Improvements in Apparatus for Indicating Temperature or Pressure.
Year: 1886

page_text: _Date of Application, 3rd Mar., 1886.
Complete Left, 3rd Dec., 1886.
Complete Accepted, 25th Jan., 1887.
Improvements in Apparatus for Indicating Temperature or
Pressure.
JAMES MURRIE, 206 Gallowgate Street, Glasgow, Lanarkshire, North Britain
Engineer, do hereby declare the nature of this invention to be as follows:-
My present invention is a further development of the apparatus for indicating
temperature or pressure described in my complete specification No. 30385.
In the aforesaid apparatus for indicating temperature of confined fluids, more par-
ticularly when the temperature is comparatively low, and the confined liquid of
comparative great volatility, said liquid has a tendency to boil or vapourize between
the expansion chamber and the indicator, and in consequence has a tendency to affect
the accuracy of the indications.
To obviate this an initial pressure is made to act on the confined liquid which it is
desired to maintain in a liquid condition. This is most easily effected by having the
expansion chamber placed at a greater elevation than the indicator, or, by having a
vertical column containing a liquid, which is in communication with the aforesaid
apparatus acting on the liquid in an analogous manner to the liquid in the ascending
column leading to the expansion chamber.
.
My second improvement relates more particularly to the mode of obtaining a fixed
zero or starting point in the pressure indicator, and enabling indications of tem-
perature or pressure being obtained under varying conditions of exterior pressures.
In an ordinary pressure indicator, such as the Bourdon type, the starting point of the
instrument is the atmospheric pressure, which in the aforesaid apparatus tends to
make the instruments less sensitive and less accurate than would be the case were the
indicators made to start from absolute zero, that is a perfect vaccuum, or from a point
which was practically constant. Besides the application of the apparatus is limited
to conditions where the external pressure is that of the atmosphere at or close to the
7

page_text: earth's surface. The apparatus being more or less inapplicable to taking indications
of temperature or pressure at comparatively great heights, where the external pressure
is less than that existing at the earth's surface: or, when enveloped in a fluid where
the pressur is greater, more or less, than the atmospheric pressure, as for instance
in taking indications of pressure or temperature in cisterns, ponds or other bodies
of water, where it is an object to obtain indications of depth, and surrounding
temperature.
My second improvement therefore consists in protecting the pressure indicator from
varying conditions of exterior pressures, and in having as near as practicable a con-
stant exterior pressure acting on the pressure indicator proper, and when desired
freeing the indicator entirely from external pressure. This is effected by enveloping
the main parts of the indicator in a casing, which casing is either hermetically sealed,
or constructed in such a fashion, that it can be made air or water tight when desired.
The joint between the casing and the neck of the indicator, or part of the indicator
which usually serves as the mode or means of connecting the pressure gauge to the
generator or source of pressure,-being made in any known manner. The interior
of the coil or curved tube in the gauge being in communication with the fluids in the
expansion chamber; or, with the exterior fluids, in the usual manner.
The casing or envelope in which the indicator is placed may be completely exhausted
of air or fluids of any kind, more particularly when the apparatus is employed to
indicate comparative low pressure; or, may be wholly or partially filled with a fluid
when the external pressure to be measured is comparatively great. Care being taken
that the exterior pressure, which in this case represents or is the pressure tending to
burst the casing, remains constant or nearly so. The casing or envelope may be
provided with pet cocks, set pins, or other contrivance to permit the confined fluids
being increased or decreased. The casing may also be provided temporarily or per-
manently with an exhausting apparatus of any known design. Instead of the type
of gauge known as the Bourdon being employed, any known form of pressure
indicator may be adapted to work in an analogous manner to the foregoing. The
indicators may or may not be provided with maximum or minimum indicators, the
pointers being re-set by any known method. The aforesaid casing may also be
provided with attachments, when employed in taking indications of pressure or
temperature at greater or less distances from the operator. In taking indications of
temperature or pressure simultaneously at points inaccessible to the operator, two
indicators are combined or connected to the main apparatus, one of the indicators
being employed to record the pressure of the surrounding fluid, and the other to
record the temperature, thro' being in communication with a confined fluid such as
ammonia or analogous fluid as described in the aforesaid complete specification
No. 30385. The expansion chamber jacket being in this case unnecessary.
My third improvement relates more particularly to the mode of setting, or in other
words, regulating the volume of the confined fluid or fluids in the aforesaid apparatus
for indicating temperature. To effect this an air space may or may not be left
between the fluid in the connecting tube and the indicator, which confined air may
be brought in contact with the atmosphere when desired by means of a pet cock, set
pin, or by temporarily unscrewing the indicator from the connecting tube. Instead
of atmospheric air being employed, any desired fluid may be used instead.
My fourth improvement relates more particularly to apparatus for indicating tem-
perature of the atmosphere, where it is desired to ascertain the atmospheric temperature
with great accuracy and at same time the pressure of the atmosphere. The aforesaid
apparatus for indicating temperature may have combined with it any other known
form of thermometer, such as the common glass mercurial instrument, also any known
forin of barometer may be placed on a common stand. A time indicator may or may
not be set in the same frame.
My fifth improvement relates to the construction of the apparatus where a wider
range of readings is desired than can be conveniently shewn on one dial, either thro'
the expansion of the liquid being too limited to be shown on one dial, or thro' the

