Method of inspecting coated web material to detect the presence of downlines thereon

摘要

This invention relates to a method of inspecting coated web material in order to detect the presence of downlines. The coated web material is transported past an inspection station and is inspected transversely point by point across the web width. Data signals are produced responsive to variations in coated thickness. The inspection operation is repeated as the web pass the inspection station and the data signals from points at the same distance across the web width are summed to produce an average signal waveform. Any abnormal excursions of the averaged signal waveform are registered as faults.