| 摘要 |
A method for the sealing of a cover strip onto packing containers, in particular non-returnable containers for liquid foodstuffs, which containers are of the type which are manufactured from laminated material comprising layers of, among others, thermoplastics, is disclosed. Packing containers of this type are generally provided with an opening arrangement in the form of a pouring opening punched out in the top side of the container, which is covered by a tear-off cover strip. The cut edge extending around the pouring opening is in this case situated inside the container which makes necessary special measures in order to prevent the occurrence of bacteria-collecting corners and pockets. This is a problem in particular in the relatively thick type of packing laminate which comprises layers of foamed thermoplastic material. It is often also necessary to seal off the free cut edge, since the laminate occasionally comprises layers which for various reasons must not come into contact with the contents. The difficulties are overcome in accordance with the invention in that the thermoplastic layers in the edge areas of the laminate adjoining the pouring opening are melted and made to flow over the edge and are joined on the one hand to one another, and on the other hand to the side of the cover strip facing towards the package. This is achieved by simultaneously heating and compressing the actual material area with the help of a mandrel and a holding-up tool and subjecting the material area to ultrasound. |
