US1954319A - Glow tube piezo oscillator - Google Patents

Description

2 Sheets-Sheet l INVENTOR A.HUND

GLOW TUBE PI-EZO OSCILLATOR Filed May 26, 1932 .T T@l e M \m \w m @IWW .N NN 4 m\ w. d1 QN m E 777g N\Q\\ @N du@ FQ August Hund April l0, 1934.

April l0, 1934. A. HUND' 1,954,319l

GLOW TUBE PIEZO OSCILLATOR Filed May 26. 1952 2 sheets-sheet 2 INVENTCR August Hund ras Patented Apr. 10, 1934 UNITED STATES` PATENT OFFICE` 1,954,319 GLOW TUBE PIEZO OSCILLATR tion of Delaware Application May 26, 1932, SerialNo. 613,710

3 Claims.

This invention relates to electrical oscillator systems and more particularly to oscillator circuits in which glow discharge tubes having no filament excitation may be utilized for sustaining i oscillations and in which a piezo electric element may be employed to fix the frequency.

An object of my invention is to provide a system for which a fllamentless tube is found to be suitable.

Another object of my invention is to so arrange the elements of the oscillator system in relation to one another that a stable and otherwise dependable source of oscillations may be obtained and wherein elements may be uised which, because of their structural characteristics have a relatively long life.

Another object is to make practical use of my discovery thatby the application of suitable voltages for excitation of the several` electrodes of a glow discharge tube of the class herein described, it becomes' more efficient both for generating oscillations and for amplification when a secondary glow is set up in the neighborhood of the Work circuit anodeas distinguished from the primary glow which heretofore it has been considered necessary to confine to the region of the gap between the ionizing electrodes.

The objects and advantages of my invention will best be understood from the following description and by reference to the accompanying drawings in which:

Fig. 1 is a circuit diagram of a regenerative oscillator system employing a four-element gaseous discharge tube in association with a piezo electric crystal;

Fig. 2 is a circuit diagram of an alternative oscillator having a parallel connection in the output circuit for its anode feed and for its tank circuit; and

Fig. 3 is' a circuit diagram of an oscillator wherein the input and output circuits are inductively coupled in order to obtain the desired back-feed.

Referring to Fig. 1, I show a gaseous discharge tube 1 which comprises four electrodes 2, 3, 4 and 5, enveloped in a suitably attenuated gas or mixture of gases. The electrodes 2 and 3 are used for setting up an ionizing discharge, electrode 2 being a cathode and electrode 3 being an anode. In the arrangement shown, it appears to be somewhat advantageous to provide an anode 3 the activated area of Which is smaller than that of the ionizing cathode 2.

In suitably spaced relation to the ionizing electrodes I provide a Work anode 4 which may be (Cl. Z- 36) in the form oi' a simple Wire ring. Interposed between the anode 4 and the ionizing electrodes is a` control electrode 5, which may be in the form of of a wire helix. Some of the tubes which I have constructed for use in oscillator systemsV according to this invention have a structural arrangement of the electrodes as conventionally shown in Fig. 1; other tubes have these elec-- trodes either differently shaped or differently positioned with respect to one another, and, when proper voltages are applied to these electrodes, the performance of one type of tube com. pares favorably with that of another. In my copending application, Serial No. 590,561, iiled February 3, 1932, several types of glow discharge tubes are shown, any one of which might be employed in the oscillatory circuits of the herein described invention. In my copending application, Serial No. 603,284, filed April 5, 1932, I have shown still further modifications of glow discharge tubes suitable for use either as csaillators or for other purposes. It may be seen, therefore, that the particular structural arrangement of electrodes in accordance with the drawing is not essential so long as the respective electrodes have suitably activated areas disposed at suitable distances from one another to obtain the primary and secondary glow discharges referred to in the objects of this invention. Y

It will now be understood that many modifications of the tube structure are within the scope of the invention, which, however, is not so much directed to the details of the tube itself as to the combination of a suitable gaseous discharge tube of the class described with other elements of the oscillator circuit taken as a whole.

