Worm is similar to the teeth with spiral lines on the screw, and the teeth in one circle of turbine are similar to spiral teeth, and the two spaces are orthogonal. Worm is the driving wheel, which drives the turbine to rotate through the rotation of the screw, so as to reduce the speed and increase the torque. The advantages are: large transmission ratio, compact structure, stable spatial orthogonal arrangement, low noise and self-locking; Disadvantages: large calorific value, large axial force of input shaft, easy to wear and low efficiency.
Most reducers on escalators use this kind of driving device.