A delivery arrangement including a conveyor and take-off mechanism for delivering a series of printed sheets onto a pile in which nozzles are provided distributed along the width of a sheet, for directing a jet of air to the underside in a direction opposite the sheet movement. A guide plate spaced under the sheet and extending upstream from the nozzles serves to confine the jet. Formed on the surface of the guide plate are a plurality of upraised islands, spaced from one another over the area of the guide plate, the islands presenting plateau surfaces at approximately the same elevation above the guide plate. Consequently, when a sheet is sucked downwardly by the jet of air it engages the plateau surfaces in light frictional engagement to apply frictional drag to the body of the sheet. The source of pressurized air for the nozzles includes means for automatically varying the pressure, and hence the frictional drag, in accordance with the speed of the press. In a preferred embodiment the plateau surfaces, which are spaced both laterally and longitudinally of the guide plate, occupy less than half of the total area of the guide plate and at least a portion of the guide plate is formed with a gradual curvature in a direction downwardly away from the sheet.

A delivery arrangement for a printing press having a conveyor releasing sheets one by one and which includes a jet type vacuum pump facing and closely spaced to the path of a released sheet for slowing the forward movement thereof. The vacuum pump includes a venturi nozzle having a throat at its inlet end and over which is superimposed an injector. The injector has a central opening which is in register with the throat and which is in slightly overhanging relation so that the lip of the opening forms an annular orifice adjacent the throat, the orifice being supplied with air from a pressure chamber which surrounds the nozzle. When the pressurized air flows through the orifice in the form of an annular jet, it is deflected along the wall of the throat by the so-called "Coanda effect" and subsequently expanded, with the resulting venturi action, creating suction at the opening. The suction causes a drag on each passing sheet. A series of such vacuum pumps are spaced across the width dimension of the sheet, separately supplied by high pressure lines of small diameter but with a common exhaust at a remote point. In the preferred embodiment each pump is provided with a disc which defines a small vacuum plenum and which includes elongated transverse slits for applying suction to the sheet.

A sheet feeding apparatus with a cross-cutter in front and an arrangement, following the cross-cutter, for forming a series of underlapping sheets with lifting and holding elements in a region between two withdrawal devices driven at different feed speeds. These elements lift the rear end of each sheet to form a lead-in gap for the following sheet. The lift and holding elements are fastened, furthermore, to continually driven transport elements and are kept on a straight path in the engagement area slightly delayed relative to the following withdrawal device. The lift and holding elements are uniformly distributed across the width of the sheet, and are fastened to a strip picked up by chains located on the side. Several strips are provided spaced at sheet-to-sheet spacing. The track of the lift and holding elements descends slightly in the transport direction. The strips connected to the lateral chains are guided in lateral rails which are adjustable.

Collision between the tail and head ends of successive singly fed sheets to be overlapped is avoided by ejecting air along a frame sloped downwardly away from the line of feed of the sheets. The tail end of a preceding sheet is thus drawn down out of the path of the head end of a succeeding sheet which is to overlap the preceding sheet.

Method for guiding a sheet in vicinity of a sheet slow-down device of a sheet-processing machine. The sheet is gripped at a leading edge thereof with of a gripper system and the sheet is transported in a sheet-transport direction along a sheet travel path. The sheet has a defined region with which the sheet comes into contact with a sheet slow-down device for subsequently forming a sheet pile, and directing the sheet, in the vicinity of the sheet slow-down device, into a range of influence of a flotation guide produced along a guiding surface member by an air flow. The flotation guide, without taking into account the influence of the sheet slow-down device, is effective for bringing the sheet to a normal flotation level located above the guiding surface member. The sheet is supplied to the sheet slow-down device at a height level above the normal flotation level in order to form sheet-stabilizing vacuum forces resulting from the air flow. There is also disclosed a device for performing the method.