GB1561642A

GB1561642A - Liquidspray devices

Info

Publication number: GB1561642A
Application number: GB3100075A
Authority: GB
Original assignee: NAT RES DEV; National Research Development Corp of India
Current assignee: NAT RES DEV; National Research Development Corp of India
Priority date: 1975-07-24
Filing date: 1975-07-24
Publication date: 1980-02-27
Also published as: DE2633216A1; DE2633216C2

Description

(54) IMPROVEMENTS IN AND RELATING TO LIQUID SPRAY DEVICES (71) We, NATIONAL RESEARCH DEVEL OPMENT CORPORATION, a British Corporation established by Statute, of Kingsgate House, 66-74 Victoria Street, London, S.W.1., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to liquid spray devices and more particularly to those devices in which liquid is emitted from an orifice in the form of a thin sheet which subsequently breaks down to form droplets. The sheet can be flat in form, for example fan shape, or in the shape of a hollow cone. Generally, in known spray devices, the liquid sheet interacts with the surrounding atmosphere and waves are produced which grow to critical amplitudes with the result that there is a random fragmentary disintegration yielding a spray with a wide spectrum of drop sizes.

Generally there are large numbers of small droplets which are very easily dispersed in a moving atmosphere and, especially in the case of agricultural sprays when the liquid is highly likely to consist of or to contain materials such as toxic chemicals or fertilisers, such dispersal can cause serious drifting of these materials out of the control of the operator.

Many attempts have been made to design spray nozzles or to produce liquid formulations to minimise this danger of drift and the present invention makes another contribution to environmental pollution control by aiming at controlling the minimum droplet size and/or the numbers of small droplets.

Although emphasis is laid, herein, particularly on liquid spraying for agricultural and/ or horticultural purposes, it is envisaged that the invention may be of use under any conditions when control of the drop size of the sprayed liquid is paramount.

The present invention arises from the discovery that by subjecting the spray to an appropriate atmosphere, close to the nozzle, the break-down of the sheet may be caused to occur earlier than it otherwise would, and that this early break-down apparently leads to the formation of droplets mostly of a size having little tendency to drift at least in lightly moving atmospheres.

It is believed that use of such an atmosphere according to the present invention, inhibits the wave growth in the sheet of liquid.

The rapid breakdown of the sprayed sheet is additionally advantageous in that sprays may be produced at lower pressures than would be necessary to produce a useful spray otherwise. Thus, whereas for a standard nozzle it has been useful for pressures of 30 psig to be necessary for spraying crops or land with agrochemicals, by use of the invention has enabled effective spraying to be achieved with pressures of only 20 psig and even below.

The invention is defined by the claims at the end of this specification and will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 shows a spray head incorporating a swirl chamber and having means for supplying a hot gas atmosphere externally; Figure 2 shows a similar kind of spray head with a head to which a hot gas atmosphere is supplied; Figure 3 shows a different form of spray head with internal supply arrangements for the hot gas atmosphere; Figure 4 shows a similar form of spray head to that shown in Figure 3, but with internal hot gas ducting permitting a hot gas atmosphere to emerge within the spray sheet; Figure 5 includes a partly expolded view of a form of hot gas generator suitable for use in combination with the spray bar of standard spraying equipment; Figure 6 illustrates a version of the invention particularly suited to spraying from airborne equipment, and Figures 7 to 9 show various forms of hoods for attachment to spray heads for the purpose of directing hot gas from a supply tube into the environment of the spray sheet.

In each of the examples shown in Figures 1 to 4 a spray head 1, for use for instance in spraying agrochemicals onto crops or land through an ordinary air atmosphere comprises an end wall 2 in which a suitably shaped orifice 3 is formed from the outer edge of the orifice a thin, hollow conical sheet 4 of liquid is emitted as the result of the disposition of swirl slots 5 which lead the liquid from supply chamber 6 to a swirl chamber 7.

