US2472671A

US2472671A - Apparatus

Info

Publication number: US2472671A
Authority: US
Publication date: 1949-06-07
Anticipated expiration: 1966-06-07

Description

June 7, 1949. J.'V. M N'ULTY 2,472,671

ELECTRICAL APPARATUS Filed March 15, 1945 IN VENT 0R.

ATTORNEY Patented June 7, 1949 John vaMeNultwBinghamton, N. Y.; assignnftt Bend dyiationgqonporation, New York,:N. Yi alcorporatiomof Delaware Ani lie'atwnMamh it, 1945; Serial No.-58 2-8 96? 1"0 (ilaiins'w (c1. sis-21 3') The-zinventiomrelatesr; to'j electrical: apparatus;- and more particularly: tokreleetrical f;circuits z-andv" means .v adapted '.-f0rvuse' in producing s-ele :trical:- arcs or: sparks suchyasthoses required? at' the? spark plugs;- inrthe ignition systems; foi" inter-nail 5e combustion; engines onthedike? One; of the. objectstof:ttheepresent' .irivention' is to; provide arz-novel .condenser-rdischarge"type' of? electricalcircu-it foIr-producing 'highivoltage electtrical sparks between spaoed:.:electrodes.-1

Another object of -thevinventionds to provide a novel ignition; circuit: for; lnternalf'combustion enf-z; ginesor-the-likewhereinrtheourrentds:distributed: totransformercoilsi-ajcljapentttoron mQiint-ed in the spark plugsat-irelatively'alow vol-taeeaandzrela-i tively high ,frequencyri A further objectwis; tocproifideinovelameans for controlling the: timing a'or frequency; ore sucoesq-r sivev impulses, of: electrical.- energy directed: to: a:- series 4 of spark gaps; such: as ithersparkwpiugs iir an ignition sys-tem :of-- an :e ine-nor'; the elike.

Still another" obj ect'i;iS"'-tO;pIlOVidewa circuit of" the above character. wherein-the energy iSfS'uDe plied by a magnetmgenerator wandwhereinamighr sparking rate is: attainable: aoross-aesparkgap ;.oifia: series ofspark gaps.

A still further. object detoprovide novelvmea'ns ina condenserdischargeetsipemf electricalr; sinsuit for effecting; a periodic rdi'scharge o'f the stonage condenser," sald-zmeans being geffl-cieiit'i andi 80' dependable-in: operation: for: a; longs. period of Still: another object isetor provide a indvelielece tricaloirouit-whiohdsadapted foriusel-irntheignit tion system: of fengines 3: and: is: so con'struetedi that" a" low distributi0n.v0l.tage-= may: be-zsaif'e'ly and effeotively usedetherebyi reducingrth'ef'radio shielding: Problems: and: minimlzingelectrical losses and-failures under1alli operatingwonditionsl The-,aboveand further, obj eotsand novel 'ife 4o turesof the inventiomwvii-l iiiore fully appear" from the followingbdetailed description wvlieriwtlriersa-rna' is: read in? connection. with the ae'eompanyingi drawing; It is .ztofpbeeexpresslytunderstood;' however, that :thedratvingrisfior therrpurposetoieillus 45 trationonly-2'- andf: is. not: intended, to 7: define the limits 0f; the 1 invention;-,z. reference- 1 for this 2 lat ter purpose ebei-ngz-had iprimarily ;to the appendede claims;

In the drawingythee single;- figiire is; azisclie '56 matio diagram' illustrating one form: of spark generatingor ignition circuit which'embodies-rtlie presenttinvention; A

In the: cironitzillustratedi in the; drawing, by: wayi-ofziexamplez only; the?inventlonisishownias; 55'

being embodied inf azix ignition:: system? suitable: for use inintern'ab combustidm engine's; the alet-' trioal energy b'e'i-ng'igeneratedl.andcsupplietkby "a magneto type generator-rand dlstributedsatirelaei tivel'y low: voltageaanjderelativeimhigh frequencye: An ignition: system embodyingzthe' inventionxwilh be operable at :a'llflaititndesaattainable by-wmode" ern' aircraft'withia'gmlnimuineof: electrical-1"losses-1 and Without appreciable danger "of: electrical iaile" ures.-. By reason oii-th'egilotv xiistributionvoltagese the radio shielding -difllou'ltle sl andxrequirem'entsz; will also be substantially -redueedfln?such; a-zs'ys tem. It will the-understood; discourse;thatsithee invention is not" limitediito use iii? an'iignitiomsy'se tem'b'ut may be i usefully employed ini-thealaborae' t'ory or in ma-ny :otlierwapplficatidns iwhere'eit xis? desired to producaaEsrlesfofsparksracrossispaced? electrodes.

In" the: form" shown; thewndvelizelectrical: c'iiouit comprehended hytheifirsent -invention some: prises a magnetoegneratonr I '0? as al source of? electrical" energy. Although thewgenerator may? be in the 'iormiv ofz any-bot?many-v known types of: magnetos; the." partioiilar type-s illustratede comi-Z prises a rfour-poleimagneticvrotom IIEandtlZitWOF- pole stator l2; the polesiao'f whic-h areconnected: by a core on -.which 'i:.is'i:wouxid:'a transformei coil having a? prlmary windinglv I31 and a; secondary; winding l 42 The construction of these windings? may be varied; as is'z'well understood in the arty: for: obtainlng w'ithin rather Wide limits any de-": sired voltage in thekoiifcuitiof the secondaryawindp-i 1 ing;

In a-mannerwelleunderstoodrinrthe artiprimarya: windings I 3 has:theaoppositeiendsthereof conenected? to the points i or contacts of; a circuit'z breaker. l5? Fbrnormally urging said contajcts toward: closed-on engaged position; suitable rear silient' means .suchzaszaii spring; I 62 may. be: roe. vided, and suitable means s'uch as a rotatable calm I 7 maybe employedfifor periodically IHOViI'IfiiSflid"? points toxopencor disengaged, position; I as illus' f trated; for interrupting the 'flomof- -cii'rreiit'in "the? circuit containing. the pfimary winding [3. Alithouglr a "sex-called:compensated-F camaoommer-" cially used in* radialiitypeqengiries iS flilhlstlated ilz it :wi'llibe understoodzithatrthicam may berdt'sanyasuitable; shape ands as; wens-i understood. i ,r the I art; 'saidicamispreierabljdriven at 'a'ispeedr pros portional 'torth'e" speed-o magneto rotor: l it One}- side.ofitheiprimarycircui s:conneoted togroundai as at l8 and 1a wcoiidenseii Seisaconhectdacross? the points- 0f circuit breakenl 5 t'o' reduce: s'pa'rkf-i in wbetween'saidpointsewhenthe 'Same'aaiemQVedK to 'openepos-itidn-liy thecmi For the purpose to appear hereafter, secondary winding I4 is tapped at approximately the center thereof and connected to ground, such as at l8. In effect, this divides secondary winding I4 into two windings with respect to the primary winding l3. As shown, the ends or high potential turns of secondary windings it are connected to the input terminals of two halfwave rectifiers 2U, 20. These rectifiers may be provided in the form of gaseous tubes of the cold cathode point-to-plane type, i. e., of the type wherein one element has a large surface and the other has a relatively small surface. If desired, a single full-wave rectifier of the same type, for example one known commercially as Raytheon No. CK1004, may be used in lieu of said two halfwave rectifiers, as illustrated in my cc-pending application Serial No. 567,672. As rotor H of magneto I is rotated, alternating current is induced in primary winding l3 and the circuit which i includes circuit breaker l5. When the primary circuit is interrupted by the opening of the points or contacts of circuit breaker l5, the intervals being determined by cam I! and the opening usually occurring when the primary current is at about its maximum value, current at a higher voltage is induced in the secondary winding Hi, successive impulses being of opposite polarity. With the parts connected in the manner described above, the generated impulses of one polarity in the secondary circuit will flow through one of the rectifiers or by way of one input terminal of a full-wave rectifier and impulses of the other polarity will flow through the other halfwave rectifier 20 or by way of the other input terminal of a full-wave rectifier so that the output from the plate terminals of the rectifiers will be unipolar.

