Geneva Gear Mechanism The main component of this machine will be the Geneva mechanism (or Maltese Cross). The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation into an intermittent rotary motion. Geneva mechanism, also called Geneva Stop, is one of the most commonly used devices for producing intermittent rotary motion, characterized by alternate periods of motion and rest with no reversal in direction. Geneva Mechanisms are widely used in motion picture film projectors to intermittently advance film through a film gate having a projection aperture.
Geneva wheels having the form of the driven wheel were also used in mechanical watches , but not in a drive, rather to limit the tension of the spring , such that it would operate only in the range where its elastic force is nearly linear. If one of the slots of the driven wheel is occluded, the number of rotations the drive wheel can make is limited. In watches, the “drive” wheel is the one that winds up the spring, and the Geneva wheel with four or five spokes and one closed slot prevents overwinding (and also complete unwinding) of the spring. This so-called Geneva stop or “Geneva stop work” was the invention of 17th or 18th century watchmakers.
Other applications of the Geneva drive include the pen change mechanism in plotters , automated sampling devices, banknote counting machines, and many forms of indexable equipment used in manufacturing (such as the tool changers in CNC machines; the turrets of turret lathes , screw machines , and turret drills; some kinds of indexing heads and rotary tables ; and so on). The Iron Ring Clock uses a Geneva mechanism to provide intermittent motion to one of its rings.
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