Method of operating a headbox apparatus for a papermaking machine

A method of operating a headbox apparatus for a papermaking machine defining a predetermined machine direction and a predetermined web width, said method comprising the steps of:

• infeeding a fiber stock suspension into the headbox apparatus and sequentially passing said infed fiber stock through a distribution box, a diffusor system and a nozzle chamber of the headbox apparatus and thereby producing a paper web having a predetermined web width;
• said step of passing said infed fiber stock through said distribution box entails distributing said infed fiber stock suspension across the predetermined web width;
• said step of passing said infed fiber stock suspension through said diffusor system entails throughpassing the infed fiber stock suspension through a plurality of diffusor channels of said diffusor system;
• said step of passing said infed fiber stock suspension through said nozzle chamber entails throughpassing said infed fiber stock suspension through a delivery slice of said nozzle chamber and thereby distributing said infed fiber stock suspension at substantially a predeterminate weight per unit area distribution across said predetermined web width;
• preselecting a predeterminate opening width of said delivery slice of said nozzle chamber;
• said step of passing said infed fiber stock suspension through the headbox apparatus, entails passing said infed fiber stock suspension through said headbox apparatus at a predeterminate flow rate and in a flow direction defining substantially horizontal flow direction components;
• during said step of passing said infed fiber stock suspension through said headbox apparatus, flow-controlling the throughpassage of said infed fiber stock suspension through said headbox apparatus and thereby establishing said predeterminate weight per unit area distribution of said infed fiber stock suspension across said predetermined web width, said predetermined flow rate of said infed fiber stock suspension across said predetermined web width, and the alignment of said substantially horizontal flow direction components of said flow direction of the infed fiber stock suspension with the predetermined machine direction across said predetermined web width;
• said flow controlling step comprising the steps of:
• adjusting said preselectable opening width of the delivery slice of said nozzle chamber in a manner such that there is obtained said predeterminate weight per unit area distribution across said predetermined web width;
• controlling said predeterminate flow rate of said infed fiber stock suspension across said predetermined web width and the alignment with said predetermined machine direction of said substantially horizontal flow direction components of the flow direction of said infed fiber stock suspension across said predetermined web width;
• substantially simultaneously carrying out said steps of controlling said predeterminate flow rate and the alignment with said predetermined machine direction of said substantially horizontal flow direction components of said infed fiber stock suspension and adjusting said preselectable opening width of the delivery slice of said nozzle chamber;
• said step of passing said infed fiber stock suspension through said nozzle chamber entails sequentially passing said infed fiber stock suspension through an inlet region flow communicating with said diffusor system and an outlet region flow communicating with said delivery slice;
• said step of sequentially passing said infed fiber stock suspension through said inlet region and said outlet region of said nozzle chamber, entails the step of passing therethrough said infed fiber stock suspension at respective flow rates and under respective pressures;
• said step of controlling said predeterminate flow rate and said alignment of said substantially horizontal flow direction components of said infed fiber stock suspension entails substantially equalizing the flow rates and the pressures prevailing in said inlet region and in said outlet region of said nozzle chamber across said predetermined web width;
• selecting as said distribution box, a distribution box having a predetermined width and predetermined geometrical dimensions;
• selecting as said diffusor system and said nozzle chamber, a diffusor system and a nozzle chamber each of which has predeterminate geometrical dimensions;
• said step of passing said infed fiber stock suspension through said distribution box including the step of passing said infed fiber stock suspension through said distributing box at a predeterminate pressure profile across said predetermined width of said distribution box;
• said step of controlling said predetermined flow rate and said alignment with said predetermined machine direction of said substantially horizontal flow direction components of said infed fiber stock suspension across said predetermined web width including the step of varying at least one of (i) said pressure profile prevailing in said distribution box, (ii) the geometrical dimensions of at least one of said distribution box, said diffusor system and said nozzle chamber, and (iii) the throughpassage of said infed fiber stock suspension through at least one of said distribution box, said diffusor system and said nozzle chambers;
• said step of controlling said predeterminate flow rate and said alignment of said substantially horizontal flow direction components of said infed fiber stock suspension entails throughpassing a predeterminate fluid through throughpass means distributed across said predetermined width of said distribution box;
• said step of controlling said predetermined flow rate and said alignment of said substantially horizontal flow direction components of said infed fiber stock suspension further entailing the step of controlling the throughpass of said predeterminate fluid through said throughpass means;
• said step of controlling said throughpass of said predeterminate fluid through said throughpass means entailing the step of controlling at least one of (i) said predeterminate pressure profile prevailing in said distribution box across said predetermined width of said distribution box and (ii) the quantity of said infed fiber stock suspension delivered by said distribution box;
• said step of throughpassing said predeterminate fluid through said throughpass means entails outfeeding a predeterminate portion of said infed fiber stock suspension through said throughpass means constituting fiber stock suspension outfeed means;
• selecting as said fiber stock suspension outfeed means, fiber stock suspension outfeed means containing a reservoir;
• arranging said reservoir at a predetermined elevation relative to said distribution box;
• interconnecting said reservoir and said distribution box by a plurality of connecting conduits of said fiber stock suspension outfeed means extending into said reservoir by means of a variable length end portion remote from said distribution box at each one of said plurality of connecting conduits;
• and
• said step of controlling said throughpassage of said infed fiber stock suspension through said fiber stock suspension outfeed means entailing the step of adjusting in the manner of an elevationally adjustable overflow weir each one of said variable length end portions of said plurality of connecting conduits.