EP0962388A1 - Method and machine for fabricating packages - Google Patents

Abstract

The product is sealed between a top thermoplastic sheet and an underneath sheet. The top sheet is heated and shaped into a cover by being brought into contact with a hollow mold. The cover is positioned over the packaging unit together with the bottom sheet shaped in a trough shape (8) and supporting the product. Before sealing, the cover is shrunk by means of controlled heating to cover the product preferably without touching it. The trough has at least one curve (13) at least in its base by which the pressure inside the packaging unit sealed and cooled to the ambient temperature can be adjusted afterwards.

Description

The present invention relates to methods and devices for the production of Packings, preferably gastight packaging, by placing a product between a thermoformed upper roll and, if necessary, a thermoformed lower film packed while changing the shape of the top film and sealing the two films becomes.

It is known to pass through products in a bottom sheet deformed into troughs Shrink-wrapping with a shrinkable top film in so-called Pack vacuum packaging. The top film is sealed before the filled trough heated and after applying a vacuum, the contents to be packed shrink-wrapped according to its contours (see GB-A-1307054). This Packaging method is only suitable for packaging high, i.e. H. about products protruding from the sealing level, because due to such contours the Shrinking with a largely uniform film thickness is almost impossible is. In addition, only a certain variety can be used to manufacture these packs of top foils, namely so-called skin foils, are used.

It is also known to use products, especially food, in Pack thermoformed troughs that are heat sealed with a lidding film become. Such cover films must have a minimum heat stability and rigidity have, otherwise there would be warpage of the cover film and during the sealing process not only to unsightly packs, but also to missing parts in the Sealed seam areas can come. In addition, with this type of packaging the contents do not protrude beyond the sealing level, which is the case for products up to one certain height by providing correspondingly deep packaging troughs can be solved. On continuously running packaging machines but such troughs are made by deep drawing, with the risk of imperfections increases with increasing depth of the trough to be produced. Furthermore, this should Method step not for the speed-determining sequence of the Overall packaging process.

The object of the present invention was therefore to make sealed packs Manufacture thermoplastic material with an optically perfect appearance, whereby also packaging products with dimensions above the sealing level can be easily packed and films of any kind as cover material can be used.

According to the invention, this is achieved by providing methods for producing Packs by placing a product between a thermoplastic top sheet and Bottom film is preferably sealed gas-tight under protective gas, the Top film by heating and bringing it into contact with a hollow mold Cover deformed, the cover positioned on the respective Packing unit with, if necessary, a tray that carries the product Bottom film brought together before sealing the packing unit Cover shrinkage by controlled heating only up to one Clamping set without touching the product or under simultaneous Warm the cover of the pressure in the pack if necessary by replacing it shielding gas used to at least the ambient pressure plus weight of the film per unit area and the packing unit is sealed.

Another object of the present invention is a packaging machine with means for a separate feed, one roll each, one Bottom film on which the product to be packaged is placed and an upper film, those in a molding station, with a mold cavity open at the bottom is equipped with means for heating and pulling up the film, with a drive for the gradual advance of the bottom and top film and for Positioning the deformed top film over the product to form a packaging unit, with means for controlled heating of the deformed top film in the sealing station, Means for the controlled setting of an internal pressure of the pack before Seal the packing unit with the sealing tool and with sealing tools.

Figur 1 eine allgemeine Anordnung der Verpackungsmaschine gemäß der vorliegenden Erfindung darstellt,

Figur 2 eine gefüllte Packung (Füllgut nicht dargestellt) mit nach außen geformten Wölbungen im Boden der Verpackungsmulde darstellt,

Figur 3 eine gefüllte Packungseinheit darstellt (Füllgut nicht dargestellt), bei der die Wölbungen in der Verpackungsmulde zur Regulierung des Innendruckes bereits nach innen gedrückt sind.

