US3551083A

US3551083A - Fuel burner ignition

Info

Publication number: US3551083A
Application number: US742577A
Authority: US
Inventors: Leonard H Michaels
Original assignee: Harper Wyman Co
Current assignee: Harper Wyman Co
Priority date: 1968-07-05
Filing date: 1968-07-05
Publication date: 1970-12-29
Anticipated expiration: 1987-12-29
Also published as: FR2012330A1; DE1934009A1; GB1263191A

Description

L. H. MlcHAELs FUEL BURNER IGNITION Dec. 29, 1970 2 Sheets-Sheet Filed July 5. 1968 INVENTORI LEONARD H. MICHAELS y WW,

6 F 4 9 4 8 8 NJ P m F I m w I OI m OI M 6 6 I m 4 H u J 3 m I O 8 I ll 4. 5 4 F 6 0 5 w I.-- I f 2 7 m x 4 |.|l\1|.|||.| A "I" 4 Q m 2 9 4 0 8 If 7 2 I 6 I 4 w II o w w 1 I w m I 1 6 7L 6 w. Q l m lll Attorneys Dec. 29, 1970 Filed July 1968 L. H. MICHAELS FUEL BURNER IGNITION 2 Sheets-Sheet 3 LEONARD H. MICHAELS Attorneys United States Patent C 3,551,083 FUEL BURNER IGNITION Leonard H. Michaels, La Grange, Ill., assignor to Harper- Wyman Company, Hinsdale, 11]., a corporation of Illinois Filed July 5, 1968, Ser. No. 742,577 Int. Cl. F23n 5/00 U.S. Cl. 43166 9 Claims ABSTRACT OF THE DISCLOSURE A fuel burner is ignited automatically and safely by an electrical igniter in circuit with an electrically operated fuel valve, and fuel is not admitted to the burner unless the igniter produces a reliable ignition condition. The igniter and valve are interconnected in such a way that failure of the igniter prevents operation of the valve. The Valve is not opened unless the igniter is energized at a level sufficient to produce reliable ignition. Simultaneous energization of the igniter and valve may be controlled by a manual or thermostatically operated switch. A fuse in series with the igniter can protect against shorting of the igniter, and a transformer may be used to protect against grounding of the control circuit. In a multiple burner system, an igniter is provided for direct ignition of each burner, and a single electrically operated valve controls flow to the burners. The valve does not open unless a reliable ignition condition is produced at each burner.

The present invention relates to improved electrical ignition apparatus for fuel burners.

Many known fuel burning appliances such as gas ovens and the like are provided with automatic ignition systems for igniting a main burner from a pilot burner. The ignition pilot may operate continuously, or alternatively the system may include an intermittent pilot burner ignited either electrically or from a smaller continuous pilot burner. In automatic ignition systems it is of great importance from a safety standpoint that unignited fuel be prevented from escaping from the main burner. For this reason, it has become conventional industry practice to include a safety device in such systems for sensing the presence of an ignition pilot flame and for preventing the admission of fuel to the main burner unless an ignition flame is present.

Many types of pilot responsive safety devices are in use. One type includes a valve controlling flow of fuel to the main burner together with a flame sensing element such as a mercury filled bulb, a thermocouple, or an expansible rod for sensing the pilot flame and for opening the valve only when a flame exists at the ignition pilot. In electrically controlled systems, the safety device may take the form of a switch controlled by a flame sensing element for preventing the operation of a solenoid fuel valve when an ignition flame does not exist at the ignition pilot.

Similar considerations arise in multiple burner systems, such as space heating systems, wherein plural burners are operated simultaneously to increase the heat output. In this type of system a pilot may be used to ignite one burner and the other burner or burners may be ignited through flash tubes or the like. A pilot responsive safety device is customarily included to prevent flow to the burners unless a flame is present at the pilot. In such a system it is possible for unignited fuel to escape from a burner if the flash tube or other ignition transfer device fails to function because the safety device is opened by the pilot.

