US3764069A - Method and apparatus for spraying - Google Patents

Method and apparatus for spraying Download PDF

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Publication number
US3764069A
US3764069A US00167701A US3764069DA US3764069A US 3764069 A US3764069 A US 3764069A US 00167701 A US00167701 A US 00167701A US 3764069D A US3764069D A US 3764069DA US 3764069 A US3764069 A US 3764069A
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Prior art keywords
liquid
air
froth
pressure
film
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US00167701A
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P Runstadler
E Nord
F Wilhelm
D Hastings
D Scarbrough
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Nordson Corp
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Nordson Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/04—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge
    • B05B7/0416—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid
    • B05B7/0441—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid with one inner conduit of liquid surrounded by an external conduit of gas upstream the mixing chamber
    • B05B7/0458—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid with one inner conduit of liquid surrounded by an external conduit of gas upstream the mixing chamber the gas and liquid flows being perpendicular just upstream the mixing chamber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/12—Spray pistols; Apparatus for discharge designed to control volume of flow, e.g. with adjustable passages
    • B05B7/1209—Spray pistols; Apparatus for discharge designed to control volume of flow, e.g. with adjustable passages the controlling means for each liquid or other fluent material being manual and interdependent
    • B05B7/1245—A gas valve being opened before a liquid valve
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/24—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with means, e.g. a container, for supplying liquid or other fluent material to a discharge device
    • B05B7/2489—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with means, e.g. a container, for supplying liquid or other fluent material to a discharge device an atomising fluid, e.g. a gas, being supplied to the discharge device

Definitions

  • the apparatus for carrying out this method comprises 5 References Cited a liquid film-forming channel connected to a liquid UNITED STATES PATENTS inlet line supplied with liquid under pressure, an air injection channel terminating adjacent to the liquid ml l 239/419 X flow channel, a flow space interconnecting the liquid 26423l3 6/1953 2225; film channel and a nozzle orifice.
  • the film-forming channel is annular with 3521:8211 7/1970 Wilcox 239/4'24 5 air being injected from the outside of the channel.
  • liquid film-forming channel is planar 3,622,080 11/1971 Greenwood 239/434 x with air being injected into the film from one or both 7 FOREIGN PATENTS OR APPLICATIONS sdes chamel' 710,459 6/1954 Great Britain 239/419 43 Claims, 10 Drawing Figures 1 34 M d7 38 76) 5 an.
  • This invention relates to a method and apparatus for atomizing and spraying various liquids such as paint, fuel oil, water, various molten adhesives and other materials, and the like, and is particularly directed to a novel method and apparatus for obtaining a fine and uniform spray of liquid by interaction of the liquid with air or another gas, both the liquid and air being at relatively low pressures, e.g., pressures of from 30 to 100 psi.
  • Another type of device in which it is desired to provide a spray of fine drop size is in the field of gas scrubbers.
  • a fine water spray is contacted with a gas stream, for example, flue gas, in order that the particulates entrained in the gas can be removed before the gas is released to the atmosphere.
  • a gas stream for example, flue gas
  • the water drop size be small and uniform to provide a good intermixture of the air and gas providing optimum probability that a particulate will strike a droplet of water and adhere thereto.
  • a minimum amount of air be utilized to achieve the required atomization in order to achieve maximum economy of operation of the scrubber.
  • climate control apparatus Another form of apparatus having the same desiderata and utilizing water as a spray liquid is climate control apparatus. For example, in many areas, it is desirable to form a fine mist or fog of water particles of from 2 to 15 micron drop size to protect crops from freezing during nighttime periods. Such a spray is also useful in providing a humid environmental cover in arid climates. Again, in this type of installation it is desirable to minimize the pressure of the liquid and air and to minimize the volume of air so as to minimize the initial cost and the cost of operation of the equipment. The same general considerations apply to evaporative coolers in which water is sprayed to dissipate heat therefrom as an alternative to passing water through a cooling tower.
  • FIG. 1 Another example of an installation in which it is desirable to provide a small fine liquid spray formed with a minimal amount of air is in a spray dryer in which a food substance in liquid form is sprayed into a tower and is spray or freeze-dried to convert the liquid to a particulate or powder material.
  • This type of equipment is utilized in the preparation of many types of food products such as gelatin desserts, powdered coffee and the like.
  • the principal object of the present invention is to provide a novel method of forming a fine spray of liquid droplets utilizing small quantities of low pressure air as the atomizing agent.
  • the e present invention is predicated upon the concept of atomizing and spraying a liquid by utilizing forces stored within a myriad of microbubbles previously injected into the liquid to convert it into a froth.
  • This froth is passed through a passage and is then forced outwardly through an orifice.
  • the compressed gas bubbles expand rapidly in an explosive manner and thereby fragmentize the liquid film surrounding the bubbles causing the liquid to break up into small, minute droplets preferably in the order of from 2-100 microns in diameter.
  • the action of the exploding bubbles constitutes essentially the sole atomizing mechanism, i.e., there is no internal atomization within the nozzle nor any external shearing atomization except possibly for a very minor amount resulting from the outward flow of the spray relative to the quiescent air.
  • the orifice itself, for example, a round orifice or plane elongated slit, is ineffective to atomize a non-froth liquid stream.
  • One important aspect of the present invention is the provision of an atomizing method in which the froth is produced within a nozzle and subsequently expelled from a nozzle in such a manner as to make maximum use of the exploding bubbles to atomize the liquid.
  • optimum effectiveness of the air as an atomizing agent in this spraying method is obtained by making the froth as homogeneous as possible prior to its discharge from the nozzle.
