US 2002/0117285 A1 · Web product with isotropic fiber orientation

Abstract

Methods and apparatus to enhance paper and board forming qualities with insert tubes and/or a diffuser block in the paper forming machine headbox component which generates vorticity in the machine direction (MD) which is superimposed on the streamwise flow to generate a swirling or helical flow through the tubes of the diffuser block. Tubes of the diffuser block are designed such that the direction of the swirl or fluid rotation of the paper fiber stock may be controlled and the direction thereof is controlled in such a way to provide effective mixing, coalescence and merging of the jets of fluid emanating from the tubes into the converging section, i.e., nozzle chamber of the headbox. A specific flow inside the headbox distributes the fibers in an isotropic form, i.e., uniform in all directions, in the sheet substantially eliminating the MD preferential fiber orientation to produce an isotropic and uniform sheet. Also disclosed is the effective mixing of the jets generating cross-machine direction (CD) shear between the rows of jets that form at the outlet of the tubes inside the nozzle chamber of the headbox to align paper fibers in the cross-machine direction.

Claims14

Dependent claims

A paper forming machine headbox component for receiving a paper fiber stock and generating a jet therefrom for discharge upon a wire component moving in a machine direction (MD), the headbox component comprising:

a distributer for distributing stock flowing into the headbox component in a cross-machine direction (CD), the distributer effective for supplying a flow of said stock across the width of the headbox in the machine direction;
a nozzle chamber having an upper surface and a lower surface converging to form a rectangular outlet lip defining a slice opening for the jet;
a diffuser block coupling said distributer to said nozzle chamber, said diffuser block comprising a multiplicity of tubular elements disposed between said distributer and said nozzle chamber, said tubular elements being oriented axially in the machine direction, a plurality of the tubular elements having a longitudinal axes in the direction of the flow of stock, and the tubular elements arranged within the diffuser block as a matrix of rows and columns for generating multiple jets of said stock flowing into said nozzle chamber;
and
said tubular elements being oriented axially generate an axial vorticity which prevents fiber orientation in the machine direction in an initial converging section of said nozzle chamber being effective for swirling said stock in controlled pairs of axial vortices along the longitudinal axes of the tubular elements as said stock flows through said tubular elements promoting mixing of the jets of said stock as said jets flow into said nozzle chamber from the tubular elements to form a uniform flow of stock at the slice opening for the jet.

2 more elements

Dependencies are inferred from the claim text.

Web product with isotropic fiber orientation

Life of this patent

Web product with isotropic fiber orientation

Life of this patent

Abstract

Claims14