US3032683A

US3032683A - Ignition system

Info

Publication number: US3032683A
Application number: US785173A
Authority: US
Inventors: John G Ruckelshaus
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-01-06
Filing date: 1959-01-06
Publication date: 1962-05-01
Anticipated expiration: 1979-05-01

Description

May 1, 1952 J. G. RUCKELSHAUS 3,032,683

IGNITION SYSTEM 3 Sheets-Sheet 1 Filed Jan. 6, 1959 May 1, 1962 J. G. RUcKELsHAUs 3,032,683

IGNITION SYSTEM 3 Sheets-Sheet 2 Filed Jan. 6, 1959 May 1, 1962 J. G. RUcKELsHAUs 3,032,683

IGNITION SYSTEM Filed Jan. 6, 1959 5 Sheets-Sheet 3 f 7j l /ff @9% f 2 l a @f 5W #j United States Patent ili 3,032,683 Patented May I, i962 3,032,683 IGNITION SYSTEM lohn G. Ruckelshans, 110 Pomeroy Road, Madison, NJ. Filed Jan. 6, 1959, Ser. No. 785,173 6 Claims. (el. sis- 180) This invention relates to an ignition system utilized in internal combustion engines and more particularly to a novel, low voltage system for distributing power to surface gap ignition plugs in a multi-cylinder engine.

Present ignition systems utilized in multi-cylinder internal combustion engines include a spark plug associated with each engine cylinder. Each spark plug has a pair of spaced electrodes electrically insulated from each other. A high voltage is developed from a storage battery by means of an electro-mechanical vibrator and stepup transformer and such voltage is applied across the electrodes of the individual spark plugs in proper ring sequence by a distributor having a rotating contact maintained in timed relation to the motor speed. It is known that the conventional ignition system suffers' numerous practical disadvantages in addition to the high voltage requirement such as, for example, deterioration of the distributor contacts, the generation of interfering radiofrequency waves, deterioration of the spark plug electrodes, and loss of efficiency due to the accumulation of carbon on the spark plug electrodes.

In an ignition system having conventional spark plugs, a high voltage, of the order of 20,000 volts, is required to produce a hot spark across the electrodes to thereby ignite the compressed `gasoline-air mixture within the engine cylinder. Although the voltage requirement is high, the magnitude of the current flowing across the electrode gap during the spark period is relatively low.

There has recently been developed a surface gap plug, or igniter, which differs fundamentally from the conventional spark plug in that there is provided between the electrodes a semi-conductor material having an initial resistance of 30,000-500,000 ohms. When a voltage of 150-400 volts is applied across the electrodes of a surface gap igniter the resistance of the semi-conductor material decreases to a very low value permitting a current of several hunderd amperes to ilow between rather than jump across the electrodes.

The advantages of the surface gap igniter are numerous as, for example, such igniter will operate in extreme moisture (even immersed in water), it provides a tremendously hot spark which promotes easier engine starting at low temperature, permits the use of more economical gasoline, and it is not adversely affected by the accumulation of carbon deposits on the electrodes, thereby resulting in a longer, uniform operating life.

To date, the surface gap igniter has been employed only in single cylinder engines, such as jet engines, where the ignition system is required only to start the engine. It has not been utilized in multi-cylinder engines because of the impracticability of switching, or distributing, a current in excess of 200 arnperes at voltages up to 2,000 voltages without excessive arcing and disintegration of the distributor contacts.

An object of this invention is the provision of an efficient, economical system for the distribution of power to surface gap ignition plugs in a ymulti-cylinder engine.

An object of this invention is the provision of a low voltage ignition system for actuating a multi-cylinder engine, which system operates at relatively low voltages, does not require an electro-mechanical vibrator, does not include mechanical contact points, and produces a minimum of radio interference.

An object of this invention is the provision of a rotary gap distributorv for sequentially distributing electrical energy to a plurality of surface gap igniters.

An object of this invention is the provision of a novel distributor adapted for converting a conventional distributor for use in an ignition system utilizing surface gap igniters.

These and other objects and advantages will become apparent from the following detailed description when taken with the accompanying drawings illustrating several embodiments of the invention.

