Headbox for a machine for producing a fibrous web

摘要

A headbox includes a feed device for feeding at least one fiber suspension, a perforated distribution pipe plate arranged immediately downstream thereof and having a plurality of channels arranged in lines and columns and an intermediate channel arranged downstream thereof extending over the width of the headbox and having a plurality of apparatuses for dosing a fluid in partial fluid streams to the at least one fiber suspension in an adjustable/controlled manner. The apparatuses are spaced apart from each other in the width direction of the headbox and the individual apparatuses include a plurality of dosing channels having respective dosing channel openings on the outlet side and a dosing channel length, arriving at different levels and being connected to a common supply channel. The headbox further includes a downstream turbulence generator having a plurality of flow channels arranged in lines and columns and a headbox nozzle which is directly contiguous to the turbulence generator and which has a nozzle gap. At least some sections of the channels of the perforated distribution pipe plate have a diffuser and the perforated distribution pipe plate has a length which is ≧0.5·√{square root over (partition)} area the partition area being the surface of the downstream perforated distribution pipe plate divided by the total number of the channels of the perforated distribution pipe plate.