Paper lid

Abstract

[Problem] To form a shape with the top surface raised upward, i.e. a dome-like shape, and effectively suppress leakage of content through a wrinkle. [Solution] The present invention is provided with a top surface portion 11, an enclosing portion 12, an outward-extending portion 13, an inner fitting portion 14, a peak portion 15, and an outer fitting portion 16, wherein: the inner surface of a lower section 14a, which forms part of the inner fitting portion 14 and which is continuous with the outward-extending portion 13, is formed with vertically-extending wrinkles 27 over the entire circumference thereof; and at the time of fitting of a paper container 1, the lower section 14a is able to come into contact with the container inner circumferential surface of a paper container 2.

Description

Technical Field

[0001] The present invention relates to a paper lid.

Background Art

[0002] As a lid for paper containers such as paper cups, resin lids made of plastic or the like are used. However, when disposing of resin lids, it is necessary to separate them from paper cups and paper containers, which is troublesome for consumers. In particular, as a measure against global warming, reduction of resin usage and reduction of CO2 are required, and the switch from resin lids to paper lids is increasing.

[0003] Lids can generally be roughly classified into two types: a flat lid shape with a flat top plate and a type with a top plate bulging upward. Among them, for types that drink using a straw, such as cold beverages, a flat lid shape is applied, but for types that drink directly from the container to the mouth, such as hot beverages, or types with toppings such as cream, a so-called dome shape with a top plate bulging upward is often applied.

[0004] Patent Document 1 describes a paper lid having a flat lid shape. According to the paper lid disclosed in this Patent Document 1, the container can be freely fitted by an inner fitting portion provided on the outer peripheral side of the top plate, a top portion, and an annular recess formed by an outer fitting portion. However, this paper lid has a configuration in which the top plate enters the inner surface side of the container, and the annular recess is formed to rise above this top plate. Therefore, there is a problem that it becomes difficult to apply to types that drink directly from the container to the mouth, such as hot beverages, or types with toppings such as cream.

[0005] Moreover, such a paper lid is manufactured by drawing molding, but wrinkles are generated by the compressive force applied to the paper during this drawing molding. When such wrinkles occur so as to straddle from the inner fitting portion to the top portion, the contents in the container leak out through the wrinkles. At present, no paper lid has been devised that can effectively suppress the leakage of contents through such wrinkles.

[0006] Furthermore, after the paper is pressed and molded, the paper lid, once ejected from the mold, undergoes a dimensional change in the direction of expansion of its outer circumference as the wrinkles formed during molding try to return to their original state. When attempting to close a container with a paper lid that has undergone such dimensional changes, the fitting force is reduced. Therefore, a technology that can effectively suppress the dimensional change of the outer circumference of the paper lid due to the return of wrinkles after molding has been desired for some time. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6978606 [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, the present invention was devised in view of the above-mentioned problems, and its objective is to provide a paper lid that can be molded into a so-called dome shape with a top plate that bulges upward, and that can effectively suppress leakage of contents through wrinkles. Furthermore, the objective of the present invention is to provide a paper lid that can effectively suppress leakage of contents through wrinkles, and furthermore, can effectively suppress changes in the dimensions of the outer circumference of the paper lid due to the return of wrinkles after molding. [Means for solving the problem]

[0009] The paper lid according to the present invention is a paper lid made of paper that is fitted into a paper container, and comprises a top plate portion, a covering portion provided along the outer circumference of the top plate portion and extending downward and continuous with the top plate portion, an outer extension portion provided along the outer circumference of the covering portion and extending outward and continuous with the covering portion, an inner fitting portion provided along the outer circumference of the outer extension portion and extending upward and continuous with the outer extension portion, a top portion provided along the outer circumference of the inner fitting portion and extending outward and continuous with the inner fitting portion, and an outer fitting portion provided along the outer circumference of the top portion and extending downward and continuous with the top portion, wherein the lower portion of the inner fitting portion that is continuous with the outer extension portion has vertically extending wrinkles formed on its inner surface over its entire circumference, and the lower portion is capable of contacting the inner surface of the container portion of the paper container when the paper container is fitted. [Effects of the Invention]

[0012] According to the present invention, which has the above-described configuration, the top plate can be molded into a so-called dome shape with an upward bulge, and when the paper container is fitted, the lower portion of the inner fitting part that is continuous with the outer extension can come into contact with the inner circumferential surface of the container part of the paper container, thereby effectively suppressing leakage of contents through wrinkles.

