GB2323074A

GB2323074A - Sawtooth cutter

Info

Publication number: GB2323074A
Application number: GB9812808A
Authority: GB
Inventors: Atsuya Ozawa
Original assignee: Dai Nippon Printing Co Ltd
Current assignee: Dai Nippon Printing Co Ltd
Priority date: 1994-12-20
Filing date: 1995-12-20
Publication date: 1998-09-16
Anticipated expiration: 2015-12-20
Also published as: GB2331288B; GB9902930D0; GB2331288A; GB9812808D0; GB2323074B

Abstract

A sawtooth cutter 2 for cutting an aluminium foil or a wrapping film is made from a resin-impregnated paper sheet. The paper is preferably a long-fibre wood pulp containing little or no size. Preferably the resin ranges from 50 to 80 parts by weight per 100 parts of paper and can be hard, water soluble acrylic resins such as methyl, ethyl or butyl acrylate or methacrylate. Preferably the finished cutter is from 0.2 to 0.4 mm thick and is attached to the blank by adhesive except for welding or hot melt of the ends to the blank. An alternative cutter of resin coated, vulcanised fibre is also disclosed.

Description

SAWTOOTH CUTTER TECHNICAL FIELD The present invention a method of bonding a sawtooth cutter to a carton blank when fabricating a carton with sawtooth cutter for containing an aluminum foil or a wrapping film, a sawtooth cutter suitable for cutting an aluminum foil or a wrapping film, and a combination of a carton blank and a sawtooth cutter.

BACKGROUND ART A cuboidal carton containing a roll of an aluminum foil or a plastic wrapping film and provided with a metallic sawtooth cutter having a sawtooth cutting edge and attached to one edge of the carton has prevalently been used. The aluminum foil or the plastic wrapping film is pulled out of the carton and cut with the sawtooth cutter. Since the metallic sawtooth cutter cannot be incinerated, problem arises in the disposal of the carton. The use of nonmetallic sawtooth cutters, such as paper sawtooth cutters and vulcanized fiber sawtooth cutters, instead of metallic sawtooth cutters have been proposed, for instance, in JP-A Nos. 6-48428 and 6-144425.

Staking, which is employed in fastening a metallic sawtooth cutter to a carton blank, cannot be applied to fastening a nonmetallic sawtooth cutter, such as a vulcanized fiber sawtooth cutter, to a carton blank.

Therefore it is usual to bond such a sawtooth cutter adhesively to a carton blank with a hot-melt or an emulsion type adhesive (glue). JP-A No. 6-48428 uses ultrasonic welding for bonding a sawtooth cutter to a carton blank, and JP-A No. 6-144425 bonds a sawtooth cutter temporarily to a carton blank with spots of an adhesive, and then bonds the entire length of the sawtooth cutter to the carton blank by ultrasonic welding or heat-sealing.

When the entire length of a sawtooth cutter is bonded to a carton blank with an adhesive, it sometimes occurs that the opposite end portions of the sawtooth cutter come off from the carton during use to spoil the appearance of the carton or the sawtooth cutter comes off completely from the carton and becomes unusable. Those troubles were examined for causes and the following causes were found.

When bonding a sawtooth cutter to a carton blank with an adhesive, the adhesive is spread in a width narrower than that of the sawtooth cutter and in a length shorter than that of the sawtooth cutter to prevent the adhesive from oozing from under the sawtooth cutter. Therefore, part of the sawtooth cutter is not coated with the adhesive.

Particularly, the opposite end portions of the sawtooth cutter are not coated with the adhesive. Portions not coated with the adhesive are liable to come off. In some cases, a hygroscopic sawtooth absorbs moisture, tends to extend and, consequently, comes off the carton. Since a relatively high force is exerted on the end portions of the sawtooth cutter when cutting an aluminum foil or a wrapping film with the sawtooth cutter, which causes the end portions of the sawtooth cutter to be liable to come off.

Thus, the opposite end portions of the sawtooth cutter often come off or the sawtooth cutter often falls off from the carton during use.

