Note: Descriptions are shown in the official language in which they were submitted.
YVO91/12~ PCT/~S~1/01033
2~ 9
DEFLECTION CONTROL OF LlQUID
STREAM DURING DISPENS ~G
Field of the Invention
This invention relates to liquid dispensing.
More particularly, this invention relates to a method
and apparatus for controlled deflection of a liquid
stream d~ring dlspenslng to achieve a comple~ pattern
on a substrate or uniform coating of an irregular
surface. One preferred embodiment o~ the invention
relates to uniform coating of the entire interior
surface of a metal can with a single nozzle.
Backqround of the Invention
In the past, a number of methods have been
used to achieve a desired spray pattern for a liquid
or molten product dispen~ed from a nozzle opening.
Binary liquid spray (air spray) and airless spray are
two commonly used methods for discharging a coating
agent from a nozzle opening to achieve a spray pattern
on a substrate. Differences among spray patterns
formecl by these and other methods generally relate to
the varied ways in which compressed gas is used to
generate the spray.
WO91/120~ PCT/~91/~1033
2~ 2-
Spraying of compressed air on both sides of
a liquid stream may be used to provide another type of
spray pattern, or to alter a known spray pattern.
With any type of nozzle opening, spraying of air
side~.~ays into the liquid stream generally creates a
broad deformation of the spray pattern. One method
referred to as the swirl 'spray method creates
descending spirals forming a whirlpool by discharging
liquid downward through a nozzle opening and spraying
a heated, compressed gas in the vicinity of the
external periphery of the discharged stream from
multiple openings located in regular intervals around
the periphery of the nozzle.
With one or more of these methods~ it is
possible to obtain a uniform spray pattern from a
sinqle nozzle. However, to achieve multiple or
complex patterns, multiple spray guns and nozzles must
be used. As a result of the additional equipment, and
the increase in workers and maintenance necessitated
by the additional equipment, the cost of achieving
multiple or complex spray patterns increases signifi-
cantly.
In addition to higher cost, it is sometimes
physically impossible to conduct certain spraying
operations within the confines of a given narrow
space. Another concern arises when considering
continuous spray operations for coating a surface,
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WOgl/120~ PCT/VS~1/01033
-3- 2 ~7~
where a reflection flow layer may form on the surface
of the coated object and collide with subsequent
spray, causing additional collisions, dispersion of
spray and inefficient coverage of parts. This gener-
ally occurs when the part to be coated is concave,
such as the corner of a can. In addition to the
inefficiency of this spraying process due to reflec-
tion of this "air cushion'l, the collision and dis-
persion of the reflected spray pollutes the spraying
environment and becomes a source of contamination.
.
It is an object of the invention to provide
a method and apparatus for dispensing liquid in
multiple and/or complex patterns in an economically
feasible manner, within a minimum space, and in a
manner which minimizes deflection and/or turbulence of
atomized particles during dispensing.
Summary of the Invention
To these ends, this invention contemplates a
liquid dispensing apparatus and method that utilizes a
nozzle with a central liquid dispensing orifice and a
plurality of blowout ports surrounding the orifice,
with each blowout port being independently actuatable
to direct a flow into contact with the dispensed
liquid stream. By controlling the sequence and
duration of the independently actuatable flows during
liquid dispensing, a desired distribution pattern may
be produc2d on a substrate. The invention applies to
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.. ,:. ; . .
WO91/120~ PCr/VS91/01033
2~7~J~
--4--
a dispensed liquid stream in the form of relatively
large drops or an atomized spray.
According to onle embodiment of the inven-
tion, six blowout ports are spaced equidistant around
the central liquid dispensing orifice in the nozzle.
The blowout ports are directed inwardly toward an axis
aligned along the central liquid dispensing orifice.
By sequentially actuating each of the blowout ports
around the dispensing orifice during liquid dis-
pensing, the dispensed stream is sequentially
. .
deflected in six different directions to form a
generally circular deflection pattern on a substrate.
Alternatel~, two or more of the blowout ports could be
actuated simultaneously to create further variations
in deflection.
One particular advantage provided by this
inventive method and apparatus relates to coating of
the entire interior surface of a metal can with a
single nozzle. Due to increased versatility and
control of the direction of the liquid stream that is
dispensed from the orifice of the nozzle, the inside
surface of a can may be uniformly coated at a reduced
cost, and with minimum of undesired air cushioning.
