M- PROVEMENTS IN PRESSURE GUAGES
Year: 1857

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in
the County of Middlesex, and of 166, Buchanan Street, in the City of
Glasgow, North Britain, Gentleman, for the Invention of "IMPROVEMENTS
Sealed the 11th September 1857, and dated the 19th June 1857.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition, on the
19th June 1857.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, and of 166, Buchanan Street, in the City of Glasgow, North Britain,.
Gentleman, do hereby declare the nature of the said Invention for "M-
PROVEMENTS IN PRESSURE GUAGES," a communication from abroad, to be as
follows:-
This Invention relates to certain simple constructions and arrangements of
pressure guages for indicating the pressure of steam and fluids, whether such
pressure be above or below that of the atmosphere.
According to one arrangement of guage, a combination of a piston and
flexible diaphragm is employed, the piston being connected in an adjustable
manner with a bow or hoop spring to counterbalance the steam or fluid
pressure which is exerted against the opposite end of the piston. This
extremity of the piston rests upon a flexible diaphragm of india-rubber, or
other suitable material, and this diaphragm, which is of a cup shape when

page_text: in its normal condition, is contained within and fits a spheroidal chamber,
whereby it is prevented from bursting when any excess of pressure is applied
thereto. A three-way cock admits the steam or fluid to the diaphragm when
required, as it enables the pipe leading to the guage to be blown through, and
thereby cleared of any dirt or deposit which may have accumulated therein.
The motion of the piston is imparted to an arbor carrying an index (which
is adjustable thereon) by means of a rack and pinion or other convenient
arrangement, a small pulley serving to keep the rack in contact with the
pinion. This part of the apparatus is enclosed within a circular box with
a properly divided dial, from which the index shews the correct amount of
pressure.
According to another modification, in place of the piston and diaphragm I
employ a helical spring made wholly or in part of the form of a dome or
inverted cup, and this spring is combined with a capsule of india-rubber, or
other suitable elastic material, of a similar shape to the spring; this capsule is
placed either in the interior or on the exterior surface of the spring, and is
consequently extended or contracted with it. It serves as an impervious
medium through which the steam or fluid may act upon the spring and
produce the necessary movement for indicating the pressure on the dial. The
vertical motion of the helical spring is transmitted to the index by a rack
connected to the helical spring, and acting on a pinion, as herein-before
described, and the admission or not of the steam or fluid is effected by
a three-way cock, after the manner described in reference to the first
arrangement.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Henry Johnson in the Great Seal Patent Office
on the 19th December 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex, and
of 166, Buchanan Street, in the City of Glasgow, North Britain, Gentleman,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of June, 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
John Henry Johnson, Her special license that I, the said John Henry Johnson,

page_text: my executors, administrators, and assigns, or such others as I, the said
John Henry Johnson, my executors, administrators, or assigns, should at
any time agree with, and no others, from time to time and at all times there-
after 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 "IMPROVE-
MENTS IN PRESSURE GUAGES," a communication from abroad, upon the condition
(amongst others) that I, the said John Henry Johnson, 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 bo
performed, and cause the same to be filed in the Great Seal Patent Offico
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said John Henry Johnson, 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, reference being had to the accompanying Drawings, and
to the letters and figures marked thereon, that is to say:-
The said Invention relates to certain simplified constructions and arrange-
ments of pressure guages for indicating the pressure of steam and fluids,
whether at high or low pressures, or to be used as a vacuum guage.
According to one arrangement of guage a combination of a piston and
flexible diaphragm is employed, the piston being connected in an adjustable
manner with a bow or hoop spring to counterbalance the steam or fluid pres-..
sure which is exerted against the opposite end of the piston. This extremity.
of the piston rests upon a flexible diaphragm of india-rubber or other suitable
material; and this diaphragm, which is of a cup shape when, in its normal
condition, is contained within and fits a spherical chamber,. whereby it is
prevented from bursting when any excess of pressure is applied thereto. A
three-way cock admits the steam or fluid to the diaphragm when required, or
it enables the pipe leading to the guage to be blown through, and thereby,
cleared of any dirt or deposit which may have accumulated therein. The
motion of the piston is imparted to an arbor carrying an index (which is.
adjustable thereon) by means of a rack and pinion or other convenient
arrangement, a small pulley serving to keep the rack in contact with the
pinion. This part of the apparatus is. enclosed within a circular box with,
a properly divided dial, upon which the index shews the correct amount of:
pressure:
According to another modification, in place of the piston and diaphragm I

