IMPROVEMENTS IN APPARATUS FOR REGULATING THE SUPPLY OF AIR TO FURNACES
Year: 1880

page_text: LETTERS PATENT to Thomas Symes Prideaux, of 91, Cranfield Road, Brockley,
in the County of Kent, for an Invention of "IMPROVEMENTS IN APPARATUS
FOR REGULATING THE SUPPLY OF AIR TO FURNACES."
PROVISIONAL SPECIFICATION left by the said Thomas Symes Prideaux at
the Office of the Commissioners of Patents on the 11th March 1880.
THOMAS SYMES PRIDEAUX, of 91, Cranfield Road, Brockley, in the County of
Kent. "IMPROVEMENTS IN APPARATUS FOR REGULATING THE SUPPLY OF AIR TO
FURNACES."
This apparatus has for its object to afford furnaces, immediately after coaling, an
additional supply of air admitted above the fire-bars, which supply shall gradually
diminish and eventually cease after a certain definite period of time. To ensure the
attainment of this important object the action of the air valve which regulates this
supply is made automatic, the opening of the door (for a time sufficient to coal the
furnace) setting the valve wide open, and the shutting the door after coaling putting
in action the mechanism which gradually closes the valve in any period for which
this mechanism may be adjusted, and thus the adjustment of the air-supply to the
varying requirements of the fuel is not contingent upon the attention of the
fireman.
The apparatus consists of two parts:-
First. A furnace door, or furnace door and front combined, having an opening for
the admission of air, furnished with a cover or shutters by means of which the air
can be admitted or excluded at pleasure, and communicating with the interior of the
furnace through grating so arranged as to intercept & absorb the heat radiated
outwards-when-the air valve is closed, & to heat & distribute the stream of air
which flows through it into the furnace when the air valve is open.
Secondly. The mechanism which by its automatic action gradually closes the air
valve. This mechanism consists,―
First. Of a thin iron cylindrical cup or cistern having a tube about 1/2 an inch in
diameter, tapped into its bottom as piston rod. The bottom of this cup has on its
under side two very slightly elevated ridges, somewhat triangular in section,
forming two circles, the exterior just within the outer margin, the interior
surrounding the orifice of the tubular piston rod. The included space is pierced by

page_text: a series of orifices whose united area is about equal to 1 of its superficies. A
circular disc ground perfectly flat on its upper side is appended to the cup by 3
guides or pins in such a manner as to allow of its traversing freely & dropping
down through a limited space upon the cup being raised. These guides or pins
may be either passed through holes in the bottom of the cup & tapped into the
disc, or they may be fixed on the outer edge of the cup so as just to admit of the
easy passage of the disc within them. At a point opposite one of the holes in the
bottom of the cup the disc should be pierced with a small orifice.
Secondly. Of a cast iron cylinder of somewhat larger diameter than the cup, & of
such a depth as to permit the cup traversing within it the distance demanded to
give the required length of stroke, & having a small tube tapped into its bottom for
the passage of the connecting rod which is attached at its upper end to the top of
the cistern tube by a pin joint, & at its lower end through a link to the shutters or
lid of the airchamber in the same way. When the air valve is shut the cup rests
at the bottom of the cylinder with the charge of mercury (with which the apparatus
is worked within it, with the exception of the small portion occupying the
circumferential interstice between the cup & the cylinder. The opening of the
furnace door lifts the shutters or flap admitting air into the furnace door or air-
chamber, & simultaneously raises the cup to the top of the cylinder, the disc descends
& the mercury passes down into the cylinder in a time commensurate with the
depth of the drop & the aggregate area of the orifices. Upon the shutting of the
furnace door the cup becomes disengaged from the lifting mechanism & charged
with the weight of the shutters or lid appended to it descends & floats on the
mercury, which rises in the exterior of the cup to a height as much above the level
of the mercury in the interior as suffices to counterbalance the superincumbent
weight, whilst the higher level of the mercury in the exterior causes it to flow into
the cup through the small hole in the disc, & the cup to descend gradually in a time
determined by the size of the orifice, the quantity of the mercury, and the amount of
the pressure.
