US1736441A - Magneto - Google Patents

Description

Nv. 19, 1929. l. E. HENDRICKSON 1,736,441

MAGNET() Filed Aug. 31,v 1928 5 Sheets-Sheet 1 IN VEN TOR.

, ./,f/ BY :P7/M

ATTORNEYS.

l. E. HENDRICKSON MAGNETO Nov. 19, 1929.

Filed Aug. 31. 1928 3 Sheets-Sheet ATTORNEYS.

Nov. 19, 1929. 1. E. HENDRICKSON 1,736,441

MAGNETO Filed Aug. 51, 1928 5 Sheets-Sheet 3 INVENToR.

BY @hv L//M A TTORNEYS.

Patented Nov. 1.9, 1929 UNITED STATES PATENT OFFICE IRA E. HENDRICKSON, OF WEST SPRINGFIELD, MASSACHUSETTS, ASSIGNOR T WICO ELECTRIC COMPANY, 0F WEST SPRINGFIELD, MASSACHUSETTS, A CORPORATION 0F MASSACHUSETTS MAGNET@ Application filed August 31, 1928. Serial No. 303,308.'

'rms invention relates to an improved magneto of the type having an unwound,

rotary inductor or armature,-sometirnes known as nthe flywheel type" when the Hywheel is utilized as the inductor.

The prior art discloses a large number of magnetos of this type, which may for convenience be subdivided into two general classes. ln oneA` of these classes, the magnetic field elements,-except for the inductor,-and the generating coils are maintained stationary,-leaving the inductor as the only rotary element. In the other class, the magnets rotate. rlhe only magnetos of the stated type which have had any substantial commercial success, so far as -l am aware and have been able to determine, are of the second-named class and these have many disadvantages.`

Contrasted with magnetos of the rst class,

i magnetos of the second class are more expensive to manufacture. Also, their use leads to many complications. Usually they must be specially designed for each engine installation and thus built into the engine'as distinguished from a unitary structure which can be added onto any engine without necessitating special design of engine parts. Long magnetsfbent up into substantially circular form, are often used and these are expensive due to the special work in shaping them, as well as to the large amount of material involved. Such magnets have to be surrounded by non-magnetic material, which is more eX- pensive than cast iron. For example, it is common to make the flywheel of aluminum. lt is also common to house the magnets, as well as all other parts of the magneto in the vwheel. This practice makes the magneto relatively inaccessiblefedicult to in.- stall and difficult to remove when servicing is required. Also, it is not feasible in magnetos of the second class to reduce the clearance between the pole pieces and the inductor to such Ylow limits as is practical in magnetos of the first class and, therefore, the former are less efficient than the latter, other factors being equal.

That there are so many disadvantages to magnetos of the second class has led me to direct my invention entirely to magnetos of the first class, and l seek by the utilization of a less amount of material in a less expensive way to produce better results. ln this field, however, there are many troubles to be overcome., The prior art abounds in examples of magne'tos of this class, but it is, l believe, a fact that no one of such magnetos has ever niet with any substantial degree of commercial success. Something has been lacking fin each instance which prevented a commercially successful solutionfof the problem. At intervals over a long period of years atl tempts have been made to solve this problem,

in the prior art have been retained and otherl bad features eliminated, and the result is a novel arrangement of elements cooperating in an improved way to produce successful results.

More particularly, l set forth the objects of my invention by stating conditions which l deem necessary to assure successful results in a magneto of the stated type and class. 'llhe magnets, cores, and coils should be stationary and assembled as one compact, unitary structure, which can be applied to any engine in a conveniently accessible location and without substantial alterations in the latter. This unit, which should include two magnetic pole pieces, should preferably be mounted for convenient adjustment toward or away from the rotary inductor in or ler to adjust the clearance between the rotor and pole pieces and, for efficient utilization of the magnetic flux, such clearance should be exceedingly small and as near physical contact as possible. For proper adjustment and maintenance of such clearance, it is essenn tial that both pole pieces should lie on the .same side of the engine crankshaft. Due to The ture and lpole pieces, it is essential that the magneto ave both-primary and secondary coils,-otherwise, the spark produced will be too feeble to satisfy the requirements. The

inductor, for maximum ei iency, must pro-v vide foi` a sharp and double break in the magnetic circuit and, sofar as is practical, must tat other times hold the magnetic circuit closed, A simple form of breaker point mechanism should referably be used to control the primary clrcuit, which requires one opening and closing for each cycle of o ration of the magneto. These breaker points should ^normally hold the rimary circuit closed and should preferab y'open at substantially the time when the double break in the ma etic circuit occurs to allow the s ark to produced on breaking, rather than on maklng, of the magnetic circuit.

