Improvements in Steam Boilers and in the Furnaces used in connection therewith.
Year: 1893

page_text: Date of Application, 6th June, 1893-Accepted, 12th Aug., 1893
COMITIDIM DIEULTIVATION,
Improvements in Steam Boilers and in the Furnaces used in
connection therewith.
I, CASSIUS CARROLL PECK of Ellwanger and Barry Building Rochester,
New York, United States of America, Mechanical 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:-
My invention relates especially to the class of steam boilers known as shell
boilers, and is applicable to the three divisions or types thereof known as stationary,
marine and locomotive boilers.
The main object of my invention is to increase the efficiency of shell boilers, to
render them more safe in use than heretofore, and to insure the production of dry
steam.
This I accomplish by, and the first feature of my invention consists in, the
special combination and arrangement as herein set forth of a tubular shell boiler or
heater and a steam separating drum, the two being connected and communicating
with each other at two points below the water line, one connecting passage entering
the lower portion of the heater shell for the return of the water thereto, and the
other connecting passage opening into the heater shell a comparatively short
distance below the water line. By this means I attain a continuous even, uniform,
natural circulation of the whole body of water between and through the heater
shell and the steam separating drum, entirely below a common water level with the
least possible disturbance of the said water surface.
The effects of this uniform movement of the boiler water continuously in one
direction may be summarized as follows. In firing up, the boiler water circulation
commences as soon as fire is lighted in the furnace, the whole mass of water par-
taking of the gyratory motion imparted by the furnace heat according to the well
known principles of water circulation. Thus, as the water in the heater becomes
warm it rises in the heater and passes through the upper connection into the steam
separating drum, below the water level and a corresponding amount returns to the
boiler from the separating drum by means of the lower connection. This causes
the whole structure to become uniformly heated, and preserves it from the immense
strains due to unequal expansion, which strains prove very injurious in practice,
and oftentimes destructive in shell boilers of large size and of the usual construc-
tion. This objectionable feature of shell boilers as heretofore constructed is so well
known that means are often employed for effecting a mechanical circulation of the
water to insure uniform heating when starting a fire in the boiler furnace.
The steady and rapid circulation of all boiler water which I effect below the
water level prevents settling of cold feed water in any part of the structure, and
also tends to bring all solid deposits from the water to points where they can be
blown out or removed by hand.
In its effect upon steam production the constant movement of the whole mass of
water thus effected by me through the shell of the heater and the separator below
a common water level common to both, is of especial importance. In passing over
the heated surfaces of the fire tubes the water wipes off or absorbs heat rapidly,
and at the same time removes steam bubbles as fast as formed, and conveys them
in the most direct way to the point of delivery from the comparatively quiet surface
of the water in the steam separating drum. In ordinary multitubular boilers there
is necessarily great confusion of currents which reduces the efficiency or value of
the heating surface, and results in the generation of wet steam. The rising currents
of steam and more highly heated water are met and opposed by corresponding
currents of descending cooler water, thus interfering with the escape of steam

page_text: bubbles and increasing the tendency to foam, while lessening the amount of heat
which can be carried away from the tube surfaces.
By my arrangement of the connections and circulation entirely below the water
line I maintain an extended area of comparatively smooth undisturbed surface in
the separator from which the steam readily escapes in a practically dry state.
This is a result of unusual practical importance, and one not heretofore attained for
the reason that the agitation incident to the various prior forms of circulation has
invariably resulted in the production of wet steam.
I am aware that steam boiler shells have been constructed with steam drums or
cylinders above said shells, and connected thereto at two, or more points by means
of short pipes extending from the upper part of the cylindrical boiler shell to the
under side of said cylinder or drum above, but such structures are not the equivalent
of my invention. In such cases the connections are all practically on the same
level and do not materially affect the circulation of water; whereas in my invention
the essential feature is the creation and maintenance of a natural but nevertheless
positive circulation of the whole body of water below the water level between and
through the boiler shell and steam separating chamber by conducting the more
highly heated water from the top of the boiler shell to the steam separating chamber,
below the water level and returning the cooler water from the said steam separating
chamber to the lower portion of the boiler shell. Unless the lower portion of the
steam separating chamber is thus connected with the lower portion of the steam
boiler shell below the water line the essential conditions of my invention are
lacking and there can be no positive uniform circulation of the whole body of water
in one direction below the liquid level common to both boiler and separator.