page_text: readings being too indistinct. The aforesaid apparatus may therefore have two
indicators with a common or independent expansion chambers as desired.
My sixth improvement relates to cases where the apparatus may be employed to
indicate rise of temperature in vessels, rooms or ovens, where it is necessary to have
indications of rise of temperature in any of the spaces without necessarily having an
indicator for each expansion chamber. The aforesaid apparatus may therefore have
leading from a common connecting tube any desired number of branch tubes leading
to expansion chambers placed at any desired point, the temperature shewn on the
indicator being the maximum temperature in any one of the apartments or spaces.

page_text: JAMES MURRIE, 45 West Nile Street Glasgow N. B. Engineer 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 :-
My Invention consists essentially in improvements in apparatus for indicating
temperature or pressure more particularly apparatus of the kind wherein a fluid or
fluids is confined in a hollow tube or clongated chamber, one end being sealed by a cap
or other contrivance and the other end of the tube sealed by a pressure indicator, one
extremity of the apparatus serving as an expansion chamber in which the confined fluid
on being heated expands or vapourizes and the other end serves to connect to the in-
dicator, which indicates the temperature or pressure of the fluid in said expansion
chamber, the pressure being transmitted from the expansion chamber to the indicator
by means of the liquid or fluid confined in the intermediate part of the tube or
elongated chamber. In order that the improvements referred to be readily understood
these will be explained and described by reference to the figures illustrating each.
Fig. 1. Illustrates one of the improvements wherein the intermediate fluid, such as
water or analogous fluid of comparative great volatility is prevented from vapourising
or boiling by being subjected to an initial pressure.
A Represents the expansion chamber in which the fluid which is subjected to the
action of the heat is confined. B represents the connecting tube intermediate to the
expansion chamber A and the indicator, placed vertically or nearly vertical, so that the
pressure gradually increases from the expansion chamber A. Crepresents the indicator
for registering the temperature or pressure of the fluid in the expansion chamber.
It is not essential that the apparatus be placed in a vertical position as shewn in
the Fig. The result may be obtained by placing the connecting tube at an angle,
with the expansion chamber at a higher elevation than the indicator, or at a higher
elevation than the point where the connecting tube B is isolated from, or is not
subjected to the action of the heated fluid in which the expansion chamber A is
enveloped.
Fig. 2. Illustrates the apparatus wherein the pressure indicator has a fixed starting
point or zero point, wherein the indicator coil or elastic membrane is freed from all
external pressure by being enveloped in a complete or partial vacuum. D represents
the coil or hollow bent tube, which changes or tends to change its position on being
subjected to variations in pressure. E, the mechanism set in motion by the coil D.
"F" the maximum and minimum indicators which register the extreme variations of
pressure. G represents the exterior casing or shell which serves to protect the internal
mechanism and at same time prevents the atmosphere or surrounding liquid or
fluid from acting on the exterior part of the coil referred to or machanism. H repre-
sents the connection for exhausting apparatus. I the connections for a line or wire
when the apparatus is employed to take observations of pressure at a distance from
the operator. K the connection between the bent tube D and the casing G.
The interior of the casing G being isolated from or free from any fluid which varies
on being subjected to variations in temperature or pressure, it follows that the starting
point constant, without taking into consideration the pressure of the surrounding
Huid, or the temperature of the surrounding atmosphere, which otherwise serves to
conduct the heat to the internal mechanism.

