BACKGROUND Currently there are containers that keep their contents warm or cold such as vacuum flasks, insulated lunchboxes and eskies. There are also cold bricks, sometimes known as "blue ice", which are containers of liquid such as water, that are frozen separately, and which can then be placed into these insulated containers to help keep the contents cool.

However, there are various disadvantages with these containers, and it would be useful to have a container that more effectively can keep its contents either cool or warm.

BRIEF DESCRIPTION OF INVENTION An alternative container has now been developed that can effectively keep its contents at a non-ambient temperature for a period of time.

In its broadest form, the invention concerns a container adapted to maintain the temperature

of its contents at a non-ambient temperature for a period of time, wherein the container includes a thermal medium that retains heat or cold, the thermal medium being integral with the container.

Preferably, the container has a compartment for holding the contents, the compartment being defined by a plurality of walls, wherein at least a portion of the walls may comprise the thermal medium. It is also preferred that the compartment may be substantially fully enclosed. Another preferred feature is for one of the walls to comprise a latchable lid. In this situation, preferably the lid may be hinged to the rest of the container. It is also preferred that the lid contains the thermal medium.

In one embodiment the thermal medium retains cold. In another, the thermal medium retains heat. Ideally, the thermal medium may be located substantially within the compartment.

Another preferred feature is that the lid may be hinged so that it may be separated from and re-attached to the rest of the container repeatedly.

It is further preferred that the container has a visual indicator of its temperature. As an alternative, the container may have a visual indicator of the temperature of the thermal medium. Ideally, the visual indicator may be located on the exterior surface of the latchable lid of the container. In another embodiment, the visual indicator may be a thermochromatic material. In this situation, the thermochromatic material may be applied in the form of any one or more of: printing, pictures, colours, designs, patterns, logos, words, letters or numbers.

It is also preferred that the container may have a carry handle. Also, optionally, the container may be at least partly temperature insulated. As a further option, the walls may have spacing means within the compartment so as to keep the contents substantially apart from the walls.

Also optionally, the container may have an air gap between the compartment and a surface upon which the container is placed.

In one embodiment, the container may be a lunch box. In another the container may be a carrying box for medical materials.

The invention also concerns a method of maintaining the temperature of the contents of a container at a non-ambient temperature for a period of time, the container including a thermal medium that retains heat or cold, and the thermal medium being integral with the container, where this method comprises heating or cooling using external means of the thermal medium, and adding the contents to the compartment.

The invention is now discussed in more detail.

BRIEF DESCRIPTION OF DRAWINGS The invention is now discussed with reference to drawings, where: Figure 1 shows a container in accordance with the invention, in one embodiment as a lunchbox.

Figure 2 shows a cross-section of the lunchbox from Figure 1, at a point marked"A"in Figures 1 and 3.

Figure 3 shows a rear-view of the lunchbox from Figure 1.

Figure 4 shows a top view of the lid of the lunchbox from the previous Figures, after separation from the rest of the lunchbox.

Figures 5A, 5B and 5C show top views of the lid, attached to the rest of the lunchbox, with a variety of temperature indications displayed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to the drawings, in Figure 1 a container is illustrated as one embodiment of the invention as a lunchbox. The lunchbox (1) comprises a removable and re- attachable lid (2) that is hinged to the rest of the lunchbox. The rest of the lunchbox comprises a compartment (3) for holding the contents of the lunchbox (1), such as food and drink. The lid (2) can be opened as shown in Figure 1, and can be closed to seal the compartment (3), and in this embodiment the lid has a flexible one-piece hinge (4), which is detachable from the compartment portion of the lunchbox.

The lunchbox (1) has a handle (5), which in this example is split between the lid (2) portion and the compartment (3) portion, so that it still functions as a handle for the lid portion when the lid is detached from the lunchbox compartment portion. These two handle separated portions seal together to form a unitary handle when the lid is closed. As well, and as further options, there may be separate handles on each of the lid and compartment portions, or a handle on only one of these two portions, or alternatively, no handle at all on the lunchbox. In the example of Figure 1, the handle is integral with the lunchbox, and has a generally oval aperture through which the fingers are inserted, and the

external part on the outside of the aperture allows a grip to be maintained on the handle.

The lid (2) and compartment (3) portions may be held closed by a latching means (6a & 6b). As shown in Figure 1, this is located on the exterior of the handle, but it may also be located elsewhere in the container, at the join between the lid and compartment. The latch as shown in the Figure, may be a hinged flap (6a) on the lid portion having a hole through the flap, this hole being adapted to receive and retain a correspondingly shaped projection or lug (6b) that is located on the compartment portion of the container, in a position opposite each other. This snap fastener may also be in the reverse orientation, with the hinged flap located on the compartment portion and the projection on the lid. Other methods of latching the lid on to the compartment may also be utilised, such as by using a clip, a hook and eye, magnetic fasteners, keyed locks, two coextensive eyes able to receive a separate padlock, as well as other means for securing the compartment and the lid of the container together when in use. Also, more than one type of latching or fastening means may be used if desired.

The compartment (3) is of a generally oblong or square shape, having a base and four sides extending laterally from the base. The edges where the base and walls meet, and where the walls meet with each other, may be rounded or sharp, and so may the corners. The container should be large enough for its intended use. Special shapes other than oblong or square may be used, particularly if the container is intended to carry specific articles. For example, when used to carry medical items or supplies such as blood, organs, or tissue samples, for example, which require temperature control. In this situation, the shape

may be chosen to more closely match that of the shape of the contents, for example.

The container may be constructed from any suitable material, such as polymeric materials and plastics, including polyethylene, polypropylene, or PVC for instance, or from wood, metal and other substances, or from mixtures of such materials.

The lid portion (2) may have a rim around it (7) and a block of thermal material (8) located on its underside, or integrated within it. The thermal medium may extend down into the compartment below, but preferably is only as deep as the lid itself ; only extending approximately the depth of the rim that extends around edge the lid. Ideally the thermal material is integral with the lid portion, so that when the lid is detached from the rest of the container as one preferred option allows, then the lid portion, which is smaller in size than the container as a whole, can conveniently be placed in an external means of supplying either cold or heat to it.

The lid, with its thermal material, can therefore be place within the freezing compartment of a refrigerator to cool it, and then replaced and re-attached to the lunchbox compartment section to keep contents of the lunchbox cooler than the ambient temperature for a period of time.

Similarly, a lid with its integral thermal material may be placed into a microwave oven and heated there, which will keep the contents of the container warmer than the ambient temperature for a period of time, once the lid is re- attached to the lunchbox and latched closed.

Figure 2 displays a front-to-back cross-section of the lunchbox represented in Figures 1 and 3 at approximately the location shown as'A'in these Figures. Again, this

example of the lunchbox (1) consists of a compartment portion (3) and a lid portion (2). Walls (9) define the compartment, and its base has an air gap (10) between the surface it rests on, and the compartment, which helps to insulate any contents. This air gap (10) may be constructed by indenting the central portion of the base of the lunchbox, leaving a gutter (14) around the outer edge of the base.

Alternatively, the interior of the lunchbox may contain means to space apart the contents from the base and walls, to provide an air gap between the contents and these surfaces. The spacing means may be ribs, or a platform within the compartment, or a layer of other insulating material.

The handle (5) is split into two parts joined to the lid and to the compartment portions, which form an integrated, easy to grip, handle when the lid is closed upon the compartment. There may also be a step or ridge (11) around the rim of either or both of the edges of the lid and the compartment where the lid and compartment come together. This allows them to sit firmly in place, and to form a barrier to the outside air penetrating into the container, which assists with insulating the contents inside. Other means to create an airtight seal may also be employed.

The walls may be of any thickness, and may include a void, optionally containing a vacuum, or a layer of insulation.

