U.S. patent number 3,672,570 [Application Number 05/069,662] was granted by the patent office on 1972-06-27 for sequence control of color change.
This patent grant is currently assigned to Nordson Corporation. Invention is credited to Don R. Scarbrough, Burton J. Vilagi.
United States Patent |
3,672,570 |
Scarbrough , et al. |
June 27, 1972 |
SEQUENCE CONTROL OF COLOR CHANGE
Abstract
A pneumatically controlled color change system for use with
automatic multi-color paint spray apparatus and the like wherein an
entirely pneumatically controlled system employing a pneumatic
timer including pneumatic sequence valves controls a quick-color
change system in which a plurality of colors of paint are connected
to various inputs of a manifold, each through a check valve which
isolates each of the manifold ports from each other and in which a
source of solvent is connected to another input of the manifold. An
exceedingly high-speed system is provided in which a metered charge
of solvent only partially filling the system is injected through
the manifold and forced through the system with the new color to be
selected, thereby purging the system of the old color. High-speed
valve timing is provided in the order of magnitude of 1 second per
valve of the sequence.
Inventors: |
Scarbrough; Don R. (Elyria,
OH), Vilagi; Burton J. (Amherst, OH) |
Assignee: |
Nordson Corporation (Amherst,
OH)
|
Family
ID: |
22090433 |
Appl.
No.: |
05/069,662 |
Filed: |
September 4, 1970 |
Current U.S.
Class: |
239/70;
239/112 |
Current CPC
Class: |
B05B
12/14 (20130101); B05B 12/149 (20130101) |
Current International
Class: |
B05B
12/00 (20060101); B05B 12/14 (20060101); A01g
027/00 () |
Field of
Search: |
;239/61,62,70,124,125,112 ;222/144.5 ;137/238,240,244 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: King; Lloyd L.
Claims
What is claimed is:
1. An automatic quick-change system for replacing an old coating
liquid with a new coating liquid in an apparatus for selectively
depositing a coating liquid on a sub-strate, said system
comprising:
a. a discharge gun having an input port, an exhaust port, a passage
therein communicating with said input and exhaust ports, a nozzle,
a check valve connected between said passage and said nozzle for
connecting said nozzle to said passage when said check valve is
opened;
b. an exhaust line;
c. a fluid-controlled dump valve having a pilot port and connected
between said gun exhaust port and said exhaust line for connecting
said gun exhaust port to said exhaust line in response to control
pressure at said dump valve pilot port;
d. a manifold having an output port, a solvent input port, an
elongated passage therein communicating with said output port and
said solvent port, and a plurality of coating liquid input ports
communicating with said manifold passage intermediate said output
and said solvent input ports;
e. a feed line connected between said manifold output port and said
gun input port;
f. a source of pressurized solvent;
g. a fluid-controlled solvent valve having a pilot port and
connected between said solvent source and said solvent input port
of said manifold for connecting said solvent source to said
manifold input port in response to control pressure at said solvent
valve pilot port;
h. a plurality of sources of different pressurized coating
liquids;
i. a plurality of fluid-controlled coating liquid valves each
having a pilot port and each connected to a different one of said
coating liquid sources and a different one at said one of said
sources with said one of said ports in response to control pressure
at said coating liquid valve pilot port;
j. a fluid control circuit including:
1. a source of pressurized control fluid,
2. a fluid timing circuit,
3. a variable pressure regulator connected between said control
pressure source and said timing circuit,
4. a main valve connected between said regulator and said timing
circuit for opening and closing a path therebetween,
5. a selector valve having a plurality of output ports each
connected to the pilot port of a different one of said coating
liquid valves, an input port selectively connectable to any one of
said output ports for selecting said new coating liquid,
6. said timer comprising a plurality of fluid-actuated timing
valves connected in sequence, each of said valves having
a. a first output port, a second output port, a pilot port, and an
input port normally connected to said first output port and
alternatively connectable to said second output port in response to
control pressure at said pilot port,
b. a variable restriction valve connected between said timing valve
input port and said pilot port for communicating control pressure
to said pilot port at some delayed time after pressure is applied
to said input port, said delay time being variable by the combined
settings of said restriction valve and said regulator,
c. said plurality of timing valves including:
1. first fluid-controlled timing valve having its input port
communicating with the output port of said main valve, its first
output port communicating with the pilot port of said solvent valve
and with the pilot port of said dump valve, and its second output
port communicating with the input port of said selector valve for
communicating control pressure to said pilot ports in accordance
with the positions of said first timing valve and said main
valve,
2. a second fluid-controlled timing valve having its input port
communicating with the second output port of said first valve, its
first output port communicating with the pilot port of said dump
valve for communicating control pressure to said pilot port in
accordance with the positions of said first and second timing
valves and said main valve.
2. A pneumatically controlled system according to claim 1
wherein:
said fluid control circuit is a pneumatic control circuit, said
source of pressurized control fluid being a source of pressurized
air, and said fluid timing circuit being a pneumatic timing
circuit.
3. A system according to claim 1 wherein said manifold further
comprises:
a plurality of double-check valves, one connected in each of the
input ports of said manifold, each including a pair of opposed
check valves, one of the valves of said pair being said source
control valve.
4. A system according to claim 1 wherein said selector valve
further comprises:
a pneumatically controlled selector lock having a pilot port
connected to the output of said main valve to lock said selector
when said valve is open.