The second feature of my invention consists in forming the cylindrical boiler
shell with a cylindrical extension which constitutes a smoke box when closed by a
suitable cover arranged upon the outer end of the extension and opposite to the
head of the boiler through which the fire tubes open into the smoke box; and in
forming and combing with said smoke box an exhaust fan by which the products
of combustion are drawn through the fire tubes of the boiler and out of the smoke
box, and forcibly expelled directly through the said exhaust fan.
I am aware that it is common to employ an induced draught with steam boilers,
and I do not seek to cover this feature broadly. I am not aware however that a
cylindrical boiler shell has been extended into a smoke box and combined directly
with a fan exhaust for disposing of the products of combustion by passing them
through the said fan exhaust substantially as herein shown and described, and this
special construction and arrangement of parts is the feature I believe to be original
with myself and which I desire to cover. As compared with the use of a steam jet
or air blast employed in the uptake of a chimney to intensify the natural chimney
draught, or with the pulsating jet of exhaust steam from locomotive boilers, the fan
exhaust directly combined and arranged with the boiler shell extension smoke box
as shown and described herein has important advantages. The chimney jet is weak
and an expensive device and it is practically impossible to create thereby the high
rate of combustion in a furnace attainable by my method; while the locomotive
exhaust jet with its intermittent action is far less effective and satisfactory than the
steady pull of the exhaust fan, since with a steady draught combustion is more
perfect, and less intensity of draught is required for burning a given amount of fuel.
My improvements relate to the mechanical production of draft through the
furnaces of steam boilers generally; I am aware that heretofore both the forced
and the induced draft have been employed independently in convection with steam
boilers, but there have been certain practical objections attending their use.
the forced draft injury to the boiler occurs if the forcing be carried beyond a certain
point, that is, if the pressure or plenum, of furnace gases in contact with the boiler
exceeds a certain limit, because heat taken up by the metal of the boiler is not
carried away by the water with sufficient rapidity; while with the exhaust or
induced draft the partial vacuum caused by fan or chimney decreases the value of
the boiler heating surfaces in proportion to the degree of vacuum.
It is evident
With

page_text: that if any desired amount of draft can be produced without the evils due to forcing,
or the loss in efficiency of heating surface due to partial vacuum the best possible
conditions for the rapid production and absorption of heat without injury of
structure will be attained; and it is the object of my invention to secure the
advantageous features of both the forced and the induced draft without their
attendant disadvantageous as heretofore used.
The third feature of my invention consists essentially in the simultaneous use of
both a forced draft and an induced draft; the first supplying fresh air to support
combustion in the furnace, and the latter withdrawing the products of combustion
through the boiler, and ejecting them from the apparatus. I am aware that it
has heretofore been proposed to return the products of combustion to the furnace,
together with fresh air, by means of a single fan blower arranged to exhaust the
gases from the boiler and force them back into the furnace; but this is not the
equivalent of my invention. While my forced and induced drafts are in operation
simultaneously they are distinct in that there is no communication between the
exhaust and the supply passages except through the furnace and boiler, and
distinct forcing and exhausting devices are employed,-which however move
synchronously.
In the accompanying drawings
Figure 1, is a front view of one form of my improved construction of boiler;
Figure 2, is a side elevation of the same, the furnace and supporting masonry
being shown in vertical section on plane of line x, x, Figure 1;
Figure 3, a central longitudinal vertical section also upon plane of line x, x,
Figure 1;
Figure 4, a rear elevation of the boiler;
Figure 5, is a transverse vertical section upon plane of line y, y, Figure 2, showing
the connection between the upper part of the boiler shell and the steam
separating drum ;
Figure 6, is a transverse section upon plane of line z, z, Figure 2, showing a
connection between the steam separating chamber and the lower portion of the
boiler shell;
Figure 7, is a transverse sectional elevation showing the separator chamber
arranged vertically with relation to the horizontal boiler shell;
Figure 8, is a sectional elevation illustrating modifications in the relative
arrangement of the boiler shell and steam separating chamber;
Figure 9, is an end elevation of a modified arrangement of the boiler showing
the exhaust arranged at the side of the smoke box;
Figure 10, a side elevation of the same;
Figure 11, a central vertical sectional elevation of the modification shown in
the last two figures in which the products of combustion enter the fire flues at the
rear of the boiler and are exhausted at the front of the boiler;
Figure 12, is a longitudinal sectional elevation of another modification in which
both a forced and an induced draft is produced;
Figure 13, is a rear view of the same;
Figure 14, a transverse section upon plane of line y, y, Figure 12;
Figure 15, a transverse section upon plane of line y, y, Figure 12;
Figure 16, a plan representing diagrammatically the induction and eduction
draft passages.
