FR3040083A1 - SAFETY VALVE FOR INFLATABLE ENVELOPE - Google Patents

Abstract

A safety valve (10) for inflatable envelope (14) comprises a first synthetic film (12) forming part of or being pressed against a wall of the envelope, the first film being provided with an orifice (16), a shutter body (20) cooperating with the orifice and a second elastomeric film (22) joined to the first film at the periphery of the shutter body, the shutter body being fixed to the second film by a fastener (26) and constrained in the closed position by the tension of the second film. The valves according to the invention can be used, eg in the fields of packaging (eg large volume, for the storage and / or transport of satellites or other goods to be protected), inflatable space structures, stratospheric or ionospheric balloons, or for any application to create a clean space or temporary controlled atmosphere.

Description

Technical Field [0001] In general, the invention relates to a safety valve for an inflatable envelope made of thin synthetic film (thickness ranging from 1 pm to 250 pm).

Background Art [0002] US Patent 4,966,185 discloses an inflation valve for sealing an inflation port of an inflatable envelope. The valve comprises an outer washer with a central passage opposite the orifice and which carries a sealing ring. An inner washer holds a membrane that extends over the orifice and defines gas inlet channels. In case of overpressure on the inside, the membrane is pressed against the sealing ring and thus closes the orifice. In case of overpressure on the outside, the membrane is lifted from the sealing ring and opens gas passages between the outside and the inside of the envelope.

US Patent 5,326,176 discloses a pressure relief valve for a packaging container which prevents contamination of the inner atmosphere of the package with ambient air. The valve comprises a flexible membrane of generally rectangular shape which extends over holes in the packaging casing. Two sides of the membrane are glued to the envelope by bevelled adhesive strips, so that a free glue channel results in the area between the adhesive strips, the spacing between the envelope and the membrane being in this channel. In case of overpressure in the package, the membrane rises from the envelope in the channel area which allows the passage of gas from the inside to the outside.

US patent application 2006/0076058 A1 relates a single-use pressure relief valve which can be applied against the wall of a package containing a product releasing gases. The valve includes a bottom sheet and a topsheet that are joined to each other by a waterproof peripheral seal. The bottom sheet includes an opening in a first sector of the closed perimeter and the topsheet includes micro openings in a second sector of the closed perimeter. A liquid substance is between the two leaves in the second sector. In case of overpressure in the package, the gases enter the first sector via openings in the package and opening in the bottom sheet. Then, if the pressure is sufficient, capillary passages are formed in the first sector and allow the gases to escape out via the micro-openings in the topsheet.

Known valves often have a large surface area compared to the density of the envelope on which they are applied. Therefore, they are hardly compatible or incompatible with certain applications, eg the missions of high-altitude balloons or ionospheric balloons. Some of the existing valves are also incompatible with use on very thin synthetic films (less than 250 μm, preferably less than 50 μm). It is therefore an object of the invention to provide a valve of a construction more suitable for these applications.

GENERAL DESCRIPTION OF THE INVENTION [0006] According to a first aspect of the invention, a safety valve for a synthetic film inflatable envelope comprises a first synthetic film forming part of or being applied against a wall of the inflatable envelope. the first film being provided with an orifice. The valve further comprises a shutter body cooperating with the orifice, the shutter body having a first face facing said orifice and a second face diverted from the orifice, and a second elastomeric film joined to the first film at the periphery of the body shutter. The second film is mounted with a mounting stretch. The shutter body is fixed to the first or second elastomeric film by a fixing and constrained in the closed position by the mounting tension of the second film.

In the context of this document, the term "synthetic film" refers to a thin and flexible film of synthetic material, eg polypropylene, acrylic polymer, polyamide, polyimide, polyethylene terephthalate (PET), polyester, etc. The films can be monolayer or multilayer, metallized or not. The thickness of the films is preferably between 1 μm and 250 μm, more preferably between 3 μm and 50 μm. The term "elastomeric film" refers to a thin and flexible elastomeric polymer film.

Preferably, the aforementioned fixing secures the shutter body to the second film and is on the second face thereof. Advantageously, this attachment is centered on the axis of the orifice, that is to say in the (virtual) extension of the orifice towards the outside.

The fastener fixing the shutter body may comprise one or more glued or welded joints (heat-bonded). Alternatively or additionally, the fixing fixing the obturator body could comprise an anchoring element, eg in the form of pin, mushroom or rivet. The heat-sealing can be practiced on polyester or polyethylene or any other film compatible with this technology. The welded joints can be obtained by ultrasonic welding, by laser welding. Preferably, the second film is joined to the first film at the periphery of the shutter body by a gasket bonded or welded tightly over the entire circumference of the obturator body and the second film comprises at least one perforation allowing the escape of gas from the enclosure formed between the first and second films.

