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Патент USA US2404597

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July 23, 1946.
c. H. MCCLAIN
2,404,597 ’
TEMPERATURE CONTROLLER
Filed April 21, ~1943
2 Sheets-Sheet l
macaw HM‘CL/UN
July 23, 1946.
2,404,597
c, H, McCLAl‘N
TEMPERATURE CONTROLLER
Filed April 21, 1943
2 Sheets-Sheet 2
_
INVENTOR
CZ/FFO/PD H. McCLA/N
"/11 l/
BY
1.’
'
{WIT/IQ
ATTORNEYS ‘
2,404,597
Patented July 23, 1946
UNITED STATES PATENT OFFICE
2,404,597
TElVIPERATURE CONTROLLER
Clifford H. McClain, Lansdowne, Pa., assignor to
Hoffman Specialty 00., Indianapolis, Ind., a
corporation of Illinois
Application April 21, 1943, Serial No. 483,831
7 Claims. (Cl. 236—91)
1
Z
The present invention has as a primary object
the provision of a temperature control device
This invention relates to temperature con
trollers and to systems using the same to control
the variations in one temperature in a nredeter»
mined relation to variations in another, com—
monly for the regulation of a third temperature
affected by such variations. The invention has
many applications and is advantageous, for ex
ample, for the control of hot water heating sys_
tems or cooling systems for homes or other build
ings where it is desired to keep room tempera 10
which is automatically operative to supply heat
to a building at a temperature which will main
tain the temperature of the building substantially
constant under varying outdoor Weather condi
tions. It is a more general object of the invention
to supply the heat demands of a heat exchange
system where the temperature of the heat supply
medium must vary as a curvilinear function of
variationsin the temperature of a control me
dium. It is a special object of the invention to
tures approximately constant under changing
outdoor Weather conditions.
control automatically the temperature of a radi- _
Temperature controllers have been provided
heretofore which embody lever means movable
ator or convector system in accordance with
according to the varying positions of two or more
phere in such a manner as to supply heat to a
building at a rate which will maintain its tem—
to regulate ‘the temperature of a heating ?uid 15 changes in the temperature of the outside atmos
thermally responsive expansion devices. In ap
plying such controllers to hot Water heating sys
perature substantially constant under variable
outdoor weather conditions. Other objects and
cated, respectively, in the circulating hot water 20 features of the invention will be obvious from its
special embodiments as illustrated hereinafter.
and in the air outside the enclosure being heated.
To maintain the temperature of a building at
The expansion devices work against arms of the
tems, the bulbs of two expansion devices are lo
‘70° F. with a hot water heating system where the
optimum demands for maintaining such a tem
perature are 150 B. t. u.’s per hour, the optimum
temperature to maintain this supply of heat is
controller lever and cause it, by certain move
ments, to operate a valve control switch or other
means to change the temperature of the circulat
ing water. The lever arms have a ?xed operat
ing ratio that establishes a linear relationship be
tween changes in the temperature of the outdoor
water at a mean temperature of 170° F. (i. e., a
temperature of 180° F. at the inlet and 160 F. at
the outlet of the system); if the drop in water
temperature in the circulating system is 20° F.
air and the temperature changes in the circulat~ .
ing Water. Manually operated means have been
provided also for changing the effective lengths
of the lever arms by a lateral shifting of the ful
crum. When the position of the fulcrum is estab
lished, however, the controlled temperature is
again varied linearly in accordance with vari
ations in the controlling temperature.
between the incoming and outgoing Water, then
7.5 lbs. of water must flow through the heating
elements per hour to supply the necessary heat.
It is known that the average temperature of the
water necessary to supply a speci?c number of
B. t. u.’s per hour is given by the formula:
If the lever arm ratio has been selected prop
105
erly for a certain outdoor temperature and other
t, 65 +l_li [15)
use conditions, the controller will function at that
V H
temperature to control the circulating water so 40
where
that it emits enough heat to counteract heat losses
and keep the room temperature approximately
t-izaverage Water temperature in convector
uniform. On the other hand, when the outdoor
H:heat out-put of convector in B. t. u. per hour.
temperature changes the water temperature is
and that the temperature of the Water entering
varied according to the ?xed ratio, and the heat
the system is given by the formula:
emission of the system then may not balance the
heat loss. This unbalanced condition occurs in
H
practice because, although the heat loss may vary
t1: ta + .S'W
directly as the difference between the outdoor
temperature and the room temperature, the actual 50 where
heat emission from such a system varies as an
tiztemperature of water entering convector
exponential or curvilinear function of the tem
Hzheat out-put of convector in B. t. u. per hour
perature variations of the heating medium rather
Wzconstant water circulation in pounds per hour.
than as a linear function of such temperature
v
variations.
