| 摘要 |
<p>1530676 Control systems for microwave ovens PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 9 June 1976 [12 June 1975] 23884/76 Heading H2H A control system for a microwave oven comprises two changeover switches S12, S13 operated by opening the oven door, the fixed contacts of the switches being cross connected so that switch S13 causes de-energization of the oven when the door is opened but, should either of the switches stick when the oven door is opened, a circuit is completed by way of the cross connections so that after a delay, operation of a further switching device will de-energize the oven. As described, when the start switch S6 is closed, relay RE7 is energized so that contacts S8, S11 energize the magnitron 2, until RE7 is released by a timer 1. In normal operation the door switch S13 is arranged mechanically (Fig. 2, not shown) to operate before S12 when opening the door. If S13 fails to open, a circuit is complete via S12 and a NTC resistor R16 so as to blow fuse VL17 and release relay RE7. In the event of less dangerous faults associated S12, S13, a further NTC resistor R15 is included so that the fuse VL17 blows after 1-10 seconds. A timer 3 operates a warning buzzer RE4 under fault conditions. Fuse VL17 may be replaced by a relay or thyristor.</p> |
