worm gear traction

Worm gear traction elevators are geared traction elevators in which the gears driving the sheave are in the form of a screw-like cylinder (a "worm") meshed with a wheel indented with diagonally-aligned teeth (a "worm gear").

The screw-like worm meshes with the toothed wheel to transmit rotation to the hoisting mechanism. The cable sheave remains part of a geared traction system.

Helical gear traction uses toothed wheels with diagonal teeth instead. The distinction is in the gear arrangement rather than the cab's use or passenger capacity.