In this video I will explain how to Scott Russell straight line generator work. As you see, it is 4 bar linkage type. What is special?
As picture above, link AB can hinge at A. Link CD can hinge at B that follow link AB, hinge at C that follow roller which restricts it to horizontal oscillating movement. When link AB oscillates Point D of link CD will move as straight line, roller reciprocate left and right.
You can see this video below for more detail.