Sheet formation process and wet end to produce a pulp web

Abstract

A sheet formation process and associated wet end to produce a pulp web with improved fibre orientation in a paper or board machine. A fluid is added to the pulp suspension from the side through openings ( 9, 9′ ) located after a turbulence block ( 3 ) in a headbox ( 1 ) at the machine wet end.

1 . A method of forming a sheet of pulp suspension to produce a pulp web in a paper or board machine with a wet end having a headbox ( 1 ) including turbulence block for depositing the pulp suspension on a wire moving in a machine running direction and a wire edge limitation ( 7 ) to prevent lateral edges of the deposited pulp suspension from flowing over lateral edges of the wire, wherein the improvement comprises adding a fluid at the lateral edges of the pulp suspension after the turbulence block ( 3 ). 
     
     
         2 . The sheet formation method according to  claim 1 , wherein the fluid is white water. 
     
     
         3 . The sheet formation method according to  claim 1 , wherein the fluid is a pulp suspension. 
     
     
         4 . The sheet formation method according to  claim 1 , wherein the fluid is a gas. 
     
     
         5 . The sheet formation method according to  claim 1 , wherein the fluid is added substantially in the machine running direction. 
     
     
         6 . The sheet formation method according to  claim 5 , wherein the fluid is added in the machine running direction at several successive points located one after the other, and the fluid addition at successive points is at one or both of a different flow velocity or different quantity rate. 
     
     
         7 . The sheet formation method according to  claim 6 , wherein the quantity rate or flow velocity of the fluid at the individual points increases in machine running direction. 
     
     
         8 . In the wet end of a machine to produce a pulp web, with a headbox ( 1 ) for depositing a pulp suspension on a wire moving in a machine running direction and a wire edge limitation ( 7 ) to prevent lateral edges of deposited pulp suspension from flowing over the lateral edges of the wire, wherein the headbox ( 1 ) includes a distributor ( 2 ), a turbulence block ( 3 ) and a headbox nozzle ( 5 ), and the wire edge limitation ( 7 ) directly adjoins the headbox nozzle ( 5 ), the improvement comprising fluid flow channels ( 10 ,  10 ′) with openings ( 9 ,  9 ′) in at least one of the wire edge limitation ( 7 ) and the headbox nozzle after the turbulence block ( 3 ). 
     
     
         9 . The wet end according to  claim 8 , where the openings ( 9 ′) are located in a side wall ( 8 ′) of the headbox nozzle ( 5 ). 
     
     
         10 . The wet end according to  claim 8 , where the openings ( 9 ) are located in a side wall ( 8 ) of the wire edge limitation ( 7 ). 
     
     
         11 . The wet end according to  claim 9 , wherein the flow channels ( 10 ,  10 ′) end at said openings ( 9 ,  9 ′) at the side wall ( 8 ,  8 ′) and are oriented substantially in parallel with the machine running direction. 
     
     
         12 . The wet end according to  claim 8 , wherein the openings ( 9 ,  9 ′) are provided on both lateral sides of the wet end as viewed in machine running direction. 
     
     
         13 . The wet end according to  claim 9 , wherein the side wall ( 8 ,  8 ′) has at least one recess ( 11 ,  11 ′) after each opening ( 9 ,  9 ′), which recess has a narrowing cross-section in the machine running direction, and the side wall ( 8 ,  8 ′) provides a guiding surface for the fluid added in the recess ( 11 ,  11 ′). 
     
     
         14 . The wet end according to  claim 8 , wherein at least three openings ( 9 ,  9 ′) are provided at each lateral side of the wet end, one after the other viewed in the machine running direction. 
     
     
         15 . The wet end according to  claim 10 , wherein the flow channels ( 10 ,  10 ′) end at said openings ( 9 ,  9 ′) at the side wall ( 8 ,  8 ′) and are oriented substantially in parallel with the machine running direction. 
     
     
         16 . The wet end according to  claim 10 , wherein the side wall ( 8 ,  8 ′) has at least one recess ( 11 ,  11 ′) after each opening ( 9 ,  9 ′), which recess has a narrowing cross-section in the machine running direction, and the side wall ( 8 ,  8 ′) provides a guiding surface for the fluid added in the recess ( 11 ,  11 ′).