EP2604942B1 - Gas extraction opening with automatic adjustment and method for manufacturing such an opening - Google Patents

Description

The invention relates to a gas extraction mouth intended to be mounted in a partition of a lumen for example separating a room to ventilate a gas exhaust duct. More particularly, the invention relates to such an extraction opening for regulating the flow rate of a gas extraction flow as a function, on the one hand, of the pressure difference between the part to be ventilated and the duct. evacuation and secondly the humidity prevailing in the room to be ventilated. The invention also relates to a method of manufacturing such an extraction mouth.

The ventilation of the inhabited premises has the function of renewing the air of these premises by admitting outside fresh air in the main rooms or dry rooms (for example living room, dining room, bedrooms) and evacuating the stale air of the rooms. service rooms or wet rooms (eg kitchen, bathroom, WC). In order to minimize the energy expenditure required, in the heated premises, to heat the incoming cold air flow, while maintaining a healthiness of the air present in the premises, it is necessary to regulate the flow of the extraction flow of air according to many parameters.

For example, in a residential building with several floors, it is common to have one or more vertical extraction ducts to extract stale air apartments from the ground floor to the top floor. There then reigns in the vertical extraction duct a variable depression which, to be sufficient to ensure the ventilation of an apartment on the ground floor, is such that in the absence of adjustment means, the ventilation of the last floors is too important and a source of energy waste. In addition, the depression in the extraction duct may be affected by sudden variations related, for example, to wind and / or to a thermal current due to temperature variations in the duct and / or to variations caused by an extraction device. mechanical (eg stato-mechanical or electric) placed on the roof.

In addition, ventilation is necessary only in proportion to the amount of exhaust air generated. For example, an unoccupied dwelling does not require a ventilation rate as high as an apartment occupied by many people who emit water vapor and carbon dioxide because of their breathing or the use of sanitary equipment or cooked.

It has therefore been proposed adjustable air extraction vents, either depending on the pressure difference between the indoor atmosphere and the suction duct, or depending on the humidity, and more precisely the rate of hygrometry, service pieces.

For example, document is known FR 2,847,661 a gas extraction mouth automatically adjustable according to the pressure difference. This mouth comprises a housing attached to a partition separating a service part of the suction duct and closing a light formed in this partition. A flexible and resilient membrane extends cantilever over openings of the housing allowing the passage of a gas flow between the room to be ventilated and the suction duct. Depending on the pressure difference prevailing on both sides of the partition, the flow rate of the gas flow varies and the membrane bends and partially closes the openings so as to regulate the flow rate of this flow.

However, this exhaust mouth does not take into account the use of the room to ventilate and does not allow to take advantage of the full flow that could provide a strong depression to quickly evacuate a large amount of moist air as is the case after using a bathroom for example.

Other devices are known, for example from the document FR 2,508,606 , based on the principle of the hair hygrometer, in which a wire or braid whose length increases with the moisture level acts on a mechanical element such as a flap to vary an air passage section . Besides these devices do not take into account the flow variation that can be caused by a variation of the pressure difference on either side of the device, they are sensitive to the fouling of the wire or braid by the particles. , especially the fat particles, driven by the extraction stream and are expensive to achieve because of the complexity of the drive mechanism of the mechanical element.

The document FR 2,729,746 proposes an adjustable extraction mouth having an elastic membrane suspended to a cross member, said membrane abutting, under the effect of the depression, against a tensioned wire which limits its movement. According to this document, the wire may be tensioned manually or by an external mechanical member depending on the temperature, humidity or a clock system. In such an extraction mouth, the position of the membrane (and therefore the extraction rate) is dictated exclusively by the depression until it abuts against the tensioned wire, then the position of the membrane is exclusively dictated by humidity (or temperature, time and manual setting).

The invention therefore aims to provide a gas extraction mouth which allows to cumulate by combining the advantages of the two known techniques for controlling the flow of extracted air.

It also aims to provide such a mouth of extraction that is simple and inexpensive to achieve.

The invention also aims to provide such an extraction mouthpiece that is robust, resistant to greasy pollutants or chemical and reliable over time.

The invention also relates to a method of manufacturing such an extraction mouth, and in particular a membrane for such a mouth of extraction, which is relatively simple and reliable and allows the adjustment of the extraction characteristics of the mouth.

• un boitier adapté pour pouvoir être fixé à la cloison de manière à couvrir la lumière de la cloison, doté d'ouvertures définissant un passage à travers le boitier pour la circulation d'un flux gazeux, dit flux d'extraction, selon une direction globale dite direction d'extraction et un sens dit sens d'extraction,
• une membrane élastique, flexible et autoportante, comportant au moins une aile fixée par un bord à une traverse du boitier et s'étendant en porte à faux en regard des ouvertures, dans une position de repos en l'absence de flux d'extraction de façon à pouvoir ployer et venir obturer partiellement les ouvertures sous l'effet d'un flux d'extraction, afin de limiter un débit du flux gazeux sous l'effet d'une différence de pression de part et d'autre de la cloison,

caractérisée en ce que la membrane présente une courbure et/ou une élasticité variables en fonction de l'humidité s'opposant à la flexion de la membrane sous l'effet du flux d'extraction de sorte que le débit du flux d'extraction traversant la bouche est simultanément variable en fonction de l'humidité contenue dans le flux d'extraction et de la différence de pression de part et d'autre de la cloison.To do this, the invention relates to a gas extraction mouth intended to be mounted in a light of a partition, comprising:

