Double-layer headbox for a machine for producing a double-layer fibrous web

Abstract

The invention relates to a dual-layer material ramp for a machine for producing a dual-layered fibrous web, in particular a dual-layered paper or cardboard web, from two fibrous suspensions, comprising a material ramp nozzle with two nozzle spaces extending along the width and separated from one another on the inside by a separating wedge, said nozzle spaces guiding a respective fibrous suspension during operation of the dual-layer material ramp as fibrous suspension streams and coming together, each of said nozzle spaces comprising an upstream feed device, a downstream outlet gap with a gap width, said gap extending along the width and an outer wall on the outside, wherein the separating wedge comprises two separating wedge surfaces that are contacted by the respective fibrous suspension stream during operation of the dual-layer material ramp. The dual-layer material ramp according to the invention is characterized in that the separating wedge comprises two separating wedge areas, each having a separating wedge angle, an upstream separating wedge starting area and a downstream separating wedge end area, that the two separating wedge angles of the two separating wedge areas assume different angular values, wherein the separating wedge starting angle of the upstream separating wedge starting area assumes a greater angular value than the separating wedge end angle of the downstream separating wedge end area, and that a non-planar transition area is provided between at least one separating wedge surface of the separating wedge between the two separating wedge areas of the separating wedge.

1 . A double-layer headbox for a machine for producing a double-layer fibrous web produced from two fibrous suspensions, the double-layer fibrous web being one of a double-layer paper web and a double-layer cardboard web, said double-layer headbox comprising:
 one headbox nozzle including two converging nozzle chambers and one separating wedge, said two converging nozzle chambers extending across a width and being separated from each other on an inside by said separating wedge, each of said two converging nozzle chambers respectively guiding one of the fibrous suspensions formed respectively as a fibrous suspension stream during operation of the double-layer headbox, each of said two converging nozzle chambers respectively including one upstream feed device, one downstream outlet gap with a gap width and extending across said width, and an outer wall on an outside, said separating wedge including two separating wedge surfaces each of which is contacted by a respective said fibrous suspension stream during operation of the double-layer headbox, said separating wedge including two separating wedge areas each having a separating wedge angle, one of said two separating wedge areas being an upstream separating wedge starting area, another of said two separating wedge areas being a downstream separating wedge end area, said separating wedge angle of said upstream separating wedge starting area being a separating wedge starting angle, said separating wedge angle of said downstream separating wedge end area being a separating wedge end angle, said separating wedge starting angle having a different angular value than said separating wedge end angle, said separating wedge starting angle of said upstream separating wedge starting area having a greater angular value than said separating wedge end angle of said downstream separating wedge end area, said separating wedge including at least one non-planar transition area between said two separating wedge areas of said separating wedge, said at least one non-planar transition area being on at least one of said two separating wedge surfaces of said separating wedge.   
     
     
         2 . The double-layer headbox according to  claim 1 , wherein a respective said non-planar transition area is provided at both said two separating wedge surfaces of said separating wedge between said two separating wedge areas of said separating wedge. 
     
     
         3 . The double-layer headbox according to  claim 1 , further including an upstream separating wedge retainer, at least said upstream separating wedge starting area of said separating wedge being aligned symmetrically with one straight line extending through said upstream separating wedge retainer. 
     
     
         4 . The double-layer headbox according to  claim 3 , wherein said separating wedge includes a separating wedge tip, said upstream separating wedge starting area of said separating wedge and said downstream separating wedge end area of said separating wedge being aligned symmetrically with said straight line extending through said upstream separating wedge retainer so that said separating wedge tip of said separating wedge is positioned on said straight line extending through said upstream separating wedge retainer. 
     
     
         5 . The double-layer headbox according to  claim 1 , wherein said non-planar transition area is on one of said two separating wedge surfaces of said separating wedge between said two separating wedge areas of said separating wedge, said separating wedge including a planar transition area, said planar transition area being on another of said two separating wedge surfaces of said separating wedge between said two separating wedge areas of said separating edge. 
     
     
         6 . The double-layer headbox according to  claim 5 , further including an upstream separating wedge retainer, at least said upstream separating wedge starting area of said separating wedge being aligned symmetrically with one straight line extending through said upstream separating wedge retainer. 
     
     
         7 . The double-layer headbox according to  claim 5 , further including an upstream separating wedge retainer, said upstream separating wedge starting area of said separating wedge and said downstream separating wedge end area of said separating wedge being aligned asymmetrically to a straight line extending through said upstream separating wedge retainer. 
     