5. A system according to claim 1 wherein:
said first timing valve has a time delay of T.sub.1, T.sub.1 being
sufficiently long to allow solvent to flow into said manifold but
shorter than the time required for solvent to flow to said gun, for
introducing a slug of solvent into said line; and
said second timing valve has a time delay of T.sub.2, (T.sub.1 plus
T.sub.2) being sufficiently long to allow the new coating liquid to
flow into said manifold to force some of said solvent into said gun
passage, but shorter than the time required to force all of said
solvent out of said exhaust line.
6. An automatic quick-change system for replacing an old coating
liquid with a new coating liquid in an apparatus for depositing a
coating liquid on a sub-stratum, said system comprising:
a. a discharge gun having an input port, an exhaust port, a passage
therein communicating with said input and exhaust ports, a nozzle,
a fluid-controlled check valve having a pilot port and connected
between said passage and said nozzle for connecting said nozzle to
said passage in response to control pressure at said check valve
pilot port;
b. an exhaust line;
c. a fluid-controlled dump valve having a pilot port and connected
between said gun exhaust port and said exhaust line for connecting
said gun exhaust port to said exhaust line in response to control
pressure at said dump valve pilot port;
d. a manifold having an output port, a solvent input port, an
elongated passage therein communicating with said output port and
said solvent port, and a plurality of coating liquid input ports
communicating with said manifold passage intermediate said output
and said solvent input ports;
e. a feed line connected between said manifold output port and said
gun input port;
f. a source of pressurized solvent;
g. a fluid-controlled solvent valve having a pilot port and
connected between said solvent source and said solvent input port
of said manifold for connecting said solvent source to said
manifold input port in response to control pressure at said solvent
valve pilot port;
h. a plurality of sources of different pressurized coating
liquids;
i. a plurality of fluid-controlled coating liquid valves each
having a pilot port and each connected to a different one of said
coating liquid sources and a different one at said coating liquid
input ports of said manifold for connecting said one of said
sources with said one of said ports in response to control pressure
at said coating liquid valve pilot port;
j. a fluid control circuit including:
1. a source of pressurized control fluid,
2. a fluid timing circuit,
3. a variable pressure regulator connected between said control
pressure source and said timing circuit,
4. a main valve connected between said regulator and said timing
circuit for opening and closing a path therebetween,
5. a selector valve having a plurality of output ports each
connected to the pilot port of a different one of said coating
liquid valves, an input port selectively connectable to any one of
said output ports for selecting said new coating liquid;
6. said timer comprising a plurality of fluid-actuated timing
valves connected in sequence, each of said valves having
a. a first output port, a second output port, a pilot port, and an
input port normally connected to said first output port and
alternatively connectable to said second output port in response to
control pressure at said pilot port,
b. a variable restriction valve connected between said timing valve
input port and said pilot port for communicating control pressure
to said pilot port at some delayed time after pressure is applied
to said input port, said delay time being variable by the combined
settings of said restriction valve and said regulator,
c. said plurality of timing valves including:
1. first fluid-controlled timing valve having its input port
communicating with the output port of said main valve, its first
output port communicating with the pilot port of said solvent valve
and with the pilot port of said dump valve, and its second output
port communicating with the input port of said selector valve for
communicating control pressure to said pilot ports in accordance
with the positions of said first timing valve and said main
valve,
2. a second fluid-controlled timing valve having its input port
communicating with the second output port of said first valve, its
first output port communicating with the pilot port of said dump
valve for communicating control pressure to said pilot port in
accordance with the positions of said first and second timing
valves and said main valve,
3. a third fluid-controlled valve having its input port
communicating with the second output port of said second valve and
its first output port communicating with the pilot of the check
valve of said gun for for communicating pressure to said pilot port
in accordance with the positions of said first, second and third
timing valves and said main valve, and having a delay time
T.sub.3.
7. A pneumatically controlled system according to claim 6
wherein:
said fluid control circuit is a pneumatic control circuit, said
source of pressurized control fluid being a source of pressurized
air, and said fluid timing circuit being a pneumatic timing
circuit.
8. A system according to claim 6 wherein said manifold further
comprises:
a plurality of double-check valves, one connected in each of the
input ports of said manifold, each including a pair of opposed
check valves, one of the valves of said pair being said source
control valve.
9. A system according to claim 6 wherein said selector valve
further comprises:
a pneumatically controlled selector lock having a pilot port
connected to the output of said main valve to lock said selector
when said valve is open.
10. A system according to claim 6 wherein:
said first timing circuit has a time delay of T.sub.1, T.sub.1
being sufficiently long to allow solvent to flow into said manifold
but shorter than the time required for solvent to flow to said gun,
for introducing a slug of solvent into said line,
said second timing circuit has a time delay of T.sub.2, (T.sub.1
plus T.sub.2) being sufficiently long to allow the new coating
liquid to flow into said manifold to force some of said solvent
into said gun passage, but shorter than the time required to force
all of said solvent out of said exhaust line; and
said third timing circuit has a time delay of T.sub.3, T.sub.3
being sufficiently long to purge said old liquid from said
nozzle.
11. A system according to claim 10 wherein T.sub.1 and T.sub.2 are
in the range of from 0.1 to 10 seconds and T.sub.3 is in the range
of from 0.1 to 3 seconds.
12. A quick-change system for replacing any one liquid from a
multiplicity of liquids with a new one of said multiplicity in a
discharge apparatus operable to selectively discharge said liquids,
said system comprising:
a discharge nozzle;
an exhaust line;
a feed line;
a nozzle control valve for selectively connecting said nozzle to
said feed line;
an exhaust control valve for selectively connecting said exhaust
line to said feed line;
a source of liquid solvent;
a solvent control valve for selectively connecting said solvent
source to said feed line;
a source of each of said multiplicity of liquids;
a multiplicity of liquid control valves for selectively connecting
each of said sources of liquids to said feed line; and
a source of pressurized control fluid;
an all fluid operated control circuit, said circuit including a
fluid timing circuit which is operative upon connection of said
source of pressurized control fluid into said circuit to
automatically control the sequencing of said exhaust control valve,
said solvent control valve and said liquid control valves so as to
purge said feed line of one liquid by means of solvent flow through
said feed line, and to then fill said feed line with a second
liquid.