  • optimum initial injection of air bubbles into the liquid is obtained by forming the liquid into a film in the area of air injection.
  • the homogeneity of the froth is further increased by causing the froth to flow through a space in which there is a slight degree of internal turbulence such as that incident to flow through a smooth wall passage, and in which the pressure decreases causing the bubbles to expand.
  • the bubbles tend to move closer together with only thin walls of liquid between them. These thin walls are more readily ruptured when the bubbles expand and explode after discharge through the nozzle and no sizeable volume of liquid without air bubbles is expelled through the nozzle to cause oversize drops.
  • the atomizing effectiveness of the exploding bubbles is optimized by causing the bubbles at the discharge orifice to be under as high a pressure relative to the inlet pressures of the liquid and air as possible. More particularly, as is explained in detail below, the pressure of the froth at the discharge orifice bears a critical ratio to the inlet or stagnation pressure. We have determined that for the range of inlet pressures utilized and for the types of materials sprayed, as discussed above this critical ratio approaches a maximum value (giving a maximum orifice pressure of the gas bubbles) when the mass ratio of air to liquid is entrained in the range of from 0.] to 1.6. We have further determined that the froth in the passage behind the nozzle should not be subjected to substantial turbulence or the outlet pressure will drop and the effectiveness of the exploding bubbles will be decreased.
  • One of the principal advantages of the present method is that it requires only relatively low air and liquid pressures; the liquid pressure being from 30 to 100 psig, and the air pressure only slightly higher, e.g., 0.5 to 2 psi higher than the liquid pressure adjacent to the injection area. Moreover, the method requires only relatively small quantities of air, for example, one-tenth the amount of air previously required in conventional air spray nozzles. As a result, the present method can be used advantageously in any of the environments described above.
  • a paint spray system employing the present method can be used in installations in which air is supplied from a shop air line carrying a conventional pressure of perhaps psi.
  • the paint or other coating materials can be supplied from a low pressure pump or from a pressurized tank.
  • the cost of the initial installation as well as the cost of operating the system is relatively low.
  • the coating material being sprayed is not enclosed in a large quantity of high velocity moving air.
  • undesirable overspray and bounce-back are either minimized or substantially eliminated. This not only results in an appreciable material saving, but also facilitates the use of a substantially smaller ventilating and filtration system to prevent air pollution.
  • Another advantage of the present spraying method is that it not only results in small drop size, but also results in a relatively uniform drop size. This again is advantageous in the operation of many of the types of systems described above.
  • a still further advantage of the present invention is that it facilitates the provision of fine spray characteristics utilizing less critical spray nozzles than have been required heretofore. Specifically, since the nozzle orifice itself does not perform an atomizing function, as for example does a conventional airless paint spray nozzle, the nozzle geometry can be larger and is less critical and thereby less difficult to machine.
  • FIG. 1 is a partial vertical sectional view through one form of a spray gun constructed in accordance with the principles of the present invention.
  • FIG. 2 is an enlarged vertical cross-sectional view through the nozzle end of the gun.
  • FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2.
  • FIG. 4 is a cross-sectional view taken along line 41-4 of FIG. 2.
  • FIG. 5 is a perspective view of the collar member.
  • FIG. 6 is a perspective view of the orifice plate member.
  • FIG. 7 is an end view of the nozzle.
  • FIG. 8 is a top plan view of a modified form of spray nozzle embodying the principles of the present invention.
  • FIG. 9 is an end view of the modified form of nozzle shown in FIG. 8.
  • FIG. 10 is a cross-sectional view taken along line 10-10 of FIG. 8.
  • the present method can be employed to atomize and spray various liquids in many different applications in which it is desired to have a fine spray formed utilizing only a small quantity of air or other gas with relatively low pressures on both the liquid and air.
  • the present method can be utilized to spray commercial fuel in oil burners, molten liquids such as adhesives, water in gas scrubbers, evaporative coolers, and climate control equipment, for example, equipment for creating a fog to prevent nighttime freezing of citrus or similar crops, automotive fuel in automotive combustion systems, liquid foods such as gelatin in freeze driers, and the like.
  • the liquid being sprayed is substantially incompressible and is atomized by means of a compressible gas such as air.
  • the liquid being sprayed is first caused to flow in the form of a thin film of from 0.005 to 0.050 inches in thickness.
  • the liquid is under a pressure of the order of 30 to 100 psi.
  • a compressible gas is then injected through a small orifice into this film.
  • the gas pressure at the orifice is preferably slightly above, e.g., 0.5 to 2 psi greater than,
  • liquid film pressure so that the film shears off the gas into a myriad of microbubbles which are entrapped in the film to convert it to a froth.
  • the froth is then advanced in a confined area toward a nozzle orifice.
  • the pressure in the froth drops somewhat so that the entrained bubbles in the froth expand slightly creating a more homogeneous mixture in the froth.
  • the pressure of the froth before it emerges from the nozzle cannot drop below a certain critical pressure, for example 60% of the pressure of the liquid at the inlet.
  • the pressurized bubbles entrained in the froth suddenly expand and in fact seem to explode. In so doing, they break up the liquid matrix into a large number of very small droplets, for example, droplets of the order of 2 to 100 microns in size. These droplets are propelled forwardly from the nozzle at a relatively small velocity, for example, a velocity of the order of 200 feet per minute at adistance of inches from the nozzle.
  • the exploding froth constitutes the sole atomizing mechanism.
  • the present method can be carried out utilizing nozzles having small circular orifices, or elongated slit orifices which, by themselves, are ineffective to cause any atomization whatsoever of a plain liquid stream at their pressures.
