Electric heating elements

The method of heating a medium by use of an electric heating element having an active heating portion which includes a thermoplastic sheath, a resistance member within said sheath and compacted heat-conducting material within said sheath for spacing said resistance member from the inner wall surface of said sheath, comprising,

• immersing said active heating portion in said medium,
• and maintaining the temperature of said medium at a level below the melting point of the thermoplastic material of said sheath,
• whereby the heat-modifying effect on said sheath caused by immersion of said active heating portion within said temperature-controlled medium will permit said resistance member to generate heat above the melting point of said thermoplastic without causing failure of said sheath.

An electric heating element having a terminal portion including terminals adapted to be connected to a source of electrical energy, and also including an active heating portion adapted to be immersed within a temperature-controlled environment,

• said active heating portion comprising a tubular thermoplastic sheath, a resistance member within said sheath and electrically connected to said terminals for generating heat when said terminals are connected to said energy source, and granular heat-conducting material in which said resistance member is embedded, said heat-conducting material being in compacted form to transversely fill said sheath and to hold said resistance member spaced from the inner wall surface of said sheath,
• said heating element being adapted for use only in an environment which has its temperature limited to an amount below the melting point of the thermoplastic forming said sheath,
• whereby the heat-modifying effect on said sheath caused by immersion of said active heating portion within said temperature-controlled environment will permit said resistance member to generate heat above the melting point of said thermoplastic without causing failure of said sheath.