US2116322A - Furnace - Google Patents

Description

May 3, 1938. A; c. MUiR ET AL .2,116,322

FURNACE Filed Aug. 29, 193e,

4 Sheets-Sheet 1 Patented May 3, 1938 FURNACE Andrew C. Muir, Lansdowne, and William C.

Griffiths, Narberth, Pa.

Application August Z9, 1936, Serial No. 98,570

Claims.

which is at once easy and inexpensive to manufacture and well suited to the needs of service.

A further purpose is to provide a reciprocating grate with major and minor air passages, to by pass the grate and to close the major air passages when the grate is bypassed.

A further purpose is to control the pressure drop through a fuel bed, and thereby the rate of fuel combustion, by suitable back and forth shiftings of a grate supporting the fuel.

-A further purpose is to determine the high and low combustion rates of a thermostatically controlled furnace by thermostatically shifting the vfuel bed, to close and open respectively a space beyond the grate which connects the fire chamber to the ash chamber.

A further purpose is to aid the delivery of ashes out of a' fuel bed into an. ash compartment by back and forth shiftings of a grate supporting the fuel bed to positions that respectively determine high and low rates of combustion.

A further purpose is to operate a stoker and the back and forth shifting of a grate by thermostatically controlled common mechanism using successive shiftings of the grate to successively increase and check the rate of heat development and the corresponding retracting and feeding strokes of the Stoker to 'add fuel to the furnace` with each checking of the furnace.

A further purpose is to operate the stoker at time intervals while the thermostat is in the more heat position. i

A further purpose is to provide novel, effective and inexpensive mechanism respectively for supporting a bed of burning fuel and for adding fresh' fuel, preferably each timethe furnace is put on high heating, and during high heating.

Further purposes will appear in the specification and in the claims. ,y We have elected to show one only of the differ- V ent forms of our invention, selecting a form however that is practical and eicent in operation and which well illustrates the principles involved.

Figure 1 is a vertical section to illustrate a desirable embodiment of the invention as applied to a domestic heater. In its more broad features the heater illustrationis'intended for a conventional illustration of any heater `to which the invention may be applied. The grate is in the 5 draft bypass position in Figure 1. i

Figure 1a. is Va diagrammatic view of the electric circuit. I

Figure 2 is a horizontal section of Figure 1, taken upon the line 2-2 thereof and to enlarged 10 scale. Y

Figures 3 and 4 are Ydetail sections of Figure 2, upon the lines 3--3 and 4--4 thereof respectively, to show supporting mechanismof the furnace floor, as well as draft bypass.

Figure 5 is a left side el 4vation of Figure 1. omitting motor and thermostatic control equipment shown in Figure 1.

Figure 6 is a broken vertical sectioncorresponding to a portionof Figure 1 but with the 20 hopper structureof Figure 1 not shown in Figure 6, the hopper having been wheeled aside for hand firing. The grate is in the high combustion position in Figure 6.

Figure 7 is a left side elevation of Figure 6.

Like numerals refer to like parts in all figures.

Describing in illustration and not in limita.- ton and referring to the drawings:-

Our invention relates toheaters of the type used for domestic heating and for industrial installations, burning solid fuel such as anthracite coal, bituminous coal; coke, petroleum coke, etc; The problem of' controlling the combustion in such heaters has received extensive attention and has been solved in the main by the use of various doors, dampers,'etc., the correct use of which is an art only imperfectly understood by the ordinary householder.

By our invention it is possible to greatly simplify the control of domestic heaters operating 40 on natural draft or on mechanical draft. The entire control of the heater is accomplished by changing the position of the grate, and only grate positions corresponding with high heating or checking of the re aie necessary. 'The di- 45 culty of prior art shiftable grate constructions, that the grate air passages necessary when the fire is on high heating proves to be excessive when the fire is checked, has been corrected by employing major and minor grate air passages, bypassing the grate air passages by a passage of relatively zero air friction compared to the' grate air passages when the fire'is checked, and concurrently closing the major but not the minor grate' air passages, and leaving the major and preferably some of the minor grate air passages open when the re is on high heating.

