Apparatus for liquid coating thickness control

Claim 1

In combination with a pair of opposed nozzles, a bath of liquid coating which will harden to form a solid coating on a substrate, means for moving a continuous imperforate web lengthwise through the bath of liquid coating, the web issuing from the bath having excess liquid coating thereon and means for moving the coated strip upwardly between the nozzles in such closely spaced relation to each nozzle as to make the nozzle operative for impinging a stream of fluid under pressure against the web for removing excess liquid coating from the web and wherein the two opposed streams of fluid under pressure normally cause a heavier liquid coating to remain on the longitudinal marginal portions of the imperforate web after the web has passed the nozzles, the improvement for preventing the accumulation of such heavier coating on the web in which each nozzle comprises an elongated body member having its length dimension disposed transversely of the length of the web, an elongated plenum chamber enclosed by the body member and extending along the length thereof, fluid discharge orifice forming means facing toward the web and extending along the length of the body member for placing the plenum chamber in communication with the exterior of the body member, fluid inlet port forming means associated with the body member in fluid communication with the plenum chamber in only an intermediate zone along the length of the plenum chamber, the fluid inlet port forming means constituting the only fluid inlet means in fluid communication with the plenum chamber, the fluid inlet port forming means being elongated in the direction of the length of the body member, the smallest cross-sectional area of the fluid inlet port forming means having a length dimension at least several times the width dimension of such area but not greater than one-half the length of the fluid discharge orifice means, baffle means located within the plenum chamber interposed in the path of fluid moving from the fluid inlet port forming means through the plenum chamber to the fluid discharge orifice forming means, the baffle means being shaped to change the direction of movement of fluid passing through the fluid inlet port forming means and impinging on the baffle means, and internal wall surfaces presented by the plenum chamber shaped to impart to fluid impinging on the baffle means and moving through each end portion of the fluid discharge orifice forming means movement having a component parallel to the associated surface of the web and in a direction toward the associated marginal portion of the web to thereby move liquid coating on the associated marginal portion of the web outwardly and downwardly relative to the surface of the web.