JP7683263B2 - Microwave safe paper cups - Google Patents

Description

This invention relates to a microwave-safe paper cup (paper container). Microwave-safe means that it can be used in a microwave oven, but is not intended to be limited to use only in microwave ovens.

Paper cups are widely used not only for ready-to-eat foods and snacks, but also for beverages, prepared foods, etc. In some cases, food, beverages, etc. are heated and cooked in a microwave oven while still in these paper cups.

When a paper cup containing food is heated and cooked in a microwave oven, there is a problem that the threads formed by extending the bottom end of the body of the paper cup can burn. In particular, the joints where the paper overlap generate a large amount of heat (the amount of heat released is not large), and it is thought that heat is easily stored and burning is likely to occur in these joints. On the other hand, the heat generated in the parts that come into contact with the food is absorbed by the food, so burning is less likely to occur.

Patent Document 1 describes a paper cup for use in a microwave oven that is composed of a body and a bottom, with the lower end (thread edge) of the body bent inward and joined to cover the outer periphery of the bottom.

JP 2002-345639 A

An embodiment is disclosed in which the lower part of the thread end is bent inward at a 90 degree angle, 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 that occur when the bent part is folded are absorbed and reduced. The wedges (concave parts) are set to a size that makes wrinkles less noticeable, and are preferably provided at 4 to 8 equally spaced locations.

Bending only the lower part of the thread end inward requires higher processing precision than bending the entire thread end inward. In addition, if four to eight wedges (concave parts) are formed after bending only the lower part of the thread end inward at a 90-degree angle, unevenness tends to form around the wedges, making the product highly likely to lack self-supporting stability.

The purpose of this invention is to provide a paper cup that is unlikely to burn when used in a microwave oven and can stand stably on its own.

The invention also aims to improve adhesion between the bent portion and the bottom surface of the cup.

The microwave-safe paper cup of this invention has a cylindrical body and a bottom that closes the lower end of the body, the lower end of the body is bent inward, and multiple concave and convex portions are formed alternately on the outer surface of the inwardly bent lower end of the body, the lower end of the body and the outer surface of the bottom are in close contact with each other at the concave portions, and a gap is formed between the lower end of the body and the outer surface of the bottom at the convex portions.

The lower end of the body, which is bent inward (the thread tip), is placed over the outer surface of the bottom. If the tubular body is cylindrical and the bottom that closes the lower end of the tubular body is circular, the bent lower end of the body is placed in a ring shape over the outer peripheral edge of the outer surface of the circular bottom.

According to this invention, multiple concave and convex sections are formed alternately on the outer surface of the inwardly bent lower end of the body. In the concave sections, the lower end of the body and the outer surface of the bottom are in close contact with each other, so when the contents are heated in a microwave oven, heat is transferred (dissipated) from the contact area to the contents, making them less likely to burn when heated in a microwave oven.

On the other hand, unlike the concave portion, in the convex portion, the lower end of the body and the outer surface of the bottom are not in close contact with each other, and a gap is formed between the lower end of the body and the outer surface of the bottom. Although the convex portion is not expected to dissipate heat as much as the concave portion, multiple concave and convex portions are formed alternately, and the convex portion is sandwiched between concave portions on the left and right, so the heat generated in the convex portion is transferred to and absorbed by the contents in the adjacent concave portions on both sides, and the convex portion is less likely to burn when heated in a microwave oven.

Furthermore, according to this invention, the gap formed in the convex portion absorbs the excess portion that occurs at the lower end of the body when the lower end of the body is folded inward, making it less likely that random wrinkles will occur at the lower end of the body that is folded inward. This is because the presence of the gap prevents the lower end of the body and the outer surface of the bottom from being fixed in position at the convex portion, and deformation of the gap can also contribute to absorbing the excess portion. The paper cup can stand on its own stably. Furthermore, by making it less likely that random wrinkles will occur, it is possible to improve adhesion to the bottom portion at the concave portion.

Preferably, the inwardly bent lower end of the body is bent at an angle greater than a right angle around the entire circumference. The entire convex surface of the inwardly bent lower end of the body does not contact the ground in a flat manner, but at least the outer periphery (outer end) of the convex surface contacts the ground in a linear manner. Even if height differences occur in the multiple convex surface portions, the effect is small on the outer periphery, and therefore the paper cup can stand upright.

In one embodiment, a linear step is formed at each boundary between the concave and convex portions, and the linear step is formed in a direction extending toward the center of the bottom. By forming concave and convex portions in a balanced manner on the outer surface of the bottom of the paper cup, the linear step at the boundary between the concave and convex portions extends toward the center of the bottom. This improves the stability of the paper cup when it stands on its own.

