US2105818A - Voltage indicating electron discharge tube - Google Patents

Description

2 Shegts-Sheet l JNVENTOR MIMI 20. @m/Fcm H. W. PARKER AGE INDICATING ELECTRON DISCHARGE TUBE Jan. 18, 1938- Filed June 22, 1957 Jan. 18, 1938. H. w. PARKER 2,105,818

VOLTAGE INDICATING ELECTRON DISCHARGE TUBE 2 Sheets-sheaf 2 Filed June 22, 1937 I INVENTOR. +zsn-v. Q0. 9 m

BY t

ATTORNEY.

Patented Jan. 18, T938 UNITED STATES VOLTAGE INDICATING ELECTRON nrs- CHARGE TUBE Henry W. Parker, Toronto, Ontario, (Lanada, as-

signor to Rogers Radio Tubes Ltd., Toronto, Ontario, Canada, a corporation of Ontario,

Canada Application June 22, 1937, Serial No. 149,559

4 Claims.

My invention relates to voltage indicating devices and more particularly to thoseof such devices which employ fluorescence produced by electron bombardment to, by varying configurations of contrasted luminous and dark areas, indicate varying voltages.

Such electronic voltage indicators, as they may be termed, have many uses: for example, to indicate the resonant or tuning position of radio 30 receivers, in test equipment and modulation meters. Voltage indicators of this type, as now made, have several undesirable features which severely limit their eifective use. They have low contrast ratio, that is, differentiation between 15 luminous and non-luminous areas. They have low aspect ratio, that is, insuificient configuration contrast between the area-illuminated and the dark area for different degrees of voltage excitation. They have low sensitivity and finally the 2d target is subject to fatigue. This is one of the chief difficulties with such voltage indicators as now made. Fatigue is the diminution ofbrightness of the fluorescent screen with time of operatlon. The reason for this diminution is not that the fluorescent material loses the capacity of fluorescing, but is due to the formation of a surface film of foreign atoms which develops on and covers the fluorescent material as a thin coat approximately one atom thick. The ratio a of formation of this film is linear with respect to time of operation and depends upon the number of coulombs of electron charges which have bombarded the screen. The surface layer which causes fatigue can be evaporated off by heating 6 the target in a radio frequency furnace. The film and the fatigue process will, however, start all over again.

I have discovered, experimentally verified and proven by actual construction and demonstration that if the target is coated with black carbon in the form of soot and the fluorescent material placed on such carbon soot coating, and the target employed with the novel construction and arrangement hereinafter described, that all of the above noted undesirable features can be eliminated.

One of the principal objects of my invention comprises producing an electron voltage indi- 50 cator having long life and minimum fatigue.

A further object comprises producing an elec tronic voltage indicator having maximum aspect ratio and maximum contrast ratio.

A further object comprises producing an elec- I' tronlc voltage indicator which is simple, effective and efficient and one having maximum sensitivity to impressed voltages.

I accomplish all of the above noted desirable objects and results and others which will hereafter be apparent by means of the novel 5 construction, combination and arrangement of parts which will be hereafter more specifically described with reference to the accompanying drawings forming a part of this specification and in which like reference numerals designate cor- 1 responding parts throughout.

In the drawings:

Fig. 1 is an enlarged, partially broken and partially sectioned, side view of my improved voltage indicator;

Figs. 2, 3, 4, and 5 are reduced plan views of the target of Fig. 1 showing variousdegrees and configurations of illumination dependent upon variant impressed voltages;

Fig. 6 is a sectional plan view taken on the line B6 of Fig. 1;

Fig. 7 is a sectional plan view taken on the line 1-1 of Fig. 1; and

Fig. 8 is a schematic diagram of the connections of my improved voltage indicator showing the preferred potentials and polarities applied to the electrodes.

Referring now to the drawings and in particular to Figs. 1, 6 and 7, the envelope i may be constructed, as shown, of glass and is provided with the usual stem and press 2. The stem and press serve to support the electrodes within the envelope. The triode section comprising a cathode 4, grid 5, and anode 6 is supported in the usual manner between ceramic supports as shown and 3 maintained in position on standards It and i2 by means of metallic locking bars 1 and 8 attached to the standards. Terminals emerging through the envelopes are provided as shown for the cathode heater,3, grid 5 and anode 6. Standards l3 and I4 serve to support the target section comprising the flared target l1 mounted on metallic plate l5, which is in turn rigidly attached to standards l3 and M, as shown. Mica separators 9 and iii are provided between the target 5 and the triode sections and are attached to standards I3 and Hi. These serve to support the target cathode i8, which is separate from the triode section cathode 4, but heated by the same heater 3. vanes 22 and 23 are positioned 180 apart and between the target i1 and the target cathode l8, as shown. Vane 23 is attached to and supported by standard Ii, while vane 22 is attached t0 a d supported by standard i2. The vanes are I interconnected electrically by means of the triode section holding bars 1 and 8 and are further con- I nected to the anode 6 of the triode section by metallic strap 25. A terminal 20 is provided for the target cathode i8. As usual, ,the cathode sleeves bear, as indicated, active electron emissive material thereon. A light shield is to block off direct light from the cathode I8 is supported on standards as 24 which are welded to cars as 21 in metallic plate IS. The inner surface of the flared target I1 is coated and is positioned with such inner surface facing the extremity of the envelope I. The electrodes are centered within the envelope by means. of

mica disk It.

It should be particularly noted that while the cathodes I and I8 are provided with a common heater 8, they are otherwise separate and insulated from each other. It should be further noted that target I! is through standard l3 provided with a terminal separate from the terminals of the other electrodes in the tube whereby the prong terminal base. not shown in the drawings, I

is in the usual manner attached to the bottom of the envelo e.

The li ht shield is preferably made of carbonized nickel. while the target is constructed of nickel. The soot or black carbon is formed on the cold nickel of the target by sooting it over a flame of acetylene. This coating of soot is very soft and cannot be handled and acts as the imbedding medium for the fluorescent material willemite (zinc silicate) which is sprayed in the usual manner on top of the soot coating so that the fluorescent material is not in contact with the nickel but rests in a cushion of' soft soot. The carbon has a high thermionic work function and is a good electrical conductor. The carbon bein black assists in greatly im roving the contrast ratio between luminous and dark areas. Due to the high work function of the carbon the secondary emission of electrons therefrom is reduced to a minimum. thus still further improving the contrast ratio. The carbon also acts as a means for separating the fluorescent material from the nickel of the target. Nickel tends to poison the active centers of the fluorescent material. hence the separation of the fluorescent material from the nickel of the target allows greater luminous efliciency from the fluorescent material. The carbon also acts as an absorber of gases and thus minimizes the formation of the fllm producing fatigue. Also, the carbon moderates the temperature elevation of the fluorescent material during the exhaust process and further prevents the formation of a zinc mirror and its necessary redistillation. The use of carbon thus greatly increases the useful life and brilliance of the device.

By the use of a cathode for the target section separate from the cathode of the triode. section v the deflection capability of each target vane is greatly improved so that two vanes each giving an angle of shadow greater than 90 may be effectively utilized to render the aspect ratio a with carbon black soot and fluorescent material as hereinafter described zero voltage input;

I strong voltage excitation.

' sensitivity is increased.

I I have found that with the potentials and polarities impressed on the electrodes as shown in Fig. 8 and with the cathode heaters properly energired, and the voltages to be indicated applied to the input terminals and II, that my improved voltage indicator exhibits for various voltages the configurations of light and shadow as shown in Figs. 2, 3, 4, 5, in which the shaded portions indicate dark areas and in which:

- Fig 2 illustrates the aspect of the target at Fig. 3 illustrates the aspect of the target at relatively low voltage input; I

Fig. 4 illustrates the aspect of the target under medium voltage excitation; and

Fig. 5 shows the appearance of the target under Figs. 2-5, inclusive, are reduced views of the target of Fig. 1 with the voltage indicator tipped toward the observer from the sheet upon which it is drawn and clearly show the improved aspect ratio achieved by the wide shadow angle for each vane.

