US1421286A - Magneto ignition system for internal-combustion engines - Google Patents

Description

1. L. MILTON. MAGNETO IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES.

APPLIQATION FILED NOT/.12. 1910. RENEWED NOV. 8, I9I9.

1 42 1 286 Patented June 27, 1922.

3 SHEETSSHEET"I.

J. L. MILTON.

MAGNETO IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILED Nov. I2, I9Io. RENEWED NOV. 8,1919.

1,421,286. Patented June 27, 1922-.

"3 SHEETS-SHEET 2.

With/163,5 e5 .4 fnvenzar- Y J. I MILTON. MAGNETO IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES.

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JOHN LEWIS MILTON, or CLEVELAN OHId; ASSIGNOR T MOTOR IGNITION & DEVICES COMPANY, A CORPORATION or wEs'r VIRGINIA.

MAGNETO IGNITION SYSTEM FOR INTERNAL-COMBUSTION ENGINES.

Specification of Letters Patent. Patented June 2*? 1922,

' Application filed November 12, 1910, Serial No. 591,930. Renewed November 8, 1919. Serial No. 336,735.

To all whom it may concern: v

Be it known that I, JOHN L. MILTON, a citizen of the United States, residingat Cleveland, in the State of Ohio, have nvented a certain new and Improved Magneto Ignition System for Internal-Combustion Engines, of which the following is a full, clear, concise, and exact description,

reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to magneto ignition systems for internal combustion engines and has for its object'the provision of a system and circuit arrangement in which the high tension cabling to the spark plugs is obviated thereby eliminating the cause. of much of the trouble to which magneto lgnition systems are subject, especially 'when used on automobiles. It is the object of my invention also to provide a simple yet efiicient ignition system of comparatively low cost.

" In accordance with my invention,I mount in association with each of the spark plugs of a multiple cylinder engine a separate induction coil or transformer. These are composed of a primary coil of coarse wire wound over a secondary coil of fine wire, both coils being impregnated with vulcanized rubber.

These coils have no iron core whereby their coeflicient of self induction is low. The generator used in conjunction with these individual coils delivers a low tension alternating current preferably of a voltage rather higher than is ordinarily used in the low tension circuitof. a high tension magneto ignition system. The alternating current from the generator is normally delivered through the contacts of an interrupter, one wave being delivered'through the primary winding of one coil connected with the spark plug of one cylinder and the nextwave being-delivered through the primary winding of the next coil associated with the spark plug of the next'cylinder, and so on. The contacts through which these alternating current waves are delivered are slowly opened by a suitable cam mechanism at the time when the spark is to pass between the contacts of the plug. The opening of the .Thissurge of current having charged the condenser, it immediately tends-to discharge itself through any available path. Since the contacts of the interrupter are made to open slowly, at least as compared with the speed of condenser charges and discharges, the are which will persist between the contacts of the interrupter provides.a path suiiicient to carry the discharge from the condenser, the condenser discharge being reinforced current wave which is still being delivered from the generator winding. The impulse thus delivered upon the break ofthe circuit at the interrupter contacts passes through the primary winding of the connected coil thereby inducing a, high tension impulse in the secondary winding and it is this secondary impulse of high tension which finds its path across the gap between the contacts of the plug to produce the spark necessary for ignition purposes.

Since the coils may be mounted directly upon the spark plugs, and since it is only a low tension current which is delivered from the generator and interrupter and distributer mechanism to the coils, the cabling isvery much simplified, it being necessary to run but a single conductor from each spark-plug to the distributer mechanism. Furthermore since these conductors carry only low tension 1 currents, their insulation becomes a matter of great simplicity and consequently reduced expense. It is the high by the tems and this large cause of trouble is wholly eliminated in the system of my invention.

The details of the best means for carrying out my invention so far as I am aware are shown in the accompanying drawings in which v Figure 1 is a diagrammatic circuit drawing,

Figure 2 is avi'ew largely in cross section and partially in diagrammatic form showing the construction of a generator, interrupter and distributer which are adapted for'usein the circuit of Figure 1,

Figure 3 is a cross sectional view of the generator taken on line 3--3 of Figure 2.

Figure 4 is a view of the interrupter taken on line of Figure 2.

Figure 5 is a front elevation of one of the transformer coils.

Figure 6 is a side elevation of the same.

Figure 7 is a cross-sectional view of such a coil.

Figure 8 is a plan view of one of the connecting clips.

Figures 9 and 10 show the means for fastening the connecting clip to the coil proper.

Figure 11 is a view of a piece of the duplex rubber tape used, in making the transformer coils.

Figure 12 is a cross sectional view of a mold containing the coil to be vulcanized.

Figure 13 is a cross sectional view of themold and coil taken on line 13-13 of Figure 12.

Figure 14 is a plan of the distributer contact plate.

Before attempting to explain the system and its operation as a whole, I shall describe briefly one of the features which contributes largely to the successful operation of the whole, namely the special transformer coil which is directly associated with each of the spark plugs.

Ordinarily transformer or induction coils used in high tension ignition systems are insulated by wax which permeates the inter stices between the several turns of the coil. It is necessary that the turns should be perfectly insulated and that the spaces between the conductors be so filled as to exclude moisture. While a wax impregnated coil serves very well under ordinary conditions, it cannot be associated immediately with the spark plu of an internal combustion engine because of the high temperature and generally the severe conditions to be met in such a location. The heat would melt the wax which would run out of the coil and leave the conductors without proper insulation and without proof against moisture. In accordance with my invention I provide a coil in which the interstices between the several turns are filled with vulcanized rubher which is a better dielectric than wax and which furthermore is not subject to deterioration by the heat in the vicinity of the spark P e- In making the coil I provide vulcanized fiber hub 20, as shown in Figure 7. Then with a suitable arbor I hold the spool heads or flanges 21 in engagement with the ends of the hub while I wind successive layers of wire and rubber.

Rubber is laid in the form of a tape cut from a sheet of material comprising a fabric backing 22 coated with compounded rubber very thin layer of Para gum 24 upon the compounded rubber 23. The compounded rubber is very sticky or tacky and the layer of Para rubber therefore adheres firmly to it. The sheet of duplex rubber thus prepared is cut into strips or tapes a trifle wider than the distance betweenthe spool heads 21, 21 and the layer of duplex rubber is wound about the hub 20, the fabric 22 being removed from the rubber in this process. The compounded rubber is made to face the center of the coil with the Para rubber outside.

When this layer of rubber has thus been laid, a layer of fine secondary wire is wound over the rubber, the tension being adjusted so that the wire will press down into the rubber. The inner end of the secondary wire is attached to a U-shaped connector 25 which is fitted into the hub before the winding. is commenced.

'When the first layer of wire has been wound a circlet of the duplex rubber is laid over the wire, whereupon a second layer of wire is wound. In this manner the successive layers of fine wire forming the secondary winding are laid up. When a layer of wlre is laid, it presses the rubber between it and the next lower layer not only into the grooves between the conductors which is being laid, but also into the grooves between the conductors of the layer which has been laid. The rubber is thus forced to occupy in large measure the interstices between all of the conductors of the secondary winding.

Since the copper of the conducting wire is subject to attack by the sulphur contained in the compounded rubber when the wound coil is vulcanized, I have found it desirable to tin the copper wire very carefully. The tinned wire is, to a large extent. proof against the attack of the sulphur. I have found, furthermore, that silk covering of the fine secondary wire will not withstand thehigh temperature necessary to' vulcanize the coil. I therefore employ a tinned wire covered with a single layer of cotton. The cotton seems to withstand the process of vulcanization very much betterthan will the sillt finer wire constituting the secondary turns 27. I have found that one layer of primary wire suffices in these coils and either end of the single primary layer is therefore connected with one of the terminal clips 28 or 29, each clip being provided with an eyelet 30 into which one end of the primary winding may be inserted and soldered. 'The small holes 31 punched in the base of the clip permit the rubber, due to its expansion when vulcanized, to press into these holes to form studs which aid in holding the clip in place. The clip also is bound down by the linen thread 32 which passes about the coil) Over the base of the clip and this linen thread I wind one or more layers of the-duplex rubber tape, when the coil is ready toreceive the rubber heads 33 and 34, these taking the place of the tinned metal spool heads 21, 21. The heads when applied to the coil are of unvulcanized rubber which sticks quite firmly to the concentric layers of rubber which intervene, between the layers of wire. It will be remembered that the tape forming these intervening layers was cut a little wider than the space between the spool heads thus insuring a sufliciency of rubber at the exposed end of each layer. The coil thus formed of wire and uncured rubber, with the connecting clips in place is clamped within the.

