JP2024048055A - Packaging box - Google Patents

Abstract

To provide a packaging box in which an insertion portion can be easily inserted into an insertion hole. [Solution] A packaging box 1 formed from a cardboard sheet has a peripheral wall W formed into a cylindrical shape by a pair of first side walls 10 and a pair of second side walls 11, a pair of upper outer flaps 12 connected to the pair of first side walls 10, and a pair of upper inner flaps 13 connected to the pair of second side walls 11, an insertion fold line L6 is formed in the upper outer flap 12, an engagement piece 21 is defined by cutting an insertion cutting line in the upper inner flap 13, the insertion cutting line has a first cut 22A and a second cut 22B, and the edges along the engagement piece 21 and the second cut 22B are made into a first thin-walled portion, an insertion portion 25 of the upper outer flap 12 bent at the insertion fold line L6 is pressed against the engagement piece 21, so that the engagement piece 21 is pushed in and forms an insertion hole 21A, and the upper outer flap 12 is straightened from the bend at the insertion fold line L6 so that the insertion portion 25 is inserted into the insertion hole 21A. [Selected Figure] Figure 1

Description

The present invention relates to a packaging box made of corrugated cardboard sheets.

A cardboard packaging box is known in which the opening of the body is closed by a pair of first flaps and a pair of second flaps (Patent Document 1). On both sides of the first flap, there is an insertion portion that is continuous at the front in the insertion direction and has a cut-and-raised structure in which the other parts are cut off. On both sides of the second flap, there is an insertion portion that is inserted while pressing down on the insertion portion.

JP 2005-8221 A

In the above-mentioned packaging box, depending on the thickness of the cardboard, a large force was sometimes required to bend the inserted portion of the first flap. When the insert portion of the second flap was pressed against the inserted portion in order to bend the inserted portion, the inserted portion did not bend, and the entire first flap sometimes fell inside the body. In other words, it was not easy to insert the insert portion into the inserted portion.

Taking the above circumstances into consideration, the present invention provides a packaging box that allows the insertion part to be easily inserted into the insertion hole.

The present invention relates to a packaging box formed of a cardboard sheet, comprising a peripheral wall formed into a cylindrical shape by alternately connecting a pair of first side walls and a pair of second side walls, a pair of outer flaps connected to the pair of first side walls and folded in a direction to close an opening of the peripheral wall, and a pair of inner flaps connected to the pair of second side walls and folded in a direction to close the opening, at least one of the pair of outer flaps has at least one insertion portion which is a corner region of the outer flap and an insertion fold line which extends in a direction along a first side fold line (L2, L3) which is a boundary with the first side wall, at least one of the pair of inner flaps has at least one engagement piece which is defined by cutting at least one insertion cut line so as to form an insertion hole for inserting the insertion portion, and the insertion cut line has a first cut extending from the base end side in the insertion direction toward the tip side along a second side fold line that is the boundary between the second side wall and the inner flap, and a second cut extending from the tip of the first cut in the insertion direction toward the free end side of the inner flap, and the edge portion along the second cut that is the tip side of the engagement piece and the insertion hole in the insertion direction is a first thin-walled portion in which the core of the cardboard sheet is crushed, and the pair of inner flaps are folded in the direction to close the opening, and the insertion portion of the outer flap bent at the insertion fold line is pressed against the engagement piece, so that the engagement piece is pressed inside the peripheral wall to form the insertion hole, and the outer flap is folded in the direction to close the opening and the bend at the insertion fold line is straightened, so that the insertion portion is inserted into the insertion hole.

In this case, the insertion fold lines may be curved or bent so as to protrude from both side ends of the outer flap toward the center toward the free end.

In this case, the second cut has an engagement cut that extends from the end that is the free end side of the inner flap to the tip side in the insertion direction, and when the insertion portion is inserted into the insertion hole, a portion of the free end side of the outer flap that corresponds to the engagement cut may be a second thin-walled portion in which the core of the cardboard sheet is crushed.

In this case, when the insertion portion is inserted into the insertion hole, an engagement cut line is cut along the insertion direction on the free end side of the outer flap corresponding to the engagement cut line, which divides the pressing portion overlapping the surface of the pair of inner flaps and the insertion portion, and an engagement auxiliary piece is formed on the pressing portion, which is divided by an engagement auxiliary fold line that extends while curving so as to bulge from the end of the engagement cut line in the cutting direction toward the free end of the outer flap, and the second thin portion is formed on the edge of the insertion portion adjacent to the engagement cut line, and a pressing portion is formed on the inner flap adjacent to the engagement piece across the second cut and overlapping the surface of the insertion portion inserted into the insertion hole, and the engagement A plurality of first sliding cuts are cut at intervals in the insertion direction on the edge of the pressing part adjacent to the cut, sloping from the tip side to the base end side in the insertion direction from the engagement cut toward the base end side of the inner flap, and a plurality of second sliding cuts are cut at intervals in the insertion direction on the edge of the engagement auxiliary piece adjacent to the engagement cut line, sloping from the base end side to the tip side in the insertion direction from the engagement cut line toward the opposite side to the insertion part, and when the insertion part is inserted into the insertion hole, the engagement auxiliary piece is folded back at the engagement auxiliary fold line, and the edge where the plurality of second sliding cuts are formed rides up on the edge of the pressing part where the plurality of first sliding cuts are formed.

In this case, when the insertion portion is inserted into the insertion hole, a notch is provided on the free end side of the outer flap corresponding to the vicinity of the end of the second cut, which is the free end side of the inner flap, to separate the pressing portion overlapping the surface of the pair of inner flaps from the insertion portion, and the edge of the notch may be a second thin-walled portion formed by crushing the core of the cardboard sheet.

In this case, the engagement piece may have an auxiliary insertion fold line formed in the vicinity of the second side fold line and extending in a direction along the second side fold line.

In this case, the insertion auxiliary fold line is preferably formed across the entire width of the outer flap and the inner flap so as to be parallel to the first side fold line and the second side fold line at a distance from the first side fold line and the second side fold line, and is an outer fold line for folding the inner flap and the outer flap outward.

According to the present invention, the plug can be easily inserted into the plug hole.

1 is a perspective view showing a packaging box according to a first embodiment of the present invention; FIG. 1 is a plan view showing a blank for a packaging box according to a first embodiment of the present invention. 4 is an explanatory diagram (cross-sectional view) illustrating a method for forming an outer fold line of the packaging box according to the first embodiment of the present invention. FIG. 1 is an enlarged plan view showing a portion of a blank for a packaging box according to a first embodiment of the present invention; FIG. FIG. 2 is a perspective view of the packaging box according to the first embodiment of the present invention, illustrating an operation of forming the bottom surface of the peripheral wall. FIG. 2 is a perspective view of the packaging box according to the first embodiment of the present invention, showing a state in which the bottom surface of the peripheral wall has been formed. FIG. 2 is a perspective view of the packaging box according to the first embodiment of the present invention, illustrating an operation of forming a top surface of a peripheral wall. FIG. 11 is a plan view showing a blank for a packaging box according to a second embodiment of the present invention. FIG. 11 is a plan view showing a blank for a packaging box according to a third embodiment of the present invention. FIG. 10 is a plan view showing a blank for a packaging box according to a fourth embodiment of the present invention. FIG. 11 is an enlarged plan view showing a portion of a blank for a packaging box according to a fourth embodiment of the present invention. FIG. 11 is a perspective view showing a packaging box according to a fourth embodiment of the present invention.