  • the present method of atomizing liquid, air or other gas is intermixed with the liquid in a quantity such that the mass ratio, i.e., the ratio of air to fluid in the froth, is in the range of from 0.1 to 1.6.
  • the use of air and liquid in these ratios results in obtaining optimum spraying effectiveness utilizing the minimal quantity of air. The reasons for this can best be understood from a somewhat more detailed consideration of the process in terms of the hydrodynamic properties of the materials involved.
  • the properties of this homogeneous mixture or froth are similar to those of a compressible fluid.
  • a pressure appreciably above atmospheric e.g., a pressure from 30 to 100 psi
  • the flow will exhibit compressible, choked-flow characteristics if the orifice pressure ratio is sufficiently large.
  • the exit flow velocity is sonic.
  • the sonic velocity of the mixture will be quite low (relative to that of air at standard temperature and pressure) so that the exit velocity from the choked nozzle will be of the order of feet per second.
  • the orifice pressure of the mixture is raised appreciably above the critical choke value, then the entrained bubbles expand suddenly and explodewhen they enter the ambient pressure field. This violent expansion fragments the film of liquid surrounding the bubbles to form a uniform fine spray.
  • a theoretical analysis of a two phase mixture such as a liquid-air mixture is based upon certain simplifying assumptions which include the following: (1 the liquid is incompressible, (2) effects due to viscosity and vapor pressure of the liquid are not important, (3) the gas is an ideal gas with constant specific heat, (4) the mixture is truly homogeneous in that the gas bubbles are assumed to be so small that an arbitrarily small sample contains the same mass ratio of gas to liquid, (5) the flow is adiabatic and the gas and liquid are always at equal temperature, (6) the flow is assumed one dimensional and inertial transients are neglected, (7) it is assumed that a pressure signal is transmitted through the mixture with a definite speed of sound.
  • the critical pressure ratio is optimized at approximately 0.6 when the mass ratio of air to liquid is maintained within the range of from 0.1 to 1.6. Within this range the air exits at the highest pressure possible for a given inlet pressure so that maximum fragmentation of the liquid is obtained from each individual air bubble. Moreover, there is sufficient air entrained to effectively atomize all of the liquid matrix. At the same time, there is not a substantial excess of air involved which might cause deleterious results such as, for example, overspray in a paint system or conversion of a froth with liquid as the continuous phase to air as the continuous phase.
  • the substantial uniformity of drop size results from achievement of a homogeneous froth at the discharge orifice.
  • This homogeneity is achieved by providing a short flow space between the region in which air bubbles are injected into the froth and the orifice. There is a slight amount of turbulence as the froth flows through this region which aids in homogenizing the froth, and there is a continuous pressure drop which results in an expansion of the individual bubble size. During this expansion the skins of the bubbles tend to get thinner, reducing the amount of liquid between individual bubbles and thereby preventing the flow through the orifice of any appreciable body of liquid not containing air bubbles effective to fragment the liquid when the bubbles explode.
  • the amount of internal turbulence is kept at a very low level, for any substantial turbulence in the interior of the nozzle functions to lower the stagnation pressure level P,,. Since the orifice pressure P* R P,, any lowering of the stagnation pressure P causes a lowering of the orifice pressure P*. The lowering of this orifice pressure reduces the pressure differential on the bubbles after they leave the orifice and, hence, decreases their explosive, atomizing effect.
  • the principle atomizing mechanism is the explosive action of the entrained bubbles in the froth. There is a slight secondary atomizing effect obtained from the shearing effect of the environmental air on the liquid particles as they move forwardly from the nozzle. There is no internal, mechanical atomizing action within the nozzle, nor is there any external, mechanical atomizing action through the use of externally directed air jets or the like. Moreover, under the relatively low pressure through which material is extruded through a nozzle, the nozzle orifice itself does not create any significant mechanical atomization.
  • the present method can be carried out with many different forms of apparatus. These different forms of apparatus, however, have several basic elements in common, i.e., a fluid inlet line, means for forming a thin fluid film, means for injecting a stream of air into the film to form a froth in which a myriad of microbubbles of air are entrained within the liquid, a confined space through which the froth passes prior to its exit from the nozzle, and an orifice through which the froth is emitted.
  • a fluid inlet line means for forming a thin fluid film
  • means for injecting a stream of air into the film to form a froth in which a myriad of microbubbles of air are entrained within the liquid
  • a confined space through which the froth passes prior to its exit from the nozzle and an orifice through which the froth is emitted.
  • FIG. 1 A typical spray gun adapted to utilize the present atomizing means of the present invention for spraying paint is shown in FIG. 1.
  • spray gun 10 could be used to apply a decorative or protective coating to a product, such as refrigerator, automobile part, furniture, containers, or the like.
  • the coating materials to be sprayed include not only paints, but also enamels, lacquers, stains, varnishes, emulsions, waxes, adhesives and the like.
  • the word paint is used in a very generic sense to encompass all of these various types of coating materials. It is to be understood, however, that spray gun 10 is merely exemplary and the atomizing means of this invention can be incorporated in many different devices.
  • spray gun 10 is a hand-held, non-electrostatic gun
  • the present atomizing means can be incorporated advantageously in non-hand-held automatic paint spray guns of the general type shown in J uvinall U.S. Pat. No. 3,169,883.
  • spray gun It is not shown as being provided with any paint charging means
  • the present atomizing means can be used advantageously in connection with electrostatic spray guns having any suitable means for applying a charge to the paint spray.
  • One generally suitable form of paint charging device is shown in Juvinall et al. US. Pat. No. 3,169,882.
