How Does a Gas Station Refueling Gun Automatically Stop Fuel Flow?

Hello.
The question is a bit off the topic. Can someone explain to me the principle of operation of a refueling gun such as in traditional gas stations.
It is about the moment of "breakout" what is it, whether it is fuel retraction or pressure?
What is the mechanism, etc.
Cheers and thanks in advance.

Hello
When you open the fuel tank flap and unscrew the cap, you will see a filling hole with a gasket. At the top of the gasket there is a small hole (indentation) which must be exposed during refueling, otherwise the gun "knocks out" when you start refueling. It is about venting, the fuel vapors fill the tank, and while refueling, you still inject fuel, which means that the pressure must equalize. To avoid "knocking out", point the pistol slightly downwards (or in the opposite direction from the hole, depending on the car)

And here is the construction diagram of the gun:

Badyl91: now read the post of the author of the thread again and write something, but already on the topic

I used to repair mainly ZVA pistols and the principle is simple. In the fusion (spout) you have the main pipe where the fuel is poured, and there is a tiny one in it which it has to suck in air through. When you block the smaller tube, the diaphragm, which is at the height of the handle (in the middle), will close the fuel flow and the gun "bounces". In diels there was always a problem with premature "bounce", so all you had to do was saw this little tube in the center of the spout and the problem was gone. Even the smallest "burrs", "lips" in this tiny tube are also important, it also causes problems and the so-called. premature kickback / disconnection of the gun. Today, as I know, filling guns with a special spout cover should be used at every petrol station in order to suck up vapors escaping from the fuel tank during refueling, but this requires the use of special hoses: distributor / gun (and not only), and not all of them they still use it. Reason for the price. It is the same with the tank venting system when the tanker fills the tanks at the stations. Needs to connect two hoses. One for the sink and the other for the fumes. Well, this, in turn, slows down the whole process very much, so although the law prohibits, I still see the so-called "breathing valves". If you want to learn how to repair pistols, I advise you to be careful, because inside there is such a nice spring that can MANY (!) ... end up with a broken lamp or a black eye. Regards.