US2728004A - Glow tube - Google Patents

Description

J. A. VlcToREEN ET AL 2,728,004

Dec. 20, 1955 GLOW TUBE Filed NOV. 16, 1948 2 Sheets-Sheet l INVENTORS JOHN A. VIGTOREE/V JAMES H. EDDLESTON Dec. 20, 1955 J. A. VICTOREEN ET AL 2,728,004

GLOW TUBE 2 Sheets-Sheet 2 Filed Nov. 16, 1948 FIG. 2

JAMES H EDDLESTO/V United States Patent Q crow TUBE.

John A. Victoreeu and James H. Eddleston, Cleveland;

Ohio, assignors to The Victoreen Instrument Company, Cleveland, Ohio, at company of Ohio Application November 16, 1948, Serial No. 60,254 11' Claims. (Cl. 313-54) This invention relates to electron discharge devices of gaseous conduction type andmore particularly to. the method and apparatus foraffording a more exact striking voltage for the operation of such tubes.

Heretofore, it has been common knowledge to provide gaseous conduction tubes which are utilized for a. great many purposes of which the most common is for. voltage regulation. One of the most common defects of such tubes was the fact thatv the striking or starting voltage needed to start the operation was considerably higher than the voltage necessary to maintain a state of ionization in. the tube. Although this was not a serious deficiency for a great many of the uses to which such tubes were put, it did place serious limitations upon their utilization.

For instance, such tubes were of little or no value in circuits where it was desired to use a tube to indicate a critical potential or to cause the operation of another device when a critical potential had been reached. The present invention. may be used to construct tubes which are extremely simple in. their internal structure and, therefore, capable of. operation in the presence of and to withstand extremely large shocks up to and including over 35,000 gravities. Furthermore, tubes can be made by our invention which will fire within .3 of a volt within the critical potential in. temperature ranges between minus 40 degrees and plus 55 degrees C., and with a starting time of within 2 milli-seconds.

In the more limited aspects. of the invention, the-structure of the device is such. that the striking voltage may be regulated within certain limits. Since the invention may be used in the construction of so-called cold cathode types of tubes it is particularly desirable. for voltage regulation or the other purposes to which it may be put, in circuits where current consumption is a critical limitation.

Still other advantages of.v the invention and the invention itself will become more apparent from the following description of some embodiments thereof and which description is illustrated by the accompanying drawing.

In the drawings:

Fig. 1 is an enlarged view of a tube utilizing our invention with certain parts broken away to provide a clearerillustration of parts which would otherwise be hidden;

Fig. 2 is a diagrammatic view of a modified form of the invention;

Fig. 3 is a view of another embodiment of: our invention; and

Fig. 4 is a view of still another embodiment of our invention.

Throughout the drawings, like parts have been designated by like reference characters.

Referring now to Fig. 1, wherein there is a greatly enlarged illustration of a tube embodying the invention, as can be seen, it includes a. glass envelope 10 having. a press 11 at the lower end, through which a. pair t lead-in wires. 12 and 13 extend. The lead-in wires extend into the glass envelope and the wire12 is. connected 2,728,004 Patented Dec. 20, 1955 to onev ot the twosupport wires 14. The two support wires. 14 each have. an inwardly bentcenter portion 15 which is spot welded: toa cylindrical. cathode 17. The wires and cathode. may be made of any suitable material such as nickel: The lower extremities of the wires 14 are disposed in. openings in a circular ceramic support disc 18 which extends inv close proximity to the envelope wall. One of the wires is bent at 14' to engage theunderside. of the. disc adjacent. the hole, and the point 12 of thelead-in wire. 12 where it is welded to the other support. wire engages the ceramic disc adjacent the point where the. support; wire goes through the disc.

The upper end of the cylinder 11 abuts a. mica disc 20 which rests on the end of. the cylinder. The ends of the support wires 14 extend through the disc, and are. upset. at 22, to hold the disc securely in position. The: mica disc, like. the. ceramicv disc, extends, close to: the envelope. wall- A. getter 23 is carried by the ends of the support wires 14 in. such a position that, when it is flashed, the getter material flashes against the upper end of the envelope.

The extremity oftheenvelope is shown with a tip 24 through which the tube may be evacuated and/0r filled with gas to the desired pressure before sealing oil.

