AN IMPROVED INSTRUMENT FOR INDICATING THE PRESSURE OF STEAM
Year: 1857

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County
of Middlesex, Engineer, for the Invention of "AN IMPROVED INSTRUMENT
FOR INDICATING THE PRESSURE OF STEAM."-A communication.
PROVISIONAL SPECIFICATION left by the said William Clark at the Office
of the Commissioners of Patents, with his Petition, on the 9th April
1857.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer, do hereby declare the nature of the said Invention for "AN IM-
PROVED INSTRUMENT FOR INDICATING THE PRESSURE OF STEAM," (a communication,)
to be as follows:-
This Invention relates to an instrument or apparatus for indicating visibly
the pressure of steam in boilers, and for indicating audibly or giving an alarum
when such pressure is excessive and beyond the proper limits.
It consists of a small cylinder or chamber, in which a piston or diaphragm
is placed. This piston is exposed to the pressure of the steam in the boiler
by the tube of communication. This tube, or it may be another tube or
communication, is connected with a steam whistle. The passage of the steam
to the whistle is shut off by means of a valve, which opens when the steam
rises to an excessive pressure. It is opened by the motion of the piston or
diaphragm, but not until its motion has exceeded the ordinary limits by

page_text: excessive pressure of the steam. The piston or diaphragm rod also communi-
cates motion to a segment or arc of teeth, which communicates motion to a
pinion, on whose axis a hand is placed. It indicates the pressure of the steam
on a suitable dial. The piston or diaphragm rod transmits motion by certain
suitable mechanical parts to release a detent holding the valve before men-
tioned, which release takes place when any excess of pressure is generated
in the boiler beyond what is required. The force of a spring is opposed to
the motion of the piston or diaphragm produced by the pressure of the steam.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Clark in the Great Seal Patent Office on the
9th October 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of April, in the year of our Lord One
thousand eight hundred and fifty-seven, in the twentieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the
said William Clark, Her special licence that I, the said William Clark,
my executors, administrators, and assigns, or such others as I, the said
William Clark, 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
INSTRUMENT FOR INDICATING THE PRESSURE OF STEAM," a communication, upon
the condition (amongst others) that I, the said William Clark, 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 William Clark, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following

page_text: statement, reference being had to the Sheet of Drawings hereunto annexed,
and to the letters and figures marked thereon (that is to say):
==
Pressure guages or indicators of the expansion of fluids generally suffice
to indicate the degree of pressure, but do not make up for any neglect of
the workmen, who from want of observing their instruments let the pressure
rise above the proper limits in the apparatus entrusted to their care.
The
consequences of this neglect may be very serious as regards the duration of
the apparatus and the public security.
This alarum or whistling pressure guage is intended, besides indicating the
pressure, to open an outlet at a pressure previously determined for the escape
of the compressed fluid, and also to cause this fluid, so escaping, to act on a
whistle, bell, vibrating spring, or any other alarum apparatus, and thus make
known at a distance that the maximum pressure has been exceeded, and to
attract the attention of the person in charge of the apparatus.
The annexed Drawings represent, Figs. 1 and 2, section and elevation of
the mechanism of an alarum pressure guage, having a steam chamber per-
pendicular to the dial; Figs. 3 and 4, front and side views of the mechanism
of a pressure guage, having a steam chamber parallel to the dial; Figs. 5
and 6, front and side views of an alarum pressure guage, having a steam
chamber parallel to the dial, and transmitting motion to the hand by means
of a screw or helical surface.
Figs. 1 and 2 a, steam chamber, communicating by a pipe j with the
vessel containing or generating the compressed fluid; i, metallic partition,
which is elastic under the pressure of steam; b, piston, resting on the partition
i; h, spring; k, toothed segment, gearing with a pinion, giving motion to a
hand indicating the pressure on a dial, which hand and dial are, however,
not represented in the Drawings; d, rod, receiving the pressure of the spring
and raising the part f; e, detent, resting on the valve g; f, hinge, retaining
the detent; 1, whistle; m, rod, serving to shut the valve g. The inflections
of the partition i determine the indications of the hand. When the proper
pressure is exceeded, the segment k, raised by the spring h, under the action
of the piston b, pushes against the rod d, which lets go the detent e that
retains the valve g; this valve rises and affords outlet to the steam, which
causes the apparatus to whistle, as in the ordinary steam whistle.
Figs. 3 and 4, front and side views of the pressure guage (with the dial
removed), which merely indicates the pressure.
a, turned metal plate, carrying at its back part the tube 6 for the admission
of the elastic fluid, and at its front part the reservoir or box c, the side & of
which is flexible. This side is concave on its two sides, that is to say, its

