CERTAIN IMPROVEMENTS IN MANOMETERS
Year: 1873

page_text: LETTERS PATENT to Pierre Hugon, of Paris, in the Republic of
France, Engineer, for the Invention of "CERTAIN IMPROVEMENTS IN
MANOMETERS."
Sealed the 20th October 1873, and dated the 2nd May 1873.
PROVISIONAL SPECIFICATION left by the said Pierre Hugon at the
Office of the Commissioners of Patents, with his Petition, on the
2nd May 1873.
I, PIERRE HUGON, of Paris, in the Republic of France, Engineer,
do hereby declare the nature of the said Invention for "CERTAIN IM-
PROVEMENTS IN MANOMETERS," to be as follows:-
In ordinary manometers which have outlets to the atmosphere and
columns of mercury or other fluid, great disadvantage is experienced
from the tendency of the mercury or fluid to be spurted or thrown from
the apparatus on sudden variations of pressure occurring.
Now the object of my Invention is to provide against this difficulty,
and otherwise to improve the construction of manometers.

page_text: "
In order to avoid useless repetition I herein-after use the word
mercury" for either mercury or other liquid or agent that
may be
employed instead of mercury in the manometer; and I use the words
(elastic fluid) to imply the steam, gas, vapour, aeriform, or elastic
fluid, the density, rarefaction, or pressure of which has to be measured, 5
indicated, or regulated by the manometer.
My improved manometer consists of two vessels, cisterns, or chambers
connected together at the required distance apart and closed at the
ends, but caused to communicate by two tubes opening into each
vessel at different levels. The tubes may sometimes serve as the 1
connections. The lower chamber communicates with the elastic fluid,
and the upper chamber communicates with the outer air or any desired
vessel.
The capacity of the chambers, and the length or height of the tubes,
are regulated to correspond with the maximum density or pressure, that 1
is to say, with the density or pressure at which (or on-exceeding which)
the elastic fluid should escape.
The lower chamber is charged with mercury to a certain level above
the lower openings of the tubes. When the elastic fluid enters this
chamber at a greater pressure than the atmospheric or normal pressure 2
the mercury as the pressure increases rises through the tubes into the
upper chamber, and when the mercury in the lower chamber falls below
the bottom of one of the two tubes the elastic fluid rushes up through
this tube driving the mercury before it, and escapes through the orifice
The escape 2
of the chamber without throwing out the mercury.
upper
continues until the pressure of the elastic fluid becomes reduced to or
below the normal pressure, when the mercury falls and again closes
the bottom of the tube. The manometer thus acts as a safety valve,
especially if the outlet orifice is so contrived that the fluid in escaping
whistles or sounds.
:.
To indicate the level a plunger or float with index, weight, or stud
travelling on a graduated scale may be added.
The tubes and connections may be moveable or adjustable to accom-

page_text: In one such arrangement the tubes of the manometer are jointed, or
work on an axis, pivot, or hinge, and the upper chamber is also jointed
or works on a pivot, axis, or hinge, so that the upper end of the tube
may be brought to any desired point on a graduated arc or scale corre-
sponding with the level of the mercury, and with the point at which
the pressure or density of the elastic fluid is to be at or beyond its
maximum, and at which level or point its escape is to take place until
such pressure be reduced.
•
I sometimes mount or fit the chambers or cisterns on bevelled axes
or supports connected by hollow or tubular passages, which serve as
tubes for the rise and fall of the mercury.
The joints may consist of caoutchouc or other elastic or flexible
couplings or connections, whereby the tubes are connected with the
chambers or cisterns, so that the upper chamber and the tubes may be
turned or moved to the required level or angle.
There may be partitions or diaphragms in the upper chamber to
prevent escape of the mercury.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Pierre Hugon in the Great Seal Patent Office
on the 1st November 1878.
."
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PIERRE
HUGON, of Paris, in the Republic of France, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Second day of May, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Pierre Hugon, Her special license
that I, the said Pierre Hugon, my executors, administrators, and
assigns, or such others as I, the said Pierre Hugon, my executors;
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise;
and vend, within the United Kingdom of Great Britain and Ireland, the

