Package making – Methods – Forming a cover adjunct or application of a cover adjunct to...
Reexamination Certificate
1999-08-30
2002-08-06
Rada, Rinaldi I. (Department: 3721)
Package making
Methods
Forming a cover adjunct or application of a cover adjunct to...
C053S452000, C053S455000, C053S133800, C493S212000
Reexamination Certificate
active
06427420
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for the manufacture of a pack, particularly intended for undergoing preservation treatment, from at least one film comprising two plastic layers, an upper and a lower, which form the outer and inner faces of the said pack, and a light-metal central layer sandwiched between the said upper and lower layers.
It also relates to a flexible pack, particularly intended for undergoing preservation treatment, especially after it has been filled and closed, comprising two flanks connected at their lateral edges, each flank comprising plastic inner and outer faces and a light-metal central layer sandwiched between the two inner and outer faces, the said pack being produced particularly by such a method.
The invention is used especially advantageously in the production of pouches or bags containing food substances, particularly food substances for animals, such pouches or bags being intended to be closed hermetically by welding and treated thermally after being filled and closed.
2. Description of the Prior Art
At the present time, such packs have various forms.
They may be flat with three or four welds or gusseted with three welded sides or three welded sides and a gusset-shaped welded bottom.
Such packs may also comprise two lateral gussets or two gussets positioned at the top and bottom of the pack with welded lateral edges.
These packs may be sterilized by being heated in a humid atmosphere or under pressure.
In order to withstand such thermal treatment, they are produced from one or more films having a special structure.
More especially, they are usually manufactured from one or more films, each film comprising an upper layer and a lower layer which are intended for forming the outer and inner faces of the said packs, the said outer and inner faces being produced from plastic, and a central layer sandwiched between the said upper and lower layers, the said central layer being produced from light metal.
In general, the upper layer is a polyethylene terephthalate layer combined or not with a polyamide layer. The central layer is produced from aluminium and the lower layer is a polypropylene layer combined or not with a polyamide layer.
Between each layer is provided an adhesive coating making it possible to connect the various layers to one another.
Moreover, the polyethylene terephthalate layer may be printed on its inner face.
The polyethylene terephthalate layer serves generally as a printing support and gives the packet's external appearance.
The aluminium central layer forms a barrier to gas, particularly to oxygen and steam, so as to insulate from outside the substances which are contained within the pack.
The polyamide layer forms an anti-perforation layer, when this is necessary in accordance with the subsequent uses of the pack, and the polypropylene layer serves as a welding agent for making the pack, gives the pack general mechanical stability and ensures sealing at the welds of the said pack.
Such packs may contain solids of a moist nature, liquids or else a combination of solid and liquid.
Some packs may comprise a start-off-tear notch on their lateral edges. In this case, this notch is made in a lateral weld of the pack that makes it possible to open the latter by tearing.
These already known packs have some disadvantages, particularly with regard to the method of opening them.
In fact, it is not very practical to use a cutting tool of the type of a pair of scissors or a knife, since, for example, this tool may be soiled by the product contained within the pack.
When the pack can be opened by tearing, started with the aid of a start-off-tear notch, the tearing force has to be relatively great and sometimes makes it necessary to employ a tool.
In fact, the tearing force of a multi-layer film usually depends on the tearing force of the materials forming the pack and on the adhesive force between the various layers forming the said pack, and these forces may be adversely affected after the latter has undergone preservation treatment.
The tearing direction is generally propagated in the flanks of the pack in a non-oriented manner. Thus, either partial opening of the pack is obtained, or there is a tear below the level of the product contained in the pack, thereby causing this product to flow out undesirably.
In order to attempt to overcome the above-mentioned disadvantages, mainly regarding the opening of these packs, packs have already been provided which comprise on the outer faces of their flanks a precut made by laser.
Such packs are described, in particular, in the documents EP-540,184, EP-473,517, U.S. Pat. No. 5,158,499 and U.S. Pat. No. 5,630,308.
However, the main disadvantage of this precut, carried out by applying a laser beam to the outer face of the flanks of the pack, is that it adversely affects the external appearance of the pack, once the latter has been produced.
Moreover, document U.S. Pat. No. 5,000,321 discloses a pack which comprises on its outer and inner faces weakening zones which are produced by means of a laser beam. These weakened zones are obtained by thinning the layers forming the outer and inner faces of the said pack.
However, such a system is not entirely satisfactory, since the weakening of the layers forming the outer and inner faces of the pack may be insufficient to bring about an exact and directed opening of the pack.
SUMMARY OF THE INVENTION
The present invention, then, provides a new method for the manufacture of a pack, particularly intended for undergoing preservation treatment, which makes it possible to produce a pack having easy and guided opening over its entire width.
More especially, according to the invention, there is provided a method for the manufacture of a pack, particularly intended for undergoing preservation treatment, from at least one film comprising two plastic layers, an upper and a lower, which form the outer and inner faces of the said pack, and a light-metal central layer sandwiched between the said upper and lower layers. It is characterized in that, prior to the operations to make the said pack, a laser beam is applied solely to the lower layer of the said film, the said lower layer forming the inner face of the said pack, in order to produce, virtually in the entire thickness of the said lower layer, at least one perforation forming at least one precut line.
Within the scope of the present invention, by preservation treatment will be meant any treatment known to the average person skilled in the art, especially thermal treatments, such as conventional sterilization, flash sterilization and pasteurization.
Thus, according to the invention, the lower film layer forming the inner face of the pack is embrittled along a defined line by the application of a laser beam. The laser beam is absorbed by the plastics forming the lower layer of the film and is reflected totally by the light-metal central layer. In the region of the impact of the incident beam, the materials are heated, melt and evaporate. This results in a perforation of the lower layer as far as the light-metal layer along the laser beam application line.
When the pack produced according to the manufacturing method is opened, the tear is propagated along the precut line thus made and continues along this line over the entire width of the pack.
Directed and exact opening of the pack is thus obtained.
According to one embodiment of the method according to the invention, each perforation is a continuous perforation which extends over part of the width of the film.
According to another preferred embodiment of the method according to the invention, each perforation is a succession of micro-perforations forming a precut line.
The perforation on the lower film layer forming the inner face of the pack advantageously makes it possible to avoid adversely affecting the central layer and the outer face of the pack and to maintain the long-term sterilization performances of the pack thus produced.
The production of micro-perforations in the form of dots makes it pos
Blanchard Daniel
Ferry Vincent
Lefebvre Jean-François
Olivieri Alain
Dorsey & Whitney LLP
Rada Rinaldi I.
Tawfik Sameh
Unisabi
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