One-way valve for food packages

Abstract

A one-way valve, a food package comprising such a one-way valve, and a method of manufacturing such a one-way valve are disclosed. The one-way valve comprises a first membrane with a top surface and a bottom surface, wherein the first membrane has a first surface area. The one-way valve further comprises a second membrane with a proximal surface and a distal surface. The second membrane has a second surface area smaller than the first surface area and wherein the second membrane has two longitudinal edges on opposite sides of the second membrane and two lateral edges on opposite sides of the second membrane. Moreover, the proximal surface of the second membrane is fixed to the bottom surface of the first membrane such that a footprint of the second membrane is completely enclosed within the bottom surface of the first membrane and the first membrane extends past all edges of the second membrane. Moreover, the portion of the bottom surface of the first membrane that extends past all edges of the second membrane is coated with a first adhesive Furthermore, the first membrane extends past one or both longitudinal edges of the second membrane by a shorter distance than a distance by which the first membrane extends past the other edges of the second membrane.

Description

TECHNICAL FIELD

[0001] The disclosed technology relates to a one-way valve for food packages. In particular, but not exclusively the disclosed technology relates to a one-way valve designed to be mounted on a food package and arranged to open in response to a pressure inside the package exceeding a threshold pressure. The herein disclosed technology also relates to a food package comprising such a one-way valve and a method for manufacturing such a one-way valve.BACKGROUND

[0002] A growing trend in the world is the consumption of so called ready-to-eat food, i.e. food which does not need cooking or has already been cooked. Such meals are either frozen or refrigerated in order to have a reasonable long shelf life. Frozen food may be regarded as less tasty and looking less appetizing, while refrigerated food generally appears more appetizing, it has considerably shorter shelf life. In order to prolong the shelf life for such refrigerated ready-to-eat food pasteurisation is used. Often, the process of pasteurisation is combined with a removal of oxygen from the interior of the package in order to minimise bacterial growth. Such removal of oxygen may be either of creating a slight vacuum in the food package or the replacement of the oxygen by injection of some other suitable gas into the food package.

[0003] In a cooking and pasteurisation method used by the applicant the food is placed in a food package comprising a plastic tray having a plastic cover in the form of a see-through thin film which is sealed along the tray edges to create an interior which is completely sealed off from the surroundings. Further, a valve may be provided in this plastic film which may be automatically opened when an overpressure occurs within the package. Such overpressures are e.g. created when the package is positioned in a microwave oven and the food is cooked by exposing it to electromagnetic radiation. It may also be created through convection in e.g. furnaces with air heating and steam, or by exposing the package to thermal radiation, e.g. through infra-red radiation. When the food is cooked, a large amount of steam is created. The steam is building up an overpressure such that the valve is opening and letting both oxygen and steam out. When the food has been cooked the microwave oven is shut off, whereby the steam production instantaneously stops. The valve is then designed to close immediately due to the reduction of internal overpressure and the lowering of the ambient temperatures. The food packages are cooled to a suitable storing temperature and may be delivered to retailers for later use. An important aspect is that these types of valves differ from other valves used in the food industry, such as e.g. those used in connection with packages for coffee or the like. In more detail, these valves open at much higher relative overpressures, in the range of 100 hPa, as compared to those used in connection with packages for coffee which open at relative overpressures in the range of 10 hPa. The term relative overpressure here to be construed as how much the pressure inside the package exceeds the pressure outside of the food package, i.e. the difference between the internal and the external pressure. This consequently results in different requirements for the different types of valves.

[0004] The closure of the valve after cooking is important in order to seal the interior of the package and food from ambient air and contaminating substances. The valve must hence be designed such that it is certain that it is not affected by e.g. food residuals or moisture that may be blown into the valve during cooking. Such valves are per se known, and for example disclosed in EP 1 383 693 B1.

[0005] However, a problem with many of the one-way valves for food packages that are known today is that the associated manufacturing processes are relatively complex with a multitude of process steps and parameters that need to be continuously adjusted in order to reduce waste.