A furnace IIJ is shown as a water heater type, with ash and re compartments I I and I2 and the hot gases escaping to a chimney I3 by flue passages I4 to 20. 3The butterfly damper 2| is indi,- cated as being open, and the damper door 22 as being closed, since neither the butterfly damper nor the damper door is used in control of the furnace in accord nce with our invention and they are illustrate; merely for completeness. A water space 23 surrounds the ue passages except at doorways 25, 26 and 21 for poking, charging and clean out, respectively. Doorway 24 in the base is provided for ash removal.

A composite floor 28, separating the ash and re compartments, and replacing any hitherto usual grate mechanism, is supported preferably on several posts 29 and 30 in the, ash pit, near opposite sides of the front and rear thereof, respectively.v 'I'he posts 23 and 38 are preferably flanged at 28' and 30. The composite floor, usually preferably horizontal, comprises a movable grate 3| and a stationary centrally open framelike member 32 which peripherally fits the interior of the 'furnace and at the front 33 and opposite sides 34 of its central opening overlaps the front and sides-respectively of the grate 3|.

In its rearward position the gra-te, except for its own ai'r passages, closes the entire opening of the stationary member 33, the rearward edge 35 of the grate then registering against the forwardly presented rear wall 33 of the opening as shown in-Figure 6.

In its forward position, as in Figure 1, the grate leaves an opening 31 back of the grate and in front of the wall 33, which opening 31 will then effectively check' the lire, since it reduces substantially to zero the difference in pressure between the ash and fire compartments and therefore the fall in pressure through the fuel bed.

We provide the grate with major and minor air' passages 38 and 33,l respectively, in alternate laterally spaced transverse rows, with the maior passages 38 for use when the grate is rearward and therefore in its high heating position.. with the opening 31 closed, and the minor es 33 for use when the grate is forward and therefore in its low heating or nre checking position. 'Ihis is accomplished by means of stationary closure strips 40 under and transversely across the grate and fastening at their ends to grate-side-sulde portions 4I of the stationary member 32. The

minor air passages are preferably tapered with variant with quite widely the smaller opening at the top as shown so that ash entering them will readily drop through.

The strips 48 are located to close the'rows of maior air passages 38 when the. grate is in its forward position as shown in Figure 1. The air passages are uncovered when the grate is moved back to its rearward position. Obviously the bm form and spacing and number for the air passages 33 will be quite widely different fuels and free-burning will require than will be furnaces so that smaller sizes of or non-coking. coals, for example,

most suitable for larger fuel. y

We prefer to provide the movable grate with roller support. suitably on casters supported in bearings 42 secured to the under-structure by bolts 43 carrying spacing washers 44. l

Rear side rollers 45 are supported upon a `cross connection. suitably a pipe 43 between the posts 33; forward side rollers 41 are supported upon a cross connection 48 between the posts 29; and front rollers 48 are supported upon branch members 58 from the cross members 48. The cross connections 48 and 48, and side connections 5I, are integrated into a strong structure by ttings 52 which form parts of the posts 29 and 30.

'Ihe grate is shiftable back and forth, respectively, back into its high heating position and forward into its low heating or checking position, by any suitable means, such as hand manipulation or back and forth movements of a rocker shaft 53, crank 54 thereon and link 55 connecting the crank to a and rigidly fastened to the grate 3l. The rocker shaft 53 is pivotally supported on posts 51.

The operation oi the grate may be purely manual and non-automatic. For automatic operation, if such be desired, we provide thermostatically controlled means for operating the rocker shaft 53 and therefore for positioning the grate for high or low heating according to the need or lack of need for high heating.

