Link 1 has annular projection a and rotates about fixed axis A. When driving link 1 rotates, cam b (shown by dash lines) rigidly mounted on link 1, engages a pin c of driven pin wheel 2, turning the wheel about fixed axis B. At this, two other pins c slide along slots d of annular projection a. When two pins c of pin wheel 2 are inside and two outside, annular projection a freely passes between them and wheel 2 has a dwell until cam b, after one revolution, engages the next pin c on wheel 2. Thus, to each revolution of driving link 1, driven wheel 2 turns through an angle of 90°.
$2621$PG,D$