In order to clarify the method according to the invention, reference is made to the attached FIGS. 1 to 3, wherein

1 shows a general arrangement of the packaging machine according to the present invention,

FIG. 2 shows a filled package (product not shown) with bulges in the bottom of the packaging trough which are shaped outwards,

FIG. 3 shows a filled packing unit (filling material not shown), in which the curvatures in the packaging tray are already pressed in to regulate the internal pressure.

As can be seen from FIG. 1, the method according to the invention is preferably based on a continuously running packaging machine (1). The Upper film (2) in a forming station (3) by heating and pulling it into one Large number of covers (4) open at the bottom deformed. The bottom film (5) is withdrawn from a supply roll (6), through in a further forming station (7) Deep drawing into a variety of contiguous, open top Packing trays (8) deformed. These packing troughs come with the product filled and in front of the sealing station (10) with a positioning device that is not is shown, positioned to a pack unit with the cover (4) and on the overlapping edges sealed together. After sealing in the Sealing station (10) are the packs by appropriate cutting device, not shown, isolated.

According to the top film is according to the dimensions of the packing material is deformed into covers by the film preferably heat radiation and / or contact heating and pulling in or Pressing into a hollow mold, which preferably with evacuation devices for Pulling in or compressed air is equipped to press in the film becomes.

This cover preferably remains in its dimensions after leaving the Forming station stable until the sealing process. The shrinkage force is in the forming station the top film, which in the production of packaging according to the invention without Pressure adjustment of the internal pressure of the package when sealing is necessary, set. This shrinkage force is determined according to DIN 53369 and is a common one Size for characterizing foils under the influence of heat shrink. A top film pretreated in this way is then in the sealing station as soon as the cover with the bottom film carrying the product, which preferably forms a Trough is deformed, positioned to a packing unit, heated in a controlled manner. This controlled heating to the extent of the shrinkage of the cover so to control that packaging goods are in no way shrunk, but that Product carrying base film, preferably formed into a trough, only taut without Touched at the highest point of the product to be packaged, d. H. is covered by taking into account known heat radiation which generates sealing heat that is released during heat sealing.

In order to control the shrink temperature as precisely as possible, the temperature for sealing and the temperature for shrinking separated by the installation of cooling, insulation and heating elements are checked. The different temperatures can be queried by sensors. The The machine's control system then adjusts the temperature value. The Sealing temperatures are preferably in the range from 80 to 180 ° C. The Temperature in the rest of the sealing tool, d. H. the shrink temperature can can be controlled separately from this value and preferably up to ± 30 ° C Need differ.

Since it is known (according to DIN 53396), the shrinking force increases continuously Determining the temperature for a specific film material is simple Preliminary tests to determine what temperature before and during the shrinking process is to be adhered to during the sealing process in order to achieve the desired extent of To produce shrinkage. This free shrinkage S is usually in Expressed in percent and can be represented by the following equation.

Free linear shrinkage in vertical or horizontal direction in% S% = [(D 0 -D 1 ) / D 0 ] x100 where D _{0 is} the original length in one direction and D _{1 is} the length in the same direction after shrinkage.

Preferably, the shrinkage force of the top film becomes during the deformation Cover by appropriate stretching in the softening area of the Foil material adjusted so that the free shrinkage at the sealing temperature is at least 10%, preferably up to 60%.

According to the invention, however, it is also possible to use the upper film preformed as a cover after their positioning to a respective packaging unit with the, if applicable, to a Deformed bottom film in the tray carrying the product to be packaged Sealing station to heat and at the same time the pressure by supplying air or Shielding gas, which is already inside the packing unit in the usual way has been exchanged for air so that the internal pressure is at least corresponds to the ambient pressure plus the weight of the film per unit area. The packaging unit can be sealed practically synchronously. The The upper film deformed into a cover is heated by the radiation heat and / or convection heat released during heat sealing and if necessary additionally by heat radiating elements. By warming the The top film increases its flexibility and the pressure inside the packaging unit can preferably be set so that the covering and with the edges the upper film, which is preferably deformed into a trough, is sealed packaged good not touched at its highest point, even if the dimensions of these packaging goods are such that they protrude beyond the sealing level. The pressure is preferably set such that at least when packaging Products that protrude the top film above the sealing level and sealed at the sealing edges, tight, d. H. Wrinkle-free, is present. Most notably preferably the pressure inside the pack is always set so that the The upper film is arched and sealed to the lower film is present.