As illustrated in Figures 1a and l, a thermostat 58 controls the operation of a reduction gear motor unit 53, connecting rod GI, has at 62 a lost motion operative connection with an arm 63 fastened to the rocker shaft 53. A stop switch 64, suitably operatively connectd to the shaft 53, as by a spring full-stroke connection 53', stops the motor at the completion of each shift movement.

In the diagrammaticl electric connections of Figure 1a, the thermostat 58 and the stop switch arm 84', pivoted at 842. connect to the motor terminals by conductors I5 and B6, suitably in series with a current source 81. A thermostat contact 63, with which connection is made when more heat is demanded, is connected by leads 68 and 63 with the contact 883 of switch 64, and a thermostat contact 69 with which connection is made when less heat is demanded, is connected by lead 83 with contact 382 of switch 64. An aquastat switch 10 operatively connected to the water temperature of the heater breaks connection between the more heat" wires 88', Gliz if or when the water temperature of the heater reaches any selected high linut, at the same time connecting the conductors 35 and 63 to effect a "less heat shift of the grate if ever or whenever the water temperature reaches this selected high limit.

We add fuel to the furnace at least once for each back and forth shifting cycle of the grate, preferably adding this charge of fresh fuel each time the grate moves rearward into its position for high combustion, since in this position the grate has 'progressed the fuel bed toward the rearward end of the grate, leaving space at the V"forward'end for fresh fuel.

In order to provide for the supply of successive increments of fuel in case the thermostat remains in the more heat position for a substantial period of time, it has been found desirable to operate the stoker at predetermined time intervals while the thermostat continues to demand more heat. In Figure la. a time switch 1I is shown having a rotatable switch arm 1I' driven in one direction by a time clock 12. The switch arm 'Il' passes over any suitable number of contacts 1I?, 1I. '|I4, 1I. 1I, 'II'l which are suitably connected through switches 13', 132, 133, 134, 13', 13 to a lead 14 extending to the lead 65. A lead 15 likewise extends from the switch arm 1 I to the lead 33'. Any of the contacts 1|2 to 1V' may be rendered ineffective by opening the corresponding switch 13' to 13.

yoke 56 extending downward fromwhich, through a crank 60 and As illustrated Va hopper `16 is removably mounted to present the open end 11 of its delivery `livery mechanism per at the sides spout 18 into an opening 19 cut in the furnace charging door 80, an auxiliary door 8| normally closing the opening 19 when the hopper is out of its operating position in front of the furnace. As illustrated, the auxiliary door 8| has alternative lug supports at 82 and 83, respectively, on the charging door and on the furnace wall above the charging door.

vThe hopper 16 is mounted on means of suitable frame structure 85. The deincludes a' movable stoking plate. 86 that in effect forms a bottom of the hopper shaping toward the furnace. The stoking plate is preferably roller supported, as at 81, and is shifted from the rocker shaft 53 that shifts the grate, preferably toward the furnace each time the grate is shifted rearward into its more heat position and away from the furnace each time the grate is shifted to its less heat position.

A vertically adjustable gate 88 in the delivery spout extending downwardly fromithe roof thereof enables the operator to properly relate the fuel feed to the rate of combustion within the furnace. i

The operating mechanism between the rocker shaft 53 and the stoking plate 86, as shown, includes a rocker shaft 89 plvotally supported at 90 on the frame structure 85, having crank and link connection at 9| and 92 with a downward lug 93 from Ithe stoking plate 86, and having crank and link connection at 94 and 95v with a crank 96 upon the rocker shaft 53. 'I'he rocker shaft 53 is thus a common shifter for the grate 3| and for the stoking plate 86.

We preferably provide a catch compartment 91 below the stoking plate, to catch fuel dust and fuel particles that may escape from the hopand forward end of the shifting stoking plate. ment 91 far enough at 98 to inclose the end 99 of the stoking plate when the plate is retracted to its furthermost position.

A bottom slide |00 of the catch compartment permits an easy periodic cleaning out of the compartment. For -easy assembly and disassembly, each of the links 55, and 92 mayhave hook connection with eitheror both of the cranks driving it and the member that it in turn drives.

