ONE-WAY VALVE FOR FOOD PACKAGES

Abstract

A one-way valve, a food package comprising such a one-way valve and a method for manufacturing such a one-way valve is disclosed. The valve comprises a first membrane and a second membrane having a smaller surface area than the first membrane and furthermore being fixed to a bottom surface of the second membrane. The valve is furthermore adapted to be fixed to the food package and cover the aperture such that a canal is formed between the food package and the second membrane when a gas pressure inside the food package exceeds a threshold value, the canal extending from the aperture to the peripheral edge of the first membrane along the second membrane.

Claims

1. A one-way valve for mounting over an aperture formed on a food package for at least one of cooking, storing and heating of ready-to-eat food, said one-way valve comprising: a first membrane with a top surface and a bottom surface, the first membrane having a first surface area; a second membrane with a proximal surface and a distal surface, the second membrane having a second surface area smaller than the first surface area, wherein the distal surface is coated with an adhesive and the proximal surface of the second membrane is fixed to the bottom surface of the first membrane such that a peripheral edge of the second membrane aligns with or extends past a peripheral edge of the first membrane; and wherein the one-way valve is adapted to be fixed to said food package in order to cover said aperture with said second membrane such that a canal is formed between the food package and the second membrane when a gas pressure inside the food package exceeds a threshold value, said canal extending from said aperture to the peripheral edge of the first membrane along said second membrane.

2. The one-way valve according to claim 1, wherein said second membrane defines the canal through which gas inside the food package can exit when the gas pressure inside the food package exceeds the threshold value.

3. The one-way valve according to claim 1, wherein the distal surface of the second membrane is coated with a first adhesive, and wherein the bottom surface of the first membrane is coated with a second adhesive, said first adhesive having a lower adhesion than the second adhesive.

4. The one-way valve according to claim 3, wherein the lower adhesion is provided by a release coating.

5. The one-way valve according to claim 1, wherein the first membrane extends past at least two sides of the second membrane.

6. The one-way valve according to claim 1, wherein the first membrane is made of a thermoelastic material which has a production machine direction, and wherein the second membrane 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.

7. The one-way valve according to claim 6, wherein said thermoelastic material is in an elastic state at temperatures exceeding 50 C.

8. The one-way valve according to claim 7, wherein the first membrane is made of poly(vinyl chloride), and the second membrane is made of a different polymer.

9. A food package for at least one of cooking, storing and 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, the plastic film including an aperture, wherein said food package further comprises a one-way valve covering said aperture, said one-way valve comprising: a first membrane having a top surface and a bottom surface, the first membrane having a first surface area; 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, wherein the distal surface is coated with an adhesive and the proximal surface is fixed to the bottom surface of the first membrane such that a peripheral edge of the second membrane aligns with or extends past a peripheral edge of the first membrane; and wherein the one-way valve is arranged on said plastic film so that the second membrane covers the aperture whereby a canal is formed between the food package and the second membrane when a gas pressure inside the food package exceeds a threshold value, said canal extending from said aperture to the peripheral edge of the first membrane along said second membrane.

10. The food package according to claim 9, wherein the distal surface of the second membrane is coated with a first adhesive, and wherein the bottom surface of the first membrane is coated with a second adhesive, said first adhesive having a lower adhesion than the second adhesive.

11. The food package according to claim 9, wherein the aperture in the plastic film is a cut.

12. A method for manufacturing a one-way valve for mounting over an aperture formed on a food package for at least one of cooking, storing and heating of ready-to-eat food, said method comprising: providing a first membrane having a top surface and a bottom surface, the first membrane having a first surface area; providing 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; coating the distal surface of the second membrane with a first adhesive; coating the bottom surface of the first membrane with a second adhesive, the first adhesive having lower adhesion than the second adhesive; fixing the proximal surface second membrane to the bottom surface of the first membrane, such that a peripheral edge of the second membrane aligns with or extends past a peripheral edge of the first membrane.

13. The method according to claim 12, wherein the coating of the respective adhesives on the first and second membranes is accomplished by spraying.

14. The one-way valve according to claim 1, wherein the canal further extends from the aperture to an opposing peripheral edge of the first membrane.

15. The one-way valve according to claim 2, wherein the distal surface of the second membrane is coated with a first adhesive, and wherein the bottom surface of the first membrane is coated with a second adhesive, said first adhesive having a lower adhesion than the second adhesive.

16. The one-way valve according to claim 15, wherein the lower adhesion is provided by a release coating.

17. The one-way valve according to claim 1, wherein the first membrane is made of poly(vinyl) chloride, and the second membrane is made of a second polymer.

