GB2093732A - Spraying system - Google Patents

Abstract

Apparatus for electrostatic spraying of liquid pesticides from a vehicle comprises a coupling 12 for receiving a container 10 and a system for conveying liquid therefrom to one or more sprayheads 16, the system including flow control means (such as an electrically-controlled pump 14 or a valve) responsive to means carried by the container, so that liquid can only flow when the correct container is correctly installed. On installing the container pairs of contacts are connected so that the correct voltage can be applied (via preset variable resistance 36). Further contacts complete a circuit to high voltage generator 20 connected to the nozzles 16, which are of electrically- conducting plastics. A system for automatically mixing two liquids and/or a diluent is also described (Fig. 3, not shown), as are systems for indicating malfunctions such as a blockage or short-circuit, (Figs. 4, 5, not shown). <IMAGE>

Description

SPECIFICATION Spraying system The present invention relates to spraying systems, and more particularly to spraying systems for use in applying agricultural chemicals, e.g. pesticides, to land or to crops or weeds growing therein.

In nearly every country of the world, agricultural spraying of land or crops is widely carried out, frequently from a vehicle such as a tractor or an aircraft. Spraying is usually carried out using an active ingredient (e.g. a herbicide) dissolved or disposed in a diluent (e.g. oil or water). Thus, a tractor may carry a spraytank pulled with water, into which a concentrated liquid or powder formulation of the active ingredient is poured and mixed prior to spraying.

This arrangement has drawbacks. Pesticide active ingredients are frequently toxic to man to a greater or lesser Patent, particularly in concentrated form. Thus, in some cases, emptying a concentrated pesticide formulation into a spraytank can represent a hazard, in particu lar to unskilled or poorly trained operators. It is also possible for such operators to make mistakes in the dilution procedure, by putting in either too little pesticide (perhaps in consequence leaving 2 crop unprotected) or too much (which is wasteful and could damage a crop or the enviroment).

There is in consequence a need for spraying systems which do not involve dilution of concentrated pesticides by the operator. In such systems, either the pesticide formulation is not diluted at all (as is now sometimes done, for example, in uitra-low volume spraying of insecticides from a rotary atomiser, and has also been proposed for certain electrostatic spraying systems) or it is diluted automatically e.g. by being detered into a stream of diluent from a diluent storage tank carried on the tractor. Now a practical sprayer requires to be able to spray pesticides of several different kinds.

Some pesticides are conveniently formu- lated more concentrated than others, or need to be applied at lower rates. Thus the rate at which liquid flows through the sprayer to the sprayhead generally needs to be controllable.

It may of course be controlled manually, by some device or other, but this may sometimes lead to operator error.

The present invention is particularly (though not solely) applicable to electrostatic agricultural spraying, which has particular advantages. Thus it provides more even cover of plants with much improved cover of under leaf surfaces; reduces drift and contamination of the environment; and often enables lower rates of pesticide to be applied than are effective with uncharged sprays. It may be found, however, best to vary the applied voltage varied according to the nature of the pesticide formulation it is desired to apply.

The present invention provides a system for spraying pesticides in whch manual dilution (with consequent operator hazard and possibly diltution errors) is avoided and the delivery rate of pesticide to spray nozzles may if desired be completely automatically determined.

According to the present invention we provide apparatus for spraying of liquid agrochemical formulations from a vehicle which comprises: container coupling means for receiving a container for said liquid; at least one sprayhead for discharging said liquid; a delivery system for conveying liquid from the container via the coupling means to the sprayhead; and flow control means for said delivery system, said flow control means being responsive to signal means carried on the container. In a preferred embodiment, means are provided to charge electrostatically liquid emerging from the sprayhead; and these charging means may also be responsive to signal means carried on the container.

We further provide, for use in such spraying apparatus a liquid container adapted to be mounted on a vehicle, having a mouth for delivering liquid, coupling means for holding the mouth in fluid-tight engagement with coupling means carried on the vehicle, and carrying signal means disposed to actuate flow control operating means carried on the vehicle.

The flow control means may take various forms. It may, for example, be a variable valve, for example a mechanical valve, such as a stopcock or iris, operated by electromagnetic relay. Another suitable type of valve, particularly readily operable by electronic control, is a variable electrostatic valve of the type described in our copending European Patent application no. 80302767. One particularly convenient form of control means is a variable flow-rate metering pump. Such a pump may suitably be electrically driven, e.g. from an electrical power supply on the vehicle, and its speed is then readily controlled by electrical or electronic means controlling the power of frequency of the electrical supply to the pump.A metering pump, though more complex than a variable valve, can control liquid delivery more accurately since it does not depend on gravity to propel the liquid.