When the entire length of a sawtooth cutter is bonded to a carton blank by ultrasonic welding like methods disclosed in JP-A Nos. 6-48428 and 6-144425 do, a laterally elongate horn is necessary. Such a laterally elongate horn lacks in durability and needs large output power for sealing the joint of a large area of surfaces. Although a disk-shaped horn like that employed in JP-A No. 6-144425 may be used, the disk-shaped horn needs an apparatus of a complicated construction. When bonding the entire length of a sawtooth cutter to a carton blank by heat-sealing, large power is necessary, it is difficult to apply heat and pressure uniformly to the elongate joint of surfaces, adhesive strength is liable to be distributed irregularly, heat-sealing takes much time, and the productivity is low.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing problems and it has been an object to provide a bonding method of a sawtooth cutter capable of satisfactorily bonding a nonmetallic sawtooth cutter to a carton blank without requiring any ultrasonic welding machine or any heat-sealing machine of a complicated construction and a high output capacity.

An object of the present invention is to provide a sawtooth cutter suitable for carrying out the aforesaid sawtooth cutter bonding method.

According to one aspect of the present invention, a sawtooth cutter has at least one sawtooth edge and is formed from a resin-impregnated paper sheet made by impregnating a paper sheet containing a small amount of size with a synthetic resin.

According to a second aspect of the present invention, a sawtooth cutter has at least one sawtooth edge and is formed from a vulcanized fiber sheet having a surface coated with a synthetic resin.

7he entire length of a sawtooth cutter is bonded to a carton blank with an adhesive, and then at least the opposite end portions of the sawtooth cutter are bonded by ultrasonic welding or heat-sealing to the carton blank. Therefore, the opposite end portions of the sawtooth cutter, which are liable to come off, are bonded securely to the carton blank and hence the sawtooth cutter will not come off during use. Since only the opposite end portions having a small area of the sawtooth cutter need to be bonded by ultrasonic welding or heat-sealing, the opposite end portions can securely be bonded to the carton blank by an ultrasonic welding machine or a heat-sealing machine of a simple construction. When necessary, optional portions of a small area of the sawtooth cutter, in addition to the opposite end portions, may be bonded to the carton blank by ultrasonic welding or heat-sealing. Preferably, the width and length of portions to be bonded by ultrasonic welding or heat-sealing to the carton blank are in the range of 5 to 20 mm to bond those portions to the-carton blank securely by low energy.

Since the synthetic resin contained in the resinimpregnated paper sheet forming the sawtooth cutter melts and exerts adhesion, the sawtooth cutter need not be subjected to a secondary process, such as a polyethylene coating process, and can be bonded to the carton blank by ultrasonic welding or heat-sealing. Since the resinimpregnated paper sheet absorbs moisture scarcely, the sawtooth cutter will not be deteriorated and nor come off from the carton blank due to moisture absorption during use. The sawtooth cutter need not necessarily be bonded by the foregoing method; the step of bonding the sawtooth cutter to the carton blank with an adhesive may be omitted and the entire length of the sawtooth cutter may be bonded to the carton blank by ultrasonic welding or heat-sealing.

BRIEF DESCRIPTION OF THE DRAWINGS Figs. l(a), l(b) and l(c) are schematic perspective views illustrating steps of a bonding method of a sawtooth cutter in a preferred embodiment according to the present invention; Figs. 2(a) and 2(b) are schematic side views of an apparatus for carrying out steps of the bonding method of a sawtooth cutter illustrated in Figs. 1(a) to l(c) for forming a sawtooth cutter by punching and bonding the sawtooth cutter to a carton blank in different phases of operation, respectively; Fig. 3 is a schematic ultrasonic welding machine employed in carrying out the bonding method of a sawtooth cutter illustrated in Figs. 1(a) to l(c); Fig. 4 is a schematic side view of the ultrasonic welding machine of Fig. 3; Fig. 5 is a schematic plan view of a combination of a carton blank and a sawtooth cutter formed by bonding a sawtooth cutter to a carton blank; Fig. 6 is a schematic plan view of a carton blank and a sawtooth cutter to be bonded to the carton blank; Fig. 7 is a schematic perspective view of a carton formed by assembling the parts shown in Fig. 6; Fig. 8 is a schematic plan view of another combination of a carton blank and a sawtooth cutter formed by bonding a sawtooth cutter to a carton blank at another position on the carton blank; and Fig. 9 is a schematic plan view of a sawtooth cutter in a modification.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described hereinafter.

