How works an organ with deairing system

In the world of mechanic music instruments there are several ways to record music and to let it play again. The data medium can be in different of forms. In music boxes you find often a metal barrel with pins. In old hand cranked organs, there is a wooden barrel with brass pins and bridges. In Dutch street organs you will find cardboard books with rectangular holes. As the cardboard moves, metal pins fall into these holes and cause valves to open, allowing air into the corresponding pipes. In German organs you find cardboard books or paper rolls with round holes. When air flows through these holes , it causes a valve to move and open the holw which leads to the pipe. You can distinguish two systems in this:the airing and deairing system. We will look more closely at the last one.

An organ needs air under pressure. Therefore bellows will be brought in movement assymetrically, though which the air pressure is more constant. In upperstanding animation, the air under pressure has a blue color. The bellow spring takes care for the wanted air pressure, while the valve on the bellow prevents that the bellow blows up itself too much. This pressed air will be lead to a windchamber. In this wind chamber there are air valves with membranes. The trick sits in the air pressure upper and under the membrane. If there should not be played a note, the air pressure is equal though the bypass channel. Decreases the air pressure on the upper side, then the membrane with the valve will move upwards though the pressure of the wind chamber. The air channel (conduct) towards the pipe comes free and there will be a tone produced. With the adjusting screw you can control the control wind for an correct valve working.