Republic Steel Corporation

Theodore L Page

Harold C Overton

A system for controlling the thickness and distribution of a coating applied to a moving substrate includes a pair of 'air knives' which discharge pressurized fluid onto a moving substrate as it emerges from a coating bath to screed excess coating from the substrate and leave a coating deposit having a desired thickness and distribution. Each air knife has a plenum chamber which supplies pressurized fluid to a pair of nozzle lips that define an elongated nozzle opening. Fluid flow influencing devices are provided between the plenum and the nozzle lips of each air knife. The flow influencing devices preferably include a baffle plate, a screen assembly, a shutter plate, and a vane assembly. The baffle plate and the screen assembly help assure that a laminar, equally pressurized flow is supplied to the shutter plate. The shutter plate has specially configured flow restricting openings that cause the pressure profile of fluid discharging from the air knives to vary in a predetermined manner along the length of their nozzle openings, whereby coating profiles are caused to vary in a predetermined manner across the width of the substrate. The vane assembly includes vanes which help to control the directions of fluid discharge through the nozzle openings. Pressurized fluid is supplied to the air knives by a system which includes a blower, and blower speed is controlled in response to sensed line speed of the moving substrate to assure that a coating deposit of desired thickness remains on the substrate.

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Gadsden, AL, United States of America

Theodore L Page