In one fsrm of the invention, the signal means on the container comprises a coded signal which is sensed by the flow control means and which determines how the flow control means activates the delivery system. It may also determine how the changing means is activated. The coded signal may produce a range of effects. It may simply act as an 'on' switch, so that the machine will only work where the signal received has a predetermined value. The system may be designed to provide several different combinations of flow rate through the delivery system and voltage from the high potential source corresponding to different values of the coded signal on the container.The system may also be designed to vary voltage, or flow rate, or both, continuously between minimum and maximum values according to corresponding variation in the value of the coded signal (or signals). Coded signals may be provided in various forms, e.g.

mechanical, electrical, magnetic or optical.

The signal means on the container may control the flow control means by providing to it an elelctrical signal. This electrical signal may be used (either directly or after amplification) to operate the high potential source, or the liquid delivery system, at outputs corresponding to the magnitude of the signal.

A specific embodiment of the invention will now be described with reference to the drawing, in which Figure 'is a schematic diagram of a system according to the invention in operation Figure 2 is a vertical section through a spray nozzle Figure 3 is a schematic diagram of a second type of spraying system according to the invention Figure 4 shows diagrammatically a sprayhead malfunction detector circuit Figure 5 shows diagrammatically a second type of sprayhead malfunction detector circuit.

The system is mounted on a tractor (not shown). It comprises a demountable container 10 of about 25 litres capacity. A male scrnw- thread coupling 11 on the neck of the container 10 cooperates to give a liquid-tight seal with corresponding female screw-thread coupling means 1 2 carried on the tractor and forming part of the liquid distribution system 1 3. Liquid delivery system 1 3 leads from coupling means 1 2 via an electrically operated metering pump 14 to a spray boom 1 5 carrying a number of nozzles 16. The construction of these is shown in more detail in Fig. 2.Each nozzle is surrounded by an annular electrode 26 which is earthed. The body of each nozzle is made of electrically conducting plastic, and is electrically connected via leads 1 7 to a junction-box 18, which communicates via high-tension lead 1 9 with one high voltage output terminal 21 of high-voltage generator 20. Generator 20 is powered from the 12-volt tractor battery 22 via the container 10.

The positive pole of the tractor battery 22 is connected, via switch 23, to a contact 24 carried on the tractor. This abuts a contact 25 on the container, which connects via a variable resistance 26 to the contact 27 on the container abutting a contact 28 carried on the tractor. Contact 28 is connected via lead 29 to an input terminal of generator 20. By a similar arrangement, pump 14 is powered from battery 22 via container 10. A lead 30 conveys current from battery 22 via switch 23 to a contact 31 carried on the tractor. This abuts a contact 32 on the container, which connects via a variable resistance 36 to a contact 33 on the container which abuts a contact 34 on the tractor. A lead 35 connects contact 34 to pump 14.

In operation, the container 10 is supplied from the manufacturer, having been filled with a suitable organic liquid pesticide formulation and sealed under safe factory conditions. At the factory the variable resistances 26 and 36 are adjusted to values suitable to the liquid in the container. This is conveniently carried out in a way which prevents the customer subsequently changing the setting; e.g. the resistances 26 and 36 may be adjustable only from inside the container. At the site where spraying is to be carried out, the container 1 0 is mounted on the tractor, unsealed and coupled to the liquid delivery sys tem 1 3 via couplings 11 and 1 2, ensuring that the four sets of contacts (24,25; 27,28; 31,32; 33,34) are in contact.The tractor is then driven past the crops it is desired to spray, and the switch 23 closed. This activates the pump 14 and the generator 20, the output of both being controlled to the desired degree by control of the current supplied to each, which is a function of the setting of resistances 26 and 36. Spray is conveyed to nozzles 1 6 by the action of pump 14, where the the spray is charged by direct contact at the potential delivered by generator 20. Spray leaving the nozzles 1 6 breaks up into electrically charged droplets under the action of the electrostatic field between nozzles 1 6 and earthed electrodes 26, and is attracted to the plants to be treated.

