By adding a cut out to the yoke of the scotch yoke mechanism that is the same shape as the
locus of the pin it is possible to make the yoke stay still for a portion of the wheel’s travel. This stationary time is know as dwell.
In this case the dwell at each end of the yokes movement is 90 degrees. This changes the characteristics of the movement
and has all sorts of possible uses.
Mixing both the dwell scotch yoke and the standard scotch yoke in one mechanism adds an extra layer of interest. The way the ends of the two yokes move differently could be harnessed to create a secondary movement. Perhaps a grabbing hand or a lifting flap.