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@5%. l5, 1946.
_Filed Deo. .2, 1942
2 Sheets-Sheet l
Filed nec. 2, 1942
.2 sheets-sheet 2
Patented Oct. l5, 1946
James M. Guthrie, Allison Park, Pa., assigner to
Frederick S. Bloom, Pittsburgh, Pa.V
Application December 2, i942, Serial No, 467,586
My invention relates to furnaces, boilers, lehrs,
and other equipment heated by the combustion
of fuel, and particularly to pre-mix ñring systems
ation With conventional protective or safety de
vices for firing systems, afford a solution of the
On September 22, 1942, Letters Patent of the
therefor. A pre-mix firing or combustion system
United States, Nos. 2,296,255 and 2,296,256, Were
consists in apparatus that mixes the air and fuel
granted for improvements in pre-mix firing sys
for combustion in predetermined proportions at
tems to one Frederick S. Bloom, the assignee of
a mixing station remote from the combustion
record of the invention herein disclosed. The ñr
chambers of the furnaces, or other equipment in
ing systems illustrated and described in such
which combustion is to be maintained.
Letters Patent embody devices intended to safe
It has long been realized that more accurate
guardthe systems against the danger of backfir
combustion control and better fuel economy can
`ing, and it- is in such safeguarded systems that
be obtained through the use of pre-mix firing
my burner is particularly, though not exclusively,
systems, but the fact is that such systems have
serviceable. While the ñring systems shown in
hitherto been dangerous, this being for the rea
these Bloom patents are considered in and of
son that the mixture of air and fuel is essentially
themselves to be perfectly adapted for certain
an explosive mixture, Which is particularly haz
conditionsof service, there are cases in which the
ardous when itis confined, as in practice it must
added safety of my improved burner is desirable-_
be confined, in ducts leading from the mixing sta
in some cases indispensable. For purposes of il
tion to the point or points at which combustion
is to be maintained. The patented art in this 20 lustration, I shall herein describe my invention
as it may be incorporated With the pre-mix firing
field attests to the efforts that have been made to
system of Bloom Patent No. 2,296,256.
eliminate the danger inherent in the operation of
Referring to the drawings, the reference nu
such ñring systems.
meral la is applied to a furnace, or a lehr, for
More particularly, my invention is centered in
an improved burner for use in pre-mix i-lring sys 25 heating or heat-treating articles formed of~
metal, glass, or other material. A line of burners
tems. The burner of the invention is provided at
2 is mounted on each of the opposite side Walls
its outlet with a valve adapted automatically to
of the furnace, and in service these burners are
close when the pressure of the combustible mix
adapted toproject burning columns of fuel and
ture drops to a value at which there is danger of
backfire. Additionally, the burner includes a trap 30 air into the furnace chamber. A supply duct 3a '
delivers a combustible mixture of air and fuel
which closes in case a backfire occurs Within the
burner structure, the closed trap preventing the
spreading of the explosion to the ducts that sup
ply the mixture to the burner. Thus, it will be
understood that my burner is characterized by
(the fuel in this case being a combustible gas)
into a manifold ila, and from the manifold the
mixture is fed through branch pipes 40 to the
burners. More speciñcally, gaseous fuel is deliv
ered, undersuperatmospheric pressure, from. a
a double safeguard against backflring.
pipe 6 into duct 3a, and air is supplied to the duct,
In the accompanying drawings, Fig. I is a dia
by means of a blower or fan 5, and the mixed air
grammatic view in side elevation of an industrial
and fuel are delivered from the duct 3a to the
furnace equipped With a typical firing system in
which my burner may be employed, to provide 40 burner-feeding manifolds 4a on the opposite
sides of the furnace.
an organization of the invention defined in cer
The firing or combustion system comprises
tain of the appended claims. And Fig. II is a view
means for establishing and automatically main
in Vertical section of an exemplary form of my
taining at predetermined Value the ratio of air
burner, the Wall of the furnace and the supply
duct of the pre-mix firing system with which the 45 _to fuel in the mixture, and such means, including
a piece of apparatus |00 obtainable on the open
burner is organized being shown fragmentarily.
