Патент USA US2406752код для вставки
Sept. 3, 1946. s, G. E$K|N ET AL v ' SAFETY CONTROL .FOR GASEOUS FUEL BURNERS ‘ Filed April l0, 1943 -2,406,752 2,406,752 Patented Sept. 3, 1.946 UNITED'STATES PATENT OFFICE ' v 2,406,752 SAFETY CONTROL FOR GASEOUS FUEL . BURNERS ' Samuel G. Eskin and Charles K. Strobel, Pitts burgh, Pa., assignors to Robertshaw Thermostat Company, 'Youngwood Pa., a corporationof Pennsylvania ‘ f' Application April 1o, 1943, serial No. 482,592 15 claims. `(c1. 15s-117.1) more particularly, tocombined safety and condi when such current is reduced below a certain Operation of the main con . trol-valve I6 from'closed to open position will tion controlling means for fuel burners and the like» ' " ` 2 sufficient energizing current is supplied to the solenoid of valve I8 and to be closed by gravity Thisiinvention relates to control systems and, Lminimum value. " In application S. N. 439,148 filed April 15, 1942,- "Si permit ñow of fuel from the pipe I4 to the pilot now Patent No. 2,366,774, granted January 9, 1945, there is disclosed aV safetyfsystem for fuel burners employing both av flame or heat sensitive - burner I2, but fuel is not supplied to theV main burner IIl'unless the solenoid Valve IS is also in open position. y. device anda current sensitive device for con trolling operation l of Van' electromagnetic fuel valve. The valve in this systemV was used solely for safety purposes and would function to ter minate the supply of fuel to the main burner upon extinguishment offthe flame to which the flame sensitive device was exposed. In this present invention it is proposed to employ the electromagnetic valve„as disclosed in‘the former application, both to regulate the ñow of fuel to the main burner for temperature regulation and also terminate suchflow in the event of. ñame _ failure. It will readily be apparent> that in its broad aspects the present invention may be utilized both for condition and safety control as previously indicated. _ ' ' . An object of this invention is to permit utiliza- v tion of the condition regulating means for safety control also. . K, , Electric current for the operation of the ap pa'ratus is supplied by the line wires 20 connected to the primary of a transformer 22 which, in this instance, receives commercial current at the primary where a voltage variation from 105~to 125 volts -can occur.l In this> embodiment the main valve I6 has a main switch combined there with which is connected to one line wire 2Uv by wires 24 an'd- 26. Any suitable means may be in corporated in the combinedY valve and switch structure to close the switch when the main valve Itis-actuated to open position. The secondary of the transformer 22 delivers the current from line wires 20 at voltages varying in accordance with the primary Yvoltage variation above and below an averager of six volts. Connected to one terminal of thetransformer secondary by a wire 28 is one junction A of a parallel mesh of which a name sensitive element 30 forms one branch .Another object of the invention is to insure a and is connected at'oneend by wire 29 to wire 28 minimum -time lag in the response of the control when operation of the burner should be termi 30 and at the other end by wire 3| to wire 32 at the nated. ‘ _. ~ Another object of the invention is to render the device substantially uniform as to operating time opposite junction B of the mesh. .The element 30 is positioned adjacent the pilot burner I2 exposed to the heat of the flame thereof and may be in 1 the form of a coil of wire formed from material over a range of operating conditions. Other objects and advantages will become ap 35 having normally a relatively low resistance and a positive temperature coeflicient of resistance forming a ballast resistor. It will be apparent that other types of flame sensitive, heat respon wherein: sive or thermal resistance elements havingV the Fig. 1 is a schematic view of a combined safety and condition controlling apparatus for a fuel f required characteristics may be substituted and that it is not essential that the flame of the pilot burner embodying the invention; burner I2 actually impinge on the coil. Fig. 2 is a schematic View of a detail in one op Therother terminal of the flame sensitive ele erating position; and l ment 30 is connected by wires 3l and 32 with one Fig. 3 is a schematic View of the same detail in 45 end of another parallel mesh included in the another operating position. ' . . secondary. circuit, the other end of this parallel Referring more particularly to the drawing, a mesh being connected by a wire 34 to the other gaseous fuel burner I0 and an associated pilot terminal of the secondary of the transformer 22. burner I2 are shown as being supplied with fuel One branch of this parallel mesh comprises a re by a main fuel pipe I4. The fuel supply- to both burners is controlled by. a main valve I6 which 50 sistance` element 36 whichy will be hereinafter parent from the following description taken in connection with theA Y accompanying drawing, may be manually‘operated. Interposed in the fuel supply line I4 between the main