DE69406673T2 - FOAM INSERT FOR BEVERAGE CONTAINERS - Google Patents

Abstract

An insert (20) is provided containing gas under pressure, for insertion in a carbonated beverage can (11) to nucleate release of gas from solution when the can is opened. The insert has a jetting orifice (25) closed by a burstable sealing strip (26) which is held closed until the can is opened. The insert may be weighted (24) to float in a given orientation with the jetting orifice submerged. The sealing strip may be made of moisture sensitive material, which weakens in the can and ruptures on opening of the can. Alternatively, a moisture sensitive adhesive may be used. The insert may be pre-charged with non-oxidising gas under pressure, or may be pressurised by gas from the beverage.

Description

This invention relates to a foam-forming insert for a beverage container.

Beer is expected to form a head of foam when it is poured into a glass, with the head being created by the release of carbon dioxide dissolved in the beer under pressure. Pouring the beer initiates the release of gas to create the head through a foaming effect.

It is often necessary to form a head of foam when the container is opened, e.g. when the contents are to be drunk directly from the container, and for some years it has been known to provide means to initiate the foaming action as soon as the container is opened and pressure in the container is released. This is usually done by providing a secondary chamber in the container containing gas under pressure. The gas is released through a nozzle when the main container is opened to cause "seeding" of the gas release from the contents of the container.

Of course, beverages other than beer can be included, and the gas dissolved in the beverage can be nitrogen as well as carbon dioxide. The gas provided in the secondary chamber is usually carbon dioxide or nitrogen.

An early example of such a container is disclosed in GB-A-1266351 published in 1972. The secondary chamber was fixed to the bottom of the container with a nozzle opening facing the container contents. The contents of the main container chamber and the secondary chamber are under pressure equalization until the main chamber is opened, the pressure differences causing the release of a stream of bubbles from the secondary chamber.

In this document it is disclosed that the nozzle can be sealed by gelatin to allow charging of the secondary chamber with gas prior to filling the main chamber with a beverage. The gelatin seal is dissolved by beverage to open the nozzle, contaminating the beverage.

The document also discloses the alternative of providing a valve instead of the gelatin seal, whereby the valve can open due to a pressure gradient when the main chamber is opened.

Since then, there have been many developments of the basic principles disclosed in this patent specification, as disclosed, for example, in GB-A1331425, WO92/00096, WO92/00097, GB-A-2211813, GB-A-2240960, EP-A-0360375, EP-A-0360373, GB-A-2256628, WO91/13006, GB-A-2257132, WO91/09781, GB-A-2183592, GB-A-1588624, WO91/00825, GB-A-2257107 and WO91/07326. The preamble of claim 1 is based on WO91/07326.

In some of these documents the principle is disclosed of filling a separate insert with gas and inserting the insert into the container before filling the container. GB-A-2240960 discloses such a Insert that is held magnetically beneath the liquid container contents.

GB-A-2183592 and WO91/07326 disclose, among many proposals, the provision of a floating insert which is filled with gas and floats on the beverage in such a way that it protrudes into the head space. The nozzle is held under the liquid by weighing down the floating insert.

A disadvantage of using a secondary chamber, the nozzle of which is opened to the contents of the main chamber before the main chamber is opened, is that a significant amount of the liquid contents enters the secondary chamber. This is caused by changes in pressure due to temperature changes. The container and its contents are usually subjected to a pasteurization step before being cold stored.

When using a valve, the valve must remain closed before and after the insert is placed in the container and only open when the container is opened. One way of achieving this, as disclosed in WO91/07326, is to fill the insert with gas above atmospheric pressure and to maintain the insert at superatmospheric pressure until the container has been sealed. This method is clearly difficult to implement.

The document discloses an alternative in which the insert is filled at atmospheric pressure and the pasteurization step is used to bring about a permanent reduction in volume of the insert so that the gas in the insert is pressurized after insertion into the container.

Another alternative disclosed is to fill an insert with liquefied gas prior to insertion. A valve member is held by an elastic wall in a position closing a nozzle, whereby the pressure subsequently built up in the insert acts on the valve member to urge it in the closing direction. The pasteurization step is used to deform the insert and move the valve member into a position in which it is permanently held. When the container is opened, the elastic wall releases the valve member to open the nozzle.

This is a complex arrangement that is expensive to manufacture to function reliably. Another disadvantage is that when the pressure drop across the valve decreases, the valve closes again, so that only part of the gas filled is used.

Plastics have significant advantages due to the ease of manufacturing an insert, but have one fundamental disadvantage. The entire can, including its insert, should be made of the same material to enable recycling.

Plastic causes recycling problems when inserted into aluminium or steel cans. The insert should primarily be aluminium if the cans are made of aluminium, but aluminium is also suitable for recycling when used in steel cans.

TASKS OF THE INVENTION

An object of the invention is to provide a foam-forming or foam-inducing insert for a beverage container which can be filled with gas before being inserted into the container and stored at atmospheric pressure.

Another task is to provide an insert that is cheap and easy to manufacture.

Another object of the invention is to provide an insert with a sealing member for its jet opening, the sealing member breaking open to cause a sudden release of pressure from the insert into the beverage.

