FIELD OF THE INVENTION
[0001] The present invention refers to a container having flexible walls and an overpressure
relief valve, hermetically sealed, designed to contain a product which can generate
overpressure inside the container, which can cause the container to break.
[0002] The container of the invention will be preferably made of plastic and it can be designed
to store food with a certain degree of humidity and which, before eaten, must be heated,
usually in a microwave.
BACKGROUND OF THE INVENTION
[0003] When a hermetically sealed container having food with a certain degree of humidity
is placed in a microwave, this humidity transforms into steam, producing overpressure
inside the container. If this overpressure is not controlled, it can cause the destruction
of the container, and as a result, the product contained is spilt or scattered.
[0004] It is very frequent to use this type of plastic containers with flexible walls, hermetically
sealed, containing some sort of food product, capable of producing overpressure inside
said container, due to steam formation or degasification of the product contained.
To prevent the overpressure responsible for the possible breaking of the container,
these containers have an overpressure relief valve, which is manufactured as an independent
component from the container, generally made of materials other than the one forming
the container walls, and which is attached or fixed to said container during the mounting
process.
[0005] This solution requires that the valve be manufactured separately and later assembled
to the container, thus these operations causing an increase of the container manufacturing
costs.
DESCRIPTION OF THE INVENTION
[0006] The object of the present invention is a container having flexible walls and an overpressure
relief valve, which instead of being an independent component is formed from two of
the container walls, said walls being part of the valve.
[0007] In this way, the valve can be made in the container itself during the manufacturing
process of the container.
[0008] According to the present invention, the container has in one of the aforementioned
walls a hole, and the two walls forming the valve are joined together in a contour
around said hole, at certain distance from it. Thus, the outlet of the container through
said hole is closed by the union of the walls in the aforementioned contour, keeping
the airtightness of the container. However, this union between the two walls of the
container will have a resistance to the separation of the walls lower than the resistance
to the breaking down of the container.
[0009] With this arrangement, when there is overpressure inside the container for any reason,
before any breaking down of the container can occur, the two walls separate, at least
partially, to define an outlet for the overpressure.
[0010] The valve controlling the overpressure is constituted by the walls of the container
itself and the union between them in a contour around the hole made in one of the
walls, which will be the outlet for the overpressure, when the container walls separate
from each other at some point of the union contour between said walls.
[0011] Preferably, the container walls will be made of a thermoplastic material, and the
union between said walls in a contour around the aforementioned hole will be made
by thermo-welding.
[0012] The resistance of the union between the two walls, according to the contour described,
will be calculated so that the breaking down or separation occurs when there is a
specific overpressure inside the container.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The following drawings show an example of an embodiment which will help understand
better the characteristics of the container of the invention. In the drawings:
Figure 1 shows a container in the form of a bag, constituted according to the invention.
Figure 2 shows a partial cross sectional view of the container, according to the cutting
line II-II of figure 1, at a larger scale.
Figure 3 shows detail A of figure 1.
Figure 4 shows a partial cross sectional view of the container, according to the cutting
line IV-IV of figure 3, at a larger scale.
DETAILED DESCRIPTION OF AN EMBODIMENT
[0014] Figures 1 and 2 show a container 1 in the form of a bag, with a general constitution
that is well-known, obtained for example from a sheet made of a plastic material which
is folded at a medium cross line, the longitudinal edges being joined in thermowelded
strips 2 and also at the free cross edges in a thermo-welding area 3 with the shape
of a bag, with the two opposite walls 4 and 5. In the thermowelded longitudinal lines
2 it is possible to drill notches 6 to facilitate the opening of the bag.
[0015] The container of the invention, which can have the aforementioned arrangement or
any other arrangement, will have flexible walls, preferably made of a thermoplastic
material, and an overpressure relief valve, indicated with the reference number 7.
This valve, as it can be seen better in figures 3 and 4, comprises a hole 8, drilled
in one of the container walls 4, in any area thereof, and the union between the two
walls 4 and 5 preferably made by thermo-welding, in a contour 9 which is bigger than
the hole 8.
[0016] The union 9 between the two walls 4 and 5 will have a resistance to the separation
of said walls which will be lower than the resistance to the breaking down of the
container walls or to the breaking down of any of the closing strips 2 and 3 of the
container itself.
[0017] In this way, if there is overpressure inside the container, before any breaking down
of the container or of the union or closing strips thereof can occur, there is a separation
of the two walls along at least part of the union 9 between both walls. The overpressure
created inside the container will be released through the hole 8 and the part of the
union 9 which is broken or detached.
[0018] The overpressure which can be produced inside the container will cause, first of
all, the breaking down of at least part of the union 9, with the resulting separation
of the two walls, the overpressure being thus released through the open area 10 between
the two walls, until the outlet hole 8 is reached.
[0019] The union 9 between the two walls can define a contour of any shape, such as circular,
polygonal, etc. In any case, the contour of the union area 9 and the open area 10
between walls 4 and 5 are concentric with the hole 6.
[0020] The aforementioned constitution forms an overpressure relief valve, which has a simple
constitution and manufacturing process as well as a reduced cost, and which can be
obtained during the manufacturing process of the container itself.
[0021] The container can have a constitution and arrangement other than those herein described,
as long as it has two walls which can be joined in a contour 9, around the hole 8
drilled in one of these walls.