US1795945A - Furnace cycle control - Google Patents

Description

H. s. GANO 1,795,945

FURNACE CYCLE CONTROL Filed Nv. 50, 1926 5 Sheets-Sheet l March 10, 1931.

A@ v mm INVENTOR f l q ATTORNEY 1n n Hor/670 5 Gana.

WITNEssEs; M7 ffm/w March 10, 1931. H. s GAN@ 1,795,945

FURNAOE CYCLE CONTROL I Filed Nov. 30, 1926 3 Sheets-Sheet 2 Q y@ /Var/a/J 5 6000. f/m/' y* ATTORNEY I 5 sheets-sheet 3 Filed Nov,

LME

INVENTOR /Vdr/a/v 60H0- ATTO'RNEY WITNESSES:

yf/227@ *Y Patented Mar. 19, 1931 HABLAN S. GANO, OF MANSFIELD, OI-10, ASSIGNOR TO VESINGI-IOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA FUR-NACE CYCLE CONTROL Application filed November' 30, v1926. Serial No. 151,694.

My invention relates to furnace cycle control systems and particularly to electrical control systems for rotary furnaces.

e An object of my invention is to provide an eiiicient cycle control system for a furnace.

Another object of my invention is to provide an automatic control system' for an intermittently operating rotary furnace.

Another object of my'invention is to provide electric means for chronometrically controlling the operation of a conveyer and of Va hea th-tray dumping mechanism in a furnace. n

Another object of my invention is to pro- Y vide means vfor preventing simultaneous operation of a conveyer and of a tilting mechanism. y

Another objectzoff my invention is to provide an automatically-actuated mechanism for operating the charging door of a furnace.

Another object of my invention is vto provide a control system for a plural-hearth-tray rotary furnace, in which means operatively associated with the rotary hearth cle-energizes a hearth turning motor, which, in turn, cnergizes a 'tray-tilting motor, re-energizes the hearth-turning motor and then cle-energizes its own circuit, this cycle being continuted indefinitely. Y

Another object of my invention is to provide manual control means for a furnace that shall operate independently of the automatic control.

` Other objects of my invention will be apparent from the disclosure.

" In practisingmy inventionin accordance with thel present embodiment, l provide separate electric motors for driving theconveyer and the hearth-tray dumping mechanism, respectively. Since these motors are intended to operate alternately, interlociing means are provided to prevent both motors operating at the ysame time.

Chronometric means is provided Vfor controlling the operation of these motors. Such means is started byv means controlled by the conveyer. The chronometric means periodically and alternately causes the energization of the conveyer-driving motor and of the tilting motor. The deenergization of the conrchamberl 15 therein. y are yprovided for supporting the furnace.

Vey-er motor and of the tilting motor iscaused by means controlled by the conveyer and the tilting mechanism, respectively. The chron-r ometric means is self-stopping.

Pneumatic means is provided for opening the charging door. Such means is automatically governed by means controlled by thel conveyer. i i

Manually operable means are provided for controlling the operation of the conveyer, the tilting mechanism and the charging door, independently of the automatic control means.

ln the drawings,

Figure 1 is a view, in vertical section, of a furnace to which my control system is applied. y

2 is a view, in vertical section, of onehalf of the furnace, showing the chargingdoor mechanism, V'

Fig. 3 is adiagram of the wiring of the control system, Y

F ig. 4L is a detail diagrammatic view of a modification of the. timing drum, and

`F ig. 5 is a vieW, in'vertical section and on an enlarged scale, of a door-actuating means.

Referring to the drawing for a more de- V tailed description of my invention, a furnace 19, shown in Figs. 1 and 2, comprises an outer cylindrical casing 12, an inner cylindrical casing 13 and an annular refractory heat and electric-insulating` lining 14 within the casings, the lining 14 having an annular Suitable supports 16 Suitable heating means is provided and, in the present embodiment of my invention,- such heating means comprises electric heating elements 18 positioned in the chamber 15 and secured to the chamber walls. rllhese heating elementsare connected to` a source of energy (not shown). i

Any annularpassage or run-way 20 is providedin the bottom of the furnace,the top thereof communicating with the annular ehamberl.v An annular conveyor 22 comprises a refractory insulating. portion 28 and a metallic bottom portion 24 and is of such dimensions Vas to permit of rotation in thel i annular passage 20. The bottom portion 24' is provided with a plurality of pairs of spaced "itegral depending lugs or fiange members 25, wheels 27 beingv suitably mounted between the ings of each pair. rEhese wheels run on a circular traclr 28, thus providing a means for rotatably supporting the conveyer 22. Suitable concentric sand seals 29 are provided to prever o loss by reason of convection currents of air through the spaces between the walls of runway and the conveyor 22.

