Nozzle assembly for electrostatic spray guns

Claim 1

In a system for the coating of articles with a liquid coating material supplied from a pressurized bulk coating source wherein said liquid coating material is emitted from a coating material spray device in the form of an atomized spray produced by impacting a central stream of liquid coating material under pressure with a pressurized gas stream encircling said central liquid stream and wherein the articles to be coated are spaced from said spray device, the combination comprising: a source of liquid coating material under pressure; a source of pressurized atomizing gas; a material spray device having a liquid conduit with flow control means therein adapted to be connected to said source of pressurized liquid coating material for providing relatively low liquid coating material flow rates in the approximate range of 11/2-6 fluid ounces of material per minute, and having a gas conduit therein adapted to be connected to said source of pressurized atomizing gas; and a spray coating nozzle assembly made which is substantially constructed of nonconductive plastic material comprising a liquid tip communicating with said liquid conduit and having a nozzle portion through which said liquid coating material is emitted in a central stream at said relatively low flow rate, and an air cap communicating with said atomizing gas conduit through which gas is ejected for impinging and atomizing said central stream of liquid coating material emitted from said nozzle portion of said liquid tip, said air cap being positionably supported by said spray device only in the rear region of said air cap to effectively leave the forward region thereof positionably unsupported by said spray device, said air cap having a central bore and a plurality of circumferentially spaced holes aligned with the axis of said central bore and intersecting the edge thereof defining a plurality of circumferentially spaced axial gas flow passages with spaced, radially inwardly extending ribs therebetween, said ribs engaging the outside surface of said liquid coating tip nozzle portion to positively align the center axis of said liquid coating nozzle portion on said axis of said central bore to provide uniform atomizing gas flow around said liquid coating tip nozzle portion for producing at said relatively low flow rate a finely atomized uniform spray pattern of said coating material emitted from said liquid tip.

Claim 6

The system of claims 1 wherein the diameter of said bore is about 0.103 inch, and the axial length of said ribs is from about 0.02 to about 0.06 inch, and wherein said axial gas flow passages are formed by holes of about 0.031 inch equally spaced on about a 0.103 inch diameter.