The brown driving pulley transmits rotation to the blue shaft through a friction clutch. Number of turns the shaft can rotate: around 12.is overcome at the expense of increased device length by providing a stop pin in the orange traveling nut.
The engagement between the pin and the rotating finger must be shorter than the thead pitch so the pin can clear the finger on the first reverse turn. Using rubber ring and oil-impregnanted metal grommet for the sliding joint of the traveling nut and the lower rod helps lessen the impact