A Novel Worm Gear of High Efficiency

Abstract

This note describes a novel form of worm gear, in which the worm pinion has teeth that run straight round it and join up with themselves, so that they form rings (‘ring teeth’). These rings are free to turn on bearings whose axes are parallel to the axis of rotation of the whole pinion, but eccentric to it by a small amount r, such that the centres of the rings lie on a helix, radius r.

The teeth of the worm wheel are formed in the inside of a torus, so that they embrace the pinion somewhat. They have a small helical angle so that as a ring tooth rolls round the space between two worm teeth it forces them forward. Before that ring tooth disengages at one side of that worm wheel tooth space, the next ring tooth has engaged with the next wheel tooth space, and so on.

Because the ring teeth roll on the wheel teeth, with only a little spin and transverse sliding, the efficiency is very high. However, the construction of the pinion is elaborate and the load capacity of the drive is limited by that of the bearings on which the ring teeth rotate, which in turn is small because of the limits on space.