Below, an embodiment of the present invention will be described with reference to the attached drawings. Note that Fr, Rr, L, R, U, and D shown in the drawings indicate front, rear, left, right, top, and bottom. The front-to-back, left-to-right, and up-to-down directions are perpendicular to each other. Terms indicating directions and positions are used in this specification, but these terms are used for convenience of explanation and do not limit the technical scope of the present invention. Furthermore, the terms indicating directions and positions are based on the directions and positions when the packaging box is assembled and used.

[First embodiment]
A packaging box 1 according to a first embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a perspective view showing the packaging box 1. Fig. 2 is a plan view showing a blank 1A of the packaging box 1. Fig. 3 is an explanatory diagram (cross-sectional view) for explaining a method of forming an outer fold line L4.

The packaging box 1 is a box made of a so-called A-type corrugated cardboard sheet. As shown in FIG. 1, the packaging box 1 has a peripheral wall W formed in a roughly rectangular cylindrical shape, and a number of flaps 12-15 (the lower flaps 14, 15 are not shown in FIG. 1) that close the openings at both the top and bottom ends of the peripheral wall W. As will be described in detail later, these flaps 12-15 keep the openings closed without using staples, adhesives, adhesive tape, etc.

The packaging box 1 is assembled from a blank 1A shown in FIG. 2. The blank 1A is composed of a single sheet of cardboard made of paper. The cardboard sheet is, for example, a double-sided cardboard sheet in which a front liner 9B and a back liner 9C (see FIG. 3) are attached to a corrugated core 9A. The core 9A extends along the axial direction of the peripheral wall W from the base end of the multiple flaps 12 to 15 toward the tip (free end). Note that FIG. 2 and other figures show the front liner 9B side (the outer surface of the packaging box 1). In this specification, the direction parallel to the core 9A of the cardboard sheet is called the "step direction", and the direction perpendicular to the step direction is called the "flow direction". In the drawings, "X" indicates the "step direction" and "Y" indicates the "flow direction".

[blank]
As shown in FIG. 2, the blank 1A includes a pair of first side walls 10, a pair of second side walls 11, a pair of upper outer flaps 12, a pair of upper inner flaps 13, a pair of lower outer flaps 14, and a pair of lower inner flaps 15. Since the pair of parts has substantially the same shape, one part will be described in this specification unless otherwise specified. In addition, in this specification, when the upper outer flap 12 and the lower outer flap 14 are described collectively, they will be simply called "outer flaps 12, 14", and when the upper inner flap 13 and the lower inner flap 15 are described collectively, they will be simply called "inner flaps 13, 15". In addition, the upper flaps 12, 13 may be described collectively, the lower flaps 14, 15 may be described collectively, or all the flaps 12 to 15 may be described collectively.

<First Side Wall, Second Side Wall>
A pair of first side walls 10 and a pair of second side walls 11 are alternately connected in the flow direction via a first fold line L1. The first side walls 10 and the second side walls 11 are formed in a substantially rectangular shape. In detail, the second side walls 11 are formed in a substantially rectangular shape that is longer in the flow direction than the first side walls 10. A joint piece 16 is connected to one end of the second side walls 11 in the flow direction via the first fold line L1.
<Upper outer flap, upper inner flap>
The upper outer flap 12 is connected to one end (upper end) in the step direction of the first side wall 10 via the second fold line L2. The upper outer flap 12 is formed in a substantially rectangular shape, and its dimension in the step direction (extension dimension) is set to be substantially half the dimension in the flow direction of the first side wall 10. The upper inner flap 13 is connected to one end (upper end) in the step direction of the second side wall 11 via the second fold line L2. The upper inner flap 13 is formed in a substantially rectangular shape, and its extension dimension is substantially the same as the extension dimension of the upper outer flap 12.

<Lower outer flap, lower inner flap>
The lower outer flap 14 is connected to the other end (lower end) in the step direction of the first side wall 10 via the third fold line L3. The lower inner flap 15 is connected to the other end (lower end) in the step direction of the second side wall 11 via the third fold line L3. The lower outer flap 14 has a generally rectangular shape that is generally the same size as the upper outer flap 12, and the lower inner flap 15 has a generally rectangular shape that is generally the same size as the upper inner flap 13.

An outer fold line L4 is formed across the entire width (entire flow direction) of the pair of lower outer flaps 14 and the pair of lower inner flaps 15, so as to be parallel to the third fold line L3 at a distance from the third fold line L3. The outer fold line L4 is an approximation of a reverse crease formed by squeezing the cardboard sheet in the thickness direction from the front liner 9B side, and is used to fold the lower outer flaps 14 and the lower inner flaps 15 outward.

The first to third fold lines L1 to L3 are general-purpose creases that crush the cardboard sheet in the thickness direction from the back liner 9C side. The general-purpose creases mainly have the function of folding the cardboard sheet so that the back liner 9C faces inward (mountain fold or normal fold). The first to third fold lines L1 to L3 are not limited to general-purpose creases, but may be any structure for folding the cardboard sheet in a desired direction, such as perforation lines with multiple cuts formed at a predetermined interval or lead creases with perforation lines formed on general-purpose creases. The second fold line L2 and the third fold line L3 are an example of a first side fold line that is the boundary between the first side wall 10 and the outer flaps 12, 14, and an example of a second side fold line that is the boundary between the second side wall 11 and the inner flaps 13, 15, as referred to in the claims.

The cardboard sheet that constitutes blank 1A is manufactured by processing cardboard base paper using a device called a corrugator (not shown). The corrugator advances core 9A in the flow direction while attaching liners 9B, 9C to both sides of core 9A. The corrugator also forms second fold line L2, third fold line L3, and outer fold line L4 on the cardboard sheet advancing in the flow direction, and cuts the cardboard sheet that is continuous in the flow direction to a predetermined length. In this way, the second fold line L2, third fold line L3, and outer fold line L4 are formed by the corrugator in a continuous state across the entire flow direction of blank 1A.

As shown in FIG. 3, the outer fold line L4 is formed by a pair of reverse crease rings R1, R2 provided on the corrugator. One of the reverse crease rings R1 has one convex portion formed, and the other reverse crease ring R2 has a pair of convex portions formed. The pair of reverse crease rings R1, R2 sandwich the cardboard sheet moving in the flow direction from both sides in the thickness direction, forming the outer fold line L4 on the front liner 9B of the cardboard sheet. At this time, a pair of groove-shaped recesses G are formed on the back liner 9C of the cardboard sheet at a position that sandwiches the outer fold line L4, by being lightly crushed by the pair of convex portions of the other reverse crease ring R2.

The cut cardboard sheet is punched out with a wooden die (punch) attached to a device such as a flexo folder gluer or a punching machine (not shown) to be processed into a blank 1A. By punching the cardboard sheet with the wooden die, unnecessary parts are cut out and the first fold line L1 and the like are formed. The flexo folder gluer can also print the desired image on the front liner 9B, fold back the first side wall 10 and the second side wall 11 located on both outer sides in the flow direction of the blank 1A at the first fold line L1, and glue the joint piece 16 to the inner surface of the first side wall 10 on the opposite side. This produces a double-folded packaging box 1 (not shown).

[Lock section]
As shown in Fig. 2, the pair of upper outer flaps 12 and the pair of upper inner flaps 13 are provided with a first locking portion 20 that keeps the upper opening of the peripheral wall W closed. The pair of lower outer flaps 14 and the pair of lower inner flaps 15 are provided with a second locking portion 30 that keeps the lower opening of the peripheral wall W closed. The first and second locking portions 20, 30 will be described below with reference to Figs. 2 and 4. Fig. 4 is an enlarged plan view of a portion of the blank 1A.

