US2375766A - Dry spray equipment - Google Patents

Description

May 15, 1945. Q w BRrI-CHER 2,375,766

DRY SPRAY EQUIPMENT Filed June 26, 1943 2 Sheets-Sheet 1 W [I 1212. 20 @J 10 INVENTOR C luzr'ks' Wi'llabmz Brz'Zc/er ATTORNEYS y 1945- c. w. BRITCHER ,37 ,766

DRY SPRAY EQUIPMENT Filed June 26, 1945 2 Sheets-Sheet 2 66 Z H328 Q 71 6 7 4 Fig.4.. W5

85 INVENTOR Charles William Bra'zc/zer BY ad M QKM ATTORNEYS 4&8?!

. Patented May 15, 1945 UNl'l'ED STATES PATENT OFFICE ar SPRZI l'J ZZIPMENT v Charles William Britcher, signor to Craig Corpora Glen Ridge, N. .l., astlon, New York, N. Y.,

a corporation of New York Application June 26, 1943, Serial No. 492,345

26 Claims.

The present invention relates to spraying apparatus of the type used to spray dry, ground or powdered material, and more especially to distribute such material uniformly over the width of a surface to be sprayed, and this through aligned spray apertures relative to which such surface is moved lengthwise.

The invention is an improvement upon that of the prior patent to Herbert Cole, No. 2,266,849, of December 23, 1941, and while it has an important application to the graphic arts, it has a wider field of application for spraying ground or powdered material in other industries, among which are the following: rubber, coated fabrics, oil cloth floor covering, plastic sheeting, insulating cloth, linoleum, food products, face brick, confectionery and baking, wall board and metallired paper.

It is among the objects of the invention to provide apparatus of the above type of simple construction, which is substantially proof against clogging as long as the powder is kept dry and which assures uniform distribution under all conditions of operation. I

Another object is to provide apparatus of the above type, the operation of which may be readily and reliably checked, in which the supply may be readily replenished, manually or automatically even during operation, and in which the distributing ducts may be readily cleared when operation is to be discontinued to avoid clogging during the period of idleness, especially where a hygroscopic powder is used.

In the accompanying drawings in which are shown one or more of various possible embodiiments of the several features of the invention,

Fig. 1 is a front elevation showing the complete apparatus other than the spray jet tube and powder feed hose,

Fig. 2 is a transverse sectional view of tank shown on a larger scale,

Fig. 3 is a side elevation of one embodiment of spray distributor tube,

Fig. 4 is an end elevation thereof showing the direction of spray discharge, 7

Fig. 5 is a fragmentary view on a larger scale of the mid portion of the distributor tube of Fig. 3 and taken on line 5 5 thereof, a

Fig. 6 is a plan view of the spray distributor of the spray Fig. 3,

Fig. 7 is a detailed sectional view of the spray distributor on a larger scale taken on line 1-1 of Fig. 3.

Fig. 8 is a side elevation similar to Fig. 3 of spray tank 0 which air from a suitable compressor (not shown) conan alternative embodiment of spray distributor tube, and

Fig. 9 is a fragmentary part of the front elevation showing a slight modification of the blow-out detail of the embodiment shown in Fig. 1.

In the accompanying drawings, Fig. 1 shows the various elements of the equipment which are mounted upon an upright panel l0 and from which is supplied the controlled spray for delivery to the distributor tube T shown in Figs. 3 to 7. The elements mounted on the panel include a is supplied with compressed nected through an appropriate tube (not shown) to inlet fitting H which discharges into air filter l2 that communicates by way of pipe l3 and cross pipe [4 to the bottom of a dehydrator tank ll, desirably filled with silica gel. From the top. of tank I! pipe it leads to header I! from which cross-conduit it! leads into the lower end of said spray tank C. Adjacent the lower end of spray tank 0 the panel carries an electrical motor I! which, through reduction gearing (not shown) through a valve 2| with powder "when ing compressed air through the equipment,

The spray tank C is preferably in the form of an upright metal shell rounded at top and bottom, as shown, and bolted by bracket 25 to the In the unitary cylindrical extension 28 at the bottom of the spray tank is fitted a bushing 21, which mounts a cylindrical air supply fitting 28 that rests at its internally steeply beveled lower end 29 upon the corresponding coneshaped nozzle end 30 of the upwardly extending air feed'plug 3|. The air feed plug II is mounted in support sleeve 32 above which its conical end 30 extends, and to which it is clamped by packing nuts 33.

