Two cranks and yellow rack create a parallelogram mechanism.
Input: pink crank rotating continuously.
Output: green gear performing harmonic oscilation. Oscilating angle depends on the crank radius.
Input and output axes are skew at 90 deg. angle.
Output axis is not perpendicular to the plane created by two crank axes.
Blue conrod jointing two eccentrics of the cranks is for overcoming dead positions.