Internal Geneva Mechanism

Aim: To simulate the internal Geneva mechanism for the given condition and plot the graph

Objective:

• Prepare 3-D model driver and driven part of internal Geneva mechanism.
• Create the assembly of a Geneva mechanism.
• Simulation of the Geneva mechanism at 10 and 20 RPM
• Compare the graph for the precise contact and non-precise contact force.
• Compare the graph of the angular velocity of the driver and driven at 10 and 20 RPM
• Get the graph of angular displacement.

Introduction

Geneva mechanism is used for the transfer continuous rotary motion into the intermediate rotary motion. This use in most of the automation work or feeding mechanism. There are mainly three types of Geneva mechanism internal, external, and spherical.

In the Geneva mechanism Driver Rotate the Driven Part. The driver is rotating at the constant speed and when its pass from the slot of the driven member its rotate the Driven member.

During this contact, some force is developed between Pin and Contact surface of the driven member. We have to analyze that force for the precise and non-precise contact also we have to compare the effect of the RPM on contact force, angular displacement, and angular velocity.

One application of the Geneva drive is in film movie projectors and movie cameras, where the film is pulled through an exposure gate with periodic starts and stops. The film advances frame by frame, each frame standing still in front of the lens for a portion of the frame cycle (typically at a rate of 24 cycles per second), and rapidly accelerating, advancing, and decelerating during the rest of the cycle. This intermittent motion is implemented by a Geneva drive, which in turn actuates a claw that engages sprocket holes in the film. The Geneva drive also provides a precisely repeatable stopped position, which is critical to minimizing jitter in the successive images

Model and Assembly:

Driver Member:

Driven Member:

Assembly:

Results obtained by the motion analysis of the mechanism:

1. At 10 rpm with precise contact:

Contact Force:

Angular Displacement:

Angular Velocity:

2. At 10 rpm without precise contact:

Contact Force:

Angular Displacement:

Angular Velocity:

3. At 20 rpm with precise contact:

Contact Force:

Angular Displacement:

Angular Velocity:

4. At 20 rpm without precise contact:

Conclusion:

• From above figure it is clear that contact force increases with increase in rpm.
• Preise Contact gives aacurate results
• Angular velocity of driven member increase with increase in rpm
• Angular velocity for the driver member its constant for the constant RPM but when we show in Excel graph it shows variation at some point. For 10 RPM angular velocity is 0 Deg/sec and for 20 RPM angular velocity is 120 Deg/sec.

• In Contact force graph we got a peak in the graph at a different point because when the pin of driver moves inside the driven member slot due to clashing between pin and the surface we got a higher peak value

Animation: