US781606A - Method of producing oscillatory currents. - Google Patents

Description

F AL am um l/toz 5 5' 1 414 Qlttomu QM Av W No. 781,606. i. ,PATENTED JAN. 31 1905. P. 0. HEWITT.

METHOD OF PRODUCING OSGILLATORY CURRBNTS.

APPLICATION FILED JULY 28, 1904.

Patented January 31, 1905.

UNITED STATES PATENT OFFICE.

PETER COOPER HEINITT, OF NEWV YORK, N. Y., ASSIGNOR TO COOPER HEWITT ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEIV YORK.

METHOD OF PRODUCING OSCILLATORY OURFIENTS.

SPECIFICATION forming part of Letters Patent No. 781,606, dated. January 31, 1905'. Original application filed February 9, 1903, Serial No. 142A51. Divided and this application filed July 23, 1904. Serial No. 218,479.

f0 all whom/ it may concern:

Be it known that I, PETER CooPiiR HEWITT, acitizen of the United States, and a resident of New York, county of New York, State of New York, have invented certain new and useful Improvements. in Methods of Producing Oscillatory Currents, of which the following is a specification. I

My invention relates to means for producing oscillatory electric currents of the general character employed in wireless telegraphy and also the radiation of energy thereby.

The invention is useful notonly for wireless telegraphy, but for other purposes. The oscillatory electrical currents of the kind referred to are commonly produced'by the discharge through an inductance of a charged condenser or capacity. The condenser discharge may be oscillatory if R2 is less than I L/ C, R being the resistance, L the inductance, and C the capacity. Where R2 is greater than 4 L, C, no oscillations take place. In practice all losses,including those d no to friction, induction, or radiation may, be included or reckoned as resistances. WVher'e oscillatory, the oscillations are in the natural period of the system as determined by the inductance capacity and resistance thereof, and the persistence of the oscillations or wave trains may be increased by minimizing the incidental fr ctional or otherlosses. Losses by radiation are of course inevitable. since in wireless telegraphy particu larly radiation represents the useful work to be performed. The internal frictional losses are detrimental and serve no useful purpose. Of these internal detrimental losses that which occurs at the spark-gap is of considerable importance. As ordinarily constructed all of the energy stored in the condenser is forced to cross the spark-gap twice, first in one direction and then in the other, for each complete wave or oscillation; and the object of my invention is to provide an auxiliary oscillator designed, proportioned, and arranged in such relation to the prime oscillator that the said prime oscillator will transfer to said auxiliary oscillator all, or at least a large fraction, of the energy of the prime discharge. The function of the auxiliary oscillator is to elasticallyabsorb said energy in such manner that it will oscillate persistently in its own natural period. The auxiliary oscillator has no spark-gap, and

oscillations therein once initiated will persist much longer than is the case where all the energy must cross a spark-gap twice for each complete oscillation. It is obvious that where a unidirectional discharge device or arrange ment like my vapor-lamp interrupter is substituted for the spark-gap the advantages of an auxiliary oscillator such as described are very great, the auxiliary oscillator being excited or charged quite as eificiently by a single unidirectional discharge as it would be by several oscillations.

The invention can best be understood by reference to the accompanying drawings, in Which Figure 1 is a diagram showing one organization of apparatus suited to carrying out the invention, and Figs. 2 and 3 illustrate modifications. Fig. 4 illustrates a special form of discharge device or spark-gap.

Referring to the drawings, 1 represents a transformer whose primary 2 is supplied with alternating currents ofa suitable periodsay sixty cycles. have the required potential, which may be in the neighborhood of, say, ten thousand or twenty thousand volts. The terminals of the secondary coil 3 are connected 'to the conductors 4 and 5, which constitute a portion of the secondary circuit. In Fig. 1 the circuit 3 4 '5 is completed through the inductance l0 and condenser 11, which are in series with the transformer-Winding and in parallel with each other. This is a well-known form of resonant circuit, sometimes called an "antiresonant circuit because of its peculiar properties. It is Iiot necessary to enter into elaborate technical description of the internal reactions of such a circuit in order to understand my present invention. It issufiicient to say that the inductance branch 10 and the condenser branch 11 together form acircuit resonant to one critical frequency and that when the current im pressed thereon through the conductors t 5 is condenser 9 and spark-gap 8.

