US2602149A - Ignition system - Google Patents

Description

July 1, 1952 H. E. BRUNELLE, JR., ETAL 2,602,149

IGNITION SYSTEM Original Filed Oct. 11, 1949 COPEMSAT/ONAM FIRM/c mrnmu. I I

r .--1 Inventors: Henry E. Brunelle,

' Luther S. Molde,

by MW heir Attorney Patented July 1, 1952 2,602,149 IGNITION SYSTEM Henry E. Brunelle, Jr., Schenectady, N. Y., and Luthard S. Molde, Montevideo, Minn, assignors to General Electric Company, a corporation of New York Original application October 11, 1949, Serial No. 120,752. Divided and this application August 10, 1950, Serial No. 178,652

12 Claims. 1

This invention relates to ignition systems which employ magnetogenerators as the source of electrical power, and more particularly to voltage doubler ignition systems of the type described and claimed in U. S. Patent 2,456,475 to Wargin et al., dated December 14, 1948.

In ignition systems which utilize two voltage impulses in connection with a voltage doubler circuit to fire a single spark plug, the timing of the voltage impulses is very important. This is particularly true in cases, such as in aircraft engines, where it is necessary to operate a larg number of spark plugs from a single distributor. In; such cases the space between distributor electrodes and the time between spark plug discharges are both limited, making it difficult to insure that two complete charges are generated before the time for discharge. It is an object of this invention to provide an ignition system which insures that two complete charges are generated before the time for discharge is reached.

It is a further object of the present invention to provide an ignition system which utilizes irregularly occurring voltage impulses.

In carrying out our invention in one form, we provide an alternating qpolarity magnetogenerator of the inductor type having teeth on alternate stator poles of unequal width. Such a magnetogenerator is claimed in our copending application Serial No. 120,752, filed October 11, 1949, now Patent 2,553,298, issued May 15, 1951, of which the present application is a division.

The unbalanced alternating flux produced by the rotation of the rotor of such a magnetogenerator results in alternating voltage impulses in the voltage output coils of the magneto separated by different time intervals for one polarity than for the other. This alternating voltage is applied to a voltage doubler circuit in a breakerless type ignition system providing for low tension distribution. The voltage doubler circuit, in turn, impresses the aggregate of two complete charges for each spark plug operation on transformer type spark plugs through an air-gap type distributor. The use in our ignition system of voltage impulses which occur at irregular intervals insures that two complete charges are generated before each spark plug discharge because it is possible with such an arrangement to generate two complete charges in a shorter interval than would otherwise be the case.

For a clearer and more complete understanding of our invention, reference should be had to the accompanying drawing in which Fig. 1 is a schematic diagram of a preferred embodiment of i the invention; Fig. 2 is a partial schematic diagram illustrating the magnetogenerator in a different rotational position than Fig. 1,; while in Figs; 3A, 3B and 30 there are shown curves to facilitate the understanding of the invent on.

Referring to Fig. l of the drawing, there is shown a breakerless ingition system of the low tension high frequency type for which electrical power is supplied by a magnetogenerator indicated generally at l. The magnetogenerator illustrated isof the inductor type and comprises a rotary member 2 mounted on a drive shaft 3, which may be driven by any suitable means (not shown). The rotor 2 is formed of magnetic material and is prefer'ablyof laminated construction, the rotor being provided with a plurality of circumferentially spaced teeth 4. Extending around the rotor member 2 is a stator member comprising four spaced arcuate pole pieces 5, 6, l and 8. Stator pole pieces 5 and 1 are provided with a plurality of inwardly extending projections or teeth 9, while pole pieces 6 and 8 are provided with a plurality of inwardly extending teeth 10. The stator teeth 9 and I0 cooperate with the rotor teeth 4 in establishing different low reluctance magnetic circuit paths through the rotor and the stator pole pieces as is subsequently described in detail.

The magnetogenerator l is provided with twooutput coils H and 12 which are mounted, respectively, on magnetic core members 13 and I4. As illustrated in the drawing, the core member 13 is arranged magnetically to interconnect the stator pole pieces 5 and 6, while core member M is arranged magnetically to interconnect stator pole pieces I and 8, the core members I3 and 14 being located on diametrically opposite sides of the stator.