Means are provided for driving the conveyer to cause it to rotate and, in the present embodiment, such means comprises a circular rach 8O that may be integral with the bottom portion 2e and is adapted to mesh with a bevel gear 8l that is keyed on one end of a shaft 82, which is rotatably mounted on a support it. bevel gear is lreyed to the other end of the shaft 82 and engages a bevel gear 85 lreyed on the lower end of a shaft 36 that extends vertic ily through the central portion of the furnace and is rotatably mounted in bearings 37 and 88.

The shaft 86 is held in place, at its upper end, by any suitable means, uch as a collar 39. A bevel gear wheel d() is rigidly secured to the upper end of the shaft and engages a bevel gear pinion el that is rigidly secured to a shaft 4:2 of a speed-reducing device comprising a worm gear in a casing 43 and a worm actuated by an electric motor ed. TheV motor may be designated the conveyor-driving motor or the hearth-motor.

A plurality of hearth supports e5 are rigidly mounted at equal intervals on the top of the refractory insulating portion 28 of the conveyor 22. A material-receiving hearth tray e7 is pivotally secured, at its outer end, to each hearth support normally in the position shown by the full lines (Figs. The hearth tra-ys e7 are open at their outer ends for a purpose hereinafter to be made clear. rIhe inner ends of trays e7 extend beyond the hearth support e5 to permit engagement with means for periodically effecting the discharge of material from the hearth tray.

Such means, in the present embodiment of my invention, consists of a tilting mechanism comprising a vertical shaft slidably positioned in a passageway 5l and having a projection 52 that extends under the inner ofr a hearth tray when the tray is opposite a discharge outlet 54 and above a quench tanlr 55. A connecting rod 56 operatively connects the shaft 50 with a gear Wheel rlhe gear wheel 58 is operatively connected, through a speed reducing device 59, to a prime mover 60, that may be an electric niotor. The gear wheel 58 engages a gear wheel 62 that has a substantially circular cam 63 associated therewith and driven thereby for a 'purpose hereinafter to be made clear. The diameter of gear wheel 62 is the same as that of gear wheel 58 so that they will operate at the same number of revolutions per minute.

A sand seal 65 is provided to prevent heat loss upwardly through the passageway 5l.

A charging door 67 is provided to normally closea charging opening 68, (see Fie. 2). rlhe charging opening is preferably positioned close to the discharge outlet to permit the charging ofa hearth tray that has been dumped there being one tray between tiem. This is to provide a space between the outlet and the charging opening. A charging platformV 69 may be provided, if desired, in order to facilitate the charging of the successive trays.

Means are provided to automatically operate the door 67. Such means comprises, in the present embodiment of my invention, a pneumatically operated piston 70 (see Fig. 2) slidably tting in a cylinder 72 and connected to one end of a piston rod 7 3 the other end of which is operatively connected to the charging' door 67 by means of a cable 7 4; passing over a pulley 75. The Weight of the door 67 is such that it will normally remain in its closed position andwill hold the piston 70 near the outer end of the cylinder 72.

One end of a pipe 77 is connected to the outer end of the cylinder 70 and the other end thereof is connected to a chamber 78 of an air-valve housing 79 (see Figs. 2 and 5). The housing 79 comprises the' central chamber 78, and upper chamber 80, a lower chamber 8l and partitions 82 and 83 that have valve seats 84 and 85, respectively, therein. f

A valvev 86 is maintained normally seated on the valve seat 85 by means of a compression spring 87 located in the lower chamber 8l. The valve 86 is secured to a valve rod 89. Spaced from the valve 86 and also secured to the valve rod 89 is a valve 90 that is adapted to seat on the valve seat 8st but is normally maintained in an open position by the spring 87.

Normally, the lowerv chamber 8l is not in communication with the chamber 78 While the chamber 8O is in communicationtherewith. The chamber is provided with an outlet 91 that leads to the outside atmosphere. an inlet pipe 92 that is connected to a source of compressed air (not shown).

