US1168837A - Method of producing electrical oscillations. - Google Patents

Description

E. vow LEPEL;

METHOD OF PRODUCING ELECTRICAL OSCILLATIONS.

APPLICATION FILED 05c. 29, 1914.

1,168,837. Patented Jan. 18, 1916.

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E. VON LEPEL.

METHOD OF PRODUCING ELECTRICAL OSCILLATIONS.

APPLICATION FILED DEC. 29, I914.

Patented Ja11.18, 1916.

3 SHEETS-SHEET 2- Fig.9.

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. METHOD OF PRODUCING ELECTRICAL OSCILLATIONS.

APPLICATION FILED DEC. 29,]914. Patented Jan. 18, 1916.

3 SHEETS-SHEET 3.

WI /I') ess es 974 W rM PATENT EGBERT VON LEPEL, OF BERLIN-WILMERSDORF, G'ERIVIANY.

METHOD OF PBOD UCING ELECTRICAL OSCILLATIONS.

Specification of Letters Patent.

Patented Jan. 18, 1916.

Application filed December 29,'1914., Serial No. 879,587.

To all whom it may concern:

Be it known that I, EGBERT VON LEPEL, a subject of the King of Prussia, residingat Berlin-Wilmersdorf, in the Empire of Germany, have invented new and useful Improvements in Methods of Producing Electrical Oscillations, of which the following is a specification.

It is known to produce electrical oscillations of high frequency by periodically discharging a condenser over spark gaps. The periodical discharge may be effected either directly over the spark gap, or indirectly by frequency; Figs. 7' and 8 are curves illust-ratin'g the theory of operation of the systems shown in Figs. 1 to 5; Fig. 9 is a curve illustrating the theory of operation of the system embodying the present invention; Figs. 9 and 9 represent separately the course of the current in the condenser branch of'the circuit and in the spark gap branch of the circuit of Fig. 6, when the spark gaps 4: produce a quenching effect; Fig. 10 is a curve illustrating the theory of operation of the system when the. supply current is maintained absolutely constant; Figs. 10 and 10 separately illustrate the course of the current in the condenser branch of the circuit and in the commutator wheel'branch of the circuit of Fig. 6; Figs. 11 and 12 illustrate portions of rotating commutators for charging and discharging condensers; and Fig.

v13 diagrammatically illustrates a systemj embodying my invention and in which two pairs of condensers are employed.

Various methods are illustrated in Figs. 1 to 5 of the accompanying drawings- In Fig. 1 the condenser 1 which is fed from the direct current source 2 becomes discharged over the spark gap 4 in anoscillatory circuit on every half turn of the rotating blocking condenser 3, in connection with which a change of charge of the blocking condenser 3 takes place each time. The coupling coil 5transmits the energy of the high frequency oscillations thus produced to the circuit ofthe antenna. If a feeding current of high potential is used additional spark gaps 8 may be inserted in a number corresponding to the potentialof the current. The object of the resistance 6 and the selfinduction 7 will be explained later on.

In Fig. 2 a similar arrangement is shown except that the blocking condenser 3 is, by means of the rotating commutator 9, alternately charged and discharged whereas in Fig. 1 the charge is periodically changed.

With the method illustrated in Fig. 3 the charge of the blocking condenser 3 is periodically changed but this change is initiated by means of artificial ignition, instead of by means of a rotating commutator. For this purpose the pairs of spark gaps 10 and 11 are alternately bridged, in a well known manner, by artificial ignition whereby the blocking condenser 3 is oscillatorily commutated in constantly changing direction.

With the method illustrated in Fig. 4 the blocking condenser is dispensed with; a rapidly rotating short circuiting wheel 9 is used instead. Since in this case the discharging current and the energy supplied from the current source '2 are not blocked the danger that are formation will occur by reason of the short-circuiting of the current source must be met by a rapid rotation of the short circuiting wheel 9. Another measure (73. e. tuning the feeding current circuit) is frequently applied for the same purpose, and will be described later on.

