CURVED AIR BEAM

Abstract

The invention relates to an inflatable beam intended for producing a frame for a shelter, extending in a longitudinal direction, comprising two flat faces, respectively called the upper and lower faces, each consisting of a fabric impervious to inflation gases, the upper face being connected to the lower face by a connecting structure comprising flexible wire elements, called stays, extending between the upper face and the lower face, regularly spaced in the longitudinal and transverse directions of the beam, characterized in that the ratio of the modulus of the lower face Einf to the modulus of the upper face Esup, measured in the longitudinal direction of the beam, is greater than or equal to 7 and in that the modulus of the upper face in the longitudinal direction of the beam is less than or equal to 350 MPa.

Description

Title of the invention: CURVED INFLATABLE BEAM Technical field of the invention

[0001] The subject of the invention is an inflatable beam intended for producing a frame for a shelter comprising two flat faces connected by a supporting structure, the beam having a curvature when it is inflated. Prior art

[0002] Shelters or equipment comprising inflatable frames have been known for a long time. For example, document FR 2 621 944 presents an inflatable structure capable of sheltering an aircraft, this structure being made up of a plurality of inflatable beams.

[0003] Inflatable frames are often made up of one or more cylindrical beams, the desired shapes being obtained by welding a plurality of straight elements and / or by preforming the constituent elements of these frames. Document FR 2 741 373 discloses inflatable beams intended in particular for producing a frame for a shelter which can be produced according to these two embodiments. The curvature can in particular be obtained by securing stiffening means to one of the faces in order to limit its elongation.

[0004] Preforming allows a curved shape to be obtained, but makes storage of the structures more difficult. Welding a set of straight elements also allows a curved shape to be approached in a simple manner but does not solve the problem of the size of the deflated element, while requiring particular vigilance at the level of the welding points so as not to generate problems of sealing or fragility. Indeed, the load capacity of the structures is directly linked to the inflation pressure. The higher it is, the more the welding points and the materials will be stressed.

[0005] Document US 2,743,510 discloses an element that takes a curved shape when inflated. The curvature of the element is obtained by making one of the faces using a non-extensive fabric, while the other face is made using a fabric that can contract or expand when subjected to heat treatment, for example an untreated nylon fabric. When the gas-tight coating is vulcanized, the face that can contract or expand takes its shape, thus giving its curvature to the element. Due to this method of production, the curvature obtained is irreversible, the upper and lower faces being, after heat treatment, of different dimensions, and cannot be adjusted.

[0006] Document US 2009 / 0049757 proposes to improve the disclosed inflatable element in US 2,743,510, and in particular its buckling resistance in order to make such inflatable elements not only easy to store, but also capable of supporting the weight of, for example, a surfer. One of the faces of the inflatable element is stiffened by applying to it a reinforcing structure that is as rigid as possible, for example a high modulus sheet made of Kevlar, glass fibers, metal alloys, sufficiently flexible to be able to be rolled with the element. The other face can also be stiffened in order to further increase the buckling resistance of the assembly. This document does not aim to obtain an element whose curvature can be adjusted during inflation.

[0007] Thus, to the applicant's knowledge, there is no inflatable beam that can be used in particular for producing a frame for a shelter that is simple to deploy and store, the curvature of which can be easily adapted and allows the carrying of significant loads at a given pressure. Definitions

[0008] The carbon-containing compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. This includes in particular polymers, coating resins, etc.

[0009] By "substantially parallel" or "extending substantially along" is meant that the angle formed by the two directions in question is less than 10°, preferably less than 5°, more preferably less than 2° and very preferably less than or equal to the error in measuring the angle by a suitable method.

[0010] Two lengths are substantially equal if they are equal, to the measurement tolerance usually used to measure such lengths or to the tolerance of the manufacturing process using these elements of substantially the same length.

[0011] By plastic deformation of an element, it is meant, as known to those skilled in the art, that when this element is stretched in its general direction, its deformation is irreversible. In other words, it does not return to its initial shape when the stress is stopped.

[0012] A fabric is said to be deformable if at least a portion of the surface of said fabric is deformable. Detailed description of the invention Inflatable beam

[0013] The invention relates to an inflatable beam intended for producing a frame for a shelter, extending in a longitudinal direction, comprising two flat faces, respectively called upper and lower, each being made of a fabric sealed against inflation gases, the upper face being connected to the lower face by a connecting structure comprising flexible wire elements, called stays, extending between the upper face and the lower face, regularly spaced along the longitudinal and transverse directions of the beam, characterized in that the ratio of the modulus of the lower face Einf to the modulus of the upper face Esup, measured along the longitudinal direction of the beam, is greater than or equal to 7 and in that the modulus of the upper face along the longitudinal direction of the beam is less than or equal to 350 MPa.

[0014] The beam is inflatable. The upper and lower faces are therefore connected by their edges by transverse faces impermeable to the inflation gases. In a preferred arrangement, the upper and lower faces are welded to each other along their longitudinal edges.

[0015] The term "longitudinal modulus" refers to the modulus measured along the longitudinal direction of the inflatable beam. The term "transverse modulus" refers to the modulus measured along the transverse direction of the inflatable beam, the transverse direction being substantially perpendicular to the longitudinal direction.

[0016] When the beam is inflated, the upper face, whose longitudinal modulus is lower than that of the lower face, extends further and allows the beam to curve, forming an arch. The inflated beam has a deflection height H and a wheelbase length D (see [Fig. 5]). By wheelbase is meant, in a manner known to those skilled in the art, the distance D between the two ends (support points on the receiving surface of the beam) of the inflated beam in the longitudinal direction. By deflection height is meant, in a manner known to those skilled in the art, the maximum distance between the lower face of the beam and the horizontal plane (parallel to the receiving surface) passing through the two ends of the inflated beam.

[0017] The deflection rate r designates the ratio of the arrow height to the wheelbase length, r=H / D. It is possible to vary this deflection rate by varying the inflation pressure.

[0018] When the beam is made up of two flat faces, called respectively upper and lower, each being made up of a fabric impervious to inflation gases, the upper face being connected to the lower face by a connecting structure comprising flexible wire elements, called stays, extending between the upper face and the lower face, regularly spaced along the longitudinal and transverse directions of the beam, characterized in that the ratio of the modulus of the lower face Einf to the modulus of the upper face Esup, measured along the longitudinal direction of the beam, is greater than or equal to 7, the deflection rate is proportional to the inflation pressure: T=a-Pinflation (see [Fig.l]). This coefficient a is defined as the ease of arching the inflatable beam. The higher it is, the more the inflation pressure allows for arching. in an effective arch.

[0019] The inflatable beam comprises flexible wire elements, called stays, extending between the upper face and the lower face, regularly spaced along the longitudinal and transverse directions of the beam. Such a fabric comprising two faces and a connecting structure between these faces is well known in the state of the art and described for example in documents FR3124526 and US2009 / 0049757. Surprisingly, it has been discovered that the ease of arching the inflatable beam does not depend solely on the ratio of the longitudinal moduli of the upper face and the lower face, but also on the longitudinal modulus of the upper face. The longitudinal modulus of the lower face and the moduli of the upper and lower faces measured along the transverse direction of the beam mainly enable the beam to ensure the load bearing required for its use as a reinforcement.

[0020] [Fig. 2] compares the ease of arching an inflatable beam according to the invention and an asymmetrical cylindrical beam constructed from an upper face and a lower face identical to those of the beam according to the invention, these faces being connected edge to edge along the longitudinal direction of the asymmetrical cylindrical beam. The beam according to the invention and the asymmetrical cylindrical beam have the same section, this being measured in a plane perpendicular to the longitudinal direction of the beam.

[0021] In both cases, it is observed that the ease of arching evolves as a function of the longitudinal modulus of the upper face according to a power law, the beam according to the invention having a higher ease of arching for a given longitudinal modulus. In other words, for a given longitudinal modulus, the desired deflection will be achieved with a lower inflation pressure with the beam according to the invention than with a cylindrical beam. Consequently, for a given inflation pressure, it will be possible to use a fabric having a higher longitudinal modulus, thus allowing an overall higher load bearing. Upper and lower sides of the fabric

[0022] Preferably, the fabric of the upper face is a fabric comprising warp filamentary elements (Cl), substantially parallel to each other, regularly spaced at a pitch p measured in the transverse direction of the beam and extending in the longitudinal direction of the beam, weft filamentary elements (Tl), substantially parallel to each other and extending in a weft direction, different from the longitudinal direction of the beam, the modulus of said fabric, calculated according to Esup=ECi*SCi / (p*etissu), being less than or equal to 350 MPa, where ECi and SCi respectively represent the modulus, measured in accordance with standard ASTM D885-3, and the section of a warp filamentary element and etissu the thickness of the fabric. Preferably, the weft direction is substantially perpendicular to the longitudinal direction of the beam.

