Spraying Apparatus

Abstract

In a spraying apparatus in which a liquid is atomized by a pulsating stream of combustion gases discharged through an elongated exhaust pipe from a combustion chamber equipped with a carburetor for use of liquid fuel, the exhaust pipe is equipped with at least two atomizing nozzles. One nozzle near the free orifice of the exhaust pipe is fed the active agent to be sprayed, and the other nozzle near the combustion chamber is supplied with water or similar cooling liquid which evaporates in the combustion gases and cools the same sufficiently to permit a dispersion of heat-sensitive insect pathogens, such as Bacillus thuringiensis, to be atomized at the nozzle near the exhaust pipe orifice.

Description

This invention relates to spraying apparatus of the type in which a liquid to be sprayed is atomized by combustion gases discharged from a combustion chamber in a pulsating stream, and particularly to an improvement in the apparatus of the commonly owned U.S. Pat. No. 3,575,349.

The apparatus disclosed in the earlier patent includes a combustion chamber supplied with a fuel mixture which is ignited in the chamber. The resulting combustion gases are discharged through a long, straight exhaust pipe, and the liquid to be sprayed is fed to one or more nozzles located near the discharge orifice of the exhaust pipe and atomized by the rapid stream of exhaust gases.

While spraying apparatus of the known type has been used successfully for dispersing insecticides and like crop treating chemicals, it is not applicable to active agents which are heat sensitive, such as Bacillus thuringiensis and like biological insecticides which do not leave residues potentially harmful to humans on plants protected by spraying. Very few of the biological insecticides presently available on a commercial scale can survive an atomizing temperature much higher than the temperature of the surrounding atmosphere. The combustion gases are discharged from the combustion chamber of the known apparatus at about 900.degree.C, and the walls of the exhaust pipe, although cooled by the surrounding air, cannot extract sufficient thermal energy from the rapidly flowing gas stream.

It has now been found that an additional nozzle in the exhaust pipe located in the terminal portion of the pipe which is joined to the combustion chamber, and substantially nearer to the chamber than to the discharge orifice of the pipe, permits even heat sensitive active agents to be atomized without heat damage from another nozzle located in the other terminal portion of the exhaust pipe near the discharge orifice if the nozzle near the combustion chamber is supplied with a liquid capable of being vaporized at the temperature of the exhaust gas so that the heat of evaporation is extracted from the combustion gases.

Other features and many of the attendant advantages of this invention will readily be appreciated as the same becomes better understood by reference to the following detailed description of preferred embodiments when considered in connection with the appended drawing in which:

FIG. 1 shows spraying apparatus of the invention in elevational section; and

FIGS. 2 and 3 show respective modifications of the apparatus of FIG. 1 in fragmentary plan sections.

Referring now to FIG. 1, there is shown spraying apparatus having many features in common with the apparatus of the earlier patent, and such common features will be described only briefly.

A combustion chamber 10, generally cylindrical about a horizontal axis, is connected to one longitudinal end of a straight, cylindrical, coaxial, exhaust pipe 12 by a conically tapering juncture. A combustible fuel mixture is supplied to the combustion chamber 10 through a radial nipple remote from the pipe 12 from a carburetor 22. The carburetor is essentially a converging-diverging tube whose throat communicates with a fuel line 24 and a nozzle 26 for starting air. During normal operation, air is drawn into the carburetor through its enlarged end 40 remote from the chamber 10. A conical baffle 30 and a valve plate 32 normally control the admission of air to the carburetor 22 which is mounted on the sprayer casing 53, only partly visible in the drawing.

Air for starting the spraying apparatus is blown into the carburetor throat by compressing a rubber bulb 42 connected to the nozzle 26 by a check valve 38 and equipped with a suction valve 43 for entry of ambient air when the bulb 42 is released and expands resiliently. The carburetor orifice in the nipple of the chamber 10 is covered with a screen or grid 16 which further disperses coarse fuel drops and a sharp circular edge 25 permits a liquid film collected on the nipple wall to be dispersed by the passing air stream. A spark plug 14 mounted on the nipple ignites the combustible fuel mixture as it enters the combustion chamber.

A liquid to be dispersed in the combustion gases as they stream from the chamber 10 through the exhaust pipe 12 toward the flaring orifice 88 of the latter, may be stored in a tank 70 whose supply opening is normally sealed hermetically by a cap 86. A feed conduit 78 permits the liquid in the tank 70 to be supplied to an atomizing nozzle 84 located in the exhaust pipe 12 near the orifice 88. The end portion 72 of the conduit 78 in the tank 70 is flexible and is held near the bottom of the tank by a tubular metal weight 74.

A rotary multiple-way valve 76 in the conduit 78 permits the air space above the liquid in the tank 70 to be vented to the atmosphere, but normally supplies air under pressure from a line l8 connected to the converging part of the carburetor 22. A check valve 20 in the pressure line 18 prevents fluid flow toward the carburetor. In yet another angular position of the valve 76, air under pressure flows directly from the pressure line 18 through the valve 76 and the conduit 78 to the nozzle 84 for removing residual liquid, if so desired.

