and other Furnaces.
Year: 1885

page_text: and other Furnaces.
I JOHN ALEXANDER MACMEIKAN of The Gables, Great Missenden in the county
of Buckingham Barrister at Law do hereby declare the nature of my invention
for "IMPROVEMENTS IN THE MEANS OF REGULATING THE DRAUGHT. IN BOILER AND
OTHER FURNACES to be as follows:-
"3
This invention relates to improvements in the means of regulating the draught in
boiler and other furnaces, and consists of the arrangement of an apparatus by which,
(1) The apertures over the bridge at the back end of the furnace may be increased
or diminished at will, from the front of the boiler, according to the nature of coal
used and the work to be performed by the boiler. (2) The opening may be not
only regulated but also closed entirely or in part at will from the front of the
boiler. (3) The opening may not only be regulated but also automatically
closed entirely or in part by the opening of the door of the furnace.
The object being-(1) To enable the aperture over the bridge to be reduced as
much as possible, consistently with a good draught being obtained in order to
secure the combination of the gases, generated in the furnace at the highest
temperature.-(2) To enable the aperture over the bridge to be closed entirely or
in part either at will or automatically, in order to prevent the rush of cold air
through the flues when the furnace door is opened for firing or cleaning.
My apparatus consists of the following parts:-A bridge plate fixed across the
furnace tube at the back end of the furnace, upon which a fire brick bridge may be
constructed; A diaphragm plate placed across the furnace tube, and so adjusted
with reference to the bridge plate as to form a hinge for the movable bridge. The
movable bridge fits and works closely on the upper edge of this plate, and may be
protected with a fire brick covering. Its lower extremity projects downwards into
the ash pit and acts as a counterpoise to the upper part.-To the forward extremity
is attached a chain, which may pass over a pulley fixed to the diaphragm plate, or
in suitable position, and extend to the front of the boiler, where it may be either
operated and secured at will by the stoker, or be fixed to a suitably formed arm, on
the furnace door, in order to be automatically actuated by the opening of the door.
The chain is provided with a shackle, by means of which the height of the bridge

page_text: can be adjusted.—The arm on the fire door is constructed with holes for the adjust-
ment of the travel of the chain, to correspond with the normal position of the bridge
as required. In some cases a slight modification of the above described arrangement
would be necessary, such as the substitution of a rod for the whole or part of the
chain or a slightly different arrangement of the diaphragm plate.
Improvements in the Means of Regulating the Draught in Boiler
and other Furnaces.
I JOHN ALEXANDER MACMEIKAN of The Gables Great Missenden in the county
of Buckingham Barrister-at-Law, 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 improvements in the means of regulating the draught in
boiler and other furnaces, and consists of the arrangement of an apparatus by which
(1.) The aperture over the bridge at the back end of the furnace may be increased
or diminished at will from the front of the boiler, according to the nature of coal
used and the work to be performed by the boiler. (2.) The opening may be not
only regulated, but also closed entirely or in part at will manually from the front
of the boiler. (3.) The opening may not only be regulated but also automatically
closed entirely or in part by the opening of the door of the furnace.
The object being :-(1.) To enable the aperture over the bridge to be reduced as
much as possible consistently with a good draught being obtained in order to
secure the combination of the gases generated in the furnace at the highest
tensperature and to present an advantageous section so as to bring the heat into
contact with a larger surface of the furnace tube. (2.) To enable the aperture over
the bridge to be closed entirely or in part, either at will, manually, or automatically,
in order to prevent the rush of cold air through the flues when the furnace door is
opened for firing or cleaning.
The accompanying drawings clearly illustrate my invention. Figure 1, is a
longitudinal section, showing also attachments to furnace door. Figure 2, a part
sectional plan. Figure 3, a cross section on line a, b, figure 1. Figure 4, a part
plan view of furnace door showing attachments for arrangement shown in figure 1.
Figure 5, is a longitudinal section of alternative arrangements. Figure 6, is a part
plan view of furnace door showing attachments for arrangement shown in Figuro 5.

