US3521817A - Nonthermal aerosol fog generator - Google Patents

Description

July 28, 1970 R. R. CURTIS ET AL NONTHERMAL AEROSOL FOG GENERATOR Filed July 8, 1968 2 Sheets-Sheet l CONCENTRATE COMPRESSOR CARR\ER 11V VEIV T 0125 HussELL R. CURTIS and CONRAD D. M6nwws BY zuawa MA M d Mw w flf/araep Fig. 1.

July 28, 1970 R. R. CURTIS ET AL NONTHERMAL AEROSOL FOG GENELKATOR 2 Sheets-Sheet 2 Filed July 8, 1968 a. a in JNVLNTOR RUSSELL R. Cum/s and Fig. 3.

CONRAD M- GINN/S zo id z/RMMMAQ @140 ,l/farne s United States Patent NONTHERMAL AEROSOL FOG GENERATOR Russell R. Curtis, Indianapolis, and Conrad D. McGinnis,

Noblesville, Ind., assignors to Curtis Dyna-Products Corporation, Westfield, Ind., a corporation of Ohio Filed July 8, 1968, Ser. No. 743,119 Int. Cl. A01n 17/10 U.S. Cl. 239-77 6 Claims ABSTRACT OF THE DISCLOSURE Disclosed is fog generator which produces an aerosol fog, used for example as an insecticide, by supplying high velocity, low volume air and a mixture of a carrier fluid and an insecticide concentrate material to multiple low volume nozzles, the inert carrier fluid and the concentrate being mixed just upstream of the nozzles, the atomized fog or dispersion issuing from the nozzles being propelled and directed from the fog generator by a low velocity high volume air stream provided by a ducted fan.

BACKGROUND OF THE INVENTION Field of the invention Fog or mist generators function to discharge relatively fine particles in a high velocity air stream and have particular use in insect control. One type heats the insecticide material to vaporize it and then discharges the vapor to produce the finely divided mist or fog. An example of this type of fog producing apparatus is disclosed in US. Pat. 2,576,976. Another type of fog producing apparatus is the nonthermal type in which the insecticide is atomized pneumatically, rather than by thermally induced vaporization, and is introduced into a high velocity, high volume air stream for propelling or dispersal to the desired area. This latter type has the advantage of being directionally controllable to a much higher degree than the thermal type. The fog generator of the present invention is of the nonthermal type.

Description of the prior art Nonthermal fog generators of the prior art are generally one of three types: (1) Single or multiple nozzles that are aspirated by high velocity, high volume air flow across the nozzle or nozzles. In these devices the air flow causes a reduced internal pressure in the nozzle allowing liquid to be drawn to the nozzle; (2) single or multiple nozzles fed by a low pressure liquid pump and aspirated by high velocity, high volume air flow; (3) single or multiple nozzles fed by a high pressure liquid pump, the nozzle or nozzles using the high liquid pressure to fracture the liquid. The established spray or mist is then carried oif by a high velocity, high volume air stream. The inherent problem in devices of all these types is the power required to generate the high velocity, high volume air flow. High pressure nozzles are used on prior art devices and because the insecticide or other material moving through the nozzle is at relatively high pressure, the fluid is introduced into the high pressure system in premixed condition, that is, the inert carrier (usually kerosene) and the insecticide concentrate are already mixed before introduction into the high pressure nozzle system. This pre-mixing of concentrated chemicals and carrier oils creates serious problems in these prior art fog generating devices. Because the solution is mixed before introduction into the fluid circulating system, pump corrosion and deterioration and sludge formation in pumps, tanks, hoses, nozzles and filters usually occurs after sustained use of the apparatus. Pre-mixing also forecloses the often useful possibility that the carrier and concentrate relative proportions be adjusted to particularly suit some 3,521,817 Patented July 28, 1970 ioealized or temporary condition. Further, many of the chemicals used will not readily stay in solution with the carrier liquid and, after standing for extended periods, must be agitated to assure uniform solution strength. All of these difliculties can be eliminated if the mixing of the active chemicals and the inert carrier is delayed and takes place just upstream of the nozzle.

SUMMARY The present invention provides a fog generator in which low volume nozzles deliver finely divided carrierconcentrate mixture to a low velocity, directionally controlled air stream provided by a ducted fan. The carrierconcentrate mixture is delivered at relatively low pressure to the nozzles and the inert carrier liquid and the chemical concentrate can, therefore, be mixed just upstream of the nozzles, eliminating the problems inherent in premixing and facilitating flushing of the system after use, necessary to remove corrosive chemicals from fluid lines and system elements. Since the carrier and chemicals are mixed adjacent the nozzles, and not premixed, their relative proportions can be readily varied by valve adjustments at the fog generator. The fog is produced at the nozzle by high velocity, low volume air passing through the nozzle and the particles are then carried oif in a high volume, low velocity air stream. The total power requirement to establish the two air streams is less than that of prior art devices because both the high velocity, low volume air put through the nozzles and the low velocity, high volume air stream acting as a transport medium can be produced by a reduced power expenditure compared to that required for the high velocity, high volume air stream characteristic of the prior art.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view of the elements forming the fog generator of the present invention and showing the interconnections between the elements.

