JP2008115633A - Double air membrane structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the rigidity of a double air membrane structure against short term loading such as wind pressure, and to solve the problems peculiar to the double air membrane structure such as higher maintenance/administrative expenses for a blower or the like, and rupture phenomenon of a membrane, and necessity of reinforcement. <P>SOLUTION: This double air membrane structure (1) is so constructed that a number of cores 4 are housed in a transmembrane area 5 of flexible membranes 2, 3. A suction pipe 7 communicates with the transmembrane area, and a suction means 8 sucks air in the transmembrane area. A sealing means 9 functions to keep the negative pressure of the transmembrane area. The transmembrane area is decompressed so that the core and the flexible membrane closely adhere to each other and the cores closely adhere to each other. The core is formed of an air sac obtained by enclosing gas in the flexible membrane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a double air membrane structure, and more particularly, to a double air membrane structure configured to maintain air pressure acting between flexible membranes to maintain a shape. is there.

  There is known an air film structure (pneumatic structure) that uses air pressure to stabilize the form of the film body by applying tension to the film surface and to ensure the resistance to external loads such as wind and snow by the tension of the film surface. Yes. The air film structure is classified into a single air film structure and a double air film structure according to a difference in a method of confining air. The single air membrane structure is a membrane structure of a system that holds the membrane in a predetermined shape such as a dome by the air pressure of the indoor space, and the double air membrane structure confines air between the double membranes, and the air pressure between the membranes It is a film structure of a system that obtains the tension of the film.

  The single air film structure is advantageous in terms of lightness, flexibility, natural light utilization, etc., but it is necessary to control, maintain and manage the air pressure of large volume indoor spaces and maintain the airtight state of indoor spaces. This is disadvantageous in terms of the necessity of an airtight structure of the opening for the purpose. On the other hand, the double air membrane structure is advantageous over the single air membrane structure in that the space between the double membranes is pressurized so that the indoor space can be set at normal pressure (atmospheric pressure). .

For example, the arch or dome structure of the double air membrane structure is, for example, the World Exposition held in 1970 (Osaka World Expo, EXPO'70) and the International Science and Technology Exposition held in 1985 (TSUKUBA EXPO '85). Are used as roof structures for exhibition halls. The structure of such a conventional double air membrane structure is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 7-293046, 10-159392, 11-36667, and 2003-82887. ing.
JP 7-293046 A JP 10-159392 A JP-A-11-36667 JP 2003-82887 A

  In the conventional double air membrane structure, air is injected into the space between the double membranes, and the region between the double membranes is maintained and managed at a positive pressure or a positive pressure. It has been pointed out that an out-of-plane tensile force acts on the joint between the fallen thread and the membrane that interconnects the membrane, the fallen thread and the membrane junction are easily damaged, and the occurrence of a peeling phenomenon between the outer skin and the partition wall is pointed out. Yes.

  The conventional double air membrane structure is also relatively low in rigidity against short-term loads such as wind pressure, and therefore, there is a need for reinforcement and restrictions on the form and scale of the structure. On the other hand, if the internal pressure between the membranes is set to a high pressure in order to improve the horizontal rigidity of the double air membrane structure, the operating cost of the blower is increased, the membrane may explode, the high stress acting on the constituent members, and the high internal pressure are resisted. Problems such as the need for reinforcement and the complexity of the structure associated with the reinforcement arise.

  The present invention has been made in view of such problems, and improves the rigidity of the double air membrane structure against short-term loads such as wind pressure, and increases the maintenance and management costs of the blower, etc., and the membrane explosion phenomenon It aims at solving the problems peculiar to the double air membrane structure such as necessity of reinforcement.

In order to achieve the above object, the present invention provides a double air membrane structure that maintains the shape by maintaining the air pressure acting between the first and second flexible membranes.
A large number of cores are accommodated in an intermembrane region formed between the flexible membranes having airtightness, the intermembrane region is decompressed, and the core and the flexible membrane are brought into close contact with each other. Provided is a double air membrane structure characterized in that they are in close contact with each other.