The output or plate terminals of the rectifiers 2|), 20 are connected to each other and to one terminal of a storage condenser 2|, the other terminal of which is connected to ground as at 22. It is a characteristic of rectifiers of the type illustrated that current will flow therethrough in only one direction, that is, current will flow from point to plane but will not flow in the opposite direction. Accordingly, when the rectifiers are connected in the manner shown, the electrical impulses passing therethrough from the generator will be effective to charge condenser 2i but the latter will be unable to discharge back through the rectifiers or rectifier, as the case may be, through the coil of the magneto or other source. It is another characteristic of these rectifiers that the same will not become conductive below a predetermined voltage which is known as the on-set voltage. For most desirable operation, therefore, the maximum voltage generated across the secondary circuit of the magneto at the minimum operating speed thereof must be at least as great as the on-set voltage of the rectifiers and is preferably approximately 100 or more volts higher than the on-set voltage in order to provide a margin or factor of safety. For example, if the on-set voltage of the rectifiers is approximately 500 volts, the voltage across the secondary circuit of the magneto at minimum operating speed should preferably be about 600 volts or more. The voltage of the charge storedon condenser 2| may be varied by varying the capacity of said condenser. After'calculating on determining the energy supplied to the condenser from the secondary circuit of the particular magne'to employed, it is possible to choose a condenser with a suitable capacity for obtaining the desired voltage across the condenser. These calculations may be made by the use of simple well known electrical formulas.

Novel means are comprehended by the present invention for controlling and timing the successive discharges of storage condenser 2| for the purpose of creating periodic timed sparks across a gap or a. series of gaps, said means being of such a nature that the elements thereof will have a long operating life and at the same time permit a high sparking rate. In the form shown, said means comprises a cold cathode gaseous discharge tube 23 which may be of the type known commercially as a strobotron connected between condenser 2| and the load or work portion of the circuit to be hereinafter described. The high potential side of condenser 2| is connected to the plate or anode 24' of tube 23 and the cathode 25 thereof is connected to the load through a lead 29. A grid 26 is provided between plate 24 and cathode 25 of the tube 23, said grid being normally maintained at ground potential or at some minimum potential to act as a block to the passage of electrical current from the anode to the cathode. In the circuit shown, grid 26 is permanently connected to ground, as at 21, through a suitable resistance 28, the function of which will appear hereinafter. Normally, therefore, tube 23 is non-conductive and prevents the discharge of condenser 2|.

For the purpose of rendering tube 23 conductive to permit the discharging of condenser 2|. novel means are provided for periodically creating a potential between grid 26 and cathode 25. Said means in the form shown comprise a condenser 30, one terminal of which is connected to ground as at 27 and a resistance 3| which is connected between the other terminal of said condenser and the supply line from the source of electrical energy. Condenser 3G and resistance 3| are thus connected in series with each other and in parallel with condenser 2!. Any suitable means such as a contactor 32 may be provided for periodically connecting the high potential terminal of condenser 30 to grid 26 at a point between the latter and resistance 28 in order to excite or trigger the tube 23, i. e., to render the tube conductive for the discharge of condenser 2|. As illustrated contactor 32 is constructed in the same manner as circuit breaker I5 and the same is operated by a spring 33 and a rotatable cam 34, the latter being driven by the engine at a speed proportional to the speed of the engine crankshaft and, hence proportional to the speeds of rotation of rotor II and cam When the above described circuit is employed for supplying electrical energy to the spark plugs of a multi-cylinder internal combustion engine, the output terminal or cathode 25 of tube 23 may be connected through lead 29 to the rotatable element 35 of an ignition distributor 36. As is well understood in th art, element or arm 35 carries an electrode or brush which moves into successive conductive relationship with a series of circumferentially arranged terminals 31. In one suitable type of distributor, the rotatable arm 35 carries a carbon brush adapted to yieldably and successively engage contacts or terminals 31. Each of the latter is connected to the primary winding 38 of a, high frequency step-up transformer coil 38, the secondary winding 0 of which is connected across the electrodes of a spark gap 4| such as the electrodes of a spark plug. One end of each of the windings 38 and 40 and one terminal of spark gap 4| are connected Ii desired, the coils 39 may be housed within the radio shielding casing of the spark plugs. Since suitable distributors, coils and spark plugs are known and do not, per se, constitute a part of the present invention, it is believed to be unnecessary to illustrate and describe the same in more detail.

