U.S. patent number 3,740,859 [Application Number 05/149,627] was granted by the patent office on 1973-06-26 for drying system.
This patent grant is currently assigned to Interlake Steel Corporation. Invention is credited to Victor D. Beaucaire, Naaman H. Keyser, Vernon L. Langdon, Louis A. Marlin, Richard S. Patton.
United States Patent |
3,740,859 |
Patton , et al. |
June 26, 1973 |
DRYING SYSTEM
Abstract
A system for continously applying paint to a continuously moving
metal strap and thereafter continuously drying the paint on the
metal strap. The system disclosed herein includes a drying station
disposed above the paint pot includes a number of induction coils
through which the painted metal straps pass and have induced
therein eddy currents which heat the metal strap to dry the paint
thereon. Means are provided automatically to maintain the level of
the paint and the concentration of solids in the paint contained in
the paint pot, and means are provided automatically to vary the
output from the induction coils in response to the speed and
temperature of the metal strap to maintain constant the temperature
of the metal strap exiting from the drying station.
Inventors: |
Patton; Richard S. (Flossmor,
IL), Keyser; Naaman H. (Hinsdale, IL), Langdon; Vernon
L. (Tinley Park, IL), Beaucaire; Victor D. (Homewood,
IL), Marlin; Louis A. (Crestwood, IL) |
Assignee: |
Interlake Steel Corporation
(Chicago, IL)
|
Family
ID: |
26846903 |
Appl.
No.: |
05/149,627 |
Filed: |
June 3, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
888215 |
Dec 29, 1969 |
3616459 |
|
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|
Current U.S.
Class: |
34/247;
219/667 |
Current CPC
Class: |
C25D
13/16 (20130101); G05D 23/19 (20130101) |
Current International
Class: |
C25D
13/16 (20060101); C25D 13/12 (20060101); G05D
23/19 (20060101); B01k 005/00 () |
Field of
Search: |
;34/1,44,48,52
;219/10.77 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dority, Jr.; Carroll B.
Parent Case Text
This application is a division of copending application Ser. No.
888,215, filed Dec. 29, 1969 and now U.S. Pat. No. 3,616,459 for
PAINT APPLYING AND DRYING SYSTEM.
Claims
What is claimed is:
1. A system for continuously drying a painted continuously moving
metal strap, said system comprising a drying station including an
induction coil for heating the metal strap to dry the paint
thereon, drive mechanism for continuously passing the metal strap
through said induction heating coil, a variable power supply for
said induction heating coil for controlling the output therefrom,
means for sensing the speed of movement of the metal strap with
respect to said induction heating coil, means for sensing the
temperature of the painted metal strap immediately after the
passage thereof from said induction heating coil, and a control
circuit responsive to said metal strap speed sensing means and to
said painted metal strap temperature sensing means for controlling
said variable power supply and thus the heating produced by said
induction heating coil to heat the painted metal strap to a
predetermined temperature at said temperature sensing means,
whereby to dry the paint on the metal strap throughout the length
thereof passing through said induction heating coil.
2. The system set forth in claim 1, wherein said induction heating
coil is operated at a frequency of about 200 kilohertz.
3. The system set forth in claim 1, wherein said drive mechanism is
adapted to pass the metal strap through said induction heating coil
at a speed of about 500 feet/min.
4. A system for continuously drying a painted continuously moving
metal strap, said system comprising a drying station including an
induction coil for heating the metal strap to dry the paint
thereon, drive mechanism for continuously passing the metal strap
through said induction heating coil, a variable power supply for
said induction heating coil for controlling the output therefrom,
means for sensing the speed of movement of the metal strap with
respect to said induction heating coil, means for sensing the
temperature of the painted metal strap immediately after the
passage thereof from said induction heating coil, and a control
circuit responsive to said metal strap speed sensing means and to
said painted metal strap temperature sensing means for controlling
said variable power supply and thus the heating produced by said
induction heating coil to heat the painted metal strap to a
predetermined temperature at said temperature sensing means, said
control circuit including limit means responsive to said metal
strap speed sensing means for deenergizing said induction heating
coil when the speed of the metal strap with respect to said
induction coil is below a predetermined value, whereby to dry the
paint on the metal strap throughout the length thereof passing
through said induction heating coil.
5. The system set forth in claim 4, wherein said limit means is
operative to deenergize said induction heating coil when the speed
of the metal strap is below about 50 feet/min.
Description
This invention relates to a system for continuously applying paint
to a continuously moving metal strap and continuously drying the
paint thereon, and more particularly, this invention relates to a
system for induction heating the paint by heating the metal strap
which carries the paint thereon.
