EP0757000A1 - Blank for forming packages - Google Patents

Abstract

The foil blanks have indented bending lines (BL) formed by grooved indents (5) the bottom of which has alternating zones (8,9) of greater depth (T2) and reduced depth (T1). The zones (9) of reduced depth are defined by circular arcs (10) whose radius R is at least 1.1 mm and whose centre of curvature (M) lies on the other side of a line (l) connecting together the zones of greater depth. The greater depth is at least 40% and at most 90% of the foil thickness D. The reduced depth is at least 25% of the foil thickness. The lengths of the zones of greater depth can be between 0.5 and 5 mm. The ratio of the lengths of the zones of greater depth to that of reduced depth is between 0.5 and 1.

Description

The invention relates to a film blank for packaging, in particular for folding boxes, with embossed bending lines in the form of groove-shaped depressions which start from a film surface and are closed at the bottom of the depressions with respect to the other film surface, the bottom of the depressions alternating in the longitudinal direction from zones of greater depth T ₂ and zones of shallower depth T ₁ .

Such film cuts consist in particular of transparent films made of thermoplastics from the group consisting of polyethylene terephthalate (PET), polypropylene (PP) and polyvinyl chloride (PVC), PVC having recently lost importance due to its chlorine content from environmental considerations. However, PET and PP cause some additional problems in production that have not yet been completely mastered.

The packaging is preferably, but not exclusively, a lid, but above all a folding box. Such packaging allows prospective buyers an unobstructed view of the content, which can be made very decorative together with the packaging.

Folding boxes, which are usually delivered lying flat and in batches, are subject to high demands in the packaging company, which is equipped with fully automatic packaging machines. For example, the individual flat-lying folding boxes must be individually picked up from a stack, placed in the machine and erected in the machine, so that a cavity is formed with a prismatic cross section, for example. The product in question is now pushed into the erected folding box, whereupon it is closed at both ends by flaps or tabs. The basic prerequisite for this is that the film material on the bending lines is easily deformable without the film fields lying between the bending lines being deformed, and that the bending lines do not produce any noticeable restoring forces. In addition, no sharp edges, serrations, burrs or the like are to be formed by the bending or folding process. During the manufacturing process of the film cuts, it should also be noted that the deformation of the films in the areas of the bending lines does not lead to a curling of the film fields located between the bending lines, a process which is at least promoted by a certain material displacement.

The foils under discussion here usually have a thickness between 0.150 mm and 1.0 mm, the mass of the foil blanks having a thickness between 0.200 mm and 0.400 mm. Usually the film thickness increases with the packaging size, but this does not apply to all possible cases.

The switch from PVC to PET and PP has caused considerable difficulties in the packaging and bottling plants.

US Pat. No. 4,064,206 discloses a thermal process for the production of bending lines, in which bending edge rulers, which have the function of electrodes, are pressed against the film, against an insulating material plate and against a counter electrode. High frequency is applied to the bending edge rulers and the counter tool, causing the film material in the middle and under the bending edge rulers to be partially melted and laterally displaced under the embossing pressure, which creates so-called edge beads that accompany the bending edges on both sides. Such devices generate high investment and operating costs due to the use of high frequency, and the procedure also proves to be difficult, since the temperature of the bending edge rulers is difficult to control despite the presence of a regulated cooling plate and the device occasionally despite the presence of an insulating plate leads to flashovers. The method and device in question were also primarily developed for the processing of PVC films.