The hinge (4) that allows the lid to be opened and closed, preferably also allows the lid to be separated from the compartment portion of the lunchbox. A variety of approaches may be used to allow this. One approach is shown

in Figures 2,3 and 4. Figure 3 shows the back of a lunchbox in accordance with one embodiment of the invention, with its lid in a closed position. The hinge assembly (4) is permanently fixed to the lid portion (2) of the lunchbox, but is removably fixed to the compartment portion (3). This may be done in a variety of ways.

One approach is that demonstrated in Figures 2,3 and 4. The hinge assembly (4) in this example has two projecting prongs where each prong (12) has a barb (15) located on its outside edge. The rear outer surface of the compartment has two matching collars (13) that project from the outer surface of the compartment. Each collar has a vertical passage running from top to bottom, the width of the prong and barb. Each collar is positioned on the rear surface of the compartment to receive each prong through its vertical passage. But each collar is biased slightly to centre on the middle of each prong, ignoring somewhat the shape of the barb.

Each collar permits the prong, including the barb portion on each prong, to pass through from the top passage opening. The collar (13) retains the prong (12) alongside and against the rear surface of the compartment portion.

The hinge assembly (4) is connected to the prongs, and when these prongs are seated within the collars, the lid can open and close to cover and seal the top of the compartment.

The prongs (12) are made of a resilient material, that allows bending of the two prongs towards each other, without damaging or altering permanently their shape. The barbs (15) catch against the lower edges of the collars (12) and normally retain the lid in place. However, the prongs can be released from their collars by using finger

pressure to slightly bend the two prongs towards each other, which then allows the barbs to proceed through the passage within each of the collars. After release, the prongs spring back to their normal shape and configuration.

A top view of the lid, with the hinge assembly not bent is displayed in Figure 4. The prongs can be inserted into the collars using some downwards pressure.

The lid would normally be opened before attempting to remove it from the compartment portion. Ideally, the prongs are sufficiently far apart from each other to allow their compression towards each other using one hand, which leaves the other hand free to pull the lid and its attached prongs upwards, and out of their slots in the collars.

Other means can be used to retain the lid in place, and to allow for its opening and closing over the open top of compartment, and also to allow for its repeated removal.

Once removed, the lid may be placed in a freezer until the thermal medium that it contains is frozen. Once cold, the lid is re-attached to the compartment, then contents such as lunch is placed within the compartment, and the lid is shut and latched to keep the contents cool for a period of time.

Also, as shown particularly in Figures 2 and 4, the thermal medium (8), in one preferred embodiment of the invention, is integrated in the lid. It may sit on the interior surface of the lid, or may be integrated with the lid as shown in the example of Figures 2 and 4.

The thermal medium may comprise a variety of substances, and the choice of one or more of these substances will usually depend on whether the medium is used for cooling or heating. Although it is quite possible to choose a single medium that will operate satisfactorily

to help cool or at another time to help heat the contents of the container.

The thermal medium may be a uniform substance or a mixture of different substances. The medium may be a solid, a liquid, a gas or a combination of these, as well as intermediate forms, such as gels and powders. The medium may change from one state to another in use, such as becoming a solid when frozen, and melting to a liquid or gel when warming to ambient temperatures again. If not a uniform solid, then the medium will normally be enclosed within a receptacle. Such a receptacle may be separately manufactured and joined to the rest of the container, or it may be integral with the wall of the container to which it is combined. The receptacle may be reinforced to prevent its contents from rupturing it when the medium is frozen for example. Otherwise, the receptacle may be flexible or expendable for the same reason, such as being a strong flexible plastic bag for instance. The receptacle may be attached to the inside of the lid, or may extend through the lid and fixed within a central aperture in the lid.

Commonly, a substance that will heat up in a microwave oven may be chosen if the thermal medium is intended for keeping the contents of the container warm for a time. Any suitable material known for this purpose may be used. Care may need to be taken to choose a material that will not heat too much, so as not to damage the material of the surrounding walls of the container. It may also be preferred to surround the outer surface of the thermal medium and surrounding material with a layer of thermal insulation.

