US2178747A - Shielded metal discharge tube - Google Patents

Description

Nov. 7, 1939. w. ESPE SHIELDED METAL DISCHARGE TUBE Filed Jan. 6, 1939 INV EN TOR.

WERNER ESPE A TTORN E Y.

Patented Nov. 7, 1939 SHIELDED METAL DISCHARGE TUBE Werner Espe, Berlin- Siemensstadt, Germany, as-

signor to Fidea Gesellschaft fiir die Verwaltung und Verwertung von gewerblichen Schutlrecliten mit beechritnkter Haitung, Berlin, Germany, a corporation of Germany Application January 6, 1939, Serial No. 249,585-

In Germany March 22, 1938 2 Claims.

This invention relates to means for shielding lead-in conductors in electron discharge devices with metal envelopes.

The usual discharge tube with a metal envelope has the advantage that electrodes in the envelope are shielded from extraneous or outside electrical influences. In addition the-heat dissipated in the electrode assembly, by virtue of the higher thermal conductivity of a metallic bulb or shell, can be carried away more rapidly.

One important problem in manufacturing discharge tubes with shells or envelopes concerns the insulatingly sealing of the lead-ins for the electrodes to insure permanent vacuum-tightness. The preferred seal, because of its ruggedness, good insulating properties and ease of manufacture, is the type with a glass disc containing the leads sealed to a ring, U-shaped in cross section, which is welded to the flared rim of the metal shell. However, in this case shielding between leads carrying high frequency currents is not as eiiective as desired. In other types of tubes known in the art, a metal plate or header is employed to close the tube, this plate being provided with tubular extensions or eyelets positioned at right angles to the plate in which the current-supply leads are sealed by glass. One difliculty which arises in these tubes is insufllcient insulation between the current supply leads and the metal header. The result is that if metallic vapors such as getter vapors are liberated in the interior of the tube either during manufacture or during use, these vapors deposit on the insulation, and establish a conducting path between the tubular eyelets, the lead-ins themselves and the header. Also in the tube with the glass disc type of header, the difiiculties with deposited metal on the insulation arise quite often According to this invention, the advantages of the glass disc header is retained while the leads are efiectively isolated fromeach other for high frequency interaction, insulating surfaces of the header are protected from metal deposits, and the electrodes within the tube are completely enclosed in metal. According to the invention, an electric discharge tube having a metallic shell is closed at the bottom end by a conventional glass disc header which is united gastight with the metal shell. Into the glass disc are sealed the current-supply leads and inside the tube, spaced a short distance above the glass disc, is disposed a plate of metal designed'tc cover up the glass plate and extend to the periphery of the glass disc. The metal plate has perforations or holes through which the leadin wires are passed, the holes being large enough to'insulatingly space the edges of the holes from the wires.

The interior of a tube constructed according to this invention is completely shielded from external electric disturbances, the glass stem or disc carrying the leads is protected from conducting deposits, and electrostatic coupling be-' tween leads is effectively reduced. Contrary to the expected results, the metal plate parallel to the glass disc and normal to the lead wires, deflects and intercepts most of the electrostatic lines of force emanating from each wire and prevents their linking with other wires.

The appended drawing shows by way of example ways and means for carrying out the basic idea of this invention. Figures 1 and 3 are sectioned views of tubes made according to this invention and Figure 2 is a detailed view oi. an interelectrode shield.

A tube according to the invention as shown in Figure 1 comprises a metal envelope or shell I which is closed at its lower end by a glass plate or disc 2. The tube shell and glass plate are hermetically joined by an elastic intermediate ring 3 with a radial flange which, along the areas 4 and 5, is united by welding or brazing in a vacuum-tight manner with the flared rim of the metal shell. The'ring 3 is U-shaped in cross section and in the embodiment shown in Figure 1, the ring is telescoped into the shell and between the shell and ring is held the flange 6 of a metal plate I. The flange 6 may be spot welded to the ring. The cover plate I has perforations, such as 8 and 9, centrally through which pass the current-supply lead-in wires Ill and il without touching the plate itself. The size of said holes is so chosen that touching between the current-supply wires and the plate is prevented.

In the particular tube shown two systems or assemblies of electrodes are employed. These electrode systems are shielded from each other by means of a vertical partition or separator wall 12, which is secured to plate I simply by welding the angle portion H to the plate. The partition may be of mica as shown at H in Figure 2 and joined to the plate with a metal piece I 8, The glass disc 2 which supports the current-supply leads is centrally fitted with a glass exhaust tube It through which the envelope is connected with the vacuum pumps.

Another preferable embodiment is illustrated in Figure 3. The shell of the vessel I which, ior instance, may consist of iron. has its flanged rim 4 welded to a flange IQ of the header consisting of pure or of galvanized iron. To prevent diflusion of gas into the interior of the vessel, it is advantageous to nickel-plate the shell or the vessel on the outside. The inner cylinder II of the U-shaped section of the ring 3 may be a separate piece and of material such as chrome iron or 50-50 ferro-nickel selected to seal well with glass. Flange 19 may be tinned or galvanized to facilitate welding with the shell. Cylinder 2| may be provided with a bent-over or flanged edge 23 in which is rested and held the plate I.

In making such a discharge vessel, the procedure is first to fabricate ring 3 by welding or brazing gas-tight parts I! and 2|, mold in the glass disc 2 with the lead wires, place plate 1 on the ring and spotweld to ring 3, assemble the electrodes on the leads and then join the shell to header flange IS. A few metal prongs or lugs I formed on the ring 2| may be bent over plate I to hold it in place and electrically connect the,

plate to' the shell. The interposition of the shell-metal ring 3 between the glass disc and the flange-to-shell weld at 4l9 prevents cracks in the seal caused by welding shock.

It is desirable that plate 1 be placed as close to the glass disc 2 as practical. The plate I in Figure 3, for example, may be pressed from sheet metal with a saucer-shaped configuration to bring the plane of the plate within a few thousandths of an inch of the top surface of the disc and clear of the glass knobs about the lead wires while the rim of the plate rests on the top oi ring 3.

Electrodes mounted in electron discharge devices constructed according to this invention are completely surrounded with metal to shield them from external electrical disturbances although the envelope is closed with 'an all-glass disc of considerable size. Electric coupling between the leads is reduced 'and conductors connected to the control grid and to the anodes may be sealed into the glass disc and thus eliminate the diihculties and expense of sealing these two leads in opposite ends of the envelope. Conductive deposits on the glass disc between the lead-ins are reduced to a minimum since metallic vapors, such as getter vapors, condense first on the metal plate I.

What is claimed is:

1. An electron discharge device comprising a cylindrical metal envelope closed at one end with a header, the header comprising a metal ring telescoped into said end of the shell and Joined gas-tight to the rim of the shell, a glass disc sealed gas-tight along its periphery to said ring, lead-in conductors for electrodes sealed in said disc, and a metal shielding plate parallel to said glass disc in the shell and supported along its edge on said ring.

2. An electron discharge device comprising a cylindrical metal envelope, a header for closing the end of said envelope comprising a ring U- shaped in cross section with an annular mge joined gas-tight to the rim of the envelope, a vitreous disc sealed gas-tight in an opening in the wall of the ring, lead-in conductors sealed gas-tight through said disc, a plurality of electrode assemblies mounted side by side on said conductors, and means for shielding said electrode assemblies from each other and from external electrical disturbances comprising a metal plate parallel to said disc and joined to said ring in the envelope, and a partition erected on said plate between said electrode assemblies.

, WERNER ESPE.

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