market under the name Askania ratio regulator,
The patented art contains several pre-mix
are fully described in said Letters Patent No.`
combustion systems in which my burner may be
2,296,255. To those skilled in the art it will suf
used to obtain the advantages in mind. Prefer
ably,if not essentially, the ñring system in which 50 ñce to say that the duct leading from the blower
5 includes an orifice plate ll and the fuel line B
my safety burner is used will itself include one
an orifice plate l2; that leads I3 and I4 establish '
or more devices functioning to safeguard the sys
communication between the regulator- |00 and
tern against conditions which might lead to an
the pipes 3a, `and 6 at points on opposite sides of
explosion. The backfire-neutralizing means of my
improved burner, brought into functional associ 55 the orifice plates, as shown; that a butterñy Valve
-I is arranged in the fuel pipe 8 on the upstream
side of the oriñce plate I2; that the plunger 9
of a pneumatic cylinder I 9 is connected to swing
or falls (other things being equal), the valve 32
pneumatic pressures in the two leads I'I and I8
in accordance with variations in the pressure dif
ferential between the fuel and the air supplied
to the duct 3a, and, as the difference between the
pressures in said leads rises and falls, the plungerA
9 shifts in the cylinder IE) in one direction or the.
other, correspondingly swinging the valve -I in
the fuel line 6 towards open or closed position.
above the value at which the flame can work
back through the oriñce 2S and cause an explo
sion in the burner body 28.
If the pressure of the combustible mixture
should drop to a Value at which a safe velocity
through oriñce 23 cannot be maintained, the valve
3_2, under the urging of spring 35, moves into fully
closed position, and in such position the valve is
effective to prevent explosive back-firing. It is
merely a matter of properly adjusting the effec
tive force of spring 35 to insure that the valve
shall close before the danger point is reached.'
The body of the valve, it is to be noted, includes
is shifted to the right or to the left, and accord
ingly increases or decreases the effective area
of the orifice 23, with the consequence that the
such valve; and that leads I'.' and I8 extend from
the regulator to the opposite ends of said cylinder. C21 velocity of the gases flowing through the port
The regulator IBI] operates in known way to vary
block 3i is maintained above critical value
In such manner the ratio of air to fuel in the mix
ture in duct 3a is established and maintained at
optimum value, regardless of fluctuations in the
supply pressures of the air and ñuel, and irrespec
tive of the usual variations in the demands or
requirements of the furnace. The air and fuel
are thus mixed in proportions that will afford
one or more small passages 38, which, when the
valve is in closed position, permit the flow of a
highest eñìciency of combustion and greatest
slight but sufficient quantity of the combustible
mixture into the throat 39 of the port-block, to
economy of fuel, but it will be understood that
such a mixture within a closed ñring system is
explosive and dangerous.
The burner included in the pre-mix lfiring- sys
tem embodies several features of design and op
eration common- tothe burners of the above
noted Bloom patent. Turning to Figure II, the
burner of my- invention will be understood to
sustain a pilot flame.
The valve 32 is arranged to control the flow of
the combustible mixture, not at some point in the
line of iiow removed a substantial interval from
the inlet end of the passage 29, 3D, but immedi
ately at the inlet end of such passage and pref
erably immediately at the inlet end 30av of the
conical throat of the port-block 3|.
A pipe t9 opens through the burner wall, and
through such pipe (as presently will appear) air
or other ñuid under pressure is supplied to the
diaphragm chamber within the burner, on oppo
site side of the diaphragm 33 from that upon
which the pneumatic pressure of the combustible
mixture is effective. By regulation of the pres
sure of the air in line 39, the position of the valve
d2; may be adjusted, the pneumatic pressure thus
established on the right-hand side of the dia
phragm supplementing the pressure of the spring
comprise a metal body 28 that includes a valve-y
chest or chamber 82. The burner is adapted to
be mounted on the sidewall of the furnace, as
shown, with the outlet oriñce or mouth 29 of the
burner in registry with the outer and smaller
end of a conical passage 3D in a refractory port
block 3I which is, as usual, embodied in the fur
nace side wall. The combustible mixture of fuel
and air enters> the chest 82 by way of one of the
branchy pipes ¿IB` leading from manifold 4a, and
within the chest a valve 32 is arranged to control
the mouth or oriñce 29.
