SHEATH HEATER

• Main Authors: YAMAZAKI KATSUHIRO, ABE TERUO
• Format: Patent
• Language: English
• Published: 13.01.1989
• Subjects: ELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR; ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR; ELECTRICITY

PURPOSE:To increase insulation resistance at high temperatures and improve durability by filling a metal pipe having a coiled heater wire provided at the center inside with electric insulating material, and using material consisting of magnesia powders and a component of silica mixed in a predetermined ratio for the material of the electric insulating material. CONSTITUTION:A coiled heater wire 3 is disposed in a metal pipe 1 at the center inside the metal pipe 1, and electric insulating material 4 is filled in the metal pipe 1. This insulating material 4 consists of magnesia powders and silica powders mixed by 0.8-2wt.% and is electromelting. After the heater wire 3 is inserted into the metal pipe and the electric insulating material 4 is filled in it, the outer diameter of the metal pipe 1 is reduced in a predetermined ration to increase filling density, and it is annealed and moulded, and then both ends are sealed with glass 5, so a sheath heater is formed. For this sheath heater, silica powders penetrate between magnesia powders in the electric insulating material 4, so heat conductivity is improved, and temperature difference between the heater wire 3 and the pipe 1 isa reduced, and insulation resistance is improved at high temperature as in the conventional devices.