There have been many proposals for seif-heating or self-cooling beverage containers. WO 96/29255, for example, discloses a can having the same external dimensions and shape as conventional beverage cans, but having an indented base to define an external cavity in which means to cool or heat the contents of the can are received.

Heating or cooling of the contents of the can can be achieved by using two chemical reactants which are stable when separated, but which produce an exothermic reaction or an endothermic reaction when mixed. US patent No.

5,626,022 shows just one example, from many, of an insert for a self-heating or self-cooling can which enables mixing of the reactants when required.

This construction, as is common, proposes the use of a module, which is pre-assembled and is then inserted into the can.

WO 01/24672 describes a self-heating or a self-cooling container in which there is no requirement to form the heating or cooling means into a sub- assembly. Instead, the individual components of the heating or cooling means are simply assembled within an external cavity of the container. The first and second reactants are loaded into respective chambers in the external cavity defined and separated by a breakable membrane.

When the reactant materials are mixed, by piercing of the breakable membrane, there will generally be a chemical reaction, for example, to produce a heating or a cooling effect. Such a chemical reaction may be associated with pressure changes, as well as temperature changes.

The breakable membrane is pierced by pressing a button or moving some other device to effect the mixing of the reactants. In the arrangement

illustrated in WO 01/24672, for example, the button, which is made of plastics material carries an elongate piercing member such that pushing the button extends the piercing member through the membrane whereby it is pierced or ripped. Not only does the piercing of the membrane effect the chemical reaction, it also destroys the barrier between the chemical reactant which was sealed behind the breakable membrane and the button or other operating device. With some reactant materials, the ability of the first reactant material to escape from the originally sealed chamber can cause problems. This is particularly the case where the two chemicals are to be reacted to produce a heating effect as the reactant material which was originally sealed behind the breakable membrane is not only able to move out of the chamber but will also be extremely hot.

In an embodiment of a self-heating container, for example, quicklime may be sealed within the first chamber by the breakable membrane and heated when the membrane is pierced by the mixing thereof with water. The temperature of the reacting quicklime can become very high and can be sufficient to melt or deform a plastics button. This could cause a failure in the integrity of the container and be potentially dangerous.

The need to prevent contact between reacting quicklime and specific parts of a container has been identified previously and there have been proposals, specifically for modular heat exchange units to provide a physical barrier between the reacting quicklime and a plastics material button, for example. For example, one or more paper or foil discs have been mounted in the water chamber. However, the provision of such barriers overly complicates the construction.

It is an object of the present invention to provide a solution to the identified problems which is effective yet easily incorporated in an appropriate unit.

According to the present invention there is provided a unit for enabling two reactant materials to be mixed comprising an elongate cavity having first and second spaced ends, the first end of the cavity being closed, a breakable membrane extending across said cavity spaced from said first end to define a

first chamber, a first reactant material sealed within said first chamber by said breakable membrane, a closure member closing the second end of said cavity whereby a second chamber is defined between said breakable membrane and the closure membrane, a second reactant material retained within said second chamber, and piercing means movable to break or pierce the breakable membrane whereby said first and second reactant materials can mix, the unit further comprising a retention member extending across the first chamber adjacent said breakable membrane, said retention member being arranged to allow passage of said second reactant material therethrough but to generally resist passage therethrough of the first reactant material whereby the first reactant material is retained in said first chamber.

With an embodiment of a self-heating container incorporating a unit of the invention, for example, the provision of the retention member is able to resist exit of heated and reacted first reactant material from the first chamber.

In this way, the types of problems identified above are reduced or overcome.

In a preferred embodiment, the retention member has an annular rim to which the breakable member is sealed. Thus, the provision of the retention member enables simplification of the assembly of the container.

In an embodiment, the retention member comprises a disc which extends across the first chamber adjacent the breakable membrane, the disc having a plurality of apertures therein to generally allow passage of the second reactant material therethrough whilst resisting passage of the first reactant material therethrough.

