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Abstract

System for controlling a document feeder which receives documents of various lengths one-at-a-time with their ends touching or overlapping and delivers them at a constant speed and with fixed spaces between their ends. The document feeder employs a variable speed servo, which drives a group of low-speed rollers and a group of high-speed rollers while maintaining a constant speed ratio between the two groups. A natural gap develops between first and second documents in a track of the feeder between the time the first document and the second document pass from control by the group of low-speed rollers into control by the group of high-speed rollers. Sensors are positioned along the track to detect passage of trailing and leading edges of successive documents. A processor responds to signals from the sensors to determine the length of the natural gap formed between the first and second documents and adjusts the speed of the servo system to change the gap, if needed, and then adjusts the speed to match that of rollers in the track downstream of the document feeder. Performance of the system is monitored by measurement of the gap downstream and changes in signals to the processor which accompany changes in the gap downstream are used to adjust the gap to the desired length.

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