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Oct. 30, 1923. 1,472,583 W Oct. 30, 1923. 1,472,583 W. G. CADY . METHOD OF MAINTAINING ELECTRIC CURRENTS OF CONSTANT FREQUENCY Filed May 28. 1921 Patented Oct. 30, 1923. 1,472,583 UNITED STATES PATENT OFFICE, WALTER GUYTON CADY, OF MIDDLETowN, connECTICUT. METHOD OF MAINTAINING ELECTRIC CURRENTS OF CONSTANT FREQUENCY, To all whom it may concern:Application filed May 28, 1921. Serial No. 473,434. REISSUED Be it known that I, WALTER G. CADY, a tric resonator that I take advantage of for citizen of the United States of America, my present purpose are-first: that prop residing at Middletown, in the county of erty by virtue of which such a resonator, 5 Middlesex, State of Connecticut, have in whose vibrations are maintained by im vented certain new and useful Improve pulses; received from one electric circuit, ments in Method of Maintaining Electric may be used to transmit energy in the form B) Currents of Constant Frequency, of which of an alternating current into another cir the following is a full, clear, and exact de cuit; second, that property which it posses 0 scription. ses of modifying by its reactions the alter The invention which forms the subject nating current of a particular frequency or of my present application for Letters Patent frequencies flowing to it; and third, the fact that the effective capacity of the resonator andis an maintainingimprovement alternatingin the art ofcurrents producing of depends, in a manner which will more fully 5 constant frequency. It is well known that hereinafter appear, upon the frequency of heretofore the development of such currents the current in the circuit with which it may to any very high degree of precision has be connected. been unattainable by ordinary means and In the description and explanations of my great difficulty has been experienced in invention which follow, I have assumed the producing alternating currents of high and piezo-electric resonator to comprise a sin constant frequency and free from fluctua gle suitably prepared plate cut from a piezo tions due to disturbances in or near the electric crystal, and provided with the usual generating system. coatings, and utilizing the so-called trans The useful applications of my invention verse effect; but all statements made apply 25 are numerous. It may be employed in the equally to crystal preparations utilizing transmission or the reception of intelligence the longitudinal effect, and in general, to by means of high frequency currents, or it any mechanical vibrating system whatever, may be used for the testing and measure having suitable preparations of piezo-elec ment of such currents and of those in cir tric crystals for setting the system into vi 30 cuits associated therewith in all cases where bration and for utilizing its reactions. the frequency may be controlled by the The nature and purpose of the invention electrical constants of the system, and, in may be most readily comprehended by ref general, the invention is applicable to cur erence to the diagrams which I have used in rents of any frequency. - its explanation and which are exhibited in 35 In an application filed by me on Jan. 2S, the accompanying drawing. 1920, Serial No. 354,659, which has ma In this drawing:- 90 tured into Patent No. 1450,246, April 3, Fig. 1 is a diagram of the well known 1923. I have shown and described what I and universally recognized Armstrong os 40 have termed a piezo-electric resonator, cillating circuit, selected for illustrative pur which, in general, connprises a plate of piezo thereto:poses and showing my invention applied electric crystal with coatings on its opposite 95 face. Such a device has a natural period of Fig. 2 is a diagram of a three-stage am vibration, but when set in vibration by a plification system of well-known type, with source of alternating current connected to my invention applied, thereto; its coating, the amplitude of such vibrations Figs. 3 and 4 are other diagrams similar is very slight unless the frequency of the to Fig. 1 illustrating further modifications; alternating current approximates or equals and the natural or critical frequency, in which Figs. 5 and 6 are diagrams used in ex case the reaction of the deformed crystal plaining the principles of the invention. upon the circuit may be such as to practi The above described diagrams are illus cally choke back the alternating current. trative examples of various ways in which 05 In carrying out my present invention I uti a piezo-electric resonator may be employed lize this piezo-electric resonator in the man to maintain constant frequency in an os ner hereinafter to be described. cillatory electric circuit. It will be under