IMPROVEMENTS IN STEAM ENGINES
Year: 1862

page_text: LETTERS PATENT to William Macnab,. of Greenock, in the County of
Renfrew, North Britain, Engineer, for the Invention of "IMPROVEMENTS
IN STEAM ENGINES."
Sealed the 16th April 1862, and dated the 11th February 1862.
PROVISIONAL SPECIFICATION left by the said William Macnab at the
Office of the Commissioners of Patents, with his Petition, on the 11th
February 1862.
I, WILLIAM MACNAB, of Greenock, in the County of Renfrew, North
Britain, Engineer, do hereby declare the nature of the said Invention of
"IMPROVEMENTS IN STEAM ENGINES," to be as follows, that is to say:-
This Invention comprises improved arrangements applicable to various
kinds of engines in which the same steam works in two or more cylinders,
that is to say, in combined cylinders, and also a general arrangement of
marine engines, in which, amongst other improvements, such combined
cylinders are disposed in a novel manner.
The improved arrangements applicable in carrying out the combined
cylinder system are specially designed for working with superheated steam,
and they consist of provision made in connection with the steam chamber or
passage which receives the eduction steam from the high-pressure cylinder
previous to its passing into the low-pressure cylinder, whereby the fresh super-
heated steam, before entering the high-pressure cylinder, gives up some
surplus heat to the steam, which is on its way from the high-pressure to the
low-pressure cylinder. For this purpose, the superheated steam, before
O entering into the high-pressure cylinder, or a part of it, is introduced from
the-main steam pipe into a series of piping or other equivalent contrivance,

page_text: which is inside the eduction steam chamber, after passing through which the
superheated steam, which has then parted with some of its surplus heat, is
admitted through the regulating valve into the high-pressure cylinder. It is
also arranged that a part of the steam may pass directly from the main steam
pipe through a regulating valve into the high-pressure cylinder. Highly
superheated steam may also be introduced into a series of piping or other
equivalent contrivance arranged inside the eduction steam chamber, aud after
passing through it, be caused to circulate through the jackets, thereby greatly
augmenting the temperature of the eduction steam from the high-pressure
cylinder on its way to the low-pressure cylinder. Valves are applied for the
purpose of regulating the respective quantities of steam passing directly and
otherwise.
In the improved generál arrangement of marine engines, there are four
horizontal cylinders disposed two on each side of the shaft, which has two
cranks placed at right angles to each other. There is on each side one high-
pressure and one low-pressure cylinder, and the high-pressure cylinder on one
side acts upon the same crank as the low-pressure cylinder on the other side. In
one modification the low-pressure cylinders are fitted with double trunks, from
within which connecting rods pass to the crank, whilst each high-pressure
piston rod is connected to the opposite low-pressure piston by a crosshead
and rods passing through stuffing boxes in the cylinder cover. In another
modification the more ordinary arrangement of piston rod and connecting.rod
is adopted. All the cylinders, covers, and eduction or intermediate, steam
chambers are provided with steam jackets; the eduction or intermediate steam
chambers are connected and in communication with one another, but may be
kept separate if preferred. Four bearings are provided on the engine framing
for the crank shaft, two of them being between the cranks. The eccentrics
for working the valves of the low-pressure cylinders are between the two inner
bearings, whilst those for working the valves of the high-pressure cylinders
are in each case between the crank and the inner bearings.
It is intended to use surface condensers with these engines, two being
placed against the forward end of the engines, whilst the air pumps, feed.
pumps, and circulating pumps arranged in immediate connection with the
condensers are conveniently worked by a prolongation of the shaft. The
arranging of two pairs of combined cylinders so that the individuals of each
pair work cranks at right angles to each other, and more or less, as herein-
before described, may also be adopted in the case of engines having vertical or
inclined cylinders.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Macnab. in the Great Seal Patent Office on the
11th August 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
MACNAB, 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 Eleventh day of February, in the year of our
Lord One thousand eight hundred and sixty-two, in the twenty-fifth year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said William Macnab, Her special licence that I, the said
William Macnab, my executors, administrators, and assigns, or such others
as I, the said William Macnab, my executors, administrators, and 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. William Macnab, my executors or administrators, by an
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
inimediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Macnab, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, 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 comprises improved arrangements applicable to various
kinds of engines in which the same steam works in two or more cylinders,
that is to say, in combined cylinders, and also a general arrangement of marine
engines, in which, amongst other improvements, such combined cylinders are
disposed in a novel manner.
And in order that my said Invention, and the manner of performing it
may be properly understood, I have hereunto appended a Sheet of expla-
natory Drawings, showing the application of the improvements to a set of
marine engines, Figure 1 thereof being a transverse vertical section, Figure 2