18. The one-way valve of claim 17, wherein the second polymer is selected from the list consisting of: polypropylene, polyethylene, polystyrene, and polyurethane.

19. The one-way valve of claim 4, wherein the first and second adhesives are the same adhesive.

20. The one-way valve of claim 10, wherein the first and second adhesives are the same adhesive, and wherein the lower adhesion is provided by a release coating applied to the second membrane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] For exemplifying purposes, the invention will be described in closer detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:

[0034] FIG. 1A illustrates a perspective view of a valve in accordance with the prior art as applied on a food package;

[0035] FIG. 1B illustrates a perspective and partially exploded view of a one-way valve applied on a food package, in accordance with an embodiment of the invention;

[0036] FIG. 2A illustrates a top view perspective of the one-way valve arranged on a food package in FIG. 1B;

[0037] FIG. 2B illustrates a top view perspective of a one-way valve arranged on a food package, in accordance with another embodiment of the invention;

[0038] FIG. 3A illustrates a cross-sectional view taken along the line A-A in FIG. 2A, in accordance with an embodiment of the invention;

[0039] FIG. 3B illustrates another embodiment of the invention from the same perspective as in FIG. 3A;

[0040] FIG. 4A illustrates a perspective view of the one-way valve from FIG. 1B, with an open canal, in accordance with an embodiment of the invention;

[0041] FIG. 4B illustrates a perspective view of a one-way valve, with an open canal, applied on a food package, in accordance with another embodiment of the invention; and

[0042] FIG. 5 illustrates a flow chart representation of a method for manufacturing a one-way valve in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0043] In the following detailed description, embodiments of the invention are 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 invention, it will be apparent to one skilled in the art that the 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 invention.

[0044] FIG. 1A shows a one-way valve 100 intended for application on a food package 10, in accordance with the prior art. More particularly, the one-way valve 100 is intended to be arranged to cover an aperture or opening 12 formed in the food package 10. The conventional one-way valve 100 includes a two-layer structure, where the bottom layer 102 is provided with an aperture 103 which should be aligned with the aperture 12 formed in the food package 10 when the valve 12 is mounted onto the food package 10. Once the gas pressure inside the food package 10 exceeds some threshold value (e.g. during heating of the food package 10) a canal is formed between the two layers 101, 102. In order to provide the gas releasing function, the intermediate surfaces of the two layers 101, 102 (i.e. the surface of each layer 101, 102 facing the other layer 101, 102) are generally fixed together by means of two different adhesives. In more detail, a stronger adhesive is applied to a first surface portion surrounding the intended canal, and a weaker adhesive is applied only to a second surface portion which is intended to define the canal. However, instead of using different adhesives, one can coat the entire intermediate surfaces with a weaker adhesive and ultrasonically weld the surface portion surrounding the intended canal (i.e. the surrounding edge surfaces) during a subsequent process step. In order to alleviate problems associated with bubble and wrinkle formation, both of the layers 101, 102 are made from thermoelastic PVC, which results in an increased risk of the food content of the food package 10 coming in contact with the contaminants associated with the thermoelastic PVC.

[0045] FIG. 1B 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 an embodiment of the invention. The food package here is in the form of a rigid container, preferably made of a suitable plastic material, covered with a plastic film 11 for sealing the inside of the food package from the ambient atmosphere. The plastic film 11 is fixed along the outer circumference of the rigid container of the food package 10.

[0046] The one-way valve 1 comprises a first membrane 2 (which may also be referred to as a top layer or a top membrane) with a first surface area and a second membrane 3 (which may also be referred to as a bottom layer or a bottom membrane) with a second surface area which is smaller than that of the first membrane 2. The first membrane 2 has a bottom surface 5, which is preferably coated with an adhesive in order to stick to the proximal (i.e. the top surface) of the second membrane 3 and also to the plastic film 11 of the food package 10. The first membrane 2 can, for example, be made from thermoelastic PVC. 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.

[0047] 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 is mounted onto the food package 10. The second membrane 3 has a rectangular shape and the first membrane 2 extends past three sides or edge 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.

[0048] The one-way valve 1 is to be mounted to the food package 10, as indicated by the downwardly directed arrows in FIG. 1B, 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, for example 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 a (predefined) threshold value. The canal will accordingly extend from the aperture 12 towards a peripheral edge 21 (see FIGS. 2A, 2B, 4A, 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 of the force exerted on the bottom surface 7 of the second membrane 3 by the expanding gas.

[0049] The aforementioned peripheral edge of the first membrane 2 is aligned with a peripheral edge of the second membrane 3. Also, the second membrane 3 defines or delineates the canal through which gas inside the food package 10 can exit when the gas pressure inside the food package 10 exceeds the threshold value.