For the purpose of providing a source of magnetic flux which is periodically directed through the core members l3 and M in opposite directions upon the rotation of the member 2, there are provided two permanent magnets l5 and 16 located on diametrically opposite sides of the stator. As shown, the permanent magnet 15 is arranged so that its polar extremities abut the adjacent ends of pole pieces 6 and 1 and thereby forms a magnetic link between these two pole pieces. The permanent magnet 16 is similarly arranged with its polar extremities abutting the adjacent ends of pole pieces 5 and 8, and acting as a magnetic link interconnecting these two pole pieces.

When the rotor 2 of the magneto rotates, the magnetic flux of the permanent magnets l5 and I8 is caused first to pass through the core members l3 and M in one direction and then to be rapidly changed or switched so as to flow through the core members in the reverse direction, this alternate and rapid flux switching causing high induced voltages in the magneto output coils H and [2. This flux switching action of the magnetogenerator may be more easily understood by consideration of the low reluctance magnetic flux paths when the generator rotor is in each of 3 the two different positions illustrated, respectively, in Figs. 1 and 2 of the drawing. When the rotor is in the position shown in Fig. 1 of the drawing, the rotor teeth 4 lie opposite the stator teeth It on pole pieces 6 and 8, whereby'a low reluctance path is established .interconnecting these two pole pieces diametrically across the rotor. At this time the teeth. 3 of pole pieces .5 and I are out of registration with the rotor teeth so that the flux path between these two pole pieces extending diametrically across the rotor is of relatively high reluctance. With the rotor of the generator in the position shown in Fig. 1,

two low reluctance magnetic circuit paths are established, one of which may be traced as follows: The north pole of magnet l6, stator .pole piece 5, core member l3, stator pole piece 6, diametrically across rotor memberi, stator pole piece 8 and back to the south pole of permanent magnet [6. The other of these two paths may be traced from the north pole of magnet l5 through stator pole piece 6 diametrically across rotor member 2, through stator pole piece 8, core member 14, stator pole piece 1 and back to the south pole of magnet 15.

When the rotor member 2 of the magnetogenerator rotates counter-clockwise an amount approximately equal to one-half the pitch of the rotor teeth, it occupies the position shown in Fig. 2 of the drawing. Referring to this figure, it will be-seen that the rotor member 2 now establishes a low reluctance magnetic circuit path extending diametrically across rotor 2 between pole pieces 5 and I. At this time, rotor teeth 4 are out of registration with teeth on stator pole pieces 6 ands so that the reluctance of the magnetic circuit path extending diametrically across the rotor between pole pieces 6 and 8 is relatively high. With the rotor in the position shown in Fig. 2, it will be noted that there are now two low reluctance magnetic paths whereby the magnetic flux-of permanent magnets l and It threads the core members l3 and It in the opposite direction from that shown in Fig. 1. One of these paths may be traced as follows: The north pole of permanent magnet'lfi, stator pole piece 6, core member 13, stator pole piece 5, diametrically across rotor 2, stator pole piece I and back to the south pole of permanent mag-net I5.

It will be noted from Figs. 1 and 2 that teeth 9 on stator pole pieces 5 and 1 are of greater width and, hence, of greater lateral cross-section than teeth Hi on pole piecesfi and 8, although all stator teeth are made relatively narrow for reasons which are given subsequently. The eiiect of the difierence in lateral dimensions of stator teeth 9 :and H3 is to cause the magnetic flux through core members l3 and [4 to reverse at irregular intervals. This is due to the fact that rotor teeth 3 are opposite the wider stator teeth 9 in flux conducting relationship therewith for a greater interval than for the narrower teeth [0, the radial air gap between rotor teeth 4 and the stator teeth being substantially the same in both cases. These irregularly spaced flux reversals produce alternating voltages in coils H and I2 having a diiierent interval for one polarity than forthe other, and these are used to advantage in our improved ignition system, as is explained below.

