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Patented Aug. 20, 1.946
William M. Schweickart and Fred G. Julyan,
Euclid, Ohio, assignors to Pocahontas Fuel
Company Incorporated, New York, N. Y.,a cor
poration of Virginia
Original application August 28, 1937, Serial No.
161,494, now Patent No. 2,306,189, dated Decem
ber 22, 1942. Divided and this application
August 8, 1941, Serial No. 405,894
6 Claims. (01. 110-45)
This invention relates to improvements in auto
matic coal burners.
A primary feature of this invention is the pro
vision of a burner that will burn different types
of coking coal efficiently and economically, in
small domestic installations as Well as in larger
furnaces, and which is adapted to utilize var
ious sizes of coal down to slack.
der widely varying conditions and economical in
Other objects and advantages of the invention
will appear from the following description con
sidered in connection with the accompanying
drawings in which,
Fig. 1 is a perspective view of the assembly;
Fig. 2 is a longitudinal vertical section through
The burner is arranged to provide a novel com
bustion zone properly related to the feed so as to
the burner;
assure e?'icient coking, ignition and combustion
of the solid and gaseous components without dan
ger of back coking or clinkerformation at points
that would interfere with the coal feed and e?i
broken away;
Fig. 2a is a plan view of the burner with parts
Fig. 3 is a detailed side elevation of the grate
4 is a fragmentary view of the coal and
cient combustion, arranged moreover to avoid the 15 airFig.
feed tubesand air control;
back ?ow of gas under appropriate operating con
Fig. 5 is a fragmentary side elevation of the
blower and air control viewed from the side of
Another object is to provide a burner that will
have high combustion efficiency, particularly
the assembly which is to the rear as shown in
Figs. 1 and 4;
when burning bituminous coal. The burner is
arranged to produce ‘a relatively thin bed of burn 20v Fig. 6 is a diagram of an electrical control ar
rangement schematically applied to the burner
ing fuel, and to eliminate di?iculties with clinker
installed in a domestic furnace; and
formation and ash accumulation which would
Fig. 7 is a diagram illustrating the operation of
tend to interfere with proper combustion. The
ash removal mechanism removes the ashes and 25 the banking control switch shown in Fig. 6.
In the speci?c embodiment shown (Fig. 1) the
small clinkers rapidly and uniformly without in~
apparatus comprises a drive unit B, a burner unit
terference with the ?re bed, conveying them con
0, and an ash discharge unit D.
tinuously to an ash discharge.
A coal collector unit, not shown, ispositioned
Another purpose is to improve the e?iciency
and control of the air supply to the ?re. The 30 in the coal bin and supplies coal to the coal feed
tube 22 in which is positioned the coal screw 2|,
forced draught is introduced in a zone at the top
with the collector unit driven from the coal feed
of the retort and outward over the grate, and is
screw 2|. A suitable collector unit is shown and
provided with an adjustment to meet the condi
described in our Patent No. 2,233,085 granted Feb
tions of each installation as well as the varying
ruary 25, 1941.
fusion points and other characteristics of com 35
Where the conveyor tube 22 requires a bend.
bustion of different types of coal. Under bank
this is preferably made as an angle, for instance,‘
ing conditions provision is made for independ
a right angle, through a feed knuckle (not shown)
ent regulation of the air drawn by natural
provided for conveying the coal around the angle.
draught, permitting the efficient and certain
The drive unit B includes the motor with its
maintenance of a suitable fuel bed.
40 controls, the blower and air supply, the drive for
An eincient electrical control system has been
the coal feed and ash discharge screws, the grate
provided, which may be incorporated in combi
rotor drive and gas withdrawal construction.
nation with standard proven electrical devices.
The drive assembly is mounted on a base 72
In general, the drive unit is controlled from the
room thermostat and is protected by safety de 45 provided with a longitudinal cylindrical passage
for the coal to which sections of the coal feed tube
vices. An important feature of the invention is
22 are connected and through which the last sec
the provision of an ef?cient, sensitive and reliable
tion of the coal feed screw 2| passes. Supported
banking control cooperating with the burner con
upon the base 12 is the motor 15 having the rotor
struction and the banking air control to assure
the maintenance of a minimum ?re by automati 50 11 of the blower 18 secured to one end of its shaft.
A housing 80 surrounds the blower air inlet, and
cally providing fuel and forced draught accurate
air is admitted to the housing by the air inlet
ly as needed.
82. The other end of the shaft of motor 15
An important object is to provide apparatus
is connected to the ash removal shaft 89 through
embodying features set forth herein which is sim
reduction gearing contained within the casing 86
ple, compact, strong, suitable for installation un
and through a sprocket and chaindrive including
handle I523 extending outside of the drive unit
edge onto the grate structure through which the
the chain QI which engages a sprocket mounted
upon the ash removal shaft 89. These connec
tions may include a clutch operable from the
The burner unit C hereinafter described in
cludes a rotating grate structure which is inter
mittently operated by reciprocating shaker rod .'
I58. A suitable mechanism is provided for im
parting such reciprocating movement at the 10
proper rate. In the form shown best in Fig. l,
the sprocket engaged by chain 9! and mounted
ashes pass. In the arrangement disclosed the
section of the coal feed tube 22 extending from
the drive unit base 12 is clamped in the burner
body I50 and supplies coal to the throat I5I at
the bottom of the ?re pot I52, which preferably
‘is tapered outwardly from throat I5I.