~ It is clear from these formulas that, the rela
I
2,404,597
3
tionship between the temperature of the water in
the heat transfer system and the amount of heat
generated or transferred is not a linear function
but is in fact a curvilinear function of the tem
perature of the water. The graph representing
the relationship between the temperature of such
a system and the amount of heat supplied is
4
stituting appropriate cams. The cam may also be
an integral part of the lever means,
In this manner I provide a temperature con~
troller embodying a mechanism which automat~
ically effectuates an in?nite number of changes in
the ratio between the temperature variations of
the controlled temperature and the controlling
temperature in conformity to a predetermined
exchanged with the surrounding atmosphere
calculated or experimentally determined desired
where a room temperature is constant in direct 10 exponential or curvilinear relationship between
known as the temperature curve.
Since heat is
proportion to variations in the temperature of the
surrounding atmosphere, it is seen that a tem
such temperature variations.
When my con
troller is applied to a hot water or similar heating
perature control device which regulates the tem
system which is to have its temperature con
perature of a heating medium in proportion to
trolled by not water controlled by temperature
variations in the temperature of the surrounding 15 variations in the outside atmosphere, the tem
atmosphere will not maintain the temperature
perature of the heating ?uid may be regulated
of a building constant, but will in fact cause the
to maintain the heat emission of the system in
temperature of the building to vary or ?uctuate.
conformity to the so-called temperature curve,
If the temperature of a building is to be main~
i. e., equal to the heat demands of the space to
tained relatively constant, it is necessary to have 20 be heated. In this way the temperature of a room
a temperature control device of such flexibility
or other enclosed spaced losing heat to the out
that it is operative to vary the relationship be~
side air may be maintained at any desired uni
tween the temperature of the control medium
form or substantially uniform temperature.
and the heat supply medium in such a manner
Other features and advantages of my invention
that the rate of heat emission will substantially 25 will be apparent from the following detailed de
follow the so-called temperature curve. It has
scription of a preferred and speci?c embodiment
not been possible to achieve this result with
of my invention as illustrated in the drawings.
known temperature controllers.
Figure l is a diagrammatic representaton of
My invention provides new and improved tem
a temperature regulator embodying my invention.
perature controllers and heat exchange systems
Figure 2 is diagram of a heating system em
using the same, which are operative, for example,
bodying the application of my invention to a con
to control the temperature of a heating ?uid so
tinuously circulating hot water heating system.
as to keep the heat emission of a heating system
Figure 3 is a part sectional detail view of the
at all times approximately equal to the heat re
control valves of the system illustrated in Fig
quirements as measured by a variable control
ure 2.
temperature, such as that of the outdoor air. My
Figure ll is a diagrammatic representation of a
invention thus contemplates heating systems
hot water heating system using a different form
which will keep room temperatures approximately
of ?ow control valve.
constant under changing weather conditions. It
As shown in Figure 1, the temperature con
also contemplates cooling systems operative to
toller comprises two levers la and ll and two
counteract heat gains by equivalent cooling ef
thermostatic bellows i2 and it, provided with in
fects over a wide range of outdoor or other con
ternal guides i202 and led. Lever it] has two op
trol temperatures.
positely extending arms lila and lllb, and lever I I
In the temperature controller of my invention
has two oppositely extending lever arms Ha and
I utilize lever means or the like to control the
Nb. Lever it rotates about a stationary pin M
temperature of a heating medium, which lever
which acts as its fulcrum, while lever H rotates
means are positioned by two thermal expansion
about a stationary pin l5 which acts as its ful
devices respectively responsive to temperature
cruin. The position of the levers at any time is
variations in the control and the heating medium.
determined by the relative position of extension
I provide means, however, which coact with the
element it of the bellows l2. Arm liib of lever H!
lever means and the thermal expansion devices
is held in contact with the inner portion of a yoke
in such a manner that the ratio between the tem
ll, which contacts the extension element l6 by
perature variations of the two media is subjected
means of a coil spring Na and the arm Ha of
automatically to an in?nite number of changes
lever i i normally is moved toward the cam at the
over the operative temperature ranges. For ex
lower end of the arm lilc of the lever Ill by spring
ample, I may provide a cam or cams to coact with
the levers and the expansion. devices to automat
ically vary the effective lever arms and effectu
ate an in?nite number of desired
continual
l'lb.