JP-GM 4-9345 discloses a film cut according to the preamble of claim 1 and a stamping tool provided therefor, a so-called bending edge ruler, in which the zones of greater and lesser depth are connected to one another by sharp edges by surfaces which are exactly perpendicular to the Longitudinal direction of the bending line are aligned. During the bending process, this spatial shape leads to surface irregularities both on the inside and on the outside of the bending lines, which can damage the contents of the packaging, but can also damage sensitive materials if they come into contact with the outside of the packaging. Fine silk fabrics such as those for are particularly sensitive Ties are used. When touching such packaging, threads can be drawn from the silk fabric. It should be noted that part of such packaging can be used as a gift box for ties. In addition, a certain risk of breakage was observed with such bending lines. In this regard, it should be noted that the film fields adjacent to the bending line not only have to be bent by 90 ° to one another, but in some cases also by 180 ° for the purpose of shipping, so that film fields lie flat on one another. When erecting such flat-lying folding boxes, this bend of 180 ° must then be returned to a bend of 90 °, ie the film material is deformed in some directions by bending back and forth in both directions. Stress peaks that occur at the sharp-edged interfaces of the surfaces and lines can be assumed to be the cause of the rough course of the bending lines and the risk of breakage.

EP 0 563 781 A1 also deals with the disadvantages of the object according to JP-GM 4-9345 and proposes to remedy this that the surfaces of the zones of lesser depth have a radius between 0.05 mm and 1 at the ends. 0 mm. The document in question discloses two versions, namely a first version, in which the zone of greater depth penetrates the entire film thickness, that is to say the film is punched through, and a second version, in which the film also retains a residual cross section in the region of the zones of greater depth. In both cases, however, the transition in the area of the film surface on the other side is sharp-edged, and the side surfaces of the zones of less depth are - apart from the radius mentioned - perpendicular and sharp-edged to the longitudinal direction of the bending line. In addition to the fact that the effect of a rounding in the range of 0.05 mm can no longer be determined, this known solution still gives rise to considerable roughness in the area of both film surfaces, and the risk of breakage has not been significantly reduced. For the rest, it is stated in the cited publication that the conditions deteriorate again beyond a radius of curvature of 1.0 mm, for example due to the occurrence of very high deformation forces.

The invention is therefore based on the object of specifying a film cut of the type mentioned at the outset which is distinguished by ease of manufacture, low tolerances with regard to the bending behavior and high insensitivity to kink breaks in the bending lines. In particular, the use of high frequency should be avoided, and the bending lines should have as smooth a course as possible on both sides of the foils, so that no threading takes place, and furthermore the foil fields lying between the bending lines should not suffer any disturbing deformation.

The object is achieved with the film cutting specified at the outset according to the invention in that the zones of shallower depth T ₁ are delimited by arcs whose radius R is at least 1.1 mm and whose center of curvature lies beyond a line which defines the zones of greater depth T ₂ connects with each other.

The circular arc radius is therefore greater than the maximum possible film thickness, and the inventive position of the center of curvature M beyond the line L ensures that the circular arcs do not run at right angles to the longitudinal direction of the bending lines at their ends, but at an acute angle that also can have the value 0, which will be explained in more detail below.

The spatial shape or geometry of the bending lines according to the invention ensures easy manufacture, ie the stamping process stabilizes itself to a certain extent with respect to a progressive increase in the stamping forces, so that only slight tolerances can be observed with regard to the bending behavior. The invention Bending lines are highly insensitive to kink fractures, ie the bends lying on both sides of the *) can also be bent back and forth several times by more than 90 ° without breaking. The special strength against cutting the bending lines can be determined by trying to tear the film cut apart along a bending line. The use of high frequency can be completely dispensed with. The bending lines have an extremely smooth course on both sides of the foils, so that threading does not occur even when they come into contact with sensitive fabrics, such as fine silk fabrics. The film fields lying between the bending lines are also not subject to any disturbing deformation, such as bulging or denting. Nevertheless, the film cuts are easy to bend without undue restoring forces occurring which would be extremely disruptive for processing on automatic packaging machines. In particular, the configuration of the bending lines according to the invention also means that the previously problematic processing of PET and PP is considerably facilitated and improved.
*) Foil fields

The bending behavior can of course be influenced by the depths T ₁ and T ₂ and their relationship to one another. It is particularly expedient if the greater depth T _{2 is} at least 40% and at most 90% of the film thickness D. It is also advantageous if the smaller depth T _{1 is} at least 25% of the film thickness D. It is of course important to ensure that a difference in thickness remains, which is guaranteed by specifying the limit values mentioned.