  • spray gun 10 includes a body portion 11, a handle portion 12, and a spray head portion 13 mounted on the forward end of a barrel portion 14 and having a nozzle 15 mounted at its forward end.
  • the handle portion 12 of the gun is provided with a suitable fitting 16 for coupling the gun to an air line, for example, a shop air line under a pressure of 50 psig.
  • the barrel portion 14 is provided with a paint inlet conduit 17. This conduit is adapted to be connected to a paint spray line by means of any suitable coupling.
  • the paint spray line is normally fed with paint which is pumped under pressure from a paint supply tank, or alternatively, is fed from a pressurized tank.
  • the paint pressure at the gun is relatively low and is preferably in the range of from 30 to psi immediately upstream from the air injection area.
  • Valve member 23 is carried by a stem 25 which extends forwardly from the handle into engagement with a pad 26 formed on the rear surface of trigger 18.
  • Valve 23 is spring-urged to its closed position by means of a compression spring 27 disposed within chamber 22. This spring, acting through stem 25, is likewise effective to urge the trigger to its forwardmost position.
  • Tapered sleeve member 28 which forms a seat for valve 23, is provided with a plurality of radial passageways 30 effective, when valve 23 is unseated, to interconnect chamber 22 and, hence, air inlet conduit 21 with a passageway 31.
  • This passageway in turn communicates through a bore 32 to elongated passageway 33. Air moves forwardly along this passageway through an orifice 34 controlled by a needle valve 35.
  • the needle valve threadably engages body 11 and is adapted to be held in its adjusted position by a conventional lock nut arrangement.
  • Orifice 34 communicates with a bore 36 and annular groove 37.
  • aAnnular groove 37 in turn communicates with a plurality of longitudinal passageways 38 terminating in an enlarged chamber 40.
  • air is supplied from this chamber to the atomizing section of the gun through air injection slots 41 formed in collar member 42.
  • Trigger member 18 also is effective to control the flow of paint to the atomizing means. More particularly, as is best shown in FIGS. 1 and 2, paint enters the gun through paint conduit 17. Paint flows from this conduit forwardly through a passageway 43 surrounding valve stem 44.
  • the valve stem is provided with a tapered end 45 adapted to seal against seat 46 formed in fluid tip member 47.
  • Valve stem 44 extends rearwardly through a suitable packing member 48 carried by the barrel and through an enlarged opening formed in trigger member 18.
  • the valve stem carries a sleeve member 50 which is slidably mounted in the gun body 11.
  • Sleeve 50 has a head member 51 formed adjacent to its forward end and disposed for abutment with a pad 52 formed on the rear surface of the trigger.
  • the atomizing section of the gun comprises an orifice member 54 best shown in FIGS. and 6.
  • the orifice member 54 includes a base portion 55 including an annular peripheral rim 56 and three inwardly extending radial spiders 58 interconnecting the rim and a cylindrical projection 57 which extends forwardly of the base.
  • the orifice plate is mounted in the gun with the rear face 61 of base portion 55 in abutment with the forward face 62 of the tip member 47.
  • Rim 56 of orifice member 54 is partially telescopically received within a rearwardly extending flange 63 of collar member 42.
  • Collar member 42 includes a transverse wall 64 having a central bore 65 of slightly larger diameter than the diameter of cylindrical projection 57. This bore is at least partially in registry with flow passageways 60 defined by the inner face of rim 56, spiders 58 and projection 57, the wall of bore 65 together with the outer periphery of projection 57 defines an annular filmforming flow channel 68. Preferably this channel is between 0.005 inch and 0.050 inch in thickness.
  • Two diametral cross slots 41 are milled in the forward face of the collar member. These slots extend across the complete diameter of the collar member and are cut completely through a forwardly extending rim or flange 71. In one preferred embodiment each of the slots is 0.13 inch wide and 0.015 inch deep as measured from the forward face of transverse wall 64. In this same embodiment the diameter of projection 57 is equal to 0.120 inch while the diameter of collar opening 65 is 0.160 inch so that the annular film-forming channel 68 is 0.20 inches in thickness. It is obvious that inwardly connected air passageways of these configurations than slots 41 can be utilized if desired.
  • the length of The forward face of the coller member 42 abuts a annular ring 72 which in turn abuts nozzle member 15.
  • This ring 72 is centered with respect to collar member 42 by engagement of the periphery of the ring with the inner wall of forwardly extending flange 71 of the collar member.
  • the rear face 73 of the ring 72 engages the four quadrantal pad-like portions 74 formed on the forward face 64 of the collar member in the areas between the cross channels 41.
  • the ring cooperates with the collar to form four radial air injection channels interconnecting chamber 40 with annular paint flow passage 68.
  • this ring can be formed integral with nozzle member 15 as desired.
  • Nozzle member 15 is telescopically engaged by a rim 69 formed on ring 72.
  • Nozzle member 15 further includes a forwardly extending cylindrical bore, or passage, 75 which adheres from a maximum diameter section 89 to the size of orifice 78.
  • the diameter of section 89 is equal to that of central bore 65 in the collar member and-opening 79 in ring 72.
  • orifice 78 is 0.035 inch in diameter and passes through a wall section 0.035 inch thick.
  • the nozzle member protrudes through a central opening 76 in retaining nut 77 with the outer end of the nozzle having orifice 78 being disposed forwardly of the end of nut 77.
  • the nozzle member 15, ring 72, collar 42 and orifice plate 54 are held in stacked relationship against one another and against tip member 47 by the retaining nut 77.
  • the forward end of this nut is provided with a recessed shoulder 82 which abuts an annular shoulder 83 formed on the forward portion of nozzle base member 87.
