AN IMPROVED PRESSURE GAUGE
Year: 1873

page_text: LETTERS PATENT to Horace Jones Fairchild, of Manchester, in the
County of Lancaster, for the Invention of "AN IMPROVED PRESSURE
GAUGE."-A communication from abroad by John Wesley Stiles, of
the City of New York, in the United States of America.
PROVISIONAL SPECIFICATION left by the said Horace Jones Fairchild
at the Office of the Commissioners of Patents, with his Petition, on
the 21st March 1878.
I, HORACE JONES FAIRCHILD, of Manchester, in the County of
Lancaster, do hereby declare the nature of the said Invention for "AN
IMPROVED PRESSURE GAUGE," (a communication to me from abroad by John
Wesley Stiles, of the City of New York, in the United States of America)
to be as follows:-
This Invention is designed principally as a pressure gauge for steam
boilers, but it is equally applicable for ascertaining and indicating the
pressure of any other elastic fluid or gas. It consists principally of a
hollow iron float of a cylindrical form placed within a hollow iron vessel

page_text: "
or reservoir of a slightly larger diameter and containing mercury. The
steam or other fluid acts upon the upper end of a piston or plunger, the
lower end of which bears upon the top of the float, so that the pressure
on the piston causes the float to be depressed in the mercury,
and by
displacing the latter to a corresponding degree indicates the pressure.
The piston or plunger works steam tight in a small cylinder in connection
(by means of a tap) with the steam boiler. Outside the reservoir con-
taining the mercury in which the float is suspended there is a vertical
glass tube so connected at. its lower end with the interior of the said
reservoir that the mercury rises in the tube to the same level as it reaches
in the space between the outside of the float and the inside of the reser-
voir, and this tube is provided with a scale so graduated that when there
is no pressure on the float and it merely displaces its own weight of
mercury, the level of the latter in the tube is opposite to the "zero" point
on the graduated scale. As soon, however, as the tap in the steam pipe
is opened the pressure of the steam on the piston depresses the float and
causes the mercury to rise in the glass tube to a corresponding degree
and thus indicate the pressure on the graduated scale. Suppose, for
example, that the steam pressure in the boiler is one hundred pounds to
the square inch and the area of the top of the piston is just equal to one-
quarter inch square (one-sixteenth of a square inch) the pressure on the
piston will be six pounds and a quarter, which pressure being communi-
cated direct to the float will press it down into the mercury (say) about
half an inch, causing the mercury to rise in the annular space between
the float and the reservoir, and in the tube (say) about two inches and
three-quarters to the point marked 100 pounds on the scale. It will
also be evident that as the pressure increases the float will be relatively
depressed and the level of the mercury raised to a corresponding degree,
and as the pressure decreases the float will be relieved and the weight
of the mercury will in turn displace. the same, and the level of the
mercury fall towards the "zero" point, and hence every increase and
decrease of pressure will be indicated by the rise and fall of the mercury
in the glass tube, and can be correctly read off on the graduated scale
attached thereto.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Horace Jones Fairchild in the Great Seal Patent
Office on the 19th September 1878.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HORACE
JONES FAIRCHILD, of Manchester, in the County of Lancaster, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-first day of March, 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 Horace Jones Fairchild, Her special license
that I, the said Horace Jones Fairchild, my executors, administrators,
and assigns, or such others as I, the said Horace Jones Fairchild, 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 Channel Islands, and Isle of Man, an Invention for "AN IMPROVED
PRESSURE GAUGE," (a communication to me from abroad by John Wesley
Stiles, of New York City, in the United States of America) upon the
condition (amongst others) that I, the said Horace Jones Fairchild, 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 be 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 Horace Jones Fairchild, 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 and accompanying Drawings (that is to
say) :-
This Invention is designed principally as a pressure gauge for steam
boilers, but it is equally applicable for ascertaining and indicating the
pressure of any other clastic fluid or gas. It consists principally of a
hollow iron float of a cylindrical form placed within a hollow iron vessel