Preferably, the linear step is formed from the tip (inner end) of the inwardly bent lower end of the body to partway along the lower end of the body (i.e., without reaching the outer end of the lower end of the body). In other words, there is no step on the outer peripheral edge of the inwardly bent lower end of the body, and no concave or convex surface is formed on the outer peripheral edge. When the entire circumference of the lower end of the body is bent at an angle exceeding a right angle, the entire circumference of the outer peripheral edge can be linearly grounded, improving the self-supporting stability of the paper cup.

FIG. 2 is a partially cutaway front view of a microwave-safe paper cup. FIG. 2 is a partially cutaway front view of a microwave-safe paper cup. FIG. 2 is a partially enlarged oblique view of the bottom of a microwave-safe paper cup. 4 shows a process for forming an annular bend. 4 shows a process for forming an annular bend. 4 shows a process for forming an annular bend.

The microwave-safe paper cup of this invention will be described in detail below with reference to the drawings.

Figures 1 and 2 are both partially broken vertical cross-sectional views of a microwave-safe paper cup according to an embodiment of the present invention, each showing a vertical cross-section of a different portion of the microwave-safe paper cup. Figure 3 is a partially enlarged perspective view of the bottom (outside) of the microwave-safe paper cup. In Figures 1 and 2, the thickness of the components that make up the paper cup is emphasized for ease of understanding.

Referring to Figures 1 and 2, a microwave-safe paper cup 10 is composed of a body member 11 and a bottom member 12, whose main strength material is paper. The body member 11 is shaped like a truncated cone, with a larger diameter at the top and a smaller diameter toward the bottom. The top end of the body member 11 is curled outward (away from the portion of the paper cup 10 that holds the contents, outward), forming a so-called curled portion (top curl portion) 11A. A lid (not shown) is placed over the curled portion 11A, or it is joined (glued or welded).

The lower end of the body member 11 is bent inward (towards the part of the paper cup 10 that contains the contents) at an angle slightly greater than a right angle (90 degrees) (the bent part is indicated by the reference symbol 11B), and the tip of the bent part 11B is folded back inward (the folded part is indicated by the reference symbol 11C). The bottom member 12 is circular, and its peripheral part 12A fits snugly inside the lower end of the body member 11. The peripheral part 12A of the bottom member 12 is folded back outward (the folded part is indicated by the reference symbol 12B), and the folded part 12B of the bottom member 12 is sandwiched between the bent part 11B and the folded part 11C of the body member 11.

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

The outer peripheral edge of the bottom member 12 of the paper cup 10 is covered with an annular portion where the bent portion 11B and folded portion 11C of the body member 11 overlap with the folded portion 12B of the bottom member 12. Hereinafter, the entire annular portion that covers the outer peripheral edge of the bottom member 12 of the paper cup 10 is referred to as the "annular bent portion 20."

Referring to Figure 3, on the surface (outer surface) of the annular bend 20, convex portions 21 and concave portions 22, each of which is substantially rectangular (slightly narrower at the tip (inner end) side), are alternately formed and arranged in a ring shape. As shown in Figure 3, the convex portions 21 and the concave portions 22 may be of the same shape, or the convex portions 21 may be wider and 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 convex portions 21 and concave portions 22 can be adjusted as appropriate.

Figure 1 shows a cross-sectional view of the convex portion 21, and Figure 2 shows a cross-sectional view of the concave portion 22.

Referring to Figures 1 and 3, at the convex surface 21, the bent portion 11B and folded portion 11C at the lower end of the body member 11 and the folded portion 12B of the bottom member 12 sandwiched between them are completely joined (glued, welded) to each other (fixed). On the other hand, the outer surface of the peripheral portion 12A of the bottom member 12 and the folded portion 11C are not joined, and a gap 25 is formed between the peripheral portion 12A of the bottom member 12 and the folded portion 11C.

Referring to Figures 2 and 3, at the concave surface 22, the sandwiched portions 12A, 11C, 12B, and 11B are all fully joined (glued, welded) (fixed) to each other.

Referring to Figures 1 to 3, the multiple convex portions 21 and multiple concave portions 22 are all slightly inclined toward the bottom member 12 as they move toward the inside of the paper cup 10, and the outer end 28 (outer peripheral edge) of each of the multiple convex portions 21 and multiple concave portions 22, i.e., over the entire circumference of the annular bend 20, protrudes furthest outward (toward the bottom of the paper cup 10), and the inner end 29 (inner peripheral tip) is positioned higher (closer to the bottom member 12) than the outer end 28. The outer end 28 of the annular bend 20 of the paper cup 10 comes into contact with the ground.

A linear step 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. In other words, the width of the convex portion 21 and the concave portion 22 formed in the annular bend portion 20 at the inner end 29 is slightly narrower than the width at the outer end 28.

The linear step 27 is not formed over the entire annular bend 20, but is formed partway from the inner end 29 to the outer end 28 of the annular bend 20, and does not reach the outer end 28 (outer edge). In other words, there is no step at the outer end 28 of the annular bend 20, and the convex surface portion 21 and the concave surface portion 22 are not formed at the outer end 28 of the annular bend 20.