In Fig. 5 stationary quenching spark gaps 12 (according to v. Lepel) are used in place of the rotating short circuiting wheel 9. Herewith, the almost continual oscillations of this arrangement may be, for telephonic transmission, rhythmically subdivided by means of a tuning circuit 15. The effect of avoiding arc formation, obtained in Fig. 4

by rapid rotation of the electrodes, is secured in the method illustrated in Fig. 5 by means of Lepels quenching spark gaps. However, it is well to point out that are formatlon 1s more perfectly and in quite a different manspark after the first half surge, that is, much quicker and more regularly.

With the methods thus described it is often advantageous to insert choking coils. 6 (see Figs. 1 to 5) into the feeding circuit for limiting and damping the supply current. \Vhere blocking condensers are wanting (see Figs. 4, 5) the arrangement of such choking coils, or automatic maximum interrupters, is advisable in order to prevent short circuits.

Frequently, besides choking coils 6, small self-inductances 7 (see Figs. 1 to 5) have been proposed and used for the supply circuit of the described arrangements; and this for two different reasons: Firstly, to protect the direct current sourcev from returning high frequency oscillations. Practical experience has shown that'air choking coils having about 100 windings serve this purpose. In many cases an additional condenser is connected in paralleloto the source of current to farther protect the latter. Secondly, j in some cases a tuning of the supply circuit to assume, after the oscillatory equalization,

a correspondingly lower' value V. This decrease of potential effected by the spark is indicated in the diagram of Fig. 7 by means a of the heavy line 1617. The charging of condenser 1 now follows: if

which is mostly the case in practical working arrangmcnts, this charging proceeds oscillatorily, w in the foregoing formula being equal to 211: times the frequency of the electromotive force of the supply circuit, L representing the inductance of the circuit, and a representing the capacity of the condenser. The curved line 16, 17, e 16, 17 e,'and so on, is a representation of the potential 6 prevailing at the condenser 1, while the feeding current follows the dotted line i. Now, since with a complete oscillatory charge of a condenser 50 per cent. of the supplied energy is lost through production of heat, a special advantage is secured bylnot permitting the upward oscillating energy that passes during the first -3; wave length far beyond the supply potential E (in fact it increases to the value 2E-V) to die away, but to start the next spark ignition in the maximum point 18 of the first half oscillation. Thereby the loss of half the energy is prevented and the advantage is secured that one is enabled to work, at the moment of the ignition.

vwith a condenser potential equal to2E-V.

This state is easily obtained by tuningthe supply circuit by means of self-induction coils 7 in such a Way that the increase of the potential e'from' the value E to the value 2EV concurs with the rhythm of the commutations, that is, the spark series. The po-- tential e and the supply current i would then I ply current z' passes zero at the moment of the ignition, hence, it is an advantageous measure for averting the above mentioned danger of arc formation. This tuning system is charged with various defects, principally because it is not always easy to obtain the proper tuning and to prove its existence u-nobjectionable. Moreover, since the ignitions are to occur as accurately as possible, in the maximum point 18 of the value of the potential, and since anoccasional irregu larity of a single ignition will affect the subsequent ignitions and will in consequence disturb the regularity of the spark series, the tuned state is rather sensitive to disturbing series.

Nicola Tesla in his British Patent 20981 influences, to which defects must be added I A. D. 1896 and in his U. S. Patent 577670 of 1897 has described arrangements for the production of oscillations of high frequency which arrangements are in some respects than those of the above mentioned coils that I i have a self-induction large enough to keep the current i inthe supply circuit entirely or approximately constant for the length of the interval T between two oscillation im- In the following these coils will I pulses. I briefly be called lnertla-coils. The electrical conditions of this method are explalned 1n the diagram Fig. 10; for the sake of simplicity it is supposed that ideal inertia-coils (2'. e. infinitely large ones with regard to the rhythm of the oscillation impulses) are arranged which keep the supply current i absolutely constant for the length of the interval between two oscillation impulses. It may be seen that in this case too the tension e of the condenser 1 that is being charged by the feeding current i kept constant increases lineally, in the way graphically explained by the straight tension lines 20, 19 in Fig. 10. The current 2' flowing in the feeding circuit, is represented by the straight horizontal line 2'. Since a blocking condenser is absent in Teslas-arrangement the condenser tension A, in the short-circuit position sinks from the initial value A to zero after all ofthe oscillation surges have died away; this phenomenon is indicated by the vertical lines 1917. At the same time the current 2', kept constant by means of the inertia-coil, takes its course over the short circuiting wheel 9 and there remains .constant until disconnected by rupture.