• a housing adapted to be fixed to the partition so as to cover the light of the partition, provided with openings defining a passage through the housing for the circulation of a gas stream, said extraction stream, in a global direction said direction of extraction and a meaning said sense of extraction,
• an elastic membrane, flexible and self-supporting, comprising at least one wing fixed by an edge to a cross member of the housing and extending cantilevered opposite the openings, in a rest position in the absence of extraction flow of to be able to bend and come to partially close the openings under the effect of an extraction flow, in order to limit a flow rate of the gas flow under the effect of a pressure difference on both sides of the partition,

characterized in that the membrane has a variable curvature and / or elasticity as a function of the moisture opposing the bending of the membrane under the effect of the extraction flow so that the flow rate of the extracting flow through the mouth is simultaneously variable depending on the humidity contained in the extraction stream and the pressure difference on either side of the partition.

In the present text, the term "curvature" means the proper curvature of the membrane, that is to say the intrinsic curvature taken by it "at rest" or in the presence of a predetermined pressure difference to the exclusion of an external influence to the membrane / housing system, such as, for example, a curvature imposed by a stop or any other mechanical member coming to exert a point force on the membrane.

By using a membrane whose curvature varies according to the humidity contained in the fluid passing through the extraction mouth such that, when the fluid is loaded with moisture, this curvature moves the membrane away from the openings it is intended to to mask, the flow rate of the gas stream passing through the extraction mouth is increased at equal pressure difference between the upstream and downstream of the extraction mouth. Thus, for an increasing rate of relative humidity of the fluid, the rest position of the diaphragm extends at an increasing distance from the openings, therefore the flow rate of the fluid through the openings increases for a constant pressure difference on both sides. of the partition. Conversely, when the relative humidity of the fluid is low, the curvature of the membrane is reversed and it takes a rest position close to the openings and the flow rate of the gas stream is reduced to equal pressure difference . The curvature of the membrane is thus continuously variable according to the humidity and also and simultaneously continuously variable according to the depression. Therefore, the flow rate of the gas flow is a continuous function of the two humidity and depression variables over the entire range of flow rates.

The same applies when the parameter of the membrane varying with humidity is the elasticity (or its inverse, the stiffness) of the membrane in the direction of the cantilever. By choosing a membrane such that its stiffness increases with the relative humidity rate of the gas flow, the bending of the membrane to mask the openings requires an increasing pressure difference and therefore the flow rate through the extraction mouth is increased. .

Advantageously and according to the invention, the membrane has a coefficient of expansion as a function of the anisotropic moisture in a direction normal to the surface of the membrane. Some materials, for example synthetic materials have the property of expanding in the presence of moisture. By designing a membrane whose coefficient of expansion is variable in the direction of the thickness thereof, one of the faces of the membrane may have the property of expanding in at least one of the two directions of the plane tangent to this face with a coefficient of expansion greater than that of the other face. Thus in the presence of moisture, the face having a higher coefficient of expansion sees the dimensions in the plane of this face increase compared to those of the other face. Therefore, there is a curvature of the membrane whose center of curvature is located on the side of the membrane having the lowest coefficient of expansion.

Advantageously and according to the invention, the membrane is formed of at least two layers of material having a coefficient of expansion as a function of the different humidity. A simple way to obtain this anisotropy of the coefficient of expansion as a function of humidity consists in forming the membrane by an ordered stack of layers of material each having a coefficient of expansion greater than the previous layer and lower than the next layer.

Advantageously and according to the invention, the membrane comprises a first film, said support film, of a hydrophobic material assembled to a second film, called a sensitive film, of a material, called a hygrosensible material, having a moisture recovery rate greater than or equal to five times that of the support film.

In the text of the description and the claims, the term hydrophobic material is a material which has the property of rejecting water, whether in the gaseous form of water vapor or in the form of droplets, and which by consequently, does not absorb or almost no moisture. Such a material has the particularity of being substantially invariant, as regards its dimensions, in the presence of a variable humidity level.

By hygrosensitive material is meant a material capable of absorbing moisture (in the form of vapor or liquid) and therefore of having a mass and / or dimensional variation as a function of the level of humidity to which it is exposed. Moisture absorption is referred to as "moisture uptake" and is measured by the rate of moisture uptake.

By assembling in the form of a membrane two films whose moisture absorption characteristics and the variation of the dimensional characteristics are different, a "bimetallic effect" is obtained: the hygrosensible film expands in the presence of moisture according to at least one of the two directions of the plane of the film while the hydrophobic film remains substantially invariant. This differential expansion of the two film layers causes a curvature of the membrane whose concavity is located on the hydrophobic film side. Conversely, in the presence of dry air, the moisture trapped in the hygrosensitive film gradually disappears and the hygrosensible film contracts in at least one of the two dimensions of the plane, reducing or even reversing the curvature of the the membrane.

