Microwave heating jig

Abstract

To provide a technology capable of suppressing defects caused by metal when an article stored in a metal can container is heated in a microwave oven. [Solution] The microwave heating jig 10A is a non-metallic microwave heating jig used to place a metal can container 21 inside the microwave oven at a wider distance from the bottom surface W1 of the oven when heating an item 22 contained in the metal can container 21 in the microwave oven, and includes a cylindrical support portion 11 and a flat reinforcing portion 12 connected to one opening of the support portion 11, and has one or more recesses R at the position of the ridge portion 13 connecting the support portion 11 and the reinforcing portion 12, each recessed toward the inside of the microwave heating jig 10A.

Description

[Technical Field]

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

[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 and is heated in a microwave oven, the movement of free electrons in the metal layer is activated by the microwaves, which can cause discharge (sparks) between the metal layer and the grounded wall surface inside the microwave oven.Patent Document 1 describes a method of 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2017-95163 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[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 at 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 including a cylindrical support portion and a flat reinforcing portion connected to one opening of the support portion, and at the position of the ridge line connecting the support portion and the reinforcing portion, there is provided one or more recesses that are each recessed toward the inside of the microwave heating jig.

[0009] According to another aspect of the present invention, there is provided a microwave heating jig relating to the above aspect, wherein the support part includes a lower part having a cylindrical shape, an upper part having a cylindrical shape and an inner diameter at the lower end that is larger than the inner diameter at the upper end of the lower part, and an intermediate part connecting the upper end of the lower part and the lower end of the upper part and having an annular upper surface.

[0010] According to yet another aspect of the present invention, there is provided a microwave heating jig relating to the above aspect, wherein the one or more protrusions formed on the inner surface of the microwave heating jig by the one or more recesses each have an upper surface that is equal in height to the upper surface of the intermediate portion.

[0011] 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 concave structure consisting of one or more recesses does not have an axis of rotational symmetry at the center of the orthogonal projection of the microwave heating jig onto a plane perpendicular to the height direction of the microwave heating jig onto said plane.

[0012] 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.

[0013] 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.

[0014] According to yet another aspect of the present invention, there is provided a microwave heating jig as defined in claim 1 according to any one of the above aspects, wherein the wall portion has one or more through holes.

[0015] 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.

[0016] According to yet another aspect of the present invention, there is provided a canned product with a jig attached, wherein the canned product has an upper end or a lower end inserted into the support portion.

[0017] According to yet another aspect of the present invention, there is provided a canned product with a jig according to any of the above aspects, wherein the canned product has a double seam at its upper or lower end, and the inner diameter of the double seam is larger than the outer diameter at the lower end of the microwave heating jig.

[0018] 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. [Effects of the Invention]

[0019] 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. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view of a microwave heating jig according to one embodiment of the present invention. [Figure 2] 2 is another perspective view of the microwave heating jig shown in FIG. 1. FIG. [Figure 3] 3 is a cross-sectional view taken along line III-III of the microwave heating jig shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of a canned food product with a jig attached, including the microwave oven heating jig shown in FIGS. [Figure 5] FIG. 5 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. [Figure 6] FIG. 6 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. [Figure 7] FIG. 7 is a perspective view of a microwave heating jig according to a modified example. [Figure 8] 8 is another perspective view of the microwave oven heating jig shown in FIG. [Figure 9] FIG. 9 is a perspective view of a structure in which the microwave oven heating jigs shown in FIGS. 1 to 3 are stacked. [Figure 10] FIG. 10 is a perspective view of a structure in which the microwave oven heating jigs shown in FIGS. 7 and 8 are stacked. DETAILED DESCRIPTION OF THE INVENTION

[0021] 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.

[0022] Fig. 1 is a perspective view of a microwave heating jig according to one 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.

[0023] 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.

[0024] The support portion 11 has a cylindrical shape. Here, the support portion 11 has a substantially cylindrical shape whose diameter increases from one opening to the other opening.

[0025] When microwave heating jig 10A is used in a microwave oven, the larger diameter opening of support part 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.

[0026] The support portion 11 here includes a lower portion 11b, an upper portion 11t, and a middle portion 11m.

[0027] The lower portion 11b has a cylindrical shape whose diameter increases upward. Here, the lower portion 11b has a cylindrical shape whose diameter increases upward. 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.

[0028] 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.

[0029] 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 surface.

