IMPROVEMENTS IN APPARATUS FOR PREVENTING EXPLOSIONS IN STEAM BOILERS
Year: 1844

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
LIDDELL, of Newcastle-upon-Tyne, and County of the same, Engineer, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-first day of February, in the seventh year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Thomas Liddell, Her especial licence, full power, sole privilege and authority,
that I, the said Thomas Liddell, my exors, adññors, and assigns, or such others
as I, the said Thomas Liddell, my exors, admors, or assigns, should at any
time agree with, and no others, from time to time and at all times during the
term of years therein expressed, should and lawfully might make, use, exercise,
and vend, within England, Wales, and the Town of Berwick-upon-Tweed, my
Invention of "IMPROVEMENTS IN APPARATUS FOR PREVENTING EXPLOSIONS IN STEAM
BOILERS;" in which said Letters Patent is contained a proviso that I, the said
Thomas Liddell, shall cause, a particular description of the nature of my said
Invention, and in what manner the same is to be performed, to be inrolled in
Her said Majesty's High Court of Chancery within six calendar months next
and immediately after the date of the said in part recited Letters Patent, as in
and by the same, reference being thereunto had, will more fully and at large
appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Thomas Liddell, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof, reference being had

page_text: to the Drawings hereunto annexed, and to the figures and letters marked
thereon (that is to say) :-
My Invention relates,--First, to the application of a hollow metal or other
proper float, to act on the safety valve, and in such manner that should the
level of the water fall below that which is the proper level, the float shall be
of sufficient weight to open the safety valve, and thus prevent explosion by
allowing the steam free vent from the boiler so long as the level of the water
in the boiler allows the hollow metal or other proper float to descend.
Secondly, my Invention relates to the application of a syphon with mercury
therein, so arranged that when the pressure within the boiler becomes greater
than the proper working pressure, in consequence of the safety valve sticking
to its seat, the column of mercury, which otherwise is capable of resisting the
pressure of the steam, is overcome, and the pressure of steam in the boiler is
brought to act on the lever of the safety valves as well as against the valve
itself, and thus offering more powerful means for lifting the safety valve; and
in order that the Invention may be most fully understood and readily carried
into effect, I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
a is the ordinary
Figure 1 represents the section of part of a steam boiler.
safety valve, having a weight suspended thereto, and within the boiler, but the
weight may be external of the safety valve, so as to press it into the seat.
And it should be remarked that my Invention is not confined to any particular
construction of safety valve or manner of weighting it, but consists in applying
a hollow metal float in such manner as to raise the safety valves when the
water in the boiler falls too low. 6 is a lever connected to the safety valve,
moving on a fulcrum or axis at c, as is shewn. d is a rod, attached at its
lower end to a hollow metal float, of such a weight as will be sufficient to
open the safety valve in the event of the water falling below the proper level
in the boiler. The rod moves through a stuffing box at e, and is guided and
retained vertical by the fixed guides f, through which the rod is capable of
sliding freely. On the upper part of the rod d is applied a nut or stop g,
which, when the hollow metal float descends, comes down on the lever b, and
draws down that end of the lever, and consequently will open the safety
valve; for it will be understood that not only is the safety valve under such
circumstances pressed on by the steam with a tendency to open it, but the
weight of the float, which exceeds the weight pressing on the safety valve,
comes into action by the falling of the water in the boiler, and aids the steam
in opening the safety valve.

page_text: Figure 2 shows another arrangement of the apparatus for such cases as will
not admit of the requisite hollow metal float being within the boiler, in which
case a vessel h is applied, as is shewn at Figure 2; in other respects the
apparatus is similar to that above explained.
I will now describe the second part of my Invention, which, as before
stated, relates to a mode of using a column of mercury in a syphon pipe
within the boiler, and Figure 3 shows the section of so much of a steam
boiler and of the apparatus as will enable me to describe this part of my
Invention. is the safety valve; a¹ is the weight above; b is the lever moving
on a fulcrum or axis at c; this lever is attached by means of a connecting
rod to the safety valve a; d is a piston moving in the cylinder e, the piston
rod passing through the lever b. From the interior of the cylinder e descends
an iron pipe f, forming a bend or syphon, as is shewn. In this tube mercury
is filled to such a height that the column will be equal to the pressure of the
proper working steam, and it will readily be understood that in case of the
pressure of steam becoming greater than is proper, and yet not able to lift
the safety valve, the column of mercury will be overcome and driven into the
cylinder e, when the pressure of the steam will act on the piston d, and thus
aid in lifting the safety valve; g is a screw plug for running the mercury
again into the syphon tube. The dotted lines shew that the syphon pipe may
be turned down under the water, in which case, when the pressure rises too
high in the boiler, the steam pressing in the water will drive it into the syphon
pipe, and the water will then press on the piston d in place of the steam.
Having thus described the nature of my Invention, and the best means I
am acquainted with for performing the same, I would have it understood that
I do not confine to the details shewn, so long as the peculiar character of
either part of my Invention be retained. But what I claim is,-
First, the application of a hollow metal or other proper float, in such
manner as to act on the safety valve and cause it to open when the level of the
water in a steam boiler falls too low.
And, secondly, I claim the application of a syphon pipe with a column of
mercury in the manner herein described to act on the safety valve of a steam
boiler, and cause it to open when the pressure in the boiler becomes too great.
In witness whereof, I, the said Thomas Liddell, have hereunto set
my hand and seal, the Thirteenth day of August, in the
year
of our
Lord One thousand eight hundred and forty-four.
THOMAS (L.s.) LIDDELL.

page_text: AND BE IT REMEMBERED, that on the Thirteenth day of August, in the
year of our Lord 1844, the aforesaid Thomas Liddell came before our said
Lady the Queen in Her Chancery, and acknowledged the Specification afore-
said, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
Enrolled the Twenty-first day of August, in the year of our Lord One
thousand eight hundred and forty-four.