Improvements in Steam Boilers.
Year: 1892

page_text: Date claimed. for Patent under Sect. 103 of Act,
being date of first Foreign Application (in 9th Apr., 1892
United States of America),
Date of Application (in United Kingdom), 3rd Nov., 1892
Complete Specification Left, 3rd Nov., 1892-Accepted, 3rd Dec., 1892
Complete Specification Left, 3rd Nov., 1892-Accepted, 3rd Dec., 1892
COMPLETE SPECIFICATION.
Improvements in Steam Boilers. .
I, FRED THAYER STEVENS, of Bryant's Pond, in the County of Oxford, and
State of Maine, United States of America, General Mechanic, do hereby declare
the nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :—
My invention relates to an improvement in steam boilers, the object of which is
to bring an inclosed small quantity of hot water in contact with the the hotest part
of the fire, converting this into steam, and keeping this space continually supplied
with heated water. This I accomplish by constructing my boiler with an inner
shell inclosing the tubes, an outer shell surrounding said inner shell, the centre of
said inner shell being preferably below that of the outer shell, so that a space will
be formed between the two shells smaller at the bottom than at the top. This
space is supplied by heated water from the inner shell passing through openings in
the inner shell, preferably above the tube-level.
My invention is illustrated in the accompanying drawings, in which―
Figure 1 is a central longitudinal section, and
Fig. 2 is a section on the line of Fig. 1.
A represents the grate, B the bridge-wall, F the front wall, G the rear wall,
the steam dome, and E the chimney-flue, of any ordinary horizontal tubular
boiler.
i is the front tube shell, and the back tube shell, d being the tubes. Instead of
a single shell, as in ordinary boilers, I use two shells C and D, one inside of the
other. I prefer to construct them, as here shown, with common tube-shells at
either end. The inner shell D incloses and surrounds the tubes, and the feed-
pipe e opens into it at the back end near the bottom. The outer shell C is placed,
preferably, out of centre with the inner shell, the centre of the outer shell being
the higher, so that the space I between the two shells will be smaller at the bottom
than at the top, the object being to make the layer of water at the bottom as thin
as possible, so that it will be the more quickly heated, and to make the steam space
at the top as large as possible. Openings d' d' are provided in the inner shell, by
which the water flows from the space within the inner shell to the space between
the two shells. These openings I prefer to place forward and above the tube
level, so that the tubes will always be covered.
In operation the feed water will enter the inner shell at the rear and pass
upward through the tubes, overflowing at its hotest point through the openings d'd¹
into the space between the two shells. Any sediment brought with the water will
be deposited in the bottom of the inner shell and will not be brought in contact
with the fire, as is the case in ordinary boilers. A comparatively thin layer of
very hot water contained in the lower part of the space I will thus be brought into
contact with the hotest part of the fire and converted into steam, which rises along
the sides and collects in the upper part of the space 1. The fact that a small
amount of water confiued in a narrow space and highly heated comes in contact

page_text: with the fire enables steam to be generated by less fire and at an expenditure of
less heat. The combustion will not be impeded by the cooling of the flame coming
in contact with the cold water of the bottom of the boiler, as is usually the case,
and the hot and burning gases will continue to the rear of the boiler and enter the
tubes, where the efficiency of the fire is much more than it is at the bottom of the
boiler. The heating power of the flame is thus increased, a smaller fire is needed
to run a large boiler, less fuel is used, and steam can be more quickly generated on
starting the boiler, because the whole mass of water does not have to be heated to
boiling point before steam begins to be generated. If desired, the upper part of
the shell D may be cut away, making more steam space; but I prefer to have two
complete shells, as described.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
clain is :-
1. In a tubular steam boiler, an inner shell inclosing the tubes, an outer shell
surrounding said inner shell, said inner shell having an opening for the flow of
water from within to the space between the shells, substantially as described.
2. In a tubular steam boiler, an inner shell inclosing the tubes, an outer shell
surrounding said inuer shell, the centre of said inner shell being below that of the
outer shell, the said inner shell having one or more openings through its walls,
substantially as described.
3. In a tubular steam boiler, an inner shell inclosing the tubes, an outer shell
surrounding said inner shell, the said inner shell having one or more openings
immediately above the tube level, substantially as described.
Dated this 3rd day of November 1892.
F. W. BARKER,
Applicant's Agent.