IMPROVEMENTS IN PRESSURE GAUGES
Year: 1876

page_text: LETTERS PATENT to Thomas Baldwin, of Manchester, in the County of Lan-
caster, Engineer, and William Henry Bailey, of Salford, in the said County,
Engineer, for the Invention of "IMPROVEMENTS IN PRESSURE GAUGES."
Senled the 9th February 1877, and dated the 16th August 1876.
PROVISIONAL SPECIFICATION left by the said Thomas Baldwin and William
Henry Bailey at the Office of the Commissioners of Patents on the 16th
August 1876.
THOMAS BALDWIN, of Manchester, in the County of Lancaster, Engineer, and
WILLIAM HENRY BAILEY, of Salford, in the said County, Engineer. " IMPROVE-
MENTS IN PRESSURE GAUGES."
Our improvements consist in so combining a barometer which indicates the
pressure of the atmosphere and a pressure gauge to indicate the difference between
the pressure of the atmosphere and the pressure of steam or other elastic fluid in
the vessel to which the said pressure gauge is attached; such a vessel is the con-
denser or the exhaust passage of a condensing steam engine, and for the purpose of
ascertaining the pressure in such condenser or exhaust passage the instrument is
more particularly intended to be used.
A sliding scale having the pressure in pounds per square inch or in inches of
mercury, or both, is so placed that its zero or line of no pressure may at any time
be moved, so as to coinside or agree with the surface of the mercury or with the
index hand of the barometer, and so enable the absolute pressure in the condenser
of a steam engine to be read off at once by noting the position on the said sliding
scale of the surface of the mercury, or the position of the index hand of the said
pressure gauge, which will show at once the absolute pressure of the fluid in the
condenser, whatever the pressure of the atmosphere may be at any time; and the
zero line may also be ascertained, and marked on an indicator diagram to show the
true absolute pressure thereon, and the condenser tested at any time as to its proper
working condition.
This absolute ". vacuum gauge may be made with the index hands concentric
when the barometer and pressure gauge are constructed in a similar manner to the
Aneroid or Bourdon, or other spring gauge or barometer, and the sliding scale for
showing the absolute pressure may be made to slide in the required curve for that
purpose.

page_text: When glass tubes are used for the barometer and for the gauge the sliding scale
is by preference placed between the two tubes, so that the absolute pressure shown
by the distance between the surfaces of the mercury in the two tubes may be more
easily measured, and the absolute pressure in the condenser determined.
A light disc or curved arm or ring may be attached to the index hand of the
barometer with a scale upon it, the zero of which will always show the pressure
of the atmosphere, and the said scale will always be in the right position without
sliding, so that the index hand of the gauge attached to the condenser will point
to it, and at once indicate the absolute pressure in the condenser.
The scale for pressures and the sliding scale may when required, if an Aneroid
or other spring gauge or barometer is used, be made straight instead of curved
by using any suitable gearing for the purpose, such, for example, as a light rack
and pinion, or any suitable combination of link work.
We propose to call this Invention by the name of the absolute "vacuum
gauge.
"
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Baldwin and William Henry Bailey in the Great Seal Patent
Office on the 13th February 1877.
THOMAS BALDWIN, of Manchester, in the County of Lancaster, and WILLIAM
HENRY BAILEY, of Salford, in the said County, Engineers. "IMPROVEMENTS IN
PRESSURE GAUGES."
Our improvements consist in so combining a barometer which indicates the
pressure of the atmosphere and a pressure gauge to indicate the difference between
the pressure of the atinosphere and the pressure of steam or other elastic fluid in
'the vessel to which the said pressure gauge is attached; such a vessel is the con-
denser or the exhaust passage of a condensing steam engine, and for the purpose of
ascertaining the pressure in such condenser or exhaust passage the instrument is
more particularly intended to be used.