of that particular frequency the opposite re-. actances of 10 and 11 balance each other in such manner as to produce a relatively great current-flow in the circuit 10 11. Under these conditions the current in 4 5 is ata minimum. The whole circuit 4, 5. 10, 1-1 is called antiresonant because the conditions in 4 5 are quite the opposite to what they would be if the inductance 10 and condenser 11 were in series with each other, as well as in series with 4 5, instead of being, as they are, in parallel with each other and in series with 4 5. In such an antiresonant circuit the branches 1O 11 together offer a great impedance to the passage therethrough of impressed currents of the one critical frequency to which they are resonant, whereas they offer much less impedance to impressed currents of all other frequencies. By way of illustration, suppose the inductance 10 and condenser 11 of Fig. 1 adjusted so as to be resonant to a frequency of sixty cycles and the spark gap closed. Then if the generator be run at such a speed as to give a frequency of twenty-five cycles practically all-of the current may be made to flow through the inductance 10, restrained only by a relatively small impedance of said inductance, and Very little of it will flow through the condenser 11, which offers a comparatively great impedance to currents of such low frequency. ()n the other hand, if the generator be rotated at a speed very much higher 4 say one hundred and twenty-five cycles-the inductance 10 will offer a relatively great impedance to such high frequency, whereas for said frequency the condenser 11 will offer a relatively low impedance, and most of the current will therefore flow through the condenser branch. If, however, the generator be rotated at a speed which will give a frequency of exactly sixty cycles, (the frequency to which the circuit 10 11 is adjusted for resonance,) then approximately equal energies may pass in 10 and -11. The resonant rise of current therein will be great, and comparatively little current will How in 4 5. his opposition of'10 and 11 to the passage of currents of a particular critical frequency and the resonant rise of current of such frequencyin said branches 10 and 11 are utilized in a very eflicient manner in the systems shown in Figs. 1 and 2, which figures will be recognized as embodying an oscillating circuit 4 5, with the usual The branches 10 and 11 are not made resonant to the sixtycycle frequency of the generator, but to the natural oscillatory period or frequency of the circuit 9, 4, 6, 7, 10, 5. v This is accomplished by making the condenser 1 1 approximately the same capacity as the condenser9 and then adjusting the same until the maximum resonance effect is obtained. With such systems if wireless telegraphy is the intended purpose the natural period of discharge of the circuit may be, for example, one million per dred-and-twentieth of a second.

second, in which case the frequency to which the branches 1O 11 are resonant and to which they oifcr great impedance and in response to which they develop great resonant rise of current is the same frequency million per second.

The operation of this system of circuits involving my invention may be described somewhat as follows: The alternating current induced in the secondary 3 beingof a frequency of sixty cycles, the time period of a half cycle or pulsation in one direction is one one-hun- It is evident, therefore, that the rate of charge of the condenser 9 from the secondary 3 is enormously slower than the rate of discharge of said condenser through the circuit 4, 8, 10, 11, 5. It is so slow, in fact, that the potential rises uniformly through the circuit on each side of the spark-gap 8 and one of the plates of the namely, one

condenser 9 without the accumulation of any appreciable drop across the condenser 11 or across the coil 10. This slow rise of voltage continues until the spark-gap or equivalent breaks. down, permitting abrupt discharge of the condenser 9. As has been explained, the system is so constructed that the natural or free discharge period of the condenser 9 across the spark-gap 8 is substantially the same as the period to which the circuit 1O 11 is resonant. The equilibrium of the circuit 1011 being thus abruptly disturbed in accordance with its own time period absorbs substantially all of the energy of the discharge of the condenser 9. The oscillatory disturbance being thus initiated, the inductance 10 and the capacity 11 continue discharging the one into the other until the energy is dissipated in radiation, frictional, or similar losses. This probable operation of the system may be made evident by considering that any circuit containing a condenser and a coil is set in oscillation when its electrical equilibrium is disturbed either by sudden charge or sudden discharge, the disturbed, equilibrium being restored by oscillatory reactions between the condenser and the coil, which continue until the energy of the disturbance has been absorbed or dissipated. The'circuit 1O 11 is itself a closed circuit containing a condenser and a coil capable of such equilibrium disturbance by sudden charge or discharge, and when thus disturbed equilibrium is again restored. From the above it will be evident that after the first violent discharge of the condenser 9 practically all of the energy is absorbed in the circuit 10 11 and oscillates therein after the manner described and that thus the invention secures persistent oscillations which are not subject to the great losses incident to forcing a discharge-path for the energy across a spark-gap twice for each complete oscillation or double vibration. The

spark-gap loss is practically limited to a single discharge in one direction following each charge of the condenser 9.

vergy.

