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 wheel dwell corresponds to approximately straight portions y-y of the path of point A of roll a. These portions make an angle of 90° with each other. Concentric surface d of crank 1 slides along concave surfaces e of Geneva wheel 3 to prevent unintentional rotation of the wheel during its dwell periods. In one full revolution of crank 1, Geneva wheel 3 is indexed through 90°.
$1755$GL,D$