It is also possible that the second film is joined to the first film at the periphery of the shutter body by a discontinuous bonded or welded joint so as to define a gas exhaust channel between the first and second films.

According to an advantageous embodiment of the invention, the shutter body has the shape of a lens or a disk. It is preferably made of a polymer material.

According to an advantageous embodiment of the safety valve, the fastener fixing the shutter body is arranged so as to allow the second film to bulge in case of overpressure by sliding on at least a portion of the shutter body. The second film is preferably provided with at least one perforation located in an area that due to the sliding caused by the bulge separates from the obturator body. In this embodiment, the obturator body face diverted from the orifice closes the perforation (s) of the second film as long as the bulge of the second film does not move the perforation (s) past the edge of the obturator body.

The fixing fixing the shutter body is preferably arranged locally and centrally on the second face of the shutter body and fixed the shutter body to the second film so as to allow the sliding of the second film on the shutter body in an annular area around fixing and thereby dilation of the second film with respect to the shutter body. Advantageously, the second film then comprises at least one perforation in said annular zone. It will be appreciated that this embodiment provides two levels of sealing: between the shutter body and the first film and between the shutter body and the second film.

According to a preferred embodiment of the invention, the valve has a valve seat comprising a flange-shaped portion attached to the first film and a cylindrical portion arranged coaxially with the orifice, the shutter body being configured so that to slide axially in the cylindrical portion between an open position and the closed position.

The second film is preferably silicone rubber or fluorosilicone, butadiene rubber, butyl rubber, EPDM (ethylene-propylene-diene monomer), and so on.

For a better seal of the valve, a grease or a sealing oil may be provided between the shutter body and the first film and / or between the shutter body and the second film. Similarly, the materials in contact at the valve and / or seat may have a low Young's modulus to promote a sealed contact. A specific coating on one or more surfaces in contact can be retained.

According to an advantageous embodiment of the invention, the valve comprises a reinforcing element stiffening the first film (which may be the film of the envelope) around the orifice, whose edge serves as a valve seat to the shutter body.

A second aspect of the invention relates to an inflatable envelope of synthetic film, comprising one or more safety valves as described above.

[0020] Other aspects of the invention relate to enclosures comprising one or more inflatable envelopes provided with safety valves. Examples of enclosures are, in particular, packaging (eg of large volume, for storing and / or transporting satellites or other goods to be protected), an inflatable spatial structure (eg a Antenna reflector, a mat, a structure carrying a solar panel), a stratospheric or ionospheric balloon, a tent (eg to house an advanced command center, a medical facility, a makeshift hospital space, a computer center , etc., or to create a living space), a transport enclosure (eg for transporting contagious patients), a greenhouse or a clean room. In general, any application to create a clean space or temporary controlled atmosphere may use one or more envelopes according to the second aspect of the invention.

The safety valve according to the invention is equally suitable for single-wall inflatable envelopes as for inflatable double-walled envelopes. Compartmental inflatable structures may also be equipped with safety valves according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0022] Other features and characteristics of the invention will become apparent from the detailed description of certain advantageous embodiments presented below, by way of illustration, with reference to the appended drawings which show:

Fig. 1: an exploded view of a first example of a safety valve according to the invention;

Fig. 2: a cross section of the valve of Figure 1 in the closed state;

Fig. 3: a cross section of the valve of Figure 1 in the open state;

Fig. 4: a cross section of a second example of a safety valve according to the invention, in the closed state;

Fig. 5: a cross section of the valve of Figure 4 in the open state;

Fig. 6: a cross section of a variant of the valve of Figures 1 to 3;

Fig. 7: a cross section of a variant of the valve of Figures 4 and 5, in the closed state;

Fig. 8: a cross section of the valve of Figure 7 in the open state;

Fig. 9: a schematic view of a satellite packaged in a thin synthetic film envelope;

Fig. 10: a schematic view of an ionospheric balloon;

Fig. 11: a cross section of a particularly advantageous embodiment of a safety valve according to the invention;

Fig. 12: a three-dimensional view of the valve seat and the valve body of the valve of Figure 11;

Fig. 13: a cross section of a safety valve with a valve of generally frustoconical shape;

Fig. 14: a cross section of a safety valve with a valve-shaped router;

Fig. 15: a perspective view of an inflatable igloo double wall;