If the annular bent portion 20 is simply bent inward without any processing, the excess portion will randomly wrinkle the annular bent portion 20. If the random wrinkles occur, the bottom of the paper cup will be difficult to flatten, and the paper cup will lack stability when it is made to stand on its own. In contrast, the above-mentioned paper cup 10 has multiple convex and concave portions 21 and 22 arranged alternately and in a ring shape, and since the annular bent portion 20 is not bonded to the outer surface of the bottom member 12 in the convex portion 21 (has a gap), the relative positions are not fixed, and the gap 15 can also be deformed, so that the excess portion that occurs in the annular bent portion 20 when the annular bent portion 20 is bent inward is absorbed. Of course, the linear step portion 27 between the convex portion 21 and the concave portion 22 also absorbs the excess portion when the annular bent portion 20 is bent inward. Random wrinkles do not occur or are unlikely to occur in the annular bent portion 20, which allows the paper cup 10 to stand stably.

If random wrinkles occur in the annular bent portion 20, poor adhesion between the annular bent portion 20 and the outer surface of the bottom member 12 is likely to occur. By suppressing the occurrence of random wrinkles as described above, the annular bent portion 20 (the folded 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 concave portion 22, and the annular bent portion 20 and the bottom member 12 of the paper cup 10 can be firmly joined to the area where they are in close contact. Therefore, 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 threads, it is less likely to burn even when heated in a microwave oven.

Because a gap 25 is formed at the convex portion 21, the convex portion 21, unlike the concave portion 22, does not contribute to bringing the annular bending portion 20 into close contact with the bottom member 12 of the paper cup 10 (maintaining the bent state). However, by forming multiple concave portions 22 on the annular bending portion 20 (and further by forming them on the annular bending portion 20 in a dispersed manner rather than being concentrated locally), the entire annular bending portion 20, including the convex portion 21, can be firmly maintained bent inward.

As described above, it has been confirmed that the presence of the gap 25 can absorb excess material that would cause wrinkles in the annular bend 20, preventing random wrinkles from occurring in the annular bend 20, thereby improving adhesion (preventing unintended peeling).

Furthermore, since the circular outer end 28 is the part that protrudes most outward on the bottom surface of the annular bend 20, the paper cup 10 can be firmly supported by the outer end 28.

Figures 4 to 6 show the manufacturing process of the paper cup 10 described above. Figures 4 to 6 show the paper cup 10 in an upside-down state.

Referring to Figure 4, a paper cup is first created with the annular bend 20 unfolded, i.e., with a thread edge, so to speak.

Referring to Figure 5, a stamping die having a width obtained by dividing the circumference of the annular bent portion 20, for example, by 32, is pressed from the outside of the annular bent portion 20 at a specified interval to press it. The pressed portions become the concave portions 22, and the unpressed portions become the convex portions 21. The annular bent portion 20 is formed with 16 convex portions 21 and 16 concave portions 22 arranged alternately in a ring shape. By pressing from the outside, the entire annular bent portion 20 is slightly tilted inward.

Referring to FIG. 6, ultrasonic pressing is performed from the outside of the annular bent portion 20 that is inclined inward. The annular bent portion 20 is bent completely (at an angle of more than 90 degrees). As described above, the concave portion 22 is bonded to the outer surface of the base member 12 (see also FIG. 2), while a gap 25 is left at the convex portion 21 (see also FIG. 1). In addition, a linear step 27 is formed at the boundary between the convex portion 21 and the concave portion 22. A microwave-safe paper cup 10 that is firmly supported by the outer end 28 of the annular bent portion 20 is completed.

10 Microwave-safe paper cups
11 Body member
12 Bottom member
20 Circular bend
21 Convex part
22 Concave part
25 Gap
27 Linear step
28 Outer end
29 Inner end

Claims (2)

The container has a cylindrical body and a bottom that closes the lower end of the body.
The lower end of the body is bent inward,
A plurality of concave and convex portions are alternately formed on the outer surface of the inwardly bent lower end of the body portion,
The lower end of the body and the outer surface of the bottom are in close contact with each other at the concave portion,
A gap is formed between the lower end of the body and the outer surface of the bottom at the convex portion,
The inwardly bent lower end of the body is bent at an angle exceeding a right angle over the entire circumference, and the outer circumferential tip of the lower end of the body protrudes outward beyond the inner circumferential tip of the bent lower end of the body,
a linear step portion is formed at each boundary between the concave surface portion and the convex surface portion, the linear step portion extending toward the center of the bottom portion and gradually becoming deeper toward the center of the bottom portion;
Microwave safe paper cups. The linear step portion is formed from the tip of the inwardly bent lower end portion of the body portion to a middle of the lower end portion of the body portion.
2. The microwaveable paper cup of claim 1 .

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