JP7630170B2 - How the lid is manufactured - Google Patents

Description

This disclosure relates to a method for manufacturing a lid, and in particular to a method for manufacturing a lid for a disposable food container.

Food containers are well known that have a container body for storing food such as boxed lunches and fresh foods, and a lid that fits over the container body and closes the top opening. These 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.

JP 2018-20850 A

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.

Therefore, this disclosure was devised in consideration of the above circumstances, and its purpose is to provide a method for manufacturing a lid that can form a small vent hole in the lid.

According to one aspect of the present disclosure,
A method for manufacturing a lid for a disposable food container, comprising:
The present invention provides a method for manufacturing a lid, 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.

Preferably, the ventilation hole has a diameter or minimum width of 0.1 mm or more and 1 mm or less.

Preferably, the ventilation holes are slotted, circular, Y-shaped, crank-shaped or cross-shaped.

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

Preferably, the press die includes a punch plate that supports the punch, and the punch plate has a punch insertion hole into which the punch is inserted and a protrusion that is provided around the punch insertion hole and protrudes toward the tip of the punch.

Preferably, the punch has a shear angle.

According to this disclosure, it is possible to form a small vent in the lid.

FIG. 2 is a diagram showing a food container according to the present embodiment. FIG. FIG. 13 is an enlarged plan view showing another ventilation hole. FIG. 2 is a front cross-sectional view showing a press die. FIG. 5 is a diagram showing a cross-sectional shape of a punch (ZZ cross section in FIG. 4). FIG. 5 is a diagram showing the cross-sectional shape of a die hole (ZZ cross section in FIG. 4). 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; FIG. 11 is a front cross-sectional view showing the configuration of a first modified example. FIG. 11 is an enlarged plan view showing a ventilation hole of a second modified example.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. Please note that the present disclosure is not limited to the following embodiments.

Figure 1 shows a food container according to an embodiment of the present disclosure, with (A) being a plan view and (B) being a front cross-sectional view (cross-sectional view taken along line Ib-Ib in (A)). For convenience, the front, back, left, right, top and bottom directions are defined as shown in the figure. However, please note that these directions are defined merely for convenience of explanation. Also, please note that the dimensions of the figures described below may be exaggerated for ease of understanding and are not necessarily accurate.

The food container 1 is a disposable type container that is used only when selling food at stores such as convenience stores and supermarkets. 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 its upper opening. The food F in this embodiment is a boxed lunch, and the food container 1 is used, for example, as an airtight container for holding boxed lunches sold at convenience stores. The container body 2 and lid 3 in this embodiment are circular in plan view as shown in Figure 1 (A), but the shape is not limited and may be rectangular, elliptical, etc.

The container body 2 and the lid 3 are both made of plastic and are formed by vacuum forming or the like of a plastic sheet material. Examples of plastic materials 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.

The container body 2 and the lid 3 may be made of materials other than plastic, for example paper.

The container body 2 is circular bowl-shaped, and its upper edge 2A is folded back radially outward. The outer peripheral edge 3A of the roughly disk-shaped lid 3 is tightly fitted to 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 inside the outer peripheral edge 3A is a horizontal disk-shaped central portion 3B that is positioned lower than the outer peripheral edge 3A.

In the center 3B of the lid 3, a vent hole 4 is formed to keep the food F fresh inside the container 1. In particular, in this embodiment, a number of very small vent holes 4 are formed by a hole processing process 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).

The number, position, arrangement, etc. of the ventilation holes 4 are arbitrary, and may be one or a number other than six.

As shown enlarged in FIG. 2, in this embodiment, the ventilation hole 4 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. In addition, 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.

As mentioned above, in order to prevent external dust and the like from entering the container 1 through the ventilation hole 4, it is desirable for the size of the ventilation hole 4 to be 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 the punch can be made smaller than a normal press die, and it is possible to process a minute hole such as the ventilation hole 4.

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.

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

Incidentally, the shape of the ventilation hole 4 can also be a circle as shown in FIG. 3. In this case, it is preferable that the diameter D of the ventilation hole 4 is 0.1 mm or more and 1 mm or less.

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.

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 inside the container 1 can be maintained.

On the other hand, food F in container 1, which is covered and sealed with lid 3, is planned to be heated in a microwave oven along with container 1. During this heating, water vapor and steam (called water vapor, etc.) are generated from food F, which must be released to the outside.