Fig. 16: A detail of the igloo of figure 15.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION [0023] FIGS. 1 to 3 show a first example of a safety valve 10 making it possible to avoid an overpressure in an inflatable envelope. The valve 10 comprises a first plastic film 12, in the form of a washer, hermetically applied against the outer wall of the inflatable envelope 14 (FIGS. 2 and 3) and forming a rigidified valve seat compared to the single envelope 14. The central orifice 16 of the first film is placed in the continuation of an aperture 18 formed in the inflatable envelope 14. The passage formed by the aperture 18 and the orifice 16 is closed on the outside of the envelope by a valve 20 (made of synthetic material or rubber) acting as valve body of the valve 10. The valve 20 may have a frustoconical shape or more advantageously a lenticular shape whose surface in contact is a spherical bearing or else a top that exerts a concentrated pressure at the orifice 16 of the seat. This valve is applied against the valve seat by the tension of a second film 22 made of elastomeric material. The second film 22 (or elastomeric disk) is joined to the first film 12 by a peripheral seal 24. The assembly ring 28 has a ring of small studs 29 which are assembled in the orifices 13 opposite the first film 12 in the form of a washer. Beforehand, the elastomeric disk 22 is mounted on the assembly ring 28. The elastomer disk also has orifices 23 and the assembly sets the elastomeric disk 22 with initial calibrated tension. The assembly ring is preferably made in the same material as the first film 12. In this case, the studs are advantageously heat-sealed to the first film 12. On the side turned away from the orifice 16, the valve 20 is joined to the second film 22 by a bonding 26 positioned in the axis of the passage formed by the aperture 18 and the orifice 16. The valve 20 is held against the first film 12 by the tension of the second film 22 (elastomeric disk). The inner chamber 30 formed between the films 12 and 22 and housing the valve 20 is connected to the atmosphere (or vacuum) outside the envelope 14 by perforations 32. In the example of Figures 1 to 3, the perforations 32 are placed radially outside the perimeter of the valve 20.

The base of the safety valve 10, formed by the first film 12, is attached to the inflatable envelope 14 by an adhesive or a sealed seal 34.

As long as the internal pressure of the envelope remains below a certain threshold, the valve 20 prevents gas leakage via the valve 10 (FIG. 2) because the normal component of the tension force of the second synthetic film keeps the valve 20 in contact with the valve seat. In case of overpressure, the valve 20 rises from the valve seat and allows the gas to escape to the outside through the perforations 32 (Figure 3). As soon as the pressure difference falls below the threshold value, the valve 20 returns to the closed position. Gluing 26 ensures that the valve 20 remains in place. The internal limiting overpressure of the casing triggering the opening of the valve is regulated by the initial stretching of the second film 22, by its mechanical stiffness, by the diameter of the orifice 16 and that of the valve 20 as well as by the angle a between the elastic film 22 and its laying plane in the closed position.

Figures 4 and 5 illustrate a second example of safety valve 110. In this example, the first film 112, which forms the base of the valve 110, is an integral part of the envelope 114. The first film 112 comprises an orifice 116 closed on the outer side of the casing 114 by a valve 120 of flexible synthetic material. The valve 120 has the shape of a disc and is applied against the outer wall the casing 114 by the force resulting from the tension of a second film 122, elastic, fixed to the first film by a bonding bead or peripheral weld 124. The valve 120 is held in place against the second film 122 by a central bonded or welded joint 126, placed substantially in the axis of the orifice 118. Around this central seal 126, an annular contact zone is formed between the valve 120 and the second elastic film 122, in which there is no attachment between the valve 120 and the second elastic film 122 and wherein the second film 122 can slide on the valve 120. In this annular zone, the second elastic film 122 is also provided with perforations 132 which are radially close to the perimeter of the valve 120.

When the inner pressure of the casing 114 is less than the discharge pressure, the valve 120 closes the orifice 118 in the first film 112 and the perforations 132 in the second film 122 (Figure 4). When the internal pressure of the envelope 114 rises, the second film begins to bulge (Figure 5). This bulge is accompanied by a radial stretching of the second film in the annular zone between the central seal 126 and the peripheral seam or bonding bead. The stretch, illustrated by the double arrows 128 in FIG. 5, in the presence of the elevation of the internal pressure, causes a sliding of the second film on the edge of the valve 120 and causes the perforations 132 to migrate radially towards the wall. outside of the valve 120. A gas evacuation passage 130 is formed as soon as the valve 120 takes off from the first film 112 and releases at least one of the perforations 132. An oil (silicone) can be applied to the contact surfaces valve to increase sealing and to facilitate sliding.

