Powder spray gun

An electrostatic spray gun apparatus (10) includes a spray gun housing (4) and a nozzle (2) attached to a spray end of the housing (4), and a powder path that extends in a substantially straight line along an axis of the housing (4) from the powder inlet to the powder outlet. The powder path is in the form of an enclosed smooth powder passage that is substantially continuous and uninterrupted from the powder inlet to the powder outlet to eliminate substantially all recesses or gaps that could capture or trap powder. The powder passage is formed by a plurality of tubular segments that are aligned along the housing axis and abut end to end. that when assembled in the housing axially compress the segments together to substantially eliminate dead spots or recesses to form the continuous smooth powder path. A gun purge function is provided that allows a purge line to be installed on the gun assembly. A cartridge valve and conductor assembly is provided between the gun electrode in the nozzle and the output of the voltage multiplier. The cartridge includes a conductive path to provide electrical continuity from the multiplier to the gun electrode, and also includes valve, preferably in the form of a stem check valve, that closes when the gun electrode is removed or at least unseated from the nozzle. The gun also includes a tube mount arrangement wherein the tube mount is rigidly held together with the gun housing in axial compression by a tie bar.