.breaker points should close shortly thereafter. Preferably, the inductor should be so arranged'as to move into position to at .least partially complete the magnetic circuitbefore the breaker points close so that a substantial building up of flux occurs under the favorable condition of an open circuited primary winding. The inductor should hold the magnetic circuit closed as long as possible to hold such iux as has been built up, during the instant that the breaker 'points are open, and afl/so to allow time for 'additional nbuilding up of the flux, if and when necessary,under the sloweif and less favorable condition of a closed circuited primary windo far as I am aware there has been no magneto heretofore which will satisfy all these conditions and therein-I believe is vthe lreason for the failure of magnetos of this Aclass to attain commercial success.

Perhaps the closest approach to a satisfactory solution of the pro lemis disclosed in the Clark Patent No. 1,486,229, dated March 11, 1924, which states many" ofthe diiculties encountered in magnetoes of this type and offers as a solution a special quick-open-v ing and quick-closing breaker-point mecha# nism. Such' mechanism leads to complications which I Ldesire to avoid. As dis- \tinguished from the Clark patent, I have provided a different type of inductor, which enables me to dispense with the necessity of usingI his special breaker point mechaiiism and enables me to utilize one of ordinary construction. At the same time, by so doing,

sli t change in the shape of the polar faces ana change in the breaker pomt mechanism, this magneto is suitable for use with a rotary inductor. I need, then, to' provide merely a simple mounting to support the magneto unit from the engine and to place a rotaryinductor on the crank shaft or other suitable rotary part of the engine, in order to equip any engine with`a satisfactory rotary inductor type magneto and this can be done lat a cost far lower than that of magnetoes of the second-named class, as above defined.

Other objects and advantages will appear from the following description and will be pointed out in the appended claims.

The invention will be disclosed with reference to the accompanying drawings, in which- Fig. 1 is a plan view, with parts broken away, showing a magneto, embodying my invention, applied to an internal combustion engine ;-1 y

Fig. 2 is a side elevation view thereof,--a part of the flywheel being broken away to reveal the magneto;

yFigs. 3 and 4 are fragmentary sectional views taken on the lines 3-3 and 4-4, respectively, of Fig. 1;

Fig. 5 is a diagrammatical view taken similarly to Fig. 3 but showing a different relative positioning of parts;

Fig. 6 is a diagrammaticalview illustrative of the magnetic and electrical circuits of the magneto; and f "5 Fig. 7 is a fragmentary longitudinal sectional view illustrative of a modification.

Referrin to Fi s. 1 and 2, the invention has been il ustrate as applied to a standard type of small internal combustion engine.

Such engine, in so far as a description of it is necessary to an understanding of this invention, includes a single cylinder a, bolted to a ycrank case b, mounted on a suitable bed plate c. The crankshaft is indicated at d and carries a. flywheel e of usual form andgna- -terial. A s ark plug' f is connected by a high tension cab e gto the magneto unit M. The pedal his part of the usual mechanisml for cranking the engine. To stop the engine, a

flexible, metallic arm z', secured to cylinder a' and thereby grounded, is arranged to be flexed and drawn into contact Lwith the terminal of the spark plug f by pulling on the wire j. The particular engine shown is of the two cycle type. Accordinglyfor -this particular engine, the magneto is required to produce one spark per revolution. This engine, of

course, is merely illustrative of one of many suitable types with which my magneto may be used and other installations may require a different number of sparks per revolution. I The magneto unit M may be of any suitable type embodying a magnetic source and a pair of cores with primary and secondary coils thereon. Such parts are shown conventionally in Fig. 6,`wherein two cores 10,\connected one to each polar extremity of a bank of permanent magnets 11, carry primary and secondary coils 12 and 13, respectively, and

plied to any engine. The standard type of4 magneto shownin such patent may be used by removing the breaker point mechanism angel substituting another later to be desc ibed, and by milling or otherwise shaping ,the lower ends of cores 10, and any intervening part,- to conform to the curvature of the inductor.' In Figs. 2 and 3 the cores 10 are indicated in part only but sufliciently to show the polar faces 14 and the recess 16 which permits the inductor to rotate in close proximity to such faces. 7

