IMPROVEMENTS IN APPARATUS FOR PREVENTING STEAM BOILER EXPLOSIONS
Year: 1856

page_text: application for Letters Patent was not given within the time prescribed
by the Act.)
PROVISIONAL SPECIFICATION left by John Knowelden at the Office
of the Commissioners of Patents, with his Petition, on the 15th July
1856.
I, JOHN KNOWELDEN, of 3, South Street, Southwark Square, in the Borough
of Southwark, in the County of Surrey, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN APPARATUS FOR PREVENTING STEAM BOILER
EXPLOSIONS," to be as follows:-
For the purpose of obviating the risk of explosion from negligence or
ignorance in loading the safety valve, I propose using two valves, which I
arrange in the following manner :-On top of and connected to one of the
valves I joint the end of a lever, which in the direction of its length passes
over and rests upon the top of a second valve, which at times acts as fulcrum
to the lever, as herein-after described. From the top of the first-named
valve and above the lever joint proceeds a spindle, the top of which works in
a guide, screwed into the top of a chamber or box which encloses the valves;
this chamber or box having a slot in it to allow the lever to pass through, the
valves being locked up in the box, the weight and portion of lever only being
on the outside on top of the first-named valve to which the lever is jointed,
and-fitting loosely round the spindle proceeding from the same. I fix a
spiral spring, one end of which presses against the spindle guide on the top

page_text: if
of chamber, the other pressing on the valve with a force equal to double the
working pressure of steam desired. On the end of the lever I place the
weight in the usual manner, which acts in the ordinary way upon the second
valve. The advantage I gain by the addition of the first-named valve is that
any additional weight be placed upon the lever, for the purpose of increasing
the
pressure in the boiler, the second valve becomes the fulcrum of the lever,
and the first-named valve then becomes the working one; by this arrangement
it is impossible by neglect, ignorance, or' design, to load the valves above the
working pressure to which they have in the first instance been set. To
prevent explosions from want of water or extreme pressure in the boiler, I
adapt the following arrangement to it, by which means I prevent the generation
of steam after the water comes below a certain level. Into the bottom of the
boiler I screw or fix a tube, which tube ends on the
and in the inside at a point below the low-water level.
inside the boler is fitted with and closed by a spherical valve, which valve is
fixed to and kept in position by means of a hollow or other float, of sufficient
buoyancy to keep the spherical valve water-tight under any ordinary working
pressure. I so arrange the valve and float that so long as sufficient water
for-safe working remains in the boiler, the spherical valve is kept closed; but
directly the water gets below the proper level in the boiler the float following
opens the valve, or should the steam exceed the proper working pressure
the float and valve will be depressed in either case, the water still being above
the valve rushes through the tube, terminating over the fire, extinguishing .it
and preventing further generation of steam.
it
outside over the fire,
The end of the tube