| 摘要 |
1,057,909. Making cathodes; destructible cores. MATSUSHITA ELECTRONICS CORPORATION. April 30, 1964 [April 30, 1963], No. 18036/64. Headings B3A and B3E. [Also in Division H1] A method of making a cathode element for electron tubes such as miniwatt cathode-ray tubes comprises coiling a heating filament of for example tungsten about a mandrel of soluble metal, for example molybdenum, flattening the filament and the mandrel providing an insulating layer on at least one surface of the element and dissolving away the mandrel. The element is trimmed to form terminals 8 and coated with an electron emissive oxide layer 10 by spraying, electro-deposition or immersion to form a directly heated cathode, Fig. 4. To provide the insulating layer the flattened assembly is placed in a mould 11, Fig. 5 (not shown), preferably of molybdenum which is filled from alternate sides with insulating paste of e.g. aluminium oxide with distilled water or a nitrocellulose solution and heated to 1600/ 1700‹ C. in hydrogen. Alternatively a flattened assembly is embedded in powdered aluminium oxide between dies, Fig. 9 (not shown). After removal from the mould, the ends are shaped and the flattened mandrel dissolved away. An indirectly heated cathode is formed by inserting an insulated element 21 into a nickel sleeve 22, Fig. 10 (not shown), with an insulating layer 24 of e.g. aluminium oxide therebetween and providing an emissive oxide layer 26 on the outer sleeve 22. The layer 24 may be obtained by immersing one end of the assembly into an insulating solution so that capillary action fills the space 23 and finally drying the assembly. Alternatively the sleeve 22 may be pressed about the element 21 in dies, Fig. 11 (not shown). One or both sides of the insulating material may be directly coated with a layer of electron emissive oxide or with a thin metal sheet which is subsequently oxidized. |
