The lengths of the links comply with the conditions: A͞B=D͞C and B͞C=A͞D. The same kind of motion can be transmitted to slider 4 by crossed-crank linkage ABCD as by elliptical gears 5 and 6. Points A, B, C and D should be the foci of ellipses 5 and 6. Uncertainty of motion of crossed-crank linkage ABCD in its extreme (dead centre) positions is eliminated by the provision of pins F and G on links 1 and 3 that enter the corresponding slots, L and K, of these links.
$1514$SC,6L$