A sliding scale having the pressure in pounds per square inch or in inches of
mercury, or both, is so placed that its zero or line of no pressure may at any timo
be moved, so as to coincide or agree with the surface of the mercury or with the
index hand of the barometer, and so enable the absolute pressure in the condenser
of a steam engine to be read off at once by noting the position on the said sliding
.scale of the surface of the mercury or the position of the index hand of the said
pressure gauge, which will show at once the absolute pressure of the fluid in the
condenser, whatever the pressure of the atmosphere may be at any time; and the
zero line may also be ascertained and marked on an indicator diagram to show the
true absolute pressure thereon, and the condenser tested at any time as to its proper
working condition.
"
This absolute " vacuum gauge may be made with the index hands concentric
when the barometer and pressure gauge are constructed in a similar manner to the
Aneroid or Bourdon, or other spring gauge or barometer, and the sliding scale for
showing the absolute pressure may be made to slide in the required curve for that
purpose.
When glass tubes are used for the barometer and for the gauge the sliding scale
is by preference placed between the two tubes, so that the absolute pressure shown
by the distance between the surfaces of the mercury in the two tubes may be more
easily measured, and the absolute pressure in the condenser determined.
A light disc or curved arm or ring may be attached to the index hand of the
barometer with a scale upon it, the zero of which will always show the pressure of
the atmosphere, and the said scale will always be in the right position without
sliding, so that the index hand of the gauge attached to the condenser will point to
it, and at once indicate the absolute pressure in the condenser.

page_text: The scale for pressures and the sliding scale may when required, if an Aneroid or
other spring gauge or barometer is used, be made streight instead of curved by
using any suitable gearing for the purpose, such, for example, as a light rack and
pinion, or any suitable combination of link work.
We propose to call this Invention by the name of the absolute "vacuum
gauge.
"
"
Fig. 1 of the accompanying Drawing shows our improved absolute "vacuum
gauge when a mercurial column is made to indicate by its height the pressure of
the atmosphere, and the pressure in the condenser of a steam engine.
a is a glass tube containing mercury, constructed as shown, and similar to the
common mercurial barometer. The pressure of the atmosphere acts on the surface
of the mercury b, and as there is a vacuum in the interior of the tube at its upper
end the surface of the mercury c near that end indicates the pressure of the
atmosphere, which may be read off in pounds and fractions of a pound on the
scale d, which is usefull for fixing the zero line on indicator diagrams taken from
the cylinders of steam engines, so as to obtain the absolute pressure.of the steam
at any part of the figure forming the diagram. A sliding scale e actuated by a
wheel and rack at f, the scale of which is divided into pounds on the square inch, and
a pointer attached to the zero line of this sliding scale points to the mercury in the
tube a, and can be adjusted and set to the surface of the mercury at c to suit the
varying pressure of the atmosphere, as indicated by the rise and fall of the murcury
in the tube a, and the said surface of the mercury shows the zero line of no
pressure; and when the said pointer is set to it that pointer is the zero to the
scale e, and reads downwards, as shown in the Drawing. The glass tube g has its
upper end communicating with the condenser of the engine by the pipe h, and the
other end of the glass tube g dips into a cistern i containing mercury. The surface
of the mercury in the said cistern is shown at b₁, and coinsides, or nearly so, with
the surface of the mercury b in the cistern i. The scale shows the difference
between the pressure of the atmosphere, as indicated by the surface of the inercury
in the tube a, and the absolute pressure in the condenser is indicated by the surface
of the mercury in the glass tube y, as shown at n in the Drawing, at about twelve
pounds on the square inch, and the absolute pressure in the condenser is measured
on the sliding scale e from zero, or the surface of the mercury in the tube a to the
surface of the mercury in the tube g, that is, as shown in the Drawing from c to n,
which shows in this case about two pounds and seven-tenths on the square inch of
absolute pressuro.
If the pressure of the atmosphere remain constant, and the absolute pressure in
the condenser is increased, which may be caused by leakage or any other defect in
the engine, the surface of the mercury at n in the tube g will fall, and the absolute
pressure in the condenser will increase, as will be shown on the scale e, which in
this case will remain stationary.