FIG. 2 is a perspective view of the fog generator of the present invention.

FIG. 3 is a sectional view of the nozzle body, the section being taken generally along the line 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1, the apparatus includes a tank or container forming a carrier fluid reservoir 10 and a container forming a chemical concentrate fluid reservoir 11. A primary drive means 12, which might take the form of an internal combustion engine or an electric motor as desired, drives an air compressor identified at 13. When driven at substantially rated speed the compressor supplies air under 20 psi. at its outlet line 14.

By means of a drive connection 16 the motor 12 also drives a carrier fluid pump 17 which draws carrier fluid from the reservoir 10, through the filter 18 and delivers it through the pump output line 19. A drive connection 21 from the prime mover 12 also drives the flexible drive element 22 which operates a ducted fan indicated generally at 23.

The fan 23 is provided with an encircling discharge duct 24, the fan and duct being directionally movable as indicated in FIG. 2. Mounted in the duct 24, adjacent to and downstream of the fan 23 is an annular nozzle (or manifold) indicated generally at 26.

The manifold construction is shown in detail in FIG. 3 and, in general, includes an annular fluidchamber or header 27 and an annular pressurized air chamber 28. The fluid inlet line 29 (FIG. 1) communicates with the chamber 27 (FIG. 3) and the air input line 31 (FIG. 1) communicates with air chamber 28 (FIG. 3). Extending through the pressure chamber 28 are a plurality of nozzle bodies 32 which are provided with a plurality of spaced ports 33. The nozzle bodies accommodate nozzle stems 34, having nozzle body cavities 36 and nozzle plates 40. Orifice members 37 provide restricted flow communication between the fluid chamber 27 and the nozzle body cavity 36. Liquid is forced under low pressure through orifice member 37 into nozzle body cavity 36. Liquid in body cavity 36 is at relatively low pressure, the pressure being just sufficient to maintain liquid flow through nozzle stem 34 to outlet aperture 38. The outlet end of nozzle stem 34 is chamfered so that the nozzle 34 has a knife edge on its periphery at outlet aperture 38. Air from pressure chamber 28 is delivered through spaced ports 33 into the stem body and discharged through the nozzle plate opening 39. As the pressurized air travels around the nozzle 34 and out opening 39, a thin, hollow, cylindrical stream of high velocity air is established at the knife edged periphery of nozzle aperture 38. This high velocity, low volume air stream tears the liquid from the knife edge forming finely divided particles. Each of the nozzle assemblies provides a relatively low volume nozzle with consequent good atomization. Use of a plurality of nozzle elements provides a relatively high volume liquid output, even though each of the nozzles is of low volume characteristic, this resulting in reduced power requirements when compared to prior art devices.

The minor components and interconnections between the fluid reservoirs and the ducted fan and nozzle assembly include, as previously mentioned, the carrier fluid line 19 which communicates with a reducing and regulating valve 41. A bypass return line 42 permits fluid to be directed by the valve 41 back to the carrier fluid reservoir 10. The outlet line 43 from the valve 41 supplies a pressure gage 44 and also communicates with a manually operated flushing valve 46. The line 43 permits the carrier liquid to move through a carrier liquid rotometer indicated generally at 47 and of conventional design. A line 48 directs the carrier fluid into a tangential inlet 49 to a fluid mixing chamber, indicated generally at 51. The mixing chamber outlet 52 communicates with the line 29 to the fluid chamber 27 (FIG. 3) of the nozzle assembly.

The compressor outlet line 14, previously mentioned, extends to a reducing and regulating valve 53 and, from the valve 53, a line 54 provides low pressure air (under p.s.i.) to the chemical concentrate reservoir 11 to place the fluid in the reservoir under pressure and move it from the reservoir through the chemical fluid line 56. A line 57 from the valve 53 introduces air at approximately psi. into the line 31 leading to the air chamber 28 (FIG. 3) of the nozzle assembly.