Air cushioning is reduced by sequentially
actuating the blowout ports located around the dis-
pensinq opening to supply radially inwardly directed
flows from directions which rotate circumferentially
W~1/120~ PCT/U~91~01033
J~
5--
around the liquid stream. Rotational deflection of
the liquid stream, particularly a liquid stream that
is an atomized spray, prevents undesired reflection
and dispersion of the stream. As a result, a problem
of prior coating methods, that of uneven c~ating in
the corners o~ the can, is eliminated.
According to a preferred embodiment of the
invention, this liquid dispensing apparatus includes a
liquid dispensing gun with a timer actuated solenoid
valve that controls flow of the dispensing liquid from
an inner chamber and out of an orifice in a nozzle
connected to the end of the gun. The nozzle also
includes six radially directed bores which communicate
with six respective blowout ports, each blowout port
aimed to intersect the liquid stream from the nozzle
orifice at a slight distance away from the tip of the
gun. Six conduits connect to the radial bores and
supply compressed gas to the hlowout ports. The flow
of pressurized gas through the conduits, the bores and
out of the blowout ports is controlled by electrically
actuated solenoid valves connected to the conduits.
The solenoid valves are actuated by the timer whicn
also controls the liquid flow valve of the gun. The
timer is preferably a pulse controller capable of
supplying current pulses ranging from about 4 milli-
seconds to 50 milliseconds.
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W~91/120~ PCT/US91~01033
By controlling the timing sequence and
duration of the current pulses from the timer to the
liquid dispensing valve and the valves which control
the flow of blowout gas ~Erom the blowout ports, the
dispensed liquid stream may be deflected in a desired
manner to achieve a comp:Lex distribution pattern on a
substrate.
The central dispensing orifice may be a
single orifice at the end of a liquid passage that
extends to a liquid reservoir. The nozzle and gun may
.
also be equipped for an airless spray nozzle. Alter-
nately, the nozzle may also include a concentric
atomizing port located intermediately between the
nozzle opening and the blowout ports for-binary liquid
spray dispensing. These latter two embodiments enable
controlled deflection of a stream of particles that
have already been atomized. The gun and nozzle may
also be adaptable for extruding a liquid.
According to additit~n~l embodiments of the
invention, the nozzle opening may include two or more
orifices for liquid dispensing of two or more types of
liquid. The multiple orifices may be arranged side-
by-side, or concentrically. One of the orifices may
be used to mix aelosGl into another dispensing liquid.
Additionally, aerosol may be used as the deflecting
agent through the blowout ports for deflecting the
mixture.
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WO91/120~ ~ ~ PCT/US91/01033
Because the liquid stream may be deflected
in a varied number of directions, this invention
promotes increased spraying or dispensing versatility
from a single nozzle within a minimum amount of space.
This invention also reduces the cost of spraying
multiple or complex patterns because a single nozzle
can be used to achieve a wide range of distribution
patterns. If desired, additional blowout ports may be
prov~d2d ~o further increase versatility in achieving
complex deflection patterns.
These and other features of the invention
will be more readily understood in view of the
following detailed description and the drawings.
Brief Description of the Drawin~s
Fig. l is a cross-sectional schematic view
of a liquid dispensing apparatus in accordance with a
first preferred embodiment of the invention.
Fig. 2 is a view taken along lines Z-2 of
Fig. l.
Fig. 3 shows a dot pattern formed on a
substrate by the apparatus depicted in Fig. l.
Fig. 4 is an enlarged, cross-sectional
schematic showing the liquid dispensing apparatus of
Fig. l equipped with an airless spray nozzle in
accordance with a second preferred embodiment of the
invention.
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- "
WO91/120~ ~CT~US91/~1033
2~ J~ 8-
Fig. 5 shows a spray pattern formed on a
substrate by the apparatus depicted in Fig. 4.
Fig. 6 is a cross-sectional schematic view
similar to the liquid die;pensing apparatus shown in
Fig. l, but modified to :incorporate a nozzle equipped
for binary liquid spray dispensing in accordance with
a third preferred embodiment of the invention.
Fig. 7A is a timing diagram for operation of
the apparatus shown in Fig. l. The timing diagram
depicts current pulses that control liquid dispensing
_
from the nozzle ar.d gas flows from the blow out ports.
Pig. 7B shows an alternate timlng diagrar~
for controlling liquid dispensing and gas flows from
the blow out ports.
