Method and apparatus for producing finished foam containers

DETAILED DESCRIPTION A convolute roll of elongated preprinted stock of longitudinally oriented heat shrinkable material such as polystyrene foam sheet is formed into a cylindrical container blank.
Similarly, a disc shaped bottom blank is also formed from a like material.
A series of final forming mandrels are carried on an endless chain or turret and are shaped in cross-section like a desired ultimate container such as a cylindrical food can with a rounded bottom edge or a frustro-conical drinking cup.
In a preferred embodiment, the mandrels have the shape of a dual tapered frustro-conical drinking cup.
This dual taper of the mandrel allows the finished container to also be dual tapered, allowing a plurality of the finished containers to have a reduced stack height for shipping and distribution.
This dual tapered feature is also used to prevent the stacked cups from sticking together.
A bottom blank may be placed on each of the final forming mandrels and held there by vacuum while the sidewall of the ultimate container, namely, the cylindrical blank is transferred from a cylindrical blank forming station onto the final forming mandrel.
As the mandrel is driven by endless chain or a rotary turret, the mandrel moves to a cylindrical blank tamper assembly which tamps the cylindrical blank securely onto the final forming mandrel upon which clamps are provided to securely fasten the cylindrical blank.
The mandrel then moves past a series of radiant heaters which progressively shrink and soften the bottom blank and cylindrical blank to form a container having a shape corresponding to the final forming mandrel.
In all cases, in the preferred embodiments of the present invention, the cylindrical blanks exceed the axial length of the final forming mandrels such that the bottom edge of the sidewall shrinks around the outer edges of the bottom blank to provide a heat-sealable bottom seam.
The final heat sealing is effected by any suitable heating means such as a conformally shaped bottom ironer.
In the preferred embodiments of the present invention, a generally frustro-conical or cup-shaped container is desired