CUTTING EDGE FOR PACKAGING CONTAINER AND PACKAGING CONTAINER HAVING THE SAME

TECHNICAL FIELD

The present invention relates to a packaging container which accommodates a wrap film rolled around a cylindrical core, and to a cutting edge used for the packaging container.

BACKGROUND ART

Various types of packaging containers for wrap films have been known in the prior art. Most of these are made of cardboard, and are constructed with a container body that houses a rolled wrap film, and a cover formed integrally with the container body. The wrap film drawn out from the container is cut with a serrated cutting edge attached to the back side of the front wall of the cover.

The cutting edge is usually made of metal from the viewpoint of cutting power and durability, but in recent years non-metal materials such as paper or resins have been studied in consideration of environmental problems and user safety.

Such non-metal cutting edges do not readily exhibit the same satisfactory cutting power as metal cutting edges, and since a large force is required to cut highly elastic wrap films such as polyethylene, polypropylene or polyvinylidene chloride, improvement in the cutting power has been desired.

Various cutting edge forms have been proposed as solutions. Examples of straight-line cutting edges that have been proposed include those wherein the tips on both ends of the cutting edge are directed outward to facilitate penetration of the teeth into the wrap film (Patent documents 1 and 2, for example), those with a V-shaped cutting edge, wherein the center of the cutting edge is nearer the base of the container than the sides and larger teeth are arranged at the apex of the V-shape to facilitate penetration of the teeth into the wrap film at the initial cutting (Patent documents 3 and 4, for example), and those with an inverse V-shaped cutting edge that is the reverse of the aforementioned V-shape, wherein the side areas of the cutting edge protrude more than the center and the teeth at both ends have outwardly directed tips (Patent document 5, for example).

Incidentally, the method in which a wrap film is cut with a cutting edge provided on a packaging container generally differs depending on the shape of the cutting edge. For a V-shaped cutting edge, for example, the wrap film housed in the packaging container is drawn out, a desired amount of the wrap film drawn out from the packaging container is contacted with the protruding teeth at the center, the packaging container is twisted, and the teeth penetrate the center of the wrap film and cut it. For a straight-line or inverse V-shaped cutting edge, the wrap film housed in the packaging container is drawn out, a desired amount of the wrap film drawn out from the packaging container is contacted with one end of the cutting edge, the teeth penetrate the end of the wrap film, and then the wrap film is pulled to cut it from that end of the cutting edge toward the opposite end.

[Patent document 1] Japanese Utility Model Application Laid-Open HEI No. 6-20224

[Patent document 2] Japanese Utility Model Application Laid-Open HEI No. 11-151

[Patent document 3] Registered Utility Model No. 2547868

[Patent document 4] Japanese Patent Publication Laid-Open HEI No. 5-178344

[Patent document 5] Japanese Patent Publication Laid-Open HEI No. 8-40433

DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention

The present inventors have studied the cutting power, cutting sharpness and durability of cutting edges with various shapes for wrap films. As a result, it has been found that the conventional straight-line cutting edges described in Patent documents 1 and 2 do not allow smooth cutting of the wrap film after the wrap film has been penetrated and thus have insufficient wrap film cutting power, compared to the conventional V-shaped cutting edges described in Patent documents 3 and 4. It has also been found that a cutting edge such as described in Patent document 5, which is provided with protruding teeth at the ends of the cutting edge, also tends to prevent smooth cutting of the wrap film after the wrap film has been penetrated while also having problems of teeth durability, compared to the conventional V-shaped cutting edges described in Patent documents 3 and 4.

However, upon more detailed examination, the present inventors found that cutting power is insufficient even when using the conventional V-shaped cutting edges described in Patent documents 3 and 4, as explained below. Specifically, despite cutting edges with the various shapes mentioned above used in wrap film packaging containers, the user often fails to confirm the shape of the particular cutting edge to employ the optimal cutting method, instead cutting the wrap film from the end of the cutting edge toward the opposite end even with a V-shaped cutting edge. It was found that the conventional V-shaped cutting edge described in Patent document 3 or 4 does not exhibit sufficient cutting power when the wrap film is cut by such a method of cutting from the end of the cutting edge.

The present invention has been accomplished in light of these circumstances, and its object is to provide a cutting edge with satisfactory cutting power, and satisfactorily excellent feeling and durability during cutting, whether the wrap film is cut from the apex of a V-shaped cutting edge or from either end of the cutting edge, as well as a packaging container comprising the cutting edge.

Means for Solving the Problems

The cutting edge of the invention is a non-metallic V-shaped cutting edge comprising a plurality of teeth, that is mounted on a packaging container housing a packaged roll and that serves to cut the packaged roll, the cutting edge being characterized in that

(a) it is divided into a center area comprising the apex portion of the V-shape, a pair of side areas each including one of the ends of the V-shape, and a pair of intermediate areas each sandwiched between the pair of side areas and the center area,

(b) the center area has a plurality of first teeth all of the same tooth height and having the greatest tooth height, and a plurality of second teeth all of the same tooth height and having a smaller tooth height than the first teeth,

(c) one of the first teeth is situated at the apex portion while the rest of the first teeth are arranged at prescribed intervals centering around the first tooth at the apex portion,

(d) the second teeth are arranged between the first teeth,

(e) a first straight line connecting the tips of the first teeth, a second straight line connecting the tips of the second teeth and a third straight line connecting the bases of the first and second teeth are parallel to each other, the second straight line being located between the first and third straight lines,

(f) the intermediate area has a plurality of intermediate teeth,

(g) the tips of the intermediate teeth are located on the second straight line or between the second and third straight lines,

(h) the side areas have a plurality of side teeth, and

(i) the tips of the side teeth are located on the second straight line or between the first and second straight lines.

By providing a center area having the tooth configuration described above on the cutting edge, cutting of the wrap film medium is separated into stages when cutting of the wrap film is initiated from the center area containing the apex portion of the V-shape of the cutting edge: an initial “piercing” stage at the center area and a subsequent “incision” stage at the intermediate areas and side areas. The “piercing” stage is further separated into two steps: a piercing step by the first teeth which have the greatest tooth height, and a piercing step by the second teeth which have a lower tooth height than the first teeth. Since only the first teeth are in contact with the wrap film at the start of cutting, less force is necessary for piercing. With the first teeth alone, force would be necessary to pierce the wrap film due to the resistance of the valleys (bases of teeth) between the first teeth, but once it has been pierced with the first teeth, the second teeth penetrate through the wrap film, thus further facilitating the “piercing” stage during the initial cutting of the wrap film. The intermediate teeth with relatively low tooth heights, provided in the intermediate area, thereafter facilitate movement from the “piercing” stage to the “incision” stage. The wrap film is then smoothly incised at the side areas as well, so that the wrap film is cut. Cutting of the wrap film medium is also separated into stages when cutting of the wrap film is initiated from the side areas of the cutting edge: an initial “piercing” stage at one side area and a subsequent “incision” stage at the other areas. Since the side teeth in the side areas have greater tooth heights than the intermediate teeth in the intermediate areas and therefore protrude, the only teeth in contact with the wrap film at the initial cutting are the few side teeth on the end sides of the cutting edge. Thus, less force is necessary to pierce the wrap film at the initial cutting. The intermediate teeth with relatively low tooth heights, provided in the other intermediate area, thereafter facilitate movement from the “piercing” stage to the “incision” stage. The wrap film is then smoothly incised at the center area, the other intermediate areas and the other side areas as well, so that the wrap film is cut. Thus, the wrap film can be easily and smoothly cut whether cutting of the wrap film is initiated from the end of the wrap film or whether it is initiated from the center of the wrap film. The tooth height of each tooth can be measured as the shortest distance between the bottom sections at the valleys formed by adjacent teeth, i.e. a third straight line connecting multiple base of teeth, and the tip of the tooth.

At least one tip of the side teeth is preferably directed further outward than the tips of the first teeth, second teeth and intermediate teeth. That is, the oblique line on the top side of the cutting edge of at least one of the side teeth is preferably longer than the oblique line on the end side of the cutting edge.

If the tips of the side teeth in the side area are thus directed further outward than the tips of the first teeth, second teeth and intermediate teeth, it will be even easier to pierce the wrap film when cutting of the wrap film is initiated from the end of the wrap film, i.e. from the side area of the cutting edge. In addition, the wrap film is even less easily caught during incision in the side area even when cutting of the wrap film is initiated from the center area which contains the apex portion of the V-shape of the cutting edge, so that cutting of the wrap film at the “incision” stage can be accomplished even more smoothly.

The tooth heights of the side teeth are preferably equal to or higher than those of the second teeth, and lower than those of the first teeth.

By providing such side teeth in the side area, it is even easier to pierce the wrap film when cutting of the wrap film is initiated from the side area of the cutting edge.

According to another aspect, the cutting edge of the invention is a non-metallic V-shaped cutting edge comprising a plurality of teeth, which is mounted on a packaging container housing a packaged roll and serves to cut the packaged roll, the cutting edge being characterized in that

(a) it is divided into a center area comprising the apex portion of the V-shape, a pair of side areas each including one of the ends of the V-shape, and a pair of intermediate areas each sandwiched between the pair of side areas and the center area,

(b) the center area has a plurality of first teeth all of the same tooth height and having the greatest tooth height, and a plurality of second teeth all of the same tooth height and having a smaller tooth height than the first teeth,

(c) one of the first teeth is situated at the apex portion while the rest of the first teeth are arranged at prescribed intervals centering around the first tooth at the apex portion,

(d) the second teeth are arranged between the first teeth,

(e) a first straight line connecting the tips of the first teeth, a second straight line connecting the tips of the second teeth and a third straight line connecting the bases of the first and second teeth are parallel to each other, the second straight line being located between the first and third straight lines,

(f) the intermediate area has a plurality of intermediate teeth,

(g) the tips of the intermediate teeth are located on the second straight line or between the second and third straight lines,

(h) the side areas have a plurality of side teeth, and

(j) at least one of the tips of the side teeth is directed further outward than the tips of the first teeth, the second teeth and the intermediate teeth.

The intermediate teeth with relatively low tooth heights, provided in the intermediate area, thereafter facilitate movement from the “piercing” stage to the “incision” stage. The wrap film is then smoothly incised at the side areas as well, so that the wrap film is cut. Since at least one of the tips of the side teeth in the side area is directed further outward than the other tips, the wrap film is even less easily caught during incision in the side area, so that cutting of the wrap film at the “incision” stage can be accomplished even more smoothly.

Cutting of the wrap film medium is also separated into stages when cutting of the wrap film is initiated from the side areas of the cutting edge: an initial “piercing” stage at one side area and a subsequent “incision” stage at the other areas. Since side teeth directed further outward than the tips of the first teeth, second teeth and intermediate teeth are provided in the side area, less force is necessary for piercing of the wrap film at the initial cutting. The intermediate teeth with relatively low tooth heights, provided in one intermediate area, thereafter facilitate movement from the “piercing” stage to the “incision” stage. The wrap film is then smoothly incised at the center area, the other intermediate area and the other side area as well, so that the wrap film is cut. Thus, the wrap film can be easily and smoothly cut whether cutting of the wrap film is initiated from the end of the wrap film or whether it is initiated from the center of the wrap film.

The tooth height of each tooth can be measured as the shortest distance between the bottom sections at the valleys formed by adjacent teeth, i.e. a third straight line connecting multiple base of teeth, and the tip of the tooth.

In addition, the intermediate area preferably has large and small intermediate teeth with different tooth heights, alternately arranged.

Providing such intermediate teeth in the intermediate area can reduce the number of intermediate teeth that simultaneously contact the wrap film during transition from the “piercing” stage to the “incision” stage and during the “incision” stage, when cutting the wrap film. This smooths transition from the “piercing” stage to the “incision” stage compared with the case that intermediate teeth of the same tooth height are provided, thus allowing incision cutting of the wrap film to be accomplished with lower force.

The tooth heights of the intermediate teeth are preferably equal to or smaller than those of the second teeth.

By providing such intermediate teeth in the intermediate area it is possible to cut wrap film with an even superior feel during the “incision” stage when the wrap film is cut.

Preferably, the oblique line of at least one of the first teeth, second teeth, intermediate teeth and side teeth has an inwardly recessed arc-shape, i.e. the teeth are shaped like gingko leaves.

Such a shape creates an acute angle for the tip angle to ensure cutting power, while also increasing the inter-tooth pitch. This will eliminate the need to increase the number of teeth in a fixed range of length in the lengthwise direction of the cutting edge, and will limit the increase in force necessary for piercing of the wrap film. An effect of improved tooth durability is also obtained since the width is increased by the extent of the ends.

If the cutting edge of the invention is attached to a packaging container it is possible to provide a packaging container with excellent cutting power. The cutting edge of the invention is preferably attached to the back side of the front wall of the packaging container via a modified polyethylene resin. This will allow the cutting edge to be securely anchored to the packaging container with sufficient strength. As modified polyethylene resins there may be mentioned ethylenevinyl acetate copolymers, ethylenemethacrylic acid copolymers, and ionomers composed mainly of ethylene resins. Ethylenemethacrylic acid copolymers are particularly preferred among these.

EFFECT OF THE INVENTION

According to the invention it is possible to provide a cutting edge with satisfactory cutting power whether the wrap film is cut from the apex of a V-shaped cutting edge or from either end of the cutting edge, and satisfactorily excellent feeling and durability during cutting, as well as a packaging container comprising the cutting edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the form of a packaging container 10 according to the invention.