In service the combustion of the gaseous mix
Indeed, in some cases the spring may be dis
turestreaming through oriñce 29 and port-block
pensed with, leaving the valve-shifting dia
-3I into the furnace is initiated in the conical 45 phragm responsive solely to pneumatic pressures.
passage 30 in the port-block, and so long as the
velocity of the streaming gases is above va critical
value, there is no danger of the ñame burning
back >through the oriiice 29. and causing prema
ture combustion andexplosion in the burner body
23 and branch pipe lill. With this circumstance
Other known pressure-operated devices than
flexible diaphragms may be arranged to shift the
burner valves in the desired manner, such as the
Sylphon illustrated and described in the said
50 Bloom patents. '
The rate of combustion is regulated in such
manner as to maintain the desired temperature
in mind, it is> to be understood that the burner
conditions within the furnace. In the exemplary
structure includes, advantageously, means for ad
apparatus herein disclosed the rate of combustion
justing the valve 32 in accordance with variations
in the pressure of the combustible mixture sup 55 is controlled by the same valve 32 as serves to
safeguard the burners from back-firing, means
plied, to the burner, so that, regardless of the
being provided for shifting the Valves towards or
pressure at which the combustible mixture enters
away from their seats 29 according as the tem
the burner, the velocity of flow through the ori
perature within theV furnace rises or falls from a
ñce 2,3 will either be held above critical value, or
the valve 32 Will shift into position entirely to 60 critical or predetermined value. The means for
close the orifice or mouth of the burner.
so` shifting the valves in this case are pneumatic,
Such means may consist in a ñeXible dia
and are adapted' automatically to vary the differ
phragm 33, to which the stem 34 of valve 32 is
ential pressure on the valve-shifting members 33
secured. AV spring 35, whose eiîective force may
within the burners. '
be adjusted by means of a screw 36, bears upon 65
The air-control pipe 39 of each burner is con
nected by a lead 4I to a pyrometer 24a, which is
in turn connected by a lead 251) to a pipe 25a
that leadsV from a supply of compressed air (not
one side-of the diaphragm, and tends to shift
the rod 3l! in right-to-leftA direction and to move
the valve 32 towards closed position, While the
pressure of the combustible mixture, transmitted
through a passage 66 in a partition 3'I in the
valye-chest, is eifective on the opposite side of
the diaphragm, and, opposing the force of spring
3,5', tends to move the valve away from the mouth
or oriñce 29.
As in service the pressure of the
combustible mixture supplied to the chest risesA
shown). A thermocouple, 26a., exposed to the
o temperature within the furnace, is connected
to the pyrometer. In the illustrated furnace it
is. desirable to provide different temperatures‘at
various points in the length of the furnace, and
inl such an installation, Athe burners are arranged'
75 in groups longitudinally of the furnace. and a
pyrometer Zfia and a thermo-couple 26a are pro
vided for each group. The burners 2 of the fur
nating pressure is immediately established on the
right-hand face of the diaphragm. The valve 32
nace I a, are shown to be arranged in three groups
is instantly closed. Thus itis that the air line 43
of three burners each, and the pneumatic control
and valve ¿t comprise auxiliaryV means for
pipes 39 of the burners in each group are con
quickly varying the relative value of the pressures
nected in common to the control pipe ¿l of a
acting on the valve-controlling diaphragm. It
pyrometer 2da. The pyrometers include valves
will be perceived that the branches 43 of all of
(not shown) that open and close in response to
the burners of the furnace may be connected
the increase and decrease of the thermo-electric
through a single valve to the predominating pres
currents in circuits Zia, and, as such valves in 10 sure supply, whereby the burners will respond si
the pyrometers open and close, the fluid pressure
multaneously to the control of the attendant. In
in pipes ¿li leading to the Valve-controlling dia
still further rennement the attendant’s valve or
phragrns 33 (which diaphragms are exemplary
valves may be automatically operated in response
of the several types of pneumatic motors that
to certain critical pressures or temperatures in
may be used) correspondingly rises and falls;
the installation, but it is needless to involve this
that is to say, as the temperatures rise or fall (in
specification with this or other refinements and
the regions of the furnace into Which thermo
modifications that the engineer may supply.
