IM- OR CONNECTED WITH STEAM BOILERS
Year: 1871

page_text: LETTERS PATENT to David Davidson, of Glasgow, in the County of
1
Lanark, North Britain, Boiler Maker, for the Invention of "IM-
OR CONNECTED WITH STEAM BOILERS."
DRAVEMENT IN
Sealed the 23rd January 1872, and dated the 26th July 1871.
PROVISIONAL SPECIFICATION left by the said David Davidson at the
Office of the Commissioners of Patents, with his Petition, on the
26th July 1871.
I, DAVID DAVIDSON, of Glasgow, in the County of Lanark, North
Britain, Boiler Maker, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN OR CONNECTED WITH STEAM BOILERS," to be as follows,
that is to say:-
This Invention has for its object by means of certain improvements
in and additions to steam boilers to render them safer, more efficient,
and more economical in fuel than existing boilers of the same general
dimensions.

page_text: The improvements are by preference applied to the now common form
of land boiler, known as the Cornish boiler whether constructed with
external or internal furnaces.
In carrying out the Invention according to one modification with
external furnaces, an arch-shaped casing is placed over each furnace
at the front end of the boiler, and from the back ends of the casings
tubes are carried along the flue below the boiler to the back end, where
they are turned up and made to enter the boiler at or a little above the
water level. The lower part of the front end of the boiler is made to
communicate by means of one or more pipes with the forward parts of
each casing. With these arrangements the water is made to circulate
vigorously through the casings, the tubes, and the main boiler. The
after parts of the tubes are by preference made smaller in the bore than
the forward parts. The fire-bars of the furnaces are made to consist of
wrought-iron tubes having their ends fixed in casings which may be
connected to the casings herein-before referred to, or may be separate
therefrom, and the feed water is made to pass through these tubes before
entering the main boiler, so that they will be kept cool and so be
rendered more durable than ordinary fire-bars, whilst at the same time
they contribute additional surface for heating the water. The fire-door
is made hollow with apertures on the outside near the bottom for the
admission of air, and with internal flanges or partitions to lead the air
by a zig-zag course so as to become heated on its way upwards to an
aperture or apertures on the inner side through which it enters the
furnace. A nozzle is fitted in the centre of each aperture, and steam
is supplied thereto by a flexible tube for the purpose of inducing the
requisite ingress of air, the small quantity of steam used for this purpose
having itself an advantageous action in the furnace.
In applying the improvements to Cornish boilers with internal
furnaces the arch-shaped casings herein-before described as extending
over the furnace may be arranged in the same way or they may be
reduced to narrow casings for the attachment of the front ends of the
tubes, and be situated just beyond the furnace bridges, branch pipes
leading the water into such casings from the sides of the main boiler
flues. Or the narrow casings may be placed at the front ends of the
furnace spaces with the tubes partly over the fires.
The herein-before described series of tubes in the main flues may
however be arranged without the casings at their front ends, either

page_text: when the furnaces are external or when they are internal, and in such
cases the front ends of the tubes are turned up and made to communicate
separately with the main boiler but at points as far below the water
level as can be conveniently arranged.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David Davidson in the Great Scal Patent Office
on the 25th January 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
DAVIDSON, of Glasgow, in the County of Lanark, North Britain, Boiler
Maker, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-sixth day of July, in the year
of our Lord One thousand eight hundred and seventy-one, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said David Davidson, Her special licence
that I, the said David Davidson, my executors, administrators, and
assigns, or such others as I, the said David Davidson, 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 OR CONNECTED WITH STEAM BOILERS," upon the condition (amongst
others) that I, the said David Davidson, 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 Davidson, 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, that is to say :-

