Means and method for production of box blanks, boxes formed therefrom and apparatus useful therewith

A method for forming rigid cartons from flat blanks coated wholly or in part with a varnish containing thermoplastic solids in an amount sufficient to constitute a bonding medium when activated by heat, said blanks being die cut to provide base, side, end, and overlapping flap elements, said method comprising

• placing the blank over an open female forming die so made as to define the corners of the carton base element, and to fold inward the side, end, and overlapping flap elements,
• pressing the blank into the said open forming die with a plunger having projections on those of its surfaces which face each pair of carton elements which are to be bonded,
• bringing the flat face of a sonotrode against the outer of each pair of elements to be bonded with pressure sufficient to cause the projections on the surfaces of the plunger opposite to compress the said pair of elements in contact therewith, thereby reducing the distance between each sonotrode and the anvil at the welding interfaces of the pair of elements to be bonded,
• energizing the sonotrodes to heat the bonding medium to at least a tacky state,
• deenergizing the sonotrodes while holding them under pressure against the outer surfaces of the formed carton until the bond has been effected,
• and withdrawing the sonotrodes to their initial positions.