[First lock part]
As shown in FIG. 2, the first locking portion 20 has two pairs of engaging pieces 21, two pairs of insertion portions 25, and a pair of insertion fold lines L6. The two pairs of engaging pieces 21 are formed on a pair of upper inner flaps 13. The two pairs of insertion portions 25 and the pair of insertion fold lines L6 are formed on a pair of upper outer flaps 12. Note that the two engaging pieces 21 formed on one upper inner flap 13 are formed line-symmetrically with respect to a line that bisects the upper inner flap 13 in the flow direction, so the following description will mainly focus on one engaging piece 21. In the same spirit, the following description will mainly focus on one insertion portion 25 and one insertion fold line L6.

<Engagement piece of first locking portion>
As shown in Fig. 2, the two engagement pieces 21 are spaced apart from each other in the flow direction and are formed at positions closer to the center from both outer ends in the flow direction of the upper inner flap 13. Also, the engagement pieces 21 are formed at positions closer to the base end side (the side of the second side wall 11) in the step direction of the upper inner flap 13. As shown in Fig. 4, the engagement pieces 21 are defined on the upper inner flap 13 by cutting an insertion cutting line 22. The insertion cutting line 22 is formed into a generally L-shape (crank-shape) by a first cut 22A and a second cut 22B.

(First cut of first locking part)
The first cut 22A extends from the outside to the inside in the flow direction of the upper inner flap 13 (from the base end side to the tip side in the insertion direction) along the second fold line L2. In detail, the first cut 22A is slightly inclined from the outside to the inside in the flow direction toward the free end side (the tip side in the step direction) of the upper inner flap 13. In addition, the outside of the flow direction of the first cut 22A is curved toward the free end side of the upper inner flap 13. The dimension (S1) of the first cut 22A in the flow direction is approximately equal to the dimension (S2) of the second fold line L2 on the outside of the first cut 22A in the flow direction.

(Second cut of first locking part)
The second cut 22B has a main cut 22C and an engagement cut 22D. The main cut 22C of the second cut 22B extends from the inner end of the first cut 22A in the flow direction (the tip in the insertion direction) toward the free end side of the upper inner flap 13. In detail, the main cut 22C is formed in a straight line inclined toward the inside of the flow direction (the tip side in the insertion direction) from the base end of the upper inner flap 13 toward the free end side. The main cut 22C is bent so as to form a corner with respect to the first cut 22A. The engagement cut 22D of the second cut 22B extends from the end of the main cut 22C, which is the free end side of the upper inner flap 13, toward the inside of the flow direction (the tip side in the insertion direction). The inside of the flow direction of the engagement cut 22D is curved toward the free end side of the upper inner flap 13.

(Insertion auxiliary folding line of the first lock part)
An auxiliary insertion fold line L5 extending in a direction along the second fold line L2 is formed in the engagement piece 21 near the second fold line L2. The auxiliary insertion fold line L5 extends substantially parallel to the straight portion of the first cut 22A from the curved end of the first cut 22A to a position where it contacts the main body cut 22C of the second cut 22B.

(Insertion hole and pressing portion of first lock portion)
The engagement piece 21 opens the insertion hole 21A by being bent inward along an imaginary line V1 (see FIG. 4) that connects both ends of the insertion cutting line 22 (the both ends of the first cut 22A and the engagement cut 22D (or the main body cut 22C)). As will be described in detail later, the engagement piece 21 is bent to form the insertion hole 21A, and an insertion portion 25, which is a corner region of the upper outer flap 12, is inserted. In addition, the upper inner flap 13 is formed with a pressing portion 23 adjacent to the engagement piece 21 with the second cut 22B in between. The pressing portion 23 is part of the upper inner flap 13 and is a portion that overlaps the surface of the insertion portion 25 inserted into the insertion hole 21A.

(First thin portion of first lock portion)
As shown by the diagonal lines in FIG. 2, the edge portion along the second cut 22B (the edge portion of the pressing portion 23 adjacent to the second cut 22B) which is the inside of the flow direction of the engagement piece 21 and the insertion hole 21A (the tip side in the insertion direction) is the first thin-walled portion 24 formed by crushing the core 9A of the cardboard sheet. The first thin-walled portion 24 is formed in a range (shape) that is an enlargement of the engagement piece 21 so as to include the engagement piece 21 and the insertion cut line 22. The first thin-walled portion 24 is formed thinner than other portions of the upper inner flap 13 by crushing the core 9A from the back liner 9C side. In the first thin-walled portion 24, the core 9A does not need to be completely crushed, but only needs to be slightly crushed. In addition, the diagonal lines shown in FIG. 2 do not strictly indicate the exact range of the first thin-walled portion 24. In addition, in FIG. 4, the first thin-walled portion 24 (diagonal lines) is omitted in order to clearly show the insertion cut line 22 and the like.

<Insertion Portion of First Locking Part>
2 and 4, both corner regions on the free end side of the upper outer flap 12 are formed as a pair of insertion portions 25 to be inserted into a pair of insertion holes 21A opened in the pair of upper inner flaps 13. The insertion portions 25 may be considered as portions that are inserted into the insertion holes 21A and face the rear surface of the pressing portion 23. In addition, the central region on the free end side of the upper outer flap 12 between the pair of insertion portions 25 is formed as a pressing portion 26. The pressing portion 26 overlaps the surface of the pair of upper inner flaps 13 when the insertion portions 25 are inserted into the insertion holes 21A.

(Second thin portion of first lock portion)
As shown by the diagonal lines in Fig. 2 and Fig. 4, a pair of second thin-walled parts 27 are formed on the free end side of the upper outer flap 12 so as to separate the pair of insertion parts 25 and the pressing part 26. The second thin-walled part 27 is formed thinner than the other parts of the upper outer flap 12 by crushing the core 9A of the cardboard sheet, similar to the first thin-walled part 24. The second thin-walled part 27 is a substantially semicircular range (shape) and is formed in a part of the free end side of the upper outer flap 12 corresponding to the engagement cut 22D of the second cut 22B when the insertion part 25 is inserted into the insertion hole 21A. In the second thin-walled part 27, the core 9A does not need to be completely crushed, but only needs to be slightly crushed. In addition, the hatched part shown in Fig. 2 does not strictly indicate the exact range of the second thin-walled part 27.

<First locking part insertion fold line>
The insertion fold line L6 extends in the upper outer flap 12 in a direction along the second fold line L2. The insertion fold line L6 is formed on the base end side (first side wall 10 side) of the center of the tier direction of the upper outer flap 12. The insertion fold line L6 is curved so as to protrude from both ends (both side ends) of the upper outer flap 12 in the flow direction toward the center toward the free end side. The protrusion amount of the insertion fold line L6 is about several mm, for example, about the thickness of a cardboard sheet.

[Second lock part]
The second locking part 30 will be described with reference to Figures 2 and 4. In the description of the second locking part 30, components similar to or corresponding to those of the first locking part 20 described above will be given the same names with the reference numerals changed, and descriptions thereof will be omitted as appropriate.

As shown in FIG. 2, the second locking portion 30 has two pairs of engaging pieces 31, two pairs of insertion portions 35, and a pair of insertion fold lines L8. The two pairs of engaging pieces 31 are formed on a pair of lower inner flaps 15. The two pairs of insertion portions 35 and the pair of insertion fold lines L8 are formed on a pair of lower outer flaps 14. As with the first locking portion 20, the following description will mainly focus on one engaging piece 31, one insertion portion 35, and one insertion fold line L8.

