Examples described herein include devices and methods for adjusting a suction force for a media holddown, comprising detecting an advancement of a media (114) relative to a media holddown surface along a media advancement direction (X), wherein the holddown surface has a plurality of suction zones arranged along the media advancement direction, and adjusting a suction force in the respective suction zones in accordance with the advancement of the media relative to the media holddown surface.

The invention relates to a vacuum system for securing items in printing machines, comprising a printing table (2) with a perforated surface and, in relation thereto, a vacuum system for securing the items to be printed, which comprises a box structure (8) connected to a suction system and provided with a perforated wall in relation to the surface of the printing table (2), said box structure (8) having lateral panels that vertically close the interior thereof, which panels can be moved in order to adjust the gap between them in relation to the width of the items to be printed.

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.

A vacuum table (18) includes an introduction section (102) in fluid communication with a vacuum chamber (120) and a compartment (139) dividable by an adjustment partition (156) into primary and secondary vacuum chambers (139a, 139b). Adjustment plates (130) having adjustment apertures (138) are positionable over apertures (128) of the conveying surface (100) of the vacuum table (18) generally perpendicular to the conveying direction. Film (20) extends from between the nip of pinch rollers (12, 13) to the conveying surface (100) and is tensioned therebetween to be cut in excess of 105 cuts per minute by a servo motor controlled rotary cutter (30) which stops after each cut. The shaft (32) of the rotary cutter (30) includes a bore (310) extending from the idle end to provide servo-control loop stability.

A vacuum table (18) includes an introduction section (102) in fluid communication with a vacuum chamber (120) and a compartment (139) dividable by an adjustment partition (156) into primary and secondary vacuum chambers (139a, 139b). Adjustment plates (130) having adjustment apertures (138) are positionable over apertures (128) of the conveying surface (100) of the vacuum table (18) generally perpendicular to the conveying direction. Film (20) extends from between the nip of pinch rollers (12, 13) to the conveying surface (100) and is tensioned therebetween to be cut in excess of 105 cuts per minute by a servo motor controlled rotary cutter (30) which stops after each cut. The shaft (32) of the rotary cutter (30) includes a bore (310) extending from the idle end to provide servo-control loop stability.

A sheet transport apparatus includes a first belt having a first pattern of first vacuum holes, and a second belt having a second pattern of second vacuum holes. The first belt is positioned on and contacts the second belt. The first belt contacts sheets to be transported. When transporting the sheets on the first belt separated by spaces between the sheets, the first pulleys and second pulleys rotate together and the first belt and the second belt move together. When not transporting the sheets, a controller controls pulleys to move the first belt relative to the second belt so as to leave blocked-hole regions of the first belt where the spaces between the sheets are located. The blocked-hole regions are locations of the first belt where the first vacuum holes are unaligned with the second vacuum holes and the first vacuum holes are blocked by the second belt.

A sheet 200 for an array of vacuum apertures 152 in a substrate support unit 150 of a printer is provided. The sheet 200 comprises a plurality of valves 202 formed into the sheet 200. The sheet 200 is made from a resilient material. Each valve 202 comprises a valve head 204 for sealing a vacuum aperture 152 in the substrate support unit 150, and a valve lever arm 206 for permitting movement of the valve head 204 towards and away from the vacuum aperture 152 in order to open and close the valve 202.

An inkjet printer system includes a porous printing table and thereunder a vacuum chamber that may be divided into sub-vacuum chambers by a movable vacuum divider and a brush attached to prevent contamination and vacuum leakages in the vacuum chamber.