Conveyors for box making machines

Abstract

A vacuum belt conveyor sequentially delivers sheet articles to a digital printer. The sheets are held in position by vacuum on the underside of the sheets through apertures in the belts and covered by the sheets. A plurality of independent plenums on the underside of the belt have chambers respectively communicating with rows of apertures extending along the belt. Vacuum is selectively applied from a manifold only to the plenum chambers that supply apertures that are covered by the sheets so that the ink from the printer will not be directed from its intended position on the sheet by vacuum from adjacent uncovered belt apertures. The sheets are fed to the conveyor in synchronism with the conveyor speed by a timed feeder so that the sheets are carried by the conveyor with a predetermined gap between the sheets and no belt apertures in the gap. A sensor counts the apertures in the belt and activates the feeder at predetermined time intervals.

What is claimed is: 
     
         1 . 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 planar articles with a gap between the articles along said path to said printer, said belt having a plurality of apertures for introducing a vacuum to the underside of articles on said belt to hold the articles on the belt,   means for opening a number of said apertures to a source of vacuum and for closing other apertures in the belt to a source of vacuum while said first number of apertures are open to said vacuum source, and   sensor means for sensing the apertures in the belt as the belt is moving along said path and for sending a signal for feeding articles to the conveyor in a predetermined position relative to the apertures.   
     
     
         2 . Apparatus defined in  claim 1  including:
 a feeder for feeding articles on said belt in a timed manner, 
 a computer for controlling said feeder, and 
 wherein said sensor means sends said signal to said computer for feeding articles to the conveyor in a predetermined position relative to said apertures for printing the articles. 
 
     
     
         3 . Apparatus defined in  claim 1  wherein said sensor means counts the apertures in the belt. 
     
     
         4 . Apparatus defined in  claim 3  wherein said apertures are provided in rows in the belt extending along said path. 
     
     
         5 . Apparatus defined in  claim 1  wherein said sensing means senses the position of said apertures as the conveyor belt moves along said path. 
     
     
         6 . Apparatus defined in  claim 5  including means for shifting the position of said conveyor belt in response to the position of said belt apertures as sensed by said sensing means. 
     
     
         7 . A method of printing planar articles with a digital printer positioned along a generally horizontal path of conveyance of the articles including the steps of:
 sequentially conveying the articles along the path with a vacuum belt conveyor having a belt including apertures in the belt for holding the articles on the belt by a vacuum applied to apertures covered by the articles,   sensing the apertures in the belt as the belt moves along said path, and   feeding the articles along said path in a predetermined position relative to said apertures in accordance with the sensing of the apertures.   
     
     
         8 . The method defined in  claim 7  including the step of counting the apertures with a sensor as the belt moves along said path, and sending a signal with the sensor for feeding the articles on the conveyor. 
     
     
         9 . The method defined in  claim 7  including the step of sensing the position of the apertures in the belt as the belt moves along said path, sending a signal for feeding the articles on the belt in a predetermined position in accordance with the position of the apertures as sensed.