A normally closed control valve 80 connects the conduit 78 to the nozzle 84, and is opened by the dynamic pressure of a stream of combustion gases in the pipe 12 entering the orifice of a tube 82 connected to the valve 80, the orifice being directed toward the combustion chamber 10.

The structure described in connection with the tank 70 is substantially duplicated to permit a second liquid to be dispersed in the stream of combustion gases in the exhaust pipe 12, or to increase the amount of a single active agent dispersed in a given amount of combustion gas. There is thus provided a second tank 70a adapted to hold a liquid to be atomized in the combustion gases. A flexible terminal portion 72a of a feed conduit 78a is held near the bottom of the tank 70a by a tubular weight 74a, and a multiple-way valve 76a in the conduit 78a connects the air space above the liquid in the tank 70a with the converging portion of the carburetor 22 during normal sprayer operation by way of the afore-mentioned pressure line 18 and a branch pipe 18a. The supply opening of the tank 70a is normally sealed by a cap 86a so that air pressure can lift liquid from the tank 70a through the conduit 78a and a pressure responsive valve 80a to a nozzle 84a closely adjacent the afore-mentioned nozzle 84 and the orifice 88 of the exhaust pipe 12. The valve 80a is operated by gas pressure picked up by the afore-mentioned tube 82. A conduit 93 equipped with a shut-off valve 90 connects the air spaces of the tanks 70,70a, and a similar conduit 95 equipped with a valve 92 connects the bottom portions of the tanks. The valves 90,92 may be kept open when the same liquid is to be discharged from the atomizing nozzles 84,84a.

The apparatus described so far is not significantly different from corresponding features of the device disclosed in the earlier patent. The present invention additionally provides a nozzle 84b whose orifice is located in the exhaust pipe 12 closely adjacent the juncture of the pipe with the combustion chamber 10 where the combustion gases are close to their maximum temperature. The nozzle 84b is backed by a liquid supply system closely analogous in part to the devices associated with the nozzles 84,84a, that is, a tank 70b, normally sealed from the atmosphere by a cap 86b closing the supply opening of the tank. A tubular weight 74b holds the flexible end portion 72b of a conduit 78c under the liquid level and near the bottom of the tank 70b, and a multipleway valve 76b in the conduit 78c permits air under superatmosphic pressure from the pressure line 18 to be admitted to the gas space in the tank 70b through a branch tube 18b. The valve 76b also may be set for directing liquid lifted from the tank 70b under air pressure through a line 78e into an annular compartment 91 which surrounds the conically tapering juncture of the chamber 10 and the pipe 12, and the liquid supply to the nozzle 84b may be drawn from the compartment 91 through a conduit 78d and a selector valve 80b.

The valve 80b may alternatively connect the nozzle 84 to the conduit 78c, the conduit 78d, or ultimately a conduit 78b leading to the valve 76 associated with the tank 70, and permitting liquid to be supplied from the tank 70 to the nozzle 84 by suitably setting the valves 76 and 80b.

The compartment 91 is separated from the combustion gases entering the exhaust pipe 12 by the conical metal wall of the juncture between the chamber 10 and the pipe 12, and thermal energy is transferred to the body of liquid in the compartment 91 from the hot gases through the common wall. When liquid from the tank 70b is fed to the nozzle 84b through the compartment 91, it is preheated before being exposed to the gases and evaporated at the orifice of the nozzle 84b.

Conduits 93b,95b connect the air and liquid spaces respectively of the tanks 70,70b and are equipped with shut-off valves 90b,92b. The tank 70 may thus be coupled with the tank 70a and associated elements to increase the flow of liquid to be atomized in the exhaust pipe 12 near the orifice 88, and for simply increasing the stored supply of liquid to be discharged from the nozzle 84a. Alternatively, the tank 70 may be sealed from the tank 70a and the nozzle 84, and used for holding an additional amount of the liquid stored in the tank 70b and/or for supplying more of the same liquid to the nozzle 84b.

The liquid supplied to the rear terminal portion of the exhaust pipe 12, that is, the terminal portion near the combustion chamber 10, evaporates upon contact with the hot combustion gas, and the heat of evaporation is derived from the combustion gases which are cooled correspondingly. The temperature of the combustion gases may be controlled over a wide range by choosing the nature of the liquid dispensed from the nozzle 84b and its rate of flow. Water is the preferred cooling liquid when the apparatus is employed for spraying or fogging agricultural crops with biological insecticides, and the amount of water is preferably chosen so that the combustion gas becomes supersaturated by loss of thermal energy to the air-cooled, metallic exhaust pipe 12 before it reaches the orifice 88. A multiplicity of fine water droplets is thus formed near the nozzles 84,84a and mixes with the liquid atomized at the nozzles 84,84a. As the stream emerges through the orifice 88, it is further cooled by the ambient air, and the droplets grow quickly beyond the sub-micron size in which water drops are known to have phytotoxic effects, yet they remain small enough to produce a slowly settling, dense fog of the type preferred for crop protection.