FIG. 2 is a partial magnified view of the center of a cutting edge according to a first embodiment of the invention.

FIG. 3 is a partial magnified view of one side of a cutting edge according to the first embodiment of the invention.

FIG. 4 is a perspective view of the form of a packaging container 10 according to the invention.

FIG. 5 is a partial magnified view of one side of a cutting edge according to a second embodiment of the invention.

FIG. 6 is a partial magnified view of one side of a cutting edge according to a third embodiment of the invention.

FIG. 7 is a partial magnified view of the center of a cutting edge according to a modification of the first, second and third embodiments of the invention.

EXPLANATION OF SYMBOLS

10: Packaging container, 12: paper pirn, 14: wrap film, 16: container body, 18: cover, 20: container body rear wall top edge, 22: cover front wall, 22a: back side, 24, 24a, 24b, 24c: cutting edge, 26: container body front wall base, 28: center area, 29, 29a, 29b: intermediate areas, 30, 30a, 30b: side areas, 31: intermediate first teeth (intermediate teeth), 32: intermediate second teeth (intermediate teeth), 33: side small teeth (side teeth), 34: side large teeth (side teeth), 35: small teeth, 36: medium teeth (second teeth), 38: large teeth (first teeth), 39, 40: side teeth, 50: laminated section, 52: adhesive layer, 54: sealant material.

BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment

FIG. 1 is a perspective view of the form of a packaging container 10 according to the invention. The packaging container 10 is constructed from a single cardboard sheet, and preferably a coated board sheet. As shown in FIG. 1, the packaging container 10 comprises a container body 16 which houses a wrap film 14 rolled around a cylindrical paper pirn 12, and a cover 18 formed integrally with the container body 16. When covered, the overall shape of the packaging container 10 is essentially rectangular solid. For this embodiment, the wrap film is made of polyvinylidene chloride.

The top of the container body 16 is open, as an opening to allow the wrap film 14 to be drawn out. The cover 18 extends continuously from the top edge 20 of the rear wall of the container body 16. The cover 18 is thus formed so as to be rotatable with respect to the container body 16 while covering the opening of the container body 16.

The front edge of the front wall 22 of the cover 18 is V-shaped, and a V-shaped cutting edge 24 matching its shape is used. The cutting edge 24 of this embodiment is divided into five areas: a center area 28 containing the apex portion of the V-shape, a pair of intermediate areas 29 situated on both sides thereof, and a pair of side areas 30 situated on the sides of the intermediate areas 29 opposite the center area 28 side. The cutting edge 24 of this embodiment will now be explained in detail.

FIG. 2 is a partial magnified view of the center of the cutting edge according to the first embodiment of the invention. The cutting edge 24 of this embodiment has bilateral symmetry centered around a center line passing through the apex of the V (labeled as CL in FIG. 2), and it comprises a center area 28 and intermediate areas 29 on either side thereof.

The center area 28 of this embodiment is composed of 15 teeth 35, 36, 38, as shown in FIG. 2. The center area 28 has 3 types of teeth: teeth with a small tooth height (hereinafter referred to as “small teeth”) 35, teeth with a larger tooth height than the small teeth 35 (second teeth: hereinafter referred to as “medium teeth”) 36, and teeth with an even larger tooth height than the medium teeth 36 (first teeth: hereinafter referred to as “large teeth”) 38. In the explanation that follows, alphabetic letters will be appropriately added to the reference numerals 36, 38 for the medium teeth and large teeth. The tooth heights of the teeth can be measured as the shortest distance between a straight line connecting the bases (third straight line) L3 and the apexes of the teeth.

One of the large teeth 38 (38a) is positioned at the apex portion of the V-shape of the cutting edge 24 (the center in the lengthwise direction of the center area 28), while the other large teeth 38b, 38c are positioned at prescribed intervals with two on either side around the central large tooth 38a as the center. The tip of the first large tooth 38a at the center and the tips of the second and third large teeth 38b, 38c on either side can be connected by a straight line, and the straight line (first straight line) L1 on either side is ahead of the tips of the medium teeth 36 on either side of the center area 28 (away from the front edge of the cover front wall 22 in FIG. 1). That is, the tips of the medium teeth 36 are located between the straight line connecting the bases (third straight line) L3 and the straight line L1.

Also, four medium teeth 36 in the center area 28 are located on either side, for a total of eight. The four medium teeth 36a, 36b toward the center are situated at a prescribed interval between the large teeth 38a, 38b, 38c, and the other four medium teeth 36c, 36d are situated on the outside of the third large tooth 38c at the same interval as the large teeth. The tips of the medium teeth 36a, 36b, 36c and 36d on either side can be connected by a straight line (second straight line) L2, the straight line L2 on either side being essentially parallel to the straight line L1 and located further behind the straight line L1 (nearer the front edge of the front wall 22 of the cover). That is, the straight line L2 is situated between the straight line L1 and the straight line L3.

Intermediate teeth 31, 32 of two different tooth heights in the lengthwise direction of the cutting edge 24 are alternately provided in the intermediate area 29. The intermediate teeth with smaller tooth heights than the intermediate teeth 32 (hereinafter referred to as “intermediate first teeth”) 31 have the same tooth heights as the small teeth 35 in the center area 28, while the intermediate teeth with greater tooth heights than the intermediate first teeth 31 (hereinafter referred to as “intermediate second teeth”) 32 have the same tooth heights as the medium teeth 36 in the center area 28. Also, the straight line L2 connecting the tips of the medium teeth 36 in the center area 28 passes through the tips of the intermediate second teeth 32 in the intermediate area 29.

The straight line (fourth straight line) L4 connecting the tips of the small teeth 35 in the center area 28 and the tips of the intermediate first teeth 31 in the intermediate area 29 is essentially parallel to the straight line L1 and the straight line L2, and the straight line L4 is located further behind the straight line L2 (nearer the front edge of the front wall 22 of the cover). That is, the straight line L4 is situated between the straight line L2 and the straight line L3. Thus, the tips of the intermediate teeth 31, 32 in the intermediate area 29 are situated on a straight line which is on the same straight line as or parallel to the straight lines L1 and L2, thus allowing even smoother incision of the wrap film.

FIG. 3 is a partial magnified view of the center of one side of a cutting edge according to the first embodiment of the invention. The cutting edge 24 of this embodiment has a side area 30 on the side of the intermediate area 29 opposite the center area 28 side. Although the end of the cutting edge 24 is not shown in FIG. 3, the cutting edge 24 has the same teeth 39 shown in FIG. 3 up to the end. The cutting edge 24 of this embodiment also has the same teeth shown in FIG. 3 in the other side area 30, as well.

