Patent GB-707045-A (GB)
Abstract: 707,045. Ignition systems; sparking plugs. BENDIX AVIATION CORPORATION. June 8, 1950 [June 9, 1949; May 8, 1950], No. 14380/50. Class 7(4) In electrical ignition apparatus comprising a spark gap, such as a low tension sparking plug, in series with a source of electrical energy, for example a magneto 10, Fig. 1, and consisting of a pair of electrodes 28, 29, in spaced relationship to each other, the gap being normally non-conducting at the voltage supplied by the source, there is provided a resistance element 31 in contact with the electrodes 28. 29 on one side thereof to bridge the gap therebetween and ionize the gap at the voltage of the source; the energy source may charge a condenser 21 which is arranged to be connected to the plug. The magneto 10 supplies energy to a condenser 21 through a full-wave or two half-wave rectifiers 20, the condenser 21 being periodically discharged by a switch 23 and the discharge being taken to the plugs through a distributer 26. Sparking plugs. One plug electrode 28 consists of a disc concentrically disposed within a ring earthed electrode 29, the end faces of both electrodes being bridged by the flat surfaced resistor element 31 so that initial discharge of the condenser 21 causes a current to flow across the surface member 31 which thereby ionizes the gap between electrodes 28, 29. The element 31 has a resistance of about 10,000 ohms and may be made from fused mixtures of silicon carbide, iron powder or similar conductors and aluminium oxide or comprised by an insulator with conductive material in the surface of interstices thereof; the annular gap between the electrodes is about 0.02 inches. Ignition circuit. Condenser 21 may be connected directly to the spark plug; the distributer rotor 25 and the cam 24, operating the switch 23, should be synchronized but it is not necessary that either of these parts are synchronized with the cam 15 operating the magneto circuit breaker 14, which latter cam is rotated in timed relation to the magneto rotor. The condenser 21 may be charged by a small high-speed magneto as distinct from the one shown. In another embodiment, a battery 35, Fig. 2, supplies a primary winding 38 through a radio filter 36 the primary circuit being completed by a circuit breaker 40 operated by a cam driven from an electric motor 45 energized by the battery 35. The secondary winding 39 supplies energy to a storage condenser 47 through a half-wave rectifier 46, the condenser discharge being taken to the sparking plugs 48, 49 by way of two switches 50, 51 operated by a cam 52 driven through reduction gearing (not shown) from the motor 45 so that each plug is alternately energized. In a further embodiment, the voltages of a battery 110; Fig. 3, is stepped-up by a transformer 113, the circuit through the primary winding 114 of which is completed by an electromagnetic reed-type vibrator 117 which provides for double the number of current fluctuations, in the transformer compared with the two contact type shown in Fig. 2. The output from secondary winding 118 passes through two half-wave rectifiers 120 in series and progressively charges a condenser 119, which upon attaining a predetermined voltage causes breakdown of a spark gap 121 and connects the condenser to the sparking plug 123. A radio filter 111 is provided between the battery and transformer whilst a variable resistance 116 in the primary circuit is used to adjust the rate of discharge in the system. The transformer core may incorporate an air gap. Specification 661,779 is referred to,