  According to the said structure of this invention, each core contacts an adjacent core and a flexible film | membrane by the differential pressure of the pressure of an intermembrane area | region, and atmospheric pressure. The contact pressure between the core and the flexible membrane acts to maintain the position of the core, and the contact pressure between the cores acts to increase the shear rigidity (displacement resistance) between the cores and integrate the entire core. To do. Therefore, according to the double air membrane structure of the present invention, an integrated structure composed of a large number of cores pressed against each other and a flexible membrane in surface contact with the cores under pressure is realized. The inventor's experiment has revealed that the double air film structure having such a configuration exhibits high rigidity with respect to an in-plane load acting as a shearing force. Therefore, when such a double air membrane structure is applied to a roof structure, the roof structure exhibits high rigidity against short-term loads such as wind pressure. Further, the shear resistance and contact pressure of the contact surface obtained by the pressure-contact between the cores give the double air membrane structure out-of-plane rigidity that resists its own weight and snow load.

  Moreover, according to the double air membrane structure of the said structure, since the rigidity of the double air membrane structure with respect to a short-term load can be improved, without using an excessive capacity | capacitance or an operating load blower, it accompanies horizontal rigidity improvement. Increases in maintenance and management costs for blowers and the like can be suppressed.

  Furthermore, in the double air membrane structure having the above-described configuration, the expansion force accompanying the pressure reduction in the intermembrane region acts on each core, while the contraction force due to the pressure contact between the adjacent core and the flexible membrane acts on each core. That is, the expansion force and the contraction force acting on each core act so as to cancel each other, so that the explosion of the core or the breakage / damage of the core skin can be prevented.

  In addition, in the double air membrane structure having the above-described configuration, it is not necessary to dispose a reinforcing material such as a drop thread or a partition wall in the intermembrane region, so that the configuration of the double air membrane structure can be simplified.

  Moreover, according to the double air membrane structure of the said structure, since the form of a structure is fixed by deaeration of an intermembrane area | region, the quantity, arrangement | positioning, form, etc. of a core can be set arbitrarily. This greatly improves the degree of design freedom regarding the structure shape of the double air membrane structure. In addition, in the double air membrane structure having the above configuration, the shape is fixed by deaeration of the intermembrane region, but the shape retention force can be released by supplying air to the intermembrane region. Therefore, it is possible to relatively easily adjust the form of the structure after construction or change the form.

  According to the present invention, the double air membrane structure improves the rigidity of the double air membrane structure against short-term loads such as wind pressure, increases the maintenance and management costs of the blower and the like, the membrane explosion phenomenon, the necessity of reinforcement, etc. Problems unique to the structure can be solved.

  According to a preferred embodiment of the present invention, the double air membrane structure includes a suction pipe that communicates with the intermembrane area, and a suction means such as a suction fan or a blower that sucks air in the intermembrane area via the suction pipe. And a sealing means for maintaining a negative pressure in the intermembrane region. The sealing means includes, for example, a check valve or a backflow prevention valve interposed in the suction pipe, or a valve or a sealing plug that closes the suction port in the intermembrane region.

  If desired, a flexible membrane made of a transparent or translucent material is used, and a structure with a wide variety of visual variations is realized by appropriately selecting the material, form, size, color, pattern, etc. of the core. be able to.

  Preferably, the core is formed of a sphere in which a fluid, a fluid substance, or a viscous substance is enclosed in a flexible skin, and has a deformability with respect to an external force. More preferably, the core is composed of an air sac in which a gas such as air or an inert gas (helium or the like) is enclosed in a hermetic hollow sealed body of a flexible membrane. The air sac has a deformability with respect to an external force, is in close contact with each other when the intermembrane region is decompressed, and is generally deformed into a polyhedron so as to be in surface contact with the adjacent air sac. In the film of the flexible membrane, an expansion force due to the reduced pressure in the intermembrane region acts, and a contraction force due to the pressure contact with the adjacent air sac and the membrane acts. The expansion force acting on the air sac membrane is at least partially counteracted by the contractile force acting on the air sac membrane. Therefore, the explosion of the air sac or the breakage / damage of the air sac film is suppressed by the contractile force acting on the air sac.

  The air sac is deformed and fluctuates in response to an external force or impact, and absorbs or buffers the external force or impact. Therefore, the double air membrane structure of the present invention can be used as an external force absorbing means or an impact buffering means. Moreover, since the air sac encapsulating gas exhibits high heat insulation performance, the double air membrane structure of the present invention can be used as heat insulation means.

