US2890765A - Methods and apparatus for generating an aerosol - Google Patents

Description

June 16, 1959 M. v. FRIEDELL 2,890,765

METHODS AND APPARATUS FOR GENERATING AN AEROSOL 2 Sheets-Sheet 1 v INVENTOR. fVm r BY M, fifg /h g Filed June 1, 1955 June 16, 1959 v FR|EDELL 2,890,765

METHODS AND APPARATUS FOR GENERATING AN AEROSOL Filed June 1, 1955 2 Sheets-Sheet 2 United States Patent 1 2,890,765 NIETHODS AND APPARATUS FOR GENERATING AN AEROSOL Morley V. Friedell, Wheatridge, Colo., assignor to C. A.

Norgren Company, a corporation of Colorado Application June 1, 1955, Serial No. 512,416

9 Claims. (Cl. 184-55) This invention relates to an aerosol or fog generating device in which liquid is supplied in relatively small quantities to a flow of compressed gas to atomize the liquid for conveyance in a suspended state by the gas to a point of consumption.

The particular device illustrated and to be described is used in producing air-borne oil fog for lubricating air tools, bearings and other machine parts. The device, however, may be used for producing an aerosol of other liquids, including for example, insecticides, fumigants, coatings and hydrates.

The general object of the present invention is to provide a generator which will produce an aerosol or fog of much higher concentration of atomized liquid in the gas stream leaving the generator than prior generators would produce.

Another object is to provide such a generator which will operate equally well over a wide range of inlet gas pressures and provide relatively uniform fog concentration.

Another object is to provide an aerosol generator having means for atomizing a liquid and provided with means for baflling and further breaking up atomized particles immediately after their formation so as to prevent their reclassification.

A further object is to provide an oil fog generator having means utilizing an air stream for atomizing oil and producing a stream of air and atomized oil and means providing additional air streams directed transversely into the previously formed and moving air-oil stream to baflle and further atomize the oil particles.

Other objects and advantages will become readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:

1 is a vertical sectional view taken on the line 11 of Fig. 2, illustrating an aerosol type lubricator incorporating a preferred form of the invention;

Fig. 2 is a top plan view of the lubricator;

Fig. 3 is a horizontal sectional view taken on the line 33 of Fig. 1;

Fig. 4 is an enlarged fragmentary sectional view similar to Fig. 1, showing the preferred form of the invention to better advantage;

Fig. 5 is a vertical sectional view taken on the line Fig. 7 is a fragmentary sectional view taken on the line 7-7 of Fig. 6.

While there is shown in the drawings and will be hereinafter described a preferred form of the invention, together with a modification thereof, embodied in a fogtype lubricator, it is to be understood that this is not intended to limit the invention to the particular forms and arrangements shown or to the use of the invention in a lubricator. It is contemplated that changes in the construction and arrangement may be made without departing from the spirit and scope of the invention as defined in the appended claims.

In the form illustrated in Figs. 1 to 5, the invention is embodied in an air line lubricator of the fog generating type and which comprises generally a fog generating means 8 located in a head member or casing 10 forming a closure for a transparent cylindrical oil reservoir 12 in ice v which a supply of oil is maintained. The casing is equipped with a transparent dome 14 and is provided with an air inlet 16 on the left-hand side of Fig. l and an air outlet 18 on the right-hand side, to facilitate connection into an air line. The underside of the casing is formed with an annular groove 20 into which the upper edge of the reservoir 12 extends and is clamped to the casing by a ring 22. Screws 24 are provided to secure the ring to the casing. Caps 25 are removable fromthe tops of refilling passages formed in the casing to permit filling the reservoir with oil. The casing is sealed to the reservoir by a suitable gasket 26.

The top of the casing 10 has an annular flange 28 which is screw threaded to receive a collar 30 for securing a dome 14 in place, and the interior of the dome forms an oil feed chamber 31 sealed to the casing by a sealing ring.

Preferably, oil from the reservoir 12 is drawn into the oil feed chamber 31 through a siphon (Figs. 1 and 5) comprising a tube 36 extending from the bottom of the reservoir to the casing 10, a connecting passage 38 (Fig. 5) through the casing, and a tube 40 extending into the dome 14. As described more fully hereinafter, oil from the oil feed chamber and air from the inlet 16 are brought together in an aerosol generator positioned in the center section of the casing to form the aerosol orfog.

In the preferred form illustrated in Figs. 1 to 5, the fog generator is located in a vertical stepped bore 44 in the casing 10 and is made in two sections or parts, a hollow cylindrical housing member 46 and a venturi tube 48 therein. The housing member 46 is positioned in the vertical bore and is sealed therein by rings 50. The housing member has an integral oil supply passage extending downwardly from the upper end thereof comprising connecting bores 60 and 61 adapted to discharge oil into one end of the venturi section 54 formed in the venturi tube 48. The housing member 46 is also provided with gas passageway means including a restricted air inlet port 58 which leads from the air inlet 16 to an annular chamber 56 surrounding the oil feed bore 60. The lower end of the exterior of the oil feed tube is tapered to form an annular entrance passage 59 affording communication between the chamber 56 and the throat 62 of the venturi section 54.

Thus the air which passes into the fog-generator through the port 58 passes through the chamber 56 and annular passage 59 to the venturi throat 62 where it combines with and atomizes oil fed downwardly into the venturi through the oil feed bore 61. This creates an air-oil fog and air-oil mixture which passes as a stream of aerosol downwardly through the expanding venturi section 54. The stream then discharges into a hollow cylindrical diffusion tube 66 which is screw threaded into the underside of the casing 10 and serves to hold the housing member 46 in place. The internal bore 68 of the diffusion tube is formed on a diameter substantially larger than that of the venturi section and larger than the expanded lower open end of the venturi section which forms an expansion chamber 72. The lower end of the diffusion tube 66, as shown, has six outwardly and downwardly inclined discharge openings 70 through which the airoil fog and mixture passes into a settling chamber 12" in the upper portion of the reservoir 12 above the oil level,

In the settling chamber the heavier oil particles are separated by gravity from the finer particles and thus are automatically returned to the oil reservoir. The finer particles, of the order of two microns and smaller, are carried by the air stream to and out of the outlet 18. These finer particles will remain as an aerosol until they impinge with relatively high velocity against a solid surface or other reclassifying means, whereupon they will Patented June 16, 1959 be reclassified as a result of impact into larger particles suitable for lubrication or other purposes. The surfaces of the difiusing tube 66, the walls of the reservoir 12 and even the surface of the liquid in 'the reservoir may also provide suitable (although undesired) solid surfaces on which the aerosol may be so reclassified. Such unwanted reclassification results principally from the fact that the aerosol stream leaving the venturi section is moving at a sufiiciently high velocity as to cause reclassification onimpact with. such surfaces and as a result, former standard aerosol generators were able to produce a concentration ofonly about fifteen drops of lubricating oil in each cubic foot of air and thenonly if operated at about 60 pounds-per square inch (p.s.i.) of air pressure. According to the present invention however, a concentration of thirty drops of lubricating oil per cubic foot of air can be attained even atlair pressures as low as 20 p.s.i.

This increase in efiiciency has been achieved by creatingan air bafile which intercepts the rapidly moving aerosol stream as it leaves the venturi section. The air bafile is formed by directing a plurality of jets of air across and substantially normal to the aerosol stream with the jets combining to form, in effect, a wall or bafiie ofair opposing the aerosol stream and thus reducing its velocity while not providing a solid surface which would create sufficient impact for reclassification. The jets also have the effect of reducing to usable size (two microns or-less) many of the larger particles in the aerosol stream, thus increasing the usable concentration.

For this purpose there is provided a plurality of jets 74 formed in the periphery of the expansion chamber 72 with the jets being directed inwardly toward and substantially normal to the axis of movement of the aerosol stream. Preferably, at least three jets 74 are provided as his desired to provide jet streams of air moving across the aerosol stream having a total area sufiicient to form a baffle intercepting substantially the entire stream. The jets 74 are supplied with air under pressure from the inlet 16 and form the terminus of air conduit means including an annular chamber 76 surrounding the member 48, which chamber is in communication with the inlet through a-port 78 and with the jets 74.

It willbe noted that the port 78 is larger than the port 58 and thus air at higher pressure with resulting greater velocity is delivered through the jets 74 than is delivered through passage 59. The relation of venturi velocity to jet velocity to produce maximum efiiciency appears to be about 60%. Thus, as venturi velocity approaches 60% of jet velocity, efliciency is increased. Above that point little change is noted, with the maximum efficiency being maintained over a wide range beyond. that point. Thus, for example, the size of the orifice 58 may be proportioned to give a venturi pressure of p.s.i. in chamber 56, and orifice 78 proportioned to give a pressure of 20 p.s.i. in the jets 74, with the result of a velocity of air from the jets 74 approximately 60% higher than in the throat 62 of the venturi. At this ratio of velocities, maximum efiiciency is attained.

A slightly modified form of construction is shown in Figs. 6 and 7. The aerosol generator of Figs. 6 and 7 is. similar in many respects to the aerosol generator already described, and thus to avoid needless repetition of description, similar parts have been given similar but primed reference characters.

