US2303280A - Spray gun - Google Patents

Description

Nov. 24, 1942. 'A. F. .JENKINS 2,303,280

' SPRAY GUN Filed Sept. 9, 1940 Patented Nov. 24, 1.942

SPRAY GUN Alexander F. Jenkins, Baltimore, Md.

Application September 9, 1940, Serial No. 356,054

6 Claims.

This invention relates to spray guns and more particularly to improvements in the nozzles of such guns whereby the eiciency ofthe spray gun in the atomizing, diffusing and spreading of coating liquids or other fluent; materials is greatly enhanced.

The general object of the invention is to provide. novel and improved spray guns of the type described which include improved arrangements for projecting certain atomizing and spray pattern shaping jets of air under pressure upon the axialjet of liquid material issuing from the nozzle; the predetermined impingement of these air jets upon the liquid jet and upon each other resulting in a nely diffused, evenly distributed spray of improved-covering properties.

In its preferred embodiments, the invention contemplates the provision of an air cap which may be made in two parts and adapted to be fitted to the centrally disposed liquid nozzle member and clamped rmly to the body of the gun. The inner element or portion of the air cap arrangement comprises a, cup-shaped member, having a circular opening which fits around the liquid nozzle tip to form an annular oriiice for the main tubular jet of aspirating air. Around this annular opening is arranged a circular series of iine openings the axes of which preferably converge toward the axis of the liquid jet. The central portion of the face of the cap through which these openings are formed is preferablyv formed with a conical depression, the angularity of which is complementary to that of the angle of convergence of vthe openings..

One form of cap particularly adapted for use in the case of spray guns having a syphon feed, is preferably provided with openings .having parallel or non-convergent axes. j

Cooperating with these provisions, is a novel arrangement involving the auxiliary spray iiattening jets which are usually projected from converging horn-like protuberances disposed upon diametrically opposite sides of the forward face of the air cap. This improvement comprises the provision of a pair of orifices adjacent the bases of each of these protuberances'or horns, through which issue additional spray modifying jets of air which lmpinge'upon the main modifying jets and Atogether strike the aspirated and partially atomized axial stream of fluid to complete `the atomization and ilatten the jet to change its circular cross-section to a wide substantially oblong configuration. g Although capable of being used toA advantage with any type of spray gun, the inventionas passageway' I2 inv order to control the liquidv orice at-the fonvard end of the nozzle. These'l thus broadly' outlined is especially effective when employed in connection with the main spray modifying side jets of hollow expanding tubular form such as are projected by means of the annular orifices which characterize the spray guns covered by my prior United States Patents Nos. 2,126,888 and 2,126,889; and this arrangement combined with the present additional modifying jets and the multiple central atomizing orices aiords a maximum of eiiiciency and convenience in the application of coating or treating materials. One application in which the invention has demonstrated its superiority is in the coating of airplane surfaces, onv which an extremely smooth satin finishf is provided.

Other objects and features of novelty will be apparent fromthe following specication when read in connection with the accompanying drawing in which certain embodiments of the `invention are illustrated by way of example.v

In the drawing:

Figure 1 isv a view` in vertical longitudinal section on an enlarged scale of the forward nozzle carrying end of a spray gun embodying the principles of the invention;

Figure 2 is a view in front elevation of the nozzle assembly;

Figures 3, 4 and 5 are longitudinal sectional viewsof three forms of aspirator caps or inserts which surround the liquid nozzle member `and form parts of the air cap structure; and

Figure 6 is a fragmentary sectional view of a portion of the air cap ltaken substantiallyv on line 6 6 of Figure l, Aand villustrating the converz-:fence of the auxiliary spray modifying jets.`

The body of the spray gun, a portion of which is indicated in Figure 1 at I0, isjof the same typeas that shown in my copending application,v

Serial No. 184,301, led January 10,y 1938, now Patent No. 2,235,708, issued Mar. 18, 1941. This part of the'gun is preferably made of aluminum and is provided with the usual centrally disposed liquid passageway I2 fed through the connections designated generally by the reference numeral I4, and the lmain air passageway,` I5y through. which the aspirating, a'tomizing, ,and modifying jets of air are supplied.v -Suitable controls for the main air supply are provided in the rear portionl of the gun where also certain operating means are disposed Afor moving the needle valve I6 longitudinally within the'llquid controls are usually made'adjustableand are nating in a narrow cylindrical tip 22 provided with the liquid orifice controlled by the attenuated forward end of the needle valve I6. At a point intermediate its length, the liquid nozzle member 20 is provided with a circular radially extending flange 25 through which are drilled the annular series of openings or passageways 26.

Disposed between the flange 25 and theforward face of the body portion I of the spray gun is the annular insert element 30. 'Ihis insert is adapted to be clamped against the forward face of the gun by means of the' flange 25 when the liquid nozzle member 20 is .threaded into place at I8. Suitable gaskets 3| and 32 are interposed between the annular insert 38 and the face of the body of the gun. This insert serves two purposes, namely the provision of a member comprised of a harder metal than the body of the gun to vwhich the clamping ring for the air cap may be threaded, and also to provide a tortuous bailled passageway for the air supplies.

The air cap of the gun, in the illustrated embodiment, is made in two separable parts-the first section being an interiorly positioned cuplike cap portion 35 disposed adjacent the liquid nozzle member 20, and the second an outer annular cap section' 36 which carries the horns or projections 38 through which-the spray fiatten ing air jet orifices are formed. The inner cap element 35 is somewhat frusto-conical in general outline and having rearwardly directed walls 31 the ends of which are adapted to abut the radial this valve seat 58 being controlled by the needle valve 52 actuated fromI the rear of the gun. An annular groove 55 is formed in the forwardface of the spray gun through which air supplied through the passageway 5I may pass around the entire circumferences. The insert 30 is provided with an annular chamber 56 containing angular baille rings or washers 51 and 58, and this chamber is supplied with air through the peripherally spaced openingsA 59 leading from the groove 55. The outer air 'cap element 36 has an annular wall 60 tted snugly around the walls 31 of inner cap member 35 and abutting rearwardly the annular flange 62 formed on the element 35. This flange 25 of the liquid nozzle member and to fit around the forward annular flange 39 formedl thereon. On the forward end of the element 35 there is formed a central opening which fits about the tip 22 of the liquid nozzle member with sufficient clearance to provide the annular aspirating air orifices 40 in the central portion of the face of thel cap element 35. Around the orifice 40 there is disposed a circular series of flne orifices 42 the axes of which, in the embodiment illustrated in Figures 1 and 3 of the drawing converge toward the main axis of the spray gun. In the embodiment shown, this convergence includes approximately an angle of 30, but it may be varied somewhat as circumstances may require. The forward face of the cap in which the openings areformed is rearwardly convergent to provide a re-entrant conical surface the included angle being, in the embodiment shown, about 150", so that the openings 42 are substantially perpendicular to the surface of the cap.

'Ihe cap element 35 forms a forward air chamber 45 around the forward end of the liquid nozzle 20 and behind the openings 40 and 42. Air is supplied to this chamber through the passageways 28 which pass through the flange 25 from the annular rear chamber 46 containing the baille ring 41, this chamber being formed between the front wall of the gun and the flange 25 and being supplied with air through the'passageway or channel 48 leading .from the main air supply passageway I5.

The air for the auxiliary spray modifying yjets is supplied in the following way. The forward flange 62 is spaced from the flange 25 sufficiently for the insertion of a screw driver or other tool whereby the element 35 may be disconnected from the inner liquid nozzle. The outer cap element 36 is also provided with a rearwardly disposed radial flange 64 around which is fitted the shoulder 65 of a clamping ring 66 which is threaded to the insert element 30 and serves to retain the outer cap member rmly in place.

The projection horns 38 formed on the outer air cap member 36 for the provision of the spray modifying jets may conveniently be constructed of separate elements including a hollow tubular element 68 into which a plug 68 may be inserted from the rear end and secured as by soldering. The plug 69 is provided with a projecting pin 10 whichis spaced from the enlarged wall of the element 68 to provide the annular orifice 12 Yfor the hollow tubular spray modifying jet. The air supply for these jets passes from the chamber 56 in the member 30 into the annular rearward chamber 14 with outer air cap member 36 and thence through the diametrically oppositely disposed forwardly directed passageways 15 to the orices 12.

The spray modifying or flattening jets impinge from opposite sides of the device upon the axially directed partially atomized central spray, at a rather steep angle, as clearly shown in Figure 1. In order to aid in the effective atomization and spreading of the liquid, there is also provided additional orifices adjacent the side jets which have just been described. The protuberances or horns 38 of the air cap are undercut or notched upon their interior sides as at and a pair of relatively fine converging passageways 82 are drilled through the wall of the projections and into the passageway 15 therein. 'Ihe angularity of these pairs of passageways is indicated by the lines 85 in Figure 1 of the drawing and the included angle is approximately 70 in this particular `embodi" ment. The openings 82 of each pair also converge toward each other by a slight angle as indicated in Figure 6 of the drawing this angularity being in the particular example illustrated approximately 8. l

By this means the spray modifying jets upon either side of the main spray are to some extent broken up and themselves modified at points just prior to or immediately upon impinging on the aspirated and partially atomized spray issuing from the central liquid orifice; which spray has been preliminarily broken up and diffused by means of the air jets issuing from the annular series of fine orifices 42 disposed adjacent the aspirating orice 4l.

As already indicated, the auxiliary atomizing and modifying jets 42 and 82 each have a beneflcial effect when employed individually in a spray gun of conventional type, but their effects are notably increased when employed together and are particularly effective when used in connection with the hollow tubular type of modifying jet such as issues from the annular orifices 12.

In Figure 3 there is shown as a separate article of manufacture the inner air cap element 35 described in connection with Figure l of the drawing. The embodiment designated 35 illustrated in Figure 4 of the drawing is quite similar in construction and function but is provided with a raised or protruding central portion 90 which has advantages in the spraying of certain types of material which have a tendency to build up upon, the forward face of the nozzle. vThe inclination of the axes of the orifices v42 in this case is substantially the same as in Figure 3.

In Figure 5 there is illustrated an embodiment of the air cap which is designated 352 and in which the orifices 422 are parallel. The use of this type of cap is of advantage when the liquid material is syphoned from a container by the-action of the spray gun rather than introduced by forced feed.

'intersect the axis vof the axial spray of material, and a pair of air discharge passageways positioned adjacent each one of said first named passageways, but upon opposite sides of said diameter and adapted to deliver jets of air toward the axes both of the material spray and of the flattening jet from the-adjacent one of the rst named DaSSageWa'YS.

It is understood that various changes and modifications may be made in the embodiments illustrated and described herein without departing from the scope of the invention as'deflned by the following claims. v l

Having thus described the invention, what is claimed as new and desired to be secured by I et.

ters Patent is: Y

1. In a spray gun for coating materials or the like.'a nozzle at the forward end thereof for thev fecting further atomization and diffusion of saidl spray and for also altering its cross-.sectional configuration, said last named means consisting solely of a pair of forwardly converging air dis- 3.(In a spraying device of the class described, n

air upon the material spray from points radially outwardly of said annular jet, and means for projecting a group of air jets toward the axis of said material spray from diametrically opposite sides of said nozzle, each of said last named means comprising three` orificesv disposed at the apices of an isosoeles triangle, one altitude of each of j said triangles lying in a longitudinal plane pass-y ing through theaxis of the material spray.f

v4. In a spraying device of the class described, a nozzle having a central orifice for discharging f an axial jet of coating material or thelike, means for enveloping said jet withan annular jet of atomizing and aspirating air, and means for fur-'- ther atomizing and shaping said spray by directing an annular series of ne'converging jets of air'u'pon the material spray from points radially outwardly of said annular jet, and means for project-ing a groupof air yjets toward the axis of charge passageways disposedupon opposite sides of said nozzle, the'axes of said p assagewaysl ocv cupying a longitudinal plane which also includes a diameter of said nozzle, said passageways adaptled to deliver spray flattening jets of air which-y said material spray from diametrically opposite sides of said nozzle each of said last named means comprising three orifices disposed at the apices of an isosceles triangle, one altitude of each of said'triangles lying in a longitudinal plane passing through the axis of the material sprayQthe g Aoutermost one of said orifices in each lgroup being annular in form for the projection of a hollow tubular jet of air therefrom. K v, 5. In a spray gun nozzle of the class described, incombinationL an air cap member :having an axially locatedopening for accommodating a cen-- traljet of `sprayed material, and diametrically opgp'ositelydisposed forwardly projecting -horns thereon-,converging vpassagewaysin saidvhorns said diameter and adapted to deliver jets of air ther atomization and diusion ofsaid spray and for also altering its cross-sectional configuration, said last named means comprising apair of forwardly converging annular air discharge passageways disposed upon opposite sides'of `said nozzle, the axes of said passageways occupying a. longitudinal plane which also includes a diameter of 'I0l said nozzle, said passageways adapted to deliver lhollow tubular spray attening jets of air which for projecting vjets of spray modifying air'toward the axis of the jet of sprayed material, notches cut in the inwardly facing surfaces of said horns.'A and a pair. of air` discharge princes/formed in said notched sides one of each pair being disposed, Aupon opposite sidesvof a diametrical plane containing the axes of said passageways and ofsaid material spray.

6.- In a spray gun nozzle of the class described. in combination, an air cap member having an axiallylocated opening for accommodating a centrol jet of sprayedmaterial. and diametrically oppositely disposed v forwardly projecting horns l thereon, converging annular passageways in said hornsfor projecting hollow -tubular jets of spray.

modifying air toward the axis of the jet of sprayed material, notches cut in vthe inwardly facing surfaces of said horns, and a pair of air discharge oriflcesformed in said notched sides one of each Y pair being disposed upon opposite sides oi' a dia-

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