US2729762A - Cold cathode switch tube - Google Patents

Description

Jan. 3, 1956 Q HAGEN ET AL 2,729,762

COLD CATHODE SWITCH TUBE Filed April 18, 195o pOLVTOM/C GAI.

United States Patent COLD CATHODE SWITCH Glenn E. Hagen, Lawndale, Charles R. Williams, .Hawtheme, and Robert D. Hancock, Compton, Calif., ,assigners to Northrop Virc'r'af'lnc., Hawthorne, Calif., a corporation of California Application April 18, :19.50, Serial No. 156,659

12 Claims. (Cl. 3.1332185.)

The present invention relates to ,cold cathode .glow tubes and more particularlyto agloyv .tn be Switch .or Hip-op suitable vfor use in `.matl, ier'riatical .counters .and computers. Y

Essentially a flip-flop .is a device which has two stable states and is capable of being triggered from .one state to the other as by .an input *.pul'se. `The term ilip-op has assumed independent status inthe art. When .glow tubes are utilized'in flip-dop ,circuits ,such as shown, de scribed, and claimedby Hagen in a `copending application, Serial No. 100,178, -tiled Iune20, 1-949, now Patent 2,575,516 for example, it is"desirable .thatfthe glow discharge path to .one lcathodebe quickly defionized .as the path to the other cathode is energized, in order .to reduce the possibility .of restrikinga .discharge along the same path when the potential .thereon is again raised. Furthermore, fast dre-ionization `in .the tube leads to .increased speed of operation .and higher .accurate counting rates.

It is an object o f the present invention to provide a means and method of increasing .the'accuracy of .cold cathode Aiip-ilop tubes .b'ydec'r'easing the deeionirzation time in current paths the tube. J Itis -,still .another object to provide `a glow l:tube switch vorllip-flop having a higher sensitivity, higher voltage' swing ,on .the tube, lower input pulse, and a higher .frequency of ,operation .than has heretofore been found .'practicall'. M

In brief, the present invention includes .the use, in a switch circuit, of la cold cathode Vglovv .discharge rtube having an anode symmetrically .positioned 'between two substantially identical cathodes, in which a`illing of noble gas such as helium is .deliberately yContutrtinated with a polyatomic gas in an .amount on .the 'order `.of from 1% to 5%. Preferred .examples .are .water vaporanjd pure hydrogen, .or combinations ',thereof.

Our invention will be morev `fully .understood by reference tothe drawing `which Yshows .a tube embodying the present invention as .used vin a llipfiip circuit disclosed the Hagen application cited above.

In the figure, a cold cathode glow -.tube 1 is provided in accordance with the present invention, having an envelope 2 of glass with an external pinch 3 at one end thereof. A .central straight wire anode 4 is held in pinch 3 and extends upwardly'only a very short distance .into the tube. The anode wire 'is continuedoutside of the envelope through the stem as an anode lead '6.

Two cathode wires 7 and 8 pass Athrough the pinch 3 as continuations of cathodeleads 9 and '10,' respectively, and are identical in extent with, parallel to, .and one on each side of anode 4.

In order to obtain maximum sensitivity and counting speed, we till the envelope l2 with a mirture .of noble and polyatomic gases. For example, helium `at Apressures from 10G to 250 mm. Hg have, .been .found satisfactory, with a deliberate .contamination of H,from 1% 1,05% water vapor or pure hydrogen as a preferred impurity used as a quenching gas.

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It is believed `at the present time, on the .basis .of .experimental evidence, that a polyatomic impurity .tends t0 .de-ionize the ionized path of the ,glow discharge :when ,the energization is withdrawn.

The quenching gas .characteristics are ,as follows:

l. The .quenching gas must .dissociate on 4impact .with noble gas ions.

2. This dissociation must absorb energy. The .ebsorption of energy is necessary ,to .cause .an inelastic col.- lision wherein the speed vvof .the ion is reduced. ,(As opposed t/o the elastic lcollision between noble gas ions or atoms in which 'Choy rebound without loss 'of speed.) Since recombination of ions and electrons (deionizationl) is roughly inversely proportional Ato the speed of the ns, prompt deionization results when they are .stopped by collision. This qualification excludes the .use .of endothermic compounds as quenching gases i. e., .those .that release energy rather than absorb it'. For example, nitro.- glycerine vapor is de linitely not suitable.

