Package Valve System

Abstract

A valve system for a container (4, 5), especially for food containers whose contents are intended to be heated, comprises an adhesive layer (3) arranged over an opening portion (6) in the container (4). The adhesive layer (3) is arranged to at least partly release the container (4) adjacent an opening portion (1) in the adhesive layer in case of overpressure and thus form an opening to allow a flow out of the container (4, 5) and, in this flowing-out, emit an acoustic signal by means of said opening portion (1) in the adhesive layer (3) which is made to oscillate by the flow. The valve system comprises at least a second opening portion (2) arranged, in heating of the contents of the container (4, 5), to open before the above-mentioned opening portion (1) in the adhesive layer (3).

Description

FIELD OF THE INVENTION

The present invention relates to a valve system for a package or container, especially for food containers whose contents are intended to be heated, said valve system comprising an adhesive layer arranged over an opening portion in the container, the adhesive layer being arranged to at least partly release the container adjacent an opening portion in the adhesive layer in case of overpressure and thus form an opening to allow a flow out of the container and, in this flowing-out, emit an acoustic signal by means of said opening portion in the adhesive layer which is made to oscillate by the flow.

BACKGROUND ART

In a food container of, for instance, the type that contains prepared one person dishes and that is sold in refrigerated and frozen-food counters to be heated or finally cocked in a microwave oven, the food is usually placed in a heat-resistant tray and covered with a plastic film. For heating, either the plastic film is removed or it is punctured and then the entire tray is placed in the microwave oven. Due to the fact that different types of microwave oven have different performances and the food absorbs microwave energy in different ways due to composition and temperature, the time for heating varies significantly. It is therefore difficult to give the consumer recommendations as to how long the food is to be heated to be ready. For the consumer, this may require that the microwave oven be opened several times to allow him to sense whether the food is thoroughly hot or ready cocked. However, it is difficult to sense whether all the food is hot or whether the food is locally still cold due to the inherent difficulty of the microwave oven of evenly heating the food. Nor should the food be extra heated since the tray or the remaining plastic film can then locally melt and destroy the food or since extra heating makes the food soft, overcooked and unpleasant to eat. This makes it necessary for the consumer to remain close to the microwave oven throughout the heating in order to check whether the food is ready to eat.

One way of eliminating the above drawback is to use a valve which is adapted to open at an overpressure arising in the container during heating and which besides is arranged to emit an acoustic signal in said opening. The valve consists alternatively of an indication of fracture, a slit or a hole, over which an adhesive layer is arranged. The adhesive layer is arranged to be forced to move when a flow of steam/gas passes out of the valve, whereby an acoustic signal occurs. A common variant of such a valve comprises a slit in the container, over which slit an adhesive layer is arranged, which adhesive layer at least in a portion is provided with an adhesive suited for use with food since the invention in the first place aims at food containers. Moreover, the adhesive layer usually is an adhesive tape, preferably elastic, so as to be able to follow the motions of the container material during handling and not release the base.

However, it has been found difficult to control the opening of the valve. Different foodstuffs generate different amounts of steam while at the same time a valve as stated above practically always opens at the same overpressure. As a result, some foodstuffs are thus not sufficiently heated when the valve first emits an acoustic signal. In experiments of controlling the opening using an adhesive with different degrees of adhesiveness, it has been found that with a slightly stronger adhesive, instead the joints of the container crack before the valve opens. It is thus a very narrow range in which it is possible to control opening. Even if it is theoretically possible to control when a valve is to open using the adhesive, this means at the same time that a unique valve is required for each type of food. Consequently this is too complicated if the costs are to be kept down.

SUMMARY OF THE INVENTION

The object of the present invention therefore is to alleviate the above problems.

This object is achieved by a valve system of the type stated by way of introduction being given the features as defined in claim 1. Preferred embodiments of the valve system are stated in the claims dependent from claim 1.

The present invention is described based on valve systems for food containers. Foodstuffs normally generate steam when heated, bur the valve system according to the present invention can also be used for other types of containers where the contents are to be heated and, instead of steam, a gas can be used to cause the opening.

