Hourglass worm gears designed to concentrate surface normals

To avoid the influence of small displacement of gear axes under load, the authors propose that all contact normals of a tooth surface should be at right angles to the direction of the small displacement induced at each contact point under load. On the basis of this state of surface normals, a few methods of tooth surface generation have been devised for realizing the concept. In this research, an hourglass worm gear was made using one of the generating methods, and tested experimentally. As a result, the validity of this designing concept was substantiated.