| 摘要 |
A heating element 29 for an electric blanket comprises a heating conductor 14 wound concentrically with a sensing conductor 22 but separated from it by a temperature- sensitive insulating layer 28, current flowing through resistor 20 in the event of overheating tripping a thermal switch 16. In the event of local overheat, however, the magnitude of the current through resistor 20 will depend on the position of the local overheat, and will be insufficient to trip switch 16 if the overheat occurs in a first portion AC of the element 29. To overcome this, the element 29 is physically arranged in doubled formation (Fig. 4) so that the unprotected length AC of conductor 14 is physically adjacent and alongside the protected length CB thereof. <IMAGE> |