The lengths A or A 'and B or B' of the zones of smaller and greater depth naturally also have an influence on the bending behavior of the bending lines. The absolute lengths A and A 'of the zones of greater depth T ₂ and the absolute lengths B and B' of the zones of less depth T ₁ can both be chosen between 0.5 mm and 5 mm, and the ratio of the lengths of the zones of greater depth to the Lengths of the zones of less depth can be between 0.5 and 4. At values below 1, the lengths of the zones of greater depth are smaller than the lengths of the zones of less depth. Conversely, for values over 1, the lengths of the zones of greater depth are greater than the lengths of the zones of less depth.

These numerical relations already show that the film cutting according to the invention is relatively insensitive to changes in size. However, very usable conditions have already arisen if the aspect ratio A: B is in the range of 1, that is to say that both zones are at least approximately the same length.

In the course of an advantageous further embodiment of the film blank according to the invention, it is particularly advantageous if the transition points between the zones of greater depth T ₂ and the zones of less depth T ₁ are rounded off concavely. It can be assumed that any stress peaks that occur during the bending process are further reduced, so that the conditions improve further.

Further advantageous embodiments of the film blank according to the invention result from the remaining subclaims.

Exemplary embodiments of the subject matter of the invention and the embossing tools required for this are explained in more detail below with reference to FIGS. 1 to 16.

Figur 1

einen flach liegenden Folienzuschnitt,

Figur 2

einen Längsschnitt durch ein erstes Ausführungsbeispiel einer Biegelinie,

Figur 3

eine erste Variante des Gegenstandes nach Figur 2,

Figur 4

eine zweite Variante des Gegenstandes nach Figur 2,

Figur 5

eine Seitenansicht eines Prägewerkzeugs für die Herstellung der Biegekante nach Figur 2,

Figur 6

einen Ausschnitt aus Figur 5 in vergrößertem Maßstab,

Figur 7

eine perspektivische Darstellung eines Ausschnitts aus Figur 5 in vergrößertem Maßstab,

Figur 8

einen Längsschnitt durch eine weitere Variante einer Biegelinie in einer Darstellung analog Figur 2,

Figur 9

eine erste Variante der Biegelinie nach Figur 8,

Figur 10

eine zweite Variante der Biegelinie nach Figur 8,

Figur 11

eine Seitenansicht eines Prägewerkzeugs für die Herstellung der Biegelinie nach Figur 8,

Figur 12

einen Ausschnitt aus Figur 11 in vergrößertem Maßstab,

Figur 13

eine perspektivische Darstellung eines Ausschnitts aus Figur 11,

Figur 14

einen Ausschnitt aus einem um 90 ° gefalteten Folienzuschnitt mit einer Biegelinie nach Figur 2,

Figur 15

einen Querschnitt durch einen Folienzuschnitt im Bereich einer Biegelinie, und

Figur 16

einen Ausschnitt aus einem um 90 ° gefalteten Folienzuschnitt mit einer Biegelinie gemäß Figur 8.

Show it:

Figure 1

a flat foil cut,

Figure 2

2 shows a longitudinal section through a first exemplary embodiment of a bending line,

Figure 3

2 a first variant of the object according to FIG. 2,

Figure 4

a second variant of the object according to Figure 2,

Figure 5

3 shows a side view of an embossing tool for producing the bending edge according to FIG. 2,

Figure 6

5 shows a detail from FIG. 5 on an enlarged scale,

Figure 7

3 shows a perspective illustration of a detail from FIG. 5 on an enlarged scale,

Figure 8

3 shows a longitudinal section through a further variant of a bending line in a representation analogous to FIG. 2,

