A NEW OR IMPROVED STEAM PRESSURE AND VACUUM GAUGE
Year: 1860

page_text: Sealed the 11th December 1860, and dated the 11th October 1860.
PROVISIONAL SPECIFICATION left by the said John Silvester at the
Office of the Commissioners of Patents, with his Petition, on the 11th
October 1860.
I, JOHN SILVESTER, of the Firm of George Salter and Company, of West
Bromwich, in the County of Stafford, Manufacturers, do hereby declare the
nature of the said Invention for "A NEW OR IMPROVED STEAM PRESSURE AND
VACUUM GAUGE," to be as follows:-
My Invention consists of a steam pressure and vacuum gauge in which the
pressure of the steam or other pressure is transmitted from an elastic dia-
phragm to a rack, which said rack engages with a pinion on an axis which
carries a finger or index traversing a graduated dial. In order to give to the
rack a greater range of motion than that of the diaphragm, I construct the
parts transmitting the pressure as follows:-A dise of much smaller diameter
than the diaphragm, and bearing upon the diaphragm carries a rod, which is
connected at top to the rack, the said rod passes through a tube, the lower
expanded end of which also bears or nearly bears upon the diaphragm. The

page_text: said rod and tube are connected at their upper parts by a coiled spring. Upon
the said tube is another coiled spring, the lower end of which bears against
the bottom or expanded end of the tube, and the upper end against a shoulder
in the case of the instrument. When steam or other pressure is applied to
the diaphragm, the central rod rises in the tube, and the tube rises in the
outer coiled spring, and the rack is moved with a motion equal to the sum of
these motions. There is thus transmitted to the rack a sufficient motion for
accurate indication of the pressure without unduly straining the elastic
diaphragm.
In making vacuum guages I sometimes dispense with the rack and index
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Silvester in the Great Seal Patent Office on the
9th April 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
SILVESTER, of the Firm of George Salter and Company, of West Bromwich,
in the County of Stafford, Manufacturers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eleventh day of October, in the year of our Lord
One thousand eight hundred and sixty, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Silvester, Her special licence that I, the said John Silvester, my
executors, administrators, and assigns, or such others as I, the said John
Silvester, 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 "A NEW OR IMPROVED
STEAM PRESSURE AND VACUUM GAUGE," upon the condition (amongst others)
that I, the said John Silvester, my executors or administrators, by an instru-
ment 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.

page_text: NOW KNOW YE, that I, the said John Silvester, 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
thereof, that is to say:-
My Invention consists of a steam pressure and vacuum gauge constructed
in the manner herein-after particularly described and illustrated in the
accompanying Drawing.
In my new or improved steam pressure and vacuum gauge the pressure is
transmitted from an elastic diaphragm to a rack, which said rack engages
with a pinion on an axis, which latter carries a finger or index traversing a
graduated dial.
In pressure and vacuum gauges made according to my Invention, a greater
range of motion may be given to the elastic diaphragm without risk of injuring
it than in gauges with elastic diaphragms, as ordinarily constructed, and a
more accurate indication of the
pressure obtained.
Figure 1 of the Drawing represents in elevation on a small scale one of my
new or improved steam gauges; and Figure 2 represents in vertical section
the essential working parts of the same of the full size; Figures 11 and 12
represent side elevations of the same; and Figures 3, 4, 5, 6, 7, 8, 9, and 10,
represent detached portions of the same, as herein-after explained. The same
letters are employed to indicate the same parts in the several Figures of the
Drawing.
The parts transmitting the pressure to the graduated dial are constructed as
follows:-a is an elastic diaphragm of vulcanized india-rubber; b is the steam
pipe, by which the steam, the pressure of which is to be gauged, is admitted
under the diaphragm a. The part is represented separately in elevation in
Figure 3, and the parts a and b are represented in vertical section in Figure 4.
A disc c of much smaller diameter than the diaphragm a rests upon the said
diaphragm, and the said disc c carries a rod d, which said rod is connected at
top with the rack which actuates the index finger e. The said disc c and
rod d are shown separately in elevation in Figure 5. A coiled spring f rests
upon the disc c, the upper end of the said spring bearing against the top of the
chamber g. A short tube h surrounds the disc c, and a coiled spring i resting
upon the short tube h bears at its upper end against the shoulder at the top
of the chamber g. Another short tube somewhat shorter than the tube h
surrounds the said tube h, and a coiled spring m resting upon the tube / bears
at top against the shoulder k. The short tubes h and I are shown in elevation
and section in Figures 6 and 7 respectively, and the coiled springs f, i, and m,
are represented in elevation in Figures 8, 9, and 10, respectively. The disc c

page_text: and rings h and 1 constitute an clastic support to the diaphragm a, which
support permits of a greater range of motion in the elastic diaphragm without
unduly straining the said elastic diaphragm than in gauges with elastic
diaphragms of the ordinary construction. Figure 11 represents in elevation
the position of the disc c and short tubes h and in the chamber g when there
is no pressure exerted upon the elastic diaphragm beneath them; and Figure
12 represents the position of the said disc c and short tubes h and in the
chamber g when the elastic diaphragm beneath them is pressed upon the said
disc and short tubes. In the latter position the rod d is raised, and its motion
transmitted through a rack and pinion to the index finger e on the graduated
dial, and indicates thereon the pressure of the steam, as is well understood.
In constructing vacuum gauges according to my Invention the arrangement of
parts represented in Figure 2 is inverted.
Having now described the nature of my Invention, and the manner of carrying
the same into effect, I wish it to be understood that I do not limit myself to
the precise details herein described and represented, as the same may be
varied without departing from the nature of my Invention; but I claim as
my Invention a new or improved steam pressure and vacuum gauge, in which
the elastic diaphragm of the said guage is supported by an elastic support,
constructed essentially in the manner herein-before described and illustrated
in the accompanying Drawing.
In witness whereof, I, the said John Silvester, have hereunto set my
hand and seal, this Sixth day of April, in the year of our Lord One
thousand cight hundred and sixty-one.
Witness,
GEORGE SHAW.
JOHN SILVESTER. (L.S.)