Method and apparatus for silencing of webs

摘要

Noise-causing vibrations in the span of a tensioned web running over and away from an arcuate guide surface area of a circular perimeter fixed guide bar at a speed such that in the off-running angle between the web and the curved perimeter of the bar, air moving in the direction of the web in such angle would tend to follow the curvature of the bar (Coanda effect) and cause splitting of the air between the web and the bar, inhibited by locating spoiler means in a plane extending substantially tangentially from the off-running side of the arcuate guide surface area. The spoiler means is desirably in the form of one or more ribs providing surface in the tangential plane. Where the web span runs between spaced fixed circular perimeter bars, spoiler means may also be located in a plane extending substantially tangentially toward the on-running side of the arcuate guide surface of the bar located at the downstream end of the span.