Well, I have done some experiment but I have not solved the problem.
To explain better what I want to do I have put here an image of my work.
I want to simulate a camera diaphragm, using 8 levels (blades)
Each blade is locked on an corner and rotate on it.
In the image that follow you can see the result

Blade number 1 is the topmost, blade number 8 is the lower.
For a correct simulation blade 1 must be on the top but must also go under blade 8 and also under blade 7
Of course when the diaphragm close the number of blades that must go on Blade 1 increase see the image below:

The result shoud have to be :

I have no idea how to simulate this.
Thanks for any advice.
Alberto