Fail-safe gas feed and ignition sequence control apparatus and method for a gas-fired appliance

Page 1scan →

Jaaited States Patent (19)

Elaay

(54 fail-safe gas feed and ignition

Sequence control apparatus and

Method for a gas-fired appliance

75 inventor: Richard A. Elmy, Louisville, Ky.

73 Assignee: W. M. Cissell Manufacturing

Company, Louisville, Ky.

52 U.S. C. .......................................... 432/46; 431/6;

58. Field of Search ..................... 431/2, 6, 66, 67, 69,

2,954,080 9/1960 Prouty et al........................... 431/71 3,367,386 2/1968 Thunander ............................. 431/71 3,536,308 10/1970 White ..................................... 432/44 3,806,308 4/1974 Cahoe et al. ...... . 431/66 X 3,871,814 3/1975 Das et al. ............................... 431/66 4,019,853 4/1977 Sears et al. ............................. 431/67

Primary Examiner-Carroll B. Dority, Jr.

Assistant Examiner-Lee E. Barrett

Attorney, Agent, or Firm-Wood, Herron & Evans

A fail-safe apparatus and method for controlling the sequence of gas feed and ignition, such as by an incan descent igniter, in a gas-fired appliance, such as a ther mostatically controlled timer activated clothes dryer. When the appliance is activated by the timer, the con trol apparatus energizes the igniter and opens a gas valve only after the igniter is energized for a period that is sufficient to heat the igniter to the temperature re quired to kindle the gas. If the gas is ignited, the control apparatus holds the gas valve open so that the gas con tinues to burn. If, however, the gas is not ignited, the control apparatus inhibits any further attempt at gas feed and ignition. If a temporary electrical power out age occurs, if the gas supply is interrupted, if the ther mostat cycles on and off, or, in the case of a clothes dryer, if a loading/unloading door is opened and then shut again, the control apparatus repeats the gas feed and ignition sequence in an attempt to rekindle the gas. 9 Claims, 1 Drawing Figure

Drawings

Page 2drawing sheetscan →

Page 3scan →

Summary of the invention

Fail-safe gas feed and ignition

SEQUENCE CONTROL APPARATUS AND Accordingly, one objective of this invention is to METHOD FOR A GAS-FIRED APPLIANCE provide a combustion control apparatus and method for controlling the sequence for gas feed and ignition by an

BACKGROUND OF THE INVENTION incandescent igniter, such as a silicon carbide igniter, This invention relates to combustion control. More which is reliable and has a long life expectancy. An other objective is to provide apparatus of such type particularly, this invention relates to a fail-safe gas feed which is fail-safe. A further objective is to provide a and ignition sequence control apparatus and method for 10 fail-safe apparatus which is thermostatically controlled. controlling combustion in a gas-fired appliance, such as An additional objective is to provide a fail-safe appara a clothes dryer. tus for a thermostatically controlled timer activated The prior art discloses many different forms of com clothes dryer having a safety means associated with the bustion control apparatus and methods for controlling loading/unloading door.

the feed of fuel, generally, fuel oil or natural gas, and 15 In accordance with a preferred embodiment of this ignition of the fuel in appliances such as furnaces, water invention, a fail-safe combustion control apparatus is heaters, cooking ovens, clothes dryers, etc. In some provided which comprises circuitry that includes an instances, the temperature of the environment heated by incandescent igniter, a gas feed time delay switch the appliance is controlled by a thermostat. In other 20 means, a solenoid means for controlling a gas valve, a instances, as in the case of cooking ovens and clothes holding resistor, a flame sensing means and a time delay lockout switch means connected in circuit with the dryers, the appliance is activated by a timer.

Much of the prior art relates to combustion control power leads of an electrical power source. A timer, a apparatus of a type which includes a pilot burner for thermostatsafety means, and/or, in the case of a clothes dryer, a such as a loading/unloading door safety igniting fuel fed to a main burner when heat is de 25 switch, are preferably manded. Such type was developed when fuel was plen tion control apparatus connected between the combus tiful as well as cheap and energy waste was tolerable. tively control the supply of electricalsource and the power to selec power to the

Furthermore, electrical igniters, such as spark igniters circuitry which comprises the combustion control ap and incandescent igniters, had not been developed to paratus.

the point where they were reliable and had a long life 30 The igniter, the operator of the gas feed time delay expectancy.

