Патент USA US2403411код для вставки
Juli’ 2, 1946- I ‘ ’ . v ' c. K. STROBEL _ 2,403,411 COIiTROL SYSTEM FOR FUEL BURNERS Filed ‘Aug. 23, 1944 IN VEN TOR 2' 'BY HIS ATTORNEY 2,403,411 Patented July 2, 1946 UNITED STATES ‘PATENT OFFICE " CONTROL SYSTEM FOR FUEL BURNERS‘ Charles K. Strobel, Pittsburgh, Pa., assignor to - Robertshaw Thermostat Company, Youngwood, Pa... a corporation of Pennsylvania ' Application August 23, 1944, Serial No. 550,755 ' 10 Claims. - (01. 158-1171) This invention relates to control and ignition systems for fuel burners and, more particularly, and a series resistor 34 is associated therewith to facilitate adjustment of the current values in the to systems for domestic gas water heaters em secondary circuit. A ballast resistor. 36 having bodying water temperature andsafety controls. normally a relatively low resistance and a. posi An object of this invention is to control ig nition and fuel flow in conjunction with a bum tive temperature coe?icient of resistance is posi tioned to be exposed to the ?ame of the burner It! for causing, either directly or in cooperation with other devices to be described, operation of the solenoid valve l8 under certain conditions. It will be understood that although the ballast resistor 36 is thermally responsive to the passage er under a number of di?erent conditions includ ing ?ame failure and water temperature. Another object of the invention is to achieve economy in operation by eliminating a constant burning gas pilot. . Another object of the invention is to prolong the life of the electrical ignition device by deen ergizing it as soon as the burner is ignited. Another object of the invention is to utilize an 15 of current therethrough, it isprimarily the heat ing thereof by the burner ?ame which causes the variation in resistance relied upon in this embodiment. ' - electrical bridge type of control circuit in which very little power is consumed during off periods As indicated hereinbefore, a control resistor 38 is provided for cooperation with the ballast of the burner. ' resistor 35 to control operation of the solenoid Other objects and advantages will become ap valve 56 and serves to render the adjustment of parent from the following description taken in 20 the circuit constants less critical. In order to connection with the accompanying drawing, accelerate the operation of the solenoid valve it upon a change in the value of the current sup wherein _ I Fig. 1 is a schematic view of a safety control plied thereto, the control resistor 38 may also _ apparatus and ignition system for a gaseous fuel vary appreciably in resistance value upon ther- -_ mal changes and have normally a relatively low burner embodying the temperature control fea resistance and a positive temperature coezmcient tures of this invention; and Fig. 2 is a circuit diagram showing the elec of resistance, asin the case of the ballast resis trical connections. tor 36. The resistor 381s not, however, exposed Referring more particularly to the drawing, a to the heat of any ?ame but is adapted to become gaseous fuel burner i0 is supplied with fuel by a 3.0 heated upon passage of electric current there through and will vary in resistance value in ac— main fuel pipe l2‘. The fuel supply is controlled -cordance with changes of temperature caused by ' by a main valve it! which, in this instance, is ar changes in the value of the current ?owing ranged for manual operation by a suitable knob through'it. A cut-out 40 is also included in the _ or handle it but which may be arranged for thermostatic operation if desired. Interposed in 35 secondary circuit and is preferably of the ther the fuel supply pipe I? between the main valve M and the burner I0 is an electromagnetic or mal type having time-delayed operation for a‘ purpose which will be apparent hereinafter. Such devices are constructed with predetermined time-current characteristics and usually contain solenoid gas valve iii of any known type which is arranged to be opened by energization of the solenoid and closed by gravity, spring or other 40 a heater element in addition to and a?‘ecting a fusible member which opens the circuit by pas bias upon deenergization or reduction of the cur rent value thereto below holding value. sage of ovcrcurrent. _ , The operating coil of the solenoid valve to is Electric current for the operation of the ap- ‘ paratus is'supplied by the line wires .20 which. arranged to be short-circuited by switching may carry commercial current'at a voltage vari 45 means ,of any suitable type for a predetermined period of time following operation of the main ation from 105 to 125 volts. In this embodiment, switch of valve I 4. Moreover, after the expira the main valve M has a main switch (not shown) tion of a second and longer predetermined pe combined therewith which is of the double-pole riod of time. the igniter 82 is deenergizedand re type having two terminalsconnected in series circuit with the line Wires 20 by wires 24 and 26. 