Link 2 of four-bar linkage BCDE has pin (roll) a at point A. This roll engages slots b of Geneva wheel 3. When crank 1 rotates about fixed axis B, roll a of link 2 drives Geneva wheel 3 intermittently with dwells. The period of wheel dwell corresponds to portion y-y of the path of point A of roll a. Link 4, driven by crank 1 through gears 5 and 6, serves to prevent unintentional rotation of wheel 3 during dwell periods by the sliding of concentric surface c along concave surfaces d of Geneva wheel 3. In one full revolution of crank 1, Geneva wheel 3 is indexed through an angle of 40°.
$1753$GL,D$