[0013] According to the present invention, which has the configuration described above, leakage of contents through wrinkles can be effectively suppressed, and furthermore, changes in the dimensions of the outer circumference of the paper lid due to the return of wrinkles after molding can be effectively suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1(a) is a schematic plan view showing an example of a paper cover according to one embodiment of the present invention, and Figure 1(b) is a schematic cross-sectional view along the line IB-IB in Figure 1(a). [Figure 2] Figure 2 is a schematic cross-sectional view showing an enlarged view of the area within the dashed frame II in Figure 1(a). [Figure 3] Figure 3 shows an example in which the lower portion of the internal fitting is enlarged outward, and the upper portion, which is above the lower portion, is extended upward with approximately the same diameter. [Figure 4] Fig. 4(a) is a schematic perspective view showing an example of a paper lid according to an embodiment of the present invention, and Fig. 4(b) is a schematic perspective view showing a part of the schematic perspective view shown in Fig. 4(a) with a notch cut out. [Figure 5] Fig. 5(a) is a cross-sectional view in the depth direction of the paper surface in Fig. 2 at the inner fitting portion, and Fig. 5(b) is a cross-sectional view showing an example narrowed by compressing the wrinkles inward in the circumferential direction. [Figure 6] Fig. 6 is an enlarged view of the contact portion between the inner fitting portion and the inner peripheral surface of the container portion of the paper container. [Figure 7] Fig. 7 is a diagram showing the result of verifying the presence or absence of leakage of the contents of the paper container between the wrinkles without any treatment and the wrinkles compressed in the circumferential direction. [Figure 8] Fig. 8 is a diagram showing the result of verifying the presence or absence of leakage of the contents with respect to the height of the inner fitting portion. [Figure 9] Fig. 9 is a diagram showing the result of verifying the degree of leakage of the contents for an example in which the compressive force is increased by applying a press load. [Figure 10] Fig. 10(a) is an example in which a bent portion that bends outward is formed on the outer fitting portion, and Fig. 10(b) is an enlarged view of the region surrounded by the dotted line in Fig. 10(a). [Figure 11] Fig. 11(a) is a diagram showing an example in which no bent portion is formed on the outside of the outer fitting portion, and Fig. 11(b) is a diagram showing an example in which a bent portion is formed on the outside of the outer fitting portion. [Figure 12] Fig. 12 is a diagram for explaining the formation position of the bent portion. [Figure 13] Fig. 13 is a diagram showing an example in which a bent portion that bends inward is formed in the outer fitting portion. [Figure 14] Fig. 14 is a schematic cross-sectional view showing an example of a processing machine that can be used for manufacturing the paper lid according to an embodiment of the present invention. [Figure 15] Fig. 15 is a diagram for explaining a method of drawing and molding the top plate portion and the wrapped portion by using the processing machine. [Figure 16]FIG. 16 is a diagram for explaining a method of drawing and molding an outer extension portion, an inner fitting portion, a top portion, and an outer fitting portion by using a processing machine. [Figure 17] FIG. 17 is a diagram for explaining a method of drawing and molding a curled portion by using a processing machine. [Figure 18] FIG. 18 is a diagram for explaining a method of drawing and molding by pushing down a first side holder in a downward direction in a state where a tapered surface is formed. [Figure 19] FIG. 19 is a diagram showing an example of measuring the paper thickness of an actually molded paper lid based on a drawing and molding method. [Figure 20] FIG. 20 is a diagram for explaining a method of forming a bent portion that bends outward in an outer fitting portion. [Figure 21] FIG. 21 is a diagram for explaining another method of forming a bent portion that bends outward in an outer fitting portion. [Figure 22] FIG. 22 is a diagram for explaining a method of forming a bent portion that bends inward in an outer fitting portion.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of a paper lid to which the present invention is applied will be described in detail with reference to the drawings.

[0016] (Paper lid) FIG. 1(a) is a schematic plan view showing an example of a paper lid according to an embodiment of the present invention, and FIG. 1(b) is a schematic cross-sectional view taken along line IB-IB in FIG. 1(a). FIG. 2 is a schematic cross-sectional view showing an enlarged view of the inside of the broken line frame II in FIG. 1(a).

[0017] As shown in Figures 1(a), 1(b), and 2, the paper lid 1 consists of a blank 10 mainly made of paper and includes a top plate portion 11, a covering portion 12, an outward extension portion 13, an inner fitting portion 14, a apex portion 15, an outer fitting portion 16, and a curled portion 17. The shape of the paper lid 1 in plan view is, for example, circular. Hereinafter, in Figures 1 and 2, the outside (direction X1) refers to the outward direction with respect to the paper container 2, which is to be fitted, such as a paper cup; the bottom (direction X2) refers to the downward direction when the paper container 2 is placed on the bottom surface; and the top (direction X3) refers to the upward direction when the paper container 2 is placed on the bottom surface. However, these bottom (direction X2) and top (direction X3) are not limited to perfectly vertical downward and vertical upward directions, but also include diagonally downward and diagonally upward directions that are offset from vertical downward and vertical upward directions, respectively.

[0018] Furthermore, the top plate portion 11 and the encasing portion 12 are responsible for the function of the paper lid 1 as a lid, preventing the contents inside the paper container 2 from scattering or leaking, while the remaining peripheral portion OEP (outer extension portion 13, inner fitting portion 14, top portion 15, outer fitting portion 16, curl portion 17) is responsible for fitting with the paper container 2.

[0019] The top plate portion 11 extends outward (direction X1). The top plate portion 11 has a top surface 11a and a container surface 11b. The container surface 11b is on the underside of the top surface 11a. When the paper lid 1 is fitted onto the paper container 2, the container surface 11b faces the container portion of the paper container 2.

[0020] The covering portion 12 is provided along the outer circumference of the top plate portion 11 and extends downward (in direction X2) from the top plate portion 11. This covering portion 12 is continuous with the top plate portion 11. In this case, the covering portion 12 may be molded so that its diameter gradually increases towards the bottom, in other words, so that it slopes outward when viewed in a side cross-section. The continuous portion between the covering portion 12 and the top plate portion 11 may also be molded in a rounded, streamlined shape. With a covering portion 12 having such a form, the top plate portion 11 can be closed at a position spaced apart from the paper container 2. Furthermore, these top plate portion 11 and covering portion 12 can be molded to form a so-called dome shape that bulges upward, making it applicable to types where hot beverages are consumed directly from the container, or types with toppings such as cream.

