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July 9, 1943- ‘
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‘
c. N. HoYLER
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2,403,300 -
‘METHQD OF‘AND APPARATUS FOR DRYING‘? MOISTURE ‘IZJIADEN ARTICLES
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July 9, 1946.
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METHOD OF AND APPARATUS FOR DRYING MOISTURE LADEN ARTICLES
Filed Dec. 51, 1941
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July 9, 1946.
c_ N, HOYLER
2,403,800
METHOD OF AND APPARATUS FOR DRYING MOISTURE LADEN ARTICLES
Filed Dec. 31, 1941
I
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3 Sheets-Sheet 3
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3mientoi:
Cyril N'HOyZer -
Patented July 9, 1946
2,403,800
UNITED STATES PATENT OFFICE
2,403,800
METHOD OF AND APPARATUS FOR DRYING
MOISTURE LADEN ARTICLES
Cyril N. Hoyler, Audubon, N. J., assignor to Radio
Corporation of America, a corporation of Dela
ware
’
‘Application December 31, 1941, Serial No. 425,170
18 Claims. (Cl. 34-1‘)
1
2
,
identified copending application of Bierwirth.
According to Bierwirth’s method, the rayon is
placed in a‘ radio frequency fieldand advantage
This invention relates to a method of and ap
paratus for expelling moisture irom moisture-la
den articles and has special reference to the dry
is taken of the impedance of the moist cakes to
radio frequency energy to effect heating and dry
ing of water-laden rayon “cakes,” the present in
vention being an improvement upon that dis
closed and claimed in thecopending application
ing thereof. The heating takes place in a vac
uum so that the moisture-can be expelled at a
of Rudolph A, Bierwirth, Serial No. 407,619, ?led
August 20, 1941, now Patent No. 2,325,652, and
assigned to Radio Corporation of America.
In the manufacture of rayon, after the thread
has been formed, it is wound up into what is
known as “cakes” and placed in cloth containers,
after which the cakes are thoroughly washed in
temperature far below 140° F. Moreover, the
cakes are heated uniformly throughout and
therefore a thread of higher quality is obtained.
Added to these is the very important advantage
that the cakes can be dried by the Blerwirth
method in about an hour, as compared with 60 to
100 hours required by the previously practiced
water to remove the sulphuric acid or other chem
ical employed in coagulating the viscose mate 15 method.
Now it has been found that, in vacuum drying
rial. One of the problems encountered in the
of the rayon cakes by radio frequency energy as
manufacture of rayon is the drying of the yarn
suggested by Bierwirth, the power demands on
or thread after it has been through a washing
the oscillation generator change considerably.
or dyeing process, the rayon absorbing about
twice its own weight of water after it is washed. 20 For example, in one arrangement wherein one
cake was placed between a pair of electrodes in
an evacuated chamber, an input of considerably
ations can be carried out.
over 1200 watts was required during the first
In accordance with the prior art practice, it
This water must be removed before further oper
thirty minutes or so, while during the last thirty
has been customary to pass the cakes through
large drying ovens in which they are subjectedto 25 minutes of drying the input dropped to rather low
values. Thus, a generator is required which is
a stream of heated, dry air. This method pre
capable of delivering much more power than is
sents several dif?culties. For example, the time
actually used during the major portion of the
required to dry a cake ranges from about 60 to
drying cycle.
.
100 hours, and with ovens having a capacity of
The primary object of my present invention is
even as great as 1000 cakes per hour, it is obvious 30
to provide an improved method of and appara
that a great many ovens are required -to handle
tus for dryinglmoisture-laden articles, such as
the rayon output, which is in the neighborhood
rayon cakes, employing the teachings of Bier
of over 20,000 lbs. (each dry cake weighing a
pound) per hour.‘ Another difficulty which is
wirth but utilizing the output of the radio fre
quency generator much more ef?ciently,
encountered is that considerable care must be ex
ercised to prevent the rayon from reaching a
More particularly, it is an object of my present
temperature in excess of 140° F. since, above that
invention to provide an improved method and
temperature, the qualities of the thread are im
apparatus as aforesaid in which the drying will
paired and further manufacturing
We sses can- '
take place in a plurality of stages‘ and wherein
not be carried out successfully. Still another 40 new or fresh, moisture-laden cakes may be loaded
difliculty which is encountered resides in the fact
into the apparatus while at the same‘ time un
that not only do the outside layers of the cakes
loading the dried cakes, thereby making the proc
dry ?rst with some attendant shrinking and con
sequent tensioning of the threads at the outer
layers, but the inner layers of the thread fre
quently buckle up and wrinkle as a result of the
ess a continuous one.