Fig. 6 shows a carton blank I and a nonmetallic sawtooth cutter 2 to be bonded to the carton blank 1 by a bonding method of a sawtooth cutter in a preferred embodiment according to the present invention, which will be described later. The sawtooth cutter 2 is made by cutting the leading end of a long material along a zigzag line and has opposite sawtooth edges 2a and 2b. The sawtooth cutter 2 is attached to a hatched region 3 on the outer surface of the carton blank 1, and then the carton blank 1 is cartoned to make a carton 1A. The sawtooth edge 2a of the sawtooth cutter 2 projects from one edge of the carton 1A. An aluminum foil, a wrapping film or the like is held in the carton 1A. When using the aluminum foil, the wrapping film or the like, a necessary length of the aluminum foil, the wrapping film or the like is pulled out from the carton 1A and cut off with the sawtooth edge 2a of the sawtooth cutter 2. The sawtooth cutter 2 need not necessarily be attached to the carton blank 1 at the position shown in Fig. 6; for example, the same may be attached to a region 3A (a region along a tear score line 4) on the inner surface of a flap section la of the carton blank 1 as shown in Fig. 8.

The material from which the sawtooth cutter 2 is made is a nonmetallic material having a proper hardness enough to form a sawtooth cutting edge, and a melt-welding property that enables ultrasonic welding or heat-sealing.

A resin-impregnated paper sheet formed by impregnating a paper sheet containing long-fiber wood pulp as a principal component, and not containing any size or containing a small amount of size with a resin is a suitable material for forming the sawtooth cutter 2. A suitable resin content of the resin-impregnated paper sheet is in the range of 50 to 80 parts by weight to a paper sheet content of iOO parts by weight. The strength of the sawtooth cutter is insufficient when the resin content is less than 50 parts by weight, and a resin content exceeding 80 parts by weight makes resin-impregnation difficult. Size content of the paper sheet to be impregnated with the resin is determined so that the paper sheet can be impregnated with the resin in a resin content in the aforesaid range. The resin content can be controlled by adjusting sizing degree through the adjustment of size content.

The thickness of the resin impregnated paper sheet suitable for securing sharpness and strength required of the sawtooth cutter is in the range of about 0.2 to about 0.4 mm. Suitable resins to be impregnated into the paper sheet are hard, water-soluble acrylic resins including methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate.

The resin impregnated paper sheet is used as a material for forming the sawtooth cutter without subjecting the same to a secondary process, for instance, for forming a resin film on its surface.

A vulcanized fiber is another material suitable for forming the sawtooth cutter. Since a vulcanized fiber does not have any welding property, at least one surface thereof to be set in contact with the carton blank 1 must be coated with a resin to provide the vulcanized fiber with a welding property. Suitable coating resins for coating a vulcanized fiber are ethylene-acrylic-acid copolymers (ionomers), ethylene-propylene copolymers, vinyl-acetate-polyolefine copolymers and the like. The vulcanized fiber may be coated with such a resin by a gravure coater. A desirable amount of the coating resin per unit area of the vulcanized fiber is in the range of about 3 to about 6 g/m2 (dry base).

A bonding method of a sawtooth cutter in a preferred embodiment according to the present invention for bonding the sawtooth cutter formed from the aforesaid material will be described hereinafter. Referring first to Fig. l(a), an adhesive 6 is extruded through an adhesive applicator nozzle 5 to apply the adhesive 6 to a required portion of a carton blank 1 of a predetermined shape punched out from a material, in which the carton blank 1 is moved in the direction of the arrow relative to the adhesive applicator nozzle 5. The carton blank 1 may be held stationary and the adhesive applicator nozzle 5 may be moved in a direction opposite the direction of the arrow. The adhesive may be any suitable adhesive such as a hot-melt adhesive or an emulsion adhesive. Suitable hot-melt adhesives are, for example, EVAs (ethylene-vinyl-acetate copolymers), APPs PEs (polyethylenes), Siss (styreneisoprene copolymers), SBSs (styrene-butadlene copolymers) and polyamides.

