How the lid is manufactured

Abstract

To form a vent hole having a small size on a lid.SOLUTION: A method for manufacturing a lid 3 in a disposable type food container includes a hole processing step of simultaneously forming a vent hole, and a cantilever valve 5 for openably / closably closing the vent hole on the lid by partially punching the lid using a punch 11 in a press die 10.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a lid, and more particularly to a method for manufacturing a lid for a disposable food container. [Background technology]

[0002] Food containers are known that have a container body for storing food such as boxed lunches and fresh food, and a lid that fits over the container body to close the top opening. Such food containers are generally disposable and are used only when food is sold at stores such as convenience stores and supermarkets, and the lid is made of a transparent plastic sheet so that the contents can be seen. In addition, the lid has ventilation holes to maintain the freshness of the food inside the container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-20850 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to make the size of this ventilation hole as small as possible so that external dust and other particles do not enter the container through the ventilation hole.

[0005] The present disclosure has been made in view of the above circumstances, and has an object to provide a method for manufacturing a lid that is capable of forming a small vent hole in the lid. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, A method for manufacturing a lid for a disposable food container, comprising: The method includes a hole processing step of simultaneously forming an air hole in the lid and a cantilever-shaped valve that closes the air hole in an openable and closable manner by partially punching out the lid using a punch in a press die. A method for manufacturing a lid is provided.

[0007] Preferably, the vent has a minimum width of at least 0.1 mm and not more than 1 mm.

[0008] Preferably, the press die includes a die plate that cooperates with the punch to partially punch out the lid, The punch has a shearing portion that shears the lid together with the die plate, and a non-shearing portion that does not shear the lid.

[0009] Preferably, the non-shearing portion of the punch is inserted into the die hole of the die plate with a clearance therebetween.

[0010] Preferably, the non-shearing portion of the punch is not inserted into a die hole in the die plate.

[0011] Preferably, the press die includes a stripper plate having a punch guide hole through which the punch is always slidably inserted.

[0012] Preferably, the press die includes a punch plate supporting the punch, the punch plate having a punch insertion hole into which the punch is inserted, and a convex portion provided around the punch insertion hole and protruding toward the tip side of the punch. Effect of the Invention

[0013] According to the present disclosure, a small vent hole can be formed in the lid. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing a food container according to the present embodiment. [Diagram 2] FIG. [Diagram 3] FIG. 4 is a front cross-sectional view showing ventilation holes and the like. [Figure 4] FIG. 2 is a front cross-sectional view showing a press die. [Diagram 5] 5 is a diagram showing a cross-sectional shape of a punch (ZZ cross section in FIG. 4). FIG. [Figure 6] FIG. 5 is a diagram showing cross-sectional shapes of a punch and a die hole (ZZ cross section in FIG. 4). [Figure 7] FIG. 5 is an enlarged view of a main part of FIG. [Figure 8] 5 is a diagram showing a cross-sectional shape of a punch insertion hole (Zh-Zh cross section in FIG. 4). FIG. [Figure 9] FIG. 11 is a front cross-sectional view showing the configuration of a first modified example. [Figure 10] FIG. 11 is a front cross-sectional view showing the configuration of a second modified example. [Figure 11] FIG. 13 is an enlarged plan view showing ventilation holes and the like of a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the following embodiments.

[0016] FIG. 1 shows a food container according to an embodiment of the present disclosure, where (A) is a plan view and (B) is a front cross-sectional view (cross-sectional view taken along line Ib-Ib in (A)). For convenience, the directions of front, back, left, right, top and bottom are defined as shown in the figure. However, it should be noted that these directions are defined merely for convenience of explanation. It should also be noted that the dimensions of the figures described below may be exaggerated for ease of understanding and are not necessarily accurate.

[0017] The food container 1 is a disposable container that is used only when selling food at a store such as a convenience store or supermarket. The food container 1 comprises a container body 2 that holds food F, and a lid 3 that fits over the container body 2 and closes the upper opening. The food F in this embodiment is a boxed lunch, and the food container 1 is used as an airtight container for holding the boxed lunch sold at a convenience store, for example. The container body 2 and lid 3 in this embodiment are circular in plan view as shown in Fig. 1(A), but the shape is not limited thereto and may be rectangular, elliptical, or the like.

