| 摘要 |
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. |