A. center anode electrode 26 is provided which comprises a stiff Wire or rod extending coaxially with the cylindrical cathode, the end extending through the ceramic support 18 and having welded thereto at 27 the lead wire 13.

, .A tube such as. this is usuallyfilled witha mixture of noble gases. Such a mixture could comprise. argon and neon at a pressure. of between 10 and 30 mm. of mercury. The. amount. of neon gas; is normally small being as little as 4 It will be appreciated that others of the noble gases may be used. and, that the proportions and pressure may vary; for. instance, a, mixture of 2% argon and 98% helium atv a pressure of between and 100 mm. of, mercury is very satisfactory. The pressure of the gas to some degree determines the flash point or striking voltage.

As previously stated, a tube such as: has been described is commonly known as a glow tubeand when voltage.

of. a. suflicient amplitude. is applied, knownv as striking voltage, the: gas will become ionized. and conducting. During the time when it is conducting, it will maintain its. conductive state. at a considerably lower voltage than that needed to start it. Furthermore,, the starting voltage varies throughouta wide range. Therefore, although the. regulation may be very good after it once starts, the variations in the starting voltage seriously limits the uses to which it may be put.

Prior to the. invention, there. was no tube-of. this character available. where. the striking, voltagev was always the: same or. within reasonable limits of a predetermined value. Furthermore, the time of the starting might vary. That is, if. a starting. voltage of volts was sutficient to start it within a fraction. of a second at one time,

this same voltage might not start it for several seconds.

at another time.

Among other things, prior glow tubes exhibited large and. variable dark currents in the region prior to and as the potential approached the breakdown point. This.

caused a region of instability'as mentioned above.

We have. discovered that. this limitation on the striking; voltage may be corrected by placing a source of energized particles such as electrons or alpha particles in the tube. One materialv which. we have found to be highly efiective is by welding: a small piece of metallic ribbon 30havinga substance such, as radium impregnated therein to the anode. The radium emits alpha particles and high speed electrons. It. will be appreciated that this substance can be'placed anywhere in. the tube so long as a proper degree of ionization is produced at the point of discharge.

We have found that a gold ribbon with a minute quantity of radium therein is extremely effective in its action and that a tube so constructed and designed for a striking voltage of 120 volts will always strike Within .3 of a volt regardless of variations in ambient temperature when the degree of ionization is satisfactory.

We also contemplate, and in some instances prefer, a substance such as polonium which is essentially an alpha particle emitter. The use of alpha particles for stabilizing the starting voltage is particularly dictated in places where beta and gamma rays are undesirable. It will be appreciated that a great many of the isotopes may be useful and in some instances preferred, the principal limitation being that the half life of the material must be taken into consideration.

The reason that a tube embodying the invention can be stabilized to provide a substantially exact starting voltage is because the radiation produces a sufficient degree of ionization to cause the gas to break down at a predetermined voltage depending on'the various parameters of the tube. This is equivalent to saying that the tube is presensitized by providing enough ions at the point of discharge that the addition of a critical potential gradient across the discharge point is sufiicient to cause the gas to break down, making it unnecessary for the added potential to provide the necessary ions before the breakdown potential is reached. When the radio active material is apt to contaminate or have any undesirable effect upon the other elements in the tube, it may be completely enclosed such as by being placed in a bore 26a, as indicated by the dotted lines, in the anode itself, thu permitting only theenergized particles to escape.

Such a tube may be connected into a circuit wherein when the potential in the circuit reaches a predetermined maximum desired value, the tube will strike causing a discharge of the circuit. With this type of circuit, the discharges which may succeed one another may be produced at a rate greater than that at which the circuit may build up succeeding potentials. Thus, the discharge may also be used to indicate when the critical potential is reached.

It has been commonly accepted theory that a tube,

of the character described as prior art, would discharge in the presence of an ionizing event, such as the passage of a high speed electron or alpha particle between the discharge electrodes. This result has, according to accepted theory, been obtained at a result of the passage into the device and between the electrodes of a cosmic ray. This has largely been responsible for the inconsistencies in striking voltage, for, any one single event is not sufficient to produce the required degree of ionizatlon.

