IMPROVEMENTS IN DUPLEX STEAM ENGINES
Year: 1884

page_text: I, MILAN WOODBURN HALL, of N° 17 Adams Street, in the City of Brooklyn, in
the State of New York, United States of America, Mechanical Engineer, do hereby,
declare the nature of my Invention for IMPROVEMENTS IN DUPLEX STEAM ENGINES,
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
This Invention relates to duplex steam engines or those which consist of two
engines, each with cylinder, piston and valve complete, arranged side by side and.
adapted to each control the operation of the valve of the other. Such engines are
most commonly used for pumping but are adapted also for other uses.
In the Drawings, Figure 1 is a side elevation of the engine constructed as a
pumping engine. A is the stean engine and B the pump. The two storm cylinders
are arranged in line with the two pump-cylinders and are connected by a yoke a.
Each engine has one piston-rod 6 which bears the steam-piston on one end and the
pump-piston on the other end. The pump B may be of any desired construction
and forms no part of this Invention.
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3
Figure 2 is a vertical longitudinal mid-section of one steam-engine as denoted
by the line 2 - - 2 in Figure 3; Figure 3 is a transverse section through the two
engines, as denoted by the lines 3--
----3 in Figures 2, 4 and 6. Figure 4 is a
plan of the steam-cylinders alone, the valve-chests having been removed.
CC are the two steam-cylinders, and D D₁ are their pistons fixed on the
piston-rods b b. Each cylinder has two steam-ports c'c¹ opening into them at
their extreme ends, and two exhaust-ports d d¹ opening into them a short distance
from their ends (see Figure 2). These ports extend toward the middle and
between them is the exhaust-port e as usual, which opens into the main exhaust-
passage E. This passage extends across between the ports ee of the two engines,
and leads to an outlet E¹ (Figure 4) where the exhaust pipe F (Figure 1) is to be
connected.
A plate G fits over the flat top of the two cylinders C C (Figures 2 and 3) and
the several ports c c, d d, and e extend up through it. Over this plate works a
flat slide-valve.H (Figure 2) which operates in the usual way. It is moved back
and forth by a plunger I the enlarged ends of which form pistons which work in

page_text: cylindrical chambers f. f¹. in the steam-chest J. The valve H¹ plunger I¹ and
steam-chest J of the other engine are of the same construction. The two steam
chests J J are connected by a steam-passage K (Fig. 3) and they fit over the
plate G, as shown.
Figures 5 and 6 show the plate G removed. Figure 5 is a plan of the underside
of the plate, and Figure 6 is a plan of its upper side. Figure 7 is a plan of the
underside of the steam-chests J J and their connecting-passage K.
Through the ends of the plate G are formed two holes g g (Figures 5 and 6)
which open into the steam-spaces h h (Figure 3) in the steam-chests J J¹ and
coincide with two cavities g₁g' in the cylinder casting beneath. One of these
cavities is closed by a plug and the steam pipe L connects with the other. Thus
the steam pipe may be connected to either side of the engine, and the steam flows
from it through the cavity g¹ and hole g into the interior of one steam-chest and
thence through the passage K to the other steam-chest.
Referring to Figure 2, where the valve H is standing at the right, the steam
flows from the steam-chest down the port c¹ into the cylinder C, where it drives
the piston D toward the right, and the exhaust steam escapes through the port d¹,
under the valve H, into the port e and exhaust passage E. When the piston moves
far enough to the right it covers the exhaust-port and the remaining steam
before it acts as a cushion to stop the piston easily. The piston then stops and
remains stationary for awhile, thus giving the water-valves in the pump B
(Figure 1) time to seat themselves gently. While the piston of one engine is at
rest, the piston of the other engine is moving, and when one piston is stopping
the other is just starting. The column of water is thus lifted uniformly and
steadily by the pump.
This operation is produced by the reciprocal operation of the valves, which will
now be described. The valves are "steam-actuated," the plungers I I¹ which
actuate the valves being moved from side to side by means of steam taken from
the cylinders C C. It is an important characteristic of this Invention that the
steam which moves the plunger of either engine comes from the cylinder of the
other engine, and first passes through the valve of the other engine. The exhaust
steam from either plunger also escapes through the valve of the other engine.
Referring to Figures 2, 3 and 4 there are two small steam-ports i and ¹, in each
cylinder casting which open into the cylinder as shown. Holes or ports i i¹ are
also formed through the plate G, coinciding with those in the cylinder casting.
These ports i open upward under the valve H or Hand each is arranged in line
with two other ports, as shown in Figure 6. The six ports are thus arranged in
two rows of three ports each, all covered by the valve. In one row is the cylinder-
port, a connection-port j, and an exhaust-port k. In the other row is the
cylinder-port, a connection-port 1, and an exhaust port kl. The valve H H¹
(Figure 7) have each (in addition to the usual main exhaust cavity e¹) two
grooves m and m', which coincide with the two rows of ports. The connection
ports, being in the middle always communicate with these grooves m m¹, and
when the valve is at the right they are connected through the grooves with the
ports and respectively (the ports i and being then covered by the valve and
closed) and when the valve is at the left the ports ; j' are connected respectively
with the ports i and ³ (the ports k and being then closed). The exhaust-ports k
and pass down through the plate G and extend into the exhaust-ports d and d
respectively. They are formed by grooves oo on the underside of the plate
(Figure 5) and holes o o¹ drilled in the cylinder casting, (Figure 4).
The connection ports j and ¹ of each engine communicate through passages n
and n respectively with the chambers f and f' respectively in the steam-chest of
the other engine. These four passages n n¹n n¹ are formed by grooves p p in
the upper and lower faces of the plate G as shown in Figures 5 and 6. Where the
passages n n¹ cross each other, the respective grooves pp are on opposite sides of
the plate so that they do not interfere, and they connect through the plate by..

