U.S. patent application number 11/331412 was filed with the patent office on 2006-08-03 for coating system.
Invention is credited to Christopher J. Cote, Wesley O. Davis, Drew D. Erickson, Stuart J. Erickson, Norman R. Faucher.
Application Number | 20060169202 11/331412 |
Document ID | / |
Family ID | 46323588 |
Filed Date | 2006-08-03 |
United States Patent
Application |
20060169202 |
Kind Code |
A1 |
Erickson; Stuart J. ; et
al. |
August 3, 2006 |
Coating system
Abstract
Disclosed is a coating system for the selective application of
coatings to substrates to apply a uniform coating to selected areas
of the substrate without the need for masking. The system comprises
a first coating applicator for coating large areas of the
substrate, a second coating applicator for coating small areas of
the substrate, a motion and positioning system for both coating
applicators and a system controller. Also disclosed is an
ultrasonic spray coating system comprising an ultrasonic transducer
with spray forming head, integrated fluid delivery device with air
and liquid supply passage ways, support brackets and an ultrasonic
power generator.
Inventors: |
Erickson; Stuart J.;
(Marblehead, MA) ; Erickson; Drew D.; (West
Newbury, MA) ; Davis; Wesley O.; (Plaistow, NH)
; Cote; Christopher J.; (Amesbury, MA) ; Faucher;
Norman R.; (Londonderry, NH) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
28 STATE STREET
28th FLOOR
BOSTON
MA
02109-9601
US
|
Family ID: |
46323588 |
Appl. No.: |
11/331412 |
Filed: |
January 11, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10927547 |
Aug 26, 2004 |
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11331412 |
Jan 11, 2006 |
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PCT/US04/09549 |
Mar 29, 2004 |
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10927547 |
Aug 26, 2004 |
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60643024 |
Jan 11, 2005 |
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60458487 |
Mar 28, 2003 |
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Current U.S.
Class: |
118/323 ;
118/305; 118/313; 239/102.1; 239/290; 239/659 |
Current CPC
Class: |
H05K 3/0091 20130101;
B05C 5/0216 20130101; B05B 7/0815 20130101; B05B 7/02 20130101;
B05B 12/18 20180201; H05K 2203/0285 20130101; H05K 2203/1366
20130101; B05B 17/0623 20130101; B05B 17/0607 20130101; B05B 7/0807
20130101; B05B 12/02 20130101 |
Class at
Publication: |
118/323 ;
118/313; 118/305; 239/102.1; 239/659; 239/290 |
International
Class: |
B05B 3/00 20060101
B05B003/00; B05B 1/08 20060101 B05B001/08 |
Claims
1. A coating system comprising: a first large area coating
applicator for coating large areas of a substrate, a second small
area coating applicator for coating small areas of the substrate, a
motion and positioning system for both coating applicators, and a
system controller.
2. The coating system of claim 1, wherein the second coating
applicator is used to apply coatings to pre-selected small areas of
a substrate, as small as 1 mm.sup.2, at the same coating thickness
formed with the first coating applicator.
3. The coating system of claim 2, wherein the second coating
applicator is used to apply low viscosity liquids of the same
formulation applied by the first coating applicator.
4. The coating system of claim 2, wherein the second coating
applicator produces a small coating segment in the form of a thin
line or dot, with a coating segment width of about 1 mm.
5. The coating system of claim 2, wherein the second coating
applicator uses a common liquid storage and delivery system with
the first coating applicator.
6. The coating system of claim 2, wherein the second coating
applicator is adapted to apply a coating accurately from a distance
up to 20 mm above the substrate.
7. The coating system of claim 2, wherein the second coating
applicator is adapted to allow adjustment of the coating flow rate
electronically using a drive circuit for the dispensing head.
8. The coating system of claim 2, wherein the second coating
applicator further comprises a multi-axis motion and positioning
system (X-Y-Z-.theta.-O) to control the velocity and position of
the micro-line dispensing head for the application of coating to
selected areas on the substrate.
9. An ultrasonic spray coating system comprising an ultrasonic
transducer with spray forming head, integrated fluid delivery
device with air and liquid supply passage ways, support brackets
and an ultrasonic power generator.
10. The ultrasonic spray coating system of claim 9, wherein the
integrated fluid delivery device comprises an integrated fluid
applicator.
11. The ultrasonic spray coating system of claim 9, wherein the
system is capable of spraying liquids onto substrates in a pattern
about 1/16 inch to about 3/16 inch wide, at a distance of up to
1.75 inches from the substrate.
12. The ultrasonic spray coating system of claim 9, wherein the
ultrasonic transducer comprises an ultrasonic converter that
converts high frequency electrical energy into high frequency
mechanical energy.
13. The ultrasonic spray coating system of claim 12, wherein the
converter has a predetermined resonant frequency.
14. The ultrasonic spray coating system of claim 12, wherein the
spray forming head is coupled to the converter and is resonant at
the same resonant frequency of the converter.
15. The ultrasonic spray coating system of claim 9, wherein the
spray forming head has a spray-forming tip and concentrates the
vibrations of the converter at the spray-forming tip.
16. The ultrasonic spray coating system of claim 9, wherein the
integrated fluid applicator comprises separate passageways for
liquid and air.
17. The ultrasonic spray coating system of claim 9, wherein the
integrated fluid applicator comprises a liquid output surface, an
air output annulus and an air-shaping ring.
18. The ultrasonic spray coating system of claim 17, wherein the
integrated fluid applicator comprises separate ports for air and
liquid.
19. The ultrasonic spray coating system of claim 18, wherein the
air inlet port is connected to a ring shaped annulus.
20. The ultrasonic spray coating system of claim 18, wherein the
inlet port for liquid is connected to the output surface of the
applicator.
21. The ultrasonic spray coating system of claim 18, wherein the
air-shaping ring attaches to the bottom of the fluid applicator to
enclose the air annulus to form an air passageway to supply air to
the holes in the air-shaping ring.
22. The ultrasonic spray coating system of claim 21, wherein the
angle of the holes in the air-shaping ring can be set to achieve a
specific "focal point" of the liquid spray, thus producing the
desired spray pattern size.
23. The ultrasonic spray coating system of claim 21, further
comprising an air director and mounting ring.
24. The ultrasonic spray coating system of claim 21, further
comprising a pneumatically actuated air director positioner for the
air director.
25. The ultrasonic spray coating system of claim 21, further
comprising additional solenoid valves to activate air flow to the
air director and to the air director positioner.
