The present invention relates to a package, in particular, to a package in which a contained object generates steam when heated in a microwave oven.
In this type of package, cooked food or the like is contained and sealed in a packaging container for prevention of entry of dusts or others. The package as above may be heated in a microwave oven in order to cook the contained object.
Patent Literature 1, for example, discloses a tray-type packaging container sealed with a top seal.
Patent Literature 1: JP 2014-239661 A
However, since the packaging container disclosed by Patent Literature 1 is sealed, if the packaging container is heated as it is, the inner pressure thereof will continue to increase, and the package may burst so that the contained food may possibly be spattered to dirty the inside of the microwave oven. In order to prevent such situation, before the package is heated, a portion of the top seal needs to be peeled to provide a vent hole. Accordingly, the top seal of the packaging container of Patent Literature 1 is provided with a holding part for peeling, from which a portion of the top seal is to be peeled, and there is a drawback that an action of peeling a portion of the top seal from the holding part is required.
The present invention has been made to remove the conventional drawback as described above and an object of the present invention is to provide a package with which a contained object can be cooked without the need to peel a portion of a top seal before being heated in a microwave oven.
A package to be heated in a microwave oven according to the present invention includes: a packaging container that includes a containing part composed of a bottom part and a peripheral wall part and opening upward and that is provided with a flange part, the peripheral wall part rising from a periphery of the bottom part, and the flange part extending along a whole circumference of the peripheral wall part and projecting from an upper edge of the peripheral wall part outward with respect to the containing part; a contained object that is contained in the containing part and that generates steam when heated; and a top seal a portion of which is joined to the flange part along a whole circumference of the flange part to thereby seal the containing part, wherein the packaging container includes a curving part that is a portion of the peripheral wall part, the portion curving to protrude toward the containing part, and a maximum deformation amount point is formed within the curving part, a deformation amount being largest at the maximum deformation amount point in the peripheral wall part when an inner pressure of the containing part increases to deform the top seal, and wherein, when the package is heated in the microwave oven, the inner pressure of the containing part increases due to steam generated from the contained object or gas expansion through heating so that the packaging container and the top seal deform, a bending angle formed between the top seal and the portion joined to the flange part of the packaging container becomes larger at the maximum deformation amount point than a bending angle at any other point along the peripheral wall part except the maximum deformation amount point, the top seal thus deformed and the flange part are pulled away from each other, and the top seal peels from the flange part at the maximum deformation amount point when the inner pressure of the containing part exceeds a set value, whereby steam in the containing part is discharged.
The upper edge of the peripheral wall part may include a pair of sides opposing each other, and the packaging container may include the curving part at each of the pair of sides.
Preferably, the upper edge of the peripheral wall part forms a substantially rectangular shape, and the packaging container includes the curving part at each of a pair of long sides of the rectangular shape.
The packaging container may include a handle part provided to the peripheral wall part except the curving part.
The flange part may include a joining projection part projecting in a direction opposite from the bottom part and extending along the whole circumference of the flange part.
Preferably, the top seal is joined to the flange part so as to have a joining width that is substantially same throughout the whole circumference of the flange part.
The contained object may be food, and may be frozen food. In addition, the packaging container may be made of resin or paper.
Moreover, the present invention can also constitute a packaging container used in these packages.
According to the present invention, a packaging container includes a curving part that is a portion of a peripheral wall part curving toward a containing part; a maximum deformation amount point is formed within the curving part, at which a deformation amount is largest throughout the peripheral wall part when an inner pressure of the containing part increases and the containing part receives a tensile force from a top seal that has deformed; when being heated in a microwave oven, the inner pressure of the containing part increases due to steam generated from a contained object so that a flange part is pulled up from the deformed top seal; and when the inner pressure of the containing part exceeds a preset value, the top seal is peeled from the flange part at the maximum deformation amount point, whereby steam in the containing part is discharged. Accordingly, the contained object can be cooked without the need to peel a portion of the top seal before being heated in a microwave oven.
Embodiment 1 of the present invention is described below based on the appended drawings.
The packaging container 11 includes a bottom part 12 in a substantially rectangular planar shape, and a peripheral wall part 13 is formed at the periphery of the bottom part 12. The peripheral wall part 13 is rising from the periphery of the bottom part 12 as illustrated in
In the peripheral wall part 13, portions corresponding to a pair of long sides of the rectangular shape and extending in the first direction D1 curve to protrude toward the containing part 14 and each constitute a curving part C.
