US Patent 6963053 Corrugated metal ribbon heating element

A sheathed electrical resistance heater is provided with a metal corrugated resistance heating element located internally within a surrounding metal sheath and separated from the sheath by a compacted insulating material such as magnesium oxide. The preferred corrugated resistance element is a flat strip of metal that has been corrugated such as by passing the strip through the nip of a pair of gears. The corrugated strip resistance element is thicker than a foil and may be used to provide sheathed, electrical resistance heaters where it is too difficult to wind large diameter wires, which are desired for a low resistance ohm of 0.12 ohm/inch or less, on a small arbor to form a coiled wire resistance element. A heater may be formed with a resistance of 0.05 ohm/inch using the corrugated metal ribbon and may be 200 inches in length and have a finned sheath. Preferably, the sheath is compressed in a die to reduce the cross-sectional area of the heater without a substantial elongation of the sheath.