Two-wire former for paper-making machines

Double-wire gap former for the production of a fibrous paper web from a stock suspension, said double-wire former comprising:

• a first wire and a second wire, said first and second wires jointly forming a double wire;
• a headbox for producing a suspension jet directly between said first and second wires, the suspension jet contacting the second wire at a point of impingement;
• and
• first and second convex dewatering elements defining a curved nonrotating perforated surface;
• said first and second convex dewatering elements being spaced apart and defining a free distance therebetween;
• said first dewatering element having a first convex surface in contact with the second wire, said first surface defined by a first arc having a radius R.sub.1, wherein R.sub.1 .ltoreq.1000 mm, said first surface beginning at a first edge adjacent the point of impingement, and said radius R.sub.1 having a chord height which is greater than or equals one-half the thickness of the suspension jet;
• said second convex dewatering element disposed immediately after the first dewatering element in a direction of travel of the first and second wires, the second convex dewatering element having a second convex surface defined by a second arc, said second arc having a second radius of curvature R.sub.2, wherein R.sub.2 >2000 mm.

Method for producing a fibrous paper web comprising:

• providing first and second endless wire loops, wherein the endless wire loops form an entrance gap;
• injecting a stock suspension jet from a headbox into the entrance gap between the wire loops and impacting the second endless wire loop at a point of impingement;
• dewatering the stock suspension contained between the first and second endless wire loops with at least one dewatering unit thereby forming a fiber web;
• the dewatering unit comprising a dewatering element having a first wire-contacted surface with a convex curvature, said surface comprising a plurality of dewatering slats arranged successively;
• rotating endless wire loops whereby said wire loops proceed curved and under tension across said first surface from the point of jet impingement, the first wire-contacted surface beginning a first edge adjacent the point of jet impingement, the first wire contacted surface at least two radii of curvature R.sub.1 and R.sub.2 forming said convex curvature, wherein first R.sub.1 defines the first wire contacted surface immediately following the first edge and immediately precedes radius R.sub.2 in a direction of travel of the first and second wire loops, first radius R.sub.1 is smaller than the radius R.sub.2, said radius R.sub.1 has a chord height which is than or equals one-half the thickness of the suspension jet, and R.sub.1 .ltoreq.1000 mm.