Abstract: A measuring head is used to measure a yarn characteristic while generating a continuous signal proportional to variations in the measured characteristic. The signal is multiplied by an identical second signal obtained either from a second measuring head located downstream of the first measuring head a distance corresponding to a predetermined periodic interval of yarn length (L) or by a time-delay of the first signal corresponding to the periodic interval (L). The multiplication of the signal deviations occurring at the periodic intervals, should such be present, produces a strong output signal indicative of the yarn irregularities. This output signal can be used to interrupt operation of the yarn processing machinery.

Abstract: The start-stop program for the open-end spinning machine causes the external suction means to be rendered ineffective during the stopping process before the rotor falls below a speed necessary to maintain tension in the fiber ring in the fiber collecting groove of the rotor. Also, the program causes the external suction means to be effective on the rotor during a start-up only after the rotor has reached a speed sufficient to maintain the fiber ring tensioned in the collecting groove.

Abstract: A suction means and a severing means are located behind the friction drive drum to receive a yarn when the bobbin holder is lifted into a idling position and to sever the yarn when the holder is returned to the operating position with a fresh tube in place. The suction means and severing means are actuated via the holder and are positioned to one end of the fresh tube so that the short yarn end can be wound onto the tube in a reserve winding zone. The yarn is thereafter moved into the usual yarn traversing zone of the tube to form a bobbin.