Jig for microwave oven heating

Abstract

Provided is a technology that, when a microwave oven is used to heat an article that is accommodated in a metal can container, can suppress the occurrence of problems due to the metal. A jig (10A) for microwave oven heating is not made of metal, is used for positioning a metal can container (21) in the interior of a microwave oven at a distance from an interior bottom surface (W1) of the microwave oven when using the microwave oven to heat an article (22) accommodated in the metal can container (21), and includes: a support part (11) that has a cylindrical shape; and a plate-shaped reinforcement part (12) that is connected to one opening of the support part (11), wherein the support part (11) is configured so at to fit with both a first canned product end part and a second canned product end part that are different from each other in at least one of shape and dimension.

Description

Microwave heating jig

[0001] The present invention relates to a microwave oven heating jig.

[0002] Microwave ovens are a well-known method for heating packaged foods, and are widely used due to their simplicity.

[0003] However, when a container contains a metal layer, heating it in a microwave oven can activate the movement of free electrons in the metal layer, causing discharge (sparks) between the metal layer and the grounded wall surface of the microwave oven. Patent Document 1 describes a method for preventing this spark from occurring, in which a container body made of a composite sheet containing a resin sheet and metal foil formed into a cup shape is placed in a paper box and heated in a microwave oven.

[0004] Metal cans have the advantage of being more suitable for long-term storage of contents than plastic containers, and are stronger and therefore less likely to break, making them popular as containers for various types of canned food.

[0005] Furthermore, some metal cans can be opened almost entirely without using special tools. Food stored in such metal cans can be eaten as is without transferring it to another container. In this case, the food can be eaten at room temperature or after heating it in a hot water bath or the like.

[0006] Japanese Patent Publication No. 2017-95163

[0007] An object of the present invention is to provide a technology that can prevent problems caused by metal when an item stored in a metal can container is heated in a microwave oven.

[0008] According to one aspect of the present invention, there is provided a non-metallic microwave heating jig used to install a metal can container in a microwave oven with a wider distance from the bottom of the microwave oven when heating an item contained in the metal can container in a microwave oven, the microwave heating jig including a cylindrical support portion and a flat reinforcing portion connected to one opening of the support portion, the support portion being configured to fit with both a first canned product end portion and a second canned product end portion which differ from each other in at least one of their shapes and dimensions.

[0009] According to another aspect of the present invention, there is provided a microwave heating jig according to the above aspect, wherein each of the first canned product end and the second canned product end includes a large diameter portion, and the support portion includes a first fitting portion that fits with the large diameter portion of the first canned product end and a second fitting portion that fits with the large diameter portion of the second canned product end.

[0010] According to yet another aspect of the present invention, there is provided a microwave heating tool according to any of the above aspects, further comprising a removal assisting part that assists in removing the metal can container containing the heated article from the interior of the microwave oven without contacting the metal can container or the support part, wherein the support part includes a part that is placed between the metal can container and the interior bottom surface when the article is heated in the microwave oven.

[0011] According to yet another aspect of the present invention, there is provided a microwave oven heating jig relating to the above aspect, wherein the removal assisting portion includes two or more protrusions that each protrude in a direction away from the support portion and the metal can container when the portion of the support portion is installed between the metal can container and the interior bottom surface of the microwave oven.

[0012] Alternatively, according to yet another aspect of the present invention, there is provided a microwave oven heating jig relating to the above aspect, wherein the removal assisting portion includes two or more plate-shaped portions that fit along the can body of the metal can container when the portion of the support portion is installed between the metal can container and the interior bottom surface.

[0013] Alternatively, according to yet another aspect of the present invention, there is provided a microwave oven heating jig relating to the above aspect, wherein the removal assisting portion includes a sleeve portion that surrounds the metal can container when the portion of the support portion is installed between the metal can container and the interior bottom surface.

[0014] According to yet another aspect of the present invention, there is provided a microwave heating jig relating to any of the above aspects, wherein the smallest square circumscribing the orthogonal projection of the removal assisting portion onto a plane perpendicular to the height direction has the same dimensions as or is smaller than the smallest square circumscribing the orthogonal projection onto the plane of the portion of the microwave heating jig excluding the removal assisting portion.

[0015] According to yet another aspect of the present invention, a dielectric constant at 2.45 GHz is 5 or less and a dielectric loss tangent at 2.45 GHz is 7.0 × 10 －３ There is provided a microwave oven heating tool according to any one of the above aspects, which is made of the following material.

[0016] According to yet another aspect of the present invention, there is provided the microwave oven heating jig according to the above aspect, wherein the material is a cured resin.

[0017] According to yet another aspect of the present invention, there is provided a canned product with a jig, comprising the metal can container and the item contained therein, and a microwave heating jig according to any of the above aspects.

[0018] According to yet another aspect of the present invention, there is provided a jig-attached canned product according to the above aspect, in which the canned product has its upper end as one of the first canned product end and the second canned product end, and its lower end as the other of the first canned product end and the second canned product end.

[0019] According to yet another aspect of the present invention, there is provided a canned product with a jig attached according to any of the above aspects, wherein the smallest square circumscribing the orthogonal projection of the removal assisting part onto a plane perpendicular to the height direction has dimensions equal to or smaller than the smallest square circumscribing the orthogonal projection of the metal can container onto the plane.

[0020] According to yet another aspect of the present invention, there is provided a jig-attached canned product according to any of the above aspects, wherein the canned product and the microwave heating jig are arranged side by side in the height direction of the canned product, and the height Ht of the jig-attached canned product and the height Hk of the canned product satisfy the relationship shown in the following inequality (1): 0.9×(n+1)×Hk≦n×Ht≦1.1×(n+1)×Hk (where n represents an integer in the range of 2 to 5).

[0021] According to yet another aspect of the present invention, there is provided a canned product with a jig attached, wherein the microwave heating jig has an overall cylindrical shape and is attached to the upper end of the canned product.

[0022] According to yet another aspect of the present invention, there is provided a packaged article comprising a plurality of jig-attached canned products stacked vertically and a packaging material containing or holding together the plurality of jig-attached canned products, each of the plurality of jig-attached canned products being a jig-attached canned product according to any of the above aspects.

[0023] According to yet another aspect of the present invention, there is provided a kit for canned products with a jig, comprising the microwave heating jig according to any one of the above aspects and the metal can container.

[0024] According to yet another aspect of the present invention, there is provided a kit for canned products with a jig according to the above aspect, in which the canned product including the metal can container and the item contained therein has an upper end portion as one of the first canned product end portion and the second canned product end portion, and a lower end portion as the other of the first canned product end portion and the second canned product end portion.

[0025] According to yet another aspect of the present invention, there is provided a jig-attached canned product kit according to any of the above aspects, wherein the microwave heating jig is arranged in line with the height of the canned product when the jig-attached canned product includes a canned product including the item and the metal can container containing the item, and the microwave heating jig, and when the item contained in the metal can container is heated in a microwave oven, the metal can container is placed in the microwave oven with its distance from the bottom of the microwave oven increased, and the height Ht of the jig-attached canned product and the height Hk of the canned product satisfy the relationship shown in the following inequality (1): 0.9×(n+1)×Hk≦n×Ht≦1.1×(n+1)×Hk (where n is an integer ranging from 2 to 5).

[0026] The present invention provides a technology that can prevent problems caused by metal when an item stored in a metal can container is heated in a microwave oven.

[0027] FIG. 1 is a perspective view of a microwave heating jig according to a first embodiment of the present invention. FIG. 2 is another perspective view of the microwave heating jig shown in FIG. 1. FIG. 3 is a cross-sectional view of the microwave heating jig shown in FIG. 1 taken along line III-III. FIG. 4 is a cross-sectional view of a jig-attached canned product including the microwave heating jig shown in FIGS. 1 to 3. FIG. 5 is a cross-sectional view showing the jig-attached canned product shown in FIG. 4 with the microwave heating jig attached in a different position. FIG. 6 is a perspective view of an example of a microwave oven in which the microwave heating jig shown in FIGS. 1 to 3 can be used. FIG. 7 is a cross-sectional view showing an open canned product placed on the bottom of the microwave oven via the microwave heating jig shown in FIGS. 1 to 3. FIG. 8 is a perspective view of a microwave heating jig according to a modified embodiment of the first embodiment. FIG. 9 is a cross-sectional view of a jig-attached canned product including the microwave heating jig shown in FIG. 8. FIG. 10 is a cross-sectional view showing the jig-attached canned product shown in FIG. 9 with the microwave heating jig attached in a different position. FIG. 11 is a perspective view of a microwave heating jig according to a second embodiment of the present invention. FIG. 12 is another perspective view of the microwave heating jig shown in FIG. 11. FIG. 13 is a cross-sectional view of the microwave heating jig shown in FIG. 11 taken along line XIII-XIII. FIG. 14 is a cross-sectional view of a jig-attached canned product including the microwave heating jig shown in FIGS. 11 to 13. FIG. 15 is a front view showing a stack formed by stacking canned products included in the jig-attached canned product shown in FIG. 14 in the height direction, and a stack formed by stacking the jig-attached canned products shown in FIG. 14 in the height direction. FIG. 16 is a cross-sectional view showing an opened canned product placed on the bottom surface of a microwave oven via the microwave heating jig shown in FIGS. 11 to 13. FIG. 17 is a perspective view of a microwave heating jig according to a third embodiment of the present invention. FIG. 18 is another perspective view of the microwave heating jig shown in FIG. 17. FIG. 19 is a cross-sectional view of the microwave heating jig shown in FIG. 17 taken along line XIX-XIX. Figure 20 is a cross-sectional view of a canned product with a jig attached, including the microwave heating jig shown in Figures 17 to 19. Figure 21 is a cross-sectional view showing an open canned product placed on the bottom of a microwave oven via the microwave heating jig shown in Figures 17 to 19.Fig. 22 is a top view showing an example of a packaged article comprising a plurality of jig-attached canned products. Fig. 23 is a perspective view of a microwave heating jig according to a modified example of the third embodiment of the present invention. Fig. 24 is a perspective view of a jig-attached canned product including the microwave heating jig shown in Fig. 23. Fig. 25 is a perspective view of a microwave heating jig according to a fourth embodiment of the present invention. Fig. 26 is a side view of a jig-attached canned product including the microwave heating jig shown in Fig. 25. Fig. 27 is a perspective view of a microwave heating jig according to a modified example of the fourth embodiment of the present invention. Fig. 28 is a side view of a jig-attached canned product including the microwave heating jig shown in Fig. 27. Fig. 29 is a perspective view of a microwave heating jig according to a fifth embodiment of the present invention. Fig. 30 is a side view of a jig-attached canned product including the microwave heating jig shown in Fig. 29.

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific embodiments of any of the above aspects. The following items can be incorporated into each of the above aspects, either singly or in combination.

[0029] <First embodiment> Fig. 1 is a perspective view of a microwave heating jig according to a first embodiment of the present invention. Fig. 2 is another perspective view of the microwave heating jig shown in Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III of the microwave heating jig shown in Fig. 1.

