Patent ID: 7398575

Claim:
An electric toothbrush comprising: a handle defining a hollow interior region with a motor disposed therein; a head comprising a movable bristle holder, wherein said movable bristle holder has bristles disposed thereon; a neck extending between said handle and said head; and a drive shaft defining a longitudinal axis, wherein said drive shaft extends through said neck and operatively connects said motor to said movable bristle holder for transferring power from said motor to said movable bristle holder, wherein upon operation of said motor, said drive shaft undergoes reciprocating motion, and wherein said drive shaft comprises at least one spring element integrally formed with said drive shaft between said motor and said movable bristle holder, said at least one spring element being substantially rigid and unchanged in shape when said drive shaft adjacent said movable bristle holder is not excessively loaded to transfer power from said motor to said drive shaft adjacent said movable bristle holder without any significant loss in efficiency and relatively flexible upon application of an excessive load to said drive shaft adjacent said movable bristle holder which limits movement thereof so that said motor causes said at least one spring element to undergo repeated displacements by absorbing at least some of the power from said motor which enables said motor to continue to operate while consuming ordinary levels of power even though said drive shaft adjacent said movable bristle holder is excessively loaded and has its movement limited.