Valves and Packages

Abstract

According to one aspect of the invention, a pressure relief valve is provided, comprising a cup-shaped body (1) having a bottom (11) and a peripheral wall (12) and fastened to a flexible packaging material. The bottom has at least one through hole (14) forming a passage through the body. A valve membrane abuts the body on the packaging side in an area around the through hole (14), with a sealing liquid between the body and the valve membrane. The valve membrane thereby covers the at least one through hole (14). On the packaging side, the bottom has a system of grease grooves (21, 22, 23) for accommodating a portion of the sealing liquid, the system of grease grooves comprising at least one outer grease groove (22, 23) having a circumferentially extending main part and having radially extending parts (24, 25) extending radially from the main part.

Description

[Technical field]

[0001] The present invention is in the field of pressure relief valves for food packages. [Background technology]

[0002] Certain foods, such as freshly roasted coffee beans or coffee powder, tend to degas for a while. Therefore, some food packages, such as coffee pouches, have a pressure relief valve. The pressure relief valve allows gases generated inside the package, such as carbon dioxide, to escape while preventing ambient air from entering the package, so that oxygen does not enter the package and freshness is maintained.

[0003] A pressure relief valve usually has a cup-shaped body, and the peripheral wall of the body among the edges is welded or glued to the inside of the packaging material. The bottom of the body and the package each have an opening. At the bottom of the body there is a disk as a valve membrane, and between the bottom and the disk there is oil, e.g. silicone oil, which acts as a sealing liquid. When there is overpressure in the package, the gas communicating through the opening of the bottom lifts the disk, so that the gas can escape to the inside of the body and from there to the outside of the package through the opening of the package. When there is no overpressure in the package, the disk abutting the bottom of the body ensures a leak-proof seal.

[0004] This type of pressure relief valve is beneficial in that it allows fresh food products to be directly packaged and delivered to the end customer without the need for intermediate repackaging. In addition to ensuring freshness for the customer, this also has benefits from an ecological perspective. However, pressure relief valves increase the environmental footprint of the package.

[0005] The overpressure required inside the package to trigger the pressure relief valve depends on the geometry of the body and the materials of the body, the valve membrane and the sealing liquid. Also, the pressure required to trigger the valve may depend on the package in which it is used and its contents. According to the prior art, given a certain size of the valve and its components, the adhesion force was adjusted by using sealing liquids of different compositions depending on the desired adhesion and therefore the trigger pressure. However, fine-tuning the adhesion force by changing the chemical composition is a challenge. This requires experimentation. In particular, it is a challenge to adjust the adhesion force without compromising with respect to other properties, especially when the materials of the valve membrane and the body are selected taking into account other properties and there is no freedom to adapt them. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the object of the present invention is to overcome the drawbacks of the prior art pressure relief valve. In particular, the object of the present invention is to provide a method for setting the adhesion force. Another object of the present invention is to provide a pressure relief valve having a structure suitable for being made from environmentally friendly materials. [Means for solving the problem]

[0007] According to one aspect of the present invention, a pressure relief valve is provided, the valve comprising a cup-shaped body having a bottom and a peripheral wall and fastened to a flexible packaging material. The bottom has at least one through hole forming a passage through the body. The valve membrane is in contact with the body on the package side (in a cup constituted by the body) in an area around the through hole, and there is a sealing liquid between the body and the valve membrane. Thereby, the valve membrane covers the at least one through hole. On the package side, the bottom has a system of grease grooves for accommodating a portion of the sealing liquid, the system of grease grooves comprising at least one outer grease groove having a main part extending in a circumferential direction and having a radial extension part extending radially from the main part.

[0008] The side of the bottom opposite the package side is referred to herein as the "product side." The outer grease groove in this case is a groove in the bottom located at a radially outer position, meaning that it is located at a radial distance from at least one through hole. In particular, the outer grease groove may be closer to the peripheral wall than to the center of the bottom.

[0009] It is known in the art that the body may be provided with grease grooves on the bottom package side. Grease grooves are shallow depressions in the surface area of ​​the body that the valve membrane contacts. The grease grooves act to contain and act as a reservoir for excess sealing liquid. They are beneficial, and often necessary, to ensure that the space between the valve membrane and the surface it contacts is always provided with a uniform amount of sealing liquid.

[0010] According to the present embodiment, in addition to having this well-known function, the grease groove has a further function, namely, the function of adjusting the adhesive force.

