AU715834B2

AU715834B2 - Process for manufacture of a pack and pack manufacturable therewith

Info

Publication number: AU715834B2
Application number: AU36186/97A
Authority: AU
Inventors: Bernd Albrecht; Gerd Busch; Herbert Cordes; Gebhard Kregel; Jurgen Luttmann; Heinz-Dieter Rabbe
Original assignee: Effem GmbH
Current assignee: Mars GmbH
Priority date: 1996-06-17
Filing date: 1997-06-17
Publication date: 2000-02-10
Anticipated expiration: 2017-06-17
Also published as: NO985859L; NO985859D0; DE59706253D1; CA2258645A1; EP0912400B1; EP0912400A1; WO1997048607A1; DE19634759A1; DE19634759C2; AU3618697A; DK0912400T3; EP0912400B2; NZ333794A

Description

METHOD FOR MANUFACTURE OF A PACK AND PACK MANUFACTURABLE THEREWITH The invention relates to a method for the manufacture of a pack, essentially consisting of plastic film, with means for opening the pack without the aid of a tool, as well as a pack manufacturable therewith.

Packs which can be opened without the aid of a tool, such as e.g. a knife, can opener, etc., i.e. so-called easy open systems, have acquired increased significance over the past few years due to the much easier handling for the consumer. In the case of plastic film packs tear strips are known, which are either incorporated into the film material or are subsequently applied to the filled pack by welding on and accompanied by simultaneously stamping.

The hitherto known systems frequently suffer from the fact that they are difficult to handle from the manufacturing standpoint. Particular problems arise in this connection, e.g. when manufacturing a cylindrical pack, such as is used in both the human and pet food sector for sausage-like products.

S prorThe problem of the present invention is to overcome the disadvantages of the prior art and make available a method with which it is reliably possible to implement S• an easy-open concept in the case of a plastic film pack.

20 According to a first aspect of the invention there is provided a method for the manufacture of a pack, which essentially comprises a plastic film, with means for opening the pack without the aid of a tool, said method including the steps of: supplying the plastic film from a roll to a cutting station; at the cutting station, making a plurality of cuts in the plastic film, the spacing 25 between individual cuts being dependent upon the size of the park, each cut being formed substantially straight, and each cut having a width less than the width of the plastic film and being completely cut through the thickness of the plastic film and; applying to the plastic film, in the vicinity of the cuts, cover strips which completely cover the cuts in a sealing but removable manner.

According to a second aspect of the present invention, there is provided a pack including a plastic film, able to be opened without the aid of a tool, said film having formed therein, substantially straight cuts, each having a width which is less than the width of the plastic film, and extending through the entire thickness of the film, wherein cover strips are removably applied to completely cover and seal said cuts.

It is preferable that the width of the cut is 1/4 or 3/4, more preferably 1/3 to /2 and most preferably approximately 1/3, of the plastic film width.

In a preferred embodiment the cuts are made by a plurality of partial cuts separated by webs.

In one alternative, the width of the partial cuts and/or the webs at different points of the cuts can be the same or, in a second alternative, different.

The invention further suggests that a first sequence of partial cuts of constant width comprising a number n of partial cuts is made in alternating manner with a second sequence of partial cuts of constant width comprising a number m of partial cuts, the width of the partial cuts belonging to the first sequence differing from the width of the partial cuts belong the second sequence.

a preferred embodiment, n is equal to 1 and m is equal to 1.

S° In an alternative, preferred embodiment, n is equal to 1 and m is equal to 2.

20 The plastic film is preferably a laminate having the following sequences of layers: polypropylene, single-layer or mutlilayer polyamide, polypropylene, the polyamide layer preferably being either a coextruded polyamide or at least two polyamide layers, one 00. polyamide layer having high barrier characteristics, whereas the other polyamide layer has a high shrinkage capacity.

The material for the cover strips is preferably constituted by a laminate, whose inner layer placed over the cut in the plastic film comprises an adhesive, removable plastic, preferably a copolymer of polyethylene and polypropylene.

