US2029423A - Air nozzle for flat spraying appliances - Google Patents

Description

E. GUSTAFSSON AIR NOZZLE FOR FLAT SPRAYING APPLIANCES Feb. 4, 1936.

Filed Feb. 28, 1935 2 Sheets-Sheet l E. GUSTAFSSON AIR NOZZLE FOR FLAT SPRAYING APPLIANCES Feb. 4, 1936.

Filed Feb; 28, 1935 2 Sheets-Sheet 2 Patented Feb. 4, 1936 UNITED STATES AIR NOZZLE FOR FLAT SPRAYING I APPLIANCES Eric Gustafsson, Chicago, Ill., assignor to Binks Manufacturing Company, Chicago, 11.. a corporation of Delaware Application February 28, 1935, Serial No. 8,699

10 Claims.

spraying appliance of the type in which a projected stream of generally liquid material is converted into a fine spray, and also flattened, by the action of opposed air jets.

When commercially employed on a large scale for applying liquid materials to automobile parts or furniture, or for applying generally liquid coating materials to bath tubs, such spray appliances are commonly used in the form of spray guns. With such spray guns, the cost of applying a given coating material to a given surface area of an object depends both on the time required for the spray gun to project the corresponding amount of the coating material, and on the amount of compressed air required both for atomizing this quantity of the coating material and for causing the resulting spray to be flattened to the desired cross-section.

Such spray guns usually are also constructed so as also to project a compressed air in the form of a tube around and so close to the initial portion of the projected material stream that this air speedily merges with the material to form a partially aerated material, and so that the velocity at which the just recited part of the compressed air also increases the velocity at which the material is propelled after its ejection from the'spray gun.

Owing to this effect on the velocity of the aerated stream of material, the time required for projecting a given quantity of a given coating material with a spray gun of the above mentioned type can readily be reduced by increasing the rate at which air is emitted in the said initially tubular form. But with an increase in the velocity of the stream of aerated material, this stream moves past the opposed air jets at a correspondingly increased velocity, so that the amount of air needed for the spray-flattening side jets of air must likewise be increased.

If the cross-section of the resulting spray were immaterial, this increase in the side jet air might be obtained by merely enlarging the side ports from which these opposed side jets are emitted. But if these ports were enlarged beyond their new customary size, where each has a diameter .materially smaller than the outlet of the material projecting nozzle, the so-called target (or cross-section of the spray of material when this reaches the object against which it is directed) could no longer have the shape which is commercially most advantageous, namely that of an ellipse which is so elongated as to present almost parallel sides.

However, this increase in the amount of side jet air which reaches the aerated stream of material during a given length of time can be obtained, without an increase in the area of the side ports, by increasing the pressure at which My invention relates to improvements in a fiat this side air is emitted. But with a given size of such side ports, the extent to which the pressure of the emitted air can be increased, for any given material, is limited by the resistance of that material to the thrust of the opposed air jets, since an undue increase of this thrust will indent or even split the resulting spray;

In my United States Patent #1,990,823 of February 12, 1935, I disclosed simple means for avoiding such a deleterious deformation of the crosssectional shape of the resulting spray by providing an additional air port at each side of, and close to v the central air port of the air nozzle through which air is projected as a tube merging with the projected material, these additional air ports being disposed so that the air jets emitted from them will merge with the partially aerated material stream to form longitudinal ribs against which the usual side air jets of the spray gun impinge.

In practice, the improvement disclosed in my said patent has provenadequate for enabling the spray guns to be used at a considerably increased rate of material spraying without changing the cross-section or target of the spray, and without requiring an increased consumption of compressed air proportionate to the increased rate of spraying. So also, the Long and Gustafsson Patent #l,897,l73 of February 14, 1933 (of which I was one of the applicants) had disclosed means for causing auxiliary air to merge with the side portions of the material stream intermediate those on which auxiliary air produces the projecting ribs of my said Patent #1,990,823.

