Diaphragm valve
A diaphragm valve is a pilot operated valve. It is very similar to a piston valve in therory, but replaces it's hard cylinder with a flexible diaphragm.
Construction
The diaphragm is sometimes made of a simple piece of pliable material, for instance, thick neoprene (about 1/4" of the rubber is common) or a section of tupperware lid. However, there is often a problem with the material not being strong enough. In this case, the center of it is often re-inforced with a pair of washers; one a bit bigger than the barrel's diameter on the pilot side, and one a bit smaller than it on the barrel/chamber side.
These valves are often used on coaxials and over/unders. In an over/under, the valve is built in a "T" fitting. The barrel is put coaxially through one end, the pilot and diaphram are put in the opposite one, and a chamber is conected to the perpendicular opening with a 90° elbow.
Use
Opperation:
- Air is added by filling behind the diaphragm (C).
- The diaphragm (E) is flexed forwards, and seals against the barrel (A).
- More air is added, and leaks around the diaphragm (or through a small equilization hole) and into the chamber (B), filling it to the desired pressure.
- The pilot valve (D) behind the diaphram is opened, the pressure in the pilot volume (C) drops, and the higher pressure in the chamber area pushes the diaphragm away from the barrel.
- The air flows around from the chamber, and into the barrel, propelling the projectile.
The preformance of these valves can be calculated with the GGDT. If your valve honks, it is probably a good idea to invest in a better pilot valve.