Means for automatically operating the valve rod 89 comprises a core member 93 (see Figs. l and of an electromagnet that is rigidly secured to the valve rod 89, a coil 9e for energizing said core member and means for energizing the solenoid to be hereinafter described lt will 'be obvious from the foregoing, that, when the coil 9e is energized, the valve rod 89 will be moved downwardly to seat the valve 90 and to unseat the valve 86, and compressed air will iow from pipe 92 into cham- The chamber 8l is provided with l ber 81'through the open seat 85 into the chamber 7 8 and the conduit 77` and into the outer end portion of the cylinder 72, and will operate the piston 70 against the weight of the door 67 and cause an .upward movement of the door.

lt will also be apparent from the drawing` and the foregoing description that, when the motor le is operating, the ccnveyer 22 will be driven to cause the hearth trays l? to progress through the chamber lt will also be apparent that, when the motor 60 is operated, the gear 58 will turn and the connecting rod 56, which is operatively secured thereto, will move the shaft 50 iirst upwardly and then downwardly. ln moving upwardly, the shaft 50 will cause the projection 52`to engage Vthe hearth tray i7 that is oppoy site to the discharge outlet 511, and the tray will thereby be tilted to cause the heattreated articles located thereon to tall through the discharge outlet 511 into the quench tanlr 55 that is preferably lilled with oilto a level above the lower endvof the discharge spout 541 yand thus provide an oil seal for the discharge opening.

l provide control means for causing the periodical operation of the hearth conveyor,

of the tilting mechanism and of the chargingv door mechanism. Preferably, inthis type oi furnace, the conveyer is stationary while the tilting mechanism is operating, and vice versa. f 4

Fig. 3 shows one embodiment of my control system for periodically eilecting the a`oovenoted operations, in proper sequence. ln addition to the motors ,All and and the door operating air cylinder 7 9, a timing-device driving motor 101 is connected to a contact drum 102 through a variable-speed reduction device 103, the latter being shown schematically in the drawing, as it forms no. essential part of my present invention. rEhe device 103 may be of any suitable type purchasable in the market and effective to vary the rotating speed of the drum 102 within relatively wide and adjustable limits. The'dru'm is shown in Fig. 3 in a developed condition; that is, all of the peripheral surface oit the drum is shownras located in one plane, order to illustrate more clearl'I he shape ci a conduct- .ing plate 1011 secured to the surface thereof.

he plate 104 comprises tour integral portions 105, 106, 107, and 108, located in longitudinally spaced relation on the drum and all voi substantially the same width. Portion 105 extends entirely around the periphery oi" the drum, and is engaged by a fixed contact brush 109. Portion 106 is shor er in the peripheral direction so that its peripheral extent is less than 3600 and is engaged by a brush 111. Portion 107 is relatively short peripherally and is engaged by a brush 112, :he portion being so located perinherally, that it is engaged by the brush very shortly after turning movement of the drum 102 has been started. Portion 108 is also relatively short peripherally and is so located as to be engaged by a brush 113 when the drum has been turned through almost 360o. The laxial width of' the vwhich will be hereinafter described indetail.

llfhen the switch 114 is in the position shown in Fig. 3, the control system is connected for automatic operation, but it may be controlled manually when the switch blades are thrown to the opposite position, as will be hereinafter described more in detail.

The motor actuates intermittently a switch lever 113 that is pivotally mounted on a suitable lined member, (not shown), by

means oi spaced lugs 119 secured to a portion ot the rotating hearth, as is shown more parel'tl 11l'lld ti`t ticularry in nie lower y,eitian perdon o. lho. 1 of the drawing. The lever switch 113 c D has its or roller end maintained in yielding engagementwith a portion of the sand seal, hereinbet'ore described, by a'suitable spring. The illustration of this device in Tig. 3 ot the drawings is schematic only. The number of lugs 119 is equal to the number et heartn trays 17. The outer or contact end of the lever 118 normally engages a iixed contact member 121 but is disengaged therefrom and caused to a second contact member 122 when the inner end of the lever is engaged by one of the lugs 119. The peripheral width of the respective lugs 119 is such that th lover 118 engages contact member 1221er a very short time only, this time being that when one tray has arrived in a position for unloading material located thereon and when, simultaneously, the second preceding tray is in position for reloading. No mounting means lier .contact members 121 and V122 is shown in either ll 1 or Fig. y3 of the drawings, as any support suitable for the purpose may be employed.

