IMPROVEMENTS RELATING TO SAFETY VALVES FOR STEAM BOILERS
Year: 1875

page_text: LETTERS PATENT to Joseph Hopkinson, of the Firm of J. Hopkinson,
& Co., Engineers, of Huddersfield, in the County of York, for the
Invention of "IMPROVEMENTS RELATING TO SAFETY VALVES FOR STEAM
BOILERS"
.Sealed the 11th February 1876, and dated the 28th August 1875.
PROVISIONAL SPECIFICATION left by the said Joseph Hopkinson at
the Office of the Commissioners of Patents, with his Petition, on
the 28th August 1875.
I, JOSEPH HOPKINSON, of the Firm of J. Hopkinson, & Co., Engi-
neers, of Huddersfield, in the County of York, do hereby declare the
nature of the said Invention for "IMPROVEMENTS RELATING TO SAFETY VALVES
FOR STEAM BOILERS," to be as follows:-
My Invention relates to apparatus wherein I employ a vessel con-
taining mercury and a mercurial column as an auxiliary device for
opening a safety valve to relieve the boiler from excessive pressure, or
to prevent the existence of excessive pressure within the said boiler.

page_text: This Invention is applicable to either "dead weight" valves or
weighted lever valves, and is essentially so arranged that the valve is
controlled in the ordinary manner solely by the weight until a certain
predetermined limit of pressure in the boiler is exceeded, and then tho
diminished weight of mercury in the vessel causes a free discharge of the
steam.
According to my. Invention I arrange in any convenient position
within the boiler a lever, which at one end carries a weight, and whose
other end is provided with a vessel containing mercury; and the stem or
rod of the said valve is arranged in relation to the said lever between this
end and its fulcrum. While the pressure in the boiler remains below
the limit for which the apparatus is adjusted, the weight on the lever and
the vessel containing the mercury counterbalance each other, or nearly
so, and the said lever is inoperative, and the valve acts freely and inde-
pendently like any other ordinary weighted safety valve; but when the
pressure of steam in the boiler rises above this limit the quantity of
mercury in the vessel is diminished by being forced up the pipe into the
higher receiver, and the weight on the lever acts to diminish the effect
of the weight on the valve spindle, which retains the valve on its seat.
The valve is thereby made free to open to its full extent, immediately
reducing the pressure in the boiler to its determined limit, as above
stated. The normal weight of mercury in the said vessel is then
restored, and the said lever is again in a state of equilibrium and
inaction.
"
It is obvious that the parts of my improved apparatus may be
variously constructed and arranged, but the following is a convenient
manner of carrying the said Invention into practice in connection with
a "dead weight' safety valve-The aforesaid lever has its fulcrum
fixed at one side of the stem or spindle of the said valve, and the said
lever has a hole or eye through which the said stem or spindle passes.
The said spindle is provided with a collar, or disc, or other projection,
which is adjustable, and may be fixed thereon at any required distance
above the said lever. A weight is placed at the end of a lever on the
opposite side of the fulcrum to the valve stem, so that this weight tends
always to raise the lever into contact with the said collar or disc. At
the other end of the said lever I suspend a cup containing mercury, in
which is immersed the end of a tube that extends up through the top of
the boiler.

page_text: Or instead of suspending the cup on the lever I may fix the said cup
inside the boiler, and attach to the end of the lever a weight which
floats in the mercury in the cup, the weight at the opposite end of the
lever being dispensed with.
The said tube is made of such a length or height as to hold a column
of mercury that will balance the pressure of steam at which it is
desirable the safety valve should open, and the cup holds such a quantity
as will counterbalance the weight on the opposite end of the lever when
the pressure of the boiler does not exceed the determined limit. At the
upper end of the said pipe there is a chamber or receiver, into which the
mercury enters if it rises in the said tube, and if required there may be
two or more of these receivers, one above-the other.
At any increase of pressure of steam in the boiler above the proper
and determined limit, the mercury is forced out of the cup up the tube
into the said receiver or chamber, thus diminishing the weight of
mercury in the cup, and acting upon the lever. The weight at the
other end of the lever then preponderates, and raises the part of the
lever through which the valve spindle passes; the lever then acting on
the collar or other projecting surface on the spindle counteracts the
effect of the weight on the said spindle, and allows the valve to open to
its full extent, thereby ensuring a free discharge of the excess of steam.
The reduced pressure due to this discharge allows the mercurial column
to descend in the tube and restore the equilibrium of the lever, and
again renders the safety valve independent of the said lever, as above
described.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Joseph Hopkinson in the Great Seal Patent Office
on the 17th February 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH
0 HOPKINSON, of the Firm of J. Hopkinson & Co., Engineers, of Hudders-
field, in the County of York, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-eighth day of August, in the
year of our Lord One thousand eight hundred and seventy-five, in the
+