The adhesive 6 is spread on the carton blank I in a region substantially corresponding to the entire length of the sawtooth cutter 2 as indicated in a hatched region in Fig. 5. The area coated with the adhesive 6 is smaller than the total area of the sawtooth cutter 2 in order tat the adhesive 6 may not ooze out from under the sawtooth cutter 2 when the sawtooth cutter 2 is pressed against the region coated with the adhesive 6. The opposite end port onus 2c cf a length in the range of, for example, about 2 to abut 5 mm of the sawtooth cutter 2 lie outside the region coated with the adhesive 6.

Then, as shown in Fig. l(b), the sawtocth cutter 2 of a predetermined shape is punched out from the leading end of a material 7 and the sawtooth cutter 2 is pressed against the region coated with the adhesive 6 of the carton blank 1 to bond the sawtcoth cutter to the carton blank 1.

The sawtooth cutter 2 is formed by punching and bonded to the carton blank 1 by an apparatus shown in Fig. 2.

Referring to Fig. 2, the apparatus comprises conveyor rollers 8 for conveying the carton blank 1, a table 9 for supporting the carton blank I at a portion including a region to whIch the sawtooth cutter 2 is bonded, a fixed die 10 provided at its free end wIth a sawtooth blade Iota, a mcvable die 11 provided at its free end with a sawtooth blade lla to be brought into engagement with the sawtooth blade lOa, a cylinder actuator for vertically movIng the movable die 11, and sheet feed rollers 13 for feeding a length of the material 7 ccr-esponding to the width o the sawtooth cutter 2 at a time. The apparatus functions as follows. Suppose that a length of the material 7 corresponding to the width of the sawtooth cutter 2 is projected forward from the sawtooth blade lOa of the fixed die 10 as shown in Fig. 2(a) and held stationary. In this state the material 7 is held on the fixed die 10 by suction. The material 7 may be held on the fixed die 10 by an appropriate mechanical clamping means instead of holding the same by suction.

In this state, a carton blank 1 having a region coated with the adhesive 6 is fed onto the table 9 and fixedly positioned at a predetermined position. Then, as shown in Fig. 2(b), the movable die 11 is lowered to cut off a sawtooth cutter 2 from the leading end portion of the material 7 in cooperation with the fixed die 10 and presses the sawtooth cutter 2 against the region coated with the adhesive 6 of the carton blank 1. Then, the movable die 11 is raised to its standby position, the carton blank 1 is delivered to the next process, and the sheet feed rollers 13 feeds the material 7 by a length corresponding to the width of the sawtooth cutter 2 for the next cycle of operation. The same cycle of operation is repeated sawtooth cutters 2 are bonded to carton blanks 1 successively. Although the substantially entire length of the sawtooth cutter 2 is thus bonded to the carton blank 1 with the adhesive 6, the opposite end portions 2c of a small area of the sawtooth cutter 2 lie outside the region coated with the adhesive 6 as shown In Fig. 5.

Then, as shown in Fig. l(c), the opposite end portions of the sawtooth cutter 2 bonded to the carton blank 1 with the adhesive 6 is bonded to the carton blank 1 by ultrasonic horn units 20 included in an ultrasonic welding machine shown in Figs. 3 and 4 by ultrasonic welding.

Referring to Figs. 3 and 4, the ultrasonic welding machine comprises conveyor rollers 15 for conveying the carton blank 1, a pair of anvils 16 disposed so that the opposite end portions of the sawtooth cutter 2 bonded to the carton blank 1 overlie the pair of anvils 16 when the carton blank 1 is stopped at a predetermined position, a main frame 17 disposed at a fixed position, support members 18 fixed to the main frame 17, horn holding members 19 vertically movably supported on the support members 18, the ultrasonic horn units 20 attached to the horn holding members 19, and pneumatic cylinder actuators 22 for vertically moving the horn holding members 19. Each ultrasonic horn unit 20 has, as principal components, a converter 20a, a booster 20b and a horn 20c.

