When turning green lever clockwise, its gear sector pushes the blue rack up.
When turning green lever counterclockwise, gear force pushes the gear sector out of contact with the rack so the latter is kept immobile thanks to orange pawl. Blue spring forces the pawl towards the rack.
Axle of the green gear sector moves in a curved groove.
To lower the rack keep the gear sector out of contact with the rack and turn the pawl clockwise.
This video was made based on US patent 964905, 1909.
Inventor files of this
آی-ویدئو