13. A quick-change system according to claim 12 wherein:
said fluid control circuit is a pneumatic control circuit and said
source of pressurized control fluid is a source of pressurized
air.
14. A quick-change system according to claim 12 wherein said
control circuit further comprises:
fluid valve means for selecting said second liquid from said
multiplicity.
15. A quick-change system according to claim 12 wherein:
said fluid control circuit includes a first control output
connected to apply control fluid to said solvent and exhaust
control valves to open said valves to purge said feed line, and a
second control output connected to apply control fluid to said
exhaust and second liquid control valves to open said valves to
fill said feed line.
16. A system according to claim 12 wherein said timing circuit
includes fluid means for varying the time of operation thereof.
17. A system according to claim 12 wherein:
said control circuit includes fluid means for operating said nozzle
control valve under control of said fluid timing circuit to cause
solvent to flow through said nozzle to purge said nozzle.
18. A system according to claim 12 wherein:
said fluid timing circuit comprises a plurality of fluid-actuated
timing valves each of said valves having
a. a first output port, a second output port, a pilot port, and an
input port normally connected to said first output port and
alternatively connectable to said second output port in response to
control pressure at said pilot port,
b. a variable restriction valve connected between said timing valve
input port and said pilot port for communicating control pressure
to said pilot port at a delayed time after pressure is applied to
said input port.
19. An automatic, quick-change system for replacing an old liquid
with a new liquid in a discharge apparatus for selectively
discharging a coating liquid, said system comprising:
a discharge nozzle;
an exhaust line;
a feed line;
a check valve for selectively connecting said nozzle to said feed
line;
a dump valve for selectively connecting said exhaust line to said
feed line;
a source of solvent;
a solvent valve for selectively connecting said solvent source to
said feed line;
a source of said new liquid;
a source valve for selectively connecting said new liquid source to
said feed line;
controls for operating said dump, solvent, and source valves to
cause the presence in said feed line, at some time during a liquid
replacing operation, of said old liquid followed by said new liquid
with a slug of solvent immediately therebetween.
20. The system of claim 19 wherein:
said controls are operable to open said dump and solvent valves for
a time T.sub.1 and thereafter to open said dump and new liquid
valves for a time T.sub.2 ;
time T.sub.1 being sufficiently long to allow solvent to flow into
said feed line but shorter than the time required for solvent to
flow to said nozzle, so that a slug of solvent is introduced into
said line during said time T.sub.1 ; and
the sum of the times T.sub.1 and T.sub.2 being sufficiently long to
allow the new liquid to flow into said feed line to force at least
some of said solvent past said check valve, but shorter than the
time required to force all of said solvent out of said exhaust
line.
21. A system according to claim 19 wherein:
said controls further operate to open said new source and check
valves for a time T.sub.3, time T.sub.3 being sufficiently long to
allow some of said slug of solvent to pass through said nozzle.
22. A system according to claim 20 wherein:
the time T.sub.1 is in the range of from 0.5 to 5 seconds, and
the time T.sub.2 is in the range of from 1 to 10 seconds.
23. A system according to claim 22 wherein:
said timing circuit opens said check and new source valves for a
time T.sub.3 in the range of from 0.1 to 1 second.
24. An automatic, quick-change system for replacing an old liquid
with a new liquid in a discharge gun for selectively discharging
said liquids, said system comprising:
a discharge nozzle;
an exhaust line;
a feed line;
a check valve for selectively connecting said nozzle to said feed
line;
a dump valve for selectively connecting said exhaust line to said
feed line;
a manifold having an output port, connected to said feed line, a
solvent input port, an elongated passage therein communicating with
said output port and said solvent port, and a plurality of liquid
input ports communicating with said manifold passage intermediate
said output and said solvent input ports;
a plurality of double-check valves, one connected in each of the
input ports of said manifold, each including a pair of opposed
check valves, one of the valves of said pair being said source
control valve;
a pressurized source of solvent;
a solvent valve for selectively connecting said solvent to said
solvent input port of said manifold;
a plurality of pressurized sources of liquids;
a plurality of source valves each for selectively connecting a
different one of said liquid sources to a different one of said
liquid input ports of said manifold.
Description
The present invention relates to a quick-change system for use with
a single gun operable to selectively discharge different coating
liquids, such as paints of different color, or varnishes, waxes,
protective coating materials or other surface treating liquids upon
a substrate. More particularly, the present invention relates to a
quick-color change system in which the paint is sprayed or
discharged from the nozzle, and deposited upon a substrate or
object to be painted. The present invention is specifically
directed to such a quick-change spray system for changing from one
liquid to another without the previously used old liquid
contaminating the new liquid when it is sprayed.
The increased use of automated painting and coating apparatus such
as in assembly lines on automobile plants, or a series of objects
to be painted or otherwise coated pass a paint station, and in
which these objects typically require the applications of different
coatings and colors, have resulted in an increased demand for
multiple color paint spray systems. While systems have been
proposed utilizing a separate apparatus having a separate nozzle
for each of the colors or coating liquids to be sprayed, such
systems are cumbersome and unduly expensive. The utility of systems
wherein a single apparatus having a single discharge nozzle, or
single set of nozzles as the requirement may be, for spraying the
plurality of coating liquids one at a time, has resided in the
ability of the color change system to change from one color to
another quickly with a minimum waste of paint and solvent.