Figure 6 shows a variant of the example of Figures 1 to 3. Only the differences from the basic example will be detailed later. The central weld 26 is replaced in this variant by a mechanical anchoring element 226 of the valve 220 in the second film 222. Another difference lies in the fact that the peripheral seal 224 is discontinuous, so as to define an exhaust passage of gas 232 between the first and second films 212, 222. The perforations 32 of the second film have thus been omitted in this variant. Finally, the variant of FIG. 6 does not include an assembly ring 28.

Figures 7 and 8 illustrate a variant of the example of Figures 4 and 5. Only the differences from the basic example will be detailed later. The central glued or welded joint between the valve 320 and the second film 322 is replaced in this variant by a glued or welded joint 326 between the valve 320 and the first film 312. The bonded or welded joint 326 is placed so as to allow the flap to flex together with the second film while staying attached to it, when the internal pressure of the envelope rises. As the second film 322 bombs, it stretches and slides on the valve 320, which remains dimensionally more stable. The stretch is illustrated by the double arrow 328. The second film 322 is provided with at least one perforation 332 located in an area which due to the relative sliding caused by the lifting and the bulge is no longer masked by the valve 320 As in the example of FIGS. 4 and 5, a gas discharge passage 330 is formed as soon as the valve 320 takes off from the first film 312 and releases at least one of the perforations 332.

Figures 11 to 12 show a variant of safety valve 410 more sophisticated. The valve 410 comprises a valve seat 412 of synthetic material and a valve 420 cooperating with the valve seat 412. The valve seat 412 is in the form of a tube 412a ending in a flange 412b applied tightly against the outer wall of the Inflatable envelope 414. The valve 420 comprises a cylindrical end 420a which fits into the tubular portion 412a of the valve seat 412, a head end 420b, opposite the cylindrical end 420a, which serves to support a film elastomer 422. The elastomeric film 422 is attached to the periphery of the flange 412b of the valve seat by an assembly ring 428. Between the head end 420b and the cylindrical end 420a, the valve 420 is provided with a circumferential projection or ring 420c intended to bear against the valve seat 412 and to close the orifice in a sealed manner. The valve 420 further comprises through holes 421 in the wall of the cylindrical end.

The valve 420 is applied against the valve seat 412 by the tension of the elastomeric film 422. In case of overpressure in the casing, the valve 420 moves axially outwardly in the tubular portion 412a of the valve seat by stretching the elastomeric film 422. The circumferential protrusion 420c rises from the valve seat 412 and the through holes 421 approach the inner edge of the flange 412b of the valve seat. The gas inside the casing can then begin to escape outwards, through the perforations 432 in the elastomeric film 422. If the internal pressure of the casing rises further, the through holes exceed the inner edge of the flange 412b of the valve seat, which then causes a faster escape of the gas. preferably, the mechanical parts (the valve seat and the valve) have thin thicknesses (between about 100 μm and 1 mm) in order to limit their mass and to ensure their compatibility of an assembly technology with the films of the envelopes. The mechanical parts are advantageously molded parts (by injection or by another molding technique), made of polymeric material and / or elastomer.

An advantage of the valve of Figures 11 and 12 is the best accuracy on the value of the opening pressure. The interlocking play between the seat and valve cylinders allows a first reduced exhaust flow of the valve with a low detachment of the valve. If the overpressure is greater, the valve rises further and discovers the through holes on its cylinder that allow a more intense gas exhaust. In the raised position, the resulting force is increased and therefore corresponds to a higher overpressure: the system self-regulates the flow as a function of the positive pressure advantageously.

Figures 13 and 14 show variants of the safety valve of Figures 1 to 3. The valve of Figure 13 comprises a valve-shaped truncated cone 520, the valve of Figure 14 comprises a valve-shaped 620. It is noted that the tip of the router could also be rounded.

[0034] Exhaust valves or safety valves as described above are adapted to the technology of inflatable envelopes. They are intended to control the overpressure of an inflated envelope. Their design is particularly suited to the technology of thin and flexible films constituting the inflatable envelopes. They solve the problem of overpressure, which can cause the envelope to burst. The thicknesses of the films are advantageously between 3 μm and 250 μm. Such casings therefore have very low surface area masses and the valves described have the advantage that they can also be produced with very small masses (typically less than 0.5 grams for balloon applications). Thus, the average surface density or the total mass of an envelope equipped with one or more of these safety valves are hardly increased.

