US2794677A - Method of and apparatus for spraying - Google Patents

Description

G. COLLARDIN ETAL.

METHOD OF AND APPARATUS FOR SPRAYING June 4, 1957 3 Sleets-Sheet l Filed March 23, 1953 v mm.

IHVENTOKS4 GERARDO coLLARUId ANP FELIX VON R'HLlr/G' June 4, 1957 G. coLLARDlN ETAL 2,794,677

Y METHOD 0F AND APPARATUS FOR SPRYING Y Filed March 25, 12355V s seets-sneet 2 IHVEHTDRS June 4, 1957 G. coLLARDiN l:s1-Al.

METHOD oF AND APPARATUS FOR SPRAYIYNG Filed March 2s, 1955` 3 Sheets-Sheet 3 mvermRS'. Y Gemma CoLLARv/H ANP FEI-1X von RHLm/G SY'. v

METHOD F AND APPARATUS FR SPRAYNG Gerardo Colardin, Eoin-Ehrenfeld, and Felix Von Rhling, Koln-Lindenthal, Germany; said 1Von Rhling assignor to said Soilartin Appiication March 23, E53, Serial No. Seal-,172

Claims priority, application Germany March 29, 1952 2e Claims. (Cl. 299-23.@

This invention relates to a method of spraying and apparatus for carrying ont the method.

In known methods of spraying atomizable increments of material in liquid, powder, paste, or rod form are ejected as a jet from the front outlet of a nozzle system. This is effected by subjecting said increments to the action of a compressed propellent gas, which in most cases consists of compressed air, in rarer cases of inert gases, such as nitrogen, carbon dioxide, or the like. The material passes at a controlled rate from a container through a duct in the device into the stream of propellent gas, which is also controlled as to pressure and rate, and which emerges from the outlet of the nozzle system to impinge, e. g., on a workpiece to be coated. To atomize material in paste or rod form, the same must be heated sufciently for atomization and spraying. To this end it must pass through a flame or another source of heat either before leaving the nozzle system or close to the outlet thereof.

Dimculties are encountered if the material in liquid, paste, or rod form contains combustible or readily inflammable substances whereas it must be heated for other reasons, e. g., for physical or chemical reasons, to form well adhering coatings on the workpiece. Though the stream of propellent gas containing the particles of material expands as it leaves the nozzle and thus cools down, the latter is mostly unable to exercise on a flame surrounding the jet, or on a gas of highly elevated temperature enveloping the jet, an inliuence strong enough to prevent burning of the particles of material or the inflammable substances thereof. Usually the surrounding flame is fed by admixing thereto compressed fuel gases, and oxidizers such as oxygen, compressed air, or the like. Even an expensive substitution of the llame kby an electric resistor or an overheated gas envelope is mostly unable to prevent the combustion or ignition of particles of material in the jet of propellent gas. If such combustion or ignition does occur, however, the coated product or the powder of material obtained isV mostly worthless.

To prevent this it has been suggested to interpose inside the inner peripheral surface of the tubular or jacket ame enveloping the jet a shield of protective gases, e. g.V of compressed air or inert gases. Thereby the nozzle system of the spraying device is complicated. In the second place the continual adjustment of the necessary controls required every time the particles of matter are changed requires an alteration of the pressure and rate settings of propellent air, combustion, oxidizing, and protective gases. Y

In the third place the spraying operator must direct al1 his attention to the progress of his spraying work. He can only concern himself with achieving the desired grain size of the material and a coat of the desired thickness, and with coating only those parts of the workpiece which are to be protected. In some cases only parts of the surface of the workpiece are to be coated and the coat is to be of varying thickness, e. g., parts of the workpiece more highly exposed should be coated heavily, others only with a thin layer. For this reason the spraying oper- 2,794,677 Patented June` 4, v1957 ator cannot set the controls while spraying. This must be done before the beginning of the work.

