US 2984421 A
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Description (OCR text may contain errors)
y 15, 1961 J. w. HESSION, JR 2,984,421
ADJUSTABLE AEROSOL DEVICE Filed Aug. 11, 1958 FIG.I.
United States ADJUSTABLE AEROSOL DEVICE Filed Aug. 11, 1958, Ser. No. 754,387
Claims. (Cl. 239-406) My invention relates to aerosol fog spray devices and more particularly to an improved adjustable nozzle construction in which gas entering a frusto-conical chamber adjacent the final outlet orifice is induced to rotate at a high velocity and form a whirlpool, the converging center of which is adjacent a centrally located fluid dispeusing nozzle.
The term aerosol used therein is commonly defined in the art as a fog or cloud of particles, either liquid or solid, which by reason of extremely small sizes and consequent small masses, will remain suspended in still air for varying periods of time depending on the size of the particle, in accordance with Stokes law for the rate of fall of a small sphere in a viscous fluid. To come within the aerosol range a sample of the cloud under microscopic examination must show the largest particle to be no more than 50 microns in diameter, and the mass average of all particles in the sample to be not more than 20 microns. Since the particles increase in mass as the cube of the diameter, it is readily seen that if the mass average is for example, microns, nearly all of the particles must be well below this figure if any particles on the order of 40 to 50 microns are found in the sample.
In general, purely hydraulic nozzles of conventional design are not capable of producing such fine particles except under conditions of impractically great pressures of 12. to 30 thousand p.s.i. Therefore liquids are generally diluted in the nozzles by air, steam, or combinations of gases, and generally compressed air is used, the objective being to produce a fog having the maximum amount of liquid at the finest possible particle average to the minimum amount of air compressed to the lowest usable pressure.
Most of the conventional high pressure nozzles being manufactured are designed to operate at about 40 p.s.i. or more, relying on the high axial velocity of the liquidgas dispersion to achieve a satisfactory fog, resulting in a relatively large air-liquid ratio. The nozzle described herein on the other hand, although still in the high pressure class, is such as will produce the desired fine average size particles with an air consumption of only about /2 c.f.m. at about 20 p.s.i., to about .85 to 1.0 oz. per minute of liquid converted to aerosol, and is adjustable to provide the desired fog for liquids of different weights and viscosity and for changes in suction head.
An object of the present invention is to construct an improved aerosol fog spray nozzle operable preferably at a pressure of about 10 to 20 p.s.i., although satisfactory results have been obtained at higher pressures, and adjustable to give a relatively high percentage of liquid having extremely small particle sizes.
Another object of the invention is to simplify the construction of aerosol nozzles which are manufactured to extremely close tolerances by providing a highly simplified nozzle having means for accurately maintaining critical dimensions therein.
A further object of the invention is to provide an improved aerosol nozzle by constructing a nozzle body having a frusto-conical shaped chamber in which a whirlpool of air is produced, the converging center of which is adjacent an outlet orifice, preferably an adjustable centrally positioned liquid outlet.
Yet another object of the invention is to improve aerosol nozzles by providing a simplified assembly of parts which individually are readily machined to close tolerances and adapted to fit together to provide the required gas passages and chambers.
A still further object of the invention is to facilitate cleaning and assembly of aerosol nozzles by providing a three-part construction having chambers and passages which become readily accessible on disassembly.
Still another object of the invention is to improve the operation of aerosol nozzles by providing a simplified nozzle construction having means for making extremely fine adjustments measurable in fractions of thousandths of an inch.
For a more complete understanding of my invention, reference may be had to the accompanying drawing illustrating a preferred embodiment of the invention in which like reference characters refer to like parts throughout the several views and in which:
Fig. 1 is an enlarged longitudinal cross-sectional view of a preferred structure embodying the invention.
Fig. 2 is a cross-sectional view taken on the line 2-2 of Fig. 1.
Fig. 3 is a cross-sectional view taken on the line 3-3 of Fig. 1, and
Fig. 4 is an elevational end view of the device as seen from the line 4-4 of Fig. 1.
Nozzles of this type are rather small, the small dimension across the hexagonal illustrated in Fig. 2 being preferably only about inch or less, and operable at pressures above 6 p.s.i. In the drawing, the preferred aerosol device is illustrated as comprising a housing structure 10 having a straight walled longitudinal recess or bore 11 terminating at a conical inner end surface or wall 12 and a short axially disposed outlet orifice 13 open to the vertex of the conical inner end wall 12. Such a housing is obviously relatively simple to machine in one or at most tWo operations, making it relatively inexpensive. The housing has a radially extending port 14 in which a fitting 15 is preferably press fit. The fitting 15 is preferably screw threaded as shown for connection to the outlet 16 of any gas pressure producing device 17 (not shown in detail), the fitting having a gas passage 18 as indicated.
The end of the housing 10 remote from the orifice 13 is screw threaded as at 19 for assembly with a knurled adjusting collar 20. The threads 19 are extremely fine, such that a small turning movement or adjustment of the collar 20 effects a relatively micrometrically minute axial displacement.
