Good morning, everyone, I think I have understood, please let me confirm:
In this photo (photo 1) air arrives on admission ( marker A ), which will commission the stem command turbo (marker B).

On the next (photo 2) when it accelerates, the metal (soft C) just press the command turbo (marker B), the stem of the membrane (marker A) does not move, and the fins are open.

On the last (photo 3) when the desired pressure is achieved, the stem of the membrane (marker C) supports on the metal part (A marker), leaving the command back fins (marker B) is cut the build up of fins.

That is what I understand