Improvements in Furnace Fittings for Use with Forced Draught.
Year: 1886

page_text: Date of Application, 9th June, 1886
Complete Left, 1st Mar., 1887.
Complete Accepted, 1st Apr., 1887.
Improvements in Furnace Fittings for Use with Forced Draught.
We, JOHN ALLISON of 2 Saint Georges Road, Leyton, in the County of Essex,
Engineer, and ADAM THOMSON of 26 Saint Georges Road, Leyton, in the County
of Essex, Engineer, do hereby declare the nature of this invention to be as
follows:-
Our invention relates to improvements in the fittings of furnaces in which a forced
draught is used and consists in an improved arrangement of furnace front by which
the forced draught is cut off automatically from access to the grato or furnace when
the fire door is opened, and at the same time the arrangement can be immediately
converted from the condition suitable for a forced draught to that suitable for a
natural draught.
To carry out our invention we lead the compressed air or forced draught from any
convenient source of supply through suitable pipes into the hollow furnace front.
Thence it passes through valve seats, preferably two in number, one on each side
of the door, and provided with flap valves, into the lower part of the furnace front,
whence it is free to escape by suitable orifices under or over the fire. The lower part
of the furnace or the ash-pit is closed, to prevent the forced draught from escaping
except through the fire, but the said cover of the ash pit is provided with a door,
which can be opened when desired to allow the natural draught access to the fire,
when the forced draught is shut off or absent.
The automatic cutting off of the forced draught when the door is opened is effected
as follows:
The aforesaid flap valves in the furnace front are provided with a projecting knob
under each valve, which projects into or through a suitable opening in the inner sides
of the furnace door opening.
To the front of the fire-door is fitted a handle turning on its axis, and provided
with two crank arms on opposite sides to one another, which, by means of two
connecting links, operate two sliding bolts. When these bolts are thrust outwards
by the rotation of the said handle, they press against the aforesaid projections on the
under sides of the said valves. The said valves are thus lifted from their seatings

page_text: and the forced draught is free to pass. When the sliding bolts are withdrawn, the
valves fall by their weight upon the seatings, which are inclined accordingly, and the
forced draught or compressed air is shut off from access to the fire or furnace.
The said bolt handle in the fire door is so set, weighted, or spring pressed, that
it naturally falls or moves into that position in which the bolts are withdrawn and the
valves consequently closed. The said bolt-handle is provided with a notch or catch,
or so constructed that when the usual hasp or latch of the fire door is latched, and
the door closed, the bolt handle is secured in position by the said hasp or latch,
so that the bolts are shot outwards and the valves raised.
It may be observed that the valves must be opened by a specific movement of
the bolt-handle, after the door is closed, and therefore the valves cannot inadvertently
be opened too soon.
Also the valves must close automatically, as or even before the door can be opened,
and by the very action that is necessary to open the fire door.
Thus automatic
and instantaneous cutting off of the forced draught is ensured.
When it is desired to cut off the forced draught from any individual furnace this may
be done very easily by leaving the bolt handle in the normal position in which
the bolts are withdrawn.
The valves are thus allowed to remain closed even when the door is shut, and
the forced draught is thus easily cut off without interference with any other furnace,
supplied from the same main.
The opening of the ash-pit door permits the access of the natural draught when
desired.

