Package making – Methods – Conforming by stretching or shrinking of cover over contents
Patent
1998-02-06
2000-02-29
Johnson, Linda
Package making
Methods
Conforming by stretching or shrinking of cover over contents
53557, 533709, 533723, B65B 5302
Patent
active
06029423&
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a process for producing synthetic packaging, in particular by using sheets made of synthetic material, synthetic material projecting in areas of lateral edges of the goods to be packaged being heat-shrunk by means of heat supply. Further, the present invention concerns an apparatus for carrying out a process for producing plastic packaging.
Examples of methods and apparatus reflecting background art are disclosed in, inter alia, WO 84/03872 and DE-A-1 778 422.
Shrink synthetic packaging and processes for producing such shrink synthetic packaging are known in the state of the art. Sheets to be shrunk, using heat supply, around goods to be packaged, are placed around these goods or bundles and are shrunk in projecting lateral areas, which results in tight packaging. For this, only specific shrink sheets are used. A disadvantage of the known process is that the packaging is not suitable for all goods, especially not for heat-sensitive goods which deteriorate because of heat supply or, because of their sensitivity to heat, undergo a change in texture, melting or the like. Moreover, shrink packaging is not suitable for packaging having a large surface and produces a packaging edge which cannot be visually reproduced. The sheets shrink in an uncontrolled manner in areas which have heat applied to them, and partly produce very unpresentable edge areas. Finally, all known shrink-sheet packaging processes are not always economically applicable because of the time needed for complete shrinking.
Futhermore, it is known for sensitive goods also to be packaged in synthetic sheets which are stuck together.
Based on this state of the art, the present invention is aimed at improving a process for producing synthetic packaging of this type, which can be used on heat-sensitive goods and which can be used on extensive packaging areas, while producing a visually attractive and partly reproducible packaging edge.
This aim is achieved by the process and apparatus according to the appended claims. To achieve this aim, it is proposed by the present invention that heat supply be interrupted as soon as a shrinking process begins in a given area of synthetic packaging subjected to heat and that mechanical pressure be applied to heated areas of synthetic packaging immediately afterwards.
Using a process in accordance with the present invention, corresponding areas of synthetic packaging are not subjected to heat until they are fully shrunk, instead only until shrinking has just begun. This moment is not to be exactly mathematically recorded, instead it is a moment at which parts of the synthetic packaging begin to shrink while other parts have become soft because of the heat supplied. At this moment, mechanical pressure is exerted on the heated areas so that the parts melted or softened by heat supply join together in a flat form. A packaging edge produce in this way offers, in terms of packaging, sufficient mechanical holding, without as much heat needing to be supplied as may adversely affect heat-sensitive goods.
The present invention enables the use of synthetic packaging in general, which does not necessarily have to involve particular shrink sheets of a conventional type. A process in accordance with the present invention can also be used on heat-sensitive goods, as these are not subjected to heat.
An important field of use is the packaging of plastic items. It is known, for example, for plastic waste bags, in a rolled-up form, used also for congealing and frozen materials and the like, to be sold packaged such that the bundle rolls cannot be unrolled. For marketing reasons, it is desirable to use, for example, presentably printed plastic sheets to package such bundles. If conventional shrink sheets should be shrunk on in the lateral areas by a corresponding heat supply, bags in such bundles would simultaneously also be melted, whereby these would acquire at least an unattractive exterior. Such bundles can be packaged, in a visually attractive form, in plastic sheets, using a process in accordance
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patent: 5237796 (1993-08-01), Bonkowski
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FAS Converting Machinery AB
Johnson Linda
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