The air supply fitting 28 has an upstanding rim :4 rising from the bushing into the lower end and spaced, as shown, from the wall of said spray tank C. Upon said upstanding rim rests the face of the agitator plate 35, which desirably has a downwardly extending flange or pilot-sm extendi into and encompassed by said rim. Agitator site 35 has one or more small ducts 31 desirably of .086 inch bore, shown L-shaped in the drawings, for passage of air therethrough, to discharge laterally therefrom into the spray tank.

Supported upon the agitator plate 35 is the air injector tube as which extends axially of the spray tank to near the top thereof. The lower end of the injector tube 38 extends into the axial bore of the agitator plate, and a lock nut 39 holds said tube securel to said plate.

The agitator plate 35 is preferably rotated in operation, desirably by an intermittent motion, so that the air jet through its duct 31 will enter the powder in the spray tank at constantly changing parts of the tank bottom, thus to prevent the air stream blowing a single hole or tun nel through the body of the powder 40 packed in the spray tank; for cavitation would result in little of no powder being entrained with the air stream passing through such tunnel. Thus assurance is had that the desired cloud of powder will be effectively stirred up at the upper part of the spray tank.

For intermittently rotating the agitator plate the motor l3 drives a ratchet wheel 4! encompassing and aillxed to the air supply fitting 28 and operated by a coacting ratchet 42 pivoted as at 43 to a crank rod 44 driven from the crank wheel 45, which is slowly turned through reductiongearing (not shown) of the motor IS. The.

agitator plate 35 is rigidly attached as by threadingupon the air supply fitting 28, soas to turn therewith for the operation set forth. The air supply fitting 28 also carries a ball check valve 46 to prevent clogging of the passages therebelow after the power has been shut off.

Mounted in the outlet head 41 of the spray tank is an injector sleeve 48 which has one or more upwardly directed injector apertures 49 therein. The power end of the sleeve 48 is telescoped over the upper end of the injector tube which latter has an outlet aperture 56 in its otherwise closed upper end.

The upper part of the spray tank is desirably equipped with a glass bull's-eye i and an electric lamp 52 adjacent thereto, under control of the switches 22 and 23. The lamp is constantly illuminated while the device is operating, so that the powder cloud set up in the spray tank may be inspected to check on the operation of the machine.

To obviate the obscuration of the bull's-eye and lamp from the heavy deposit of powder thereon incurred in operation of the device, the injector tube 38 is preferably provided with one or more small lateral apertures 53 directed upwardtoward the lamp and the bull's-eye. Preferably, the injector tube is amxed with respect to the air supply fitting 28 and the agitator plate 35, so as to be rotated as a unit therewith and cause the clearing apertures 53 to sweep past the lamp and bull's-eye in the course of operation and periodically to clear the same of powder and promote visibility.

Desirably, the rotating inJector tube 38 also carries a propeller 54 near its midsection, the upstanding arms 55 of which sweep along the lateral wall of the spray tank and prevent adhesion thereto. A like propeller 56 near the bottom, conformed to the curved shape of the tank thereat performs primarily the function of propelling powder inward to the agitator plate 35, to assure setting up an adequate cloud at the upper part of the tank.

Preferably, the head 41 has an enlarged mixing chamber 60 above feed valve 5|.to facilitate mixing of air and powder. A plurality of outlet couplings 59 are carried in the multiple fitting 56 that is supplied from the mixing chamber. To these couplings are connected hose or conduits 6| that lead to the spray distributor T shown in Figs. 3 to 7. Each of the outlet couplings has a hand-cock 62 to turn on and off the air stream,

as desired.