[0023] Preferably, the fabric of the lower face is a fabric comprising warp filamentary elements (C2), substantially parallel to each other, regularly spaced at a pitch p2 measured in the transverse direction of the beam and extending in the longitudinal direction of the beam, weft filamentary elements (T2), substantially parallel to each other and extending in a weft direction, different from the longitudinal direction of the beam, the modulus of said fabric being calculated according to Einf=EC2*Sc2 / (p2*etissuinf), where EC2 and SC2 respectively represent the modulus, measured in accordance with standard ASTM D885-3, and the section of a warp filamentary element and etissuinf the thickness of the fabric. Preferably, the weft direction is substantially perpendicular to the longitudinal direction of the beam.

[0024] Preferably, the modulus of the upper face measured in the longitudinal direction of the beam is less than or equal to 200 MPa, preferably less than or equal to 150 MPa, preferably less than or equal to 100 MPa.

[0025] The fabric of the upper face is characterized in that it is deformable in the longitudinal direction of the beam. By deformable, it is meant that the fabric can extend without breaking in at least the longitudinal direction of the beam. Thus and preferably, the fabric of the upper face is a fabric whose warp filamentary elements are plastically or elastically deformable when the beam is put under pressure. Preferably, the fabric of the upper face is a fabric whose warp filamentary elements are elastically deformable, which in particular allows on the one hand the beam to return to its initial shape when it is deflated, thus facilitating its storage and transport and on the other hand to adjust the curvature of the beam to the desired value by means of the inflation pressure.

[0026] Deformable fabrics are well known to those skilled in the art. The deformability of the fabric can be achieved by multiple means. For example, the deformability can be achieved by the weave of the fabric or by the nature of the stitches in the case of a knit. It can also be achieved by the nature of the warp thread elements and / or the weft thread elements.

[0027] Preferably, the fabric of the upper face is deformable in the longitudinal direction of the beam, and not deformable in the transverse direction of the beam.

[0028] In a preferred arrangement, when the fabric of the upper face is a woven fabric, this fabric comprises at least one warp filamentary element ED deformable in tension such that, for any filamentary element ED deformable in tension, there is an elongation AED, less than the elongation at break ARED, such that M1ED / M2ED<1, with M1 ED representing the modulus of the deformable filamentary element ED for any elongation less than or equal to K1xAED%, M2ED represents the modulus of the deformable filamentary element ED for any elongation greater than or equal to K2xAED%, ARED re showing the elongation at break of the ED element in %, with Kl ranging from 0.8 to 0.95, and K2 ranging from 1.05 to 1.2, the moduli M1ED, M2ED and the elongation at break ARED being measured according to ASTM D885-03.

[0029] Such a wire element ED exhibits a so-called “bi-module” behavior, known elsewhere to those skilled in the art, this element exhibiting a higher resistance to elongation when the elongation of the element ED is greater than AED than when this elongation is less than AED.

[0030] Such an element makes it possible to obtain a deformable fabric having low resistance to deformation at the start of inflation of the beam and high resistance to deformation when the internal pressure of the beam approaches the target inflation pressure, making it possible to obtain a beam which is both easy to shape, and therefore to position, and having good geometric stability once inflated.

[0031] Preferably, each wire element ED comprises first and second wire members. Preferably, each wire member has a different modulus and / or has a different length for a given length of wire element ED in order to obtain this bi-modulus behavior.

[0032] Preferably, the second wire member is substantially rectilinear, the first wire member being wound substantially in a helix around the second wire member.

[0033] Preferably, for each wire element ED, the second wire member has within the wire element ED an elongation before rupture greater than AED%, and the first wire member has an elongation before rupture within the wire element ED less than AED%.