page_text: holes p p. Where these grooves p p end at 9999 (Figure 6) the passages
nnnn are continued upward by holes rrrr (Figure 7) formed through the
steam-chests J J¹ into the chambers ƒƒ¹ƒƒ¹ (Figure 2).
All these ports and passages can be easily traced in Fig. 8, which is a diagram,
where all the working-parts and passages are shown in one view and all nearly on
the same plane. The steam pipe L is here shown in the centre, between the steam
chests. The valves H H¹ are shown in two parts, one being a section through the
exhaust-cavity e¹ and the other a section through the two grooves m m', which are
supposed to be arranged end-for-end instead of side-by-side. Referring to this
Figure, the operation will now be described: Steam enters cylinder C through
port cand drives piston D to the right. When the piston reaches nearly the end
of its stroke it uncovers port i¹ and live steam passes through that port, through
groove m¹ in valve H into port 1, thence through passage n¹ to the chamber f¹ of
the steam-chest J₁, thus pressing the plunger F to the left, as shown, and shifting
the valve H¹ to the left. At the same time the steam in the chamber f at the other
end of the plunger I escapes through passage n, port j, groove m in valve H, and
passage to the exhaust passage d' where it joins the exhaust steam flowing out
from cylinder C. The shifting of the valve H¹ admits steam through the port c to
cylinder C¹ and starta piston D¹ (which has been at rest) on its leftward stroke.
When this piston uncovers port i no effect is produced, because this port is covered
by the valve H¹. But when it uncovers port i steam will flow through this port,
through groove m of valve H' into port j, and thence through passage n into
chamber of steam chest J, where it will shift plunger I and valve H to the left.
Meanwhile the steam in chamber f¹ at the left of plunger I will escape through
passage n¹ to port 1, through groove m¹ of valve H', and through port k¹ into
exhaust port d of cylinder C. The shifting of the valve H to the left will start
the piston D (which will previously have come to rest) on its leftward stroke, and
the same series of operations will be repeated.
The passages n n¹ enter the chambers ff' at a little distance from the ends of
these chambers, thus leaving a cushioning space beyond then in the ends of the
chambers to stop the plungers II gently. A groove t is formed in the wall of
each chamber ff¹ and extends from the end of the chamber back a distance equal
to the depth of the cushioning space plus the width of the piston on the end of
the plunger I or 1. When the plunger passes over and closes the opening n or n',
the groovet is opened to the pressure of steam in the middle of the steam-chest,
and this steam flows through this groove into the cushioning-space, thus stopping
the movement of the plunger. The plunger is then balanced, with live steam at
both ends. Assuming the plunger I to be at the right, as shown, as soon as the
valve H moves to the left the chamber fl is opened to the exhaust, and the
superior pressure of live steam in the chamber f will force the plunger I to the left
a short distance, as shown in dotted lines in Fig. 8, sufficient to close the groove t
and open the passage n. Then when the live steam from cylinder C¹ is admitted
through the port i and passage n it will freely enter the chamber f and force the
plunger I to the left.
Prior to the present Invention great difficulty has been experienced in engines of
this character because of the tendency of the "back-pressure" in the cylinders
when the valves are shifted to prematurely shift the valve-pistons or plungers and
consequently derange the action of the valves. For instance, referring to Figure 8,
the piston D is about to stop: When it has remained stationary until the piston D¹
uncovers the port i in cylinder C₁, the plunger I and valve H will be shifted to the
left. Previously the space in cylinder C to the left of piston D has been filled
with live steam at high-pressure. The shifting of the valve H connects this space
with both chambers ff¹ of steam chest J, and this pressure of steam escapes from
cylinder C not only through the exhaust-port d, but also through the port i and
passage n to chamber f, and through the port d, port k¹ and passage n¹ to
chamber f. In this improved engine, the same pressure passes from the cylinder C

