IMPROVEMENTS IN STEAM BOILERS
Year: 1868

page_text: LETTERS PATENT to John Millward, of Curzon Chambers, Paradise.
Street, Birmingham, in the County of Warwick, Civil Engineer,.
for the Invention of "IMPROVEMENTS IN STEAM BOILERS."-A com-
munication from abroad by Joseph Nason, of the City and County
of New York, in the State of New York, United States of America..
Sealed the 2nd March 1869, and dated the 9th September 1868..
PROVISIONAL SPECIFICATION left by the said John: Millward at the-
Office of the Commissioners of Patents, with his Petition, on the.
9th September 1868.
I, JOHN MILLWARD, of Curzon Chambers, Paradise Street, Birmingham,
in the County of Warwick, Civil Engineer, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN STEAM BOILERS," to be as:
follows:-
This Invention relates to that class of boilers known as "drop-tube"
steam boilers, or boilers having groups of straight or curved tubes with
: closed lower ends and inner circulating tubes suspended from the crown,

page_text: plates of the fire-boxes or flues of the boilers, and its object is to provide
more effectually than has hitherto been done for the free and separate
action of the descending and ascending currents at or near the upper
ends of the double tubes, and for the direct escape of the partieles or
bubbles of steam from the water flowing from the outer or heating tubes
when the boiler is in action, and also for the subsidence of such
disturbed water into a state of comparative repose and density previous
to its return down the inner or circulating tubes.
This Invention consists in providing the upper ends of the outer or
heating tubes of such boilers with or affixing thereto short extension
pieces forming prolongations of the said tubes, and rising to some
suitable height into the body of the water or fluid above the crown plate
of the fire-box or flue, and in providing the inner or circulating tubes
at their upper ends with or affixing thereto elbows or branches passing
through the sides of the extension tubes at some distance below the
tops of the same, and a little above the tube or crown plate. By this
arrangement each inner tube communicates, by means of its junction or
junctions with the extension part of its corresponding outer tube, with
the water above the tube plate in such a manner that the water passes
in below the level and out of the way of the discharge of water and
steam from the outer tubes. By these means therefore the heated water
as it rises from the outer tubes surcharged with bubbles or particles of
steam will escape directly into the water above the extension tubes,
which water will be in a somewhat similar condition, and as it is
relieved and separated from the steam it will subside into the spaces
around the said extensions of the outer tubes, and flow back through the
side openings and inner tubes or passages.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Millward in the Great Seal Patent Office
on the 8th March 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
MILLWARD, of Curzon Chambers, Paradise Street, Birmingham, in the
County of Warwick, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of September, in the year

page_text: of our Lord One thousand eight hundred and sixty-eight, in the
thirty-second year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said John Millward, Her
special licence that I, the said John Millward, my executors, adminis-
trators, and assigns, or such others as I, the said John Millward,
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," a communication to me from abroad
by Joseph Nason, of the City and County of New York, in the State of
New York, United States of America, upon the condition (amongst
others) that I, the said John Millward, 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 John Millward, 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
Sheet of Drawings, and to the figures and letters marked thereon, that
is to say:
This Invention relates to that class of boilers known as drop-tube
steam boilers, or boilers having groups of straight or curved tubes, with
closed lower ends and inner circulating tubes suspended from the crown
plates of the fire-boxes or flues of the boiler; and its object is to provide
more effectually than has hitherto been done for the free and separate
action of the descending and ascending currents at or near the upper
ends of the double tubes, and for the direct escape of the particles or
bubbles of steam from the water flowing from the outer and heating
tubes when the boiler is in action, and also for the subsidence of such
disturbed water into a state of comparative repose and density previous
to its return down the inner or circulating tubes.

page_text: This Invention consists in providing the upper ends of the outer of
heating tubes of such boilers with or affixing thereto short extension
pieces forming prolongations of the said tubes, and rising to some
suitable height into the body of the water or fluid above the crown plate
of the fire-box or flue, and in providing the inner or circulating tubes at
their upper ends with or affixing thereto elbows or brauches passing
through the sides of the extension tubes at some distance below the tops
of the same, and a little above the tube or crown plate. By this
arrangement each inner tube communicates, by means of its junction
or junctions with the extension part of its corresponding outer tube,
with the water above the tube plate in such a manner that the water
passes in below the level and out of the way of the discharge of water
and steam from the outer tubes. By these means therefore the heated
water as it rises from the outer tubes surcharged with bubbles or particles
of steam will escape directly into the water above the extension tubes,
which water will be in a somewhat similar condition, as it is relieved
and separated from the steam it will subside into the spaces around the
said extensions of the outer tubes, and flow back through the side
openings and inner tubes or passages.
But in order that the said Invention may be fully understood, I shall
now proceed more particularly to describe the manner of performing the
'same, and for that purpose shall refer to the several Figures on the
accompanying Drawing, the same letters of reference indicating corre-
sponding parts throughout all the corresponding Figures.
Figure 1 is a partial section of a steam boiler shewing several drop-
tubes constructed and applied in accordance with this Invention.
Figures 2 and 3 are enlarged vertical and cross sections of the drop-
tubes and their attachments, showing one method of joining the inner
tubes of the extension tubes.
Figures 4 and 5 are vertical and cross sections showing another
method of performing this junction.
A represents a crown plate of fire-box or flue, into which are inserted
the outer tubes B; these may be fastened or connected with the plate by
any of the usual methods of fastening tubes, but by preference with
screw joints with slightly tapered threads, which are perfectly
secure and tight, and have the advantage of allowing the tubes to be
inserted or taken out without the necessity of gaining access to the inner

page_text: side of the tube plate. C, C, are the inner or circulating tubes open at
both ends.
The novel and essential feature of this Invention now to be described
consists in the prolongation or extension of the tubes B a certain distance
into the water above the tube plate A, and the lateral deflection or
curvature of the tubes C into and through openings in the sides of the
extension tubes just above the tube plate.
Two methods of effecting this are shewn in Figures 2, 3, 4, and 5. In
cach of these methods the tube B is prolonged above the tube plate by
means of an extension piece or tube D which is simply a metal tubo
with its edges brought nearly together, as at d³, but left open to make it
slightly elastic to hold its place in the tube B by frictional contact.
In the side of the extension tube D, and very near the tube plate A is
an opening to which, as shewn in Figures 4 and 5, is fastened a bend
or elbow E of malleable cast iron or other metal turning downwards,
and in the lower end of which is inserted the inner tube c, which is thus
held and suspended in the outer tube B.
In the method of forming the junction of the outer and inner tubes
shewn in Figures 2 and 3, the elbow E is omitted, and the tube C has
its upper end closed, and a side opening of which the edges are formed
into a mouth corresponding to the opening in the extension tube D and
passing through the same, the junction being secured by bending the
sides of this mouth outward and over the edges of the opening in
extension piece D.
In
The construction may be further varied by casting or forming the
extension tube D and the elbow E in one piece, or the separate extension
tube may be omitted altogether, and the main tube B prolonged above
the tube plate, perforated in its side, and joined to the tube C by either
of the methods just described, or by any other similar means.
place of only one side opening in the tube D, two or more may be
formed therein, either side by side or in different parts of the circum-
ference; but this would not be so good an arrangement as that shown,
as the currents passing into the different tubes might interfere with
each other.
By this Invention, when the water contained in the annular spaces
between the outer tubes B, B, and the inner tubes C, C, becomes heated,
and rises by its lesser gravity into the boiler, its place is supplied by the

page_text: cooler water flowing back from the boiler through the side openings in the
extension tubes D, D, into and through the tubes C, C; when the water
in the boiler has been heated by this process of circulation to the point
of ebullition, the water in the annular spaces before mentioned will
become more or less surcharged with bubbles or particles of steam, and
under the action of an intense fire may become so subdivided as to
assume the condition of foam, and thus ascend into the boiler, in which
case the greater part of the water in the boiler above the extension
tubes D, D, will be similarly surcharged and attenuated by steam
bubbles, which constantly tend to the surface. As these become in turn
released and separated, the water will subside into the spaces between
the extension tubes D, D, in a state of comparative repose and density,
and from thence will flow back through the side openings and
tubess C, C, into the tubes B, B, the direction of the currents being
indicated by arrows in Figures 1, 2, and 4. The distance of the tubes
apart and the diameter of the outer tubes (which may ordinarily range
from one to three inches) may be varied to suit the purposes for which
a boiler is intended, but by the use of this Invention tubes of a smaller
diameter may be safely employed, and the surfaces consequently be more
closely aggregated than with any other mode of constructing drop-tubes
hitherto in use.
By this Invention also, the circulation of water is rendered much more
rapid and distinct than heretofore, and the heating power and durability
of the tubes consequently much increased.
Having thus described the nature of the said Invention and the
manner in which the same is to be performed, as communicated to me
by my foreign correspondent, I wish it to be understood that I do not
limit myself to the precise details of construction and arrangement
herein-before described with reference to the accompanying Drawing, as
these may be variously modified without departing from the nature of
the Invention; but what I claim as new and desire to be secured to me
by the herein-before in part recited Letters Patent is,-
First. Providing the outer tubes B with an extension passing up some
distance above the tube plate, and having one or more lateral openings
adapted to receive the return or downward current of water, and conduct
it into the inner tubes C, substantially in manner and for the purposes
herein-before set forth.

page_text: Second. I also claim in connection with the before-mentioned ex-
tension of the outer or main tube B, making such extension in a separate
piece D adapted to the inner tube C, and to the other parts, substantially
as and for the purposes herein-before set forth.
In witness whereof, I, the said John Millward, have hereunto
set my hand and seal, this Sixth day of March, in the year
of our Lord One thousand eight hundred and sixty-nine.
JOHN MILLWARD. (L.S.)