IMPROVEMENTS IN THE PREVENTION OF STEAM BOILER EXPLOSIONS
Year: 1858

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
IN THE PREVENTION OF STEAM BOILER EXPLOSIONS."-A communication from
Jane H. Lloyd, George T. Parry, and Henry D. Beylard, all of the City.
of Philadelphia, State of Pennsylvania, United States of America.
Sealed the 19th October 1858, and dated the 31st August 1858.
COMPLETE SPECIFICATION filed by the said John Henry Johnson at the
Office of the Commissioners of Patents, with his Petition and Declaration,
on the 31st August 1858, pursuant to the 9th Section of the Patent
Law Amendment Act, 1852.
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 I have this day presented my petition to Her most Excellent
Majesty Queen Victoria for a grant to me, my executors, administrators, and
assigns, of Letters Patent in respect of an Invention for "IMPROVEMENTS IN
THE PREVENTION OF STEAM BOILER EXPLOSIONS," a communication from Jane
H. Lloyd, George T. Parry, and Henry D. Beylard, all of the City of
Philadelphia, State of Pennsylvania, United States of America.
.
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

page_text: 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 a peculiar system or mode of preventing
steam boiler explosions arising from scarcity of water in the boiler, and an
undue heating of the plates, and consists simply in placing within the boiler a
metallic electric conductor insulated from the boiler plates, and made to com-
municate with the exterior of the boiler, whereby an electrical equilibrium is
maintained between the inside of the boiler and the outside thereof, and an
explosion of the boiler when the water becomes low, and the plates unduly
heated, is prevented.
The hypothesis upon which this Invention is based is, that when steam is
exposed to the action of red hot plates, a gas or gases of an intensely explosive
nature is or are generated, and that these gases possess the peculiarity
common to other explosive gases, namely, that of being ignitable only by
contact with a flame or with an electric spark, and not by contact with
a red hot or incandescent surface merely. Now, in generating steam,
electricity is given out, and this electricity is supposed to be restrained
within the boiler, its escape being prevented by the lining of mineral sub-
stance which is deposited in the interior of the boiler, and adheres to the
plates. So long as this lining or coating of deposit, which is a non-conducting
material, remains entire or unbroken, no explosion can take place, even
though the boiler plates be heated to redness; but if the non-conducting
lining or deposit become broken or cracked, so as to expose the heated
surface of the plate, this surface forms an electric communication between the
negative electricity outside the boiler, and the positive electricity in the interior
thercof, whereby an electric spark is produced, which ignites the gas or gases
herein-before referred to, and causes the explosion of the boiler.
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 in the Sheet of Drawings hereunto annexed,
the same letters of reference indicating corresponding parts throughout all the
Figures.
Figure 1 of the Drawings represents a sectional elevation of an ordinary
steam boiler, illustrating the improved mode of preventing explosions; Figure 2
is a corresponding sectional plan of the same; and Figure 3 is an enlarged
sectional detail of the mode of insulating the conducting rod which passes
through the boiler.
A represents the shell of the boiler, to the top of which is secured a socket B,

page_text: arranged to receive the gland or follower C; D is an insulator, composed of
glass, or other good non-conducting material. It is made in the form of a tube,
with an enlargement or collar a near the middle, such collar fitting into the
socket B, and being surrounded by packing contained within the recess
between the gland C and the bottom of the socket, in the manner of an
ordinary stuffing box. By this means, the insulator which projects above the
gland and down into the boiler is maintained stationary and steam-tight.
In the interior of the boiler is the metallic conducting rod E, which is
furnished with a number of attracting points b, b, and is attached to the
vertical rod F, the latter being screwed or otherwise secured to the rod G,
which passes through the insulator, to which it is confined by the collar c and
metal cap d. It is obvious, on referring to the Drawings, that an electric
equilibrium will be maintained by means of the conductor between the
exterior and interior of the boiler, thus obviating the danger of
any ignition
Having now described and particularly ascertained the nature of the said
Invention, and in 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 variations may be made therefrom without deviating
from the principles or main features of the said Invention; but what I consider
to be novel and original, and therefore claim as the Invention secured to me
by the herein-before in part recited Letters Patent is, the system or mode of
preventing steam boiler explosions, by placing within the boiler an insulated
metallic conductor, arranged so as to communicate with the outside of the
boiler, or with any matter surrounding the same, or in connection therewith,
in order to maintain an electrical equilibrium between the inside and outside
of such boiler, as herein-before described.
of the explosive gas or gases through the agency of electric sparks.
In witness whereof, I, the said John Henry Johnson, have hereunto set
my hand and seal, this Thirtieth day of August, One thousand eight
hundred and fifty-eight.
J. HENRY JOHNSON. (L.S.)