It is an important object of the present invention to provide improved ignition systems for fuel burners.

Another object of the invention is to provide an automatic ignition system which prevents the escape of un ignited fuel, and which is considerably simpler and less expensive than known arrangements.

A further object is to provide an improved ignition apparatus in which the need for an ignition pilot and associated safety device and sensing element is eliminated without sacrifice of safety.

Another object is to provide an improved multiple burner ignition system for igniting and preventing the escape of unburned fuel from a plurality of burners.

Briefly, in accordance with the present invention there is provided an improved ignition system of great sim plicity and economy wherein the usual ignition pilot, sensing element and safety device are not necessary. More particularly, the ignition apparatus of the present invention may include a valve for controlling the flow of fuel to one or more fuel burners, together with an electrically operated igniter disposed adjacent each burner. The valve is operated by an electrically operated actuator in circuit with the igniter or igniters so that operation of the actuator, and thus operation of the valve, is conditioned upon satisfactory operation of each igniter in producing an ignition condition at the burner or burners.

The invention together with the above and other objects and advantages may be best understood from consideration of the followingdetailed description of certain illustrative embodiments shown in the accompanying drawing in which:

FIGS. 1, 2, 3 and 4 are diagrammatic and schematic illustrations of alternative embodiments of the invention.

Referring now to the drawing, and initially to FIG. 1, there is illustrated a new and improved ignition system constructed in accordance with the principles of the in vention and designated as a whole by the reference numeral 10. In accordance with the present invention, the novel ignition system 10 serves automatically and safely to ignite fuel flowing from a burner 12 and to prevent the escape of unignited fuel from the burner.

Fuel is supplied to the burner 12 from a supply or manifold 14 by Way of an electrically operated valve assembly generally designated as 16 including a normally closed valve 18 controlled by an electrically operated actuator in the form of a solenoid winding 20. The solenoid valve 16 is illustrated only diagrammatically and schematically since many varieties are commercially available and the construction and operation of such valves are well known to those skilled in the art. Fuel flowing.

to the burner 12. enters the burner in the usual manner through an inlet fittin 22 and mixing tube 24 and escapes from the burner through burner ports 26.

In order to ignite fuel flowing from the burner ports 26 of the burner 12, an electrically operated igniter 28 is mounted adjacent one or more of the ports 26. In the illustrated embodiments of the invention, the igniter comprises an electrical resistance heating element, although other types of electrically operated igniters are within the contemplation of the invention. One type of resistance heating element that has been found to be satisfactory is a length of wire formed of molybdenum silicide with ceramic additives, available under the name Kanthal- Super from the Kanthal Corporation of Bethel, Conn. This material is preferred because it reaches an ignition temperature very rapidly upon energization, but it should be understood that resistance heating elements of other types and formed of other materials might be used without departing from the scope of the invention.

In the operation of ignition systems for igniting fuel burners, it is desirable that unignited fuel be prevented from escaping from the burner under any circumstances. Obviously, the escape of unignited fuel could present a safety hazard from explosion, asphyxiation and the like. In ignition systems of a type used in the past a pilot burner is used for ignition, and a sensing element responsive to a pilot flame controls a safety device to prevent flow of fuel to the burner unless a pilot flame exists. Such arrangements, although adding complexity and expense to past ignition systems, are necessary to establish proof of ignition-in other words to provide a reliable implication that fuel introduced to the main burner is ignited.

In accordance with an important feature of the present invention, it is possible to dispense with an ignition pilot and associated sensing element and safety device without sacrificing safety of the ignition system. In accordance with this feature of the invention, the electrically operated valve 16 and the electrically operated igniter 28 are adapted to be energized simultaneously and at related energization levels from a power source represented by a pair of

power supply terminals

30 and 32 by a control circuit generally designated as 34. The arrangement is such that if the igniter element 28 fails, the electrically operated valve 16 does not open to admit fuel to the burner 12. In addition, should the power supply be incapable of energizing the igniter 28 at a level sufficient to produce a reliable ignition condition, the electrically operated valve 16 is not opened.

