Abstract: A tribo-electro-gas-dynamic powder coating apparatus with an obstruction-free barrel having a semi-toroidal section throat at the inner end and having an opening at the outer end. An end cap is connected to the barrel end over the semi-toroidal section to form an annular chamber circumferentially surrounding the semi-toroidal section and having a clearance between the section and the end cap leading from the chamber to the barrel bore.

Abstract: A powder feeder pick-up tube having a central powder delivery tube receiving powder entrained in a propellant gas, an outer concentric tube delivering propellant gas to the powder delivery tube and evenly entraining powder in the gas as the powder enters the powder delivery tube. The propellant delivery tube has an inwardly curving end that forms a gap with the open end of the powder delivery tube, and the geometry of the curving end and the size of the gap are factors determining the operational characteristics of the pick-up tube. Variations on the basic pick-up tube include a concentric fluidizing tube surrounding the propellent delivery tube and locally fluidizing powder around the opening of the powder pick-up tube. The shape of the fluidizing orifice at the outlet of the fluidizing tube may be modified to alter its fluidizing characteristics. The tube is immersed in a hopper of powder when operating and the entire hopper may be fluidized and vibrated to assist the operation of the pick-up tube.