IMPROVEMENTS IN THE CONSTRUCTION OF BOILERS FOR GENERATING STEAM
Year: 1874

page_text: LETTERS PATENT to Vaughan Pendred, of Crohill House, Angles Road,
Streatham, in the County of Surrey, Engineer, for the Invention
of "IMPROVEMENTS IN THE CONSTRUCTION OF BOILERS FOR GENERATING
STEAM."
Scaled the 4th August 1874, and dated the 10th February 1874.
COMPLETE SPECIFICATION filed by the said Vaughan Pendred at the
Office of the Commissioners of Patents, with his Petition and
Declaration, on the 10th February 1874, pursuant to the 9th
Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, VAUGHAN
PENDRED, of Crohill House, Angles Road, Streatham, in the County of
Surrey, Engineer, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS IN
THE CONSTRUCTION OF BOILERS FOR GENERATING STEAM," and have petitioned
Her Majesty to grant unto me, my executors, administrators, and
assigns, Her Royal Letters Patent for the same, and have made solemn
Declaration that I am the first and true Inventor thereof.

page_text: NOW KNOW YE, that I, the said Vaughan Pendred, do hereby
declare that the following Complete Specification, under my hand and
seal, fully describes and ascertains the nature of the said Invention and
in what manner the same is to be performed, in and by the following
statement, that is to say :-
"
"
This Invention refers firstly to that class of steam generators fitted
with tubes containing water to be evaporated, the tubes being disposed
horizontally or nearly so in an uptake. or tube chamber as described
in the Specification of a former Patent granted to me and dated 14
March 1871, No. 679; and secondly, to that class of boilers commonly
known as "sectional boilers" in which the steam is generated in water
tubes set horizontally or nearly so in a casing or oven, constructed by
preference of fire-brick although other materials may be used, in the
lower part of which the furnace is placed.
39
The present Invention consists in an improved method of securing the
circulation of water and steam in horizontal water tubes, which I
effect by placing within each tube a "helical diaphragm or twisted
plate of metal made by taking a strip of thin metal as wide as the
diameter of the tube in which it is to be inserted, and by preference a
little longer than the tube; this plate is twisted round transversely so
as to make a long screw of half a turn so that the under surface of the
plate or diaphragm at one end of the tube is the upper surface at the
other end. Into each tube one of these helical diaphragms is to be
inserted in such a way that an untwisted portion is left at each end,
which shall be horizontal and project a short distance beyond the mouth
of the tube at each end. In this case I generally dispense with the
nozzles or aprons described in the Patent herein-before referred to.
Sometimes, however, I apply them so that they are directed upwards or
downwards at both ends of the tube, and instead of covering the whole
tube they only cover one-half or that portion above the diaphragm.
But I do not claim the use of aprons in this way except in combination
with the helical diaphragms herein-before described.
As regards sectional boilers and boilers with only one end of the
horizontal water tube open, I arrange the helical diaphragm somewhat
differently, that is to say, I give the plates only one quarter twist and the
diaphragm is made somewhat shorter than the tube, but it projects
slightly in front or at the open end. The back end of the diaphragm
stands vertical while the front end is horizontal.