For example, the plurality of apertures may be formed by a plurality of slots or perforations in the disc. Alternatively, the disc may incorporate, or be formed by, a mesh.

In a currently preferred embodiment, the retention member comprises an outer, substantially cylindrical wall, sealed into an end of the first chamber adjacent the breakable membrane, and the outer cylindrical wall supports an apertured disc extending generally radially with respect thereto and across the first chamber.

Generally, the outer wall is used to secure the retention member in position. This may be by the shape and configuration of the outer wall, and/or by sealing the outer wall to the wall of the first chamber, for example, by an appropriate adhesive.

The retention member may further comprise a second, inner, substantially cylindrical wall arranged radially within the outer substantially cylindrical wall, the second wall being connected to the outer wall by a web, and wherein the apertured disc is affixed to the second, inner wall.

To enable the piercing member to pierce the membrane without risk of fouling the retention member, the apertured disc of said retention member is preferably longitudinally spaced from an outer end of said retention member.

In an embodiment, the apertured disc is split into a plurality of separate segments able to diverge with respect to each other upon the application of pressure thereto. This enables the retention member to accommodate expansion of the first reactant material upon reaction thereof on mixing.

Preferably, the cavity is shaped to define a protruberance therein on which the breakable membrane is supported. For example, the protruberance may be a flange or a bead, or have any other configuration. In a preferred embodiment, the protruberance is annular.

In an embodiment, the retention member has a rim at one end thereof which is affixed to the protruberance within the cavity, and wherein the breakable membrane is fixed to the rim of the retention member.

The rim of the retention member is preferably annular.

In a preferred embodiment, the breakable membrane is affixed to the retention member to form a hermetic seal.

The first reactant material sealed within the first chamber may be in a powder, granular, or other particulate form, and the second reactant material in the second chamber may be a fluid.

The breakable membrane may be formed by a disc of a metal foil secured to the cavity to extend across it.

The present invention also extends to a container having a tubular peripheral wall, a top member closing one end of the peripheral wall, and a base member closing the other end of the peripheral wall, an internal cavity for the contents of the container being defined within the peripheral wall, and wherein the base member is indented to define an external cavity which extends within the peripheral wall but is separated from the internal cavity, and wherein a unit for enabling two reactant materials to be mixed as defined above is assembled within the external cavity defined by the base member, the external cavity forming the elongate cavity of the heating or cooling unit.

Preferably, the container further comprises pressure venting means associated with the closure member and/or with the container.

Whilst a unit of the invention can be used whenever it is required to mix two reactant materials at the point of use, it is particularly useful where mixing of the two materials generates a heating or cooling effect which can be utilised to heat or cool the contents of the container in which the unit is incorporated.

When it is required to cool or heat the container, it is inverted to provide access to the base of the closure member which is then pressed to cause the piercing member to pierce the breakable membrane. This releases the fluid in the second chamber such that it flows into the first chamber to begin the chemical reaction. The use of a second reactant material in fluid form assists in the mixing process.

For a self-heating container, for example, quicklime may be filled within the first chamber and water retained within the second chamber. Lime is extremely hydroscopic and it has been found that sealing the lime by the breakable membrane within the first chamber improves the shelf life of the container greatly as the lime is thereby sealed from contamination.

The breakable membrane may be of any material capable of sealing the first reactant material in the first chamber, and supporting the weight of that

material when the container is in its normal upright position. For example, the breakable membrane may be formed by a disc of a metal foil secured to the external cavity to extend across it.

Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows schematically a self-heating beverage container, Figure 2 shows a further example of a container incorporating a retention member of the invention, Figure 3 shows a perspective view of a further embodiment of a retention member, Figure 4 shows a section through the retention member of Figure 3, Figure 5 shows a plan view of an internal end of the retention member of Figures 3 and 4, and Figure 6 shows a plan view of an alternative embodiment of a retention member.

