Improvements in the manufacture of Metallic Tubes suitable for Internal Fire-boxes and Flues of Steam Boilers and in Plates for the Construction thereof.
Year: 1888

page_text: Date of Application, 18th Oct., 1888
Specification Accepted, 30th Nov., 1888
Improvements in the manufacture of Metallic Tubes suitable for
Internal Fire-boxes and Flues of Steam Boilers and in Plates for
the Construction thereof.
I, JAMES SHEPHERD, of 11, Lower Thornhill Street, Wakefield, in the County
of York, Engineer, 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:-
Internal fire boxes and flues of steam boilers are usually made cylindrical, and
when of the corrugated type have the internal and external ridges of the corrugations
of equal diameters respectively.
Fire boxes and flue tubes of the latter type are much stronger to resist external
pressure than plain ones.
The object of my invention is to produce tubes having ridges and grooves or
undulations around them at right angles to their axes, capable of resisting a greater
collapsing strain than has heretofore been usual, while at the same time, tubes con-
structed according to my invention are so formed as to retain the flame and heated
gases within them for a much longer period than is the case with tubes as heretofore
constructed and thus to economise fuel.
For this purpose I cause metallic plates from which my improved tubes are con-
structed to be made somewhat thicker in the centre of their breadth than in the other
parts and in some cases I use plates of equal thickness throughout.
The plates are creased or have the undulations formed thereon by being passed whilst
hot between rolls having around their peripheries configurations corresponding to
those required on the finished tubes, the creases or undulations being deeper in the
middle of the breadth of the plates than near the edges thereof.-In some cases, in
addition to making the creases, ridges or undulations deeper in the middle of the plate
as just referred to, I cause the pitch of the said creases, ridges or undulations to
gradually diminish from the centre of the plate towards each edge thereof; or when
the said creases, ridges or undulations are made of an equal pitch they have a greater
depth in the middle of the plates as above referred to and similar in depth to those
plates having a greater pitch in the middle.
I sometimes diminish both the pitch and depth of the ridges and grooves from the
middle of the plates towards the outer edges, in steps of two or more at a time, the

page_text: thickness of the plate in this case may be equal throughout or otherwise. When
the plates have had the creases or longitudinal undulations formed upon them as
above referred to, they are reheated and bent into the required tubular form and
jointed by rivetting or welding, or the plain plate may first be bent to a cylindrical
form and welded, and afterwards have the creases or undulations formed thereon.
In the accompanying drawings, Fig. 1. Sheet 1. shews a tube according to my
invention, in which the metal is of equal thickness and the external ridges of equal
diameter, but with the pitch of the creasings or undulations unequal and deeper in
the middle of the length of the tube than near each end, the lines b, b, passing over
the internal ridges of the creasings from the middle of the said tube towards each
end, diverge, so that flame or heated gases passing through a tube of this configuration
partake somewhat of a wave-line and have a tendency to dwell longer in the tube and
to be more effective in generating steam than if the creasings or ridges were of
equal diameter. c is the axis or centre line of the tubes in all the Figures.
Fig. 2. shews a tube of similar form to that just described, but made of a plato
that is thicker in the middle of its breadth than at its edges, and therefore is capable
of withstanding greater external pressure than the tube shewn in Fig. 1.
Figs. 3. and 4. shew tubes in which the pitch and depth of the creasings are
variable as in Figs. 1. and 2. the metal in Fig. 3. being of equal thickness and that
in Fig. 4. variable, the lines a, a, that pass across the external ridges from the middle
of the tube towards the ends converge, and the lines b, b, that pass across the internal
ridges from the middle towards the ends, diverge.
Figs. 5. and 6, sheet 2, shew tubes in which the pitch of the creasings are equal,
but the depths thereof variable as above referred to, the external ridges being of
equal diameter, lines b, b, passing over the internal ridges, diverge in each direction
from the middle of the tube as above described with reference to Figs. 1. 2. 3. and 4.
The thickness of metal in Fig. 5. being equal, and that in Fig. 6, variable.
Fig. 7. shows a modification in the arrangement of the creasings, ridges or undula-
tions, their external diameters being equal while the pitch and depth thereof are variable,
and in steps of two or more at a time. One of the objects being in all cases, to
diminish the internal diameter of the tube at or about the middle of its length as
well as to increase evaporative effect and strength to resist collapse.
Fig. 8. is a partial end view of a tube shewing a lap rivetted joint.
Fig. 9. is a partial end view of a tube shewing a butt joint, with single butt strip
and rivetted. Fig. 10, is a partial end view of a tube shewing a butt joint with
internal and external butt strips and rivetted.
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
claim is
1. The improvements in the manufacture of metallic tubes for the internal fire
boxes and flues of steam boilers with creases or undulations at right angles to their
axes so arranged that the internal diameter at or about the middle of their length is
less than at the ends thereof, and constructed of plates either of equal or variable
thickness substantially as hereinabove described and illustrated for the purposes
specified.
2. The use in the construction of metallic tubes for the internal fireboxes and flues
of steam boilers, of plates thicker in the middle of their breadth than at the edges
thereof, substantially as hereinabove set forth.
Dated thin 10th dow of October 1888