if the initial inflation pressure is
At 1.0 psig, a 1420% increase occurs.
When the initial pressure is 0.5 psig the increase is 2940% and for an initial pressure of 10.0 psig the increase is 147%. The diffusion of ambient air into the chamber initially inflated with supergas is described in Patent Application No. 1840-1983.
This is confirmed by analysis of the gas in the insole of the type shown in the figure. The midsole was first inflated to a pressure of 22 psig with pure sulfur hexafluoride gas on December 10, 1975. On January 24, 1978, more than two years after the initial inflation, the pressure within the midsole was measured and found to be 19.5 psig.
Over the course of almost two years, the thickness of the midsole increased by about 15.3%, indicating an increase in the volume of the midsole chamber. If this volume were kept constant, approximately 2
After a year the pressure in the midsole would have been higher than the measured pressure of 19.5 psig. The gas in the bottom was analyzed by mass spectrometry in late January 1978. This analysis revealed that the insole contained 52% air by volume (nitrogen, oxygen and argon in the same proportions as in ambient air), 47% sulfur hexafluoride and 0.6% carbon dioxide. Although the gas initially introduced into the insole chamber was 100% sulfur hexafluoride, analysis showed that over a period of two years, air diffused through the elastomer enclosure into its interior, while a small amount of It was demonstrated that the raw sulfur hexafluoride diffused into the atmosphere through the elastomeric material of the midsole. Found to exist within the insole chamber
0.6% carbon dioxide is about 20 times the amount normally found in ambient air. This relatively large amount of carbon dioxide is typical of urethanes and results from outgassing from the basic components of the urethane film. As a result of the back or inward diffusion of ambient air into the insole or other specific device that initially contains the supergas, the total gauge pressure within the insole is maintained at or near the initial inflation pressure, e.g., about 20 psig. be done.
However, the composition of the gas pressures contributing to the total gauge pressure has changed significantly after the insole expansion. Initially, 100% of the gauge pressure (and also absolute pressure) within the insole comes from supergas (SF ₆ ). After two years, the volume of the midsole has increased by 25-40% due to the stretching of the highly stressed envelope that forms the midsole chamber. A small amount of pressure loss also occurs due to outdiffusion of supergas from the chamber. Moreover, except for an intervening small pressure increase during the first approximately two months following initial inflation (see FIG. 5), the useful gauge pressure remains essentially unchanged. As shown by the above mass spectrometry analysis, more than 50% of the total useful pressure within the insole comes from the pressure of the ambient air diffused into the system. It has thus been conclusively demonstrated that a diffusion pumping phenomenon is occurring and that the pressure increase shown is not the result of other mechanisms, such as a chemical reaction between the gas and the film or the film's emitted gas. The reverse or inward diffusion pumping action of ambient air entering the enclosure containing at least a small amount of supergas is
Continuously during the life of the insole, operating energy is automatically extracted from the ambient atmosphere and added sequentially over time to the initial stored energy within the insole, thereby providing tensile relaxation of highly stressed films or sheets. volume increase due to turbulence, absorption of supergas into the barrier film, saturation, small pressure drop due to outward diffusion of supergas, external air pressure change due to altitude,
and almost completely compensates for internal air pressure losses due to cyclic loading. It is important to note that the supergas partial pressure is like a building block in collaboration with the air. It is always additive to the partial pressure of air in the system. The total useful gauge pressure contribution by air of 14.7 psia is a constant stable basis for supergas pressure. The 14.7 psia air pressure is in perfect equilibrium with the external air pressure, so it will never leak. This condition further contributes to long-term expansion of the insole since the pressure component from the supergas is now much lower than the initial full total pressure. At lower differential pressures, the normally very low diffusion rate of the supergas is reduced to a fraction of the higher pressure value, creating a state of substantial permanent expansion. As previously mentioned, long-term pressurization of a closed body at a relatively constant pressure level using a maximum amount of air at equilibrium pressure with external air and a minimum amount of one or more supergases as the expansion medium. This approach to is called the "permanent expansion technique." When long-term cyclic loading and/or pressure changes occur that create an imbalance between internal and ambient air pressure, the diffusion pumping action of the air becomes effective and extends the useful life of the product. For example, if a chamber that has reached stable air equilibrium at sea level is brought to a higher altitude (e.g. in an aircraft or in the mountains) where the ambient air pressure is lower, the stiffness of the device will be the optimum value for chambers manufactured at sea level. It will be bigger. Since the air pressure inside the chamber is greater than the outside air pressure, the air self-compensates and outward diffusion occurs.
This reduces overpressurization and restores the device to a substantially original condition with the desired load-bearing characteristics. If the same chamber is then returned to sea level, the partial pressure of the air within the insole will be lower than the ambient air pressure, so it will be slightly softer than desired. However, within a few hours, the diffusion pumping action of the air builds up the internal air pressure and restores equilibrium. The total pressure within the chamber will have automatically recovered again to a level close to the desired useful gauge pressure. Additionally, the pressure build-up can be further reduced if the chamber is not expanded to its full stress-free volume during the initial expansion and is in a wrinkled state immediately after the initial expansion. In this condition, the gauge pressure is only slightly above zero psig (14.7 psia for supergas). As the pressure increases due to diffusion pumping, the chamber expands and the supergas pressure decreases. The key to this approach is to allow the partial pressure of the supergas to drop to the design pressure once the chamber is fully inflated. Ambient air passes through the elastomeric film and enters the chamber, increasing the pressure inside it. That is, the partial pressure of air will be added to the partial pressure of supergas to create a total pressure greater than zero psig.
However, due to the initial wrinkled state, the volume of the chamber expands, and this expansion continues until the final volume of the chamber is reached due to diffusion pumping. This takes several weeks to reach steady state, and the desired final internal pressure is, for example, 0.5 psig.
At this point, the air pressure in the apparatus is 14.7 psia and the supergas pressure has dropped to 0.5 psia.
This is the ideal condition for long-term permanent expansion.
That is, the device has been expanded according to the "permanent expansion technique" described above. Figures 3 and 4 show an embodiment in which the present invention is applied to a diffusion pump action air lift device. This device is a good example of using diffusion pumping to work. A bag or bellows 30 consisting of a permeable sheet of elastomer is suitably closed at its lower end by a base 31 and at its upper end by a horizontal platform 32.
and the weight W is placed on this platform.
is placed. The bag or bellows 30 is inflated with supergas to such an extent that the platform is at the desired height _H1 . Since the gauge pressure to which this elastomer seal is inflated must always support the weight W, such gauge pressure remains constant. As the energy of the oxygen, nitrogen and argon in the surrounding air diffuses into the enclosure, the volume of gas within the enclosure increases and the platform 32, together with the weight W above it, rises to a height _H2. . The platform continues to rise until the air pressure within the enclosure reaches 14.7 psia (atmospheric pressure) at standard sea level conditions and 70°C (21°C). Weight W from height H ₁
No external force is required to raise it to H ₂ . Lifting is achieved automatically as a result of diffusion pumping, ie, inward diffusion of nitrogen, oxygen, and argon from the ambient air into the expandable elastomeric enclosure 30. The total pressure within the enclosure 30 is maintained at atmospheric pressure above the ambient pressure required to support the weight plus the total pressure increment. At the time of initial expansion, the total pressure is due to the supergas
It is 100%. As air enters the enclosure and the platform rises, the total pressure remains constant.
However, the portion of the total pressure due to the partial pressure of air increases as the platform rises. Correspondingly, the partial pressure of the supergas decreases. The platform continues to rise until the partial pressure of air reaches its maximum value, 14.7 psia. At this point the supergas partial pressure has reached its lowest value. However, the total pressure (air + supergas) remains unchanged. It is the same as the total pressure at the time of initial expansion. The work that can be done with air lift equipment is very substantial, especially in large size applications. For example, the table below shows the amount of work that can be accomplished with three different sizes of equipment having platform diameters of 1 foot, 2 feet, and 3 feet. In each case, a 1000 pound weight is placed on the platform and the bellows are inflated with 100% supergas to an initial height of 1 foot.

[Table] * Attributable to diffusion pump action The above data shows that the larger the device, the more effective it is. For example, a 3-foot diameter device can do 9 times the work of a 1-foot diameter device with 6 times as much supergas. This large device uses 55 times more air than a small device. Another embodiment of the invention is associated with a protective enclosure or structure as shown in FIGS.
The closure includes an end wall 41 secured to an inverted tubular arch 42 and an intervening inverted tubular arch 45 and a longitudinal tubular elastomeric member 46.
The ends of each elastomeric member 46 are attached to and communicate with tubular arms 45, 42 to form a unitary structure. The entire structure can be transported and stored in the folded state. That is, when there is no air or gas within the interconnecting tubular members 42, 45, 46, the end wall 41, side wall 43 and top wall 44 are flexible and collapsible. When the location where the enclosure is to be erected, a small amount of one of the supergases mentioned above is pumped into the interconnecting tubular members 42, 45, 46. The amount of supergas may be sufficient to inflate the tubular members of the structure to about 1/10 to 1/5 of their maximum fully expanded state. At this point, the supergas gauge pressure is essentially zero (i.e.
(only a few ounces higher than the ambient pressure of 14.7 psia). The structure is still in a soft, wrinkled state, slightly expanded from its "lying flat on the ground" state. The structure is now ready for diffusion pumping energy transfer that causes it to self-expand to a fully upright, rigid state. The diffusion pumping action causes each tubular member to expand into its arcuate or linear configuration such that the tubular members become substantially rigid and the end walls 41, side walls 43, and top wall 44 become taut. A significant amount of work is done by diffusion pumping during uprighting of the structure. When fully erected, the structure is pressurized according to a "permanent inflation technique" so that the pressure maintains the desired elevated value over an extended period of time.
The enclosure 40 is easily transported when in the deflated, folded state and easily inflated with a selected supergas or supergas and air mixture to a desired pressure above atmospheric pressure at which the enclosure will be able to maintain its fully upright position. It assumes a rigid state. The advantages of diffusion pumping are further demonstrated in FIGS. 12 and 13. FIG. 12 shows the inflatable structure in a fully pressurized upright configuration with only air used as the inflation medium. In this case it is necessary to maintain the pressure within the structure by some type of mechanical pumping device 100.
That is, the pump must supply fresh air to replace the air that has flowed out of the structure due to diffusion. The bar chart of FIG. 12a shows that expansion is generated by pump 100, thereby forcing air into arches 42, 45 and longitudinal member 46, resulting in an air pressure of 17.7 psia. On the other hand, if supergas and diffusion pumping are used to self-erect the structure,
The structure will remain fully rigid for an extended period of time. This occurs because at the end of the self-pressurization cycle due to diffusion pumping, the structure is automatically expanded to a "permanent expansion technology" state. This state is shown in FIG. The bar chart (Figure 13a) is
Structure inflation is 3.0psia with a maximum amount of air of 14.7psia
is achieved with the least amount of supergas. This small amount of supergas can maintain the structure permanently upright. The reason is that supergas is supported on a 14.7 psia "base" of air. There is no need to use an air pump to supply energy to this system as in the case of FIG. 12. The bar chart of FIG. 14 shows the pressure conditions within the structure at initial inflation (bar A) and at the end of the diffusion pumping cycle when the structure is fully erected (bar B). As shown in the diagram, the total pressure is 100% due to super gas at the time of initial expansion.