Since the advent of the spark igniter and the incan switch means means and the cold contact of the flame sensing are connected in series across the power leads.

descent igniter, such as the silicon carbide igniter, hav The solenoid means for controlling the gas valve is ing reliability and long life expectancy, a shift toward a connected in series with a normally open contact of the type of combustion control apparatus which includes an 35 gas feed time delay switch means across the power electrical igniter has become evident in the prior art. leads. When the power source is selectively connected The shift has received added emphasis in view of fuel to the power leads, preferably through the timer, the shortages as well as the increased expense of fuel which igniter is energized.

makes energy waste intolerable. When the igniter has been energized for a period that Of the electrical igniters, the incandescent igniter has is sufficient to heat the igniter to the temperature re the advantage that the circuitry which comprises the quired to kindle the gas, the operator of the gas feed combustion control apparatus is simpler and cheaper. time delay switch means closes the normally open This is because the incandescent igniter does not require contact to connect the solenoid means directly across a generator means for triggering sparks required for a the power leads. Consequently, the solenoid means spark igniter but only requires a means to electrically 45 opens the gas valve so that gas flows over the igniter. heat the incandescent igniter. If the gas is not kindled, the operator of the time Although the prior art mentions various safety prob delay lockout switch means, which is connected in lems and in some instances provides combustion control series with the cold contact of the flame sensing means apparatus which to some degree is fail-safe, prior art 50 across the power leads, opens a normally closed contact combustion control apparatus of the type which in to isolate the igniter and the solenoid means from the cludes an incandescent igniter by and large is not fail before power source. Consequently, the timer must time out safe. For example, if the incandescent igniter were de gized. Inthethetime delay lockout switch means is de-ener fective or if the fuel were to fail to ignite, a valve would inside at the end of case a clothes dryer, damp clothes found the timed drying period indicate a nevertheless feed fuel so as to cause the danger of fire or 55 malfunction. As a result, explosion. Furthermore, if a temporary electrical power gas is not kindled for anyfail-safe reason. operation results if the outage were to occur or if the fuel supply were inter If the gas is kindled, the flame sensing means is actu rupted, extinguishment of the ignited fuel would occur, ated but fuel would again feed through the valve on restora of thesoflame that the cold contact is opened and a hot contact sensing means is closed. Consequently, the tion of the electrical power or fuel supply so as to cause solenoid means is connected in series with the holding the danger of fire or explosion. Additionally, in some resistor and the hot contact across the power leads. As applications where a thermostat controls temperature a result, the solenoid means is energized to hold the gas or where there is a safety means, such as a loading/un valve open even after the normally open contact of the loading door safety switch for a clothes dryer which gas feed time delay switch means is reopened due to assures that fuel is not ignited when the door is open, 65 de-energization of the operator of the gas feed time the danger of fire or explosion similarly exists when the delay switch means after the cold contact is opened. thermostat cycles on and off or the safety means is Whereas direct energization of the solenoid means actuated and then deactuated again. through the normally open contact of the gas feed time 4 delay switch means opens the gas valve, energization of When the power source 11 is connected to the power the solenoid means through the hot contact of the flame leads 12 and 13, preferably through a timer 20, which is sensing means and the holding resistor merely holds the shown schematically, the igniter 14 is energized gas valve open. Consequently, if a temporary electrical through a circuit including the power lead 12, the nor power outage occurs and the gas valve closes but the mally closed contact 21NC of a time delay lockout hot contact remains closed when electrical power is switch means 22, which will be described later, the restored, the resultant energization of the solenoid igniter 14, the operator 15 of the gas feed time delay means through the holding resistor is insufficient to switch means 16, the cold contact of the flame sensing open the valve. As a result, fail-safe operation results if means 17, the timer 20 and the power lead 13. When the a temporary power outage occurs so that the entire gas 10 igniter 14 has been energized for a period that is suffi feed and ignition sequence must be repeated, as will cient to heat the igniter to the temperature required to happen once the cold contact of the flame sensing kindle the gas, that is, to about 1800 F., the negative means is again closed. In the case of an applicant having thermal characteristic of the igniter 14 allows the opera a thermostat and/or, in the case of a clothes dryer, a tor 15 of the gas feed time delay switch means 16 to be loading/unloading door safety switch, analogous fail 15 energized sufficiently to close the normally open safe operation takes place whenever the thermostat contact 15NO.

