Method and apparatus for manufacturing a container having an inner end closure

A method for manufacturing a can-like container comprising a sleeve formed container jacket and an end closure for at least one end of the jacket, at least one of the container jacket and the end closure being made of a material comprising a base layer of cardboard material or a similar stiff material which does not absorb high frequency current energy and a further layer, located on the base layer, and fabricated of a material which can absorb high frequency current energy and at least one of the common surfaces of the jacket and the at least one end closure of the container to be manufactured comprising a weldable layer of a material which can be welded using high frequency current energy, said method comprising:

• making said container jacket out of a planar punched blank which is formed into the container jacket;
• placing said container jacket in a jacket carrier which supports the jacket at least adjacent the open end thereof;
• making said end closure out of a planar punched blank which is formed into a cup form end closure having a planar bottom and, extending from said bottom, an upwardly and outwardly projecting closure rim extending around the end enclosure, said end closure being formed from said planar punched blank by being pressed through a formation ring to form said end closure into a cup form shape having a planar bottom of a size which is slightly smaller than the internal cross section of the open end of said container jacket;
• pressing the end closure down into an open end of the container jacket by means of a press piston to form a common surface between the jacket and the end closure rim;
• resiliently compressing a part of the height of the common surface between the jacket and the end closure rim at a location intermediate the extremities of said common surface with greater pressure than the remaining parts, while maintaining the end closure and the jacket axially motionless in relation to each other, by expanding an expandable press ring, having a surface of curved convex shape in cross section for contacting the end closure rim and forming a part of the press piston, when the latter is in the pressed down position thereof so as to press the end closure rim and the corresponding jacket portion into engagement with each other over said part of the height of said common surface;
• applying a high frequency current across the common surfaces between the jacket portion and the end closure rim until the at least one weldable layer thereof is melted while maintaining said pressure on said part of the height of the common surface between the jacket and the end closure rim;
• cutting off the high frequency current;
• allowing the weld to solidify;
• and retracting the expandable press ring and moving the press piston out of the closed container end.