A spool member 25 is disposed in the bore 11 and comprises an inner end portion 26 defining with said conical wall an inner frusto-conical chamber 27 an outer end portion 28 closely fitting in the bore 11, and a reduced diameter intermediate portion 29 defining an annular gas chamber 3%} into which opens the port 14.
The inner end portion 26 is provided with spiral peripheral grooves 31, the lands 32 between the grooves contacting the bore 11, such as to provide gas passages connecting the annular chamber 30 with the frustoconical chamber 27, the gas being angularly directed into the frusto-conical chamber 27 near its periphery to impart a rotary motion and to produce a converging Whirlpool of gas in the chamber 27 with the vertex adjacent the orifice v13, the linear velocity of the swirling gas being accelerated as same flows toward the orifice 13.
The inner end of the spool member .25 is provided with "a nozzle 35 which extends axially into the frustoconical chamber 27 and has a nozzle tip 36 disposed inwardly adjacent the orifice 13 to provide a restricted annulus substantially at the vertex of the whirlpool of gas, The diameter of the orifice 13 is preferably about .010 inch larger than the diameter of the nozzle tip 36. Thus the gas and fluid are mixed together at the point where the linear velocity of the gas is at a maximum and prior to when same decelerates on passing through the outlet orifice 13.
The spool member 25 has an axial passage 37 therethrough opening at an outlet port 38 in the nozzle tip 36. A fitting 39 is preferably press fit into the outer end of the passage 37 and is preferably provided with a fir-tree and 40 adapted for connection with a flexible plastic or rubber tube 41 leading from a source of fluid supply, generally a liquid (not shown). The outer end of the spool member 25 has a radially outwardly extending flange 42 adapted to abut aradially inwardly extending flange 43 provided on the collar 20. A resiliently compressible O-ring member 44 is disposed between the inner side of the flange 42 and the outer end of the housing adjacent the bore 11, and serves as a means resiliently urging the spool member 25 outwardly. This O-ring member particularly provides means permitting the spool member 25 to be axially adjusted pistonlike within the straight walled bore 11, within limits, to provide extremely fine alterations in the clearance be tween the nozzle tip 36 and the inner end of the orifice 13 and in the cross-sectional area of the restricted annulus.
The above adjustment makes it possible to adjust the nozzle to correct for changes in air pressure, changes in viscosity, changes in suction head and for the operation of groups of nozzles from one air source to overcome unavoidable manufacturing tolerances. In adjusting nozzles for optimum performance on an insecticide, the suction head and air pressure are preferably constant, but slight variations in the suction head and air pressures do occur at times and anyone of such changes require adjustment to the nozzle whereby to provide the desired aerosol spray with no fall-out of large particles.
In constructing the present device in accordance with the principles of my invention, the axial nozzle tip-tohousingorifice dimension may sometimes be about .004
der of extremely small fractions of thousandths of an inch for satisfactory operation of the individual device.
In operation, gas under a pressure of about 10 to 20 psi. is angularly directed into the frusto-conical chamber 27 by the grooves 31 and is thus caused to rotate at high velocity, creating a whirlpool effect in the chamber 27. The angular velocity of the gas naturally increases or accelerates as it converges to a vortex at the orifice 13. As seen in Fig. 1, the closeness of the nozzle tip 36 to the orifice 13provides a restriction just at this location, creating an area of low pressure adjacent the liquid outlet port 38 which serves to asperate fiuid into the high velocity vortex of the whirlpool, breaking the liquid up into the small particles desired. The still rotatingmixture of gas and liquid then moves axially out of the orifice 13, where the combined effect of sudden expansion, axial velocity and centrifugal forces cause an'immediate dispersal, such that the rapid increase in ;microscopic distance between fluid particles reduces any tendency to coalesce.
As noted before, the positioning of the nozzle tip 36 is critical within limits, which will vary between nozzles and 'under ditfering conditions ofoperation, such asfor different air pressures, viscosities, and suction head. If the tip 36 is too close to the orifice 13, the axial and radial motion of the gas past the tip is too great and will not effectively intersect the fiuid being drawn from the port 38 in time to produce the desired breakup of fluid into particles small enough to form the desired fog. When the tip '36 is too far from the orifice 13, it is too far from the converging center of the whirlpool of gas, such that the angular velocity of gas is not enough to produce the desired dissociation of liquid particles. Moreover, the negative pressure at the nozzle tip 36 rapidly goes to positive at a certain distance inwardly of the whirlpool vortex, and the present device is intended to asperate liquid without without the aid of pumps or other devices. Thus, as the individual fog devices are assembled, each is tested and adjusted by means of the collar 20 to position the liquid outlet port 38 at that precise part of the whirlpool of gas formed in the frustoconical chamber 27 in which the most eflicient dissociation of liquid into particles of the size desired. It will be apparent that the nozzle can be adjusted durng operation and thus permit visual observation of the spray.