Advantageously and according to the invention, the hydrophobic material is chosen from a metal, a polyvinyl chloride or a polyethylene terephthalate. These materials are chosen for their dimensional stability in the presence of moisture.

Advantageously and according to the invention, the hygrosensitive material is a polyamide, and more particularly a polyhexamethylene adipamide. The presence of polar groups makes the polyamides moisture-sensitive and varies their dimensional characteristics, making them particularly suitable for the production of a hygrosensitive film.

Advantageously and according to the invention, the membrane is oriented so that the hygrosensitive film is placed opposite the openings of the housing. Therefore, the curvature of the membrane is directed so that the membrane moves away from the openings when the gas flow through the extraction mouth is heavily loaded with moisture, increasing the free passage between the membrane and the openings and thereby reducing the generated pressure drop which allows a large fluid flow for a given pressure difference. In the presence of a dry gas stream or weakly loaded with moisture, the curvature of the membrane is reversed, bringing it closer to the openings of the housing and closing at least partially the passage of the gas stream. In addition, the hygrosensitive film is not directly in contact with the incident gas stream and is therefore protected against any deposits of fatty particles that may disturb the sensitivity.

Advantageously and according to the invention, the housing comprises fluid inlet openings on at least one side of the housing facing a free end of the membrane opposite the cross-member, so that the flow of fluid is directed towards the openings of the case when the flow of fluid is loaded with moisture. Thanks to these lateral openings, positioned opposite the free end of the membrane, the flow of fluid entering through the openings is directed downstream of the membrane, towards the extraction openings, when the membrane has a characteristic curvature d high humidity, thus making it possible to further increase the rate of extraction of the gas stream.

Advantageously and according to the invention, the membrane comprises two symmetrical wings on either side of a central cross member of the housing. Thus for the same width of the extraction mouth, the free length of the wings is reduced and they have an improved reactivity to humidity variations. In addition, this arrangement allows a symmetry of the extraction mouth and particular to increase extraction flows by positioning side gills on both sides of the housing.

• on utilise un boitier adapté pour pouvoir être fixé à la cloison de manière à couvrir la lumière de la cloison, doté d'ouvertures définissant un passage à travers le boitier pour la circulation d'un flux gazeux, dit flux d'extraction, selon une direction globale dite direction d'extraction et un sens dit sens d'extraction,
• on fixe en porte à faux une membrane élastique, flexible et autoportante à une traverse du boitier en regard des ouvertures, dans une position de repos en l'absence de flux d'extraction de façon à pouvoir ployer et venir obturer partiellement les ouvertures sous l'effet d'un flux d'extraction,

ledit procédé étant caractérisé en ce qu'on utilise une membrane présentant une courbure et/ou une élasticité variables en fonction de l'humidité s'opposant à la flexion de la membrane sous l'effet du flux d'extraction de sorte que le débit du flux d'extraction traversant la bouche est croissant en fonction de l'humidité contenue dans le flux d'extraction.The invention also extends to a method of manufacturing an extraction mouth intended to be mounted in a light of a partition, according to which:

• a box adapted to be fixed to the partition is used to cover the light of the partition, having openings defining a passage through the housing for the circulation of a gas stream, said extraction stream, according to a overall direction said direction of extraction and a meaning said sense of extraction,
• a resilient, flexible and self-supporting diaphragm is fixed cantilevered to a cross-member of the housing facing the openings, in a rest position in the absence of extraction flow so as to be able to bend and partially close the openings under the opening. effect of an extraction flow,

said method being characterized by using a membrane having a variable curvature and / or elasticity as a function of the moisture opposing the bending of the membrane under the effect of the extraction flow so that the flow rate extraction flow through the mouth is increasing according to the moisture contained in the extraction stream.

Advantageously and according to the invention, the membrane is produced by assembling at least two layers of material having a coefficient of expansion as a function of the different humidity.

Advantageously and according to the invention, a first film, said support film, consisting of a hydrophobic material is assembled to a second film, called a sensitive film, of a material, called a hygrosensible material, having a higher moisture uptake rate. or equal to five times that of the support film.

Advantageously and according to the invention, the assembly is carried out in an enclosure with predetermined temperature and relative humidity as a function of the desired characteristics of the membrane. By performing this assembly under predetermined environmental conditions, particularly with regard to the hygrometry rate, an essential characteristic of the membrane is defined: the nominal hygrometry rate for which the rest position of the membrane corresponds to an absence of curvature (flat membrane).

Advantageously and according to the invention, before application to the various films, a plurality of cycles of variation of the moisture content are applied. This step consists of subjecting the various films to water sorption / desorption cycles of controlled duration and conditions and makes it possible to stabilize the response of the material to humidity variations.

Advantageously and according to the invention, after assembly to the membrane is applied a plurality of cycles of variation of the moisture content. These cycles of variation between two extreme values of the ambient relative humidity rate have the effect of stabilizing the properties of the assembly, for example for the relative sliding between the films.