[0018] Both the container body 2 and the lid 3 are made of plastic, and are formed by vacuum forming or the like of a plastic sheet material. Examples of the plastic material that can be used include polyethylene, polypropylene, polystyrene, and polyethylene terephthalate. For example, the container body 2 can be made of polypropylene, and the lid 3 can be made of polyethylene. The lid 3 is transparent so that the contents can be seen.

[0019] The container body 2 and the lid 3 may be made of a material other than plastic, for example, paper.

[0020] The container body 2 is shaped like a circular bowl, and its upper edge 2A is folded back radially outward. The outer peripheral edge 3A of a substantially disk-shaped lid 3 is tightly fitted onto the outside of this upper edge 2A, sealing the inside of the container 1. The outer peripheral edge 3A of the lid 3 also has a folded back shape that matches the upper edge 2A of the container body 2. The part of the lid 3 that is inward from the outer peripheral edge 3A is a horizontal disk-shaped central portion 3B that is positioned lower than the outer peripheral edge 3A.

[0021] A vent hole 4 for maintaining the freshness of the food F in the container 1 is formed in the center 3B of the lid 3. In particular, in this embodiment, a cantilevered valve 5 for opening and closing the vent hole 4 is formed at the same time as the vent hole 4 by a hole processing step described later. In this embodiment, six pairs of vent holes 4 and valves 5 (for convenience, referred to as a hole pair) are provided and arranged in a lattice pattern. In this embodiment, the group of six hole pairs (for convenience, referred to as a hole pair group) is arranged radially outward (to the front) from the center of the lid 3, as shown in FIG. 1(A).

[0022] The number, positions, arrangement method, etc. of the hole sets are arbitrary, and may be one or a number other than six. The same applies to the hole set groups.

[0023] 2, the vent hole 4 and the valve 5 in one hole set are U-shaped (or hairpin shaped) extending in the left-right direction in this embodiment. A U-shaped slit 6 is formed in the lid 3, separating the vent hole 4 and the valve 5. A straight dashed line 7 represents the base end (one end) of the vent hole 4 in the longitudinal direction and the base end (one end) of the valve 5 connected to the lid 3 in the longitudinal direction. Meanwhile, reference numeral 8 represents the tip end (other end) of the semicircular shape of the vent hole 4 and the valve 5 in the longitudinal direction.

[0024] The vent hole 4, the valve 5 and the slit 6 (referred to as vent hole 4, etc.) are very small and extremely elongated. In this embodiment, the width B of the vent hole 4, etc. is 0.3 mm, and the length A is 5.0 mm. The width B is constant in the direction of the length A. These dimensions can be changed.

[0025] 3, under normal circumstances, the valve 5 almost completely closes the vent hole 4. The only gap between them is the slit 6. Therefore, it is possible to almost completely prevent external dust and the like (dust, insects, foreign objects, etc.) from entering the container 1 through the vent hole 4. The lid 3 of this embodiment is extremely advantageous in preventing the intrusion of external dust and the like into the container 1.

[0026] At this time, air can circulate between the inside and outside of the container through the slits 6. This allows the food F in the container 1 to be kept fresh.

[0027] Even if the valve 5 is opened for some reason, the width B of the ventilation hole 4 is very small, so that the risk of intrusion of dust and the like through the ventilation hole 4 can be minimized.

[0028] Meanwhile, food F in container 1, which is covered and sealed with lid 3, is planned to be heated in a microwave oven together with container 1. During such heating, water vapor and steam (called water vapor, etc.) are generated from food F, which must be released to the outside.

[0029] At this time, the valve 5 is pushed by the steam etc. V as shown by the imaginary line a and elastically bends upward, opening the vent hole 4. This allows the steam etc. V to be smoothly discharged through the vent hole 4, allowing heating to be performed smoothly and safely. In this way, the vent hole 4 also functions as an excellent steam release hole.