page_text: employ a helical spring made wholly or in part of the form of a dome or
inverted cup, and this spring is combined with a capsule of india-rubber, or
other suitable elastic material, of a similar shape to the spring. This capsule
is placed either in the interior or on the exterior surface of the spring, and is
consequently extended or contracted with it. It serves as an impervious
medium through which the steam or fluid may act upon the spring and
produce the necessary movement for indicating the pressure on the dial: The
vertical motion of the helical spring is transmitted to the index by a rack
connected to the helical spring and acting on a pinion, as herein-before
described, and the admission or not of the steam or fluid is effected by a three-
way cock, after the manner described in reference to the first arrangement.
And in order that the said Invention may be fully understood, I shall now
proceed more particularly to describe the same, and for that purpose I shall
refer to the several Figures on the Sheet of Drawings hereunto annexed, the
same letters of reference indicating corresponding parts throughout all the
corresponding Figures.
Figure 1 on the accompanying Sheet of Drawings represents a front eleva-
tion of a guage constructed according to this Invention; Figure 2. is an
interior view of the same, partly in section, with the dial plate removed; and
Figure 3 is a transverse vertical section of the same. A is a circular box or
case of metal, or other material, containing part of the piston B, the spring C,
the arbor a of the index d and the mechanism for transmitting motion to the
said arbor from the piston, the front of the said box serving for the gradu-
ated dial, which is protected, as is also the index d, by a glass D, which is
fitted to a frame D* that screws on to the exterior of the box. The lower part
of the box A carries a metal cylinder E, which is bored truly and perpendicu-
larly to the axis of the box to receive the piston B, which is fitted truly but
easily thereinto, and whose upper part enters the box A.
The cylinder E has a screw thread cut on the lower part of its exterior, for
the purpose of screwing on to it a metal cup F, which is represented as form-
ing part of the casting of the socket of a cock G, but which may consist of a
separate piece and have the cock attached below it. The bottom of the
cylinder E has a concave recess, which combines with the interior of the cup
F to produce a chamber of spheriodal form (see Figure 2 & 3), in which
works the flexible diaphragm e, upon which the pressure of the steam or other
fluid is received, and through which the said pressure acts upon the piston B.
This diaphragm e, which should be of vulcanized india-rubber or gutta percha,
is in its normal state of such cup-like form, as is shewn in detail at Figure 4,
so that it will fit either to the top of the chamberf in the cylinder E, or to the

page_text: bottom thereof in the cup F; it has a narrow flanch eat its edges, which is
clamped between the cup F and the bottom of the. cylinder sufficiently tight
'to prevent the escape round its edges of the steam or other fluid whose pres-
sure is to be guaged. A washer g of metal is. placed between the flanch e
and the bottom of the cylinder, to enable the flanch to be clamped more
tightly.
The spring C is bow-shaped, having the convex side 'downwards, and it's
ends are attached to two small radius arms g, g, which are fitted to work easily
on stationary pivots h, h, secured within the box, the said arms serving as
bearings for the spring, and at the same time providing for the movement of
its ends necessary to permit of variations in its deflection, by changes of pres-
sure upon it. The spring has a hole bored through it at the middle of its
length to receive the stem. B of the piston, which has a screw thread cut upon
it to receive two nuts;t, t, between which the spring is clamped to connect it
with the piston.
The arbor a of the index is fitted to bearings in a small frame i, i, which is
secured to the back of the box by screw bolts j,j, the said arbor being placed
in the, centre or axis of the box. It is furnished with a pinion k, which gears
with a toothed rack,l attached to the stem of the piston. A roller m carried
in bearings in the frame i, i, works against the back of the rack / to keep it
in-gear with the pinion. The index'd is fitted to the arbor in such a way as
to be adjustable, and is secured by a nut n fitting to a screw thread on the
end of the arbor. The mode of securing the spring to the piston by the two
nuts also provides for the correct adjustment of the guage.
The bottom of the cock G is furnished with a screw thread s'in its interior,
to receive a pipe communicating with the boiler or other reservoir containing
the steam or other fluid whose pressure is to be guaged. The cock is what is
known as a "three-way cock," having a passage p directly through it to admit
the steam or other fluid to the chamber f to act on the diaphragm c, and a
passage to communicate with a side opening r, for the purpose of allowing
the pipe to be blown out to remove any dirt or obstruction.
The steam or other fluid admitted through the cock to act upon the dia-
phragm raises the piston B, which acts through the rack and pinion upon the
index, and as the pressure increases and raises the piston higher the spring
becomes nearer straight, and its force increases in a proper ratio, so that it
always balances the pressure on the piston, and keeps the index steady in the.
proper position relatively to the dial, to indicate the pressure.
The spheroidal form of the chamber f in which the diaphragm works, and
the corresponding cup-like form of the diaphragm in its normal state, cause

