Container

Abstract

To provide a container having a container body, an inner lid and an outer lid for effectively preventing the liquid leakage of a content.SOLUTION: A container 400 includes a container body 300, an inner lid 200 internally fitted to the container body 300 to close a storage part 390 of the container body 300, and an outer lid 100 internally fitted to the inner lid 200 to close the storage part 290 of the inner lid 200 and also internally fitted to the container body 300 to close the storage part 390 of the container body 300. The container main body 300 includes the container-side fitting portion 340 to which the inner lid 200 is internally fitted on the inner surface side of the peripheral wall portion 220 of the container-side accommodating portion 390, the inner lid 200 includes the inner lid-side fitting portion 240 to which the outer lid 100 is internally fitted on the inner surface side of the peripheral wall portion 320 of the inner lid-side accommodating portion 290, and when the inner lid 200 closes the container main body 300, the container-side fitting portion 340 of the container main body 300 and the inner lid-side fitting portion 240 of the inner lid 200 are vertically separated from each other.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a container comprising a container body, an inner lid, and an outer lid. [Background technology]

[0002] BACKGROUND ART Containers for storing food such as prepared dishes and boxed lunches have been used in supermarkets, convenience stores, and the like.

[0003] There are various types of containers, and the container in Patent Document 1 comprises a container body, an inner lid, and an outer lid. The container body can be closed with the inner lid when food is placed in the container body, and the outer lid can be closed with food also placed in the inner lid to seal the container. In this way, food can be sold as a three-piece container consisting of the container body, inner lid, and outer lid. Food can also be sold as a two-piece container by removing the inner lid and outer lid set from the container body. Furthermore, food can also be sold as a two-piece container by directly attaching the outer lid to the container body without using the inner lid. However, regardless of the type of container (three-piece type or two-piece type), there is a problem in that the leakage of the contents cannot be sufficiently prevented. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6860900 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above, the present invention provides a container that includes a container body, an inner lid, and an outer lid, and that effectively prevents leakage of the contents contained therein. [Means for solving the problem]

[0006] In order to solve the above problem, the container according to claim 1 of the present invention is a container comprising a container body, an inner lid that fits into the container body to close the container-side storage section of the container body, and an outer lid that fits into the inner lid to close the inner lid-side storage section of the inner lid and can also close the container-side storage section of the container body, wherein the container body has a container-side fitting section into which the inner lid is fitted, on the inner surface of the peripheral wall of the container-side storage section, and the inner lid has an inner lid-side fitting section into which the outer lid is fitted, on the inner surface of the peripheral wall of the inner lid-side storage section, and when the inner lid closes the container body, the container-side fitting section of the container body and the inner lid-side fitting section of the inner lid are spaced apart from each other vertically.

[0007] According to the above features, the inner lid-side storage portion of the inner lid and the container-side storage portion of the container body are sealed in an internally fitted manner, thereby effectively preventing leakage of the contents. Furthermore, the container-side fitting portion of the container body and the inner lid-side fitting portion of the inner lid are spaced apart from each other vertically, making it easy to separately remove the fitting between the outer lid and the inner lid and the fitting between the inner lid and the container body.

[0008] In order to solve the above problem, the container according to claim 2 of the present invention is characterized in that the container-side fitting portion of the container body has an arc-shaped longitudinal cross section and is consistent in shape with the outer surface of the peripheral wall portion of the inner lid, and the inner lid-side fitting portion of the inner lid has an arc-shaped longitudinal cross section and is consistent in shape with the outer lid-side fitting portion of the outer lid.

[0009] According to the above feature, the fitting portion is arc-shaped and provides a high degree of adhesion, so that leakage from the contents can be prevented more effectively. [Effects of the Invention]

