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.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001]This is a continuation of PCT application No. PCT / EP2009 / 063549, entitled “DUAL-LAYER MATERIAL RAMP FOR A MACHINE FOR PRODUCING A DUAL-LAYERED FIBROUS WEB”, filed Oct. 16, 2009, which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002]1. Field of the Invention[0003]The invention relates to a double-layer headbox for a machine for producing a double-layer fibrous web, in particular a double-layer paper or cardboard web produced from two fibrous suspensions, with one headbox nozzle comprising two converging nozzle chambers extending across the width and separated from each other on the inside by a separating wedge, each respectively guiding one fibrous suspension in the form of a fibrous suspension stream during operation of the double-layer headbox, each of said nozzle chambers comprising one upstream feed device, one downstream outlet gap with a gap width, said gap extending across the width and an outer wall on the ou...

AI Technical Summary

Benefits of technology

[0026]The two fibrous suspension streams emerging from the headbox nozzle as one combined fibrous suspension stream can moreover have different stream speeds. For example, the at least one difference in the two stream speeds can assume a value in the range of 10 to 60 m/min, preferably 15 to 25 m/min. This substantially reduces spreading of the mixing cone in the fibrous suspension stream to the relevant fibrous suspension layer. These requirements can, as already known, also depend on the...

Problems solved by technology

Increasing production speeds, as well as increasing raw material and energy costs increasingly demand the production of double-layer products with lower base weights.

However, this increases the demands upon stream stability, as well as on ...

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