Patent GB-662717-A (GB)
Abstract: 662,717. Ignition systems. MACKAY, E. G. Aug. 18, 1949 [Sept. 17, 1948], No. 21516/49. Class 7(iv) [Also in Group XXXV] In an ignition system for internal-combustion engines comprising an induction  coil having, for example a magneto primary winding 11, Fig. 1, means for energizing the primary winding and a plurality of contact-breakers 2 wired in circuit with the winding, there is provided contact selector means, such as a commutator 8, which is also included in the circuit and is capable of being electrically connected with any one of the contact-breakers 2 for successively including each - contactbreaker in the circuit in order to obtain a greater output of electrical impulses than would be possible if the ignition system included a single contact-breaker only for making and breaking the primary winding, and without reducing the minimum time required for ensuring effective closing of the plurality of contact-breakers; each circuit-breaker, , which may be cam operated, can be wired in series with the commutator and the cams may be connected to the commutator so that their speeds are synchronized. Four contactbreakers 2 are arranged around a common single-lobe cam 3 whilst the commutator brush 7 and cam 3 are arranged either on the magneto or other common shaft or each disposed on separate shafts so that normally each commutator segment makes and the associated contact. breaker 2 breaks the circuit, although at high speed the breakers 2 may perform both functions. In a modification, the magneto, commutator and circuit breakers are constructed as a unit, the commutator brush being carried by an extension of the magneto shaft and contacting the inner surface of fixed segments, whilst a lay shaft driven through reduction gearing from the magneto shaft is provided with one cam to operate all the breakers. When two or more longitudinally spaced cams are used to operate the breakers, the latter are arranged in pairs, each pair being operated by a multilobe cam. In a further modification, the number of commutator segments is arranged to be a multiple of the number of contact-breakers and the speed of the breaker cam is adjusted accordingly in order that the polarity of the contacts of each breaker may be changed at each successive operation. In another modification, the contact breakers are arranged as a separate assembly that may be remotely located in relation to the magneto which latter may be of the inductor type. A battery ignition system may replace the magneto in the embodiment of Fig. 1. In a further modification, the centre point of the primary magneto winding 11, ,Fig. :8; is connected to a battery 26 whilst the ends of the winding are joined to a pair of breakers 2 and the comutator 32, under which circumstances the commutator also serves to alternately include each half of the winding 11 in the battery circuit in such manner that the battery current, flows first in one direction in one half of the winding and then in the opposite direction in the other half, thereby alternately reversing the battery current flux in the winding to match the alternating magneto flux therein. In a further modification, the magneto primary is wound in. two separate parts and-the commutator functions to connect the breaker circuit through the pre-selected part of the winding. In another modification, .a pair of matched primary coils 29, 31, Fig.-10, are wired in circuit with a battery 26, whilst. four contact-breakers 2 are arranged in two pairs, each pair being operated by a four lobe cam.3a. The commutator has four segments 6 and the speed of the mag- .neto and commutator brush is four times that of the cam shaft 16. Where a dual ignition system is provided a common magneto ratio and commutator may be used for both systems. Specification 662,698 is referred to.