Figure 9

8 a first variant of the bending line according to FIG. 8,

Figure 10

8 a second variant of the bending line according to FIG. 8,

Figure 11

3 shows a side view of an embossing tool for producing the bending line according to FIG. 8,

Figure 12

11 shows a detail from FIG. 11 on an enlarged scale,

Figure 13

3 shows a perspective illustration of a detail from FIG. 11,

Figure 14

3 shows a section of a film blank folded by 90 ° with a bending line according to FIG. 2,

Figure 15

a cross section through a film blank in the region of a bending line, and

Figure 16

a section of a film blank folded by 90 ° with a bending line according to FIG. 8.

FIG. 1 shows a film blank 1 which has been punched out of a film along a punching line 2 surrounding it. This film blank 1 has a whole number of bending lines BL in a cross-shaped arrangement. Such film blanks with differently shaped bending lines are state of the art, so that there is no need to go into them further.

The bending lines are designed as groove-shaped depressions 5 which, according to FIG. 2, start from a film surface 3 and are closed on the opposite film surface 4. As can be seen from FIG. 15, the side walls 6 and 7 are at an angle β to one another which can be 60 °, but this dimension is not critical.

According to FIG. 2, the bottom of the depression 5 consists alternately of zones 9 of lower depth T ₁ and of zones 8 of greater depth T ₂ , the lengths of these zones 8 and 9 being designated A and B, with A = in the exemplary embodiment according to FIG B is. The zones 9 of lower depth T ₁ are delimited by arcs 10, while the zones 8 of greater depth T ₂ are delimited by straight lines 11. The lines 11 all lie on a common line L, the imaginary sections of which also run through the zones 9.

As can be seen from FIGS. 14 and 15, the zones 9 - to be more precise - are each delimited by two circular arcs 10, which represent an acute-angled section of a cylindrical surface on both sides, as can be seen from Figure 15. When bending into a position according to FIG. 14, this section of a cylindrical surface is naturally deformed, but this is irrelevant for further considerations.

As can further be seen from FIG. 2, on the left, the center of curvature M lies beyond the line L, which connects the zones 8 of greater depth T _{2 to} one another. The expression “beyond” refers to a starting point in the film surface 3. In this case, the center of curvature M is even beyond the film surface 4, likewise seen from the film surface 3. It is thereby achieved that the ends of the circular arcs 10 extend at an acute angle α to the line L, this angle α being 45 ° in the exemplary embodiment according to FIG. Depending on the ratio of T ₁ to T ₂ and the ratio of A: B, this angle α can also assume other values, such as 60 °, or it can tend towards 0, which is discussed in more detail in connection with FIGS. 8 to 10 becomes.

3, the ratio of A: B is less than 1, and in the embodiment of FIG. 4, the ratio A: B is greater than 1.

FIGS. 5, 6 and 7 now show cutouts from an embossing tool 12 for producing bending lines according to FIG. 2. In its initial state, this embossing tool has a cutting edge 13 which is interrupted at regular intervals by cutouts 14, the surface of which is a gusset-shaped cutout from a cylindrical surface represents, as can be seen in particular from Figure 7. As can be seen from FIG. 6, the center of curvature M ′ is also beyond a cutting edge 15, which is used to generate the straight lines 11. Naturally, the cutting edge 13 is complementary to the bending line shown in FIG. 2, ie the ends of the cutouts 14 merge into the cutting edge 15 at an acute angle, but under Formation of peaks at the points marked with arrows P in FIG. 7.

