| 摘要 |
<p>The continuously driven drive disc carries a drive pawl and a retracting lever on the same pivot. The pawl is biased against the lever by a compressed spring. The lever is held in retractive position by a tension spring. The lever includes a cam which engages a tab (projecting from the timer end plate) to move the lever to an inactive position against the bias of the tension spring while the drive pawl is restrained from following by reason of engagement of a depending finger with a second tab. Continued rotation of the disc clears the finger from the second tab allowing the compressed spring to drive the pawl into engagement with the internal teeth on the timer cam drum thus driving the drum until the lever clears its tab and is retracted by the second (tension) spring. As the lever is retracted it picks up the pawl and retracts the pawl and the drive step is completed. The drive is more economical than the usual stored energy step drive but is more expensive than a creep-type drive. It makes possible variations in steps (degrees and frequency) and even continuous (rapid) drive.</p> |
