A Geneva mechanism is a type of cam with a set of specialized gears that works as a timing device by reducing a rotating drive gear’s motion to an intermittent rotary motion in its mated, driven gear. This produces an alternating stop and start motion in the driven gear. The mechanism can also be used to rotate its shaft to a specific degree.
The Geneva drive’s characteristic stop and start motion is accomplished through a circular drive wheel’s unique single-pin configuration, situated on the drive wheel’s face rather than its edge. This pin on the mechanism’s driving wheel slides into specialized deep radial channels of its mated gear, forcing its rotation until the drive gear’s continuous motion pulls the pin out of the channel, causing the mated gear to cease its rotation. This cycle repeats once the pin comes around again to meet the next radial channel in the driven gear.
Geneva Mechanism Uses
The earliest uses of Geneva mechanisms were in mechanical-style watches, which were famously made in Geneva, Switzerland, earning the mechanism its name. However, in these watches the mechanism was used as a watch spring tension-limiter, which prevented both overwinding and complete unwinding.
Versions of the Geneva drive mechanism were incorporated into film movie cameras and projectors, which benefited from the Geneva mechanism’s indexing ability to precisely start, advance, and stop the motion of the film.
Modern Uses
While intermittent motion mechanisms like the Geneva gear mechanism find uses in many different forms over the years, modern Geneva mechanisms often find their home in precision manufacturing and applications that require intermittent rotary movement, including:
- Index-style counting machines
- Plotters - pen switching mechanism
- CNC machines - automatic tool changers
- Turret lathes & drills
- Assembly line indexing tables
Since a Geneva drive offers limited flexibility regarding speed, they are occasionally replaced in these types of machines with stepper belts or retrofitted with spindle carrier indexing kits to achieve more efficient motion, higher speeds (with less vibration) and less gear backlash.
Looking for a Geneva Mechanism?
Anyone with a need for a drive that can transfer continual rotary motion into intermittent stops and starts should get in contact with expert gear engineers like the experienced team at WM Berg. Drawing on our experience in designing and manufacturing precision mechanical devices like the Geneva gear, our team of engineers will deliver innovative solutions for your motion control needs.