In the exemplary embodiment according to FIGS. 8, 9 and 10, the transition points P 'between the zones 8 of greater depth T ₂ and the zones 9 of less depth T _{1 are} rounded off concavely, so that the formation of peaks is avoided at this point. Due to the circular concave transition at the transition points P ', the lengths A to A' and B to B 'change slightly depending on the radius of curvature r at these points. This radius of curvature can be between 0.1 mm and 1.0 mm. The appearance of a bending edge bent by 90 ° is shown in FIG. 16, ie the ends of the zones 9 of smaller depth T _{1 also} merge into the straight lines 11 without edges. An embossing tool 16 for the production of bending edges according to FIGS. 8 and 16 is shown in FIGS. 11, 12 and 13. This embossing tool 16 also has a cutting edge 17 with cutouts 18 through which a cutting edge 19 is interrupted. However, it is made clearly visible that roundings are provided at the transition points P ', by means of which the formation of sharp corners is avoided. It can be assumed that locally narrow flow processes during the embossing process are facilitated, as is also the avoidance of stress peaks or internal stresses in the film material. In any case, tests have shown that this not only makes the embossing process easier, but also that the film cuts have better bending behavior. The experiments have also shown that such a design of the embossing tool further reduces the risk of breakage of the film cut when bending back and forth several times.

The following table contains the most important dimensions of film cuts that have been tried and tested with success with corresponding bending lines. Bending line data Film thickness (µm) 200 250 350 600 R (mm) 1.1 1.2 1.3 3.0 T ₁ (µm) 50 80 165 380 T ₂ (µm) 175 220 315 540 DT ₂ = G (µm) 25th 30th 35 60 DT ₁ (µm) 150 170 185 220 A (mm) 1.1 1.4 1.2 2.4 B (mm) 1.0 1.2 1.2 1.8 A: B 1.1 1.17 1.0 1.33

Claims (11)

Foil cutting for packaging, in particular for folding boxes, with embossed bending lines (BL), in the form of groove-shaped depressions (5) which start from a foil surface (3) and are closed at the bottom of the depressions (5) with respect to the other foil surface (4), the base of the depressions (5) alternating in the longitudinal direction being composed of zones (8) of greater depth T ₂ and zones (9) of smaller depth T ₁ , characterized in that the zones (9) of reduced depth T _{1 are composed} of arcs (10) are limited, whose radius R is at least 1.1 mm and whose center of curvature (M) lies beyond a line (L) which connects the zones (8) of greater depth T ₂ with one another. Film cutting according to claim 1, characterized in that the greater depth T _{2 is} at least 40% and at most 90% of the film thickness D. Film cutting according to claim 1, characterized in that the smaller depth T _{1 is} at least 25% of the film thickness D. Foil cutting according to claim 1, characterized in that the lengths A, A 'of the zones (8) of greater depth T _{2 are} between 0.5 and 5 mm. Foil cutting according to claim 1, characterized in that the lengths B, B 'of the zones (9) of smaller depth T _{1 are} between 0.5 and 5 mm. Foil cutting according to claim 1, characterized in that the ratio of the lengths A, A 'of the zones (8) of greater depth T ₂ to the lengths B, B' of the zones (9) of smaller depth T _{1 is} between 0.5 and 1. Foil cutting according to claim 1, characterized in that the ratio of the lengths A, A 'of the zones (8) of greater depth T ₂ to the lengths B, B' of the zones (9) of smaller depth T _{1 is} between 1 and 4, preferably between 1 and 2. Foil cutting according to claim 1, characterized in that the zones (9) of smaller depth T ₁ merge into the zones (8) of greater depth T ₂ at an acute angle "α" from 0 ° to 60 °. Foil cutting according to one or more of claims 1 to 8, characterized in that the transition points (P ') between the zones (8) of greater depth T ₂ and the zones (9) of lower depth T ₁ are rounded off concavely. Foil cutting according to claim 9, characterized in that the radius of curvature "r" at the transition points (P ') is between 0.1 and 2 mm, preferably between 0.2 and 1.0 mm. Foil cutting according to claim 1, characterized in that for foil thicknesses D between 200 and 400 µm the difference (D - T ₁ ) is between 120 and 200 µm.

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