These prime discharges of the condenser 9 across the sparkgap 8 may be made to succeed each other with the greatest possible rapidity. Indeed,

it would be desirable if they could be made to follow each other so closely as to supply fresh energy to oscillatory circuit 10 11 before the oscillations caused therein by the preceding spark had been damped out.

The persistently-oscillatory circuit 1011 may be utilized as a source of high-frequency oscillatory energy in any desired way. For purposes of Wireless telegraphy, for which it is more particularly designed, the ground connection is led from one terminal of the coil 10 and the aerial from the other terminal of said coil. As shown, additional coils or windings 12 are provided in inductive rela tion with the windings of the coil 10, the two coils together constituting what is known as an autotransformer or autoconverter. An additional coil 15 may be added either as a part of the winding 12 or as a separate coil, and this may be utilized for adjusting the emitting- wire 13, 10, 12, 15, 16 so that its natural period of oscillation will be the same as that of the circuit 9, 4, 8, 10, 5. This condition may be approximated by making the entire length of the wire and windings 13, 10, 12, 15 16 of a physical length slightly less than onequarter ofthe length in either of a wave having a time period equal to the time'period of the oscillations in 9, 4, 8, 10, 5, or it may be an odd multiple of such quarter-wave length. Synchronism of the circuits may then be perfected by adjusting the inductance of 15 until the maximum effect is observed.

[it will be seen that the broad principle of the above arrangement involves elastic ab sorption of the condenser discharge in an auxiliary part of the system, thereby decreasing the potential available at the terminals of the spark-gap or equivalent discharge device to such an extent that after the first sparkthe potential at that point will'not again reach the critical value necessary to disrupt the dielectric. As has been explained, even as arranged in Fig. 1 there will be some tendency to activity of the circuit 9, 1, 6, 5 even after the first spark; butthis may be still further decreased by making the connected open circuit 13,10, 12,15, 16 a good oscillator, which of course means a circuit of low resistance and capable of holding in the form of electrification or magnetization a considerable amount of en- Of course all energy passing into this circuit 13, 12, 15, 16, whether radiated from 16 or retained in an oscillatory state, represents the load on the primary circuit 10 11 and decreases the electromotive force available to sustain unnecessary activity of the condensercircuit 9, 4, 8, 5. The amount of energy that can be held in 13, 12, 15, 16 may be greatly increased by making the electrical length of said circuit an odd multiple (as, say, three fourths) of the wave length, though for wireless-telegraphy purposes it is usually preferable to make this length one-fourth rather than three-fourths. When the emitting-circuit is made three-fourths of a wave length, the coils 10, 12, and 15 may be so proportioned that together their capacity and inductance would give a time period to the-oscillation equal to one-quarter of a wave length, 10 12 being in inductive relation. Then they will .form a true resonant circuit and oscillate freely. The ground connection 13 10 will be made equal to a second one-fourth wave length and the emitter 16 equal to athird one-fourth wave length, making three-fourths all together, though an equivalent arrangement would be to' make 15 16 together a quarter of a wave length.

Another way of making the emitting-circuit a persistent oscillator capable of elastically absorbing and holding in the form of electrification or magnetization a sufficient amount properly adjusting the lengths of 20. 17, 21 the oscillation thereof may be made to corre' spond and synchronize with those of the rest ofthe system, particularly if 10 and 20 are so wound as to have considerable mutual capac ity between the turns. The precise adjustment is best found by trial. With such parallel inductance-coils used in connection with a very large capacity-radiator, such as shown at 16, the emitting system 13,21,17,20, 10,12, 16 may be made to absorb a'suificiently large fraction of the energy of the discharge of the prime condensers 9 9 as to render the spark discharged non-oscillatory This arrangement, like the others, is particularly useful in connection with the unidirectional vapor-lamp discharge device, and also with the spark-gap it IS usefuhforeven ifthe proportions are not such as 'to prevent some oscillations across the spark-gap they wrllnevertheless store up a considerable fraction of theenergy, and

thus decrease spark-gap losses, even though not preventing them altogether. The action.