[0011] In particular, the radial extension of the grease groove may act to effectively shorten the shortest path along the valve membrane between the volume communicating with at least one through hole and any other hollow space. In this case, the volume communicating with at least one through hole may be constituted by the through hole itself or by a recess / groove around the through hole, such as the inner grease groove. The next other hollow space is, according to the approach described herein, the outer grease groove itself. The length of this path is one of the parameters that defines the trigger pressure; the shorter this path is, the less adhesive force needs to be overcome to lift the pressure relief valve and release the overpressure. The length of this shortest path, and therefore in embodiments the length of the extension itself, may be used to set the adhesive force.

[0012] This approach solves two problems simultaneously. Firstly, if the triggering force needs to be changed for different applications, it is enough to adjust the length of the radial extension. Thus, the radial extension approach allows the use of standard sizes of body and valve membrane as well as sealing liquids with a relatively high tendency to adhere for all packages. This expansion reduces the effective length of the path through which the valve membrane adheres to the body surface. This also reduces the adhesive force that the pressure buildup in the package must overcome before the valve is actuated, and the reduction in adhesive force that must be overcome increases with the size of the radial extension. Thus, to adapt the valve to different applications requiring different actuation / triggering pressures, only one parameter needs to be changed, namely the size (radial dimension) of the radial extension. This is a single geometric parameter, and the effect is quite predictable.

[0013] Secondly, this configuration allows for different types of materials to have a flat valve membrane and the surfaces it contacts. According to the prior art, a configuration with a curved membrane was sometimes necessary so that the adhesion would not be too strong, so that the elasticity of the membrane counteracts the adhesive force to some extent. However, this has the drawback that if the properties of the valve membrane material change, for example due to aging or moisture uptake, the properties of the pressure relief valve will also change. In particular, environmentally friendly biodegradable materials have this tendency. The approach according to the present invention ensures that the effective length of the path where the valve membrane adheres to the body surface is reduced by extension. In this way, a method is provided to overcome the drawbacks of the prior art so that environmentally friendly materials can be used as valve materials.

[0014] The radial extension approach allows for a standard size body and valve membrane, as well as a sealing liquid that has a relatively high tendency to stick, to be used for all packages.

[0015] In an embodiment, the radial extension, or at least one of the radial extensions, is a radially inward extension.

[0016] In these embodiments, the shortest path along the valve membrane between the volume in communication with at least one through hole and any other hollow space may be from the volume in communication with at least one through hole to the innermost point of the inward extension, if the radially inward extension extends closer to the volume in communication with the hole than any other structure.

[0017] In one group of embodiments, the body comprises a plurality of external grease grooves, for example the external grease groove may comprise a circular array of at least two external grease grooves that together form an (interrupted) ring.

[0018] In particular, the outer grease grooves may comprise a circular array of first outer grease grooves and a circular array of second outer grease grooves, the first outer grease grooves being arranged around the second outer grease grooves. In such a configuration, the second outer grease grooves may be staggered with respect to the first outer grease grooves, such that the second outer grease grooves cover the gaps between the first outer grease grooves, such that there is no radial line from the center of the base to its periphery that is not blocked by the outer grease grooves.

[0019] In embodiments where the outer grease grooves are provided in at least one circular array, there may be one inward extension per grease groove. If there are several circular arrays, one inward extension per grease groove in one of the arrays may be sufficient.

[0020] In an embodiment having two circular arrays of grease grooves, the radially inward extensions may be inward extensions of a first outer grease groove, and may optionally extend through a gap between the second outer grease grooves to a location radially inward of the location of the second outer grease groove.

[0021] Thereby, in addition to the function of adjusting the adhesion force mentioned above, the radial extension balances the distribution of sealing liquid between the first outer grease groove and the second outer grease groove.

[0022] In embodiments having two circular arrays of grease grooves, the second outer grease groove may include a radially outward extension that extends outwardly into the space between the first outer grease grooves, thereby improving the distribution of sealing liquid between the grease grooves.

[0023] In addition to the outer grease grooves, the grease groove system may also include inner grease grooves extending around at least one of the through holes. The outer grease grooves may be deeper than such inner grease grooves (if any).

[0024] The body inside the peripheral wall in the plane defined by the valve membrane may comprise an extended accommodation groove, which provides a space in which the valve membrane can expand so as not to bulge when inflated, for example when absorbing moisture.

