Note: Descriptions are shown in the official language in which they were submitted.
CA 02408149 2002-10-29
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SPRAYING OF LIQUIDS
Technical Field
This invention relates to a method and equipment for delivering a fluent
material,
especially a liquid product onto a household article or household plant. More
particularly, the invention relates to a method and equipment for applying a
liquid
product onto a household article for purpose of cleaning, wetting, coating,
polishing,
fabric treatment and the like, using a spray generated by electrostatic or a
combination of
electrostatic and hydrodynamic forces. The invention also relates to a method
and
equipment for watering household plants. The method and equipment of the
invention
provide effective liquid delivery and watering of plants together with mess-
and drip-free
operation, improved safety and reduced overspray.
Background of the Invention
Electrostatic spraying and electrodeposition of liquids is well known in the
art.
Electrostatic spraying is based on the generation of charged droplets and
their delivery
onto a grounded target surface. An advantage of electrostatic spray over other
spray
techniques results from the fact that the electrical field generated by
charged droplets
gives rise to a very uniform distribution of the liquid being sprayed. Another
advantage
of electrostatic spray is the ability to wrap around the surface being sprayed
and to
increase the amount of liquid deposited onto the target. Electrostatic spray
has a wide
range of applications. It is used, for example: i) industrially to coat an
active material,
such as paint onto a surface (e.g., US-A-5,208,078 and US-A-5,443,642); ii) in
agriculture for deliver of pesticides onto crops (e.g., GB-A-1,569,707 and US-
A-
4,356,528) and iii) at a personal level to deliver cosmetic and personal care
products (e.g.,
US-A-5,945,111).
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The prior art (e.g., GB-A-1,569,707 and US-A-4,356,520 teaches that suitable
electrostatic spray for agricultural use is attained when the size of the
spray droplets is in
the aerosol particle size range, e.g. below about 50 qm. This fact limits the
range of
liquids that can be successfully sprayed as well as the range of flow rates
that can be
achieved. The teaching from the prior art is that, with many systems, only
high resistivity
liquids can be sprayed at practical flow rates. Another limitation found with
known
electrostatic spray systems is that charged particles tend to seek the closest
earthed object
to discharge their electrical charge, therefore they are not appropriate for
use in household
or other closed environments.
For these and other reasons, electrostatic spray has not been applied
commercially in the
household environment for treatment of household articles. However, the use of
electrostatic spray in the household environment could be highly beneficial
when a
selective and uniform coverage of surfaces is required, e.g., cleaning
products onto
ornamental objects or furniture, fabric treatment products onto clothes,
bedding, linen and
the like, etc.
The application of electrostatic spray techniques could be especially
beneficial in the
household environment for watering of plants. Users often find that they need
to take
their plants outside when spraying plant care products if they wish to avoid
liquid landing
on the plant surroundings. However, the existing electrostatic spray systems
are not
adequate for use in a domestic or closed environment to apply water, plant
care products,
hard surface cleaning or treatment products, etc. This is due to a number of
reasons: i)
plant care and household cleaning products are usually aqueous and have low
resistivity
therefore they cannot be sprayed with existing hand held electrostatic
devices, such as
those used for cosmetics applications; ii) potted plants and other articles
commonly found
in house interiors are not grounded, charge dissipation taking place directly
or indirectly
via the operator which is both potentially unsafe and leads to poor spray
characteristics;
iii) conventional electrostatic spray systems used in agriculture have high
flow rates and
high velocities, possibly attained with the use of air-assistance, and thus
are not selective
enough to deposit significant quantities of liquid whilst avoiding the
deposition of liquid
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onto the surroundings; iv) conventional electrostatic spray systems are not
generally
designed to be mess- or drip-free or to the extent necessary to ensure safe
and effective
operation in a domestic environment, for example they may include nozzle
systems .that
readily clog with foreign matter or which are difficult to clean or which
display poor
spray characteristics, especially at the start and end of spraying; and v)
conventional
electrostatic spray systems are not generally designed from the ergonomic,
electrical and
control viewpoint so as to be easy and safe to use in a domestic situation. .
Accordingly the present invention provides in one or more embodiments
electrostatic
spray equipment and methods that allow for effective and selective spraying of
individual
household items in a domestic environment with reduced overspray, that have
mess- and
drip-free operation, that include grounding mechanisms that ensure operator
safety and
effective spray delivery, that are ergonomically designed, and that include
mechanisms
for control of the equipment to improve the safety thereof and the
effectiveness of the
equipment for spraying household items.
Summary of the Invention
According to a first aspect of the invention, there is provided electrostatic
spray
equipment for use in spraying a liquid onto a household article or plant for
the purpose of
cleaning, wetting, coating, polishing, fabric treatment, plant watering and
the like, the
spray equipment comprising:
a) a reservoir for containing the liquid;
b) a nozzle in fluid communication with the reservoir having at least one
orifice for
generating a spray of droplets;
c) means for delivering the liquid from the reservoir to the nozzle;
d) means for controlling the spray equipment; and
e) means for electrically charging the liquid.
The means for electrically charging the liquid preferably comprises a
generator having
high and low voltage outputs and in preferred embodiments is electrically
isolated from
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the operator/user. In addition, the spray equipment preferably also includes
means for
grounding the household article or plant for the purpose of charge
dissipation.
Preferably, the means for grounding comprises: i) a connector in electrical
contact with
the low voltage output of the generator and which is maintained at low or zero
electrical
potential; and ii) a pin, spike or other fastening means in electrical contact
with the
household article or plant and which is capable of being electrically isolated
from the
connector and from ground.
