US2833963A - Electrical apparatus - Google Patents

Description

May 6, 1958 T. TOGNOLA 2,333,963

ELECTRICAL APPARATUS Filed April 17, 1953 INVENTOR. jlE. 5 v 'TULLIO TOGNOLA ATTORNEY ELECTRICAL APPARATUS Tnllio Tognola, Sidney, N. Y., as'sig'nor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application April 17, 1953, Serial No. 349,444 18 Claims. (Cl. 315 232) This invention relates to electrical apparatus and more particularly to electrical systems adapted for producing relatively high energy electrical impulses.

One of the objects of the present invention is to provide novelmeans for controlling the discharge of an electrical condenser, said means being of extremly simple construction.

Another object of the invention is to provide electrical apparatus including a novelly constructed spark gap de vice for controlling the discharge of a charged condenser or 'the like.

I A further object is to provide a novelly constructed electrical circuit of the above type which is dependable in operation and adapted for use during long periods without danger of operating failures.

Still another object is to provide novel electrical apparatus for producing sparks or arcs, such as for igniting combustible charges in combustion engines of all types.

A still further object is to provide a novel and greatly simplified electrical circuit which is capable of producing sparks or arcs having a very considerable energy between relatively widely spaced electrodes atrelatively low voltages.

Another object is to provide electrical apparatus of the condenser discharge type which embodies novel means for producing a series of high energy impulses from a condenser charged step-by-step.

Another object is to provide a novel ignition circuit which embodies only a small number of parts, requires only a small space for installation, and is reliable and efficient in operation.

The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. l is a diagram illustrating an electrical circuit embodying the invention; and

Fig. 2 is a diagram of another form of electrical circuit embodying the invention.

The two embodiments of the invention illustrated in the accompanying drawings are, by Way of example, shown in the form of apparatus or "circuits adapted for use as ignition systems in combustion engines including piston engines and so-called .jet and gas turbine type engines. The systems shown are capable of producing high energy sparks between rather widely spaced electrodes at relatively low voltages.

As shown in Fig. 1, one suitable embodiment of the in vention comprises, as a source of electrical energy, ,a battery which may be connected to the remainder of the circuit by means of a switch 11 and a ground or equivalent connection 12. It will be understood, however, "thato'ther known types of sources of electrical en- I States Patet ergy may be used, either simultaneously with or 'alt'e'h natively in lieu of the battery. The battery 10 maybe of the storage battery type having a 24-'volt rating and capable of delivering as much as about 30 volts when connected to a suitable charging means,-such as a charging generator. If there is need for it, such as in instances where the source of energy supplies other circuits, suitable filtering means 14 may be provided to-prevent radio frequencies from feeding back into circuits emanating from the battery or other source. In the particular embodiment shown, the filtering means comprises three bypass condensers connected between ground and the power supply line 15, in which there is an inductance 9, but other known types of filters maybe used, and in some installations none is necessary.

The battery voltage may he stepped up to a desired higher voltage by any suitable means, such as a vibrator, which may be connected to the battery in any suitable known manner to effect an interrupted current flow. -As illustrated, the vibrator includes a transformer comprising a primary winding 16 inductively coupled with a secondary winding 17. The primary winding is connected at one end to power supply lead 15 from one terminal of the battery and at its other end through separable contacts 18-, 19 and ground or other suitable return to the other terminal of the battery. Contact 18 is stationarily mounted, whereas contact 19 is mounted on a pivoted or resilient armature 2 0 to which may be attached a spring 21 for normally holding the contacts in closed or engaged position. When the circuit is closed through contacts 18, 19, electrical current flowing through primary winding 16 creates a magnetic field whichis capable of magnetically actuating armature 20 against the efiorts of spring 21 to separate said contacts and open or break the primary circuit. The magnetic field then collapses and the spring becomes effective to re-engage contacts l8, 19 to again close the circuit through the battery and primary winding. This cycle of operation is repeated in rapid succession and the interrupted current flow through coil 16 at battery voltage is effective to induce a higher voltage across secondary winding 17.

