Curtain- or spray coating equipment for fibrous web used to make e.g. paper or card, runs web over one or more rollers with textured surfaces allowing escape of air boundary layer

摘要

Either or both of the rollers (5, 6) on either side of the curtain (4) coating nozzle (3a) in the coating unit (3), is constructed as a known form of spreading roller (50, 60). The spreading roller (50, 60) has a structured surface with a hardness between 20 and 90 as measured by the P&J plastometer. The structure comprises depressions with intervening strips, which offer a volume for air escape. The pattern is repeated over each half length of the roller, with opposed spiral configurations in each half (i.e. a chevron-like texture). An alternative surface structure for the roller(s) comprises wavy strips and grooves running axially along the roller surface. This pattern alternatively extends radially or transversely with respect to the roller. In a further variant, the depressions form small cups, or the strips form a number of studs or grids, with uniform distribution over the entire circumference.