IMPROVEMENTS IN APPARATUS FOR INDICATING TEMPERATURE OR PRESSURE
Year: 1885

page_text: Iressure.
I, JAMES MURRIE, of 206 Gallowgate, Glasgow, in the County of Lanark,
North Britain, Engineer, do hereby declare the nature of my said invention for
IMPROVEMENTS IN APPARATUS FOR INDICATING TEMPERATURE OR PRESSURE to
be as follows, that is to say :—
"
"
My said Invention has for its object to improve the construction of apparatus
for indicating temperature or pressure, and more especially apparatus of the kind
described in my patent specifications Nos 9393, and 15947 of 1884.
In apparatus of the kind referred to mercury or another liquid either alone or
together with one or more compressible or elastic fluids is entirely enclosed in
a tube or in a tube combined with one or more bulbs or enlargements, and the heat
to be indicated or measured is applied at or near one end of the tube so as to heat
the mercury or liquid at that end, the indication or measurement being derived
from the movement of the other end of the mercury or liquid due to expansion
but under conditions differing from those obtaining in ordinary thermometers.
A thermometer of the kind referred to when made with mercury is designed for
indicating high temperatures above the point at which mercury boils under
atmospheric pressure, the boiling point being raised, however, in the thermometer
in consequence of the opposing pressure which increases with the temperature.
With the heat and pressure which are under such circumstances in action on the
lower end of the column of mercury, the shell of the bulb or tube containing the
mercury is liable to have its shape altered which would render the indications
shown by the top of the mercury quite inaccurate. One of my present improve-
ments has for its object to meet this difficulty and consists in enclosing the lower
part or if preferred the whole of the thermometer in an outer casing forming
a jacket space in which mercury or a liquid of the kind in the thermometer is
placed, this jacket space being closed so that when heat is applied the same or
nearly the same pressure will be generated in the jacket space as the pressure
acting inside the thermometer itself. The pressure inside the bulb or thermometer
being thus balanced or nearly so will not produce alteration of shape, whilst any
alteration of the shape of the outside casing will not affect the indications of the
enclosed thermometer itself.

page_text: A second improvement relates to the compressible or elastic fluid which in some
modifications of my thermometers is applied at a distance from the point of
application of the heat to oppose the expansion of the mercury or other liquid;
and it consists in causing such fluid to have a greater than atmospheric pressure at
ordinary temperatures by being forced in by a pump or by being acted on by
a column of mercury, the object being to allow of the indication of a greater range
of temperature within a given length of scale. In the outer jacket space to be
used according to the first improvement a similar initial excess of pressure may be
produced by a column of mercury or in any other suitable manner.
The indications shown by my improved thermometers correspond exactly to
pressures generated by the heating of the mercury or liquid and may be read
as indications of such pressures. It therefore follows that the apparatus may be
used for indicating pressures which may not necessarily be directly generated by
heat, all that is necessary for this purpose being to cause the fluid the pressure of
which it is wished to indicate to act through a pipe on the mercury or liquid in the
indicating apparatus.
EDMUND HUNT,
Applicant's Agent.

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Indicating Temperature or
Pressure.
JAMES MURRIE, 206 Gallowgate Street, Glasgow Lanarkshire, North Britain,
Engineer do hereby declare the nature of my invention for IMPROVEMENTS IN
APPARATUS FOR INDICATING TEMPERATURE OR PRESSURE and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :—
My said Invention has for its object to improve the construction of apparatus
for indicating temperature or pressure, and more especially apparatus of the kind
described in my patent Specifications N° 9393 and 15947 of 1884.
In apparatus of the kind referred to mercury or another liquid either alone or
together with one or more compressible or elastic fluids is entirely enclosed in
a tube or in a tube combined with one or more bulbs or enlargements, and the heat
to be indicated is applied at or near one end of the tube so as to heat the mercury
or liquid at that end, the indication or measurement being derived from the
movement of the other end of the mercury or liquid due to expansion but under
conditions differing from those obtaining in ordinary thermometers.
A Thermometer of the kind referred to when made with mercury is designed
for indicating high temperatures above the point at which mercury boils under
atmospheric pressure, the boiling point being raised, however in consequence of the
opposing pressure which increases with the temperature. With the heat and
pressure which are under such circumstances in action on the lower end of the
column of mercury, the shell of the bulb or tube containing the mercury is liable
to have its shape altered which would render the indications shown by the top of
the mercury quite inaccurate. One of my present improvements has for its object
to meet this difficulty and consists in enclosing the lower part or if preferred the
whole of the thermometer in an outer casing forming a jacket space in which
mercury or a liquid of the kind in the thermometer is placed, this jacket space
being closed so that when heat is applied the same or nearly the same pressure
will be generated in the jacket space as the pressure acting inside the thermometer
itself The pressure inside the bulb or thermometer being thus balanced or nearly
so will not produce alteration of shape, whilst any alteration of the shape of the
outside casing will not affect the indications of the enclosed thermometer itself.
A second improvement relates to the compressible or elastic fluid which in some
modifications of my thermometers is applied at a distance from the point of
application of the heat to oppose the expansion of the mercury or other liquid;
and it consists in causing such fluid to have a greater than atmospheric pressure at
ordinary temperatures by being forced in by a pump or by being acted on by
a column of mercury, the object being to allow of the indication of a greater range
of temperature within a given length of scale. In the outer jacket space to be
used according to the first improvement a similar initial excess of pressure may be
produced by a column of mercury or in any other suitable manner.