It is. The supergas pressure is 15.0 psia, which is only a few ounces above ambient pressure. The closure is therefore only slightly expanded and essentially in a collapsed state. However, when the diffusion pumping cycle ends and the structure is fully erected, the supergas pressure has dropped to 1/5 to 1/10 of its initial value of 15.0 psia and is now 3.0 psia. This pressure drop is due to the increase in volume of the enclosure during the uprighting process. While this is occurring, air continues to enter the enclosure so that the air pressure within tubular members 42, 45, 46 reaches 14.7 psia. Air pressure is at the highest level and supergas pressure is at the lowest level, again illustrating the "permanent inflation technique". Throughout the time that the structure is expanded in this way, diffusion pumping continues to play an important role. For example, diffusion pumping compensates for the effect that changes in ambient temperature have on the pressure within the enclosure. This compensation effect can be understood by referring to FIGS. 15, 16, and 17. Figure 15 shows the structure on a summer day at 80°C (27°C). Birchat A indicates the level of partial pressure of air and supergas within the structure. When supported at 14.7psia (base) of air,
A supergas pressure of 3.0 psia is sufficient to maintain the tubular members of the structure in a rigid condition. However, when the outside air temperature drops by 80° to 0° during the night (FIG. 16), the supergas pressure and air pressure inside the device are reduced by the cooling effect. inside the structure
A total pressure of 15.0 psia may not be sufficient to keep the device from collapsing. However, the structure does not collapse. That is, as the air within the tubular enclosure gradually cools, a pressure difference is created between the outside air and the inside air, which causes the outside air to diffuse inward to maintain the inside air pressure at 14.7 psia. For ease of explanation, FIG. 16 shows a cold ambient temperature condition as if the temperature drop were instantaneous. A comparison of the external air pressure (bar B) and internal air pressure (bar A) shows that a pressure difference of 2.2 psi exists due to the diffusion pumping action. 1st
Figure 7 shows the final equilibrium state for a low temperature day and shows that the diffusion pump action increases the internal air pressure regardless of temperature changes.
14.7 psia, which has been shown to maintain sufficient total pressure within the tubular structure to keep it properly upright and stiff. Gauge pressure is 21st
The pressure is 2.5 psig, as shown by bar chart A in the figure. The structure can also be pressurized upright by "permanent inflation techniques" at the time of initial inflation. Instead of inflating with 100% supergas, as would be the case if inflation was followed by a self-erecting cycle,
An initial expansion is made with a mixture of air and supergas sufficient to provide a 14.7 psia partial pressure of air and a suitably small pressure increment of supergas. One way to do this is to first inflate the structure upright with an air pump and then add a small amount of supergas. Excess air pressure (above ambient pressure) diffuses out and establishes an equilibrium condition. Another application of the diffusion pumping phenomenon is in connection with the manufacture of competition balls such as tennis balls, volleyballs, basketball balls, and the like. These balls are hollow and made from permeable elastomeric material. These balls are first inflated with a suitable mixture of ambient pressure air and supergas, after which the pressure within each ball is automatically increased by inward diffusion to a predetermined pressure level above atmospheric pressure. After initial full expansion is achieved as a result of this diffusion pumping action, the ball exhibits the permanent expansion characteristics described above. The ball therefore remains inflated indefinitely. In the case of tennis balls, it eliminates the need to pack the balls into a hermetically sealed pressurized metal container to maintain their proper internal pressure. In use, the ball loses some pressure as the nitrogen, oxygen, and argon within the ball are forced outward through the permeable membrane;
When not in use, a diffusion pump action occurs and the total internal pressure returns to the desired value. Diffusion pumping can also compensate for altitude changes, as discussed above. Such compensation is particularly useful in the case of tennis balls. The diffusion pump action maintains the ball's gauge pressure at its proper value (typically 14.0 psig) at all altitudes at which the tennis ball is used. In the case of current tennis balls, it is necessary for ball manufacturers to manufacture balls with specific pressures for some regions with extreme altitude conditions.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an inflatable enclosure or structure illustrating an embodiment of the invention. FIG. 2 is an enlarged cross-sectional view taken along line 2--2 in FIG. 1. FIG. 3 is a longitudinal sectional view of another embodiment of the invention. FIG. 4 is a view similar to FIG. 3 showing the chamber expanded to a large volume.
FIG. 5 is a graph representing the pressure within a sealed chamber over time, with various gases being used to initially inflate the chamber. FIG. 6 is a graph in which a part of the left side portion of FIG. 5 is enlarged.
FIG. 7 is a graph representing the pressure over time in sealed chambers made of different elastomeric materials and initially inflated with the same gas (C ₂ F ₆ ). FIG. 8 is a diagram similar to FIG. 7 showing the relatively fast rate at which nitrogen diffuses through a typical polymer film. FIG. 9 is a graph illustrating the diffusion pumping action of an elastomer chamber due to back-diffusion of air into the chamber. 10th
The Figure is a graph similar to Figure 9 showing the pressure increase due to diffusion pumping in an elastomeric chamber, with different mixtures of air and other gases initially in the chamber. FIG. 11 is a bar chart showing the percent pressure rise due to diffusion pumping in a constant volume enclosure initially filled with special gases at different pressures. Figure 12 shows that the structure is made of air.
