| 摘要 |
A machine includes a scheme for detecting the level of curl in sheets in a stack by measuring the time it takes to acquire a sheet with a bottom corrugation vacuum feeder (BVCF). A vacuum switch changes state at a preset vacuum level thereby detecting any significant rise in vacuum which occurs when a sheet has been acquired by the BCVF. A digital control circuit senses the change of state which takes place in the vacuum switch and feeds a signal to the machine's microprocessor which in turn signals an air knife in the BVCF to increase or decrease air pressure toward the sheet stack to compensate for the stressed state of the sheets.
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