An additional task is to create an insert that floats on the beverage and can be held in a position in which the blow-out (nozzle) opening is immersed in the beverage during blow-out.

Another additional task is to provide an insert that can contain an oxidizing gas and does not have to be purged of oxygen.

Another additional task is to provide a uniform blow-out of the gas into a beverage during the blow-out phase.

SUMMARY OF THE INVENTION

The invention provides a foam-inducing insert for inclusion in a container containing a beverage containing gas dissolved therein under pressure, for initiating the release of gas from the insert upon opening of the container, which insert comprises:

a housing with one chamber,

gas contained in the chamber,

which chamber has a blow-out (nozzle) opening through the housing,

a closure means closing the opening which can be opened under the pressure difference or effective pressure across the opening caused by opening the container in use, thereby releasing gas into the container,

wherein the closure means comprises a sealing member secured around the opening for producing a seal and the closure means is burstable under the effective pressure, which is characterized in that

(i) the sealing member is frangible and sensitive to moisture, so that in its dry state it can withstand a higher pressure than after exposure to moisture, or

(ii) the sealing member is bonded around the opening using a moisture-sensitive adhesive whose adhesive properties are reduced when exposed to moisture.

In one embodiment, the chamber is filled with pressurized gas and the sealing member is rupturable and moisture sensitive. The insert can be stored under dry conditions with the sealing member intact. However, inside the beverage container, the sealing member absorbs moisture and weakens. When the container is opened, the weakened member ruptures under the sudden drop in pressure. The preferred material is an ethylene vinyl alcohol (EVOH) copolymer.

In an alternative embodiment, the sealing member is glued around the opening using a moisture-sensitive adhesive, e.g. an EVOH or a polyvinyl alcohol adhesive, which allows the insert to be stored dry, but softens in the beverage container so that when the container is opened, the seal is broken by the yielding of the sealing member. The sealing member can be held to the insert using a non-moisture-sensitive adhesive by gluing a portion of the member to the housing.

In another embodiment, the sealing member is frangible (but not necessarily moisture sensitive) and is bonded in an interior region around the opening using a moisture sensitive adhesive. The member is more strongly bonded in an exterior region. When the container is opened, the weaker adhesive of the interior region releases the member while the exterior region remains securely bonded. This exposes a larger area of the member to the pressure shock, causing the member to rupture.

Rupture of the sealing member is preferable, as this is highly effective in initiating bubble release. This arrangement also allows a delay between opening the container and the actual rupture.

In a further embodiment, the housing comprises a second chamber with a membrane which divides the chamber and is arranged so that the pressure in the second chamber acts on the first chamber through the membrane. The second chamber is pressurized by connection to the interior of the container.

This connection can be ensured by a small loading opening, which only allows the gas to pass slowly through it in order to achieve a slow pressure equalization within the container.

Optionally, a larger opening covered with a gas-permeable film can be provided.

The second chamber is preferably filled with a non-oxidizing gas, e.g. nitrogen, to prevent oxidation of the container contents. An oxygen scavenger may be provided in the second chamber to bind oxygen from the headspace of the container. The second chamber may exist in the container only under pressure, with the membrane initially in contact with the housing.

To prevent air from entering the second chamber during storage of the device, the loading opening is preferably closed by a gas-impermeable rupturable film which bursts under the pressure gradient that occurs when the insert is sealed in a pressurized beverage container.

The membrane is preferably made of a pliable or malleable material, e.g. soft aluminum, which collapses in a uniform manner so that a uniform expulsion of gas from the first chamber through the collapsing membrane is achieved. This creates a controlled bubbling over a period of time rather than a rapid drop in pressure which leads to a rapid drop in bubbling.

This arrangement also makes it possible to vary the volume of gas to be expelled without changing the external dimensions and shape of the housing. It is therefore possible to use the same insert placement device for different inserts for different types of beer. The variation is possible by changing the size of the first chamber, or by adjusting the pressure in the first chamber relative to that in the second chamber during manufacture, thereby varying the size of the first chamber.

There may be provided a filling or loading opening communicating with a single chamber of the insert, the filling opening being closed in use when the pressure inside the insert exceeds the pressure inside the container and being openable when the pressure inside the container exceeds the pressure inside the insert.

This arrangement makes it possible to fill the insert with gas and store it at atmospheric pressure, with the valve preventing the gas from escaping.

The filling pressure can be increased during pasteurization of the beverage. The valve opens when the pressure increases during pasteurization and closes again when the pressure drops during cooling. During this process, gas, beverage or mixture enters the insert from the container and is retained in the insert. The valve remains closed after the container has been opened and gas or gas-liquid mixture is expelled only through the second opening.

Preferably, substantially only gas is expelled through the second opening. This is achieved by ensuring that the first opening only communicates with the headspace. Preferably, the second opening is also submerged in the beverage when and shortly after the container is opened so that the gas is expelled into the beverage. This arrangement creates the best conditions for initiating foam formation, making optimal use of the internal volume of the insert.

Preferably, the insert also floats or floats on the drink, which means that it is not necessary to attach the insert to a fixed place in the container.

According to a further feature of the invention described below, it is possible to orient the floating insert to ensure that the contents of the insert are blown out into the drink and not into the headspace.