S5 The special properties of the piezo-elec stood that they do not purport to show the only possible arrangements for securing 10 1472,583 and 16, which in turn alter the potential dif this result, and even as to those shown it will ference across the condenser 10, and hence be further understood that the illustrated the potential of the grid itself. arrangements may be modified in various Whether amplitude of the potential of the ways which, however, are obyious to those grid be thereby increased or diminished, de 70 skilled in the art and familiar with high pends upon which of the coatings 15 or 16 frequency apparatus and which will not al is connected to the grid, and upon the phase ter the essential part played by the piezo relations in the electric circuits and in the electric resonator. piezo-electric resonator itself. I shall assume, for purposes of this case, The phase of the vibration of the reso 10 that in each case the high frequency oscil. nator is modified by the fact that the po lations are produced through the agency of tential difference between the coatings 15 and the three electrode vacuum tube of the type 16 is influenced by the periodic voltage, al commonly used in radio-telegraphy, but I ready existing across the condenser 10. In may state that this is not essential and that order to effect the maximum reinforcement 80 5 the only requirement is that the source of of the oscillations, it may be advisable to energy shall be capable of generating cur control the phase of the vibrations of the rents of a frequency determined or con resonator. This may be done, for example, trolled by the electric constants of the oscil by giving the coil 8 a certain resistance, lating circuit, and when I use the term “coat or by inserting in series with the coil 8 an 85 ings' in referring to the resonator I mean other inductance and a resistance and con 20 either thin layers of metal on the crystal necting the coatings 13 and 14 in parallel itself, or ei plates in fixed relation to with such inductance and resistance instead the crystal, or, in general, any means where of in parallel with the coil 8. by an electric charge may be conducted to The frequency of the electric oscillations 00 2 5 the resonator in such a Way as to produce an as determined by the inductance of coil 7 electric field in the proper direction through and the capacity of the condenser 9, may be that of the fundamental vibration of the theWith crystal. the above understanding I now refer- piezo-electric resonator, or of one of its to Fig. 1. In this figure the numeral 1 harmonics. In any case, the two pairs of 95 30 represents the filament of the vacuum tube, 2 coatings on the resonator should have such is the filament battery, 3 a regulating re a size and position relatively to the ends of sistance, 4 the grid and 5 the anode of the the crystal plate, as to cause the greatest vacuum tube. The battery in the anode possible amplitude of vibration at the de circuit is designated by 6. These are the sired frequency. It is also of great impor 00 main essential parts of one of the numerous tance that the coating be so disposed, and types of circuit commonly used for the gen the plate so supported that the vibrations eration of high frequency oscillations, the shall be damped as little as possible. other elements being the coils 7 and 8 in the If, under the conditions assumed, while grid and anode circuits respectively, 9 a. the oscillations are being reinforced through 05 4. variable condenser in parallel with the coil. the vibrations of the piezo-electric resonator, 7 for the purpose of controlling the fre and at any of the frequencies mentioned quency of the oscillations, 10 the grid con above, the coupling between coils 7 and 8 be denser, and 11 the leak. All these are old. loosened to such a degree that the circuit, and well known. with the resonator absent, would just fail 10 4. The plate or crystal of the piezo-electric to oscillate, with the resonator present it resonator is indicated by 12 and this plate will be found that the oscillations still per has four coatings 13, 14, 15 and 16, the two sist; and, moreover, that a variation in the former being connected to the terminals of capacity of the condenser 9 over a certain the coil 8, the two latter to the grid circuit range has no appreciable effect upon the fre 5 O around the condenser 10. quency in the circuit. In other words, this The operation of the system is as follows: frequency is determined solely by the period When the coupling between the two coils 7 and 8 is of proper character or value, the ofas vibrationsa matter of of fact, the resonatoroften an advantageitself.
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