US2647221A - Poly-anode flip-flop tube - Google Patents

Description

uly 28, 3 c. R. WILLIAMS EI'AL POLY-ANODE FLIP-FLOP TUBE Filed April 16, 1951 0 NWO 4 4 f r 0 7 r ,0 M M M a, W@ g cm W Patented July 28,}953

Charles R. Williams, Hawthorne, and Chris S. Andersen, Bell, Calif., assignors to Northrop Aircraft, Inc., Hawthorn of California e, Cali1'., a corporation Application April 16, 195;, Serial No. 221,256

The present invention relates to multiple electrode cold cathode glow tubes, and more particularly to such a glow tube having two anodes and a single, surface divided, cathode suitable for use as a switch, or flip-flop tube.

Essentially, a flip-flop is a device which has two stable states. The dual anode tube of the present invention has two conducting stable states; either one anode is conducting, or the "other anode is conducting. The tube is made to be non-conducting onlyduring relatively short transition times when changing from one state to the other, and suflicient supply voltage is provided to insure re-ignition.

Hagen, in his application, Serial No. 100,178, filed June 20, 1949, has shown, described and claimed a three electrode cold cathode glow tube useful as a switch or flip-flop. This tube has a single, preferably central, anode flanked by two cathodes, immersed in gas at glow discharge pressure. When each cathode is connected to a resistance bridged by a capacity, with these RC circuits connected together, and then through a potential source and a limiting resistor to the single anode, with the source sufficiently high to strike a glow discharge between the anode and one of the cathodes, a negative pulse applied. to the anode will cause the glow to momentarily cease. Subsequent refiring forced by the high potential source will occur between the of a glow tube of this general Hagen type would operate well.

Such a tube would have a single cathode and two anodes, with the RC circuits connected to the anodes and-with the polarity of the source reversed. It is a fact, however, that such a reciprocal tube does not operate at all, because the voltage difierential necessary to obtain the switching cannot be maintained between the two anodes. The two anodes will conduct simultaneously to the common cathode as a stable-condition. 'Whenan attempt is made to raise the potential of one anode above the other, the first anode will draw the majority of the cathode current and the glow will creep 9 Claims. (01. 3154167).

around'th e cathode to the side favoring the first anode.

In the present invention suitable anode toanode differential voltage necessary for switching is obtained by dividing the cathode surface into separate areas, one facing and favoring each anode such that for an anode to conduct a substantial current it must strike a glow-to its favored area. an unfavored cathode area requires extra anode to cathode potential necessary for the glow. path to surmount the obstruction separating the cathode. areas, such conduction existing alone would be unstable because of the tendency of the glow to jump to the favoredv cathode area.

In the present invention, if an anode is conducting a stable current to a glow in its favored cathode area, then a second anode, can be raised to and maintained at a potential above that of the first anode without drawing more than a small-portion of the glow current. The glow will remain entirely within the firstarea. Now,:if a quenching pulse isapplied to the tube, and the, voltage differential between the anodes ismaintained, the glow will restrike on the second cathodearea and the second anode will assume the majority of the glow current. In a circuit-which automatically maintains the non-conducting anode at a potential higher than the conducting anode, the glow current can be switchedv alternately from one anode to the otherby a succession, of quenching pulses.

It might further appear that two separate gas diodes could be connected at their cathodes to form a dual anode flip-flop circuit. However, in such a circuit it is difficult, if not impossible, to obtain reliable switching action. The conducting bulb will always refireat a lower potential than the non-conductingbulb; hence, the glow will simply return to the same bulb after quenching. Further, it is difiicult to keep two separate bulbs matched-in their .electrical characteristics as aging p ogressively alters them. v

In the. present invention all electrodes of the flip-flopare exposed to the same gas and to equal residual ionization after trigger pulse quenching so that with symmetrical, construction equal anode to cathode refiring potentials are obtained regardless of which anode was previously conducting. The external circuits need supply only a small. and easily self-obtained anode to anode differential voltage to cause the previously nonconducting anode to strike to its cathode section. Also, aging afiects both anodes equally so that Conduction from an anode to .to transfer conduction from one anode to the other, to provide a usable output pulse, and a usable voltage diiferential between the anodes.

