EP0615910B1 - Apparatus for cutting out one or more cups out of a plastic web - Google Patents

Description

The invention relates to a device for punching single and multiple containers from plastic films, in particular films with a high elongation at break, for example polypropylene films, according to the preamble of claim 1.

In the manufacture of containers, e.g. B. for the packaging of yogurt or similar products, plastics from the polystyrene product group (hereinafter referred to as "PS") have been used for the containers. PS foils or aluminum foils were also used for the associated lids. For reasons of environmental protection, which will not be discussed in more detail here, attempts have been made for some time to completely remove the above-mentioned packaging, i. H. Manufacture containers and lids from plastics from the polypropylene product group (hereinafter referred to as "PP").

Since the mechanical properties of the PS films and those of the PP films are fundamentally different, there are problems when punching out the finished containers from PP film, which only limitedly permitted the use of the films in packaging technology. For the sake of understanding, the most important differences between the slides should be briefly described.

The tensile strength of the PS film is 45 to 65 N / mm², while that of the PP film is 21 to 37 N / mm².

The elongation at break of the PS film is 3 to 4% PP film, however, 20 to 800%.

From these values it can be seen that the PS film is hard and brittle and can easily be broken. The PP film, on the other hand, is tough-elastic and can hardly be broken and can only be torn with great effort.

Since part of the material is cut and the rest broken during punching, the PS film is easy to punch.

Another problem is that the multiple containers are interconnected so that individual containers can be broken off from the multiple pack by the end user. This is very easy to do with PS films due to their brittleness by simply anchoring the film with a chisel-shaped notch stamp. Due to the predetermined break line in the film, the PS film breaks off slightly at this point. With the PP film, however, breaking off is not possible due to the high elongation at break as with the PS film. With the tool according to the invention, it is possible to manually separate individual containers from a multiple pack without aids, since the tough plastic film, for example PP film, can be cut at the separation point to a residual amount of 0.03 mm to 0.05 mm, as a result of which the containers are connected to each other only by a thin film and this film is additionally cut at both ends. This makes it relatively easy to separate a container despite the high toughness of the film. A cover film is completely cut through.

For tools for PS foils, it is sufficient to use chisel-shaped notches to notch the foil down to 0.02 mm to 0.03 mm. Due to the brittleness of the foils, the containers at the notch are blown apart. In addition, the predetermined breaking point can be immersed less deeply of the notch stamp (approx. 1/3 to 1/2 of the total film thickness) can be scored for breaking off (breaking edge for the end user). Notch stamps, which can be adjusted by means of slides, can achieve that single packs or multiple packs with a predetermined breaking edge can be produced in one tool without having to disassemble the tool for a changeover. This is a well-known and proven version of so-called multi-punches for PS foils.

The punching technique for PS foils is not suitable for PP foils.

There is another problem: Up to now it has not been possible to manufacture single or multiple packs of containers in different numbers of containers in one tool without time-consuming disassembly and retrofitting of the tool.

The object of the present invention is therefore to design a tool for punching containers from plastic films with high elongation at break, in particular from polypropylene film, so that, on the one hand, individual containers can also be effortlessly separated from multiple packs without aids and, on the other hand, the optional manufacture of single or multiple packs with different numbers of containers is possible without expensive disassembly and retrofitting of the tool.

This object is achieved by the training according to the characterizing part of claim 1.

Advantageous and expedient developments of the task solution according to the invention are specified in the subclaims.

With the tool according to the invention it is possible to manually separate individual containers from a multiple pack without aids, since the tough plastic film, for example PP film, except for one at the separation point The remaining amount of 0.03 mm to 0.05 mm can be cut, whereby the containers are connected to one another only by a thin film and this film is also cut at the two ends. This makes it relatively easy to separate a container despite the high toughness of the film. A cover film is completely cut through.

With the tool according to the invention it is possible to produce either single or multiple packs; the change from single to multiple containers is done automatically by the press control. This can reduce the time for a change from several hours to a few seconds. Possible errors caused by the conversion and the resulting damage to the tool can be prevented.

The invention will be explained below with reference to the accompanying drawings.

Fig. 1

schematisch den Einsatz von meißelförmigen Kerbstempeln zum Austrennen eines Behälters und zum Ankerben eines Behälters bei Verwendung von Polystyrolfolie für eine Behältermehrfachpackung (Stand der Technik),

Fig. 2

einen Schnitt durch ein erfindungsgemäßes Werkzeug zur Fertigung von Behältereinzel- und Mehrfachpackungen in auseinandergefahrener Stellung (Ausgangsstellung),

Fig. 3.1 und 3.2

eine schematische Darstellung von beim Werkzeug nach Fig. 2 verwendeten Messern und Sternstempeln und-deren Schnitteinsatzweise für Behälterfolien aus Polypropylen,

Fig. 4

eine Draufsicht auf eine beim Werkzeug nach Fig. 3 verwendete Schnittplatte,

Fig. 5

einen Folienlaufplan für Behältereinzelpackungen,

Fig. 6 bis 8

das Werkzeug nach Fig. 2 in mehreren Zufahrstellungen und Schnittstellungen (teilweise zugefahrene Stellung bis Endstellung) zum Stanzen von Einzelpackungen,

Fig. 9

einen Folienlaufplan für 2X4-fach-Behälterpackungen und

Fig. 10 bis 13

das Werkzeug nach Fig. 2 in mehreren Zufahr- und Schnittstellungen (teilweise zugefahrene Stellung bis Endstellung) zum Stanzen von 2X4-fach-Packungen.

It shows:

Fig. 1

schematically the use of chisel-shaped notch stamps for cutting out a container and for anchoring a container when using polystyrene film for a container multipack (prior art),

Fig. 2

2 shows a section through a tool according to the invention for the production of single and multiple packs of containers in an extended position (starting position),

Fig. 3.1 and 3.2

2 shows a schematic representation of the knives and star stamps used in the tool according to FIG. 2 and their cutting insert for container films made of polypropylene,

Fig. 4

3 shows a plan view of a cutting plate used in the tool according to FIG. 3,

Fig. 5

a film schedule for individual container packs,

6 to 8

2 in several approach positions and sectional positions (partially closed position to end position) for punching individual packs,

Fig. 9

a slide schedule for 2X4-fold container packs and

10 to 13

2 in several feed and cutting positions (partially closed position to end position) for punching 2X4-fold packs.

As far as appropriate, the same reference numerals are used in the figures of the drawing for the same components.

1 shows the use of chisel-shaped notch stamps 60 and 62 according to the prior art for separating and anchoring containers in a container film 64 made of polystyrene, which is also provided with a cover film 66 also made of polystyrene or aluminum. To cut out, it is sufficient to use the chisel-shaped notch stamp 60 to notch the polystyrene film down to 0.02 mm to 0.03 mm. Due to the brittleness of the film, the containers are then blown apart at the notch.

For anchoring, it is sufficient to produce the predetermined breaking point intended for the consumer by immersing the notch stamp 62 less deeply, namely to about 1/3 to 1/2 of the total film thickness.

2 of the drawing shows a tool 2 according to the invention, which consists of a base plate 4, onto which a cutting plate 6 is screwed, from a first punch holding plate 8, under which the first knife 10 for the Cutting lines are attached, which always cut through without conversion, further from a second stamp holder plate 12, to which second knives 14 are fastened, which either cut or only cut, and consists of a head plate 16, to which star stamps 18 are fastened, which fasten the corners of Cut the containers to be separated (not shown) with a fillet 19.

All plates 4, 6, 8, 12, 16 are always fixed to one another in the correct position via corresponding guide units.

The two punch holding plates 8 and 12 are each held by spacing units 20 and 22 in relation to the head plate 16 such that the lower cutting edges of all the star punches and knives lie in one plane when the tool is moved apart.

Between the die holding plates 8 and 12 and the head plate 16 there are compression springs 24 and 25 which, as described later, absorb the respective cutting forces and serve to adjust the preload. Fixed or adjustable stops 26 and 28 are located between the base plate 4 and the two punch holding plates 8 and 12, which limit the immersion depths of the corresponding knives to the cutting plate when the tool is closed.

All of the star stamps 18 and the knives 10 which cut through the film without any change (i.e. without corresponding adjustment of the stops 26) have straight-cut edges 30, cf. Fig. 3.1. By extending the stops 26, for example by means of wedge slides 50 ', which can be driven, for example, by air cylinders 51', it can be achieved that the knives 10 cut the film only to a predetermined depth, so that a residual film remains.

