Patent ID: 6399157
Filing Date: 2002-06-04
Classification: B05C,B05D,G03C,Y10S

Abstract:
A method for charging a length of moving web to a voltage level to provide a coating assist with a charging device prior to coating a liquid composition onto a surface of the web with a curtain coating apparatus, an extrusion coating apparatus, or a bead coating apparatus, the method comprising the steps of:(a) inputting at least one of a plurality of parameters selected from web speed (U), web permittivity (&egr;), web thickness (d), web incoming voltage (Vin), and a desired web voltage (Vweb) into a programmable controller; (b) calculating web capacitance per unit area; (c) determining using the programmable logic controller an output voltage for the charging device based on the web capacitance per unit area and the at least one of the parameters of web speed (U), web capacitance per unit area, and web incoming voltage (Vin) input in step (a) to achieve the desired web voltage; (d) detecting an event in the moving web requiring electrostatic charge deposition, the event being a start-up or a splice; (e) controlling a power supply to deliver the output voltage to the charging device; and (f) depositing an electrostatic charge onto the moving web with the charging device operating at the output voltage for a predetermined time period or for a predetermined length of the web to achieve the desired web voltage (Vweb) after detecting the event requiring electrostatic charge deposition, and stopping the depositing of the electrostatic charge after the predetermined time period or the predetermined length of the web required by the event.