Paper machine edge fiber alignment control by angled headbox sides

摘要

A headbox is provided which provides an improved uniformity in the velocity profile of the stock solution across the slice opening. As a result, improved fiber alignment is provided across the width of the entire slice opening and mis-alignment of the fibers towards the outer edges of the slice opening is avoided. The headbox includes an improved nozzle design with pondsides that are not parallel to one another but which are angled inwardly as they extend from the tube bank to the slice opening. Further, several columns of outer tubes of the tube bank may also be angled inwardly as they extend from the header to the nozzle section. The center tubes would be disposed in a parallel relationship to one another. A sealing arrangement is provided between the roof of the nozzle section and the pondside which permits the incorporation of a double knuckle for extending and retracting the roof to adjust the L/b ratio. In an alternative embodiment, the roof includes a rectangular extraction which is retracted and extended by a double knuckle and which needs no special sealing arrangement between the extension and the pondsides.