Substances that retain cold are also known. Some store and release cold by utilising their latent heat of fusion

when changing between the solid and liquid phases, for instance. The latent heats of fusion may be greater than the heat capacity of the substance alone. Thus, the amount of energy absorbed upon melting is often greater than the amount of energy absorbed by increasing or decreasing the temperature of the substance by 10 or so degrees C. Melting will absorb a large quantity of energy in the vicinity of its melting/freezing point.

For example the ice/water phase change is frequently used for temperature regulation at 0 degrees C. Soluble additives can be added to the water, such as NaCl, NH4NO3, urea, ethanol, polyethyleneglycol, glycerine, or sugar.

These additives depress the freezing point of water to below 0 degrees C, but they also decrease the latent heat of fusion of the resulting solution to less than that of pure water. Commonly also, a gelling agent is added to pure water, to make the resulting thermal medium easier to handle. Other additives are preservatives, and anti- microbial agents are also added to such mixtures and gels.

A colouring agent may also be present, to give an attractive appearance, or to prevent the medium being accidentally consumed if the receptacle is broken.

The thermal medium may also comprise materials that do not require external cooling or heating to function, such as materials that heat or cool using a thermochemical reaction, often when two components are mixed together.

Some of these are one-use only, while other such formulations may be re-used, but often these will require external heating or cooling to function after the first use.

A further embodiment of the invention involves having a thermal indicator that indicates the temperature of the container, or of the thermal medium.

One example of this is to attach a thermometer to the container, or to the thermal medium, preferably in a manner so that the temperature it measures is visible from outside the container, without it having to be opened first.

However in some situations, it may be preferable to have a temperature indicator inside the container, as well as, or instead of, one on the outside of the container or visible from outside the container. With temperature controlled containers for medical purposes, it may be useful to have an indicator on the outside to give an approximate inside temperature, and one inside to give a more accurate temperature of the contents in the container.

The indication of the temperature may be precise, such as indicating the exact temperature to one degree, or less precise, such as giving the temperature in a 10 degree band for example. It may also be even less precise, such as merely indicating"hot"or"cold", or the like, for instance.

As a further alternative, instead of using a precise temperature measuring mechanism, like a thermometer or thermocouple for example, it is a preferred embodiment of the invention to use, one or a multiplicity of thermochromatic materials to indicate temperature changes by means of colour changes. Sometimes,"thermochromatic" materials are also known as"thermochromic"materials.

The perceptible change in a thermochromatic material as its temperature changes is generally a change in colour. In one approach, the thermochromatic material changes opacity, typically being more opaque when cool than when at a higher

temperature. A further approach is to provide a pattern or some text on the container and to cover this with a thermochromatic coating that is opaque when cool, ie, at temperatures around 0 degrees C. When the thermochromatic coating warms to ambient temperature, it becomes visually transparent and displays the underlying patter n or text.

This informs anyone that the contents in the container are no longer cool. The pattern or text includes various visible features, including colours, patterns, designs, or one or more words, figures, letters or numbers, for instance.

The pattern or text may consist of thermochromatic inks, dyes or pigments, and be printed or coated on the container. Such thermochromatic inks may change from a colour such as blue when cold, to colourless as they warm up. Conversely, if the ink is cooling down across the activation temperature, it will change from colourless to blue. In other words, at room temperature, the ink may be in its warm (colourless) state. The material printed or coated on or in the container may therefore change colour to indicate the temperature of the underlying substrate.

For example, a thermometer-like design may be created in thermochromatic inks, with the colour changing from blue to red as the temperature increases, by printing a red base layer, and overprinting this with a blue thermochromatic ink that becomes colourless, and thus allows the underlying red to display as it warms past a 15 degree activation temperature, for example.

Reversible thermochromatic inks and coatings are readily available. Such heat-activated inks change colours or disappear when they exceed a certain temperature, then change back when the temperature decreases to below that

same activation temperature. They are commonly available in a variety of standard activation temperatures: such as 15, 31 and 45 degrees C, but customised temperatures are available from-5 C to 65 C. Such inks and coatings may be obtained for example from"Chromatic Technologies Inc"of Colorado Springs, CO, USA.