The two ultrasonic horn units 20 bond the opposite end portions of the sawtooth cutter 2 bonded to the carton blank 1 fixedly held at the predetermined position to the carton blank 1, respectively. Each ultrasonic horn unit 20 is disposed so that the lower surface of the horn 20c, i.e., a working surface of the horn 20c, is able to cover the end portion 2c of the sawtooth cutter 2 and a narrow region contiguous with the periphery of the end portion 2c.

The size of the lower surface of each horn 20c is determined so that the end portion 2c of the sawtooth cutter 2 of a length in the range of about 5 to about 20 mm, preferably, a length of about 10 mm can be welded to the carton blank 1. The effect of ultrasonic welding is insufficient and the end portions 2c of the sawtooth cutter 2 is liable to cme off if the length of a welded portIon of the end portions 2c is less than 5 mm. The length of the end portions 2c greater than 20 mm is not preferable because the size of the ultrasonIc horn units 20 st be relatively large and the effect of ultrasonic welding does not increase significantly according to increase in the length of the end portions 2c to be welded to the carton blank 1 beyond 20 mm. Therefore, i is preferable that the length of the end portions 2e to be welded to the carton blank 1 by ultrasonic welding in in the aforesaid range.

Ultrasonic welding conditions for welding the end pcrtIor of, for example, 10 mm by 15 mm In area are, for example, 20 kz in oscIllatIon frequency, 3 kg/ca~ in pressure and C.\ Se.

The ultrasonic welding machine functions as follows.

Referring to Figs. 3 and 4, the carton blank 1 provided on its upper surface with the sawtooth cutter 2 is conveyed to and fixedly positioned at a predetermined position. Then, the pneumatic cylinder actuator 22 are actuated to press the ultrasonic horn units 20 against the opposite end portions 2c of the sawtooth cutter 2 for ultrasonic welding. After the predetermined welding time for ultrasonic welding has elapsed, the ultrasonic horn units 20 are raised, the carton blank 1 is delivered to the next process and the next carton blank 1 is fed to complete one cycle of operation, The cycle of operation is repeated to weld the opposite end portions 2c of the sawtooth cutter 2 to the carton blank 1. Thus, the end portions 2c of the sawtooth cutter 2 lying over regions not coated with the adhesive 6 are welded firmly to the carton blank 1. The sawtooth edge 2a of the sawtooth cutter 2 must not be bonded to the carton blank 1. A region lb underlying the sawtooth edge 2a is coated with a releasing OP varnish and hence the sawtooth edge 2a cannot be welded to the carton blank 1 by ultrasonic welding. If there is any possibility that the sawtooth edge 2a is welded to the carton blank 1, the anvils 16 may be located so that portions of the carton blank 1 corresponding to the sawtooth edge 2a are not on the anvils 16.

The carton blank 1 thus processed is delivered to the next process, the carton blank 1 is cartoned to make a carton 1A, and a roll of an aluminum foil or a wrapping film is put in the carton 1A for use. Since the opposite end portions 2c of the sawtooth cutter 2, which are liable to come off, are welded to the carton blank 1 by ultrasonic welding after bonding the entire length of the sawtooth cutter 2 to the carton blank 1 with the adhesive 6, the opposite end portions 2c of the sawtooth cutter 2 are bonded firmly to the carton blank 1. Consequently, the opposite end portions 2c will not come off or will not be loosened during use, and functions properly for an extended period of use. Since the resin impregnated into the opposite end portions 2c of the sawtooth cutter 2 is melted by heat generated by ultrasonic welding and the density of the opposite end portions 2c is increased by pressure applied to the opposite end portions 2c, the hardness of the opposite end portions 2c is increased and the cutting ability of the opposite end portions 2c is enhanced. The aluminum foil or the wrapping film can easily be cut because the opposite end portions 2c, on which a maximum force acts in the initial stage of operation for cutting the aluminum foil or the wrapping film, are very sharp.