Figs. 8A and 8B depict spray patterns formed
by the apparatus shown in Fig. 1 when operated
according to the timing diagrams of Figs. 7A and 7B~
respectively.
Fig. 9 shows a timing diagram for control-
ling liquid dispensing and the gas flows from blowout
ports for the binary liquid gas dispenser shown in
Fig. 6.
Fig. lOA depicts a spray pattern formed by
the apparatus shown in Fig. 6 when operated according
to the timing diagram of Fig. 9.
Fig. lOB depicts a spray pattern formed by
:.,
the apparatus shown in Fig. 6, but with the timing
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WO9~/120~ ~7~ PCT/~S91/01033
diagram of Fig. 9 slightly varied to include a delay
before the initial gas flow from the blowout ports.
Figs. llA and llB depict timing diagrams for
operating the liquid dispensing apparatus shown in
Fig. 6.
Fig. 12A depicts a spray pattern that may be
formed with the liquid dispensing apparatus shown in
Fig. 6, when operated according to the timing diagram
of either Fig. llA or Fig. llB.
Fig. 12B depicts an alternate spray pattern
that may be formed with the device of Fig. 6 and the
timing diagram of either Fig. llA or Fig. llB, if a
time delay is included between initial liquid dis-
pensing and the first gas flow.
Fig. 12C shows dot patterns that may be
formed with the device of Fig. 1 if liquid dispensing
occurs intermittently.
Fig. 12D is similar to Fig. 12C, but in-
cludes a time delay between initial liquid dispensing
and the first gas flow.
Figs. 13A, 13B, 13C and 13D depict addition-
al, complex spray patterns that may be formed by the
liquid dispensing apparatus of Fig. 6 if equipped with
a nozzle having additional blowout ports and, with
respect to Fig. 13B, Fig. 13C and Fig. 13D, additio~al
blowout ports and either varied angles of directional
gas flow or variation in volume of gas flows.
. . .
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W~91/12~ P~T/US91/01033
--10--
J~ ~ Fig. 14A is a cross-sectional view of an
airless spray nozzle for multiple liquid, mixed
sprays.
Fig. 14B is a bottom view, looking upwardly,
of the airless spray nozzle stream in Fig. 14A.
Fig. 14C is a bottom view, similar to Fig.
14B, of a binary liquid spray nozzle for multiple
liquid, mixed sprays.
Fig. 15 is a cross-sectional view of a
liquid dispensing apparatus which mixes aerosol with
another dispensing liquid and deflects the mixture
with aerosol, according to a fourth preferred embodi-
ment of the invention.
Fig. 16A and 16B show dot patterns formed
with a thermoplastic resin, such as a hot melt adhe-
sive agent, wa~ or a similar substance.
Fig. }6C shows a dot pattern similar to
those of Figs. 16A and 16B, but formed with multiple,
parallel nozzles.
Figs. 17A, 17B, 17C, 17D and 17~ show
various dot patterns that may be formed in accordance
with the teachings of this invention.
Fig. 18 depicts a uniform spray pattern
particularly sui~able for coating the inner surface of
a metallic can.
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WO91/120~ PCT/US91/01033
9~
Figs. l9A and 19B show alternate methods of
uniformly coating the inside surface of a metallic can
according to the invention.
Detailed Description of the Invention
Fig. 1 shows a liquid dispensing apparatus,
or gun, designated generally by numeral 20, according
to a ~irst preferred embodiment of;the invention. The
gun 20 is connected to a nozzle 21 for dispensing of a
liquid therefrom. The aligned gun 20 and nozzle 21
form a central liquid passage 23 which terminates in
an orifice 24 through which liquid is dispensed.
While this invention contemplates liquid dispensing as
drops, droplets or atomized particles in a spray, the
dispensed liquid is generally referred to in the
application as a liquid stream, and designated by
numeral 26. The surface upon which the stream 26 is
dispensed and distributed is referred to generally as
substrate 27.
The dispensing liquid is contained within
the c:~ 20 inside an annular chamber 28. Fluid `
supplled to the chamber 28 is provided by an external
pump 29 connected to the gun 20. Flow control of
dispensing liquid from chamber 28 is accomplished by
operation of a liquid valve 30 which extends through
chamber 28 and seats within an upper end of central
liquid passage 23.
- . ~ ,. -
:, . - ,. . . . ..
.. , :.