2 is another view of the pressurizing structure of FIG. 1, 100% inflated and pressure maintained at the appropriate level by an electric motor and pump combination; FIG. 12th
Figure a is a bar chart showing the type of gaseous medium required to maintain the required pressure within the structure of Figure 12. FIG. 13 is another view of the pressurized structure of FIG. 1 inflated with supergas and air.
FIG. 13a is a bar chart showing the composition of the gaseous medium to maintain the required pressure within the structure of FIG. Figure 14 shows the relative amounts of air and supergas within the inflatable structure at the time of initial inflation and after the structure has been erected from the collapsed state to a fully pressurized state by diffusion pumping. This is a bar chart. 15th, 16th,
Figure 17 is a series of birts showing the changes in supergas and air pressure within the expandable structure during changes in ambient temperature and the self-compensating effects of diffusion pumping. 30... Bellows, 31... Base, 32... Platform, W... Weight, 40... Protective seal, 41
...End wall, 42...Tubular arch, 43...Side wall, 44...
Top wall, 45... tubular arch, 46... tubular elastomer member.

Claims (1)

[Scope of Claims] 1. At least one member formed by an inflatable member
at least a portion of the expandable member comprises an elastomeric material, and the chamber formed by the elastomeric material initially comprises an inert, non-polar, large molecular gas having a low solubility coefficient after molding. Expanded by a gaseous medium, the elastomeric material characteristically has a relatively low permeability to resist outward diffusion of the gas and a relatively high permeability to the ambient air surrounding the chamber. , thereby allowing diffusion of the ambient air through the elastomeric material and into the inflated chamber, with a total pressure being the sum of the partial pressure of gas in the chamber and the partial pressure of air in the chamber. is provided in the chamber, and the diffusivity of the gas through the elastomeric material is substantially lower than the diffusivity of nitrogen through the elastomeric material. 2. Claim 1, characterized in that said chamber initially contains said gas at above atmospheric pressure, and said air diffusing through said elastomeric material adds its partial pressure to the initial pressure of gas in said chamber.
Self-expanding structure as described in Section. 3. The self-expanding structure of claim 2, wherein said chamber is formed entirely of a permeable elastomeric material. 4. The self-expanding structure of claim 1, wherein said chamber is formed entirely of said elastomeric material. 5. The elastomer material constituting the chamber is polyurethane, polyester elastomer,
Fluoroelastomer, chlorinated polyethylene, polyvinyl chloride, chlorosulfonated polyethylene, polyethylene/ethylene vinyl acetate copolymer, neoprene, butadiene acrylonitrile rubber, butadiene styrene rubber, ethylene propylene polymer, natural rubber, high strength silicone rubber,
A self-expanding structure according to claim 1, which is selected from low density polyethylene, adduct rubber, sulfide rubber, methyl rubber or thermoplastic rubber. 6. The self-expanding structure of claim 1, wherein the gas comprises hexafluoroethane. 7. The self-expanding structure of claim 1, wherein the gas comprises sulfur hexafluoride. 8. The self-expanding structure of claim 1, wherein said elastomeric material is polyurethane. 9. The self-expanding structure of claim 1, wherein said chamber initially contains a mixture of said gas and air. 10. The self-expanding structure of claim 1, wherein said chamber initially contains a mixture of said gas and nitrogen. 11. The self-expanding structure of claim 1, wherein said chamber initially contains a mixture of said gas and oxygen. 12. The self-expanding structure of claim 1, wherein said chamber initially contains a mixture of gas and argon. 13 The gas is hexafluoroethane, sulfur hexafluoride, perfluoropropane,
Perfluorobutane, perfluoropentane, perfluorohexane, perfluoroheptane, octafluorocyclobutane, perfluorocyclobutane, hexafluoropropylene, tetrafluoroethane, 1,1,2-trichloro-1,2,
2. A self-expanding structure according to claim 1, wherein the self-expanding structure is selected from ditrifluoroethane, chlorotrifluoroethylene, promotrifluoromethane, or monochlorotrifluoromethane.