US2205230A - Gas or vapor filled controllable electric discharge device - Google Patents

Description

June 18, 1940. STEENBECK 2,205,230

GAS 0R VAPOR FILLED CONTROLLABLE ELECTRIC DISCHARGE DEVICE Filed Aug. 6, 1938 WITNESSES: A I INVENTOR Q @524 j Max 67eenecK ATTORNE Patented .iune l 59% UNITED STATES PATENT GAS R VAPOR FILLEI) CONTROLLABLE ELECTRIC DISCHARGE DEVICE Max Steenbeck, Berlin-'Siemensstadt, Germany, assignor to Patentvertungs-Gesellschaft mit beschrankter Haitung "Hermes, Berlin, Germany, a corporation of Germany Application August 6, 1938, Serial No. 223,542 I In Germany- August 7, 1937 This invention relatesto gas orvapor-filled electricdischarge devices. 3

In discharge devices, for instance, in, rectiflers, grid-controlled rectifiers and in static frequency changers having an auxiliary discharge, (e. g. a mercury cathode with a keep-alive arc) serving as an electron-source, the discharge path is subjected substantially to the potential of the cathode on the negative half-cycle of the supply voltage; -i. e. the half cycle in which the (normal) "cathode" of the tube is positive relative to the electrode which is normally positive, and so nornaliy, the anode" of the tube. Owing to the electric field between the (then) positive cathode and the (then) negative anode no electrons are drawn from the arc path towards the anode, but positive ions are attracted to the tube anode: and these ions, particularly at high operating voltages, give rise to backfires resulting from secondary emission when impinging upon the anode.

A principal obiectof my invention is to eliminate the foregoing'troubles. To this end two or more grid-shaped electrodes extending across the discharge path are charged in the negative half-cycles (or at least during such time as the anode is strongly negative) from the cathode in such a way that looking-toward the anode, a positively charged grid follows a negatively charged grid. By designing and arranging the rids in the manner disclosed herein, as well as by selecting the voltage supplied thereto, a discharge between the cathode and the positively charged grid is, prevented by the negatively charged grid lying in front of the positively charged grid. By the arrangement in which suitably biased grids are arranged between the cathode region and the anode, positive ions are prevented from passing from the cathode region .front of which the discharge begins; a negative grid; a positive grid; if necessary, an intermediate electrode, and an anode. In this case the intermediate electrodes may serve as re-combiv nationelectrodes, i. e. electrodes the presenceof 6 Claims. (01. 115-35 4) "which causes re-combination between the posi-,

tive and negative ions present in the discharge path in their vicinity. In order that the grids may exert their effect they must be arranged in a region which is poor-in ions. To this end, 6

they may either bepositioned a certain distance back in the anode arm or they may be separated from the discharge region with the aid of cylindrical shields.

In the accompanying drawing is shown an em- 10 bodiment of the invention. i is the discharge device, 2 a mercury-cathode from which an auxiliary are passes to the auxiliary anode 8. l is the main anode which is arranged at the end of a tubular extension of the discharge device I.

Alternating-current power is supplied by the alternating-current source 9 and transmitted to the circuit of the current consuming device H.

The control grid 5 is supplied with alternating voltage by the control set l2. A positive bias is supplied to the grid 6 by the biasing battery It. The grids 5 and 6 are positioned in the discharge path. At least in the half-cycles in which the anode 4 is strongly negative to cathode 2 the grid 5 issubjectcd toa negative potential and. the 95 grid 8 to a positive potential. Both grids are arranged within the metallic shield 1. Between the shield l and the anode 4 are disposed several intermediate electrodes 8 which on the one hand may serve to uniformly distribute the voltage between the anode and cathode and on the other hand may serve as re-combination electrodes. 'I'heshield I is allowed to float in potential. The grid 5 may act at the same time in the above-described device as a control grid.

However, a separate control grid may also be arranged within the-shield I.

What is claimed is: i. In combination with'a unilaterally-conducting gaseous electrical discharge device havingan 40 anode which does not spontaneously emit electricity and a cathode which is the source of negatively electrified particles, a source of alternating voltage connected to cause current flow between said anode and said cathode during alter nate half-cycles, a grid across the current path of said cathode to said anode, means for making said grid negative inpotential relative to said cathode at least during the half-cycles when no current flows between said anode and said caththan the first said grid, and means for making said second grid positive in potential relative to said cathode at leastdurlng those half-cycles I ode, a-second grid positioned nearer said anode when no current flows between said cathode and said anode. v 2. An arrangement in accordance with claim '1 in which the two said grids are located in a region which is poor in ions during their half periods in which no current flows between said anode and said cathode.

3. An arrangement in accordance with claim 1 in which said grid electrodes are positioned .in a shielding electrode which is insulated so as to float electrically.

4. In combination with an alternating-current source, an electrical discharge tube drawing current therefrom and having an evacuated container provided with a non-emissive anode, a mercury cathode having a keep-alive arc, a first grid electrode and a second grid electrode which is more remote from said cathode than is said first grid electrode, means for making said first grid electrode negative relative to said cathbde during those half-cycles of said source in which no current flows between said anode and said trical potential relative to said cathode an'd said 15 anode.

MAX STEENBECK.

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