Note: Descriptions are shown in the official language in which they were submitted.
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SPRAYING SYSTEM
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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 r a tractor may carry a spraytank filled with
water, into which a concentrated liquid or powder formul~
ation of the active ingredient is poured and mixed prior to
spraying.
This arrangement has drawbac~s. Pesticide active
ingredients are frequently toxic to man to a greater or
lesser extent, particularly in concentrated form. Thus, in
some cases, emptying a concentrated pesticide formulation
into a spraytank can represent a ha~ard, in parti.cular to
unskilled or poorly trained operators. It i5 also possible
for such operators to make mistakes in the dilution pro-
cedure, by putting in either too little pesticide (perhaps
in consequence leaving a crop unprotected) or too much
(which is wasteful and could damage a crop or the
environment).
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
iormulation is not diluted at all (as is now sometimes
done, for example, in ultra-low volume spraying of insect-
icides from a rotary atomiser, and has also been proposed
for certain electrostatic spraying systems) or it is
diluted automatically e.g. by being metered into a stream
of diluent ~rom a diluent storage tanX carried on the
tractor. ~ow a practical sprayer requires to be able to
spray pesticides of several different kinds.
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Some pesticides are conveniently formulated 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 control-
lable. It may of course be controlled manually, by s~medevice or other, but this may sometimes lead to operatcr
error.
The present invention is particularly (though not
solely) applicable to electrostatic agricultural spraying,
which has particular advantages. Thus it provides more evsn
cover of plants with much improved cover of under-lea
surfaces; reduces drift and contamination of the
environme'nt; and often enables lower rates of pesticide to
be applied than are effective with uncharged sprays. ~-' may
be found, however, best to vary the applied voltage varied
according to the nature of the pesticide formulation .t is
desired to apply.
The present invention provides a system for spraying
pesticides in which manual dilution (with consequent
operator hazard and possibly dilution 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 ror
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 sprayhed; and these charging means may
also be responsive to signal means carried on the container.
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We further provide, for use in such spraying appara.;~s
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 couplin~
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
electronic control means though an electromagnetic relay.
Another suitable type of valve, particularly readily
operable by electronic control, is a variable electrostati;
valve of the type described in our European Patent No. 25280
published 18 March 1981. One particularly convenient form
of control means is a v~riable 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 or f~equency of the electri.cal 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 form of the invertion, 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 delivary system. It may also
deterimine how the charging 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 sys~em 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,
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continuously between minimum and maximum values accordin~
to corresponding variation in the value of the coded sig~al
~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 electrical sign~'.
This electrical signal may be used (either directly or
after amplification) to operate the high potential sourc~
or the liquid delivery system, at outputs corresponding .-~
the magnitude of the signal.
A specific embodiment of the invention will now be
described with reference to the drawing, in whlch
Figure 1 is a schematic diagram of a system accordir.g
to the invention in operation
Figure 2 is a vertical section through a spray nozzl~
Figure ~ 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.
l~e system is mounted on a tractor (not shown). It
comprises a demountable container 10 of about 25 litres
capacity. A male screw-thread coupling 11 on the neck o~
the container 10 cooperates to give a liquid-tight seal
with corresponding female screw~thread coupling means 12
carried on the tractor and forming part of the liquid
distribution system 13. Liquid delivery system 13 leads
from coupling means 12 via an electrically operated
~etering pump 14 to a spray boom 15 carrying a number of
nozzles 16. ~ _ _
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The construction of these is shown in more detail in figure
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 17 to a junction-box 18, which
communicates via hi~h-tension lead 19 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 a 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 con~Jeys
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;
~0 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 10 is mounted on the tractor,
unsealed and coupled to the liquid delivery system 13 via
couplings 11 and 12, ensuring that the four sets of
contacts (24,25; 27~8; 31,32; 33,34) are in contact. The
tractor is then driven past the crops it is desired to
spray, and the switch 23 closedO
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This activates the pump 14 and the generator 20, the OUtptlt
of both being controlled to the desired degree by contrc!
of the current supplied to each, which is a function of ~he
setting of resistances 26 and 36. Spray is conveyed to
nozzles 16 by the action of pump 14, where the spray is
charged by direct contact at the potential delivered by
generator 2Q. Spray leaving the nozzles 16 breaks up into
electrically charged droplets under the action of the
electrostatic field between nozzles 16 and earthed
electrodes 26, and is attracted to the plants to be
treated.