The distance of the shifting movements of the grate 3| and of the stoking plate 86 may be adjusted together by adjusting the lost motion lat one or both of the stops 62, to adjust the reciprocating action Vof the rocker shaft 53, and, if desired, either the grate or the stoking plate may be adjusted separately by an adjustment of the effective length of one or more of the appropriate cranks 54, 9|,'94 or 96, as indicated at |0| for the crank 94. The effective length of the link 95 may be adjusted at |0| for any effective length of the crank 94.

' hand firing or When it is desired to move the hopper assembly away from before the furnace, as for continuous for an initial building of a fire, Aor to fill the' hopper at the coal bin, the link 95 is disconnected from the crank 94, as by unhooking, and any blocking of the wheels 84 is removed,

after which the hopper assembly will readily wheel away. If desired the hopper may be entirely omitted.

It will be seen that when the hopper assembly -is in place before the furnace, it seals therewith at a gasket |02. suitably of asbestos, compressed wheels s4 bv' We extend the catch compartair around the fuel bedis now closed.

v 3 between the furnace `door and a peripheral shoulder |03 of the hopper spout 18.

While the contour of the burning fuel bed will vary quite widely with different fuel characteristics as well as with different operatingl conditions that will make essential different adjustments at the gate 88, a typical contour may be about as indicated by the line |04, Figure 1;

The manual operation of the device is vvery simple when the hopper 16 is not used. Any suitable solid fuel such as hard or soft coal, coke or petroleum coke of any one of the commercial sizes burned in domestic heaters is chargedfrom time to time at the upper end of the fuel bed |04. As long as it is desired to check the fire, the grate 3| remains in its forward position as shown in Figure I. The air then passes almost entirely through the bypass opening 31 between the end of the grate and the edge 36 of the rear plate. 'I'he closure strips 40 prevent substantial flow of air through the major grate air passages 39, thus avoiding the diliicultyl that substantial flow of air will take place through the grate and cause burning up of the relatively thin end |04 of the fuel bed when the fire is intended to be checked. Substantially the only air passing through thefuel bed when the lre is checked is that passing through the minor ,grate air passages 39 and causing very gradual combustion at the relatively thin end |04' of the fuel bed.

If now' it be desired to obtain high heating from the fire, grate 3| may be slid manually to its rearward position as shown in Figure 6, thereby uncovering the major grate air passages 38 (and incidentally obstructing some of the minor grate air'passages 39 which are relatively unimportant at this time). Air passing from the ash chamber to the )combustion chamber must now pass through the major grate air passages 38 and such of the minor grate air passages 39 as remain open, thus causing vigorous combustion, as the opening 31 which formerly bypassed the 'tity of ash at the rearmost end of the grate drops into the ash pit, where it 'can be removed manually or mechanically asdesired, in any well known manner.

'It will be noted that the buttery damper 2|, damper door 22 and the various -furnace doors have no function whatever in the control of the fire, which is controlled wholly by movement of the grate to one or the other of its limiting positions. The doorway 24 is continuously open, and the doorways 25 and 26 are continuously closed except for the charging opening in the doorway 26 which will normally be connected with the hopper. It is intended to maintain the hopper sufficiently full of fuel so that air will not enter shifted the grate to its forward position as seen in Figure 1, let' us assume that the thermostat 58 demands more heat, thus moving to a position touching contact 68. This completes a circuit from the source 61 through the lead 66, the motor, the lead 65, the thermostat 58, the lead 68', the aquastat contacts, the lead 68, the switch contact 683, the switch arm 64' in the position shown in Figure 1, and the lead 66.

'I'he motor starts up, moving the crank 60 clockwise for example for a half revolution, and thus carrying the connecting rod 6|, the crank 63, the rocker 53, the crank 54, the link 55, the lug 56 and the grate 3| to the position of Figure 6. Actually the connecting rod 6| moves much farther than the link 55, but the overtravel is taken care of by the lost motion connection 62 which is adjusted so that the latter part of the stroke of the connecting rod 6| will be operative to move the grate.

