Improvements in or relating to electrical ignition apparatus

684,639. Ignition systems. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Aug. 13, 1951 [Aug. 14, 1950; Sept. 22, 1950; Oct. 12, 1950; Nov. 3, 1950], Nos. 20168/50, 23336/50, 24973/50 and 26932/50. Class 7 (iv). In ignition apparatus for use with surface discharge sparking plugs 26-29, Fig. 2, comprising a relatively high-tension two-electrode spark-gap, such as that formed between the moving electrode 21 and any one of the fixed electrodes 22-25 of a jump-gap distributer, and a low-tension condenser 13 across which the spark gap is connected in series with connections for a sparking plug, there is provided means, such as a high-frequency transformer 16, 17 and a trigger condenser 15, for applying across the spark gap a high-tension transient of sufficient voltage to break it down so that in operation a discharge at one of the surface discharge sparking plugs 26-29 is initiated by a relatively high-tension transient across the spark gap and is prolonged by low-voltage energy from the main condenser 13. When each successive impulse from a magneto, ignition coil or alternator, not shown, is applied to leads 11, 12, the main condenser 13 is charged directly and the trigger condenser 15 is charged through resistance 20; when the charge voltage due to each impulse reaches a given value a spark gap or other switch device 14 breaks down and the trigger condenser 15 discharges through. the gap 14 and transformer primary 16, the resulting high-frequency current inducing in the secondary 17 the high-tension transient: The resistance may be inserted in the circuit where indicated in broken lines, 20a. In a modification, the trigger condenser is connected directly in parallel with the resistance so that the main condenser only is charged by each impulse and upon the spark gap breaking down energy flows from the main condenser through the spark gap and transformer primary to charge the trigger condenser thereby resulting in a transient voltage in the transformer secondary. In another modification, the spark gap 14, Fig. 4, is arranged in a local circuit containing. also the transformer primary 16 and trigger condenser 15, the gap 14 in this embodiment being, arranged to break down at a lower voltage than the distributor gap. In operation, each impulse charges the main condenser 13 until the voltage there across is sufficient to cause the gap 14 to break down whereupon current flows in the local circuit and charges the trigger condenser 15 at the same time inducing in the t