JP7484545B2 - Packaging box - Google Patents

Description

The present invention relates to a packaging box that functions as both a shipping box and a display box.

Among packaging boxes, there are shelf-ready packages (SPRs) that can be easily opened without using a cutter or the like, and that allow products to be displayed in stores as is. For example, the packaging box of Patent Document 1 includes a body having a pair of width sides and a pair of length sides, an inner flap connected to the upper edge of the width sides, and an outer flap connected to the upper edge of the length sides. The body also includes a break line that runs continuously around the circumference. The length sides and width sides that make up the body are provided with opening start sections (first operating section, second operating section) where fingers or other hands can be inserted, at positions that overlap the break lines.

This type of packaging box can be opened by inserting a finger or other hand into the opening start portion and pulling upward above the breaking line to expose the contained items. The lower part of the packaging box is then used as a tray for displaying the items.

International Publication No. 2018/235789

However, when packaging boxes are stacked during transportation, the lower packaging box is subjected to the weight of the packaging boxes stacked on top of it, causing the weaker breaking line area to bulge outward and deform.

The present invention was made in consideration of the above problems, and aims to provide a packaging box that can suppress deformation of the body due to a load from above.

The packaging box for solving the above problem has a body surrounded by multiple side panels, and top flaps connected to each upper edge of the body to form a top surface, and is provided with flap creases on each upper edge of the body that allow the top flaps to be folded, guide creases that extend in the same direction close to the flap creases, and a break line that is provided around the entire circumference of the body.

With the above configuration, even if a load is applied from above, the side panels are bent inward at the guide lines, forming a stepped section, which preferentially supports the load. This makes it possible to suppress deformation of the packaging box that would otherwise bulge outward at the break line.

In the above-mentioned packaging box, at least one pair of opposing side panels among those constituting the body may be configured to have an opening start portion that contacts the break line. With the above-mentioned configuration, a hand such as a finger can be inserted into the hand hole, and the break line can be cut in the process.

In the above packaging box, the opening start portion has an upper edge and a lower edge, the upper edge is part of the break line, and has a convex shape that slopes downward from the apex to both sides, and the break line may be configured to slope upward from both ends of the upper edge. With the above configuration, when inserting a hand such as a finger into the hand hole and continuing to cut the break line, the break becomes even easier.

In the above packaging box, a notch may be provided between the upper side and the lower side of the opening start portion. With the above configuration, the opening start portion can be opened by opening on both sides of the notch.

In the above packaging box, the lower side of the opening start portion may be configured with a foldable line extending from the intersection with the cut toward both ends of the opening start portion. With the above configuration, the piece blocking the opening start portion can be folded inward via the line.

In the above packaging box, the side panel having the opening start portion may be configured to have a pair of opening assist lines extending from the vicinity of both ends of the opening start portion toward both corners on the top surface side. With the above configuration, the side panel is deflected at the opening assist lines, making it easier to break the break lines.

In the above packaging box, the guide crease may be configured to include a parallel portion parallel to the flap crease and an inclined portion connecting the end of the parallel portion to the end of the flap crease at each upper side of the body. According to the above configuration, the inclined portion connects the end of the parallel portion to the end of the top flap crease, so that a step-deformed portion is easily formed by a load from above.

The present invention makes it possible to suppress deformation of the torso due to loads from above.

FIG. 2 is a perspective view of the packaging box according to the first embodiment, seen from above. FIG. 2 is a development view of the packaging box according to the first embodiment. FIG. 2 is a perspective view showing a state in which packaging boxes are stacked in the first embodiment. 4 is a perspective view showing a method for opening the packaging box in the first embodiment. FIG. FIG. 11 is a perspective view of a packaging box according to a second embodiment, seen from above. FIG. 11 is a development view of a packaging box according to a second embodiment. FIG. 11 is a perspective view showing a state in which packaging boxes are stacked in a second embodiment.

Hereinafter, a packaging box to which the present invention is applied will be described with reference to the drawings.
First Embodiment
As shown in Fig. 1, a packaging box 1 to which the present invention is applied is used as a transport box for transporting products and is also used when displaying products in stores. The packaging box 1 has a body 2, and products are contained in the body 2. The body 2 has a continuous break line 32 in the circumferential direction (hereinafter also referred to as the horizontal direction), and the upper side above the break line 32 is an upper half 3 that is cut away, and the lower side below the break line is a lower half 4 that is used as a tray when displaying products. When the upper half of the packaging box 1 is removed, the products arranged in the lower half 4 are exposed.

