US2491735A - Stem structure for electron tubes - Google Patents

Description

INVENTOR. 6to/*don Z/z/O w65 BY a Dec. 20, 1949 yfrs 'A'.HQWES STEM STRUCTURE FOR ELECTRON TUBES Filed June 2, 1947 .IIA mn..

Patented Dec. 20, 1949 STEM` STRUCTURE FOR ELEGTRGN'TUBES' Gordong T. Howes,y Belmont., Galifa, assigner?v to;` EitelMcCullcugh. Inc.,r San- Bruna Cama., a corporation ofCalfornia Application June 2, 1947, Serial No. 751,847

1 Claim. l

The invention relates to electron tubes such as vacuum tubes, and more particularly to an improved stem structure for such tubes.

The principal object of the invention is to provide a compact stem structure which affords terminal connectors for an electrode land also prolvides an exhaust tubulation for the tube envelope.

The invention possesses other objects and features of advantage, some of which, with the foregoing, ywill be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species of my invention as I may adopt variant embodiments thereof within the scope of the claim.

Referring to the drawing the single figure is a vertical sectional view of an electron tube embodying the improvements.

In terms of broad inclusion, the improved electron tube comprises an envelope enclosing an electrode, and a tubul-ar metallic stern member on the envelope, which member is ported into the envelope to provide an exhaust tubulation and projects externally of the envelope to provide a terminal for the electrode, the outer end of the member having its side walls compressed together to close the tubulation. In the preferred construction a pair of coaxial stem members are provided, the inner of which serves as the exhaust tubulation.

In greater detail, and referring to the drawing, the improved stem structure is shown in a diode type of electron tube, it being understood that the improvements may be incorporated in tubes having more electrodes such `as triodes or the like. The tube illustrated is a 4diode of small physical size adapted for use in compact spaces such as in a probe, and comprises an elongated evacuated envelope having a cylindrical 4wall section 2 of vitreous material such as glass. An anode 3 at one end of the envelope is formed by the inner end of a metallic rod 4 such as tungsten sealed to the upper end of the wall section 2.

A cathode is supported by the improved stem structure at the other end of the envelope. This stem structure comprises an outer tubular metallic stern member 1 sealed to the lower end of wall section 2, and an inner metallic stem member 8 coaxial with the outer member. These stem members provide terminal connectors for the cathode, and by their coaxial arrangement are adapted for plugging into a socket or the like. The inner stem member 8 is also tubular and is ported into the envelope to provide an exhaust tubulation. After evacuation the tubular member 8 is pinched off at tip 8 to compress the side (Cl. Z-27.5)

2 walls of the tubulation together to seal the envelope. To facilitate this pinching off operation the inner stem member 8 is preferably made of a relatively soft metal such as copper.

An extension II of thinner wall metal tubing is brazed to member 8 and is aligned with another section of tubing I2. These sections are connected together and electrically isolated by a sealing ring I3 of vitreous material such as glass. A metal supporting sleeve I4 is braced at the upper end to stem section I2 and at the lower end to outer member 'I at Ibraze I6. By this arrangement the inner parts of the stem structure may be assembled as a unit and inserted into the open end of the outer stem member 1, the parts being finally secured together by the braze I6 iat the lower registering edges.

The cathode illustrated is of the indirectly heated type comprising an emitter body I1 heated by a resistance coil I8. Body I1 may be of nickel coated with suitable oxides for electron emission purposes, in accordance with the common practice of making cathodes of this kind. The cathode body I1 is connected to the outer stem member 1 -by supporting wires I9 projecting from tubular piece I2. Heater coil I8 is surrounded by ya heat shield 20 and is connected at the upper end to cathode body I1 and at the lower end to a center rod 2I secured to inner stem member 8. A ring 22 formed at the lower end of rod 2| facilitates brazing this rod in position. By these connections it will be seen that the cathode body is connected to the outer stem member and that the heater is connected across the inner and outer stem members. It is understood that the cathode may be of the filament-ary type such as a thoriated tungsten iil-ament, in which case the filament would be connected across the terminal members in a manner similar to the heater coil I8.

In order to shield the envelope and other parts of the tube from material sputtered from the cathode a tubular metal shield 23 is preferably mounted on sleeve I 4 to project upwardly inito the regions surrounding the cathode. For similar reasons a transverse shielding disk 24 is preferably provided below the cathode body, held in shield 23 by a retaining ring 26. It is understood that the entire cathode structure is mounted on the inner stem assembly prior to inserting sleeve III into the outer stem member 1. After inserting the inner stem assembly the iinal braze I6 is made to complete the envelope. At this stage the tubulation member 8 is, of course, open ended for purposes of exhausting the envelope. Following evacuation the exhaust tubulation is pinched off at tip 9 to seal the envelope and leave the tubulation in condition to function as a terminal member.

The improved stem structure above described, incorporating the exhaust tu-bulation as a terminal connection for the cathode, has special advantages in tubes of small 'physical size where space is at a premium.

I claim:

An electron tube comprising electrodes and an 10 of the envelope to provide an exhaust tubulation 1 and rprojecting externally of the envelope. the

outer end of said member having its side walls compressed together to close the tubulation, said outer projecting end being exposed externally of the envelope to provide a rigid terminal prong.

GORDON T. HOWES.

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

UNITED STATES PATENTS Number Name Date 2,431,337 Litton Nov. 25, 1947 2,455,957 Spencer Dec. 14, 1948

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