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1. (WO1999009249) A MULTI-PLY WEB FORMING METHOD AND APPARATUS AND A MULTI-PLY PAPER OR BOARD PRODUCT FORMED HEREBY

Pub. No.:    WO/1999/009249    International Application No.:    PCT/SE1998/001490
Publication Date: Feb 25, 1999 International Filing Date: Aug 19, 1998
IPC: D21F 9/00
D21F 11/04
Applicants: SCA RESEARCH AB
NORDSTRÖM, Bengt
Inventors: NORDSTRÖM, Bengt
Title: A MULTI-PLY WEB FORMING METHOD AND APPARATUS AND A MULTI-PLY PAPER OR BOARD PRODUCT FORMED HEREBY
Abstract:
A multi-ply web forming method and apparatus are disclosed for forming a top ply onto a base ply. A fibre suspension jet is by means of a secondary headbox (21; 21', 26) delivered into a twin-wire roll nip created by two tensioned wires (16, 22; 16', 22'; 22, 27) one of which (16; 16', 22) carries the moist base ply. The web forming of the top ply is performed solely by means of roll forming (23, 23', 28) of the kind where the fibre suspension jet is delivered to said twin-wire nip at such a high speed to cause a yielding deflection of the outer of said two tensioned wires, while maintaining substantially constant tension during said deflection of the outer wire by guiding said wire on rotating supports (31a-c; 31a'-c'; 32a-c) at least one of which is resiliently or displaceably mounted to compensate for said deflection, wherein the speed of said fibre suspension yet delivered to said twin-wire nip is at least 300 m/min and the wire tension of the outer as well as the inner wire is at least 4 kN/m.