As shown in FIG. 2, the torso 2 has a first side plate 11, a second side plate 12, a third side plate 13, and a fourth side plate 14 in an unfolded state. The first side plate 11 and the third side plate 13 form the length surface of the torso 2, and the second side plate 12 and the fourth side plate 14 form the width surface of the torso 2. Vertical lines 15 are provided between the first side plate 11 and the second side plate 12, between the second side plate 12 and the third side plate 13, and between the third side plate 13 and the fourth side plate 14. Furthermore, the first side plate 11 has a joining piece 16 for joining to the fourth side plate 14 via the vertical lines 15.

The lower edge of the first side panel 11 has a bottom outer flap 21 through the bottom flap crease 17, the lower edge of the second side panel 12 has a bottom inner flap 22 through the bottom flap crease 17, the lower edge of the third side panel 13 has a bottom outer flap 23 through the bottom flap crease 17, and the fourth side panel 14 has a bottom inner flap 24 through the bottom flap crease 17. The bottom outer flaps 21 and 23 are butted flaps. The bottom surface is formed by folding the bottom inner flaps 22 and 24 inward through the bottom flap crease 17, and then folding the bottom outer flaps 21 and 23 inward through the bottom flap crease 17. The bottom surface is formed by butting the bottom outer flaps 21 and 23 together. The bottom outer flaps 21 and 23 are joined by a joining means such as adhesive tape or staples.

The bottom surface is not limited to this configuration, and may be configured, for example, by providing engaging portions on the four flaps that make up the bottom surface and engaging these engaging portions with each other.

The top edge of the first side panel 11 has a top outer flap 26 through the top flap crease 18, the top edge of the second side panel 12 has a top inner flap 27 through the top flap crease 18, the top edge of the third side panel 13 has a top outer flap 28 through the top flap crease 18, and the fourth side panel 14 has a top inner flap 29 through the top flap crease 18. The top outer flaps 26, 28 are butted flaps. The top surface is formed by folding the top inner flaps 27, 29 inward through the top flap crease 18, and then folding the top outer flaps 26, 28 inward through the top flap crease 18. The top surface is formed by butting the top outer flaps 26, 28 together. The top outer flaps 26, 28 are joined by a joining means such as adhesive tape or staples. In addition, the joint piece 16 also overlaps with the top outer flap 26 in the vertical direction, and the top flap crease 18 also extends to the joint piece 16.

When the top inner flaps 27, 29 are folded inward, their tips are separated to form a gap. The tip of the top outer flap 28 located above this gap is provided with a hand hole 28a that serves as a hand hole when opening the top. The hand hole 28a is composed of two notches provided from the tip edge toward the top flap crease 18 and a crease provided between the two notches. The hand hole 28a becomes a hand hole when the area surrounded by the notches and the crease is pressed by a hand such as a finger and folded inward from the crease. The hand hole 28a may be provided in the top outer flap 26, or may be provided in both the top outer flaps 26, 28. Furthermore, the hand hole 28a may be a pre-formed hole.

The first side panel 11 to the fourth side panel 14 have guiding lines 31 that extend in the same direction as the top flap lines 18 and are close to the top flap lines 18. The guiding lines 31 are provided between the top flap lines 18 and the break lines 32. Specifically, the guiding lines 31 are provided closer to the top flap lines 18 than the break lines 32. The guiding lines 31 also extend to the joint piece 16, but the guiding lines 31 of the joint piece 16 overlap with the guiding lines 31 of the fourth side panel 14.

The first side panel 11 to the fourth side panel 14 have break lines 32 arranged in the horizontal direction below the guide lines 31 at approximately the center of the first side panel 11 to the fourth side panel 14 in the vertical direction. The break lines 32 also extend to the joint piece 16, but the break lines 32 of the joint piece 16 overlap with the break lines 32 of the fourth side panel 14. The break lines 32 are formed, for example, by perforations.

The first side plate 11 to the fourth side plate 14 are provided with opening start portions 36a to 36d in contact with the break line 32. Specifically, the first side plate 11 has a first opening start portion 36a located closer to the second side plate 12 than the horizontal center, and the second side plate 12 has a second opening start portion 36b located in the horizontal center. The third side plate 13 has a third opening start portion 36c located closer to the fourth side plate 14 than the horizontal center, and the fourth side plate 14 has a fourth opening start portion 36d located in the horizontal center.

