US1950955A - Photo-electric tube - Google Patents

Description

March 13, 1934. s. WEIN PHOTO-ELECTRIC TUBE Filed Jan. 28, 1950 INV A WW2 BY A TTORNE Y.

Patented Mar. 13, 1934 UNITED STATES PHOTO-ELECTRIC TUBE Samuel Wein, New York, N. Y., assignor to Radiovision Corporation, New York, N. Y., a corporation of New York Application January 28, 1930, Serial No. 423,984

1 Claim.

This invention relates to photoelectric tubes.

The invention has for its object the construction of a photoelectric tube which can be readily duplicated, and which is simple to manufacture.

The conventional photoelectric tube, 1. e., in which an alkali metal is deposited on the inner wall of the glass container is difficult to manufacture as great skill and care must be exercised to distill the alkali metal on the inner surface of the glass. Tubes so constructed are seldom alike, irrespective of the fact that a plurality of these tubes are made simultaneously and under the same conditions. The costs of manufacturing such tubes are high, because not all the tubes made can be used.

By the present invention, photoelectric tubes are easier to manufacture, and the tubes may readily be reproduced having the same characteristics. The constructional design permits of manufacture by automatic machinery, in the same fashion as is done with incandescent lamps, radio and other tubes.

In the accompanying drawing:--

Figure l is a rear view, partly in section, of a photoelectric tube embodying the invention, and

Figure 2 is a front view showing the arrangement of the parts of the photoelectric tube, of Figure 1, with the container omitted.

The numeral 1 denotes a container preferably a glass vessel, such as the ordinary tube. It is obvious of course that quartz, or other transparent material, may be used.

The cathode 2 may take the form of a metal box, on to which is deposited a thin and homogeneous film of any of the oxides of the alkali metals. This film is indicated at 3. Many metals may be used for the box and the film, depending upon the results desired.

The cathode may be of any shape or form, such as a tube, as long as it serves to cut off light from the heater element or filament, as hereinafter referred to.

The outer surface of the cathode may be oxidized in any convenient manner, either before being mounted in the container, or after being assembled. Any suitable method of depositing the sensitive film thereon may be used and several methods are known.

The cathode 2 may be made of one piece, or of several pieces conveniently folded over and spot welded as indicated at 4. If metal tubes are used, there is no need of folding the metal over, a top and bottom cap being applied to same.

8 is a bottom plate with a slot therein, as shown in Figure 1, so as to permit the filament terminals to enter the cavity within the cathode. This bottom plate may be made of the same material as the cathode 2, or it may be made of a refractory material or glass.

The heavy wires 9 are supports to hold up the cathode 2 and one of them continues through the press or seal of the tube and connects to one of the circuit terminals thereof.

Inside of the cathode 2 is placed filament 7. This filament may be made of platinum or nickel with a film of alkali metal oxide thereon, or it may be made of thoriated tungsten, molybdenum, etc.

The heater element 7 may be of any suitable type, and need not necessarily be a filament which is shown merely by way of illustration.

The filament is supported by spring 6, which is intended to take up the filament 7 during stretching. Spring 6 is held in position by the insulator 5 mounted upon the cathode.

By the construction just described, light from the filament or heater 7 is prevented from impinging upon the sensitive surface 3 of the cathode. Such light would interfere with the operation of the tube, for obvious reasons.

The filament '7 may be used in the production of the metal oxide, as for instance by passing a potential through same thereby causing the metal box to become hot, and if oxygen at a low pressure is admitted to the glass container, the metal surface or alkali metal film on the cathode will be converted into the corresponding oxide.

If a potential is passed between the cathode 2 and the anode grid or collector 10, while element 2 is hot (or cold) in the presence of a low pressure in oxygen, it will convert the metal film 3 into the corresponding oxide. This potential may be either D. C. or A. C. of suitable voltage.

After the metal film constituting the sensitive surface 3 has been formed, the glass vessel is highly evacuated and sealed off. The tube so formed is now mounted on the usual support or base and provided with the necessary terminals (not shown) for the filament, anode and cathode.

Noble or inert gases may be incorporated in the glass container prior to its being sealed off.

The filament 7 may be used as a means to bombard the cathode 2, without actually heating the same, the heating effect in this case being of secondary consideration as the tube will function by bombardment only under certain conditions.

Many modifications of this photoelectric tube construction are possible, without however departing from the appended claim.

I claim: 7

A photoelectric tube comprising an envelope housing a hollow cathode coated upon the exterior surface with a photo-sensitive coating of an alkali-metal oxide and having within a heater element therefor, and a foraminous anode mounted in front of said cathode.

SAMUEL WEIN.

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