Advantageously and according to the invention, the different layers of material are assembled by gluing. Alternatively or in combination, the various layers are assembled by welding or by coextrusion. Thus the different films constituting the membrane can be assembled by many processes. Preferably, the deposition of an adhesive layer, for example polyurethane sheet adhesive between the facing faces of two adjacent films followed by calendering provides good results. Of course, other means of assembling the different films forming the membrane may also be used, such as, for example, an ultrasonic weld between the various films, whether over the entire surface of the films or according to a suitable drawing such as a grid of weld lines or a plurality of parallel weld lines. If the materials chosen for the constitution of the membrane allow it, it is also possible to use a method of coextruding the films to assemble them at the surface during their manufacture.

Of course, all the solutions within the reach of those skilled in the art to assemble two flexible films between them can be envisaged and adapted if necessary.

Advantageously and according to the invention, the edge of the membrane is bent hot to weld the different layers together. Once the various films have been assembled, for example in plates having a surface greater than the dimensions of the membrane used in the extraction mouth, the membrane is cut to the necessary dimensions by a laser cut (for small series) or at the same time. punch (for larger series) having a heated blade, so as to obtain a peripheral weld of the different layers of the membrane in order to limit the risks of delamination of the membrane and to guarantee the tightness of the edges of the membrane this.

Advantageously and according to the invention, the membrane is produced by modifying the surface properties of a single material. Alternatively to the assembly of a plurality of layers of different materials, it is possible to make the membrane from a homogeneous sheet of a single material and to modify the surface properties of one of the faces of the sheet. .

Advantageously and according to the invention, a film of hygrosensitive material is chosen and one of the main faces is metallized. The metallization of one of the faces of a hygrosensible film makes this face impermeable and therefore hydrophobic at least as regards the adsorption of water. Therefore, the face protected by the metallization is substantially dimensionally invariant (vis-à-vis the moisture) while the opposite face has the dimensional variation characteristics of the hygrosensible film. In the presence of moisture, the hygrosensitive surface expands and the membrane has a curvature whose concavity is turned towards the metallized face.

Advantageously and according to the invention, a film of hydrophobic material is chosen and one of its faces is treated to render it sensitive to moisture. For example, a mechanical or chemical treatment is carried out to increase the porosity of one of the faces of the hydrophobic film. By performing a mechanical or chemical etching of a face of a hydrophobic film, its adsorption capacities are increased on this face, which can then have dimensional variations greater than those of the opposite face in the presence of moisture.

The invention also relates to an extraction mouth and a method of manufacturing such a mouth characterized in combination by all or some of the characteristics mentioned above or below.

• la figure 1 représente une coupe schématique transversale d'une bouche d'extraction selon l'invention,
• la figure 2 représente en coupe un détail de l'extrémité de la membrane équipant une bouche d'extraction selon l'invention,
• la figure 3 est une coupe schématique de la bouche d'extraction selon l'invention représentant les positions de repos de la membrane en présence d'un taux d'humidité relative minimum, nominal et maximum.

Other objects, features and advantages of the invention will become apparent from the following description and the appended drawings in which:

• the figure 1 represents a schematic cross section of an extraction mouth according to the invention,
• the figure 2 represents in section a detail of the end of the membrane equipping an extraction mouth according to the invention,
• the figure 3 is a schematic section of the extraction mouth according to the invention showing the rest positions of the membrane in the presence of a minimum relative humidity, nominal and maximum.

In the present description, terms such as upper / lower, top / bottom, etc. are used. with reference to the extraction mouth as shown in the drawing. This does not prejudge in any case the position of the extraction mouth of the invention which can be mounted on a vertical or horizontal partition, and in any angular orientation with respect to a reference axis such as the vertical for a mounting on a vertical partition for example. The terms upstream / downstream are also used with reference to the direction of flow of the gas stream passing through the extraction mouth.

The extraction mouth 1 according to the invention comprises a housing 2 adapted to cover a slot 4 formed in a partition 3 separating a room to ventilate a gas evacuation conduit for example. The housing 2 can be adapted to simply come to apply to the partition 3 or to be at least partially embedded in the slot 4. The case 2 comprises on its upper face a grid 20 substantially parallel to the light 4 allowing a gas inlet from the room to be ventilated. It also comprises on at least one flank 8 of the housing 2 gills 14 and 15 lateral gas inlet which will be described further in the following description.

The housing 1 also has an inner wall 9 separating the upstream from the downstream and provided with at least one opening 5 allowing the flow of gas flow from upstream to downstream. The inner wall 9 has a flat portion, said cross 9a, substantially parallel to the plane of the grid 20. This cross 9a extends, depending on the conformation of the housing 2, or on a side of the housing as shown in FIG. figure 1 either centrally along an axis of symmetry of the case as shown schematically in the figure 3 . Other configurations may also be considered, as will be seen later.

