Conveyors for box making machines

Apparatus for digital printing of planar articles comprising, in combination:

• a digital printer, a conveyor having a conveyor belt movable along a generally horizontal path for moving overlying planar articles which cover or overlie said conveyor belt with a gap between the planar articles along said path to said printer;
• said belt having a plurality of belt vacuum holes or apertures for introducing a vacuum to the underside of said overlying planar articles on said belt to hold the overlying planar articles on the belt;
• wherein said overlying planar articles which cover or overlie said conveyor belt also cover some of said plurality of belt vacuum holes or apertures, providing a covered plurality of belt vacuum holes or apertures, and wherein said gap between the planar articles provide an uncovered plurality of belt vacuum holes or apertures;
• said apparatus further comprising a source of vacuum responsive to a vacuum control system said vacuum control system being configured to (a) open to said source of vacuum and apply vacuum to only said covered plurality of belt vacuum holes or apertures and (b) close said source of vacuum to said uncovered plurality of belt vacuum holes or apertures while said vacuum is applied to said covered plurality belt vacuum holes or apertures;
• said apparatus further comprising a belt vacuum hole or aperture sensor for sensing said plurality of belt vacuum holes or apertures as the belt is moving along said path and for sending a belt vacuum hole sensor trigger signal for feeding said planar articles to the conveyor in a predeteiiiiined position relative to said plurality of belt vacuum holes or apertures, and wherein said sensor senses said plurality of belt vacuum holes or apertures as the conveyor belt moves along said path;
• said apparatus further including a computer which receives said belt vacuum hole sensor trigger signal and generates a computer calculated feed time delay interval for shifting the position of said conveyor belt in response to said belt vacuum hole sensor trigger signal;
• wherein said sensor comprises a photo-electric sensor which senses said plurality of belt vacuum holes or apertures as the conveyor belt moves along said path;
• wherein said planar articles may be deposited and held in a position such that a gap between successive planar articles will not overlie any of said belt vacuum holes or apertures;
• and
• wherein said planar articles comprise boards or sheets;
• wherein the computer calculated feed time delay interval is used for shifting the position of said conveyor belt and the boards or sheets in response to the position of said belt vacuum holes or apertures as sensed by said sensor;
• and
• wherein said digital printer also includes a plurality of print heads, each of said print heads having a nozzle for discharging a jet of ink onto a sheet, and wherein said boards or sheets are deposited and held in a position such that a gap between successive boards or sheets will not overlie any of said belt vacuum holes or apertures, and whereby a discharged ink jet is not diverted by vacuum from said belt vacuum holes or apertures.