Improvements in the Construction of Steam Boilers.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in the Construction of Steam Boilers.
I WILLIAM MALAM of Edgemoor in the County of Newcastle State of Delaware
United States of America Boiler Maker 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 :-
One object of my invention is to so construct a corrugated crown sheet for the
firebox of a boiler of the locomotive type that pressure upon the crown sheet will
not cause any other than a direct vertical strain upon the side sheets of the firebox
or upon the joint formed between the upper edges of the side sheets and flanges of
the crown sheet, a further object being to so form the corrugated crown sheet as to
insure the best heating effect, and a still further object being to attain substantially
similar results as regards resistance to strain in connection with the smoke box
casings of boilers generally.
In the accompanying Drawings,
Figure 1 is a longitudinal section of sufficient of a boiler of the locomotive type
to illustrate my Invention,
Figure 2 is a transverse section on the line 1-2, Figure 1,
Figure 3 is a section of part of the firebox casing on a still larger scale,
Figure 4 is a similar view on a smaller scale, and illustrating another form of
firebox to which my Invention may be applied; and
Figures 5 and 6 are respectively longitudinal and transverse sectional views
illustrating the application of my Invention to one form of smoke box casing.
In Figures 1 to 4, A represents part of the outer shell or casing of the boiler,
B the rear sheet of the firebox, D the front or tube sheet, E the tubes, F F the
opposite side sheets of the firebox, and G the crown sheet, which is corrugated
transversely, so as to impart to it such rigidity as will render unnecessary the
employment of the usual crown bars and stays for the crown sheet.
In the boiler shewn in Figures 1 and 2, the crown sheet has at each side a
vertical flange a, which is riveted to the upper edge of the side sheet F of the firebox,
and the corrugations in the crown sheet are carried out full to these flanges, so that
throughout the entire length of the crown sheet, that is to say, from the front end
to the rear end of the same, the ends of the corrugations are in the same vertical
planes as the sides of the firebox.
By this means, the rigidity of the crown sheet due to the corrugating of
the same, is maintained up to the very edges of the sheet, hence, there is
no weakening of the sheet at and near the edges, and the pressure upon the
crown sheet therefore is transmitted to the side sheets of the firebox in a true vertical
plane, or in a direction transversely to the axes of the rivets. The separation of the
crown sheet from the sides of the firebox will thus necessitate the actual shearing off
of these rivets, and accidental rupture or straining of the joint is rendered extremely
improbable.
The opposite flanges a of the crown sheet preferably follow the corrugated contour
of the same, so that a longer line of rivets can be used for securing the crown sheet
and side sheets of the 'firebox than if the flange and securing line of rivets were
straight. A straight flange and straight line of rivets may, however, be employed
without departing from my invention, '(see Figure 3, for instance).
It will be observed on reference to Figure 1, that the depth of the corrugations
in the crown sheet gradually increases from the rear to the front of the firebox, that
is to say, the shallowest corrugation is adjacent to the rear plate B of the fire box,
and the deepest corrugation is adjacent to the flue sheet D of the same, so that the
corrugations are deepest and the surface exposed to the action of the products of
combustion is greatest at those points where said products of combustion are hottest.

page_text: In carrying out my invention, however, it is not absolutely necessary that the
corrugations should be graduated, nor that the crown sheet should be separated from
the side plates of the firebox, and in Figure 4 I have shown an instance in which
the crown sheet and side plates are in one piece, this structure however, showing the
essential features of the invention, that is to say, the carrying of the corrugations of the
crown sheet fully out to the edges of the same, so that the ends of said corrugations
shall be in the same plane as the side sheets of the firebox.
Although the crown sheet shown is in one piece extending from front to rear of the
fire box, it may in long fire boxes, be composed of several sections suitably secured
together. It is advisable, however, in all cases to make the crown sheet continuous
from side to side of the fire box, but the sheet may in some cases be arched trans-
versely, as shown by dotted lines in Figure 2 for instance.
In applying the invention to a smoke box casing G¹, such as shown in Figures 5
and 6, which may be similar to that shown in my Patent No. 10,020 dated
August 24th 1885, the corrugations of the casing are carried out full to the front
tube plate D', and to the front plate J of the boiler casing to which they are secured
by the vertical flanges a' of the casing G¹. The same means may be employed
in connection with the smoke box casings of marine boilers.
Having, thus described my Invention I claim and desire to secure by Letters
Patent-
First-The combination in the firebox of a steam boiler of the side sheets and a
transversely corrugated crown sheet having the corrugations carried out full to the
ends of the shoet and sides of the box so that the strains upon the end portions of the
crown sheet will be in the same plane as the sides of the box, substantially as
specified.
Second The combination in the firebox of a steam boiler of the side sheets, and
the transversely corrugated crown sheet, the corrugations of the crown sheet
increasing in depth from the rear to the front of the firebox and being carried out
full to the ends of the crown sheet and sides of the box whereby the strains on the
end portions of the crown sheet will be in the same plane as the sides of the firebox
substantially as specified.
Third:-The combination of the shell of a boiler with the corrugated casing of the
smoke box, having flanges at the ends for securing it to the plates of the boiler shell
and having the corrugations carried out full to these flanges so that the strains will be
directly in line therewith substantially as specified..
Dated this 14th day of December 1889.