An elastic, flexible and self-supporting membrane 6 is arranged in the casing 2 so as to extend cantilevered above the openings 5. The membrane 6 comprises at least one wing 7 fixed by one of its edges 7b to the transom 9a by a fastening means such as one or more rivets 10. Of course, when the housing 2 is arranged so that the cross member 9b is central, the membrane 6 extends on either side of this cross member and has two symmetrical wings 7. The remainder of the description will be limited to the case of a single wing 7 cantilevered as shown in FIG. figure 1 the case of the central cross-member and of the membrane with two symmetrical wings being deduced by symmetry.

The flexibility and elasticity of the membrane 6 allows the wing 7 to take a rest position away from the opening 5 in the absence of gas flow generated by a pressure difference between the upstream and downstream from the extraction mouth. In the presence of a pressure difference, a gas flow is then established as represented by the arrow F of the figure 1 and the flange 7 of the membrane 6 is flexible enough to bend and gradually come to mask the opening 5 so as to reduce the flow section and therefore the flow rate of the gas flow. In this way, the flow rate of the gas flow is regulated as a function of the pressure difference between the part to be ventilated and the exhaust duct.

According to the invention, the membrane 6 is characterized in that its curvature and / or its elasticity are also variable as a function of the humidity prevailing in the flow of gas passing through the extraction mouth. In particular, the membrane is designed to present, in the rest position (that is, in the absence of upstream / downstream depression), a zero curvature, that is to say that the flange 7 extends substantially in a plane parallel to the plane of the grid 20 for a predetermined relative humidity rate, said nominal HR rate , gas passing through the extraction mouth. This rest position of the membrane is represented on the figure 3 by the dotted outline marked 18 of the wing 7 of the membrane.

When the flow of gas has a relative humidity rate higher than the nominal RH, the curvature of the diaphragm in the rest position is oriented so that this curvature opposes the bending of the membrane under the effect of the flow. gas. For example, as represented by the dashed sketch labeled 16 on the Figure 3 , the curvature of the membrane has a concavity facing the gate 20, opposite the opening 5, in the presence of a maximum humidity RH max. In this way, for a given pressure difference between the upstream and downstream of the extraction mouth, the bending of the wing 7 of the diaphragm towards the opening 5 is all the less pronounced that the Relative humidity rate of the gas stream is important.

Conversely, for a relative humidity rate of the gas flow lower than the nominal HR, the curvature of the membrane in the rest position is oriented so as to have a concavity in the direction of the opening 5, as shown in FIG. figure 3 by the marked position 17 of the wing 7 for a minimum humidity RH min. In this position, the wing 7 is close to the opening 5 and for the same upstream / downstream pressure difference, the gas flow through the extraction port is reduced.

This gives an adjustment of the extraction rate which is continuous as a function of the two humidity and depression variables. For example, even in the presence of high humidity, a large pressure difference can press the wing 7 on the opening 5 and reduce the flow rate of the gas stream to the minimum flow values imposed by the regulations.

The same is true if the variable parameter as a function of humidity is the elasticity (or the stiffness) of the membrane. For a stiffening of the membrane increasing according to the humidity of the flow of gas passing through the mouth extraction, the wing 7 will decline all the less towards the opening 5 and for the same pressure difference upstream / downstream, the flow of gas through the mouth will increase depending on the relative humidity of the gas.

To obtain a membrane 6 having such characteristics of curvature and / or variable elasticity as a function of the relative humidity, the inventors have found that it is sufficient for the membrane to have a coefficient of expansion as a function of the variable humidity ( preferably monotonically) as a function of a normal direction on the surface of the membrane. Thus, if one of the faces of the membrane has a coefficient of expansion as a function of humidity greater than the coefficient of expansion of the opposite face of the membrane, there is a "bimetal" effect resulting in a curvature of the membrane of which the concavity is oriented towards the side with the lowest coefficient of expansion. This property of dilation as a function of humidity is a known phenomenon of different materials, natural as horsehair or synthetic as polyamides and is due to the ability of these materials to absorb water molecules in their structure in the presence humidity.

The invention proposes various methods for obtaining a membrane having an anisotropy of the coefficient of expansion as a function of moisture oriented orthogonally to the surface of the membrane.

Preferably, the invention proposes to produce the membrane 6 by an assembly of at least two layers of materials having different coefficients of expansion as a function of humidity. For example, the membrane 6 may be constituted, as shown in FIG. figure 2 of the drawing, an assembly of a first film, said support film 11, hydrophobic material such as metal or polyvinyl chloride (PVC) or polyethylene terephthalate (PET), with a second film, said film hygrosensitive 12 consisting of a hygrosensitive material. The support film 11 is of a thickness ranging between 0 and 300 microns depending on the material used. For example, to obtain a membrane 6 adapted for operation of the extraction mouth with an upstream / downstream pressure difference of 5 to 30 Pa, a PVC film 150 μm thick is used.

To obtain a variation of curvature of the membrane that is sufficiently sensitive for the intended use, a hygrosensitive material having a moisture uptake rate, that is to say an ability to absorb water molecules in its structure, is selected. , which is at least five times greater than that of the hydrophobic material of the support film 11. Preferably, a hygrosensible material is selected from polyamides, and more particularly a polyhexamethylene adipamide (PA6-6). The hygrosensible film 12 is generally chosen with a thickness varying between 0 and 100 μm. As an example of a hygrosensitive film that can be used to obtain a membrane 6 having the characteristics mentioned above, the film sold by the brand AEROVAC under the reference CAPRAN 526 can be used in a thickness of 50 μm (preferred) or 75 μm.