cycles on and off and/or the loading/unloading door is When the operator 15 of the gas feed time delay opened and then shut again. switch means 16 closes the normally open contact Even if the source of gas is temporarily interrupted 15NO, the solenoid means 18 is energized through a and the flame is extinguished, the hot contact of the 20 circuit including the power lead 12, the normally closed flame sensing means is opened to de-energize the sole contact 21NC of the time delay lockout switch means noid means. Consequently, the entire gas feed and igni 22, the solenoid means 18, the normally open contact tion sequence must be repeated, as will happen once the 15NO of the gas feed time delay switch means 16, the cold contact of the flame sensing means is again closed. 25 timer 20 and the power lead 13. Consequently, the gas The combustion control apparatus and method in valve 19 is opened to feed gas over the igniter 14 when accordance with the preferred embodiment of this in the solenoid means 18 is energized upon closure of the normally open contact 15NO of the gas feed time delay vention advantageously has fail-safe operation so that switch means 16.

the danger of fire or explosion is eliminated. Notwith standing this advantage, the preferred embodiment is 30 Preferably, a thermostat 24 is also included in the circuit through which the solenoid means 18 is ener simple to construct and economical and yet is reliable gized.

and has a long life expectancy. The preferred embodi such In the case of a clothes dryer, a safety means 23, ment has been found particularly advantageous when tionally aconnected as loading/unloading door safety switch, is addi in the energizing circuit for the sole incorporated in a gas-fired clothes dryer, but applica noid means 18.

tion in appliances, particularly thermostatically con 35 If the gas is not kindled, the cold contact of the flame trolled and/or timer activated appliances such as fur sensing naces, cooking ovens, etc., would also have advantages. operatormeans 17 remains closed. Consequently, the 21 of the time delay lockout switch means 22 is

BRIEF DESCRIPTION OF THE DRAWING energized through a circuit including the power lead 12, This invention will be better understood and its con 40 the operator 21 of the time delay lockout switch means comitant advantages will become clear to those skilled 22, the20cold contact of the flame sensing means 17, the in the art through a consideration of the drawing in timer and the power lead 13. The time delay lockout conjunction with the description which follows. The means 22 may comprise an electrical time delay relay or a thermal time delay relay with a 60-second time delay, single FIGURE of the drawing is a schematic circuit for example. If the flame sensing means 17 fails to detect diagram of a preferred embodiment for the fail-safe 45 ignition of the gas so that the cold contact of the flame combustion control apparatus of this invention. sensing means 17 remains closed, the operator 21 of the DESCRIPTION time delay lockout switch means 22 opens the normally closed contact 21NC.

The gas feed and ignition sequence control circuitry When the normally closed contact 21NC of the time of the preferred embodiment for the fail-safe combus 50 delay tion control apparatus of this invention, designated meanslockout switch means 22 is opened, the solenoid generally by the numeral 10, is connected to a source of closes. 18 is deenergized. Consequently, the gas valve 19 electrical power 11 through two power leads 12 and 13. The operator 21 of the time delay lockout switch The power source is preferably a readily available do means 22 continues to be energized through a holding mestic alternating current power supply. 55 circuit including the power lead 12, the operator 21 of An incandescent igniter 14, such as a silicon carbide the time delay lockout switch means 22, the cold igniter, is connected in series with the operator 15 of a contact of the flame sensing means 17, the timer 20 and gas feed time delay switch means 16, such as an electri the power lead 13. Consequently, the time delay lock cal time delay relay or a thermal time delay relay. The out switch means 22 provides a fail-safe if the gas is not series-connected igniter 14 and operator 15 are con kindled for any reason, such as if the igniter 14 is defec nected across the power leads 12 and 13 when the cold tive, the flame sensing means 17 is inoperative, the gas contact of a flame sensing means 17, such as a Harper fails to ignite for any reason or the gas supply is cut off. Wyman Co. single-pole, double-throw flame switch The timer 20 must time out before the time delay lock #6313, is closed. Furthermore, a solenoid means 18 for out switch means 22 is deemergized. In the case of a controlling a gas valve 19, which is shown schemati 65 clothes dryer, damp clothes found inside at the end of cally, is connected in series with a normally open the timed drying period indicate a malfunction. contact 15NO of the gas feed time delay switch means If the gas is kindled, the flame sensing means 17 is 16 across the power leads 12 and 13. actuated so that the cold contact is opened and a hot 5 contact of the flame sensing means 17 is closed. Al causes the cold contact of the flame sensing means 17 to though the operator 15 of the gas feed time delay switch be closed due to extinguishment of the flame, the igniter neans i3 is de-energized when the cold contact is 14 and the operators 15 and 21 of the respective gas feed opened, the gas feed time delay switch means 16 is of time delay switch, means 16 and time delay lockout the siow-to-release type, so that the normally open 5 switch means 22 are again energized. Consequently, contact SNC does not open until such time as the hot recycling is initiated, and the above-described gas feed contact of the flane sensing means 17 has already and ignition sequence is repeated in an attempt to rekin closed. Consequently, the solenoid means 18 is ener dle the flame.

