AN IMPROVED MODE OF PREVENTING THE OVER-HEATING AND BURSTING OF STEAM BOILERS
Year: 1857

page_text: LETTERS PATENT to Edward Halliday Ashcroft, of the State of Massa-
chusetts, of the United States of America, for the Invention of "AN
IMPROVED MODE OF PREVENTING THE OVER-HEATING AND BURSTING OF STEAM
BOILERS." A communication from John Absterdam and William Burnett,
foreigners residing in the aforesaid State of Massachusetts
Sealed the 19th January 1858, and dated the 11th November 1857.
COMPLETE SPECIFICATION filed by the said Edward Halliday Ashcroft,
at the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 11th November 1857, pursuant to the 9th section of
the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME,
BE IT KNOWN, that I, EDWARD HALLIDAY ASHCROFT, of the State of
Massachusetts, of the United States of America, am in possession of "AN
IMPROVED MODE OF PREVENTING THE OVER-HEATING AND BURSTING OF STEAM
BOILERS," (the same having been communicated to me by John Absterdam
and William Burnett, foreigners residing in the aforesaid State of Massa-
chusetts,) and I 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 Specification and the accompanying
Drawing:-

page_text: The nature of the Invention consists in a new or improved mode of
applying fusible metal to a boiler; the same consisting in inserting in a steam
boiler, at a point below the proper water line thereof, a pipe which shall
extend out of the boiler; and have at a suitable distance from said boiler a
stopping plate of fusible metal or other fusible compound, so arranged that
by a free exposure of the said pipe to the atmosphere outside of the boiler
the water contained in the pipe shall have its temperature so far reduced by
radiation as to preserve the fusible plate in a solid state, such plate being
easily melted by the temperature of the steam in the boiler when the water
level shall have fallen so low as to admit the steam into the pipe. When
the plate of fusible metal shall have been thus melted, the steam issuing
from the pipe may be conducted into the furnace by arranging the pipe as
represented in the Drawing, such arrangement being for the purpose of
extinguishing the fire of the furnace. Or, instead thereof, the steam may be
used to give notice by its noise or through an alarm whistle that the water
has become too low in the boiler.
To enable others skilled in the art to make and use my Invention, I will
proceed to describe its construction and operation, reference being had to the
accompanying Drawing, which is a transverse sectional elevation of a common
cylindrical steam boiler, represented as provided with two internal flues, and
set in brickwork in the usual manner. The Drawing also denotes two appli-
cations of the Invention to the said boiler: in the one case it being applied
to the top, and in the other to the side thereof. A, A, represents the boiler;
B, B, two internal return flues; C, the flue under the boiler, and leading
from the furnace D; E, E, grate bars; F, ash-pit; G, G, brickwork setting
as commonly employed; H indicates the proper water line at which the water
should be in order to cover the surface exposed to the action of the flame of
the furnace. The pipe I, I, which has one of its ends inserted in the boiler
at J, and the other opening into the furnace at K is stopped up by a plate or
plug of fusible alloy L, the said alloy being so compounded as to melt with
the temperature of steam of atmospheric pressure, and consequently with
steam of all higher pressures.
The operation of the Invention is as follows: When the water in the
boiler is at the proper height, as shown at H, the pressure of the steam on its
surface will cause such water to be forced up into the pipe I, I, as far as the
plate of fusible metal L, which will prevent its further egression. The
distance of the said plate of fusible metal from the boiler should be such that
by a free exposition of the intermediate pipe to the atmosphere the water
contained therein shall have its temperature so far reduced by radiation as to

page_text: preserve the said plate of fusible metal from being melted. Under these
circumstances, when the water level in the boiler may fall below the mouth
of the pipe or dotted line shown at N, the comparatively cool water in the
pipe will run from it into the boiler, and the steam above the surface of
the water will enter the said pipe and melt the plate of fusible metal, so as
to allow the steam to pass through the pipe and issue from its end K into
the furnace and on the fire therein, so as either to wholly or partially ex-
tinguish the same. The cock M is for the purpose of stopping the com-
munication with the boiler, in order that the plug or plate of fusible metal
may be renewed, and also in case of the said plug or plate having been fused,
such cock may be employed to stop the flow of steam into the furnace when
the fire therein shall have been sufficiently extinguished..
D
My Invention as applied to the side of a boiler has that part of the pipe
containing the plate of fusible metal a little elevated above the point of
insertion in the boiler, such being for the purpose of facilitating the running
of the water out of the pipe when the water level shall have become too low
in the boiler. In its application to the top of the boiler the pipe must be
extended down within the said boiler, as shown in the Drawing, so that the
mouth of the said pipe shall have the same position with regard to the water
and fire lines as if it had been inserted in the side of the boiler without any
such extension of the pipe into the boiler, as described. The vertical pipe is
bent, as shown at O, so as to effectually prevent steam from entering the said
pipe except when the water is too low in the boiler. The fusible plate or
plug L may be put into the pipe in any way that the artizan may find
sufficiently convenient and durable, but I use a case (as shown in the
Drawing) capable of being easily separated or opened, so as to enable a
person to conveniently renew the plug when it may have been fused. The
part P, P, is made so that it may be unscrewed from the part Q, Q, after
which it may be easily separated at R, R, where the joint may be made
steam-tight by means of india-rubber or any other convenient means. The
plate of fusible metal L instead of being inserted in the pipe I, I, in the
position represented in the Drawing, may be inserted at the red line shown
at S, in the vertical part of said pipe, by which arrangement the water of the
boiler will be effectually prevented from coming in contact with the said
fusible plate, as the air originally contained in the whole of that part of the.
pipe which is below the fusible plate, and leads from the boiler, will always
occupy a space inversely as the pressure to which it may be subjected. Thus,
the water while the fusible plate remains whole can never wholly occupy the
pipe, as there will be a condensed volume of air between the surface of the

page_text: water and the fusible plate of metal. Such an arrangement is for the purpose
of preventing any deposit of sediment or scale on the fusible plate by which
its fusibility might be impaired in the slightest degree.
What I claim is the above-described mode of. applying a fusible plate or
plug to a steam boiler, that is, so arranging in a pipe which is connected with
a steam boiler a fusible plug or disc that it shall be removed so far from the
said boiler, and so connected with the water therein, that when the water is
sufficiently high the plug or disc may be in contact or so surrounded with
water cooler than that in the boiler as to prevent it from being fused; but
when the water in the boiler shall fall below a proper height, the steam shall
enter the pipe and come in contact with said plug, or so surround it as to
cause it to melt and allow the escape of steam, as specified.
In testimony whereof; I have hereunto set my signature and seal, this
Twenty-third day of October, in the year of our Lord One thousand
eight hundred and fifty-seven.
EDWARD HALLIDAY ASHCROFT.
L.S.)