Need Help Understanding Extruder

Hi Folkes

I have the typical extruder (AKA Stock) extruder that comes with my Anet A8 iPrusa. I am a little confused about how it works though. Here's how it started... I did see it wasn't extruding properly and when I took the filament out, the side of the filament that was facing the spoked wheel had a gouge in it meaning (I think?) it was not able to push the filament into the nozzle.I took it apart, heated the J Head and cleared the nozzle. Now I'm ready to put it back together and I am trying (before I do so) to wrap my head around how the tension adjustment works.

Looking at the attached picture, The only purpose for the screw and nut on the top of the extruder (red arrow) that I can see, is to adjust how far down you can press the screw when removing or replacing filament! Is this right? Am I missing something here? The spring (green arrow) always has the same tension on it and the nut at the bottom (blue arrow) is not moved to adjust anything.

Would someone out there please take a moment and explain the operation of the extruder and how (or if) the tension on the filament can be adjusted... I just have this feeling that somehow I have misplaced a part that goes in this thing...

Thanks again for your help guys!
Don

I dont have a nut at the top(red) part just the screw, just underneath the metal lever I have a cap head screw in the top of the spring, the screw from the top comes through the lever into the socket of the screw at the top so it doesnt bind on the spring but can spin for adjusting the tension, the tighter the spring the more it pushes back, I also dont have the nuts you have(but perhaps if you want ot lock things off they can help....bottom of spring just sits on another screw/hex, but not the cap, the cap is under the bottom part.
Maybe I have a picture.

Ok. I think I may have figured this thing out. You have to use the bolt head on the bottom to adjust the tension. The top one, is simple to give you a peg )of sorts) To release the tension and allow feeding of the new Filament into the hot end.

Thanks for your help MechaBits!

I wouldnt adjust spring to change filament just use the lever, that way tension will remain same once changed.