Unwinding unit and method for unwinding a strip of heat sealing material for forming boxes from blanks

A method for unwinding a strip of heat sealing material suitable for sealing the edges of side segments of a box forming blank juxtaposed to define a corner edge,

• comprising a step of pulling the strip along a feed path and in a feed direction, diverting it between an initial, horizontal stretch of the feed path and a final, vertical stretch of the feed path, defining a curved connecting stretch between the initial stretch and the final stretch, and making on the strip an extended crease line running along the strip itself starting from the curved stretch or downstream of the curved stretch, in the feed direction of the strip.

A method for forming a cardboard box from a flat forming blank comprising a base and a plurality of segments which can be folded relative to the base in such a way that edges of adjacent segments define vertical corner edges of a side wall of the box, comprising:

• carrying out the following steps for positioning a portion of the strip of predetermined length vertically to face each of the corner edges:
• pulling the strip along a feed path and in a feed direction, diverting it between an initial, preferably horizontal stretch of the feed path and a final, preferably vertical stretch of the feed path, defining a curved connecting stretch between the initial stretch and the final stretch, and making on the strip an extended crease line running along the strip itself starting from the curved stretch or downstream of the curved stretch, in the feed direction of the strip;
• heating and pressing each portion of the strip against the corresponding corner edge in order to heat seal it to, and thereby close, the corner edge itself.