GB632987A - Improvements in or relating to devices comprising an incandescent-cathode rectifier - Google Patents

Abstract

632,987. Thermionic power converters. PHILIPS LAMPS, Ltd. Feb. 13, 1946, No. 4484. Convention date, April 11, 1941. [Class 39 (i)] To reduce the danger of back-firing in a lowpressure gas- or vapourfilled rectifier having an incandescent cathode and a magnetic field to reduce the arc voltage, the anode is so shaped and arranged that those magnetic lines of force which intersect the cathode do not intersect the anode ; the active surface of the anode, either a cylinder or a flat ring, or a sector thereof subtending an angle of at least 120 degrees at the axis or centre, is coaxial with the field; the axial length of the cylinder or radial depth of the ring is not less than the mean diameter of the magnetic poles; and the magnetic field strength at the anode is small compared with that at the cathode. The filling may be mercury at 0.001 mm. In one form, a cylindrical anode 3, Fig. 1, surrounds the cathode 2 and the field from external poles 8, 9 causes the visible discharge to be confined to the hatched area and to be intercepted by cathode-connected shields 10, 11. Internal poles 22, 23, Fig. 2, may themselves form the intercepting electrodes. The cathode 21 is surrounded by a screen 26 which prevents it from " seeing " the anode 20 ; further screens 24, 25 are provided. The anode may be a disc 15, Fig. 3, situated at the neutral point of the magnetic field of internally-arranged dipoles 16 ; a screen 17 for the cathode is again provided. The field may be further diverted from the active face of the anode by making the. anode of magnetic material. A number of anodes may be arranged as sectors of the cylinder or disc. Specification 396,928 is referred to.