WO2009036745A1

WO2009036745A1 - Plastic film having a target tear line and tool for applying the same

Info

Publication number: WO2009036745A1
Application number: PCT/DE2008/001549
Authority: WO
Inventors: Ursula Weck
Original assignee: VICTOR Güthoff & Partner GmbH
Priority date: 2007-09-20
Filing date: 2008-09-17
Publication date: 2009-03-26
Also published as: DE112008003160A5

Abstract

The invention relates to a tearable plastic film (11), the strength of which is reduced along a target tear line (14), and to a tool for applying such a target tear line. Along at least one side of the target tear line, the film (11) is provided with two separating cuts (28), which extend up to the target tear line and with the same enclose an angle different from zero or 180º, wherein the respective lateral separating cut (28) on the end thereof facing the target tear line continues as a perforation of the same, forming an extension of the lateral separating cut (28) that runs in a tear direction (60). The tool used for applying the target tear line (14) comprises a cutter roll (42), on the lateral surface (48) of which a cutter system (45) having a cutter component is attached, which is used to produce a perforation corresponding to a target tear line.

Description

Plastic film with a target tear line and tool for attaching the same

The invention relates to a plastic film, in particular for packaging purposes, whose strength is reduced along a desired tear line, and a tool for attaching this target tear line. The latter may be formed by perforation or otherwise.

When using, for example, a plastic film as packaging material, which encloses the package contents and must be torn open in order to open the package, problems frequently arise because the crack resulting from opening the package does not run along a predetermined tear line defined by, for example, a perforation but deviates from this. As a result, the opened package can have an ugly appearance and in many cases can not be neatly closed. The storage of the torn and possibly partially emptied pack may be associated with difficulties, for example because it has not retained its original shape, is unsightly and possibly also poorly handled, for example such that the remaining contents of the pack after opening it no more or can only be held together by using special measures.

A deviation from the desired tear line can also take place when tearing a blank from a film web, which consists for example of a plurality of preferably identical blanks, which are delimited by predetermined tear lines against each other, the blanks are demolished individually as needed. Such film webs generally come in roll form on the market. From the individual blanks, bags or sacks can be formed, for example, for receiving frozen goods, waste or other goods.

The deviation from the desired tear line in known from a sequence of blanks existing film webs or known packages may be due, inter alia, that the plastic films due to production direction dependent zones have lower and greater strength, by a corresponding orientation of the Polymer chains are caused. This As a result, if the target tear line does not extend along a zone of low strength, the crack resulting from the opening, for example, tends to continue away from, for example, the perforation-defined target tear line in a direction in which the tear strength is noticeably less than in other 5 directions, for example the direction along which the desired tear line runs. Another, possibly additional cause may be that the direction of the tensile force differs markedly from the direction in which the target tear line extends, and this is especially true in those cases in which the tear line obliquely or perpendicular to the longitudinal axis or one Symmetry axis of Pa-0 ckung or film web runs. For the film webs consisting of a sequence of blanks, the desired tear lines will generally extend perpendicular to the course of the zones of lesser strength.

The desired tear line may have a straight course. But it can also run at least curved on parts of its extension.

The perforation defining the desired tear line can consist of a plurality of cuts weakening the film material, possibly completely severing, which are arranged one behind the other in the direction of the longitudinal extent of the perforation, for the purpose of tearing along the desired tear line the gap remaining between two successive incisions Foil material, which is generally referred to as a web, is torn through. In this tearing operation, there is the aforementioned possibility of deviating the cracking from the target tearing line, so that the object of the invention is to design a foil of the kind described in the introduction in such a way that e.g. the tearing off of a blank and the like from a film web or the tearing of at least one part of the envelope forming film is improved, in particular such that when tearing or tearing a deviation from the desired tear line is at least considerably more difficult, without requiring a greater effort would be required. With regard to the tool for attaching the o target tear line, the task is to design the tool so that a

Perforation is produced, in which a deviation of the actual tearing operation is prevented by the target tear line, at least in the majority of cases.