It is another object of the present invention to provide a three electrode cold cathode glow tube, together with a circuit that will provide for switching the glow discharge in the tube between two anodes and the surface sections of a oinele cathode.

In brief, the tube of the present invention includes an envelope containing a noble gas at glow discharge pressure and having three or four rodlike electrodes therein, preferably located side by side in a common plane. The center electrode or electrode pair is provided with means for limit ing a cathode glow thereon to two glow surf-aces thereof, in a more general case three or more. one of these glow surfaces facing one of the lateral electrodes, the other glow surface facing the other lateral electrode.

When used as a switch in a fiipflop circuit. a resistancewapacitv circuit is connected to each outer electrode, these circuits being connected together and to the center electrode through a potential source and a current limiting resistance, with the outer electrodes energized 'positiveiy as anodes, the center electrode energized negatively as a cathode. The source is made suflic-iently high in voltage so that a glow discharge is struck between one anode and the cathode glow surface facing the conducting anode. Upon application of a positive pulse to the cathode, the already established glow will cease, and the glow will be rte-established between the other cathode glow surface the other anode. The glow limiting means prevents the glow from travelling from one side of the cathode to the other, unless a discontinuous or switching action occurs.

The present invention will be more fully understood by reference to the drawings in which:

Figure l is a perspective view, the envelope being cut away, of a tube embodying the present invention.

Figure la is a perspective view of another form with a re-entrant stem 2 sealed to one end thercof, stem 2 having three leads 3', 4 and 5 sealed at apinch s therethroug'h. The inner ends of leads *3, l and 5 extend beyond the pinch 6 to form a central cathode 8 and lateral anodes 9 and HI. Cathode 8 is divided as by a saw out H, this out being filled with an insulating plate 12 made of glass, mica or ceramic, for example. Plate 12 extends at right angles to the common plane of the cathode and anodes. It is preferred that plate l2 divide the cathode into two glow surraces 14 and 15, one facing each anode and placed so'theit no s'ur faceof thecathode is exposed compiletely around the cathode.

The envelope is evacuated according to stand-- ard practice and filled with neon, for example, at glow discharge pressure, .e., from 100 mm. of mercury pressure to tone-half atmosphere pressure, for example. .A tnacercf polyatomic gas may he added to decrease deionization "time and to prmrote triggering.

The tube of Figure 1 can be used as a flip-flop in the circuit shown in Figure 2, for example.

Here, each anode 9 and i0 is connected to ground through a resistance 20 bridged by a capacity 2|, both RC circuits preferably being alike. Cathode lead 4 is connected through a current limiting resistance '22 to-the negative pole 23 of a potential source 24, the positive pole 25 thereof being grounded.

An input circuit 26 is connected to cathode lead 4 and an output circuit, such as an output circuit 21, can be connected to either or both anodes.

in operation, the potential of source 2a is sufiiciently high or a glow discharge to strike between one of the anodes and the nearest cathode face. Upon the application of a positive pulse P to the cathode through input line 26, the glow is extinguished, and automatically restruck between the other cathode face and the other anode. An output pulse is thus provided in each output circult 21..

If the surface of cathode ii were not to be divided into two parts, the two anodes would share the cathode current equally and they would remain at substantially equal potentials and lack the voltage differential necessary for switching. The tube is then inoperative as a switch. When, however, the glow on the cathode surface facing the struck anode is prevented from spreading to the opposite side of the cathode, the side facin the idle anode-as by the use of shield 12, a positive input pulse cause the original glQ-W discharge to cease entirely and then to be rte-established on the opposite surface facing the other anode. Additional pulses will then switch the discharge from one anode to the other in the desired flipflop fashion.

While we prefer to split the cathode and insert a shield therein to separate the surfaces facing the two anodes, the glow can be prevented from spreading from one side of the cathode to the other in several other manners. For example, the cathode surfaces racing the two anodes can be isolated by a dividing line 3'0 of non-conducting material such as insulating paint or ceramic as shown in figure 1a. The cathode can also he formed of two electrically connected but spaced wires (as shown diagrammatically in Figure 29 with or without :a shield between. In any event, the main desidcratum is some means to prevent the cathode glow from spreading from one side or the other thereof without a :break in current.

The tube of the present invention operates with positive input pulses as contrasted with the negative input pulsm .requ-iued to be placed on the single anode of the Hagen tube in the application cited above. For this reason, the-tube finds good use, aloneor in combination with the Hagen type tube, binary counters depending upon flipfiop action for operation.

From the alcove description it will be apparent that there is thus provided a device of the character described possessing the particular features piadvantage before enumerated as desirable, but obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any or its ad- While in order to comply with the statute, the invention has been described in language more or less specific as to structural fieatures, it is to be understood that the invention is not limited to the specific ifeatures shown, but that the means and construction herein disclosed comprise a proferred form of putting the invention into effect, and the invention is, therefore, claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

1. A cold cathode glow tube comprisingan envelope containing a filling of gas at glow discharge pressure, a pair of anodes and means providing electrically continuous cold cathode surfaces positioned between said anodes, said electrodes being in a common plane, said surfaces of said cathode being separated into separate cathode glow areas, with a cathode glow area facing each anode.

2. A cold cathode glow tube comprising an envelope containing a filling of gas at glow discharge pressure, a pair of anodes and a cold cathode positioned between said anodes, said electrodes being in a common plane, and glow preventing means separating the surface of said cathode into separate cathode glow areas, with a cathode glow area facing each anode.

3. Apparatus in accordance with claim 2 wherein said glow preventing means is a coating of insulating paint on said cathode.

4. Apparatus in accordance with claim 2 wherein said cathode is divided in a plane at right angles to the plane of said electrodes, and wherein an insulating shield is positioned between the divided portions of said cathode.

5. Apparatus in accordance with claim 2 wherein said cathode is divided in a plane at right angles to the plane of said electrodes, and wherein an insulating shield is positioned between the divided portions of said cathode, and wherein said shield extends outwardly beyond the extent of said cathode in directions at right angles to the plane of said electrodes.

6. The tube of claim 1 in combination with a circuit for causing a glow discharge between one anode and the facing cathode glow area,

and means for applying an input pulse to said cathode to switch said discharge to the other of said anodes and the other of said glow areas.

7. A cold cathode glow tube consisting of an envelope containing a filling of gas at glow discharge pressure, a pair of anodes sealed within said envelope and having separate electrical leads therefor, and means providing electrically con tinuous cold cathode surfaces sealed within said envelope between said anodes and having a common electrical lead therefor, said surfaces of said cathode being separated into separate cathode glow areas within said envelope, with a cathode glow area. facing each anode, whereby a glow discharge between one anode and its facing cathode area will not efiect a glow on the other cathode area.

8. A bi-stable flip-flop circuit comprising a cold cathode glow tube having an envelope containing a filling of gas at glow discharge pressure, a pair of anodes and a cold cathode positioned between said anodes, glow preventing means separating said cathode into separate cathode glow areas within said envelope, with a cathode glow area facing each anode, means for striking a glow between one anode and the facing cathode glow area, means for maintaining a potential difference between the active and inactive anode, and means for applying a positive input pulse to said cathode to switch said glow between the other of said anodes and the other of said cathode areas.

9. Apparatus in accordance with claim 8 including output circuit means connected to each of said anodes.

CHARLES R. WILLIAMS. CHRIS S. ANDERSEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,812,764 Story, Jr. June 30, 1931 2,349,012 Spaeth May 16, 1944 2,527,552 Hough et a1 Oct. 31. 1950

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