The films used for the manufacture of envelopes preferably consist of one or more of the following materials: polypropylene; acrylic polymer; o polyester (PE); polyimide (PI); polyamide (PA), eg nylon; o polyethylene terephthalate (PET); o etc.

The films in question can be metallized or non-metallized, depending on the application of the envelope. Films suitable for the manufacture of inflatable envelopes are commercially available. Examples are Mylar (trademark) metallized or non-metallized films, Kapton (trademark) films.

Applications of inflatable envelopes envisaged are found, inter alia, in the following areas: o Packaging and / or storage, in particular, bulky goods sensitive to moisture and / or purity of the product. air, whose protection against particles, dust is required; o the provision of temporary clean spaces with single or double envelopes; stratospheric and / or ionospheric balloons, in particular the ionospheric balloons described in the French patent application registered under number 14/02317; o inflatable space structures (such as deployable mats, solar panel structures, antenna reflectors, etc.); o the protection of sensitive equipment against the cold (eg lander probes, parts of spacecraft, etc.) Envelopes equipped with safety valves are particularly suitable for packaging, specifically for packaging payloads that require large clean spaces free of particles, are sensitive to moisture and / or air purity and / or have fragile parts. Examples of such payloads are, among others: satellites (in transfer between their place of production and the launch site), launching elements, aeronautical engines, turbines, telescopes, airplane cockpits, etc. Envelopes are especially useful in case of packing exposed to aggressive external conditions, such as salt air, sand, smoke, etc.

In case of large packages (eg several cubic meters), it is useful to distribute several safety valves on the envelope. Once, the payload placed in the envelope, the distributed valves ensure the passive management of overpressures. The packaging can be equipped with a compressed gas cylinder to maintain in the envelope a minimum overpressure a priori lower than the pressure that triggers the valves. The valves open especially in case of overpressure caused by the change of the external pressure (typical in the case of transport by plane) or by an increase of the temperature. Contamination of the inside of the casing by the outside air is prevented by the valves as they close for a positive pressure difference between inside and outside.

The thin envelopes do not necessarily protect their payload against shocks, wind and / or rain. If necessary, the payload packaged in its envelope is therefore advantageously placed in a conventional container. With the envelope, the container does not have the constraint of being airtight or particle and / or pressurized. The payload envelope can be put or removed from the container in a room that does not have the constraint of being a clean room.

[0040] Figure 9 schematically illustrates a satellite 40 packaged in a thin film envelope 42 for storage on the ground or for transport to the launch site. The envelope 42 is pressurized by a pressurization system 44. The envelope 42 is equipped with a plurality of safety valves 46.

It should be noted that the pressurization of the envelope allows it to maintain itself without relying on the payload. The envelope may, however, be attached to the container by shoulder straps or be stiffened by bulges inflated to a higher pressure structuring the edges of the envelope. The mass of the envelope remaining very small despite the large volume, for most payload damage caused by the envelope on the payload are not to be feared.

The pressurized envelopes are likely to facilitate the handling of sensitive payloads. For example, the containerization can be performed outside the protected space (clean room) once the load has been placed with its envelope on an interface board.

Sizing example: a cubic envelope of 5 meters side made of Mylar film (trade mark) 25 pm thick represents a mass of about 5 kg. It may, for example, be pressurized to 100 Pa, although an overpressure of only about 2 Pa is sufficient to suspend the envelope.

In addition to transportation, the thin film envelopes can be used as storage packages or temporary clean rooms. The storage of sensitive goods outside the clean room, but in an area sheltered from rain and wind, is therefore possible. Such an envelope can be designed to allow the entry of personnel, by the establishment of an airlock that can be achieved using the same technology of thin and pressurized envelopes. This can make it possible to carry out operations on the payload outside the protected area (clean room). This possibility will be particularly appreciated for: o unplanned specific interventions in a clean room, such as, for example: powering up, checking for good health, setting up a gas sweep, removing safety devices, etc. ; o and tests that are typically not feasible in the clean room, such as particle accelerator tests, magnetic tests, antenna-base tests, outdoor antenna measurements, optical sight tests, and so on.

The use of a thin synthetic film envelope for producing a protected space of the external environment may be recommended, eg for the following reasons: o need particulate cleanliness and / or bacteriological; o protection in a hostile environment: sand dust, smoke o temperature regulation in cold or hot environment o need a controlled atmosphere (eg in terms of humidity, gas content, etc.) [0046] The envelope can be deployed for temporary use in a shelter protected from wind and weather. In particular, the following applications are being considered: o ad hoc installation for medical interventions (makeshift hospital space); o implementation of a command center with computer resources; o implementation of an inhabited space in a hostile environment: dust (volcanic fallout, asbestos), ash (fire, forest fire), humidity, smoke, toxic emanation, bacteriological risk, chemical pollution (industrial accident), etc. o Experimentation of living under a controlled atmosphere.