The one-way valve can be omitted if the first opening is made significantly smaller than the second opening. With this arrangement, the internal pressure of the insert after pasteurization and during storage equalizes with that of the container due to the connection through the first opening. However, by providing a valve it is possible to use a relatively high internal pressure in the insert and therefore the insert can have a smaller volume.

The advantage of orienting the floating insert with its ejection orifice submerged in the beverage is mentioned in GB-A-2183592. However, the only disclosure, in brief, is to weight the insert. WO91/07326 describes and illustrates a weighted, floating insert, wherein the insert is made of a plastic.

Plastics have significant advantages due to the ease of manufacturing an insert, but they also have a significant disadvantage. The insert should be made from a material that allows recycling.

Aluminium and steel cans are widely used and the liner should be made of aluminium for recycling purposes. Aluminium is an expensive material and must be used sparingly, resulting in a light weight liner.

It has now been found that the recoil force generated when gas is ejected from the liner, if the metal liner is light enough, can propel or drive the liner against the top of the container. Preferably, therefore, the dimensions of the floating liner parallel to the container axis are sufficiently large relative to the depth of the headspace to ensure that the ejection opening remains submerged. This problem would not normally arise with plastic liners.

If the insert is light enough, the angular orientation of the insert can be determined by contact between the inner surface of the top of the can and the top of the insert, and such contact could cause the exhaust port to open into the headspace. This is prevented by providing at least three points of contact between the contact surfaces.

The floating stability of the insert is also important to ensure that the insert remains in the desired position. The problem of angular alignment would be alleviated by using a large insert with a relatively shallow depth, but such an insert would be stable in an inverted floating position and would also be tipped over when the container is opened by the protrusion of a hinged opening part into the interior of the container.

Due to various constraints, including gas capacity, an elongated insert is preferred, floating with a generally upright longitudinal axis and having at least the characteristic of having three contact points so that the exhaust opening always remains submerged.

A weight is provided under the liquid level to tilt the floating cylinder to a vertical position. Plastic weights with a plastic insert would not achieve this effect due to the low density of the plastic.

It has been found that in these bottlenecks the weighting of the insert can be reduced so that the insert generally floats upright but with its long axis at an acute angle to the vertical. For a cylindrical insert this angle should be θ or less, where

θ = tan⊃min;¹ R/L

where R is the radius of the cylinder and L is the distance from the top of the cylinder to the point where the lift vector coincides with the

Cylinder axis. The lift vector is in line with the weight vector.

Preferably, the insert is made to float in a given rotational orientation by asymmetrically weighting the insert, with the exhaust opening spaced from the longitudinal axis toward the region of greatest weighting.

In another embodiment, liquid is contained in the insert to reduce the size of the required aluminum weight.

The above calculation assumed that an additional weight of solid aluminum in the form of a circular disk was added to the original cylinder at its lower end. If this same aluminum disk is rigidly attached so that its own center of mass is located away from the lower end of the original cylinder, less additional mass is required.

Likewise, less additional weight is required if the lower section of the hollow cylinder is filled with liquid instead of a gaseous product.

The problem of the insert being thrown against the top of the container can be avoided by reducing the diameter of the vent, although this may affect the foaming effect of the gas vented into the beverage. The critical maximum diameter can be determined by:

Critical diameter ≤ 4 x Wt/Π x pressure

It is important to prevent contact between the oxygen and the beverage in the container as this could render it unusable. It was necessary to carefully clean the oxygen from the inserts before filling and closing the container. One reason for this is that the inserts were made of plastics which are gas permeable as disclosed in WO91/07326, allowing the oxygen to pass through to the beverage. In some inserts which have an opening open to the beverage, oxygen could also pass from the insert through the opening into the beverage.

The use of aluminium for the insert body, coupled with the provision of a valve to close the insert interior from the beverage, eliminates this disadvantage. It is possible that the gas in the insert may contain oxygen, as this cannot escape from the insert to the beverage until the container is opened. If the insert has two valves, as described above, the first one-way valve, which closes when the pressure inside the container is less than the pressure inside the insert, prevents oxygen from escaping from the insert. The insert can therefore be filled in air without protection.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

Fig. 1 is a sectional view of a sealed beverage can with a floating insert according to the invention,

Fig. 2 is a sectional view of a first embodiment of an insert according to the invention,

Fig. 3 is a schematic representation of a sealing strip of the insert of Fig. 2,

Fig. 4 is a schematic representation of an alternative sealing strip for use in Fig. 2,

Fig. 5 is a view taken along line 5-5 of Fig. 4,

Fig. 6 a schematic representation of an alternative sealing strip,

Fig. 7 is a sectional view of another embodiment of an insert according to the invention,

Fig. 8 is a schematic representation of a closure strip for use in Fig. 7,

Fig. 9 is a view similar to Fig. 7 showing a partially collapsed membrane after pressurizing the insert in a beverage can,

Fig. 10 is a view similar to Fig. 9 showing the fully collapsed membrane after opening the beverage can,

Fig. 11 is a sectional view of another embodiment of an insert according to the invention,

Fig. 12 is a sectional view of a modification of the insert of Fig. 11,

Fig. 13 is a sectional view taken along line 12-12 in Fig. 12,

Fig. 14 is a view similar to Fig. 11 of a modified insert floating in an inclined position,

Fig. 15 a view similar to Fig. 14 of a modified insert with liquid,

Fig. 16 is a view similar to Fig. 14 of an insert with a modified alignment weight and a repositioned blow-out opening,

Fig. 17 is a view similar to Fig. 16 of an insert with a modified upper end,

Fig. 18 is a graph showing the elongation resistance from a tear test or tensile test carried out on a dry EVOH film,

Fig. 19 is a graphical representation similar to Fig. 18 for a similar film soaked in beer at room temperature, and

Fig. 20 is a graph similar to Fig. 19 for a similar film soaked in beer at about 2ºC.

