Abstract: A self-regulating heating element having a resistor with a positive temperature coefficient as a heat source, the resistor(s) being located within a thermoplastic casing between metal parts which it (they) contact(s) in a heat-exchanging manner. For safety the element is provided with a double insulation: one part which is manufactured by moulding and which is, secondly, provided internally and/or externally with a layer of an elastomer by means of a solution.

Abstract: Self-regulating heating element comprising one or more PTC-resistor bodies enclosed in a synthetic resin filler material mixture. The potting compound is provided with channels. This prevents explosion.

Abstract: A controllable electric heating device uses a PTC resistance body having first areal electrode on one surface and two spaced apart areal electrodes of different areal size on the opposite surface in overlapping relation with a part of the first electrode to provide at least two current paths through the resistance body between the opposite surfaces. The first electrode is connected to one terminal of a voltage source. A switching device selectively connects one or more of the two spaced apart electrodes to the other terminal of the voltage source so that the effective electrode areas are altered thereby adjusting the current flow in the PTC body to produce different temperature levels of the heating device.