Internal Geneva Mechanism

Aim :

• Create 3D models for driver and driven wheels of internal Geneva Mechanism.
• Creating assembly of Internal Geneva Mechanism.
• Motion study of the Internal Geneva Mechanism assembly.
• Plot a graph of angular displacement and contact force as a function of time.

Introduction :

Geneva mechanism is a gear mechanism that translate a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step.

Classification of Geneva Mechanism –

• External Geneva Mechanism
• Internal Geneva Mechanism

In External Geneva Mechanism ,the Geneva cross is connected with cam drive externally which is the most popular and can withstand higher mechanical stress.

In Internal Geneva Mechanism, the Geneva cross and cam drive are connected internally in the closed box.

Theory of the Motion study :

In the most common arrangement, the driven wheel has four slots and thus advances by one step of 90 degree for each rotation of the drive wheel. If the driven wheel has n slots, it advances by 360 degree/n per full rotation of the drive wheel.

Procedure :

• First we draw the CAD model of driver and driven wheel of Internal Geneva in Solidworks using the required dimension.
• Then assemble the driver and driven wheel.
• Now go for the motion analysis and add rotary motor to driver wheel specifying rpm as 10 & 20.
• Define the contact group between driver and driven wheel.
• Finally calculate it and go for the results.

Models :

1. Driving wheel

2. Driven wheel

3. Assembled driven and driver wheel

Cases :

• rpm of motor = 10 and without precise contact (60 frames/sec)
• rpm of motor = 10 and with precise contact (60 frames/sec)
• rpm of motor = 20 and without precise contact (120 frames/sec)
• rpm of motor = 20 and with precise contact (120 frames/sec)

Precious Contact :

At 10 rpm

At 20 rpm

Results & Plots :

Figure 1 : Contact force with precision (10 rpm)

Figure 2 : Contact force without precision (10 rpm)

Figure 3 : Angular Displacement of driven wheel (10 rpm)

Figure 4 : Angular Velocity of driver wheel (10 rpm)

Figure 5 : Contact force with precision (20 rpm)

Figure 6 : Contact force without precision (20 rpm)

Figure 7 : Angular Displacement of driven wheel (20 rpm)

Figure 8 : Angular Velocity of driver wheel (20 rpm)

Animation :

Conclusion :

• Anugular velocity of thr driver wheel increased at first an then decreased and finally for some time it remains constant. And this pattern repeats.
• Contact force with precision is differ from that of without precision.