couples 2te extend) thepressures on the right
laying described a firing system that includes
hand faces of the burner diaphragms increase or
instrumentalities of the sort with -which the irn
decrease relatively to the pressure of the com
provements of my invention are adapted to be
bustible mixture on the left-hand faces of the
associated, I shall now;turn to a description'of
diaphragms, and in consequence the burner
such improvements.
valves are shifted either towards closed positions
in accordance with the invention each burner
or into more widely opened positions. Thus the
quantity of the fuel and air mixture delivered
into the furnace is regulated. in organizing the
burners in groups severally controlled by pyrome
ters that are individually responsive to thermo
couples arranged at successive points longitudi
nally of the furnace, the temperatures at such
points or regions of the furnace may be accu
rately maintained, and the desired temperature
gradient in the furnace may be established and
The apparatus admits of great versatility in
the matter of temperature regulation. The
grouping of the burners may be quickly altered to
provide the desired temperature gradient from
2 includes a trap that serves, in the.event of a
backiire in the burner, to prevent the spread oi
combustion to the branch pipe ¿lll and other parts
of the pre-mix ñring system. The backfire trap
comprises, in this case a flap-valve 66 arranged in
the line of iiow of the combustible mixture be-tween the inlet and outlet of the burner. The
nap-valve is pivoted, at 6l, to a member S2 se
cured in the burner Wall, to receive in threaded
union the delivery end of feed-pipe dll. The mem
ber E32 is provided with an annular valve-seat @3
which the flap-valve â@ adapted, as will appear
below, snugly to engage. Normally the nap-valve
is, by the impingement of the gaseous mixture
streaming through the burner, held away from
one end of the furnace to the other; one burner
the seat $3. If required a light spring E@ may be
on each side of the furnace may be connected to 40 arranged to assist the streaming mixture of air
one pyrometer, and ñve burners on eachside may
and fuel in normally sustaining the flap-valve in
be connected to another, and so on; indeed, all of
the open position in which it is illustrated.
the burners may be connected to a single pyrom
If the valve 32 should for any reason fail to
eter, if the conditions should require a single con
function in such way as to prevent a backfire
trol. This interchangeability of burner grouping y.. i.' Within the burner, the gaseous pressure produced
is made practical and economical, due to the ease
by the backfire operates to close the flap-Valve 8@
with which the small tubing 39, :El may be taken
upon seat t3 and thus prevent the spread of com
apart and re-connected in such Way as to provide
bustion to the pipe @15. It will be noted that the
the desired burner grouping.
nap-valve 5d is normally inclined (when in
An automatic valve ¿l2 is arranged in the fuel
open position) in the burner body that the pres
supply line 6. Ii for any reason the pressure of
sure produced by a backfire through the inlet of
the air, or of the combustible mixture, should fall
the burner is eiîective instantly to drive the flap
to the danger point the valve ¿l2 closes and com
valve to its seat.
pletely shuts oiî the supply of fuel. The fan 5
Advantageously, means are provided for locking
will continue in operation, and in such case will
the iiap-valve to its seat, once it has been driven
scavenge the lines 3a and ¿ia of the combustible
there by a backfire, for in such Way the flap or
mixture therein. The valve ¿52 is a known type
disk-valve is prevented from rebounding from its
of pneumatically operated valve, adapted in
seat in such way that i'lre momentarily lingering
known way to close the fuel line when the pres
in the burner after the valve has been “slapped”
sure of the gases in pipe 3a falls below critical
closed cannot spread. Said means may consist in
» a resilient catch 65 that engages the edge of the
If for any reason it should prove desirable to
flap-valve as it is “slapped” into closed position,
close down a burner, other than through the oper
and locks the valve to its seat. The catch is man
ation of the automatic means described, the at
ually releasable, so that the flap-valve may, after
tendant may do it. That is to say, a branch 43
is provided for the air line 39 of each burner, and ' the occurrence of a back-fire, be reset for normal
operation of the burner. Means to this end may
this branch is connected to a supply of air or other
comprise a finger 76 that is vertically reciprocable
fluid under a predominating' pressure. The
in the member 52. The upper end of the linger is
branch includes a valve di! adjacent to the burner,
but it will be understood that this valve may, if 70 tapered, as shown, so that, when the accessible
lower end of the finger is pressed, and the finger
desired, be located at a remote control station.
moved upward, the catch is engaged and swung
The valve is normally closed, and the burner
into valve-releasing position. The pressure of
functions in the System, as desired. However, if
the combustible mixture in the pipe lill, together
it becomes desirable to shut the burner down, the
attendant merely opens the valve, and a predomi 75 with the tension of the spring 64 (if such a spring
into Yinlet-closing 'position -in the event that said
is used), is effective to restore the valve to posi
tion for normal operation of the burner.