In the operation of the illustrated system,

'upon rotation of magnetic rotor I I alternating electrical current impulses are generated in primary winding I3, in a manner well known and understood in'the art, when the contacts of circuit breaker I5 are in closed or engaged position. The circuit breaker I5 is periodically opened by cam II, preferably each time the current flow in winding I3 approaches a maximum, thereby breaking the primary circuit and causing a current to be induced in secondary winding Hi. This alternating secondary current at a somewhat higher voltage is fed through the rectifiers 20, in the manner fully described above for building up successive unidirectional or unipolar charges on condenser 2 I. It will be clear that the energy "for building up the desired charge on condenser 2| may be supplied by a direct current generator or other suitable direct current source without the use of rectifiers, but this is not suitable in all installations or applications since the voltage developed by such a generator varies substantially with variations in the speed of the rotor. Although the timing of the operation of circuit breaker I5 is not critical, it will be understood that for best results the same should be properly coordinated in a known manner with the 0peration of magneto rotor II and preferably the construction is such that the contacts of circuit breaker I5 will be separated just prior to each closing of the points of contactor 32 which effects the proper timing of the sparks at gap 4 I.

As will now be apparent from the drawing, the electrical energy from the source will be divided between the parallel connected branches of the circuit which include condensers 2 I and 30. Thus, both of these condensers will be charged simultaneously upon each opening of circuit breaker I5, at which times the points of contactor 32 will be in open position. The presence of resistance to the flow of current from anode 24 to cathode 25 and, hence, permit the discharging of condenser 2i. The resistance 28 is inserted in the ground connection for grid 26 in order to allow a potential'to be built up between the grid and cathode 25 when the contactor 32 closes. The connection through resistance 28 also ties the f grid 26 down electrostatically as hertoiore pointed out and stabilizes the gap between anode 24 and I cathode 25, thereby insuring against any discharging of condenser 2I before the -closing of contactor 32. Accordingly, upon closure of contactor or circuit maker 32, the charge on condenser 2I is discharged through tube 23 and distributor 35 to the primary winding 38 of one of the coils 39. As is known, the discharge of condenser 2| is a high frequency or oscillating discharge so that a similar high frequency current is induced in secondary winding 40 of the coil 39 at a considerably higher voltage, the step-up in voltage being determined by the construction of coil 39. A spark and usually a shower or series of sparks are thus created across gap 4|. The foregoing cycle of operation may be repeated at high speed for producing periodic sparks across gap 4| or across a series of gaps connected in the same manner with terminals 3'! of the distributor.

In one suitable embodiment of the invention in the form illustrated in the drawing and heretofore specifically described, a standard magneto generator of the type currently used on modern aircraft engines was employed, the same being adapted to generate a'voltage of from 2-50 to 300 volts across the primary circuit thereof. This voltage was stepped up to about 600 volts in the secondary circuit of the magneto when rectifiers having an on-set voltage of approximately 500 volts were used. Condenser 2I had a capacity of approximately .5 microfarad so that the voltage across the same when charged was approximately 350 volts. Resistor 3I "had a resistance of approximately 100,000 ohms and the capacity of condenser 30 was only .005 microfarad so that the voltage across the same when charged was approximately volts. The current flow through contactor 32 was on the order of a milliampere, thereby eliminating detrimental sparking at and consequent deterioration of the contactor points. This also eliminates the erratic timing which is normally experienced with contactors which are required to carry large currents at high voltages. The resistor 28 may have a resistance on the order of 500,000 ohms. It will be understood, of-course, that the foregoing examples are illustrative only and that the electrical values of the various elements of the circuit may be varied between rather wide limits.

There is 'thus provided a novel electrical circuit and novel control means therefor for producing electrical sparks which circuit, by way of example but not by way of limitation, is

' adapted for use in the ignition systems of internal combustion engines or the like. Said circuit embodies novel simplified means for controlling the discharge of a condenser and, hence, for timing the occurrence of sparks at one or a plurality of spark gaps. The circuit or system comprehended is reliable and efiicient in operation at all altitudes and permits the production of sparks at a high rate while using a single source of electrical energy and a single control means. Other attributes of said circuit are long life and low cost of manufacture, installation and upkeep.

Although only a single embodiment of the invention is schematically illustrated in the draw ings and described in detail in the foregoing specification, it is to be expressly understood that the same is not limited thereto. For example, other Well known types of circuit breakers may be substituted for those illustrated and suitable sources of electrical energy other than that illustrated.

may be employed; If accurate timing is not essential the contactor 32 may be eliminated. Various other changes may also be made, particularly in the design and arrangement of the parts illustrated without departing from the spirit and scope of the invention, as will now be understood by those skilled in the art. For a definition of the limits of the invention, reference is had primarily to the appended claims. What is claimed is: 1. In an ignition system or the like, a storage -.cond.enser, a. second condenser, means for charging said condensers, asparkgap, a normally nonconductive. electronic discharge device connected .between saidstorage condenser and said gap, and means including a periodically and mechanically operable circuit maker for opcrably connecting said second condenser tolsaid device rfor renderingsaiddevice conductive .tcthe discharge of said storage condenser.