     
         8 . The double-layer headbox according to  claim 7 , wherein said separating wedge includes a separating wedge tip which is positioned on said straight line extending through said upstream separating wedge retainer. 
     
     
         9 . The double-layer headbox according to  claim 1 , wherein said separating wedge starting angle of said upstream separating wedge starting area has an angular value in a range of 8° to 20°, and that said separating wedge end angle of said downstream separating wedge end area has an angular value in a range of 1.5° to 8°. 
     
     
         10 . The double-layer headbox according to  claim 1 , wherein said separating wedge starting angle of said upstream separating wedge starting area has an angular value in a range of 10° to 15°, and that said separating wedge end angle of said downstream separating wedge end area has an angular value in a range of 2.5° to 4.5°. 
     
     
         11 . The double-layer headbox according to  claim 1 , wherein said downstream separating wedge end area of said separating wedge has a downstream separating wedge end length in a range of 10 mm to 100 mm. 
     
     
         12 . The double-layer headbox according to  claim 1 , wherein said downstream separating wedge end area of said separating wedge has a downstream separating wedge end length in a range of 15 mm to 75 mm. 
     
     
         13 . The double-layer headbox according to  claim 1 , wherein said downstream separating wedge end area of said separating wedge has a downstream separating wedge end length in a range of 25 mm to 50 mm. 
     
     
         14 . The double-layer headbox according to  claim 1 , wherein said headbox nozzle includes an outlet gap, said downstream separating wedge end area of said separating wedge protruding beyond said outlet gap of said headbox nozzle in a range of 10 to 25 mm. 
     
     
         15 . The double-layer headbox according to  claim 1 , wherein said non-planar transition area at said separating wedge surface between said two separating wedge areas of said separating wedge is angular. 
     
     
         16 . The double-layer headbox according to  claim 1 , wherein non-planar transition area at said separating wedge surface between said two separating wedge areas of said separating wedge is round with a radius in a range of 20 mm to 1000 mm. 
     
     
         17 . The double-layer headbox according to  claim 1 , wherein non-planar transition area at said separating wedge surface between said two separating wedge areas of said separating wedge is round with a radius in a range of 100 mm to 500 mm. 
     
     
         18 . The double-layer headbox according to  claim 1 , wherein non-planar transition area at said separating wedge surface between said two separating wedge areas of said separating wedge is round with a radius in a range of 150 mm to 250 mm. 
     
     
         19 . The double-layer headbox according to  claim 1 , wherein two of said fibrous suspension stream emerging from said headbox nozzle as one combined fibrous suspension stream have different stream speeds. 
     
     
         20 . The double-layer headbox according to  claim 19 , wherein said stream speeds differ relative to each other by a value in a range of 10 to 60 m/min. 
     
     
         21 . The double-layer headbox according to  claim 19 , wherein said stream speeds differ relative to each other by a value in a range of 15 to 25 m/min. 
     
     
         22 . The double-layer headbox according to  claim 1 , wherein one controlled supply stream is added to at least one of the fibrous suspensions when producing a mixed stream with a mixed concentration, said controlled supply stream being a dilution water stream. 
     
     
         23 . A machine to produce a double-layer fibrous web from two fibrous suspensions, the double-layer fibrous web being one of a double-layer paper web and a double-layer cardboard web, from two fibrous suspensions, said machine comprising:
 at least one double-layer headbox including one headbox nozzle including two converging nozzle chambers and one separating wedge, said two converging nozzle chambers extending across a width and being separated from each other on an inside by said separating wedge, each of said two converging nozzle chambers respectively guiding one of the fibrous suspensions formed respectively as a fibrous suspension stream during operation of said at least one double-layer headbox, each of said two converging nozzle chambers respectively including one upstream feed device, one downstream outlet gap with a gap width and extending across said width, and an outer wall on an outside, said separating wedge including two separating wedge surfaces each of which is contacted by a respective said fibrous suspension stream during operation of said at least one double-layer headbox, said separating wedge including two separating wedge areas each having a separating wedge angle, one of said two separating wedge areas being an upstream separating wedge starting area, another of said two separating wedge areas being a downstream separating wedge end area, said separating wedge angle of said upstream separating wedge starting area being a separating wedge starting angle, said separating wedge angle of said downstream separating wedge end area being a separating wedge end angle, said separating wedge starting angle having a different angular value than said separating wedge end angle, said separating wedge starting angle of said upstream separating wedge starting area having a greater angular value than said separating wedge end angle of said downstream separating wedge end area, said separating wedge including at least one non-planar transition area between said two separating wedge areas of said separating wedge, said at least one non-planar transition area being on at least one of said two separating wedge surfaces of said separating wedge.