AN IMPROVED MANOMETRO-BAROMETRIC APPARATUS AND VACUUM GAUGE, APPLICABLE ALSO TO A-SAFETY VALVE
Year: 1869

page_text: LETTERS PATENT to Bristow Hunt, of No. 1, Serle Street, Lincoln's
Inn, in the County of Middlesex, Gentleman, for the Invention of
"AN IMPROVED MANOMETRO-BAROMETRIC APPARATUS AND VACUUM GAUGE,
APPLICABLE ALSO TO A-SAFETY VALVE." A communication from abroad
by Jean Baptiste Java Mignon and Stanislas Henri Rouart, of Paris,
France, Engineers.
lealed the 3rd August 1869, and dated the 8th February 1869.
SPROVISIONAL SPECIFICATION left by the said Bristow Hunt at the
Office of the Commissioners of Patents, with his Petition, on the
8th February 1869.
BRISTOW HUNT, of No. 1, Serle Street, Lincoln's Inn, in the County,
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "AN IMPROVED MANOMETRO-BAROMETRIC APPARATUS AND VACUUM
GAUGE, APPLICABLE ALSO AS A SAFETY VALVE," (a communication to me
From abroad by Jean Baptiste Java Mignon and Stanislas Henri Rouart,
of Paris, France, Engineers,) to be as follows:-
a

page_text: magnified, and indicated by means of apparatus which (in order to be
sensitive) must necessarily be very delicate and hence susceptible of
becoming deteriorated and of falsifying the indications.
The Inventors have considered that by taking membranes of a
sufficient dimension they might endeavour to record not the infinitely
small deflexions to which they are submitted under the influence of
the variations of pressure,
but the variations of volume which are
the consequences thereof and which are generally of a much larger
order, besides which these variations of volume are extremely easy to
register by means of the displacement of a liquid mass. To carry out
this idea let us suppose a metallic lens formed by two very thin
membranes and having a glass tube connected to any part of its
circumference. If this lens be filled with liquid and submitted to an
external pressure the liquid which fills the same will be forced into
the glass tube to a distance which will be longer in proportion as the
internal diameter of the glass tube is smaller than the volume of the
lens.
The latter is enclosed in a case connected by means of a pipe
with the pressure to be indicated. If the pressure to which the lens
is submitted externally does not deflect the membranes beyond the
limits of their elasticity as soon as the pressure ceases they will return
to their original position, and the liquid will re-enter the lens.
results from these facts that the oscillation of the liquid column may
serve to measure the variations of the external pressure.
It
A simple modification of this arrangement may also be made with a
single membrane of an undulated form enclosed in a casing; the lower
part of which below the membrane is connected by a tube with the
pressure to be indicated. The upper part or cover of the casing above
the membrane is provided with a glass tube, and the space between the
membrane and the cover is filled with the indicating fluid (generally
mercury), which rises or falls in the glass tube according to the variations
of the pressure in the lower part of the casing.
It will be obvious that various other modifications in which two,
three, or more membranes are employed might be made without
departing from the principle of the Invention, namely, the displacement
of a column of the indicating fluid by the deflexion of the membrane or
membranes. When used as a vacuum gauge the glass tube should be
filled with the mercury and open to the atmospheric pressure. As the
pressure acting on the membrane diminishes it is evident that the

page_text: liquid will descend in the glass tube. To convert the apparatus into
a barometer all that is required is to close the top of the glass tube and
form a vacuum above the manometric column and to leave the lenticular
reservoir or the membrane exposed to the atmosphere, the varying
pressure of which will be recorded by the liquid column in the glass
tube. When it is to be used as a safety valve one of the membranes is
provided with a point. When the pressure exceeds a certain limit the
deformation of the manometer is complete, and one of the membranes
becomes pierced by the point and thus allows the steam, air, or gas to
escape,
SPECIFICATION in pursuance of the conditions. of the Letters Patent,
filed by the said Bristow Hunt in the Great Seal Patent Office on
the 5th August 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BRISTOW
HUNT, of No. 1, Serle Street, Lincoln's Inn, in the County of Middlesex,
Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of February, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Bristow Hunt, Her special licence that
I, the said Bristow Hunt, my executors, administrators, and assigns,
or such others as I, the said Bristow Hunt, my executors, adminis-
trators, 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 Channel Islands,
and Isle of Man, an Invention for "AN IMPROVED MANOMETEO-BAROMETRIC
APPARATUS AND VACUUM GAUGE, APPLICABLE ALSO AS A SAFETY VALVE," (a com-
munication to me from abroad by Jean Baptiste Java Mignon and
Stanislas Henry Rouart, of Paris, France, Engineers,) upon the con-
dition (amongst others) that I, the said Bristow Hunt, my executors or
administrators, by an instrument in writing under my, or their, or one of
their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to bo