<Engagement piece of second locking portion>
As shown in Fig. 2, the two engaging pieces 31 are formed on both sides of the lower inner flap 15 in the flow direction, similar to the pair of upper engaging pieces 21. Also, as shown in Fig. 4, the base end of the engaging piece 31 in the step direction crosses the outer fold line L4 and contacts the third fold line L3. In other words, the outer fold line L4 crosses the engaging piece 31, and the outer fold line L4 formed on the engaging piece 31 is set as the insertion auxiliary fold line L7. Also, the insertion cut line 32 that divides the engaging piece 31 is formed in a substantially L-shape by a first cut 32A and a second cut 32B.

(First cut of second locking part)
The first cut 32A extends along the third fold line L3. The outer side of the first cut 32A in the flow direction is curved toward the free end side of the lower inner flap 15 beyond the outer fold line L4. The straight portion of the first cut 32A is formed between the outer fold line L4 and the third fold line L3, and is slightly inclined so as to contact the third fold line L3 from the outer side toward the inner side in the flow direction. The dimension (S2) of the first cut 32A in the flow direction is slightly shorter than the dimension (S4) of the third fold line L3 on the outer side of the first cut 32A in the flow direction.

(Second cut of second locking part)
The second cut 32B extends linearly from the inner end of the first cut 32A in the flow direction (the tip in the insertion direction) toward the free end of the lower inner flap 15. The second cut 32B has a shape similar to that of the upper second cut 22B with the engagement cut 22D omitted. The tip side of the second cut 32B in the step direction is curved toward the outside of the lower inner flap 15 in the flow direction.

(Insertion hole and pressing portion of second lock portion)
The engagement piece 31 opens the insertion hole 31A by being bent inward along an imaginary line V2 (see FIG. 4) that connects both ends of the insertion cut line 32. The pressing portion 33 is formed on the lower inner flap 15 so as to be adjacent to the engagement piece 31 with the second cut 32B in between. The pressing portion 33 is a portion that overlaps with the surface of the insertion portion 35 inserted into the insertion hole 31A.

(First thin portion of second lock portion)
As shown by the diagonal lines in Fig. 2, the edge of the pressing portion 33 adjacent to the engaging piece 31 and the second cut line 32B is made into a first thin-walled portion 34. The first thin-walled portion 34 is formed in a range (shape) that is an enlarged size of the engaging piece 31 so as to include the engaging piece 31 and the insertion cut line 32. Moreover, the diagonal lines shown in Fig. 2 do not strictly indicate the exact range of the first thin-walled portion 34, and in Fig. 4, the first thin-walled portion 34 (diagonal lines) is omitted in order to clearly show the insertion cut line 32, etc.

<Insertion portion, notch portion, and second thin portion of second lock portion>
Both corner regions on the free end side of the lower outer flap 14 are a pair of insertion parts 35, and a central region on the free end side of the upper outer flap 12 between the pair of insertion parts 25 is a pressing part 36. The insertion part 35 may be considered as a part that is inserted into the insertion hole 31A and faces the back surface of the pressing part 33. As shown by hatching in Figs. 2 and 4, a pair of notches 38 are recessed on the free end side of the lower outer flap 14 so as to separate the pair of insertion parts 35 and the pressing part 36. The notches 38 are substantially trapezoidal recesses, and are formed on the lower outer flap 14 so as to correspond to the vicinity of the end of the second cut 32B on the free end side of the lower inner flap 15 when the insertion part 35 is inserted into the insertion hole 31A. The edge of the notch 38 is a second thin part 37 (see the hatched part in Figs. 2 and 4). It should be noted that the hatched areas shown in FIGS. 2 and 4 do not indicate the precise range of the second thin-walled portion 27 .

<Second lock section insertion fold line>
The insertion fold line L8 extends in a direction along the third fold line L3 at the base end side (the first side wall 10 side) in the step direction of the lower outer flap 14. The insertion fold line L8 is curved so as to protrude from both ends (both side ends) of the lower outer flap 14 in the flow direction toward the center toward the free end side.

The insertion fold lines L6, L8 are general-purpose creases, but are not limited to these and may be any structure for folding the cardboard sheet in the desired direction, such as lead creases. The insertion fold lines L6, L8, the insertion cut lines 22, 32, the first thin-walled portions 24, 34, and the second thin-walled portions 27, 37, etc. are formed in the process of manufacturing the blank 1A using a wooden die (punching die).

[Assembly of packaging boxes]
Next, the assembly work of the packaging box 1 will be described with reference to Fig. 1 and Fig. 5 to Fig. 7. Fig. 5 is a perspective view explaining the work of forming the bottom surface of the peripheral wall W. Fig. 6 is a perspective view showing the state after the bottom surface of the peripheral wall W has been formed. Fig. 7 is a perspective view explaining the work of forming the top surface of the peripheral wall W. In Fig. 5 and Fig. 6, the bottom surface of the peripheral wall W is oriented upward in consideration of workability. Also, the packaging box 1 is folded twice (not shown) as an initial state before assembly.

The worker folds the pair of first side walls 10 and the pair of second side walls 11 at approximately right angles along the first fold line L1. The pair of first side walls 10 and the pair of second side walls 11 are alternately connected in the circumferential direction to form a rectangular cylindrical peripheral wall W (see FIG. 5, etc.). The peripheral wall W has openings at both the top and bottom ends.

To close the lower opening (bottom surface) of the peripheral wall W, the worker folds the pair of lower inner flaps 15, then folds the pair of lower outer flaps 14 to stack them on the pair of lower inner flaps 15, and secures the pair of lower outer flaps 14 to the pair of lower inner flaps 15 with the second locking portion 30. Note that the procedure for securing the pair of lower outer flaps 14 is the same, so the following description will focus mainly on one lower outer flap 14.

As shown in FIG. 5, the worker folds the pair of lower inner flaps 15 along the third fold line L3 in a direction to close the bottom surface (opening) of the peripheral wall W. The tips of the pair of lower inner flaps 15 are butted together.

The worker then folds the lower outer flap 14 forward at the insertion fold line L8 to bend it into a mountain shape, and directs the tips of the pair of insertion portions 35 toward the pair of engagement pieces 31 provided on the pair of lower inner flaps 15. Because the insertion fold line L8 is curved so as to bulge toward the tips of the lower outer flap 14, the lower outer flap 14 bent at the insertion fold line L8 bends in an arch shape so that the pair of insertion portions 35 are positioned lower than the pressing portion 36. As a result, the pair of insertion portions 35 (the tips) come into contact with the surfaces of the pair of engagement pieces 31 before the pressing portion 36 does.

The worker presses the tips of the pair of insertion portions 35 of the lower outer flap 14, which are bent at the insertion fold line L8, against the pair of engagement pieces 31. As the insertion portions 35 are pressed against the engagement pieces 31, the engagement pieces 31 are bent (pressed) inwardly into the peripheral wall W along the imaginary line V2 (see FIG. 4), and an insertion hole 31A is formed (opened) at the site where the engagement pieces 31 were carved out of the lower inner flap 15. The engagement pieces 31 including the imaginary line V2 are the first thin-walled portions 34, which have reduced rigidity, making them easier to bend.

The worker pushes the insertion portion 35 diagonally downward while stretching the lower outer flap 14 bent at the insertion fold line L8 (see the thick arrow in Figure 5). The lower outer flap 14 is folded in the direction to close the bottom surface while stretching the bend at the insertion fold line L8, so that the insertion portion 35 is inserted into the insertion hole 31A (see Figure 6). The insertion portion 35 is inserted into the insertion hole 31A and slides into the back side of the pressing portion 33. The pressing portion 36 moves while keeping its tip in contact with the surface of the pair of lower inner flaps 15.

