Method and apparatus for operating an open-end rotor spinning unit
An open-end spinning unit, which comprises a spinning rotor 1 that rotates during the spinning operation at a high rotational speed in a closed rotor housing 2. The spinning rotor is rotated by an individual electric motor drive 18 and supported in a smoothly running bearing assembly. When the drive is disconnected and the rotor housing is properly closed by a cover element 8, the spinning rotor is biased and rotated by an airflow resulting from a vacuum prevailing in the rotor housing and the motor drive operates as a generator. At least one of the electric quantities P v , G v which develop during the generator operation of the drive 18 is monitored, and upon exceeding a threshold value which can only be attained when the cover element is properly closed, a signal S is generated and processed in a control unit 30 to cause the cover element 8 on the rotor housing 2 to be locked, and thereafter the drive 18 is connected to its electrical supply to rotate the rotor at high speed.
1. A method for operating an open-end rotor spinning unit, which comprises a spinning rotor that rotates during the spinning operation at a high speed in a closed rotor housing which is closed by a cover element which is moveable between open and closed positions, with the spinning rotor being operated by an individual electric motor drive and supported with its rotor shaft in a smoothly running bearing assembly, said method comprising the step of
biasing and rotating the spinning rotor by an airflow resulting from a vacuum which is generated in the rotor housing and while the drive is disconnected from its energy supply and is operated as a generator,
monitoring at least one of the electric quantities that develop during the generator operation of the drive,
generating a signal upon the monitored electric quantity exceeding a predetermined threshold value which can only be attained when the cover element is properly closed,
processing the signal in a control unit so as to cause the cover element on the rotor housing to be locked in the closed position, and then
connecting the drive to its energy supply to rotate the spinning rotor.
2. The method of claim 1 , wherein the drive comprises a DC motor, and wherein the phase voltage (P v ) is used to monitor the rotating field of the motor.
3. The method of claim 1 , wherein the drive comprises a DC motor, and wherein the generator voltage (G v ) of the motor is monitored.
4. The method of claim 1 , wherein as the threshold value for the monitored electric quantity (P v , G v ), a rotational speed of the spinning rotor is used, which is about 2000 rpm.
5. The method of claim 1 , wherein upon reaching a rotational speed limit, which is clearly below the rotational speed at which the threshold value is reached, the spinning rotor is decelerated for a limited time to a lower rotational speed at least once by short-circuiting the motor connections of the drive, and that it is only then accelerated to a rotational speed at which the threshold value is reached.
6. The method of claim 1 , wherein the step of processing the signal includes actuating an actuator which electrically locks the cover element on the rotor housing such that an opening of the rotor housing will no longer be possible, when the rotational speed of the spinning rotor exceeds a rotational speed limit.
7. The method of claim 6 , wherein the step of connecting the drive to its energy supply includes releasing a switching element for restarting the drive of the spinning rotor only when the cover element has previously been locked in a proper manner.
8. An open end rotor spinning apparatus comprising
a spinning motor mounted in a housing for rotation at high speed during the spinning operation,
a cover element pivotally mounted for movement between a closed position closing the housing and an open position,
an individual electric motor drive for rotating the spinning rotor and which is capable of operating in generator mode when it is disconnected from its energy supply and is externally driven,
a vacuum system for drawing a partial vacuum in the housing while causing the spinning rotor to rotate from the resulting airflow through the housing and thereby cause the electric motor drive to operate in generator mode,
a control unit for monitoring an electric quantity of the electric motor drive while running in generator mode and for generating a signal when a predetermined threshold value of the electric quantity is reached, and
an actuator responsive to receiving the signal from the control unit for locking the cover element in said closed position.
9. The apparatus of claim 8 further comprising a switching element for selectively connecting the electric motor drive to an energy supply, and wherein the control unit is configured to actuate the switching element to cause the electric motor drive to rotate the spinning rotor upon receipt of a signal from the actuator that the cover element has been locked in the closed position.
10. The apparatus of claim 9 wherein the electric motor drive is a DC motor.
11. The apparatus of claim 8 wherein the predetermined threshold value is selected so as to be attainable only when the cover element is properly in said closed position.
12. The method of claim 1 , comprising the further subsequent steps of
disconnecting the drive from its energy supply to cause the drive to operate as a generator while the rotor continues to rotate,
monitoring at least one of the electric quantities that develop during the generator operation of the drive to provide an indication of the rotor speed, and
processing the at least one of the electric quantities to release the locked rotor housing only when the rotor speed falls below a predetermined value.