page_text: The capacity of the chambers and the length or height of the tubes
are regulated to correspond with the maximum density or pressure, that
is to say, with the density or pressure at which (or on exceeding which)
the steam or other elastic or non-elastic fluid should escape.
The lower chamber is charged with mercury to a certain level above
the lower opening of the tubes. When the elastic fluid enters this.
chamber at a greater pressure than the atmospheric or normal pressure.
the mercury as the pressure increases rises through the tube into the
upper chamber, and when the mercury in the lower chamber falls below
the bottom one of the tubes, the steam or other fluid to be measured will
rush up through this tube, driving the mercury before it, and will escape
through the outlet of the upper chamber without throwing out the
mercury. The escape continues until the pressure of the steam or other
fluid becomes reduced to or below the normal pressure, when the
mercury will fall and again close the bottom of the tube. The
manometer thus acts as a safety valve especially when the outlet orifice
is so contrived that the fluid in escaping whistles or sounds.
To indicate the level a plunger or float with index weight or stud,
travelling on a graduated scale may be added.
The tubes and connections may be moveable or adjustable to
accommodate the manometer for various or differential densities or
pressures, or in other words, so that the escape of the steam or other
fluid may take place at any desired height or level of the mercury.
In one such arrangement the tubes of the manometer are jointed or,
work on an axis, pivot pin, joint or hinge, and the upper chamber is also
jointed or works on a pivot axis joint or hinge so that the upper end of
the tube may be brought to any desired point on a graduated arc,
quadrant, or scale corresponding with the level o fthe mercury, and with
the point at which the pressure or density of the clastic fluid is to bo at,
or beyond its maximum, and at which level or point its escape is to take
place until such pressure be reduced.
I sometimes mount or fit the chambers or cisterns on bevelled axes or
supports connected by hollow or tubular passages which serve as tubes
for the rise and fall of the mercury.
The joints may consist of caoutchouc or other elastic or flexible
couplings or connections whereby the tubes are connected with the

page_text: chambers or cisterns so that the upper chamber and the tubos may be
turned or moved to the required level or angle.
There may be partitions or diaphragms in the upper chamber to
prevent escape of the mercury.
I proceed to describe with reference to the accompanping Drawings
various arrangements or modifications of my improved manometer con-
structed according to my Invention.
The principle of construction on which all these arrangements or
modifications are based, and which is common to them all, is exemplified
by the apparatus shewn in Figure 1, which is a vertical section of the
manometer, and Figure 1* is a bottom plan or plan of the under surface
thereof.
A is a cylindrical cistern, chamber, or vessel formed of glass, metal, or
other material usually employed for the mercury cisterns of manometers;
B is a similar cistern, vessel, or chamber. The cisterns A, B, are
connected together by stays, frame bars, or tie rods C, D; each cistern or
chamber A, B, is closed by a cover or end at top and bottom. These
cisterns or chambers communicate with each other by means of two
tubes or hollow columns E, F, made of glass, motal, or other convenient
material, the tubes passing through the bottom of the upper cylindrical
chamber B and the top cover of the lower cylindrical chamber A. The
tubes E, F, open at bottom into the vessel A. at different levels, and
these tubes open at top into the vessel B at different levels. G is a stop
cock in the cover of the chamber B; H, stop cock in the bottom of the
chamber A.
Instead of having a stop cock G, the chamber B may have in its cover
or upper end a tube or other outlet opening into the chamber at its
lower end, while at its upper end it opens into the air or any desired
receiver, or it is provided with a valve or contrivance communicating
with the air or with any desired vessel or receiver.
The outlet orifice may be so formed, fitted, or disposed that the
elastic fluid in escaping may make a whistling or other sound.
The chamber A is filled with mercury to the line or level a. Now if
the cock H be opened so as to bring the mercury in communication
with the air, steam, gas, or other fluid to be measured, such fluid having
a pressure greater than the atmospheric pressure; say, for example, to