page_text: The indications shewn by my improved thermometers correspond exactly to
pressures generated by the heating of the mercury or liquid and may be read as
indications of such pressures. It therefore follows that the apparatus may be used
for indicating pressures which may not necessarily be directly generated by heat,
all that is necessary for this purpose being to cause the fluid the pressure of which
it is wished to indicate to act thro' a pipe on the mercury or liquid in the indicating
apparatus.
In order that my present improvement or improvements of the aforesaid
apparatus may be understood and readily carried into effect, I will describe the
drawing hereinto annexed.
Figs. 1 and 2. Illustrates the method of adapting the jacket to the different
modifications of the aforesaid thermometers more particularly described in Patent
Specification N° 159478.
"
Fig. 3 Illustrates an application of the jacket to another modification of the
apparatus, wherein the thermometer proper is entirely enveloped by the casing.
In Fig. 1. The thermometer is constructed substantially as described in patent
Specification N° 1594784. A," represents the expansion chamber or end of the
tube containing the fluid or fluids: "B" the connecting tube; "C" the transparent
part of the tube which contains the elastic fluid. D," represents the jacket,
which in this case consists of a casing made of steel or other suitable material,
which resists oxydation and is chemically neutral to the enclosed fluid, "E" repre-
sents the cap for charging the annular space with the fluid.
«
*
In Fig. 2. The instrument is substantially constructed in the same manner as
the form of apparatus described under Fig. 1. "A," represents the bulb or
expansion chamber, shewn of a more elongated form in this case, B," the con-
necting tube. "C," the improved form of pressure gauge described in my patent
Specification N° 166218. "D" the jacket, made correspondingly elongated to
envelope the expansion chamber "A."
"
In Fig. 3. The instrument is shewn made of glass, completely enveloped in an
outer jacket, also of glass. A," represents the expansion chamber," "B," the
connecting tube "C," the end of the tube containing the elastic fluid, "D" the
jacket.
This form of instrument may also be made in the same form as shewn in the
Figs. 1 and 2. With the jacket partially made of metal in combination with
glass. The glass being connected to the metal by the ordinary method adopted in
gauge glasses, the joint being sufficiently clear of the expansion chamber & of the
graduations on the scale, whether the inner tube be marked or an outside scale be
attached in the manner previously described. In either case this form of apparatus
is limited in its readings, the maximum scale being about 900° Fahr.
In the aforesaid apparatus the inner bulb is charged with mercury or other
liquid or liquids, depending on the temperature which it is desired to register,
which fluid or fluids is in direct communication with the elastic fluid or pressure
indicator at the opposite end of the tube, substantially as described in my aforesaid
patents. The jacket space between the inner bulb and the casing is likewise
charged with a fluid of the same kind as that placed in the bulb or chamber A.
care being taken that sufficient space exists in both cases to allow vapour to be
generated simultaneously or nearly so, with the object of obtaining corresponding
pressures as uniformly as practicable. On taking measurements of temperature,
the bulb with its jacket is exposed to the action of the heat, the fluid in the
annular space necessarily becomes heated and generates a pressure, said pressure
depending on the nature of the fluid and the temperature. The fluid in the inner
bulb likewise becomes heated to a corresponding or nearly corresponding tempe-
rature as that in the annular space, and the two fluids being of a like nature,
a corresponding pressure is generated in the inner chamber, which pressure is
transmitted throughout the whole interior of the apparatus, the opposing force,
being the elastic fluid at the opposite end of the instrument, which is practically

page_text: a gauge for measuring pressure, and in consequence such pressure may be indicated
by any known form of pressure indicator.
The inner bulb or end of the apparatus exposed to the action of the heat, which
forms part of the thermometer proper, is thus entirely free from any tendency to
distortion, or liability to be destroyed, so long as the aforesaid jacket remains
intact, or so long as any liquid, when a liquid is employed, remains in the jacket
space.
In addition to preventing distortion of the inner bulb, the jacket serves as a
means of preventing leakage in the inner vessel, more particularly when the
enclosed fluid is partly or wholly gaseous.
By means of the aforesaid jacket, the apparatus described in my aforesaid
patents, can be employed to indicate temperatures continuously for a comparatively
long period, without becoming inaccurate through the liquid leaking, or the part
exposed to the heat being partially destroyed.
The aforesaid apparatus practically is a pressure generator combined with a
pressure indicator, and it follows that to measure pressures not necessarily generated
by heat direct, it is only necessary to connect the outside pressure apparatus with
any part of the aforesaid apparatus, in such a way that the fluids are placed in
communication with one another, the pressure being indicated by the gauge.
The second Improvement described in my provisional specification is essentially
a modification of the apparatus, wherein the aforesaid jacket is the.main element,
and which has been sufficiently described in the preceding description.
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 a thermometer or apparatus for indicating temperatures, wherein a fluid or
fluids is enclosed in a tube or tubes, the use of an outer jacket, having a corre-
sponding fluid or fluids in the jacket space, for the purpose of preserving the inner
tube or tubes from distortion and preventing leakage of the contents, through the
pressure in the jacket space corresponding or nearly so to the pressure in the
inner chamber or chambers, substantially as herein before described.
DL: out 1
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