GB717755A - Improvements in and relating to ignition systems - Google Patents

Abstract

717,755. Ignition systems; sparking plugs. BRITISH THOMSON-HOUSTON CO., Ltd. July 4, 1951 [July 6, 1950], No. 15875/51. Class 7(4) In an ignition system comprising two separate spark-electrode units 3, 4 each having a single electrode 5, 9, respectively, and means for energizing the electrodes simultaneously with potentials of opposite polarity to cause a spark to jump therebetween, the energizing means includes two separate but inter-connected H.T. windings 13, 16 which are connected in series between the electrodes, two separate but interconnected L.T. windings 12, 15 and a source of sparking voltage, such as a battery 19, connected to the L.T. windings. The L.T. windings 12 and 15, are connected in series through a common point 18, the circuit including a condenser 21 and a switch 20; the H.T. windings 13, 16 are also connected in series through the point 18, the outer end of each winding being connected to one of the electrodes 5, 9 in the combustion chamber 1 of a jet engine, the two electrodes forming between them a spark gap of about half-an-inch in length. Each electrode is located in a ceramic insulator 6 within a metal housing 7 which has a flange 8 whereby it is secured to the chamber 1. Connected across the condenser 21 is a vibrator 22 so that when switch 20 is closed and the circuit of the L.T. windings is interrupted by the vibrator 22 the condenser 21 is charged by the voltage induced in the L.T. windings, the cables and electrodes of the H.T. circuit also being charged by the voltage induced in the H.T. windings 13, 16. When the voltage between the electrodes 5, 9 reaches the breakdown value a high-frequency spark will jump the gap and dissipate the energy stored in the capacitance of the H.T. circuit after which the condenser 21 discharges through the gap at a lower frequency to be followed by the discharge of the inductive energy of circuit. Due to the arrangement of coils and electrodes the sparking voltage is about double the usual value as is the capacitive and inductive energy in the circuit. The system is used for starting purposes.