valve I6 and the burner I0 is an electromagnetic or solenoid designated as a valve control resistor. This re sistor 36 is preferably in the form of a coil of wire of material having normally a ‘relatively low re sistance and a positive temperature coefficient of gas valve VYI8 of any known type which maybe arranged, asin this instance, to be opened when 55 resistance >forming a ballast resistor, althougnas $2,406,759 3 4 will appear hereinafter, a constant resistor could be employed. The resistor 35 is not, however, eX posed to the heat of any flame but is adapted to to the coil of the solenoid valve i8 to actuate this become heated upon passage of electric current valve to open position. The fuel issuing from the pilot burner l2 may be ignited by a match and the relatively small therethrough and will change its resistance in Cl heating effect of the current on the flame sensi accordance with changes of temperature caused tive element 3i? is amplified by themuch greater by changes in the value of current fiowing through heating effect of the pilot burner which will then it. occur. Assuming that the control thermostat is The other branch of the parallel mesh com prises a constant resistance elementA 53 forming a pick-up resistor for the solenoid valve, and' a control switch connected in series circuit there in the cold contact position with the contact 46 with. The control switch may take the form of a thermostat composed of a bimetal arm lll! carry ing on one end thereof a pair of contacts HI, 43 disposed one on each side and which upon warp ing of the arm will engage alternately with con tacts ¿l2 and (it, designated hot contact and cold Contact respectively, and spaced one from the other. The control switch may be placed in the space tobe heated by the main burner It and the arm t3 be subjected tothe temperature variations therein forming a space thermostat of special form. To this end, the cold contact ‘t3 is prefer engaged by related contact on arm All), then the circuit Will be as previously described, that is, the parallel mesh of pick-up resistor 35i and valve control resistor 36, the parallel mesh of solenoid valve I3 with its cut-out 58 and name sensitive element 3l), all in series with the transformer secondary. Upon heating of the flame sensitive resistor 30 by the pilot flame in this starting or cold Contact position, the shunting of the valve control resistor 36 by the pick-up resistor 38 and cold contact 423 causes sufficient currentV to ñow through the solenoid valve I8 to actuate this valve to open position. As in the case of application Se rial No. 439,148 previously referred to, this effect is produced by a relatively large increase of' re ably carried upon a second bimetal arm M which 25 sistance with increase of temperature of the llame is adapted to warp upon passage of electric cur sensitive resistor St. However, if the flame sensi rent therethrough so that only the hot contact ft2 tive resistor 33 is not heatedV by the pilot flame can be considered as a relatively iixed contact for there is insufñcient current impressed upon the the thermostatic switch. A limit stop 48' is inter coil of the solenoid valve I8 to effect actuation of posed between the bimetal arms 46 and 44 in posi 30 the valve to open position as previously described tion to be engaged by thearm dû to restrain move therein. ment thereof toward the arm ¿i4 for a purpose Operation of the main burner I3 Will serve to which will be> apparent hereinafter. increase the temperaturev ambientto the thermo The hot contact 42 is connected by a ’wire 53 stat causing movement of the bimetal arm til to one end of a constant resistance element 52, 35 toward the hot contact 42. It may be assumed for the other end of which is connected by a wire 5I the purpose of this description that the bimetal to wire 23 at junction A' of the parallel mesh. arm 150 now movesito a neutral position engaging Another branch of this mesh includes a cut-out neither the cold contact 48 nor the hot contact 58 which is thermally sensitive and may be of the ä2. A circuit is then established from the valve slow acting bimetallic snap switch type. One ter 40 control resistor 36, the parallel mesh of solenoid minal of the cut-out 58'is connected‘by a wire 53 valve It with its cut-out 58 and flame sensitive to‘ the wire 23 at junction A and the other termi element 33 all in series with the transformer nal is connected by'wire 54 to one terminal of the secondary. In this circuit the resistor 33 and solenoid valve I8. The other vterminal of the resistor 52 are disconnected as will be apparent solenoid valve I3 is connected by a wire 56 to the ‘ and the current through the solenoid valve I8 is wire 32 at the junction B, thus placing the' name consequently reduced by removal of resistor 3S sensitive element' 33’ in parallel circuit with the from parallel relation with the valve control re cut-out 58 and solenoid valve i3. sistor 33. However, when the thermostat moves InV the operation of the’ apparatus the closing as describedfrom the cold contact to neutral posi of the main switch of' valveV I6 is effective upon 50 tion the current value impressed on solenoid manual opening of this valve, as described, and valve I8 is not reduced below the minimum value permits fuel to flow to the pilot burner I2.