Патент USA US2127445код для вставки
Aug. 16, v1938. 2,127,445 R. MIHARDGROVE CONTROL MECHANISM FOR FURNACES Filed March‘ 12, 1955 FLOW RESPONS/VE 2 Sheets-Sheet l INVENTOR Ralph M. Hardgrove. BY » m’zmw/éd. ATT NEY ‘Aug. 16, 1938. R. M. HARDGROVE 2,127,445 CONTROL MECHANISM FOR FURNACES Filed March 12, 1935 2 Sheets-Sheet 2 RESPONSIVE w 3 QF/G. 3 24 PMmywm PM L az 7 mp Em mHRm VH/NMJ (W ATT mm m EY 2,127,445 Patented Aug. ' 116, 1938 r UNITED STATES PATENT. OFFICE-i CONTROL MECHANISM Fort FURNACES ‘ Ralph M. Hardgrove, West?eld, N. J., assignor to Bailey Meter Company, a corporation of Dela ware Application March 12, 1935, Serial No. 10.667 4 Claims. (01. mas-2s) ' Another object of the invention is to provide In connection with the operation of furnaces and especially furnaces utilizing fuels burned in suspension, such as oil, gas, or pulverized fuel, in connection with a furnace having .a plurality of fuel burners an interlocking arrangement such the danger exists that in kindling a. ?re an‘ ex-‘ 5 ploslon may occur if, at the timeof lighting, an that the ignitingmeans will be effective for each and. every burner at which the fuel supply is available to obviate the possibility that‘ the ignit explosive mixture of fuel and air is in the furnace. To avoid this it is the practice in kindling a ?re ing means might function in front of a burner in a furnace to ?rst thoroughly purge or‘scavenge at which fuel is not available, while another the furnace by effecting a flow of air through burner some distance away was feeding fuel to 10 it. This may be done by natural draft or by the furnace but the igniting means for» that‘ starting up one of the draft fans, usually the in burner was‘ not effective, thus resulting in a duced draft fan, and operating it for a length loading of the furnace with a mixture which eventually might become ignited with disastrous of time sufhciently to thoroughly purge or scav 15 enge the furnace, after which the fan may or may not be stopped as found desirable and the fire lighted. 20, 1933, I have disclosed and claimed a method ' and apparatus of control mechanism for a fur-‘ 20 nace whereby it is not possible for an operator to supply fuel to a furnace and kindle a ?re therein without having ?rst scavenged the fur nace and whereby if having scavenged'the fur nace .he delays kindling the ?re until‘ the air 25 flow through the furnace decreases below a cer tain value, then he mustagain scavenge the furnace in order that he may supply fuel there to’. By this arrangement there is avoided the possibility that the operator may scavenge the 30 furnace, delay kindling the ?re until the scav enging may have become ineffective, and then kindle the ?re without properly again scaveng ing the furnace. ‘ l 35 in connection with a- furnace a‘fuel supplying means, a fuel igniting means, and a control means able through a burner its fuel igniting means is made operative. ‘ ‘ A-still further object is that the main fuel supply to all of the burners of a boiler closes upon the failure of air flow through the furnace below a predetermined value, or upon failure of ?ame within the furnace. ' Still another object is‘ an interlock arrange mentresponsive not only to the rate of air ?ow through the furnace but also to the rate of supply of fuel to the furnace. Still further objects will become apparent from a study of the drawings and speci?cations‘ relating thereto. 30 For a consideration of what I believe to be novel and my invention, attention is directed to thereto. . vIn the drawings: 35 Fig. 1 is a diagrammatic view of a furnace _ whereby‘ the fuel supplying means and the fuel provided with control mechanism embodying my igniting ‘ means cannot be rendered operative invention. until a predetermined ?ow of air obtains in the Fig. 2 is a diagrammatic view of a plurality of burners and control therefor, similar to'the 40 furnace,’ the arrangement preferably being such that, the fuel supplying means cannot be oper ated until after the fuel igniting means has been started._ H , , < l ‘ . Modern furnaces, and particularly boiler' fur naces, maybe equipped with a large number of ‘ burner and control arrangement of Fig. 1.