Improvements in the Methods of Transmitting the Indications of Thermometers and other Instruments.
Year: 1888

page_text: Date of Application, 30th May, 1888
Complete Specification Left, 13th Nov., 1888
Complete Specification Accepted, 14th Dec., 1888
Improvements in the Methods of Transmitting the Indications of
Thermometers and other Instruments.
I ALEXANDER PELHAM TROTTER, Civil Engineer 2 Victoria Mansions Westminster
in the County of Middlesex do hereby declare the nature of this invention to be as
follows:-
My invention relates to that class of instruments in which the indications are
transmitted by the motion of a fluid in a tube, or by the tension of a wire, or by
similar mechanical means. Such instruments may be considered as consisting of
three parts, firstly the transmitting part which is affected by the conditions which it is
desired to indicate or measure; such as the bulb of a thermometer; secondly the
intervening part which conveys the indications, such as the tube connecting the bulb
of a thermometer with the graduated portion; and thirdly, the indicating part, such
as the graduated portion of a thermometer. Where.for example it is desired to
indicate the temperature of a refrigerated chamber on a scale or dial in the engine
room, near the refrigerating machinery, or the temperature of a malting house, or of
a wine cellar on a scale in the office of the superintendent, the tube connecting
the bulb with the graduated portion is liable to be exposed to various temperatures.
The purpose of this invention is to prevent these various temperatures from
producing any error in the readings of the scale.
In carrying out my invention in its application to thermometers, 1 use as a "bulb":
a vessel of considerable size, say 10 to 20 cubic inches in volume, so that the expansion
produced by a rise of temperature of the fluid contained in the said vessel may be
considerable compared with the variations which may take place by alterations of the
temperature at any part of the intervening tube. I connect the said vessel with the
scale end of the thermometer by means of a tube of fine bore, say one tenth or one
twentieth of an inch in diameter. At the scale end I attach to the tube of fine bore
a tube preferably of glass, of an internal diameter such that the motion of the free
surface of the fluid may be of convenient amplitude.
In order to prevent
evaporation of the fluid, I prefer to make the tube of a U shape, and fill it partly
with mercury.
The surface of the mercury may be used for reading against the
scale.

page_text: This combination of vessel, intervening tube, and U tube, I call the thermometer
proper.
I carry a precisely similar tube of fine bore alongside the said intervening tube, and
make them both of the same length. This second tube is merely closed at the end
distant from the scale, and is not connected to any "bulb." At the scale end, this
second tube is terminated in a manner exactly the same as the thermometer proper,
preferably by a U tube containing mercury.
This combination of a tube of fine bore, and a U tube I call the compensating
tube.
The variations of the surface of the liquid in the compensating tube will clearly be
due to those variations of temperature whose disturbing influence it is desired to
avoid.
The simplest way of making use of the compensation is to take the surface of the
mercury in the U tube of the compensating tube as a point to which a mark on
the scale of the thermometer proper is to be set, before taking a reading. The
scale is arranged to slide up and down, and may be provided with a rack and
pinion.
In another method I use a float in the compensating tube, and attach the scale to
this float, thus making the motion of the scale automatic.
In a third method, I fill the compensating tube with a liquid differing from that in
the thermometer proper, and 1 provide floats in both tubes, and attach an index
or pointer to the floats in such a manner that a differential motion is produced by
the expansion and contraction of the liquids so far as it takes place in the tubes of fine
bore.
When it is desired that rapid changes of temperature he indicated, I arrange the
vessel constituting the "bulb" of the thermometer in the form of a long tube coiled
in a helix-or spiral. When it is. desired that the mean temperature of a room or
chamber be indicated, I run such a tube along the walls and ceiling, or suspend it in
the chamber.
The tubes of fine bore are generally filled with the same fluid as that contained in
the "bulb" of the thermometer, but another fluid may be used, and the separation of
-the-fluids-may be effected by the use of a U tube partly filled with mercury.
In applying this invention to thermometers consisting of bimetallic or compound
strips or bars, or depending simply on the expansion and contraction of a solid body
as in some pyrometers where the indicating arrangement is actuated by the tension of
a wire, or the movement of a rod, I provide a second wire or rod of similar material
and dimensions, for the purpose of moving a mark to which the scale can be set
before reading, or for moving the scale automatically, or I make them of different
materials, and produce a differential movement of an index or pointer.
The same method of compensation may be applied to any other instruments which
are liable to errors by reason of the expansion or contraction of the parts connecting
the transmitting portion with the indicating portion; and the instruments thus compen-
sated may be connected to timepieces for the purpose of automatic registration, or to
alarm signal apparatus.
Dated this 29th day of May 1888.

