Roland Offsetmaschinenfabrik Faber & Schleicher Ag

Harry Brandes

A sheet flattener for a sheet-fed printing press or the like in which sheets having a tendency to curl are conveyed edgewise from a source to a receiver along a path of flow. A pair of cylindrical members, or rollers, define between them a receiving space which extends cross-wise with respect to the direction of sheet movement. A vacuum is applied in the receiving space so that a conveyed sheet is drawn against the rollers in a cusped profile, undergoing an abrupt bend at the point of the cusp in a direction opposite to the direction of curling tendency so that the curl is neutralized. At least the downstream one of the roller is mounted for rotational movement at the speed of the sheet thereby to reduce the frictional drag of the sheet. In the preferred embodiment both rollers are mounted for rotation and the surfaces thereof are roughened with a two-dimensional pattern of shallow projections to minimize contact with the surface of the sheet and to prevent relative slippage. In a further embodiment, both of the rollers are positively driven at a peripheral speed which corresponds to the speed of conveyance to prevent periodic slow-down of the rollers between successive sheets and to thus further insure against slippage between the sheet and roller surfaces.

De-curling device for printing presses

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.

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Munich, Georgia

Harry Brandes