The yellow input shaft carrying the red pawl rotates continuously anti-clockwise. The violet disk (ratchet wheel) has a pin that slides in a slot of the yellow slider.
The slider goes up by the ratchet mechanism action but goes down by its weight (when the slider moves faster than the input shaft) so that the motion cycle time is reduced. For this prototype, 4 revolutions of the input shaft correspond 7 double strokes of the slider.