2. Spark, producing-apparatus comprising a storage condenser, a source .ofelectrical energy for charging; said. condenser, a second condenser connectedtosaidsourcednparallel with saidstorage condenser, .a;.discharge :device having an .anode connected .to said. storage condenser, a cathode and a grid, at sparkgap connected to said cathode, and mechanically controlled means for periodically connecting said second condenser to said grid .-for rendering said device conductive to the discharge of said storage condenser.

3. In apparatus of the-class described, a storage condenser, means for-charging said condenser to a, predetermined voltage, a spark gap, a discharge device connected betweensaid condenser and said gap, said device being .normally non-conductive at said voltage, .andmeans including a contact maker .and a second condenser, connected with said charging .means for periodically rendering said devicesufliciently conductive to permit said firstenamedcondenser itodischarge through said device.

4. In apparatus :of thdclass described, a first condenser; a second condenser and a resistance connected in series witheach other and in parallel with said first'condensenan electronic discharge device having an element-connected to said first condenser and being normally non-conductive to a charge thereon, mechanically Operated means for periodicallyconnecting another element of said device to said second condenser to thereby render. said 1 device capable of conducting the discharge of said first condenser.

5. In apparatus of the class described, a first and a second condenser connected in parallel branches of a circuit, an electronic discharge device having an anode; a cathode and a grid,

means connecting said first condenser to said anode, means permanentlyconnecting said grid to a point of low potential such as to ground through a resistance, and means for periodically connecting said grid to the high potential side of said second condenserto render said device conductive to the discharge of said first condenser.

6. In apparatus of theclass described, a source of unidirectional electrical current,circuit means connected to said source including three branches connected in parallel with each other, one of said branches including a condenser adapted to be charged by said source,;another of said branches including acondenser and a resistance connected between said second-namedcondenser and said source, another of said branches including an electronic discharge device having the anode thereof connected to said first-named condenser, means for connecting theagrid of said device to the high potential side ,of' said second-named condenser, means for periodically opening and closing said last-named-connecting means, means including a resistance for permanently connecting said grid to a poit of low potential such as ground, and a spark gap adapted tobe connected to the cathode of said device.

7. In apparatus of the class described, a con- ,.denser,. a, source cfunidirectional current; forcharging saidcondenser, a transformer, normally non-conductive electronic-means connected between saidcondenser and .said transformer, and means including .a second condenser connected with said source and mechanically controlled means for periodically. connecting said second condenser withsaid electronic means for render ing the latter conductive to permit said first condenser to discharge across .saidtransformer.

8. Inapparatus of the class described, a source of alternating current, means for rectifying the same, condenser means supplied from said rectifying means,..electronic ,valve means connected to the output of said condenser means, an induction coil also connected to the :condenser means and the valve means-whereby the latter controls the energization of, the coil from said source, and means for periodically triggering said valve means including a second condenser means and a mechanically operable timing means for periodically connecting said second condenser means to the control element of said .valve means for rendering the latter conductive .to the charge on said firstnamed condenser ,means.

9. In apparatusof the. class described, a source of electrical energy, condenser means chargeable .by said source, electrical valve -means and .an

energy-consumingload, such as the primary and across said load, said triggering means comprising a condenserchargeable by said source and a cam operated circuit maker for periodically connecting the high potential side of said condenser to the control element of-said valve means ,to render the latter conductive to the charge on said condenser means.

10. In apparatus of the class described, a source of electrical energy, condenser means chargeable by said source, electrical valve means and an energy-consuming-load, such as the primary winding .of a transformer, connected in circuit with said condenser means, and means for periodically triggering said valve means to permit said condenser means to discharge therethrough and across said load, said triggering means comprising a condenser chargeable by said source, means including a contact maker for periodically connecting the high potential side of said condenser to e the control element of said valve means to render the latterconductive to the charge on said condenser means, and means including a resistor for permanently connecting said control element to potential, such as to ground.

JOHN- V. McNULTY.

a point of low:

" REFERENCES CITED The following reterences are of record in the file of this patent:

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