page_text: thirty-ninth year of Her reign, did, for Herself, Her heirs and succes-
sors, give and grant unto me, the said Joseph Hopkinson, Her special
licence, that I, the said Joseph Hopkinson, my executors, adminis-¯
trators, and assigns, or such others as I, the said Joseph Hopkinson, my
exccutors, 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
"IMPROVEMENTS RELATING TO SAFETY VALVES FOR STEAM BOILERS," upon the
condition (amongst others) that I, the said Joseph Hopkinson, 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 the
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.
NOW KNOW YE, that I, the said Joseph Hopkinson, do hereby
declare the nature of my 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
Drawing forming a part of this Specification:-
My Invention relates to apparatus wherein I employ a vessel con-
taining mercury and a mercurial column as an auxiliary device for
opening a safety valve to relieve the boiler from excessive pressure, or
to prevent the existence of excessive pressure within the same.
.
The object of my Invention is to give safety valves an increased capa-
bility of discharging the steam from a boiler when the pressure exceeds
a predetermined limit, to which the valve is set or adjusted. It is well
known that when a safety valve is discharging steam at over-pressure,
the passage by which the steam escapes is merely the narrow space
due to a slight separation of the valve from the valve scat, and although
the pressure in the boiler may be increased beyond the limit to which
the valve is set, yet the valve will not open proportionately or rise
sufficiently from its scat to relieve the boiler from the excess of steam
generated; therefore the boiler is subject to the danger of explosion.
But by my improved apparatus I so increase the lift or opening of a

page_text: safety valve as to obtain thereby an area for the escape of steam equal
or nearly equal to the area of the orifice on which the valve is seated,
thereby providing a discharging capacity that will automatically prevent
any rise of the pressure above the predetermined limit.
The said Invention is applicable to cither "dead weight" valves or
weighted lever valves, and is essentially so arranged that the valve is
controlled in the ordinary manner solely by the usual weight until the
predetermined limit of pressure in the boiler is exceeded, and then the
diminished weight or quantity of mercury in the vessel containing the
same causes a free discharge of the steam.
According to my Invention I arrange in any convenient position
within the boiler a lever, which at one end carries a weight, and whose
other end is provided with a vessel containing mercury; and the stem or
rod of the said valve is arranged to be actuated by the said lever between
this end and its fulcrum. While the pressure in the boiler remains below
the limit for which the apparatus is adjusted, the weight on the lever
and the vessel containing the mercury counterbalance each other, or
nearly so, and the said lever is inoperative, and the valve acts freely and
independently like any other ordinary weighted safety valve; but when
the pressure of steam in the boiler rises above this limit, the quantity of
mercury
in the vessel is diminished by being forced up the pipe or tube
into a receiver, and the weight on the lever acts to diminish the effect
of the weight on the valve spindle, which retains the valve on its seat.
The valve is thereby made free to open to its full extent, immediately
reducing the pressure in the boiler to its determined limit, as above
stated. The normal weight of mercury in the said vessel is then
restored, and the said lever is again in a state of equilibrium and
inaction.
The said tube is made of such a length or height as to hold a column
of mercury that will balance the pressure of steam at which it is
desirable the safety valve should onen, and the cun holds such a quantity

