US2003468A - Electric gas filled discharge tube - Google Patents

Description

June 4, 1935.

H. RINIA ET AL 2,003,468

ELECTRIC GAS FILLED DISCHARGE TUBE Filed Oct. 23, 1931 :Ei .ll

5 INVENTOR5 HERRE mm 11 Patented June 4, 1935 UNITED STATES PATENT OFFICE ELECTRIC GAS FILLED DISCHARGE TUBE ration of Delaware Application October 28, 1931, Serial No. 571,488 In the Netherlands October 30, 1930 3 Claims.

This invention relates to an electric gas filled discharge tube for converting variations in voltage or current into variations in illumination.

Discharge tubes of this kind are frequently,

.3 used in television devices for receiving, in conjunction with talking film apparatus and the like, images transmitted by telegrapliy or wireless telegraphy.

The invention has for its object to provide a discharge tube adapted to produce a considerably concentrated and intense beam of light although the voltage between the electrodes of the tube is low.

An electric gas filled discharge tube according to the invention comprises an electron emitting cathode, i. e. a cathode adapted to be heated directly or indirectly by a separate electric current, and a cooperating electrode, said electrode being mounted in one part and said cathode in another part of the bulb of the discharge tube, these parts communicating thru a spout or small narrow tube, i. e. a tube the length of which is several times greater than its diameter. This narrow tube or spout need not necessarily be round, but may have, for example, a quadrangular or another shaped cross section. During the operation of this discharge tube, the light produced by the discharge is concentrated within the narrow tube and radiated axially thereof. Viewed from a point in alignment with the tube the discharge constitutes a source of illumination of small area and great intensity. The spacing between the electrodes may be comparatively large, yet the operating and starting voltages of the discharge are low owing to the presence of a thermionic cathode, which is very important in connection with various uses.

A gaseous filling is to be understood hereinafter to mean not only a filling consisting of one or more gases but also a filling consisting of one or more vapours or of a mixture of gas and vapour at a pressure such that the discharge responds to variations in the voltage impressed upon it.

In order that the invention may be better understood and readily carried into efiect two discharge tubes constructed in accordance therewith will now be described more fully by way of example with reference to the accompanying drawing in which Figure 1 shows a discharge tube partially in longitudinal section,

Figure 2 the same tube in elevation and normal to the plane of Figure 1. and

Figure 3 is a view partly in longitudinal section of a modified form of the discharge tube.

The discharge tube shown in Figs. 1 and 2 has an envelope or bulb of glass or similar material to which a re-entrant stem 2 comprising a press 3 is sealed. The press 3 has fixed to it a small narrow tube or spout 4 which projects from and is coaxial with the stem and which may be of refractory material, for example, of quartz, and which is preferably non-transparent. The lower part of this spout 4 is surrounded by a glass tube 5 sealed to the press 3. The length of the narrow tube or spout 4 is several times greater than its diameter.

v The lower part of the tube 4 contains an electrode 6 preferably of carbon or tungsten, and connected to'a leading-in wire 1. Arranged laterally of the tube 4 is an electron emitting electrode, such as a cathode 8 connected to two leading-in wires 9 and I0 and consisting, for example, of a helically wound tungsten wire coated with a substance capable of copiously emitting electrons, for example, barium oxide. The part of the discharge tube in which the anode or electrode 6 is enclosed and that part in which the cathode 8 is mounted communicate thru the narrow tube or spout 4 so that the path of discharge between the electrodes is mainly within the tube or spout 4. Mounted a short dis-- tance from the open end or mouth of the tube or spout 4 is a disc shaped screen i I carried upon a supporting rod I2, and having in it an aperture l3 in front of or in registry with the mouth of the spout 4.

The discharge tube contains a gaseous filling of a rare gas, such as neon, argon, or the like at a pressure such that the discharge will respond to variations in impressed voltage, and which is usually under a pressure of a few millimeters of mercury. This gaseous filling may also contain some mercury vapour, and to this end a drop of liquid mercury may be introduced into the discharge tube, in which case it is sometimes desirable that the envelope or wall of the discharge tube should be at least for part of its length of material transparent to ultra-violet rays.

During the operation of the discharge tube shown in Figs. 1 and 2 the cathode 8 is heated by a separate source of current up to the temperature of electron emission. When a suitable ,5

voltage is applied between the cathode 8 and the electrode 8, which functions as an anode, there is struck between the anode and cathode a luminous discharge which is mainly concentrated within the tube or spout 4. If voltage variations are superimposed on the normal voltage between the electrodes 6 and 8, the intensity of the light radiated by the discharge has corresponding variations. Owing to the fact that the spout 4 is long and narrow, the light radiated axially of this spout will have great intrinsic brilliance. In spite of the use of this long spout 4 the voltage necessary to sustain the discharge between the electrodes is very low. After the discharge has been started, the voltage between the electrodes of the discharge tube shown is, for example, merely about 20 volts, whereas the current intensity is, for example, 200 milliamperes and can be increased even to a much higher value.

The screen I l in the upper part of the discharge tube serves to retain particles of material which are evaporated from the electrode 6 and which, if they were precipitated on the wall of the discharge tube, would decrease its transparency to the rays to be emitted.

The discharge tube shown in Figure 3 has an envelope l4 enclosing an electron emitting cathode l5 mounted on a press l6 and containing a metal hood I! sealed to the wall of the envelope and consisting, for example, of chrome iron. This hood terminates in a narrow metal spout l8 having the same function as the tube 4 of the discharge tube shown in Figures 1 and 2. The spout I8 is surrounded by a metal cylinder or anode I! which is carried by a lead 20 fixed to a press 2| and connected to a leading-in wire 22 extending thru the press 2|. The hood I! is connected to a leading in wire 23 which is also taken out thru the press 2 I. This discharge tube has also a suitable gaseous filling, such as is used in the tube shown in Figures 1 and 2.

In the discharge tube shown in Fig. 2 a luminous discharge is struck between the electrodes I5 and IS. The starting of the discharge may be facilitated by supplying voltage to the hood H which thus has the function of an auxiliary electrode. The discharge is concentrated within the spout l8 and owing to the use of the electron emitting cathode the voltage necessary to sustain the discharge between the electrodes is low in spite of the large spacing between them.

We claim:

1. A gaseous conduction luminous discharge device comprising a sealed envelope, a re-entrant stem, a spout mounted coaxial with and extending from said stem, an anode mounted on said stem within said spout and at that end remote from the mouth of the spout, and an electron emitting cathode mounted on said stem outside said spout and intermediate the stem and the mouth of .said spout.

2. A gaseous conduction luminous discharge device comprising a sealed envelope, a metal partition in said envelope having an elongated spout, an electron emitting cathode in said envelope on one side of said partition, remote from the spout, an anode in said envelope on the other side of said partition, and surrounding the spout, and a lead wire connected to said partition.

3. A gaseous conduction luminous discharge device comprising a sealed envelope enclosing a partition of chrome iron sealed at its edges to the wall of said envelope to divide said envelope into two chambers and having a spout which forms a passage between said chambers, an electron emitting cathode mounted in one chamber, an anode mounted in the other chamber and out of registry with the spout of said partition, and'a lead wire connected to said partition.

HERRE RINIA. HENDRIK J OHANNES MEERKAMP VAN EMIBDEN.

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