  The double air membrane structure of the present invention can be preferably applied to a roof structure such as an arch or a dome, or a wall of a structure. However, by utilizing the properties of such a double air membrane structure, a vehicle body or a bumper is used. The double air membrane structure of the present invention may be applied to a body part such as a body, a structure of a play facility, a part or member, various event supplies, a fine art work, and the like.

  A gel material, a granular material, a viscous material, or the like may be enclosed in the core. A core encapsulating such a substance exhibits physical properties different from those of an air sac enclosing air or the like with respect to deformability against external force.

  As a modification, the core may be formed of a foamed resin molded body, a resin cured body such as a thermosetting resin or a photocurable resin, or a rigid body such as a metal or ceramic. Even when such a relatively high-rigidity core is accommodated in the intermembrane region, by appropriately designing the material of the flexible membrane, the suction pressure during decompression, etc., the pressure contact state between the cores is maintained, The integrity of the double air membrane structure can be maintained.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 to 3 are a plan view and a sectional view showing a basic configuration of a double air membrane structure according to the present invention.

  As shown in FIG. 1, the double air membrane structure 1 is composed of upper and lower flexible membranes 2, 3 and a large number of air sac 4 inserted in an intermembrane region 5 between the membranes 2, 3. The flexible films 2 and 3 are made of, for example, a resin film such as polyester resin or fluororesin, and have the same shape in plan view. The outer edge portions of the flexible films 2 and 3 are restrained in an airtight state by the frame body 6.

  1 to 3 show only the portion of the frame body 6 that restrains the edge portions on both sides of the flexible membranes 2 and 3, but the frame body 6 is the whole of the flexible membranes 2 and 3. It extends over the circumference. The air sac 4 is composed of a spherical balloon (balloon) filled with air in an airtight outer skin having flexibility, and is accommodated in the intermembrane region 5 in an independent state. The outer skin of the air sac 4 is made of a resin film or a resin sheet, for example, a resin film such as a polyester resin or a fluororesin.

  The initial pressure in the intermembrane region 5 is substantially the same pressure as the surrounding atmosphere (in this example, atmospheric pressure). A suction tube 7 for sucking air in the intermembrane region 5 is inserted into the intermembrane region 5. The suction port 7 a of the suction pipe 7 opens into the intermembrane region 5. The suction pipe 7 extends outside the membrane and is connected to the suction port of the suction fan 8. The suction fan 8 is a forced exhaust fan that exhausts the air in the intermembrane region 5 to the atmosphere. An electric motor (not shown) of the suction fan 8 is connected to a drive power source (not shown). A check valve or a control valve 9 for preventing backflow that prevents backflow of air from the suction fan 8 to the intermembrane region 5 is interposed in the suction pipe 7.

  When the suction fan 8 is operated, the exhaust suction pressure of the suction fan 8 acts on the intermembrane region 5 via the suction pipe 7. The air in the intermembrane region 5 is sucked into the suction fan 8 through the suction pipe 7 and released to the atmosphere. The intermembrane region 5 is depressurized, and the upper and lower membranes 2 and 3 approach each other. At the same time, the air sac 4 approaches each other, and the gap between the air sac 4 is reduced. As the intermembrane region 5 is depressurized, the membranes 2 and 3 start to come into close contact with the air sac 4, and the air sac 4 starts to come into point contact with each other and become integrated. Such a state at the time of decompression is shown in FIG. If desired, the air sac 4 may be forcibly moved when the intermembrane region 5 is decompressed.

  When the operation of the suction fan 8 is continued, the intermembrane region 5 is further depressurized, and the pressure in the intermembrane region 5 is stabilized at a pressure corresponding to the exhaust capability of the suction fan 8. At the time of depressurization of the intermembrane region 5, the expansion force related to the depressurization of the intermembrane region 5 acts on each air sac 4. At the same time, contraction force acts on each air sac 4 as a reaction that occurs when each air sac 4 is pressed against the adjacent air sac 4 and the membranes 2 and 3. The expansion force acting on the film of the air sac 4 at the time of decompression is at least partially canceled by the contraction force acting on the film of the air sac 4. Therefore, the explosion of the air sac 4 or the damage / damage of the air sac film due to the expansion force at the time of decompression is suppressed or alleviated by the contraction force acting on the air sac 4.