When the insertion portion 35 is inserted into the insertion hole 31A and the lower outer flap 14 is straightened at the insertion fold line L8 (including a lightly bent state), the insertion portion 35 is sandwiched between the engagement piece 31 and the pressing portion 33, and the pressing portion 36 overlaps the surface of the free end side of the pair of lower inner flaps 15. The cutout portion 38 (second thin portion 37) of the lower outer flap 14 is arranged to surround the vicinity of the end of the second cut 32B of the insertion cutting line 32. The pair of insertion portions 35 and the pressing portion 36 bend so as to twist in the vertical direction around the cutout portion 38, so that the pair of lower inner flaps 15 are sandwiched between the pair of insertion portions 35 and the pressing portion 36. This makes it difficult for the insertion portion 35 to be pulled out of the insertion hole 31A.

In this way, the bottom surface of the packaging box 1 is formed without using adhesive tape or the like. The worker places the box with the bottom surface facing downwards and places a product (not shown) inside the peripheral wall W through the opening at the top of the peripheral wall W. The placed product presses the insertion portion 35, making it difficult to pull the insertion portion 35 out of the insertion hole 31A. Even if the product does not press the insertion portion 35, the insertion portion 35 cannot be easily pulled out of the insertion hole 31A.

Next, the worker closes the opening (top surface) above the peripheral wall W (sealing the packaging box 1). Note that the procedure for forming the top surface is the same as the procedure for forming the bottom surface, so it will be explained briefly below.

After folding the pair of upper inner flaps 13, the worker folds the pair of upper outer flaps 12 to stack them on the pair of upper inner flaps 13, and secures the pair of upper outer flaps 12 to the pair of upper inner flaps 13 with the first locking portion 20. Note that the procedure for securing the pair of upper outer flaps 12 is the same, so the following description will focus mainly on one upper outer flap 12.

As shown in FIG. 7, the pair of upper inner flaps 13 are folded along the second fold line L2 in a direction to close the top surface (opening) of the peripheral wall W, and their tips are butted together. Next, the worker bends the upper outer flap 12 into a mountain shape at the insertion fold line L6, and points the tips of the pair of insertion portions 25 toward the engagement pieces 21 of the pair of upper inner flaps 13. The upper outer flap 12 bent at the insertion fold line L6 bends in an arch shape so that the pair of insertion portions 25 are positioned lower than the pressing portions 26, so that the pair of insertion portions 25 (the tips) come into contact with the surfaces of the pair of engagement pieces 21 before the pressing portions 26.

The worker presses the tips of the pair of insertion portions 25 of the upper outer flap 12, which are bent at the insertion fold line L6, against the pair of engagement pieces 21. As the insertion portions 25 are pressed, the engagement pieces 21 bend along the imaginary line V1 (see FIG. 4) and are pushed into the inside of the peripheral wall W to form (open) the insertion hole 21A. The engagement pieces 21 including the imaginary line V1 are the first thin-walled portions 24, which have a reduced rigidity, making them easier to bend.

The worker pushes the insertion portion 25 diagonally downward while stretching the upper outer flap 12 bent at the insertion fold line L6 (see the thick arrow in Figure 7). The upper outer flap 12 is bent in the direction of closing the top surface while stretching the bend at the insertion fold line L6, so that the insertion portion 25 is inserted into the insertion hole 21A (see Figure 1). The insertion portion 25 is inserted into the insertion hole 21A and slides into the back side of the pressing portion 23, and is sandwiched between the engagement piece 21 and the pressing portion 23. The holding portion 26 overlaps the surface on the free end side of the pair of upper inner flaps 13. The second thin portion 27 of the upper outer flap 12 enters the engagement cut 22D of the insertion cutting line 22 and is sandwiched (bitten) between the engagement piece 21 and the pressing portion 23. The pair of insert parts 25 and the pressing part 26 bend so as to twist vertically around the second thin part 27, so that the pair of upper inner flaps 13 are sandwiched between the pair of insert parts 25 and the pressing part 26. This makes it difficult for the insert part 25 to be pulled out of the insert hole 21A.

In this way, the top surface of the packaging box 1 is formed without using adhesive tape or the like, and the assembly work (sealing work) of the packaging box 1 is completed (see Figure 1). Note that in the above-mentioned assembly work of the packaging box 1, the top surface is formed after the bottom surface, but the bottom surface may be formed after the top surface. In this specification, the terms "top" and "bottom" are concepts established for the convenience of explanation, and their positional relationship may be reversed.

According to the packaging box 1 of the first embodiment described above, the engaging pieces 21, 31 are separated from the second side wall 11 by the first cuts 22A, 32A of the insertion cutting lines 22, 32 (see FIG. 2, etc.), so that the engaging pieces 21, 31 can be folded while suppressing interference with the second side wall 11. In addition, the periphery of the insertion cutting lines 22, 32 including the engaging pieces 21, 31 is made into the first thin-walled portion 24, 34 that is thinner than the other portions of the inner flaps 13, 15, and the rigidity is weakened, so that the engaging pieces 21, 31 can be easily folded at the base portion (imaginary lines V1, V2). According to this configuration, when the insertion portions 25, 35 of the outer flaps 12, 14 are pressed against the engaging pieces 21, 31, the inner flaps 13, 15 are prevented from falling into the inside of the peripheral wall W, and the engaging pieces 21, 31 can be bent appropriately and easily. This allows the insertion holes 21A, 31A to be opened smoothly, and the insertion portions 25, 35 can be easily inserted into the insertion holes 21A, 31A. In addition, by setting the dimensions (S1, S3) of the first cuts 22A, 32A to be greater than or equal to the dimensions (S2, S4) of the second and third fold lines L2, L3, the engagement pieces 21, 31 can be made even easier to bend.

In addition, according to the packaging box 1 of the first embodiment, the insertion fold lines L6, L8 are curved so as to be convex toward the free end side of the outer flaps 12, 14, so that by folding the outer flaps 12, 14 at the insertion fold lines L6, L8, both corner regions (a pair of insertion portions 25, 35) of the outer flaps 12, 14 can be oriented downward relative to the center portion (pressing portions 26, 36). This allows the insertion portions 25, 35 to be pressed against the engagement pieces 21, 31 before the pressing portions 26, 36 come into contact with the inner flaps 13, 15. As a result, the engagement pieces 21, 31 can be pushed in while preventing the inner flaps 13, 15 from dropping, so that the insertion portions 25, 35 can be smoothly inserted into the insertion holes 21A, 31A.

In addition, according to the packaging box 1 of the first embodiment, a portion of the free end side of the upper outer flap 12 corresponding to the engagement cut 22D is made into the second thin-walled portion 27, making it easier to insert the second thin-walled portion 27 between the engagement piece 21 and the pressing portion 23 (the second cut 22B).

In addition, according to the packaging box 1 of the first embodiment, the notch 38 is recessed on the free end side of the lower outer flap 14, so the insertion portion 35 can be inserted deeper into the insertion hole 31A than if the notch 38 were not present. This increases the overlap width (overlapping area) between the insertion portion 35 and the pressing portion 33, making it difficult to pull out the insertion portion 35. As a result, even if the product contained in the packaging box 1 is heavy, for example, it is possible to prevent the bottom of the packaging box 1 from falling out. In addition, because the edge of the notch 38 is the second thin portion 37, it is possible to easily insert the insertion portion 35 between the engagement piece 31 and the pressing portion 33.