In use, the connector and fastening means are brought into electrical
connection in order
to establish a charge-dissipation grounding loop. For this purpose, the
electrostatic spray
equipment preferably includes means associated with either or both of said
connector and
fastening means for electrically connecting said connector and fastening
means, said
means for electrically connecting being selected from mechanical comiection
means such
as mechanical clips and male-female connectors, magnetic connection means,
electromagnetic connection means, and the like.
The connector itself can take the form of or comprise an electrically-
conductive wire, the
length of which can be selected to control the maximum permissible spraying
distance
between the equipment and the household article or plant. Alternatively, the
wire can be
marked with indicia to provide the user with a visual indication of the
spraying distance.
The fastening means, on the other hand, preferably takes the form of a pin,
spike or peg of
generally cylindrical shape, although other means for providing electrical
contact with the
household article or plant are suitable herein including generally flat or
planar plates,
adhesive strips, etc. The pin or other fastening means should be formed of a
material that
is non-corrosive in the application environment (e.g. the soil). Furthermore,
the pin or
other fastening means can provide other functionality, for example, it can act
as a plant
feeding stick or can form part of a 'smart advising system' as described in
detail below.
The electrostatic spray equipment can also includes various means for
controlling the
equipment, including one or more of the following:
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a) means for switching the equipment on or off;
b) means for regulating delivery of the liquid from the reservoir to the
nozzle;
c) means for regulating spray characteristics, for example application rate,
spray
direction, trajectory, shape and size of spray pattern, etc;
d) means for storing operational and/or environmental information; and
e) means for computing optimum operational characteristics dependant upon said
operational and/or environmental information.
In addition, the spray equipment according to the invention can comprise means
for
providing feedback of operational or environmental information to the spray
equipment
control means or to the user for the purpose of controlling the equipment or
for advising
the user of operational and/or environmental conditions. Suitably, the means
for
providing feedback comprises means associated with the fastening means and/or
connector for sensing operational and/or environmental conditions and means
for
communicating information generated by the sensing means to the spray
equipment
control means and/or to the user. Suitable means for communicating information
includes wire-based communication means, optical fibre communication means,
radio
communication means such as Bluetooth, infra-red communication means, etc.
In preferred embodiments, the means for sensing comprises means associated
with the
fastening means for one or more of the following functions:
a) switching the spray equipment on or off;
b) regulating delivery of the liquid from the reservoir to the nozzle;
c) regulating spray characteristics;
d) providing operational and/or environmental data, for example monitoring
humidity,
temperature, soil pH, moisture, salinity, nutrients, etc; and
e) preventing the spray equipment from switching on unless the connector is
electrically
connected to the fastening means.
The present invention also relates to a method of spraying a liquid onto a
household
article or plant for the purpose of cleaning, wetting, coating, polishing,
fabric treatment,
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plant watering and the like. In a preferred aspect, the method comprises the
use of spray
equipment comprising:
a) a reservoir for containing the liquid;
b) a nozzle in fluid communication with the reservoir having at least one
orifice for
generating a spray of droplets;
c) means for delivering the liquid from the reservoir to the nozzle;
d) means for controlling the spray equipment
e) means for electrically charging the liquid, said means comprising a
generator having
high and low voltage outputs; and
f) means for grounding the household article or plant for purpose of charge
dissipation,
said means for grounding comprising a connector in electrical contact with the
low
voltage output of the generator and which is maintained at low or zero
electrical
potential;
the method further comprising
i) bringing the household article or plant into electrical contact with a pin
or other
fastening means which is electrically isolated from the connector and from
ground; and
ii) bringing the connector and fastening means into electrical connection in
order to
establish a charge-dissipation grounding loop.
The electrostatic spray equipment herein also comprises a nozzle in fluid
communication
with the reservoir for generating a spray of droplets. While suitable nozzles
can comprise
one or more orifices, highly preferred herein from the viewpoint of mess- and
drip-free
spray characteristics is a nozzle that comprises a multi jet spray-head having
a plurality
of orifices adapted to discharge the liquid under a combination of
electrostatic and
hydrodynamic forces and preferably in a plurality of non-capillary flow paths.
Thus, according to another aspect of the invention, there is provided
electrostatic spray
equipment for use in spraying a liquid onto a household article or plant for
the purpose of
cleaning, wetting, coating, polishing, fabric treatment, plant watering and
the like; the
spray equipment comprising:
a) a reservoir for containing the liquid;
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b) a nozzle in fluid communication with the reservoir for generating a spray
of droplets
and wherein the nozzle comprises a multi jet spray-head having a plurality of
orifices
adapted to discharge the liquid under a combination of electrostatic and
hydrodynamic forces;
c) means for hydrodynamically delivering the liquid from the reservoir to the
nozzle;
and
d) means (including an electrode) for electrically charging the liquid.
Preferably, the multi jet spray-head comprises form about 2 to about 200,
preferably from
about 3 to about 60 orifices and each orifice has an outlet diameter in the
range from
about 10 ~m to about 250 ~,m, preferably from about 20 ~m to about 100 Vim.
Especially
preferred for use herein is a spray-head comprising form about 5 to about 20,
preferably
from about 6 to about 13 orifices wherein each orifice has an outlet diameter
in the range
from about 22 pm to about 60 Vim, preferably from about 25 ~m to about 50 Vim.
The
orifices are preferably of a non-capillary type whereby they are capable of
discharging
liquid in a plurality of non-capillary flow paths. By non-capillary is meant
that the
orifices have a length:width ratio on average of no more than about 50:1,
preferably no
more than about 20:1.
