Patent ID: 6117272
Filing Date: 2000-09-12
Classification: D21F

Abstract:
A headbox assembly for a papermaking machine for distributing pulp suspension with additives over the working width of the assembly, the headbox assembly comprising:a headbox having an upstream end region having an upstream side with a headbox inlet for receiving the pulp suspension, the upstream end region of the headbox being comprised of a plurality of sections across the width of the headbox;the headbox having an opposite downstream side and a discharge outlet from the downstream side of the headbox for discharging pulp suspension from the headbox for further processing;the headbox having a turbulence generator disposed between the inlet and the discharge outlet;means for adjusting the concentration of the pulp suspension over the width of the discharge outlet to produce a desired basis weight cross profile and a desired fiber orientation cross profile in the paper being produced by the machine, the adjusting means comprising:for each section across the width of the headbox:the headbox inlet being at each section and at the upstream side of the headbox;a first supply conduit for a first stream of a first liquid Q.sub.H having a first concentration; a first connection to the inlet from the first supply conduit for introducing the first stream to the inlet at the section;a second supply conduit for a second stream of a second liquid Q.sub.L having a second concentration; a second connection to the inlet from the second supply conduit for introducing the second stream to the inlet at the section, wherein at least one of the first and second concentrations is a pulp concentration;sectional flow adjustment means between at least one of the first and second supply conduits for the section and the headbox inlet at the section for controlling the volume and rate of flow from the one supply conduit to the inlet, with respect to the volume and rate of flow from the others of the supply conduits at the inlet at the other respective sections, for providing mixing of the first and second streams for the section and for adjusting a ratio of the volumetric flows of the streams Q.sub.H and Q.sub.L for the section and for enabling the mixing of the first and second streams to form a respective sectional mixed stream Q.sub.M with a concentration C.sub.M which depends on the ratio of the volumetric flows of the streams Q.sub.H and Q.sub.L, whereby the concentrations of the pulp suspension at the inlet at each of the sections over the width of the upstream end region of the headbox may be adjusted relative to each other;a third supply conduit for an additive flow Q.sub.ad to the pulp suspension, the third supply conduit being connected so that the additive flow Q.sub.ad combines into the sectional mix stream Q.sub.M in the headbox upstream of the turbulence generator;additive flow adjustment means for adjusting the volume and rate of flow of the additive flow in the third conduit; the sectional flow adjustment means for controlling the flow rate of the sectional mixed stream Q.sub.M cooperating with the additive flow adjustment means for selecting a particular concentration of pulp suspension in the sectional mixed stream Q.sub.M and a particular concentration of additives in the stream Q.sub.M while maintaining the total sectional flow of the streams Q.sub.H, Q.sub.L and Q.sub.ad together for setting the value of the sectional mixed stream Q.sub.M with Q.sub.ad at a level for maintaining a selected basis weight cross profile, additive distribution and fiber orientation cross profile of the paper produced from the suspension, and wherein the only streams entering the turbulence generator are the respective sectional mixed streams Q.sub.M with Q.sub.ad.