50 mains inoperative during the remainder of the ' running period of the burner M. A thermal tim The other two terminals ' of ‘the double-pole ing switch generally designated 4! is provided switch are connected by wires 28—30 in series for these purposes and includes abimetal switch An electrical igniter 32, preferably of the re arm 42 having a heater coil 44 and resistor 45 as sistance coil type, is provided for the burner-10 55 sociated therewith; a long time-delay- switch arm . circuit with the primary of a transformer 22. ' 2,403,411 3 4 , 48 and a short time-delay switch arm 48 both ' facilitate illustration of the circuit connections‘ of which are resilient and movable in response but without otherwise altering the essential char to warping of switch arm 42. The long delay arm 48 carries contacts 58-—5i on opposite sides it is connected. acter of this timing device or the circuit wherein 8 _ thereof which are movable into and out of op The thermostatic or manual opening of the . erative engagement with contacts 48 and 52 car main valve l4 by its handle l8 permits fuel to ried on bimetal arm 42 and switch arm 48, re ?ow in the main fuel pipe [2 as far as the electro-. magnetic or solenoid valve [8 which is initially closed. As the main switch combined with the spectively. Both switch arms 48 and 48 are initially po sitioned with their contacts 5| and 52 engaged 10 main fuel valve I4 is also operated to closed po sition when the main fuel valve is opened the and with contacts 58 and '48 also engaged, and electrical bridge circuit is established as follows are adapted to open their contacts upon warping with reference to Fig. 1 of the drawing: From the , of the bimetal arm 42 due to the heat of the coil lower terminal of the secondary of the trans 44. Suitable stops may be provided to limit movement of switch arms 48-48 during the 15 former 22, wire 12 to junction A, wire 18, solenoid valve l8, wire 14 to junction B, wire 18, switch opening movement. 'In this embodiment of the arm 48, contacts 58-48, wire 18, resistor 84, wire invention the switch arm 48 has the longer time 88, igniter 32, wire 82, contacts 88-18, wire 8| delay before opening ‘of the contacts 48-58 and to junction C, wire 84, resistor 38, wire 88 to this delay period may be eighteen seconds after the main switch of valve i4 is closed. The switch 20 junction D, and wire 81, resistor 88, wire 88 to . junction A. Wire 88 connects jun'ction- C to the arm 48 has the shorter time delay before open upper terminal of the secondary of transformer ing of the contacts 5I—'52 following the closing 22. i of the main switch of valve l4 and this period may be ?ve seconds. Means responsive to a condition caused by op eration of the burner l8 are provided for con The cut-out 48 is connected as the detector arm 25 of the bridge in this initial or starting period circuit by a wire 88 connecting one terminal thereof to junction B and a wire 82 connecting the other terminal thereof to junction D. The temporary short-circuiting of the solenoid valve 30 I8 is established by a shunt path across junctions A and B by a wire 88 from junction A, wire 84, the drawing, the knob or handle i8 for operating switch arm 48. contacts 52-5 l , switch arm 48 and the combined valve and switch i4 could be uti wire 18 to junction B. The heater coil 44 for lized for setting the temperature regulator 54 to the bimetal switch is connected at one end by a operate at a desired temperature. As indicated schematically in this ?gure, the temperature reg 35 wire 88 to the wire 88 and the opposite end thereof is connected by a wire 88 to one end of resistor 45 ulator 54 may comprise a pair of levers 58-58 the opposite end of which is connected by a wire connected by an overcenter spring 88 and sup I80 to contact 88. ported at opposite ends for snap-action in knife By referring to Fig. 2 of the drawing it will be edgc bearings carried on a pivoted frame 82. The apparent that the bridge consists of the valve coil lever 58 is adapted to be engaged by the actuat iii in one arm in series with the adjacent arm ing portion of a thermally sensitive element 84, formed of the long time-delay switch“, resistor the other portions of the thermal element com 84, igniter 32 and the thermostatic switch 54. prising‘ the usual capillary tube .88 and bulb 88 The other two arms in parallel with‘the fore which is located in the space to be heated by the going consist individually of resistor 88 and re main burner l8. As previously indicated herein sistor 88 'in series. Thus, the current‘from ‘the this space could well be the water tank of a secondary of transformer 22 enters the bridge at domestic water heater and the temperature could junctions A and C while the cut-out 48 is con be regulated by operation. of the thermostat 54 nected as the detector arm at junctions B and in accordance with the setting of the handle £8. The lever 58 carries, at the end opposite the knife 50 D. The short-circuiting of the valve coil is shown as being established by switch arm 48 edge bearing therefor, a contact 88 adapted for connected at junctions A and B. The heater coil movement into and out of engagement with a sta 44 and resistor 45 are shown as connected in par- ' tionary contact 18 to open and close the circuit allel with all the elements of the ?rst two bridge as hereinafter described. It will be apparent that the snap-acting thermostatic regulator 54 55 arms except the thermostatic switch 54 which is in series. circuit therewith. ‘disclosed herein is in schematic form only and In Figs, 1 and 2 the parts are shown in the various modi?cations could be made