Paper cup compatible with microwave oven

Abstract

To provide a paper cup which is hardly burned when used in a microwave and can self-stand stably.SOLUTION: A paper cup compatible with microwave comprises a shank 11 in a truncated cone shape and a bottom part 12 closing a lower end of the shank 11. The lower end of the shank 11 is bent to the inside and an annular bent part 20 is put on an outer surface of the bottom part 12. A plurality of concave parts 22 and convex parts 21 are alternately formed on an outer surface of the annular bent part 20. The annular bent part 20 and the outer surface of the bottom part 12 are in a close contact at the concave part 22. On the other hand, a gap 25 is formed between the annular bent part 20 and the outer surface of the bottom part 12 at the convex part 21.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] This invention relates to a paper cup (paper container) compatible with a microwave oven. Being compatible with a microwave oven means it can be used in a microwave oven, and it is not intended to be limited to use only in a microwave oven.

Background Art

[0002] Paper cups are widely used not only as containers for instant foods and snack foods but also for beverages, prepared foods, etc. There are cases where foods, drinking water, etc. are put in these paper cups and then heated or cooked in a microwave oven.

[0003] When a paper cup containing contents is heated or cooked in a microwave oven, there is a problem that burning may occur in a so-called thread rim portion formed by extending the lower end portion of the body of the paper cup. In particular, at the joint portion where the paper overlaps, the amount of heat generated increases (the amount of heat dissipated does not increase), heat is easily stored, and burning is likely to occur. On the other hand, in the portion in contact with the contents, the generated heat is taken away by the contents, so burning is less likely to occur.

[0004] Patent Document 1 describes a paper cup for a microwave oven composed of a body and a bottom, in which the lower end portion (thread rim) of the body is bent inward and joined to the peripheral edge portion of the bottom so as to cover it from the outside.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] An embodiment is disclosed in which the lower part of the thread edge is bent inward at an angle of 90 degrees, and a concave wedge is provided at the bent part. The wedge is formed in a concave shape that becomes deeper towards the tip. By providing the wedge, wrinkles generated when bending the bent part are absorbed and reduced. The wedge (concave part) is set to such an extent that the generation of wrinkles is less noticeable, and is preferably provided at 4 to 8 locations at equal intervals.

[0007] To bend only the lower part of the thread edge inward requires higher processing accuracy compared to bending the entire thread edge inward. Also, after bending only the lower part of the thread edge inward at an angle of 90 degrees, when forming 4 to 8 wedges (concave parts), unevenness is likely to occur around the wedges, and there is a high possibility of lacking self-standing stability.

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of this invention is to provide a paper cup that is not easily burned even when used in a microwave oven and can stably stand on its own.

[0009] Another object of this invention is to improve the adhesion between the bent part and the bottom surface of the cup.

Means for Solving the Problems

[0010] The paper cup compatible with a microwave oven according to this invention includes a cylindrical body part and a bottom part that closes the lower end of the body part. The lower end part of the body part is bent inward, and a plurality of concave surface parts and convex surface parts are alternately formed on the outer surface of the lower end part of the body part bent inward. The outer surface of the lower end part of the body part and the outer surface of the bottom part are in close contact with each other in the concave surface part, and a gap is formed between the outer surface of the lower end part of the body part and the outer surface of the bottom part in the convex surface part.

[0011] The lower end part of the body part (thread edge) bent inward is covered on the outer surface of the bottom part. If the cylindrical body part is cylindrical and the bottom part that closes the lower end of the cylindrical body part is circular, the lower end part of the body part bent on the outer peripheral edge of the outer surface of the circular bottom part is covered in a ring shape.

[0012] According to the present invention, a plurality of concave portions and convex portions are alternately formed on the outer surface of the lower end portion of the body portion bent inward. In the concave portion, since the outer surfaces of the lower end portion of the body portion and the bottom portion are in close contact, when the contents are heated in a microwave oven, the heat generation at the contact portion is transmitted (radiated) to the contents, and thus it is difficult to burn even when heated in a microwave oven.

[0013] On the other hand, unlike the concave portion, in the convex portion, the outer surfaces of the lower end portion of the body portion and the bottom portion are not in close contact, and a gap is formed between the lower end portion of the body portion and the outer surface of the bottom portion. Although heat dissipation cannot be expected at the location of the convex portion compared to the location of the concave portion, since a plurality of concave portions and convex portions are alternately formed and the convex portion is sandwiched by the concave portions on its left and right, the heat generation at the location of the convex portion is transmitted to and taken away by the contents in the adjacent concave portions on both sides, and it is also difficult for burning to occur at the location of the convex portion when heated in a microwave oven.

