Abstract: 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 (?p) of ?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 >30 ms to ?300 ms.

Abstract: 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.

Abstract: 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.

Abstract: 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 (?p) of ?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 >30 ms to ?300 ms.

Abstract: A headbox includes a feed device feeding the fibrous material suspension, a nozzle, and a turbulence-generating device. The fibrous material suspension is guided in the turbulence-generating device in sub-flows through turbulence-generating channels. Within the individual turbulence-generating channel of the turbulence-generating device, at least one region forming a fluidization region is provided, in which a pressure loss can be generated in the sub-flow of the fibrous material suspension guided through said region. The nozzle and the turbulence-generating device are designed and dimensioned such that they are suitable for setting a dwell time of ?200 ms of the fibrous material suspension flowing through the same from a final fluidization region of an individual turbulence-generating channel before inlet into the nozzle as far as the outlet gap of the nozzle, and a pressure loss of ?50 mbar in the final fluidization region upstream of the inlet into the nozzle.

Abstract: A headbox for a machine for producing a fibrous web, in particular a paper, cardboard or tissue web from at least one fibrous stock suspension, includes a feeding device for feeding the at least one fibrous stock suspension; a perforated distribution pipe plate which is arranged immediately downstream from the feeding device in the flow direction of the at least one fibrous stock suspension and which includes a plurality of flow channels arranged in rows and columns; an intermediate channel which is arranged immediately downstream from the perforated distribution pipe plate in the flow direction of the at least one fibrous stock suspension and which extends in a width direction of the headbox and includes two walls, for example having the width of the machine; a turbulence generator which is arranged immediately downstream of the intermediate channel in the flow direction of the at least one fibrous stock suspension and which has a plurality of flow channels arranged in rows and columns; and a headbox nozzle

Abstract: Headbox for a machine to produce a fiber web, in particular a paper, cardboard or tissue web from at least one fibrous suspension, having a headbox nozzle comprising an upper nozzle wall and a lower nozzle wall, as well as two side walls tapering to form an outlet, and having an inner chamber through which the fibrous suspension flows in flow direction during operation of headbox, whereby on upper nozzle wall of headbox nozzle a baffle is arranged on the outlet side which is movable by way of several elements and which extends across machine width, and which has a baffle protrusion and a baffle immersion depth and which has at least two surfaces—an upstream ramp surface and a subsequent main surface contacted by a fibrous suspension during operation of headbox. The inventive headbox is characterized in that between ramp surface of baffle and main surface of baffle at least one refraction surface which is in contact during operation of headbox with a fibrous suspension is provided on baffle.

Abstract: 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.

Abstract: The invention relates to a headbox for a machine for producing a fibrous web, in particular a paper or cardboard web, from at least one fibrous stock suspension, having a feed apparatus which feeds the at least one fibrous stock suspension, having a distributor-pipe perforated plate which is adjacent downstream and has a multiplicity of channels which are arranged in rows and in columns, having an intermediate channel which lies downstream of the latter, extends over the width of the headbox and has a plurality of means which are spaced apart from one another in the width direction of the headbox for the preferably regulatable/controllable metering of a fluid in fluid part streams into the at least one fibrous stock suspension.

Abstract: The invention relates to a headbox which comprises a feed device feeding the 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, an intermediate channel arranged downstream thereof, extending over the width of the headbox and having a plurality of means for dosing a fluid in partial fluid streams to the at least one fiber suspension in a preferably adjustable/controlled manner, the means being spaced apart from each other in the width direction of the headbox and the individual means comprising a plurality of dosing channels having respective dosing channel openings and an opening center line, arriving at different levels and being connected to a common supply channel.

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.