AN IMPROVED PYROMETER OR THERMOMETRICAL INDICATOR
Year: 1877

page_text: LETTERS PATENT to Henry Gardner, of the Firm of Robertson, Brooman, and
Company, of 166, Fleet Street, in the City of London, Patent Agents, for the
Invention of "AN IMPROVED PYROMETER OR THERMOMETRICAL INDICATOR."
A communication from abroad by Messieurs Joseph Antoine Tremeschini,
Engineer, and Felix Lion, junior, Manufacturer of Barometers, both of Paris,
France.
Sealed the 11th January 1878, and dated the 14th July 1877.
PROVISIONAL SPECIFICATION left by the said Henry Gardner at the Office
of the Commissioners of Patents on the 14th July 1877.
HENRY GARDNER, of the Firm of Robertson, Brooman, and Company, of 166, Fleet
Street, in the City of London, Patent Agents. "AN IMPROVED PYROMETER OR
THERMOMETRICAL INDICATOR." A communication from abroad by Messieurs Joseph
Antoine Tremeschini, Engineer, and Felix Lion, junior, Manufacturer of Barometers,
both of Paris, France.
A great many pyrometers or instruments for measuring the high temperatures
which exist in muffle furnaces, glass-making furnaces, gas furnaces, reverberatory
furnaces, puddling furnaces, blast furnaces, and the like, have already been
contrived.
The apparatus constructed and used up to the present can only give vague and
indifferent indications, because the high temperature to which these instruments
are exposed permits of employing only substances capable of supporting without
deterioration these high temperatures, but which on the other hand are not liable to
dilatations easy to be distinguished.
The pyrometers are formed to estimate the temperature of the furnace direct, that
is to say, they are themselves subjected to the high temperature.
My pyrometer is based on an entirely different principle; the observing apparatus
is not directly subjected to the heat to be measured, but is subjected to the height
of temperature which a fluid of any kind, gaseous or liquid, undergoes, circulating
in a tube placed in the interior of a furnace fire-place, or in a liquid, or in melting
metal, of which it is desired to find the temperature.

page_text: The fluid in my apparatus serves as a heat carrier; it becomes heated by the
contact of the circulation tube placed in the furnace or interior of which the
temperature is to be found. According to the temperature of this heat carrier
marked by any thermometer receiving directly the heated fluid current, or placed
at a distance from this current is determined the temperature of the furnace. This
determination can be made with the more exactitude, as the fluid current which
heats itself in the furnace has a temperature comparatively low, easily distinguished,
and permitting the employment of apparatus of an excessive sensibility.
In a word, this Invention gives the exact measure of the interior temperature of
a furnace, fire-place, or of all interiors whatsoever by the employment as an
auxiliary heat carrier of a fluid, gas, or liquid, which becomes heated in the furnace,
and of which the temperature is found by any thermometer. From the temperature
of the fluid is ascertained that of the furnace.
The pyrometer is not only composed of a thermometrical apparatus measuring
the nominal temperature; the essential part consists of a circulation tube of an
auxiliary fluid, and the heating of this fluid, which heat is measured by the
thermometer, from which is found the real temperature of the furnace.
The circulation of the auxiliary fluid in the tube placed in the furnace or interior
may be natural, or be forced by an air exhauster or blower, which would be put
into action at the time of operation.
For finding the variations of temperature of the fluid heat carrier, the known
laws of the emission of heat by radiation are applied, that is to say, that this heat
transmits itself in a straight line, and that the intensities of heat emitted vary in
inverse ratio to the square of distances. If therefor a thermometer placed at a
certain distance from the circulation tube of the auxiliary fluid indicates a given
temperature, if on the other hand in consequence of a over heating of the fluid,
it is necessary to take the therinometer to a distance double that of the preceding
one to observe the same degree, it may be concluded that the final temperature is
quadruple the initial temperature of the fluid.
I do not always conclude that the temperature of the furnace has been quadrupled,
and will now indicate how, according to these considerations, always bearing in mind
the laws of the transmission of heat, I graduate my apparatus.
Any known thermometer may be employed, but I prefer the thermometer of the
system Tremeschini, which is based on the dilatation of a thin blade of metal, of
which one end is kept fixed by a special agency of compensated dilatation bars,
whereas the opposite end causes to move, by the intermediation of special parts, a
needle which in displacing itself above an indicating dial gives the indications of
temperature. Suppose a furnace, the interior of which it is desired to ascertain the
exact temperature, an opening formed on one of the sides permits the interior heat
to act on a Melloni pile in communication with a galvonometer.