‘ ‘ Fig. 3 illustrates diagrammatically a further embodiment of the invention applied to a plu rality of burners. ‘ , Fig. 4; diagrammatically illustrates a still furf 45 separate burners for pulverized fuel, oil or gas, ther embodiment of the invention in connection and in some cases, there maybe as high as with ‘a plurality of burners. Referring ?rst to Fig. l, 1 indicate‘ therein a. ' furnace ‘l which may be of any suitable type, twenty or thirty such burners for an individual furnace. The kindling or lighting off of such a furnace presents a problem to the solution of which the method and means of the present in but shown in the present instance as being a fur vention cated at t. are directed. ‘ ' , ‘ - ‘ One object of my invention‘is to provide an improved construction, and arrangement of con-‘ in C? _ ‘the following speci?cations and claims appended 7 My prior patent is further directed to provide if ‘ , A further object is to provide an interlocking arrangement such that if and when fuel is avail In my prior Patent No. 1,914,949, granted June 40 effects. trol mechanism for a furnace whereby the fuel 50 nace for heating a boiler having boiler tubes indi ‘ ‘ ‘ “ At 3 is indicated a fuel supply for the furnace and in the‘ present instance‘ represents a gas supply line from which a maincontrol valve t igniting means cannot be ‘made operative until a for the boiler 'l controls the supply of gaseous predetermined ‘flow of scavenging ' air ,_;e_xists ‘xfl'lel to a‘ header'?common to all'of the burners through the furnace and whereby thefuelwqfe‘ed-ly I,‘ supplying the boiler l. The fuel supply, orvgas ing means preferably cannot be operated until . 6 the fuel igniting means have been‘ started,“ , line‘ 3, islt‘o be taken asltypical .of any suitable ‘means for supplyingfu‘el to a furnace‘ and may co ‘ 2,127,445 represent, for example, a means for supplying oil, gas, pulverized fuel or the like. In the pres ent instance the control valve 4 is spring loaded by a spring '3 to normally closed or shut off posi tion and adapted to be opened for ?ow there 'through by the energization of a solenoid ‘I. In Fig. 1 I illustrate a single burner and its control leading from the header 5 to the furnace I, while in Fig. 2 I show‘a plurality of such burn ers and the interlocking control circuit therefor. The single burner and related apparatus of Fig. 1 may be considered as the only burner feeding the boiler_ I, or may be considered as one of the plu 15 rality'of burners illustrated in Fig. 2. Likewise the three burners constituting the plurality of burners of Fig. 2 may all be feeding the‘ furnace I or may be a part only of a larger number of burn _ ers all related to the furnace I. Referring particularly to Fig. l, a pipe 3 leads 20 from the header 5 to a burner 9. Interposed in the pipe-3 are two control valves I 2, II whose functioning and purpose will be described herein \ after. ' connections are shown as being made across the second and third passes of the boiler furnace. It will be understood however that this is only by way of example and that the connections may be . made to any two suitable points, the essential thing being that the bells be subjected to a di?'er ential pressure of sufficient value to eifect the operation of the ?ow responsive device 22. The movable element of contact 24 is connected by conductors I30, Hi to one side of electrical 10 supply lines 32. Interposed between the conduc tors l3lI, I3l is a ?ame failure detector 33 which may comprise electrodes of a carbonaceous mate rial such, for example, as silicon carbide posi tioned in the path of the ?ame within thev fur 15 nace. While I have shown but a- single ?ame failure detector positioned adjacent one of the burners of Fig. l and Fig. 2, it is my concept that there might be a single ?ame failure detector for an entire furnace, or one for each burner of a 20 furnace (Fig. 3), or intermediate number. Shunted across the ?ame failure detector 33 is a switch blade 34 shown in open position. The stationary element of contacts 24 is connected by a conductor 35 to the other side of the supply 25 Theburner 3 extends through a wind-box? l2 supplied with forced draft by a motor driven blower I3. I4 indicates a torch, such as an oil ' lines 32, such conductor including the winding of or gas torch, for use in kindling or lighting the furnace. The ?ow of fuel through it is controlled by a valve I5 adapted to be opened by a solenoid 30 I3 and closed by a spring I I6. At I1 is an igniting means for the torch, such as a spark plug. It is connected to the secondary winding of a trans former I3. I3 indicates the stack of the furnace and 20 35 indicates an induced draft fan driven by an elec tric motor 2I. The furnace construction so far described is illustrated only diagrammatically and by way of example and is to be taken as repre sentative of any suitable. furnace provided with a 40 fuel feeding means and a means for effecting ?ow of air through the furnace. _ According to the embodiment of my invention illustrated in the drawings I provide a mechanism ' 22 which is responsive to the rate of flow of air 45 through the furnacevand I provide such device with a contact closing arm 23 which when the flow of air through the furnace reaches or ex ceeds a predetermined value effects the closing of a pair of contacts 24. Contacts 24 are biased 60 ' toward open position so that they are. open except a solenoid 36. Solenoid 38 has a pair of contacts 31 which are bridged, or close-circuited, when ever solenoid 36 is energized. The primary winding of transformer I8 and the 30 winding of solenoid it are connected in series to one of the supply lines 32 by conductor 38, in cluding the contacts 31 of the solenoid 36. The other side of the transformer primary winding is connected to the other supply line 32 by a con 85 ductor 39, hand switch blade 42, and conductor I3I; conductor 38 including contacts 40 which are open-circuited at all times the valve II is closed. - When valve II is opened through the agency of hand wheel SI, then contact bar 4I immediately 40 engages and closes the circuit of contacts 40. throughout all positions of opening of the valve I I. The switch blades 34 and 42 are Joined for si multaneous ‘operation and with them a third switch blade 43 which Joins conductor 38 with a conductor 44, the latter leading to the winding of solenoid ‘I. A conductor 41 joins the other termi nal of solenoid ‘I with a hand operable switch 48 connected by conductor 43 to the electrical sup ply lines 32. Solenoid ‘I when energized is adapt ed to close the circuit across the contacts 45, thus by-passing the switch blade 43 to lock valve 4 in when held closed by the flow responsive mecha nism. In the present instance the flow responsive de ' an open position. vice is shown as comprising a casing 25 in which is The circuit of solenoid 'I on the main fuel valve 55 a sealing liquid, such as oil, for sealing two in .4 may be traced as follows; power line 32, con verted bells 26, 21 connected to opposite ends of a ductor 46, switch 43, winding of solenoid 1, con lever arm 23 pivoted centrally to a ?xed point. .ductor 44, switch blade 43, conductor 38, and con Contact arm 23, is connected to lever arm 23 and tacts 31 to the other side of power line 32. As forms a part of it. The arm 23 extends at an previously mentioned the switch blade 43 may be angle to the lever arm 23 and is weighted by by-passed by a holding-in circuit including the 60 means of a suitable weight 29, which biases the contacts 43. bell structure to a position as shown in the draw In the pipe 3 in the direction of gas flow to ings, which position it occupies at no air ?ow through the boiler furnace. When arm 23 is the burner 3 is located a hand operable valve III of a bleeder type‘having a small bleeder port 50 65 moved into engagement with contacts 24 it moves 65 toward vertical position but does not move beyond leading to the atmosphere and arranged so that when the valve I0 is closed off the bleeder port the vertical, that is beyond dead center. It- tends always therefore to move toward the position 50 is opened to the atmosphere to bleed from be shown in‘ the drawings wherein contacts 24 are tween the valves IO and II any gas leakage past 70 open. .Bells 26, 21 are connected by pipes 33 and the valve ll toward the furnace. The valve II 70 3 I _to points of differential pressure in the furnace located in the pipe 3 between the valve III and the whereby the bells are subjected to a differential burner 3 is of a hand operable type adapted in its - pressure which bears a definite relation to the closed position to open-circuit the contacts 40 and 'u ' rate of flow of air and/or products of combustion through the furnace. In the present instance the thus effectively de-energize solenoid I8 and trans former primary ll. When solenoid It is so de 75 2,127,445 ' energizedthe spring H6 immediately closes the torch valve I5. , Referring now in particular to Fig. 2, I show 3 . such a flow "of air of a definite predetermined magnitude is established the furnace cannot be kindled. , e i As the flow of air through the furnace increases therein three burners, 9, 9A‘and 9B, which are _representative of a plurality of burners similar a differential pressure is appliedto the flow re to the burner 9 of Fig. 1, and each provided with sponsive device 22. which differential increases a torch and igniting means as in Fig. 1. The a with the rate of ?ow in known manner. As soon ' various equipmentand arrangement of Fig. 2 is as a predetermined rate of flow is reached the similar to that of Fig. 1 except that in Fig. 2 differential pressure applied to bells 28, 21 will I illustrate diagrammatically my proposed ar be sufficient to turn lever arm 28 on its pivot in 10 rangement of interlocking for operation of the r a clockwise direction and move contact arm 23 to a position wherein it closes the contacts 24. The various burners of a plurality of burners on a single furnace. The valves l8. IOA, I03 may be arrangement is such that a predetermined flow similar. to the ‘valve in of Fig. 1 and may be of air and/or gases through the furnace is re provided with leakage'ports 50. ' quired before the contacts 24 are close-circuited. 