'
Extension element i5 is operated by thermo
sensitive bellows I2 connected through tube Hi
to bulb Ell located in a medium of variable tem
changes in the ratio between the temperature 60 peratures, such as the outside atmosphere, and
variations of the controlled and the controlling
extension element l to is operated by thermo-sen
media.
sitive bellows it connected through tube 2! to
By an appropriate adjustment of the contour
bulb 22 located in the medium to be controlled,
of such coacting devices the temperature of the
such as the hot water, the bellows, the bulbs and
controlled medium may be regulated to approxi
the tubes being ?lled with a thermally expansive
mate any desired curvilinear temperature curve
fluid.
even though parts of the curve may be straight.
There are various methods by which the ap
propriate contour of the cam surface may be ob
Lever arm Nib has a curved surface l?c for con
tacting yoke l l, which surface may be so designed
that the effective length of the lever arm lila is
tained, including both analytical and graphical 70 always the same throughout the expansion and
methods. It will be obvious that there are cer
tain advantages in having these cams con
structed as separate parts of the temperature
controller since such controllers may then be ad
justed to meet di?erent control conditions by sub
contraction range of bellows l2. Lever arm 500.
is provided with an interchangeable compensat
ing cam Ht, which automatically varies the effec
tive length of this lever arm, thereby elfectuat
75 ing a predetermined in?nite variation in the rela
2,404,597
5
tive movement of lever H and in the ratio be
tween the temperature variations in the control
ling medium and in the controlled medium.
It will be understood that a plurality of cams
l8 may be provided and the proper cam installed
to suit the requirements of the system at the loca
tion in which it is installed. It will also be under
- stood that a cam or curved surface may be per
6
ed in the movable yoke 40 and operates either to
open the switch or to close either of circuits A
or B. These circuits serve to energize the coils
of motor M for changing or regulating the posi
tion of the valves which control the hot water
?ow either through or around the boiler HB.
When the lever l I is in an intermediate position,
both circuits A and B are open and the reversible
manently ?xed to the lever arm Illa and a similar
motor M remains stationary.
In this position
lever arm Ila.
they happen to be when the circuit is broken and
or complementary cam surface may be placed on 10 the control valves remain in whatever position
conected to the extension [6 and carries an ex
the ratio of hot water to recirculated water re
mains constant until either circuit A or B is closed
tension l'lc which is guided and slidably mount
ed in a guide 25, and the yoke 40 which may be
integrally or separably connected with the ex
tension ISa carries an extension 40a which is
guided and slidably mounted in a guide 26.
Figure 2 shows the application of this type of
perature remains constant and the position of
lever H is not shifted, if the temperature of the
Water circulating in the pipes P drops, the bellows
l3 will contract, extension element ISa which is
The yoke I‘! may be integrally or separably
and the motor M started to change the position
of the control valves. When the outside tem
controller to a forced feed circulation hot water 20 connected to yoke 40 will move vertically down
ward and the end of lever arm Hb will contact
with the upper contact of switch S to close cir
cuit A, thereby actuating the reversible motor
E by a circulating water pump P1.
heating system, in which hot water is circulated
through pipes P and radiators R, in an enclosure
In this system the bulb 20 connected with the
M, which in turn slowly opens the butterfly valve
the enclosure E and the bulb 22 is located in the
correspondingly closes the valve 31 in the by-pass.
boiler and partially through the by-pass.