  A state in which the intermembrane region 4 is substantially completely deaerated is shown in FIG. The air sac 4 is in surface contact with the adjacent air sac 4 and the membranes 2 and 3 and is generally deformed into a polyhedron. Each air sac 4 is consolidated as the differential pressure between the pressure in the intermembrane region 5 and the atmospheric pressure increases. As a result, the contact pressure between the air sac 4 increases, and the contact pressure between the air sac 4 and the membranes 2 and 3 increases. The contact pressure between the membranes 2 and 3 and the air sac 4 acts so as to maintain the position of the air sac 4, and the contact pressure between the air sac 4 increases the shear rigidity (displacement resistance) between the air sac 4 to increase the number of air sac 4. Are consolidated and integrated. Thus, an integral double air membrane structure 1 composed of the flexible membranes 2 and 3 and a large number of air sac 4 disposed in the degassed intermembrane region 5 is formed.

  In the conventional double air membrane structure, in order to maintain the shape, a drop thread connecting the upper and lower membranes is disposed in the intermembrane region, and a tensile force acts on the drop yarn. In the double air membrane structure 1 of the invention, the differential pressure between the atmospheric pressure and the pressure in the intermembrane region 5 acts on the upper and lower membranes 2 and 3, and the shape of the double air membrane structure 1 is maintained by this differential pressure. Is done.

  4 and 5 are a front view and a cross-sectional view showing the configuration of the specimen used in the shear deformation experiment of the double air membrane structure 1, and FIG. 6 is a diagram showing the experimental result of the shear deformation experiment. .

  4A and 4B show a specimen in which a square frame 56 is accommodated in an airtight bag 50 of a flexible resin film as a comparative example. The frame body 56 is made of a wooden frame in which four belt-like wooden boards are assembled to a square frame, and the connecting portion (corner portion) of the frame body 56 is joined by a pin-joint-type joining structure that does not exhibit substantial shear rigidity. Has been.

  A specimen 51 shown in FIGS. 4C and 4D has an air sac 54 arranged in a square frame 56 vertically and horizontally (orthogonal arrangement), and the frame 56 and the air sac 54 are made of a flexible resin. It has the structure accommodated in the airtight bag 50 of a film. A specimen 51 ′ shown in FIGS. 5 (A) and 5 (B) has a staggered arrangement of air sac 54 in a square frame 56, and the frame 56 and air sac 54 are placed in an airtight bag 50 of a flexible resin film. It has the structure accommodated in. The front portion of the airtight bag 50 corresponds to the above-described flexible membrane 2, and the back portion of the airtight bag 50 corresponds to the above-described flexible membrane 3.

  A suction tube 57 connected to the suction fan 58 is inserted into the intermembrane region 55, and a suction port 57 a of the suction tube 57 opens into the intermembrane region 55. A check valve or a control valve 59 for preventing backflow is interposed in the suction pipe 57. By the operation of the suction fan 58, the intermembrane region 55 is depressurized.

  In the shear deformation experiment, the dimensions of the frame 56 are set such that the width W = 450 mm (internal dimension), the total height H = 450 mm (internal dimension), the depth D = 90 mm, and the initial diameter R of the air sac 4 is 90 mm. Was set. The suction fan 58 was activated, and the intermembrane region 55 was depressurized under the maximum exhaust capacity of the suction fan 58.

  FIG. 4G shows a state where the intermembrane region 55 of the specimen according to the comparative example (FIGS. 4A and 4B) is decompressed. The airtight bags 50 are in close contact with each other in the intermembrane region 55. 4 (E) and FIG. 4 (F) show a state in which the specimens 51 in which the air sac 54 are arranged in a staggered manner are shown in FIG. 4 (E) and FIG. 4 (F). ) And FIG. 5 (D). The front portion and the rear portion of the airtight bag 50 were in surface contact with the air sac 4, and the air sac 4 was in close contact with the adjacent air sac 4 and deformed into a polyhedron.

  The specimens 51 and 51 ′ after deaeration are compressed in a diagonal direction as shown by an arrow P (compression load) in FIGS. 4E and 5C, and the frame body 56 and the specimens 51 and 51 ′. The deformation (the amount of displacement in the diagonal direction) was measured. Also in the specimen according to the comparative example, as shown by an arrow P (compression load) in FIG. 4A, the diagonal compression load P is applied to the frame 56, and the deformation of the frame 56 (displacement in the diagonal direction). Amount) was measured. The measurement result of the displacement is shown in FIG.