[0021] The extension portion 13 is provided on the peripheral edge OEP of the paper lid 1, along the outer circumference of the encasing portion 12, and extends outward (direction X1). This extension portion 13 is continuous with the encasing portion 12. The extension width of this extension portion 13 is not particularly limited, but as will be described later, it may be sized so that the inner fitting portion 14 can contact the inner circumferential surface 21 of the container portion of the paper container 2 when the paper container 2 is fitted.

[0022] The inner fitting portion 14 is provided on the peripheral edge OEP of the paper cover 1, along the outer circumference of the outer extension portion 13, and extends upward (direction X3). This inner fitting portion 14 is continuous with the outer extension portion 13. The inner fitting portion 14 may have a substantially uniform diameter, in other words, it may rise up to the top portion 15 in a substantially vertical direction in a cross-sectional view, but it is not limited to this, and may gradually widen outward up to the top portion 15. Also, as shown in Figure 3, the inner fitting portion 14 may have a lower portion 14a that widens outward, and an upper portion 14b located above the lower portion 14a that extends upward with a substantially uniform diameter.

[0023] The top portion 15 is provided on the peripheral edge OEP of the paper cover 1, along the outer circumference of the inner fitting portion 14, and extends outward (direction X1). This top portion 15 is continuous with the inner fitting portion 14. In its cross-section, the top portion 15 includes a curved surface that is convex upward (direction X3).

[0024] The outer fitting portion 16 is provided on the peripheral edge OEP of the paper lid 1, along the outer circumference of the top portion 15, and extends downward (direction X2). This outer fitting portion 16 is continuous with the top portion 15. The outer fitting portion 16 is separated from and opposite the inner fitting portion 14. Below the top portion 15, an annular recess 20 is provided between the inner fitting portion 14 and the outer fitting portion 16, with the inner fitting portion 14 and the outer fitting portion 16 as the surrounding walls and the top portion 15 as the base. The annular recess 20 is fitted into the paper container 2. At this time, the inner fitting portion 14 fits into the inner circumferential surface 21 of the container portion of the paper container 2, and the outer fitting portion 16 fits into the outer circumferential surface of the curl portion 28 of the paper container 2.

[0025] The curl portion 17 is provided on the peripheral edge OEP, along the circumferential direction of the outer fitting portion 16. The curl portion 17 extends outward (direction X1) and is continuous with the outer fitting portion 16. The curl portion 17 includes the end portion 10a of the paper lid 1. The curl portion 17 may, but is not limited to, have a shape that curls upward in cross-section. By forming such a curl portion 17, when fitting the annular recess 20 to the paper container 2, it becomes possible to guide the paper container 2 into the annular recess 20 via this curl portion 17.

[0026] In other words, in the cross-section of the paper lid 1, the encasing portion 12 bends downward (direction X2), the extension portion 13 bends outward (direction X1), the inner fitting portion 14 bends upward (direction X3), the top portion 15 bends outward (direction X1), the outer fitting portion 16 bends downward (direction X2), and the curled portion 17 bends outward (direction X1). That is, each of the top portion 11, the encasing portion 12, the extension portion 13, the inner fitting portion 14, the top portion 15, the outer fitting portion 16, and the curled portion 17 is obtained from a single blank 10.

[0027] In a paper lid 1 of this shape, the boundaries between the top plate portion 11 and the encased portion 12, the encased portion 12 and the extension portion 13, the extension portion 13 and the inner fitting portion 14, the inner fitting portion 14 and the top portion 15, the top portion 15 and the outer fitting portion 16, and the outer fitting portion 16 and the curled portion 17 may be defined, for example, as the inflection point or the vicinity of the inflection point that occurs when the blank 10 is drawn into shape.

[0028] Figure 4(a) is a schematic perspective view showing an example of a paper lid according to one embodiment of the present invention. Figure 4(b) is a schematic perspective view showing a portion of the schematic perspective view shown in Figure 4(a) cut out. As shown in Figures 4(a) and 4(b), wrinkles 27 are formed outwards on at least the peripheral OEP (outer extension portion 13, inner fitting portion 14, top portion 15, outer fitting portion 16, curl portion 17) of the paper lid 1. These wrinkles 27 are naturally generated by the compressive force applied to the blank 10 during the drawing process. Numerous wrinkles 27 exist on both the inner and outer surfaces of the peripheral OEP and are formed around the entire circumference of the paper lid 1.

[0029] Figure 5(a) shows a cross-sectional view of the inner fitting portion 14 in the depth direction of the paper in Figure 2. That is, in this cross-sectional view, the direction of the arrow in the figure is the circumferential direction of the paper cover 1. As shown in Figure 5(a), wrinkles 27 are formed on the inner surface 31a and the outer surface 31b, respectively, at intervals from each other. These wrinkles 27 may be formed by compression toward the inside in the circumferential direction. That is, the width of the wrinkles 27 can be narrowed from a relatively wide wrinkle without any treatment, as shown by the dotted line in Figure 5(a), by compressing it toward the inside in the circumferential direction (dotted line in Figure 5(b)), as shown in Figure 5(b). As a result, the void area of ​​the wrinkles 27 can be reduced. The void area here refers to the cross-sectional area of ​​the wrinkles 27, and can be calculated from the relationship between the depth and width of the wrinkles, as shown in the figure. This void area can be calculated from the image of the cross-section taken with an optical microscope.

[0030] Such circumferential inward compression of the wrinkles 27 is not required to be applied from the beginning to the end of the wrinkles 27, but only needs to be applied at least at the inner fitting portion 14. Figure 6 is an enlarged view of the contact portion between the inner fitting portion 14 and the inner circumferential surface 21 of the container portion of the paper container 2. Fitting is achieved when the lower portion 14a of the inner fitting portion 14 comes into contact with the inner circumferential surface 21 of the container portion of the paper container 2. At this time, because the wrinkles 27 formed on the lower portion 14a of the inner fitting portion 14 are compressed circumferentially inward, it is possible to effectively suppress leakage of liquid contents from inside the paper container 2 along these wrinkles 27.

