US2073482A - Vacuum tube insulator shield - Google Patents

Description

March 9, 1937. P. KNIEPEN VACUUM TUBE INSULATOR SHIELD Filed March- 28, 1936 INVENTOR.

2 PETER KNIEPEN ATTORNEY. I

Patented Mar. 9, 1937 UNETED STATES PATENT OFFICE many, assignor to Allgemiene Elektricitats Gesellschaft, Berlin, Germany, a corporation of Germany Application March 28, 1936, Serial No. 71,349 In Germany October 4, 1934 Claims.

If in an electric discharge vessel, more particularly in transmitting tube, the electrodes are mounted in insulating spacers such as ceramic plates or mica discs, insulation trouble may be 5 observed where relatively high voltages are used.-

These disturbances arise with widely varying insulation materials, and to overcome the trouble it has proved necessary to more and more increase the distances between parts with a corresponding increase in size of the vessels.

According to this invention spark discharges and energy losses between conductors over insulation are prevented by surrounding the conductors with metallic umbrella or conical shaped members or shields which are kept at the potential of the conductors. The shields may be so designed that their outer rims or edges are spaced from the insulation. The field intensity at the point of contact between the insulation and conductors according to this invention is appreciably diminished.

If the metallic parts of the tube are to be heated on exhaust by high frequency eddy-currents it may be found desirable to split the shields a number of times, as, for example, by three to twelve radial slits, the number of slits being larger with shields of greater diameter.

At least one slit should be provided so that in operation eddy-currents will not be able to flow over a circular path around the live conductor. In order that this slit may not be short-circuited by the conductor, the shield piece may be mechanically separated from the conductor, preferably by a cylinder of insulation, and an electrical connection should be made between the conductor and shield by an auxiliary wire fastened as by welding.

A number of exemplified embodiments of the protective means here disclosed are shown by way of example in the annexed drawing in which Figures 1 to 5 show preferred embodiments of the invention.

Figure 1 shows conductor l which extends through an insulating plate 2. A conducting shield 3 which is secured to the conductor l by clamped or welded rings 4 or other fastening means overlies the surfaces of the insulating plate immediately surrounding the conductor. With the conductor adjacent the edge of the insulating plate, the shield may be formed U- shaped to overlie the edge of the plate and may be curled or rolled up at the ends in such a manner that no sharp edges remain which might give rise to point or needle discharges.

Figure 2 shows a similar embodiment for a conductor which is not near the edge of the insu lation plate. The shield 3 in this case consists of two parallel discs positioned parallel tothe plate with a tubular junction surrounding the conductor. The tubular part may, if desired, be dispensed with by welding the two discshaped shields on the conductor above and below the insulating plate 2.

Other embodiments of this invention are illustrated in Figures 3, 4 and 5. The conductor l where it contacts with the insulating plate 2 is here surrounded by radially split shields or umbrella shaped members of truncated-cone, or calotte or hemispherical form as indicated at 5 and 6 in Figures 3 and 4 respectively. These shields may be pressed by means of bushings 1, Figure 3, or by rings 4, Figure 4, against the insulator. In case it is desired to space the shield from the conductor, insulating discs or collars 8, Figure 3, of mica or ceramic material may be interposed between the bushings 'l and the truncated cones 5 and to prevent direct flow of eddycurrents from the cone to the conductor during high frequency exhaust. The truncated cone pieces may then be electrically united with conductor I by wires 9 fastened as by welding. In the embodiment shown in Figure 4 the shallow cup pieces 6 are separated from the conductor l by means of insulation tubelets It, the latter being fastened on insulation plate 2, for example, by a readily sintering substance. The conductor I may then conveniently be secured in the insulator by rings II or the like fastened to the conductor by welding or clamping. Figure 5 is a top view of the embodiment in Figure 3. The slits by means of which a direct flow of eddy-currents about the conductor is prevented during the high frequency treatment may extend inward and below the insulating mica disc. One of these slits, say, the slit denoted by l2, extends all the way inside in order to insure complete division of the disc. In one embodiment which has proved successful the shielding member 5 of Figures 3 and 5 had a diameter amounting! to about five times the thickness of the plate. The distance from the edge of the plate was a little less than one-half the thickness of the plate. It is obvious that other constructions may be employed to electrically connect the shield to the conductor without reducing the impedance of the shield to the flow of high frequency currents. It may, for example, be feasible in some embodiments of the invention to omit the insulating collars 8 or I 0 and press the shield over the conductor in a snug fit.

Instead of the sheet-metal bodies illustrated in the drawing, it would also be feasible to use solid bodies.

I claim:

1. An insulating body in an electrical discharge device, a high potential conductor extending through said body, and protective means for said body where it contacts said conductor with this characteristic feature that said means comprises a conducting shield of umbrella shape secured around said conductor with the apex of the shield adjacent the insulator and the periphery of the shield spaced from the insulator, and an with the vertex of said conical member adjacent said insulator and with the base of said conical member spaced from said insulator concentrically around said conductor.

l. In an electron discharge device an insulator, a high potential conductor extending therethrough, means to reduce field intensities in said insulator surrounding said conductor comprising a metal cylinder surrounding and engaging said conductor at its junction with said insulator, the cylinder being flared at its end with its rims spaced from said insulator.

5. In combination, an insulating plate, a conductor extending therethrough and means for reducing the field strength at said conductor comprising a metal cup-shaped member set upon said plate and around said conductor with its rim concentric with said conductor and spaced above the plane of said plate and with its convex surface in contact with said plate, an insulating cylinder surrounding said conductor to space said member from the conductor and an electrical connection between said member and said conductor.

PETER KNIEPEN.

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