Adjustable ballast system for the holddown belt in a double facer

A system for selectively varying the vertical ballast load applied to an upper surface of a moving holddown belt and an underlying corrugated paperboard web traveling therewith over a plurality of heating units positioned in the direction of web movement in a double facer, said system comprising:

• a plurality of rows of belt engaging ballast members, each row extending over the heating units, and said plurality of rows positioned in parallel side-by-side relation transversely across the belt and underlying web;
• a vertical actuator for at least some segments of a row which segments overlie a heating unit, said actuator operable to move each said segment between a lower full load ballast position, and an upper no load position;
• a support structure overlying the belt and the heating units, and wherein each row includes:
• a continuous flexible membrane;
• a series of membrane support members spaced along the membrane and defining the segments of the row;
• the upstream end of said membrane attached to said support structure;
• and,
• each of said actuators mounted on said support structure and including a vertically positionable link operatively connected to a membrane support member.