[0034] Preferably, the fabric of the upper face and the lower face comprise, independently of one another, a material chosen from a polyester, a polyamide, a polyketone, a polyurethane, a natural fiber, a mineral fiber, a cellulosic fiber and an assembly of these materials, preferably chosen from a polyester, a polyamide, a polyketone, a polyurethane, a natural fiber, a cellulosic fiber and an assembly of these materials, more preferably chosen from a polyester, a polyamide and an assembly of these materials.

[0035] In a preferred arrangement, at least one of the faces comprises a flame retardant material, by its nature or by a flame retardant treatment.

[0036] Preferably, the ratio of the modulus of the upper face to the modulus of the fabric of the upper face, measured in the longitudinal direction of the beam, is less than or equal to 1.5, preferably less than 1.3, more preferably less than 1.2 and very preferably less than 1.1. In other words, it is the nature of the fabric, preferably the woven fabric, which contributes in the majority to the longitudinal modulus of the upper face, and not other elements possibly present in the su- upper, in particular gluing and waterproofing compositions.

[0037] As shown in [Fig. 3], the ease of arching varies, for a given longitudinal modulus of the upper face, depending on the ratio of the longitudinal modulus of the lower face to the longitudinal modulus of the upper face. Adjusting the ratio of the longitudinal moduli of the upper and lower faces alone is therefore not sufficient to ensure optimal arching of the inflatable beam, i.e. the best use of the inflation pressure. Excellent arching is obtained when the ratio of the modulus of the lower face E inf to the modulus of the upper face Esup, measured along the longitudinal direction of the beam, is greater than or equal to 7 and the modulus of the upper face measured along the longitudinal direction of the beam is less than or equal to 350 MPa.

[0038] Preferably, the ratio Einf / Esup0'5 is in the range from 50 to 200, preferably from 60 to 160, preferably from 120 to 150, preferably from 130 to 140. When this ratio is in this range, the optimal arching, corresponding to the best use of the inflation pressure, is obtained.

[0039] Preferably, the modulus of the lower face measured in the longitudinal direction of the beam is greater than or equal to 500 MPa, preferably greater than or equal to 750 MPa and preferably greater than or equal to 1000 MPa.

[0040] Preferably, the modulus of the upper face and the modulus of the lower face, measured in the transverse direction of the beam, are each greater than or equal to 300 MPa, preferably greater than or equal to 500 MPa. This modulus allows the beam to withstand the inflation pressure and to carry the load effectively.

[0041] Preferably, the inflation pressure is between 0.1 and 2.5 bar relative. Connection structure

[0042] The upper face of the beam according to the invention is connected to the lower face by a connecting structure comprising flexible wire elements, called stays, extending between the upper face and the lower face, regularly spaced along the longitudinal and transverse directions of the beam.

[0043] Each stay has a resting length h; and extends from an attachment point on the fabric of the upper face to an attachment point on the fabric of the lower face.

[0044] Preferably, the stays of the connecting structure are substantially parallel to each other when the beam is inflated. Preferably, each stay of the connecting structure has a resting length substantially equal to the average resting length h,„ of the stays.

[0045] By average resting length hm of the stays is meant the average of the resting lengths of the stays of the connecting structure, the total number of stays of the connecting structure of the panel according to the invention being equal to m, an integer strictly greater than 0. Thus, 1' _ J_yW! 1.. The total number of shrouds is adjusted depending on the desired stiffness effect. The elongations at break of the wire elements are measured according to the ASTM D885-03 standard. Preferably, the stays are distributed uniformly along the longitudinal and transverse directions of the beam, this distribution making it possible to obtain a uniform appearance of the beam once inflated.

[0046] By resting length of the stay, we mean the length of the stay in its main direction in the absence of any external stress exerted on the stay (other than atmospheric pressure). A stay at rest in its main direction is neither in extension nor in compression in this direction and therefore has zero elongation in this direction. Similarly and generally, by resting length of a wire element, we mean the length of the wire element in its main direction in the absence of any external stress exerted on the wire element (other than atmospheric pressure).