More specifically, the control circuit 34 includes a series circuit arrangement of the solenoid 20, the igniter element 28 and a manually operated control switch 36 In normal operation, the switch 36 is closed in order automatically to operate the burner 12 by admitting fuel to the burner and igniting fuel flowing from the burner ports 26. When the switch 36- is closed, a circuit is completed in which the igniter element 28 and the solenoid 2.0 are connected in series across the

power supply terminals

30 and 32. As a result, the solenoid is effective to open the valve 18, and at the same time current flowing through the igniter element 28 heats the igniter element and provides ignition for fuel flowing from the burner ports 26.

Since the igniter element 28 and solenoid 20- are in series with one another, protection is provided against a situation wherein the igniter element fails. For example, if the igniter element burns out or is broken, an open circuit is created and current cannot flow through the solenoid 20. Thus if an attempt is made to operate the burner 12 by closing the switch 36, the valve 18 does not open and an unsafe condition is avoided.

Another aspect of the invention has to do with a novel arrangement for preventing operation of the valve 16 in the event that the igniter element 28 receives insufiicient current to produce a reliable ignition condition. For any given design of the igniter element 28, in the illustrated arrangement, there exists a predetermined energization level at which the igniter element reaches a temperature sufiicient to provide reliable ignition. This energization level can be represented as a predetermined current flowing through the igniter element. In accordance with the invention, the solenoid winding 20 is designed so that it is incapable of producing a sutficient electromagnetic force to open the valve 18 unless the current flowing through the circuit 34 is above the predetermined level required for safe operation of the igniter element 28. Thus, if an attempt is made to operate the burner 12 by closing the switch 36 when the voltage available from the power supply is below the required level, the solenoid is not operated and unignited fuel is prevented from escaping from the burner 12.

Thus it can be seen that the ignition system 10 shown in FIG. 1 serves to control the operation of the burner 12 by controlling flow to and ignition of the burner. The system prevents the escape of unignited fuel from the burner upon either failure of the igniter element or variation in the power supply. The need for an ignition pilot ,4 burner, flame sensing element and safety device is avoided.

The basic ignition system 10 illustrated in FIG. 1 can be adapted to many applications, and can be readily associated with existing equipment. FIG. 2 illustrates one alternative embodiment of the invention including an ignition system generally designated as 40 similar in some respects to the system 10 described above. The system 40 serves to operate the burner 42 of an oven 44 in a gas range not otherwise illustrated, and includes an electric thermostatic control generally designated as 46 for thermostatically regulating the oven temperature by control of the flow of gas to the oven. The ignition system 40, like the system 10, protects against the escape of unignited fuel due to failure of the ignition element and due to variation of the supply voltage. In accordance with further features of the invention, the system 40* also protects against additional potential unsafe conditions such as shorting of the igniter element and grounding of exposed portions of the control circuit.

More particularly, the burner 42 is supplied with gas from a manifold 48 associated with the gas range through a conventional shutoff valve 50 and an electrically operated valve 52 including an electrically operated actuator or solenoid 54 controlling a normally closed valve 56. Gas is supplied to the burner 42 through an inlet fitting 58 and mixing tube 60 and emerges from burner ports 62, where it is ignited by an electrically operated igniter in the form of -a resistance heating element 64.

In accordance with the invention, the solenoid 54 and the igniter element 64 are energized simultaneously and at related energization levels from a power supply represented by a pair of

power supply terminals

66 and 68 by a control circuit generally designated as 7-0. Solenoid 54 and element 64 are connected in series with one another :and, as described in more detail above in connection with the arrangement of FIG. 1, protection is afforded against failure of the element 64 and against a decrease in input voltage.

