A NEW OR IMPROVED PRESSURE GUAGE
Year: 1856

page_text: LETTERS PATENT to John Inshaw, of Birmingham, in the County of
Warwick, Engineer, for the Invention of "A NEW OR IMPROVED PRESSURE
GUAGE."
Sealed the 25th July 1856, and dated the 6th February 1856.
PROVISIONAL SPECIFICATION left by the said John Inshaw at the
Office of the Commissioners of Patents, with his Petition, on the
6th February 1856.
I, JOHN INSHAW, of Birmingham, in the County of Warwick, Engineer,
do hereby declare the nature of the said Invention for "A NEW OR IMPROVED
PRESSURE GUAGE," to be as follows:-
My Invention consists of a guage for measuring the pressure of steam and
other fluids, constructed as follows:-I take two discs of sheet steel, or other
elastic material, and secure them together at their edges by an air-tight
junction. I prefer to plate the, inner surfaces of these discs with silver. A
pipe connected with the boiler, or other reservoir, opens into the space between
the discs, and by the pressure of the steam or other fluid the said dises are
made to bulge or assume a convex figure. The end of an arm or lever presses
against the centre of one of the discs, and passing in the direction of a radius
turns round the edge of the discs, and taking a radial direction. on the other
side terminates in a rack near the axis of the discs, but at a distance from
them. A second arin presses against the centre of the other disc, and passing

page_text: to the other side of the discs is jointed to the. first described arm at a short
distance from where it presses upon the disc... As the discs become convex the
ends of the arms are made to separate, and the rack, which terminates the first
い
°
described arm, engaging in a pinion, communicates motion to a finger traversing
a dial. By the arrangement described the guage is twice as sensitive as it
would be if the motion of the rack were effected by the change of figure in one
of the discs only.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Inshaw in the Great Seal Patent Office on the
4th August 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I; JOIN
INSHAW, of Birmingham, in the, County of Warwick, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date.the Sixth-day of February, in the year of our Lord One
thousand eight hundred and fifty-six, in the nineteenth year of 'ler reign,
did, for Ierself,. Her heirs and successors, give and grant unto me, the
said John Inshaw, Her special licence that I, the said John Inshaw, my
executors, administrators, and assigns, or such others as I, the said. John
Inshaw, 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
PRESSURE GUAGE," upon the condition (amongst others) that I, the said Jolin
Inshaw, 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 'tlic
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.
.1.
NOW KNOW YE, that I, the said John Inshaw, 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
statement thereof, that is to say
Th
My Invention consists of a new or improved pressure guage for measuring

page_text: the pressure of steam and other fluids, constructed in the manner herein-after.
described, and illustrated in the accompanying Drawing.
Figure 1 represents a front elevation of one of my new or improved guages;
Figure 2 represents a front elevation of the same with the dialsandvindex
figure removed; Figure 3 represents in elevation the back of the same with
the case removed; and Figure 4 réprésents a transverse section of the same.
a, b, are two discs of sheet steel; or other elastic material, secured together
at their edges with an air-tight" joint between them: I prefer to plate the
inner surfaces of the said discs a, b, with silver or other metal or substance:not
liable to corrosion is a pipe by which the guage is screwedron to the boiler
or otlier reservoir.The said pipe d communicates with the space between the
dises ab; as represented in Figure 4. When the pressure on 'the'dises' a,b;:is
the same on both sides the said discs" are parallély, astropresented; but when
the pressure between, the said discs, is, greater than that on, their outer surfaces,
each of the said discs, assumes a, bulged or convex figure. The degree of
convexity is dependent upon the pressure; and is indicated on the diale in the
following manner is an arm or lever, one end of which is jointed at g to
the pin h, which said pin h bears against the disc b. The arm or lever f-passes
in the direction of a radius around the edge of the discs-a, b; and taking a
radial direction on the other side terminates in a rack i; the said rack i
engages in a pinion k on the axis of the index finger l. The lever f and pin h
are kept to their bearing by a spring m; n is a second arm or lever, of a shape
somewhat resembling the arm or. lever f. One end of the lever n terminates
in a pin o, which bears against the centre of the disc a.. The pin o is kept to
its bearing by the spring p, which is soldered or otherwise attached to the pin o,
and supports the lever n. The loose end n¹ of the lever n passes through a
slot in the lever f; the hooked end of n' bearing against f at the point marked q...
When the discs a, b, become convex, the pins h and o, bearing on the discs
a, b, separate from one another; and the levers f and n, connected respectively
with the pins h, o, also move in opposite directions; but the lever n bearing
against the lever f at the point marked q, the said lever f is made to turn upon
the centre g; the rack i consequently moves in a nearly vertical direction about
the centre g, and gives motion to the pinion k and index finger l. The said
finger indicates upon the dial e the amount of the pressure of the steam or
other fluid between the discs a, b.
By the arrangement described the guage is twice as sensitive as it would be
if the motion of the rack were effected by the change of figure in one of the
dises only. If the lever f bore against a fixed fulcrum at q, the convexity of
the plate only would affect the said lever f and rack i; but as the fulcrum

page_text: against which the lever fbears at q is the end n' of the lever n, the said
fulcrum travels in an opposite direction to the lever f, and a greater range of
motion is consequently given to the rack i.
Having now described the nature of my said 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 said Invention; but I claim
as my Invention the new or improved pressure guage, constructed in the
manner herein-before described, and represented in the accompanying Drawing,
that is to say, causing the convexity produced in two parallel discs by pressure
upon them to be registered by a rack and pinion, or other mechanical arrange-
nient, the motion of which is produced by the joint action of both the said,
convex dises by. the system of levers described and represented.
In witness whereof, I, the said John Inshaw, have hereunto set my
hand and seal, this First day of August, in the year of our Lord One-
thousand eight hundred and fifty-six.
Witness,
RICHARD SKERRETT,
Clerk to George Shaw.
JOHN INSHAW. (L.S.)