In addition, the average spacing between neighbouring orifices of the spray-
head is
preferably in the range from about 100~m to about 20mm, more preferably from
about
1.5 to about lOmm, this being desirable from the viewpoint of minimizing
electrostatic
interference between the corresponding neighbouring jets and for ensuring that
the liquid
is discharged in mess-free manner and in a narrow spray cone.
In preferred embodiments, the nozzle comprises an assembly of components
including a
spray-head and one or more additional nozzle components. The assembly is
preferably
constructed in such a way that it can be dissembled as necessary for cleaning
or servicing
purposes. One preferred additional nozzle component is a filter introduced for
the
purpose of reducing clogging of the spray-head and for preventing damage
thereto.
Preferably, the design of the nozzle is such that the filter and spray-head
are detachable
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either separately or as a unit from the remainder of the assembly for the
purpose of
cleaning or replacement thereof. For this purpose, the filter and spray-head
are preferably
mounted downstream of the liquid-charging electrode means.
In preferred embodiments, the nozzle additionally incorporates means for
reducing
dripping of liquid during and especially at the start and end of spraying,
said means
comprising a pressure control valve used in conjunction with hydraulic pump
means and
which is responsive to an increase or decrease in pressure respectively above
and below
given trigger and cut-off threshold values so as to control the flow of liquid
through the
nozzle. The pressure control valve preferably has trigger and cut-off
threshold values of
from about 5% to about 50%, more preferably from about 6% to about 20%, yet
more
preferably from about 8% to about 15%, and most preferably about 10%
respectively
above and below the operating flow pressure of the spray equipment, these
threshold
values being particularly important in the case of spray equipment based on
peristaltic or
other pump types Which seal hydraulically at rest. The pressure control valve
is also
preferably mounted in the nozzle assembly in the vicinity (preferably
immediately
upstream) of the spray-head, which leads to better valve control and reduced
dripping at
the start and end of spraying. Once again in preferred embodiments the liquid-
charging
electrode means is positioned upstream of the pressure control valve.
Embodiments in
which the pressure control means is located upstream of the nozzle assembly
itself are
also envisaged herein, though such embodiments are less preferred.
Thus, according to a further aspect of the invention, there is provided
electrostatic spray
equipment for use in spraying a liquid onto a household article or plant for
the purpose of
cleaning, wetting, coating, polishing, fabric treatment, plant watering and
the like, the
spray equipment comprising: a) a reservoir for containing the liquid; b) a
nozzle in fluid
communication with the reservoir for generating a spray of droplets; and c)
means for
delivering the liquid from the reservoir to the nozzle, said means preferably
comprising
hydraulic and especially peristaltic pump means; and wherein the nozzle
comprises an
assembly of nozzle components including:
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i) a spray-head having one or more orifices adapted to discharge the liquid in
the form
of a spray;
ii) a filter for preventing or reducing clogging of the spray-head;
iii) means for reducing dripping of liquid during and especially at the start
and end of
spraying, said means comprising a pressure control valve responsive to an
increase or
decrease in pressure respectively above and below given trigger and cut-off
threshold
values so as to control the flow of liquid through the nozzle, said pressure
control
valve preferably being mounted in the vicinity of the spray-head; and
iv) means for electrically charging the liquid.
As described herein, the spray-head and filter are preferably detachable from
the
remainder of the assembly including the pressure control valve and the means
for
electrically charging the liquid for the purpose of cleaning or replacement
thereof.
Alternatively, pressure control can be achieved using an orifice in the form
of a slit seal
valve, i.e. a slit (preferably x-shaped) in the surface of an elastomeric
membrane which
has a trigger or cracking pressure such as to allow normal jet formation to
take place
without cracking but which cracks or opens by inversion of the membrane at
pressures
above the cracking pressure caused by the presence of clogging material. Spray
equipment comprising a nozzle having one or more orifices in the form of a
slit-seal valve
thus comprise another separate and valuable aspect of the invention.
The orifices themselves (including slit-seal orifices) can be made by
conventional
micromachining, laser drilling, photoetching or similar techniques. The
manufacture of
mufti jet spray heads is complex, however, and presents a number of
difficulties using the
known techniques. An alternative approach to making mufti jet spray-heads is
to make a
series of grooves or ridges in a plate which is then brought into sealing
engagement with
a second plate so as to form a series of channels between the plates. By using
plates in
cylindrical form and dimensioned to provide sealing engagement between the
plates, this
approach allows the manufacture of a mufti jet head of generally circular
configuration
with a series of orifices set around the circumference of the cylinder.
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The electrostatic spray equipment herein preferably also includes means
associated with
the nozzle for regulating and adjusting the spray pattern, said means being
selected from
(1) means for selecting the number of orifices of a given diameter, (2) means
for changing
orifice diameter, (3) means for selecting a mix of orifices of differing
diameter, and (4)
means for adjusting orifice cross sectional shape so as to change the diameter
of the
resulting jet (for example, means for lengthening or shortening one dimension
of an oval
cross-section).
In a preferred nozzle assembly, the filter, pressure control valve and spray-
head are
mounted within a housing equipped with a fluid inlet port and high voltage
supply port at
the inlet end of the housing and with a detachable hood or sliroud at the
outlet end of the
housing and which acts as a deflector or shaping device for the spray as
described in
detail hereinbelow. The hood or shroud is secured to the housing by screw or
similar
engagement means on the outlet end of the housing and is detachable from the
housing in
order to permit disassembly of the nozzle. The spray-head is mounted at the
outlet end of
the housing and comprises an orifice portion, a sleeve portion and a
circumferential lip
portion. The filter is mounted at the inlet end of the housing and comprises a
filter
element and a filter holder having an annular flange. The pressure control
valve is
mounted intermediate the spray-head and the filter. When assembled, the hood
or shroud
bears on the circumferential lip portion of the spray-head while the outermost
portion of
the annular flange of the filter holder bears on the sleeve portion of the
spray-head,
whereby the hood or shroud and the filter holder together act to hold the
spray-head in
position within the housing. The pressure control valve on the other hand is
mounted
with one end within the sleeve portion of the spray-head and with its other
end engaging a
projection on the annular flange of the filter holder.