in the de trolling operation of the thermal timing switch 4| through its heater coil 44 and may comprise a temperature regulator 54 of the snap-acting type. As indicated in broken lines in Fig. 1 of running position with the thermostat calling for heat. Upon initial closing of the main switch of The description of the operation of the device, 60 valve M the elements comprising the bridge cir which now proceeds, includes a description of ' cuit are unheated and the coil of the solenoid the electrical connection for the various parts 01' valve 18 is short-circuited by the short time-delay the apparatus and-reference may be had to Fig. 2 switch comprising switch arm 48 and contacts of the drawing for a clearer understanding of the 8I—52. It will be apparent, therefore, that at 65 precise form of electrical circuit. It will be ap this time the bridge ‘network is considerably un parent from the diagram showri‘in Fig. 2 of the balanced so that the current through the wires drawing that upon initial closure of the main 88—82 to the cut-out 48 is large until the circuit switch of valve l_4 the various elements are con elements heat up and the bridge balance is im nected in abridge type of circuit, except insofar proved. However, due to the time lag of the cut as the heater coil 44 and the short time-delay out 48 the large inrush current upon initial clos switch arm 48 and associated contacts are con- ing of the main switch of valve I4 is ineffective cerned. It will further be observed that the ther to cause operation of the cut-out. Upon expira mal timing element 4| vwhich is shown as a unit tion of the specified ?ve seconds time-delay the in Fig. 1 of the drawing has been separated into two switching devices in Fig. 2 of the drawing to 75 short time-delay switch opens and causes re tails of construction and operation for commer- , cial use. , solenoid valve I8 at the end of the starting pe riod if the ballast resistor 36 has not become heated, a similar provision is made for such valve moval of the short-circuit from the coil I8 01’ the solenoid valve. . - During this preliminary period the igniterv 32 is preheated before any fuel flows from the burn er ‘In and reaches igniting temperature. The solenoid valve I8 is now actuated to open posi closureduring the running period. Thus, if at any time during the operation of the apparatus the flame of the burner I8 ceases, then the ballast tion through the circuit previously traced and the fuel ?owing from the burner III is ignited to produce a ?ame. It will be understood that the current supplied to the coil of the solenoid resistor 38 will cool and its resistance be lowered in consequence so that the current through the valve I8 to cause the pick-up from closed posi tion may be of greater value than that required to maintain this valve in open position. As the igniter 32 is still connected in the circuit when the pick-up occurs and is establishing a rela 15 whereupon closure will occur. tively low impedance therein, it is apparent that coil of the solenoid valve I8 is rendered insu?l- - cient to maintain the valve in open position The heater coil 44 of thebimetallic time-de lay switch, together with the coil of the solenoid valve I8, remains energized until the contacts 88—‘I0 of the thermostat are opened due to the thermostat becoming satisfied. When this oc curs, the heater coil 44 in series circuit with the required value of the current is available these contacts becomes deenergized causing bi even if the ballast resistor 36 is unheated by the“ metal arm 42 to return toward its initial posi burner ?ame and is of relatively low resistance. ~It may be assumed that the ballast resistor 38 20 tion closing ?rst the long delay switch contacts and the control resistor 38 have now become 49-50 and then the short delay switch contacts heated, the former due to the ?ame from the burner I8 and the passage of current'there through and the latter due to the passageoi cur 5I-—5.2. The coil I8 of the solenoid valve con tinues to receive current above release vvalue during this switch closing action and the fuel rent therethrough only. Consequently, the 25 continues to ?ow from the burner I0 until the contacts 5I--52 of the short time-delay switch bridge‘ balanceis improved to such an extent close and cause the coil to be short-circuited. When the temperature of the water in the tank falls below that for which the thermostat has of regardless of whether the main switch of valve I4 is manipulated in on-off-on cycles at this 30 been set then the contacts 83-18 again close ‘ that current through the cut-out 40 is reduced to a value insufficient to cause operation there period of starting operation. The cut-out will . and the sequence of operations previously de now operate only on passage of overcurrent and scribed will commence. thus protects the circuit against failure of the ballast resistor 38 during the running operation. At the expiration or the eighteen-second It will be apparent that the introduction of the high resistance branch circuit in parallel with the coil of the solenoid valve I8 upon, en gagement of the contacts 49-50 of the long _ time-delay of the long time-delay switch com prising switch arm 48 and contacts 50 and 48, - the igniter 32 and series resistor 34 become de energized by operation