'I'he motion of rocker shaft 53 as it travels beyond its intermediate position will move full stroke device 53' and throw switch arm 64' to a position against switch contact 692, thus breaking the motor circuit and causing the motor to stop. By selection of a motor and gear reduction having sufcient friction, it is possible tomake the motor stop reliably at the half circumference, although if desired a spring detent |05 may be made to engage in one of the slots |86 of the crank disc to limit the stroke to a half revolution. The contact between the switch arm 64' and the contact 692 is at thispoint ineiective to re-start the motor because the thermostat is presumably still demanding more heat.

At the same time that the rocker shaft 53 turns to shift the grate 3| to its rearward position, it likewise moves the stoker plate 86 to its feeding position by imparting motion to the crank 96, link 95, crank 94, rocker shaft 89, crank 9|, link 92 and lug 93.

Unless the time switch 1| closes the circuit between the leads 65 and 69', the stoker plate and grate remain in the position indicated until the ythermostat 58 demands less heat and thus completes the motor circuit from the source 61 through lead 66, the motor, lead'65, contact 69, lead 69', contact 692, switch arm 64 and lead 66, thus causing the motor to travel another half revolution in the same direction and move the grate and stoker plate from the position of Figure 6 back to the position of Figure 1, concurrently dropping oil ash from the end oi' the grate and retracting the stoker plate.

Assuming that the thermostat is in the "more heat position and has shifted the grate to the corresponding position as shown in Figure 6, and assuming that the climatic condition is such that more heat" is demanded for a substantial period of time,.the time switch arm 1|' will after a predetermined time interval touch one of the contacts 1|2 to 1|? whose corresponding switch 13 to. 13 is closed, thus completing the circuit between the leads 65 and 69', and operating the motor to move the grate into the less heat position as shown in Figure 1, to charge the stoker plate and to move the switch arm 64' Figure 1a.

If during the interval of shifting of the gate Y to the position of l currrently operate the Stoker plate to feed a charge of fuel to the fire. This series of operations will be repeated while the thermostat demands more heat, as long and as often as the time switch arm 1|' touches a contact 1|2 to 1| 7 whose corresponding switch 13 to 136 is closed.

In this way it is possible to provide repeated charges of fuel during the period that the thermostat is demanding more heat Without any shift in the thermostat position. The number of charges of fuel supplied in a given time may be varied by changing the size of the contacts 1|z to 1|'I and by opening and closing the switches 13' to 13.

The fresh charges of fuel are successively carried rearward along the grate by the successive rearward movements of heating position. l

An important feature of the invention is the use of major grate air passages when the fire is on high heating and the closure of the major grate air passages when the grate air passages are bypassed and the re is checked.

Since the invention is intended particularly to apply to domestic heaters, it will be evident that it affords a very convenient means of controlling such heaters, dispensing with the numerous dampers and checks which have previously been used.

In view of our invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled inthe art to obtain part or all of the benefits of our invention without copying the structure shown, and we, therefore, claim all such in so far as they fall within the reasonable spirit and scope of our invention.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A furnace having fire and ash compartments and a composite grate between the compartments comprising relatively movable members, said grate having openings at intervals which are open in one position of the members for passing air through the fuel bed and having a by-pass opening which is open in another position of the members for by-passing air around the fuel bed,-

normally supporting the main body of the fuel,.

and structure sealing 4against the back edge of the grate in the back position thereof and leaving a byrpass opening between lthe' structure and the grate in the forward position thereof and sealing the side and forward portions of the grate in both positions thereof and thermostatically controlled means for shifting the grate back and forth to determine respectively high and low rates of combustion, said thermostatic means holding the grate in its', forward position as long as combustion is to' proceed at a low rate, and holding the grate in its back position as long as combustion is to proceed at a high rate. .Y

- 3 A heater burning solid fuel including a grate the grate to its high.

having major and minor air passages, the grate being supported to reciprocate between limiting positions, there being a. bypass air opening around an edge of the grate when the grate is in a limiting position corresponding with checking of the re and closure strips cooperating with the major air passages to restrict them when the grae is in the checking position, the -minor air openings being open when the grate is in the checking position and the closure strips permitting the major grate openings to open when the grate is in the position for high heating and the bypass opening is closed.

