FRICTION GEAR INCLUDES IDLER ENGAGING FACING CONCAVESURFACES:
(under the class definition) Subject matter wherein said rotary motion transmitting parts include a first rotatable element having a first concave surface, a second rotatable element having a second concave surface facing the concave surface of said first rotatable element so as to define a cavity therebetween, and a third rotatable element rotatable about its own axis and mounted in said cavity; said third rotatable element including surface portions in contact with said first and second concave surfaces to transmit rotary motion from said first element to said second element via said third element by surface friction of rolling contact between said contacting surfaces. [figure]