Also, since the purpose of the present device is to produce aerosol sprays as distinguished from conventional coarse spray, regulation is an absolute necessity in compensating for differences within the prescribed manufacturing tolerance limits, and for variables of liquid weight, viscosity, and suction head; that is, the height of the nozzle from the liquid container. For example, if a nozzle is set for maximum efficiency when using an insecticide based 'on kerosene, the suction head being substantially constant, and it is desired to use some other liquids having different weights and/or viscosities,-.such as heavy oil or water, a readjustment must be made to continue the performance without droplet fall-out." Also, if the suction head were to be changed substantially, such as by lowering the liquid container 4m 5 feet, the quantity of liquid being atomized would be reduced by a large factor. Corrections may then be made by moving the spool inward to reduce the cross-sectional area of the restricted'annulus to produce a higher suction for this particular condition, restoring the desired performance.
Although I have shown only one preferred embodiment of the invention, it will be apparent to one skilled in the art to which the invention pertains that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.
1. An aerosol fog spray device comprising'anaerosol nozzle for generating a fog'comprising liquid particles,
the mass median diameter of which isin the order of.
about 15 to 20 microns and in whichabout of said particles'are less than about 30 microns in diameter and in which all particles are less than about 50 microns in diameter, said nozzle comprising a housing provided with a cylindrical recess having a conical inner end wall and an outlet orifice at the vertex of said conical inner end wall, a spool member axially slidably disposed in said cylindrical recess and having a tip portion, the extreme end thereof disposed adjacent to and axially spaced rearwardly from the outlet orifice about .004 to .006.inch, said tip defining with said conical end wall of said recess a frustoconical chamber, said spool'member having gas passages open to said chamber adjacent the larger periphery thereof and angularly disposedwith respect to the axis thereof to impart rotary motion .to thegas. entering said chamber and to produce a converging whirlpool of gas therein with the vertex adjacent-said outlet orifice and forward of the extreme'end of said tip,- and meansconnecting said passages withasource of gas under pressure,
said spool member having a nozzle :portion projecting into said-frusto-conical chamber and having'an outer diameter of about .010.inch.-less than-the .diameter of said outlet orifice and thereby providing an opening comprising a restricted annulus extending rearwardly of the outlet orifice, said spool member having a liquid passage and a discharge opening in the nozzle tip portion disposed concentrically with respect to the axis of said frusto-conical chamber and said restricted annulus, liquid inlet means connected with said liquid passage, and means axially adjusting said spool member in said cylindrical recess to provide minute variations in the cross-sectional area of said restricted annulus by varying the axial clearance between the nozzle tip and said outlet orifice.
2. An aerosol fog spray device as defined in claim 1, in which said adjusting means is disposed exteriorly of said housing to permit adjustment of said restricted annulus while said device is being operated.
3. An aerosol fog spray device as defined in claim 2, and in which said adjusting means comprises a collar screw threaded on said housing and abutting the outer end of said spool member, and means resiliently urging said spool member outwardly against said collar.
4. An aerosol fog spray device as defined in claim 1, and in which the outer end of said spool member extends outwardly of said recess and is provided with a radially outwardly projecting flange, said adjusting means comprising a collar screw threaded on said housing and having a radially inwardly projecting flange abutting the outer side of said spool member flange, and a resiliently compressible O-ring member disposed between the opposite side of said spool member flange and the end of the housing adjacent said recess.
5. An aerosol fog spray device as defined in claim 1, and in which said spool member comprises axially spaced land portions contacting with the surface of the cylindrical recess and a reduced diameter portion disposed intermediate said land portions to define an annular gas chamber, said forward land portion having spiral grooves disposed peripherally about the outer cylindrical surface thereof forming the gas passages connecting said annular gas chamber with said frusto-conical chamber to impart rotary motion to the gas entering said :frusto-conical chamber ahead of said forward land portion, said rear land portion serving to support said spool member in the cylindrical recess and to maintain the said spool memher in substantially true concentric alignment, and to substantially seal said annular gas chamber from leakage to the outside of said device, said means connected with said source of gas pressure opening directly into said annular gas chamber.
References Cited in the file of this patent UNITED STATES PATENTS 622,245 Luttrell Apr. 4, 1899 1,478,370 Adolphscn Dec. 25, 1923 1,491,318 Shearer et al Apr. 22, 1924 1,564,064 Hannah Dec. 1, 1925 1,559,625 Kutis Nov. 3, 1925 1,678,459 Bowland July 24, 1928 1,813,083 Pyankow July 7, 1931 1,989,696 Kelley Feb. 5, 1935 2,050,368 Neely Aug. 11, 1936 2,379,161 Kraps June 26, 1945 2,596,909 Mufich et al. May 13, 1952 FOREIGN PATENTS 47,572 Denmark July 12, 1933 163,122 Austria May 25, 1949 505,535 France May 10, 1920