A delivery apparatus for a sheet-fed printing press includes a detector, a control unit and a solenoid. The detector detects a moving amount of suction wheels moved by adjustment and generates a signal corresponding to the moving amount. The control unit is connected to the detector and a timing unit of the printing press and generates a signal representing a predetermined length corresponding to the sheet size. The solenoid is located between a powder container and an air source and opens an air path for only a time interval corresponding to the signal supplied from the control unit.

A powder-dusting apparatus (4) which inside a printing machine dusts the pre-dried printed products coming from the printing unit with a powder, for example of corn-starch, comprises in a manner known per se a plurality of nozzles (6), which are charged with a mixture of powder and carrying air from a mixing device (8). The nozzles (6) are arranged in the vicinity of the plane of transport defined by the transport system (1) of the printing machine and are able to assume two different spacings with respect to that plane: ordinarily the nozzles (6) are located comparatively close to this plane of transport; during these times the mixture of powder and carrying air emerges from the nozzles (6) towards the printed products moving past. If, however, a gripping device (2), which is part of the transport system (1) and which holds the printed product, enters the vicinity of the nozzles (6), a suitable control means (9 to 12) causes the nozzles to move into a second position. In this position there is between the underside of the nozzles (6) and the plane of transport of the transport system (1) sufficient space for the gripping device (2) to be able to pass.

In order to prevent a coating liquid from scattering outside the surface of a printed sheet, an on-demand coating head having plural jet sections is arranged along a direction parallel to the left and right edges of the printed medium, and jets only liquid droplets along a predetermined direction by vibration of a piezoelectric vibrator plate and a coating area with a width extending along a direction parallel to the edges of the printed medium. That is, the head is in a reciprocating manner moved on the printed medium along a direction perpendicular to a direction of arrangement of the jet sections, and the head is in a relative manner moved on the printed medium along a direction perpendicular to the above moving direction by a secondary coating scanning control circuit. Edge position signals are produced which respectively indicate an edge position of an effective image in the primary coating scanning direction of the printed medium, and an edge position of the printed medium and jet of liquid droplets from the on-demand control coating head and a reciprocal movement thereof are controlled based on the edge position signals.

A powder apparatus for a sheet-fed rotary printing press includes a nozzle, valve, state detection unit, arithmetic operation unit, and controller. The nozzle sprays powder onto a printed surface of a sheet delivered after printing. The valve adjusts a quantity of powder sprayed from the nozzle. The state detection unit detects a quantity of powder attaching to the sheet. The arithmetic operation unit and controller control the valve on the basis of data output from the state detection unit and indicating a powder quantity.

Apparatus for protecting the surface of freshly printed sheets which are deposited upon one another to form a sheet pile includes an applicator for applying to the respective sheets a separating-agent layer formed of solid particles of separating agent, the layer of separating agent being formed of a mixture including at least one degradable separating agent substance, an aqueous vehicle liquid, and at least one mixture component which degrades the separating agent substance upon simultaneous contact with the separating agent substance and the vehicle liquid.