Method and device for manufacturing and positioning upon a container an undercut thermoplastic lid, and container provided with such a lid

Method for manufacturing and positioning an undercut plastic lid made from a thermoplastic band upon a container, comprising the steps of:

• (a) applying a heated thermoplastic band against the lower edge of a forming bell with a holding clamp;
• (b) locating a container in a support, said container overhanging the upper portion of said support;
• (c) positioning the container and support beneath the part of the band delimited by the bell, and moving the container and support upwardly until the upper part of the support and the upper part of the container penetrate inside the bell, thereby stretching the heated band, the support cooperating with the bell to substantially close off the bell at the level of the lower face thereof, thus defining a stamping die or male forming mold for the part of the band between the inner lower edge of the bell and the upper container edge;
• and
• (d) creating a gas pressure inside an enclosure defined by the bell and the stretched band, and applying, under said pressure, the part of the band between the inner lower edge of the bell and the upper container edge against the outer face of the upper part of the container and the support.