IMPROVEMENTS IN SAFETY-VALVES FOR STEAM-BOILERS
Year: 1880

page_text: LETTERS PATENT to Charles Stuart, of Bletchley Iron Works, Fenny
Stratford, in the County of Bucks, Mechanical Engineer, for an Invention of
"IMPROVEMENTS IN SAFETY-VALVES FOR STEAM-BOILERS."
PROVISIONAL SPECIFICATION left by the said Charles Stuart at the Office
of the Commissioners of Patents on the 17th November 1880.
CHARLES STUART, of Bletchley Iron Works, Fenny Stratford, in the County
of Bucks, Mechanical Engineer. "IMPROVEMENTS IN SAFETY VALVES FOR STEAM
BOILERS."
The object of my Invention is to obtain a more rapid closing of the valve
or valves when the pressure of steam in the boiler is diminished, and also to
utilize that pressure itself in obtaining the requisite force to act
on the
valve or valves in lieu of the heavy weights or springs generally employed
for that purpose, especially in marine safety valves. The valve chest is of
cast iron with a branch pipe in the usual manner, and fitted with a brass
valve seat. The casing is partly closed above and bored out for the reception of
a brass bush, in which a seat is turned to receive the upper end of the main valve,
while the lower end rests in the brass seat at the bottom of the valve chest. A
flange above the upper seating prevents the escape of steam downwards through
the upper seat when the valve lifts. The bush is closed above by a screwed plug
in which works a small valve kept in its seat by an adjustable spiral spring, and
the valve, screw, and spring, &c., are enclosed in a brass cylinder screwed to the
plug by a flange at its lower end. The cylinder is inserted in a bush screwed into
the top of the cast iron valve chest, the bush being formed with an octagonal head
by which it can be turned, thus raising or lowering the valve, bush, and all
attached to it, so as to accurately adjust the two seats of the main valve.
index works in a vertical slot in the brass cylinder indicating the pressure to
which the small valve is loaded, and the cylinder is covered by a cast-iron dome
screwed to the valve chest, and a bracket is cast on the dome to support the lever
which operates on the cap.
An
In action the steam impinges on the main valve through the bottom of the casing
in the usual manner, but the valve instead of being solid above has a small opening

page_text: bored through its top by which the steam enters the space between the main valve
and the plug. The plug being closed by the small valve, the steam between the
valves attains the same pressure as that in the boiler, but the upper seat being
larger than the lower the valve is held down with a pressure due to the difference
between their two areas. When the pressure in the boiler becomes sufficient to
raise the small valve against its spring a decrease of the pressure between the
valves at once takes place, and when the escape of steam through the small valves
reduces the pressure between the valves to less than that below the main valve,
the latter lifts, allowing the steam to escape through the seating and out of the
branch-pipe. Directly the pressure in the boiler decreases the small valve comes
down, the pressure between the valves becomes again more than that below the
main valve, and the latter closes instantly.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Stuart in the Great Seal Patent Office on the 16th May
1881.
CHARLES STUART, of Bletchley Iron Works, Fenny Stratford, in the County of
Bucks, Mechanical Engineer. IMPROVEMENTS IN SAFETY VALVES FOR STEAM
BOILERS."
"
The object of my "Invention" is to obtain a more rapid opening and closing of
the valve or valves when the pressure of steam in the boiler is higher or lower
than that required, and also to utilize that pressure itself in obtaining the requisite
force to act on the valve or valves in lieu of the heavy weights or springs
generally employed for that purpose, especially in marine safety valves.
The valve chest is of cast iron with a branch pipe in the usual manner and
fitted with a brass valve-seat. The casing is partly closed above and bored out
for the reception of a brass bush in which a scat is turned to receive the upper
end of the main valve, while the lower end rests in the brass seat at the bottom
of the valve-chest. A flange above the upper seating prevents the escape of steam
downwards through the upper seat when the valve lists. The bush is closed above
by a screwed plug in which works a small valve kept in its seat by an adjustable
spiral spring, and the valve, spring, and screw are enclosed in a brass cylinder
screwed to the plug by a flange at its lower end. The cylinder is inserted in a
bush screwed into the top of the cast iron valve chest, the bush being formed with
an octagonal head by which it can be turned, thus raising or lowering the valve,
bush, and all attached to it, so as to accurately adjust the two seats of the main
valve. An index works in a vertical slot in the brass cylinder indicating the
pressure to which the small valve is loaded, and the cylinder is covered by a cast
iron dome screwed to the valve chest, and a bracket is cast on the dome to support
the lever which operates on the cap. In action the steam impinges on the main
valve through the bottom of the casing in the usual manner, but the valve
instead of being solid above has a small opening bored through its top by which
the steam enters the space between the main valve and the plug. The plug being
closed by the small valve the steam between the valves attains the same pressure
as that in the boiler, but the upper seat being larger than the lower the valve is
held down with a pressure due to the difference between their two areas. When
the pressure in the boiler becomes sufficient to raise the small valve against its
spring a decrease of the pressure between the valves at once takes place, and when
the escape of steam through the small valve has reduced the pressure between the
valves to less than that below the main valve the latter lifts, thus allowing the
steam to escape through the seating and out of the branch pipe. Directly the
pressure in the boiler decreases the small valve comes down, the pressure between
the valves becomes again more than that below the main valve, and the latter
closes instantly.
In further explanation of my said Invention I annex two Sheets of Drawings.
In Sheet No. 1, A is the cast iron valve chest with brass valve seat B.
C is the brass bush, and D the main valve.
E is the screwed plug, and F the small valve.
F is the spiral spring, and G the enclosing cylinder.

page_text: Having thus explained the nature of my Invention, I declare my claim to be,-
Operating one or more valves of unequal areas by one or more regulating valves
weighted with either springs or dead weights, substantially as herein described, so
that the area of discharge is increased without the need for heavy weights or
powerful springs.
In witness whereof, I, the said Charles Stuart, have hereunto set my hand
and seal, this Thirteenth day of May, in the year of our Lord One thousand
eight hundred and eighty one.
CHARLES STUART. (L.S.)