The invention will be described hereinafter specifically with reference to a self-heating beverage container. However, the container of the invention, which is described below, may alternatively be arranged to be self-cooling. In fact, the invention finds general application whenever it is required to package goods in a manner requiring two materials to be mixed at the point of use.

The invention is also described specifically hereinafter with reference to a self-heating container in which the individual components of the heating or cooling means are simply assembled within an external cavity of the container.

However, the present invention finds application also in a unit which is formed as a subassembly and then mounted into a container by any appropriate means. For example, a cylindrical modular unit could be seamed into the base of a substantially conventional beverage container. As set out above, the unit could be used whenever it is required to mix two reactant materials at the point of use. However, the present invention is particularly useful when the two reactants generate a heating or cooling effect on mixing whereby the unit is a heating or cooling unit.

The container shown in Figure 1 may be a metal or plastics material container 10 having a substantially cylindrical peripheral wall 12 which is closed at one end by a top member 14. As described in WO 96/29255, a base member 16 of the container is indented to define an elongate external cavity 20 which extends within the peripheral wall 12. It will be appreciated that the peripheral wall 12 and the top and base members 14 and 16 of the container together define an internal cavity 22 in which contents, such as a beverage, are received. It will be seen that the external cavity 20 extends within this internal cavity 22, but is separated therefrom by the wall of the base member 16.

The container 10 illustrated in Figure 1 is configured to have the same external dimensions and shape as a conventional beverage can. This means that the can 10 can be filled and treated on existing filling lines.

As described in WO 01/24672, the external cavity 20 of the can 10 is to be utilised to contain heating or cooling means. Where the can 10 is a self- heating can, for example, the heating means may comprise quicklime (calcium oxide) filled within a first chamber 28 within the cavity 20. A second chamber 32 within the cavity 20, separated from the first by breakable membrane 24, is filled with water. The second chamber 32 is closed by closure 30.

When it is required to heat the contents of the can 10, the can is, as illustrated in Figure 1, inverted and stood on its top member 14 so that the base of the closure 30 is accessible. A button 50 on the bottom of the base is depressed whereby an elongate piercing member 42 carried thereby pierces the membrane 24 so that water from the chamber 32 flows over the quicklime 22 to cause the exothermic reaction. The steam which is generated is allowed to vent around the periphery of the closure 30 through vents or recesses (not illustrated) formed in either the periphery of the closure 30 or in the wall of the cavity 20 or in both. It is generally recommended that once the water has drained from the chamber 32, the can be returned to its upright position, as this aids heating. After the exit of steam has been completed, the contents of the can should have been heated to a satisfactory temperature.

It will be seen that the base member 16 is shaped to define at least one annular flange 34 in the wall of the external cavity 20. This flange 34 is used to

support the breakable membrane 24 whereby the external cavity 20 is divided into the first chamber 28 and the second chamber 32. It will be appreciated that the breakable membrane 24 may be piercable, rupturable or breakable in any manner.

In a preferred embodiment, the breakable membrane 24 is a disc of metal foil. After the first reactant material, for example, quicklime, has been charged into the first chamber 28, the membrane 24 is positioned in the cavity 20 and bonded or otherwise sealed along its periphery to the annular flange 34.

Preferably, and as shown in Figure 1, the closure 30 is formed from plastics material and is integral with the elongate piercing member 42. The closure 30 comprises a substantially circular member having an annular peripheral rim 36. This rim 36 defines an annular recess 38 which enables the closure 30 to be clipped on to the base of the can 10. It will be seen that in the embodiment illustrated, the free edge of the rim 36 carries an annular projection 40 which is arranged to engage within an annular groove provided externally of the base edge of the can 10.

The self-heating container described and illustrated can be filled on conventional filling lines, and the contents thereof may be subjected to any treatment required. For example, contents of the container may be pasteurised and/or sterilised. Thereafter, it is a simple matter to invert each completed and filled container and provide it with heating means in its external cavity 20.

