US2138300A - Air nozzle for flat-spraying appliances - Google Patents

Description

Nov. 29, 1938. E. GUSTAFSSON AIR NOZZLE FOR FLAT-SPRAYING APPLIANCES Filed Dec. 23, 1957 liven/2597;

dim/25y Patented Nov. 29, 1938 UNITED STATES AIR NOZZLE'FOR APP FLAT- SPRAYING LIANCES Eric Gustafsson, Chicago, 111.,

assignor to Binks Manufacturing Company, Chicago, 111., a corporation of Delaware Application December 23, 1937, Serial No. 181,398

8 Claims.

My invention relates to an improvement in the air-emitting nozzle of the so-called spray head of a fiat-spray-producing spray appliance such as a modern paint spray gun. Such a spray head usually comprises a material nozzle for forwardly projecting a stream of generally liquid coating material, and an air nozzle having a central air port for emitting air in merging and propelling relation to the said stream. This nozzle also has side ports for projecting forwardly converging side jets of air against opposite sides of the said stream, thereby flattening the stream and spreading it to the shape of a fan.

During the just recited transformation, the generally cylindrical stream is spread out to an elliptical cross-section, or even a rectangular one if the air nozzle also has suitable auxiliary air-emitting provisions; and, owing to the speed at which the said stream moves betweenthe said side air jets, the flattening action of these opposed jets causes portions of this stream to move with high velocity and in relatively opposite directions away from the axis of the stream. Consequently, this sudden movement of particles toward the stream sides behind the side edges of the fan-shaped spray will tend to project heavy particles of a stream of non-homogeneous material beyond the said stream sides, and such detached particles later on will produce a so-called "off spray by depositing spaced coating particles beyond the ends of the spray pattern. V

Moreover, if even a slight scratch has been formed in a part of the central bore of the air nozzle which is at or near the plane along which the stream and spray are flattened, such a scratch or nick is apt to produce a corresponding projection or rib on the stream of material, which later on will detach as a sliver to produce a similar off spray even with an entirely homogeneous sprayed material. Consequently, almost microscopic nicks formed in the. central bore of the air nozzle may cause offspray which must thereafter be wiped off the coated surface.

My present invention aims to provide a simple method and means for overcoming the just recited dimculties by causing auxiliary jets of air to carry such unduly projected or sliver-forming material particles back within the contour of the flattened stream part before that part breaks up into a spray; also to insure a definite fan-shaped spread of the spray (as well as a more sharply defined spray pattern or target and shape) when the central port of the air nozzle is slightly imperfect or has become somewhat worn, or when the sprayed material includes heavy particles suspended in a much lighter liquid carrier.

Illustrative of the means by which I accomplish my above recited objects, Fig. 1 is an enlarged and fragmentary front elevation of an air nozzle embodying my invention and suitable for employing my novel ofiset-preventing and spray-shape defining method.

Fig. 2 is a reduced section, taken along the line 2--2 of Fig. 1, and including a partially sectioned elevation of a material-projecting nozzle associated with the air nozzle.

Fig. 3 is a section drawn on a larger scale than Fig. 1 and taken at right angles to that of Fig. 2 along the common plane of the two nozzles, including dotted port axis lines and a partial outline of the rearward part of the gradually flattened out aerated material stream.

Fig. 4 is a fragmentary front elevation, allied to the central part of Fig. 1, but drawn on a somewhat larger scale than Fig. 1, showing the central air port as also including the port enlargements of the Long and Gustafsson Patent 1,897,173.

Fig. 5 is a fragmentary section taken along a line such as 5-5 in Fig. 3 through a fan edge portion and the corresponding auxiliary jet of air.

Figs. 6 and '7 are figures allied to Fig. 5, taken when the axis of a novel auxiliary port of the air nozzle is somewhat shifted, in relatively opposite directions, from that shown in Fig. 5.

In Figs. 1 and 3, the illustrated portions of a spray head include the major part of a material nozzle M having an axial and forwardly projecting tubular discharge tip T, through the bore of which tip the liquid (or generally liquid) material issues, and having air passages P ex- 40 tending through the main part of this nozzle.

