IMPROVEMENTS IN STEAM ENGINES
Year: 1858

page_text: LETTERS PATENT to David Rowan, of Greenock, in the County of
Renfrew, North Britain, Engineer, for the Invention of "IMPROVEMENTS
IN STEAM ENGINES."
Sealed the 22nd February 1859, and dated the 15th December 1858.
PROVISIONAL SPECIFICATION left by the said David Rowan at the,
Office of the Commissioners of Patents, with his Petition, on the
15th December 1858.
I, DAVID ROWAN, of Greenock, in the County of Renfrew, North Britain,
Engineer, do hereby declare the nature of the said Invention of "IM-
PROVEMENTS IN STEAM ENGINES," to be as follows, that is to say:-
This Invention relates to certain improved arrangements of the parts of
steam engines, such arrangements being more particularly designed for marine
purposes, and to improved valvular mechanism suitable for double cylinder
and duplex cylinder steam engines.
In one arrangement which may be called the "inverted duplex cylinder
design," and which is suitable for driving a screw propeller, an inverted
cylinder is placed on a suitable framing directly over the shaft, and this
cylinder has a smaller one placed (by preference concentrically) within it, the
two together constituting what is herein termed a "duplex cylinder," which
comprises a central cylindrical space surrounded by an annular space. Pistons
working in these two spaces are connected by their rods, which pass out through

page_text: the bottom covers to one cross head, a connecting rod or rods passing thence
to a crank on the shaft. The fresh steam from the boiler first enters the
central cylinder, next passes thence to the opposite end of the annular
cylinder, and finally passes from the annular cylinder to the condenser; a
complete set of engines comprises two or more duplex cylinders connected
to different cranks in the usual way.
In a second arrangement, which may be called the "oscillating duplex
cylinder design," and which is susceptible of various modifications suitable for
driving various kinds of propellers, one or more duplex cylinders is or are
mounted on hollow trunnions, and the piston rods are directly jointed upon
the crank or cranks, without the intervention of a connecting rod or rods.
The fresh steam from the boiler is supplied to each duplex cylinder through
onc trunnion, as in ordinary oscillating engines, and after operating in the
duplex cylinder, as herein-before explained in describing the first design, passes
through the other trunnion to the condenser.
In one modification of the improved valvular mechanism as applied to a
duplex cylinder, a single slide valve is used for both the central and the
annular cylinder, and it works in the steam chest on a port facing in the
ordinary way. There are two sets or rows of ports in the port facing, and the
slide valve is made duplex, one side governing each set of ports. The end
port of one set of ports leads to one end of the central cylinder, and the other
end port of the same set leads to the opposite end of the annular cylinder,
and there is a passage in the slide valve, which, at the proper periods,
brings these two ports into communication to transfer the steam from the
central to the annular cylinder. The other set of ports are similarly arranged,
but in inverted positions, the central port in each set leads to the condenser ;
the valve is worked in the ordinary way, and alternately uncovers the
ports leading to opposite ends of the central cylinder for the admission of
fresh steam. The ports communicating with opposite ends of the annular
cylinder are each alternately in communication with the respective passage in
the slide valve, by which they receive steam from the central cylinder, and
with the hollow or cups of the slide valve, by which a communication is formed
with the exhaust port, but they are never uncovered so as to receive fresh
steam. This valvular mechanism may be modified in various ways, thus two
slide valves working simultaneously may be used, and these may be arranged in
one or in two steam chests, or the arrangement may be applied in duplicate,
or, again, the improvement may be embodied in a rotating or partially rotating
valve

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said David Rowan in the Great Seal Patent Office on the
13th June 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
ROWAN, of Greenock, in the County of Renfrew, North Britain, Engineer,
send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of December, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said David Rowan, Her special licence that I, the said David
Rowan, my executors, administrators, and assigns, or such others as I, the
said David Rowan, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
STEAM ENGINES," upon the condition (amongst others) that I, the said David
Rowan, my executors or administrators, by a instrument in writing under
my, or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after the
date of the said Letters Patent.
NOW KNOW YE, that I, the said David Rowan, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement in writing, reference being had to the accompanying Drawings,
and to the letters and figures marked thereon, that is to say :-
My said Invention relates to certain arrangements of the parts of steam
engines, such arrangements being particularly designed for marine purposes,
and to improved valvular mechanism suitable for double cylinder and duplex
cylinder steam engines.
In one arrangement, which may be called the "inverted duplex cylinder
design," and which is suitable for driving a screw propeller, an inverted
cylinder is placed on a suitable framing directly over the shaft, and this
cylinder has a smaller one placed (by preference concentrically) within it, the two
together constituting what is herein termed a "duplex cylinder," which comprises