In the drawings wherein like reference characters denote like parts in the several views:

FIGURE l is an elevation view of a surface gap igniter, with parts shown in cross-section;

FIGURE 2 is a schematic diagram of an ignition system made in accordance with this invention;

FIGURE 3 is a diagram showing a transistor power supply for energizing the ignition system;

FIGURE 4 is a fragmentary diagram showing a full wave rectifier for rectifying the output voltage of the high voltage transformer;

FIGURE 5 is a fragmentary diagram showing another embodiment of the invention;

FIGURE 6 is an elevation view of my novel distributor with portions of the housing broken away and with parts shown in cross-section;

FIGURE 7 is a fragmentary, plan View, looking down into the distributor base and showing the essential parts of a conventional distributor for automatic spark advancement by means of conventional vacuum bellows; and

FIGURE 8 is essentially, a cross-sectional view taken along the line 8 8 of FIGURE 7 and with the distributor top attached to the distributor base, portions of the housings being broken away.

Referring to FIGURE l, the surface gap igniter, or spark plug, comprises a metal shell I0 provided with a lower, threaded end 11 adapted to be threaded into a suitable hole provided in the wall of an engine cylinder. The threaded end 11 constitutes the outer electrode which is grounded to the engine and the other electrode cornprises an axially-disposed, headed rod 12 that extends upwardly through an insulator 13, which may be glass, ceramic, or etc. Extending along the gap between the electrodes 11 and 12, at the lower ends thereof, is a semiconductor material I4, which is fired -on to the lower end of the ceramic and which, by reason of the concentric disposition of the electrodes, takes the form of a washer. Intimate contact between the semi-conductor material and the electrodes is desirable although not required for efficient ignition. The initial resistance of the semi-conductor material, taken radially between the electrodes, may vary from 30,000 to 500,000 ohms and this resistance may increase or decrease after the igniter has been used, depending upon the atmosphere within the combustion chamber of the cylinder. With a voltage of between -400 volts applied across the electrode-s 10 and 12 the resistance of the semi-conductor material decreases tremendously, whereby a current having a magnitude of hundreds of amperes flows along the surface of the semiconductor material from the center electrode to the outer electrode, thereby producing a tremendously-hot spark to ignite the gasoline-air mixture within the combustion chamber. It is interesting to note that the igniter will lire at 150-400 volts, regardless of the compression ratio of the engine in which the igniter is used.

Surface gap igniters are well known, but such devices are generally produced with a flush surface between the electrodes and the semi-conductor material. I prefer to construct the igniter so that the end of the inner electrode extends somewhat beyond the lower surface of the outer electrode whereby the semi-conductor material forms a truncated'cone, as specifically sho-wn in FIGURE l. 'In an igniter so constructed, the inner electrode tip and the sem-i-conductor material extends substantially into the gasoline-air mixture and I have found by actual tests such igniters provide instant and positive ignition at high engine speeds.

Reference is now made to FIGURE 2 which is a diagrammatic showing of my novel ignition system as applied to a six (6) cylinder engine. A conventional 6 or l2 volt storage battery l5 is connected to the primary Winding 16 of a step-up transformer 17 through a vibrator or chopper 18, the battery being grounded in accordance with conventional practice. 'The vibrator may be of any standard construction and its function is to apply the battery voltage across the transformer winding in a series of pulses so as to produce in the secondary winding 19 a periodically-varying voltage of increased level, as is well known. In this particular application, I prefer to make the transformer turns ratio such that the voltage developed in the secondary winding is approximately 2,000 volts. The output voltage of the transformer is applied across a capacitor 20, through a current-limiting resistor 21 and a rectier 22. With the rectifier conducting in the indicated direction, the capacitor will become charged as indicated by the polarity marking during each half cycle of the transformer output voltage.

'Ihe reference numeral 23 identities the distributor comprising a sealed chamber with six (6) fixed electro-des or points, 24-29, extending therethrough and a rotatable electrode 30. The rotatable electrode is secured to the distributor shaft whereby such electrode rotates throughout 3 60 degrees in precise, timed relation with the engine speed. The construction of the distributor will be described in detail hereinbelow, with specific reference to FIGURE 6. Suffice to say', at this point, that the rotatable electro'de 30 has a pointed tip spaced from the pointed, inner tips of the xed electrodes thereby forming what may be termed a rotary gap.

