BEVERAGE FOAMING DEVICES

Description

[0001] The present invention relates to a closure for a beverage container according to the preamble of claim 1 (see e.g. US-A-5 203 140).

[0002] When a carbonated beverage is served from a container, such as a can or bottle, at a low temperature of, say, 5°C or less, the increasing solubility of CO₂ in water with decreasing temperature, means that the beverage may scarcely give the appearance of being carbonated at all because most of the CO₂ remains in solution and does not appear in the form of gas bubbles rising through the liquid. This is of particular significance in connection with beer because consumers are used to seeing many beers, particularly of lager or stout type, in a highly "lively" state, that is to say with many CO₂ bubbles rising up through it, and with a substantial "head", that is to say covering of foam. The absence of a large number of rising gas bubbles and of a "head" renders the beer aesthetically unattractive to many consumers.

[0003] It is known to provide containers, e.g. bottles or cans, containing beer with a foaming device or widget which acts to inject a fine high pressure jet of gas, typically nitrogen, into the beer at the instant that the container is opened. This jet of gas imparts a high degree of turbulence to the beer in the vicinity of the widget and this turbulence results in the generation of a substantially increased number of CO₂ bubbles in the beer and thus in the rapid generation of a head on the beer so that when it is poured from the container a few seconds later it has the appearance that consumers expect.

[0004] There are two known types of widget. The first is of pre-pressurised type and consists of a small gas reservoir provided in the beverage container, typically at the bottom. The reservoir has a small gas discharge orifice in its wall. A liquid nitrogen charge is introduced into the reservoir immediately before the widget is inserted into the container and the container is then sealed immediately before all the nitrogen can escape. Once the gas pressure in the container headspace has increased to a level equal to that in the reservoir, no further gas leaves the reservoir until the container is opened and the pressure in the headspace drops to atmospheric. As it does so, the pressurised gas is discharged in a fine powerful jet through the orifice into the beer and creates the desired aesthetic appearance. However, this is expensive, in practice, and it has become more usual to use widgets of so-called scavenging type. Such widgets are not provided with a pressurised charge of gas prior to their insertion into the container but instead become filled with gas once they are in the container. One known type of scavenging widget comprises a reservoir which is weighted or constructed to float on the surface of the beer with a predetermined orientation and is provided with a one-way gas entry valve above the liquid surface and a gas discharge orifice below the liquid surface. After the container has been filled with beer, the widget is placed into the container and floats on its surface in the predetermined orientation and a small volume of liquid nitrogen is also inserted into the container, e.g. on the surface of the beer. The nitrogen immediately begins to vaporise and thus displaces all the atmospheric oxygen in the headspace of the container. Before the vaporisation is complete, the container is closed and sealed and the remaining nitrogen thus pressurises the headspace. This increased pressure is transmitted to the interior of the reservoir which thus becomes filled with pressurised nitrogen through the gas entry valve. When the container is opened and the pressure of the headspace falls to atmosphere, the pressurised nitrogen is expelled in a fine rapid jet into the beer through the gas discharge orifice and thus produces the desired effect on the appearance of the beer by the time it is poured from the container.

[0005] However, the provision of a widget with a one-way entry valve is expensive and the insertion of the widget into the container is an additional manufacturing step, which inherently increases the manufacturing expense.

[0006] It is, therefore, the object of the present invention to provide a beverage foaming device which is cheaper and simpler than known devices and which further reduces the number of steps required in the manufacturing process.

[0007] According to the present invention, a closure for a beverage container includes a closure plate and a diaphragm, which together define a fluid or gas reservoir, the diaphragm including a relatively movable portion in which a gas charge/discharge orifice is formed, the relatively movable portion being connected to the remainder of the diaphragm by at least two spaced annular fold lines of opposite sense, whereby the application of a greater pressure to the interior of the reservoir than to its exterior results in rotational movement about the fold lines and thus in movement of the relatively movable portion away from the remainder of the diaphragm.

