Throw-on/throw-off device for a blanket cylinder with a printing speed dependent control system for a sheet-fed offset press

摘要

A throw-on and throw-off device for a blanket cylinder in the printing unit of an offset press is provided wherein two parallel double- acting fluid pressure cylinders connected to the blanket cylinder via a toggle- like linkage can be individually supplied with compressed air either consecutively or simultaneously so that, in the first case, precise sequential throw-on of the blanket cylinder on the plate cylinder and subsequently on the impression cylinder can be achieved and, in the latter case, there can be a very rapid throw-off of the blanket cylinder from both the impression cylinder and the plate cylinder. Compressed air energization of the two pressure cylinders is triggered by a control unit in accordance with the position of grip edge zones of the blanket, plate and impression cylinders being in registration. In order to ensure that throwing on and throwing off take place when the grip edge zones of the printing cylinders are positioned immediately opposite one another, the control unit detects the position of the printing unit cylinders relative to one another by way of an angular position sensor and also detects the actual speed of the press via a speed sensor. The control unit forms speed-dependent throw-on and throw-off actuating times which are advanced in the direction of rotation of the printing unit cylinders so that the reaction time is outside the time slot for grip edge zone registration.