The inductor 15 is simpl a cylindrical body of magnetic material w ich is built up of circular laminations suitably held together, as by rivets 17, and which is substantially equal in length to the thickness of cores 10.A This bodyr is suitably fixed to turn with crank- 'shaftah as by being driven on to the hub k of flywheel e. The inductor, for the particular engine shown, is provided with two nonmagnetic portions 18 which are so spaced as to simultaneously register with the two polar faces of cores'lO, as shown in Fig. 3. These portions 18, as shown, are formed by notching the periphery of thelinductor, but the prior art shows that notches filled with some meallic and nonmagnetic material are equivalents -for the purpose. The notches, or nonmagnetic portions 18, are preferably a little wider than the polar faces 14 with which they cooperate. Otherwise, the optimum break in the magnetic circuit would not beobtained. The preferred length of each notch 18, relative to that of its polar face, has been shown in Fig. 3, and this has been found toyield the a best magnetic-break. Notches of anyl greater length add nothing to the effectiveness of the magnetic break and are bad because they interfere with the building up` of flux and lessen the dwell 'period during which the magnetic circuit is closed, as will appear in greater. detail hereinafter.

I The effort in the present case has been to cut away as little of the periphery of the inductor as is'p'ractical and restrict the ,length of the non-magnetic portions 18 to the minimum necessary for the proper and most efficient performance of their' function. -The intervening part 19 is most important and without it successful results could not beobtained because this part, not only adds to the dwell period inwhich the magnetic circuit is closed, but also enables asubstantial part, and it is believed, the larger part of the flux to be built up under the tion; i. e., before the breaker points close, as will appear in more detail hereinafter. Another important feature'is that the notches-'18 are spaced apart by an angle less than 180 degrees and therefore both notches lie on one side of the shaft as distinguished from a diametrically opposed relationship ofsuch notches, whichv would render most diicult the adjustment and maintenance of the clearance between the inductor and polar faces within the small limits sought for in this case.

For the maximum efficiency the polar faces 14 should contact with the inductor and, while it is not feasible to obtain the intimate and actual contact of the inductor with these polar faces,which can be obtained in a magneto of the reciprocating armature type, the object here is to approach that condition as closely as is feasible. To this end, both olar faces 14 are located on the same side o the shaft and provisions are made whereby 'the unit M may be thrust bodily and in a radial Vdirecmost favorable condition to simultaneously carry both polar faces into exceedingly close proximity to the inductor with only what may be termed rubhing clearance. Any suitable means may be provided for this purpose.

As shown in Figs. 1 and 2, a plate 20 is suitably secured as by bolts 2 1 toone side of the crankcase b of the engine to serve as a support for the magneto unit M. In plate 20, there is a slot 22 (Figs. 1 and 4) which is disposed horizontally and substantially radially with respect to crankshaft d'. A stud 23, ixed and closely fits the same. This arrangement allows the magneto unit M to be moved radially in or out with respect to inductor 15 and also to be tilted up or down as` may be necessary tof-bring the polar faces 14 into proper relation with the inductor and with equal'clearance. A cam 24 (Fig. 4), folcrumed at 24 on the`unit M, bears on bed plate c, and provides a means for tilting the unit Mi The plate 20 also has a vsecond slot, marked 25 through which a cap screw 26 passes.` Slot 25 is wide enough to allowenough up or down play of stud 26 therein to enable the vertical adjustment of the unit M by cam 24 to be effected, and is long enough to permit the radial movement described. The outer end of plate 2O has an outwardly turned lug 27 in which the shank of an eyebolt 28 is slidable. c The stud 26 passes through the eye of eyebolt 28 as well as through slot 25 and threads into the frame of the magneto unit M. Stud 26 serves to clamp such unit to the magneto unit M, projects into this slot in adjusted position.n A nut 29 threaded on the outer end of the shank of eyebolt 28, serves as a means for drawing the magneto unit M away fromthe inductor's, when stud 26 is 5 loosened. With stud 26 loosened, the unit M is thrust inwardly until magnetic attraction draws the polar faces into contact with the inductor and cam 24 is adjusted to hold the magneto at the proper elevation. The nut 29 is then turned to pull the unit M outwardly just enough to 'create the very small clearance above described. The means described for effecting the radial and vertical adjustments of unit M are merely illustrative of one of various suitable means which may be usedfor the stated purposes.