The principal difierence incorporated in the modified form is the difference in construction of the side walls of the housing member 46 which, it will be noted, does not provide anopening similar to-the opening 78 of the first embodiment, but rather provides for direct communication between the inlet 16' and annular passage 76' which in turn communicates with the jets 74'. Furthermore, the expansion chamber 72' has been modified somewhat in shape so asto have a top'and bottom por tion in the shapeof a truncated cone and an intermediate cylindrical portion in which the jets 74 are located. The

operation and function of the various parts is, of course, the same as the corresponding parts of the first described embodiment.

In operation of the aerosol generator of the present invention, air under pressure is admitted intothe inlet 16 and flows via passages 58, 56 and 59 to the throat 62 of the venturi where it enters the venturi section 54 at high velocity; The effect of the velocity of air flow at the throat of the venturi is to reduce the pressure at that point, and this reduction in pressure is transmitted through tube 60 into the interior 31 of the dome, and thence via tubes 44) and 36 to the reservoir 12, thereby serving to draw oil upwardly through said tube to drop into the tube 60. Drops of oil passing downwardly through the tube 60 are broken up into-fine particles by the action of the high velocity air flow emerging from the throat of the venturi and the aerosol thus formed moves as a stream through the venturi section 54 toward the bore 68 of the diffusion tube. As the aerosol stream moves toward the open end of the venturi section, it encounters what is in effect an air wall or bafile created by the jets of air fiovving inwardly through the jet opening 74. The effect of the stream striking this air bafile and at the same time entering an area of larger volume (the expansion chamber) is to greatly reduce the velocity of the aerosol stream and simultaneously to further subdivide many of the larger particles of liquid carried in the stream and thereby to increase the concentration of the fine particles. After passing through the expansion chamber, the aerosol stream may then expand into the bore 68 of the diffusion tube and finally enter the settling chamber 12' through the opening 70. Any large particles remaining in the aerosol stream may fall by gravity into the oil in the reservoir, while the fine particles are carried by the exiting air to and through the outlet 18 to a point of usage.

I claim:

1. An aerosol generator comprising a casing having an inlet to be connected to a source of gas under pressure and an outlet, means in the casing forming a venturi section open at one end, a liquid supply passage in the casing opening to the throat of the venturi section, a settling chamber communicating with the venturi section and with the outlet, gas passageway means communicating at one end with said inlet and opening at the other end into said throat of the venturi section adjacent said liquid supply passage opening, said passageway means serving to conduct gas at high velocity into said venturi section to break up liquid from said supply passage into a fine spray and to move the spray generally longitudinally of the venturi section toward the open end thereof and into the settling chamber, and means for creating a gas bafile intercepting said movement of the spray intermediate the throat of the venturi section and the settling chamber including gas conduit means communicating at one end with said inlet and terminating at the other end in at least three jets directed toward and normal to the axis of spray movement to further break up the spray and to reduce the velocity of movement of said spray toward said settling chamber.

2. An aerosol generator comprising a casing having an inlet to be connected to a source of gas under pressure and an outlet, means in the casing forming a venturi section open at one end, said venturi section being enlarged at its open end to form an expansion chamber, a liquid supply passage in the casing opening to the throat of the venturi section, a settling chamber communicating with the expansion chamber and the outlet, gas passageway means communicating at one end with the inlet and opening at the other end into said throat of the venturi section adjacent said liquid supply passage opening, said passageway means serving to conduct gas at high velocity into said' venturi section to break up liquid from said supply passage into a fine spray and to move the spray generally longitudinally ofthe venturi sectiontoward; the

expansion chamber and into the settling chamber, and means for creating a gas bafile intercepting the spray as it moves through the expansion chamber including gas conduit means communicating at one end with said inlet and terminating at the other end in a plurality of jets spaced around the periphery of the expansion chamber and directed inwardly toward and generally normal to the axis of spray movement to further break up the spray and to reduce the velocity of movement of said spray toward said settling chamber.

3. An aerosol generator comprising a casing having an inlet to be connected to a source of gas under pressure and an outlet, means in the casing forming a venturi section open at one end, said venturi section being enlarged at its open end to form an expansion chamber, a settling chamber communicating with the outlet, a diifuser having a bore into which said expansion chamber opens and having a plurality of openings therein opening into the settling chamber, a liquid supply passage in the casing opening to the throat of the venturi section, gas passageway means communicating at one end with the inlet and opening at the other end into said throat of the venturi section adjacent said liquid supply passage opening, said passageway means serving to conduct gas at high velocity into said venturi section to break up liquid from said supply passage into a fine spray and to move the spray generally longitudinally of the venturi section toward the expansion chamber and into the bore of the difiuser, and means for creating a gas baffle intercepting the spray as it moves through the expansion chamber including gas conduit means communicating at one end with said inlet and terminating at the other end in at least three jets spaced around the periphery of the expansion chamber and directed inwardly toward and generally normal to the axis of spray movement to further break up the spray to increase the concentration of fine particles therein and to reduce the velocity of movement of said spray toward said settling chamber.

