| 摘要 |
1,259,806. Metal sheathed heating elements. GENERAL ELECTRIC CO. 30 Jan., 1969 [1 Feb., 1968], No. 5188/69. Heading H5H. [Also in Division C1] A sheathed electrical heating element comprises an electrical resistance element, a metal sheath, and an electrical insulating embedding composition formed from 99À9-80À0 wt. per cent of fused magnesium oxide and 0À1-20À0 wt. per cent of an additive selected from silica, clay, a silicate of an earth alkali metal (i.e. Ra, Ba, Sr, Ca, Mg and Be), of an earth metal (i.e. Ac, La, Y, Sc, Al and B) or of a carbon group metal (i.e. Th, Ce, Zr and Ti) and mixtures of these and containing less than 5 wt. per cent of an alkali metal salt or an alkali metal oxide. Additives used in the Examples are bentonite, kaolinite, silica, quartz, zircon, ball clay, mullite, kyanite, wollastonite, and olivine; many other minerals are listed as suitable additives. |