As already explained, the second fold line L2 and the third fold line L3 extending in the flow direction are formed in the process of manufacturing the cardboard sheet with a corrugator, and the first fold line L1 and the insertion cut lines 22, 32, etc. are formed in the process of manufacturing the blank 1A with a wooden mold. For example, if the positions of the cardboard sheet and the wooden mold are slightly misaligned, the insertion cut lines 22, 32 (engagement pieces 21, 31) may be formed so as to intersect with the second fold line L2 and the third fold line L3. In this case, when trying to push the engagement pieces 21, 31 into the inside of the peripheral wall W in sealing the packaging box 1, the ends of the engagement pieces 21, 31 may interfere with the end face (cross section) of the second side wall 11 divided by the first cuts 22A, 32A, and there is a risk that the engagement pieces 21, 31 cannot be pushed in properly.

In response to such a problem, in the packaging box 1 according to the first embodiment, the insertion auxiliary fold line L5 is formed on the engagement piece 21 so as to be spaced apart from the second fold line L2 and approximately parallel to the second fold line L2. In addition, the outer fold line L4 (insertion auxiliary fold line L7) is formed on the engagement piece 31 so as to be spaced apart from the third fold line L3 and approximately parallel to the third fold line L3. With this configuration, even if the ends of the engagement pieces 21 and 31 interfere with the end face of the second side wall 11, the engagement pieces 21 and 31 can be pushed into the inside of the peripheral wall W while being folded backward at the insertion auxiliary fold lines L5 and L7. In addition, by forming the engagement pieces 21 and 31 as the first thin-walled portions 24 and 34 and forming the insertion auxiliary fold lines L5 and L7, the engagement pieces 21 and 31 can be easily folded at the insertion auxiliary fold lines L5 and L7. This allows the insertion holes 21A and 31A to be opened properly, and the insertion parts 25 and 35 can be smoothly inserted into the insertion holes 21A and 31A.

In addition, with the packaging box 1 according to the first embodiment, the outer fold line L4 as the insertion auxiliary fold line L7 can be formed with high precision when the cardboard sheet is manufactured. Also, for example, when the top surface is formed first during the assembly work of the packaging box 1 and then products are placed inside, the outer fold line L4 allows the lower inner flap 15 and the lower outer flap 14 to open outward from the peripheral wall W, making it easier to place the goods inside.

[Other embodiments]
Next, packaging boxes 2 to 4 according to other embodiments will be described with reference to Figs. 8 to 12. Fig. 8 is a plan view showing a blank 2A of a packaging box 2 according to a second embodiment. Fig. 9 is a plan view showing a blank 3A of a packaging box 3 according to a third embodiment. Fig. 10 is a plan view showing a blank 4A of a packaging box 4 according to a fourth embodiment. Fig. 11 is a plan view showing an enlarged portion of the blank 4A of a packaging box 4 according to the fourth embodiment. Fig. 12 is a perspective view showing a packaging box 4 according to the fourth embodiment. In the following description of packaging boxes 2 to 4 according to other embodiments, the same components as those of the packaging box 1 according to the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted.

[Second embodiment]
In the packaging box 1 according to the first embodiment, the insertion cut lines 22, 32 formed on the inner flaps 13, 15 are bent to form corners at the connecting portions between the first cuts 22A, 32A and the second cuts 22B, 32B, but the present invention is not limited thereto. As shown in Fig. 8, in the packaging box 2 (blank 2A) according to the second embodiment, the insertion cut lines 22, 32 formed on the inner flaps 13, 15 are curved to form a curve at the connecting portions between the first cuts 22A, 32A and the second cuts 22B, 32B. In this case, the curve at the connecting portion may be interpreted as extending in the direction along the second fold line L2 or the third fold line L3 and may be regarded as a part of the first cut 22A, or may be interpreted as curving away from the second fold line L2 or the third fold line L3 and may be regarded as a part of the second cuts 22B, 32B. Alternatively, the ranges extending in a generally straight line may be regarded as the first cut 22A and the second cut 22B, and the first cut 22A and the second cut 22B may be regarded as being connected via a curved portion. Note that in Fig. 8, the pair of first thin-walled portions 24, 34 (hatched lines) are omitted from illustration in order to clearly show the insertion cutting lines 22, 32, etc.

The packaging box 2 according to the second embodiment can achieve the same effects as the packaging box 1 according to the first embodiment, such as being able to easily insert the insertion portions 25, 35 into the insertion holes 21A, 31A.

[Third embodiment]
In the packaging box 1 according to the first embodiment, the second side wall 11 (inner flaps 13, 15) is formed longer in the flow direction than the first side wall 10 (outer flaps 12, 14), but the present invention is not limited thereto. As shown in FIG. 9, in the packaging box 3 (blank 3A) according to the third embodiment, the second side wall 11 (inner flaps 13, 15) is formed shorter in the flow direction than the first side wall 10 (outer flaps 12, 14). According to the packaging box 3 according to the third embodiment, the insertion portions 25, 35 can be easily inserted into the insertion holes 21A, 31A, and other effects similar to those of the packaging box 1 according to the first embodiment can be obtained. In FIG. 9, the pair of first thin portions 24, 34 (hatched lines) are omitted in order to clearly show the insertion cut lines 22, 32, etc. In addition, the features of the packaging box 2 according to the second embodiment described above may be applied to the packaging box 3 according to the third embodiment (not shown).

In the packaging boxes 1 to 3 according to the first to third embodiments, the first locking portion 20 is provided on the upper flaps 12, 13 and the second locking portion 30 is provided on the lower flaps 14, 15. However, the first locking portion 20 may be provided on the lower flaps 14, 15 and the second locking portion 30 may be provided on the upper flaps 12, 13 (not shown).

[Fourth embodiment]
The packaging box 4 (blank 4A) according to the fourth embodiment has a third locking portion 40 which differs in minor details from the first locking portion 20 of the packaging box 1 according to the first embodiment. As shown in Fig. 10, the third locking portion 40 has two pairs of engagement pieces 21, two pairs of insertion portions 25, and a pair of insertion fold lines L6, similar to the first locking portion 20 of the first embodiment.

As shown in FIG. 11, the insertion cut line 22 that divides the engagement piece 21 is composed of a first cut 22A and a second cut 22B, but the curvature of the second cut 22B on the inside of the flow direction of the engagement cut 22D (the tip in the insertion direction) is omitted. In addition, three first sliding contact cuts 41 are cut at intervals (approximately equal intervals) in the flow direction (insertion direction) on the edge of the pressing part 23 adjacent to the engagement cut 22D. The three first sliding contact cuts 41 are inclined from the inside to the outside of the flow direction (the tip to the base end in the insertion direction) from the engagement cut 22D toward the base end side of the upper inner flap 13 (approximately 45 degrees with respect to the engagement cut 22D).

As shown in FIG. 11, an engagement cut line 42 is cut along the step direction (insertion direction) on the free end side of the upper outer flap 12, separating the pressing portion 26 and the insertion portion 25. Unlike the notch portion 38, the engagement cut line 42 is composed of a single cut. The second thin portion 27 is formed on the edge of the insertion portion 25 adjacent to the engagement cut line 42 (see the diagonal lines in FIG. 10).

The holding portion 26 is formed with an engagement auxiliary piece 43 adjacent to the engagement cut line 42. The engagement auxiliary piece 43 is partitioned in the holding portion 26 by an engagement auxiliary fold line L9 that extends while curving so as to bulge from the end of the engagement cut line 42 in the cutting direction toward the free end of the upper outer flap 12. Four second sliding contact cuts 44 are cut at intervals (approximately equal intervals) in the step direction (insertion direction) on the edge of the engagement auxiliary piece 43 adjacent to the engagement cut line 42. The four second sliding contact cuts 44 are inclined from the base end side to the tip end side in the step direction (insertion direction) from the engagement cut line 42 toward the opposite side to the insertion portion 25 (approximately 45 degrees with respect to the engagement cut line 42).