Each opening start section 36a to 36d has an upper side 35a and a lower side 35b extending in the horizontal direction of the body 2, and a notch 35c connecting the upper side 35a and the lower side 35b. The upper side 35a is connected to the break line 32 at both ends in the horizontal direction of the opening start section 36a to 36d, and is configured as part of the break line 32. In other words, the upper side 35a is configured as a perforation that continues with the break line 32. The lower side 35b is configured as a foldable line that extends from the intersection with the notch 35c toward both ends of the opening start section 36a to 36d. The upper side 35a has a convex shape that slopes downward on both sides from the apex. The lower side 35b has a concave shape that slopes upward on both sides from the bottom point of the central notch 35c. In other words, the opening start sections 36a to 36d have a diamond shape. The notch 35c is provided between the top edge 35a and the bottom edge 35b, connecting the bottom point of the apex. When opening the packaging box 1, by inserting a hand such as a finger into the opening start portions 36a to 36d, the pieces on both sides of the notch 35c are folded inward from the bottom edge 35b, forming an operation opening.

Each break line 32 in the first side panel 11 to the fourth side panel 14 has a curved portion 38 that is connected to the mountain-shaped upper side 35a of the opening start portion 36a to 36d on both sides of the opening start portion 36a to 36d. The curved portion 38 is configured to extend from both ends of the upper side 35a so as to slope upward, and then slope downward. In other words, both ends of the opening start portion 36a to 36d become the bottom points of the concave shape, and a convex shape is configured on the outside of the bottom points. Each opening start portion 36a to 36d is a place where a hand such as a finger is inserted and an opening force is applied to open the opening by directly pulling it outward and pulling it upward. By providing the curved portion 38 so that it slopes upward from the connection point with the downwardly sloping upper side 35a of the opening start portion 36a to 36d, each break line 32 is easily torn along the break line 32 from the opening start portion 36a to 36d by the opening force. In addition, the break line 32 includes a wavy portion formed by the upper edge 35a of the opening start portions 36a to 36d and the curved portion 38. This makes the break line 32 less likely to break than if it were a straight line, even if an external force is applied during transportation or storage.

Each of the first side panel 11 to the fourth side panel 14 has a first opening assist line 37a to a fourth opening assist line 37d extending from near both ends of the opening start portion 36a to 36d toward both corners of the top surface between the guide line 31 and the break line 32. Specifically, the first side panel 11 has a first opening assist line 37a extending from near both ends of the first opening start portion 36a toward the top surface flap line 18, and the second side panel 12 has a second opening assist line 37b extending from near both ends of the second opening start portion 36b toward the top surface flap line 18. In addition, the third side panel 13 has a third opening assist line 37c extending from the vicinity of both ends of the third opening start portion 36c toward the top flap line 18, and the fourth side panel 14 has a fourth opening assist line 37d extending from the vicinity of both ends of the fourth opening start portion 36d toward the top flap line 18.

Each of the first to fourth side panels 11 to 14 has two opening assist lines 37a to 37d. Each of the two opening assist lines 37a to 37d in each of the side panels 11 to 14 has a first end on the upper side and a second end on the lower side. The first end on the upper side is located on the guide line 31, and the second end on the lower side is located on the break line 32 near both ends of the opening start parts 36a to 36d. The distance between the first ends of the two opening assist lines 37a to 37d is set wider than the distance between the second ends. Note that each of the opening assist lines 37a to 37d in each of the first to fourth side panels 11 to 14 may be connected to both lateral ends of the opening start parts 36a to 36d, but is not connected here.

In the packaging box constructed as described above, the body 2 is formed by connecting the first side panel 11 and the fourth side panel 14 via the joining piece 16, and then the bottom surface is formed by folding the bottom surface inner flaps 22, 24 and the bottom surface outer flaps 21, 23 inwardly along the bottom surface flap crease 17. In this state, a product is stored inside the body 2. After this, the top surface is formed by folding the top surface inner flaps 27, 29 and the top surface outer flaps 26, 28 inwardly along the top surface flap crease 18.

