| 摘要 |
An electric toothbrush has an eccentric unbalanced drive shaft extension constrained by a brush head to rotate freely about a longitudinal axis inside a cavity in the brush head. The shaft extension and the brush head are flexibly coupled to a drive shaft and a remote end of a shank, respectively. When the shaft is rotated by an electric motor in a handle of the toothbrush, the brush head is caused to vibrate. The handle is not caused to vibration to any significant extent.
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