The method of the present invention has numerous advantages which, at least in this combination, have not hitherto been implemented in prior art methods. Firstly by the application of the cut to the plastic film, in the manner the latter is supplied from the roll, i.e.

prior to any further shaping, e.g. to a cylindrical ,,sausage pack", it is easily possible to make the cut for the subsequent opening of the pack precisely at the correct location. Secondly, a pack manufactured according to the method of the invention can be particularly easily opened and the content removed by pulling off the cover strip over the cut and breaking open the pack by the deformation thereof in the vicinity of the cut.

The described advantages are particular relevant when the filled pack is submitted to a sterilization process. On the one hand, the described system is readily able to resist the temperatures and internal pressures during such process, on the other hand, the packing material undergoes shrinkage, during such heat treatment, thereby facilitating the breaking open of the pack by deformation after pulling off the cover strip over the cut. The described advantages with packs submitted to a sterilization process, are not achievable with known easy-open systems.

The use of the preferred materials both for the plastic film and for the cover strip leads to further advantages. The particularly preferred laminate plastic film offers an adequate stability to ensure that through the removal from the roll there is no expansion and tear propagation of the cut made. By applying the cover strip under heat action, there is not only a reliable sealing of the cut, but also the upper layer of the laminate plastic is premelted and forms an additional -4seal for the cut in a partial area, so that on tearing the cover strip the product is not immediately exposed, but can be easily exposed by a slight deformation of the pack.

In that in a preferred embodiment of the invention each of the cuts made in a cycle adapted to the size of the final pack and whose width is smaller than the width of the plastic film and completely severs the plastic film is made by a plurality of partial cuts separated by webs, in general an increased mechanical stability of the pack manufacturable by the method is obtained. This increased mechanical stability is manifested in the peel-off behaviour during film transport in the packaging machine in that it is possible to use thinner films. In addition, there is a reduced film tearing propagation risk.

Finally, as a result of the higher mechanical stability in the peel-off behaviour, waves or corrugations of the film in the vicinity of the cut are avoided when it is transported from a cutting station to a sealing device, in which the cut comprising a plurality of partial cuts separated by webs is sealed to a cover strip completely covering the same and in which the cover strip is applied in sealing, but peel-off manner.

There is simultaneously a rise in the quality of the sealing seam due to the greater strength. In addition, the heating energy requirement necessary for the sealing on of the cover strip is reduced.

A further method advantage results from the fact that as the cut is formed by a plurality of partial cuts separated by webs, the supply of the heating energy necessary for sealing can be provided in simplified manner from the side facing the tear-off strip.

The pack manufacturable by the method of the invention has higher mechanical stability against transportation stresses, which not only leads to a reduction of product losses caused by transportation damage but, particularly in the case of products which deteriorate, reduces the risk of microbial deterioration.

It falls within the scope of the present invention, that the width of the partial cut bounded by two webs is larger, smaller or the same as the width of a web.

The invention is illustrated in greater detail in the following description of embodiments by means of the attached drawings, wherein show: Fig. 1 An apparatus for performing the method according to the invention and the method sequence.

Fig. 2 The structure of a special embodiment of the pack according to the invention in the vicinity of the covered cut in cross-section.

Figs. 3 to 7 show different embodiments of the cut made by a plurality of partial cuts separated by webs and whose width is smaller than the plastic film width and which completely severs the plastic film.

As can be grathered from fig. 1, the plastic film 10 used for the pack is supplied from a supply rolls by means of not shown rollers in order to render the film run uniform, to a cutting station In said cutting station 20 a cut 11 is made by means of a cutting tool 25. Advantageously the cut 11 is made centrally in the film 10, the width of the cut 11 being so selected that, as a function of the plastic material used, by the further removal of the film there is no expansion or tear propagation of the cut. It is important that the cut 11 not only weakens the plastic material, but also fully cuts through the latter.

