Multiple steam applicator controller

Abstract

The invention provides multiple steam applicators which are used to distribute steam against a web during calendering. The invention includes a primary steam applicator located adjacent a side of the web to which steam is applied. The primary steam applicator has a manifold, a primary inlet valve, and a plurality of steam valves spaced along the primary manifold. Each steam valve regulates a steam flow distributed to a cross-directional section of the web. A secondary steam applicator is located adjacent the side of the web to which steam is applied. The secondary steam applicator has a manifold, a secondary inlet valve, and a plurality of steam valves spaced along the secondary manifold, each steam valve regulating a steam flow distributed to a cross-directional section of the web. A gloss sensor measures the gloss finish of the web. A computer means, responsive to the gloss sensor, computes a cross-directional gloss error by comparing the gloss measurement at each cross-directional section against a predetermined gloss value for the cross-directional section. The computer means also computes a machine-directional gloss error by comparing the average of the gloss measurements against a predetermined average gloss value. A valve control means, responsive to the computer means, adjusts the primary and secondary steam applicator steam valves to minimize the cross-directional gloss error. Finally, a steam pressure controller means, responsive to the computer means, adjusts the primary and secondary inlet valves to minimize the machine-directional gloss error.