[0010] The container of the present invention effectively prevents leakage of the contents contained therein. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1(a) is a plan view of the outer lid 100, and FIG. 1(b) is a front view of the outer lid 100. As shown in FIG. [Figure 2] 2(a) is an AA end view, and FIG. 2(b) is an enlarged end view of the vicinity of the outer lid side fitting portion 140 in the AA end view. [Figure 3] FIG. 3(a) is a plan view of the inner lid 200, and FIG. 3(b) is a front view of the inner lid 200. As shown in FIG. [Figure 4] 4(a) is a BB end view, and FIG. 4(b) is an enlarged end view of the vicinity of the inner lid side fitting portion 240 in the BB end view. [Figure 5] 5(a) is a plan view of the container body 300, and FIG. 5(b) is a front view of the container body 300. As shown in FIG. [Figure 6] 6(a) is a CC end view, and FIG. 6(b) is an enlarged end view of the vicinity of the container-side fitting portion 340 in the CC end view. [Figure 7] FIG. 7 is a front view of the container 400 with each part separated. [Figure 8] FIG. 8(a) is a plan view of the container 400, and FIG. 8(b) is a DD end view. [Figure 9] FIG. 9 is a front view of the container 400 with each part separated. [Figure 10] FIG. 10(a) is a plan view of the container 400, and FIG. 10(b) is an end view taken along the line EE. [Explanation of symbols]

[0012] 100 Outer lid 200 Inner lid 220 Peripheral wall section 240 Inner lid side fitting part 290 Inner lid side storage section 300 Container body 320 Peripheral wall section 340 Container side fitting part 390 Container side storage section 400 containers DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, "upward" refers to a direction that faces upward in the vertical direction when a container is placed on a horizontal surface, and "downward" refers to a direction that faces downward in the vertical direction.

[0014] First, Figures 1 and 2 show the outer lid 100 of a container 400 according to the present invention. Figure 1(a) is a plan view of the outer lid 100, Figure 1(b) is a front view of the outer lid 100, Figure 2(a) is an A-A end view, and Figure 2(b) is an enlarged end view of the vicinity of the outer lid-side fitting portion 140 in the AA end view.

[0015] As shown in Figures 1 and 2, outer lid 100 is made of a synthetic resin sheet, has a shallow dish shape that opens downward, and is generally circular in plan view. It includes a flat, horizontally extending top portion 110, a peripheral wall portion 120 that extends downward from top portion 110, a flange portion 130 that extends outward from peripheral wall portion 120, and an inwardly concave outer lid-side fitting portion 140 that is provided between a lower end 121 of peripheral wall portion 120 and flange portion 130. An arc-shaped portion 150 is provided between lower end 121 of peripheral wall portion 120 and outer lid-side fitting portion 140. Peripheral wall portion 120, flange portion 130, outer lid-side fitting portion 140, and arc-shaped portion 150 are provided continuously or intermittently around the entire periphery of outer lid 100. Furthermore, although the outer lid 100 has a substantially circular shape in plan view, it is not limited to this and may have a square shape in plan view or any other shape.

[0016] Furthermore, the outer lid side fitting portion 140 has an arc shape, and an upper end 141 is continuous with the flange portion 130. Furthermore, the outer lid side fitting portion 140 is configured so that it can be internally fitted into an inner lid side fitting portion 240 of the inner lid 200, which will be described later, and a container side fitting portion 340 of the container body 300. Although the outer lid side fitting portion 140 has an arc shape, it is not limited to this and may have any shape as long as it can be internally fitted into the inner lid side fitting portion 240 of the inner lid 200 and the container side fitting portion 340 of the container body 300.

[0017] The arc-shaped portion 150 is disposed below the outer lid-side fitting portion 140, and the upper end 151 of the arc-shaped portion 150 is connected to the lower end 142 of the outer lid-side fitting portion 140, with the connecting portion being convex outward. The lower end 152 of the arc-shaped portion 150 is connected to the lower end 121 of the peripheral wall portion 120 via the flat portion 122.

[0018] Furthermore, protrusions 112 are provided intermittently on the outer edge 111 of the top portion 110 of the outer lid 100. These protrusions 112 protrude above the top portion 110, and prevent the bottom of another container from coming into contact with the protrusions 112 and falling when another container is stacked on the outer lid 100. Furthermore, a knob 131 is provided on a part of the flange portion 130, extending further to the side than the flange portion 130.

[0019] The outer lid 100 is made by sheet molding (e.g., vacuum molding, compressed air molding, hot plate molding) using a sheet-shaped synthetic resin with a thickness of approximately 0.1 mm to 1.0 mm (millimeters).For example, the material for the outer lid 100 can be polystyrene, polypropylene, polyethylene, A-PET, polylactic acid, or biaxially oriented versions of these.