[0025] The surface portion of the body that the valve membrane contacts may be flat, as opposed to the curved (arched) surface portion of prior art valves. Such a flat structure may be beneficial, particularly when the valve membrane and / or body are made of biodegradable materials, since the adhesive forces do not change when properties such as material elasticity change slightly due to moisture uptake or aging. A flat structure is particularly beneficial in conjunction with an extended containment groove, since this combination allows for precise seating of the valve membrane by adapting its diameter to the inner diameter of the cup-shaped body, without the risk of the membrane arching or otherwise deforming upon expansion.

[0026] In an embodiment, when the package contains a particulate product such as coffee powder (ground coffee), the valve further comprises a permeable membrane attached to the bottom product side, which is permeable to gas while covering at least one through hole so that the product does not clog the through opening. The permeable membrane may be a fabric membrane. In this specification, "fabric" is used to cover all kinds of flexible materials from interlocked fibers or yarns or threads, including nonwovens, woven or knitted fabrics or other textile structures.

[0027] In one group of embodiments, particularly when the valve has a permeable membrane, the body has at least one recess on the product side, thus forming a recessed portion. At least one through hole, or at least one of the through holes, has its product-side mouth in the recessed portion. This means that the mouth of the through hole on the product side is offset with respect to the outermost product side surface. This means that, if a permeable membrane is present, the mouth of the through hole is offset with respect to the plane of the permeable membrane. The recessed portion can effectively constitute a system of vent grooves with spacers between them.

[0028] In an embodiment, the spacers have rounded edges, so there is less risk of damaging the permeable membrane when the package is subjected to mechanical stress.

[0029] In an embodiment, the valve further comprises a fixing part. The fixing part is shaped to rest on the package side of the valve membrane. This prevents the valve membrane from falling off from the body even in situations where the valve is subjected to significant mechanical shock. If the valve is provided as a bulk material, it may be subjected to such shock especially during the transportation and assembly process. In situations of mechanical shock, the fixing part holds the valve membrane in place even if the adhesion by the sealing liquid is not sufficient. The fixing part may be held against the body by a peripheral wall of the body forming an undercut, so that the fixing part can click into the body.

[0030] In an embodiment, the valve may be biodegradable, i.e., all components may be made from biodegradable materials. As mentioned above, the grease groove structure makes the valve particularly suitable for a valve membrane of biodegradable material and / or a body of biodegradable material. In an embodiment, the optional other components are also biodegradable.

[0031] In this specification, "biodegradable" may mean biologically degradable according to European standard EN 13432 (as of the end of 2021). Additionally or alternatively, it may mean biologically degradable according to European standard EN 14995 (as of the end of 2021). Thus, "biodegradable" refers in particular to "biodegradable according to EN 13432 and / or EN 14995".

[0032] Insofar as water-soluble polymers are mentioned in this specification, such water-soluble polymers may optionally be degradable in sewage treatment plants (aerobic biodegradable) as determined according to the so-called Zahn-Wellens test in accordance with DIN EN ISO9888 (as of the end of 2021).

[0033] In particular, at least one component of the valve, such as the body, may be made from a polymeric composition comprising a water-soluble polymer. In embodiments, the polymeric composition further comprises a salt, in particular a hygroscopic salt.

[0034] In addition to including a water-soluble polymer and a salt, the composition may include a plasticizer, which may be selected from the group consisting of polyols (oligo- and polyhydroxy compounds) and low molecular weight amides.

[0035] In an embodiment, each of the body and, if present, the permeable membrane and the fixing portion is a polymer composition comprising polyvinyl alcohol (PVOH) as a water-soluble polymer, a salt, and glycerin as a plasticizer.

[0036] In an embodiment, the valve membrane is a polymeric composition that is not water soluble but is biodegradable, such as polyhydroxybutyrate (PHB).

[0037] In addition to relating to a pressure relief valve, the present invention also relates to a package, in particular a coffee pouch for coffee beans or ground coffee. The package comprises a flexible, pliable packaging material as described herein, and a pressure relief valve. The body of the pressure relief valve is attached to the packaging material. In particular, the annular end face of the pressure relief valve may be attached to the packaging material with the valve membrane (and the fixing part, if present) located in the hollow space between the bottom of the body and the packaging material. The packaging material is generally airtight, but has an opening or other permeable structure at a position surrounded by the peripheral wall of the body.

