Headbox for a machine for producing a fibrous web

Abstract

The invention relates to a headbox (1) which comprises a feed device (4, 5) feeding the at least one fiber suspension (2), a perforated distribution pipe plate (6) arranged immediately downstream thereof and having a plurality of channels (7) arranged in lines (Z) and columns (S), an intermediate channel (8) arranged downstream thereof, extending over the width (B) of the headbox (1) and having a plurality of means (9) for dosing a fluid (10) in partial fluid streams (10.T) to the at least one fiber suspension (2) in a preferably adjustable / controlled manner, the means (9) being spaced apart from each other in the width direction of the headbox (1) and the individual means (9; 9.1) comprising a plurality of dosing channels (11) having respective dosing channel openings (11.1) on the outlet side and a dosing channel length (11.L), arriving at different levels and being connected to a common supply channel (12). The headbox further comprises a downstream turbulence generator (13) having a plurality of flow channels (14) arranged in lines (Z) and columns (S) and a headbox nozzle (16) which is directly contiguous to the turbulence generator (13) and which has a nozzle gap (17). At least some sections of the channels of the perforated distribution pipe plate (6) have a diffuser (20) and the perforated distribution pipe plate has a length (L) which is = 0.5 vparting surface (I), TF being the surface of the downstream perforated distribution pipe plate divided by the total number of the channels of the perforated distribution pipe plate (II).

Description

technical field [0001] The invention relates to a headbox for a machine for producing a fibrous material web, in particular a paper or cardboard web, from at least one fibrous material suspension, said headbox having: Conveying device for conveying at least one suspension of fibrous material; downstream distribution tube orifice plate with a large number of channels arranged in rows and columns; center located downstream of distribution tube orifice plate and extending over the width of the headbox channel, said central channel has a plurality of means spaced apart from one another in the width direction of the headbox, said means for feeding the fluid into at least one fiber material suspension, preferably in an adjustable / controllable manner in a fluid split metering In the liquid, wherein, each said mechanism includes a plurality of dosing input channels with corresponding dosing input channel openings, opened at different heights and connected with a common supply channel;...

AI Technical Summary

Problems solved by technology

Due to relatively high fluid friction, high flow velocities, etc., longer lengths lead to high pressure losses in the fibrous material suspension, which have a negative impact on the operating stability of the individual headboxes and the desired Compactness is a disadvantage

Furthermore, the known distribution tube orifice (here the orifice or the tube table) is expensive to produce

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