15 > The closing of contacts 24 completes one step ,The circuit for controlling and igniting each torch includes the primary of the transformer l8, in the sequence necessary to energize the sole the solenoid _l 6, and the contacts 48, in series with noid 38. When the switch blade 34 is closed (by-passing the ?ame failure detector 33) sole each other across the conductors 38, 49. For a noid 36 is energized closing contacts 31 for the 20 20 plurality of burners, as in Fig. 2, the igniting cir energization of conductor 38. ~ cuit for each of the burners-is connected in par Simultaneously with switch 34 the switch ?n- _ allel across conductors 38, 49. The arrangement .is such that the torch valve I5 is closed (by spring gers 42, 43-are closed; switch 42 energizing con H6) and transformer I8 ineifective when the fuel ductor 48, and switch "accomplishing one step in completing the circuit to the fuel supply valve 25 25 supply valve H is in a tight closed position where by contact bar 4| does not short the contacts 48. . solenoid ‘I, which is further controlled by switch Immediately the valve ll begins to open and for 48. The switch 34, 42, 43 may be closed by the all positions of opening, the contact bar 4i shorts the contacts 48, energizing solenoid IE to open operator either before or after purging the boiler. ' Assume for the moment that the boiler has been 30 30 the torch supply valve l5 and at the same time purged, contacts 24 closed and that switch 34, energizing the transformer l8 to actuate the ig niting spark l1. This, assuming for the moment that conductors 38, 49 are alive. Conversely when the valve II is closed, thus 35 stopping the flow of fuel through the burner 8. immediately the torch l4 and igniter II are made the possibility of an igniting ?ame opposite a 40 burner through which no fuel is being admitted to the furnace. As will be seen hereinafter, the arrangement is such for each of the burners as to prevent the possibility of having fuel admis sion through a given burner without having the 45 igniting means and torch operative for igniting same. ' making energy available on conductors 38, 49 and also effecting energization of the circuit of sole noid 1 except for the switch 48. , ' If This prevents . closed at this point, fuel will be available at ineffective, regardless of the condition of the re mainder of the electrical circuit. 42, 43 is‘likewise closed. The resulting energize. tion of solenoid 36 will cause contacts‘3‘i to close, r The arrangement just brie?y described pri marily effects a safeguard against fuel being ad mitted through the .burner 8, for example, to the 50, furnace with the igniter l1 and torch l4 inopera tive and at the same time no-fuel being admitted through the burner 93 while the igniter “B and torch MB were operative. This hazardous condi tion which is prevented by my arrangement would Switch 48 may be closed now or later. valves Ill. IOA, IOB, or if these valves are open then at valves II, “A, “B. If for example, 40 valve II is open then its opening will have com pleted the circuit between conductors 38, 48 for energizationof torch valve 5 and ignition trans former l8 so that torch I4 is available for light ing burner 8 when fuel arrives. Valve ll may be opened either before or after main supply valve 4. If opened prior to the opening of valve 4 then immediately as it un seats, the torch i4 is lighted and is thereafter available when solenoid ‘I is energized and gas 50 flows through the burner 8. i ; As long as switch 34, d2, 43 is closed each igniter becomes active as soon as its valve II is opened and stays active until switch 34', 42,43 burner to the furnace at a distance of possibly 15 is opened, which can only be done after detector 55 33 is heated up and passes current through the flame. to ‘20 feet fromv the point where the torch was lighted, and thus the filling to a. large extent of 60 the furnacewith a combustible'mixture before solenoid ‘l is energized and immediately com pletes a holding circuit around contact d3 by 60 in C, allow on a large modern furnace for the feeding of a . considerable volume of fuel through one ' ‘With the closing of contacts 31, d3, t8 the ' the contacts 4%. the same became ignited. As soon as flame exists across the detector 33 The operation is as follows: Assume that the furnace is shut down and that to the extent of completing circuit, switch“, “2, d3 may be opened, thus'de-energizing the trans it is desired to kindle same. The air-flow respon formers l8 and ‘allowing springs iii to close off ' sive device it will occupy the position illustrated ‘ in