| 摘要 |
Device for under-thread monitoring, especially on a two-thread lockstitch machine, with a light signal which is directed axis-parallel towards the flange of the under-thread bobbin, emanates from a light-signal transmitter and passes through orifices in the bobbin flange and which strikes a signal receiver having a photocell, as soon as an optical connection between the signal transmitter and signal receiver is made as a result of a predetermined decrease of the under-thread roll surrounding the bobbin core, whilst an infrared reflex sensing head (21), known per se and having a signal transmitter (1) and signal receiver (2) in one unit (3), is arranged at a short radial and axial distance from the core (4) of the under-thread bobbin (5), and a light-reflection surface (7) perpendicular to the transmission beam (6) is arranged directly on the under-thread bobbin (5). <IMAGE>
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