Headbox for a machine to produce a fiber web

Abstract

Headbox for a machine to produce a fiber web, in particular a paper, cardboard or tissue web from at least one fibrous suspension, having a headbox nozzle comprising an upper nozzle wall and a lower nozzle wall, as well as two side walls tapering to form an outlet, and having an inner chamber through which the fibrous suspension flows in flow direction during operation of headbox, whereby on upper nozzle wall of headbox nozzle a baffle is arranged on the outlet side which is movable by way of several elements and which extends across machine width, and which has a baffle protrusion and a baffle immersion depth and which has at least two surfaces—an upstream ramp surface and a subsequent main surface contacted by a fibrous suspension during operation of headbox. The inventive headbox is characterized in that between ramp surface of baffle and main surface of baffle at least one refraction surface which is in contact during operation of headbox with a fibrous suspension is provided on baffle.

1 . A headbox for a machine to produce a fiber web from at least one fibrous suspension, said fiber web being one of a paper web, a cardboard web, and a tissue web, said headbox comprising:
 a headbox nozzle including an upper nozzle wall, a lower nozzle wall, two side walls tapering to form an outlet, and an inner chamber through which the fibrous suspension flows in a flow direction during an operation of the headbox, said upper nozzle wall including an outlet side;   a baffle, on said upper nozzle wall of said headbox nozzle said baffle being arranged on said outlet side, said baffle being movable by way of a plurality of elements, said baffle extending across a machine width, said baffle having a baffle protrusion and a baffle immersion depth, said baffle having at least two surfaces which include an upstream ramp surface and a subsequent main surface contacted by the fibrous suspension during said operation of the headbox, said baffle including thereon at least one refraction surface which is between said ramp surface of said baffle and said main surface of said baffle and which is in contact during said operation of the headbox with one said fibrous suspension.   
     
     
         2 . The headbox according to  claim 1 , wherein said refraction surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox, viewed in said flow direction of the at least one fibrous suspension, has a convex curved surface shape with a curvature radius in a range of 0.1 to 5 mm. 
     
     
         3 . The headbox according to  claim 1 , wherein said refraction surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox, viewed in said flow direction of the at least one fibrous suspension, has a convex curved surface shape with a curvature radius in a range of 0.5 to 3 mm. 
     
     
         4 . The headbox according to  claim 1 , wherein said refraction surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox, viewed in said flow direction of the at least one fibrous suspension, has a convex curved surface shape with a curvature radius of 1 mm. 
     
     
         5 . The headbox according to  claim 1 , wherein said refraction surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox, viewed in said flow direction of the at least one fibrous suspension, has a convex curved surface shape with a curvature radius in the range of ≧5 mm. 
     
     
         6 . The headbox according to  claim 1 , wherein said refraction surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox, viewed in said flow direction of the at least one fibrous suspension, has a planar surface shape with a surface length in a range of 0.2 to 2 mm and an angle bisecting surface arrangement. 
     
     
         7 . The headbox according to  claim 6 , wherein said surface length is in a range of 0.5 to 1.5 mm. 
     
     
         8 . The headbox according to  claim 6 , wherein said surface length is 1 mm. 
     
     
         9 . The headbox according to  claim 6 , wherein said baffle includes an infeed-side refraction side surface and an outlet-side refraction side surface, said infeed-side refraction side surface being located upstream from said refraction surface of said baffle, said outlet-side refraction side surface being located subsequent to said refraction surface of said baffle, said refraction surface being in contact with the fibrous suspension during said operation of the headbox. 
     
     
         10 . The headbox according to  claim 1 , wherein said upper nozzle wall includes an inside surface, said main surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox being aligned parallel to said inside surface of said upper nozzle wall of said headbox nozzle. 
     
     
         11 . The headbox according to  claim 1 , wherein said upper nozzle wall includes an inside surface, said main surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox being aligned below a divergent angle of up to 15° to said inside surface of said upper nozzle wall of said headbox nozzle. 
     
     
         12 . The headbox according to  claim 11 , wherein said divergent angle is up to 10°. 
     
     
         13 . The headbox according to  claim 11 , wherein said divergent angle is up to 5°. 
     
     
         14 . The headbox according to  claim 11 , wherein said ramp surface of said baffle and said inside surface of said upper nozzle wall of said headbox nozzle encompass an angle in a range of ≦150°. 
     
     
         15 . The headbox according to  claim 11 , wherein said ramp surface of said baffle and said inside surface of said upper nozzle wall of said headbox nozzle encompass an angle in a range of ≦135°. 
     
     
         16 . The headbox according to  claim 11 , wherein said ramp surface of said baffle and said inside surface of said upper nozzle wall of said headbox nozzle encompass an angle in a range of ≦120°. 
     
     
         17 . The headbox according to  claim 1 , wherein said baffle protrusion is in a range of >0 to 10 mm. 
     
     
         18 . The headbox according to  claim 1 , wherein said baffle protrusion is in a range of 1 to 6 mm. 
     
     
         19 . The headbox according to  claim 1 , wherein said baffle protrusion is in a range of 2 to 5 mm. 
     
     
         20 . The headbox according to  claim 1 , wherein said baffle has a baffle thickness in a range of 10 to 40 mm. 
     
     
         21 . The headbox according to  claim 1 , wherein said baffle has a baffle thickness in a range of 12 to 25 mm. 
     
     
         22 . The headbox according to  claim 1 , wherein said lower nozzle wall of said headbox nozzle, viewed in said flow direction of said at least one fibrous suspension, has a protrusion in a range of 6 to 30 mm compared to said baffle. 
     
     
         23 . The headbox according to  claim 1 , wherein said lower nozzle wall of said headbox nozzle, viewed in said flow direction of said at least one fibrous suspension, has a protrusion in a range of 12 to 25 mm compared to said baffle. 
     
     
         24 . The headbox according to  claim 1 , wherein said main surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox is arranged at a vertical distance of at least 6 mm from said lower nozzle wall of said headbox nozzle. 
     
     
         25 . The headbox according to  claim 1 , wherein said main surface of said baffle which is in contact with the fibrous suspension during said operation of the headbox is arranged at a vertical distance of at least 12 mm from said lower nozzle wall of said headbox nozzle. 
     
     
         26 . The headbox according to  claim 1 , further including a plurality of lamellas which are arranged in said headbox nozzle, the headbox including an area of said baffle, said plurality of lamellas including a plurality of downstream lamella tips which are located in said area of said baffle. 
     
     
         27 . The headbox according to  claim 1 , wherein the headbox is a multi-layer headbox having at least one separator element. 
     
     
         28 . A machine to produce a fiber web from at least one fibrous suspension, the fiber web being one of a paper web, a cardboard web, and a tissue web, said machine comprising:
 at least one headbox including:
 a headbox nozzle including an upper nozzle wall, a lower nozzle wall, two side walls tapering to form an outlet, and an inner chamber through which the fibrous suspension flows in a flow direction during an operation of said headbox, said upper nozzle wall including an outlet side; 
 a baffle, on said upper nozzle wall of said headbox nozzle said baffle being arranged on said outlet side, said baffle being movable by way of a plurality of elements, said baffle extending across a machine width, said baffle having a baffle protrusion and a baffle immersion depth, said baffle having at least two surfaces which include an upstream ramp surface and a subsequent main surface contacted by the fibrous suspension during said operation of said headbox, said baffle including thereon at least one refraction surface which is between said ramp surface of said baffle and said main surface of said baffle and which is in contact during said operation of said headbox with one said fibrous suspension.