In so far as the main feature of my invention is concerned,-the maintenance of
a circulation of the boiler water through the boiler and steam separator, below
the common water line, it is immaterial whether the boiler shell A, is placed
horizontally, vertically or at any intervening angle.
In like manner the steam separating chamber B, may be placed horizontally,
vertically or at any intervening angle; and its position with relation to the boiler
shell A, may be varied. Thus in the first six figures of the drawings, both
boiler shell and separating chamber are shown as arranged horizontally and
parallel to each other, one, above the other; in Figure 7, they occupy positions

page_text: relatively at right angles to each other; while in Figure 8, the boiler shell is
arranged vertically, and the separating chamber is represented first, in vertical
position in solid lines, and second, in horizontal position by dotted lines B¹.
In all of these arrangements the connections between the boiler shell A, and
the steam separating chamber B, are essentially the same,-the upper connection a,
uniting the upper portion of the boiler shell with the steam separating chamber B,
below the water level w, and the lower connection b, uniting the said steam
separating chamber B, below the water line w, with the lower portion of the
boiler shell. Thus in either case the principle of operation remains the same,
the heated boiler water and steam being delivered from the upper end or side of
the heater shell into an independent evaporating and circulating cylinder, from
which the boiler water returns to the lower portion of the heater shell, with the
result of maintaining a continuous current of the whole body of boiler water
below the water line in one direction through both shells.
A preferred arrangement however is that illustrated in the first six figures of
the drawings, in which the boiler and evaporating chamber are arranged horizontally,
the upper or short connections a, being made between the top of the boiler shell
and the under side of the evaporating chamber near the front or furnace end of the
apparatus; and the lower or long connection b, between the under side of the
steam separating chamber B, and the lower portion of the boiler shell A, consisting
of an annular passage or jacket surrounding the boiler shell and opening into the
bottom of the boiler through an aperture a¹, shown in Figure 6. Instead of thus
constructing the lower connection b, in the form of an annular jacket, a pipe of
circular cross section may be used, or two pipes, one on either side of the heater A,
can be used to connect the latter with the separating drum B.
The whole area of the shell A, (except the space for man holes not shown) is
occupied by longitudinal tubes or flues c, arranged at suitable distances apart with
relation to each other, the intervening space being filled by the boiler water which
extends up to the level w, in the steam separating chamber B.
It will be noticed that by the arrangement illustrated in Figures 1 to 6, the
circulation of the boiler water will be effected below the water line in a direction
opposite to that taken by the products of combustion through the fire flues, thus
rendering the transfer of heat from the furnace gases to the boiler water more
effective, and at the same time augmenting the circulation of the water since it
attains to the highest degree of heat at the furnace end of the shell immediately
under the short eduction passage a, leading from the top of the boiler shell to the
steam separating chamber.
The front end of the boiler shell A, is set in, and enclosed by the fire brick
composing one wall of the furnace F, so that only the end plate or head and tubes
are exposed to the direct action of the furnace gases. This will be seen by
reference to Figures 2, 3, 8, 11 and 12, Figure 8, showing a section of the solid
wall of fire brick or other refractory material in which the end of the boiler shell
is set.
The whole furnace is made of fire brick or other refractory material, the walls
being of a thickness sufficient to prevent the escape of heat in any considerable
degree. In Figures 2, 3, and 12, the upper front part f, of the furnace, is inclined
towards the exposed head or end of the boiler shell cylinder so as to more
effectually deflect and radiate the gases and heat into the fire flues.
C,
The rear end of the boiler shell is formed with an extension H, beyond the rear
end plate or head a², in which the fire tubes end. This extension H, is enclosed
by an end plate h, and thus constitutes a smoke box into and from which the
products of combustion are drawn by means of a rotating fan I, the suction passage
of which i, opens directly into and forms a continuation of the smoke box H.
I am aware that a boiler and an independent steam separating chamber have been
arranged one above the other and connected by pipes for the purpose of effecting
a circulation of the water between them, but in such case the inlet into the
independent steam separating chamber has been above the water level therein

page_text: whereas the essential and distinguishing feature of my invention, and the one to
which I restrict myself, consists in arranging both the inlet and outlet passages so
that they open into the independent steam separating chamber below the water
level therein.