These objects are achieved by the teaching of claim 1 or the An-5 award 9.

The second, lateral separating cuts are expediently arranged in each case behind a web which is located between two successive perforations or first separating cuts, wherein these lateral separating cuts are in each case in continue the separating cut of the target tear line located behind this web.

The deviation of the crack formation from the desired tear line is easily avoided by the invention, since even if the web between two successive dividing webs, which define the desired tear line, is relatively long, with a deviation in the web forming tear of the desired tear line of the crack can only arise up to the arranged behind the web and approximately transverse lateral separation section. The cracking is limited by this separating cut, because when it stops the tearing stops and by means of each subsequent, associated with the lateral separation cut perforation or the like of the target tear line is inevitably led to the latter and thus the respective following web.

The attachment of the lateral separation cuts is not a great deal of effort, since they can be produced in the manufacture of the package in one operation with the other, the perforation of the target tear lines forming separating cuts.

From the above-described contexts, the dimensioning of the length of the transverse separating cut and / or the web results for the person skilled in the art. The former should be sufficiently long to "intercept" any change in direction of the forming tear occurring as the web is severed, thus bringing about a controlled tearing action After reaching the respective lateral cut, as already mentioned, the tearing process returns to the desired tear line due to the fact that the lateral severing cut continues into the respectively associated separating cut of the perforation of the desired tear line, so that the direction to the following bar is predetermined, because the set tear line determines the direction of the least resistance the material properties, the tear strength of the respective film, the thickness and, for example, on the nature of the desired tear line play a role.

Conveniently, the arrangement will be made so that the second separating cut in the film are arranged on the side of the target tear line on which the force acting on the film tearing acts.

The length of the lateral separating cuts can be a few millimeters, for example 2 to 3 mm. The distance between two successive lateral separating cuts, which may also be influenced by the configuration of the perforation of the desired tear line, can be, for example, 4 to 5 mm, without excluding, as in the case of the length of these separating cuts, other length dimensions should. The length of the perforations in the desired tear line can be a few 1/10 mm, possibly even more than more than 1 mm, without also here other length dimensions should be excluded.

To be particularly advantageous, an embodiment has been found in which the lateral end sections with the lying in the tear direction behind the respective separating section portion of the target tear line an angle which is smaller than 90 °, for example, for example 45 °.

The solution of the design of the tool related task consists in an embodiment of the cutting tool according to claim 9.

The second, lateral knife sections are expediently arranged such that the lateral separating cuts in the film brought about by them are in the tear direction in each case in front of the first section of the main cutting knife, with which they can be connected by cutting technology and form a cutting unit.

Arrangement and length of the lateral blade portion or its blade and thus the (s) caused by this separating cut should be sufficiently long and run at such an angle to the target tear line producing knife component that the forming in the film crack at each In general, the lateral blade sections can be shorter, the shorter the distances between the two successive perforations of the target tear line and thus also the tear-through But even if the distance between two successive sections of the knife component for the production of the target tear line defining perforation is relatively large and thus the distance corresponding web in the perforated film is relatively long, different deviations can be "intercepted" by appropriate dimensioning of the lateral blade sections and / or appropriate choice of the course of the lateral blade sections.

The second blade sections can only on one side of the blade component for

Making the desired tear line be provided. But there are also applications conceivable in which the presence of second blade sections are provided on both sides of the target tear line defining blade component. Depending on the example, it may depend on the course of the nominal tear line, which is by no means im- mer extends along a straight line, be expedient, provide in the one part of the blade component for producing the target tear line, the second blade sections on one side and in another portion on the other side.