[0020] Next, Figures 3 and 4 show the inner lid 200 of the container 400 according to the present invention. Figure 3(a) is a plan view of the inner lid 200, Figure 3(b) is a front view of the inner lid 200, Figure 4(a) is a B-B end view, and Figure 4(b) is an enlarged end view of the vicinity of the inner lid-side fitting portion 240 in the B-B end view.

[0021] 3 and 4, inner lid 200 is made of a synthetic resin sheet, has a shallow dish shape that opens upward, and is generally circular in plan view. It includes a flat, horizontally extending bottom 210, a peripheral wall 220 that extends upward from bottom 210, a flange 230 that extends outward from peripheral wall 220, and an inwardly convex inner lid fitting portion 240 that is provided on the inner surface of peripheral wall 220 near its upper end 223. In addition, upper end 223 of inner lid 200 is provided with an upper arc-shaped portion 250 and a lower arc-shaped portion 260. The interior of inner lid 200 is an inner lid-side storage portion 290 that is surrounded by bottom 210 and peripheral wall 220. The peripheral wall portion 220, the flange portion 230, the inner lid side fitting portion 240, the arc-shaped portion 250, and the arc-shaped portion 260 are provided continuously or discontinuously around the entire circumferential direction of the inner lid 200. Furthermore, although the inner lid 200 has a substantially circular shape in a plan view, it is not limited to this and can have a square shape in a plan view or any other shape.

[0022] Furthermore, inner lid side fitting portion 240 has an arc shape, and an upper end 241 of inner lid side fitting portion 240 is positioned higher than flange portion 230, and is continuous with flange portion 230 via step portion 232. Although inner lid side fitting portion 240 has an arc shape, it is not limited to this and may have any shape as long as outer lid side fitting portion 140 of outer lid 100 can be internally fitted into inner lid side fitting portion 240.

[0023] Furthermore, the arc-shaped portion 250 is disposed below the inner lid side fitting portion 240, and an upper end 251 of the arc-shaped portion 250 and a lower end 242 of the inner lid side fitting portion 240 are connected by a planar connecting portion 224. Therefore, the shape of the outer surface of the peripheral wall portion 220 is such that the upper portion is flat and not recessed due to the connecting portion 224, and the lower portion is recessed inward in an arc-like shape due to the arc-shaped portion 250.

[0024] Furthermore, arc-shaped portion 260 is disposed below arc-shaped portion 250, and an upper end 261 of arc-shaped portion 260 and a lower end 252 of arc-shaped portion 250 are connected by a planar connecting portion 225. Therefore, the shape of the outer surface of peripheral wall portion 220 is such that the upper portion is flat and not recessed due to connecting portion 225, and the lower portion is recessed inward in an arc-like shape due to arc-shaped portion 260. Furthermore, lower end 262 of arc-shaped portion 260 is connected to step portion 222.

[0025] Furthermore, a portion of the peripheral wall 220 below the inner lid-side fitting portion 240 (for example, a step portion 222 of the peripheral wall 220) is provided with a ventilation portion 280 that allows steam and the like from the contents stored in the inner lid-side storage portion 290 to escape. The ventilation portion 280 has a downwardly recessed shape, so that, as will be described later, even when the outer lid 100 is internally fitted into the inner lid 200, the ventilation portion 280 is not blocked by the outer lid-side fitting portion 140 of the outer lid 100, etc., and therefore, steam and the like that occurs when the contents in the inner lid 200 are heated can escape through the ventilation portion 280. Furthermore, when the outer lid 100 is internally fitted into the inner lid 200, air can escape from the ventilation portion 280 inside the inner lid 200, making it easy to internally fit the outer lid 100 into the inner lid 200. Furthermore, a knob portion 231 that extends further to the side than the flange portion 230 is provided on a part of the flange portion 230 .

[0026] The inner lid 200 is made by sheet molding (e.g., vacuum molding, pressure molding, hot plate molding) using a sheet-shaped synthetic resin with a thickness of approximately 0.1 mm to 1.0 mm (millimeters).For example, the material for the inner lid 200 can be polystyrene, polypropylene, polyethylene, A-PET, polylactic acid, or biaxially stretched versions of these.

