| 摘要 |
<p>1,113,909. Control systems for electrically heated bedcovers. GENERAL ELECTRIC CO. 8 Nov., 1966 [30 Dec., 1965], No. 49882/66. Heading H2H. Apparatus for preventing over-temperature occurring in an electrically heated device such as a bedcover 40 comprises two co-operating thermally responsive elements 12, 13 having associated therewith heating devices 26, 27 respectively and a pair of concentrically arranged conductors 43, 46 separated by a sensor material 53 having a negative temperature coefficient of impedance. The heat differential between the elements 12, 13 is increased by arranging a heat dissipating member in contact with the element 13 and the sensor material 53 is arranged to shunt the heating device 26. During normal operation the sensor material has a high impedance such that closure of a switch 41 establishes a circuit including heating device 27, conductor 43, heating device 26 and conductor 44. The device 26 has a higher resistance than the device 27. Thus, since the element 13 loses heat more quickly than the element 12, the element 12 deflects a greater amount than the element 13 to close the contacts 14, 15, thereby energizing the heater 46 of the bedcover 40. Should the bedcover develop an over-temperature, the impedance of the sensor material 53 will fall, causing a leakage current to flow between conductors 43, 44. The current flowing through the device 26 is thus reduced allowing the contacts 14, 15 to open to deenergize the heater 46. The contacts 14, 15 will cycle OFF-ON until the cause of the overtemperature is eliminated. Ambient temperature compensation and the operating temperature of the bedcover is provided by thermally responsive element 50 heating device 51, contacts 47, 48 and control knob 52.</p> |