The assembly of the support film 11 with the hygrosensible film 12 is preferably carried out by gluing by means of a glue film 13, deposited by various processes (spraying, extrusion, interposition of a film of glue with or without a support, etc. Different glue compositions may be employed, for example polyurethane or acrylic glues. Depending on the glue application method, the adhesive film may have a thickness ranging between 0 and 100 .mu.m. For example, it is possible to use adhesive transfer films marketed by the company 3M under the references 9453 (89μm acrylic), 9471 (acrylic 50μm)

Other means of assembly can be envisaged, such as welding the films together by means of ultrasound or microwave, leading to heating uniformly distributed or localized between the surfaces in contact with the two films. In the case of a localized weld, different forms of welds can be envisaged: in parallel lines, in braces, etc.

It is also possible to envisage the production of a membrane 6 by coextrusion of the support and hygrosensitive films.

The curvature characteristics as a function of the humidity of a membrane 6 thus produced are a function of the materials used, the method of assembly, etc. It is therefore necessary to define a method of manufacturing the membrane 6 which makes it possible to produce a membrane corresponding to the expected characteristics in terms of nominal relative humidity, rate for which the membrane is substantially flat.

• Cyclage avant assemblage : On soumet le film hygrosensible à des cycles de sorption / désorption d'eau par exposition successive de durée contrôlée à des ambiances à forte humidité relative (85-100% HR - 2 heures) puis à faible humidité relative (0-35% HR - 1 heure) afin de stabiliser la réponse du matériau vis-à-vis de l'humidité.
• Étape de stabilisation : les différents éléments constituant la membrane sont soumis pendant une durée prédéterminée (de l'ordre de quelques heures) à une ambiance contrôlée en température et humidité correspondant aux conditions de température et d'humidité nominales souhaitées pour la membrane.
• Assemblage en atmosphère contrôlée : L'assemblage de la membrane se déroule dans les mêmes conditions d'ambiance que l'étape de stabilisation et comporte les sous-étapes suivantes :
  • ▪ Dégraissage et préparation de surface des films support 11 et hygrosensible 12. La préparation de surface peut comporter une ou plusieurs opérations visant à améliorer l'adhérence des films, par exemple opérations mécaniques telles que sablage, dépolissage ; chimiques telles que flammage, traitement UV, plasma, Corona, etc. ; application de primaires d'accrochage ou de promoteurs d'adhérence...
  • ▪ Application de l'adhésif par tout procédé connu (projection, pulvérisation, extrusion, application d'un film transfert...)
  • ▪ Collage des films à plat de manière à définir un profil plan de la membrane pour les conditions d'humidité et de température déterminées
  • ▪ Durcissement de l'adhésif par tout moyen approprié en fonction de l'adhésif utilisé (UV, température, etc.)
• Cyclage final: la membrane assemblée est soumise à des cycles de sorption / désorption d'eau de même type que ceux appliqués au matériau hygrosensible en début de processus. Cette étape a pour but de stabiliser les propriétés de la membrane assemblée (précontrainte et/ou glissement relatif des couches entre elles par exemple).
• Découpe aux dimensions : cette étape peut être réalisée en suite des étapes précédentes ou bien être différée pour être intégrée dans le procédé d'assemblage de la bouche d'extraction. Préférentiellement le détourage de la membrane aux dimensions requises est effectué à chaud, par exemple au moyen d'un laser ou d'un emporte-pièce chauffé de manière à souder les deux films entre eux le long du bord de la membrane en une soudure 19. Grâce à cette soudure du bord, on limite les risques de délaminage de la membrane.
• Étuvage / emballage / stockage : les membranes prédécoupées ou les plaques ou rouleaux de membrane sont ensuite étuvés en ambiance contrôlée pour limiter l'humidité lors du stockage, puis emballés de manière étanche avant d'être dirigés vers les étapes d'assemblage de la bouche d'extraction.

The method of manufacturing the membrane, for example for a bonding assembly, therefore comprises the following steps:

• Cycling before assembly: The hygrosensible film is subjected to cycles of water sorption / desorption by successive exposure of controlled duration to atmospheres with high relative humidity (85-100% RH - 2 hours) and then at low relative humidity (0- 35% RH - 1 hour) to stabilize the material's moisture response.
• Stabilization step: the various elements constituting the membrane are subjected for a predetermined duration (of the order of a few hours) to a controlled atmosphere temperature and humidity corresponding to the desired temperature and humidity conditions for the membrane.
• Assembly in controlled atmosphere: The assembly of the membrane takes place under the same ambient conditions as the stabilization stage and comprises the following substeps:
  • ▪ Degreasing and surface preparation of the support films 11 and hygrosensitive 12. The surface preparation may comprise one or more operations to improve the adhesion of the films, for example mechanical operations such as sanding, etching; chemicals such as flaming, UV treatment, plasma, corona, etc. ; application of adhesion primers or adhesion promoters ...
  • ▪ Application of the adhesive by any known method (projection, spraying, extrusion, application of a transfer film, etc.)
  • ▪ Bond flat films in order to define a plane profile of the membrane for the determined humidity and temperature conditions
  • ▪ Hardening of the adhesive by any appropriate means depending on the adhesive used (UV, temperature, etc.)
• Final Cycling: the assembled membrane is subjected to water sorption / desorption cycles of the same type as those applied to the hygrosensitive material at the beginning of the process. This step aims to stabilize the properties of the assembled membrane (prestressing and / or relative sliding of the layers together for example).
• Cutting to dimensions: this step can be carried out following the previous steps or be deferred to be integrated in the assembly process of the extraction mouth. Preferably the clipping of the membrane to the required dimensions is carried out hot, for example by means of a laser or a punch heated to weld the two films together along the edge of the membrane in a weld 19 Thanks to this edge welding, the risk of delamination of the membrane is limited.
• Steaming / Packing / Storage: Precut membranes or membrane plates or rolls are then baked in a controlled environment to limit moisture during storage, and then packaged tightly before being directed to the assembly steps of the mouth extraction.

During the assembly of the extraction mouth, the membrane 6 is fastened to the crossmember 9b of the housing by fastening means such as rivets 10. When fixing the membrane 6, the latter is oriented that the hygrosensible film 12 is oriented towards the opening 5 facing it. In addition to this provision is functionally necessary to guide the curvature of the membrane, it is found that in this way the gas flow represented by the arrow F on the figure 1 does not strike directly on the hygrosensitive film and any greasy particles that can be transported by this flow do not settle on the hygrosensitive film. An extraction mouth according to the invention is therefore much less sensitive to fouling and the loss of performance related thereto than an extraction mouth of the prior art in which the extraction flow passes through a braid sensitive to moisture.

The other steps of the manufacturing method of the extraction mouth according to the invention are conventional mechanical assembly steps within the reach of those skilled in the art and are therefore not described in more detail.

Of course, there are other possibilities for producing a membrane 6 having the characteristics of the invention. For example, one can choose a film consisting of a single material and change the surface properties, for example the adsorption capacity of one of the faces to introduce anisotropy of the coefficient of expansion as a function of moisture.

For example, the membrane 6 may be formed from a single film of hygrosensitive material which is metallized on one side, for example by vapor deposition. In this case, the metallized side becomes hydrophobic and prevents the penetration of moisture on this face. The quantity of water molecules absorbed by the hygrosensitive film just below the surface metallization is then much less than that absorbed by the non-metallized face, which leads to a dilation due to the different humidity between the two faces and therefore at a variable curvature depending on the humidity.

Similarly, it may be envisaged to start from a hydrophobic film and to treat one of the faces to increase its adsorption capacity, for example by a chemical or mechanical etching allowing a surface entry of water molecules and therefore a dilatation of the treated surface superior to that of the opposite face.

As has been seen previously, the housing 2 also comprises on at least one sidewall 8 of the housing 2 of the gills 14 and 15 lateral gas inlet. These openings 14 and 15 are arranged to cooperate with the end 7a of the wing 7 of the membrane 6. For example, the hearing 14 is placed so as to be upstream of the end 7a of the membrane when this one is in the position marked 17 at the figure 3 position corresponding to a minimum relative humidity RH min. The additional F1 flow of gas from the part to be ventilated passing through the orifice 14 is thus deflected upstream thereof and is subjected to the restriction of flow formed by the wing 7 of the membrane above the 5. As soon as the humidity of the gas increases, the wing 7 of the membrane rises and the additional F1 flow is directly directed towards the opening 5 in a proportion of up to 100% when the moisture of the gas reaches the nominal HR rate. It is the same for the hearing 15 which is arranged to guide an additional flow F2 to the opening 5 when the humidity of the gas exceeds the nominal HR rate to reach the maximum HR max.

Thanks to this arrangement, in the presence of a high humidity, the additional extraction streams F1 and F2 circulate below the wing 7 of the membrane and therefore do not contribute to bending it to the Accordingly, the extraction rate is maximum regardless of the pressure difference between upstream and downstream. The regulation of the flow is therefore primarily a function of the humidity.

At average humidity, the majority of the gas flow passing through the extraction mouth follows the path shown by the arrow F at the figure 1 and contributes to bending the membrane towards the opening 5, thus allowing automatic regulation of the gas flow rate as a function of the upstream / downstream pressure difference. The regulation of the flow is therefore primarily a function of the pressure difference.

At low humidity, the effects of moisture and pressure difference combine to reduce the ventilation rate.

The extraction mouth according to the invention thus has variable flow characteristics in function simultaneously of the two important parameters conditioning the safety and energy saving that are the pressure difference between the room to be ventilated and the exhaust duct and the humidity prevailing in the room to be ventilated.

Of course, this description is given by way of illustrative example only and the person skilled in the art can make numerous modifications without departing from the scope of the invention, such as for example making a cylindrical extraction mouth, in which a circular membrane 6 is fixed at its center and is deformed in section whose concavity is turned upstream in the presence of a high humidity.