Typically, these systems employ a manifold to which the plurality
of coating liquids is connected and through which one of the
plurality of coating liquids is selectively connected to the
coating apparatus. When changing from one coating liquid to
another, it is necessary to purge the manifold, the feed line
connecting the manifold to the apparatus, and the apparatus itself
of the old coating liquid prior to the injection of a new coating
liquid. Commonly, the solvent material is injected into the system
to force the old liquid out of the system through a dump valve and
to flush the system of the old coating liquid. A common method
employed by the prior art systems have been to manually cause the
solvent to be injected into the system and to visually observe a
clean solvent being exhausted through the dump valve. Then, either
air is injected into the system to purge the system of the solvent,
or the new coating liquid is injected to push ahead of it the
solvent from the system. These systems of the prior art have
consumed much valuable time and wasted a great deal of paint and
solvent in changing color in this manner. Indeed, in automotive
paint lines, where each of the objects is to be painted a different
color, the waste of time and paint can be a major cost factor.
Furthermore, automated systems of the prior art rely principally
upon valves controlled by electrical solenoids to automatically
sequence a change cycle. Since such systems are almost always used
in a highly explosive atmosphere, these electrical control systems
have been encased in sealed, armored explosion-proof cabinets. In
many cases, the cabinets have been installed at greater cost than
the systems themselves. Another disadvantage of such
explosion-proofing has been the requirement that the entire system
be shut down whenever any maintenance is required upon the system,
even minor maintenance, for the explosion-proof cabinet had to be
opened to allow such maintenance to proceed.
Accordingly, it has been the principal object of the present
invention to provide an explosion-hazard-free control system which
uses entirely fluid-controlled valves and fluid-controlled timing
circuits to operate the valves. Another object of the present
invention has been to provide a change system which operates faster
than comparable systems of the prior art, typically in the order of
1 to 5 seconds in situations where prior art systems have required
25 seconds and above; and generally not more than 20 seconds for a
complete change cycle in some of the more special application
systems which utilize high viscosity liquids, very long lines or
lower pressure, in which systems the prior art devices have
typically required a minute or longer for such a change.
Accordingly, the present invention is predicated in part upon the
concept of providing an all-fluid-controlled valve system which is
controlled entirely through the use of a fluid control circuit
which includes a fluid-operated timing circuit for controlling the
sequencing of the valves during a liquid change cycle. More
particularly, the present invention provides a fluid control system
employing variable time delay pneumatic sequence valves which
deliver control pressure from a variable control pressure source to
operate the liquid flow control valves in a programmed color change
sequence.
The present invention is also predicated in part upon the concept
of injecting a metered slug of solvent into the lines of the
system, the slug being only long enough to purge the system of the
old color, and then forcing the slug through the system with the
new coating liquid to be applied. Furthermore, the present
invention employs valve opening times in order of magnitude of 1
second each.
Furthermore, the present invention employs a novel manifold
arrangement wherein each of the input ports of the manifold
includes a double-check valve arrangement. More particularly, one
of the check valves of this double-check valve arrangement is the
remote control valve which connects the particular liquid to the
system, and the other is a check valve which isolates from the
manifold all but a small region in the path of the solvent passing
through the manifold and thereby presents an area easily flushed of
the solvent. The advantage of this manifold arrangement is that it
is easily and quickly cleaned or flushed of one liquid preparatory
to the introduction of another.
The primary advantages of the present invention reside in the
provision for an automatic, quick-change system which is completely
safe for use in an explosive environment without the need for
expensive explosion-proof cabinets and the impairment for servicing
during operation which they entail. An additional important
advantage is in the provision for high-speed paint change system,
wherein the complete change from one coating liquid to another in
an airless system takes the time of typically 4 to 10 seconds. A
further advantage resides in the variable timer of such a system so
that the times of the various steps of the cycle can be varied
either independently or collectively to account for different types
and viscosities of coating liquids. Another advantage is that it
substantially reduces any wasted paint and solvent which results
from the use of this liquid change apparatus.
Other advantages of the present invention which will be more
readily apparent from the detailed description of the present
invention reside in the provisions for positive interlocking
sequencing of the quick-change system, manual emergency shut-off of
the system, a system which is essentially the same regardless of
the number of colors or different coating liquids to be used, and a
system which can be constructed virtually from standard
components.
Other objects and advantages of the present invention will be more
readily apparent from the following detailed description of the
drawings illustrating one preferred form of a quick change system
according to the present invention in which:
FIG. 1 is a fluid control diagram of a quick change system
according to the present invention;
FIG. 2 is a timing diagram of the operation of the system of FIG.
1;
FIGS. 3-6 are diagrams of the system of FIG. 1 illustrating the
states of the different coating liquids and solvent at the
different times illustrated at t.sub.3 -t.sub.6 in FIG. 2;
FIG. 7 is a partial cut-away view of the coating liquid and solvent
distribution manifold;
FIG. 8 is an enlarged cross-sectional view of the double check
valve at an input port of the manifold of FIG. 7; and,
FIG. 9 is a cross-sectional view of a coating liquid discharge
gun.
Referring to the system diagram of FIG. 1, a quick change system
according to one of the principles of the present invention
includes a paint discharge gun 10 which is of the circulating type,
that is, it includes three ports, including an input port 11
through which paint enters the gun, and outlet port 12 through
which paint exits that particular gun, and a nozzle 13 through
which paint or other coating material is sprayed upon a substrate
to be coated.