page_text: or reservoir of a slightly larger diameter and containing mercury. The
steam or other fluid acts upon the upper end of a piston or plunger, the
lower end of which bears upon the top of the float, so that the pressure
on the piston causes the float to.be depressed in the mercury, and by
displacing the latter to a corresponding degree indicates the pressure.
The piston or plunger works steam tight in a small cylinder in connection
(by means of a top) with the steam boiler. Outside the reservoir con-
taining the mercury in which the float is suspended there is a vertical
glass tube so connected at its lower end with the interior of the said
reservoir that the mercury rises in the tube to the same level as it
reaches in the space between the outside of the float and the inside of
the reservoir, and this tube is provided with a scale so graduated that
when there is no pressure on the float and it merely displaces its own
weight of mercury, the level of the latter in the tube is opposite to the
"zero" point on the graduated scale. As soon, however, as the tap in
the steam pipe is opened the pressure of the steam on the piston
depresses the float and causes the mercury to rise in the glass tube to a
corresponding degree and thus indicate the pressure on the graduated
scale. Suppose, for example, that the steam pressure in the boiler is
one hundred pounds to the square inch and the area of the top of the
piston is just equal to one-quarter inch square (one-sixteenth of a squaro
inch) the pressure on the piston will be six pounds and a quarter, which
pressure being communicated direct to the float will press it down into
the mercury (say) about half an inch, causing the mercury to rise in
the annular space between the float and the reservoir, and in the tube
(say) about two inches and three-quarters to the point marked 100 lbs.
on the scale. It will also be evident that as the pressure increases the
float will be relatively depressed and the level of the mercury raised to a
corresponding degree, and that as, the pressure decreases, the float will be
relieved and the weight of the mercury will in turn displace the same,
and the level of the mercury fall towards the."zero" point, and hence
every increase and decrease of pressure will be indicated by the rise and
fall of the mercury in the glass tube, and can be correctly read off on
the graduated scale attached thereto.
Instead of a glass tube a vertical opening may be made in the side of
the reservoir and a strip of plate glass being fixed in front of the same
the height of the mercury in the interior of the reservoir can be readily
seen through the glass.

page_text: Such being the nature and object of the said Invention for An
Improved Pressure Gauge," 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 clearly
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:-
b
In the Drawing Fig. 1 is an elevation and Fig. 2 a vertical section of
the improved pressure gauge; a is a small vertical chamber fitted with
the piston or plunger 6, and connecting with the steam boiler by the
tube c, the steam being admitted or shutt off by a tap. This piston or
plunger 6 operates downwards, and rests or acts by its lower end on the.
top of the float e, which is enclosed within the cylindrical reservoir ƒ,
and is the sixteenth of an inch more or less greater in diameter than the
float, thereby forming a small annular space between the float and the
reservoir. The top e* of this float I prefer to make in the form of a cap,
and projecting so as to close or cover the annular space. The lower part
of the reservoir contains mercury, which is preferred for this purpose by
reason of its great weight, and for the purpose of indicating the pressure
a glass tube g may be used, which should be furnished with a graduated
scale as usual in such cases, so as to express the pressure of the steam
within the boiler by the height at which the mercury stands in the tube.
The piston 6 is of small diameter or area of cross section, and the float
e is of much larger area of cross section. By this arrangement a con-
siderable pressure of steam upon the piston 6 will be counterbalanced by
a comparatively low column of mercury, as before described.
If preferred the float e may be made to operate a radial index by a
rack and pinion or other suitable mechanism, in which case the pressure
of the steam would be indicated by the position of the index on a circular
dial, and other changes may be made in its construction and arrangement
without thereby changing its principle. This apparatus should be
accurately made, and the steam piston and float should be so secured as
to work vertically and in the centre line of the reservoir, and where
mercury is used as the weighing medium the material out of which the
float and reservoir are made should be such or so prepared or fortified as
to resist the action of the mercury upon them.
Having now described the nature and object of the said Invention,

page_text: or carried into practical effect I wish it to be understood that I claim as
the Invention communicated to me by the said John Wesley Stiles, the
combination and arrangement of the steam piston 6 and its chamber a,
with the float e, reservoir f, and weighing fluid in the manner and for
the purpose substantially as described.
In witness whereof, I, the said Horace Jones Fairchild, have here.
unto set my hand and seal, this Eigteenth day of September, in
the year of our Lord One thousand eight hundred and seventy-
three.
Witnessed by
GEORGE DAVIES, C.E.,.
Patent Agent,
Manchester.
H. J. FAIRCHILD. (L.S.)