In the case of workpieces that are stationary or of large volume, e. g., metal structures, bridges, portable engines, wagon tanks, and the like, the spraying work is often performed in the open. In unfavorable Weather, e. g., in storm, rain, snow, or hail, the llames sustained by supplied gases or gas mixtures tend to extinguish or Waver, thus affecting the desired fineness of grain of the material conveyed by the jet of propellant gas. Such big workpieces must be delivered mostly in a completely coated condition within the time specified. A n interruption of the spraying work in the open, even when due to unfavorable weather, means loss of wages, and may mean even penalties for nonfulfillment of contract to the contractor. All these circumstances must be considered in calculating the cost of a spraying job.

It is known to utilize the suction of a jet of compressed air entraining particles of spray material and ejected from the nozzle of the spraying apparatus. In most cases this is eifected with a cover concentrically surrounding the nozzle caps of the apparatus, which cover is open at its front and rear ends. The suction draws atmospheric air forwardly through the cover space. Thus the expanding jet of compressed air is enveloped by air cooling the nozzle caps and the workpiece in front of them. Where a gas-fired llame is produced close to the nozzle outlet, it appears suitable to have the nozzle and workpiece cooled. It is also known to heat the cover along its length. The source of heat for that purpose may be arranged in the cover space or before the nozzle outlet and workpiece.

It has also been suggested to give the cover a cylindrical, polygonal, forwardly or rearwardly widening shape. A double-walled, rearwardly tapering cover may be attached with its narrowest rear part directly to the outer periphery of the outer nozzle cap. In that case a supply line for compressed air ejects thersame at the front end of the tapering cover. In known modifications the rear end of the cover may be closed and the jet of compressed air may be ejected forwardly through the axial cover space, whereas either hot or cold fluids, gases or liquids, are conducted by means of inlet and outlet connections through the peripheral cover space, in order to impart desired properties to the material conveyed by the jet of compressed air. Y

As compared with the prior art it is an object of this invention to provide a spraying apparatus suitable for carrying out with its main parts substantially all spraying work encountered in practice. For this reason the invention is applicable independently of the state of matter of the material supplied, which may be a powder, a liquid, a paste or dough or a hard substance (in rod form). Further that material may comprise readily inflammable substances or maybe uninflammable. The propellent gas, such as compressed air, may be supplied to the nozzle system in a cold or heated condition. Further the spraying apparatus may have connectedthereto a container for the material to be sprayed or said material maybe supplied in the form of a rod to the apparatus Aby a motor. The workpiece may be preheated or may be cooled by ,a cold jet of compressed air after Vthe coating has been sprayed. All work can be performed in the open air or in shops. Y Y r The features whereby the invention distinguishes from the prior art are set forth more particularly in the appended claims and will be apparent, as well as other objects of the invention, f rompthe following description of several embodiments of the invention shown -byway of illustration in the partly diagrammatical accompanying drawings, in which V g Y v Y Fig. 1 is a longitudinal section of a lirst embodiment of a spraying apparatus; Y

Fig. la is an angular section on line A-B of Fig. l;

Fig. 1b is a schematic view of the various paths of the propellent and combustion gases; and

Figs. 2 to ll are diagrams showing moditicationsof the apparatus shown in Figsfl, la,v lbjandV fullling the requirements enumerated sub (1)'to (9) above.

20a designates the horizontal part of the body of the device, 2D designates tne rear handle thereof, 31 designates a nozzle carrier detachably connected to the part 20a by means 31d; 27 designates an inner nozzle cap surrounding theV control needle 32 so as to leave free in the nozzle carrier the cavity 31e and screwed to the nozzle carrier; and 28 designates a jacket cap, which is also screwed to the nozzle carrier 31. The latter is passed through by two transverse bores 31b and 30, which are at an angle with each other and meet in the cavity 31a. The bore 30 extends downwardly through a boss 31a of the nozzle carrier and is normally closed by a screw plug 31C.

