US Patent 6920660 Electric toothbrush reduction gearbox

An electric toothbrush includes a handle, a bristle head and a neck extending from the handle to the bristle head. A drive shaft extends through the neck to the bristle head. A motor is situated within the handle and has a pair of spaced recesses and an output shaft situated between the recesses. A reduction gearbox receives torque from the output shaft of the motor and transmits it to the drive shaft at a reduced speed. The gearbox has a base plate having a pair of projections extending into the recesses of the motor, a cover plate fixed to the base plate and at least one gear set between the base plate and the cover plate to transmitting torque from the motor to the drive shaft.