page_text: a central cylindrical space surrounded by an annular space.
Pistons working
in these two spaces are connected by their rods, which pass out through the
bottom covers to one cross-head, a connecting rod or rods passing thence to a
crank on the shaft. The fresh steam from the boiler first enters the central
cylinder, next passes thence to the opposite end of the annular cylinder, and
finally passes from the annular cylinder to the condenser. A complete set of
engines comprises two or more duplex cylinders connected to different cranks
in the usual way.
In a second arrangement, which may be called the " oscillating duplex
cylinder design," and which is susceptible of various modifications suitable
for driving various kinds of propellers, one or more duplex cylinders is or are
mounted on hollow trunnions, and the piston rods are directly jointed upon the
crank or cranks without the intervention of a connecting rod or rods. The
fresh steam from the boiler is supplied to each duplex cylinder through one
trunnion as in ordinary oscillating engines, and after operating in the duplex
cylinder, as herein-before explained in describing the first design, passes
through the other trunnion to the condenser.
In one modification of the improved valvular mechanism as applied to a
duplex cylinder, a single slide valve is used for both the central and the
annular cylinder, and it works in the steam chest on a port facing in the
ordinary way. There are two sets or rows of ports in the port facing, and
the slide valve is made duplex, one side governing each set of ports. The end
port of one set of ports leads to one end of the central cylinder, and the other
end port of the same set leads to the opposite end of the annular cylinder;
and there is a passage in the slide valve which, at the proper periods, brings
these two ports into communication to transfer the steam from the central to the
annular cylinder. The other set of ports are similarly arranged, but in inverted
positions. The central port in each set leads to the condenser, or the two
central ports may be in one.
The valve is worked in the ordinary way, and
alternately uncovers the ports leading to opposite ends of the central cylinder
for the admission of fresh steam. The ports communicating with opposite
ends of the annular cylinder are each alternately in communication with the
respective passage in the slide valve, by which they receive steam from the
central cylinder, and with the hollow or cup of the slide valve, by which a
communication is formed with the exhaust port, but they are never uncovered
to receive fresh steam.
This valvular mechanism may be modified in various ways; thus, two slide
valves working simultaneously may be used, and these may be arranged in one
or in two steam chests, or the arrangement may be applied in duplicate; or,

page_text: again, the improvement may be embodied in a rotating or partially rotating
valve.
And in order that my said Invention may be properly understood and
carried into effect, I have delineated upon a Sheet of explanatory Drawings
hereunto appended, and shall now proceed to describe, two examples of
engines, one constructed according to a modification of my "inverted duplex-
cylinder design," and the other constructed according to a modification of my
oscillating duplex cylinder design," whilst both examples are represented as
provided with my improved valvular mechanism.
Figures 1 to 5 appertain to the "inverted duplex cylinder design;"
Figure 1 being a transverse vertical section; Figure 2, a side elevation partly
in longitudinal vertical section; Figure 3, a plan of the cylinders and valve
chest partly in horizontal section; Figure 4, an elevation showing the cylinder
port face with the slide valve removed; and Figure 5, a face view of the slide
valve as turned over from Figure 4, the right and left sides of Figure 5
corresponding with the left and right sides respectively of Figure 4, whilst
Figures 4 and 5 correspond to Figure 3 as regards the relative positions of
the parts.
In these engines, which are suitable for driving a screw propeller, the crank
or propeller shaft A is carried in bearings in the base plate B, and directly
over it are placed the two inverted duplex steam cylinders C, these cylinders
being mounted on a framing D of a kind commonly adopted in inverted cylinder
engines. The cylinders C are each by means of a concentric cylinder divided
into two spaces, a central cylindrical space E, and an outer annular space F.
A piston G of the ordinary kind with its rod H works in the central space E,
whilst an annular piston I with two rods J works in the annular space F, the
latter piston being provided with metallic packing on its inner as well as on
its outer edge. The three piston rods H, J, J, pass through stuffing boxes
arranged in a straight line in the bottom of each cylinder C, and are all three
attached to a single crosshead and guide block K, which works between guide
surfaces formed on the frames D, and upon which is jointed the connecting
rod L passing down to the crank shaft A. The crosshead K is formed with
pins or journals at its opposite ends to receive links connecting it to levers
working the air pump M (the air pump levers are not shown in the Drawing).
A single steam chest N serves both cylinders C, and this is shown as partly in
section in Figures 2 and 3, as are also the steam ports or passages, and one of
the slide valves P. Each port face (Figure 4) has formed in it two sets of
ports Q, R, S, T, with a double exhaust port U. The port and passage Q
communicates with the top of the central cylinder E, as shown in Figure 2.