‘
Another object of my present invention is to
'. provide an improved method of and apparatus
for drying moisture-laden articles as above set
pressure exerted by the tense, outer thread layers,
and an increased possibility of tangling of the
thread results. Furthermore, in each strand of
forth in which the drying may be effected rap
idly and in great quantities.
In accordance with my present invention, and
thread, a skin shrinkage occurs by reason of the 50 in order to provide more uniform loading to the
outer surface thereof drying before the, inner
portion thereof dries with resultant nonuniform
appearance in the strand.
The foregoing and other similar di?lculties are
overcome by the method disclosed in the above 55
oscillator, I provide an arrangement which in
cludes a plurality of operating stations at least
one of which is a loading and unloading station,
a second of which is an evacuating station, and
one or more other ones of which ,are drying sta
A
2,408,800
3
tions. These stations are arranged in endless
fashion and the cakes loaded at the loading sta
tion are carried around through the various sta
tions and eventually returned to the first station
for unloading the dried cake and loading a new.
moisture-laden cake.
Suitable means are pro
vided for evacuating. at the evacuating stations,
the chambers in which the ‘cakes have been de—
posited and for thereafter maintaining the vac
uum at the successive drying stations.’
As each cake becomes drier, its impedance in
creases and it becomes more difficult to get power
into the cake. This is equivalent to saying that
4
vacuum pump (not shown) coupled to the charm
her through a conduit i3. A cooling coil i5 "within
the enclosure I may be connected to a suitable
source of cooling ?uid for condensing the mois
ture which is expelled from the cakes, the con
~ densed moisture being "withdrawn in any suitable
manner, as through the vacuum line ii.
The primary electrodes 5 and ‘I are preferably
constituted by circular plates, the lower electrode
1 being supported on an insulator i‘l. One or
more rayon cakes i8 may be placed between the
electrodes 5 and ‘l and a high frequency electric
field applied thereto by the oscillator. A pair of
the voltage across each cake must be increased
secondary electrodes, such as the guard rings II
as the moisture is expelled therefrom. For this 15 and 23, are preferably arranged around the pri
purpose, I arrange the drying stations so that
mary electrodes 5 and 1 external to the container
each of the cakes therein constitutes an imped
i and are connected in shunt relation with ‘the
ance element in one of a plurality of parallel
primary electrodes, the secondary electrodes serv
related lad circuits which are connected in series
ing to help make the field through the cake or
with the oscillator, each of the load circuits also 20 cakes i9, as the case may be, more uniform by
including a capacitor and each of the capacitors
confining the end effects between the primary
having a different value such that the appropriate
electrodes ii and ‘I to a region well outside of the
voltage is applied to each of the cakes at the re
cake IS, with a consequent improvement in the
spective drying stations. By introducing, at in
uniformity of drying.
,
tervals, a fresh cake of maximum moisture con~ 25
After the vacuum in the enclosure i has reached
tent to the load while a dried cake is being re
a value of about 28 or 29 inches of mercury, the
moved. it is obvious that, as the input require
ments to one cake drop, another cake demanding
high input is added to the oscillator load. Thus,
_ output of the oscillator is connected across the
primary electrodes ii and ‘I through the series ca
pacitor ii. At a vacuum of about 29 inches of
the variation in load on the oscillator can be 30 mercury, the boiling point of water is in the
maintained within relatively narrow, predeter
neighborhood of 80° F. During the early stages
mined limits, and the output thereof used most
of drying, the cake i9 will accept considerable
ei'liciently.
power. As the cake I! becomes drier, its imped
The novel features that I consider characteristic
ance increases and it becomes more difficult to
of my invention are set forth with particularity
get power into it. Thus, it is necessary to in
in the appended claims. The invention itself,
crease the voltage across the cake. This may be
however, both as to its organization and method
done by tuning the capacitor II as frequently as
of operation, together with additional objects and
may be found necessary, current through the load
advantages thereof, will best be understood from
being maintained at a suitable level.
