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Патент USA US2410384

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Oct. 29, 1946.
H. w. LINDSAY
2,410,384
FURNAGE CONTROL SYSTEM
'
Filed Feb. 3, 1945
2 Sheets-Sheet 1
‘Q
l
INVENTOR
HA @OLD I/V. L/NDSA Y
ATTORNEY. ‘
ocr. 29, 1946.
H. w. LINDSAY ~
2,410,384
FURNACE CONTROL SYSTEM
F'iled‘Fe'b. :5, 1945
2 sheets-sheet 2
.WSE
HAROLD'W L/NosAY
BYM
ATTORNEY.
Patented Oct. 29, 1946
2,410,384
UNITED STATES PATENT OFFICE
2,410,384
FURNACE CONTROL SYSTEM
Harold W. Lindsay, Oakland, Calif., assignor to
the Government of the United States as rep
resented by the Director of the Office 0f
Scientific Research and Development, Olïicc for
Emergency Management
Application February 3, 1945, Serial No. 576,125
l
4 Claims.
The present invention relates to heat exchange
systems and more particularly to furnace control
systems.
In many heat treating operations, such as in
the annealing of glass, it is desirable to heat a
batch substantially uniformly throughout and
fairly rapidly from the ambient temperature to a
predetermined relatively high temperature, to
hold the relatively high temperature of the batch
substantially uniformly throughout for a prede
termined time interval, to cool the batch sub
stantially uniformly throughout and reasonably
rapidly from the relatively high temperature to
a predetermined relatively low temperature above
the ambient temperature. Moreover, in view of
theçmass, composition, and other characteristics
of the batch, the relatively high temperature and
the relatively low temperature must be selectively
and independently adjustable Within given
ranges, and also the predetermined time interval ~
must be selectively adjustable within a given
range.
.
(Cl. 219-20)
2
jects and advantages thereof, will best be under
stood by reference to the following specification
taken in connection with the accompanying
drawings in which Figure l is a diagrammatic
illustration of a furnace control system embody
ing the present invention; and Fig. 2 is a graph
illustrating a typical heat treating schedule which~
may be carried out in the furnace enclosure of
the furnace control system.
Referring now more particularly to Fig. l of
the drawings, there is illustrated a heat exchange
system in the form of a furnace control system
embodying the features of the present invention
and comprising a, furnace I0. Preferably, the
furnace I0 is of lconventional construction and
arrangement including heat insulated wall struc
ture deñning an enclosure or work receiving space
I I and provided witha doorway and associated
door, not shown, permitting ready placement and
removal of the work within the enclosure I I.
Also the furnace I0 is provided with an electric
heating element I2 adapted to supply heat to the
` Heretofore these operations have been carried
out in furnaces provided with manually control
enclosure II, and a main> fan I3 operative to
lable adjustments by operators utilizing data
cards and charts, together with such instruments
induce circulation of air or a suitable heating
medium over the electric heating element I2 and
through the enclosure I I in order to effect a sub
as stop watches and pyrometers.
stantially uniform distribution of heat through
Accordingly, it is' an object of the present
out the enclosure or work receiving space II.
invention to provide a control system that is
operative automatically to govern an associated 30 The electric heating element I2 is illustrated as
being of the three-phase alternating current
furnace in order to carry out a heat exchange
delta-connected type, although it may be of any
schedule of the general character specified.
suitable form. Moreover, the electric heating
Another object of the invention is to provide in
element I2 may be carried by a support disposed
a heat exchange system, including a work receiv
ing enclosure and facility for selectively setting a, 35 Within the enclosure II; or, on the other hand,
it may be distributed about and secured directly
desired temperature within a given range and for
to the wall structure of the furnace I0 within the
selectively setting a desired time interval Within
enclosure II. Further, the furnace I0 comprises
a given range, an arrangement for automatically
an auxiliary fan I4, and an electric motor I5
regulating the temperature of the enclosure
throughout a time duration respectively corre 40 operatively connected to the main fan I3 and to
the auxiliary fan I4, whereby both of the fans I3
sponding substantially to thev preset desired tem
and I4 are commonly operated by the motor I5.