The present invention is a valve system for a container, especially for food containers whose contents are intended to be heated, said valve system comprising an adhesive layer arranged over an opening portion in the container, the adhesive layer being arranged to at least partly release the container adjacent an opening portion in the adhesive layer in case of overpressure and thus form an opening to allow a flow out of the container and, in this flowing-out, emit an acoustic signal by means of said opening portion in the adhesive layer which is made to oscillate by the flow, wherein the valve system comprises at least a second opening portion arranged, in heating of the contents of the container, to open before the above-mentioned opening portion in the adhesive layer. When heating a container with its contents, the pressure first rises until said second opening portion opens, and after that the pressure falls. In the continued heating, the temperature thus rises and the flow out of the container increases and causes after a while the opening of said first opening portion. In other words, said second opening portion is arranged to open at a lower temperature than said first opening portion.

This second opening portion is thus designed so as not to emit an acoustic signal when gas or steam flows out of this portion. When heating the container with its contents, steam is generated depending on the supplied energy and the contents of the container after different periods of time. In most cases, the food is not sufficiently heated as the first steam is generated. The idea of the invention is to release this first steam through an opening that does not generate any sound. Once the food is heated to the correct temperature, a much greater amount of steam is generated, which the opening first formed cannot manage. This steam therefore presses up the adhesive layer so that the specially designed opening portion is made to oscillate due to the flow of steam. This means that an acoustic signal is not generated until the food is sufficiently heated. The expression “adhesive layer” is adapted to include, for example, an adhesive tape or a self-adhesive label.

It is most common to use microwave ovens for heating as described above, but other types of heating will work as well, such as a convection oven (steam box/steam oven).

In a variant of the invention, said second opening portion is arranged in the adhesive layer. This allows a relatively simple solution since the actual container has to be provided with only one opening portion over with the adhesive layer is arranged.

An alternative is to form said second opening portion in the adhesive layer as a slit, most advantageously a straight slit and preferably more than one slit, which, for example, can be aligned with each other to form a “dashed line”. Slits are relatively easy and inexpensive to make in an adhesive layer.

In one embodiment of the invention, the opening portion in the container is a slit. The slit can be formed in various ways, for example a straight slit, an arcuate slit or two or more slits intersecting each other.

When said second opening portion is arranged in the adhesive layer, it is suitable for the second opening portion to be arranged closer to the opening portion in the container than said first opening portion in the adhesive layer. Theoretically, said second opening portion could instead be arranged at a greater distance if, for example, adhesives with different degrees of adhesiveness are used. An alternative embodiment could further be obtained with two adhesive layers, one adhesive layer comprising the opening portion that is to open for the first steam produced in heating, and the second layer would then comprise the opening portion that generates an acoustic signal in producing a great amount of steam when the contents in the container are ready to eat.

In one embodiment, said second opening portion is arranged to close when said first opening portion in the adhesive layer opens. If all the flow out of the container passes through the opening that generates the acoustic signal, a louder acoustic signal is obtained, which in some contexts can be advantageous.

In an alternative embodiment, at least part of the container is perforated. Film that is perforated is normally used for, for example, vegetables which, without being heated in an oven, sometimes generate gases, that is an overpressure in the container which without these microopenings could destroy the entire container. A perforated portion of the container could be used to supplement the valve system according to the present invention. Alternatively, it could constitute said second opening portion, that is the opening portion in the valve system that does not generate an acoustic signal.

In some ranges of application, it is advantageous for the adhesive layer to be resealable. In certain production of, for example, one person dishes, the foodstuffs are prepared in their final containers in microwave tunnels. These containers should then be provided with a valve that can close after heating to prevent a flow into the container from occurring in the subsequent refrigeration when a negative pressure is automatically generated in the container. The same valve is used once more when the final user heats the container with its contents.

Preferably, said first opening portion in the adhesive layer has the shape of a flap. This shape has been found particularly convenient for generating an acoustic signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the accompanying drawings which by way of example illustrate currently preferred embodiments of the present invention.

