IMPROVEMENTS IN STEAM BOILERS
Year: 1866

page_text: LETTERS PATENT to David Thomson, of No. 3. Old Street, Saint Luke's,
in the County of Middlesex, for the Invention of "IMPROVEMENTS IN
STEAM BOILERS."
Sealed the 24th October 1866, and dated the 28th April 1866.
PROVISIONAL SPECIFICATION left by the said David Thomson at the
Office of the Commissioners of Patents, with his Petition, on the 28th
April 1866.
I, DAVID THOMSON, of No. 3, Old Street, Saint Luke's, in the County of
Middlesex, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN STEAM BOILERS," to be as follows:-
My Invention has for its object certain improvements in steam boilers,
whereby they are brought into a very compact form, so as to occupy the least
possible space, while they at the same time afford a very large amount of
heating and steam generating surface, are readily accessible for cleaning and
repairs, and have a very good draught. For this purpose I construct the
shell of the boiler similar to that of a single or double flue Cornish boiler, but
of a very limited length in proportion to its diameter. The flue or flues of such
boiler I form slightly tapering in diameter towards the back end, the flange of
which is rivetted to the inside of the shell, while the flange of the front end is
rivetted to the outside of the shell. By this arrangement, and by making the
hole or holes in the front sufficiently large to allow the flange of the back end
Price 8d.1

page_text: of the flue or flues to pass through, I am enabled to fix the flue or flues by
simply passing it or them through the hole in the front of the boiler and
rivetting the flanges; and the flue or flues may also be readily removed in the
same way for repairs by simply cutting off the outside rivet heads and drawing
it or them out. The fire-grate or grates are inside the flue or flues, similar
to Cornish boilers, and at the end of the flue or flues is placed a fire-brick
partition, having a number of openings through which the flames pass (thereby
heating the partition to a red heat) into a fire-brick smoke chamber at the
back of the boiler, which chamber is closed at the top at a height cor-
responding with the water line of the boiler. In applying this arrangement
to marine boilers I construct the smoke chamber either of iron lined with
fire-brick or I form it with a double iron casing forming a water jacket.
From this smoke chamber the flames pass through a number of fire tubes of
small diameter fixed longitudinally in the boiler in the space between the
upper surface of the flue and the water line. In front these fire tubes open
into a wrought-iron box enclosing the entire upper part of the front of
the boiler and accessible by doors, and the flames pass thence through
a number of fire tubes of large diameter passing longitudinally through the
steam space of the boiler. From the back end of these tubes the flames or
hot gases pass through a flue formed over the before-mentioned smoke chamber
into the chimney. In order to produce an effective draught I prefer to fix in
the chimney a cylindrical pipe of comparatively small diameter and somewhat
contracted a little above a point at which I introduce a steam jet from the
exhaust steam of the engine. In place of or in combination with such exhaust
steam jet I also introduce a small steam jet into the front end of each of the
large fire tubes by means of a small steam pipe leading from the steam space
of the boiler into the before-mentioned wrought-iron box, where it passes in
front of each of the large tubes and is in such places provided with small
openings or nozzles. In order to render the inside of the boiler and the outer
surfaces of the flue and fire tubes readily accessible for cleansing purposes I
leave a considerable space between the surface of the boiler flue and the
small fire tubes surrounding the same, as also between the upper surfaces of
the small fire tubes and the under surfaces of the large ones, and I form a
man-hole in the front of the boiler on each side of the flue, or where two flues
are used one or two man-holes between the flues, whereby ready access can be
gained to the bottom inner surface of the boiler and to the entire surface of
the flue or flues, as also to the under surfaces of the small fire tubes.
furthermore form another man-hole communicating with the space between
the upper surfaces of the small fire tubes and the under surfaces of the large
I

page_text: ones, the latter being so arranged as to allow of sufficient space in the front of the
boiler for this man-hole. I also leave a considerable space between the
small fire tubes just over the top of the flue or flues, as also between such
fire tubes and the sides of the boiler, in order both to allow of free circulation
of the water and to afford free access to the tubes for cleansing purposes.
In order to draw the steam equally from all parts of the boiler I fix a pipe
In the steam space extending the whole length of the boiler, the upper surface
of which pipe is perforated to allow the steam to enter it, and a shield is fixed
just below this pipe, extending some distance across the boiler so as to cause
the steam rising just below the pipe to pass laterally and against the surfaces
of the large fire tubes before it can enter the perforated steam pipe, so as
thereby both to heat the steam and to prevent the tubes from attaining so
high a temperature as to injure the metal. The steam is taken from the
latter either at one end, or where a steam dome is nsed the ends of the pipe
are closed and a branch from the same conducts the steam into the steam
dome, which has no other communication with the steam space of the boiler.
In some cases strengthen the internal flue or flues of the boiler by forming
it or them with transverse corrugations extending along the whole or a part
of its or their length; or instead of such arrangement I divide the tubes into
two or more lengths, which I connect together by means of flanged rings of a
trough-shaped transverse section, similar to that of a bridge rail.
Although I have described my various improvements as though all were
employed in combination, yet they may also be employed separate and apart
from such combination.
Another part of my Invention has for its object to construct steam boilers
which shall afford the same advantages as the ordinary cylindrical boiler in
point of strength, and shall at the same time occupy considerably less space
than these.
My Invention consists in imparting to such boilers the form of two or
more cylinders intersecting each other in a direction parallel to their axis, and
in staying such cylinders by means of transverse stays passing from one line of
intersection of the cylinders to the other or others. The arrangement of such
boilers may be variously modified, thus they may consist of two or more such
intersecting or partial cylinders combined vertically one above the other, or
horizontally side by side, or they may be combined in groups of three, four, or
more round a central axis. Such boilers may be used either with an internal
flue and fire-grate or with an external fire-grate.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said David Thomson in the Great Seal Patent Office on the
27th October 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
THOMSON, of No. 3, Old Street, Saint Luke's in the County of Middlesex,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-eighth day of April, in the year of our
Lord One thousand eight hundred and sixty-six, in the twenty-ninth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said David Thomson, Her special licence that I, the said David
Thomson, my executors, administrators, and assigns, or such others as I, the
said David Thomson, 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 BOILERS," upon the condition (amongst others) that I, the said David
Thomson, 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 immediately after the
date of the said Letters Patent.
NOW KNOW YE, that I, the said David Thomson, 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 thereof, reference being had to the accompanying Drawing, and
to the Figures and letters marked thereon, that is to say:
My Invention has for its object certain improvements in steam boilers,
whereby they are brought into a very compact form, so as to occupy the least
possible space, while they at the same time afford a very large amount of
heating and steam generating surface, are readily accessible for cleaning and
repairs, and have a very good draught. For this purpose I construct the
shell of the boiler similar to that of a single or double flue Cornish boiler, but
of a very limited length in proportion to its diameter. The flue or flues of
such boiler I form slightly tapering in diameter towards the back end, the
flange of which is rivetted to the inside of the shell, while the flange of the

page_text: front end is rivetted to the outside of the shell. By this arrangement, and by
making the hole or holes in the front sufficiently large to allow the flange of
the back end of the flue or flues to pass through. I am enabled to fix the flue
or flues by simply passing it or them through the hole in the front of the
boiler, and rivetting the flanges; and the flue or flues may also be readily
removed in the same way for repairs, by simply cutting off the outside rivet
heads and drawing it or them out. The fire-grate or grates are inside the
flue or flues, similar to Cornish boilers, and at the end of the flue or fluès is
placed a fire-brick partition having a number of openings, through which the
flames pass (thereby heating the partition to a red heat) into a fire-brick
smoke chamber at the back of the boiler, which chamber is closed at the
top at a height corresponding with the water line of the boiler. In applying
this arrangement to marine boilers, I construct the smoke chamber either of
iron lined with fire-brick, or I form it with a double iron casing forming a
water jacket. From this smoke chamber the flames pass through a number
of fire tubes of small diameter fixed longitudinally in the boiler, in the space
between the upper surface of.. the flue and the water line. In front these
fire tubes open into a wrought-iron box enclosing the entire upper part of the
front of the boiler and accessible by doors, and the flames pass thence
through a number of fire tubes of large diameter passing longitudinally
through the steam space of the boiler. From the back end of these tubes
the flames or hot gases pass through a flue formed over the before mentioned
smoke chamber into the chimney: In order to produce an effective draught
I prefer to fix in the chimney a cylindrical pipe of comparatively small
diameter, and somewhat contracted a little above a point at which I introduce
a steam jet from the exhaust steam of the engine. In place of or in com-
bination with such exhaust steam jet, I also introduce a small steam jet into
the front end of each of the large fire tubes by means of a small steam pipe
leading from the steam space of the boiler into the before-mentioned wrought-
iron box, where it passes in front of each of the large tubes and is in such
places provided with small openings or nozzles. In order to render the inside
of the boiler and the outer surfaces of the fluc and fire tubes readily
accessible for cleansing purposes, I leave a considerable space between the
surface of the boiler flue and the small fire tubes surrounding the same, as
also between the upper surfaces of the small fire tubes and the under surfaces
of the large ones, and I form a man-hole in the front of the boiler on each
side of the fuel, or where two flues are used one or two man-holes between
the flues, whereby ready access can be gained to the bottom inner surface of
the boiler and the entire surface of the flue or flues, as also to the under

page_text: surfaces of the small fire tubes. I furthermore form another man-hole
'communicating with the space between the upper surfaces of the small fire
tubes and the under surfaces of the large ones, the latter being so arranged
as to allow of sufficient space in the front of the boiler for this man-hole. I
also leave a considerable space between the small fire tubes, just over the top
of the flue or flues, as also between such fire tubes and the sides of the boiler,
in order both to allow of free circulation of the water and to afford free access
to the tubes for cleansing purposes. In order to draw the steam equally from
all parts of the boiler I fix a pipe in the steam space extending the whole
length of the boiler, the upper surface of which pipe is perforated to allow
the steam to enfer it and a shield is fixed just below this pipe extending
'some distance across the boiler, so as to cause the steam rising just below the
pipe to pass laterally and against the surfaces of the large fire tubes before
it can enter the perforated steam pipe, so as thereby both to heat the steam and
'to prevent the tubes from attaining so high a temperature as to injure the
metal. The steam is taken from the latter either at one end, or where a steam
dome is used the ends of the pipe are closed and a branch from the same
conducts the steam into the steam dome, which has no other communication
with the steam space of the boiler.
At Figures 1 and 2 on the accompanying Drawing is shown the con-
struction of a boiler having my before-described improvements. Figure 1
shows a part front elevation and part transverse section of the boiler, and
Figure 2 shows a longitudinal section through the same with the setting and
chimney flue.
The shell A of the boiler is short in proportion to its diameter, and the
flue B is made slightly smaller in diameter at the back end than at the front
end, and the hole in the front plate C is made sufficiently large to allow the
flange b of the flue to pass through, which flange is rivetted to the inside
of the black plate D, while the flange b' is rivetted to the outside of the
'plate C. The grate E extends nearly to the back end of the boiler, and in
the back end is placed a fire-brick partition F, having spaces or perforations
through which the flames pass into the smoke chamber G of fire-brick formed
outside the boiler. From the chamber G the flames and hot gases pass
through a number of fire tubes I, I, which conduct the same through the
water space of the boiler and into a front smoke box "J; whence the flames
'pass back again through other fire tubes K, K; in the steam space of the
boiler, and through a flue H formed over the smoke chamber G into the
'chimney L. For producing an effective draught a pipe M of smaller diameter
than the chimney is fixed in the latter, and the exhaust steam from the steam

page_text: engine is allowed to pass from a blast pipe N up the same. In order further
to increase the draught a steam pipe O conducts steam from the boiler to a
number of small nozzles P, P, situated inside the smoke box J in front of each
of the fire tubes K, from which nozzles jets of steam consequently pass into the
tubes and thus accelerate the passage of the flames or gases through the same.
This latter arrangement of steam jets issuing into the front ends of the fire
tubes may also be employed for steam boilers having only one set of fire tubes
passing directly from the furnace in front to the chimney at back. Sufficient
space is left between the small fire tubes I and the surface of the flue B, as
also between the small tubes I and the large ones K to render the surfaces of
the flue and the tubes accessible for cleansing purposes; man-holes Q and R being
formed in the front of the boiler communicating with these spaces. The
smoke box J is provided with doors for gaining access to the man-hole R, as
also to the interior of the fire tubes for cleansing them. A space is also left
at x between the small fire tubes, and at y between these and the sides of the
boiler, in order both to render the surfaces accessible for cleaning and to allow
of the free circulation of the water. S is a pipe fixed in the steam space of
the boiler and extending nearly the whole length of the same, which pipe is
perforated on its upper surface and is closed at the ends, while in the middle
it communicates by means of a branch s with the steam dome T which has no
other communication with the boiler. The steam is made by this means to
pass equally from all parts of the boiler into the perforated pipe, and thence
into the steam dome, and by the application of a shield U just below the per-
forated pipe the steam rising just beneath it is made to pass against the
surfaces of the tubes K, and to take up heat therefrom before passing into the
perforated pipe. In place of taking the steam from the middle of the pipe S,
as shown, it may also be taken from one end of the same.
Figure 3 shows a modified arrangement of the smoke chamber G which I
prefer to employ for marine boilers. In this case the chamber G is formed of
sheet iron a fixed to the end of the boiler and lined internally with fire-brick d,
which I prefer to fix to the iron casing by means of bolts formed either as at c
with a large flat head fitting into a deep recess in the fire-brick which is filled
out with fire-clay after the bolt is inserted, or I form the bolt with a tapering
shank as at c' fitting into a tapering hole in the fire-brick, or the bolts may
be fixed in the fire-brick during the process of manufacture. The passage H
also lined with fire-brick conducts the flames and hot gases from the tubes K
directly into the up-take V. As before stated, in place of or in addition to
the lining of fire-brick the smoke chamber may be provided with a water
jacket. In whatever way the said smoke box may be arranged I provide one

page_text: or more apertures closed by doors for gaining access to the interior thereof
for cleansing or repairs.
Having now described the nature of my Invention, and the manner of
performing the same, I wish it to be understood that I do not limit myself to
the employment of all the before-described improvements in combination as
shown in Figures 1 and 2 of the accompanying Drawing, as several thereof
may be employed separate and apart from such combination, as set forth in
the following claims, neither do I limit the application of my several improve-
ments to the precise form of the boiler, shown at Figures 1 and 2 on the
accompanying Drawing; but what I claim is,-
First, constructing steam boilers with single or double internal flues of a
limited length in proportion to the diameter, having a smoke chamber, at the
back outside the boiler, and having furthermore fire tubes arranged in the
water space of the boiler, through which the flames pass from the said smoke
chamber at the back into a smoke box in front of the boiler, whilst other
fire tubes arranged in the steam space of the boiler serve to conduct the
flames from the front smoke box into the chimney or uptake of the boiler, sub-
stantially as herein-before described.
Second, the employment of steam jets introduced into the front ends of the
fire tubes of steam boilers to increase the draught, substantially as and for the
purposes herein-before described.
Third, I claim, in combination, the general arrangement of single or double-.
flued steam boilers herein-before described with reference to the accompanying
Drawing.
In witness whereof, 1. the said David Thomson, have hereunto set my
hand and seal, this Twenty-fifth day of October, in the year of our
Lord One thousand eight hundred and sixty-six.
DAVID THOMSON. (L.S.)