of the long delay switch to open position. The bridge nature of the cir , cuit is thus eliminated unless the network is considered a bridge with‘ in?nite impedance in one arm. This operation of the switch having the longer‘time-delayed action to open position is entirely automatic and occurs regardless of whether the ballast resistor 38 is heated by the burner ?ame or even whether the burner has be come ignited. As previously indicated, the cur rent to the coil of‘the solenoid valve I8 is now _ time-delay ‘switch during the shutting-off pe riod of the burner does not affect the operation of any part of the system as this branch only 40 carries a fraction of an ampere of current. How? ever, this small current can be eliminated if de sired by substituting a double-pole thermostat for the single-pole type disclosed herein. Such substitution would also eliminate the small amount ' of current which ?ows through the igniter 32' during part of the time the thermo stat contacts 68—'I8 are open. It will be ap parent that‘the substitution of the double-pole thermostat would merely involve the introduc at the predetermined minimum value su?lcient tion of an extra pair of contacts in the circuit of the heater coil 44 as indicated in the broken lines, to retain the valve in open‘ position. Fig. 1 of the drawing. reduced below pick-up value and need be only ' ' It will be seen that a complete condition and safety control system has been provided in con sistor 38 should have become heated by the burn- 55 I junction with ignition means for the main burn er of a water heater or like appliance. While er ?ame and its resistance have increased su?i a preferred embodiment has been disclosed here ciently to cooperate with resistor 38 and raise. in, it will be apparent that many changes can the resistance of the shunt established thereby be made in the arrangement and combination around the coil ‘of the solenoid valve I8 and cut out 48 to compensate for the increase in' total 60 of parts and in the details of construction herein disclosed within the ‘ scope of the appended circuit resistance. Unless this increase in re claims without departing from the spirit of the sistance has occurred'then the current to the solenoid valve coil will decrease below the pre— I claim: determined minimum value for holding purposes 1. In a control system ‘for fuel burners, an elec and the valve I8 will be released to closed posi 65 trical igniter, an energizing circuit for said igniter, tion. It will be understood that the predeter a thermal switch having contacts operable for mined minimum current value referred to herein opening and closing said circuit, a heater for said~ is established by adjustment of the-circuit con switch, and a control switch having contacts oper stants and takes into account the ?uctuations in able ior'controlling said heater and being coop~ the line voltage. Such action of the resistors era-ble with said thermal switch contacts for con 38 and 38 is accelerated by providing that re trolling said circuit. sistor 38 be subject to the heating effects of the When the contacts 49-58 of the long time-de lay switch become disengaged the ballast re invention.‘ . current passing therethrough and the valve clos ing time is generally short. , ' - ' In addition to the provision for closing oi the _ . 2..In a control system for a fuel burner, an electrical igniter, an energizing circuit for said igniter, a thermal switch having contacts oper 2,403,411 I7 8 . adapted in one position to short-circuit said con able for opening and closing said circuit, a heater trol device, a heater for said thermal switch con connected in parallel circuit with said igniter and ' _ thermal switch and causing operation» of said - thermal switch contacts for supplying heat‘ to said thermal switch, a control switch having con trolled by thelcontact iposition of said control switch, and means responsive to the demand for heat from the burner for actuating said control tacts operable for opening and closing said heater switch. 8. A safety control system for fuel, burners, circuit and being cooperable with said thermal comprising in combination, an electrical bridge switch contacts for controlling said energizing circuit having a plurality of resistors in two arms circuit, and- means responsive to the demand for heat from the burner for actuating said control 10 thereof, one ‘of saidresistors being exposed to ' the burner flame and adapted to vary in resistance switch. » 3. A safety control and ignition system for fuel value when heated thereby; an electrically oper burners comprising in combination an electrical able fuel control device and a control switch in the other two arms ‘respectively, said other two arms bridge circuit having a plurality of resistors in two arms thereof; a pair of bridge arms in par 15 being in parallel circuit with said resistor arms, the current value to said control device being allel circuit with said resistor arms and includ ing an electrically operable fuel control device in varied according to said resistance value to control one of said pair of bridge arms, an igniter in an operation of said device; means affording a cur rent path across intermediate points of said bridge other of' said pair of bridge arms, and a pair of switches having contacts in said