Note: Descriptions are shown in the official language in which they were submitted.
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~~A liquid applicator device"
Introduction
The present invention relates to a liquid applicator device particularly for
applying
weedkiller.
One of the major problems encountered in gardening, particularly for the
amateur
in the small garden, is the need to apply weedkiller to weeds in a controlled
1o manner, whereby the weedkiller is not applied to the plants that it is
desired to
keep, such as flowers, vegetables and the like. It has been known to tackle
this
problem by the use of a number of different weed applicators however, none of
the conventional weed applicators is entirely satisfactory.
~ s One particular problem is in applying the weedkiller in a manner that is
effective
and yet easily implemented by the user. Conventional applicators require
careful
use to avoid spreading the weedkiller to adjacent plants. There are also
diffllculties
in controlling the amount of weedkiller applied and to controlling the flow of
weedkiller generally.
The present invention is therefore directed towards providing a liquid
applicator
device which will overcome at least some of these problems.
Another related problem in horticultural situations is the controlled feeding
and or
2s watering of seedlings and plants.
The invention also relates to liquid dispensing devices in general which
conventionally incorporate either a permanent air intake or an air inlet that
can be
opened and shut as required together with a discharge opening remote from the
3o inlet. One problem with such conventional liquid dispensing devices is that
the
flow rate varies. In particular, in the case of a container the flow rate
varies
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depending on the quantity of liquid within the container, as the head of
liquid
above the outlet determines the flow rate. When it is desired to provide
containers
which, irrespective of the amount of liquid contained therein, will discharge
at a
constant flow rate, relatively expensive pieces of equipment are required such
as
s for example positive displacement pumps and the like metering devices.
There are many situations where such expensive equipment is impractical and in
which it is required to control the rate of discharge of a liquid, especially
from a
container, which rate of discharge is independent of the head height of liquid
stored within the container. One can readily consider such medical uses as
intravenous feeding, saline drips and the like. Similarly, in industry and in
the
home and ofl~ce there are many situations where the discharge of liquid in a
controlled manner is extremely desirable whether it be for such mundane tasks
as
the application of adhesives, paints, nail polishes, or indeed any form of
liquid
15 within a container.
The invention is also directed to a liquid dispensing device which will
overcome at
least some of the problems described above.
2o Statements of Invention
According to the invention there is provided a weedkiller liquid applicator
device
comprising:
25 a main reservoir for weedkiller liquid to be applied; and
a liquid retention means for receiving an amount of liquid from the
main reservoir corresponding to multiple applicator doses and to
deliver a substantially uniform single dose of liquid on application.
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In one particularly preferred embodiment of the invention the liquid retention
means is of a material to store multiple applicator doses and to apply a
single dose
on contact application.
Preferably the liquid retention means is of cellular structure. Most
preferably the
liquid retention means is of a foam material, especially a polyurethane foam
material.
In an especially preferred embodiment of the invention the device includes
control
t o means for regulating the delivery of liquid through a discharge opening
from the
main reservoir.
Preferably the control means includes an air regulator for controlling the
flow of
air through an air inlet to provide substantially uniform flow of liquid from
the
main reservoir means.
Most preferably the control means includes a liquid discharge valve which is
movable by an actuating means from a closed position closing the liquid
discharge
opening to an open position for delivery of liquid.
Ideally the air inlet to the main reservoir is located above the liquid
discharge
opening from the main reservoir. Most preferably the air inlet is located a
distance above the liquid discharge outlet corresponding to a desired delivery
flow
rate through the liquid discharge opening.
In one embodiment of the invention the air regulator is provided by a non-
return
valve to prevent flow of liquid through the air inlet. Preferably the non-
return
valve includes a diaphragm which is movable by air pressure from a normally
closed position closing the air inlet to an open position for delivery of air
through
the air inlet.
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In one arrangement the liquid discharge valve actuating means comprises a
plunger projecting from the valve, the plunger being pushed against a surface
to
open the valve.
In a preferred embodiment of the invention the device includes an intermediate
chamber between the main reservoir and the liquid retention means, liquid
being
delivered from the main reservoir into the intermediate chamber. The
intermediate chamber assists in controlled delivery of liquid to the liquid
retention
means.
to
Preferably the main reservoir comprises an elongate tube, one end of the tube
defining a liquid inlet and the liquid retention means being mounted at the
other
end of the tube. Usually the liquid inlet is closed by a closure cap.
t 5 In another aspect the invention provides a liquid dispensing device having
a liquid
discharge opening and an air inlet wherein the air inlet is located above the
liquid
discharge opening to provide a substantially uniform flow of liquid from the
dispensing device. Preferably the air inlet is located a distance above the
liauid
discharge outlet corresponding to a desired delivery flow rate through the
2o discharge opening.
In a preferred embodiment of the invention the device includes an air
regulator for
controlling the flow of air through the air inlet to provide a substantially
uniform
flow of liquid. Preferably the air regulator is provided by a non-return valve
to
25 prevent the flow of liquid through the air inlet. In a preferred
arrangement the
non-return valve includes a diaphragm which is movable by air pressure from a
normally closed position closing the air inlet to an open position for
delivery of air
through the air inlet.
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In one embodiment of the invention the device includes a liquid discharge
valve
which is movable by an actuating means from a closed position closing the
liquid
discharge opening to an open position for delivery of liquid.
s Ideally the non-return air valve is located above the discharge opening, and
preferably when this happens the air inlet is at a position where its outlet
into the
container will always be within the liquid in the container until almost all
the last
bit of liquid has been discharged out of the container.
to The discharge opening may incorporate a normally closed liquid outlet valve
operative by a plunger projecting therefrom whereby on pushing the plunger
against the surface the valve opens and liquid is discharged.
In an embodiment of the invention a liquid containing material may be mounted
~ 5 adjacent the discharge opening for retention of liquid discharged
therefrom.
A particularly suitable construction is to incorporate both the normally
closed
liquid outlet and the non-return air valve in the one discharge opening
assembly.
With this arrangement which is particularly suitable for example for the
2o application of weedkiller the liquid container is an elongated tube, the
bore
forming a closure at one end for liquid inlet and a discharge opening at the
other
end for reception of the combined air inlet and discharge valve as
hereinbefore
described.
2s It is also envisaged that a discharge valve for a sealed liquid container
may be
provided according to the invention in which the discharge valve incorporates
a
non-return air inlet. It will be appreciated that such a valve can be used for
almost
any liquid container requiring a relatively steady discharge output.
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For example, when a saline drip needs to be dispensed the discharge valve may
be
a separate unit connected to tubing and having an inlet for connection to an
infusion bottle.
s Brief Description of t_he Drawings
The invention will be more clearly understood from the following description
thereof given by way of example only with reference to the accompanying
drawings, in which:-
Fig. 1 is a perspective view from one end of a weedkiller applicator
according to the invention;
Fig. 2 is a perspective view from the other end of the applicator;
is
Fig. 3 is an exploded perspective, partially cross sectional view of the
applicator;
Fig. 4 is a perspective view of some of the parts, assembled;
Fig. 5 is a cross sectional view of the applicator with a liquid discharge
valve closed;
Fig. 6 is a cross sectional view of an air regulator part of the applicator in
the position of Fig. 6;
Fig. 7 is a cross sectional view of the applicator with a liquid discharge
valve open; and
3o Fig. 8 is a cross sectional view of an air regulator part of the applicator
in
the position of Fig. 7.
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Detailed Description
Referring to the drawings there is illustrated a weedkiller applicator
indicated
generally by the reference numeral 1, comprising a main reservoir for liquid
s defined by a container 2 in the shape of an elongated tube forming a liquid
inlet
having an end cap 3 mounted on the end of the container 2. Remote from the end
cap 3 is a discharge valve assembly indicated generally by the reference
numeral 4.
The discharge valve assembly 4 comprises a cylindrical body member divided
into
two compartments, namely an interior compartment 5 communicating directly
1o with the interior of the container 2 and an intermediate chamber defined by
an
exterior compartment 6 separated therefrom by a partition wall 7. Mounted in
the
partition wall 7 is a valve plunger 8 having a plurality of axially arranged
liquid
passageways 9. A spring 10 biases the valve plunger 8 into a normally closed
position. Mounted on the end of the valve plunger 8 projecting into the
exterior
t s compartment 6 is an in-line actuator 11. A block of liquid retaining
material, in
this case a portion of foam/sponge 12, surrounds the actuator 11 and bears
against an annular flange 13 having a plurality of holes 14. The flange 13 is
a
press-fit within the discharge valve assembly 4 and the sponge 12 which is of
polyurethane material is cut to have an undersize bore and an oversize outer
2o diameter to form a force-fit due to its own elasticity.
The foam/sponge block 12 defines a liquid retention means for receiving an
amount of liquid from the main reservoir defined by the tube 2 corresponding
to
multiple applicator doses. The cellular structure of the foam/sponge material
also
2s delivers a substantially uniform dose of liquid by contact application to
the leaves
of a weed. The flow of weedkiller liquid from the container 2 into the
intermediate chamber 6 is controlled by a control means which regulates the
delivery of liquid through a discharge opening into the liquid passageways 9.
The
control means comprises an air regulator for controlling the flow of air
through an
3o air inlet to provide substantially uniform flow of liquid from the
container 2 into
the intermediate chamber 6. The control means also includes the liquid
discharge
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valve 8 which is movable by the actuator 11 from a closed position closing the
liquid discharge opening (Fig. 5) to an upper position (Fig. 7) for delivery
of liquid
into the intermediate chamber 6. The chamber 6 spreads the liquid partially
across the top of the sponge/foam 12 which soaks the liquid through the holes
14
s in the wall 13.
The control means defined in this case by the air regulator and liquid
discharge
valve are mounted together in the valve assembly 4.
The air regulator comprises a non-return air valve 20 which is mounted on a
spigot 26 extending upwardly from the partition wall 7. The non-return air
valve
20 comprises a bored valve stem 21 having a bore 22 mounted within a rigid
tube
23. A diaphragm 24 covers the bore 22 and is retained in position by an end
cap
25 having openings 27 communicating with the interior of the container 2.
In use, depression of the actuator 11 against any hard surface causes the
plunger 8
to move upwards within the interior compartment 5 and thus within the
container
2 allowing weedkiller liquid to flow down the liquid passageways 9 into the
exterior compartment 6 and then through the holes 14 in the annular Mange 13
onto the sponge 12 which is then wetted with the weedkiller: The flow of
liquid is
indicated by single headed arrows in Fig. 7. The air valve 20 ensures that
there is
a constant rate of flow. There will always be air in the exterior comparnnent
6
which will act on the underneath of the diaphragm 24 and will raise it to
allow air
discharge out through the end cap 25 into the liquid in the container 2 until
equalisation of pressure on the diaphragm 24. Thus the pressure for discharge
will
always be constant and equal to the pressure obtained at the bottom of a
liquid
column of height x, where x is the difference between B and C on the drawing,
i.e.
between liquid outlet and air outlet.
3o The diaphragm 24 effectively floats between an open or sealed position and
once
the container is open to the atmosphere e.g. on filling it will be sealed shut
by the
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head of the liquid. The flow of air is schematically illustrated by double-
headed
arrows in Figs. 7 and 8.
In the applicator of the invention when the liquid valve is opened, the liquid
wants
to discharge at a rate that is consistent with pressure generated by the water
column at the valve. For this to happen air must enter the enclosed tube.