The sharpness of the sawtooth cutter 2 was tested on a tensile tester. In the test, the carton blank provided with the sawtooth cutter 1 was set on the tensile tester at inclinations of 45 , 45' and 300 to a X, a Y and a Z axis, z film was pulled at a fixed pulling speed of 500 mm/min, and the maximum load at the breakage of the fiim (the maximum load at which the film starts breakIng) was measured. Whereas the film engaged with a portion of the sawtooth cutter bonded to the carton blank only with the adhesive broke at a load of 308 g, the film engaged with a portion of the sawtooth cutter welded by ultrasonic welding (10 mm x 15 mm in area, 20 kHz in oscillation frequency, 3 Xs/cm2 in pressure and 0.1 sec in oscillatIon time) broke at a load of 225 g. The test results proved the high sharpness of the portions of the sawtooth cutter bonded by ultrasonic weldIng. Although this embodiment bonds only the opposite end portions 2c of the sawtooth cutter 2 to the carton blank 1 by ultrasonic welding after bonding the sawtooth cutter 2 to the carton blank I with the adhesive 6, appropriate small regions of the sawtooth cutter 2 between the opposite end portions 2c mayoe bonded to the carton blank 1 by ultrasonic welding when necossary.

Although thls embodiment employs the straight sawtooth cutter 2, the present inventIon is applicable to a case ere an obtusely V- shaped sawtcot cutter 2A is bonded to the inner surface of a flap section la of a carton blank 1 as shown in Fig. 9. When the sawtooth cutter 2A of such a shape is employed, the opposite end portions 25 enclosed by alternate long and two short dashes lines of the sawtooth cutter 2A may be bonded to the carton blank 1 by ultrasonic welding after attaching the substantially entire length of the sawtooth cutter 2A to the carton blank 1 with an adhesive.

When the sawtooth cutter 2A is thus bonded to the carton blank 1, the opposite end portions 25 and the V-shaped middle portion 26, which are liable to come off, can securely be bonded to the carton blank 1 and are able to function properly for an extended period of use.

Although foregoing embodiment uses ultrasonic welding for bonding the opposite ends 2c of the sawtooth cutter 2, or the opposite ends 25 and the V-shaped middle portion 26 of the sawtooth cutter 2A to the carton blank 1, those portions may be bonded to the carton blank 1 by heat-sealing.

As is apparent from the foregoing description, at least the opposite end portions of the sawtooth cutter are bonded to the carton blank by ultrasonic welding or heat-sealing after bonding the substantially entire length of the sawtooth cutter to the carton blank with the adhesive. Therefore, the opposite end portions of the sawtooth cutter which are liable to come off can surely and firmly be bonded to the carton blank and the opposite end portions will not come off during use. Since the area of the opposite end portions to be bonded to the carton blank by ultrasonic welding or heat-sealing is small, the ultrasonic welding machine or the heat-sealing machine for bonding the opposite end portions to the carton blank may be of a relatively small output capacity and of a simple construction, and the opposite end portions can securely be bonded to the carton blank. Furthermore, since the opposite end portions of the sawtooth cutter are bonded to the carton blank by ultrasonic welding or heat-sealing, the resin density of the opposite end portions increases because the opposite end portions are heated and pressed.

Consequently, the cutting ability of the opposite end portions, on which a maximum force acts when cutting a wrapping film or the like, is enhanced, whereby the wrapping film or the like can easily be cut.

Since the sawtooth cutter is formed from the resinimpregnated paper sheet, the welding property of the resin contained in the sawtooth cutter is available; that is, ultrasonic welding and heat-sealing are effective even if the resin-impregnated paper sheet is not coated with a polyethylene by a secondary process. Accordingly, the sawtooth cutter capable of being bonded to the carton blank by ultrasonic welding or heat-sealing can be manufactured at relatively low manufacturing costs. Since the resinimpregnated paper sheet absorbs moisture scarcely, the sawtooth cutter will not be deteriorated and not come off due to moisture absorption during use.

Claims

1. A sawtooth cutter having at least one sawtooth edge and formed from a resin-impregnated paper sheet made by impregnating a paper sheet containing a small amount of size with a resin.

2. The sawtooth cutter according to claim 1, wherein the sawtooth cutter is formed from a resin-impregnated paper sheet having a paper content of 100 parts by weight and a resin content in the range of 50 to 80 parts by weight.

3. A sawtooth cutter having at least one sawtooth edge formed from a material produced by coating the surface of a vulcanized fiber with a resin.

4. A sawtooth cutter substantially as herein described with reference to the accompanying drawings