In the drawings embodiment of the invention are shown, show

FIG. 1 perspective view of a pack,

FIG. 2 shows a view in the direction of the arrow II of FIG. 1, wherein the blank of the foil from which the sheath is produced is indicated,

FIG. 3 shows a top view of a film web and a perforation tool assigned to it in a highly schematic representation,

FIG. 4 shows the associated side view,

5 shows a view in the direction of the arrow V-V of Figure 4,

FIG. 6 shows a section VI from FIG. 3 on a larger scale,

FIG. 7 shows a section VII from FIG. 6 on a larger scale,

8 shows an illustration corresponding to FIG. 5 of a perforation according to the prior art, FIG.

9 is a plan view of a section of the lateral surface of the knife roller of the tool with blade sections, for example according to the detail IX of FIG. 3, FIG.

FIG. 10 shows a section along the line X-X of FIG. 9,

11 shows a section along the line XI-XI of Figure 9th

According to Figures 1 and 2, the package 10 at least partially enveloping plastic film is provided with a tear-tab 12 which is bounded by two lateral target tear lines 14, the sections 14a converge towards the free end 18 of the tab 12 so in that they extend at an angle of approximately 45 ° to the longitudinal axis 16 of the package. The two sections 14a of the target Tear line can be connected to each other at the free end 18 of the tab 12 by a relatively short separation cut 20, the length of which makes it possible at least for compliant contents, such as napkins or handkerchiefs, to engage with the finger, the free end 18 of the tab 12 to the package by tearing the tab 12 along the desired tear lines 14 to open. At the free end 18 of the tab facing away from the end of the same, the two set tear line 14 each continue in a section 14b. Both sections 14b extend parallel to the longitudinal axis 16. The arrangement may be made such that the two sections 14a extend on top of the finished package, whereas where the two mutually parallel sections 14b, which correspond to the height of the package, along a lateral Extend limitation of the finished package.

At its free end 18 of the tab 12 end portion that remains connected to the envelope forming film blank, so that the package after tearing the tab may be closed again For this purpose, a small self-adhesive portion 32 may be provided from suitable material, such as paper, which is adhered to the tab with a portion of its adhesive surface and adhered to the remainder of the portion adjacent the tab of the envelope. In this case, an edge region of this section can be without adhesive, such that it can be detected in order to reopen the package by tearing along the desired tear lines for the first time or after resealing. This section 32 may be, for example, a label.

Approximately parallel to the axis 16 of the package is also the direction along which the plastic film, which comes from the film forming the film section, during their production was moving, so for example, was withdrawn from the extrusion head. This direction of the film corresponds to the arrow 24. It is for the wrapping forming the wrapping of the package in so far of importance, as the forces acting on the latter during the production of the plastic film can cause a certain orientation of the polymer chains with the result that the tear strength of the film in the running direction or parallel thereto lowest and consequently in directions which are transverse or otherwise deviating from 0 ° or 180 ° Angles are greater.

Thus, it can be assumed that in the two sections 14a of the desired tear line, the tear resistance can be greater than in the two sections 14b extending approximately parallel to the running direction, whereby this greater tear resistance can lead to the wrapping of the pack Although it ruptures, but not along the target tear line. Normally, the deviating tear lines will then form within the flap 12 approximately parallel to the longitudinal axis 16, but opposite to the direction of the arrow 24, as indicated at 34. This has the consequence that the resulting opening is narrower than intended, so that the removal of l o of the items received by the pack becomes more difficult and possibly leads to a completely uncontrolled further tearing of the package.

In order to at least reduce the possibility that the actual tear lines deviate from the respective desired tear line, in particular in the sections 14a when the tab 12 is pulled out, the latter are configured in a special way. At the

