Internal Geneva Mechanism
Internal Geneva Mechanism - Introduction
Geneva mechanism is the one that translates continous rotary motion into an intermittent rotary motion. The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel ( driven wheel ) that advances it by one step at a time. The main wheel also has an elevated circular blocking disc that locks the rotating driven wheel in position between steps.
Aim:
The main aim of this project is to design an internal geneva mechanism using Solidworks and make a motion study that analyzes the contact forces, angular velocities and angular displacements for variours motor speeds and contact types.
Study setup:
This study consists of a driven wheel with four slots and a driving wheel with a pin that attaches to the slot and turns the driven wheel by a certain degree (90 degrees in this case) for one complete rotation of the driving wheel.
The below image shows the driven wheel.
The below image represents the driving wheel.
They are assembled by providing necessary constrains and the motion study is set up by introducing a motor at the central axis of the driving wheel. A solid body contact is established between these two wheels and the motion study is started.
Results:
1. Non precise Contact force between the pin on the driving wheel and the face of the driven wheel (slot) with which it makes a contact. The contact force is indicated by the spikes in the graph.
Then a precise contact was setup to obtain more accurate results.
2. Precise Contact force between the pin on the driving wheel and the face of the driven wheel (slot) with which it makes a contact. The contact force is one of a very important design parameters.
3. Angular displacement of the driven wheel
4. After this, the motor speed was set to 20 rpm and the angular velocity of the driving wheel was plotted. It can be seen that the angular velocity of the driving wheel was almost a constant because the motor was a constant speed motor.
Conclusion:
Thus the internal geneva mechanism was designed usind Solidworks and a motion study was conducted on it for a time of 20 seconds.