IMPROVEMENTS IN MARINE STEAM ENGINES
Year: 1867

page_text: LETTERS PATENT to William Macnab, of Greenock, in the County of
Renfrew, North Britain, Engineer and Shipbuilder, for the Invention
PROVISIONAL SPECIFICATION left by the said William Macnab at the
Office of the Commissioners of Patents, with His Petition, on the
23rd November 1867.
I, WILLIAM MACNAB, of Greenock, in the County of Renfrew, North
Britain, Engineer and Shipbuilder, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN MARINE STEAM ENGINES," to be as
follows, that is to say :-
This Invention relates to improvements in marine steam engines of the
kind described in the Specification of Letters Patent granted to the present
applicant, and dated 11th February 1862 (No. 854), and consists in disposing
the low-pressure. cylinders which have trunks and the high-pressure cylinders
which have solid piston rods horizontally and vertically respectively, or
otherwise at right angles or other convenient angles to each other, but with
both low-pressure and high-pressure cylinders of each pair acting on one
crank pin. These improved engines may be used in single pairs, but engines
comprising two pairs or in all four cylinders, with the crank of one pair at

page_text: right angles to that of the other pair, form a very good and steadily working
arrangement for large powers.
In one convenient modification the two high-pressure cylinders are inverted
and over the crank shaft, being supported on framing similar to what is in use
with ordinary inverted cylinder screw engines, but combined with the framing
of the horizontal low-pressure trunk cylinders below. The trunk cylinders
are disposed on one side of the shaft with the condenser or condensers
and pumps on the other side, and the whole forms a compact and well
balanced arrangement. The steam on its passage between the high-pressure
and the low-pressure cylinders may be dealt with as described in the earlier
Specification herein-before referred to, or in the same manner as in various
existing marine engines of the same class.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Macnab in the Great Seal Patent Office on the
22nd May 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
MACNAB, of Greenock, in the County of Renfrew, North Britain, Engineer
and Shipbuilder, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of November, in the year of our
Lord One thousand eight hundred and sixty-seven, in the thirty-first year
of er 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 "IM-
PROVEMENTS IN MARINE 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 inmediately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said William Macnab, do hereby declare
the nature of the 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, that
is to say:
My said Invention relates to improvements in marine steam engines of the
kind described in the Specification of certain Letters Patent granted to me,
and dated the Eleventh of February, One thousand eight hundred and sixty-two
(No. 354), and consists in disposing the low-pressure cylinders which have
trunks and the high-pressure cylinders which have solid piston rods horizontally
and vertically respectively, or otherwise at right angles or other convenient
angles to each other, but with both low-pressure and high-pressure cylinders of
each pair acting on one crank pin. These improved engines may be used in
single pairs, but engines comprising two pairs or in all four cylinders, with the
crank of one pair at right angles to that of the other pair, form a very good
and steadily working arrangement for large powers.
And in order that my said Invention and the manner of performing the
same may be properly understood I have hereunto appended a Sheet of
explanatory Drawings to be herein-after referred to, and representing an
example of my improved engines as constructed with four cylinders.
Figures 1 and 2 are elevations at right angles to each other one of the
condensers 1 being omitted in Figure 2, and Figure 8 is a sectional plan of
one-half of the engines and with the high-pressure cylinder 2 omitted. The
same reference numerals are used to mark the same or like parts in all the
Figures. In this example the two high-pressure cylinders 2, 2, are inverted and
over the crank shaft 3, being supported on framing 4, 5, similar to what is in
use with ordinary inverted cylinder screw engines, but combined with the
framing 6, 7, of the horizontal low-pressure trunk cylinders 8, 8, below. A
rectangular bed frame is formed by the combination of the lower parts 9 of the
trunk cylinder castings on one side of the crank shaft 3 with three transverse
castings 7 having upon them the crank shaft bearings, and with two longitudinal
castings 6 on the other side of the crank shaft, and carrying the condensers 1
and air and other pumps 10. Down upon the last-mentioned bed frame
castings 6 are bolted the cast-iron standards 4 for supporting one side of each
of the high-pressure cylinders 2, whilst the other sides of those cylinders are
supported upon a long cast-iron or malleable iron box 11 which rests upon
wrought-iron columns 5 fixed in the castings 7 below, the whole thus forming
a compact and well balanced arrangement. The box 11 serves as an
intermediate chamber to receive the steam after it has acted in the high-

page_text: pressure cylinders 2. The steam on its passage between the higb-pressure
eylinders 2 and the low-pressure cylinders 8 may be dealt with as described in
my earlier Specification herein-before referred to. If preferred however the
steam may be dealt with in the same manner as in any of the various existing
marine engines of the same class. The steam passes from the intermediate
chamber 11 by pipes 12 to the valve chests of the low-pressure cylinders 8.
On the accompanying Drawing there are shown or indicated in a manner
that will be easily understood by makers of marine engines what I consider to
be the most convenient arrangements of the pump gear, valve gear, and other
minor details, but these arangements are obviously susceptible of considerable
modification without the main features of the design being departed from.
Having thus particularly described my said Invention, and the manner in
which the same is to be performed, I have to state that I do not restrict myself
to the precise details herein described or delineated; but that 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, the combination or arrangement of
parts forming the design of marine engines substantially as herein-before
described, and more particularly the combining of an inverted vertical high-
pressure cylinder with a horizontal trunk low-pressure cylinder both connected
to the same crank pin, substantially as herein described and exhibited on the
Drawings annexed.
In witness whereof, I, the said William Macnab, have hereunto set my
hand and seal, this Twenty-first day of May, in the year of our Lord
One thousand eight hundred and sixty-eight.
Witness,
BRISTOW HUNT,
Solicitor and Patent Agent,
1, Serle Street,
Lincoln's Inn.
WILLIAM MACNAB. (L.B.)