One feature of the invention resides in the use of an isolation transformer 72 between the

power supply terminals

66 and 68 and the secondary circuit including the solenoid winding 54 and the element 64. Preferably the primary winding 74 of the transformer 72 has more turns than the secondary winding 76 so that the

terminals

66 and 68 can be connected directly to an avail-able source of power such as a 120 volt AC supply, while a substantially smaller and therefore safer voltage is applied to the secondary circuit, portions of which may be exposed in the oven 44. In addition the secondary circuit is isolated or floating. As a result if any portion of the circuit becomes accidentally grounded to the oven body the operation of the circuit is not disturbed, and in particu lar the solenoid 54 cannot be inadvertently energized without simultaneous operation of the igniter element 64.

Since the element 64 may be exposed in the oven 44 adjacent the burner 42, it is possible that the igniter element 64 could be shorted out and thus rendered ineffective by inadvertent contact with a conductive medium. In order to prevent operation of the solenoid valve 52 under such circumstances, a current responsive fuse 78 is placed in circuit with the solenoid winding 54 and element 64. The increased flow of current toward the element 64 resulting upon shorting of the element causes the fuse 78 to open the circuit for energization of the solenoid winding 54 thereby to prevent the escape of unignited gas from the burner 42.

In order thermostatically to control the temperature of the oven 44 by control of gas flow to the burner 42, the system 40 includes the electric thermostatic control 46. The control 46 may be of known construction, and may for example be a control of the type disclosed and claimed in United States Pat. No. 3,354,279 of Charles C. Lamar. In general the control 46 includes a temperature sensing element 80 in the form of a bulb filled with expansible fluid and located in the oven cavity. The bulb 80 communicates via a tube 82 with a suitable power element and mechanical connection, illustrated at 84 as a broken line, for controlling :a circuit breaking structure, illustrated for convenience as a single switch 86, in accordance with oven temperature. It should be understood that the control 46 may include an on-ofi' and temperature selector control (not shown) for selecting the temperature at which the switch 86 is opened by the expansion of fluid within the bulb 80. Reference may be had to the above-mentioned Pat. No. 3,354,279 for a further description of the construction and operation of the control 46.

In operation of the embodiment of the invention shown in FIG. 2, when the shutoff valve 50 is opened and the control 46 is adjusted to maintain a desired oven temperature, the switch 86 is initially closed, assuming the oven temperature is below the selected temperature. As a result a circuit is completed for the flow of current through the primary transformer winding 74, and a voltage is induced in the secondary winding 76. Current flows through the series connected igniter element 64, solenoid winding 54 and fuse 78 causing the valve 56 to open and admit gas to the main burner. Simultaneously the igniter 64 produces an ignition condition for gas es caping from the burner ports 62. When the selected oven temperature is attained, the switch 86 is opened and the solenoid winding 54 is deenergized to discontinue flow to the burner. The burner is then cycled on and off through operation of the control 46 to maintain the selected temperature.

The ignition system 40 prevents the emission of unburned gas into the oven chamber under various circumstances. If the element 64 burns out or breaks an open circuit is created in the secondary circuit and the solenoid 54 cannot be energized. If the supply volt-age decreases below a level sutficient to produce a reliable ignition ternperature, design of the solenoid 54 assures that the current in the secondary circuit is insufficient to cause operation of the solenoid valve 52. If the igniter 64 is shorted out, the fuse 78 opens the circuit for energization of the winding 54. If the transformer 72 fails to function, the valve 56 remains closed. Grounding of any part of the secondary circuit does not affect the system operation. Thus it can be seen that the system 40 provides safe automatic ignition of the burner 42.

In a system designed in accordance with the present invention, the following circuit construction was found to produce satisfactory results. Thesedetails are given to illustrate one possible arrangement only, and should not be taken to limit the scope of the invention. The transformer 72 had a rating of amperes and produced about 3.75 volts across the secondary winding when used with a standard 120 volt 6O cycle power source. A current of about 5 amperes flowed in the secondary circuit, and the voltage across the igniter element was about 3 volts, the igniter element attaining a temperature of about 2600 F. in about one second. The fuse 78 was chosen so that the circuit would be opened if the steady state current exceeded about 8 amperes.

