Constant pressure of foam in coating fountain - is maintained by pressure sensor in fountain controlling air supply to foam generator and flow to fountain

摘要

Appts. for coating webs with a foamed material has a foam generator formed by a mixing chamber to which separately compressed air and the liquor are supplied. Each supply line is provided with a flow meter and a redn. valve. Formed foam is fed to a distributor and coating fountain of rectangular cross-section and having an open base one longitudinal edge of which is associated with an adjustable doctor blade. Ends of base are adjustable to the width of the web which is fed to the base. To maintain constant pressure in the coating fountain there a pressure sensor is provided which controls the flow of the foam into the fountain. Indicated sensor value is compared with a preset value and the resultant differential is used for controlling the air supply which for a given ratio of liq. to air controls the amt. of foam produced.