In FIGURE 2, there are shown six (6) surface gap igniters 31-36 of the general construction shown in FIG- URE l. When installed in -a six cylinder engine, the outer electrodes of the ign-iters are grounded and there exists a resistance of 30,000 to 500,000 ohms between the inner and outer electrodes of each igniter as represented in the drawing by the resistances SL42. Because of this resistance, an air gap is required between the igniter and the capacitor 20, so that the latter can be instantly and fully charged. Assuming a fully charged capacitor, it Will be apparent that as the distance between the distributor rotatable electrode 30 and, for example, the ixed electrode 24, is reduced to a minimum, pre-set air gap, the Voltage existing across the capacitor will ionize the gap between the aligned distributor electrodes and the capacitor will discharge through a series circuit consisting of such air gap, the igniter electrodes and the ground return to the other side of the capacitor. If the frequency of the rectified voltage applied across the capacitor exceeds the time during which the rotatable distributor electrode 30 moves between adjacent fixed electrodes, the capacitor will become substantially fully charged during the time interval that the rotatable electrode rotates from one to the next xed electrode. By applying approximately 2,000 volts across the capacitor during the charging period, the voltage level to which the capacitor becornes charged, during even minute charging periods, will at least exceed the minimum voltage required to ionize the gap between aligned distributor electrodes and result in a voltage applied across the igniter electrodes to cause positive ring. Consequently, upon continuous rotation of the rotatable electrode 30, current will flow from the rotatable electrode successively to each of the ixed electrodes and through and over the surface of the semi-conductor material between the electrodes of the associated igniter. Those skilled in this art will understand that the individual igniters are connected to the fixed contacts of the distributor so as to obtain the correct tiring order. Also, although I have shown, in FIG- URB 2, an ignition system for a six cylinder engine, it is apparent that the system may be used on an engine having any number of cylinders in which instance the number of xed contacts equally spaced in the distributor will correspond to the number of igniters and the frequency of the voltage applied to the capacitor will be selected to assure full charging of the capacitor at maximum engine speed.

The energy discharged by the capacitor 20 is very high for ignition use, being of the order of 0.2 joule and running as high as 5.0 joules. The current during the discharge period can be as high as a few thousand amperes. This current, at 2,000 volts, produces a very serious switching problem, especially in conned space, as in the cap of a distributor, and has been the main reason Why surface gap igniters heretofore have not been adapted for use in multi-cylinder engines. I have overcome this problem by providing a rotatable gap disposed within a sealed chamber so as to exclude oxygen and other gases which promote and enhance the burning of electrical contacts breaking heavy currents at high voltages.

There is still another reason Why the switching problem is not as serious as in prior art circuits. Conductor and other conductors coupled to the capacitor 20 and ground include some small resistance values and some inductance. When the capacitor first discharges through the gap and ignitor, the current builds up to a maximum value and then is reduced to a negligible amount as the capacitor is fully discharged. Because of the inductance in the Wiring, the current is made slightly oscillatory and the current is reversed by a small amount, charging the capacitor 20 in an opposite direction. The resistance in the conductors, gap, and igniter reduce the oscillatory voltage to a very small amount, the net result being a steep reduction in igniter current to zero before the distributor arm leaves the stator electrode. This action reduces spark deterioration and permits higher engine speeds.