It was found that the igniter element was capable of producing a reliable ignition condition if the current flow was at least 4 amperes. The solenoid valve was designed so that it would not open unless the current flow exceeded 4 amperes. With the particular valve construction used, a winding of about 8 feet of number 18 wire produced the desired result. The voltage drop across the sollenoid winding in normal operation was about 0.7-5 V0 t.

In some installations it may be desired to use a thermostatic gas control rather than the electric thermostatic control illustrated in FIG. 2, and the novel ignition system of the present invention is applicable to this type of system as well. In FIG. 3 there is shown another embodiment of the invention including an ignition system generally designated as 100 for use with a thermostatic control generally designated as 102. Many elements of the embodiment of FIG. 3 may be identical to their counterparts in FIG. 2, and these elements are provided with identical reference numerals and will not again be described in detail.

In the arrangement of FIG. 3 gas flow between the manifold 48 and the burner 42 is thermostatically controlled in accordance with a selected oven temperature by the control 102. The control 102 may comprise any well known type of thermostatic oven control, and includes a temperature sensing element in the form of a fluid filled bulb 104 communicating with the control 102 by way of a tube 106. A suitable power element and mechanical connection, indicated by a broken line 108, serve to operate a flow controlling valve 110 in accordance with oven temperature. A control knob 112 is rotated from its illustrated off position to a selected temperature or operating position, thereby to condition the control 102 thermostatically to maintain the desired oven temperature. As will be apparent to those skilled in the art, if thermostatic control of the oven is not desired, the control 102 can be replaced by a simple shutoff or throttling valve with a control knob movable between off and operating positions.

The ignition system is operated automatically and safely to produce ignition of the burner 42 when the control 102 is turned on. A switch 114 in series with the power supply and the primary winding 74 of transformer 72 is held open in the off position of the control 102 by a switch operator or cam 116 coupled to the control knob 112. When the knob 112 is moved from the off position, the switch 114 is closed to complete a circuit for operation of the ignition system 100.

Operation of the embodiment shown in FIG. 3 will be apparent in view of the above. When it is desired to operate the oven 44, the control knob 112 is rotated to a position corresponding to a desired oven temperature, and the valve is opened, assuming the oven temperature is below the selected temperature. Closure of the switch 114 causes current to flow from

power supply terminals

66 and 68 through primary winding 74, thereby inducing a voltage in secondary winding 76. Current flows through the series connected igniter 64, solenoid winding 54 and fuse 78 to simultaneously produce an ignition condition and open the valve 56. The flow of gas to the burner 42 is thermostatically regulated by the control 102 in the usual manner to maintain the selected temperature.

The novel and important safety features of the system 100 are similar to the embodiments of FIGS. '2 and 3. In each case protection is afforded against breaking, burning out and shorting of the igniter element. In addition, an unsafe condition cannot arise from variations in the power supply. The isolation transformer protects against an unsafe condition arising if the secondary circuit is grounded, and also reduces the voltage applied to exposed circuitry in the even and thus the danger of electrical shock.

As illustrated in FIG. 4, the principles of the present invention are applied to a multiple burner heating system to provide a simplified and safe ignition system in which unignited fuel is prevented from escaping from any of the burners. This arrangement includes a novel ignition system generally designated as for controlling the operation of three simultaneously operating

burners

132, 134 and 136 in order to heat a space such as a room or larger structure. More or fewer burners could be used if desired.

More specifically, the inlets of the burners are connected in common to a manifold 138, and fuel reaches the burners via a conventional shutoff valve 140 and an electrically operated valve 142 including an electrically operated actuator or solenoid 144 controlling the operation of a normally closed valve 146. Fuel is supplied to the burners in the usual manner through inlet fittings 148 and mixing tubes 150, and emerges simultaneously from all of the burners through burner ports 152.