The lower portion of pot I52 may consist of a
pot wall I53 integral with burner body I55, and
a frusto-conical pot liner I54 having a smooth,
preferably enameled inner surface, ?tting within
wall I53 and resting on a suitable ledge I55 to
provide a smooth continuation of the surface of
on ash removal shaft 89 is provided with a suit
able cylindrical face cam I II] engaging cam roller
A pocket I58 extending beyond throat I5I con
I I I rotatably mounted on the upper end offrocker 15 .centric with the axis of coal feed screw 2I has
arm I I2 pivoted at its lower end to base I2;
H3 is pivoted at one end on rocker arm I i2 ‘with
mounted‘ therein a reverse screw I51. One end
of this reverse screw is connected to the adjacent
section of feed screw H by a connecting shaft I55
and the other end is connected to a terminal shaft
its other end engaging ratchet Iii which‘is ro-J .
tatably mounted on base 12 and is prevented from
backlash by a silent detent cam H5 having an 20 I60 which extends through the bearing I59 at
offset pivotal mounting III? on vertical Web II1
the end of pocket I55, the projecting end of shaft
of the base 12 arranged so that therunbalanced
I55 having a sprocket 239 mounted thereon by
weight of cam H5 will maintain its 9am surface
in locking engagement with the teeth of ratchet
, ‘means of which the terminal shaft I58, reverse
screw ‘I51, connecting shaft I58, coal feed screw
I I4 to prevent backlash, lug I IE on eamI I5 being
positioned to engage the upper face o'f'web H1
when cam II5 is rotated out of engagement‘ with
ratchet H4, preventing cam H5 from being acci
dentally jarred or otherwise shifted into inopera
tive position.
Means for regulating the throw of pawl II; and
thereby varying the actuation of the rotary grate
structure includes an upward extension H9 on
pawl I I3 positioned to engage stop lllg I20 adjust
ably mounted as by a slot and a locking screw on
web I I1 to control the length of the return throw
of pawl H3. The lug I25 acts to swing the pawl
H3 downward into engaging position with the
ratchet H4. Cam roller III is suitably main
tained in engagement with cai'n IIB, as by leaf
spring I23 bearing against base 12 and rocker
arm H2.
The intermittent movement of ratchet H4,
which in the form shown is actuated twice during
each revolution of sprocket engaged by chain 9!,
is suitably transmitted to the ash grate, as by
eccentric I24 mounted on ratchet H4 and carry
ing eccentric strap I25 on connecting rod I26
which may be connectedto shaker rod I59 by a
suitable shock absorbing arrangement. For [this]
BI and the mechanisms of the coal collector unit
(not shown) are driven.
To provide for supply of air to the burning fuel,
inlet air chamber I6! surrounds the pot wall I53,
formed by bottom wall I62 and outer wall I53 and
generally open at the top.
A suitable upper margin for the pot I52 is
provided preferably in separable form and is gen
erally referred to as a retort. While the retort
may be formed and mounted in various ways, it
is advantageous to provide a retort base ring
I65 which may perform a number of functions.
In the form illustrated ring I56 is held in position
by ‘bolts I61 threaded into lugs I64 on outer wall
I53 of air chamber IBI, and may have 'a sealed
engagement therewith by employing an asbes
tos gasket I63. Base ring I65 may likewise form
a closure for the junction between pot wall I53
and pot liner I54, the form shown having an
annular ridge I10 engaging a seal ring I69 of
asbestos or the like located on the suitably bev
eled edges of wall ‘I53 in liner I54. The ring
I65 is provided with openings I'II (Fig. 2a) to
. permit the air from air chamber IGI to pass up
50 wardly to the retort.
The retort I12 is removably mounted on the
purpose rod I25 may terminate in frame I21 in
base ring I65 and forms a continuation of the
which the spring cage IE8 is mounted,.including
pot I 52, being provided with air outlets or tuyere's
end flanges I29 in which shaker rod I89 is slid
for furnishing air in the most advantageous zone
ably mounted, between which ?anges shock ab
sorber spring I35 is set under initial compression 5-5 for e?icient operation. In the form shown the
retort I12 is provided with an inner wall I13
and maintained in compressed condition by com
forming a continuation of pot I52 and ‘the inner
pression collar ISI held in suitable position on rod
face of base ring I55, and resting on an asbes
IE9 by stop pins I33 projecting from shaker rod
tos gasket I14 in a suitable depression in base
I09 in position to engage the adjacent ?ange I29
and collar I3l under pressure of spring I35. Col 60 ring IE6. The outer wall I15 slopes outwardly
and downwardly to thegrate structure, and rests
lar ISI is held against rotation by ‘engagement
on an asbestos gasket I16 in a suitable depression
with cage I28, and operates through clamp screw
in base ring I65. The retort crown I11 provides
I32 to hold rod I09 in adjusted position. Cage
an integral smooth curve between walls I13 and
I28 is preferably mounted removably on frame
I21. This shaker rod spring construction will 65 I15, and is ‘preferably relatively narrow to pre
vent retention of material thereon.
allow the stoker to run even though the grates
Suitable tuyére openings I18 extend through
are jammed, the rest‘of the mechanism continu
the retort I12 at appropriate points. It has been
ing to function normally and the placing, of the
determined that the most advantageous construc
absorber spring I35 under initial compression is
tion comprises provision of a series of tuyere
important to quiet operation.
openings I18 in the upper part of the inner re
This rotary grate structure surrounds an inner
tort wall I13, preferably sloping slightly down
retort of the burner unit C of the type in. which
ward-and a smaller number of 'tuyere openings
the coal is forced‘upwardly through the bottom
I18-extending through the upper part‘ of the outer
of the burner retort or pot structureyburning
‘a retort
wall I15 at about the same level. The
the upper portion thereof and traveling over the
retort I72 is held in place by means which pref
erably permits its ready removal and replace
ment, such as hooks I19 which may be cast in
tegral with the retort walls I73 and I15, and which
engage the lower face of the retort base ring
I68 through suitable retort lock Openings,
The rotary grate structure located around the
ing space normally ?lling with ashes, which form
the air seal across the narrow slot between the
apron margin and ring I8I.