page_text: COMPLETE SPECIFICATION.
Improvements in Furnace Fittings for Use with Forced Draught.
We, JOHN ALLISON, of 2 Saint Georges Road, Leyton, in the County of Essex,
Engineer, and ADAM THOMSON, of 26 Saint Georges Road, Leyton, in the County
of Essex, 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:
Our invention relates to improvements in the fittings of furnaces in which a forced
draught is used, and consists in an improved arrangement of furnace front, by
which the forced draught is cut off automatically from access to the grate or furnace,
when the fire loor is opened; and at the same time the arrangement can be
immediately converted from the condition suitable for a forced draught, to that
suitable for a natural draught.
In order that our invention may be the better understood, we now proceed to
describe the same in relation to the drawings hereunto annexed, reference being had
to the letters and figures marked thereon.
Figure 1 is a front elevation of a boiler front, fitted with our improved doors,
showing different views and part sections in each flue respectively.
Figure 2 is a horizontal section through our improved door.
Figure 3 is a vertical section of same.
To carry out our invention we lead the compressed air or forced draught from
any convenient source of supply through suitable pipes A A A into the hollow
furnace fronts B B B. Thence the air passes through valve seats CC (seen in
the central sectional view, figure 1, and in the horizontal section, figure 2). These
are preferably two in number, one on each side of the door, and provided with flap
valves. The compressed air or forced draught thus passes into the lower part D of
the furnace front, whence it is free to escape by suitable orifices under or over the
fire. The lower part of the furnace or ash pit E is closed, to prevent the forced
draught from escaping except through the fire, but the said cover of the ash pit
is provided with a door F, seen in figures 1 and 3, which can be opened, when
desired, to allow the natural draught access to the fire when the forced draught
is shut off or absent.
The automatic cut off of the forced draught, when the fire door is opened, is effected
as follows:
The aforesaid flap valves C C in the furnace front are provided with a projecting
knob H H (figures 1 and 2) under each valve, which projects into or through a
suitable opening in the inner sides of the furnace door opening.
To the front of the fire door is fitted a handle K (figures I and 3) turning on its
axis, and provided with two crank arms L L on opposite sides to one another on the
axis as seen in the right hand furnace front, figure 1, in which the front plate of the
fire door has been removed, to show the construction of these crank arms. The said
crank arms are connected by links M M to two sliding bolts N N, seen best in

page_text: figure 2.
When these bolts are thrust outwards by the rotation of the said handle,
they press against the aforesaid projections H H on the under side of the said
valves C C. The said valves are thus lifted from their seatings, and the forced
draught is free to pass. When the sliding bolts N N are withdrawn by the reverse
action of the fire door handle K, the valves CC fall, by their weight, upon the
seatings, which are inclined accordingly, and the forced draught or compressed air
is thus shut off from access to the fire or furnace.
The said bolt handle K of the fire door is so set, weighted, or spring pressed, that
it naturally falls or moves into that position in which the bolts are withdrawn,
and the valves consequently closed. The said bolt handle K is provided with a notch
or catch k, or so constructed that when the usual hasp or latch P of the fire door
is latched, and the door closed, the bolt handle K is secured in position by the said
hasp or catch P, so that the bolts N N are shot outwards and the valves CC raised.
It may be observed that the valves CC must be opened by a specific movement
of the bolt handle K after the door is closed, and therefore the valves cannot
inadvertently be opened while the fire door is open.
Also the valves CC must close automatically as or even before the door G can
be opened, and by the very action that is necessary to open the said door. Thus
automatic and instantaneous cutting off of the forced draught is ensured.
When it is desired to cut off the forced draught from any individual furnace, this
may be done very easily by leaving the bolt handle K in the normal position to
which the bolt handle naturally falls, in which the bolts N N are withdrawn, and the
valve CC thereby closed. The valves may thus at any time remain closed, even
when the fire door G is shut, and the forced draught is thus easily cut off, without
interference with any other furnace supplied from the same main.
The opening of the ash pit door F permits the access of the natural draught
when desired.
Having now particularly described and ascertained the nature of our said invention
and in what manner the same is to be performed we declare that what we claim is :-
1st. The automatic shutting off of a forced draught to a furnace by the opening of
the fire door, substantially as described.
2nd. The combination with a fire door of a locking bolt and sliding locks, opening
valves, which permit acccess of a forced draught to the furnace when required, and
ensure automatic cut off of the said forced draught, upon the opening of the said
doors, substantially as described.
3rd. The construction of such a locking bolt with a T lever head, operating sliding
bolts by links, and weighted or spring pressed, so as to normally lie in the position
which permits the valves to automatically close, and provided with a notch or detent
by which the bolts are kept locked and the shut off valves open when the forced
draught is on, substantially as described.
Dated this 23rd day of February 1887.
FELL & WILDING,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicants.