GENEVAMECHANISM A common form of intermittent motion device is the Geneva
mechanism shown in Figure 2-12a. This is also a transformed fourbar linkage in
which the coupler has been replaced by a half joint. The input crank (link 2) is typically
motor driven at a constant speed. The Geneva wheel is fitted with at least three equispaced,
radial slots. The crank has a pin that enters a radial slot and causes the Geneva
wheel to turn through a portion of a revolution. When the pin leaves that slot, the Geneva
wheel remains stationary until the pin enters the next slot. The result is intermittent
rotation of the Geneva wheel.
The crank is also fitted with an arc segment, which engages a matching cutout on
the periphery of the Geneva wheel when the pin is out of the slot. This keeps the Geneva
wheel stationary and in the proper location for the next entry of the pin. The number
of slots determines the number of "stops" of the mechanism, where stop is synonymous