The gun includes an internal passage 14 which communicates with the
input and exhaust ports directly, and also communicates with the
nozzle 13 through a trigger valve 15. The trigger valve 15 is
typically lever-operated when the gun is a hand-held type. In the
embodiment shown, however, the gun 15 is remotely controlled
through the application of control pressure to the pilot port 16.
This form is preferred when the gun is either fixedly or movably
mounted upon a support such as might be found adjacent a paint line
in an automobile assembly plant. An outlet line 17 is connected
through a dump valve 18 to a return line 22 which communicates with
the exhaust port 12 of the gun 10. The dump valve operates in
response to control pressure at the pilot port 19 to open the
exhaust line 17 to allow paint to be purged from the gun 10 and
drained into a scrap drum 20. The dump valve 18 is normally closed
to block the exhaust line 17 in the absence of control pressure at
the pilot port 19.
Paint is supplied to the gun 10 through a feed line 21 which is
connected to the input port 11 of the gun 10. Whereas the gun 10 is
preferably of the circulating type as herein described in order
that the maximum amount of trapped old paint can be purged from the
system through the outlet port rather than the nozzle, it is within
certain of the broader concepts of the present invention to operate
without such a circulating gun. In such cases, it is preferable
that a T be incorporated and connected to the feed line at some
point prior to the input 11 of the gun 10 and preferably as close
thereto as possible. A return line, external of the gun, is then
connected between the T and the dump valve.
The selected color of paint or coating liquid is supplied to the
gun through a manifold 25. The manifold has an output port 26 which
connects to the feed line 21, and a plurality of input ports 27
each connecting through a shut-off valve 28 to any one of a
plurality of lines 29 which are connected to various sources of
coating liquid.
The manifold 25 has therein an elongated passage or through-port 30
(FIGS. 3-7) which communicates each input port 27 with the output
port 26. The manifold also includes an input port 31 which is
connected through a cut-off valve 32 to line 33 which is connected
to a source of pressurized solvent. The input port 31 communicates
with the passage 30 at a point which is the most remote from the
output 26 of the manifold. Thus the input ports 27 communicate with
the passage 30 at points intermediate the solvent input port 31 and
the output port 26 so that the solvent when passed by valve 32, can
most effectively flush the manifold 30 clear of the old coating
liquid of the previous application prior to subsequent application
of a different coating liquid.
The pressure of the sources of coating liquid connected to the
source lines 29 is typically 200 to 1,000 psi for spray systems of
the airless type, and is typically 3-75 psi for systems of the air
spray type. An airless system is one in which paint is sprayed at
high pressure and atomized solely by forcing the high pressure
liquid through the nozzle of a paint spray gun. In an air system,
the liquid is injected as an extruded stream at low pressure into a
stream of high pressure air which causes it to atomize. The present
invention can operate with either system, but in the preferred
embodiment shown, the airless system is employed with source
pressures of approximately 500 psi.
Each of the coating liquid valve 28 and the solvent valve 32 are
normally closed. The coating liquid valves 28 are opened in
response to control pressure at their pilot ports 34, and the
solvent valve 32 is opened in response to control pressure at its
pilot port 38. Each of the pilot ports 34 of the liquid coating
valves 28 connect to the output ports 36 of a rotary selector valve
37. The pilot port 38 of solvent valve 32 is connected to an output
39 of the selector switch 37 to allow for selection of the solvent
as one of the coating liquids. As is described in more detail
below, the solvent valve 32, is however, also operated under the
control of a timing circuit which applies control pressure through
a control line 41. The selector switch output 39 and the line 41
are alternately connected to the pilot port 38 of the solvent valve
32 through the shuttle valve 42.
The selector 37 also has an input port 44 which is selectively
connectable to any one of the output ports 36 or 39 through the
manually movable spool 45 which is controlled either by the dial 46
or automatically through a programmer (not shown) to select new
coating materials. The ports 36 which are not connected to the
input port 44 are normally connected to an exhaust port 47 at
atmospheric pressure. A fluid pressure responsive selector lock 48
is provided to lock the spool 45 of the selector valve 37 and
thereby prevent a change in selection while an automatic change
cycle is in progress.
The automatic control and timing circuit is entirely a
pneumatically-controlled system in which the source of control
pressure is supplied from an air pressure source 50. The control
pressure is normally maintained at approximately 40-70 psi. The air
pressure source 50 connects through a filter 51 and a variable air
pressure regulator 52 to the input port 53 of a manually actuatable
four-way valve 54. The valve 54 is the main control valve which
provides for the manual starting and stopping of the color change
cycle. The valve 54, however, could also be automatically
controlled by a programmer, for example, if the present invention
were used as part of a completely automated painting process. The
valve 54 has an exhaust or drain port 55 and a pair of output ports
56 and 57. When the valve is in its de-actuated condition, the port
57 is normally connected to the pressure input port 53 to
communicate a ready signal to a pressure responsive indicator 58,
while the output port 56 is connected to exhaust port 55. This
removes pressure from the control circuit, and, because all valves
are normally closed, the change system is at this time disabled.
The valve 54 has a manual override to utilize this feature for
emergency cut off of the system. When the valve 53 is actuated the
output port 56 communicates with the input port 53 thereby opening
the pressure path through the valve 54 to a line 61 connected to
the output port 56 to initiate the change cycle. Line 61 is
connected through a line 62 to the pilot port 49 of the
pneumatically controlled selector lock 48 to energize the lock 48
and lock the selector switch 37. The line 61 is also connected
through line 63 to the pneumatic timing circuit illustrated
generally at 65.