A flange part 15 is formed around the whole circumference of the peripheral wall part 13 so as to project from the upper edge of the peripheral wall part 13 outward with respect to the containing part 14. At a portion extending in the second direction D2 in the peripheral wall part 13, a handle part 16 is formed so as to project outward from the flange part 15 formed at the upper edge of the peripheral wall part 13; the handle part 16 is integrally connected with the flange part 15.
Since the curving part C curves to protrude toward the containing part 14, in the flange part 15, a portion formed on the upper edge of the curving part C curves to protrude toward the containing part 14.
A step part 17 is formed in the bottom part 12, and, in addition, a plurality of step parts 18 are also formed in the bottom part 12 and the curving part C. The step part 17 and the plurality of step parts 18 reinforce the strength of the packaging container 11 and are formed by arranging steps at parts of the bottom part 12 and the curving part C.
The packaging container 11 as above can be made of resin or paper.
As illustrated in
The top seal 21 is joined to the whole circumference of the flange part 15, and, accordingly, the containing part 14 is sealed with the top seal 21. At this time, the top seal 21 is joined so as to have an approximately same joining strength throughout the whole circumference of the flange part 15.
In
As a result of the simulation, since the inner pressure of the containing part 14 sealed with the top seal 21 was increased, the top seal 21 deformed so as to swell upward and the peripheral wall part 13 also deformed. Such result was obtained perhaps because the whole circumference of the flange part 15 received a tensile force from the deformed top seal 21 while the increased inner pressure of the containing part 14 acted on the entire peripheral wall part 13.
When the inner pressure of the containing part 14 was increased, the curving part C and the peripheral wall part 13 except the curving part C each deformed toward the containing part 14, with the deformation amount of the curving part C being larger than the deformation amount of the peripheral wall part 13 except the curving part C. This result suggests that the curving part C is more deformable than the peripheral wall part 13 except the curving part C. In addition, it was found that a maximum deformation amount point M at which the deformation amount is largest throughout the peripheral wall part 13 would be formed within the curving part C. The maximum deformation amount point M is situated at a portion, in the boundary portion between the top seal 21 and the flange part 15, where the curving part C and the second central axis L2 shown in
When the package 19 shown in
As illustrated in
The simulation result of the package 19 as described above shows that, as illustrated in
Accordingly, as illustrated in
Since the maximum deformation amount point M is formed in the curving part C where the peripheral wall part 13 coincides with the second central axis L2 shown in
As illustrated in
At this time, since the deformation amount at the maximum deformation amount point M is larger than the deformation amount of the peripheral wall part 13 except the maximum deformation amount point M, the bending angle θ2 shown in
When the bending angle of the top seal 21 becomes larger, of the tensile force the flange part 15 receives from the top seal 21, a force component perpendicular to the flange part 15 becomes larger.
As illustrated in
Since the bending angle θ2 shown in
As the inner pressure of the containing part 14 increases, the deformation amounts of the top seal 21 and the peripheral wall part 13 become large, whereby the bending angle of the top seal 21 becomes large. Furthermore, the tensile force of the top seal 21 also becomes so large that the force component perpendicular to the flange part 15 becomes large. The force component influences the process of peeling of the top seal 21; when a preset peeling force is reached, the top seal 21 peels from the flange part 15.
As the inner pressure P of the containing part 14 increases as illustrated in
When the inner pressure P of the containing part 14 exceeds the preset value while the force component Fv2 of the tensile force of the top seal 21 at the maximum deformation amount point M reaches the preset peeling force in this manner, a portion of the top seal 21 peels from the flange part 15 at the maximum deformation amount point M, whereby steam is discharged from the containing part 14. While the pair of curving parts C of the packaging container 11 each have the maximum deformation amount point M, the peeling process of the top seal 21 starts at either one of the pair of maximum deformation amount points M due to variations in shape and strength of the packaging container 11, variations in joining strength between the top seal 21 and the flange part 15 or other variations resulting from the production tolerances. Following the discharge of steam through a space between the peeled top seal 21 and the flange part 15, the inner pressure P of the containing part 14 rapidly decreases.
