| 摘要 |
774,831. Electric heating elements. GENERAL ELECTRIC CO. March 31, 1955 [April 26, 1954], No. 9450/55. Class 39(3) A sheathed wire heating element for heating metal objects or heating loads in direct contact with the sheath, e.g. utensils on a surface heating unit of a cooking range, comprises a resistance conductor having a high temperature co-efficient of resistance, and a composite enclosing sheath consisting of an inner layer or sheath of a metal having high thermal conductivity and an outer layer or sheath of a heat and corrosion resistant metal. As shown, a resistance conductor 1 composed of substantially 97 per cent iron and 3 per cent silicon is embedded in magnesium oxide 4 which is compacted so as to readily conduct heat from the conductor 1 to a sheath 2 which may be of copper. The oxide is compacted by reducing and elongating the sheath 2 which may be effected by swaging or rolling, the sheath then being fitted into or encased by a sheath 3 of alloy which may consist of 80 per cent nickel. 14 per cent chromium and 6 per cent iron. The outer sheath is then reduced and elongated to cause it to tightly grip the inner sheath 2. Each end of the element is hermetically sealed by means of a metal sleeve 6 which may be welded or silver soldered to the sheath 3 and secured to a ceramic bushing 9 by titanium hydride solder, a tube 10 being welded to a terminal 5 and sealed to the bushing. Aluminium or silver are also specified for the inner sheath and the outer sheath may be of stainless steel or a chromium nickel alloy. Pure nickel or a nickel-iron alloy are also specified for the resistance conductor. Specications 516,285 and 687,535 are referred to. |