- In Fig. 2, there has been shown schematically another embodiment of our invention wherein the anode 26 has the radio active material 30a in the form of a flag disposed on a stem 31 that is welded to the anode at 32. The cathode wall opposite to the flag is provided with a cup 33 in which a barium, cerium or magnesium compound 34 is disposed, and is adapted to be flashed, to provide a suitable cathode coating surface'on the wall at 35 having the desired work function. r

In Fig. 3, there has been shown another embodiment of the invention. In this case, the usual glass envelope a is provided. A tube 40 of metal, such as nickelcobalt-iron, glass sealing alloy, of which there is one on the market known as Kovar, extends through the press 11a and has secured to it at its upper end a pair of support rods 41 which may be welded to the side of the tube. The supports 41 carry a cup 43, from the center of which extends a rod 44 which comprises the anode. On the end of the rod is the ionizer 45 which may be constructed of any of the materials specified.

The tube is degassed and supplied with the ionizable gas through a second tube 47 which may be of copper, although other metals may be employed.

The cup 43 is provided with a material 43' of which a type having a thermic action to release the material is desired and causes it to coat the wall and form a cathode by evaporation. Such a'compound could be a mixture including barium and/ or magnesium which, when flashed, causes a metallic layer to be deposited on the wall 48. A cathode rod 49 extends into the tube through the upper end and makes contact with the metallic layer, thus forming the cathode and its connection.

The tube after being evacuated and degassed in the usual manner is then flashed. After flashing, the ionizable gas such as argon and neon may be admitted through the tubes 47 and 40 filling the tube to a pressure close to but slightly lower than the desired pressure. The tube 47 is then pinched off and sealed at 50.

The tube 47 may be pinched as indicated at 52, to change the pressure in the tube until it is at the exact point where the desired striking voltage causes it to start.

One method of conditioning the tube contemplates filling the tube with gas to a lower pressure than that ultimately desired, applying a voltage to determine the striking voltage and then ultimately increasing the pressure and applying a voltage that will cause it to strike until the desired pressure is reached at which it will strike at the desired voltage.

In Fig. 4, there is shown a greatly enlarged view of a glow tube manufactured according to our invention. In this particular instance, it should be mentioned that it is possible to manufacture glow tubes according to our invention that are of a very small size. For instance, the actual tube of Fig. 4 can be constructed A; of an inch in diameter and one inch long to provide an extremely rugged device capable of withstanding great shocks.

Referring to Fig. 4, the tube may comprise a cylindrical envelope 60 of Kovar or steel or other metal having a flange 61 at the lower end and being necked in slightly at 62. A sleeve 64 of magnesium is inserted in the envelope, it being of a diameter to provide a good electrical contact with the outer metal and forms the cathode. The upper end of the sleeve engages the shoulder 65 formed by the necked-in portion. The lower end of the envelope is closed by a base which includes a short cylinder 66 having a flange 67 adapted to be welded or soldered to the flange 61. The interior of the cylinder 66 is filled with glass 69 which is fused to the cylinder and which glass supports the anode rod 70 coaxially of the cylinder 60.

It will be seen that this structure allows for standardization in the tube structure and still enables certain changes to be made that will change the operating range or striking potential of the tube. For instance, the magnesium sleeve could be in various thicknesses thus changing the spacing between the electrodes; or other metals than magnesium, such as aluminum, barium, etc., may be used to provide a cathode having the desired work function.

The upper surface of the bead may be provided with a circular flange 72 extending upward and surrounding the anode.

The upper end of the anode carries a flag, or point 74, which may be of metal carrying the ionizing substance as previously indicated.

The reduced end 62 of the envelope has welded thereto a copper tube 75. This copper tube is adapted to be pinched off at 76 and sealed when the desired pressure of gas is reached, or it may be sealed at the end as indicated at 77 and then deformed to increase the pressure as indicated in connection with the description of Fig. 3.

It will therefore be seen that there has been discovered a means for establishing a degree of ionization in the gas in a tube of the character described whereby the striking voltage can be relied upon to be effective within certain predetermined limits. This enables the device to be used in circuits where the striking voltage must be accurately forecast. It also lends itself to uses where the device is used as a protective device that will definitely break down at a predetermined voltage and where a cold cathode type of device is desirable.

