PURPOSE: To stabilize ink transfer rate and prevent a change in printing density by providing a cooling device in an ink fountain roller and a doctor roll, and controlling the cooling function of both cooling devices in accordance with the speed of a machine using a cooling control.
CONSTITUTION: The opening of a flow control valve 21a, 21b is automatically controlled and set according to the speed of machine by means of a cooling control. This results in the supply and circulation of cooling water into a cooling device 20a provided in an ink fountain roller 5. Consequently a friction heat generated by the peripheral speed of a delivery roller 7 and the ink fountain roller 5 or a heat by ink shearing and a heat by the elastic action of a rubber on the delivery roller 7 are eliminated. At the same time, a cooling water is supplied and circulated into a cooling device 20b to dissipate a friction heat generated between a doctor blade 6b and the doctor roller, a heat by ink shearing between an ink application roller 9a, 9b and the doctor roller, a heat by the elastic action of a rubber on the delivery roller 7.