The lighted area of the target is controlled by means of the vanes 22 and 23 and as these are connected directly to the anode 6 of the triode, they have at all times the triode anode potential thereon and as the triode anode potential falls due to an increase of anode current through the 1 megohm resistor (see Fig. 8) the vanes likewise fall in potential so that they are negative with respect to the target but positive with respect to the target cathode. This action causes the electron beam to cast a shadow for each vane on the target and the angle of this shadow is a direct function of the vane potential or the triode anode potential which is in turn a direct function of the input signal potential. The triode section is used not only as a controlling means for the illumination of the target, but also to amplify the voltage of the impressed electromotive forces which it is desired to observe so that the potentials impressed on the. vanes will have a wider range and produce a greater control of the fluorescence on the target.

It will be apparent from the foregoing that I have produced an improved electronic voltage indicator having long useful life and increased brilliancy; one exhibiting a minimum of fatigue and having maximum aspect and contrast ratios; further, that my voltage indicator is simple, effective and emcient and has maximum sensitivity to impressed voltages. v

Although Ihave shown and fully described, by

way of example, only one embodiment of my invention, it will be apparent that many changes may be made therein without departing from the intended scope and spirit of the invention. I do not, therefore, desire to limit myself to the foregoing except as may be pointed out in the appended claims in which I claim:

1. An electronic voltage indicator comprising, a substantially evacuated envelope, which is transparent, a cathode, control vanes, and an electron target disposed within said envelope with terminals therefor emerging from said envelope, said target surrounding said cathode and vanes and being insulated therefrom, the surface of said target facing said cathode being coated with carbon in the form of black soot and bearing on such coating an additional coating of substance adapted to be rendered fluorescent upon electron bombardment, said coated one end of surface g which is transparent,

thereon a coating of a being disposed facing the transparent portion of said envelope and further electronic means enclosed in said envelope and connected within said envelope to said vanes for controlling the bombardment of said. target by electrons from its associated cathode.

2. An electronic voltage indicator comprising, a. substantially evacuated envelope, one end of which is transparent, a cathode, control vanes, and an electron target disposed within said envelope with terminals therefor emerging from said envelope, said target surrounding said cathode and vanes and being insulated therefrom, the surface of said target facing said cathode being coated with black carbon soot bearing thereon a coating of substance adapted to be rendered fluorescent upon electron bombardment, said coated surface being disposed facing the transparent portion of said envelope and further electronic means enclosed in said envelope and including a cathode separate from said first-mentioned cathode and an anode connected within said envelope to said vanes for controlling the bombardment of said target by electrons from its associated cathode.

3. An electronic voltage indicator comprising, a substantially evacuated envelope, one end of a cathode, control vanes, and an electron target disposed within said envelope with terminals therefor emerging from said envelope, said target surrounding said cathode and vanes and being insulated therefrom, the surface of said target facing said cathode being coated with black carbon soot bearing substance adapted to be rendered fluorescent upon bombardment by electrons, said coated surface being disposed facing the transparent portion of said envelope, an additional cathode, a grid and anode enclosed in said envelope with terminals therefor emerging from said envelope, said anode and said control vanes being interconnected within said envelope whereby the bombardment of said target by electrons from its associated cathodes may be controlled.

4. An electronic voltage indicator comprising, a substantially evacuated envelope, an end portion of which is transparent, enclosing a cathode, grid and anode constituting a. triode section, and a cathode, a pair of control vanes and target constituting a target section, said being separate from said triode cathode and said vanes being located 180 from each other and between said target cathode and said target, and said vanes being interconnected within said envelope, said target being flared and positioned with the inner surface of said flare facing the transparent portion of said envelope and surrounding its cathode, said inner surface of said target being coated with carbon in the form of soot and on such coating bearing a coating of substance adapted to be rendered fluorescent upon bombardment by electrons and said anode of said triode section being connected within said envelope to said vanes to control the bombardment of said target.

HENRY W. PARKER.

target cathode

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