[0030] The inner diameter of the lower end of the upper part 11t is larger than the inner diameter of the upper end of the lower part 11b. The upper part 11t is positioned such that its lower end surrounds the upper end of the lower part 11b.

[0031] 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 case.

[0032] As will be described later, when heating an item housed in a metal can in a microwave oven, the lower end of the canned product is inserted into the open end of the microwave heating jig 10A, supporting the canned product so that the metal can is sufficiently spaced from the bottom surface of the microwave oven chamber. The microwave heating jig 10A can also be distributed as a jig-attached canned product in combination with the canned product. In one example, the jig-attached canned product has the upper or lower end of the canned product inserted into the open end of the microwave heating jig 10A. The upper surface of the middle portion 11m can form at least a portion of the contact surface with which the upper or lower end of the canned product abuts when inserted into the open end of the microwave heating jig 10A.

[0033] The reinforcing portion 12 has a disk shape and closes the lower opening of the support portion 11. The reinforcing portion 12 improves the shape retention of the support portion 11. The edge of the reinforcing portion 12 is continuous with the lower end of the support portion 11.

[0034] Microwave oven heating jig 10A has one or more recesses R, each recessed toward the inside of microwave oven heating jig 10A, at the position of ridge line 13 connecting support part 11 and reinforcing part 12. In this example, microwave oven heating jig 10A has four recesses R. The number n of recesses R and the circumference L of a circle circumscribing the underside of reinforcing part 12 are expressed as P and the width W of the opening of the recess R at the position of the plane on the outer peripheral surface of the lower portion 11b is expressed by the inequality 3nW≦L P It is preferable that the number n of recesses R is in the range of 1 to 17, and more preferably in the range of 2 to 12.

[0035] As described above, the number n of recesses R may be 1. However, from the viewpoint of the load resistance and stackability of microwave oven heating jig 10A, the number n of recesses R is preferably 2 or more.

[0036] The number n of recesses R is preferably sufficiently large from the viewpoint of the load resistance of the microwave oven heating jig 10A. P For a given value, excessively increasing the number n of recesses R shortens the distance between adjacent recesses R, potentially reducing the strength of the portion of microwave heating jig 10A sandwiched between adjacent recesses R. For example, when a load is applied in the height direction to a jig-attached canned food product formed by attaching microwave heating jig 10A to the upper or lower end of the canned food product, the buckling load of microwave heating jig 10A increases as the number n of recesses R increases, as long as the number n is within the range of 1 to 17. However, when the number n of recesses R exceeds 17, the distance between adjacent recesses R becomes shorter, so increasing the number n does not further increase the buckling load. Furthermore, increasing the number n of recesses R can lead to molding defects, such as a reduction in the thickness of the wall portions forming recesses R or the formation of holes in the wall portions forming recesses R, when microwave heating jig 10A is manufactured by pressure forming, for example. Therefore, it is preferable that the number n of recesses R be equal to or less than the above-mentioned upper limit.

[0037] The recessed structure formed by these recesses R has an axis of four-fold rotational symmetry when orthogonally projected onto a plane perpendicular to the height direction of microwave heating jig 10A, at the center of the orthogonal projection of microwave heating jig 10A onto this plane. As will be described later, recesses R serve to increase the strength of microwave heating jig 10A. By arranging recesses R so that the orthogonal projection of the recessed structure onto the above plane has an axis of rotational symmetry at the center of the orthogonal projection of microwave heating jig 10A onto the above plane, it is possible to reduce strength bias in microwave heating jig 10A.

[0038] Here, each of the recesses R has an opening width W on the outer peripheral surface of the lower portion 11b that decreases upward, and a depth D based on the outer peripheral surface of the lower portion 11b that decreases upward. The width W does not have to decrease upward. For example, the width W may be constant in the height direction. Furthermore, the depth D does not have to decrease upward. For example, the depth D may be constant in the height direction.

[0039] The depth D of the reinforcement portion 12 in a plane including the underside thereof is preferably within a range of 5% to 35% of the diameter L1 of a circle circumscribing the underside of the reinforcement portion 12, and preferably within a range of 8% to 18% of the diameter L1. The depth D, the diameter L1, and the diameter L2 of a circle inscribed in the recessed structure in a plane including the underside of the reinforcement portion 12 satisfy the relationship expressed by the equation L2 = L1 - 2D. When the microwave heating jig 10A is attached to a canned food product as described below, the area enclosed by the circle inscribed in the recessed structure in a plane including the underside of the reinforcement portion 12 can be used as a display surface or a main portion thereof for displaying images, text, etc., using a printed layer or label. Increasing the ratio of the depth D to the diameter L1 reduces the display surface or a main portion thereof. On the other hand, making this ratio too small reduces the strength-enhancing effect of the recess R.

