Web Tension Control with Vacuum Tension Rolls
Vacuum tension rolls and belts provide web tension control by generating a web force against the roll or belt that is independent of the web tension differential (Tension In and Tension Out). The discussion that follows is based on vacuum rolls, but generally applies to vacuum belts as well.
Two things happen when the vacuum is applied to the roll. First, the vacuum under the wrap angle creates a pressure difference between the vacuum level and atmospheric conditions. This pressure difference forces the web against the roll and...