Solid-state electronic brush speed sensing control

Claim 1

For use in a vacuum cleaner having a suction head and means for drawing air and entrained material through the head with a brush rotatably mounted in the head for loosening material on a surface being cleaned to cause entrainment thereof in the drawn air and a drive including an electric motor for rotating the brush at a normal operative speed with a connection for connecting the motor to a source of AC electric power, the improvement comprising a control for disconnecting the motor from the electric power source, the control including means for sensing the rotational speed of the brush, means for disconnecting the motor from the electric power source when the brush is rotating at a predetermined tripout speed well below its normal operative speed, and means for automatically varying the predetermined tripout speed in direct relation to variations in the voltage from the source of electric power, the automatic varying means including means for converting the AC power from the electric power source to DC power so as to provide a DC power supply for the control, and a zener diode connected between the DC power supply and the sensing means for the rotational speed of the brush.