[0050] The distal surface 7 of the second membrane 3 is coated with an adhesive. However, the adhesive coated on the distal surface 7 of the second membrane 3 has a lower adhesion than the adhesive provided on the bottom surface 5 of the first membrane 2. By providing a relatively weak adhesive on the distal surface 7 of the second membrane 3 it is possible to control the threshold value for the gas pressure inside the food package. In other words, by using a weaker adhesive the threshold value can be lowered, and by using a stronger adhesive the threshold value can be increased. Stated differently, the threshold gas pressure is preferably controlled by controlling the adhesion of the adhesive applied on the distal surface 7 of the second membrane 3, i.e. by increasing or decreasing the adhesive strength of the adhesive applied on the distal surface 7. This can be tested in a peel test, for example.

[0051] 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. Preferably the opening pressure is in the range of 20-130 mbar, 40-160 mbar, or even 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.

[0052] FIGS. 2A and 2B show top view perspectives of a one-way valve fixed to plastic film 11 of a food package in accordance with an embodiment of the invention. The second membrane 3 is preferably in the general form of an elongated structure, such as a rectangle, as in the embodiment shown. However, the skilled artisan readily realizes that other shapes such as ellipse, 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 appropriately arranged and perpendicular axes extending along the surface of the membrane.

[0053] FIGS. 3A and 3B show two different embodiments of a one-way valve 1 arranged on a plastic film 11 of a food container 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, for example by means of ultrasonic welding, whereby there is no adhesive layer between the two membranes 2, 3. The bottom surface 7 of the second membrane 3 is coated with a first adhesive 8. The parts of the bottom surface 5 of the first membrane 2 which extends beyond the outer lateral edges of the second membrane 3 are however coated with a second adhesive 6, which has a higher adhesion than the first adhesive 8.

[0054] In FIG. 3B the bottom surface 7 of the second membrane 3 is coated with a first adhesive 8 and the entire bottom surface 5 of the first membrane 2 is coated with a second adhesive 6, the first adhesive 8 having lower adhesion than the second adhesive 6. By coating the whole bottom surface 5 of the first membrane 2 with a second adhesive 6 and using the same adhesive for fixing the two membranes 2, 3 to each other and also to fix the one-way valve to the food package, manufacturing complexity is reduced since otherwise more complex steps such as ultrasonic welding or using two different adhesives on different portions or sections of the same surface, can be omitted.

[0055] 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 second membrane 3 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 the bottom surface of the second membrane 3 temporarily breaking due to the surface pressure exerted by the gas onto the second membrane 3 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 10 closes as a result second membrane 3 having an adhesive coating, and on account of resiliency of the first membrane 2, which resumes its original position in contact with the plastic film 11. Moreover, the adhesive applied onto the distal surface of the second membrane 3 is such that, once the gas pressure inside is reduced, to a level below the threshold value, the second membrane 3 adheres to the plastic film again.

[0056] 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 another embodiment. 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.

[0057] FIG. 5 is a schematic flow chart representation of a manufacturing method 500 in accordance with an embodiment of the invention. In more detail, it is a method 500 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 500 beings at step 501, wherein a first membrane with a first surface area is provided. 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 at step 502. The second surface area is smaller than the first surface area.

[0058] Next, at step 503, the distal surface of the second membrane is coated with a first adhesive. At step 504, the bottom surface of the first membrane is also coated with a second adhesive, the first adhesive having lower adhesion than the second adhesive. As indicated in the figure, the adhesives may be sprayed onto the distal surface. However, other optional means for coating an adhesive are feasible, such as e.g. printing, dispensing, roll coating, transfer printing, screen printing, applying a solid film adhesive, brushing, etc. Also, as an alternative, the two surfaces (distal surface of the second membrane and bottom surface of the first membrane) may be coated with the same adhesive and the distal surface of the second membrane may additionally be coated with a release coating in order to lower the adhesion of the adhesive in a subsequent step.

[0059] At step 505, the two membranes are fixed to each other by fixing the proximal surface of the second membrane to the bottom surface of the first membrane. The two membranes are furthermore fixed to each other such that a peripheral edge of the second membrane aligns with or extends past at least one peripheral edge of the first membrane. The small illustrations next to block 505 indicate how the peripheral edges of the two membranes may be aligned (upper illustration) or how a peripheral edge of the second membrane may extend past a peripheral edge of the first membrane (lower illustration).

[0060] Even though the invention has been described with reference to specific exemplifying 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.

[0061] 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.