[0040] The width W of the reinforcing portion 12 in a plane including the lower surface thereof is the circumference L of a circle circumscribing the lower surface of the reinforcing portion 12. P It is preferable that the circumference L PAs described above, the number n of recesses R and the circumference L are more preferably in the range of 2% to 6%. P and the width W of the reinforcing portion 12 in a plane including the lower surface thereof are expressed by the inequality 3nW≦L P It is preferable that the number n of recesses R and the circumference L satisfy the relationship expressed by the following formula: P When the width W is constant, increasing the width W reduces the distance between adjacent recesses R, which may result in a decrease in the strength of the portion of the microwave heating jig 10A sandwiched between the adjacent recesses R.

[0041] Here, each recess R is formed by a pair of first wall portions Rw1, second wall portions Rw2, third wall portions Rw3, and fourth wall portions Rw4. The first wall portions Rw1 are respectively continuous from the support portion 11 and the reinforcing portion 12 and face each other. The second wall portion Rw2 is continuous from the reinforcing portion 12 and connects a portion of one first wall portion Rw1 to a portion of the other first wall portion Rw1. The third wall portion Rw3 is continuous from the support portion 11 and connects another portion of one first wall portion Rw1 to another portion of the other first wall portion Rw1. The fourth wall portion Rw4 connects the second wall portion Rw2 to the third wall portion Rw3 and also connects yet another portion of one first wall portion Rw1 to yet another portion of the other first wall portion Rw1.

[0042] Each of the first wall portions Rw1 is preferably inclined so that the width W decreases upward. In this case, the angle formed by the main surface of each of the first wall portions Rw1 with respect to the height direction of the microwave oven heating jig 10A is preferably within a range of 0.5° to 10°, and more preferably within a range of 1° to 10°.

[0043] The second wall portion Rw2 is preferably inclined so that the depth D decreases upward. In this case, the angle formed by the main surface of the second wall portion Rw2 with respect to the height direction of the microwave oven heating jig 10A is preferably in the range of 0.5° to 10°, and more preferably in the range of 1° to 10°.

[0044] The microwave heating jig 10A can be manufactured by, for example, pressure molding or injection molding. Increasing the angle makes it easier to remove the molded product from the mold. Furthermore, when pressure molding is used, the angle can affect the thickness of the wall that forms the recess R. Specifically, in pressure molding, a sheet made of thermoplastic resin is heated and then pressed against the mold with compressed air. When the angle is large, more thermoplastic resin moves to the portion of the mold that corresponds to the recess R than when the angle is small. As a result, the thickness of the wall that forms the recess R increases, and the strength of the microwave heating jig 10A at the position of the recess R is increased.

[0045] The main surface of the third wall portion Rw3 is perpendicular to the height direction of the microwave heating jig 10A. The third wall portion Rw3 may be inclined so that the height on the support portion 11 side is greater.

[0046] The fourth wall portion Rw4 is a so-called fillet portion. Although the fourth wall portion Rw4 can be omitted, the fourth wall portion Rw4 can contribute to alleviating stress concentration.

[0047] The length of the fourth wall portion Rw4, i.e., the distance from the second wall portion Rw2 to the third wall portion Rw3, is preferably 0.25 mm or more, more preferably in the range of 0.5 mm to 3.0 mm. To mitigate stress concentration, it is desirable for the length of the fourth wall portion Rw4 to be sufficiently long. Furthermore, when pressure molding is used, the length of the fourth wall portion Rw4 can affect the thickness of the wall portion forming the recess R, particularly the thickness of the fourth wall portion Rw4. Specifically, reducing the length of the fourth wall portion Rw4 reduces the amount of thermoplastic resin moving to the portion of the mold corresponding to the recess R, thereby reducing the thickness of the wall portion forming the recess R, particularly the thickness of the fourth wall portion Rw4. Furthermore, reducing the length of the fourth wall portion Rw4 may result in holes being formed in the fourth wall portion Rw4, depending on factors such as the time required between the completion of heating of the thermoplastic resin sheet and the start of pressurizing the mold with compressed air. Increasing the length of the fourth wall portion Rw4 not only prevents holes from occurring in the fourth wall portion Rw4, but also increases the thickness of the wall portion forming the recess R, particularly the thickness of the fourth wall portion Rw4, thereby achieving higher strength.