15 formed by a series of first separating cuts 26 respective target tear line 14 additional second separating cuts 28 are provided along the portion 14a on the tab 12, which at a deviating from 0 ° or 180 ° angle to the target tear line extending at its the target The tear-line facing end in the separation section 26 located there in each case at the free end 18 of the flap 12 zugewand- 0 th end pass, so that along the desired tear line sections 14 a, a sequence of separating cut units is present, each composed of the two interconnected separating cuts 26 and 28. Between two each successive along the desired tear line extending separating cuts 26 remains a web 30 is present, which must be severed during the tearing 5 must. In the embodiment shown in the drawing thus corresponds to the number of second, lateral separating cuts the number of webs 30 along the sections 14a, wherein the distances between two successive lateral separating cuts resulting from the length of the target tear line defining first separating cuts. By approximately transverse to the direction 24 each extending second separating cuts 28, which are in the embodiment shown in the drawing on that side of the respective target tear line 14, which acts on the tearing force, to prevent that possibly initially along the If the tear 14 deviates from the nominal tear line and continues, for example, continues into the tab 12 and continues there in a crack 34 which is approximately parallel to the direction indicated by the arrow 24, in which in the production of the film the polymer chains have experienced some orientation.

Reference is made to FIG. 8, which shows the crack 34 deviating from the desired tear line 14, which runs essentially parallel to the direction of movement 24 of the film during its production. In Figure 7 of the drawing is shown as due to the

Presence of the second, lateral separating cuts 28 in the web 30 of the

Target tear line 14 deviating crack 58 prevented by the in the desired tear direction 60 respectively following second separating cut 28 on the further development and on the directly subsequent first separating cut 26 again to the target tear line, the

Soll-tear direction corresponds, is returned.

The cutting tool 40 shown in Figures 3 to 5 has a rotatably mounted knife roller 42 and a plate 44, which serves as an abutment. The provided with the perforations film web 46 is preferably continuously see between the lateral surface of the rotating knife roller 42 and the plate 44 in the direction of arrow 47 and thereby provided on the plate slidably with the perforations. For this purpose, the knife roller 42 is provided with a knife system 45, the knife sections are mounted according to the configuration of the perforations in the film on the lateral surface of the knife roller 42.

In particular, FIG. 3 shows that the film web 46 is to be subdivided into individual blanks 11, which are used to produce a wrapping for a package, which may for example contain paper napkins or the like, usually in a stacked arrangement. In general, the cutting tool 40 is part of a subdivision of the film web 46 in their individual blanks 11 and the manufacturer Position of the individual packages causing packaging machine or such upstream.

To produce the prescribed perforations, the knife roller 42 is provided on its lateral surface 48 with a knife system 45, which has a knife component for producing the tab 12 delimiting the first separating cuts 26, which also define the desired tear line 14. In the regions 52a and 52b (FIG. 9) of the knife system, which correspond to the perforation regions 22a, 22b, this knife component consists essentially of knife sections 54 arranged in alignment with each other along the longitudinal course of the regions 52a, 52b, which are arranged one behind the other at small spacings 50 produce first separating cuts 26 of the perforation. In the areas 52a, each blade section 54 has a second blade section 56 assigned to it in such a way that the first section 54 and the second blade section 56 each form a unit in terms of cutting technology and enclose an angle of slightly more than 100 degrees.

The lateral, second blade portions 56 are arranged on the side at which the tab 20 is located. Thus, the second, lateral blade portions 56 of both portions 52a of the blade system face each other. In addition, the second, lateral blade sections of each region 52a extend parallel to one another. However, both are not absolutely necessary, and in view of the function of the to be attached by the lateral blade sections separating cuts also not always possible, for example, when the blade component for producing the target tear line has a non-linear, curved course.

In the two areas 52b, no second lateral blade sections 56 are provided, since there are the first blade sections and thus those produced by them

Perforations approximately parallel to the direction 24 least strength of the film run.

In the drawing, the blades are shown only schematically. In practice, the knife system may include brackets in which blades are interchangeably attached are. The blades will, in the majority of cases, be formed so that the parting cuts are made without removing sheet material. The illustrations in FIGS. 6 to 8 are merely stated differently for the sake of clarity.

It is also not necessary that the cuts cut the film material always and everywhere completely, but it is important to weaken the film material so that the desired effect is achieved.