However, for reasons hereafter described, the improvements disclosed in both of the said pat ents were limited in the extent to which the rate of spraying could be increased, particularly with certain materials. Consequently, even these improvements have not satisfied the demands of some of the larger commercial users-as for example the automobile manufacturers who have been eager for a still further reduction of the labor cost of the spraying, and also an increase in the number of parts of given area which can be spray-coated per hour in a single spray booth. v I

My present invention relates to further improvements in spray appliances of the recited class, for enhancing the resistance of a material stream to radial spreading tendencies to a much greater extent than has been found feasible with the disclosure of the aforesaid patents.

Illustrative of the manner in which my invention overcomes the above recited limitations, and

of the novel mode of operation on which my inventlon is based,

Fig. 1 is a greatly enlarged diametric section through the head portion of a spray gunof the], v I general .type disclosed in the Bramsen Patent #1,910,673, but equipped with a type of my new single auxiliary air port close to the central air I air nozzle designed for spraying a ceramic enamel.

Fig. 2 is a front elevation of the said head portion, showing the disposition of the new pairs of auxiliary air ports in the air nozzle.

Fig. 3 is an enlargement of the central portion.

of Fig. 2.

Fig. 4 is a fragmentary front elevation of an air nozzle of the type disclosed in my U. S. Patent #l,990,823, drawn on a somewhat larger scale than Fig. 2, for comparison with the latter.

Fig. 5 is a fragmentary front elevation of the ports shown in Figs. 1 to 3 are used in combination with the central air port enlargements of the Long and Gustafsson Patent #1,897,173.

Fig. 7 is a fragmentary front elevation of an air nozzle, having a circular main air port, showing the use of counterpart triplets of my closely spaced auxiliary air ports.

Fig. 8 is a fragmentary front elevation of an air nozzle, allied to Fig. 5, but showing counterparttriplets of my closely spaced auxiliary air ports in substitution for the similarly disposed pairs of ports in Fig. 5.

Fig. 9 is a fragmentary front elevation, allied to Fig. '7, but showing the use of counterpart pairs of closely spaced air ports in substitution for the triplets of such ports in Fig. 7, with the more out-'- ward port of each'such pair of smaller diameter than the companion port.

Fig. 10 is a fragmentary enlargement of the sectional view of Fig. 1, showing the approximate shaping of the fluid streams projected by the illustrated portions of the air nozzle and material nozzle.

Fig. 11 is an enlarged cross-section of the ribbed stream of aerated material before theside air jets of the spray gun impinge on it, taken along the line Hll of Fig. 10. Fig. 12 is a section allied to Fig. 11, showing what.the cross-section of the ribbed stream of material would be if the air nozzle only had a port.

Fig.- 13 is a fragmentary front elevation of an air nozzle having the port arrangement of Fig. 5

ofmy Patent #1.990,823, for comparison with Inthe drawings, Fig. 1 is a central and longitudinal section through forward portions of a .1 'co,i nmercial spray gun, drawn in about four times 't e-actual dimensions, showing my present intionas employed for preventing the (sprayttening)'-side air jets from indenting or splitg-the resulting spray, and also for preventing {heavy constituents of the projected material from being flicked out at the side edges of the generally fan-shaped spray.

*nFig. 2 is a fragmentary elevation of the same 1 ,Qne-jef these isan'axial .port 3 through which the usual material nozzle 4 extends freely and the other port 5 is controlled by a needlevalve 6 which is shown in a port-opening position.

Bearing rearwardly against a part of the gun body front radially outwardof the axial port 3 is a tubular partition I which freely surrounds a part of the material nozzle and upon a more'fcrward portion of which partition a tubular portion 8a of an air nozzle 8 is sleeved; The tubularpartition I also has a peripheral flange la, against whichan annular and corrugated spring 9 bears rearwardly.

Bearing rearwardly against this spring, and fitted upon a more forward portion of the material nozzle 4, as at 4, is an air nozzle 8 which has a central circular port C (Fig. 3) coaxial with and freely housing the tubular tip la of the materia'l nozzle. This air nozzle also has the usual forwardly projecting horns H, diametrically opposite its said central. port, which horns have the side ports II for projecting spray-flattening air jets along forwardly converging axes J which intersect on the common axis l3 of the material nozzle outlet 4a and the central air port C of the air nozzle.

When the air nozzle is clamped against the.

material nozzle by the usual retaining ring is which freely surrounds the baflie- -flange 1a on the tubular partition air can flow from the air chamber 2 in the gun body along the dotted air flow line f, so as to issue as a tube of air close to.

and around the materialwhich is projected through the outlet 4a when the material-control valve I5 is drawn back as illustrated. With this air tube so close to-the ejected stream of material, the conjoint forward movement of this stream and of the tube of air instantly moves the intervening air forwardly with it, thereby producing such a. vacuum that the atmospheric pressure of the air around the said tube of air causes the air of this tube to intermingle with the stream.

The resulting partially aerated material stream can. be increased in its resistance to the simultaneous impact of the opposed side air jets issuing from the horn outlets l2, as disclosed in my Patent #1,990,823, by providing an auxiliary air port A at each side ofthe central air port C, if these auxiliary air ports have their axes in the same plane (diametric of the central air port) in which the side jet axes J also are disposed and if each auxiliary port is so close to the central air port that atmospheric air pressure will also press the air issuing from that auxiliary port against the partially aerated material stream. So, also, experience with the just described arrangement of my last named patent showed that i when each such auxiliary air port had its axis approximately parallel to that of the central air port, and was materially smaller in diameter than the central air port, the intermingling of the added air with the material stream would produce longitudinal ribs on that stream, against which ribs the side air jets would respectively i.m

plnge.

However, with the auxiliary air ports A of such I a quite minor diameter in proportion to that of central air port C, the radial thickness d (Fig. 12) of each of the ribs on the stream is also quite small in proportion to the'diameter of theunribbed parts of the stream, so that the resulting to produce stream ribs of correspondingly greater radial thickness and stiffening effect. However, my experiments have shown that such a diametric enlargement of an auxiliary port also spreads the emitted air so much more circumferentially of the material stream (as shown in dotted lines at IS in Fig. 4) that the resulting ribs on the material stream are not proportionately thicker radially of the stream than a port U (shown in dotted lines in Fig. 4) proportioned as in my Patent '#1,990,823.

To make a greater amount of air at each side of the central air port really effective for a stream ribbing, I have found by my experiments that the auxiliary port provision at each side of the central air port should spread much farther radially of the stream from the central port than its spread circumferentially of that port, and that this circumferential spread should preferably be less than half the radius of the unaugmented air port.

For spray appliances of much larger dimensions than the present commercial spray guns. these requirements could be met by providing the central air port C (Fig. 13) with relatively quite narrow, andpreferably parallel-side port enlargements I! both of which enlargements have their medial planes in common with the plane P in which the axes of the side air jets are disposed, as shown by Fig. 5 of my Patent #1,990,823.

But with the relatively small dimensions of the parts of a spray gun light enough to be manipulated by a hand holding it, an accurate and not too expensive forming of such bore enlargements I8 is not feasible. For example, in a modern spray gun designed for speedy spraying, the central air port is less than an eighth of an inch in diameter, while the width of an efficient bore enlargement of the shape shown in Fig. 13 would be about one-fortieth of an inch, and such a narrow I slot could no easily be formed accurately in the tough material required for durability--namely, a drop forged hard bronze.

However, I have also found by experiment that I can accomplish my desired objects quite readily, and even more effectively than through the enlargement slots of Fig. 13, by providing a plurality of easily bored circular ports at each side of the central air port in such a disposition that the air jets issuing from the plural air ports at either side of the material stream will merge with the said stream to produce a stream rib against which the corresponding side air jet thereafter impacts.

Thus, in Figs. 1, 2 and 3, the auxiliary air port A at each side of the central air port C is supplemented by a second auxiliary port A farther from the axis of the central port, this more outward port being sufficiently close to the more inward port A so that the vacuum produced between the air jets emitted from these two auxiliary ports will cause atmospheric air pressure to press the air jet from the outward port A against the air jet issuing from the more inward port A (which latter port, after the manner of my Patent #1,990,823 is so close to the central air port that the air jet issuing from it merges speedily with both the air issuing (along the narrow line l3 of Fig. 1) through the central air port and with the material stream.

When the two pairs of auxiliary ports all have their axes in the same plane P which includes both the axis of the material stream and the axes J of the two side air jets, the velocity'of the auxiliary air jets tends to keep them away from the initially projected circular-sectioned stream, so that the surface tension of the liquid holds liquid intermingled with these jets as a radially projecting rib which remains clearly visible upon the material stream for a considerable distance forwardly beyond the intersection l8 (Fig. l) of the axes J of the side air jets if no air is emitted from these side jets.

Moreover, since the vacuum produced between two such adjacent auxiliary ports A and A also tends to flex the more inward port A outwardly toward the companion port, the effect of the atmospheric pressure does not spread the air of the inner stream nearly as much as it would do if I had only the single formerly used auxiliary port A.

For example, I have found that even when the side jets are being projected for flattening the partly aerated maierial stream (as shown in son) in Fig. 12, I not only produce stream ribs of a radial thickness d (Fig. 11) more than twice the corresponding thickness d in Fig. 12, but also produce stream ribs of smaller average width circumferentially of the stream. Consequently, I enormously increase the stiffening effect of each such rib in comparison with that which would be afforded by the rib l6 of Fig. 4 with the same consumption of compressed air. Moreover, the principles which permit this effective use of a pair of auxiliary ports at each side of the material stream, as in Figs. 1 to 3 can also be extended further by increasing the number of such ports at each side of the central air port. Thus, Fig. 7 shows the use of three consecutive auxiliary ports A, A and A at each side of the central air port.

Since the readiness and extent to which a vacuum is produced between adjacent and coparallel streams of fluid depends on the velocity of these streams, the spacing of the several air ports in the central portion of the air nozzle may be varied somewhat according to the velocity of the emitted air. According to my already conducted tests, the clear spacing S between the central air port C and each auxiliary air port A directly adjacent to it may be approximately equal to the diameter of the port A, because of the intensity of the air suction produced by the air which issues initially in tubular form from the central air port, although I preferably make it somewhat smaller than this diameter.

However, I have found it advisable to make clear spacing between two auxiliary air ports A and A in a nozzle having two pairs of such ports considerably less than the diameter of either of these ports, owing to the relatively smaller suction between them. When using three air ports at each side of the central air port, I have also found it advisable to make the clear spacing S between the two ports farthest from centralair port still smaller, as for example not greater than-the radius of the more inward one of these two ports.

Since such cylindrical air ports can easily and speedily be bored (even in tough metal) with simple and easily reground drills, the providing of my heretofore described additional auxiliary ports adds much less to the manufacturing costs than my sawing or milling of slots (as contemplated by Fig. 13). Moreover, my plural port provisions can readily be employed with spray appliances of such small dimensions as would make the just mentioned sawing or milling operation highly difficult. For example, in the spray guns of the here described type as now used by large automobile manufacturers, the central air port is less than one-eighth of an inch in diameter, and the desirable maximum width of an air port enlargement IS in the nozzle of which a portion is shown in Fig. 13 would be about onefortieth of'an inch.

When the nature of the material and the desired fineness of atomization require it, the above described principle of employing plural auxiliary air ports disposed for conjointly, producing a rib on a stream of material can also be employed in substitution for the enlargementsof the central air port as contemplated by the long and Gustafsson Patent #1397173, or for the single air ports' dispmcd adjacent to the central air port and with their axes in the plane along which the spray is to be flattenedi Illustrative of this feature of my invention, Fig. 6 shows the central portion ofan air nozzle provided with the same pairs of stifiening-rib producing auxiliary air ports as described in connection with Figs. 1 to 3, and also shows the central air port C as having opposed port enlargement C (after the manner illustrated in the Long and Gustafsson patent) for emitting air in such a manner as to prevent heavier constituents of the material such as ground vitreous enamel from being projected beyond the general confines of the spray. Fig. 5, shows the same pairs of auxiliary ports effectively disposed for stifiening the stream against the impact of the usual side air jets, together with two supplemental air ports ll disposed after the manner of my Patent #1,990,824

for producing two other stream ribs between the ones resulting from the use of the said pairs of auxiliary ports.

