GB624325A - Improvements in electrical ignition systems - Google Patents

Abstract

624,325. Ignition systems. BRITISH THOMSON-HOUSTON CO., Ltd., WELCH, D. F., and GRIEVE, A. July 2, 1947, No. 17476. [Class 7 (iv)] In an ignition system in which a high frequency discharge at a sparking plug is obtained by intermittently charging a condenser C1 and discharging it through a spark gap, the condenser is provided with a pair of discharge gaps connected in series therewith the breakdown voltage of one of them G2 in Fig. L or G 1 in Fig. 2 being of the order of and preferably just greater than the maximum value of the generated voltage applied to the condenser and the breakdown voltage of the other gap being of the order of half that of the first mentioned gap, the gaps being caused to break down by applying to the common connection between them, which connection is maintained substantially at the generated voltage (Fig. 1) or at zero potential (Fig. 2) an initiation voltage obtained by a peaking transformer Tp or peaking choke Chp energised by the charging current flowing into the condenser. The choke and the transformer are arranged to be saturated at a given value of the charging current and thus give a peak when the charging current falls to zero at peak voltage on the condenser. The voltage peak in the system of Fig. 1 causes the breakdown of the gap G2 and thus brings the full voltage of the condenser across the gap G1, which then ruptures. In Fig. 2 the voltage peak from the choke is fed to. the gap junction by a condenser G2. The value of a resistance R is chosen so that when taken in conjunction with the capacity C2 the relatively slow rise of generated voltage across S1 should result in little or no voltage appearing across G2 while the rapidly applied voltage from the peaking choke should appear across G 1 with the minimum of loss. The gap G1 is supplied by the voltage across Sl and R, the impedance of Chp being zero while it is saturated. When the voltage peak occurs due to the fall to zero of the charging current the gap G1 is ruptured first causing breakdown of gap G2. The spark gaps may be of the hermetically sealed type and enclosed in a single sealed envelope with an intermediate electrode forming a common electrode of the two gaps. Specifications 525,492, 529,458, 529,558, 545,857 and 598,053 are referred to.