METHOD AND APPARATUS FOR CONTROL OF THE DRY LINE OR FOR CONTROL BASED ON THE DRY LINE IN A FOURDRINIER PAPER MACHINE

摘要

The system enables automatic observation of the dry line on the wire of the Fourdrinier paper machine on the basis of which one can carry out control actions. To produce an image in the range of the dry line on the wire, it illuminates the latter by means of a large diffuse illumination surface (20) of regular brightness. The material present on the fabric displacement (10) is shown in images by means of an optoelectric camera (40) on a detector, so that the surface of the pulp preceding the dry line and reflecting specularly is homogeneous and clear, while the surface of the reflective tape and following diffusely homogeneous but more matt and darker. The electrical image signal provided by the detector is transmitted to a computer (50) wherein the dry line is identified as the border line of said surfaces of different lights. These deviations from the target values ​​are determined for both the mean value and different values ​​in the transverse direction and the corresponding actuators are adjusted to control the paper web on the basis of differences observed for these different parts or its entire width. The dry line as well as quantities and values ​​characterizing the differences are also displayed on a display device, so that a human observer can also intervene at the controls.