Fitted upon the forwardly tapering main part of the material nozzle is an air nozzle A which has its central frontal part formed to afford an air space a into which the said passages open, and also having an axial and generally cylindrical bore B into which the discharge tip of the material nozzle freely extends. In addition, the air nozzle also has the usual forwardly projecting horns H, symmetrically disposed at opposite sides of the axis I of the nozzle. Each such horn has a side-air port S to which compressed air is supplied from an interior groove G in the air nozzle, the air being supplied through ports 9 as shown in Fig. 3.

With the Just described spray head or nozzle assembly, compressed air passing through the annular space between the material nozzle tip and the bore B of the central air port mingleswith, and both aerates and aids in propelling. the liquid stream issuing from the tip T of the material nozzle, and this stream is thereafter fiattened by the air Jets issuing from the side'air ports 8. These side ports have their axes 3 disposed in a common plane along the axis i of the air nozzle and intersecting on the latter axis, and the said side ports are symmetrically disposed with respect to the latter axis so that the air jets from these side ports flatten and spread the projected aerated stream of material into the shape of the fan having forwardly diverging side edges symmetrical with respect to the nozzle axis i along which a stream of material is discharged from the tip T of the material nozzle, the rearward portion of the fan shape being for example as shown in dotted lines at F in Fig. 3.

To prevent or (at least greatly reduce) the projection of oifspray-producing particles beyond these fan-side edges (which edges would continue forwardly substantially along the straight lines 5 in Fig. 3, as will readily be understood by spray-appliance operators) I provide my improved air nozzle also with two auxiliary air ports 4 of counter part size which respectively have forwardly diverging axes 5 extending respectively along, or at least near to, the previously mentioned forwardly diverging edges of the fan sides of the resulting spray. To accomplish this, the two auxiliary ports have their axes 5 disposed in the common plane 7 (Fig. 3) along which the spray is to be flattened, namely a plane along the axis 1 of the central air port P and at right angles to the common plane of the axes of the side air ports along which the section of Fig. 2 was taken in Fig. 3.

These auxiliary port axes 5 are symmetrical with respect to the said central port axis I and intersect on the latter axis at a common point 6 within the air nozzle. Moreover, the outlet ends of the said auxiliary ports preferably are equally spaced from the central air port axis and equally spaced rearwardly from the outlets of the side air ports S, so that the emitted auxiliary air jets (which expand in diameter as they move away from their points of emission) will have equal diameters when they impinge upon the corresponding side edge portions of the fan shape into which the material stream is being converted.

When such an auxiliary port has its axis alining with the straight-sided edge portion which the spray-fan would have if the air nozzle were not provided with my novel auxiliary ports, the resulting auxiliary air jet J will cut' partly through and wrap partly around the fan-spray F, as shown in Fig. 5. Or, if the axes of the auxiliary ports diverge forwardly at a somewhat lesser angle, as shown at 5a in Fig. 3, each auxiliary air jet will cut through more of the fan-spray edge portion tangentially to that edge, as shown in Fig. 6. So also if the axes of the auxiliary air ports diverge somewhat more than in Fig. 3, each auxiliary air jet may cut only slightly through the fan edge, as shown in Fig. '7.

In each case, the air of each auxiliary air jet immediately gathers up material particles projected beyond the contour of the fan portion through which that jet brushes, so that stream-spreading action of the which are desirable withapproximately tangential to the engaged fan side edge, as shown in Fig. 7. The auxiliary air jet may then somewhat indentthe convex section of the adjacent side so as to aid in flattening the corresponding end of the spray pattern.

While thus accomplishing the above described stray-particle gathering and spray-shape defining action, each auxiliary air jet also supplies additional air for aerating the laterally outward portions of the fan-shaped spray, and for additionally propelling the spray so as to compensate for a portion of the reduction in velocity which necessarily results from the lateral opposed side air jets issuing from the side ports S.

By thus using air in addition to that of the side air jets for augmenting the atomization of the spray, I am able to effect the often desired fine atomization without increasing the pressure of the side port air to an economically wasteful extent, or to such a degree as to have the side air jets indent the spray pattern. Moreover, I can obtain this advantage without increasing the diameter of'the side ports, and for my here presented purposes the novel auxiliary ports 4 may be considerably smaller in diameter than the side about 60 percent the diameter of the latter.

