GB900205A - Improvements in and relating to sources for the evaporation of metals and other materials under vacuum - Google Patents

Abstract

900,205. Electric vaporizers. FLETCHER, R. J. Oct. 15, 1958 [July 15, 1957], No. 15514/57. Class 39 (3). [Also in Group II] Metals, e.g. aluminium, are evaporated in a vacuum by contact with a graphite or carbon filament 1 secured in electrodes 2 cooled by a circulation in pipe 3. In Fig. 5 a tubular graphite or carbon filament 10 has a watercooled shield 12 and a side opening 11 for introduction of the metal wire 13 and for escape of the metal vapour. The hollow retains any slag, the melted wire rising up the inside of the tube to the opening 11 where it evaporates. The wire metal 13 may be substituted by block metal introduced at the ends. The filament 10 may contain a refractory metal, e.g. tungsten, tantalum or zirconium in the form of a bundle of wires or sheet or powder. The bottom of the filament 10 may be pierced by small holes. Al-bronze at a high temperature may be fed to a molten pool of aluminium in the filament to ensure instant evaporation. To evaporate zinc a graphite filament is first wetted with molten copper with or without prior treatment with aluminium. The zinc is fed into the copper pool with which it alloys and then evaporates. A carbon or refractory scraper may scrape the filament. The filament may be oscillated or rotated, supported in an aluminium trough where a hopper 18 supplies the metal under the surface of the molten pool. In Fig. 10 a web of paper or other sheet material is metallized under vacuum. The heating filament 22 is mounted in electrodes 23 supported by insulating blocks 24 in a water-cooled shield 25. The metal wire 26 to be evaporated is fed to the filament. Angularly adjustable water-cooled shields 27 concentrate the heat of the filament and determine the area of open space through which the evaporated metal may pass. The paper &c. web comes from a supply roller 29 and is coated and received on a roller 30. In Fig. 15, graphite connectors 39 holding the filament 38 are seated in ceramic insulators 40 and held by clamps 41 which may be cooled.