According to this embodiment, water vapor and the like can be effectively released through the ventilation holes 4. In addition, since multiple ventilation holes 4 are provided, the total area of the ventilation holes 4 can be increased, and the total area required for discharging water vapor and the like can be sufficiently secured. In this way, the ventilation holes 4 function as effective steam release holes.

However, the uses of the ventilation hole 4 are 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 that contain a lot of water, the vegetables may sweat and water may accumulate inside the container. In this case, the ventilation hole 4 can also be used as a draining hole.

The size, number, and shape of the ventilation holes 4 are optimally set to satisfy the above functions.

This embodiment provides a method for manufacturing a lid 3 that can form such excellent small-sized ventilation holes 4 in the lid 3.

The method for manufacturing the lid 3 in this embodiment includes a forming step in which a plastic sheet material is cut and formed (particularly vacuum formed) to produce a lid 3 of a predetermined shape, and a hole processing step in which the vent hole 4 is formed in the lid 3 produced by the forming step. In particular, the manufacturing method in this embodiment is characterized in that in the hole processing step, the vent hole 4 is formed by completely punching out the lid 3 using a punch in a press die, which will be described later. 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 of the same shape as the cross-sectional shape of the punch.

Figure 4 is a front cross-sectional view showing the press die used in the hole processing process. Note that since the six ventilation holes 4 are made in the same manner, for the sake of convenience, the following explanation will be given for the case where there is only one ventilation hole 4.

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 the movable upper die 15 of the press, and the die plate 12 is fixed to the fixed lower die 16 by bolts or the like (not shown).

The punch 11 is elongated in the vertical direction and has a blade portion 17 at the tip side (lower end side) where punching is performed, and a supported portion 18 at the base side (upper end side) that is supported by the punch plate 13. As shown in Figure 5, the punch 11 has an elongated hole-like cross-sectional shape over its entire length that is the same shape and size as the ventilation hole 4. Therefore, the blade portion 17 and the supported portion 18 also have a cross-sectional shape as shown in Figure 5. The tip of the punch 11 has a V-shaped cross section as shown in Figure 4, and the punch 11 is provided with a shear angle θ.

As with the ventilation 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. The press die 10 of this embodiment incorporates such ingenuity in many places.

The upper surface of the die plate 12 is provided with a die hole 19 for inserting the blade 17 of the punch 11. As shown in FIG. 6, the die hole 19 has the same cross-sectional shape as the blade 17. The blade 17 of the punch 11 and the periphery of the die hole 19 shear the lid 3 and punch out the vent hole 4. Scrap (punch waste) 20 after punching passes through the die hole 19 and a tapered scrap hole 21 continuing downward from it and falls onto the lower die 16 located at the bottom of the hole.

The punch plate 13 is provided with a punch insertion hole 22 for inserting the supported portion 18 of the punch 11 into a snug 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 adhesive. The base end surface (upper end surface) 23 of the punch 11 or the supported portion 18 is made flush with the 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. Because both base end faces 23 and 24 are 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.

A protrusion 25 is provided around the punch insertion hole 22 in the punch plate 13, protruding downward, i.e., toward the tip of the punch 11. This lengthens the punch insertion hole 22, increasing 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.

As is well known, the stripper plate 14 is attached to the punch plate 13 via a spring (not shown) so that it can be raised and lowered. The stripper plate 14 serves to press the lid 3 onto the die plate 12 just before punching by the punch 11, and to separate the lid 3 from the punch 11 when the punch 11 rises after punching.

In particular, in this embodiment, the stripper plate 14 is used to guide the punch 11 and suppress the wobbling of the punch 11. That is, the stripper plate 14 is provided with a punch guide hole 26 through which the blade portion 17 of the punch 11 is always inserted so as to be slidable. 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, so it is also 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. As a result, even if the blade portion 17 tries to bend due to a reaction force during punching, the bending is suppressed. The wobbling of the blade portion 17 is suppressed, and punching can be performed accurately and stably.

Figure 4 shows the state after punching when the punch 11 is at the bottom dead point, but the blade portion 17 or the portion of the punch 11 that protrudes downward from the protrusion 25 is always inserted into the punch guide hole 26. Therefore, the punch 11 can always be guided by the punch guide hole 26 from the top dead point to the bottom dead point of the punch 11, and the punch 11 can be raised and lowered stably on a constant trajectory.

