Headbox for papermaking machine with more uniform flow

A headbox for a papermaking machine for distributing pulp suspension over the working width of the papermaking machine, comprising:

• (a) a pulp suspension guide having an upstream side, a downstream side and a plurality of separate channels therethrough for conducting pulp suspension from the upstream side to the downstream side;
• (b) a discharge nozzle including a discharge outlet, the nozzle being located downstream of the downstream side of the pulp suspension guide, the headbox being structured and arranged so that the direction of flow of the pulp suspension between the downstream side of the pulp suspension guide and the discharge outlet as viewed from a side of the headbox remains essentially unchanged until down to the discharge outlet thereby to prevent mixing of the pulp suspension from the respective channels of the pulp suspension guide;
• (c) means for adjusting the concentration of the pulp suspension over the width of the discharge outlet to produce a desired basis weight cross profile of a paper web produced, said adjusting means comprising:
• a plurality of flow elements arranged upstream of the pulp suspension guide, each flow element provided with at least two connections for the introduction of respective streams (Q.sub.H, Q.sub.L) into the flow element to form a mixed stream (Q.sub.M) with a concentration C.sub.M in the flow element which concentration depends on the ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L), at least one (Q.sub.H, Q.sub.L) of each flow element stream having a pulp concentration, at least one of the connections of each flow element including means for providing a respective stream (Q.sub.H, Q.sub.L) with a predetermined throughput to adjust a ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) of each flow element,
• each flow element feeding at least one of the channels of the pulp suspension guide with the respective mixed stream (Q.sub.M), each flow element further comprising an outlet for discharging of the respective mixed stream into the pulp suspension guide;
• and
• means maintaining the mixed stream (Q.sub.M) of pulp suspension of each flow element at a volumetric flow that is a constant for each flow element during the adjustment of the ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) for maintaining a desired fiber orientation cross profile in the paper web produced.

A headbox for a papermaking machine for distributing pulp suspension over the working width of the papermaking machine, comprising:

• a pulp suspension guide having an upstream side, a downstream side and a plurality of separate channels therethrough for conducting pulp suspension from the upstream side to the downstream side;
• a discharge nozzle, including a discharge outlet, the nozzle being located downstream of the downstream side of the pulp suspension guide, the headbox being structured and arranged so that the direction of flow of the pulp suspension between the downstream side of the pulp suspension guide and the discharge outlet as viewed from a side of the headbox remains essentially unchanged until down to the discharge outlet thereby to prevent mixing of the pulp suspension from the respective channels of the pulp suspension guide;
• and
• means for adjusting the concentration of the pulp suspension over the width of the discharge outlet to produce a desired basis weight cross profile of a paper web produced, said adjusting means comprising:
• flow means arranged upstream of the pulp suspension guide, the flow means having at least two sections, at least one section provided with at least two connections for the introduction of respective streams (Q.sub.H, Q.sub.L), at least one stream (Q.sub.H, Q.sub.L) having a pulp concentration, at least one of the connections of the at least one section including means for providing at least one of the respective streams (Q.sub.H, Q.sub.L) of the at least one section with a predetermined throughput to adjust a ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) of the at least one section,
• in the at least one section of the flow means the streams (Q.sub.H, Q.sub.L) are mixed to form a 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, Q.sub.L), and
• each section of the flow means feeding at least one of the channels of the pulp suspension guide, said at least one section feeding at least one of the channels with the mixed stream (Q.sub.M), the flow means further comprising an outlet for discharging of the mixed stream into the pulp suspension guide, and
• means maintaining the mixed stream (Q.sub.M) of pulp suspension at a volumetric flow that is a constant during the adjustment of the ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) for maintaining a desired fiber orientation cross profile in the paper web produced.

A headbox for a papermaking machine for distributing pulp suspension over the working width of the papermaking machine, comprising:

• (a) a pulp suspension guide having an upstream side, a downstream side and a plurality of separate channels therethrough for conducting pulp suspension from the upstream side to the downstream side;
• (b) a discharge nozzle including a discharge outlet, the nozzle being located downstream of the downstream side of the pulp suspension guide,
• (c) means for adjusting the concentration of the pulp suspension over the width of the discharge outlet to produce a desired basis weight cross profile of a paper web produced, said adjusting means comprising:
• flow means upstream of the pulp suspension guide having partitions dividing the flow means into a plurality of sections extending in the direction of flow of the pulp suspension and arranged side by side over the width of the papermaking machine,
• each section having at least two connections for the introduction of respective streams (Q.sub.H, Q.sub.L), at least one stream (Q.sub.H, Q.sub.L) of each section having a pulp concentration;
• at least one of the connections of each section including means for providing at least one of the respective streams (Q.sub.H, Q.sub.L) of that section with a predetermined throughput to adjust a ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) of that section,
• in each section of the flow means the streams (Q.sub.H, Q.sub.L) are mixed 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, Q.sub.L), and
• each section of the flow means feeding at least one of the channels of the pulp suspension guide with the respective sectional mixed stream (Q.sub.M), and
• means maintaining the sectional mixed stream (Q.sub.M) of pulp suspension of each section at a volumetric flow that is a constant for the respective section of the flow means during adjustment of the ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) for maintaining a desired fiber orientation cross profile in the paper web produced.

A headbox for a papermaking machine for distributing pulp suspension over the working width of the papermaking machine, comprising:

• a pulp suspension guide having an upstream side, a downstream side and a plurality of separate channels therethrough for conducting pulp suspension from the upstream side to the downstream side;
• a discharge nozzle, including a discharge outlet, the nozzle being located downstream of the downstream side of the pulp suspension guide,
• means for adjusting the concentration of the pulp suspension over the width of the discharge outlet to produce a desired basis weight cross profile of a paper web produced, said adjusting means comprising:
• flow means arranged upstream of the pulp suspension guide, the flow means having at least two sections, at least one section provided with at least two connections for the introduction of respective streams (Q.sub.H, Q.sub.L), at least one stream (Q.sub.H, Q.sub.L) having a pulp concentration, at least one of the connections of the at least one section including means for providing at least one of the respective streams (Q.sub.H, Q.sub.L) of the at least one section with a predetermined throughput to adjust a ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) of the at least one section,
• in the at least one section of the flow means the streams (Q.sub.H, Q.sub.L) are mixed to form a 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, Q.sub.L), and
• each section of the flow means feeding at least one of the channels of the pulp suspension guide, said at least one section feeding at least one of the channels with the mixed stream (Q.sub.M), the flow means further comprising an outlet for discharging of the mixed stream into the channels of the pulp suspension guide, and
• means maintaining the mixed stream (Q.sub.M) of pulp suspension at a volumetric flow that is a constant during the adjustment of the ratio of the volumetric flows of the streams (Q.sub.H, Q.sub.L) for maintaining a desired fiber orientation cross profile in the paper web produced.