Device for applying a selected moisture content to a web made of a fibrous material

Claim 1

A dampening device for applying a selected moisture content to a web made of a fibrous material, said dampening device comprising in combination: at least one spray nozzle including a first duct for a spray medium in liquid form and a second duct for a spray medium in gaseous form, each of said ducts terminating at one end in a nozzle opening, the nozzle opening of the second duct encompassing the nozzle opening of the first duct, said spray nozzle having an inner member defining said second duct and encompassing said inner member, said members being axially displaceable with reference to each other thereby correspondingly varying the stream of nebulized spray media as emanating from said nozzle openings; first conduit means for connecting a supply of liquid spray medium to the other end of the first duct; second conduit means for feeding a flow of gaseous spray medium to the other end of the second duct; storage means included in the first conduit means for collecting therein a supply of the liquid spray medium substantially free of pressure; control means included in said conduit means for controlling the supply of liquid in said storage means; and an air expansion chamber included in the second conduit means for reducing in said chamber the pressure of gaseous spray medium passing through said second conduit to a pressure slightly above atmospheric pressure; whereby the air flow emanating from the nozzle opening of the second duct sucks out liquid contained in said storage means and sprays the sucked-out liquid in nebulized form upon the web to be moistened.