Improvements in or pertaining to Steam Boiler and other Furnaces.
Year: 1894

page_text: Date of Application, 7th Apr., 1894
Complete Specification Left, 7th Jan., 1895-Accepted, 9th Feb., 1895
PROVISIONAL SPECIFICATION.
Improvements in or pertaining to Steam Boiler and other
Furnaces.
I, WILLIAM MUSGRAVE, of the Globe Iron Works, Bolton, in the County of
Lancaster, Engineer, do hereby declare the nature of this invention to be as
follows:-
According to this invention in order to prevent or reduce the flow of cold air
beyond the fire-bridge of a boiler or other furnace whilst the furnace door or doors
is or are open (as for example when firing or cleaning out) the opening of the said
door or doors more or less is made to cause through suitable connecting means the
partial or complete closing of a suitable valve or damper or valves or dampers so
arranged as to arrest or reduce the flow of air from the space above the burning
fuel to the space behind the bridge.
This may be effected in various ways. In one arrangement the valve or damper
is a plate located behind the fire-bridge and fixed upon a short shaft upon which
is also fixed a toothed wheel or part wheel in gear with a toothed segment fixed
upon a shaft that extends under the fire grate to the front of the furnace where
it is connected with the fire door through bevel gearing, the arrangement being
such that when the fire door is opened the valve or damper will be caused to turn
upward in its own plane and close, or nearly so, the opening over the fire-bridge,
and when the door is closed the valve or damper will be caused to move from
opposite the said opening over the fire-bridge. The toothed wheel or part wheel
and segment is or may be enclosed in a metal box or holder that serves to protect
them to some extent from heat and dirt as well as to carry the fire bricks formning
the fire bridge.
In a modified construction the damper consists of two plates fixed upon two
parallel shafts geared together and one of which is provided with a toothed segment
in gear with the segment fixed on the operating shaft as in the previously described
arrangement.
In another arrangement the damper is mounted to turn in its own plane between
the fire-bridge and a box which encloses the toothed wheel or part wheel and
segment and is or may be protected at the top by refractory material forming an
extension of the fire-bridge.
In another arrangement the damper, in the form of a plate, is fixed to a lever
which is carried by a shaft mounted in bearings behind the fire-bridge and has
connected to it a chain or other flexible connection that is led over suitably arranged
guide rollers to the front of the furnace when it is passed round a chain wheel or
pulley fixed to the hinge pin of the fire door so that when the door is opened the
chain or connection will be operated and the valve or damper turned upward so as
to close the passage above the fire-bridge more or less according to the extent to
which the door is opened, the valve or damper falling into its inoperative position
by gravity when the door is closed. In one such arrangement the valve or damper
is arranged to fall upon a horizontal plate supported by an extension of the fire-
bridge and carrying at its lower side bearings for the shaft carrying the lever to
which the valve or damper is connected. In another arrangement the lever is
pivotted to the underside of the top of a box which carries the brickwork forming
the bridge and also serves to limit the opening movement of the valve or damper.

page_text: When there is more than one fire door to the furnace, each door may be similarly
connected to the lever carrying the valve or damper.
In a further arrangement suitable for a Lancashire or similar boiler, the damper
or each damper consists of a circular plate of refractory material fixed upon a
horizontal spindle arranged at right angles to the furnace Hue at the rear end
thereof and connected through suitable mechanism with the furnace door, the
arrangement being such that when the damper is in its inoperative position, it
occupies a horizontal position so as to offer very little obstruction to the hot gases
flowing through the flue and when moved into its fully operative position it will
close the rear end of the flue or nearly so.
In a still further arrangement, the damper, consisting of a plate of refractory
material, is fixed upon a vertical spindle extending through the fire-bridge and
mounted in suitable bearings so as to turn about a vertical axis, the said spindle
leing connected with the fire door through suitable connections, as for example
by an endless chain or wire passing around a pulley fixed to the spindle and around
a pulley fixed to an extension of the hinge pin of the fire door, so that when the
door is closed the damper will be caused to assume a position in line with the axis
of the furnace flue, and when the door is opened it will be caused to assume a
position at right angles to the flue and more or less close the same.
The valve or damper may in some cases be arranged to slide instead of to turn
about a centre and be made in separate sections. It may also. be made hollow to
admit of the passage therethrough of a cooling medium such as air.
Also instead
of being arranged at or near the fire-bridge, or the end of the furnace flue, it may
be arranged in the uptake or chimney of the furnace, in which case it could be in
the form of a common butterfly valve.
In connection with each valve or damper there may be provided a device such as
a mercurial balance or cataract cylinder adapted to delay the opening of the valve
or damper until after the fire door has been closed for a predetermined time.
When using a mercurial balance the arrangement may be such that upon opening
the fire door the mercurial balance will be disturbed and the valve or damper held
by a catch until the normal position of the mercury is again reached, when the
catch will be released and the valve or damper allowed to move into its open
position.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
Improvements in or pertaining to Steam Boiler and other
Furnaces.
I, WILLIAM MUSGRAVE, of the Globe Iron Works, Bolton, in the County of
Lancaster, 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 :-
According to this invention in order to prevent or reduce the flow of cold air
beyond the fire-bridge of a boiler or other furnace whilst the furnace door or
doors is or are open (as for example when firing or cleaning out), the opening of
the said door or doors more or less is made to cause, through suitable connecting
means, the partial or complete closing of a suitable valve or damper or valves or
dampers so arranged as to arrest or reduce the flow of air from the space above
the burning fuel to the space behind the bridge.
This may be effected in various ways as I will now proceed to describe by the