The stripper plate 14 has a recess 27 into which the protrusion 25 of the punch plate 13 fits with a gap.

As described above, the press die 10 of this embodiment suppresses the vibration of the punch 11, thereby improving the machining accuracy of the ventilation hole 4. In addition, because 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 size of these clearances CLa and CLb can be changed as appropriate depending on the material, thickness, etc. of the lid 3.

In this embodiment, the punch 11 is provided with a shear angle θ, which reduces the impact on the punch 11 during punching and suppresses shaking of the punch 11. It also prevents 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 of the scrap 20 remaining attached to the lid 3 and being accidentally mixed into the container.

By suppressing the vibration of the punch 11, it is also possible to suppress galling that occurs when the punch 11 comes into contact with the die plate 12 during punching.

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

Similarly, the die hole 19, punch insertion hole 22, and punch guide hole 26 are also produced by wire electric discharge machining. This allows the small cross-sectional shape of each hole, as shown in Figure 6, to be produced with high precision and ease.

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

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

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

That is, the supported portion 18 of the punch 11 is inserted and fitted into the punch insertion hole 22, as described above. However, it is not fixed with adhesive. Instead, the punch 11 is positioned and fixed in the punch insertion hole 22 by a key 28 and a key groove 29.

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

Meanwhile, the key groove 29 is provided on the inner surface (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. The 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.

The punch 11 and key 28 are removably inserted into the punch insertion hole 22 and key groove 29, respectively. The key 28 is inserted into the key groove 29 so as to fit snugly. This prevents the punch 11 from shifting in position in the front-rear, left-right, and circumferential directions. In the inserted state, the tip face (lower end face) 30 of the key 28 contacts 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 contact 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, preventing the punch 11 from shifting in position in the axial direction relative to the punch insertion hole 22.

In this way, the punch 11 is essentially fixed in the punch insertion hole 22.

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 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. This makes it easy to replace the punch 11 when it deteriorates or is damaged.

[Second Modification]
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, they can be made to have a relatively complex cross-sectional shape. Therefore, the ventilation hole 4 can be made to have a more complex shape. According to this embodiment, it is possible to easily produce a minute ventilation hole 4 and the like that has a high degree of freedom in design.

Figure 9 shows a modified example of the ventilation hole 4. Of course, the cross-sectional shape of the punch 11 and other parts can be changed to match the change in the shape of the ventilation hole 4.

Figure 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° apart) in the circumferential direction. The tip 34 of the extensions 33 is formed in a semicircular shape, and a pair of side edges 35 of the extensions 33 are parallel to each other and linearly extend in the radial direction.

The base ends of the extensions 33 are constricted, and the base ends of the closer side edges 35 of adjacent extensions 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 ventilation hole 4. As mentioned above, this minimum width is preferably 0.1 mm or more and 1 mm or less.

Figure 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 Figure 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, and this width B defines the minimum width of the ventilation hole 4. The minimum width is preferably 0.1 mm or more and 1 mm or less.

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

The base ends of the extensions 33 are constricted, and the base ends of the closer side edges 35 of adjacent extensions 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 ventilation hole 4. This minimum width is preferably 0.1 mm or more and 1 mm or less.

By the way, if the cross-sectional shape of the punch 11 is changed to match the shape of the ventilation hole 4 shown in Figures 9 (A) to (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 precision of the hole shape.

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 modified as appropriate. The ventilation hole 4 may have other simple shapes, such as a rectangle or an oval.

The configurations of the basic embodiment and each of the modified examples 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-described embodiments, and all modified examples, 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 in a restrictive manner, and can be applied to any other technology that falls within the scope of the concept of the present disclosure.

1 Food container 3 Lid 4 Vent 10 Press die 11 Punch 13 Punch plate 14 Stripper plate 22 Punch insertion hole 25 Convex portion 26 Punch guide hole θ Shear angle

Claims (4)

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: The method for manufacturing a lid according to claim 1 , wherein the air vent is Y-shaped, crank-shaped or cross-shaped. The method for manufacturing a lid according to claim 1 or 2 , wherein the punch has a shear angle. A method for manufacturing the press die used in the method for manufacturing the lid according to any one of claims 1 to 3,
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