In the case of Figure 1, a "second atmosphere" comprising hot combustion gas is led to the vicinity of orifice 3 through a tube 8. In one particular example of the use of this embodiment it has been found that successful spraying with acceptable drift control can be achieved with gases from a methane burner emerging at a temperature of the order of 300-4000"C and at a spraying pressure of about 20 psig or less using a standard nozzle, such as the "Blue" fertiliser nozzle or the "Green" herbicide nozzles supplied by J.W.

Chafer Ltd. Such an arrangement is particularly suited for use on a multi-spray boom pipe for mounting on a tractor, or on an aircraft with screening from wind currents, the pipe being provided with hot gas tubes extending from it.

For example, as illustrated in Figure 5, a hot gas outlet 20 may be associated with a common supply pipe 21, from which air supplies can be taken at different points for association with gas outlets for each spray head. The outlet 20 is formed on a combustion chamber portion 22 of a burner 23 comprising a propane pilot jet 24 (Size No. 6, Model 2001). Propane is fed through inlet tube 25 connected by flexible tubing 26 to a supply of liquefied propane which may take the form of an ordinary domestic container. The burner is completed by the igniter 27 which is energised by current through the wires 28, 28a the latter of which is earthed to the burner body through a metal strip 29. Other gases may, of course, be used for the burner and gauzes may be found to be necessary upstream and/or downstream of the burner jet.

The hot gas outlet 20 may be connected to tube 8 which is arranged to play on to the outside of the spray sheet as indicated in Figure 1.

The gas velocity is controlled so that it does not reach values such that the spray sheet is deformed because, in that case, the small droplets will tend to reappear. Where spraying with a standard nozzle (see above) at 20 psig or less, it was found to be desirable for the maximum gas velocity to be about 4 metres per second. It may be found desirable to surround the spray sheet with a hood such such as shown in any one of Figures 7 to 9. As shown each form of hood has a radially extending connecting tube and has a fixation hole by the edge of which the hood is secured to the spray lens. In Figure 7 the hood comprises a flat circular disc with an edge flange at right angles to the disc. It will be understood that the edge flange can be deeper. In Figure 8 the hood is of conical shape and in Figure 9 there are two flat discs, the hole in the disc opposite to the spray head fixation hole being of larger diameter than the fixation hole to surround the spray sheet.

As an alternative adaptation of the arrangement indicated in Figure 1, the tube 8 could be connected to a common feeder into which the exhaust system of a tractor engine or of an aircraft engine could vent. Such common feeder can be a pipe which is adapted to be swung into position as required and may form an integral structure with a spray bar for the purpose. It appears to be advantageous to provide thermal insulation for such a feeder and its connections and interconnections, especially if the spray bar were to be mounted on a purpose-built spraying machine which has to be towed by a tractor; in such a case the length of the common feeder pipe would be greater than for a tractor borne spray bar.

Provision will probably be required for the injection of water or water vapour into the exhaust gas stream particularly in view of the rather lean fuel-air mixtures generally employed in tractor diesel engines.

In the arrangement of Figure 2, the head 1 has a hood 9 which engages the outer wall of the spray head and has a supply connection 10 for the supply of hot combustion gas to the space between the hood and the head. The gas emerges through the opening 11, which is of diameter commensurate with the size of the spray 4 at the particular point.

In the arrangement of Figure 3, a duct 12 is provided within the head 1; the outlet 13 from the duct in this arrangement allows hot combustion gas to be introduced within the space bounded by the hollow, conical spray sheet 4. It will be appreciated that in this configuration the size of the outlet 13 will allow only relatively small quantities of hot gas to pass and this may be limiting for certain applications.

The arrangement of Figure 4 is similar to that shown in Figure 3 but the outlet 14 from the duct 12 is extended through the spray orifice 3 so that the hot combustion gas emerges within the space bounded by the spray sheet. In this arrangement, one or more slots may be provided at the end of the outlet 14 to deflect the stream of gases directly on to the spray sheet but it should be understood that this may not be necessary since breakdown of the sheet may be obtained without direct deflection. The same consideration applies to the size of the outlet as with the arrangement of Figure 3 and this, again, may be a limitation for certain applications.

