AN IMPROVED CONSTRUCTION OF PRESSURE GAUGE
Year: 1856

page_text: LETTERS PATENT to Alfred Chadburn, of Sheffield, in the County of York,
Optician, for the Invention of "AN IMPROVED CONSTRUCTION OF PRESSURE
GAUGE."
Sealed the 17th October 1856, and dated the 5th May 1856.
PROVISIONAL SPECIFICATION left by the said Alfred Chadburn at the
Office of the Commissioners of Patents, with his Petition, on the
5th May 1856.
I, ALFRED CHADBURN, of Sheffield, in the County of York, Optician, do
hereby declare the nature of the said Invention for AN IMPROVED CONSTRUCTION
OF PRESSURE GAUGE, to be as follows:-
This Invention relates to a novel arrangement of mechanism for indicating
the deflection of a flexible disc or plate while under the pressure of steam or
other fluid. In the rear of the disc (which I prefer to make of what is termed
"doctor metal") a bell crank lever is hung loosely, and in such manner that
the short limb is always in contact with the disc. The longer limb of this lever
is connected by a rod to an arm projecting from an axle that carries the index
hand. This index hand plays over a segment scale, the graduated spaces of
which enlarge as the numbers on the scale rise, thus rendering the indication
more evident as a dangerous pressure is approached. On the pressure of
steam being applied to the plate or disc, the crank lever in contact therewith
is rocked, and caused to draw or push forward the rod which connects it with

page_text: the axle of the index hand. This movement causes the index hand axle to
turn in its bearings and move the hand over the segment scale a distance
proportionate to the pressure exerted on the plate. By this simple. arrange-
ment of mechanism great precision of indication is obtained, as the liability to
derangement is considerably reduced, no wheels, pinions, or other gearing
being employed to assist in the indication.
SPECIFICATION in pursuance of the conditions of the Letters Patent,'filed
by the said Alfred Chadburn in the Great Seal Patent Office on the
5th November 1856.
our
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALFRED
CHADBURN, of Sheffield, in the County of York, Optician, send greeting.
WHEREAS Her most. Excellent Majesty Queen Victoria, by Her Letters
.of
year
Lord One
Patent, bearing date the Fifth day of May, in the
thousand eight hundred and fifty-six, in the nineteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Alfred Chadburn, Her special license that I; the said Alfred Chadburn, my
executors, administrators, and assigns, or such others as I, the said Alfred
Chadburn, 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
terin 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 CONSTRUCTION OF
PRESSURE GAUGE," upon the condition (amongst others) that I, the said Alfred
Chadburn, an instrument in writing under my hand and seal, should par-
ticularly 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 Alfred Chadburn, do hereby declare
the nature of my said Invention, and in what manner the same. is to be
performed, to be particularly described and ascertained in and by the following
statement, reference being had to the Drawings hereunto annexed, and to the
letters and figures marked thereon (that is to say):-
My Invention of "An Improved Construction of Pressure Gauge." relates
'to a novel arrangement of mechanism for indicating the deflections of a flexible
plate or disc caused by the pressure of steam or other fluid or liquid.. Behind