[0030] As described above, according to this embodiment, it is possible to achieve a good balance between preventing the intrusion of dust and other particles into the container under normal conditions and promoting the discharge of water vapor and the like out of the container when heated.

[0031] However, the use of the vent hole 4 is not limited to the above. For example, when the food F is noodles for instant yakisoba, the vent hole 4 can be used as a drain hole. In this case, the valve 5 is pushed by the hot water and bent upward, so that the hot water in the container can be smoothly drained through the vent hole 4.

[0032] Furthermore, when the food F is a vegetable or the like that contains a lot of water, the vegetable or the like may sweat and water may accumulate inside the container. In this case, the ventilation hole 4 can also be used as a drain hole.

[0033] The size, number, shape, etc. of the ventilation holes 4 etc. are optimally set so as to satisfy the above functions.

[0034] The present embodiment provides a method for manufacturing the lid 3 that can form such an excellent small-sized vent hole 4 with a valve 5 in the lid 3.

[0035] The manufacturing method of the lid 3 of this embodiment includes a forming step in which a plastic sheet material is cut and formed (particularly vacuum formed) to create the lid 3 in a predetermined shape, and a hole processing step in which the vent hole 4 and the valve 5 are simultaneously formed in the lid 3 created by the forming step. The manufacturing method of this embodiment is characterized in that a press die, which will be described later, is used in this hole processing step.

[0036] In particular, in the hole processing step, the lid 3 is partially punched out using a punch in a press die, thereby simultaneously forming the vent hole 4 and the valve 5 in the lid 3. Here, "partially punching out the lid 3" means that the lid 3 is sheared only at a part of the circumference of the punch, and the remaining part is not sheared.

[0037] With a normal press die, there is a limit to how small the punch can be, and it is only possible to simply form a vent hole larger than that of this embodiment. However, in this embodiment, a high-precision press die is used to perform so-called partial punching, as described later, so that a small hole such as the vent hole 4 can be processed with a punch smaller than that of a normal press die, and the valve 5 can be formed at the same time.

[0038] The width B defines the minimum width (Bmin) of the ventilation hole 4. Here, the minimum width refers to the width of the portion of the ventilation hole 4 that has the smallest width. In this embodiment, this minimum width can be made smaller than when a normal press die is used, and can be made as small as 0.1 mm. On the other hand, the minimum width of a normal press die exceeds 1 mm. Therefore, the minimum width of the ventilation hole 4 in this embodiment is preferably 0.1 mm or more and 1 mm or less. As mentioned above, the width B of the ventilation hole 4 in this embodiment is 0.3 mm.

[0039] 4 is a front cross-sectional view showing a press die used in the hole processing step. Since the six ventilation holes 4 etc. are made in the same manner, the following description will be given for the case where there is only one ventilation hole 4 etc., for the sake of convenience.

[0040] The press die 10 includes a punch 11 for partially punching out the lid 3, a die plate 12 into which the punch 11 is inserted during punching and which cooperates with the punch 11 to partially punch out the lid 3, a punch plate 13 for supporting the punch 11, and a stripper plate 14 for removing the lid 3 from the punch 11 after punching. The punch plate 13 is fixed to an upper die 15 on the movable side of the press, and the die plate 12 is fixed to a lower die 16 on the fixed side by bolts or the like (not shown).

[0041] The lid 3 is placed upside down on the die plate 12 and is punched out from the back side, that is, the lower side in the use state (see FIG. 3).

[0042] Punch 11 extends in the vertical direction and has a blade portion 17 at the tip end (lower end) where punching is performed, and a supported portion 18 at the base end (upper end) that is supported by punch plate 13. As shown in Fig. 5, punch 11 has a U-shaped cross-sectional shape along its entire length, which is the same as the air vent 4, etc. Therefore, blade portion 17 and supported portion 18 also have the cross-sectional shape as shown in Fig. 5. The length Ap and width Bp of the cross-section of blade portion 17 are equal to the length A and width B of the air vent 4, etc.

