Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1985-05-09
1986-10-14
Grimley, Arthur T.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
174 88R, 219300, 219 1051, H05B 300, H02G 1510
Patent
active
046174494
ABSTRACT:
An improved power cable for a heating system that utilizes the skin effect of alternating current, and a method and apparatus for joining lengths of the improved cable. In one embodiment, the cable includes a stranded copper conductor (20) surrounded by a semiconductive layer (22) formed by carbonized tetrafluoroethylene (TFE) tape which is surrounded by a primary insulation layer (24) formed by pressure extruded, perfluoroalkoxy resin (PFA), the thickness of which is determined by an equation that considers the eccentric positioning of the power cable in a heat tube (14). In a second embodiment, the cable comprises a central conductor (30) surrounded by a semiconductive layer (32), followed by a primary insulation layer (34) formed by pressure extruded PFA. A shield layer (36) formed by a layer of semiconductor material (38) and several helically wrapped drain wires (40) surrounds the primary insulation layer. A protective PFA jacket (42) is pressure extruded over the shield layer. Lengths of the improved cable are joined by first removing predetermined portions of the insulating and semiconductor layers from a terminal end (50) and a feed end (52) of respective cable lengths. The exposed conductors (30') are mechanically joined and covered by a spirally wrapped carbonized TFE tape (60). An insulating layer (62) is formed over the junction by spirally wrapping uncured, nonadhesive tetrafluoroethylene tape with a 50% overlap and then heat fusing the layer. Shield extensions (66), (68) are formed by spirally wrapped, carbonized TFE tape that extend into noncommunicating, isolated overlapped relationship from the respective shield layers (38) of each cable end. The entire splice is covered with a layer of insulation (73) formed by uncured, nonadhesive TFE tape which is subsequently heat fused. The drain wire (40) from the terminal end is grounded to the heat tube.
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Parman David G.
Weitzel Harold B.
Grimley Arthur T.
Nimmo Morris H.
Ricwil, Incorporated
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