page_text: Figure 7, is a part longitudinal section of apparatus applied to a marine boiler,
Similar letters indicate similar parts in all of these figures.
.00
The apparatus consists of the following parts:-A, is a fixed bridge or diaphragm
plate as in figures 1, and 5, preferably forming the front side of a box placed across
the furnace tube and bricked in at the sides to keep it in position. This bridge
plate A, carries the usual brick bridge B, which is constructed of sufficient height
to afford suitable protection to a hinge hereinafter described. Behind the brick
bridge B, a movable plate C is arranged, either passing through a slot w in A, and
capable of movement upon one edge of the slot, or hinged upon a projection as at
figure 7, or otherwise suitably arranged capable of movement from about the
horizontal to an angle of about 45°. The lower part C, of the plate C projects
down as shown into the ashpit and acts as a counterpoise to the upper part. The
counterpoise C, may be either, (1.) constructed lighter than the upper part of the
door C, as shown in figures 1, 2, and 3, and a chain F, or equivalent connection
attached to it and passed round a pulley G, suitably fixed upon the lower part of
the bridge plate A, and carried to the front of the boiler, where it can be fixed, and
manipulated, and regulated by the attendant, according to the work required to be
done by the boiler; or (2.) the action may be reversed as shown in Figure 5, where
the counterpoise C¹, is made heavier than the upper part of the.movable plate C, so
that in its normal position it is raised and closed as shown in the figure. In this
case the pulley G, is not required and the chain or equivalent connection F, is
secured to the lower part C¹, of plate C, and carried direct to the front of the boiler
where it can be fixed and manipulated by the attendant as above described.
When it is desired that the action of the movable plate C shall be automatic instead
of manual, so that it shall be shut when the furnace door is open and thus prevent
a rush of cold air through the boiler flues, and open when the furnace door is shut,
the end of the chain F, is attached to an arm or lever a fitted to the lower
extremity of and also at right angles to a bar g, fixed upon the furnace door H,
and extending downwards. In Figures 1 and 2, where a pull on the connection F.
is required to close the plate C, as described, the arm a is at right angles to the
door H and projects towards the flue when the door is closed. Thus the opening
of the door H will exert a pull on F and raise C, closing the flue. In this case in
order to prevent the pull on the lever a shutting the door H, the back end of the
sneck h, may be extended and bent as shown in figures 1, 2, and 4, so that when
the door is open it will engage with a catch b, suitably fixed to the front of the
boiler; or in the second case, where, owing to the weight of the part C, a slackening
of the chain or connection F, is required to close the plate C as described, the arm a
at right angles to the door H projects away from the flue when the door is closed
as shown in figures 5 and 6. Thus when the door H is open the counterpoise C²,
being heavier raises the plate C, and the chain is slack; while the closing of the
door H exerts a pull on the chain F, raising the counterpoise and opening plate C,
thus dispensing with the necessity for the arrangement for holding the door H open.
It will thus be seen, by either of the above described alternative arrangements, the
action of the plate C, C¹, may be either regulated from the front of the boiler by
the attendant, or, by affixing the connection to the levers on the door, may be made
to act automatically and simultaneously with the opening and closing of the said
door H.
Another arrangement by which my invention may be applied to marine boilers,
and where from the position of the bridge the other arrangements hereinbefore
described are inapplicable, is shown in figure 7. A plate J is here fixed in the
combustion chamber and an aperture O is formed in it as shown, to allow any grit
or deposit to fall through and not interfere with the hinge x². The movable
plate C, shown in section constructed of a form to fit the mouth of the furnace tube,
is suitably hinged and capable of movement at and about x', and a rod or extension
of the plate C, is formed as shown at C. A chain or connection f is attached to C³,
and passes over a pulley G, and is provided with a counter balance weight K,
sufficiently heavy to give the plate C, a tendency to close up against the back end

page_text: of the furnace tube. The operating chain F is affixed to the lower extremity of C¹,
and passes to the front of the boiler, where it may be actuated by the method
secondly above described. The weight K, being heavier than C, the plate C will
remain as shown until the door is closed. The chain F, may be provided with a
shackle L, or suitable means for adjusting its length and the consequent travel of
plate C. The arm a is also provided with holes or a slot to adjust the travel of
the chain to correspond with the desired position of the plate C. The plate C, may
be constructed with ribs c, and provided with fireclay lining to prevent burning.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what
I claim is
1. In internally fired steam generators; the means of regulating the draught of
furnaces from the front of the furnace tube either manually or automatically by a
movable plate in combination with the means of adjustment, and counterpoise or
counterbalance weight all arranged substantially as and for the purposes set forth.
2. In internally fired steam generators; the regulating and opening, and closing
of the aperture over the bridge, either manually or automatically, simultaneously
with the closing and opening of the furnace door respectively by means of the
movable plate and means of adjustment in combination. with the arrangement of
levers fixed upon the furnace door the whole arranged substantially as and for the
purposes described and illustrated.
3. In a marine boiler the means of regulating the draught either manually or
automatically as described and claimed above by means of the movable plate of the
form shown, in combination with aperture O, chain F or its equivalent and counter-
poise or counterbalance K, all arranged substantially as and for the purposes set
forth and illustrated.
Dated this ninataanth