Abstract:
A foam generator employing a foam generator nozzle that injects compressed air and ambient air into the nozzle body where the air impinges upon a spray of foam liquid within the nozzle body is disclosed. The foam generator nozzle further includes spaced apart first and second fluid dispersion media downstream from the air-liquid mixture to generate a substantially dry foam suitable for application to agricultural crops for frost protection. The method for generating the substantially dry foam is also disclosed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a unique foam generator for producing and dispensing a substantially dry foam on an agricultural crop for frost protection. The foam generator utilizes a unique foam generator nozzle that injects compressed air and ambient air through a venturi nozzle body where the air impinges upon a spray of foam liquid within the nozzle body to create a first foam. The first foam passes, by excess air pressure, through a first fluid dispersion medium that is downstream from the venturi nozzle and the liquid nozzle to create a second foam. The second foam then passes through a second fluid dispersion medium downstream from the first fluid dispersion medium to generate the substantially dry foam suitable for application to agricultural crops. Operational parameters for generating the substantially dry foam are also disclosed and claimed.  
         [0003]     2. Description of the Prior Art  
         [0004]     Numerous devices, methods, and compositions useful for generating foams are certainly well known in the prior art. Such devices include aerosol dispensers for shaving cream, fire fighting equipment, and even the generation and application of foams on crops for frost protection. However, the foam generated by current, state of the art devices is substantially wet, and this is certainly the case with regard to virtually all fire fighting foams.  
         [0005]     Even foams used in agricultural settings for frost protection are substantially wet, resulting in a foam that is dense as a result of a relatively high ratio of liquid to air. In fact, these prior art devices typically inject foaming liquid through a venturi, so that ambient air is drawn into the liquid stream for the purpose of generating the foam. In order to “lighten” the foam density in a number of prior art generator devices, the initial foam is then passed through one or more screens for the purpose of mechanically dividing the foam bubbles, but the resulting foam product is still unnecessarily wet and dense, which can render the foam unsuitable for agricultural use.  
         [0006]     Wet foams not only have reduced insulating properties, but also actually may damage agricultural crops due to the weight of the applied foam. It is also desirable that foams applied to agricultural crops for frost protection should dissipate, leaving substantially no residue, within about 24-36 hours, and current, state of the art wet foams may actually leave harmful residues on the plants because of the relatively high liquid content of the foam composition. Finally, because current, state of the art wet foams include a relatively high concentration of the liquid component, the per-unit cost of such foams is necessarily greater than the cost of a dryer foam would be.  
         [0007]     It is therefore clear that, notwithstanding the availability of current foam generators, there remains a need for a foam generator capable of producing and delivering a substantially dry foam that is suitable for application to agricultural crops for frost protection wherein the volume/volume ratio of foam liquid to foam output is greater than 1/100.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to a foam generator for producing and dispensing a substantially dry foam on an agricultural crop for frost protection. The substantially dry foam is produced by a unique foam generator nozzle wherein compressed air is injected into a venturi nozzle designed and constructed to admit ambient air into the air stream as the compressed air passes through the venturi throat to the interior of the nozzle body. Downstream from the flow of compressed and ambient air, a liquid nozzle is positioned within the nozzle body to dispense droplets of foam liquid into the air stream. This results in the production of a first foam which is passed through a first fluid dispersion medium that is disposed within the nozzle body downstream from the liquid nozzle in transverse relation to the flow of the first foam. A second foam is generated by passage through the first fluid dispersion medium and next impinges upon and passes through a second fluid dispersion medium, further reducing the volume/volume ratio of liquid to air resulting in generation of the substantially dry foam which exits the nozzle body for application to the agricultural crop.  
         [0009]     According to a preferred embodiment more fully described below, the foam generator of this invention is a tractor-drawn device designed and constructed to move over one or more rows of an agricultural crop without damaging the crop. It is intended that one nozzle will cover at least each row of living plants, and in cases where plants are in closely aligned parallel rows, a single foam generator nozzle will be sufficient for two rows of plants. It is of course to be understood that the foam generator of this invention may be constructed to include one or more foam generator nozzles.  
         [0010]     Standard control valves are used for the purpose of precisely monitoring the pressure and flow rate of both the compressed air into the venturi nozzle and the foam liquid into the liquid nozzle. As set forth in greater detail below, the compressed air is injected at a pressure of about 2 psi to about 20 psi at a flow rate of about 14 cubic feet per minute (cfm) to about 221 cfm. The foam liquid is delivered to the liquid nozzle at a pressure of from about 100 psi to about 300 psi, and at a flow rate of about 0.22 gallons per minute (gpm) to about 1.02 gpm.  