The engagement auxiliary fold line L9 is a lead crease, but it is not limited to this and may be any structure for folding the cardboard sheet in the desired direction. The first sliding cut 41, the second sliding cut 44, the engagement cut line 42, and the engagement auxiliary fold line L9 are formed in the process of manufacturing the blank 4A using a wooden die (punch die). The second sliding cut 44 formed on the tip side of the engagement auxiliary piece 43 is slightly separated from the engagement cut line 42 (see Figure 11, etc.). This prevents the triangular portion defined by the second sliding cut 44 and the engagement cut line 42 from separating from the engagement auxiliary piece 43 and becoming punch waste.

The procedure for closing the lower opening (top surface) of the peripheral wall W is the same as that of the packaging box 1 according to the first embodiment, but in the process of inserting the insertion portion 25 into the insertion hole 21A, the engagement auxiliary piece 43 slides on the surface of the upper inner flap 13 while bending (reverse folding) upward along the engagement auxiliary fold line L9. In addition, because the second thin portion 27 is formed on the edge of the insertion portion 25 adjacent to the engagement cut line 42, the insertion portion 25 can be smoothly inserted between the engagement piece 21 and the pressing portion 23 (edge of the second cut 22B).

12, when the insertion portion 25 is inserted into the insertion hole 21A, the engagement auxiliary piece 43 is folded back at the engagement auxiliary fold line L9, and the edge portion on which the multiple second sliding contact cuts 44 are formed is placed on the edge portion of the pressing portion 23 on which the multiple first sliding contact cuts 41 are formed. Since a restoring force (elastic force) around the engagement auxiliary fold line L9 acts on the engagement auxiliary piece 43, the edge portion on which the multiple second sliding contact cuts 44 are formed is pressed against the edge portion of the pressing portion 23 on which the multiple first sliding contact cuts 41 are formed. With this configuration, the insertion portion 25 and the engagement auxiliary piece 43 hold the pressing portion 23 in place, so that the insertion portion 25 can be maintained in a state inserted into the insertion hole 21A. In addition, even if an attempt is made to pull out the insertion portion 25 from the insertion hole 21A, the multiple second sliding contact grooves 44 and the multiple first sliding contact grooves 41 rub against or engage with each other, making it difficult to pull out the insertion portion 25.

In the packaging box 4 according to the fourth embodiment, three first sliding cuts 41 and four second sliding cuts 44 are formed, but this is not limited thereto, and it is sufficient that two or more first sliding cuts 41 and two or more second sliding cuts 44 are formed. In addition, the inclination angle, length, interval, etc. of the first sliding cut 41 and the second sliding cut 44 may be freely changed. In addition, the first sliding cut 41 and the second sliding cut 44 are formed at an angle at the same angle, but the present invention is not limited thereto. For example, in the state of the blank 4A, the first sliding cut 41 may be cut parallel to the first fold line L1, and the second sliding cut 44 may be cut parallel to the second fold line L2 (not shown).

In addition, in the packaging box 4 according to the fourth embodiment, the third locking portion 40 is provided on the upper flaps 12 and 13, but this is not limited thereto and it may be provided on the lower flaps 14 and 15 (not shown).

In the packaging boxes 1 to 4 according to the first to fourth embodiments, the first to third locking parts 20, 30, 40 may be freely combined. That is, one selected from the first to third locking parts 20, 30, 40 may be provided on the upper flaps 12, 13, and one selected from the first to third locking parts 20, 30, 40 (which may be the same as or different from the upper flaps 12, 13) may be provided on the lower flaps 14, 15. Also, any one of the first to third locking parts 20, 30, 40 may be provided on only one of the upper flaps 12, 13 and the lower flaps 14, 15 (not shown). In this case, the flaps on which the first to third locking parts 20, 30, 40 are not provided may be closed by an existing method such as adhesive tape (not shown).

In addition, in the packaging boxes 1 to 4 according to the first to fourth embodiments, a pair of engagement pieces 21, 31 (a pair of insertion cutting lines 22, 32, a pair of insertion holes 21A, 31A, a pair of first thin portions 24, 34) and two sets of first sliding cuts 41 are formed on each of the inner flaps 13, 15, but the present invention is not limited to this. One engagement piece 21, 31, etc. may be formed on each of the inner flaps 13, 15 (not shown). Also, one or a pair of engagement pieces 21, 31, etc. may be formed on only one of the inner flaps 13, 15 (not shown). Also, the insertion portions 25, 35, the insertion fold lines L6, L8, the second thin portions 27, 37, the cutout portions 38, the engagement cutting lines 42, the engagement auxiliary pieces 43, the second sliding cuts 44, etc. may be formed on the outer flaps 12, 14 so as to correspond to the number and positions of the engagement pieces 21, etc. (not shown). That is, at least one engaging piece 21, etc., may be formed on at least one of the pair of inner flaps 13, 15, and at least one inserting portion 25, 35, etc. may be formed on at least one of the pair of outer flaps 12, 14. Note that if only one of the outer flaps 12, 14 has an inserting portion 25, 35, etc., and the corresponding engaging piece 21, etc., is formed on the pair of inner flaps 13, 15, the other outer flap may be folded forward of the pair of inner flaps 13, 15, and the pair of inner flaps 13, 15 may be laminated on the surface of the other outer flap (not shown).

In addition, in the packaging boxes 1 to 4 according to the first to fourth embodiments, the first cuts 22A, 32A of the insertion cutting lines 22, 32 are slightly inclined with respect to the second or third fold lines L2, L3, but this is not limited thereto and may be formed parallel to the second or third fold lines L2, L3 (not shown). In addition, the first cuts 22A, 32A may be formed linearly or may extend while slightly curved or bent (not shown). In other words, it is sufficient that the first cuts 22A, 32A are formed so as to follow the second or third fold lines L2, L3. In addition, the second cuts 22B, 32B (main body cuts 22C) of the insertion cutting lines 22, 32 are slightly inclined with respect to the row direction (first fold line L1), but this is not limited thereto and may be formed parallel to the first fold line L1 (not shown). Additionally, the second cuts 22B, 32B (main body cuts 22C) may be formed linearly, or may be curved or bent inward in the flow direction and extend toward the tip side in the step direction (not shown).

In addition, in the packaging boxes 1 to 4 according to the first to fourth embodiments, the insertion fold lines L6, L8 are curved so as to protrude from both side ends of the outer flaps 12, 14 toward the center toward the free end side, but the present invention is not limited to this. For example, the insertion fold lines L6, L8 may be bent approximately at the center and formed into an approximately V-shape (not shown). Also, the insertion fold lines L6, L8 do not have to be curved or bent, and may be formed in a straight line that crosses the outer flaps 12, 14 (not shown).

In addition, in the packaging boxes 1 to 4 according to the first to fourth embodiments, the second thin-walled portion 27 is formed in the outer flaps 12, 14, but this is not limited thereto, and the second thin-walled portion 27 may be omitted (not shown).

In addition, in the packaging boxes 1 to 4 according to the first to fourth embodiments, the outer fold line L4 formed on the lower flaps 14 and 15 is also used as the insertion auxiliary fold line L7 of the engagement piece 31, but the present invention is not limited to this. The outer fold line L4 may be omitted, and an insertion auxiliary fold line L5 may be formed on the engagement piece 31, similar to the engagement piece 21 of the first locking part 20 (not shown). Conversely, the outer fold line L4 may be formed on the upper flaps 12 and 13, and the outer fold line L4 formed on the engagement piece 21 of the first locking part 20 or the third locking part 40 may also be used as the insertion auxiliary fold line L5 (not shown). The insertion auxiliary fold line L5 and the outer fold line L4 (insertion auxiliary fold line L7) may also be omitted (not shown).