If a Melloni pile is placed in connection with a Leslie cube containing hot water
at 100°, one may observe the deviation of a galvonometer needle, and then measure
the distance from the cube to the thermo-electric pile. In these conditions it is
only necessary to place successively the pile at fixed points so as always to observe
the deviation of the needle, so that as the interior temperature of the furnace is
elevated, the distances to the furnace from the fixed points, according to the laws of
distances for radiation, may be concluded for the real temperatures of the furnace
in its different conditions. By then observing at the time the thermometer, and
by progressively removing it farther from the tube that it indicates always the same
temperature, the rule will be graduated on which the thermometer displaces itself,
more often would be the displacement operated by means of a pinion actuating a
rack, which is carried by the thermometer; the displacement of the pinion, in con-
sequence, the separation of the thermometer, and the temperature to which it
corresponds are indicated by the displacement of a needle on an indicating dial.
It is found by experiments that the distances of the thermometer from the tube
varied in the same ratio as the distances of the thermo-electric pile to the furnace.
This new application of the laws of radiation for ascertaining very high temperatures,

page_text: which forms part of this Invention, has the advantage of permitting the employ-
ment of the most delicate and sensitive thermometrical apparatus as an impressionable
indicating organ in the formation of the pyrometer. In effect, suppose that the
heat of the fluid heat carrier which radiates through the blackened parts of the
conducting tubes, corresponding to the impressionable organ of the thermometer,
rises even to 500 or 600 degrees centigrade, it is evident that this organ will not be
subjected to any deterioration in consequence of this enormous temperature, because,
according to my system this organ not placed in immediate contact with the
heated part, but is placed at a certain distance which is regulated as I have said,
according to the laws of radiation of heat.
To insure the circulation of the fluid I arrange a tube in the form of a thermo-
siphon, presenting an enlargement at its upper part, while one of the lower branches
is encircled by a refrigerant. The refrigerant can be established on the same hori-
zontal line as the tube.
In order that the thermometer may be sensitive, a special command of the axle
of the needle is adopted, this axle carries a screw thread acting with a lever rod
fastened to the moveable end of the blade of the Tremeschini thermometer; or again,
this axle carries a double helicoidal groove which commands a fork which terminates
this lever rod. This imperative command gives a precision which is not obtained
with the ordinary means used for the same object, such as rack and pinion, silk
thread, or chain winding on the axle.
The Invention therefor consists in the manufacture and exclusive working of a
pyrometer, characterised by the employment (as an organ and integral part of an
instrument) of a suitable fluid, such as air or steam, also of a liquid serving as a con-
ductor or carrier of heat to be measured, and acting in the following manner:-This
fluid or this liquid circulates in a tube, of which one part is plunged in the interior of
a furnace or other body, of which it is desired to know the temperature, and another
part is placed facing the impressionable organ of the thermometer, so that the latter
may directly receive the transmission of heat which goes through the sides of that
part of the tube at a suitable distance and calculated beforehand, according to the
physical laws of the radiation of heat.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Gardner in the Great Seal Patent Office on the 12th January
1878.
HENRY GARDNER, of the Firm of Robertson, Brooman, and Company, of 166, Fleet
Street, in the City of London, Patent Agents. AN IMPROVED PYROMETER OR
THERMOMETRICAL INDICATOR." (A communication from abroad by Messieurs Joseph
Antoine Tremeschini, Engineer, and Felix Lion, junior, Manufacturer of Barometers,
both of Paris, France.)
A great many pyrometers or instruments for measuring the high temperatures
which exist in muffle furnaces, glass-making furnaces, gas furnaces, reverberatory
furnaces, puddling furnaces, blast furnaces, and the like, have already been
devised.
The apparatus constructed and used up to the present can only give vague and
indifferent indications, because the high temperature to which these instruments
are exposed permits of employing only substances capable of supporting without
deterioration these high temperatures, but which on the other hand are not liable to
dilatations easy to be distinguished.
The pyrometers are formed to estimate the temperature of the furnace direct, that
is to say, they are themselves subjected to the high temperature.
My pyrometer is based on an entirely different principle; the observing apparatus
is not directly subjected to the heat to be measured, but is subjected to the height
of temperature which a fluid of any kind, gaseous or liquid, undergoes, circulating
in a tube placed in the interior of a furnace, fire-place, or in a liquid, or in melting
metal, of which it is desired to find the temperature.
The fluid in my apparatus serves as a heat conductor; it becomes heated by the
contact of the circulation tube placed in the furnace or interior of which the tem-
perature is to be found. According to the temperature of this heat conductor
marked by any thermometer receiving directly the heated fluid current, or placed
at a distance from this current, is determined the temperature of the furnace. This
determination can be made with the more exactitude, as the fluid current which
heats itself in the furnace has a temperature comparatively low, easily distinguished,
and permitting the employment of apparatus of an excessive sensibility.