  • the opposite end of the retaining nut is provided with internal threads as at 84 for engagement with a threaded cylindrical extension 85 on barrel member 14.
  • trigger 18 is pressed to open air valve 23 and paint valve 44. Paint under a pressure of from 30-80 psig flows past open needle valve 44 and through the discharge opening in the tip member 47. Paint passes through flow openings 60 in the orifice plate 55 and enters annular film-forming channel 68 formed between projection 57 and the surrounding spaced wall of the collar member 42. Air under pressure flows past needle valve 35 through passageways 36 and 38 into chamber 40 and, hence, radially inwardly along four channels formed by cross slots 41.
  • the pressure of the air line is regulated by needle valve 35 so that the pressure of the air at the ends of the air injection slots 41 where the air intersects the paint film in flow channel 68 is slightly greater, e.g., 2 psi greater, than the paint pressure in the flow channel.
  • Air emerging from the inner ends of slots 41 intersects the annular film of paint and is sheared off in the form of a myriad of entrained microbubbles in the paint.
  • the paint with the entrained air bubbles moves forwardly as a froth through the chamber provided by the opening 79 in ring 72 and the passageway 75 formed in the nozzle.
  • the pressure in the froth gradually decreases so that the bubbles tend to expand slightly, thereby tending to make the froth more uniform or homogeneous.
  • the turbulence is not of a sufficient magnitude to appreciably lower the stagnation pressure.
  • the bubbles As the froth exits from orifice 78, the bubbles, which are still pressurized at the critical pressure which is approximately six-tenths of the paint pressure in the channel, are surrounded by atmospheric pressure, the bubbles rapidly expand fragmenting the surrounding paint into uniform small droplets believed to be of the order of from 10 to 100 microns.
  • the spray of paint thus formed moves forwardly from the nozzle toward the target to be painted.
  • the spray contains a relatively small quantity of air, for example, the mass ratio of airto-paint is in the range of 0.5 to 1.6.
  • this general atomizing structure i.e., the annular film-forming flow chamber, the inwardly-directed air injection ports, and a nozzle having an orifice and a froth-homogenizing chamber intermediate the air injection area and the orifice can be utilized without the remaining elements of the spray gun to spray other types of material, such as fuel oil in a commercial burner, fuel oil for an automobile engine, water for environmental control apparatus, liquids for spray drying and the like.
  • FIG. 8, 9 and 10 Another form of spraying equipment embodying the present invention for spraying any of these latter materials is shown in FIG. 8, 9 and 10.
  • the apparatus comprises a body 100 formed of two sections 101 and 102.
  • Section 101 is provided with a generally rectangular recess 103 along the inner face in abutment with the planar face 104 of body section 102.
  • This recess together with face 104 constitutes a flow passage 106 including a film forming area, an air injection area, a homogenizing flow space, and a discharge orifice.
  • Passage 106 extends from the interior of the spray unit body 100 to forward face 105 of the body and is preferably from 0.005" to 0.050 inch in thickness. In one preferred embodiment the width of the flow passage formed between the two members is approximately 1.5 inches, while the length of the passage from the air injection area to the discharge orifice is approximately 0.3 inch.
  • the inner ends of the passage may be rounded as shown at 107 in FIG. 8.
  • a liquid inlet passage 108 and an air inlet passage 110 are formed in body member 102. These passages are connected in any suitable manner to liquid and air supply lines respectively. These supply lines (not shown) are supplied respectively with liquid, such as fuel oil, water, or the like, under a pressure of from 30 to 100 psig and with air or other gas also under pressure.
  • liquid flows through conduit 108 to liquid supply bores 111 which are 0.060 inch in diameter and which is open into passage 106 0.010 inch in thickness. In this passage, the liquid spreads out to form a film and flows outwardly to the discharge orifice.
  • Air is introduced through conduit 110 which is connected to any suitable source of compressed air. Air flows from conduit 110 through an air injection slot 112 which is 0.030 inch in width and which interconnects the conduit with passage 106 intermediate fluid inlet port 108 and the exit orifice 113.
  • the air pressure in conduit 110 is regulated so that the pressure of the air in port 112 is preferably slightly in excess, e.g., 2 psi, of the pressure in the paint adjacent the discharge end of injection port 1 12. Air is thus forced from injection port 112 into the film of paint. The air is sheared off in the form of a myriad of microbubbles which become entrained in the paint film converting it to a froth. This froth flows outwardly toward exit orifice 113. As it moves forwardly, the pressure of the forth decreases, but does not drop below the critical pressure which is approximately six-tenths the pressure of the liquid in bore 111. During the travel of the froth toward the orifice slot, the froth homogenizes. When it leaves the exit orifice the entrained air bubbles which have been maintained under the critical pressure are suddenly subjected to atmospheric pressure. These bubbles expand rapidly and burst to break up the liquid into a fine spray which is projected forwardly from the slot.
  • the critical pressure
  • FIGS. 8-10 it may be found desirable in some cases to provide a second air injection channel 112 opening into flow passage 106 from the opposite side of channel 112 (from the bottom in FIG. 10). If such a second air injection slot is provided, it is formed in body section 101. It is identical with air injection slot 112 and is fed through a second conduit 110. The second injection slot extends transversely of passage 106 parallel to slot 1 l2 and is positioned either slightly rearwardly or forwardly of the slot 112 with no overlap between the slots.
