GB1002698A - Improvements in coating of webs and the like - Google Patents

Abstract

1,002,698. Coating webs. OXFORD PAPER CO. April 24,1962,No. 15434/62. Heading D1L. Apparatus for coating a web 14, e.g. of paper comprises a backing roll 12, preferably having a cover 13 of resilient material, about which the web passes to be engaged by a spreader blade 37 which forms, at least in part, the bottom wall of a reservoir for the coating liquid. The blade which is of spring steel having a thickness between ten and thirty thousanths of an inch, projects between three-eighths and one-and-three-quarter inches from its holder, the plane of the black at the holder making an angle of between forty and fifty degrees with a tangent to the roll 12 drawn at the point where the said plane meets the roll. The reservoir, formed by: -the blades 37, a bottom wall 36, a back wall 45 and end walls 35 having peripheral felts 44, is carried in a frame 21 fixedly mounted on a shaft 18 which is rotatably mounted adjacent each end in bearing blocks 16. An arm 22 having associated adjusting screws 23, 24, is fixed on either end of the shaft 18 so that the angle of the reservoir (and therefore of the blade 37) to the backing roll may be adjusted, a scale 25<SP>1</SP> being provided so that the angle of the blade 37 to the roll may be read off. The blocks 16 are slidable on arms 15 of the frame 11 and fluid operated pistons and cylinders 26 act through levers 28, 27 to move the reservoir and blade 37 towards or away from the backing roll 12, the distance of closest approach being adjustably limited by means of micrometer-like devices 29 the blocks 16 are connected by links 32 and 33 to a shaft 34 to ensure uniformity of movement between them. Since blade 37 is flexible its adjustment towards or away from the roll governs the angle of the blade to the surface of the roll at its point of contact; preferably this angle is thirty three degrees. The blade 37 is mounted with some play between the bottom wall 36 of the reservoir and a plate 38 bolted thereto and it may be projected from or retracted into its mounting by rotation of an adjusting screw 41. The precipitation of solid particles in the reservoir is prevented, in part, by ensuring that the cross section of the reservoir decreases towards the blade 37 and that the walls thereof are smoothly centoured. However, since it is found that foreign bodies and particles in the liquid tend to accumulate in certain regions of the reservoir liquid is pumped out from these regions and passed through filters before being returned to the reservoir, fresh liquid being added to that returning. In alternative embodiments the bottom and back walls are formed by a single plate and the end walls 35 may be dispensed with, in which case the material flowing through the end gaps is collected and pumped through filters before being returned. Specific examples of papers with heavy coatings are given. Specification 542,625 and 995,360 are referred to.