DESCRIPTION OF PREFERRED EMBODIMENTS

In Fig. 1, a container in the form of an elongated, cylindrical metal can 11 of conventional design is shown, which contains a carbon dioxide-added beverage 12, eg beer. The can 11 is closed by a lid 13 which is peripherally attached to the can to seal the can, the lid 13 being provided with a conventional sealed tear strip 14 which can be opened. A headspace 15 is provided between the upper surface 16 of the beverage 12 and the lid 13. The inner surface 18 has a slightly concave dome shape in the conventional manner.

A pressurized gas-containing insert 20 is provided in the can and floats on the beverage 12, with a lower portion 20a submerged and an upper portion 20b extending into the headspace 15.

The insert 20 is shown more clearly in Fig. 2 and comprises a hollow housing 21 with a housing body 22 in the form of an inverted cup and is closed by a disc 23. The housing body 22 is made of a rigid aluminum alloy and the disc may be of a heavier metal or carry a weighted portion to weigh down the insert so that it floats on the liquid with the disc below the liquid surface. Other materials, e.g. plastics, may be used for the housing.

The disc has an opening 25 for blowing out gas from the inside of the housing into the liquid in the can 11.

The opening 25 is closed by a sealing member 26 which can be attached directly to the disk 23 to form a burstable seal. Preferably, however, a substrate 27 (Fig. 3) provided with a blow-out (nozzle) opening 28 is attached to the disk 23. wherein the sealing member 26 is secured to the substrate.

The sealing member in one embodiment comprises a frangible plastic strip 26 adhered to the substrate 27 by an adhesive 29 around the opening 28. A region 30 of the strip adjacent the opening 28 is not adhered to the pane.

The strip 26 comprises a moisture-sensitive material whose burst strength decreases after exposure to moisture. The housing is previously filled with gas under pressure.

The strip 26 has sufficient burst strength to allow extended storage of the insert under dry conditions. However, inside the can, the strip weakens as it is exposed to the can contents. The pressure gradient across the strip in the can is not sufficient to rupture the strip, but the sudden drop in pressure when the can is opened causes a rupture, bursting the seal and allowing gas to vent into the can contents.

The strip 26 may be made from an ethylene vinyl alcohol (EVOH) copolymer film. The copolymer preferably comprises 40% or less ethylene monomers and in one example has 32% ethylene monomers. A suitable material is that available as EF-XL grade. This film is 15 µm thick and biaxially oriented.

This material is used in the non-bonded area 30 of the strip and an internal gas pressure of 3 atmospheres is 2 mm in diameter (approximately 3 mm²).

This construction was determined to be storable in a dry state. When the sealing strip was left in a can filled with beer containing carbon dioxide and nitrogen under pressure, the sealing strip remained intact, but when the can was opened, the sealing strip broke in the unbonded area 30.

Plastics lose strength when stored under stress and can experience time cracking, and it is important to select a material for the sealing strip that will lose less strength when stored dry for this reason than due to moisture sensitivity. The material disclosed above meets these requirements and it is believed that the biaxial orientation reduces the tendency to time cracking. To reduce this tendency, storage at low temperatures is preferable.

The time rupture behavior can be used to achieve a delay in rupture after opening the container. The sealing strip is arranged so that it expands under the pressure gradient and then suddenly ruptures after a time delay of one second or more.

The EVOH sealing strip is temperature sensitive and has a greater burst strength when cold. This property prevents premature opening of the sealing strip, as will be disclosed later in this description.

The EVOH layer can be coated or covered with a film that reduces its sensitivity to moisture. This also helps prevent premature opening by reducing the Strength is delayed until pressure in the can has been built up by the escape of gas from the beverage.

The general relationship between the internal pressure of the unbonded area zone and the strip thickness is as follows:

PA1/2/t = 0.35,

where P - gauge pressure in atmospheres

A - unbonded area in mm²

t Film thickness in µm

The casing can be filled with air, avoiding the need to use a non-oxidizing gas, since EVOH has good gas barrier properties even after moisture has spread, so that oxygen does not penetrate significantly into the can and spoil the can contents.

In a variation, a moisture-insensitive strip 26 may be used, with the seal being breakable by using a moisture-sensitive adhesive 29, e.g. an EVOH adhesive, which releases the strip to reveal the opening.

In another embodiment, as shown in Figures 4 and 5, a frangible strip 35 is adhered to the substrate 27 in two areas. A moisture sensitive EVOH adhesive is used to adhere the strip 35 to an inner annular area 36 of the substrate around the opening 28. An outer annular adhesive area 37 provides greater adhesion. This is achieved by using a stronger moisture-resistant adhesive or the same adhesive is used over a significantly larger area.

