Design of an airbrush like paint spraygun with good control to proportion the paint feed to the nozzle. All parts must be durable and easy to clean (in a solvent for example), replaceable parts (especially for the parts that wear).
SPREE-GUN by Outer Limits Ltd.
Rendering above shows details of the connection method. Small round spring through a hole in a connection pin. These connect the trigger handle to the needle. The needle protrudes 2 mm out of the nozzle (opening 0.3 mm).
The needle is pushed by a spring against the nozzle opening. The spring pressure can be adjusted by the needle spring retainer cap. The spring pressure closes the paint feed completely.
The paint side is sealed of from the air side by three leather rings. The O-ring (here in light gray) seals the paint side from the outside. Both O-ring and leather seals will wear over time but are easy and cheap to replace.
Assembly order for needle assembly.
Cut true of the needle assembly. The front two O-rings seal of the air-side.
Further details will follow ....