Fig. 1, namely, contacts 24 being open. The, the various torches l4. Thereafter while the operator ?rst effects a flow of air through the furnace is in normal operation the system as a furnace to scavenge it. This may be done by whole is under the protection of contacts 24, de natural draft or by means of the induced draft tector 33, or hand switch $18. If it is desired to fan, the forced draft blower, or both, the means cut off the fuel from the boiler as a whole, then by which the flow of air is established, depending a hand switch it may be pulled. it air flow de upon the nature of the particular furnace in stallation to which the invention is applied. The essential thing is that a flow of air be established through the furnace to scavenge it and that until creases to a predetermined minimum then con tacts 2“ will automatically open tie-energizing solenoid 36, opening contacts ill, and thus de-_ energizing‘ solenoid ‘l to shut off the fuel supply. 75 4 $121445 . Similarly should ?ame fail at the detector 33 it de-energizes solenoid 36 resulting in a closure of main fuel valve 4. It will be observed that the main fuel supply :1 to the furnace, as well as the ignition and kindling means for each and every burner, are all under the direct control of the air flow re sponsive contact 24 and/or the ?ame detector 33. It will .be understood that the circuit may be arranged to have a detector 33 opposite each of the burners or one detector common to all of the burners. Fig. 3, for example, illustrates an em bodiment wherein there is a detector 33 opposite control valve 4 for that particular furnace. They therefore are independent of the opening of valve 4. Between the torch supply takeoff and valve 4 I indicate at 13 an ori?ce, or other re striction in the pipe line 3, for creating a pres sure di?erential bearing a known relation’ to the rate of flow of fuel through the pipe 3 toward the burners 9. Connected to be responsive to such differential pressure is a diaphragm meter 12 adapted to close a switch 14 when a prede 10 termined rate of fuel flow exists. The hand switch 15 is used to start the furnace and “indicates the contacts of the air ?ow re ‘ sponsive device 22 previously mentioned. 64 and In brief, after the furnace is in operation the 65 indicate solenoids, the former controlling con 15 solenoid 36 controls the supply of fuel to the tacts 66, 6'! and the latter controlling contacts furnace and to all burners thereof and the sole 68, 69. The various torch controlling solenoids hold 36 will fail if the ?ame fails at the flame l6 and ignition transformers iii are for each failure detector 33, ‘or if air ?ow through the burner connected in parallel across conductors 20 furnace decreases below a predetermined‘. value, W, ‘H. 20 thus opening contacts as. ; [it ‘i I have indicatedv a coil, such as the sole In Fig. 3 I illustrate a further embodiment noid ‘I of the remainder of the drawings and each burner. wherein a flame detector is located adjacent each of the burners of a plurality of burners. Fur which may be a torque motor or a thruster. The requirement being that the valve 4 remain 25 thermore the switches 34, 42, 43 have been omit; open only when the coil 1 is energized. ted and each igniter is ready at all times to act. All that is required is that the detector 33 be cool and that contacts '40 be closed. The circuit for the solenoid ‘i is under control 30 of the hand switch 43 and the flow responsive switch 24. The ignition and torch means of In kindling the furnace of Fig. 4-1 assume ?rst that switches 14,15, and 24‘ are open as indicated. The furnace is purged or scavenged by effecting a flow of air and/or gases su?lcient to actuate the device 22 and close the contacts 30' 24. Such closure energizes solenoid 64 which closes contacts 66, 61. If it is now desired to each burner are under the control of flow re sponsive switch 24, detector 33,‘and contacts 453. In kindling the furnace switch 24 automatical 35 ly closes when the air flow reaches a predeter mined value. The detector 33 being cool, the solenoid 62 is in the shown position with contact 63 closed and as soon as valve ll begins to be opened (closing contacts 40) ?ow-is established 40 through torch l4 and igniter i1 is actuated. This regardless of whether or not hand switch 43 has previously been closed, thus opening valve 4. Any or all of the burners 3, 3A, etc. may be 45 lighted off in this manner, for the ignition and . 