page_text: My said Invention has for its object by means of certain improvements
in and additions to steam boilers to render them safer, more efficient,
and more economical in fuel than existing boilers of the same general
dimensions.
And in order that my said Invention and the manner of performing
the same may be properly understood, I hereunto append a Sheet of
explanatory Drawings to be herein-after referred to, and representing
modifications of boilers as fitted with my improvements. In these
Drawings the same reference numerals are used to mark the same or
like parts wherever they are repeated.
I prefer to apply my improvements to the now common form of land
boiler known as the Cornish boiler, whether constructed with external
or internal furnaces, but they can also be applied to other land boilers
and to marine boilers.
In carrying out my Invention according to one modification, which
is shown in longitudinal vertical section in Figure 1, and in transverse
vertical section in Figure 2, and which comprises two external furnaces 1,
an arch-shaped casing 2 is placed over each furnace at the front end of
the boiler 3, and from the back ends of the casings 2 tubes 4, 5, are
carried along the flue below the boiler to the back end, where they are
turned up and made to communicate with the boiler 3 at or a little
above the water level. The communication with the boiler is effected
by means of a transverse box 6, to the bottom of which the ends of the
tubes 5 are fixed, and which is itself connected to the boiler 3 by three
short pipes 7. The lower part of the front end of the boiler 3 is made
to communicate by pipes 8 with each casing 2. With these arrange-
ments the water is made to circulate vigorously through the casings 2,
through the tubes 4, 5, and through the main boiler 3. The after parts 5
of the tubes are by preference made smaller in the bore than the
forward parts 4. The casings 2 may be extended round under the
ash-pits as indicated by dotted lines at 9 in Figure 2, so as to form
complete circles in cross section. In Figure 2 one half the section is
as at the back end of the boiler, but the other half is partly as imme-
diately behind the casing 2. The brickwork beneath the boiler is
shaped as shown at 10, so as to confine the fire gases to the immediate
neighbourhood of the tubes 4.
A second modification is shown in Figures 3, 4, and 5, the boiler 3
being in this case one with two internal furnaces 1. Figure 3 is one

page_text: half an end elevation and the other a transverse vertical section as at
the inner end of the furnace. Figure 4 is a longitudinal vertical section
as taken through the centre of one of the furnaces, and Figure 5 is an
elevation of the back end of the boiler. The fire-bars of the furnaces
are made to consist of wrought-iron tubes 11, having their front ends
fixed in a transverse horizontal casing 12, connected to the lower part
of the boiler 3 by pipes 13. The inner ends of the tubes 11, may be
fixed to a casing similar to the front one 12, but I prefer to bend them
up as shown, and to fix them to the flat top of a recess 14 formed for
the purpose in the flue so that they communicate directly with the
upper internal part of the boiler. In order to allow the fire gases to
pass freely across the turned up parts of the tubes 11, these are arranged
in sets in the manner shown in Figure 6, which is a view of the top
plate of the recess 14 with the holes in it for the tubes. The turned
up parts of the tubes 11 are not shown at the left-hand side of Figure 3.
In addition to these tubular fire-bars 11, the boiler is furnished with
an arrangement of casings 2 and tubes 4, 5, similar to those of the
modification first herein-before described, but the casing 2 is made
much shorter.
The arrangement with the internal furnaces may be modified by
placing casings 2 over the furnaces as in the first modification and either
with ordinary fire-bars or with the tubular bars 11; similarly, although
ordinary fire-bars 15 are shown in Figures 1 and 2, the tubular bars 11
may be substituted for them in the modification shown in those Figures.
Further in the case of either external or internal furnaces the narrow or
short casings 2 (Figure 4) may be placed at the front ends of the
furnace spaces with the tubes 4 partly over the fire, or the tubes 4 may
be arranged without the casings 2 at their front ends, their front ends
being bent and made to communicate with the main boiler 3, at points
as far below the water level as can be conveniently managed, or again
the inner ends of the fire-bar tubes 11 may be connected directly or
through the intervention of a casing to the other set of tubes 4, 5.
My Invention also comprises an improved arrangement of fire door
to be used in combination with the herein-before described improvements
but also applicable without them. It is shown in plan in Figure 7,
in front elevation in Figure 8, and in vertical section in Figure 9. The
fire-door is made hollow and with an opening 16 on the outside near
the bottom for the admission of air, with internal flanges or partitions

page_text: to lead the air by a zig-zag course so as to become heated on its way
upwards to an aperture 17 on the inner side through which it enters
the furnace. Nozzles 18 are fitted in the upper space or opening 17,
and steam is supplied thereto by means of a flexible tube 19, for the
purpose of inducing the requisite ingress of air, the small quantity of 5
steam used for this purpose having itself an advantageous action in the
furnace. An adjustable valve 20 is applied to the air inlet 16.
Having thus particularly described my said Invention, and the manner
of performing the same, I have to state that I do not restrict myself
to the precise details herein described or delineated, but that what I 1
believe to be novel and original, and claim as the Invention secured to
me by the herein-before in part recited Letters Patent is,―
1. The arranging or combining together of the parts of steam boilers
substantially in the improved modes herein described and delineated.
2. The constructing of fire-doors for steam boiler furnaces substantially 1
in the improved manner herein described and delineated.
In witness whereof, I, the said David Davidson, have hereunto
set my hand and seal, this Twenty-fourth day of January, in
the year of our Lord One thousand eight hundred and seventy-
two.
2
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
DAVID DAVIDSON. (L.S.)