In practice, the divergence angle between the axes of the auxiliary air ports and the locations of their outlets can readily be varied according to the spread of the angle of divergence between said straight side edge portions of the spray, as I have found my here presented air nozzle modification and its method of operation suitable when the divergence angle 1 of Fig. 3 is even as small as about 20 degrees. So also, the frontal shape of the nozzle portion through which the auxiliary bores 4 extend is immaterial, this being here. shown as the usually flat frontal disk like shape.

However, I preferably dispose the auxiliary air ports 4 so that their outlets will not be materially farther forward than the outlet of the central port P of the air nozzle, so that each auxiliary air jet will travel and expand diametrically sufilciently (before meeting the fan spray) to wrap considerably around the corresponding edge of the spray. cAlso, to obtain an effective angle of divergence between the axes of the two auxiliary ports, I preferably dispose the outlet of each of the ports much nearer, than either of the side ports, to the axis l of the air nozzle.

k By thus disposing the outlets of the auxiliary ports in approximately a common plane with the outlet of the central port P and auxiliary ports of counterpart size leading from a common interior portion of the generally capshaped air-nozzle, I cause these auxiliary ports to emit air jets of equal size and under equal pressure, so as to equally eflect the two side edges of the fan-shaped spray.

making these ports S, as for example In practice, my here disclosed novel auxiliary port provisions can also be used in air nozzles of the same general class which also have other air port provisions in addition to the usual central and side ports. Thus Fig.4 shows a frontal part of an air nozzle including both my novel auxiliary ports and the central air port enlargements E disclosed in the Long and Gustafsson Patent 1,897,173.

so also, it is to be understood that many other modifications might be made without departing either from the spirit of my invention (either as to the novel structural features or as to the resulting novel method of operation) or from the appended claims.

I claim as my invention:

1. In the creation of a flattened spray of a generally liquid material by the impacting of stream-flattening air jets against laterally opposite portions of a forwardly projected stream of material so as to reshape a part of the stream initially to the shape of a fan presenting forwardly diverging side edges, the method of smoothing and substantially defining the side edges of the resulting spray, which method consists in projecting two forwardly diverging auxiliary air jets respectively forwardly along and in merging relation to side edges of the said reshaped stream. I

2. The method of claim 1, in which each auxiliary air jet is initially of smaller diameter than the initial diameter of either one of the said stream-flattening air jets.

3. The method of claim 1, in which each auxiliary air jet is of such initial diameter, and has its point of origin sufficiently spaced from the portions of the said fan side edges toward which that air jet is directed, so that the auxiliary air jet expands to a diameter sumcient for at least partly wrapping around the fan side edge part toward which this jet is directed.

4. In the creation of a flattened spray by the impacting of stream-flattening air jets against laterally opposite portions of a forwardly projected stream of material so as to reshape a part of the stream initially to the shape of a fan presenting forwardly diverging side edges, the method of smoothing and substantially defining the side edges of the resulting spray, which method consists in projecting two auxiliary air jets diverging forwardly symmetrically with respect to the axis of the forwardly projected stream, the axes of the auxiliary jets being disposed in a plane including the said stream axis and at right angles to a plane housing the axes of the stream-flattening air jets, the auxiliary jet axes alining approximately with the said forwardly diverging side edges of the fan-shaped spray.

5. The method of claim 4, in which each auxiliary air jet is of smaller diameter than either one of the said stream-flattening air jets.

6. An air nozzle for a flat-spraying appliance, of the class in which the air nozzle has an axial air port and also is provided with two side ports forward of the outlet of the axial port, symmetrically disposed at opposite sides of the axial air port, the said side air ports having their axes disposed in a plane along the axis of the said axial port and intersecting on the latter axis at a point still farther forward from the outlet of the said axial port; the air nozzle being characterized by also being provided with two auxiliary air ports having their axes disposed in a second plane diametric of the air nozzle and at right angles to the aforesaid plane; the said auxiliary ports having their axes converging rearwardly symmetrically with respect to, and intersecting at a common point on the axis of the axial air port.

7. An air nozzle as per claim 6, in which the auxiliary air ports are of smaller bore than the said side ports.

8. An air nozzle as per claim 6, in which the spacing of each auxiliary air port from the axis of the axial port is considerably smaller than the spacing of a side port from the last named axis.

ERIC GUSTAFSSON.

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