4. Afurnace burning solid fuel including agrate having sets of major and minor air passages,`

rollers beneath and supporting the grate, walls ylimiting the movement of the grate between a high heating and a checking position, closure strips cooperating with the major air passages in the checking position and uncovering the minor air openings in this position, there being a bypass air opening behind the grate in the checking position, and the closure strips uncovering the major air openings in the high heating position.

5. A furnace having fire and ash compartments and a composite floor between the compartments comprising a grate shiftable back 'and forth and for normally supporting the main body of the fuel, and structure sealing against the back edge of the grate in the back position thereof and sealing the side and forward; portions of the grate'in both positions thereof., the grate having major air passages and minor air passages, closures under the grate registering with the major air passages in one limiting position of the grate and uncoveringthe said majorair passages in another limiting position and thermostatically 'controlled I means for shifting the grate back and forth between its limiting positions which correspond with high and low rates of combustion.`

6. A heater burning solid fuel, including combustion and ash chambers, and including a grate having air passages and supported for movement between two limiting positions, provided at its rearward end with a by-pass opening between the combustion and the ash chamber to discharge ash and by-pass air when the grate is in its forward position, there being an opening for introduction of fuel at a substantial height above the grate at the forward end, thereby producing ari inclined fuel bed from the opening to the rear end of. the grate, a thermostat having a position demanding more heat and a position demanding less heat, means operating when the thermostat is in the position demanding more heat for moving the grate to the rearward position to direct the draft through the air passages into the fuel l bed and means operating when the thermostat is in the position demanding less heat for reciprocating the grate to its forward position to divert the draft through the by-pass opening. '7. A furnace having iire and ash compartments and a composite grate between the compartments comprising relatively movable members, said grate lhaving openings at intervals which are open in one position of the members for passing .air through the fuel bed and having a by-pass opening which is open in another position of the members for by-passing air around the fuel bed,` and thermostatically controlled means having .a position demanding less heat and a position demanding more heat for relatively shifting the said members back and forth,

v progressing the fuel bed'toward the bil-pass openand not through the fuel bed when said means demands less heat and passing the air through the fuel bed when said means demands more heat, and for delivering additional fuel into the furnace.

8. 4A furnace having fire and ash'compartments and a composite floor between the compartments comprising a grate shiftable back and forth'and normally supporting the main body of the fuel, and structure sealing against the back edge of the grate in the back position thereof and sealing the side and forward portions of the grate in both positions thereof but leaving a by-pass opening at the back edge of the grate when it is in its forward position, and thermostatically controlled means for shifting the grate back and forth, progressing the fuel bed toward the by-` pass opening, passing the air through the by-pass opening and not through the fuel bed when the thermo'static means demands less heatand passing the air through the fuel bed when the thermostatlc means demands more heat, and means for delivering additional fuel into the furnace.

9. A heater burning solid fuel on natural draft, including a substantially horizontal grate having air passages through the grate, means for supporting, guiding and reciprocating the grate, there beinga by-pass opening open-behindthe grate at one limiting `position and'closed by the grate in the other limiting position, there being considerable air ow through the passages in the grate and through the fuel bed in the high heatingv position and there being bypassing of air through the by-pass opening in the checking position, a Stoker devicecharging fuel labove the forward end of the grate, a thermostat having a position demanding less heat and a positiondemanding more heat, 'means operatively connecting' the thermostat, the grate and the stoker for moving the grate into the forward position, discharging ash through the by-pass opening and bypassing the draft around the fuel bed and retracting the stoker when the thermostat demands less heat` and means operatively connecting the thermostat, the grate and the stoker for moving the grate into the high heating position and operating the stoker to introduce a charge of fuel when the thermostat demands more heat.