In some instances, particularly where the space is very confined between the top
of the furnace door & the bottom of the smoke box, the regulating cylinder cannot
conveniently be placed above the air valve. In such cases I modify the construction
of the cylinder so as to permit of its being placed on a level with the lid of the air-
valve instead of above. To obtain this result I connect the motion of the cup in the
cylinder with the motion of the air valve by the partial rotation of a horizontal
axle issuing from the cylinder on a level with its flanges. The principle & respective
mode of action of the cup, disc, & cylinder, are the same as before described, but
the details of construction are varied as follows:-There is no opening in the
bottom of the cylinder, nor any tube tapped into the cup, the piston rod, if such
it may be called, consisting simply of a small rod attached to the bottom of the
cup by a pin joint, & to an arm projecting at right angles from the horizontal
shaft in the same way; there being no opening in the bottom of the cup, the
interior circular ridge surrounding the orifice of the tubular piston rod becomes
superfluous.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Symes Prideaux in the Great Seal Patent Office on the 6th
September 1880.
THOMAS SYMES PRIDEAUX, of No. 91, Cranfield Road, Brockley, in the County of
Kent. "IMPROVEMENTS IN APPARATUS FOR REGULATING THE SUPPLY OF AIR
TO FURNACES."
This apparatus has for its object to afford furnaces immediately after coaling an
additional supply of air admitted above the fire bars, which supply shall gradually
diminish and eventually cease after a certain definite period of time. To insure the
attainment of this important object, the action of the air valve which regulates this
supply is made automatic, the opening of the door (for a time sufficient to coal the
furnace) setting the valve open, and the shutting the door after coaling putting in
action the mechanism, which gradually closes the valve in any period for which
this mechanism may be adjusted, and thus the adjustment of the air supply to the
varying requirements of the fuel is not contingent upon the attention of the
fireman.
The apparatus consists of two parts:-First, a furnace door or a furnace door
and front combined (a), having an opening for the admission of air furnished with
a cover (8) or shutters, by means of which the air can be admitted or excluded at
pleasure, and communicating with the interior of the furnace through grating, so
arranged as to intercept and absorb the heat radiated outwards when the air valve
is closed, and to heat and distribute the stream of air which flows through it into
the furnace when the air valve is open.
+
Secondly. The mechanism which by its automatic action causes the air valve to
close gradually. This mechanism consists, first, of a thin iron cylindrical cup or
cistern (c) having a tube (t) about half an inch in diameter tapped into its bottom
as piston rod.
The bottom of this cup has on its under side two very slightly elevated ridges
(r,.) (somewhat triangular in section) forming two circles, the exterior just within
the outer margin, the interior surrounding the orifice of the tubular piston rod.
The included space is pierced by a series of orifices (o) whose united area is about
equal to one sixth of its superfices.
A circular disc (d) ground perfectly flat on its upper side is appended to the
cup by three guides (g) or pins in such a manner as to allow of its traversing freely,
and dropping down through a limited space upon the cup being raised. These
guides or pins may be either passed through holes in the bottom of the cup and
tapped into the disc, as in Figure 2, or they may be fixed on the outer edge of the
cup so as just to admit of the easy passage of the disc within them, as in Figure 4,
in which latter case the rotation of the disc must be prevented by a small guide
pin (g).
At a point opposite one of the holes in the bottom of the cup the disc should be
pierced with a small orifice (2).
Secondly. Of a cast iron cylinder (7) of somewhat larger diameter than the cup,
and of such a depth as to permit the cup traversing within it the distance
demanded to give the required length of stroke, and having a small tube (t) tapped
into its bottom for the passage of the connecting rod (n), which is attached-at-its
upper end to the top of the cistern tube (t) by a pin joint (5), and at its lower end
through a link to the shutters or lid of the air chamber in the same way. When
air valve is shut the cup rests at the bottom of the cylinder with the charge of
mercury (with which the apparatus is worked) within it, with the exception of the
small portion occupying the circumferential interstice between the cup and the
cylinder. The opening of the furnace door lifts the shutters or flap by means of
mechanism suitably arranged for this purpose, admitting air into the furnace door

page_text: or airchamber, and simultaneously raises the cup to the top of the cylinder, the disc
descends, and the mercury passes down into the cylinder through the orifices (0, 0,)
in the bottom of the cup, in a time commensurate with the depth of the drop and
the aggregate area of the orifices. Upon the shutting of the furnace door the cup
becomes disengaged from the lifting mechanism, and charged with the weight of
the shutters or lid appended to it descends upon the disc closing the orifices
(o, o), and floats on the mercury which rises on the exterior of the cup to a height
as much above the level of the mercury in the interior as suffices to counter-
balance the superincumbent weight, whilst the higher level of the mercury on the
exterior causes it to flow into the cup through the small hole (i) in the disc, and
the cup to descend gradually in a time determined by the size of the orifice, the
quantity of the mercury, and the amount of the pressure.