[0030] The microwave oven heating jig 10A shown in Figures 1 to 3 is used to place a metal can container in a microwave oven with the metal can container positioned at a greater distance from the bottom of the microwave oven when heating an item contained in the metal can container in a microwave oven. The microwave oven heating jig 10A is made of a non-metallic material. The microwave oven heating jig 10A includes a support portion 11 and a reinforcing portion 12.

[0031] The support portion 11 has a cylindrical shape. Here, the support portion 11 has a substantially cylindrical shape in which the diameter of one opening is smaller than the diameter of the other opening.

[0032] When microwave heating jig 10A is used in a microwave oven, the larger diameter opening of support portion 11 is positioned above the smaller diameter opening. Hereinafter, with respect to microwave heating jig 10A and its components, the terms "above" and "below" are used in reference to the relative positions when microwave heating jig 10A is used in the microwave oven.

[0033] The reinforcing portion 12 has a disk shape and is connected to the lower opening of the support portion 11. The reinforcing portion 12 improves the shape retention of the support portion 11.

[0034] Here, the reinforcing portion 12 is provided so as to close the lower opening of the support portion 11. The reinforcing portion 12 may be provided with one or more through holes. Also, here, the lower surface of the reinforcing portion 12 is flush with the lower end surface of the support portion 11. The lower surface of the reinforcing portion 12 may be located higher than the lower end surface of the support portion 11.

[0035] In this microwave heating jig 10A, the support portion 11 is configured to fit into both a first canned product end and a second canned product end that differ from each other in at least one of shape and size. The first canned product end and the second canned product end may be the upper and lower ends of the same canned product, or may be the lower ends of different canned products. Here, as an example, the first canned product end is one of the upper and lower ends of the canned product, and the second canned product end is the other of the upper and lower ends of the canned product. Also, here, as an example, the first canned product end and the second canned product end are assumed to have different diameters.

[0036] As will be described later, when heating an item contained in a metal can in a microwave oven, the microwave heating jig 10A supports the canned product by inserting the lower end of the canned product into the upper end of the support portion 11 (hereinafter sometimes referred to as the open end of the microwave heating jig 10A) so that the metal can is sufficiently spaced apart from the bottom surface of the microwave oven chamber. Furthermore, the microwave heating jig 10A allows the canned product, heated to a high temperature, to be removed from the microwave oven chamber without touching it by manually carrying the microwave heating jig 10A attached to the lower end of the canned product outside the microwave oven chamber. Because the support portion 11 of the microwave heating jig 10A fits over the lower end of the canned product, the canned product is less likely to shift position relative to the microwave heating jig 10A during removal, and therefore, unintended contact with the heated canned product or the item contained therein is less likely to occur. Furthermore, when the canned product is distributed or when an opened canned product is stored, the upper end of the canned product is inserted into the opening end of the microwave heating jig 10A, thereby protecting the upper surface of the canned product and items contained in the metal can container from dirt, etc.

[0037] A more detailed description will be given of the structure of the support portion 11. Here, the support portion 11 includes a base portion 11b (or a lower portion 11b), a first fitting portion 11g1, and an enlarged diameter portion 11e.

[0038] Base 11b has a cylindrical shape with a constant inner diameter in the height direction. Here, base 11b is continuous with reinforcing portion 12 at its lower end. When an item stored in the metal can is heated in a microwave oven, base 11b is positioned between the metal can and the bottom surface of the microwave oven, and serves to widen the distance between the metal can and the bottom surface of the microwave oven. Base 11b may have a diameter that widens upward.

[0039] The first fitting portion 11g1 is located between the base portion 11b and the enlarged diameter portion 11e. The first fitting portion 11g1 is a portion that fits into the large-diameter portion of the first canned product end. Here, the first fitting portion 11g1 has a cylindrical shape with a first groove extending circumferentially formed on its inner surface. The first groove enables the microwave heating jig 10A to engage with the large-diameter portion of the first canned product end. The first fitting portion 11g1 may have a cylindrical shape with a diameter that tapers downward and with a first groove extending circumferentially formed on its inner surface. Alternatively, the first fitting portion 11g1 may have one or more protrusions formed on its inner surface instead of the first groove, which enable the microwave heating jig 10A to engage with the large-diameter portion of the first canned product end.

[0040] The enlarged diameter portion 11e has a cylindrical shape whose diameter increases in a direction away from the first fitting portion 11g1. The enlarged diameter portion 11e includes a second fitting portion 11g2 that fits with the large-diameter portion of the second canned product end. Here, the second fitting portion 11g2 has a second groove extending circumferentially formed on its inner surface. The second groove allows the microwave heating jig 10A to engage with the large-diameter portion of the second canned product end. The inner diameter of the second fitting portion 11g2 at the bottom of the second groove is larger than the inner diameter of the first fitting portion 11g1 at the bottom of the first groove. Instead of a second groove, the second fitting portion 11g2 may have one or more protrusions formed on its inner surface that allow the microwave heating jig 10A to engage with the large-diameter portion of the second canned product end.

[0041] The microwave heating jig 10A preferably widens the distance between the metal can container and the bottom surface of the microwave oven chamber to a range of 1 mm to 50 mm, and more preferably to a range of 10 mm to 30 mm. Increasing this distance reduces the likelihood of sparks occurring between the metal can container and the bottom surface of the microwave oven chamber. However, increasing this distance increases the bulk of the microwave heating jig 10A or the canned food product attached to the jig, including the metal can container and the canned food product. Furthermore, increasing this distance excessively shortens the distance from the metal can container to the top surface of the microwave oven chamber, making it more likely for sparks to occur between them. Note that, in this case, this distance is approximately equal to the height of the base 11b.

[0042] The microwave oven heating jig 10A has a relative dielectric constant of 5 or less at 2.45 GHz and a dielectric loss tangent of 7.0×10 at 2.45 GHz. －３ It is preferable that the dielectric material is made of a material that satisfies the following conditions. Here, 2.45 GHz is the frequency of microwaves used in microwave ovens. The dielectric loss tangent is a value obtained by measuring at a temperature of 23±5°C and a humidity of 50±10% RH using the method specified in JIS K6911-1995.

[0043] This material preferably has a relative dielectric constant of 4.0 or less at 2.45 GHz. Although there is no lower limit to the relative dielectric constant of this material at 2.45 GHz, most materials suitable for microwave oven heating jig 10A have a relative dielectric constant of 2.0 or more at 2.45 GHz.

[0044] In addition, this material has a dielectric loss tangent of 6.0 × 10 at 2.45 GHz. －３ Preferably, it is 5.0 × 10 or less. －３ More preferably, it is 4.0 × 10 or less. －３ Although there is no lower limit to the dielectric loss tangent of this material at 2.45 GHz, many of the materials suitable for microwave oven heating jig 10A have a dielectric loss tangent of 1.0×10 at 2.45 GHz or less. －５ That's all.

[0045] Examples of materials having the above physical properties include specific cured resins. The cured resins are, for example, cured thermosetting resins or cured thermoplastic resins. When the material is a cured resin, the microwave heating jig 10A can be, for example, a molded product obtained by molding the entire jig as a single unit.

[0046] Examples of cured resins having the above physical properties include polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), polyamideimide (PAI), high impact polystyrene (HIPS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polycarbonate (PC), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polypropylene (PP), polytetrafluoroethylene (PTFE), and polyethylene (PE).

[0047] Among these, acrylonitrile-butadiene-styrene copolymer (ABS), polyamideimide (PAI), high impact polystyrene (HIPS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polycarbonate (PC), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polypropylene (PP), polytetrafluoroethylene (PTFE), and polyethylene (PE) are preferred.

[0048] Among these, acrylonitrile-butadiene-styrene copolymer (ABS), high impact polystyrene (HIPS), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polycarbonate (PC), polypropylene (PP), polytetrafluoroethylene (PTFE), and polyethylene (PE) are particularly preferred.

[0049] Figure 4 is a cross-sectional view of a jig-attached canned food product including the microwave heating jig shown in Figures 1 to 3. Figure 5 is a cross-sectional view of the jig-attached canned food product shown in Figure 4 with the microwave heating jig attached to a different position.

[0050] The jig-attached canned product 1A shown in Figs. 4 and 5 includes the microwave oven heating jig 10A and a canned product 20A.

[0051] The canned product 20A includes a metal can container 21 and an item 22 contained therein.

[0052] The metal can container 21 is a three-piece can in which the can bottom 21b and the can body 21a are integrated by double seaming, and the can lid 21c and the can body 21a are integrated by double seaming. The can lid 21c includes a disk-shaped can lid body 21c1 having a score such as a V-groove on its surface and a pull tab 21c2 attached to the disk-shaped can lid body 21c1. Pulling the pull tab 21c2 can cause the can lid body 21c1 to break along the score. The can lid 21c may also be a disk-shaped can lid body without a score such as a V-groove on its surface and without a pull tab.

[0053] The item 22 contains water. In this example, the item 22 is a food product containing a first food product 22a and a second food product 22b. At least one of the first food product 22a and the second food product 22b contains water. According to one example, the first food product 22a is a solid food product containing water, and the second food product 22b is a liquid food product such as a seasoning liquid. The item 22 containing such a first food product 22a and a second food product 22b is, for example, yakitori or corn soup. One of the first food product 22a and the second food product 22b may be omitted.

[0054] Here, S / V ( / cm) is defined by defining the area of ​​the opening in the can lid 21c of the metal can container 21 by opening the lid as S and the volume of the item 22 as V. The canned product 20A preferably has an S / V of 6 / cm or more, more preferably 15 / cm or more. Microwaves can be incident on the item 22 only through the opening in the can lid by opening the lid. Increasing the S / V enables more efficient heating. There is no upper limit to the S / V, but in one example, the S / V is 45 / cm or less.

[0055] The metallic can container 21 has a double seamed portion at its lower end as a large-diameter portion 21e1 and a double seamed portion at its upper end as a large-diameter portion 21e2. Each of the large-diameter portions 21e1 and 21e2 forms a circumferentially extending ridge-like protrusion on the outer peripheral surface of the metallic can container 21. The outer diameter of the large-diameter portion 21e2 at the upper end of the metallic can container 21 is larger than the outer diameter of the large-diameter portion 21e1 at the lower end. The large-diameter portion 21e1 at the lower end of the metallic can container 21 fits into the first fitting portion 11g1, and the large-diameter portion 21e2 at the upper end of the metallic can container 21 fits into the second fitting portion 11g2. The outer diameter of the large-diameter portion 21e2 at the upper end of the metallic can container 21 may be smaller than the outer diameter of the large-diameter portion 21e1 at the lower end.

[0056] In Fig. 4, the upper end of the metal can container 21 is inserted into the opening end of the microwave oven heating jig 10A so that the ridge-like convex portion formed on the outer peripheral surface of the metal can container 21 by the large diameter portion 21e2 is positioned in the second groove of the second fitting portion 11g2. In Fig. 5, the lower end of the metal can container 21 is inserted into the opening end of the microwave oven heating jig 10A so that the ridge-like convex portion formed on the outer peripheral surface of the metal can container 21 by the large diameter portion 21e1 is positioned in the first groove of the first fitting portion 11g1.

