GB2051948A - Repetitive Gas Ignition Means - Google Patents

Abstract

A capacitor C is charged through diode D2 from an AC supply and discharged through an SCR switch Q into primary P of transformer T of which the secondaries S are connected to spark gaps G. The switch Q is triggered by the voltage across capacitor C1 charged through R1 which forms a time constant circuit providing repetitive discharge of C. To ensure that the delay before initial firing is not substantially greater than the interval between successive firings, D1 provides for C1 to be fully discharged at each cycle. <IMAGE>

Description

SPECIFICATION A Gas Ignition Means (Repetitive) This invention relates to a gas ignition means producing a series of gas igniting sparks at regular intervals.

With such devices using simple neon tube firing circuits it is usual for an initial switch-on delay to occur which is much longer than the subsequent spark repetition rate. If the repetition rate is set to a convenient value, then the switchon delay time becomes excessive and unacceptable.

According to this invention there is provided a repetitive gas ignition means comprising a charge storage capacitor connected across the primary of a spark producing transformer through a switch means which can be rendered conductive to discharge the capacitor into the primary, the capacitor being charged from an alternating current supply through a rectifier means, a trigger circuit for operating the switch means and responsive to the voltage across a further capacitor connected across the first capacitor through a resistor and forming therewith a time constant circuit defining the discharge and spark repetition rate, a diode connected between the second capacitor and the junction of the switch means and transformer primary, whereby on operation of the switch means substantially complete discharge of the second capacitor is effected.

A circuit diagram showing an embodiment according to the invention is depicted in the accompanying drawing by way of example.

Referring to the drawing, a transformer T includes secondary windings S having associated gas igniting spark gaps G and a primary winding P effectively in parallel with a charge storage capacitor C and including a series switch means formed by a thyristor Q. The capacitor C is charged from alternating current mains supply through rectifier D2 with a series limiting resistor R2. The thyristor is fired by a neon N fed with the voltage occurring at the junction between capacitor C1 and resistor R1 forming a time constant circuit defining the spark repetition rate.

In order to avoid excessive initial switch-on delay, due to the requirement for C1 to charge from zero potential at the start, in contrast to same being partly charged during normal repetitive operation where full discharge does not occur due to the neon N characteristics, a diode D1 is provided to ensure full and rapid discharge of C1 when thyristor Q is fired.

With this arrangement, the time constant of Ri, Ci can be selected to give a suitable repetition rate without lengthy switch-on delay occurring. During normal charging diode D1 has no effect as it is connected across resistor R1 in a reverse biassed sense.

Claims

1. A repetitive gas ignition means comprising a charge storage capacitor and a switch means which can be rendered conductive to discharge the capacitor, the capacitor being charged through a rectifier means, a trigger circuit for operating the switch means and responsive to the voltage across a second capacitor connected across the first capacitor through a resistor and forming therewith a time constant circuit defining the discharge and spark repetition rate, discharge means being provided whereby on operation of the switch means substantially complete discharge of the second capacitor is effected.

2. Means in accordance with Claim 1, wherein the discharge means comprises a diode connected across the second capacitor and switch means.

3. A repetitive gas ignition means comprising a charge storage capacitor connected acrosethe primary of a spark producing transformer through a switch means which can be rendered conductive to discharge the capacitor into the primary, the capacitor being charged from an alternating current supply through a rectifier means, a trigger circuit for operating the switch means and responsive to the voltage across a second capacitor connected across the first capacitor through a resistor and forming therewith a time constant circuit defining the discharge and spark repetition rate, a diode connected between the second capacitor and the junction of the switch means and transformer primary, whereby on operation of the switch means substantially complete discharge of the second capacitor is effected.

4. A repetitive gas ignition means as herein described with reference to the accompanying drawings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A Gas Ignition Means (Repetitive) This invention relates to a gas ignition means producing a series of gas igniting sparks at regular intervals. With such devices using simple neon tube firing circuits it is usual for an initial switch-on delay to occur which is much longer than the subsequent spark repetition rate. If the repetition rate is set to a convenient value, then the switchon delay time becomes excessive and unacceptable. According to this invention there is provided a repetitive gas ignition means comprising a charge storage capacitor connected across the primary of a spark producing transformer through a switch means which can be rendered conductive to discharge the capacitor into the primary, the capacitor being charged from an alternating current supply through a rectifier means, a trigger circuit for operating the switch means and responsive to the voltage across a further capacitor connected across the first capacitor through a resistor and forming therewith a time constant circuit defining the discharge and spark repetition rate, a diode connected between the second capacitor and the junction of the switch means and transformer primary, whereby on operation of the switch means substantially complete discharge of the second capacitor is effected. A circuit diagram showing an embodiment according to the invention is depicted in the accompanying drawing by way of example. Referring to the drawing, a transformer T includes secondary windings S having associated gas igniting spark gaps G and a primary winding P effectively in parallel with a charge storage capacitor C and including a series switch means formed by a thyristor Q. The capacitor C is charged from alternating current mains supply through rectifier D2 with a series limiting resistor R2. The thyristor is fired by a neon N fed with the voltage occurring at the junction between capacitor C1 and resistor R1 forming a time constant circuit defining the spark repetition rate. In order to avoid excessive initial switch-on delay, due to the requirement for C1 to charge from zero potential at the start, in contrast to same being partly charged during normal repetitive operation where full discharge does not occur due to the neon N characteristics, a diode D1 is provided to ensure full and rapid discharge of C1 when thyristor Q is fired. With this arrangement, the time constant of Ri, Ci can be selected to give a suitable repetition rate without lengthy switch-on delay occurring. During normal charging diode D1 has no effect as it is connected across resistor R1 in a reverse biassed sense. Claims

1. A repetitive gas ignition means comprising a charge storage capacitor and a switch means which can be rendered conductive to discharge the capacitor, the capacitor being charged through a rectifier means, a trigger circuit for operating the switch means and responsive to the voltage across a second capacitor connected across the first capacitor through a resistor and forming therewith a time constant circuit defining the discharge and spark repetition rate, discharge means being provided whereby on operation of the switch means substantially complete discharge of the second capacitor is effected.

2. Means in accordance with Claim 1, wherein the discharge means comprises a diode connected across the second capacitor and switch means.

3. A repetitive gas ignition means comprising a charge storage capacitor connected acrosethe primary of a spark producing transformer through a switch means which can be rendered conductive to discharge the capacitor into the primary, the capacitor being charged from an alternating current supply through a rectifier means, a trigger circuit for operating the switch means and responsive to the voltage across a second capacitor connected across the first capacitor through a resistor and forming therewith a time constant circuit defining the discharge and spark repetition rate, a diode connected between the second capacitor and the junction of the switch means and transformer primary, whereby on operation of the switch means substantially complete discharge of the second capacitor is effected.

4. A repetitive gas ignition means as herein described with reference to the accompanying drawings.