         [0011]     While a variety of foam liquids are available for use, of particular utility with the foam generator of this invention is the agricultural foam product disclosed in pending U.S. patent Ser. No. 11/054,759, filed Feb. 10, 2005.  
         [0012]     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth and the operating parameters defining the method for producing and dispensing a substantially dry foam.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:  
         [0014]      FIG. 1  is a side elevation of a preferred embodiment of the foam generator of this invention being tractor drawn over a crop row.  
         [0015]      FIG. 2  is a side elevation of the foam generator illustrated in  FIG. 1 .  
         [0016]      FIG. 3  is a side elevation of a preferred embodiment of the foam generator nozzle of the present invention.  
         [0017]      FIG. 4  is a sectional view of the foam generator nozzle shown in  FIG. 3 , also showing the foam liquid conduit.  
         [0018]      FIG. 5  is a sectional view of the venturi nozzle taken along line  5 - 5  of  FIG. 4 .  
         [0019]      FIG. 6  is a sectional view of the interior of the nozzle body showing the first fluid dispersion medium and the liquid nozzle taken along line  6 - 6  of  FIG. 4 .  
         [0020]      FIG. 7  is a sectional view of the interior of the nozzle body showing the second fluid dispersion medium and the liquid nozzle taken along line  7 - 7  of  FIG. 4 . 
     
    
       [0021]     Similar reference characters refer to similar parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION  
       [0022]     Referring to the view of  FIG. 1 , the foam generator of this invention is generally indicated as  10 . In this preferred embodiment, foam generator  10  is mounted on trailer  12  and towed by tractor  14  over a row of agricultural crop, generally indicated as  16 . A substantially dry foam  18  is shown as being dispensed from the foam generator nozzle, generally indicated as  20 .  
         [0023]     Referring to the more detailed view of  FIG. 2 , it can be seen that, in addition to foam generator nozzle  20 , foam generator  10  comprises a source of compressed air  22  and a foam liquid source  24 . The source of compressed air  22  may be powered by an engine  26 , as illustrated. Alternatively, the source of compressed air may be powered by a power take off from tractor  14 . A pump (not shown) is also provided for the purpose of supplying foam liquid to the foam generator nozzle  20  through liquid conduit  28 . Compressed air is delivered to foam generator nozzle  20  through air conduit  30 .  
         [0024]     It is to be understood that while the views of  FIGS. 1 and 2  provide for a single foam generator nozzle  20 , the scope of the present invention is not to be limited thereby. Dependent upon operating conditions and the type and spacing of the particular agricultural crop being foamed, foam generator  10  may comprise a plurality of foam generator nozzles  20 , with each such nozzle  20  operatively connected to the source of compressed air  22  and the foam liquid source  24 , preferably in a parallel arrangement. It is also to be understood that depending upon the number and size of the foam generator nozzles  20  that are operatively mounted on a foam generator  10 , the use of booster pumps, or similar delivery devices, for the foam liquid and the compressed air may be added in accord with well-known techniques.  
         [0025]     Turning to the views of  FIGS. 3 and 4 , structural details of the preferred foam generator nozzle  20  are provided. According to the preferred embodiment shown in  FIGS. 3 and 4 , foam generator nozzle  20  comprises a substantially cylindrical nozzle body  32  having a proximal end  34  and a distal end  36 , to define an interior volume there between. The inside diameter of nozzle body  32  is about  6  inches, and the axial distance between proximal end  34  and distal end  36  is slightly more than 10 inches. Of course, these precise dimensions are not to be interpreted as limiting factors on the scope of the present invention.  
         [0026]     Operatively attached to nozzle body proximal end  34  in fluid-delivery relation to the interior volume of nozzle body  34  is a venturi nozzle  38 . As perhaps best seen in the view of  FIG. 4 , venturi nozzle  38  comprises a venturi throat  40  having a first end  42  operatively connected to the source of compressed air  22  by air conduit  30  and air delivery fitting  44 . Compressed air from compressed air source  22  passes through venturi throat  40 , past venturi throat discharged end  46 , and into the interior volume of nozzle body  32 , as indicated by the directional arrows A in  FIG. 4 .  
         [0027]     Referring to the sectional view of  FIG. 5 , one can see that first end  42  of venturi throat  40  further comprises a plurality of ambient air ports  48  whereby ambient air is also drawn through venturi throat  40  to the interior volume of nozzle body  32 . Support arms  50  are provided for the purpose of attaching air delivery fitting  44  to first end  42 .  