[0047] By wire element is meant any elongated element of great length relative to its cross-section, whatever the shape of the latter, for example circular, oblong, rectangular or square, or even flat, this wire element being able to be for example twisted or wavy. When its cross-section is of circular shape, the diameter of this section is preferably less than 5 mm, more preferably within a range going from 10 qm to 1.2 mm.

[0048] Each wire element of the connecting structure, in particular each stay which connects the internal faces of the first and second fabrics to each other, can be characterized geometrically by its resting length LP and by its average section SP, which is the average of the sections obtained by cutting the stay by all the surfaces parallel to the first and second fabrics and included between the first and second fabrics. In the most frequent case of a constant section of the wire element and the stay, the average section SP is equal to this constant section.

[0049] Each wire element of the connecting structure, in particular each stay, typically has a smallest characteristic dimension E of its average section SP, preferably at most equal to 0.02 times the average rest length hm of the stays and a shape ratio R of its average section SP preferably at most equal to 3. A smallest characteristic dimension E of the average section SP of the supporting element at most equal to 0.02 times the average rest length hm of the stays excludes any massive supporting element having a large volume.

[0050] A shape ratio R of its mean section SP at most equal to 3 means that the largest characteristic dimension V of its mean section SP is at most equal to 3 times the smallest characteristic dimension E of its mean section SP. As a of examples, a circular mean section SP, having a diameter equal to d, has an aspect ratio R=l, a rectangular mean section SP, having a length V and a width V', has an aspect ratio R=V / V', and an elliptical mean section SP, having a major axis B and a minor axis B', has an aspect ratio R=B / B'.

[0051] The average resting length hm of the stays is preferably greater than 8 mm, preferably between 10 and 2000 mm, preferably between 10 and 1000 mm, preferably between 10 and 500 mm, very preferably between 30 and 150 mm. This average resting length can be adjusted according to the intended use of the beam according to the invention.

[0052] A stay has a wire-like mechanical behavior, that is to say that it can only be subjected to extension or compression forces along its mean line. Each stay of the connecting structure is flexible. That is to say that it can bend without breaking or plastically deforming. The connecting structure is such that it cannot support by itself the spacing between the two faces of the beam according to the invention. Without internal pressure, the two faces can move towards each other without effort.

[0053] In a preferred embodiment, each wire element of the connecting structure is textile. By textile, it is meant that each wire element of the connecting structure is non-metallic, for example made of a material chosen from a polyester, a polyamide, a polyketone, a polyvinyl alcohol, a cellulose, a mineral fiber, a natural fiber, an elastomeric material or a mixture of these materials. Among the polyesters, mention will be made, for example, of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PPT (polypropylene terephthalate), PPN (polypropylene naphthalate). Among the polyamides, mention will be made of aliphatic polyamides such as polyamides 4-6, 6, 6-6 (nylon), 11 or 12 and aromatic polyamides such as aramid.

[0054] For example, each filamentary element of the connecting structure is a textile assembly comprising one or more monofilament or multifilament textile fibers, twisted together or not. Thus, in one embodiment, it will be possible to have an assembly in which the fibers are substantially parallel to each other. In another embodiment, it will also be possible to have an assembly in which the fibers are wound in a helix such as a twist or an overtwist. In yet another embodiment, each filamentary element is made of a monofilament. Each monofilament or multifilament fiber has a diameter which can range from a few hundredths of a millimeter to a few millimeters, typically between 0.001 and 5 mm, preferably between 5 and 50 μm, preferably between 10 and 40 μm.

[0055] In a preferred arrangement, each filamentary element of the bonding structure is a multi-filament textile fiber, each fibril constituting the textile fiber having a diameter between 0.001 and 0.5 mm, preferably between 5 and 50 μm, preferably between 10 and 40 μm. Such wire elements have the advantage of being more flexible than monofilament wire elements. The beam according to the invention comprising such wire elements can thus be stored very compactly by bringing the upper and lower internal faces closer to each other. Preferably in this arrangement, the wire elements are arranged in such a way that the stays cannot, by themselves, maintain the spacing between the internal faces of the two faces when the beam is subjected to a compressive force, that is to say to a force exerted on the beam perpendicular to its surface and in its direction.This arrangement is achieved by adjusting the guy density, expressed as the number of guys per square meter, and / or by adjusting the flexibility of the guys through the thread count or chemical nature of the wire elements. However, the guys must have sufficient strength to maintain the spacing between the two internal faces of the beam faces once the beam is pressurized by means of an inflation gas. This strength can be adjusted by the guy density and / or their toughness and / or their chemical nature.

