Automatic brake in worm hoists

The red arrow represents load (to be raised or descended) applied to the hoist.
The blue arrows represent driving force applied to the hoist.
The yellow worm block can move axially a little so its male cone can contact with the female cone of the pink ratchet wheel.

The video shows three stages for the load:
1. Moving up: The worm is turned anticlockwise. Gearing force of the worm drive pushes the worm to the right to contact with the ratchet wheel. The cone clutch closes. The ratchet wheel rotates together with the worm.
2. Stop (no driving force): The load tends to turn the worm clockwise and pushes it towards the ratchet wheel. The cone clutch closes. The orange pawl prevents the load from descending.
3. Moving down: The worm is turned clockwise. Gearing force of the worm drive pushes the worm to the left: no more contact with the ratchet wheel. The cone clutch discloses. The worm wheel can rotate to descend the load. If the load descends faster than worm turning velocity, the situation said in item 2 happens. The moving down is a jerk process.
The key factor is the left hand thread of the worm in this case.
There is no need to use self locking worm drive.

Inventor files of this video are available at