The timing circuit 65 is an entirely pneumatically controlled
timing circuit for generating a series of timed-delayed control
signals. The timing circuit 65 employs sequence valves or
series-connected timed-delay valves which actuate at some delayed
time after pressure is applied to their input terminals. The
specific circuit illustrated employs three such valves, 71, 72, and
73, however, more or less than three could be employed as will be
explained more fully below. Each of the valves 71 and 73 are
substantially identical and will be explained here by reference to
valve 71.
The first timing valve 71 includes a four-way valve 77, having an
input port 78 and a pair of ports 79 and 80. The output port 79 is
a normal through-port of the valve while the second output port 80
is normally connected to an exhaust port 81. When the valve is
actuated, the output ports are reverse connected and the first
output 79 is connected to the exhaust port 81 while the second
output port 80 is connected to the input port 78. The valve 77
actuates in response to control pressure of a certain predetermined
level at a pilot port 82. The pilot port 82 is connected through a
variable restriction valve 83 to the input ports 78. The
restriction valve 83 serves to impede the flow to the pilot port 82
thereby delaying the time at which the predetermined pressure
required to actuate the valve is attained at the pilot port 82.
This time delay can be variably controlled by the setting of the
valve 83. It should also be noted, that the actual time delay is
also dependent upon the setting of the pressure regulator 52.
Setting the valve 83 varies the delay time of valve 81
independently of other valves in the circuit, while setting the
regulator 52 varies the response of all valves of the circuit by
approximately the same factor. A check valve 84 is provided to
quickly release the pressure on the pilot port 82 when the pressure
on the input port 78 is removed. Thus, when pressure is applied to
the input port 78 by the opening of the main valve 54, a control
pressure signal is present at the output 79. After a certain time
delay determined by the setting of the restriction valve 83, the
four-way valve 77 is actuated and pressure on line 79 is removed
and applied to port 80.
In like manner valve 72 has an input port 87, first output port 88
and a second output port 89. The input 87 is connected to the
output port 80 of the valve 71. The valve 72 includes a variable
restriction valve 91, which determines the time delay constant of
the valve 72. Thus, when the valve 71 is actuated, a control
pressure signal appears at port 88, and after a predetermined time
delay determined by the setting of the valve 91, the signal is
removed from the port 88 and transferred to the port 89.
Similarly, the valve 73 includes an input port 92 connected to the
second output port 89 of the valve 72, and a first output port 93
and the second output port 94. The valve 73 includes a variable
restriction valve 95 which determines the time delay constant to
the valve 73. Thus, after valve 72 is actuated, a control signal
appears at port 93, and after a time delay determined by the
setting of the valve 95, the signal is removed from the port 93 and
transferred to port 94. Connected to port 94 is a pressure response
indicator 96 which signals the completion of a change cycle.
The output port 79 of the valve 71 is connected to line 41 and
through the shuttle valve 42 to the pilot port 38 of the solvent
valve 32, and also through a shuttle valve 97 to the pilot port 19
of the dump valve 18. The output 80 of the valve 71 is connected to
the input 44 of the selector valve 37. (This is equivalent to
connecting the selector input 44 through a shuttle valve to ports
89 and 93 of the timer and this latter method would be preferred if
an additional step were added to the system.) The output 88 of the
valve 72 is connected through another port of the shuttle valve 97
to the pilot port 19 of the dump valve 18. The output 93 of the
valve 73 is connected to a shuttle valve 98 to the pilot port 16 of
the trigger valve 15 of the gun 10. Also connected through the
shuttle valve 98 to the pilot port 16 of the trigger valve 15 is a
control line 99 through which a signal is provided to operate the
paint spray gun 10 during painting operations between
change-cycles.
Briefly, the timing operation can be understood by reference to the
timing diagram of FIG. 2. Prior to a change cycle, the main valve
54 is in the closed condition and the ready indicator is "ON" as
illustrated by the curve 101 on the diagram. At some time t.sub.3
the main valve is opened, as illustrated by curve 102. At this time
control pressure is applied to energize the selector lock as
illustrated by curve 103 and to open the solvent and dump valves as
illustrated by curves 104 and 105. This initiates the time delay
T.sub.1 of the first of the sequence valves 71 at the end of which
valve 71 is actuated at a time represented by t.sub.4 in FIG. 2. At
time t.sub.4 the solvent valve is closed and the new color valve as
selected by the setting of the selector valve 37 is opened as
illustrated by curve 106.
At time t.sub.4 control pressure is also removed from the pilot
input 19 of the dump valve 18, however, this pressure is reapplied
through the valve 72 and in practice this time is too short to
result in a closing of the dump valve 18. After a time delay
T.sub.2 the valve 72 closes, and causes the dump valve 18 to close
as shown by curve 105. This is illustrated at time t.sub.5 in FIG.
2. At t.sub.5 pressure is applied through the third of the timing
valves 73 to momentarily open the trigger valve 15 for a period of
time T.sub.3 after which valve 73 closes, and time t.sub.6 closing
the new color valve, and the trigger valve, of the gun as shown by
curve 106 and 107. Also at time t.sub.6 the complete indicator is
turned on as illustrated by curve 108 in FIG. 2 and the selector
lock 48 is de-energized as illustrated by curve 103. At this point
the main valve 54 can either be manually or automatically
disengaged as the color change-cycle is complete.
The change-cycle can best be understood by reference to FIGS. 3
through 6 which illustrate the highly efficient manner in which the
lines are only partially purged by the injection of solvent, and
then finally purged of the old coating liquid 111 through the
injection of the new coating 115 which pushes ahead of it a metered
slug of solvent which clears the lines of the old material. With
reference back to the timing diagram of FIG. 2, FIG. 3 illustrates
the system prior to a change-cycle at time t.sub.3. It will be seen
that the passage 30 of the manifold 25, the feed line 21, the
passage 14 of the gun 10 and the nozzle 13 are filled with the old
coating material 111 being supplied through valve 34-B.