[0048] Here, the fourth wall portion Rw4 is provided as a fillet portion at the connection point between the second wall portion Rw2 and the third wall portion Rw3, but fillet portions may also be provided at other connection points. Specifically, a fillet portion may also be provided at one or more connection points between the first wall portion Rw1 and an adjacent wall portion. Also, a fillet portion may also be provided at one or more connection points between the second wall portion Rw2 and an adjacent wall portion. Furthermore, a fillet portion may also be provided at one or more connection points between the third wall portion Rw3 and an adjacent wall portion. These fillet portions preferably satisfy the conditions described above for the fourth wall portion Rw4.

[0049] The recesses R each form a protrusion P on the inner surface of the microwave heating jig 10A. Here, the protrusion P has an upper surface that is equal in height to the upper surface of the middle portion 11m. In this case, the upper surface of the protrusion P can form another part of the contact surface described above.

[0050] The microwave heating jig 10A preferably increases the distance between the metal can and the microwave oven's interior bottom surface to within a range of 1 mm to 50 mm, and more preferably to within a range of 10 mm to 30 mm. Increasing this distance reduces the likelihood of sparks occurring between the metal can and the microwave oven's interior bottom surface. However, increasing this distance increases the bulk of the microwave heating jig 10A or the canned food product that includes the jig and the canned food product. Furthermore, increasing this distance excessively shortens the distance from the metal can to the microwave oven's interior top surface, making sparks more likely to occur between them. Note that the above distance is approximately equal to the height of the middle portion 11m or the upper surface of the protruding portion P relative to the lower surface of the reinforcing portion 12.

[0051] The thickness of the wall portion constituting microwave oven heating jig 10A is preferably within the range of 0.16 mm to 6 mm, and more preferably within the range of 0.19 mm to 0.90 mm.

[0052] It is preferable that microwave heating jig 10A has one or more through holes in its wall. The through holes provided in the wall of microwave heating jig 10A allow ventilation between the internal and external spaces of microwave heating jig 10A when microwave heating jig 10A is attached to canned goods and when microwave heating jig 10A is detached from canned goods, thereby reducing the pressure difference between these spaces. Therefore, by providing one or more through holes in the wall of microwave heating jig 10A, microwave heating jig 10A can be easily attached to canned goods and detached from canned goods.

[0053] 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. -3It is preferable that the 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.

[0054] 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.

[0055] This material also has a dielectric loss tangent of 6.0×10 at 2.45 GHz. -3 Preferably, it is 5.0 x 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 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.

[0056] Examples of materials having the above physical properties include specific cured resins. The cured resins are, for example, cured thermosetting resins or 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.

[0057] Examples of cured resins having the above physical properties include polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), polyamide-imide (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).

[0058] Among these, acrylonitrile-butadiene-styrene copolymer (ABS), polyamide-imide (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.

[0059] 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.

[0060] FIG. 4 is a cross-sectional view of a canned food product with a jig attached, including the microwave oven heating jig shown in FIGS.

[0061] The canned product with jig 1 shown in FIG. 4 includes the microwave heating jig 10A and the canned product 20.

[0062] The canned product 20 includes a metal can container 21 and an item 22 contained therein.

[0063] The metal can container 21 is a two-piece can in which the can bottom 21b and the can body 21a are integrally formed, and the can lid 21c and the can body 21a are integrated by double seaming. The metal can container 21 may also be 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.

[0064] Here, the can lid 21c includes a disk-shaped can lid body 21c1 having scores such as V-grooves on its surface, and a pull-tab 21c2 attached thereto. Pulling the pull-tab 21c2 can cause the can lid body 21c1 to break along the scores. The can lid 21c may also be composed of a disk-shaped can lid body that does not have scores such as V-grooves on its surface and does not have a pull-tab attached.

[0065] 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. In 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.

[0066] Here, S / V ( / cm) is defined by defining the area of ​​the opening created 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 20 preferably has an S / V of 6 / cm or more, and more preferably 15 / cm or more. Microwaves can be incident on the item 22 only through the opening created in the can lid by opening the lid. Increasing S / V enables more efficient heating. There is no upper limit to S / V, but in one example, S / V is 45 / cm or less.