page_text: The action of these diaphragms is as follows:-Water enters the tube
from each end in the cross tube boiler, and being heated tends to rise in
obedience to a well-konwn law, but this it can only do by following the
direction of the screw diaphragm. The water which enters at the lower
portion of each tube at each end under the diaphragm is directed by the
screw as it rises, and is delivered at the upper portion of the tube or over
the diaphragm at the opposite end of the tube, and these two currents of
steam and water constantly traverse cach tube in opposite directions
without mixing or interfering with each other.
In the case of sectional boilers with tubes having one end closed the
water enters the lower part of the tube below the screwed diaphragm,
and rising along it it passing to the back end, here the steam which
has been formed and the heated water together pass to the opposite side
of the diaphragm, and once more following the direction of the screw
are delivered above the diaphragm, and these two opposite currents
traverse the tube without mutual interference.
In order that my Invention may be more fully understood, I will
proceed to describe the same by aid of the accompanying Sheet of
Drawings, reference being had to the Figs. and letters marked thereon.
Fig. 1 is a section of the improved water tube detached from the
boiler containing one of the helical diaphragms, the arrows shewing
the course of the two opposite currents. It will be understood that
the water flows in at one end of the tube beneath the diaphragm and
escapes with the steam at the other end of the tube above the diaphragm,
and as the same action takes place at both ends of the tube two currents
constantly pass through the tube in opposite directions and are kept
apart by the diaphragm, the heated water and steam always tending to
rise from the lowest to the highest portion of the tube, which they
accomplish by sweeping round and along the helical diaphragm from a
lower to a higher position of the tube.
Figs. 2 & 3 shew a diaphragm fitted to a tube closed at one end where
it will be seen that the diaphragm has only a quarter twist, the arrows
shewing the direction of the current as herein-before described.
The diaphragms may be secured in the tubes in any convenient way,
as for example, in the way set forth in Figs. 4 & 5. Here a flat strip of
metal A is rivetted or bolted to the projecting ends of the diaphragms,
and so prevents them from moving in the tubes. These strips of metal.

page_text: may with advantage be curved in some portion of their length, and
carried in an inclined position accross the tube plate as shewn, so as to
keep the currents flowing into and out of the tubes distinct, and thus to
lead the currents of steam and water in different directions, as shewn by
the arrows in Fig. 6.
Fig. 7 shews a section of a boiler constructed as described in my
former Specification except that the "nozzles" or aprons are omitted,
the circulation being secured by helical diaphragms as shewn, A being a
diaphragm in the tube B. In constructing such boilers I prefer, instead
of making the top removable at an angle iron or other ring joint as has
been my practice hitherto, to construct the boiler substantially as shewn.
The upper portion of boiler C remains unmoved when the boiler is
opened, but that portion marked D, D, can be dropped down by breaking
the joints E, F, and thus complete access may be had to the tube
chamber for cleaning or repair, without disturbing the steam pipes or
fittings on the upper portion. The ring or part D, D, can be raised and
lowered by the use of light tackle or blocks hooked on to the eye
bolts G, G, G, G, but any other means may be adopted for raising and
lowering the ring which will secure the same object. The joints are
made in any way recognised as sufficient in the ordinary practice of
engineering.
"
Figs. 8 & 9 shew a
" sectional boiler constructed according to this
Invention; A, A, are two flat sided stayed chambers united by water
tubes B, B, in each of which is fitted a helix C. This helix I sometimes
utilize as a stay by rivetting to each end of the helix the end of a short
screwed bar which passes through a lid or cover fitted opposite the ends of
each tube in the outer plate of the boiler, as shewn in the Figs. 8 & 10.
By preference I make the nuts T, T, bear on an elastic washer, such
as Pagets' Patent washer. R, R, shews the brick oven or chamber in
which the tubes are enclosed, the grate being at S and the escape flues
at Y, but I do not claim this construction or any special construction of
oven as my Invention.
Another modification is shewn in Figs. 11 & 12. Here the water
tubes B, B, instead of being fixed in flat stayed chambers, as shewn
in Fig. 8, are fixed in circular chambers A, A. These chambers are
connected by necks V, V, and are fitted at the outer ends with dished
plates secured by bolts and nuts. By removing these dished plates or

page_text: lids access is had to the tubes. The flame passes up round the outsides
of the tubes in a way which will be readily understood. The currents
of steam and water, the first rising, the second descending, are kept
distinct by the curved diaphragm X, Fig. 11.
Having now described and ascertained the nature of my said Inven-
tion and the manner of carrying the same into effect, I would observe
that what I consider to be new and original, and therefore claim is,—
Firstly. The use of helical diaphragms or twisted plates for producing
circulation in water tube steam generators, substantially as herein set
forth and described.
Secondly. The arrangement of the outer shell of a boiler in com-
bination with cross tubes containing twisted diaphragms, substantially
as herein set forth and described.
In witness whereof, I, the said Vaughan Pendred, have hereunto
set my hand and seal, this Tenth day of February, in the year
of our Lord One thousand eight hundred and seventy-four.
V. PENDRED. (L.S.)