US2422828A - Thermionic tube - Google Patents

Description

June 24, w w EITEL ETA]? THERMIONIC TUBE Fild Oct. 10, 1941 INVENTO'RS WILL/AM w E THE"? ATTORNEY Patented June 24, 1947 THERMIONIC TUBE William W. Eitel and Jack A. McCullough, San Bruno, Calif., assignors to Eitel-McCullough, Inc., San Bruno, Calif., acorporation of, California Application October 10, 1941, Serial No. 414,504 v2 Claims. (01.250585) l 1 Our invention relates ing a thermionic operating unit including electrodes such ascathode, grid and anode.

It is among the objects of our invention to pro- Vide an improved vacuum tube construction, particularly adapted for high frequency work.

Another object is to provide improved means for mounting and establishing electrical connections with the electrodes.

Another object is to provide an improved ar to a vacuum tube ,hav- 4 rangement of leads for the electrodes, adopted for making dual connections with certain of the electrodes, and disposed to effect maximum spacing between the leads.

Still another object is ,to provide an improved envelope for keeping the leads short, yet providing thenecessary spacing between the envelope wallsand theanode.

. A further, object includes the provision of a tube inwhich the design of envelope and arrangementof leads facilitates the assembly and alignment of. theelectrodes.

The invention possesses otherobjects and features of advantage, some of which, with theforegoing, will be set forth in the following descriptio of our. invention. It is to be understood that we do not limit ourselves to this disclosure of speciesof our invention, as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure 1 is a vertical sectional view through the envelope of a tube embodying the improvements of our invention, parts of the internal structure being shown in section and parts in elevation; and

Figure 2 is a similar view taken in a plane through th envelope at right angles to that of Figure 1.

In terms of broad inclusion, our thermionic tube comprises an envelope containing coaxial electrodes including a cathode, grid and anode. Aligned leads extending through the sides of the envelope are disposed transversely of the electrod axis, and means are provided for supporting an electrode on the inner ends of the leads. Both the anode and grid are preferably provided with leads so arranged, and these leads preferably lie in the same plane with the electrode axis. The envelope is preferably cylindrical in shape and is provided with a circumferential bulge disposed about the anode.

In greater detail, and referring to the drawing, our preferred tube comprises an evacuated envelope 2 of glass enclosing a cathode 3, grid 4 and structures.

anode 5. These electrodes may be of any suitable construction, preferably arranged coaxially in theenvelope. H Anode 5 is preferably cylindrical with a hemispherical end cap 6 to shield the upper end of the envelope from heat and electron bombardment. Corrugated fins l are arranged'longitudinally of the anode for radiating heat. Grid 4 is preferably of ordinary cage construction havingvertical wires terminating at a base ring 8 disposed adjacent the lower end of the anode. i

Cathode 3 is of the coiled filament type connected at its ends to supporting leads 9 welded to extension leads I I projecting through pinch l2 of a reenterant stem l3 at the lower portions of the envelope. Since th tube is designed for high frequency work the leads I l preferably project" directly out through the base of th tube to avoid the congestion in the usual pronged base Leads H are preferably somewhat larger than the inner leads 9 for purposes of rigidity; These leads are made of metallic rods, such as tungsten.

A cup-shaped metallic shield I4 is preferably provided on the stem to protect it against heat and electron bombardment. Leads 9 project through a slot in the top of the shield, and the shield is grounded to one of the leads by a welded lip I6. After the shieldhas been assembled a strip I1 is secured in place over th slot to cover the opening leaving only a, small clearance about the other lead. Apertures I8 in the sides of the shield provide openings through which air may be quickly withdrawn during the exhaust process.

