US2038926A - Electrode supporting structure - Google Patents

Description

April 28, 1936. w. w. EI TEL ET AL ELECTRODE SUPPORTING STRUCTURE Filed Nov. 5, 1932 7 a U m H Y O L G M 2 I W c A M O A M W m M w .m w 5, m. 4 m 2 5 B a a 5T a L. B a 2 7 a E E, ELF? FEE??? :L ,MmHU, l E E E E E E; E E E E: E E E E E E E E E E L u u U IE EE E E E E E E ,L :EEZEIE E EEE EE 5 L 4 1:11:13 11; :JTE r I G G a a U r I a l a vlfllllllarvllll m a z 2 Patented Apr. 28, 1936 UNITED STATES ELECTRODE SUPPORTING STRUCTURE William W. Eitel, San Bruno, and Jack McCullough, Palo Alto, Calif., assignors to .Heintz & Kaufman, Ltd., San Francisco, Calif., a corporation of Nevada Application November 5, 1932, Serial No. 641,400

1 Claim.

Our invention relates to an electrode supporting structure for vacuum tubes, and more particularly to such a structure which removes all mechanical stresses from the lead-in wires.

Among the objects of our invention are: To provide a support for the electrodes of a vacuum tube which does not strain the lead-in wires; to provide a support insulated from all the electrodes of a vacuum tube which carries all the weight of the electrodes; to provide a vacuum tube in which the electrodes are supported independently of the lead Wires, and in which all electrodes are flexibly connected to the lead wires to remove danger of damage by mechanical stresses; and to provide a vacuum tube structure capable of rough handling without damage to the lead wire seals.

Other objects of our invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but we do not limit ourselves to the embodiment of our invention herein described, as various forms may be adopted within the scope of the claim.

In tubes used for radio transmission purposes, particularly those in which the electrodes are of cylindrical shape, concentrically mounted, it is customary to support the electrodes directly on the lead wires. These lead wires are usually tungsten rods sealed through a stem of boro-silicate glass, and are very stiff. The mechanical stresses due to the weight of the elements and the leverage applied, often break the seal around the wires and cause gas leakage and failure of the tube. We have found that such breakage is completely eliminated by independently supporting all the elements, preferably from the body of the tube stem, and resiliently connecting all of the lead wires to the electrodes with flexible links.

In the drawing a preferred form of transmitting tube is shown embodying this form of electrode support.

Figure l is a longitudinal sectional view showing the electrode assembly and support.

Figure 2 is a cross sectional view taken along a plane indicated by the line 2-2 in Figure 1.

Figure 3 is a plan view of the shield covering the ends of the control grid and cathode.

Other features of the tube herein described are disclosed and claimed in our United States Patent No. 1,975,140, issued October 2, 1934.

An envelope l is provided with a double reentrant stem 2 having an outwardly extending pinch 4 through which heater leads 5-5 are sealed. The inner circumference 6 of the reentrant stem has four equally spaced electrode leads 1 sealed therethrough, making a total of six leads through the stem. This construction gives a maximum of separation to the leads and the entire stem is of sturdy construction.

A metal clamp 9 is frictionally applied to the stem, having a small insert of gauze l'll between the clamp and the stem to increase the gripping power of the clamp. Four equally spaced risers H are welded to the clamp and support a stemend insulating positioning member l2. This member is preferably a disc of lava, or like material having good high frequency characteristics, and is drilled with a large number of positioning holes M.

The electrodes of the tube are all in concentric relation and comprise in order, beginning from the outside, an anode l5 provided with cooling fins l6, an outer grid ll, a central grid I9, an inner grid 20, a cathode cylinder 2|, the latter provided with an oxide coating having high electron emitting properties, and a hairpin heater filament 22 positioned inside the cathode cylinder.

The anode and the three grids each have four equally spaced support wires 23 which extend both above and below the body of the electrodes. The cathode cylinder has two stem-end extension wires 24 and two anode end extensions 25. The heater filament is supported at the stem end by heater extensions 26.

All of the support wires and all of the extensions extend through the holes M in the positioning member l2, project slightly on the other side, and are held firmly in place by small wire retainers Z'l welded one above and one below the positioning member. The stem end, or lower end of the electrodes are thus held in spaced relationship as determined by the spacing and positioning of the holes l4.

While we have shown the support wires and extensions entering the positioning member along the same radii, we find it advantageous to stagger the insertions to obtain greater distances between the leads. In any event the anode leads are inserted preferably midway between the insertion of the risers l I so that there may be no chance for anode potentials to reach the clamp 9.

The two heater extensions 26 are connected to the heater leads 5 by flexible heater links 29, and one extension from each of the three grids and the cathode cylinder are connected one to each of the electrode leads 1 around the circumference of the stem by flexible electrode links 30.

The entire electrode structure is thus supported by the clamp 9 through the medium of the risers H and the stem-end positioning member l2. No

shocks or strains of any kind can be transmitted to the leads from the electrode assembly, as the leads are connected to the assembly only through flexible links, and. no anode potential is placed on the clamp 9, as the risers H are dead-ended at the member l2.

The upper extensions and lead wires project through an anode-end positioning member 3|, which in order to reduce weight may be formed as a cross of insulating material of the same kind as the stem-end positioning member. The extensions are secured as in the stem-end member, that is by having a wire retainer 21 welded above and below the member.

As the heater filament is in the form of a hairpin, a tension spring 32 is mounted on the top of the member 3|, having a hook projecting through to engage the apex of the hairpin, and thus maintain it in position.

An anode lead 33 is welded to one of the anode extension wires, of flexible wire and after leaving a small amount of slack, is welded to an anode lead 34 sealed through the upper end of the envelope. On the exterior this lead is fastened to a cap 35 held to the envelope by cement 36.

A shield 31 either in grid form, or a solid piece of metal, is welded by support wires 38 to the center grid extension, on the top of the upper or anode-end positioning member, and extends over and shields the extensions of the inner grid, the cathode cylinder, and the heater tension spring.

It will be seen that all of the weight of the tube electrodes is supported by the risers H, in turn supported by the clamp 9 applied to the main body of the stem. No mechanical stresses can be transmitted to the lead wires through the flexible links, and the leads are relieved from any strain which would tend to break out the seals. It should be noted also that no potential can reach the clamp 9 because of the isolated insertion of the risers in the insulating positioning member l2, and thereby all electrical stresses have been removed from the stem. It is common to support the anode on risers from a stem clamp, and in that case, full anode potentials are applied to the stem adjacent the other leads. Such construction gives rise to stem punctures, particularly when the tube is used as an oscillator at high frequencies.

The structure as described removes both electrical and mechanical stresses from the stem, and practically eliminates danger of failure of the tube due to stem troubles.

We claim:

In combination, a vacuum tube comprising an envelope, a reentrant stem closing one end of said envelope, lead wires sealed through said stem, a plurality of electrodes including a cathode and an anode enclosed in said envelope, an insulating positioning member having apertures therein, certain of said apertures being adapted to receive position defining extensions attached to said electrodes, a clamp of conductive material frictionally applied to said stem, and conductive risers terminating in apertures in said positioning member unoccupied by said extensions, said risers and said clamp being the direct and sole support of said electrodes through the medium of said positioning member without electrical contact with any of said electrodes.

WILLIAM W. EITEL. JACK MCCULLOUGH.

Images