What Is Geneva Drive?
Geneva drive is a gears mechanism that translates rotational motion into intermittent rotary motions. The rotating drive wheels have a pin that enters the slot of the driven wheel and rotates it step by step. The driving wheel also has an elevated half-circle which locks the driven wheel in position between the steps.
The main difference between Geneva Drive & other gears is that Geneva Drive has unusual teeth. Unlike other gears, the interaction between driving in Geneva operates, and the driven part is not continuous, and the resulting motion is intermittent.
The Geneva Drive or Maltese Cross is a gear mechanism that converts continuous rotation into intermittent motion. The rotating drive wheels have a pin that reaches into a slot of the driven wheel that moves it one step.
The drive wheel consists of a raised circular resistor disk that locks the driven wheel in position between the steps. Because the apparatus requires good lubrication, it is often enclosed in an oil capsule.
Working of Geneva Drive:
Geneva drives are commonly used sequencing mechanisms where an intermittent motion is required. Inverted Geneva drives, which are a variation of the Geneva system, are used where the wheel has to rotate in the same direction in the crank.
This requires less radial space and maybe a circular section attached to the locking device crank that locks by wiping against the rim built on the perimeter of the wheel.
The design and construction of a conventional Geneva system are generally simple and inexpensive because it does not have a particularly curved profile on any component except for straight lines and circular arcs.
However, due to the dissection of the acceleration at the beginning and end positions, the drawback to using a traditional Geneva mechanism has a large effect when the driving crank is attached, and the wheel disengages with the slot.
Geneva Drive has two wheels, driving and driving wheels. The driving wheel has a bit higher than the pin and semi-circular disc, which is elevated.
The driven wheel has 4, 6, or more slots in which the pin of the driving wheel passes and rotates the driven wheel at an angle depending on the number of slots.
If it has 4 slots, it will be rotated 90 degrees in one step, and if it has 6 slots, it will be rotated 60 degrees in one step. After each step, an elevated circular disc is used to close the driven wheel.
Types of Geneva Drive:
- External Geneva Drive
- Internal Geneva Drive
- Spherical Geneva Drive
#1. External Geneva Drive
In this externals Geneva drive, the driven wheel is externally connected with a rotating drive wheel. It is the most popular Geneva drive and is used in many mechanical products such as watches and film projectors. It can withstand high mechanical stresses.
#2. Internal Geneva Drive
In the internal Geneva drive, the driven wheel is internally connected with a rotating drive wheel. Both the driver & the driven wheel rotate in the same direction. Its disadvantage is that it cannot be made small, and it cannot withstand high mechanical stresses like external Geneva drives.
#3. Spherical Geneva Drive
In spherical Geneva drives, the driven wheel is spherical in shape and is externally connected to the rotating drive. In this, driving and driven wheels are on vertical shafts, i.e., input and output shafts are perpendicular to each other.
Applications of Geneva Drive:
- Modern film projectors can also use an electronically controlled sequencing mechanism or stepper motor, which allows the film to be fast-forwarded.
- Geneva wheels in the form of a driven wheel were also used in mechanical clocks, but not in a drive, but to limit the tension of the spring, as if it operated only in the range where its elastics force was almost linear.
- Plotter in Geneva Drive, automatic sampling devices include pen change mechanism.
Tables Indexing in Assembly Lines, Tool Changers for CNC Machines, and so on.
- The Iron Ring Clock uses the Geneva system to provide intermittent motion in one of its rings.
- The most commons application of Geneva Drive is a movie projector.
- Banknote counting machine.
- Automatic Sampling Machines.
- Plotter – plotter is a computer printer to print vector graphics.
Advantages of Geneva Drive:
- Geneva drives may be the simplest and least expensive of all intermittent speed mechanisms.
- They come in a variety of sizes, ranging from those used in instruments to axle carriers used in machine tools, weighing several tons.
- They have good speed curve characteristics compared to rats but exhibit more “jerk” or instantaneous changes in acceleration than better production systems.
- Geneva maintains good control of its load at all times, as it is provided with locking ring surfaces.
Disadvantages of Geneva Drive:
- Geneva is not a versatile system.
- The ratio of speed to speed duration is also established once the number of inhabitants per revolution was not selected.
- All Geneva acceleration starts decreasing and ends with finite ac- creation and deceleration.
- This means that they cause a setback.