` As required to hold the valve in its open or operat the solenoid valve I8 remains closed, no fuel can ing position, but the circuit constants are ad flow to the main burner Iû at this time. The cir justed at the lowest line- voltage which may be cuit thus-established may be traced from the line Ul Ul 105 volts at the primary so that the normal, steady operating current is slightly above the wire 23 to wire 23, electric switch of main valve I6 and wire 26 to the primary of the transformer minimum Value. The resistance of the parallel circuit in> operating condition is increased sulîi 22, from the secondary of the transformer by wire ciently by the higher resistance value of the dame 28 to wire 53, cut-out 58, wire 54, to one terminal of solenoid valve I8, wire 56 to wire 32, valve 60 sensitive element 30 when heated to permit sufii cient current to the solenoid valve t0 maintain it control resistor 33 and wire 34 to the other side of in the open position. the transformer secondary. Current also flows After the main burner I3 has been operating in the shunt established by the flame sensitive ele ment 3l! which is connected by wires 29 and 3I 65 for some time the bimetal arm 4i) may move to the hot contact position due to the thermostat around the coil of the solenoid valve I3» causing becoming satisfied, whereupon a circuit arrange the element 30 to become heated to some extent. ment is established from the transformer second During this starting operation the control ther ary and the valve control resistor 36 in series mostat is usually in cold-contact position so that pick-up resistor 38 is connected in parallel cir 70 with the three-branch parallel mesh of flame sen sitive resistor 33, solenoid valve IS and cut-out 58, cuit with the valve control resistor 33. The cur and constant resistor 52 with the hot contact d2. rent values in the circuit are adjusted so that The constant resistor 52 which acts as an adjust when these circuit conditions exist and the flame ing resistor for the solenoid valve I8 is of such a sensitive element 3i! remains unheated by the pilot burner flame, there is insuflicient current flowing 75 Value as to shunt sufficient current from the sole 2,406,752 5 noid valve I8 tocause this valve to move to closed position. ' . f . » When the thermostat moves fromV the hot con tact 42 tothe neutral position the solenoid vvalve I8 remains closed until the bimetal arm warpsl to close the cold contact 46. In' such event the 6 viewed in Fig. 3, and a separation of the cold contact 46 from arm 40 can occur as soon as the arm 44 becomes heated by passage of current therethrough. The separation of the cold con tact thus has the same effect as movement of the arm 40 to neutral position` and the valve closing cycleis repeated due to the flame sensitive ele ment Vill) being heated by the pilot burner. In timeisgenerally short. Y It will be apparent that a heater coil could be used in place of conducting case the llame sensitive element 30 becomes open ' current directly to the arm 44 and such variation circuited, sufficient current flows through the cut 10 is Within the scope of this invention. It will be understood that aconstant resistor out .58;to cause it to operate to close the valve, could beused in place ofA the current sensitive providing the thermostat is inl either the cold resistor asthe valve control. The system would contact position or neutral position. If, however, then operate over a narrower range of voltages the thermostat is in the hot contact position, the solenoid valve I8 is closed due to the shunting 15 and the valve closing times would be increased. However, the system would not in such case be action of the resistor 52. ‘ V quite as sensitive as the preferred form to rapid The foregoing sequence of operation continues voltage variations, and the advantages of reduced during the normal running condition of the valve closing times and an extension of the' pri burner to control a condition caused by operation mary voltage range over which the system will of the burner. The operation of the safety device operate are believed superior. Considerable flexi will now be described. o If the Aflame of the pilot burner I2 becomes ex ' bility of circuit arrangement results as the value of the respective resistances canbe varied to suit diiierent operating conditions. The single sole~ 40 is in the het contact position, vor in the neutral noid valve functions as condition and safety con position upon warping from the hot contact posi trol in the arrangement described and it will be tion, then the solenoid valve I8 is already closed apparent that various changes may be made in at the time of the flame failure. If, however, the the form .and arrangement of parts within the bimetal arm 40 is in theneutral position upon scope of the appended claims. warping from the cold'contact position, the sole- y We claim: noidzvalve I8 is open. IThe flame sensitive ele y l. A control system for fuel burners having ` ment 3l)Y will cool in the `absence of pilot burner main and pilot burners comprising in combina name and its resistancewill decrease causinga tion, electrically operable control means movable corresponding decrease in current value to the between positions for controlling the main burner, solenoid valve I8 which then closes. Such clos ing of the solenoid valve occurs in a relatively 35 a controller in circuit with said means and re sponsive to changes in a condition caused by op short time Vdue to the combined action- of the eration of the main burner, a ballast resistor ex flamesensitive resistor 30 and the valve rcontrol posed to the heat of the pilot burner iiame and resistor 36. As previously described, the current electrically connected to said control means for impressed upon the solenoid valve I8 in the neu varying theV current value supplied thereto upon tral position of the thermostat is only slightly variations in the resistivity of said resistor due to above the minimum value required to hold the the presence or absence of said flame, and a valve in its `open or operating position. Thus, plurality of resistance circuits adapted to be by making the valve control resistor 36 sensitive establishedalternately'by operation of said con to Vcurrent changes the decrease in voltage drop troller and including said control means and said across the coil'of the solenoid valve will be accel ballast resistor, said resistance circuits having erated` whenever an increase of resistance of the different resistance values for varying the cur valve control resistor occurs upon cooling of the rent values to said control means, said means flame sensitive resistor 36 and consequent in being movable to one position upon establishment crease in current through the valve control re sistor. The resulting temperature increase in 50 of one said_ resistance circuit for impressing a predetermined current value thereon and main valve control resistor 36 causes increase in voltage tained in said position upon establishment of an drop across this resistor and the rapid decrease other said circuit for impressing a different cur in voltage drop across solenoid valve I8, rent value thereon, said resistor being adapted by ln order to make the adjustment of the circuit constants less critical and the shut-01T times of ' said variations in resistivity thereof for cooperat ing with said resistance circuits to determine the solenoid valve comparatively short, the cold whether said control means is moved and main contact 46 of the thermostat is mounted on the tained in said position. , bimetal arm 44. Thus, uponclosure of the cold 2. A control system for fuel burners having contact the bimetal arm 44 will warp, after the circuit has been established, from the position 60 main and pilot burners comprising in combina tion, electricallyoperable control means movable shown in Fig. 2 to that shown in Fig. 3. Even if between Ypositions for controlling the main burn the thermostat arm 40 remains in cold contact er, alcontrol switch having a pair of contacts position, the contacts separate and rejoin several adapted to be opened and closed for controlling times as the arm 44 heats and cools upon auto current supplytosaid means in response to matic making and breaking of the circuit. Thus, changes in a condition caused by operation ofv the bimetal arm 44 serves to open the cold con tinguished for anyreason when the bimetal arm , tact 46 independently of the controlled tempera ture. when the cold Contact remains closed for a givenlength of time.` VThe normaloperation of the system is not affected by this action o_f the arm 44 as once the solenoid valve is actuated to ' open position it remains open until the hot con tact Yis made; Due to the provision` of the stop the main burner, a ballast resistor exposed to heat `of the pilot burner flame and electrically connected to said control means for varying the current value supplied thereto upon variations in the resistivity of said yresistor due to the presence’or absence of said flame, a resistance circuit adapted to be established upon closure of said contacts and including saidcontrol means 4B, the thermostat"armv 40 is restrained from fol lowing movement ofthe arm _44_to the left as .7.5 andsaid ballast _resistor for adjusting thev cur 2,406,752 rent value to said control means and causing main and. pilot burnersI comprising in combina movement thereof to> one position, and> a second tion, electrically operable control means movable between‘positions'fcr controlling the main burn er,a control switchf> having hot and cold contacts for controlling current supply to’ said means in response toz‘chaniges in ar condition caused by operation of the- main burner, said switch Ibeing movable to a neutral position for establishing circuit conditions differentfrom those established in said hot. and cold> contact positions, a ballast resistor exposed to heat ofY the pilot burner flame and electrically> connected to said control means for varying the current value supplied thereto upon variations.V in` the'. resistivityY of said resistor resistance circuit established upon opening of said contacts and. includingr said control means and said ballast resistor, said second resistance circuit having a resistance value difierentifrom the first said resistance circuit for changing the current value to said control means, the last said current value being insufilcient to. cause said movement but suiìcient to maintain said posi 10 tion, said resistor being adapted by said varia tions in resistivity thereof for cooperating with both said resistance circuits to determine whether saidl control means is moved' and maintained in said position. 