[0006] Accordingly, there is always a need for improvements in the art, particularly there is always a need for one-way valves that are more cost effective, easier to manufacture and is more in compliance with coming governmental health regulations. Stated differently, there is still a need for a one-way valve that may be easily and reliably fastened to a plastic film of a food package in a manner that is less complicated, as compared to the state of the art.SUMMARY

[0007] The herein disclosed technology seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art to address various problems relating to manufacturing complexities and regulations related to one-way valves for food packages.

[0008] Various aspects and embodiments of the disclosed technology are defined below and in the accompanying independent and dependent claims.

[0009] A first aspect of the disclosed technology comprises a one-way valve for mounting over an aperture formed on a food package for cooking, storing and / or heating of ready-to-eat food. The one-way valve comprises a first membrane with a top surface and a bottom surface, wherein the first membrane has a first surface area. The one-way valve further comprises a second membrane with a proximal surface and a distal surface. The second membrane has a second surface area smaller than the first surface area and wherein the second membrane has two longitudinal edges on opposite sides of the second membrane and two lateral edges on opposite sides of the second membrane. Moreover, the proximal surface of the second membrane is fixed to the bottom surface of the first membrane such that a footprint of the second membrane is completely enclosed within the bottom surface of the first membrane and the first membrane extends past all edges of the second membrane. Moreover, the portion of the bottom surface of the first membrane that extends past all edges of the second membrane is coated with a first adhesive Furthermore, the first membrane extends past one or both longitudinal edges of the second membrane by a shorter distance than a distance by which the first membrane extends past the other edges of the second membrane.

[0010] A second aspect of the disclosed technology comprises a food package for cooking, storing and / or heating of ready-to-eat food, the food package comprising a food container and a plastic film for sealing the food package from ambient air, where the plastic film has an aperture. The food package further comprises a one-way valve according to any one of the embodiments disclosed herein. With this aspect of the disclosed technology, similar advantages and preferred features are present as in the other aspects.

[0011] A third aspect of the disclosed technology comprises a method for manufacturing a one-way valve for mounting over an aperture formed on a food package for cooking, storing and / or heating of ready-to-eat food. The method comprises providing a first membrane having a top surface and a bottom surface, the first membrane having a first surface area, and providing a second membrane having a proximal surface and a distal surface. The second membrane has a second surface area smaller than the first surface area and wherein the second membrane has two longitudinal edges on opposite sides of the second membrane and two lateral edges on opposite sides of the second membrane. The method further comprises coating the bottom surface of the first membrane with a first adhesive, and fixing the proximal surface second membrane to the bottom surface of the first membrane, such that a footprint of the second membrane is completely enclosed within the bottom surface of the first membrane and the first membrane extends past all edges of the second membrane, and such that the first membrane extends past one or both longitudinal edges of the second membrane by a shorter distance than a distance by which the first membrane extends past the other edges of the second membrane. With this aspect of the disclosed technology, similar advantages and preferred features are present as in the other aspects.

[0012] The disclosed aspects and preferred embodiments may be suitably combined with each other in any manner apparent to anyone of ordinary skill in the art, such that one or more features or embodiments disclosed in relation to one aspect may also be considered to be disclosed in relation to another aspect or embodiment of another aspect.

[0013] An advantage of some embodiments is that the one-way valve is more cost-effective and less complex to manufacture as compared to prior known one-way valves for food packages.

[0014] An advantage of some embodiments is that the risk of the valve inadvertently opening (e.g., during transport) is reduced since the first membrane extends past all edges of the second membrane, thereby ensuring a strong seal during transport.

[0015] An advantage of some embodiments is that the one-way valve emits a sound signal when a gas pressure inside the food package exceeds a threshold value due to vibrations at the peripheral edge of the first membrane, indicating to the user that the food has been adequately heated.

[0016] An advantage of some embodiments is that compliance with health regulations is facilitated as the second membrane (bottom membrane) does not have to be made from thermoelastic PVC, i.e. PVC treated with plasticisers / plasticizers. Consequently, any contact between the food content and thermoelastic PVC can be avoided.

