Method and apparatus for use in a paper machine in the lateral alignment of the cross-direction quality profile of a web manufactured by the machine

摘要

The invention relates to a method and apparatus for the lateral alignment of the cross-direction profile control of a web (W) as required by a papermaking process. According to the method, a certain cross-direction profile of a dried web, particularly the basis weight profile thereof, to be aligned is gauged. The profile measurement signal (BW) thus obtained is taken to the control system (45) of the paper machine which provides a control signal (C) suited to control the adjustment means (321-32N; 241-24S) of said cross-direction profile control provision. According to the invention, the web (W) is provided with at least one marker line (M;M1-MR), whose lateral shift ( DELTA x) or shifts ( DELTA xi) is/are detected at the measurement point (40) of said cross-direction profile of the dried web (Wd), or in the vicinity thereof. The detection of said detected lateral shift(s) ( DELTA x; DELTA xi) is used to generate a measurement signal (M( DELTA x)) of said shift(s) which signal is employed to control the lateral alignment of the web profile adjustment provision. The information obtained from said detected lateral shift(s) ( DELTA x; DELTA xi) is then used in the control of the lateral alignment of the consistency profile control provision adapted in conjunction with the paper machine headbox (10). The marker agent used to make the marker line (M;M1-MR) is injected to the stock at the inlet side of the stock feed channel to the paper machine headbox (10), most advantageously close to the control valve set (321-32N) of the consistency profile control provision.