[0014] Also according to the present invention, the surplus portion generated at the lower end portion of the body portion when the lower end portion of the body portion bent inward is absorbed by the gap formed in the convex portion, and random wrinkles are less likely to occur on the lower end portion of the body portion bent inward. This is because the presence of the gap does not fix the positions of the outer surfaces of the lower end portion of the body portion and the bottom portion in the convex portion, and the deformation of the gap can also contribute to the absorption of the surplus portion. The paper cup can be stably self-standing. In addition, by making it less likely for random wrinkles to occur, the adhesion to the bottom surface portion at the location of the concave portion can also be improved.

[0015] Preferably, the lower end portion of the body portion bent inward is bent at an angle exceeding a right angle over the entire circumference. The entire convex portion of the lower end portion of the body portion bent inward does not contact the surface, and at least the outer peripheral edge portion (outer end portion) of the convex portion contacts linearly. Even if a height difference occurs in a plurality of convex portions, the influence is small at the outer peripheral edge portion, and thus the self-standing property of the paper cup can be improved.

[0016] In one embodiment, linear stepped portions are formed at respective boundaries between the concave surface portion and the convex surface portion, and the linear stepped portions are formed in a direction extending toward the center of the bottom portion. By forming the concave surface portion and the convex surface portion on the outer surface of the bottom of the paper cup in a well-balanced manner, the linear stepped portions at the boundaries between the concave surface portion and the convex surface portion extend toward the center of the bottom portion. The self-standing stability of the paper cup is improved.

[0017] Preferably, the linear stepped portion is formed from the tip (inner end) of the lower end portion of the body portion bent inward to the middle of the lower end portion of the body portion (that is, without reaching the outer end of the lower end portion of the body portion). That is, there is no stepped portion on the outer peripheral edge portion of the lower end portion of the body portion bent inward, and no concave surface portion and convex surface portion are formed on the outer peripheral edge portion. When the lower end portion of the body portion is bent at an angle exceeding a right angle over the entire circumference, the entire circumference of the outer peripheral edge portion can be linearly grounded, and the self-standing stability of the paper cup is improved.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, a paper cup compatible with a microwave oven according to the present invention will be described in detail.

[0020] FIG. 1 and FIG. 2 are partial cutaway longitudinal sectional views of the microwave-compatible paper cup according to an embodiment of the present invention, showing longitudinal sections of different portions of the microwave-compatible paper cup, respectively. FIG. 3 is a partially enlarged perspective view of the bottom surface (outer side) of the microwave-compatible paper cup. In FIGS. 1 and 2, for clarity, the thicknesses of the members constituting the paper cup are emphasized and shown.

[0021] Referring to FIGS. 1 and 2, the microwave-compatible paper cup 10 is composed of a body member 11 and a bottom member 12 mainly made of paper. The body member 11 has a frustoconical shape with a larger diameter at the upper part and a smaller diameter downward. The upper end portion of the body member 11 is wound outward (in a direction away from the portion where the contents of the paper cup 10 are placed, outward), and a so-called curl portion (top curl portion) 11A is formed. A lid (not shown) is placed on or joined (adhered, welded) to the curl portion 11A.

[0022] The lower end portion of the body member 11 is bent at an angle slightly exceeding a right angle (90 degrees) inward (in a direction toward the portion where the contents of the paper cup 10 are placed, inward) (the bent portion is indicated by reference numeral 11B), and further, the tip portion of the bent portion 11B is folded back inward (the folded-back portion is indicated by reference numeral 11C). The bottom member 12 is circular, and its peripheral portion 12A fits snugly inside the lower end portion of the body member 11. The peripheral portion 12A of the bottom member 12 is folded back outward (the folded-back portion is indicated by reference numeral 12B), and the folded-back portion 12B of the bottom member 12 is sandwiched between the bent portion 11B and the folded-back portion 11C of the body member 11.

[0023] Depending on the contents, a protective film (such as a resin film, resin sheet, etc.) is coated on the inner surface and / or outer surface of the body member 11 and the bottom member 12 as necessary. Specific examples of the protective film include, for example, polyethylene (PE), polypropylene (PP), polyester, ethylene-vinyl acetate copolymer, etc. These also have the advantage that they can be used for bonding by heat sealing.