Advantageously, the protected space includes an airlock for the personnel, a pressurization system with filtering of the external atmosphere for the initial inflation and for the maintenance of the overpressure. For some specific uses, compressed gas may be used.

Depending on the duration of use, the acceptable risk of loss of sealing vis-à-vis the outside, the thickness of the envelope can be chosen in the range of 25 pm to 250 pm. Preferably, the floor portion of the enclosure comprising the thin film envelope includes a walkable surface, eg PVC (polyvinyl chloride) flooring. The envelope is advantageously self-supporting, compartments or partitioned portions at higher pressure provide additional rigidity to the envelope. The envelope can also be mechanically provided by a supporting structure, such as a mast system.

The advantages of the thin envelope solution are the rapid implementation, and the transportability of the installation thanks to its low mass and small footprint in folded configuration.

An enclosure comprising a thin film envelope can also be implanted inside a clean room with a filtration of the inflation air to create an even cleaner space. This solution is an alternative to equipment with blowing ceiling, which is advantageous in terms of level of cleanliness, airflow produced and the means used.

According to a more sophisticated use of the technology of thin envelopes, the envelope comprises compartments forming partitions, carrier structures, etc.. It is therefore possible to create self-supporting double or multiple wall enclosures that withstand higher wind speeds and can be deployed outdoors.

According to a preferred embodiment, the main volume of the chamber remains pressurized which allows for the control of the indoor atmosphere. The jacket can advantageously use the thin film technology because of the inflation pressure of the limited partitioned portion (a few hundred mb) which essentially ensures the carrying and maintenance of the structure. The internal pressure of the chamber also contributes to this maintenance and makes it possible temporarily to undergo buckling conditions of the partitioned portion without causing the shell to collapse while the internal pressure is significantly lower (several tens of mb) than that partitioned parts. Thus, the main volume is maintained at a lower pressure than the structural elements of the enclosure, such as bulkheads and compartments in the form of coil, spherical cap, arch, etc. The overpressure of the partitioned elements ensures the rigidity of the walls of the enclosure, its resistance to bending and buckling. The applications may be the same as those already mentioned before. However, other applications are possible because of the self-supporting and rigid nature of the structure and therefore the fact of the possibility of deploying these structures out of closed buildings: covered public reception area, protected and air-conditioned (double thickness ensuring better insulation), exhibition space, conference, show, ceremony. A constraint remains the access of the people by a system of locks to guarantee the pressurization of the principal volume. If the control of the atmosphere is not necessary, if the risk of buckling is minimal, one can use the enclosure without pressurization of the internal volume and maintained by the only rigidity of the double pressurized walls.

The pressure relief valves are advantageously located on the compartments with an exhaust to the outside and on points distributed with a simple thickness (flange joint or via emptying tube) between the internal space and the outside.

This double-envelope topology can also be adapted to create a confined space isolated from the outside, the discharges of which can be filtered. In this case, the compartments of the valves also escape inward and the exhaust valves are removed from the main interior space to the outside to pass through a filtered centralized evacuation. The enclosures thus produced could be used for: o Quarantine or transport of patients; o experimentation on bacteria; o biological or agronomic experimentation (with the aim of ensuring non-dissemination); o the handling of toxic chemicals.

For applications using large envelopes, low complexity and low cost of the valves can distribute their function on the entire surface of the envelope. Since these are large volumes of gas inside the enclosure (eg 100 m3 to 2000 m3), this solution is preferable to a centralized valve system. For example, to avoid overpressure in the event of an increase in temperature, the volumes of gas to be evacuated are important: when the temperature of the air or the internal gas increases from 20 ° C to 21 ° C, it is necessary to evacuate approximately 0.35% of the initial volume, which is approximately 3500 liters for an initial volume of 1000 m3 As the casing films are thin, low overpressures (of the order of 0.1 kPa and 1 kPa) can cause the envelope to burst and should be avoided. When the temperature of the inner gas initially at atmospheric pressure and at about 20 ° C increases by 1 ° C in a constant volume, the resulting overpressure is about 0.34 kPa. If this overpressure can endanger the envelope, the safety valves are dimensioned and arranged so as to evacuate the gases with sufficient reactivity. This reactivity is better ensured by the distribution of the valves. Local pressure variations and pressure waves are other important reasons for valve distribution. Acoustic pressure waves or overpressures caused by a gust of wind or by a convective circulation of indoor air can easily reach the order of magnitude that can cause damage to the envelope. To absorb these local pressure peaks in large spaces, a centralized solution is not suitable.