,
the following description of several embodiments
Referring, now, to Figure 3, the curve of which
thereof, when read in connection with the accom
represents the average of the power input to the
panying drawings, in which
oscillator taken at various times during the dry
Figure 1 is a diagrammatic view of an improved
ing process of several individual cakes, it will be
arrangement in accordance with one form of my
noted that the total energy used wec approxi
45 mately 1.2 kilowatt hours. This includes plate
present invention,
Figure 2 is a central sectional view of one of
grid and other oscillator losses. The curve also
the drying chambers formed according to my
shows that during the ?rst thirty minutes or so
present invention,
of drying, the input was considerably above 1200
Figure 3 is a curve showing the oscillator input
watts, but during the last thirty minutes of drying
50
for drying a single rayon cake,
the input dropped to rather low values. If, now.
Figure 4 is a set of curves showing the oscillator
fresh cakes could be introduced in the load
input requirements per cake for a number of such
at the same time that dried cakes were removed
cakes, and the total input to the oscillator when
at various intervals, so that, as the input require
a fresh cake is added at suitably spaced intervals,
ments to one cake dropped, another cake de
Figure 5 is a central sectional view of a mod 55 manding high input would be added to the oscil
i?ed form of drying chamber.
lator load, the latter would be kept much more
Figure 6 is a fragmentary, sectional view of one
constant. The arrangement shown in Figure l
form of apparatus which may be employed for
is one way of accomplishing this result.
maintaining a vacuum in the drying chambers
In the system shown in Figure 1, there is pro
and for supplying cooling fluid to the condenser 60 vided a rotatable platform or turntable 25 adapted
coils therein, and
,
Figure 7 is a somewhat enlarged, sectional view
taken on the plane of the line VII-VII of Fig
ure 6.
Referring more particularly to the drawings,
wherein similar reference characters designate
corresponding parts throughout, and‘ more par
ticularly, first, to Figure 2, I have shown a suit
able enclosure I of dielectric material supported
on a base or platform 3 and providing a chamber
within which are a pair of spaced, primary elec
trodes 5 and 1 connected to the tuned circuit 9 of
a suitable oscillator through a variable capacitor
i i in series with the tuned circuit 9. The interior
of the enclosure i may be evacuated by a. suitable
to be rotated by any suitable means, such as a
motor 21, in a manner such that any point on the
turntable will successively pass a plurality of sta
tions I to VI, inclusive, arranged in an endless
path. At each of the stations may be located an
enclosure i and associated parts, as described
above in connection with Figure 2. Let it be
assumed that station I represents the loading and
unloading station from which a fresh, moisture
laden cake is started on its path in the drying
cycle, and to which it is subsequently returned
when dry, stations II and III constitute evacuat
ing stations at which the respective enclosures or
chambers l are evacuated, and stations IV, V and
VI constitute successive drying stations at which
5
2,403,800
the drying operations take place, in turn. The
wet cakes at stations IV, V and VI constitute
impedance elements connected in series with
their respectively associated capacitors Ila, Nb
and I I0, these three series circuits constituting
chamber I may be evacuated in a manner shortly
to be set forth.
The pipes I2 and I4 extend above the closure
I 8, as can be seen from Figure 6, and the pipe
load circuits for the oscillator and being ar
oI.’ closely spaced ports I 2a extending' circum
ranged in parallel relation to each other, although
each is serially connected to the tuned circuit 9
of the oscillator. In the form of the invention
under consideration, each 01' the enclosures I
may have united therewith one plate or electrode
I2 is formed near its upper end with a plurality
i'erentially around it. A sleeve valve 26 which is
formed with the same number of internally
threaded bosses 28 as there are bosses 24 surrounds
the ports I2a and is rotatably mounted on the
pipe I2. Each of the bosses 28 is connected to the
inlet of a separate one of the condenser coils I5
by a coupling tube 20, the outlet of each coil I5
A1 to Avr, inclusive, of the capacitor H, the plates
Ar-Avr moving in unison with their respectively
associated enclosures I. The capacitor II may, in
being brought outto the top 01' the pipe I4 by a
each case, be completed by a cooperating elec 15 tube 22.