Fig. 2 shows the use of two groups of supplemental ports, l8, l8 a and 18b respectively at opposite sides of the central air port C, each group being symmetrical with respect to a plane I9 diametric ofthe central air port and at right angles to the common plane P of the axes of the pairs of rib-producing auxiliary ports A and A In Fig. 3, these supplemental ports at each side of l the central air port also are three in number,

namely two ports 23 and 2| disposed so close to the central air portas readily to merge with the air from the latter and with the material stream,

and an intermediate port 22 suiiiiently close to l the ports 20 and 2i so that the air from all three ports will speedily merge.

When arranged as in Fig. 3, namely with all three ports at approximately the same distance from the axis of the central air port, I have found the'effect to be substantially as with the port enlargements C when the ports are bored so as to slope forwardly toward the axis of the central air port, as shown by the section of Fig. 6, thus producing the eifect described in the Long and Gustafsson patentwith a cheaper manufacturing cost. However, if the ports are bored parallel to the axis of the central air port, and particularly when the central one of the three supplemental ports is spaced farther from the just named axis than the other two (as in Fig. 3) each group of supplemental ports conjointly produces-a stream rib of greater width than its radial thickness Moreover, my pairs of plural. auxiliary air ports not only can be used in the above recited general manner for affecting the material stream;

merely along the plane P in which the usual side jets are projected, or in the plane IQ (of Fig. 3) along which the spray is to be flattened, but also with manyother arrangements of the air ports in the central part of the air nozzle, and the plural air ports of each group need not necessarily be of the same diameter.

Thus, Fig. 9 shows the inward auxiliary port A of each pair of ports as of larger diameter than the companion port A and Fig.- 8 shows trios of auxiliary ports (as in Fig. 7)...along with the'single auxiliary ports I! of Fig. 5. Nor am I here claiming the novel method of operation involved in the ribbing oi the material stream, by the use of pluralities of air ports disposed as heretofore described, this bcing reserved for a corresponding divisional application.

I claim as my invention: I

1. In a spray appliance of the class in which a forwardly projected stream of generally liquid material is flattened in a plane diametric of said stream by the conjoint action of forwardly converging air jets which have their axes in a second plane diametric of the said stream and at right angles to the first named plane, means for forwardly projecting two counterpart pluralities ofv air jets respectively at opposite sides of the said stream with each of the said pluralities symmetrically disposed in relation to one of the said planes, with the constituent jets of each of the said pluralities sufli'eiently close to each other and to the said stream so that atmospheric pressure will cause each such plurality of jets to merge with the said stream before the said converging air jets act upon the stream.

2. In a spray appliance oi the class in which a stream of generally liquid material is forwardly projected through a material nozzle, and in which an air nozzle has botha central port through which air is forwardly projected around and in merging relation to the said material stream and two side air ports for projecting forwardly converging -jets of air respectively against opposite sides of the said stream, an air nozzle characterized by also having two counterpart pluralities of auxiliary ports respectively at opposite sides of the central air port; all of the said auxiliary ports having their axes substantially coparallel with the axis of the central air port and in a common plane with both the axis of the said central port and the axes of the side air ports; the clear spacing of the central air port from each of the auxiliary ports nearest to it being not materially greater than three times the radius of the said nearest port, and the spacings between adjacent auxiliary ports being not materially greater than the diameter of one of these auxiliary ports.

3. In a spray appliance in which compressed air is projected forwardly through the central air port of an air nozzle in speedily merging relation'to a stream of generally liquid material projected forwardly through and coaxial with the part pluralities of auxiliary air ports respectively at opposite sides oithe central air port, both of the said pluralitie's of auxiliary air ports being all) symmetrical with respect to the same one of the said two planes, the spacings between the auxiliary air ports constituting each such plurality and the spacing of at least one of these constituent ports from the central air port being sufficiently small so that atmospheric air pressure will press the air jets issuing from the constituent ports of each of the said pluralitles'of ports to merge with each other and with the aerated material stream before the said stream is impacted by the said air jets.

4. A spray appliance of the recited class includ ing an air nozzle as per claim 3,, the said air nozzle having the outlet ends of its auxiliary port arrangements in a common plane at right angles to the axis of the central air port,

5. A spray appliance of the recited class including an air nozzle as per claim 3 the said air noz zle having thev outlet ends of its auxiliary port arrangements in a common plane at right angles to the axis of the central air port and approxi-' mately in a common plane with the outlet of the said material nozzle.