In order that the voltages induced in coils II and i2 may be as high as possible, the magneto rotor and stator teeth are so designed as to cause a very rapid change in the magnetic flux threading core members I3 and M While the rotor memher 2 is rotating. In orderto accomplish this, the stator teeth 9 and l G are formed so that their width is relatively small. In many cases, these teeth are made as narrow as possible consistent with rigid construction and good manufacturing practices. In most cases, the stator teeth are appreciably narrower than the rotor teeth 4, although this may not be the case in a relatively high speed magneto. While the expedient of making a single stator tooth narrow is desirable from the standpoint of obtaining a rapid flux change, it .has'the disadvantage that it reduces the longitudinal cross-sectional area of the stator tooth for an axial tooth length of any given value. The amount of magnetic energy required to be stored in the magnetic circuit of the magneto for each impulse determines the longitudinal crosssectional area of the stator teeth and, therefore, in the conventional single-tooth stator construction this results in unduly long stator-teeth, which is undesirable from the size standpoint. In the present arrangement, this difiiculty is obviated by using a plurality of parallel stator teeth on eachpole piece so as to provide a plurality'of parallel flux paths across the air gap-to the'rotor. Thus, it will be noted that each of the stator pole piecesli, 6, and 8 is provided with three inwardly extending teeth. This arrangement permits the necessary amount of-pole piece cross-sectional area to conduct the required amount of flux without necessitating undesirably long stator teeth. Obviously, more or less than three stator teeth perpole-can be used, depending upon the number of rotor teeth being used and the amount of flux which is required in a particular case.

Referring now to the details of the ignition distribution arrangement, and more particularly to the distribution arrangement associated'with magneto output coil I I, it will be noted that there is provided apair of series connected storage condensers I1 and [8 having a common terminal [9 which is connected to one of the output leads 2llof the coil II. The remaining terminal 25 of the condenser ll is connected to the other coil lead-2| through a half-wave rectifier 22. Theremaining terminal 23 of the condenser I8 is also connected to the coil-lead 2| through a parallel circuit, including another half-wave rectifier 24. The magnetic and electrical polarities are so selected in connection with the current conducting directions of rectifiers 22 and 24 that when the output of coil ll is-of one polarity, one of the condensers, say condenser H, is charged. Due to the action of rectifiers22 and 24, thenext succeeding voltage impulse of oppositepolarity of coil H causes the condenser l8 to be charged while the charge on condenser I! is maintained. The polarities of the condensers I1 and t8 when chargedare such that they are-series aiding or additive, that is, the voltage across terminals 2| and 23, when the condensers are fully charged, is substantially greater than across either 'condenser alone, and may be approximately twice as great for the illustrated case wheretwo condensers were used.

In order to utilize this cascading arrangement advantageously, a circuit arrangement is provided whereby the voltage across the terminals 2| and 23 is periodically supplied by a distributor to various ignition circuits to fire spark plugs associated therewith. To this end, the terminal 25 is grounded, as indicated, and the terminal 23 is connected through a lead 26 to a rotary distributor, indicated generally at '21. The distributor 27 is shown as comprising a plurality of stationnism with the rotor member 2 of the magnetogenerator. The lead 26 is connected to distributor finger 29 through a slip ring arrangement 30 of conventional construction.

The ignition circuits illustrated are of the socalled low tension high frequency type. For the purpose of simplicity, only one such circuit is illustrated in Fig. 1 for distributor 21, but it will be understood that in actual practice there is a separate ignition circuit and associated spark plug connected to each of the stationary distributor electrodes. I

The ignition circuit shown in connection with the distributor 21 comprises a step-up transformer 3! having a primary or low voltage winding 32 and a secondary or high voltage winding 33. The high voltage winding 33 is connected to energize a spark plug 34, while the primary winding 32 is arranged to be periodically connected by the distributor 21 to be energized by series-connected condensers I1 and I8. In ignition systems of this type, a sparkgap is used to initiate a high frequency oscillatory discharge in the primary circuit of transformer 3i and in the illustrated arrangement the distributor used is of the air-gap type in which the required spark discharge takes place between the rotary distributor finger 29 and stationary electrodes 28. Thus, as distributor finger 29 rotates, it approaches to within arcing distance of the electrodes 28, but does not actually come in contact with them. An advantage of this type of ignition circuit lies in the fact that the distributor voltage may be of relatively low magnitude, for example, on the order of three kilovolts, while the high voltage applied to the spark plugs, which may, for example, be of the order of 18 kilovolts, is confined to the spark plug andthe secondary winding of the step-up transformer. In order to eliminate corona loss to the surrounding atmos phere, step-up transformer 3| may be advantageously hermetically sealed in the spark plug, as will be well understood by those skilled in the art.

In ignition systems for radial engines, there must be provided compensation for timing irreg ularities which occur because of the use'of articulated piston rods. In conventional ignition systems of the breaker type, this compensation is usually provided by properly selecting the angular relation of the cam lobes used to operate the breaker switch. In the present breakerless system, some other method must be used. Such timing compensation can be conveniently obtained in the present system by an appropriate circumferential spacing of the stationary distributor electrodes.