[0027] Next, Fig. 5 and Fig. 6 show the container body 300 of the container 400 according to the present invention. Fig. 5(a) is a plan view of the container body 300, Fig. 5(b) is a front view of the container body 300, Fig. 6(a) is a CC end view, and Fig. 6(b) is an enlarged end view of the vicinity of the container-side fitting portion 340 in the CC end view.

[0028] As shown in FIGS. 5 and 6 , the container body 300 is made of a synthetic resin sheet, has a deep dish shape that opens upward, and is generally circular in plan view. The container body 300 includes a flat, horizontally extending bottom 310, a peripheral wall 320 that extends upward from the bottom 310, a flange 330 that extends outward from the peripheral wall 320, and an inwardly convex container-side fitting portion 340 provided on the inner surface of the peripheral wall 320 near the upper end 323. An arc-shaped portion 350 is also provided at the upper end 323 of the container body 300. The interior of the container body 300 forms a container-side storage portion 390 surrounded by the bottom 310 and the peripheral wall 320. The peripheral wall 320, the flange 330, the container-side fitting portion 340, and the arc-shaped portion 350 are provided continuously or intermittently around the entire periphery of the container body 300. Furthermore, although the container body 300 has a substantially circular shape in plan view, it is not limited to this and may have a square shape in plan view or any other shape.

[0029] Furthermore, the container-side fitting portion 340 has an arc shape, and an upper end 341 of the container-side fitting portion 340 is positioned higher than the flange portion 330, and is continuous with the flange portion 330 via a step portion 332. Note that although the container-side fitting portion 340 has an arc shape, it is not limited to this and may have any shape as long as the outer lid-side fitting portion 140 of the outer lid 100 can be internally fitted into the container-side fitting portion 340 and a portion of the outer surface of the peripheral wall portion 220 of the inner lid 200 can be internally fitted into the container-side fitting portion 340.

[0030] Furthermore, arc-shaped portion 350 is disposed below container-side fitting portion 340, and upper end 351 of arc-shaped portion 350 and lower end 342 of container-side fitting portion 340 are connected by planar connecting portion 324. Therefore, the shape of the inner surface on the upper end 323 side of peripheral wall portion 320 is an arc-shaped portion that protrudes inward at the top due to container-side fitting portion 340, a flat surface without recesses at the middle due to connecting portion 324, and an arc-shaped portion that protrudes inward at the bottom due to arc-shaped portion 350.

[0031] Furthermore, a lower end 352 of the arc-shaped portion 350 is connected to the step portion 322. Furthermore, a part of the peripheral wall portion 320 below the container-side fitting portion 340 (for example, the step portion 322 of the peripheral wall portion 320) is provided with a vent portion 380 that allows steam and the like of the contents stored in the container-side storage portion 390 to escape. Because the vent portion 380 has a downwardly recessed shape, as will be described later, even when the outer lid 100 or the inner lid 200 is internally fitted into the container body 300, the vent portion 380 is not blocked by the outer lid-side fitting portion 140 of the outer lid 100 or the inner lid 200, etc., and therefore steam and the like generated when the contents in the container body 300 are heated can escape through the vent portion 380. Furthermore, when fitting the outer lid 100 or the inner lid 200 into the container body 300, air can be released from the container-side storage section 390 through the ventilation section 380, making it easy to fit the outer lid 100 or the inner lid 200 into the container body 300. Furthermore, a knob section 331 that extends further to the side than the flange section 330 is provided on a part of the flange section 330.

[0032] The container body 300 is formed by sheet molding (e.g., vacuum molding, compressed air molding, hot plate molding) using a sheet-shaped synthetic resin with a thickness of approximately 0.1 mm to 1.0 mm (millimeters). For example, the material for the container body 300 may be polystyrene, polypropylene, polyethylene, A-PET, polylactic acid, or biaxially oriented versions of these.

[0033] 7 and 8 show a state in which the container body 300 is closed by the inner lid 200 and the inner lid 200 is closed by the outer lid 100 in the container 400 of the present invention. Note that Fig. 7 is a front view of the container 400 with each part separated, Fig. 8(a) is a plan view of the container 400, and Fig. 8(b) is a D-D end view.

