IMPROVEMENTS IN STEAM, AIR, AND GAS, AND IN FLUID OR HYDRAULIC ENGINES
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by William Firth at the Office
of the Commissioners of Patents, with his Petition, on the 23rd
September 1870.
I, WILLIAM FIRTH, of Rose Villa, Viewforth, Edinburgh, Scotland,
Secretary to the North British Rubber Company, Limited, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN STEAM,
AIR, AND GAS, AND IN FLUID OR HYDRAULIC ENGINES," to be as follows:-
These improvements relate to the construction of the cylinders or
actuating chambers of such engines, and of the pistons which move
therein, and to the manner of applying the elastic force of steam, air,
and gas, and the pressure of water or other fluid to cause said pistons to
move in said cylinders.
These improvements in part consist essentially in employing about
one-half of the motive force of the steam, gas, air, or fluid used in any
such engine to transmit motion by any suitable connecting piece or
connecting rod to machinery external thereto during the motion of the
piston in one direction, and in accumulating the other half of the motive
force to be given out or transmitted to the machinery by causing the

page_text: piston to move in the opposite direction when relieved from the direct
motive force of the engine.
These improvements I carry out in practice by constructing on one side
of the piston a cushion of india-rubber or other elastic material alone, or
a cushion or cushions of india-rubber in combination with solid elastic
materials, such as steel in the form of springs, or with gaseous materials,
such as common air. The spaces on the other side of the piston, and
between the sides of the cylinder and the elastic cushion or cushions just
described, and also the pipes or passages leading from or to the cylinder,
are filled with water or other fluid, on the surface of which is applied
(and by means of which is transmitted) the pressure or force of the
motive element of the engine (whether it be steam, gas, air, or water, or
other fluid) to the elastic and compressible piston in the cylinder
(primary cylinder). The water or other fluid in the cylinder surrounding
the piston can be kept cold, and any desired part of the water or other
fluid in the pipes or passages (secondary cylinder) leading thereto (the
primary cylinder) may be kept at any desired temperature, and thus,
any rapid condensation of steam or cooling of the gas or air may be
prevented, and the exhaust steam, heated air, or gas, may be employed
to heat the fluid piston thus formed by applying it to the outside surfaces
of the pipes or passages or secondary cylinder or cylinders in which the
fluid piston moves.
In working the valvular arrangement or the arrangement by which
the motive force of the engine is applied intermittingly or otherwise to
the fluid piston, and by it to the compressible and elastic piston of the
engine, I employ the buoyant power of the fluid piston in connection
with a suitable vessel floating thereon for working the valvular arrange:
ment; but I sometimes employ the ordinary slide valve arrangements
well known and hitherto in use in working steam engines.