Year: 1886

page_text: I, JOHN ELISHA WHITE, gentleman residing at Syracuse, in the County of
Onondaga, State of New York, one of the United States of America, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
This invention has relation to Alarm Thermometers, and has special reference to
that class of the same which comprises a thermometric tube provided with a body
of mercury and with the terminals of an electric circuit which are normally
arranged separate from each other and which are thrown into electrical connection
with each other by the contact therewith of a portion of the mercury within the
tube, the closing of said connection, that is the completion of the circuit, being
caused by an increase of the temperature of the mercury.
The object of the invention is to produce an Alarm Thermometer of the class
mentioned which shall be sensitive, reliable and accurate in its operation and
which shall be of such construction that no corrosion or other disadvantageous
action of the mercury upon the wires of the circuit can occur by reason of the
contact therewith of the mercury when not in the act of closing the circuit.
Referring to the drawings:-
Figure, 1, is a front elevation; and,
Figure, 2, a central vertical section of an Alarm Thermometer constructed in
accordance with my invention.
Figure, 3, is a like section of a modification; and,
Figure, 4, is a detail in plan.
Like letters of reference indicate like parts in all the figures of the drawing.
A represents a tube of glass, terminating at one end in an elongated or other
shaped bulb, A¹, and at the opposite end in an exterior annular lip, A. At the
lower end of the straight portion, A³, of the bore of the tube said bore is gradually
expanded, preferably in a symetrical cone-shaped manner, as at A+, to form the
chamber, As for the mercury, B,
This chamber is expanded laterally so that the walls thereof are comparatively
thin in order that the mercury contained therein may be largely exposed and
sensitive to, changes in temperature. The upper end of the bore, A³, of the tube
is expanded into the form of an inverted cone A6

page_text: The terminals, C, C¹, one being positive and the other negative, of an electric
circuit, are arranged within the cone, Aº, and preferably they may rest upon the
end surface of said cone and project toward each other though not in contact at
the apex of said cone.
For the purpose of a clear understanding of the arrangement of the terminals,
they are shown as separate from and not in contact with the inner surface of the
cone, but when arranged in contact with said surface they are supported and are
less liable to be brought into contact with each other by sudden jars or otherwise
than when arranged independently of said surface as shown.
By reason of the extremely slight calibre of the terminals C, C³, which are
preferably of platinum, the insertion of the same within the cone and with due
relation to each other is facilitated by passing them along the inner surface of the
cone, but as before stated, for the purpose of illustration, they are not shown in
such position.
To maintain the terminals in a desired position, I may fill a portion of the
cone, A, with any desired device, material or cement, the terminals passing
therethrough, or I may first insert a cork, D, through which the terminals pass and
I may or may not facilitate the insertion of the terminals through the cork by
forming slits, D¹, in opposite sides thereof and then forcing the cork into the open
end of the tube, thus closing it hermetically.
Such closure of the tube. may be further secured by the application of any
desired cement or plastic, E, which to give further security, may extend over so as
to embrace, cover, and include the lip, A³, of the tube, or as is customary in electric
glass-appliances, the terminals may be inclosed or imbedded in the glass of the
tube itself by melting the same and compressing it into a desired form. A further
modification is illustrated in figure, 3, wherein the terminals, C, C¹, are passed
directly through the walls of the upper cone of the tube the same being extended
to form a mouth which, in this instance, is closed by any suitable plug or cement.
This form is also fully adapted to the method of hermetically sealing the upper
end of the tube by fusing the glass and compressing it for that purpose.
F, indicates the gradeomark of the Alarm Thermometer. Heretofore, mercurial
thermostats have been constructed with one terminal of the circuit arranged at the
-lower end of the tube, passing through the glass thereof and into the body of the
mercury therein, and the other terminal has been inserted above the mercury,
either directly into the bore of the tube or through the walls thereof into said borę.
This construction is accompanied with the constant action of the mercury upon the
terminal immersed therein, which in time corrodes the terminal following the metal
thereof into and possibly through the aperture in the tube through which it passes,
thereby producing in Alarm Thermometers which have been a long time in use
a leakage of the mercury therefrom, whereby a greater degree of heat than that
originally required to cause the mercury to expand a sufficient distance to close the
"circuit is demanded.
Furthermore, this construction subjects the glass at the point of entrance of the
terminal to expansion and contraction by reason of the changes of temperature to
which it is subjected, and in this manner the glass either becomes cracked or a leak
is formed and a loss of mercury results, whereby the instrument is rendered
imperfect, unreliable, as well as in time inoperative. Now by experiment, the
quantity of mercury, the size and length of the bore, and the position of the ends
of the terminals in the cone, may be regulated so that a predetermined degree of
heat is rendered essential to produce the desired operation of the mercury.
For example, the tube, A, with a quantity of mercury therein is subjected to
a heat of one hundred and twenty degrees, when the mercury will rise in the
tube up to the point, "F," where an indicating mark is placed upon the tube,
as shown.
The terminals are inserted in the cork so that they will reach below the
point, "F" The cork is firmly set and each of the terminals is drawn upwardly
until they coincide with the mark. “F.” when they are sealed in that position,