It is an object of the present invention to provide a method and equipment for
applying a
liquid product or other fluent material onto a household article for purpose
of cleaning,
coating, polishing, fabric treatment and the like with reduced mess, overspray
and
improved safety. It is another object of the present invention to provide a
method and
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equipment for watering a household plant with reduced mess, overspray and
improved
safety. By 'watering' is meant the delivery of an aqueous liquid to any part
of the plant,
including the root system and surroundings soil but preferably to the leaves
and more
preferably to both sides of the leaves. The liquid can be water itself or any
aqueous or
non-aqueous liquids suitable for household article or plant care. Aqueous
liquids are
preferred herein but non-aqueous liquids such as oil based' products or
emulsions/suspensions can also be used. By overspray is meant the percentage
by weight
of liquid that lands on the household article or plant surroundings (excluding
the soil).
The method and equipment of the invention involves the use of an electrically
charged
spray. The spray is obtained by a balance of hydrodynamic, gravitational,
electrical and
drag forces in such a way that the generated spray droplets deposit
preferentially onto the
surface of the household article or target plant. The forces acting on the
spray droplets
are mainly determined by: i) the physical properties of the, such as surface
tension,
density and viscosity, ii) the initial conditions of the liquid, such as
pressure gradient and
flow rate and iii) the electrical condition of the liquid such as resistivity
and applied
potential.
One of the factors that has been found to determine the amount of overspray in
electrostatic spraying and plant watering systems is the spray trajectory. In
particular,
improved deposition and reduced overspray at high application rates is
obtained when
spraying in a generally upward or downward direction using spray droplets of
defined
size, exit velocities and charge.
It has been surprisingly found that optimum watering and liquid delivery is
obtained
using droplets size of at least about 40 ~m and preferably in the range from
about 75 to
about 500 ~m when the liquid is discharged upwardly at an exit velocity in the
range
from about 3 to about 40 m/s, preferably from about 3 to about 20 m/s and at
an applied
potential in the range from about 0.2 to about 50 kV. Such embodiments, are
sometimes
referred to herein as "upward spray" or "watering can" mode embodiments.
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Thus, according to another aspect of the present invention, there is provided
a method for
applying a liquid product onto a household article for purpose of cleaning,
wetting,
coating, polishing, fabric treatment and the like with reduced overspray or a
method of
watering a household plant with an aqueous liquid suitable for plant care and
with
reduced overspray, the method comprising discharging the liquid in the form of
an
upwardly directed spray of droplets having an average droplet size of at least
about 40
~,m and preferably in the range from about 75 to about 500 ~.m and at a
proximal distance
of from about 0.1 to about 1 m from the household article or plant, the liquid
being
delivered at an exit velocity in the range from about 3 to about 40 m/s,
preferably from
about 3 to about 20 m/s and at an applied potential in the range from about
0.2 to about
50 kV, whereby the overspray is less than about 40%. As used herein, exit
velocity refers
to the velocity of liquid exiting the orifice or orifices of the spray nozzle
and is equal to
the flow rate divided by the cross-sectional area of the orifice or orifices.
Average
droplet size on the other hand is measured using a Malvern Size Analyser, and
refers to
the average droplet size measured at a distance of 10 cm from the orifice or
orifices of the
nozzle.
In preferred upward spray mode embodiments of the invention the exit velocity
is from
about 4 mls to about 15 mls and more preferably from about 5 m/s to about 12
m/s and
the spray of droplets is upwardly directed at a spray angle of from about
20° to about 70°,
preferably from about 30° to about 60° to the vertical. As used
herein, spraying angle
refers to the direction of the liquid immediately prior to ejection from the
nozzle orifice
and, in the case of multiple orifices, is the average spray angle for the
different orifices.
The invention herein can also be applied to liquid delivery and plant watering
methods
and equipment in so-called "downward-spray" or "shower" mode. Thus, according
to a
further aspect of the invention, there is provided a method for applying a
liquid product
onto a household article for purpose of cleaning, wetting, coating, polishing,
fabric
treatment and the like with reduced overspray or a method of watering a
household plant
with an aqueous liquid suitable for plant care and with reduced overspray, the
method
comprising discharging the liquid through a spray nozzle in the form of a
downwardly
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directed spray of droplets having an average droplet size of at least about 40
~,m and
preferably in the range from about 75 to about 500 ~m and at a proximal
distance of from
about 0.1 to about 1 m from the household article or plant, the liquid being
discharged
through the spray nozzle at an exit velocity in the range from about 0 to
about 2 m/s and
at an applied potential in the range from about 0.2 to about 50 kV, whereby
the overspray
as herein defined is less than about 40%.
In preferred downward-spray mode embodiments of the invention the exit
velocity is
from about 0.1 m/s to about 1.5 m/s, preferably from about 0.5 m/s to about 1
m/s and the
spray of droplets is downwardly directed at a spray angle of from about -
30° to about 30°,
preferably from about -15° to about 15° to the vertical.
In both "upward-spray" and "downward-spray" modes of operation, the overspray
should
be less than about 40%, preferably less than about 30% and more preferably
less than
about 20% by weight. Overspraying can be measured by weighing the amount of
liquid
that deposits onto the target system (eg a potted plant) and subtracting from
the total
discharged liquid.
