Improvements in Triple Expansion Engines.
Year: 1895

page_text: [Communicated from abroad by THOMAS MELVIN EDWARDS, of Mountain
Avenue, New London, Connecticut, Mechanical Engineer, U.S.A.]
Improvements in Triple Expansion Engines.
I WILLIAM HUMPHREY WHEATLEY of 40 Chancery Lane, in the County of
London, Patent Agent, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
This invention is in triple expansion engines of the marine type and its
immediate object is to produce a novel arrangement of cylinders, steam-valves
and ports whereby great economy in the use of steam shall be assured.
Figure 1 is a plan view of the cylinders of an engine embodying this invention
and Figure 2 is a vertical, sectional view of the same taken on line -. Figure 3
is a similar sectional view on line y-y.
Figure 4 is a plan view of a modified form of said invention and Figure 5 is a
vertical, sectional view of the same on line -2. This figure also shows a portion
of the crank shaft in proper position relative to the cylinders and piston rods.
In carrying the said invention into effect, it will be noted, that the high pressure
cylinder is preferably located between the two companion or low pressure cylinders
and the various ports, ducts and valves are so arranged that the steam, after
having served its purpose in one cylinder, is conducted by the shortest possible,
and most direct course to the next cylinder of the series; one of the objects of this
or, in
invention being to utilize the steam before appreciable condensation sets in
other words, while in its dry condition.
Referring to the drawings, A-B and C denote the three cylinders in the order
of their arrangement to take steam, and the letters a-b and e indicate their
respective pistons.
a, b and c denote their piston rods which may be connected to a crank-shaft D
in the usual, or any other desired manner, such connections forming however no
part of this present invention.
The high pressure cylinder A, it will be noticed, is formed with central walls a²
which in effect provides two "end-to-end" cylinders, whose pistons are carried by
the same rod (a) and which shortens the stroke to conform to that of the low
pressure cylinders. The duplex high pressure cylinder, thus provided (unlike its
companion cylinders) takes steam only at one side of each piston, its upper piston
being acted upon to produce the "up" stroke and the lower or companion piston
being acted upon to produce the "down" stroke.
Between the walls a² is an annular space a³ into which steam is first introduced
through the opening marked a" in Figure 3. At one side of cylinder A and
connecting with the described annular chamber a³ is a cylindrical chest a* in which
are two sets of cut-off valves a-a, of piston form, that are carried by a single
valve-rod a and are so distributed that they may register and co-act with the
ports a and a³ of the duplex cylinder A in manner substantially like ordinary
slide valves, but it should be noted that the valve pistons a³ and a are so set that
live steam is introduced only to the lower end of the upper chamber and to the
upper end of the lower chamber, the ports as being used only for exhaust purposes,
as hereinafter explained.
By means of the steam chamber a3 and the described ports and cut-off valves,
steam may be thus alternately introduced into the two chambers of cylinder A.