In the following station 30 for the application of the cover strip 15, the latter is produced, supplied and applied by per se known procedures. Firstly there is a supply from a supply roll 32 to a cutting station 34, in which the cover strip 15 is produced with the desired width, e.g.

6 to 12 mm. The cover strip is fixed by a vacuum on a punch 35 of a sealing device 36. The sealing device 36 is then rotated by 1800 and the vacuum fixed cover strip 15 is so sealed onto the next supplied cut 11 in the plastic film 10 at a temperature of about 210oC, that the cut is covered in a completely sealing manner.

Subsequently, in the embodiment shown, the pack is supplied to a per se known tube formation and filling station (not shown), in which e.g. a sausage-like product is produced.

As can be gathered from fig. 2, the preferred material according to the invention comprises two layers of polypropylene 12, 12', between which there is a one-layer or multilayer polyamide layer 13. The polyamide layer can be a coextruded polyamide or can consist of two polyamide layers 13', 13", whereof the upper layer, i.e. the layer 13' facing the outer polypropylene layer 12, comprises a polyamide having high barrier characteristics, whereas the lower layer 13" facing the inner polypropylene layer 12' comprises a polyamide with high shrinkage properties. As a result of such a structure of the plastic material it is possible to make available a packing material, which first has excellent barrier characteristics with respect to oxygen and steam and which can also undergo optimum printing on the polyamide layer. Obviously the sequence of the polyamide layers 13' and 13" can be reversed.

Over the cut 11 is applied a cover strip 15 completely covering the width and length thereof and which is preferably also in the form of a laminate. It must be ensured that the laminate layer 16 facing the cut has the necessary adhesion properties, i.e. can be firmly fixed over the cut, but can be simultaneously removed or peeled off in an optimum manner.

Particular preference is given to a copolymer of polyethylene and polypropylene. The composition of the layers 17, 18 placed over the same is less critical. In the represented embodiment these can be a PET layer 17 and a finishing polypropylene layer 18, but other materials can also be used.

-7- On sealing the cover strip 15 over the cut 11, as a result of the temperature application there is a premelting of the outer polypropylene layer 12 of the laminate plastic film 10, so that there is an additional weak seal in the outer area of the cut 11. This ensures that even after the removal of the cover strip 15, the product does not immediately pass out of the interior of the pack. However, a slight deformation of the pack leads to an immediate breaking open in the cut area, which allows an easy opening and emptying of the pack.

Fig 3 shows a cut comprising a sequence of partial cuts 11 b of constant width separated by webs 11 a of constant width, the width of the partial cuts being a multiple of the width of the webs separating the partial cuts.

Fig. 4 shows a cut construction in which the width of the partial cuts 11 b is roughly the same as the width of the webs 1 1a located between the partial cuts.

Fig. 5 shows an embodiment in which the width of the webs 1 la between the partial cuts 1 lb is smaller than the width of the partial cuts, the partial cuts comprising an alternating sequence of partial cuits, in which once again the width of a partial cut is larger or smaller than that of the following partial cut.

Fig. 6 shows an embodiment in which a sequence 11 c comprising two partial cuts is made in alternatively manner with a sequence 11 d of one partial cut. The partial cuts in the first sequence have the same width, but are shorter than the width of the partial cut of the second sequence. The width of the webs between the different sequences is roughly constant over the entire width of cut. The width of the webs located between the partial cuts of the first sequence is roughly the same as the width of the webs located between the partial cuts of the second sequence.

Finally fig. 7 shows a cut performance, which is similar to that shown in fig. 4, but both the width of the webs and also that of the partial cuts is significantly reduced, so that in the present case a perforation line is formed.

The method according to the invention is particularly suitable for the manufacture of cylindrical packs with a sausage shape and this can either apply to sausage products for the food sector, or to pet products offered in sausage form, such as e.g. a so-called dog sausage and in the latter case the filling can be a moist to semimoist, lumpy dog food. Other applications are conceivable, because the method according to the invention provides an easyopen concept, which offers advantages with many pack types.

