A power toothbrush with a drive train that is easy to manufacture,
reliable in service and that enables multiple heads or other complex
design or functional elements is provided. In an illustrative embodiment,
the power toothbrush includes a sealed case that encloses a motor with a
pinion gear joined to an eccentric link. This eccentric link can be a
circular rack having an eccentric pin that rides in a slot on a drive
plate. The drive plate is joined to a push rod, typically constructed of
metal that passes up a hollow toothbrush shaft through an elastomeric
seal to a head assembly. The head assembly includes one or more moving
disks that are each connected to generally circular brush heads, which
project outwardly from the head assembly. One disk receives a bent end of
the drive shaft in a hole located eccentrically to the axis of rotation.
When the circular rack rotates in a single direction, it drives the shaft
in a reciprocating motion that, thereby, rotates the disk in a
corresponding reciprocating circular motion about its axis. Additional
disks can be linked by a short connecting shaft or link to the first disk
via eccentric holes--other linkages, such as mating gears between disks
can be used to simultaneously drive further disks, thereby providing a
multiple moving-head power toothbrush.