Method and apparatus for forming a material web

摘要

A web is formed from particulate material, for example wood fibres, by depositing the fibres on a movable deposition surface in a chamber. The particulate material is carried to the surface in an air stream to form a composite material flow which is caused to oscillate across the surface by impulses from separate control means preferably disposed on opposite sides of the stream. The control means is preferably opposed control flows which are caused to vary alternatingly between a minimum and a maximum impulse by use of one or more fluidistors. The fluidistors may be controlled by self-oscillation or by measuring the evenness of the particulate material deposited on the deposition surface. The control may also be effected by adjusting the walls of the chamber to utilize the coanda-effect. The particulate material may be admixed with additives from the control flow and may be charged electrostatically.