US3480374A - Spark ignition system - Google Patents

Description

Nov.-25, 1969 ET AL 3,480,374

SPARK IGNITION SYSTEM Filed July '7, 1967 SPAR K CONTROL SPARK IGNITOR 32 Rev mvmoas JOHN T.' LAMB CARL L. ANDERSON ATTORNEYS United States Patent U.S. Cl. 431-66 4 Claims ABSTRACT OF THE DISCLOSURE A fail-safe spark ignition system for cooking range burners consisting of circuitry for monitoring spark energy and controlling the gas valve thereby, including a fuse enabling circuit for prevention against circuit malfunctions and spark gap disabling means to eliminate radio interference.

This invention relates to cooking ranges and more particularly to ranges utilizing a spark ignition system for igniting the various burners of the range.

The problem of devising a system for igniting the various burners including the oven burner in a cooking range has been several solutions. Predominant among these is the use of a pilot light which remains burning at all times in close proximity to each of the burners so that when the gas valve is turned on, the gas will flow near the flame of the pilot light to ignite the burner. Failure of these devices is sometimes monitored by a thermostatic element which is energized by the heat of the pilot light and which serves to prevent the flow of gas to the burner in the event of the absence of the pilot light flame. Such ignition systems, of course, are wasteful of gases in that a continuous flame is required even during idle times of the range with the subsequent rapid deterioration of burner ports and the like, and also present the danger of having an open flame at the range.

Glow type igniter elements have also been utilized to provide a sufficiently high temperature in the area of the combustible gases. However, these devices are subject to frequent burnout and in addition, require auxiliary means to detect when there is a failure of the element.

The spark ignition system circumvents many of the faults of previous systems in that the spark mechanism need only be energized when the appropriate valve for the burner is turned on and additionally, is not subject to wear or breakdown as is common in the earlier systems. In the spark ignition system, however, it is still desired to know whether some extraneous material has somehow faulted the spark gap or whether the ignition system itself is producing sufficient spark to ignite the gases. Furthermore it is desirable, in order to prevent outside interference from the energy radiated from the spark gap, to extinguish the spark when it is determined that the appropriate burner has ignited.

Therefore, it is an object of this invention to provide an improved spark ignition system which is more reliable than previous systems and includes means for extinguishing the spark when the burner has ignited.

It is another object of this invention to provide an improved spark ignition system which monitors the intensity of the sparks occurring at the gaps and prevents the flow of gas if there is insufficient or no spark available.

It is still another object of this invention to provide an improved spark ignition system which detects faults within the components of the system itself and prevents flow of gas to the burners.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

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To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a schematic representation of a range burner system with a spark ignition system;

FIG. 2 is an electrical schematic of the circuit of the spark ignition system.

A typical range burner system is shown in FIG. 1 and consists of an input gas line 10 leading to a burner 12. Such burner 12 might comprise a surface cooking unit of a range or the oven burner and may take the configuration of a greater number of burners since the teachings of this invention are applicable to all such embodiments. Interposed in the input gas line 10 prior to the burner 12 is a manually operated gas valve 14 for controlling flow of gas to the burner 12. The valve 14 includes an electrical switch 16 connected to the spark control system 18 by the lines 20 such that opening of the valve 14 to allow flow of gas to the burner 12 closes the switch to actuate the spark control 18.

Also interposed in the input gas line 10 leading to the burner 12 is an electromagnetic gas valve 22 which in this embodiment of the invention is located on the input side of the manual valve 14. In a multiple burner system the electromagnetic valve controls the flow of gas to all burners and the valve would be responsive to actuation by the spark control system which would provide the spark ignition at all burners.

A single spark gap 24 is shown in proximity with the burner 12 of the range, however, it will be appreciated that the teachings of this invention apply as well to multiple gap arrangements, either in single or in plural burner ranges. The gaps are located in close association with each of the burners in such a position as to be in proximity to the flow of unburned gases emanating from the respective burner. The spark gap 24 consists of a pair of electrodes 25 separated a small distance and retained in position by a ceramic insulating block 26 which may be mounted to the range. Electrical leads 27, 28 lead to the spark control and carry voltage sufficient for arcing to the gap 24.

The spark control 18 includes a spark igniter 30 shown in box form which is representative of any type of ignition producing device which generates adequate voltage for arcing across the gap 24 of the burner 12. In a simple form such spark igniter 30 may be merely a transformer Which converts ordinary household voltage to voltage suitable for the production of an arc across the gap 24.

It will be apparent, then, that the following operation of the spark ignition system is desired. When the manual valve 14 is turned on in order to light the burner 12, the spark igniter 30 is energized to create sparks across the gap 24 associated with the burner 12. Recognition of the occurrence of adequate sparking will cause the electromagnetic valve 22 to be actuated to allow the flow of gas into the burner 12. If for any reason insufficient sparking occurs at the gap 24, the electromagnetic valve 22 will be deenergized, thereby shutting 01f the flow of gas into the burner 12.

In the circuitry for the spark ignition system ordinary household voltage as a typical supply of power is applied on lines 32 to the spark igniter 30 and on lines 34 to the circuitry for controlling the electromagnetic valve 22. The switch 16 associated with the manually operated gas valve 14 is shown in association with the spark igniter 30 and it will be understood that closure of the switch 16 will energize the spark igniter to cause a sufiicient voltage to be applied at the output terminals 34, 35. The spark gap 24 is connected in series together with a capacitor 36 across the output terminals 34, of the spark igniter 30, terminal 35 of the spark igniter 30 being connected also to the chassis ground of the range. Connected across the capacitor 36 are a resistor 38 and neon lamp 40 in series, which provide a means for monitoring the energy at the spark gap 24.

Thus, in operation when a spark of the correct energy is developed by the spark igniter 30 and appears across the spark gap 24, such spark current will cause a charge to occur across the capacitor 36. The capacitor 36 is provided to accumulate the spark energy and holds enough charge between sparks to maintain the neon lamp 40 in a lit condition. The flow of current through the resistor 38 and the neon lamp 40 will, of course, tend to discharge the capacitor 36 and by a proper selection of components, the discharge time of this circuit may be adjusted so as to maintain the neon lamp 40 in a lit condition only when sufficient energy is provided. A resistor 42 or rheostat (shown in dotted lines) may be connected in parallel across the capacitor 36 to vary the discharge time of the circuit and adjust the circuit for desired spark conditions.

In the electromagnetic valve circuit, household voltage is applied on lines 34 to the electromagnetic valve which is connected in series with a fuse 44 and an amplifier circuit 46 for providing a flow of current through the valve 22. The amplifier circuit 46 provides the energization for the electromagnetic valve 22 and in this embodiment is a silicon controlled rectifier 48 having its anode connected to one side of the electromagnetic valve 22 and its cathode connected to one of the input lines 34. The SCR 48 is poled to conduct current fiow through the electromagnetic valve 22 in the forward direction as indicated by the arrow when the SCR 48 is triggered into conduction. As is typical in devices of this type, current flow occurs on alternate half cycles of the applied alternating current input voltage. A diode 50 is connected in parallel across the electromagnetic valve 22 having its anode connected to the anode of the SCR 48 and its cathode connected to the junction between the fuse 44 and the electromagnetic valve 22, thereby being poled to conduct reverse current flow in a direction opposite to that indicated by the arrow. Thus, in the normal operation of the electromagnetic valve circuit, the diode 50 will have no effect upon the current passing through the electromagnetic valve 22 since the diode 50 is back biased and exhibits a high resistance.

A triggering network for the SCR 48 consists of a photoelectric device 52 and a resistor 54 which are connected in series between the anode and cathode of the SCR 48. The common junction 56 between the resistor 54 and the photoelectric device 52 is connected to the gate lead of the SCR 48 and produces the voltage for triggering the SCR 48 into conduction. The type of photoelectric device 52 is not critical to this invention since it is only necessary that it alter the bias of the SCR 48 and this may be accomplished if the device 52 provides a high resistance when no light is falling upon it and a substantially lower resistance when it receives light from the neon lamp 40. Thus, the photoelectric device 52 and resistor 54 act as a voltage divider, taking a proportion of the voltage applied across the SCR 48 to be applied to the gate lead of the SCR 48. When little or no light is falling upon the photoelectric device 52, the high resistance will provide insufiicient voltage at the junction 56 and at the gate lead to the SCR 48 to cause triggering of the SCR 48. When a sufficient amount of light falls upon the photoelectric device 52, a greater proportion of the voltage applied across the SCR 48 will appear at the junction 56 and by suitable selection of the photoelectric device 52 and the resistor 54, may be made sufficient to cause conduction of the SCR 48. It will be apparent that the resistor 54 could as well be a variable resistor to provide a convenient means of adjustment of the triggering level of the SCR 48.

It will be appreciated by those skilled in the art that the photoelectric device 52 may have sufficient capacity to directly energize the electromagnetic valve without the necessity of intermediate power amplification. An alternating voltage arrangement may be employed or a series diode may be utilized for direct current operation of the valve 22. In such an arrangement however, the on-off characteristic supplied by the SCR 48 circuit will not be available.

The light beam connection between the neon lamp 40 and the photoelectric device 52 provides an electrical isolation between the spark gap circuitry and the circuitry for energizing the electromagnetic valve 22, both of which may be operating at substantially dilferent levels of poten tial. Although the neon lamp 40 and photoelectric device 52 are shown as separate units, it will be understood that recently available devices which incorporate these two units into a single assembly may be utilized as well since there is still isolation between the two circuits. In a similar manner, it will be apparent that different means might be utilized for monitoring the spark energy and transmitting this information to the electromagnetic valve circuitry for controlling the energization of the electromagnetic valve 22. Thus, as one example, an incandescent lamp could be substituted for the neon lamp 40 if sufficient energy were provided in the spark igniter circuit. Alternatively, the neon lamp 40 may be utilized only as a visual indicator to register proper operation of the spark ignition.

In normal operation of the electromagnetic valve circuit when the SCR 48 is triggered into conduction, current flow will occur through the series circuit consisting of the fuse 44, the electromagnetic valve 22 and the SCR 48 on positive half cycles of the applied input voltage, the current being of an average value sufficient to energize the electromagnetic valve 22 at its nominal current rating. Due to the relative sensitivity to breakdown of the semiconductor material of the SCR 48 due to line transients and the like which might be caused, for example, by nearby lightning strokes, this circuitry also provides means for detecting such faults in the circuitry to prevent against energization of the electromagnetic valve 22 and a turn-on of the gas flow. In the normal operating condition the fuse 44, which may also be a circuit breaker or interrupter, is selected to have a current rating slightly greater than the average current flow through the e1ectromagnetic valve 22. If the SCR 48 should break down due to line transients or internal defects and become a short circuit, both the positive and negative half cycles of the input voltage will be applied across the electromagnetic valve 22. This will result in a current flow through the valve 22 of twice the value of the normal operating current. Since a typical electromagnetic valve in this environment would require approximately 75 ma., increased current fiow due to the short circuit would result in a flow of approximately ma. Such differential in current levels is not readily recognized or definable by a fuse or circuit breaker since these devices do not ordinarily have a close tolerance. They are usually selected to carry current somewhat greater than the normal current flow so as not to cause burnouts within the normal range of line transients, due to the switching of currents within the circuit itself or to normal input voltage transients due to other devices connected to the external line circuitry. Therefore, the diode 50 across the electromagnetic valve 22 is provided to detect this reverse current flow through the electromagnetic valve 22, the diode 50 in this condition being forward biased to allow a substantially greater amount of current flow in the circuit and suificiently great to overrate the fuse 44 and cause its burnout.

