US1844090A - Device to prevent the occurrence of back-firing in mercury arc rectifiers - Google Patents

Description

Feb. 9, 1 932. A. GAUDENZI 1,844,090

DEVICE TO PREVENT THE OCCURRENCE 013 BACK FIRING IN MERCURY ARC RECTIFIERS Filed Aug. 15, 1929 l'fomey Patented Feb. 9, 1932 UiTEl) STATES ARTHUR GAUDENZI, or renew, SWITZERLAND, essrenon 'ro nxrinnensnnnsonnnr renown :eovanr & can, or BADEN, swrrznanann, A JOINT-STOCK coiurenv or SWITZERLAND DEVICE TO PREVENT THE OCCURRENCE OF BACK-FIRING IN MERCURY ARC RECTIFIER/S Application filed August 15, 1929, Serial No. 386,184, and iniGermany August 16, 1929,

As is already known, the occurence of backfiring in mercury arc rectifiers with glass or metal containers is to some extent prevented by surrounding the anodes on all sides with sieve patterned anode grids which lie in the so-called Hittorfs or Crookes, dark space, i. e., the dark space lying between the anode surface and the negative glow space evidenced during periods of negative potential charges of the anode. The danger of back-firing is still further reduced by dimmishing the density of the vapour in the pro);- imity of the anode. For this purpose, as 1s already known, not only the anodes them selves but also the arc guiding shields are heated. Further, it has already been proposed to make the sieve type anode grids surrounding the anodes of a hollow construction and to cool them in order to prevent the formation of corona spots on the anode. Such devices, however, have not entirely averted the danger of back-firing.

According to the invention, the grids of mercury arc rectifiers, in which the anodes are each surrounded on all sides within the defined Hittorfs dark space by a grid of the sieve pattern, are provided with additional heating, independent of the rectifier opera tion, in order to diminish the Vapour density in front of the anode. By means of this heating, which does not reduce the quantity of heat developed during operating conditions, the vapour immediately surrounding the anodes is expanded so that streams of vapour rising from the cathode to the anodes will be deflected from the anodes. The heating has the further advantage, over the methods already known in which the grids are heated by the main arc and by radiation from the anodes, that the temperature in the proximity of the anodes is considerably higher. The heating can be arranged in a Suitable manner by means of electric current. Any other desired means may however be employed. The grid would, for example, be made hollow to allow the circulation of a gas or a liquid should either of these be used; In order to diminish further the vapour density in the neighborhood of the anodes, the anodes themselves may besides be addi- AT n o'rFicE j tionally heated as is already known,by elec v trical or by other means. As is also known the anodes and anode grids are most suitably manufactured from an electrically :conduck tive material having a high v'meltingpoint such. as tungsten, molybdenum etc'., or instead from graphite. 7

Thedrawing -shows an example of the struction of the invention.

It represents a rectifier in section, the left half of the figure illustrating an electrical method of heating the grid and the right half showing the hollow construction of the same which allows it to be heated, on the circulation principle, by any desired medium. a is the double walled cooled rectifier container of metal having the anodes b, 0 which enter the cover but are insulated from it and which are fed from the trans former (Z. The cathode is markede. f and f are the anode grids which surround the anodes on all sides and which lie within the Hittorfs dark space 9 shown shaded. The

OOl1- source It supplies heating current both to sieve patterned anode grid f towhich it isconnected as well as to the windingi which serves to heat the anode. The grid f on the other hand is designed in the form of a hollow heating spiral which allows any desired medium whether liquid or gas to be circulated through it. a i

The invention claimed is:

1. In a mercury arc rectifier. the combina tion with an anode. and a grid surrounding said anode within the Hittorfs dark space, of means for heating the said grid to reduce the vapor density adjacent the said anode.

2. In a mercury arc rectifier, the combination with ananode subject to destructive e'ffects of excessive vapor pressures, and a sievelike grid wholly surrounding the said grld within the Hittorts dark space, of means for electrically heating the said grid to regrids to reduce the vapor density adjacent the said anodes.

4:. In a mercury arc rectifier comprising a plurality of anodes, a grid surrounding each of said anodes Within the Hittorfs dark space, means for heating each of said anodes to reduce the vapor density adjacent thereto, and means for heating each of said grids to additionally reduce the vapor density adjacent the said anodes.

5. In combination With a mercury arc rectifier comprising a plurality of anodes subject to injurious effects resulting from excessive Vapor pressures, a grid surrounding each of said anodes Within the Hit-torfs dark space,

means for heating said grids from the said anodes and electricalmeans for additionally heating said grids to reduce the vapor pressures adjacent the said anodes.

In testimony whereof I have hereunto subscribed my name this 29th day of July A. D.

. ARTHUR GAUDEYNZI.

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