[0024] At the peripheral edge of the outer surface of the bottom member 12 of the paper cup 10, an annular portion is covered where the bent portion 11B and the folded-back portion 11C of the body member 11 and the folded-back portion 12B of the bottom member 12 overlap. Hereinafter, the entire annular portion covering the outer peripheral edge of the outer surface of the bottom member 12 of the paper cup 10 is referred to as the "annular bent portion 20".

[0025] Referring to FIG. 3, on the surface (outer surface) of the annular bent portion 20, convex portions 21 and concave portions 22 that are substantially rectangular (with a slightly narrower width on the tip (inner end) side) are alternately formed and arranged annularly. As shown in FIG. 3, the convex portions 21 and the concave portions 22 may have the same shape, or the width of the convex portions 21 may be wider and the width of the concave portions 22 may be narrower, or vice versa. For example, 16 convex portions 21 and 16 concave portions 22 are alternately arranged. The number of the convex portions 21 and the concave portions 22 can be adjusted as appropriate.

[0026] FIG. 1 shows a cross-sectional view at the location of the convex portion 21, and FIG. 2 shows a cross-sectional view at the location of the concave portion 22, respectively.

[0027] Referring to FIGS. 1 and 3, at the location of the convex portion 21, the bent portion 11B and the folded-back portion 11C at the lower end of the body member 11 and the folded-back portion 12B of the bottom member 12 sandwiched therebetween are entirely joined (adhered, welded) (fixed) to each other. On the other hand, the outer surface of the peripheral portion 12A of the bottom member 12 and the folded-back portion 11C are not joined, and a gap 25 is formed between the peripheral portion 12A of the bottom member 12 and the folded-back portion 11C.

[0028] Referring to FIGS. 2 and 3, at the location of the concave portion 22, the portions 12A, 11C, 12B, and 11B that sandwich each other are all entirely joined (adhered, welded) (fixed) to each other.

[0029] Referring to FIGS. 1 to 3, both the plurality of convex portions 21 and the plurality of concave portions 22 are slightly inclined so as to approach the bottom member 12 as they go toward the inside of the paper cup 10. In any of the plurality of convex portions 21 and the plurality of concave portions 22, that is, over the entire circumference of the annular bent portion 20, its outer end portion 28 (outer peripheral edge portion) protrudes most outwardly (toward the bottom of the paper cup 10), and the inner end portion 29 (inner peripheral tip portion) is located above the outer end portion 28 (near the bottom member 12). The outer end portion 28 of the annular bent portion 20 of the paper cup 10 is in contact with the ground.

[0030] A linear step portion 27 is formed at the boundary between the convex portion 21 and the concave portion 22 in a direction extending toward the center of the bottom member 12. That is, both the convex portion 21 and the concave portion 22 formed in the annular bent portion 20 are slightly narrower in width at the inner end portion 29 than at the outer end portion 28.

[0031] The linear step portion 27 is not formed over the entire annular bent portion 20, but is formed only up to midway from the inner end portion 29 to the outer end portion 28 of the annular bent portion 20 and does not reach the outer end portion 28 (outer edge). That is, there is no step portion at the outer end portion 28 of the annular bent portion 20, and the convex portion 21 and the concave portion 22 are not formed at the outer end portion 28 of the annular bent portion 20.

[0032] If the annular bent portion 20 is simply bent inward without any treatment, wrinkles will randomly occur in the annular bent portion 20 due to the surplus portion. When wrinkles occur randomly, it is difficult for the bottom of the paper cup to become flat, and the paper cup lacks stability when standing on its own. On the contrary, in the above-described paper cup 10, a plurality of convex portions 21 and concave portions 22 are arranged alternately and annularly. In the convex portion 21, the annular bent portion 20 is not adhered to the outer surface of the bottom member 12 (there is a gap), so their relative positions are not fixed. Furthermore, since the deformation of the gap 15 is also possible, when the annular bent portion 20 is bent inward, the surplus portion generated in the annular bent portion 20 is absorbed. Of course, at the linear step portion 27 between the convex portion 21 and the concave portion 22, the surplus portion when the annular bent portion 20 is bent inward is also absorbed. Random wrinkles do not occur or are difficult to occur in the annular bent portion 20, and thus the paper cup 10 can stand stably on its own.

