Apparatus for the application of a liquid or pasty medium onto a moving material web, in particular of paper or board

Apparatus for applying a liquid or pasty medium onto a moving web, the apparatus comprising:

• a rotating roll having a surface thereon which is selectively usable either for taking up the medium to subsequently transfer the medium to the web or for guiding the web over the roll as the medium is applied directly to the web;
• an application unit placed at a section of the surface on the roll for applying the medium either to the roll for subsequent delivery to the web or to the web passing the application unit on the roll;
• the application unit comprising:
• an application doctor blade and means supporting the application doctor blade at the surface on the roll to which the medium is applied;
• a cleaning doctor blade spaced at a distance around the surface on the roll from the application doctor blade in the direction opposite the rotation direction of the roll and therefore upstream of the application doctor blade, so that the application doctor blade and the cleaning doctor blade bound and define an application chamber for the medium to apply the medium in the application chamber to the surface on the roll moving past the application chamber;
• and means supplying the medium into the application chamber;
• the cleaning doctor blade including a blade bar holder located toward the surface on the roll moving past the application unit and including a blade bar supported by the blade bar holder generally at the surface on the roll;
• the blade bar holder including a blade base which receives the blade bar and including a holding link that supports the blade base and that extends away from the blade base and from the roll;
• the holding link being of such material and thickness and being so oriented at and in the vicinity of the blade base as in that vicinity to extend in a direction that enables the holding link to deflect radially of the surface on the roll as it carries the blade bar, as the blade bar rides along the surface of the roll;
• at least one of the blade base and the holding link of the blade bar holder having and defining openings or channels therethrough from inside the application chamber to outside thereof, the openings or channels being placed and directed so that the medium exits the application chamber generally in the direction opposite the direction of rotation of the roll and impinges outside the application chamber onto the surface on the roll adjacent to the cleaning doctor blade before the surface on the roll passes the cleaning doctor blade entering the application chamber.