GB2052199A - Pulse generator - Google Patents

Abstract

A gas ignition means has a main storage capacitor C2 charged from AC supply through switch S1 and diode D1 and connected across the primary P of a spark producing transformer T1 through a SCR switch Q. The secondaries S of the transformer are connected to spark gaps G. A second capacitor C1 is charged via diode D2 to a voltage which is combined, through divider R2, R3, with that across C2 to produce a voltage at X which is nominally zero. C1 is a much smaller value than C2 so that opening S1 causes C1 to discharge rapidly and the voltage at X to rise to a value firing neon N and hence Q is made conductive. <IMAGE>

Description

SPECIFICATION Electrical gas ignition means (single shot) This invention relates to an electrical gas ignition means.

In a known ignition means for "single-shot" operation, a switch system is used, which, in one position, charges a capacitor from rectified mains voltage and, in a second position, discharges the capacitor through the primary of a transformer; the secondary of the transformer includes spark gaps connected thereto for igintion of the gas. A disadvantage of this system is the requirement for a heavy duty switch.

According to this invention there is provided a gas ignition means with a transformer having the primary connected across an energy storage capacitor through a switch device forming part of a trigger circuit, the secondary of the transformer being arranged for connection to one or more gas igniting spark gaps, a first rectifier means to supply a charging current to the storage capacitor to produce a voltage thereacross of one polarity, and a second rectifier means to supply a charging current to a second lesser value capacitor to produce thereacross of opposite polarity, the said capacitors being connected through a voltage divider with the tap thereof supplying the trigger circuit, the tap voltage being below the firing point of the trigger circuit so long as alternating current feed to the two rectifier means is maintained, further switch means in the alternating current feed being provided which when opened allows a rapid decay of voltage across the second capacitor allowing the voltage at the tap of the voltage divider to rise to fire the trigger circuit causing the first capacitor to be discharged through the transformer primary.

An embodiment according to the invention is described in conjunction with the accompanying drawing of a circuit diagram showing an example.

Transformer T1 has secondary windings S connected to conventional spark gaps G and primary P effectively in paraliel with an energy storage capacitor C2 and connected therewith through thyristor Q which forms part of a trigger circuit, or firing circuit, also including neon N, C3, R4 and R5. D3 forms a reverse transient suppressor across the thyristor Q.

A.C. mains is fed through switch S1 which, when closed, causes a first rectifier D1 to charge capacitor C2 through R1. Q, being non-conducting at this time, prevents discharge through primary P.

Simultaneously a second rectifier D2 charges a second capacitor C1 in opposite polarity and a voltage divider formed from equal high value resistors R2, R3 produces at the tap X a nominally zero potential. C1 is typically 47nF and C2 2.2F.

In this state the neon N is non-conductive and below its striking voltage.

When switch S1 is opened then, as the charge stored in C2 is much greater than in C1, the latter rapidly goes positive thus charging C3 and applying a positive and high voltage at X to the neon N which then fires causing 0 to conduct and with the resultant discharge of C2 through the transformer primary P.

This arrangement ensures that the switch S1 is only subject to light A.C. loads and a mechanical switch in the discharge circuit is not required.

1. A gas ignition means with an energy storage capacitor dischargeable to produce a gas ignition pulse by a switch device forming part of a trigger circuit, a first rectifier means to supply a charging current to the storage capacitor to produce a first voltage thereacross and a second rectifier means to supply a charging current to a second lesser value capacitor to produce a second voltage thereacross, the said capacitor being connected so that a resultant voltage is below the firing point of the trigger circuit so long as alternating current feed to the two rectifier means is maintained, removal of said feed current producing a rapid decay of voltage across the second capacitor to fire the trigger circuit causing the first capacitor to be discharged through the transformer primary.

2. Means according to Claim 1, wherein the capacitors are connected through a voltage divider with the tap thereof supplying the trigger circuit, the top voltage being the resultant of the difference between the voltages of the respective capacitors.

3. A gas ignition means with a transformer having the primary connected across an energy storage capacitor through a switch device forming part of a trigger circuit, the secondary of the transformer being arranged for connection to one or more gas igniting spark gaps, a first rectifier means to supply a charging current to the storage capacitor to produce a voltage thereacross of one polarity, and a second rectifier means to supply a charging current to a second lesser value capacitor to produce a voltage thereacross of opposite polarity, the said capacitors being connected through a voltage divider with the tap thereof supply the trigger circuit, the tap voltage being below the firing point of the trigger circuit so long as alternating current feed to the two rectifier means is maintained, further switch means in the alternating current feed being provided which when opened allows a rapid decay of voltage across the second capacitor allowing the voltage at the tap of the voltage divider to rise to fire the trigger circuit causing the first capacitor to be discharged through the transformer primary.

4. A gas ignition means substantially as shown in the accompanying drawing and described herein.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical gas ignition means (single shot) This invention relates to an electrical gas ignition means. In a known ignition means for "single-shot" operation, a switch system is used, which, in one position, charges a capacitor from rectified mains voltage and, in a second position, discharges the capacitor through the primary of a transformer; the secondary of the transformer includes spark gaps connected thereto for igintion of the gas. A disadvantage of this system is the requirement for a heavy duty switch. According to this invention there is provided a gas ignition means with a transformer having the primary connected across an energy storage capacitor through a switch device forming part of a trigger circuit, the secondary of the transformer being arranged for connection to one or more gas igniting spark gaps, a first rectifier means to supply a charging current to the storage capacitor to produce a voltage thereacross of one polarity, and a second rectifier means to supply a charging current to a second lesser value capacitor to produce thereacross of opposite polarity, the said capacitors being connected through a voltage divider with the tap thereof supplying the trigger circuit, the tap voltage being below the firing point of the trigger circuit so long as alternating current feed to the two rectifier means is maintained, further switch means in the alternating current feed being provided which when opened allows a rapid decay of voltage across the second capacitor allowing the voltage at the tap of the voltage divider to rise to fire the trigger circuit causing the first capacitor to be discharged through the transformer primary. An embodiment according to the invention is described in conjunction with the accompanying drawing of a circuit diagram showing an example. Transformer T1 has secondary windings S connected to conventional spark gaps G and primary P effectively in paraliel with an energy storage capacitor C2 and connected therewith through thyristor Q which forms part of a trigger circuit, or firing circuit, also including neon N, C3, R4 and R5. D3 forms a reverse transient suppressor across the thyristor Q. A.C. mains is fed through switch S1 which, when closed, causes a first rectifier D1 to charge capacitor C2 through R1. Q, being non-conducting at this time, prevents discharge through primary P. Simultaneously a second rectifier D2 charges a second capacitor C1 in opposite polarity and a voltage divider formed from equal high value resistors R2, R3 produces at the tap X a nominally zero potential. C1 is typically 47nF and C2 2.2F. In this state the neon N is non-conductive and below its striking voltage. When switch S1 is opened then, as the charge stored in C2 is much greater than in C1, the latter rapidly goes positive thus charging C3 and applying a positive and high voltage at X to the neon N which then fires causing 0 to conduct and with the resultant discharge of C2 through the transformer primary P. This arrangement ensures that the switch S1 is only subject to light A.C. loads and a mechanical switch in the discharge circuit is not required. CLAIMS

1. A gas ignition means with an energy storage capacitor dischargeable to produce a gas ignition pulse by a switch device forming part of a trigger circuit, a first rectifier means to supply a charging current to the storage capacitor to produce a first voltage thereacross and a second rectifier means to supply a charging current to a second lesser value capacitor to produce a second voltage thereacross, the said capacitor being connected so that a resultant voltage is below the firing point of the trigger circuit so long as alternating current feed to the two rectifier means is maintained, removal of said feed current producing a rapid decay of voltage across the second capacitor to fire the trigger circuit causing the first capacitor to be discharged through the transformer primary.

2. Means according to Claim 1, wherein the capacitors are connected through a voltage divider with the tap thereof supplying the trigger circuit, the top voltage being the resultant of the difference between the voltages of the respective capacitors.

3. A gas ignition means with a transformer having the primary connected across an energy storage capacitor through a switch device forming part of a trigger circuit, the secondary of the transformer being arranged for connection to one or more gas igniting spark gaps, a first rectifier means to supply a charging current to the storage capacitor to produce a voltage thereacross of one polarity, and a second rectifier means to supply a charging current to a second lesser value capacitor to produce a voltage thereacross of opposite polarity, the said capacitors being connected through a voltage divider with the tap thereof supply the trigger circuit, the tap voltage being below the firing point of the trigger circuit so long as alternating current feed to the two rectifier means is maintained, further switch means in the alternating current feed being provided which when opened allows a rapid decay of voltage across the second capacitor allowing the voltage at the tap of the voltage divider to rise to fire the trigger circuit causing the first capacitor to be discharged through the transformer primary.

4. A gas ignition means substantially as shown in the accompanying drawing and described herein.