[0017] Further embodiments are defined in the dependent claims. It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components. It does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0018] These and other features and advantages of the disclosed technology will in the following be further clarified with reference to the embodiments described hereinafter.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above aspects, features and advantages of the disclosed technology, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings, in which: Fig. 1 illustrates a perspective and partially exploded view of a one-way valve applied on a food package, in accordance with some embodiments. Fig. 2A illustrates a top view perspective of the one-way valve arranged on a food package in Fig. 1. Fig. 2B illustrates a top view perspective of a one-way valve arranged on a food package, in accordance with some embodiments. Fig. 2C illustrates a top view perspective of a one-way valve arranged on a food package, in accordance with some embodiments. Fig. 2D illustrates a top view perspective of a one-way valve arranged on a food package, in accordance with some embodiments. Fig. 3A illustrates a cross-sectional view taken along the line A-A in Fig. 2A, in accordance with some embodiments. Fig. 3B illustrates another embodiment from the same perspective as in Fig. 3A. Fig. 4A illustrates a perspective view of the one-way valve from Fig. 2A, with an open canal, applied on a food package, in accordance with some embodiments. Fig. 4B illustrates a perspective view of a one-way valve from Fig. 2B, with an open canal, applied on a food package, in accordance with some embodiments; Fig. 5 illustrates a flow chart representation of a method for manufacturing a one-way valve in accordance with some embodiments. DETAILED DESCRIPTION

[0020] In the following detailed description, embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention.

[0021] In the following description of exemplary embodiments, the same reference numerals denote the same or similar components. It will be understood that, although the term first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0022] The following description will use terms such as "top", "bottom", "upper", "lower", "lateral", "longitudinal", "edge", etc. These terms generally refer to the views and orientations as shown in the drawings. The terms are mainly used for the reader's convenience and shall not be construed as limiting.

[0023] Fig. 1 shows a perspective and partially exploded view of a one-way valve 1 mounted over an aperture 12 formed in a food package 10 for cooking, storing and / or heating ready-to-eat food, in accordance with some embodiments. The food package 10 comprises a rigid container 13 covered with a plastic film 11 for sealing the inside of the food package from the ambient atmosphere. The rigid container 13 may for example be made of hard plastics or paper (e.g., carton board) having a suitable coating (e.g., polyethylene (PE) coating). The plastic film 11 may be fixed along the outer circumference of the rigid container 13 of the food package. Even though the food package 10 referred to herein is generally in the form of a rigid container with a plastic cover film, the one-way valve 1 may be used with other types of food packages, such as plastic pouches or bags.

[0024] The one-way valve 1 comprises a first membrane 2 (may also be referred to as a top layer or top membrane) with a top surface 4 and a bottom surface 5. The first membrane 2 has a first surface area and the bottom surface 5 of the first membrane is coated with a first adhesive. The first membrane 2 can e.g. be made from thermoelastic PVC. The one-way valve 1 further comprises a second membrane 3 with a proximal surface 9 and a distal surface 7. Moreover, the second membrane 3 has a second surface area smaller than the first surface area and wherein the second membrane 3 has two longitudinal edges 21, 22 on opposite sides of the second membrane 3 and two lateral edges 23, 24 on opposite sides of the second membrane 3. In other words, the footprint of the second membrane 3 is smaller than the footprint of the first membrane 2. It should be noted while the figures generally depict rectangular membranes 2, 3 it should not be construed as limiting as other shapes are feasible. For example, the membranes 2, 3 could have an oval shape, square shape, or any suitable polygonal shape as readily understood by the skilled person in the art. In the case of an oval shaped membrane, the longitudinal edges may then be the edges at the end of the minor axes from the centre and the lateral edges could be the edges at the end of the main axes from the centre. However, as mentioned, the labels "longitudinal" and "lateral" with respect to the edges of the membranes are mainly used for the reader's convenience and shall not be construed as limiting.

[0025] Furthermore, the proximal surface of the second membrane 3 is fixed to the bottom surface of the first membrane 2 such that a footprint of the second membrane 3 is completely enclosed within the bottom surface 5 of the first membrane 2 and the first membrane 2 extends past all edges of the second membrane 3. The term "footprint" refers to the amount of physical space that a membrane, occupies within a given environment. In other words, a "footprint" refers to the amount of space on a surface that something, in this case a membrane, needs. Typically, the footprint is measured in terms of surface area.

