What are the names, positions and functions of the three valves in the nozzle of the oxyacetylene cutting machine?

Open the last valve of the cutting gun to control acetylene, which can adjust the firepower. When using the cutting gun, only open the other two valves and then ignite. The valve in the middle and lower part of the cutting gun is opened to control oxygen. When in use, after the acetylene is ignited, the oxygen is turned on and adjusted so that the blue flame in the middle of the flame is as close as possible to the nozzle of the cutting gun. The valve in the middle and upper part of the cutting gun is opened to control the mixed gas (oxygen and acetylene). When in use, the object to be cut is heated by the flames of the first two parts. You can control this time by yourself, that is, when it is about to burn red, then open the mixture for cutting. Exercise is very dangerous, so we must pay attention to it. When tempering, turn off the mixed gas in time, then turn off acetylene and oxygen at the same time. After all valves are closed, start the mixing action to clean the nozzle of the cutting gun twice to see if there is any foreign body blocking. When tempering, the most important thing is to cut off all the gas in time and practice slowly. Let me be specific. Please invite me to dinner when you come back.