| 摘要 |
<p>A folding device for the zigzag folding of a sheet, comprising two pairs of folding rollers (13, 14; 16, 17) which form folding nips (12, 15) and which are drivable alternately in opposite directions of rotation, and feed rollers (4, 5) which alternately feed a sheet for folding to the folding nips (12, 15). The speed of conveyance of the folding rollers (13, 14; 16, 17) is initially 120% of the speed of conveyance of the feed rollers and after passage of the leading sheet edge through the first folding nip (12) it is 110% of said speed of conveyance. After each reversal of the direction of rotation of the folding rollers (13, 14; 16, 17) the speed of conveyance of the folding rollers is initially 110% of the speed of conveyance of the feed rollers (4, 5) and shortly after passage of a fold made in the associated folding nip (15, 12) it is 100% thereof. For realising a desired folding length the set process time between the start of a folding cycle and the change of the direction of drive of the folding rollers (13, 14; 16, 17) is automatically adjusted in dependency of this folding length (V) and the total sheet length (L). <IMAGE></p> |
