Web-fed rotary printing unit

A web-fed rotary printing unit comprising:

• a plurality of printing mechanisms, each printing mechanism including an impression cylinder and further cylinders comprising a form cylinder and a transfer cylinder;
• a first drive motor associated with the impression cylinder of a first printing mechanism, the first drive motor having a first drive connection to the further cylinders of the first printing mechanism through the impression cylinder of the first printing mechanism;
• a second drive motor for driving the further cylinders of the first printing mechanism which is connected to the first drive motor by the first mechanical drive connection;
• a drive coupling in the first mechanical drive connection that is in an engaged position during printing operation in order to prevent stressing the first and second drive motors with a a restraining moment between the impression cylinder and the further cylinders of the first printing mechanism and that is in a disengaged position during setting up operation such that the further cylinders of the first printing mechanism are independently drivable by the second drive motor;
• a second printing mechanism including the impression cylinder of the first printing mechanism and further cylinders comprising a form cylinder and a transfer cylinder;
• and
• a third drive motor for driving the further cylinders of the second printing mechanism, the third drive motor not being connected to the first mechanical drive connection.