Preferably, the electric motor I5 is disposed exte
perature and to the preset desired time interval.
A further object of the invention is to provide
in a furnace control system, including facility for
riorly of the furnace ID and is provided with an
operating shaft extending through the wall struc
carrying out automatically a predetermined heat
treating schedule, an improved signal arrange
ment for selectively indicating and identifying
the successive heating and cooling steps as they
ture of the furnace I0 and commonly connected
to the fans I3 and I4 disposed within the enclo
sure II. As illustrated, the electric motor I5 is
of the three-phase alternating current type,
are carried out.
A still further object of the invention is to pro
vide a furnace control system comprising an irn
50
although it may be of any suitable form. Asso
-ciated with the auxiliary fan I4 is a vane switch
SI5 provided with an operating arm carrying a
proved and extremely simplified electric circuit
network.
vane I6 and controlling contacts I1, the vane I6
being arranged in the blast delivered from the
The invention, both as to its organization and
method of operation, together with further ob 55 auxiliary fan I4. Accordingly, it will be under
stood that when the motor I5 is operated, the
2,410,384
3
main fan I3 is operated to induce circulation of
a heating medium over the electric heating ele
ment I2 and through the enclosure II, and the
auxiliary fan I4 is operated in order to effect
operation of the vane switch SI5 to close the
contacts I'I for a, purpose more fully explained
hereinafter. Finally, the furnace I0 comprises a
temperature responsive element 2| in the form
of a thermocouple arranged within the enclosure
I I and controlled by the temperature of the heat
ing medium circulated therein.
,
Also the system comprises a temperature regu
lator TR20 of the conventional Leeds & Northrup
type, including an electric operating motor 22,
two temperature dials XD and YD, two switches
XS and YS, and two mechanisms indicated gen
erally at 23 and 24. The temperature regulator
TR20 is connected to the thermocouple 2l; the
mechanism 23 is governed jointly by the tempera
ture dial XD, the thermocouple 2I and the oper
ating motor 22, and selectively controls the switch
XS; while the mechanism 24 is governed jointly
by the temperature dial YD, the thermocouple
2| and the operating motor 22, and selectively
controls the switch YS. The temperature dial
XD may be manually set to a relatively low tem
perature, within a given range, below which it
is not desired to make an observation with rei
erence to the temperature of an article or batch
of material undergoing heat treatment in the
enclosure I I; while the temperature dial YD may
be manually set to a rela-tively high temperature,
within a given range, at which it is desired to
maintain the temperature of the article or batch
of material undergoing heat treatment in the
enclosure I I.
Further, the system comprises a timer T36 of
a conventional type including an electric operat
ing motor 3|, a time dial TD, a switch TS, and
4
2, assume that the elements or the circuit net
work lill) occupy their normal rest positions il
lustrated, and that an article or batch of mate
rial that is to be subjected to a heat treating
schedule has been placed in the enclosure II.
The operator first closes the master switch
M_Siîîi, thereby completing a circuit including
the contacts 3ft oi the switch TS, the contacts
ISS of the relay Ritt, and the contacts YS of
the temperature regulator TREO, for energizing
the winding of the relay Rl'àil. When thus en
ergized, the relay Ri 2B operates to complete at its
contacts I2I a stick circuit including the master
switch MSIQI and the contacts YS of the tcm
perature regulator TREK), for energizing the wind
ing thereof. Also, the relay RIZ!) prepares at, its
contacts |22 a circuit, ltraced hereinafter, for il
luminating the red lamp lil, and interrupts at its
contacts |23 a further point in multiple circuits,
traced hereinafter, for illuminating the yellow
and blue lamps 42 and 43 and for operating the
motor 3I .
Next, the operator sets the temperature dial
XD of the temperature regulator TRZG to a rela
tively low temperature, within its range, below
which it is not desired to make an observation
with reference to the temperature of the article
or the batch of material which is to undergo
heat treatment in the enclosure II; and sets the
temperature dial YD of the temperature regulator
TRZB to a relatively high temperature, within its
range, at which it is desired to maintain the tem
perature of the article or batch of material which
is to undergo heat treatment in the enclosure.
Finally, the operator sets the time dial TD
on the timer TSB to a time interval, within its
range, during which time interval it is desired
to subject the article or batch of material which
is to undergo heat treatment in the enclosure II
to the temperature preset by the temperature
The 40 dial YD of the temperature regulator TRZI).
mechanism 32 is governed jointly by the time dial
When the time dial TD on the timer T3() is set
TD and the operating motor 3|, and selectively
to establish the time interval mentioned, the as
controls the switch TS. The time dial TD may
sociated switch TS is operated through the mech
be set manually to a time interval, within a given r..
anism 32 to open its contacts 34 and to close its
.Li
range, during which it is desired to subject the
contacts 33. More particularly, when the switch
article or the batch of material undergoing heat
TS is operated, it interrupts at its contacts 34 the
treatment in the enclosure I I to the temperature
previously traced operating circuit for energiz
preset by the temperature dial YD of the tem
ing the winding of the relay RIM; however, the
a mechanism indicated generally at 32,
perature regulator TRZD, as explained more fully
hereinafter.
Further, the system comprises a lamp panel
LP 4D including red, yellow, and blue lamps 4 I7 42,
and 43, respectively; and a circuit network |03 in
cluding a master switch MSiIlI, live relays Ri Iii,
RI20, RI3II, RI40, and RIM, a source of three
phase alternating current 24U-volt power supply,
and a source of control supply (a battery, the
terminals of which are indicated by the signs -I
and _). While the source of power supply has
been indicated as being three-phase alternating
current 24U-volt, it will be understood that it may
be any appropriate source of power supply effec
tive to operate the electric heating element I2
and the motor I5; and while the source of ccn
trol supply has been indicated as being a bat
tery, it will be understood that it may be any
appropriate source of control supply, and in fact
may include one phase of the source of pzwer
latter relay remains in its operated position at this
time due to the previously traced completed stick
circuit for energizing the winding thereof. Also,
when the switch TS is operated it completes at its
contacts 33 a circuit including the master switch
MSIilI for energizing the winding of the relay
RI I0. When thus energized, the relay RI I0 op
erates to complete at its contacts III an obvious
circuit for energizing the winding of the relay
RI38, and completes at its contacts II2 a circuit
including the master switch MSIIlI, the contacts
33 of the switch TS, and the contacts |22 of the
relay RIZEI, for illuminating the red lamp 4I.
The illumination of the red lamp 4I on the lamp
panel LP40 indicates that operation of the sys
tem has been initiated but that the temperature
of the enclosure II has not reached the desired
relatively high temperature preset by the temper
ature dial YD of the temperature regulator TRZB.
When thus energized, the relay RISSI operates to
complete at its contacts I3I a multiple circuit in
cluding the contacts III of the relay RIID, for
operating the motor 22 and for energizing the
winding of the relay RIMS. Also, the relay RI30
order to carry out a heat treating schedule in
interrupts at its contacts I33 a further point in
the enclosure I l.
the previously traced operating circuit for ener
Referring now more particularly to Figs. l and 75
supply. The connection and arrangement or the
circuit network |30 will best be understood in
conjunction with the following description of
the operatic-n of the furnace control system in
2,410,884
5
gizing the winding of the relay RI 20, and pre
pares at its contacts |32 a circuit traced herein
after for illuminating the blue‘lamp 43. Opera
tion of the motor 22 renders the temperature reg
ulator'TR2Il effective in a manner more fully
explained hereinafter.
When thus energized, the relay RI5|l operates
to complete at its contacts I5| a connection be
tween the source of power and the motor I5,
above, the thermocouple 2| governs the tem
perature regulator TRZI), whereby the motor 22
through the mechanism 24 operates the switch
YS. When the switch YS is thus operated, it
interrupts the previously traced multiple cir
cuit for energizing the windings of the relays
RI20 and- RMU, thereby to cause the latter relays
to restore. Upon restoring, the relay RI20 in
terrupts `at its contacts I2I a further point in
the previously traced stick circuit for energizing
the Winding thereof, interrupts at its contacts
|22 the previously traced circuit for illuminating
the red lamp 4I, and completes at its contacts
|23 the previously mentioned multiple circuit for
illuminating the yellow lamp 42 and for operat
ing the motor 3|. This multiple circuit for il- _
luminating the yellow lamp 42 and for operat
ing the motor 3| extends from the positive ter
minal by way of the master switch MSIUI and
whereby operation of the motor I5 is initiated,
eiTecting operation of both the main fan I3 and
the auxiliary fan I4. The blast from the main
fan I3 is directed over the electric heating ele
ment I 2 which is not operated at this time, where
as the blast from the auxiliary fan I4 is directed
upon the vane I6, effecting operation of the vane
switch SI5, whereby its contacts I'I are closed
to complete a circuit for energizing the winding
of the relay RIM). The last-mentioned circuit
extends from the positive terminal by way of the
master switch MSIIII, the contacts 33 of the 20 the contacts 33 of the switch TS, to the yellow
lamp 42 and to the motor 3|, and from the nega
switchTS. the contacts II2 of the relay RI Ill, the
tive terminal by way of the contacts |23l of the
contacts I'I of the switch SI5, the winding of the
relay RIZU to the yellow lamp 42 and to the mo
relayRI40, and the contacts YS of the temper
tor 3|. Upon restoring, the relay R|40 inter
ature regulator TRZI) to the negative terminal.
rupts
at its contacts I4I the previously men
When thus energized, the relay RI 40 operates to
complete at its contacts IIII a connection between
the source of power and the electric heating ele
ment I2, whereby the electric heating element
I2 is heated. At this time, the blast of air from
the main fan I3, directed over the electric heating
element I2, induces circulation of the heating
medium in the enclosure I I, whereby the article or
batch of material in the enclosure II is heated.
Also, the heating medium is circulated past the
thermocouple 2| in order to control the temper
ature regulator TR20, in a manner more fully
explained hereinafter.
Y s
tioned connection between the source of power
and the electric heating element I2, whereby the
electric heating element I2 begins to cool due to
continued operation of the main fan I3 by the
motor I5. At this time, the temperature of the
enclosure II begins to fall back toward the rela
tively high temperature established by the tem-z
perature dial YD of the temperature regulator
TR20, and in fact slightly therebelow.
`
On the lamp panel LP40, when the red lamp
4I is extinguished and the yellow lamp 42 is
illuminated, it indicates that the relatively high>
temperature preset on the temperature dial YD
of
the temperature regulator TRZI) has been
from the ambient temperature toward the rela
tively high temperature established by the tem 40 reached in the enclosure II of the furnace I0,
and that the timing operation established by the
perature dial YD of the temperature regulator
time dial TD of the timer T30 has begun. Also,
TR20, and the red lamp 4I on the lamp panel
operation of the motor 3| initiates the timing
LP40 is illuminated in order to indicate that the
operation of the timer T30 preset on the time
temperature of the article or batch of material C dial
TD thereof.
in the enclosure II has not yet reached the rela
Now
assuming that the temperature of the>
tively high temperature mentioned. When the
relatively low temperature established by the enclosure II has reached the relatively high
temperature established by the temperature dial
temperature dial XD of the temperature regu
YD
of the temperature regulator TRZ'U, and in
lator TR20 is reached, the thermocouple 2| gov
fact has fallen slightly therebelow, the thermo
erns the temperature regulator TRZU, whereby
couple 2| governs the temperature regulator
the motor 22 through the mechanism 23 oper
TRZII,
whereby the motor 22 through the mecha
ates the switch XS. More particularly, when the
nism 24 operates the switch YS. When the
switch XS is thus operated, a multiple lock cir
switch YS is thus operated, it recompletes the
cuit for energizing the windings of the relays RI30
At this time, the enclosure II is heated up
and RI50 and for operating the motor 22 is com
pleted. This multiple lock circuit extends from
the positive terminal by way of the winding of the
relay RI30 and its contacts I3I to the switch XS,
from the positive terminal by way of the winding
of the relay RI5U to the switch XS, from the posi
tive terminal by way of the motor 22 to the switch
XS, and from the switch XS to the negative ter
minal. At this time, the temperature of the en
closure II continues to rise from the relatively
low temperature established by the temperature
dial XD of the temperature regulator TR2() to
ward the relatively high temperature established
by the temperature dial YD of the temperature
regulator TR20.
Now assuming that the temperature of the
enclosure II of the furnace I0 has reached the
relatively high temperature established by the
temperature dial YD of the temperature regu
lator TR20, and in fact has risen slightly there
" previously traced circuit for energizing the wind
ing of the relay RJ45); however, the previously
traced multiple stick circuit for energizing the
winding of the relay RI2II is not completed at
this time. When thus energized, the relay R|40
reoperates; whereas the relay RI20 remains in
its restored position. Upon reoperating, the re
lay RI40 again completes at its contacts |4| the
previously mentioned connection between the
source of power and the electric heating element
I2, whereby the electric heating element I2 is
again heated in order to cause the temperature
of the enclosure II to rise again to the relatively
high temperature established by the tempera
ture dial YD of the temperature regulator TRIO,
and in fact slightly thereabove.
The two above-described operations are re
peated alternately in a cyclic manner, whereby
the electric heating element I2 is connected to
and disconnected from the source of power, re
spectively as the temperature of the enclosure AI I
2,410,384
relatively high temperature established by the
temperature regulator TR20, the thermocouple
2| governs the temperature regulator TR20,
whereby the motor 2 2, through the mechanism 23,
operates the switch
More particularly at this
temperature dial YD of the temperature regu
lator TR20, in order that the average tempera
ture of the enclosure II is closely held at the
relatively high temperature mentioned. More
time, when the switch XS is thus operated, the
previously traced multiple lock circuit for ener
particularly, the cyclic operation above described
continues for the time interval established by
the time dial TD of the timer T30; and upon the
expiration of the time interval mentioned, the
timer T30, through the mechanism 32, resets
the time dial TD to its normal position. In the
timer T30, when the time dial TD is reset to its
normal position, the switch TS is operated back
to its normal position through the mechanism 32.
More particularly at this time, upon operating
the switch TS interrupts at its contacts 33 the
previously traced multiple circuit for illuminating
the yellow lamp 42 and for operating the motor
3|, whereby the yellow lamp 42 is extinguished
and operation of the motor 3| is arrested. Also,
8
furnace I0 reaches the relatively low temperature
established by the temperature dial XD of the
falls slightly below and rises slightly above the
gizing the windings of the relays RI3S] and RI50
and for operating the motor 22 is interrupted,
whereby the relays RISil and RIES restore and
operation of the motor 22 is arrested.
Upon restoring, the relay RIM interrupts at
its contacts |3| a further point in the previously
traced lock circuit for energizing the winding
thereof, interrupts at the contacts |32 the pre
viously traced circuit for illuminating the blue
lamp 43, and recompletes at its contacts |33 the
previously traced operating circuit for ener
20 gizing the winding of the relay Rl'lil. When thus
energized, the relay RIîil reoperates, thereby to
complete at its contacts I‘BI the previously traced
stick circuit for energizing the winding thereof
and to prepare at its contacts |252 the previously
traced circuit for illuminating the red lamp 4|.
When the blue lamp 43 on the lamp panel LPM)
is extinguished, it indicates that the temperature
of the enclosure I I has fallen below the relatively
low temperature established by the temperature
30 dial XD of the temperature regulator TRIS.
Upon restoring, the relay Riâiil disconnects at its
the switch TS interrupts at the contacts 33 the
previously traced circuit for energizing the wind
ing of the relay R|40, in the event the latter relay
happens to be operated at this time, thereby to
cause the relay R|40 to restore and disconnect at
its contacts |4| the electric heating element I2
from the source of power. Further, upon operat
ing the switch TS interrupts at its contacts 33 the
previously traced circuit for energizing the wind
ing of the relay RI I0, thereby to cause the latter
contacts I5! 'the motor I5 from the source of
relay to restore. Upon restoring, the relay RI I3
power, whereby further operation of the motor I3,
interrupts at its contacts | I`I the previously traced
and consequently the main fan I3, is arrested.
operating circuit for energizing the winding oi
the relay RI30; however, the latter relay remains 35 At this time, the temperature of the enclosure II
continues to fall from the relatively low tempera
in its operated position at this time, due to the
ture established by the temperature dial XD of
previously completed lock circuit for energizing
the temperature regulator TRZU toward the am
the winding thereof. Also, upon operating the
bient temperature, entirely due to radiation and
switch TS completes at its contacts 34 a circuit
other heat losses, in that the operation of the
for illuminating the blue lamp 43, this circuit eX
main fan i3 has been arrested.
tending from the positive terminal by way of the
At this time, another heating schedule of the
master switch MS I 0 I , the contacts 34 of the switch
enclosure II may be initiated by the operator
TS, the contacts |32 of the relay RI3I), the blue
merely by reoperating the time dial TD on the
lamp 43, and the contacts |23 of the relay RIZD,
timer
T30 to the appropriate time interval, assum
45
to the negative terminal. Accordingly, at this
ing that the operator is satisñed with the pre
time on the lamp panel LP40, the yellow lamp 42
viously-set relatively high and relatively low tem
is extinguished and the blue lamp 4,3 is illumi
peratures
which have been established by the
nated, thereby to indicate that the heating of
the enclosure II has been arrested and that it is
temperature
the temperature
dialsregulator
YD and XD, respectively,
On the other
undergoing forced cooling by the main fan I3.V
hand, in the event that the enclosure ll is to be
More particularly, at this time, in the circuit
reoperated through a heating schedule
diiier
network IIT-8 the relays RIIII, RI20,
RIM?
occupy their restored positions, while the relays
RI30 and RI50 occupy their operated positions,
theV last-mentioned relays being retained in their -~
operated positions due to the previously completed
multiple lock circuit for energizing the windings
thereof. Also at this time, the operation or the
motor 3| of the timer T30 is arrested, while opera
b tion of the motor 22 of the temperature regulator
TRM continues. The operated relay R I 53 retains
at its contacts |5I the previously mentioned. con
nection between the motor I5 and the source of
power,~ whereby operation of the motor I5, and
consequently the main fan I3, is continued.
Operation cf the main fan I3 at this time, when
the electric heating element I2 is disconnected
from the source of power, effects a forced cooling
of the enclosure II, whereby the temperature of
the enclosure I I falls from the relatively high
temperature established by the temperature dial
YD of the temperature regulator TREO to the rela
tively lcw temperature established by the temper
ature dial XD of the temperature regulator TR2-ß.
When the temperature of the enclosure I I of the
ent relatively high and relatively low tempera
tures, the temperature dials YD and XD of the
temperature regulator TRìil are adjusted by the
operator to the appropriate temperatures, within
their ranges, prior to resetting the time dial TD
of the timer T30 to the desired time interval,
within its range, in the manner previously ex
plained. Finally, when no further operation of
the furnace I9 is required, the niastea` switch
MSIilI is operated to its open position, thereby to
interrupt the previously traced stiel: circuit for
energizing the winding of the relay R12?! in order
to cause the latter relay to restore. At this time,
all of the apparatus incorporated in the furnace
control system is completely released.
With particular reference to Fig. 2 it will be
understood that in carrying out the heat treat
70 ment schedule above-described that the main fan
I3 is operated during the initial heat-up period
in order to cause the temperature of the enclo
sure I| to be raised substantially uniformly
throughout from the ambient temperature to the
relatively high temperature established by the
2,410,384
temperaturedial YD, during the heat-hold pe
riod in order to cause the temperature of the en
closure II to be maintained substantially uni
formly throughout at the relatively high tempera
ture established by the temperature dial YD, and
10
arresting operation. of said first signal and' for
initiating operation of said second signal and for
initiating said desired timing operation of said
timer, means governed by said temperature regu
during the fan cooling period in order to cause 5 lator after thev temperature of said furnace
reaches said desired furnace temperature for se
the temperature of the enclosure II to be low
lectively controlling the operation of said heating
element, thereby to maintain the temperature of
said furnace substantially at said desired furnace
temperature dial YD to the relatively low tem
perature established by the temperature dial XD. l0 temperature, and stop means controlled by said
timer in response to the completion of said desired
Also in carrying out the heat treatment schedule
timing
operation thereof for arresting operation
operation of the main fan I3 is arrested during
ered substantially uniformly throughout from the
relatively high temperature established by the
of said second signal and for arresting operation
of said heating element.
toA normal heat losses from the relatively low 15 2. A heating system comprising structure de
lining> an enclosure, a heating element operative
temperature established by the temperature dial
to supply heat, means operative to induce cir
XD to the ambient temperature; during which
culation of a heating medium past said >heating
period forced cooling by the main fan I3 is not
element
and through said enclosure, a tempera
required as substantially uniform cooling of the
enclosure II is of no particular importance. Fi 20 ture regulator adapted to be set selectively with
in given ranges to a relatively high desired en
nally, it is noted that the temperature of the
closure temperature and to a relatively low de
batch arranged within the enclosure I I closely
sired control temperature, a timer adapted to
follows the changes in temperature of the enclo
the »static cooling period in order to cause the
temperature of the enclosure I I to be lowered due
be set selectively within a given range to a de
sure II described above.
In view of the foregoing description of the 25 sired'timing operation, start means for initiat
ing operation of said circulation-inducing means,
connection and arrangement and the mode of
means controlled by the operation of said cir
operation of the furnace control system in con
culation-inducing means for initiating operation
junction with the heat treating schedule of an
of said heating element, whereby the tempera
article or batch of material placed in the en
closure of the furnace, it will be understood that 30 ture of said enclosure is increased from an am'
bient temperature through said desired control
the operations are -entirely automatic after the
temperature toward said desired enclosure tem
appropriate controls have been set and rendered
perature, means controlled by said temperature
effective in the manner explained. Also, it will
be appreciated that both the relatively high tem
regulator in response to the temperature of ’said
perature which is to be held in the enclosure 35 enclosure reaching said desired enclosure tem
perature for initiating said desired timing op
of the furnace and the relatively low tempera
eration of said timer, means governed by said
ture below which it is not desirable to make ob
temperature regulator after the temperature of
servations and below which forced cooling of the
said enclosure reaches said desired enclosure
enclosure is not required may be s_et selectively
within given ranges; and that also, the time du 40 temperature for selectively controlling the op
eration of said heating element, thereby to main
ration of the relatively high temperature which
tain the temperature of said enclosure substan
is to be held in the enclosure may be set selec
tially at said desired enclosure temperature,
tively within a given range. The last-mentioned
means controlled by said timer in response to
feature is very advantageous, in view 0f the fact
that in the furnace control system the relative 45 the completion of said desired timing operation
thereof for arresting operation of said heating
ly high temperature which is to be held in the
element, whereby the temperature of said en
enclosure of the furnace is held for the required
closure is decreased from said desired enclosure
time interval, regardless of the ambient tempera
temperature through said desired control tem
ture of the enclosure of the furnace when opera
50 perature toward the ambient temperature, and
tion is initiated.
stop means controlled by said temperature regu
While there has been described what is at pres
lator in response to the temperature of said en
ent considered to be the preferred embodiment
closure reaching said desired control tempera
of the invention, it will be understood that vari
ture for arresting operation of said circulation
ous modifications may be made therein, and it is 55 inducing
means.
intended to cover in the appended claims all such
3.
A
heating
system comprising structure de
modifications as fall within the true spirit and
ñning an enclosure, a heating element operative
scope of the invention
to supply heat, a fan associated with said heat
What is claimed is:
ing element and operative to circulate a heating
1. A heating system comprising a furnace, a
heating element associated with said furnace and 60 medium past said heating element and through
said enclosure, a temperature regulator adapted
operative to supply heat thereto, first and sec
to be set selectively within given ranges to a rela
ond signals associated with said furnace, a tem
perature regulator adapted to be set selectively
Within a given range to a desired furnace tem
perature, a timer adapted to be set selectively
within a given range to a desired timing opera
tion, start means for initiating operation of said
heating element and for initiating operation of
said first signal, whereby the temperature of said
furnace is increased from an ambient tempera
ture toward said desired furnace temperature,
means controlled by said temperature regulator
in response to the temperature of said furnace
reaching said desired furnace temperature for
tively high desired enclosure temperature and
2,410,384
enclosure temperature for initiating said desired
timing operation of said timer, means governed
by said temperature regulator after the tempera
ture of said enclosure reaches said desired en
closure temperature for selectively controlling
the operation of said heating element, thereby
to maintain the temperature oi said enclosure
substantially at said desired enclosure tempera
ture, means controlled by said timer in response
to the completion of said desired timing opera
12
the operation of said fan for initiating op
eration of said heating element, whereby the
temperature of said enclosure is increased from
an ambient temperature through said desired
control temperature toward said desired eri
closure temperature, means controlled by said
temperature regulator in response to the tem
perature of said enclosure reaching said desired
enclosure temperature for arresting operation o!
said first signal and for initiating operation of
said second signal and for initiating said desired
timing operation of said timer, means governed
tion thereof for arresting operation of said heat
ing element, whereby the temperature of said
by said temperature regulator after the tempera
enclosure is decreased from said desired enclo
ture of said enclosure reaches said desired en
sure temperature through said desired control
closure temperature for selectively controlling
temperature toward the ambient temperature,
the operation of said heating element, thereby
and stop means controlled by said temperature
to maintain the temperature of said enclosure
regulator in response to the temperature of said
substantially at said desired enclosure tempera
enclosure reaching said desired control tempera
ture, means controlled by said timer in response
ture for arresting operation of said fan.
4. A heating system comprising structure de 20 to the completion of said desired timing opera
tion thereof for arresting operation of said sec
ilning an enclosure, a heating element operative
ond signal and for initiating operation of said
to supply heat, a fan associated with said heat
third signal and for arresting operation of said
ing element and operative to circulate a heating
heating element, whereby the temperature of
medium past said heating element and through
said enclosure is decreased from said desired en
said enclosure, first and second and third sig
closure temperature through said desired control
nals associated with said enclosure, a tempera
temperature toward the ambient temperature,
ture regulator adapted to be set selectively with
and stop means controlled by said temperature
in given ranges to a relatively high desired en
regulator in response to the temperature of said
closure temperature and to a relatively low de
sired control temperature, a timer adapted to 30 enclosure reaching said desired control tempera
ture for arresting operation of said fan and for
be set selectively within a given range to a de
arresting operation of said third signal.
sired timing operation, start means for initiat
ing operation of said fan and for initiating op
HAROLD W. LINDSAY.
eration of said nrst signal, means controlled by
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