Where the inlet is situated above the water level the water has to be raised
bodily above the said water line, and this can only be done by the use of a
comparatively small pipe or passage so as to compel the steam formed in the boiler
to carry upward with it a certain amount of water, as happens in the objectionable
features of "priming" to which this operation would be equivalent. If the upward
passage to the independent separating chamber were made large enough the steam
would bubble up freely through the water without carrying any appreciable quantity
of the latter over and the water would stand permanently in the connection pipe at
the same level as that in the separating chamber, which water level being below
the mouth of the inlet would effectually prevent any material circulation of the
water between the boiler and the separating chamber. Again if the connection or
inlet pipe to the separating chamber is made small enough to compel the steam to
prime or carry over the water into the steam separating chamber, it not only
impedes rapid circulation of the water but also inevitably produces wet steam, one
of the very results sought to be avoided by applicant.
65
"
I am also aware that water coils have been arranged in a furnace and connected
with an exterior steam separating chamber by a return conduit below the water
line and a steam and hot water conduit opening into the said separator chamber at
or above the water line as in the U.S. Patent to Brocks No. 121,079 of Nov. 21st, 1871,
but such an arrangement is not the equivalent of mine, which is designed especially
for the production of dry steam, whereas in the use of the coil referred to it would
be practically impossible to obtain anything but wet steam.
For instance, the water level in one form of the Brock apparatus is below the
inlet while in the other form it barely reaches above the lower edge of the small
circular inlet, so that while a natural circulation below the boiling point would be
impossible in one form it would be so slow and slight in the other form as to be of
no practical utility; and even whatever slight circulation might be possible, below
the boiling point, over the lower edge of the inlet port would be at the maximum
only when the water approximated very nearly to the boiling point, and could not
remain long undisturbed for the reason that at the moment steam began to form in
the coil it would displace the water, and the discharge into the separator would be
an agitated mixture of steam and water, which it is the express object of my
invention to obviate.
In fact by my invention I overcome the defects of all prior circulatory systems
and am enabled to evolve perfectly dry steam from a comparatively smooth liquid
surface under which the circulation is maintained constantly and uniformly, the
steam having ample opportunity in which to rise to the surface from the circulating
water without agitating or disturbing the latter.
I am aware that it has been proposed to connect together independent tubular
boilers in such manner as to afford a circulation of both water and steam between
them, the products of combustion passing from the primary boiler through the
secondary boiler for the purpose of utilizing as far as possible the heat carried from
a single furnace by the products of combustion; but in such case the steam is
withdrawn directly from both boilers, and the secondary boiler is in no sense the
equivalent of my steam separating chamber from which alone the steam is with-
drawn. According to my invention the boiler is practically filled all the time with
water and no steam whatsoever is separated and drawn off from the boiler shell,
the whole gist of the invention consisting in the use of a separating chamber in
which the steam is separated from the water at the water level above all connections
with the boiler, the circulation being confined to the water and being entirely below
the water line maintained in the separating chamber, and the boiler being ordinarily
below the said water line, and consequently full of water. The only exceptions to
this might be that in the case of a vertical boiler a small space might be left in the

page_text: boiler above the water level common to both boiler shell and separating chamber,
but in this case the boiler would be considered as practically full, since there would
be no escape for steam collecting above the water line in the boiler, no circulation
of steam and the circulation of water would be maintained entirely below the
water line, the results being practically the same as in the arrangement of
horizontal boilers and separating chamber herein shown and described.
The furnace F, may be set at either end of the boiler. Thus in the arrangement
shown in Figures 1, 2, 3, 4, 5, 6, and 12, 13, 14, 15 and 16, it is arranged at one
end of the boiler, the shell of which is embedded in the rear wall of the furnace,
whereas in Figures 9, 10 and 11, it is shown as underneath the boiler, and as
accessible from the opposite end of the boiler; but in either case the products of
combustion are conducted to the fire tubes at the same end of the boiler and without
contact with the shell thereof.
The cover h, for the smoke box extension H, may be secured in position in any
suitable manner. As shown in the drawings the cover h, fits the end of the shell,
to which it is held by buttons h¹, h¹.
The exhaust fan I, may be arranged at the side of, or below the smoke box as
shown in the accompanying drawings, or in any other suitable manner according to
the requirements of special use, provided its connections i, with the smoke box H,
is made as short and direct as possible.
