| 摘要 |
1279478 Electric furnace heating elements CARBORUNDUM CO 9 Dec 1969 [16 Dec 1968] 60101/69 Heading H5H A three-phase star connected heating element 10 or 20 for an electric furnace comprises three tubular conductors 11, 12, 13 or 21, 22, 23, respectively, joined together with their ends closed by a common connecting member 14 or 24, each conductor preferably being of uniform outside diameter composed, at least in part, of silicon carbide and having a low resistance segment 15, 25, and a high resistance segment 16, 26. Connecting member 14, 24, is of silicon carbide and has a resistivity lower than that of the tubular conductors. Projections 19 on member 14 close the ends of conductors 11, 12, 13. Segment 15 is of carbonaceous material impregnated with silicon and has an aluminium coating 18 for terminal connections. Pins 17 prevent the element 10 from slipping into the furnace. Segment 16 is large grain silicon carbide, of preferred resistivity of 0À09 to 1À10 ohm cm., while the preferred resistivity of segment 15 is 0À002 to 0À003 ohm cm. (at room temperature). The inner diameter of segment 15 is less than that of segment 16. Segment 26 of element 20 has a uniform helical slit 27 in its wall. The conductors 21, 22, 23, fit through holes in a frusto-conical plug 29<SP>1</SP> in the furnace upper wall. The length of the connecting member 24 or 14 is no greater than the distance between the extreme portions of conductors 21 and 23 or 11 and 13, so that the elements 20 or 10 can be inserted through a hole in the furnace wall of the smallest possible size. |