FIGURE 3 illustrates a transistor inverter, or power supply for energizing my ignition system. The two

transistors

44, 45 operate as switches, one being on while the other is o. Assume that the transistor-44 is conducting and the transistor 45 is blocked. This effectively connects the battery 15 across the upper half of the center-tapped primary winding e7 of the transformer 48, thereby inducing a voltage in the secondary winding 49 and in the auxiliary winding 50. At the instant that transistor 44 starts to conduct, the voltages in the transformer windings Will assume a maximum voltage level. This condition will continue to exist until the core of the saturable reactor 51 begins to saturate at which time the rate of change of flux will decrease. During the same time interval, the induced voltages first decrease in value and then become Zero. This decreases and then removes the base drive to transistor 44. The current now begins to decrease and causes the transformer flux to build up in the opposite direction whereby a voltage of opposite polarity is induced in the transformer windings and the transistor 45 begins to conduct. The cycle is then repeated. The voltage output of the inverter will be a square wave whose frequency and amplitude are determined by the number of turns on the primary winding of the transformer, the voltage of the battery, and the saturation flux of the reactor. The

resistors

52 and 53 implement the starting of oscillation of the circuit by biasing the transistors out of the non-linear, low current region, and the R-L network, consisting of the auxiliary winding 50, inductance 51 and the variable resistor 54, determines the oscillation frequency of the inverter circuit. I prefer to design the inverter components so that the voltage appearing across the transformer secondary winding 49 will have a frequency of about 800 cycles per second and a magnitude of 2,000 volts. I have found that a voltage of this level and frequency results in sufficient charging of the capacitor 20, when the rotatable electrode of the distributor 23 rotates at maximum engine speeds normally encountered in eight cylinder engines, to assure proper firing of the igniters. Toward this same purpose, the alternating voltage of the highvoltage transformer may be fully rectified as shown in the fragmentary circuit diagram of FIGURE 4. In such arrangement, the charging voltage pulses applied to the capacitor 20 will be at a rate twice that of the halfwave systems shown in FIGURES l and 2, since both positive and negative waves are rectified by .the rectifier 59.

FIGURE 5 illustrates a modification of the ignition system. In this case, the rotatable contact 57 of the distributor 23 has a tip which actually engages the tips of the fixed electrodes, thereby clsoing the electrical circuit between the secondary winding 49 of the transformer 48 and one of the igniters 31', 32', 33', etc. The igniters are here presented in .terms of electrical equiv- -alents, namely, a gap formed between the inner and outer electrodes with the resistances 37', 38", 39 representing the shunting resistance across the gap arising by reason of the semi-conductor material. Separate capacitors 20a, 20b, 20c, are associated with each igniter as are separate fixed, gaps 58a, 58b, 58C. As shown in the drawing, the rotatable contact 57, of the distributor, is in contact with the fixed Contact 24e, thereby completing the electrical circuit between the transformer winding 49 and the capacitor 20c through the current-limiting resistor 21 and the rectifier 22. This charges the capaci- 4tor 20c. When the rotatable contact 57 moves out of contact with the fixed contact 24C, the capcaitor 20c discharges through the gap 58C and through the igniter. This cycle is repeated as the rotatable distributor contact is brought sequentially into and out of engagement with the fixed contacts, resulting in a corresponding sequential charging of the individual capacitors 20a, 2Gb, 20c and Ithe discharging thereof through the associated igniter and gap. Since the switching is done ahead of the capacitor, the contacts carry only a small current which, together with the sealed casing 29', lresults in a long contact life. Further, by making the rotatable and fixed contacts of a radio active material, the cooperating contacts need not actually come into physical contact, in which case the distributor becomes a rotary gap similar to the one in the FIGURE 2 embodiment.

FIGURE 6 illustrates the construction of the rotary gap distributor used in the ignition systems shown in FIG- URES 2, 3 and 4. Although such distributor may include a housing of any appropriate design, the housing shown in the drawing is that of a conventional distributor consisting of the base 60 and cap 61. This is intended to show that my novel distributor is adapted for quick and easy substitution for the present distributor on an engine to thereby adapt the engine for operation with surface gap igniters. In fact, my distributor cap is readily mounted on the base of a conventional distributor installed on an engine without requiring adjustment of the timing. Toward this end, the contact and breaker points of the conventional distributor merely are removed.