' '
The grate ring I88 is suitably mounted on rotor
ring I8I' to permit ready removal without affect
ing the rigidity and reliability of the mounting
under service conditions. A suitable arrange
retort H2 is adapted to receive the burning coal
ment is indicated best in Fig. 2a, and includes
and ashes which flow outwardly'over'the retort, ‘ beveled wedge lugs I 91 on rotor ring ,I8I engag
sifting the ashes into a suitable annular receiver 10 ing beveled wedge lugs I98 on grate ring I88 to
in which they are carried around the burner to
force the grate ring downwardly into proper po
a point of discharge. The various parts are car
sition by rotating it relative to rotor ring 'I8I ;
ried by a-rotor ring I8I which is rotatably mount
stop lugs I99 on- rotor ring I 81 and removable
ed on the pot I522. The mounting-of rotor ring
locking slugs 288 ?tting between stop lugs I99 and
IN on ball bearings is such that the parts may 15 wedges I98 when the grate ring I88 has been
be readily assembled, the bearing will be easily
turned into proper position.
accessible and the structure will function smooth
. The grate rotor structure is preferably provid
ly under the substantial variations in temperature
ed with an- ash table 284, receiving ashes which
and consequent expansion and contraction of the
pass the grate segments I89 and conveying such
parts encountered under these conditions, the ball 20 ashes to a point of discharge. A plurality of ash
race being formed by cast surfaces. The arrange
ment comprises a ball race groove I 82 in the
tablesegments 285 forms a continuous annular
platform around rotor ring I8I adapted to receive
the ashes. Each table segment 285 is provided
with an inner ?ange 288 extending inwardly and
inner face of the upper part of rotor ring I 8I.
An upwardly beveled ?ange I83 on wall I83 and
a downwardly beveled ?ange I84 on base ring 25 upwardly, resting on an annular shoulder 281 on
I88 are arranged to provide a ball race groove
I85 cooperating with groove I82 to retain the
balls I88. By the removal of retort base ring
rotor ring I8I, the abutting edges of the table
segments 285' being preferably in overlapping re
lationship to provide continuity and accurate
registration. The lower rim 288 of grate ring I88
as the faces of grooves I82 and-I85 are substan 30 bears against ?anges 288 and securely locks the
tially at 90° to each other, their spacing permits
table segments 285 in ?rm ?xed position when
smooth unobstructed travel of the balls under
the rotor ring and grate ring wedge lugs are in
various conditions of expansion due to changes
terlocked as above described. ‘Table segments 285
in temperature.
may be accurately located by positioning lugs on
The outer margin of the retort base ring I88 35 rotor ring I8I engaging corresponding position
is provided with an apron I81 extending out
ing recesses in segments 285.
wardly and downwardly over the upper edge of
An ash trough extends around and below the
the rotor ring IIH, apron I87 providing a smooth
ash table segments 285, for the direct discharge
path of ?ow for ashes around the ball bearing
of ashes from the ash table. The ash trough 289 structure and beyond the outer face of rotor ring 40 has an outer wall 2H1, a bottom 2II extending
I8I, the adjacent faces of apron E8‘! and rotor
beneath and slightly spaced from the table seg
ring I8I being suitably shaped to provide a rela
ments 285, and an inner ?ange 2I2 extending up
tively slight clearance and prevent‘ substantial
wardly substantially beyond the lower face of
amounts of ashes from reaching the balls I 88, the
table segments 285. Segments 285 are preferably
opening I89 below said balls permitting any ashes 45 provided with diagonally tangential ribs 2I3
or the like to fall out of the raceway. The an
which serve to plow outwardly toward wall 2I9
nular pocket 233 below apron I81 accumulates
ashes which fall between ash table 284 and wall
ashes and an inner seal of ashes 234 is formed
2I8, preventing the ashes from escaping over
at the lower edge of the apron, restricting the
?ange 2I2 while avoiding any engagement be
passage of air to' the space above the grate.
50 tween the rotating and ?xed parts. The ashes
In the embodiment shown a grate ring I88 is
brushed outward by the ribs 2I3 accumulate at
utilized, removably mounted on rotor ring I8I
the outer edge of the bottom plate 2“ and form
and adapted to receive removable grate segments
an outer ash seal 28I at the periphery of the
I89. These segments are preferably flat integral
table 284 so as to restrict the ?ow of air to the
I68, the balls ‘I88 will be readily accessible; and
castings provided with an inner flange I 98 ex 55
tending into close relationship to retort base ring
apron I87. Suitable slots permitting ashes to
pass the segments I 89 include the radial slots
space above.
The ashes carried around by ash table 284 are
vcontinuously discharged by a scraper 2M in
cluding an ash plow or vertical plate on the outer
I9I, restricted margina1 slots I92 in ?ange I98,
wall 2I8 of the ash trough extending into juxta
preferably angled inwardly in the direction of 60 position to the ash table 284 and grate ring I88
rotation, and the spaces left between the periph
and de?ecting ashes outwardly through a dis
ery of each segment I89 and the adjacent parts.
charge opening 2I5 in wall 2 I8 into the ash dis
Segments I89 are mounted on the grate ring
charge pocket 2I8 formed in said wall (Figs. 1
I88 in suitable manner securely held in opera
and 6). An ash discharge chamber 2I'I forms
tion but permitting ready removal and prefer 65 a downward continuation of pocket 2I6' and
ably adapted to construction by casting. In the
houses the receiving end of the ash removal screw
form shown each grate segment IE9 is provided
with two downwardly extending slightly elongated
2I8 mounted on ash removal shaft 89 (Fig. 6).
A suitable arrangement ‘is provided for sup
annular sockets i93 adapted to receive support
porting ash trough 289 and for connecting it to
ing studs I94 on the upper margin of grate ring
furnace body. For convenience, trough 209
I88. An integral locking tongue on the advance 70 may be constructed in three segments, supported
end of each segment I89 extends'beneath a look
at the right of the burner (Figs. 1 and 2) by two
ing lug formed on the upper edge of grate ring
bracket legs 228 overlying the two junctions of
I88. Grate ring I88 may extend to a point higher
the segments and removably mounted on the
than the lower edge of apron I81, the interven 1‘; burner body I58 to permit convenient mounting
and, disassembly of the ash v‘trough 209. The re
maining junction between segments 2l'9 overly
ing the coal feed tube 22 is supported by a bracket
22l on the burner body I56, provided with a de
tachable clamp 222 overlying the junction and
which may be detachably fastened to the bracket
unit when the blower :is not in'operation. These
functions may all be performed by a single mech
anism comprising'a valve flap 2'“ ?xed to pivot
spindle 222 located in the upper part of a sec
tion of the air control housing 265 in advance of
damper 264 and engaging 'valveseat 213, which
is preferably inclined in the direction of air flow
from the blower. The end of spindle-212 may be
The upper margin of the ash trough 209 is con
bent downwardly outside of housing 265 to form
nected to the furnace ‘body to close the space
a pointer 214 serving in conjunction with suitable
between the body and the burner unit. This may
marks 215 or the like on the outer face of housing
be accomplished by providinga closure plate 224
265 to indicate the position of ?ap 211.