The cavity 31e opens at its front end into another cavity The control needle 32 is urged forwardly in the manner known per se by a compression spring, which is not shown. The rear portion of that spring is terminated by a cap bushing shown in elevation. A trigger 34 the rear end of which is pivoted to the part 20a and with which the control needle 32 is connected by a stud, which is not shown, can be moved by hand to displace the control needle rearwardly against the force of its spring, whereby particles of material are allowed to emerge from one of the transverse bores 30, 31h through the spaces 31e, 27a. h The base part 7a of the material container 5 carried by nozzle carrier 31 is bored axially and the bore 7 is coaxial with the transverse bore 31b of nozzle carrier 31. Obviously the transverse bore 3117 does not intersect the compressed-air duct 33, 'to 'bei discussed later, as is shown in' Fig. l. In fact, duct 33 lies in part 20a and nozzle carrier 31 and is arranged laterally of bore 31b. The duct 33 is shown in section in Fig. l only to facilitate explanation and for greater clarity. Y

The handle 2t)V is passed through longitudinally by several ducts, of'which duct 15 carries compressed fuel gas supplied to it through a hose which is not shown and provided with a nipple 22. The fuel gas, the pressure and rate of which are controlled by a needle control 36, flows at the top through a transition duct 35 into a chamber 11, controlled by a needle control 12. Differently from the showingpin Fig. l, transition duct 35 does not intersect with'duct 33, which lies also laterally of transition duct 35. The upper continuation of the fuel gas guide duct 15, which lies laterally of duct 33, can be connected to or disconnected from a pipe 9 through the vertical bore 13 of a control 16which is provided with a turning handle 8 and at the same time closes duct at the top. The vertical bore 13 opens at the periphery of` control 10 so that when turning handle 8 is positioned accordingly fuel gas will ow forwardly through pipev9.

Duets 16, 17 and 14 are controlled by a three- way cock 18, 18a and 19. Duct 16 is supplied with compressed air through a nipple holder 23 and an insert pipe 21 at the handle end. The respective rate of compressed air is determined by the position Vof handle 19 of the three-way cock. The plug is of cylindrical shape. The crowned part projecting from its front end is shown in Fig. 1 to shut olf the upper part of the duct 16 from the'lower part. In that position of the plug of the three-way cock the compressed air can enter from the upper part of the insert pipe 21 into an axial cavity of the plug. When the handle is turned to adjust the plug so that a transverse bore 18a is in register with the lower end'of the adjacent duct 17, then compressed air will flow into duct 17 and through conduit 17aY into tube 2, in spite of the fact that the two parts of duct 16 are shut on from each other.

As the plug is turned farther, the transverse bore 18a will come out of register with'duct 17 and the transverse bore 18 will come into register with the lower end of duct 14. Then compresesd air will flow through duct 14 into duct 33. Finally the plug can be turned through part of its range to remove the afore-described separation between the upper and lower parts of lduct 16 to such extent that part of the compressed air is conveyed into the upper part of duct 16. When now the control needle 12 has opened the further path for the compressed air to chamber 11, then the compressed air will mix in tube 1 with the fuel gas ilowing from duct 15 through conduits 11, 35.

The front end of the compressed-air pipe 2 has a screw joint 26 and ends in a cover 24 suitably consisting of a hollow body, which is arranged at least in part in front of the caps 27, 28 of the nozzle carrier. The shape of the cover 24 may be that of a cone or truncated pyramid, or of a cylinder. lts length is such that it projects forwardly beyond nozzle caps 27, 28 and a tube ring 25 jacketed by cover 24. In the irst place cover 24 acts as a wind guard against bumpy, lateral gusts ofY air, in order to prevent the extinction or directional change of the fuel gas mixture ignitedin the form of a llame and emerging from the front openings of tube ring 25. In the second place it acts as a guide space for a protective gas, preferably non-pressurized air, which is induced from the rearwardly open end of the cover by the suction of thc emerging jet of compressed air. That non-pressurized air is induced in the directionof the arrows 251'; between the inner peripheral surface yof cover 24 and the outer peripheral surface of ring tube 25, and between the inner peripheral surface of the latter and cap 28, in the direction of arrows 25a. In the third place the cover vigorously accelerates the induced air heated by contact with the llames of tube ring 25. Thereby the velocity of the jet of cornpressed air expanding in the space of the cover, and the velocity of the particles `of material in said jet, are increased too.

The rear end of the hollow cover, at a point diametrally opposite to the connection of pipe 2, is gas-conductively connected to the boss 31a of nozzle carrier 371 by adel tachable connection 26 of a pipe bend 29, which at the Vsame time forms a second support for the cover body.

An inclined connection bore 29a in the boss provides for Vthe conductive connection of the jacket space of the cover with the passagebetween nozzle caps 27, 2S. The jacket space of cover 24 itself, and the axial space confined by the inner peripheral surface of the cover, are heated by the gases tiowing out of the openings of ring tube 25 and ignited to form flames. rfhat heat is transmitted as far as to nozzle carrier 31 and its caps 27, 28. Besides, pipe 1 need not conduct a mixture of fuel gas and fresh air. Instead of a plug of a three-way cock supplying to pipe 1 a mixture of gas and compressed air, the front end of pipe 1 may be constructed as a nozzle, as shown in Fig. 1, which enters the interior `oftube ring 25, whereas external air enters in the direction of the arrows 1a through an annular gap into the interior of tube ring 25. This construction also intensities, in the manner of a`Bunsen burner, the radiant heat of the mixture of fuel gas and air, when ignited to form tiames. It is emphasizedthat the admission of non-pressurized external air, shown in Fig. l, around the front end of 'pipe 1 is only a modification of the normal arrangement, in which a mixture of fuel gas and compressed air flows from the rear to the front end of pipe 1. In the normal case tube ring 25 (see Figs. 2 to 7 and 9 to lll) is a closed tubular body carried by pipe 1.

The rear end of cover 24 remains open whenever only non-pressurized air is to flow through the axial space surrounded by the inner peripheral surface of the cover. However, the rearend of the cover is closed, and a line is arranged openinginto the axial space of the cover, when inert gas is induced instead of air by the jet of propellent gas. The forwardlyl conducted induced air or inert gas envelops the jet of compressed air as long as it expands in all radial directions at the front end ofthe cover.

Accelerated owing to the temperature riseof the protective gas flowing along the inner periphery of the cover, andthe Vtemperature rise of the compressed air as it passes peripherally of the cover, the particles `of material in the jet of compressed air, which are of higher specic gravity, impinge with a higher momentum on the surface of the workpiece, whereby the adhesion -of the coating formed on the workpiece is increased substantially.

rthese effects are promoted when the axiallyl bored base 7, 7a of the material container 5, or the material container in its entire height, is heated. To this end the front end of the fuel gas pipe 9 is directed toward said base and the material container is provided with a jacket cap, which is open at its lower end whereas at its top end, below the cover 4 carrying a handle, it snugly contacts the outer peripheral surface of container 5. T he jacket cap 6 has two mutually opposite rib extensions 6a, which at. the top leave a transition path for the waste gases. If several upwardly directed outlet openings for the fuel gas areprovided in the front part of pipe 9, the waste gases from the flames formed when said gas has been ignited pass upwardly in the rear and are guided downwardly in the front half of the annular gap. Thus the bottom part of the container, or the entire container 5 and its jacket 6 are heatable. rlhe heat of the downwardly discharged waste gases is utilized for preheating the front portions of pipes 1 and 2 by means 4of a baille 3, the front portion `of, which is shaped like a beak and which is carried by Vmeans of a stay 3a by nozzle carrier 31. ;a substantial elevation of the temperature and increase` Vof the speed of the induced protective gas and of the 'jet of compressed air and its particles of material.

This enables With other purposes in mind, the following arrange- 'rnent is made:

When the front end of the hollow cover body 24 is formed as a ring cap (not shown), which can be screwed from the main body of the cover, a plurality of upstanding radially guided webs 24a of shorter length than the internal length of the cover jacket space can be pushed individually into the hollow cover after such ring cap has been removed. This is facilitated when, as shown, the spacing between the two peripheral walls of the cover 29 continuously increases towards its front end. In that case pairs of adjacent webs 24a form a passage for the compressed air. When it is assumed that the rst two webs 24a are arranged to the right and left of the opening 26 of the connection of pipe 2 to the hollow cover body 24, whereas the transition points 24h are at the front end, behind the ring cap screwed on the main body, the stream of compressed air discharged by pipe 2 be divided inside the front part of the cover body and will flow rearwardly between the next adjacent webs 24a. rl`hen the streams of compressed air can ow forwardly again past the rear transition points 24C. T hat llow pattern is followed out until the last guide path between adjacent webs 24a, arranged on both sides of the opening of bottom pipe 29, has been passed. Then the re-united stream of compressed air flows through pipe bend 29 from the rear into the nozzle system between caps 27, 23.

