US2495681A - Electric discharge tube - Google Patents

Description

FM 331,, Iififl G. F. ASKER I 2,4953%] ELECTRIC DISCHARGE TUBE Filed April 4, 1946 m INVENTOR.

GQSTA E ASKER @TTORNEY atented Jan. 31, 1950 w th ELECTRIC DISCHARGE TUBE Giista F. Asher, Stockholm, Sweden, assignor to International Standard Electric Corporation,

New York,

N. Y., a corporation of Delaware Application April 4, 1946, Serial No. 659,482

Sweden March 22, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires March 22, 1965 6 Claims. (01. 25027.5)

The present invention relates to electric discharge tubes and more particularly to a tube filled with a rare gas or metal vapor. The invention more specifically pertains to a tube provided with at least two electrodes and having a low ignition voltage and a low voltage drop of substantially the same value amounting to approximately forty volts maximum and prefer ably ranging between five and fifteen volts even when alternating current is applied across the electrodes.

It is known to provide a gas discharge tube with two cathodes. Such tubes are the type for the generation of light such as mercury vapor lamps or neon tubes. In such known gaseous discharge devices, the cathodes are so arranged and the gas pressures are so selected that the greatest voltage drop is obtained in the gas in order to provide eflicient light-producing tubes. These prior tubes having two cathodes require about one hundred volts for ignition and the electrodes have been of the unheated type.

As distinguished from the prior devices, it is an object of the present invention to so arrange the electrodes and to so select the gas pressure that the voltage drop'in the gas becomes negligible in comparison with the total voltage drop over the tube.

Another object of the invention is to provide means for preventing the dissipation of heat from the cathodes and to increase the current carrying capacity of these electrodes and to provide for the re-radiation of heat to the cathodes.

Other objects and features of the invention will be more apparent as the present disclosure proceeds and upon consideration of the accompanying drawing and the following detailed description wherein an exemplary embodiment of the invention is disclosed.

In the drawing:

Fig. 1 is an axial sectional view of a tube embodying the invention.

Fig. 2 is a plan view of the tube shown in Fig. 1.

In the embodiment of the invention illustrated in the drawing the gaseous discharge tube is provided with two indirectly heated cathodes mounted on a stem which forms an integral part of the envelope and these parts of the tube are of the type employed in conventional radio tubes. The cathodes are to increase their current-carrying capacity and at the same time to re-radiate heat to the cathodes and to prevent dissipation of the heat from these electrodes. The tube may be filled with a rare gas or metal vapor such as mercury vapor in provided with screens adapted order that the desired low ignition voltage may be obtained.

Referring to the drawing, the glass envelope is shown at l which may be formed integral with a conventional type stem Bwhich projects upwardly from the base of the tube. The discharge tube includes two indirectly heated cathodes 2 which are supported by a plurality of heat resistant insulating plates 3 which may be formed of mica. The filaments for heating the cathodes are shown at 4 and these filaments extend into the interior of the hollow cathodes 2 in a wellknown manner. The filaments 4 are connected in parallel as shown in Fig. 1. The filaments 4 are supplied with heating current through a pair of leads 9 which extend through stem 6 to the base of the tube.

Each cathode is surrounded by a screen 5. The screens 5 may be formed of metal and are supported between the mica plates 3. It will be noted that the cathodes 2 extend beyond the ends of the screens 5 and project beyond the mica plates 3. The screens 5 serve as means for preventing heat radiations from the cathodes and the screens are adapted to increase the current-carrying capacity of these electrodes. The opposed open sides of each screen may be provided with shield portions 12 adjacent the ends ot the cathodes to protect the glass envelope and stem from discharges occurring at the ends of the cathodes. The screens 5 are also supported by a pair of posts I l which extend upwardly from the stem 6 and may be welded or ptherwise attached to the screen 5. The posts II also support the mica plates 3.

A pair of leads I extend through the stem of the tube and are connected to the posts H and therefore provide conductors to the screens 5. The cathodes are provided with leads 8. The conductors 1 and 8 are connected to each other either within the tube base or by means of external connections as shown in Fig. 1.

If a variable alternating current is impressed across the leads 8 and a resistor is connected in series with an alternating current supply, then the peak amplitude of the alternating voltage across the tube will be constant and approximately of the same magnitude as the ionization voltage of the gas even if the current varies within wide limits. If the cathode surface is approximately four square centimeters and the tube is filled with a rare gas there is provided a substantially constant glow voltage when the current varies between 10- and 1 ampere With an applied voltage of approximately three volts, the current through the tube is of a magnitude of about 10* amperes. This current decreases rapidly with a fall in voltage.

The gas discharge tube herein described may be utilized for many purposes such as a voltage protector or blocking means in association with radio receivers. The tube may, for example, be connected between the antenna of a receiver and ground. Under such circumstances the voltage cannot reach a value detrimental to the receiver. The voltages between the antenna of a receiver and ground are normally such that the current through the tube becomes so small that the sensitivity of the receiver is not appreciably influenced. The gaseous discharge tube may also be employed for transforming a sine wave alternatlng current voltage into alternating current voltage of a reactangular wave shape; Under such circumstances the sine wave alternating current voltage is supplied to the tube in series connection with a resistance. The tube will then function as a voltage limiting device for the two half waves of the alternating current voltage so that each will result in a substantially rectangular wave form.

While the invention has been described with reference to specific structural details, it will be appreciated that changes may be made therein such as employing directly heated cathodes. Various other modifications of the tube structure may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim:

1. In a gaseous discharge tube, an envelope having a portion of given diameter, a plurality of electrodes spaced apart at a distance less than said diameter, a screen surrounding each electrode on three sides in spaced relation with respect, thereto, and means providing an electrical connection between each electrode and the associated screen.

2; In a gaseous discharge over-voltage control device of relatively lowv ignition potential for signal receiving apparatus, an envelope, two substantially parallel cathodes supported from one end of said envelope, a screen embracing one cathode and spaced outwardly therefrom, a screen embracing the other cathode and spaced outwardly therefrom, said screens being open toward each other, and an electrical connection between each cathode and its embracing screen.

3. In a gaseous discharge device for selectively firing at a predetermined low voltage level, an envelope, an ionizable gas filling said envelope, two substantially parallel cathodes mounted in close adjacency at one end of said envelope, means for heating said cathodes, and a screen substantially enclosing each cathode except the opposing sides thereof.

4. In an electric discharge over-voltage control device of relatively low ignition potential for signal receiving apparatus, an envelope, a stem sealed to said envelope at one end thereof, a pair of posts extending from said stem, a screen having a U-shaped cross-section attached to each post, with the open side towards the other post and an electron emitting electrode mounted within each screen.

5. In an electrical discharge over-voltage control device of relatively low ignition potential for signal receiving apparatus, an envelope including a stem, a pair of posts extending upwardly from said stem, a pair of spaced insulation members supported by said posts, a screen having a U- shaped cross-section connected to each post and extending between said insulation members with the open side of said screen towards the other post, and a cathode mounted within each screen.

6. A gas discharge device comprising an envelope, two electron emissive cathodes mounted at one end of said envelope, 2. screen embracing each cathode but spaced therefrom, each screen being open toward the other and an ionizable gas within said envelope.

GC'JSTA F. ASKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,815,762 Charlton July 21, 1931 1,897,482 Kenty Feb. 14, 1933 1,963,008 Weeks June 12, 1934 2,128,051 Lowry Aug. 23, 1938 2,157,552 Macksoud May 9, 1939

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