of inductance 20 may beaccounted forin several Ways. By being in parallel with inductance 10 it enables the adjustment of the inductance of the circuit without touching other parts of the apparatus by making the inductance10 equivalent to a smaller inductance,

inasmuch as the two are in parallel. Further,

the loss from 20 will be very slight and will again react on the circuit, as its energy is not absorbed by the circuit at the same time as the inductance 10, inasmuch as 20 is out of inductive relation with the remaining portions of the circuit, although it may aid in maintaining suitable phase relations.

It will be noted that one skilled in the art will be able to practically employ the inductance 20 whatever may be its theory of action, because the proper proportion thereof can best be determined by adjusting the same until the maximum effect is observed.

In Fig. 2 a modified arrangement is shown, wherein the spark-gap 8 is located in a position corresponding to that of the condenser 9 in Fig. 1, and the condenser 9 is located in a position corresponding to that occupied by the spark-gap in said Fig. 1. A second condenser, 9", is placed symmetrically with the condenser 9. The location and function of the inductance 10 and condenser 11 is the same as in Fig. 1, and, as in said figure,they form a closed circuit havingthe same natural period as the circuit 9, 10, 9 7, 8, 6. In Fig. 2 the secondary winding in inductive relation to the primary 10 is made separate from the latter after the manner of the more usual or conventional form of transformer construction, although the arrangement employed in Fig. 1 may be employed, if desired. In this system the emitting- circuit 13, 12, 15, 16 is adjusted to synchronism with the oscillatory circuit 10 11, as in the arrangement of Fig. 1.

As there is difficulty in practice in adjusting the primary circuit to be exactly in tune with the secondary circuit, I'usually prefer to so adjust the circuits that the primary oscillations shall tend to be shorter rather than longer than those of the secondary circuit. Where the secondary circuit is freely oscillatory, it tends to hold and bring the primary circuit into its own period. The tendency will then be for the secondary circuit to maintain its own period and to cause the primary circuit to adjust itself to that period, causing it to deliver its energy at the proper times. By having the secondary circuit oscillatory and approximately in tune with the period of the primary circuit I am enabled to accumu- ,late an enormous amount of oscillating electrical energy in the secondary or discharge circuit when the secondary circuit is of such capacity and inductance as to give the maximum resonant rise at its terminal, and therefore to secure a corresponding radiation of energy from the emitting-circuit.

It will be understood that various forms of spark-gaps or discharge devices 8 may be employed. In practice I have found a device of the general character of the gas or vapor electric apparatus described in certain patents issued to me on the 17th day of September, 1901, when adapted to this purpose may well serve the purpose.

In Fig. 4 I have indicated a discharge device 8, comprising an electrode 6*, which may be of any suitable material-such, for instance, as mercury-and an electrode 7, here represented as being of mercury, both inclosed in a suitable air-tight vessel previously exhausted and containing a rarefied atmosphere of mercury. I have found that such a device while opposing a very high initial resistance will permit a discharge under the influence of a high difference of potential, and the resistance between the electrodes 6 and 7 will almost instantly fall to a very low resistance upon the passage of a spark, thereby quickly draining the circuit, thus creating a v ery sharp and effective oscillation, and, further, the high initialresistance will reassert itself after the discharge of the condenser, thus necessitating its recharge.

This application is a division of my application filed February 9, 1903, Serial No. 1 12, 151.

I claim as my invention 1. The method of producing oscillatory effects in an emitting-circuit of a wireless-telegraph system, which consists in generating electric currents, producing primary oscillations therefrom in an oscillatory circuit including a discharge device, reinforcing such oscillations by subsidiary intervening synchronous oscillations independently of the discharge device.

2. The method of obviating oscillations in a primary circuit, which consists in absorbing energy from the primary circuit by an oscillatory secondary circuit and dissipating the energy by means of oscillations of'the secondary.

Signed at New York, in the county of New York and State of New York, this 21th day of June, A. D. 190 1.

PETER COOPER HEIVITT.

Witnesses:

WM. H. CAPEL, GEORGE H. STOOKBRIDGE.

ICC

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