In the system described above with reference to Fiaure
1, the contents of container 10 are sprayed without fu ther
dilution. Figure 3 shows a tractor-mounted system in which
dilution takes place; this however is carried out
automatically, without the need for any manual mixing an~
consequent risk of errors or accidents. The sysl:em of
Figure 3 comprises a reservoir 155 for an oil di].uent (e~g.
diesel fuel) for delivering diluent via a tap 156 to a
mechanical pump 157 driven by the tractor power take-of~.
Two containers 158, 159 of generally similar type to that
shown in Figure 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 ormulation passes to a boom 168
carrying electrostatic sprayheads 169 of the same type as
shown in Figure 1~ The sprayheads 169 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 genera~or 170 is illustrated,
though such may readily be provided if required. Meterin~
pumps 164, 165 are also powered from battery 171 via
variable resistances 172, 173 mounted on containers 158 and
159, in the ~ame way as battery 22 powers pump 14 in Figure
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In operation, the rate at which pesticide from containers
158, 159 is controlled by the current provided to pumps
164, 165, which in turn is controlled by the setting ~f
resistances 172,173, without the need to make up special
formulations. To spray two different incompatible
pesticides, the flows from containers 158 and 159 may be
directed to separate sprayheads. To spray an aqueous
liquid pe~ticide formulation, use may be made of the
electrostatic system for forming and spraying emulsions
described in our copending unpublished UK patent
application 8102823 of 30 January,1981 entitled 'Spra~ing
Emulsions'.
Systems such as that shown in figure 3, containing a
separate source of diluent, may conveniently be made to
flush pesticide out oE the nozzles and liquid delivery
system, using pure diluent. The system is thereby
cleaned for re-use with different pesticides. Such flushing
may be made automatic.
In our invention, it i5 not necessary that flow
through the liquid delivery system be determined uniquely
by the signal means carried 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
doppler 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 erop heavily infested with pests may be usefully
sprayed at 150% or 200% o the normal rate; and a lightly
infested one at 50 or 75% of the normal rate.
Means may be provided to detect malfunctioning o~ th2
electrostatic sprayheads used in the invention. One s~ch
possible means is shown schematically in figure 4. In the
lead 100 conveying high potential from generator 99 to
sprayhead 1~1, a high resistance 102 (say 1 megohm) is
inserted. Means 103 are provided for sensing the potential
~rop across this resistance. Usir.g a voltage of about
20 KV, and a liquid charsing current of about 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.~. 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 103 with standard satisfactory limits,
and if these are exceeded circuit 105 lights a warning
light 106 in the tractor driver's cab. Thi5 tells the
~river that one sprayhead is not operating correctly (and
which it is). In mechanical spraying systems, sprayhead
hlockages may go undetected for substantial pericds, and
lead to crop loss through failure to apply correct rates
of pesticide. A second possible means for detecting
malfunctioning is shown in Figure S. A probe 110 adjacent
2S a sprayhead nozzle 111 has a charge induced on it which
depends on the charge on the liquid leaving the no zle 111,
This charge is sensed by a field-effect (high input
impedance~ transistor 112. A circuit 113 is provided to
compare the charge sensed by the transistor 112 against an
appropriate range of standard values, and if the range is
~xceeded 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
voltag~ supplied to nozzle 111.
If desired, signals from detector means of the type
shown in Figure 4 or Figure 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
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system until the combined signal is within pre-set l~its.
Alternatively or additionally, means responsive to s~ch
variations may be provided to vary the voltage from th~
high potential system until the combined sianal is within
pre-set limits.
Figure 2 is a detail, in vertical section, of a~
electrostatic sprayhead used in the invention. It
comprises a nozzle 60 having a lLquid outlet or mout~ 64 in
the ~orm of an annular gap between an outer hollow cy~inder
61 formed ~rom conductive plastics and an inner soli~
cylinder 62 formed from conductive plastics. Around ~ozzle
60, and behind the mouth 64, an annular elec'rode 65 ~t
bare metal is symmetrically disposed.
As an added safety measure to prevent re~illing with
concentrated to~ic mater~als by spray operators under
potentially hazardous c,onditions, the containers of our
invention may include a device preventin~ re-use. Such a
device may be of a t~pe that has to be re-set at the
factory once the container has been emptied, e.y. a ~use in
the lowest part of the con~ainer 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, th~ delivery system may include one or
more electrostatic valves of the type dislosed in our
aforesaid European Patent ~o. 252~0.
Liquids sprayed by the process of our invention may
be solutions, emulsions, or free-flowing 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 (Figures 12-14).
~R/SPEC214/aji
13 Jan 82
