Detector for irregularities in continuous plastic webs - monitoring light reflection using optical fibres for irradiation and reflection

摘要

Irregularities in a moving continuous web of plastic material are detected by means of an optical device with optical fibres. Partic. suitable process for molecularly oriented materials and for operation at high temps. In a suitable embodiment a moving continuous belt of e.g. transparent polyethylene terephthalate tape with highly reflective surface is provided. The monitoring device has a halogen-quartz lamp, and this sends light through an optical fibre which ends in a block mounted at ca. 15 cm above the tape. Another optical fibre is also mounted in the block and conducts reflected light to a photosensitive. Schmitt-Trigger detector whose signal is passed to an amplifier and thence to an alarm device.