page_text: the index plate is placed a disc (which I prefer to make of what is terined
"doctor metal"), and against one side of this metal plate or disc is mounted a
peculiar form of bell crank lever, which is so placed as to allow the short limb
of such lever to be always in contact with the central part of the metallic
plate or disc, against which the steam or other fluid or liquid exerts its
pressure. In order to reduce the friction of the end of the lever against the
plate or disc to a minimum, I find it advisable to adapt to the central part of
the disc a flat piece of Brazilian pebble, agate, or some hard material on
which the lever will work. The longer limb of the bell crank lever is con-
nected by a rod to an arm or lever projecting from an axle that carries the
index hand. This index hand works or vibrates over a segmental scale, the
graduated spaces of which may, by this arrangement, be increased in size as
the numbers on the scale rise, thus rendering the indications more evident as a
dangerous pressure is approached.
In order, however, that my improvements may be clearly understood, I have
shewn, in the accompanying Drawings, three views of a steam-pressure gauge
constructed according to my improved plan.
Fig. 1 is a front view of the instrument, shewing the segmental dial or
index plate with the index hand in front thereof; Fig. 2 is a back view,
shewing the principal working parts, the back plate of the outer box or. case
being removed for the purpose of exposing the interior to view; Fig. 3. is a
longitudinal section of the same in the line 1, 2 of Fig. 1. The working parts
are placed in a metal box or case a, a, which may, if required, be furnished at
each side with lugs or ears, whereby it may be secured in any convenient and
suitable place. The interior of the box is divided by a strong rigid partition b, b,
having a recess made at its central part, as shewn in Fig. 3. c, c, is a metal
plate or disc, which is securely held against the back of the partition 6 of the
box by means of the strong plate or collar d, and therefore leaves a space A
between the partition and plate c. Into this space the steam or other fluid
or liquid, the pressure of which it is desired to ascertain, is admitted through a
suitable opening from the pipe B, communicating with the boiler in the case
of a steam gauge. By the pressure of the steam on the upper side of the
plate c, the latter will be caused to deflect and act upon the shorter arm of
the lever e, which is kept constantly in contact therewith. The under side of
the plate c is provided at its central part with a small flat disc of Brazilian
pebble, agate, or other hard substance, as shewn at f, against the surface of
which the short end of the lever e works.. The opposite end of the lever e is.
connected by means of a rod g to the end of another lever h, mounted at the
lower end of the spindle or shaft i, the upper end of which passes through the

page_text: dial or index plate j, and carries the index arm.k. The dial and index are
covered up by a strong plate of glass l, which will prevent either from being
injured by accident, or tampered with by design. On steam being admitted
through the pipe B from the boiler, the pressure thereof will act on the metal
plate or disc c and depress the crank lever e; this lever will be thereby
turned on its centre, and caused to push forward or draw back the rod. g, which
connects it to the lever h on the shaft or spindle i of the index hand. By thus
acting on the levers e'and h, the spindle or shaft of the index hand will be
made to turn on its bearings and move the hand k over the segmental scale
of the dial a distance proportionate to the pressure exerted by the steam on the
plate c. By this simple arrangement of mechanism great precision of in-
dication is obtained, as the liability to derangement is considerably reduced, no
wheels, pinions, or other gearing being employed to assist in transmitting, the
motions of the plate c to the index or indicating arm k. When the gauge.is
used for indicating the pressure of steam, it is advisable that the chamber A
should be filled with water, so that the variation of temperature may not
injuriously affect the internal parts of the gauge. It will be understood, that
if the gauge be below the aperture whereby it is connected to the boiler, no
arrangement will be required to keep water in the chamber; but if the gauge
be placed above the boiler, or the aperture connecting thereto, a syphon tube
must be placed between the gauge and the boiler, in order to prevent the
water from being drawn out of the chamber A of the gauge.
It has been said, that by the above arrangement or construction of parts the
manufacturer is enabled to augment the size of the divisions of the scale as
the pressure of the steam increases, but, if preferred, the divisions of the scale
may be made of similar dimensions by simply altering the position of the
lever h on the spindle of the indicator arm or index, or by changing the form
and position of the first lever e, as will be well understood by all persons con-
versant with mechanics.
Having now described my Invention of "An Improved Construction of
Pressure Gauge," I would remark that my Invention is applicable to all kinds
of pressure gauges, whether employed to indicate the pressure of steam in a
boiler, or the vacuum or degree of exhaustion in any vessel or chamber; and
I would observe, in conclusion, that although I have shewn and described the
best means with which I am acquainted for carrying the same into effect; I do
not mean or intend to confine myself rigidly thereto, as the construction of
some of the parts may, doubtless, be varied in some particulars without
departing from the nature and object of my Invention; but that which I con-
sider to be new in the above-described instrument, and therefore wish to claim

page_text: as the Invention secured to me by Letters Patent as aforesaid, is, the combina-
tion with the flexible plate c of the levers e and h, or any mere modification
thereof, for the purpose of operating upon and actuating the spindle or shaft of
the indicating arm or index.
In witness whereof, I, the said Alfred Chadburn, have hereunto set my
hand and seal, the Fourth day of November, in the year of our Lord
One thousand eight hundred and fifty-six.
Witness,
FRED. WALKDEN,
66, Chancery Lane.
ALFRED CHADBURN. (L.s.)