3. The gas vmust .automatically recombine within .the tube so as not `to be quiclly consumed. This :is true of all diatomic elemental gases such as hydrogen, nitrogen, oxygen, etc. It is also true .of many vcompound :gases provided proper catalysts .aro Present. Water vapor, am.- monia, carbon dioxide, hydrogen chloride, .ae examples. Kovar, the most ydesirable electrode material from the standpoint of manufacturing cost, is .a Agood catalyst .for recombination of water vapor. P la-tirnnn lis good for .all those gases mentioned as `well as many others. Most of the heavier organic gases, however, will not .qualify .in this respect. Alcohol vapor, widely used .as .a .quenching gas in commercial Geiger tubes, does not recombine, and thus limits the life Yof the tube. v

.4. Thedissociation products of .thequenchinggas must not form undesirable 'Slussos .or .on .tuboolomonts- .In general, any eas Satisfying .(3) .will .also Satisfy this. requirement.

5,- Tho quonohng gas must not .react .Chemically o1 physioallywith .electrodos in .an undesirable manner. .Hy-

drogen .Polishos .tho .electrodes .Clean by V@.knomlo.al re.. foat'wator vapor oxidizos. them heavily; .vor both .clean and oxidized .oleotrodos porforrn .satisfactorily .in .those cases.

'6- 'Tho quooohis .sos must knot .rapidly .disappear .by adsorption or absorption into electrodes l or "s walls'.

Hydrogen has been found to. bo the best Possible ses with respect 1o requirements. 5 .and .6.. Watrraporhas also been vused because it is very good yfrom the' stand Point of requirements '1 Vand We Prefer the Water vapor to hydrogen.

In any' event the addition of any polyatomic Agas has been found to stabilize the tube, ,prevent retiring f an gas alone. It has also been found that ,the .addition of .measured quantities ofthe impurity results in tubes with reproducible characteristics. Tubes, .So iilled 'have been accurately operated at pulse input speeds of lQkc The tube as above described is ideal tor use .in high speed counters when -usel as a flip-glop device, Such .as can be. aooomplishod by tho oroaifls. .of the Hasen application cited above.

As shown in the ligure, in one ot such circnits, anode 4 is connected to a source of positive potential y1111, such as 300 v. to 1,000 V fOr example. The cathodes 7 and 8 are grounded to the negative side .of the som-ce 11 through respective cathode resistors 7g. and 8g, `and then through a Common, resistor 12.. An inputline 14 .isconnectedvto .the junction 'J .of .cathode resistors In and 18s.-

nected through cathode leads 9 and 10 to cathodes 7 and 8. Each output line contains a blocking condenser 17. A cathode condenser 18 connects both the cathode circuits.

In operation, it will be assumed that an initial discharge will take place between anode 4 and the cathode 7. Since this will cause current to flow through common resi-ster 12, the basic voltage of both cathodes 7 and S with respect to the anode 4 will be less than that of the anode supply voltage. In addition, due to the current flowing in cathode resistor 7a, the voltage on cathode 7 will be more positive than that on cathode 8, so that condenser 18 will charge.

When a positive pulse is applied to the input line 14, i. e., to both cathodes, the potential of this pulse is sufcient to raise the potential of the cathode 7 involved in the glow discharge to a value where the glow discharge to cathode 7 is extinguished.

Current then ceases to flow through common resistor 12 and the voltage between anode 4 and the two cathodes 7 and 8 tends to rise quickly to the potential of the anode source. However, the two cathodes 7 and 8 are not now at the same potential, due to the charge on condenser 18, so that the greatest drop across the tube is now between the anode 4 and cathode 8. The discharge thereupon strikes between anode 4 and cathode 8, and condenser 18 charges in the opposite direction, so that when the next positive input pulse arrives, the discharge will be switched back to cathode 7. Thus each positive pulse will switch the glow discharge from one cathode to the other.

The output lines 15 and 16, being attached to each cathode, will thus carry an output pulse in accordance with which cathode is involved in the glow discharge, so that output pulses will alternately occur in the output circuits, following a succession of positive input pulses in the single input line 14. Thus the device operates as a ip-op circuit, useful in computing devices, .with two stable states alternating under successive input pulses. The output of the device at the cathodes is essentially a square wave but, because of the particular embodiment of the invention shown in the figure, the output voltages momentarily swing too far to the negative direction as the circuit is flipped. Thus a clean, true, square wave is not generated directly with this particular circuit, but the output is useful, nevertheless, for circuits such as frequency dividers, for example. However, the circuit shown is representative of the action of the tube.