An important object of the present invention is to provide a system
for continuously drying a painted continuously moving metal strap,
said system comprising a drying station including an induction coil
for heating the metal strap to dry the paint thereon, drive
mechanism for continuously passing the metal strap through the
induction heating coil, a variable power supply for the induction
heating coil for controlling the output therefrom, means for
sensing the speed of movement of the metal strap with respect to
the induction heating coil, means for sensing the temperature of
the painted metal strap immediately after the passage thereof from
the induction heating coil, and a control circuit responsive to the
metal strap speed sensing means and to the painted metal strap
temperature sensing means for controlling the variable power supply
and thus the heating produced by the induction heating coil to heat
the painted metal strap to a predetermined temperature at the
temperature sensing means, whereby to dry the paint on the metal
strap throughout the length thereof passing through the induction
heating coil.
A still further object of the present invention is to provide a
system for continuously drying a painted continuously moving metal
strap in which the control circuit includes limit means responsive
to the metal strap sensing means for de-energizing the induction
heating coil when the speed of the metal strap with respect to the
induction heating coil is below a predetermined value.
The invention, both as to its organization and method of operation,
together with further objects and advantages thereof, will best be
understood by reference to the following specification taken in
connection with the accompanying drawings in which:
FIG. 1 is a schematic and diagrammatic illustration of the system
of the present invention for continuously applyig paint to a
continuously moving metal strap and continuously drying the paint
thereon;
FIG. 2 is a schematic and diagrammatic view of the continuous
paint-applying system of the present invention;
FIG. 3 is a side elevational view partly in section of the
electrophoretic paint distributing apparatus shown in FIG. 2 taken
along line 3--3 thereof;
FIG. 4 is a front plan view of the electrophoretic paint
distributing apparatus shown in FIG. 3;
FIG. 5 is a side elevational view of the continuous drying station
of the present invention;
FIG. 6 is a view partially in section of the drying station shown
in FIG. 5 taken along line 6--6 thereof;
FIG. 7 is a block diagram of the control system for the continuous
paint applying system of the present invention; and
FIG. 8 is a block diagram of the control system for the paint
drying station of the present invention.
There is disclosed hereinafter a system 100 for continuously
applying paint to a continuously moving metal strap 50 and
continuously drying the paint thereon, the metal strap 50 being
driven along a predetermined path by a drive mechanism 75 through a
paint applying station 105 and then through a paint drying station
110. As seen particularly in FIG. 1, the metal strap 50 passes
along the predetermined path into a paint pot 115 in which paint is
electrophoretically applied to the metal strap 50, and thereafter a
painted metal strap 51 passes upwardly through a plurality of
heating units 245 where the paint uniformly applied in the paint
pot 115 is dried by the induction heating of the painted metal
strap 51 to produce a metal strap 52 having a uniform coating of
paint applied thereto and dried thereon.
FIG. 2 shows the spatial relationship between some of the apparatus
connected with the electrophoretic deposition of paint on the metal
strap 50, the paint applying station 105 including a paint pot 115,
a variable power supply source 170, a paint solids source 180, a
paint refrigeration unit 190 and a paint diluent source 177. There
is further shown a drive mechanism or bridle 75 for continuously
moving the metal strap 50 along its predetermined path, a paint
holding tank 188 for storage of paint during maintenance periods in
which the paint pot 115 is serviced and a pair of recirculating
pumps 185 and 186, for a purpose hereinafter explained.
With particular reference to FIGS. 2, 3 and 4, there is shown the
paint applying station 105 including the paint pot 115, the paint
pot 115 including an enclosed metal container 116 supported by two
spaced-apart generally parallel I-beams 117 each of which rests on
a grouting 118, the paint pot 115 being provided with a synthetic
plastic resin liner 119 on the inside thereof and firmly connected
to the metal container 116. A rotatable shaft 120 is disposed
within the paint pot 115 near the bottom thereof and is positioned
generally horizontally, the shaft 120 being journaled at either end
thereof in a bearing 121, the bearings 121 are connected to and
supported by a flange 122, the flange 122 being fixedly secured to
the metal container 116. A plurality of flanged wheels 125 are
fixedly connected to the shaft 120 and are rotatable therewith, the
flanged wheels 125 each supporting a metal strap 50 as particularly
shown in FIG. 4. The metal strap 50 may be a single strap having a
substantial width or, as in the case herein shown, the metal strap
50 may comprise a plurality of individual straps arranged side by
side in a row, 12 such straps being shown. The flanged wheels 125
serve to maintain the straps 50 in their spatial relationship one
to the other, thereby to prevent them from becoming
disoriented.
The metal straps 50 enter the paint applying station 105 by passing
over and in contact with an anode roll 130, the anode roll 130
being journaled on a shaft 131 positioned above the paint pot 115
and held in place by a pair of spaced-apart supports 132 fixedly
connected to several I-beams 133 hung from a mezzanine floor or
rafter 134. The anode roll 130 receives its charge through the
shaft 131 which passes through each of the supports 132 and is
electrically insulated therefrom by the insulators 137, the shaft
131 carrying at both ends thereof a connector 135, each of the
connectors 135 being connected to a slip ring 136. The slip rings
136 are connected to the variable power supply 170 by means of a
cable 140 which leads from the power supply 170 to a pull box 141,
there being two pull boxes 141, each one of which being associated
with a respective slip ring 136. A pair of connecting cables 142
serve to transmit the current from the pull boxes 141 to the slip
rings 136, the slip rings 136 being of conventional construction
and operating in a conventional manner to provide a charge from the
variable power supply 170 to the anode roll 130. The slip rings 136
serve to transmit a positive charge to the anode roll 130 and
thereby a positive charge to the metal strap 50 contacting and
passing over the anode roll 130.
