FORMING OF A PAPER OR BOARD WEB IN A TWIN-WIRE FORMER OR IN A TWIN-WIRE SECTION OF A FORMER

The invention concerns a method in the twin-wire forming section of a paper or board machine, wherein fibrous stock supplied by a headbox (1) is guided in between forming wires (11, 12) formed as wire loops, where water is removed from the fibrous stock in at least two successive dewatering zones (Z1, Z2). At least a part of the first dewatering zone (Z1) is formed with the aid of a fixed forming shoe (3) having a curved surface and against which one of the forming wires (12) is supported while the opposite forming wire (11) is unsupported in the area of the forming shoe (3). The other dewatering zone (Z2) is formed by fixed dewatering blades (21) on the other side of the forming wires (11, 12) and supported against the fibrous stock located in between them (21) and on the opposite side of the forming wires (11, 12) by dewatering blades (24), which can be loaded in a controlled manner against the fixed dewatering blades (21) at gaps (22) between these in such a way that pulsating dewatering is caused in the fibrous stock in the second dewatering zone (Z2). The forming wires (11, 12) are guided from the beginning of the twinwire forming section into the area of the fixed forming shoe (3) of the first dewatering zone (Zl) in such a way that the fixed forming shoe (3) is used to cause essentially non-pulsating dewatering in the fibrous (stock travelling in between the forming wires (11, 12), which dewatering is applied to the fibrous stock in the area after the leading edge (7) of the fixed forming shoe (3). The invention also concerns a twinwire forming section. L'invention concerne un procédé mis en oeuvre dans la partie de formation double toile d'une machine à papier ou à carton, dans lequel la pâte fibreuse fournie par un caisson de tête (1) est guidée entre les toiles de formation (11, 12) se présentant sous forme de toiles en boucles, au niveau desquelles l'eau est enlevée de la pâte fibreuse dans au moins deux zones d'épaississement successives (Z1, Z2). Au moins une partie de la première zone d'épaississement (Z1) est formée à l'aide d'un sabot de formation fixe (3) possédant une surface courbe et supportant une des nappes de formation (12) alors que la toile opposée (11) n'est pas supportée dans la zone du sabot de formation (3). L'autre zone d'épaississement (Z2) est formée par des lames d'épaississement fixes (21) de l'autre côté des toiles de formation (11, 12) et est supportée par la pâte fibreuse située entre elles (21) et du côté opposé des to