PURPOSE: To provide a safety device for regulation or control of an operation unit released from connection with a printing machine, the device preventing all collisions of mechanical members in failure or abnormality of regulation or control.

CONSTITUTION: A printing machine which is driven by a plurality of motors 9, 13 through gear transmissions 12, 14 when individual units 1, 2 or unit groups are mechanically disconnected from one another is provided with a clutch 18 between the gear transmissions 12, 14 of adjacent two units 1, 2 as a safety unit. Clutch halves 19, 20 of a clutch are connected with a synchronously running gearwheel of each gear transmission 12, 14 in normal state of a regulator 17 or controller. The clutch halves are connected for torque transmission after exceeding a predetermined angle difference between the clutch halves 19, 20.