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 forming a vent hole 4 on the lid by completely 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 devised in light of the above circumstances, and has an object to provide a method for manufacturing a lid that is capable of forming a small-sized ventilation 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: A hole processing step is provided in which the lid is completely punched out using a punch in a press die to form an air hole in the lid. A method for manufacturing a lid is provided.

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

[0008] Preferably, the vent hole is slot-shaped, circular, Y-shaped, crank-shaped or cross-shaped.

[0009] Preferably, the press die includes a stripper plate having a punch guide hole through which the punch is always slidably inserted.

[0010] 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.

[0011] Preferably, the punch has a shear angle. Effect of the Invention

[0012] According to the present disclosure, a small vent hole can be formed in the lid. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram showing a food container according to the present embodiment. [Diagram 2] FIG. [Diagram 3] FIG. 13 is an enlarged plan view showing another ventilation hole. [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 a cross-sectional shape of a die hole (ZZ cross section in FIG. 4). [Figure 7]FIG. 4 is a front cross-sectional view showing clearances between a punch and a die hole and between a punch guide hole and the punch; [Figure 8] FIG. 11 is a front cross-sectional view showing the configuration of a first modified example. [Figure 9] FIG. 11 is an enlarged plan view showing an air hole of a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] The container body 2 and the lid 3 may be made of a material other than plastic, for example, paper.

[0019] 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.

[0020] A vent hole 4 is formed in the center 3B of the lid 3 to keep the food F fresh in the container 1. In particular, in this embodiment, a plurality of very small vent holes 4 are formed by a hole processing step described below. In this embodiment, six elongated vent holes 4 are arranged in a lattice pattern. In this embodiment, the group of six vent holes 4 is offset radially outward (toward the front) from the center of the lid 3, as shown in FIG. 1(A).

[0021] The number, position, arrangement and the like of the ventilation holes 4 are arbitrary, and the number may be one or any number other than six.

[0022] As shown enlarged in Fig. 2, the ventilation hole 4 in this embodiment is an elongated hole extending in the left-right direction. The ventilation hole 4 has a length A and a width B. The width B is constant in the length A direction. The base end (right end) 5 and the tip (left end) 6 of the ventilation hole 4 in the length A direction are formed in a semicircular shape. Furthermore, the front and rear side edges 7, 8 connecting the base end 5 and the tip 6 are linear and parallel to the left-right direction.

[0023] As described above, in order to prevent external dust and the like from entering the container 1 through the ventilation hole 4, it is desirable that the size of the ventilation hole 4 is as small as possible. In the hole processing step described below, the ventilation hole 4 is formed in the lid 3 by completely punching out the lid 3 using a punch in a press die. With a normal press die, there is a limit to how small the punch can be made, and it is not possible to process a minute hole such as the ventilation hole 4 of this embodiment. However, in this embodiment, a high-precision press die as described below is used, so that the punch can be made smaller than that of a normal press die, and it is possible to process a minute hole such as the ventilation hole 4.

[0024] 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.

[0025] In this embodiment, the width B of the vent hole 4 is 0.3 mm. Meanwhile, the length A is larger, 5.0 mm. These dimensions can be changed.

[0026] Incidentally, the shape of the ventilation hole 4 may be a circle as shown in Fig. 3. In this case, the diameter D of the ventilation hole 4 is preferably 0.1 mm or more and 1 mm or less.

[0027] As described above, the ventilation hole 4 of this embodiment has a very small size. Therefore, it is possible to effectively prevent external dust and the like (dust, insects, foreign objects, etc.) from entering the container 1 through the ventilation 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.

[0028] Of course, air can circulate between the inside and outside of the container through the ventilation holes 4, so the freshness of the food F in the container 1 can be maintained in a good condition.

[0029] 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.

[0030] According to this embodiment, water vapor and the like can be efficiently released through the ventilation holes 4. Furthermore, since a plurality of ventilation holes 4 are provided, the total area of ​​the ventilation holes 4 is increased, and the total area required for discharging water vapor and the like can be sufficiently secured. Thus, the ventilation holes 4 function as efficient steam release holes.

