US1514751A - Vacuum-tube oscillator chronometer - Google Patents

Description

Nov. 11 1924. 1,514,751

- P. l. WOLD I VACUUM TUBE OSCILLATOR CHRONOMETER /nven for:

Pefer' Wo/d. "X W- A772 Patented Nov. 11, 1924.

UNITED STATES.

1,514,751 PATENT OFFICE.

PETER IRVING WOLD, OF EAST ORAN GE, NEW JERSEY, ASSIGNOR WESTERN ELEC- TRIC COKPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

VACUUM-TUBE OSCILLATOR CHRONOMETIDEL.

Application filed August 24, 1920. Serial No. 405,844.

To all whom it may concern."

Be it known that I, PETER IRVING won), a citizen of the United States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Vacuum-Tube Oscillator Chronometers, of which the fol lowingis a full, clear, concise, and exact descri tion. J

T is invention relates to .a vacuum tube oscillator chronometer and more articularly to a method of increasing t e constancy of certain operating. characteristics 'of such apparatus.

An object of the invention is to utilize an oscillation generator of the type in which the frequency of oscillation is determined by the constants of a freely oscillating circuit, to performmechanical work.

Another object of the invention is to provide a chronometric system of exceptional constancy and accuracy by the ex edient of usi as the actuating means for t e time controlling element an oscillation generator of the type in which the frequency 1s set by the constants of a freely oscillating circuit.

A further object of the invention is to provide an oscillator chronometer of the above mentioned type having a high degree of constancy.

The inventor has discovered that the comparative constancy of the oscillation genera: tor of the type disclosed, which 1S distinuished broadly from other types by the feature that its frequency is determined by the'constants of an oscillation circuit associated therewith, fits such a. generator for use as the driving means in a chronometric system, and that an accuracy and constancy heretofore unattained could be made possible by such use.

The ty of generator proposed has become familiar through use as a generator of high frequency currents in radio transmission and this type is adaptable to the use proposed, that is, in a chronom'etric system, in any one of its generic forms. If the 1nput and output circuits of an amplifylng or repeating device are related 1n such a manner that energy is fed back from the-outut to the input circuit, it is possible to develop oscillations if the physical and electrical constants of the. amplifier or repeater and the electrical constants of the associated circuits are pro rly proportioned. A coupling which may e inductive or electrostatic may be used for this pur ose and in the case of vacuum tube ampli ers, this may. even be effected throughthe internal capacity between the elements or electrodes of the tube itself. It is desirable for certain purposes that such vacuum tube circuits include an oscillatory tuned circuit. Such a tuned circuit may be connected in the input or output circuit or in common in both of thesecircuits. If the tuned circuit comprises the principal portion of the impedance elements in the tube circuits it may be made to substantially determine the frequency of the oscillations generated. It is therefore possible to make the generated frequencies substantially as desired by properly adjusting the constants of this circurt.

The inherent advantage of the use of this type of actuating means for the time controlling elements are at once apparent when it is noted that there is an entire absence of moving structure and that the frequency depends on the value of the electrical constants of inductance and capacity, which quantities are readily capable of adjustment for different frequencies, and with a given frequency, are or can be made remarkably stable and invariable under the conditions imposed by use in this system.

Oscillation generators of the type describedhave been made to operate efficiently at a frequency as low as one cycle in ten seconds and as high as a hundred million cycles a second. It has been difiicult to design an oscillator at the lowest frequencies having an approximately pure sine Wave form since it is ordinarily necessary when attaining oscillations of frequencies less. than one thousand or two thousand per second to use inductances containing iron, although it has been shown in Scriven Patent 1,354,657 November 2, 1920, how this may beaccomplished by utilizing the difference frequencies resulting from the interaction of two sets of oscillations of higher frequency. In the present invention the employment of iron core inductances is not only not attended by an disadvantages, but even has a positive a vantage in that it .makes possible a more efficient use of the device for the performance of mechanical work.

' pli'ng The invention in its second aspect relates to the means suggested above for increasing the constancy of frequency of the generator. As is well known, the equation which expresses the natural frequency of a freely oscillating circuit contains the product L C, which letters designate respectively the nductance and capacity of the oscillating circuit, these being the principal variable quantities concerned. If this product can be kept constant, the frequency of the circuit will be constant.

That the product may be constant, under certain conditions, even though the component quantities L and C are Vt11}'111g, lS obvious. It is the essence of this invention to so choose the inductance and capacity containing elements that they vary, under similar conditions of physical change, in an opposite sense so that their product remains substantially constant.

For a more detailed disclosure of the vention, reference is made to the description which follows, taken in connection with the accompanying drawing, Figure 1 of which shows, in diagrammatic form, one embodiment of the invention; Fig. 2 shows an alternative arrangement of the mechanical elements actuated by the oscillator;

Fig. 3 shows a method of interposi ng an electromagnetic relay between the oscillator and the actuated mechanism; and

Fig. 1 shows an arrangement similar to Fig. 3 but having the electromagnetic relay replaced by a vacuum tube amplifier.

In Fig. 1 there is shown a circuit arrange-- ment of an oscillation generator, such as is disclosed in Hartley Patent 1,356,763, October 26, 1920, although other types may equally well be used, the essential feature being a freely oscillating circuit and a conbetween the grid and the space current circuits of the generator. A highly evacuated tube 1 contains the usual hot filament cathode 2, plate electrode 4. and impedance controlling grid 3. The filament is energized by a direct current source 5 in circuit with which is the filament resistance (3. A two- part inductance 7, 7 is connected to a variable condenser 8 to form a closed tuned circuit, one terminal of the condenser 8 being connected through space current source 9 to plate 4, while the other terminal is connected to grid 3 preferably through a source 10 which serves to keep the grid at a potential which is negative relative to that of the cathode. An intermediate point of the two part inductance is connected to the cathode. A variable resistance 11 may be inserted in the space current circuit in order to provide means for slight adjustment of oscillation frequency. Altho in general the constants of the freely oscillating circuit determine the frequency very slight changes may be effected by means such, for example, as the dbOYc.

The inductances 7 and 7 may be inductively related but this is not essential. The tube 1 and its associated circuits as described constitute an oscillation generator which serves to produce oscillations of a frequency determined by the constants of the closed tuned circuit. In certain applications of this generator, as for example, in chronometric applications where such a low frequency as one cycle per second may be desirable the inductances 7 and 7 would ordinarily have iron cores. The presence of the magnetic core results in the introduction of higher frequency harmonics in the generated wave, and the wave form is accordingly of insufficient purity for certain other applications which require higher frequency, but the constancy of the frequency is not affected therebyas long as the product L C does not change and, since the'frequency alone enters as an element in the equation of efficiency of the arrangement of this invention, the presence of the iron does not affect the efficient operation of the device. It does, in fact, make possible an efficient use of the output current in operating the mechanical movement shown. This mechanical movement is shown as an element of a clock; the coils 7 and 7 with their common iron core functioning, with the armature 13 and the toothed wheel 12 as an escapement device through which the stored energy of the coil spring 14 may be applied to actuate the hands of the clock 31 through a train of mechanical movements according to principles well known in the art of horology the spring 15 serves to retract the armature 13 when the magnetic pull of the coils 7 and 7 is reduced to zero. Although the attractive power of an electromagnet depends greatly on the presence of a magnetic core, as is well known, such core is not essential and this invention should be understood to embrace the use of an oscillation generator of any frequency whatever and with or without magnetic'parts, to perform mechanical work. In Fig. 2 the coils 7 and 7 with the common iron core function with the armature 13 as a reciprocating motor to impart by means of lever 16 and pawls 17 and 18 a step-by-step motion to the toothed wheel 12 and therethrough to the hands of the clock. In this IOU arrangement the spring 1& shown in Fig. I

shows an arrangement of the invention to provide for this case. The armature 13 when attracted to the electromagnet pole causes a circuit comprising a battery 22 and an electromagnet 23 to be closed through contacts 20 and 2]. thus energizing the electromagnet 23 and attracting the armature 24:. The armature 24 and lever 25 take the place of the armature 13 and lever 16 of Fig. 2 and may be adapted to impart a step-by-step mo tion to a clock mechanism in the manner there shown. The relay means in the above is essentially an amplifying means intermediate between the time controlling circuit of the invention and the mechanical element of the stepping mechanism. In place of the amplifying means as above a vacuum tube amplifier may equally well be used to erform this function and its application in a system such as that shown is illustrated in Fig. 4. Coil 26 is inductively coupled to the coils 7 and 7 and serves to translate the current variations therein to potential variations on the grid of the vacuum tube 27. The plate circuit of the vacuum tube contains the electromagnet 23, and energizing battery 28 which is connected to the filament of the vacuum tube through a choke coil 29 and a condenser 30, which serves to prevent the passage of the battery current through the windings of the electromagnet 23. Armature 24 and lever 25 are associated with electroma net 23 as shown also in Fig. 3 and may be adapted to actuate the hands of the clock in the manner described in connection therewith. The current oscillations in coils 7 and 7 are reproduced by the action of the vacuum tube 27 with am lified energy in the electromagnet 23"and tliereby caused to impart to the armature 24 and lever 25 a periodic motion which is transmitted to the clock mechanism as already described.

It remains to describe the means of the invention to insure a high degree of constancy of the system disclosed. As has been pointed out, the accuracy of this arrangement as a time device depends chiefly on the constancy of the product of L and C. These ordinals are being used to designate respectively the inductances 7 and 7 considered as one inductance, and capacitance 8. A higher constancy than would ordinarily be expected can be obtained by having the capacity and inductance change in opposite directions for any given physical change. The chief changes to be considered are temperature changes and the effects of ageing. The method of this invention should effectively compensate for these changes.

In the case of iron core inductance elements, which .would ordinarily be used in chronometric systems, the permeability, and therefore the inductance, decreases slightly as the temperature increases. In other words, an iron core inductance has a negative temperature coefficient. A resistance shunted by a capacity is equivalent in effect in a circuit to a negative inductance having avalue given by the equation L:CR in which R designates the resistance and C the shunting capacity. Accordingly, the temperature coeflicient of an inductance element which has associated with it a resistance and a shunt capacity will be artially determined by the temperature coefficient of said resistance and capacity and it is possible to produce inductances having either a negative or a positive temperature coefficient. An inductance having a positive temperature coefficient will increase with increase of temperature, the converse being true in the case of an inductance having a negative temperature COGffiCIlBIlt.

In regard to condensers, one of the most constant and reliable forms is the dry stack mica condenser. These have a positive temperature coefficient which may be in the neighborhood of a .00007 per degrees Farrenheit and the coeflicient is fairly constant over a wide range. The coefiicient will vary considerably with different condensers or different types of condensers and some may even have a negative coefficient. Taking into account the possibility of using other dielectric materials, however, it is possible to obtain acondenser having any temperture coefficient within the limits of variation between the reactive constants of different inductance elements, still further it would not be very difficult to obtain one which would just neutralize that of the coil. In the above the meanin s of positive and negative temperature coe cients are readily derivable by analogy from the meanings as applied to inductances.

As regards the effect of ageing, it has been found that generally mica condensers increase slightly in capacity with age, while inductances decrease slightly so that the changes may be made to offset each other, thus compensating for changes that occur over a long interval of time.

Since condensers can readily be obtained which have either a positive or a negative temperature coefficient, as has been pointed out, it is clear that a condenser may be selected which will compensate for the negative or positive temperature coefficient of an inductance. Accordingly, the method proposed is equally applicable for an oscillation generator-of all frequencies, or for any tuned circuit in which it is desired that the frequency should be automatically regulated.

It should be noted that the actuation of the armature 13 necessarily involves a change in the reluctance of the magnetic circuit of the coils with attendantvariation in inductance and oscillation frequency, and it might seem that there would thereby be introduced an element of uncertainty that would nega- 6 wave form without affecting its periodicity.

In other words, the frequency of this reluctance variation is the same as that of the frequency of'oscillation, and is therefore without effect thereon.

10 Although the, frequency is dependent al most wholly on the value of L and C in the oscillatory circuit, there are other variable factors in such a vacuum tube oscillator. For example during its life the internal impedance of the tube would change slightly, in

general increasing with time. Such a change could be taken care of with more or less accuracy by having a resistance such as 11 in series with the plate which could be changed gradually with time, the clock. mechanism operating to bring about this change or the z change may be accomplished by hand if de sired at definite intervals, the change, of course, being in the reverse direction to the change within the tube. For extreme accuracy, it would, of course, be necessary to attain as high a constancv' as possible for other factors such as the filament heating current and the plate voltage, but it should be noted that the frequency of the oscillator is only very slightly affected by changes in these factors even as compared with the effect of the factors already mentioned, which are themselves very slight.

