IMPROVEMENTS IN THE MANUFACTURE OF PNEUMATIC INSTRUMENTS FOR MEASURING TEMPERATURE
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Charles Max Sombart at the Office
of the Commissioners of Patents on the 17th April 1880. A communication
from Friedrich Wiske, of Immendorf, near Wolfenbüttel, in the Empire of
Germany.
CHARLES MAX SOMBART, of the Firm of Buss, Sombart, and Company, Engineers
and Patent Agents, of Magdeburg, in the Empire of Germany. "IMPROVEMENTS IN
THE MANUFACTURE OF PNEUMATIC INSTRUMENTS FOR MEASURING TEMPERATURE."
A communication from Friedrich Wiske, of Iminendorf, near Wolfenbüttel, in the
Empire of Germany.
This Instrument is constructed on the principle of the aneroid barometer a
variable pressure of air of any suitable gas acting against a vacuum by means of
elastic walls or diaphragms, the deviations of which are transferred to a scale.
The Invention consists chiefly in producing the variation of pressure of a constant
quantity of enclosed air (or other suitable gas) by a variation of its temperature,
thus indicating the temperature of the enclosed air (or other gas) by means of its
pressure.
It is preferred to use nitrogen or other chemically indifferent gas in a more or
less diluted state, while the vacuum on the other side removes the influence of the
variable atmospheric pressure. The elastic walls or diaphragms consist of two
equal springs (similar to those used for pressure gauges), which close separately
the two spaces for the vacuum and for the gas, and are placed and connected in
such a manner that the atmospheric pressure on one spring balances the atmospheric
pressure on the other (counter spring.) The springs may be disc shaped, made
of corrugated sheet metal and connected in the centre by a stem which transmits
the motion of the springs upon a lever, which communicates it by any suitable and
known connections or gearing to a pointer moving over a dial. Or the two springs
may be tubes, such as used in Bourdon's pressure gauges, one containing a vacuum,
and the other communicating with a closed vessel containing diluted air or gas.
The alteration of tension produced in the latter spring by a change of temperature,
causes a deviation of the springs, which is transferred to an indicator or pointer by
any suitable means.
In the following cases the construction of the apparatus is somewhat modified.
Instruments designed for use in the open air or as thermometers in rooms are
Imade without the air vessel and its connecting tube

page_text: If a simple gauge spring is substituted for the two counter springs the pointer
with its mechanism must be placed in a hermetically closed casing provided with a
strong glass as cover.
An aneroid barometer may advantageously be connected with the pneumatic
thermometer above described in the following manner :-
If the thermometer is constructed with disc springs an elastic plate may be
substituted for the fixed bottom of the vacuum box, and connected with the hand
of the barometer. With Bourdon springs a separate barometer spring has to be
applied.
A separate steel spring for the assistance of the closing springs may also be used
in the pneumatic thermometer.
The motion of the transmitting lever (connected with the central stem of the
disc springs or with the Bourdon tubes) may be made to actuato a registering
apparatus (for instance Hipp's), so as to obtain a registering thermometer.