Extending centrally through the distributor base 60 is a conventional distributor shaft 62 provided with a fiat portion 63 which serves for removably coupling my distributor to such shaft while maintaining a proper timing relation. The open end of the distributor cap 61 (which may be molded of a clear plastic, as shown), is closed by means of a metal plate 63 that is secured in position by a plurality of circumferentially-spaced screws 64. It is preferable that the interior of the cap be sealed, the

washers

65, 66 being provided for this purpose. To maintain the sealed character of the distributor, a Vander Graff shaft seal 67 is utilized. Such seal comprises a metal housing 68 (which, in this instance, is welded centrally to the plate 63) and the

washers

69, 70, 71 tightly igniters, associated with a particular engine.

encircling the shaft 72. It will be noted that the shaft 72 is provided with reversely-threaded portions 73, 7 4 so that rotation of the shaft 72 will tend to throw grease (which fills the chamber within the bushing 68) toward the central washer 70 and away from the end-sealing

washers

69, 71, thereby promoting the maintenance of a good seal between the shaft 72 and the interior of the distributor cap 61. The grease may be inserted into the seal 67 through the opening provided upon removal of the screw 75.

In order to reduce radio-frequency interference to a minimum, the plastic distributor cap 61 is disposed within a metal shell 77, which shell has an inwardly-directed flange 78 and ay reduced-diameter, extended portion 79. The latter is provided with an undercut ridge whereby the metal shell 77 may be removably secured to the distributor base 60 by conventional latching clamps 80. The fiange 78 provides a convenient means for securing the cap 61 to the shell 77 as by a plurality of circumferentiallyspaced screws 81. It will be noted that the outer end of the shaft 72 is provided with a diametric hole through which is inserted a drive pin 82. A coupling collar 83 has a diametric slot formed therein for accommodating the pin 82 and the forward end of the collar is provided with a bore such that the coupling collar can be inserted over the end of the distributor shaft 62. It will be apparent that such arrangement affords a means for quick, positive and accurate coupling and uncoupling of the

shafts

62 and 72. Thus, to remove the metal housing 77, which carries the cap 61, from the base 60, it is only necessary to unsnap the latching clamps and draw the housing 77 away from the base, the latter generally being firmly secured to the engine. Conversely, to install the distributor in operative position, it is only necessary properly to align the bore in the coupling collar 83, slide same over the shaft 62 and close the latching clamps 80.

The 'inner end of the shaft 72 has secured thereto an insulator bushing 85, as by the screws 86. The rotatable electrode 87 extends radially from a contact plate 88, being secured thereto by a set screw 89, and the Contact plate is, in turn, firmly secured to the insulator bushing 85 by suitable screws 90. It may here be pointed out that the electrode 87 is preferably made of tungsten and the contact plate 88 is made of brass or copper and has a substantial mass so that it acts as a heat sink to keep the electrode relatively cool.

A conventional distributor cap, such as the cap 61, shown in FIGURE 6, includes integral, upstanding bosses or insulator bushings which serve to position individual terminal rods. These terminal rods, which may be molded directly into the plastic cap or otherwise firmly secured in position, have individual leads soldered thereto, which leads preferably are of the shielded cable type and pass outside of the metal shell 77 through a suitable opening. The center terminal rod 91 has an axial bore formed in the inner end for the accommodation of a helical spring 93 and the inner end of a carbon brush 94. Thus, it is apparent that a good electrical circuit is established between the rotatable electrode 87 and the terminal rod 91 through the medium of the contact plate 88 and the spring-biased brush 94. Circuitwise, the lead 95, secured to the center terminal rod 91, is connected to the positive side of the capacitor, see particularly FIGURE 3. Each of the other leads (connected to the other terminal rods) individually are connected to the center electrode of the associated igniter.

Although only four terminal rods, namely, those identified by the numerals 96-99, are visible in FIGURE 6 in addition to the center rod 91, those skilled in this art will understand that the number of such additional terminal rods corresponds to the number of spark plugs, or The fixed electrodes of the distributor are carried by individual screws 100 which are threaded through aligned, threaded holes formed in the side wall of the cap 61 and the associated terminal rod. Force-fitted into an axial bore formed in each screw is a pointed electrode 101, the tips of such fixed electrodes lying in the plane generated by the rotatable tip 87 upon rotation of the distributor shaft 62. Access to each of the screws 100, as by means of a screwdriver, is obtained upon removal of the threaded plugs 102 whereby the spacing between the tip of the rotatable electrode and the tips of the fixed electrodes may be individually adjusted to a precise distance. It is here pointed out that the

tips

87 and 101 preferably are made of tungsten and are pointed, the former promoting long, operating life and the latter providing very accurate timing inasmuch as the gap distance may be adjusted, with due consideration given to the discharge voltage of the capacitor, so that the capacitor will discharge when the rotatable tip 87 is substantially in precise alignment with a fixed electrode point.

