Improvements in Pressure Gauges, suitable especially as Piezo- meters, Barometers, Thermometers, and the like.
Year: 1891

page_text: Date of Application, 19th June, 1891
Complete Specification Left, 18th Mar., 1892-Accepted, 23rd Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in Pressure Gauges, suitable especially as Piezo-
meters, Barometers, Thermometers, and the like.
I, HUGH LONGBOURNE CALLENDAR, of 2 Princes Mansions, Victoria Street,
in the City of Westminster, Fellow of Trinity College, Cambridge, do hereby
declare the nature of this invention to be as follows:-
:-
The upper end of the indicating tube is connected to a bulb containing air or
other gas, and its lower end is connected to the lower end of a bulb (which
I will call the compensating bulb) containing mercury, sulphuric acid or other non-
volatile liquid and also to the lower end of a tube (which I will call the pressure
tube) whose upper end is connected to the vessel or space in which the pressure is
to be ascertained. The lower part of the pressure tube and of the indicating tube
are filled with the liquid. The size of the compensating bulb is so adjusted that
changes of temperature shall not affect the height of the liquid in the indicating
tube the difference of pressure in the air bulb due to the change being counterbalanced
by the variation of height of the column of liquid in the pressure tube owing to the
expansion or contraction of the liquid in the compensating bulb.
In air thermometers to be read at a distance the connecting tube from the
thermometer bulb is led to the upper end of the pressure tube and one end of a
second tube running parallel and close to the connecting tube throughout its length
is connected to the upper end of the indicating tube its other end being closed.
Since the conditions of the connecting tube and the tube parallel to it are always
similar and they are connected to opposite ends of the indicating tube variations of
temperature in them will produce no result whilst variations of temperature in the
indicating apparatus are compensated for as above described.
Dated this 18th day of June 1891
HUGH L. CALLENDAR.
COMPLETE SPECIFICATION.
Improvements in Pressure Gauges, suitable especially as Piezo-
meters, Barometers, Thermometers, and the like.
I, HUGH LONGBOURNE CALLENDAR, of 2 Princes Mansions, Victoria Street,
in the City of Westminster, Fellow of Trinity College, Cambridge, 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 :-
The upper end of the indicating tube is connected to a bulb containing air or
other gas, and its lower end is connected to the lower end of a bulb (which I will
call the compensating bulb) containing mercury, sulphuric acid or other non volatile
liquid and also to the lower end of a tube (which I will call the pressure tube)
whose upper end is connected to the vessel or space in which the pressure is to be
ascertained. The lower part of the pressure tube and of the indicating tube are
filled with the liquid. The size of the compensating bulb is so adjusted that
changes of temperature shall not affect the height of the liquid in the indicating.
tube the difference of pressure in the air bulb due to the change being counter-
balanced by the variation of height of the column of liquid in the pressure tube
owing to the expansion or contraction of the liquid in the compensating bulb.
In air thermometers to be read at a distance the connecting tube from the
thermometer bulb is led to the upper end of the pressure tube and one end of a
second tube running parallel and close to the connecting tube throughout its length
Ruins 1
1

page_text: is connected to the upper end of the indicating tube its other end being closed.
Since the conditions of the connecting tube and the tube parallel to it are always
similar and they are connected to opposite ends of the indicating tube variations of
temperature in them will produce no result whilst variations of temperature in the
indicating apparatus are compensated for as above described.
DESCRIPTION OF THE DRAWINGS.
The drawing shows a thermometer constructed according to my invention it is
graduated from 200 to 500 degrees centigrade but it will be understood that the
instrument can be adjusted to read between any ranges of temperature.
A is the indicating tube having at its back a graduated scale B. The upper end
of the tube A. is connected to a bulb C and a tube D whose end is closed at /. The
lower end of the tube A is connected to a bulb A¹ provided with a filling tube A²
whose end is sealed. The lower end of the bulb A' is connected to the lower end
of the bulb E (the bulbs A and E being the compensating bulbs) whose upper end
is connected to the pressure tube F which throughout its length runs close to the
tube D so that the two are always at the same temperature. The pressure tube F
terminates in the bulb G which is exposed to the temperature it is desired to
measure. The middle portions of the tubes D and F from D' to D' and F to F¹
respectively are preferably made of soft metal and may be in one piece with each
other, the remainder of the apparatus is of glass which is connected to the soft
metal by short tubes H of platinum fused to the glass and soldered to the soft
metal. The joints are protected by being held between boards screwed together as
indicated.
If the temperatures to be measured are sufficiently high to soften glass the
bulb G and the portion of the tubes D and F adjacent to it are made of glazed
porcelain.
When the instrument is properly adjusted changes of temperature in any other
part than the bulb G do not affect the readings for any variation of pressure in
the tubes F and D due to the change balance one another their ends being connected
to different ends of the same pressure gauge, whilst the difference of pressure in
the bulb C due to the change is balanced by the variation of the height of the
column of liquid in the tube Fowing to the expansion or contraction of the liquid.
When the instrument is to be used for indicating the pressure in any space the
bulb G is omitted the tube F being connected to the space and similarly when the
instrument is to be used as a barometer the end of the tube F is open to the air.
The ratio of the mass of air in the bulb C and tube D to the mass of air in the
bulb G and tube F should be the same as the ratio of the sectional areas of the
tubes D and F.
If the temperature at the indicating end is kept constant or if its variation may
be neglected the compensating bulb E may be omitted.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed declare that what I
claim is :-
1. The combination of an indicating tube, a bulb containing air or other gas and
connected to the top of the indicating tube, and a bulb containing liquid connected
at its lower end to the indicating tube and at its upper end to the vessel or space in
which the pressure is to be ascertained, substantially as described.
2. A thermometer or pyrometer having two tubes in close proximity throughout
their lengths connected to separate bulbs and communicating with different ends of
the same pressure gauge substantially as described.
3. Piezometers, thermometers, pyrometers, barometers and other pressure gauges
substantially as described and shewn in the drawings.
D
301
1
.
1900
HUGH L. CALLENDAR.