Side teeth 39 with the tips directed outward are formed in the side area 30. The tips of the side teeth 39 can be connected by a straight line (fifth straight line) L5, the straight lines L5 on either side being essentially parallel to the straight line L2 connecting the tips of the intermediate second teeth 32 in the intermediate area 29 and the straight line L4 connecting the apexes of the intermediate first teeth 31, and each is located further forward than the straight lines L2 and L4 (further from the front edge of the front wall 22 of the cover in FIG. 1). The straight line L5 connecting the tips of the side teeth 39 is located further behind the straight line L1 connecting the tips of the large teeth 38 in the center area 28 (nearer the front edge of the front wall 22 of the cover). That is, the straight line L5 is situated between the straight line L1 and the straight line L2. The tips of the side teeth 39 may also be located on the straight line L2. Thus, the tips of the side teeth 39 in the side area 30 are situated on a straight line which is parallel to the straight lines L2 and L4, thus allowing even smoother incision of the wrap film.

The orientation of the tips of each of the teeth can be determined based on the orientation of the straight line connecting the tip of each tooth with the center between the bases on either side of the tooth. Since the straight line (K1) for the side teeth 39 extends further than the straight line (K2) for the intermediate teeth 31, 32 (FIG. 2) in the direction away from the center line CL of the cutting edge, in front of the cutting edge 24 (the projecting direction), the tips of the side teeth 39 are directed further outward than the tips of the intermediate first teeth 31 and intermediate second teeth 32.

In the cutting edge 24 of this embodiment, the tip angle α of each of the small teeth 35, medium teeth 36, large teeth 38, intermediate first teeth 31 and intermediate second teeth 32 (FIGS. 2 and 3) are suitable angles for piercing of the wrap film 14. For this embodiment wherein the wrap film 14 is made of polyvinylidene chloride, the tip angle α is preferably in the range of 30°-90° and more preferably 40°-70°. If it is larger than 90° a greater amount of force will be necessary to pierce the wrap film 14, and if it is smaller than 30° the durability of the teeth 31-38 themselves will tend to be impaired. The tip angle β of the side teeth 39 is also an angle suitable for piercing of the wrap film 14.

For this embodiment wherein the wrap film 14 is made of polyvinylidene chloride, the tip angle β is preferably in the range of 20°-60° and more preferably 20°-40°. If it is larger than 60° a greater amount of force will be necessary to pierce the wrap film 14, and if it is smaller than 20° the durability of the side teeth 39 themselves will tend to be impaired.

For the side teeth 39, the angle γ (FIG. 3) formed between the straight line which is parallel to the center line CL of the cutting edge 24 (FIG. 2) and passes through the bases on the outside of the side teeth 39 (the end side of the cutting edge), and the oblique line on the outside of the side teeth 39 (the end side of the cutting edge), is preferably 2-20°. This will allow a higher level of cutting power to be obtained both when the side teeth 39 are used for piercing of the wrap film and when they are used for incision of the wrap film.

Also, the shapes of the small teeth 35, medium teeth 36, large teeth 38, intermediate first teeth 31 and intermediate second teeth 32 may be simple isosceles triangle shapes, but for this embodiment it is preferred for at least one of the oblique lines to form a divergent shape or gingko leaf shape, with the arc recessed inward.

The shapes of the side teeth 39 may have straight lines as the triangular oblique lines, but preferably at least one of the oblique lines forms a divergent shape or gingko leaf shape, with the arc recessed inward. This is in order to maintain acute angles for the tip angles α and β, while improving durability. When such a shape is used, it is possible to reduce the number of teeth within regions of the same length compared to using straight-lines for the oblique lines, thus contributing to less force required for cutting.

A method for cutting a wrap film 14 using a packaging container 10 having a cutting edge 24 according to this embodiment will now be explained with reference to the accompanying drawings. The method for cutting the wrap film 14 may be either of the two cutting methods illustrated in FIG. 1 and FIG. 4. FIG. 1 and FIG. 4 are perspective views of the form of a packaging container 10 wherein the invention is applied. The packaging containers 10 shown in FIG. 1 and FIG. 4 are each provided with a cutting edge 24 having the tooth configuration shown in FIG. 2 and FIG. 3.

One cutting method (the method shown in FIG. 1) is a method in which the wrap film 14 is first pierced in the center area 28 containing the apex portion of the V-shape of the cutting edge 24, and then the pierced wrap film 14 is incised in the order: intermediate area 29 on both sides, side area 30 on both sides (hereinafter referred to as “cutting method 1” for convenience). Another cutting method (the method shown in FIG. 4) is a method in which the wrap film 14 is first pierced in one of the side areas 30a of the cutting edge 24, and then the pierced wrap film 14 is incised in the order: one intermediate area 29a adjacent to that side area 30a, center area 28, other intermediate area 29b and other side area 30b (hereinafter referred to as “cutting method 2” for convenience).

In cutting method 1, first the packaging container 10 is held with one hand, the center front edge of the wrap film 14 is taken with the other hand, and the desired amount is drawn out, as shown in FIG. 1. The thumb of the hand holding the packaging container 10 is pressed against the center of the cover front wall 22, and the packaging container 10 is twisted forward, i.e. in the direction of the arrow A.

During this time, the first large tooth 38a in the apex portion of the cutting edge 24 is contacted with the wrap film 14 first, and pierces it (FIG. 2). Almost simultaneously, the second large teeth 38b and the third large teeth 38c contact the wrap film 14 and pierce it. Thus, since the wrap film 14 is first contacted with only the five large teeth 38 with a large inter-tooth pitch and the largest tooth height, a smaller force is necessary to twist the packaging container 10 at the initial cutting. That is, since the minimum force necessary to pierce the wrap film 14 with each of the large teeth 38 is constant, the minimum force for twisting of the packaging container 10 is only about 5 times that force. When the tip angle is small and the inter-tooth pitch is small, as in the prior art, the number of teeth contacting the wrap film 14 is increased, so that a greater force must necessarily be applied to the packaging container 10 and the feeling during use is impaired, but such a problem does not arise with this embodiment.

The medium teeth 36 contact the wrap film 14 next, with the wrap film 14 being penetrated by the medium teeth 36. If no medium teeth 36 were present the pitch between the large teeth 38 would be wider, thus producing more resistance in the valleys between the teeth 38 (areas between the teeth) and increasing the force needed to incise the wrap film 14. With this embodiment, however, the wrap film 14 between the large teeth 38 is penetrated by the medium teeth 36 after the wrap film 14 has been pierced by the large teeth 38, so that piercing of the wrap film 14 is accomplished more smoothly.

