Patent ID: 9427294
Filing Date: 2016-08-30
CPC Classification: A61C,G01R,H02P

Claim Text:
1. A method of operating a hand-held electrical appliance selected from the group consisting of an electrical toothbrush and an electrical razor, the appliance comprising a resonant motor for driving a vibratory component, the method comprising the steps of: driving the resonant motor with a predetermined driving frequency and constant duty cycle; measuring a motion-induced voltage of the resonant motor at a predetermined time of measurement (t determining a phase shift by measuring whether the motion-induced voltage value coincides with or crosses over a predetermined target voltage; and generating a signal when the measured voltage value has reached or exceeded the target value in response to an increase in mechanical load that causes a phase shift, the signal being selected from the group consisting of an acoustic signal, an optical signal, and a tactile signal.