[0067] The can body 21a of the metal can container 21 has an expanded diameter portion near its lower end. The diameter of the can body 21a at the expanded diameter portion is larger than the diameter of a circle inscribed in the protrusions 11p. In FIG. 4, these protrusions 11p indicate that the lower end of the canned product 20 is inserted into the open end of the microwave heating jig 10A, and the expanded diameter portion of the metal can container 21 is located below the protrusions 11p. This allows the microwave heating jig 10A to be locked onto the metal can container.

[0068] It is preferable that the outer diameter of the metal can container 21 at its upper end is smaller than the inner diameter of the microwave heating jig 10A at its upper end. In this case, the upper end of the canned product 20 can be inserted into the open end of the microwave heating jig 10A. Here, as an example, it is assumed that the microwave heating jig 10A can be attached to the upper end of the canned product 20.

[0069] In the jig-attached canned products 1, it is preferable that the inner diameter at the top end of the metal can container 21, i.e., the inner diameter of the double-seamed portion, is larger than the outer diameter at the bottom end of the microwave heating jig 10A. When such jig-attached canned products 1 are stacked vertically, the bottom end of the microwave heating jig 10A of the upper jig-attached canned product 1 can be positioned within the area surrounded by the double-seamed portion of the metal can container 21 of the lower jig-attached canned product 1. This stabilizes the stacked state of the jig-attached canned products 1.

[0070] FIG. 5 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.

[0071] 5 is a so-called flat table type microwave oven that does not have a turntable. Microwave oven 100 includes microwave oven body 110 and door 120.

[0072] 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. 5 illustrates interior bottom surface W1, which is the surface of the bottom plate, interior side surface W2, which is the surface of the left side panel, and interior side surface W3, which is the surface of the back side panel.

[0073] 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.

[0074] The microwave heating jig 10A shown in Figures 1 to 3 may be used in a so-called turntable-type microwave oven having a turntable. Furthermore, the microwave heating jig 10A shown in Figures 1 to 3 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.

[0075] FIG. 6 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.

[0076] Figure 6 shows one embodiment in which microwave heating jig 10A described with reference to Figures 1 to 3 is used to heat canned product 20 in microwave oven 100 described with reference to Figure 5. Figure 6 depicts only bottom plate 112 of microwave oven 100, the upper surface of which is interior bottom surface W1. Canned product 20 shown in Figure 6 is obtained by removing the portion of can lid body 21c1 surrounded by the scores together with pull-tab 21c2 from canned product 20 described with reference to Figure 4 by pulling pull-tab 21c2, thereby converting can lid body 21c1 into can lid body 21c1' that is open in the center.

[0077] When heating the items 22 in the metal can container 21 in the microwave oven 100, first, as shown in FIG. 6 , the microwave heating jig 10A is attached to the bottom end of the open canned product 20. Specifically, the bottom end of the canned product 20 is inserted into the open end of the microwave heating jig 10A, and the enlarged diameter portion provided near the bottom end of the can body 21a is positioned below the protrusion 11p. As a result, the canned product 20 is placed on the protrusion P, for example, on the middle portion 11m and the protrusion P, and the microwave heating jig 10A is engaged with the bottom end of the canned product 20. The canned product 20 may be opened after the microwave heating jig 10A is attached to the bottom end of the canned product 20.

[0078] Next, canned product 20 with microwave heating jig 10A attached to its lower end is placed on interior bottom surface W1 of microwave oven 100 so that lower portion 11b is positioned below canned product 20. Canned product 20 is preferably placed approximately in the center of interior bottom surface W1.

[0079] In this way, the metal can container 21 is placed inside the microwave oven 100 with the distance from the interior bottom surface W1 increased. Specifically, the metal can container 21 is placed inside the microwave oven with the distance increased by the height of the middle portion 11m or the upper surface of the protruding portion P compared to when the canned products 20 are placed on the interior bottom surface W1 without the microwave oven heating jig 10A.

[0080] 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 20 is open, microwaves can be incident on the item 22. Therefore, the item 22 is heated.

[0081] In the above method, the microwave heating jig 10A is attached to the bottom end of the canned product 20, thereby increasing the distance from the interior 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, when the item 22 stored in the metallic can container 21 is heated in the microwave oven 100, it is possible to prevent problems caused by the metal.

[0082] Furthermore, microwave heating jig 10A can be used as an aid for removing heated canned products 20 from the interior of the oven. That is, when removing heated canned products 20 from the oven, microwave heating jig 10A attached to the bottom end of canned products 20 is manually carried outside the oven, whereby canned products 20 and microwave heating jig 10A can be removed from the oven without coming into contact with canned products 20, which are hotter than microwave heating jig 10A.

