US Patent 7120960 Electric toothbrushes

An electric toothbrush has a brush head which is mounted in a movable manner, and a drive for producing an oscillating operating movement in the brush head. The drive includes a cyclically movable drive part and a follower part. The follower part is biased against the drive part so that the follower part follows the drive part's cyclic drive movement. A sensor determines the brush head's contact pressure by sensing the extent of coupling between the follower part and the drive part, and determining the contact pressure of the brush head based on the extent of coupling.