  As shown in FIG. 6, the test sample of the comparative example (FIG. 4 (G)) that does not contain the air sac 4 was broken at a compressive load P = 50N. However, although the specimen 51 with the orthogonally arranged air sac 54 increases the amount of displacement as the compressive load P increases, the specimen 51 is destroyed by the compressive load P exceeding the compressive load P = 100 N, and the staggered air sac 54 is embedded. Although the specimen 51 ′ increased in displacement as the compressive load P increased, the specimen 51 ′ was broken at the compressive load P exceeding 200N.

  As a result of such shear deformation experiment, the deaerated specimens 51 and 51 ′ containing the air sac 54 are sheared much higher than the comparative specimen (FIG. 4G) without the air sac 54. It was found to exhibit rigidity. That is, the above-described double air membrane structure 1 composed of the flexible membranes 2 and 3 and a large number of air sac 4 arranged in the degassed intermembrane region 5 has a high shear which can withstand a load in the in-plane direction. It was confirmed to exhibit rigidity.

  Further, the experimental results show that the shear rigidity is different depending on the disposition of the air sac 54, and the double air membrane structure 1 including the air sac 4 in the zigzag arrangement has the double air film structure 1 including the air sac 4 in the orthogonal arrangement. It shows that it exhibits high shear rigidity compared to.

  FIG. 7 is a photograph showing the form of the deaerated double air membrane structure 1 in which the air sac 4 is accommodated between the flexible membranes 2 and 3. The air sac 4 is arranged in a staggered arrangement, the flexible membranes 2 and 3 are in close contact with the air sac 4, and the air sac 4 are in surface contact with each other and generally deformed into a polyhedron.

  FIG. 8 is a schematic sectional view showing a dome-like roof structure to which the double air membrane structure of the present invention is applied, and FIG. 9 is a partially enlarged sectional view of the roof structure shown in FIG.

  The dome 10 having a double air film structure shown in FIGS. 8 and 9 is constructed on an annular base 16 corresponding to the frame 6 described above. The outer edge portions of the flexible films 12 and 13 are restrained in an airtight state by the frame body 6. A large number of air sac 14 made of a resin spherical balloon enclosing air is accommodated between the flexible membranes 12 and 13. A suction tube 17 for sucking air in the intermembrane region of the flexible membranes 12 and 13 opens in the intermembrane region, and the suction pressure of the suction fan 18 acts on the intermembrane region. A check valve or a control valve 19 for preventing backflow is interposed in the suction pipe 17. By the operation of the suction fan 18, the intermembrane region is decompressed to a state close to a vacuum state. The valve 19 functions to maintain a negative pressure or a negative pressure formed in the intermembrane region.

  FIG. 10 is a schematic perspective view of an arched roof structure formed by a double air membrane structure, and FIG. 11 is an enlarged exploded view of a roof surface part of the roof structure shown in FIG.

  The roof structure shown in FIGS. 10 and 11 includes an arch 20 having a double air film structure in which an outer edge portion is restrained in an airtight state by a base portion 26. The base portion 26 has a rigid structure in which left and right horizontal base portions 26a and an arch portion 26b extending in a semicircular shape on the wife side are integrated. A large number of air sac 24 made of a resin spherical balloon filled with air is accommodated between the flexible membranes 22 and 23. A suction tube 27 for sucking air in the intermembrane region of the flexible membranes 22 and 23 opens to the intermembrane region, and the suction pressure of the suction fan 28 acts on the intermembrane region. A check valve or a control valve 29 for preventing backflow is interposed in the suction pipe 27. By the operation of the suction fan 28, the intermembrane region is decompressed to a state close to a vacuum state. The valve 29 functions to maintain a negative pressure or a negative pressure formed in the intermembrane region.

  In such a dome 10 and arch 20, as a result of the depressurization of the intermembrane region, the air sac 14 comes into surface contact with the adjacent air sac 14 and the membranes 12 and 13 and is generally deformed into a polyhedron. Initially, a large number of independent air sacs 14 are consolidated as the pressure difference between the pressure in the intermembrane region and the atmospheric pressure increases. Due to the increase in the contact pressure between the air sac 14 and the increase in the contact pressure between the air sac 14 and the membranes 12, 13, the many air sac 14 are consolidated together, and the air sac 14 and the membranes 12, 13 are integrated. As a result, a high shear rigidity (slip resistance) that can withstand a vertical load such as the weight of the dome 10 or the arch 20 and a snow load and resist short-term loads such as wind pressure is generated between the air bags 14.