  • a method of atomizing a liquid comprising the steps of injecting a plurality of microbubbles of gas into a stream of liquid to form a froth,
  • said froth consisting of a mixture of gas and liquid in which the mass ratio of gas to liquid is in the range of 0.1 to 1.6,
  • the method of atomizing a liquid comprising the steps of forming a thin film of said liquid, causing said thin film to pass transversely of an air stream directed against said film to thereby inject a plurality of microbubbles of air into the thin film to form a froth,
  • the method of spraying paint comprising the steps of forming a thin film of paint, causing said thin film of paint to pass transversely of an air stream directed against said film to thereby inject a plurality of microbubbles of air into the thin film to form a froth,
  • said apparatus having a gas conduit and a liquid conduit
  • said gas being injected into said channel in a transverse direction intermediate said orifice and the region where said liquid is introduced into said channel.
  • Apparatus for atomizing a liquid comprising a body portion
  • a collar member including a transverse wall having a central opening receiving said projection to define an annular film-forming channel
  • the orifice plate having an opening extending therethrough to place said film-forming channel in fluid communication with said liquid conduit
  • said air injection channel being in fluid communication with said air conduit
  • a nozzle member having a nozzle orifice formed therein
  • a paint spray gun for spraying paint comprising a body portion,
  • a collar member including a transverse wall having a nozzle member having a nozzle orifice formed therein,
  • Apparatus for atomizing a liquid comprising a body portion,
  • said orifice member including a base portion having a rear face in engagement with said tip portion, a cylindrical projection extending forwardly of said base portion,
  • a collar member including a rearwardly extending flange embracing the periphery of said orifice base, and a transverse wall having a central opening receiving said projection to define an annular filmforming channel
  • the orifice plate having a passageway extending therethrough to place said film-forming channel in fluid communication with the liquid discharge opening of said tip,
  • said collar member including a forwardly projecting peripheral flange, the forward face of the transverse wall or the collar member having an inwardly projecting slot formed therein and communicating with said central opening, said slot also extending outwardly through said forwardly projecting flange,
  • nozzle means providing an internal passage and including a nozzle orifice, whereby when air is injected into said film of paint a froth is formed which flows outwardly through the space in said nozzle and when the froth is discharged from the nozzle orifice the air bubbles expand to break up the paint in a spray of fine particles.
  • the apparatus of claim 36 further comprising a retaining nut surrounding said tip, orifice member, collar, and base of said nozzle member, said retaining nut defining an air chamber interconnecting the air conduit and said air injection channel.
  • a paint spray gun for spraying a flat fan spray said gun comprising a body portion,
  • said orifice member including a transverse base portion having a rear face in engagement with said tip portion, a cylindrical projection extending forwardly of said base portion,
  • a collar member including a rearwardly extending flange embracing the periphery of said orifice base, and a transverse wall having a central opening receiving said projection to define an annular filmforming channel
  • the orifice plate having a passageway extending therethrough to place said film-forming channel in fluid communication with the paint discharge opening of said tip,
  • said collar member including a forwardly projecting peripheral flange, the forward face of the transverse wall or the collar member having an inwardly projecting slot formed therein and communicating with said central opening, said slot also extending outwardly through said forwardly projecting flange,
  • nozzle means providing an internal passage and including a nozzle orifice, whereby when air is injected into said film of paint a froth is formed which flows outwardly-through the space in said nozzle and when the froth is discharged from the nozzle orifice the air bubbles expand to break up the paint in a spray of fine particles.
  • the paint spray gun of claim 40 further comprising a retaining nut surrounding said tip, orifice member, collar, and base of saidnozzle member, said retaining nut defining an air chamber interconnecting the air conduit and said air injection channel.

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US00167701A 1971-07-30 1971-07-30 Method and apparatus for spraying Expired - Lifetime US3764069A (en)

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US16770171A 1971-07-30 1971-07-30

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US (1) US3764069A (de)
JP (1) JPS547961B1 (de)
AU (1) AU475688B2 (de)
BE (1) BE786900A (de)
CA (1) CA963509A (de)
DE (1) DE2236035A1 (de)
FR (1) FR2149149A5 (de)
GB (1) GB1404984A (de)
IT (1) IT961729B (de)
NL (1) NL7210337A (de)
SE (1) SE394858B (de)

Cited By (39)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4216174A (en) * 1977-12-31 1980-08-05 Osrodek Badawczo-Rozwojowy Samochodow Malolitrazowych "Bosmal" Method and apparatus for preparation and control of an air-fuel mixture
