Method and apparatus to monitor thread spinning operation of open end spinning machines and effective thread stop motion

Thread production monitoring system to supervise thread being spun by an open end spinning machine, having a spinning turbine,

• and having a thread thickness sensor (1, 2) providing an electrical signal (V.sub.S) representative of thread thickness and having peaks where the thread thickness deviates from an average condition;
• wave shaping circuit means (3, 4, 5) providing trigger signals upon occurrence of signal peaks in the electrical signal;
• and comprising,
• a blocking timing circuit (6) triggered by the wave-shaped trigger signals and providing a pulse (V.sub.T-1) and having a blocking time which is a little less than the repetition time of periodically repetitive defects in the thread, as determined by the spinning turbine diameter and pull-off speed of the spinning machine to permit the timing circuit (6) to be retriggered by periodically repetitive signals but to remain in its blocked state during the predominant portion of time between periodically recurring thread defects;
• counter circuit means (7, 8) counting the pulses from the blocking timing circuit (6) and defect signal generating means (9) providing a defect signal when the counter circuit means has counted a predetermined number of pulses from the blocking timing circuit (6) indicative of a plurality of periodically recurring defects in the thread.