Method for folding sheet-shaped plastic material and folded sheet-shaped plastic material obtained by carrying out this method

摘要

Method for forming a folded sheet of plastic with reinforcing ribs disposed transverse to the line of fold. The line of fold or weakening line is provided with a plurality of weakening grooves separated by unweakened material of the sheet. When the sheet is folded, unweakened material is drawn out to form reinforcing ribs transverse to the weakening line and in the dihedral angle of the fold. The length of the unweakened material between the grooves is dimensionally variable to provide an adjustable resistance to folding.