resting on shoulder 225 formed at the upper mar
To arrest valve flap 21l at a predetermined
gin of outerwa1l'2lo’of theash trough, and ex
variable distance from seat 213 we pro
tending outwardly to the furnace walls. A suit
vide a natural draft regulator spindle 216 thread
able'?lling or lagging 226, such as furnace cement
ed in housing 255, provided with a laterally ex
or the like, maybe employed tofill the spaces
tending stop arm 211 within housing 255 posi
between plate 224 and thefurnace walls, which
tioned for engagement with the face of ?ap 2H
are shown as comprising vthe usual water leg 221'
and serving as a variable stop for arresting the
of a domestic furnace. Plate 224 may be locked
downward movement of ?ap 21! at any point be
on ‘shoulder 225 by segmental locking plates 228
the valve seat 213 and the maximum de
?tting into an annular recess 229 in the upper
sired opening of flap 21! by rotation of spindle
margin of the outer wall 2“) of the ash trough
216 by means of knob 218, spindle 216 being fric
and provided with a longitudinal .rib 230.
held in adjusted position as by spring
The mechanism for rotating the grate unit
employs an intermittent drive, imparting a. peri
The air control housing 255 is connected to a
odic impact to the. rotating structure, as such an
air duct 28B running to air inlet cham
arrangement serves to break up the fuel mass
ber 28! (Fig. 5) in the burner body I55, and merg
and. to facilitate the sifting of .the ashes and
ing, around the casing for the coal feed passage,
small clinkers through the grate. In the con
with‘ the air inlet chamber ISI to provide a, gen
struction shown the shaker rod ")9 extends be
erally tangential air feed adapted to distribute
neath the ash trough 2G9 and ispivotally con
the air evenly throughout the air chamber l6!
7 nected at its end to the lower'end of 1a feed dog
and thence to tuyére openings I18.
arm 2“ extending upwardly between the air
A suitable arrangement is provided for auto
chamber ~|5| and the grate rotor ring l8l and
matically removing the ashes from the burner
having at its upper end a feed dog 242 projecting
unit C and discharging them at an appropriate
laterally between the support flange 243 on the
point, the construction shown including an ash
inner face of rotor ring WI, and rack 244 on said
removal conveyor and an elevator for transfer
ring overlying ?ange 243. The feed dog 242 is
provided with "a rocking face 245 riding on ?ange
243, and suitable teeth 246 at its forward end
adapted to engage rack 244. The arrangement is
such that when the shaker rod lilois shifted to
the left of ‘Fig. 3 the dog 242 will be rocked on
face 245 until teeth 245 engage rack 244, further
ring the ashes from the conveyor to a suitable
-". discharge point. In the form illustrated the
ashes are removed from the ash discharge cham
ber 211 by ash removal tube 285 mounted in the
burner body l5!) and forming a continuation of
chamber 211. Tube 285 extends to an appro
priate point and is shown as terminating adjacent
movement of the shaker rod I69 serving to ro- ».
drive unit B (Fig. 1). At this point a suitable
elevator unit D is positioned to receive the ashes.
A convenient construction is disclosed, employing
an arrangement in which the ash removal tube
285 terminates in an elevator pocket formed in
tate ring l8l and the grate parts mounted there
on, while ring Hll will be free from dog 242 at
the end of such stroke and during the return
stroke of shaker rod H39 owing to the disengage
ment of teeth 24!; when the dog 242 is rocked
in the reverse direction by continued travel of
the grate rotor ring l8! under its own momen
tum or by the return travel of shaker rod I89.
To prevent reverse rotation of the grate ring
l8! and associated parts a detent dog 241 is pro
vided on detent arm 248 pivotally mounted on
stud 249 on the burner body I50 at any con
elevator base 288.
Ash removal screw 2H3 ter
minates at the pocket while the shaft 89 on which
the screw is mounted extends through the pocket
and a suitable’bearing at the opposite side of the
elevator base 268, and thence to the drive mecha
nism as already set forth.
An elevator tube 29:: is mounted in elevator
base 288 extending from the elevator pocket up
wardly in any desired direction to permit dis
charge at any appropriate point dictated by local
conditions, the angle of tube 290 being readily ad
justed by clamping base 288 in any desired rotated
position about ash removal tube 285 through a
venient circumferential point and held yieldably
in operative position as by counterweight .1269.
Figs. 4,5 and 6 show the air supply and con
trol system between the blower ‘18 and the burner
unit C. The volume of air from blower 18 is
suitably regulated, as by butter?y damper 284
mounted in air control housing 265 on spindle
suitable clamping screw.
An elevator screw is
266 preferably provided with suitable locking 135 positioned in tube 298 to pick up ashes discharged
into the elevator pocket and raise them in tube
means, the form illustrated having a lockingdisc
261 mounted on the end of spindle 256 at the
rear of housing 265 (Fig. 5) and held iniadiust
ed position by locking knob 268 threaded on
screw stud 269 extending through'concentric slot
210 andmounted on housing 265.
Means are provided for indicating the flow of
air from blower 18,’for preventing backflow into
the blower system from the burner unit C, and
for permitting aregulable-flowof air to the burner
295 to a discharge at the upper end of the tube.
A suitable discharge arrangement is provided
at the upper end of elevator tube 29:]. This may
comprise a discharge head 3B8 mounted on the
upper end of elevator tube 290 and carrying an
upper bearing for the elevator shaft. Head 306
is provided with suitable spout discharge means,
the illustrated construction employing two dis
charge spouts, each of which may be provided
with a flexible tube 3I0 clamped thereto for die
recting the ashes to any suitable receptacle, such
as ash can 3I I (Fig.1).