Of course, the system can work in a standard horizontal mode as well with the
spray
directed at +/- 15° to the horizontal and an exit velocity of from
about 4 m/s to about 15
m/s and more preferably from about 5 m/s to about 12 m/s. However, this mode
can
result in slightly more overspray because of inertial effects, with overspray
of less then
50%, preferably less than 30%, and more preferably less than 20%.
The spray is generated by delivering the liquid to the spray nozzle under a
combination of
electrical and hydrodynamic forces. The liquid is charged at or prior to the
nozzle orifice
or orifices by passing through an electrical field generated by a charged
electrode. The
electric field strength is mainly dependent upon the voltage applied to the
electrode and
the distance from the target. The liquid can be delivered to the nozzle by any
means, but
is preferably delivered hydrodynamically, for example with external mechanical
work
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input so as to provide an operating or total pressure greater than the static
pressure of the
fluid in the system. Preferably the liquid is delivered by hydraulic pressure
using a pump,
especially preferred being a peristaltic pump. Typically a suitable pump would
have an
operating pressure in the range from about 5 to about 2000 kPa, preferably
from about 10
to about 1050 kPa, and more preferably from about 50 to about 150 kPa. The
threshold
values of the pressure control valve are adjusted accordingly. The discharge
capacity of
the equipment (defined as flow rate/orifice) on the other hand, is preferably
at least about
0.1 mL/min/orifice, more preferably from about 0.2 to about 20 mL/min/orifice,
yet more
preferably from about 0.5 to about 10 mL/min/orifice and especially from about
1 to
about 5 mL/min/orifice.
Plant care products include any liquid based composition used to treat plants,
for example
pesticides, insecticides, herbicides, fungicides, plant growth enhancers,
plant food, plant
nutrients, plant cleaners, leaf varnishes, plant shine agents, water and
mixtures thereof.
Although any liquid base could be used herein, aqueous solutions are preferred
in the
present invention. Suitable products for delivery to inanimate household
articles include,
for example, hard surface cleaning products, cleaning products for curtains,
walls,
venetian blinds, silver care products, floor and furniture polishes, glass and
window
cleaning products, fabric treatment products, ironing products, stain removal
products,
fabric care products, laundry products, bleaching products, bathroom and
kitchen
cleaning products, etc. Suitable products for personal or non-human animal use
include,
for example, cosmetics, sunscreens, moisturizers, deodorants, color cosmetics,
make-up
compositions, wound care compositions, shampoos, etc: Mariy of these products
are
highly conductive aqueous liquids and have a resistivity lower than about 104
ohm cm.
Higher resistivity liquids can also be successfully sprayed using the present
method and
equipment.
Most of the plants found in the household environment are potted, either in a
plastic pot
or in a ceramic pot. Both materials are insulators, whereby "insulator" or
"insulating
material" refers to a material having a resistivity generally above about 1012
ohm cm.
Therefore, the pot insulates the plant and as consequence it will not attract
charged
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particles. If a liquid is electrostatically sprayed in the proximity of a
potted plant, the
spray will be as likely to go to the plant surroundings as to the plant. In
one method for
watering a potted plant, therefore, watering is carried out using an
alternatively positively
and negatively charged spray. In another method, the circuit is completed by
using
grounding means such as a spike inserted in the soil in the vicinity of the
plant. This
makes the spray preferentially go to the plant and soil in the pot, thus
avoiding
undesirable mess and product waste.
Other articles found in the household environment can also be classified as
insulators (for
instance, glass ornaments, windows and plastics objects). Insulators can be
electrostatically sprayed, for instance, by using an alternatively positively
and negatively
charged spray. Other articles can be classified as semi-insulators materials
(for instance
furniture and cloth) whereby "semi-insulator" or "semi-insulating material"
refers to an
object or material having a resistivity generally between about 10~ and about
1012 ohm
cm. Semi-insulators and insulators can be electrostatically sprayed, for
instance, with the
help of grounding means such as clamps, pins or other fastening means attached
to the
object as described hereinabove.
The equipment and methods of the present invention can be applied to both
inside plants,
i.e., plants normally growing inside buildings such as houses, greenhouses,
workplaces,
etc, or outside plants, for example plants growing in a garden, allotment,
plant nursery,
patio, etc. The term "household plant" is to be construed accordingly. In
general,
however, the method is applied to individual household plants or where a
number of
household plants are being watered, the individual plants will usually be
treated
sequentially. Similarly, the equipment and methods of the present invention
can be
applied to articles both inside and outside the house, workplace, etc, to both
inanimate
and animate articles (human and non-human animals) and to items which are not
necessarily always in the house but which have a more general household
association,
e.g. bicycles, cars, etc. The term "household article" is to be construed
accordingly.
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A highly preferred method of the invention includes the additional step of
shaping the
spray using spray shaping means, the spray shaping means comprising either a)
an
insulating element whereby in use the first droplets to contact the element
generate an
electrostatic field for shaping the spray, or b) a conductive element whereby
in use the
element is charged so as to generate an electrostatic field for shaping the
spray. In a
preferred spray shaping method, the spray shaping means comprises an
insulating
element in the form of a surface or surface covering extending generally under
and
around the household article or plant. Suitable insulating elements include,
for example,
the surface of a table which is insulated from ground or an insulated mat
which is
designed to be placed on a surface and on which the household article or plant
is placed.
Suitable insulating elements also include mats in the form of an annulus
wherein the
household article or plant is located in the central region of the mat.
Suitable spray
shaping means also include spray deflector means, situated adjacent the nozzle
orifice as
described in detail below.