As a further alternative, where the thermal medium is incorporated into the lid of the lunchbox, or other type of container, as illustrated in Figure 2, then if the medium is essentially transparent when in a liquid form and essentially opaque when frozen, like water/ice is, then any patterns, colours or text printed on the lower surface of the medium will only be clearly visible when the medium is liquid. If using water/ice, then its receptacle should be transparent as well.

Examples of different approaches to indicating the temperature for the lunchbox that forms one embodiment of the invention are given in Figure 5A, 5B and 5C.

In Figure 5A, the lunchbox has the words"Heating Up" appearing as the thermal medium reaches a threshold temperature (eg 15 C). These words may be printed on the outer surface across the thermal medium block, and coated with a thermochromatic layer, which is opaque at temperatures below 15 C (say), and transparent at temperatures above this. Alternatively, the words may be printed on the inner surface of a transparent receptacle filled with water. These words will be mostly hidden when the water is frozen, but visible from the outside when the water finally melts.

In Figure 5B, a pattern resembling a thermometer is printed on the surface of the lid adjacent the thermal medium using thermochromatic inks. Various transition

temperatures (eg, 10 C and 20 C) of the thermochromatic inks are used to indicate by a change in colour when the temperature is 0 C, 10 C, and when it reaches to 20 C.

Figure 5C illustrates another approach, where a pie chart'design has quadrants that progressively become coloured as the temperature increases.

In more general terms, the container that retains heat or cold, may be of any suitable shape and size for its intended purpose, and may be constructed from any suitable materials. It may be open, but preferably is enclosed, and it then would have a base, side walls, and a lid that opens and closes, and which preferably can be latched shut.

The material from which the body of the container is made is preferably a polymeric material, but metals, glass, wood, and similar materials used commonly to make such containers may also be utilised, or included in the construction of the container. A suitable polymeric material is a polypropylene copolymer, or high-density polyethylene, or the like. The container may also be decorated or coloured in an attractive manner.

Any suitable thermal medium may be used, as mentioned above. One example is for a cold-keeping medium that consists of a receptacle made from an extruded high-density polyethylene (eg,"DowlextM"2045. 02 AC polyethylene resin).

The receptacle contains a gel consisting mostly of water, but also containing additives, such as a gelling agent (eg, "SanwetTM"from Orica Australia that essentially is the sodium salt of a cross-linked acrylic acid copolymer).

Other additives include"Gasill^"super absorbent, and a preservative (eg sodium benzoate), and Blue Silica.

Suitable thermal mediums that retain heat and can be heated in a microwave oven, or by using a heat source are known in the industry, and may also be utilised.

Ideally, the lid that contains a thermal medium can be removed, and then placed in a freezing compartment of a refrigerator, for example. The thermal medium is left to give up heat energy, and freeze. The lid is replaced on the container, and the frozen thermal medium continues to absorb heat from the contents in the container, keeping it cool, for a time. Eventually the thermal medium reaches thermal equilibrium with the environment around it, but by this time the medium has served its purpose, by keeping lunch in the container cool and fresh.

The container may conveniently be sold to customers with more than one lid. There may be two lids, so one may be being prepared in the freezer compartment, while the other is in use. Otherwise, there may be one lid for keeping the contents cold with a suitable cooling thermal medium, and another for keeping the contents warm, having a different thermal medium.

As mentioned above, the temperature indicator is a preferred feature, which is ideally included upon the outside of the lid, adjacent to the thermal medium located there. Other designs, printing and logos can also be included on the container, in additional to the preferred thermochromatic materials.

Ideal uses of the container are as a lunchbox or medical materials container. But such a container can be applied in many other situations, where the contents of a container need to be kept at a non-ambient temperature for a period of time, or where there are advantages in keeping the contents at such a temperature.

It will be apparent that obvious variations and modifications of the invention in accordance with its spirit can be made without departing from the scope of the invention, and these are intended to be part of the invention.