[0056] In another embodiment, each wire element of the connecting structure is metallic, for example a metallic monofilament or an assembly of metallic monofilaments, each metallic monofilament having a diameter which can range from a few hundredths of a millimeter to a few millimeters, typically between 0.01 and 5 mm. In one embodiment, each wire element of the connecting structure is made up of an assembly of several metallic monofilaments. In another embodiment, each wire element is made up of a metallic monofilament.

[0057] Preferably, in the arrangement where the fabric of the upper face and the lower face is a woven fabric, the connecting structure is anchored in the weft wire elements of the upper face and the lower face. Preferably, in this arrangement, the breaking strength of the stays is lower than the breaking strength of the weft wire elements. This arrangement makes it possible to maintain the integrity of the fabric structure if the tension imposed on the wire elements of the beam were to result in breaking, the stay breaking before the wire element to which it is anchored.

[0058] The invention also relates to a shelter comprising at least one beam according to the invention. Description of figures

[0059] [Fig-1] [Fig. 1] shows the evolution of the deflection rate as a function of the inflation pressure for an inflatable beam according to the invention.

[0060] [Fig.2] [Fig.2] shows the ease of arching for a beam according to the invention and an asymmetrical cylindrical beam.

[0061] [Fig.3] [Fig.3] shows the evolution of the ease of arching for a module longitudinal of the upper face given as a function of the ratio of the lower longitudinal modulus to the upper longitudinal modulus.

[0062] [Fig.4] [Fig.4] shows, for different beams, the sinkage obtained for dif different forces applied to the beam deflection.

[0063] [Fig.5] [Fig.5] is a schematic representation of an inflatable beam (1) when this beam is inflated, the beam (1) having a wheelbase D corresponding to the distance between the two lowest points of the beam, and a deflection height H, corresponding to the height between the straight line connecting the two lowest points of the beam and the highest point of the lower surface of the beam.

[0064] [Fig.6] [Fig.6] is a schematic representation of the indenter section used for the indentation test implemented in the examples below, the results of which are presented [Fig.4].

[0065] [Fig.7] [Fig.7] is a schematic representation of the section of a beam (1) according to the invention in which an upper face (2) and a lower face (3) are welded along their longitudinal edges (4, 5), the upper face (2) being connected to the lower face (3) by means of a connecting structure (6). Examples

[0066] The fabrics whose characteristics are disclosed in Table 1 are available.

[0067] [Tables 1] Material Title Tex Yarn density Pitch Yarn surface nia? Yarn modulus Mpa Fabric thickness mm Equivalent modulus Mua fabric Warp filament elements Nylon 2.3.5 ■1.04 0.02 1000 0.2 ï < Upper face: 1st belly Upper face Seine X'ünti'e Filament elements-3 t YV PET lit) 23 t 4km 0.9 0.0¾ .3000. 0.2 1330 Second fabric E ent filants 4e 1 au - PET 16; 104 ± 47dm. 1.04 0.12 3000 0.2 lï 45 Lower face 1st neutral Lower face Sente beam E -net fi] aires de tn PET 110 90 ± 47dm 00 .3000 0.2 133? Thirtieth L-neu warp wires ^ET as 104 ± 4 ''dm 1 / 34 0.48 .CW 0.2 0023 Upper faceK-2nd beam Lower face 2nd txmter Wire elements of frame PET 63 £0 ± 4 ;'dm 0 0 0.45 3000 0.2 . sooo: Arch test, ease of arching

[0068] A first inflatable beam of circular section, called “asymmetrical cylindrical”, is constructed by welding the longitudinal edges of a piece of first fabric and a piece of second fabric, each piece having a width of approximately 33 cm and a length of 167 cm.

[0069] A second inflatable beam of circular section, called “multi-section”, is made from 11 cylindrical sections, welded together so as to constitute an arch, each section being made up of two pieces of the third fabric welded to each other along their longitudinal edges, each piece having a width of approximately 33 cm and a length of 167 cm.