26. The ultrasonic spray coating system of claim 25, adapted for
operation in one or more of the following spray modes; (a) narrow
mode; (b) wide mode; and/or (c) side mode.
27. The ultrasonic spray coating system of claim 21, further
comprising two additional solenoid valves to activate air flow to
the air director and to the air director positioner.
28. The ultrasonic spray coating system of claim 17, adapted for
operation in one or more of the following spray modes; (a) narrow
mode; (b) wide mode; and/or (c) side mode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from copending Provisional
Application Serial No. 60/643,024, filed 11 Jan. 2005. This
application is also a continuation-in-part of application Ser. No.
10/927,547, filed 26 Aug. 2004. That application was a
continuation-in-part of PCT Application No. PCT/US2004/009549 filed
29 Mar. 2004, which designates the United States. The PCT
Application claimed priority from commonly owned, copending U.S.
Provisional Application Serial No. 60/458,487, filed 28 Mar. 2003.
The disclosures of these applications are hereby incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] The present invention provides a coating system that
represents an improvement over prior art coating systems, in which
a precision dispensing valve, for coating small areas, is used in
conjunction with a spray or other large area coating device.
BACKGROUND OF THE INVENTION
[0003] The present invention provides a coating system that
represents an improvement over the coating systems described in
U.S. Pat. Nos. 5,409,163, 5,540,384, 5,582,348 and 5,622,752, the
disclosures of which are hereby incorporated herein by reference.
The coating system of the present invention can be used in the
methods taught in these patents, and can also be used as described
herein.
[0004] There is an increasing need in industry to apply coatings to
selected areas on a substrate, for example applying protective
coatings to printed circuit boards. In this example, a protective
coating needs to be applied to soldered connections and not to
other areas such as electrical connectors, heat sinks, light
emitting diodes (LED) or displays. In many cases, the areas to be
coated are immediately adjacent to the areas where coating cannot
be applied. If coating is applied to the "no-coat" areas, the
circuit board will not function properly due to the presence of the
coating.
[0005] In many cases it is necessary to apply a masking material,
such as tape, to the no-coat areas prior to application of the
coating to ensure that these areas remain free of coating.
Typically the masking is applied prior to application of coating
and removed after the coating is dry. The application and removal
of the masking material is time consuming and labor-intensive. The
elimination of the masking process is desirable in a manufacturing
process to reduce production time and reduce labor costs,
especially for high volume production.
[0006] In recent years, automated coating systems have been
developed for the application of coatings with the goal of
eliminating the masking and de-masking process. The systems
typically consist a coating applicator for large areas, a coating
applicator for small areas, a motion and positioning mechanism for
the coating applicators and a system controller.
[0007] Typically spray valves or film coating heads are used for
coating the large areas on the substrate quickly to minimize time
required for coating application. However, typical large area
coating applicators deposit the coating patterns with irregular
edges. The coating cannot be applied close to the no-coat areas
with these applicators due to the irregular edge of coating
deposition. In order to reach the goal of elimination of masking
another applicator is required to coat the smaller areas
immediately adjacent to the no-coat areas of the substrate.
[0008] Typically dispensing valves that produce a bead or line of
coating are used for coating small areas on the substrate. The
dispensing valves are comprised of a piston actuated internal
needle in seat arrangement. An air-actuated piston that raises the
needle out of the seat is used to activate the coating flow. A
stroke of the piston is manually adjusted to set the flow rate of
the coating. The coating flows from the valve in the form of a bead
or is directed through an external needle to the substrate.
[0009] The motion and positioning system is used to move both
coating applicators over the substrate to apply coating to the
desired areas. The system controller operates the motion and
positioning system as well as the coating applicators and enables
programs to be created and stored for various coating patterns.
[0010] These automated systems have been effective in certain
circumstances but they do not produce a uniform coating application
and have not completely eliminated the requirement for masking.
[0011] In many cases, it is desirable to apply a thin, uniform
coating to a substrate, such as the application of protective
coatings to printed circuit boards. For example, the coating
thickness must be precisely controlled with the new water-based
conformal coatings. If these coatings are applied at a greater
thickness than is optimal for curing, cracks will form during the
drying process, reducing the coating's protective properties. Spray
coating applicators are capable of applying a thin coating on a
substrate. To facilitate spray application and formation of a thin
film on the substrate, the coating is typically formulated with a
lower viscosity of less than 100 Centipoise. However, difficulties
arise if the same low viscosity coating formulation is used in the
dispensing valve. The dispensing valve produces a bead or line of
coating on the substrate and the coating will tend to flow or wet
out on the substrate unpredictably with low viscosity coating
mixtures. To overcome this problem, higher viscosity coating
formulations are used with the dispensing valves, which produce a
thicker coating application than the spray valve. The use of a low
viscosity formulation for the spray applicator and a higher
viscosity coating formulation with the dispensing applicator
results in a non-uniform coating on the substrate.
[0012] Additional limitations of dispensing valves include
imprecise flow rate control, difficulty producing short coating
lines segments, heavy coating deposition at the start and end of a
coating segment and susceptibility to uneven or warped substrate
surfaces. The coating flow rate on a dispensing valve is set with a
manual screw adjustment to adjust the stroke of the piston. This
manual adjustment is subjective and will necessarily produce
different results each time to valve is adjusted.
[0013] The needle and seat arrangement of dispensing valves
produces discontinuities as the flow starts and stops. This coupled
with the head motion profile tends to produce heavy spots at the
start and end of a coating segment and makes is difficult to create
a short coating segment. This effect can somewhat be overcome with
programming techniques for the system controller, but this process
is tedious and not repeatable. To apply coatings accurately to very
small areas or in straight lines with a dispensing valve, an
external needle is required. To achieve optimal results, the outlet
of the needle must be very close to the substrate, typically within
1 mm. If the substrate is uneven or slightly warped coating skips
may result due to changing distance between the needle and
substrate. Additionally, the needle has a tendency to contact
previously applied coating and pull it along with it causing skips
and smears. The needle is also subject to being damaged if it comes
into contact with the substrate.
[0014] In summary, the limitations of current selective coating
systems include: [0015] (1) Inability to provide a uniform coating
thickness for both large and small areas to be coated. [0016] (2)
The requirement to use different coating formulations for the
coating applicator for the large areas and the coating applicator
for the small areas. [0017] (3) Manual adjustment of the coating
flow rate, which produces inconsistent results, due to subjective
process setup. [0018] (4) Difficulty controlling the dispensing
process due to unpredictable coating flow-out on the substrate,
heavy spots ant the beginning and end of coating segments and
susceptibility to irregular substrate surfaces.
