Loading patent…
AssigneeStora Enso OYJ
InventorsJari Rasanen, Seppo Karine
Estimating the term…
The invention relates to a method and an apparatus for drying a moving web of material at a paper or board machine. The drying is performed by a heated drying cylinder (1) transverse to the direction of travel of the web, past which the web is being led. According to the invention, the drying cylinder (1) has been constructed so that its temperature can be adjusted independently at different locations in the longitudinal direction of the cylinder, i.e. the transverse direction of the web. With the adjustability of the drying cylinder it is possible to eliminate moisture differences occurring in the transverse direction of the web in connection with the drying. Especially, it is possible to eliminate moisture lines in the longitudinal direction of the web, which are generated when forming the web on the wire. The drying can be done by independently adjustable resistance wires (12) arranged at different locations of the cylinder, by heating vapour supplied independently to different zones of the cylinder, or by using both drying methods simultaneously in the same drying cylinder.
A method for drying a moving web of material (13) at a paper or board machine, in which the web is dried with a heated drying cylinder (1) transverse to the direction of travel of the web, past which the web is being led, characterised in that the temperature of the drying cylinder (1) is adjusted independently at different locations in its longitudinal direction for balancing moisture differences in connection with the drying, the differences occurring in the transverse direction of the web (13) and being due to moisture lines (17) in the longitudinal direction of the web that are generated upon forming the web on the wire.
Method according to one of the preceding claims, characterised in that resistance wires (12) have been arranged at different locations in the longitudinal direction of the drying cylinder (1), and the electric current travelling in each wire is adjusted independently.
An apparatus for drying a moving web of material (13) at a paper or board machine, comprising at least one heated drying cylinder (1) transverse to the direction of travel of the web, past which the web is arranged to travel, characterised in that resistance wires (12) extending annularly around the cylinder have been arranged at different locations in the longitudinal direction of the drying cylinder (1) the electric current being adjustable independently in each of the wires, so that the temperature of the drying cylinder can be adjusted independently at different points in its longitudinal direction for balancing in connection with the drying moisture differences occurring in the transverse direction of the web (13), the differences being due to moisture lines (17) in the longitudinal direction of the web.
Dependencies are inferred from the claim text.