IMPROVEMENTS IN MARINE STEAM BOILERS
Year: 1878

page_text: LETTERS PATENT to Thomas Archer, junior, of Dunston Engine Works, in
the Town of Gateshead, and County of Durham, Engineer, for the Invention
of "IMPROVEMENTS IN MARINE STEAM BOILERS."
Sealed the 9th May 1879 in pursuance of an Order of the Lord Chancellor, and
dated the 7th November 1878.
PROVISIONAL SPECIFICATION left by the said Thomas Archer at the Office
of the Commissioners of Patents on the 7th November 1878.
THOMAS ARCHER, junior, of Dunston Engine Works, in the Town of Gates-
head, and County of Durham, Engineer. "IMPROVEMENTS IN MARINE STEAM
BOILERS."
I construct marine steam boilers so as to contain the usual internal arrangements
within a series of small cylinderical chambers instead of, as usual, in one large
cylinderical chamber; and I am thus enabled to diminish the thickness of the
external plates of such chambers, and thus the weight of the whole boiler, while
preserving the same relative strength to resist pressure. I further by this con-
struction diminish the quantity of contained water when in working order, and to
the extent of that diminished weight of water and reduced weight of boiler am
enabled to utilize further the carrying capacity of the ship. I further am enabled,
while preserving the other advantages referred to, to afford easy access to all parts
of the boiler, and in the event of accident to one part it can be replaced at less cost
than by the present system.
For a single ended boiler I prefer to construct three cylinders, one of which con-
tains the furnace, and one the set of tubes, and one the combustion chamber. Each
of the two first mentioned cylinders is joined to that containing the combustion

page_text: chamber at right angles or nearly so at their ends, so as to form with it approxi-
mately the appearance of a square letter U; but the two first named cylinders may
be joined to each other by the continuance of each, so as to meet the other in the
form of a circular letter U, and without the interruption of the third seperate
cylinder above described. For a double ended boiler I extend the length of the
cylinders containing the tubes and furnaces, and attach the cylinder containing the
combustion chamber at right angles or nearly so to their centres, so as approximately
to form the appearance of the letter H. When it is necessary to increase the steam
space I attach to the cylinder containing the nest of tubes a fourth cylinder, so as
to act as a steam dome and reservoir.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Archer in the Great Seal Patent Office on the 9th May
1879.
THOMAS ARCHER, junior, of Dunston Engine Works, in the Town of Gateshead,
and County of Durham, Engineer. "IMPROVEMENTS IN MARINE STEAM BOILERS."
I construct marine steam boilers so as to contain the usual internal arrangements
within a series of small cylindrical chambers instead of, as usual, in one large
cylindrical chamber; and I am thus enabled to diminish the thickness of the
external plates of such chambers, and thus the weight of the whole boiler, while
preserving the same relative strength to resist pressure. I further by this con-
struction diminish the quantity of contained water when in working order, and to
the extent of that diminished weight of water and reduced weight of boiler am
enabled to utilize further the carrying capacity of the ship. I further am enabled,
while preserving the other advantages referred to, to afford easy access to all parts
of the boiler, and in the event of accident to one part it can be replaced at less cost
than by the present system.
For a single ended boiler I prefer to construct three cylinders, one of which
contained the furnace, and one the set of tubes, and one the combustion chamber.
Each of the two first mentioned cylinders is joined to that containing the combustion
chamber at right angles or nearly so at their ends, so as to form with it approxi-
mately the appearance of a square letter U; but the two first named cylinders may
be joined to each other by the continuance of each so as to meet the other in the
form of a circular letter U, and without the intervention of the third separate
cylinder above described.
For a double ended boiler I extend the length of the cylinders containing the
tubes and furnaces, and attach the cylinder containing the combustion chamber at
right angles or nearly so to their centres, so as approximately to form the appearance
of the letter H. When it is necessary to increase the steam space I attach to the
cylinder containing the nest of tubes a fourth cylinder so as to act as a steam dome
and reservoir.
Having thus described the nature of my Invention I will proceed more particu-
larly to describe the manner in which the same is to be carried out, having reference
to the Drawings hereto attached. The Drawings illustrate what I consider the
most convenient and best arrangement of boiler according to my Invention, but
not the only convenient or good arrangement.
Fig. 1 is a vertical section through the centre of the boiler, as shewn in Fig. 4,
and paralel to the view given in that Figure; Fig. 2 is a front view of the boiler;
Fig. 3 is a section of Fig. 4 on the line A, B ; and Fig. 4, an external side view of
the boiler as complete. The parts of each Drawing are lettered similarly in each
view. a, a, a, a, is the shell of a cylindrical chamber surrounding the furnace;
b, b, b, b, is a shell of a cylinderical chamber surrounding the combustion chamber;
and c, c, c, c, the shell of a cylinderical chamber surrounding the tubes; d, d, d, d,
are the plates of the furnace itsself, which is also cylinderical; e, e, e, e, the walls of
the combustion chamber; and f, f, f, f, f, f, are ordinary boiler tubes.
As it is advisable on account of the casy attachment of the tubes to have a flat
back tube plate I make the front side of the combustion chamber flat, and stay it
with bar and screw stays, as shewn at g, 9, 9, g; and I make the back of the
combustion chamber semi-cylinderical so as to support itself; and as there is a
difference of strength in the joining together at right angles of two cylinders due to
the obliquity of the joint and its consequent oval section, I introduce a stay or
stays h, h, from the combustion chamber to the shell, but with these exceptions,―
I prefer to dispense entirely with stays, excepting gusset stays at its front ends, as
shewn, i, i, i, i, and which I make of such strength as not only to support the flat
ends of the boiler against the internal pressure due to its flat surface, but to carry

page_text: the thrust due to the pressure on the back of the combustion chamber against the
space occupied by the furnace or the tubes. I joint the stays h, h, as shown in the
Drawing, so that a movement for expansion becomes possible without producing
undue steam. j, j, is a dome to afford increased steam space without increase of
size of boiler shell, and k, k, is a provision for circulation of water and escape of
steam from above the furnace. The weight of the furnace I support on ribs l, l,
attached inside the bottom of the lower shell, which are not attached however to
the furnace.
Having thus described the nature of my Invention, and the manner in which the
same may be performed, I would have it understood that I do not confine myself to
the details I have described, which it must be manifest are susceptible of variation
in many ways; but what I claim as my Invention is the construction of marine
steam boilers so as to contain the usual internal arrangements within a series of
small cylindrical chambers instead of in one large cylindrical chamber, substantially
as described.
In witness whereof, I, the said Thomas Archer, junior, have hereunto set my
hand and seal, this Fifth day of May, in the year of our Lord 1879..