During this time (1720) the condenser 1 being short-circuited is Without tension, hence, the tension curve 0 coincides with the zero line during .theinterval 17-20. After the rupture, the current i, still kept constant, may only go to the condenser which now is not any. longer short-circuited and which becomesrecharged by the current i. It will be seen that the current in the feeding circuit serves alternately as charging current (from 20-17) and as short-circuit current (from 17-20).

For the sake of completeness, the current diagrams of the condenser branch e. the charging current) and of the commutator wheel branch (71. e. the short-circuit current) are separately illustrated in Figs. 10 and 10. Both together represent the constant current i flowing through the supply circuits.

Since the inertia-coil has only a regulating efi'ect and therefore gives off always so much electrical energy as it had magnetically stored previously, the current values and tension values will always adjust themselves in such a way that the lined rhombical surface 23, 17, 20, 24:, representing the energy stored, equals the lined triangular surface 24, 19, 23 representing the energy given off. From this it follows that the initial tension A of the condenser 1 at the moment of ignition exceeds the feeding tension E both before and after the oscillatory equalization has'taken place. This effect would be very advantageous if it were not accompanied by the short circuit-currents illustrated separately in Fig. 10 Since the inertia-coil keeps the current in the feeding circuit constant the short cir- 'cuit-cur'rents are to be interrupted in their full intensity whereby, naturally, violent and dangerous rupture arcs occur. As the rupture phenomenon, in addition, is very irregular on account of the sensitivity of the arc, disturbing fluctuations Wlll occur in the tension line and, hence, in the rhythm as well as in the intensity of the impulse.

These disadvantages Weigh so heavily technically that this method has never been Worked in actual practice so far as applicant is aware. Moreover, the defects of tuning, as explained above, are put up with in order to have to break but weak currents at the moment of the short-circuiting position. As is already said, the requirement of high regularity has to be foregone. according to this invention a special advantage may be obtained if through the use of suitable spark gaps each spark is extinguished immediately after the first half of its surge and if the supply current which on account of the extinction of the spark goes solely to the condenser 1 is kept entirely or approximately constant by means of a self-induction of sufficiently high order for intervals of the order of the spark series, so that by the combined effect of spark extinction and the keeping constant of the supply current the tension of the condenser in the moment of the ignitionin connection with any spark rhythm is increased so much or approximately so much above the feeding which, however, corresponds to the. new

method only if the spark gaps 4: produce a quenching effect, the diagram of 1g. 9 would correspond. The diagrams Fig. 9

.and Fig. 9 represent separately the course of the currents in the condenser branch and in the spark gap branch, in the same way as do the diagrams Fig. 10 and Fig. 10*. Since a blocking condenser 3 is provided, the condenser tension e consequently will not decrease to zero after the oscillatory equalization, but only drops to the value of the equalization tension V. The difference obtaining on a comparison with Fig. 10 and which forms a feature of'this invention 1s at once apparent: Points 17 and 20 (Fig. 10) will in this case join in the single point 17 (Fig. 9), the charging current (Fig. 9*) remains constant, the infinitesimally small duration of time occupied by the first half surge not considered, and the short circuit currents following the oscillatory equalization, and which are detrimental in several respects, do not occur.