SUMMARY OF THE INVENTION
[0019] One embodiment of the present invention provides a coating
system for the application of coatings to substrates without the
need for masking.
[0020] In one especially preferred embodiment, the system comprises
a first coating applicator for coating large areas of the
substrate, and a second coating applicator for coating small areas
of the substrate. It also comprises a motion and positioning system
for both coating applicators and a system controller. In an
especially preferred embodiment, this invention utilizes a device
to produce very small coating segments in conjunction with the
large area coating applicator to eliminate the limitation of
currently available selective coating systems that utilize needle
in seat dispensing valves.
[0021] This embodiment of the present invention achieves the
following benefits over the systems of prior art: [0022] (1)
Supplement to a coating applicator for larger areas, such as a
precision ultrasonic spray head or other large area coating head,
to apply coatings to selected very small areas of a substrate, as
small as 1 mm.sup.2, at the same resulting coating thickness as the
coating applied with the large area coating applicator. [0023] (2)
Apply low viscosity liquids of the same formulation and viscosity
used by the other spray or coating applicator used to apply coating
to larger areas. [0024] (3) Produce a small coating segment in the
form of a thin line or dot (approximately 1 mm coating segment
width). [0025] (4) Use a common liquid storage and delivery system
between the coating applicator for large areas and the dispensing
head. [0026] (5) Apply the coating accurately from a distance up to
20 mm above the substrate. [0027] (6) Adjust the coating flow rate
electronically using a drive circuit for the dispensing head. This
eliminates subjective manual adjustments associated with
conventional dispensing valves. [0028] (7) Use a multi-axis motion
and positioning system (X-Y-Z-.theta.-O) to control the velocity
and position of both the large area coating applicator and the
small area coating applicator.
[0029] Another embodiment of the present invention provides an
ultrasonic spray coating system comprising an ultrasonic transducer
with spray forming head, integrated fluid delivery device with air
and liquid supply passage ways, support brackets and an ultrasonic
power generator.
[0030] This embodiment of the invention preferably comprises an
ultrasonic spray coating system with an integrated fluid
applicator. In one especially preferred embodiment, the system is
capable of spraying liquids onto substrates in narrow ( 1/16'' to
3/16'' wide), well-defined patterns at a distance of up to 1.75
inches from the substrate.
[0031] In addition to the directed air stream produced by the
air-shaping ring to focus the spray the following additional
embodiments have been made: [0032] 1) An air director and mounting
ring. [0033] 2) A pneumatically actuated air director positioner
for the air director. [0034] 3) Two additional solenoid valves to
activate air flow to the air director and to the air director
positioner.
[0035] These improvements enable the spray head to operate in any
one of the following three-modes (or combinations thereof): [0036]
1) Narrow mode--where the airflow is directed through the
air-shaping ring to focus the ultrasonically produced spray. [0037]
2) Wide mode--where the airflow is directed through the air
director to expand the ultrasonically produced spray. Impinging the
directed air stream on the flat surface of the spray-forming tip
expands the spray. The directed air stream is impinged on the
opposite surface to the liquid feed surface. [0038] 3) Side
mode--where the air director positioner is actuated, moving the air
director to the lower position and airflow is directed through the
air director to direct the ultrasonically produced spray at an
oblique angle from the spray forming tip. The purpose of directing
the spray at an oblique angle is to coat a vertical surface, such
as the side of a tall component that would not otherwise be coated
if the spray were directed in the normal vertical path.
[0039] In many coating applications, such as the application of
conformal coatings to printed circuit boards, there are various
size areas that require a uniform coating. Due to production
volume, the time available to apply the coating may be limited. It
is critical to have the ability to accurately apply coatings to
small areas without applying coating to adjacent areas or
components (keep out areas). This can be achieved with a narrow,
focused spray pattern. However, if a larger area needs to be
coated, many passes will be required with the narrow width spray.
This may exceed time limitations imposed by production volume. A
wider spray pattern will enable larger areas to be coated more
quickly. Additionally, coating may need to be applied to the side
surfaces of taller components. A spray applicator that is able to
deliver a narrow pattern for small areas, a wider pattern for
larger areas as well as the ability to apply coating to the side
surfaces of taller components would meet these requirements.
[0040] Thus, the improved spray head embodiment of the present
invention provides the following benefits: [0041] 1) The ability to
apply a narrow coating pattern and a wider coating pattern with the
same spray head. [0042] 2) The ability to apply a narrow coating
pattern, a wider coating pattern and a sideways coating pattern
with the same spray head. [0043] 3) The ability to change between
the three modes of operation without manual adjustments. Pattern
changes are initiated through the coating system software and
control components. [0044] 4) The ability to expand the narrow
coating pattern by a multiple of up to 5 times the narrow pattern
width. For example, from a narrow pattern width of 5 mm, to a wide
pattern width of 25 mm. [0045] 5) The ability to significantly
reduce the time to coat a substrate with both small areas and large
areas to be coated.
[0046] The ultrasonic transducer consists of an ultrasonic
converter that converts high frequency electrical energy into high
frequency mechanical energy. The converter has a resonant
frequency. A spray forming head is coupled to the converter and is
resonant at the same resonant frequency of the converter. The spray
forming head has a spray-forming tip and concentrates the
vibrations of the converter at the spray-forming tip.
[0047] The integrated fluid applicator contains separate
passageways for liquid and air, a liquid output surface, an air
output annulus and an air-shaping ring. The fluid applicator has
separate ports for air and liquid. The air inlet port is connected
to a ring shaped annulus. The inlet port for liquid is connected to
the output surface of the applicator. The air-shaping ring attaches
to the bottom of the fluid applicator to enclose the air annulus to
form an air passageway to supply air to the holes in the
air-shaping ring. The angle of the holes in the air-shaping ring
can be set to achieve a specific "focal point" of the liquid spray,
thus producing the desired spray pattern size.
[0048] The spraying end of the system contains the necessary
elements to produce the desired spray pattern: 1) atomizing surface
of the spray forming head, 2) liquid applicator output surface and
3) air delivery ring. These elements are arranged in a manner that
allows spraying end to be contained within a small in area (less
than 0.75 in.times.0.69 in). This small envelope allows the spray
system to be positioned in tight areas for spray coating between
objects protruding from the substrate (e.g., components attached to
a printed wiring board).