[0043] The blade portion 17 of the punch 11 has, on its outer periphery, a shearing portion 41 that shears the lid 3 together with the die plate 12, and a non-shearing portion 42 that does not shear the lid 3. As can be seen by comparing with Fig. 2, the shearing portion 41 is U-shaped like the cut 6, and the non-shearing portion 42 is straight like the broken line 7.

[0044] As shown in FIG. 4, a tip surface 43 of the blade portion 17 of the punch 11 is a flat surface perpendicular to the longitudinal direction of the punch 11 (the vertical direction).

[0045] As with the vent hole 4, the cross-sectional size of the punch 11 is very small and the punch 11 is extremely slender, so some ingenuity is required to prevent the punch 11 from shaking during punching. Such ingenuity is incorporated throughout the press die 10 of this embodiment.

[0046] 6 and 7, a die hole 19 for inserting the blade portion 17 of the punch 11 is provided on the upper surface of the die plate 12. The cross-sectional length Ah of the die hole 19 is greater than the cross-sectional length Ap of the blade portion 17, and the cross-sectional width Bh of the die hole 19 is substantially equal to the cross-sectional width Bp of the blade portion 17. During punching, the blade portion 17 is inserted into the die hole 19 at its leftmost position. Moreover, the blade portion 17 is inserted into the die hole 19 all around to a depth H approximately equal to the thickness tl of the lid 3.

[0047] As a result, the shearing portion 41 of the blade portion 17 cooperates with the adjacent peripheral portion (shearing portion 44 ) of the die hole 19 to shear the lid 3 and form the vent hole 4 and the cut 6 .

[0048] On the other hand, the non-shearing portion 42 of the blade portion 17 is inserted into the die hole 19 across a clearance CL. This clearance CL is large enough to leave a part of the lid 3 between the non-shearing portion 42 and the peripheral portion (non-shearing portion 45) of the die hole 19 facing it. In this embodiment, the clearance CL is formed to be approximately the same as the thickness tl of the lid 3. As a result, the non-shearing portion 42 of the blade portion 17 bends the lid 3 into a crank shape, and a valve 5 connected to the lid 3 is formed at this bent portion.

[0049] In this way, the vent hole 4, the valve 5 and the slit 6 can be easily formed simultaneously in one press operation. The cutting edge 17 and the die plate 12 are formed with rounded portions 46, 47 for rounding the edges and easing the crank bending.

[0050] Returning to FIG. 4, the punch plate 13 is provided with a punch insertion hole 22 for inserting the supported portion 18 of the punch 11 into a tight fit. The punch insertion hole 22 penetrates the punch plate 13 in the vertical direction, and has the same cross-sectional shape as the supported portion 18 as shown in FIG. 8. The supported portion 18 is inserted into the punch insertion hole 22 over the entire length. In this embodiment, the supported portion 18 is fixed to the punch insertion hole 22 by an adhesive. A base end surface (upper end surface) 23 of the punch 11 or the supported portion 18 is made flush with a base end surface (upper end surface) 24 of the punch plate 13. In particular, after the supported portion 18 is fixed to the punch insertion hole 22, the base end surface 23 of the supported portion 18 and the base end surface 24 of the punch plate 13 are polished at the same time and positioned on the same plane with high accuracy. Since these base end surfaces 23, 24 are both in surface contact with the upper die 15, the downward force from the upper die 15 can be efficiently and stably transmitted to the punch 11. In addition, the reaction force of the punch 11 during punching can be reliably received by the upper die 15.

[0051] A protrusion 25 that protrudes downward, i.e., toward the tip side of the punch 11, is provided around the punch insertion hole 22 in the punch plate 13. This lengthens the punch insertion hole 22, thereby lengthening the support length of the punch 11 and shortening the protruding length of the punch 11 protruding from the punch insertion hole 22, thereby suppressing the wobble of the punch 11.

[0052] As is well known, the stripper plate 14 is attached to the punch plate 13 via a spring or the like (not shown) so as to be capable of rising and falling. The stripper plate 14 serves to press the lid 3 onto the die plate 12 immediately before punching by the punch 11, and to separate the lid 3 from the punch 11 when the punch 11 rises after punching.