page_text: "
centre is much thinner than its edges, which difference of thickness constitutes
one of the important points of the Invention.
The elastic fluid arrives through a pipe e, joined to a tube b, and enters
the reservoir c, where it exercises its pressure, and deflects the side dan
extent according to the pressure. If the pressure guage is simply to indicate
pressure, the tube b.is_plugged or stopped against the admission of the steam
from the pipe e. If the pressure guage is, on the contrary, a safety or alarum
apparatus, this tube b is closed by a valve g, of greater or less dimensions,
opening to the atmosphere, or to an alarum organ at h. The elastic side d
acts by a guide bracket i on an intermediate spring j, fixed to the base or
plate a, & transimits the action of the elastic fluid to this spring, and causes it
to act on the cam j¹, mounted on the axis k, by means of a toothed segment
1, fixed on the same axis. The segment 1 gears into a pinion on the axis m,
which also carries the indicating hand, to which motion is thereby imparted.
A helical spring surrounding the axis l always brings back the cam ¹, which
bears on the spring j. The hand indicates the pressure on a dial graduated
for that purpose. These parts complete the indicating pressure guage.
.In the alarum or safety pressure guage the valve is held by the hook or
detent n, moving on the axis o, the lever p of which presses on the valve g,
which closes the orifice r. The hook n is held by the spring parts, the regu-
lating screw t of which rests on the intermediate spring j. When the
maximum pressure (which is regulated by the screw t) has been exceeded,
the spring takes effect on this screw and raises the part s, which lets go the
hook or detent n; the valve being no longer held, riscs, when the fluid escapes
to the open air & creates a noise by the steam whistle or other alarum organ.
When the escape has taken place, and the stoker is warned that the instrument
must resume its original position, the part n is hooked by acting on the hand
lever v, which at the same time presses on the valve g.
Figs. 5 and 6. This arrangement is intended to transmit the motion due
to the pressure to the indicating hand without the use of toothed gear. For
this purpose the motion of the intermediate spring ; acts on the extremity of
the lever u, the other extremity of which presses on a helical surface x,
mounted on the axis o of the hand. The pressure of the lever compels this
axis, and consequently the hand, to revolve. The axis always tends to bring
the helical surface a back against the lever u, under the action of the spring
y, wound round this axis.
Having described the nature of the Invention, and the manner of performing
the same, I declare that what I claim as the Invention intended to be secured
by the herein-before in part recited Letters Patent is, the addition to

page_text: pressure guages of an alarum apparatus or warning organ acting by means
of the escape of the compressed fluid and the kinds of pressure guages
herein-before described, having an alarum apparatus characterised, first, by
the flexible partition, thin at the centre and thick at the edges; secondly, by
the guide bracket acting on an intermediate spring; thirdly, by the readjust-
ment (return of the hand) by means of a helical spring; fourthly, and lastly,
by the transmission of motion to the indicating hand by means of a helical
surface mounted on an axis, all as herein-before described.
In witness whereof, I, the said William Clark, have hereunto set my
hand and seal, this Ninth day of October, in the year of our Lord
One thousand eight hundred and fifty-seven.
Witness,
WILLIAM G. E. SWINNOCK.
WILLIAM CLARK. (L.S.)