초록 ▼

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

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.

대표청구항 ▼

A heating device comprising a resistance body having two opposite boundary surfaces and made of a material having a positive temperature coefficient of resistance and provided with at least three electrodes, one of the boundary surfaces being provided with a first electrode which covers a major part

A heating device comprising a resistance body having two opposite boundary surfaces and made of a material having a positive temperature coefficient of resistance and provided with at least three electrodes, one of the boundary surfaces being provided with a first electrode which covers a major part of the surface area of said one boundary surface and the other boundary surface including at least two other electrodes which together cover a major part of the surface area of said other boundary surface thereby to provide at least two parallel current paths in the resistance body between said opposite boundary surfaces, means connecting at least said first electrode of the resistance body to one terminal of a voltage source, and a switching device for selectively connecting one or more of said other electrodes to the other terminal of the voltage source so as to selectively alter the relative effective electrode surface areas so that the heat developed in the resistance body is dependent on the electrodes selectively energized by the switching device.