A suitable arrangement is provided for driving
the coal feed screw 2I from shaft 89. In the
arrangement indicated shaft 89 extends through
a bearing in chamber 2!‘! and a bearing on a
bracket on burner body I50, and drives coal feed
screw 2| through a sprocket on shaft 89, sprocket
chain 240 and sprocket 239 mounted on shaft I60
to which the coal feed screw 2I is connected.
by a thermal element located suitably for prompt
and sensitive reaction to changes in the tem
perature of the ?re. There are extreme differ
ences in such temperature between periods of
maximum operation and the low ?re bed which
it is desirable to maintain under banking con
ditions when the effort is simply to maintain a
minimum heating as in domestic installations in
spring and fall.
Electrical control apparatus regulating the
operation of motor ‘I5 in connection with the
While ‘various proportions and designs may be
house thermostat system may have appropriate
employed in the different parts of the apparatus
thereof mounted as shown in control hous
disclosed herein, the proportions are of impor
ing I33 (Fig. 1) carried by a bracket on drive
tance in various parts, and particularly in the 15 casing
86. It has been found advantageous to
burner structure, the size and proportions of the
thermally responsive element of the
pot, retort, grate segments, ash slots in the spac
banking control apparatus in the combustion
ing thereof, having been determined after sub
chamber 34 I at a distance from the ?re su?icient
stantial experiment as adapted to most e?icient
permit the employment of a sensitive thermal
operation with coking bituminous coal; and the
which will operate accurately with slight
drawings herein are drawn to scale to show the
changes in temperature. For instance, such de
proper dimensional relationships between the
vice may be located upon or at the furnace door
various parts.
in suitable position .to be directly affect
A suitable electrical control arrangement is
ed by both radiation and convection from the
illustrated in Fig. 6, and may be of the type in
?re, without being in?uenced by various factors
which the motor ‘I5 is operated at full speed at
affecting temperature at other points in the fur- .
suitable intervals, though the invention is not
nace. Speci?cally, it has been found that the
necessarily restricted to a control of this type.
absorption and radiation of heat by portions of
Motor 15 is connected to the line 320 by motor
the furnace such as the water legs 22'! and 342,
the variations in draught due to dampers and
stack openings such as those shown at’ 343, and
other variations in draught and temperature con
itions seriously affect a sensitive thermal con
trol unit located in the furnace at points other
than the combustion chamber 3“.
In the form shown the thermal element com
overheating of the motor.
a bimetal coil 335 arranged to extend
The motor circuit 32I includes the upper con
through a suitable opening in the furnace door
tacts 326 of duplex relay 32'! whose coil 328 is
in line 323 passing through the secondary of 40 or other part of the furnace into position in the
combustion chamber 34! where there will be no
the low voltage transformer 339 whose primary is
obstructions between thermal coil 345 and the ?re
connected across the main line 325. The main
in retort I12.
secondary lead 329 carries the protective and
The thermal coil 3ll5is connected at its rear
control devices in the heat generating apparatus,
which in the present instance is illustrated by a ;. end to rotary switch rod 351. Switch arm 358
is centrally mounted on the end of rod 351
domestic hot water furnace 33I. Invthe form
and is provided at its lower end with a clip
illustrated the line 329 carries a high point out
the mercury type bank switch 353. The
out switch 332 operative to break the circuit when
mercury type out switch 35I is carried by av clip
the heating medium has reached a predetermined
which is preferably mounted on arm 353 by
temperature or pressure, and this line 329 also
means permitting the angular adjustment of
carries the banking control switch unit 333 here
switch 36I relative to switch 360.
inafter described. Line 3223 continues to the lower
Under certain circumstances, and particularly
contact 334 of a room thermostat 335 of the
when burning certain types of coal, gases may be
type which includes a bimetal strip 335 operative
when the room drops below the desired tem 55 forced back through the coal feed tube 22, and an
arrangement is provided for preventing the es
perature to close contacts 333 initially and after
cape of such gases. Such an arrangementmay
a further temperature drop to close the con
include a trap in which the gases will collect, and
nected upper contacts 331, thermostats of this
means for conducting the gases from the trap
type being well known.
The contacts 334 and 33? are connected ill to a suitable discharge. In the preferred arrange
ment the gases- are conveyed to the burner.
through strip 333 and holding circuit line 338
Owing to the relatively low velocity of such gases
with the lover contacts
of relay 32? which
it has been found that under certain conditions
connect with the main circuit 323. The upper
there is a tendency for ?ne solid particles to
room thermostat contacts 337 are connected
in the return pipe and eventually to
through shunt circuit line 343 with the line 329 I
clog the pipe. The preferred form therefore
at relay 327.
includes means for preventing such accumulation
The banking control switch unit 333 is pro
dust and the like, and for returning the gases
vided with two switches, a bank switch arranged
to the burner or elsewhere by positive means,
to start motor ‘I5 when additional fuel and air
such as a suitable supply of air, which may be
are required during banking periods, stopping
taken from the blower system.
motor 15 automatically after a suitable period;
An arrangement of this type is embodied in
and an out switch arranged to stop motor ‘I5
the preferred form illustrated herein, and is
automatically if its operation under control of
shown best in Fig. 4. It includes afresh air con
the bank switch does not result in a suitable
nection I35 with the outlet of blower ‘I8 con—
pickup of the ?re. These switches are operated
circuit 32I in which suitable motor protective de
vices are located, such as the overload cutout 322
and the thermal type cutout 323 which may in
clude a heating coil 324 and a bimetal strip 325
adjacent thereto. The thermal cutout 323 may
be mounted directly on the motor so that it may
be affected rapidly by all conditions which cause
nected by air pipe I36 and return bend I 37 with'
for only a short distance from the burner, an
jet nozzle I38 extending through a wall of the
arrangement which not only reduces to a mini
gas pocket I39 formed in the upper face of the
mum the power necessary for feeding at this
coal feed passage 13 in base 12. The fresh air
most exacting point, but which also is desirable
connection I35 thus utilizes a higher pressure
since a full feed tube 22 for a short distance
from the blower than can be found anywhere be
from the burner is serviceable in forcing the gases
yond the damper control. A gas return pipe hi0
to travel upwardly through the burner and not
extends through the other side of pocket 139 in
back through tube 22.
alinement with nozzle I38 and spaced therefrom
In burner retorts of the prior art di?iculties
by 'a distance suitable for obtaining an injector
been encountered because of the tendency
effect under the conditions of air pressure and
of the coal under certain conditions to burn down
dimensions employed in the arrangement. The
in the pot toward the feed screw, resulting in the
gas return pipe M0 is connected to the burner
formation of coke and clinkers which obstruct
unit C at the ash discharge pocket 216. Gas
the feed and burning of the coal and may result
pocket I39 is sealed by a removable cover Ml.