[0008] Thus the present invention provides a composite container closure and fluid injection device or widget and the closure itself constitutes part of the injection device. The reservoir is of scavenging type and defined by a portion of the closure, namely a closure plate, and by a diaphragm. A portion of the diaphragm is moveable with respect to the remainder of the diaphragm by virtue of the provision of at least one pair of annular fold lines of opposite sense. In use, when the closure is applied to the container, annular webs forming part of the diaphragm are connected together by annular fold lines and are situated relatively close to one another. If the pressure within the reservoir should be significantly higher than that outside the reservoir, this pressure differential acts on the moveable portion of the reservoir, which causes rotation of the webs about the fold lines and thus in movement of the moveable portion of the diaphragm away from the closure plate. In practice, the moveable portion is so constructed and the fold lines are of a sufficient number that the gas charge/discharge orifice is moved from a position in which it is above the surface of the beverage stored within the container, to which the closure is applied, to a position in which it is situated below the surface of the liquid. The pressurised gas within the reservoir, e.g. nitrogen, is injected, once the seal of the container is broken, into the beverage, typically beer, to achieve the effect described above. The fluid injected into the beverage will usually be only pressurised gas. However, there could also be an amount of liquid within the reservoir, e.g. beverage which entered the reservoir through the charge/discharge orifice. Any such liquid will be situated immediately above the opening, in the normal orientation of the container and will therefore be expelled first by the pressure of the gas above it followed by the gas itself.

[0009] The beverage foaming device, which is constituted by the closure plate and diaphragm, is of scavenging type. In use, the container is filled with a liquid, typically beer, and a small amount of liquid gas, typically nitrogen, is introduced into the head space of the container. The closure is then rapidly applied to the container after the atmospheric oxygen in the head space has been purged by the vaporising nitrogen but before all the nitrogen has vaporised and dissipated. The remaining liquid nitrogen then pressurises the head space of the container. The diaphragm is constructed and the bottle is filled to a level such that the gas charge/discharge orifice is situated above the liquid level. The increased pressure of the head space is thus communicated to the gas reservoir, which becomes filled with pressurised nitrogen. When the closure is to be removed from the container, the gas seal is broken and the pressure in the head space is suddenly reduced to atmospheric pressure. The application of this pressure differential to the movable portion of the diaphragm, due to the fact that its external pressure is substantially less than its internal pressure, results in the movable portion instantaneously moving away from the closure plate to an extent sufficient to move the gas charge/discharge orifice to a position below the liquid level. This occurs before a significant proportion of the nitrogen has escaped from the gas reservoir. The pressurised nitrogen in the gas reservoir or the liquid beneath the pressurised nitrogen is then discharged under the action of the pressure differential into the liquid in the container in a thin rapid jet and produces the desired turbulence and mixing and, in the case of beer, the desired head on its surface.

[0010] As a result of the fact that the injection device or widget is an integral part of the container closure, it is necessarily applied to the container simultaneously with the closure and the number of steps required in the manufacturing process is therefore reduced. No one-way valve is required because the single orifice formed in the gas reservoir is positioned in the head space when the container is sealed but is situated within the liquid as soon as the seal is broken.

[0011] The movable portion of the diaphragm may be made of a variety of materials but it is preferably made of plastic material, such as polypropylene. It is preferred that the movable portion of the remainder of the diaphragm constitutes a one-piece injection moulding.

[0012] The gas charge/discharge orifice must be large enough to ensure that the gas jet flowing through it into the beverage is sufficient to cause significant turbulence but small enough to ensure that the pressurised gas takes some seconds to escape through it. In practice, it is preferred that it has a diameter of between 0.1 and 0.5 mm, e.g. about 0.3 mm.

[0013] The volume of the gas reservoir must of course be sufficient to store sufficient pressurised gas to perform the desired function adequately and it is found that a volume between 1.5 and 40 cm³ is sufficient for this purpose and readily achievable.

[0014] Thus in a very simple embodiment, the movable portion of the diaphragm may constitute a depending tube connected to the remainder of the diaphragm by two fold lines of opposite sense separated by an annular web. The top of the tube will be open and thus communicates with the reservoir while the bottom of the tube is substantially closed and has the charge/discharge orifice formed in it. In practice, this construction may well not be able to produce sufficient vertical movement of the charge/discharge orifice. In a modified version of this embodiment, the relatively movable portion again constitutes a tube but in this case the wall of the tube has a plurality of pairs of fold lines of opposite sense formed in it and is thus of concertina construction.

[0015] In an alternative embodiment, the moveable portion constitutes a pocket or depression extending away from the closure plate with respect to the remainder of the diaphragm. The invention also embraces a beverage container containing a carbonated beverage and sealed by a closure of the type referred to above, the gas reservoir containing pressurised gas and the gas charge/discharge orifice being situated above the liquid level and the movable portion being so constructed and arranged that the application of a greater pressure to the interior of the reservoir than its exterior results in the movable portion moving away from the closure plate such that the gas charge/discharge orifice is situated below the liquid level.

[0016] The container closure may take a wide variety of forms and thus may be, e.g., of conventional screwcap form applied to a beverage bottle. In this event, it will comprise a closure plate, which extends over the mouth of the bottle and connected to whose periphery there is an integral depending flange. Alternatively, the closure might simply constitute the lid of a can, which is manually removable by means of a ring pull or the like. In this event, the closure will be of substantially planar construction constituting a single thin metal plate, connected to whose underside of course is the diaphragm, with which the plate defines the gas reservoir.

[0017] Further features and details of the invention will be apparent from the following description of two specific embodiments which is given by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic axial sectional view of the top portion of a wide-mouthed beer bottle sealed by a first embodiment of closure in accordance with the invention before breaking the gas seal;

Figure 2 is a similar view showing the closure in the initial stages of removal from the bottle, that is to say immediately after breaking the gas seal; and

Figures 3 and 4 are views corresponding to Figures 1 and 2 respectively, of a second embodiment of closure.

Figure 1 shows the upper portion of a beer bottle 2, which is filled with beer to a level 4 and has a neck 6. Formed on the outer surface of the neck shortly below the rim of the bottle is a downwardly facing peripheral shoulder 8.

[0018] Referring firstly to Figures 1 and 2, the bottle is closed by a closure which includes a closure plate 10, which is of concave shape and thus extends a certain distance into the neck of the bottle. The outer edge of the closure plate 10 is integral with an annular web 12, which extends over the rim of the bottle. Integral with the outer edge of the web 12 is a depending skirt 14 which extends down around the upper portion of the neck. Integral with the inner surface of the depending skirt 14 and connected to it by means of an integral hinge 16 is a sealing flange 18. The sealing flange 18 is elongate and extends substantially parallel to the longitudinal central axis of the bottle and has an end surface which extends substantially perpendicular to the axis of the bottle. This free end of the sealing flange 18 engages the underside of the shoulder 8 and retains the lid in position on the bottle. The closure is applied to the bottle such that the depending skirt 14 is in tension, whereby the sealing flange 18 is drawn upwardly into contact with the shoulder 8 and thus forms a seal with it. The tension also draws the annular web 12 downwardly into contact with the rim of the bottle and a further seal is thus formed. In this specific embodiment, the integral hinge 16 is resilient and urges the sealing flange 18 inwards into contact with the external surface of the neck of the bottle and yet a further seal is thus formed.