[0070] A third inflatable beam of oblong section, in accordance with the invention, is assembled by joining a piece of the first fabric with a piece of the second fabric by means of a connecting structure whose flexible wire elements are 55 Tex PET threads, regularly spaced along the longitudinal and transverse directions of the beam with a density of 14,000 stays per m2. This beam has a width of 34 cm and a thickness of 10 cm and a length of 167 cm. A schematic representation of the section of this beam is illustrated [Fig.7].

[0071] Each of these beams is inflated until a deflection rate of 0.25 is reached. The pressure required to inflate the asymmetrical cylindrical beam is 1.31 bar. The pressure required to inflate the multi-section beam is 0.2 bar. The pressure required to inflate the beam according to the invention is 0.81 bar. The pressures are expressed in relative bar.

[0072] The inflation pressure required to achieve the desired deflection rate for the beam according to the invention is therefore between that of the multi-section beam and that of the asymmetrical beam.

[0073] The ease of arching of different asymmetrical cylindrical beams and different inflatable beams of oblong section in accordance with the invention is evaluated as a function of the longitudinal rigidity of the upper face of these beams, the lower face being made of a fabric corresponding to the second fabric in Table 1.

[0074] The results are presented [Fig.2]. It is observed that the beams according to the invention exhibit better ease of arching than asymmetrical cylindrical beams, in particular for longitudinal rigidities less than or equal to 350 MPa. Indentation Resistance Test

[0075] To evaluate the rigidity of inflatable beams, an indentation test is carried out. The beam under test is arched so as to achieve a deflection ratio of 0.25. The ends of the beam are blocked so that they cannot slip. An indenter is applied to the upper face of the beam, perpendicular to the longitudinal direction of the beam and at the level of its deflection, the end of which in contact with the beam is of semicircular section, 50 mm in diameter, and of a length greater than the width of the beam under test. [Fig.6] shows a schematic representation of the section of this indenter.

[0076] On the one hand, the force applied to the beam by means of the indenter is recorded, and on the other hand, the displacement of the beam's deflection, called depression, induced by the application of this force. The more rigid the beam is, that is to say, the more capable it is of supporting a heavy load, the less the deflection for a given applied force will be.

[0077] The results are shown in [Fig.4]. It is observed that the beam according to the invention has excellent load resistance. Despite a lower inflation pressure than the asymmetrical cylindrical beam, it has a higher rigidity. This difference makes it possible, for a given rigidity, to use fabrics for the upper and lower faces with lower breaking stresses than those of a multi-section or asymmetrical beam. Mass testing

[0078] A fourth inflatable beam of rectangular section, in accordance with the invention, is assembled by joining a piece of the fourth fabric with a piece of the fifth fabric shown in Table 2 by means of a connecting structure whose flexible wire elements are 55 Tex PET threads, regularly spaced along the longitudinal and transverse directions of the beam with a density of 14,000 stays per m2. This beam has a width of 34 cm and a thickness of 10 cm, i.e. a section of 340 cm2.

[0079] [Tables2] Material Title Tex Yarn Density Fourth Fabric Warp Yarn Elements Nylon 23.5 90 / dm Weft Yarn Elements PET 66 104 / dm Fifth Fabric Warp Yarn Elements PET 167 90 / dm Weft Yarn Elements PET 66 104 / dm

[0080] This fourth beam is compared to the second inflatable beam of circular section, called “multi-section”, which has, once inflated, a circular section of diameter 20.8 cm and surface area 340 cm2.

[0081] The second and fourth inflatable beams therefore have an identical section.

[0082] The second inflatable beam has a reinforcement mass of 146 g per meter of beam. The fourth inflatable beam has a reinforcement mass of 152 g per meter of beam. The waterproof coating masses are similar between the two beams.

[0083] These two beams, which are sized to carry substantially the same load, therefore have roughly the same mass despite the presence of the stays and a higher fabric surface area per meter of beam.