The knives 14, which optionally cut through the film or only cut in, have on the underside recessed cut edges 32, which are hollow or concave in the drawing inwards or upwards, with a central, essentially straight region 32 ', cf. Fig. 3.2. A container film 31 with a cover film 33 are also shown schematically in FIGS. 3.1 and 3.2 in order to show the respective cutting method of the knives and punches more precisely.

A plurality of recessed cut openings 34 and raised cut openings 36 are alternately formed in a checkerboard fashion on the cutting plate 6, cf. 2 and 4, so that alternately a container is cut into the cutting plate 6 and the other container remains on the cutting plate 6. The reference numeral 35 denotes the openings in the cutting plate for the container. The knives cut out the containers each at the recessed cut openings 34. The star stamps 18 cut the rounded corners of the containers in two stages, one part each on the raised cut openings 36 and the rest on the recessed cut openings 34, see FIG. 4.

The usually existing scraper plates on the upper part of the tool and the usual ejectors in the lower part of the tool should not be discussed in detail, since they are of no importance for the function of the present invention for cutting PP films, but only contribute to the general function of the tool. For this reason, they have not been shown in FIGS. 2 to 4.

The function of the tool for producing individual packs is to be described below with reference to FIGS. 5 to 8:
If a film 30 with deep-drawn containers (not shown) is inserted into the tool 2 and this Tool driven by the usual press, not shown, feeds (see arrow direction A), all star punches 18 and knives 10, 14 first cut into the film at the raised locations 36 of the cutting plate 6, cf. 6 and 7.

If the punch holding plates 8 and 12 of the knives 10 and 14 rest on the stops 26 and 28, the punch holding plates are held in their position relative to the cutting plate 6 against the spring force of the compression springs 24 and 25, which have previously applied the required cutting forces that a further immersion of the knives 10 and 14 in the film 30 and thus in the cutting plate 6 is prevented, cf. Fig. 7. In this position of the tool 2, all four container sides 40, 42, 44, 46 of the container film 31, cf. Fig. 5 (foil flow chart), through the knives 10 and 14 and the rounding 19 'of the container corners resting on the raised cutting plate parts, cut through by the star stamp 18.

When the press continues to drive, the head plate 16 is moved further down until it rests on the second upper punch holding plate 12. As a result, the star punches 18 are extended further relative to the knives and cut the remaining roundings 19 ″ of the container corners in the further course of the pressing movement through, whereby all containers are cut from the container film 31 and can be removed as an individual container from the tool. The rounding cutouts fall out of the tool train via drop openings 56 formed in the cutting plate 6 and base plate 4.

The function of the tool 2 for the production of 2X4-fold packs will be described below with reference to FIGS. 9 to 13:
FIG. 9 shows the associated film flow chart with the pages 27 to be cut through between the packs of 4 and with the thin tear-open edges 29 to be produced within each 4-pack.

In the case of multiple packs, the stops 28 for the second upper stamp plate 12 are changed in length by wedge slides 50, which are moved, for example, by means of air cylinders 51, for example extended by approximately 0.5 mm, compared to the stops 28 in the tool 2 for single packs.

When the tool 2 closes with the deep-drawn containers (not shown) when the film 31 is inserted, all the star stamps 18 and knives 10, 14 cut into the film along the raised areas 36 of the cutting plate 6, cf. 11 and 12. Since the stops 28 have been lengthened mechanically, the punch holding plate 12 with the knives 14 comes on prematurely and is held in this position. The first stamp holding plate 8 with the knives 10 and the head plate 16 with the star stamps 18 initially move on in a defined manner, in such a way that a cut is made at the separation point to a remaining amount of 0.03 mm to 0.05 mm, by a thin one To produce film 54, over which the containers of the multi-pack are connected, wherein the lid film 33 is cut. Since the knives 14 are hollow ground from below, that is to say they have an approximately concave cutting edge, cf. 3.2, the thin film 54 is provided with incisions 52 on the side, cf. 12 and 3.2, by means of which the container film 31 can be easily separated along the thin film 54 by tearing the film open, for example by hand, in the continuation of the incisions. The first punch holding plate 8 with the knives 10 is placed on the stops 26 and is held in this position, cf. Fig. 12. The head plate 16 with the star stamps 18 continues to the lower position of the tool, whereby the rest of the fillets as with the individual containers is cut out, see FIG. 13. The rounding cutouts fall out of the tool via the outlet openings 56 formed in the cutting plate 6 and base plate 4.