page_text: CHO MOTORS OT
C литра модо
Thermometers and other Instruments.
I, ALEXANDER PELHAM TROTTER of 2, Victoria Mansions Westminster in the
county of Middlesex, Civil 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 relates to that class of instruments in which the indicators are
transmitted by the motion of a fluid in a tube, or by the tension of a wire, or by
similar mechanical means. Such instruments may be considered as consisting of
three parts, firstly the transmitting part, which is affected by the conditions which it
is desired to indicate or measure, such as the bulb of a thermometer; secondly, the
intervening part, which conveys the indications, such as the tube connecting the bulb
of a thermometer with the graduated portion, and thirdly, the indicating part, such
as the graduated portion of a thermometer. Where it is desired, for example, to
indicate the temperature of a refrigerated chamber on a scale or dial in the engine
room near the refrigerating machinery, or the temperature of a malting house, or a
wine cellar, on a scale in the office of the superintendant, the tube connecting the
bulb to the graduated portion is liable to be exposed to various temperatures.
The purpose of this invention is to prevent these various temperatures from pro-
ducing any errors in the reading of the scale.
In carrying out my invention in its application to thermometers, I use as a "bulb," a
vessel of considerable size, say 10 to 20 cubic inches in capacity; so that the expansion
produced by a rise of temperature of the fluid contained in the said vessel may be con-
siderable, compared with the variations which may take place by alterations in the
temperature at any part of the intervening tube. I connect the said vessel with
the scale end of the thermometer by means of a tube of fine bore, say one tenth, or
one twentieth of an inch in internal diameter. At the scale end, I attach to the tube
of fine bore, a tube, preferably of glass, of an internal diameter such that the motion of
the free surface of the liquid may be of convenient amplitude. In order to prevent
the evaporation of the fluid, I prefer to make the tube of U shape, and fill it partly
with mercury. The surface of the mercury may be used for reading against the
scale.
This combination of vessel, intervening tube, and U tube, I call the thermometer
proper.
I carry a precisely similar tube of fine bore alongside the said intervening tube,
and make them both of the same length. This second tube is merely closed at the
end distant from the scale, and is not connected to any bulb or similar vessel. At the
scale end, this second tube is terminated by a U tube in a manner exactly similar to
the thermometer proper, and the whole of the tube and scale is precisely like, and
arranged alongside, the thermometer proper, and is filled with a similar or other
liquid.
This combination of a tube of fine bore, and a U tube, I call the compensation
tube.

page_text: The variations of the surface of the liquid in the compensation tube will clearly be
due to those variations of temperature whose disturbing influence it is desired to
avoid.
The simplest way of making use of this compensation is to take the surface of the
liquid in the U tube which terminates the compensation tube, as a point to which a
mark on the scale of the thermometer proper is to be set, before taking a reading.
The scale is arranged to slide up and down for this purpose, a rack and pinion being
provided if required.
In another method, I provide a float in the compensation tube, and attach a scale to
the float.
In a third method, I fill the compensating tube with a liquid differing from that of
the thermometer proper,
and I provide floats in both tubes, and attach an index or
pointer to these floats in such a manner that a differential action is produced by the
expansion and contraction of the liquids.
The tubes are generally filled with the same liquid as that contained in the bulb of
the thermometer, but any suitable fluid may be used, and may be connected by a
U tube containing mercury, to prevent the mixing of the fluids.
"
When it is desired that rapid changes of temperature shall be indicated, the form of
the "bulb may be that of a long tube, coiled in a helix or spiral, and when it is
desired that the mean temperature of a chamber be indicated, this tube may be run
along the walls or ceiling, or may be suspended in the chamber.
In applying this invention to thermometers consisting of bimetallic or compound
bars or strips of metal, which actuate an indicating arrangement by the tension of a
wire, or the like, or where the expansion is that of a solid body, as in some pyrometers,
I provide a second wire or rod of similar material and length and size as a compensa-
ting rod and use this for moving a mark to which the scale is to be set, before taking
a reading, or for moving the scale automatically, or for producing a differential motion
of the index or pointer. In like manner other instruments whose indications are
transmitted by similar means, may be compensated by duplicating-that-part-which.
transmits the indications, and using this second part either for moving a mark to
which the scale is set before taking a reading, or for automatically moving the scale,
or for producing a differential motion of the pointer. Instruments thus compensated
may be connected with time pieces for registration of their indications, or to alarm
signal apparatus.
Having thus indicated the nature of my invention, I will now proceed more
particularly to describe the same by reference to the annexed drawings.
Fig. 1. is a front elevation of the scale end of a thermometer constructed in
accordance with the invention; Fig. 2. is a diagrammatic view on a small scale, of
the thermometer with a spiral tube at the "bulb " end.
In Fig. 1. A A is the U tube of the thermometer proper, as arranged for use in
a refrigerating chamber. The upper part is expanded into a bulb, so that while under
ordinary circumstances the mercury stands somewhere within the limits of the scale B;
in case of a stoppage of the refrigerating machinery, the mercury would rise and
overflow into the bulb; and thus an excessive length of tube is avoided.
The intervening tube of fine bore is shown at C, while the greater portion may be
of composition or tin, the last few inches may be preferably of copper tinned inside.
This copper tube is soldered to a short piece of platinum tube D, and this is melted into
the glass, thus forming a good joint.
At E is a branch tube, forming an air trap. It is convenient to fill the thermometer
from the "bulb" end by means of a pump; and by the use of this air trap, the air
from the tube is enabled to escape. The liquid is brought close up to the fine end
of the trap which may then be scaled off. The liquid used in the tube and "bulb"
may be methylated spirit, or any other suitable fluid. With suitable precautions, air
or mercury may be used."
The tube which forms the termination of the compensation tube is constructed in
precisely the same way, with a platinum joint, and air trap. A cover or cap F is
fixed over each air trap, as the point, being fine, is liable to be broken off.

page_text: The scale B is provided with slots, and a rack and pinion G, which enables the
mark H to be brought to the free surface of the mercury in the compensation tube.
A drum or barrel K. may he provided, arranged to revolve by clockwork. A float
in each tube carries a pon which thus gives a record of the indications.
Alarm signals may be operated by electricity, by means of wires of platinum melted
into the U tubes, or inserted from the top when no floats are used.
The wires shown by dotted lines proceeding from the terminals screws L, L, are
arranged, in this case, to give an alarm if the temperature at the bulb rises to
30 degrees; and the wires proceeding from the terminal screws M, M, will operate
another alarm if fire breaks out in the neighbourhood of the intervening tubes,
whether the thermometer proper be provided with an alarm or no. Similarly an
alarm may be operated if the temperature falls below a certain point.
If the bulb "be situated at a considerable height abovo the scale end of the
thermometer, the weight of the liquid will tend to form a Torricellian vacuum in the
"bulb." This may be obviated by making the height of the column of mercury in
the open leg of the U tube sufficient to balance the hydrostatic pressure of the fluid in
the bulb and intervening tube.
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. The combination with an instrument which indicates readings on a scale at a
distance, of a compensating arrangement consisting of the duplication of the parts
which intervene between the transmitting and the receiving end of the instrument,
operating substantially as heroinbefore described.
2. The method of compensating an instrument which indicates readings on a scale at
a distance, by means of a moveable mark to which the scale may be adjusted in the
manner substantially as described.
3. The method of compensating an instrument which indicates readings on a
scale at a distance, by means of a scale automatically adjusted substantially as
described.
4. The combination with a compensated instrument of the kind described, with a
recording apparatus driven by clockwork, operating substantially as described.
5. The combination with a compensated instrument of the kind referred to, with
electric alarins operating substantially as described.
Dated this 13th day of November 1888.
ALEXANDER PELHAM TROTTER.