page_text: a sectional plan, Figure 3 a longitudinal vertical section through one side of
the engines, and Figure 4 a transverse vertical section through the steam
chamber on one side, or at the line 1, 2, in Figure 3.
The improved arrangements applicable in carrying out the combined-
cylinder system are specially designed for working with highly superheated
steam, and they consist of provision made in connection with the steam
chamber or passage, which receives the eduction steam from the high-pressure
cylinder previously to its passing into the low-pressure cylinder,' whereby the
fresh and highly superheated steam before entering the high-pressure cylinder
gives up some surplus heat to the steam, which is on its way through the said
chamber or passage from the high-pressure to the low-pressure cylinder. For
this purpose, the highly superheated steam, before entering into. the high-
pressure cylinder, or a part of that steam, is introduced from the main steam
pipe into a series of piping, or other equivalent contrivance which is inside the
eduction steam chamber, after passing. through.which. the superheated. steam,
which has then parted with some of its surplus heat, is admitted through.the
regulating valve into the high-pressure cylinder. It is also arranged that a
part of the steam may pass directly from, the main steam pipe through a
regulating valve into the high-pressure cylinder, and this provision gives the
power of regulating the action of the steam with great nicety. Highly super-
beated steam may also be introduced into a series of piping or other equiva-
lent, contrivance arranged inside the eduction steam chamber, and after
passing through it, be caused to circulate through the jackets, thereby greatly.
augmenting the. temperature of the eduction steam from the high-pressure
cylinder on its way to the low-pressure cylinder. Valves are applied for the
purpose of regulating the respective.quantities of steam passing directly, and
otherwise.
A modification of practical arrangements for carrying out these improve-
ments is represented in the accompanying Drawings in engines, the general:
arrangement of which forms another part of the present Invention.
The improved general arrangement of marine engines comprises four hori-
zontal cylinders A, B, A', B¹, disposed two on each side of the shaft C, which
has two cranks D, D', placed at right angles to each other. There is on each
side one high-pressure cylinder A. or A¹, and one low-pressure cylinder B
or B', and the high-pressure cylinder A on one side acts on the same.crank D.
as the low-pressure cylinder B' on the other side.. The low-pressure cylinders
B, B', are in this example fitted with double trunks E, E', from within which.
connecting rods F, F', pass to the cranks D¹, D, whilst each high-pressure.
piston rod G, G' is connected to the opposite low-pressure piston by a cross-

page_text: head H, H, and pair of rods I, I', passing through stuffing boxes in the
cylinder cover; in other modifications, however, the more ordinary arrange-
ment of piston rods and connecting rods is adopted. All the cylinders, covers,
and eduction or intermediate steam chambers are provided with steam jackets. -
The eduction or intermediate steam' chambers J, situated in the mid spaces
between the high-pressure and low-pressure. cylinders on each side are con-
nected, and in communication with one another by a pipe K; they may,"
however, be kept separate if preferred. Four bearings L, M, N, O, are pro-
vided on the engine framing for the crank shaft C, two of them, M, N, being"
between the cranks 'D, D¹. The eccentrics P, P¹, for working the valves of.
the low-pressure cylinders B, B', are between the two inner bearings M, N,
whilst those Q, Q, for working the valves of high-pressure cylinders: A, A',
are in each case between the crank D or D¹ and the inner bearing M or N.
The condensers R are of the "surface" kind,. and are placed against the
forward end of the engines, whilst the air pumps S, feed pumps T, bilge.
pumps t, and circulating pumps U, arranged in immediate connection with
the condensers R are conveniently worked by a prolongation c of the shaft C.
The arranging of two pairs of combined cylinders so that the individuals. of:
each pair. may work cranks at right angles to each other, or in an equivalent
I manner, and more or less, as herein-before described, may also be adopted in
the case of engines having vertical or inclined cylinders..
.
The arrangements for causing the steam to act in the improved manner
described in the earlier part hereof will be best understood from Figures.3,
and 4. The highly superheated steam enters from the main steam pipe x,
through a stop valve into a series of pipes W, X, inside the intermediate steam
chamber J. The communications at the tops and bottoms of these pipes W, X,
are arranged to lead the steam alternately down and up the individual
pipes W, then across by the branch w to the pipes ✗; next alternately down
and up these last, and thence to the external bend Y, where a throttle or
regulator valve may be fitted. From the external bend Y the steam finds
its way by a suitable passage to a casing Z, surrounding the high-pressure
cylinder A, and thence to the middle of the valve cylinder a by the double-
piston valve b, of which it is directed to either end of the high-pressure
cylinder A. This cylinder and its valve cylinder a are, as it were, immersed
in the intermediate chamber J, of which the spaces j form a part, and the
steam, after operating in the cylinder A, is discharged from either end of the
valve cylinder a into the intermediate chamber J. In this chamber the partly
used steam takes up heat from the pipes W, X, thereby acquiring an accession
of elastic force, and at the same time moderating the otherwise excessive high

page_text: temperature of the fresh steam. From the intermediate chamber J the
steam is directed by a slide valve d of the ordinary kind to the ports of the
low-pressure cylinder B, and finally passes off to the condenser by the exhaust
passage e. A branch pipe f, with a regulator valve is provided to permit of
more or less of the steam being admitted to the high-pressure cylinder A,
without first passing through the internal-pipes. W, X. A steam jacketing g,
receiving its steam direct from the boiler is made to surround the low-pressure
cylinder B, the intermediate chamber J, including the spaces j; round the
high-pressure cylinder A, the cylinder covers, and the vertical sides of the
intermediate.chamber J.
Having thus particularly described my said Invention, and the manner in
which the same is or may be performed, I have to state that I do not
restrict myself to the precise details herein described or delineated; but that
what I consider 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 causing of the fresh steam. in combined high and low-pressure
engines to give up a portion of its heat to the partly used steam, substantially
in the manner herein-before described:
Second, the combining together of two pairs of high-pressure and, low-
pressure cylinders with the individuals of each pair acting at right angles,
substantially in the manner herein-before described.
Third, the general design or arrangement of parts of marine engines herein-
described and delineated.
In witness whereof, I, the said William Macnab, have hereunto set my
hand and seal, this Eighth day of August, in the year of our Lord
One thousand eight hundred and sixty-two.
Witness,
EDMUND HUNT,
Patent Agent,
28, St. Enoch Square,
Glasgow.
WILLIAM MACNAB. (L.S.)