[0053] Particularly in this embodiment, the punch 11 is guided by using the stripper plate 14 to suppress the deviation of the punch 11. That is, as shown in FIG. 7, the stripper plate 14 is provided with a punch guide hole 26 for allowing the blade portion 17 of the punch 11 to be slidably inserted at all times. The punch guide hole 26 penetrates the stripper plate 14 in the vertical direction, and has the same cross-sectional shape as the blade portion 17 as shown in FIG. 8. The cross-sectional shape of the punch guide hole 26 is the same as the cross-sectional shape of the punch insertion hole 22, and is shown in FIG. 8 for convenience. When the blade portion 17 is inserted into the punch guide hole 26, the blade portion 17 is supported all around by the inner peripheral surface of the punch guide hole 26. As a result, even if the blade portion 17 tries to bend due to a reaction force during punching, the deflection is suppressed. The deviation of the blade portion 17 is suppressed, and punching can be performed accurately and stably.

[0054] 4 and 7 show the state after punching when punch 11 is at the bottom dead point, but the part of punch 11 protruding downward from blade portion 17 or convex portion 25 is constantly inserted into punch guide hole 26. Therefore, punch 11 can always be guided by punch guide hole 26 from the top dead point to the bottom dead point, and punch 11 can be stably raised and lowered on a constant trajectory.

[0055] The stripper plate 14 is provided with a recess 27 into which the protrusion 25 of the punch plate 13 fits with a gap.

[0056] In this way, according to the press die 10 of this embodiment, the vibration of the punch 11 is suppressed, and as a result, the machining accuracy of the vent hole 4 can be improved. In addition, since the vibration of the punch 11 is suppressed, the clearance CLa between the punch 11 and the sheared portion 41, 44 of the die hole 19, and the clearance CLb between the punch 11 and the punch guide hole 26 can be reduced as shown in FIG. 7, which also leads to improved machining accuracy. In this embodiment, the former clearance CLa is 0.005 mm, and the latter clearance CLa is 0.003 mm. However, the size of these clearances CLa, CLb can be appropriately changed depending on the material, thickness, etc. of the lid 3.

[0057] In this embodiment, the lid 3 is partially punched out, so that no scraps (punch waste) are generated by punching, and therefore the risk of scraps adhering to the lid 3 and being mixed in the container by mistake can be eliminated.

[0058] Since the vibration of the punch 11 is suppressed, galling caused by the punch 11 coming into contact with the die plate 12 during punching can also be suppressed.

[0059] In this embodiment, punch 11 is produced by wire electric discharge machining. That is, punch 11 is produced by hollowing out a conductive metal (particularly iron) material having a thickness equal to or greater than the length (vertical dimension) of punch 11, by wire electric discharge machining, so as to have the cross-sectional shape shown in Fig. 5. In this way, the small cross-sectional shape of punch 11 can be produced easily and with high precision.

[0060] Similarly, the die hole 19, punch insertion hole 22, and punch guide hole 26 are also made by wire electric discharge machining. This makes it possible to easily make the small cross-sectional shape of each hole as shown in Figures 6 and 8 with high precision.

[0061] If possible, at least one of the punch 11, the die hole 19, the punch insertion hole 22 and the punch guide hole 26 may be machined by a high-precision machining center.

[0062] Next, modified examples of the present disclosure will be described. Note that a description of the same parts as those in the basic embodiment will be omitted, and the following description will focus mainly on the differences from the basic embodiment.

[0063] [First Modification] 9 shows the configuration of the first modified example. In this first modified example, the method of partially punching the lid 3 is changed. That is, in the basic embodiment, a clearance CL is provided between the punch 11 and the die hole 19 to prevent a portion of the lid 3 from being sheared off, but in this modified example, a portion of the punch 11 is not inserted into the die hole 19 to prevent a portion of the lid 3 from being sheared off.

[0064] 9 shows the state when the blade portion 17 of the punch 11 is at the bottom dead point. At this time, the shearing portion 41 of the blade portion 17 is inserted into the die hole 19, but the non-shearing portion 42 of the blade portion 17 is not inserted into the die hole 19. The tip surface 43 of the blade portion 17 is inclined with respect to a direction perpendicular to the longitudinal direction (up-down direction) of the punch 11, and is inclined so that the left side (the side of the tip 8 of the vent hole 4) is lower than the right side (the side of the base end 7 of the vent hole 4). In other words, the tip surface 43 of the blade portion 17 is provided with a predetermined shear angle θ.

[0065] As a result, the shearing portion 41 of the blade portion 17 cooperates with the adjacent peripheral portion (shearing portion 44 ) of the die hole 19 to shear the lid 3 and form the vent hole 4 and the cut 6 .

[0066] On the other hand, the non-shearing portion 42 of the blade portion 17 is not inserted into the die hole 19, and therefore does not naturally shear the lid 3. Therefore, the valve 5 connected to the lid 3 at this non-shearing position is formed.

[0067] The tip surface 43 of the blade portion 17 is inclined so that the left side is lower than the right side, so that the shearing is performed sequentially from the left side to the right side, and the cuts 6 can be made. This allows the cuts 6 to be made neatly.

[0068] In this modified example, since no clearance CL is provided between the punch 11 and the die hole 19, the cross-sectional shape of the die hole 19 is modified to be the same as the cross-sectional shapes of the punch insertion hole 22 and the punch guide hole 26 shown in FIG.

[0069] [Second modified example] 10 shows the configuration of the second modified example, in which the method of fixing the punch 11 to the punch plate 13 is changed.

[0070] That is, the supported portion 18 of the punch 11 is inserted and fitted into the punch insertion hole 22 in the same manner as described above. However, the punch 11 is not fixed by adhesive, but instead is positioned and fixed in the punch insertion hole 22 by a key 28 and a key groove 29.

[0071] The key 28 is integrally provided on the side surface (left side surface in the illustrated example) of the punch 11 so as to protrude therefrom, and extends a predetermined length from the base end surface (upper end surface) 23 toward the tip side (lower side) of the punch 11. As illustrated, the key 28 has a vertically elongated rectangular cross-sectional shape.

[0072] Meanwhile, the key groove 29 is provided on the inner surface (the left inner surface in the illustrated example) of the punch insertion hole 22, and extends from the base end surface (upper end surface) 24 of the punch plate 13 toward the tip side (lower side) the same length as the key 28. As illustrated, the key groove 29 also has a vertically elongated rectangular cross-sectional shape. Moreover, the horizontal width (width in the left-right direction) of the key groove 29 is slightly larger than that of the key 28. The base end side of the key groove 29 is open.

[0073] The punch 11 and the key 28 are detachably inserted into the punch insertion hole 22 and the key groove 29, respectively. The key 28 is inserted into the key groove 29 to fit snugly. This prevents the punch 11 from being displaced in the front-rear, left-right and circumferential directions. In the inserted state, the tip face (lower end face) 30 of the key 28 comes into contact with the tip face (lower end face) 31 of the key groove 29. In addition, the base end face 23 of the punch 11 and the base end face 32 of the key 28 come into contact with the upper die 15. As a result, the key 28 is sandwiched between the tip face 31 of the key groove 29 and the upper die 15 and is restrained in the axial direction, so that the punch 11 can be prevented from being displaced in the axial direction relative to the punch insertion hole 22.

[0074] In this manner, the punch 11 is substantially fixed in the punch insertion hole 22 .

[0075] According to this embodiment, the punch plate 13 can be removed from the upper die 15, and the punch 11 can be pulled out toward the base end side and removed from the punch plate 13. The punch 11 can also be attached to the punch plate 13 by following the procedure in the reverse direction. Therefore, the punch 11 can be easily replaced when it deteriorates or is damaged.

[0076] [Third Modification] The vent holes 4 and the like are not limited to the U-shape shown in Fig. 2, but can be changed to various shapes. In particular, since the punch 11 and the like are produced by wire electric discharge machining, they can be made to have a relatively complicated cross-sectional shape. Therefore, the vent holes 4 and the like can be made to have a more complicated shape. According to this embodiment, the degree of freedom in designing the minute vent holes 4 and the like can be increased.