25 kindle the furnace, starting switch 15 is closed by hand,- which in conjunction with contacts GB eil'ects energization of solenoid 65, thereby clos 35 ing contacts 68, 69. Fuel supply valve 1 opens due to energization from a circuit completed through contacts 61 and 68 but no gaseous fuel ?ows toward the burners unless the various hand valves at the outlet of valve 4 and the valves iii in individual burner lines are opened. Simultaneously with the energization of the coil 1, occurs actuation of each and every torch valve l6 and igniting transformer l8 through torch means are always available, and as soon as a circuit controlled by contact 69. v The torches 45 any valve II is opened thus closing contacts 40, being supplied through each or all of the burner are all lighted irrespective of whether gas is the torch will be lighted, if a predetermined ?ow , pipes 9, 9A, 3B. Whichever one of the burner of air exists whereby contacts 24 are closed. pipes has gas ?owing through it will then be During operation if-at any time air flow falls kindled. ‘As soon as a predetermined ?ow of gas to a predetermined minimum, the switch 24 will - occurs through the valve 4, effective upon the 50 open, thus closing the fuel supply valve 4 for the furnace. Failure of ?ame at a detector 33 de energizes solenoid 62, closing contacts 63 whereby the ignition means immediately comes into play and assuming that valve ll remains open, it lights it off immediately. If, however, valve H has been closed then the ignition means remains in condition to immediately function upon open 60 ing of valve ii. ' The common ?ame detector of Fig. 2 could still be retained to close valve 4 if desired. In Fig. 4 I show a further embodiment of my invention applied to a plurality of burners, each equipped with torch and igniting means, but for the sake of simplicity I have not included in this part of the drawings the ?ame detectors 33, al though it will be understood'that they may be applied to this arrangement as well as to the 70 ones previously described. Herein I introduce a further safety feature, namely, in connection with the rate of supply of fuel to the plurality of burners. . The torches l4, I4A, I43 ~ are supplied with 75 gaseous fuel from the conduit. 3 ahead of the meter 12, the switch" is closed, thus by-pass ing contact 68 and locking in the coil '5 whereby ‘ valve 4 stays open even after the ignition means are extinguished by opening the starting switch 55 15. After the furnace is in operation if at any time the gas ?ow through the ori?ce 13 decreases to a predetermined minimum then the switch 14 is opened, de-energizing coil 1 and closing valve 60 4. Before valve 4 can again be opened and gas admitted to the furnace the starting switch ‘276 must be closed by hand to actuate solenoid 65. During operation the entire fuel supply and igniting system is under the control of the air 65 flow actuated switch 24, so that if air ?ow through the furnace decreases to a predetermined mini mum, switch 24 opens deenergizing solenoid 36, opening contact 61, and closing fuel supply valve 4. 70 In connection with all four of the ?gures of the drawings it will be seen that by my invention in starting the furnace the operator must ?rst effect a ?ow of air through the furnace so as to thoroughly scavenge or purge it prior to kindling 75 5 2,127,445 the ?re and that a ?ow of air sufficient to main tain the flow responsive device in the position wherein it closes contacts 24 must be maintained. or the fuel feeding means and the igniting meansl cannot be put into operation. In this connec-. tion the flow responsive‘ device may be so ar ing means will be operated in the absence of flame from the corresponding burner and ren dered inoperative in the presence of ?ame from the corresponding burner; ranged that having been moved by a prede termined ?ow of air through the furnace to effect closing of contacts 24 it will, due to weight 29 having moved to a more nearly vertical posi— tion, stay in such position until the flow de . _ creases by a certain amount. By this means the draft through the furnace may be decreased somewhat over that required to close the con 15 tacts 24, and still the contacts will remain closed, which means that if desired the arrangement 2. In combination with a . furnace having a plurality of burners, a conduit for supplying fuel to all of said burners, a main valve in said con duit, means responsive to the flow of air through said furnace, means controlled by said first named means for opening said main valve when a prede 10 termined or greater rate of air fiow exists through said furnace and closing said valve when > the rate of air flow falls below said predetermined‘ rate, an individual burner valve for admitting fuel to each of said burners,‘fuel igniting means 15 associated with each of said burners, means per mitting operation of each of said igniting means to scavenge the furnace, after which the draft. when the corresponding burner“ valve is open may be shut down somewhat during the kindling and preventing operation