In the system described with reference to Fig. 1, the contents of container 10 are sprayed without further dilution. Fig. 3 shows a tractor-mounted system in which dilution takes place; this however is carried out automatically, without the need for any manual mixing and consequent risk of errors or accidents. The system of Fig. 3 comprises a reservoir 1 55 for an oil diluent (e.g. diesel fuel) for delivering diluent via a tap 1 56 to a mechanical pump 1 57 driven by the tractor power take-off. Two containers 158, 159 of generally similar type to that shown in Fig. 1 contain concentrated organic liquid pesticide formulations and are connected via couplings 160, 161 to metering pumps 164, 165 which serve to inject pesticide into the diluent stream at 166, 167. From here the diluted pesticidal formulation passes to a boom 1 68 carrying electrostatic sprayheads 1 69 of the same type as shown in Fig. 1. The sprayheads 1 69 are connected to one high-voltage terminal of a high-voltage generator 170, powered by the tractor battery 171. No provision for varying the output voltage of generator 1 70 is illustrated, though such may readily be provided if required. Metering pumps 164, 1 65 are also powered from battery 1 71 via variable resistances 172, 1 73 mounted on containers 1 58 and 1 59, in the same way as battery 22 powers pump 14 in Fig. 1.In operation, the rate at which pesticide from containers 158, 1 59 is controlled by the current provided to pumps 164, 1 65, which in turn is controlled by the setting of resistances 172, 173, without the need to make up special formulations. To spray two different incompatible pesticides, the flows from containers 1 58 and 1 59 may be directed to separate sprayheads. To spray an aqueous liquid pesticide formulation, use may be made of the electrostatic system for forming and spraying emulsions described in our copending unpublished UK patent application 8102823 of 38 Januar, 1981 entitled 'Spraying Emulsions'.

Systems such as that shown in Fig. 3, containing a separate source of diluent, may conveniently be made to flush pesticide out of the nozzles and liquid delivery system, using pure diluent. The system is thereby cleaned for re-use with different pesticides. Sueh flushing may be made automatic.

In our invention, it is not necessary that flow through the liquid delivery system be determined uniquely by the signal means car ried on the container. It is possible, for example, for the signal means to determine a base value for the flow rate, corresponding to a standard vehicle forward speed. Means may then be supplied to sense the actual forward speed of the spray vehicle and vary the flow rate from ths standard to compensate for variations from the standard forward speed, in such a way that the amount of pesticide delivered per unit area remains constant over a range of forward speeds. Speed may be sensed by the rotation rate of a vehicle wheel, or by doppier sound or radar measurements.

It is also possible to provide means for the spray operator to vary the standard flow rate, eg in exceptional circumstances. For example, a crop heavily infested with pests may be usefully sprayed at 150% or 200% of the normal rate; and a lightly infested one at 50 or 75% of the normal rate.

Means may be provided to detect malfunctioning of the electrostatic sprayheads used in the invention. One such possible means is shown schematically in Fig. 4. In the lead 100 conveying high potential from generator 99 to sprayhead 101, a high resistance 102 (say 1 megohm) is inserted. Means 103 are provided for sensing the potential drop across this resistance. Using a voltage of about 20 KV, and a liquid charging current of avout 2 micro amperes per nozzle, the potential drop across resistance 102 will be about 2 volts. if sprayhead 101 becomes wholly or partially blocked, the current will stop or reduce and the voltage will drop correspondingly. If there is a short circuit, e.g. between sprayhead 101 and earthed electrode 104, current and voltage will increase.Accordingly a control circuit 105 is provided to compare the potential drop sensed by means 1 03 with standard satisfactory limits, and if these are exceeded circuit 105 lights a warning light 106 in the tractor driver's cab. This tells the driver that one sprayhead is not operating correctly (and which it is). In mechanical spraying systems, sprayhead blockages may go undetected for substantial periods, and lead to crop loss through failure to apply correct rates of pesticide. A second possible means for detecting malfunctioning is shown in Fig. 5.A probe 110 adjacent a sprayhead nozzle 111 has a charge induced on it which depends on the charge on the liquid leaving the nozzle 111, This charge is sensed by a field-effect (high input impedance) transistor 11 2. A circuit 11 3 is provided to compare the charge sensed by the transistor 4 11 2against an ap- propriate range of standard values, and if the range is exceeded to light a warning light 114 in the tractor-driver's cab. Here a nozzle blockage will reduce the charge induced on probe 110, as will any reduction in the voltage supplied to nozzle 111.