In the form shown the low potential ends of windings 16, 1'7 are connected together although winding 17 may :be connected independently to ground or, if desired, the windings need not be connected other than inductively. A storage condenser 22 is connected across secondary winding 1'7 in series with one or more rectifie'rs 23. The capacity of condenser 22 may vary widely, depending upon the energy required in the igniting spark. For combustion engine uses it has been found suitable to use condensers having capacities ranging from .25 to 5 microfarads. The condenser charging circuit may be completed through ground,--or any other suitable connection. The rectifier means'may be, of the gaseous tube type or of any other suitable known type, such as selenium rectifiers, adapted for passing energy of a selected polarity to storage condenser '22 and for blocking its return flow from the condenser to the transformer. Thecondense'r will thus be charged step-by-s't'e'p or in successive increments to a voltage determined'by-the design of the transformer and the voltage of the source of electrical energy. The rectifier means maybe dispensed with it the source of electrical energy is of such aperture as to be capable of charging condenser 22 to a desired high voltage by a silngle impulse or otherwise in such a manner that the condenser is not permitted to discharge back through the charging circuit.

Although it is not necessary, a resistor 22' may be con-- system for overhaul or repair. A ten ('10) megohm rev;

This "avoids the sister is ample and will not appreciably afiect the normal operation.

For the purpose of controlling the discharge of condenser 22 through a load circuit to attain a novel and useful result, there is connected across or in parallel with said condenser a first branch circuit which is novelly constructed to determine or control the voltage at which the storage condenser is permitted to discharge. Said branch or control circuit is connected at one end to the high potential terminal of the storage condenser and comprises a shunted surface spark gap 36, a control or triggering gap 24, and a small condenser 26. The return connection to condenser 22 may be through ground or otherwise and preferably a resistor 27 is connected in shunt with condenser 26.

Shunted surface gap 36 comprises spaced electrodes 33, 35 and a high resistance or semi-conductive element 37 which bridges the gap between the electrodes in a manner now well understood in the art. The width of the gap between electrodes 33 and 35 may be such that the normal spark-over voltage thereof without element 37 is greater than the voltage of the charge impressed upon storage condenser 22 but this is not essential. However, when some of the charge on the storage condenser is permitted to pass through or along the surface of element 37 which engages electrodes 33, 35 the spark-over voltage of the gap 36 is reduced, apparently by the ionizing effect of impressing a voltage across or passing current through said element, and the gap becomes conductive to the charge on the storage condenser. The shunted surface gap 36 is preferably but not necessarily sealed in an envelope 32 with an output electrode 34 which forms with electrode 33 a hold-off spark gap 33, 34, the purpose of which is more fully discussed below.

Spark gap 24 is designed to have a relatively predetermined or constant break-down or spark-over voltage and is accordingly preferably of the sealed type, so that the spark-over or break-down voltage thereof remains substantially constant and independent of surrounding pres sures and other atmospheric conditions at different altitudes. One type of spark gap which has been found suitable is disclosed in Linkroum et a1. U. S. Patent No.

2,540,399. The capacity of condenser 26 is preferably small in comparison to that of storage condenser 22 so that only a relatively small amount of energy from the storage condenser is required to fully charge it. Accordingly, the current carrying burden placed upon control or triggering gap 24 is minimized and the life and efficiency thereof are substantially increased. The weakest link in prior known comparable electrical systems has thus been materially strengthened, thereby making possible the use of a relatively delicate or sensitive low-voltage control gap while simultaneously improving the durability and dependability of the system as a whole. The resistance 27 is effective to bleed ofi or absorb any residual charge on condenser 26 after each cycle of operation of the system in the manner to be hereinafter explained. The resistor also dissipates any energy which may leak past control gap 24 during the charging of condenser 22 to the breakdown voltage of said gap to thereby insure a constant or pie-determined flow of energy from condenser 22 to condenser 26 during each cycle of operation.