In accordance with the invention, each

burner

132, 134 and 136 is provided with an electrically operated

igniter

154, 156 and 158 respectively, these being disposed in ignition relation to burner ports 152 of the respective burners. A control circuit designated generally as 160 interconnects the solenoid winding 144, the

igniters

154, 156 and 158, and a current responsive fuse 162 in such a manner that the operation of the valve 142 is conditioned upon the successful operation of each of the igniters. In the illustrated preferred embodiment these elements are all connected in series, but other circuit configurations could be used without departing from the scope of the invention in its broader aspects.

An isolation transformer 164 includes a floating sec ondary winding 166 in circuit with the igniters and a primary winding 168 in circuit with a power source illustrated as a pair of

power supply terminals

170 and 172. Energization of the circuit 160 is controlled by a thermostatic control 174 of any known type and including a switch 176 which is closed by a suitable mechanism (not shown) when heat is demanded.

In operation, when the switch 176 is closed current flows in the primary winding 168 including a voltage in the secondary winding 166. As a result, current flows in the secondary circuit causing operation of the solenoid valve 142 and fuel is admitted to the

burners

132, 134 and 136. Simultaneously current flows in the corresponding

igniters

154, 156 and 158 producing ignition of fuel at the burners.

In the event that any of the

igniters

154, 156 and 158 burns out or breaks, ignition at the corresponding burner would not take place. However the novel system 130 serves to prevent the admission of fuel to the burners in this case so that unignited fuel cannot escape. Since the igniters are in series with the solenoid 144 controlling the normally closed valve 146, if one of the igniters produces an open circuit current cannot flow to the solenoid and the valve remains closed.

An unsafe condition is also avoided should any one of the

igniters

154, 156 and 158 be inadvertently shorted out and thus rendered ineffective. If this occurs, the resistance in the secondary circuit is reduced and the magnitude of current flow increases. The fuse 162 is chosen so that it is unaffected by normal variations in current. However, if the current level increases to the extent caused by shorting of one of the igniters, the fuse 162 produces an open circuit and thus prevents energization of the solenoid 144.

Variations in the supply voltage or other factors could cause a potentially unsafe condition if the energlzation level of the igniters is reduced to the extent that a reliable ignition condition is not attained. For example 111 the illustrated embodiment, if the current flow 1n the secondary circuit is reduced below a predetermined level, the resistance elements may not reach a sufficient temperature to provide satisfactory ignition. In accordance with the invention the solenoid valve 142 is designed so that the solenoid is ineffective to open the valve 146 unless the energization level is sufiicient to produce reliable ignition. By way of example, in one system designed in accordance with the invention, it was determined that the current fiow in the secondary circuit should be at least 4 amperes to operate the igniters at an energization level sufiicient to produce a reliable ignition condition. The solenoid valve 142 was designed so that the actuator solenoid 144 was incapable of opening the valve 146 unless the current exceeded 4 amperes.

The embodiment of FIG. 4 is similar to the arrangements illustrated in FIGS. 2 and 3 in that the isolation transformer 164 prevents inadvertent opening of the solenoid valve 142 should any portion of the secondary circuit become grounded. In addition, the secondary circuit may be maintained at a relatively low and therefore safe voltage.

In addition to the important advantages of the present invention common to both single burner and multiple burner applications, a further important aspect of the invention can be realized in multiple burner systems. For example in the arrangement shown in FIG. 4, flow to all of the burners is controlled by the single solenoid valve 142, and separate igniters for each burner accomplish direct ignition of each burner. This is an improvement over known systems wherein flash tubes or other ignition transfer devices are required, and over systems using separate valves for each burner. In addition, the single solenoid valve 142 is disabled by a failure of any of the igniters to operate, so the system is not only simple and direct, but also safe.

