Patent Application
20110271643
The present invention refers to a method for operating a packaging machine and to a packaging machine.
In products on which further, mostly small-sized, loose product add-ons are positioned, as is e.g. the case with a pizza, and which are offered for sale in freezers or on cooling shelves, it is customary that these products are vacuum-packaged in a film. On the one hand, this type of film packaging provides for a longer life of the product contents on account of the small amount of residual oxygen due to evacuation and permits, on the other hand, due to the close contact of the film on the product that—for example in the case of a pizza—the topping, which is made up of many small products, is fixed so that it cannot shift during transportation and the product maintains its desired, optically appealing, shape. Such a fixation by way of the close-lying film is achieved through a great pressure difference relative to the atmosphere.
Specifically with skin packages, a thin upper film is heated in a sealing station of a deep-drawing packaging machine and the heated film is placed over the product. In the evacuating process and subsequently due to the pressure difference relative to the atmosphere said film will closely and gently nestle against the product. This is only possible in the case of evacuated packages. However, with many products it is neither possible, nor desired, to bring the products into contact with a heated upper film because this will negatively affect the cooling period, the storage life and the appearance of the product.
To considerably prolong the storage life of a product, such as a pizza, it is conceivable to evacuate the interior of the package according to the prior art and then to gas-treat it with a gas mixture, for instance nitrogen and carbon dioxide. This, however, will entail a package that will no longer tightly nestle against the product, thereby no longer fulfilling the function of fixing the product with the topping, for instance in the case of a pizza.
Packages have become known in which a cover film is deformed such that the film is formed towards the package bottom, thereby providing further room relative to the sealing plane, which room can be filled with further products, and subsequently a second cover film is flat-sealed onto the package mostly in a printed form. The formed cover film offers an enhanced stability of the whole package and a good reclosability of the package after products have been removed from the lower packaging chamber, as well as a reclosing of this chamber.
It is the object of the present invention to provide a method for operating a packaging machine in which the above-described drawbacks can be eliminated.
This object is achieved with a method comprising the features of claim 1 and with a packaging machine according to claim 7. Advantageous developments of the invention are indicated in the sub-claims.
The method according to the invention for operating a deep-drawing packaging machine comprises the following steps:
The method also comprises the (de)forming of the first cover film prior to supply into the first sealing station, so that the heating of the cover film needed for deformation can cool down to such an extent that it does not heat the food that is preferably cold or cooled during contact.
After the first sealing station a second cover film can be supplied into a second sealing station to be welded in the second sealing station to the first cover film and/or the packaging tray or to be fed into a joint sealing station with the first formed cover film. The space or chamber between the formed cover film and the second cover film can be evacuated and/or gas-treated.
The method according to the invention preferably comprises a controller which controls the amount of gas or gas mixture and/or the pressure inside the package containing the foodstuff, and by means of which the parameters gas pressure or gas amount are also adjustable. For instance, an optimal combination between prolonged storage life of the foodstuff through the gas amount or gas mixture and a fixation suited for the foodstuff by means of the force of the formed cover film acting on the foodstuff can be achieved because the pressure prevailing inside the packaging container is smaller than the outer atmospheric pressure.
A packaging container for foodstuff, particularly pizza, produced according to the method of the invention and comprising a formed packaging tray and a formed cover film fixes the foodstuff by means of the formed cover film, and the enclosed room is here gas-treated. This offers a longer storage life of the foodstuff together with a product fixation inside the packaging container at the same time so as to display the foodstuff not only in a lying position, but also in a standing or upright variant in a sales area.
In the absence of a product in the packaging container the distance of the bottom of the formed cover film from the packaging tray would be smaller than the product height. Without any atmosphere exchange inside the package this overlap will create a press force of the cover film on the product, whereby the product is fixed within the package. In the event of an atmosphere exchange by evacuation and gas treatment it is possible to control the gas amount and the gas pressure, respectively, inside the package in such a way that the formed cover film is not lifted to such an extent that the action of a force on the product is reduced too much, while the shelf life is prolonged at the same time.
To enable the formed cover film to adapt also to the contour of the upper side, the formed cover film is preferably configured to have a thickness ranging from 70 μm to 120 μm so as to fulfill the properties of the packaging container according to the invention, such as fixation of the product in the package, contact of the cover film with the upper side of the product, and fixation of the product add-ons located on the product. Film thicknesses outside the specified range are also feasible if the films are designed as multilayer films and corresponding properties, such as flexibility, can thus be chosen in a specific way.
According to the invention it is also possible to apply a second cover film that is preferably flat-sealed in the sealing plane with the packaging tray and the first cover film. This film can be designed as a printed variant, whereby information about the food positioned in the interior can be displayed, and it is also suited for the application of labels or for printing e.g. the best-before date.
The second chamber created thereby between first and second cover film can be evacuated and/or gas-treated and also filled with further products.
To permit a display of the foodstuff in an upright position, the packaging container preferably comprises a package bottom formed in an appropriate way for this. With a flat or linear shape provided at one side and in parallel with a side of the packaging container and with the packaging rim provided at the same side, an upright display e.g. on a cooling shelf is possible.
An advantageous embodiment of the invention shall now be explained in more detail with reference to a drawing.
Like components are provided with like numerals throughout the figures.
A second cover film 13 is drawn off from a material reservoir 14 and supplied to the second sealing station 4 and sealed in said station to the bottom film 9 and/or first cover film 11.
A discharge device 15 in the form of a conveyor belt with which finished isolated packages 16 are transported away is provided at the output side on the packaging machine 1. Furthermore, the packaging machine 1 comprises an advancing device (not shown) that laterally grips the first web-shaped material 9 and further transports it at the main work cycle cyclically in the operating direction R. The advancing device may e.g. be realized by laterally arranged transport chains.
A product 18 is inserted in the area of the insertion path 17. In the cover-film molding station 12 the first cover film 11 is formed such that the formed surface is oriented towards the product 18 during supply into the first sealing station 3 and also gets into contact with said product.
A partly (straight) edge 21 is here provided at a side of the package 16. The first formed cover film 13 is deep-drawn in the area of the package bottom in parallel with this edge, so that an edge 22 is formed. Both edges 21, 22 that are in parallel with each other form the standing surface for an upright or standing package 16.
In the first sealing station 3 the space 25 between the packaging tray 10 and the formed cover film 11 is evacuated and subsequently gas-treated again, so that the formed cover film 11 exerts a desired press force F on the product 18, 19. Said force F can be metered via the gas amount and the gas pressure, respectively, in the space 25 by means of a controller (not shown), preferably the machine controller. The parameters needed therefor can be entered by the operating personnel via an input unit (not shown) into the controller and stored. In an advantageous design it is possible to store the machine settings for different products and production methods in recipes.
The second cover film 13 is preferably applied to lie flat on both films 9 and 11 and is sealed with both films 9, 11. It is preferably colored to furnish information on the product 18, 19 and/or to provide a surface for labels 27 to be applied.
The properties of the first and second cover films 11, 13 may be different. The first cover film 11 is configured in a first design without a barrier layer and the second cover film 13 is made airtight. The space 26 between the two cover films 11, 13 may here be gas-treated so a to increase the press force F of the first cover film 11 on the product 18, 19, and thereby to be able to control or regulate the desired press force F in an improved way.
In a further variant, the package according to the invention is without a second cover film 13. The first cover film 11 is here made airtight preferably with a barrier layer. Labeling and/or printing can also be carried out on the underside of the package bottom.
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