page_text: performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the
said Letters Patent..
NOW KNOW YE, that I, the said Bristow Hunt, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement in writing, and on reference being had to the
accompanying Sheet of Drawings, that is to say:-
The metallic manometers hitherto in use are based on the employment
of flexible membranes, the slightest deflections of which are received,
magnified, and indicated by means of apparatus which (in order to be
sensitive) must necessarily be very delicate and hence susceptible of
becoming deteriorated and of falsifying the indications.
The Inventors have considered that by taking membranes of a
sufficient dimension they might endeavour to record not the infinitely
small deflections to which they are submitted under the influence of the
variations of pressure but the variations of volume which are the
consequences thereof and which are generally of a much larger order,
besides which these variations of volume are extremely easy to register
by means of the displacement of a liquid mass. To carry out this idea
let us suppose a metallic lens formed by two very thin membranes and
havin a glass tube connected to any part of its circumference. If
this lens be filled with liquid and submitted to an external pressure
the liquid which fills the same will be forced into the glass tube to
a distance which will be longer in proportion as the internal diameter
of the glass tube is smaller than the volume of the lens. The
latter is enclosed in a case connected by means of a pipe with the
pressure to be indicated. If the pressure to which the lens is submitted
externally does not deflect the membranes beyond the limits of their
elasticity as soon as the pressure ceases they will return to their original
position, and the liquid will re-enter the lens. It results from these facts
that the oscillations of the liquid column may serve to measure the
variations of the external pressure.
A simple modification of this arrangement may also be made with a
single membrane of an undulated form enclosed in a casing, the lower
part of which below the membrane is connected by a tube with the
pressure to be indicated. The upper part or cover of the casing above

page_text: the membrane is provided with a glass tube, and the space between the
membrane and the cover is filled with the indicating fluid (generally
mercury), which rises or falls in the glass tube according to the variations
of the pressure in the lower part of the casing.
Such being the nature and object of the said Invention for "An
Improved Manometro-barometric Apparatus and Vacuum Gauge, appli-
cable also as a Safety Valve," I will now proceed to describe more in
detail the manner in which the same is to be or may be performed or
carried into practical effect, and in order that the same may be
distinctly understood I have annexed hereunto a Sheet of Drawings
illustrative thereof, and have marked the same with Figures and letters
of reference corresponding with those in the following explanation
thereof, that is to say:-
Figure 1 represents a simple arrangement of this principle, A, A, being
the glass tube, and B, B, the metallic lens formed of two very thin
membranes surrounded by an envelope in which the pressure is
exercised and which brings the apparatus to the ordinary form of
manometers. The apparatus may be constructed of different forms all
depending upon the same principle.
Figure 2 shows in section and plan view a very simple manometer
with a single undulated membrane a, a. B is a cover which fills a great
portion of the cavity of the membrane; C is an envelope containing the
fluid which serves to exert the pressure. The cover B is pierced with a
hole D in which is fitted a tube of glass E, and which terminates in a
smaller hole f which is in connection with the cavity comprised between
a and B. The membrane a, the cover B, and envelope C are connected
together by means of screws which serve to compress rings of india-
rubber. The envelope C is provided with a short tube H, by means of
which it is put in communication with the pressure by an ordinary union
joint. To the tube E is applied a scale graduated as shown, or in any
other convenient manner. The cavity comprised between a and B is
filled with a liquid (by preference mercury), which will rise in the glass
tube in proportion as the pressure exerted beneath the membrane a
increases.
Figure 3 represents in face view and section which, all other things
being equal, is so arranged as to have double the sensibility of that
previously described. It is composed of two membranes a and a¹, which
each fulfil a function analogous to that which is accomplished by the

page_text: single membrane of the previously described manometer. The two
membranes are attached to a fixed or inert block B which carries on one
side the glass tube E and by the other H is connected with the pressure.
This fixed block serves not only for the putting together of the apparatus,
but it is also useful to partly counteract the effects of the dilatation of the
mercury. Each membrane is covered by an envelope C, C', in which the
pressure is exerted. The fluid which gives the pressure enters the
envelope by the holes K, K', and the mercury rises in the glass tube E,
passing through the holes 1, 1.
יד ,''
As the
It will be obvious that various other modifications in which two, three,
or more membranes are employed might be made without departing
from the principle of the Invention, namely, the displacement of a
column of the indicating fluid by the deflection of the membrane or
membranes. When used as a vacuum gauge the glass tube should be
filled with the mercury and open to the atmospheric pressure.
pressure acting on the membrane diminishes it is evident that the liquid
will descend in the glass tube. To convert the apparatus into a
barometer all that is required is to close the top of the glass tube and
form a vacuum above the manometric column and to leave tlie lenticular
reservoir or the membrane exposed to the atmosphere, the varying
pressure of which will be recorded by the liquid column in the glass
tube. When it is to be used as a safety valve one of the membranes
is provided with a point. When the pressure exceeds a certain limit
the deformation of the manometer is complete and one of the membranes
becomes pierced by the point and thus allows the steam, air, or gas, to
escape.
This apparatus has been principally arranged with a view to its being
utilized in the ammoniacal vapor engines (Carre's system) manufactured
by the Inventors for freezing and refrigerating, in which case they are
also arranged to act as safety valves. Take, for instance, a double
membrane manometer (Figure 3), and let one of the membranes be
provided with a point; when the pressure exceeds a certain definite limit
the deformation of the manometer reaches its fullest extent and one of
the membranes become pierced, giving vent to the steam or vapors.
The glass tube may be either opened or closed at its upper extremity;
if the latter it will become broken and the liquid would escape
before the rupture of the membrane, which would be a sufficient
indication.

page_text: Having now described the nature and object of the said Invention
for "An Improved Manometro-barometic Apparatus and Vacuum
Gauge, applicable also as a Safety Valve," together with the manner in
which the same is to be or may be performed or carried into practical
effect, I would remark on conclusion that I claim as the Invention
(communicated to me by the above-named Jean Baptiste Java Mignon
and Stanislas Henri Rouart, an apparatus indicating the variations of
pressure by the deformation of a metallic or other reservoir, such defor-
mations acting on a column of liquid in direct communication with the
said reservoir, substantially as herein-before described.
In witness whereof, I, the said Bristow Hunt, have hereunto set my
hand and seal, this Fourth day of August, in the year of our
Lord One thousand eight hundred and sixty-nine.
BRISTOW HUNT. (L.s.)