Dupro Ag

Duepro Ag

Peter Woerwag

Disclosed is an apparatus for controlling the rotational speed of an electric motor based upon the load encountered by the electric motor. A load sensor provides a voltage level based upon the operating load of the electric motor and accumulates this voltage in accordance with the cycle of the alternating current supplied to the motor. If during a cycle of the alternating current, the voltage exceeds a predetermined level, a transistor will be biassed into conduction, said transistor turning off a thyristor and preventing any further conduction of the thyristor during that cycle of the alternating current. Thus the duty cycle of the thyristor determines the total amount of current supplied to the electric motor and this current level determines the rotational rpm of the motor.

Speed control circuit for electric motor

Disclosed is an improvement in a vacuum cleaner having a roller-shaped brush mounted in the vacuum nozzle thereof. A separate rotational speed control is provided for the electric motor which operates the roller-shaped brush and in preferred embodiments this rotational speed control is adjustable by the operator of the vacuum cleaner. In a further embodiment, two separate rotational speed controls are provided, one controlling the speed of the roller-brush motor and the other controlling the speed of the vacuum-generating motor. A still further embodiment comprises a single rotational speed control which can be interchangeably switched into or out of connection with either the roller-brush motor or the vacuum-generating motor. A still further embodiment discloses a roller-brush motor speed control which can be added to existing vacuum cleaners.

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Stuttgart, Germany

Peter Woerwag