The web 30 remaining between each two successive individual first separating cuts 26 may have a length of e.g. 1 mm, wherein the separating cuts 26 can have a length of 4.5 mm and the respective second cutting cut can have a length of 2.8 mm. However, the length of these cuts and also the webs depends on the particular circumstances, in particular the nature of the film, so the material used, and the strength thereof.

In the embodiment shown in the drawing, the individual sections of the desired tear line extending substantially linear and the second separating sections parallel to each other. However, this is not a requirement for the applicability of the invention. Rather, the desired tear line or sections thereof can also run in a curved manner depending on the respective requirements, in which case also the second separating cuts in each case depending on the particular circumstances, that is, for example, on the orientation of the polymer chains, under correspondingly different angles to the desired May be broken line.

First and second separating cuts 26 and 28 can be produced by simply cutting through the film, without thereby removing film material. The latter is not mandatory for the application of the invention.

The film may have a thickness of e.g. 25 microns, but other thicknesses are possible. It may consist of polypropylene, polyethylene or other suitable material, in particular thermoplastic.

When the invention is applied to a film web consisting of a sequence of blanks, the lateral separating cuts are preferably made on the blank. he be attached by a common target tear line blanks, which is separated respectively. The achievable by the application of the invention advantageous effect is particularly clear in such film webs also because they can be two or more layers to form the bag or bag from the respective blank.

Claims

Plastic film with a target tear line and tool for attaching the same

1. A tearable plastic film (11), in particular for packaging purposes, whose strength is reduced along a desired tear line (14), characterized in that the film (11) extends along at least one side of at least one partial section (14a ) of the desired tear line (14) is provided with separating cuts (28) which extend to the desired tear line and enclose therewith an angle deviating from zero or 180 degrees, and the respective lateral separating cut (28) at its the target tear line facing

End continues in a perforation (26) of the same, which forms an extension in the tear direction (60) extension of the lateral separating cut (28).

2. Plastic film according to claim 1, characterized in that the lateral separating cut (28) forms an angle with the section of the nominal tear line (14) lying in the tear direction (60) behind this separating cut is less than 90 degrees.

3. plastic film according to claim 1, dadu rch ge ken nzeich- net, that between two successive perforations (26) located web (30) of film material which is severed during the tearing process, by the respective lateral separating cut (28) is limited.

4. Plastic film according to claim 1, since you do not net, that the lateral separating cuts (28) along the side of the target tear line (14) are arranged, which acts on the breaking force.

5. Plastic film according to claim 1, characterized in that the perforation (26) of the desired tear line (14) are formed as separating cuts.

6. Plastic film according to claim 1, characterized in that the target tear line (14) does not run parallel to the main direction of the force causing the tearing.

7. Plastic film according to at least one of claims 1 to 6, characterized in that the film is used to produce a tearable pack (10).

8. The plastic film according to claim 1, wherein the film is used to produce a plastic film web which has a sequence of blanks serving as packages, which are produced by means of a target Clues are limited.

9. tool (40) for attaching a perforation to a plastic film, wherein the tool has a rotatably mounted knife roller 42, the lateral surface 48 with a knife system (45) with a knife component for producing a desired tear line (14) corresponding perforation The knife component (52a, 52b) has first knife sections (54) arranged successively along its longitudinal path, between which there are spacings (50), characterized in that along at least one side of at least one section (52a) of the knife component second blade portions (56) are provided, each extending to a first blade portion (54) and include with this a deviating from zero or 180 ° angle and the respective second blade section continues at its end facing the first blade section in the latter.

10. Tool according to claim 9, characterized in that a first blade portion (54) has an extension of a second blade portion

(56).

11. Tool according to claim 9, characterized in that between two successive first blade sections (54) befindli- distance (50), which the web (30) of the perforation along the setpoint

Tear line corresponds, is also limited by the respective second blade portion (56).

12. Tool according to claim 9, characterized in that the second blade portion (56) with the respectively associated first blade portion (54) forms an angle which is at least 80 °.