Preferably, the cross-pipe l8v has a shut-off cook 63, and at the inlet side thereof a pressure reducing valve 64 and a pressure gauge 65 which serve to facilitate the control of air pressure, as required.

In the embodiment of Figs. 3 to '7, the spray distributor tube T is fed from both ends through hoses 5| supplied from the respective outlet couplings 59 at the top of the spray tank. The spray distributor tube desirably extends horizontally between brackets 66 and directly over or, if desired, under the usual horizontal surface to be sprayed therefrom. The spray distributor tube preferably comprises a pair of aligned metal pipes 61 and 68, the inner ends of which are telescoped in alignment into the bored ends 69 of a solid hexagon tube connector 10. The connector 10 has a pair of small bores ll transversely therethrough adjacent the ends of the respective bores 63 but beyond the extremities 12 of the respective tubes 61 and 68.

In a preferred embodiment the length of each spray tube T is corrugated, as shown, along the eifective width of the surface to be coated. These corrugations 18 are desirably uniform in length and height. The corrugations are preferably of such height that the crests thereof in the wall of the bore are substantially aligned with the troughs thereof at the diametrically opposite wall portion as shown by dot and dash lines in Fig. '7.

The distributor tube has spray apertures 13 that are equidistant and at one side of the tube T and in linear alignment. They are preferably not at the very trough of the corrugations, but each aperture is spaced slightly behind said trough, that is, somewhat farther from the tube inlet than is the bottom of the trough. The spray apertures are preferably inclined as best shown in Fig. 7 so that they slope from the bore of the tube outward in direction opposed to that of the air flow therethrough. I

While the dimensions of the spray distributor tube and its apertures may be variedto suit different requirements, it has been found from experience that a particularly desirable arrangement, suitable in a wide variety of uses, consists of a tube of M inch bore with a distance between successive troughs of about 2 inches, preferably 1 /32 inches. The spray apertures 13 are desirably about .030 inch in diameter, and preferably inch in advance of the troughs. The spray apertures 13 are bored into the tube after the same has been corrugated. Preferably, the axis of the pipe is inclined slightly to an angle of about 4% degrees for such drilling so that the vertically directed drills will bore the apertures at that outward inclination found to operate best and shown in Fig. 7.

Upon closure of the switches 22 and 23 the magnetic valve 24 is opened, the motor i9 is operated, and the lamp 52 is illuminated. Compressed air will pass from the compressor through the coupling ll through filter It, where it is cleaned, and through the dehydrator l where any moisture is removed therefrom. The pressure on the dehydrator is regulated by reducing valve Hi to a value read upon the gauge 1. The

clean dry air thence passes through pipe l6 and by way of reducing valve 64, set to desired value read upon the gauge 66 through the open valve 63 upward through conical feed plug 3| and air supply fitting 28. The air stream divides above valve 46, to follow paths that are in parallel, part passing through the duct 31 in agitator plate 35 and the rest passing longitudinally through the injector tube 38. The motor IS in its continuous rotation steps the air supply fitting 28 and with it the agitator plate 35 and injector tube 38 in a slow step-by-step movement about its axis. Accordingly, the jet of air through duct 3'! in the agitator plate 35 disturbs the dry powder filling the lower part of the spray tank and sets up a cloud thereabove. This cloud is further agitated by air blown through the clearing hole 53 in the agitator tube, which serves in the course of rotation to sweep past the lamp 52 and bulls-eye 5|, periodically to clear the latter of the powder settled thereon. At the same time the propeller 64 scrapes the tank wall and propeller 56 assures a supply of powder at all times in the path of agitator duct 31. It is important to note in this connection that the arrangement of duct 31 with its outlet facing laterally of agitator plate 35 has the advantage of precluding clogging thereof by the packing of powder therein as might occur if such port faced upwardly.

