Improvements in Steam Boilers.
Year: 1890

page_text: Date of Application, 11th Nov., 1890
Complete Specification Left, 10th Aug., 1891-Accepted, 12th Sept., 1891
PROVISIONAL SPECIFICATION.
Improvements in Steam Boilers.
I THOMAS LEDWARD of No. 9 Pendrell Road, Brockley, in the County
of Kent, Engineer do hereby declare the nature of this invention to be as
follows:-
This invention relates to improved means for obtaining forced circulation in
steam boilers or generators, with the object of promoting the more rapid trans-
mission of heat through the plates which are exposed to the action of the
furnace and hot gases, and thereby preventing unequal expansion, cracking, and
leakage at the joints of the plates, and further tending to reduce the deposit of
scale on the plates by the strong scouring action of the induced and continuous
currents of water over them.
One part of my invention consists in attaching, inside and close to the outer
shell of any cylindrical boiler, whether with or without internal flues,-certain
sheet iron or other metal plates in such a manner that the said plates are kept
at a fixed distance of a few inches from the outer shell of the boiler, and form
a lining to the same, extending from near the bottom of the boiler to a point
either above or below the water line. The arrangement is such that the cooler
water in the boiler enters at the bottom between the liner and the outer shell
and becoming heated by the external heat on the sides of the boiler, rises
rapidly and issues at a high velocity from the opening or openings near the
water level. This causes a rapid circulation of the water over the heated plates
forming the outer shell of the boiler, and where the outlet is made below the
water line, this action commences as soon as heat is applied, that is as soon as
the furnace fires are lighted, so that the whole body of water in the boiler
becomes gradually and uniformly heated and the plates of the boiler equally
expanded.
Another part of my invention consists in attaching to the crown plates of the
flues, fireboxes, or combustion chambers of any class of boiler, whether marine,
stationary, or locomotive, certain tubes resembling the well-known "Field " tube,
but which may be made of any possible diameter and length. These tubes are
closed at the bottom, and pass through the plates of the boiler so as to be
exposed to the heat of the furnace gases. Inside the outer tube is an inner
one which I call the "supply-pipe," and this supply-pipe is connected by a
conduction-pipe to any part of the boiler from which it is desired to remove the
cold or stagnant water. The inner "supply-pipe" reaches nearly to the bottom
of the outer tube, and the latter is continued upwards to near the level of the
water in the boiler. It may end either above or below the water line, and is
preferably contracted at its opening to prevent the influx of water by any other
way than through the supply-pipe. The action of this circulating tube is as
follows: As soon as heat is applied to the outer tube the water in it naturally
rises and issues through the opening or openings at the top of the tube, and
fresh water flows in through the inner supply-pipe to take its place. As this
supply-pipe is connected to some distant part of the boiler not exposed to heat,
it follows that the cooler water from this part becomes gradually removed, and
the warmer water which has issued from the mouth of the circulating tube
gradually takes its place. I employ any number of these circulating tubes and
any number of conduction-pipes, so that the whole body of water may become
gradually heated and unequal expansion of the plates prevented.
In one improved form of horizontal cylindrical boiler without internal flues I
combine these two methods in such a manner that the boiler is fitted with the

page_text: internal lining already described, and has also at the bottom, one or more rows
of the "circulating tubes" which project downwards vertically or at a slight
angle and receive the direct heat of the fire and hot gases.
In another improved form of horizontal cylindrical boiler with one or more
internal flues I combine one or both of the herein-before described circulating
apparatus with a
"saddle-circulator" which is placed over and almost surrounds
the flue or flues. This latter circulator is the invention of Mr. B. H. Thwaite
and is described and illustrated in his Specification No. 594 of 1888.
Since the powerful circulation produced by these various means tends to
prevent the solid matter from attaching itself to the plates, and keeps it more
or less in suspension in the water, I provide where desirable a separate "mud-
drum" beneath the boiler and not exposed to any direct heat, into which the
solid particles may subside, as the water is here comparatively quiescent. When
the mud and solid particles have collected here in sufficient quantity they may
be got rid of by opening a blow-off cock. By thus periodically blowing-off the
dirt and foreign matter contained in the water, the boiler may be kept com-
paratively free from incrustation, with great advantage to its evaporative power
and durability.
Dated this 12th day of November 1890.
THOMAS LEDWARD.
COMPLETE SPECIFICATION.
Improvements in Steam Boilers.
I, THOMAS LEDWARD of 9 Pendrell Road, Brockley in the County of Kent,
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 :-
This invention relates to improved means for obtaining forced circulation in
steam boilers or generators, with the following objects:-(1st) Promoting the
more rapid transmission of heat through the plates which are exposed to the
action of the furnace and hot gases; (2nd) Preventing unequal expansion,
cracking, and leakage at the joints of the plates; and (3rd) Retarding the
deposit of scale on the plates by the strong scouring action of continuous currents
of water over them.
One part of my invention consists in attaching,-inside and close to the outer
shell of any cylindrical boiler, whether with or without internal flues,-certain
sheet-iron or other metal plates in such a manner that the said plates are kept
at a fixed distance of a few inches from the outer shell of the boiler, and forin
a lining to the same extending from near the bottom of the boiler to a point
slightly above or below the water line. This is shewn in Fig. 1 of the accom-
panying drawings, in which B is the outer shell of the cylindrical boiler, and
Lis the sheet-iron lining so fixed as to direct the heated water upwards. D repre-
sents the point of discharge.
The arrangement is such that the cooler water in the boiler enters at the
bottom between the liner and the outer shell and becoming heated by the
external heat on the sides of the boiler, rises rapidly and issues at a high
velocity from the opening or openings near the water level, and so causes a
thorough circulation of the whole body of water in the boiler and equalizes the
temperature throughout.
Another part of my invention consists in attaching to the crown plates of
the flues, fireboxes, or combustion chambers of any class of boiler, whether
marine, stationary, or locomotive, certain "circulating tubes" which may be
made of any possible diameter and length, and which are closed at the bottom,
and pass through the plates of the boiler so as to be exposed to the heat of
The
the furnace gases; at the top they are in communication with the water.

page_text: outer tube contains an inner one which I call the supply pipe, and this supply-
pipe is connected to any part of the boiler from which it is desired to remove
the cold or stagnant water. The inner supply pipe reaches nearly to the bottom
of the outer tube, and the latter is continued upwards to a point slightly above
or below the water line and is preferably contracted at its opening to prevent
the influx of water by any other way than through the supply pipe. This
opening may be of any shape, round, square, or annular, and may be pointed
in any direction in which it is desired to throw the heated water.
This part of my invention is shewn in Fig. 2, in which T represents the
outer tube; S is the supply pipe which may be connected to any part of the
boiler below the water line, and D shews the point of discharge.
The action of this device is such that the water is drawn through the pipe S
from any desired point and forced out through D. I employ any number of
these circulating tubes and any number of supply and conduction tubes so that
equal circulation takes place over the whole boiler.
In one improved form of horizontal cylindrical boiler with or without internal
flues I combine these two methods in such a manner that the boiler is fitted
with the internal lining already described and has also at the bottom one or
more rows of the "circulating tubes" which project downwards vertically or at a
slight angle and receive the direct heat of the fire and hot gases. This combination
is illustrated in Fig. 3 of drawings, the same letters referring to the same parts as
in Figs. 1 and 2.
In another improved form of horizontal cylindrical boiler with one or more
internal flues I combine one or both of the herein-before described circulating
apparatus with a "saddle circulator" which is placed over and partially surrounds
the flue or flues.
In Fig. 4 are shewn my improvements in the construction and application of this
device; I construct the saddle circulators in sections of about one foot in length,
each section being complete in itself so that it may be placed over any part of the
flue and any number may be connected together.
Each section is constructed of three pieces, namely, two side pieces and one
central deflector, and the three are connected together by one long stud made fast
to the central deflector, and having nuts on each end to bind the side pieces in
position. The side pieces have flanges on each end curved to the radius of the flue
and forming a close waterway about twelve inches wide and two or three inches
deep between the sides of the flue and the saddles. I construct the parts preferably
of cast-iron, but wrought-iron or any suitable metal may be used. To secure the
best results I carry the saddles slightly above the water level so that the heated
water is discharged above this line as shewn.
In Fig. 4, L represents the flanged side pieces already mentioned, of which the
right and left hand pieces are alike and reversible, and F represents the central
deflector between the two. H is the long stud which is fastened to F as shewn and
which serves to bring the two side pieces L into close contact with F and secures
the parts rigidly together.
Since the powerful circulation produced by these various means tends to prevent
any solid matter from attaching itself to the plates and keeps it more or less in
suspension in the water, I provide where desirable a separate mud-drum beneath the
boiler and not exposed to any direct heat, into which the solid particles may subside,
as the water is here comparatively quiescent. This is shewn by M in Fig. 4.
When the mud and solid particles have collected here in sufficient quantity they
may be got rid of by opening the blow-off cock, and the boiler thus kept free from
incrustation.
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 arrangement as shewn in Fig. 1 of the accompanying drawings of a thin

page_text: metal liner L so fixed to the shell B of any steam generator or other fluid boiler as
to cause continuous currents to flow from the bottom of the boiler upwards in the
manner herein described and illustrated.
2.) In water tubes which project downwards from the crown of the furnace, flue,
or combustion chamber of any type of steam generator, the arrangement of a
separate supply-pipe as shewn at S in Fig. 2 of accompanying drawings, so con-
structed that it may be connected to any part of the boiler in order to draw the
water away from that part in the manner herein described and illustrated.
3.) The employment in connection with the supply pipe S, Fig. 2, of an outer
water tube T which has its orifice of discharge D contracted and carried above or
near the water line, to prevent the influx of water by other ways than through S,
as herein described and illustrated.
4.) In plain cylindrical boilers or in tubular boilers or in boilers with internal
flues the combination as shewn in Fig. 3 of a thin metal liner L, together with
circulating water tubes T and S for the purpose herein described.
5.) In the device known as a saddle circulator, for attachment to any internal
flue or flues, I claim the special construction of the saddles as herein before
described and illustrated in Fig. 4 of the accompanying drawings; and my claim is
for the employment in combination of two separate flanged side pieces L as shewn,
together with a separate deflector F, and the central stud-bolt H for locking the
whole together.
D15. 104.
1001