‘-trode Brv, Bv, Bvr in each or the load circuits
‘Assuming that one ormore wet cakes I! have
28a, 29b and 290, respectively,'the electrodes BIV,
been loaded into one of the chambers I at the
By, Bv: being stationary. As the turntable 25 is
loading station I, then, as the platform or tum
rotated step-by-step at suitable intervals, it is
table 25 rotates in the direction of the arrow in
.obvious that each chamber I, after being suit 20 Figure 1, the sleeve valves" and 26 will rotate
ably‘ evacuated at stations II and III, will ?rst
with it in the same direction and the newly loaded
reach station IV at which its electrode A will co
chamber will soon reach a position where its con
operate with the electrode Brv o1’ capacitor I Ia
duit I3 will be in communication with the vacuum
to apply a predetermined voltage to the cake or
line III through the port I Ila. Evacuation'oi' the
cakes contained therein. Subsequently, when the 25 air in the chamber will therefore begin and will
particular chamber under consideration is moved
continue past the stations II and III until the
to station V, its electrode A will cooperate with
end Y 01' the port Ina will have been reached.
the capacitor plate Bv and a higher voltage will
At about this time, the condenser plate asso
be applied to the cake or cakes therein. Finally,
ciated with the particular chamber under con
when the same chamber is moved to station VI, 30 sideration (for example, the electrode A!) will 'I
~ its capacitorelectrode A will cooperate with the
have come into cooperative relation with the con
electrode BVI to cause a still greater voltage to be
denser electrode Biv whereby the wet cakes will
applied to the cake. Since, however, a fresh
become coupled to the oscillator and drying will
cake is introduced to station IV from station III
begin. Meanwhile, since the condenser coil I5
each time the turntable 25 is advanced one step 35 is coupled to the water inlet pipe I2 through the
and the cake or cakes previously at station IV
ports I2a. cooling water will flow continuously
are advanced to station V, and so on, it is appar
therethrough and the water vapor driven out of
ent that the load on the oscillator will be main
the cakes being dried will be condensed to liquid
tained well within certain predetermined limits
form and will collect at the bottom of the cham
which have been found expedient.
420 ber. As the turntable continues to rotate, the
For producing and maintaining a suitable
port IUb is eventually reached. This connects the
vacuum in each of the chambers I and for supply- -
ing cooling fluid to the several coils I5 as the plat
form 25 is rotated to carry the several chambers
chamber to the vacuum line again for a short pe
riod to withdraw the water which has been con
densed in the chamber, and this step is repeated
45
around the endless path. a system such as shown
at the ports I00 and Illd. Shortly after the cham
in Figures 6 and 7 may be employed. This may
ber being considered has passed the port IUd, its
consist of three concentric, stationary pipes l0.
conduit I3 is brought into communication with
I2 and ll of which the pipes Ill and I2 are closed
the opening or port We and the air inlet pipe 20.
at their upper ends by ?uid-tight closures I6 and
Air from the atmosphere then rushes into thev
I8, respectively, and the pipe I4 is open at its 60 chamber to break the vacuum therein just before
upper end. The pipe III is connected to any suit
the station I is reached. When the latter station
able vacuum pump and is formed, near its upper
is reached, the dried cakes are removed and are
end, with a plurality of ports IOa, I01), I Do and
replaced by wet cakes, and the above described I
cycle is repeated.
I?d. The port Illa is preferably elongated and
may extend from a point X between the stations
Instead of rotating the turntable 25 in a coun
I and II to a point Y shortly in advance of the
terclockwise direction, as shown by the appended
arrow in Figure l, the same effect may be pro
station IV. The port I?b may be relatively short
duced by making the platform 25 stationary and
and is located between the stations IV and V.
Similarly, the ports IDc and Illd are short and 00 rotating the capacitor electrodes BIV, Bv, and Bvr
as a unit in a clockwise direction. This arrange~
are located, respectively, between the stations
ment may be preferable wheresuitable couplings
V and VI and between the stations VI and I.
cannot be made at the various stations (1) to
Between the port "id and the station I, the pipe
effect and maintain the desired vacuum in each‘
I0 is formed with an opening We in which a tube
or pipe 20 is secured with a ?uid-tight connection. 65 of the chambers, and (2) to effect circulation of
the water or other cooling medium through the
the pipe 20 being brought out to the atmosphere
condenser coils I5. In a system wherein the con
in any suitable manner.
denser plates BIV, Bv and Bvi are rotated, it is ob~
Surrounding the ports IUa to I02 and rotatable
vious that each of the stations will become, succes
on the pipe I0 is a sleeve valve 22 having a plu
rality of internally threaded bosses 24 thereon 70 sively, ?rst a loading and unloading station, then
the ?rst evacuating station, then the second evac
corresponding in number to the number of sta
uating station, and then each of the successive
tions I to VI and spaced circumferentially from
drying
stations in turn, before again becoming a
each other on the same angles as are the several
loading and unloading station.
