Orange conrod, green and upper yellow cranks create a parallelogram mechanism.
R1: pitch radius of green gear
R2: pitch radius of blue gear
i = R1 / R2 = 40 / 19. This ratio is needed to meet requirement when green gate rotates α = 58 deg., blue gate rotates 90 deg. in relation with the green gate.
i changes when α has different values. i = 1 if α = 90 deg.
If necessary a supporting swivel wheel for the blue gate is mounted at its lower right corner.
This video was made on request of Mr. JC Lo from Malaysia.
The two gears can be replaced by a bar to get similar effect. See:
   • Folding barrier 2a  
Link for downloading STEP files of this video:
http://www.mediafire.com/download/p8b...
Inventor files of this video:
http://www.mediafire.com/download/oc0...