Means are also provided to safeguard the bur-n
valve »tails to move into backfire-preventing posi
tion said outlet.
2. A'-I‘he structure of claim 1, said backfire trap
er >body against rupture under 'the stress of an
comprising a valve member hinged adjacent to
explosive backñre. Such means comprise essen
the edge thereof which is nearer to said outlet
tially a pressure-releasing device which may, as
and adapted to swing on its hinge into outlet
here shown for purposes of illustration, consist in
closing position, said last named valve member
a plate 51 normally closing an oriñce 58 in the
being inclined from said edge in a direction away
burner body. The plate 6l is held in hermetic
engagement with the wall of the valve body by 10 from said outlet, substantially for the purpose
means of springs 69, and if and when a dangerous
3. The structure of claim l, together with man
pressure is developed Within the burner, such as is
ually releasable means for locking said trap in
developed by an explosive backñre, the plate is
closed position, whereby the burner requires man
forced from its seat, and escape is afforded for the
ual attention before the system can be returned
gases under excessive pressure Within the burner.
to normal operation after the trap has been closed
The foregoing specification gives a full disclo
by abnormal conditions within the burner.
sure of the invention, and it will be understood
4. A pre-mix liring system for a furnace ln
that various modifications and refinements are
stallation including a combustion chamber, a
permissible within the terms and intent of the
appended claims.
20 burner, and means for supplying a mixture of air
I claim as my invention:
1. A pre-mix firing system for a furnace in
stallation including a combustion chamber, a
burner, and means for supplying a mixture of
and fuel to said burner, the body of said burner
closed position on said inlet under the effect of -
in said burner body drops to critical value, said
trap being arranged and preconditioned to move
into inlet-closing position in the event that said
having an inlet for said mixture and an outlet
for the passage of the mixture into said com
bustion chamber, a valve arranged in the burner
air and fuel to said burner, the body of said 25 body to regulate the effective area of said outlet,
a pneumatic device, a member connecting said
burner having an inlet for said mixture and an
pneumatic device to said valve and being mov
outlet for the passage of the mixture into said
able to adjust the position of said valve in re
combustion chamber, a valve arranged in the
spense t0 variations in the diiîerential of two
burner body to regulate the effective area of said
outlet, a pneumatic device, a member connecting 30 pressures acting in opposition on said member,
one pressure being the pressure of said mixture,
said pneumatic device to said valve and being
with the effect that the velocity of the mixture
movable to adjust the position of said valve in
streaming into said combustion chamber is nor
response to variations in the dilîerential of two
mally held at backfire-preventing value and a
pressures acting in opposition on said member,
one pressure being the pressiu’e of said mixture, 35 backfire trap disposed across the mouth of said
inlet in the line of flow between the inlet and the
with the effect that the velocity of the mixture
outlet, said backñre trap being movable into
streaming into said combustion chamber is nor
closed position on said inlet under the eiîect of
mally held at backfire-preventing Value, said out
gaseous pressure acting in reverse direction to
let being disposed adjacent to one end of the
burner body and said inlet being disposed be 40 the normal line of mixture flow between said in
let and said outlet, said outlet valve being ar
tween said outlet and said pneumatic device, and
ranged and preconditioned to operate under the
a backñre trap disposed across the mouth of said
effect of said pneumatic device to close said out
inlet in the line of flow between the inlet and
let against backfire when the mixture pressure
the outlet, said backfire trap being movable into
gaseous pressure acting in reverse direction to
the normal line of mixture flow between said inlet
valve -fails to move into backfire-preventing po
and said outlet, said outlet valve being arranged
and preconditioned to operate under the eiîect
sition in said outlet, and manually releasable
of said pneumatic device to close said outlet 50 means for locking said trap in closed position on
against backñre when the mixture pressure in
said inlet.
said burner body drops to critical value, and said
trap being arranged and preconditioned to move
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