~091/12~ PCT/US91/01033
_ ~ q~ -12-
Nozzle 21 includes six blowout ports,
designated consecutively by numerals 33a-33f. Gas
blown from the blowout ports deflects the dispensed
liquid stream 26 to provide a desired deflection
distribution on substrate 27. While six blowout ports
33a-33f are shown, it is contemplated that an optimal
arrangement would include up to thirty-six blowout
ports. Each blowout port communicates with a respec-
tive, radially directed bore in the nozzle 21, des-
ignated consecutively by numerals 34a-34f and shown in
phantom in Fig. 2. Six conduits designated consecu-
tively by numerals 35a-35f connect to the outer
circumference of the nozzle 21 for fluid communication
with radial bores 34a-34f, respectively. Valves
36a-36f are located along conduits 35a-35f, respec-
tively, although only valves 36a and 36d are shown in
Fig. l. The valves 36a-36f regulate the flow of
pressurized gas toward blowout ports 33a-33f, respec-
tively. At least two solenoid valves 38 and 39 are
operatively connected to the conduits 35a-35f to
control flow of pressurized gas from a pressurized gas
source 37, along the conduits 35a-35f, through the
bores 34a-34f and eventually out of the blowout ports
'.~ 33a-33f. Solenoid valves 38 and 39 are electrically
connected to a timer 4l, and, as depicted, each of
these valves 38 or 39 control gas flows from three of
the blowout ports. If additional blowout ports are
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WO91/12088 2r~ ~r/US~1/01033
-13-
used, additional solenoid valves may be necessary.
The timer 41 actuates the solenoid valves 38 and 39
according to a desired sequence and duration to
produce a predetermined distribution pattern of the
liquid stream 26 onto the substrate 27.
Preferably, the timer 41 is a current pulse
controller capable of providing square wave current
pulses of selectable durations. Particularly in spray
coating applications, since disturbances referred to
as air cushions may cause undesired reflection of the
gas flows, as described in the background, it is best
if the time duration of the current pulses from timer -
41 are kept under 500 milliseconds. Preferably, the
timer 41 should be capable of delivering current
pulses ranging in duration of several milliseconds,
i.e., about 4 milliseconds, up to about 50 milli-
seconds. ;^`
The timer 41 is also electrically connected
to a solenoid valve 42 which controls the supplying of
dispensing liquid from pump 29 to chamber 28. Dis-
pensing liquid may be supplied from a liquid tank 44,
: - :
` a pressurized liquid tank 45 or a gravity pressure
tank 46. A feedback line 47 may also be used to
connect chamber 28 with pump 29 to assist regulation
of pressure and/or flow conditions of dispensing
liquid in chamber 28. With the liquid in chamber 28
pressurized by pump 29 and its peripherally connected
~'
WO91/120~ PCT/US91/01033
2f'~ Y~ -14-
components, raising of valve 30 from its seated
position within passage 23 causes pressurized liquid
in the chamber 28 to flow along passage 23 and out of
orifice 24. To raise valve 30, the timer 41 elec-
trically actuates a solenoid valve 48 to permit
pressurized gas flow into a cylinder 50 at the top of
the gun 20. The pressurized gas moves a piston 51
upwardly within the cylinder 50 to raise the valve 30.
When no pressurized gas is supplied from solenoid
valve 48, downward force from a spring 52 acts against
the top surface of the piston 51 to hold valve 30 in a
normally closed position. A valve 49 may be used to
variably control the volume of gas that flows into
cylinder 50 when soIenoid valve 48 is actuated.
Fig. 2 shows the radial orientation of the
six blowout ports 33a-33f with respect to orifice 24.
From this view, it can be readily seen that the
alignment of the blowout ports 33a-33f enables a
liquid stream 26 to be deflected from the opening 24
in any one of six radial directions, the six direc-
tions being spaced 60~ around the exterior of the
orifice 24.
Fig. 3 shows a dot pattern formed on a
substrate 27 using the gun 20 depicted in Fig. l.
When valve 30 is raised to an "open" position, the
liquid in chamber 28 moves through passage 23 and out
orifice 24 in a downward direction. If the liquid has
WO91/120~ ~ PST/US9ltOI033
-15-
a relatively low pressure in contrast to a relatively
high viscosity, a high cohesive force is created. For
instance, a rubber type :Liquid substance or a hot-melt
adhesive agent would fit this description and produce
a high cohesive force. As a result, the effluent flow
will create a linear for~ of discharge flow. Com-
pressed gas is then blown out sequentially from each
of the multiple, independently actuatable gas blowout
ports 33a-33f. As the gas blowout flows strike the
linear outgoing flow, the liquid stream 26 is
deflected, or redirected in a different direction.