15 due to the presence or absence of said flame, a S. A control system for fuel burners having resistance circuit adapted to be" established upon main and pilot burners comprising in combina closure of said cold contacts and including said tion, electrically operable control means movable control means and said ballast resistor for ad between positions for controlling themain burn justing the current value to said control means er, a control switch having a pair of contacts 20 and causing movement thereof to one position adapted to be opened and closed for controlling if the resistivity of said resistor has varied current supply to said control means in response as aforesaid due to the presence 0f a flame, to changes in a condition caused by operation of meansio-r rendering said cold contacts responsive the main burner, means for rendering one of said to current i‘low in said circuit to cause move contacts responsive to current flow acting to’ open 25 ment thereof to said neutralr position, a second said contacts when closed, a ballast resistor ex resistance circuit including> said control means posed to heat of the pilot burnerv llame and and said ballast resistor having a greater resist electrically connected to said control means for ancel value than the first said circuit and estab varying the current value supplied thereto upon lished in said vneutral position for causing a re variations in the resistivity of said resistor due duction in the current Value to said control means to the presence or absence of said flame, a pair to an amount suñicient to maintain'said one posi of resistance circuits adapted to be established tion thereof' but insuñlcient to cause said move alternately by closure and opening of said con »ment of said control means, said ballast> resistor tacts and including said control means and said being effective by said variations in resistivity ballast resistor, said resistance circuits having 35 thereof under both said circuit conditions to de different resistance values for adjusting the cur termine whether said control means is moved and maintained in said position, and means estab rent value to said control means, said control means having suiiicient current value impressed lishing a- third> resistance circuit upon closure of thereon when said contacts are closed. to cause said hot contacts and including said control movement thereof to one position and having means, said ballast resistor and said second re only suliicient current value impressed thereon sistance circuit, said third resistance circuit hav when said contacts are open to maintain said ing a greater resistance value than said second one position, said resistor being adapted by said resistance circuit for reducing the current value variations resistivity thereof for cooperating to saidl control means and causing: movement with both said resistance circuits to determine thereof from said one position to initial position whether said control means is moved and main.. irrespective of the heated or unheated condition tained in said position. of said Iballast resistor. 4. A control system for fuel burners having 6. A control system for fuel burners having main and pilot burners comprising in combina main and pilot burners comprising in combina tion, electrically operable control means movable 50 tion; electricallycperable control means movable between` positions for controlling the main burn between positions for controlling the main burn er, a control switch having a pair of contacts er, a control switch having hot and cold contacts adapted to be opened and closed for controlling for controlling current supply to said means in current supply to said means in response to response to changes in a conditionA caused by changes in a condition caused by operation of the 55 operation of the main burner,_said switch being main burner, means for rendering one of said movable to a neutral position for establishing contacts responsive'to current flow acting to open circuit conditions different from those established said contacts when closedfa ballast resistor con in said hot and cold contact positions, a ballast nected in parallel circuit with said control means resistor connected in parallel circuit with said and exposed to heat of the pilot burner flame 60 control means and exposedV to heat of the pilot for varying the current value supplied thereto burner flame and electrically connected to said upon