Importance

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Abstract

A high volume low pressure air spray gun has an atomizing air orifice for atomizing a stream of liquid coating material into a conical spray and opposed side port air orifices for flattening the spray into a fan-shaped pattern. The gun receives air at pressures up to about 100 psi, and an air flow restriction in the form of a venturi is in an air supply passage in the gun barrel. A valve stem for controlling the flow rate of air to the side port orifices extends through the venturi, and is configured to vary the venturi air flow area in response to changes in the flow rate of air to the side port orifices. When the valve stem is positioned for maximum air flow to the side port orifices, it establishes a maximum air flow area through the venturi, such that a high pressure of air at the gun air inlet, after flowing through the venturi, results in a high volume low pressure air flow at the atomizing and side port orifices. When the valve stem is positioned to reduce air flow to the side port orifices, it correspondingly reduces the flow area through the venturi to maintain the pressure of air at the atomizing orifice below a selected maximum value. The gun may carry a paint cup, in which case the cup is pressurized by air downstream from the venturi to prevent overpressurization of the cup.

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First Claim