Next, the operation of the packaging box configured as above will be described.
As shown in FIG. 3, such packaging boxes 1 are stacked when transporting products. Then, the lower packaging box 1 is subjected to the load of the packaging box 1 stacked above. The number of packaging boxes stacked on the lowest packaging box 1 is one in FIG. 3, but more packaging boxes may be stacked. Also, packaging boxes of different types or packaging boxes containing different products may be stacked. Then, due to the load of the stacked packaging boxes, the lower packaging box 1 near the top surface is crushed and folded inward at the guiding line 31, forming a stepped portion 39. The stepped portion 39 is folded more at the guiding line 31 because the load is greater for the packaging box 1 located lower. The stepped portion 39 crushed at the guiding line 31 supports the load of the packaging box 1 located above with priority over the side panels 11 to 14. As a result, the position of the break line 32 is a portion with low strength, but is prevented from bulging outward.

As shown in FIG. 4, when opening each packaging box 1, the worker first places the second side panel 12 or the fourth side panel 14 opposite each other. Then, the opening start portions 36a, 36c of the opposing first side panel 11 and third side panel 13 are opened by hand, such as fingers. Then, the first side panel 11 and the third side panel 13 are subjected to an opening force for pulling them outward and upward. As a result, the first side panel 11 and the third side panel 13 are bent so that the area between the opening assist lines 37a, 37c bulges from the opening start portions 36a, 36b at the opening assist lines 37a, 37c. Then, the breaking line 32 starts to be cut from the opening start portions 36a, 36b through the curved portion 38 (see (1) in FIG. 4). Then, almost the entire area of the breaking line 32 of the first side panel 11 and the third side panel 13 is broken.

Next, the worker makes the first side panel 11 or the third side panel 13 face each other. Then, the opening start parts 36b, 36d of the opposing second side panel 12 and fourth side panel 14 are opened by a hand such as a finger. Then, an opening force is applied to the second side panel 12 and the fourth side panel 14. As a result, the second side panel 12 and the fourth side panel 14 are bent so that the area between the opening assist lines 37b, 37d swells from the opening start parts 36b, 36d as starting points. Then, the breaking line 32 starts to break from the opening start parts 36b, 36d through the curved part 38. Then, the packaging box 1 is divided into upper and lower parts at the position of the breaking line 32 over the entire circumference (see (2) in FIG. 4). As a result, the upper half 3 of the packaging box 1 is removed, and the product is exposed and displayed. At this time, the lower half 4 is used as a tray.

When removing the upper half 3, the first side plate 11 and the third side plate 13 are the length surfaces, and the first opening start portion 36a is biased toward the second side plate 12, and the third opening start portion 36c is biased toward the fourth side plate 14. In other words, the first opening start portion 36a and the third opening start portion 36c are provided near the diagonal corners of the body 2, and are provided at particularly distant positions within the body 2. For this reason, in the step (1) in FIG. 4, there is a risk that the break line 32 of the first side plate 11 will not break near the fourth side plate 14. Also, there is a risk that the break line 32 of the third side plate 13 will not break near the second side plate 12.

In this regard, in the step (2) in FIG. 4, the second side plate 12 and the fourth side plate 14 are entirely broken along the break lines 32. Even if there are remaining unbroken portions of the break lines 32 of the first side plate 11 and the third side plate 13, the remaining unbroken portions of the break lines 32 of the first side plate 11 and the third side plate 13 can also be broken in the series of steps for breaking the break lines 32 of the second side plate 12 and the fourth side plate 14.

In addition, as a method of opening the packaging box 1, it is also possible to first break the break lines 32 in the second side panel 12 and the fourth side panel 14 (see (2) in Figure 4), and then break the break lines 32 in the first side panel 11 and the third side panel 13.

According to the packaging box 1 of the first embodiment described above, the following effects can be obtained.
(1-1) Even if a load is applied to the packaging box 1 from above, the packaging box 1 is folded inward at the guide lines 31, and the load is preferentially supported by the stepped portions 39. This makes it possible to suppress deformation of the packaging box 1, which is caused by the packaging box 1 bulging outward at the positions of the fracture lines 32.

(1-2) The guide line 31 is provided between the break line 32 and the top flap line 18, closer to the top flap line 18 than the break line 32. In other words, the guide line 31 is provided closer to the top flap line 18 than the break line 32. This prevents the step-flattened portion 39 from becoming too large, and can stably support the packaging boxes 1 stacked on top. In addition, because the step-flattened portion 39 is small, deterioration in the appearance of the stacked packaging boxes 1 can be suppressed.