As shown in Fig. 3, when liquid with a high
cohesive force is deflected from a downward linear
direction, a dot pattern is achieved, the size and ^
spacing of the dots deper.ding upon the blowout pres-
sure of the distribution gas. Fig. 3 shows dots
55a-55f produced b~ gas flows from blowout ports
33a-33f, respectively. It is noted that each dot
resides on the opposite side of the blowout port from
which it was deflected.
Fig. 4 shows an enlarged view of a nozzle 21
suitable for use in gun 20 in accordance with a second
preferred embodiment of the invention. According to
this embodiment, the nozzle 21 is equipped with an
airless spray orifice 57, which makes it possible to
obtain a complex spray pattern from a liquid stream 26
that is atomized. All of the other elements of the
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: . . . . :
WOgl/120~ PCT/US91/0~033
16-
gun 20 are similar to those shown in Fig. l, although
higher liquid pressures may be necessary. The liquid
used to produce the dot pattern of Fig. 3 had a
relatively high viscosity, but the liquid used with
the airless spray orifice 57 has a relatively low
viscosity (for instance a solvent, coating agent,
emulsion, oil, atomized gas, etc.). Because the
liquid stream 26 is atomized during discharge, the
resulting pattern which appears on substrate 27 is a
spray coating pattern, as shown in Fig. 5. Instead of
the dots 55a-55f of Fig. 3, the airless spray orifice
57 produces spray regions 58a-58f of atomized droplets
corresponding to directional gas flows from the
blowout ports 33a-33f, respectively.
Fig. 6 shows a third preferred embodiment of
the invention, which contemplates use of a gun 20
equipped to provide binary liquid spray to achieve
., ,
atomization of the liquid stream 26. According to
this embodiment of the invention, the gas blowout
ports 33a-33f surround the periphery of a nozzle
orifice 59 and atomization o the dispensed liquid is
achieved by discharging atomizing gas from the nozzle
21 via a concentric atomizing gas outlet 60 located at
an end of a longitudinal, concentric passage 61. The
atomization creates a spray flow for the liquid stream
26. Similar to the first and second embodiments
described above, the atomized liquid stream 26
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,, , . . :.: . ::.. ., ::: . .. .
WO 91/12U8~ 2~ P~r/US91/01~33
combines with multiple distribution gas l~lowout flows
from the blowout ports 33a-33f. When the gas blowout
ports 33a-33f are ac tuated sequentiall~r to produce gas
flows which strike the atomized liquid stream 26,
deflection occurs and it is possible to obtain a
desired complex spray pattern as shown in Fig. 5.
The binary liquid spray gun 20 of Fig. 6 is
similar to that of Fig. 1, except for the modifica-
tions necessary to spray atomizing air along passage
6l and from outlet 60 into the liquid stream 26. More
particularly, the gun 20 includes the passage 61 which ;~
terminates in a bore 64, and the bore 64 is connected
to a conduit 65 which is in turn connected to the
pressurized source 37 via a solenoid valve 68.
Solenoid valve 68 is electrically actuated by timer 4l
to permit pressurized air flow along conduit 65,
through bore 64, along passage 61, and eventually out
of outlet 60 during liquid dispensing from orifice 23,
thereby to atomize the liquid stream 26. An addition-
al flow valve 67 may be used along conduit 65 to
provide additional control over the flow of atomizing
gas therethrough.
Fig. 7A depicts current versus time for the
current signals from timer 41 which control operation
of the liquid dispensing valve 30 and gas flows from
the blowout ports 33a-33f. Curve 70 represents the
timing of the discharge of the liquid from orific~ 24.
~ . . . -, ................................ : .,
.
~VO91/12~ PCT/US91~01033
2~ 9
When a signal is received from the timer 41 or pulse
controller 41 in Fig. 1, the operational position of
the solenoid valve 48 will be the "open" position, and
the operating air will be connected directly to the
gun 20 so that it will penetrate inside the air
cylinder 50 to raise piston 51 and valve 30 to dis-
charge the liquid.