The major portion of each charge built up on storage condenser 22 is discharged through and utilized in a second branch or sparking circuit which is also connected across or in parallel with said storage condenser. This second branch includes an energy-consuming load which in the illustrated embodiment is a spark or igniter gap 28 that comprises spaced electrodes 29 and 30 and may be in the form of a spark plug or igniter plug of the type used in ignition systems for combustion engines. As shown in Fig. 1 the gap 28 is of the type which is bridged by a high resistance or a semi-conductor 31 to facilitate the formation of a high energy spark or are across the electrodes of the gap at relatively low voltage. able form of igniter plug or device embodying a gap thus bridged is disclosed in co-pending U. S. application Serial No. 221,435, filed April 17, 1951, now Patent No. 2,786,- 158. The bridged igniter gap is, like gap 36, of the type now commonly referred to in the art as a shunted surface spark gap.

Connected in series with igniter gap 28 in the sparking circuit is the hold-oft" spark gap comprising the spaced input and output electrodes 33 and 34, respectively. This spark gap is also preferably but not essentially of the sealed type and segregates the igniter gap from the storage condenser while the latter is being charged to the desired voltage. The normal spark-over voltage of gap 33, 34 is somewhat greater than the spark-over voltage of control gap 24 and hence, greater than the maximum voltage to which condenser 22 is normally charged. The hold-ofi gap is rendered conductive to the charge on the storage condenser by partial discharge of said condenser across shunted surface gap 36. Such a partial discharge is eflective to ionize the gaseous medium within envelope 32 sufficiently to lower the spark-over voltage of the hold-off gap 33, 34 to the level of the voltage of the charge on the storage condenser.

In one practical embodiment of the above described circuit or system, the source of electrical energy may, as pointed out above, comprise a standard 24-volt storage battery which, when the ignition switch 11 is closed, causes current to flow through primary winding 16 and the normally closed vibrator contacts 18, 19. As further pointed out above, the operation of the vibrator contacts results in the flow of interrupted direct current through primary winding 16 which induces a higher voltage across secondary winding 17. The vibrator transformer may be designed to produce any of a wide range of secondary voltages. For the ignition system of a present-day jet type engine, it has been found that a secondary voltage of about 2,500 to 3,000 volts is desirous in a system such as that shown in Fig. 1. Energy is thus caused to flow through rectifier means 23 in pulses to charge storage condenser 22 in increments or step-by-step to a voltage of about 2,500 to 3,500 volts or other chosen voltage. Each of the rectifiers has a selected hold-off voltage and the sum of these voltages should be in excess of the maximum charge desired on the storage condenser to prevent the latter from discharging back through secondary winding 17. Transformer 16, 17 may be a step-up transformer having a ratio of about 3 to 1 and resistors 27 and 55 may have a value of about .1 megohm.

The sealed control gap 24 is so designed that when the storage condenser attains a charge of about 2,500 volts or other selected voltage, the gap will become conductive and permit a partial discharge of condenser 22 into condenser 26. This small condenser acquires a full charge yery rapidly without absorbing any appreciable percentage of the charge built up on condenser 22. For example, the storage condenser may have a capacity of from about .25 to about 5 microfarads, whereas the capacity of the condenser 26 may be as little as .01 to .03 microfarad. Accordingly, the flow of current across control gap 24 is of short duration and the resultant deterioration of the gap electrodes is relatively small, thereby increasing the effective life thereof. When the gap 24 becomes conductive the initial energy discharged from the storage condenser is effective in the manner above described to ionize or otherwise affect the condition of gap 36 so that the same becomes conductive at the available voltage. The discharge across gap 36 is effective to ionize the gaseous medium in envelope 32 between hold-off gap electrodes 33, 34. The break-down or spark-over voltage of the latter gap is thus reduced so that the gap becomes conductive at the voltage then existing across condenser 22. The latter will accord ingly discharge the major portion of its charge across the hold-0E gap to the shunted surface igniter gap 28. The

One suitnormal break-down voltage of the. spark gap between electrodes 29and 30 is materially greater than the' voltage.

to. which condenser 22 is charged, but initially a small amount ofenergyfrom the condenser passesthrough or along the surface of element 31' between the electrodes. This flow of. energy is apparently effective to ionize the gaseous-medium of the gap between electrodes 29, 30 andthereby reducethe resistance of said medium so that the condenser will discharge across the gap and create an arc of very' considerable energy at a relatively low voltage considering the width of the gap. The spark gap 28may be of such width that in the absence of resistor or semiconductor 31, a' voltage in excess of 4,000 volts or'more would be required to bridge it and-hence create a spark at atmospheric pressure.

The sparking rate at gap 28' may be determined with a reasonable degree of accuracy by properly, designing the various elements of the system, such as the vibrator, transformer, rectifiers, condensers, etc. It will be understood, of course, that the sparking rate will vary with changes in the source voltage, but this variation may be countered or reduced to a substantial extent by properly designing'the' vibrator transformer 16, 17 in the light of the known variation in the source voltage. This is accomplished by designing the transformer to operate at the available voltages along the so-called knee of the magnetization curve of the transformer core, which may be of the air gap typeto thereby give good energy transfer without excessive variation.

During; each cycle of operation some of the charge attained by condenser 26 may be discharged across gap 33, 34 and the igniter gap 28 while these two gaps are conducting thedischarge of condenser 22. Any residual charge remaining on condenser 26 at the end of each cycle of operation as well as any energy which may leak past control gap 24 during the charging of the storage condenser-isdissipated by resistor 27. The ohmic value ofthis resistance may be'in the vicinity of .1 megohm. Upon initiation of each discharge of condenser 22 through the control gap, the condenser 26 will be atsubstantially zero potential, thus assuring a maximum voltage differential between the two condensers.

In the embodiment or modification shown in Fig. 2, a magneto 40 is provided as the source ofelectrical energy forrepeatedly chargingstorage condenser 22 through two sets-of rectifiers 41- and 42 in a manner well understood in the art. The secondary winding 43 of the magneto coil'has' a center tap whichis grounded at 44' so that current of one polarity flows through rectifiers 41 and current of opposite polarity flows through rectifiers 42 to charge-condenser 22 step-by-step or in small increments. The primary winding 45' of the magneto coil isconnected in circuit in the usual manner with acircuit breaker 46 which mayv be cam operated and across which is connected a condenser47.

The energy stored in condenser 22 may be intermittently released in. the same manner as described above in connection with the embodiment of Fig. 1; that is, underthecontrol of a control spark gap in circuit with shuntedsurface gap 36' and condenser 26. However, if accurately timed impulses are desired the spark gap may be replaced by a contactor 48 which is normally held in open position by a spring 49 and is intermittently closed by a rotatably driven cam 50. When contactor 48 is closed, condenser 22 will discharge and the resultant operation of the system is the same as that described above in connection with the circuit. of Fig. 1. If desired one set of the rectifiers 41, 42 may be dispensed with, but inthat event the storage condenser will be charged only about half as fast.

Although that portion of the circuit connected to the output electrode 34 ofthe hold-01f spark gap device. in envelope 32 maybe the same as the corresponding portion ofthe circuit shown in Fig. l, a modified form has been illustrated. As shown, therefore, in Fig. 2, one branch of two parallel circuits connected to the output knownhigh tension type wherein the electrodes are wholly,

insulated from one another; In modern engines a spark gap of this type is usually designed to have a normal spark-over voltage of about 15,000'volts inthe combustion chamberof anengine, that is, a voltage which may be several times greater than themaximum voltage across condenser 22. Accordingly,- igniter gap 51 must be first ionized to permit the lower voltage charge from the storage condenser to flow across the same for creating the highenergy igniting'spark. This is accomplished by connecting the output side of gap 33, 34 to parallel branches or circuits, one of which includes a condenser 52 thatisof small capacityin comparison to storage condenser 22 and is connected in series with the primarywinding 53 of a step-up transformer. The capacity of condenser 52. may be comparable to that of condenser' 26. The other said branch or circuit includes-the secondary winding-54 inductively coupled with primary winding 53 and the igniter gap 51' in series. For dissipating residual energy on condenser 52 after each operation of the circuit, thereis provided in shunt therewith a resistor 55.

