Web coating method and apparatus

摘要

A coater includes an impression cylinder and a gravure cylinder rotatably mounted. A first pivot arm unit is pivoted on the impression cylinder shaft and supports a pivot shaft. Depending pivot arms on the shaft support an offset cylinder to one side of the impression cylinder and above the gravure cylinder. Nip adjustment units for the pivot arm unit and the depending pivot arms each include a pre-loaded ball bearing lead screw coupled to a slide housing and a separate power cylinder connected to the pivot unit and pivot arms respectively. The power cylinder unit forces the pivot structure into engagement with the lead screw follower which acts as a stop. A stepping motor rotates the lead screw and accurately positions the stop and thereby the pivot structure as a result of the power cylinder units. The lead screws separately control the nip setting of the off-set cylinder relative to the impression cylinder and the gravure cylinders. The stepping motors may be separately actuated to establish precise parallelism of the cylinders and simultaneously actuated to set the nip position. A coating thickness sensor coupled to the coated web is connected to a programmable controller having an output connected to operate the stepping motors to maintain a selected coating. In the method of operating the apparatus, a direct mode is used to apply coating to a web passing between the gravure and offset cylinders, or an indirect mode is used to apply coating to a web passing between the offset and impression cylinders.