IMPROVEMENTS IN APPARATUS FOR. INDICATING AND REGULATING THE PRESSURE OF STEAM IN BOILERS
Year: 1856

page_text: was not given
time prescr
by the Act.).
PROVISIONAL SPECIFICATION left by Colin Farquharson and William
Grimshaw at the. Office of the Commissioners of Patents, with their
Petition, on the 3rd October 1856.
We, COLIN FARQUHARSON and WILLIAM GRIMSHAW, both of Mitcham, in
the County of Surrey, Engineers, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN APPARATUS FOR. INDICATING AND REGULATING
THE PRESSURE OF STEAM IN BOILERS," to be as follows:-
Our improved apparatus for regulating and indicating the pressure of steam
consists of a hollow flexible vessel filled with water or other fluid, which is
subject to the pressure of the steam in the boiler, and which thereby exerts
a force to distend the flexible vessel. We form this vessel of india-rubber or
other suitable material somewhat in the form of a globe with a tube stem
depending therefrom. We enclose this vessel and tube in a metal case fitting
closely round it to prevent accident from bursting. The lower part of the
tube is connected with a bent metal tube, which turns upwards, and then
A
proceeds thence to the boiler. This bend is always kept full of water.
piston or disc rests on the upper part of the globular vessel, of sufficient area
and form to prevent injury to the flexible material. From this piston a stem
or rod projects upwards through the top of the metal case enclosing the globe,
which rod is counected with a lever across the top, in a manner similar to
an ordinary safety valve. The pressure of the steam acting to distend the

page_text: flexible vessel forces up the piston and rod, and so raises the lever. This lever
is weighted according to the pressure required. The weight and lever rest on
a suitable stop, and keep the globular vessel in a partially collapsed state so
long as the pressure of the steam on the piston is insufficient to raise it, and
the weighted lever keeping it down; but so soon as the pressure becomes
excessive, and above what is required in the boiler, the flexible vessel expands
and forces up the piston and its weighted lever, thereby indicating the excess
of pressure. In order to regulate the pressure in the boiler, we connect the
lever by suitable rods or other means with the damper in the chimney, which
is closed, or partially so; when the lever is so lifted, the fire is thereby
damped, and will be kept so damped until the excess of pressure in the boiler
subsides, when the vessel will again collapse, and thus permit the piston and
lever to fall, which action again opens the damper. With a view to indicate
the different gradations of pressure, and gradually to act on the damper, we
depress the lever by. the opposing force of a spring, which force increases the
more it is lifted; or by a number of weights, which are lifted by the lever in
succession according to its rise. In this arrangement the lever will begin to
rise at any pressure at which it may be adjusted, and will continue to do
so according as the pressure increases, so as to lift a greater weight on the
lever than that.it then sustains, and will so gradually rise and also close the
damper. As the pressure subsides the damper will again gradually close.
A graduated scale may be adjusted opposite the free end of the lever to
indicate the several gradations of pressure; or a second lever, or index hand
may be actuated from the first lever, or by the motion of the piston, & in
connection with a proper scale for the purpose.