Click to enlarge
When driving pin wheel 1, carrying two pins, 4 and 5, turns through angle ψ about fixed axis K, intermediate sprocket 2 and pin wheel 3, constantly engaged to sprocket 2, turn about fixed axes F and H through an angle of two teeth. Thus pin wheel 3, carrying 20 pins, turns through one tenth of a revolution. Alternate teeth of sprocket 2 have a shorter face width. During each idle period of pin wheel 3, two full width teeth of sprocket 2 engage the outer circumference of driving pin wheel 1, thereby preventing unitentional rotation of pin wheel 3.