'The motor 60 actuates a cam 63 having a single relatively narrow depression in its peripheral surface, which surface is engaged by the inner or roller'ends ot two switch levers 123 and 124, which are pivotally mounted on suitable means, not shown, intermediate their ends. rllhe outer ends oi the respective contact levers cooperate with substantially lined contact members 125 and 126. rllhe lever 123 normally in engagement with its cooperating contact member 125 and disengagement therebetween is effected ronly when the roller end thereo drops into the single recess inthe cam surface. r"the lever 124 is normally out et engagement with the contact member 126 llo 611101301' 142. Reeys designe-ted by numerals 145 and 147 ae evelead lelays, the cells 01 v1 leb me Connected 111 che eSpeCmv-e motel' only when 111e crcts etwee bhe circuit beekere and the ,I atm @011e en espeebve m01' re, *ehe COTS U z thereby being 'tl-:mfesed the Seule errent Clli 44 or t1 e motor 60 soeve', so tfzuf'erses them and the 'elaye 147 N111 open the lough 'the 180 and e i eaung eirf-md heeby e bhe motroie th 0, coi

1 ich 118, ceechczors 14,1

r- A v l, budgmg 141, conductor 146, endgeonduete i d be deszgneea e beek #le other aum ry the peedle heel nd 117119111111211111- e ufHy-eonbreled che, door Ugemtng The e ebenen paie 104, herein- -reut,a.nd these ,1V1111e1 11er beeesebed befere described a eceied en drum 11A detail. 102, is eenneeed y-crcu; conductor on C11-enden Switch 1431 'f iet@ 11" ",conduet0f148, i member of relay Contact and bdgng memb' 147, conucte 146, bz 111g m mbel' o-relay relay 145 esse 145, onde/ter 144, @Rc1 Switch 143,150 supply dueto? 146,0011'f1ae idg-lng circuit conducto-f 141. This eeut may be en over10ed relay n b1 A y desgeeed, im? future leference, as a i3 44, eeudueor 1--1-Q 1 b1ae 11Ty reime Circuit.

tor 140,0011d1e" The timing-1110101" holding circuit eommembe1 121, C020 1 pllees conducto? 142, pmt c- Conductor 157, blade 115, conde ter 1 e011 15S e011 ef e1ay 158, condueor 165, bnf-.sb 111, breaker 134, 0011111911 1 1v 5, back portions 106 and 105 of plete 104 and brush ""5 member 139, eonduetos 15G and 109 to line 141 by the above-describedreturn circuit which serves to maintain the coil of relay 158 energized after the timing-motor starting circuit has been opened by disengagement ofswitch 118l from contact inember 122. f l

` The tilting-motor starting circuit comprises conductor 157 connected to supply-circuit conductor 142, conductor 156, baci; bridg' The tilting-motor holding circuit com` prises conductor 157 connectedl to supply-circuit conductor 142, part of conductor 156, back bridging member 188, conductor 166, coil 187, conductor 167, blade 116, conductor 168, contact member 125, lever arm 123, associated with motor 60, conductors 171, 172, 151, and 149, blade 117, conductor 148, bridging member of relay 147, conductor 146, bridging member of coil 145, conductor 144 and through switch 148, to supply-circuit conductor 141. Theclosing of this circuit ensures energization of the tilting-motor independently of the drum. l,

The periodic hearth-motor starting circuit comprises conductor 157 connected to supplycircui't conductor 142, conductor 156, bridging member 139, conductor 155, coil 186, conductor 154, blade 115 and conductors 153 and 178 to brush 113, through portions 108 and 105 to brush l109 and from thereback to the other supply-circuit conductor 141 by, JShe above-described return circuit?7 s f The automaticallycontrolled chargingdoor operating circuitcomprises a part of conductor 157 connected to supply-circuit conductor 142, conductors 186 and 185, a normally closed push-button switch 184, conductor 183, the coil of a relay 177, conductor 182,

Vcontact member 126, arm 124,'conductors 17,1,

172, 151 and 149,7blade 117, lconductor 148, bridging member of relay 147, conductor 146, bridging member of relay 145, conductor 144 'and switch- 148 to supply-circuit conductor 141.