of the igniting means when the corresponding burner valve is closed, 20 ' _ '20 operation. It will be. understood that it is not absolutely means under the joint control of said ?rst named necessary for the air supply responsive mech- means and each ?ame responsive device to insure that the corresponding igniting means will be anism to be interlocked with both the fuel sup may be such that a stronger draft must be used plying means and the fuel igniting means as I 25 may utilize an arrangement wherein the air sup ply responsive means is interlocked only with the fuel supply means or only with the fuel igniting means. , It is to be understood that while I have illus .30 trated my invention in connection with a fur nace burning gas, this is only by way of ex ample, and that the invention may be utilized in connection with furnaces burning other fuels, such as oil or pulverized coal for example. Fur it is not necessary to have the 35 thermore furnace arranged for heating a vapor generating boiler, but'the furnace may be of any type or for operated in the absence of ?ame from the corre sponding burner and rendered inoperative in the presence of ?ame from said burner. 3. In combination with a furnace having a plurality of burners, a conduit for supplying fuel to all of said burners, a main valve in said conduit, means responsive to the flow of air 30 through said furnace, means controlled by said ?rst named means for opening said main valve when a predetermined or greater rate of air flow exists through said furnace'and closing said valve when the rate of air flow falls below said 35 predetermined rate, an individual burner valve for admitting fuel to each of said ‘burners, fuel igniting means asociated with each of said burn ers, and means under the joint control of said 40 rated in the system. For example it is not essen- - ?rst named means and- each ?ame responsive de 40 vice to render said igniting means operative in tial that all of the interlocking be done elec the absence of ?ame from the corresponding trically. It may be readily accomplished hy burner and when said predetermined or greater draulically or by pneumatic means and instru mentalities differing from those which I have air flow exists through the furnace; and to render illustrated and described may readily be adapted said igniting means inop'erative in the presence 45 of ?ame from the corresponding burner or when to the invention. > In accordance with the provisions of the patent the air flow through the furnace falls below said predetermined rate. statutes I have described the principle of opera 4. In combination with a furnace having a ‘ tion of my invention together with the apparatus plurality of burners, a conduit for supplying fuel 50 which I now consider to represent the best em to all of said burners, a main valve in said con bodiments thereof, but I desire to have it under duit, means responsive to the flow of .air through stood that the apparatus shown is only illustra said furnace, means controlled by said first named tive and that the invention may be carried out by means for opening said main valve when a pre other means. determined or greater rate of air flow exists 55 .What I claim as new, and desire to secure by through said furnace and closing said valve when 55 Letters Patent of the UnitedStates, is: the rate of air flow falls below said predetermined 1. In combination with a furnace having _a plu rality of burners, a conduit for supplying fuel to rate, an individual burner valve for admitting fuel to each of said burners, fuel igniting means asso all of said burners, a main valve in said conduit, ciated with each of said burners, and means 60 means responsive to the flow of air through said 60 , under the joint control of said ?rst named means any service. ' , Various forms of apparatus may be incorpo furnace, means controlled by said ?rst named ' means for opening said main valve when a pre determined or greater rate. of air ?ow exists throughv said furnace vand closing said valve when the rate ofv air flow falls below said pre 65 determined rate, an individual burner valve for admitting fuel to each of said burners, fuel igniting means associatedv with each of said burners, and means under the joint control of said ?rst named means and each flame respon 70 sive device to insure that the corresponding ignit and each of said burner valves for permitting operating of the corresponding igniting means when said predetermined or greater air ?ow exists through said furnace and the corresponding burner valve is open; and preventing operating of the corresponding igniting means when the rate of air flow falls below said predetermined rate or when the corresponding burner valve is closed. ' RALPH M. HARDGROVE.