page_text: aid of the accompanying drawings which show the best ways now known to me of
carrying my invention into practical effect. In these drawings,
Fig. 1 is a longitudinal vertical section and Fig. 2 a front view, showing one
arrangement of apparatus according to this invention, as applied to a boiler that
may be of the Lancashire or Cornish type.
In this arrangement the valve or damper 1 (hereinafter called a damper) consists
of a plate of refractory material such as iron or steel located behind the fire-
bridge 2 and fixed upon a short shaft 3 upon which is also fixed a chain wheel 4
connected by a chain 5 with another chain wheel 6 fixed upon a shaft 7 that extends
under the fire grate 8 to the front of the furnace where it is provided with a bevel
wheel 9 in gear with a bevel wheel 10 fixed on the lower end of the hinge pin or
spindle 11 fixed to the fire door 12. The two bevel wheels are so proportioned,
and the arrangement as will be seen is such that when the fire door 12 is moved
into its full open position, the damper 1 will be turned upward in its own plane
so as to close, or nearly so, the opening 2ª over the fire-bridge 2, and when the
door is closed the damper I will be caused to move from opposite the said
opening and leave the same full open. 13 is a metal box or support that serves
to carry the shaft 3 and protect the same and the chain gearing to some extent
from heat and dirt as well as to carry the fire-bricks forming the fire-bridge 2.
In some cases I provide the ash pit 14 with a damper 15 to prevent cold air
from rushing up the ashpit when the furnace door is open. The ash pit damper is
arranged to close when the furnace door opens and vice versa. In the arrangement
now being described, the ash pit damper 15 is shown as a plate provided with
lugs 15 by which it is fixed to a shaft 16 mounted in bearings 17 attached to
the sides of the ash pit. To one end of the said shaft is secured a bevel
segment 18 gearing into the bevel wheel 9 on the shaft 7. Thus, as will be seen,
the arrangement is such that when the furnace door 12 is opened both the flue and
the ash pit dampers 1 and 15 will be automatically closed and they will be opened
again when the furnace door is closed. 19 is a weight secured to the ash pit
damper 15 for the purpose of balancing the damper 1; such a balance weight may
be secured in any other suitable position, e.g. on the shaft 3.
Figs. 3 and 4 are similar views to Figs. 1 and 2 illustrating another arrangement
in which the damper 1, also in the form of a plate of refractory material, is carried
by a lever arm 1ª fixed to a shaft 3 which is mounted in bearings at the underside
of the top of the box or support 13 and has fixed upon it a lever arm 1 in the form
of a segment of a pulley. This lever arm 1 has connected to it a chain or other
flexible connection 5ª that is led over a suitably arranged guide pulley 20 and is
cornected by a rod 7ª to a chain 9ª located at the front of the furnace and which
passes round a chain wheel 10 fixed to the spindle 11 of the fire door 12, so that
when the door is opened, the damper 1 will be turned upward into the position
shown and close the passage 2ª above the fire-bridge more or less according to the
extent to which the door is opened the damper falling into its inoperative position
by gravity when the door is closed. The wheel 18 on the shaft 16 of the ash pit
damper 15 is in this case made as a chain wheel arranged to be actuated by the
chain 9 as shown.
Figs. 5, 6 and 7 illustrate another arrangement as applied to a Lancashire boiler,
Fig. 5 being a vertical longitudinal section, Fig. 6 a horizontal section, and Fig. 7 a
front elevation.
Fig. 8 is a longitudinal section showing this arrangement applied to a marine
boiler.
In this arrangement, the damper 1, which consists of a plate of refractory
material such as fire clay or asbestos, or, it may be, of iron, steel, or any other
suitable substance capable of withstanding intense heat is fixed upon a vertical
spindle 3 extending through the fire-bridge 2 and mounted so as to turn about a
vertical axis, in a suitable bearing 13 cast with or bolted to the metal support 13
of the fire-bridge, the said spindle being geared by bevel wheels 4 and 6ª to a
shaft 7 through which and bevel wheels 9 and 10, it is connected to the fire door 12

