Optical apparatus for monitoring for thread breakage

摘要

A laser beam scanning device (17) is provided for monitoring for thread breakage in tufting machines (31) in which a carrier web (16) is passed from below to a spiked roller (11) and is deflected by the spiked roller into a substantially horizontal direction so that it can be passed beneath a row of needles (12). The row of needles (12) periodically introduce threads into the carrier web (16) by up and down movement in order to form tufted material. A narrow retro-reflecting strip (14) is arranged directly below and behind the tips of the needles and directly above the tufted material (15) parallel to the row of needles (12) and substantially at right angles to the surface of the tufted material. The scanned light beam (18) is regularly interrupted by the threads which pass through the needles (13) when the needles are in the elevated open position and, after reflection at the retroflecting strip (14) and other optical elements, is received by a photoelectric receiver (19) where it generates an AC output signal. If one of the threads is broken then the scanning beam (18) is not interrupted at this position and this is recognised in the output signal from the light receiver (19).