There is further provided a plurality of cathode plates 145, the
cathode plates 145 being positioned within the paint pot 115 and
arranged vertically in two sets each containing three pairs of
cathode plates 145, each pair including two plates 145 spaced apart
and generally parallel one to the other. The cathode plates 145 are
fixedly secured at each end thereof to vertically disposed frame
member 146, the frame members 146 being electrical conductors each
depending from an angle iron 147 resting on an insulator 148 all of
which is disposed on a support member 149. The support member 149
extends entirely across the top of the paint pot 115 thereby to
support the cathode plates 145 in their positions within the paint
pot 115 and electrically to insulate the cathode plates 145
therefrom. To this end, the liner 119 also insulates the paint pot
115 from the electrically charged paint therein. As may be seen,
there are two sets of cathode plates 145, each set being disposed
to one side of the flanged wheels 125 so that the metal strap 50
passes between the cathode plates 145 when entering the paint pot
115 from the anode roll 130 and when exiting the paint pot 115 to
be transported to the paint drying station 110.
The cathode plates 145 are electrically connected to the variable
power supply 170 and the cable 140 leading therefrom by a plurality
of pull boxes 151, there being three such pull boxes disclosed
herein. The cable 140 from the variable power supply 170 leads to
each of the pull boxes 151 and a cable 152 thereafter leads from
the pull box 151 to each of the frame members 146 supporting, as
shown herein, three vertically spaced-apart cathode plates 145,
each of the cables 152 leading to a connector 153 disposed on an
angle iron 154 suitably connected to a corresponding one of the
angle irons 147, such as by welding. It is seen therefore, that the
cathode plates 145 are electrically connected to the variable power
supply 170 due to the electrical conducting frame 146 which is
electrically connected to the cables 152 and thereby the cable 140
leading from the variable power supply 170.
There is further disclosed a paint level sensing device 160
positioned above the paint pot 115 for sensing the paint level
therein, the paint level being denoted by the line 165 in phantom,
the paint level sensing device 160 including a sensor 161 extending
downwardly into the paint pot 115 and a cable 162 leading from the
sensing device 160 to a junction box 163 and thereafter to a
recorder (not shown). There is further provided an aperture 164 in
the paint pot 115 for various piping connections, for instance, a
paint-return pipe. When the painted metal strap 51 leaves the paint
pot 115 after having paint electrophoretically applied thereto it
passes through a sponge 242 positioned above the paint pot 115, the
sponge 242 serving to wipe excess paint from the painted metal
strap 51, the sponge 242 being suitably connected to an angle iron
243 and a support 244.
As is known, in the electrophoretic deposition of paint, the
substrate to which the paint is to be applied, in this case the
metal straps 50, is provided with a positive charge and the paint
solid particles are provided with a negative charge. In the present
case the metal straps 50 pass over the anode roll 130 to have
imparted thereto a positive charge and the paint particles in the
paint pot 115 come in contact with the cathode plates 145 to have
imparted thereto a negative charge. When the paint particles
carrying a negative charge come into proximity to the metal straps
50 carrying a positive charge the negatively charged paint
particles are attracted thereto, the advantage of the
electrophoretic deposition of paint being that the paint is
attracted to all the surfaces of the metal straps 50 to provide
uniformly coated metal straps 51. As the paint builds up on the
metal straps, the current density in the metal straps 51 drops as
the film thickness increases until current flow stops and there is
no more deposition of paint solids on the painted metal straps 51.
The variables which must be controlled in order adequately to
provide for the electrophoretic deposition of paint on continuously
moving metal straps 50 are the solids concentration of the paint,
the temperature of the paint, the speed of the metal straps 50
passing through the paint and the voltages used to produce the
current densities applied to the metal straps 50. The control
system for the aforementioned variables will hereinafter be
explained.
It can be seen therefore that there is provided herein a paint
applying station 105 including a paint pot 115 into which the
unpainted metal straps 50 are passed. After contacting an anode
roll 130 which imparts to the straps 50 a positive charge, the
straps 50 pass through a cathode area around a flanged wheel and
upwardly through a second cathode area to have electrophoretically
deposited thereon paint solids from a paint contained within the
paint pot 115 and maintained at a level 165 to produce uniformly
painted metal straps 51. The control system for varying the current
fed to the anode roll 130 and the cathodes 145, for maintaining the
paint level as at 165, for maintaining the paint composition at a
predetermined paint solids concentration and for maintaining the
temperature of the paint at a predetermined level will be
hereinafter disclosed.