In addition, the packaging boxes 1 to 4 according to the first to fourth embodiments are so-called A-type cardboard boxes, but the present invention is not limited to this. For example, the packaging box may be a half A-type cardboard box in which the upper flaps 12, 13 or the lower flaps 14, 15 are omitted (not shown). In addition, the packaging box may be another type of box (not shown) as long as it has multiple flaps that close the opening of the peripheral wall W. In addition, in the packaging boxes 1 to 4, the pair of inner flaps 13, 15 are butted together to completely close the opening of the peripheral wall W, but this is not limited to this, and the pair of inner flaps 13, 15 may be so-called short flaps that separate the tips from each other (not shown). In addition, the pair of outer flaps 12, 14 may be formed so that their tips are butted together (not shown).

In addition, although the packaging boxes 1 to 4 according to this embodiment are formed from double-sided cardboard sheets made of paper, the present invention is not limited to this. The packaging boxes 1 to 4 may be formed from single-sided cardboard, double-sided cardboard, or quadruple-sided cardboard. Furthermore, the dimensions (width, depth, height) and shape of each part of the packaging boxes 1 to 4, the thickness of the sheets, the direction in which the core 9A extends, etc. may be freely changed.

The above embodiment is merely an example of the packaging box of the present invention, and the technical scope of the present invention is not limited to the above embodiment. The present invention may be modified, substituted, or altered in various ways without departing from the spirit of the technical concept, and the claims include all embodiments that may fall within the scope of the technical concept.

1, 2, 3, 4 Packaging box 9A Inner core 10 First side wall 11 Second side wall 12 Upper outer flap (outer flap)
13 Upper inner flap (inner flap)
14 Lower outer flap (outer flap)
15 Lower inner flap (inner flap)
21, 31 Engagement piece 21A, 31A Insertion hole 22, 32 Insertion cut line 22A, 32A First cut 22B, 32B Second cut 22D Engagement cut 23, 33 Pressing portion 24, 34 First thin portion 27, 37 Second thin portion 25, 35 Insertion portion 26, 36 Pressing portion 38 Notch portion 41 First sliding contact cut 42 Engagement cut line 43 Engagement auxiliary piece 44 Second sliding contact cut L2 Second fold line (first side fold line, second side fold line)
L3 Third fold line (first side fold line, second side fold line)
L4 Outer fold line L5, L7 Insertion auxiliary fold line L6, L8 Insertion fold line L9 Engagement auxiliary fold line W Peripheral wall

Claims (7)

A packaging box (1, 2, 3, 4) formed of a corrugated cardboard sheet,
A peripheral wall (W) formed in a cylindrical shape by alternately connecting a pair of first side walls (10) and a pair of second side walls (11);
a pair of outer flaps (12, 14) connected to the pair of first side walls and folded in a direction to close the opening of the peripheral wall;
a pair of inner flaps (13, 15) connected to the pair of second side walls and folded in a direction to close the opening,
At least one of the pair of outer flaps is
At least one insert (25, 35) in a corner region of the outer flap;
and an insertion fold line (L6, L8) extending in a direction along a first side fold line (L2, L3) that is a boundary with the first side wall,
At least one of the pair of inner flaps has at least one engagement piece (21, 31) defined by cutting at least one insertion cutting line (22, 32) to form an insertion hole (21A, 31A) for inserting the insertion portion,
The insertion cutting line is
a first cut (22A, 32A) extending from the base end side toward the tip end side in the insertion direction along a second side fold line (L2, L3) that is a boundary between the second side wall and the inner flap;
A second cut (22B, 32B) extending from a tip of the first cut in the insertion direction toward a free end side of the inner flap,
The edge portion along the second cut line, which is the tip side of the engagement piece and the insertion hole in the insertion direction, is a first thin-walled portion (24, 34) formed by crushing the core (9A) of the cardboard sheet,
A packaging box characterized in that a pair of the inner flaps are folded in a direction to close the opening, and the insertion portion of the outer flap bent at the insertion fold line is pressed against the engaging piece, thereby forcing the engaging piece into the inside of the peripheral wall to form the insertion hole, and the outer flap is folded in the direction to close the opening while straightening the bend at the insertion fold line, thereby inserting the insertion portion into the insertion hole. The packaging box according to claim 1, characterized in that the insertion fold lines are curved or bent so as to protrude from both side ends of the outer flap toward the center toward the free end side. The second cut has an engagement cut (22D) extending from the end that is the free end side of the inner flap to the tip side in the insertion direction,
3. The packaging box according to claim 1, wherein when the insertion portion is inserted into the insertion hole, a portion of the free end side of the outer flap corresponding to the engagement notch is formed as a second thin-walled portion (27, 37) formed by crushing the core of the cardboard sheet. When the insertion portion is inserted into the insertion hole, an engagement cut line (42) is cut along the insertion direction on the free end side of the outer flap corresponding to the engagement cut line, the engagement cut line separating the insertion portion from a pressing portion (26) overlapping the surfaces of the pair of inner flaps,
The pressing portion is formed with an engagement auxiliary piece (43) defined by an engagement auxiliary fold line (L9) that extends while curving so as to bulge from the end of the engagement cut line in the cutting direction toward the free end of the outer flap,
The second thin portion is formed on an edge of the insertion portion adjacent to the engagement cut line,
A pressing portion (23) is formed on the inner flap, adjacent to the engagement piece across the second cut and overlapping a surface of the insertion portion inserted into the insertion hole,
A plurality of first sliding contact cuts (41) are cut at intervals in the insertion direction from the engagement cut toward the base end side of the inner flap in the insertion direction, the first sliding contact cuts (41) being inclined from the tip end side to the base end side in the insertion direction from the engagement cut toward the base end side of the inner flap,
A plurality of second sliding contact cuts (44) are cut at intervals in the insertion direction on the edge of the engagement auxiliary piece adjacent to the engagement cut line, the second sliding contact cuts inclining from the base end side to the tip end side in the insertion direction from the engagement cut line toward the opposite side to the insertion portion,
4. The packaging box according to claim 3, characterized in that, when the insertion portion is inserted into the insertion hole, the engagement auxiliary piece is reverse folded at the engagement auxiliary fold line, so that the edge portion on which the plurality of second sliding contact cuts are formed is placed over the edge portion of the pressing portion on which the plurality of first sliding contact cuts are formed. When the insertion portion is inserted into the insertion hole, a notch (38) is recessed on the free end side of the outer flap corresponding to the vicinity of the end of the second cut, which is the free end side of the inner flap, to separate a pressing portion (36) overlapping the surfaces of the pair of inner flaps from the insertion portion,
3. The packaging box according to claim 1, wherein an edge of the cutout portion is a second thin-walled portion (37) formed by crushing the core of the cardboard sheet. The packaging box according to claim 1 or 2, characterized in that the engagement piece is formed with auxiliary insertion fold lines (L5, L7) near the second side fold line and extending in a direction along the second side fold line. The packaging box according to claim 6, characterized in that the insertion auxiliary fold line (L7) is formed across the entire width of the outer flap and the inner flap so as to be parallel to the first side fold line and the second side fold line at a distance from the first side fold line and the second side fold line, and is an outer fold line (L4) for folding the inner flap and the outer flap outward.

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