However, the
stations I to VI. Each conduit I3 is connected to
overall effect is the same in either case.
a separate one of the bosses 24 whereby each 75
The curves C of Figure 4 show the loading re
quirements of each individual cake for a plurality
of cakes (assuming only one cake is placed in each
of the chambers i at one time). It will be noted
that each of the individual curves is similar to
the curve shown in Figure 3. It will also be noted
to cooperate with a separate one of said stations
during a predetermined drying interval, and
means for bringing each of said elements succes
sively into cooperative relation with each of said
stations for successive drying intervals.
3. In apparatus for drying moisture-laden arti
cles, the combination of a plurality of enclosures
The curve D of Figure 4 shows the loading re
constituting a plurality of drying chambers each
quirements in a system such as that illustrated in
adapted to receive at least one article to be
Figure l on the basis of a new cake of maximum 10 dried, means for maintaining a vacuum in each
moisture content added every twenty minutes.
of said chambers, means for simultaneously sup
From the curve D, it will be noted that the ratio
plying heating energy in at least certain of said
of maximum to minimum oscillator input is ap
chambers for drying the articles therein, a plu
proximately 6 to 5. It follows, therefore, that with
rality of control elements for controlling the en
a system such as that shown in Figure 1, the oscil 15 ergy supplied to said stations by said second
lator may be employed much more emciently than
named means, said elements being each adapted
when a single cake is dried at one time, and at
to cooperate with a separate one of said cham
the same time the output of dried cakes can be
bers during a predetermined drying interval, and
very greatly increased. 0f course, any number
means for successively bringing each of said ele
of‘ evacuating and drying stations may be em 20 ments into cooperative relation with each of said
ployed, the number shown in Figure 1 being used
chambers for successive drying intervals.
merely for the purpose of illustration.
4. In apparatus for drying moisture-laden arti
In Figure 5. I have shown a somewhat different
cles and including a loading station, an evacuat
form of drying chamber which may be used on
ing station and a drying station, the combina
the turntable 25 instead of the One shown in Fig 25 tion of means providing a closed chamber adapt
ure 2. In the form shown in Figure 5, the enclo~
ed to receive at least one of said articles at said
sure may be constituted by a metal base 3i and
loading station, means for successively advanc
a metal cover 33 fitted together with a cylindrical
ing the loaded chamber to said evacuating and
glass drum or spacer 35. Two or more gaskets
drying stations, means for creating a vacuum
I1 may be employed for providing airtight con 30 in said chamber at said evacuating station and
nections between the plates 3| and 33 on the one
for maintaining the vacuum in said chamber
hand, and the drum or cylinder 35 on the other.
while said chamber is subsequently at said dry
The advantages oifered by this form of chamber
ing station, and means for supplying heating en
are (1) that a relatively small volume of air would
ergy to said chamber at said drying station for
have to be evacuated, (2) that each cake would 35 drying said article.
be dried under uniform ideal conditions, and (3)
5. In apparatus for drying moisture laden arti
that high electrica1 efficiency would be obtained
cles and including a loading station, at least one
because of the insulation afforded by the glass
evacuating station, and a plurality of drying sta
cylinder 36.
tions, the combination of means providing a
40
Although I have shown and described several
closed chamber adapted to receive at least one of
forms of my invention, it will be apparent to I
said articles at said loading station, means for
those skilled in the art that many other mod
successively advancing the loaded chamber ?rst
iiications thereof, as well as changes in those de
to said evacuating station and then to each of
scribed, are possible, For example, instead of
said drying stations in turn, means for creating
providing a, turntable 25, the chambers I may be
a vacuum in said chamber at said evacuating sta
mounted on an endless conveyor of other suitable
tion and for maintaining the vacuum in said
form, it being advisable, however, in the interest
chamber while said chamber is subsequently at
of proper continuity and e?iciency, although not
each of said drying stations, means for supplying
absolutely necessary, of course, that the various '
heating energy to said chamber at each of said
chambers return to their original loading stations
drying stations for drying said article, and
at the end of the drying operation. Many other
means located at each of said drying stations for
similar changes will, no doubt, readily suggest
controlling the amount of energy delivered by
themselves to those skilled in the art. I therefore
said last named means at the respective drying
desire that my invention shall not be limited ex
stations.
