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The present invention rela-tes to a method o~ making packages slip-proof.
Especially in connection with the transpor-t and storage of goods in packages, such as sacks and boxes, the problem of keeping the packages in a stacked position have caused substantial difficulties. The reason is to be found in the desire to stack the packages in high stacks which, however, presupposes that the stacking takes place with utmost care, and the fact that a great number of packages consist wholly or partly of plastic. Especially plastic bags and sacks, but also boxes of e.g. wellpap, have a smooth surface, which re-sults in that even one wrongly positioned package can make the whole stack tip over.
One way of avoiding this inconvenience consists of making the packages of a non-slip material. It has for example been suggested to manufacture such packages, especially sacks of a plastic material, wherein one surface has been made coarse for instance, by applying to an ordinary plastic foil a thin layer which forms an irregular net-like structure. This packaging material, which is suitable per se, is however primarily intended to be used for certain purposes, especially for sacks consisting entirely of this material, and the above mentioned disadvantages still remain when the packaging material consists e.g. of paper or cardboard.
`The present invention removes these disadvantages by ;
utilizing a plastic product of the above mentioned kind in such a way that it can be used also for packages made of any material, especially of cardboard and paper.
According to the present invention there is provided `` 30 a method of providing non-slippery areas on the normally ;slippery exterior surfaces of bags, sacks or the like flexible walled containers, comprising forming a non-slip plastic strip .
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by extruding a plastic foil in the form of a tube with a eoarse non-slippery net-like surface at least on one side of the foil, eutting the tube longitudinally to form a strip of the plastic foil, winding the strip into a eoil, pulling off a length of the eoil strip and removing a portion therefrom, and fixing the portion to the exterior surfaee of the container so that the coarse net-like surface, or one of the surfaces, of the portion lies outwardly.
The present invention thus provides a method of additionally treating the plastic product obtained in tube form so that it can be applied to any package in such areas whereby it, when stacked, transported or under similar conditions will eome into contaet with those surfaees with whieh sliding .
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might take place. These areas are primarily the upper and the lower surfaces of the package, which come into contact with the adjoining packages, and according to the invention it is thus possible to provide these surfaces with one or more strips of the non-slip material. It is also suitable to use these adhesive strips for closing the packages, the closing strips simultaneously forming a non-slip surface to which another package grips even when this has a smooth surface.
~lthough the invention also includes a method according to which the tubular plastic foil is cut so that only one or two flat plastic webs are obtained, which can be wound onto a corres-- ponding number of rolls, the method primarily comprises cutting the foil into a plurality of strips, which are wound onto easily managable separate rolls. According to one and the same method strips of varying width can be manufactured and it is also possible to wind strips of varying length onto the different I rolls.
¦ According to the invention the plastic foil can be made sticky either by applying thereto an adhesive, or by thermally softening (thermal sealing) those surfaces intended to come into engagement with the packages. The thermal softening can be effected by means of conventional devices which, if desired, can soften the whole area of the plastic foil or only those parts which are to stick to the packages, for instance, in form of bands, dots or lines.
The adhesive can be applied to the plastic foil after cutting up the same when this lies in one or in two planes one above the other, which foil webs thereafter or not until cut up ;~
into their final widths are fed over suitable adhesive rolls which apply adhesive to one of their surfaces. Naturally it is also ¦ possible to apply the adhesive by spraying or in any other known way and it is also possible after applying the adhesive -to dry
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the adhesive e.g. by feeding the foil over suitable heating rolls.
Thus, according to the above described method rolls are obtained wherein the coiled foil strip has its adhesive surface always engaging directly the norl-slip surface of the underlying layer. When desired the foil strips can also be provided with a conventional protective layer, which covers the adhesive surface and which is ripped off beEore using the strip. These protective coverings can be applied as a continuous layer onto the entire ! web width after providing the same with an adhesive layer, or alternatively after cutting the strips into their final width.
In the last mentioned case it is then possible to make the pro-tective layer somewhat wider than the foil strip which facilitates ¦ its removal.
It is also possible to provide the adhesive foil with reinforcing threads or a reinforcing net which is applied in connection with the application of the adhesive or in connection with the extrusion of the plastic foil.
As the manufacturex of the adhesive products in question are completely free to choose the width of the strips in any desired manner, it is understood that the expression "strip" also comprises fairly wide strips which are of importance when e.g.
cardboard boxes of predetermined dimensions are to be provided with such strips. The width of the strip can then be chosen exactly as desired, for example so that the whole bottom and/or top of the cardboard box is covered with a non-slip foil strip of corresponding size. It is, however, to be understood that also fairly narrow strips corresponding to the commonly used tape-strips, e.g. for closing packages, can provide a big enough non-slip surface which prevents the packages from sliding when in contact with slippery surfaces.
The adhesive strips may be wound up onto rolls in con-tinuous lengths, which are not cut into suitable lengths by means _ 3 _ :, .
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of conventional cutting devices until the strips are to be used.
It is however, also possible to provide the strips with trans-verse perforations so that adhesive s-trips of a predetermined length can be torn off. This perforation is made in a conventional manner and at any desired manufacturing stage. In case the adhesive surface is protected with a protective layer of paper or plastic, the perforations can include also this layer. It is also possible to stamp out from a wide foil provided with a ' protective layer variously shaped bodies such as triangular, circular, annular bodies and the like, which may be only per-forated in order to be separated completely only at time of use.