\Vhile with the tuning method the intensity of the charging current i and its sinusoidal path (see Fig. 8) is essentially 1nfluenced by the self-induction L of the sup- However,

ply current circuit and with Teslas method, by the duration of the short-circuit currents, so that the current intensity is in a'state of stable equilibrium with regard to the selfinductionor the short-circuit currents; with the, novel method the intensity of the feeding current i is only depending upon the number of discharges, and is in condition of indifferent equilibrium with regard to the self-induction of the inert coil (which keeps the current constant for the space of time of the series of sparks butdoes not influence it in its'absolute value beyond this). For instance, if the number, or the quantity, of the discharges is slowly increased, the intensity of the feeding current i will increase (like a slowly increasing direct current). Condenser 1 works in combination with the rotating blocking condenser under the in- ,The provision of the periodically commutating blocking condenser has an efiect upon the continuous current circuit like a stationary condenser in an alternating current circuit: forming an apparent resistance, 2'. e. a current restricting resistance.

Although the inertia-coils do not influence the feeding current i in its absolute quantity they still suppress any fluctuation of current within the interval of -two succeedingsparks, with the result that the current shows a constant medium value. Likewise, for the same physical reason, the tension of the condenser 1, at the moment of ignition, will under the influence of the inertia-coil and'the extinction effort of the spark gaps lie as much, or approximately as much, above the feeding tension E as below the latter after the oscillatory equalization. Geometrically considered, in this'case, too, theshaded triangle 23, 17, 24: must equal in i 7 surface the triangle 24, 19, 23. Hence, with combined application of inertia-coils and quenching spark gaps the feeding tension will be therefore A 2EV.

Furthermore, it'may be generally stated that with the condenser 3 connected in parallel to the condenser 1, the equalization tension equals for blocking condenser 3 offers the inverted equalizatlon tension V toward condenser l.

The following mathematical equalizations will apply: V(a+b):Aa-|-Bb= 7 2E aVaVb: Ea V(a-ib) wherefrom the equalization tension may be obtained as follows:

On giving, for instance, both condensers 1 and 3 an equal capacity a b, the following values are obtained:

A :1%E Z:AB:2E

wherein Z represents the total tension of ignition.

The energy taken from condenser 1 at each discharge amounts to I If T is the time of charging, the energy conducted into condenser 1 at each discharge amounts to is started by charging and discharging blocking condenser 3, then,

B=O v and for the equalization tension the value is obtained.

Ifa b the followingvalues result:

l b=2/3 Z representing the total ignition tension. In a similar manner the proper values for V, A, Z and i may be determined if the gaps 4., or 1.0, 11 respectively have quenching effects.

WVhat distinguishes the novel method essentially from the known arrangements, is the feature of applying inertia-coils and quenching spark gaps combined. From the effect of this combination as above described in detail it follows that with the novel method the ohmic resistance 6 may be substantially smaller, ormay be dispensed with entirely, as in Fig. 6. For, since the system 13, under the influence of the inertia-coils and the quenching spark-gaps, works apparently like a resistance, the efiect of the resistance 6 may be obtained, entirely or partly, by means of this system; which is very advantageous because the loss of energy entailed by the use of the resistance is completely or partly avoided. Aprotecting condenser connectedin parallel to the source of current is not required with this system. course, the Figs. 1 to 5 do not exhaust all possibilities. For instance the commutator of the rotating blocking condenser 3 may be combined with artificial ignition; by means of this artificial ignition the jump of the spark will then be started when the distance of the electrodes has reached its minimum whereby a very accurate series of sparks is secured.

If the rhythm of the spark series is accelerated or delayed, this will entail an increase or a decrease of the intensity of the feeding current, as has been mathematically shown above. This increase or decrease of the currents will suffer, on account of the inertia-coils, a slight delay in comparison with the speed governing the alteration of the rhythm. Since a like delay Occurs also with the ignition tension, an after ignition, or a prior ignition, results therefrom at the rotating electrodes, which may give rise to irregularities if the alteration happens comparatively quickly. It may thus happen that the ignition which normally. starts at the point 30 of the toothed electrode 29 (Fig. 11), occurs during the acceleration at 31 or 32, or during the delay at 33 or 34:. The electrode 28 is, then, at the moment of the ignition, opposite of a sharp edge of the toothed electrode 29, which position might easily favor arc formation, since experience proves that sharp edged. or pointed electrodes on account of the high local heat production favor the transition of a spark into an arc. If, however, two fiat electrodes are opposing each other at so small a dis,

tance that they Work as quenching. spark gaps, on'suddenly increasing the distance in some cases it is expedient not to give the commutating electrodes sharp edged sides running parallel to the axis of rotation as shown in Fig. 11 but to choose electrodes with slightly undulated surfaces as illus trated in Fig. 12. 1

