IMPROVEMENTS IN STEAM BOILERS
Year: 1876

page_text: LETTERS PATENT to David Davidson, of Glasgow, in the County of Lanark,
North Britain, Boiler Maker, for the Invention of "IMPROVEMENTS IN STEAM
BOILERS."
ealed the 28th March 1877, and dated the 9th October 1876.
PROVISIONAL SPECIFICATION left by the said David Davidson at the Office
of the Commissioners of Patents on the 9th October 1876.
DAVID DAVIDSON, of Glasgow, in the County of Lanark, North Britain, Boiler
Maker. "IMPROVEMENTS IN STEAM BOILERS."
This Invention has for its object to render steam boilers safer, more efficient, and
more economical in fuel than existing boilers of similar dimensions; and in carrying
it out improved and simple arrangements are adopted for causing a thorough
circulation of the water in the boiler, being for want of such circulation that many
existing boilers are defective and even dangerous.
One modification of the improvements is specially applicable to land boilers of the
Cornish class with internal furnaces and with the flues from such furnaces crossed
by conical or what are known as Galloway tubes, and consists in continuing such
Galloway tubes through the water above the flue tubes up to or nearly up to the
water level. In a new boiler the tubes may be made sufficiently long to extend
across the flue tube and up to the desired height, but in the case of existing boilers
short additional tubes may be attached to the upper ends of the Galloway tubes;
and this may be done if preferred even in new boilers. Caps are fitted over the
upper ends of the tubes to prevent the water from being thrown up into the steam
space. With these improvements the water which is made by the heat to flow
upwards through the tubes must be supplied from below, and a vigorous circulation
consequently takes place. In some cases the Galloway tubes may be extended
downwards as well as upwards.
In a second modification suitable for marine purposes the boiler comprises a large
upper cylindrical shell or boiler with sinall flue tubes passing through it, and having
beneath it two smaller cylinders with one large flue tube through each and with
furnaces in such flue tubes. The back ends of the large flue tubes of the lower
cylinders communicate with a flame chamber enclosed by water spaces combined
with brickwork, and after passing through this chamber the fire gases return to the
[Price 8d.1

page_text: front of the boiler through the tubes in the upper boiler or shell The upper shell
communicates with each lower cylinder by stools or short wide tubes at the front
and back ends, and to the communications at the back ends pipes are attached
inside the upper shell and extend up to about the water level, an arrangement
which causes a vigorous circulation to take place through the upper and lower
shells.
In a third modification, also suitable for marine purposes and not differing much
from the second modification, there is an upper cylindrical shell with small tubes
and a single lower shell formed so as to contain two furnaces at its lower part and
with a single flame chamber at its back part, all encased by water spaces, and the
flame chamber extending upwards so that its upper part may communicate by an
opening through the shell with the tubes of the upper cylindrical shell. Front and
back water communications are formed between the shells, the back ones termi-
nating at a higher level than the front ones so as to cause the desired circulation.
In a fourth modification the flame chamber is formed in a casing which is a
continuation backwards and downwards of the upper cylindrical shell, the furnaces
being in large flue tubes in two lower cylindrical shells as in the second modi-
fication.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said David Davidson in the Great Seal Patent Office on the 6th April
1877.
DAVID DAVIDSON, of Glasgow, in the County of Lanark, North Britain.
PROVEMENTS IN STEAM BOILERS."
IM-
My said Invention has for its object to render steam boilers safer, more efficient,
and inore economical in fuel than existing boilers of similar dimensions; and in
carrying it out improved and simple arrangements are adopted for causing a thorough
circulation of the water in the boiler, it being for want of such circulation that many
existing boilers are defective and even dangerous.
One modification of my improvements is specially applicable to land boilers of the
Cornish class with internal furnaces and with the flues from such furnaces crossed
by tubes which may be cylindrical or conical or what are known as Galloway tubes,
and consists chiefly in forming continuations of such tubes in a manner to secure
improved circulation and to prevent priming.
În a second modification suitable for marine purposes the boiler comprises a large
upper cylindrical shell or boiler with small flue tubes passing through it, and having
beneath it two smaller cylinders with one large furnace and flue tube through each.
A flame chamber enclosed by water spaces combined with brick work forms a
communication at the back between the lower large flue tubes and the upper small
tubes, and water communications are made between the upper and lower shells in
such a way as to cause a vigorous circulation downwards at the front, and upwards
at the back.
A third modification, also suitable for marine purposes, resembles the second
excepting that the flame chamber is formed in a casing joined to the two lower
cylindrical shells; whilst in a fourth modification the flame chamber is formed in a
casing which is a continuation backwards and downwards of the upper cylindrical
shell.
And in order that my said Invention and the manner of performing the same
may be properly understood, I hereunto append four Sheets of explanatory Draw-
ings to be herein-after referred to and representing examples of my improved boilers.
In these Drawings the same reference numerals are used to mark the same or like
parts wherever they are repeated.
On Sheet 1 of the Drawings are shown modifications of my improvements as
adapted to Cornish boilers; Figure 1 being a longitudinal vertical section, but

page_text: showing different modifications towards either end, whilst Figures 2 and 3 are trans-
verse vertical sections corresponding to the different modifications shown in Figure 1.
The boiler is shown as formed in a common manner with an external cylindrical
shell 1 and flat ends 2, and is traversed by two large flue tubes 3, having a furnace +
at the front end of each. The large flue tubes 3 are crossed by smaller water
tubes 5, 6, placed each in succession at a different angle. One of my improvements
consists in continuing the flue crossing water tubes 5, 6, above the tops of the flue
tubes 3, and up to the water level or a little above or below that level.
•
In the modification shown, towards the furnace end in Figure 1 and in Figure 2
the tubes 5 are cylindrical, excepting a very slight taper at their upper ends, and
their bottom ends are rivetted by flanges formed on them directly to the inside of
the flue 3, whilst their upper ends have rivetted or welded to them short cones 7,
which are rivetted by flanges formed on their bottom edges to the outside of the flue 3
so as to form a space for the access of the fire gases round the upper parts of the
tubes 5.
In the modification or variation shown at the inner end of the boiler in Figure 1
and in Figure 3, the water tubes G crossing the flue tubes 3 are of a conical form
and arrangement and known as Galloway tubes, and in this case my improvement
is carried out by applying short tubes 8, which may be of any convenient shape, to
the tops of the Galloway tubes; caps 9 are fitted over the upper ends of the flue
crossing water tubes 5, 6, or of their continuations 7, 8, to prevent the water from
being thrown up into the steam space. With these improved continuations to the
tubes 5, 6, it will be obvious that the water which is made by the heat to flow
upwards through the tubes must be continually supplied from below, and in con-
sequence of this a vigorous circulation takes place.
In some cases the Galloway or other flue-crossing water tubes 5, 6, may be
extended downwards by the addition of short tubes 10, so as to make the circulation
affect the water at the lowest parts of the boilers. This improvement whilst render-
ing the general circulation more complete will prevent unequal heating and
injurious strains on the boiler shell from unequal expansion when the boiler is first
heated up.
The continuation tubes 8, 10, can be easily applied to existing boilers made with
Galloway or other flue-crossing tubes, and new boilers may be made in the same
way with Galloway or other flue-crossing tubes made and fixed as heretofore and
with the upper or lower or both continuation tubes 8, 10, added; or new boilers
may be made with tubes of the necessary total length in single pieces.
Figures 4 and 5 on Sheet 2 are a vertical section and a sectional end elevation
of a modification of my improved boilers suitable for marine purposes, the section
in Figure 1 being as at right angles to Figure 2. This boiler comprises a
large upper cylindrical shell 11 with flat ends 12 and with small flue tubes 13
passing through it, and it has beneath it two smaller cylinders 1 with one large flue
tube 3 through each, and with furnaces 4 in such fluo tubes; the back ends of the
large flue tubes 3 of the lower cylinders 1 communicate with a flame chamber 14
enclosed by water spaces 15 combined with brickwork, and after passing through
this chamber 14 the fire gases return through the tubes 13 in the upper boiler or
shell 11 to a smoke box 16 at the front. The upper shell 11 communicates with
each lower cylinder 1 by stools or short wide tubes 17, 18, at the front and back
ends, and to the communications 18 at the back ends pipes 19 are attached inside
the upper shell 11 and extend up to about the water level, an arrangement
which causes a vigorous circulation to take place through the upper and lower
shells 11, 1. The minor details of construction will be easily understood from the
Drawing.
Figure 6 on Sheet 3 of the Drawings is a vertical section of a modification of my
improved boilers suitable for marine purposes in which two lower cylinders 1 with
furnace flue tubes 3 in them are united to and form one casing with a shell 20,
having within it the flame chamber 14 surrounded by water spacing. The flame
chamber 14 extends upwards, and an opening 21 is formed from it through the water

page_text: space and outer shell 20 for the fire gases to pass through to tho tubes 13 of the
upper boiler or shell 11. The water communications 17, 18, 19, are arranged
between the lower cylinders 1 and the upper shell 11, as in the modification shown
on Sheet 2 of the Drawings and herein-before described, and a pipe 22 is provided
between the upper shell 11 and the top of the flame chamber casing 20.
Figure 7 on Sheet of the Drawings is a vertical section of a modification of my
improved boilers suitable for marine purposes which differs from that shown on
Sheet 3 simply in having the shell 20, which encloses the flame chamber 14 and its
surrounding water spacing, formed in one casing with the upper cylindrical shell 11,
instead of with the lower cylinders 1.
Having thus particularly described my said Invention and the manner of per-
forming the same, 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,―
1. The making or fitting of the flue-crossing water tubes of Cornish boilers with
continuations above the flue tubes, substantially as and for the purposes herein-
before described.
2. The making or fitting of the flue-crossing water tubes of Cornish boilers, with
continuations above and below the flue tubes, substantially as and for the purposes
herein-before described.
3. The combining of parts to form a boiler for marine and other purposes sub-
stantially in the manner herein-before described with reference to Sheet 2 of the
accompanying Drawings.
4. The combining of parts to form a boiler for marine and other purposes, sub-
stantially in the manner herein-before described with reference to Sheet 3 of the
accompanying Drawings.
5. The combining of parts to form a boiler for marine and other purposes, sub-
stiantially in the manner herein-before described with reference to Sheet 4 of the
accompanying Drawings.
In witness whereof, I, the said David Davidson, have hereunto set my hand
and seal, this Fourth day of April, in the year of our Lord One thousand
eight hundred and seventy-seven.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
DAVID DAVIDSON. (L.S.)