text: 1. Field of the Invention
  This invention relates to mechanisms which rotate a shaft with selective bi-directional rotary rotation and selectively an axial oscillation. Specifically, the invention is described in the foregoing specification as within the field of electrically operated toothbrushes.
  2. Description of the Prior Art
  Electrically powered toothbrushes have been known to those skilled in the art for some time. Dentists have long recognized that proper brushing of teeth requires that the tooth brush move food particles away from one's gum line and also polish one's teeth. The above rotary toothbrushes typically are A.C. powered and uni-directional. They therefore move food particles away from the gum line for only one-half of all teeth. The above rotary oscillation toothbrushes typically have a 45 degree -90 degree arc of travel about it's axis in one direction before it oscillates back. Thus the gum line is subjected to brushing away from and also toward same. The net effect is that the gum line is not subjected to the contineous brushing away from the gum line as favored by dentists.
  Additionally, the latter toothbrush is powered by levers, gears and such mechanisms which are very prone to wear and greatly reduces the mechanical efficiency of the toothbrush.
  An additional category of toothbrushes attemps to provide axial oscillations by the use of a vibrating motor or solenoid. These however have proved ineffective due to the small displacement of the motors/solenoids.