Method and system for cleaning a paint supply line and changing paint

Abstract

Method and system are provided for cleaning a paint supply line and changing paint colors by inserting and propelling a termination piston or slug having an outer diameter which forms a sliding fit within the supply line to wipe paint off the interior walls of the supply line. Preferably, the supply line is elastic and the termination piston squeegees the paint off the interior walls. In order to more fully clean the supply line prior to changing paint colors, a predetermined amount of cleaning fluid such as a solvent is injected into the supply line behind the termination piston from a common passage of a manifold. A leading piston or slug is then inserted immediately ahead of a new paint color in the supply line. The pistons may be disposable or may be reused by recirculating them by means of shuttle assemblies and a return line. The manifold is fitted with various valves to selectively supply pressurized air, solvent and two or more paint colors to the supply line. The shuttle assemblies are also fitted with valves to shuttle the pistons between the supply and return lines. A process controller controls the timing of the valves of the manifold and the shuttle assemblies. The method and system can also be used to retrofit existing color changers in an economical yet environmentally sound fashion.