page_text: Instead of suspending the cup on the lever I may fix the said cup
inside the boiler, and attach to the end of the lever a weight which
floats in the mercury in the cup. In this case the weight -at-the-
opposite end of the lever may or may not be dispensed with.
In the accompanying Drawing I have shewn a convenient manner of
carrying my said Invention into practice in connection with a
"dead
weight" safety valve, but the apparatus may be somewhat modified
in its application according to circumstances, and yet effect the same
results without in any way deviating from the principle of the said
Invention
Figure 1 shows & portion of a boner in longibamar section mustrating
the application of my improved apparatus to a "dead weight" valve,
with suspended cup of mercury on one end of lever and weight on
the other.
Figures 2 and 3 show modifications of my Invention, herein-after
described.
Like letters indicate the same parts throughout the Drawing.
A is the valve block attached to the boiler; B is the safety valve
placed upon the valve scat. The said valve is made of any suitable
diameter, and is weighted internally to the required pressure, as shown
at C. On the valve spindle D is a collar F, which can be adjusted to
any required height. The lever G is suspended in the boiler by a joint
or fulcrum I. H is a cup containing a quantity of mercury sufficient to
fill the column pipe L (which varies in length according to the pressure
of steam), and also to balance the weight K.
It will be seen that the said valve is free to act in the same manner as
an ordinary dead weight valve until the steam attains a pressure to
which the column pipe L and the receiver O are adjusted; then the
mercury being displaced by the pressure and forced from the suspended
cup H into the receiver O, the end carrying the weight K becomes the
heaviest end of the lever. When this happens the tips X on the lever
act on the collar F of the valve spindle, and raise the valve from its seat,
discharging the surplus or excess of steam as it is generated until the
normal maximum pressure in the boiler is restored; then the lever

page_text: returns to a state of equilibrium and rest, and the valve closes again
quite tightly, and is as free as an ordinary valve. The screws P³, P³, aro
provided to regulate the position and traverse of the said lever.
In the modification of my Invention shewn in Figure 2 I employ a
weight suspended on the lever, and floating in mercury in a stationary
cup H¹ fixed in the boiler. The pressure forces the mercury out of, this
stationary or fixed cup H up the pipe L into the receiver O; the
weight N then sinks in the cup and assists to raise the valve B from its
seat by the tips and collar, as above described.
The weight K is in this modification of my Invention used merely as
a balance weight. In Figure 3 I have shown the apparatus without this
weight.
The cup of mercury, whether suspended or fixed, may be placed out-
side the boiler in a suitably constructed and arranged casing, and
connected with the end of the inside lever. The cup containing mercury
may be surrounded with water to protect the mercury from a high degree
of temperature, such as it is exposed to when in the boiler.
At any increase of pressure of steam in the boiler above the proper
and determined limit, the mercury is forced out of the cup up the
column pipe into the said receiver or chamber, thus diminishing the
weight or quantity of mercury in the cup, and acting upon the lever;
the said lever then acting on the collar or other projecting surface on
the spindle counteracts the effect of the weight on the said spindle, and
allows the valve to open to its full extent, thereby ensuring a frèe dis-
charge of the excess of steam. The reduced pressure due to this
discharge allows the mercurial column to descend in the tube and
restore the equilibrium of the lever, and again renders the safety valve
independent of the said lever, as above described.
Having thus fully described my said Invention and the manner of
performing the same, I wish it understood that I claim,―
First. In combination with a weighted safety valve, a lever inside the
boiler, with a cup of mercury suspended on one end thereof, so operating
in connection with a column pipe and a receiver as to raise or open the
said valve on any increase of pressure above a predetermined limit, as
above described.
Second. In combination with a weighted safety valve a lever pro-

page_text: vided at one end with a weight, which floats in a fixed cup of mercury
inside-the-boiler, and so arranged in connection with a column pipe and
a receiver that the said valve is raised or opened on any increase of
pressure above a predetermined limit, as above described.
Third. A cup containing mercury so connected with a column pipe
and lever that the pressure within the boiler displaces the mercury and.
forces it from the said cup into the column pipe, and that the said cup
and mercurial column act as auxiliary means for giving a greater lift
or opening to a weighted safety valve, arranged in combination with
the said lever.