When in addition thereto suitable substances, e. g. of chemical or catalytic activity are fed to the aforedesciibed guide passages between adjacent webs to cause the streams of compressed air to sweep over such substances, these streams can entrain at least traces of those substances. In many cases such traces are sufficient to impart certain properties to the particles of material conveyed or to the coatings formed on the Work piece.

Particularly if the material in the container contains readily inflammable constituents, such as benzines, benzenes, acetones, or the like, the heating effected by burners 25 and 9 can be controlled to prevent the combustion of particles of material in the jet of compressed air when contacted by said induced air. For instance, the velocity of ow of the jet of compressed air flowing through the axial cover space and discharged out of the nozzle system 6 can be controlled to have a velocity`equal to or larger than the flame-propagation velocity of the particles of material conveyed by the jet of compressed air.

Fig. 2 shows diagrammatically a vertical section of a rst modification of the apparatus. ln that case the jacketed cover body 24 widens forwardly in the shape of a funnel and the ring burner 25 is arranged in front of the outlet of the nozzle system.

Fig. 3 shows diagrammatically a vertical section of a second modification of the apparatus, in which a cylindric hollow cover is substituted for the hollow cover of cone or truncated-pyramid shape.

Fig. 4 shows diagrammatically a longitudinal section of a third modication of the apparatus, which comprises a cover 37, which has one wall against the inner peripheral surface of which a pipe coil 38 is applied, which is connected with its upper end -to pipe 2, with its lower end to pipe bend 29. When the turns of pipe coil 38 contact each other without intervening air gaps, the onewalled cover part 37 can be eliminated, the pipe coil 38 itself forming the guide cover.

Fig. 5 shows diagrammatically the longitudinal section of a third modilication of the apparatus, in which electric resistors 39 are incorporated in the hollow cover 37a. In that modification a front portion of the pipe 1 for the fuel gas mixture to be supplied to burner 25 is also provided with a jacket 453 and electric resistors 41 are incorporated between the latter and pipe l.

Fig. 6 shows diagrammatically a longitudinal section of a fifth modification of the apparatus, in which the rear end of cover 24 is closed by a wall 42 and an inert gas supply pipe 43 opens into the axial space of the cover. That inert gas is induced instead of the non-pressurized air by the suction of the jet of compressed air leaving the nozzle system and envelops the jet of compressed air just as the induced air does.

Inthe sixth modification of the apparatus, shown diagrammatically in longitudinal section in Fig. 7, the base of material container 5, 6 may have a jacket extension 5a terminated by a projecting flange supported by a plate Slf of nozzle carrier 31. Pipe 9 extends through the jacket extension 5a and the fuel gases of pipe 9, which are ignited to form llames, pass through openings in a parti- -tion 5b and, as waste gases, through openings in the jacket extension 5a. The latter gases mix with the induced air and heat directly the nozzle carrier 31.

Fig. 8 shows diagrammatically in its top part a longitudinal section of a further modification of the apparatus shown in Fig. 7, and in its lower part a plan view of the detachable front part 44 of burner pipe 9. That part surrounds in the shape of a ring the base 7a of container 5, 6. Whereas the burner 44 has openings 44a directedtoward the base 7a, the fuel gases leaving openings 46, 47 of the front end of the pipe and ignited to form flames heat the rear annular gap space between the oute wall 5 of the container and the inside surface of ject In the modication of the apparatus shown in longitudinal section in the diagrammatical Fig. 9, two spraying systems are provided, the nozzles of which are set with their axes at an angle to each other and yto the axis of the common cover 24 and ring burner 25. The angular position of the spraying systems is set by a holder 48. The nozzle systems of both spraying devices are surrounded by a single hollow cover body 24, which accommodates in its intake zone a ring burner 25 coaxial therewith.

.The two spraying systems shown diagrammatically in Fig. l0 in longitudinal section and set at an angle to each other are fixed in position by a holder 48a. The difference from Fig. 9 resides in the fact that each spraying system has its own cover 24 and ring burner 25.