AThe air-valvesolenoid energizing circuit comprises conductor 141, switch 148, conductor 144, bridging member of relay 145, conductor 146, bridging member of relay 147, conductor 148, blade 117 conductor 149, 174 and 175, Contact members and the lower bridgingy member 176 of relay 17 7 conductor 178, coil 94 of the air-fvalve device, conductors 179 and 186 and, through a part of conductor 157, to supply-circuit'conductor 142.

The air-valve-solenoid holding circuit comprises conductor 141, switch 148, conductor 144, bridging member of relay 145, conductor 1,46, bridging member of relay 147, conduct@ 148,-blade 117 conductors 149, 174 and 17 5 bridging member 181 of relay 17 7 conductor 182, coil of relayy l177, conductor 188,V pushbutton switchf184, conductors 185 yand 186 anda part of Conductor 157 to supply-circuit conductor 142.

As has been noted hereinbefore, the system will operate automatically only so long as switch 114 is inthe position shown in Fig. 8 of the drawings.y When it is desired,vfor any reason,`toY control the respective devices manually, the switch blades are thrown to the left andA cer-tain circuits may be energized as will be hereinafter setforth.k

r1`hehearth-motor inching circuit comprises conductor 142, conductors 157 and 156, bridg.

ing member189, conductor 155, coil oiAA relay 186, conductor 154, blade 115, conductor 187l vto a normally open push-button switch 188, conductor 189, yconnected to one of the terminals of switch 188,. conductor 148, bridging member ofrelay 147 ,conductor 14.6, bridging member oi@A relay 145, conductor 144 and, through switch 143 to supplyeeircuit conductor141. rlihis circuit is, of course, energized'only when switch 188 is held in its closed position, and if switch 114 is thrown to its eft-hand position.

rllhe tilting-motor Y prises conductor 142, conductor 157 apart inching circuit comof conductor 156, to the back bridging mem- Y ber 188, conductor 166, coil 187, conductor 167 to blade y116, conductor 191 to one-terminal of a normally/)open push-button switch 192, conductor 189y which is connected also to one terminal 4of switch 192, conductor 148, bridging member of relay 147, conductor 146, bridging member of relay 145, conductor 144 and through switch 143, to conductor 141. This circuit is energized only so long as switch 192 is held'closedby an operator, andwhen the switch 114 has been thrown to its left-hand position. y

A manually-controllable chargingdoor energizing circuit comprises conductor 141, switch 148, conductor-144, bridging member of relay 145, conductor 146, bridging member of relay 147 f,y conductor 148, blade 117 con-k the positions shown in Fig. 8 of the drawings, and when the switch 143 (which is shown in its open position but which will remain in either its open @rits closed position afterv having once been moved thereto and until again manually actuated to its other position) is closed, the main hearth-motor starting circuit will be closed, thus energizing coil 136, whereby the breaker 134 is closed, the motor 44 is energized and will actuate the hearth as hereinbeore described.

The motor 44 will drive conveyer 22 until a tray filled with the heat-treated material arrives opposite to the discharge outlet, at which time the roller end of switch lever 118 will be engaged by a lug 119. as shown in Fig'. 1 of the drawings, and will be thrown to a position opposite to that shown in Fig. 3. In this position of the switch lever, the timing- 'motor starting circuit will be closed, thus energizing coil 158, closing the circuit through the timing motor by the bridging members 161 and 162.

The timing motor being thus started will, in turn, cause the drum 102 to rotate, and the rotation thereof will cause the engagement of brushes 111 112 with the conducting surfaces 106 and 107, respectively` .shortly after the drum has begun to turn.

When the stationary contact member 111 enga ges the portion 106.v the ti ming-motor-holding-circuit will be closed. through the coil of relav 158. to maintain the relay in its closed position independently of the initial energizing circuit closed by the switch 118, as previously described.

Since the switch 118 is in a position opposite to that shown -in Fig. 3. the main hearthmotor starting circuit will be opened, relay 136 will be deenergized and breaker 134 will be in its open position so that motor 44 will be deenergized and the conveyer 22 will be stationary.

When stationary contact member 112 engages the portion 107 of the conducting surface 104, it is evident that the tilting-motor starting circuit will be closed, and coil 137 will be energized, thus effecting closing of circuit breaker 135, whereby tilting-motor 60 is energized and causes an upward and then a downward movement of the tilting means actuated by the motor 50, as has been Ahereinbefore described.