(1-3) It is possible to insert a finger or other hand into the opening start portions 36a to 36d and then cut the breaking line 32. This makes it easy to remove the upper half 3 of the packaging box 1.

(1-4) At the opening start portions 36a to 36d, the upper edge 35a of the breaking line 32 is inclined downward from the apex to both sides, and has curved portions 38 that extend upward from both ends. Therefore, the breaking line 32 can be easily broken from the opening start portions 36a to 36d by the opening force.

(1-5) A notch 35c is provided between the upper edge 35a and the lower edge 35b, so that the opening start portions 36a to 36d can be opened by opening on both sides of the notch 35c.

(1-6) The bottom side 35b is formed with a foldable line extending from the intersection with the notch 35c toward both ends of the opening start portions 36a to 36d. Therefore, the pieces blocking the opening start portions 36a to 36d can be folded inward via the line.

(1-7) The break line 32 includes a wavy portion formed by the upper edge 35a and curved portion 38 of the opening start portions 36a to 36d. This makes the break line 32 less likely to break even if an external force is applied during transportation or storage, compared to a straight break line. In other words, the break line 32 is configured to be easily broken when opening, but is not easily broken at other times.

(1-8) When removing the upper half 3, the first side panel 11 to the fourth side panel 14 can bend at the opening assist lines 37a to 37d so that the area between the opening assist lines 37a to 37d bulges, thereby assisting in the breaking of the break line 32. In particular, because the opening assist lines 37a to 37d are connected to the break line 32 and the guide line 31, they are easily bent by the opening force starting from the opening start portions 36a to 36d, which assists in the breaking of the break line 32 and makes it easier to remove the upper half 3.

Second Embodiment
In the packaging box 1 as the second embodiment, the guiding crease 41 and the top flap crease 18 in the first side plate 11 to the fourth side plate 14 are provided so as to have a trapezoidal shape. That is, as shown in Figs. 5 and 6, the guiding crease 41 has a parallel portion 41a parallel to the top flap crease 18, and two inclined portions 41b located on both sides of the parallel portion 41a. The parallel portion 41a has a linear shape that is shorter than the top flap crease 18 in the first side plate 11 to the fourth side plate 14. Each of the two inclined portions 41b has a first end and a second end, the first end being connected to the end of the parallel portion 41a, and the second end being connected to the end of the guiding crease 41 in the first side plate 11 to the fourth side plate 14. The first interval 42 of the first end of the two inclined portions 41b is set to be narrower than the second interval 43 of the second end. The second end of each inclined portion 41 b is located at an upper corner of the packaging box 1 .

Even when the packaging boxes 1 in the second embodiment configured as described above are stacked, the weight of the packaging box 1 stacked on top is applied to the lower packaging box 1. Then, as shown in FIG. 7, this weight causes the lower packaging box 1 near the top surface to bend inward at the guiding line 41, forming a stepped portion 39. The stepped portion 39 that is crushed by the guiding line 41 supports the weight of the upper packaging box 1. As a result, although the location of the break line 32 is an area of low strength, it is prevented from bulging outward.

According to the packaging box 1 of the second embodiment described above, the following effects can be obtained.
(2-1) Since the end of the parallel portion 41a and the end of the top flap crease 18 are connected by the inclined portion 41b, the stepped portion 39 is easier to form than in the first embodiment.

The first and second embodiments described above can be modified as follows.
- In the second embodiment, the second spacing 43, which is the spacing between the second end portions connected to the ends of the top flap crease 18 in the inclined portion 41b, may be narrower than the first spacing 42 between the first end portions connected to the ends of the parallel portion 41a.

The inclined portion 41 b may be omitted, and only the parallel portion 41 a may be provided. In this case, the parallel portion 41 a is spaced apart from the vertical ruled line 15.
In the first and second embodiments, unlike the above-described example, each of the opening assisting lines 37a to 37d may be connected to both lateral ends of the opening start portions 36a to 36d. Also, the opening assisting lines 37a to 37d may be omitted.

- In the first and second embodiments, the curved portion 38 may be omitted and the break lines 32 may be linear. When the break lines 32 are linear, the break lines 32 in the first to fourth side panels 11 to 14 may be parallel to the top flap crease 18 or may be inclined upward or downward toward the vertical creases 15 located on both sides.

