Patent ID: 6916404

Claim:
A method for web threading in a drying section of a machine, the method comprising a first phase and a second phase; the first phase comprising: forming and at least one second strip by cutting a full-width web coming to a cylinder drying group of the drying section, and guiding the leader forward in the drying section from a first drying cylinder of the cylinder drying group where the web can be run down, and the second phase comprising spreading the leader to the width of the full-width web, wherein an underpressure box is arranged at an opening gap between said first drying cylinder and a drying wire, such that the underpressure box is on a side of the drying wire away from the web, whereby the underpressure box is capable of directing an underpressure p 1 against the web and the underpressure p 1 is controllable in a cross direction of the machine, said underpressure box creates an underpressure region between the leader and the underpressure box, the underpressure region having underpressure p 1 at a detachment point located in an area where the drying wire is detached from said first drying cylinder, and the underpressure p 1 is sufficient to detach the leader from said first drying cylinder or to aid in making the leader follow the drying wire, and a protection zone is provided between the underpressure region and a region adjacent to the underpressure region, the protection zone having a barrier between the underpressure region and the region adjacent to the underpressure region, the region adjacent to the underpressure region has a pressure p 2 that is different from the underpressure p 1 and which is an underpressure of lesser magnitude than the underpressure p 1 , a zero pressure, or an overpressure, in order to maintain the underpressure p 1 in the underpressure region.