?ciently to maintain the desired temperature in
the heat exchange medium, the bellows [3 will
V bellows I2 is located in the atmosphere outside 25 35 in the passage from the heating boiler HB and
In this way a greater portion of the water is
supply water line CW. Hot water is supplied
caused to circulate through the boiler HB and
from a hot water boiler HB and the pipes P are
more hot water is introduced into the circulatory
arranged so that the water circulated by the
pump P1 may either pass through the boiler HB 30 system and the temperature of the circulating
water rises. When the temperature has risen suf
or through a by-pass B? or partially through the
The boiler l-IB may be heated by conventional
heating devices. Usually, it is preferable to main
expand and move the extension [3a and yoke 40
tain the boiler water at a substantially uniform
temperature which may be achieved by using an
so as to break the circuit A and stop further move
ment of the motor M. If the temperature of the
circulating water should continue to rise, exten
oil burner regulated by a thermostat. As shown
sion element IBa will move yoke 40 into such a
in Figure 2, oil burner D is provided with an elec
position that the lower contact of switch S will
tric motor which is controlled by the thermostat
C, connected to power lines F and G‘. The ther 40 contact the end of arm I lb and circuit B will close,
thereby reversing the operation of motor M, clos
mostat C is so adjusted that it closes the electric
ing the butter?y valve 35 in the boiler water pas
circuit and turns on the electric motor of oil
sage and opening the butter?y valve 31 in the by
burner D whenever the water reaches a certain
pass to reduce the temperature of the circulating
minimum temperature. Likewise, the reverse
water. As soon as equilibrium is established
happens when the water reaches a desired maxi
under the existing conditions, the bellows l3 will
mum temperature.
again contract breaking the contact of circuit B
Figure 3 shows in greater detail the flow con
and stopping the motor M.
trol valves used in the heating system illustrated
If now we assume a condition of changing out
in Figure 2. The reversible motor M is connected
by a shaft 30 having a friction slip connection 30a 50 door temperatures, the position of lever l I will be
changed relative to the contacts of switch S to
likewise operate the motor M to control the flow
of water to compensate for either increase or de
actuates the movement of operating gear 34 which
crease of the outdoor temperatures. This is
in turn actuate-s movement in butterfly valve 35.
Operating gear 34 meshes with operating gear 36 55 brought about by movement of the extension ele
ment I6 which will cause lever arm N22 to take
connected with the butterfly valve 31, so that
an intermediate position or a position closing
when valve 35 is being moved to open position,
circuit A or B, whether bellows l3 expands or
valve 31 will be moved toward closed position,
contracts or remains stationary. Assuming that
and when valve 35 is being moved toward closed
position, valve 31 will be moved toward open posi 60 lever arm Hb is in an intermediate position, it is
seen that a decrease in the outdoor temperature
tion. The valve system is provided with stop
would cause bellows l2 to contract and extension
switches 38 and 39 operated by an arm 35a con
element [6 to move in a direction away from lever
nected to the shaft of the valve 35 to assure opti
arm 1017. Under such conditions the tension of
mum operation of the valves and to stop their
movement when they have reached fully open or 65 coil spring Ila causes lever arm Illa to move to
the left in Figure l, and lever arm Hlb to move
fully closed positions without causing breakage
to the right, thereby remaining in contact with
of any parts. For instance, when butter?y valve
the yoke ll of extension element H3. The move
35 has reached the position where the flow of
ment of lever I0 causes cam Hi to move along the
water through the pipe is either a maximum or
a minimum, the operation of the motor M is dis 70 contacting surface of the lever arm Ila to move
the arm I la downward and the arm Hb upward.
continued by the arm 35a contacting one of the
This movement will close the circuit A to start
stop switches, shown at 38 and 39, to stop the
the motor M to open the valve 35 and close the
motor.
valve 31 to thereby increase the temperature of
As shown in Figures 1 and 2, lever arm Ilb
carries one contact of a two-way switch S mount 75 the water ?owing through the pipes P and ra
to a worm 3 I, which functions to operate a worm
gear 32. Worm gear 32 has a pinion 33 which
aeossev
7
diators R to compensate for the decrease in the
outdoor temperature. In a like manner, if the
outside temperature should rise, the relative
movement of levers iii and it would be reversed
and circuit B would be closed, which in turn
would eifectuate a lowering of the temperature of
8
be selected to give the desired ratio and the cams
may be designed or changed to satisfy the re
quirements of any situation. Cam l8 may be
made to conform to the contour of a curve cor
responding to the theoretical relationship be
tween the desired temperature variations of the
controlled and the controlling medium, or it
may be constructed to conform to an empirically
derived curve.
Thus, it is possible to maintain
the controlled medium.
In normal operation, the movements of bellows
l2 and it under the influence of the varying tem
peratures to which the bulbs 26 and 22 are sub 10 the temperature of the heat exchange medium
jected will take place simultaneously and there
will be frequent adjustments of the position of
the contacts effecting the circuits A and B to
the motor M, and frequent changes in the amount
relatively constant regardless of whether it is
necessary to vary the temperature of the con
trolled medium as a curvilinear function of the
temperature variations in the controlling medium
of heat imparted to the water circulated in the 15 or as mixed linear and curvilinear functions of
pipes P to compensate for increases or decreases
such variations. For an “ideal” heating system,
in the outside temperature.
the cams may be prepared in advance and ap
Figure 4 shows a heating system similar to Fig_
propriate cams installed for maintaining rela
ure 2, with the exception that an off or on type
tively constant a predetermined range of desired
of valve is used to direct the flow of water either
temperatures in the heat exchange medium.
through the by-pass circuit or partly through
Where the conditions of the installation require
the boiler and partly through the by~pass. The
special treatment, a cam can be designed and
valve regulating the relative flow of water through
installed for the particular installation.
a heating unit HB and the by-pass may be of the
It will be understood further that the desired
type shown in the patent to Gillett’ et al., No.
predetermined in?nite variations in the ratio be
2,181,480, or it may be a valve of the solenoid
tween the temperature variations of the control
type. In valves of this type it is only necessary to
medium and the controlled medium may be
provide means for opening the valve since the
achieved by applying the principles of this in
valve is provided with positive means for keep
vention to a temperature controller using a sin
ing it normally closed. Consequently circuit B 30 gle lever rather than a plurality of levers. It
may be omitted and only circuit A used for en
will be understood also that the surface lilo of
ergizing the solenoid and holding the valve open
the lever arm is may be designed as a cam sur
when the system calls for more heat.
face to- give partial or complete control over the
In Figure 4 the hot water boiler is indicated
relationship of the levers I ll and H. Likewise,
at HB, the outgoing line to the radiators is in
the desired ratios between the temperature vari
dicated at R1, the lines from the radiators are
ations of the control and the controlled medium
indicated at R2 and the pump is indicated at P1.
may be procured by a proper correlation of the
The by-pass is indicated at BP and the valve at
curvatures of two or more contact surfaces. Ob
SV. The valve SV is normally in closed position
viously, it is preferable to effectuate the desired
to prevent circulation of water through the boiler 40 result by varying a single contact surface in ac
I-IB unless the condition of the system calls for
cordance with the embodiment described herein.
more heat, in which event the contact through
The present invention is not limited to the
the circuit to the Valve SV will be closed and the
details nor to the exact procedures described
valve SV will be held open to permit part circula
herein, but contemplates all applications of the
tion of the water through the boiler until suf?“ 45 methods and structures herein described which
cient additional heat has been added to the sys
are within the scope of the appended claims.
tem to satisfy its requirements, whereupon the
I claim:
bulb 22 in the water supply line R1 to the radia
1. In a circulating fluid heating system hav
tors will cause the bellows it to expand to break
ing means to add heat to the circulating ?uid of
the circuit A to the valve SV and cut oil? further 50 said system, apparatus for controlling the addi
circulation through the boiler HB.
tion of heat to said fluid comprising a thermo
Referring again to Figure 1, the U -shaped por
stat responsive to outside air temperature, a ther
tions of yokes H and M} are provided with point
mostat responsive to the circulating ?uid tem
ers 42 and 43, which indicate the outdoor air
perature, a lever system operated by one of said
temperature and the water temperature, respec
55 thermostats, said lever system cooperating with
tively, on scales 23 and 212. The U-shaped por—
means operated by the other thermostat to con
tion of the yoke i‘! has an adjustable stop ‘27,
trol the addition of heat to said circulating ?uid,
which is adapted to contact switch 28 which cuts
and means predeterminedly curvilinearly chang
the pump P1 out of operation whenever the out
ing the movement of said lever system by one of
door temperature is high enough that no heat is 60 said thermostats relative to the means operated
needed in the enclosure and may also be made
by the other thermostat at a greater rate as out
to cut the entire heating plant. Thermo-sensi
tive bellows i3 is provided with an adjustment
nut 29 which permits the position of the bellows
side temperature decreases.
