| 摘要 |
<p>An improvement in a logic controlled sewing machine which permits an operator to vary by electronic means ornamental pattern bight and feed, manual stitch control, or individually control forward and reverse feed to achieve, for example, an optimum balanced buttonhole or ornamental variations to patterns. Operator influenced means are effective to signal the logic to apply a holding signal to FET switches, maintaining the FET switch in the conductive state. Closing of the FET switch inserts the wiper of a rheostat in bypass arrangement in the feedback circuit of an operational amplifier between a digital-to-analog converter for feed or bight and, respectively, a feed or bight servo amplifier system. By changing the magnitude of the resistance in the feedback circuit of the operational amplifier, the gain may be altered, thereby to control the signal to the feed or bight linear actuator for variation of stitch length or pattern width, respectively. An additional FET switch is maintained in the conductive state by the logic means only during reverse feed thereby applying a variable voltage to a summing point prior to the servo amplifier for exclusive control of reverse stitch length during pattern stitching.</p> |
