US1863394A - Cathode for electric discharge devices - Google Patents

Description

June 14, 1932. J w S 1,863,394

CATHODE FOR ELECTRIC DISCHARGE DEVICES Filed Dec. 28., 1929 Inventor: James W Case, by

His Abner-neg.

Patented June 14, 1932 UNITED STATES PATENT OFFICE JAMES W. CASE, OF SCHENECTADY, NEW YORK, ASSIGNOR T GENERAL ELECTRIC COM- PANY, A CORPORATION OF NEW YORK CATHODE FOR ELECTRIC DISCHARGE DEVICES Application filed December 28, 1929. Serial No. 417,240.

My'invention relates to electrodes for electric discharge devices and has for its principal object the provision of an improved cathode arrangement for mercury arc recti- I fiers.

Large power rectifiers which are provided with metallic tanks have hitherto been provided with porcelain insulators positioned be-- tween the tank and the metallic cup which holds the mercury cathode. This insulator is exposed to a high temperature gradient during operation and being fragile is liable to breakage either because of physical shock or because of uneven expansion and contrac- 16 tion.

In accordance with my invention these disadvantages are obviated by the provision of means including a porous and rugged insulator positioned between the tank and cathode and surrounded by a vacuum chamber which also encloses the cathode.

My invention will be better understood from the following description when considered together with the accompanying drawing and its scope will be pointed out in the appended claims.

The single figure in the accompanying drawing illustrates in cross section, a cathode structure built in accordance with my invention and a fragmentary cross section of the rectifier tank to which it is attached.

Referring thereto in detail, 1 illustrates a cross section of the lower end of the rectifier tank. The mercury cathode 2 is contained in a metallic cup or dish 3 which is provided with a water jacket 4:. The dish 3 is separated by an insulator 6 from a metallic flange 5, which is arranged to be attached to the tank 1. This insulator is preferably composed of layers of mica which tend to make the insulator porous yet impervious to mercury vapor. The dish 3 is rigidly bolted to flange 5 by insulated bolts 7 and a jacket 8 is arranged to surroimd both the insulator and the dish. This jacket is Welded to flange 5 and insulated from the cathode terminal 9 and water jacket connections 10 by gas im pervious vitreous seals. Seals of this type are made by compressing a plastic mass of vitreous material such as a mixture of mica and glass, between two metallic members I which are then joined respectively to the members to be insulated from each other.

It will be evident from the above description that the cathode dish 3 can be cooled by passing cooling fluid through the jacket 4 and insulated connections 10. Since the insulator 6 is porous, the space between jackets 4L and 8 is evacuated through the insulator 6 and is maintained at a pressure substantially that of the main tank. This evacuated space or chamber provides heat insulation between the cathode and the room temperature said dish and flange, and an evacuated cham ber surrounding said insulator and dish.

2. In an electric discharge device provided with a metallic tank, a cathode structure including a flange attached to said tank, a metallic dish attached to said flange and provided with a cathode terminal, a porous insulator between said dish and flange, and a jacket surrounding said insulator and dish.

3. In a mercury arc rectifier provided with a metallic tank, a cathode structure including a flan e attached to said tank, a metallic dish provi ed with a water jacket and cathode terminal, an insulator between said dish and flange, an evacuated chamber surrounding said insulator and dish, and insulated connections for said water jacket extending through said evacuated chamber.

In witness whereof, I have hereunto set my hand this 27th day of December, 1929.

JAMES W. CASE.

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