Improvements in Electric Contact- and Alarm-thermometers,
Year: 1889

page_text: Date of Application, 14th Feb., 1889
Specification Accepted, 130th Mar., 1889
Improvements in Electric Contact- and Alarm-thermometers,
We, MAX HUHL, JOSEPH MATHIAS LANTENSCHLÄGER, and FRANZ LANTEN-
SCHLÄGER, of 35 Gneisenau Strasse Berlin, in the Empire of Germany, Manufacturers,
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 relates to an improved contact-thermometer with air-exhausted
closed capillary tube for scientific and other use, and has for its purpose to allow any
previously fixed degree of temperature to be indicated by an electric alarm device and
to remove at the same time the various drawbacks inherent on similar apparatus
heretofore employed.
The contact-thermometers with closed capillary tube hitherto known are adapted to
indicate but one certain point of the latter, where a platinum wire is melted in, their
applicability being consequently very limited, while those having a capillary tube
open at the top, although adjustable for any. suitable degree by displacing the platinum
contact wire by hand or mechanically, lack the exactness-particularly essential for
scientific purposes of closed thermometers.
Moreover, in open thermometers, the formation of oxides covering the surface of
the mercury with a layer of no, or deficient, electric conductivity is inevitable, not to
speak of the uncertainty of contact and consequent disturbances, caused by the
admission of particles of dust and by the requisite displacements of the upper platinum
wire.
The above inconveniences are entirely obviated in the improved thermometer,
illustrated by the accompanying drawing, which has a completely closed air-exhausted
capillary tube and is nevertheless adapted to be adjusted to any degree of temperature,
even to fractions of the tenth part of a degree.
For this purpose, a solid projection or obstacle a is so provided within the capillary
tube below the scale as to leave on one side a capillary passage for the mercury.
Said obstacle may be of any convenient material, but suitably consists of a thin glass
pin melted together with the side of the capillary tube. Or the latter may be bent
inward on one side or otherwise narrowed to produce the said internal projection.
D
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page_text: The outer
Closely below the obstacle a, a platinum wire is melted into the capillary tube
while another platinum wire c is provided in a like manner in the bulb.
extremities of said platinum wires are adapted to be connected with the conducting
wires of an electric bell or alarm, one of the conducting wires being suitably arranged
between the inner and outer glass tube of the thermometer.
The improved thermometer is operated and works as follows:
To cause a certain temperature, for instance 47 degrees, as illustrated in the
drawing, to be indicated by the electric alarm, the bulb of the thermometer is heated
over any suitable flame or otherwise until the mercurial column has reached the
respective degree on the scale. The thermometer being subsequently allowed to
cool, the mercurial column is divided by the obstacle a, and its lower portion recedes
past the contact 6 into the bulb, while the upper column remains over the obstacle a.
The thermometer, being thus adjusted, is placed into the operating room and
connected with the electric alarm. As soon as the previously fixed degree of
temperature is attained, the lower portion of the mercurial column comes in contact
with the platinum wire b, thereby engaging the current and actuating the alarm. It
is understood, that the small free space left within the capillary tube between the
obstacle a and the contact wire 6, is to be compensated by a corresponding preliminary
connection of the scale.
To use the improved thermometer again for a higher temperature, the bulb is
merely heated over a flame or otherwise, till the mercurial column has reached the
requisite degree on the scale. If however a lower temperature than previously is to
be indicated, the upper mercurial column, prior to performing the above described
process, is joined to the lower portion by means of a shaking or rocking movement
similar to that applied to maximum thermometers.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, we declare, that what
we claim, is:
In electric contact and alarm-thermometers, the application of a solid projection or
obstacle a provided below the scale within the capillary tube, in combination with
contact wires b and c, melted below a into the capillary tube and bulb respectively,
substantially as and for the purpose set forth.
Dated this Fourteenth day of February 1889.
HUELSER & Co.,
Agents to Applicants.