gized through a holding circuit including the power The combustion control apparatus in accordance lead 12, the normally closed contact 21NC of the time 10 with the preferred embodiment of this invention advan delay lockout switch means 22, the loading/unloading tageously has fail-safe operation in the event of failure door safety switch 23, the thermostat 24, the solenoid to ignite the gas for any reason, an electrical power means i8, a holding resistor 25, the hot contact of the outage, interruption flame sensing means 17, the timer 20 and the power lead mostat and/or, in theofcase the gas supply, cycling of a ther of a clothes dryer, opening of 13 before the normally open contact 15NO is opened. 15 the loading/unloading door. This eliminates the danger As shown in the drawing, when the cold contact of the flame sensing means 17 is opened, the igniter 14 and of fire or explosion. Notwithstanding this advantage, the preferred embodiment is simple in construction and the operator 21 of the time delay lockout switch means economical.

22 are also de-energized. This extends the life expec cent igniter, Due the to the incorporation of an incandes preferred embodiment is reliable and tancy of the igniter 14 and, of course, prevents the time 20 delay lockout switch means 22 from inhibiting further hasAlthough a long life expectancy. the preferred embodiment is energized by operation of the igniter 14 and the solenoid means 18.

Energization of the solenoid means 18 through the an alternating current power supply, the circuitry could holding circuit is sufficient to maintain the gas valve 19 be readily modified for energization by a direct current open but is not sufficient to open the gas valve 19. This 25 power supply by substituting direct current switch provides a fail-safe in the event a temporary electrical means, such as electronic switches, for the gas feed time power outage occurs, the thermostat 24 cycles on and switch delay switch means 16 and the time delay lockout off or, in the case of a clothes dryer, the loading/un means 22 and a direct current solenoid means for oading door safety switch 23 is actuated and then deac the solenoid means 18. These and other modifications tuated again. 30 will become apparent to those of skill in the art without Specifically, if a temporary electrical power outage departing from the scope of this invention. occurs, the solenoid means 18 is de-energized so that the The preferred embodiment has been found particu gas valve 19 closes and the flame is automatically extin larly advantageous when incorporated in a gas-fired guished. Furthermore, if the thermostat 24 switches on clothes dryer and has been described in connection with and then off again, the holding circuit for the solenoid 35 such an application. Nevertheless, application in other means 8 is opened. Similarly, if the loading/unloading appliances, particularly thermostatically controlled door is opened and then shut again, the holding circuit and/or timer activated appliances such as furnaces and for the solenoid means 18 is opened. In the event that cooking ovens, would provide similar advantages as the thermostat 24 cycles on and then off again or the will be apparent to those of skill in the art. loading/unloading door safety switch is actuated and Having described my invention, I claim: then deactuated again, so that the holding circuit for the 1. A fail-safe combustion control apparatus for con solenoid means 18 is opened, the solenoid means 18 is trolling the gas feed and ignition sequence in a gas-fired de-energized so that the gas valve 19 closes and the appliance, comprising circuitry including: flame is extinguished. power leads selectively connected to an external If the electrical power is restored, the thermostat 45 source of electrical power;

cycles on again or the loading/unloading door is shut an incandescent igniter for kindling gas to provide a again before the hot contact of the flame sensing means flame;

17 is reopened, the re-established energization of the a gas feed time delay switch means having an opera solenoid means 18 through the holding circuit is insuffi tor and a normally open contact; cient to open the gas valve 19. This prevents the feed of 50 a flame sensing means having a cold contact and a hot gas, since the gas might not be rekindled. contact for detecting said flame; if the timer 20 has not timed out, however, because a time delay lockout switch means having an operator electrical power outage, thermostatic control or open and a normally closed contact; ing of the loading/unloading door causes the cold said incandescent igniter, said gas feed time delay contact of the flame sensing means 17 to be closed due 55 switch means operator, said normally closed to extinguishment of the flame, the igniter 14 and the contact of said time delay lockout switch means operators 15 and 21 of the respective gas feed time delay and said cold contact being connected in series switch means 16 and time delay lockout switch means across said power leads;

