US3428823A

US3428823A - Spark igniter

Info

Publication number: US3428823A
Application number: US677992A
Authority: US
Inventors: Balthasar H Pinckaers
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1967-10-25
Filing date: 1967-10-25
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18
Also published as: NL6814852A; CH497055A; BE722803A; GB1251394A; FR1590017A; DE1804837A1

Description

Feb. 18, 1969 a. H. PINCKAERS SPARK IGNITER Filed 001;. 25, 1967 VALVE l6 ATTORNEY.

3,428,823 SPARK IGNITER Balthasar H. Pinckaers, Edina, Minn., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Oct. 25, 1967, Ser. No. 677,992 U.S. Cl. 307106 Int. Cl. F23n 5/00; H03k 3/00 Claims ABSTRACT OF THE DISCLOSURE A spark igniter having a step-up ignition transformer whose secondary winding is connected in a closed series circuit with the primary winding of a second transformer, the winding of a valve, and a high impedance resistor across which spark ignition electrodes are connected; hav-- ing a low voltage source connected to apply a low-voltage checking pulse to the primary winding of the ignition transformer to cause a circulating current to flow through the above mentioned series circuit if circuit continuity exists; and having a high-voltage ignition pulse source connected to be controlled by the secondary winding of the second transformer to apply a high voltage pulse to the primary winding of the ignition transformer only if circuit continuity exists.

Background of the invention My invention relates to the art of spark igniters and t0 means to check for the existence of a spark. In my copending application Ser. No. 602,641, filed Dec. 19, 1966, for a Spark Proving and Utilization Device and System, I disclose a spark igniter which insures that a spark exists in the high voltage circuit and utilizes the rectification effect of the spark to charge a capacitor connected in parallel with a fuel valve. With the device of my copending application, the valve will not open when the spark electrodes are shorted. I have since found that if a double failure occurs wherein the spark electrodes are shorted, and at the same time a spark-sustaining open circuit occurs in series with the spark electrodes, the fuel valve may still open.

The present invention is directed to means to detect the existence of an open circuit, in the high voltage circuit, which may exist at other than the ignition spark gap, and to render the spark igniter inoperative (fail-safe) in the presence of such an unintentional open circuit.

Summary of the invention The present invention utilizes a high impedance shunt for the ignition electrodes connected in closed series circuit with the secondary winding of the ignition transformer together with means to apply a low-voltage checking pulse to the series circuit to check circuit continuity, and means controlled as a result of circuit continuity to apply a high-voltage ignition pulse to the series circuit.

More specifically, a first capacitor is connected to be charged to a high voltage during a first half cycle of an AC source, the discharge of this capacitor through the primary winding of the ignition transformer being controlled by switch means. A second capacitor is connected to be charged during the alternate half cycle of the AC source. Low-voltage responsive means effects a discharge of the second capacitor through the primary winding of ice the ignition transformer early in the alternate half cycle; whereupon, if circuit continuity exists, the switch means is actuated and the first capacitor is discharged to cause a spark to occur during the alternate half cycle.

Brief description of the drawing The single figure is a schematic showing of the preferred embodiment of my invention.

Description of the preferred embodiment Referring to the single figure, reference numeral 10 designates a high-voltage, step-up ignition transformer having a secondary winding 11 and a primary winding 12. The primary winding is energized from conductors 13 and 14 which are adapted to be connected to a source of AC voltage, not shown. Secondary winding 11 is connected to

terminals

41 and 42 which are adapted to be connected to ignition electrodes 15 to apply a high voltage in the range of 10,000 volts to these electrodes to cause an ignition spark to occur at the spark gap which separates the electrodes. Electrodes 15 are adapted to be associated with a fuel burner, not shown, to ignite fuel flowing from the fuel burner. Reference numeral 16 identifies generally a valve, shunted by capacitor 17, to allow fuel to flow to the burner when the valve is energized. In accordance with the teachings of my above mentioned copending patent application, valve 16 is energized only when spark exists at a gap in the high voltage circuit, intended to be at electrodes 15.

A first capacitor 20 is connected to conductors 13 and 14 by a circuit including diode 50. Capacitor 20 is charged to a high voltage during the half cycle of the AC source in which conductor 13 is positive, the upper terminal of the capacitor being positive with respect to the lower terminal. This half cycle of the AC source will be designated the first half cycle.

The discharge of capacitor 20 through the primary winding of transformer 10 is controlled by switch means 26 in the form of an SCR having an

output circuit

27, 28 and an

input circuit

28, 29.

A second capacitor 21, shunted by diode 22, is connected to conductors 13 and 14 by a circuit including resistor 23. During the above mentioned first half cycle, diode 22 conducts to short capacitor 21. During the second half cycle, when conductor 13 is negative, capacitor 21 charges, the left-hand terminal being positive with respect to the right-hand terminal. Reference numeral 24 identifies a voltage responsive switch in the form of a breakdown diode, such as a four-layer diode. This switch responds to the presence of a low voltage on capacitor 21, for example 10 volts, and becomes conductive to discharge capacitor 21 through diode 25 and the primary winding of transformer 10.

Reference numeral 30 identifies current responsive means in the form of a transformer having a primary winding 31 and a secondary winding 32. The primary winding of this transformer is connected in a closed series circuit with the secondary winding of ignition transformer 10, the winding of valve 16 and a high magnitude impedance 40 which is connected to

terminals

41 and 42 and is adapted to shunt ignition electrodes 15. Specifically, impedance 40 is a resistor which may, for example, have a magnitude of 1 megohm.

The secondary winding of transformer 30 is connected to the

input electrodes

28, 29 of SCR 26.

Considering now the operation of the preferred embodiment, on the first half cycle of AC source 13, 14, capacitor 20 charges to a high voltage, the upper terminal of the capacitor being positive with respect to the lower terminal. On the second half cycle of the AC source, capacitor 21 charges through resistor 23. Early in this second half cycle, capacitor 21 reaches a charge to cause diode 24 to break down. Thus, capacitor 21 discharges through the circuit including diode 25 and the primary winding of ignition transformer 10. This discharge produces a low magnitude voltage checking pulse which circulates a current through the closed

series circuit

11, 40, 16, and 31. It is of significance that the magnitude of this checking pulse does not produce a spark at electrodes 15 and would likewise not produce a spark at an open circuit which might exist in the above mentioned closed series circuit. Furthermore, this checking pulse does not result in the energization of valve 16 even if electrodes 15 are shorted.

A circuit discontinuity, such as in the secondary winding of the ignition transformer, may well be of the type which would, at the higher ignition pulse voltage, allow a spark to exist at the discontinuity or open, and then valve 16 would be energized even if the electrodes 15 are shorted. The purpose of the checking pulse is to insure that in fact no such discontinuity exists. This is done by making continuity in the high voltage circuit a pre-condition for applying the higher ignition pulse voltage. The electrodes 15 may be shorted but this already prevents the valve 16 from being energized in accordance with the teaching of my copending application.

With my present invention, an output exists at the secondary winding of transformer 31 as a result of the checking current pulse only when circuit continuity exists.

The secondary winding of transformer 31 is then effective to render SCR 26 conductive during this same second half cycle of AC source 13, 14. Thus, during the same second half cycle, capacitor 20 discharges through the primary winding of ignition transformer 10 and a high voltage ignition pulse is supplied to the above mentioned closed series circuit. In this event, however, the high voltage produces a spark at electrodes 15.

In accordance with the teachings of my above copending application, valve 16 is energized to allow fuel to flow to the burner only when a spark exists, the spark producing a unidirectional current in the above mentioned series circuit, to charge capacitor 17 and maintain valve 16 energized and open.

While I have shown a specific means of achieving a low voltage checking pulse and a high voltage ignition pulse, the practice of my invention does not require these specific means. My invention requires the high magnitude impedance 40 to shunt ignition electrodes 15 to form a closed series circuit through which a lowvoltage checking pulse current may circulate when circuit continuity exists, along with current responsive means 30 to respond to this circulating current to then cause a high voltage ignition pulse to be applied to the series circuit to produce a spark at electrodes 15.

With the structure of the preferred embodiment of my invention, one spark is produced at electrodes 15 for each line cycle. Thus, should source 13, 14 be a 60-cycle per second source, 60-pulses per second will be produced at electrodes 15.

Theembodiments of the invention in which an exelusive property or right is claimed are defined as follows:

1. A spark igniter for use with spark ignition means, comprising;

a step-up ignition transformer having a primary winding and a secondary winding,

a pair of terminals connected in circuit with said secondary winding and adapted to be connected to the spark ignition means, an impedance connected between said terminals to complete a circuit through said secondary winding,

ignition-pulse generating means having an input to initiate operation thereof, and having a high volt age output connected to said primary winding,

checking-pulse generating means having a low voltage output connected to produce a low voltage current flow through said circuit including said secondary winding and said impedance,

and current responsive means responsive to said current flow and connected to control said input to initiate operation of said ignition-pulse generating means.

2. A spark igniter as defined in claim 1 wherein said checking-pulse generating means is connected to said primary winding and said current responsive means is connected in circuit with said secondary winding and said impedance.

3. A spark igniter as defined in claim 1 wherein said current responsive means is a transformer having a first winding connected in circuit with said secondary winding and said impedance, and having a second winding connected to said input.

4. A spark igniter as defined in claim 1 wherein said ignition-pulse generating means includes a capacitor and circuit means adapted to charge said capacitor to a high voltage, and includes a controllable switch to discharge said capacitor through said primary winding, and wherein said current responsive means is connected to control said switch.

5. A spark igniter as defined in claim 4 wherein said current responsive means is a transformer having a first winding connected in circuit with said secondary winding and said impedance, and having a second winding connected to control said switch.

6. A spark igniter as defined in claim 1 wherein said checking-pulse generating means includes a capacitor and circuit means adapted to charge said capacitor, and means including a low-voltage responsive switch connecting said capacitor to said circuit including said secondary winding and said impedance.

7. A spark igniter as defined in claim 6 wherein said low-voltage responsive switch is connected to said primary winding to discharge said capacitor through said primary winding when said capacitor is charged to the low voltage.

8. A spark igniter as defined in claim 7 wherein said current responsive means is a transformer having a first winding connected in circuit with said secondary winding and said impedance, and having a second winding connected to said input.

9. A spark igniter as defined in claim 1 including terminal means adapted to be connected to a source of AC voltage; wherein said ignition-pulse generating means includes a capacitor and circuit means connected. to said terminal means and adapted to charge said capacitor to a high voltage during a first half cycle of the AC source, and further includes a controllable switch to discharge said capacitor through said primary winding; wherein said current responsive means is connected to control said switch; and wherein said checking-pulse generating means includes a second capacitor and circuit means connected to said terminal means and adapted to charge said second capacitor during the opposite half cycle of the AC source, and further includes means including a low-voltage responsive switch connecting said second capacitor to said circuit including said secondary winding and said impedance.

10. A spark igniter as defined in claim 9 wherein said low-voltage responsive switch is connected to said primary winding to discharge said second capacitor through said primary winding during said opposite half cycle; and wherein said current responsive means is a trans- References Cited UNITED STATES PATENTS 2,628,676 2/1953 Shottenfeld 43166 6 3,277,949 10/ 1966 Walbridgc 431-6 3,291,183 12/1966 Fairiey 43166 3,384,439 5/1968 Walbridgc 43124 5 CHARLES J. MYHRE, Primary Examiner.

R. A. DUA, Assistant Examiner.

US. Cl. X.R.