A direct current for setting up an ionization discharge between the electrodes 2 and 3 is derived from the source 6, the ionizing circuit including a protective resistance '7, and, if desired, 95 a current indicator 8. Another direct current source!) creates a suitable potential drop in the work circuit from the Work-anode 4 to the ionizing anode 3. The current emanating from the source 9 may, if desired, be measured by means 100 of the meter 19. In series between the battery 9 and the anode 4 is a tank circuit comprising an inductance 10 shunted by variable condenser 11.

If desired, the point of connection between the battery and the inductance may be varied by means of an adjustable contact 12 or a suitable tap associated with the inductance 10. This arrangement affords a desirable degree of ilexibility of adjustment to meet the regenerative requirements of the system, as will presently be no shown with respect to the manner of connecting the piezo electric crystal into the input circuit.

The piezo electric element 13 has a natural frequency characteristic suitable for the purposes required. It is connected on one side to a conductor leading to the control electrode and on the other side preferably to a switch blade 14 which may be set alternatively to connect the crystal through the contact 15 to the work circuit anode 4, or, if desired, to connect the piezo electric element to the ionizing anode 3. This may be done by shifting the switch blade 14 over to its Contact 16.

When the piezo electric element is across the control electrode 5 and the ionizing anode 3, the load in the external branch of the work anode 4 must be inductive for the chosen crystal frequency. This condition can be obtained by adjustment of the condenser 11 while the tap 12 along the coil l10 provides a means for increasing the power output. If, however, the crystal is between the control electrode 5 and the work circuit anode 4, the load in the external work anode branch must be capacitive and the arrangement shown provides the proper flexibility of adjustment to meet this condition.

The control electrode 5 may be biased, when that condition is found to be advantageous, the bias potential being obtained from the direct current source 17. The bias may be adjusted by means of a variable resistor 18, or, if desired, a suitable choke coil may be substituted for the resistance 18.

A condenser which shunts the battery 9 and the current indicator 19 serves to by-pass the generated alternating currents around these elements. Another condenser 21 may be used optionally as a by-pass around the battery 6 and current indicator 8, but the capacitance of this condenser must be such that no relaxation oscillations are set up in the ionizing circuit. Condenser 21 is usually preferred but is not always essential.

In the operation of my invention according to Fig. 1, primary ionization takes place between the electrodes 2 and 3. It will be understood that the tube construction, the kind of gas or mixture of gases and the gas pressure within the envelope of the tube are determining factors in controlling the extent both of the primary glow and the secondary glow as mentioned inthe objects of this invention.

The structural details of the tube itself are not, however, further discussed in this application because they constitute subject matter of my aforementioned copending applications, Serial No. 590,561 and Serial No. 603,284. It is sufficient here to state that the negative ions (mostly electrons) are projected through the openings in the control electrode 5 and toward the work anode 4. Due to the high positive potential applied to the anode 4, secondary ionization takes place in the space intervening between the electrodes 5 and 4. The current set up in the work anode branch is, therefore, greatly increased over that which would result in the absence of work-anode ionization, that is, secondary ionization. The result is that considerable power can be controlled by means of the variable potential applied to the control electrode. The circuit being regenerative, any transient currents occurring may excite the piezo electric crystal 13 and cause it to set up a fluctuating piezo electric voltage at one of its natural frequencies. This will accordingly change the potential of the control electrode.

Amplified variations of current in the output circuit including the work anode are thereby produced which are then fed back into the input circuit and in the final state sustained oscillations are set up in accordance with the chosen crystal frequency.

Referring to Fig. 2, a circuit is shown which employs a gaseous discharge tube l, similar to that shown and described in respect to Fig. 1. The ionizing electrodes 2 and 3 are similarly connected to the direct current source 6 through the protective resistance 7. The feature of this modification, however, is that parallel work-anode feed is employed. The direct current feed to the work-anode 4 is in parallel with the tank circuit 11-12. The direct current is kept out of the tank circuit by means of a stoppage condenser 23, positioned as shown. The control electrode 5 is biased by means of the direct current source 17 in series with a choke coil 24. If desired, however, a suitable resistance may be substituted for the element 24.

The piezo electric crystal 13 may be permanently connected across the leads to the work-anode 4 and to the control electrode 5, or, if desired, it may be connected across the control electrode 5 and ionization anode 3.

