Particulate material applicator and pump

A nozzle for a powder spray gun, the nozzle comprising:

• a nozzle body having an outlet end and an inlet end, a powder flow path through said nozzle body between said inlet and outlet, and an expansion chamber between said inlet and outlet with said outlet having a cross-sectional area that is equal to or greater than said inlet cross-sectional area.

A powder coating system comprising:

• a powder pump and a powder spray gun, said pump having at least one pump chamber in fluid communication with a powder supply and a powder spray gun, said pump chamber being selectively sealed from communication with said gun and supply, a spray nozzle on said gun and having an inlet and an outlet, wherein said outlet has a cross-sectional area that is equal to or greater than said inlet cross-sectional area.

A method for applying powder coating materials, comprising:

• providing a powder flow into an inlet of a spray nozzle and out through an outlet of the nozzle, forming said outlet with a cross-sectional area that is equal to or greater than a cross-section area of the inlet.

A pump for dry particulate material, comprising:

• a pump chamber connectable to a source of material, said pump chamber having a pressure chamber associated therewith, a source of negative pressure and a source of positive pressure that are alternately applied to said pressure chamber to suck material into said pump chamber and push said material out of said pump chamber, and a reservoir that stores negative pressure from said negative pressure source for use by the pump.