[0057] FIG. 6 is a perspective view showing an example of a microwave oven in which the microwave oven heating jig shown in FIGS. 1 to 3 can be used.

[0058] 6 is a so-called flat table type microwave oven that does not have a turntable. The microwave oven 100 includes a microwave oven body 110 and a door 120.

[0059] Microwave oven body 110 has a heating chamber surrounded by metal plates and open at the front. Of the surfaces of these metal plates, Fig. 3 illustrates an interior bottom surface W1 which is the surface of the bottom plate, an interior side surface W2 which is the surface of the left side panel, and an interior side surface W3 which is the surface of the rear side panel.

[0060] An opening is provided in the rear side panel. A waveguide is installed between this opening and the magnetron. A cover body 111 that covers the opening is attached to the rear side panel. The cover body 111 is made of, for example, mica, and allows microwaves to pass through.

[0061] The microwave heating jig 10A shown in Figures 1 and 2 may be used in a so-called turntable-type microwave oven having a turntable. Also, the microwave heating jig 10A shown in Figures 1 and 2 may be used in a microwave oven having an opening in the right or left side panel and configured to introduce microwaves into the heating chamber through this opening, in a microwave oven having an opening in the bottom panel and configured to introduce microwaves into the heating chamber through this opening, or in a microwave oven having an opening in the top panel and configured to introduce microwaves into the heating chamber through this opening.

[0062] FIG. 7 is a cross-sectional view showing the state in which an open canned product is placed on the bottom surface of the microwave oven via the microwave oven heating jig shown in FIGS.

[0063] Figure 7 shows one embodiment in which microwave heating jig 10A described with reference to Figures 1 to 3 is used to heat canned product 20A in microwave oven 100 described with reference to Figure 6. Figure 7 illustrates only bottom plate 112 of microwave oven 100, the upper surface of which is interior bottom surface W1. Canned product 20A shown in Figure 7 is obtained by removing the portion of can lid body 21c1 surrounded by the scores together with pull tab 21c2 from canned product 20A shown in Figures 4 and 5 by pulling pull tab 21c2, thereby converting can lid body 21c1 into can lid body 21c1' that is open in the center.

[0064] When heating the item 22 in the metal can container 21 in the microwave oven 100, first, as shown in Fig. 7, the microwave heating jig 10A is attached to the bottom end of the open canned product 20A. Specifically, the bottom end of the canned product 20A is inserted into the open end of the microwave heating jig 10A until the large diameter portion 21e1 at the bottom end of the metal can container 21 is fitted into the first groove provided on the inner surface of the first fitting portion 11g1. The canned product 20A may be opened after the microwave heating jig 10A is attached to the bottom end of the canned product 20A.

[0065] Next, canned product 20A with microwave heating jig 10A attached to its lower end is placed on interior bottom surface W1 of microwave oven 100 so that base 11b is positioned below canned product 20A. Canned product 20A is preferably placed approximately in the center of interior bottom surface W1.

[0066] In this way, the metal can container 21 is placed inside the microwave oven 100 at a wider distance from the interior bottom surface W1. Specifically, the metal can container 21 is placed inside the microwave oven at a wider distance by the height of the base 11b than when the canned product 20A is placed on the interior bottom surface W1 without the microwave oven heating jig 10A.

[0067] Thereafter, the door 120 of the microwave oven 100 is closed, and microwave irradiation is performed by the microwave oven 100. Since the lid of the canned product 20A is open, microwaves can be incident on the item 22. Therefore, the item 22 is heated.

[0068] In the above method, the microwave heating jig 10A is attached to the bottom end of the canned product 20A, thereby increasing the distance from the bottom surface W1 of the microwave oven 100 to the metallic can container 21. Increasing this distance reduces the gradient of the electric field therebetween, making it less likely that sparks will occur. Therefore, it is possible to prevent problems caused by the metal when heating the item 22 stored in the metallic can container 21 in the microwave oven 100.

[0069] Furthermore, microwave heating jig 10A can be used as an aid for removing heated canned products 20A from the oven. That is, when removing heated canned products 20A from the oven, microwave heating jig 10A attached to the bottom end of canned products 20A is manually carried outside the oven, whereby canned products 20A and microwave heating jig 10A can be removed from the oven without coming into contact with canned products 20A, which are at a higher temperature than microwave heating jig 10A.

[0070] Furthermore, in the above method, microwave heating jig 10A is attached to the lower end of canned product 20A, and then they are placed inside microwave oven 100. Because support portion 11 of microwave heating jig 10A is configured to fit into the lower end of canned product 20A, for example, when placing canned product 20A and microwave heating jig 10A inside the microwave oven or when removing them from the microwave oven, the canned product 20A is less likely to shift in position relative to microwave heating jig 10A. Therefore, for example, when removing canned product 20A and microwave heating jig 10A from the microwave oven, unintentional contact with canned product 20A or item 22 heated to a high temperature is less likely to occur. Furthermore, if microwave oven 100 has a turntable, the above-mentioned positional shift due to the rotation of the turntable is less likely to occur.

[0071] In the above-described method, when microwave oven heating jig 10A is attached to the bottom end of canned product 20A, the ridge-like protrusions formed on the outer surface of metal can container 21 by large-diameter portion 21e1 fit into the first groove formed on the inner surface of first fitting portion 11g1, thereby engaging microwave oven heating jig 10A with the bottom end of canned product 20A. Therefore, when placing canned product 20A with microwave oven heating jig 10A attached to its bottom end inside the microwave oven, for example, by carrying canned product 20A into the microwave oven with one hand, canned product 20A can be placed on microwave oven bottom surface W1 so that base 11b is positioned below canned product 20A. This engagement also makes it less likely that canned product 20A will shift position when removed from the microwave oven or when the turntable is rotated.

[0072] Furthermore, when the canned product 20A is unopened, attaching the microwave heating jig 10A to the top end of the canned product 20A as shown in Figure 4 can protect the top surface of the canned product 20A from dirt, etc. Also, when an opened canned product 20A is stored, attaching the microwave heating jig 10A to the top end of the canned product 20A can make it less likely for foreign matter to get into the item 22 contained in the metal can container 21 or for liquid components contained in the item 22 to evaporate, etc. Because the microwave heating jig 10A engages with the top end of the canned product 20A, it is less likely to unintentionally fall off the canned product 20A.

[0073] Furthermore, when the microwave oven heating jig 10A is made of a material having the above-mentioned relative permittivity and dielectric loss tangent, it further exhibits the effects described below.

[0074] As described above, when a container body made of a composite sheet containing a resin sheet and a metal foil formed into a cup shape is placed in a paper box and the contents of the container body are heated in a microwave oven in this state, sparks are unlikely to occur. However, the inventors have found that when a metal can is used instead of the above-mentioned container body, although sparks are unlikely to occur, the paper may become scorched.

[0075] The inventors of the present invention believe that one of the causes of this scorching is the moisture contained in the paper. That is, because paper contains moisture, the temperature of the paper rises rapidly when irradiated with microwaves. The inventors of the present invention believe that this makes the paper more susceptible to scorching.

[0076] Therefore, the inventors investigated the effect of the moisture content of paper on the occurrence of scorching, and surprisingly found that the moisture content of paper does not affect the occurrence of scorching.

[0077] The inventors of the present invention further investigated the possibility that the main cause of scorching lies elsewhere. Specifically, they hypothesized that microwaves act on components such as cellulose contained in paper, or on their functional groups or bonds, causing scorching on paper containers. Based on this hypothesis, they investigated whether or not various materials would scorch when irradiated with microwaves. They found that all materials whose temperature did not rise excessively when irradiated with microwaves possessed the above-mentioned physical properties.

[0078] Furthermore, by increasing the distance from the interior bottom surface W1 to the metallic can container 21, the gradient of the electric field therebetween can be reduced, as described above, making it less likely that sparks will occur. Increasing this distance also reduces the confinement of microwaves in the area between the interior bottom surface W1 and the bottom surface of the metallic can container 21, which is caused by microwave reflection by these two surfaces, and also prevents excessive irradiation of microwaves to the microwave oven heating jig 10A.

[0079] Therefore, when heating an item 22 contained in a metal can container 21 in a microwave oven 100, by using a microwave heating jig 10A made of a material having the above-mentioned physical properties and increasing the distance from the bottom surface W1 of the oven interior to the metal can container 21, it is possible to prevent sparks from occurring and the jig from burning or melting.

[0080] Various modifications are possible to the microwave heating jig and the canned product attached to the jig. Fig. 8 is a perspective view of a microwave heating jig according to a modification of the first embodiment. The microwave heating jig 10B shown in Fig. 8 is the same as the microwave heating jig 10A described with reference to Figs. 1 to 3, etc., except for the following points.

[0081] That is, compared to microwave heating jig 10A, microwave heating jig 10B has a larger height dimension of first fitting portion 11g1 and a larger width of the first groove provided on the inner surface of first fitting portion 11g1. Also, microwave heating jig 10B has a support portion 11 that includes second fitting portion 11g2 and intermediate portion 11m instead of expanded diameter portion 11e.

[0082] The intermediate portion 11m is a portion located between the first fitting portion 11g1 and the second fitting portion 11g2. The intermediate portion 11m has a cylindrical shape with a constant inner diameter in the height direction. The inner diameter of the intermediate portion 11m is slightly smaller than the inner diameter of the first fitting portion 11g1 at the bottom surface of the first groove. The intermediate portion 11m may have a cylindrical shape with a diameter that increases toward the open end of the microwave oven heating jig 10B. In this case, the inner diameter of the intermediate portion 11m on the first fitting portion 11g1 side and the inner diameter on the second fitting portion 11g2 side are smaller than the inner diameter of the first fitting portion 11g1 at the bottom surface of the first groove and the inner diameter of the second fitting portion 11g2 at the bottom surface of the second groove, respectively.

[0083] The second fitting portion 11g2 has a generally cylindrical shape. A second groove extending in the circumferential direction is provided on the inner surface of the second fitting portion 11g2. The inner diameter of the second fitting portion 11g2 at the position of the bottom surface of the second groove is larger than the inner diameter of the intermediate portion 11m.

[0084] Fig. 9 is a cross-sectional view of a jig-attached canned product including the microwave heating jig shown in Fig. 8. Fig. 10 is a cross-sectional view showing the jig-attached canned product shown in Fig. 9 with the microwave heating jig attached to a different position.

[0085] Jig-attached canned product 1B shown in Figures 9 and 10 is similar to jig-attached canned product 1A described with reference to Figures 4 and 5, respectively, except for the following point: Jig-attached canned product 1B includes microwave heating jig 10B and canned product 20B instead of microwave heating jig 10A and canned product 20A.