[0083] Furthermore, in the above method, microwave heating jig 10A is attached to the lower end of canned product 20, and then they are placed inside microwave oven 100. Support part 11 of microwave heating jig 10A is configured to fit with the lower end of canned product 20, so that, for example, when canned product 20 and microwave heating jig 10A are placed inside the oven or when they are removed from the oven, the relative position of canned product 20 with microwave heating jig 10A is unlikely to shift. Furthermore, if microwave oven 100 has a turntable, the above-mentioned positional shift due to the rotation of the turntable is unlikely to occur.

[0084] In the above method, when microwave oven heating jig 10A is attached to the lower end of canned product 20, the enlarged diameter portion provided near the lower end of can body 21a is positioned below protrusion 11p, so that microwave oven heating jig 10A engages with the lower end of canned product 20. Therefore, when placing canned product 20 with microwave oven heating jig 10A attached to its lower end inside the microwave oven, for example, canned product 20 can be carried into the microwave oven with one hand, and canned product 20 can be placed on microwave oven bottom surface W1 so that lower portion 11b is positioned below canned product 20. This engagement also makes it less likely that canned product 20 will become misaligned when removed from the microwave oven or when the turntable is rotated.

[0085] Furthermore, when the canned product 20 is unopened, the upper surface of the canned product 20 can be protected from dirt and the like by attaching the microwave heating jig 10A to the upper end of the canned product 20. Also, when an opened canned product 20 is stored, attaching the microwave heating jig 10A to the upper end of the canned product 20 makes it less likely that foreign matter will get mixed into the item 22 contained in the metal can container 21 or that liquid components contained in the item 22 will evaporate.

[0086] Furthermore, the microwave heating jig 10A has a recess R on the ridge 13. The microwave heating jig 10A having this structure further achieves the following effects. Specifically, jig-attached canned products 1 are typically transported in multiple stacked rows. For example, a packaged product in which multiple jig-attached canned products 1 are arranged vertically and horizontally and stacked in multiple layers is transported inside a box. Alternatively, a packaged product in which multiple jig-attached canned products 1 are arranged vertically and horizontally and stacked in multiple layers on a pallet and integrated with a film or sheet is transported. The microwave heating jig 10A 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 10A caused by such force.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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 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.

[0094] The microwave heating jig and the canned product with the jig can be modified in many ways. Fig. 7 is a perspective view of a microwave heating jig according to a modified example, and Fig. 8 is another perspective view of the microwave heating jig shown in Fig. 7.

[0095] The microwave oven heating jig 10B shown in Figs. 7 and 8 is similar to the microwave oven heating jig 10A described with reference to Figs. 1 to 3, etc., except for the following points.

[0096] That is, in microwave heating jig 10B, the recessed structure consisting of recesses R does not have an axis of rotational symmetry at the center of the orthogonal projection of microwave heating jig 10B onto a plane perpendicular to the height direction of microwave heating jig 10B. That is, while recesses R are arranged at equal intervals in microwave heating jig 10B, they are not arranged at equal intervals in microwave heating jig 10B.

[0097] This modified example also provides the same effects as the above-described embodiment. Furthermore, since the recesses R are not arranged at equal intervals, microwave heating jig 10B according to this modified example has a greater imbalance in strength compared to microwave heating jig 10A, but it also provides the effects described below.

[0098] Fig. 9 is a perspective view of a structure in which the microwave heating jigs shown in Fig. 1 to Fig. 3 are stacked one on top of the other. Fig. 10 is a perspective view of a structure in which the microwave heating jigs shown in Fig. 7 and Fig. 8 are stacked one on top of the other. In Fig. 9 and Fig. 10, two microwave heating jigs are arranged one on top of the other.

[0099] As described above, in microwave oven heating jig 10A, the recessed structure consisting of recesses R has an axis of four-fold rotational symmetry when orthogonally projected onto a plane perpendicular to the height direction of microwave oven heating jig 10A onto this plane. When microwave oven heating jigs 10A with this structure are arranged one on top of the other, there is a high possibility that the position of the recesses R of the upper microwave heating jig 10A will match the position of the recesses R of the lower microwave heating jig 10A. When these positions match, as shown in Figure 9, the protrusion P of the upper microwave heating jig 10A will fit into the recesses R of the lower microwave heating jig 10A, and the lower part 11b and upper part 11t of the lower microwave heating jig 10A will fit into the lower part 11b and upper part 11t of the upper microwave heating jig 10A, respectively. As a result, the microwave heating jigs 10A adhere tightly to each other, and for example, in a device that attaches the microwave heating jigs 10A to canned products 20, it may be difficult to separate the microwave heating jigs 10A from each other.