US4247581A (en) * 1977-10-14 1981-01-27 Nordson Corporation Method of coating with film-forming solids
US4258885A (en) * 1979-03-23 1981-03-31 Legeza Thomas B Nozzle tip and method of manufacture
US4278418A (en) * 1975-12-15 1981-07-14 Strenkert Lynn A Process and apparatus for stoichiometric combustion of fuel oil
US4396529A (en) * 1978-11-13 1983-08-02 Nordson Corporation Method and apparatus for producing a foam from a viscous liquid
US4462543A (en) * 1981-12-24 1984-07-31 The Procter & Gamble Company Nozzle
US4630774A (en) * 1982-10-22 1986-12-23 Nordson Corporation Foam generating nozzle
US4632314A (en) * 1982-10-22 1986-12-30 Nordson Corporation Adhesive foam generating nozzle
US4720290A (en) * 1985-11-08 1988-01-19 Conoco Inc. Reduction of liquid atomizer droplet size
US4785996A (en) * 1987-04-23 1988-11-22 Nordson Corporation Adhesive spray gun and nozzle attachment
US4815660A (en) * 1987-06-16 1989-03-28 Nordson Corporation Method and apparatus for spraying hot melt adhesive elongated fibers in spiral patterns by two or more side-by-side spray devices
US4925101A (en) * 1988-08-26 1990-05-15 Nordson Corporation Wax spray gun and nozzle
US4969602A (en) * 1988-11-07 1990-11-13 Nordson Corporation Nozzle attachment for an adhesive dispensing device
USRE33481E (en) * 1987-04-23 1990-12-11 Nordson Corporation Adhesive spray gun and nozzle attachment
US4983109A (en) * 1988-01-14 1991-01-08 Nordson Corporation Spray head attachment for metering gear head
US4987854A (en) * 1988-12-12 1991-01-29 Nordson Corporation Apparatus for gas-aided dispensing of liquid materials
US5026450A (en) * 1989-10-13 1991-06-25 Nordson Corporation Method of applying adhesive to the waist elastic material of disposable garments
US5030303A (en) * 1989-07-28 1991-07-09 Nordson Corporation Method for forming disposable garments with a waste containment pocket
US5065943A (en) * 1990-09-06 1991-11-19 Nordson Corporation Nozzle cap for an adhesive dispenser
US5114752A (en) * 1988-12-12 1992-05-19 Nordson Corporation Method for gas-aided dispensing of liquid materials
US5169071A (en) * 1990-09-06 1992-12-08 Nordson Corporation Nozzle cap for an adhesive dispenser
US5197800A (en) * 1991-06-28 1993-03-30 Nordson Corporation Method for forming coating material formulations substantially comprised of a saturated resin rich phase
US5215253A (en) * 1990-08-30 1993-06-01 Nordson Corporation Method and apparatus for forming and dispersing single and multiple phase coating material containing fluid diluent
US5323935A (en) * 1992-02-21 1994-06-28 The Procter & Gamble Company Consumer product package incorporating a spray device utilizing large diameter bubbles
US5337926A (en) * 1992-02-07 1994-08-16 The Procter & Gamble Company Spray pump package employing multiple orifices for dispensing liquid in different spray patterns with automatically adjusted optimized pump stroke for each pattern
US5397058A (en) * 1991-11-28 1995-03-14 Asturo Mec S.R.L. Low pressure fumeless spray gun
US5407267A (en) * 1992-12-30 1995-04-18 Nordson Corporation Method and apparatus for forming and dispensing coating material containing multiple components
US5407132A (en) * 1993-10-20 1995-04-18 Nordson Corporation Method and apparatus for spraying viscous adhesives
US5443796A (en) * 1992-10-19 1995-08-22 Nordson Corporation Method and apparatus for preventing the formation of a solid precipitate in a coating material formulation
US5490726A (en) * 1992-12-30 1996-02-13 Nordson Corporation Apparatus for proportioning two components to form a mixture
US5598974A (en) * 1995-01-13 1997-02-04 Nordson Corporation Reduced cavity module with interchangeable seat
US6015100A (en) * 1997-07-15 2000-01-18 The Fountainhead Group, Inc. Foam generating nozzle assembly with interchangeable nozzle tip
US6561438B1 (en) 1997-07-15 2003-05-13 The Fountainhead Group Foam generating nozzle assembly
US20060163384A1 (en) * 2005-01-21 2006-07-27 Specialty Minerals (Michigan) Inc. Long throw shotcrete nozzle
US20080014364A1 (en) * 2004-03-16 2008-01-17 Gerhard Brendel Water-Vapor Assisted Lacquering Method
US20100055003A1 (en) * 2008-08-28 2010-03-04 General Electric Company Surface Treatments And Coatings For Flash Atomization
US20100136231A1 (en) * 2007-04-10 2010-06-03 BSH Bosch und Siemens Hausgeräte GmbH Method for producing a refrigeration device
US20100331428A1 (en) * 2007-11-07 2010-12-30 Aridis Pharmaceuticals Sonic Low Pressure Spray Drying
US10413920B2 (en) * 2015-06-29 2019-09-17 Arizona Board Of Regents On Behalf Of Arizona State University Nozzle apparatus and two-photon laser lithography for fabrication of XFEL sample injectors

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1100450A (en) * 1978-11-13 1981-05-05 Charles H. Scholl Method and apparatus for producing a foam from a viscous liquid
DE2924174C2 (de) * 1979-06-15 1984-04-19 Heinrich Bühnen KG Maschinenfabrik, Im- und Export, 2800 Bremen Verfahren und Düse eines Gerätes zum Aufbringen eines Klebers auf ein Substrat

Cited By (46)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4278418A (en) * 1975-12-15 1981-07-14 Strenkert Lynn A Process and apparatus for stoichiometric combustion of fuel oil
US4247581A (en) * 1977-10-14 1981-01-27 Nordson Corporation Method of coating with film-forming solids
US4216174A (en) * 1977-12-31 1980-08-05 Osrodek Badawczo-Rozwojowy Samochodow Malolitrazowych "Bosmal" Method and apparatus for preparation and control of an air-fuel mixture
US4396529A (en) * 1978-11-13 1983-08-02 Nordson Corporation Method and apparatus for producing a foam from a viscous liquid
