| 摘要 |
<p>A timing control system and timer sub-assembly for microwave cooking source parallel connected with a timer and series connected with an interval time switch and a defrost cycle switch and a power level selector. The timer is operable to cycle the defrost switch at a fast rate for selected operating timer intervals of a given value or greater and a slow rate for selected interval less than the given value. The timer provides progressively decreasing «on» time of the defrost cycle switch for each cycle. The timer sub-assembly has a pawl-driven ratchet wheel having a toothed sector of lesser pitch diameter and a meshing rachet wheel having periodic deep notches spaced thereabout for permitting the drive pawl to periodically engage the teeth of lesser pitch diameter for slower advance of the driven ratchet for indexing a plurality of rotary cam tracks for microwave source switch actuation.</p> |