[0049] As set forth in greater detail below, embodiments of the
ultrasonic spray coating system of the present invention comprise
an ultrasonic spray head assembly and an ultrasonic power
generator. The ultrasonic spray head assembly consists of two major
components: 1) an ultrasonic transducer with spray forming head and
2) an integrated fluid applicator. This system is constructed in
the same manner, and from the same materials, as are the prior art
ultrasonic spray systems defined in the patents recited above. The
prior art systems are commercially available from Ultrasonic
Systems, Inc. of Haverhill, Mass., the assignee of the present
invention.
[0050] This embodiment of the present invention can be used for
applying thin, uniform coatings to virtually any substrate. In
particular, this device can be used to apply conformal coatings to
printed circuit board assemblies, either to cover the entire board
assembly or to apply the coating selectively to the board. The
advantages that this device provides over conventional spray
devices include: [0051] (1) Improved transfer efficiency--over 90%
of the sprayed coating is transferred to the board vs. 40% to 60%
for air assisted spray nozzles; [0052] (2) Smooth, defect free
coatings--since the primary mechanism for atomization is
ultrasonic, the applied coating appears smooth and is free of
bubbles and pin-holes. Conventional air assisted spray nozzles use
compressed air to atomize the coating, which results in a coating
that has an "orange peel" like appearance and can have bubbles and
pin holes due to the atomizing air pressure. To overcome these
"defects" air assisted nozzle coatings are applied in higher volume
resulting in a thicker coating--typically between 0.005'' to
0.010''; [0053] (3) Thinner coatings--since this device provides a
uniform, defect free coating the resulting coating thickness is
typically between 0.001'' to 0.005''. The thinner, defect free
coating applied at a higher transfer efficiency results in coating
material savings. [0054] (4) In certain embodiments, finer, more
narrow spray patterns--the air shaping ring, as part of the
integrated fluid applicator allow the spray pattern to be focused
and to allow superior "edge definition" at a greater distance from
the substrate allowing for greater flexibility in positioning the
spray device for selectively coating a populated circuit board.
[0055] (5) More precise control over coating deposition--since the
liquid is applied externally to the vibrating spray forming tip,
precise amounts of liquid can be applied to the tip and dispersed
as a spray to the substrate providing precise coating deposition
control.
[0056] This device can also be used to apply proprietary liquid
coatings to green tape used in the production of fuel cells. Other
applications include applying: "micro volume" liquid coatings to
semiconductors devices (e.g., flux to solder balls (C4 technology)
for flip chips), polymer coatings (drug coatings) for stents,
conductive inks on ceramic substrates and many more. Many of the
advantages listed above over existing spray nozzle technology are
applicable to these applications.
[0057] This device will typically be attached to an end effector
that is part of an X, Y, Z programmable robot that controls the
position and speed of the device relative to the substrate,
thereby, allowing the user to apply coatings of any desired pattern
to the substrate.
[0058] Finally, the two preferred embodiments described herein, can
be combined, either in whole or in part, to achieve coating systems
having the combined attributes of each preferred system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] FIG. 1 illustrates a preferred Micro-Line Dispensing valve
used in the coating system embodiment of the present invention;
[0060] FIG. 2 illustrates a circuit diagram used with preferred
embodiments of the coating system of the present invention;
[0061] FIG. 3 is a graphical representation of Voltage
(specifically Spike Voltage and Hold Voltage) vs. Valve ON Time
(T.sub.ON) for the valves used in preferred embodiments of the
coating systems of the present invention; and
[0062] FIG. 4 is a graphical representation of Dispense Volume (in
microliters) vs. Pressure (in PSI) for water (dispensed as a test
liquid) by embodiments of the coating system of the present
invention.
[0063] FIG. 5, which includes six parts (5A, 5B, 5C, 5D, 5E and 5F)
illustrates a preferred spray head embodiment of the present
invention.
[0064] FIG. 6, which has two parts (6 and 6A) illustrates the
preferred concave feed blade of a spray head embodiment of the
present invention.
[0065] FIG. 7, which includes seven parts (7A, 7B, 7C, 7D, 7E, 7F
and 7G) illustrates the Integrated Liquid Delivery System (ILDS)
employed in a spray head embodiment of the present invention.
[0066] FIG. 8, which includes five parts (8A, 8B, 8C, 8D and 8E)
illustrates the Air Shaping Ring of the Integrated Liquid Delivery
System (ILDS) employed in a spray head embodiment of the present
invention.
[0067] FIG. 9 is an exploded view of the component parts showing
the relationships between the ultrasonic spray head with ILDS and
the pulsed liquid delivery system embodiment of the present
invention.
[0068] FIG. 10, which has two parts (10 and 10A), illustrates the
operation of one spray head embodiment of the present invention and
shows one example of a precise spray pattern obtained
therefrom.
[0069] FIG. 11 illustrates one spray head embodiment of the present
invention with an air director and an air-director positioner. As
illustrated, three solenoid control valves (#1, #2 and #3) are
mounted thereon, namely Narrow Mode (#1), Wide Mode (#2) and Side
Mode (#3).
[0070] FIG. 12 illustrates one spray head embodiment of the present
invention with the air director positioner used for wide mode (up)
and side mode (down).
[0071] FIG. 13 illustrates one spray head embodiment of the present
invention with the air director positioner used for wide mode
spraying.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0072] As depicted in FIGS. 1-4, one embodiment of the present
invention comprises a spray coating system for the selective
application of coatings to substrates to apply a uniform coating to
selected areas of the substrate without the need for masking.
[0073] The preferred embodiment of the system comprises a first
coating applicator for coating large areas of the substrate, a
second coating applicator for coating small areas of the substrate,
a motion and positioning system for both coating applicators and a
system controller. The focus of this invention is the integration
of a device for producing small coating segments with the other
components of the coating system.
[0074] In a preferred embodiment, the first coating
applicator--i.e., the applicator for larger areas, is a precision
ultrasonic spray head or other large area coating head. The second
coating applicator is specifically designed to apply coatings to
selected very small areas of a substrate, for example, as small as
1 mm.sup.2, but at the same resulting coating thickness as the
coating applied with the first applicator--the large area coating
applicator. The small coating segment can be in the form of a thin
line or dot of approximately 1 mm coating segment width. Other
desired spray patterns and sizes can be selected by the user. The
two applicators advantageously use a common liquid storage and
delivery system, thereby maintaining a consistency and uniformity
for the coatings applied by the two applicators. In the preferred
embodiment, these coatings can accurately be made at a distance of
up to 20 mm above the substrate. The coating flow rates are
adjusted electronically using a drive circuit for the dispensing
head. This eliminates subjective manual adjustments associated with
conventional dispensing valves. Finally, the preferred system
includes a computer controlled multi-axis motion and positioning
system (X-Y-Z-.theta.-O) to control the velocity and position of
both the large area coating applicator and the small area coating
applicator. Such systems are commercially available.
[0075] Several spray coating systems with which the precision
dispensing valve can be used are those taught in U.S. Pat. Nos.
5,409,163, 5,540,384, 5,582,348, 5,622,752, and U.S. Patent
Publication No. 2005-0035213, the disclosures of which are hereby
incorporated herein by reference. The skilled artisan can likewise
select other commercially available large area coating devices,
including, but not limited to, air atomized spray valves, and other
film coat applicators heads, and/or valves, such as those available
from Asymtek of Carlsbad, Calif., for use with the precision
dispensing valve, without departing from the scope of this
invention.
[0076] The Micro-Line Dispensing System
[0077] As illustrated in FIG. 1, the Micro-Line Dispensing Valve
100 includes the following functional components; valve power
connection 102, liquid inlet 104, O-ring 106, valve rear housing
108, housing nut 110, retainer snap ring 112, valve retainer 114,
liquid metering needle 116, valve front housing 118, and valve
liquid supply tube 120.
[0078] In addition to the valve parts shown in FIG. 1, the
micro-line dispensing head further includes the high-speed driver
circuit shown in FIG. 2. Needle 116 includes a precision orifice.
The orifice and needle are connected to the outlet of the solenoid
valve. The coating liquid is delivered to the inlet of the solenoid
valve from the storage reservoir by pressurizing the reservoir with
up to 30 PSI. The solenoid valve is pulsed rapidly by the driver
circuit (see FIGS. 2 and 3) and the liquid is forced through the
orifice and directed through the needle in the form of a small
stream.
[0079] The stream of coating is deposited on a substrate by moving
the dispensing head relative to the substrate producing a coating
segment. The width of the coating segment is proportional to the
velocity of the dispensing head and the liquid flow rate.
[0080] The preferred Micro-Line solenoid valve is commercially
available from The Lee Company, Westbrook, Conn. The solenoid valve
is chemically inert, has a response time of less than 0.25
milliseconds and operates at speeds up to 1200 Hz. The valve has an
open flow capacity, with water, of 20 cc/min at 20-PSI pressure
(see FIG. 4).
[0081] In operation, first the dispense volume per pulse is
determined ON time (T.sub.ON) Of the valve. This is based upon the
type fluid to be dispensed. The effective flow rate is calculated
by multiplying the number of pulses per second (or operating
frequency) of the valve. The ON time of the valve can be varied
from between 0.2 milliseconds and 0.5 milliseconds. The operating
frequency of the valve can be varied from 10 Hz to 1200 Hz. This
system can accurately control flow from 0.5 microliters/second to
800 microliters/second (based on water at standard temperature and
pressure).
[0082] As shown in FIGS. 2 and 3, a high-speed driver circuit is
used to operate the solenoid valve. This circuit applies a high
voltage level to the valve (called the "spike voltage") to quickly
open the valve, and then applies a lower voltage (called the "hold"
voltage") to keep the valve open. The length of time the spike
voltage is applied is set via potentiometer P3. The total time the
valve is to be kept open is set either by potentiometer P1, or via
a 0-5V signal applied to the "On Time" terminal. The range of time
that the valve is held open is set via potentiometer P2.
Momentarily switching the "Trigger" terminal to ground via and
external controller activates the circuit. The switching time of
the external controller set the valve operating frequency.
[0083] As illustrated in FIGS. 5-13, another embodiment of the
ultrasonic spray coating system comprises of an ultrasonic spray
head assembly and an ultrasonic power generator. This ultrasonic
spray head assembly consists of two major components: [0084] (1) an
ultrasonic transducer with spray forming head and [0085] (2) an
integrated fluid applicator.
[0086] Spray Head Description
[0087] Referring in detail to FIG. 5, the ultrasonic spray head is
comprised of an input end, a body and a spray forming tip. The
spray forming tip or output end contains a feed blade and an
atomizing surface. The spray head has a resonant frequency (fsh)
and has a length equal to one-half wavelength (.lamda./2) of the
resonant frequency. The wavelength for a particular spray head is
defined by: [0088] .lamda.=cm/fsh Where: [0089] .lamda.=Wavelength
(inches) [0090] Cm=material's speed of sound (inches/second) [0091]
fsh=resonant frequency (Hertz or 1/second)
[0092] The practical resonant frequencies range from 20 kHz to 120
kHz for atomizing liquids (20 kHz.gtoreq.fsh.ltoreq.120 kHz). The
spray head is constructed of metal, either 6A1-4V titanium or
7075-T6 aluminum; titanium is preferred because of its strength and
corrosion resistance properties.
[0093] The input end is comprised of a coupling surface and a
coupling screw. The input end of the spray head is connected to an
ultrasonic converter. The input must be flat and smooth for optimal
mechanical coupling to the converter. The ultrasonic converter has
a resonant frequency (fc) that is matched to the resonant frequency
of the spray head (fsh) or fc=fsh.
[0094] The body connects the input end to the output end and is
formed to concentrate ultrasonic vibrations on the output end. To
achieve ultrasonic amplification through the body, the input end
must be larger than the output end. The profile of the body can be
stepped, linear, exponential or Catenoid. The Catenoid shape is
preferred because it provides the largest amplification of the
sound wave through the body to the output end, which in turn,
provides maximum atomizing capability. Preferable ratios of output
end diameter (d2) to input end diameter (d1) are:
4.gtoreq.(d1/d2).ltoreq.8 The Catenoid shape is described by the
catenoidal equation: Y=Yo*cosh[m(X-Xo)] Where: [0095] X.fwdarw.X
coordinate [0096] Y.fwdarw.Y coordinate at X [0097] Xo.fwdarw.X
coordinate of the lowest point on Catenoid [0098] Yo.fwdarw.Y
coordinate of the lowers point on Catenoid [0099]
Cosh.fwdarw.hyperbolic cosine [0100] M.fwdarw.Constant (depends on
the end points of the catenoid)
[0101] The spray forming tip has two main features: 1) an atomizing
surface that provides concentrated ultrasonic vibrations with
sufficient energy to atomize a flowing liquid, 2) a feed blade that
allows a liquid that is applied to it to flow to the atomizing
surface.
[0102] The spray forming tip is preferably rectangular but it can
be round or square. The shape of the spray forming tip influences
the shape of the spray that forms on the atomizing surface. A round
tip produces a more or less round spray, a square tip produces a
more or less square spray and a rectangular tip produces a more or
less rectangular spray.
[0103] The purpose of the feed blade is to direct all of the liquid
flow towards and onto the atomizing surface. The feed blade shape
can be convex (round), concave or flat. With a round or convex feed
blade the liquid streams to the atomizing surface but some also
flows around the spray forming tip before finally reaching the
atomizing surface. The flat feed blade performs better with most of
the liquid going to the atomizing surface, however some liquid
still flows onto the sides of the feed blade before going to the
atomizing surface. This spurious liquid flow causes the spray
pattern to become erratic resulting in ragged, ill defined edges on
the coating pattern.
[0104] Referring in detail to FIG. 6, a concave feed blade performs
best because the dish shaped surface helps to contain the flow to
the feed blade causing all of the liquid to flow directly to the
atomizing surface. The concave feed blade eliminates spurious
liquid flow and therefore facilitates a coating pattern with well
defined edges.
[0105] This embodiment of the present invention further comprises
an ultrasonic spray coating system with a converter mechanism for
converting high frequency electrical energy into high frequency
mechanical energy to thereby produce vibrations. The converter
mechanism is designed to have one resonant frequency. A spray
forming head is coupled to the converter mechanism and is resonant
at the same resonant frequency. The spray forming head has a spray
forming tip and concentrates the vibrations of the converter at the
spray forming tip. The spray forming tip has a feed blade and an
atomizing surface. The spray forming tip concentrates a surface
wave on the feed blade and a displacement wave on the atomizing
surface from the vibrations of the converter. A high frequency
alternating mechanism is electrically connected to the converter
mechanism to produce a controllable level of electrical energy at
the proper operating frequency of the spray forming head/converter
mechanism such that the spray forming tip is vibrated
ultrasonically with a surface wave concentrated on the feed blade
and a displacement wave concentrated on the atomizing surface.
[0106] A liquid supplier is provided having a liquid applicator in
close proximity with the feed blade of the spray forming tip and
spaced therefrom. The liquid applicator includes an output surface
having an orifice therein. The output surface is in close proximity
with the feed blade of the spray forming tip and spaced therefrom.
The output surface of the liquid applicator and the feed blade of
the spray forming tip are at substantially right angles to each
other such that liquid supplied from the liquid applicator forms a
bead or meniscus between the output orifice of the liquid
applicator and the feed blade of the spray forming tip. The
meniscus is formed and sustained by the flow of liquid from the
output orifice of the liquid applicator and the ultrasonic surface
wave that exists on the feed blade of the spray forming tip. The
ultrasonic surface wave enables the liquid to `wet-out` and adhere
to the feed blade of the spray forming tip. The surface tension of
the liquid allows the meniscus to form and constant flow of liquid
sustains the meniscus. The longitudinal displacement wave (that
displaces the atomizing surface) pumps the liquid from the feed
blade to the atomizing surface. A film of liquid then forms on the
atomizing surface and is transformed into small drops and propelled
from the atomizing surface in the form of a rectilinear spray.
Finally, a controllable gas entrainment mechanism is associated
with the spray forming head for affecting and controlling the
velocity and pattern of the resultant spray.
[0107] Integrated Liquid Delivery System (ILDS)
[0108] The ILDS provides the liquid delivery means and air delivery
means to facilitate a narrow, well defined spray pattern on a
substrate. The ILDS: 1) provides the means to apply a flowing
liquid to the feed blade of the spray head and 2) provides a
directed air stream in the direction of the atomized coating to
"focus" the resulting spray pattern onto a substrate. The ILDS is
sized to fit the nominal diameter of the spray head. Referring in
detail to FIG. 7, an ILDS consists of nine components:
TABLE-US-00001 (Item-1) Liquid Applicator (Item-2) Fluids
Applicator Body (Item-3) Air Shaping Ring (Item-4) Air Shaping Ring
Retainer (Item-5) Air Diffuser (Item-6) Inner Gasket (Item-7) Outer
Gasket (Item-8) Air Shroud (Item-9) Air Inlet
[0109] First, the Liquid Applicator attaches through a cutout
feature in the side of the Applicator Body. Second, the Air
Diffuser mounts concentrically to a seating surface in the bottom
of the Applicator Body. Next, the Inner and Outer Gaskets mount
concentrically to the Air Diffuser. Then, the Air Shaping Ring
mounts against the Inner and Outer Gasket's surface. After that,
the Air Shroud is pressed into the Air Shaping Ring. Last, the Air
Shaping Ring retainer is threaded to the bottom of the Applicator
Body pushing the Air Shaping Ring against the gaskets to form a
sealed air passageway.
[0110] Air flows from the Air Inlet to the annulus in the
Applicator Body, through the diffuser into the air passageway
formed by the gaskets and inside surface of the Air Shaping Ring
out through the holes in the Air Shaping Ring. The Air Diffuser
evenly distributes the air to the holes in the Air Shaping Ring
from the air supply port in the Applicator Body. The Air Shroud
prevents the air curtain from curling inward towards the spray
forming tip and interfering with the ultrasonic atomizing
process.
[0111] The Air Shaping Ring is used to control the 1) width of the
spray pattern, 2) quality of the edges of the coating pattern and
3) to facilitate high quality coating patterns at a distance of
more than 20 mm from the substrate. Control over coating width is
important to facilitate coating patterns as small as 1 mm (e.g.,
for applying liquid solder flux to solder balls on a semiconductor
package) up to 20 mm (e.g., for applying conformal coating between
components on a printed circuit assembly).
[0112] Controlling the quality of the coating edges is important to
minimize coating going onto areas where it is not wanted. Applying
the coating from at least 20 mm away from the substrate is
important to avoid objects protruding from the substrate (i.e., for
avoiding circuit components on a printed circuit assembly).
[0113] Referring in detail to FIG. 8, the Air Shaping Ring delivers
a conically shaped air curtain to entrain the atomized liquid
flowing from the Spray Forming Tip to create a well-defined coating
pattern on a substrate. The width of the spray pattern "w" is
determined by the angle (.theta.) of the air passageway holes the
Air Shaping Ring. In general, when the angle .theta. is zero, the
spray pattern is widest and there is minimal control over the
quality of the edges of the coating. This is because the air
curtain does not intersect with the column of atomized coating. It
has been found through experimentation that the angle .theta. must
be between 5 degrees and 15 degrees, depending on the diameter of
the hole pattern in the Air Shaping Ring, for optimal coating
pattern quality.
[0114] The Liquid Applicator is comprised of 1) a liquid applicator
block and 2) a liquid applicator feed tube. The liquid applicator
block contains a liquid inlet port that is coaxially connected to a
liquid passageway that in turn connects to an outlet port. The
outlet port provides the mounting means for the liquid applicator
feed tube. The liquid applicator feed tube is formed from stainless
steel hypodermic tubing and has a straight portion that is the
inlet end has a bent portion that is the outlet end. The inlet end
of the liquid applicator feed tube is connected coaxially to the
outlet port of the liquid applicator block. The Liquid Applicator
is mounted to the Applicator Body such that the inlet port and
outlet port are at a 22 degree angle with respect to the centerline
of the Applicator Body and so that the outlet end of the feed tube
is at a 90 degree angle to the centerline of the Applicator Body.
The Liquid Applicator is detachable from the Applicator Body for
maintenance purposes. The liquid applicator is constructed from
stainless steel or engineering thermoplastic such as PPS or
PEEK.
[0115] The Applicator Body has an outside diameter (OD) and an
inside diameter (ID) and a height (h). The inside diameter provides
clearance for the spray head and ranges from 6 mm to 10 mm. The
outside diameter is a small as practical but large enough to
contain the air passageways for the Air Shaping Ring and cutout
feature for the Liquid Applicator. The outside diameter ranges from
17.5 mm to 25 mm. The height of the Applicator Body is 14.5 mm. The
applicator body has a top surface and a bottom surface that are
parallel to each other and perpendicular to the OD and ID. The top
surface has two chamfered features that are opposite each other
about the centerline axis; the first chamfer starts at the
centerline and is cut at a 9 degree angle to the OD of the part,
the second chamfer is offset from the centerline and is cut at a 22
degree angle to the OD of the part, 180 degrees opposite the first
chamfer. The first chamfer provides a surface for the air inlet
port. The second chamfer is to match the angle of the Applicator
Block inlet port surface.
[0116] The Applicator Body has an air inlet port connected to an
air passageway. The air inlet port is perpendicular to the first
chamfered surface in the top of the Applicator Body and connects
coaxially with an air passageway that goes through to the bottom
surface of the Applicator Body.
[0117] The Applicator Body has a cutout pocket feature to hold the
Liquid Applicator. This feature starts from the top surface and OD
of the part and goes 10 mm from the top surface into the applicator
body and intersects the ID. The width of the cutout matches the
width of the Liquid Applicator and is centered on the centerline of
the part, 180 degrees opposite the air inlet port.
[0118] The bottom surface of the Applicator Body has an air
annulus, seating surfaces for the Air Diffuser, Inner and Outer
Gaskets and Air Shaping Ring and a threaded feature that the Air
Shaping Ring retainer threads onto. The threads are cut into the OD
of the Applicator Body over a 3 mm length from the bottom surface.
A seating surface is bored into the part to a 2 mm depth from the
bottom surface. An annulus for air is cut into the seating surface
3 mm wide and 1 mm deep such that the air passageway intersects the
center of the annulus.
[0119] The Air Diffuser distributes the air flowing from one
relatively large air supply port in the Applicator Body over many
smaller holes to provide an even flow distribution to the air ports
in the Air Shaping Ring. The Air Diffuser is a thin disk (0.003 in.
thick) with an OD and ID such that it mounts concentric to the ID
of the Applicator Body and against the seating surface. The
diffuser is made up of one hundred and eight (108) holes arranged
in an array of three concentric rings. The inner and outer
diameters of the array of holes match the annulus in the Applicator
Body so that the array of holes is aligned to the annulus. Each
ring has thirty six holes evenly spaced over the diameter. The each
hole in each ring is offset by 5 degrees to the hole in the
adjacent ring. The effective area of the array of holes should be
twice the area of the air supply hole in the Applicator Body.
[0120] The Inner and Outer Gaskets provide an air tight seal
between the Air Diffuser and the inside surface of the Air Shaping
Ring. The annulus between the gaskets and the Air Shaping Ring form
the air passageway that supplies air to the holes in the Air
Shaping Ring. The gaskets are constructed of a rubber-like material
such as a perfluoroelastomer for maximum chemical resistance. The
gaskets are 0.75 mm thick. The ID of the inner gasket matches the
ID of the Applicator Body and the OD of the Inner Gasket matches
the OD of the air annulus. The OD of the Outer Gasket matches the
diameter of the seating surface bore and the ID of the Outer Gasket
matches the OD of the air annulus.
[0121] The Air Shaping Ring is a disk that has an inlet side and an
outlet side and is 2 mm thick. The OD of the ring matches the OD
bore of the seating surface in the Applicator Body. The ID of the
ring matches the ID of the seating surface bore. The inlet side has
an air annulus that is 0.25 mm deep and that matches the annulus
formed by the inner and outer gaskets. An array of between six (6)
and twelve (12) through holes is machined in the annulus at an
angle between 5 and 15 degrees with respect to the longitudinal
axis of the ring. The diameters of the holes are the same and range
from 0.3 mm to 0.5 mm. A counter bore is formed into the outlet
side of the Air Shaping Ring to accept the Air Shroud. The Air
Shaping Ring is constructed from either stainless steel or an
engineering thermoplastic that is chemically resistant, such as PPS
or PEEK.
[0122] The Air Shroud is a cylindrical shaped device that shields
the atomization process on the spray forming tip from the air
issuing from the Air Shaping Ring. Without the Air Shroud atomized
coating is pulled back into the ILDS by the Air Shaping Ring air
causing coating material to build up in the ILDS and drip off.
Coating material dripping from the ILDS causes defects in the spray
pattern and also causes coating to be deposited in unwanted areas.
It has been found through experimentation that the Air Shroud
should protrude from the outlet surface of the Air Shaping Ring 1.6
mm.
[0123] Ultrasonic Spray Head with WLDS and Pulsed Liquid Delivery
System
[0124] Referring in detail to FIG. 9, the ultrasonic spray head
with ILDS and pulsed liquid delivery system has thirteen
components: TABLE-US-00002 (Item-1) Ultrasonic transducer (Item-2)
Micro flow control valve (Item-3) Air flow control valve (Item-4)
Liquid feed tube (Item-5) Integrated fluids applicator (Item-6)
Spray head mounting bracket (Item-7) Mounting thumb screw (Item-8)
Fluids applicator mounting bracket (Item-9) Cam adjuster (Item-10)
Micro flow control bracket (Item-11) Filter bracket (Item-12) Fluid
filter (Item-13) Liquid spray tube
[0125] The ILDS is fixed in position relative to the spray forming
tip with a precision bracket system that allows the ILDS to be
adjusted in the "Z" direction and the "X" direction. The mounting
surface of the ILDS attaches to the fork shaped end of the ILDS
bracket with two machine screws. The ILDS mounting holes in the
bracket are slotted to allow the ILDS to be positioned in the "X"
axis relative to the spray forming tip. The ILDS bracket attaches
to the slots in the "tee" shaped leg of the spray head bracket with
two machine screws and wave washers. The barrel of the adjuster cam
mounts in a hole in the spray head bracket underneath the ILDS
bracket. The slotted end of the adjuster cam protrudes from the
backside of the tee leg to allow the cam to be rotated with a
screwdriver. The eccentric pin portion of the adjuster cam mates
with a slot in the ILDS bracket. When the cam adjuster is rotated
the eccentric pin moves the ILDS bracket up and down to provide the
"Z" adjustment of the ILDS relative to the spray forming tip.
[0126] The spray head is clamped in the spray head bracket. The
spray head is "keyed" to the bracket to orient the spray forming
tip to the ILDS.
[0127] Pulsed Liquid Delivery
[0128] A precision liquid delivery system controls liquid flow to
the spray forming tip. The liquid delivery system consists of a
high-speed miniature solenoid valve and a high-speed driver
circuit. The valve is commercially available from The Lee Company,
USA. The solenoid valve is chemically inert, has a response time of
less than 0.25 milliseconds and operates at speeds up to 1200 Hz.
The valve has an open flow capacity, with water, of 20 cc/min at
20-PSI pressure. See FIGS. 2, 3, and 4, discussed above.
[0129] Thin, precisely defined coating patterns are achievable
using the ultrasonic spray system with the precision liquid
delivery system.
[0130] Coating Segment Shape
[0131] Referring in detail to FIG. 10, the ultrasonic spray head
with ILDS and precision liquid delivery system produces a coating
segment with a predetermined shape. The width of the coating
segment is proportional to the 1) ID of the liquid feed tube in the
ILDS; 2) the liquid flow rate; and 3) the speed of the spray head
relative to the substrate. The coating segment width is directly
proportional to the ID of the liquid feed tube--the smaller the ID
of the liquid feed tube, the narrower the coating segment width.
The coating segment width is directly proportional to the liquid
flow rate--the lower the flow rate, the narrower the coating
segment width. The coating segment width is inversely proportional
to the head speed--the faster the speed of the head, the narrower
the coating segment width.
[0132] The precision liquid delivery system enables accurate
control over the shape of a coating segment. Precisely metering the
liquid flow to the spray forming tip provides a smooth transition
from a flow "off" to a flow "on" condition and vice versa. The
rapid on/off metering of the liquid flow eliminates heavy (wide)
sections at the beginning and end of spray segments that would
normally result if a conventional solenoid valve or pneumatically
actuated needle valve were used. Additionally, the precision liquid
delivery system allows the liquid flow rate to be changed
electronically with the system control software. Thus, the coating
thickness and coating segment width can be changed independent of
coating head speed providing a more versatile, fully programmable
selective coating system.
[0133] Referring in detail to FIGS. 11, 12 and 13, in addition to
the directed air stream produced by the air-shaping ring described
above, the following additional improvements in the spray head have
been made: [0134] 1) An air director and mounting ring. [0135] 2) A
pneumatically actuated air director positioner for the air
director. [0136] 3) Two additional solenoid valves to activate air
flow to the air director and to the air director positioner.
[0137] These improvements enable the spray head to operate in any
one of the following three-modes (or combinations thereof): [0138]
1) Narrow mode--where the airflow is directed through the air ring
to focus the ultrasonically produced spray (i.e., as described
above). [0139] 2) Wide mode--where the airflow is directed through
the air director to expand the ultrasonically produced spray.
Impinging the directed air stream on the flat surface of the
spray-forming tip expands the spray. The directed air stream is
impinged on the opposite surface to the liquid feed surface. See,
FIGS. 12 and 13. [0140] 3) Side mode--where the air director
positioner is actuated, moving the air director to the lower
position and airflow is directed through the air director to direct
the ultrasonically produced spray at an oblique angle from the
spray forming tip. The purpose of directing the spray at an oblique
angle is to coat a vertical surface, such as the side of a tall
component that would not otherwise be coated if the spray were
directed in the normal vertical path. See, FIGS. 11 and 12.
[0141] Referring in detail to FIG. 11, the ultrasonic spray head
with ILDS, precision liquid delivery system, air director
positioner, air director and air director mounting ring produces a
coating segment with a shape. When solenoid valve #1 is activated,
airflow is directed to the air-shaping ring producing a narrow
pattern as described previously. When solenoid valve #2 is
activated, airflow is directed through the air director, which
impinges the air stream on the flat surface of the spray-forming
tip on the opposite side to the liquid feed tube. The impinged air
stream expands the ultrasonically produced spray emanating from the
spray-forming tip producing a wide pattern up to five times the
width of the narrow mode pattern. When solenoid vale #3 is
activated the air director positioner is actuated to move the air
director to position in which the air stream through the air
director (activated by solenoid #2) is directed directly into the
ultrasonically produced spray emanating from the spray-forming tip.
The resulting spray pattern from the simultaneous activation of
solenoid valves #2 and #3, produces a sideways spray in which
coating is applied to a vertical surface.
[0142] Referring in detail to FIG. 12, solenoid vales #2 and #3 are
activated, moving the air director to direct the air stream into
the ultrasonically produced spray. The spray is directed to the
side (vertical) surface of a component.
[0143] Referring in detail to FIG. 13, solenoid valve #2 is
activated, directing the airflow through the air director to
impinge upon the side surface of the spray-forming tip. The
impinged air expands the ultrasonically produced spray to a width
up to five times the narrow mode width (FIG. 10).
[0144] The present invention has been described in detail,
including the preferred embodiments thereof. However, it will be
appreciated that those skilled in the art, upon consideration of
the present disclosure, may make modifications and/or improvements
on this invention and still be within the scope of this invention
as set forth in the following claims.
* * * * *