[0038] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, in which like numbers indicate like or corresponding elements. [Brief description of the drawings]

[0039] [Figure 1] FIG. 2 is an exploded view of the components of the pressure relief valve. [Diagram 2] This is the main body in the figure. [Diagram 3] FIG. 1 shows a cut and assembled valve. [Figure 4] This is the main body from a different perspective. [Diagram 5] FIG. [Figure 6] FIG. 13 is a further view of the cut and assembled valve. [Figure 7] FIG. 2 is a schematic diagram of a valve in a package. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The pressure relief valve shown in Figures 1, 3 and 6 comprises a body 1, also shown in Figures 2, 4 and 5. The body 1 has the overall shape of a flat cup having a bottom 11 and a peripheral wall 12. The bottom 11 has a sealing surface and a product surface opposite the sealing surface.

[0041] The peripheral wall 12 surrounds the sealing surface of the bottom 11 and has at its end opposite the bottom 11 a flange 13, i.e. an outwardly projecting collar, which results in a wider annular end surface 16 carrying the package-side energy-guiding rib 18. The bottom as at least one through hole 14 (in the embodiment shown there are three through holes 14) is covered by the valve membrane 2 which contacts the bottom 11 on its sealing surface. Between the bottom 11 and the valve membrane 2 there is a thin layer of sealing liquid, in particular an oil, for example silicone oil. Silicone oil is known for this purpose. The sealing liquid will therefore not be described in further detail here.

[0042] The pressure relief valve for use is placed inside an airtight flexible package in that the annular end surface of the peripheral wall 11 is joined to the package inner surface, for example by welding. The package material has at least one gas passageway (for example at least one small through hole or permeable section) at the location surrounded by the annular end surface. When there is overpressure in the package, the gas lifts the valve membrane 2 from the bottom 12, forming a gas passageway. The excess gas can then escape through the through hole 14, between the valve membrane and the bottom, and through the gas passageway of the package. When there is no overpressure in the package, the membrane closes the package by contacting the bottom, and capillary forces cause the sealing liquid to adhere to the bottom and the valve membrane to form a seal.

[0043] The body 1, defined by the valve membrane 2 inside the peripheral wall 12 in a plane, is provided with an extending receiving groove 41. Such a groove 41 has been found to be beneficial for the following reasons: the valve membrane 2 may be of a biodegradable polymer composition. In contrast to prior art valve membrane materials, it has been found that these materials may be prone to undergo dimensional changes depending on the environmental conditions. For example, they may expand slightly when exposed to moisture.

[0044] In an embodiment, the pressure relief valve has a permeable membrane 3 in addition to the body 1 and the valve membrane 2. In contrast to the valve membrane 2, the permeable membrane 3 is gas permeable. It may be, for example, a fabric, such as a nonwoven fabric. The permeable membrane is attached to the bottom product-side surface and covers at least the through opening 14. The permeable membrane is useful when the package contains particulate products, especially ground coffee, in that it prevents the product from clogging the opening and coming into contact with the sealing liquid and the valve membrane 2. It is not essential that the package contains, for example, coffee beans or other crude products.

[0045] The permeable membrane 3 may be of polymeric material, for example by being a fabric of thermoplastic fibers. In an embodiment, it may be welded to the body. For this purpose, the body has product-side energy-guiding ribs 38 on the side facing the packaged product.

[0046] On the sealing face side, the body has a plurality of grease grooves. More specifically, the body has an inner grease groove 21 surrounding the opening, and further has a ring of three first outer grease grooves 22 and a ring of three second outer grease grooves 23, the first outer grease grooves 23 being arranged around the second outer grease groove 22. The outer grease grooves 22, 23 generally extend in a circumferential direction, each having a main portion 27 extending in a circumferential direction parallel to the circumferential wall. Each of the second outer grease grooves 23 has an outward extension 24 extending radially outward from the main portion 27 into the gaps between the first outer grease grooves 22. Each of the first outer grease grooves 22 has an inward extension 25 extending radially inward from the main portion 27 into the gaps between the second outer grease grooves 23 and further extending radially inward.

[0047] As used herein, "radial" as well as "outer" or "inner" or "circumferential" are meant to refer to the axis 10 of the body; the existence of a central axis does not necessarily imply axial symmetry, although such symmetry is an option.

[0048] The outer grease grooves have the function as reservoirs for sealing liquid. For this purpose, they are located in a radial position so that they are covered by the valve membrane (see, for example, FIG. 3 or FIG. 6). For example, if the valve is subjected to temporary mechanical loads, for example during transportation of the valve before bonding to the package or during transportation of the package with the valve, it may happen that the sealing liquid is pushed out from between the bottom 11 and the valve membrane 2. The grease groove ensures that capillary forces can then draw the sealing liquid out again from the grease groove under the valve membrane. Similar considerations apply to the manufacturing process. For the grease groove, it is sufficient that a drop of sealing liquid is dispensed on the bottom or on the membrane, the grease groove ensures that the sealing liquid is well distributed and that the sealing membrane adheres uniformly to the bottom over the entire circumference of the through hole 14.

[0049] In addition to having this well-known function, the special structure of the outer grease grooves 22, 23 allows for better control of the adhesive forces: the distance between the inner grease groove 21 and the outer grease grooves 22, 23 determines the minimum length p of the path along which the adhesive forces must be overcome in order to trigger the valve by lifting the valve membrane 2 off the bottom 11. l If no internal grease groove is present, the quantity of interest is the distance between the through hole 14 and the inward extension 25.

[0050] As shown in FIG. 5, this path length p l may be controlled by selecting the length of the inward extension 25.

[0051] Both the outward extension 24 and the inward extension 25 have the further function of distributing sealing liquid between the grease grooves. For example, the outward extension 24 and the inward extension 25 may provide communication of sealing liquid between a first outer grease groove and a second outer grease groove, and between different first grease grooves and different second grease grooves.

[0052] Nevertheless, a system comprising a circular array of at least two (three in the illustrated embodiment) first external grease grooves 22 and / or a circular array of at least two (three in the illustrated embodiment) second external grease grooves 23 features the advantage that the sealing liquid is better distributed along the periphery of the bottom 11 than an arrangement in which the grease grooves are an uninterrupted ring, even in situations in which the valve is maintained in an unchanging vertical orientation for long periods of time.

[0053] In an embodiment, the pressure relief valve has a fixed part 4 in addition to the body 1 and the valve membrane 2, possibly in addition to the permeable membrane 2. The fixed part 4 is optional and may function as a spacer between the flexible packaging material and the valve membrane 2, ensuring that the valve membrane 2 cannot be displaced even in the event of severe mechanical violent vibration. In the illustrated embodiment, the fixed part 4 is star-shaped with three rays. It has a first distance-keeping rib 51 and a second distance-keeping rib 52. The entire star shape and the distance-keeping ribs 51, 52 constitute a material-saving shape and still have a stable orientation. The star shape also ensures a certain degree of elasticity of the fixed part 4.

[0054] As can be seen for example in figure 6, the shape of the peripheral wall 12 forms a slight undercut 42 on the inside, and the inner surface of the body is slightly conical. This undercut shape allows the fastener 4 to be clicked into the body and remain there due to its elasticity.

[0055] On the side facing the product, the body 1 is constructed with a system of ventilation grooves 31 and spacers 33. The system is such that the through holes 14 are at the bottom of the ventilation grooves, i.e. in a position where the product-side surface is recessed. The radial channels 32 belonging to the system of ventilation grooves 31 ensure that the gas diffusing through the permeable membrane into the ventilation channel can reach the through holes 14. Thereby, the gas can diffuse through a relatively large surface area, in that it encounters less resistance and the membrane is not pressed against a flat surface by the overpressure inside the package. Rather, the spacers 33 move the membrane away from the plane in which the through holes 14 have their mouths.

[0056] A further advantage of the system of ventilation grooves is that it prevents the permeable membrane 3 from sticking to the body in the area around the through holes 14. Such sticking can occur during the process of joining the permeable membrane 3 to the body, for example by ultrasonic welding.

[0057] For example, as shown in FIG. 5, the spacers 33 have rounded edges 35 so that there is less risk of damaging the permeable membrane when the package is subjected to mechanical stress.

[0058] The overall shape of the body with the flange 13 and the wide end face 16 (joined to the packaging material) provides further improvements with regard to the process of joining the valve to the packaging material and the stability of the joint: the shoulder defined by the flange, which is an outwardly protruding collar, provides a joint surface 17 on which the tool for joining the valve to the packaging material can directly act. Thereby, the energy coupled by the tool into the body 1 for the joining process (usually ultrasonic energy) does not have to be coupled through the entire height (axial extension) of the body, but only through the thickness of the flange 13. This makes the joining process more efficient compared to the situation where the tool presses against the product-side end face of the body.