Claims (17)

1. Gas extraction unit (1) intended to be mounted in a hole (4) of a partition wall (3), comprising:

   - a case (2) adapted to be able to be fastened to the partition wall in such a way as to cover the hole of the partition wall, provided with openings (5) defining a passage through the case for the circulation of a gas flow, named extraction flow (F), according to a global direction named extraction direction and a course named course of extraction,

   - an elastic, flexible and self-supporting membrane (6), comprising at least one wing (7) fastened by an edge (7b) to a crosspiece (9b) of the case and overhangingly extending facing the openings, in a rest position in the absence of an extraction flow in such a way as to be able to bend and partially seal the openings under the effect of an extraction flow, so as to limit a flow rate of the gas flow under the effect of a difference in pressure on either side of the partition wall,

   characterised in that the membrane (6) has a curvature and/or elasticity that vary according to the moisture that opposes the inflection of the membrane under the effect of the extraction flow in such a way that the flow rate of the extraction flow passing through the unit can vary simultaneously according to the moisture contained in the extraction flow and to the difference in pressure on either side of the partition wall.
2. Extraction unit according to claim 1, characterised in that the membrane (6) has a coefficient of expansion according to the anisotropic moisture according to a direction normal to the surface of the membrane.
3. Extraction unit according to one of claims 1 or 2, characterised in that the membrane is formed from at least two layers (11, 12) of material that have a different coefficient of expansion according to moisture.
4. Extraction unit according to one of claims 1 to 3, characterised in that the membrane comprises a first film, named support film (11), a hydrophobic material assembled to a second film, named hygrosensitive film (12), constituted of a material, named hygrosensitive material, having an ingress rate of moisture greater than or equal to five times that of the support film.
5. Extraction unit according to claim 4, characterised in that the hydrophobic material is chosen from a metal, a polyvinyl chloride or a polyethylene terephthalate and in that the hygrosensitive material is a polyamide, in particular a polyhexamethylene adipamide.
6. Extraction unit according to one of claims 4 or 5, characterised in that the membrane is directed in such a way that the hygrosensitive film (12) is placed facing the openings (5) of the case.
7. Extraction unit according to one of claims 1 to 6, characterised in that the case comprises louvers (14, 15) for the intake of fluid over at least one flank (8) of the case (2) across from a free end (7a) of the membrane opposite the crosspiece (9b), in such a way that the flow of fluid is directed towards the openings of the case when the flow of fluid is loaded with moisture.
8. Extraction unit according to one of claims 1 to 7, characterised in that the membrane comprises two symmetrical wings on either side of a central crosspiece of the case.
9. Method for manufacturing an extraction unit (1) intended to be mounted in a hole (4) of a partition wall (3), according to which:

   - a case (2) adapted to be able to be fastened to the partition wall is used in such a way as to cover the hole of the partition wall, provided with openings (5) that define a passage through the case for the circulation of a gas flow, named extraction flow (F), according to a global direction named extraction direction and a course named course of extraction,

   - an elastic, flexible and self-supporting membrane (6) is overhangingly fastened to a crosspiece (9b) of the case facing the openings, in a rest position in the absence of an extraction flow in such a way as to be able to bend and partially seal the openings under the effect of an extraction flow,

   said method being characterised in that a membrane is used that has a curvature and/or an elasticity that vary according to the moisture opposing the inflection of the membrane under the effect of the extraction flow in such a way that the flow rate of the extraction flow passing through the unit increases according to the moisture contained in the extraction flow.
10. Method for manufacturing an extraction unit according to claim 9, characterised in that the membrane is carried out by assembling at least two layers (11, 12) of material that have a different coefficient of expansion according to the moisture.
11. Method for manufacturing an extraction unit according to claim 10, characterised in that a first film, named support film (11), constituted of a hydrophobic material is assembled to a second film, named hygrosensitive film (12), of a material, named hygrosensitive material, having an ingress rate of moisture greater than or equal to five times that of the support film.
12. Method for manufacturing an extraction unit according to one of claims 10 or 11, characterised in that the assembly is carried out in an enclosure at a predetermined temperature and relative humidity according to the characteristics of the membrane (6).
13. Method for manufacturing an extraction unit according to one of claims 10 to 12, characterised in that the various layers of material are assembled by a method chosen from gluing (13), welding and co-extrusion.
14. Method for manufacturing an extraction unit according to one of claims 10 to 13, characterised in that the edge of the membrane is hot cut in order to weld the different layers together.
15. Method for manufacturing an extraction unit according to claim 9, characterised in that the membrane is carried out by modification of the surface properties of a single material.
16. Method for manufacturing an extraction unit according to claim 15, characterised in that a film is chosen from a material that is sensitive to the moisture and in that one of the main faces is metallised.
17. Method for manufacturing an extraction unit according to claim 15, characterised in that a film is chosen from a hydrophobic material and in that a mechanical or chemical treatment is carried out in order to increase the porosity of one of the faces of the hydrophobic film.

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