Web-wide Cutting Knife

With the winding concepts, where the nip between drum and finished roll is opened, the web can be cut with a web-wide knife operated in the open draw. As the new spool is already wrapped by the web, the system is self-threading. The system has a very high tum-up efficiency and is mainly applied for lower and medium basis weights up to about 120 g nT.  

The air-supported tum-up systems have their main applications at basis weights up to 100 g nr, or in special cases up to 150 g m . A blowpipe formed like a gooseneck gave the name to one of these turn-up systems. A small cut of a few centimeters in the cross machine direction will be created, e.g. with a needle, in the middle of the web before the drum. The thus weakened web can be blown by the gooseneck blowpipe to the empty reel spool. The tear in the cross direction will be supported by two nozzles blowing from the middle to the edges between the primary and the secondary nip. 

For very small paper machines one or two blowpipes in the cross direction, positioned at the edges after the primary nip, are sufficient. They cut the web from the edges and transfer it to the empty spool. The so-called Cobra system can also be used to support the gooseneck for large paper web widths. 

The air-supported systems only need compressed air as a medium and they have a quite simple design. As web cutting is not clearly defined the tum-up quality depends on the paper properties and the machine speed. As a further consequence some bottom broke may occur. 

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