Thus, the external cavity 20 is charged with a predetermined amount of quicklime, a breakable membrane 24 is inserted and is bonded or otherwise fixed by appropriate means to the annular flange 34, a charge of water is then filled into the thus defined second chamber 32, and the closure 30 is clipped onto the container 10. To ensure that the chamber 32 is substantially water tight, the periphery of the closure 30 has an integrally formed seal in the form of an annually extending wiper 52. It is also possible to incorporate within the peripheral region of the closure 30 a one way valve or seal (not shown) arranged to prevent the ingress of air from the outside. Such an atmospheric valve is effective to seal water within the chamber 32 but enables venting of the chamber.

It will be appreciated that not only is it necessary to ensure that a container as in Figure 1 is sufficiently robust to enable it to withstand normal transport and handling, it is also important to ensure that the contents are safely retained and that the container is resistant to abuse.

It will be seen that in the embodiment of Figure 1, once the membrane 24 has been broken or removed, the quicklime can come into contact with the button 50. Of course, the quicklime will, at this stage, have been heated to a high temperature by its reaction with the water and relatively large pieces of the reacted quicklime will be particularly hot. Such large and hot pieces of quicklime are, in fact, capable of deforming or melting the button 50. This can cause a failure in the integrity of the closure 30 and is a source of potential danger.

Figure 2 shows a similar container to that of Figure 1 but with a retention member 100 sealed within the first chamber 28 adjacent to the membrane 24.

This retention member 100 is arranged to generally prevent the quicklime from exiting the first chamber 28 and to perform this function both before the quicklime and water are mixed and after the chemical reaction thereof.

However, to ensure that the heating reaction can be caused when required, the retention member 100 is also arranged to allow the passage of water therethrough. Accordingly, and as indicated in Figure 2, the retention member 100 is formed as a plug of perforated material or is formed from a mesh. The apertures in the retention member 100 are sufficiently small to generally retain the quicklime in the first chamber 28 but similarly allow the passage of water through the retention member when the membrane 24 is pierced.

It will be seen that the external surface of the plug 100, which faces the piercing means 42, is shaped so that the piercing means can extend through, and pierce, the membrane 24.

With a retention member, as 100, fixed into position within the opening of the first chamber 28 adjacent the membrane 24, the reacting quicklime is prevented from moving towards and damaging the button 50 of the closure 30.

In addition, the retention member also prevents damage to the membrane 24 by contact with the quicklime before the membrane is pierced. It will be

appreciated that this adds to the robustness of the container during normal transport and handling.

In the embodiment shown in Figure 2, any steam or other gases generated when the quicklime and water react are vented by way of a pressure relief valve 110 which is carried by the closure 30 and sealed against the can 10.

The retention member 100 shown in Figure 2 is generally a separate plug which is affixed or otherwise sealed within the first chamber 28 generally adjacent the membrane 24. Figures 3 and 4 show a perspective view and a longitudinal section through a retention member 100 arranged not only to retain the quicklime in its cavity, but also to secure the breakable membrane 24 reliably in place. As can be seen in Figures 3 and 4, the retention member 100, which is preferably made from a plastics material, has an outer substantially cylindrical wall 102 on one end of which an annular rim 104 is formed. In use, the inwardly facing, generally radial surface 106 of the annular rim 104 will be secured against a flange, as 34, within the cavity 20. As indicated in Figure 4, the breakable membrane 24 can, at an appropriate time, be sealed to the annular rim 104 of the retention member 100 to secure the membrane in position and effectively seal the first chamber 28. The breakable membrane 24 forms, with the retention member 100, a hermetic seal for the first chamber 28.