If desired, signals from detector means of the type shown in Fig. 4 or Fig. 5 (or both) may be combined, and means responsive to variations in the combined signal may be provided to vary the flow through the delivery system until the combined signal is within pre-set limits. Alternatively or additionally, means responsive to such variations may be provided to vary the voltage from the high potential system until the combined signal is within pre-set limits.

Fig. 2 is a detail, in vertical section, of an electrostatic sprayhead used in the invention.

It comprises a nozzle 60 having a liquid outlet or mouth 64 in the fsrm of an annular gap between an outer hollow cylinder 61 formed from conductive plastics and an inner solid cylinder 62 formed from conductive plastics.

Around nozzle 60, and behind the mouth 64, an annular electrode 65 of bare metal is symmetrically disposed.

As an added safety measure to prevent refilling with concentrated toxic materials by spray operators under potentially hazardous conditions, the containers of our invention may include a device preventing re-use. Such a device may be of a type that has to be re-set at the factory once the container has been emptied, e.g. a fuse in the lowest part of the container which overheats and blows when no longer covered with liquid. It may be somewhat more complex, eg a device measuring liquid flow rate out of the container, which, after the container has been emptied, modifies the signal means to cause the control means to stop operation of the delivery system.

If desired, the delivery system may include one or more electrostatic valves of the type disclosed in our European Patent application No 80302767.

Liquids sprayed by the process of our invention may be solutions, emuisions, or freeflowing suspensions of finely-divided solids in liquid. Instead of the annular nozzles shown in the drawings, it is possible to use one or more linear sprayheads, eg of the type shown in our UK Patent 1569707 (Figs 12-14).

Claims (16)

1. Apparatus for spraying of liquid agrochemical formulations from a vehicle which comprises: container coupling means for receiving a container for said liquid; at least one sprayhead for discharging liquid from the container via the coupling means to the sprayhead; and flow control means for said delivery system, said flow control means being responsive to signal means carried on the container.

2. Apparatus as claimed in claim 1 wherein means are provided to charge electrostatically liquid emerging from the sprayhead.

3. Apparatus as claimed in claim 2, wherein the electrostatic charging means are responsive to signal means carried on the container.

4. Apparatus as claimed in any of claims 1 to 3 which comprises coupling means for receiving at least two containers; each such coupling means leading to a liquid delivery system having flow control means responsive to signal means on the container coupled thereto.

5. Apparatus as claimed in any of claims 1 to 4 which additionally comprises a diluent reservoir for introducing spray diluent or flushant into the liquid delivery system.

6. Apparatus as claimed in any of claims 1 to 5 wherein the flow control means comprises a variable flow rate metering pump.

7. Apparatus as claimed in any one of claims 1 to 6 in which the signal means are sensed electrically by the operating means.

8. Apparatus as claimed in claims 2 or 3 wherein one or more of the sprayheads is provided with an electrical sensor for detecting malfunctioning of the sprayhead.

9. Apparatus as claimed in claim 8 wherein the electrical sensor comprises a means for detecting the potential drop across a high resistance in series with the sprayhead charging electrode.

10. Apparatus as claimed in claim 8 wherein the electrical sensor comprises a field effect transistor for sensing the charge induced on a probe adjacent the sprayhead.

11. Apparatus as claimed in any of claims 8 to 10 wherein electrical signals from the electrical sensor are displayed in the vehicle driver's cab.

1 2. A liquid container suitable for use with the apparatus of claim 1 and adapted to be mounted on a vehicle, having a mouth for delivering liquid, coupling means for holding the mouth in fluid-tight engagement with coupling means carried on the vehicle, and carrying signal means disposed to actuate flow control operating means carried on the vehicle.

1 3. A liquid container as claimed in claim 1 2 in which the signal means provide an electrical signal, and one or more electrical contacts are provided on the container for engagement with corresponding contracts carried on the vehicle.

14. A liquid container as claimed in claim 13, in which the electrical contacts include a contact for receiving electrical power from the vehicle.

1 5. A liquid container as claimed in any of claims 1 2 to 14 which additionally comprises signal means arranged to determine the electrical potential of electrostatic sprayheads carried on the vehicle.

16. Apparatus for spraying of liquid agrochemical formulations from a vehicle which comprises: container coupling means for receiving a container for said liquid; at least one sprayhead for discharging said liquid; a liquid delivery system for conveying liquid from the container via the coupling means to the sprayhead; and flow control means for said delivery system, said flow control means responsive to signal means carried on the container; and means for charging electrostatically liquid emerging from the sprayhead, said charging means being responsive to signal means carried on the container.