Claims

Claims

1. Inflatable beam intended for producing a frame for a shelter, extending in a longitudinal direction, comprising two flat faces, respectively called upper and lower, each being made of a fabric impervious to inflation gases, the upper face being connected to the lower face by a connecting structure comprising flexible wire elements, called stays, extending between the upper face and the lower face, regularly spaced in the longitudinal and transverse directions of the beam, characterized in that the ratio of the modulus of the lower face Einf to the modulus of the upper face Esup, measured in the longitudinal direction of the beam, is greater than or equal to 7 and in that the modulus of the upper face in the longitudinal direction of the beam is less than or equal to 350 MPa.

2. Inflatable beam according to the preceding claim in which the fabric of the upper face is elastically deformable.

3. Inflatable beam according to any one of the preceding claims in which the wire elements of the connecting structure are substantially parallel to each other.

4. Inflatable beam according to any one of the preceding claims in which the ratio of the modulus of the upper face to the modulus of the fabric of the upper face, measured in the longitudinal direction of the beam, is less than or equal to 1.5, preferably less than 1.3, more preferably less than 1.2 and very preferably less than ii

5. 1.

1. Inflatable beam according to any one of the preceding claims in which the modulus of the upper face measured in the longitudinal direction of the beam is less than or equal to 200 MPa, preferably less than or equal to 150 MPa, preferably less than or equal to 100 MPa.

6. Inflatable beam according to any one of the preceding claims in which the modulus of the lower face measured in the longitudinal direction of the beam is greater than or equal to 500 MPa, preferably greater than or equal to 750 MPa and more preferably greater than or equal to 1000 MPa.

7. An inflatable beam according to any preceding claim wherein the modulus of the upper face and the modulus of the lower face, measured along the transverse direction of the beam, are each greater than or equal to 300 MPa, preferably greater than or equal to 500 MPa.

8. An inflatable beam according to any one of the preceding claims wherein the first and second fabrics comprise, independently of each other, a material selected from a polyester, a polyamide, a polyketone, a polyurethane, a natural fiber, a mineral fiber, a cellulosic fiber and an assembly of these materials, preferably selected from a polyester, a polyamide, a polyketone, a polyurethane, a natural fiber, a cellulosic fiber and an assembly of these materials, more preferably selected from a polyester, a polyamide and an assembly of these materials.

9. Inflatable beam according to any one of the preceding claims in which the average resting length hm of the stays is greater than 8 mm, preferably between 10 and 2000 mm, preferentially between 10 and 1000 mm, preferentially between 10 and 500 mm, very preferentially between 30 and 150 mm.

10. Inflatable beam according to any one of the preceding claims in which the fabric of the upper face is a fabric comprising warp filamentary elements (Cl), substantially parallel to each other, regularly spaced at a pitch p measured in the transverse direction of the beam and extending in the longitudinal direction of the beam, weft filamentary elements (Tl), substantially parallel to each other and extending in a weft direction, different from the longitudinal direction of the beam, the modulus of said fabric, calculated according to Esup=ECi*SCi / (p*etissu), being less than or equal to 350 MPa, where ECi and SCi respectively represent the modulus and the section of a warp filamentary element and etissu the thickness of the fabric.

11. Inflatable beam according to the preceding claim in which the weft direction is substantially perpendicular to the longitudinal direction of the beam.

12. Inflatable beam according to any one of claims 10 or 11 in which the fabric of the upper face comprises at least one warp filamentary element ED deformable in tension such that, for any filamentary element ED deformable in tension, there is an elongation AED, less than the elongation at break ARED, such that M1ED / M2ED<1, with M1ED representing the modulus of the deformable filamentary element ED for any elongation less than or equal to KlxAED%, M2ED represents the modulus of the deformable filamentary element formable ED for any elongation greater than or equal to K2xAED%, ARED representing the elongation at break of the ED element in %, with Kl ranging from 0.8 to 0.95, and K2 ranging from 1.05 to 1.2, the moduli M1ED, M2ED and the elongation at break ARED being measured according to ASTM D885-03.

13. Inflatable beam according to any one of the preceding claims in which the ratio Einf / Esup0'5 ranges from 50 to 200, preferably from 60 to 160, preferentially from 120 to 150, preferably from 130 to 140.

14. Inflatable beam according to any one of the preceding claims in which the inflation pressure is between 0.1 and 2.5 bar relative.

15. Shelter comprising at least one beam according to any one of the preceding claims.

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