cept insofar as is made necessary by the spirit
6. The invention set forth in claim 5 charac
of the appended claims.
terized in that said loading, evacuating and dry
I claim as my invention:
ing stations are arranged in endless formation
1. In apparatus for drying moisture-laden ar
whereby said chamber is returned to said loading
ticles, the combination of means providing a plu
station from the last of said drying stations for
rality of drying stations, means for supplying
unloading of the dried article and loading of an
heating energy to each of said stations for dry
other moisture-laden article.
ing the articles, variably effective means for con
7. In apparatus for drying moisture-laden arti
trolling the energy supplied to said stations by said
cles and including a loading station, at least one
second named means, and means for bringing said
evacuating station and a plurality of drying sta
variably effective means successively into cooper 65 tions all arranged in endless formation, the com
ative relation with each of said stations whereby
bination of means providing a closed chamber
to control the energy delivered at said stations.
at each of said stations, means for advancing said
2. In apparatus for drying moisture-laden ar
chambers in an endless path past said stations
ticles, the combination of means providing a plu
whereby each of said chambers is broug- t, in
rality of drying stations, means for simultaneously 70 succession, first from said loading station to said
supplying heating energy to each of said stations
evacuating station, then from said evacuating
for drying the articles, a plurality of variably ef
station to each of said drying stations in turn.
fective control elements for controlling the en
and ?nally from the last oi.’ said drying stations
ergy supplied to said stations by said second
back to said loading station, said chambers each
named means, said elements being each adapted TI being adapted to have a dried article therein ex
that, for drying a single cake, the ratio of maxi
mum to minimum oscillator input is about 3 to 1.
2,408,000
changed for a moisture-laden article when at
said loading station, means for creating a vacu
10
the value of the reactance device connected to
any one of said chambers at any particular time.
um in each of said chambers while at said evacu
12. In electrical apparatus for drying mois
ating station and for thereafter maintaining the
ture-laden articles, the combination with a high
frequency oscillation generator including a tuned
circuit of a plurality of parallel-related, movable
load circuits selectively coupled in series with
said tuned circuit, each of said load circuits in
cluding a reactance element and being adapted
vacuum therein while said chambers are subse
quently at each of said drying stations, means
for simultaneously supplying heating energy to
all the chambers at said drying stations for heat
ing the respective articles therein, and means lo
cated at each of said drying stations for con 10 . to receive in series with its reactance element a
trolling the amount of energy delivered by said
variable impedance element having a different
last named means at the respective drying sta
impedance than the impedance of any other of
tions.
said load circuits, said impedance elements each
8. The invention set forth in claim 7 charac
consisting of at least one of the articles being
terized in that the effectiveness of said control 15 dried, and said reactance elements being of dif
means is different at each of said drying sta
ferent values to couple predetermined high fre
tions.
quency power to each of said impedance ele
9. In electrical drying apparatus for drying
ments in accordance with the relative positions
moisture-laden articles, said apparatus including
of said articles.
'
a loading station, at least one evacuating station 20
13. The invention'set forth in claim 12 char
and a plurality of drying stations, the combina
acterized in that the articles adapted to be re
tion of means providing a chamber adapted to
ceived in and constituting the impedance ele
receive at least one of said articles at said load
ments of each of said load circuits have different
ing station, a pair of cooperative electrodes in
‘moisture contents than the articles of any other
said chamber between which said article is adapt 2.5 of said load circuits, the values of said reactance
ed to be disposed, means for successively ad
elements corresponding to the moisture content
vancing the loaded chamber ?rst to said evacuat
of their respectively associated articles.
