IMPROVED VALVE MOTION FOR REVERSING STEAM ENGINES."
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Frederick Joseph Bird at the Office
of the Commissioners of Patents on the 21st November 1876. A communication
from abroad by Hiram Stevens Maxim, of the City, County, and State of
New York, United States of America.
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FREDERICK JOSEPH BIRD, of Kingsland, in the County of Middlesex. IMPROVED
VALVE MOTION FOR REVERSING STEAM ENGINES." A communication from abroad
by Hiram Stevens Maxim, of the City, County, and State of New York, United
States of America.
This improved valve motion for reversing steam engines is suitable also for steam
jackets, hoisting engines, and all purposes where it is desirable to change the point
of cut-off or the direction of rotation, and also the Invention relates to that class of
steam engines used for steam boats, &c., where the engine has to run either forward
or backward. The reversing is accomplished with but one eccentric, that being
moved in a straight line from the full forward to the full back, the lead being about
constant at all points of cut-off. As an example, I take an engine with the cylinder
and steam chest mounted on frame and bed plate. On the crank shaft is a drum
enclosing the valve gear, said drum forming a fly wheel to steady the motion of the
engine.
A reversing lever, with its fulcrum and a clutch, is provided, that operates a
sliding sleeve. This lever has a catch that drops into notches in an arch.
The eccentric may be moved in any direction, either forward or backward, by
means of a bell-crank lever. To the eccentric is attached the strap and rod con-
nected to the slide valve rod.
The operation is as follows:-On rising the catch and moving the reversing lever
forward the sleeve is also moved in the same direction; this moves the bell-crank
lever, and slides the eccentric in a direction to diminish its throw, and at the same
time increase its angular advance, so that the lead of the slide valve may not be
changed. When the lever has reached a half-way or nid gear position the engine
stops, as at that point the throw is only equal to the lap and lead. Now let the
lever be thrown still further over, and the throw of the eccentric is increased until
steam is admitted to the cylinder during, say, 7, of its stroke. It will thus be
seen that the steam may be cut off at any point, or the engine reversed quite as
[Price 20.1

page_text: well as with two eccentrics and a costly and cumbersome link motion; besides
when the eccentric is thrown either side of its centre its centrifugal force inclines it
still further in that direction; thus all loss motion in the ports is avoided, the lever
being easily moved, and with no tendency to stake. The eccentric is cast in one
piece with a spider that is secured to the fly wheel in such a manner that while it
is free to move in a straight line it cannot move in any other direction. The iron
composing the shifting gear of the eccentric revolves with the shaft, and is encased
in the drum, which with them constitutes a fly wheel; it will therefore be seen that
the iron is made to serve a twofold purpose, while it is very desirable where weight
is restricted.
When the engine is used in small boats, and is operated by amateurs, it is easily
understood and kept in order, as to go astern the lever is moved ahead and pulled
back to back. Whichever way the lever is moved in that way the boat goes, and
it has no complicated moving parts to require constant attention and adjustment.
It produces the same result as that obtained by the best link motion, and at much
less cost and weight of parts.