page_text: as in the arrangement shown in Figs. 1 and 2, so that when the door 12 is closed,
the damper 1 will be caused to assume a position along or parallel to the axis of
the furnace flue, and when the door is opened the damper will be caused to assume
a position at right angles to the flue and more or less close the same. The spindle 3
may advantageously consist of a cast iron tube through which and a corresponding
hole in the damper 1 a current of comparatively cold air will flow, when the ash pit
is open, for the purpose of keeping it cool. At its lower end the spindle may be
provided with a hardened point, as shown, bearing upon a hardened footstep 21 so
as to reduce friction and permit the spindle and damper to be easily turned. The
ash pit is shown provided with a damper 15 arranged to be operated as in the
arrangement shown in Figs. 1 and 2.
Figs. 9 and 10 illustrate the application of this arrangement to an externally fired
boiler of which Fig. 9 is a longitudinal section and Fig. 10 a cross section. In the
example shown, the boiler is of the elephant type, 22 being the upper steam and
water drum and 23 two lower water vessels connected therewith by inclined tubes 24.
The damper 1 of the right hand furnace flue is shown open in Fig. 10 and that of the
left hand flue is shown closed. The spindles of the fire door and the damper are in
this case connected by a rod 7° the ends of which are jointed to lever arms 25 and 26
secured on the spindle 3 and 11 respectively.
Fig. 11 is a part longitudinal section of a Lancashire boiler provided with
another arrangement in which the damper 1 consists of a circular plate of
refractory material fixed upon a vertical spindle 3 arranged at the rear end of the
furnace flue 27, and connected with an upward extension of the fire-door spindle 11
by bevel wheels 4ª & 6ª, a shaft 7 that runs along the top of the boiler-setting and
bevel wheels 9 & 10, the arrangement being such that when the damper is
automatically moved into its inoperative position by the closing of the fire-door 12
it occupies a position that is longitudinal as regards the furnace flue 27 so as to offer
very little obstruction to the hot gases flowing through the flue, and when moved
into its fully operative position by the opening of the fire door, it will close the rear
end of the flue, or nearly so. The ash-pit damper 15 in this case is actuated through
the toothed segment 18 which is in gear with a bevel wheel 10" on the lower end of
the fire-door spindle 11.
In cases where there is more than one fire door to the furnace, each door may
be connected to the shaft or spindle carrying the damper for the purpose herein
described.
The valve or damper instead of being arranged at or near the fire-bridge, or the
end of the furnace flue, as herein described and shown in the drawings annexed,
may be arranged in the uptake or chimney of the furnace, in which case it
could be in the form of a common butterfly valve. As will be obvious my invention
can be applied in connection with furnaces of steam generators of various types
besides those shown, and also to various types of furnaces other than steam boil r
turnaces.
As will be readily understood by my invention I prevent an abnormal amount
of cold air rushing through the furnace flue when the fire door is opened for the
purpose of throwing on fuel and thus I prevent to a very large extent the alternate
heating and cooling of the flue plates which usually takes place in working boilers
of ordinary construction and which, as is well known, has a very serious effect
upon the life of the boiler. Furthermore when clearing the fire, cold air is
prevented from entering the furnace flue and cooling the boiler, to such an
extent as to cause a rapid fall in the steam pressure therein, as heretofore usual,
consequently by my invention I greatly increase the efficiency of the boiler as a
steam generator.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A steam boiler or other furnace in which the opening of the fire door or doors.

page_text: more or less, is made to cause through suitable connecting means, the partial or
complete closing of a valve or damper or valves or dampers so arranged in the
furnace flue or passage beyond the fire as to arrest or reduce the flow of air from
the space above the burning fuel to the space beyond the fire bridge for the
purposes herein set forth.
2. In a steam boiler or other furnace, the combination with the fire door or
doors of the furnace, of a valve or damper adapted to arrest or reduce the flow of
air and hot gas through the furnace flue or passage at a point beyond the furnace,
and means connecting the said valve or damper with the fire door or doors in such
a way that the valve or damper will be moved into its closed or partly closed
attitude when the door or either door is opened, and will be moved into its open
position when the door or either door is closed, substantially as herein described for
the purpose specified.
3. In a steam boiler or other furnace, a valve or damper carried by or arranged
in proximity to the fire-bridge of the furnace and capable, when moved into its
closed position, of preventing or reducing the flow of cold air through the opening
above the said fire-bridge, and mechanism connecting the said valve or damper with
the fire door of the furnace in such a way that the valve or damper will be closed
when the fire door is opened, and opened when the fire door is closed, substantially
as herein described for the purpose specified.
4. For controlling the flow of cold air through a steam boiler or other furnace on
the opening of the fire-door thereof, apparatus constructed arranged and operating
substantially as hereinbefore described with reference to and shown in the several
examples illustrated in the drawings annexed, whether or not an ash-pit damper
such as 15 be used.
Dated this 7th day of January 1895.
WILLIAM MUSGRAVE.
W. Lloyd Wise,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.