[0019] The closure as thus far described constitutes a one-piece injection moulding of plastic material, such as polypropylene. However, the closure also includes a further one-piece moulding of polypropylene or the like comprising a diaphragm 20 of circular concave shape, the outer edge of which is connected to the underside of the annular web 12 and is situated between the web 12 and the rim of the bottle. The connection of the diaphragm to the web may be effected by welding or adhesive or by snap-fitting the edge of the diaphragm into a groove or the like in the web 12 or plate 10. Alternatively, the web 12 or plate 10 may carry an annular ridge or bead into which the edge of the diaphragm may be push-fitted and the diaphragm is then retained in position by virtue of a small degree of deformation against its resilience. The outer edge of the diaphragm 20 is thus sealed to the underside of the web 12 and the lower surface of the outer edge of the diaphragm 20 is urged by the web 12 into sealing engagement with the rim of the bottle. The concavity of the diaphragm 20 is greater than that of the closure plate 10, whereby these two components define between them a space which constitutes a gas reservoir 22. Integral with the centre of the diaphragm 20 is a moveable portion constituted in this case by a depending tube 24, the upper end of which is open, whereby the interior of the tube communicates with the gas reservoir 22. The lower end of the tube 24 is substantially closed by a plate or web 26, formed in which, e.g. in the centre of which, is a gas charge/discharge orifice 28. At least a portion of the length of the tube 24 and in this case the entire length of the tube 24 is of concertina construction, whereby a plurality of pairs of concentric circumferential folds of opposite sense are formed along its length, each fold being in the opposite sense to each adjacent fold. The construction of the tube is thus very similar to the articulated portion which is now commonly provided in many drinking straws.

[0020] When the closure is to be fitted to the mouth of a bottle, the sealing flange 18 is initially in a configuration in which it extends downwardly and inwardly towards the central axis of the lid. The closure is lowered onto the neck of the bottle and the sealing flange 18 engages the outer surface of the neck and is caused progressively to rotate upwardly about the resilient integral hinge 16. The underside of the outer edge of the diaphragm 20 is moved into engagement with the upper surface of the rim of the bottle but the downward pressure on the closure cap is increased, thereby slightly compressing the edge of the diaphragm and the annular web 12. The free end of the sealing flange 18 now passes the downwardly directed shoulder 8 on the neck of the bottle and the resilience of the integral hinge 16 then rapidly rotates the flange 18 inwardly to a position in which it is located beneath the shoulder 16. The downward pressure applied to the closure cap is then removed and the resilience of the compressed portion of the diaphragm 20 and web 12 draws the sealing flange 18 upwardly so that its free end surface is urged into sealing engagement with the underside of the shoulder 8 whilst the seal between the upper edge of the rim of the bottle and the underside of the diaphragm 20 is maintained and a residual tensional stress in the depending skirt 14 remains. The closure cap now forms a reliable gas-tight seal of the bottle. Prior to application of the closure cap, the bottle is filled with a beverage, such as beer, to a level 4 shortly below the diaphragm. The height of the level 4 is matched to the length of the tube 24 such that the closure plate 26 and thus the gas charge/discharge orifice 28 are situated above the liquid level 4. Immediately before the closure cap is applied to the bottle, a small volume of liquid nitrogen is introduced onto the liquid surface. This immediately begins to vaporise, thereby displacing all atmospheric oxygen from the headspace of the bottle. The application of the closure cap to the bottle as described above is then performed immediately, that is to say before vaporisation of the nitrogen has finished. Once the closure cap has been applied, the remaining liquid nitrogen continues to vaporise, thereby building up a substantial nitrogen gas pressure in the headspace. This pressure, which is typically of 2 to 3 bar or more, is communicated to the gas reservoir 22 via the gas charge/discharge orifice 28 and the reservoir 22 thus becomes filled with nitrogen under pressure. When it is desired to open the bottle, the lid is removed, e.g. with a conventional bottle opener of the type used to remove conventional bottle tops of so-called crown type or by pulling on a rip tab, which is not shown, forming an integral part of the closure cap and thereby partially destroying it so that it can be readily removed by hand. As the removal process proceeds, the gas seal of the bottle is broken and the headspace is vented to atmosphere, whereby its pressure rapidly reduces to atmospheric. However, the very small diameter of the gas discharge orifice 28 of e.g. 0.3 mm, means that the gas reservoir 22 cannot be vented down to atmospheric pressure that rapidly and there is therefore now a pressure differential across the diaphragm 20 due to the fact that the pressure within the reservoir 22 is higher than that in the headspace. This increased pressure acts on the closure plate 26 at the bottom of the tube 24 and causes the tube 24 to extend rapidly, that is to say to increase its length by virtue of rotation of adjacent wall portions of the tube 24 about the fold line between them. The tube 24 is constructed and dimensioned such that this virtually instantaneous increase in length results in its lower end and thus the gas charge/discharge orifice 28 moving to a position below the level 4 of the liquid in the bottle, as shown in Figure 2. The high pressure nitrogen within the reservoir 22 is now injected in a fine rapid stream through the orifice 28 into the liquid, which is typically beer, to produce the effects referred to above.