page_text: the extent of half an atmosphere, the mercury will rise in the tubes
E, F, to one-half of the height of these tubes, say, 38 centimetres of the
mercury. Then if the increase of pressure be continued until it reaches
one atmosphere, the mercury will continue to rise equally in the two
tubes until it reaches the upper chamber B, and will continue to rise
until it sinks in the lower chamber A to the level b, that is to say, just
below the level of the bottom opening of the tube F, so as to open or
uncover the bottom of that tube, and the elastic fluid will be free to
escape up the tube F into the chamber B, driving before it the column
of mercury contained in the tube F, and it will pass out through the
cock G or other fluid way or outlet at the top of the chamber B without
any portion of it being spirted out or ejected. The elastic fluid will
continue to rise through the tube F so long as the pressure is equal to
or higher than one effective atmosphere in the chamber A, the column
3. of mercury contained in the tube E being, say, 76 centimetres above the
line or level b.
If the pressure becomes reduced below one atmosphere then the
mercury will at once rise again in the chamber A, and will again stop
up the bottom opening of the tube F, in which the column of mercury
will also rise, and the elastic fluid will not escape until the pressure
in the chamber A shall again have reached or gone beyond one atmo-
sphere.
:
Now suppose the tubes, instead of being 76 centimetres long were
only half that length then the elastic fluid must escape at 38 centi-
3 metres of mercury at a pressure of say, a half atmosphere.
Now what is true for one atmosphere is true for two atmospheres, or
ten, or any number of atmospheres, provided only that the capacity of
the chamber, vessel, or cistern containing the mercury, and the length
or height of the tubes E, F, (and of course their bore or sectional area)
) are increased or regulated to correspond with the maximum pressure or
pressure at which the elastic fluid is to be allowed to escape.
Now when a manometer thus constructed is placed in communication
with a vessel or receiver containing fluid under pressure to be measured,
it acts as a safety valve, because it will quite prevent the maximum
pressure, determined by the height of the column of mercury, from being
exceeded without notice being given by the escape of the elastic fluid
through the outlet G, and if this outlet be fitted with a whistle or tho

page_text: like the fluid in issuing will produce a sound which will act as a signal
or warning. It closes fluid-tight by its own action soon as the pressure
becomes reduced below the maximum point for which the instrument is
constructed.
One of the tubes E, F, may be of metal, and the other of glass, formed 5
in sections or of one piece, according to the length, or both tubes may be
of metal or opaque material, and in this case the degrees of pressure to
which the mercury rises in the chamber A may be indicated without
using a separate metal pressure gauge thereon by employing any
ordinary means for the purpose; as for instance, a float or piston lighter 10
than the mercury may be fitted in the tube F, and connected with an
index pointer or with a chain carrying a weight.
In my manometer the elastic fluid escapes at a pressure dependent on
and corresponding with the length or height of the tubes.
If the degree or amount of pressure at which the escape is to take 15
place is to be variable, that is to say, if it be desired to construct the
manometer in such manner that the elastic fluid may escape at various
pressures less than the maximum or extreme, pressure, this is effected
by rendering the tubes and their connections with the mercury chambers
moveable by joints, as exemplified in Figure 2. By such means the 20
elastic fluid can be caused to escape at various degrees of pressure
varying from a short column of mercury to a number of atmospheres
determined by the length of the tubes.
Figure 2 is an elevation partly in section, and Fig. 2* a plan of a mano-
meter constructed according to this arrangement. Two manometers are 25
here shown, one at the side of the other, one is the manometer K, the
tubes of which are jointed so that they with the upper mercury chambers
may be moved into any angle or position between the horizontal and the
vertical, say between 90° and 0°. The other manometer I is the mano-
meter first described in reference to Figure 1. It is only shewn here to 30
facilitate the explanation.
The two manometers are supposed to be connected and in commu-
nication with one and the same mercury cistern J, in order better to
explain how the jointed manometer K works. L is the upper mercury
chamber of the manometer K (it corresponds with the upper 35
chamber B of Figure 1). It is a cylindrical vessel fitted on a joint or