[0086] The canned product 20B is similar to the canned product 20A described with reference to Figures 4 and 5, except for the following points. Specifically, the metal can container 21 included in the canned product 20B is a two-piece can in which the can bottom 21b and the can body 21a are integrally molded. The can body 21a has an expanded diameter portion near its lower end. This metal can container 21 has the expanded diameter portion near the lower end of the can body 21a as a large diameter portion 21e1, and a double-seamed portion at the upper end as a large diameter portion 21e2. The metal can container 21 has different shapes at its upper and lower ends.

[0087] As shown in Fig. 9, when the microwave heating jig 10B is attached to the upper end of the canned product 20B, the ridge-like protrusions formed on the outer surface of the metal can container 21 by the large diameter portion 21e2 are fitted into the second groove formed on the inner surface of the second fitting portion 11g2, thereby locking the microwave heating jig 10B to the upper end of the canned product 20B. Also, as shown in Fig. 10, when the microwave heating jig 10B is attached to the lower end of the canned product 20B, the ridge-like protrusions formed on the outer surface of the metal can container 21 by the large diameter portion 21e1 are positioned below the middle portion 11m, thereby locking the microwave heating jig 10B to the lower end of the canned product 20B. This modified example also provides the same effects as the above embodiment.

[0088] Second Embodiment The second embodiment provides a technique useful for attaching a microwave heating jig to a canned product and distributing the canned product in the form of a jig-attached canned product. The following description of the second embodiment will focus mainly on the differences from the first embodiment.

[0089] Fig. 11 is a perspective view of a microwave heating jig according to a second embodiment of the present invention. Fig. 12 is another perspective view of the microwave heating jig shown in Fig. 11. Fig. 13 is a cross-sectional view taken along line XIII-XIII of the microwave heating jig shown in Fig. 11.

[0090] 11 to 13 is similar to microwave heating jig 10A or 10B except for the following points: In microwave heating jig 10C, support part 11 has a generally cylindrical shape whose diameter increases from one opening to the other, and includes lower part 11b, upper part 11t, and middle part 11m.

[0091] The lower portion 11b has a cylindrical shape whose diameter increases toward the top. Here, the lower portion 11b has a cylindrical shape whose diameter increases toward the top. The lower portion 11b may have a cylindrical shape whose inner diameter is constant in the height direction, for example, a cylindrical shape whose inner diameter is constant in the height direction.

[0092] The upper portion 11t has a cylindrical shape whose diameter increases upward. Here, the upper portion 11t has a cylindrical shape whose diameter increases upward. The upper portion 11t may have a cylindrical shape whose inner diameter is constant in the height direction, for example, a cylindrical shape whose inner diameter is constant in the height direction.

[0093] The inner surface of the upper portion 11t is provided with a plurality of protrusions 11p each extending in the circumferential direction. These protrusions 11p are arranged at a distance from each other in the longitudinal direction. Instead of providing a plurality of protrusions 11p on the inner surface of the upper portion 11t, a single protrusion extending in the circumferential direction may be provided around the entire circumference.

[0094] The upper portion 11t has a larger inner diameter at its lower end than the inner diameter at the upper end of the lower portion 11b. The upper portion 11t is positioned such that its lower end surrounds the upper end of the lower portion 11b.

[0095] The intermediate portion 11m connects the upper end of the lower portion 11b and the lower end of the upper portion 11t. The intermediate portion 11m has an annular upper surface, which is annular in this example.

[0096] Like microwave heating jigs 10A and 10B, microwave heating jig 10C can be combined with a canned product and distributed as a jig-attached canned product. According to one example, the jig-attached canned product is one in which the upper end of the canned product is inserted into the open end of microwave heating jig 10C. The upper surface of middle portion 11m can form at least a part of the contact surface against which the upper end of the canned product abuts when the upper end of the canned product is inserted into the open end of microwave heating jig 10C.

[0097] The edge of reinforcing portion 12 is continuous with the lower end of support portion 11. When microwave heating jig 10C is attached to the upper end of a canned product as described below, the lower surface of reinforcing portion 12 can be used as a display surface for displaying images, text, etc. using a printed layer or label.

[0098] Microwave oven heating jig 10C has four recesses R, each recessed toward the inside of microwave oven heating jig 10C, at the position of ridge line 13 connecting support part 11 and reinforcing part 12. As will be described later, recesses R serve to increase the strength of microwave oven heating jig 10C.

[0099] The recesses R respectively form protrusions P on the inner surface of the microwave oven heating jig 10C. Here, the protrusions P have upper surfaces that are equal in height to the upper surface of the intermediate portion 11m. In this case, the upper surfaces of the protrusions P can form another part of the contact surface described above.

[0100] Recesses R may be omitted if the upper surface of middle portion 11m of microwave heating jig 10C can support the canned product when the canned product is inserted into the open end of microwave heating jig 10C. The number of recesses R may be changed to any number greater than or equal to 1, and is preferably in the range of 1 to 17, and more preferably in the range of 2 to 12.

[0101] In addition, in the microwave heating jig 10C, the height of the middle portion 11m or the upper surface of the convex portion P relative to the lower surface of the reinforcing portion 12 is approximately equal to the distance created by the microwave heating jig 10C between the metal can container and the bottom surface of the microwave oven interior.

[0102] The microwave heating jig 10C preferably has one or more through holes in its wall. The through holes provided in the wall of the microwave heating jig 10C allow ventilation between the internal and external spaces of the microwave heating jig 10C when the microwave heating jig 10C is attached to the canned goods and when the microwave heating jig 10C is detached from the canned goods, thereby reducing the pressure difference between these spaces. Therefore, by providing one or more through holes in the wall of the microwave heating jig 10C, it becomes easier to attach the microwave heating jig 10C to the canned goods and to detach the microwave heating jig 10C from the canned goods.

[0103] FIG. 14 is a cross-sectional view of a canned food product with a jig attached, including the microwave oven heating jig shown in FIGS.

[0104] The jig-attached canned product 1C shown in Figure 14 includes the microwave heating jig 10C and the canned product 20A. The canned product 20A and the microwave heating jig 10C are arranged side by side in the height direction of the canned product 20A. Specifically, the microwave heating jig 10C has an overall cylindrical shape and is attached to the upper end of the canned product 20A. It is preferable that the microwave heating jig 10C fits onto the upper end of the canned product 20A to form a fitted body together with the canned product 20A.

[0105] The can body 21a of the metal can container 21 has double-seamed portions at its upper and lower ends as enlarged diameter portions. In Fig. 14, the outer diameter of the metal can container 21 at the double-seamed portion at the upper end is larger than the outer diameter of the double-seamed portion at the lower end. In this case, as shown in Fig. 14, if the upper end of the canned product 20A can be inserted into the opening end of the microwave heating jig 10C, the lower end of the canned product 20A can also be inserted into the opening end of the microwave heating jig 10C.

[0106] 14, the outer diameter of the double-seamed portion at the top end of the metallic can container 21 is larger than the diameter of the circle inscribed in the protrusion 11p provided on the inner surface of the upper part 11t of the microwave oven heating jig 10C. The protrusion 11p is located below the double-seamed portion at the top end of the metallic can container 21. This allows the microwave oven heating jig 10C to be fastened to the top end of the metallic can container 21.

[0107] In the jig-attached canned products 1C, the inner diameter of the lower end of the metal can container 21, i.e., the inner diameter of the double-seamed portion at the lower end, is preferably larger than the outer diameter of the end of the microwave heating jig 10C facing the reinforcement portion 12. When such jig-attached canned products 1C are stacked vertically, the end of the microwave heating jig 10C facing the reinforcement portion 12 of the lower jig-attached canned products 1C can be located within the area surrounded by the double-seamed portion at the lower end of the metal can container 21 of the upper jig-attached canned products 1C. In other words, when the jig-attached canned products 1C are stacked, an overlapping portion may occur between them. This stabilizes the stacked state of the jig-attached canned products 1C.

[0108] In the jig-attached canned product 1C, the height Ht of the jig-attached canned product 1C and the height Hk of the canned product 20A satisfy the relationship shown in the following inequality (1): 0.9×(n+1)×Hk≦n×Ht≦1.1×(n+1)×Hk (where n represents an integer in the range of 2 to 5).

[0109] The technical meaning of this inequality (1) is explained below. Existing canned products that do not come with microwave heating tools are produced by manufacturers, packaged in packing boxes such as cardboard boxes, transported by truck or ship, stored in a logistics warehouse, and then unpacked and displayed on display shelves at retail stores. In this distribution format, canned products are packed in packing boxes in a stacked state without leaving excessive gaps in the vertical direction of the packing box to prevent damage during transportation. Furthermore, canned products are arranged on display shelves in a stacked state without leaving excessive space in the vertical direction of the display shelf, taking into account shelf storage efficiency, while leaving appropriate gaps in the vertical direction of the display shelf to allow customers to remove canned products from the display shelf. In this way, the relationship between the overall height of the stacked canned products and the height of the packing box, and the relationship between the overall height of the stacked canned products and the height of the display shelf, are generally optimized.

[0110] When considering that jig-attached canned products 1C are distributed stacked in two to five layers using existing packaging boxes and existing display shelves used for existing canned products, it is desirable that the total height THt of n stacked jig-attached canned products 1C (n is an integer ranging from 2 to 5) be approximately equal to the total height THk of (n+1) stacked canned products 20A. This relationship can be expressed as the above inequality (1).

[0111] The above inequality (1) indicates that the total height THt of the jig-attached canned products 1C when jig-attached canned products 1C with a height Ht are stacked in n layers (n is an integer between 2 and 5) is within the range of ±10% of the total height THk of the canned products 20A when canned products 20A with a height Hk are stacked in (n+1) layers. The total height THk of the canned products 20A can be expressed by equation (1a): (n+1) × Hk. Furthermore, the total height THt of the jig-attached canned products 1C can be expressed by equation (1b): n × Ht. As mentioned above, when jig-attached canned products 1C are stacked, there may be overlaps between them. However, equation (1b) does not take such overlaps into account. Similarly, when canned products 20A are stacked, there may be overlaps between them. However, equation (1a) does not take such overlaps into account.

[0112] Here, if the total height THt of the jig-attached canned products 1C is excessively greater than the total height THk of the canned products 20A, it will be impossible to store n jig-attached canned products 1C in a stacked state in an existing packaging box designed to pack (n+1) canned products 20A in a stacked state. Also, if the total height THt of the jig-attached canned products 1C is excessively greater than the total height THk of the jig-attached canned products 1C, it will be impossible to display n jig-attached canned products 1C in a stacked state on an existing display shelf designed to display (n+1) canned products in a stacked state, or even if it is possible to display n jig-attached canned products 1C in a stacked state on an existing display shelf, it will be difficult for customers to remove the jig-attached canned products 1C from the display shelf.

