| 摘要 |
Depressing one of the cycle selection switches sets up a circuit through the shaded pole motor to drive the timer at high speed until the wiper on the end of the cam arbor finds an open circuit on the printed circuit board. During the high speed advance of the timer, the machine circuits are de-energized and, upon finding the open circuit, the shaded pole motor is de-energized, the machine circuits are energized, and the timer drive motor is actuated to sequence the timer through the selected cycle. The stepping mechanism is operated by the slow rise fast drop cam operating a pawl which engages the ratchet teeth on the cam arbor. Particularly during high speed advance, there may be a tendency for the arbor to overstep and, therefore, the pawl, in effect, is a double pawl or verge which jams two teeth at the conclusion of a step. This locks the ratchet in the step-completed position. Switching during an interval is accomplished by means of cams associated with the stepping cam and actuating sub-interval switches. This enables the performance of various functions during an interval of the timer. This type of timer is generally referred to as a power timer.
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