US2373595A - Spray nozzle - Google Patents

Description

April 10, 1945. D P f 2,373,595

SPRAY NOZZLE Filed March 15, 1943 FIG. 2

INVENTOR. Donald J. Pe e pa A TTORNE Y.

Patented Apr. 10, 1945 SPRAY NOZZLE,

Donald J. Peeps, Toledo, Ohio, assignor to The DeVilbis's Company, Toledo, Ohio, acorporation of Ohio Application March 15, 1943, Serial No. 479,284

4 Claims. (01. 299-1401) This invention relates to a spray nozzle and particularly to one for use 'in painting the interior of hollow objects. Considerable trouble has been encountered when it has been necessary to insert a nozzle within a cavity to coat the surfacethereof because of the deposit of particles of paint around the nozzle discharge port. I

When a spray device is used in the open, either natural air currents aided by the flow of air from the device, or air currents created by exhaust fan means tend todraw the spray fumes arising from the spray operation, away from the nozzle. In a confined space such as the cavity in a shell or standard metal container, such currents have no effect and the spray fumes must pass back along the spray nozzle to reach the opening into the cavity. The aspirating effect of the air discharging from the nozzle is inclined to drawsome wisps of the spray fumes back in'to'the spray discharge. On this return travel a portion of the paint particles in such wisps of the spray Fig. 2 is an enlarged view partly in section of the nozzle shown in Fig. 1; and

Fig. 3 is a view of an extension nozzle-in spraying position within a cavity with the spray disfumes will be deposited upon the edges of the main' nozzle discharge port. 1

This deposit frequently accumulates to an extent that the nozzle port becomes partly blocked. This interference with the flow of air from the nozzle causes poor atomization and the spray pattern to be irregular in shape. Consequently the coating sprayed upon the surface will not be uniform and willprove unsatisfactory from a protective standpoint. Should the spraying operation be interrupted frequently to clean the nozzle, the coating production rate would be considerably reduced.

The principal object of my invention is to overcome this difficulty by the provision'of means for releasing a low velocity curtain of air in surrounding relation to the spray discharge as it leaves the nozzle. This means comprises a secondary air cap which overlies the standard air cap or nozzle member. The air curtain prevents any paint particles from reaching the surfaces of the inner atomizing air cap. The paint particles instead are drawn to the outer nozzle and accumulate about its air discharge opening. This is so much larger in diameter than the atomizing air nozzle opening that this accumulation will not affect the spray pattern nor the formation and charge pattern indicated with dash-lines. V

Referring'to the drawing and particularly to Figs. 1 and 2 the extension nozzle has a main body section l which is fastened at its rear to air extension tube 2. 'Also fastened to the body portion 1 is spray liquid supply tube 3. The atomizing air travels from tube 2 through passage 4 in the body portion to annular chamber 5. From here it continues througha series of ports 6 spaced around the flange 'l of the liquid tip 8 Then the air goes through the space between mean cap 9 and the tip 8 to the nozzle discharge opening Ill. The cap is held in place by retaining ring 22 threadedly engaged to body I. Within the 'cap 9 is a spiral insert ll designed to give the air a whirling motion. This spreads the resultant spray laterally and makes it more satisfactory for coating the interior walls of a hollow article. The air passing through the discharge opening l0 strikes and 'atomizes the liquid coating material discharged from the liquid tip 8 when the liquid needle valve I 2 is withdrawn rearwardly.

In. this embodiment of my invention I provide a secondary air cap I3 which" fits over and is threadedly connected to the atomizing air cap 9. Circumferentially spaced around in the wall of cap! are several restricted passages I4 connecting the air space between the tip 8 and the cap 9 with an annular groove I5 in the outer surface of cap 9. Air reaching this chamber passes from it into the space between atomizing'cap 9 and the cap l3 and hence into the atmosphere in surrounding relation to the air and liquid mixture discharged by the. liquid and the air nozzles B and 9. This protecting sheath of air issues at low pressure because of the restricted size of the ports M in comparison with the large space provided for this air between the air caps. The bafliing flange IS on the outlet side of the groove 15 acts to distribute the air for the sheath uniformly around the nozzle before it is discharged.

In Fig. 3 is shown an extension nozzle inserted within a container 2|. The spray pattern is indicated in dash lines and the spray fumes are illustrated travelling rearwardly past the nozzle.

The vacuum or aspirating effect produced by the discharge movement of the spray draws particles of the spray fumes toward the central nozzle opening and along with the spray discharge as indicated by arrows in Fig. 3. When a spray nozzle is out in the open air, thisattraction is not strong enough to cause much trouble,' but when the fumes are forced to travel close to the nozzle, considerably more of them are drawn across its face. Also in a confined space the rebound from the surface toward the nozzle is greater. Because of the sticky nature of these paint particles they adhere readily to the spray nozzle and in time will build up around the nozzle orifice. If this build-up extends over into the discharge orifice, it will interfere with the flow of air from the nozzle and thereby affect the spray pattern and the quality of the deposited coating.

By having the protecting cap 13 and the shielding wall of air discharged from it, the particles of paint fumes will not reach the inner cap but will collect only on the outer cap as shown at '20 in Figs. 2 and 3. The spray Pattern thereby will not be disturbed and the quality of the coating will be maintained. The outlet opening of the protecting cap I3 is considerably larger than the central nozzle. discharge orifice and consequently the edge of the opening is spaced laterally from the path of the spra discharge. Because of the low velocity of the protective sheath of air it does not have sufficient force to seriousl deform th spray pattern.

It does however appear to somewhat restrict the natural outward flaring or spreading action of the spray discharge. If this becomes objectionable it may be overcome by either using a spiral insert in the atomizing air passage or, in case one is already being used,.by increasing the whirling of the .atomizing air stream with :a more effective spiral insert.

It may be seen that I have provided a simple but efiective means of avoiding he difficulty previously encountered in the spraying of the surfaces of hollow articles.

Although I have described my invention in a certain specific embodiment, the better to explain the operation thereof, I am aware that .numerous and extensive departures may be made without departing from the spirit of the invention.

I claim:

1. In a spray nozzle, central port means to discharge a liquid coating material and air under pressure to atomize the material, a cap centrally positioned upon the discharge end of the nozzle to provide a comparatively large air passage space between it and the nozzle, an air supply passage to supply air to said space, andan annular inwardly directed outlet opening in the cap in surrounding relation to the central port means of the nozzle, said opening being considerably larger than and extending forwardly of and beyond the central port means.

2. In a spray device a spray discharge nozzle having concentric .air and liquid discharge ports and a forwardly and inwardly extending partition forming a forwardly converging air passage terminating at the edge of the partition, said edge extending forwardly beyond the concentric air and liquid discharge ports and forming a circular opening concentric with but considerably .larger in diameter than said ports.

.3. In a spray nozzle, an inner liquid discharge nozzle member, an outer atomizi-ng air discharge cap, concentric outlets .in said member and cap, an atomizing air passage between said member and cap, means in the air passageto give the air a whirling motion as it leaves the nozzle, a conisally shaped shield piece mounted on the spray nozzle in surrounding relation :to the air cap, an air passage formed by said shield Piece,:means to supply air under comparatively low pressure to said passage, and a discharge port in the shield concentric with but positioned forwardly of the outlets in the member and the cap to direct a curtain .of the low pressure air forwardly around theoutlet of the air dischargecap.

4. A spray nozzle asset forth in claim 1 in which restrictive port means of a capacity .considerably less than that of the outlet opening of the cap is located in the passage leading to the outlet opening whereby the flow of air through the outlet is reduced in pressure and volume.

DONALD J. .PEEPS.

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