[0113] Alternatively, if the total height THt of the jig-attached canned products 1C is excessively smaller than the total height THk of the canned products 20A, when n jig-attached canned products 1C are stored in a stacked state in an existing packaging box for packing (n+1) canned products in a stacked state, excessive gaps will be created in the vertical direction, resulting in problems such as reduced transport efficiency and susceptibility to shocks due to vibrations during transport. Also, if the total height THt of the jig-attached canned products 1C is excessively smaller than the total height THk of the canned products 20A, when n jig-attached canned products 1C are stacked and arranged on an existing display shelf for displaying (n+1) canned products in a stacked state, excess space will be created in the vertical direction, resulting in reduced storage efficiency on the display shelf.

[0114] From the above, if the height Ht of jig-attached canned product 1C and the height Hk of canned product 20A satisfy the relationship shown in inequality (1) above, the height of jig-attached canned product 1C is adjusted so that it can be efficiently stored in an existing packing box or efficiently displayed on an existing display shelf, and it can be used without modifying the height of the existing packing box or the height of the existing display shelf. In other words, if the height Ht of jig-attached canned product 1C and the height Hk of canned product 20A satisfy the relationship shown in inequality (1) above, it can be said that the height of jig-attached canned product 1C is compatible with the height of the existing packing box or the height of the existing display shelf.

[0115] The above-mentioned effect is exhibited when multiple jig-attached canned products 1C are stacked vertically for distribution. Therefore, in the jig-attached canned products 1C, it is preferable that the number of microwave heating jigs 10C and the number of canned products 20A match.

[0116] Furthermore, when jig-attached canned product 1C is distributed, if microwave heating jig 10C is attached to the upper end of canned product 20A, it is possible to prevent the upper surface of can lid 21c, i.e., the opening of the canned product, from becoming soiled, as shown in Figure 14. In this case, when canned product 20A is heated in a microwave oven, microwave heating jig 10C must be reattached to the can bottom 21b side of canned product 20A, as will be described later.

[0117] In the jig-attached canned product 1C, the height Ht of the jig-attached canned product 1C and the height Hk of the canned products 20A preferably satisfy the relationship shown in the following inequality (2): 0.95×(n+1)×Hk≦n×Ht≦1.05×(n+1)×Hk (where n is an integer ranging from 2 to 5). Inequality (2) indicates that the total height THt of the jig-attached canned products 1C when jig-attached canned products 1C with a height Ht are stacked in n layers (n is an integer ranging from 2 to 5) is within the range of ±5% of the total height THk of the canned products 20A when canned products 20A with a height Hk are stacked in (n+1) layers.

[0118] In each of inequalities (1) and (2), n is preferably an integer in the range of 2 to 4, and more preferably 3 or 4.

[0119] The height Hk of the canned products 20A is, for example, in the range of 26 to 124 mm, and preferably in the range of 26 to 52 mm. The height of the microwave oven heating jig 10C is, for example, in the range of 4 to 83 mm, and preferably in the range of 6 to 43 mm.

[0120] Figure 15 shows an example of a stack of two jig-attached canned products 1C having the structure shown in Figure 14. Figure 15 is a front view showing a stack structure formed by stacking the canned products included in the jig-attached canned product shown in Figure 14 in the height direction, and a stack structure formed by stacking the jig-attached canned products shown in Figure 14 in the height direction. Figure 15 shows that the total height THt of the jig-attached canned products 1C shown in Figure 14 when stacked in two layers, i.e., the height of a stack CB made up of two jig-attached canned products 1C, is approximately the same as the total height THk of the canned products 20A included in the jig-attached canned product 1C when stacked in three layers, i.e., the height of a stack CA made up of three canned products 20A.

[0121] In the stack CA, the lower end of the metal can container 21 constituting the upper canned product 20A is located within the area surrounded by the double-seamed portion of the upper end of the metal can container 21 constituting the lower canned product 20A. That is, when the canned products 20A included in the jig-attached canned product 1C shown in FIG. 14 are stacked, overlapping portions occur between the canned products 20A, and the total height THk of the canned products 20A is slightly smaller than the value calculated by formula (1a): (n+1)×Hk. Specifically, if the height of the overlapping portion between the canned products 20A is represented by dH1, the total height THk of the canned products 20A is expressed by formula (3a): (n+1)×Hk−n×dH1. dH1 is, for example, within the range of 2 to 6 mm.

[0122] Furthermore, in the stack CB, the end of the microwave heating jig 10C of the lower jig-attached canned product 1C on the side of the reinforcement portion 12 is located within the area surrounded by the double-seamed portion of the lower end of the metal can container 21 of the upper jig-attached canned product 1C. That is, when the jig-attached canned products 1C shown in FIG. 14 are stacked, overlapping portions occur between the jig-attached canned products 1C, and the total height THt of the jig-attached canned products 1C is slightly smaller than the value calculated by equation (1b): n × Ht. Specifically, if the height of the overlapping portion between the jig-attached canned products 1C is represented by dH2, the total height THt of the jig-attached canned products 1C is expressed by equation (3b): n × Ht - (n - 1) × dH2. dH2 is, for example, within the range of 2 to 6 mm.

[0123] In this case, ideally, the height Ht of the jig-attached canned product 1C and the height Hk of the canned product 20A will satisfy the relationship shown in the following inequality (3): 0.9×{(n+1)×Hk-n×dH1}≦n×Ht-(n-1)×dH2≦1.1×{(n+1)×Hk-n×dH1} (where n represents an integer ranging from 2 to 5).

[0124] However, in equation (3a): (n+1)×Hk-n×dH1, n is small and dH1 is small, so the second term of equation (3a) (i.e., n×dH1) is sufficiently small relative to the first term of equation (3a) (i.e., (n+1)×Hk). Also, in equation (3b): n×Ht-(n-1)×dH2, n is small and dH2 is small, so the second term of equation (3b) (i.e., (n-1)×dH2) is sufficiently small relative to the first term of equation (3b) (i.e., n×Ht). Furthermore, the second term of equation (3a) and the second term of equation (3b) are not significantly different. For these reasons, the second term of equation (3a) and the second term of equation (3b) can be ignored in the above inequality (3). In other words, there is no need to take into consideration the case where overlapping portions exist between jig-attached canned products 1C when stacked, or the case where overlapping portions exist between canned products 20A when stacked.

[0125] FIG. 16 is a cross-sectional view showing the state in which an open canned product is placed on the bottom surface of the microwave oven via the microwave oven heating jig shown in FIGS.

[0126] In Figure 16, the outer diameter of the metal can container 21 at the double-seamed portion at the top end is larger than the outer diameter at the double-seamed portion at the bottom end. Therefore, the top end of the canned product 20A fits into the open end of the microwave heating jig 10C, while the bottom end of the canned product 20A is inserted into the open end of the microwave heating jig 10C without fitting. The portion of the upper part 11t sandwiched between the protruding portion 11p and the middle portion 11m corresponds to the second fitting portion 11g2 in the first embodiment. Therefore, by modifying the structure of the upper part 11t to further include the first fitting portion 11g1 described above in the first embodiment, the microwave heating jig 10C can be fitted into both the top end of the canned product 20A and the bottom end of the canned product 20A. This microwave heating jig 10C achieves the effects described above for the microwave heating jigs 10A and 10B.

[0127] The microwave heating jig 10C also has a recess R on the ridge 13. The microwave heating jig 10C having this structure further provides the following advantages. Specifically, jig-attached canned products 1C are typically transported in multiple stacked rows, arranged lengthwise and widthwise. For example, a packaged product in which multiple jig-attached canned products 1C are arranged lengthwise and widthwise and stacked in multiple layers is transported in a box. Alternatively, a packaged product in which multiple jig-attached canned products 1C are arranged lengthwise and widthwise and stacked in multiple layers on a pallet and integrated with a film or sheet is transported. The microwave heating jig 10C may be subjected to a large force in its vertical direction due to vibrations and other factors during transport of the packaged product. The recess R reduces the risk of damage to the microwave heating jig 10C caused by such force.

[0128] As described above, a plurality of jig-attached canned products 1C can be packed or wrapped in a packaging material to form a package. Specifically, the package includes a plurality of jig-attached canned products 1C stacked vertically and a packaging material that contains or holds the plurality of jig-attached canned products 1C together. In the package, for example, two to five jig-attached canned products 1C are stacked. Examples of the packaging material include a box, film, or sheet.

[0129] The jig-attached canned products 1C described above are typically transported in a state in which multiple products are arranged lengthwise and widthwise and stacked in multiple layers. Therefore, an example of a packaged product is a packaged product in which multiple jig-attached canned products 1C are arranged lengthwise and widthwise and stacked in multiple layers inside a box. Another example is a packaged product in which multiple jig-attached canned products 1C are arranged lengthwise and widthwise and stacked in multiple layers on a pallet, and these are integrated with a film or sheet.

[0130] Furthermore, the jig-attached canned products 1C described above are sold in a state where, for example, multiple products are stacked vertically and integrated with a film or sheet. Therefore, yet another example of a packaged article is a packaged article in which multiple jig-attached canned products 1C are stacked vertically and integrated with a film or sheet.

[0131] As described above, the jig-attached canned products 1C included in the package satisfy the relationship shown in inequality (1) above, where the height Ht of the jig-attached canned products 1C and the height Hk of the canned products 20A. That is, the total height THt of n stacked jig-attached canned products 1C (n is an integer ranging from 2 to 5) is within the range of the total height THk of the (n+1) stacked canned products 20A ±10%. Therefore, the package can achieve the same effects as those described above for the jig-attached canned products 1C.

[0132] As explained above, it is preferable that the inner diameter of the lower end of the jig-attached canned product 1C included in the packaged product be larger than the outer diameter of the end of the jig 10C near the reinforcement 12, i.e., the inner diameter of the double-seamed portion at the lower end. When such jig-attached canned products 1C are stacked vertically to form a packaged product, the jig-attached canned products 1C have the end of the lower jig 10C near the reinforcement 12 within the area surrounded by the double-seamed portion at the lower end of the metal can container 21 of the upper jig-attached canned product 1C, as shown in stack CB in Figure 15. In this case, the stacked state of the jig-attached canned products 1C is stabilized, facilitating the packing and wrapping operations for producing the packaged product, and the packed state can be maintained during distribution even when packed in a box. In this case, if the jig-attached canned products 1C are removed from the packaging material in a stacked state, the plurality of jig-attached canned products 1C can be handled as a single assembly.

[0133] The microwave heating jig 10C described above can also be distributed as a kit for jig-attached canned products in combination with metal can containers 21 that do not contain an item 22. In order to achieve the same effects as those described above for the jig-attached canned products 1C in the kit for jig-attached canned products, it is preferable that the number of microwave heating jigs 10C and the number of metal can containers 21 match.

[0134] This kit includes the metal can container 21 described above and the microwave heating jig 10C described above. In this kit, the metal can container 21 does not contain an item 22. A manufacturer of items to be contained in metal can containers can obtain this kit, fill the container body of the metal can container 21 with the item 22, seal it with a lid, produce a canned product 20A, and then arrange the resulting canned product 20A and the microwave heating jig 10C so that they are aligned in the height direction, thereby producing a jig-attached canned product 1C.