US4258885A (en) * 1979-03-23 1981-03-31 Legeza Thomas B Nozzle tip and method of manufacture
US4462543A (en) * 1981-12-24 1984-07-31 The Procter & Gamble Company Nozzle
US4630774A (en) * 1982-10-22 1986-12-23 Nordson Corporation Foam generating nozzle
US4632314A (en) * 1982-10-22 1986-12-30 Nordson Corporation Adhesive foam generating nozzle
US4720290A (en) * 1985-11-08 1988-01-19 Conoco Inc. Reduction of liquid atomizer droplet size
US4785996A (en) * 1987-04-23 1988-11-22 Nordson Corporation Adhesive spray gun and nozzle attachment
USRE33481E (en) * 1987-04-23 1990-12-11 Nordson Corporation Adhesive spray gun and nozzle attachment
US4815660A (en) * 1987-06-16 1989-03-28 Nordson Corporation Method and apparatus for spraying hot melt adhesive elongated fibers in spiral patterns by two or more side-by-side spray devices
US4983109A (en) * 1988-01-14 1991-01-08 Nordson Corporation Spray head attachment for metering gear head
US4925101A (en) * 1988-08-26 1990-05-15 Nordson Corporation Wax spray gun and nozzle
US4969602A (en) * 1988-11-07 1990-11-13 Nordson Corporation Nozzle attachment for an adhesive dispensing device
US4987854A (en) * 1988-12-12 1991-01-29 Nordson Corporation Apparatus for gas-aided dispensing of liquid materials
US5114752A (en) * 1988-12-12 1992-05-19 Nordson Corporation Method for gas-aided dispensing of liquid materials
US5030303A (en) * 1989-07-28 1991-07-09 Nordson Corporation Method for forming disposable garments with a waste containment pocket
US5026450A (en) * 1989-10-13 1991-06-25 Nordson Corporation Method of applying adhesive to the waist elastic material of disposable garments
US5215253A (en) * 1990-08-30 1993-06-01 Nordson Corporation Method and apparatus for forming and dispersing single and multiple phase coating material containing fluid diluent
US5330783A (en) * 1990-08-30 1994-07-19 Nordson Corporation Method and apparatus for forming and dispensing single and multiple phase coating material containing fluid diluent
US5169071A (en) * 1990-09-06 1992-12-08 Nordson Corporation Nozzle cap for an adhesive dispenser
US5065943A (en) * 1990-09-06 1991-11-19 Nordson Corporation Nozzle cap for an adhesive dispenser
US5197800A (en) * 1991-06-28 1993-03-30 Nordson Corporation Method for forming coating material formulations substantially comprised of a saturated resin rich phase
US5397058A (en) * 1991-11-28 1995-03-14 Asturo Mec S.R.L. Low pressure fumeless spray gun
US5337926A (en) * 1992-02-07 1994-08-16 The Procter & Gamble Company Spray pump package employing multiple orifices for dispensing liquid in different spray patterns with automatically adjusted optimized pump stroke for each pattern
US5411185A (en) * 1992-02-07 1995-05-02 The Procter & Gamble Company Spray pump package employing multiple orifices having an orifice selector system
US5323935A (en) * 1992-02-21 1994-06-28 The Procter & Gamble Company Consumer product package incorporating a spray device utilizing large diameter bubbles
US5443796A (en) * 1992-10-19 1995-08-22 Nordson Corporation Method and apparatus for preventing the formation of a solid precipitate in a coating material formulation
US5407267A (en) * 1992-12-30 1995-04-18 Nordson Corporation Method and apparatus for forming and dispensing coating material containing multiple components
US5490726A (en) * 1992-12-30 1996-02-13 Nordson Corporation Apparatus for proportioning two components to form a mixture
US5407132A (en) * 1993-10-20 1995-04-18 Nordson Corporation Method and apparatus for spraying viscous adhesives
US5598974A (en) * 1995-01-13 1997-02-04 Nordson Corporation Reduced cavity module with interchangeable seat
US5873528A (en) * 1995-01-13 1999-02-23 Nordson Corporation Reduced cavity module with interchangeable seat
US6015100A (en) * 1997-07-15 2000-01-18 The Fountainhead Group, Inc. Foam generating nozzle assembly with interchangeable nozzle tip
US6561438B1 (en) 1997-07-15 2003-05-13 The Fountainhead Group Foam generating nozzle assembly
US20080014364A1 (en) * 2004-03-16 2008-01-17 Gerhard Brendel Water-Vapor Assisted Lacquering Method
US20060163384A1 (en) * 2005-01-21 2006-07-27 Specialty Minerals (Michigan) Inc. Long throw shotcrete nozzle
US7854397B2 (en) * 2005-01-21 2010-12-21 Specialty Minerals (Michigan) Inc. Long throw shotcrete nozzle
US20100136231A1 (en) * 2007-04-10 2010-06-03 BSH Bosch und Siemens Hausgeräte GmbH Method for producing a refrigeration device
US20100331428A1 (en) * 2007-11-07 2010-12-30 Aridis Pharmaceuticals Sonic Low Pressure Spray Drying
US8268354B2 (en) 2007-11-07 2012-09-18 Aridis Pharmaceuticals Sonic low pressure spray drying
US8673357B2 (en) 2007-11-07 2014-03-18 Aridis Pharmaceuticals Sonic low pressure spray drying
US20100055003A1 (en) * 2008-08-28 2010-03-04 General Electric Company Surface Treatments And Coatings For Flash Atomization
US8038952B2 (en) 2008-08-28 2011-10-18 General Electric Company Surface treatments and coatings for flash atomization
US10413920B2 (en) * 2015-06-29 2019-09-17 Arizona Board Of Regents On Behalf Of Arizona State University Nozzle apparatus and two-photon laser lithography for fabrication of XFEL sample injectors

Also Published As

Publication number Publication date
NL7210337A (de) 1973-02-01
FR2149149A5 (de) 1973-03-23
AU4372872A (en) 1974-01-03
IT961729B (it) 1973-12-10
GB1404984A (en) 1975-09-03
BE786900A (fr) 1972-11-16
JPS547961B1 (de) 1979-04-11
DE2236035A1 (de) 1973-02-08
CA963509A (en) 1975-02-25
AU475688B2 (en) 1976-09-02
SE394858B (sv) 1977-07-18

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