In use, when the can is opened, the strip 35 is released inside, with a larger area of the strip being exposed to the pressure drop caused, so that the strip breaks or bursts.

The seal may be provided on an insert sleeve which is fixed in an opening in the insert and is provided with a blow-out opening.

The insert corresponding to one of the preceding embodiments can be easily recycled together with the can. There is no need to deoxygenate the insert, nor does storage or shipping need to be carried out in an oxygen-free environment.

In a further embodiment of the invention shown in Fig. 6, it is not necessary to fill (the insert) with pressurized gas beforehand and to store it in a moisture-free environment.

In this embodiment, a thin, rupturable, gas-impermeable layer 60 is provided between the substrate 27 with the blow-out (nozzle) opening 28 and the disk 23 of the insert body. The sealing strip 61 is made of gas-permeable material, and the substrate is also preferably gas-permeable. The sealing strip 61 is rupturable and is adhered to the substrate 27 by an adhesive ring which, as described above, may be moisture sensitive.

In use, the insert is filled with an oxidizing gas, e.g. air, essentially at atmospheric pressure.

When used in a closed beverage can, the pressurized gas in the can can pass through the permeable layers, so that pressure builds up on one side of the gas barrier layer 60. The pressure built up eventually breaks the gas barrier layer, so that the pressure on the sealing strip 61 can equalize.

The sealing strip 61 breaks or bursts due to the sudden drop in pressure when the can is opened.

In a variation, the arrangement shown in Fig. 2 is modified by providing a gas barrier layer on the inside of the disk 23 of the insert body, with the blow-out (nozzle) opening located in the disk instead of in the substrate (Fig. 6).

In a further embodiment according to Fig. 7, the insert comprises a housing 121 with a housing body 122 and a disk 123 as in the previously described embodiments

The insert has an inner membrane 150 which is cup-shaped and divides the interior of the body into upper and lower chambers 151, 152. The membrane is compressible, but is sufficiently stiff to retain the cup shape until subjected to collapsing forces. It can be made, for example, from a soft aluminum alloy.

The disc 123 has a blow-out (nozzle) opening 125 which is closed by a sealing member 126, and the lower chamber 152 contains a gas, which may be air, under atmospheric pressure or negative pressure.

The upper chamber includes a charging or filling opening 160 in the top of the housing which is closed by a sealing strip 161. This chamber contains non-oxidizing gas, such as nitrogen, at atmospheric pressure or a slight vacuum. The sealing strip 161 comprises two superimposed layers which are weakly bonded together. The outer layer 162 comprises a gas-permeable material, while the inner layer 163 comprises a rupturable, gas-impermeable material.

After the insert is placed in a sealed beverage can, the pressurized gas in the can penetrates the outer gas permeable layer 162 and the inner layer 163 is caused to rupture due to the pressure gradient across the layer. The gas then flows through the fill port 160 to pressurize the upper chamber 151.

This pressure is transmitted through the membrane 150 to the lower chamber 152, which membrane begins to rupture so that the pressure in the lower chamber becomes almost equal to that in the upper chamber. The partially collapsed membrane and the ruptured layer 163 are shown in Fig. 9.

When the can is opened, the sudden pressure drop on the sealing strip 126 breaks it open, and the gas is expelled or blown out from the lower chamber into the can.

During blow-out, the membrane is compressed when the pressure in the lower chamber is lower than the in the higher chamber. All of the gas is exhausted at significant pressure, with a generally uniform exhaust velocity throughout the exhaust period. This collapsed membrane and the ruptured sealing strip 126 are shown in Fig. 10.

At the end of the purge period, some gas remains under pressure in the upper chamber, but it is dissipated by the gas permeable layer 162 of the closure strip 161.

It is not essential for an insert functioning in this way to float in the can, and the insert could also be filled below the liquid level if desired.

However, in a floating application it is possible to do without the closure strip 161 if the opening 160 is kept very small so that the gas can only flow very slowly through the opening.

Preferably, however, a rupturable seal is provided, e.g. by means of a breakable layer covering the opening. This prevents oxygen from penetrating the insert during storage.

The rupturable material of the sealing strip 126 and the rupturable layer 163 of the closure strip 161 may be made of a highly gas-impermeable polymer, e.g. EVOH, polyvinylidene chloride, polyamide or polyester, or may comprise two or more layers with a gas-barrier layer. Other possible materials include thin metal films, or metalized plastic films, or a film coated with inorganic oxides. coated plastic film, e.g. silicon oxide applied by vapor deposition.

The gas permeable layer 162 may comprise low density polyethylene (LDPE), or an ionomer such as Surlyn, a cellulose acetobutylate, or a porous plastic paper such as Tyvek.

Similar materials can be used in the embodiment according to Fig. 6.

The upper chamber 151 can contain an oxygen radical scavenger.

Potassium sulphite is often used in beer cans for this purpose, but because it is soluble in beer, it spoils the taste and contaminates the beer. When added to the can, it also scavenges atmospheric oxygen during the handling and filling processes before the can is sealed.