Numerals 73a-73f represent the current
pulses that generate the gas flows from respective
multiple distribution gas blowout ports 33a-33f. When
the distribution blowout ports (six in this case) have
identical allocations for liquid discharge time,
sequentially distributed gas is blown out from each of
the blowout ports 33a-33f during only one allocated
time pulse. Fig. 7A shows blowout from the first
blowout port 33a occurring simultaneously with the
pulse 70 which initiates discharge of the liquid
stream 26. Subsequently, the other blowout ports 33b,
` 33c, 33d, 33e and 33f are actuated sequentially by
respective pulses 73b, 73c, 73d, 73e and 73f. When a
gas flow from a blowout port strikes the liquid stream
26, the two flows combine to create a deflected
directional flow that eventually lands on the surface
of the substrate 27.
With six distribution gas blowout ports, six
liquid agglomerates can be gradually distributed into
respective locations, sequentially and one by one.
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WO91/12~ .?~ PCT/US91/01033
According to the timing of the liquid signal 70 and
the pulses 73a-73f shown in Fig. 7A, the substrate 27
will be coated according 'to the following sequence of
coating regions 74a, 74b, 74c, 74d, 74e and 74f. If
the timing is modified, the sequence will be altered.
Furthermore, if necessary, when the gas flow is
interrupted, the liquid stream 26 will flow vertically
downward and form a central region 80 residing within ~'
the center o~ the six regions 74a-74f on the substrate
27. Fig. 7B depicts a timing diagram in which the
.
first gas flow commences a time delay 76 later than
initial discharge of the liquid stream 26.
Figs. 7A and 7B show timing for continuously
discharged liquid with sequentially blown out gas.
With continuous liquid dispensing, some of the direc-
tion of the liquid stream 26 will be retained during
distribution as it existed before the change of the
direction. More particularly, a tail, such as those
shown in Figs. 8A and 8B will be added to each of the
dot shapes or coated regions 74a-74f. Note that
central dot 8Q remains unaffected in Fig. 8B.
Fig. 9 shows an example of the coordination
of the current pulses ?, 78 and 73a-73f for producing
discharge of liquid, atomized gas and distributed gas
flows, respectively, using the binary liquid spray gun
20 shown in Fig. 5. The timing pulses of Fig. 9
produce distribution of the liquid stream 26 on a
WO91/120~ PCT/US91/01033
20- -
substrate 27 in the pattern shown in Fig. lOA. If a
time lag between signal 70 and signal 73a were to be
used, and all of the other gas flows were sequenced
and of the same duration, the pattern shown in Fig.
lOB would be produced on substrate 27.
Fig. llA depicts current pulses which
produce intermittent discharge of liquid stream 26 and
intermittent actuation of atomized gas. Fig. llB
depicts current pulses which produce intermittent
discharge of the liquid stream 26 with continuous
blowing out of atomized gas. In both o~ these cases,
when the intermittent liquid stream 26 strikes the gas
from the ports 33a-33f, the direction of the flow
during the previous change of each of the spray flows
is not maintained. In other words, since there is a
discontinuation in liquid dispensing, i.e., signal 70,
the spray distribution patterns of Figs. 12A and 12B
are produced without tails. Again, Fig. 12B depicts a
central coated region 80 that would be caused if the
first gas flow were to lag behind initial liquid
dispensing. This current control scheme is not
depicted. In both Fig. llA and Fig. llB the current
pulses to actuate the gas flows, i.e., 73a-73f, are
sequenced and staggered.
Although the above examples relate to an
atomized liquid stream 26, it is also possible to use
current pulses to intermittently actuate the liquid
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'' ., .: . ' ' : " ' . ,' . , . . ' ' , ' , ' '
WO91/120~ P~T~US91/01033
-21-
stream 26 produced by the device of Fig. 1 for the
purpose of obtaining dot shape patterns, as shown in
Figs. 12C and 12D. Note that Fig. 12D depicts a
pattern that would be for~ed if a time lag were used
between initiation of liquid dispensing and the first -~`
gas flow from the blowout ports. In all cases, if the
liquid dispensing is inte!rmittent, the spray pattern
will not have tails.