After the painted metal straps 51 exit from the paint applying
station 105 with a uniform coating of paint thereon, the paint
containing a substantially uniform amount of paint solids therein,
the painted metal straps 51 pass upwardly to the paint drying
station 110, the paint drying station 110 including a plurality of
spaced-apart heating units 245, there being five such heating units
shown herein. Each of the heating units 245 include an induction
heating coil 250, each of the induction heating coils 250 being in
the form of a hollow metal strap having a rectangular cross
section. The induction heating coils 250 are positioned inside the
heating unit 245, the heating units 245 including two spaced-apart
vertically disposed end walls 251 resting on two spaced-apart
horizontally disposed bottom insulating boards 252, the bottom
insulating boards 252 forming therebetween a slit for the passage
of the painted metal straps 51 therethrough. Bottom angle irons 253
serve to connect the end walls 251 with the bottom insulating
boards 252 and top angle irons 254 serve to connect the end walls
251 with a pair of horizontally disposed spaced-apart top mounting
boards 255, the top mounting boards 255 also being spaced apart to
form therebetween a slit for the passage therethrough of the
painted metal straps 51. Each of the heating units 245 is held in
piece above the paint applying station 105 by a support structure
including four vertical support frame members 256 interconnected by
horizontal support frame members 257 and a pair of coil support
brackets 258 suitably supporting a respective one of the bottom
insulating boards 252. The entire support structure is positioned
within a tower 260 surrounding both the paint drying station 110
and the paint applying station 105, the tower 260 including
vertical support members 261 and horizontal support members 262.
The tower 260 further includes a plurality of idler rollers 263
which serve to position the straps 50 upon entering the paint
applying station 105 and then exiting the paint applying station as
painted straps 51 and pass upwardly through the paint drying
station 110 and exiting therefrom as dried painted straps 52.
The dried metal straps 52 thereafter pass over several of the idler
rollers 263 and out of the tower 260 for further processing down
the line, there being provided a plurality of aligning wheels 265
further to maintain the straps 52 in their side by side
arrangement. As the painted metal straps 51 passes upwardly through
the slits formed by the bottom insulating boards 252 and the top
mounting boards 255 and through the induction heating coils 250,
eddy currents are induced in the metal straps 51 by the passage
thereof through the fields of the induction heating coils 250, as
hereinafter explained, to provide heating within the straps 51,
thereby to dry the paint thereon from the inside of the paint
coating to the outside to provide a uniform paint coating without
the usual blisters caused by trapped air and the like formed when
paint dries from the outside in. The power supplied to the
induction heating coils 250 together with the amount of metal
passing through the fields and the speed of the straps determine
the amount of heating induced in the painted metal straps 51, the
power supplied to the induction heating coils 250 being controlled
both by the speed of the metal straps 51 as measured by a
tachometer 320 and by the temperature of the dried metal straps 52
as it exits from the paint drying station 110 as measured by an
infrared sensor 340, all as hereinafter explained.
With particular reference to FIG. 7, the control system for the
paint applying station 105 will hereinafter be described, the
control system including a rectifier for a variable power source
170 connected as by a conductor 210 to a control 171 therefor, the
control 171 serving to provide means for manually varying the
output from the variable power source 170. The output from the
power source 170 is transmitted as by a conductor 211 to a current
recorder 172 and thence by conductor 213 to the anode 130 and by
conductor 212 to contactors 173. The contactors 173 are connected
to a plurality of ammeters 174, there being one ammeter 174 for
each cathode plate 145. An emergency stop 175 is provided and is
connected as by a conductor 221 to the contactors 173 thereby to
provide manual means for halting the flow of current to the
cathodes 145.
There is further provided a paint diluent source 176, as shown here
the city water supply, connected by a pipe 238 to deionizing tanks
177, the deionizing tanks 177 serving to deionize and demineralize
the city water. The deionized water from the deionizing tanks 177
flows through a pipe 239, into the paint pot 115, via a solenoid
valve 178, controlled by a flow control 179, the flow control 179
being suitably connected by a conductor 222 to the float switch 160
disposed within the paint pot 115. A paint solids source in the
form of the paint solids drums 180 is provided, and since the paint
solids are extremely viscous as provided there is also a drum
warmer 181 for warming the paint solids within these paint solids
drums 180. A pipe 231 connects the paint solids drums 180 with a
paint solids pump 182, that paint solids pump 182 serving to
withdraw paint solids from the drums 180. The paint solids pump 180
may be an air driven motor mounted on the drums and pumps the paint
solids from the drums 180 through the piping 231 to an in-line
blender 183. Paint in the paint pot 115 is withdrawn therefrom
through a pipe 230 by the action of a recirculating pump 185, there
also being provided a spare recirculating pump 186 suitably
isolated from the line by a valve 187. The paint coming from the
paint pot 115 in the line 230 is mixed with solids withdrawn by the
paint solids pump 182 and fed as at 232 to the in-line blender 183.