While the apparatus is adapted for use with 15 in breakage or stoppage of the mechanism. The
travel of the coal upwardly in the pot may like
various types of coal it has been particularly de
wise be obstructed by the formation of clinkers
signed to solve certain special problems encoun
and the like which adhere to the pot walls, and
tered in the burning of bituminous coal, which
by mechanical obstructions provided by the wall
has special characteristics affecting its collec
surfaces.’ In the present construction a retort
tion‘, transportation and combustion.
is provided in which the zone of active combus
tion is restricted to the upper portion, and which
extends downwardly for a suf?cient distance be
low the lowest point of air supply so that the
conditions. There is also secured a careful bal 25 fire will not reach the region where formation
of clinkers, coke and the like will interfere with
~ancing between the rate of coal feed, the rate of
the feed mechanism. Any clinker formation de
air supply and the combustion characteristics of
veloping will ‘be prevented from adhering to the
the coal, both as to the time required to burn to
pot by the smooth liner I54 but will be forced up
ash and the volatilization of combustible gases.
ward and broken up by the incoming coal.
The latter problem is especially important in the
Under full draught conditions the relation be
burning of" bituminous coal, and involves like
tween the coal feed and the rate of combustion
wise the formation of coke, which heretofore has
is such that the burning fuel over?ows gradually
been a source of serious di?iculty and obstruction
across the retort I72 and over grate segments
due to the tendency of’the coal to coke back into
I89, and may reach the Walls of the furnace.
the feed zone, interfering with the operation of
The relatively slight projection of the retort I12
the feed mechanism and frequently causing com~
above segments I89 facilitates the lateral flow,
plete stoppage ofv the machine. The design also
and is particularly advantageous in bituminous
contemplates the effect of oil which is frequently
coal combustion in which the incandescent coke
used for dust prevention.
is more or less ?uent, the arrangement permit
The rotating element I51 provided at the side
ting the formation of a relatively wide thin ?re
of the throat opposite to the discharge end of
which produces maximum efficiency, rather than
the coal feed tube serves to prevent the coal from
a high ?re above the retort. The rate of com
forming a packed mass at this point, and thereby
bustion will naturally increase with the spread
increasing notably the facility with which it may
be forced upwardly by the horizontal pressure of 45 ing of the ?re until it will equal the rate of coal
feed when the fire has reached its maximum area
the feed screw. In one sense it may be said that
at the walls of the furnace. The inner tuyere
this auxiliary screw increases the relative fluidity
openings I18 assure full combustion of gases
or ?owing qualities of coal at this point. In the
which pass upwardly from the coking zone and
preferred form the rotating element is in the
form of a' reverse screw exerting a counterbal 50 provide an adequate supply of air for full com
bustion, the outer tuyére openings in wall I75
ancing horizontal pressure on the coal discharged
assisting if necessary in the combustion of the
by the feed screw while likewise preventing the
portion of the fire outside of the retort H2. The
formation of a solidly packed mass of coal, the
spreading of the fire is facilitated by the unu
result being that the coal will travel upward as
gradually as may be desired without exerting any 55 sual power of the upward thrust of the coal,
which likewise serves to scour away any clinkers
pressure whatever on the surfaces opposite the
which may tend to form on and adhere to the
coal feed tube discharge. The reverse screw may
surface of the pot structure or retort I72.
be arranged to impel coal continuously away from
When the drive unit is cut off and the ?re op
the feed screw bearing, which may therefore be
of any desired type. The elimination of the 60 erates under banking conditions, the portion of
the burning coal beyond retort H2 will gradually
tendency to pack the fuel in throat l5! further
burn up, and if banking conditions are main
more permits the maintenance ofv fuel feed in
tained for a sufficient period, the fire area will
tube 221 at substantially less than the full ca
gradually contract toward retort I72. Eventu
pacity of the tube as already indicated, since sub
stantial. back pressure on the fuel at the burner 65 ally the ?re may contract to a zone in the upper
part of retort H2 limited in depth by the dis
owing to the resistance caused by forcing the
tance that air will penetrate from tuyére open
fuel'upward under previous conditions causes the
ings H8. This arrangement, limiting the bank
coal to back up along the feed screw; and even
tuyere to a zone at the top of the pot substan
if.’ feeding at less than coal tube capacity is at
tempted, substanti'al‘back‘ pressure at the ‘burner 70 tially spaced from the feed Worm 2 l , eliminates the
possibility of coking back under banked condi
and the resultant accumulation of coal in the
tions, a serious difficulty with prior arrangements.
tube "will'm'ake it impossible to operate the feed
Atthe same time a small zone of de?nitely burn
tube- zlipartially ‘?lled ’ at any point within asub
ing fuel is maintained so that when the drive
stantial' distance of the burner. With the con
‘struction illustratedhowever the feed tube is?lled 75 unit is again started and the coal feed is re
The burner unit C is particularly designed to
provide thoroughly efficient combustion both un
der active operating conditions during coal feed
and operation of the blower, and under banking
sumed, there will be no difficulty about kindling
moval mechanism abruptly after motor. ‘I5 is up
promptly the green coal that is more or less
to speed, exerting a sudden impulse that may be
valuable in dislodging a slight obstruction. The
apparatus is likewise arranged so that the motor
‘I5 will be stalled before breakage of any of the
abruptly forced upwardly in the pot I52.