The exhaust fan I, may deliver the products of combustion either directly to a
chimney, or to an economizer located between the blower and the chimney, or to
any other apparatus for utilizing the residual heat of the gases. It may be driven
from any convenient source of power supply, an independent engine being a
convenient arrangement, by means of which any desired speed of the fan can be
obtained.
is a
The advantages of a directly induced draught as compared with a forced draught
in effecting a concentration of power without detriment to the structure, as
illustrated by the intermittent steam jet in the case of the locomotive boiler,
strong argument in favour of this feature of my invention, by which however results
superior to those obtained in the locomotive are attained by me owing to the steady
uniform nature of the air current induced. By my invention the advantages
attendant upon the employment of an induced, in contradistinction to a forced,
current through the furnace and boiler tubes may be attained in connection with
both stationary and marine boiler shells.
I am aware that the draught in chimneys connected with steam boilers has been
augmented by air-forcing devices arranged to inject air under pressure into the
smoke flue and thus drive out the products of combustion, but this is a crude and
expensive expedient as compared with my plan of forming a smoke box at the end
of the boiler and drawing off all the products of combustion therefrom directly
In my
through the exhaust fan itself, to be disposed of in any desired manner.
method a chimney is not essential, or is of secondary importance, and there is no
waste of power expended in the introduction of extraneous air to act as a vehicle
for the products of combustion, the latter alone having to be disposed of by my
exhaust. In the case referred to the air blast itself is the primary cause of the
increased draught without regard to the means by which the blast is produced,
whereas in my case the exhaust fan itself is the direct cause of the increased
draught.
In the case of the air blast but a small percentage of the power expanded is
utilized whereas in my apparatus the full efficiency of the exhaust fan is expended
directly upon the products of combustion and there is no loss or waste of power.
In the modified construction shown in Figures 12 to 16, inclusive, the rear wall f¹,
of the furnace F, is formed with an air space or chamber f2, opening into the ash
pit below the furnace bars through a flue or through flues c.
The flue c, is controlled by a damper D, operated from the exterior, as will be
understood by reference to Figure 14. Air is forced into the chamber, through
connecting flues or ducts c', by the forcing fan J. The opposite end of the

page_text: boiler A, is formed with the extension or smoke-box H, into and from which the
products of combustion are drawn by the exhaust fan I, which discharges them through
a flue i, connected with a chimney, an economizer, or other suitable means of
disposing of them. A damper 2, is interposed in the conduit i, between the smoke
box H, and the exhaust fan I. G, is to represent any suitable motor for driving
the fans I, and J.
Although other air moving devices differing from fans may be employed to effect
the same result I shall confine the description to fans as being the most generally
available and practicable mechanism for carrying out my method of producing
duplex drafts. In order to economize room and cost, and to facilitate convenient
working of the apparatus, I prefer to mount the exhausting fan I, and the forcing
fan J, on one shaft K, the two fan cases i, j, joining each other, and the exhaust
fan I, placed at the greatest distance from the shaft bearing, or journal box k, in
order that the shaft may be cooled by contact with the draught of cold air passing
through the forcing fan case. This arrangement obviates the necessity for using
a water-box for cooling the shaft of the exhaust fan. In order that the weight of
the fan wheels may be carried without vibration when the fans are in motion, the
shaft is made of large diameter, the journal boxes are very long, and the fan wheels
are accurately balanced.
When conditions of use make the double fan, or combined fans, less suitable than
two separate and independent fans, the forcing fan J, and the exhausting fan I,
may be as widely separated as circumstances require, each being located where
most convenient.
The duty on each of the two fans I, J, is apparently one half of that on a single
fan producing the same amount of draught, but practically it is less; so that some-
what less power is required for a given amount of draught with two fans as
compared with a single fan. In other words a given amount of air can be impelled
through the fire with expenditure of less power by employing the two fans as
described than with a single fan. This result is due to the co-action of the
propelling and the inducing forces in moving a body of air through the mass of
coals in the furnace and through the boiler passages, the double action being
attended with less frictional resistance.
In operation the damper in the air duct of each fan will ordinarily be left wide
open, so that the inducing and the propelling forces may be pretty nearly
balanced; in which case the tension of air in the ash-pit will be somewhat greater
than that of the atmosphere; in the furnace the gases will closely approximate
atmospheric tension; and in the boiler passages the tension will be slightly less
than that of the atmosphere. By partially closing the damper in the connection
between boiler and exhaust fan the tension or pressure of gases in contact with the
boiler surfaces will be increased; but if the damper in the connection between
forcing fan and ash-pit be partially closed, a corresponding lessening of the tension
of the gases in the furnace and in contact with the boiler will result. With
dampers in the air passages of both fans wide open the fire can be urged to almost
any extent without material alteration of the tension of the furnace gases. In case
of a single fan used for producing draught the tension of the gases would change
nearly in direct ratio to the extent to which the fire was urged, if a forcing fan
were used in the pressure would increase to the point where the boiler water would
not carry off the heat sufficiently fast enough to prevent overheating of the metal,
while if an exhauster were employed the degree of vacuum would increase so as to
materially lessen the value of the boiler heating surfaces. The double fan supplies
means for maintaining a nearly uniform tension of furnace gases, and at the point
best suited for giving maximum results, without liability to damage. For this
reason the amount of coal burned may with propriety be increased as compared
with the single fan system.
