IMPROVEMENTS IN APPARATUS BY MEANS OF WHICH AIR IS HEATED BEFORE IT IS ADMITTED INTO A FURNACE AS DRAFT
Year: 1876

page_text: LETTERS PATENT to Charles Thonger, of the Village of Courtright, in the
County of Lambton, and Province of Ontario, Canada, Miller, for the Invention
of "IMPROVEMENTS IN APPARATUS BY MEANS OF WHICH AIR IS HEATED BEFORE
IT IS ADMITTED INTO A FURNACE AS DRAFT."
Sealed the 2nd June 1876, and dated the 12th April 1876.
COMPLETE SPECIFICATION filed by the said Charles Thonger at the Office of
the Commissioners of Patents on the 12th April 1870.
CHARLES THONGER, of the Village of Courtright, in the County of Lambton, and
Province of Ontario, Canada, Miller. "IMPROVEMENTS IN APPARATUS BY MEANS
OF WHICH AIR IS HEATED BEFORE IT IS ADMITTED INTO A FURNACE AS DRAFT."
The object of my Invention is to utilise the heat in the smoke escaping from the
boiler and of that in the exhaust steam for the purpose of warming the air previous
to its being admitted into the furnace as draft. The said object I attain by con-
ducting the smoke through tubes arranged in a casing, into which the cold air is
conducted, and circulates around the said tubes previous to passing through into the
furnace as hereafter more fully described.
In the Drawings-On Fig. 1 is a cross section of boiler and heater in brickwork;
on Fig. 2 is a longitudinal section of the same; on Fig. 3 is a sectional plan of the
same.
Fig. 4 shews my Invention as applied to a steamboat; and Fig. 5 shews the
same as applied to a locomotive.
The accompanying Drawings are merely intended as suggestions, shewing how
my heater can be applied.
I wish it to be distinctly understood that I have no intention of confining
myself exactly to the plans shewn, as there are various ways of arranging and
carrying out my Invention. These arrangements I consider merely mechanical,
which can be altered from time to time to suit the taste of the engineer who may
adopt my Invention.
Figs. 1, 2, and 3, illustrate my Invention as applied to a return flue boiler. A is
the fire-box, the smoke passes from it under the boiler into the chamber B, back
through the tubes into the chamber C from which it escapes through the tubes D,
and from thence by the chamber E out through the chimney, as will be noticed in
Fig. 3. Through the aperture F cold air is admitted, which circulates around the
[Price 6d.]

page_text: tubes D, becomes heated, finally passing down through the channel G constituting
the draft for the furnace A.
By reference to Fig. 1 it will be noticed that the grate does not extend entirely
across the fire-box, but that the fire is boxed in, leaving an open space on each side
of the grate; immediately over these spaces are placed the guards H. By this
arrangement the draft as it enters the ash-pit passes up through the grate bars, and
also through the spaces on each side of same, the guards H direct the draft passing
through the latter down upon the fire, thereby greatly assisting combustion. Should
it be found advisable the air on entering the heater J might be made to pass
through it in a zig-zag manner by partitions suitably arranged, and also should it be
found that the draft was not quick enough a fan might be used with advantage for
the purpose of forcing a draft.
Fig. 4 shews how my "draft heater" can be applied to a marine boiler. The cold
air is in this case being brought down from the deck in the same manner as though
it were about to be used for ventilating, but is conducted instead into the heater,
and from thence into the ash-pit. The only difference in this application is the
position and general arrangement of the heater, the principle of conducting cold air
through a chamber heated by the smoke passing through tubes arranged in the said
chamber for the purpose of warming the draft being in every case the only point to
be attained. A here represents the furnace, and the letters B, C, D, and E, represent
the course of the smoke, the letter D representing the tubes of the "draft heater."
The smoke from each furnace is kept separate by partitions; F is a flue common to
all the furnaces, and leads to the foot of the smoke stack H; K is a casing which
extends round and encloses the smoke stack, leaving a space between the two. The
upper part of the casing is enlarged, and one half of it being removed makes a
hood, through the opening of which the cold air for the furnace draft enters, passing
down through the passage I which is extending the whole length of the boilers fore
and aft; from this passage it finds its way down to the chamber L, and from thence
following the direction of the arrows circulates among the "heater" tubes, and by
the passage G finds its way to the ash-pit. The tubes represented in section in the
chamber L are intended to conduct the exhaust steam on its way from the cylinders
of the engine to the condenser, the current of air passing over these tubes will
absorb a portion of the heat of the exhaust steam. Owing to the fact that in this
case the cold air enters at a point much above the furnace the natural draft
produced by the chimney may not be sufficient, this draft is however increased by
the motion of the vessel, which forces the air into the hood and down the passage
referred to, and to still further improve the draft a horizontal fan might be intro-
duced in the foot of the smoke stack, which fan could be driven from the engines,
and when at rest would offer little obstruction to the draft. By a proper application
of dampers each furnace and its proper tubes and flues can be isolated from the
general system for the purpose of cleaning, &c., and by opening the door in the hot
draft casing opposite the ash-pit would be entirely independent of the hot draft.
Fig. 5 illustrates my Invention as applied to a locomotive, and as the application
is rather.peculiar a slight description of it may be advisable. The smoke passes
through tubes into the smoke box A as usual, but returns over the boiler through
the tubes B into the chamber. C and from thence out. The air enters into the
chamber E as indicated by arrows, circulates around the chamber where the tubes D
are arranged, becomes thoroughly warmed as may be understood, and is finally
conducted through the pipes G into the ash-pan, constituting the draft for the
furnace. By this arrangement it becomes necessary to carry the exhaust steam
through the tubes b.
I have not mentioned it but it is of course understood that dampers are applied
in suitable positions for the purpose of regulating the draft, and also in the
applications illustrated on Fig. 1.
It may sometimes be advisable to exhaust through the tubes in order to increase
the draft as when applied to a locomotive.
In the first part of this Specification I refer to using the exhaust steam for the

page_text: purpose of heating the draft; this may be done either by exhausting through the
tubes D with or without the smoke, or through tubes in a separate chamber
similar to J.
I claim as my Invention,-
Causing the air before being admitted into the furnace A to pass through a
chamber J heated by the smoke or exhaust steam for the purpose of producing a
warm draft for the said furnace, substantially as described and for the purpose
specified.
The furnace A of a steam boiler in combination with a chamber J or its equi-
valent heated by the gases produced by combustion within the said furnace,
substantially as described.
The aperture F leading to the chamber J in combination with the channel G
leading to the ash-pit of the furnace A, substantially as and for the purpose
specified.
In witness whereof, I, the said Charles Thonger, have hereunto set my hand
and seal, the Twentieth day of February, in the year of our Lord One
thousand eight hundred and seventy-six.
CHA. THONGER. (L.S.)