How the toilet tank water shut off valve works

[K Yung]

This is more for my learning purpose. I looked at an old toilet which uses a black ball as a float, As the water fill up, the ball float to a level. The rod acts as a lever and close a needle valve to shut off the water. I have a new toilet which uses a float that wraps around the water pipe. The float looks like a cup inside a cup. The float rises as the water fill up and push the level to cause the water to stop. I do not see the needle valve like the older type. All I can see is lever seems to just plug up a needle hole and the water stops. Can some one explain how this new type works and why the float looks like a cup inside a cup ?

 

[hj]

It is a "pilot operated" valve. When the "hole" is open, water above a diaphragm leaks out and pressure underneath it pushes it up to turn on the water. When the float pushes the pin to close the hole, water fills the void above the diaphragm and forces it down to shut off the flow. All the cup within a cup really needs is the top inverted portion, which is all some valves had for years, for floation, with the "cup" portion on top filled with water to give it ballast weight to drop the float.

 

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[Chucky_ott]

This diagram explains how this type of valve works