[0031] Figure 7 shows the results of verifying whether or not the contents of the paper container 2 leak out relative to the maximum void area between wrinkles 27 that have not undergone any treatment (Comparative Example 1) and wrinkles 27 that have been compressed in the circumferential direction (Example 1 of the present invention). The maximum void area referred to here is the largest void area among the measured cross-sectional areas of the wrinkles 27. In the verification in this embodiment, the cross-section of the inner fitting portion 14 was actually cut in the circumferential direction, and the cross-section was imaged on an optical microscope to calculate the maximum void area. The maximum void area of ​​Comparative Example 1 was 6741 μm². 2 In contrast, the maximum void area of ​​Example 1 of the present invention is 4359 μm². 2 The result was as follows. In this test, the contents were assumed to be water. In the actual test, the paper lid 1 was closed onto the paper container 2 containing the contents, and then the paper container 2 was tilted 90° and held for 1 minute to check for leaks.

[0032] In Comparative Example 1, which had no treatment applied, leakage of the contents was observed 7 seconds after the start of the experiment. In contrast, in Example 1 of the present invention, in which the wrinkles 27 were compressed in the circumferential direction, no leakage of the contents was observed even after 1 minute. For this reason, it is desirable to compress the wrinkles 27 in the circumferential direction, and the maximum void area is 4359 μm². 2 It is desirable to do so.

[0033] Furthermore, according to the present invention, as shown in Figure 6, it is desirable that, when fitted, the lower portion 14a of the inner fitting portion 14 is subjected to an outward (direction X1) pressing force against the inner circumferential surface 21 of the container portion 2 of the paper container 2. As a result, the wrinkles 27 formed on the lower portion 14a of the inner fitting portion 14 are compressed through the pressing force against the inner circumferential surface 21 of the container portion 2 of the paper container 2, effectively suppressing leakage of liquid contents from inside the paper container 2 along the wrinkles 27. This pressing force on the lower portion 14a of the inner fitting portion 14 is applied based on the force that causes the extension portion 13, which is continuous with the inner fitting portion 14, to expand in diameter. This force that causes the extension portion 13 to expand in diameter can be applied, for example, by designing the dimension of the extension portion 13 in the direction X1 to be slightly larger, or by adjusting the dimension of the top plate portion 11 in the direction X1 or the expanding width of the encased portion 12 in the outward direction.

[0034] Furthermore, in order to suppress leakage of the contents from the paper container 2, it is desirable to set the height h of the inner fitting portion 14 shown in Figure 6 to a higher level. By setting the height of the inner fitting portion 14 to a higher level, the contact area of ​​the lower part 14a of the inner fitting portion 14 that contacts the inner circumferential surface 21 of the container portion 2 of the paper container can be increased, which helps to suppress leakage of the contents. In addition, by setting the height of the inner fitting portion 14 to a higher level, the length of the wrinkles 27 in the inner fitting portion 14 can be increased, as a result the propagation distance over which the contents leak out along the wrinkles 27 can be increased, which helps to suppress leakage of the contents.

[0035] Figure 8 shows the results of verifying whether or not there was leakage of the contents relative to the height of the inner fitting portion 14. Comparative Example 2 had an inner fitting portion 14 height of 3 mm, Comparative Example 3 had an inner fitting portion 14 height of 5 mm, and Example 2 of the present invention had an inner fitting portion 14 height of 7 mm. In this verification, the contents were water. In the actual verification, the paper lid 1 was closed on the paper container 2 containing the contents, and then the paper container 2 was tilted 90° and held for 1 minute to check for leakage.

[0036] Verification revealed that leakage of contents was observed in both Comparative Examples 2 and 3. In contrast, no leakage of contents was observed in Example 2 of the present invention. Therefore, it can be seen that by making the height of the inner fitting portion 14 7 mm or more, leakage of contents through the wrinkles 27 can be effectively suppressed. Furthermore, by making the height of the inner fitting portion 14 greater than 5 mm, leakage of contents can be suppressed in the same way as when it is 7 mm.

[0037] Furthermore, as shown in Figure 3, by widening the lower portion 14a of the inner fitting portion 14 outward and extending the upper portion 14b upward with approximately the same diameter, as will be described in detail later, a press load can be effectively applied to the wrinkles 27 during the deep drawing process during manufacturing. As a result, the wrinkles 27 can be further compressed from the circumferential direction and in all directions. Consequently, leakage of contents through the wrinkles 27 can be prevented even more effectively.

[0038] Figure 9 shows the results of verifying the degree of leakage of the contents in two examples of the present invention: Example 3, which does not apply any special pressing load, and Example 4, which increases the compressive force by applying a pressing load. The verification was performed using a leak test (N5), and the contents were hot coffee. Incidentally, the maximum void area of ​​the wrinkle 27 in Example 3 was 4220 μm². 2 Therefore, the maximum void area of ​​the wrinkle 27 in Example 4 of the present invention is 2457 μm². 2 In this test, a paper container 2 containing 85°C coffee was closed with a paper lid 1, and then the paper container 2 was tilted 90° and held for 1 minute to check for leaks. In this test, a "leak" was defined as when droplets of the contents fell onto the table, and a "smudge" was defined as when the contents accumulated in the gap between the paper container 2 and the paper lid 1 without falling. Leaks were considered to be superior to smudges in terms of performance. In addition, the time it took for droplets to fall onto the table was measured for leaks.

[0039] Verification results showed that in the leak test (N5), Example 3 of the present invention leaked in 4 out of 5 cases (average 41.8 seconds) and seeped in 1 out of 5 cases. In contrast, in Example 4 of the present invention leaked in 1 out of 5 cases (50 seconds) and seeped in 3 out of 5 cases. Therefore, it can be seen that Example 4 of the present invention has an improved effect in suppressing leakage of the contents.

[0040] By forming the wrinkles 27 in this manner, in addition to suppressing leakage of the contents inside the paper container 2, the wrinkles 27 can be freely opened in the circumferential direction, and the annular recess 20 itself can be freely expanded in diameter. Therefore, the following effects are also achieved.

[0041] While the outer (inner) diameter of the paper containers 2 produced under normal circumstances is fixed, tolerances exist, resulting in dimensional differences of approximately 0.5 to 1 mm. Even for paper containers 2 with a smaller inner diameter, the paper lid 1 can be easily fitted by expanding the expandable annular recess 20. In other words, by introducing wrinkles 27 in advance, it is possible to prevent the formation of additional wrinkles when fitting the lid to a paper container 2 with a smaller inner diameter, thereby preventing the contents from leaking out through those additional wrinkles.

[0042] It should be noted that the present invention is not limited to the embodiments described above. For example, as shown in Figure 10(a), the outer fitting portion 16 may have a bent portion 31 that bends outward. Figure 10(b) is an enlarged view of the area enclosed by the dotted line in Figure 10(a). This bent portion 31 can be formed by bending the outer and inner surfaces of the outer fitting portion 16 outward around point P1, then folding the bent outer and inner surfaces back around point P2, and further bending the folded outer and inner surfaces at point P3.

[0043] Such a bent portion 31 is formed to intersect with the wrinkles 27 formed in the outer fitting portion 16. In particular, wrinkles 27 that have been compressed in the circumferential direction tend to return to their original state, as shown in Figure 11(a). However, by forming this bent portion 31 to intersect with the wrinkles 27, as shown in Figure 11(b), the tendency of the circumferentially compressed wrinkles 27 to return to their original state can be suppressed by this bent portion 31. Since the wrinkles 27 are continuous from the inner fitting portion 14, the top portion 15, to the outer fitting portion 16, which forms at least the annular recess 20, the tendency of the wrinkles 27 that intersect with the outer fitting portion 16 to return to the opposite side of the compression direction can be suppressed via the bent portion 31 formed on the outer fitting portion 16, all the way to the continuous inner fitting portion 14.

[0044] Therefore, the bending portion 31 prevents the wrinkles 27 in the inner fitting portion 14 from returning to their circumferential position, allowing the wrinkles 27 in the inner fitting portion 14 to maintain a circumferentially compressed state. As a result, it is possible to prevent the contents of the paper container 2 from leaking out through the wrinkles 27 in the inner fitting portion 14.

[0045] Furthermore, this bent portion 31 has an advantageous effect in that, even when the wrinkle 27 is not compressed inward in the circumferential direction, it can suppress the force that would cause the wrinkle 27 to open up through the bent portion 31.

[0046] Furthermore, if a bent portion 31 is provided, the configuration of the encased portion 12 and the extended portion 13 surrounding the top plate portion 11 may be omitted. In this case, the outer circumference of the top plate portion 11 is directly connected to the lower end of the lower portion 14a of the inner fitting portion 14.

[0047] The position of this bent portion 31 is preferably such that it can contact the lower side of the curled portion 28 at the upper end of the paper container 2 when the paper container 2 is fitted into the annular recess 20, as shown in Figure 12, for example. That is, by bending this bent portion 31 outward, the inner surface 31a that is folded around P1 may bulge inward. This bulging inner surface 31a can lock the curled portion 28 of the paper container 2, making it possible to fit the paper lid 1 in a stable state.

[0048] Furthermore, in order to securely fit the paper lid 1, a bent portion 32 that bends inward may be formed in the outer fitting portion 16, as shown in Figure 13(a). The detailed configuration of the bent portion 32 is the same as that of the bent portion 31, so a detailed explanation is omitted below. This bent portion 32 is formed in a position that can contact the lower side of the curled portion 28 of the paper container 2 when fitting the paper container 2 into the annular recess 20, as shown in Figure 13(a). As a result, the bent portion 32 can lock the curled portion 28 of the paper container 2, making it possible to securely fit the paper lid 1. Figure 13(b) shows another embodiment of the bent portion 32 that bends inward. In this embodiment, the bent portion 32, which is configured in a triangular cross-section in Figure 13(a), is finished in a flattened shape. The curled portion 28 of the paper container 2 can be locked more securely through this flattened bent portion 31. In this configuration, the structure of the curled portion 17 may be omitted, and although the inner fitting portion 14 is erected vertically, it is not limited to this configuration.

[0049] Next, an example of a method for manufacturing the paper lid 1 to which the present invention is applied will be described.

[0050] (Manufacturing method for paper lid 1) <An example of a processing machine> Figure 14 is a schematic cross-sectional view showing an example of a processing machine that can be used to manufacture a paper cover according to one embodiment of this invention.

[0051] The processing machine 100 is, for example, a press machine. For example, by using a processing machine 100 as shown in Figure 14, a paper cover 1 having an annular recess 20 can be manufactured from a blank 10.

[0052] The processing machine 100 includes a draw die 110, a blank holder 120, a draw punch 130, a plunger 140, a second side holder 150, and a first side holder 160. Furthermore, a mounting table 170 is provided outside the draw die 110 and blank holder 120 of the processing machine 100. Figure 14 shows the cross-sectional shape of the processing machine 100, which is formed in the circumferential direction.

[0053] In actually manufacturing this paper cover 1 using the processing machine 100, first the blank 10 is placed on the mounting surface 142 of the plunger 140, the mounting surface 112 of the draw die 110, and the mounting table 170.

[0054] Next, as shown in Figure 15(a), the blank holder 120, draw punch 130, and first side holder 160 are moved downward in the ZD direction, holding the blank 10 between the draw die 110, plunger 140, and second side holder 150. Then, with the blank held in place, the draw die 110, blank holder 120, draw punch 130, plunger 140, second side holder 150, and first side holder 160 are pushed downward in the ZD direction. As a result, the draw die 110, blank holder 120, draw punch 130, plunger 140, second side holder 150, and first side holder 160, which are sandwiching the blank 10, move downward in the ZD direction within the space enclosed by the mounting table 170. Consequently, the blank 10 is punched out between the mounting table 170 and the blank holder 120, making it possible to construct the blank 10 in a roughly circular shape in plan view.

[0055] The draw die 110 has a guide hole 111 and a mounting surface 112. The guide hole 111 is, for example, a circular hole. The mounting surface 112 is located outside the guide hole 111. The mounting surface 112 faces the blank holder 120. The mounting surface 112 is a surface on which the blank 10 can be placed. In addition, a round groove-shaped curling portion 115 is provided at the intersection of the mounting surface 112 and the guide hole 111 in the draw die 110.

[0056] The blank holder 120 has a guide hole 121 and a pressing surface 122. The guide hole 121 is a circular hole. The pressing surface 122 is located outside the guide hole 121. The pressing surface 122 faces the mounting surface 112. The blank holder 120 holds down the blank 10 placed on the mounting surface 112. In addition, a round groove-shaped curling portion 125 is provided at the intersection of the guide hole 121 and the pressing surface 122 in the blank holder 120.

[0057] The draw punch 130 is movable within the guide hole 121 in both the upward direction ZU and the downward direction ZD. Both the upward direction ZU and the downward direction ZD intersect, for example, perpendicular to, the mounting surface 112. The downward direction ZD is opposite to the upward direction ZU. A punch surface 132 is formed at the tip of the draw punch 130. The punch surface 132 is formed as a flat surface and presses against the blank 10. The draw punch 130 also has a first side circumferential surface 131a located on the upward direction ZU side and a second side circumferential surface 131b located on the downward direction ZD side.

[0058] The plunger 140 is movable within the guide hole 111 in both the upward direction ZU and the downward direction ZD. A mounting surface 142 is provided at the tip of the plunger 140. The mounting surface 142 faces the punch surface 132. The diameter D1 of the mounting surface 142 is less than or equal to the diameter D2 of the punch surface 132 of the draw punch 130. The plunger 140 also has a side circumferential surface 141.

[0059] The second side holder 150 is movable within the guide hole 111 in the upward direction ZU and the downward direction ZD, with its side circumferential surface 151 in contact with the guide hole 111. The second side holder 150 has an annular projection 152 formed at its upper end, and further, a stepped portion 153 is provided outside the annular projection 152, with a step extending downward from the tip of the annular projection 152.

[0060] The first side holder 160 is movable within the guide hole 121 in the upward direction ZU and the downward direction ZD, with its side circumferential surface 161 in contact with the guide hole 121. The first side holder 160 has an annular projection 162 formed at its lower end, and further, a stepped portion 163 is provided outside the annular projection 162, with a step extending upward from the tip of the annular projection 162.

[0061] Furthermore, the upward movement ZU and downward movement ZD of the draw die 110, blank holder 120, draw punch 130, plunger 140, second side holder 150, and first side holder 160 are all performed by air cylinders (not shown), but are not limited to these, and of course any other well-known driving means may be used.

[0062] Next, as shown in Figure 15(b), only the draw punch 130 and the plunger 140 are pushed down in the downward direction ZD. During this time, the peripheral region of the blank 10 is held in place by the draw die 110 and the blank holder 120. As a result, the blank 10 stretches in the downward direction ZD, and the central region of the blank 10 is pushed in, resulting in the formation of the external shape corresponding to the top plate portion 11 and the encased portion 12.

[0063] Next, as shown in Figure 16(a), the draw die 110, the blank holder 120, and the first side holder 160 are pushed down in the downward direction ZD. As a result, the annular projection 162 on the first side holder 160 fits into the stepped portion 153 on the second side holder 150, and the annular projection 152 on the second side holder 150 fits into the stepped portion 163 on the first side holder 160, bringing them closer together. Consequently, the blank 10 deforms according to the proximity shapes of these annular projections 162 and the stepped portion 153, and the annular projections 152 and the stepped portion 163, resulting in the formation of the external shape corresponding to the outer extension portion 13 and the inner fitting portion 14 described above. In other words, in this process, the annular projection 162 of the first side holder 160 pushes in from a region spaced outward from the outer circumference of the encased portion 12, corresponding to the annular projection 152 of the second side holder 150, thereby forming a shape that precisely corresponds to the outer extension portion 13.

[0064] Next, as shown in Figure 16(b), only the draw die 110 and the blank holder 120 are raised in the upward direction ZU. As a result, the end of the blank 10 is formed in the upward direction ZU while being held between the guide hole 111 of the draw die 110 and the side surface 161 of the first side holder 160. As a result, the external shape corresponding to the top portion 15 and the outer fitting portion 16 is formed. That is, in this process, the draw die 110 pushes in from an area spaced outward from the outer circumference of the inner fitting portion 14, corresponding to the stepped portion 153 of the second side holder 150, thereby forming a shape that precisely corresponds to the top portion 15.