         [0028]     Returning to the sectional view of  FIG. 4 , further details of the nozzle body  32  are provided. As shown in that figure, a liquid nozzle  52  is operatively disposed within the interior volume of nozzle body  32  downstream from nozzle body proximal end  34 . Liquid nozzle  52  comprises a foam liquid receiving end  54  and a foam liquid spray end  56 . Foam liquid spray end  56  further comprises a spray tip  58  that preferably emits a substantially solid, conical spray  60  of foam liquid. The intimate mixture of the flow of compressed and ambient air A, indicated by arrows with spray  60  creates a first foam that impinges upon first fluid dispersion medium  62 .  
         [0029]     As the first foam passes through first fluid dispersion medium  62  by the excess pressure created within the interior of nozzle body  32  the foam bubbles are further broken down, resulting in the formation of a second foam downstream from the first fluid dispersion medium  62 . In this preferred embodiment, first fluid dispersion medium  62  comprises a substantially circular #81 nylon screen. It is to be understood that neither this precise material nor screen size is intended to limit the scope of the present invention, for other similar materials of appropriate size would also be useful.  
         [0030]     Downstream from first fluid dispersion medium  62 , and still within the interior volume of nozzle body  32  is placed a second fluid dispersion medium  64 . According to the preferred embodiment, second fluid dispersion medium comprises of substantially circular #104 nylon screen. Of course, as already indicated above, the scope of this invention is not to be limited to that particular material, nor that precise screen size. However, it is important that the apertures through the second fluid dispersion medium  64  be smaller than the apertures through the first fluid dispersion medium  62 . Thus, as the second foam passes through second fluid dispersion medium  64 , the bubbles are further broken down to result in the formation of the substantially dry foam  18  of the present invention. Dry foam  18  is dispensed as indicated by arrows B.  
         [0031]     Having thus set forth a preferred construction for both the foam generator  10  and the foam generator nozzle  20  of the present invention, attention is now invited to the operating parameters which are significant in proper use of this invention to generate an acceptable substantially dry foam  18  used for frost prevention.  
         [0032]     First, it is to be understood that both the operating pressure and flow rate of foam liquid and compressed air are important for the formation of a substantially dry form  18 . This is particularly true because, unlike current, state of the art foam generators, it is the compressed air and ambient air that are passed through venturi nozzle  38  to impinge and mix with conical spray  60  of the foam liquid, rather than passing the liquid through a venturi. Acceptable operating pressures for the compressed air fall in the range of from about 2 psi to about 20 psi, and acceptable flow rate for compressed air is from about the 14 cfm to about 221 cfm. With regard to the foam liquid, the liquid is delivered to liquid nozzle  52  at a pressure of from about 100 psi to about 300 psi, and at a flow rate of about 0.22 gpm to about 1.02 gpm. Spray tip  58  comprises a spray aperture of from about 0.031 inches to about 0.063 inches. In this preferred embodiment, spray tip  58  is centrally disposed along the axis of the interior of nozzle body  32  approximately 6 inches downstream from discharge end  46  of venturi throat  40 . First fluid dispersion medium  62  is approximately 4 inches downstream from spray tip  58 , and second fluid dispersion medium  64  is approximately 2 inches downstream from first fluid dispersion medium  62 .  
         [0033]     According to a second preferred method for generating dry foam  18 , compressed air is delivered to first end  42  of venturi throat  40  at a pressure of from about 3 psi to about 11 psi, and at a flow rate of about 35 cfm to about 48 cfm. Foam liquid is delivered to liquid nozzle  52  at a pressure of from about 100 psi to about 300 psi, and at a flow rate of about 0.3 gpm to about 1.02 gpm.  
         [0034]     A third preferred set of operating parameters comprises delivering compressed air to first end  42  of venturi throat  40  at a pressure of about 3 psi to about 5 psi, and at a flow rate of about 35 cfm. In this third preferred embodiment, foam liquid is delivered to liquid nozzle  52  at a pressure of about 300 psi, and at a flow rate of about 0.5 gpm. The spray aperture of spray tip  58  is about 0.036 inches. Utilizing this third preferred operating embodiment, foam generator  10  will produce about 700 gpm of substantially dry foam  18 .  
         [0035]     It will thus be seen that the objects set forth above, among those made apparent from the preceding description are efficiently attained, and since certain changes may be made in the construction set forth and in carrying out the above method without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrated and not in a limiting sense.  
         [0036]     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall there between.  
         [0037]     Now that the invention has been described,