HVLP spray gun

Details HVLP spray gun HVLP spray gun

2000-10-25

2004-03-23

Hwu, Davis D. (Department: 3752)

Fluid sprinkling, spraying, and diffusing

Including supplemental gas shaping or shielding jet

Plural sets of gas jet orifices

C239S290000, C239S291000, C239S297000, C239S300000

Reexamination Certificate

active

06708900

ABSTRACT:

TECHNICAL FIELD
1. Background Art
HVLP (high volume low pressure) paint spray guns have recently become increasingly popular for providing a high quality finish with good transfer efficiency.
2. Disclosure of the Invention
It is therefore an object of this invention to provide an HVLP spray gun which is easy to use, versatile, provides a high quality finish, and high transfer efficiency.
The spray gun of the instant invention is provided with a long needle guide nay relatively light spraying which enables the gun to have a very low trigger force. The surface on which the nozzle rests and is screwed into is located at the forward most end of the gun body (once the air cap and retaining ring are removed) thereby allowing the nozzle to be easily gripped and mounted or removed from the gun by hand without the need for any tools.
As with most air spray and HVLP guns, an air line extends downwardly out of the gun body to a tube which in turn attaches to a fitting on the top of the paint cup. Located on the inner side of this fitting on the paint cup (inside the paint container) is a polyurethane molded duckbill valve which serves as a check valve to prevent the flow of paint up into the air valve. Such a valve is a substantial improvement on the check valves of prior art devices which tend to become clogged with paint and which are more expensive to manufacture.
An air adjustment valve assembly has two parts—a total airflow adjustment valve and a spray pattern adjustment valve. The total flow valve adjusts exactly what it says—the amount of airflow into the gun for atomizing and spray pattern adjustment while the spray pattern adjustment valve adjusts only the width for the spray pattern. While this is referred to as a spray pattern adjustment, this adjustment is also commonly referred to as fan air or shaping air. The air valve assembly slides into the back of the gun, which enables it to be removed without the need for tools.
On the air cap, a 55° angle between the center hole (the centerline of the gun) and the side holes provides the best spray pattern with a chamfer on the center hole reduces the amount of large droplets at the side of the spray pattern and allows a uniform spray pattern. A radius of 0.015 inches on the front edge of the nozzle allows air to smoothly interface with the liquid flow stream resulting in an improved uniform droplet sized distribution on the spray pattern. Five lengths of nozzles for five different fluid sets allow the gun to use the same air cap with different flows. The nozzle housing is provided with nine 0.1718″ holes and eight 0.156″ holes to allow air to pass into the air cap.
In the gun body, airflow is divided into two streams by utilizing two separate holes. A 0.35″×0.70″ hole with a 48° angle provides air to the air cap center hole for atomization. While the 0.800″ hole and a 1.32″ slot introduces air to the side holes on the air cap providing fan air.


REFERENCES:
patent: 4386739 (1983-06-01), Kwok
patent: 5078322 (1992-01-01), Torntore
patent: 5165605 (1992-11-01), Morita et al.
patent: 5201466 (1993-04-01), Hynds
patent: 5279461 (1994-01-01), Darroch
patent: 5803367 (1998-09-01), Heard et al.
patent: 6068203 (2000-05-01), DeYoung et al.

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