[0031] However, the use of the ventilation hole 4 is not limited to the above. For example, when the food F is noodles for instant yakisoba, the ventilation hole 4 can be used as a draining hole. Also, when the food F is vegetables or the like that contain a lot of water, the vegetables 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 draining hole.

[0032] The size, number, shape, etc. of the ventilation holes 4 are optimally set so as to satisfy the above functions.

[0033] The present embodiment provides a method for manufacturing the lid 3 that can form such excellent small vent holes 4 in the lid 3.

[0034] The manufacturing method of the lid 3 of this embodiment includes a forming step of cutting and forming (particularly vacuum forming) a plastic sheet material to produce the lid 3 in a predetermined shape, and a hole processing step of forming the ventilation hole 4 in the lid 3 produced by the forming step. In particular, the manufacturing method of this embodiment is characterized in that in the hole processing step, the ventilation hole 4 is formed by completely punching out the lid 3 using a punch in a press die described below. Here, "completely punching out the lid 3" means that, as in normal piercing, the lid 3 is sheared around the entire circumference of the punch, and the lid 3 is punched out so as to form a through hole having the same shape as the cross-sectional shape of the punch.

[0035] 4 is a front cross-sectional view showing a press die used in the hole processing step. Since the six ventilation holes 4 are made in the same manner, the following description will be given for the case where there is only one ventilation hole 4, for the sake of convenience.

[0036] The press die 10 includes a punch 11 for punching the vent hole 4 from the lid 3, a die plate 12 into which the punch 11 is inserted during punching, 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 a movable upper die 15 of the press, and the die plate 12 is fixed to a fixed lower die 16 by bolts or the like (not shown).

[0037] Punch 11 extends in the vertical direction and has a blade portion 17 at the tip end (lower end) that performs punching, 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 an elongated hole-like cross-sectional shape over its entire length that is the same shape and size as air hole 4. Therefore, blade portion 17 and supported portion 18 also have the cross-sectional shape shown in Fig. 5. The tip end of punch 11 has a V-shaped cross-section as shown in Fig. 4, and punch 11 is provided with a shear angle θ.

[0038] 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.

[0039] 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 die hole 19 has the same cross-sectional shape as the blade portion 17, as shown in Fig. 6. The blade portion 17 of the punch 11 and the peripheral edge of the die hole 19 shear the lid 3, and the vent hole 4 is punched out. Scrap (punched waste) 20 after punching passes through the die hole 19 and a tapered scrap hole 21 continuing downward therefrom, and falls onto the lower die 16 located at the bottom of the hole.

[0040] 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. 6. The cross-sectional shape of the punch insertion hole 22 is the same as the cross-sectional shape of the die hole 19, so it is shown in FIG. 6 for convenience. The supported portion 18 is inserted over the entire length of the punch insertion hole 22. 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 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 precision. Since both base end faces 23, 24 are in surface contact with upper die 15, the downward force from upper die 15 can be efficiently and stably transmitted to punch 11. In addition, the reaction force of punch 11 during punching can be reliably received by upper die 15.

[0041] 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.

[0042] 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.

[0043] Particularly in this embodiment, the punch 11 is guided by utilizing the stripper plate 14 to suppress the deviation of the punch 11. That is, 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. 6. The cross-sectional shape of the punch guide hole 26 is also the same as the cross-sectional shape of the die hole 19, and is therefore shown in FIG. 6 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. This suppresses the deviation of the blade portion 17 even if it tends to bend due to a reaction force during punching. This allows accurate and stable punching.

[0044] 4 shows 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.

[0045] The stripper plate 14 is provided with a recess 27 into which the protrusion 25 of the punch plate 13 fits with a gap.

[0046] 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. Furthermore, since the vibration of the punch 11 is suppressed, the clearance CLa between the punch 11 and 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 sizes of these clearances CLa and CLb can be appropriately changed depending on the material, thickness, etc. of the lid 3.

[0047] In this embodiment, the punch 11 is provided with a shear angle θ, which reduces the impact applied to the punch 11 during punching and suppresses shaking of the punch 11. It also suppresses the scrap 20 from adhering to the punch 11 due to static electricity and being lifted up together with the punch 11. This significantly reduces the risk that the scrap 20 will remain attached to the lid 3 and be mistakenly mixed into the container.

[0048] 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.