Whether the condition of a constant feeding current so essential for the new method is attained can only be ascertained by the insertion into the feeding circuit of measuring instruments adapted for a continuous and for an alternating current. Since the continuous current instrument will indicate the mean value of the instantaneous current the spark will be interrupted, Therefore, a

intensity, the alternating current instrument, however, the square root of the mean value of the square of the currents, both instruments, if the feeding current takes a sinusoidal or otherwise undulating path, will give dissimilar indications, whereas they will show the same reading only if the feeding current is absolutely constant. It is, however, simpler to measure the sec ondary tension of an auxiliary coil placed, for that purpose, around the iron-core of the inertia-coil. This secondary tension will equal zero, or will approximate to zero, if the feeding current is perfectly or approximately constant.

Whether the equally important quenching effect exists may be inferred, in a well known manner, from the degree of coupling which corresponds to the best efiect, and from the produced oscillations having a single resonance maximum. After some experience the existence of the quenching effect may be rec ognized from the character of the sparks and from the exact and arc-free operation. Furthermore, for high tensions, the described method may be extended to comprise two, or more, condensers instead of one, in such a way A that condenser 1 is charged in a parallel system but 1s discharged over the blocking condensers connected in series.

In Fig. 13, byway of example, an arrangement for two pairs of condensers 1s shown in accordance with this principle. Of course, in a similar manner, an arrangement may be made for three, or more, pairs of condensers. Fig. 13 directly shows that through the rotation of the synchronously revolving commutating devices (which may be mounted on a common shaft) the con- 'densers 1 are charged in parallel at the frein the discharge position there are not onlyv inserted one ora plurality of spark gaps between each two charging condensers (1 and 1 connected in series, but also a blocking condenser 3,, whereby the danger of a short circuit (which the diagram indicates) is entirely obviated, whereas Braun proposes, for

the same purpose, the use of resistances in the feeding line.

What I claim 'is: p

' 1. The method of producing electric oscillations of high frequency which comprises charging a condenser from a source of current, establishing a spark discharge across a suitable spark gap by periodically discharging the condenser over said spark gap, and extinguishing each spark after the first half oscillation or after the first train of v oscillations of the discharge energy, feeding during the spark extinction the charging current solely to the condenser and maintaining said current at an approximately constant strength so that the combined efi'ectof the spark extinction and substantially constant strength of the charging current will render the potential of the condenser, with any frequency of sparks, as much above the potential of the charging source at the moment of discharge as it is below after the discharge. 1

2. The method of producing electric oscillations of high frequency which comprises charging a condenser from a source of direct current and through suitable self inductances, establishing a spark discharge across a quenched spark gap by periodically dis-- charging the condenser over said spark gap,

and extinguishing each spark after the first half oscillation or after the first-train of oscillations of thedischarge energy, feeding the charging current during the spark extinction solely to the condenser and maintaining said current at an approximately constant strength by the self inductance in the supply circuit so that the combined effect of the spark extinction and substantially constant strength of the charging current will render the potential of the condenser, with any frequency of sparks, as much above the potential of the charging source at the moment of discharge as it is below after the discharge.

3. The method of producing electric oscillations of high frequency which cornprises charging a condenser from a source of direct current which current issupplied to said condenser through inertia self induction-coils, establishing a sparkdischarge across a quenched spark gap by periodically discharging the condenser over said spark gap, extinguishing each spark after the first half oscillation or after the first train of oscillations of the discharge energy, feeding the charging current during the spark vextinction solely to the condenser and maintaining said current at an approximately constant strength so that the combined effect of the spark extinction and substantially constant strength of the charging current will render the potential of the condenser, with any frequency of sparks, as much above the 7 potential of the charging source at the moment'of discharge as it is below after the discharge. 7