[0135] Third Embodiment The third embodiment provides a form of technology that is useful for facilitating the handling of canned products equipped with a microwave heating jig. The following description of the third embodiment will focus mainly on the differences from the second embodiment.

[0136] Fig. 17 is a perspective view of a microwave oven heating jig according to a third embodiment of the present invention. Fig. 18 is another perspective view of the microwave oven heating jig shown in Fig. 17. Fig. 19 is a cross-sectional view taken along line XIX-XIX of the microwave oven heating jig shown in Fig. 17.

[0137] The microwave heating jig 10D shown in Figures 17 to 19 is similar to the microwave heating jig 10C except for the following points: the height of the lower part 11b of the microwave heating jig 10D is smaller than that of the microwave heating jig 10C, and the microwave heating jig 10D further includes a removal assisting part 14x.

[0138] The removal assisting portion 14x is a portion that assists in removing a metal can container containing an item heated in a microwave oven from the inside of the microwave oven without contacting the metal can container or the support portion 11. The removal assisting portion 14x includes two or more protrusions that each protrude in a direction away from the support portion 11 and the metal can container when the lower portion 11b of the support portion 11 is placed between the metal can container and the bottom surface of the microwave oven. In this example, the removal assisting portion 14x includes two protrusions.

[0139] The two protrusions serving as removal assisting portions 14x are positioned so that the line connecting their centers passes through the center of the open end of microwave heating jig 10D. When a jig-attached canned product, with its lower end inserted into the open end of microwave heating jig 10D, is heated in a microwave oven and then removed from the oven, removal assisting portions 14x allow the user to grasp the two protrusions with the fingers of their right and left hands, respectively, and transport the jig-attached canned product outside the oven. For this reason, removal assisting portions 14x preferably have a shape and dimensions suitable for being grasped by the user's fingers. Here, removal assisting portions 14x have a crescent shape. Alternatively, the protrusions may have openings or recesses on their undersides, allowing the user to insert their fingers into the openings or recesses.

[0140] The removal assisting portion 14x may be made of the same material as the material constituting the support portion 11 and the reinforcing portion 12, or may be made of a different material. Furthermore, the removal assisting portion 14x may be molded integrally with the support portion 11 and the reinforcing portion 12, or may be molded separately from the support portion 11 and the reinforcing portion 12. The removal assisting portion 14x is preferably made of a material with low thermal conductivity, and more preferably, the entire microwave heating jig 10D, including the removal assisting portion 14x, is made of a material with low thermal conductivity. The thermal conductivity of such a material is preferably 0.5 W / m·K or less.

[0141] Figure 20 is a cross-sectional view of a canned product with a jig attached, including the microwave heating jig shown in Figures 17 to 19. Figure 21 is a cross-sectional view showing an open canned product placed on the bottom of a microwave oven via the microwave heating jig shown in Figures 17 to 19.

[0142] The jig-attached canned product 1D shown in Figures 20 and 21 includes the microwave heating jig 10D and the canned product 20A. In the jig-attached canned product 1D, the lower end of the metal can 21 is inserted into the open end of the microwave heating jig 10D so that the ridge-like protrusions formed on the outer surface of the metal can 21 by the large-diameter portion 21e1 are positioned below the protrusions 11P. This allows the microwave heating jig 10D to be engaged with the metal can 21. The portion of the upper portion 11t positioned below the protrusions 11P is a mating portion 11g that mates with the large-diameter portion 21e1. The mating portion 11g corresponds to the first mating portion 11g1 described in the first embodiment.

[0143] 20 and 21 , the outer diameter of the metal can container 21 at the double-seamed portion at the top end is larger than the outer diameter at the double-seamed portion at the bottom end. Therefore, while the bottom end of the canned product 20A fits into the open end of the microwave heating jig 10D, the top end of the canned product 20A may not fit into or may not be inserted into the open end of the microwave heating jig 10C. By modifying the structure of the upper part 11t to further include the second fitting portion 11g2 described above in the second embodiment, the microwave heating jig 10D can fit into both the bottom end and the top end of the canned product 20A. This microwave heating jig 10D achieves the same effects as those of the microwave heating jigs 10A and 10B.

[0144] Furthermore, microwave heating jig 10D has the following advantages. When jig-attached canned product 1D is heated in a microwave oven, metal can container 21, which is opaque to microwaves, reaches a higher temperature than a resin or glass container, which is transparent to microwaves. Furthermore, microwaves reflected from the side of metal can container 21 reach interior bottom surface W1 of microwave oven 100 in which jig-attached canned product 1D is placed, causing the interior bottom surface W1, excluding the area directly below jig-attached canned product 1D, to also reach a higher temperature.

[0145] When using a microwave heating jig that does not include the removal assisting portion 14x, a user must grasp the support portion 11 to remove the heated canned product from the microwave oven. Because the grippable portion of the support portion 11 is not large, the user's fingers may come into contact with the metal can container 21 and the interior bottom surface W1, which are at a higher temperature than in conventional use environments. Furthermore, because the grippable portion of the support portion 11 is not large, the canned product is easily dropped. Furthermore, when the canned product is heated in the microwave oven 100, the lid of the canned product 20A is in an open state. Therefore, when removing the canned product heated in the microwave oven 100, the metal can container 21 must be held horizontally to prevent the items 22 contained therein from spilling. When using a microwave heating tool that does not include the removal assistance portion 14x, as described above, the portion of the support portion 11 that can be grasped is not large, making it difficult to remove the canned product 20A horizontally, and the canned product 20A is likely to tilt, which makes it easy for the item 22 to spill.

[0146] In contrast, by using the microwave heating jig 10D equipped with the removal assisting portion 14x, the possibility of the user touching the hot metal can container 21 when removing the jig-attached canned product 1D heated in the microwave oven 100 can be reduced. This allows the user to remove the metal can container 21 containing the item 22 heated in the microwave oven 100 with bare hands without feeling the heat. Furthermore, by using the removal assisting portion 14x, the user can more securely hold the jig-attached canned product 1D after heating. Therefore, using the microwave heating jig 10D makes it less likely that the jig-attached canned product 1D will be dropped. Furthermore, using the microwave heating jig 10D makes it easier to remove the jig-attached canned product 1D horizontally. The microwave heating jig 10D equipped with the removal assisting portion 14x can more effectively prevent metal-related problems when heating the item 22 contained in the metal can container 21 in the microwave oven 100.

[0147] Furthermore, the microwave oven heating jig 10D has a recess R on the ridge line 13. Therefore, the microwave oven heating jig 10D has the same effects as those of the microwave oven heating jig 10C.

[0148] The microwave oven heating jig 10D and jig-attached canned product 1D described above preferably have the structure described below.

[0149] FIG. 22 is a top view showing an example of a packaged product containing multiple jig-attached canned products 1D. As described above, jig-attached canned products 1D are typically transported in a multi-tiered arrangement, with multiple products arranged lengthwise and widthwise. For example, a packaged product containing multiple jig-attached canned products 1D arranged lengthwise and widthwise and stacked in multiple tiers is transported in a box. Alternatively, a packaged product containing multiple jig-attached canned products 1D arranged lengthwise and widthwise and stacked in multiple tiers on a pallet and integrated with a film or sheet is transported. In a packaged product containing jig-attached canned products 1D in this manner, if the removal assisting portion 14x is excessively large, the removal assisting portion 14x of the microwave heating jig 10D for a certain jig-attached canned product 1D will interfere with the removal assisting portion 14x of the microwave heating jig 10D for the jig-attached canned product 1D adjacent thereto in the vertical, horizontal, or diagonal direction.

[0150] In the packaged article shown in Figure 22, square S indicates the smallest square circumscribing the orthogonal projection of removal assisting portion 14x onto a plane perpendicular to the height direction of jig-attached canned product 1D. Here, this square S coincides with the smallest square circumscribing the orthogonal projection of metal can container 21 (canned product 20A) onto said plane. Also, here, the orthogonal projection onto said plane of the portion of microwave heating jig 10D excluding removal assisting portion 14x approximately coincides with the orthogonal projection onto said plane of metal can container 21.

[0151] In this way, it is preferable that the smallest square S circumscribing the orthogonal projection of removal assisting portion 14x onto a plane perpendicular to the height direction of jig-attached canned product 1D has the same dimensions as or is smaller than the smallest square circumscribing the orthogonal projection of metal can container 21 (canned product 20A) onto the same plane, since this prevents interference between removal assisting portions 14x as described above. Also, it is preferable that the smallest square circumscribing the orthogonal projection of removal assisting portion 14x onto a plane perpendicular to the height direction of microwave oven heating jig 10D has the same dimensions as or is smaller than the smallest square circumscribing the orthogonal projection of the portion of microwave oven heating jig 10D excluding removal assisting portion 14x onto the same plane.

[0152] The dimensions of the protrusion included in the removal assisting portion 14x are preferably, for example, as follows. That is, in FIG. 22 , the distance between the first end A and the second end B, which are the two ends of the protrusion of the removal assisting portion 14x on the upper portion 11t side, is defined as width Lx1. Furthermore, the distance from the point on the contour of the protrusion of the removal assisting portion 14x that is located farthest from the upper portion 11t to the upper portion 11t is defined as protrusion length Lx2. Note that, here, protrusion length Lx2 is the distance from intersection point C to intersection point D, where a line passing through the midpoint between the first end A and the second end B and perpendicular to the line segment connecting the first end A and the second end B intersects with the contour of the protrusion on the upper portion 11t side and on the opposite side, respectively. When the width Lx1 and the protruding length Lx2 are defined in this manner, from the viewpoint of ease of gripping the removal assisting portion 14x and suppressing the interference of the removal assisting portion 14x, the width Lx1 is preferably in the range of 0.5 cm or more and Ls × √2 / 2 cm or less, and the protruding length Lx2 is preferably in the range of 0.5 cm or more and Ls × (√2-1) / 2 cm or less, where Ls means the length (cm) of one side of the square S.

[0153] From the viewpoint of ease of gripping the removal assisting portion 14x, it is more preferable that the width Lx1 be in the range of 0.5 cm or more and Ls × √2 / 2 cm or less, and the protruding length Lx2 be in the range of 1 cm or more and Ls × (√2-1) / 2 cm or less. In this case, the width Lx1 is, for example, in the range of 0.5 cm or more and 8 cm or less, and in another example, in the range of 0.5 cm or more and 7 cm or less. The protruding length Lx2 is, for example, in the range of 1 cm or more and 3 cm or less, and in another example, in the range of 1 cm or more and 2 cm or less.

[0154] Alternatively, from the viewpoint of ease of gripping the removal assisting portion 14x, it is more preferable that the width Lx1 is in the range of 1 cm or more and Ls × √2 / 2 cm or less, and the protruding length Lx2 is in the range of 0.5 cm or more and Ls × (√2-1) / 2 cm or less. In this case, the width Lx1 is in the range of 1 cm or more and 8 cm or less, and in another example, in the range of 1 cm or more and 7 cm or less. The protruding length Lx2 is in the range of 0.5 cm or more and 3 cm or less, and in another example, in the range of 0.5 cm or more and 2 cm or less.

