US2381490A

US2381490A - Electronic tube

Info

Publication number: US2381490A
Application number: US450755A
Authority: US
Inventors: William W Eitel; Jack A Mccullough
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1942-07-13
Filing date: 1942-07-13
Publication date: 1945-08-07
Anticipated expiration: 1962-08-07

Description

w. w. EITEL ET AL ELECTRONIC TUBE Filed July 15, 1942 2 Sheets-Sheet 1.

Au 7, 1945. I

WILLIAM dAC A. M5 CU L THEIR A'ITORNIY INVENTORS W. E I T L y UCFH Aug. 7, 1945. w. w. EITEL ET AL $381,490

ELECTRONIC TUBE Filed July 15, 1942 '2 Sheets-Sheet 2 EL Z 5/ IIN'VENTORS WILL/AM w. EITEL v v dA K A. MEC LLOUGH r4 15 BY g THEIR ATTORNEY ing an exhaust tubulation 1.

r Patented Aug. 7,1945,

- IEIIIJECTRONIC TUBE' William W. ,Eitel, San Ban-0, anaiJ'ack. A. I. h,'Millbrae, Calif.', assignors to Eii McCullough, Inc., SanB 1 ,tiqnrorosliforma.

ri1no,"0alif., a corpora v Applicationluly13, 194.2,v samNmli ges I i'ol im. (crimp-+2.75)

Our'iinventionyrelatesjto an electronic tube" It is among the objects of our'invention to providean improved structure of, arrangement for. and mounting of the electrodes and leads in the envelope of a tube.

Another object is to provide an electrode" I mountingwhich protects the glass sealabout a lead from cracking under heat originating at the electrode.

The invention possesses other objects and feae tures of advantage, some of which, with the foregoing, will be set forth inthe followingdescription of our invention. Itis to be understood that We do not limit ourselves to this disclosure of species of our invention, as we may adoptvariant embodiments thereof Wi thin the scope of the claim. 9

Referring to the drawings:

Figure 1 is a perspective view of a tube embodyingthe improvements of our invention; and,

Figure 2 is a vertical sectional view of the same.

.Figure 3 is a fragmentary perspective view I showing a modified plate support.

' In terms of broad inclusion,your tube comprises an envelope having a reentrant stem at one end thereof. A plurality of electrodes including a plate, andgrid and cathode are arranged in theenvelope. The cathode leads are sealed to the stem; the plate lead to the opposite end of the envelope; and the grid lead to a side wall. Improved-means are provided for mounting; the plate; and improved means are further provided for protecting the envelope from cracking at the lead seals.

v In greater detail, and referring to the draw ings, our tube comprises anenvelope of glass or the like having a bulb-shaped body 2 terminating at the top in a reduced neck 3-and atthe bottom in a larger neck 4 carrying a reentrant stem 6 havfitted with a cup-shaped base 8 of metal having a bottom disk 9 of porcelain carrying prongs II.

This base is secured to'neck 4 by a suitable cement l2.

Within the envelope are disposed a plurality of coaxial electrodes including a cathode l3, grid Hand plate or anode H5. The plate is a hollow cylindrical body of suitable material, say tantalum, preferably formed of sections having flanges welded together to form heat radiating fins H. The lower end of plate I6 is open, facing stem 6. A hemispherical cap I8of tantalum is secured to the upper end of the plate by-depending tabs [9 particularly adapted for transmission purposes.

. welded to therirn. Arched recesses 21. in'the cap between tabs l9 provide vent openings..- This end cap forms part of the plate supporting means, and also protects the glass at the upper end of the envelope against heat and electron bombardment.

Plate lead 22 of tungsten projects'thru the end of top neck 3 at seal 23 and carries an external terminal button 24. In'order to stop heat from flowing out along the tungsten lead and cracking the glass at the seal, the inner end ofthis lead is terminated short of the electrodes, leaving a considerable spacing between the inner end of the lead and cap I8. A tubular bracket 26 of tantalum, preferably conical in shape, is interposed to the cap. This conical bracket on the dome of the hemispherical cap provides a strong mounting having sufiicient rigidity, to hold the plate in proper alignment even under severejarring of The envelope is the-tube. v

The thin walls of the tubular bracket augment the heat radiating surface provided by cap 18, so that both bracket and cap cooperate to thermally insulate the lead and its seal 23 from the heat zone at the plate. The heat that tends to flow by conduction toward seal 23 is thus largely dissipated by radiation before it reaches lead 22. Our improved structure overcomes the problem of cracked seals so bothersome in tubes where a lead is brought in close to the heat zone at the electrodes.

' 'Grid I4 is of the cage type, preferably of platinum wire, terminating in a tantalum base ring 21. This electrode is supported by a bracket 28 ona lead having an upturned portion 29 and a transverse portion 3! projecting thru the side of the envelope at seal 32; the latter seal being preferably formed in the cylindrical wall of neck 4.

Bracket 28 is made of a strip of tantalum bent '.Tab 34, formedas a knock-out when thedisk aperture is made, is conveniently welded to the lead.

I Cathode l3 preferably'comprises a pair of hairpin filaments of thoriated tungsten having the" lower ends secured to a pair of leads 36 sealed .in press 3'! of stem 6. The upper ends of the filaments are hooked over a cross piece 38 slidable on a central standard 39; the filament wires being held under tension by a spring 4 I encircling the standard and bearing against a sleeve 42 engaging under cross piece 38.

Since stem 6 faces the lower open end of plate 16, and is subject to considerable heat and electron bombardment, a cup-shaped metallic shield 43 is arranged over the end of the stem. The shield is provided with openings in the top, thru which cathode leads 36 project. COnnection between central standard 39 and the shield is effected by tabs 44 welded to the parts.

Figure 3 shows a modified plate mounting in which the bracket has an elongated tubular core 46 with longitudinally extending fins 41. This will dissipate more heat thanthe structure first described, and is adaptable for larger tubes. Because the tubular bracket lies between the end of lead 48 and cap 49 it cooperates with the latter to thermally isolate the lead from plate 5|. The lower portion of the bracket is preferably made of tantalum, with outturned tabs 52 welded to the dome of cap 49. This joint is easily made as tantalum welds readily to tantalum, A tantalum to tungsten weld is more difficult to make however, so we prefer to form the upper portion of the bracket of nickel. Nickel welds nicely with both the other two metals, producing strong clean joints. The welding problem is taken care of in the structure first described by means of a nickel sleeve 54 interposed between the lead and bracket.

We claim:

An electronic tube comprising an envelope having a reentrant stem at one end thereof, a hollow plate in the envelope having an open end facing the stem, means interposed between the plate and stem for shielding the stem against heat and electron bombardment from the open endtof the plate, a capon the other end of the plate, a lead sealed to the envelope, means supporting the plate on said lead, a cathode adjacent the' plate, and leads for the cathode sealed 20 to the stem.