As the gear wheel 62 is in engagement Awith the gear wneel 58, it will be rotated when the tilting' motor 60 is started. The cam 63, associated with the gear wheel, is adapted to normally maintain switch lever 123 closed, that is, the outer contact end thereof engages the contact member 125.

When switch 123 isclosed, it will close the tilting-motor holding circuit, thus maintaining a. circuit ythrough coil 137 so that breaker 135, which controls the circuit of motor 60, will be maintained in its closed position after brush 112 is disengaged from the contact portion 107, by the rotation of drum 102. When the gear wheels 58 and 62 have Vcompleted a one-halt` revolution, the recess in cam 63 will be engaged by the normally open switch 124 so that this switch can engage contact member 126. Y A

The momentary engagement of switch lever 124 with the fixed contact member 126 closes the automatically-controlled chargingdoor operating circuit and will thus energize solenoid 17 7, this action occurring when the hearth tray being dumped is in its highest raised position. The energization of the coil of relay 177 closes the air-valve-solenoid energizing circuit, so that coil 94- is energized and core member 93 and the valve stem and t-he valves operatively connected therewith are in their lowered positions, unseating valve 86 and sea-ting valve 90, so that compressed air may flow into chamber 78 from conduit 92 and into the pipe 77 to operate the door-raising device. rEhe charging door 67 is thus raised to permit of charging the second tray ahead of the tray being dumped. The door will be held open for apredetermined period sutlicient for charging purposes. by the interlock member 181 maintaining the energizing circuit of the coil of rei av 177.-

Vhen the switch 124 has its roller end in engagement with the recess in cam 63. it will be closed, whereby the circuit through relay 177 is closed. The air-valve coil 94 will, therefore, be maintained in an energized condition until this circuit is interrupted'momentarily by push-button switch 184. This deenergizes the coil of relay 177 and, therefore` interrupts the circuit through coil 94. The spring- 87, associated'with the valve stem, will again move the air valve into the position shown, for instance. in Fig. 5 of the drawings. In this position. the supply of compressed air to cylinder 72 is shut oil| and permits the door 67 to move piston 70, forcing the air from cylinder 72 past valve 90 to the outside air, whereby door 67V will be closed. n i

When gear wheels 58 and 62 have made one complete revolution, and the hearth trav has been restored to its initial position.` switch 123 will again engage the recess in cam 63 that it will be opened., thus opening the tilting-motor holding circuit and deenergizing coil 137, thus causing breaker 135 to open, whereby the motor 60 is deenergized and the tiltingmechanism is stopped. l

Shortly after this, the contact member 113 ot the timing-motor device will engage portion 108 of contact surfaces 104 because of the continued rotation of drum 102. This engagement closes the periodic hearth-motor starting circuit, and coil 136 will be energized, which will cause the closing of breaker 134, so that hearth motor 44 is energized to restart the conveyor 22. Rotation of the conveyer will eiiect the disengagement of switch 118-with lug 119, thus permitting switch 118 CII Y 158 to open, wherebythe timing-motor energizing circuit is opened, and the timingdevice drive motor is stopped.

Since the timing motor 101 may be a synchronous motor, it is obvious that the timing motor and the drum switch 102 may operate as a chronometric controlling device to time the opera-tion of the conveyor, the tilting mechanism and the charging-door mechanism. Since the motor 101 is connectedto the drum through la variable-speed mechanism, the speed of rotation of the drum 102 may be varied within relatively wide limits.

rlhe above described cycle of operations will be continued indefinitely in the same sequence, so long as the supply circuitis energized and no change in connections is made.

If it is desired to make repairs to the conveyor or to the tilting mechanism, switch 114 is thrown to a position opposite to that shown in Fig. 3, which permits the closing either of the hearth-motor inchiiig circuit or the tilting-motor inching circuit by means of push- buttons 188 or 192, respectively.

If push-button 188 is held closed by the operator, coil 136 is energized, and breaker 134 will bev closed, thus causing the energization and operation of motor 44 and conveycr 22. The push-button may be held closed for a time necessary to bring the conveyor to the desired position. ln like manner, the tilting mechanism may be caused to operate by closing push-button switch 192 holding it closed for such length of time as will cause the members to move into the desired positions.