Thus, the dual cathode gas tube flip-liep of the present invention has two conducting stable states; either one cathode is conducting or the other cathode is conducting. The tube is non-conducting only during relatively short transition times and suicient supply voltage is utilized to guarantee reignition. Thus the usual difficulty of an on-o bi-stable gas tube, i. e., that of maintaining consistent ionization during the oft or nonconducting state to stabilize firing voltage, is avoided.

As a basic computer component the cold cathode gas discharge flip-flop tube of the present invention offers many advantages, as follows:

l. Small size, smaller than a dual triode subminiature tube. A satisfactory tube need only be l inch long by l/z inch in diameter.

2. Simple and extremely rugged electrode construction.

3. Low power consumption. The total heat dissipation can be as little as 0.1 watt per flip-flop stage.

4. Self indicating, due to cathode glow.

5. Fewer components are required to construct a flipop stage than with conventional dual triode circuits.

6. Increased reliability-no filament to burn out.

7. High operating speed, on the order of 1G kc.

Complete binary and ring counters, number storage devices, and digital delay lines have been constructed with the tube of the present invention without the aid of'vacuuml tubes. This versatile three electrode glow tube can also be used to regulate voltage; as an oscillator; a pulse generator; a pulse amplifier and a one-shot device. As a flip-flop it can control diode gates, operate relays and indicators, as well as self-indicate its state.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specic as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred 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:

l. A three electrode cold cathrode glow tube switch comprising an envelope containing an anode, and a cathode on each side of said anode, and a filling of a noble gas mixed with from 1% to 5% of water vapor.

2. A three electrode cold cathode glow tube switch comprising an envelope containing an anode, and a cathode on each side of said anode, and a filling of a noble gas mixed with from 1% to 5% of water vapor, said electrodes being formed of a material tending to recombine dissociated water vapor.

3. A three electrode cold cathode glow tube switch comprising an envelope containing an anode, and a cathode on each side of said anode, and a filling of a noble gas mixed with from 1% to 5% of water vapor, said electrodes being formed of platinum.

4. A three electrode cold cathode glow tube switch comprising an envelope containing an anode and a cathode on each side of said anode, said envelope containing a filling of helium at from to 250 mm. of mercury pressure, mixed with from 1% to 5% of water vapor.

5. A three electrode cold cathode glow tube switch comprising an envelopecontaining an anode and a cathode on each side of said anode, said envelope containing a filling of helium at from 100 to 250 mm. of mercury pressure, mixed with from 1% to 5% of water vapor, said anode and cathodes being of wire of uniform section.

6. An electrical discharge device of the kind having a sealed envelope containing a noble gas mixed with a small amount of a polyatomic gas, including: three electrodes sealed in said envelope and arranged to provide an unobstructed discharge path initiated at the normal striking potential between the two electrodes functioning at any instant as anode and cathode and thereafter maintained between the same two electrodes unaffected by the other electrode until the extinction of said discharge; and circuit means whereby apulse establishes an uninterrupted discharge path between two of said electrodes and each succeeding pulse extinguishes the discharge between said pair of electrodes and establishes an uninterrupted discharge path between one of said pair of electrodes and the other electrode.

7. An electrical discharge device as set forth in claim 6 comprising a single anode and a cathode arranged at each side of said anode.

8. An electrical discharge device as set forth in claim 7 comprising an anode and two identical cathodes, each of a single length of straight wire extending a small distance into said envelope.

9. An electrical ,discharge device as set forth in claim 8 comprising an envelope filling of helium at a pressure of 100 to 250 mm. of mercury mixed with from 1% to 5% of a recombinable polyatomic gas.

10. An electrical discharge device device as set forth in claim 9 in which the recombinable polyatomic gas is hydrogen.

11. An electrical discharge device of the kind having a sealed envelope containing a noble gas mixed with a small amount of a polyatomic gas, including: a single anode with a cathode arranged at each side thereof and providing an unobstructed discharge path initiated at the normal striking potential between said anode and one or the other of said cathodes, said anode and two cathodes being each formed of a single length of Wire extending a small distance into said envelope.

12. An electrical discharge device as set forth in claim 11 comprising an envelope filling of helium at a pressure 6 of 100 to 250 mm. of mercury with from 1% to 5% of hydrogen.

References Cited in the tile of this patent UNITED STATES PATENTS

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