  Thus, the dome 10 and the arch 20 having the double air membrane structure of the present invention mainly adhere to each other with the shape retention force of the flexible membranes 12, 13, 22, and 23 that are in close contact with a large number of air bags 14 and 24. The shear rigidity (displacement resistance) acting between the air bags 14 and 24 resists vertical loads such as its own weight and snowfall, and exhibits high rigidity against short-term loads such as wind pressure.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. Is possible.

For example, in the above embodiment, an air sac in which air is sealed in an airtight resin outer shell is used as a core, but a spherical cell in which a liquid, a gel-like substance, a granular substance, a viscous substance or the like is enclosed in the outer skin, etc. The sealed body may be used as the core.
In the above embodiment, a controller for detecting the pressure in the intermembrane region and controlling the pressure in the intermembrane region may be provided in the control system of the suction fan.

  The double air membrane structure of the present invention is preferably applied to a roof structure such as an arch or dome, or a wall of a structure.

  The double air membrane structure of the present invention may be applied to a vehicle body part such as a vehicle body or a bumper, a structure of a play facility, a part or member, various event supplies, a fine art work or the like.

  Since the structure to which the double air membrane structure of the present invention is applied can be mass-produced relatively easily by standardization of the core, etc., it is suitable for practical use and can be applied to various uses. Its practicality is extremely high.

It is the top view and sectional view showing the basic composition of the double air membrane structure concerning the present invention, and the state before depressurizing the field between membranes is shown. It is the top view and sectional drawing of the double air film | membrane structure shown in FIG. 1, and the pressure reduction process of the area | region between membranes is shown. It is the top view and sectional drawing of the double air film | membrane structure shown in FIG.1 and FIG.2, and the state after the film | membrane area pressure reduction is shown. It is the front view and sectional drawing which show the structure of the specimen of the air bag orthogonal arrangement | sequence used for the shear deformation experiment of the double air film | membrane structure. It is the front view and sectional drawing which show the structure of the test piece of the air bag zigzag arrangement | sequence used for the shear deformation experiment of the double air film | membrane structure. It is a diagram which shows the experimental result of a shear deformation experiment. It is a photograph which shows the form of the double air membrane structure of the deaeration state which accommodated the air bag between the flexible membranes. It is a schematic sectional drawing which shows the dome-shaped roof structure to which the double air membrane structure of this invention is applied. It is a partial expanded sectional view of the roof structure shown in FIG. It is a schematic perspective view of the arched roof structure to which the double air membrane structure of the present invention is applied. It is a roof surface part expansion expanded view of the roof structure shown in FIG.

Explanation of symbols

1 Double air membrane structure 2 Flexible membrane 3 Flexible membrane 4 Air sac (core)
5 Intermembrane region 6 Frame 7 Suction pipe 8 Suction fan 9 Check valve or control valve 10 for preventing backflow Dome (double air membrane structure)
12 Flexible membrane 13 Flexible membrane 14 Air sac (core)
16 Base 17 Suction pipe 18 Suction fan 19 Check valve or control valve 20 for preventing backflow Arch (double air film structure)
22 Flexible membrane 23 Flexible membrane 24 Air sac (core)
26 Base 27 Suction tube 28 Suction fan 29 Check valve or control valve for backflow prevention

Claims (4)

In the double air membrane structure that maintains the air pressure acting between the first and second flexible membranes and maintains the shape,
A large number of cores are accommodated in an intermembrane region formed between the flexible membranes having airtightness, the intermembrane region is decompressed, and the core and the flexible membrane are brought into close contact with each other. Double air membrane structure characterized by being in close contact with each other.   A suction tube communicating with the intermembrane region, a suction means for sucking air in the intermembrane region via the suction tube, and a sealing means for maintaining a negative pressure in the intermembrane region. The double air membrane structure according to claim 1, wherein   The double air membrane structure according to claim 1 or 2, wherein the core is formed of a sphere in which a fluid, a fluid substance, or a viscous substance is enclosed in a flexible skin, and has a deformability with respect to an external force.   The double air membrane structure according to claim 1 or 2, wherein the core comprises an air sac in which gas is sealed in an airtight flexible membrane.

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