Vacuum holddown device for moving belts

Claim 1

A vacuum holddown device for use with flexible web material for holding the same in flattened condition during movement of the material relative to the device comprising a plenum plate formed with a plurality of openings for permitting the flow of air therethrough and having a side surface across which the material is moved, a plurality of extending portions extending substantially perpendicularly from the other side of said plate, one of said portions completely surrounding the other extended portions, a manifold mounted to the said other side of said plate and including a section positioned in spaced relation relative to the extended portions of the plenum plate, said manifold also including an edge member adapted to surround said one extended portion and for attachment to said other side of the plate for defining an enclosed space between said manifold and the plate, said manifold being made of material adapted to flex when the air pressure on one side thereof is reduced to a normal operating level, such flex being sufficient to cause said manifold to move toward said plenum plate and contact said extending portions, and means for connecting the space to a vacuum producing means for reducing the air pressure within said space below the predetermined level thereby drawing the web material to said side surface.