[0155] Fig. 23 is a perspective view of a microwave oven heating jig according to a modified example of the third embodiment of the present invention. Fig. 24 is a perspective view of a canned food product with a jig attached, including the microwave oven heating jig shown in Fig. 23.

[0156] The microwave oven heating jig 10E shown in FIGS. 23 and 24 is similar to the microwave oven heating jig 10D described with reference to FIGS. 17 to 19, etc., except for the following points.

[0157] That is, in microwave oven heating jig 10E, removal assisting portion 14x includes four protrusions that each protrude in a direction away from support portion 11 and metal can container 21. Two of these protrusions are positioned so that the line connecting their centers passes through the center of the open end of microwave oven heating jig 10D. The remaining two of these protrusions are also positioned so that the line connecting their centers passes through the center of the open end of microwave oven heating jig 10D. Here, the line connecting the centers of the former two protrusions is perpendicular to the line connecting the centers of the latter two protrusions. The angle between these two lines is not limited to 90 degrees.

[0158] This modification also provides the same effects as the third embodiment. Furthermore, because microwave oven heating jig 10E according to this modification has four protrusions on removal assisting portion 14x, it also provides the following additional effects. That is, when microwave oven 100 has a turntable, microwave oven heating jig 10E, which has four protrusions on removal assisting portion 14x, is more likely to have the protrusions on removal assisting portion 14x in a position that is easy to grasp when removing jig-attached canned product 1E from the oven after heating, compared to microwave oven heating jig 10D, which has two protrusions on removal assisting portion 14x.

[0159] In this way, the number of protrusions that removal assisting part 14x has does not have to be two. The number of protrusions that removal assisting part 14x has may be three or more. Furthermore, the number of protrusions that removal assisting part 14x has may be one. For example, if removal assisting part 14x has only one protrusion, and this protrusion has a dimension that exceeds half the circumference of the opening of the microwave heating jig in the circumferential direction of the opening, the above-mentioned gripping is possible.

[0160] <Fourth Embodiment> The fourth embodiment provides another form of technology that is useful for facilitating the handling of canned products equipped with a microwave heating jig. Hereinafter, the fourth embodiment will be described, focusing mainly on the differences from the third embodiment.

[0161] Fig. 25 is a perspective view of a microwave heating jig according to a fourth embodiment of the present invention, and Fig. 26 is a side view of a canned food product equipped with the microwave heating jig shown in Fig. 25.

[0162] The microwave oven heating jig 10F shown in Figs. 25 and 26 is similar to the microwave oven heating jig 10D described with reference to Figs. 17 to 19, etc., except for the following points.

[0163] That is, in microwave oven heating jig 10F, removal assisting portion 14y includes two or more plate-like portions that fit along can body 21a of metal can container 21 when lower portion 11b of support portion 11 is placed between metal can container 21 and interior bottom surface W1 of the microwave oven. Here, microwave oven heating jig 10F includes two plate-like portions.

[0164] The two plate-shaped portions extend upward from the upper end of the upper portion 11t. These plate-shaped portions are positioned so that the line connecting their centers is aligned with the centerline of the microwave heating jig 10F. When removing a heated canned product 1F equipped with the microwave heating jig 10F from the microwave oven, for example, the can body 21a is grasped with one hand via the removal assisting portion 14y and carried out of the microwave oven. This embodiment can achieve the same effects as the third embodiment. This removal configuration also allows the heated canned product 20A to be removed from the microwave oven with one hand.

[0165] The dimensions of the plate-shaped portion included in the removal assisting portion 14y are preferably as follows, when the length of the plate-shaped portion in the height direction of the microwave heating jig 10F in Figure 25 is defined as Ly1 and the length in the direction perpendicular to the height direction as Ly2.

[0166] That is, the length Ly1 is preferably 0.5 cm or more from the viewpoint of ease of gripping the removal assisting portion 14y, and is preferably a length that does not cause interference of the above-mentioned removal assisting portion 14y when multiple jig-attached canned products 1F are stacked in multiple layers. The length Ly2 is preferably 0.5 cm or more from the viewpoint of ease of gripping the removal assisting portion 14y, and is preferably Lc / n (cm) or less. Here, Lc represents the circumferential length (cm) of the opening end of the microwave oven heating jig 10F, and n represents the number of plate-shaped portions included in the removal assisting portion 14y, and is an integer of 2 or more.

[0167] From the viewpoint of ease of gripping the removal assisting portion 14y, it is more preferable that the length Ly1 is 0.5 cm or more and the length Ly2 is 1 cm or more. In this case, the length Ly1 is, for example, in the range of 0.5 cm to 7 cm, and in another example, in the range of 0.5 cm to 6 cm. The length Ly2 is, for example, in the range of 1 cm to 27 cm, and in another example, in the range of 1 cm to 14 cm.

[0168] Alternatively, from the viewpoint of ease of gripping the removal assisting portion 14y, it is more preferable that the width Lx1 is 1 cm or more and the length Ly2 is 0.5 cm or more. In this case, the length Ly1 is, for example, in the range of 1 cm to 7 cm, and in another example, in the range of 1 cm to 6 cm. The length Ly2 is, for example, in the range of 0.5 cm to 27 cm, and in another example, in the range of 0.5 cm to 14 cm.

[0169] Fig. 27 is a perspective view of a microwave oven heating jig according to a modified example of the fourth embodiment of the present invention. Fig. 28 is a perspective view of a canned product with a jig attached, including the microwave oven heating jig shown in Fig. 27.

[0170] The microwave oven heating jig 10G shown in Figures 27 and 28 is similar to the microwave oven heating jig 10F described with reference to Figures 25 and 26, etc., except for the following points.

[0171] That is, in the microwave oven heating jig 10G, the removal assisting portion 14y includes four plate-shaped portions that fit along the can body 21a of the metal can container 21 when the lower portion 11b of the support portion 11 is placed between the metal can container 21 and the microwave oven interior bottom surface W1. Two of these plate-shaped portions are positioned so that a line connecting their centers passes through the center of the open end of the microwave oven heating jig 10G. The remaining two of these plate-shaped portions are also positioned so that a line connecting their centers passes through the center of the open end of the microwave oven heating jig 10G. In this case, the line connecting the centers of the former two protruding portions is perpendicular to the line connecting the centers of the latter two protruding portions. The angle between these two lines is not limited to 90 degrees.

[0172] This modified example also achieves the same effects as the fourth embodiment. Furthermore, because microwave heating jig 10G according to this modified example includes four removal assisting portions 14y, it further achieves the same effects as the modified third embodiment. That is, when microwave oven 100 has a turntable, microwave heating jig 10G, which has four plate-shaped portions of removal assisting portion 14y, is more likely to have the plate-shaped portions of removal assisting portion 14y in positions that facilitate gripping when removing jig-attached canned product 1G from the oven after heating, compared to microwave heating jig 10F, which has two plate-shaped portions of removal assisting portion 14y.

[0173] In this way, the number of plate-shaped portions that removal assisting portion 14y has does not have to be two. The number of plate-shaped portions that removal assisting portion 14y has may be three or more. Furthermore, the number of plate-shaped portions that removal assisting portion 14y has may be one. For example, if removal assisting portion 14y has only one plate-shaped portion and this plate-shaped portion has a dimension that exceeds half the circumference of the opening of the microwave heating jig in the circumferential direction of the opening, the above-mentioned gripping is possible.

[0174] Fifth Embodiment The fifth embodiment provides yet another form of technology that is useful for facilitating the handling of canned products equipped with a microwave heating jig. The following description of the fifth embodiment will focus mainly on the differences from the third embodiment.

[0175] Fig. 29 is a perspective view of a microwave oven heating jig according to a fifth embodiment of the present invention, and Fig. 30 is a side view of a canned food product equipped with the microwave oven heating jig shown in Fig. 29.

[0176] The microwave oven heating jig 10H shown in Figures 29 and 30 is similar to the microwave oven heating jig 10D described with reference to Figures 17 to 19, etc., except for the following points.

[0177] That is, in the microwave heating jig 10H, the removal assisting portion 14z includes a sleeve portion that surrounds the metal can container 21 when the lower portion 11b of the support portion 11 is placed between the metal can container 21 and the microwave oven chamber bottom W1. The sleeve portion extends upward from the upper end of the upper portion 11t. When removing a heated canned product 1H equipped with the microwave heating jig 10H from the microwave oven chamber, for example, the can body 21a is grasped with one hand via the removal assisting portion 14z to transport the canned product 1H outside the microwave oven. This achieves the same effects as the third embodiment. Furthermore, this removal configuration allows the canned product 20A, after being heated in a microwave oven, to be removed from the microwave oven chamber by grasping it with one hand.

[0178] When the length of the sleeve portion in the height direction of the microwave oven heating jig 10H in FIG. 29 is defined as Lz, the dimensions of the sleeve portion included in the removal assisting portion 14z are preferably as follows:

[0179] That is, Lz is preferably 1 cm or more from the viewpoint of ease of gripping of the removal assisting portion 14z, and is preferably a length that does not cause interference of the above-mentioned removal assisting portion 14z when multiple jig-attached canned products 1H are stacked in multiple layers. In one example, Lz is in the range of 1 cm or more and 7 cm or less, and in another example, is in the range of 1 cm or more and 6 cm or less.

[0180] Other modifications are possible for the microwave oven heating jig and the canned product with the jig according to the first to fifth embodiments.

[0181] For example, the structure described in one embodiment may be combined with the structure described in one or more other embodiments. For example, microwave oven heating jig 10A or 10B may be provided with recess R as described above for microwave oven heating jigs 10C to 10G, or with any of removal assisting portions 14x to 14z as described above for microwave oven heating jigs 10D to 10G, or with both recess R and any of removal assisting portions 14x to 14z.

[0182] As described above, the metal can container included in the canned product to be combined with the microwave oven heating jig may be a three-piece can or a two-piece can.

[0183] Each of microwave heating jigs 10A to 10H has a circular shape when orthogonally projected onto a plane perpendicular to its height direction. The orthogonal projection of the microwave heating jig onto a plane perpendicular to its height direction does not have to be circular. For example, the orthogonal projection of the microwave heating jig onto a plane perpendicular to its height direction may be a square, a rectangle, a square with rounded corners, or a rectangle with rounded corners.

[0184] The microwave heating jig can be distributed alone. Alternatively, the microwave heating jig can be combined with unopened canned products and distributed as a jig-attached canned product. In a jig-attached canned product, the number of microwave heating jigs and the number of canned products may be the same or different. In the latter case, the jig-attached canned product may include, for example, one microwave heating jig and multiple canned products.

[0185] The microwave heating jig can also be combined with empty metal can containers and distributed as a kit for canned products with a jig. In the kit for canned products with a jig, the number of microwave heating jigs and the number of metal can containers may be the same or different. In the latter case, the canned product with a jig may include, for example, one microwave heating jig and multiple metal can containers.