Prior to the color change, the selector dial 46 of the selector
valve 37 is set to the new paint color or coating liquid and the
main valve 54 is actuated.
During this first step (FIG. 4) of the cycle, the solvent valve 32
and the dump valve 18 are opened, and the trigger valve 15 of the
gun 10 is closed. This allows solvent to enter into the manifold
passage 30 and to force the old paint through the dump valve 18
into the scrap drum 20. At time t.sub.4 a slug of solvent 112 has
entered the manifold passage 30 and proceeded partially down the
length of the feed line 21 to point 113. The solvent slug 112 is
not allowed to completely extend through the entire feed line 21 to
purge the entire system since this is not necessary. Instead, only
a slug of sufficient length to clear the passage 30 is employed.
Typically about 2-5 feet of manifold passage and feed line would be
filled with solvent. At this point and as shown in FIG. 5, the
solvent valve 32 is closed and the new liquid valve 34-E is opened.
The new liquid 115 is introduced into the manifold passage 30 and
along the feed line 21 to advance the slug of solvent 112 as far as
the juncture of the trigger valve 15 with the passage 14 of the gun
10. At this point it is still not necessary to completely purge the
old liquid 111 from the exhaust line 17. The length of the slug 112
is sufficient to completely wash the line 21 of the old liquid.
FIG. 5 illustrates the state of this system at time t.sub.5.
Referring to FIG. 6, the dump valve 18 is closed but the source
valve 34-E remains open communicating the pressurized new color
with the paint lines 21. At this time the trigger valve is opened
and preferably the new paint color is fed through the nozzle,
thereby discharging the old paint 111 which remains in the nozzle.
In some applications, however, it may be desirable to eject a small
amount of solvent through the nozzle to purge it of old paint. At
time t.sub.6 the trigger valve 15 closes and the system is ready
for operation with the new color 115.
Referring back to FIG. 5, it will be noted that it is possible for
a small amount of solvent to remain trapped in the manifold in the
region 117. This solvent, however, is normally selected such that
it is compatible with the coating and will diffuse and dissipate
into the new liquid mixture without affecting the quality of the
coating. As will be explained below, the manifold of this system
has the particular advantage of minimizing the amount of this
trapped solvent.
As mentioned above it is possible to operate this system with fewer
or more timing valves than the three illustrated in FIG. 1. For
example, where the hand-held gun is employed, the valve 73 is not
required, in this case, the operator, merely by aiming the gun into
the scrap drum and momentarily depressing a manual trigger can
thereby expel the old liquid 111 from the nozzle into the drum. In
other cases, it is sometimes desirable to employ more valves than
three in situations where more steps are required. For example,
when incompatible coating liquids are to be employed in consecutive
steps, it may be desirable to produce a charge of air to purge the
old paint from the system and through the exhaust line 17. It also
may be required in such situations to employ different solvents and
to separate the solvents by a charge of air. Occasionally, a strong
solvent might be used which is incompatible with the coating
liquid. This solvent would be injected in the same manner through
the sequences illustrated of the FIG. 4, but then followed by a
charge of air to expel the solvent through the exhaust line 17,
which is then followed by the new coating liquid.
Referring more particularly to the details of the manifold 25, this
is best illustrated by reference to FIG. 7. The manifold 25
includes a housing 120 having the through port or central passage
30 extending substantially therethrough. The output port 26 is
provided in one end of the passage 30 and the solvent input port 31
is provided adjacent the innermost end. Intermediate these extreme
ends the plurality of input ports 27 are connected to passage 30,
each connecting through one of the coating liquid valves 28 through
lines 29 to corresponding coating liquid sources. The solvent input
port 31 connects through the solvent input valve 32 to the solvent
source line 33 which is connected to a solvent source. The dump
valve 18 is also physically mounted on the manifold housing 120 and
connects through a passage 121 therein to the exhaust line 17. The
passage 121 is, however, completely isolated hydraulically from the
passage 30.
In one embodiment, each of the valves 18, 28 and the valve 32 may
be identical and hence only one valve 28 is illustrated in the
cut-away portion of the drawing (FIG. 7). However, in a preferred
embodiment for many applications, the valves 28 are of the
circulating type and each will be identical to that illustrated for
the trigger valve 15 of the gun 10 in FIG. 9. The dump valve 18,
however, and the solvent valve 32, are usually non-circulating even
in this preferred embodiment. An example of such a circulating type
system is completely illustrated and disclosed in U.S. Pat. No.
2,754,228 of Bede, issued July 10, 1966. As noted above, the valve
includes the input line 29 which communicates with an internal
passage 122. The passage 122 communicates through a pneumatically
controlled check valve 123 to the input 27 of the manifold. Control
pressure for opening the check valve 123 is supplied through the
pilot port 34. The details of the source valves 28 and 32 are
identical to the details of the operating mechanism of the trigger
valve 15 of the gun 10 and will be explained in more detail in
conjunction with the description of the trigger valve of the FIG.
9.
The check valve 123 forms one of the check valves of a double-check
valve assembly 125. This check valve arrangement prevents back flow
of the coating liquid or solvent and thereby prevents contamination
of one liquid coating with another. The valve also presents a
minimum washing area for the solvent to purge of coating material.
