May 13, 2009

Geneva Wheel Design - A Wonderful Intermittent Motion Mechanism

Geneva Wheel Mechanism

The fascination for Geneva Wheel never ends. I always wondered to our ancestors  innovated such a brilliant mechanism. Some of the interesting applications of Geneva Wheels are movie projectors, watch over winding protection, tool changing turrets, automated sampling devices, indexing tables for machine shops and so on.

Geneva_mechanism_6spoke_animationNow, the Geneva wheel is one of the most useful mechanisms for providing high-speed, intermittcnt, rotary motion. In the position shown in this first diagram the roller is on the point of entering the slot and about to begin driving the star wheel. Drive ceases when the roller has moved through angle a. The star is locked during its rest periods because thc concentric shoulder of the driving member has engaged the corresponding edge of the star. To permit the drive wheel to continue turning it must have a recess for star clearance. When a Geneva mechanism is used in a machine, the machine speed depends upon the speed at which the star can be driven.

Geneva mechanism can theoretically have from 3 to any number of slots. In practice from 4 to 12 is enough to cover most requirements. Once the number of slots and crank dia are known, the layout can be constructed with the basic knowledge of geometry. Keep exploring this interesting mechanism.

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