Thermoplastic inflatable ball made from foil

摘要

Several (e.g. 6) thermoplastic sheets, all of same width, are fed continuously as a stack through a welding machine. Top and bottom sheets are laid flat, the others are folded once, with their folded edges all together and sandwiched between the top and bottom sheets. The layers are then welded in pairs, along curved arcs, trimmed outside the welds, and separated to form a hollow ball.