The normally open push-button vswitch 192 may be closed to cause the opening of charging door 67 by energizing the manually-controlled charging-door operating circuit, and particularly of coil 94 When this push-biitton is released it will again open the circuit, permitting the valvesA lto again move to the position shown in 5er' they drawings, so that the door 67 .is again closed, as was described above.

Bridging members 138 and 139 and their cooperating Contact members provide electric interlocking means for preventing simultaneous operation of the tilting motor and of the hearth motor. that bridging member 139 is open when molt will be notedv tor 60 is operating, because ofV the closing of the main contacts, as hereinbei'iore described,

while bridging member 138 will be disengaged from its Contact members when the motor 44 isv energized by closing breaker 134. rlhe vcircuitthrough coil 137 cr coil 136 being interrupted, will prevent energization of the corresponding motor.

A modii'ied iorm of lectric-connecting surfaces on the drum 102 to be operated by motor 101 is shown in Fig. 4 of the drawings. The drum is here provided with substantially'the same electric-conducting surta- ces 105, 106, 107v and 108, as hereinbeiiore described to cooperate with stationary contact members 109,111, 112 and 113, and, in addition thereto, a contact `portion 201 and a cooperating brush or contact member 202 are provided. The portion 201 is located in substantially the same peripheral position as is portion 107. When this form of electric-conducting surface is used, conductor 182 is electrically connected to brush 202 in-v stead o to lever 124, so that, when brush 202 engages lsuritace 201,-the following circuit 1T:

is established:

From conductor 141, through switch 143,

conductor 144, through the bridging members ofrelays 145 and 147 connected by con- 'ductor 146, conductor 148, blade 117, conductor 149, partv of conductor 151, conductor 104, the electric-conducting surfaces on drum 102, portion 201, brush V.202, conductor 182, coil or relay 177, conductor 183, switch 184, ccnductors'185 and 186 and part of conductor 157, to supply-circuit conductor 142. This energizes relay 177 so kthat this relay will opcrate to energize coil 94 and cause door 67 to open. r1`he v:air-valve holding circuit for the above-described circuit will be established automatically, as was hereinbefore set forth.

instead of employing an air valve 79 for operating the door, an electric motor may be utilized, the energizing circuit of which may be controlled in the same manner and by t1 same circuits as have been already described.

The energized condition of the hearthmoving motor circuit may be indicated by a visual signal 203 which is connected to contact member 113 of the timing device and t0 supply-circuit conductor 142, and it will therefore, be energized as long as the hearthmotor circuit is closed.

Merely by vway of example and to indicate the times of Aoperations of the respective devices, it may be noted that the operating time oi" the hearth motor in moving the hearth overa peripheral distance equal to the distance between the successive hearth trays is on the order. oit 20 seconds, while thetime during which the hearth-moving motor is deenergized may be varied from less than one minute to four or live minutes. Ahearth tray is tilted during this time, and the second preceding hearth is reloaded, both of these operations usually inquiring less than the four oi' live minutes mentioned` above. HOW- evef, this time is necessary oidei to insure that Jdie i" erial being` heat tient-ed sliall remain in el s uiinece chamber a piepei lengtli tim be properly tie-ated.

d, l may omit the tilting;v motor, case, tlie material will be iaked :em the ,ys man: elly by an oiieiatoi". 10 Vani-.ous moe lifications may be made in the systen'i and "evices embodying' my invention without depeieing tiom the sjeiiit and scege tlieieot., and l cesiie that only such limitatiene eliall lie placed theieen as are imposed by the pile? art ei aie set oitli in the appended claim.

l claim es my invention:

The combination with a fuinace, of a conveyei, an electiic motor for driving seid conveyei, a plurality of hearth-trays pivotally mounted on said conveyer, mechanism ter tilting said lieaitli-tiays te successively diseliaige mateiial therefrom, a oi diiving said tilting mechanism, a p an" of noimally open ciicnit interrupters for controlling the operation of the cenveyerdiving metoi and the tilting meter, respectively, electiomagnets fer operating `said circuit inteiruptei's, a netay drum switcli toi controlling the circuits of said electomagnets, a synchronous meter foi" clnonometiically driving said drum switch, a ielay for contiolling said synclnenous meter, and means controlled by said eenveyei for initially energizing said' ielay., ln testimony whereof, l have hereunto subscribed my name this 17 day of Novembei,

HABLAN S. GANO.

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