If the pressure of the atmosphere, as shown by the surface of the mercury in the
tube a at c, should decrease from 147 pounds on the square inch, as shown in the
Drawing to 14 pounds on the square inch, and the absolute pressure in the con-
denser remained constant, then the sliding scale will require to be brought down
by the action of the wheel at f until the pointer at c coinsides with 14 on the
scale d; and, since the pressure of the atmosphere has decreased seven-tenths of a
pound on the surface of the mercury at b, it will also have decreased the same
amount on the surface of the mercury b, in the cistern i, which will cause the surface
of the mercury at n in the tube g to fall also exactly seven-tenths of a pound in
pressure, as will be shown on the scale h, and the absolute pressure in the condenser
in pounds per square inch will be shown on the sliding scale e to be unaltered, and
will read on that scale exactly as it did before the atmospheric pressure changed,
that is, it will still show an absolute pressure in the condenser of two pounds and
seven-tenths on the square inch as before, and whether the pressure of the atmo-
splicre or the absolute pressure in the condenser vary, or if both vary we can easily
ascertain the absolute pressure in the condenser by moving the zero line on the

page_text: sliding scale e to the surface of the mercury in the tube a, and reading off that
absolute pressure on the scale e, as shown by the surface of the mercury in the
tube g, and hence the state of the engine as to back pressure may at any time
in a few minutes be ascertained, and the absolute pressure in the condenser
noted.
For marine engines the tube a is constructed of a similar form to the tube used
in the marine barometer.
By the use of our Invention the state of the "vacuum" in the condenser, or the
exhaust passage leading thereto, can always bo ascertained, whilst the common
"vacuum" gauge gives results varying in the amount of error with the varying
pressure of the atmosphere, whereby a loss in fuel may easily occur, whilst with
the use of the absolute "vacuum gauge any signs of loss through increased back
pressure is immediately detected.
"
When a spring gauge is used to ascertain the pressure in the condenser, as well
as the pressure of the atmosphere, the scale on the barometer is divided into pounds
on the square inch, and may have concentric with it another scale divided into
equivalent inches of mercury, as in the common barometer. The scale on the spring
gauge attached to the condenser has also its scale divided into pounds on the square
inch, and the spring of the Bourdon gauge attached to the condenser may be placed
round the Aneroid gauge, or in front of the index or behind it, and by means of a
small bracket for carrying the index hand of the condenser gauge the two hands
can be placed concentric, and the same scale of pounds will answer for both gauges;
and by placing a light curved index on the pointer of the barometer with the zero
at the point of the hand, and the index divided into pounds, so as to read back-
wards, this small curved scale will always show the absolute pressure in the con-
denser by reading the difference between the positions of the two concentric hands
named.
Instead of the light curved index, before named, a detached concentric sliding
scale having the light curved index fixed on it just above the pointers of the hands
of the barometer and the condenser gauge, and movable by a central stud similar
to the brass hand used on the Aneroid or common wheel barometer, can be used to
measure the absolute pressure in the condenser.
Having described the nature of Invention, and the manner in which the said
Invention is to be performed, we wish it to be understood that what we claim
is,―
Firstly. The combination of the two pressure gauges, as shown in Fig. 1 of the
accompanying Drawing, and the sliding scale and combination of parts as herein
described and illustrated, and for the purpose herein set forth.
Secondly. The combination of two spring gauges and the combination of parts
as herein described, and for the purpose herein set forth.
Thirdly. The attaching of the sliding scale, herein named, to the ordinary
vacuum" gauge, so that it may be set to the pressuro indicated by a detacl.ed
barometer and the absolute pressure read off on the said "vacuum gauge.
""
In witness whereof, we, the said Thomas Baldwin and William Henry Bailey,
have hereunto set our hands and seals, this Fifth day of February, in the
year of our Lord One thousand eight hundred and seventy-seven.