variations in the resistivity of said resistor control means for varying the' current value sup due to the presence or absence of said llame, plied thereto upon variations in the resistivity and a pair of resistances in mutual parallel rela of said resistor due to the presence or absence of tion and jointly connected in series circuit with 65 said name, a pair of resistances in mutual parallel said control means and said ballast resistor, one relation and adapted to be jointly connected in of said resistances being connected in said series series circuit with said control means and said circuit by operation of said contacts and being ballast resistor, one of said resistances being con cooperable with the other said resistance for nected in said series circuit «by closure of said adjusting the current value to said control means 70 cold contacts and’ being thereby cooperable with when said contacts are closed whereby said con the other said resistance for adjusting the cur trol' means is caused to move to one of said posi tions upon the variation in resistivity of said ballast resistor due to the presence of said iiame. rent value to said control means to cause move ment thereof‘to one of said positions upon the variationY in` resistivity oi said ballast resistor due 5. A control system for fuel vburnersA having 75 tol the presence of said flameV as aforesaid, and a 2,406,752 s l9 Y10 , thirdv _resistance >adapted to' be connected in of said resistor due to the presence or absence parallel circuit with saidfcontrol means and said ballast resistor and in series circuit with said other resistance upon closure of said hot con tacts for adjusting the current value to said control means and causing movement thereof of said flame, a pair of resistorsone of which changes its resistivity upon a change in tempera from said one position toinitial position irre spective of the heatedor unheatedV condition of said ballast resistor. Y f e ' 7. In a combined temperature and safety con ture of said one resistor due to the flow of current in said'circuit, a bimetal switch arm in said con troller movable in one direction when said main burner is not operating for connecting said pair of resistors in said circuit in mutual'parallel rela tion and in series circuit with said control means and first resistor in mutual parallel relation trol for fuel burners, the combination with elec thereby causing sufficient current to be impressed trically operated _fuel ‘control means and a plu rality of electrical circuits for said means having different resistance values, of a control switch on said control means to actuate it to a position operable for alternatively establishing said cir cuits and thereby varying the currentvalue to said means, said switch comprising a thermally responsive element movable in response to changes in ambient temperature caused by op eration of Va burner, a second thermally respon sive element movable in response to passage of electric current therethrough, switching means .for supplying fuel to said main burner when saidv first resistor is heated', a second bimetal switch -arm in said controller movable in one di rection in response to current ñow in said circuit for electrically disconnecting the other one of said pair of resistors from said circuit, said first resistor and said one resistor having a combined resistance value such as to cause a reduction in the current value impressed upon said control means to an amount Sufficient only to maintain operable by movement of said ñrst element upon said position but insufficient to effect actuation one ambient temperature condition to establish thereof, and means cooperable with said first bi `one of said circuits and cause variation in the 25 metal arm upon'movement thereof in another direction'forintroducing additional resistance in current value to said control means, said second parallel circuit withY said control means While the element being moved upon said operation of said switching means to discontinue said passage of current value thereto is so reduced to render said current therethrough and cause return Vof said current insufficient to maintain said position and second element to initial position to -establish a 30 cause discontinuance of fuelfsupply to the main second one of said circuits and another variation 10. A control> system for fuel burners having in the current value to .said control means; and main and pilotburners, comprising an electrically second switching means operable by movement operable device for controlling supply of fuel to of said first element upon another ambient tem the main burner, said fuel supply being contingent perature condition to establish a third one of said upon current of a predetermined minimum value circuits and cause a'further _variation in the cur being supplied- to said device, a source of current rent value to said control means. i supply for said device and being of at least said 8. The combination with a fuel burner Asystem minimum value, a ballast resistor electrically con comprising a main fuel burner, a, pilotfburner, electrically operable