Although the explanation above describes six
distribution gas blowout ports 33a-33f and the pat-
terns have a generally circular shape, the number of
these distribution gas blowout ports may be increased
to twelve LO obtain a ring shape, such as the one
shown in Fig. 13A. This example and the prior exam-
ples all used identical angles for the blowout ports,
as well as identical blowout pressures and blowout
times. However, if these variables are changed, it
becomes possible to obtain more complex patterns, such
as those shown in Figs. 13B, 13C and 13D. For
instance, the patterns shown in Figs. 13B and 13C
require a total twelve ports, similar to Fig. 13A, but
with some of the ports angled differently than the
others. Alternately, the same designs could also be
achieved if the durations of the current pulses were
varied to change the volumes of the gas flows con-
tacting the liquid stream 26. The pattern of Fig. 13D
requires sixteen blowout ports and variation in the
WO91/120~ PCT/US91/01033
22-
angles of the ports, or alternately, variation in the
duration of the current pulses which generate the gas
flows. While Figs. 13A-13D show the effects of
variation in blowout port angles or current pulse
duration for the spray, the same techniques can also
be applied to the apparatl~s shown in Fig. 1 to obtain
dot shaped patterns.
While use of the blowout ports to achieve
single directional deflection has been described, it
is also possible to use-a combination of intersecting
. . .
gas flows. It is also possible to use gas flows to
create a twist to the liquid stream 26. Such a
technique is a particularly efficient method of
applying dot shapes in a desired distribution pattern.
.~ccording to another embodiment of the
invention, multiple liquids may be discharged from
multiplè nozzles, as shown in Figs. 14A, 14B and 14C.
By mixing the discharged liquids, a combined flow is
achievad. This would enable the addition of a
hardening agent or similar agent for mixing in
advance, so that the dispensed liquid would harden
more readily. Figs. 14A and 14B ~how an airless spray
nozzle 85 for mixing liquids dispensed from an inner
orifice 86 and an outer, concentric orifice 87. Both
orifice 86 and orifice 87 reside within the blowout
ports 33a-33f. Fig. 14C shows a variation for
spraying a liquid stream 26 of liquid from three
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WO9lJ120~ PCT/US9l/01033
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orifices 89, sO and 91, located within a concentric
atomizing outlet 92, with blowout ports 33a-33f `^
located further outside.
one of the additionally mixed liquids may
also be liquid aerosol, as shown in Fig. 15, with
aerosol supplied by one, or both, of the conduits ~5
or 96 ~onnected to tanks 97 and 98, respectively.
Flow of liquid aerosol to orifice 87 of the gun 20 via
line 104 is controlled by a solenoid valve 101 con-
nected to timer 41. Valve 102 provides additional
control of aerosol flow through line 104.
Fig. 15 also shows that aerosol conduits 96
and 99 from tanks 97 and 98, respectively, inter-
connect to solenoid valves 38 and 39. Thus, according
to this invention, the aerosol is supplied to the
blowout ports 33a-33f and used as the blowing ~gent to
deflect the mixed liquid stream 26 formed from both
liquids dispensed out of nozzle 21~ It would also be
possible to supply diffsrent aerosols to each of the
blowout ports 33a-33f, provided that additional pipe
lines were used for each of the aerosols.
Mixing of the liquid that forms the aerosol
can be conducted with a solvent, a catalyst, a
hardening agent, a liquified gas, etc. When a solvent
is used, it is more effective to use self-cleaning of
the orifice 23 and of the distributed gas blowout
ports 33a-33f. Furthermore, it is well known that
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~091/1~ PCT/US91/01033
-24-
when a catalyst and a hardening agent are used, adding
amine to epoxy-type paints is an effective manner of
vapor curing. Also, when liquified gas is used, the
high amount of energy created by expansion during
mixing of the gas and liquid accelerates atomization.
It is also possible to use this invention
for deflecting fine particles of ice. Recently, Taiyo
Oxygen KK Co. and Mitsubishi Electronics KK Co.
proposed the injection of demineralized water into
liquid nitrogen to create icing particles as a method
to clean wafers. Other methods of using liquid
nitrogen to create icing structures of liquid were
described by The University of Gumma and other orga-
nizations in ICLAS '78 Proceedings (International
-Conference on Liquid Atomization and Spray System).
These concepts may be readily applied to this inven-
tion by deflecting a liquid stream 26 of iced parti-
cles formed by mixing demineralized water and liquid
nitrogen. This mixture would preferably be atomized
by injection of the demineralized water into the
liquid nitrogen.