6. In a spray appliance of the class in which a stream of generally liquid material is forwardly projected through a material nozzle, and in which an air nozzle has both a central port through which air is forwardly projected around and in speedy merging relation to the said material stream, and in which the air nozzle also has two side air ports for projecting forwardly converging jets of air respectively against opposite sides of the said stream so as to flatten the said stream in a plane diametric of the said-central port, an

air nozzle characterized by also having two counterpart pluralities of auxiliary ports respectively at opposite sides of the central air port; all of the said auxiliary ports having their axes substantially coparallel with the axis of the central air port, and both pluralities of auxiliary ports being symmetrical with respect to the said plane; the clear spacing of the central air port from-each of the auxiliary ports nearest to it being not materially greater than three times the radius of the said nearest port, and the spacings between adjacent auxiliary ports being not materially greater than the diameter of one of these auxiliary ports.

'7. In a spray appliance of the type including a material streaniprojecting nozzle and also including an air nozzle having a central air port coaxial with and freely housing the discharge end of the said material nozzle to permit air to issue around the said discharge end from an air space behind the central part of the air nozzle, an air nozzle characterized by also having two counterpart pluralities of auxiliary air ports axially substantially coparallel with each other and with the central air port; the said pluralities being respectively at opposite sides of and adjacent to the central air port and disposed for emitting air from the said air space, both of the said pluralities of auxiliary ports being symmetrical with respect to a common plane diametric of the central air port, the auxiliary air ports constituting each of the said pluralities being sumciently close to one another, and at least one constituent port of each such plurality being sufficiently close to the said central air port, so that atmospheric pressure will causethe air jetsemitted by all constituent ports of each such plurality to merge with each other and with the material stream.

8. In a, spray appliance of the recited type, an air nozzle as per claim 7, in which each of the ports recited as sufilciently close to the central air port is spaced from the central air port by a distance not more than three times the radius of that suiliciently close port. a

9. In a spray appliance of the class in which a forwardly projected stream of generally liquid material is flattened in a plane diametric of the said stream by the conjoint action of forwardly converging air jets which have their axes in a second plane-diametric of the said stream and at right angles to the first named plane, an air nozzle having a flat fronted central portion provided with a central air port for emitting air around in merging relationto the said stream, the said cen tral portion of the air nozzle being also provided with two counterpart pluralities of auxiliary air ports respectively at opposite sides of the central air port and all having their rear ends disposed for admitting air at the same pressure as the said central air port, and the said auxiliary air ports all having their axes substantially parallel to the axis of the central air port and disposed in a common plane with the axes of said converging air jets; the auxiliary air ports constituting each of the said pluralities being sufliciently close to one another, and one of these ports nearest to the central air port being suiliciently close to the said central air port, so that atmospheric pressure will cause the air emitted by all of the constituent ports of each such plurality to merge with the material stream before the said stream is acted upon by the said converging air jets.

10. In a spray appliance of the class in which a stream of generally liquid material is forwardly projected through a material nozzle, and in which an air nozzle has both a central air port through which air is forwardly projected in the initial form of a tube around and in merging relation to the said material stream and two side air ports for projecting forwardly converging jets ofair respectively against opposite sides of the said stream, an air nozzle characterized by also having auxiliary port arrangements for projecting two counterpart pairs of columns of air forwardly respectively at the said opposite sides of the material stream with the axes of all of the said air columns in the same plane diametric of the stream with the axes of the said side air ports: the auxiliary port arrangements being such thatthe column of each pair nearest to the material stream is sufiiciently close to this stream so that the partial vacuum produced between the said tube and the said nearest air column causes that air column to be pressed against the said stream, and such that the other air column is sufliciently close to the companion column of the same pair that the partial vacuum produced between the two columns of that pair by the forward movement of these two columns of air causes these columns to be pressed toward each other; thereby causing the material stream to merge also with the air of both pairs of the said columns of air to form an aerated stream having longitudinal ribs projecting at its opposite sides, against which ribs the said side air jets respectively impact.

ERIC GUSTAFSSON.

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