Connected across the spark gap 24 is a bimetal conductive leaf 60 which acts as a movable contact to electrically shunt the spark gap 24. The bimetal leaf 60 is located in close association with the burner 12 such that the heat emanating from the burner 12 when it has ignited acts upon the leaf 60 to cause a differential bending thereof and a closure of the leaf 60 across the spark gap 24. Such shorting of the spark gap 24 after the burner 12 has been ignited for a short interval of time serves to extinguish the spark and prevent the emission of radio frequency interference. The shorting of the gap 24 will not substantially affect the spark energy emanating from the spark igniter 30 and thus does not substantially affect the monitoring circuit consisting of the resistor 38, capacitor 36 and neon lamp 40, and the neon lamp will remain in a lit condition. The output of the monitoring circuit then will maintain the electromagnetic valve 22 circuit in an energized condition maintaining the flow of gas to the burner 12. The shutting off of the gas to the burner 12 by means of the manual valve 14 will cause a cessation of heating of the bimetal strip 60 and a consequent opening of the gap 24 thereby preparing the circuit for relighting of the burner 12 when so desired. The time response of the bimetal strip 60 is ordinarily in the range of only several seconds which allows insufficient time for a great quantity of unburned gas to flow from the burner 12 before the ignition system becomes effective again.

It will be apparent to those skilled in the art that the apparatus of this invention has provided an improved spark ignition system that not only detects the presence of proper sparking at the gap but also recognizes failures within the system itself to prevent an accumulation of gases, and in addition, provides sparking only when required. Such a system is a considerable improvement over prior art systems and provides a fail-safe operation in an environment which requires dependable control.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following cliams or the equivalent of such be employed.

We, therefore, particularly point out and distinctly claim as our invention:

1. In combination with a gas range burner, a spark ignition system for controlling the flow of gas to the burner and for igniting the gas, comprising a spark gap in close association with the burner, means for supplying voltage to said gap to cause sparking thereacross and igntion of the gas emanating from the burner, means for monitoring the voltage at said spark gap and for providing a signal representative thereof, an electrically energized gas valve for controlling the flow of gas to the burner, means coupled to said monitoring means and responsive to the signal thereof for energizing said gas valve, said energizing means being opertaive in response to sufficient signal to open said gas valve to supply gas to the burner, and means responsive to the heat of the ignited gas for shunting said spark gap to prevent arcing thereacross.

2. The combination as set forth in claim 1 wherein said shunting means comprises a bimetal switch operatively connected to said spark gap in normally open condition, said switch being closed in response to heat from the burner to conduct energy from said supply means directly to said monitoring means to maintain said gas valve in an energized condition.

3. In combination with a gas burner, a spark ignition system operative from a source of power for controlling theflow of gas to the burner, comprising means forming a spark gap adjacent the burner, means for applying voltage to said spark gap means to cause arcing thereacross, means for monitoring the spark energy comprising a charging circuit connected to said spark gap means and an indicator lamp connected to said charging circuit to provide illumination proportional to the spark energy, a solenoid valve for controlling the flow of gas to the burner, a silicon controlled rectifier serialy connected with said solenoid valve for conducting unidirectional forward current flow in response to an electrical signal, light responsive means coupled to said indicator lamp for generating such electrical signal when sufficient light is received indicating adequate sparking, a circuit breaker connected in series with said silicon controlled rectifier andsaid solenoid valve, said circuit breaker having a rating slightly greater than the operating current level of said solenoid valve, and a diode connected across said solenoid valve, said diode being poled to conduct reverse current flow so that when said silicon controlled rectifier conducts reverse current due to component failure, said circuit breaker will be actuated to open the circuit to said solenoid valve.

4. The combination as set forth in claim 3 wherein said circuit breaker is a fuse which burns out upon excessive reverse current flow to open the circuit to said solenoid valve.

References Cited UNITED STATES PATENTS 1,899,744 2/ 1933 Breisky et al.

2,406,185 8/ 1946 Aubert.

2,675,069 4/1954 Shotterfeld.

2,771,942 11/1956 Miller.

3,306,339 2/1967 Barton et al.

3,276,507 10/1966 Eldridge et al 43179 X 3,410,646 11/1968 Telford 43166 EDWARD G. FAVORS, Primary Examiner US. Cl. X.R. 31743

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