In a conventional package, since the packaging container is sealed, a portion of the top seal is required to be peeled to achieve a state where a vent hole is provided before being heated and thereafter the package is heated in a microwave oven. Accordingly, there is the need to peel a portion of the top seal from a holding part provided to the top seal, requiring an additional action.
On the other hand, in the package 19 according to Embodiment 1, even if the package 19 is heated in a microwave oven with the containing part 14 being sealed, once the inner pressure of the containing part 14 increases to exceed the preset value, the top seal 21 automatically peels, and then the inner pressure of the containing part 14 decreases. That is, the inner pressure of the containing part 14 does not continue to increase, and the contained object 20 is not caused to be spattered inside the microwave oven, so that the inside of the microwave oven does not become dirty. Accordingly, the contained object 20 can be cooked without requiring an action of peeling a portion of the top seal 21 before being heated.
In addition, until a portion of the top seal 21 automatically peels, the contained object 20 is cooked with the containing part 14 being sealed. Since the containing part 14 is sealed, steam with heat energy is not released outside and thus not wasted, and it is possible to cook with the higher pressure than the atmospheric pressure with the containing part 14 being filled with steam. Therefore, the required cooking time can be also shortened.
In this case, as with Embodiment 1, when the package 31 is heated in a microwave oven, the top seal automatically peels from the flange part 15 at the maximum deformation amount point formed in the curving part C, whereby the contained object 20 can be cooked without requiring an action of peeling a portion of the top seal before being heated.
The upper edge of the peripheral wall part 13 of the packaging container 42 forms a closed shape, and the upper edge of the peripheral wall part 13 includes a pair of sides extending in the first direction D1 and opposing each other. The curving part C may be provided to each of the pair of sides.
Since the packaging container 42 is provided with the curving parts C in this manner, as with Embodiments 1 and 2, the package 41 can be heated and the contained object 20 can be cooked in a microwave oven without requiring an action of peeling a portion of the top seal before being heated.
A portion of a predetermined range in the peripheral wall part 13 of the packaging container 52 is bent toward the containing part 14, whereby the curving part C can be formed.
Even when the packaging container 52 has such circular or oval shape when viewed from above, as with Embodiments 1 to 3, the package 51 can be heated and the contained object 20 can be cooked in a microwave oven without requiring an action of peeling a portion of the top seal before being heated.
It should be noted that as illustrated in
In addition, while a joining width between the top seal 21 and the flange part 15 may be substantially same throughout the whole circumference of the flange part 15, as long as the top seal 21 has the substantially same joining strength, the joining width is not necessarily required to be substantially same throughout. Moreover, as long as the sufficient joining strength is ensured throughout the whole circumference of the flange part 15, the joining width between the top seal 21 and the flange part 15 at the curving part C may be narrower than the joining width between the top seal 21 and the flange part 15 at the peripheral wall part 13 except the curving part C.
The top seal 21 may be joined by any conventional method, e.g., by using an adhesive or by heat-sealing. In addition, while the packaging containers 11, 32, 42 and 52 and the top seal 21 are formed of a resin film in Embodiments 1 to 4, any material such as, for example, a paper material laminated with resin may be used as long as the material allows joining between the top seal and the packaging container and does not release the inner pressure.
Furthermore, the handle part 16 of the packaging container 11, 32 or 42 used in the package 19, 31 or 41 in Embodiments 1 to 3 is not necessarily required to be integrally connected to the flange part 15; it is sufficient that the handle part 16 is formed on the peripheral wall part 13 except the curving part C. In addition, the packaging containers 11, 32 and 42 in Embodiments 1 to 3 may be configured so as not to include the handle part 16.
In Embodiments 1 to 4, uncooked food, frozen food and various other contained objects that generate steam when heated may be used in place of cooked food as the contained object 20.
11, 32, 42, 52 packaging container; 12 bottom part; 13 peripheral wall part; 14 containing part; 15 flange part; 16 handle part; 17, 18 step part; 19, 31, 41, 51 package; 20 contained object; 21 top seal; 22 joining projection part; C curving part; M maximum deformation amount point; θ0, θ1, θ2 bending angle; P inner pressure; Fv1, Fv2 force component; D1 first direction; D2 second direction; L1 first central axis; L2 second central axis.
Number | Date | Country | Kind |
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2015-137848 | Jul 2015 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2016/066869 | 6/7/2016 | WO | 00 |