page_text: Fig. 3. Illustrates the improved apparatus wherein readings can be taken of the
temperature or pressure of the surrounding fluid-simultaneously the arrangement
essentially consists in the combination of a pressure gauge having the internal curved
tube or elastic diaphragm isolated from the surrounding fluid as explained under
Fig. 2. with a temperature indicating apparatus wherein the indicator of said apparatus
is likewise protected from the action of the surrounding fluid. A represents the expan-
sion chamber in which aminonia, Ether or other volatile fluid is confined.
fluid.
represents the pressure indicator which registers the pressure of the surrounding
The remaining letters correspond to the apparatus hereinbefore described
under Fig. 2.
Fig. 4. Illustrates the improved arrangement for regulating the contents of the
temperature indicating apparatus hereinbefore described. M represents the cup, plug,
pet cock, or like contrivance which serves either to allow part of the contents to escape
or to permit fresh fluid or fluids to enter.
Fig. 5. Illustrates the combination of one form of the apparatus for indicating
tomperature hereinbefore described with a chronometer, barometer, or glass mercurial
thermometer of the ordinary description.
Fig. 6. Illustrates an arrangement wherein two indicators are employed to register
the temperature in the expansion chamber fig. A or chambers when two chambers are
employed.
Fig. 7. Illustrates one modification of the apparatus for indicating temperature or
pressure wherein two or more expansion chambers are employed, the indicator C
registering the maximum temperature existing throughout the chambers A.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I declare that what I claim is
1. In an instrument for indicating temperature wherein said indications are obtained
by subjecting a confined liquid such as water or analogous fluid to the action of the
heat, and wherein the expansive action of said confined fluid is measured by a
pressure indicator, the prevention of boiling or vapourization of the liquid inter-
mediate to the vapour and the indicator by creating an initial pressure on said liquid,
cither by elevating the expansion chamber above the indicator or by elevating the
vapour space above the intermediate liquid which is subjected to the action of
the beat.
2. In a pressure indicator of any known form or design the obtaining a fixed zero
or starting point irrespective or independent of external pressures by placing the
elastic part of the gauge-i.e. the part which changes its position on being subjected
to variations in pressure in a fluid tight chamber or casing partially or wholly
exhausted of atmospheric air or other fluid, substantially as hereinbefore described.
3. The combination of a pressure indicator of any known form or design with a
temperature indicating apparatus, the indicators being with or without the Huid tight
shield substantially as hereinbefore described.
4. The cap, plug, or other contrivance on the connecting tube of the temperature
indicating apparatus for regulating the volume of the confined fluids substantially as
hereinbefore described.
5. The combination of the temperature indicating apparatus of the kind herein-
before described with a timepiece or barometer of any known form or design.
6. In apparatus for indicating temperature of the kind hereinbefore described, the
double indicators for showing the pressure in the expansion chamber.
7. In apparatus for indicating temperature or pressure of the kind hereinbefore
described the employment of two or more separate expansion chambers leading to a
common indicator.
JAMES MURKIE.