[0065] Next, as shown in Figure 17(a), only the draw die 110 and the blank holder 120 are lowered in the downward direction ZD. Alternatively, the plunger 140, the first side holder 160, the second side holder 150, and the draw punch 130 are raised in the upward direction ZU. As a result, the end of the blank 10, which has been formed in the upward direction ZU, fits perfectly into the round groove-shaped curling portions 115 and 125. Then, as the draw die 110 and the blank holder 120 gradually descend, the end of the blank 10 deforms along the round groove shape of the curling portions 115 and 125, resulting in the formation of a curled portion 17. This makes it possible to manufacture a paper cover 1 to which the present invention is applied from the blank 10.

[0066] Next, as shown in Figure 17(b), the draw punch 130 is moved upward in the ZU direction to separate it from the blank 10. Furthermore, the draw die 110 and the second side holder 150 are lowered in the downward ZD direction to discharge the completed paper cover 1.

[0067] The manufacturing method for the paper lid 1, which is produced by going through the process described above, makes it possible to create a so-called dome shape that bulges upward due to the top plate portion 11 and the encasing portion 12, which are characteristic parts of the paper lid 1. Specifically, as shown in Figure 15(b), the shapes corresponding to the top plate portion 11 and the encasing portion 12 are created by lowering only the draw punch 130 and the plunger 140, and then the shapes of the outer extension portion 13 and the inner fitting portion 14 are created as shown in Figure 16(a). After going through this process, as shown in Figure 17(a), the curl portion 17 can be formed via the round groove-shaped curling portion 115 and curling portion 125 through the downward pressing of the draw die 110 and the blank holder 120, or through the upward movement of the plunger 140, the first side holder 160, the second side holder 150, and the draw punch 130 in the upward direction ZU, and moreover, these characteristic shapes can be realized in one cycle by the processing machine 100.

[0068] In this invention, in the process of forming the internal fitting portion 14 shown in Figure 16(a), as shown in Figure 18, a tapered surface 162a is provided at the base of the annular projection 162 of the first side holder 160, and a tapered surface 152a is also provided near the upper end of the annular projection 152 of the second side holder 150. The tapered surface 162a is constructed by inclining only the base portion from the annular projection 162 to the stepped portion 163. The tapered surface 152a is constructed by inclining only near the upper end of the annular projection 152. By bringing the second side holder 150 and the first side holder 160 close together, these tapered surfaces 152a and 162a face each other, and the blank 10 sandwiched between them deforms along the inclination of the tapered surfaces 152a and 162a. As a result, as shown in Figure 3, it becomes possible to mold the inner fitting portion 14 in such a way that the lower portion 14a is enlarged outward, and the upper portion 14b, which is above the lower portion 14a, is extended upward with approximately the same diameter.

[0069] With the tapered surfaces 162a and 152a formed in this manner, by pushing the first side holder 160 downward in the ZD direction, the load vector direction can be decomposed from the downward ZD direction into a load vector in the thickness direction of the blank 10, as shown by the arrow in Figure 18. As a result, the wrinkles 27 inside the blank 10 that were generated during the drawing process described above are compressed, and are also compressed inward in the circumferential direction. As a result, by increasing the compressive force on the wrinkles 27 based on the load vector in the thickness direction of the blank 10, the maximum void area can be made smaller, as shown in Example 4 of the present invention in Figure 9, and leakage of the contents can be firmly suppressed.

[0070] Figure 19 shows an example of measuring the paper thickness of a paper lid 1 actually molded based on the drawing molding method described above. Compared to the original blank 10, which has a paper thickness of 0.32 mm, the paper thickness increases from the top plate portion 11 to the encasing portion 12 and then to the outer portion 13. This is due to the effect of wrinkles 27 that form as a result of the drawing molding, and the paper thickness increases in proportion to the wrinkles 27. On the other hand, the paper thickness is thinner, especially in the lower portion 14a of the inner fitting portion 14. This is because a compressive force is applied to the lower portion 14a of the inner fitting portion 14 during the drawing molding process by pushing the first side holder 160 downward in the ZD direction, resulting in a thinner paper thickness. At this time, with the tapered surfaces 162a and 152a formed as described above, by pushing the first side holder 160 downward in the ZD direction, a load vector is applied to the thickness direction of the blank 10, resulting in a thinner paper thickness in the lower portion 14a, and making it possible to make the paper thickness itself approximately uniform. Furthermore, by applying compressive force to thin the paper thickness of the lower portion 14a of the inner fitting portion 14, the lower portion 14a itself can be made harder, and as a result, it becomes easier to apply a pressing force from the lower portion 14a of the inner fitting portion 14a to the inner circumferential surface 21 of the container portion of the paper container 2, effectively suppressing leakage of liquid contents from inside the paper container 2. The upper portion 14b and the top portion 15, which are separate from the lower portion 14a, have a thicker paper thickness than the lower portion 14a. However, by applying more load to the thinner lower portion 14a during the drawing process, it is possible to prevent that portion from tearing by avoiding applying load to the thicker portions of the paper.

