Patent ID: 7364643
Filing Date: 2008-04-29
Classification: D21F

Abstract:
1. A method of forming a web in a twin-wire formation section of a paper or board machine, comprising the steps of: supplying a lip jet of fibrous stock from a headbox to a first forming wire forming a first wire loop so that the fibrous stock travels only on the first forming wire; moving a second forming wire forming a second wire loop against a fixed forming shoe, the forming shoe having a leading edge and a deck having a curved surface, the second forming wire being supported by and moves against an area defined by the curved surface of the forming shoe deck; bringing the fibrous stock on the first forming wire into engagement with the second forming wire on the curved surface of the forming shoe deck at a position after the forming shoe leading edge, the first forming wire being unsupported in the area defined by the curved surface of the shoe; guiding the fibrous stock between the first and second forming wires so that dewatering of the fibrous stock begins after the shoe leading edge, wherein essentially non-pulsating dewatering takes place in the first dewatering zone; removing water from the fibrous stock in a successive second dewatering zone through which the first forming wire, the second forming wire and the fibrous stock therebetween travel, the second dewatering zone formed by fixed dewatering blades which extend in a cross-machine direction, and engage one of the forming wires, the fixed dewatering blades defining gaps therebetween; and supporting against the other of the forming wires movable dewatering blades, which are loaded in a controlled fashion opposite the gaps and between the fixed dewatering blades against the fibrous stock between the forming wires so that the second dewatering zone causes pulsating dewatering in the fibrous stock.