[0033] When random wrinkles occur in the annular bent portion 20, poor adhesion is likely to occur between the annular bent portion 20 and the outer surface of the bottom member 12. By suppressing the occurrence of random wrinkles as described above, the annular bent portion 20 (the folded-back portion 11C of the body member 11) can be firmly and reliably adhered to the peripheral portion 12A of the bottom member 12 of the paper cup 10 at the location of the concave portion 22, and the annular bent portion 20 and the bottom member 12 of the paper cup 10 can be firmly joined within the adhered range. Therefore, the problem of poor adhesion between the bottom member 12 and the annular bent portion 20 is unlikely to occur. Furthermore, since the paper cup 10 does not have a thread edge, it is not easily burned even when heated in a microwave oven.

[0034] Since a gap 25 is formed at the location of the convex portion 21, unlike the location of the concave portion 22, the location of the convex portion 21 does not contribute to adhering (maintaining the bent state) the annular bent portion 20 to the bottom member 12 of the paper cup 10. However, by forming a plurality of concave portions 22 on the annular bent portion 20 (moreover, dispersing them on the annular bent portion 20 without concentrating them locally), the state in which the entire annular bent portion 20 including the convex portion 21 is bent inward can be firmly maintained.

[0035] As described above, the presence of the gap 25 can absorb the surplus portion that causes wrinkles in the annular bent portion 20, preventing random wrinkles from occurring in the annular bent portion 20, and it has been confirmed that this enhances the adhesion (prevents unintentional peeling).

[0036] Furthermore, since the outermost protruding part at the bottom surface of the annular bent portion 20 is the circular outer end portion 28, the paper cup 10 can be firmly self-standing by the outer end portion 28.

[0037] Figs. 4 to 6 show the manufacturing state of the above-described paper cup 10. Figs. 4 to 6 show the paper cup 10 in an upside-down state.

[0038] Referring to Fig. 4, first, a paper cup with a so-called thread edge, in which the annular bent portion 20 is not bent, is created.

[0039] Referring to Fig. 5, a pressing die having a width obtained by dividing the circumference of the annular bent portion 20, for example, into 32 parts is pressed against the outside of the annular bent portion 20 at predetermined intervals. The pressed portions become the concave portions 22, and the non-pressed portions become the convex portions 21. Sixteen convex portions 21 and sixteen concave portions 22 are alternately formed in an annular shape on the annular bent portion 20. By being pressed from the outside, the entire annular bent portion 20 tilts slightly inward.

[0040] Referring to Fig. 6, ultrasonic pressing is performed from the outside of the annular bent portion 20 that is tilted inward. The annular bent portion 20 is completely bent (at an angle exceeding 90 degrees). As described above, the portions of the concave portions 22 are joined to the outer surface of the bottom member 12 (see also Fig. 2), while gaps 25 are left at the portions of the convex portions 21 (see also Fig. 1). Also, a linear stepped portion 27 is formed at the boundary between the convex portion 21 and the concave portion 22. The electronic range-compatible paper cup 10, which is firmly supported by the outer end portion 28 of the annular bent portion 20, is completed.

Explanation of Reference Numerals

[0041] 10 Electronic range-compatible paper cup 11 Body member 12 Bottom member 20 Annular bending part 21 Convex surface part 22 Concave surface part 25 Gap 27 Linear step part 28 Outer end part 29 Inner end part

Claims

1. A cup having a cylindrical body and a bottom closing the lower end of the body, wherein the lower end of the cylindrical body is bent inward, wherein a plurality of concave portions and convex portions are alternately formed on the outer surface of the inwardly bent lower end of the cylindrical body, wherein the lower end of the cylindrical body and the outer surface of the bottom are in close contact with each other in the concave portion, wherein a gap is formed between the lower end of the cylindrical body and the outer surface of the bottom in the convex portion, wherein the inwardly bent lower end of the cylindrical body is bent at an angle exceeding a right angle over the entire circumference, and the outer peripheral tip of the lower end of the cylindrical body protrudes outward more than the inner peripheral tip of the bent lower end of the cylindrical body, wherein linear stepped portions extending toward the center of the bottom and gradually becoming deeper as they extend toward the center of the bottom are formed at respective boundaries between the concave portions and the convex portions, A paper cup compatible with a microwave oven.

2. The linear stepped portion is formed from the tip of the inwardly bent lower end of the cylindrical body to the middle of the lower end of the cylindrical body, The paper cup compatible with a microwave oven according to Claim 1.

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