The provision of an oxygen radical scavenger in the upper chamber 151 means that it never comes into contact with the beer and is also sealed from the surrounding air during handling by the closure strip 161. The oxygen is trapped within the upper chamber without coming into contact with the beer.

In another embodiment (not shown), the membrane is omitted and the entire interior of the insert receives its pressure from the beverage. The filling opening can be closed by providing the burstable gas barrier film inside the insert and the gas-permeable film on the outside of the insert.

If a very small filling opening is planned, the gas-permeable film can be omitted.

Another embodiment of an insert 220 is shown in Figures 11 and 13 and comprises a hollow, elongated, cylindrical body 221 closed at both ends by upper and lower end walls 222, 223. Other designs may be used for the body.

The insert includes a disk-shaped plumb weight 224 secured to the bottom wall 223 within the body so that the body floats with a vertical axis. The weight may be made of metal, for example. The body may be made of a molded plastic, but is preferably made of metal, e.g. aluminum.

The cylindrical wall 226 of the insert body includes a filling or charging port 227 in the upper portion 220b of the insert, which is positioned to connect the interior of the insert body with the headspace 215. The charging port is closed by a one-way valve 228 in the form of a flap valve. The valve may be formed by a flexible strip which is bonded at one end 228a to the inner surface of the cylindrical wall 226, the remainder of the strip being deflectable to close or open the port. This arrangement functions such that the valve is urged to the closed position when the internal pressure exceeds the external pressure and only opens when the external pressure is above the internal pressure.

The lower end wall 223 of the body is provided with a blow-out (nozzle) opening 230, and the plumb weight 224 comprises an opening 225 which establishes a connection of the opening 230 with the interior of the body. The exhaust opening 230 is closed by a frangible member 231 in the form of a strip glued to the outer surface of the lower end wall 223 around the opening. The opening can open when the internal pressure of the body is greater than the external pressure and the pressure gradient exceeds a predetermined threshold. This can be determined by structuring the strip so that it breaks when the threshold is exceeded. This can be achieved by gluing the strip in such a way that a sufficiently large zone or area around the opening is not glued. With a heat and pressure sensitive adhesive, for example, the non-glued zone can be determined by not allowing heat and pressure to act in this zone. On the other hand, if the threshold is exceeded, the adhesive may rupture, causing the sealing member to be blown away from the blow-out (nozzle) opening, thus forming a destructible seal.

Figure 12 shows a modified construction of the rupturable sealing member. The strip 231A is held between the plumbing weight 224A and the bottom wall 223A of the insert. The plumbing weight 224A has a small opening 225A which forms the blow-out opening, and the bottom wall 223A has a large opening 230A to allow the strip 231A to be ruptured at the desired threshold pressure. The strip 231A can be held compressed between the weight and the bottom wall, or can be glued to either the weight or the bottom wall, or both.

This modification ensures a clean, predictable break of the strip at threshold pressure.

This threshold value is determined such that the actuator or control element 231 remains in the closed state until the can is opened, the threshold value only being exceeded under these circumstances.

In use, the insert 220 is filled with a pressurized gas via the charging port 227. After charging, the gas is retained in the insert body by automatically closing the one-way valve 228, the external pressure being atmospheric pressure.

The filled insert is inserted into a can 11 before the can is filled with a beverage 12, so that the insert floats or drifts on the beverage. The can lid 13 is attached to the intended location. The weighting of the insert causes it to float with the actuating or control element 231 immersed in the beverage, with the feed valve 228 projecting into the head space 15.

The filled can is then subjected to pasteurization which causes an increase in pressure within the can. The one-way feed valve 228 opens when this pressure exceeds the pressure in the liner body to allow the gas from the headspace 15 to enter the liner. The can is then cooled and the one-way valve 228 closes again, maintaining the increased internal pressure within the liner while the can cools.

The control element 231 is designed to withstand the pressure differences resulting from the pasteurization and cooling steps.

When the can is opened at point 14, a sudden drop in pressure occurs in the can. This creates a pressure gradient at the device 231 that is sufficient to exceed the threshold value, so that the device is permanently open and gas is blown out into the beverage through the opening 230.

The inventor of the present invention has discovered that this venting action can force the insert 220 away from the beverage 12 so that it comes into contact with the lid 13. To ensure that the gas is vented into the beverage 12 and not into the headspace 15, the insert 220 is made long enough relative to the depth of the headspace so that the vent opening remains submerged when this occurs.

The outer surface of the upper end wall 222 is also made flat so that it makes peripheral contact with the inner surface 218 of the cover 13. This arrangement does not cause angular movement of the insert which could bring the exhaust port into communication with the headspace.

If the insert body is made of aluminum, it is coated against corrosion. The formation of the openings 227, 230 results in edges that can corrode. However, the edge of the blow-out opening 230 is protected from corrosion by the strip 231. The edge of the feed opening 227 is less susceptible to corrosion since it is only exposed to the head space 15 or is exposed therein.

The insert can be made to float with its longitudinal axis at an acute angle to the vertical V, as shown in Fig. 14. This is particularly useful when the insert body 420 and weight 424 are made of aluminum, so that the amount of aluminum used can be reduced.

The insert floats at an angle of θ to the perpendicular or vertical V and has a flat top 422 to contact the interior of the can lid as the insert is driven against the lid by the blow-out force.