4. An aerosol generator comprising a casing having an inlet to be connected to a source of gas under pressure and an outlet, means in the casing forming a venturi section open at one end and an expasion chamber having a cross section area greater than the maximum cross section area of the venturi section and into which said venturi section opens, a liquid supply passage in the casing opening to the throat of the venturi section, a settling chamber communicating with the expansion chamber and the outlet, restricted gas passageway means communicating at one end with the inlet and opening at the other end into said throat of the venturi section adjacent said liquid supply passage opening, said passageway means serving to conduct gas at high velocity into said venturi section to break up liquid from said supply passage into a fine spray and to move the spray generally longitudinally of the venturi section toward the expansion chamber and into the settling chamber, and means for creating a gas baflle intercepting the spray as it moves through the expansion chamber including gas conduit means communicating at one end with said inlet and terminating at the other end in a plurality of jets spaced around the periphery of the expansion chamber and directed inwardly toward and generally normal to the axis of spray movement, said conduit means being of larger diameter than said gas passageway means to direct into said expansion chamber gas at a higher pressure and velocity than the velocity and pressure of gas introduced into the venturi section by the passageway means.

5. The aerosol generator of claim 4 in which said gas conduit means is proportioned to pass gas into the expansion chamber at a velocity approximately 60% higher than the velocity of gas passed into the venturi section by the gas passageway means.

6. The method of forming an aerosol of liquid in a gas and preventing premature reclassification thereof which comprises feeding liquid to a venturi, directing gas under predetermined pressure at high velocity into the venturi to break up the liquid into an aerosol and to create a stream of aerosol moving rapidly in a predetermined direction, and then reducing the velocity of said stream while it is still moving in said direction by direct ing at least three jets of gas under a pressure of the order of twice said predetermined pressure substantially normal to the direction of movement of said stream to form a gas bafile intercepting the stream and opposing the general movement thereof.

7. The method of forming an aerosol of liquid in a gas and preventing premature reclassification thereof which comprises feeding liquid to a venturi, directing gas at high velocity into the venturi to break up the liquid into an aerosol and to create a stream of aerosol moving rapidly in a predetermined direction and then reducing the velocity of said stream while it is still moving in said direction by moving said stream into an expanding chamber and directing at least three jets of gas under pressure substantially normal to the direction of movement of said stream as it enters said expanding chamber to form a gas baflle intercepting the stream and opposing the general movement thereof.

8. An aerosol generator comprising, in combination, means forming a compressed air passage having an inlet and an outlet end, a first part positioned in said passage having an oil jet tube provided with a conical end and an oil feed duct therethrough, an annular groove around said tube and a restricted inlet port for conducting air under reduced pressure to said annular groove, and a second part comprising a tubular member forming a venturi passage with a contracting portion surrounding said conical end of the oil jet tube and cooperating therewith to form an annular passage therebetween extending from said annular groove to the throat of the venturi and cooperating with the side wall of the venturi tube to form the venturi throat, said tubular member having a passage of expanding diameter on the discharge side of said throat and a conical expansion chamber of more rapidly expanding diameter into which the main venturi passage discharges, a plurality of cross fire jets in the wall of said expansion chamber and directed radially inwardly toward the center thereof, and means for supplying air under full inlet pressure to said jets.

9. An aerosol generator comprising, a casing having a longitudinal bore and an intersecting vertical bore, a hollow housing member press fitted within the vertical bore, said member having an internal annular chamber and a port connecting the chamber with the longitudinal bore, a liquid feed tube formed in the upper end of said housing and extending downwardly within the housing member past said annular chamber, a sleeve-like member press fitted in said housing member with an upper portion thereof extending about the liquid feed tube to form an annular passage about the feed tube connecting the annular chamber with the interior of the sleeve-like member so that both said annular passage and feed tube open into the interior of said sleeve-like member, a plurality of air jets formed in the lower portion of said sleeve like member each communicating with the longitudinal bore and being directed radially into the interior of the sleevelike member, and means for supplying air to the longitudinal bore and liquid to the feed tube for forming aerosol within the sleeve-like member and baffling the so formed aerosol by air from the jets.

References Cited in the file of this patent UNITED STATES PATENTS 2,057,434 Jaden et al. Oct. 13, 1936 2,707,657 Paasche May 3, 1955 2,718,934 Norgren et a1 Sept. 27, 1955 2,779,437 Schweisthal Jan. 29, 1957 OTHER REFERENCES Lubrication Engineering, August 1953, page 226.

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