Abrißüberwachungseinrichtung für Papierbahnen

摘要

A cutting-off device and at least one tear detector are provided for cutting a web of paper in a press end of a paper machine, in response to a tear in the web of paper in a single-tier dryer end, the tear of the web of paper being recognized via a tear signal and transmitted to the cutting-off device. The tear detector has a transmission/reception base unit, which, on the one hand, at the start of a production cycle, or whenever a tear in the paper web is detected, records and stores the spectrum of the existing shade of color of the corresponding dryer felt, and possibly updates the stored shade of color at the time of subsequent tears. On the other hand, upon a later tear in the paper web, the base unit compares the shade of color of the dryer felt at the existing tear and the previously stored shade of color. If they match, the base unit activates the cutting-off device when (and only when) the stored shade of color of the dryer felt is recognized.