An apparatus for an optional cross folding of successively following, sequentially printed sheets, comprising:
- a first transport segment on which the sequentially printed, first printed sheets to be cross-folded and second printed sheets not to be folded, are transported successively in a guide plane and are respectively made available in a folding position;
- at least two folding rolls arranged on a first side of the guide plane which respectively include a rotational axis and together define a folding gap therebetween for cross folding the first printed sheets, wherein the rotational axes are oriented substantially parallel to each other and parallel to the guide plane;
- a compressed air device oriented substantially parallel to the rotational axes of the folding rolls on a second side of the guide plane and arranged opposite the first side of the guide plane and in a region of the folding gap, wherein the compressed-air device is connected to a compressed air source and a control unit, and includes at least one exit opening for focusing compressed air onto the folding gap;
- a second transport segment for cross-folded first printed sheets and a third transport segment for non-folded second printed sheets, wherein the first, second and third transport segments have a joint first segment point at which the first transport segment ends and the second and third transport segments start, wherein the joint first segment point is positioned on a line of intersection between the guide plane and a folding plane that extends through the at least one exit opening of the compressed air device;
- wherein the compressed air device includes a first control element connected to the control unit for optionally triggering or suppressing a compressed air blast coming from the at least one exit opening of the compressed air device, such that respectively starting with the folding position, one of the first printed sheets is moved for the folding operation into the second transport segment or one of the second printed sheets bypasses the folding operation and is moved to the third transport segment;
- wherein the third transport segment empties downstream of the folding rolls into the second transport segment, at a joint second segment point;
- and
- further including a fourth transport segment downstream of the joint second segment point that adjoins the second and third transport segments at the joint second segment point;
- wherein the third transport segment is longer than the second transport segment or can be operated at a slower speed than the second transport segment such that a first sequence of printed sheets, following successively on the first transport segment, is identical to a second sequence of first cross-folded sheets and second non-folded printed sheets following successively on the fourth transport segment.