22 are again energized. Consequently, recycling is initi a solenoid means for controlling a gas valve; ated, and the above-described gas feed and ignition said solenoid means, said normally closed contact of sequence is repeated in an attempt to rekindle the flame. said time delay lockout switch means and said nor Even if the gas supply is temporarily interrupted so mally open contact of said gas feed time delay that the flame is extinguished, the hot contact of the switch means being connected in series across said flaine sensing means is reopened. Consequently, the power leads;

holding circuit for the solenoid means 18 is opened so 65 said time delay lockout switch means operator and that the solenoid means 18 is de-energized and the gas said cold contact being connected in series across valve 19 closes. As a result, however, if the timer 20 has said power leads; and not timed out, because interruption of the gas supply a holding resistor;

Page 6scan →

said holding resistor, said hot contact, said solenoid fails to detect kindling of a flame, thereby provid means and said normally closed contact of said ing fail-safe operation if the gas is not kindled; time delay lockout switch means being connected energizing the solenoid means only through the resis in series across said power leads. tor under control of the flame sensing means when 2. The fail-safe combustion control apparatus of claim a flame is detected so that the gas valve is held 1 further including: .. open;

a timer for selectively connecting said external source de-energizing the time delay lockout switch means of electrical power to said power leads. under control of the flame sensing means when a 3. The fail-safe combustion control apparatus of claim flame is detected;

1 further including: O de-energizing the solenoid means so as to close the a thermostat, said thermostat being connected in se gas valve, under control of the holding resistor ries with said series-connected normally closed when the electrical power source fails, thereby contact of said time delay lockout switch means, providing fail-safe operation if a temporary electri solenoid means, holding resistor and hot contact cal power outage occurs; and de-energizing the solenoid means so as to close the 4. The fail-safe combustion control apparatus of claim gas valve under control of the flame sensing means 3 wherein said gas-fired appliance is a clothes dryer when the gas supply is interrupted, thereby provid having a loading/unloading door and further including: ing fail-safe operation if the gas supply is temporar a loading/unloading door safety switch, said loading ily interrupted.

Munloading door safety switch being connected in 20 6. The method of claim 5 further including the step series with said series-connected thermostat, nor of:

mally closed contact of said time delay lockout re-initiating the gas feed and ignition sequence under switch means, solenoid means, holding resistor and control of the flame sensing means in the event of hot contact across said power leads. fail-safe operation except due to failure to kindle a 5. A method for controlling the gas feed and ignition 25 flame.

sequence in a gas-fired appliance having a combustion 7. The method of claim 5 or 6 wherein the circuitry control apparatus comprising circuitry including an further electrical igniter, a gas feed time delay switch means, a nects theincludes a timer and the timer selectively con electrical power source to the power leads.

solenoid means for controlling a gas valve, a holding 8. The method of claim 5 or 6 wherein the circuitry resistor, a flame sensing means and a time delay lockout 30 further switch means connected in circuit with power leads of of: includes a thermostat, further including the step an electrical power source selectively connected to the power leads, including the steps of: de-energizing the solenoid means so as to close the selectively connecting the electrical power source to gas valve under control of the thermostat, thereby the power leads; - 35 providing fail-safe operation whenever the desired energizing the igniter, the gas feed time delay switch temperature of the environment heated by the gas means and the time delay lockout switch means fired appliance is reached.

9. The method of claim 5 or 6 wherein the gas-fired when the flame sensing means detects that no flame appliance is present; is a clothes dryer having a loading/unloading energizing the solenoid means under control of the 40 door and wherein the circuitry further includes a loa gas feed time delay switch means when the igniter ding/unloading door safety switch, further including heats to a temperature required to kindle the gas, the step of:

thereby opening the gas valve so that gas feeds de-energizing the solenoid means so as to close the over the igniter; • gas valve under control of the loading/unloading inhibiting further operation of the igniter and the 45 safety switch, thereby providing fail-safe operation solenoid means under control of the time delay whenever the loading/unloading door is opened. lockout switch means if the flame sensing means