Vacuum within a pallet conveyor for a printing system

Abstract

In one example, a pallet conveyor for a printing system is described, having a track, a pallet to support a print substrate and move on the track, and a vacuum mechanism to selectively apply a vacuum at the pallet. A boundary of the vacuum applied at the pallet is synchronised with an edge of the print substrate.

1 - 15 . (canceled) 
     
     
         16 . A support for a print substrate in a printing system that includes a printing mechanism defining a print zone to apply printing fluid to the print substrate, the support comprising:
 a pallet to support a print substrate through the print zone; and   a vacuum mechanism to apply a vacuum to the pallet to draw and removably secure a print substrate to the pallet, the vacuum mechanism to apply the vacuum to the pallet selectively beginning near a leading edge of a print substrate on the pallet and ending near a trailing edge of the print substrate on the pallet as the pallet supports the print substrate through the print zone.   
     
     
         17 . The support according to  claim 16 , wherein the print substrate comprises multiple print substrates and the vacuum mechanism is to apply the vacuum selectively beginning near a leading edge of a first print substrate on the pallet and ending near a trailing edge of a last print substrate on the pallet. 
     
     
         18 . The support according to  claim 16 , wherein the vacuum mechanism comprises:
 an elongate vacuum chamber arranged parallel to a conveyance direction of the pallet; and   first and second valves for supplying vacuum to the chamber; and   a moveable surface inside and moveable along a length of the chamber, such that the moveable surface defines a boundary of the vacuum applied to the pallet when one of the first valve and the second valve is open and the other is closed.   
     
     
         19 . The support according to  claim 16 , wherein the vacuum mechanism comprises:
 an elongate vacuum chamber arranged parallel to a conveyance direction of the pallet;   a rotatable tube inside the chamber;   openings regularly spaced along a length of a surface of the tube, each opening circumferentially transposed with respect to a preceding opening; and   apertures regularly spaced along a surface of the chamber, such that rotation of the tube varies alignment between the openings in the surface of the tube and the apertures in the surface of the chamber to define a boundary of the vacuum applied to the pallet.   
     
     
         20 . A support for a print substrate in a printing system that includes a printing mechanism defining a print zone to apply printing fluid to the print substrate, the support comprising:
 a pallet to support a print substrate through the print zone; and   a vacuum mechanism to apply a vacuum to the pallet to draw and removably secure a print substrate to the pallet, the vacuum mechanism comprising:
 an elongate vacuum chamber arranged parallel to a conveyance direction of the pallet; and 
 a boundary defining an area where vacuum is to be applied to the pallet, the boundary moveable along a length of the chamber beginning near a leading edge of a print substrate on the pallet and ending near a trailing edge of the print substrate on the pallet as the pallet supports the print substrate through the print zone. 
   
     
     
         21 . The support according to  claim 20 , wherein the print substrate comprises multiple print substrates and the boundary is moveable along the length of the chamber beginning near a leading edge of a first print substrate on the pallet and ending near a trailing edge of a last print substrate on the pallet. 
     
     
         22 . The support according to  claim 21 , wherein the pallet comprises multiple pallets, a first one of the pallets to support the leading edge of the first print substrate and a second one of the pallets to support the trailing edge of the last print substrate. 
     
     
         23 . The support according to  claim 20 , wherein the vacuum mechanism comprises:
 first and second valves to supply vacuum to the chamber; and   a surface inside and moveable along the length of the chamber to form the boundary where vacuum is to be applied to the pallet when one of the first valve and the second valve is open and the other is closed.   
     
     
         24 . The support according to  claim 20 , wherein the vacuum mechanism comprises:
 a rotatable inside the chamber;   openings regularly spaced along a length of a surface of the tube, each of the openings circumferentially transposed with respect to a preceding opening; and   apertures regularly spaced along a surface of the chamber, such that rotation of the tube varies alignment between the openings in the surface of the tube and the apertures in the surface of the chamber to form the boundary where vacuum is to be applied to the pallet.   
     
     
         25 . The support according to  claim 20 , wherein the pallet comprises multiple pallets and a first one of the pallets comprises a train pallet and a second one of the pallets comprises a wagon pallet connected to the train pallet.