page_text: to both chambers ff' so that the plunger I is practically balanced, but in previous
engines of this character the back-pressure has been permitted to pass from the
cylinder to one chamber for f', and the other chamber has had direct communi-
cation with the main exhaust, so that the pressures on opposite ends of the plunger I
have been unequal, thus frequently shifting the plunger prematurely. I further-
more provide against the accidental or premature movement of the plunger by
using a slide-valve, which is "loaded" by the pressure of steam above it.
In case at any time the engine should fail to start when steam is turned on, it
may be started by the hand-levers N N, (Figure 3) which are fixed to rocking-bars,
which pass into the tops of the steam-chests J J¹, and have arms P P which
hang down into the slots in the plungers I I'. By rocking the hand-levers the
arms P P are caused to press against the ends of the slots and so move the
plungers.
Figure 9 is a diagram similar to Figure 8, which shows a modified construction
of the engine. The general operation is the same, but the passages n n¹ are used
only for conducting the live steam to shift the plungers or pistons I I. The
exhaust-steam from the chambers ff¹ is conducted away by additional passages u u¹
which are tinted in the Figure. The cushioning grooves tt are omitted, the
plungers II being cushioned in the same way as the pistons D D².
Figure 10 is another diagram showing another modified construction. In this
the slide valves are replaced by piston-valves H H H¹¹ working in cylindrical
valve-chambers J J J¹ J¹, and formed in connection with central pistons I I¹. The
grooves m m m¹ m¹ are cut around the stems of the valves. The passages n n¹
serve both as steam-passages and exhaust-passages. The exhaust ports or passages
are tinted in the Drawing. The passages n n¹ have branches 8 s at one end,
entering the piston-chambers ff¹, (having check-valves, not shown, to prevent
outflow of steam through them) and have exhaust branches u u at their other ends,
for communicating with the exhaust-ports k k¹. The steam enters the steam-chests
at L L and escapes by exhaust-passage E. The operation is substantially the same
as already described.
Having now described and particularly ascertained the nature of my said
Invention, and in what manner the same is to be performed. I declare that what
I claim is :-
1. A duplex steam-engine constructed and adapted to operate substantially as
set forth, in such manner that the valve of each engine is actuated by steam taken
directly from the cylinder of the other engine, so that the two engines reciprocally
control each other.
2. A duplex steam-engine wherein the two engines reciprocally control each
other by means of steam-actuated valves in connection with steam passages
extending from the cylinder of each engine through the valve of that engine and
across to the valve-operating piston or plunger of the other engine, whereby the
main piston and valve of each engine shall control the admission of steam to actuate
the valve of the other engine, substantially as set forth.
3. A duplex steam-engine constructed with steam-passages extending from the
cylinder of each engine to the valve-operating piston or plunger of the other, and
exhaust passages extending from the valve-operating piston or plunger of each
engine through the valve of the other engine to the inain-exhaust, combined and
arranged to operate substantially in the manner and for the purposes set forth.
4. A duplex steam-engine wherein the two engines reciprocally control each
other by means of steam actuated valves, constructed with steam-passages and
exhaust-passages extending from opposite sides of the valve-operating piston or
plunger of each engine to the cylinder of the other engine in such manner, as
described, that the "back-pressure" in the cylinder shall be conducted equally to
opposite sides of the valve-operating piston or plunger, and consequently will be
balanced and impotent to move the piston or plunger prematurely, all substantially
as set forth. ..

page_text: 5. The improved construction of duplex steam-engines shown in Figures 2 to 7
of the Drawings, consisting of the cylinders and the steam-chests and valves, with
the plate G arranged between the steam-chests and the cylinders, and grooves on
the top and bottom of this plate forming the several steam-passages for actuating
the valves, substantially as described.