It is also to be understood that molten
liquids may be used with this invention to produce a
thermoplastic resin, a hot melt adhesive agent, wax,
or a similar substance with a relatively low viscosity
under 200C. According to prior methods for dot
shaped coating of hot melt adhesives onto substrate,
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WO 91/120~ ~f,~ - ~" ~ PCT/US91/01033
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the adhesive was discharged intermittently from a
no~zle opening while the substrate was moved relative
to the nozzle in order to achieve a straight line of
coating. Figs. 16A and 16B show distribution patterns
of dots that can be attained with the gun shown in
Fig. 1. Fig. 16C shows a dot distribution pattern
obtainable with multiple, parallel guns 20 of this
type. Figs. 17A-17D also show distribution patterns
attainable with a gun 20 of the type shown in Fig. 1,
but with additional blowout ports added and liquid
_ . . .
dispensing during relative movement of the gun 20 and
substrate 27.
It is also possible to apply prior art
electrostatic coating methods to this invention. By
charging the liquid with static electricity when the
liquid is supplied to the gun, or attaching a corona
pin to the vicinity of the nozzle oririce 24 for the
liquid, the liquid can be charged as it is dispensed
from the gun 20. Ch2~sing of the liquid stream 25
accelerates atomization, thereby reducing particle
size to microscopic dimensions and improving the
adhesion characteristics on a coated substrate 27.
Perhaps the most important commercial
advantage of the invention relates to coating the
interior surfaces of a hollow product such as a
metallic container. To prevent the contamination of
the food contents of a can by the metal of the can, it
WO91/120~ PCT/US91/OID33
~n~ 26-
is generally necessary to coat the entire interior
surface of the can in a uniform, even manner. Other-
wise, the food contents :in the can may lose their
aroma or taste. According to one prior method of
coating the interior of a can, a spray nozzle was
located inside the can and the can was revolved until
the entire inside circumferential surface had been
coated. However, it is known that centrifugal force
created by rotation of the can causes some of the
spray coating to accumulate in the corners of the can,
~- resulting in uneven coating cf the inside corners of
the can. Moreover, the corners of the can were
particularly susceptible to spray reflection.
This invention proposes two methods for
uniformly coating the inside surfaces of a can.
- First, adjustments are made to the timer 41 to produce
a spray distribution pattern of the type shown in Fig.
1~, with seven generally circularly shaped spray
regions. Then, as shown in Fig. l9A, the nozzle 21 is
inserted into the inside of a can 109 and spraying is
conducted near the bottom of the can 109. The liquid
stream -5 s distributed by changing the direction of
each of the gas flows from the blowout ports 33a-33f
so that there are no reflection flows within the can
109. Because the direction of the liquid stream 26
may be shifted within a short period of time, i.e., 20
milliseconds or less, this invention eliminates the
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WO91/120~ PCT/US91/01033
-27-
occurrence of air cushions within the can 109 during
spray coating. With this method and apparatus, the
time of one cycle of gas i--lows, i.e., one gas flow
from each blowout port 33a-33f, is approximately 120
milliseconds.
With this method, it is not necessary to
revolve the can 109 during coating, as required by
prior methods. However, even if the can is revolved,
it may be revolved at a relatively low speed so that
the influence of centrifugal force is relatively
small. By raising the nozzle upward with respect to
the fixed can 109, or lowering the can 109 with
respect to the nozzle 21, coating is applied uniformly
to the inner surfaces of the can 109 by a number of
additional spraying cycles, with each cycle directing
a coating at a predetermined position or level of the
can 109. Spraying may occur while there is continuous
relative movement between the gun 20 and the can 109,
or while the gun 20 is stationary within the can 109
at each of a finite number of different spraying
positions~
According to another method of coating the
inside surfac of a metal can, as shown in Fig. l9B,
three different coating steps or stages are used.
Each stage supplies coating to a different region of
the can 109, and each stage employs a gun located
outside of the can but pointed toward the can. For
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WO91/12088 PCT/US91/01033
.
''~' ~ 5~ 28-
instance, at stage 111, the nozzle 21A supplies
coating to a bottom portion of can lO9A, while nozzle
21B at stage 112 supplies coating to a midportion of
the can lO9B and nozzle 21C at stage 113 supplies
coating to an upper portion of can lO9C. Fig. l9B
shows coating the internal surfaces of cans lO9A, lO9B
and lO9C with three different nozæle and gun set ups,
one for each coating stage. Alternately, more or less
nozzles could be employed for more or less spraying
stages, particularly if the dimensions of the can 103
increases or decreases.
From the above disclosure of the general
principles of the present invention and the preceding
detailed description of the preferred embodiments,
those skilled in the art will readily comprehend the
various modifications to which the present invention
is susceptible. Therefore, we desire to be limited
only by the scope of the following claims and equiva-
lents thereof.
We claim: