US Patent 9919437 Personal care device

A personal care device comprising a main housing, a hair-cutting module displaceable with respect to the main housing against spring force in a direction parallel to a main axis, and a sensor comprising a first sensor unit connected to the main housing and a second sensor unit connected to the hair-cutting module. The hair cutting module is also tiltable in directions relative to the main housing. By measuring average displacement of the hair cutting module at multiple locations, the sensor is sensitive only to displacement parallel to the main axis. The sensor measures such displacement and determines the force needed to effect such displacement. If the force is larger than a predetermined value, a warning signal will be produced.