[0186] The following describes tests carried out in connection with the present invention.

[0187] <1> The effect of moisture on the occurrence of scorching or melting: A 0.6 mm thick polypropylene sheet was left in a room environment for a long period of time. Next, several square samples, each 10 cm on a side, were cut out from the sheet. The masses (initial masses) of these samples were measured, and then they were divided into groups A, B, and C.

[0188] For each sample in Group A, the following heating test was performed immediately after the initial mass measurement. A flat table-type microwave oven was used for the heating test. The sample was placed approximately in the center of the flat turntable. A metal can with its lid open and containing 70 g of tap water was placed on the sample. The metal can was a three-piece can with an aluminum lid, a steel body, and a steel bottom, an opening diameter of 72 mm, and a height of 30 mm. Microwave heating was performed for 30 seconds at 500 W in the microwave oven. Immediately after heating, the metal can was removed from the sample, and the entire sample was imaged with an infrared thermography camera. The maximum temperature of the sample was obtained from the image obtained. Furthermore, the sample after microwave heating was imaged with a conventional camera, and the image was observed. The sample after microwave heating was also visually examined for the occurrence of scorching or melting.

[0189] After measuring the initial mass of each sample in Group B, the sample was dried for 7 days in a hygrostat set at 50°C. The mass after drying was measured, and then the heating test described above was carried out. This resulted in the maximum temperature of the sample. The sample was then examined for the occurrence of scorching or melting using the same method as described above.

[0190] For each sample in Group C, after measuring the initial mass, the sample was dried for 7 days in a hygrostat set at 50°C. The mass after drying was measured, and the sample was then allowed to absorb moisture for 7 days in a hygrostat set at 50% RH and 23°C. The heating test was then performed to obtain the maximum temperature of the sample. The sample was then examined for scorching or melting using the same method as above.

[0191] Sheets made of different materials were also subjected to the same tests as for the polypropylene sheet, and the results are shown in Table 1 below.

[0192]

[0193] In Table 1, the abbreviation "PBS / PLA" represents a polybutylene succinate / polylactic acid blend resin. "A" indicates that no scorching or melting was observed in either the naked eye or the image of the sample. "B" indicates that no scorching or melting was observed in the image, but scorching or melting was not noticeable at first glance when the sample was observed with the naked eye. "C" indicates that no scorching or melting was clearly observed in the image, but scorching or melting was clearly noticeable at first glance when the sample was observed with the naked eye. "D" indicates that scorching or melting was clearly observed just by observing the image.

[0194] As shown in Table 1, no correlation was observed between the moisture content of the sheet and the maximum temperature. Also, no correlation was observed between the moisture content of the sheet and the occurrence of burning or melting.

[0195] <2> Effect of the type of jig material on the occurrence of burning or melting A microwave heating jig was created from the materials shown in Table 2 below. The microwave heating jig was created so that, when used, the distance from the bottom of the microwave oven to the metal can container would be increased to 1.0 cm. In Table 2, the abbreviation "A-PET" stands for amorphous polyethylene terephthalate, the abbreviation "POM" stands for polyacetal, the abbreviation "PA" stands for polyamide (here, nylon 66), the abbreviation "PBS / PLA" stands for polybutylene succinate / polylactic acid blend resin, and the abbreviation "PVDF" stands for polyvinylidene fluoride.

[0196] A paper box was also prepared as a microwave oven heating jig. The paper box was formed into a rectangular parallelepiped shape with a square bottom. The rectangular parallelepiped had a base of 6 cm and a height of 1.0 cm.

[0197] Next, the following heating test was conducted. A flat table-type microwave oven was used for the heating test. The microwave heating jig was placed approximately in the center of the flat table. A metal can container with its lid open and containing 70 g of tap water was placed on the microwave heating jig. The metal can container used was a three-piece can with an aluminum lid, a steel body and bottom, an opening diameter of 72 mm, and a height of 30 mm. Microwave heating was then performed in a microwave oven at 500 W for 60 seconds. After that, the microwave heating jig sample was photographed with a conventional camera, and the image was observed. The microwave heating jig sample was also visually observed to check for the occurrence of scorching or melting in the microwave heating jig sample. The results are shown in Table 2 below.

[0198]

[0199] The evaluation criteria for "burnt / melted state" in Table 2 are the same as the evaluation criteria for "burnt / melted state" in Table 1.

[0200] In addition to the evaluation results, Table 2 also shows the dielectric constant at 2.45 GHz and the dielectric loss tangent (tan δ) at 2.45 GHz. The dielectric constant of PTFE is a value at 10 GHz, but its dielectric constant at 2.45 GHz is in the range of 1 to 5. The dielectric constants of PVC, PMMA, and PVDF are values ​​at 1 GHz, but their dielectric constants at 2.45 GHz are in the range of 1 to 5.

[0201] As shown in Table 2, the dielectric loss tangent is 7.0 × 10 －３ The microwave oven heating jig made of the material below did not show any noticeable burning or melting. －３ The microwave heating jigs made of the following materials did not burn or melt.

[0202] 1A...canned product with jig, 1B...canned product with jig, 1C...canned product with jig, 1D...canned product with jig, 1E...canned product with jig, 1F...canned product with jig, 1G...canned product with jig, 1H...canned product with jig, 10A...microwave oven heating jig, 10B...microwave oven heating jig, 10C...microwave oven heating jig, 10D...microwave oven heating jig, 10E...microwave oven heating jig, 10F...microwave oven heating jig, 10G...microwave oven heating jig, 10H...microwave oven heating jig, 11...support portion, 11b...base or lower portion, 11e...expanded diameter portion, 11g...fitting portion, 11g1...first fitting portion, 11g2...second fitting portion, 11m...middle portion, 11p...convex portion, 11t...upper portion, 12...reinforcing portion, 13...ridge line portion, 14x...removal assist portion, 14y...removal assist portion, 14z...removal assist portion, 20A... Canned product, 20B...canned product, 21...metal can container, 21a...can body, 21b...can bottom, 21c...can lid, 21c1...can lid main body, 21c1'...can lid main body, 21c2...pull tab, 21e1...large diameter portion, 21e2...large diameter portion, 22...item, 22a...first food, 22b...second food, 100...microwave oven, 110...microwave oven main body, 111...cover body, 112...bottom plate, 120...door, A...first end, B... Second end, C...intersection, CA...stacked body, CB...stacked body, D...intersection, dH1...height of overlapping portion between canned products, dH2...height of overlapping portion between canned products attached to the jig, Hk...height of canned products, Ht...height of canned products attached to the jig, THk...total height of canned products, THt...total height of canned products attached to the jig, P...convex portion, R...concave portion, S...square, W1...bottom surface of interior, W2...side surface of interior, W3...side surface of interior.

Claims

1. A non-metallic microwave heating jig used to place a metal can container in a microwave oven with a wider distance from the bottom of the oven when heating an item contained in the metal can container in a microwave oven, the microwave heating jig comprising a cylindrical support part and a flat reinforcing part connected to one opening of the support part, the support part being configured to fit with both a first canned product end and a second canned product end that differ from each other in at least one of shape and size.

2. The microwave heating jig of claim 1, wherein the first canned product end and the second canned product end include large diameter portions, and the support portion includes a first fitting portion that fits with the large diameter portion of the first canned product end and a second fitting portion that fits with the large diameter portion of the second canned product end.

3. A microwave heating tool as claimed in claim 1 or 2, further comprising a removal assisting part that assists in removing the metal can container containing the heated item from the inside of the oven without contacting the metal can container or the support part, and the support part includes a part that is placed between the metal can container and the bottom surface of the oven when the item is heated in the microwave oven.

4. A microwave oven heating jig as described in claim 3, wherein the removal assisting portion includes two or more protrusions that each protrude in a direction away from the support portion and the metal can container when the portion of the support portion is installed between the metal can container and the bottom surface of the interior of the oven.

5. A microwave oven heating jig as described in claim 3, wherein the removal assisting portion includes two or more plate-shaped portions that conform to the body of the metal can container when the portion of the support portion is installed between the metal can container and the bottom surface of the interior of the oven.

6. A microwave heating jig as described in claim 3, wherein the removal assisting portion includes a sleeve portion that surrounds the metal can container when the portion of the support portion is installed between the metal can container and the bottom surface of the interior of the oven.

7. A microwave heating jig as claimed in any one of claims 3 to 6, wherein the smallest square circumscribing the orthogonal projection of the removal assisting portion onto a plane perpendicular to the height direction has the same dimensions as or is smaller than the smallest square circumscribing the orthogonal projection onto said plane of the portion of the microwave heating jig excluding the removal assisting portion.

8. The relative dielectric constant at 2.45 GHz is 5 or less and the dielectric loss tangent at 2.45 GHz is 7.0 x 10 －３ 8. The microwave oven heating jig according to claim 1, which is made of the following material:

9. The microwave heating jig according to claim 8, wherein the material is a cured resin.

10. A canned product with a jig, comprising the metal can container and the item contained therein, and the microwave heating jig described in any one of claims 1 to 9.

11. A jig-attached canned product as described in claim 10, wherein the canned product has an upper end as one of the first canned product end and the second canned product end, and a lower end as the other of the first canned product end and the second canned product end.

12. A jig-attached canned product according to claim 10 or 11, wherein the canned product and the microwave heating jig are arranged side by side in the height direction of the canned product, and the height Ht of the jig-attached canned product and the height Hk of the canned product satisfy the relationship shown in the following inequality (1): 0.9 x (n + 1) x Hk ≦ n x Ht ≦ 1.1 x (n + 1) x Hk (where n represents an integer ranging from 2 to 5).

13. The canned food product with a jig attached as described in claim 12, wherein the microwave heating jig has an overall cylindrical shape and is attached to the upper end of the canned food product.

14. A packaged article comprising a plurality of jig-attached canned products stacked vertically and a packaging material containing or holding together the plurality of jig-attached canned products, each of the plurality of jig-attached canned products being the jig-attached canned product described in claim 12 or 13.

15. A kit for canned products with a jig, comprising the microwave heating jig according to any one of claims 1 to 9 and the metal can container.

16. A canned product kit with a jig as described in claim 15, wherein the canned product including the metal can container and the item contained therein has an upper end as one of the first canned product end and the second canned product end, and a lower end as the other of the first canned product end and the second canned product end.

17. A jig-attached canned product kit as described in claim 15 or 16, wherein the microwave heating jig is arranged in line with the height of the canned product when the jig-attached canned product, which includes the item and the metal can container containing the item, and the microwave heating jig, is distributed; and when the item contained in the metal can container is heated in a microwave oven, the metal can container is placed in the microwave oven with its distance from the bottom of the oven increased, and the height Ht of the jig-attached canned product and the height Hk of the canned product satisfy the relationship shown in the following inequality (1): 0.9×(n+1)×Hk≦n×Ht≦1.1×(n+1)×Hk (where n is an integer ranging from 2 to 5).

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