The blow-out opening remains below the liquid surface in the floating orientation of the insert, and abutment of the flat top 422 against the lid aligns the long axis of the insert closer to the vertical when the can is opened so that the opening remains below the liquid surface. The weight 524 can be reduced even further, as shown in Fig. 15, if some liquid 530 is provided in the insert.

If it is desired to allow a large amount of liquid to flow in, the feed opening is placed below the liquid level. It should be noted that the level of liquid filling in the liner that can be achieved in this way is not limited to the height of the liner corresponding to the original level of the beverage liquid in the main container. One reason for this is that the buoyancy of the liner is reduced as it fills with liquid and the liner sinks deeper into the (beverage) liquid. The other reason is that liquid penetrates into the liner until the gas pressure above the liquid in the liner is equal to that inside the can. If desired, the liquid level can be within the insert by providing two loading openings, one below the liquid level in the can and one above this level.

Another embodiment is shown in Fig. 16. The insert 620 has a similar structure to that of Fig. 14 with a weight 624. However, in this embodiment the total weight is distributed asymmetrically about the longitudinal axis. This is achieved by placing an additional weight 640 at a specific location on the circumference closest to the insert bottom. Instead, an asymmetric disk could be provided. The additional weight 640 dictates the rotational orientation of the insert when it floats at an angle θ to the vertical V.

The blow-out (nozzle) opening 630 is offset from the longitudinal axis towards the position of the additional weight 640. This means that the opening is positioned at a lower point than if the insert were floating with a vertical orientation.

A variation of the embodiment of Fig. 16 is shown in Fig. 17. In this embodiment, the upper end 722 of the insert 720 is angled relative to the lower end 723 so that the upper end is horizontal in the floating orientation of the insert.

Therefore, when the insert is driven against the lid, it maintains the floating orientation.

The insert can therefore be shorter in relation to the head space than in the embodiments of Fig. 11 or 16.

The position of the insert relative to the liquid surface during charging in the pasteurization step is determined by its buoyancy, and its position during blowdown (of gas) is determined by its longitudinal dimension relative to the headspace. If one wishes to partially fill the insert with liquid and then later allow the liquid to flow out above the beverage liquid level, this can be done by reducing the buoyancy of the insert to the point where the charging opening is covered with liquid during charging and providing sufficient headspace height for the insert to rise in response to its blowdown. This allows foam to form in this liquid closest to the surface while the rest of the liquid retains its inherent bubbles.

In a modification, the one-way valve 228 shown in Fig. 11, for example, can be omitted. In this modification, the feed opening 227 is smaller in area than the blow-out (nozzle) opening 230, so that the pressure loss at the feed opening 227 when the container is opened is not sufficient to prevent the control element 231 from opening and the blowing out (of gas) through the blow-out opening 230.

In this variation, the internal pressure in the insert is relatively low, as it balances out with the internal pressure in the container.

The diameter of the blow-out (nozzle) opening can be, for example, 0.8 mm and that of the feed opening 0.1 mm. The loss of gas through the feed opening would be only 2% when opening the container with this arrangement.

In this variation, there should be essentially no oxygen in the insert, since oxygen could pass through the charging opening to the container contents. The insert would therefore preferably be filled in a non-oxidizing atmosphere and protected against diffusion of oxygen into the insert before it is inserted into the container. With a small charging opening, significant diffusion would take several minutes, so protection during insertion into the container and closing of the container would not be necessary.

The insert could be protected during shipping and storage by using oxygen-blocking packaging or blocking the loading opening with oxygen-blocking tape. The packaging could include a bag containing a plurality of inserts and an oxygen scavenger.

The inserts are exposed to moisture in the can for a considerable period after sealing until pressure is built up due to the release of gas from the liquid. The filling process is carried out at low temperatures in order to maintain a high gas content in the liquid. This means that the moisture-sensitive layer is exposed to both moisture and a high pressure gradient for some time until the pressures equalize. It would therefore be expected that a moisture-sensitive layer could weaken while exposed to pressure and moisture and burst before temperatures (or pressures) equalize.

However, it was found that EVOH is relatively insensitive to moisture at such low temperatures, so the expected problem did not occur. EVOH layer absorbs moisture at higher temperatures and therefore only becomes weaker once pressure equalization has already occurred.

Example

An insert was made as disclosed in Figure 2 with a strip 26 made from EF-XL as disclosed with reference to that figure.

The insert was inserted into an empty can body, which was then filled with beer at a temperature of about 2ºC. Within a few seconds of filling, the can body was sealed with a lid. The can was then turned upside down and pasteurized at 60ºC for about 15 minutes, and then cooled to about 7ºC and stored at that temperature.

The can was then opened and the film broke immediately upon opening and foam formed inside the can.

After pouring the beer from the can into a glass, the whole beer contained small bubbles that created a head of foam on the beer, which is typical of draft beer.

Fig. 18 shows a dry EF-XL film subjected to a room temperature tensile test. The film showed a slow increase in elongation with increasing load up to about 55 mPa.

Fig. 19 shows results of the same test performed on a wet EF-XL film soaked in beer at room temperature. The film showed a slow increase in strain only up to about 20 mPa, showing a significant reduction in strength relative to a dry film.