When hold oft gap 33, 34 is rendered conductive in the manner described above, the voltage is insufiicient to bridge gap 51, and hence, the initial flow of energy is into'condenser 52"andtl1rough primary winding 53. The small condenser 52 is charged very rapidly and the charg ing current-which flows through primary winding 53rises very rapidly or-abruptlyto a relatively high peak value and induces a sufficientlyhigh voltage across secondary winding 54 to-impress a spark across the electrodes and thus ionize or trigger igniter gap 51. The spark-over voltage of this gap is thus reduced so that the remainder of the charge on condenser 22 finds the path of least resistance across the-ionized igniter gap and creates the high energy spark or arc which contains the desired.

amount of heat for igniting the combustible charge in the engine. The major portion of the charge on condenser 52 will also be discharged across the igniter gap with the main'charge from the storage condenser. Any residual. charge on condenser 52 aftergap 51v ceases to be conductive will be dissipated by resistor 55 thus insuring a maximum voltage difierential between condensers22 and 52 when holdeotf gap 33, 34 becomes conductive.

If a plurality-of igniter gaps 28 or 51 are required tobe fired in succession or in. timed relation, a suitabledistributor of known construction may be inserted at a suitable place in either circuitand parts on the outputside of the distributor, including the igniter gaps, may be multiplied in accordance with the number ofigniter gaps required. It will also be apparent that the shunted surface type of igniter gap employed in the embodiment ofi Fig. 1 may be replaced by that portion of the circuit of Fig. 2 which is connected to the output terminal of holdoff spark gapdevice in envelope 32. This alternative embodiment which includes elements 51 to 54, inclusive, is illustrated in Fig. 1 and may be connected, in lieu of igniter gap 28, to spark gap terminal 34 by means of a switch 60; Additionally in some installations, the output terminal of the spark gap device in envelope 32 may be connected directly to a sparking device having insulated electrodes somountcd that the normal spark-over voltage thereof does not exceed the voltage of the charge on-the storage condenser.

Although only a limited number of embodiments and" modifications of the invention have been illustrated in the accompanying drawing and described in the foregoing specification, it is to be expressly understood that the invention is not so limited, but may be embodied in other specifically. different circuits. For example, other wellknown sourceslof interrupted, pulsating, direct or alternating current may be provided in lieu of the magnetoor battery-vibrator combination illustrated, such as a direct- 7 current or alternating current generator, and other suitable types of rectifiers known to the art may be utilized in lieu of the type illustrated and specifically mentioned. Additionally, the various parts of the circuit, particularly many of the parts which are series connected, may be rearranged with respect to each other without appreciably atfecting the operation of the circuit. Various other changes may also be made, such as in the electrical values suggested herein, by Way of example, Without de parting from the spirit and scope of the invention, as the latter will now be understood by those skilled in the art.

What is claimed is:

1. Electrical apparatus comprising a source of electrical energy including a storage condenser, a second condenser, and means connecting said source and said second condenser including a shunted surface spark gap and a control gap connected in series with said second condenser.

2. Electrical apparatus as defined in claim 1 comprising a hold-elf spark gap and an igniter gap connected in series across said storage condenser, said hold-oil gap and said shunted surface spark gap having a common electrode.

3. Electrical apparatus as defined in claim 2 wherein said igniter gap is a shunted surface spark gap.

4. Electrical apparatus as defined in claim 2 comprising the secondary winding of a transformer connected in series with said igniter gap, and the primary Winding of said transformer and a condenser connected in series across said secondary winding and said igniter gap.

5. An electrical system comprising a storage condenser, a source of electrical energy connected with said condenser for charging the same to a pre-determined voltage, a sparking circuit comprising a shunted surface igniter gap and a hold-cit spark gap in series across said condenser, said hold-off spark gap having spaced input and output electrodes and being normally non-conductive to the charge attained by said condenser, and a control circuit comprising in series across said condenser a shunted surface spark gap including said input electrode, a control gap which is conductive at said pre-determined voltage to which said condenser is charged and a second condenser which is of small capacity in comparison to said storage condenser.