The chemical concentrate line 56 extends through an on-oif metering valve 61 to a chemical concentrate rotometer 62. The bypass line 63 provides communication, above valve 61, between the lines 19 and 56 when the flush valve 46 is open. A line 64 provides communication from the rotometer 62 to the axial inlet 66 to the mixing chamber 51. The volume of carrier fluid is of the order of twenty times the concentrate volume and the mixing chamber functions to mix the tangentially entering carrier fluid and the axially entering chemical concentrate and to provide a homogenous mixture in the line 29 to the nozzle assembly 26. I

As may best be seen in FIG. 2 the elements described are mounted on a base 71 over which an arched support member 72 extends and pivotally carries a mounting bracket 73. The mounting bracket 73 pivotally supports the duct element 24 and handles 74 and 76 permit manual, adjustable movement of the duct 24 in two planes.

In operation, with the prime mover 12 in operation, carrier fluid will be moved by the pump 17 from the reservoir 10 to the mixing chamber 51. Operation of the air compressor 13 delivers air to the inlet 31 of the nozzle assembly and functions to pressurize, through the line 54,

the chemical concentrate in the reservoir 11. The chemical concentrate flows through lines 56 and 64 into the mixing chamber 51 and the carrier and chemical concentrate mix is delivered to the nozzle chamber 27 (FIG. 3) through the flexible line 29. The flow of atomized liquid is directed by the low velocity, high volume air flow induced by the fan 53 from the duct 24 in the desired direction.

Flushing of those portions of the system above or downstream of the valve 61 may be easily accomplished by shutting valve 61 and opening valve 46. This diverts inert carrier liquid through the chemical concentrate rotometer 62 and the line 64 and mixing chamber 51. Operation of the system with the valves 46 and 61 thus actuated serves to circulate the inert carrier fluid through the sensitive portions of the system for flushing out the chemically active, corrosion forming concentrate.

The arrangement is such that the pump 17 is separated from the corrosive chemical concentrate since mixing takes place just upstream of the nozzle assembly. Premixing of the carrier and the chemical concentrate, with its attendant difliculties, is thus eliminated. By adjusting valve 41 and metering valve 61 various mixing ratios of the carrier fluid and the chemical concentrate can be easily obtained. The flushing arrangement is self-contained within the system and the particle size of the atomized fluid issuing from the duct 24 can be easily controlled by adjusting the pressure output of the compressor at the line 57 in conjunction with adjustments of the rate of flow of liquid to the mixing chamber 51.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being made to the appended claims.

We claim:

1. A fog generator comprising in combination: separate carrier fluid and chemical fluid reservoirs, a ducted fan movably mounted so that the air stream induced by the fan can be directionally controlled, a plurality of atomizing nozzles aligned to discharge parallel to the direction of said air stream, said nozzles having a common air intake chamber and a common fluid intake chamber, air pressure producing means connected to said chemical fluid reservoir and to said nozzle air intake to pressurize said chemical fluid and to provide atomizing air respectively, a carrier fluid supply line and a pump for moving carrier fluid from said carrier fluid reservoir through said supply line, a chemical fluid supply line connected to said chemical fluid reservoir for supplying pressurized fluid from the reservoir, and a mixing chamber connected to both of said supply lines and to said nozzle fluid intake.

2. A fog generator as claimed in claim 1 having a valve-controlled line communicating with both of said supply lines upstream of said mixing chamber to permit introduction of carrier fluid into the chemical concentrate line for flushing that portion of the concentrate supply line downstream of said valve-controlled line.

3. A fog generator as claimed in claim 1 in which the plurality of atomizing nozzles are carried in an annular body whose central aperture is generally aligned with the central axis of the air stream induced by said ducted fan, and said common air intake chamber and common fluid intake chamber extend around the interior of said annular body.

4. A fog generator as claimed in claim 1 in which at least one of said supply lines is provided with a flow control valve to permit adjustment of the relative proportions of the carrier fiuid and the chemical fluid entering said mixing chamber.

5. A fog generator as claimed in claim 1 in which said air pressure producing means is a compressor, and in which a unitary power means is adapted to drive said ducted fan, said pump and said compressor.

6. A fog generator comprising in combination: separate carrier fluid and chemical fluid reservoirs, a ducted fan movably mounted so that the airstream induced by the fan can be directionally controlled, a plurality of atomizing nozzles aligned to discharge parallel to the direction of said airstream, said nozzles having a common air intake chamber and a common fluid intake chamber, means for supplying air under pressure to said nozzle air intake, a carrier fluid supply line communicating with said carrier fluid reservoir, a chemical fluid supply line connected to said chemical fluid reservoir for supplying fluid from the reservoir, and a mixing chamber con- UNITED STATES PATENTS 2,925,222 2/1960 Spreng 239172 X M. HENSON WOOD, JR., Primary Examiner M. Y. MAR, Assistant Examiner US. Cl. X.R. 239--306, 307, 550

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