The modication. of the apparatus shown in longitudinal section in the diagrammatical Fig. l1 indicates that the principle of the invention can be adoptedeven Where lno material containerv is provided but the material 4 5 in wire or rod form is motor-fed. This requires the removal of the` material container 5, 6, 6a, theY closing of an upper part of the material guide duct 311:, and the removal of the needle control 32 as well as of its loading compression spring. These aspects and the arrangement necessary need not be dealt with in detail here because they will be obvious to a man skilled in the art to which this invention pertains. In any case it is apparent that the spraying apparatus isralso adaptable to the introduction of motor-fed spraying material to be used for coating purposes.

We claim:

l. The method of spraying which comprises'ejecting a jet of propellent gas having spray material entrained therein from a nozzle, Vguiding said jet through a guide space communicating with a supply of incombustible protective gas and inducing said protective gas into said guide space with said jet, and guiding said protective gas thus induced in two separate streams, one of which flows adjacent to said nozzle and the other of whichows adjacent to the periphery of said guide space.

2. The method of spraying, which comprises presenting spray material to a stream of propellent gas for entraining said material in said stream, guiding said stream having said material entrained therein through a guide space, producing gas-fired flames in said guide space, and passing said propellent gas before it contacts said spray material through a peripheral space surrounding and in heat transfer relation with said guide space.

3. The method of claim 2, which `comprises electrically preheating fuel gas and burning said fuel gas to produce said llames.

4. Spraying apparatusk which comprises a nozzle system for ejecting propellent gas, means for presenting spray material to said propellent gas to cause said material to be entrained by said gas, a cover radially spaced from and coaxial with said nozzle system, said cover dening a guide space forwardly open in front of said nozzle system, and a closed peripheral space having an inlet and an outlet arranged diametrallyropposite each other at the rear end of said peripheralrspace, means for supplying propellent gas to said inlet, means for conducting propellent gas from said outlet through said nozzle system and past said means for presenting spray material, and means for heating said peripheral space,

5.V Spraying apparatus as set forth in claim 4, in which the means for heating said peripheral space comprise electric resistors arranged therein.

6. lSpraying apparatus as set forth in claim 4, in which the radial width of said peripheral space increasesfrom the rear to the front of said cover.

7. Spraying apparatus as set forth in claim 4, in which said peripheral space accommodates between said inlet and said outlet on either side an odd number of longitudinal, peripherally spaced webs, the odd-numbered of said webs, when counted from the inlet to the outlet, extending Vto the rear end and being spaced from the front end of said peripheral space, and any even-numbered of said webs, when counted in the same sense, extending to the front end and being spaced from the rear end of said peripheral space.

8. Spraying apparatus as set forth in claim 7, in which material to be entrained by said propellent gas is arranged between said webs.

9. Spraying apparatus as set forth in claim 4, which comprises a carrier having said nozzle system, cover, and means for heating said peripheral space rigidly and detachably connected thereto, said carrier being formed with a spray material conduit communicating with said means for presenting spray material, and having a boss formed with two bores, one of said bores leading from the open to said spraymaterial conduit, the other of said bores communicating with saidrnozzle system,` said apparatus further comprising a spray material control member removably mounted in said spray material conduit, a removable closure for said one bore, and a conduit between said outlet and said other bore.

l0, Spraying apparatus as set forth in claim 9, which comprises a spray material container rigidly and detachably connected to said carrier, said container having a bottom bore and said carrier having a bore coaxial with said bottom bore and opening into said spray material conduit adjacent to said one bore of said boss.

l1. Spraying apparatus as set forth in claim 4, in which said peripheral space is defined by a tube wound to form turns laterally adjoining each other.

l2. Spraying apparatus which comprises a spray nozzle system, a cover radially spaced from and coaxial with said nozzle system, said cover defining a guide space forwardly open in front of `said nozzile system, a ring burner having front outlet openings, said yring burner being arranged in said guide space and coaxial therewith and radially outwardly spaced from said nozzle system, and a fuel gas supply tube carrying and discharging into said ring burner, said ring burner being axially adjustable in said guide space.