Figures 15 and 16 show an inflatable envelope shaped igloo or dome. The igloo 60 is an example of a closed space made with a double-walled envelope.

The interior volume is pressurized with a low overpressure via two pumping groups 62, this internal overpressure ensuring the envelope to be self-supporting. However, the igloo 60 is also stiffened by a system of partitioned compartments 64, divided into petals numbered consecutively 1 to N (N = number of petals) and a top slab 66. The compartments 64 allow the igloo 60 to maintain in outdoor environment and withstand exposure of wind and weather. The compartments 64 together form the double-walled envelope of the igloo 60. The overpressure of these compartments 64 is substantially greater than the overpressure of the (large) interior volume. The overpressures are independently assured by the two pumping groups 62. The first group ensures the pressurization of the petals of odd number and the second group that of the petals of even number. Both groups also provide internal overpressure. This alternating supply of the overpressure in the cloisonné petals makes it possible to ensure redundancy of the maintenance of the dome of the igloo 60.

The overpressure is distributed at the level of the upper slab 66. The slab 66 is partitioned between an upper portion 68 and a lower portion 69. The upper portion 68 distributes the overpressure of the odd number petals, the lower portion 69 distributes the overpressure of petals of even number (or vice versa). This distribution is performed by means of pressure relief valves 70 so as to preserve the pressure of each compartment 64 in case of depressurization of one of them.

With respect to the external pressure, each compartment 64 is protected from excess pressure by one or more valves 72 escaping to the outside. The internal volume is also protected against overpressure by valves 74 connected to the outside by a conduit passing through the partitioned compartments 64.

The valves are distributed over the entire dome with a spacing dependent on the allowable overpressure margin and sudden changes in pressure envisaged (typically, one can have a spacing of a few meters). Exhaust compartment valves may also be provided to the interior volume because it is substantially larger than the volume of a compartment.

The flow rate of the interior volume of the valves is substantially greater than that of the partitioned compartments to evacuate the same overpressure. Thus the valves of the interior volume preferably have an exhaust port of larger diameter. The valves of the compartmentalized compartments are calibrated for a value of overpressure significantly higher than the calibrated value of the valves of the interior volume.

A pressurized airlock 76 provides access to the interior volume or to leave it. The overpressure of the airlock is preferably lower than that of the interior volume to limit the air inlets.

The airlock 76 may comprise openings known in the field of tents, eg webs closing with zippers. For a more convenient use, the airlock 76 may also include a system of rigid doors mounted on rigid walls, whose surface remains very limited compared to that of the envelope.

The floor of the igloo 60 consists of either a rigid and sufficiently tight floor, or a thick tarpaulin, footprint resting on a floor, on a slab or on a flattened ground. The envelope connects to the floor or to the tarpaulin to ensure the necessary tightness of the interior volume.

Another interesting application of thin film envelopes is that of stratospheric or ionospheric balloons.

The term "ionospheric balloon" means the balloons described in the French patent application 14/02317. An ionospheric balloon is intended to be injected into the (very) upper atmosphere to make a descent to the earth. Such a balloon, a copy 50 of which is illustrated in FIG. 10, comprises an envelope 52 containing in its interior an inflation substance in a condensed state (solid and / or liquid), for the pressures and temperatures intended for storage and the start. When the envelope 52 is finally exposed to vacuum or at very low pressures, this substance swells the envelope 52 by vaporization or sublimation. The ionospheric balloon 50 is equipped with at least one safety valve 54 to avoid the overpressure incurred during the thermal peak of the atmospheric reentry at about 120 km altitude. The ionospheric balloon 50 carries a payload 56, in particular a platform carrying measuring instruments and recording and / or communication means.

On stratospheric balloons, the safety valves allow to evacuate the gas from the envelope and thus prevent or at least delay the bursting of the envelope during the rise of the balloon.

There is also the concept of inflatable structures for space applications having a gas source and an exhaust. The casing has a supply of solid or vaporizable liquid contained in a conditioning tank at the saturation vapor pressure. This reservoir releases a flow of gas to the inflatable envelope and therefore holds it inflated to a lower pressure. This pressure is regulated by the constant escape of gas via valves to the vacuum.

