Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Patent
1994-06-23
1995-08-15
Nilson, Robert G.
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
239126, B05B 708, B05B 712
Patent
active
054410770
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a feedback air pressure sensing system and more particularly to spray guns in which the spray of atomised fluid can be controlled to produce a fan to round spray pattern.
As a result of increased regulations to control the emission of fluids, e.g. paint from spray guns into the atmosphere there is a need to control the pressure of the air flow in the spray gun's air cap to a maximum of 10 psi (0.7 bar). All known spray guns do not provide for an automatic control of this pressure e.g. when changing the gun's set-up from one spray pattern to another.
To ensure the correct pressure of 10 psi (0.7 bar) at the air cap the operator currently checks the pressure in the air cap by either direct measurement using a test cap, or by tabulations which indicate that the pressure reading on the main air pressure supply gauge will provide a pressure of 10 psi (0.7 bar) at the air cap.
Many conventional air supply systems to spray guns have the disadvantage that they cannot maintain 10 psi (0.7 bar) at the air cap during the change of the spray pattern setting between a fan shaped and a round shaped spray. Control of the pressure is at present made by balancing orifices requiring special baffles or bodies for each air cap and the fluid tip set-up used. In such an arrangement the input pressure has no obvious relationship with the output pressure.
An aim of the present invention is to provide a feedback air pressure sensing system with an automatic regulator for controlling the output pressure to overcome the above mentioned disadvantage.
According to the present invention there is provided a feedback air pressure sensing system comprising an air supply and an air outlet, the air supply being monitored by an air pressure feedback circuit which connects the air outlet with a regulator so that any change in pressure at the air outlet is sensed and fed back to the regulator to increase or decrease the air supply to maintain the air pressure at the air outlet at a predetermined pressure, characterised in that the regulator comprises a body, an inlet for a main air supply to first and second air chambers, an inlet for a feedback air supply to a feedback chamber, a first diaphragm between an outlet chamber and a pilot chamber, the first diaphragm being supported in the regulator body and connected to a main spring loaded valve to control the flow of air from the first chamber to the outlet chamber, a second diaphragm between the feedback chamber and a spring loaded adjustment means and a feedback valve and feedback relief stem associated with the second air chamber and the second diaphragm to control the pressure in the pilot chamber, so that adjustment of the adjustment means controls the main air pressure entering the outlet chamber to a predetermined sensed pressure at the air outlet.
Conveniently, the air pressure feedback circuit is fed from the atomising outlet of the spray gun air cap via a trigger-operated air valve/feedback valve to a feedback regulator.
The air regulator is preferably connected with a pressure guage in the feedback section to indicate the pressure at the air outlet.
An embodiment of a feedback air pressure sensing system, according to the present invention, for use with a spraygun will now be described, byway of example only, with reference to the accompanying diagrammatic drawings, in which:
FIG. 1 is a diagrammatic view of a feedback air pressure sensing system according to the invention;
FIG. 2 is a detail diagrammatic view of a time delay valve;
FIG. 3 is a diagrammatic cross-section of a regulator; and
FIGS. 4 and 5 are enlarged diagrammatic cross-sectional details of the regulator shown in FIG. 3, with some separation between components for added clarity.
Referring to FIG. 1, the spray gun incorporates an air pressure feedback line 1 which enables a main air regulator 2, which is normally mounted at a distance from the spray gun, to sense the spraying, i.e. the atomising pressure, within an air cap 3 of the spray gun.
Air is supplied from an air line 4 via the main air
REFERENCES:
patent: 1361271 (1920-12-01), Neal
patent: 1843953 (1932-02-01), McKinney
patent: 2583006 (1952-01-01), Niesemann
patent: 2736337 (1956-02-01), Parks
Garlick Paul L.
Smith Rowland C.
ITW Limited
Nilson Robert G.
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