[0021] Figures 3 and 4 illustrate the second embodiment and the same reference numerals are used to designate similar components. This embodiment differs from the first embodiment only in that the movable portion of the diaphragm 22 is not constituted by a depending tube but by a pocket or pouch 30 which extends downwardly from the diaphragm in its centre. The pouch 30 comprises a short depending tube 32, whose upper edge is integral with the remainder of the diaphragm and whose lower edge is connected by two pairs of concentric fold lines 34 of opposite sense, extending between which are annular webs 36. The fold lines are again of circular shape, when viewed from above and are centred on the charge/discharge orifice 28. The innermost web is integral with the upper end of a further depending tube, whose upper end is open and whose lower end is closed by a plate or web 26, formed in the centre of which is a gas charge/discharge orifice 28.

[0022] The operation of this embodiment is precisely the same as that of the first embodiment. When the lid is removed and the headspace of the bottle vented to atmosphere, there is a pressure differential across the diaphragm which results in the rotation of adjacent webs 36 in opposite senses about the intervening fold line 34. The pocket 30 thus moves downwardly to the position shown in figure 4, in which the orifice 28 is situated below the surface of the beer and the pressurised gas in the reservoir 22 is thus injected into the beer.

[0023] It will be appreciated that numerous modifications may be effected to the embodiment described above. Thus the diaphragm may be connected to the closure by any appropriate means including a snap connection. The diaphragm may be significantly smaller than the closure plate and in this event would not be sandwiched between the closure plate and the rim of the container. Although it is preferred that the movable portion of the diaphragm extends down below the remainder of the diaphragm even before it has been moved downwardly by the pressure differential, this is not essential and the movable portion could lie in substantially the same plane as the surrounding portion of the remainder of the diaphragm.

Claims

1. A closure for a beverage container including a closure plate (10) and a diaphragm (20), which together with the closure plate defines a fluid or gas reservoir (22), characterised in that the diaphragm includes a relatively movable portion (24, 30) in which a gas charge/discharge orifice (28) is formed, the relatively movable portion being connected to the remainder of the diaphragm by at least two spaced annular fold lines of opposite sense, whereby the application of a greater pressure to the interior of the reservoir than to its exterior results in rotational movement about the fold lines and thus in movement of the relatively movable portion (24, 30) away from the remainder of the diaphragm.

2. A closure as claimed in Claim 1 in which there are at least two pairs of concentric, spaced annular fold lines of opposite sense.

3. A closure as claimed in Claims 1 or 2 in which the relatively movable portion is connected to the remainder of the diaphragm by a tubular portion which projects from the diaphragm in the direction away from the closure plate.

4. A closure as claimed in any one of the preceding claims in which the relatively movable portion constitutes a tube (24), the end of which remote from the closure plate (10) is substantially closed but has the gas charge/discharge orifice (28) formed in it and the wall of which has a plurality of pairs of fold lines of opposite sense formed in it and is thus of concertina construction.

5. A closure as claimed in Claim 2 in which the movable portion constitutes a pocket (30) or depression extending away from the closure plate (10) with respect to the remainder of the diaphragm (20).