The exchange of air in the package inside against an inert gas filling is preferably carried out at perishable foodstuffs, wherein in fresh meat filling a CO ₂ / O ₂ gas mixture, in other foods, such. B. sausage or ham sliced, gas mixtures of CO ₂ / N ₂ or only N ₂ are used. One speaks then of MAP packages (Modified Atmosphered Packaging).

When the sealed package cools to ambient temperature, it may become necessary to at least readjust the pressure inside the package. For this purpose, the method according to the invention is preferably used designed packaging trays used, at least in their floor area have at least one curvature.

Figure 2 shows a pack (12) with a trough (8), the bottom of which is outward has arched curvatures (13).

These bulges can be used to change the volume and thus change the pressure be pressed at the top.

In Figure 3 a packaging tray is shown, the bulges inward having.

These bulges in the packaging troughs can be used in their Design can be changed once the pack is at ambient temperature has cooled and / or there is a pressure drop inside due to the storage of the pack the pack is to be expected. So that the inner volume of the pack and thus the pressure is changed so that the top film is smooth, optically perfect Keeps appearance. It also touches the packaged product prevented, which can otherwise increase its perishability.

The packaging tray shown in Figure 3 shows the state of the Packaging tray after sealing and readjusting the pressure by the Bulges in the bottom of the packaging tray are curved inwards. Until after sealing the pack can cause the dents to face down remain, so that if necessary, as explained above, by deforming the bulges the volume is reduced internally and the gas pressure changes again leads to a wrinkle-free, optically perfect appearance of the top film.

The necessary changes in the curvature of the curvatures can be done by mechanical action are made, preferably after Packaging process in the packaging machine.

The use of packaging trays designed in this way is preferably only used in such Packs selected that are intended for longer storage, products packed containing, which can absorb gas during storage and / or Top films are used, which have a small dimensional change, preferably in the form of shrinkage with decreasing temperature.

The top films and bottom films used are preferred unstretched films, such as are usually used for the production of sealed packs a top and bottom film can be used.

So-called hard foils are used in particular as sub-foils due to their mechanical stability for the production of packaging trays excellent through deep drawing. These are especially polyester, Polystyrene, polyamide or polypropylene films, preferably foamed, as exemplified in EP-A-0 570 221, in EP-A-0 520 028, WO / 42029 are described. The corresponding disclosures from these references are hereby introduced as a disclosure of the present application.

Both hard foils and soft foils can be used as top foils with a Bottom sheet identical or different structure are used. In particular, these are films made of polypropylene, polyester or polyamide, preferably with a multilayer structure. Point to seal with the bottom film these top foils preferably have a sealing layer that seals in Temperature range from 80 ° C to 180 ° C allowed. Are very particularly preferred thereby transparent films with the basic structure Polyamide / polyethylene vinyl alcohol / polyethylene or Polystyrene / polyethylene vinyl alcohol / polyethylene or Polyester terephthalate / polyvinylidene chloride / polyethylene. The layer serves Polyethylene vinyl alcohol or polyvinylidene chloride as a barrier layer to one Avoid gas exchange with the environment.

The bottom film can also preferably have a multilayer structure, wherein this multilayer structure preferably also comprises a gas barrier layer to largely prevent gas exchange with the environment.

It is also possible to use the known shrink films, the so-called skin films Use top sheets provided temperature controlled shrinkage of the Top film coverage is sought while sealing.