page_text: I thus produce an Alarm Thermometer which requires one hundred and twenty
degrees of heat to operate it.
By connecting the terminals of one or of a series of such Alarm Thermometers
arranged at suitable places within several compartments of a building with an
electrical conductor suitably arranged in said building and connected with an
alarm, a rise of temperature in any of said compartments to one hundred and
twenty degrees will cause said alarm to be sounded.
In this manner the Alarm Thermometer is applied for detecting the presence of
fire or other abnormal heat. This capability of indicating a rise of temperature
renders the Alarm Thermometer capable of use in many arts; for example, they
may be used in detecting a rise of temperature in cellars or other store-rooms for
beer where it is desired to maintain a uniform temperature which rising to a point
to sound the alarm can be regulated at once by the person in charge of the same.
They may also be applied to bearings of machinery to indicate the heating of
journals, and for indicating changes in temperature in the bodies of persons under
medical treatment and otherwise.
I am aware that attempts have been made to utilize the expansion of mercury
to close electrical circuits in Alarm Thermometers wherein both terminals have been
conducted into the open mouth of the vessel having mercury therein, but in such
cases the body of mercury has been disproportionate to the object in view, in that
an excessive degree of heat was required to expand the same without diminution
of the area of the upper surface to cause it to come into contact with and connect
the terminals.
In my improvement I may employ a relatively large body of mercury, but by
the cone, A, I restrict to a marked degree, the area of its upper surface to that of
the relatively slight diameter of the bore, A³, whereby not only a less degree
of heat is required to cause the mercury to ascend a desired distance but greater
sensitiveness as well as greater accuracy is secured in the operation of the Alarm
Thermometer as a whole.
Furthermore, in passing the terminals freely in the open end of the tube, as
heretofore, the action of the air, and in manufacturing establishments, the action
of gasses and other chemical properties commingled with the air, oxidizes and
otherwise renders impure the mercury, so that by hermetically sealing the upper
end of the tube I obviate this disadvantage.
I have demonstrated by actual experiment and use the accuracy and sensitiveness
of the Alarm Thermometer herein shown, and I attribute the same to the peculiar
form, proportion and construction herein before described.
It is not essential in any degree to the accomplishment of my purpose that the
upper enlarged chamber of the bore should be in the form of an inverted cone, as
any enlargement which will give room for the terminals will suffice.
I may also duplicate the circuit and terminals if desired, that is, have four or
more instead of two terminals.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
•
1. An Alarm Thermometer comprising a tube having a central bore terminating
below in a mercury bulb and above in an enlarged chamber in which are arranged
out of contact with each other the terminals of an electric circuit, the upper surface
of the mercury reaching normally a point below said enlarged chamber substantially
as specified.
2. An Alarm Thermometer comprising a tube, the lower end of the bore of which
is extended to form a bulb and the upper end of which is gradually expanded to
form an inverted cone, in combination with terminals hermetically arranged
separately in the upper cone from which the mercury is separated by a reduced bore
of the tube, substantially as specified.

page_text: 3. An Alarm Thermometer comprising a tube the bore of which is expanded to
form a bulb, a grade-mark at a point on the tube to which the mercury therein
rises at a certain temperature, and terminals arranged in the upper end of the tube
and projected to said point, substantially as specified.
4. The combination of the tube, A, having the bore, A³, the cone shaped
symetrical enlargement thereof, A, the mercury bulb A", and the inverted conc, A6,
with the terminals, C, C¹, arranged within said cone, A6, and means for her-
metically sealing said terminals in the tube, the mercury being separated by the
reduced bore from the enlargement, A*, substantially as specified.