Although the present invention has been described in connection with certain illustrative embodiments, many other modifications and embodiments may be devised by those skilled in the art. Details of the described embodiments should not be taken to limit the invention as described in the following claims.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. In an ignition system for a fuel burner used to heat a space, the combination comprising:

an electrical resistance heating element adapted to operate at a predetermined current level;

an electrically operated normally closed valve controlling flow of fuel to the burner;

an actuator for said valve in series with said element and having an operating characteristic such that said valve remains closed below said current level;

a transformer having a secondary winding in series with said element and said actuator and having a primary winding adapted to be connected in circuit with a power supply;

a switch for selectively completing the circuit between said primary winding and power supply; and

a fuse in series with said element, said actuator and said secondary winding, said fuse having an operating characteristic such that it produces an open circuit if the current level increases substantially above said predetermined level.

2. The combination of claim 1, further comprising temperature sensing means in the heated space, and means interconnecting said temperature sensing means and said switch for closing said switch when the sensed temperature is below a selected temperature.

3. The combination of claim 1, wherein said switch is manually operated.

4. The combination of claim 3, an additional valve in series flow relation with said electrically operated valve for regulating flow to the burner, a manual control coupled to said additional valve and movable between an off position and an operating position, and switch operating means coupled between said manual control and said switch for closing said switch when the manual control is moved to the operating position.

5. An ignition apparatus for igniting and controlling the admission of fuel to a burner comprising in combination an electrical resistance igniter element mounted adjacent the burner in ignition relation to fuel flowing from the burner; a normally closed valve adapted to communicate with a supply of fuel and communicating with the inlet of the burner for controlling the admission of fuel thereto; an electrically operable actuating means for controlling the opening of said valve; a transformer having a primary winding; a switch connected to said primary winding for controlling the connection of said primary winding to a source of electrical power; an electrically isolated transformer secondary circuit including secondary winding means coupled electrically to both said igniter element and said actuating means for simultaneous energization of said igniter element and said actuating means at a predetermined current level; fuse means electrically coupled to both said actuating means and said igniter element for disabling said actuating means in response to an increase in current flow to said igniter element above said predetermined level; and said igniter element and actuating means being electrically coupled to one another in such a manner that open circuiting of said igniter means disables said actuating means.

6. The apparatus of claim 5, said actuating means and said igniter element being connected in series.

7. The apparatus of claim 2, said fuse being connected in series with said actuating means and igniter element.

8. An ignition apparatus for igniting and controlling the admission of fuel to a plurality of burners comprising in combination a plurality of electrical resistance igniter elements each mounted adjacent one of said burners in ignition relation to fuel flowing from the burner; a normally closed valve adapted to communicate with a supply of fuel and communicating with the inlets of the burners for controlling the admission of fuel thereto; an electrically operable actuating means for controlling the opening of said valve; a transformer having a primary winding; a switch connected to said primary winding for controlling the connection of said primary winding to a source of electrical power; an electrically isolated transformer secondary circuit including secondary winding means coupled electrically to both said igniter elements and said actuating means for simultaneous energization of said igniter elements and said actuatin means at a predetermined current level; fuse means electrically coupled to both said actuating means and said igniter elements for disabling said actuating means in response to an increase in current flow to said igniter elements above said predetermined level; and said igniter elements and actuating means being electrically coupled to one another in such a manner that open circuiting of any one of said igniter means disables said actuating means.

9. The apparatus of claim 8, said actuating means and said igniter elements being connected in series.

References Cited UNITED STATES PATENTS 2,510,526 6/1950 Smith 12639 3,358,474 12/1967 Liesse 43171 3,282,324 11/1966 Romanelli 43166X 3,441,356 4/1969 Walbridge 43166 FOREIGN PATENTS 1,244,624 9/1960 France 43 1254 650,237 10/1962 Canada 43166 EDWARD G. FAVORS, Primary Examiner US. Cl. X.R.