| 摘要 |
A first and a second printing roller are provided, each of which prints a different side of a sheet. A transfer roller is located between these printing rollers and forms tangent points with the same. The transfer roller has a hollow suction bar which extends over its entire axial length and which, when the sheet travels on the first printing roller and its trailing edge moves through the tangent point, picks the trailing edge off the surface of the first printing roller and furnishes it to a combined suction-and-mechanical gripper unit which takes the trailing edge from the suction bar and, during further rotation of the transfer roller, offers it to grippers of the second printing roller so that, when the trailing edge is engaged by the grippers of the second printing roller, and is then pulled onto the second printing roller for printing of the sheet thereon, the trailing edge becomes converted into the leading edge, so that the sheet is reversed side-for-side during the transfer between the first and second printing roller by the transfer roller.
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