The mixed paint solids and paint exits from the in-line blender as
at 233 and flows through the recirculating pump 185 (unless the
valve 187 is open in which case the mixed paint and paint solids
flows through line 234 and the spare recirculating pump 186) via
the line 235 to the paint refrigerator 190 wherein the paint is
cooled and returned to the paint pot throughout the pipe 236. The
paint refrigerator 190 is run by a motor 191 and is connected to
the plant cooling system 192 by means of piping 237. There is
further provided a paint holding tank 188 connected to the pipes
233 and 235, the paint holding tank 188 serving to hold the paint
when the paint pot 115 is being serviced. As the recirculating pump
185 or the spare pump 186 is continuously running, paint is
constantly being withdrawn from the paint pot 115 and circulating
through the aforementioned piping.
A connection to the line 235 is provided to bleed a small part of
the paint from the line 233 to a viscometer 195, the viscometer 195
being of the pneumatic type and serving to measure the viscosity of
the paint in the paint pot. Paint is returned to the paint pot from
the viscometer 195 by the pipe 240 thereby to provide a closed loop
through the viscometer 195. A signal from the viscometer 195 is fed
as by an electrical conductor 215 to a viscosity recorder 196 and a
temperature recorder 197, the output from the temperature recorder
197 being fed by conductor 217 to a refrigerator control 198, which
control 198 is connected as by conductor 218 to the paint
refrigerator 190, thereby to control the temperature of the paint
in the paint pot 115. The output from the viscosity recorder 196 is
carried as by the conductor 215 to a paint feed control 201, the
paint feed control 201 also receiving an input from an amp-hour
recorder 200, the amp-hour recorder 200 receiving an input from the
current recorder 172 connected to the amp-hour recorder 200 by a
conductor 212. The output from the amp-hour recorder 200 is carried
as by a conductor 214 to the paint feed control 201, the paint feed
control 201 receiving inputs from both the amp-hour recorder 200
and the viscosity recorder 196 and generating a signal which is
carried by a conductor 216 to the paint solids pump 182. There is
further provided a tachometer 205 to measure the speed of the metal
strap 50 entering the paint pot 115, the tachometer 205 having an
output therefrom fed to the rectifier for the variable power source
170 as by conductor 219 and having an output therefrom also fed as
by a conductor 219 to a line relay 206 and from there by a
conductor 220 to the contactors 173.
In operation, the amount of paint deposited on the metal strap 50
is controlled in part by the amount of current fed to the cathodes
145 and the anodes 130 which is fundamentally controlled by the
tachometer 205. Since the faster the metal strap 50 passes through
the painting station 105 the less time it will reside in the paint
pot 115 the greater will have to be the current fed to the anode
130 and the cathodes 145 to deposit the same amount of paint on the
straps 50 as would be deposited on the metal straps 50 if passed
through the paint pot 115 at a slower speed with a lower current
being supplied to the anode 130 and the cathodes 145. It is seen
therefore that the principal control for the amount of power
supplied from the variable power source 170 is provided by the
tachometer 205 which measures the line speed of the metal straps
50. The amount of current fed to the anode 130 and the cathodes 145
determines, for the most part, the amount of paint deposited on the
metal straps 50, current densities in the strap 50 being from about
0.1 to about +5 amp/ft., the power supply 170 producing from about
50 to about 250 volts. In the electrophoretic deposition of paint
the solids content of the deposit coating is generally between 80
and 95 percent with only from about 5 to 15 percent of the coating
being the paint diluent; therefore, it is seen that as the paint
coating is deposited on the metal strap the paint will become
deficient as paint solids, thereby necessitating the addition of
paint solids to the paint to maintain the concentration of solids
in the paint between about 5 and about 15 percent. To this end the
amp-hour recorder 200 records the amount of current fed to the
anode 130 and the cathode 145, which amount of current is
proportional to the amount of paint being deposited on the metal
strap 50 as it passes through the paint. The amp-hour recorder 200
sends a signal to the paint feed control 201 which counts the
signals from the amp-hour recorder 200 and at a predetermined time
sends a signal to the paint solids pump 182 which activates the
same to withdraw a predetermined amount of paint solids from the
drum 180. The paint solids pump 182 operates for a predetermined
time to withdraw the predetermined amount of paint solids from the
drum 180 and feeds the paint solids to the in-line blender 183
which mixes the withdrawn paint solids with the paint withdrawn
from the tank by the recirculating pump 185. The mixed paint solids
and the paint are thereafter pumped to the paint refrigerator 190.
Since the electrophoretic deposition of paint creates heat, it is
necessary to remove heat from the paint in order to maintain it at
the desired temperature, which temperature is between about
75.degree. F. to about 100.degree. F., the paint refrigerator 190
being controlled by the refrigerator control 198 which in turn
receives its signal from a temperature recorder 197 associated with
the viscosity recorder 196. The temperature of the paint is
important not only because of the electrophoretic deposition
process but also because the viscosity measurement of the paint
will vary according to the temperature thereof, thereby it being
important that the paint be within a certain temperature range to
provide the proper viscosity measurement.