The manufacturing processes for both the lower films and the upper films are are known and are preferably carried out by extruding or coextruding at one Multi-layer construction, on casting rolls, on which the foils cool down. You get the so-called cast foils.

The thickness of the lower film is preferably in the range of 70 to 1500 μm, around one to have sufficient dimensional stability even after deep-drawing into hollows. So-called stable foils with sufficient are therefore preferred Intrinsic stability as lower foils for the production of the packs according to the invention used.

The upper films are preferably thinner than the lower films, their thickness in Range from 10 to 350 microns, preferably 50 to 250 microns

The process according to the invention is preferably carried out continuously on filling and molding Seal packaging machines performed.

The equipment of these machines according to the invention is specified above.

The packaging machine according to the invention preferably also has a second one Forming station to form troughs from the bottom film, and means for producing of bulges at least in the bottom of these hollows.

The method according to the invention is suitable for packaging goods of all kinds, especially of goods with complicated dimensions, particularly preferred those that protrude beyond the sealing level. Particularly preferred the inventive method and the device for packaging Food, preferably perishable food, such as fresh meat with or without leg, poultry, cheese or cold cuts.

The present invention therefore also relates to packs especially with food as packaging, available after Method according to the invention using the device according to the invention.

Claims (14)

Process for making packs by placing a product between one thermoplastic top film and a bottom film, if necessary, under protective gas is sealed, characterized in that the top film by heating and bringing into contact with a hollow mold to deform a cover that Cover under positioning on the respective packaging unit with the deformed into a trough, the film carrying the product the shrinkage before sealing the package unit the cover by controlled heating only up to one preferably non-contact reclamping of the product set or while heating the cover, the pressure in the package, if necessary through the shielding gas used for the exchange to at least the Ambient pressure plus weight of the film per unit area and the Packing unit is sealed A method according to claim 1, characterized in that the bottom film to at least one trough is formed, at least in its bottom area has at least one curvature with which the pressure inside the Ambient temperature cooled, sealed package unit at least can be adjusted. Method according to claim 2, characterized in that the curvature (s) is directed outwards at the latest when the trough is sealed. Process according to claims 1 to 3, characterized in that the pressure in the sealed packaging unit, if necessary, is repeatedly adjusted so that the packaged product is not touched by the cover. Method according to one of claims 1 to 4, characterized in that the atmosphere inside the packing unit against a protective gas is exchanged. Method according to one of claims 1 to 5, characterized in that the heating of the cover by the heat that is released during heat sealing Radiant heat and / or convection heat and / or radiant heat Elements. Process according to claims 1 to 6, characterized in that the Packing unit in the overlapping edge area from covering Top film and bottom film is sealed. Process according to Claims 1 to 7, characterized in that the Upper film and / or the lower film made of a thermoplastic mono- or There is multilayer film, which is preferably a gas barrier layer having. Process according to claims 1 to 8, characterized in that the The shrinking force of the top film when it is deformed to form the cover is set in this way the free shrinkage at the sealing temperature is at least 10% is. Packages are obtained by the process according to claims 1 to 9. Packages according to claim 10 containing perishable as packaged products Foodstuffs, preferably fresh meat with and without leg, poultry, parts thereof, Pieces of cheese or cake. Packaging machine with means for a separate feed of each a supply roll of a bottom film on which the product to be packaged is placed, and an upper film, which in the forming station with one after mold cavity open at the bottom equipped with means for heating and Pulling up or pulling in the film is deformed with a drive for gradual feed of the bottom and top film and for positioning the deformed top film over the product to a pack unit, with means for controlled heating of the deformed top film in the sealing station and means for the controlled setting of an internal pack pressure sealing the packing unit with the sealing tool and with a Sealing tool. Packaging machine according to claim 12, characterized in that it a second molding station for molding containers from the bottom film having. Packaging machine according to claim 13, characterized in that it still further shaping means for producing curvatures at least in the Bottom of the container and means for changing the configuration of the Bulges before sealing and after sealing the Package unit has.

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