Method for coating using an open-ended ink chamber having restrictions for partially limit ink flow

Abstract

A method .[.and apparatus.]. for coating wherein the horizontal flow of coating liquid is restricted adjacent the ends of the coating roll to overcome foaming by high flow rates of liquid flow while avoiding fouling of the roll journals.

I claim: 
     
       1. In a method for applying a liquid coating to a moving web by applying ink to a rotating roll for transfer to said web, the steps of introducing a coating liquid generally centrally of a horizontally elongated chamber having said roll mounted for rotation therein while positioning a vertical chamber wall closely adjacent to said roll, said wall adjacent the bottom thereof being equipped with a doctor blade for metering liquid to said roll, the improvement comprising applying said coating liquid to said web while partially restricting the flow of liquid horizontally along said wall slightly inward of the ends of said roll to provide a substantially uniform liquid level in contact with said roll along the length thereof while avoiding both foaming of liquid and fouling the roll end faces said partially restricting including the positioning of barrier inserts at least about 2 mm away from the ink applying surface of said roll collecting the liquid flowing past said roll ends and reintroducing the same into said chamber. 
     
     
       2. The method of claim 1 in which the restriction of the flow occurs at least about 8 to 10 mm. inward of the roll ends. 
     
     
       3. The method of claim 1 in which said blade is oriented to provide a scraping action relative to said roll. 
     
     
       4. The method of claim 1 in which said blade is oriented to provide a wiping action relative to said roll. 
     
     
       5. The method of claim 1 in which said web is moving in the same direction as the portion of the roll in contact therewith. 
     
     
       6. The method of claim 1 in which said web is moving in a direction opposite to the direction of the portion of the roll in contact therewith. 
     
     
       7. The method of claim 1 in which said web is in contact with a portion of said roll. 
     
     
       8. The method of claim 1 in which a second rotating roll is interposed between the first mentioned rotating roll and said web to provide offset coating. 
     
     
       9. The method of claim 1 in which the restricting offlow is varied as a function of the viscosity of the liquid. .[. 
     
     
       10.  Apparatus for applying a coating liquid to a moving web comprising a frame, a roll rotatably mounted in said frame to transfer coating liquid to said web, said frame being equipped with a horizontally elongated chamber adjacent the lower portion of said roll for partially confining said coating liquid, said chamber including a vertical wall positioned closely adjacent said roll, said wall adjacent the bottom thereof being equipped with a doctor blade for metering coating liquid to said roll, said wall adjacent the roll ends but slightly inward thereof being equipped with restriction means to partially limit the flow of liquid coating horizontally to maintain a substantially uniform level in contact with said roll along the length thereof while avoiding both foaming of liquid and fouling the roll end faces, said restriction means including inserts positioned at least about 2 mm away from the ink applying surface of said roll and collection means operably associated with said chamber for collecting the liquid flowing past said roll ends and for reintroducing the same into said chamber..]. .[.11. The apparatus of claim 10 in which a liquid receiving pan constituting said collection means is provided about the lower portion of said roll, said pan having end walls spaced at least 60 mm. from the adjacent end faces of said roll..].