[0026] The term "distal" in reference to the surfaces of the second membrane 3 is to be understood as the surface situated away from the point of attachment to the first membrane 2, i.e. the surface facing away from the first membrane 2. Analogously, the term "proximal" in reference to the surfaces of the second membrane 3 is to be understood as the surface situated nearer to the point of attachment to the first membrane 2, i.e. the surface facing towards the first membrane 2.

[0027] Moreover, the first membrane 3 extends past one or both longitudinal edges 21, 22 of the second membrane 3 by a shorter distance than a distance by which the first membrane 2 extends past the other edges of the second membrane 3. In other words, while the second membrane 3 is completely encompassed or enclosed within the first membrane 2, it is arranged such that one or both of the longitudinal edges 21, 22 are closer to an edge of the first membrane 2 as compared to the remaining edges of the first membrane are to an edge of the first membrane. Turning briefly to Figs. 2A-2D, this means that distance D1 is smaller than any one of distances D2, D3, or D4 (Fig. 2A and 2C) or that either one of distances D1 and D2 are smaller than D3 or D4 (Fig. 2B and 2D).

[0028] In some embodiments, the first membrane 2 extends past one or both longitudinal edges 21, 22 of the second membrane 3 by a first distance and extends past the other edges of the second membrane 3 by a second distance, the second distance being at least twice as long as the first distance. In reference to Figs. 2A-2D, this may be understood as that each one of distances D2, D3, and D4 are twice as long as distance D1 (Fig. 2A and 2C), or that each one of distances D3 and D4 are twice as long as either one of distances D1 and D2 (Fig. 2B and 2D). Moreover, in some embodiments the first distance (i.e., distance D1 or both distances D1 and D2) is in the range of 2 mm to 10 mm, such as e.g., 5 mm, 6 mm, 7 mm, or 8 mm.

[0029] The second membrane 3 is as mentioned fixed to the bottom surface 5 of the first membrane 2 and adapted to be sandwiched between the food package 10, and the first membrane 2, when the one-way valve 1 is mounted onto the food package 10. In the depicted embodiments, the second membrane 3 has a rectangular shape and the first membrane 2 extends past all four sides or edges of the second membrane 3 in order to fix the second membrane 3 to the food package 10. The second membrane 3 can be made from PP (polypropylene) or from other suitable synthetic polymers such as, polyethylene, polystyrene, polyurethane, etc. However, the second membrane may alternatively be made from polyethylene coated carton board.

[0030] The one-way valve 1 is to be mounted to the food package 10, as indicated by the downwardly directed arrows in Fig. 1, such that the second membrane 3 covers the aperture 12, here in the form of a cut, formed in the plastic film 11 of the food package 10. In use, e.g. when the food package 10 is heated, a canal is formed between the plastic film 11 and the second membrane 3 when a gas pressure inside the food package exceeds some value. The canal will accordingly extend from the aperture 12 towards a peripheral edge 31, 32 (see Figs. 4A and 4B) of the first membrane 2, along the second membrane 3. The canal forms because the second membrane 3 separates from the plastic film 11 of the food package 11 as a result from the force exerted on the bottom surface 7 of the second membrane 3 by the expanding gas. The expanding gas then further exerts a force on the first membrane 2 around the second membrane 3 in a substantially even manner. However, since one or both of the longitudinal edges 21, 22 of the second membrane 3 are closer to the corresponding peripheral edge(s) 31, 32 of the first membrane 2, the gas will exit at the peripheral edge(s) closest to the second membrane 3.

[0031] In other words, the one-way valve 1 may be adapted to be fixed to the food package 10 in order to cover the aperture 12 with the second membrane 3 such that a canal is formed between the food package 10 and the one-way valve 1 when a gas pressure inside the food package 10 exceeds a threshold value. Moreover, the canal may then extend from the aperture 12 to one or two peripheral edges 31, 32 of the first membrane 2 along the second membrane 3 via the one or both of the longitudinal edges 21, 22 of the second membrane 3. Thereby, the canal formation when heating the food package 10 is controlled, and the gas can exit at a predicted location. Moreover, due to the overlap of the first membrane 2, the exiting gas will cause the peripheral edge(s) 31, 32 of the first membrane 2 to vibrate and emit a sound signal to indicate that the contents of the food package 10 have been sufficiently heated. If the first membrane 2 would not extend past the longitudinal edge 21, 22 of the first membrane, the thickness of the two membranes 2, 3 together prevents the emission of a sound signal by impeding the necessary vibrations. In particular, if the second membrane 3 comprises a more rigid material than the first membrane 2.

