Method and apparatus for spraying

Abstract

A low volume-low pressure spray gun ( ) for spraying a fluid has a housing ( ), a gas input ( ), a trigger valve mechanism, and a nozzle ( ). The gun ( ) has lower and upper air passages ( ) which connect the gas input ( ) to the trigger valve mechanism ( ), and the trigger valve mechanism to the nozzle ( ), respectively. The upper passage ( ) is offset from the lower passage ( ) and is substantially conical in shape, the layout of the passages ( ) producing a gas vortex in the upper passage ( ) which creates a gas acceleration to compensate for the low pressure of the gas entering the gas input ( ). The trigger valve mechanism comprises a piston valve ( ), a liquid control needle valve ( ), and a trigger ( ). The piston valve ( ) may include inner and outer apertured sleeves ( ), the sleeves being co-axial with the inner sleeve ( ) located inside the outer sleeve ( ). The inner sleeve ( ) is rotatably adjustable relative to the outer sleeve ( ) so that the apertures ( ) of the sleeves ( ) may be aligned, partially aligned, or closed, thus permitting adjustment of the gas vortex.