Important features of the invention reside in the structure of the envelope and improved means for supporting and establishing connections with the anode and grid. As shown in Figures 1 and 2, the envelope is cylindrical in shape, having a top dome l9 and joined to stem 13 by a, base flare 2|. In a tube having an anode diameter of about inch the diameter of the envelope is about 2 inches. This gives a relatively close spacing between th'e envelope side walls and the electrodes for purposes of making short connections. In order to relieve the envelope from the heat zone about the anode, additional clearance is provided by a circumferential bulg 22 lying between the planes defined by the ends of the anode. This bulge provides an annular recess with the greatest wall spacing at the mid section of the anode where the heat is greatest.-

A pair of aligned leads 23 are provided for the anode, which leads are disposed transversely of th electrode axis adjacent the upper end of the anode. These anode leads extend through seals on horns 24 arranged on opposite sides of the cylindrical envelope wall above bulge 22. The anode is supported on the inner ends of leads 23 by arcuate brackets 26 each welded at one end to an anode flange and at the other end to one of the leads. Each bracket is made from two pieces of metal welded to opposite sides of the anode fin and shaped so that when lying together they form a flanged hollow sleeve for embracing lead 23. This gives strength to the bracket, and the flanges function to radiate heat.

Aligned leads 2! are also provided for grid 4, which leads are also disposed transversely of the electrode axis. These grid leads extend through seals on horns 28 arranged on opposite sides of the cylindrical envelope Wall below bulge 22. Leads 23 and 21 he in the same plane with the axis of the electrodes. The grid is supported on the inner ends of leads 2'! by brackets 29 each secured at one end to ring 3 and at the other end to one of the leads. Brackets 26 and 29 of the anode and. grid are made of a ductile material such as tantalum, while the leads 23 and 21 are rigid rods of say tungsten.

The structure above described provides a pair of leads for both the anode and grid. Connections may thus be made to the electrodes through either one or both of the leads in each pair; and utilizing the dual leads the electrodes may be inter-posed in an external circuit so as to balance capacity. 7

An important feature of our construction is that alignment of the leads provides 'a maximum spacing between the leads in each pair. Another important feature is that the leads extend through the cylindrical walls of the envelope lying closest to the electrode axis; so that the electrical path to the electrodes is kept short. Furthermore, the presence of bulge 22 increases the length of glass path between the anode and grid leads. These are desirable features in a tube for high frequency work.

In addition to the above advantages the tube is easy to fabricate and the electrodes readily assembled in proper alignment. Ease of assembly andalignment of the parts is enhanced-because the electrodes and cylindrical envelope are all concentric, and because the transversely extending leads are aligned in pairs all lying in the same plane with the axis of the electrodes and envelope. Furthermore, the cylindrical envelope with its annular bulge 22 provides a compact tube having improved mechanical strength.

We claim:

1. An electronic tube'c'ompr'ising a substantially cylindrical envelope, an anode andgrid in the envelope, said envelope having a circumferential bulge providing an interior recess disposed about the anode, a lead connected with the anode and extending through the envelope above the bulge, and a lead'connecte'd with the grid and extending through-the envelope below the bulge, said leads being'disposed transversely of the envelope axis.

2. An electronic tube comprising a substantially cylindrical envelope, an anode and grid in the envelope, said envelope having a circumferential bulge providing an interior recess disposed about the anode, a lead connected with the anode and extending through the envelope above the bulge, a lead connected with the gridand extending through the envelope belowthe'bulge, a cathode in the envelope, andleads for the cathode extending through the lower portions of the envelope.

WILLIAM W. EITEL. JACK A. McCULLOUGI-I.

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

UNITED STATES PATENTS Number Name Date D. 127,757 Eitelet al. 1 June 10, 1941 1,937,355 Murphy Nov. 28, 1933 2,019,611 Kolster 'Nov'. 5, 1935 2,022,212 Lippincott etal.' Nov. 26, 1935 1,463,860 Wilson Aug. 7, 1923 1,758,803 Pike 1 May 13, 1930 1,182,290 Meikle May 9, 1916 1,930,713 Heintz et al. Oct. 17, 1933 1,959,019 Clavier May 15, 1934 1,994,219 Hollmann 1 1 Mar. 12, 1935 2,005,257 Eitel et'al. June 18, 1935 2,030,362 Eitel et al Feb. 11, 1936 2,092,886 Kuhle et'al Sept. 14, 1937 2,152,335 Tr'evor'et a1 Mar. 28, 1939

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