[0049] 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.

[0050] 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 Figure 6 with high precision.

[0051] 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.

[0052] 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.

[0053] [First Modification] 8 shows the configuration of a first modified example. In this first modified example, the method of fixing the punch 11 to the punch plate 13 is changed.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] In this manner, the punch 11 is substantially fixed in the punch insertion hole 22 .

[0059] 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.

[0060] [Second modified example] The ventilation hole 4 is not limited to the elongated hole shape shown in Fig. 2 or the circular shape shown in Fig. 3, but can be changed to various shapes. In particular, since the punch 11 and the like are produced by wire electric discharge machining, a relatively complex cross-sectional shape can be formed. Therefore, the ventilation hole 4 can be made into a more complex shape. According to this embodiment, it is possible to easily produce a minute ventilation hole 4 and the like with a high degree of freedom in design.

[0061] 9 shows a modified example of such an air hole 4. Of course, the cross-sectional shapes of the punch 11 and the like can be changed in accordance with the change in the shape of the air hole 4.

[0062] 9(A) shows a Y-shaped ventilation hole 4. This ventilation hole 4 has three extensions 33 that extend radially from the hole center O. These extensions 33 are arranged at equal intervals (120° intervals) in the circumferential direction. A tip 34 of the extensions 33 is formed in a semicircular shape, and a pair of side edges 35 of the extensions 33 are linear and parallel to each other and extend in the radial direction.

[0063] The base ends of the extending portions 33 are constricted, and the base ends of the closer side edges 35 of adjacent extending portions 33 are connected by an arc portion 26. The minimum distance between a pair of opposing arc portions 26 defines the minimum width (represented by Bmin) of the air hole 4. As described above, this minimum width is preferably 0.1 mm or more and 1 mm or less.

[0064] Fig. 9(B) shows an oblique crank-shaped ventilation hole 4. This ventilation hole 4 can be said to be the elongated hole-shaped ventilation hole 4 shown in Fig. 2 that has been extended in the longitudinal direction, bent into a crank shape, and then rotated. This ventilation hole 4 has a width B, which defines the minimum width of the ventilation hole 4. The minimum width is preferably 0.1 mm or more and 1 mm or less.

[0065] 9(C) shows a cross-shaped ventilation hole 4. This ventilation hole 4 is the Y-shaped ventilation hole 4 shown in FIG. 9(A) modified to a cross shape. As before, the ventilation hole 4 has four extensions 33 extending radially from the hole center O. These extensions 33 are disposed at equal intervals (90° intervals) in the circumferential direction. The extensions 33 have a tip 34 and a pair of side edges 35.

[0066] The base ends of the extending portions 33 are constricted, and the base ends of the closer side edges 35 of adjacent extending portions 33 are connected by an arc portion 26. The minimum distance between a pair of opposing arc portions 26 defines the minimum width (represented by Bmin) of the air hole 4. This minimum width is preferably 0.1 mm or more and 1 mm or less.

[0067] 9(A) to 9(C), the strength of the punch 11 can be increased. Therefore, changing the shape of the ventilation hole 4 in this way is also effective in improving the accuracy of the hole shape.

[0068] 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 cover 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 may have another simple shape, such as a rectangle or an ellipse.

[0069] 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]

[0070] 1 Food containers 3 Lid 4 Ventilation holes 10 Press mold 11 Punch 13 Punch Plate 14 Stripper plate 22 Punch insertion hole 25 Convex 26 Punch guide hole θ Shear angle

Claims

1. A method for manufacturing a lid for a disposable food container, comprising: a hole processing step of forming an air hole in the lid by completely punching out the lid using a punch in a press die; The vent has a diameter or minimum width of 0.1 mm or more and 1 mm or less; the press die includes a punch plate supporting the punch, a die plate into which the punch is inserted during punching, 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 die plate has a die hole into which the blade portion of the punch is inserted, 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 a lid comprising the steps of:

2. The vent hole is Y-shaped, crank-shaped or cross-shaped. A method for manufacturing the lid according to claim 1.

3. The punch has a shear angle A method for manufacturing the lid according to claim 1 or 2.

4. A method for manufacturing the press die used in the method for manufacturing a lid according to any one of claims 1 to 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:

Images