[0100] In contrast, in microwave heating jig 10B, the recessed structure consisting of recesses R does not have an axis of rotational symmetry at the center of the orthogonal projection of microwave heating jig 10B onto a plane perpendicular to the height direction of microwave heating jig 10B. When microwave heating jigs 10B with this structure are placed one on top of the other, it is unlikely that the position of the recesses R of the upper microwave heating jig 10B will perfectly match the position of the recesses R of the lower microwave heating jig 10B. Therefore, it is unlikely that microwave heating jigs 10B will adhere tightly to each other, and therefore, for example, in a device that attaches microwave heating jigs 10B to canned products 20, it is unlikely that it will be difficult to separate microwave heating jigs 10B from each other.

[0101] Other variations of the microwave heating fixture and the canned product with the fixture are possible.

[0102] 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.

[0103] Each of microwave heating jigs 10A and 10B has a circular shape when orthogonally projected onto a plane perpendicular to its height direction. The shape of the microwave heating jigs when orthogonally projected onto a plane perpendicular to its height direction does not have to be circular. For example, the shape of the microwave heating jigs when orthogonally projected 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.

[0104] 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.

[0105] 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. [Example]

[0106] The following describes tests carried out in connection with the present invention.

[0107] <1> The effect of moisture on the occurrence of burning or melting A 0.6 mm thick polypropylene sheet was left in a room environment for a long time. Then, several square samples, each measuring 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.

[0108] For each sample in group A, the following heating test was carried out immediately after the initial mass measurement. A flat tabletop 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. The sample was heated at 500 W for 30 seconds. 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 determined from the image obtained. The sample after microwave heating was also imaged with a conventional camera, and the image was observed. The sample was also visually inspected for the occurrence of scorching or melting.

[0109] 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 obtaining 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.

[0110] For each sample in Group C, after measuring the initial mass, it was dried for 7 days in a hygrostat set at 50°C. The mass after drying was measured, and then the sample was 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 occurrence of scorching or melting in the sample was then examined using the same method as above.

[0111] Sheets made from different materials were also subjected to the same tests as for the polypropylene sheet, and the results are shown in Table 1 below.

[0112] [Table 1]

[0113] In Table 1, the abbreviation "PBS / PLA" represents 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.

[0114] 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.

[0115] <2> The 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.

[0116] In addition, a paper box was created as a microwave oven heating jig. This paper box was formed into a rectangular parallelepiped shape with a square bottom. The base of the rectangular parallelepiped was 6 cm and the height was 1.0 cm.

[0117] Next, the following heating test was carried out. A flat-table 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 with its lid open and containing 70 g of tap water was placed on the microwave heating jig. 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. The can was then heated 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 inspected for the occurrence of burning or melting. The results are shown in Table 2 below.

[0118] [Table 2]

[0119] The evaluation criteria for "burnt / melted state" in Table 2 are the same as the evaluation criteria for "burnt / melted state" in Table 1.

[0120] In addition to the above 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.

[0121] As shown in Table 2, the dielectric loss tangent is 7.0 × 10 -3 The microwave 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.

[0122] <3> Effect of the number of recesses on the load capacity of the jig A computer simulation was conducted to investigate the effect of the number of recesses provided at the ridgeline on the load-bearing capacity of a microwave oven heating jig. In this computer simulation, the following conditions were assumed:

[0123] That is, the microwave heating jigs had a structure similar to microwave heating jig 10A described with reference to Figures 1 to 3. Each microwave heating jig had a diameter of 85.7 mm of a circle circumscribing the outline of the underside of reinforcing part 12, a width W of 5.0 mm in a plane including the underside of reinforcing part 12, a depth D of 4.9 mm in a plane including the underside of reinforcing part 12, and an overall wall thickness of 0.30 mm. Each microwave heating jig was made of polypropylene, and its elastic modulus and yield stress were 1624 MPa and 31.6 MPa, respectively.