The features of the invention disclosed in the description, drawings and claims can be t essential both individually and in random combinations for the implementation of the different embodiments of the invention.

"ccmprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof 0* 06 00 0 0 *0

Claims

1. A method for the manufacture of a pack, which essentially comprises a plastic film, with means for opening the pack without the aid of a tool, said method including the steps of: supplying the plastic film from a roll to a cutting station; at the cutting station, making a plurality of cuts in the plastic film, the spacing between individual cuts being dependent upon the size of the park, each cut being formed substantially straight, and each cut having a width less than the width of the plastic film and being completely cut through the thickness of the plastic film and; applying to the plastic film, in the vicinity of the cuts, cover strips which completely cover the cuts in a sealing but removable manner.

2. Method according to claim 1, characterised in that the width of the cuts is i ~about 1/4 to 3/4 of the plastic film width.

3. Method according to claim 2, characterised in that the width of the cuts is about 1/3 to 1/2 of the plastic film width. 0 0

4. Method according to claim 3, characterised in that the width of the cuts is *99o°* S" about approximately 1/3 of the plastic film width. Method according to any one of the preceding claims, characterised in that the cuts are made by a plurality of partial cuts separated by webs.

6. Method according to claim 5, characterised in that the width of the partial cuts and/or the webs at different points of the cut is are the same.

7. Method according to claim 5, characterised in that the width of the partial cuts and/or the webs at different points of the cut differ.

8. Method according to any one of claims 5 to 7, characterised in that a first sequence of partial cuts of constant width comprising a number n of partial cuts is made in alternating manner with a second sequence of partial cuts of constant width comprising a number m of partial cuts, the width of the partial cuts belonging to the first sequence differing from the width of the partial cuts belonging to the second sequence.

9. Method according to claim 8, characterised in that n is equal to 1 and m is equal to 1.

10. Method according to claim 8, characterised in that n is equal to 1 and m is equal to 2. oo 9 o

11. Method according to any one of the preceding claims, characterised in that the plastic film used is a laminate with the following sequence of layers: polypropylene, one-layer or multilayer polyamide, polypropylene. o.

12. Method according to claim 11, characterised in that the polyamide layer is a coextruded polyamide.

13. Method according to claim 11, characterised in that the polyamide layer includes at least two polyamide layers, a first one of said layers being of a polyamide with high barrier characteristics, whereas the other one of said layers is of a polyamide with high shrinkage capacity. 11

14. Method according to any one of the preceding claims, characterised in that the cover strip material is a laminate, the laminate including an inner layer which is placed over the cut in the plastic film, the inner layer being an adhesive, peelable plastic. Method according to claim 14, characterised in that the inner layer includes a copolymer of polyethylene and polypropylene.

16. Method according to any one of the preceding claims, characterised in that the cover strip is applied under heat action.

17. Method according to any one of claims 1 to 16, including the subsequent step of processing the plastic film in known manner to form the individual packs.

18. A method for the manufacture of a pack, substantially as herein disclosed with reference to the accompanying drawings.

19. A pack manufactured according to the method of any one of claims 1 to 18. o 20. A pack, substantially as herein disclosed with reference to the accompanying drawings.

21. A pack which essentially comprises a plastic film and which is able to be opened without the aid of a tool, said film having formed therein, substantially straight cuts, each having a width which is less than the width of the plastic film, and extending through the entire thickness of the film, wherein cover strips are releasably applied to completely cover and seal said cuts.

22. A pack according to claim 17, wherein the width of each said cut is approximately 1/4 to 3/4 of the width of the plastic film. DATED this 3 0 th day of November 1999. EFFEM GMBH WATERMARK PATENT TRADEMARK ATTORNEYS UNIT 1, THE VILLAGE RIVERSIDE CORPORATE PARK

39-117 DELHI ROAD NORTH RYDE NSW 2113 AUSTRALIA. PJM:MP:RM P6031 AUOO