Ink jet coaxial drum system with inter-copy gap tracking

摘要

A media transport system provides full vacuum under media as the media traverses an entire print path of an ink jet printer while simultaneously providing for a no-vacuum inter-copy gap that moves along with the media past print heads of the ink jet printer. This is accomplished with a dual vacuum inner/outer vacuum drum system that includes a first drum that has a matrix of holes that allows for full coverage of vacuum with a second underlying drum that is shifted to align a second set of holes to match the sheet pitch. By shifting the second drum in relation to the first drum, a combination set of holes is aligned to provide full vacuum across the media while a column of holes is blocked to provide a non-vacuum inter-copy gap.

主权项

1. A dual drum vacuum sheet transport apparatus, comprising:
a first drum, said first drum having a first pattern of first vacuum holes; a second drum, said second drum having a second pattern of second vacuum holes; and a controller electrically connected to said first drum, said second drum is positioned coaxially with respect to said first drum, said first drum contacts sheets to be transported, when transporting said sheets on said first drum separated by spaces between said sheets, said first drum and second drum move together, and when not transporting said sheets, said controller controls said first drum to rotate relative to said second drum to move said first drum relative to said second drum so as to leave blocked-hole regions of said first drum where said spaces between said sheets are located, said blocked-hole regions are locations of said first drum where said first vacuum holes are unaligned with said second vacuum holes and said first vacuum holes are blocked by said second drum.