IMPROVEMENTS IN STEAM ENGINES
Year: 1856

page_text: Inis invention received Provisional Protection, out notice to proceed with the
application for Letters Patent was not given within the time prescribed
by the Act.)
PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office
of the Commissioners of Patents, with his Petition, on the 20th February
1856, A communication.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, and of Glasgow, North Britain, Gentleman, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN STEAM ENGINES," a com-
munication from Narcisse Duvoir, of Liancourt, in the Empire of France,
Mechanician, to be as follows:-
This Invention relates to certain peculiar constructions and arrangements of
steam engines applicable as stationary, marine, or locomotive engines, whereby
greater effect is obtained, combined with compactness and solidity. According
to one modification, two cylinders are employed, placed endwise in the same
axial line, either vertically, horizontally, or obliquely, fitted on to suitable fixed
supports, and divided from each other by one common division plate, serving
as the bottom to each cylinder. The two cylinders are both double-acting, and
are fitted each with a separate piston and rod of their own, passing through
stuffing boxes at the extreme ends of the combined cylinders. These rods are
connected to separate cross heads, which are again united by side rods. To
these rods at or near their centres are jointed two connecting rods, which are
united at their opposite ends by a cross head connected by a short rod to the
crank. The valve for the inlet of the steam is separate and distinct from the
escape valves, and both sets of valves are worked from separate eccentrics of
their own. The inlet valve consists merely of a rectangular plate, having a
rectangular opening in the middle of it, and this valve works in a steam chest,
placed over the division plate of the two cylinders. It is actuated by two arms

page_text: fixed to a rocking valve spindle, which is passed through a stuffing box in the
side of the steam chest. On the outer end of this spindle is a toothed segment,
gearing into a corresponding segment, which works on a stud centre. A species
of link is cast on the lower part of this last-mentioned segment, in the curved
slot of which is a sliding block or pin, which serves as an attachment for the
end of the connecting rod, and also for a rod connected with the governor.
The valve is thus enabled to work with a variable expansion through the
action of the governor. There are two ports for each cylinder in the steam
chest face, making four in all, namely, one for the top and one for the bottom
of each cylinder. The slide is so constructed, that when its central aperture
is over the port leading to the bottom of one cylinder, the edge of the slide will
be just past the port leading to the top of the other cylinder, and vice versa.
The exhaust or escape valves, of which there are four, are all connected, to one
rod, which is worked by a segment, actuated by an eccentric and rod of its own.
The steam on escaping may either enter a condenser or escape into the atmos-
phere, according as the engine is used as a condensing or high-pressure engine.
The same eccentric which works the escape valves works also a feed
pump.
When applied to a single cylinder, the arrangements herein-before. described
are necessarily slightly modified, since there is. only one piston rod to be con-
nected by the crank. In this arrangement the crank works at the opposite
end of the cylinder to that at which the piston rod comes out at, and the piston
rod is made to work in two fixed guide brackets. A cross head is fixed on to
the piston rod, and to.each side of this cross head is attached a connecting rod,
tle, two .connecting rods, being united behind the cylinder by another cross
head, which is connected by a short rod to the crank. In this modification,
the two side rods in the double cylinder.arrangement are dispensed with. The
rest of the parts remain the same or nearly so as those. referred to in the first-
described, arrangement. The inlet slide valve, when one cylinder only is used,
may be slightly modified, and may consist of a long plate extending from the
top to the bottom port of the cylinder, such ports opening direct into the
steam chest, which is extended for that purpose, in place of having long steam
passages cast in the cylinder.,