4; The method of producing electric oscillations of high frequency which comprises charging a condenser from a source of direct current and establishing. a spark I discharge byperiodically discharging said condenser through-an oscillation circuit containing a blocking condenser and a spark gap, and extinguishing each spark after the first half oscillation or after the first train of oscillations of the discharge energy, the

spark gaps by periodically discharging said condensers 1n series over said spark gaps, extinguishing each spark after the first half oscillation or after the first train of oscilla-r tions of the discharge energy, feeling the charging current during the spark extinction solely to the charging condensers and,

maintaining said current at an approximately constant strength by said self-induction coils during the period b etween-successive spark discharges, so that by the vcombined effect of the spark extinction and the substantially constant strength of the charging current, the potential of the charging condensers, with any frequency of sparks, will be as much above the potential of the charging source at the moment of discharge as it is below after the discharge.

6. In an apparatus for producing high frequency oscillations, the combination of a source of direct current, an oscillation circuit including a spark gap, a charging condenser connected'to said source of direct current and to said oscillation circuit, means charging condenser over said spark gap and I extinguishing eaeh spark after the first half oscillation or after the first train of oscillations of the discharge energy, the arrangenient being such that during the spark extinction the charging current feeds solely to the charging condenser and is maintained at an approximately constant strength during the period between the successive spark discharges whereby by the combined effect of the spark extinction and by the substantially constant strength of the charging current, the potential of the charging condensers with any frequency of sparks will be as much above the potential of the charg ing source at the moment of discharge as it is below after the discharge.

7. In apparatus for producing highfrequeney oscillations, the combination of a source of direct current, an oscillation circuit including a spark gap and a blocking condenser, a charging condenser connected to said source of direct current and to said oscillation circuit, self-induction coils in the co mections between said charging condenser and. source of current, said coils being of sufficient size to maintain the current of the supply circuit constant for the length of the interval between two oscillation impulses, and means for periodically discharging said discharging condenser over said spark gap and blocking condenser and extinguishing each spark after the first half oscillation or after the first train of oscillations of the discharge energy, whereby during the spark extinction the charging current feeds solely to the charging condenser and is maintained at an approximately constant strength during the period between the successive spark discharges by said selfinduction in the supply circuit so that by the combined effect of the spark extinction and the substantially constant strength of the charging current, the potential of the charging condenser, with any frequency of sparks, will be as much above the potential of the charging source at the moment of discharge as it is below after the discharge.

8. In an apparatus for producing high frequency oscillations, the combination ofa source of direct current, an oscillation circuit including a quenched spark gap and a blocking condenser, a charging condenser connected to said source of direct current and to said oscillation circuit, inertia coils in the connections between said charging condenser and source of current, said coils being of such size as to maintain the strength of the. current of the supply circuit absolutely constant for the length of the interval between two oscillation impulses, and means for periodically discharging said charging condenser over said spark gap andextinguishing each spark after the first half oscillation or after the firsttrain of oscillations of the discharge energy, whereby during the spark extinction the charging current feeds solely the charging eondenser and is mai ained at an approximately constant st ,ength during the period between successive spark discharges by Said inertia coils in the upply circuit so that by the combined effect of he spark extinction and the substantiall constant strength of the charging current the potential of the charging condenser, with any frequency of sparks, will be as much above the potential of the charging current at the moment of discharge as it is below after the discharge.

9. In an apparatus for producing electric oscillations of high frequency, the combination of a source of current, a plurality of charging condensers connected in parallel to said source of current, an oscillation circuit connected with said charging condensers and including a blocking condenser, and means whereby the charging condensers may be discharged over the blocking condenser in series.

10. In an apparatus for producing electric'oscillations of high frequency,'the combination of a source of direct current, a plurality of charging condensers connected in parallel to said source of current, an oscillation circuit connected with said charging condensers and including a plurality of blocking condensers and spark gaps, and means whereby the charging condensers may be discharged over the blocking condensers and spark gaps in series.

EGBERT VON LEPEL.

Witnesses HENRY HASPER, WOLDEMAR HAUPT.

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