The maximum number of medium teeth 36 that can simultaneously contact the wrap film 14 is 8, but since fewer than 8 of the medium teeth 36 actually contact the wrap film 14 simultaneously and the wrap film 14 is also pierced by the large teeth 38, thus weakening the periphery, the force required for piercing with the medium teeth 36 is even lower than when piercing is accomplished by the large teeth 38. Thus, the user does not feel resistance from the first-stage of cutting with the large teeth 38 to the second-stage of cutting by the medium teeth, and the operation is smooth.

In addition, twisting the packaging container 10 in the direction of the arrow A causes the small teeth 35 of the center area 28 to pierce the wrap film 14 between the third and fourth medium teeth 36c, 36d, so that incision of the wrap film 14 proceeds to the intermediate area 29. If an initial piercing section of sufficient size is formed in the wrap film 14, the force required to cut the wrap film 14 thereafter will not be very great, and the wrap film 14 will be smoothly incised and cut even in the intermediate area 29 comprising the intermediate first teeth 31 and intermediate second teeth 32 and the side area 30 comprising the side teeth 39 (FIG. 3).

In cutting method 2, first the packaging container 10 is held with one hand, the front edge of the side section of the wrap film 14 is taken with the other hand, and the desired amount is drawn out, as shown in FIG. 4. The container is anchored with the hand gripping the packaging container 10 while the wrap film 14 is lifted upward, i.e. in the direction of the arrow B, with the other hand, so that one end of the wrap film 14 is pressed against one side area 30a of the cutting edge 24.

The rest of cutting method 2 in which the wrap film 14 is lifted in the direction of the arrow B to cut the wrap film 14 will now be explained with reference to FIG. 3. When the wrap film 14 is lifted, the side teeth 39 in the side area 30 of the cutting edge 24, which are formed at the end of the cutting edge 24, pierce the wrap film 14. Almost simultaneously, the wrap film 14 contacts the side teeth 39 formed on the intermediate area 29 side of the side area 30.

When the wrap film 14 is further lifted in the direction of the arrow B, the wrap film 14 is penetrated by the side teeth 39. Although the wrap film 14 will usually be drawn slightly forward (toward the user) when the wrap film 14 is lifted in the direction of the arrow B, the tips of the side teeth 39 are directed further outward than the other teeth 31-38, and therefore the direction of the tips can be aligned with the pull direction of the wrap film 14, thus allowing even easier piercing of the wrap film 14.

In addition, lifting the wrap film 14 in the direction of the arrow B causes the wrap film 14 to proceed from the “piercing” stage to the “incision” stage. Specifically, if an initial piercing section of sufficient size is formed by the side teeth 39, the force required to cut the wrap film 14 thereafter will not be very great, and the wrap film 14 will be smoothly incised by the intermediate area 29 comprising the intermediate first teeth 31 and intermediate second teeth 32, which have smaller tooth heights than the side teeth 39. The wrap film 14 is then smoothly incised and cut even in the center area 28, the intermediate area 29b and the side area 30b as well, as shown in FIG. 4.

By using a cutting edge 24 according to this embodiment, a particularly large force is no longer necessary to cut the wrap film 14, and this reduces the need to excessively minimize the tip angle α of the teeth 31,32,35,36,38 and the tip angle β of the side teeth 39, thus improving the durability of the teeth 31,32,35,36,38,39.

The number of teeth provided on the cutting edge 24 can be appropriately adjusted according to the length of the cutting edge 24 in the lengthwise direction and the inter-tooth pitch. From the viewpoint of further facilitating piercing of the wrap film in cutting method 1, however, the total number of teeth in the center area 28 is preferably 5-31, more preferably 7-25 and even more preferably 9-19.

Also, from the viewpoint of allowing even smoother incision of the wrap film in cutting methods 1 and 2, the total number of teeth in each intermediate area 29 is preferably 10-100, more preferably 20-90 and even more preferably 40-60.

In addition, from the viewpoint of further facilitating piercing of the teeth through the wrap film in cutting method 2, the total number of teeth in each side area 30 is preferably 1-150, more preferably 5-100 and even more preferably 10-50. If the total number of teeth in the side area 30 is excessive, the region of the side area 30 in the cutting edge 24 will be relatively larger as a result, thus tending to interfere with satisfactory cutting power when the wrap film is cut by cutting method 1.

If the tooth height (extent of penetration) of the large teeth 38 and the medium teeth 36 or side teeth 39 is too great, the distance from the fixed part of the cutting edge 24, i.e. the distance from the front edge of the front wall 22 of the cover, will be increased, potentially impairing the durability. If the tooth height is too large, the hand of the user handling the packaging container 10 may be cut. From the viewpoint of cutting power, durability and safety, therefore, the tooth height H1 of the large teeth 38 in the center area 28, for example, is preferably 1.0-4.0 mm, more preferably 1.2-3.5 mm and even more preferably 1.2-2.5 mm, the tooth height H2 of the medium teeth 36 is preferably 0.8-2.0 mm and more preferably 0.9-1.5 mm, and the tooth height H3 of the small teeth 35 is preferably 0.4-1.5 mm and more preferably 0.5-1.0 mm.

The inter-tooth pitch of the center area 28 is preferably 3.0-9.0 mm, more preferably 3.5-7.0 mm and even more preferably 4.0-6.0 mm between the large teeth 38, and preferably 3.0-9.0 mm, more preferably 3.5-7.0 mm and even more preferably 4.0-6.0 mm between the medium teeth 36. If the inter-tooth pitch between the large teeth 38 and between the medium teeth 36 is greater than 9.0 mm, the film 14 may become caught in the valleys (bases of teeth) between the large teeth 38 at the “piercing” stage of the wrap film 14 in cutting method 1, thus causing a hindrance to cutting. On the other hand, if the inter-tooth pitch between the large teeth 38 and medium teeth 36 is narrower than 3.0 mm, the number of teeth formed in the center area 28 will be increased, resulting in greater force required for piercing and tending to interfere with satisfactory cutting power.

The tooth height 112 of the intermediate second teeth 32 in the intermediate area 29 is preferably 0.8-2.0 mm and more preferably 0.9-1.5 mm. The tooth height H3 of the intermediate first teeth 31 in the intermediate area 29 is preferably 0.4-1.5 mm and more preferably 0.5-1.0 mm. The inter-tooth pitch between the intermediate first teeth 31 and the inter-tooth pitch between the intermediate second teeth 32 is preferably 1.0-3.5 mm and more preferably 1.5-3.0 mm.

The tooth height H4 of the side teeth 39 in the side area 30 is preferably 0.8-3.5 mm, more preferably 0.9-2.0 mm and even more preferably 1.0-1.5 mm. The inter-tooth pitch between the side teeth 39 is preferably 0.5-3.5 mm and more preferably 0.7-2.5 mm.