In a word, this Invention gives the exact measure of the interior temperature of
a furnace, fire-place, or of all interiors whatsoever, by the employment as an
auxiliary heat conductor of a fluid, gas, or liquid, which becomes heated in the
furnace, and of which the temperature is found by any thermometer. From the
temperature of the fluid is ascertained that of the furnace.
The pyrometer is not only composed of a thermometrical apparatus measuring
the nominal temperature; the essential part consists of a circulation tube of an
auxiliary fluid, and it is the heating of this fluid, which heat is measured by the
thermometer, from which is found the real temperature of the furnace.
The circulation of the auxiliary fluid in the tube placed in the furnace or interior
may be natural, or be forced by an air exhauster or blower, which would be put
into action at the time of operation.
For finding the variations of temperature of the fluid heat conductor, the known
laws of the emission of heat by radiation are applied, that is to say, that this heat
transmits itself in a straight line, and that the intensity of heat emitted varies in
inverse ratio to the square of distances. If therefore a thermometer placed at a
certain distance from the circulation tube of the auxiliary fluid indicates a given
temperature t, if on the other hand in consequence of an overheating of the fluid it
is necessary to take the thermometer to a distance double that of the preceding one
to observe the same degree t, it may be concluded that the final temperature is
quadruple the initial temperature of the fluid.
I do not always conclude from this that the temperature of the furnace has been

page_text: quadrupled, and I will now indicate how according to these considerations, always
bearing in mind the laws of the transmission of heat, I graduate my apparatus.
Any known thermometer may be employed, but I prefer the thermometer of the
system Tremeschini, which is based on the dilatation of a thin plate of metal, of
which one end is kept fixed by a special agency of compensated dilatation bars,
whereas the opposite end causes a needle to move by the intermediation of special
parts, which needle in deplacing itself above an indicating dial gives the indications
of temperature. Suppose (see Figure of the annexed Drawing) a furnace F, the
interior of which it is desired to ascertain the exact temperature; T represents the
tube, in which the auxiliary fluid circulates, and t shows the thermometer, which
we will suppose placed at 1 millemetre for example from the tube T. An opening O
formed on one of the sides permits the interior heat to act on a Melloni pile in
communication with a galvanometer."
If a Melloni pile is placed in connection with a Leslie cube containing hot water
at 100°, the deflection of a galvanometer needle inay be observed, and the distance
from the cube to the thermo-electric pile may be measured. In these conditions it
is only necessary to place the pile p at points aº, a¹, a², and so on, so as always to
observe the same deflection of the galvanometer needle in proportion as the interior
temperature of the furnace is elevated, the distances from the points aº, a¹, a², to
the furnace are then measured, and from this may be concluded, according to the
laws of distances for radiation, the real temperatures of the furnace in its different
conditions. By then observing at the same time the thermometer t, and by
gradually removing it farther from the tube T that it indicates always the same
temperature, the rule will be graduated on which the thermometer displaces itself;
more often the displacment would be operated by means of a pinion actuating a
rack which is carried by the thermometer, the displacement of the pinion in con-
sequence, the separation of the thermometer, and the temperature to which it
corresponds are indicated by the displacement of a needle on an indicating dial.
It is found by experiments that the distances of the thermometer t from the
tube T varies the same ratio as the distances of the thermo-electric pile p to the
furnace F. This new application of the laws of radiation for ascertaining very high
temperatures, which forms part of this Invention, has the advantage of permitting
the employment of the most delicate and sensitive thermometrical apparatus as an
impressionable indicating organ in the formation of the pyrometer. Suppose that
the heat of the conducting fluid; which radiates through the blackened parts of the
conducting tube, corresponding to the impressionable organ of the thermometer,
rises even to 500 or 600 degrees centigrade, it is evident that this organ will not be
subjected to any deterioration in consequence of this enormous temperature, since,
according to my system, this organ is not placed in immediate contact with the
heated part, but is placed at a certain distance which is regulated as I have said,
according to the laws of radiation of heat.
Figure 2 represents the application of the apparatus to measuring the temperature
of the liquid in a boiler, the fluids preferably employed are steam or air. One
single copper tube without solder is bent so as to descend at T, to ascend at T¹,
then to re-descend at T2; at Figure 2, on the transverse section; Figure 3, following
M, N; and on the vertical section Figure 4 of the tubes T1 and T2 is shown what
are the respective positions of these three tubes; they are arranged in a tube T³
closed at its two ends; at the lower part the partition c is arranged above the end
so that the liquid fills the cavity thus formed, even when the level of the exterior
liquid falls, by evaporation that the tubes T and T¹ always plunge equally in the
liquid; observations capable of correct comparison are thus made.