- The opening start portions 36a to 36d may be configured so that the lines on the bottom side 35b are perforated and surrounded by a tear line such as a perforation. In this case, by inserting a hand such as a finger into the opening start portions 36a to 36d, the piece blocking the opening start portions 36a to 36d can be removed to open them.

- In the opening start portions 36a to 36d, the upper end position of the notch 35c may be offset to one side in the horizontal direction relative to the center of the upper side 35a. The lower end position of the notch 35c may also be offset to one side in the horizontal direction relative to the center of the lower side 35b.

The opening start portions 36a to 36d may omit the notch 35c.
In each of the opening start portions 36a to 36d, the curved portion 38 may be connected to the lower side 35b instead of the upper side 35a. In this case, it is preferable that the upper side 35a of each of the opening start portions 36a to 36d is a ruled line and the lower side 35b is a perforation.

The opening start portions 36a to 36d may be holes formed in advance.
The opening start portion may be provided on only one of the pair of opposing side plates 11 , 13 or the pair of opposing side plates 12 , 14 .

The break line 32 does not have to be located in the center in the vertical direction, but may be located above or below the center.
The guiding line 31 may be provided in a central position between the top surface flap line 18 and the break line 32. The guiding line 31 may also be provided closer to the break line 32 than the top surface flap line 18.

- In the first side panel 11, the first opening start portion 36a and the opening assist line 37a may be biased toward the fourth side panel 14, and in the third side panel 13, the third opening start portion 36c and the opening assist line 37c may be biased toward the second side panel 12.

In addition, in the first side panel 11, the first opening start portion 36a may be provided in the center in the horizontal direction. In this case, the opening assist line 37a is also provided in the center in the horizontal direction to match the first opening start portion 36a. In addition, in the third side panel 13, the third opening start portion 36c may also be provided in the center in the horizontal direction. In this case, the opening assist line 37c is also provided in the center in the horizontal direction to match the third opening start portion 36c.

The packaging box is not limited to having a rectangular parallelepiped shape. For example, the packaging box 1 may have a triangular prism shape, a pentagonal prism shape, or the like.
The packaging box may be made of cardboard or other materials instead of cardboard.

1...packaging box 2...body 3...upper half 4...lower half 11-14...first to fourth side panels 15...vertical crease 16...joint piece 17...bottom flap crease 18...top flap crease 21, 23...outer bottom flaps 22, 24...inner bottom flaps 26, 28...outer top flaps 27, 29...inner top flaps 31...guiding crease 32...breaking line 35a...upper edge 35b...lower edge 35c...notch 36a-36d...first to fourth opening start portions 37a-37d...first to fourth opening assist crease 38...curved portion 39...stepped portion 41...guiding crease 41a...parallel portion 41b...inclined portion 42...first interval 43...second interval

Claims (5)

A packaging box having a body surrounded by a plurality of side panels and a top surface flap connected to each upper side of the body to form a top surface,
A flap crease is provided on each upper side of the body portion, allowing the top flap to be folded;
A guide line extending in the same direction as the flap line in close proximity thereto;
A break line provided around the entire circumference of the body portion;
An opening start portion that is provided on at least a pair of opposing side plates among the side plates that constitute the body portion and is in contact with the break line;
A pair of opening assist lines are provided between the guide line and the opening start portion in the side panel having the opening start portion,
Each of the opening assisting lines has an upper end and a lower end,
the lower ends are located near both ends of the opening start portion, and a distance between the upper ends is set wider than a distance between the lower ends. The opening start portion has an upper side and a lower side,
The upper side is a part of the break line and has a convex shape that slopes downward from a vertex to both sides,
The packaging box according to claim 1 , wherein the break lines are inclined upward from both ends of the upper side. The packaging box according to claim 2 , wherein a notch is provided between the upper side and the lower side of the opening start portion. The packaging box according to claim 3 , wherein a lower side of the opening start portion is formed of a foldable line extending from an intersection with the cut toward both ends of the opening start portion. The packaging box according to any one of claims 1 to 4, characterized in that the guide crease has a parallel portion parallel to the flap crease and an inclined portion connecting an end of the parallel portion to an end of the flap crease at each upper side of the body portion.