| 摘要 |
An air heating unit comprises a blower casing, a centrifugal impeller and a heating element in the shape of a cylindrical cage of longitudinal guide vanes fastened to the wall of the casing. The guide vanes are made from an electric resistance alloy in sheet form in the shape of uniform strips of a length conforming to the width of the impeller, all vanes being connected at their ends by conductive bridging pieces jointing the alternate ends of each two proximate vanes, thus forming a resister in zigzag pattern provided with terminals for energizing it. The vanes and the bridging pieces may form part of a single rectangular sheet rolled up to form the cylindrical casing and provided with alternate transverse cuts along both edges which stop short of the bridging pieces. The strips between the bridging pieces are bent or curved outwardly from the sheet at a desired angle.
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