vulcanizing mold shown in Figures 12 and 13. The two halves 35 and 36 of the mold are clamped together by the screws 37,

. whereupon the plunger 38 is brought to bear smartly upon the coil by means of the pressure screws 39,39. The capillary vents 40,

4O permit the expulsion of air from the mold. I

The mold containing the coil is now heated to a temperature of about 340, this temperature being maintained for a period of about six hours, when the coil will have been vulcanized. This process of vulcanization completely cements or joins the rubber heads to the layers of rubber which intervene between the layers of wire. F urther'mo're the process of vulcanization tends to expand the rubber to some extent with the result that wires forming the several turns of the coil become wholly embedded in a practically homo-.

geneous mass of rubber in which there are no air bubbles or pockets. The 'coil has, therefore, a very high degree of-insulation. The

- vulcanized rubber forms an excellent dielectric and since it may be laid in very thin layers, the resulting coil has an extremely highefliciency in the necessary transformation of curren a As previously explained the two ends of the primary winding are connected respectively to theclips 28 and 29 and the outer terminal of the secondary winding is connected also to one of these clips,' as for example, 29. When the vulcanized coil is remove from its vulcanizing mold, a machine screw-41 'is inserted through the hole in the center of the hub where it is held in place by a nut 42., Under the head of the screw-is clamped the L-shaped connector clip 43. The

connection between the inner end of the secondary winding and this clip 43 is completed by the U-shaped connector 25, it being ordinarily unnecessary to solder the connector to the screw 41 onaccount of the high tension of the current which is carried from one part to the other.

In Figures 2, 3 and 4 I have illustrated the generator and interrupter and distributer mechanism. A pair of U-sha d permanent magnets 50, 50 embrace the po e pieces 51, 51, the pole pieces being attached to the mag nets by the screws shown in dotted lines at 52, 52. The pole pieces in turn are attached by means of the screws 53, 53 to the rocker yoke 54, this yoke having a cylindrical lug or bushing 55 which is journalled in the engine frame indicated at 56. The timing lever mechanism'is attached to the arm 57 of the yoke whereby the field magnet may be turned forward or back to advance or retard the time of the spark. production.

The iron armature 58 is mounted upon the flange 59 of the driving spindle 60, the latter being mounted in ball bearings 61 and 62 carried inside the boss 55. Upon the armature is wound the generating coil 63, the inner terminal being led out through. the hard rubber bushed opening 64.-

Upon the. farther end of the armature is' mounted the-interrupter supporting disc 65. This disc is provided at the center with a standard 66 upon which is mounted with suitable insulating bushings the distributer brush 67. The inner terminal of the armature winding is connected with this distributer brush by the wire 68. The other terminal of the armature winding is connected by means of the conductor 69 with the adjustable contact point 70. Upon-the supporting disk 65 is pivotally mounted also at 71 the interrupter blade 72. At one end the interrupter blade is adapted normally to make connection with the contact 70. At the other end the interrupter'blade is provided with a fiber stud 73. It will be apparent that the rotation of the interrupter supporting disc and the interru ter mechanism corresponds with that o the arma- 115 is mounted u on the rim turned in the pole pieces 51-i 'ovided with cam surfaces-.75 and 76 where y the rotation of the interrupter disc as indicated by the arrow 77, 12c brings the stud 73 into engagement with the cam surfaces totrip the interrupter blade 72, thus causing the electrical connection with the contact 70 to be interrupted.

Within the space enclosed by the interrupter supportlng disk 65 is mounted a condenser 78, this being electrically connected across the terminals of the armature windin as diagrammatically shown.

The gistributer brush 67 engages one after be had to Figure 1 of the drawings, where.

the reference letters corresponding with those shown in the other figures are applied so far as possible. It will be noted that Figure 1 shows the spark plugs 82, 83, 84 and 85 of a four-cylinder engine and corresponding with this a distributer brush 6'? which is adapted to make connection successively with the four distributer contacts, each of which leads to one terminal of the primary winding of a transformer coil. The arrangement shown in this Figure 1 is different in this respect from that shown in Figures 2, 3 and 4 where provision is made for but two spark plugs as in a two-cylinder engine.

Where a four-cylinder engine is involved.thc

distributor brush 67 must be geared to the. armature of the generater in a two to one ratio so that the armature may make two complete revolutions during a single revolution of the distributer blade. In the construction shown in Figures 2, 3 and 4 it is ptroper that the distributor blade should ina e but a single revolution for each revolution of the armature. In Figure 1, therefore, I have designated two diametrically opposite distributer contacts with the reference letters 79 and 80, the other two being designated respectively 79' and 80.

The circuit connections will for the most part be apparent from the description al 40 ready given with respect to Figure 2. It

may be pointed out, however, that the interrupter blade 72 is mounted without insulation directlyupon the metal parts of the generator. The generator is in turn bolted 5 to the engine frame and the spark plugs are screwed into the metal cylinders of the engine. One contact of each of the spark plugs is grounded therefore as indicated at '86 and the interrupter blade is grounded at 5 87. The grounding contact 81 is connect ed through a manually operable switch 88 with ground indicated at 89. It will be seen that the connector clips 43 of the transformer coils are connected with the insulated and ungrounded contacts 90 of the spark plugs. the clips 29 which serve as terminals both for the primary and secondary windings of their respective coils being connected by the connectors 91, 91

with the grounded portions of the spark p H a The operation may now he explained. The interrupter contacts are normally closed wherefore the current wave generated upon the rotation of the armature may be traced the primary of the transformer coil.

in Figure 1 from the armature lead 68 to the rotating distributer brush 67, thence through the dist-ribut-er Contact 80 to the primaryterminal clip 28 of the transformer coil connected with the spark plug 84, thence through the primary winding of that coil to the terminal 29, thence through the asso ciated connector 91 to ground at 86, thence through ground tothe interrupter blade 72 to the closed contact and thence by way of the wire 69 to the other terminal of the armature wlnding. The cam mechanism which is but diagrammatically shown in ,Figure 1, is timed to open the interrupter contacts slowly when the spark is to be produced in the engine cylinder. \Vhen the interrupter contacts open the path through which current has been flowing through the primary winding of the transformer coil. there is a sudden rush or surge of current into the condenser 78. This flow of current into the condenser takes place simultaneously with a sharp reduction in the amount of current flowing through the primary winding of the transformer coil. This means that the magnetism threading the secondary winding of the coil will be reduced. Almost instantaneously after the surge 'of current into the condenser there is a recoil or rebound of current which, reinforced by the continuing electromotive force of the generator winding, causes a current to jump the gap between the contacts of the interrupter and to flow through the primary winding of the transformer coil. A small arc will be produced when the interrupter contacts are opened and if they be opened comparatively slowly, the arc will persist long enough to .be available to convey the surge or recoil of current delivered by the condenser as just explained. This sharp surge of current which passes through the primary winding of the transformer coil in preference to the coil of the generator causes a rapid increase in the number of lines of force threading the 0 secondary winding of the coil wit-h the result that a-high tension current is generated in the secondary winding of the coil and this secondary current finds its path from the clip 29 through the connector 91 to the grounded contact of the plug. The current easily jumps the gap to the insulated contact 90 of the plug and flows through the connector clip 43, to the inner terminal of the secondary winding. I prefer to make the coils without iron cores in order that the reactance to the flow of the condenser discharge may be a minimum. Since the inductive opposition of the generator winding is much greater than that of the primary winding of the transformer coil and since also the continuingelectromotive force of the generator opposes the condenser discharge, the impulse of current will flow almost wholly through The gearing 99 by means of which the generator is connected to be driven by the engine is so arranged that an alternating current wave will be generated to fire the several cylinders of the engine in succession. The distributer mechanism connects the coils of the several spark plugs successively in circuit and the current wave is generated 1. An ignition system for internal 00m bustion engines comprising an alternating current generator, a condenser permanently bridged across the terminals of said generator, a transformer coil comprlsing a primarywinding, a secondary winding in inductive relation to said primary winding, a jump spark circuit including said secondary winding, electrical connections between the terminals of the primary winding of the transformer coil and the terminals of the generator, normally-closed contacts in series with the primary winding, and engine-driven devices for opening said contacts when a spark is to be created within the engine cylinder with which-the jump spark circuit 1s associated.

2. An ignition system for internal combustion engines comprisinga inagneto generator, a condenser permanently bridged across the generator terminals, a transformer co l comprising a primary winding, a secondary wlnding 1n inductive relation to said primary Winding, a jump spark circuit including said secondarywinding, electrical connections between the terminals of the primary winding and the terminals of the generator, normally-closed contacts in series with the primary winding of the transformer coil, and engine:dr1ven devices for opening said contacts slowly as compared with the speed of the condenser charges and discharges.

-3. Anignition system for internal com-v bustion engines comprising an alternating current generator, a condenser permanently bridged across the generator terminals, a plurality of transformer coils each comprising a primary winding normally connected with one termlnal of the generator, an engine-driven distributor arranged to connect the other terminals of the primary windings one after another with the second terminal of the generator, a pair of normally-closed interrupter contacts in series with the primary winding of the transformer coils,

engine-driven means for opening said contacts when a sparkis to be created in an engine cylinder, a secondary winding in inductive relation to each of said primary windings, and a jump spark circuit including each of said secondary windings.

4. An ignition system for internal combustion engines comprising a magneto generator, a condenser permanently bridged across the generator terminals, a transform-' er coil comprising a primary winding, a secondary. winding in inductive relation to the primary Winding, ajump spark circuit includin said secondary winding, means for electrical y connecting the termlnals of the primary winding with the terminals of the generator, normally-closed contacts in series with the "primary winding, and enginedriven means for opening said contacts when a spark is to be created in the jump spark circuit.

5. An ignition system for internal combustion engines comprising an alternating current generator, a condenser permanently bridged across the generator terminals, a plurality of transformer coils, each comprising a primary winding, a secondary winding in inductive relation to each of said primary windings, a jumprspark circuit includng each of said secondary windings,

means for electricallv connecting a first ter minal of eachof the primary windings with a generator terminal, a distributor arranged to connect the other generator terminal with a second terminal of each of the primary windings one after another, normally-closed contacts in series'with the primary wind-- ings, and engine-driven means arranged when a spark is to be created in one'of the jump spark circuits to open said contacts slowly as compared with the speed of the condenser charges and discharges.

6. An ignition system for internal combustion engines comprising a magneto generator, a. condenser permanently bridged across the generator terminals, a transformer coil comprising a primary Winding,

'a secondary winding in inductive'relation .to said primary winding, a jump spark circuit including said secondary winding, electrical connections between the terminals of the primary winding and the termnals of the generator, and contact mechanism in series with the primary winding arranged to close the primary circuit when no spark is required and to open said circuit when a spark is required to permit charging of the condenser and then discharge thereof across the air'gap of the contacts, substantially as described. j

7. In a structure of the class described the combination with an air core transformer of a magneto connected in series with the primary circuit of said transformer, a condenser shunted across said magneto, and said-source of current, and means for slowly 10 means for slowly opening said primary cirf opening said primary circuit and for closcuit and for closing it. ing it.

8. In a structure of the class described the In Witness whereof, I hereunto subscribe combination with a source of current of a my name this 22 day of August A. DJ 1910.

transformer having less inductance than JOHN LEWIS MILTON. said source of'current and having its pri- Witnesses: mary circuit connected in series with said ALBERT C. BELL,

source of current, a condenser shunted across LEONARD E. Boson.

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