It is developed from mechanism shown at
   • Fourbar linkage 2B  
Two such mechanisms are arranged separately in AC direction.
Two pink cranks and violet bar create a parallelogram mechanism.
Yellow plate nearly linearly translates and is always parallel to the ground.
Length of pink cranks: a
Length of green bars : 2.5a
Length of blue bars: 2.5a + 2.5a
Distances between stationary bearings AC: 2a.
This arrangement can be applied for any tracing mechanism where the translation of a plate along the traced trajectory is needed.

STEP files of this video:
http://www.mediafire.com/file/318hj7b...
Inventor files:
http://www.mediafire.com/file/q5t4n08...