AN IMPROVED CONSTRUCTION OF PRESSURE. GAUGE
Year: 1857

page_text: LETTERS PATENT to Edward Davis, of Leeds, in the County of York;-
Optician, for the Invention of "AN IMPROVED CONSTRUCTION OF PRESSURE.
GAUGE."
Sealed the 8th September 1857, and dated the 4th May 1857.
PROVISIONAL SPECIFICATION left by the said Edward Davis at the.
Office of the Commissioners of Patents, with his Petition, on the.
4th May 1857.
I, EDWARD DAVIS, of Leeds; 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:-
The object of this Invention is to avoid the "set" in the metal diaphragms'
used in pressure gauges as at present constructed for transmitting the pressure'
to the index hand. Instead of making the diaphragm of thick metal, so as
to be sufficiently strong to sustain unsupported the pressure of the steam or
other fluid submitted to its action, I make it of thin metal (copper, by pre-
ference, & coated with some less oxidizable substance,) and I enable the.
diaphragm to sustain the pressure of the fluid by superimposing on it a
flat convolute spring, which is held securely at its periphery, between the
flanges of the pressure chamber; and between this and the top of the
chamber I apply helical springs, which will have a tendency to keep
the metal diaphragm in its-normal position. The rod which leads up to

page_text: the indicator rests in a steel step, which is carried by the convolute spring.
By means of this elastic packing I enable the diaphragm to sustain the
pressure of the fluid, and at the same time avoid the tendency of the
diaphragm taking a "set," which prevents accurate indications being given by
the gauge.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Edward Davis in the Great Seal Patent Office on the
4th November 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
DAVIS, of No. 1, Albion Street, Leeds, in the County of York, Optician, send
grecting.
WHEREAS Her most Excellent Majesty Queen Victoria; by Her Letters
Patent, bearing date the Fourth day of May, 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
Edward Davis, Her special license that I, the said Edward Davis, my
executors, administrators, and assigns, or such others as I, the said Edward
Davis, my executors, administrators, and assigns, should at any time agrco
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 CONSTRUCTION OF
PRESSURE GAUGE," upon the condition (amongst others) that I, the said Edward
Davis, by an instrument in writing under my hand and seal, 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 Edward Davis, do hereby declare the
nature of my said Invention, and in what manner the same is to bo per-
formed, to be particularly described and ascertained in and by the following
statement, referenco being had to the Drawings hereunto annexed, and to the
letters and figures marked thereon (that is to say):-
The object of this Invention of "An Improved Construction of Pressure
Gauge" is to avoid the "set" in the metal diaphragms of ordinary pressure
gauges as at present constructed, and which diaphragms are cimployed for the

page_text: purpose of receiving the pressure and transmitting motion to the index hand
of the dial of the apparatus. Instead of making the diaphragm of thick
metal, so as to be sufficiently strong to sustain unsupported the pressure of
the steam or other fluid, the elastic or pressing force of which it is desired to
ascertain and indicate, I make the diaphragm of thin metal (copper, by pre-
ference, and coated with some less oxydizablo substance,) and I
support the
diaphragm behind, so as to enable it to sustain the pressure of the fluid. This
object is effected by superimposing on the diaphragm a flat convolute spring,
which is held securely at its periphery between the flanges of the pressure
chamber, and upon this convolute spring and between it and the top of the
chamber I place any convenient number of helical springs, which will have a
tendency to keep the metal diaphragm in its normal position. The rod which
leads up to the indicator rests in a steel step, which is carried by the convolute
spring. By means of this clastic packing I enable the diaphragm to sustain
the pressure of the fluid, and at the same time avoid the tendency of the
diaphragm to take a "set," which prevents accurate indications being given
by the gauge.
In the accompanying Drawings I have shewn various views of a pressure.
gauge, or parts of a gauge, constructed according to my improvements.
Fig. 1 is a sectional elevation of a gauge with the indicating dial and index;
Fig. 2 is a transverso sectional view of the dial box, shewing the mode of
transmitting the motion of the metal diaphragm to the index or pointer of the
instrument; Fig. 3 is a sectional plan view. In Fig. 1 a, a, is a metal box
provided with flanges a', a¹, to receive screw nuts, whereby the two parts are
secured together, as shewn in the Drawing, and will be well understood by all.
engineers. The box is divided internally into two compartments by the
central partition b, b, which is made of thin metal, as before mentioned. On
the top of this metal diaphragm is placed the convolute spring c shewn in plan
at Fig. 4. This spring is held between the flanges of the box' a, as shewn in
Fig. 1, and at the centre part thereof is fixed a hard steel socket or step d, which
supports the vertical rod e. On the top of the convolute spring c are placed a
number of small helical or spiral springs f,ff, which, being compressed
between the rigid top or cover of the box a and the convolute spring c and
the metal diaphragm b, tends to bring the latter back to its normal position
when the pressure exerted by the steam or other fluid or liquid on the under
side thereof is removed. The upper end of the vertical rod c is made to bear
against the under side of the short arm of the bell crank lever g,' the upper
end of which is provided (as seen in Fig. 1) with teeth in the form of a sector
rack, which gears into a toothed pinion h on the spindle or axle of the index

page_text: arm or pointer i. The lower arm of the bell crank lever g is kept down
against the upper end of the vertical rod e by means of a spring (Fig. 1), so
that at every variation of the pressure on the thin metal diaphragm 6 the arm
i
I may be caused to indicate it. The lower part of the box a is provided with
a boss k, through which is made a hole for the purpose of gaining admission to
the interior of the box. The outer part of the boss is screwed so as to admit
of its being screwed into a socket on a tube communicating with a steam
boiler or other vessel containing an elastic fluid or a liquid, the varying
pressure of which it is desired to ascertain and indicate. Upon steam or
other clastic fluid or liquid being admitted into the box a beneath the metal
diaphragm b, the latter will be lifted or concaved at its centre in proportion to
the pressure exorted thereon, and will consequently lift up the rod e and cause
the pinion to turn on its axis and carry round the index arm or pointer i,
and cause it to indicate on the dial the amount of pounds pressure on the
square inch that is being exerted on the metal diaphragm.
Having now described my Invention of "An Improved Construction of
Pressure Gauge," and having explained the manner of constructing the same
and carrying my Invention into effect, I would observe that I lay no claim to
the exclusive right of indicating the pressure of steam or other elastic fluid by
means of an elastic, metal, or other diaphragm, as similar contrivances have
been employed heretofore to effect similar objects; but that which I consider
to be new in the above described improved pressure gauge, and therefore
desire to claim as the Invention secured to me by Letters Patent as aforesaid,
is the combination of the thin metal diaphragm with the helical and convolute
supporting springs behind, for the purpose of bringing back the diaphragm to
its normal position and state when released from the pressure of the gas
or other fluid or liquid.
In witness whereof, I, the said Edward Davis, have hereunto set my
hand and seal, the Third day of November, in the year of our Lord
One thousand eight hundred and fifty-seven.
Witness,
WILLIAM P. SMITH, Consulting Engineer,
Headingley, near Leeds.
EDWARD DAVIS. (L.S.)