13. Spraying apparatus which comprises a spray nozzle system, a cover radially spaced fromrand coaxial with said nozzle system, said cover defining a guide space forwardly open in front of said nozzle system, a ring burner having front outlet openings, said ring burner being arranged in said guide space and coaxial therewith and radially outwardly spaced from said nozzlle system, and a fuel gas supply tube carrying and discharging into said ring burner, the front end of said fuel gas supply tube being formed as a nozzle and the ring burner having an opening receiving said nozzle and defining around it -a gap for the entrance of atmospheric air.

14. Spraying apparatus which comprises a spray nozzle system, a cover radially spaced from and coaxial with said nozzle system, said cover defining a guide space forwardly ropen in front of ysaid nozzle system, a ring burner having front outlet openings, said ring burner being arranged in said guide space and coaxial therewith and radially outwardly spaced from said nozzle system, and a fuel gas supply tube carrying and discharging into said ring burner, the ring burner defining with the nozzle system an annular gap communicating with -a supply of incombustible protective gas.

l5. Spraying apparatus which comprises a spray nozzle, a cover radially spaced from and coaxial with said nozzle and deiining a guide space forwardly open in front of said nozzle, a ring burner arranged in said guide space and coaxial therewith, iluid control means for controlling a stream of propellent gas to 'said nozzle, and a carrier having said nozzle, cover, ring burner, and iiuid control means rigidly land detachably connected thereto and being formed with conduits for supplying spray materiail to said propellent gas.

16. Spraying apparatus which comprises a spray nozzle, a spray material container rigidly connected to said spray nozzle, a downwardly open jacketing cap adjoining at'its upper end said container and defining a jacket space around the container, two diametrically opposite ribs dividing `said space into a front half and a rear half, and means for producing open ames for heating the rear half of said jacket space, said means for producing open llames comprising a fuel gas supply tube extending below said rear half of the jacket space and formed with a front end open toward the rear lower portion of the container, said tube having upwardly directed outlet openings below said rear jacket space.

17. Spraying yapparatus as set forth in claim 16, which comprises a fuel gas supply duct and a rotary control member having a plug formed with a longitudinal bore opening at the periphery of the plug, said plug being operable to connect said fuel gas supply duct through said longitudinal bore with said fuel gas supply tube.

18. Spraying apparatus as set forth in o'laim 16, which comprises a cover radially spaced from and coaxial with said nozzle, said cover defining a guide space forwardly open in front of said nozzle, a ring burner having front outlet openings, said ring burner being arranged in said guide space and coaxial therewith and radially outwardly spaced from said nozzle, a fuel gas supply tube carrying and discharging into said ring burner, a fuel gas supply duct, and control means operable to connect said supply duct with each of said fuel gas supply tubes.

19. Spraying apparatus which comprises a nozzle for ejecting a jet of propellent gas, means for presenting spray material to said propellent gas to cause said material to be entrained by said gas, means selectively operable to heat said propellent gas before it contacts said spray material, a spray material container vrigidly connected to said nozzle and communicating with said means for presenting Ispray material, a downwardly open jacketing cap adjoining at its upper end said container and delining a jacket space around the container, two diametrially opposite ribs dividing said space into a front half and a rear hallf, a fuel gas supply tube extending below said rear half of the jacket space and having upwardly directed openings below said rear half, and a burner detachably connected to the front end of said tube and surrounding the lower portion of said container, said burner being formed lwith radially inwardly directed outlet openings.

20. Spraying apparatus which comprises a spray nozzle, a yspray material container, a carrier rigidly and detachably connecting said container to said nozzle, a cylindrical support detachably connected to said carrier and supporting said container, a cover radially spaced from and coaxial with said nozzle, said cover defining a guide space forwardly open in front of said nozzle, and a closed peripheral space having an inlet and an outlet arranged diametrally opposite each other at the rear end of said peripheral space, means for conducting propellent gas from said outlet through said nozzle and past said means for presenting spray material, a propellent .gas supply tube connected to said inlet, a gas burner in said guide space, a fuel gas supply tube leading to said gas burner, and means for producing open llames for heating said container, said carrier having said cover rigidly connected thereto and being formed with a spray material conduit connecting said container with said means for presenting spray material, said support having a front half forming a baffle for guiding gases from said flames over said gas supply tubes.