6. A closure as claimed in Claim 1 in any one of the preceding claims in which the movable portion (24, 30) is made of plastic material.

7. A closure as claimed in Claim 6 in which the movable portion (24, 30) and diaphragm (20) constitute a one-piece injection moulding.

8. A closure as claimed in any one of the preceding claims in which the gas charge/discharge orifice (28) has a diameter between 0.1 and 0.5 mm.

9. A closure as claimed in any one of the preceding claims in which the volume of the gas reservoir (22) is between 1.5 and 40 cm³.

10. A beverage container containing a carbonated beverage and sealed by a closure as claimed in any one of the preceding claims, the gas reservoir (22) containing pressurised gas and the gas charge/discharge orifice (28) being situated above the liquid level and the movable portion being so constructed and arranged that the application of a greater pressure to the interior of the reservoir than its exterior results in the movable portion moving away from the closure plate such that the gas charge/discharge orifice (28) is situated below the liquid level.

Ansprüche

1. Verschluss für einen Getränkebehälter, enthaltend eine Verschlussplatte (10) und eine Membran (20), die zusammen mit der Verschlussplatte ein Fluid- oder Gasreservoir (22) definiert, dadurch gekennzeichnet, dass die Membran einen relativ bewegbaren Teil (24, 30) enthält, in dem eine Gaszufuhr/-ablassöffnung (28) gebildet ist, wobei der relativ bewegbare Teil mit dem übrigen Teil der Membran durch mindestens zwei beabstandete ringförmige Faltlinien mit entgegengesetzter Ausrichtung verbunden ist, wodurch die Aufbringung eines höheren Drucks auf das Innere des Reservoirs als das Äußere zu einer Drehbewegung um die Faltlinien und folglich zu einer vom übrigen Teil der Membran abgewandten Bewegung des relativ bewegbaren Teils (24, 30) führt.

2. Verschluss nach Anspruch 1, bei dem mindestens zwei Paare von konzentrischen, beabstandeten, ringförmigen Faltlinien mit entgegengesetzter Ausrichtung vorhanden sind.

3. Verschluss nach Anspruch 1 oder 2, bei dem der relativ bewegbare Teil mit dem übrigen Teil der Membran über einen röhrenförmigen Teil verbunden ist, der von der Membran in der von der Verschlussplatte abgewandten Richtung vorsteht.

4. Verschluss nach einem der vorhergehenden Ansprüche, bei dem der relativ bewegbare Teil einen Schlauch (24) darstellt, dessen von der Verschlussplatte (10) entferntes Ende im Wesentlichen geschlossen ist, aber in dem die Gaszufuhr/-ablassöffnung (28) gebildet ist, und in dessen Wand eine Mehrzahl von Paaren von Faltlinien mit entgegengesetzter Ausrichtung gebildet ist und der folglich eine Faltenschlauch-Konstruktion hat.

5. Verschluss nach Anspruch 2, bei dem der bewegbare Teil eine Tasche (30) oder Vertiefung darstellt, die sich von der Verschlussplatte (10) in Bezug zum übrigen Teil der Membran (20) abgewandt erstreckt.

6. Verschluss nach Anspruch 1 nach einem der vorhergehenden Ansprüche, bei dem der bewegbare Teil (24, 30) aus einem Kunststoffmaterial besteht.

7. Verschluss nach Anspruch 6, bei dem der bewegbare Teil (24, 30) und die Membran (20) ein einstückiges Spritzgussteil darstellen.

8. Verschluss nach einem der vorhergehenden Ansprüche, bei dem die Gaszufuhr/-ablassöffnung (28) einen Durchmesser zwischen 0,1 und 0,5 mm hat.

9. Verschluss nach einem der vorhergehenden Ansprüche, bei dem das Volumen des Gasreservoirs (22) zwischen 1,5 und 40 cm³ beträgt.