In some instances, particulary where in steamships the space is very confined
between the top of the furnace door and the bottom of the smoke box, the
regulating cylinder cannot conveniently be placed above the air valve. In such
cases I modify the construction of the cylinder so as to permit of its being placed
on a level with the lid of the air valve instead of above. To obtain this result
I connect the motion of the cup in the cylinder with the motion of the air valve, by
the partial rotation of a horizontal axle (x) issuing from the cylinder on a level
with its flanges, and attached to the air valve by the arm (2).
The principle and respective modes of action of the cup, disc, and cylinder are the
same as before described, but the details of construction are varied as follows:-
There is no opening in the bottom of the cylinder, nor any tube tapped into the
cup, the piston rod, if such it may be called, consisting simply of a small rod (y)
attached to the bottom of the cup by a pin point (p), and to an arm projecting
at right angles from the horizontal shaft in the same way (p¹).
There being no opening in the bottom of the cup, the interior circular ridge
surrounding the orifice of the tubular piston rod becomes superflous.
OL
automatic mechanism which regulates the air
supply.
Figure 2 is a view of the interior of the same seen from above, the dome cover
being removed.
The same letters indicate the same parts in all the Figures. c is a cylindrical
cup or cistern; t, a tube tapped into its bottom; r, r, two slightly elevated circular
ridges raised on the bottom of the cup; o, o, orifices in bottom of cup; d, circular
disc ground perfectly flat on its upper side; g, guides or pins attaching disc to cup;
i, small orifice in disc opposite one of the holes in the cup (o) through which the
mercury flows into the cup.
1, cast iron cylinder; t¹, tube tapped into its bottom for the passage of the con-
necting rod n; j, pin joint attaching connecting rod to top of cistern tube.
Figure 3 shows a section of a modified form of the automatic mechanism. The
principle and respective modes of action of the cup, disc, and cylinder are the same
as in Figures 1 and 2, but the parts conveying the motion to the air valve are so
arranged as to admit of the cylinder being placed on a level with the air valve
instead of above it.
Figure 4 is a view of the interior of the same seen from above, the cover being
removed; x, horizontal axle which works in sockets sunk partly into the cylinder 7,
and partly into its cover; it is provided with two arms or levers z, m, the arın or
lever "z" being connected with the lid of the air chamber (as shown in Figure 5),
and the lever m connected to the cup or cistern by means of the connecting rod
"y," and pin joints p, p.
Figure 5 shows a front elevation of a furnace front and door, and the application
of the modified form of the automatic mechanisın (Figures 3 and 4), viz., in a level

page_text: with the lid of the air chamber instead of being placed above, and attached by a
connecting rod and link, as in the case with Figures 1 and 2. a is the airchamber
comprising three portions or passages, a central forming the doorway with one on
each side furnished with iron grating suitable for heating and dividing the air in
its passage into the furnace, and for preventing the passage of heat outwards, as
exemplified in my Patent of December 1853, and in subsequent Patents; "S" is
the lid of the air chamber, and "," the modified form of automátic mechanism, as
in Figures 3 and 4.
I have now described the nature of my Invention and the mode in which it is to
be accomplished, I do not however confine myself to the precise mechanical details
provided the principles be carried out, but what I claim is, the mechanism of the
automatic cylinder, as shewn in Figures 1, 2, 3, and 4.
In witness whereof, I, the said Thomas Symes Prideaux, have hereunto set my
hand and seal, this Sixth day of September, in the year of our Lord One
thousand eight hundred and eighty.
T. S. PRIDEAUX. (L.S.)