2l. Spraying apparatus which comprises a nozzle for ejecting a jet of propellent gas, means for presenting spray material to said propellent gas to cause said material to be entrained by said gas, heating means, a heating line for subjecting sm'd propellent gas to the action of said heating means before it contacts said spray material, a cold propellent gas supply line directly connected to said nozzle, valve means operable to cont-rol the owv of propellent gas through said heating and cold Llines, a cover radially spaced from and coaxial with ysaid nozzle, said cover dening a guide space forwardly open in front of said nozzle, a ring burner having front outlet openings, said ring burner being arranged in said guide space and coaxial therewith and radially outwardly spaced from said nozzle, a fuel gas supply tube carrying and :discharging into said ring burner, and a control portion incorporating said valve means and forming a propellent gas supply duct, a duct 'leading to said fuel gas supply tube, `a duct leading to said heating line, and a duct leading to said cold lline, said valve means compiising a three-Way cock controlling the communication between said propellent gas supply duct on the one hand and the ducts leading to the fuel gas supply tube, heating line and cold line on the other hand.

22. Spraying apparatus as set forth in claim 21, in which said three-way cock has a plug formed with two transverse holes, a longitudinal bore connecting said transverse holes and opening at the front end of said plug into said propellent gas supply duct, said front end having a crowned projection extending intoV said propellent gas supply duct and controlling in dependence of its rotary position the communication between said propellant gas supply duct and said duct communicating with the fuel gas supply tube, said transverse holes being arranged to control independence of the rotary position of the plug the communication between said propellent gas supply duct on the one hand and said ducts leading to the heating and cold lines, respectively, on the other hand.

23. The method of spraying which comprises the steps of ejecting a jet of propellent gas having spray material entrained therein from a nozzle and substantially axially through an elongated tubular guide space; and drawing into said guide space by means of said jet a protective incombustible gas surrounding said jet in said guide space.

24, In a spraying apparatus, in combination, a spray nozzle for spraying a stream of material to be deposited; annular jet producing means surrounding said spray nozzle for producing a jet of gas which entrains the material to be sprayed; and tubular guide means coaxial with said jet producing means and spray nozzle having a larger diameter than the same, extending forwardly from the same, having a front open end, and communieating with a source of incombustible protective gas, whereby when the jet of gas entraining the material to be sprayed therein streams along the interior of said guide means, the suction produced by said jet will draw into the guide means a stream of said protective gas which will surround said jet and be located between the latter and said guide means.

25. In a spraying apparatus, in combination, a spray nozzle for spraying a stream of material to be deposited; annular jet producing means surrounding said spray nozzle for producing a jet of gas which entrains the material to be sprayed; and tubular guide means coaxial with said jet producing means and spray nozzle having a larger diameter than the same, extending forwardly from the same, having a front open end, and communicating with a source of incombustible protective gas, whereby when the jet of gas entraining the material to be sprayed therein streams along the interior of said guide means, the suction produced by said jet will draw into the guide means a stream of said protective gas which will surround said jet and be located between the latter and said guide means, said guide means having an open rear end through which the protective gas is drawn by the jet into the guide means.

26. in a spraying apparatus, in combination, a spray nozzle for spraying a stream of material to be deposited; annular jet producing means surrounding said spray nozzle for producing a jet of gas which entrains the material to be sprayed; and tubular guide means coaxial 'with said jet producing means and spray nozzle having a larger diameter than the same, extending forwardly from the same, having a front open end, and communicating with a source of incornbustible protective gas, whereby when the jet of gas entraining the material to be sprayed therein streams along the interior of said guide means, the suction produced by said jet will draw into the guide means a stream of said protective gas which will surround said jet and be located between the latter and said guide means, said guide means having a rear wall and communicatingthrough said rear wall with a conduit which leads the protective gas into the guide means.

References Cited in the tile of this patent UNrTED STATES PATENTS 1,880,331 Rapp oct. 4, 1932 1,928,425 Heade sept. 26, 1933 (Other references on following page) Y VUNITED STATES PATENTS Stei-nke Mar, 31V, 1936 Y FortanV Oct. 18, 1938 Ballard Nov. 19, 1946 Manning Mar. 9, 1948 Hess Apr. 4, 1950 Arvntz et al. Aug. 28, 1951

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