For convenience, I have mounted the breaker point mechanism on the outside of the magneto but in such a manner that -it is sheltered by the iywheel, as will be clear from Fig. 1. This location of such mechanism simplifies the character of the means used for controlling its operation, such means being carried by the flywheel e, or any other suitable rotary part, andy herein taking the vform of a roll 30. The breaker point mechanism ismounted on a plate 31, held to unit M by screws 32, which pass through slots 33 in the plate, whereby the mechanism may be 3'0 bodily shifted to-eifect changes in the timing' of the opening of the breaker points, by causing roll 30 t o open them earlier or later in the revolution of crankshaft d, accordingly as plate 31 is -moved down or up from the position shown in Fig. 3. Pate 31 hasan voutwardly turned part 34 to which a conducting arm 35 is secured by bolts 36. Arm 35 is suitably insulated from part 34, as indicated at 37, and carries the fixed, but adjustable, breaker point 38. The cooperating breaker point 39 is carried by one end of a lever 40, which is pivotally supported at a point intermediate its ends by a stud 41 secured to plate 31. A "spring 42 tends to normally hold oints 38 and 39 in contact. The other end o lever 40 is suitably sha ed for engagement by roll '30 and prefera ly, as shown, has a-tail 40', whereby roll 30 will hold the points 38 and 39 open for ashort interval. In some cases this tail maybe dispensed with, especially'where the installation permits time-enough for the flux'to build up against a closed circuited primary winding.

In this particular case, it is desired to control the speed of the engine by cutting out the ignition after the engine reaches a certain speed. For this purpose roll 30 is carried by one end of a'lever 43, fulcrumed at apoint intermediate its ends on a stud 44, secured to iiywheel e. The other end of the lever is relatively heavy and. is adapted to be thrown outwardly by centrifugal force but is normally restrained by a spring 45. The latter is interposed between the outer end of the lever and an'adjustable abutment 46 carried found to yield the best results.

by spring 45 and roll 30 jwill be moved in- Wardly so as not to engagethe breaker-point lever 40. A screw 49, threaded into lever 43, engages the hub lc and v limits the outward movement of roll 30.

The electrical connections are shown\`dia grammatically in Fig. 6 and are essentially as disclosed in the Brown & Louis patent, above identified. For example, the primary coils 412 are or may be connected in series by a wire 54 and one terminal of theprimary-Winding is grounded as at 51. The other terminal of such winding is connected by a wire 52 to arm 35 and thus to the fixed breaker point 38. Breaker point 39 is grounded. A condenser 53 is bridged across the breaker points in the usual manner. The secondary coils are, or may be, connected in series by a wire 50 and one terminal of the secondary winding is grounded, as at 55. The other terminal of the seconda-ry winding is connected by wire g to spark lug f.

The pre erred operation of the magneto 'willnext be described with particular reference to Figs. 2, 3, and 5. Assuming that the fiux has been built up in the magnetic circuit to the desired intensity, the rotor 15, revolving in the direction of the arrow, will eventually come into the position shown in Fig. 3 and cause an effective andf double break in the magnetic circuit. Beth notches 18 then register with their respective polar faces 14 and there is afsubstantial air gap between the upper edge of each radial/wall of each notch and the adjacent end edges of the polar faces 14. As set forth above, the notches `are made just enough longer than the polar faces to afford gaps, such as have' just been alluded to, and secure maximum effectiveness of the magnetic break. The proportions shown in Fig. 3 are those which have been At substantially the same time that this double break occurs,-roll 30 engages lever 40 and causes a quick separation of the breaker 38 and 39 and an openlng of the primary circuit, which has theretofore been maintained closed for the purpose of holding the iux in the magnetic circuit. On the substantially simultaneous opening of both the magnetic and the primary circuits, a very rapid decrease of flux occurs and an E. M. F. is generated in `the secondary, resulting in a spark at plug The flux change, utilized for the production of the spark, is that which occurs on the breaking rather than the making of the magnetic circuit and this is important because a more rapid and more effective change of flux Jccurs under thev former condition than under the latter.

Having described the production of the spark, the next and a most important consideration is the building up ofthe liux in the magnetic circuit in tion of another spark. The lever 40 prefer ably has its tail piece 40 so constructed that the breaker points 38 and 39 are held separated for a short interval. This interval is preferably such as to allow the rotor 15 to move from the position shown in Fig. 3 to that shown in Fig. 5. In Fi 5, the breaker points have just closedand in ig. 3 they have just.A opened. As will be evident from Fig. 5, this interval is long enough ing of the magnetic circuit by the rotor and, in consequence, a building up of a substantial amount of flux occurs under the-most favorable condition of an open circuited r`1- mary winding. Suchtwindin does not t en oppose and restrain the buil 'ng up of ilux and I believe that the greater part of the flux is built up during the time while the breaker points are open. While full coverage of the polar facesll by the inductor is notobtained, there is enough to permit the action described and my experiments indicate that re ing under both cores 10 sults` are not'materially improved by delaying 'the closing of the breaker y the time indicated. This is probabl the fact that the completion of the due to -when the leading notch 18 comes into regis?- tration with the lower polarface 14 and the other when the trailing IiotchlSis similarly positioned with respect t'o the upper polar face. There will undoubtedly be a loss in iux at each` of thesawo'positions but such losses are kept at a minimum because the primary circuit is'. then closed and tends to oppose change. in flux. However, the much greater intervals, when the magnete circuit is closed, permit rebuilding up of flux to an extent to adequately compensate for suchvlosses. lt is possible to arrange the magneto, as shown at M in Fig. 7, so that a single notch 18 in a solnewhat wider inductor 15 will cause a double break in the magnetic circuit by comat the Sametime. This arrangement avoids ensuing losses, such as above described. However, a different disposition of the magneto on the engine is required and one which would not in many cases, admit of the compact arrangement herein shownfwhere the magneto fits nicely into the'space rbetween the crankcase and the flyreadiness for the pr0ducto allow a'clos-l against the restrainin points beyond uildingv up of flux can be accomplished against therer'cept that the'breaker point mechanism would need to be mounted on one of the ends faces rather than 0n the'side face, as heretofore described.

It will be understood that the feature relating to thecentrifugal arrangement for cutting outxthe' magneto to control engine speed may be used or not, as occasion requires, and this feature is not essential in so far as the real invention is concerned. f

ilit has been stated that the part 19 of the rotor is most important. But for this part, it would not be feasible to close the magnetic circuit before the breaker points close and thus all of the ilux would have to be built up influence of a short circuited primary win ing. That is one reason why one long notch, extending from the leadin end of the leading notch to the trailing en of the other notch, would not be practical at all. The other, and a most important reason for the part 19 is that it adds to the length of the period during which the' magnet1c circuit is closed. The effort here is to do away with as little of the periphery of the inductor as is practical, and thereby secure as long a period as is practical for the closed condition of the magnetic circuit. The present arrangement aii'ords time for the building up of flux against il. short circuited primary winding and alsoqholds'the flux that has been built up. Altholi h a great deal of flux is built up, while the reaker points are open, as was the case in the Clark patent above referred to, much better results are obtained here, which clearly indicates the value of keeping the magnetic circuit normally closed rather than open. Also the improved results are obtained with a simple form of breaker point mechanism without going to the s eclal provisions of the Clark patent `and t e complications, which as a practical the described operation is to be taken as illustrative of what I, now believe to be the best and preferred operation, rather than in any `limiting' sense. The magneto installation is not so critical or sensitive that eXtreme care and exactitude in the adjustments of the relative positions of the parts is necessary. For example, a spark will be produced if the breaker points open earlier and before the magnetic circuit has been completely broken. The building up of ux while the breaker points are open is most desirable, important, and preferred, but it is not necessarily essential in all cases and particularly in those cases where there is a long dwell period during which the magnetic circuit is closed. ln

th'e latter case, there may be time enough for all the iux to build up against the restrainlng -influence of the. closed circuited primary winding. However,fif the inductor shouldl ary, this invention polnts out the partlcular have additional notches to produce more sparks per revolution, then the feature of building up flux while the breaker points are open would probably be essential for successful results.