10. A heater burning solid fuel, including cornlbustion and ash chambers, a grate having major and minor air passages, supports for the grate permitting the grate to reciprocate between linuting positions, structure surrounding and sealing against air flow between the ash and combustion chambers around the grate except for a by-pass air space left between the combustion chamber and the ash chamber in one limiting position, closures obstructing the major air passages when the by-pass air space is open, in the other limiting position the by-pass air space being closed and the major grate air passages being open, electric circuits respectively demanding more heat and less heat, a thermostat which selectively comchanical connections from the motor to the switch arm for throwing the switch arm to the other circuit when the motor is operating in one circuit.

.tive to divert air from 11. A heater burning solid fuel, including combustion and ash chambers, a grate having major and minor air passages and supporting a fuel bed, supports for the grate permitting the grate to reciprocate between limiting positions, structure surrounding and sealing against air flow between the ash and combustion chambers around the grate except for a by-pass vair space left between the combustion chamber and the ash chamber in one limiting position, closures obstructing the major air passages when the bypass air space is open, in the other-limiting position the by-pass air space beingl closed and the major grate air passages being open, electric circuits respectively demanding more heat and less heat, a thermostat which selectively completes the electric circuit demanding more heat or the electric circuit demanding less heat, an electric motor connected selectively in one or the other of said electric circuits by the thermostat, a switch having a switch arm which is connected alternately in one or the other of said electric circuits, mechanical connections from the motor to the grate for reciprocating the grate and mechanical connections from the motor to the switch arm throwing the switch arm to the other circuit when the motor is caused to operate in one circuit, a stoker having a stoker plate and mechani-` cal connections between the motor and the stoker plate moving the stoker plate toward the fuel b'ed when the thermostat demands more heat and away from the fuel bed when the thermostat demands less heat.

12. A furnace having fire and ash compartments and a composite floor between the com- -partments comprising a grate having air openings and which is shiftable back and forth and normally supports the main body of the fuel, and sealing structure overlapping the sides and front of the grate, open intermediate the overlapping portions and at the back edge of its opening adaptedr to seal against the back of the grate when the grate is in its rearward position and to leave a. by-pass opening when the grate is in its forward position, and means for shifting the grate between its back and forth positions to render the by-pass opening effective or ineffective to divert air from passing through the open- 'ings into the fuel bed.

13. A'furnace having fire and ash compartments and a composite `floor between the compartments comprising a grate shiftableback and forth and normally supporting the main body oi' the fuel and sealingl structure overlapping 4the sides and front of the grate, open intermediate the overlapping portions and at the back edge of its opening adapted to seal against the back of the grate when the grate isin its rearwardr position and to leave a by-pass opening when the grate is in its forward position, the grate havlngunder the opening of said structure laterally spaced rows of major air passages, laterally spaced strips under the ister with the rows of, and close the majorr air passages when the grate is in its forward position and the by-pass is open and means for shifting the grate between its back and forth positions to render the by-pass opening effective or ineffecpassing through the openings into the fuel bed..n

14.\A furnace having re and ash compartments and a composite door vbetween the compartments comprising a grate shiftable back and t forth for normally supporting the main body of the fuel and sealingstructure overlapping the grate and located to regminor air passagesvintermediate the said rows.,

laterally spaced strips under the grate located to register across the major air passages when the grate is in its forward position and the bypass is open and across certain of the minor air passages when the grate is in its rearward position and means for shifting the grate between its back and forth positions to render the bypass opening effective or ineffective to divert air from passing through the openings into the fuel bed.

l5. A furnace having re and ash compartments and a composite floor between the compartments comprising a grate having air openings shiftable back and forth and normally supporting the main body of the fuel and structure overlapping the sides and front of the grate, open intermediate the overlapping portions and at the back edge of its opening adapted to seal against the back of the grate when the grate ls in its rearward position and to .leave a by-pass opening when the grate is in its forward position, a floorsupport within the ash compartment and including posts under the stucture at portions thereof laterally beyond the grate, rollers beneath the grate and cross connections between the posts' to determine whether or not the by-pass openingl is effective to divert air from passing through the fuel bed.