page_text: the latter to be supported by the top or bottom of the chamber when exposed
to the maximum or minimum of pressure, and thus prevented from being
stretched and burst by the pressure of the steam or fluid in the one case, or of
the spring C in the other case.
Figure 5 is a front view of the piston B, exhibiting it with a hoop spring L
applied in place of the bow. spring C. This hoop spring is secured to the
stem of the piston by nuts t, t, in the same manner as the bow spring, and the
said hoop spring is intended to be secured by the screw u to the top of the
box A. The action of the spring is essentially the same as that of the bow
spring C.
Figure 6 represents a front elevation of another modification of pressure
guage, and Figure 7 is a section of the same with the front removed, shewing
the spring and capsule. A is a circular box of metal or other material, whose
front constitutes a graduated dial, over which works an index a, which is
secured to an arbor 6, fitted in suitable bearings within the box A. The box
is constructed with a cylinder B at the bottom, such cylinder standing perpen-
dicular to the arbor b, and being open at the top to communicate with the
interior of the box. This cylinder is for the purpose of containing the spring
D and capsule C, which are shown in section at Figure 7, and detail side ele-
vation in Figure 9, where it will be seen that the capsule is contained inside
of and forms a lining to the spring. A view of the spring with the capsule
side outside is shewn at Figure 8. The form of the spring and capsule is that
of a cylinder, terminating at the top in an hemispherical dome. The capsule
is made of vulcanized india-rubber, with a flanch d round its open bottom, to
enable it to be secured to the bottom of the cylinder B by means of the socket
of a cock G, which screws on to a screw thread cut on the lower part of the
exterior of the cylinder. Other suitable means of securing the flanches of the
capsule may be adopted. The lower part of the interior of the cylinder has a
screw thread cut in it, to enable two or three turns of the lower portion of the
spring, which is made of wire of suitable strength, to screw thereinto, for the
purpose of confining the said spring in its place when acted upon by the
sure of the steam in the boiler. The upper extremity of the wire rises from
the dome, as shewn at f (Figures 7 and 8), and has attached to it a toothed
rack
g, which gears with a pinion h on the arbor 6 of the index; the rack
being held in gear by a roller i placed on the back of it in suitable bearings
in the box A, as herein-before described with reference to the first modi-
fication.
pres-
The steam is admitted to the interior of the capsule by means of a pipe
which is to be screwed into the bottom of the socket of the cock G, and

page_text: entering the capsule exerts its pressure on all parts thereof, but as the capsule
is confined laterally by the spring it can only be extended lengthwise or in an
upward direction, in which direction the spring yields, and is elongated more
or less, according as the pressure of the steam exceeds that of the atmosphere.
in a greater or less degree. The spring acting through the rack and pinion'.
on the index causes the latter to stand in such a position over the face of the.
dial that it will, if the dial be properly graduated, indicate the pressure of
steam in the boiler.
:
The guage is constructed in the same manner as above described for.
guaging the pressure of any other fluid whose pressure may be greater than
that of the atmosphere; but for what is known as a vacuum guage, the cap-.
sule C will be applied to the exterior of the spring D, as is shewn in Figure 8,
which is an internal view of a guage of that kind. It is obvious that the cap-
sule must be either inside or outside the spring, according as the. inside or
outside is to be subjected to the greater pressure, otherwise the capsule could
not serve as a medium through which the spring is acted upon by the differ-
ential pressure, neither could the collapse or bursting of the capsule. be.
guarded against.
The vacuum guage in all respects, save the change in the relative posi-
tions of the spring and capsule, is constructed substantially like the steam
guage.
It may be well to remark that the action of the guage with the spring and
capsule, arranged as shewn in Figure 7, may be reversed to make it serve as.
a vacuum guage by making the box A air-tight, and connecting it by a suit-
able pipe with the vessel in which the vacuum is to be guaged, and opening
the cock G to the atmosphere. In like manner a guage with the spring and
capsule arranged as shewn in Figure 8 may be, employed as a steam guage
by making the box A steam-tight and admitting the steam to its interior by a
suitable pipe coming from the boiler and opening the cock G to the atmo-
sphere. The spring and capsule are susceptible of considerable change of
form; for instance, they may be made conical, conoidal, hemispherical, semi-
spheroidal, or of any form approximating to a dome or cup.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe, in conclusion, that I do not confine or restrict
myself to the precise details or arrangements which I have had occasion to
describe or refer to, as many variations may be made therefrom without
deviating from the principles or main features of the said Invention; nor
do I claim any of the mechanical elements of which the said apparatus and
j

page_text: parts of apparatus are respectively composed as being separately or apart
from the use or application of such elements to form the combinations consti-
tuting such apparatus and parts of apparatus respectively as being any part of
the said Invention; but what I consider to be novel and original, and there-
fore claim as the Invention secured to me by the herein-before in part recited
Letters Patent, is,-
First, the general combinations of parts constituting a pressure or vacuum.
guage, as herein-before described, and illustrated by the Drawings.
Second, the combination of a piston and flexible diaphragm, with a bow or
hoop spring and rack and pinion, in the manner and for the purpose herein-
before described:
Third, the application and use of a cup-shaped flexible diaphragm contained
within a spheroidal chamber, for the purpose herein-before described.
Fourth, the application and use of a helical spring of a dome or cup-shape,
or any other form approximating thereto, in combination with a capsule of
vulcanized india-rubber or other suitable elastic material, in the manner and
for the purpose herein-before described.
In witness whereof, I, the said John Henry Johnson, have hereunto
set my hand and seal, the Nineteenth day of December, One thousand
eight hundred and fifty-seven.
J. HENRY JOHNSON. (L.S.)