When operating under banking conditions air
is drawn through the tuyere openings I18 by the
ordinary stack draught in a manner similar to
drive parts, allowing the electrical system to
the operation of hand-?red coal furnaces. This
throw out the motor circuit and take care of emer
is made possible by the action of stop arm 21‘!
gency conditions without damage to any part
which holds valve flap ZI'I open to the proper
of the machine.
extent, thereby permitting the maintenance of 10 The blower structure has been carefully ar
a minimum bed of burning material without risk
ranged to give rapid and accurate control of an
ing the extinguishing of such bed by insu?icient
adequate supply of air at all times without the
air, sudden in?ux of fuel or the burning out of
usual excessive intake noise.
accessible fuel by excessive draught.
The general operation of the electrical control
The arrangement likewise is adapted to mini 15 system will be understood from the speci?c de
mize the tendency to form coke in the lower por
scription. Assuming that the building is at or
tion of the pot where it might interfere with
above the desired temperature for which the room
screw 2| through the depth of the pot, the air
thermostat 335 is set, the motor 15 will be out
cooled walls and the double-wall construction.
of operation, since contacts 334 and 331 of ther
If however coke should form in throat I5I, it 20 mostat 335 will be open and relay 327 will con
would not wedge between the screw and the end
sequently be de-energized, opening the motor cir
of the feed passage, as in prior arrangements,
cuit at the upper contacts 326. When the ther
but would tend to be broken up by the rotary
mal element 336 contracts due to reduction in
action of the feed screw 2| and reverse screw
room temperature thermostat contacts 334 will
25 ?rst be closed; and continued reduction in tem
The rotary ash collecting unit is arranged to
perature will thereafter close contacts 331, com
remove accumulations of ashes with a minimum '
pleting the circuit between the line 329 and the
disturbance of the ?re bed. This operation is
shunt line 340, closing relay 327 and starting
facilitated by the smooth-surfaced grate seg
motor ‘l5. At the same time the contact 333 of
ments I89 and the intermittent shaking action 30 relay 321 will be closed; and as thermostat con
imparted thereto. The formation of the de
tacts 337 open when the room becomes warmer,
scribed type of ?re bed likewise facilitates the
motor ‘I5 will continue to operate since the sec
scouring of ?ne clinkers from the retort I12 and
ondary circuit through line 329 will be completed
their discharge on to segments I83, which may be
by the holding circuit line 338 until the room is
provided with slots suf?ciently large to receive '. warm enough to open thermostat contacts 335,
whereupon relay 32? is de-energized and motor
the small clinkers as formed and to maintain a
clean ?re even under conditions which operate
‘F5 will stop. A sudden excessive load on motor
the burner at infrequent intervals. The ashes
‘Iii-will open cutout 322, while heating of motor
are effectively sealed in the ash receptacle and
15 for any reason will operate thermal cutout 323,
readily discharged ‘from the burner in a manner
affording full protection to the motor. If the
already indicated.
temperature of the heating medium should reach
Any gas which is formed will normally be gen
a point beyond which it is dangerous to continue,
erated so high in the pot I52 that it will tend
the high point cutout 332 will operate to break
to flow upwardly and to be burned; but in case
the, main secondary circuit line 329, open relay
gas is forced back through coal feed tube 22 it
321 and stop motor ‘I5. It is noted that as soon
will be positively returned to the ash pocket ZIB
as the heating medium returns below the danger
by the action of jet nozzle I38, and will pass up;
point said circuit will be closed and the motor '
wardly to combustion past the grate segments
again started, assuming of course that the room
I89. This arrangement will also provide a slight
thermostat 335 is in appropriate position with
air feed outside of the retort I12 which will be 50 the contacts 334 and 331 closed.
operative to some extent when the blower ‘I8 is
The banking control unit 333 is arranged for
not running, since the natural flue draught of
operation at times when the room thermostat
the furnace will exert a certain suction effect on
335 is open; and such operation may be readily
the gas return pipe I40. This arrangement also
understood from Fig. 6. The thermal coil 345
prevents any tendency for dust to collect in the
will naturally expand and contract in accordance
gas return line.- It may be noted that when the
with the heat given o? by the ?re, thereby ro
valve ?ap 2l'I is allowed to fall upon its seat it
tating switch rod 35‘! and the switch structure
provides positive means for preventing gases
mounted thereon. The coil 345 is constructed and
from the combustion zone from returning
arranged so that the bank switch 360 will be ap
through the blower structure, if conditions should
propriately» positioned with the mercury out of
arise that demand such an arrangement.
contact with the terminals when the temperature
The operation of the arrangement for convey
in the chamber 3!“ is above a predetermined
ing the ashes to a suitable point of discharge
minimum banking temperature. /As the tem
will be apparent from the detailed description.
perature in said chamber approaches such bank
The construction is such that the ashes may be
ing temperature rod 35'! is rotated by thermo
discharged at any desired point, and are kept
stat 345 to turn the arm-carrying switches 36!)
completely housed in conveniently located con
and MI and swing switch 350 downwardly‘until
veying tubes.
the mercury ?ows to the contacts of both switches
The drive, operated by a single motor and com
when such banking minimum temperature is
pactly arranged, is constructed so that the blower
reached'thereby closing an auxiliary circuit in
may be operated without the coal feed, which
cluding conductor I26, switch 332, switch con
may at times permit operation by hand ?ring in
tacts 36%, 36L conductors 312, 340, coil 328 of re
cold Weather pending repairs to the coal feed
lay 321 and conductor 329. The resultant closing
mechanism. The clutch islikewise arranged to
of switch 360 completes a circuit through the
permit throwing in the coal feed and ash re- - banking shunt line 372 with the shunt circuit 340
ditions the natural draft draws air through the
partly open valve ?ap 21! and damper 264 into
the spaces around the retort and through tuyere
openings I18 together with some slight leakage
from the ?re will rotate the switch rod 351 in
from the coal tube through pipe 143 and open
the ‘opposite direction until the bank switch 363
ing 2E6 into the space below the grate. There
is turned oil by the flow of mercury from its ter
may also be some seepage of air through the
minals at the maximum banking temperature,
ash seals for the rotor ring I81 and ash table
thereby opening relay 321 and stopping motor
204. In this way the air supplied below the
315. It is noted that this operation is independ
ent of the thermostat 335, and is effective only :10 grates is negligible in amount, substantially the
entire supply being through the tuyere openings
when said thermostat is not closed.
of the retort both under running and banking
The arrangement consequently serves to main
tain a minimum banking ?re independently of
This is a division of our application Serial No.
the house temperature control without interfer
ing with the operation of such control and ef 15 161,494, ?led August 28, 1937, now Patent No.