Thus according to another aspect of the invention, there is provided a method
for
applying a liquid product onto a household article or plant for purpose of
cleaning,
wetting, coating, polishing, fabric treatment, plant watering and the like,
the method
comprising discharging the liquid through a spray nozzle in the form of a
spray of
droplets at an applied potential in the range of from about 0.2 to about 50 kV
and
thereafter electrically shaping the spray of droplets whereby the overspray as
herein
defined is less than about 40%, preferably less than about 30% and more
preferably less
than about 20%.
The present invention also relates to electrostatic spray equipment,
especially plant
watering and other hand-held equipment suitable for use within the home for
application
of liquids to household articles or plants with improved coverage and reduced
overspray.
Thus according to a further aspect of the invention there is provided an
electrostatic spray
equipment comprising:
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a) a reservoir for containing a liquid suitable for application to a household
article or
plant for purpose of cleaning, wetting, coating, polishing, fabric treatment,
plant
watering and the like;
b) a nozzle in fluid communication with the reservoir and having at least one
orifice
for generating a spray of droplets;
c) means for delivering the liquid from the reservoir to the nozzle;
d) means for electrically charging the liquid; optionally
e) means for adjusting the orientation of the nozzle orifice relative to the
apparatus;
and further optionally
f) means for electrically shaping the spray of droplets after generation
thereof.
The electrostatic spray equipment of the invention can be deployed in a number
of ways
but is preferably used in one of two modes:
a) an upward mode wherein the apparatus is arranged to discharge the liquid in
the form
of an upwardly directed spray of droplets having an average droplet size of at
least
about 40 pm and preferably in the range from about 75 to about 500 ~,m, the
liquid
being discharged through the spray nozzle at an exit velocity in the range
from about 3
to about 40 m/s, preferably about 3 to about 20 m/s and at an applied
potential in the
range from about 0.2 to about 50 kV; and
b) a downward mode wherein the apparatus is arranged to discharge the liquid
in the
form of a downwardly directed spray of droplets having an average droplet size
of at
least about 40 ~m and preferably in the range from about 75 to about 500 pm,
the
liquid being discharged through the spray nozzle at an exit velocity in the
range from
about 0 to about 2 m/s and at an applied potential in the range from about 0.2
to about
50 kV.
The spray nozzle can have different configurations and geometries, a circular
orifice
cross-section produces a good spray. In the case of spray nozzles having a
single orifice,
the nozzle orifice preferably has an outlet diameter is in the range of from
about 20 ~m to
about 300 Vim, preferably from about 100 ~m to about 200 ~,m. Multiple orifice
nozzles
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on the other hand preferably have an outlet diameter in the range from about
20 ~,m to
about 250 ~.m, preferably from about 20 ~,m to about 100 ~.m. In highly
preferred
embodiments, the electrostatic spray equipment includes means for adjusting
the relative
orientation of the nozzle orifice in order that the equipment can be used at a
spray angle
that can be selected by the end-user. By relative orientation is meant the
orientation of
the nozzle orifice relative to the remainder of the device. In preferred
embodiments, the
nozzle is in fluid communication with the reservoir via a conduit and the
means fox
adjusting the relative orientation of the nozzle orifice comprise a flexible
portion of the
conduit such as a flexible neck hose or tubing. The nozzle is enclosed in a
flexible tube
in order to have complete freedom of orientation. Preferably, the nozzle
orifice or
orifices are surrounded by an annular or conical spray deflector means,
typically made of
an insulating or semi-insulating material. However, the deflector could be
flat or another
shape as well. The deflector is charged by the spray, due to its insulating
nature the
charge will stay in the surface therefore repelling further spray. The
provision of
deflector means adjacent to the nozzle orifice is valuable for electrically
shaping the
spray of droplets and for controlling the width of the spray. In addition, the
deflector can
accelerate the velocity of the spray by focusing the electrical field.
The electrostatic spray equipment can further comprises household article or
plant
grounding means as described hereinabove in order to improve the attractive
capacity of
the household article or plant towards the spray. Suitable plant grounding
means
includes, for example, a spike placed in the soil and connected either to the
device or to
earth. Other suitable grounding means includes, for example, an electrode in
the form of
clamps which in use is attached to the household article or plant and
connected either to
the equipment or to earth. Another way to ground the household article or
plant is by
introducing a permanently charged electrode, preferably an electrode of
opposite charge
to the droplets being sprayed.
The electrostatic spray equipment can also comprise spray shaping means to
improve the
selective deposition of the spray on the household object or plant. The role
of the shaping
means is to bring back to the household object or plant the spray droplets
that would
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otherwise miss the target. The shaping means can be an insulator or a
conductor. If it is
an insulator, it will be charged with the same sign electrical charge as the
spray, therefore
it will repel further spray and this spray is redirected to the target. If it
is a conductor,
current of the same sign as the spray charge needs to be constantly supplied
in order to
keep the conductor permanently charged.
The grounding means and spray shaping means can be either integral with the
spray
equipment or separate therefrom. Accordingly, the present invention also
includes
electrostatic spray kits comprising the electrostatic spray equipment,
grounding means
and/or shaping means. The grounding means may take the form of an electrode
connectable to the ground of the equipment or to earth or one which in use can
be charged
with opposite charge to the spray droplets, etc.
It will be understood of course that the equipment of the invention can
include one or
more reservoirs and/or one or more spray nozzles in fluid communication with
the one or
more reservoirs. Multiple reservoirs are valuable in the case of household
article or plant
care products which are mutually incompatible or which are designed for
application to
the household article or plant in sequential manner. Multiple nozzles are
valuable in the
case of multiple household article or plant care products requiring different
application
characteristics or for simultaneous application of household article or plant
care products
designed to interact with one another on the household article or plant or for
applying
higher flow rates of product where a single nozzle can not provide enough
flow.
