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.

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.

A stack state of a plurality of trays is collectively determined and is notified in steps. A printing apparatus includes an image forming unit configured to form an image on a sheet and create a printed material, a plurality of storage units each configured to store the printed material created by the image forming unit, a sorter unit configured to output the printed material to the plurality of storage units, and a determining unit configured to determine whether the plurality of storage units are in a nearly full state in which printed material is stored in almost all of the plurality of storage units.

A stack state of a plurality of trays is collectively determined and is notified in steps. A printing apparatus includes an image forming unit configured to form an image on a sheet and create a printed material, a plurality of storage units each configured to store the printed material created by the image forming unit, a sorter unit configured to output the printed material to the plurality of storage units, and a determining unit configured to determine whether the plurality of storage units are in a nearly full state in which printed material is stored in almost all of the plurality of storage units.

In a saddle-stitching apparatus, when a sheet is transported to a center-folding unit, a folding blade moves from a retrieved position to a nip position between a pair of folding rollers. A forward end of the folding blade comes into contact with a fold of the sheet, so that the sheet is folded along the fold. When the sheet is attached to the nip position between the folding rollers, the folding rollers start rotating and then, the folding blade inserts the center-folded sheet between the folding rollers. After the center-fold finishing is completed, the rotations of the folding rollers stop in timing at which the folding blade is pulled out of the nip position between the folding rollers. When pulling the folding blade out of the nip position between the folding rollers, the rotations of the folding rollers restart.

In a saddle-stitching apparatus, when a sheet is transported to a center-folding unit, a folding blade moves from a retrieved position to a nip position between a pair of folding rollers. A forward end of the folding blade comes into contact with a fold of the sheet, so that the sheet is folded along the fold. When the sheet is attached to the nip position between the folding rollers, the folding rollers start rotating and then, the folding blade inserts the center-folded sheet between the folding rollers. After the center-fold finishing is completed, the rotations of the folding rollers stop in timing at which the folding blade is pulled out of the nip position between the folding rollers. When pulling the folding blade out of the nip position between the folding rollers, the rotations of the folding rollers restart.

A sheet processing apparatus that can suppress a reduction in a quality of a finish of a fold part of a stack of center-folded sheets without losing an ease of center-folding. The sheet processing apparatus comprises a creasing unit for forming a folding stripe on a sheet so as to facilitate folding the sheet, and an acquisition unit for acquiring information related to a thickness of the sheet. One or more sheets to be provided with folding stripes are determined, from among a plurality of sheets to be folded, according to the information related to the thickness of the sheets, and each of the determined one or more sheets are provided with a folding stripe.

A sheet processing apparatus that can suppress a reduction in a quality of a finish of a fold part of a stack of center-folded sheets without losing an ease of center-folding. The sheet processing apparatus comprises a creasing unit for forming a folding stripe on a sheet so as to facilitate folding the sheet, and an acquisition unit for acquiring information related to a thickness of the sheet. One or more sheets to be provided with folding stripes are determined, from among a plurality of sheets to be folded, according to the information related to the thickness of the sheets, and each of the determined one or more sheets are provided with a folding stripe.

A sheet feeding device (4) includes a placing plate (34) on which a sheet is placed; a pickup roller (71) which feeds the sheet to a conveying path (25); a lift member (36) which is turned around a rotating shaft (46) to elevate the placing plate (34) and to make an downstream side end portion of an uppermost sheet in a conveying direction come into contact with the pickup roller (71); a drive unit (37) which rotates the rotating shaft (46); a variable resistor (54) which changes an electric resistance value depending on a rotating angle of the rotating shaft (46); and a control part (77) which calculates the rotating angle of the rotating shaft (46) using the electric resistance value measured by the variable resistor (54) and detects an amount of the sheets based on the calculated rotating angle.

A sheet feeding device (4) includes a placing plate (34) on which a sheet is placed; a pickup roller (71) which feeds the sheet to a conveying path (25); a lift member (36) which is turned around a rotating shaft (46) to elevate the placing plate (34) and to make an downstream side end portion of an uppermost sheet in a conveying direction come into contact with the pickup roller (71); a drive unit (37) which rotates the rotating shaft (46); a variable resistor (54) which changes an electric resistance value depending on a rotating angle of the rotating shaft (46); and a control part (77) which calculates the rotating angle of the rotating shaft (46) using the electric resistance value measured by the variable resistor (54) and detects an amount of the sheets based on the calculated rotating angle.