FIG. 1a is a simple exploded view of a valve system according to an embodiment of the present invention.

FIG. 2a is a perspective view of a portion of the valve system according to the present invention in a first heating phase.

FIG. 2b is a side view of a container with a valve system according to FIG. 2a and in the same heating phase.

FIG. 3a is a perspective view of a portion of the valve system according to the present invention in a second heating phase.

FIG. 3b is a side view of a container with a valve system according to FIG. 3a and in the same heating phase.

FIG. 4a is a perspective view of a portion of the valve system according to the present invention in a third heating phase.

FIG. 4b is a side view of a container with a valve system according to FIG. 4a and in the same heating phase.

DESCRIPTION OF PREFERRED EMBODIMENTS

A first opening portion 1 and a second opening portion 2 in an adhesive layer 3 are shown in FIG. 1. The adhesive layer is adapted to be placed over a plastic film 4 which in turn is to cover a tray 5. In the plastic film 4, a slit 6 is formed, which in this embodiment is the opening portion of the container.

FIGS. 2a and 2b illustrate how the adhesive layer 3 has started to release the plastic film 4 around the opening 6 in the plastic film 4 when a certain overpressure has occurred in the container. FIGS. 3a and 3b illustrate the next phase in heating when the overpressure in the container has made the adhesive layer 3 release the plastic film 4 so that ducts are formed all the way to three slits 2, which have formed three openings through which steam can flow. FIGS. 4a and 4b illustrate the valve system when the contents of the container are sufficiently heated. In this phase, a greater flow out of the container than in the previous phase has been produced, which has made the adhesive layer 3 further release the plastic film 4 so that a duct is formed all the way to a flap-shaped slit 1. Due to the flow, the “flap” is made to oscillate, which oscillating generates an acoustic signal. The relative position of the slit 1 and the slits 2 results in the openings formed by the slits 2 being closed when the slit 1 forms an opening.

It will be appreciated that many modifications of the above described embodiment are conceivable within the scope of invention as defined in the appended claims. For example, as described, the slit or slits in the adhesive layer which constitute the second opening portion could, of course, be formed in other ways than as straight cuts, for example with a wave shape or arch shape. It is also possible to design both opening portions to generate sound, although with, for example, different tones so that the first tone signals that there is still some time left until the food is ready to eat. An alternative would also be that, for example, one and the same slit in the adhesive layer is used for opening in a first phase, in which case the slit in additional heating opens further so as to generate an acoustic signal or alternatively change the character of the acoustic signal.

Claims

1. A valve system for a container, especially for food containers whose contents are intended to be heated, said valve system comprising an adhesive layer arranged over an opening portion in the container, the adhesive layer being arranged to at least partly release the container adjacent an opening portion in the adhesive layer in case of overpressure and thus form an opening to allow a flow out of the container and, in this flowing-out, emit an acoustic signal by means of said opening portion in the adhesive layer which is made to oscillate by the flow, wherein

the valve system comprises at least a second opening portion arranged, in heating of the contents of the container, to open before the above-mentioned opening portion in the adhesive layer.

2. A valve system as claimed in claim 1, in which said second opening portion is arranged in the adhesive layer.

3. A valve system as claimed in claim 2, in which said second opening portion comprises a slit in the adhesive layer.

4. A valve system as claimed in claim 3, in which the slit is straight.

5. A valve system as claimed in claim 4, in which slits are aligned with each other.

6. A valve system as claimed in claim 1, in which the opening portion of the container is a slit.

7. A valve system as claimed in claim 1, in which said second opening portion is arranged closer to the opening portion in the container than said first opening portion in the adhesive layer.

8. A valve system as claimed in claim 1, in which said second opening portion is arranged to close when said first opening portion in the adhesive layer opens.

9. A valve system as claimed in claim 1, in which at least part of the container is perforated.

10. A valve system as claimed in claim 1, in which said second opening portion consists of perforations in the container.

11. A valve system as claimed in claim 1, in which the adhesive layer is resealable.

12. A valve system as claimed in claim 1, in which said first opening portion comprises a flap in the adhesive layer.