control means, a controller, 40 nectedfto said device and exposed to the heat of a ñame at the pilot burner for varying the cur and an electrical circuit including said'vcontroller and control means for controlling said main burn rent value to said device according to variations er, of a first resistor exposed to the heat of the in the resistance of said ballast resistor dueto the presence or absence of said flame, a resistance pilot burner llame for varying the current value supplied thereto upon variations in the resistivity 45 element in circuit with said device and ballast resistor and cooperable with said ballast resistor of said resistor due to thepresence or absence to cause said current value to fall below said of said flame, a pair of resistors one of which minimum upon the variation in resistance of said changes its resistivity upon a change in tem ballast resistor due to the extinguishment of the perature of said one resistor due to the, ñow of current in said circuit, means associated with said 50 f flame at the pilot burner, a controller responsive to changes in a condition caused by operation of controllerY for connecting said pair of resistors in said circuit in mutual parallel -relation and in the main burner and means _controlled by said controller fory introducing additional resistance series circuit with said control means and ñrst into rsaid circuit and being cooperablev with said resistorin mutual parallel relation thereby caus ing sufhcient current to be impressed on said con 55 resistance element to cause said current value to fall below said minimum irrespective of the heated trolY means to actuate itto one controlling posi condition of said ball-ast resistor. » tion when said ñrst resistor is heated, and means K l1. A control system for >fuel burners having Y'associated withsaid controller and responsive to main andpilot burners, comprising an electrically current flow in said circuit for electrically dis connecting the other one of said pair of resistors 60 operable device for controlling supply of fuel to the main burner, said fuel supply being contin from said circuit when said control means is in gent upon current of a predetermined minimum said one controlling position, said first resistor l value being supplied to said device, a source of and said one >resistor having a combined resist current supplyV for said device and being of at ance value such as to cause only suñicient current least said minimum value, a ballast resistor elec to be impressed upon said control means to main-` burner. s l e 'f tain it in said position but insufficient to effect , trically connected to Ysaid-source in shunt with actuation thereof. said device and exposed to the heat of a flame Y at the pilot burner _for varying the current value 9. The combination with a fuel burner system to said device according to variations in the comprising` a main fuel burner, a pilot burner, electrically operable control means, a controller, 70 resistance of said ballast resistor due to the pres and an electrical circuit including said controller ence or absence of said flame, a resistance ele ment cooperable with said ballast resistor and and control means for controlling said main burn connected in series circuit with said resistor and er, of a first resistor exposed to the heat of the pilot burner flame for varying the current value device to cause said current value to fall below supplied thereto upon variations in the resistivity 75 said minimum upon the variation in resistance 2,406,752 12 111 contactpairs on a A`further rise in said' tempera of said ballast resistor due to the cxtinguishrnent of the fiame'at the .pilot burner, a-controll'er re sponsive to changes in a condition causedby ture yand having sufficiently greater resistance cause _said Vcurrent', value to fall 'below ,saidmini than »said second circuit to render the current value to `said means insufficient to maintain said means in fuel supply position in the heated vcon dition of said >ballast resistor, and thermally re sponsive means operable to cause opening of said one contact pair to establish said second circuit acircuit for -said lmeans established linltl'ie `open value suchîthatsa'id control means is’maintained operation of the vmain bur-ner, and means con trolled iby ysaid controller for introducing ¿addi tional resistance in »shunt >with said `device :and being cooperable withfs'ai-d resistance element to irrespective of said temperature condition. mum irrespective of theheated -conditicn'of said 10 14. YIna control îsystem for fuel burners, elec ballast resistor. trically operable'fuelfcontrol-means arranged for l2. A control system lfor fuel 4burnersxhaving fuel supply to -a burner when said means is vplaced 'main and pilot burners, comprising electrically in energized condition and for preventing .said operable means ,movable .between positions for fuel :supply when -placed in effectively deener controlling the fuel <supplyto ,the `main burner, ' gized condition, a control switch ,for said means a ballast resistor having -a preselected tempera- i including a'plurality of