A most important feature of the invention is that both polar faces 14 lie on the same side of the crankshaft so that by one adjustment both such faces may be moved into closely adjacent relation with the inductor. A minimum clearance between the inductor and polar faces is essential for maximum elficiency and if the polar faces were diametrically opposite such small clearances as are here used would. not be feasible because the crankshaft, in many cases, does not run true enough to permit. In applying the magneto to/an engine, which has been in use for some time, the wear in the bearings. might be enough to defeat the use of the rubbing clearance, herein desired, unless the polar faces were both located on the same side of the shaft. Also, of course, the vcores would havey to be independently adjustable, if located in diametrically opposed relation and this is seldom. feasible.

As distinguished from' the flywheel magnetos, now found in the market, the present magneto can be made up separately from the engine and requires no special design of engine parts. In fact, a standard type of magneto, already available and of proved efficiency, can be utilized with but little modification. This one compactA unit may be furnished to the enginemanufacturer, with a supporting bracket therefor and the inductor, and the magneto installation can be effected without requiring any specialskill. The necessity of designing the magneto to suit the engine is eliminated and an equipment is provided which is applicable to most engines without substantial change therein. It follows that the magneto can beproduced at much less cost. Also, it is to be noted that the magneto can be removed by removing the one screw 26 and the complete outfit, except for the inductor (which does not require servicing) is available and accessible for servicing. The flywheel e has a recess, Vindicated at e in Fig. l, which, when turned so as to be opposite the breaker-point mechanism permits passage of the latter when the magneto unit his removed. Such unit, containing all partsv on 'which service can ever be required, may be removed and shipped back to the factory for repairs and another unit,

put in place to allow continued operation. One does not have to dismantle any part of the engine to get at the magneto.

rlhe invention is characterized over magnetos in which the magnets rotate, in that a less amount of material, handled in a less expensive way, is productive of better results. As to that type of magneto in which the inductor rotates and the magnets are stationelements and arrangement thereof, which yield commercially successful results and render this type suitable where heretofore it has been unsuitable.

The invention has been disclosed herein, in an embodiment at present preferred, for illustrative purposes, but the scope of the invention is defined by the appended claims rather than by the foregoing description.

What I claim is.: I

l. A magneto, comprising, a stationary unit having a source of magnetic flux, a pair of cores connected onel to each polar extremity of said source, and primary and secondary windings on said cores; cooperating Iand relatively movable breaker points, a primary circuit including said primary winding and breaker points and arranged to be opened -and closed by the separation or engagement of said points, a rotary inductor movable in close proximity to the polar faces of said cores to maintain a normally closed magnetic circuit and arranged periodically to break such circuit substantially simultaneously at both polar faces, both said polar faces'being located on the same sid'e of the axis of revolution ofsaid inductor, and means for separating saidbreaker points at substantially the same time that the magnetic circuit is broken at both said polar faces.

2. A magneto, comprising, a stationary unit having a source of magnetic: flux, a pair of cores connected one-to each polar extremity of said source,rand primary and secondary'windings on said cores; cooperating and relatively movable breaker points, a primary circuit including said primary winding and.

breaker points and arranged to be opened and closed by the separation or engagement of said points, a rotary inductor movable in close proximity to the polar faces of said cores to maintain a normally closed magnetic circuit and varranged periodically to break such circuit substantially simultaneously at both polar faces, both said polar faces being located on the same side of the axis of revolution of said inductor, and means for separating said breaker points at substantially the same time that the magnetic circuit is broken at both said polar faces and for holding them open until the inductor again closes such circuit.