[0124] The metal can container is a three-piece can in which the double seamed portion at the top end and the double seamed portion at the bottom end have the same outer diameter. This allows the double seamed portion at the top end of the metal can container to abut against the abutment surface of the microwave heating jig when the microwave heating jig is attached to the bottom end of the canned product, and also allows the double seamed portion at the top end of the metal can container to abut against the abutment surface of the microwave heating jig when the microwave heating jig is attached to the top end of the canned product.

[0125] The double-seamed portion at the bottom of the metal can container has an inner diameter larger than the outer diameter of the bottom of the microwave heating jig. This allows the lower end of the microwave heating jig of the lower jig-attached canned product to be positioned within the area surrounded by the double-seamed portion of the metal can container of the upper jig-attached canned product when the canned products are stacked vertically, with the microwave heating jig attached to the top of the canned product. In other words, when stacked in this manner, the underside of the reinforcing portion 12 of the microwave heating jig of the lower canned product abuts against the underside of the center of the bottom of the metal can container of the upper canned product.

[0126] Each of the microwave heating jigs described above was attached to the top of a canned product having the above-described structure, and another canned product having the above-described structure was placed on top of this microwave heating jig so that the bottom end of the microwave heating jig was positioned within the area surrounded by the double seam at the bottom end of the canned product. A load was then applied to each structure in the height direction until a 1 mm compression depth was achieved, and the maximum load was calculated as the compression load. The results are shown in Table 3 below.

[0127] [Table 3]

[0128] As shown in Table 3, when the number n of recesses R was within the range of 1 to 17, the compressive load increased as the number n increased. That is, when the number n of recesses R was within the range of 1 to 17, the load-bearing capacity increased as the number n increased. However, when the number n of recesses R exceeded 17, no further improvement in the load-bearing capacity was observed with an increase in the number n. [Explanation of symbols]

[0129] 1...canned product with jig, 10A...microwave heating jig, 10B...microwave heating jig, 11...support part, 11b...lower part, 11m...middle part, 11p...convex part, 11t...upper part, 12...reinforcing part, 13...ridge part, 20...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 , 22...item, 22a...first food, 22b...second food, 100...microwave oven, 110...microwave oven body, 111...cover body, 112...bottom plate, 120...door, D...depth, L1...diameter, L2...diameter, P...convex portion, R...concave portion, Rw1...first wall portion, Rw2...second wall portion, Rw3...third wall portion, Rw4...fourth wall portion, W...width, W1...bottom surface of interior, W2...side surface of interior, W3...side surface of interior.

Claims

1. A non-metallic microwave heating tool used to place 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, A microwave heating jig comprising a cylindrical support portion and a flat reinforcing portion connected to one opening of the support portion, and at the position of the ridge portion connecting the support portion and the reinforcing portion, there are one or more recesses each recessed toward the inside of the microwave heating jig.

2. The microwave heating jig of claim 1, wherein the support portion includes a lower portion having a cylindrical shape, an upper portion having a cylindrical shape and an inner diameter at the lower end that is larger than the inner diameter at the upper end of the lower portion, and an intermediate portion connecting the upper end of the lower portion to the lower end of the upper portion and having an annular upper surface.

3. 3. The microwave heating jig according to claim 2, wherein the one or more protrusions formed on the inner surface of the microwave heating jig by the one or more recesses each have an upper surface that is equal in height to the upper surface of the intermediate portion.

4. The microwave heating jig of claim 1, wherein the concave structure consisting of one or more recesses does not have an axis of rotational symmetry at the center of the orthogonal projection of the microwave heating jig onto a plane perpendicular to the height direction of the microwave heating jig onto the plane.

5. The relative dielectric constant at 2.45 GHz is 5 or less and the dielectric loss tangent at 2.45 GHz is 7.0 × 10 －３ 2. The microwave heating jig according to claim 1, which is made of the following material:

6. 6. The microwave heating jig according to claim 5, wherein the material is a cured resin.

7. 2. The microwave oven heating jig according to claim 1, wherein the wall portion has one or more through holes.

8. a canned product including the metal can container and the item contained therein; The microwave heating jig according to any one of claims 1 to 7. A canned product with a jig attached.

9. The jig-attached canned product according to claim 8, wherein the upper end or the lower end of the canned product is inserted into the support portion.

10. The canned product with a jig attached as described in claim 8, wherein the canned product has a double seam at its upper or lower end, and the inner diameter of the double seam is larger than the outer diameter at the lower end of the microwave heating jig.

11. The microwave heating jig according to any one of claims 1 to 7, The metal can container, A kit for canned products with a jig.

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