ST-5 series automatic spray gun has an interior pneumtic piston device, a stainless steel spray needle is on top of the piston, back of piston is a group of high tension spring, when supply of compressed air stops, spring holds out forward against the piston & spray needle, meantime spray needle & nozzle cut out the passage of fluid with high tight precision. On the contrary, when compressed air starts supplying, pressure of compressed air push out the piston, so that fluid sprays out from the gap between spray needle & nozzle, then fluid immediately contact with atomized air to be atomization.

ST-5 series automatic spray gun, 'the air of piston-operated' shares with 'the air of atomization', so pressure of compressed air must higher than elasticity of piston spring (2kg/cm2), otherwise the spray gun can't normal function. ST-5 series automatic spray gun is for working environment of high requirement of atomization & low switch frequency.