By regulation of the power which drives the double fan the fire can be urged or
slackened promptly at will, and thus very perfect control of steam production be
maintained.

page_text: In constructing and locating the two fans they may be placed in any preferred
relation to each other. One of the fans may be given an up discharge, and the
other a down discharge, or both may have either an up or down or a horizontal
discharge, according to convenience in setting. The operation is practically the
same, whether a single boiler or a battery of boilers be supplied by the double fan.
When both fans are bung on the same shaft one division plate between the two
fan cases answers for both fans, the fan shaft passing through an opening in said
plate closely fitting the shaft. By placing the exhausting fan at the side of the
forcing fan, so that the shaft common to both fans passes through the case of the
latter the current of cool air moving through the case of the forcing fan is utilized
for cooling the aforesaid shaft, and thus supplies the place of the otherwise
necessary water-boxes, as the shaft is so much heated by contact with the furnace
gases passing through the exhaust case as to require cooling before entering the
nearest journal box.
It is intended that the exhauster shall be connected with the smoke passage as
near to the boiler as possible, so as to draw all the furnace gases through the fan
case with the least amount of resistance, and the forcing fan shall deliver the cold
air supply for the furnace with as much directness as possible into the ash-pit.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is;
First. The combination of a furnace, a boiler shell containing fire flues through
which the products of combustion from said furnace pass, an independent steam
separating chamber situated in such relation to the said boiler shell that a water
level and steam separating surface common to both may be maintained in the
separating chamber, a conduit situated wholly below the water level and connecting
the upper part of the said boiler shell with the separating chamber, and another
conduit also situated entirely below the water level and connecting said separating
chamber with the lower portion of the said boiler shell substantially in the manner
and for the purpose described.
Second. The combination of a furnace, a horizontal boiler shell formed with
a series of fire tubes, an independent horizontal steam separating chamber above the
boiler shell, a conduit connecting the upper portion of one end of the boiler shell
with the separating chamber above, and a conduit connecting the other end of said
separating chamber with the lower portion of the steam boiler, said last mentioned
conduit consisting in part of an annular jacket surrounding the boiler shell,
substantially in the manner and for the purpose described.
Third. The combination of a furnace, a boiler shell provided with a series
of fire tubes, a smoke box formed of an extension of the opposite end of the boiler
shell, and a rotary exhaust fan and casing connected directly with the said smoke
box and arranged to draw the products of combustion through said fire tubes and
into the said smoke box and to discharge them therefrom directly through the said
exhaust fan substantially in the manner and for the purpose described.
Fourth. The method herein set forth of creating and controlling the draught in
steam generating apparatus, consisting in simultaneously introducing fresh air under
pressure to support combustion in the furnace, drawing the products of combustion
through the boiler by means of a partial vacuum, and forcibly ejecting them from
the apparatus, substantially in the manner and for the purpose described.
Fifth. In steam generating apparatus, the combination with the furnace, of air
forcing mechanism for supplying fresh air for combustion, and air exhausting
mechanism for drawing the products of combustion through the boiler and
discharging them from the apparatus substantially in the manner and for the
purpose described.
Sixth. In steam generating apparatus, the combination with the furnace of air
forcing mechanism for supplying fresh air for combustion, means for regulating the
supply of said air to the furnace, air exhausting mechanism for drawing the products

page_text: of combustion through the boiler and discharging them from the apparatus, and
means for regulating the discharge of said products of combustion substantially in
the manner and for the purpose described.
Seventh. In steam generating apparatus, the combination with the furnace and
boiler and connecting flues, of forcing and of exhausting fans mounted upon a
common shaft the forcing fan and casing being located between the journal box and
the exhaust fan and case, substantially in the manner and for the purpose described.
Dated this Fifth day of June 1893.
CRUIKSHANK & FAIRWEATHER,
62, St. Vincent Street, Glasgow, Agents..