One of the principal advantages of this invention is that it permits such compensation, by means of angular adjustment of the stationary distributor electrodes, without detrimental effect on the operation of the ignition system. This will be more readily understood by reference to the curves of Figs. 3A, 3B, and 30 of the drawing. In Fig. 3A is shown a typical voltage wave resulting from a double voltage impulse from a magnetogenerator having voltage impulses occurring at regular intervals. In Fig. 3B is shown a typical voltage wave of an ignition system employing the present invention. It will be noted from the curve of Fig. 33 that the voltage rises to the peak voltage required to completely charge the condensers earlier in the cycle than with the conventional generator and thereby allows an ample compensation and firing interval. In Fig. 3C, is shown the magnetogenerator flux wave corresponding to the output voltage wave of Fig. 3B.

The construction of the magnetogenerator I is such that it lends itself advantageously to the dual ignition arrangement illustrated in Fig. 1, wherein separate distribution circuits are associated with each of the twooutput coils II and I2, the distribution circuit associated with coil I I having been described above. In order to utilize advantageously the output of the second magnetocoil l2, there is provided another ignition distribution system which may be, as shown, the same as the corresponding parts of the previous distribution system already described in connection with coil II. Parts of the second distribution system corresponding to those already described have been given corresponding reference numerals, except that the numerals have been primed in order to differentiate between the systems.

In order to clarify the description of operation of our improved ignition system by a concrete example, there is illustrated in Fig. 1 a system which provides dual ignition for an internal combustion engine having 14 cylinders. In the system illustrated, the rotor 2 of the magnetogenerator is provided with 14 teeth and each of the distributors is provided with 14 stationary electrodes, making a total of 28 electrodes which are connected to 28 separate ignition circuits. With this arrangement, the shaft 3 which drives the magnetogenerator rotor and the distributor finger 29 and 29' may be connected to the internal combustion engine so as to operate at one-half engine crank-shaft speed. The characteristic of the magnetogenerator l is such that it inherently produces a number of impulses of alternating polarity in each of the coils H and I2 equal to twice the number of rotor teeth for each revolution of the rotor shaft. Thus, in the illustrated arrangement, there are '28 voltage impulses of alternate polarity induced in each of the coils I l and l2 for each revolution of the drive shaft 3. Assuming the electrodes 28 and 28' to be equally spaced except for small angular irregularities to provide timing compensation, it will be clear from Fig. 33 that the magnetogenerator I produces two complete voltage impulses in the time interval required for each distributor finger to move from a position opposite one electrode to a position opposite the next adjacent electrode. Thus, the series-connected storage condensers are fully charged and ready for discharge through an ignition circuit each time a distributor finger moves opposite a stationary electrode. With this arrangement, it will be clear that the 28 ignition circuits are periodically and sequentially fired'in pairs 0 that the system can be utilized to provide dual ignition for an engine having 14'cylinders. It will also be readily understood by those skilled in the art that the system illustrated in Figs. 1 and 2 may be used to provide dual ignition for engines having an odd or even number of cylinders by providing a suitable number of teeth on the magnetorotor and suitable quantities of stationary electrodes for the distributors. Also, by utilizing only one of the output coils, provision may be made for single ignition for an odd or evennumber of cylinders. Similarly, provision may be made for more than two voltage impulses per firing interval, if desired.

.While we have showna particularmagnetogeneratorifor use in our improved 'breakerless ignition system,it should be understood that our invention is not limited to the use of this specific generator. Any generator may be used which providesan alternating potential having a different interval for one polarity than the other.

In connection with the magnetogenerator illustrated it will be noted in Figs. 1 and 2 that the circumferential spacing between the adjacent endmost teeth 9 and i9 on'adjacentstator pieces is equal to approximately one'and ahalf times thetooth-pitch of the. rotor teeth, the distance being measured between the center lines. of the stator-teeth, It Will be understood that this spacing may be any odd multiple of one-half the pitch of the rotor teeth, that is, one-half, one and one-half, two and one-half, etc.', as long as the rotor teeth! are out of'register withstator teeth Hi When they are in register with stator teeth Snand vice versa.

yiAnimportant advantage of the present invention is-that it results in a considerably wider band of no electrical activity, as shown in Figs. 3-BIand3C, in which most values of distributor electrode compensation may bespanned without the spark discharge interrupting the voltage wave. i An additional advantage is that it stabilizes the level of ,thevoltage to'which the condensers are charged for each spark, since two complete voltage impulses are applied to the condensers for each spark.