However, the air intake is governed by the liquid pressure opposing the entry
of
air at the air entry point. Should that point be just above the discharge
valve then
the pressure opposing air entry will approximate to the liquid pressure at the
t o discharge valve. As a consequence the rate at which air can enter is
dependent on
a small pressure differential. This in turn determines the rate at which
liquid can
discharge, irrespective of the height of liquid within the tube.
In the invention, the air valve is fitted with a diaphragm so that it too acts
as a one
~ s way valve. This is important to prevent liquid leakage when the tube is
being
filled, otherwise the system would work without the diaphragm. It is however
true to say that the diaphragm senses every minute variation of pressure in
the
liquid column and responds by instantly correcting the rate of air intake.
2o Given a constant flow rate the dose size is now determined by the time
interval
between the opening and closing of the liquid discharge valve. In the
invention
the sponge receives a full dose (equivalent to some 30 weed doses) when the
valve
plunger is quickly pressed and released.
2s The applicator of the invention may be used substantially continuously or
on an
intermittent basis. For example, it may be used to treat a concentration of
weeds
in a small area or a number of weeds spread over a large area. Because of the
liquid retention means, especially in the form of a cellular structure,
particularly a
foam or sponge a reservoir of a multitude of doses (such as 30 doses) is
provided.
3o This retention means may be used after a single charge to treat weeds in a
local
area or spread over a wide area without interruption to re-charge the
applicator.
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More particularly because of the construction of the liquid retention means, a
contact liquid film is easily applied to the leaves of the weed for effective
treatment.
s In addition, by virtue of the liquid retention means blockages of the
working parts
of the applicator are avoided. Because only a single charge is required for
multiple applications contact with the soil is minimised. Weed treatment is
achieved by sponge/foam to leaf contact, without pressing. The sponge/foam
effectively acts as a barrier, preventing soil from contacting the moving
parts.
s o Further, each re-charge flushes the sponge/foam.
The applicator is readily refilled without contacting parts through which
weedkiller has passed. For charging weedkiller concentrate to which water may
be added in the tube the closure ca.p may be of a volume or have an indicator
1 s marks) corresponding to a desired amount of liquid concentrate required
for
make-up of a weedkiller liquid.
It is believed that there is a constant flow of liquid because effectively the
in-flow
of the air at the level C as indicated in the drawing is in the form of
bubbles which
2o will be relatively regular sized. Bubble formation requires a certain
excess
pressure, more or less independent of flow rate. Thus, the following appears
to be
the position when the container 2 is sealed. Air enters the container at the
level C
and liquid is flowing out of the container at level B. The following appears
to be a
possible mathematical explanation.
~P = pa - p~ (1) p, = air pressure
p~ = liquid pressure at C
p~ - pn = - p g x (2) pd = liquid pressure at B where:x -
3o height difference between B and C
p = density/specific gravity
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Flow rate
cQ = pn - pa (3) Q = Flow rate
c = constant
{Posseuilles Law}
Pn = pa + cQ (4)
adding (2) + (4)
pr=pa+cQ-p g x
pr - pa = CQ - P g x
- Op=cQ_P 8 x
cQ=P g x-~P
when p g x = 0p no flow will occur
For flow then
x > DP
Pg
2o This is a possible explanation of why constant flow is achieved.
Another possible way of viewing how tire invention works is that as the entry
of
the air is through the liquid this entry is being opposed by the pressure
generated
by the column of liquid above the entry point and it is the differential
between the
negative pressure generated above the liquid and this positive pressure that
controls the flow of air. It is the natural balance between these two opposite
pressures that occurs as the liquid empties which achieves this steady flow
rate.
The invention is particularly applicable to constant rate watering or feeding
3o systems for horticultural use. It will work particularly well with remotely
sited
containers.
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It is envisaged that with the correct choice of air valve very accurate
control of
flow can be obtained either through varying the height of the air outlet above
the
liquid discharge outlet, the so called x dimension.
s
The invention is not limited to the embodiments hereinbefore described which
may be varied in both construction and detail.