The open end of the metal, outer shell 77 is closed by a metal plate 103 secured by screws 105. Thus, the entire distributor is enclosed within a metal housing which, together with the use of shielded cable leads, practically completely eliminates radio interference. The sealed character of the distributor chamber makes it possible to evacuate such chamber and/ or till same with an inert gas, all directed toward promoting long, trouble-free operation.

A conventional ignition system using convetnional spark plugs generally includes an automatic spark advance arrangement to promote quicker and easier engine starting. Briefly, such an arrangement utlizes a vacuum-operated bellows mechanically coupled to a plate carried in the base of the distributor, which plate is adapted for limited rotary movement and carries the distributor points. In tests which I have conducted with my low voltage ignition system installed on a six (6) cylinder marine engine, I have found no need for a spark-advance function. However, by making a slight modification in the construction of the distributor cap, my distributor is made adaptable for installation on a conventional distributor base provided with the automatic, spark-advance mechanism. FIGURE 8 illustrates the modified form of my'distributor, but reference is first made to FIGURE 7 `FIGURE 7 is an elevational view of a conventional distributor base 6i) with the conventional breaker points removed. A rocker plate 110 is mounted for limited rotary movement as defined by the arcuate slots 111 through which pass the locating and positioning screws 112. A iiat rod 113 is mechanically coupled to the plate 110 by means of a pin 113 that is secured to the plate and passes through a clearance hole provided in the rod. The other end of the rod 113 is attached to the vacuum-operated bellows disposed within the housing 114 that is secured to the base 60. It will be apparent that as the bellows expand and contract the plate 110 will rotate ink a clockwise and counter-clockwise direction, respectively. Secured to the plate 110, and extending upwardly therefrom, is a pin 115. This pin normally serves as one means for rotatably supporting the conventional breaker points. For my purpose, the conventional breaker points are removed and the pin 115 is utilized for coupling the rocker plate 110 to the cap of my distributor as will new be described with speciiic reference to FIG- URE 8.

As shown in FIGURE 8, the rocker plate 110 is supported by a ange 116 extending inwardly from the side Wall of the distributor base 60. The locating screws 112, which pass through the arcuate clearance holes 111 formed in the plate, are threaded into suitable holes provided in the ange 116. The coupling pin 115, which is secured to the plate 110, extends into an axial bore formed in the aligned bushing 117 secured to the plate 63 which closes the end of the distributor cap 61. The sealed character of the cap is maintained by the screws 64 and the

washers

65 and 66. In this modified construction, however, the screws 81, which secure the cap 1 to the outer shell 77, pass through enlarged holes formed in the ange '78, thereby permitting a slight rotation of the entire cap 61 in correspondence with rotation of the plate through the coupling means comprising the pin and the lbushing 117. Inasmuch as the tixed electrodes are carried by the cap 61, rotation of the cap will change the angular position at which the center rotatable electrode cornes into precise alignment with the individual, fixed electrodes, thereby changing the tiring point with respect to the angular disposition of the shaft 62.

From the above description, it is apparent that I have provided a low voltage ignition system making it possible to use surface gap igniters in a multi-cylinder engine. In the preferred form, the system does not require a switching function involving the opening and closing of an electrical circuit by the engagement and disengagement of breaker points (such as is required in conventional high voltage ignition systems) thereby promoting dependable and positive ignition with a minimum of maintenance. By using tungsten electrodes disposed within a sealed chamber the operating life of the electrodes is increased substantially. A further increase in the electrode life may be obtained by filling the sealed distributor chamber with dry air or an inert gas. In order to reduce the voltage necessary to ionize the gap between aligned electrodes, the rotary and xed electrodes may be made of a radio active material. Of equal importance is the fact that my rotary gap distributor can be installed on the base of a conventional distributor having a spark advance mechanism of the vacuum-operated and/or centrifugal type, without requiring alterations, without need of special tools, and without the necessity of retiming.

Having now described my invention in detail, in accordance with the patent statutes of the United States, those skilled in this art will nd no difficulty in making changes and modifications to meet specific operating conditions or requirements. It is intended that such changes and modications shall fall within the scope and spirit of the invention as recited in the appended claims.

I claim:

l. A low Voltage high current ignition system for an engine having a plurality of surface gap igniters comprising a rotatable gap distributor consisting of a sealed chamber, a rotatable electrode disposed within the chamber and iixed electrodes each having an end disposed within the chamber and radially-spaced from an end of the rotatable electrode; leads individually connecting each fixed electrode to the center electrode of an associated igniter; a capacitor having one side connected to the said rotatable electrode and the other side connected to the outer electrode of each igniter; a D.C. voltage source; a transformer having a secondary winding connected to the capacitor through a rectifier, a center-tapped primary winding and an auxiliary winding; and a push-pull oscillator energized by the said voltage source and supplying energy alternately to the two portions of the said center-tapped primary winding, said oscillator including an iron core inductor connected across the said auxiliary winding and having a center tap connected to the center tap of said primary winding.

2. The invention as recited in claim l, wherein the oscillator includes a pair of transistors each having a base, an emitter and a collector with the emitters connected to opposite ends of the said center-tapped primary winding, and the bases connected to opposite ends of the said inductor.

3. A low voltage, high current ignition system for an engine having a plurality of surface gap igniters comprising a rotary gap distributor consisting of a sealed chamber, a rotatable electrode disposed within the chamber and tixed electrodes each having an end disposed within the chamber and radially-spaced from an end of the rotatable electrode; leads connecting each fixed electrode to the center electrode of an associated igniter; a capacitor having one side connected to said rotatable electrode and the other side connected to the outer electrode of each igniter; a D.C. voltage source; a transformer having a secondary Winding, a center-tapped primary Winding and an auxiliary winding; circuit elements applying the voltage developed in the transformer secondary Winding to the capacitor through a rectifier; a pair of transistors each having a base, an emitter and a collector; means connecting the said center-tapped primary Winding between the transistor collectors; an iron core inductor having a centertapped winding; means connecting the ends of the inductor Winding between the transistor bases and across the transformer auxiliary winding; means connecting the transistor emitters to the positive side of the D.C. voltage source; a pair of resistors connected in series across the said voltage source; and a lead connecting the center tap on the inductor winding to the common point of said resistors.

4. The invention as recited in claim 3 including a third resistor connected between ends of the said auxiliary Winding and the inductor Winding.

5. The invention as recited in claim 4, wherein the distributor is enclosed Within a metal housing and the leads extending therefrom are shielded cables.

6. An ignition system for engines having a plurality of surface gap igniters to be red sequentially, said systern comprising a storage capacitor, a source of voltage connected across the capacitor for charging it, a rotary gap distributor including a rotatable electrode and a plurality of spaced, fixed electrodes radially spaced from an end ofthe rotatable electrode, conductors individually connecting each fixed electrode to the center of an associated igniter, and coupling means connecting the positive side of said capacitor to the rotatable electrode and the negative side of the capacitor to the outer electrode of each igniter, said storage capacitor forming a part of a resonant circuit which includes the inductance of the coupling conductors and a rectifier, said resonant circuit adapted to reduce the current through the igniters to a minimum value before the rotatable electrode leaves each of said fixed electrodes.

References Cited in the ile of this patent UNITED STATES PATENTS 2,354,302 Carlson July 25, 1944 2,544,477 West Mar. 6, 1951 2,587,780 Smits Mar. 4, 1952 2,589,164 Tognola Mar. l1, 1952 2,590,168 Felici Mar. 25, 1952 2,837,698 Segall June 3, 1958 2,852,730 Magnuski Sept. 16, 1958 2,883,539 Bruck et al Apr. 2l, 1959 2,916,704 Morey Dec. 8, 1959 FOREIGN PATENTS 724,016 Great Britain Feb. 16, 1955