GB692303A - Improvements in or relating to electric resistors and method of manufacturing same - Google Patents

Abstract

692,303. Resistance coatings and deposits; direct connections between conductors. PALUMBO, T. R. March 30,1949 [March 31,1948], No. 8606/49. Classes 37 and 38 (i). [Also in Groups V and XI] A method of manufacturing an electrical resistance element comprises heating a porous refractory body or rod of alumina, thoria or silica to a temperature within the range 800‹ to 1400‹ C. in a hydrocarbon gas, for example methane, ethane or acetylene, and maintaining the chosen temperature until the refractory oxide and carbon are combined together by a catalytic reaction occurring therebetween and the pores of the body are coated with a pure hard oxidation resistant carbon. It is made clear in the Specification that the expression " combined together by a catalytic reaction occurring therebetween " essentially means that the refractory body is combined with carbon without the use of any other catalyst than the refractory body itself. The invention is directed particularly towards provision of cathodes or heaters for cathodes in discharge tubes as exemplified in Fig. 2, wherein an aluminium oxide/carbon impregnated resistor rod 8 prepared in accordance with the process has terminals in the form of twisted-on wire coils 11, 12 secured by applying a conductive paste and heat-treating. The conductive paste may consist of a powder of the rod material mixed with a suitable binder. For use as a cathode a middle area of the rod is directly coated with electron emitting oxides such as the oxides of barium, strontium or calcium. For air operation wattage capacity may be increased by coating with fused glass or quartz or vitreous enamel. A cold-working resistor rod may be tapped for use as a potential divider.