The level of paint in the paint pot 115 is maintained at a
predetermined level by the addition of the paint diluent, in this
case water because water soluble paint solids are used herein, as
controlled by the float switch 160. The sensor 161 sends a signal
when the paint level 165 falls below a predetermined point at which
time the float control 179 is operated by a solenoid 178 to admit
deionized water or paint diluent into the paint pot 115. When the
paint level reaches a certain point, the float switch 160 sends a
signal which causes the solenoid valve 178 to close thereby
stopping the addition of paint diluent to the paint pot 115.
The viscosity of the paint in the paint pot 115 is fundamentally
maintained by the addition of diluent in response to the level of
the paint in the paint pot 115 and the periodic addition of paint
solids by means of activation of the paint solids pump 182 in
response to a certain amount of current as recorded by the amp-hour
recorder 200. When the paint viscosity remains within a
predetermined range, the paint feed control 201 sends a signal to
the paint solids pump 182 in response to the amount of current fed
to the cathodes 145 as recorded by the amp-hour recorder 200;
however, if a malfunction occurs or an unusual circumstance occurs
and the viscosity of the paint varies beyond a predetermined
amount, a signal from the viscosity recorder 196 to the paint
controller 201 will cause the addition of a larger amount of paint
solids to the paint, when the viscosity of the paint is too low, or
will result in fewer additions of paint solids to the paint when
the viscosity of the paint is too high. Since the paint solids pump
182 is essentially a batch operation in which the paint solids pump
182 operates for a given amount of time in response to a signal
from the paint feed controller 201, variation in the paint
viscosity is easily attained either by adding an additional batch
operation of the paint solids pump 182 in response to a signal from
the viscosity recorder 196 through the paint feed control 201 or by
the skipping of a cycle of the paint solids pump 182 thereby to add
fewer paint solids to the paint.
It is seen therefore, that there has been provided a system for
continuously applying paint to a continuously moving metal strap
50. The system comprises a paint applying station 105 including a
paint pot 115 and an electrophoretic distributing apparatus
including cathode plates 145 for applying a uniform coating of
paint to the metal strap 50, drive mechanism 75 for continuously
passing the metal strap 50 from a source thereof through the paint
pot 115 and the electrophoretic distributing apparatus. The system
further includes a source of paint solids, such as drums 180 in
communication with the paint pot 115 and a source of paint diluent
such as tanks 177 in connection with the paint pot 115, a paint
solids pump 182 in communication with the paint solids source 180
for withdrawing a predetermined amount of paint solids from the
paint solids source 180, a blender 183 in communication with the
paint solids pump 182 for mixing the paint solids withdrawn by the
paint solids pump 182 from the paint solids source 180 with the
paint in the paint pot 115. The control system includes the
amp-hour recorder 200 for continually sensing the power consumed in
the electrophoretic paint distributing apparatus, the viscometer
195 for continually sensing the concentration of the paint solids
in the paint pot 115, and a first control circuit responsive to the
amp-hour recorder 200 and to the viscometer 195 for activating the
paint solids pump 182 to withdraw a predetermined amount of paint
solids from the paint solids source 180 for maintaining the
concentration of paint solids within a predetermined value. A level
sensing device 160 is provided for continually sensing the level of
paint in the paint pot 115, and a second control circuit responsive
to the level sensing device 160 for connecting the source of paint
diluent 177 to the paint pot 115 for maintaining the level of paint
within a predetermined value is also provided to apply to the metal
strap 50 throughout the length of the strap 50 passing through the
paint pot 115 a uniform coating of paint containing a substantially
uniform amount of paint solids therein.
The wet painted straps 51 upon exiting from the paint applying
station 105 are transported to the paint drying station 110.
Referring now to FIG. 8, there is disclosed therein a control
circuit 275 for the heating station 110, the control circuit 275
including a variable power supply in the form of a function
generator 280 connected by an electrical conductor 281 to a
three-position switch 282. The three-position switch 282 is here
shown in the automatic position in which the function generator 280
is connected to a DC amplifier 285 by an electrical conductor from
the common terminal of the switch 282; however, the DC amplifier
285 may also be controlled by a signal from a manual control 286 in
the form of a potentiometer, the potentiometer 286 having one
terminal 287 thereof connected to a ground and the other terminal
289 thereof connected to a control voltage 290, the control voltage
290 herein being illustrated as a 10 volt DC source. The sliding
contact on the potentiometer 286 is connected as by connector 291
to the switch 282, whereby the DC amplifier 285 may receive an
input signal from the manual control of the circuit 275.