[0059] The tool may for example be a tube-shaped sonotrode with a tube diameter that corresponds approximately to the diameter of the flange 13 .

[0060] However, the flange 13 and the wide end face 16 are merely optional. In alternative embodiments, the body 1 does not have this structure. Also in these alternative embodiments, the body 1 can be welded to the packaging material in that the sonotrode impinges on the product side end face of the body. Also in these embodiments, the sonotrode used can optionally be tubular in shape, the tube diameter being larger than the outside diameter of the area with the system of ventilation grooves and spacers. However, alternatively, the sonotrode can have a flat outcoupling face.

[0061] In the illustrated embodiment, the body 1, the anchoring part 4 and the permeable membrane 3 are all made from a polymer composition which in addition to comprising a water-soluble polymer also comprises a salt.

[0062] The body 1 and the fastening part 4 are injection moulded from a polymer composition comprising, for example, poly(vinyl ester), a salt (especially sodium chloride) and PVOH obtained by saponification of glycerin. The polymer composition of the body and the fastening part may be the same.

[0063] The permeable membrane is, for example, a woven fabric of fibers of a polymer composition that also contains PVOH, obtained by saponification of poly(vinyl ester), salt (especially sodium chloride), and glycerin.

[0064] The valve membrane 2 is made from PHB. Therefore, all components are biodegradable.

[0065] Figure 7 shows a schematic representation of a package with a valve. The body 1 is welded to a packaging material 60. The packaging material has a through hole 61 for the gas to be released.

Claims

1. 1. A pressure relief valve comprising: a cup-shaped body (1) having a bottom (11) and a peripheral wall (12) and equipped to be fastened to a flexible packaging material, said bottom (11) having at least one through hole (14) forming a passage through said body, a valve membrane (2) adjoining said body on the package side in an area around said at least one through hole (14), and a sealing liquid between said body (1) and said valve membrane (2), characterized in that said bottom (11) comprises, on the package side, a system of grease grooves for accommodating a portion of said sealing liquid, said grease groove system comprising at least one outer grease groove (22, 23) having a circumferentially extending main part (27) and having radial extension parts (24, 25) extending radially from said main part (27).

2. 2. The valve of claim 1, wherein the grease groove system comprises at least one circular array of at least two first outer grease grooves (22).

3. 3. The valve of claim 2, wherein the grease groove system further comprises at least one circular array of at least two second outer grease grooves (23), the first outer grease grooves (22) being arranged around the second outer grease grooves (23) and the second outer grease grooves being staggered with respect to the first outer grease grooves.

4. 4. The valve of claim 3, wherein at least one of the first external grease grooves has a radially extending portion (25) that is an inwardly extending portion that extends inwardly between the second external grease grooves (23).

5. 5. The valve of claim 3 or 4, wherein at least one of the second external grease grooves has a radially extending portion (24) that extends outwardly between the first external grease grooves (22).

6. 10. A valve according to any one of the preceding claims, wherein the grease groove system further comprises an inner grease groove (21) extending around the at least one through hole (14).

7. 7. A valve as claimed in claim 6, wherein said at least one outer grease groove (22, 23) is deeper than said inner grease groove (21).

8. 10. A valve according to any one of the preceding claims, wherein the or at least one of the radial extensions (25) is an inward extension, and wherein when the valve membrane (2) contacts the body, the shortest path along the valve membrane (2) between a volume in communication with the at least one through hole (14) and any other hollow space leads from the volume in communication with the at least one through hole (14) to an innermost point of the inward extension.

9. 10. The valve of any one of the preceding claims, wherein at least one component of the valve is made from a polymer composition comprising a water soluble polymer.

10. 10. A valve according to any one of the preceding claims which is biodegradable.

11. 10. The valve according to any one of the preceding claims, further comprising a permeable membrane (3) of fabric secured to the body (1) so as to cover the at least one through hole (14) on a product side opposite the packaging side.

12. 10. A valve according to any one of the preceding claims, wherein the body has a system of ventilation grooves with spacers between them, and the through hole (14) or the mouth of the at least one of the through holes (14) is in the ventilation grooves.

13. 10. A valve according to any one of the preceding claims, further comprising a fixing part (4) fixed relative to the peripheral wall, such that the valve membrane (2) is sandwiched between the bottom part (11) and the fixing part (4).

14. 10. A package for packaging food products, comprising a flexible, pliable packaging material (60) and a pressure relief valve according to any one of the preceding claims, said body (1) being attached to said packaging material (60).

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