GB387150A - Improvements in or relating to electric resistances - Google Patents

Abstract

387,150. Resistance coatings and deposits. BARON, H., 231, Strand, London.-(Siemens & Halske Akt.-Ges. ; Siemensstadt, Berlin.) March 5, 1932, No. 6730. [A Specification was laid open to inspection under Sect. 91 of the Acts, March 7, 1932.] [Class 37.] A resistance comprises an insulating carrier having a resistance element consisting of a glazing in which is embedded a finely divided conductor or semi-conductor applied thereto in the form of a surface layer. An insulating material such as vitreous enamel is mixed with finely divided conducting material, such as metal, metal oxide, metalloid, carbon, or carbonaceous material, and water and is sprayed or otherwise applied to the carrier body. After drying the film the resistance is baked, preferably at more than 700‹ C. if vitreous enamel is employed. The ohmic value of the resistance may be adjusted by varying the percentage of conducting or semi-conducting material. In a modification a carrier body of steatite, porcelain, &c. is coated with an easily fusible surface layer such as glaze or enamel. A resistance layer of finely divided conducting or semi-conducting particles is then applied, e.g. by cathode disintegration or separation from a gaseous phase, and the resistance is heated to the softening point of the enamel layer so that the conducting particles are diffused therein. This heating may be effected during the deposition of the conducting particles, and may be carried out in an evacuated vessel or in one filled with a neutral gas. When iron oxide or other oxides are employed as the resistance material, the resistance may be baked at a temperature of 1000‹ C. or more. The resistance film may be coated with graphite at the connecting points, before mounting the connecting clips. The effective length of the resistance layer may be increased by cutting in spirals or other subdividing lines.