The output from the DC amplifier 285 is fed through a conductor
295, normally closed switch contacts 297 and conductors 299 to each
of five SCR voltage controls 296, there being one SCR voltage
control for each and every induction heating coil 250. The normally
closed switch contacts 297 provide automatic operation of the
control circuit as hereinafter explained. There is also provided
for each and every SCR voltage control 296 a pair of normally open
switch contacts 298, one of the switch contacts 298 being connected
to the conductor 295 and the other of the switch contacts 298 being
connected to the sliding arm on a potentiometer 300, the
potentiometer 300 having one terminal 301 thereof connected to
ground, and the other terminal 302 thereof connected to a control
voltage from a 10 volt DC source. A relay 305 has one terminal 306
thereof connected to ground and the other terminal 307 thereof
connected to a normally open switch 308, the switch 308 being
connected to a 120 volt AC source and being normally open so as to
maintain the relay 305 in a position such that the switch contacts
297 are normally closed and the switch contacts 298 are normally
open, all as hereinafter explained. The relay 305 has a mechanical
connection 310 to each pair of the normally closed switch contacts
297 and a mechanical connection 311 to each pair of the normally
open switch contacts 298, whereby closing of the normally open
switch 308 energizes the relay 305 to open the normally closed
switch contacts 297 and to close the normally open switch contacts
298, thereby to provide each of the SCR voltage controls 296 with a
manually selected voltage from the potentiometers 300 instead of
the automatically selected voltage from the function generator 280
through the DC amplifier 285, all as hereinafter explained.
The output from each of the SCR voltage controls 296 is fed via
conductor 315 to an associated RF oscillator 316 and the output
from the RF oscillator 316 is connected via a conductor 317, which
may be a coaxial cable, to the respective induction heating coil
250, the induction heating coil 250 being connected as at 318 to
ground. As the wet painted metal straps 51 exit from the paint
applying station 105 and pass upwardly through the respective ones
of the induction heating coils 250, the straps 51 are dried and
exit from the topmost of the induction heating coils 250 as dried
metal straps 52, the speed of the dried metal straps 52 relative to
the induction heating coil 250 being measured by a tachometer 320.
The tachometer 320 sends a signal along a conductor 321 indicating
the speed of the dried metal straps 52 to a recorder 323 and to a
low-speed limit circuit 324 and to one terminal 329 of a
potentiometer 330. The potentiometer 330 has the other terminal 331
thereof connected to ground and the output from the potentiometer
is fed from the sliding contact thereof by a conductor 335 to the
function generator 280. Temperature sensing means is provided near
the topmost of the induction heating coils 250 for sensing the
temperature of the dried painted metal straps 52 upon leaving the
drying station 110, the temperature sensing means being an infrared
sensing head 340 for sensing the infrared radiation given off by
the dried metal straps 52 as at 341 and sending a signal along a
conductor 342 to a DC amplifier 344. The output from the DC
amplifier 344 is conducted via a conductor 345 to the recorder 323
and to a comparator 347, the comparator 347 also receiving an input
signal from a potentiometer 350. The potentiometer 350 is the
temperature set potentiometer which feeds to the comparator 347 a
signal indicative of the desired temperature of the dried metal
straps 52 upon exiting from the topmost induction heating coil 250.
The temperature set potentiometer 350 has one terminal 351 thereof
connected to ground and the other terminal 352 thereof connected to
a 10 volt DC source. The output from the sliding contact of the
temperature set potentiometer 350 is fed by a conductor 355 to the
comparator 347 and the output from the comparator 347 is fed via a
conductor 358 to a DC amplifier 360. The DC amplifier 360 also
receives an input from the low-speed limit circuit 324 via a
conductor 325. The DC amplifier 360 has its output signal fed via a
conduction 361 to a multi-position switch 362, the switch 362
connected in its third position, as is herein shown, to a
reversible motor 365, the reversible motor 365 having its output
fed, as shown by dotted line 370, mechanically to position the
slide on the potentiometer 330, thereby to combine in the output
signal from the potentiometer 330 the signal from the tachometer
320 and the signal from the temperature sensor 340.
As the metal straps 51 exit from the paint applying station 105 and
pass upwardly through the successive induction heating coils 250,
the amount of heat generated therein is partly dependent upon the
speed of travel of the metal straps 51 and the voltage fed to the
induction heating coils 250. In the configuration as shown in FIG.
8, the control circuit 275 is in its automatic mode, wherein the
control circuit 275 automatically adjusts for variations in speed
and temperature of the metal straps 51 as they pass through the
successive heating coils 250. The automatic mode of the control
circuit 275 is shown herein, wherein the function generator 280 is
connected to the DC amplifier 285, the switch contacts 297 are in
the closed position thereof, the switch contacts 298 are in the
open position thereof, and the switch 362 is in the position
illustrated. With the control circuit 275 in the automatic mode
thereof, the tachometer 320 senses the speed of the dried painted
metal straps 52 and sends the signal to the potentiometer 330 which
thereafter sends the output signal thereof via the conductor 335 to
the function generator 280. The function generator 280
automatically generates a larger signal in response to increased
speed of the metal straps 52 through the induction heating coils
250, thereby to cause the output of the heating coils 250 to be
greater and the heating of the metal straps 52 passing therethrough
to be the same regardless of the speed of the metal straps 52, the
preferred speed of the metal straps 52 being about 500 feet/min.