16. A furnace having ire and ash compartments and a composite grate between the compartments comprising relatively movable members, said grate having openingsA at intervals which are open in one position of .the members for passing air through the fuel bed and having a by-pass opening which is open in another posi- ,tion of the members for by-passing air around the fuel, bed, and means having a position demanding less heat and a position demanding more heat for relatively shifting the said members, progressing the fuel bed toward the bypass opening, passing the air through the by? mechanism operatively connecting one of thel members and the motor and an operative connection between the motor and stop switch.

17. A heater, a furnace for the heater andA having flre and ash compartments and a composite grate between the compartments comprising relatively movable members, said grate having openings at intervals which are open in one position of the members for passing air through the fuel bed and having a by-pass opening which is open in another position ofthe members for by-passing air around the fuel bed, and means having a position demanding less heat and a position demanding more heat for'relatively shifting theA said members, progressing the fuel bed`to- Ward the by-pass opening, passing thev air through aliases bed when said means demands less heat and n passing the air through the fuel bed when said means demands more heat and said means including a motor, a source of current, a stop switch, a thermostatic three-way switch, two way more heat, and less heat" conductors between the switches, an aquastat switch connected nor-- mally to close the more heat conductor and at abnormally. high temperature of the water to open the said more hea conductor while connecting the less hea conductor to the thermovstatic switch, a circuit including the source, the

switches and the motor, mechanism operatively connecting one ofthe members and the motor f and an operative connection between the motor and the stop switch. 18. A furnace having fire and ash compartments, a movable grate therebetween supporting the main bed of burning fuel, mechanism forv shifting the grate to and from its backward and forward positions, structure relatively sealing the compartments along the sides and front of the grate when the grate is either forward or back and along the back of the grate when the grate is in its rearward position and leaving a by-pass opening back of the grate between the compartments when the grate is ln its forward position, a fuel hopperand spout having delivery into the furnace above the forward portion of the grate, having a oor of the hopper overlapping the floor of the spout, a downwardly adjustable gate in the spout, mechanism for shifting the hopper floor toward and away from the furnace and thermostatically controlled common means operating the said mechanisms with demand for more heat at the thermostat to shift the furnace grate back and the hopper floor toward the furnace and with demand for less heat at the,V thermostat to shift the furnace grate forward and the hopper floor away from the furnace.

19. A furnace including a movable grate which has openings for air passing through the fuel bed in its high heating position and opens a by-pass for the air in its fire checking position, in combination with a stoker operatively connected with the furnace, a thermostat having a more heat and a less heat position, means for shifting the grate to the high heating position when the thermostat demands more heat, means effective while the thermostat demands more heat for opierating the stoker at timed intervalsto supply fuel to the me and means for moving the grate Itoits fire checkingposition to divert the draft through the by-pass opening when the thermostat demands less heat.

20. A furnace including a movable grate which has openings for air passing through the fuel bed inr its .high heating position and opens a by-pass for the air in its re checking position, a stoker operatively connected to the furnace, a thermostat having a more heat and a less'heat position, means operated by the Stoker for concurrently moving the grate to its high heating position and moving the stoker to its position for charging fuel on the fire when the thermostat demands more heat, means operative at timed intervals while the thermostat is demanding more heat to concurrently move the grate to its fire checkinglpositicn to divert the draft through the by-pass andthe stoker to its retracted position and then to vconcurrently move the grate to its ANDREW CQMUIR.

WILLIAM c. GRIFFITHS.

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