Headbox for a paper or board making machine

Abstract

The invention relates to a headbox ( ) for a paper/boardmaking machine. The headbox ( ) including a stock flow header ( ) and, following the stock flow header, a piping system such as an inlet pipe manifold, and/or a turbulence generator ( ) and a tapered slice ( ), wherefrom the stock is passed onto the forming wire (H ). The construction of said headbox further includes a flow header (J) for a dilution liquid the flow header having connected thereto an inlet channel (S ), a return pipe (S ) and outlet channels (D , D , D , . . . ) that are distributed over the full length of said flow channel for passing the dilution water to control valves (V , V , . . . ) and, therefrom, further to different points along the cross-machine width of the headbox so as to mix with the stock delivered from the stock flow header ( ) in order to control the consistency of the stock to a desired value, thus accomplishing the control of the web basis weight profile in cross-machine direction over the headbox. The dilution water flow header (J) is structured to accomplish mixing of the dilution water flow (L ) so as to make the consistency of the dilution water flow (L ) homogeneous both along the entire length of the flow header (J) and in cross sections of the flow taken in planes perpendicular to the longitudinal axis of the flow header.