Fig. 20 shows the result of the same test performed on a wet EF-XL film at about 2ºC. The film was again soaked in beer. The film showed a slow increase in strain up to about 55 mPa, illustrating that the strength of the wet film at low temperatures is comparable to that of a dry film.

Claims (24)

1. A foam-inducing insert for inclusion in a container containing a beverage with gas dissolved therein under pressure, for initiating the release of gas from the insert upon opening of the container, which insert comprises: a housing (21) with a chamber, gas contained in the chamber, which chamber has a blow-out (nozzle) opening (28) through the housing, a closure means closing the opening which can be opened under the pressure difference or effective pressure across the opening caused by opening the container in use, thereby blowing gas into the container, the closure means having a sealing member (26) attached around the opening (28) to create a seal and the closure means being burstable under the effective pressure, characterized in that: i) the sealing member (26) is breakable and sensitive to moisture, so that in its dry state it can withstand a higher pressure than after exposure to moisture, or ii) the sealing member (26) is bonded around the opening (28) by means of a moisture-sensitive adhesive (29) whose adhesive properties decrease when exposed to moisture. 2. The foam inducing insert of claim 1, wherein the sealing member is made of an ethylene vinyl alcohol (EVOH) copolymer film. 3. A foam inducing insert according to claim 2, wherein the film contains less than 40 wt.% ethylene monomers. 4. The foam inducing insert of claim 3, wherein the film contains 32% or less by weight of ethylene monomers. 5. Foam inducing insert according to one of claims 2 to 4, wherein the thickness of the film is 10 - 20 µm (microns). 6. Foam inducing insert according to one of claims 2 to 5, wherein the film is biaxially oriented. 7. Foam inducing insert according to one of claims 1 to 6, wherein the sealing member is glued to a metal substrate or carrier (27) and the blow-out (nozzle) opening (28) is provided in the carrier. 8. The foam inducing insert of claim 1, wherein the adhesive is an EVOH or polyvinyl alcohol adhesive. 9. Foam-inducing insert according to claim 1 or 8, wherein the sealing member (35) is more firmly bonded in an outer region (37) around an inner region (36) bonded by means of the moisture-sensitive adhesive and the (sealing) member is breakable under the effective pressure when it is or becomes detached at the inner region. 10. Foam-inducing insert according to one of the preceding claims, wherein the sealing member (61) is gas-permeable and a gas barrier element (60) between the sealing member (61) and the insert interior, which gas barrier element (60) is capable of bursting under the pressure within the container. 11. Foam inducing insert according to one of the preceding claims, wherein the housing contains a membrane (150) defining a wall of the chamber (152) and on the side of the membrane remote from the chamber (152) has a feed opening (160) passing through the housing, whereby pressure prevailing in the container in use acts on the gas in the chamber via the membrane. 12. Foam-inducing insert according to one of claims 1 to 10, with a feed opening (227) passing through the housing and communicating with the chamber. 13. Foam-inducing insert according to claim 11 or 12, wherein the feed opening (160) is closed by a gas-permeable element (162). 14. Foam inducing insert according to claim 13, wherein the feed opening (160) is additionally closed by a rupturable, gas-impermeable barrier (163) which ruptures in use under the pressure prevailing in the container. 15. Foam inducing insert according to claim 11, wherein the membrane (150) is malleable and compressible under the effective pressure induced by opening the blow-out orifice (125) across the membrane, in order to expel gas from the chamber (152) at a substantially uniform rate or velocity. 16. A foam inducing insert according to claim 11, wherein the first chamber (152) contains air and the membrane (150) defines a second chamber (151) containing a non-oxidizing gas. 17. A foam inducing insert according to claim 16, wherein the second chamber (151) contains a non-oxidizing gas and an oxygen radical scavenger. 18. Foam-inducing insert according to one of the preceding claims, wherein the insert is mounted in a closed container (11) containing a beverage (12) under gas pressure. 19. Foam-inducing insert according to one of claims 1 to 17, wherein the insert is buoyant on the beverage (12) within a container (11). 20. Foam inducing insert according to one of the preceding claims, wherein the housing (21) is made of aluminium. 21. A foam inducing insert and container according to claim 18 or 19, wherein the container is sealed and contains a beverage with dissolved gas under pressure and a gas-containing headspace is provided above the beverage, the insert contains a gas under pressure, the insert has a feed opening positioned for communication with the headspace, and a one-way valve closes the first opening when the internal pressure in the insert exceeds the internal pressure in the container and can be opened when the internal pressure in the container exceeds the internal pressure in the insert. 22. A foam inducing insert according to any one of the preceding claims, wherein the insert is elongated and has a weight (224) at or near one end of the elongated insert which causes the insert to float with its longitudinal axis at an acute angle to the vertical, the weight being asymmetrically arranged relative to the longitudinal axis. 23. A foam inducing insert according to claim 22, wherein the blow-out opening (630) is arranged at a location that is offset from the longitudinal axis towards the region of greatest weight. 24. Foam-inducing insert according to one of claims 1 to 10, with a feed opening passing through the housing, communicating with the chamber, which has a smaller area than the blow-out (nozzle) opening.