[0032] The gas pressure threshold value (or also known as opening pressure) can for example be in the range of 10 - 200 mbar at 70 - 100°C. In some embodiments, the opening pressure is in the range of 20 - 130 mbar, in the range of 40 - 160 mbar, or in the range of 60 - 100 mbar, at 70 - 100°C. The gas pressure threshold value is in the present context to be understood as an "internal overpressure", i.e. a relative gas pressure difference between the inside of the food package 10 and the outside of the food package. The pressure threshold value may be set or controlled based on the shortest distance between an edge of the second membrane 3 and a corresponding edge of the first membrane (i.e., distances D1 and optionally distance D2). For example, a shorter distance will reduce the pressure threshold value while a longer distance will increase the opening threshold value. This is under the assumption that the adhesion between the second membrane 3 and the food package is weaker than the adhesion between the first membrane 2 and the food package.

[0033] By having the first membrane 2 extend past all edges of the second membrane 3 a more robust seal of the contents within the food package 10 may be provided while simultaneously providing the one-way valve functionality (re-sealing after the package has cooled down following a heating of the food package). Moreover, the risk of the one-way valve 1 inadvertently opening during for example transport may be reduced. Further, since the first membrane 2, by its extension past all edges of the second membrane 3, is used to seal off the contents of the food package 10 from the ambient atmosphere, one may omit having any adhesive coating on the distal surface 7 of the second membrane 3 (that covers the aperture 12 of the food package), thereby reducing the risk of having any adhesive coming into contact with the contents of the food package 10.

[0034] Moreover, in some embodiments, the first membrane 2 is made of a thermoelastic material which has a production machine direction, and the second membrane 3 is arranged such that the canal extends in a direction that has a relationship to said production machine direction such that an angle therebetween is within a range of 60° - 90°. Hereby, the risk of wrinkle formation is further reduced since the relaxation of the polymers will actually tighten the canal during steam / gas release. Moreover, the canal can be made shorter whereby the complete one-way valve can be made smaller. In some embodiments, the second membrane 3 is more rigid material the first membrane 2.

[0035] In some embodiments, the thermoelastic material of the first membrane 2 is in an elastic state at temperatures exceeding 50°C. As readily understood, an intended purpose of the valve 1 is that it should open when the food package 10 is subjected to heating, and steam thereby is created, and close when there is no more steam being generated within the food package 10. It may therefore be advantageous to use thermoelastic (thermoplastic) materials being in its elastic state at temperatures exceeding 50°C. Hence, when the food package 10 is being stored, e.g. in a refrigerated space, the valve membranes 2, 3 are not in their elastic sate which provides for reliable closing of the valve 1.

[0036] In some embodiments, the first membrane 2 is made of thermoelastic PVC, poly(vinyl chloride), and the second membrane 3 is made of a different polymer. The different polymer may for example be PP (polypropylene) or other suitable synthetic polymers such as, polyethylene, polystyrene, polyurethane, etc. Stated differently the second membrane 3 may be made of a non-PVC polymer. However, in some embodiments the first membrane 2 is made of other materials, such as elastomeric materials, such as a thermoplastic elastomer or various rubber materials. In some embodiments, the first membrane 2 is made of polypropylene, polyethylene, polystyrene, or polyurethane.

[0037] Figs. 2A-2D show top view perspectives of a one-way valve 1 fixed to plastic film 11 of a food package in accordance with an embodiment of the invention. The second membrane 3 may be in the general form of an elongated structure, such as e.g. a rectangle, as in the embodiment shown. However, the skilled artisan readily realizes that other shapes such as elliptic, truncated cone, etc. are feasible. The second membrane 3 may have an aspect ratio of 1:1.5-5 (width:length). For example, the second membrane 3 may have a width in the range of 5 - 15 mm, such as e.g. 8-10 mm, and a length in the range of 7.5 - 75 mm, such as e.g. 20 - 30 mm. Width and length are considered to be the distance between two opposite edges along two perpendicular axes (e.g., major axis and minor axis) intersecting a centre point of the membrane extending along the surface of the membrane.