The outer, substantially cylindrical, wall 102 of the retention member 100 is sized and shaped such that it can be pressed into the opening of the first chamber 28 whereby the retention member 100 is sealed in position. In this respect, the outer wall 102 may have a flared configuration to aid affixing the retention member 100 in position. Additionally and/or alternatively, a meltable adhesive or other fixing means may be used to retain the retention member in position. Additionally and/or alternatively, the annular rim 104 may be adhered or otherwise fixed to the flange 34 of the cavity.

The retention member 100 has a second, inner, substantially cylindrical, wall 108 which is fixed to the outer cylindrical wall 102 by a web 112 whereby a generally annular groove 114 is defined within the retention member 100. A generally circular disc 120 provided with appropriate holes and perforations, for

example, indicated at 122, extends generally radially within the retention member across the inner cylindrical wall 108. It is the apertures 122 within the disc 120 which enable passage of the water retained within the second chamber 32 into the quicklime when the membrane 24 is pierced. However, the size of these apertures 122 is restricted sufficiently so that, in the main, the quicklime will not travel through the disc 120. In this manner, protection to the material of the membrane 24 from the quicklime in its dry sealed state is provided.

It will be seen that the disc 122 is spaced from the membrane 24 inwardly within the first chamber 28. This spacing enables the membrane to be pierced without the piercing member 42 coming into contact with the disc 120.

Once the membrane 24 has been pierced, the quicklime will react with the water and larger particles of the reacted quicklime will become particularly hot. It will immediately be apparent that the apertures 122 will be totally effective in preventing passage of the larger and hotter particles of quicklime through the disc 120 whereby protection of the fabric of the closure 30 from the reacting quicklime is provided. In this respect, it would, of course, be possible to arrange that, in all circumstances and conditions, the retention member unfailingly retains the quicklime within the first chamber 28 internally of the retention member. However, in many applications, some passage of smaller particles of the quicklime through the retention member may be allowed such that, for example, there is no attenuation of the water flow into the first chamber when the membrane is pierced. In this respect, it is the larger particles of the quicklime, particularly after the reaction, which are particularly dangerous.

When assembling the retention member 100 and the membrane 24 in position it is generally preferred that the retention member 100 be affixed to the cavity 20 before the membrane 24 is affixed thereto. In this respect, in general, the membrane 24 is not generally preassembled onto the retention member 100 before the assembly is fixed into position within the external cavity as the assembling means can cause damage to the membrane.

If required, the membrane 24 may be tacked onto the retention member 100 before the member 100 is fixed into position within the external cavity.

Once the retention member 100 has been positioned, the membrane 24 may be heat sealed thereto. This assembly method may make it easier to correctly position the membrane relative to the retention member 100, and the external cavity 20.

Figure 5 shows a plan view of the inwardly facing end of the retention member 100 of Figures 3 and 4 and shows the configuration of the disc 120 and the apertures 122 provided therein. In this configuration the circular disc 120 is fixed to or formed in one piece with the inner cylindrical wall 108. In the illustrated embodiment the central area 122'of the disc 120 is shown to be solid and without apertures. However, apertures as 122 may be incorporated in this central area 122'if required.

Figure 6 shows a similar plan view of an alternative embodiment of the retention member 100 specifically arranged to cope with the expansion of the quicklime. In the Figure 6 embodiment it will be seen that the disc 120 is spaced from the inner cylindrical wall 108 and its periphery is attached thereto by a number of tags 124. In addition, the disc 120 is cut into six individual, generally triangular segments 126 which, in the initial position, come together to form the disc. However, as the quicklime expands, these triangular segments 126 are pushed outwardly by the pressure of the expansion and separate to accommodate that expansion. However, even if the separation of the segments is sufficient to enable the passage of larger particles of reacted quicklime therethrough, the energy the quicklime will have expanded in diverging the segments 126 will have been taken from the particles themselves whereby their capacity to cause damage is decreased.

It will be appreciated that modifications thereto or variations in the embodiments as described and illustrated may be made within the scope of this application.