Second Embodiment

FIG. 5 is a partial magnified view of the center of one side of a cutting edge according to the second embodiment of the invention. The cutting edge 24a of FIG. 5 differs from the cutting edge 24 of the embodiment described above in that it comprises side teeth 33 and 34 in the side area 30. Specifically, in the center area (not shown) and the intermediate area 29, the cutting edge 24a has the same tooth configuration as the cutting edge 24 of the embodiment described above (FIG. 2). The cutting edge 24a also has the same tooth configuration as FIG. 5 in the other side area and the other intermediate area.

In the side area 30 of the cutting edge 24a of this embodiment there are alternately provided side small teeth 33 which have the same shapes and tooth heights as the intermediate first teeth 31 in the intermediate area 29, and side large teeth 34 whose tips are directed outward. The tips of the side large teeth 34 are located on the straight line L2 connecting the tips of the medium teeth 36 of the center area 28 and the tips of the intermediate second teeth 32 of the intermediate area 29. The tips of the side small teeth 33 are located on the straight line L4 connecting the tips of the intermediate first teeth 31 of the intermediate area 29.

The side small teeth 33 have the same tip angle as the tip angle α of the intermediate first teeth 31 and intermediate second teeth 32. The shapes of the side small teeth 33 may be simple isosceles triangles, but preferably at least one of the oblique lines is a divergent shape or gingko leaf shape, with the arc recessed inward. This will maintain the tip angle α at a given acute angle while improving the durability. When such a shape is used, it is possible to reduce the number of teeth within regions of the same length compared to using straight-lines for the oblique lines, thus contributing to less force required for cutting.

The orientation of the tips of each of the teeth can be determined based on the orientation of the straight line connecting the tip of each tooth with the center between the bases on either side of the tooth. Since the straight line (K3) for the side large teeth 34 extends more than the straight line (K2) for the intermediate teeth 31, 32 (FIG. 2) in the direction away from the center line CL of the cutting edge, in front of the cutting edge 24a (the projecting direction), the tips of the side large teeth 34 are directed further outward than the tips of the intermediate teeth 31, 32 and side small teeth 33.

In the cutting edge 24a of this embodiment, the tip angle α of each of the small teeth 35, medium teeth 36, large teeth 38, intermediate first teeth 31 and intermediate second teeth 32 (FIGS. 2 and 5) are suitable angles for piercing of the wrap film 14. For this embodiment wherein the wrap film 14 is made of polyvinylidene chloride, the tip angle α is preferably in the range of 30°-90° and more preferably 40°-70°. If it is larger than 90° a greater amount of force will be necessary to pierce the wrap film 14, and if it is smaller than 30° the durability of the teeth 31-38 themselves will tend to be impaired. The tip angle of the side large teeth 34 is also an angle suitable for piercing of the wrap film 14.

For the side large teeth 34, the angle γ (FIG. 5) formed between the straight line which is parallel to the center line CL of the cutting edge (FIG. 2) and passes through the bases on the outside of the side large teeth 34 (the end side of the cutting edge), and the oblique line on the outside of the side teeth 39 (the end side of the cutting edge), is preferably 2-20°. This will allow a higher level of cutting power to be obtained both when the side large teeth 34 are used for piercing of the wrap film and when they are used for incision of the wrap film.

Instead of straight lines as the sides of the triangles of the side large teeth 34, preferably at least one of the oblique lines forms a divergent shape or gingko leaf shape, with the arc recessed inward. This is in order to maintain acute angles for the tip angle β, while improving durability. When such a shape is used, it is possible to reduce the number of teeth within regions of the same length compared to using straight-lines for the oblique lines, thus contributing to less force required for cutting.

A method for cutting a wrap film 14 using a packaging container having a cutting edge 24a according to this embodiment will now be explained with reference to the accompanying drawings. The method for cutting the wrap film 14 may be either of the two cutting methods illustrated in FIG. 1 and FIG. 4. FIG. 1 and FIG. 4 are perspective views of the form of a packaging container 10 wherein the invention is applied. The packaging containers 10 shown in FIG. 1 and FIG. 4 are each provided with a cutting edge 24a having the tooth configuration shown in FIG. 2 and FIG. 5.

Another cutting method (the method shown in FIG. 4) is a method in which the wrap film 14 is first pierced in one of the side areas 30a of the cutting edge 24a, and then the pierced wrap film 14 is incised in the order: one intermediate area 29a adjacent to that side area 30a, center area 28, other intermediate area 29b and other side area 30b (hereinafter referred to as “cutting method 2” for convenience).

During this time, the first large tooth 38a in the apex portion of the cutting edge 24a is contacted with the wrap film 14 first, and pierces it (FIG. 2). Almost simultaneously, the second large teeth 38b and the third large teeth 38c contact the wrap film 14 and pierce it. Thus, since the wrap film 14 is first contacted with only the five large teeth 38 with a large inter-tooth pitch and the largest tooth height, a smaller force is necessary to twist the packaging container 10 at the initial cutting. That is, since the minimum force necessary to pierce the wrap film 14 with each of the large teeth 38 is constant, the minimum force for twisting of the packaging container 10 is only about 5 times that force.

When the tip angle is small and the inter-tooth pitch is small, as in the prior art, the number of teeth contacting the wrap film 14 is increased, so that a greater force must necessarily be applied to the packaging container 10 and the feeling during use is impaired, but such a problem does not arise with this embodiment.

In cutting method 2, the packaging container 10 is held with one hand, the front edge of the side section of the wrap film 14 is taken with the other hand, and the desired amount is drawn out, as shown in FIG. 4. The container is anchored with the hand gripping the packaging container 10 while the wrap film 14 is lifted upward, i.e. in the direction of the arrow B, with the other hand, so that one end of the wrap film 14 is pressed against the other side area 30a of the cutting edge 24a.

In cutting method 2, only the side large teeth 34 provided at the end of the cutting edge 24a shown in FIG. 5 contact with the wrap film 14 at the initial cutting. Thus, it is possible to reduce the number of teeth that contact with the wrap film at the initial cutting compared to a cutting edge having only the same tooth heights in the side area, and this allows piercing of the wrap film to be easily accomplished.

The rest of cutting method 2 in which the wrap film 14 is lifted in the direction of the arrow B to cut the wrap film 14 will now be explained with reference to FIG. 5. When the wrap film 14 is lifted, the side large teeth 34 with large tooth heights in the side area 30 of the cutting edge 24a, which are formed at the end of the cutting edge 24a, pierce the wrap film 14. The tips of the side large teeth 34 are directed further outward than the other teeth 31-38, and therefore the direction of the tips can be aligned with the pull direction of the wrap film 14, thus allowing even easier piercing of the wrap film 14. When the wrap film 14 is further lifted in the direction of the arrow B, the side large teeth 34 formed in the intermediate area 29 contact with the wrap film 14 and the wrap film 14 is pierced. This forms sufficiently large initial protruding sections.