[0077] 11 shows modified examples of the ventilation holes 4, etc. Of course, the cross-sectional shape of the punch 11, etc. can be changed in accordance with the change in the shape of the ventilation holes 4, etc.

[0078] FIG. 11(A) shows an S-shaped vent hole 4, FIG. 11(B) shows an inverted T-shaped vent hole 4, FIG. 11(C) shows a T-shaped vent hole 4, and FIG. 11(D) shows a fountain-shaped vent hole 4, respectively.

[0079] Fig. 11(E) shows a K-shaped vent hole 4, Fig. 11(F) shows a Y-shaped vent hole 4, Fig. 11(G) shows an O-shaped vent hole 4, Fig. 11(H) shows an E-shaped vent hole 4, and Fig. 11(I) shows an I-shaped vent hole 4. The vent holes 4 in Figs. 11(E) to (I) together represent the name of the present applicant in English.

[0080] Also for these ventilation holes 4 etc., the minimum width (represented by Bmin) is preferably 0.1 mm or more and 1 mm or less.

[0081] By the way, if the cross-sectional shape of the punch 11 is changed to match the shape of the illustrated ventilation hole 4, etc., it is possible to increase the strength of the punch 11. Therefore, such a change in the shape of the ventilation hole 4, etc. is also effective in improving the accuracy of the hole shape.

[0082] Although the embodiment of the present disclosure has been described in detail above, various other embodiments and modifications of the present disclosure are conceivable. For example, the lid 3 does not necessarily have to be transparent, and may be opaque. The above numerical values ​​are merely examples and may be changed as appropriate. The ventilation hole 4 and the like may have other simple shapes, such as a square, a substantially circular, or a substantially elliptical shape.

[0083] The configurations of the basic embodiment and each modified example described above can be combined in part or in whole unless there is a particular contradiction. The embodiments of the present disclosure are not limited to the above-mentioned embodiments, and all modifications, applications, and equivalents encompassed within the concept of the present disclosure as defined by the claims are included in the present disclosure. Therefore, the present disclosure should not be interpreted as being limited, and can be applied to any other technology that falls within the scope of the concept of the present disclosure. [Explanation of symbols]

[0084] 1 Food containers 3 Lid 4 Ventilation holes 5 Valves 10 Press mold 11 Punch 12 Die Plate 13 Punch Plate 14 Stripper plate 19 Die Hole 22 Punch insertion hole 25 Convex 26 Punch guide hole 41 Shear section 42 Non-shear section CL Clearance

Claims

1. A method for manufacturing a lid for a disposable food container, comprising: a hole processing step of simultaneously forming an air hole in the lid and a cantilever-shaped valve that closes the air hole in an openable and closable manner by partially punching out the lid using a punch in a press die; The press die includes a die plate that cooperates with the punch to partially punch out the lid; The punch has a shearing portion that shears the lid together with the die plate and a non-shearing portion that does not shear the lid, During punching, the shearing portion of the punch is inserted into the die hole of the die plate to shear the lid, and the non-shearing portion of the punch is inserted into the die hole of the die plate with a clearance therebetween to bend the lid into a crank shape, and the bent portion forms the valve connected to the lid. A method for manufacturing a lid comprising the steps of:

2. The vent hole has a minimum width of 0.1 mm or more and 1 mm or less. A method for manufacturing the lid according to claim 1.

3. The press die includes a punch plate supporting the punch, and a stripper plate attached to the punch plate so as to be movable up and down; the punch plate has a punch insertion hole into which a supported portion of the punch is fitted and inserted to be fixed, and a protrusion provided around the punch insertion hole and protruding toward a tip end of the punch, The stripper plate has a recess into which the protrusion is fitted with a gap, and a punch guide hole formed through a bottom surface of the recess and through which the blade of the punch is always inserted in a slidable manner. A method for manufacturing the lid according to claim 1 or 2.

4. A method for manufacturing the press mold used in the method for manufacturing the lid according to claim 3, comprising the steps of: The punch, the punch insertion hole, the die hole, and the punch guide hole are fabricated by wire electric discharge machining. A method for manufacturing a press die comprising the steps of:

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