Unlike an ordinary slider-crank mechanism in this stuff speed of green slider is very high at the lower end of its down stroke thanks to blue spring.
Input: blue double crank of continuous rotation
Yellow crank rotates idly on the input crank. It rotates together with the input only when one blue crank contacts red pin fixed on the yellow crank.
The other blue crank prevents the yellow crank from inertial moving upward.
The green slider has dwell at its lowest position.