In addition, lifting the wrap film 14 in the direction of the arrow B causes the wrap film 14 to proceed from the “piercing” stage to the “incision” stage. Specifically, if an initial piercing section of sufficient size is formed by the side large teeth 34, the force required to cut the wrap film 14 thereafter will not be very great, and the wrap film 14 will be smoothly incised by the intermediate area 29 comprising the intermediate first teeth 31 and intermediate second teeth 32. The wrap film 14 is then smoothly incised and cut even in the center area 28, the intermediate area 29b and the side area 30b as well, as shown in FIG. 4.

Specifically, with the cutting edge 24a, the wrap film can be easily cut with satisfactory feeling during cutting, whether from the apex portion of the V-shape of the cutting edge 24a or from one end of the cutting edge 24a.

The preferred total number of teeth, the tooth heights and the inter-tooth pitch in the center area 28 and intermediate area 29 of the cutting edge 24a is the same as for the first embodiment. The total number of teeth in each side area 30 is preferably 1-150, more preferably 5-100 and even more preferably 10-50. If the total number of teeth in the side area 30 is excessive, the region of the side area 30 in the cutting edge 24a will be larger as a result, thus tending to interfere with satisfactory cutting power when the wrap film is cut by cutting method 1.

The tooth height H2 of the side large teeth 34 in the side area 30 is preferably 0.8-2.0 mm and more preferably 0.9-1.5 mm, and the tooth height H3 of the side small teeth 33 is preferably 0.4-1.5 mm and more preferably 0.5-1.0 mm. The inter-tooth pitch between the side large teeth 34 and the inter-tooth pitch between the side small teeth 33 is preferably 1.0-3.5 mm and more preferably 1.5-3.0 mm.

Third Embodiment

FIG. 6 is a partial magnified view of the center of one side of a cutting edge according to the third embodiment of the invention. The cutting edge 24b of FIG. 6 differs from the cutting edge 24 of the first embodiment in that it comprises side teeth 40 in the side area 30. Specifically, in the center area (not shown) and the intermediate area 29, the cutting edge 24b has the same tooth configuration as the cutting edge 24 of the embodiment described above. The cutting edge 24a also has the same tooth configuration as FIG. 6 in the other side area and the other intermediate area.

The side teeth 40 provided in the side area 30 of the cutting edge 24b of this embodiment have the same shapes as the intermediate first teeth 31 and intermediate second teeth 32 in the intermediate area 29.

The straight line L5 connecting the tips of the side teeth 40 is located between the straight line L1 connecting the large teeth of the center area and the straight line L2 connecting the medium teeth of the center area. The effect of the invention can also be obtained with this type of side teeth 40. Specifically, the wrap film can be easily cut with satisfactory feeling during cutting, whether from the apex portion of the V-shape of the cutting edge 24b or from one end of the cutting edge 24b. The cutting edge 24b comprising the side teeth 40 has even more excellent durability.

The side teeth 40 have the same tip angle as the tip angle α of the intermediate first teeth 31 and intermediate second teeth 32. The shapes of the side teeth 40 may be simple isosceles triangles, but preferably at least one of the oblique lines is a divergent shape or gingko leaf shape, with the arc recessed inward. This will maintain the tip angle α at a given acute angle while improving the durability. When such a shape is used, it is possible to reduce the number of teeth within regions of the same length compared to using straight-lines for the oblique lines, thus contributing to less force required for cutting.

In the cutting edge 24b of this embodiment, the tip angle α of each of the small teeth 35, medium teeth 36, large teeth 38, intermediate first teeth 31, intermediate second teeth 32 and side teeth 40 (FIGS. 2 and 6) are suitable angles for piercing of the wrap film 14. For this embodiment wherein the wrap film 14 is made of polyvinylidene chloride, the tip angle α is preferably in the range of 30°-90° and more preferably 40°-70°. If it is larger than 90° a greater amount of force will be necessary to pierce the wrap film 14, and if it is smaller than 30° the durability of the teeth 31-40 themselves will tend to be impaired.

Also, the shapes of the small teeth 35, medium teeth 36, large teeth 38, intermediate first teeth 31, intermediate second teeth 32 and side teeth 40 may be simple isosceles triangle shapes, but for this embodiment it is preferred for at least one of the oblique lines to be a divergent shape or gingko leaf shape, with the arc recessed inward. This is in order to maintain acute angles for the tip angle α, while improving durability. When such a shape is used, it is possible to reduce the number of teeth within regions of the same length compared to straight-lines for the oblique lines, thus contributing to less force required for cutting.

A method for cutting a wrap film 14 using a packaging container having a cutting edge 24b according to this embodiment will now be explained with reference to the accompanying drawings. The method for cutting the wrap film 14 may be either of the two cutting methods illustrated in FIG. 1 and FIG. 4. FIG. 1 and FIG. 4 are perspective views of the form of a packaging container 10 in which the invention is applied. The packaging containers 10 shown in FIG. 1 and FIG. 4 are each provided with a cutting edge 24b having the tooth structures shown in FIG. 2 and FIG. 6.

Another cutting method (the method shown in FIG. 4) is a method in which the wrap film 14 is first pierced in one of the side areas 30a of the cutting edge 24b, and then the pierced wrap film 14 is incised in the order: one intermediate area 29a adjacent to that side area 30a, center area 28, other intermediate area 29b and other side area 30b (hereinafter referred to as “cutting method 2” for convenience).

During this time, the first large tooth 38a in the apex portion of the cutting edge 24b is contacted with the wrap film 14 first, and pierces it (FIG. 2). Almost simultaneously, the second large teeth 38b and the third large teeth 38c contact the wrap film 14 and pierce it. Thus, since the wrap film 14 is first contacted with only the five large teeth 38 with a large inter-tooth pitch and the largest tooth height, a smaller force is necessary to twist the packaging container 10 at the initial cutting. That is, since the minimum force necessary to pierce the wrap film 14 with each of the large teeth 38 is constant, the minimum force for twisting of the packaging container 10 is only about 5 times that force.

When the tip angle is small and the inter-tooth pitch is small, as in the prior art, the number of teeth contacting the wrap film 14 is increased so that a greater force must necessarily be applied to the packaging container 10 and the feeling during use is impaired, but such a problem does not arise with this embodiment.

The maximum number of medium teeth 36 simultaneously contacting the wrap film 14 is 8, but since fewer than 8 of the medium teeth 36 are actually contacting the wrap film 14 simultaneously and the wrap film 14 is also pierced by the large teeth 38, thus weakening the periphery, the force required for piercing with the medium teeth 36 is even lower than when piercing is accomplished by the large teeth 38. Thus, the user does not feel resistance from the first-stage of cutting with the large teeth 38 to the second-stage of cutting by the medium teeth, and the operation is smooth.

