| 摘要 |
1,003,606. Thermionic cathodes. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. June 28, 1962 [June 28, 1961; June 29, 1961; Dec. 22, 1961], No.24811/62. Heading H1D. In manufacture of a cathode, an electronemissive foil 1, Fig. 1, is provided and a portion thereof is stamped out by use of a punching tool 3 which is also used to carry the stamping to the surface of a cathode base 2 to which the stamping in caused to adhere. The foil may comprise an alkaline earth carbonate coating on a sheet of plastic, e.g. n-butyl methacrylate. The cathode base may be coated with a plastic adhesive, containing polyisobutylene or polyacrylic acid esters or polymethacrylate acid esters, to a thickness of 1 to 10 microns, to ensure adhesion of the cathode foil. The punch 3 may be provided with a stop to prevent application of excessive pressure. To form an annular emissive coating on a cathode base, a central portion of foil 1, Fig. 2, is first punched out by use of an inner punch 5 co-operating with a die 8. The outer circumference of the emissive coating is then cut by use of outer punch 6 after replacement of die 8 with a cathode base. The cathode may be used in cathode-ray display tubes of travelling-wave tubes, the plastic adhesives being removed during cathode-activation. |