[0034] As shown in Figures 7 and 8, with food placed inside the container-side accommodating section 390 of the container body 300, the container-side accommodating section 390 is closed with the inner lid 200. At this time, a part of the peripheral wall 220 of the inner lid 200 (the arc-shaped section 250 in Figure 8) is internally fitted into the container-side fitting section 340 provided on the inner surface of the peripheral wall 320 of the container body 300. Also, with food placed inside the inner lid-side accommodating section 290 of the inner lid 200, the inner lid-side accommodating section 290 is closed with the outer lid 100. At this time, a part of the outer lid 100 (the outer lid-side fitting section 140 in Figure 8) is internally fitted into the inner lid-side fitting section 240 provided on the inner surface of the peripheral wall 220 of the inner lid 200. Therefore, the inner lid-side housing portion 290 of the inner lid 200 and the container-side housing portion 390 of the container body 300 are sealed in an internally fitted manner, effectively preventing leakage of liquid from the contents. Furthermore, as shown in FIG. 8(b), the container-side fitting portion 340 of the container body 300 and the inner lid-side fitting portion 240 of the inner lid 200 are vertically spaced apart from each other, making it easy to separately disengage the outer lid 100 from the inner lid 200 and the inner lid 200 from the container body 300. Specifically, the outer lid 100 can be easily removed alone while the inner lid 200 remains attached to the container body 300. Furthermore, the container 400 without the container body 300, i.e., the container 400 consisting of the outer lid 100 and the inner lid 200, can also be used independently.

[0035] Furthermore, since the inner lid-side fitting portion 240 of the inner lid 200 is disposed on the opening side of the upper end of the peripheral wall portion 220, the inner lid-side fitting portion 240 does not restrict the structure of the inner lid-side accommodating portion 290, allowing for a simple structure while ensuring the inner lid-side accommodating portion 290. Similarly, since the container-side fitting portion 340 of the container body 300 is disposed on the opening side of the upper end of the peripheral wall portion 320, the container-side fitting portion 340 does not restrict the structure of the container-side accommodating portion 390, allowing for a simple structure while ensuring the container-side accommodating portion 390.

[0036] Furthermore, the container-side fitting portion 340 of the container body 300 has an arc-shaped longitudinal cross section (a plane perpendicular to the bottom 310), which matches the shape of the outer surface of the peripheral wall portion 220 of the inner lid 200 (arc-shaped portion 250 in FIG. 8). Furthermore, the inner lid-side fitting portion 240 of the inner lid 200 has an arc-shaped longitudinal cross section (a plane perpendicular to the bottom 210), which matches the shape of the outer lid-side fitting portion 140 of the outer lid 100. As such, the arc-shaped fitting portion provides high adhesion, which more effectively prevents leakage of liquid from the contents. Note that if the openings of the outer lid 100, inner lid 200, and container body 300 were circular, there is a risk that the fitting would easily come loose due to external impact; however, because the fitting portions are arc-shaped, they can flexibly absorb impact and prevent accidental loosening. Furthermore, since the container body 300 is tall and bowl-shaped, there is a risk that it may easily tip over during transportation, but since the mating parts are arc-shaped and provide high adhesion, liquid leakage can be effectively prevented when the container body 300 tips over.

[0037] Furthermore, the lower arc-shaped portion 350 of the container-side fitting portion 340 matches the shape of the arc-shaped portion 260 of the inner lid 200, providing a high degree of adhesion between the arc-shaped portion 350 and the arc-shaped portion 260, further effectively preventing leakage of liquid from the contents. In particular, the upper container-side fitting portion 340 and the lower arc-shaped portion 350 provide doubly effective leakage prevention. Furthermore, the step portion 222 of the inner lid 200 and the step portion 322 of the container body 300 are spaced apart vertically, leaving a slight gap. Therefore, even if the step portion 222 bends downward due to the weight of the contents in the inner lid-side storage portion 290 or the step portion 222 or the step portion 322 is deformed by an external force, the step portions 222 and 322 are unlikely to come into contact with each other and can absorb stress by moderate elastic deformation. As a result, the adhesion between the container side fitting portion 340 and the arc-shaped portion 250, and the adhesion between the arc-shaped portion 350 and the arc-shaped portion 260 are less likely to be affected, and liquid leakage can be prevented more effectively.

