Brief Summary:

There are many everyday items that utilize a Geneva mechanism as a way of rotating their parts.  Geneva mechanisms are simple, cheaper and more robust than other mechanisms that create this rotation. 

• A Geneva mechanism is not the only way to generate the stop-and-go motion of a rotary indexing table. The table can be indexed by a ratchet-and-pawl mechanism driven by a pneumatic cylinder. The table can be indexed with a globoidal cam driven by a motor.
• A Geneva mechanism consists of two wheels: a driver and a follower. The driver is located below the follower. One to four pins or rollers are located along the outer edge of the driver. These pins engage radial slots cut into the follower at regular intervals. As the driver turns, the pin enters a slot and pushes the follower. When the pin leaves the slot, the follower stops.
• There are two main types of Geneva mechanism: external and internal. In an external Geneva mechanism, the driver is adjacent to the follower, with one wheel overlapping the other. The driver and the follower move in opposite directions, and the dwell period always exceeds the motion period. In an internal Geneva mechanism, the driver fits within the follower.
• Nevertheless, one shortcoming of Geneva mechanisms is that the beginning and end of the indexing motion are marked by sharp acceleration and deceleration. However, as the ratio between the diameter of the follower and the diameter of the driver increases, the peak acceleration and velocity of the indexing motion decrease.
• Engineers can modify the ratio of dwell time to motion time by staggering the driver pins or combining the Geneva mechanism with chain drives or gear trains.

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