[0038] In more detail, Fig. 2A and Fig. 2C illustrate a one-way valve 1 where the first membrane 2 extends past one longitudinal edge 21 of the second membrane by a shorter distance D1 than a distance D2, D3, D4 by which the first membrane 2 extends past the other edges 22, 23, 24 of the second membrane 3. Fig. 2B and 2D on the other hand show a one-way valve 1 where the first membrane 2 extends past one both longitudinal edges 21, 22 of the second membrane 3 by a shorter distance D1, D2 than a distance D3, D4 by which the first membrane 2 extends past the other edges 23, 24 of the second membrane 3. Moreover, Fig. 2C and 2D show a one-way valve 1 where a shape of the first membrane 2 is different from the shape of the first membrane 2 in Figs. 2A and 2B. In more detail, in some embodiments, an end portion of first membrane 2 has an indentation towards the centre of the first membrane 2. Stated different, the edge that extends past the longitudinal edge 21 of the second membrane 3 by the shorter distance D1 has an indentation towards the centre of the first membrane 2 (Fig. 2C). Similarly, the edges that extend past both longitudinal edges 21, 22 of the second membrane 3 by the shorter distance D1, D2 has indentations towards the centre of the first membrane 2.

[0039] Figs. 3A and 3B show two different embodiments of a one-way valve 1 arranged on a plastic film 11 of a food package 10 from a cross-sectional perspective taken along line A-A in Fig. 2A. In Fig. 3A the second membrane 3 is fixed to the first membrane 2, e.g. by means of ultrasonic welding, whereby there is no adhesive layer between the two membranes 2, 3. The parts of the bottom surface 5 of the first membrane 2 that extend beyond the outer edges 21-24 of the second membrane 3 are coated with a first adhesive 6, while the distal surface 7 of the second membrane 3 is coated with a second adhesive 8. Here, the first adhesive 6 may have a higher adhesion than the second adhesive 8. In Fig. 3B, the entire bottom surface 5 of the first membrane 2 with a first adhesive 6 and the distal surface 7 of the second membrane is not coated with any adhesive. In other words, the distal surface 7 of the second membrane 3 may be a non-adhesive surface (i.e., not coated with any adhesive). Naturally, one could also have omitted the second adhesive 8 on the distal surface 7 of the second membrane 3 of the one-way valve 1 depicted in Fig. 3A. Similarly, the distal surface 7 of the second membrane 3 of the one-way valve 1 depicted in Fig. 3B may be coated with the second adhesive (weaker than the first adhesive 6). The strength of an adhesive or its "adhesion" may typically be tested in a so-called peel test as readily understood by the skilled person in the art.

[0040] Fig. 4A illustrates a perspective view of a one-way valve 1 mounted over an aperture formed on a plastic film of a food package 10. In particular, the figure shows the one-way valve in use, i.e. in a situation when the gas pressure inside the food package 10 has exceeded a threshold value and a canal, through which gas / vapor may exit as indicated by the bolded arrow, has been formed between the one-way valve 1 and the plastic film 11. The excess pressure inside the food package 10 is generated from heating the food package 10. The canal is formed as a result of the bond between the plastic film 11 and a portion of the bottom surface of the first membrane 1 (and potentially the bond between plastic film 11 and the distal surface of the second membrane 3 should the distal surface be coated with an adhesive) temporarily breaking due to the surface pressure exerted by the gas onto the one-way valve 1 covering the aperture 12 being too strong. The term temporarily is used since upon cease of heating of the package and its contents, pressure equalization occurs, and the valve 1 closes as a result of the first membrane 1 having an adhesive coating, and on account of resiliency of the first membrane 2, resumes its original position in contact with the plastic film 11. Moreover, the adhesive applied onto the bottom surface of the first membrane 2 is preferably such that, once the gas pressure inside is reduced, to a level below the threshold value, the first membrane 2 adheres to the plastic film again 11.

[0041] Fig. 4B illustrates a perspective view of a one-way valve 1 mounted over an aperture formed on a plastic film 11 of a food package 10, according to some embodiments. The operation and functional principles are analogous to the embodiment illustrated in Fig. 4A, and will for the sake of brevity not be further elaborated upon. However, the one-way valve of Fig. 4B differs from that of Fig. 4A in that the canal, formed between the second membrane 3 and the plastic film 11, extends towards two peripheral edges of the first membrane 2. Thus, the gas / vapor from inside the food package 10 may exit through two paths as indicated by the bolded arrows.

[0042] Fig. 5 is a schematic flow chart representation of a manufacturing method S100 in accordance with an embodiment of the invention. In more detail, it is a method S100 for manufacturing a one-way valve for mounting over an aperture formed on a food package for cooking storing and / or heating ready-to-eat-food. The method S100 includes the steps of providing S101 a first membrane with a first surface area. The first membrane accordingly has a top surface and a bottom surface. Further, a second membrane having a proximal surface, a distal surface and a second surface area is provided S102. The second surface area is smaller than the first surface area.

[0043] The method S100 further comprises coating S103 the bottom surface of the first membrane with a first adhesive. Moreover, the method S100 may comprise coating S104 the distal surface of the second membrane with a second adhesive that has a lower adhesion than the first adhesive. Further, the method S100 comprises fixing S105 the proximal surface second membrane to the bottom surface of the first membrane, such that a footprint of the second membrane is completely enclosed within the bottom surface of the first membrane and the first membrane extends past all edges of the second membrane. Moreover, the two membranes are fixed S105 such that the first membrane extends past one or both longitudinal edges of the second membrane by a shorter distance than a distance by which the first membrane extends past the other edges of the second membrane.

[0044] Even though the invention has been described with reference to specific example embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. Thus, the above description of the various embodiments of the present invention and the accompanying drawings are to be regarded as non-limiting examples of the invention and the scope of protection is defined by the appended claims. For example, the opening in the plastic film need not have any specific shape, it may for example be semi-circular, star shaped, circular hole or a plurality of small holes.

[0045] Furthermore, any reference signs in the claims should not be construed as limiting the scope, and the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" does not exclude a plurality.

Claims

1. A one-way valve (1) for mounting over an aperture formed on a food package (10) for cooking, storing and / or heating of ready-to-eat food, the one-way valve comprising: a first membrane (2) with a top surface (4) and a bottom surface (5), wherein the first membrane has a first surface area; a second membrane (3) with a proximal surface (9) and a distal surface (7), wherein the second membrane (3) has a second surface area smaller than the first surface area and wherein the second membrane has two longitudinal edges (21, 22) on opposite sides of the second membrane and two lateral edges (23, 24) on opposite sides of the second membrane; wherein the proximal surface (9) of the second membrane (3) is fixed to the bottom surface (5) of the first membrane (2) such that a footprint of the second membrane (3) is completely enclosed within the bottom surface (5) of the first membrane (2) and the first membrane extends past all edges (21, 22, 23, 24) of the second membrane (3) and wherein the bottom surface (5) of the first membrane that extends past all edges of the second membrane (3) is coated with a first adhesive (6); wherein the first membrane (2) extends past one or both longitudinal edges (21, 22) of the second membrane by a shorter distance than a distance by which the first membrane (2) extends past the other edges of the second membrane (3).

2. The one-way valve (1) according to claim 1, wherein the one-way valve is adapted to be fixed to the food package (10) in order to cover the aperture (12) with the second membrane (3) such that a canal is formed between the food package and the one-way valve when a gas pressure inside the food package exceeds a threshold value, wherein the canal extends from the aperture to one or two peripheral edges (31, 32) of the first membrane along the second membrane (3) via the one or both of the longitudinal edges (21, 22) of the second membrane.

3. The one-way valve (1) according to claim 1 or 2, wherein the distal surface (7) of the second membrane (3) is coated with a second adhesive (8), and wherein the first adhesive (6) has a higher adhesion than the second adhesive (8).

4. The one-way valve (1) according to claim 1 or 2, wherein the distal surface (7) of the second membrane (3) is not coated with an adhesive.