A choke coil 25 is included inthe direct current branch of the output circuit in order to prevent the ow of useful alternating current through the battery. The resistance 26 may also be used in this circuit for adjusting the potential to be impressed upon the work-anode and for offering a still further impedance to variable currents through the battery.

The operation of my invention as shown in Fig. 2 will be readily understood by reason of the similarity of this circuit to that of Fig. 1.

Referring to Fig. 3, a relatively simple oscillator circuit is shown having its input and output circuits inductively coupled by means of the transformer 27. In this modification, the function of the piezo crystal is mainly to stabilize rather than to sustain oscillations. The tube 1 may be the same as used in the hereinbefore described embodiments of my invention. The ionizing circuit is supplied with current from the source 6 in series with which is the protective resistance 7. The ionizing cathode 2 and ionizing anode 3 are the same as heretofore described. The input circuit includes the control electrode 5, upon which a suitable bias may be impressed by means of the direct current source 17, in series with which is the resistance 18. Potential variations may also be supplied to the control electrode 5 by means of the piezo electric crystal 13 in circuit with the inductance 28. The condenser 29 is used for adjusting the degree of regeneration, while a wider range of adjustment for the same purpose may be obtained through varying the degree of coupling between the two coils 28 and 30 of the transformer 27. The output circuit includes the work-anode 4 and the inductance coil 30. A suitable potential is supplied to the work-anode 4 by means of the direct current source 9, while the by-pass condenser 20 provides a low impedance path for alternating currents of the desired frequency.

The operation of the circuit shown in Fig. 3 is as follows: Any desired degree of regeneration may be obtained, as mentioned above, by virtue of the setting of the condenser 29. Assuming, for the moment, that the crystal 13 is first disconnected from the circuit, the degree of regeneration may be made so high as to preclude the possibility o1 circuit oscillations. If, then, the crystal 13 is connected into the network as shown in Fig. 3, piezo electric oscillations will be set up and sustained in the manner set forth in connection with Fig. 1. When, however, the condenser 29 is adjusted to permit circuit oscillations without the presence of the piezo crystal 13, then the crystal, when connected into the circuit, serves the purpose of stabilizing the circuit oscillations. It will, of course, be understood that the circuit constants are adjusted in accordance with a natural frequency of the crystal, in order that the latter may perform its frequency-stabilizing function.

To those skilled in the art, other modications of my invention will, of course, be suggested by the foregoing disclosure. It do not wish, therefore, to be limited to the specic embodiments herein shown, but only in accordance with the appended claims.

I claim:

1. In an oscillator system, a gaseous discharge tube having ionization electrodes, one an anode and the other a cathode, and having two workelectrodes, one a work anode and the other a control electrode, means for setting up a primary ionization discharge between the ionization electrodes, means for impressing upon the work anode a suitably positive potential with respect to the potential of the ionization anode to cause a secondary ionization discharge in the region of said work anode, an inductive and capacitive output circuit connected to the electrodes of said tube including said work anode, a piezo electric crystal in circuit between said control electrode and one of the other electrodes of said tube, and means for adjusting the characteristics of said output circuit in relation to a natural frequency of said piezo electric crystal whereby said tube is caused to generate and sustain oscillations of the crystal frequency.

2. An oscillation system in accordance with claim 1 in which the alternating currents traversing said output circuit are by-passed around the means for impressing the positive potential upon said work anode.

3. An oscillator system comprising a gaseous discharge tube having at least four electrodes two of which are ionization electrodes and two others of which are respectively a control electrode and a, work anode; means for impressing upon two of said electrodes a difference of potential suitable for setting up a primary ionization discharge therebetween; an input circuit including a piezo crystal for generating a desired frequency, said inputrcircuit also including one of the ionization electrodes and a control electrode; an output circuit including one of said ionization electrodes, a work anode, an inductance and a capacity; direct current sources for supplying respectively a potential to said control electrode and a potential to said work anode suiciently positive with respect to said ionization electrodes to set up a secondary ionization discharge in the region of said last menti-cned electrodes; and means for causing said tube to generate and sustain oscillations by virtue of the regenerative relation between said input and output circuits.

AUGUST HUND.

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