ing station and then to each of said drying sta
14. In electrical apparatus for drying mois
tions in turn, means for creating a vacuum in
ture-laden articles, the combination with a high
said chamber at said evacuating station and for 30 frequency oscillation generator including a tuned '
maintaining the vacuum in said chamber while
circuit of a plurality of parallel-related, movable
said chamber is subsequently at each of said dry
load circuits selectively coupled in series with
ing stations, a source of high frequency electrical
said tuned circuit, each of said load circuits be
energy, and means for coupling said source to‘
ing adapted to receive therein atleast one of said '
said electrodes at each of said drying stations,
articles in a different state of dryness than an
said means including a plurality of reactance ele
article of another of said load circuits and in
ments in circuit with said source, each of said
cluding a serially connected variable reactance
reactance elements being of different value and
element, and means for transferring each of said
each being effective to couple said source to said
articles successively from one of said load cir
electrodes at a separate one of said drying sta 40 cuits to another, each of said reactance elements
tions.
having a different value whereby to couple differ
10. The invention set forth in claim 9 char
ent predetermined high frequency power to each
acterized in that said reactance elements are con
of said articles in accordance with the relative
stituted by capacitors, and characterized further
positions thereof.
in that each of said capacitors has a different 45
15. In electrical apparatus for drying mois
value corresponding to the moisture content of
ture-laden articles, the combination with a high
the article being dried when it reaches the re
frequency oscillation generator including a tuned
spectively associated drying station of each of
circuit of a plurality of parallel-related load cir
said capacitors.
50 cuits connected in series with said tuned circuit,
11. In electrical drying apparatus for drying
moisture-laden articles, said apparatus including
said load circuits each being adapted to receive
therein at least one of said articles in a different
a, plurality of drying stations, the combination
state of dryness than an article of any other of
or means providing a plurality of chambers, one
said load circuits, and means including variable
at each of said drying stations, and each adapted 55 reactance elements for altering the voltages ap
to contain at least one article to be dried, a pair
plied by said generator across each of said arti
of cooperative electrodes in each of said cham
cles in correspondence with the moisture con
bers between which the respective articles are
tent therein.
adapted to be disposed, means for maintaining a
16. In electrical apparatus for drying mois
vacuum in each of said chambers at each of said 60 ture-laden articles, the combination of a high
‘frequency oscillation generator, a plurality of
drying stations, 9. source of high frequency elec~
trical energy, a plurality of coupling circuits each
parallel load circuits coupled in series with said
including a reactance device and each coupling
generator and each adapted to receive therein at
least one of said articles in a different state of
said source to a separate pair of said electrodes,
said reactance devices each including a pair of 65 dryness than an article of any other of said load
relatively movable elements one of which is unit
circuits, and means for periodically varying the
coupling between said generotor and said load
ed with its associated chamber and the other of
circuits in accordance with the moisture contents
which is connected to said source, and said re
actance devices being of different value whereby
of said articles at predetermined times whereby
the energy supplied to said respective articles is 70 to maintain the power load on said generator,
dependent upon the particular reactance device
within certain predetermined limits.
coupled thereto, and means for effecting relative
17.111 electrical apparatus for drying mois
movement between said chambers and said
ture-laden articles, the combination of a pair of
primary electrodes disposed in spacedv relation
source whereby to effect relative movement be
tween said respective elements and thereby alter 75 to each other and adapted to receive at least one
2,4os,soo
11
of said articles therebetween, a pair of second
ary electrodes surrounding said primary elec
trodes and connected in shunt relation to said
primary electrodes, and means for coupling both
said pairs of electrodes to a source of alternat
ing electrical energy, the dielectric losses in said
article resulting from the electric field set up by
said source between said primary electrodes serv
ing to heat said article su?iciently to.expel the
moisture therefrom, and said secondary elec
trodes serving to provide a substantially uniiorm
electric iield between said primary electrodes.
18. In the method 0! drying moisture-laden
articles by subjecting said articles to an electric
field of high frequency, the steps which comprise
simultaneously subjecting a plurality of said ar
ticles, each with a di?erent moisture content, to,
said electric ?eld, each at a different station and
at a di?erent voltage, the article with the great-
'
12
est moisture content being subjected to the low
‘ est voltage at the ?rst of said stations, the ar
ticle with the lowest moisture content being sub
Jected to the highest voltage at the last of said
stations, and the articles oi progressively decreas
ing moisture between said first named article and
said last named article being subjected, respec
tively. to progressively increasing voltages at
successive stations intermediate said ?rst named
station and said second named station, periodi
cally removing said second named article from
said second named station when said latter ar
ticle is dry, simultaneously advancing each of the
remaining articles to stations or successively
higher voltages, and simultaneously introducing
to said first named station a fresh article of max
imum moisture content.
»
CYRIL N. HOYLER.
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