Although the inventlon has been disclosed or applied to a specific mechanical system it may equally be used, as has been suggested, to perform mechanical work in many other applications as, for example, to actuate a j relay contact. The invention should accordingly not be considered as so limited but only by the breadth of the appended claims. What is claimed is: p 1. The combination of a mechanically driven means and a driving means therefor,-

said last mentioned means comprising an oscillation generator of that type in which the frequency is determined by the natural.

frequency of a freely oscillating circuit.

2. The combination of a mechanically driven means and a driving means therefor {{comprising an oscillation generator of the electrical discharge type, the frequency of which is determined by the natural frequency 0 of a freely oscillating circuit forming a part thereof.

3. In combination, a mechanically driven means and a driving means therefor comprising an oscillation generator of the vacuum 5 tube type, the frequency of which is determined by the natural frequency of a freely oscillating circuit.

4. The method of actuating a driven means at a uniform speed, which comprises actuating said vmeans by an oscillation generator of the vacuum tube type, the frequency of which is determined by the natural frequency of a freely oscillating circuit.

5. The method ofregulation and actuation of a driven means which comprises the steps of actuating said means' by an oscillation generator of the vacuum tube type and regu lating the speed thereof b adjusting the natural frequency of the osci latory circuit of said oscillation generator.

6. In a timing device, in combination, a time controlling element and an actuating means therefor comprising an oscillation gen erator of the vacuum tube type, the frequency of which is varied by varying the natural frequency of its associated oscillatory circuit. r

7. In a timing device, in combination, a time controlling element, a mechanical actuating means therefor and an oscillation generator of the vacuum tube type having a tuned oscillatory circuit associated therewlth, the natural frequency of which determines the frequency of said oscillation generator, the inductance coils of said tuned circuit being so related to said mechanical actuating means thatsaid means is actuated in accordance with the frequency of the current of said inductance.

8. The method of increasing the constancy of an oscillatory circuit which consists in selecting inductance and capacity elements of said circuits of such types respectively that their constants change in opposite directions for a given physical change whereby the product of inductance and capacity is kept substantially constant.

9. The method of increasing the constancy of frequency of an oscillation generator which consists in combining in the oscillatory circuit thereof, inductance and capacity elements having oppositely varying characteristics under given physical changes. a

10. The combination as recited in claim 7, in which the inductance and capacity elements in said oscillatory circuit are of such types that their respective constants vary in opposite directions under given physical changes.

11. The method as recited in claim 4, which includes the additional step of choosing inductance and capacity elements having such characteristics that their variations under the given physical changes mutually compensate for each other.

12. A tuned circuit comprising inductance and capacity elements having oppositely varying characteristics under given physical conditions whereby these variations mutually com nsate for each other.

13. n oscillator comprising a. three element thermionic discharge device associated with a tuned circuit of the type set forth in claim 12. v

1-1. A mechanism. an electrical oscillating device having a tuned circuit for determining the frequency of its oscillations and means whereby said electrical device drives said mechanism.

15. In combination, a driven means and a driving means thcrel,or. said dri ring means comprising a frequency determining circuit having inductive and capacitive elements, said elements having oppositely varying characteristics under given physical conditions whereby these variations mutually compensate for each other.

16. An electrical system comprising a circnit including a plurality of impedance elements, said elements having impedanccs of opposite signs and means for causing the effect on sald circuit of any variation in the characteristics of one element to be com-' pensated by a (JOI'I'PSPOHCllIlg variation in the characteristics of another element having impedance of the opposite sign.

17. In combination, an oscillation generator of that type in Which the frequency is determined by the natural frequency of a freely oscillating circuit and a mechani- 'enerator of the vacuum tube type having a tuned oscillatm'y circuit associated therewith, the natural frequein'y of which determines the frequency of said generator. the inductance coil of said oscillator circuit being so related to said mechanical actuating means that the operating energy therefor is derived from said inductance coil.

In witness whereof, I hereunto subscribe my name this 18 day of August A. D., 1920.

PETER IRVING Won).

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