Cover for basement entrance 4

Yellow frame reciprocates linearly under action of grey cylinder. Thanks to parallelogram mechanism of two orange rockers, the green cover can raise up to level of the floor. In motion to the left the cover falls down due to the gravity. Pay attention to two red pins, pink and brown plates that act as stoppers. Gap between the floor and the cover is minimum. The cover occupies small space during motion. Center of mass of the cover moves up only a little so the mechanism is good in term of saving energy. The