3. A magneto, comprising, a stationary unit having a source of magnetic ilux, a pair of cores connected one to each polar extremity of s `id source, and primary and second: ary wind-ings'on said cores; cooperating and relatively movable breaker points, a primary. circuit including said primary winding and breaker points and arranged to be opeiied and `are located both on the same side of the axisof revolution of said inductor, said inductor having a pair of non-magnetic portions in its periphery spaced apart by an angle less than 180 degrees and so as to register substantially simultaneously one with each of said polar faces and create a double break in said ciiicuit, a normally closed electrical circuit including said primary Winding, and means for opening said electrical circuit substantially at the same time that said magnetib circuit is broken. f y

10. A magneto, comprising, a rotary inductor; a stationary unit havinga/ source of magnetic flux, a pair of cores connected one to each polar extremity of said source, and primary and secondary windings on said cores; said cores having polar faces with respect to which the periphery of said inductor moves in close proximity to maintain a normally closed magnetic circuit'and which are located both on the same side `of the axis of revolution of said inductor, said inductor having a pair of non-magnetic portions in its periphery spaced, apart by an angle less than 180 degrees and so as to register substantially simultaneously one with each of said polar faces and create a double break in said circuit, a normally.A closed electrical circuit including said primary winding, and means for opening said electrical circuit substantially atl the same time that said magnetic circuit is broken and holding it open until the inductor moves far enough to again close the magnetic circuit. u l

1l. A magneto, comprising, a rotary 1nductor; a stationary unit having a sonrce of magnetic flux, a pair of cores connected one to each polar extremity of said sourcefand primary and secondary. windings on said cores; said cores having pplar faces with respect to which the periphery of saidinductor moves in -close proximity to maintaina normally closed magnetic circuit and which are located both on the same side of the axis of revolution of said inductor, said inductor having a pair of non-magnetic portions in its periphery spaced apart by an angle less than 180 degrees and so as to register substantially simultaneously one with each of said olar faces and create a double break in sai cir.- cuit, a normally closed electrical circuit including'l said primary winding, means for opening said electrical circuit substantially at the same time that said magnetic circuit is broken and holding it open until the inductor moves far enough to again close the magnetic circuit, and means for bodily moving said f I unit to simultaneously move both said polar faces toward or away from the periphery of said inductor.

12. A magneto, comprising, a rotary in.- ductor consisting of a cylindrical body having in its periphery two notches which extend parallel with the axis of the body from one end face to the other and which are spaced apart by an angle less than 180 de rees; a stationary unit comprising a straight ar permanent magnet, cores extending one from cach polar extremity of said magnet toward and terminating in closely adjacent relation to the periphery of said inductor and so spaced that when one of said notches registers with one of said cores the other re Iisters with the other core, and primary an secondary windings on both Said cores; a normally closed electrical circuit including said primary winding, and means for opening said circuit substantially at the same time that both said notches register with both said cores.

13. A magneto, comprising, a rotary inductor consisting of a cylindrical body having in its periphery two notches which extend parallel with the axis of the body from one end face to the other and'which are spaced apart by an angle less than 180 degrees; a v

stationary unit comprising a straight bar permanent magnet, cores extending one from each polar extremity of said magnet toward and terminating in closely adjacent relation to the periphery of said inductor and so spacedv that when one of said notches registers with one of said cores the other registers with the other core, and primary and secondary windings on both said cores; a normally closed electrical circuit including said primary winding, and means for opening sald circuit substantially at the same time that both said notches register With vboth said cores and for holding it open until both cores are in part covered by peripheral portions of said inductor.

14. A magneto, comprising, `a rotary inductor consisting of a cylindrical body having in its periphery two notches which 'extend parallel with the axis of the body from one end face to the other and which are spaced apart by an angle less than 180 'de rees; a

stationary unit comprising a straight ar perv saidnotches register with both said cores and for holding it open until both cores are in lio u part coyered by perigheral portions of said from the iperiph@ inductor, and means ormoving said unit in a radial direction with respect to said inductor to carry said cores toward'or away thereof.

In testimony w ereof I have aixed my signature.

asl

j mi E. HENDRICKsoN.

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