2,306,189 of December 22, 1942,
fective when such control is not active. It per
We claim:
mits highly accurate and e?icient regulation of
1. A stoker combustion system comprising in
banking conditions, since it may be constructed
combination with a retort expanding and open
for any desired range of banking temperatures,
and the temperatures at which it operates may 20 ing upward, of means forming a combustion
chamber above said retort adapted to be sub
be readily adjusted by shifting arm 358. Further
jected to subatmospheric pressure by virtue of
more, it is located at a point where it is affected
the ?ue draft thereby effecting a natural draft
promptly and directly by very small changes in
of air into said chamber, means forming the bot
the banked ?re, and is sensitive to slight varia
tom of said chamber and sealing it against en
tions in temperature.
and‘through the out switch 3B|_ with the main
secondary line 329, energizing relay 321 and start
ing motor 15._ The resulting increase in heat
Out switch 36! is arranged and connected to
trance of air through the area around said retort
stop motor 15 if the ?re temperature should not
including a stationary annular ash member and
rise after the motor has been turned on by
a grate structure movable around a central axis
and comprising an annular upper grate sur
switch 36!]. If the temperature in combustion
chamber 34! drops to a predetermined extent be 30 rounding the upper portion of said retort and a
lower aSh table overlying said member, said over
low the minimum banking temperature, switch
lying table cooperating with the overlaid part of
rod 351 will continue to rotate and tilt banking
said member to form an air seal, means for sup
switch 36l until at a predetermined temperature
the mercury will ?ow away from the contacts
of switch 36l, breaking the circuit between bank
plying coal to said retort and forcing it upward
ly therethrough, and means for supplying air
under pressure to the upper portion of the coal
switch 360 and line 329 and opening relay 321.
column in said retort, said means comprising a
This arrangement is utilized to provide man
ual regulation of the coal feed and forced draught
during starting of the ?re. This is accomplished
by pressing the button 3'“, closing contacts 368
and 363, short-circuiting the out switch 361 and
blower operable to supply air above atmospheric
pressure and an air supply ori?ce for passing air
40 to said upper portion of said coal column under
starting motor 15, which runs as long as button
37! is pressed. If the ?re ignites properly the
heat will promptly affect thermal element 345,
which may be so sensitive that even very slight
heat from the ?re will be sufficient to close out
switch 36l and permit release of button 31!. In
igniting, bituminous coal ?res this period is ex
tremely short, and may be two minutes or less,
since the unit 333 preferably operates at very low -~.
temperatures and thereby reduces to an absolute
minimum the amount of coal burnt during non
heating bank periods.
The operation of control unit 333 cooperates
with the setting of the main air damper 264, .~
which controls the forced draught, and the set
ting of valve ?ap 2'“, which controls the nat
ural draught; since it is possible by employing a
sensitive control directly responsive to changes
in a very low ?re, with an air regulating means
especially suited for the maintenance of the ?re
steadily at such low point, combined with a
predetermined conditions of banking aircontrol
when said blower is inoperative and the combus
tion chamber is under pressure below atmos
2. A stoker combustion system as set forth in
claim 1 in which the retort and the grate struc
ture have cooperating parts for trapping an ac
cumulation of ashes and thereby forming an in
ner air seal.
3. A stoker combustion system as set forth in
claim 1 in which the stationary ash member
is annularly spaced from the outer surface of
the retort so as to leave an air space therebe
4. Stoker apparatus as set forth in claim 1
having an ash removing conveyor and means
cooperating with the air sealing means to form
a substantially air tight enclosure beneath the
grate for receiving the ashes sifting through the
grate and conveying such ashes to and discharg
ing them into the ash removing conveyor and for
substantially preventing the passage of air from
the furnace room to the furnace combustion
forced draught regulation which appropriately
zone by way of the furnace ash pit and the grate,
builds up such small ?re properly in a brief time,
to provide a novel and highly ef?oient banking 65 thereby providing ash collection and removal
while preserving the action of the banking air
control when the blower is not in operation.
The air supply for the ?re is intended to come
5. Stoker apparatus as set forth in claim 1
mainly from the tuyere openings of the retort
having ash collecting and removing means in
ring 115, and this supply serves in addition to
cluding an annular ash receiver positioned under
maintain a proper cooling of the retort. Under
the grate and rotatably supported upon the re
running conditions substantially all of the air
tort, an ash removal conveyor and means for
from the fan passes through the air spaces
rotating the ash receiver to transfer the ashes
around the retort tending to cool it and prevent
thereon to the entrance end of the ash removal
overheating and improper coking and clogging
conveyor, with the air sealing means of the bank
of the rising column of coal. Under banking con
ing air control including means forming an in
ner ash air seal between the ash receiver and
the retort, an annular closure means closing the
fecting a natural draft of air thereinto, means
forming the bottom of said chamber compris
ing an annular grate below the top level of said
retort and having an inner edge overlapping
said central structure and forming an ash seal
therewith against the entrance of air to the com
bustion space, an ash ring carrying said grate and
providing a lower ash seal substantially shutting
space between the furnace Walls and the grate
and having an extension projecting downward
below the grate, and means forming an outer ash
air seal between the closure extension and the ash
receiver, both such ash air seals substantially
limiting the leakage of air from the furnace room
to the furnace combustion zone by way of the 10 off the air flow to the space below said grate '
around said ash ring, means for supply coal to
clearances around the ash receiver incident to
said retort and forcing it upward therethrough,
supporting the ash receiver for rotation.
an air conduit for supplying air to the upper
6. A stoker combustion system comprising in
‘ portion of the coal column in said retort under
combination with a central structure having a
retort expanding and opening upward, of means 15 said natural draft and a blower adapted to force
forming a combustion chamber above said re
tort adapted to be subjected to subatmospheric
pressure by virtue of the ?ue draft thereby ef
air through said conduit at pressure above at
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