The main jet of air from the compressor is fed upward through the injector tube 38 and exerts eifective suction on the injector ports 49 so as to through the valve 51 and thence to the mixing chamber 60 and from there it passes through the outlet couplings 59 and by way of conduits 6| to the opposite ends of the spray distributor tube T.

In practice, the obstructions imposed by the corrugations 18 in the tube T will intercept some of the powder entrained with the air forced through the respective tube ends, while some will be blown through the apertures 13 for the spraying action desired. The location of the spray ports set forth brings about an eifective and uniform spray through the various apertures, both those near the inlet of the spray tube and those most remote from the inlet. Were the obstructions lmposedby the corrugations omitted, the spray would be far from uniform, some holes delivering considerably more powder than others. If the corrugations were of much greater amplitude than shown, uniformity of distribution would also be impaired and the same is true if they were of lesser amplitude, in which case there would be a tendency for the apertures remote from the inlet to feed more powder than those in advance thereof.

By the arrangement set forth, in which the crests of the corrugated pipe bore are aligned with the diametrically opposite troughs of such bore, it has been found that the resistance imposed in advance of each spray aperture is exactly right for bringing about the uniformity of distribution. The disposition of the spray apertures 13 slightly beyond the bottom of the trough and in the direction set forth, assures a uniform symmetrical spray, as shown, where the location of such aperture elsewhere or at a different angle would lead to a spray deflected either to the right or to the left from that shown, and thus render the distribution less uniform.

In operation, the excess air escape through the breather holes I I. These, being directed upward, will entrain relatively little powder, while the opposed apertures II that are directed downward in the connector 10 will deliver a spr y of powder upon the central part of the sheet or surface.

It will be understood, that while in general the spray apertures are at the forward side of the spray tube the corrugations of which lie' in a horizontal plane, as best shown in Figs. 4 and 6, the plane of the corrugations may for certain applications be tilted downward or, in some cases, it may be tilted upward to desired angle for spraying the undersurface or a sheet or plate passed thereabove. The length of the spray tube of the present invention may be extended obliquely or even vertically for certain special applications as, for instance, the coating of a wall or a silo. and the distribution or powder is found to be thoroughly uniform in any of such applications.

It will be understood that two Or more of the spray tubes maybe arranged in parallel and in lightly cascaded relation, for great precision of powder distribution. The head of the spray tank would in that event be equipped with a suflicient number of outlet couplings for hose to supply all of such spray distributing tubes.

Throughout operation of the spray apparatus the operator may inspect the eflicacy of the cloud and determine the level of powder in the spray tank to assure best operation.

To replenish the spray tank, powder may be passed thereinto from the supply tank 20 by opening the hand valve 2|, which connects the is shut oir, it is desirable to of powder remaining therein,

hygroscopic character. To this end riser H from the source of compressed air leads all the way to the upper end of the spray tank as at H into the outlet head thereof. For clearing the pipe the valve 51 is thrown by handle 19 from its normal position in which its diametrical bore comtube T of all powder lodged therein. The valve 51 is immediately to be reset to the initial position vby returning handle 19 to the left after such clearing operation.

In the embodiment of Fig. 8 is shown a slight modification of the spray tube which is quite similar to that shownin Figs. 3 to 7, except that it has but a single inlet 85 at one end thereof and has a small outlet aperture 80 at its opposite extremity through which the breathing action occurs. The embodiment of Fig. 9 shows a slight modification desirable in large installations, to permit clearing the injection tube 38' of any powder that may become clogged therein, and to do this by an air-blowing action.

To this end, there is provided, in addition to the cross-tube it, which connects the lower part of riser- H. to the air supply fitting, a second cross-tube 81 which is not connected to the reducing valve 64' and which has a hand-cock 88 therein. When the cook 63" that connects the reducing valve 64' to the spray tank is shut off and cock 8B is opened, a forceful spray is blown vertically through the injector tube 38' for the clearing action set forth.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the mom-- panying drawings shall be interpreted as illustrative and not in a limiting sense.

