Method for influencing fibre orientation and headbox suitable therefor

摘要

In a papermaking process a fibrous suspension is discharged (2) from a headbox (1) through an elongated horizontal jet slit (4) with converging upper (6) and lower (5) limits. The jet incorporates an array of fiber orientation vanes (7, 8). The last one third or 300 mm of the upper and lower limits (9) are esp. of variable geometry. The variable geometry is effected over the full width of the jet on both upper and lower jet faces (5, 6) Also claimed is a commensurate assembly in which the jet inner geometry is varied by fittings e.g. pressure chamber, temperature-regulated zones or piezo-electric drive units etc. In an alternative embodiment the geometry is varied by a push-fit insert.