2. In a circulating ?uid heating system hav
ing means to add heat to the circulating ?uid of
to be varied so as to properly locate the position 65 said system, apparatus for controlling the addi
of the contacts of switch S with reference to the
tion of heat to said ?uid comprising a thermo
end of lever arm lib.
stat linearly responsive to outside air tempera
It will be clearly understood from the preced
ture, a thermostat linearly responsive to the cir
ing description of my control system that any
culating ?uid temperature, a lever system oper
desired in?nitely varied temperature ratio may 70 ated by one of said thermostats, said lever sys
be maintained between a heating or cooling me
tem cooperating with means operated by the
dium and the space to be heated or cooled, even
other thermostat to control the addition of heat
though the demands for heating or cooling may
to said circulating ?uid, and means connected
change over a Wide range with changes in out
in said lever system predeterminedly curvilinear
door temperatures. The curvature of cam l 8 may 75 ly changing the movement of said lever system
2,404,597
by one of said thermostats relative to the means
operated by the other thermostats at a greater
rate as the outside temperature decreases.
3. In a circulating ?uid heating system hav
ing means to add heat to the circulating ?uid of
said system, apparatus for controlling the addi
tion of heat to said ?uid comprising a thermo
stat responsive to outside temperature, a ther
10
stats in linear relation to the temperature to
which said thermostat is responsive, a control
lever, means operated by the other thermostat in
linear relation to the temperature to which said
other thermostat is responsive, said means be
ing cooperable with said control lever to control
the supply of heat to said circulating ?uid, and
an adjustable curvilinear cam means between said
levers for transmitting movement of one lever to
ture, a lever operated by one of said thermostats 10 the other lever at a greater rate as the outside
temperature decreases.
in linear relation to the temperature to which
6. In a circulating ?uid heating system hav
said thermostat is responsive, a control lever,
ing means to add heat to the circulating ?uid of
means operated by the other thermostat in linear
said system, apparatus for controlling the addi
relation to the temperature to which said other
thermostat is responsive, said means being co 15 tion of heat to said ?uid comprising a thermo
mostat responsive to circulating ?uid tempera
operable with said control lever to control the
supply of heat to said circulating ?uid, and a
stat responsive to outside temperature, a ther—
mostat responsive to circulating ?uid tempera
ture, a lever operated by one of said thermostats
in linear relation to the temperature to which
of said control lever by said lever at a greater 20 said thermostat is responsive, a control lever
having switch contacts thereon, means operated
rate as the outside temperature decreases.
by the other thermostat in linear relation to the
4. In a circulating ?uid heating system having
temperature to which said other thermostat is
means to add heat to the circulating ?uid of said
responsive, said means having switch contacts
system, apparatus for controlling the addition of
heat to said ?uid comprising a thermostat re 25 cooperable with the switch contacts of said con
trol lever to control the supply of heat to said
sponsive to outside temperature, a thermostat re
circulating ?uid, and a curvilinear cam means
sponsive to circulating ?uid temperature, a lever
operatively connecting said levers and changing
operated by one of said thermostats in linear
the movement of said control lever by said other
relation to the temperature to which said ther
30 lever at a greater rate as the outside temperature
mostat is responsive, a control lever, means oper
decreases.
ated by the other thermostat in linear relation
7. In a hot water circulating heating system,
to the temperature to which said other thermo
means to heat said water, a by-pass for said heat
stat is responsive, said means being cooperable
with said control lever to control the supply of 35 ing means, means to circulate said water in said
system, a thermostat linearly responsive to out
heat to said circulating ?uid, and a curvilinear
door temperature, a thermostat linearly respon
means between said levers predeterminedly
curvilinear means cperatively associated with
said levers predeterminedly changing movement
changing the movement of said control lever by
said other lever at a greater rate as the outside
temperature decreases.
5. In a circulating ?uid heating system hav
ing means to add heat to the circulating ?uid of
sive to the circulating Water temperature, a lever
system operable by one of said thermostats,
40 means operable by the other thermostat coop
erating with said lever system for controlling
said Icy-pass, and means connected to said lever
said system, apparatus for controlling the addi
system predeterminedly curvilinearly changing
tion of heat to said ?uid comprising a ‘thermo
stat responsive to outside temperature, a ther
the movement of said system relative to the ther
45 mostat operating said lever system at a greater
rate as the outside temperature decreases.
CLIFFORD H. McCLAIN.
mostat responsive to circulating ?uid tempera
ture, a lever operated by one of said thermo
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