Convergent flow headbox

摘要

A headbox has a tube bank of tubes arranged in machine direction rows. The tubes extend from an outlet wall of a header to the inlet of a nozzle. The upper and lower walls of the nozzle converge toward the nozzle outlet, and planes extending from the walls (nozzle roof and apron) converge to define an imaginary centerline extending in the cross-machine direction. The rows of tubes lie along radially extending planes defined with respect to the centerline. The injection ends of the tubes define a cylindrical surface extending between the nozzle walls. Stock from each tube is directed radially toward the centerline along flow paths of equal length. Trailing vanes may be positioned between the rows of tubes so that each flow experiences almost identical flow boundary conditions as it moves towards the nozzle outlet, hence contributing to more uniform fiber orientation in the resultant paper web.