5. The one-way valve (1) according to any one of claims 1-4, wherein the first membrane (2) is made of a thermoelastic material which has a production machine direction, and wherein the second membrane (3) is arranged such that the canal extends in a direction that has a relationship to said production machine direction such that an angle therebetween is within a range of 60° - 90°.

6. The one-way valve (1) according to any one of claims 1-5, wherein the second membrane (3) is more rigid material the first membrane (2).

7. The one-way valve (1) according to any one of claims 1-5, wherein the first membrane (2) is made of poly(vinyl chloride), and the second membrane (3) is made of a different polymer.

8. The one-way valve (1) according to any one of claims 1-6, wherein the first membrane (2) extends past one or both longitudinal edges (21, 22) of the second membrane (3) by a first distance and extends past the other edges of the second membrane by a second distance, the second distance being at least twice as long as the first distance.

9. The one-way valve (1) according to claim 8, wherein the first distance is in the range of 2 mm to 10 mm.

10. A food package for cooking, storing and / or heating of ready-to-eat food, the food package comprising a food container (13) and a plastic film (11) for sealing the food package from ambient air, the plastic film (11) including an aperture (12), wherein the food package further comprises a one-way valve covering the aperture, and wherein the one-way valve (1) comprises: a first membrane (2) with a top surface (4) and a bottom surface (5), wherein the first membrane has a first surface area; a second membrane (3) with a proximal surface (9) and a distal surface (7), wherein the second membrane (3) has a second surface area smaller than the first surface area and wherein the second membrane has two longitudinal edges (21, 22) on opposite sides of the second membrane and two lateral edges (23, 24) on opposite sides of the second membrane; wherein the proximal surface (9) of the second membrane (3) is fixed to the bottom surface (5) of the first membrane (2) such that a footprint of the second membrane (3) is completely enclosed within the bottom surface (5) of the first membrane (2) and the first membrane extends past all edges (21, 22, 23, 24) of the second membrane (3) and wherein the bottom surface (5) of the first membrane that extends past all edges of the second membrane (3) is coated with a first adhesive (6); wherein the first membrane (2) extends past one or both longitudinal edges (21, 22) of the second membrane by a shorter distance than a distance by which the first membrane (2) extends past the other edges of the second membrane (3).

11. The food package (10) according to claim 10, wherein the one-way valve covers the aperture (12) with the second membrane (3) such that a canal is formed between the food package and the one-way valve when a gas pressure inside the food package exceeds a threshold value, wherein the canal extends from the aperture to one or two peripheral edges (31, 32) of the first membrane along the second membrane (3) via the one or both of the longitudinal edges (21, 22) of the second membrane.

12. The food package (10) according to claim 10 or 11, wherein the distal surface (7) of the second membrane (3) is coated with a second adhesive (8), and wherein the first adhesive (6) has a higher adhesion than the second adhesive (8).

13. The food package (10) according to any one of claims 10-12, wherein the first membrane (2) extends past one or both longitudinal edges (21, 22) of the second membrane (3) by a first distance and extends past the other edges of the second membrane by a second distance, the second distance being at least twice as long as the first distance.

14. The food package (10) according to claim 13, wherein the first distance is in the range of 2 mm to 10 mm.

15. A method (S100) for manufacturing a one-way valve for mounting over an aperture formed on a food package for cooking, storing and / or heating of ready-to-eat food, the method comprising: providing (S101) a first membrane having a top surface and a bottom surface, the first membrane having a first surface area; providing (S102) a second membrane having a proximal surface and a distal surface, the second membrane having a second surface area smaller than the first surface area and wherein the second membrane has two longitudinal edges on opposite sides of the second membrane and two lateral edges on opposite sides of the second membrane; coating (S103) the bottom surface of the first membrane with a first adhesive; fixing (S105) the proximal surface second membrane to the bottom surface of the first membrane, such that a footprint of the second membrane is completely enclosed within the bottom surface of the first membrane and the first membrane extends past all edges of the second membrane, wherein the first membrane extends past one or both longitudinal edges of the second membrane by a shorter distance than a distance by which the first membrane extends past the other edges of the second membrane.

Images