When steam is employed as a heat conductor, the tube T carries a closed funnel
E with a cock allowing the water to fall drop by drop; these drops of water
descend by their weight the length of the tube T, vaporizing and descending into
the vertical part of this tube; the steam forined is heated by the contact of the hot
liquid, it re-ascends in the tube T¹ and acts upon the "Tremeschini" thermometer t,
after which it returns by the tube T2 and issues freely at the lower end of this

page_text: latter, then the steam re-ascends in the enveloping tube T3 and escapes by the upper
chimney d, the tubes T, T¹, and T2, thus remain at a high temperature which
determines the formation of steam in the tube T, and maintains it in this state.
When air is employed as a heat conductor, the tube T is turned in the direction
T4;
the cold air is taken from the cellar or from outside; it follows the tubes T, T',
T2, and T3, and leaves by the chimney d. When air is employed the inclined part
of the tubes T, T¹, T², and T³, may be placed horizontally. The support S permits
the heightening of the apparatus at will, according to the level of the liquid of which
it is desired to find the temperature.
When it is desired to determine the temperature of a furnace, I arrange in its
interior a bent pipe of refractory clay in which the heat-conducting fluid circulates,
and from which it escapes outside.
Figures 5 and 6 show in transverse and longitudinal sections the details of tube T;
it is surrounded by an enveloping tube e, also of refractory clay, which protects it.
Outside the furnace, one of the branches of this tube T is bent vertically to take
the cool air from outside or from the cellar, the other branch is jointed by a
refractory cement to a copper tube which presents a square opening, facing the
thermometer t. This tube is, if necessary, covered with lamp black on the part
directed towards the plate of the thermometer, this latter may also be blackened ;
from thence the tube T enters the chimney.
The pyrometer is represented in detail at Figure 6; it is composed of the Patent
"Tremeschini" thermometer t, and is fastened to a rod f, forming a rack in con-
nection with a pinion g, the axis of which carries a needle handle m which turns
upon d above a divided dial o. The distance dividing the plate of the thermometer
from the tube T is determined, so that this thermometer gives constant indications
whatever the height of temperature; the distances corresponding to the positions 1,
2, 3, 4, of the plate of the thermometer vary as the squares of the temperatures.
Figure 7 represents a variation of the arrangement of the refractory tube which
serves to conduct the heat by radiation. This closed tube T traverses the furnace F;
it is furnished interiorly with diaphragms, the object of which is to intercept the
"incident" rays, and to form a cylinder of caloric rays 7, 1, which at its exit of
the tube T strikes on the thermometer t. The thermometer is removed farther
away, according to the height of temperature in the interior of the furnace; this
removal is measured as before, or else by a rule x.
In the arrangement, Figure 8, I establish in the furnace a tube T, also closed,
enclosing a bar of copper or other metal h. When the temperature is to be
measured this bar is pulled sharply outside; when it passes before the opening k of
the tube T it acts on the thermometer t; the temperature may thus be ascertained
which is often sufficiently approximate.
In order that the thermometer be sensitive, a special command of the axis of the
needle has been devised; this axis carries a double helicoidal groove which com-
mands a fork, which terminates the rod of the lever jointed to the movable end of
the plate of the "Tremeschini" thermometer, as seen at Figure 9. This imperative
command, which suppresses the spiral, gives a precision which is not obtained by the
ordinary means employed for the same object, such as rack and pinion, silk thread,
or chain wound on the axis.
"
And having now described the nature of the said Invention and in what manner
the same is to be performed, I declare that I claim as the herein-before described
Improved Pyrometer or Thermo-electric Indicator,"-
Firstly. The employment (as an organ and integral part of the instrument) of a
suitable fluid, such as air or steam, or in certain cases of a liquid serving as a
conductor or carrier of the heat to be,measured, and acting by circulating in a tube,
one part of which is plunged in the interior of which the temperature is to be
measured, and another part placed in front of the impressionable organ of the
thermometer, so that this latter may directly receive the rays of heat which traverse
the walls of this part of the tube at a convenient distance previously calculated,

page_text: according to the physical laws of the radiation of heat, as herein-before described,
and substantially as shown in the annexed Drawings.
Secondly. I claim as a new application the special employment of the "Tremes-
chini" thermometer constituting one of the organs of my new pyrometer, as
described and substantially as shown.
In witness whereof, I, the said Henry Gardner, have hereunto set my hand
and seal, this Ninth day of January, One thousand eight hundred and
seventy-eight.
HENRY GARDNER. (L.S.)