Face cam 1 rotates about fixed axis A and has a profiled ridge on one face composed of concentric circular portion b-b, along an arc described from centre A, and spiral portion a-a. Driven wheel 2 rotates about fixed axis B-B and carries rollers 3, radially mounted around the circumference of the wheel. Axes A and B-B cross and are perpendicular to each other. When cam 1 turns through angle ψ, spiral portion a-a of its ridge acts on rollers 3 and turns wheel 2 through the angle φ=(2π/z) where z is the number of rollers on wheel 2. During the remainder of the revolution of cam 1, two adjacent rollers 3 roll along the side surfaces of concentric portion b-b of the ridge, thereby preventing unintentional rotation of wheel 2. When cam 1 rotates continuously, wheel 2 rotates intermittently with one long dwell per revolution of cam 1.
$3097$SmC,ML$