| abstract |
A running web of cigarette paper or the like is perforated in a first portion of its path, thereupon tested for permeability by a pneumatic detector in a second portion of the path, and finally tested for permeability by an optical detector in a third portion of the path. Signals which are generated as a result of pneumatic testing are used to adjust the perforating unit in the first portion of the path. Signals which are generated as a result of testing by the optical detector are compared with a reference signal denoting the desired permeability of the web, and the web and perforating unit are arrested, or the cigarettes which contain defective portions of the web are segregated from satisfactory cigarettes, if the deviation of generated signals from the reference signal exceeds a threshold value. |