Voith Patent Gmbh

Markus Häussler

Wolfgang Ruf

Konstantin Fenkl

Hans Loser

Volker Schmidt-Rohr

Mathias Schwaner

Jürgen Prössl

Thomas Ruehl

Thomas Rühl

Wofgang Ruf

Stefan Schlegel

Jens Haessner

A method for operating a sheet-forming unit of a papermaking machine. At least one fibrous material suspension is fed to a headbox and is conducted in a plurality of turbulence-generating channels to form sub-flows, and fed to a nozzle. From the nozzle, the at least one fibrous material suspension is in the form of a free jet into the forming unit to define an impingement line. In a final fluidization region of an individual turbulence-generating channel a pressure loss (&#x394;p) of &#x2267;50 mbar is generated within the fibrous material suspension before inlet thereof into the nozzle, and the fibrous material suspension is guided from the final fluidization region as far as the impingement line in such a way that the dwell time of the suspension in the region defined by the final fluidization region as far as the impingement line ranges from &#x3e;30 ms to &#x2266;300 ms.

Method for operating a sheet-forming unit, and sheet forming unit

A sheet-forming system includes a separating wedge with a separating wedge protrusion in a range of 0.05 to 3.0 of the largest single gap width of at least two nozzle chambers. The separating wedge includes two separating wedge areas, each having one separating wedge angle, an upstream separating wedge starting area and a downstream separating wedge ending area. The two separating wedge angles assume different angles. The separating wedge starting angle of the upstream separating wedge initial area assumes a greater angle than the separating wedge ending angle of the downstream separating wedge end area. At least one separating wedge surface is a nonplanar transitional area between the two separating wedge areas. The fibrous material suspension free jet formed from at least two fibrous material suspension streams has a free jet length of 100 to 500 mm. The forming roll has a diameter of 1,200 to 2,500 mm.

Sheet forming system for a machine for producing a multilayer fibrous web

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 &#x2267;0.5&#xb7;&#x221a;{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.

Headbox for a machine for producing a fibrous web

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Herbrechtingen, Germany

Markus Häussler