It is thus possible to inflate a structure with a controlled pressure: the dimensional stability is less dependent on the temperature conditions. The structure can also survive micro-meteorite perforations. The thickness of the envelope must be sufficient to limit the total surface of the perforations. The flow consumed could be of the order of 100 g / year to maintain a structure such as a mast of several meters or a toric tube.

Applied to space inflatable structures, the valves allow the use of thin envelopes to achieve large structures with low mass and low pressurization. With inflation simplified by the overdose of evaporable substances, the source of evaporable substance can ensure the maintenance of pressure by slow diffusion of this substance packaged in a micro-perforated enclosure. The regulation of the pressure offers a good dimensional stability and responds to the degradation in time by the perforation of the envelope by micro-meteorites.

We can consider the deployment of large antenna mast type structures, antenna reflectors, solar panel structure.

For balloon and space structure applications, the safety valves constitute a solution of low complexity and low mass for the problem of the overpressure. It is indeed necessary to respect an objective of surface weights of between 5 g / m2 and 50 g / m2 for the membranes used for the manufacture of balloons. Similarly, the manufacture of large spatial structures will be preferred with membranes of a few tens of pm (that is to say a few tens of g / m2) to allow deployment at low internal pressure (up to a few hundred Pa ) and present a very favorable mass balance compared to rigid structures.

While particular embodiments have just been described in detail, those skilled in the art will appreciate that various modifications and alternatives to these can be developed in light of the overall teaching provided by the present disclosure of the invention. the invention. Therefore, the specific arrangements and / or methods described herein are intended to be given by way of illustration only, with no intention of limiting the scope of the invention.

Claims (15)

claims 1. Safety valve for inflatable envelope of synthetic film, comprising a first film, synthetic, part of or being applied against a wall of the inflatable envelope, the first film being provided with an orifice, a shutter body cooperating with the orifice and having a first face facing the orifice and a second face diverted from the orifice, characterized by a second film, elastomeric, joined to the first film on the periphery of the shutter body, the shutter body being fixed to the first or second film by a fixation and constrained in a closed position by the initial tension to the mounting of the second film. 2. Safety valve according to claim 1, characterized in that the fastener fixing the shutter body comprises one or more joints glued or welded. 3. Safety valve according to claim 1 or 2, characterized in that the fixing fixing the shutter body comprises a anchoring element in the form of pin, mushroom or rivet. 4. Safety valve according to any one of claims 1 to 3, characterized in that the second film is joined to the first film at the periphery of the shutter body by a seal glued or sealed on the entire circumference of the shutter body and in that the second film comprises at least one perforation. 5. Safety valve according to any one of claims 1 to 3, characterized in that the second film is joined to the first film at the periphery of the shutter body by a bonded or discontinuous welded seal defining a gas exhaust channel between the first and second films. 6. Safety valve according to any one of claims 1 to 5, characterized in that the shutter body has the shape of a lens, a router, a truncated cone or a disk. 7. Safety valve according to any one of claims 1 to 6, characterized in that the fixing fixing the shutter body is arranged to allow the second film to bulge in case of overpressure by sliding on at least a portion of the obturator body, the second film being provided with at least one perforation located in an area which due to the sliding caused by the bulge separates from the obturator body. 8. Safety valve according to any one of claims 1 to 7, characterized in that the fixing fixing the shutter body is arranged locally and centrally on the second face of the shutter body and fixed the shutter body to the second film so as to allow the sliding of the second film on the shutter body in an annular zone around the fastening and thereby an expansion of the second film relative to the shutter body. 9. Safety valve according to claim 8, characterized in that the second film comprises at least one perforation in said annular zone. 10. Safety valve according to any one of claims 1 to 8, characterized by a valve seat comprising a flange-shaped portion attached to the first film and a cylindrical portion arranged coaxially with the orifice, the shutter body being configured of so as to slide axially in the cylindrical portion between an open position and the closed position. 11. Safety valve according to any one of claims 1 to 10, characterized in that the thickness of the first and second films is between 1 pm and 250 pm. 12. Safety valve according to any one of claims 1 to 11, characterized by a grease or a sealing oil between the obturator body and the first film and / or between the obturator body and the second film. 13. Safety valve according to any one of claims 1 to 12, characterized by a reinforcing member stiffening the first film around the orifice, the edge of which serves as a valve seat. 14. Inflatable plastic film envelope, characterized by one or more safety valves according to any one of claims 1 to 13. 15. Packaging, inflatable spatial structure, stratospheric or ionospheric balloon, tent, transport enclosure, greenhouse or clean room comprising one or more inflatable envelopes according to claim 14.