The electrostatic spray equipment is preferably designed from the ergonomic
viewpoint
so as minimize operator fatigue and enhance in-use safety. To this end, the
weight of the
device should be as low as possible, preferably less than about 2000g, more
preferably
less than about SOOg, and ideally about 200g. Again the motor should be
positioned away
from the hand to minimize vibration; and hand functions, e.g. for holding the
equipment
and for pushing a start/stop button should be separated.
Detailed Description of the Invention
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Convenient for use herein are plant care products in the form of aqueous
solutions,
including water. The plant watering methods and equipment of the present
invention
allow for relatively high application rates whilst at the same time reducing
or avoiding
overspray. It has also been found that some plants respond positively to
electrically
charged liquid and can display improved growth rates. The increased growth may
be due
to the electrically charged liquid causing biostimulation in the plants.
Usually plant care
products for use in house interiors are diluted aqueous solutions, having a
low resistivity,
sometimes lower than that of pure water, due to the presence of ions in
solution. The
efficiency of pesticides, insecticides and fungicide can also be improved
according to the
invention as a result of improved underleaf coverage. This is important since
insects and
diseases are located very often on leaf undersides and other hidden areas
difficult to reach
with traditional spraying methods.
The method of the present invention can be put into practice by using an
electrostatic
spray device comprising means to deliver the liquid, means to electrically
charge the
liquid and means for generating a spray of charged droplets. The invention
will now be
described by way of example with reference to the accompanying drawings in
which:
Figure 1 is a cross-sectional view of one embodiment of the electrostatic
spray equipment
with a perspective view of the flexible neck;
Figure 2 is a fragmentary perspective view of the embodiment of Figure 1
showing the
grounding spike and grounding spike cord retraction mechanism; and
Figure 3 is a cross-sectional view of a nozzle assembly suitable for use in
the electrostatic
spray equipment.
Preferably, the droplets are positively charged. If desired however, the
droplets can be
negatively charged. The electrostatic spray equipment is preferably
constructed in a size,
shape and weight convenient for hand-held use and for easy manipulation. The
equipment of Figure 1 generally comprises housing 1, liquid reservoir 2,
nozzle 3, means
4 to deliver the liquid to the nozzle, cap-like compartment 5 which encases
electrical
means 6 to generate high voltage and flex-neck tube 7 providing a conduit to
nozzle 3 and
CA 02408149 2002-10-29
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incorporating high voltage lead 8. In the illustrated embodiment, housing 1
has the shape
and dimensions of a conventional spray bottle used for cleaning products and
which is
preferably electrically insulating, e.g. plastic material, within which the
electrical and
other hardware components of the apparatus are mounted.
In this embodiment, liquid reservoir 2 is mounted beneath cap-like compartment
5 and is
a bottle type reservoir which can be easily refilled or replaced when
necessary. The
composition to be sprayed is fed through dip-in-tube 9. If desired or as
necessary, the
apparatus may include feed means such as a hand pump, electrical pump
(especially a
peristaltic pump), pressurised gas, etc, to transfer composition from
reservoir 2 to nozzle
3 at the required rate. Typically a positive pressure of from about 10 to 1050
kPa,
preferably from about 50 to about 150 kPa will be suitable for this purpose.
In the
illustrated embodiment a pump 10 with motor 11 and gear box 12 is used to
control the
outlet flowrate.
In the illustrated embodiment, electrical means 6 to generate high voltage is
located
towards the top of the equipment in cap-like compartment 5. Towards the base
of the cap-
like compartment is housed battery 13, such as a conventional low voltage,
e.g. 1.5 to 12,
particularly 9, volts, cell, which location allows ready access to the battery
for the
purpose of replacement when necessary. High voltage generator 6 converts the
low
voltage from battery 13 into the high voltage of for example between about 12
and 18
kilovolts, which is required for raising the product to be sprayed to the high
electric
potential necessary to effect electrostatic spraying thereof.
Suitable components of high voltage generator 6 are well known in the art and
comprise
principally a coil or transformer to perform the voltage step-up function. A
"charge
pump" or "ladder"-type voltage multiplier, which consist primarily of diodes
and
capacitors, may be used in isolation or in conjunction with said coil or
transformer. This
multiplier can be of serial or parallel construction. If desired or as
necessary, various
packing elements of electrically insulating material, not shown in Figure 1,
may be
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provided in order to increase the safety aspect of the high voltage apparatus
and to reduce
unwanted leakage paths to earth when the apparatus is in use.
Above high voltage generator 6 are one or more circuit boards 14 containing
any
necessary auxiliary electrical component for ensuring effective and
satisfactory
functioning of the apparatus. Such additional circuit boards) 14 may comprise
for
example DC/AC (or vice versa) converters, as well as voltage adjustment means
to
control the high voltage applied to the product delivery means from which the
product to
be sprayed is to be delivered. High voltage generator 6 is connected through a
high
voltage lead 8 to a charge transfer piece (not shown) which contacts the
liquid before
leaving the orifice of nozzle 3. High voltage lead 8 and the fluid conduit are
enclosed
within insulating flex neck tube 7. Flex neck tube 7 allows the end-user to
orient nozzle 3
in any desired direction relative to the remainder of the device. Of course,
flex neck tube
7 could be replaced with a rigid tube with a fixed position to enforce use at
a preferred
angle. Nozzle 3 comprises an internal chamber (not shown) which terminates at
the tip of
nozzle 3 in an orifice 16 from which the product Within the chamber emerges
under the
influence of electrostatic and hydrodynamic forces. The configuration of
nozzle 3 in the
region of orifice 16 may be selected in association with other spraying
parameters in
order to give an optimised system both as regards spray properties and safety.