The valve 125 is more clearly illustrated in the cross-section view
of FIG. 8. The valve 125 comprises a narrow throat 130 adjacent the
check valve 123. A check valve 131 is provided in a close relation
to the check valve 123 and also adjacent the throat 130 opposite
the check valve 123. The check valve 131 is a passive check valve
operating entirely by the pressure of the paint from the source
through the valve 123. The valve 131 includes a ball or check 132
urged by a spring 133 against the rim of the walls 134 of the
throat section 130. The check valve 131 presents only a small
surface area 135 which lies directly in the path of the passage 30
and is easily washed by the solvent as it passes through the
passage 30.
Referring to FIG. 9, a paint spray gun is illustrated. The gun is
generally a recirculating airless-type having an input port 11, and
outlet port 12 and a nozzle 13. The nozzle is operated by a trigger
valve 15 in response to control pressure at the pilot port 16 to
connect the nozzle with the internal passage 14 of the gun 10.
While an airless spray nozzle 13 is illustrated, a typical use of
the system of the present invention is contemplated to be in
conjunction with an electrostatic spray gun having a nozzle
extension which will typically project several times a length of
the nozzle 13 as illustrated.
As it will be seen from FIG. 9, the gun 10 generally comprises a
two-piece square body 140 within which there is an axial or central
bore 141. This bore comprises the internal passage or fluid chamber
14 adjacent the front end of the body, a smaller diameter
connecting chamber 144 and a large diameter piston chamber 145. The
chamber 144 is connected to atmosphere through a bleed port 143.
The rear side of the piston chamber 145 is opened to the atmosphere
through a small diameter section 146 of the bore 141 which is
connected to the piston chamber 145 via an intermediate diameter
chamber 147. An end cap 148 is secured to the body by bolts (not
shown) and closes the fluid chamber 14. The cap 148 comprises a
central plate 149 from which hub sections 150, 151 extend
rearwardly and forwardly, respectively. The rearward hub 150 fits
within, and with an O-ring, seals the fluid chamber 14. The
forwardly extending hub section 151 is threaded on its exterior as
indicated at 154 and has an inwardly extending flange 155. An axial
bore 156 extends through the cap 148. It comprises a large diameter
rear section 157 and a smaller diameter front section 158.
A cylindrical metal insert 159 made from a hard material, as for
example, tungsten carbide, is inserted within the small diameter
section 158 of the cap. This insert defines the seat of the check
valve 15. It has a stepped axial bore which comprises a large
diameter rearward section 160 and a small diameter passage 161
interconnected by a shoulder 162. An arcuate seat 163 is machined
into the shoulder at the point where the shoulder 162 joins the
small bore 161. The seat is configurated as an annular taper so as
to cooperate with a generally semi-spherical end 165 of the check
valve head 166 to form a seal.
The nozzle 13 is made of a hard material and is welded to a nozzle
mounting disc 169. A retaining nut 170 is threaded onto the
externally threaded section 154 of the hub 151. This retaining nut
secures the disc 169, which carries the spray nozzle 13, against
the hub 151 of cap 148.
It will be seen that the check valve head 166 is controlled in its
movement into and out of engagement with the check valve seat 163
by the pneumatic piston 185. This piston 185 is connected to the
head end of the check valve by a connecting rod 186. A conventional
threaded coupling and lock nut 184 enable the rod 186 to be
adjusted in length relative to the head 166. A compression spring
187 normally biases the head and connected piston rod 186 toward
the nozzle to a position in which the check valve 15 is seated or
closed. This spring 187 bears at one end against the nut 184 and at
the opposite end against a collar 188 which is fixedly seated in
the chamber 144 of bore 141 and has a shoulder or flange 189 seated
against a shoulder 190 of the bore 141. O-rings 191 and 192 seal
the liquid chamber 14 from the pneumatic chamber 145, and vice
versa. The forward end 195 of the piston chamber 145 is also sealed
from the rear portion 196 by a pneumatic seal 197 located around
the periphery of the piston 185. The piston is secured onto the end
of the rod 186 by a pair of lock nuts 198 and 199 threaded onto the
threaded innermost end 200 of the rod 186. Air under regulated
pressure, e.g., approximately 60 psi is supplied to the inner
chamber 195 of the piston chamber 145 from the pilot port 16 via a
connecting passage 210 in the body 140 of the gun 10.
The primary advantage of this invention over quick-change color
spray systems now being used commercially is that it eliminates all
use of electrical solenoid-controlled valves and control circuits
and thereby avoids the hazard of an electrically initiated
explosion. By eliminating all electronic sequencing and control
there is no longer any need to explosion-proof the area in which
the paint is sprayed and the gun is utilized.
Another advantage of this invention is the positive sequencing
which results from the pneumatic sequencing control valves. In the
event that one valve stops or jams, it automatically stops the
complete cycle, thereby insuring a properly sequenced cycle or none
at all.
Another advantage of this invention resides in its quick cycle time
and the fact that it operates in approximately one-fourth to
one-tenth the cycle time of quick-change color systems now in
commercial use. Because it is so much faster than systems in
present use, it results in less wasted paint being dumped to scrap
and less solvent being utilized to purge the system during color
changes.
While only a single preferred embodiment of the invention is
described, those persons skilled in the art to which this invention
pertains will readily appreciate numerous changes and modifications
which may be made without departing from the spirit of the
invention. For example, it will sometimes be desired to incorporate
certain of the features and advantages derived from the fluid
operated control aspects of the present invention while omitting
the automatic sequencing feature. In such a case, the flow control
valves can be provided with independently actuatable fluid control
valves which may be, for example, manually actuatable pneumatic
remote control vales connected through control lines to the pilot
ports of the flow control valves mounted on the manifold or to the
trigger-check valves of the gun. Therefore, the present application
is not intended to be limited except by the scope of the appended
claims.
* * * * *