and the induction heating coils being preferably operated at about
200 kilohertz. If the speed of the metal straps 52 is too low, for
instance below about 50 ft./min., the low speed limit circuit 324,
which also receives an input from the tachometer 320, sends the
output signal therefrom via the conductor 303 to the function
generator 280, thereby to cease the heating, via the induction
heating coils 250, of the metal straps 52. As is seen, the output
signal from the function generator 280 is fed to the DC amplifier
285 which controls the SCR voltage controls 296 that in turn
control the RF oscillators 316, thereby directly to control the
output of the induction heating coils 250 in response to the speed
of the metal strap 52 therethrough.
As a final control, the infrared sensing head 340 senses the
temperature of the metal straps 52 upon leaving the topmost
induction heating coil 250. The recorder 323 which receives inputs
from both the tachometer 320 and the infrared sensor 340 via the DC
amplifier 344 provides a visual record of the temperature of the
metal straps 52 as compared to the speed of the metal straps 52 as
the metal straps 52 leave the topmost induction heating coil 250.
In the comparator 347, the output from the DC amplifier 344, which
reflects the temperature of the metal straps 52 leaving the topmost
induction heating coil 250, is compared with a signal from the
temperature set potentiometer 350, which signal sets a range for
the desired temperature of the metal straps 52 leaving the topmost
induction heating coil 250. When the temperature of the dried metal
straps 52 is greater or less than the predetermined temperature
range set in the potentiometer 350, the comparator 347 produces a
signal which after amplification by the DC amplifier 360 activates
the reversible motor 365 which mechanically varies the position of
the sliding contact on the potentiometer 330, thereby to vary the
input signal to the function generator 280 in response to the
temperature of the metal straps 52 leaving the topmost induction
heating coil 250. As is seen therefore, when the control circuit
275 is in the automatic mode thereof, the output from the induction
heating coils 250 is controlled both by the speed of the dried
painted metal straps 52 as they pass through the paint drying
station 110 and the temperature of the dried painted metal straps
52 as they exit from the topmost induction heating coil 250.
When the control circuit 275 is in the manually controlled mode
thereof, the DC amplifier 285 is connected to the manually
controlled potentiometer 286, whereby the signal from the DC
amplifier 285 may be manually controlled by adjustment of the
sliding contact of the potentiometer 286. Manual control of the
control circuit 275 is also provided by energizing the relay 305 to
open the normally closed switch contacts 297 and close the normally
open switch contacts 298 to permit manual control via manipulation
of the sliding contacts on the potentiometers 300 of the SCR
voltage controls 296 and hence, the RF oscillators 316 and the
output from the induction heating coils 250. The control circuit
275 is operable both manually to adjust the output of the induction
heating coils 250 or automatically to adjust the output of the
induction heating coils 250, the control circuit 275 in the
automatic mode thereof varying the output of the induction heating
coils 250 in response both to the speed of the metal straps 52 and
the temperature of the metal straps 52 leaving the topmost of the
induction heating coils 250.
It is seen therefore, that there has been provided a system for
continuously drying a painted continuously moving metal strap 52.
The system comprises a drying station 110 including an induction
heating coil 250 for heating the metal strap 52 to dry the paint
thereon, drive mechanism 75 for continuously passing the metal
strap 52 through the induction heating coil 250 and a variable
power supply in the form of a function generator 280 for the
induction heating coil 250 for controlling the output therefrom.
The system further includes the tachometer 320 for sensing the
speed of the movement of the metal strap 52 with respect to the
induction heating coil 250, the infrared sensor 340 for sensing the
temperature of the painted metal straps 52 immediately after the
passage thereof from the induction heating coil 250, and a control
circuit 275 responsive to the tachometer 320 and to the infrared
sensor 340 for controlling the function generator 280 and thus the
heating produced by the induction heating coil 250 to heat the
painted metal strap 52 to a predetermined temperature at the
temperature sensing means. The control circuit 275 also includes
limit means in the form of the low-speed limit circuit 324
responsive to the tachometer 320 for deenergizing the induction
heating coil 250 when the speed of the metal strap 52 with respect
to the induction heating coil 250 is below a predetermined value,
to dry the paint on the metal strap 52 throughout the length
thereof passing through the induction heating coil 250 without
burning the metal strap 52 or the paint thereon.
The term "electrophoresis" as used herein includes
electrodeposition wherein the paint solids exist as discrete
particles, as in an emulsion, and electrodeposition wherein the
paint solids are in solution. The term "strap" as used herein
includes strips, wires and other forms of continuous metal work
pieces.
While there has been described what is at present considered to be
the preferred embodiment of the invention, it will be understood
that various modifications may be made therein, and it is intended
to cover in the appended claims all such modifications as fall
within the true spirit and scope of the invention.
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