page_text: Fig. 4 is a vertical
A² and I are the
described in the previously explained modifications.
section, and Fig. 4* edge view of this modification.
mercury chambers or cisterns. The chamber L³ is fitted with perforated
sheet-iron partitions n³ for preventing the mercury from being ejected or
spirted out, while yet allowing for the free egress of the elastic fluid.
These partitions may be of various shapes or arrangements, provided
that they carry out this object. The rods or columns P, 0%, which
connect the conical joints or axes M³, N³, are hollow or tubular
throughout their length, and a fluid way is formed through them
between the chambers A³ and I, so that they act both as the tubes for
the rise and fall of the mercury columns, that is to say, as the fluid
passages between the chambers A³, and also as connections between
those two chambers. This manometer acts in precisely the same manner
as the one above described. Its jointed portion works on the joints or
-axes M³, N³. O³ is a glass tube fitted parallel with the hollow rod O³,
so that the rise and fall of the mercury due to the varying pressure may
be ascertained by inspection.
Figure 5 is a vertical section, and Fig. 5* plan of another modi-
fication of my jointed manometer. A³ is the lower mercury chamber,
having on the top or cover two tubular necks, on to which are fitted the
caoutchouc tubes g, h, which are connected with two glass tubes m, n,
and these tubes are also connected by similar caoutchouc tubes i, j, with
the upper mercury chamber L³, the said tubes opening therein at the
lower part thereof, the glass and caoutchouc tubes forming the passages
and connections between the chambers. This manometer acts in the
same manner as those above described. The caoutchouc joints allow the
required portions to take various positions or angles between 90° and 0°
(vertical and horizontal), the glass tubes and the chamber I³ working
on the india-rubber tubes 7, 8, which take the various curves or angles
required.
:

page_text: this cover is a tube K, made of thick glass, and communicating with the
chamber or cistern E through the opening L. This glass tube K is
closed at top by a flange or disc M; N is a float or piston resting on the
surface of the mercury contained in the vessel E; O is a rod attached at
bottom to this float or piston N, and at top to a small coloured disc or
plate P, working freely in the glass tube K. The tubes F, G, connect
the lower mercury cistern or chamber E with the upper mercury cistern
or chamber Q. R is a tube fitted in the chamber Q, and this tube is
connected with a flanged disc S; it extends upwards to a certain distance
from the flanged disc or cap T at the top of the chamber Q. This
flanged disc or cap T carries a tube U, which descends within the
chamber Q to a certain distance from the disc S. A short hollow
tube V is connected, and communicates with the tube U; f is a gra-
duated scale; x is the level of the mercury at the atmospheric pressure.
This modification of manometer acts in the manner described in respect
of the before explained modifications, but it has these additional pro-
visions: First, in the mercury chamber E the float N, carrying the
disc P, rises and falls in the glass tube K. with the rise and fall of the
mercury, and thus indicates all the various pressures between the
minimum pressure or zero and the maximum pressure determined by
the height of the tubes; next, two or more sections of tubes, the number
varying according to the variations or graduations of pressure, are pro-
vided in the upper mercury chamber Q to prevent the mercury from
being drawn and ejected through the hollow or tubular neck V when an
excess or exceptional degree of pressure occurs suddenly or unexpectedly.
Hence if fluid under pressure is brought into communication with the
mercury in the chamber E the mercury descends therein and the float N
with it, and the disc P connected therewith indicates the degree of
pressure on the graduated scale f, but at the same time the mercury will
rise in the tubes F, G, until it reaches the level of the bottom of the
tube G, through which thereupon the fluid under pressure will rise and
escape up it into the vessel Q, passing in its travel or upflow through the
annular or tubular spaces a, b, and thence into and through the tube U,
whence it will escape through the neck or tubular fitting V.
The improved manometers constructed according to my Invention
have the special advantage of preventing the loss of mercury by its
spurting out of the apparatus when sudden changes of pressure occur.
In ordinary manometers as at present constructed the mercury or

page_text: Sixth. The arrangement of tubes or portions of tubes placed in the
upper chamber Q, Figure 6, for preventing loss or ejection of mercury
or other measuring fluid, as herein-before described.
In witness whereof, I, the said Pierre Hugon, have hereunto set..
my hand and seal, this Sixteenth day of October, in the year B
of our Lord One thousand eight hundred and seventy-three.
Witness,
ANSART.
P. HUGON. (L.§.)