| 摘要 |
A rotatable knife roll with at least one foil knife secured on a portion of the body of the roll and having a sharp and endless cutting edge closed within itself to cut out window openings. There are breakthroughs for suction apertures arranged within the cutting edge. There is at least one suction-air control valve arranged on the face side of the roll body. The valve is rotatable relative to this portion of the roll. The suction-air control valve has at least one suction-air-control channel and at least one fresh-air channel. There are suction apertures for temporarily retaining a letter envelope blank over a suction and transport angle zone alpha, and for retaining a piece of material cut out by the foil knife across a suction and transport angle zone beta. The suction apertures are arranged in rows to which suction channels are allocated in the part of the roll body. The suction apertures are connected with the suction-air control channel and the fresh-air channel by the suction channels for conducting air. A 3/3-way valve is associated with the suction channel upstream of the suction-air control valve, with an open position for each suction and transport angle zones alpha, beta, and one common closing position for suction and transport angle zones alpha and beta.
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