Method and apparatus for controlling a coating head, and a coating head

摘要

A method and apparatus are described for controlling a coating head, which exerts a nip pressure to a fibrous web to be coated while the fibrous web is supported by a backing roll. An output signal of a sensor integrated within the backing roll is read, thus producing a measured indication of the nip pressure. A number of actuator control values are derived at least partly from said measured indication of the nip pressure. Said actuator control values are delivered as commands to a number of respective actuators that contribute to creating the nip pressure, to control an amount of a coating substance on the fibrous web in the coating head.

主权项

1. A method for controlling a coating head configured to exert a nip pressure profile to a fibrous web to be coated while the fibrous web is supported by a backing roll and advancing in a machine direction, comprising the steps of:
reading an output signal of a sensor which is integrated within the backing roll and which extends in a cross direction perpendicular to the machine direction, thereby producing a measured indication of the nip pressure profile of the coating head in the cross direction; deriving a plurality of actuator control values at least partly from the measured indication of the nip pressure profile; delivering the actuator control values as commands to a plurality of actuators, the commands causing the actuators to press indirectly on a coating blade through a profiler bar, wherein the pressing of the actuators affects the measured indication of the nip pressure profile, and wherein the delivered commands act to control an amount of a coating substance applied on the fibrous web; measuring the amount of coating on the fibrous web downstream from the coating head in a direction of movement of the fibrous web determining, from the measured amount of coating on the fibrous web any deviation from a desired amount of coating and determining any required deviation of the nip pressure profile needed to achieve the desired amount of coating on the fibrous web; and calculating and delivering new actuator values to the plurality of actuators to effect the required deviation of the nip pressure profile.