[0071] Furthermore, as a compressive force in the paper thickness direction is applied to the lower portion 14a of the inner fitting portion 14, a compressive force in the depth direction is also applied to the wrinkles 27. As a result, the wrinkles 27 in the lower portion 14a of the inner fitting portion 14 become shallowest, while the wrinkles in the upper portion 14b, the top portion 15, and the outer fitting portion 16 of the inner fitting portion 14 become deeper. By making the wrinkles 27 shallower in the lower portion 14a of the inner fitting portion 14, it is possible to effectively suppress leakage of liquid contents from inside the paper container 2. Note that regardless of whether the wrinkles 27 are in the lower portion 14a or the upper portion 14b, the same effect will be achieved as long as the wrinkles 27 in the inner fitting portion 14 are shallower than those in the top portion 15 and the outer fitting portion 16.

[0072] Furthermore, when forming a bent portion 31 that bends outward in the outer fitting portion 16, a draw die 110' having the shape shown in Figure 20(a) is used in the process of forming the curl portion 17 shown in Figure 17(a). Figure 20(b) is an enlarged view of the area enclosed by the dotted line in Figure 20(a) of this draw die 110'. This draw die 110' has a contact surface 115a that can contact the end 10a of the blank 10 with respect to the curling portion 115. With the end 10a of the blank 10 in contact with the contact surface 115a of the curling portion 115, only the draw die 110 and the blank holder 120 are lowered in the downward direction ZD. As a result, the portion of the blank 10 corresponding to the outer fitting portion 16 is compressed from above and below, causing it to naturally bend outward, and the bent portion 31 described above is formed. At this time, because a round groove is formed in the curling portion 115, the portion corresponding to the outer fitting portion 16 of the blank 10 is compressed from above and below, making it possible to naturally bend it outwards.

[0073] Furthermore, as shown in Figure 21, by making the flat contact surface 115a of the curling portion 115 wider, it is possible to more easily lock the end portion 10a of the blank 10 through this contact surface 115a. In this case as well, it is desirable to form at least a small groove in the curling portion 115 so that the portion of the blank 10 corresponding to the outer fitting portion 16 can be bent outward.

[0074] Furthermore, when forming a bent portion 32 that bends inward in the outer fitting portion 16, the first side holder 160' having the shape shown in Figure 22 is used in the process of forming the curl portion 17 shown in Figure 17(a). In this first side holder 160', a recess 165 is formed on the side circumferential surface 161 at a position facing the draw die 110, which is machined to be concave toward the inside. By forming such a recess 165, when only the draw die 110 and the blank holder 120 are lowered in the downward direction ZD, the end portion 10a of the blank 10 is pressed through the curling portion 125 of the blank holder 120. As a result, the portion of the blank 10 corresponding to the outer fitting portion 16 is compressed from above and below, and tries to escape in the recess 165, which is the only part that is not being held down. As a result, it becomes possible to form a bent portion 32 that bends inward in this recess 165. [Explanation of symbols]

[0075] 1 paper lid 2 paper containers 10 Blank 10a end 11 Top panel 11a Top surface 11b Container side 12 Encapsulation 13 Extended part 14 Internal fitting part 14a Lower part 14b Upper part 15 Top 16 External fitting part 17, 28 Curl section 20 Annular recess 21 Inner circumferential surface of container part 27 Wrinkles 31, 32 Bending section 100 processing machines 110 Draw Die 111, 121 Guide Hall 112 Mounting surface 115 Curling Club 115a Contact surface 120 Blank Holder 122 Pressing surface 125 Curling Club 130 Draw Punch 132 Punching surface 140 plunger 141, 151, 161 Side surface 142 Mounting surface 150, 160 side holder 152, 162 Annular projection 153, 163 Stepped section 165 recess 170 Mounting platform OEP Peripheral Area

Claims

1. In a paper lid made of paper that fits onto a paper container, The top panel and, A covering portion is provided along the outer circumference of the top plate portion and extends downward, and is continuous with the top plate portion. An outer extension is provided along the outer circumference of the covered portion and extends outward, and is continuous with the covered portion. An inner fitting portion is provided along the outer circumference of the outer extension portion and extends upward, and is continuous with the outer extension portion. It is provided along the outer circumference of the inner fitting portion and extends outward, and has a top portion that is continuous with the inner fitting portion, It is provided along the outer circumference of the top portion and extends downward, and comprises an outer fitting portion that is continuous with the top portion, The lower portion of the inner fitting portion that is continuous with the outer portion has vertically extending wrinkles formed on its inner surface along its entire circumference, so that when the paper container is fitted, the lower portion can come into contact with the inner surface of the container part of the paper container. A paper lid characterized by the following features.

2. The above wrinkles are formed by compression directed inward in the circumferential direction. The paper lid according to claim 1, characterized by the following:

3. The void area in the cross-sectional view of the wrinkles described above is 4359 μm². 2 The following is stated: The paper lid according to claim 2, characterized by the above.

4. The above-mentioned internal fitting portion is set to a height of more than 6 mm. The paper lid according to claim 1, characterized by the following:

5. The inner fitting portion described above has a lower portion that is enlarged outward, and an upper portion located above the lower portion that extends upward with approximately the same diameter. The paper lid according to claim 1, characterized by the following:

6. The above-mentioned internal fitting portion is such that, when the paper container is fitted, the lower portion can be pressed against the inner circumferential surface of the container portion of the paper container based on the force that causes the continuous outer portion to expand in diameter. The paper lid according to claim 1, characterized by the following:

7. The lower portion of the internal fitting part is thinner in paper thickness than its upper portion and the outer portion. The paper lid according to claim 1, characterized by the following:

8. The wrinkles in the inner fitting portion are shallower than those in the top portion and the outer fitting portion. The paper lid according to claim 1, characterized by the following:

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