"By making all peak Voltages uniform, this invention makes possible an increase in the altitude ceiling for ignition systems for aircraft engines, since there is no voltage higher than the desired minimum condenser charging voltage.

A still further advantageis that it reduces the amount of loss fromthe charge on the first condenserof a pair resulting from the first impulse, through the leakage of the rectifiers, .becausethere is not as muchtime for decay before the second impulse occurs.

: A'stil'l further advantage is that it makes more practical-the use of a voltage multiplier electrical circuit in-an ignition system, especially for use in engines of 14 or moreqcylindersin which the time for ignition of each spark plug and the angularispacing between distributor electrodes becomes critical.

. -While we have illustrated and described a pre- -fe1red=embodi1nent of our invention, modifications thereof may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, it should be understood that we intend-to cover by the appended claims all such modifications as fall withinthe'spirit and scope of our invention.

-What .we claimas new and desire to secure byjLetters-Patent or" the United States is:

1. In an ignition system, generator means for providing alternating polarity voltage impulses having a first interval for one polarity and a diiierent interval for the other polarity, voltage doubler type circuit means including a plurality of condensers connected series aiding, whereby a voltage impulse from said generator means charges one of said condensers and a later'voltage impulse from said generator means charges another of said condensers, and discharging means arranged to simultaneously discharge said series connected condensers through ignition apparatus.

2. An ignition system comprising generator means for producing alternating polarity voltage impulses having a lesser time interval for impulses of one polarity than the other, a pair of condensers connected series aiding, circuit means including rectifiers for connecting said condensers to said generator means in a manner such that, a voltage impulse'of one polarity charges one of said condensers and a voltage impulse of the other polarity charges the other of said condensers, and a distributor arranged to simultaneously discharge said series connected condensers through ignition apparatus.

3. In combination, an alternatingvoltage generator having a greater interval for one polarity than the other, circuitmeans of the voltage doubling type coupled to said-generator'and receiving alternating voltage therefrom, said circuit means including condenser means charged to a direct voltage greater thanthe amplitude of said alternating voltage, and dischargingcircuit means for discharging said condenser means at periodic intervals at least as great as two half cycles of said alternating voltage.

. 4. An ignition system comprising generator means for producing alternating polarity voltage impulses having a lesser intervalior one polarity thanfor the other polarity, a pairof condensers connected series aiding, circuit means including rectifiers for connecting said condensers to said generator means in a mannersuch that .a voltage impulse-of said one polarity charges one of said condensers and a voltage impulse of said other polarity charges the second of said condensers, and discharging means arranged to simultaneously discharge said series connected condensers during the latter portion of the interval for said other polarity.

5. An ignition system comprising generator means for producing alternating polarity voltage impulses, said means providing a predetermined time interval for one polarity and a'greater interval for the other polarity, voltage doubler type circuit means including a pairof condensers connected series aiding, whereby a voltage impulse of said one polarity'from said generator means charges one of said condensers and a later impulse of the other polarity 'fromsaid generator means charges the other of said condensers, and periodic dischargingv means arranged to simultaneously discharge said-series connected condensers through ignition apparatus during the latter portion of theinterval for saidother polarity. V

6. In an ignition system, analternating polarity generator for producing voltage limpulses, said generator having a, first predetermined interval for impulses of one polarity, and

a longer interval for impulses of the other-polarity, a pair-of condensers connected series aiding, circuit means including rectifier interconnecting said condensers and said generator in a manner such that a voltage impulse from said generator of one polarity charges one or" said condensers during said predetermined interval and a voltage impulse of the opposite polarity charges another of said condensers during-said longer interval, means for connecting said condensers in series so that thecharges thereon are additive, and a distributor arranged to simultaneously dis- .charge said condensers during the latter portion of said longer interval, said generator and said distributor being synchronized and correlated so that each of said condensers receives a charging impulse-from said generator prior tosaid discharge by said distributor.

'7. An ignition system comprising a magneto having a rotatable member and an output coil which produces successive voltage impulses of different duration upon rotation of said rotatable member, a pair of condensers connected series aiding, selective charging circuit means connecting said condensers to said coil so that a voltage impulse followed by an interval of one duration charges a first one of said condensers and a subsequent impulse followed by an interval of longer duration charges the other of said condensers while the charge on said first condenser is maintained, and a distributor arranged to simultaneously discharge said series connected condensers through ignition apparatus, said rotatable member and said distributor being synchronized and correlated so that each of said condensers receives a charging impulse from said output coil prior to discharge through said distributor.