Having thus described our invention, we are aware that numerous and extensive departures may be made therefrom without departing from the spirit or scope of the invention which is defined in the appended claims.

We claim:

1. The method of manufacture of a gas filled discharge device having a compressible tubulation, to predetermine the discharge point, which comprises filling the device with gas at a pressure below that required to cause discharge at a given potential and compressing the tubulation to reduce the volume of the chamber to increase the gas pressure in the tube until the desired striking voltage is attained.

2. The method of producing gas filled discharge devices having a distortable tube communicating with said device to provide a device having a volume greater than that of the ultimate device which comprises filling the device with the desired gasto a pressure below that required for the device to discharge at a predetermined voltage, applying a voltage to the device of a value which it is desired to cause the tube to discharge, distorting said communicating tube to increase the pressure in the device to the point where the tube will discharge.

3. A glow discharge tube including a cylindrical metallic member, a cathode sleeve disposed in said member in electrical contact therewith and formed of a material having the desired work function, said member being formed with an outwardly extending base flange, a base for said tube including a second cylindrical member having a flange disposed for engagement and sealed to said first flange, a glass bead filling said member and an anode supported thereby extending into the first member and exteriorly of said tube, said bead being formed with a ring surrounding said anode at the base thereof and in spaced relation thereto, and ionizer carried by said anode in the zone of discharge thereof, said first member being formed with a reduced tubular portion at the end opposite the base.

4. A gas discharge tube comprising a base member including a flanged sleeve and a glass to metal seal filling the sleeve, an anode comprising a rigid rod carried by said glass seal, coaxial with the sleeve and extending upward therefrom, a cathode comprising a second flanged sleeve, said members being held in cooperative relation 1 to each other by securing said sleeves together, and a sleeve of magnesium being disposed in closely sliding contact with said second sleeve inside said sleeve.

5. A gas discharge tube including a cylindrical metallic member, a cathode sleeve disposed in said member in electrical contact therewith and formed of a material having the desired work function, said member being formed with an outwardly extending base flange, a base for said tube including a second cylindrical member having a flange disposed for engagement and sealed to said first flange, a glass bead filling said second member and an anode supported thereby extending into the first member and exteriorly of said tube and in spaced relation thereto, and an ionizer in the zone of discharge thereof.

6. An apparatus for causing a discharge between electrodes upon the applicaion of a predetermined potential, including an envelope having two or more electrodes for connection to the source of potential, an ionizer disposed on one of the electrodes at the point of greatest field intensity, said envelope having therein a gas ionized by radio active disintegration products of said ionizer to provide suflicient free ions at the point of discharge to cause positive or definite striking at the desired potential.

7. An apparatus as set forth in claim 6 wherein the disintegration products comprise alpha particles.

8. An apparatus as set forth in claim 6 wherein the disintegration products comprise beta particles.

9. An apparatus as set forth in claim 6 wherein the disintegration products comprise gamma quanta.

10. An apparatus as set forth in claim 6 wherein the disintegration products comprise alpha and beta particles and gamma quanta.

11. An apparatus of the class described including an envelope, electrodes in said envelope and a gas filling the envelope, one of said electrodes being provided with a longitudinally extending bore therein and radium disposed in said bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,269,534 Gray June 11, 1918 1,531,301 Metzger Mar. 31, 1925 1,658,568 Moore Feb. 7, 1928 1,762,712 Charlton June 10, 1930 1,871,344 Rentschler Aug. 9, 1932 2,054,048 Braselton Sept. 8, 1936 2,071,748 Hund Feb. 23, 1937 2,078,776 Ruggles Apr. 27, 1937 2,172,205 Karl et al. Sept. 5, 1939 2,174,382 Elder et al Sept. 26, 1939 2,276,639 Ackermann Mar. 17, 1942 2,326,631 Fischer Aug. 10, 1943 2,479,882 Wallhausen et a1 Aug. 23, 1949 2,495,274 Mayer Ian. 24, 1950 FOREIGN PATENTS 396,406 France Jan. 26, 1909 OTHER REFERENCES Nottingham: Review of Scientific Instruments, January 1940, vol. 11, pp. 2-6.

Images