[0038] Furthermore, because the connecting portion 324 is disposed between the container-side fitting portion 340 and the arc-shaped portion 350, stresses acting around the container-side fitting portion 340 and the arc-shaped portion 350 are absorbed by the intermediate connecting portion 324, making it difficult for the container-side fitting portion 340 and the arc-shaped portion 350 to deform. As a result, the adhesion between the container-side fitting portion 340 and the arc-shaped portion 350 is less affected, and liquid leakage can be prevented more effectively.

[0039] Furthermore, there is a small gap between the arc-shaped portion 150 on the underside of the outer lid-side fitting portion 140 of the outer lid 100 and the arc-shaped portion 250 of the inner lid 200. For example, when removing the inner lid 200 from the container body 300 while the outer lid 100 is still attached, the flange portion 230 of the inner lid 200 is pinched with the fingers and a force is applied as if lifting, thereby disengaging the arc-shaped portion 250 of the inner lid 200 from the container-side fitting portion 340 of the container body 300. At this time, the periphery of the arc-shaped portion 250 of the inner lid 200 elastically deforms, but the gap makes it difficult for the arc-shaped portion 250 to come into contact with the arc-shaped portion 150 of the outer lid 100. As a result, stress during elastic deformation is not transmitted from the arc-shaped portion 150 of the outer lid 100 to the outer lid-side fitting portion 140, preventing the outer lid 100 from being accidentally removed. Then, the inner lid 200 can be easily removed from the container body 300 while the outer lid 100 remains attached.

[0040] 9 and 10 show an embodiment in which the outer lid 100 directly closes the container body 300 in the container 400 of the present invention. Note that Fig. 9 is a front view of the container 400 with each part separated, Fig. 10(a) is a plan view of the container 400, and Fig. 10(b) is an end view taken along the line E-E.

[0041] 9 and 10, with food placed in the container-side storage section 390 of the container body 300, the container-side storage section 390 is closed with the outer lid 100. At this time, the outer lid-side fitting section 140 of the outer lid 100 fits into the container-side fitting section 340 provided on the inner surface of the peripheral wall section 320 of the container body 300, creating a tight seal, effectively preventing leakage of liquid from the contents. In this way, the container 400 with the inner lid 200 removed, i.e., the container 400 consisting of the outer lid 100 and the container body 300, can also be used independently.

[0042] Furthermore, the container-side fitting portion 340 of the container body 300 has an arc-shaped longitudinal cross section, which is similar in shape to or coincides with the shape of the outer lid-side fitting portion 140 of the outer lid 100. Because the fitting portion is arc-shaped and provides high adhesion, leakage of liquid from the contents can be more effectively prevented. Furthermore, the lower arc-shaped portion 350 of the container-side fitting portion 340 matches the shape of the arc-shaped portion 150 of the outer lid 100, providing high adhesion between the arc-shaped portion 350 and the arc-shaped portion 150, further effectively preventing leakage of liquid from the contents. In particular, the upper container-side fitting portion 340 and the lower arc-shaped portion 350 provide doubly effective leakage prevention.

[0043] The container of the present invention is not limited to the above examples, and various modifications and combinations are possible within the scope of the claims and the scope of the embodiments, and these modifications and combinations are also included in the scope of rights.

Claims

1. A container body; an inner lid that fits into the container body to close the container-side storage section of the container body; A container comprising: an outer lid that can be fitted into the inner lid to close an inner lid-side storage portion of the inner lid, and an outer lid that can be fitted into the container body to also close a container-side storage portion of the container body, the container body includes a container-side fitting portion, into which the inner lid is fitted, on the inner surface side of the peripheral wall portion of the container-side storage portion; The inner lid includes an inner lid-side fitting portion, into which the outer lid is fitted, on the inner surface side of the peripheral wall portion of the inner lid-side housing portion, A container characterized in that, when the inner lid closes the container body, a container-side fitting portion of the container body and an inner lid-side fitting portion of the inner lid are spaced apart from each other vertically.

2. the container-side fitting portion of the container body has a longitudinal cross section that is arc-shaped and that matches the shape of the outer surface of the peripheral wall portion of the inner lid; 2. The container according to claim 1, wherein the inner lid side fitting portion of the inner lid has an arc-shaped longitudinal section and is identical in shape to the outer lid side fitting portion of the outer lid.

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