It is an application of Sarrus mechanism.
Input: pink crank that can rotate full revolutions.
The yellow object is translated vertically along an absolute straight line (no need of a runway).
Its stroke length L = 4R.
R: length of the cranks (in pink and blue) and bars (in green).
The mechanism has unstable positions when the cranks and the bars are vertical so to overcome it the blue cranks are driven thanks to orange face gear.
When the platform crosses through the center plane (all the cranks and bars are horizontal), since the pivots on the base and the platform are aligned, the bars could rotate without the platform moving if it does not have enough momentum. Therefore, avoid stopping the platform at the center plane. If not, the mechanism can’t be started.