Internal Geneva Mechanism

AIM: To create the 3D model of the internal Geneva mechanism.

Objectives of the project:

1. Create 3D models for driver and driven wheels.
2. Perform motion analysis by rotating driver wheel at 10rpm.
3. Plot of contact force(between driving and the driven wheel) as a function of time.
4. Plot of angular displacement of the driven wheel.
5. Compare the contact forces with and without “Precise contact”.

Introduction:

A mechanism that translates a continuous rotation into an intermittent rotary motion, using an intermittent gear where the drive wheel has a pin that reaches into a slot of the driven wheel and thereby advances it by one step, and having a raised circular blocking disc that locks the driven wheel in position between steps.

Geneva mechanism, also called Geneva Stop, 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. It is also used for indexing (i.e., rotating a shaft through a prescribed angle).

In the most common arrangement of the Geneva drive, the client wheel has four slots and thus advances the drive by one step at a time (each step being 90 degress) for each full rotation of the master wheel. If the steered wheel has n slots, it advances by 360°/n per full rotation of the propeller wheel.

An internal Geneva drive is a variant on the design. The axis of the drive wheel of the internal drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.

3D Model for Driver and Driven Wheels:

3D Model of Assembly of Internal Geneva Mechanism:

Obtained Results (for Motion analysis):

• At the speed of 10rpm of the driver wheel with 60fps.

Figure. Contact force between Driver and Driven wheel without precise contact.

Figure. Contact force between Driver and Driven wheel with precise contact.

Figure. Angular Displacement of Driven wheel.

Figure. Angular Velocity of Driven wheel.

• At the speed of 20rpm of the driver wheel with 120fps.

Figure. Contact force between Driver and Driven wheel without precise contact.

Figure. Contact force between Driver and Driven wheel with precise contact.

Figure. Angular Displacement of Driven wheel.

Figure. Angular Velocity of Driven wheel.

The link for the working animation of Internal Geneva Mechanism:https://youtu.be/48d6sfDRwWk