8. In an ignition system, a generator for producing voltage impulses of alternating polarity, said generator providing a greater interval for impulses of one polarity than the other polarity, a plurality of condensers connected series aiding, charging circuit means including rectifier means connected between said generator and said condensers for charging one of said condensers upon the production of a voltage impulse during the lesser interval and for charging another of said condensers upon the production of a voltage impuls during said greater interval, a, distributor arranged to simultaneously discharge said series connected condensers, and synchronizing means for said generator and distributor, said last-mentioned means driving said distributor at a rate to discharge said condensers after each has received at least one charging impulse from said generator and before the termination of said greater interval.

9. An ignition system comprising a, magneto having a rotatable member and an output coil which produces successive voltage impulses of alternating polarity upon rotation of said rotatable member, said magneto providing a greater interval for impulses of one polarity than the other polarity, a pair of condenser connected series aiding, circuit means including rectifiers for connecting said condensers to said coil so that a voltage impulse of one polarity charges one of said condensers and a voltage impulse of the opposite polarity charge the other of said condensers, and a distributor arranged to simultaneously discharge said series connected condensers through ignition apparatus, said rotatable member and said distributor being synchronized and correlated so that each of said condensers receives a charging impulse from said output coil prior to said discharge through said distributor.

10. An ignition system comprising a breakerless magneto of the inductor type having an output coil in which voltages of alternating polarity are induced, said magneto providing a greater interval for voltages of one polarity than the other polarity, a pair of series connected condensers, circuit means includin rectifiers interconnecting said condensers and said output coil in such manner that consecutive output coil voltages of alternating polarity cause sequential charging of said condensers whereby the voltage across said series connected condensers when charged is greater than the voltage induced in said output coil during each voltage impulse thereof, and a rotary distributor mechanically synchronized with said generator arranged to periodically discharge said series connected condensers after each of said condensers has received a charging impulse from said output coil.

11. An ignition system comprising an alternating polarity generator providing a lesser interval for one polarity than for the other polarity, a pair of condensers connected series aiding, charging circuit means including rectifier means connected between said generator and said condensers for charging one of said condensers upon the production of a voltage impulse during the lesser interval and for charging the other of said condensers upon the production of a voltage impulse during said greater interval, and an airgap type distributor arranged to discharge simultaneously said series connected condensers, said distributor comprising a plurality of spaced stationary electrodes positioned in circular relation and a cooperating finger member connected to said condensers and rotatable successively adjacent said stationary electrodes in operative relation therewith, said distributor and said generator being synchronized whereby said condensers are discharged successively through said stationary electrode during successive greater intervals.

12. An ignition system comprising a magneto having a rotatable member and two output coils in which successive voltage impulses are induced upon rotation of said rotatable member, said magneto providing a lesser time interval for impulses of one polarity than the other, a first circuit means of the voltage doubling type including a pair of condensers connected to one of said coils so as to be sequentially charged by successive voltage impulses from said one coil, the first of said pair of condensers being charged during said lesser interval and second during the greater interval, a second circuit means of the voltage doubling type including a pair of condensers connected to the other of said coils so as to be sequentially charged by successive voltage impulses from said other coil, the first of said second pair of condensers being charged during said lesser interval and the second during said greater interval, a pair of distributors each comprising a set of stationary electrodes and a cooperating rotatable finger member, means for rotating the finger members of said distributors and said magneto rotatable member at predetermined relative speeds, the spacing between successive electrodes of each of said distributors being such that two voltage impulses are induced in the associated magneto coil during the time interval required for a distributor finger to move from a position opposite one electrode to the position opposite an adjacent electrode, means for connecting each pair of condensers respectively to a rotating finger of one of said distributors, and an ignition circuit including a spark plug associated with each distributor stationary lectrode, whereby all of the ignition circuits may be periodically energized by discharge from said condensers in sequence or two at a time depending upon whether said distributor fingers are initially set in staggered or synchronized relation.

HENRY E. BRUNELLE, J a. LUTHARD S. MOLDE.

REFERENCES CITED UNITED STATES PATENTS Name Date Wargin et al Dec. 14, 1948 Number

Images