US2214035A

US2214035A - Spray head

Info

Publication number: US2214035A
Application number: US159544A
Authority: US
Inventors: Robert W Tracy
Original assignee: DeVilbiss Co
Current assignee: DeVilbiss Co
Priority date: 1937-08-17
Filing date: 1937-08-17
Publication date: 1940-09-10
Anticipated expiration: 1957-09-10
Also published as: FR842230A; GB509541A

Description

R. w. TRACY 5 PRAY HEAD I Filed Aug. 17, 1957 ZSheets-Sheet l Patented Sept. 10, 1940 SPRAY HEAD Robert W. Tracy, Toledo, Ohio, assignor to The De gilllliwiss Company, Toledo, Ohio, a corporation oi Application August 1'7,'1937, Serial No. 159,544

' 13 Claims. (c1; 299 140.1)

This invention relates to spray guns of the type employed. for discharging surface coating materials in spray-form, and pertains particularly to guns of this character adapted to discharge a 5 fan-shaped spray stream.

In the use of spray guns of this character, it is desirable to be able to control the width of the discharging fan spray to suit the Work to be performed, as in some cases a narrow stream and 10 in other cases a relatively wide stream is desired.

An object of the present invention is the provision, in combination with a spray head, of novel and efiicient means for'pneumatically restricting the effective spray discharge length of the spray 15 head slot to vary the width of the spray stream to suit the work to be performed. 7

Another object of the invention is the provision in connectionwith the discharge slot of a spray head, of pneumatic means for preventing acso cumulation in the ends of the slot of material being sprayed.

Another object of the invention is the provision of certain improvements in a spray head of the class described, whereby a better internal mixing 25 of the air and coating material, particularly under low air pressures, is obtained, and whereby greater capacity and speed of spraying are also obtained than with spray guns heretofore used.

The invention is fully described in the following specification, and one embodiment thereof illustratedin the accompanying drawings, in

which Figure 1 is a side elevation of a spray gun embodying the invention, with parts broken away 35 and with a part-in central verticallongitudinal section; Fig. 2 is an enlarged outer end elevation,

with .a part in section on the line 33 in Fig. 2

45 and illustrating a wider form of spray stream than that shown in Fig. 3; Figs. 6, '7 and-Bare different views of the outer spray head element in which the discharge slot is disposed, and Figs.

9 and 10 are different views of the material nozzle 50 element of the spray head.

Referring to the drawings, A designates the gun-body or stock, having atits forward end the enlargement B to which the spray head 0 is attached. The spray gun illustrated is of the general type and construction disclosed in United.

States Patent No. 2,060,894, dated November 17. 1937, except as to the construction of the spray head C, in which the present invention resides. The spray head C includes a centrally disposed material discharge nozzle I, an outerdischarge nozzle 2, which may be termed the spray nozzle, and an intermediate. nozzle 3, which may be termed the air nozzle. The material nozzle l is attached to the part B, with its bore in communication with the material supply bore 4, and its discharge orifice is controlled by a valve 5, as well understood in the art. The intermediate nozzle 3 surrounds the restricted discharge endof the nozzle I, and has its rear edge provided with a conical seat againstan annular part of the enlargement B, as at 6. The orifice I of the nozzle 3 freely receives the discharge end of the nozzle l to permit the discharge of air around the latter from the interior chamber 8 of the air nozzle. The outer nozzle 2 seats against the 0 outer side of the nozzle 3 around its orifice and has a diametrically disposed spray discharge slot 9 spaced outwardly from the discharge end of the nozzle 3 with its center in coaxial register with the discharge orifices of the nozzles land 3.

The slot 9 is provided transversely across the ridge-like end of the nozzle 2.

' A hood member l0 encircles the inner end portions of the

nozzles

2 and 3 and cooperates therewith to form an annular air passage H within the hood. The hood [0 embraces the outer edge portion of the nozzle! and when clamped to the adjacent forward edge portion of the gun enlargementB retains the

nozzles

2 and 3 seated one against the other and the nozzle 3 seated against the enlargement B. A, clamping ring I! is threaded onto the outer end of the enlargement B and has shouldered coaction with the rear edge portion of the hood l0. r I The interior of the air nozzle 3 has suitable communication with" a source of air pressure supply, as well understood in the art, while the annular air passage II, in the present instance, has communication with a suitable source of air pressure supply through a? bailled passage l5, tube side oi! the rounded inner end portion of the cavity, as shown. The disch e end of the air nozzle 3 is intended to fit into the rear end of the cavity 20, as best shown in Fig. 3, and to cooperate with the outer nozzle 2 to form a mix-' ing chamber 2| into which the air and material from the nozzles and 3 are discharged and 5 mixed before discharging from the spray slot 9.

To facilitate the 'mixing of the air and material in the chamber 2|, the air discharge orifice 1 in the nozzle 3 is provided at two diametrically opposedpoints of its outer edge portion with outwardly tapering notches 22 (Figs. 4, 9 and 10). and these notches are disposed in a diametric line which is at right angles to the diametric line of the slot 9 relative to the spray head axis. Those notches permit an expansion of air as it 5 passes therthrough in its discharge from the orifice I, so that the air stream instead of maintaining a circular form in its discharge into the mixing chamber 2| is broadened probably into elliptical form at right angles to the spray slot 9, l so as to strike the sides of the chamber below the sides of said slot and to thereby spread laterally in both directions around the interior of the chamber to eifect a more thorough and eifcient mixing of the air and material therein before discharging from the slot than would otherwise be the case.

While it is not known just what action takes place within the mixing chamber 2 I, it is thought that the expansion of air in its passage through the notches 22 acts to draw'material towards the sides onwhich the grooves are located and F that the atomizing air passing through the annularportions of the air discharge passage between the notches 22 acts to flatten out and force the discharging material towards the sides on which the grooves are located; Most of the material is thus carried against the side walls of the mixing chamber which extend up to the sides of the slot Siand it is propelled along the sur- 40 faces to the slot opening at which point the spray material from one side collides with that following the opposite wall surface. The collision is a main factor in getting the particularly fine atomization obtained with the use of this nozzle. It is found in practice that it also brings about a very thorough spread of the material within the slot itself and results in a final ray of greater fan width and more uniform through- Y out its width. It is hard to analyze or deter-.

mine the probable shape of the material passing through the mixing chamber. Undoubtedly, however, a cross-section would show itbroadened to an extent that approaches the confines of the chamber in the dimension diametric to the long dimension of the slot. The cross-section is some other 1 55 '1, a, 9 and 10. 1

For the purpose of pneumatically controlling the width. of the spray stream discharging from the slot 9, the nozzle 2 isgprov'ided at each end- ,of said slot with an air discharge passage 25,

70. which opens at its outer end through the re spective' end wall of the slot and communicates r at its inner end with a suitable source of air pressure supply, which, in the present instance, is

in the annular passage II in the spray head. 75- The discharge from the passages 25 .is against the side edges of a spray stream discharged through the slot 9 from the mixing chamber 2| and tends to narrow the width of the stream at its point of emergence from the spray slot to an extent depending on the pressure of the suppleniental air streams discharging thereagainst from the passages 25. This action is illustrated by reference to Fig. 3 in which air is shown as being discharged through the supplemental passages 25 against the side edges of the spray stream D, the latter at its point of discharge .from the slot 9 being of less width than the length of the slot. In Fig. 5, no discharge of air is taking place through the passages 25, and the spray stream at its point of passage through the slot 9 is therefore of a width substantially equal to the length of the slot. It is apparent that the width of the spray stream can be changed a greater or less extent, depending on the quantity and pressure of discharge of air from the passages 25 such discharge being controlled by a manipulation of the valve I! to suit the work 'being performed. The slot 9 is of arcuate form lengthwise thereof in the plane of the spray head axis and the discharge of air into the slot ends from the passages 25 is at an outward incline to the axis of the discharging stream.

In Figs. 3, 5, 9 and 10, the air nozzle 3 is shown as provided outwardly through its discharge end with small air discharge passages 28, which communicate at their inner ends with the interior chamber 8 of the nozzle 3 and have their outer ends opening into the mixing chamber 2| and disposed to direct their discharge against opposite sides of the material stream emitting from the material nozzle i. These passages 28 are disposed midway between the notches 22 in the nozzle 3, so that'they augment the broadening or flattening action of the stream within the mixing chamber 2| that is induced by the expansion of the air in its passage through the notches 22 in the nozzle 3. Inasmuch as the discharge ofair from the passages'28 has substantiallythe same widening action onthe material 'stream within the mixing chamber 2| a's i-s effected by reason of the presence of the notches 22, either the passages 28 or the notches 22 may be used alone to effect such action, or they may be used together, as desired.

It is found in practice that the broadened air stream discharge from the nozzle 3 within the chamber 2|, which is efiected by the presence of the opposed notches 22, not only causes a greater swirling of the air within the chamber 2| and a consequent more thorough mixing of the air and surface coating material before its discharge through the slot 9, but also tends to keep the walls of the chamber 2| free of material which would otherwise accumulate thereon and would require frequent cleaning.

I wish it understood that my invention. is not limited to any specific construction, arrangement or form of the parts, as it is capable "of numerous modifications and changes without departing from the spirit of the claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent, is:

1. In a, spray gun, a spray head having an outer discharge nozzle with a spraydischarge slot therein and with air discharge passages opening into the ends of the slot to discharge air under pressure at an outward inclineagainst the side edges of a spray stream at substantially its poiht of passage through the slot, and regulable stream discharge nozzle, the latter having a discharge slot in axial register with the inner nozzle, the ends of said slot extending rearward, said outer nozzle having air discharge passages in communication witha regulated source of air pressure and having their discharge ends opening into said slot through its ends with the discharge therefrom directed in outward converging relation toward the axis of a'spray stream discharging from said slot.

4. In a spray gun, a spray head having an air discharge nozzle and a spray discharge nozzle, the latter with a discharge slot, said nozzles cooperating to form a mixing chamber, a material discharge nozzle having its discharge through the air nozzle orifice into said chamber, and said air nozzle orifice being broadened at least at its outer edge in a diametrical line at right angles to the length of said slot.

5. In a spray gun, a spray head having an air discharge nozzle with its orifice diametrically nozzle having a discharge slot disposed diametrically oi' the axis of discharge of said other nozzles, said slot being at right angles to the line of broadening of said air nozzle orifice, saidspray and air nozzles cooperating-to iorm a mixing chamber circular in cross-section with its side walls converging inwardly away from the air nozzle. p

6. In a spray gun, a spray head having an outer spray nozzle with a diametrically disposed spray slot in its outer end, the inner side of said nozzle forming a conical cavity with its restricted forward end extending beyond the ends of said slot and open to the slot, an air nozzle seating against said outer nozzle and cooperating therewith to form said cavity into a mixing chamber, said air nozzle having outwardly tapering notches in opposite sides of its discharge edge with said notch-'- es disposed in a line at right anglesto the length of said slot whereby the air stream discharging from the air nozzle is broadened transversely of the'slot, and a material discharge nozzle projecting. at least partly into and having its discharge through said orifice toward said slot.

' 7. In a spray gun, a spray head having a spray nozzle with a cavity forming a mixing chamber and having a spray discharge slot elongated crosswise of the outer end portion of said chamber, a material discharge nozzle spaced rearwardly from-said slot and disposed to direct its discharge toward the center of the slot through the mixing chamber, and provision for directing air under pressure into said mixing chamber in surrounding relation to the material stream discharged therein and in greater volume at diametrically opposite sides of said stream to induce a broadening of the material stream within the chamber at right angles to the length of the slot.

8.1Infla spray gun, means forming a mixing chamber with forwardly and inwardly tapering side walls and a transversely extending discharge slot in the outer end portion of said chamber, means for directing a stream of material forwardly through said chamber in line with said slot, and means for directing a'circular stream of air into said chamber in enveloping relation to said material stream and also to direct streams of air against two diametrically opposite sides of the material stream within the chamber to tend to flattenand broaden the material stream within the chamber transversely of the discharge slot.

'9. In a spray gun, means forming a mixing chamber with forwardly and inwardlytaperin'g side walls and a transversely extending discharge slot in the outer endportion of said chamber,

means for directing a stream of materialforwardly through said chamber in line with said slot, and means for directing a circular stream of air into said chamber in surrounding relation to the inner end portion of said material stream and permitting an expansion of the air at two opposite sides of the stream to induce a broad-- ening of the stream within said chamber transversely of said slot, said last means also having provision for directing air streams against said material stream within said chamber to assist in the flattening and broadening of'the mate- 1 rial stream within the chamber.

. 10. In a spray gun, a spray head having a spray nozzle with a substantially conical'cavity therein forming a mixing chamber and with a discharge slot in its outer end extending crosswise of the restricted end portion of the chamber, a material discharge nozzle'for directing a stream of material forwardly through said chamber in line with the slot midway of its ends, an 'air nozzle at the rear of said chamber forming an annular air discharge orifice around the discharge end of said material nozzle for directing air'under pressure against the material stream entirely therearound in its discharge into the chamber, said air nozzle having its orifice broadened at two opposite, sides thereof at right angles to the length of the slot to permit air expansion within the chamber ina manner to induce a broadening of the material stream by the expansion action before reaching said slot and in a plane which is angulariy disposed to the slot.

11. In a spray gun, a spray headhaving means forming a substantially conical mixing chamber with a transversely extending discharge slot from its reduced end, a material discharge nozzle directing its discharge into and through said mixing chamber in line with the slot midway of its ends, andan air orifice having an annular air discharge nozzle directed into the rear endportion of the mixing chamber in surrounding relation to the material stream and having provision for directing air against two opposite sides of the material stream at right angles to the length of the slot to induce a broadening of the stream within the mixing chamber before reaching the slot and at substantially right angles thereto.

12. The method of producing a finely atomizedcausing the stream to assume a final fan-shape formof spray stream with the broad dimension 10 a broadening thereof, acting on the broadened F stream in said space by contact thereof with the space walls to bring the opposed outermost broadened portions of the stream into merging globule breaking-up relation, and then abruptly causing the stream to assume a final fanshape form of spray stream with the broad dimension f the spray stream angularly turned relative to at of the stream in said space.

ROBERT W. TRACY.