6. An electrical system comprising a storage condenser, a source of electrical energy for charging said condenser, a sparking circuit comprising an igniter gap and a holdolf gap connected in series across said condenser, the normal spark-over voltage of said hold-01f gap being greater than the maximum voltage of the charge attained by said condenser, and means including a control gap, a shunted surface spark gap and a second condenser connected in series across said storage condenser for rendering said hold-off gap conductive to the charge on said condenser.

7. An electrical system as defined in claim 6 wherein said hold-off gap and said shunted surface spark gap have a common electrode.

8. An electrical circuit comprising a storage condenser, means for charging said condenser, means for controlling the discharging of said condenser comprising a shunted surface spark gap, a control gap and a second condenser connected in series across said storage condenser, said control gap being conductive at a pre-determined voltage to which said storage condenser is charged by said charging means, and a load circuit connected across said storage condenser comprising a hold-off spark gap having a non mal spark-over voltage in excess of said pre-determined voltage, said shunted surface spark gap and said hold-off gap having a common electrode connected to said storage condenser.

9. An electrical circuit as defined in claim 8 wherein the load circuit comprises a shunted surface spark gap in series with said hold-off gap.

10. An electrical circuit as defined in claim 8 comprising an igniter gap and the secondary Winding of a transformer in series with said hold-0E gap in said load circuit, and means including a third condenser and the primary winding of said transformer connected in series with said hold-off gap across said storage condenser, said third condenser being of small capacity as compared to the capacity of said storage condenser.

11. Electrical apparatus comprising a source of electrical energy, a storage condenser connected to be charged by said source, a second condenser of less capacity than said storage condenser, and means for electrically connecting said condensers, said means including a shunted surface spark gap and a control gap for completing a circuit through said condensers whenever the voltage across the storage condenser reaches the spark-over voltage of said control gap, whereby said storage condenser discharges across the shunted surface spark gap and the control gap into said second condenser.

12. Electrical apparatus comprising a storage condenser, means for charging said condenser, a hold-oil spark gap and a shunted surface spark gap having a common electrode, means including a control gap for connecting the electrodes of said shunted surface spark gap to opposite terminals of said condenser, and an electrical load connected to the other electrode of the hold-off gap.

13. Electrical apparatus as defined in claim 12 wherein the electrical load comprises a shunted surface spark gap.

14. Electrical apparatus as defined in claim 12 wherein the electrical load comprises first and second branch circuits connected in parallel, said first branch including a condenser of smaller capacity than said storage condenser and the primary winding of a transformer and said second branch comprising an igniter gap and the secondary winding of said transformer.

15. Electrical apparatus comprising a source of electrical energy, a shunted surface spark gap, means connecting one electrode of said gap to one terminal of said source, and means for connecting the other electrode of said gap to the other terminal of said source, said lastnamed connecting means including a condenser and a spark gap.

16. Electrical apparatus comprising a source of electrical energy including a storage condenser, and circuit means connected to said storage condenser comprising a first branch including a shunted surface spark gap, a second condenser of smaller capacity than said storage condenser and normally non-conductive circuit completing means connected in series across said storage condenser, a second branch comprising a hold-off spark gap, the primary winding of a transformer and a third condenser connected in series across said storage condenser, said shunted surface gap and said hold-off gap having a common electrode, and a third branch comprising the secondary winding of said transformer and an igniter gap connected across said primary winding and said third condenser.

17. Electrical apparatus as defined in claim 16 wherein said circuit completing means comprises an intermittently operable contactor.

18. Electrical apparatus as defined in claim 16 wherein said circuit completing means comprises a control gap which is conductive at a predetermined voltage.

References Cited in the file of this patent UNITED STATES PATENTS 2,409,202 Francis Oct. 15, 1946 2,472,671 McNulty June 7, 1949 2,489,780 Hooven Nov. 29, 1949 2,571,788 Tognola Oct. 16, 1951 2,571,789 Tognola Oct. 16, 1951 2,589,164 Tognola Mar. 11, 1952

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