Internal Geneva Mechanism

INTERNAL GENEVA MECHANISM

AIM Create 3D models of driver and driven wheels of internal geneva mechanisms using solidworks . Assemble both wheel by providing appropriate mates and study the motion analysis using motor as drive wheel at 10rpm and 20rpm respectively and try to find the contact force between the two parts with and without .precision contact and also plot the angular velocity and angular displacement of driven wheel

.INTRODUCTION

Geneva Mechanism which is used to transmit the motion intermittently This type of motion is required in machine tools where spindle or worktable is required to be indexed

Geneva mechanism was originally invented by watchmaker in 17 to 18 century the watchmaker put a limited number of slots in one of the rotating disks so that the system could only go through so many rotations this prevented the spring on the watch from being wound too tight , thus giving the mechanism its other name, the Geneva stop Which is used into many of the film projector ,camera

THEORY

.In Geneva Mechanism have two primary parts DRIVER and DRIVEN

Driver or driving wheel is the wheel that transmits force or torque into the driven wheel which causes a rotation .The driver part is connected to a motor which basically makes to rotate the driven part by transferring the motion

The rotating driver part is usually equipped with a pin that reaches into a slot located in the other part (Driven part ) .that advantages 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.

Driven part is mainly used to extract output rotation which is given by driver part

OBJECTIVES

First we create 2D CAD for driver and driven part using that we create 3D model then we will assemble the 3D model .and then.we study the motion analysis of internal geneva mechanism and to compare the contact force between driven and driving wheel at 10rpm and 20rpm with and precise contact. And also study the angular velocity anangular displacement pof the driven wheel.

2D CAD

3D CAD

After the assembly of driver and driven wheel

We move to motion analysis , contact force between driver and driven wheel ..By rotating a driver wheel at 10rpm as a function of time

Result and Discussion

Angular velocity of driven wheel

Contact force with and without precise contact with (10rpm)

CONTACT FORCE WITHOUT PRECISE CONTACTCONTACT FORCE WITH PRECISE CONTACT

At 10rpm the contact force between driving wheel and driven wheel with precise contact give high permanence and accuracy as compared to contact force without precise contact

This shows a result that if we use a precise contact for motion study the force or motion will be smooth and exact.

EXCEL DOCS

CONTACT FORCE WITHOUT PRECISE CONTACTCONTACT FORCE WITH PRECISE CONTACT

Angular velocity at 10rpm and 60 frames per second give constant velocity with respect to time as we increase to 20 rpm and 120 frame per second no more the graph will give constant velocity of the driver wheel it will increase with time.

ANGULAR VELOCITY OF DRIVER AT 10rpm and 60 frames per secondANGULAR VELOCITY OF DRIVER AT 20rpm AND 120 frames per second

CONCLUSION

From the fig it's clear that contact force increase with increase in rpm

With precise contact gives accuracy and right precision and result

Max angular velocity of the driven wheel increase as we increase rpm

Angular displacement of the driven wheel remain constant as rpm increases .