If the stops 28 are extended even further by the wedge slides 50, containers 2 made from polystyrene film can also be cut and scored with this tool 2.

By combining the knives 10 and 14 with the two punch holding plates 8 and 12, individual packs and multiple packs in all possible combinations, such as, for. B. Single, double, quadruple and eight-fold packs are punched and cut to tear off. During the changeover, only the stops 26 and 28 are changed in length by suitable means, for example air cylinders with the tool 2 extended, via wedge slides.

The compression springs 24, 25, which must apply and maintain the cutting force of the corresponding knives 10, 14, can also be replaced by air cylinders or cylinders filled with nitrogen, depending on the cutting force required.

Depending on the requirements, a third punch holding plate with corresponding knives, springs, spacing units and stops may also be required, which is based on the respective requirements.

Instead of having approximately concave recesses in the cut edge, the second knives 14 can also be provided with recesses in a rectangular or trapezoidal shape.

Claims (11)

1. Apparatus for cutting individual pots and packs of pots out of a plastics sheet with a high elongation at break, particulary out of a polypropylene sheet, comprising a plurality of knives (10, 14, 18) for scoring and cutting through the sheet which may be advanced by a press in a defined manner, and a die plate (6) having depressed and raised cutting holes (34 and 36) which cooperate with the knives (10, 14, 18), characterized by

   - at least two carrying plates (8, 12, 16) for the knives (10, 14, 18), the plates being arranged one behind the other in the direction of advance, wherein the knives (14 and 18) or their carriers which pass in the direction of approach through the carrier plates (8, 12) arranged before the carrier plates (12, 16) associated therewith, and

   - stops (26, 28) for the carrier plates (8, 12), the stops being adjustable, acting at the same or different time and serving for the determination of the length of the paths of advancement of the knives (10, 14).
2. Apparatus according to claim 1, characterized in that the carrier plates include at least two holding plates (8, 12) and a top plate (16).
3. Apparatus according to claim 2, characterized in that compression springs (24, 25) or gas cylinders for the setting of the cutting forces and pretension are arranged between the carrier plates (8, 12, 16).
4. Apparatus according to claim 1, characterised in that the die plate (6) and the stops (26, 28) are arranged on a bottom plate (4).
5. Apparatus according to claim 1 or 4, characterized by wedge-shaped slides (50, 50') for the adjustment of the length of the stops (26, 28).
6. Apparatus according to any one of the preceding claims, characterised in that the knives include knives (10) with straight cutting edges (30) for cutting through or scoring the sheet, knives (14) with concave cutting edges (32) for selectably cutting through or scoring to produce a thin film where tearing is desired and lateral cutting through to produce lateral scoring, and star-shaped punches (18) for the trimming of the pot corners to provide rounding (19).
7. Apparatus according to claim 6, characterized in that the knives (10) with straight cutting edges (30) are provided on the holding plate (8) next to the die plate (6),
   the knives (14) with the concave edges are fixed on the next following holding plate (12) and pass through the holding plate (8), and
   the star-shaped punches (18) are arranged on the top plate (16) and pass through both the holding plates (8 and 12).
8. Apparatus according to claim 7, characterised in that, in the open position (starting position) of the apparatus (2), the cutting edges of the knives (10 and 14) and of the star-shaped punches (18) are situated in a plane between the holding plate (8), which is adjacent the die plate (6), and the die plate (6).
9. Apparatus according to any one of the preceding claims, characterised in that the die plate (6) and the bottom plate (4) are provided with discharge openings (56) for the rounding cut-outs cut out by the star-shaped punches (18).
10. Apparatus according to claim 1 and 6, characterised in that the stop (28) and/or the stop (26) for the knives (14) with concave cutting edges (32) and/or the knives (10) with straight cutting edges are/is adjustable such that the sheet may be scored up to a residual thickness of 0.03 mm to 0.05 mm, corresponding to the thickness of the thin film where tearing is desired.
11. Apparatus according to any one of the preceding claims, characterised in that the recess (32) of the cutting edge of the knives (14) has the shape of a trapezium, a rectangle or concave recess.

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