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

l. A dry powder spray equipment comprising a powder tank having an air inlet at its bottom, means for delivering compressed air through said inlet, an air outlet head at the top of the tank, a tube connecting said inlet and said outlet head. a

' lateral duct near the lower end of the tube and communicating with said air inlet, means for moving said duct about the axis of said tube, the compressed air delivered through said duct thereby stirring up a cloud of powder in the tank and means near the outlet head for entraining powder from such cloud with the stream of air blown through the tube, for delivery to the surface to be sprayed.

2. Powder spraying apparatus of the character described, comprising a tank containing dry powder, a source of pneumatic pressure connected to the lower end thereof, a tube through said tank connected to said source, an outlet at the top of said tank communicating with said tube, a duct for directing air laterally from near the lower end of the tube into the tank, means for moving said duct about the axis of said tube, said duct thereby generating a cloud of powder in the tank, openings associated with .said tube, within and near the upper part of said tank for injecting powder from such cloud into the outlet and means for distributing the powder from said outlet to the surface to be sprayed.

asvsaeo about the axis of said tube. said duct thereby blowing air into the powder to set up the cloud and small injector apertures near the upper end of the tube for injecting powder from such cloud for delivery to the surface to be sprayed.

4. The combination recited in claim 3 in which the lower end of the tube is mounted upon an agitator plate having a lateral edge spaced from the wall of the tank and in which the lateral duct opens through said lateral edge through which air is blown in parallel with its passage through the tube.

5. Powder spraying apparatus comprising a powder containing tank, a ring rising from the bottom thereof. an agitator plate resting upon said ring and having a flange encompassed by said ring and a lateral edge spaced from the tank wall, a tube supported by said plate and encompassed thereby at its lower end, a duct through said plate communicating from the lower end of its flange through the lateral edge thereof, an air supply delivering upward through said duct for setting up a. cloud of powder in said tank, and in parallel therewith discharging into the lower end of said tube, the upper end of saidtube having conduit connections communicating with the surface to be sprayed, and means for taking up powder from such cloud to be propelled by the flow of air through said tube.

6. The combination recited in claim 5 in which the tank has an incandescent lamp therein near the top thereof and a bull's-eye adjacent said lamp through which the illuminated. cloud in the tank may be viewed, and in which the tube has one or more small apertures therein through which air is blown to clear the lamp and the bull's-eye of powder collected thereon.

7. Powder spraying apparatus comprising a tank for dry powder, a tube rising from the lower end of said tank. an air agitator member near the lower end of said tube and having a duct therethrough in parallel with said tube for blowing air from said source laterally into the lower end of the tank. the rest of the air from said source passing through said tube, a lamp within the tank near the upper end thereof, a bull's-eye for said lamp to facilitate checking the powder cloud formed in said tank and small aperture means through said tube for directing a blast of air therefrom against the lamp and bull's-eye to clear away powder collected thereon.

8. Powder spraying apparatus comprising a tank partly filled with dry powder, a vertical tube through said tank for delivering compressed air therethrough, a lateral duct near the lower end of said tank and in parallel with said tube, a lamp and a bull's-eye near the upper end of said tank, an aperture through said tube adjacent the level of said lamp and bull's-eye, means for slowly rotating said tube about its axis, propeller means movable with said tube whereby air will be discharged through the lateral duct into the powder in the tank, the propeller will plow through the powder and air blown through the aperture will clear the powder deposited upon the lamp and the bull's-eye in the course of rotation of the tube.

9. Powder spraying apparatus comprising a tank partly filled with dry powder. a vertical tube through said tank for delivering compressed air therethrough, a lateral duct near the lower end of said tank rigid with said tube, a lamp and a bull'seye near the upper end of said tank, a clearing hole through said tube adiacent the level of said said tube about its axis for continuously changing the point or discharge of the lateral duct into the powder in the tank and for bringing said clearing hole in alignment with the lamp and with the bull's-eye in the course of rotation of said tube, for clearing therefrom the powder deposited thereon, and means to pass oil powder from said cloud through the upper part of the tank for distribution to the area to be sprayed.

l0. Powder spraying apparatus comprising a tank partly filled with powder, means for agitating the powder to form a cloud in the upper part of the tank and means for discharging powder from such cloud through the top of the tank for distribution to the surface to be sprayed, said means comprising an axially mounted tubular structure extending through the tank, said tubular structure including an air tube, a source of compressed air feeding into the lower end of said tube, said tube having a lateral branch duct opening outwardly therefrom laterally into the powder to agitate the same, said means also including an injector sleeve telescoped over the upper end of the tube and having an upwardly directed duct for injecting powder-laden air into the course of flow of air from the tube.

11. Powder spraying apparatus comprising a tank partly filled with powder, means for agitating the powder to form a cloud in the upper part of the tank and means for discharging powder from such cloud through the top of the tank for distribution to the surface to be sprayed, said means comprising an upright tubular structure extending through the tank, said tubular structure including an air tube, a source of compressed air feeding into the lower end of said tube, said structure having a lateral branch duct opening outwardly from the source of compressed air laterally into the powder to agitate the same, said means also including an upwardly directed duct.

near the upper end of said tube for injecting powder-laden air into the course of flow of air from the tube, and means for imparting a slow rotation to said upright structure to avoid cavitation of the air from the lateral duct through the powder packed in the tank.

12. Powder spraying apparatus comprising a tank partly filled with powder, means for agitating the powder to form a cloud in the upper part of the tank and means for discharging powder from such cloud through the top of the tank for distribution to the surface to be sprayed, said means comprising an axially mounted tubular structure extending through the tank, said tubular structure including an air tube having a lateral branch duct opening outwardly from the air supply laterally into the powder to agitate the same, said means also including an upwardly directed duct near the upper end of said tube for injecting powder-laden air into the course of flow through said tube a source of compressed air feeding into the lower end of said tube, and means for imparting a step-by-step rotation to said axially mounted structure to avoid cavitation oi air from the lateral duct through the powder packed in the tank, said tank having near the top thereof a lamp and a bulls-eye to facilitate checking of the cloud, said tube having a small aperture near the level of said lamp and bullseye for discharging air therethrough which is directed in the course of each rotation of the tube against the lampand bulls-eye for clearing the latter of powder deposited thereon.

13. In a powder-spraying equipment, the combination of a tank partly filled with dry powder, having an air conveyor extending axially or the axial tube resting upon ,thereinto. a collar at the upper end of said tank tank, said conveyor comprising an inlet nozzle below the tank, an air, supply fitting bearing upon said nozzle and rising into the tank, a plate resting upon and having a downwardly directed flange encompassed by said fitting, said plate having a duct therethrough communicating from the flange through the lateral edge thereof, an said plate and piloted encompassing the upper end of said tube and one or more injector ducts through said collar.

14. In powder-spraying equipment, the combination of a tank partly filled with dry powder, having an air conveyor extending axially o! the tank, said conveyor comprising an inlet nozzle below the tank, an air supp y fitting bearing upon said nozzle and rising into the tank, an agitator plate resting upon, rigid with, and having a downwardly directed flange encompassed by said fitting, said plate having a duct therethrough communicating from the flange through the lateral edge thereof, an axial tube resting upon said plate and piloted therelnto, a collar at the upper end of said tank encompassing the upper end of said tube and having one or more injector ducts therethrough, a power-driven crank connection and a pawl and ratchet drive operated therefrom for step-by-step rotation of said inlet fitting and said air agitator plate to prevent cavitation of air from said duct through the powder packedin the tank.

15. The combination recited in claim 14 in which the tube is rigidly connected to the agitator plate and turned about its axis in the step-bystep movement of the latter, in which an electric lamp and a bulls- -eye are mounted in the upper end of the tank and in which the tube has a small aperture through which in the course of rotation of the tube air is blown to clear away from the lamp and bull's-eye powder deposited thereon.

16. Powder-spraying apparatus comprising a tank having powder therein, means for stirring up a cloud of powder in the upper part of the tank, an outlet head on said tank, a powder distributor supplied from said outlet head for spraying the powder therefrom upon the surface to be coated, and a feed valve in said outlet head shutting oif the air current from the tank therebelow and directing the air blast through the valve to clear the powder distributor.

1'7. In a powder-spray apparatus, a spray tank, a source of air pressure connected thereto and serving for propelling powder therefrom for spraying, a powder storage tank adjacent to said spray tank, a manually controlled valve connection between said tanks, and means for venting air irorn said spray tank while the air thus compressed in said supply tank discharges powder therefrom into the spray tank.

18. In a powder-spraying apparatus, a source of air under pressure entraining dry powder, a distributor tube to extend across the surface to be sprayed and supplied from said source, said distributor tube having discharge apertures along the length thereof, said tube including a deflector conformation in advance of each aperture to assure substantial uniformity of simultaneous delivery through the apertures at various portions of the length of the distributor tube.

19. In a powder-spraying apparatus, a source of air under pressure entraining dry powder, a distributor tube to extend across the surface to be sprayed and supplied from said source, said tube having discharge apertures distributed along the length thereof, said tube being of uniform bore but presenting a deflecting bend in advance of each aperture to assure uniform distribution throughout the length of the tube.

20. In a powder-spraying apparatus, a source of air under pressure entraining dry powder, a distributor tube to extend across the surface to be sprayed and supplied from said source, said tube being uniformly corrugated along the spraying area thereof and having a spray aperture somewhat beyond the trough of each corrugation.

21. In a powder-spraying equipment. a source of powder-laden air under pressure, a distributing tube adjacent the surface to be sprayed, conduits from said source communicating with the opposite ends of said tube, the effective length of said tube being uniformly corrugated, aligned spray apertures in said tube near the troughs of the corrugations, the midsection of said tube having one or more breather apertures out of alignment with said spray apertures. s.

22. In a dry powder-spray apparatus, the combination of a sour-ce of powder-laden air under pressure, a horizontal spray distribution tube near the surface to be sprayed and supplied at one end thereof from said source, said tube having corrugations with the arcs thereof extending in a horizontal plane and having spray apertures adjacent the middle of the trough of each corrugation but at one side thereof, said pipe also having a breather hole near the other end thereof.

23. In a dry powder-spray apparatus, the combination of a source of powder-laden air under pressure, a spray distribution tube near the surface to be sprayed and supplied from said source, said tube having uniform corrugations in which the successive crests and troughs within the bore are substantially aligned and spray apertures through said tube at one side thereof somewhat in advance of the respective troughs.

24. In a dry powder-spray apparatus, the combination of a source of powder-laden air under pressure, a spray distribution tube near the surface to be sprayed and supplied from said source, said tube having uniform corrugations in which the successive crests and troughs within the bore are substantially aligned and spray apertures through said tube at one side thereof somewhat in advance of the respective troughs; said spray apertures extending obliquely outward in direction opposed to that of air flow.

25. In a dry powder-spray apparatus, a spray distribution tube, said tube having a bore of approximately V inch and being corrugated, each corrugation approximately two inches long and of amplitude such that the successive troughs and crests within the bore of the pipe are along a common line, each corrugation having a spray aperture therethrough approximately /4 inch in advance of the trough thereof, said spray apertures extending through the tube at an inclination opposed to the direction of air propulsion through the tube.

26. In a dry powder-spray apparatus, the combination of a source of powder-laden air under pressure, a spray distribution pipe having an inlet at one end and a reduced breather aperture at the opposite end, said tube being corrugated. the corrugations being uniform and of amplitude such that the troughs and crests within the tube are substantially aligned, each corrugation having a spray aperture therethrough somewhat in advance of the trough thereof.

CHARLES WILLIAM BRITCHER.

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