In cutting method 2, only the side teeth 40 provided at the end of the cutting edge 24b shown in FIG. 6 contact with the wrap film at the initial cutting. The wrap film can thus be easily pierced.

The rest of cutting method 2 in which the wrap film 14 is lifted in the direction of the arrow B to cut the wrap film 14 will now be explained with reference to FIG. 6. When the wrap film 14 is lifted, the side teeth 40 in the side area 30 of the cutting edge 24b, which are formed at the end of the cutting edge 24b, pierce the wrap film 14. When the wrap film 14 is further lifted in the direction of the arrow B, the side teeth 40 formed in the intermediate area 29 contact with the wrap film 14 and the wrap film 14 is pierced. This forms sufficiently large initial protruding sections.

In addition, lifting the wrap film 14 in the direction of the arrow B causes the wrap film 14 to proceed from the “piercing” stage to the “incision” stage. Specifically, if an initial piercing section of sufficient size is formed by the side teeth 40, the force required to cut the wrap film 14 thereafter will not be very great, and the wrap film 14 will be smoothly incised by the intermediate area 29 comprising the intermediate first teeth 31 and intermediate second teeth 32, which have smaller tooth heights than the side teeth 40. The wrap film 14 is then smoothly incised and cut even in the center area 28, the intermediate area 29b and the side area 30b as well, as shown in FIG. 4.

Specifically, with the cutting edge 24b, the wrap film can be easily cut with satisfactory feeling during cutting, whether from the apex portion of the V-shape of the cutting edge 24b or from one end of the cutting edge 24b.

The number of side teeth 40 provided in one side area 30 of the cutting edge 24b is preferably 5-100, more preferably 10-50 and even more preferably 20-45. If the number of side teeth 40 provided in one side teeth 30 is less than 20, the region of formation of the initial piercing section of the wrap film will be narrower in the cutting method in which cutting of the wrap film is initiated from one side area 30 of the cutting edge 24b, and smooth movement from the “piercing” stage to the “incision” stage will tend to be impaired. If the number of side teeth 40 in the side teeth 30 is greater than 100, the satisfactory feeling in the “incision” stage during cutting of the wrap film will tend to be impaired, in the cutting method in which cutting is initiated from the center area of the cutting edge 24b.

The tooth height H4 of the side teeth 40 in the side area 30 is preferably 0.8-3.5 mm, more preferably 0.9-2.0 mm and even more preferably 1.0-1.5 mm. The inter-tooth pitch between the side teeth 40 is preferably 0.5-3.5 mm and more preferably 0.7-2.5 mm.

Modified Examples of First, Second and Third Embodiments

FIG. 7 is a partial magnified view of the center of a cutting edge according to a modification of the first, second and third embodiments of the invention. The cutting edge 24c of FIG. 7 differs from the cutting edge 24 of the embodiment described above in that it comprises only side teeth 31 in the intermediate area 29. Specifically, in the center area 28 and side area (not shown), the cutting edge 24c has the same tooth configuration as the cutting edge 24 of the first embodiment.

The straight line L4 connecting the tips of the side teeth 31 is located between the straight line L2 connecting the tips of the medium teeth 36 in the center area 28 and straight line L3 connecting the bases of teeth. The effect of the invention can be obtained even when the intermediate area 29 is composed only of side teeth 31 with the same tooth heights as in the cutting edge 24c, thus allowing easy incision of the wrap film.

The above detailed explanation of preferred embodiments of the invention are naturally not intended to restrict the scope of the invention to these particular embodiments.

Although the wrap film was composed of polyvinylidene chloride in the embodiments described above, the invention may be applied to wrap films made of other resins as well. In such cases, the tooth heights, inter-tooth pitch and tip angles may be appropriately modified from the dimensions mentioned above.

In addition, the packaged roll may be aluminum or paper instead of a wrap film.

The material of the cutting edge for these embodiments may be vulcanized fiber, a resin-impregnated sheet or a resin, but a resin with high strength is preferred. The resin used may be polyester, polyethylene, polypropylene, polystyrene, acetal resin, polyphenylene sulfide, PEEK (polyether ether ketone resin), PES (polyethersulfone resin) or the like. Polyester is preferred, with polyethylene terephthalate being more preferred.

An environmentally friendly biodegradable resin may also be used. A biodegradable resin is a polymer material that is decomposed to low molecular compounds by natural microorganisms when it is disposed of after use, eventually being completely decomposed to carbon dioxide gas and water, while maintaining the same function as a conventional resin during use, and this function can provide a cutting edge that is more friendly to the environment. As examples of biodegradable resins there may be mentioned polylactic acid resins and polyglycolic acid resins.

The cutting edge of each of the embodiments described above may be formed using one of the resin materials mentioned above or a mixture of two or more thereof. An inorganic powder such as calcium carbonate, titanium oxide, silica, barium sulfate or talc may be added to one resin material or a resin material comprising a mixture of two or more thereof, in an amount of 5-70 wt % with respect to the total material of the cutting edge. Addition of an inorganic powder can improve the mechanical strength.

The cutting edge may be formed by molding such materials into a sheet with a thickness of 0.05-0.5 mm, preferably 0.1-0.3 mm and more preferably 0.20-0.28 mm, and then punching with a die. A cutting edge thickness of greater than 0.5 mm may not result in sufficiently satisfactory cutting power, while a cutting edge thickness of less than 0.05 mm may interfere with satisfactory cutting sharpness.

FIG. 8 is a schematic cross-sectional view of the laminated part of a packaging container wherein a cutting edge according to an embodiment of the invention is attached to the back side of the front wall of the cover via a resin sealant material. In the laminated section 50 of the packaging container, a sealant material 54, adhesive layer 52 and cutting edge 24 are laminated in that order on the back side 22a of the front wall 22 of the cover. The cutting edge 24 that has been bonded with a sealant material 54 composed mainly of an ethylenemethacrylic acid copolymer using a polyurethane-based adhesive (adhesive layer 52), is attached to the back side 22a of the front wall of the packaging container by bonding the sealant material 54 and the back side 22a of the front wall of the packaging container cover by ultrasonic bonding. The cutting edge 24 attached to the back side 22a of the front wall of the packaging container cover via the sealant material 54 is anchored to the packaging container cover by sufficient adhesive force, and therefore it does not easily peel from the packaging container cover.

The method of attaching the cutting edge to the back side of the front wall of the packaging container cover may be a known cold glue method or pressure-sensitive adhesive method.

INDUSTRIAL APPLICABILITY

According to the invention it is possible to provide a cutting edge with satisfactory cutting power and satisfactorily excellent feeling and durability during cutting, as well as a packaging container comprising the cutting edge.

CUTTING EDGE FOR PACKAGING CONTAINER AND PACKAGING CONTAINER HAVING THE SAME

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