Nozzle 3
with circular orifice has been found very useful for the present application,
the diameter
of the orifice being in the range from about 50 ~m to about 500 ~.m,
preferably from
about 100 ~m to about 300 Vim. In a preferred embodiment, the nozzle is
surrounded by
spray deflector (not shown), which can be an insulating or semi-insulating
material in the
form of for example a tube that goes over the spray nozzle. On use of the
equipment
spray deflector becomes charged, forcing the spray droplets away from the
device and the
user by creating an electrostatic field that has the same charge as the spray.
Shown schematically in Figure 1 as 15 is a manual trigger which constitutes
control
means for selectively switching on the unit to apply the high voltage to the
nozzle to
electrostatically spray the product therefrom. Trigger 15, like the other
elements of the
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apparatus subject to unwanted voltage leakage or shock risk, is preferably
constructed
and situated to minimise such problems, expedients for which are known in the
art.
In alternative embodiments of the equipment, the liquid reservoir can be
placed above the
cap-like compartment in order to take advantage of the gravity force for the
liquid flow.
As illustrated in Figure 2, electrostatic spray equipment in Figure 1 can
further comprises
a household article or plant grounding device or other grounding means for
purposes of
charge dissipation and in order to improve the attractive capacity of the
household article
or plant towards the spray. In the illustrated embodiment, the grounding
device takes the
form of grounding spike or other fastening means 17 which is electrically
connected with
connector cord 18 to the ground of the equipment. Cord retracted mechanism 19
is
housed on . one side of cap-like compartment 5. Other embodiments to
accomplish
grounding of the household article or plant include earthing the household
article or plant
and providing the household article or plant with a charge opposite to that of
the spray.
The electrostatic spray equipment can be used in conjunction with a spray
shaping device
(not shown) to improve the selective deposition of the spray on the household
article or
plant. The role of the shaping device is to bring back to the household
article or plant
spray droplets that miss the target. The shaping device can be an insulator or
a conductor.
If it is an insulator, it will be charged with the same sign electrical charge
as the spray,
therefore it will repel further spray and this spray can be redirected to the
household
article or plant. If it is a conductor, current of the same sign as the spray
charge needs to
be constantly delivered to the conductor in order to keep it permanently
charged.
Figure 3 illustrates a preferred embodiment of a nozzle assembly 20 suitable
for use
herein. In general terms, nozzle assembly 20 comprises filter 21, pressure
control valve
22 and spray-head 23 mounted within housing 24 equipped with fluid inlet port
25 and
high voltage supply port 34 at the inlet end of housing 24 and with detachable
hood or
shroud 26 at the outlet end of housing 24 and which acts as a deflector or
shaping device
for the spray. The hood or shroud 26 is secured to housing 24 by screw
engagement
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means on the outlet end of the housing and is detachable from the housing in
order to
permit disassembly of the nozzle. Spray-head 23 is mounted at the outlet end
of housing
24 and comprises orifice portion 27, sleeve portion 28 and circumferential lip
portion 29.
Filter 21 is mounted at the inlet end of housing 24 and comprises filter
element 30 and
filter holder 31 having annular flange 32. Pressure control valve 22 is
mounted
intermediate spray-head 23 and filter 21. When assembled, hood or shroud 26
bears on
circumferential lip portion 29 of spray-head 23 while the outermost portion of
annular
flange 32 of filter holder 31 bears on sleeve portion 28 of spray-head 23,
whereby hood or
shroud 26 and filter holder 31 together act to hold spray-head 23 in position
within
housing 24. Pressure control valve 22 on the other hand is mounted with one
end within
sleeve portion 28 of spray-head 23 and with its other end engaging a
projection 33 on
annular flange 32 of filter holder 31.
In use, a potted plant (in a plastic container) is watered using the equipment
shown in
Figure 1. Optionally, the potted plant is placed on an insulated Perspex sheet
of circular
geometry (0.5 m diameter). The plant is grounded by placing the ground spike
(shown in
Figure 2) in the soil. The user holds the electrostatic spray equipment and
manipulates
flex neck tube 7 such that the nozzle orifice is approximately 0.5 m from the
plant and
inclined upwardly over the plant at an angle of 30° to the vertical.
The liquid is charged
to an applied potential of about 8 kV and discharged from the spray nozzle at
an exit
velocity of about 10 m/s. The mean particle size of the droplets 10 cm from
the nozzle
orifice is 200 pm as measured by a Malvern Size Analyser. The amount of
overspray (the
amount of water not landing on the potted plant) is 20%.
The electrostatic spray equipment can be used in similar manner for applying a
variety of
different consumer products to household articles. For example, in one method
of use, an
ironing composition comprising a mixture of ironing aids, perfume and water,
is sprayed
onto a laundry item prior to or during ironing in the following manner. The
laundry item
is first placed on an ironing table or board having a conducting surface
connected to the
earth of the spray equipment. The user holds the electrostatic spray equipment
and
manipulates flex neck tube 7 such that the nozzle orifice is approximately 0.5
m from the
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laundry item and inclined upwardly over the item at an angle of 30° to
the vertical. The
liquid is charged to an applied potential of about 8 kV and discharged from
the spray
nozzle at an exit velocity of about 10 m/s. The mean particle size of the
droplets 10 cm
from the nozzle orifice is 200 ~m as measured by a Malvern Size Analyser. The
amount
of overspray (the amount of composition not landing on the laundry item) is
20%.