page_text: Referring now to Figure 2 it will be seen that midway the length of the upper
of said chambers is a port 12 that connects said chamber with the upper portion of
cylinder B and about midway the length of the lower chamber A is a similar
port that leads into the lower portion of cylinder B. These ports 62 and 63 serve
as exhaust ports for both the cylinders A and B, as will be described a little later,
but before doing so it is desired to call attention to similar port connections c²
and that connect the upper and lower cylinders A with the upper and lower
ends, respectively, of the low pressure cylinder C. It may also be stated here
that the relative areas of the several cylinders are, or should be, so proportioned
as to utilize to the best advantage the constantly reducing pressure of the steam.
When the steam, under high pressure, has been used in the upper cylinder A it
is exhausted through port 6 into the upper portion of cylinder B where, under
somewhat reduced pressure, it serves to force downward the piston b. In Figure 2
pistons a are shown on the up stroke and the upper cylinder A is just about to
exhaust through port to force piston b downward. As the steam thus forces
the piston downward the steam below said piston is allowed to escape through
port into the lower portion of the lower cylinder A and thence through ports e
into the lower portion of the low pressure cylinder C whose piston c is thus forced
upward.
In practice the piston b, when at its extreme highest point, as seen in Figure 2,
serves during the instant its crank is passing over the center to close the port ²
so that the steam in the upper chamber A may not too suddenly lose its hold on
the piston a by being allowed to expand into cylinder B.
Between the cylinders A and C is a cylindrical valve-chamber d in which are
located cut-off valves d² and d³ that are carried by a valve-rod d. These valves
serve to close and open, at proper times, the ports 2 and 3 and are so timed in
their action that they close said ports during the periods that steam is acting, under
high pressure, upon the pistons a, and upon said ports just following such action to
perinit the steam to pass from cylinder B through cylinders A, into the low pressure
cylinder C. It will thus be seen steam is first used, under high pressure in
the upper cylinder A and meanwhile is being exhausted from the lower portion of
cylinder B through the lower cylinder A into the low pressure cylinder C and is
finally exhausted through the ports ³ into the chamber d and outward through
a suitable discharge indicated by a dotted circle in Figure 2. The next stroke
of the engine introduces steam, under high pressure, into the lower cylinder A and
cuts it off from the upper cylinder A which latter is then utilized as a conduit or
way through which the steam in the upper portion of cylinder B is exhausted into
the low pressure cylinder C.
Two marked departures in this class of engines may now be called to notice.
First, the use with low pressure cylinders of a high pressure cylinder of duplex
form, the companion chambers of said duplex cylinder being acted upon alternately
by high pressure steam and second a similar arrangement of cylinders in which the
duplex chambers of the high pressure cylinder may be utilized as conduits or
receivers through which the steam may pass from one low pressure cylinder to the
other or last of the series.
It may be said further that ordinary triple expansion engines are always
constructed so there is a certain amount of back pressure between the cylinders
as the steam exhausts from one into the next of the train and, to relieve in some
degree this back pressure, so-called receivers are provided between the cylinders,
into which receivers the exhaust steam may first pass. In this new form of engine
the upper and lower ends of the duplex cylinder A serve the same purpose, in a
more simple manner, than when independent receivers are thus provided.
Another valuable feature of this improved engine lies in the fact that an
extremely simple and inexpensive way. is provided, to equalize the pressure on
opposite sides of pistons a. It will be noticed by reference to Figure 3, that
the cut-off a has passed upward far enough to open the port a of the lower
cylinder A, thus allowing the steam last used to exhaust through said port into

page_text: the valve chamber a and, finally, through the port 8 into the lower end of the
lower chamber where it mingles with the exhaust from cylinder B and passes
on to cylinder C. By thus opening a connection or conduit between the
opposite ends of the high pressure cylinders it is possible and feasible to
eqqualize the pressure between the high pressure and intermediate cylinders and
thus overcome the back-pressure which is universal in this class of engines.
In Figures 4 and 5 is shown a somewhat different arrangement of cylinders
relatively to each other, the high pressure cylinder A being at one end of the
train instead of intermediate the other two, but the duplex cylinder A is
constructed and is actuated in precisely the same manner as above described.
In the arrangement of cylinders shown in said Figures 4 and 5 cylinder A
exhausts immediately into cylinder B and the latter exhausts into the low
pressure cylinder C after the manner of ordinary triple expansion engines.
Having now particularly described the said invention and having ascertained
the manner in which it is to be performed, what is claimed as new and desired to
be secured by Letters Patent is :-
1. In a triple expansion engine, in combination, a high pressure cylinder formed
of two end-to-end chambers each provided with pistons and ports as set forth,
cut-off valves timed to deliver steam alternately to said chambers, and low
pressure cylinders connected with said high pressure cylinder, substantially as
specified.
2. In combination with a high pressure cylinder formed of two end-to-end
chambers each provided with pistons and ports as set forth, cut-off valves timed
to deliver steam alternately to said chambers, low pressure cylinders connected by
exhaust ports with said high pressure cylinder, and cut-off valves between the said
high pressure cylinder and the last cylinder of the train, all substantially as
specified.
3. In a triple expansion engine in combination, a high pressure cylinder formed
of two end-to-end chambers each provided with pistons and ports, as set forth,
and cut-off valves located and timed to deliver steam alternately to said chambers
at one side only of said pistons, as and for the purposes set forth.
4. In combination with a cylinder formed of two end-to-end chambers each
provided with pistons and ports as set forth, cut-off valves timed to deliver steam
alternately to said chambers at one side only of said pistons, and passages a*
connecting the opposite ends of each of said chambers whereby the exhaust may
pass around to the opposite side of the piston to equalize the pressure, ali
substantially as specified.
Dated this 15th day of January 1895.
W. H. WHEATLEY,
40, Chancery Lane, London, W.C.