10. Getränkebehälter, der ein kohlensäurehaltiges Getränk enthält und durch einen Verschluss nach einem der vorhergehenden Ansprüche abgedichtet ist, wobei das Gasreservoir (22) unter Druck stehendes Gas enthält und sich die Gaszufuhr/-ablassöffnung (28) über dem Flüssigkeitsstand befindet und der bewegbare Teil derart konstruiert und angeordnet ist, dass die Aufbringung eines höheren Drucks auf das Innere des Reservoirs als das Äußere dazu führt, dass sich das bewegbare Teil von der Verschlussplatte abgewandt bewegt, sodass sich die Gaszufuhr/- ablassöffnung (28) unter dem Flüssigkeitsstand befindet.

Revendications

1. Dispositif de fermeture pour un récipient à boisson, comprenant une plaque de fermeture (10) et une membrane (20) qui définit, conjointement avec la plaque de fermeture, un réservoir de liquide ou de gaz (22), caractérisé en ce que la membrane comprend une partie relativement mobile (24, 30) dans laquelle est formé un orifice de remplissage et d'évacuation de gaz (28), la partie relativement mobile étant reliée au reste de la membrane par au moins deux lignes de pliage annulaires espacées de sens opposé, moyennant quoi l'application d'une pression plus élevée sur la partie intérieure du réservoir que sur sa partie extérieure engendre un mouvement de rotation par rapport aux lignes de pliage et donc un mouvement d'éloignement de la partie relativement mobile (24, 30) par rapport au reste de la membrane.

2. Dispositif de fermeture selon la revendication 1, dans lequel il existe au moins deux paires de lignes de pliage annulaires espacées et concentriques de sens opposé.

3. Dispositif de fermeture selon les revendications 1 ou 2, dans lequel la partie relativement mobile est reliée au reste de la membrane par une partie tubulaire qui fait saillie à partir de la membrane dans la direction opposée à la plaque de fermeture.

4. Dispositif de fermeture selon l'une quelconque des revendications précédentes, dans lequel la partie relativement mobile constitue un tube (24) dont l'extrémité distante de la plaque de fermeture (10) est sensiblement fermée mais comporte l'orifice de remplissage et d'évacuation de gaz (28) formé dans celle-ci et dont la paroi comporte une pluralité de paires de lignes de pliage de sens opposé formées dans celle-ci et présente donc une structure en accordéon.

5. Dispositif de fermeture selon la revendication 2, dans lequel la partie mobile constitue une poche (30) ou un creux s'étendant à l'opposé de la plaque de fermeture (10) par rapport au reste de la membrane (20).

6. Dispositif de fermeture selon l'une quelconque des revendications précédentes, dans lequel la partie mobile (24, 30) est réalisée dans une matière plastique.

7. Dispositif de fermeture selon la revendication 6, dans lequel la partie mobile (24, 30) et la membrane (20) constituent un moulage par injection d'un seul tenant.

8. Dispositif de fermeture selon l'une quelconque des revendications précédentes, dans lequel l'orifice de remplissage et d'évacuation de gaz (28) a un diamètre entre 0,1 et 0,5 mm.

9. Dispositif de fermeture selon l'une quelconque des revendications précédentes, dans lequel le volume du réservoir de gaz (22) est entre 1,5 et 40 cm³.

10. Récipient à boisson contenant une boisson gazeuse et fermé hermétiquement par un dispositif de fermeture selon l'une quelconque des revendications précédentes, le réservoir de gaz (22) contenant un gaz sous pression et l'orifice de remplissage et d'évacuation de gaz (28) se trouvant au-dessus du niveau de liquide et la partie mobile étant structurée et agencée de telle sorte que l'application d'une pression plus élevée sur la partie intérieure du réservoir que sur sa partie extérieure amène la partie mobile à s'éloigner de la plaque de fermeture de sorte que l'orifice de remplissage et d'évacuation de gaz (28) se trouve en dessous du niveau de liquide.

Drawing