Patent ID: 7787980
Filing Date: 2010-08-31
Classification: B65H,Y10S

Abstract:
1. A method for controlling web tensions in a multi-web system including: providing at least first and second separate webs; passing said first web through a first web processing step and through a following first web traction element; providing a first local tension control process for controlling web tension in said first separate web; measuring said first web's tension and generating a first web tension measurement value; controlling said first web's tension using said first local tension control process to generate a first local tension control value; passing said second web through a second web processing step and through a following second web traction element; providing a second local tension control process for controlling a web tension in said second web; measuring said second web's tension and generating a second web tension measurement value; controlling said second web's tension using said second local tension control process to generate a second local tension control value; combining said at least first and second separate webs into a web strand, said first and second local tension control processes controlling said web tension in each of said at least first and second separate webs prior to combining said at least first and second webs into said web strand; providing a global tension control process for controlling relative web tension between said first and second separate webs, said global tension control process being responsive to said first web tension measurement value and to said second web tension measurement value; generating, in said global tension control process, at least one desired tension value for one of said first web's tension and said second web's tension; out-putting, from said global tension control process, said at least one desired tension value to one of said first and second local control processes in response to the measured web tension in one of said first and second separate webs deviating from a selected tension level; and controlling individual web tensions in said at least first and second separate webs using at least one of said at least first and second web traction elements.