I assume that only the bottom of the fan blades is driven, and it has a pin which catches the next blade, which has a pin which catches the next blade, ... Etc

One could also make the 2 sides hook together.
each blade on the right would have a pin That catches in a slot On the opposing blade So as each one is dropped into place it catches the one from the other side of the gate

The fan blades also could have curved sides So It looks even more impressive when it is closed