Abstract: A method is taught for preparing a coating hopper prior to initiation of coating a liquid coating composition at a predetermined coating flow rate onto a moving substrate wherein the coating hopper includes at least one internal flow path therethrough. The internal flow path(s) of the coating hopper are drained. The liquid coating composition is introduced into internal flow path(s) at a purge flow rate which may be determined empirically. The internal flow path(s) are filled with the liquid coating composition and with the liquid coating composition then discharging from the internal flow path(s) onto a slide surface of the coating hopper, the liquid coating composition flowing down the slide surface and over a lip of the coating hopper at the purge rate to a drain. The flow of the liquid coating composition through the internal flow path(s) is maintained at the purge rate until air within the internal flow path(s) has been displaced from the coating hopper.

Abstract: A versatile, multiple-slot, dual cavity, slide/extrusion hopper for assembling and coating a composite layer comprising a plurality of highly uniform, superposed compositions, and a method for determining the dimensions of the hopper are disclosed. The hopper is suitable for photographic applications and other applications requiring highly uniform layers. The hopper is versatile in that it can accommodate coating compositions that range from Newtonian to substantially shear thinning and in that fewer than the total number of elements may be supplied; the slide offsets between elements are suitable for both merging layers and for the top layer alone. The height of the secondary slot is preferably greater than the height of the primary slot. The method provides optimal cross-sectional shapes for the cavities. Versatility is achieved without greatly increasing the height or thickness of the elements.

Abstract: A hopper bar having a longitudinal channel formed in the portion of the bar which normally would support a coating lip wherein a wall of the channel is a precision cylindrical locating pin, and has a replaceable hopper lip element, formed to fit within the channel, is provided with a precision round bushing for receiving the locating pin such that upon assembly of the element to the hopper there is no offset significant to the coating process between the slide surface of the hopper bar and the slide surface of the lip element. The lip element may be attached to the hopper wall along the remainder of their mutual length by either bolts or magnets to permit independent longitudinal thermal expansion of the hopper bar and lip element.