and the exciting coils 51c and 53c are energized therefore the feed roller 3 supplies the fibers 6 into the spinning rotor 2 the fibers 6 are combed within the spinning rotor 2 by the combing roller not shown and collected into a yarn 7 and the yarn 7 is twisted within the spinning rotor 2 then the yarn 7 is traversed to and fro by the traverse guide 11 and wound around a bobbin 16 forming a conical cheese 18 2 when the push button switch pb2 is pushed the operation of the solenoid coil of the relay ms for operating the main motor 33 and the motor 36 fig1 is stopped then the main motor 33 is turned off however the main motor is connected to the feed roller 3 draw off roller 8 and the winding drum 15 and has a large inertia and consequently the main motor 33 continues its rotation for a while in addition when the relay ms is stopped the motor 36 is turned off and is brought to a standstill after a certain delay time t a the delay time t a is generated by the inertia of the spinning rotors 2 the fiber supply however is stopped when the feed roller 3 is stopped before the spinning rotor 2 is stopped at the same time the time switch t2 is energized 3 since the solenoid coil of the relay ms is open the circuit comprising the break contact ms 2 the break contact t6 of the time switch.