Such a fog could be produced heretofore only by the use of oil based active compositions. It was not possible with the apparatus of the earlier invention to produce a suitable fog from active agents alone, nor could water be atomized to the desired small drop size which is readily available in the apparatus of the present invention by condensation of the steam generated at the nozzle 84b. It would not be feasible to convert water in an aqueous suspension of an active agent to steam at a nozzle located near the discharge orifice of the known apparatus without simultaneously damaging the active ingredients, and it would hardly be possible to reconstitute a uniform dispersion after evaporation of the water.

The modified apparatus of this invention avoids the difficulties outlined above by evaporating water, or another suitable cooling liquid, in the absence of the active spray ingredients where the combustion gases are hottest, and by employing the cooled, moisture-laden gas stream for atomizing a dispersion of the active ingredient in any suitable liquid, even water.

The preheating compartment 91 has been found to facilitate evaporation at the nozzle 84b, but also greatly to reduce the operating noise of the apparatus basically due to the pulsating nature of the gas stream discharged from the orifice 88. It has been found that hot water supplied to the nozzle 84b reduces the noise level as compared to cold water, and it has further been established that a body of water surrounding the juncture of the combustion chamber 10 and the exhaust pipe 12 provides acoustical damping even when the water is not fed to the nozzle 84a. When the water supply of the nozzle 84a is switched from the conduit 78c to the compartment 91 and associated conduits, there is distinct reduction in the noise generated, and the water injection into the combustion gases is in itself beneficial in reducing operating noise. If the sound produced by the earlier apparatus or by the instant apparatus without water injection may be termed a roar, the sound generated with injection of preheated water into the combustion gases is more like a low-pitched rumbling and less obnoxious to the operator.

The operation of the illustrated apparatus will be evident from the above description. It has been used successfully for simultaneously atomizing an aqueous suspension of Bacillus thuringiensis and a chemical fungicide, respectively stored in the tanks 72,72a by means of combustion gases generated by burning gasoline with atmospheric air and saturated with moisture at about 100.degree.C by water injected through the nozzle 84b. The temperature in the exhaust pipe 12 near the nozzles 84,84a was only 10.degree.C higher than in the tanks 72,72a. The mixture discharged from the orifice 88 had the appearance of a dense rain cloud or fog.

If an unusually high ratio of dispersed active agents to combustion gases is desired, the modified spraying apparatus of FIG. 2 may be resorted to, and the apparatus partly shown in FIG. 3 is preferred where it is desired to increase the discharge velocity of the spraying mixture. As far as not specifically shown and described otherwise, the devices of FIGS. 2 and 3 include the elements of FIG. 1 and as many duplicates thereof as will be required in view of the specifically described features of FIGS. 2 and 3.

The spraying apparatus shown in FIG. 2 is provided with a single combustion chamber 100 joined to two parallel exhaust pipes 102,104. The ends of the pipes 102,104 remote from the chamber 100 are connected to a common discharge orifice or nozzle 106. Different active agents may be fed to the exhaust pipes 102,104 near the common orifice 106 by respective atomizing nozzles 112,114, and the combustion gases in each pipe may be cooled by water injected near the chamber 100 through respective nozzles 108,110.

The modified apparatus illustrated in FIG. 3 differs from that described in FIG. 2 by being provided with two separate combustion chambers 200,202 which supply combustion gases to respective exhaust pipes 204,206 merging into a common discharge orifice 208. Water may be injected into the pipes 204,206, through nozzles 210,212, and active ingredients atomized in the cooled, moistened combustion gases from nozzles 214,216 near the orifice 208.

Other modifications and variations of the apparatus illustrated in FIG. 1 will readily suggest themselves to those skilled in the art on the basis of the above teachings. It should be understood, therefore, that within the scope and spirit of the appended claims, this invention may be practiced otherwise than as specifically disclosed.

Claims

What is claimed is:

1. In a spraying apparatus having a combustion chamber, carburetor means connected to said chamber for supplying the same with a combustible mixture of a liquid fuel with air of combustion, ignition means for igniting said mixture, an elongated exhaust pipe having two longitudinally terminal portions, one of said portions being joined to said chamber in a juncture for receiving a stream of combustion gas from said chamber, and the other portion having an orifice for discharging said stream, a plurality of atomizing nozzles in said exhaust pipe, a plurality of tanks adapted to hold respective liquids to be dispersed in said combustion gas, respective conduits connecting said tanks to associated ones of said nozzles, the improvement which comprises:

a. one of said nozzles being located in said one terminal portion and substantially nearer to said combustion chamber than to said orifice, and

b. another one of said nozzles being located in said other terminal portions and substantially nearer to said orifice than to said combustion chamber.

2. In a spraying apparatus as set forth in claim 1, a portion of the conduit connecting said one nozzle to the associated tank having a wall of thermally conductive material in common with said combustion chamber.

3. In a spraying apparatus as set forth in claim 1, sound damping means for damping the sound of the combustion gases being discharged from said combustion chamber into said one terminal portion, said sound damping means including a compartment enveloping said juncture and a body of liquid in said compartment.