|
(11) | EP 0 381 072 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||||||
| (54) | High volume low pressure air spray gun |
| (57) A high volume low pressure air spray gun (20) has an atomizing air orifice (76) for
atomizing a stream of liquid coating material into a conical spray and opposed side
port air orifices (88) 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 (110) is in an air supply passage in the gun barrel. A valve stem
(54) for controlling the flow rate of air to the side port orifices (88) extends through
the venturi (110), 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
(54) is positioned for maximum air flow to the side port orifices (88), it establishes
a maximum air flow area through the venturi (110) , 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 (88). When the valve
stem (54) is positioned to reduce air flow to the side port orifices (88), it correspondingly
reduces the flow area through the venturi (110) to maintain the pressure of air at
the atomizing orifice below a selected maximum value. The gun may carry a paint cup
(124), in which case the cup is pressurized by air downstream from the venturi to
prevent overpressurization of the cup. |