page_text: The port and passage R in line with the last-mentioned port communicates
with the bottom of the annular cylinder F, as also shown in Figure 2. The
port S communicates with the bottom of the central cylinder E, whilst the
port T communicates with the top of the annular cylinder F. The coin-
munications of these two ports S and T with their respective cylinders are
indicated by dotted lines in Figure 3. The slide valve P is made with two
passages 1, t, and with a central hollow or cup u; the passage is for the
purpose of putting the ports Q, R, in communication with each other, whilst
the passage t is for communicating between the ports S, T, the two passages
being so relatively disposed as to be in action at different times, the latter t
when the slide valve is down as in Figure 2, and the former when the slide
valve is up. When the slide valve is down as in Figure 2, the port Qis
uncovered to admit fresh steam into the top of the central cylinder E, whilst
the partly used steam passes from the bottom of this central cylinder by the
port S, valve passage t, and port T, to the top of the annular cylinder F. The
annular cylinder being of larger area than the central one, the steam expands
further in it, and aids in impelling the pistons and crosshead downwards.
The steam from beneath the annular piston I passes by the port R, the
cup u of the valve, and the exhaust passage U, to the condenser, which is
formed inside the framing D. The reversal of the slide valve P causes fresh
steam to enter beneath the central piston G, the partly used steam from above
this piston to enter beneath the annular piston I, and the used steam from
above this last to pass off to the condenser.
Engines of this design combine the advantage of carrying out the system of
expansion to the extent beneficially practised only in two cylinders, with a
very much simplified disposition of the connectious and details, without the
extra top weight and complexity of parts accompanying two detached or
separated cylinders when inverted, and with the convenience attending the
inverted arrangement in cases such as those for which they are designed.
Figures 6, 7, and 8 on the Sheet of Drawings appertain to the "oscillating
duplex cylinder design;" Figure 6 being a transverse vertical section; Figure 7,
a side elevation partly in longitudinal vertical section; and Figure 8, a plan
partly in horizontal vertical section. It will be unnecessary to describe this
example in detail, the cylinders, the pistons and rods, the ports and passages,
and the slide valves, being all constructed substantially as represented in
Figures 1 to 5, already described. In the second design, however, the
cylinders C are mounted upon hollow trunnions W, X, as in ordinary
oscillating cylinder engines; they have also duplicate valve chests N and
slide valves P worked as in ordinary engines (the valve gearing being omitted.

page_text: to avoid complexity in the Drawings). The piston rods H, J, J, are fixed to
a single crosshead K, which is directly jointed upon the crank pin. The
other features of the design are such as are well known. The example of
oscillating duplex cylinder design" represented, is suitable for driving paddle
wheels, but it will be obvious that the oscillating duplex cylinders may be
arranged in various positions with reference to the shaft, so as, for example, to
drive a screw propeller direct or through gearing.
Engines constructed according to either of my improved designs may have
applied to them other kinds of valvular mechanism than that herein described,
whilst my improved valvular mechanism may be applied to engines not con-
structed according to my improved designs herein described.
Having thus particularly described my said Invention, and the manner in
which the same is or may be used or carried into effect, I have to state that I
do not restrict myself to the precise details herein-before described or delineated,
and that I do not claim to have invented every separate detail herein-before
described and delineated; but what I believe to be novel and original, and
claim as the Invention secured to me by the herein-before in part recited
Letters Patent, is,-
First, the applying and using inverted duplex cylinders, such as are herein-
before described.
Second, the applying and using oscillating duplex cylinders, such as are
herein-before described.
Third, the constructing of valvular mechanism for duplex cylinder or double
cylinder steam engines, substantially as herein-before described.
In witness whereof, I, the said David Rowan, have hereunto set my
hand and seal, this Eleventh day of June, in the year of our Lord
One thousand eight hundred and fifty-nine.
DAVID ROWAN. (L.S.)