| 摘要 |
A label-attaching machine for attaching labels carried on a partially transparent dispensing web for attachment to serially presented envelopes has a two-beam optical sensing unit to govern the synchronization of label feeding by determining the location of the leading edge of the next label to be dispensed. One beam senses the optical transmission of label-bearing regions of the web, and the other beam reads the optical transmission of label-free used web. A comparator circuit balances the signal strengths of the two beams to provide a signal condition indicative of label edge passage. A zip code sort is provided for use in conjunction with the same optical sensor. Labels of a common zip code are serially affixed to the web, and the arrival of a new zip code is flagged by an oversize gap between the last label bearing one zip code and the next label bearing the first of the new zip codes. A feed control system responsive to the optical sensing system responds to the long duration sensing of a long web gap to govern suitable sorting systems. A movable label dispensing head carries one of a pair of label-affixing pinch rollers through an arc to provide a controllable separation between the two pinch rollers, and a resilient biasing spring returns the upper pinch roller into secure contact with the media passing thereby. Media feed jamming in the case of thick media and small pinch rollers is thereby minimized.
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