contact ¿pairs 'adapted to ture coefficient of yresistance :located‘to be heated be nalternatively closed 1in response to lchanges-in by the pilot burner `and electrically connected'to a condition caused 'by'operation :of the burner, said means, a control switch‘for said >means `in said `svi/“itch .having an :open position vof all of -said cluding a plurality >of pairs .of contacts adapted to be alternatively closed ‘inresponse 'to :changes 20 contact pairsyacircuit for said fuel controlineans initially yestablished in the -zopen `position fof said ina condition caused by operation of the ymain switch, meanslresponsiveto closure of ‘oneîofzsaid burner, .separate circuits for .said means estab Contact ‘pairs .for reducing >the :total 'resistance lished respectively by closure of said contact pairs Value of lsaid circuit sufliciently to cause said and having different resistance values, one-ofsaid circuits having a resistance value iin the heated 25 fuel >control‘rnea‘nsto be'placed in said energized condition, Iand means responsive to closure .of condition `of said -ballas't resistor such »that Athe another .one >of said Contact pairs for increasing current vvalue to said means is »Isu'flicient lto «cause vthe;tota`l resistance Vvalue o‘fzsaid circuit sufficient movement thereof to l-fuel supply position and ly ‘to .cause ‘said -fuel control 'means lto Ibe rplaced another said circuit »having a `resistance value such that the ycurrent-value is insufficient to main 30 in said effectively deenergized condition, said cir cuit as Ainitially established having a vresistance tain said means in said fuel supply position, and in the condition in :Whichit has 'been placed 'by position of all .of said ‘Contact pairs Yand having a resistance value `intermediate those of said‘sep arate circuits for rendering the current value in effective‘to ycause said means -to change Athe'po sition to which it has Vbeen‘n'loved Iby establish ment of said one or another‘of said'separate-cir a preceding.closure‘of‘either said one or the other 35 ofY said contact pairs. cuits, `said `ballast resistor being eifective `upon Y extinguishment of >said flame for increasing'the resistance value Vof the last-saidvcircuit and there by reducing the current value 'to saidmeans suffi ciently to cause movement thereof from “said’fuel supply position. l5. In a control system for fuel ~burners,-electrically operable fuel control means arranged ‘for fuel supply -to a'burner whensaidmeans is placed in energized condition and for preventing said fuel 'supply when placed in effectively ydeener gized condition, a con‘trol switch vfor said Ameans including a plurality of contact pairs adapted to be alternatively closed in response yto changes in-a condition caused by‘operation ofthe burner, said switch having -an open position of all of Vsaid contactpairs, acircuit for said fuel control means initially established in the open position of «said operable means movable 'between Apositions for switch and ‘including ya resistor, means responsive controlling the supply of fuel to the main burner, to Vclosure of one of «saidcontact pairs for >introa ballast‘resistor electrically `connected to said means and >responsive to the presence or absence 50 ducing resistance means ‘in parallel circuit with said resistor for reducing lthe total resistance of a flame .at ‘the `pilot burner for varying the value of said circuit sufficiently to cause said fuel current value supplied to said means, a thermo control means to beplaced in saidenergized con static control'svvitch for said.m'eans including'two dition, and means responsive to closure of another pairs of contacts adapted to be alternatively oneof said contact pairs for introducing another closed- in response to changes in a temperature resistance means in parallel circuit with‘said fuel condition causedby operationofthe mainburner, control means for increasing the Atotal resistance a circuit for said means established upon closure value of >said circuit sufñciently to cause 'said of one of said contact pairs on Ya >drop in .said fuel control :means to be placed in said 'eifec temperature and’havinga resistance value „such tively deenergized condition, _said circuit as that the current value to said meansis sufficient initially established having a resistance value to cause movement ïthereof to fuel supply position, 13. A control system for .fuel burners having " main “and 'pilot burners, -comprising electrically a second circuit for said means „established in without either of said resistance means such that the open ,position of said two `contact `pairs on a rise insaid temperature and having aresistance value :greater than that Vof the Afirst >said ,circuit to reduce the current value .to said means ïbut insuiiiciently 'to `.cause movement from Asaid ~fuel supply position, a'third circuit for said Ymeans established `upon closure of `the other of said said control ‘means_is maintained in the condition in which it has‘been placed by apreceding closure of either saidone or the other ofsaid-contact pairs. ' SAMUEL G._ ESKIN. `CI-llAlÈtLES 4K. STROBEL.