other pair of 20 circuit to maintain said device energized irrespec tive of said switch position; a thermal switch bridge arms and in series circuit with said device and igniter; vand means operable in one contact adapted in one position to short-circuit saidcon- . position of one of said switches for operating the trol device; and a heater for said thermal switch other to open its contacts and thereby deenergize , controlled by said control ‘switch. _ " > 9. A safety control and ignition system for a 25 said igniter. '. .4. A safety control and ignition system for fuel burners comprising in combination an electrical bridge circuit having‘a plurality of resistors in fuel burnerLcornprising in combination, an-elec- ‘ trical bridge circuit having a plurality of resistors in two arms thereof, one of said resistors being two armsthereofwa pair of bridge arms in par- 1. exposed to the burner ?ame and adapted to vary allel circuit with said resistor arms and includ 30 in resistance value when heated thereby; a pair ing an' electrically operable fuel control device in of bridge arms in parallel circuit with said resistor one of said pairrof bridge arms, an igniter in a'rmsand including an electrically operable fuel another of said pair of bridge arms, and a pair control device in one of said pair of bridge arms, of switches having contacts insaid other pair of an igniter in another one of said pair of bridge bridge arms and in series circuit with said device arms, and a pair of switches having contacts in. and igniter, one of said switches being thermally‘ said other one of said pair of bridge arms‘and in operable vwith time delayed action; and heating series circuit with said device and igniter, the means controlled by the contact position of the current value to said control device being varied other said switch for operating said thermal according to said resistance value to control oper switch to open its contacts and thereby deener 40 ation of said device; means affording a current gize said igniter. ' path across intermediate points of said bridge 5. Asafety control and ‘ignition system for a circuit to maintain said device energized irre fuel burner comprising in combination an elec spective of said switch contact position; a third -, trical bridge circuit having a plurality of resis switch having contacts adapted in one position ‘ tons in two arms thereof; a pair of bridge arms in ' to short-circuit said control device; means con parallel circuit with said resistor arms and includ trolled by one of said ,pair of switches for causing ing an electrically operable fuel control device operation of the other one of said pair and said in one of said pair of bridge arms, an igniter in third switch;_and means responsive to the demand another of'said pair of bridge arms, and a pair for heat from the burner for actuating said one of switches having contacts in said other pair of 50 switch.v . bridge arms and in series circuit with said de 10. A safety control and ignition system for a vice and igniter, one of said switches being ther-' fuel‘burner', comprising in combination, an elec mally operable with time delayed action, heating trical bridge circuit having a plurality of resistors means controlled 'by the ‘contact position of the in two arms thereof, one of said'resistors being other said switch for operating said thermal 55 exposed to the burner ?ame and adapted to vary switch to open its contacts and thereby deener in resistance value when heated thereby; a third gize said igniter, and means responsive to the arm of said bridge including an electrically oper demand for heat from the burner for actuating able fuel control.device;a fourth arm of said said other switch to change said contact position. bridge including an igniter, a control switch and a 6. In a safety control system for fuel burners 60 thermal switch, said ‘switches having contacts havinga source of electrical energy, an electri-v in series circuit with said device and igniter, the cally operable fuel controldevic'e in circuit with current value to said device being varied accord the source,‘ a control switch having contacts oper ing to said resistance value to control operation ' able for opening and closing a second circuit from of said device; means “affording a current path the source, a thermal switch. having contacts 65 , across intermediate points of said bridge to main adapted in one position to short-circuit said con tain said device energized irrespective of said trol-device, and a heater for saidthermal switch controlled by the contact position of, said control switch. ' -, _ switch'contact position; a second thermal switch having contacts adapted in one position to short circuit said control device; heating means for i 7.‘ In a safety control system for a fuel burner 70 said thermal switchescontrolled by~ the'contact having a source of electrical energy, an electrically position of said control switch; and means re operable fuel control device in circuit with the source, a control switch having contacts oper-' . able for opening and closing a secondv circuit from the source, athermal‘switch having contacts 75 sponsive to the demand for heat from the burner - for actuating said control switch to change ‘said contactiposition. . a , _ , - . _ QHARLIS K. STROBEL.