Although reference has been made above, generally, to airborne spraying equipment embodying the invention, one embodiment which is particularly useful for that purpose is illustrated in Figure 6 of the accompanying drawings, in which a hollow conical spray sheet 30 is shown emerging from a head 31 and in this embodiment a tube 32 connects with a burner outlet 33. The tube 32 passes through the spray sheet and, if desired, a heat insulating ceramic covering tube 34 may be provided but, being relatively small, even with the insulating cover, little effect is evident on the efficiency of the spray. The insulation will avoid undue cooling of the hot gases which emerge from the end of the tube 32 into the interior of the spray sheet. In order to avoid the tendency of the spray liquid to coalesce on the insulator and to form large drops, the interior can be shaped to present a somewhat streamlined surface to the spray. Alternatively the tube 32 may be formed with a longer portion extending axially of the spray sheet so that penetration of the sheet takes place at a greater distance from the spray orifice. Yet again, merely coating the insulator with a non-wettable surface may be satisfactory.

If the chosen design of head 31 includes sufficient screening, it may be found that such an arrangement will be satisfactory for mounting on an airborne spray bar. However, if necessary, additional screening may be provided by a hood 35 carried by the head 31.

This hood is shown in the drawing as of gauze supported by a flanged disc 36 and in the configuration shown, with gauze of B.S.

mesh size 29 and wires 0.010 in. diameter, the arrangement has enabled agrochemical spraying to be effective in air currents equivalent to an air speed of about 110 miles per bour.

The "second atmosphere" may comprise changed species, and these into a stream of gas by directing the stream through an electric spark discharge or in the neighbourhood of an electric arc Further means of introducing charged species will be apparent as will other possible embodiments of the invention.

It may be possible that the temperature of the gas, referred to as hot, need be a matter of only a few degrees, say 30 to 40"C, above that of the immediate environment of the orifice in some instances. In general a minimum temperature of about 50"C is appropriate.

WHAT WE CLAIM IS:- 1. A device for spraying liquid in droplet form through a first atmosphere onto receiving surfaces and comprising: An orifice; Means to emit liquid from that orifice in the form of a thin sheet of the kind that, in the absence of further treatment, breaks down after a time interval within the first atmosphere into droplets falling within a spectrum of sizes; Means to create a second atmosphere; Means to subject the sheet to such further treatment by contacting it close to the orifice with the second atmosphere, whereby the sheet is not instantly broken up but a shorter time interval is required for the breakdown of the sheet into droplets and the proportion of small droplets within that spectrum of sizes is diminished, and Outlet means for discharging the liquid from the device so that it may proceed towards the receiving surfaces.

2. A device for spraying liquid, according to Claim 1, in which the second atmosphere comprises hot gas.

3. A device for spraying liquid, according to Claim 2, in which the second atmosphere also comprises charged species.

4. A device for spraying liquid, according to Claim 3, in which the charged species are introduced by passing the hot gas through an electric spark discharge, or in the neighbourhood of an electric arc.

5. A device for spraying liquid, according to Claim 2, in which the hot gas is derived from the combustion of a fuel.

6. A device for spraying liquid, according to Claim 5 and including a fuel burner for the local combustion of the fuel from which the hot gas is derived.

7. A device for spraying liquid, according to Claim 2 and in combination with a vehicle upon which the device is mounted, in which the hot gas is derived from the exhaust gases of the vehicle, and in which ducting is provided to conduct at least part of those gases so that they contact the emitted sheet of liquid close to the orifice.

8. A device for spraying liquid, according to Claim 1, in which a hood is provided for at least the initial part of the spray sheet.

9. A device for spraying liquid according to Claim 8, in which the hood is of simple flanged disc shape.

10. A device for spraying liquid, according to Claim 1, in which the emitted sheet of liquid follows the outline of a hollow cone.

11. A device for spraying liquid, according to Claim 10, in which the means to contact the sheet with the second atmosphere is positioned to deliver that atmosphere within the interior of the cone formed by the hollow sheet.

12. A device for spraying liquid, according to Claim 11, in which the means to contact the sheet with the second atmosphere passes through the conical spray sheet.

13. A device for spraying liquid, according to Claim 12, in which heat insulation is carried by the portion of said means which passes through the conical spray sheet.

14. A device for spraying liquid, according to Claim 10, in which at least those parts of the conical sheet closest to the orifice are surrounded and protected by a conical hood.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. illustrated in Figure 6 of the accompanying drawings, in which a hollow conical spray sheet 30 is shown emerging from a head 31 and in this embodiment a tube 32 connects with a burner outlet 33. The tube 32 passes through the spray sheet and, if desired, a heat insulating ceramic covering tube 34 may be provided but, being relatively small, even with the insulating cover, little effect is evident on the efficiency of the spray. The insulation will avoid undue cooling of the hot gases which emerge from the end of the tube 32 into the interior of the spray sheet. In order to avoid the tendency of the spray liquid to coalesce on the insulator and to form large drops, the interior can be shaped to present a somewhat streamlined surface to the spray. Alternatively the tube 32 may be formed with a longer portion extending axially of the spray sheet so that penetration of the sheet takes place at a greater distance from the spray orifice. Yet again, merely coating the insulator with a non-wettable surface may be satisfactory. If the chosen design of head 31 includes sufficient screening, it may be found that such an arrangement will be satisfactory for mounting on an airborne spray bar. However, if necessary, additional screening may be provided by a hood 35 carried by the head 31. This hood is shown in the drawing as of gauze supported by a flanged disc 36 and in the configuration shown, with gauze of B.S. mesh size 29 and wires 0.010 in. diameter, the arrangement has enabled agrochemical spraying to be effective in air currents equivalent to an air speed of about 110 miles per bour. The "second atmosphere" may comprise changed species, and these into a stream of gas by directing the stream through an electric spark discharge or in the neighbourhood of an electric arc Further means of introducing charged species will be apparent as will other possible embodiments of the invention. It may be possible that the temperature of the gas, referred to as hot, need be a matter of only a few degrees, say 30 to 40"C, above that of the immediate environment of the orifice in some instances. In general a minimum temperature of about 50"C is appropriate. WHAT WE CLAIM IS:-

1. A device for spraying liquid in droplet form through a first atmosphere onto receiving surfaces and comprising: An orifice; Means to emit liquid from that orifice in the form of a thin sheet of the kind that, in the absence of further treatment, breaks down after a time interval within the first atmosphere into droplets falling within a spectrum of sizes; Means to create a second atmosphere; Means to subject the sheet to such further treatment by contacting it close to the orifice with the second atmosphere, whereby the sheet is not instantly broken up but a shorter time interval is required for the breakdown of the sheet into droplets and the proportion of small droplets within that spectrum of sizes is diminished, and Outlet means for discharging the liquid from the device so that it may proceed towards the receiving surfaces.

15. A method of spraying liquid in droplet

form through a first atmosphere onto receiving surfaces, in which the liquid is emitted from an orifice in the form of a thin sheet that would in the absence of further treatment break down after a time interval into droplets falling within a spectrum of sizes, but in which the sheet is subjected to such further treatment by contacting it close to the orifice with a second atmosphere whereby a shorter time interval is required for the breakdown of the sheet into droplets and the proportion of small droplets within that spectrum of sizes is diminished.

16. A method of spraying liquid in droplet form, according to Claim 15 and in which the second atmosphere comprises hot gas.

17. A method of spraying liquid in droplet form, according to Claim 15, in which the liquid contains an agrochemical and the receiving surfaces are agricultural crops or land.

18. A device for spraying liquid, according to Claim 1 and substantially as described with reference to the accompanying drawings.